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Spinal cord injury (SCI) disrupts the blood–spinal cord barrier (BSCB) exacerbating damage by allowing harmful substances and immune cells to infiltrate spinal neural tissues from the vasculature. This leads to inflammation, oxidative stress, and impaired axonal regeneration. The BSCB, essential for maintaining spinal cord homeostasis, is structurally similar to the blood–brain barrier. Its restoration is a key therapeutic target for improving outcomes in SCI. Mesenchymal stromal/stem cells (MSCs) and their secreted extracellular vesicles (MSC-EVs) have gained attention for their regenerative, immunomodulatory, and anti-inflammatory properties in promoting BSCB repair. MSCs enhance BSCB integrity by improving endothelial–pericyte association, restoring tight junction proteins, and reducing inflammation. MSC-EVs, which deliver bioactive molecules, replicate many of MSCs' therapeutic effects, and offer a promising cell-free alternative. Preclinical studies have shown that both MSCs and MSC-EVs can reduce BSCB permeability, promote vascular stability, and support functional recovery. While MSC therapy is advancing in clinical trials, MSC-EV therapies require further optimization in terms of production, dosing, and delivery protocols. Despite these challenges, both therapeutic approaches represent significant potential for treating SCI by targeting BSCB repair and improving patient outcomes. [ABSTRACT FROM AUTHOR]

Chronic hyperglycemia results in morphological and functional alterations of the kidney and microvascular damage, leading to diabetic nephropathy (DN). Since DN progresses to irreversible renal damage, it is important to elucidate a pharmacological strategy aimed for treating DN in the early stage. Here, we used the type 2 diabetic rat model to induce DN and show a nephroprotective effect following the stimulation of PPAR-α, which stabilized renal tight junction components claudin-2, claudin-5, and claudin-16. At 14 weeks old, streptozotocin-induced DN, evidenced by elevated creatinine clearance, proteinuria, and electrolyte excretion, was followed by an elevation in oxidative stress and increasing MMP activities affecting the integrity of claudin-2 and claudin-5. Treatment with a PPAR-α agonists decreased glucose levels in diabetic rats. In addition, we found that the expressions of CLDN-5 in glomeruli, CLDN-2 in proximal tubules, and CLDN-16 in the thick ascending limb of the loop of Henle were increased after treatment. As a result, renal function improved, while the oxidative stress and enzymatic activity of MMP-2 and MMP-9 decreased. In conclusion, PPAR-α stimulation prevented the decrease in claudins through a mechanism involving a correction of hyperglycemia, decreasing it in kidney oxidative stress and MMP-2 and MMP-9 activities, showing a promising nephroprotective action in the early stage of DN. [ABSTRACT FROM AUTHOR]

5-Fluorouracil (5-Fu) is a chemotherapeutic agent widely used to treat various cancers, which causes intestinal mucositis as a common side effect. Ginsenoside Rc, an active compound with anti-inflammatory, antioxidant, immunomodulatory, and antitumor properties, has protective effects against chemotherapy-induced mucositis caused by 5-Fu. This study aims to evaluate the protective effects of Rc on 5-Fu-induced chemotherapy-related mucositis and to elucidate its underlying mechanisms. In vivo experiments were conducted to measure intestinal permeability and assess the effects of Rc on body weight loss, diarrhea, and intestinal pathology induced by 5-Fu. Network pharmacology was also employed to explore potential mechanisms. In vitro, IEC-6 cell models were used to validate the cytoprotective effects of Rc, including assessments of cell viability, apoptosis, lactate dehydrogenase (LDH) release, and changes in inflammatory cytokine levels. The results indicate that Rc significantly ameliorated body weight reduction, diarrhea, and intestinal damage in mice treated by 5-Fu. Rc significantly mitigated 5-Fu-induced cellular damage by reducing levels of inflammatory cytokines such as IL-1β, IL-6, and TNF-α and decreasing apoptosis and cell permeability. Western blot analysis revealed that Rc upregulated the expression of Bcl-2 and tight junction proteins and downregulated the expression of Bax. Furthermore, Rc exerts anti-inflammatory and anti-apoptotic effects through PI3K-AKT and NF-κB signaling pathways. In conclusion, ginsenoside Rc demonstrated significant protective effects against 5-Fu-induced intestinal mucositis via the PI3K-AKT/NF-κB signaling pathway, suggesting its potential as a therapeutic agent for chemotherapy-related mucositis. [ABSTRACT FROM AUTHOR]

High-fat diet (HFD)-induced obesity is a global health concern associated with gastrointestinal disorders. While mammalian models have elucidated the effects of a HFD on intestinal structure and function, its impact on zebrafish, a crucial model for studying diet-induced obesity and gastrointestinal dysfunction, remains inadequately characterized. This study investigated the influence of a HFD on zebrafish intestinal morphology, tight junction (TJ) protein expression, and inflammatory markers. Zebrafish fed a control diet or HFD with 40% or 60% fat exhibited significant alterations in intestinal morphology, with increased villi number but reduced villi width and length, suggesting compensatory responses to dietary stress. TJ protein expression (Claudin 2, Claudin 3, and Claudin 10) showed complex changes, particularly in the HFD60 juvenile group, indicating a multifaceted response in barrier integrity. Pro-inflammatory cytokine IL-6 and TNF-α levels were lower in both the juvenile and adult HFD60 groups than in the HFD40 and control groups, while elevated anti-inflammatory IL-10 levels in HFD60 adult zebrafish suggested activation of compensatory mechanisms. These findings highlight zebrafish as a valuable model for studying the effects of HFD on intestinal health and provide insights into the relationship between dietary fat, gut dysfunction, and inflammation. [ABSTRACT FROM AUTHOR]

The document discusses the role of extracellular vesicles (EVs) in health and diseases, highlighting their potential as biomarkers, drug carriers, and therapeutic agents. EVs are classified into exosomes, microvesicles, and apoptotic bodies, each with distinct characteristics and functions. Research articles in the special issue explore various aspects of EVs, including their proteomic cargo, therapeutic applications, and diagnostic potential in diseases like cancer, stroke, and neurodegenerative disorders. Despite challenges in standardization and isolation protocols, EVs show promise in personalized medicine and innovative diagnostic approaches. [Extracted from the article]

Dry eye is characterized by persistent instability and decreased tear production, which are accompanied by epithelial lesions and inflammation on the surface of the eye. In our previous paper, we reported that supplementation with Limosilactobacillus fermentum HY7302 (HY7302) could inhibit corneal damage in a benzalkonium chloride (BAC)-induced mouse model of dry eye, through its effects in gut microbiome regulation. The aim of this study was to determine what functional extracellular substances can alter the inflammatory response of conjunctival cells. We isolated exosomes from HY7302 probiotic culture supernatant, analyzed their morphological characteristics, and found that their average size was 143.8 ± 1.1 nm, which was smaller than the exosomes from the L. fermentum KCTC 3112 strain. In addition, HY7302-derived exosomes significantly reduced the levels of genes encoding pro-inflammatory cytokines, including interleukin (IL)-20, IL-8, IL-6, and IL-1B, in BAC-treated human conjunctival cells. Moreover, HY7302-derived exosomes significantly increased the levels of genes encoding tight junction proteins, including TJP1, TJP2, and occludin-1, in Caco-2 cells. Lastly, the HY7302 exosomes reduced mRNA expression levels of IL1B, IL20, IL6, IL8, and NFAT5 in a transwell coculture system. Our findings indicate that HY7302 exosomes have potential for use in the treatment of ocular inflammation-related dry eye disease, through gut–eye axis communication via exosomes. [ABSTRACT FROM AUTHOR]

Acute respiratory distress syndrome (ARDS) is a severe lung condition without targeted therapy that is characterized by the disruption of epithelial and endothelial barriers. The role of the tight junction protein occludin in the pathogenesis of this disease is unknown, although it has previously been deemed redundant in some tissues. The aim of the present study is to determine whether occludin is required for lung function by controlling alveolar barrier integrity in mouse models. Immunofluorescence staining of lungs from ARDS patients revealed a significant decrease in occludin expression compared to controls. Gene delivery of shRNA against occludin in the mouse lung reduced occludin levels and induced lung injury, as assessed by wet-to-dry-ratio, histology, and cellularity and protein content of bronchial alveolar lavage fluid. Conversely, gene delivery of an occludin-expressing plasmid increased occludin expression and dampened endotoxin-induced lung injury. In primary rat alveolar epithelial cells, occludin levels were positively correlated with barrier integrity, as well as membrane localization of claudin-18, another tight junction protein. Collectively, our data demonstrate that occludin plays a significant role in alveolar barrier function and that targeting occludin may provide a new therapeutic approach for ARDS. [ABSTRACT FROM AUTHOR]

It is currently impossible to perform an evidence-based risk assessment for medication use during breastfeeding. The ConcePTION project aims to provide information about the use of medicines during lactation. The study aimed to develop and characterize an in vitro model of the blood–milk barrier to determine the extent of the milk transfer of xenobiotics, relying on either on human mammary epithelial cells (hMECs) or immortalized cell lines derived from breast tissue. The hMECs were cultured and characterized for epithelial markers; further, the ability to form an epithelial barrier was investigated. Drug transporter functionality in the cultured hMECs was analyzed with specific probe substrates. The hMECs showed an epithelial morphology and the expression of epithelial markers and tight junctions. They formed a reproducible tight barrier with a transepithelial electrical resistance greater than 400 Ωcm2, unlike immortalized cell lines. Different levels of mRNA expression were detected for 81 genes of membrane transporters. Functional assays showed no evidence for the transporter-mediated secretion of medicines across the hMECs. Nevertheless, the hMEC-based in vitro model covered a 50-fold range of permeability values, differentiating between passive transcellular and paracellular-mediated transport. The cultured hMECs proved to be a promising in vitro model for biorelevance; the wide characterization of hMECs makes them useful for studying medicine partitioning in milk. [ABSTRACT FROM AUTHOR]

Rutin is a flavonoid compound with potential for treating Alzheimer's disease, preventing brain damage, mitigating cerebral ischemia–reperfusion injury, and exhibiting anti-glioblastoma activity. However, its efficacy is limited by its low solubility, poor bioavailability, and limited permeability across the blood–brain barrier (BBB). To enhance the bioavailability and brain-targeting ability of Rutin, transferrin-modified Rutin liposome (Tf-Rutin-Lip) was developed using liposomes as a delivery system. Rutin liposomes were prepared using the thin-film dispersion method, and the preparation conditions were optimized using the response surface methodology. Then, transferrin (Tf) was incorporated into the liposomes through covalent modification, yielding Tf-Rutin liposomes. The toxicity of these liposomes on bEnd.3 cells, as well as their impact on the tight junctions of these cells, was rigorously evaluated. Additionally, in vitro and in vivo experiments were conducted to validate the brain-targeting efficacy of the Tf-Rutin liposomes. A susceptible detection method was developed to characterize the pharmacokinetics of Tf-Rutin-Lip further. The optimized conditions for the preparation of Tf-Rutin-Lip were determined as follows: a lipid-to-cholesterol ratio of 4.63:1, a drug-to-lipid ratio of 1:45.84, a preparation temperature of 42.7 °C, a hydration volume of 20 mL, a sonication time of 10 min, a surfactant concentration of 80 mg/mL, a DSPE-MPEG-2000 concentration of 5%, and a DSPE-PEG2000-COOH to DSPE-MPEG-2000 molar ratio of 10%. The liposomes did not affect the cell activity of bEnd.3 cells at 24 h and did not disrupt the tight junction of the blood–brain barrier. Tf-modified liposomes were taken up by bEnd.3 cells, which, in turn, passed through the BBB, thus improving liposomal brain targeting. Furthermore, the results of pharmacokinetic experiments showed that the Cmax, AUC0-∞, AUC0-t, MRT0-∞, and t1/2 of Tf-Rutin-Lip increased 1.99-fold, 2.77-fold, 2.58-fold, 1.26-fold, and 1.19-fold compared to those of free Rutin solution, respectively. These findings suggest that Tf-Rutin-Lip is brain-targeted and may enhance the efficacy of Rutin in the treatment of brain disorders. [ABSTRACT FROM AUTHOR]

Obstructive sleep apnea syndrome (OSAS) affects a large part of the aging population. It is characterized by chronic intermittent hypoxia and associated with neurocognitive dysfunction. One hypothesis is that the blood–brain barrier (BBB) functions could be altered by exosomes. Exosomes are nanovesicles found in biological fluids. Through the study of exosomes and their content in tau and amyloid beta (Aβ), the aim of this study was to show how exosomes could be used as biomarkers of OSAS and of their cognitive disorders. Two groups of 15 volunteers from the PROOF cohort were selected: severe apnea (AHI > 30) and control (AHI < 5). After exosome isolation from blood serum, we characterized and quantified them (CD81, CD9, CD63) by western blot and ELISAs and put them 5 h in contact with an in vitro BBB model. The apparent permeability of the BBB was measured using sodium-fluorescein and TEER. Cell ELISAs were performed on tight junctions (ZO-1, claudin-5, occludin). The amount of tau and Aβ proteins found in the exosomes was quantified using ELISAs. Compared to controls, OSAS patients had a greater quantity of exosomes, tau, and Aβ proteins in their blood sera, which induced an increase in BBB permeability in the model and was reflected by a loss of tight junction' expression. Elderly patients suffering severe OSAS released more exosomes in serum from the brain compartment than controls. Such exosomes increased BBB permeability. The impact of such alterations on the risk of developing cognitive dysfunction and/or neurodegenerative diseases is questioned. [ABSTRACT FROM AUTHOR]

Cadmium is a contributing factor to cardiovascular diseases and highly toxic to vascular endothelial cells. It has a distinct mode of injury, causing the de-endothelialization of regions in the monolayer structure of endothelial cells in a concentration-dependent manner. However, the specific molecules involved in the cadmium toxicity of endothelial cells remain unclear. The purpose of this study was to identify the specific molecular mechanisms through which cadmium affects endothelial detachment. Cadmium inhibited the expression of claudin-5 and zonula occludens (ZO)-1, which are components of tight junctions (strongest contributors to intercellular adhesion), in a concentration- and time-dependent manner. Compared to arsenite, zinc, and manganese, only cadmium suppressed the expression of both claudin-5 and ZO-1 molecules. Moreover, the knockdown of claudin-5 and ZO-1 exacerbated cadmium-induced endothelial cell injury and expansion of the detachment area, whereas their overexpression reversed these effects. CRE-binding protein inhibition reduced cadmium toxicity, suggesting that CRE-binding protein activation is involved in the cadmium-induced inhibition of claudin-5 and ZO-1 expression and endothelial detachment. These findings provide new insights into the toxicological mechanisms of cadmium-induced endothelial injury and risk of cardiovascular disease. [ABSTRACT FROM AUTHOR]

Regular exercise as part of one's lifestyle is well-recognized for its beneficial effect on several diseases such as cardiovascular disease and obesity; however, many questions remain unanswered regarding the effects of exercise on the gut environment. This study aimed to investigate the impact of long-term endurance exercise on modulating inflammation and endoplasmic reticulum (ER) stress. Fifteen-week-old male Sprague-Dawley (SD) rats were subjected to six months of endurance treadmill training, while age-matched controls remained sedentary. Results showed that IL-6 mRNA levels in colon tissues were significantly higher in the exercise group compared to the sedentary group. Exercise activated a significant ER stress-induced survival pathway by increasing BiP and phosphorylation of eIF2α (p-eIF2α) expressions in the liver and colon, while decreasing CHOP in the liver. Gene expressions of MUC2, Occludin, and Claudin-2 were increased in the colon of the exercise group, indicating enhanced intestinal integrity. Furthermore, the data showed a positive correlation between microbiota α-diversity and BiP (r = 0.464~0.677, p < 0.05). Populations of Desulfovibrio C21 c20 were significantly greater in the exercise group than the sedentary group. Additionally, predicted functions of the gut microbial community in terms of enzymes and pathways supported the enhancement of fatty-acid-related processes by exercise. These findings suggest that prolonged endurance exercise can affect the colon environment, which is likely related to changes in inflammation, ER stress, mucin layers and tight junctions, associated with modifications in the gut microbiome. [ABSTRACT FROM AUTHOR]

The frequency, duration, and size of wildfires have been increasing, and the inhalation of wildfire smoke particles poses a significant risk to human health. Epidemiological studies have shown that wildfire smoke exposure is positively associated with cognitive and neurological dysfunctions. However, there is a significant gap in knowledge on how wildfire smoke exposure can affect the blood–brain barrier and cause molecular and cellular changes in the brain. Our study aims to determine the acute effect of smoldering eucalyptus wood smoke extract (WSE) on brain endothelial cells for potential neurotoxicity in vitro. Primary human brain microvascular endothelial cells (HBMEC) and immortalized human brain endothelial cell line (hCMEC/D3) were treated with different doses of WSE for 24 h. WSE treatment resulted in a dose-dependent increase in IL-8 in both HBMEC and hCMEC/D3. RNA-seq analyses showed a dose-dependent upregulation of genes involved in aryl hydrocarbon receptor (AhR) and nuclear factor erythroid 2-related factor 2 (NRF2) pathways and a decrease in tight junction markers in both HBMEC and hCMEC/D3. When comparing untreated controls, RNA-seq analyses showed that HBMEC have a higher expression of tight junction markers compared to hCMEC/D3. In summary, our study found that 24 h WSE treatment increases IL-8 production dose-dependently and decreases tight junction markers in both HBMEC and hCMEC/D3 that may be mediated through the AhR and NRF2 pathways, and HBMEC could be a better in vitro model for studying the effect of wood smoke extract or particles on brain endothelial cells. [ABSTRACT FROM AUTHOR]

Chlorogenic acid (CGA) is a natural polyphenol with potent antioxidant and anti-inflammatory activities. However, the exact role of it in regulating intestinal health under oxidative stress is not fully understood. This study aims to investigate the effects of dietary CGA supplementation on the intestinal health of weaned piglets under oxidative stress, and to explore its regulatory mechanism. Twenty-four piglets were randomly divided into two groups and fed either a basal diet (CON) or a basal diet supplemented with 200 mg/kg CGA (CGA). CGA reduced the diarrhea rate, increased the villus height in the jejunum, and decreased the crypt depth in the duodenum, jejunum, and ileum of the weaned piglets (p < 0.05). Moreover, CGA increased the protein abundance of Claudin-1, Occludin, and zonula occludens (ZO)-1 in the jejunum and ileum (p < 0.05). In addition, CGA increased the mRNA expression of pBD2 in the jejunum, and pBD1 and pBD2 in the ileum (p < 0.05). The results of 16S rRNA sequencing showed that CGA altered the ileal microbiota composition and increased the relative abundance of Lactobacillus reuteri and Lactobacillus pontis (p < 0.05). Consistently, the findings suggested that the enhancement of the intestinal barrier in piglets was associated with increased concentrations of T-AOC, IL-22, and sIgA in the serum and T-AOC, T-SOD, and sIgA in the jejunum, as well as T-AOC and CAT in the ileum caused by CGA (p < 0.05). Meanwhile, CGA decreased the concentrations of MDA, IL-1β, IL-6, and TNF-α in the serum and jejunum and IL-1β and IL-6 in the ileum (p < 0.05). Importantly, this study found that CGA alleviated intestinal inflammation and oxidative stress in the piglets by inhibiting the TLR4/NF-κB signaling pathway and activating the Nrf2 signaling pathway. These findings showed that CGA enhances the intestinal health of weaned piglets by inhibiting the TLR4/NF-κB pathway and activating the Nrf2 pathway. [ABSTRACT FROM AUTHOR]

Acinetobacter baumannii is an opportunistic Gram-negative pathogen with exquisite survival capabilities under various environmental conditions and displays widespread resistance to common antibiotics. A. baumannii is a leading cause of nosocomial infections that result in high morbidity and mortality rates. Accordingly, when multidrug resistance rates surpass threshold levels, the percentage of A. baumannii clinical isolates surges. Research into A. baumannii has increased in the past decade, and multiple mechanisms of pathogenesis have been identified, including mechanisms underlying biofilm development, quorum sensing, exotoxin production, secretion system utilization, and more. To date, the two gold-standard strains used to investigate different aspects of A. baumannii pathogenesis include ATCC 17978 and ATCC 19606. Here, we report a comparative characterization study of three additional A. baumannii clinical isolates obtained from different infection types and derived from different anatomical regions of infected patients. The comparison of three clinical isolates in addition to the ATCC strains revealed that the hypervirulent bacteremia clinical isolate, known as HUMC1, employs a completely different mechanism of pathogenesis when compared to all its counterparts. In stark contrast to the other genetic variants, the hypervirulent HUMC1 isolate does not form biofilms, is antibiotic-susceptible, and has the capacity to reach higher levels of quorum compared to the other clinically relevant strains. Our data also reveal that HUMC1 does not shed endotoxin into the extracellular milieu, rather secretes the evolutionarily conserved, host-mimicking, Zonula occludens toxin (Zot). Taken together, our hypothesis that HUMC1 cells have the ability to reach higher levels of quorum and lack biofilm production and endotoxin shedding, accompanied by the substantial elaboration of Zot, suggests a novel mechanism of pathogenesis that appears to afford the hypervirulent pathogen with stealth-like capabilities when disseminating through the circulatory system in a state of bacteremia. [ABSTRACT FROM AUTHOR]

This study investigates the underlying mechanism through which dietary supplementation of pyrroloquinoline quinone disodium (PQQ) alleviates intestinal inflammation and cell apoptosis in piglets challenged with lipopolysaccharide (LPS). Seventy-two barrows were divided into three groups: control (CTRL), LPS challenged (LPS), and LPS challenged with PQQ supplementation (PQQ + LPS). On d 7, 11, and 14, piglets received intraperitoneal injections of LPS or 0.9% of NaCl (80 μg/kg). After a 4 h interval following the final LPS injection on d 14, blood samples were obtained, and all piglets were euthanized for harvesting jejunal samples. The results showed that dietary supplementation of PQQ improved the damage of intestinal morphology, increased the down-regulated tight junction proteins, and reduced the increase of serum diamine oxidase activity, the intestinal fatty acid binding protein, and TNF-α levels in piglets challenged with LPS (p < 0.05). The proteomics analysis revealed a total of 141 differentially expressed proteins (DEPs), consisting of 64 up-regulated DEPs and 77 down-regulated DEPs in the PQQ + LPS group compared to the LPS group. The KEGG pathway analysis indicated enrichment of the tight junction pathway and the apoptosis pathway (p < 0.05). Compared to the LPS group, the piglets in the PQQ + LPS group had increased levels of Bcl-2 protein, reduced positive apoptosis signals, and a decrease in the abundance of MKK 3/6 and p-p38 proteins (p < 0.05). In conclusion, dietary supplementation of PQQ could alleviate jejunal inflammatory damage and cell apoptosis in piglets challenged with LPS through the MKK3/6-p38 signaling pathway. [ABSTRACT FROM AUTHOR]

Steroid-resistant asthma (SRA), resisting glucocorticoids such as dexamethasone (DEX), is a bottleneck in the treatment of asthma. It is characterized by a predominantly neutrophilic inflammatory subtype and is prone to developing into severe refractory asthma and fatal asthma. Currently, there is a lack of universally effective treatments for SRA. Moreover, since cold stimulation does increase the risk of asthma development and exacerbate asthma symptoms, the treatment of cold-stimulated SRA (CSRA) will face greater challenges. To find effective new methods to ameliorate CSRA, this study established a CSRA mouse model of allergic airway inflammation mimicking human asthma for the first time and evaluated the alleviating effects of 80% ethanol extract of mountain-cultivated ginseng (MCG) based on multi-omics analysis. The results indicate that cold stimulation indeed exacerbated the SRA-related symptoms in mice; the DEX individual treatment did not show a satisfactory effect; while the combination treatment of DEX and MCG could dose-dependently significantly enhance the lung function; reduce neutrophil aggregation; decrease the levels of LPS, IFN-γ, IL-1β, CXCL8, and IL-17; increase the level of IL-10; alleviate the inflammatory infiltration; and decrease the mucus secretion and the expression of MUC5AC. Moreover, the combination of DEX and high-dose (200 mg/kg) MCG could significantly increase the levels of tight junction proteins (TJs), regulate the disordered intestinal flora, increase the content of short-chain fatty acids (SCFAs), and regulate the abnormal gene profile and metabolic profile. Multi-omics integrated analysis showed that 7 gut microbes, 34 genes, 6 metabolites, and the involved 15 metabolic/signaling pathways were closely related to the pharmacological effects of combination therapy. In conclusion, integrated multi-omics profiling highlighted the benefits of MCG for CSRA mice by modulating the interactions of microbiota, genes, and metabolites. MCG shows great potential as a functional food in the adjuvant treatment of CSRA. [ABSTRACT FROM AUTHOR]

Chronic low-grade inflammation (CLGI) is associated with obesity and is one of its pathogenetic mechanisms. Lipopolysaccharide (LPS), a component of Gram-negative bacterial cell walls, is the principal cause of CLGI. Studies have found that capsaicin significantly reduces the relative abundance of LPS-producing bacteria. In the present study, TRPV1-knockout (TRPV1−/−) C57BL/6J mice and the intestinal epithelial cell line Caco-2 (TRPV1−/−) were used as models to determine the effect of capsaicin on CLGI and elucidate the mechanism by which it mediates weight loss in vivo and in vitro. We found that the intragastric administration of capsaicin significantly blunted increases in body weight, food intake, blood lipid, and blood glucose in TRPV1−/− mice fed a high-fat diet, suggesting an anti-obesity effect of capsaicin. Capsaicin reduced LPS levels in the intestine by reducing the relative abundance of Proteobacteria such as Helicobacter, Desulfovibrio, and Sutterella. Toll-like receptor 4 (TLR4) levels decreased following decreases in LPS levels. Then, the local inflammation of the intestine was reduced by reducing the expression of tumor necrosis factor (TNF)-α and interleukin (IL)-6 mediated by TLR4. Attenuating local intestinal inflammation led to the increased expression of tight junction proteins zonula occludens 1 (ZO-1) and occludin and the restoration of the intestinal barrier function. Capsaicin increased the expression of ZO-1 and occludin at the transcriptional and translational levels, thereby increasing trans-endothelial electrical resistance and restoring intestinal barrier function. The restoration of intestinal barrier function decreases intestinal permeability, which reduces the concentration of LPS entering the circulation, and reduced endotoxemia leads to decreased serum concentrations of inflammatory cytokines such as TNF-α and IL-6, thereby attenuating CLGI. This study sheds light on the anti-obesity effect of capsaicin and its mechanism by reducing CLGI, increasing our understanding of the anti-obesity effects of capsaicin. It has been confirmed that capsaicin can stimulate the expression of intestinal transmembrane protein ZO-1 and cytoplasmic protein occludin, increase the trans-epithelial electrical resistance value, and repair intestinal barrier function. [ABSTRACT FROM AUTHOR]

Crohn's disease (CD) is a type of inflammatory bowel disease (IBD) affecting the gastrointestinal tract that can also cause extra-intestinal complications. Following exposure to the mRNA vaccine BNT162b2 (Pfizer-BioNTech) encoding the SARS-CoV-2 Spike (S) protein, some patients experienced a lack of response to the biological drug Adalimumab and a recrudescence of the disease. In CD patients in progression, resistant to considered biological therapy, an abnormal increase in intestinal permeability was observed, more often with a modulated expression of different proteins such as Aquaporin 8 (AQP8) and in tight junctions (e.g., ZO-1, Claudin1, Claudin2, Occludin), especially during disease flares. The aim of this study is to investigate how the SARS-CoV-2 vaccine could interfere with IBD therapy and contribute to disease exacerbation. We investigated the role of the SARS-CoV-2 Spike protein, transported by extracellular vesicles (EVs), and the impact of various EVs components, namely, exosomes (EXOs) and microvesicles (MVs), in modulating the expression of molecules involved in the exacerbation of CD, which remains unknown. [ABSTRACT FROM AUTHOR]

Allergic rhinitis (AR) is a series of allergic reactions to allergens in the nasal mucosa and is one of the most common allergic diseases that affect both children and adults. Shi-Bi-Lin (SBL) is the modified formula of Cang Er Zi San (CEZS), a traditional Chinese herbal formula used for treating AR. Our study aims to elucidate the anti-inflammatory effects and mechanisms of SBL in house dust mite-induced AR by regulating gut microflora metabolism. In vivo studies showed that nasal allergies and the infiltration of inflammatory cells in the nasal epithelium were significantly suppressed by SBL. Moreover, SBL restored the impaired nasal epithelial barrier function with an increased tight junction protein expression and reduced the endothelial nitric oxide synthase (eNOS). Interestingly, SBL significantly reconstituted the abundance and composition of gut microbiota in AR mice; it increased the relative abundance of potentially beneficial genera and decreased the relative abundance of harmful genera. SBL also restored immune-related metabolisms, which were significantly increased and correlated with suppressing inflammatory cytokines. Furthermore, a network analysis and molecular docking indicated IL-6 was a possible target drug candidate for the SBL treatment. SBL dramatically reduced the IL-6 level in the nasal lavage fluid (NALF), suppressing the IL-6 downstream Erk1/2 and AKT/PI3K signaling pathways. In conclusion, our study integrates 16S rRNA sequencing, microflora metabolism, and network pharmacology to explain the immune mechanism of SBL in alleviating HDM-induced allergic rhinitis. [ABSTRACT FROM AUTHOR]

Recent studies point to intestinal permeability as an important factor in the establishment and development of rheumatoid arthritis (RA). Tight junctions (TJs) play a major role in intestinal homeostasis. The alteration of this homeostasis is related to RA. Furthermore, RA patients present dysbiosis and a lower microbiota diversity compared to healthy individuals. A cross-sectional study including RA patients and sex- and age-matched healthy controls was performed. The quantification of TJ proteins was carried out by ELISA. Gut microbiota was evaluated by NGS platform Ion Torrent S. The inflammatory variables included were DAS28, CRP, inflammatory cytokines (IL-6, IL-1, TNF-α) and oxidised LDL. Claudin-1 levels showed significant differences between groups. Results evidenced a correlation between claudin-1 values and age (r: −0.293; p < 0.05), IL6 (r: −0.290; p < 0.05) and CRP (r: −0.327; p < 0.05), and between zonulin values and both age (r: 0.267; p < 0.05) and TNFα (r: 0.266; p < 0.05). Moreover, claudin-1 and CRP levels are related in RA patients (β: −0.619; p: 0.045), and in patients with high inflammatory activity, the abundance of the genus Veillonella is positively associated with claudin-1 levels (β: 39.000; p: 0.004). [ABSTRACT FROM AUTHOR]

Oral bacteria are implicated not only in oral diseases but also in gut dysbiosis and inflammatory conditions throughout the body. The periodontal pathogen Aggregatibacter actinomycetemcomitans (Aa) often occurs in complex oral biofilms with Streptococcus gordonii (Sg), and this interaction might influence the pathogenic potential of this pathogen. This study aims to assess the impact of oral inoculation with Aa, Sg, and their association (Aa+Sg) on alveolar bone loss, oral microbiome, and their potential effects on intestinal health in a murine model. Sg and/or Aa were orally administered to C57Bl/6 mice, three times per week, for 4 weeks. Aa was also injected into the gingiva three times during the initial experimental week. After 30 days, alveolar bone loss, expression of genes related to inflammation and mucosal permeability in the intestine, serum LPS levels, and the composition of oral and intestinal microbiomes were determined. Alveolar bone resorption was detected in Aa, Sg, and Aa+Sg groups, although Aa bone levels did not differ from that of the SHAM-inoculated group. Il-1β expression was upregulated in the Aa group relative to the other infected groups, while Il-6 expression was downregulated in infected groups. Aa or Sg downregulated the expression of tight junction genes Cldn 1, Cldn 2, Ocdn, and Zo-1 whereas infection with Aa+Sg led to their upregulation, except for Cldn 1. Aa was detected in the oral biofilm of the Aa+Sg group but not in the gut. Infections altered oral and gut microbiomes. The oral biofilm of the Aa group showed increased abundance of Gammaproteobacteria, Enterobacterales, and Alloprevotella, while Sg administration enhanced the abundance of Alloprevotella and Rothia. The gut microbiome of infected groups showed reduced abundance of Erysipelotrichaceae. Infection with Aa or Sg disrupts both oral and gut microbiomes, impacting oral and gut homeostasis. While the combination of Aa with Sg promotes Aa survival in the oral cavity, it mitigates the adverse effects of Aa in the gut, suggesting a beneficial role of Sg associations in gut health. [ABSTRACT FROM AUTHOR]

Alginate oligosaccharides (AOSs), which are an attractive feed additive for animal production, exhibit pleiotropic bioactivities. In the present study, we investigated graded doses of AOS-mediated alterations in the physiological responses of piglets by determining the intestinal architecture, barrier function, and microbiota. A total of 144 weaned piglets were allocated into four dietary treatments in a completely random design, which included a control diet (CON) and three treated diets formulated with 250 mg/kg (AOS250), 500 mg/kg (AOS500), and 1000 mg/kg AOS (AOS1000), respectively. The trial was carried out for 28 days. Our results showed that AOS treatment reinforced the intestinal barrier function by increasing the ileal villus height, density, and fold, as well as the expression of tight junction proteins, especially at the dose of 500 mg/kg AOS. Meanwhile, supplementations with AOSs showed positive effects on enhancing antioxidant capacity and alleviating intestinal inflammation by elevating the levels of antioxidant enzymes and inhibiting excessive inflammatory cytokines. The DESeq2 analysis showed that AOS supplementation inhibited the growth of harmful bacteria Helicobacter and Escherichia_Shigella and enhanced the relative abundance of Faecalibacterium and Veillonella. Collectively, these findings suggested that AOSs have beneficial effects on growth performance, antioxidant capacity, and gut health in piglets. [ABSTRACT FROM AUTHOR]

Consumption of a high-fat diet (HFD) has been suggested as a contributing factor behind increased intestinal permeability in obesity, leading to increased plasma levels of microbial endotoxins and, thereby, increased systemic inflammation. We and others have shown that HFD can induce jejunal expression of the ketogenic rate-limiting enzyme mitochondrial 3-hydroxy-3-methylglutaryl-CoA synthase (HMGCS). HMGCS is activated via the free fatty acid binding nuclear receptor PPAR-α, and it is a key enzyme in ketone body synthesis that was earlier believed to be expressed exclusively in the liver. The function of intestinal ketogenesis is unknown but has been described in suckling rats and mice pups, possibly in order to allow large molecules, such as immunoglobulins, to pass over the intestinal barrier. Therefore, we hypothesized that ketone bodies could regulate intestinal barrier function, e.g., via regulation of tight junction proteins. The primary aim was to compare the effects of HFD that can induce intestinal ketogenesis to an equicaloric carbohydrate diet on inflammatory responses, nutrition sensing, and intestinal permeability in human jejunal mucosa. Fifteen healthy volunteers receiving a 2-week HFD diet compared to a high-carbohydrate diet were compared. Blood samples and mixed meal tests were performed at the end of each dietary period to examine inflammation markers and postprandial endotoxemia. Jejunal biopsies were assessed for protein expression using Western blotting, immunohistochemistry, and morphometric characteristics of tight junctions by electron microscopy. Functional analyses of permeability and ketogenesis were performed in Caco-2 cells, mice, and human enteroids. Ussing chambers were used to analyze permeability. CRP and ALP values were within normal ranges and postprandial endotoxemia levels were low and did not differ between the two diets. The PPARα receptor was ketone body-dependently reduced after HFD. None of the tight junction proteins studied, nor the basal electrical parameters, were different between the two diets. However, the ketone body inhibitor hymeglusin increased resistance in mucosal biopsies. In addition, the tight junction protein claudin-3 was increased by ketone inhibition in human enteroids. The ketone body β-Hydroxybutyrate (βHB) did not, however, change the mucosal transition of the large-size molecular FD4-probe or LPS in Caco-2 and mouse experiments. We found that PPARα expression was inhibited by the ketone body βHB. As PPARα regulates HMGCS expression, the ketone bodies thus exert negative feedback signaling on their own production. Furthermore, ketone bodies were involved in the regulation of permeability on intestinal mucosal cells in vitro and ex vivo. We were not, however, able to reproduce these effects on intestinal permeability in vivo in humans when comparing two weeks of high-fat with high-carbohydrate diet in healthy volunteers. Further, neither the expression of inflammation markers nor the aggregate tight junction proteins were changed. Thus, it seems that not only HFD but also other factors are needed to permit increased intestinal permeability in vivo. This indicates that the healthy gut can adapt to extremes of macro-nutrients and increased levels of intestinally produced ketone bodies, at least during a shorter dietary challenge. [ABSTRACT FROM AUTHOR]

This review addresses the role of tight junction proteins at the blood-brain barrier (BBB). Their expression is described, and their role in physiological and pathological processes at the BBB is discussed. Based on this, new approaches are depicted for paracellular drug delivery and diagnostics in the treatment of cerebral diseases. Recent data provide convincing evidence that, in addition to its impairment in the course of diseases, the BBB could be involved in the aetiology of CNS disorders. Further progress will be expected based on new insights in tight junction protein structure and in their involvement in signalling pathways. [ABSTRACT FROM AUTHOR]

In the first part of this article, the role of intestinal epithelial tight junctions (TJs), together with gastrointestinal dopaminergic and renin–angiotensin systems, are narratively reviewed to provide sufficient background. In the second part, the current experimental data on the interplay between gastrointestinal (GI) dopaminergic and renin–angiotensin systems in the regulation of intestinal epithelial permeability are reviewed in a systematic manner using the PRISMA methodology. Experimental data confirmed the copresence of DOPA decarboxylase (DDC) and angiotensin converting enzyme 2 (ACE2) in human and rodent enterocytes. The intestinal barrier structure and integrity can be altered by angiotensin (1-7) and dopamine (DA). Both renin–angiotensin and dopaminergic systems influence intestinal Na+/K+-ATPase activity, thus maintaining electrolyte and nutritional homeostasis. The colocalization of B0AT1 and ACE2 indicates the direct role of the renin–angiotensin system in amino acid absorption. Yet, more studies are needed to thoroughly define the structural and functional interaction between TJ-associated proteins and GI renin–angiotensin and dopaminergic systems. [ABSTRACT FROM AUTHOR]

Sigma non-opioid intracellular receptor 1 (Sigma-1R) is an intracellular chaperone protein residing on the endoplasmic reticulum at the mitochondrial-associated membrane (MAM) region. Sigma-1R is abundant in the brain and is involved in several physiological processes as well as in various disease states. The role of Sigma-1R at the blood–brain barrier (BBB) is incompletely characterized. In this study, the effect of Sigma-1R activation was investigated in vitro on rat brain microvascular endothelial cells (RBMVEC), an important component of the blood–brain barrier (BBB), and in vivo on BBB permeability in rats. The Sigma-1R agonist PRE-084 produced a dose-dependent increase in mitochondrial calcium, and mitochondrial and cytosolic reactive oxygen species (ROS) in RBMVEC. PRE-084 decreased the electrical resistance of the RBMVEC monolayer, measured with the electric cell-substrate impedance sensing (ECIS) method, indicating barrier disruption. These effects were reduced by pretreatment with Sigma-1R antagonists, BD 1047 and NE 100. In vivo assessment of BBB permeability in rats indicates that PRE-084 produced a dose-dependent increase in brain extravasation of Evans Blue and sodium fluorescein brain; the effect was reduced by the Sigma-1R antagonists. Immunocytochemistry studies indicate that PRE-084 produced a disruption of tight and adherens junctions and actin cytoskeleton. The brain microcirculation was directly visualized in vivo in the prefrontal cortex of awake rats with a miniature integrated fluorescence microscope (aka, miniscope; Doric Lenses Inc.). Miniscope studies indicate that PRE-084 increased sodium fluorescein extravasation in vivo. Taken together, these results indicate that Sigma-1R activation promoted oxidative stress and increased BBB permeability. [ABSTRACT FROM AUTHOR]

The ability of the immune system to combat pathogens relies on processes like antigen sampling by dendritic cells and macrophages migrating through endo- and epithelia or penetrating them with their dendrites. In addition, other immune cell subtypes also migrate through the epithelium after activation. For paracellular migration, interactions with tight junctions (TJs) are necessary, and previous studies reported TJ protein expression in several immune cells. Our investigation aimed to characterize, in more detail, the expression profiles of TJ proteins in different immune cells in both naïve and activated states. The mRNA expression analysis revealed distinct expression patterns for TJ proteins, with notable changes, mainly increases, upon activation. At the protein level, LSR appeared predominant, being constitutively present in naïve cell membranes, suggesting roles as a crucial interaction partner. Binding experiments suggested the presence of claudins in the membrane only after stimulation, and claudin-8 translocation to the membrane occurred after stimulation. Our findings suggest a dynamic TJ protein expression in immune cells, implicating diverse functions in response to stimulation, like interaction with TJ proteins or regulatory roles. While further analysis is needed to elucidate the precise roles of TJ proteins, our findings indicate important non-canonical functions of TJ proteins in immune response. [ABSTRACT FROM AUTHOR]

In cholinergic urticaria (CholU), small, itchy wheals are induced by exercise or passive warming and reduced sweating has been reported. Despite the described reduced muscarinic receptor expression, sweat duct obstruction, or sweat allergy, the underlying pathomechanisms are not well understood. To gain further insights, we collected skin biopsies before and after pulse-controlled ergometry and sweat after sauna provocation from CholU patients as well as healthy controls. CholU patients displayed partially severely reduced local sweating, yet total sweat volume was unaltered. However, sweat electrolyte composition was altered, with increased K+ concentration in CholU patients. Formalin-fixed, paraffin-embedded biopsies were stained to explore sweat leakage and tight junction protein expression. Dermcidin staining was not found outside the sweat glands. In the secretory coils of sweat glands, the distribution of claudin-3 and -10b as well as occludin was altered, but the zonula occludens-1 location was unchanged. In all, dermcidin and tight junction protein staining suggests an intact barrier with reduced sweat production capability in CholU patients. For future studies, an ex vivo skin model for quantification of sweat secretion was established, in which sweat secretion could be pharmacologically stimulated or blocked. This ex vivo model will be used to further investigate sweat gland function in CholU patients and decipher the underlying pathomechanism(s). [ABSTRACT FROM AUTHOR]

Claudins are a family of 27 proteins that have an important role in the formation of tight junctions. They also have an important function in ion exchange, cell mobility, and the epithelial-to-mesenchymal transition, the latter being very important in cancer invasion and metastasis. Therapeutic targeting of claudins has been investigated to improve cancer outcomes. Recent evidence shows improved outcomes when combining monoclonal antibodies against claudin 18.2 with chemotherapy for patients with gastroesophageal junction cancer. Currently, chimeric antigen receptor T-cells targeting claudin 18 are under investigation. In this review, we will discuss the major functions of claudins, their distribution in the normal as well as cancerous tissues, and their effect in cancer metastasis, with a special focus on the therapeutic targeting of claudins to improve cancer outcomes. [ABSTRACT FROM AUTHOR]

This study aimed to investigate the preventive effects of the total polyphenols from Nymphaea candida (NCTP) on LPS-induced septic acute lung injury (ALI) in mice and its mechanisms. NCTP could significantly ameliorate LPS-induced lung tissue pathological injury in mice as well as lung wet/dry ratio and MPO activities (p < 0.05). NCTP could significantly decrease the blood leukocyte, neutrophil, monocyte, basophil, and eosinophil amounts and LPS contents in ALI mice compared with the model group (p < 0.05), improving lymphocyte amounts (p < 0.05). Moreover, compared with the model group, NCTP could decrease lung tissue TNF-α, IL-6, and IL-1β levels (p < 0.05) and downregulate the protein expression of TLR4, MyD88, TRAF6, IKKβ, IκB-α, p-IκB-α, NF-κB p65, p-NF-κB p65, NLRP3, ASC, and Caspase1 in lung tissues (p < 0.05). Furthermore, NCTP could inhibit ileum histopathological injuries, restoring the ileum tight junctions by increasing the expression of ZO-1 and occludin. Simultaneously, NCTP could reverse the gut microbiota disorder, restore the diversity of gut microbiota, increase the relative abundance of Clostridiales and Lachnospiraceae, and enhance the content of SCFAs (acetic acid, propionic acid, and butyric acid) in feces. These results suggested that NCTP has preventive effects on septic ALI, and its mechanism is related to the regulation of gut microbiota, SCFA metabolism, and the TLR-4/NF-κB and NLRP3 pathways. [ABSTRACT FROM AUTHOR]

Nipah virus (NiV) is a highly lethal zoonotic virus with a potential large-scale outbreak, which poses a great threat to world health and security. In order to explore more potential factors associated with NiV, a proximity labeling method was applied to investigate the F, G, and host protein interactions systematically. We screened 1996 and 1524 high-confidence host proteins that interacted with the NiV fusion (F) glycoprotein and attachment (G) glycoprotein in HEK293T cells by proximity labeling technology, and 863 of them interacted with both F and G. The results of GO and KEGG enrichment analysis showed that most of these host proteins were involved in cellular processes, molecular binding, endocytosis, tight junction, and other functions. Cytoscape software (v3.9.1) was used for visual analysis, and the results showed that Cortactin (CTTN), Serpine mRNA binding protein 1 (SERBP1), and stathmin 1 (STMN1) were the top 20 proteins and interacted with F and G, and were selected for further validation. We observed colocalization of F-CTTN, F-SERBP1, F-STMN1, G-CTTN, G-SERBP1, and G-STMN1 using confocal fluorescence microscopy, and the results showed that CTTN, SERBP1, and STMN1 overlapped with NiV F and NiV G in HEK293T cells. Further studies found that CTTN can significantly inhibit the infection of the Nipah pseudovirus (NiVpv) into host cells, while SERBP1 and STMN1 had no significant effect on pseudovirus infection. In addition, CTTN can also inhibit the infection of the Hendra pseudovirus (HeVpv) in 293T cells. In summary, this study revealed that the potential host proteins interacted with NiV F and G and demonstrated that CTTN could inhibit NiVpv and HeVpv infection, providing new evidence and targets for the study of drugs against these diseases. [ABSTRACT FROM AUTHOR]

Natural compounds like flavonoids preserve intestinal mucosal integrity through their antioxidant, anti-inflammatory, and antimicrobial properties. Additionally, some flavonoids show prebiotic abilities, promoting the growth and activity of beneficial gut bacteria. This study investigates the protective impact of Lens culinaris extract (LE), which is abundant in flavonoids, on intestinal mucosal integrity during LPS-induced inflammation. Using Caco-2 cells as a model for the intestinal barrier, the study found that LE did not affect cell viability but played a cytoprotective role in the presence of LPS. LE improved transepithelial electrical resistance (TEER) and tight junction (TJ) protein levels, which are crucial for barrier integrity. It also countered the upregulation of pro-inflammatory genes TRPA1 and TRPV1 induced by LPS and reduced pro-inflammatory markers like TNF-α, NF-κB, IL-1β, and IL-8. Moreover, LE reversed the LPS-induced upregulation of AQP8 and TLR-4 expression. These findings emphasize the potential of natural compounds like LE to regulate the intestinal barrier and reduce inflammation's harmful effects on intestinal cells. More research is required to understand their mechanisms and explore therapeutic applications, especially for gastrointestinal inflammatory conditions. [ABSTRACT FROM AUTHOR]

Disease modifiers, whether from cancer, sepsis, systemic inflammation, or microbial pathogens, all appear to induce epithelial barrier leak, with induced changes of the Tight Junctional (TJ) complex being pivotal to the process. This leak—and the ensuant breakdown of compartmentation—plays a central role in disease morbidity on many levels. Accumulation of lung water in the luminal compartment of airways was a major driver of morbidity and mortality in COVID-19 and is an excellent example of the phenomenon. Increasing awareness of the ability of micronutrients to improve basal barrier function and reduce barrier compromise in pathophysiology may prove to be a low-cost, safe, and easily administered prophylactic and/or therapeutic option amenable to large populations. The growing appreciation of the clinical utility of supplemental doses of Vitamin D in COVID-19 is but one example. This narrative review is intended to propose a general theory on how and why micronutrients—at levels above normal dietary intake—successfully remodel TJs and improve barrier function. It discusses the key difference between dietary/Recommended Daily Allowance (RDA) levels of micronutrients versus supplemental levels, and why the latter are needed in disease situations. It advances a hypothesis for why signal transduction regulation of barrier function may require these higher supplemental doses to achieve the TJ remodeling and other barrier element changes that are clinically beneficial. [ABSTRACT FROM AUTHOR]

Breast cancer brain metastasis (BCBM) is a challenging condition with limited treatment options and poor prognosis. Understanding the interactions between tumor cells and the blood–brain barrier (BBB) is critical for developing novel therapeutic strategies. One promising target is estrogen receptor β (ERβ), which promotes the expression of key tight junction proteins, sealing the BBB and reducing its permeability. In this study, we investigated the effects of 17β-estradiol (E2) and the selective ERβ agonist diarylpropionitrile (DPN) on endothelial and cancer cells. Western blot analysis revealed the expression patterns of ERs in these cell lines, and estrogen treatment upregulated claudin-5 expression in brain endothelial cells. Using in vitro models of the BBB, we found that DPN treatment significantly increased BBB tightness about suppressed BBB transmigration activity of representative Her2-positive (BT-474) and triple-negative (MDA-MB-231) breast cancer cell lines. However, the efficacy of DPN treatment decreased when cancer cells were pre-differentiated in the presence of E2. Our results support ERβ as a potential target for the prevention and treatment of BCBM and suggest that targeted vector-based approaches may be effective for future preventive and therapeutic implications. [ABSTRACT FROM AUTHOR]

Claudins are one of the major components of tight junctions (TJs) that polymerize within the cell membrane and form interactions between cells. Some claudins seal the paracellular space, limiting paracellular flux, while others form selectively permeable ion channels that control the paracellular permeability of small ions. Claudin strands are known to be dynamic and reshape within TJs to accommodate large-scale movements and rearrangements of epithelial tissues. Here, we summarize the recent computational and modeling studies on claudin assembly into tetrameric ion channels and their polymerization into μm long strands within the membrane. Computational studies ranging from all-atom molecular dynamics, coarse-grained simulations, and hybrid-resolution simulations elucidate the molecular nature of claudin assembly and function and provide a framework that describes the lateral flexibility of claudin strands. [ABSTRACT FROM AUTHOR]

Claudin polymers constitute the tight junction (TJ) backbone that forms paracellular barriers, at least for bigger solutes. While some claudins also seal the barrier for small electrolytes, others form ion channels. For cation-selective claudin-15 and claudin-10b, structural models of channels embedded in homo-polymeric strands have been suggested. Here, we generated a model for the prototypic anion-selective claudin-10a channel. Based on previously established claudin-10b models, dodecamer homology models of claudin-10a embedded in two membranes were analyzed by molecular dynamics simulations. The results indicate that both claudin-10 isoforms share the same strand and channel architecture: Sidewise unsealed tetrameric pore scaffolds are interlocked with adjacent pores via the β1β2 loop of extracellular segment 1. This leads to TJ-like strands with claudin subunits arranged in four joined rows in two opposing membranes. Several but not all cis- and trans-interaction modes are indicated to be conserved among claudin-10a, -10b, and -15. However, pore-lining residues that differ between claudin-10a and -10b (i.e., R33/I35, A34/D36, K69/A71, N54/D56, H60/N62, R62/K64) result in opposite charge selectivity of channels. This was supported by electric field simulations for both claudins and is consistent with previous electrophysiological studies. In summary, for the first time, a structural and mechanistic model of complete and prototypic paracellular anion channels is provided. This improves understanding of epithelial paracellular transport. [ABSTRACT FROM AUTHOR]

Chronic rhinosinusitis (CRS) is a disease characterised by the inflammation of the nasal and paranasal cavities. It is a widespread condition with considerable morbidity for patients. Current treatment for chronic rhinosinusitis consists of appropriate medical therapy followed by surgery in medically resistant patients. Although oral steroids are effective, they are associated with significant morbidity, and disease recurrence is common when discontinued. The development of additional steroid sparing therapies is therefore needed. Mesalazine is a commonly used therapeutic in inflammatory bowel disease, which shares a similar disease profile with chronic rhinosinusitis. This exploratory in vitro study aims to investigate whether mesalazine could be repurposed to a nasal wash, which is safe on human nasoepithelial cells, and retains its anti-inflammatory effects. CRS patients' human nasal epithelial cells (HNECs) were collected. HNECs were grown at an air-liquid interface (ALIs) and in a monolayer and challenged with mesalazine or a non-medicated control. Transepithelial electrical resistance, paracellular permeability, and toxicity were measured to assess epithelial integrity and safety. The anti-inflammatory effects of mesalazine on the release of interleukin (IL)-6 and tumour necrosis factor alpha (TNF-α) were analysed using human leukemia monocytic cell line (THP-1). mesalazine did not impact the barrier function of HNEC-ALIs and was not toxic when applied to HNECs or THP-1 cells at concentrations up to 20 mM. mesalazine at 0.5 and 1 mM concentrations significantly inhibited TNF-α release by THP-1 cells. mesalazine effectively decreases TNF-α secretion from THP-1 cells, indicating the possibility of its anti-inflammatory properties. The safety profile of mesalazine at doses up to 20 mM suggests that it is safe when applied topically on HNECs. [ABSTRACT FROM AUTHOR]

This study was investigated to examine the neuroprotective effect of fermented Protaetia brevitarsis larvae (FPB) in ethanol-induced-dementia mice. Consumption of FPB by mice resulted in improved memory dysfunction in the Y-maze, passive avoidance, and Morris water maze tests. FPB significantly decreased oxidative stress by regulating levels of malondialdehyde (MDA), superoxide dismutase (SOD), and reduced glutathione (GSH) in brain tissues. In addition, FPB restored cerebral mitochondrial dysfunction by modulating levels of reactive oxygen species (ROS), mitochondrial membrane potential (MMP), and ATP. In addition, FPB enhanced the cholinergic system via the regulation of acetylcholine (ACh) content, acetylcholinesterase (AChE) activity, and expressions of AChE and choline acetyltransferase (ChAT) in brain tissues. FPB ameliorated neuronal apoptosis through modulation of the protein kinase B (AKT)/B-cell lymphoma (BCL)-2 signaling pathway. Also, FPB improved inflammation response by down-regulating the toll-like receptor (TLR)-4/nuclear factor (NF)-κB pathway. Additionally, FPB ameliorated synaptic plasticity via the increase of the expressions of synaptophysin (SYP), postsynaptic density protein (PSD)-95, and growth-associated protein (GAP)-43. Treatment with FPB also reinforced the blood–brain barrier by increasing tight junctions including zonula occludens (ZO)-1, occludin, and claudin-1. In conclusion, these results show that FPB can improve cognitive impairment via AKT/NF-κB pathways in ethanol-induced-dementia mice. [ABSTRACT FROM AUTHOR]

This work analyzes the role of the tight junction (TJ) protein ZO-2 on mechanosensation. We found that the lack of ZO-2 reduced apical membrane rigidity measured with atomic force microscopy, inhibited the association of γ-actin and JAM-A to the cell border, and instead facilitated p114RhoGEF and afadin accumulation at the junction, leading to an enhanced mechanical tension at the TJ measured by FRET, with a ZO-1 tension probe, and increased tricellular TJ tension. Simultaneously, adherens junction tension measured with an E-cadherin probe was unaltered. The stability of JAM-A and ZO-2 binding was assessed by a collaborative in silico study. The absence of ZO-2 also impacted the cell response to the substrate, as monolayers plated in 20 kPa hydrogels developed holes not seen in parental cultures and displayed a retarded elongation and formation of cell aggregates. The absence of ZO-2 was sufficient to induce YAP and Snail nuclear accumulation in cells cultured over glass, but when ZO-2 KD cells were plated in nanostructured ridge arrays, they displayed an increased abundance of nuclear Snail and conspicuous internalization of claudin-4. These results indicate that the absence of ZO-2 also impairs the response of cells to substrate stiffness and exacerbates transformation triggered by substrate topography. [ABSTRACT FROM AUTHOR]

Fluorescently labelled compounds are often employed to study the paracellular properties of epithelia. For flux measurements, these compounds are added to the donor compartment and samples collected from the acceptor compartment at regular intervals. However, this method fails to detect rapid changes in permeability. For continuous transepithelial flux measurements in an Ussing chamber setting, a device was developed, consisting of a flow-through chamber with an attached LED, optical filter, and photodiode, all encased in a light-impermeable container. The photodiode output was amplified and recorded. Calibration with defined fluorescein concentration (range of 1 nM to 150 nM) resulted in a linear output. As proof of principle, flux measurements were performed on various cell lines. The results confirmed a linear dependence of the flux on the fluorescein concentration in the donor compartment. Flux depended on paracellular barrier function (expression of specific tight junction proteins, and EGTA application to induce barrier loss), whereas activation of transcellular chloride secretion had no effect on fluorescein flux. Manipulation of the lateral space by osmotic changes in the perfusion solution also affected transepithelial fluorescein flux. In summary, this device allows a continuous recording of transepithelial flux of fluorescent compounds in parallel with the electrical parameters recorded by the Ussing chamber. [ABSTRACT FROM AUTHOR]

Vitamin D3 (VitD3) plays a crucial role in various cellular functions through its receptor interaction. The biological activity of Vitamin D3 can vary based on its solubility and stability. Thus, the challenge lies in maximizing its biological effects through its complexation within cyclodextrin (βNS-CDI 1:4) nanosponges (NS) (defined as VitD3NS). Therefore, its activity has been evaluated on two different gut–brain axes (healthy gut/degenerative brain and inflammatory bowel syndrome gut/degenerative brain axis). At the gut level, VitD3-NS mitigated liposaccharide-induced damage (100 ng/mL; for 48 h), restoring viability, integrity, and activity of tight junctions and reducing ROS production, lipid peroxidation, and cytokines levels. Following intestinal transit, VitD3-NS improved the neurodegenerative condition in the healthy axis and the IBS model, suggesting the ability of VitD3-NS to preserve efficacy and beneficial effects even in IBS conditions. In conclusion, this study demonstrates the ability of this novel form of VitD3, named VitD3-NS, to act on the gut–brain axis in healthy and damaged conditions, emphasizing enhanced biological activity through VitD3 complexation, as such complexation increases the beneficial effect of vitamin D3 in both the gut and brain by about 50%. [ABSTRACT FROM AUTHOR]

Probiotic therapy needs consideration as an alternative strategy to prevent and possibly treat corneal infection. This study aimed to assess the preventive effect of Lactobacillus reuteri and Bifidobacterium longum subsp. infantis on reducing the infection of human corneal epithelial (HCE) cells caused by Pseudomonas aeruginosa. The probiotics' preventive effect against infection was evaluated in cell monolayers pretreated with each probiotic 1 h and 24 h prior to P. aeruginosa challenge followed by 1 h and 24 h of growth in combination. Cell adhesion, cytotoxicity, anti-inflammatory, and antinitrosative activities were evaluated. L. reuteri and B. longum adhered to HCE cells, preserved occludin tight junctions' integrity, and increased mucin production on a SkinEthicTM HCE model. Pretreatment with L. reuteri or B. longum significantly protected HCE cells from infection at 24 h, increasing cell viability at 110% (110.51 ± 5.15; p ≤ 0.05) and 137% (137.55 ± 11.97; p ≤ 0.05), respectively. Each probiotic showed anti-inflammatory and antinitrosative activities, reducing TNF-α level (p ≤ 0.001) and NOx amount (p ≤ 0.001) and reestablishing IL-10 level (p ≤ 0.001). In conclusion, this study demonstrated that L. reuteri and B. longum exert protective effects in the context of corneal infection caused by P. aeruginosa by restoring cell viability and modulating inflammatory cytokine release. [ABSTRACT FROM AUTHOR]

The gastrointestinal (GI) tract of multicellular organisms, especially mammals, harbors a symbiotic commensal microbiota with diverse microorganisms including bacteria, fungi, viruses, and other microbial and eukaryotic species. This microbiota exerts an important role on intestinal function and contributes to host health. The microbiota, while benefiting from a nourishing environment, is involved in the development, metabolism and immunity of the host, contributing to the maintenance of homeostasis in the GI tract. The immune system orchestrates the maintenance of key features of host–microbe symbiosis via a unique immunological network that populates the intestinal wall with different immune cell populations. Intestinal epithelium contains lymphocytes in the intraepithelial (IEL) space between the tight junctions and the basal membrane of the gut epithelium. IELs are mostly CD8+ T cells, with the great majority of them expressing the CD8αα homodimer, and the γδ T cell receptor (TCR) instead of the αβ TCR expressed on conventional T cells. γδ T cells play a significant role in immune surveillance and tissue maintenance. This review provides an overview of how the microbiota regulates γδ T cells and the influence of microbiota-derived metabolites on γδ T cell responses, highlighting their impact on immune homeostasis. It also discusses intestinal neuro-immune regulation and how γδ T cells possess the ability to interact with both the microbiota and brain. [ABSTRACT FROM AUTHOR]

Peyer's patches (PPs) are part of the gut-associated lymphatic tissue (GALT) and represent the first line of the intestinal immunological defense. They consist of follicles with lymphocytes and an overlying subepithelial dome with dendritic cells and macrophages, and they are covered by the follicle-associated epithelium (FAE). A sealed paracellular pathway in the FAE is crucial for the controlled uptake of luminal antigens. Quercetin is the most abundant plant flavonoid and has a barrier-strengthening effect on tight junctions (TJs), a protein complex that regulates the paracellular pathway. In this study, we aimed to analyze the effect of quercetin on porcine PPs and the surrounding villus epithelium (VE). We incubated both tissue types for 4 h in Ussing chambers, recorded the transepithelial electrical resistance (TEER), and measured the unidirectional tracer flux of [3H]-mannitol. Subsequently, we analyzed the expression, protein amount, and localization of three TJ proteins, claudin 1, claudin 2, and claudin 4. In the PPs, we could not detect an effect of quercetin after 4 h, neither on TEER nor on the [3H]-mannitol flux. In the VE, quercetin led to a higher TEER value, while the [3H]-mannitol flux was unchanged. The pore-forming claudin 2 was decreased while the barrier-forming claudin 4 was increased and the expression was upregulated. Claudin 1 was unchanged and all claudins could be located in the paracellular membrane by immunofluorescence microscopy. Our study shows the barrier-strengthening effect of quercetin in porcine VE by claudin 4 upregulation and a claudin 2 decrease. Moreover, it underlines the different barrier properties of PPs compared to the VE. [ABSTRACT FROM AUTHOR]

This study investigates the intricate composition and spatial distribution of tight junction complex proteins during early mouse neurulation. The analyses focused on the cranial neural tube, which gives rise to all head structures. Neurulation brings about significant changes in the neuronal and non-neuronal ectoderm at a cellular and tissue level. During this process, precise coordination of both epithelial integrity and epithelial dynamics is essential for accurate tissue morphogenesis. Tight junctions are pivotal for epithelial integrity, yet their complex composition in this context remains poorly understood. Our examination of various tight junction proteins in the forebrain region of mouse embryos revealed distinct patterns in the neuronal and non-neuronal ectoderm, as well as mesoderm-derived mesenchymal cells. While claudin-4 exhibited exclusive expression in the non-neuronal ectoderm, we demonstrated a neuronal ectoderm specific localization for claudin-12 in the developing cranial neural tube. Claudin-5 was uniquely present in mesenchymal cells. Regarding the subcellular localization, canonical tight junction localization in the apical junctions was predominant for most tight junction complex proteins. ZO-1 (zona occludens protein-1), claudin-1, claudin-4, claudin-12, and occludin were detected at the apical junction. However, claudin-1 and occludin also appeared in basolateral domains. Intriguingly, claudin-3 displayed a non-canonical localization, overlapping with a nuclear lamina marker. These findings highlight the diverse tissue and subcellular distribution of tight junction proteins and emphasize the need for their precise regulation during the dynamic processes of forebrain development. The study can thereby contribute to a better understanding of the role of tight junction complex proteins in forebrain development. [ABSTRACT FROM AUTHOR]

Tight junction (TJ) protein cingulin (CGN) and transcription factor forkhead box protein O1 (FOXO1) contribute to the development of various cancers. Histone deacetylase (HDAC) inhibitors have a potential therapeutic role for some cancers. HDAC inhibitors affect the expression of both CGN and FOXO1. However, the roles and regulatory mechanisms of CGN and FOXO1 are unknown in non-small cell lung cancer (NSCLC) and normal human lung epithelial (HLE) cells. In the present study, to investigate the effects of CGN and FOXO1 on the malignancy of NSCLC, we used A549 cells as human lung adenocarcinoma and primary human lung epithelial (HLE) cells as normal lung tissues and performed the knockdown of CGN and FOXO1 by siRNAs. Furthermore, to investigate the detailed mechanisms in the antitumor effects of HDAC inhibitors for NSCLC via CGN and FOXO1, A549 cells and HLE cells were treated with the HDAC inhibitors trichostatin A (TSA) and Quisinostat (JNJ-2648158). In A549 cells, the knockdown of CGN increased bicellular TJ protein claudin-2 (CLDN-2) via mitogen-activated protein kinase/adenosine monophosphate-activated protein kinase (MAPK/AMPK) pathways and induced cell migration, while the knockdown of FOXO1 increased claudin-4 (CLDN-4), decreased CGN, and induced cell proliferation. The knockdown of CGN and FOXO1 induced cell metabolism in A549 cells. TSA and Quisinostat increased CGN and tricellular TJ protein angulin-1/lipolysis-stimulated lipoprotein receptor (LSR) in A549. In normal HLE cells, the knockdown of CGN and FOXO1 increased CLDN-4, while HDAC inhibitors increased CGN and CLDN-4. In conclusion, the knockdown of CGN via FOXO1 contributes to the malignancy of NSCLC. Both HDAC inhibitors, TSA and Quisinostat, may have potential for use in therapy for lung adenocarcinoma via changes in the expression of CGN and FOXO1. [ABSTRACT FROM AUTHOR]

Amidst increasing concern about antibiotic resistance resulting from the overuse of antibiotics, there is a growing interest in exploring alternative agents. One such agent is citric acid, an organic compound commonly used for various applications. Our research findings indicate that the inclusion of citric acid can have several beneficial effects on the tight junctions found in the mouse intestine. Firstly, the study suggests that citric acid may contribute to weight gain by stimulating the growth of intestinal epithelial cells (IE-6). Citric acid enhances the small intestinal villus–crypt ratio in mice, thereby promoting intestinal structural morphology. Additionally, citric acid has been found to increase the population of beneficial intestinal microorganisms, including Bifidobacterium and Lactobacillus. It also promotes the expression of important protein genes such as occludin, ZO-1, and claudin-1, which play crucial roles in maintaining the integrity of the tight junction barrier in the intestines. Furthermore, in infected IEC-6 cells with H9N2 avian influenza virus, citric acid augmented the expression of genes closely associated with the influenza virus infection. Moreover, it reduces the inflammatory response caused by the viral infection and thwarted influenza virus replication. These findings suggest that citric acid fortifies the intestinal tight junction barrier, inhibits the replication of influenza viruses targeting the intestinal tract, and boosts intestinal immune function. [ABSTRACT FROM AUTHOR]

Tight junction (TJ) proteins (Tjps), Tjp1 and Tjp2, are tight junction-associated scaffold proteins that bind to the transmembrane proteins of tight junctions and the underlying cytoskeleton. In this study, we first analyzed the tumorigenic characteristics of B16-F10 melanoma cells, including cell proliferation, migration, invasion, metastatic potential, and the expression patterns of related proteins, after the CRISPR–Cas9-mediated knockout (KO) of Tjp genes. The proliferation of Tjp1 and Tjp2 KO cells significantly increased in vitro. Other tumorigenic characteristics, including migration and invasion, were significantly enhanced in Tjp1 and Tjp2 KO cells. Zonula occludens (ZO)-associated protein Claudin-1 (CLDN-1), which is a major component of tight junctions and functions in controlling cell-to-cell adhesion, was decreased in Tjp KO cells. Additionally, Tjp KO significantly stimulated tumor growth and metastasis in an in vivo mouse model. We performed a transcriptome analysis using next-generation sequencing (NGS) to elucidate the key genes involved in the mechanisms of action of Tjp1 and Tjp2. Among the various genes affected by Tjp KO-, cell cycle-, cell migration-, angiogenesis-, and cell–cell adhesion-related genes were significantly altered. In particular, we found that the Ninjurin-1 (Ninj1) and Catenin alpha-1 (Ctnna1) genes, which are known to play fundamental roles in Tjps, were significantly downregulated in Tjp KO cells. In summary, tumorigenic characteristics, including cell proliferation, migration, invasion, tumor growth, and metastatic potential, were significantly increased in Tjp1 and Tjp2 KO cells, and the knockout of Tjp genes significantly affected the expression of related proteins. [ABSTRACT FROM AUTHOR]

Cluster of differentiation 19 (CD19) chimeric antigen receptor (CAR) T cells are a highly effective immunotherapy for relapsed and refractory B-cell malignancies, but their utility can be limited by the development of immune effector cell-associated neurotoxicity syndrome (ICANS). The recent discovery of CD19 expression on the pericytes in the blood–brain barrier (BBB) suggests an important off-target mechanism for ICANS development. In addition, the release of systemic cytokines stimulated by the engagement of CD19 with the CAR T cells can cause endothelial activation and decreased expression of tight junction molecules, further damaging the integrity of the BBB. Once within the brain microenvironment, cytokines trigger a cytokine-specific cascade of neuroinflammatory responses, which manifest clinically as a spectrum of neurological changes. Brain imaging is frequently negative or nonspecific, and treatment involves close neurologic monitoring, supportive care, interleukin antagonists, and steroids. The goal of this review is to inform readers about the normal development and microstructure of the BBB, its unique susceptibility to CD19 CAR T cells, the role of individual cytokines on specific elements of the brain's microstructural environment, and the clinical and imaging manifestations of ICANS. Our review will link cellular pathophysiology with the clinical and radiological manifestations of a complex clinical entity. [ABSTRACT FROM AUTHOR]