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Inflammatory skin diseases such as atopic eczema (atopic dermatitis [AD]) affect children and adults globally. In AD, the skin barrier is impaired on multiple levels. Underlying factors include genetic, chemical, immunologic, and microbial components. Increased skin pH in AD is part of the altered microbial microenvironment that promotes overgrowth of the skin microbiome with Staphylococcus aureus. The secretion of virulence factors, such as toxins and proteases, by S aureus further aggravates the skin barrier deficiency and additionally disrupts the balance of an already skewed immune response. Skin commensal bacteria, however, can inhibit the growth and pathogenicity of S aureus through quorum sensing. Therefore, restoring a healthy skin microbiome could contribute to remission induction in AD. This review discusses direct and indirect approaches to targeting the skin microbiome through modulation of the skin pH; UV treatment; and use of prebiotics, probiotics, and postbiotics. Furthermore, exploratory techniques such as skin microbiome transplantation, ozone therapy, and phage therapy are discussed. Finally, we summarize the latest findings on disease and microbiome modification through targeted immunomodulatory systemic treatments and biologics. We believe that targeting the skin microbiome should be considered a crucial component of successful AD treatment in the future. [ABSTRACT FROM AUTHOR]

TET2 participates in tumor progression and intrinsic immune homeostasis via epigenetic regulation. TET2 has been reported to be involved in maintaining epithelial barrier homeostasis and inflammation. Abnormal epidermal barrier function and TET2 expression have been detected in psoriatic lesions. However, the mechanisms underlying the role of TET2 in psoriasis have not yet been elucidated. To define the role of TET2 in maintaining epithelial barrier homeostasis and the exact epigenetic mechanism in the dysfunction of the epidermal barrier in psoriasis. We analyzed human psoriatic skin lesions and datasets from the GEO database, and detected the expression of TET2/5-hmC together with barrier molecules by immunohistochemistry. We constructed epidermal-specific TET2 knockout mice to observe the effect of TET2 deficiency on epidermal barrier function via toluidine blue penetration assay. Further, we analyzed changes in the expression of epidermal barrier molecules by immunofluorescence in TET2-specific knockout mice and psoriatic model mice. We found that decreased expression of TET2/5-hmC correlated with dysregulated barrier molecules in human psoriatic lesions. Epidermal-specific TET2 knockout mice showed elevated transdermal water loss associated with abnormal epidermal barrier molecules. Furthermore, we observed that TET2 knockdown in keratinocytes reduced filaggrin expression via filaggrin promoter methylation. Aberrant epidermal TET2 affects the integrity of the epidermal barrier through the epigenetic dysregulation of epidermal barrier molecules, particularly filaggrin. Reduced TET2 expression is a critical factor contributing to an abnormal epidermal barrier in psoriasis. [ABSTRACT FROM AUTHOR]

[Display omitted] • The permeability of drugs was investigated in the presence of a rotating magnetic field (RMF). • The RMF may increase the permeability of active pharmaceutical ingredients (APIs). • The enhancement of API permeation through the skin in the presence of RMF depends on the type of API used (variable diffusion profiles). The paper presents a method of increasing the permeability of various active substances through the skin by means of a rotating magnetic field. The study used 50 Hz RMF and various active pharmaceutical ingredients (APIs) such as caffeine, ibuprofen, naproxen, ketoprofen, and paracetamol. Various concentrations of active substance solutions in ethanol were used in the research, corresponding to those in commercial preparations. Each experiment was conducted for 24 h. It was shown that, regardless of the active compound used, an increase in drug transport through the skin was observed with RMF exposure. Furthermore, the release profiles depended on the active substance used. Exposure to a rotating magnetic field has been shown to effectively increase the permeability of an active substance through the skin. [ABSTRACT FROM AUTHOR]

Cannabidiol, a non-psychoactive phytocannabinoid, has antioxidant and anti-inflammatory activity in keratinocytes. However, the signaling pathway through which cannabidiol exerts its effect on keratinocytes or whether it can modulate keratinocyte differentiation has not been fully elucidated yet. We investigated whether cannabidiol modulates epidermal differentiation and scavenges reactive oxygen species through the aryl hydrocarbon receptor (AhR) in keratinocytes and epidermal equivalents. We investigated the cannabidiol-induced activation of AhR using AhR luciferase reporter assay, qRT-PCR, western blot, and immunofluorescence assays. We also analyzed whether keratinocyte differentiation and antioxidant activity are regulated by cannabidiol-induced AhR activation. In both keratinocytes and epidermal equivalents, cannabidiol increased both the mRNA and protein expression of filaggrin, involucrin, NRF2, and NQO1 and the mRNA expression of the AhR target genes, including CYP1A1 and aryl hydrocarbon receptor repressor. Additionally, cannabidiol showed antioxidant activity that was attenuated by AhR knockdown or co-administration with an AhR antagonist. Moreover, cannabidiol increased the ratio of OVOL1/OVOL2 mRNA expression, which is a downstream regulator of AhR that mediates epidermal differentiation. In addition to increased expression of barrier-related proteins, cannabidiol-treated epidermal equivalent showed a more prominent granular layer than the control epidermis. The increased granular layer by cannabidiol was suppressed by the AhR antagonist. Cannabidiol can be a modulator of the AhR-OVOL1-filaggrin axis and AhR-NRF2-NQO1 signaling, thus indicating a potential use of cannabidiol in skin barrier enhancement and reducing oxidative stress. • CBD regulates AhR in keratinocytes and epidermal equivalents. • CBD induces epidermal differentiation by modulating the AhR-OVOL1 axis. • AhR orchestrates ROS scavenging through NRF2 regulation. [ABSTRACT FROM AUTHOR]

[Display omitted] • Single-chain bolalipids PC-C24-PC and PC-C32-PC do not enhance skin penetration of a hydrophilic permeant from aqueous vehicles into porcine ear skin. • Single-chain bolalipids strongly reduce corneocyte cohesion during ex vivo tape stripping. • The effect on corneocyte cohesion resembles the behavior observed for salicylic acid as keratolyic reference substance. Synthetic single-chain bolalipids (SSCBs) are novel excipients in drug delivery, with potential as stabilizers or solubilizers. However, their impact on skin barrier function has not been comprehensively studied. Therefore, two SSCBs (PC-C24-PC and PC-C32-PC) were studied in aqueous systems for their impact on penetration of a model permeant into porcine skin. Concentrations of 0.05 – 5 % w/w were tested; PC-C24-PC formulations were low-viscosity liquids while PC-C32-PC formed viscous dispersions to gels at room temperature. Formulations were compared for their ability to enhance sodium fluorescein penetration (SF, 0.1 % w/w) into skin via tape stripping. Using NIR-densitometry, the effect of SSCB formulations on corneocyte cohesion was evaluated. Data were compared with phospholipid mixture Lipoid S-75, sodium dodecyl sulfate (SDS), and polyethylene glycol 12-hydroxystearate (PEG-HS), and distilled water as negative control. Contrary to the hypothesis, both SSCBs failed to increase SF penetration into the stratum corneum, but rather showed a significant decrease in penetration depth compared to water. Both SSCBs exhibited a keratolytic effect at 5 % w/w, leading to substantial removal of proteins from the skin surface. Consequently, SSCBs may not enhance penetration of hydrophilic drugs into skin, but could be used as keratolytic agents. [ABSTRACT FROM AUTHOR]

• The 12 main compounds of Cannabis fructus were identified using HPLC-ESI-MS/MS. Trilinolein was extracted and shown to have anti-inflammatory and antioxidant effects both in vitro and in vivo. • Trilinolein prevents dinitrochlorobenzene (DNCB)-induced atopic dermatitis (AD)-like lesions and restores the skin barrier in BALB/c mice. • Trilinolein attenuates IL-4- and TNF-α-induced mitochondrial DNA (mtDNA) release and ROS production in HaCaT cells via the AhR-Nrf2 pathway. Atopic dermatitis (AD) is a common skin condition that causes chronic and recurring eczema lesions. Prior research has indicated that Cannabis fructus , the mature fruit of Cannabis sativa, has an antioxidant effect. Historically, Cannabis fructus has been used in cosmetics and medicine. However, there is limited knowledge regarding its biological components and the mechanisms by which it prevents and treats AD. HPLC-ESI-MS/MS analysis was utilized to identify the main compounds of Cannabis fructus , and trilinolein was extracted using chromatographic techniques. The potential of trilinolein in the prevention of AD was assessed, and its underlying mechanisms of action were elucidated. The distribution of distinct cellular subpopulations and the principal biological processes implicated in the pathogenesis of AD were assessed through a comparative study involving chronic AD patients and healthy controls (HCs). Differential gene expression was validated in clinical samples from the lesions of AD patients and the healthy skin of controls. The pharmacodynamic activity of trilinolein was validated in dinitrochlorobenzene (DNCB)-induced BALB/c mice and in IL-4- and TNF-α-induced HaCaT cells. Proteomics analyse was employed to investigate its mechanisms. Single-cell transcriptome analysis revealed that chronic AD is characterized by abnormal keratinocyte differentiation and oxidative stress damage. When topically applied, trilinolein can effectively improve AD-like skin lesions induced by DNCB. It increases the expression of terminal differentiation proteins and decreases the expression of NADPH oxidase 2 (NOX2), with a therapeutic effect comparable to that of the positive control drug crisaborole. Additionally, trilinolein reduced ROS fluorescence intensity, restored mitochondrial morphology and membrane potential, and decreased mitochondrial DNA (mtDNA) release in keratinocytes stimulated with IL-4 and TNF-α. Moreover, trilinolein increased the protein expression of AhR, CYP1A1, and Nrf2 in a dose-dependent manner. The effect of trilinolein on keratinocyte terminal differentiation proteins and ROS levels was blocked by the addition of an AhR inhibitor. The study suggests that trilinolein from Cannabis fructus alleviates NOX2-dependent mitochondrial dysfunction and repair the skin barrier via AhR-Nrf2 pathway, making it a promising agent for the prevention and treatment of AD. [Display omitted] [ABSTRACT FROM AUTHOR]

Caspase recruitment domain family member 14 (CARD14) and its variants are associated with both atopic dermatitis (AD) and psoriasis, but their mechanistic impact on skin barrier homeostasis is largely unknown. CARD14 is known to signal via NF-κB; however, CARD14-NF-κB signaling does not fully explain the heterogeneity of CARD14-driven disease. Here, we describe a direct interaction between CARD14 and MYC and show that CARD14 signals through MYC in keratinocytes to coordinate skin barrier homeostasis. CARD14 directly binds MYC and influences barrier formation in an MYC-dependent fashion, and this mechanism is undermined by disease-associated CARD14 variants. These studies establish a paradigm that CARD14 activation regulates skin barrier function by two distinct mechanisms, including activating NF-κB to bolster the antimicrobial (chemical) barrier and stimulating MYC to bolster the physical barrier. Finally, we show that CARD14-dependent MYC signaling occurs in other epithelia, expanding the impact of our findings beyond the skin. [Display omitted] • CARD14 signaling directly regulates MYC in keratinocytes to promote barrier homeostasis • Pathogenic genetic variants dysregulate CARD14-MYC signaling, promoting barrier dysfunction • Skin barrier function remains intact in the context of complete CARD14 deficiency • The CARD14-MYC mechanism may contribute to diseases beyond the epidermis The epithelial protein CARD14 canonically regulates NF-κB and is associated with atopic dermatitis and psoriasis. DeVore et al. report that CARD14 also regulates MYC signaling to influence barrier homeostasis—a mechanism altered by disease-associated genetic variants. This pathway may represent a potential therapeutic target in diseases of dysregulated barrier function. [ABSTRACT FROM AUTHOR]

Our skin protects us from external threats including ultraviolet radiation, pathogens and chemicals, and prevents excessive trans-epidermal water loss. These varied activities are reliant on a vast array of lipids, many of which are unique to skin, and that support physical, microbiological and immunological barriers. The cutaneous physical barrier is dependent on a specific lipid matrix that surrounds terminally-differentiated keratinocytes in the stratum corneum. Sebum- and keratinocyte-derived lipids cover the skin's surface and support and regulate the skin microbiota. Meanwhile, lipids signal between resident and infiltrating cutaneous immune cells, driving inflammation and its resolution in response to pathogens and other threats. Lipids of particular importance include ceramides, which are crucial for stratum corneum lipid matrix formation and therefore physical barrier functionality, fatty acids, which contribute to the acidic pH of the skin surface and regulate the microbiota, as well as the stratum corneum lipid matrix, and bioactive metabolites of these fatty acids, involved in cell signalling, inflammation, and numerous other cutaneous processes. These diverse and complex lipids maintain homeostasis in healthy skin, and are implicated in many cutaneous diseases, as well as unrelated systemic conditions with skin manifestations, and processes such as ageing. Lipids also contribute to the gut-skin axis, signalling between the two barrier sites. Therefore, skin lipids provide a valuable resource for exploration of healthy cutaneous processes, local and systemic disease development and progression, and accessible biomarker discovery for systemic disease, as well as an opportunity to fully understand the relationship between the host and the skin microbiota. Investigation of skin lipids could provide diagnostic and prognostic biomarkers, and help identify new targets for interventions. Development and improvement of existing in vitro and in silico approaches to explore the cutaneous lipidome, as well as advances in skin lipidomics technologies, will facilitate ongoing progress in skin lipid research. [ABSTRACT FROM AUTHOR]

Dendrobium officinale Kimura et Migo as a valuable Chinese medicine has been used in China for more than 2000 years. Its main active components, polysaccharide (DOP), has been reported to have various pharmacological effects, including anti-inflammatory, antioxidant and alleviating AD effects. However, the precise mechanism underlying its therapeutic effect in AD remains largely unclear. The present study sought to assess the efficacy of DOP and elucidate its intricate mechanisms in ameliorating DNFB-induced AD. Mice were sensitized with DNFB and treated with DOP application for 14 days. Treatment effects were assessed using dermatitis scores, ear thickness and scratching frequency. Epidermal thickness, mast cells and CD4+ T cells infiltration were detected by using H&E, toluidine blue staining and immunofluorescence staining respectively. Serum histamine (HIS), immunoglobulin E (IgE), thymic stromal lymphopoietin (TSLP), skin SOD, MDA, GHS, CAT, inflammatory cytokines (TNF-α, IFN-γ, IL-1β, IL-4, IL-5, IL-13) and chemokine (MIP-α, MDC, MCP-1) levels were quantify by ELISA and immunohistochemistry. Additionally, qPCR and Western blot analyses were performed to assess genes and proteins expression associated with MAPK/NF-κB/STAT3 signaling pathway. The results indicated that DOP effectively mitigated AD-like skin lesions in mice through multiple pathways. It reduced epidermal thickness, ear thickness and scratching frequency in AD mice. Additionally, DOP mitigated inflammatory responses by decreasing the levels of inflammatory factors, as well as reducing serum levels of IgE, HIS, and TSLP. Moreover, DOP inhibited infiltration of mast cells and CD4+ T cells, suppressed the expression of skin chemokines such as MDC, MCP-1, and MIP-α, and enhanced filaggrin content in AD mice. Furthermore, DOP significantly boosted antioxidant capacity, as well as significantly reduced the expression of JAK1, STAT3, NF-κB p65, IκBα, ERK1/2, and p38 proteins and phosphorylated proteins such as p-JAK1, p-STAT3, p-NF-κB p65, p-IκBα, p-ERK1/2, and p-p38. These findings suggested that DOP has significant anti-AD activity, primarily through reducing inflammatory responses, improving antioxidant capacity, repairing the skin barrier, and down-regulating key genes and proteins in MAPK/NF-κB/STAT3 signaling pathway, and that this study may provide valuable insights into the development of innovative therapies for the treatment of AD. [Display omitted] • DOP possessed a significant therapeutic effect in AD mice. • DOP suppressed CD4+ T cells and mast cells infiltration and attenuated inflammatory responses. • DOP could ameliorate oxidative stress capacity in AD mice. • DOP inhibited key genes and proteins expression of MAPK/NF-κB/STAT3 signaling pathway. [ABSTRACT FROM AUTHOR]

The Short-Term Topical Application for Prevention of Atopic Dermatitis (STOP AD) study, a randomized, open-label trial evaluating the effect of short-term (from the first 4 postnatal days to age 8 weeks) skin barrier protection using Aveeno Dermexa Fast & Long-Lasting Balm (Johnson & Johnson, New Brunswick, NJ) in infants with a parent with allergic disease, demonstrated decreased cumulative incidence and decreased prevalence of atopic dermatitis (AD) at age 12 months. In the STOP AD study, we aimed to identify skin biomarkers that are associated with risk of development of AD. Skin swabs were collected from the cheek and antecubital fossa (AF) at baseline, age 8 weeks, and age 12 months from subsets of study participants from the intervention arm (n = 43 of 119) and control arm (n = 43 of 138) and were analyzed for specific cytokines (CCL27, CXCL2, human β-defensin-1 [hBD-1], IL-18, IL-8, IL-1α, IL-1 receptor antagonist [IL-1RA], IL-1β, S100A8/9, and IL-36γ) by ELISA. Higher titers of S100A8/9 at the AF at age 8 weeks in infants with the filaggrin wild-type genotype (FLG wt), but not in those with filaggrin loss-of-function mutation (FLG mut), predicted (1) development of AD in the first year of life (P =.033), (2) presence of AD at ages 6 or 12 months (P =.009 and.035, respectively), (3) persistence of AD between ages 6 and 12 months (P <.001), and (4) development of AD with the emollient intervention. Increased titers of S100A8/9 from skin swabs of the AF in high-risk infants at age 8 weeks with FLG wt were predictive of AD development in the first year of life and other AD features. These findings suggest that there are different molecular pathways leading to AD in individuals with FLG mut and in individuals with FLG wt. Early identification of infants who are likely to develop AD will allow more targeted interventions. [ABSTRACT FROM AUTHOR]

Background Newborn oil massage is a widespread practice. Vigorous massage with potentially harmful products and forced removal of vernix may disrupt skin barrier integrity. Hospitalized, very-preterm infants treated with sunflower seed oil (SSO) have demonstrated improved growth but community-based data on growth and health outcomes are lacking. Objectives We aimed to test whether SSO therapy enhances neonatal growth and reduces morbidity at the population level. Methods We conducted an open-label, controlled trial in rural Uttar Pradesh, India, randomly allocating 276 village clusters equally to comparison (usual care) and intervention comprised of promotion of improved massage practices exclusively with SSO, using intention-to-treat and per-protocol mixed-effects regression analysis. Results We enrolled 13,478 and 13,109 newborn infants in demographically similar intervention and comparison arms, respectively. Adherence to exclusive SSO increased from 22.6% of intervention infants enrolled in the first study quartile to 37.2% in the last quartile. Intervention infants gained significantly more weight, by 0.94 g · kg−1 · d−1 (95% CI: 0.07, 1.82 g · kg−1 · d−1, P = 0.03), than comparison infants by intention-to-treat analysis. Restricted cubic spline regression revealed the largest benefits in weight gain (2–4 g · kg−1 · d−1) occurred in infants weighing <2000 g at birth. Weight gain in intervention infants was higher by 1.31 g · kg−1 · d−1 (95% CI: 0.17, 2.46 g · kg−1 · d−1; P = 0.02) by per-protocol analysis. Morbidities were similar by intention-to-treat analysis but in per-protocol analysis rates of hospitalization and of any illness were reduced by 36% (OR: 0.64; 95% CI: 0.44, 0.94; P = 0.02) and 44% (OR: 0.56; 95% CI: 0.40, 0.77; P < 0.001), respectively, in treated infants. Conclusions SSO therapy improved neonatal growth, and reduced morbidities when applied exclusively, across the facility–community continuum of care at the population level. Further research is needed to improve demand for recommended therapy inside hospital as well as in community settings, and to confirm these results in other settings. This trial was registered at www.isrctn.com as ISRCTN38965585 and http://ctri.nic.in as CTRI/2014/12/005282. [ABSTRACT FROM AUTHOR]

Low epidermal filaggrin (FLG) is a risk factor for atopic dermatitis (AD) and allergic comorbidity. FLG mutations do not fully explain the variation in epidermal FLG levels, highlighting that other genetic loci may also regulate FLG expression. We sought to identify genetic loci that regulate FLG expression and elucidate their functional and mechanistic consequences. A genome-wide association study of quantified skin FLG expression in lesional and baseline non(never)-lesional skin of children with AD in the Mechanisms of Progression of Atopic Dermatitis to Asthma in Children cohort was conducted. Clustered regularly interspaced short palindromic repeat approaches were used to create isogenic human keratinocytes differing only at the identified variant rs11652075, and caspase recruitment domain family member 14 (CARD14)-deficient keratinocytes for subsequent mechanistic studies. The genome-wide association study identified the CARD14 rs11652075 variant to be associated with FLG expression in non(never)-lesional skin of children with AD. Rs11652075 is a CARD14 expression quantitative trait locus in human skin and primary human keratinocytes. The T variant destroys a functional cytosine-phosphate-guanine site, resulting in reduced cytosine-phosphate-guanine methylation at this site (but not neighboring sites) in TT and CT compared with CC primary human keratinocytes and Mechanisms of Progression of Atopic Dermatitis to Asthma in Children children's skin samples, and rs11652075 increases CARD14 expression in an allele-specific fashion. Furthermore, studies in clustered regularly interspaced short palindromic repeat-generated CC and TT isogenic keratinocytes, as well as CARD14-haplosufficient and deficient keratinocytes, reveal that IL-17A regulates FLG expression via CARD14, and that the underlying mechanisms are dependent on the rs11652075 genotype. Our study identifies CARD14 as a novel regulator of FLG expression in the skin of children with AD. Furthermore, CARD14 regulates skin FLG homeostasis in an rs11652075-dependent fashion. [ABSTRACT FROM AUTHOR]

Atopic dermatitis (AD) and food allergy (FA) are strongly associated, with one-third of children with AD developing concomitant FA. Epithelial barrier dysfunction is important in both conditions. Genetic factors, such as filaggrin mutations and IL-4 receptor alpha chain polymorphisms, are linked to increased risk. In addition, several environmental exposures lead to reduced filaggrin and contribute to skin barrier dysfunction. Staphylococcus aureus colonization appears to contribute to AD and FA, as well as activating the type 2 immune response. Comprehensive multiomic studies using skin tape stripping have identified distinct atopic endotypes with unique characteristics of the stratum corneum lipids, proteins, S aureus abundance, and type 2 cytokine expression. Our new understanding of AD and FA presents an area of opportunity to move toward improved diagnosis and prevention of atopy. [ABSTRACT FROM AUTHOR]

Background: Delgocitinib 0.5% ointment, a topical Janus kinase inhibitor, has been approved in Japan for adult patients with atopic dermatitis (AD).Objective: To evaluate the efficacy and safety of delgocitinib ointment in pediatric patients with AD.Methods: Part 1 of this study was a 4-week double-blind period in which Japanese patients aged 2 through 15 years were randomized in a 1:1 ratio to delgocitinib 0.25% ointment or vehicle ointment. Part 2 was a 52-week extension period. Eligible patients entered part 2 to receive 0.25% or 0.5% delgocitinib ointment.Results: At the initiation of the study, approximately half of the patients had moderate AD. At the end of treatment in part 1, the least-squares mean percent change from baseline in modified Eczema Area and Severity Index score, the primary efficacy endpoint, was significantly greater for delgocitinib ointment than for vehicle (-39.3% vs +10.9%, P < .001). In part 2, improvements in AD were also seen through week 56. Most adverse events were mild and unrelated to delgocitinib across the study periods.Limitations: Only Japanese patients were included. In part 2, no control group was included and rescue therapy was allowed.Conclusion: Delgocitinib ointment was effective and well tolerated when applied to Japanese pediatric patients with AD for up to 56 weeks. [ABSTRACT FROM AUTHOR]

• Impaired skin barrier function drives the pathophysiology of atopic dermatitis. • Defects in skin barrier component genes lead to impaired skin barrier function. • Environmental factors may worsen atopic dermatitis through cutaneous exposure. • The cutaneous microbiome is an important component of the skin barrier function. • Several therapies for atopic dermatitis promote restoration of the skin barrier. Atopic dermatitis (AD) is a chronic, inflammatory skin disorder characterized by eczematous and pruritic skin lesions. In recent decades, the prevalence of AD has increased worldwide, most notably in developing countries. The enormous progress in our understanding of the complex composition and functions of the epidermal barrier allows for a deeper appreciation of the active role that the skin barrier plays in the initiation and maintenance of skin inflammation. The epidermis forms a physical, chemical, immunological, neuro-sensory, and microbial barrier between the internal and external environment. Not only lesional, but also non-lesional areas of AD skin display many morphological, biochemical and functional differences compared with healthy skin. Supporting this notion, genetic defects affecting structural proteins of the skin barrier, including filaggrin, contribute to an increased risk of AD. There is evidence to suggest that natural environmental allergens and man-made pollutants are associated with an increased likelihood of developing AD. A compromised epidermal barrier predisposes the skin to increased permeability of these compounds. Numerous topical and systemic therapies for AD are currently available or in development; while anti-inflammatory therapy is central to the treatment of AD, some existing and novel therapies also appear to exert beneficial effects on skin barrier function. Further research on the skin barrier, particularly addressing epidermal differentiation and inflammation, lipid metabolism, and the role of bacterial communities for skin barrier function, will likely expand our understanding of the complex etiology of AD and lead to identification of novel targets and the development of new therapies. [ABSTRACT FROM AUTHOR]

In this study, we examined physiological functions as a key material to develop cosmeceuticals using extracts of Lagerstroemia macrocarpa Wall. Ex Kurz (L. macrocarpa). Initially, the L. macrocarpa extract was treated by different concentration and antioxidant assay (DPPH and ABTS) were performed to measure free radical scavenging ability. In the cytotoxicity experiment, the extract was treated into human epidermal keratinocytes with different concentrations to measure cytotoxicity. We found that the extract induces differentiation markers such as keratin (KRT)1, KRT2, KRT9, KRT10 in keratinocytes. Furthermore, the extract significantly induces involucrin (IVL), loricrin (LOR), claudin1 (CLDN1) , and filaggrin (FLG) expression, suggesting that it may enhance skin barrier functions. Especially, the extract restored FLG expression inhibited by interleukin (IL)-4/IL-13 in in vitro atopic dermatitis-like model. Therefore, we expect L. macrocarpa extract will be an effective material to develop the therapeutic and cosmeceutical of atopic dermatitis. [Display omitted] [ABSTRACT FROM AUTHOR]

Atopic dermatitis (AD) is a chronic inflammatory skin condition primarily driven by T helper 2 (Th2) cytokines, resulting in skin barrier defects, angiogenesis, and inflammatory responses. The marine natural product excavatolide B (EXCB), isolated from the Formosan Gorgonian coral Briareum stechei , exhibits anti-inflammatory and analgesic properties. To enhance solubility, EXCB is chemically modified into the derivatives EXCB-61 salt and EXCB-79. The study aims to investigate the therapeutic effects of these compounds on dinitrochlorbenzene (DNCB)-induced skin damage and to elucidate the underlying anti-inflammatory and anti-angiogenesis mechanism. In vitro , using lipopolysaccharide (LPS)-induced RAW 264.7 cells, all compounds at 10 μM significantly inhibited expression of inflammatory proteins (inducible nitric oxide synthase and cyclooxygenase-2), vascular endothelial growth factor (VEGF), and cytokines (interleukin (IL)−1β, IL-6, and IL-17A). In vivo , topical application of these compounds on DNCB-induced AD mice alleviated skin symptoms, reduced serum levels of IgE, IL-4, IL-13, IL-17, and interferon-γ, and moderated histological phenomena such as hyperplasia, inflammatory cell infiltration, and angiogenesis. The three compounds restored the expression of skin barrier-related proteins (loricrin, filaggrin, and claudin-1) and reduced the expression of angiogenesis-related proteins (VEGF and platelet endothelial cell adhesion molecule-CD31) in the tissues. This is the first study to indicate that EXCB, EXCB-61 salt, and EXCB-79 can treat AD disease by reducing inflammation and angiogenesis. Hence, they may be considered potential candidates for the development of new drugs for AD. [Display omitted] ● In vitro , EXCB, EXCB-61 salt, and EXCB-79 inhibited iNOS,COX-2, IL-1β, IL-6, IL-17A, and VEGF. ● In vivo , EXCB and derivatives topically mitigated DNCB-induced skin symptoms in mice, reducing serum IgE and cytokine levels. ● Histologically, these compounds moderated hyperplasia, mast cell infiltration, angiogenesis, and restored the skin barrier. ● These findings suggest EXCB and derivatives as potential AD treatments, validly reducing inflammation and angiogenesis. [ABSTRACT FROM AUTHOR]

[Display omitted] Maternal overweight and obesity have been associated with an increased risk of atopic dermatitis (AD) in the offspring, but the underlying mechanisms are unclear. Vernix caseosa (VC) is a proteolipid material covering the fetus produced during skin development. However, whether maternal prepregnancy weight excess influences fetal skin development is unknown. Characterizing the VC of newborns from mothers with prepregnancy overweight and obesity might reveal AD-prone alterations during fetal skin development. We sought to explore AD biomarkers and staphylococcal loads in VC from the offspring of mothers who were overweight/obese (O/O) before pregnancy versus in those from offspring of normal weight mothers. The VC of newborns of 14 O/O and 12 normal weight mothers were collected immediately after birth. Biomarkers were determined by ELISA and staphylococcal species by quantitative PCR. The VC from the O/O group showed decreased expression of skin barrier proteins (filaggrin and loricrin) and increased levels of proinflammatory biomarkers (IgA, thymic stromal lymphopoietin [TSLP], S100A8, IL-25, and IL-33). No differences in concentrations of antimicrobial peptides and enzymes were detected. The VC from the O/O group had a lower Staphylococcus epidermidis and Staphylococcus hominis commensal bacterial load, whereas Staphylococcus aureus bacterial load was not significantly different between the 2 groups. Maternal body mass index was negatively correlated with VC filaggrin expression and S epidermidis load and was positively associated with TSLP concentration. One-year follow-up established that the offspring of O/O mothers had a higher incidence of AD that was specifically linked with decreased VC filaggrin expression and lower S epidermidis load. VC from neonates of mothers with prepregnancy overweight and obesity exhibit skin barrier molecular alterations and staphylococcal dysbiosis that suggest early mechanistic clues to this population's increased risk of AD. [ABSTRACT FROM AUTHOR]

• Th2, Th17 cell numbers increased, and Treg cell numbers decreased in acute AD. • Treg cell number increased in chronic AD. • YAP was downregulated in Treg and upregulated in Th17 cells. • YAP downregulation in AD epidermis inhibited proliferation and migration. • YAP downregulation induced apoptosis of keratinocytes. Atopic dermatitis (AD) is characterized by impaired skin barrier function and immune system dysfunction. The expression and role of Yes-associated protein (YAP) in AD are unclear. To characterize the role of the YAP in T cell imbalance and epidermal keratinocyte dysfunction in the pathogenesis of AD. We included 35 patients with AD (21 acute and 14 chronic). An AD mouse model was constructed using 2,4-dinitrofluorobenzene, and AD-like inflammatory cell model was constructed using TNF-α/IFN-γ-activated HaCaT cells. The proportion of Th1/Th2/Th17/Treg cells was detected using flow cytometry. After mononuclear cells were obtained from human peripheral blood or mouse spleen and induced to differentiate into different T cell subsets, YAP mRNA and protein expression were analyzed. Up-regulation of YAP was induced by lentivirus and down-regulation of YAP was induced by its specific inhibitor verteporfin (VP). The expression of YAP in skin lesions and infiltrating T cell subsets was detected using immunohistochemistry and double immunofluorescence staining, respectively. We found differing degrees of Th1/Th2/Th17/Treg imbalance in acute and chronic AD. YAP expression was downregulated in Treg cells and upregulated in Th17 cells; YAP expression was downregulated in the AD epidermis. After YAP overexpression, the proportion of both Th17 and the Treg cells differentiated from mouse spleen mononuclear cells increased. There was an opposite trend after YAP inhibition. The proliferation and migration decreased and apoptosis increased after YAP inhibition in HaCaT cells. Change of YAP expression may cause T cell imbalance and hamper the healing of the epidermis in AD. [ABSTRACT FROM AUTHOR]

Recently evidence linking the effects of fine-dust (FD) on skin inflammation is exaggerating. Fucoidan derived from brown algae has great potential for ameliorating oxidative stress and inflammation. Herein, a fucoidan fraction (SHC4-6) was purified from an enzymatic (Celluclast) extract of an invasive seaweed, Sargassum horneri following gradient ethanol precipitation and anion exchange chromatography. Effectiveness of SHC4-6 in ameliorating FD (from Beijing, China)-induced inflammatory responses in HaCaT keratinocytes and recovery of skin barrier dysfunction was evaluated. SHC4-6 was comprising of sulfated mannofucans with their molecular weights distributed around 45 kDa. SHC4-6 dose-dependently lowered ROS levels in FD-induced HaCaT keratinocytes, ameliorating viability at 50 μg mL−1. SHC4–6 downregulated inflammatory cytokines, tumor necrosis factor-α, interleukin (IL)-1β, -5, -6, -8, -13, interferon-γ, and chemokines, macrophage-derived chemokine, eotaxin, and thymus and activation regulated chemokine by inhibiting mitogen-activated protein kinase and nuclear factor-κB pathways. SHC4–6 treatment ameliorated key tight junction proteins and skin hydration factors, depicting the effects of fucoidan in reducing FD-induced inflammation and skin barrier deterioration. With further studies in place, SHC4-6 could be used as an ingredient for developing cosmetics to relieve FD-induced skin inflammation. • Isolation of low molecular weight fucoidan from Sargassum horneri was described. • Selected fucoidan, SHC4-6, was treated on fine dust-induced human keratinocytes. • SHC4-6 indicated protective effects via lowering inflammatory responses and defective skin barrio functions. • NF-κB and MAPK pathways might involve in the SHC4-6 mediated anti-inflammatory effects. [ABSTRACT FROM AUTHOR]

Cold plasma technology is an emerging tool facilitating the spatially controlled delivery of a multitude of reactive species (ROS) to the skin. While the therapeutic efficacy of plasma treatment has been observed in several types of diseases, the fundamental consequences of plasma-derived ROS on skin physiology remain unknown. We aimed to bridge this gap since the epidermal skin barrier and perfusion plays a vital role in health and disease by maintaining homeostasis and protecting from environmental damage. The intact skin of SKH1 mice was plasma-treated in vivo. Gene and protein expression was analyzed utilizing transcriptomics, qPCR, and Western blot. Immunofluorescence aided the analysis of percutaneous skin penetration of curcumin. Tissue oxygenation, perfusion, hemoglobin, and water index was investigated using hyperspectral imaging. Reversed-phase liquid-chromatography/mass spectrometry was performed for the identification of changes in the lipid composition and oxidation. Transcriptomic analysis of plasma-treated skin revealed modulation of genes involved in regulating the junctional network (tight, adherence, and gap junctions), which was confirmed using qPCR, Western blot, and immunofluorescence imaging. Plasma treatment increased the disaggregation of cells in the stratum corneum (SC) concomitant with increased tissue oxygenation, gap junctional intercellular communication, and penetration of the model drug curcumin into the SC preceded by altered oxidation of skin lipids and their composition in vivo. In summary, plasma-derived ROS modify the junctional network, which promoted tissue oxygenation, oxidation of SC-lipids, and restricted penetration of the model drug curcumin, implicating that plasma may provide a novel and sensitive tool of skin barrier regulation. Image 1 • Disaggregation of stratum corneum and enhanced penetration of curcumin. • Oxidative modification of SC lipids. • Increased tissue oxygenation. • Regulation of junctional proteins. [ABSTRACT FROM AUTHOR]

Atopic dermatitis (AD) and food allergy (FA) are associated with skin barrier dysfunction. Skin biomarkers are needed for skin barrier interventions studies. In this study, skin tape strip (STS) samples were collected from nonlesional skin of 62 children in AD FA + , AD FA − , and nonatopic groups for mass spectrometry proteomic analysis. transepidermal water loss and allergic sensitization were assessed. STS proteomic analysis results were validated in an independent cohort of 41 adults with AD with and without FA versus nonatopic controls. A group of 45 proteins was identified as a principal component 1 (PC1) with the highest expression in AD FA + STSs. This novel set of STS proteins was highly correlative to skin transepidermal water loss and allergic sensitization. PC1 proteins included keratin intermediate filaments; proteins associated with inflammatory responses (S100 proteins, alarmins, protease inhibitors); and glycolysis and antioxidant defense enzymes. Analysis of PC1 proteins expression in an independent adult AD cohort validated differential expression of STS PC1 proteins in the skin of adult patients with AD with the history of clinical reactions to peanut. STS analysis of nonlesional skin of AD children identified a cluster of proteins with the highest expression in AD FA + children. The differential expression of STS PC1 proteins was confirmed in a replicate cohort of adult AD patients with FA to peanut, suggesting a unique STS proteomic endotype for AD FA+ that persists into adulthood. Collectively, PC1 proteins are associated with abnormalities in skin barrier integrity and may increase the risk of epicutaneous sensitization to food allergens. [ABSTRACT FROM AUTHOR]

Background: Graft-versus-host disease (GVHD) has various cutaneous manifestations. Little is known about the mechanisms of cutaneous GVHD with different clinical features.Objective: To characterize the immunologic features and skin barrier functions of cutaneous GVHD.Methods: The study included 19 patients with atopic dermatitis (AD)-like GVHD, 8 with lichen planus (LP)-like GVHD, 24 with AD, and 15 healthy controls. The subpopulation of T cells in peripheral blood and skin lesions was measured by flow cytometry and immunofluorescence, respectively. Filaggrin expression in skin lesions was measured by Western blot and immunohistochemistry. Transepidermal water loss was also measured using Tewameter TM 300 (Courage & Khazaka Electronic GmbH, Köln, Germany).Results: The number of peripheral blood eosinophils in AD-like GVHD was significantly higher than that in LP-like GVHD. Type 2 helper T cells in peripheral blood and skin lesions were increased in AD-like GVHD and LP-like GVHD. Regulatory T cells in peripheral blood and skin lesions were increased in AD-like GVHD. Filaggrin expression and transepidermal water loss were increased in skin lesions of AD-like GVHD and LP-like GVHD.Limitations: The number of patients is limited.Conclusion: Although AD-like GVHD and LP-like GVHD both had elevated type 2 helper T cells and impaired skin barrier, increased eosinophils and regulatory T cells were found only in AD-like GVHD. [ABSTRACT FROM AUTHOR]

Background: Previous studies showed the potential effectiveness of delgocitinib ointment, a novel topical Janus kinase inhibitor, in atopic dermatitis (AD).Objective: This study aimed to evaluate the efficacy and safety of delgocitinib 0.5% ointment.Methods: In part 1, a 4-week double-blind period, Japanese patients aged 16 years or older with moderate or severe AD were randomly assigned in a 2:1 ratio to delgocitinib 0.5% ointment or vehicle ointment. Eligible patients entered part 2, a 24-week extension period, to receive delgocitinib 0.5% ointment.Results: At the end of treatment in part 1, the least-squares mean percent changes from baseline in the modified Eczema Area and Severity Index score, the primary efficacy endpoint, were significantly greater in the delgocitinib group than in the vehicle group (-44.3% vs 1.7%, P < .001). The improvement in modified Eczema Area and Severity Index score was maintained in part 2. Most adverse events were mild and unrelated to delgocitinib across the study periods.Limitations: Only Japanese patients were included. The vehicle-controlled period lasted only 4 weeks. In part 2, topical corticosteroids were allowed for the treatment of worsening of AD.Conclusion: Delgocitinib ointment was effective and well tolerated in Japanese adult patients with moderate to severe AD for up to 28 weeks. [ABSTRACT FROM AUTHOR]

• A novel frameshift mutation in NIPAL4 was identified in an ichthyosis patient. • Expression of IL-17/TNFα-related genes was upregulated in the ichthyotic skin. • Major acylceramides were reduced in the patient's stratum corneum. • Stratum corneum acylceramide amounts were partly restored after retinoid treatment. NIPAL4 , encoding the NIPA-like domain containing 4 protein (NIPAL4), is one of the causative genes of autosomal recessive congenital ichthyosis (ARCI). The physiological role of NIPAL4 and the pathogenetic mechanisms of ARCI caused by NIPAL4 mutations remain unclear. To clarify the changes of ceramide components in the lesional stratum corneum (SC) and the gene expression profile in the lesional skin of an ARCI patient with a novel frameshift mutation in NIPAL4. We performed ultrastructural and immunohistochemical analyses of the skin. We used RNA sequencing to determine the mRNA expression in the skin of the patient and healthy individuals. We investigated ceramide components using tape stripped SC samples from the patient. mRNA expression profiling in the patient's skin showed significant upregulation of IL-17/TNFα-related genes (IL17C , IL36A , IL36G , S100A7A , S100A9) and psoriasis hallmark genes (VNN3, LCE3D, PLA2G4D), and significant downregulation of lipid-associated genes (GAL , HAO2 , FABP7). Ceramide analysis in the patient's SC revealed amounts of CER[NS] with carbon chain-length (C) 32–52 were increased, while amounts of most acylceramide with C66:2 - C72:2 were reduced relatively to those in healthy individuals. After the retinoid treatment, CER[NS] with carbon chains C46–54, CER[EOH] and CER[EOP] increased. IL-17C and IL-36 family cytokines might be involved in the pathogenetic process of ARCI with NIPAL4 mutations. Reduced amounts of the acylceramides in the SC are associated with the skin phenotype due to NIPAL4 mutations. Efficacy of the oral retinoid treatment might be due to restored amounts of CER[EOH] and CER[EOP] in the SC. [ABSTRACT FROM AUTHOR]

Xerosis cutis of the feet is one of the most common skin conditions among type 2 diabetics. Whether skin dryness among diabetic patients is different from 'general' skin dryness is unclear. The overall aim was to compare the structure, function and molecular markers of dry and cracked foot skin between diabetics and non-diabetics. The foot skin of 40 diabetics and 20 non-diabetics was evaluated. A clinical assessment of skin dryness was performed and transepidermal water loss, stratum corneum hydration, skin surface pH, epidermal thickness, skin roughness, elasticity and structural stiffness were measured. Ceramides, natural moisturizing factors, histamines, proteins and molecular markers of oxidative stress were analyzed based on a non-invasive sampling method for collection of surface biomarkers. The mean number of superficial fissures in the diabetic group was nearly three times higher than in the non-diabetic group (11.0 (SD 6.2) vs. 3.9 (SD 4.2)). The skin stiffness was higher in the diabetic group and the values of almost all molecular markers showed considerably higher values compared to non-diabetics. Malondialdehyde and glutathione were lower in the diabetic sample. The high number of superficial fissures may be based on an increased stiffness of dry diabetic foot skin combined with different concentrations of molecular markers in the stratum corneum compared to dry foot skin of non-diabetics. • The mean number of superficial fissures in the diabetic group was nearly three times higher than in the non-diabetic group. • In diabetics stiffness was generally higher at all skin areas. • The dorsal skin of diabetics showed higher roughness, was thinner and less hydrated, clinically possibly leading to higher fragility. [ABSTRACT FROM AUTHOR]

Protopanaxatriol (PPT) is an important ginsenoside produced by ginseng, a tonic plant used in many areas. PPT has beneficial effects against many disease states including inflammation, diabetes, and cancer. However, PPT's protective effects on skin integrity have been rarely studied. Previously, we reported that PPT can maintain skin moisture through activation of nuclear factor kappa B (NF-κB) and mitogen-activated protein kinases (MAPKs) pathways. However, the cellular targets for enhancing skin moisturizing effects via PPT are still unknown. We wanted to identify the upstream targets of PPT on upregulating moisturizing factor (HAS-2) expression. We investigated which upstream proteins can be directly stimulated by PPT to modulate NF-κB, MAPKs and other signaling cascades. Then, the targeted proteins were overexpressed to check the relationship with HAS-2. Next, the cellular thermal shift assay (CETSA) was conducted to check the relationship between targeted proteins and PPT. A human keratinocyte HaCaT were employed to measure the levels of moisturizing factors and the signaling proteins activated by PPT. Transfection conditions were established with DNA constructs expressing epidermal growth factor receptor (EGFR) and human epidermal growth factor receptor 2 (HER2) and their mutants prepared by site-directed mutagenesis. Further investigation on molecular mechanisms was conducted by RT-PCR, luciferase reporter gene assay, CETSA, or Western blot. We found that PPT can activate the phosphorylation of EGFR and HER2. These stimulations caused Src phosphorylation, which resulted in the activation of phosphoinositide 3-kinases (PI3K)/pyruvate dehydrogenase kinase 1 (PDK1)/protein kinase B (AKT)/NF-κB and MAPKs signaling cascades. Additionally, EGFR and HER2 activation resulted in phosphorylation of signal transducer and activator of transcription 3 (STAT3) and calcium/calmodulin-dependent protein kinase II (CaMKII). This induced the AMP-activated protein kinase alpha (AMPKα) signaling pathway. Additionally, PPT blocked peroxisome proliferator activated receptor gamma (PPARγ), which also contributed to the phosphorylation of Src. Overall, we first found that PPT offers excellent protection of the skin barrier and hydrogen supply in keratinocytes. Moreover, growth factor receptors such as EGFR and HER2 were revealed to be central enzymes to be directly targeted by PPT. These results suggest a potentially valuable role as a cosmetic ingredient. [ABSTRACT FROM AUTHOR]

The outermost epidermal layer of the skin, the stratum corneum , is not simply a barrier that safeguards skin integrity from external insults and invaders, it is also a delicately integrated interface composed of firm, essentially dead corneocytes and a distinctive lipid matrix. Together, the stratum corneum lipid matrix and sebum lipids derived from sebaceous glands give rise to a remarkably complex but quite unique blend of skin surface lipids that demonstrates tremendous heterogeneity and provides the skin with its indispensable protective coating. The stratum corneum lipid matrix is composed primarily of three major lipid classes: ceramides, non-esterified fatty acids and cholesterol, whereas sebum is a waxy mixture predominantly composed of acylglycerols, wax esters, non-esterified fatty acids, squalene, cholesterol and cholesterol esters. The balance of these skin surface lipids in terms of their relative abundance, composition, molecular organisation and dynamics, and their intricate interactions play a crucial role in the maintenance of healthy skin. For that reason, even minuscule alterations in skin surface lipid properties or overall lipid profile have been implicated in the aetiology of many common skin diseases including atopic dermatitis, psoriasis, xerosis, ichthyosis and acne. Novel lipid-based interventions aimed at correcting the skin surface lipid abnormalities have the potential to repair skin barrier integrity and the symptoms associated with such skin diseases, even though the exact mechanisms of lipid restoration remain elusive. [Display omitted] • Skin surface lipids synergistically support skin barrier homeostasis. • Changes in skin surface lipid properties are associated with various skin diseases. • Sebum is a unique waxy mixture of lipids that moisturises and protects the skin. • Ceramides, non-esterified fatty acids and cholesterol are beneficial in topical products. • Topical application of key skin-identical lipids helps restore skin barrier function. [ABSTRACT FROM AUTHOR]

Filaggrin (FLG), a skin barrier protein, is associated with higher dermal uptake of some chemicals in carriers of loss-of-function (null) mutations. This study investigates FLG mutations and systemic effects following dermal exposure to chemicals. Individuals (n = 23 FLG null, n = 31 FLG wt) were simultaneously exposed to pyrimethanil, pyrene, oxybenzone, and nickel ions for 4 h. Pre- and post-exposure, 25-hydroxyvitamin D3 (25(OH)D3, LC-MS/MS) and 92 inflammation-related proteins (proximity-extension assay) were measured. FLG null carriers exhibited significantly higher 25(OH)D3 concentrations than wt carriers, both pre- and post-exposure. Eleven proteins differed in abundance post- vs pre-exposure among FLG null carriers, and 22 proteins among wt carriers (three proteins overlapped). Twelve proteins showed median differences (post- vs pre-exposure) between FLG null and wt carriers. Overall, FLG null carriers showed an increase, while FLG wt carriers showed a decrease in inflammation-related proteins. These findings suggest FLG -dependent differences in susceptibility to systemic effects following simultaneous dermal chemical exposure. • Filaggrin (FLG) is a key protein of the skin barrier. • We performed dermal human exposure to four frequently occurring chemicals. • We measured 92 inflammation-related proteins and vitamin D before and after exposure. • FLG null carriers had higher levels of vitamin D compared to wt. • FLG genotype-dependent changes in inflammation-related proteins were identified. [ABSTRACT FROM AUTHOR]

Centella asiatica (L.) Urban (CA) is a dry herb of the Umbelliferae family, first mentioned in Shennong's Herbal Classic. It is known for its ability to clear heat and dampness, detoxify, and reduce swelling, making it a popular treatment for dermatitis, wound healing, and lupus erythematosus. Psoriasis is a chronic inflammatory skin disease that is characterized by clearly delineated erythema and squamous skin lesions. However, the effect of CA on regulating inflammation and its mechanism in the pathogenesis of psoriasis is still not fully understood. This study evaluated the effects of CA on inflammatory dermatosis by in vitro and in vivo studies. And clarified the important role of the JAK/STAT3 signaling pathway in the treatment of psoriasis with CA. Different components of CA were extracted and analyzed for their total flavonoid and polyphenol contents. The antioxidant capacity of the CA extracts was determined using DPPH, ABTS, and FRAP methods. In vitro , HaCaT cells were induced by lipopolysaccharide (LPS, 20 μg·mL-1) to establish an inflammatory injury model, and the effects of CA extracts on oxidative stress, inflammation and skin barrier function were evaluated systematically. Annexin V-FITC/PI staining was utilized for detecting cell apoptosis, while the expression of NF-κB and JAK/STAT3 pathways were detected by RT-PCR and western blot. Combined with an in vivo mice model of Imiquimod (IMQ) induced psoriasis-like skin inflammation, the most effective CA extract for alleviating psoriasis was identified and its potential mechanism was investigated. CA extracts showed high antioxidant capacity and were able to increase the content of GSH and SOD while reducing intracellular ROS generation. Notably, CA ethyl acetate extract (CAE) was found to be the most effective. Furthermore, CA extracts effectively downregulate inflammatory factors (IFN-γ, CCL20, IL-6 and TNF-α) mRNA levels and improved the gene expressions of barrier protective factors AQP3 and FLG, among them CAE and n-hexane extract of CA (CAH) had better effects. Western blot analysis indicated that CAE and CAH had anti-inflammatory effects by inhibiting the activation of NF-κB and JAK/STAT3 pathways, and CAE exhibited the best regulatory effect at the dose of 25 μg·mL-1. In vivo experiment, the psoriasis-like skin inflammation mice model was established by 5% IMQ and treated CAE solution (10, 20, 40 mg·mL-1) for 7 days, the results showed that CAE intervention reduced the skin scale and blood scab, and significantly inhibited the secretion of inflammatory factors in both serum and skin lesions at the dose of 40 mg·mL-1. Centella asiatica extracts were effective in improving skin inflammation and skin barrier dysfunction, and also alleviated psoriasis through JAK/STAT3 pathway. The results provided experimental support for the potential use of Centella asiatica in functional food and skin care products. [Display omitted] • CA extracts had high antioxidant capacity, and CAE was the best. • CAE could exert anti-inflammation by inhibiting NF-κB and JAK/STAT3 pathways in LPS-induced HaCaT cells. • CAE reduced inflammation and improved barrier function in psoriasis mice. • CAE effectively alleviated psoriasis through JAK/STAT3 pathway. [ABSTRACT FROM AUTHOR]

Bifidobacterium as probiotics, play important roles in skin status, while the potential mechanisms interaction remains unknown. The study further explored the potential mechanism of B. longum 68S in ameliorating skin barrier damage from the perspective of the gut-skin axis in aging mice. B. longum 68S supplied natural aging mouse model and fecal microbiota transplantation (FMT) experiment proves the key role of intestinal microbiota in B. longum 68S up-regulating the production of ceramide synthesis key enzyme (SPT1) and ceramide level and improving skin barrier damage. Moreover, B. longum 68S supplied SPT1 gene deletion mouse model to investigate the mechanism of B. longum 68S on improving skin barrier damage. Transcriptome analysis and 16S rRNA high-throughput pyrosequencing demonstrated that aging mice exhibited skin barrier dysfunction and intestinal dysbiosis. Meanwhile, aging mice exhibited an up-regulation in the trans epidermal water loss (TEWL) and a down-regulation in the level of SPT1 , ceramide and skin barrier-related proteins (Loricrin, Keratin 10 and Desmoglein 1). Similarity, the FMT from aging mice to normal mice and SPT1 gene deletion mice could rebuild skin barrier damage and B. longum 68S supplementation exerted a positive effect on it. Further, B. longum 68S-mediated SPT1 -derived ceramide production prevented impaired ceramide synthesis-induced endoplasmic reticulum stress and apoptotic response, ultimately improving skin barrier damage in vitro. Emerging anti-aging therapies are necessary given the poor safety profiles of current pharmaceutical drugs. B. longum 68S may be better alternatives, considering the association between the gut microbiota and healthy aging. The findings suggested that B. longum 68S - mediated gut-skin axis homeostasis, thereby exhibiting an anti-aging effect and facilitate a better understanding of the mechanisms governing the various beneficial effects of B. longum 68S. [ABSTRACT FROM AUTHOR]

The intercellular lipid matrix of the stratum corneum (SC), which consist mainly of ceramides (CERs), free fatty acids and cholesterol, is fundamental to the skin barrier function. These lipids assemble into two lamellar phases, known as the long and short periodicity phases (LPP and SPP respectively). The LPP is unique in the SC and is considered important for the skin barrier function. Alterations in CER composition, as well as impaired skin barrier function, are commonly observed in diseased skin, yet the understanding of this relationship remains insufficient. In this study, we have investigated the influence of non-hydroxy and α-hydroxy sphingosine-based CERs and their phytosphingosine counterparts on the permeability and lipid organization of model membranes, which were adjusted in composition to enhance formation of the LPP. The permeability was compared by diffusion studies using ethyl-p-aminobenzoate as a model drug, and the lipid organization was characterized by X-ray diffraction and infrared spectroscopy. Both the sphingosine- and phytosphingosine-based CER models formed the LPP, while the latter exhibited a longer LPP repeat distance. The ethyl-p-aminobenzoate flux across the sphingosine-based CER models was higher when compared to the phytosphingosine counterparts, contrary to the fact that the α-hydroxy phytosphingosine-based CER model had the lowest chain packing density. The unanticipated low permeability of the α-hydroxy phytosphingosine-based model is probably associated with a stronger headgroup hydrogen bonding network. Our findings indicate that the increased level of sphingosine-based CERs at the expense of phytosphingosine-based CERs, as observed in the diseased skin, may contribute to the barrier function impairment. Unlabelled Image • Sphingosine-based lipid membranes are more permeable than their phytosphingosine counterparts. • The α-hydroxy phytosphingosine-based ceramide model has the lowest chain packing density as well as the strongest headgroup hydrogen bonding network. • The low permeability may be related to a stronger headgroup hydrogen bonding network rather than a dense lipid tail packing. [ABSTRACT FROM AUTHOR]

Knowledge regarding the barrier properties of human skin is important for understanding skin pathology, developing of transdermal drug delivery systems and computational skin absorption models; however, the molecular pathways through human skin remains to be fully investigated on a nanoscopic level. In particular the nanoscopic pathway of molecules passing the intercellular lipid bilayers separating the corneocytes in the stratum corneum (SC) is not fully elucidated. Using stimulated emission depletion microscopy (STED) and Förster resonance energy transfer (FRET) the molecular pathways through the SC, the main barrier of the skin, are determined for lipophilic and water-soluble molecules at a nanoscopic resolution. Using STED and confocal microscopy, water-soluble dyes, were observed to be present in both the corneocytes and in the intercellular lipid matrix, whereas the lipophilic dyes were predominately in the intercellular lipid bilayers. FRET was observed in the SC between the lipophilic and water-soluble dyes, the existence of a minimum possible distance between acceptor and donor molecules of 4.0 ± 0.1 nm was found. The results indicate that lipophilic molecules penetrate the stratum corneum via the intercellular lipids bilayers separating the corneocytes in the SC, while the more water-soluble molecules penetrate the stratum corneum via the transcellular route through the corneocytes and intercellular lipid bilayers via the polar head groups of lipid molecules in the bilayers. Knowledge of the nanoscopic molecular pathways through human skin will help understand the skin barrier function and will be of use for computational skin absorption models and transdermal drug delivery strategies. • Super resolution optical microscopy resolves the intercellular lipid matrix. • FRET was observed between lipophilic and water-soluble dyes in the intercellular lipid matrix. • In SC a minimum distance between lipophilic and water-soluble molecules of 4.0 nm was found. • Water-soluble molecules can move through the intercellular lipid matrix via the polar head groups. [ABSTRACT FROM AUTHOR]

Abstract The human genome encodes nine enzymes belonging to the patatin-like phospholipase domain-containing lipase (PNPLA)/Ca2+-independent phospholipase A 2 (iPLA 2) family. Although most PNPLA/iPLA 2 enzymes are widely distributed and act on phospholipids or neutral lipids as (phospho)lipases to play homeostatic roles in lipid metabolism, the function of PNPLA1 remained a mystery until a few years ago. However, the recent finding that mutations in the human PNPLA1 gene are linked to autosomal recessive congenital ichthyosis (ARCI), as well as evidence obtained from biochemical and gene knockout studies, has shed light on the function of this enzyme in skin-specific sphingolipid metabolism rather than glycerophospholipid metabolism. PNPLA1 is specifically expressed in differentiated keratinocytes and plays a crucial role in the biosynthesis of ω- O -acylceramide, a particular class of sphingolipids that is essential for skin barrier function. PNPLA1 acts as a unique transacylase that specifically transfers linoleic acid from triglyceride to ω-hydroxy fatty acid in ceramide, thus giving rise to ω- O -acylceramide. In this review, we overview the biosynthetic route and biological role of epidermal ω- O -acylceramide, highlight the function of PNPLA1 as a bona fide acylceramide synthase required for proper skin barrier function and keratinocyte differentiation, and summarize the mutations of PNPLA1 currently identified in ARCI patients. This article is part of a Special Issue entitled Novel functions of phospholipase A 2 Guest Editors: Makoto Murakami and Gerard Lambeau [ABSTRACT FROM AUTHOR]

Abstract The protective function of biological surfaces that are exposed to the exterior of living organisms is the result of a complex arrangement and interaction of cellular components. This is the case for the most external cornified layer of skin, the stratum corneum (SC). This layer is made of corneocytes, the elementary 'flat bricks' that are held together through adhesive junctions. Despite the well-known protective role of the SC under high mechanical stresses and rapid cell turnover, the subtleties regarding the adhesion and mechanical interaction among the individual corneocytes are still poorly known. Here, we explore the adhesion of single corneocytes at different depths of the SC, by pulling them using glass microcantilevers, and measuring their detachment forces. We measured their interplanar adhesion between SC layers, and their peripheral adhesion among cells within a SC layer. Both adhesions increased considerably with depth. At the SC surface, with respect to adhesion, the corneocyte population exhibited a strong heterogeneity, where detachment forces differed by more than one order of magnitude for corneocytes located side by side. The measured detachment forces indicated that in the upper-middle layers of SC, the peripheral adhesion was stronger than the interplanar one. We conclude that the stronger peripheral adhesion of corneocytes in the SC favors an efficient barrier which would be able to resist strong stresses. Graphical abstract fx1 [ABSTRACT FROM AUTHOR]

Atopic dermatitis (AD) affects up to 20% of children worldwide and is an increasing public health problem, particularly in developed countries. Although AD in infants and young children can resolve, there is a well-recognized increased risk of sequential progression from AD to other atopic diseases, including food allergy (FA), allergic rhinitis, allergic asthma, and allergic rhinoconjunctivitis, a process referred to as the atopic march. The mechanisms underlying the development of AD and subsequent progression to other atopic comorbidities, particularly FA, are incompletely understood and the subject of intense investigation. Other major research objectives are the development of effective strategies to prevent AD and FA, as well as therapeutic interventions to inhibit the atopic march. In 2017, the Division of Allergy, Immunology, and Transplantation of the National Institute of Allergy and Infectious Diseases sponsored a workshop to discuss current understanding and important advances in these research areas and to identify gaps in knowledge and future research directions. International and national experts in the field were joined by representatives from several National Institutes of Health institutes. Summaries of workshop presentations, key conclusions, and recommendations are presented herein. [ABSTRACT FROM AUTHOR]

Abstract Human skin is a region of high metabolic activity where a rich variety of biomarkers are secreted from the stratum corneum. The skin is a constant source of volatile organic compounds (VOCs) derived from skin glands and resident microbiota. Skin VOCs contain the footprints of cellular activities and thus offer unique insights into the intricate processes of cutaneous physiology. This review examines the growing body of research on skin VOC markers as they relate to skin physiology, whereby variations in skin-intrinsic and microbial metabolic processes give rise to unique volatile profiles. Emerging evidence for volatile biomarkers linked to skin perturbations and skin cancer are examined. Microbial-derived VOCs are also investigated as prospective diagnostic markers, and their potential to shape the composition of the local skin microbiota, and consequently cutaneous health, is considered. Finally, a brief outlook on emerging analytical challenges and opportunities for skin VOC-based research and diagnostics is presented. Highlights • Review of research on skin volatiles with a focus on cutaneous health and disease from an analytical chemistry perspective. • Emerging evidence for volatile biomarkers in skin linked to skin perturbations and cancer is examined. • Microbial-derived volatile compounds are reviewed as prospective diagnostic markers. • Analytical challenges and opportunities in the translation of skin volatile markers into clinical diagnostics are discussed. [ABSTRACT FROM AUTHOR]

Abstract The superficial layer of the skin, the stratum corneum (SC), consists of corneocytes surrounded by lipid regions and acts as a protective barrier for the body against water loss, toxic agents and microorganisms. As most substances permeate the stratum corneum through the lipid regions, lipid organization is considered crucial for the skin barrier function. Here, we investigate the potential of in vivo confocal Raman spectroscopy to describe the composition and organization of the SC. Confocal Raman spectroscopy is finding increasing use in the characterization of skin in biomedical, pharmaceutical and cosmetic applications. In this work, we analyze the spectra using chemometric methods and obtain principal components that correspond to the primary skin constituents: protein (keratin), natural moisturizing factor (NMF), water and lipid contributions in both ordered (orthorhombic) and disordered structural organization. By identifying these important components of the SC, these results highlight the utility of this in vivo , non-invasive, and depth resolved tool at the forefront of skin research. Graphical abstract Unlabelled Image Highlights • Chemometric analysis of in vivo confocal Raman spectra of human stratum corneum finds components corresponding to protein, NMF, water and lipids. • Lipid organization is crucial for the skin barrier function. Our approach detects SC lipids in ordered and disordered structural organization. [ABSTRACT FROM AUTHOR]

Objective: Photodynamic therapy (PDT) is an effective treatment against skin field cancerization. Its main side effect is local inflammation in the treated area. The phenolic compound oleocanthal (decarboxy methyl ligstroside aglycone), which is present in extra virgin olive oil (EVOO), has anti-inflammatory properties. The purpose of this study was to evaluate the topical efficacy of an oily fluid enriched with oleocanthal (OC) extract, in comparison with a conventional oily fluid, in reducing the degree of inflammatory reaction after conventional PDT.Methods: Quasi-experimental pilot study, before-after with a control group, performed with a cohort of consecutive patients diagnosed with actinic keratosis/field cancerization (AK/FC) in the forehead and/or scalp, treated by PDT. The study was carried out from April 2016 to November 2017 at a speciality hospital in southern Spain. A group of 24 consecutive patients received the topical application, three times daily for one week, of an emollient oily fluid in the area treated with PDT. Subsequently, another group, of 23 consecutive patients, received the same treatment pattern with an oily fluid enriched with OC extract. The post-PDT inflammatory reaction was measured by an independent member of the hospital's dermatology department, using the following visual scale of erythema (from 0 to 4).The assessment was conducted at 30 min and at 48 h post-PDT.Results: In the assessment at 48 h after treatment, the inflammation had improved more among the patients treated with OC (median: 25%, 95%CI: -5.3 to 28.5) than in the non-OC group (median: 0%; 95%CI: -45.2 to -6.2). The difference was statistically significant (p<0.01), and the Cohen's d value was 0.89 (large effect). At three months after PDT, a complete response had been obtained by 60.9% of the patients treated with OC compared to 29.2% of the non-OC group, and the difference was close to statistical significance (p=0.059).Conclusions: The topical application of an oily fluid enriched with OC extract achieved a greater reduction in post-PDT cutaneous inflammation and a better treatment response, in comparison with the application of a conventional oily fluid. [ABSTRACT FROM AUTHOR]

Abstract Ethnopharmacological relevance Astragali Radix (AR), the root of Astragalus mongholicus Bunge, is widely applied in traditional medicine to promote skin health and tissue regeneration. Aim of the study This study investigated the effects of AR and its active compound, formononetin (FMT), on skin barrier defects in keratinocytes exposed to diesel particulate matter (PM). Materials and methods HaCaT cells and three-dimensional (3D) human skin reconstructed model were pre-treated with AR (50, 100 μg/ml) and FMT (30, 50 μM), then treated with PM (200 μg/ml). Results AR and FMT significantly enhanced the expression of Keratin (KRT) 16 in PM stimulated HaCaT cells. PM increased p53 and Bax expression as well as the subsequent cleavage of caspase 3 and PARP in HaCaT cells, while this was inhibited by AR and FMT treatment. In vitro studies using the PM stimulated 3D human skin reconstructed model revealed that AR and FMT increased the expression of KRT 16 and KRT 17. Histological examination of the 3D human skin reconstructed model showed that AR and FMT up-regulated the expression of Ki67, but down-regulated the expression of cleaved caspase 3. Both AR and FMT significantly inhibited phosphorylation of ERK, but not JNK and p38 MAPK in PM stimulated HaCaT cells. Conclusions These results suggest that AR and FMT act as anti-pollution agents and alleviate PM induced skin barrier defects through regulation of apoptosis and proliferation in keratinocytes. Graphical abstract fx1 [ABSTRACT FROM AUTHOR]

Staphylococcus aureus is the most common cause of bacterial skin infections in humans, including patients with atopic dermatitis (AD). Polymorphonuclear neutrophils (PMNs) are the first cells to infiltrate an infection site, where they usually provide an effective first line of defense, including neutrophil extracellular trap (NET) formation. Here, we show that infiltrating PMNs in inflamed human and mouse skin enhance S. aureus skin colonization and persistence. Mechanistically, we demonstrate that a crosstalk between keratinocytes and PMNs results in enhanced NET formation upon S. aureus infection, which in turn induces oxidative stress and expression of danger-associated molecular patterns such as high-mobility-group-protein B1 (HMGB1) in keratinocytes. In turn, HMGB1 enhances S. aureus skin colonization and persistence by promoting skin barrier dysfunctions by the downregulation of epidermal barrier genes. Using patient material, we show that patients with AD exhibit enhanced presence of PMNs, NETs, and HMGB1 in the skin, demonstrating the clinical relevance of our finding. [Display omitted] • Crosstalk with keratinocytes primes neutrophils for NET formation upon S. aureus infection • Enhanced presence of neutrophils and NETs induces oxidative stress in the skin • NETs induce ROS-mediated secretion of HMGB1 by keratinocytes • NETs and extracellular HMGB1 downregulate epidermal barrier genes Focken et al. show that in inflamed skin, the enhanced presence of neutrophils and NETs induces ROS-mediated secretion of HMGB1, which in turn mediates the downregulation of epidermal barrier genes, thus driving S. aureus skin colonization. [ABSTRACT FROM AUTHOR]

• The novel L-amino acid ester salts based ionic liquids obtained from nonsteroidal anti-inflammatory drugs were synthesized. • The influence of changing structure of cation on skin permeation, accumulation, and antioxidant activity was evaluated. • The obtained API-ILs showed higher bioavailability compared to the parent drugs. • L-amino acid ester as a cation positively impacts the transport of API through biological membranes. Herein, we investigated the effect of pairing the L-amino acid alkyl (propyl, isopropyl, or butyl) ester on the formation of API-ILs. The novel salts of NSAIDs (non-steroidal anti-inflammatory drugs) obtained from biodegradable cations were synthesised and characterised by nuclear magnetic resonance (NMR), Fourier transform infrared spectroscopy (FT-IR), and X-ray powder diffraction (XRD) methods. The influence of structure counterions for APIs from the NSAIDs group on their physicochemical properties was studied in detail. The comprehensive effects of cation structure on skin permeation, accumulation, and antioxidant activity of API-ILs were also evaluated. These results demonstrated that L-amino acid alkyl esters can be successfully used to synthesise API-ILs further used in topical formulations with anti-ageing, anti-inflammatory, or photoprotective effects. [ABSTRACT FROM AUTHOR]

Abstract The epidermal lamellar bodies (LBs) are specialized organelles that contain pro-barrier lipids imparting a fully lamellar internal structure, but also other cargoes such as enzymes (lipid metabolizing and proteolytic), enzyme inhibitors, and antimicrobial peptides. Thus, the LB secretory system, by virtue of delivering these cargoes to the stratum corneum (SC) interstices, is essential for forming the various skin barriers located in the SC. Ultrastructural studies have suggested that the morphologic features of LBs reflect the functional status of the SC. Several ichthyotic skin diseases as well as experimental animal models with defective epidermal lipogenesis show only partial lamellar contents or even empty appearing LB, reflecting an abnormal cargo composition. We suggest that LB polymorphism reflects a wide array of barrier adaptations to environmental challenges, rather than just a defective barrier function, based on observations on a) LB morphology in inherited skin disorders of lipid metabolism (Refsum disease, Chanarin-Dorfman syndrome) characterized by deficiency of lamellar lipids and accumulation of toxic metabolites; b) Psoriasis (with a high expression of Psoriasin antimicrobial peptide within lesions) and c) the Pitohui , a toxic bird where diet-derived toxin is eliminated via the LB secretory system that creates a chemical defense system. Morphological features of LBs from these models suggest a hitherto unrecognized function for the LBs in elimination of toxic substances from the body. We also provide preliminary evidence that indicate yet another function for the LBs- as a type of recycling endosomes allowing for uptake of certain topically applied materials by the epidermis. [ABSTRACT FROM AUTHOR]

Long-periodicity phase (LPP) lamellar structures in intercellular lipid matrixes of the stratum corneum (SC) are considered important for maintenance of skin permeability barriers. Acylceramides are essential components of LPP structures, and their absence influences skin barriers under physiological and pathological conditions, such as atopic dermatitis and dry skin. Although topical applications of acylceramide have been shown to facilitate maintenance of the skin barrier, it is unknown whether topically applied acylceramides are incorporated into intercellular lipids to form LPP structures. Thus, we assessed the effects of topical treatments with monomodal acylceramides on the formation of LPP structures in a surfactant-insulted reconstructed human epidermis model using small-angle X-ray scattering (SAXS) and transmission electron microscopy (TEM) analyses. In SAXS experiments, LPP structures give rise to a diffraction peak which indicates the presence of a structure with a 13 nm real space repeat distance. LPP patterns of intercellular lipid matrixes in the SC were disrupted’ by surfactant treatments and were recovered by topical acylceramide treatments. TEM images also showed specific repeating patterns of LPP structures, indicating that topical acylceramide treatments facilitate recovery of LPP structures in the SC. The present data show that the application of acylceramides might temporarily modify the lipid structure to resemble that of normal skin although the underlying cause of dry or diseased skin is not fully clarified. [ABSTRACT FROM AUTHOR]

Background Particulate matter (PM) is an integral part of air pollution, which is a mixture of particles suspended in the air. Recently, it has been reported that PM is associated with increased risks of skin diseases, especially atopic dermatitis in children. However, it is unclear if PM directly goes into the skin and what mechanisms are involved in response to PM. Objective To see whether PM could penetrate into the barrier-disrupted skin, produce reactive oxygen species (ROS), and elicit an inflammatory response. Methods We collected PMs during a winter in Seoul and used cultured keratinocytes for in vitro study and tape-stripped BALB/c mice for in vivo study. Results Keratinocyte cytotoxicity increased in a dose-dependent manner by PM treatment. IL-8 and MMP-1 mRNA expression and protein levels were significantly increased compared to control by qPCR and ELISA, respectively. Cellular ROS production was increased by PM treatment, and antioxidant N-acetyl cysteine pretreatment prevented induction of inflammatory cytokines IL-8 and MMP-1. In PM-treated keratinocytes, electron-dense subcellular particles were observed by transmission electron microscopy. PM was observed inside hair follicles in both intact and barrier-disrupted skin in vivo . Additionally, intercellular penetration of PM was seen in the barrier-disrupted skin. Repeated PM application induced epidermal thickening and dermal inflammation with neutrophil infiltration. Finally, N-acetyl cysteine could ameliorate skin inflammation induced by PM application. Conclusion PM penetrates into the barrier-disrupted skin, causing inflammation, demonstrating detrimental effects in the skin. [ABSTRACT FROM AUTHOR]

Aim of the study The aim of this study was to explore possible interrelationships and cutaneous response patterns at the heel and sacral skin due to prolonged loading. Materials and methods Skin stiffness, elasticity, roughness and transepidermal water loss, stratum corneum hydration, erythema, and temperature of n = 20 aged females (mean age 69.9 years) were measured before and after 90 and 150 min loading in supine position. Delta values were calculated and correlated using Spearman's rho. Strengths and directions of associations and similar patterns were subsequently identified for the heel and sacrum areas. Results At the sacral area decreased stiffness (Uf) was associated with increased TEWL and there was a positive relationship between mean roughness (Rz) and erythema. At the heel there was a positive association between TEWL and decreasing stiffness (Uf). Conclusions Our results indicate a dynamic interaction between skin changes during loading and different physiological response patterns for sacral and heel skin. There seems to be close association between transepidermal water loss and stiffness changes during loading. [ABSTRACT FROM AUTHOR]

Background Although atopic dermatitis (AD) often starts in early childhood, detailed tissue profiling of early-onset AD in children is lacking, hindering therapeutic development for this patient population with a particularly high unmet need for better treatments. Objective We sought to globally profile the skin of infants with AD compared with that of adults with AD and healthy control subjects. Methods We performed microarray, RT-PCR, and fluorescence microscopy studies in infants and young children (<5 years old) with early-onset AD (<6 months disease duration) compared with age-matched control subjects and adults with longstanding AD. Results Transcriptomic analyses revealed profound differences between pediatric patients with early-onset versus adult patients with longstanding AD in not only lesional but also nonlesional tissues. Although both patient populations harbored T H 2-centered inflammation, pediatric AD also showed significant T H 17/T H 22 skewing but lacked the T H 1 upregulation that characterizes adult AD. Pediatric AD exhibited relatively normal expression of epidermal differentiation and cornification products, which is downregulated in adults with AD. Defects in the lipid barrier (eg, ELOVL fatty acid elongase 3 [ELOVL3] and diacylglycerol o-acyltransferase 2 [DGAT2]) and tight junction regulation (eg, claudins 8 and 23) were evident in both groups. However, some lipid-associated mediators (eg, fatty acyl-CoA reductase 2 and fatty acid 2-hydroxylase) showed preferential downregulation in pediatric AD, and lipid barrier genes (FA2H and DGAT2) showed inverse correlations with transepidermal water loss, a functional measure of the epidermal barrier. Conclusions Skin samples from children and adult patients with AD share lipid metabolism and tight junction alterations, but epidermal differentiation complex defects are only present in adult AD, potentially resulting from chronic immune aberration that is not yet present in early-onset disease. [ABSTRACT FROM AUTHOR]