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Late cornified envelope (LCE) proteins are small cationic epidermal proteins with antimicrobial properties, and the combined deletion of LCE3B and LCE3C genes is a risk factor for psoriasis that affects skin microbiome composition. In a yeast two-hybrid screen, we identified CYSRT1 as an interacting partner of members of all LCE groups except LCE6. These interactions were confirmed in a mammalian cell system by coimmunoprecipitation. CYSRT1 is a protein of unknown function that is specifically expressed in cutaneous and oral epithelia and spatially colocalizes with LCE proteins in the upper layers of the suprabasal epidermis. Constitutive CYSRT1 expression is present in fully differentiated epidermis and can be further induced in vivo by disruption of the skin barrier upon stratum corneum removal. Transcriptional regulation correlates to keratinocyte terminal differentiation but not to skin bacteria exposure. Similar to LCEs, CYSRT1 was found to have antibacterial activity against Pseudomonas aeruginosa. Comparative gene sequence analysis and protein amino acid alignment indicate that CYSRT1 is highly conserved among vertebrates and has putative antimicrobial activity. To summarize, we identified CYSRT1 in the outer skin layer, where it colocalizes with LCE proteins and contributes to the constitutive epidermal antimicrobial host defense repertoire., (Copyright © 2023 The Authors. Published by Elsevier Inc. All rights reserved.)

Late cornified envelope proteins are predominantly expressed in the skin and other cornified epithelia. On the basis of sequence similarity, this 18-member homologous gene family has been subdivided into six groups. The LCE3 proteins have been the focus of dermatological research because the combined deletion of LCE3B and LCE3C genes (LCE3B/C-del) is a risk factor for psoriasis. We previously reported that LCE3B/C-del increases the expression of the LCE3A gene and that LCE3 proteins exert antibacterial activity. In this study, we analyzed the antimicrobial properties of other family members and the role of LCE3B/C-del in the modulation of microbiota composition of the skin and oral cavity. Differences in killing efficiency and specificity between the late cornified envelope proteins and their target microbes were found, and the amino acid content rather than the order of the well-conserved central domain of the LCE3A protein was found responsible for its antibacterial activity. In vivo, LCE3B/C-del correlated with a higher beta-diversity in the skin and oral microbiota. From these results, we conclude that all late cornified envelope proteins possess antimicrobial activity. Tissue-specific and genotype-dependent antimicrobial protein profiles impact skin and oral microbiota composition, which could direct toward LCE3B/C-del‒associated dysbiosis and a possible role for microbiota in the pathophysiology of psoriasis., (Copyright © 2021 The Authors. Published by Elsevier Inc. All rights reserved.)

Despite recent advances in understanding microbial diversity in skin homeostasis, the relevance of microbial dysbiosis in inflammatory disease is poorly understood. Here we perform a comparative analysis of skin microbial communities coupled to global patterns of cutaneous gene expression in patients with atopic dermatitis or psoriasis. The skin microbiota is analysed by 16S amplicon or whole genome sequencing and the skin transcriptome by microarrays, followed by integration of the data layers. We find that atopic dermatitis and psoriasis can be classified by distinct microbes, which differ from healthy volunteers microbiome composition. Atopic dermatitis is dominated by a single microbe (Staphylococcus aureus), and associated with a disease relevant host transcriptomic signature enriched for skin barrier function, tryptophan metabolism and immune activation. In contrast, psoriasis is characterized by co-occurring communities of microbes with weak associations with disease related gene expression. Our work provides a basis for biomarker discovery and targeted therapies in skin dysbiosis.

Terminally differentiating epidermal keratinocytes express a large number of structural and antimicrobial proteins that are involved in the physical barrier function of the stratum corneum and provide innate cutaneous host defense. Late cornified envelope (LCE) genes, located in the epidermal differentiation complex on chromosome 1, encode a family of 18 proteins of unknown function, whose expression is largely restricted to epidermis. Deletion of two members, LCE3B and LCE3C (LCE3B/C-del), is a widely-replicated psoriasis risk factor that interacts with the major psoriasis-psoriasis risk gene HLA-C*06. Here we performed quantitative trait locus analysis, utilizing RNA-seq data from human skin and found that LCE3B/C-del was associated with a markedly increased expression of LCE3A, a gene directly adjacent to LCE3B/C-del. We confirmed these findings in a 3-dimensional skin model using primary keratinocytes from LCE3B/C-del genotyped donors. Functional analysis revealed that LCE3 proteins, and LCE3A in particular, have defensin-like antimicrobial activity against a variety of bacterial taxa at low micromolar concentrations. No genotype-dependent effect was observed for the inside-out or outside-in physical skin barrier function. Our findings identify an unknown biological function for LCE3 proteins and suggest a role in epidermal host defense and LCE3B/C-del-mediated psoriasis risk., (Copyright © 2017 The Authors. Published by Elsevier Inc. All rights reserved.)

Background: The effectiveness of biologics for psoriasis shows heterogeneity among patients. With pharmacogenetic markers, it might be possible to predict treatment response., Objectives: We aimed to test the association between genetic markers and the response to biologics in psoriasis (etanercept, adalimumab, ustekinumab) in a prospective cohort., Methods: We investigated the copy number variation in the LCE3B and LCE3C genes, and eight single-nucleotide polymorphisms (SNPs) in HLA-C*06, CD84, IL12B, IL23R, TRAF3IP2, ERAP1, IFIH1 and TNFAIP3. The decrease in Psoriasis Area and Severity Index (PASI) was calculated as ∆PASI (absolute PASI decrease compared with baseline) and PASI 75 (proportion of patients with ≥ 75% improvement vs. baseline). Associations between genetic variants and treatment outcome were assessed using multivariable linear regression analysis (∆PASI corrected for baseline PASI, primary analysis) and Pearson's χ 2 -test or Fisher's exact test (PASI 75, secondary analysis)., Results: We included 348 treatment episodes in 234 patients. Patients heterozygous (GA) for the SNP in CD84 (rs6427528) had a better ∆PASI response to etanercept after 3 months (P = 0·025) than the homozygous reference group (GG). In addition, patients heterozygous (CT) for the IL12B variant showed a better response (∆PASI) to ustekinumab (P = 0·017) than the reference group (CC). Patients homozygous (GG) for the SNP in TNFAIP3 showed a worse response (∆PASI) to ustekinumab (P = 0·031) than the reference group (TT). The associations with ustekinumab resulting from the primary analysis were not confirmed in the secondary (PASI 75) analysis., Conclusions: We demonstrated a strong association between etanercept use in psoriasis and variations in CD84, a gene that was previously found to be a predictor of response to etanercept in rheumatoid arthritis., (© 2016 British Association of Dermatologists.)

Elucidating the poorly defined mechanisms by which inflammatory lesions are spatially restricted in vivo is of critical importance in understanding skin disease. Chemokines are the principal regulators of leukocyte migration and are essential in the initiation and maintenance of inflammation. The membrane-bound psoriasis-associated atypical chemokine receptor 2 (ACKR2) binds, internalizes and degrades most proinflammatory CC-chemokines. Here we investigate the role of ACKR2 in limiting the spread of cutaneous psoriasiform inflammation to sites that are remote from the primary lesion. Circulating factors capable of regulating ACKR2 function at remote sites were identified and examined using a combination of clinical samples, relevant primary human cell cultures, in vitro migration assays, and the imiquimod-induced model of psoriasiform skin inflammation. Localized inflammation and IFN-γ together up-regulate ACKR2 in remote tissues, protecting them from the spread of inflammation. ACKR2 controls inflammatory T-cell chemotaxis and positioning within the skin, preventing an epidermal influx that is associated with lesion development. Our results have important implications for our understanding of how spatial restriction is imposed on the spread of inflammatory lesions and highlight systemic ACKR2 induction as a therapeutic strategy in the treatment and prevention of psoriasis and potentially a broad range of other immune-mediated diseases., (Copyright © 2016 The Authors. Published by Elsevier Inc. All rights reserved.)

Background: Previous research revealed heterogeneity in the perfusion intensity within clinically homogenous-appearing plaques, without differences in erythema. In addition, an increased perfusion was found within the perilesional skin. This raises the question whether the heterogeneity in perfusion found both inside and outside a lesion influences the expression levels of genes and proteins involved in the pathogenesis of psoriasis., Objectives: To correlate the perfusion intensity to mRNA and protein expression of genes associated with the pathogenesis of psoriasis and to visualize the dynamics of the perfusion intensity over time using laser Doppler perfusion imaging., Methods: Fourteen patients with plaque psoriasis were included. The superficial microcirculation and clinical local scores (single usability metric, SUM, scores) were analysed in one representative lesion every 2 weeks. After 8 weeks 4 biopsies were taken, one from a highly perfused area (hotspot) and one from a low perfusion area (coldspot) of the lesional skin, one biopsy from the highly perfused perilesional skin and one from the distant uninvolved skin., Results: Statistically significant differences in mRNA and protein expression, including IL-17 and TBX21/T-Bet, were found between hotspots and coldspots, and between the highly perfused perilesional and the uninvolved skin. Hotspots tend to remain on the same location during 8 weeks of follow-up., Conclusions: Within homogenous-appearing psoriatic plaques, there are remarkable differences in mRNA and protein levels, which are correlated with the perfusion intensity and can be detected by using laser Doppler perfusion imaging. In addition, differences in mRNA and protein expression between the highly perfused perilesional skin and the uninvolved skin were found, indicating that several biological changes occur well before clinical changes become manifest., (© 2015 S. Karger AG, Basel.)

This study aims to investigate associations between observed clinical parameters and known genetic risk factors of psoriasis in a well-defined prospective cohort of paediatric patients with plaque psoriasis (n = 151). Significant associations were found for paediatric-onset psoriasis with ERAP1 (p = 0.002), IL23R (p = 0.01), LCE3C&#95;LCE3B-del (p = 0.00049) and HLA-C*06 (p = 3.15 × 10(-30)). Psoriasis severity was associated with the single nucleotide polymorphisms tagging IFIH1 and ERAP1 (p < 0.05). An onset before 10 years of age was associated with IL12B (p = 0.02). Nail psoriasis was more often seen in HLA-C*06-negative patients (p = 0.008). Remarkably, family history is clearly not associated with HLA-C*06 in this specific group. The large proportion of patients with a positive family history in HLA-C*06 negative patients (and the lack of correlation between the two) indicates that other genes, either alone or interaction between two or more genes, may have significant effects on heritability.

Objective: Stress is one of the factors that may exacerbate the progression of chronic inflammatory diseases such as RA and psoriasis. We exploratively compared the effects of acute stress on levels of circulating cytokines involved in disease progression and/or the stress response in patients with RA, patients with psoriasis and healthy subjects., Methods: Patients with RA, patients with psoriasis and healthy controls underwent a standardized psychosocial stress test (Trier Social Stress Test). Levels of circulating cytokines (IL-1β, IL-2, IL-4, IL-5, IL-6, IL-7, IL-8, IL-10, IFN-γ and TNF-α) were measured before and after the stress test., Results: The baseline levels of all cytokines, except IL-8, were significantly higher in patients with RA. After correction for baseline levels, patients with RA showed higher stress-induced levels of IL-1β and IL-2 than patients with psoriasis and healthy controls., Conclusion: The results suggest that patients with RA have a different immune response to stress than patients with psoriasis or healthy controls. More needs to be learned about the complex interaction between stress, immune parameters and chronic inflammation., (© The Author 2014. Published by Oxford University Press on behalf of the British Society for Rheumatology. All rights reserved. For Permissions, please email: journals.permissions@oup.com.)

Background: Psychosocial stress can be a risk factor for the maintenance and exacerbation of chronic inflammatory diseases, such as psoriasis and rheumatoid arthritis (RA)., Objectives: To gain insight into the specificity of the psychophysiological stress response during chronic inflammation, we assessed autonomic and neuroendocrine responses to stress in different chronic inflammatory diseases., Methods: Thirty patients with psoriasis (nine women, mean age 58·5 years ± 12·4), 34 patients with RA (16 women, mean age 60·8 years ± 9·2) and 25 healthy controls (16 women, mean age 55·6 years ± 8·7) underwent a standardized psychosocial stress task (Trier Social Stress Test). Salivary levels of α-amylase and cortisol and self-reported tension levels were measured before and after the stress test., Results: The cortisol response to stress was heightened in patients with psoriasis compared with patients with RA and healthy controls, whereas there were no differences in the autonomic and self-reported measures., Conclusions: The altered neuroendocrine stress response in patients with psoriasis suggests that stressful events might have different physiological consequences for specific patient groups with chronic inflammatory conditions, possibly adversely affecting disease status., (© 2013 British Association of Dermatologists.)

The interaction between keratinocytes and immune cells plays a major role in the development of inflammatory skin diseases like psoriasis and atopic dermatitis. Pharmacological intervention to inhibit T cell-derived proinflammatory mediators is an effective therapy in the treatment of psoriasis. Here, we present a model to study the interaction between keratinocytes and T cells in a three-dimensional (3D) microenvironment, based on human skin equivalents populated with CD4+ T cells. T cell migration into the dermis initiated keratinocyte activation within 2 days, with hallmarks of a psoriasiform inflammation after 4 days. Expression of epidermal psoriasis marker genes was upregulated, and proinflammatory cytokines and chemokines were highly expressed. Disturbed epidermal differentiation was shown by downregulated filaggrin expression and involucrin expression in the spinous layer. These effects were mediated via soluble factors produced by the T cells. The psoriasiform inflammation was also observed using T helper type 1 (Th1)- and Th17-polarized CD4+ T cells. We validated our model by treatment with anti-inflammatory drugs that reduced the expression of proinflammatory cytokines and chemokines and suppressed the psoriasiform inflammation. We propose that our T cell-driven inflammatory skin equivalent model has potential to study the pathogenesis of inflammatory skin diseases and may serve as a preclinical screening tool for anti-inflammatory drugs.

Background: The use of recently introduced biologics targeting specific immune mechanisms has identified crucial steps in the pathogenesis of psoriasis. Studying the dynamics of changes of these target mechanisms in sequential skin biopsies during treatment with biologics may reveal potential biomarkers. Correlation between clinical parameters and the expression of specific genes during treatments may identify markers indicative of treatment response., Objectives: This observational open-label study aimed to provide an overview of important cell biological changes in lesional skin during treatment with adalimumab, and their relationship to clinical improvement., Methods: Ten patients with moderate-to-severe plaque psoriasis were included and treated with adalimumab for 16 weeks. At baseline, and after 10 days and 16 weeks of treatment clinical scores were assessed and biopsies were taken to examine gene expression at the mRNA and protein level., Results: The expression of marker genes for innate immunity, and epidermal differentiation and proliferation was rapidly restored to normal levels, whereas genes of the adaptive immune system showed a delayed decrease. The static and dynamic course of CD1a+ Langerhans cells and Ki67+ nuclei showed a significant strong correlation to the Psoriasis Area and Severity Index score. No correlation between interleukin-17 expression and clinical scores was found., Conclusions: The innate immune system is affected during adalimumab treatment well before the changes in the adaptive immune system become apparent. We may speculate that the addition of a treatment with an early effect on adaptive immunity to adalimumab may result in superior effectiveness compared with monotherapies., (© 2013 British Association of Dermatologists.)

Diseases of the skin are amenable to RNAi-based therapies and targeting key components in the pathophysiology of psoriasis using RNAi may represent a successful new therapeutic strategy. We aimed to develop a straightforward and highly reproducible in vitro psoriasis model useful to study the effects of gene knockdown by RNAi and to identify new targets for topical RNAi therapeutics. We evaluated the use of keratinocytes derived from psoriatic plaques and normal human keratinocytes (NHKs). To induce a psoriatic phenotype in NHKs, combinations of pro-inflammatory cytokines (IL-1α, IL-17A, IL-6 and TNF-α) were tested. The model based on NHK met our needs of a reliable and predictive preclinical model, and this model was further selected for gene expression analyses, comprising a panel of 55 psoriasis-associated genes and five micro-RNAs (miRNAs). Gene silencing studies were conducted by using small interfering RNAs (siRNAs) and miRNA inhibitors directed against potential target genes such as CAMP and DEFB4 and miRNAs such as miR-203. We describe a robust and highly reproducible in vitro psoriasis model that recapitulates expression of a large panel of genes and miRNAs relevant to the pathogenesis of psoriasis. Furthermore, we show that our model is a powerful first step model system for testing and screening RNAi-based therapeutics.

To gain further insight into the genetic architecture of psoriasis, we conducted a meta-analysis of 3 genome-wide association studies (GWAS) and 2 independent data sets genotyped on the Immunochip, including 10,588 cases and 22,806 controls. We identified 15 new susceptibility loci, increasing to 36 the number associated with psoriasis in European individuals. We also identified, using conditional analyses, five independent signals within previously known loci. The newly identified loci shared with other autoimmune diseases include candidate genes with roles in regulating T-cell function (such as RUNX3, TAGAP and STAT3). Notably, they included candidate genes whose products are involved in innate host defense, including interferon-mediated antiviral responses (DDX58), macrophage activation (ZC3H12C) and nuclear factor (NF)-κB signaling (CARD14 and CARM1). These results portend a better understanding of shared and distinctive genetic determinants of immune-mediated inflammatory disorders and emphasize the importance of the skin in innate and acquired host defense.

A single previous study has demonstrated significant association of psoriasis with copy number of β-defensin genes, using DNA from psoriasis cases and controls from Nijmegen and Erlangen. In this study, we attempted to replicate that finding in larger new cohorts from Erlangen (N=2,017) and Michigan (N=5,412), using improved methods for β-defensin copy number determination based on the paralog ratio test, and enhanced methods of analysis and association testing implemented in the CNVtools resource. We demonstrate that the association with psoriasis found in the discovery sample is maintained after applying improved typing and analysis methods (P=5.5 × 10(-4), odds ratio (OR)=1.25). We also find that the association is replicated in 2,616 cases and 2,526 controls from Michigan, although at reduced significance (P=0.014), but not in new samples from Erlangen (1,396 cases and 621 controls, P=0.38). Meta-analysis across all cohorts suggests a nominally significant association (P=6.6 × 10(-3)/2 × 10(-4)) with an effect size (OR=1.081) much lower than found in the discovery study (OR=1.32). This reduced effect size and significance on replication is consistent with a genuine but weak association.

Background: Recent genome-wide association studies have identified several genetic risk factors for psoriasis, but data on their association with age at onset are lacking., Objectives: To compare the association between known risk alleles and psoriasis in well-defined cohorts with paediatric- and adult-onset psoriasis., Methods: Based on previous studies we selected seven genes and loci associated with psoriasis. Patients with paediatric-onset (< 18 years) and adult-onset psoriasis (≥ 18 years) and controls were genotyped. Genotype frequencies were compared between controls (n = 450) and all cases (n = 217), and between controls and cases stratified for confirmed age at onset (paediatric onset n = 80, adult onset n = 85)., Results: Paediatric-onset psoriasis showed a significant association with single nucleotide polymorphisms in the ERAP1 (P = 0.042) and IL23R loci (P = 0.042), LCE3C&#95;LCE3B-del (P = 0.003) and HLA-C*06 (P = 1.72 × 10(-19)) when compared with the control group. A significant association of these four genes was also demonstrated when all psoriasis cases were compared with controls. In adult-onset psoriasis a significant association was found for HLA-C*06 (P = 5.11 × 10(-6)) and for LCE3C&#95;LCE3B-del (P = 0.042). No associations were found for the IFIH1, IL12B and TRAF3IP2 loci., Conclusions: Notwithstanding the small cohort sizes, we demonstrated an association with established and recently discovered genetic risk factors in paediatric-onset psoriasis including genes involved in epidermal barrier function and adaptive immunity. Our data suggest that heritable factors may play a more important role in paediatric-onset psoriasis than in adult-onset psoriasis., (© 2012 The Authors. BJD © 2012 British Association of Dermatologists.)

Psoriasis was until recently regarded as a T-cell-driven disease with presumed (auto)immune mechanisms as its primary cause. This view was supported by clinical data and genetic studies that identified risk factors functioning in adaptive and innate immunity, such as HLA-C*06, ERAP1, the IL-23 pathway, and NF-k B signaling. Candidate gene approaches and genome-wide association studies, however, have identified copy number polymorphisms of the b-defensin cluster and deletion of late cornified envelope (LCE) 3B and 3C genes (LCE3C&#95;LCE3B-del) as psoriasis risk factors.As these genes are expressed in epithelial cells and not by the immune system, these findings may cause a change of paradigm for psoriasis, not unlike the reported filaggrin association that has profoundly changed the views on atopic dermatitis. In addition to genetic polymorphisms of the immune system, genetic variations affecting the skin barrier are likely to contribute to psoriasis. Recent studies have shown epistatic interactions involving HLA-C*06, ERAP1, and LCE3C&#95;LCE3B-del, which makes psoriasis a unique model to investigate genetic and biological interactions of associated genes in a complex disease. We present a model for disease initiation and perpetuation, which integrates the available genetic, immunobiological, and clinical data.

Background: Recent studies have emphasized the importance of heritable and acquired skin barrier abnormalities in common inflammatory diseases such as psoriasis and atopic dermatitis (AD). To date, no comprehensive studies on the effect of experimental barrier disruption on cornified envelope protein expression have been performed., Objectives: To analyse the effect of experimental skin barrier disruption on the expression of cornified envelope structural proteins and keratinocyte differentiation-regulating proteins., Methods: We examined mRNA (day 1, 3 and 7) and protein (day 1, 2, 4 and 9) expression levels of structural proteins and regulatory molecules after sodium dodecyl sulphate (SDS) application on normal skin, and tape stripping of uninvolved epidermis of patients with psoriasis and AD and healthy controls., Results: Upon tape stripping, several structural molecules were significantly downregulated (at the mRNA level as well as the protein level), including LCE5A, LCE2B, FLG, FLG2 and LOR, whereas others were upregulated: IVL, SPRR1, SPRR2, HRNR and most notably LCE3A. The epidermal crosslinking enzymes TGM1, TGM3 and TGM5 were all upregulated, whereas proteases involved in the desquamation process (CTSV, KLK5 and KLK7) were downregulated or unaffected. Most results were similar in SDS-instigated irritant contact dermatitis. There was no significant difference in response between normal epidermis and nonlesional skin of patients with psoriasis and AD., Conclusions: Skin barrier disruption induces a temporary barrier repair response composed of increased expression of several cornification-related proteins, and decreased expression of some structural and desquamation-related proteins., (© 2012 The Authors. BJD © 2012 British Association of Dermatologists.)

A multicenter meta-analysis including data from 9,389 psoriasis patients and 9,477 control subjects was performed to investigate the contribution of the deletion of genes LCE3C and LCE3B, involved in skin barrier defense, to psoriasis susceptibility in different populations. The study confirms that the deletion of LCE3C and LCE3B is a common genetic factor for susceptibility to psoriasis in the European populations (OR(Overall) = 1.21 (1.15-1.27)), and for the first time directly demonstrates the deletion's association with psoriasis in the Chinese (OR = 1.27 (1.16-1.34)) and Mongolian (OR = 2.08 (1.44-2.99)) populations. The analysis of the HLA-Cw6 locus showed significant differences in the epistatic interaction with the LCE3C and LCE3B deletion in at least some European populations, indicating epistatic effects between these two major genetic contributors to psoriasis. The study highlights the value of examining genetic risk factors in multiple populations to identify genetic interactions, and indicates the need of further studies to understand the interaction of the skin barrier and the immune system in susceptibility to psoriasis.

Deletion of the late cornified envelope (LCE) genes LCE3B and LCE3C has recently been identified as a risk factor for psoriasis. Expression of 16 LCE genes of LCE groups 1, 2, 3, 5, and 6 was examined in vivo and in vitro. Quantitative PCR demonstrated that moderate to high LCE expression was largely confined to skin and a few oropharyngeal tissues. Genes of the LCE3 group demonstrated increased expression in lesional psoriatic epidermis and were induced after superficial injury of normal skin, whereas expression of members of other LCE groups was down-regulated under these conditions. Immunohistochemistry and immunoelectron microscopy demonstrated that LCE2 protein expression was restricted to the uppermost granular layer and the stratum corneum. Stimulation of in vitro reconstructed skin by several psoriasis-associated cytokines resulted in induction of LCE3 members. The data suggest that LCE proteins of groups 1, 2, 5, and 6 are involved in normal skin barrier function, whereas LCE3 genes encode proteins involved in barrier repair after injury or inflammation. These findings may provide clues to the mechanistic role of LCE3B/C deletion in psoriasis., (Copyright © 2011 American Society for Investigative Pathology. Published by Elsevier Inc. All rights reserved.)

Human epidermis plays an important role in host defense by acting as a physical barrier and signaling interface between the environment and the immune system. Pattern recognition receptors (PRRs) are crucial to maintain homeostasis and provide protection during infection, but are also causally involved in monogenic auto-inflammatory diseases. This study aimed to investigate the epidermal expression of PRRs and several associated host defense molecules in healthy human skin, psoriasis, and atopic dermatitis (AD). Using microarray analysis and real-time quantitative PCR, we found that many of these genes are transcribed in normal human epidermis. Only a few genes were differentially induced in psoriasis (CLEC7A (dectin-1), Toll-like receptor (TLR) 4, and mannose receptor C type 1 (MRC1)) or AD (MRC1, IL1RN, and IL1β) compared with normal epidermis. A remarkably high expression of dectin-1 mRNA was observed in psoriatic epidermis and this was corroborated by immunohistochemistry. In cultured primary human keratinocytes, dectin-1 expression was induced by IFN-γ, IFN-α, and Th17 cytokines. Keratinocytes were unresponsive, however, to dectin-1 ligands such as β-glucan or heat-killed Candida albicans, nor did we observe synergy with TLR2/TLR5 ligands. In conclusion, upregulation of dectin-1 in psoriatic lesions seems to be under control of psoriasis-associated cytokines. Its role in the biology of skin inflammation and infection remains to be explored.

Background: Psychological stressors might contribute to the severity of chronic inflammatory diseases such as psoriasis by dysregulating hypothalamic-pituitary-adrenal (HPA) axis activity., Objectives: To evaluate the role of cortisol, a key component of the HPA axis, in reaction to psychological stress in patients with psoriasis., Methods: Serum cortisol, clinical indicators of disease severity (Psoriasis Area and Severity Index) and self-report measures of daily stressors were measured monthly for 6 months in 62 patients with psoriasis., Results: In addition to the previous findings in this sample showing that peak levels of daily stressors predicted an increase in disease severity a month later, the peak levels of daily stressors were also significantly associated with a lower cortisol level. Moreover, patients who persistently experienced higher levels of daily stressors had lower mean cortisol levels than patients who experienced lower levels of daily stressors., Conclusions: Results suggest that daily stressors influence disease outcome in patients with psoriasis by affecting cortisol levels at moments of high stress. Furthermore, patients with persistently high levels of stressors seem to have a specific psychophysiological profile of lowered cortisol levels and may be particularly vulnerable to the influence of stressors on their psoriasis., (© 2010 The Authors. BJD © 2010 British Association of Dermatologists.)

To identify new susceptibility loci for psoriasis, we undertook a genome-wide association study of 594,224 SNPs in 2,622 individuals with psoriasis and 5,667 controls. We identified associations at eight previously unreported genomic loci. Seven loci harbored genes with recognized immune functions (IL28RA, REL, IFIH1, ERAP1, TRAF3IP2, NFKBIA and TYK2). These associations were replicated in 9,079 European samples (six loci with a combined P < 5 × 10⁻⁸ and two loci with a combined P < 5 × 10⁻⁷). We also report compelling evidence for an interaction between the HLA-C and ERAP1 loci (combined P = 6.95 × 10⁻⁶). ERAP1 plays an important role in MHC class I peptide processing. ERAP1 variants only influenced psoriasis susceptibility in individuals carrying the HLA-C risk allele. Our findings implicate pathways that integrate epidermal barrier dysfunction with innate and adaptive immune dysregulation in psoriasis pathogenesis.

Recently, a deletion of two late cornified envelope (LCE) genes within the epidermal differentiation complex on chromosome 1 was shown to be overrepresented in 1,426 psoriasis vulgaris (PsV) patients of European ancestry. In this study, we report a confirmation of this finding in 1,354 PsV patients and 937 control individuals of German origin. We found an allele frequency of the deletion of 70.9% in PsV patients and of 64.9% in control individuals (chi(2)=17.44, P=2.97 x 10(-5), odds ratio (95% confidence interval)=1.31 (1.15-1.48)). The overall copy number of the two LCE genes had no influence on the age of onset, but we observed a dosage effect at the genotype level. There was no evidence of statistically significant interaction with copy number of the beta-defensin cluster on 8p23.1 or with an IL-23R pathway variant in a combined data set of German and Dutch individuals, whereas evidence for interaction with the PSORS1 risk allele in German individuals was marginal and did not remain significant after correction for multiple testing. Our study confirms the recently published finding that the deletion of the two LCE genes is a susceptibility factor for PsV with dosage effect, while, because of power limitation, no final conclusion regarding interaction with other PsV risk factors can be made at this stage.

Background: Microarray studies on the epidermal transcriptome in psoriasis and atopic dermatitis (AD) have revealed genes with disease-specific expression in keratinocytes of lesional epidermis. These genes are possible candidates for disease-specific pathogenetic changes, but could also provide a tool for molecular diagnostics of inflammatory skin conditions in general., Objectives: To analyse if gene expression signatures as found in purified epidermal cells from AD are also present in other eczematous conditions such as allergic and irritant contact dermatitis., Methods: We used real-time quantitative polymerase chain reaction, immunohistochemistry and bioinformatics to investigate gene expression in different forms of eczema. Normal epidermis and psoriatic epidermis were analysed for comparison., Results: Carbonic anhydrase II was highly induced in epidermis from all forms of eczema but not in psoriasis. Remarkably, the presumed neuron-specific Nel-like protein 2 showed a strong induction only in AD epidermis. Interleukin-1F9, elafin, beta-defensin-2 and vanin-3 were strongly induced in psoriasis, but not in any type of eczema. High levels of the chemokines CCL17 and CXCL10 were predominantly found in epidermis of allergic contact dermatitis. The chemokine CXCL8 was highly expressed in psoriasis, AD and allergic contact dermatitis, but not in irritant contact dermatitis. Cluster analysis or multinomial logistic regression indicated that expression levels of a set of seven genes are a strong predictor of the type of inflammatory response., Conclusions: These observations contribute to molecular diagnostic criteria for inflammatory skin conditions.

The vanin gene family encodes secreted and membrane-bound ectoenzymes that convert pantetheine into pantothenic acid and cysteamine. Recent studies in a mouse colitis model indicated that vanin-1 has proinflammatory activity and suggest that pantetheinases are potential therapeutic targets in inflammatory diseases. In a microarray analysis of epidermal gene expression of psoriasis and atopic dermatitis lesions, we identified vanin-3 as the gene showing the highest differential expression of all annotated genes that we studied (19-fold upregulation in psoriasis). Quantitative real-time PCR analysis confirmed the microarray data on vanin-3 and showed similar induction of vanin-1, but not of vanin-2, in psoriatic epidermis. Immunohistochemistry showed that vanin-3 is expressed in the differentiated epidermal layers. Using submerged and organotypic keratinocyte cultures, we found that vanin-1 and vanin-3 are induced at the mRNA and protein level by psoriasis-associated proinflammatory cytokines (Th17/Th1) but not by Th2 cytokines. We hypothesize that increased levels of pantetheinase activity are part of the inflammatory-regenerative epidermal differentiation program, and may contribute to the phenotype observed in psoriasis.

Background: There is increasing evidence that stressors contribute to the severity of chronic inflammatory diseases such as psoriasis. However, much less is known about possible individual differences between patients in their stress reactivity, particularly the role of cognitive and behavioural factors, such as the role of worrying or scratching behaviour, in reaction to itch., Objectives: To investigate the direct and moderating role of individual stress reactivity factors, particularly of cognitive and behavioural patterns of worrying and scratching, on the relationship between daily stressors and changes in disease severity [Psoriasis Area and Severity Index (PASI)] and itch in patients with psoriasis., Methods: Patients were followed for 6 months through monthly clinical and self-reported measures of daily stressors, itch, disease severity and individual reactivity factors. Data from 62 patients were suitable for analysis., Results: Cognitive and behavioural patterns of worrying and scratching were both independently related to an increase 4 weeks later in disease severity (PASI) and itch, at moments when patients experienced a high level of daily stressors. At these moments, stressors also interacted with vulnerability factors, showing that patients with more daily stress and high worrying and scratching had particularly worsened disease severity and itch., Conclusions: Patients with high levels of worrying and scratching are most vulnerable to the impact of stressors on their psoriasis, particularly at highly stressful periods.

Background: The antiprotease activity of cystatin M/E regulates skin barrier formation, as it inhibits the activity of cathepsin V, cathepsin L and legumain, thereby controlling the processing of transglutaminase 3. Misregulation of this pathway by unrestrained protease activity, as seen in cystatin M/E-deficient mice, leads to abnormal stratum corneum and hair follicle formation, and severe disturbance of skin barrier function., Objectives: Our major aim was to make a quantitative analysis of the expression of all players of this pathway in the epidermis of patients with inflammatory skin diseases. A second aim was to determine if reconstructed human skin could be used as an in vitro model system to investigate this pathway., Methods: Autopsy material from normal human tissues, biopsies from normal skin of healthy volunteers, and lesional skin from patients with atopic dermatitis and psoriasis were used to study the expression of the above-mentioned molecules at the mRNA level by quantitative real-time polymerase chain reaction. Localization of the protein was performed by immunofluorescence microscopy, and expression was quantitated by image analysis., Results: In skin, cystatin M/E is expressed at relatively higher levels than its target proteases, when compared with other tissues, which emphasizes its prominent role in cutaneous biology. We found decreased expression of cystatin M/E and cathepsin V in lesional atopic dermatitis and psoriasis epidermis at the mRNA level as well as the protein level. Cathepsin L and transglutaminase 3 were increased at the transcriptional level; however, this was not reflected by higher protein levels. Interestingly, the expression of all these molecules in reconstructed skin was qualitatively and quantitatively similar to the in vivo situation., Conclusions: Disturbance of the cystatin M/E-cathepsin pathway could contribute to the dysregulated skin barrier function observed in inflammatory dermatoses. Human reconstructed skin appears to be a valuable model to study this novel biochemical pathway in vitro.

Psoriasis is a common inflammatory skin disease with a prevalence of 2-3% in individuals of European ancestry. In a genome-wide search for copy number variants (CNV) using a sample pooling approach, we have identified a deletion comprising LCE3B and LCE3C, members of the late cornified envelope (LCE) gene cluster. The absence of LCE3B and LCE3C (LCE3C&#95;LCE3B-del) is significantly associated (P = 1.38E-08) with risk of psoriasis in 2,831 samples from Spain, The Netherlands, Italy and the United States, and in a family-based study (P = 5.4E-04). LCE3C&#95;LCE3B-del is tagged by rs4112788 (r(2) = 0.93), which is also strongly associated with psoriasis (P < 6.6E-09). LCE3C&#95;LCE3B-del shows epistatic effects with the HLA-Cw6 allele on the development of psoriasis in Dutch samples and multiplicative effects in the other samples. LCE expression can be induced in normal epidermis by skin barrier disruption and is strongly expressed in psoriatic lesions, suggesting that compromised skin barrier function has a role in psoriasis susceptibility.

Background: Previous studies have extensively documented antimicrobial and chemotactic activities of beta-defensins. Human beta-defensin-2 (hBD-2) is strongly expressed in lesional psoriatic epidermis, and recently we have shown that high beta-defensin genomic copy number is associated with psoriasis susceptibility. It is not known, however, if biologically and pathophysiologically relevant concentrations of hBD-2 protein are present in vivo, which could support an antimicrobial and proinflammatory role of beta-defensins in lesional psoriatic epidermis., Methodology/principal Findings: We found that systemic levels of hBD-2 showed a weak but significant correlation with beta defensin copy number in healthy controls but not in psoriasis patients with active disease. In psoriasis patients but not in atopic dermatitis patients, we found high systemic hBD-2 levels that strongly correlated with disease activity as assessed by the PASI score. Our findings suggest that systemic levels in psoriasis are largely determined by secretion from involved skin and not by genomic copy number. Modelling of the in vivo epidermal hBD-2 concentration based on the secretion rate in a reconstructed skin model for psoriatic epidermis provides evidence that epidermal hBD-2 levels in vivo are probably well above the concentrations required for in vitro antimicrobial and chemokine-like effects., Conclusions/significance: Serum hBD-2 appears to be a useful surrogate marker for disease activity in psoriasis. The discrepancy between hBD-2 levels in psoriasis and atopic dermatitis could explain the well known differences in infection rate between these two diseases.

Psoriasis is an inflammatory skin disease driven by aberrant interactions between the epithelium and the immune system. Anti-psoriatic drugs can therefore target either the keratinocytes or the immunocytes. Here we sought to develop an in vitro reconstructed skin model that would display the molecular characteristics of psoriatic epidermis in a controlled manner, allowing the screening of anti-psoriatic drugs and providing a model in which to study the biology of this disease. Human skin equivalents generated from normal human adult keratinocytes after air exposure and stimulation by keratinocyte growth factor and epidermal growth factor displayed the correct morphological and molecular characteristics of normal human epidermis whereas the psoriasis-associated proteins, hBD-2, SKALP/elafin, and CK16, were absent. Skin equivalents generated from foreskin keratinocytes were clearly abnormal both morphologically and with respect to gene expression. When normal skin equivalents derived from adult keratinocytes were stimulated with psoriasis-associated cytokines [tumor necrosis factor-alpha, interleukin (IL)-1alpha, IL-6, and IL-22] or combinations thereof, strong expression of hBD-2, SKALP/elafin, CK16, IL-8, and tumor necrosis factor-alpha was induced as shown by quantitative polymerase chain reaction and immunohistochemistry. Retinoic acid but not cyclosporin A was found to inhibit cytokine-induced gene expression at both the mRNA and protein levels. These results illustrate the potential of this disease model to study the molecular pathology and pharmacological intervention in vitro.

In the past decades, chronic inflammatory diseases such as psoriasis, atopic dermatitis, asthma, Crohn's disease and celiac disease were generally regarded as immune-mediated conditions involving activated T-cells and proinflammatory cytokines produced by these cells. This paradigm has recently been challenged by the finding that mutations and polymorphisms in epithelium-expressed genes involved in physical barrier function or innate immunity, are risk factors of these conditions. We used a functional genomics approach to analyze cultured keratinocytes from patients with psoriasis or atopic dermatitis and healthy controls. First passage primary cells derived from non-lesional skin were stimulated with pro-inflammatory cytokines, and expression of a panel of 55 genes associated with epidermal differentiation and cutaneous inflammation was measured by quantitative PCR. A subset of these genes was analyzed at the protein level. Using cluster analysis and multivariate analysis of variance we identified groups of genes that were differentially expressed, and could, depending on the stimulus, provide a disease-specific gene expression signature. We found particularly large differences in expression levels of innate immunity genes between keratinocytes from psoriasis patients and atopic dermatitis patients. Our findings indicate that cell-autonomous differences exist between cultured keratinocytes of psoriasis and atopic dermatitis patients, which we interpret to be genetically determined. We hypothesize that polymorphisms of innate immunity genes both with signaling and effector functions are coadapted, each with balancing advantages and disadvantages. In the case of psoriasis, high expression levels of antimicrobial proteins genes putatively confer increased protection against microbial infection, but the biological cost could be a beneficial system gone awry, leading to overt inflammatory disease.

Psoriasis is a common inflammatory skin disease with a strong genetic component. We analyzed the genomic copy number polymorphism of the beta-defensin region on human chromosome 8 in 179 Dutch individuals with psoriasis and 272 controls and in 319 German individuals with psoriasis and 305 controls. Comparisons in both cohorts showed a significant association between higher genomic copy number for beta-defensin genes and risk of psoriasis.

Avarol, a marine sesquiterpenoid hydroquinone, and 14 avarol derivatives have shown interesting anti-inflammatory properties in previous studies. In this study, avarol and derivatives were evaluated in high-throughput keratinocyte culture models using cytokeratin 10 and SKALP/Elafin expression as markers for respectively normal and psoriatic differentiation. Avarol and five of its derivatives (5, 10, 13, 14 and 15) were selected for further study. Only 10, 13, 14 and 15 were able to inhibit keratinocyte cell growth. Changes in expression levels of 22 genes were assessed by quantitative real time PCR (qPCR). From these genes, TNFalpha mRNA levels showed the strongest changes. For compound 13, 15 and dithranol (used as a model antipsoriatic drug), a dose-dependent downregulation of TNFalpha mRNA was found. The changes in TNFalpha mRNA were confirmed at the protein level for compound 13. Additionally, this compound was able to reduce also IL-8 and COX-2 mRNA levels and this effect was correlated with a reduction in COX-2 protein expression. The mechanism of action of this compound involves at least the inhibition of NF-kappaB-DNA binding activity. In conclusion, our high-throughput screening models in combination with quantitative assessment of changes in gene expression profiles identified the avarol derivative 13, a benzylamine derivative of avarol at the 4' position of benzoquinone ring, as an interesting anti-psoriatic drug candidate that inhibits keratinocyte cell growth and TNFalpha and COX-2 expression.

Recently, it was shown that lesional skin of atopic dermatitis patients expresses low levels of some antimicrobial peptides, compared with psoriasis patients. Here we performed microarray analysis on mRNA from purified lesional epidermal cells of patients with chronic plaque psoriasis and chronic atopic dermatitis, to investigate whether this is a general phenomenon for host defense proteins, and how specific it is for this class of molecules. Microarray data were confirmed on a selected set of genes by quantitative PCR and at the protein level by immunohistochemistry. We found overexpression of many antimicrobial proteins in keratinocytes from psoriatic skin compared with atopic dermatitis skin. Interestingly, we observed that markers of normal differentiation and the activated/hyperproliferative epidermal phenotype were expressed at equal levels. Chronic lesions of psoriasis and atopic dermatitis patients are remarkably similar with respect to cellular proliferation. We conclude that psoriatic epidermis expresses high levels of host defense proteins compared with atopic dermatitis epidermis, and this phenomenon appears to be specific for these proteins. It remains to be investigated whether this is caused by genetic polymorphisms in pathways leading to an epidermal antimicrobial response, or by differences in the cellular infiltrate in psoriasis compared with atopic dermatitis.

A model that explains how maintenance of normal homeostasis in human epidermis is achieved describes a heterogeneous cell population of stem cells (SC) and transit amplifying cells (TAC). There must be a tightly regulated balance between SC self-renewal and the generation of TAC that undergo a limited number of divisions before giving rise to postmitotic, terminally differentiated cells. To investigate whether this balance is disturbed in psoriatic epidermis, we have characterized flow sorted enriched SC and TAC using immunocytochemistry, flow cytometry, and real-time quantitative PCR. Our data demonstrate phenotypical and functional differences in SC (beta(1)-integrin bright) and TAC (beta(1)-integrin dim) enriched fractions between normal and psoriatic keratinocytes. Some of these were expected, such as mRNA levels of keratins 6 and 10 and of the Ki-67 antigen. Most remarkable were differences in phenotype of the psoriatic TAC compared with TAC from normal skin. These subpopulations also displayed striking differences following culture. Downregulation of markers associated with the regenerative phenotype (psoriasin, elafin, psoriasis-associated fatty acid binding protein) in cultured psoriatic dim cells in the absence of hyperproliferation suggests that proliferation and regenerative maturation are coupled. From these results, in combination with our earlier findings, we propose a model for epidermal growth control in which TAC play a crucial role.

Chondroitin sulfate (CS) belongs to the group of glycosaminoglycans (GAGs), which are linear polysaccharides, located in the extracellular matrix and on the cell surface. To study the structure and distribution of CS in human skin and skin disorders, we have selected antibodies using phage display technique against CS. Four unique human anti-CS single-chain antibodies were selected: IO3D9, IO3H10, IO3H12, and IO4C2. We determined their amino acid sequence and evaluated their CS reactivity using ELISA and immunohistochemistry. Antibodies were reactive with CS, but not with other GAGs except for IO4C2, which was also reactive with heparin. Antibody IO3D9 showed a strong reactivity with highly sulfated CS (CSE). All antibodies displayed a different staining pattern in rat kidney, indicating the recognition of unique CS epitopes. In normal skin, the papillary dermis but not the reticular dermis was strongly stained. Antibody IO3H12 also stained basal keratinocytes. We applied these antibodies to study CS expression and localization in melanoma and psoriasis. A strong immunoreactivity with the extracellular matrix of melanoma metastases could be observed for all four antibodies, while in atypical nevi a less extensive reactivity with only the papillary dermis was observed. In psoriatic lesions, CS could be observed in the papillary dermis and in the reticular dermis, whereas the specific location in the papillary dermis found in normal skin was completely lost. In conclusion, human phage-display-derived anti-CS antibodies have been selected, characterized, and applied to detect CS alterations in skin conditions. Altered CS composition was detected in melanoma and psoriasis.

Inflamed epidermis (psoriasis, wound healing, ultraviolet-irradiated skin) harbors keratinocytes that are hyperproliferative and display an abnormal differentiation program. A distinct feature of this so-called regenerative maturation pathway is the expression of proteins such as the cytokeratins CK6, CK16, and CK17 and the antiinflammatory protein SKALP/elafin. These proteins are absent in normal skin but highly induced in lesional psoriatic skin. Expression of these genes can be used as a surrogate marker for psoriasis in drug-screening procedures of large compound libraries. The aim of this study was to develop a keratinocyte cell line that contained a reporter gene under the control of a psoriasis-associated endogenous promoter and demonstrate its use in an assay suitable for screening. We generated a stably transfected keratinocyte cell line that expresses enhanced green fluorescent protein (EGFP), under the control of a 0.8-kb fragment derived from the promoter of the SKALP/elafin gene, which confers high levels of tissue-specific expression at the mRNA level. Induction of the SKALP promoter by tumor necrosis factor-alpha resulted in increased expression levels of the secreted SKALP-EGFP fusion protein as assessed by direct readout of fluorescence and fluorescence polarization in 96-well cell culture plates. The fold stimulation of the reporter gene was comparable to that of the endogenous SKALP gene as assessed by enzyme-linked immunosorbent assay. Although the dynamic range of the screening system is limited, the small standard deviation yields a Z factor of 0.49. This indicates that the assay is suitable as a high-throughput screen, and provides proof of the concept that a secreted EGFP fusion protein under the control of a physiologically relevant endogenous promoter can be used as a fluorescence-based high-throughput screen for differentiation-modifying or antiinflammatory compounds that act via the keratinocyte.

Established treatments for psoriasis act ei-ther on hyperproliferation, inflammation, aberrant epidermal differentiation or a combination of these aspects of the disease. Potential new drugs for treatment of psoriasis or other disorders with abnormalities in epidermal differentiation can be identified by high-throughput screening of large compound libraries using surrogate markers for the disease. Here we describe a screening model to detect pharmacologically active drugs in two keratinocyte-based, 96-well culture models that use expression of cytokeratin 10 (CK10) and skin-derived antileucoprotease (SKALP)/elafin as markers for normal and psoriatic differentiation, respectively, and allow multiple parameters to be determined from a single well. In this model we tested a number of compounds in a pharmacological range from 10(-7) to 10(-5) M, including known antipsoriatic drugs, and experimental drugs that are potentially useful in the treatment of psoriasis. All-trans-retinoic acid, dithranol and the p38 mitogen-activated protein (MAP) kinase inhibitor SB220025 displayed a strong inhibitory effect on SKALP expression while cyclosporin A, dexamethasone, the vitamin D(3) derivative calcipotriol and the p38 MAP kinase inhibitor SB203580 showed only moderate inhibition. Methotrexate and dimethylfumarate did not affect the expression of SKALP. With respect to CK10 expression, all-trans-retinoic acid, calcipotriol, SB203580 and SB220025 exhibited strong inhibition while dithranol showed only moderate suppression of this normal differentiation marker. Expression levels of CK10 were not significantly affected by dexamethasone, methotrexate, cyclosporin A or dimethylfumarate. This model system parallels most, but not all, findings on the in vitro effect of known antipsoriatic drugs on keratinocytes. In addition, the model identifies p38 MAP kinase inhibitors as potent suppressors of differentiation-associated gene expression. Although further delineation and validation of this model is required, we conclude that the system is amenable to down-scaling and application as a high-throughput screen for differentiation-modifying compounds., (Copyright 2002 S. Karger AG, Basel)

The imidazole derivative liarozole is a potent inhibitor of cytochrome P450-dependent 4-hydroxylation of endogenous all-trans retinoic acid, thereby increasing the levels of all-trans retinoic acid in both plasma and skin. As part of a large, double-blind, randomized clinical study, we investigated the cell biological alterations in uninvolved and lesional skin of 20 patients with severe plaque psoriasis, who were treated with either liarozole or acitretin. The extent and severity of the skin lesions, as recorded by the Psoriasis Area and Severity Index score, was significantly reduced (P

Tenascin-C is an extracellular matrix glycoprotein that is markedly upregulated in the dermis of psoriatic skin. In this study, we have addressed the question whether the presence of tenascin-C in the lesion or in serum is a marker for disease activity. Immunohistochemical staining of tenascin-C before and after treatment with different topical and systemic medication showed that tenascin-C remained abundant after clinical remission of lesions, indicating that downregulation of tenascin-C to normal values is a slow process. By using a sensitive enzyme-linked immunosorbent assay to measure levels of serum tenascin-C in psoriatic patients and unaffected individuals, we found that tenascin-C levels in most patients were within the normal range. Moreover, tenascin-C values did not correlate with disease activity. We conclude that tenascin-C is not useful as a marker for disease activity in psoriasis.

Psoriasis is a multifactorial skin disease characterised by epidermal abnormalities and infiltration by lymphocytes and polymorphonuclear leukocytes (PMN). Skin-derived antileukoproteinase (SKALP), also known as elafin, is a potent inhibitor of human leukocyte elastase and proteinase 3, two PMN-derived proteinases implicated in tissue destruction and leukocyte migration. We have shown that, at least at the protein level, SKALP is significantly decreased in lesional skin of patients with pustular psoriasis compared with plaque-type psoriasis. This finding raised the possibility that SKALP could be one of the candidate genes for pustular forms of psoriasis. We therefore performed single strand conformation polymorphism (SSCP) analysis on the SKALP gene to screen for mutations/polymorphisms in the exons of 30 patients with plaque-type psoriasis, 15 patients with pustular psoriasis and 48 healthy controls. In exon 1 a polymorphism was detected at position +43 relative to the translation start site, resulting in a substitution of threonine for alanine in the signal peptide. In the promoter region a dinucleotide repeat polymorphism was identified. Both polymorphisms were not associated with pustular psoriasis, or psoriasis in general. Our data indicate that the decrease in SKALP activity in pustular psoriasis is not caused by mutations in the coding region of the gene, and that there is no allelic association between pustular psoriasis and SKALP gene polymorphisms.

Heparan sulfate proteoglycans (HSPGs) are components of the basement membrane (BM) of various tissues. They consist of a core protein and negatively charged glycosaminoglycan side chains: the heparan sulfate (HS) moieties. In psoriasis, uninvolved skin of psoriasis patients and in normal skin, the distribution of HSPGs was studied immunohistochemically by means of three different monoclonal antibodies: JM-72, directed against the HSPG-core protein, JM-13 against the sulfated domains of HS and JM-403 against the unmodified/low sulfated parts of HS. In psoriasis JM-13 staining was consistently absent in the tips of the dermal papillae, whereas JM-13 showed a continuous staining in the BM of uninvolved and normal skin. JM-403 staining was present in BM of all specimens. In addition, a honeycomb-like staining was found in epidermis of normal skin and to a lesser extent in uninvolved skin, due to binding with plasma membrane-associated HS. In psoriasis this JM-403 staining of the epidermis was invariably absent. JM-72 showed a continuous staining of BM in all biopsies. In conclusion, normal human skin and involved psoriatic skin show clear differences in expression of HS. These data may provide insight into the role of HSPGs in psoriasis, which remains further to be elucidated.

Recently we have described two novel markers for disturbed epidermal differentiation, which are strongly upregulated in psoriatic epidermis: skin-derived antileukoproteinase (SKALP) and epidermal fatty acid-binding protein (E-FABP). No data are available on the kinetics of SKALP and E-FABP expression in vivo and the relation with epidermal growth and differentiation. We used treatment of lesional psoriatic skin with topical steroid as a model to correlate the expression pattern of SKALP and E-FABP with known cell biological events during regression of the psoriatic lesion. Expression of these markers was studied using immunohistochemistry and Northern blot analysis. After 4 weeks of treatment a substantial clinical improvement was induced by the topical steroid, whereas no significant improvement had occurred at the placebo-treated sides. The expression of SKALP following treatment with steroid was nearly undetectable both at the protein and mRNA level. Mitotic activity, as measured by Ki-67 staining, and cytokeratin 16 expression were downregulated to normal levels in the steroid-treated epidermis. In contrast, although there was a marked decrease of E-FABP mRNA, the staining pattern for E-FABP at the protein level was not affected. After 4 weeks of treatment with steroid the complete suprabasal compartment remained positive, even after considerable clinical improvement of the lesion. We conclude that SKALP and cytokeratin 16 are markers that are downregulated even before complete macroscopic clearance of the lesion. The kinetics of E-FABP expression is distinct from the other molecules and lags behind the clinical signs of psoriasis.

Skin-derived antileukoproteinase (SKALP, also known as elafin) is an inducible epidermal serine proteinase inhibitor, that we have recently characterized at the protein and DNA levels. SKALP is a strong and specific inhibitor of PMN elastase, and is putatively involved in the regulation of cutaneous inflammatory processes. In order to investigate the role of SKALP in the control of elastase in psoriatic epidermis, we compared SKALP expression in normal skin, and in skin from patients with chronic plaque psoriasis and pustular forms of psoriasis. Epidermal scales and biopsies were collected and SKALP expression was studied at the mRNA level and at the protein level both functionally and immunochemically. In epidermal scales, we found that the levels of both free and total SKALP activity in pustular psoriasis were far lower than in plaque psoriasis. A significant number of pustular psoriasis patients showed latent SKALP activity, which represents the amount of SKALP putatively complexed to elastase. In addition, we found free elastase activity in 25% of the pustular psoriasis patients, indicating a total saturation of epidermal SKALP activity. In epidermal biopsies from pustular psoriasis patients, SKALP activity was significantly decreased compared with those from plaque psoriasis patients. Northern blot analysis did not reveal differences in epidermal mRNA levels between chronic plaque psoriasis and pustular psoriasis. We hypothesize that a reduced amount of epidermal SKALP contributes to an imbalance between elastase and its inhibitor, thereby promoting the formation of epidermal pustules. We suggest that these findings could provide a rationale for the treatment of pustular psoriasis with inhibitors of PMN-derived proteinases, as a new therapeutic modality.