CD49a Expression Defines Tissue-Resident CD8+ T Cells Poised for Cytotoxic Function in Human Skin.

Tissue-resident memory T (Trm) cells form a heterogeneous population that provides localized protection against pathogens. Here, we identify CD49a as a marker that differentiates CD8+ Trm cells on a compartmental and functional basis. In human skin epithelia, CD8+CD49a+ Trm cells produced interferon-γ, whereas CD8+CD49a- Trm cells produced interleukin-17 (IL-17). In addition, CD8+CD49a+ Trm cells from healthy skin rapidly induced the expression of the effector molecules perforin and granzyme B when stimulated with IL-15, thereby promoting a strong cytotoxic response. In skin from patients with vitiligo, where melanocytes are eradicated locally, CD8+CD49a+ Trm cells that constitutively expressed perforin and granzyme B accumulated both in the epidermis and dermis. Conversely, CD8+CD49a- Trm cells from psoriasis lesions predominantly generated IL-17 responses that promote local inflammation in this skin disease. Overall, CD49a expression delineates CD8+ Trm cell specialization in human epithelial barriers and correlates with the effector cell balance found in distinct inflammatory skin diseases.

A gene-centric approach to biomarker discovery identifies transglutaminase 1 as an epidermal autoantigen.

Autoantigen discovery is a critical challenge for the understanding and diagnosis of autoimmune diseases. While autoantibody markers in current clinical use have been identified through studies focused on individual disorders, we postulated that a reverse approach starting with a putative autoantigen to explore multiple disorders might hold promise. We here targeted the epidermal protein transglutaminase 1 (TGM1) as a member of a protein family prone to autoimmune attack. By screening sera from patients with various acquired skin disorders, we identified seropositive subjects with the blistering mucocutaneous disease paraneoplastic pemphigus. Validation in further subjects confirmed TGM1 autoantibodies as a 55% sensitive and 100% specific marker for paraneoplastic pemphigus. This gene-centric approach leverages the wealth of data available for human genes and may prove generally applicable for biomarker discovery in autoimmune diseases.

Human skin long noncoding RNA WAKMAR1 regulates wound healing by enhancing keratinocyte migration.

An increasing number of studies reveal the importance of long noncoding RNAs (lncRNAs) in gene expression control underlying many physiological and pathological processes. However, their role in skin wound healing remains poorly understood. Our study focused on a skin-specific lncRNA, LOC105372576, whose expression was increased during physiological wound healing. In human nonhealing wounds, however, its level was significantly lower compared with normal wounds under reepithelialization. We characterized LOC105372576 as a nuclear-localized, RNAPII-transcribed, and polyadenylated lncRNA. In keratinocytes, its expression was induced by TGF-ß signaling. Knockdown of LOC105372576 and activation of its endogenous transcription, respectively, reduced and increased the motility of keratinocytes and reepithelialization of human ex vivo skin wounds. Therefore, LOC105372576 was termed "wound and keratinocyte migration-associated lncRNA 1" (WAKMAR1). Further study revealed that WAKMAR1 regulated a network of protein-coding genes important for cell migration, most of which were under the control of transcription factor E2F1. Mechanistically, WAKMAR1 enhanced E2F1 expression by interfering with E2F1 promoter methylation through the sequestration of DNA methyltransferases. Collectively, we have identified a lncRNA important for keratinocyte migration, whose deficiency may be involved in the pathogenesis of chronic wounds.

Chromatin interactions in differentiating keratinocytes reveal novel atopic dermatitis- and psoriasis-associated genes.

BACKGROUND: Hundreds of variants associated with atopic dermatitis (AD) and psoriasis, 2 common inflammatory skin disorders, have previously been discovered through genome-wide association studies (GWASs). The majority of these variants are in noncoding regions, and their target genes remain largely unclear. OBJECTIVE: We sought to understand the effects of these noncoding variants on the development of AD and psoriasis by linking them to the genes that they regulate. METHODS: We constructed genomic 3-dimensional maps of human keratinocytes during differentiation by using targeted chromosome conformation capture (Capture Hi-C) targeting more than 20,000 promoters and 214 GWAS variants and combined these data with transcriptome and epigenomic data sets. We validated our results with reporter assays, clustered regularly interspaced short palindromic repeats activation, and examination of patient gene expression from previous studies. RESULTS: We identified 118 target genes of 82 AD and psoriasis GWAS variants. Differential expression of 58 of the 118 target genes (49%) occurred in either AD or psoriatic lesions, many of which were not previously linked to any skin disease. We highlighted the genes AFG1L, CLINT1, ADO, LINC00302, and RP1-140J1.1 and provided further evidence for their potential roles in AD and psoriasis. CONCLUSIONS: Our work focused on skin barrier pathology through investigation of the interaction profile of GWAS variants during keratinocyte differentiation. We have provided a catalogue of candidate genes that could modulate the risk of AD and psoriasis. Given that only 35% of the target genes are the gene nearest to the known GWAS variants, we expect that our work will contribute to the discovery of novel pathways involved in AD and psoriasis.

HLA-B*27 is significantly enriched in Nordic patients with psoriatic arthritis mutilans.

OBJECTIVES: The genetic contribution to psoriatic disease is substantial with a dominating influence of the HLA region. The profile of HLA class I genotypes likely contributes to shaping clinical phenotypes. Herein we aimed to explore such genotypes in cohorts of closely characterised subsets of psoriatic disease with special focus on psoriatic arthritis mutilans (PAM), a severe and rare form of psoriatic arthritis (PsA). METHODS: Cohorts of patients with the diagnosis of psoriasis vulgaris with or without arthritis (n=1217), psoriasis without arthritis (n=534), psoriatic arthritis without mutilating disease (n=337) and psoriatic arthritis mutilans (n=63) were collected and genotyped for HLA class I and II genes, with standardised methodologies. Cases were compared with a healthy control population (n=2468). Case-only and case-control association tests were performed to address the hypothesis of genetic contribution to clinical phenotypes. RESULTS: The presence of HLA-B*27 was strikingly increased in PAM (45%) compared with PsA without mutilating disease (13%) and with healthy controls (13%). However, within the PAM population, HLA-B*27 did not correlate with clinical markers such as number of mutilating joints, radiographic scoring, disease duration and age of disease onset. CONCLUSIONS: HLA-B*27 emerges as an important genotype marker for PAM.

Non-Melanoma Skin Cancer Risk Among Patients in the Psoriasis Longitudinal Assessment and Registry (PSOLAR)

To the Editor: Patients with psoriasis are at increased risk of developing non melanoma skin cancer (NMSC), including squamous cell carcinoma (SCC) and basal cell carcinoma (BCC).1,2 The risk is especially elevated among those who previously received systemic treatment or phototherapy.2 Systemic treatments, including biologic therapies and methotrexate (MTX), are effective in managing immune-mediated diseases; however, they may increase susceptibility to NMSC due to immunosuppression or other factors.3

Tofacitinib Represses the Janus Kinase-Signal Transducer and Activators of Transcription Signalling Pathway in Keratinocytes.

Tofacitinib is a Janus kinase (JAK) inhibitor, which has shown efficacy in treating psoriasis. The mode of action of tofacitinib is not completely understood but it has been thought to be mediated by the inhibition of CD4+ T-cell activation. Here, we investigated whether the molecular targets of tofacitinib are expressed in keratinocytes, and whether tofacitinib can modulate the activity of the JAK/Signal Transducer and Activators of Transcription (STAT)-pathway in keratinocytes. Transcriptomic profiling of human keratinocytes treated with IL-22 in combination with tofacitinib revealed that tofacitinib could prevent the majority of IL-22-mediated gene expression changes. Pathway analysis of tofacitinib-regulated genes in keratinocytes revealed enrichment of genes involved in the JAK/STAT signalling pathway. Quantitative real-time-PCR confirmed the upregulation of S100A7 and downregulation of EGR1 expression by IL-22, which was prevented by tofacitinib pre-treatment. These results indicate a direct effect of tofacinitib on keratinocytes, which can have relevance for systemic as well as for topical treatment of psoriasis with tofacitinib.

MicroRNA-146a suppresses IL-17-mediated skin inflammation and is genetically associated with psoriasis.

BACKGROUND: Psoriasis is an immune-mediated inflammatory skin disease with a strong genetic background in which activation of IL-17 signaling is central in the pathogenesis. Little has been known about the role of noncoding RNAs, including microRNAs (miRNAs), in predisposition to the disease. OBJECTIVE: We sought to investigate the genetic association of single nucleotide polymorphisms in microRNA-146a (miR-146a) to psoriasis and to explore its function in the initiation and resolution of the disease. METHODS: Analysis of the genetic association of miR-146a rs2910164 and psoriasis was carried out on 1546 patients with psoriasis and 1526 control subjects. The role of miR-146a in patients with psoriasis was assessed by using miR-146a-/- mice in conjunction with the imiquimod-induced mouse model of psoriasis. The severity of psoriasis-like skin inflammation was evaluated at morphologic, histologic, and molecular levels. miR-146a was ectopically overexpressed and inhibited in keratinocytes treated with IL-17. Synthetic miR-146a was injected intradermally into mice. RESULTS: Here we report protective association of a functional polymorphism in the miR-146a precursor (rs2910164). Genetic deficiency in miR-146a leads to earlier onset and exacerbated pathology of skin inflammation, with increased expression of IL-17-induced keratinocyte-derived inflammatory mediators, epidermal hyperproliferation, and increased neutrophil infiltration. Moreover, miR-146a-deficient mice do not resolve inflammation after discontinuation of imiquimod challenge. The overexpression of miR-146a suppressed, whereas its inhibition enhanced, IL-17-driven inflammation in keratinocytes. Functionally, miR-146a impairs the neutrophil chemoattractant capacity of keratinocytes. Finally, delivery of miR-146a mimics into the skin leads to amelioration of psoriasiform skin inflammation, decreased epidermal proliferation, and neutrophil infiltration. CONCLUSIONS: Our results define a crucial role for miR-146a in modulating IL-17-driven inflammation in the skin.

Granzyme A potentiates chemokine production in IL-17-stimulated keratinocytes.

Plaque psoriasis presents with focal skin inflammation, partially maintained by IL-17-mediated interactions between infiltrating epidermal T cells and activated keratinocytes. Here we show that the majority of lesional epidermal CD8 T cells express granzyme A, alone or in combination with IL-17. To assess proinflammatory properties of granzyme A in psoriasis, primary human keratinocytes were stimulated with granzyme A in the presence or absence of IL-17. Out of 33 analysed keratinocyte-derived inflammatory mediators, granzyme A potentiated IL-17-induced secretion of CXCL 1, CXCL 12 and CCL 4. Intriguingly, all three chemokines are implicated in psoriasis pathogenesis and are involved in recruitment of T cells, neutrophils and pDCs into inflamed tissues. Our results indicate that granzyme A produced by lesional CD8 T cells specifically increase the chemokine production from inflamed keratinocytes, thereby amplifying a chemotactic inflammatory loop that sustains psoriasis lesions.

Transition from inflammation to proliferation: a critical step during wound healing.

The ability to rapidly restore the integrity of a broken skin barrier is critical and is the ultimate goal of therapies for hard-to-heal-ulcers. Unfortunately effective treatments to enhance healing and reduce scarring are still lacking. A deeper understanding of the physiology of normal repair and of the pathology of delayed healing is a prerequisite for the development of more effective therapeutic interventions. Transition from the inflammatory to the proliferative phase is a key step during healing and accumulating evidence associates a compromised transition with wound healing disorders. Thus, targeting factors that impact this phase transition may offer a rationale for therapeutic development. This review summarizes mechanisms regulating the inflammation-proliferation transition at cellular and molecular levels. We propose that identification of such mechanisms will reveal promising targets for development of more effective therapies.

Sebocytes differentially express and secrete adipokines.

In addition to producing sebum, sebocytes link lipid metabolism with inflammation at a cellular level and hence, greatly resemble adipocytes. However, so far no analysis was performed to identify and characterize the adipocyte-associated inflammatory proteins, the members of the adipokine family in sebocytes. Therefore, we determined the expression profile of adipokines [adiponectin, interleukin (IL) 6, resistin, leptin, serpin E1, visfatin, apelin, chemerin, retinol-binding protein 4 (RBP4) and monocyte chemoattractant protein 1 (MCP1)] in sebaceous glands of healthy and various disease-affected (acne, rosacea, melanoma and psoriasis) skin samples. Sebaceous glands in all examined samples expressed adiponectin, IL6, resistin, leptin, serpin E1 and visfatin, but not apelin, chemerin, RBP4 and MCP1. Confirming the presence of the detected adipokines in the human SZ95 sebaceous gland cell line we further characterized their expression and secretion patterns under different stimuli mimicking bacterial invasion [by using Toll-like receptor (TLR)2 and 4 activators], or by 13-cis retinoic acid (13CRA; also known as isotretinoin), a key anti-acne agent. With the exception of resistin, the expression of all of the detected adipokines (adiponectin, IL6, leptin, serpin E1 and visfatin) could be further regulated at the level of gene expression, showing a close correlation with the secreted protein levels. Besides providing further evidence on similarities between adipocytes and sebocytes, our results strongly suggest that sebocytes are not simply targets of inflammation but may exhibit initiatory and modulatory roles in the inflammatory processes of the skin through the expression and secretion of adipokines.

Epidermal Th22 and Tc17 cells form a localized disease memory in clinically healed psoriasis.

Psoriasis is a common and chronic inflammatory skin disease in which T cells play a key role. Effective treatment heals the skin without scarring, but typically psoriasis recurs in previously affected areas. A pathogenic memory within the skin has been proposed, but the nature of such site-specific disease memory is unknown. Tissue-resident memory T (TRM) cells have been ascribed a role in immunity after resolved viral skin infections. Because of their localization in the epidermal compartment of the skin, TRM may contribute to tissue pathology during psoriasis. In this study, we investigated whether resolved psoriasis lesions contain TRM cells with the ability to maintain and potentially drive recurrent disease. Three common and effective therapies, narrowband-UVB treatment and long-term biologic treatment systemically inhibiting TNF-α or IL-12/23 signaling were studied. Epidermal T cells were highly activated in psoriasis and a high proportion of CD8 T cells expressed TRM markers. In resolved psoriasis, a population of cutaneous lymphocyte-associated Ag, CCR6, CD103, and IL-23R expressing epidermal CD8 T cells was highly enriched. Epidermal CD8 T cells expressing the TRM marker CD103 responded to ex vivo stimulation with IL-17A production and epidermal CD4 T cells responded with IL-22 production after as long as 6 y of TNF-α inhibition. Our data suggest that epidermal TRM cells are retained in resolved psoriasis and that these cells are capable of producing cytokines with a critical role in psoriasis pathogenesis. We provide a potential mechanism for a site-specific T cell-driven disease memory in psoriasis.

Economic Burden of Psoriasis and Potential Cost Offsets with Biologic Treatment: A Swedish Register Analysis.

Estimates of direct and indirect costs of psoriasis are limited. The aim of this study was to estimate: (i) costs in patients with psoriasis compared with controls; and (ii) impact on costs from initiating biologics. The study extracted data from Swedish administrative registers and compared 31,043 patients with 111,645 sex-, age- and residency-matched referents. Mean direct and indirect costs were estimated as US dollars (USD) 1,365 (62%) and USD 3,319 (50%) higher in patients compared with referents, respectively. The study included 352 patients treated with biologics who had at least 1-year follow-up before and after initiation of biologics. Among the 193 patients persistent with biologics for one year, 1-year costs of biologics were estimated at USD 23,293 (95% confidence interval (95% CI) 22,372-24,199). This cost was partially offset, with savings in direct cost estimated to range from USD -1135 (95% CI -2,050 to -328) to USD -4,422 (95% CI -6,552 to -2,771), depending on assumptions. The corresponding estimates for indirect costs savings were from USD -774 (95% CI -2,019-535) to USD -1,875 (95% CI -3,650 to -188). The study suggests that psoriasis is associated with substantial costs, which may be modifiable with treatment.

LC-MS metabolomics of psoriasis patients reveals disease severity-dependent increases in circulating amino acids that are ameliorated by anti-TNFα treatment.

Psoriasis is an immune-mediated highly heterogeneous skin disease in which genetic as well as environmental factors play important roles. In spite of the local manifestations of the disease, psoriasis may progress to affect organs deeper than the skin. These effects are documented by epidemiological studies, but they are not yet mechanistically understood. In order to provide insight into the systemic effects of psoriasis, we performed a nontargeted high-resolution LC-MS metabolomics analysis to measure plasma metabolites from individuals with mild or severe psoriasis as well as healthy controls. Additionally, the effects of the anti-TNFα drug Etanercept on metabolic profiles were investigated in patients with severe psoriasis. Our analyses identified significant psoriasis-associated perturbations in three metabolic pathways: (1) arginine and proline, (2) glycine, serine and threonine, and (3) alanine, aspartate, and glutamate. Etanercept treatment reversed the majority of psoriasis-associated trends in circulating metabolites, shifting the metabolic phenotypes of severe psoriasis toward that of healthy controls. Circulating metabolite levels pre- and post-Etanercept treatment correlated with psoriasis area and severity index (PASI) clinical scoring (R(2) = 0.80; p < 0.0001). Although the responsible mechanism(s) are unclear, these results suggest that psoriasis severity-associated metabolic perturbations may stem from increased demand for collagen synthesis and keratinocyte hyperproliferation or potentially the incidence of cachexia. Data suggest that levels of circulating amino acids are useful for monitoring both the severity of disease as well as therapeutic response to anti-TNFα treatment.

Psoriasis: in between the skin and the fat.

Substantial epidemiological evidence indicates that psoriasis associates with a predisposition to develop metabolic dysregulation leading to obesity and insulin resistance. However, the nature of this association and the potential underlying mechanisms remain unclear. In a recent report, Gerdes et al. explored the hypothesis that wingless-type MMTV integration site, Wnt5a, which has been linked to aberrant fat cell metabolism, may be driving this process. In this study, the authors compare circulating serum levels of Wnt5a in individuals with psoriasis and compare with healthy controls matched for age, gender and BMI. The bottom-line results show higher levels of Wnt5a in psoriasis patients irrespective of BMI compared to the matched non-psoriatic controls, indicating that psoriasis per se may result in increased secretion of Wnt5a into the circulation. In addition, there was a significant difference among patients with higher levels of Wnt5a in the obese psoriasis population. The study, even though being purely descriptive, may serve to inspire a more mechanistic approach exploring not only Wnt5a, but other inflammatory pathways in between the skin and the fat.

MicroRNA-31 is overexpressed in psoriasis and modulates inflammatory cytokine and chemokine production in keratinocytes via targeting serine/threonine kinase 40.

Psoriasis is characterized by a specific microRNA expression profile, distinct from that of healthy skin. MiR-31 is one of the most highly overexpressed microRNAs in psoriasis skin; however, its biological role in the disease has not been studied. In this study, we show that miR-31 is markedly overexpressed in psoriasis keratinocytes. Specific inhibition of miR-31 suppressed NF-κB-driven promoter luciferase activity and the basal and TNF-α-induced production of IL-1ß, CXCL1/growth-related oncogene-α, CXCL5/epithelial-derived neutrophil-activating peptide 78, and CXCL8/IL-8 in human primary keratinocytes. Moreover, interference with endogenous miR-31 decreased the ability of keratinocytes to activate endothelial cells and attract leukocytes. By microarray expression profiling, we identified genes regulated by miR-31 in keratinocytes. Among these genes, we identified serine/threonine kinase 40 (STK40), a negative regulator of NF-κB signaling, as a direct target for miR-31. Silencing of STK40 rescued the suppressive effect of miR-31 inhibition on cytokine/chemokine expression, indicating that miR-31 regulates cytokine/chemokine expression via targeting STK40 in keratinocytes. Finally, we demonstrated that TGF-ß1, a cytokine highly expressed in psoriasis epidermis, upregulated miR-31 expression in keratinocytes in vitro and in vivo. Collectively, our findings suggest that overexpression of miR-31 contributes to skin inflammation in psoriasis lesions by regulating the production of inflammatory mediators and leukocyte chemotaxis to the skin. Our data indicate that inhibition of miR-31 may be a potential therapeutic option in psoriasis.

Clinical characterisation at onset of childhood psoriasis - a cross sectional study in Sweden.

Epidemiological data in childhood psoriasis are accumulating. However, reliable information captured at onset is lacking. In a cross sectional study we recruited 109 children < 16 years within 12 months of psoriasis onset and explored the clinical characteristics. Pre-pubertal children, especially boys, more often had inverse involvement (OR = 2.8, 95% CI = 1.1, 7.1, p ≤ 0.05). HLA-C*06 was positively associated with facial lesions (OR = 3.8, 95% CI = 1.5, 9.7, p < 0.01) and guttate phenotype and was more common in pubertal children. A high PASI score was not associated with overweight or early age at onset, and gender did not influence disease onset. Psoriasis can be difficult to diagnose in children, especially in pre-pubertals. Thorough examination of facial and genital areas can help in establishing the diagnosis. Our published genetic data in combination with the clinical findings presented herein indicate that puberty may separate different populations of childhood psoriasis.