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Long-term management of inflammatory skin diseases is challenging because of side effects from repeated use of systemic treatments or topical corticosteroids. This study sought to identify the mechanisms and developmental therapeutics for these diseases using genetic models and pharmacological approaches. We found that mice overexpressing SMAD7 in keratinocytes but not mice overexpressing the N-terminal domain of SMAD7 (i.e., N-SMAD7) were resistant to imiquimod-induced T helper 1/17- and T helper 2-type inflammation. We generated a Tat-PYC-SMAD7 (truncated SMAD7 protein encompassing C-terminal SMAD7 and PY motif fused with cell-penetrating Tat peptide). Topically applied Tat-PYC-SMAD7 to inflamed skin entered cells upon contact and attenuated imiquimod-, 2,4-dinitrofluorobenzene-, and tape-stripping-induced inflammation. RNA-sequencing analyses of mouse skin exposed to these insults showed that in addition to inhibiting TGFβ/NF-κB, SMAD7 blunted IL-22/signal transducer and activator of transcription 3 activation and associated pathogenesis, which is due to SMAD7 transcriptionally upregulating IL-22 antagonist IL-22RA2. Mechanistically, SMAD7 facilitated nuclear translocation and DNA binding of C/EBPβ to IL22RA2 promoter for IL22RA2 transactivation. Consistent with the observations in mice mentioned earlier, transcript levels of IL22RA2 were increased in human atopic dermatitis and psoriasis lesions with clinical remission. Our study identified the anti-inflammation functional domain of SMAD7 and suggests the mechanism and feasibility for developing SMAD7-based biologics as a topical therapy for skin inflammatory disorders.

Tape stripping is a minimally invasive, nonscarring method that can be utilized to assess gene expression in the skin but is infrequently used given technical constraints. By comparing different tape stripping technologies and full-thickness skin biopsy results of lesional and nonlesional psoriatic skin from the same patients, we demonstrate that tape stripping with optimized high-resolution transcriptomic profiling can be used to effectively assess and characterize inflammatory responses in the skin. Upon comparison with single-cell RNA-sequencing data from psoriatic full-thickness skin biopsies, we illustrate that tape-stripping efficiently captures the transcriptome of the upper layers of the epidermis with sufficient resolution to assess the molecular components of the feed-forward immune amplification pathway in psoriasis. Notably, nonlesional psoriatic skin sampled by tape stripping demonstrates activated, proinflammatory changes when compared to healthy control skin, suggesting a prepsoriatic state, which is not captured on full-thickness skin biopsy transcriptome profiling. This work illustrates an approach to assess inflammatory response in the epidermis by combining noninvasive sampling with high throughput RNA-sequencing, providing a foundation for biomarker discoveries and mechanism of action studies for inflammatory skin conditions.

Bile acids (BAs), produced in the liver and further transformed in the gut, are cholesterol-derived molecules involved in essential physiological processes. Recent studies suggest that BAs regulate T helper 17 cell function, but the underlying mechanism of this action and their therapeutic value in disease models remains unclear. Using an IL-23 minicircle DNA-based murine model of psoriasiform dermatitis, we showed that oral administration of secondary BAs, including lithocholic acid (LCA), deoxycholic acid, and 3-oxoLCA, significantly improved psoriasiform dermatitis without inducing apparent hepatotoxicity. Of the BAs tested, LCA possessed the greatest potency in treating psoriasiform dermatitis. Intravenous administration of LCA at a much lower dosage (compared with oral treatment) showed a comparable antipsoriatic effect and markedly suppressed the IL-17A response. Ex vivo experiments revealed that LCA reduced IL-17A production in IL-23-stimulated murine T cells in the absence of BA receptors TGR5 or FXR. Strikingly, BAs inhibited CCL20 expression in keratinocytes, which led to reduced migration of CCR6-expressing Jurkat cells cultured in the conditioned medium of stimulated keratinocytes. Thus, BAs improve psoriasiform dermatitis with minimal toxicity via direct inhibition of IL-17A production and blockade of CCL20-mediated trafficking, supporting the potential use of BAs in psoriasis.

Skin epidermis constitutes the exterior barrier that protects the body from dehydration and environmental assaults. Barrier defects underlie common inflammatory skin diseases, but the molecular mechanisms that maintain barrier integrity and regulate epidermal-immune cell cross-talk in inflamed skin are not fully understood. In this study, we show that skin epithelia-specific deletion of Ovol1, which encodes a skin disease‒linked transcriptional repressor, impairs the epidermal barrier and aggravates psoriasis-like skin inflammation in mice in part by enhancing neutrophil accumulation and abscess formation. Through molecular studies, we identify IL-33, a cytokine with known pro-inflammatory and anti-inflammatory activities, and Cxcl1, a neutrophil-attracting chemokine, as potential weak and strong direct targets of Ovol1, respectively. Furthermore, we provide functional evidence that elevated Il33 expression reduces disease severity in imiquimod-treated Ovol1-deficient mice, whereas persistent accumulation and epidermal migration of neutrophils exacerbate it. Collectively, our study uncovers the importance of an epidermally expressed transcription factor that regulates both the integrity of the epidermal barrier and the behavior of neutrophils in psoriasis-like inflammation.

Psoriasis is a chronic immune-mediated disease characterized by excessive proliferation of epidermal keratinocytes and increased immune cell infiltration to the skin. Although it is well-known that psoriasis pathogenesis is driven by aberrant production of proinflammatory cytokines, the mechanisms underlying the imbalance between proinflammatory and anti-inflammatory cytokine expression are incompletely understood. In this study, we report that the transcriptional coregulators CtBP1 and 2 can transactivate a common set of proinflammatory genes both in the skin of imiquimod-induced mouse psoriasis model and in human keratinocytes and macrophages stimulated by imiquimod. We find that mice overexpressing CtBP1 in epidermal keratinocytes display severe skin inflammation phenotypes with increased expression of T helper type 1 and T helper type 17 cytokines. We also find that the expression of CtBPs and CtBP-target genes is elevated both in human psoriatic lesions and in the mouse imiquimod psoriasis model. Moreover, we were able to show that topical treatment with a peptidic inhibitor of CtBP effectively suppresses the CtBP-regulated proinflammatory gene expression and thus attenuates psoriatic inflammation in the imiquimod mouse model. Together, our findings suggest to our knowledge previously unreported strategies for therapeutic modulation of the immune response in inflammatory skin diseases.

"Skin Sodium Accumulates in Psoriasis and Reflects Disease Severity" (Maifeld et al., 2021) showed that skin sodium ion (Na+) is increased in patients with a PASI > 5. Na+ concentration as well as its content were increased in these patients, supporting the proposed mechanism that increased Na+ concentrations enhance IL-17 expression from CD4+ cells. These data initially were generated using a noninvasive technique, sodium (23Na) magnetic resonance imaging, and then were verified using 23Na spectroscopy and atomic absorption spectrometry in ashed-skin biopsies in humans and also using mouse models of psoriasis. These findings suggest a novel pathologic mechanism for psoriasis development and target for treatment.

Many inflammatory skin diseases are characterized by altered epidermal differentiation. Whether this altered differentiation promotes inflammatory responses has been unknown. Here, we show that IRAK2, a member of the signaling complex downstream of IL-1 and IL-36, correlates positively with disease severity in both atopic dermatitis and psoriasis. Inhibition of epidermal IRAK2 normalizes differentiation and inflammation in two mouse models of psoriasis- and atopic dermatitis-like inflammation. Specifically, we demonstrate that IRAK2 ties together proinflammatory and differentiation-dependent responses and show that this function of IRAK2 is specific to keratinocytes and acts through the differentiation-associated transcription factor ZNF750. Taken together, our findings suggest that IRAK2 has a critical role in promoting feed-forward amplification of inflammatory responses in skin through modulation of differentiation pathways and inflammatory responses.

Although psoriasis and psoriatic arthritis (PsA) have been classically considered to be diseases of the skin and joints, respectively, emerging evidence suggests that a combination of innate and environmental factors creates widespread immune dysfunction, affecting multiple organ systems. A greater understanding of the pathogenesis of psoriasis and the systemic effects of psoriatic inflammation has allowed for the development of new, more effective treatments. The second portion of this two-part review series examines the comorbidities associated with psoriasis and PsA as well as the most recent advances in targeted systemic therapies for these conditions.

Psoriasis is a chronic inflammatory condition characterized by systemic immune dysregulation. Over the past several years, advances in genetics, microbiology, immunology, and mouse models have revealed the complex interplay between the heritable and microenvironmental factors that drive the development of psoriatic inflammation. In the first of this two-part review series, the authors will discuss the newest insights into the pathogenesis of psoriatic disease and highlight how the evolution of these scientific fields has paved the way for a more personalized approach to psoriatic disease treatment.

We previously showed that exposure to a high-sugar and moderate-fat diet (i.e., Western diet [WD]) in mice induces appreciable skin inflammation and enhances the susceptibility to imiquimod-induced psoriasiform dermatitis, suggesting that dietary components may render the skin susceptible to psoriatic inflammation. In this study, utilizing an IL-23 minicircle-based model with features of both psoriasiform dermatitis and psoriatic arthritis, we showed that intake of WD for 10 weeks predisposed mice not only to skin but also to joint inflammation. Both WD-induced skin and joint injuries were associated with an expansion of IL-17A‒producing γδ T cells and increased expression of T helper type 17 cytokines. After IL-23 minicircle delivery, WD-fed mice had reduced microbial diversity and pronounced dysbiosis. Treatment with broad-spectrum antibiotics suppressed IL-23‒mediated skin and joint inflammation in the WD-fed mice. Strikingly, reduced skin and joint inflammation with a partial reversion of the gut microbiota were noted when mice switched from a WD to a standard diet after IL-23 minicircle delivery. These findings reveal that a short-term WD intake‒induced dysbiosis is accompanied by enhanced psoriasis-like skin and joint inflammation. Modifications toward a healthier dietary pattern should be considered in patients with psoriatic skin and/or joint disease.

Psoriasis is a common inflammatory skin disease characterized by aberrant inflammation and epidermal hyperplasia. Molecular mechanisms that regulate psoriasis-like skin inflammation remain to be fully understood. Here, we show that the expression of Ovol1 (encoding ovo-like 1 transcription factor) is upregulated in psoriatic skin, and its deletion results in aggravated psoriasis-like skin symptoms following stimulation with imiquimod. Using bulk and single-cell RNA sequencing, we identify molecular changes in the epidermal, fibroblast, and immune cells of Ovol1-deficient skin that reflect an altered course of epidermal differentiation and enhanced inflammatory responses. Furthermore, we provide evidence for excessive full-length IL-1α signaling in the microenvironment of imiquimod-treated Ovol1-deficient skin that functionally contributes to immune cell infiltration and epidermal hyperplasia. Collectively, our study uncovers a protective role for OVOL1 in curtailing psoriasis-like inflammation and the associated skin pathology.

A Western diet (WD)-characterized by its high fat and simple sugar content-is thought to predispose individuals to inflammatory skin diseases such as psoriasis through the development of obesity. This scenario, however, is being challenged by emerging data suggesting that dietary components, rather than obesity itself, may exacerbate psoriasis. We herein show that short-term feeding with a diet analogous to the WD in mice leads to T helper type 1-/T helper type 17-biased skin inflammation before significant body weight gain. Feeding for as little as 4 weeks with a WD promoted mild dermatitis and accumulation of IL-17A-producing γδ T cells in the skin. Strikingly, γδ T cells from WD-fed mice exhibited enriched IL-23 receptor expression and increased the potential to produce IL-17A after IL-23 stimulation. In contrast to wild-type mice, WD-fed TCRδ-deficient and CCR6-deficient mice had reduced skin inflammation and IL-17A expression. Supplementation with a bile acid sequestrant, cholestyramine, prevented WD-induced skin inflammation along with a reduction in the infiltration of γδ T cells and the expression of proinflammatory mediators. In summary, our data revealed dietary influences in inflammatory signaling in the skin. The dysregulation of IL-23 pathways and bile acid pathways may be key to the development of WD-associated psoriasiform dermatitis.

Atopic dermatitis (AD) affects up to 20% of children and adults worldwide. To gain a deeper understanding of the pathophysiology of AD, we conducted a large-scale transcriptomic study of AD with deeply sequenced RNA-sequencing samples using long (126-bp) paired-end reads. In addition to the comparisons against previous transcriptomic studies, we conducted in-depth analysis to obtain a high-resolution view of the global architecture of the AD transcriptome and contrasted it with that of psoriasis from the same cohort. By using 147 RNA samples in total, we found striking correlation between dysregulated genes in lesional psoriasis and lesional AD skin with 81% of AD dysregulated genes being shared with psoriasis. However, we described disease-specific molecular and cellular features, with AD skin showing dominance of IL-13 pathways, but with near undetectable IL-4 expression. We also demonstrated greater disease heterogeneity and larger proportion of dysregulated long noncoding RNAs in AD, and illustrated the translational impact, including skin-type classification and drug-target prediction. This study is by far the largest study comparing the AD and psoriasis transcriptomes using RNA sequencing and demonstrating the shared inflammatory components, as well as specific discordant cytokine signatures of these two skin diseases.

Genetic variation in the NF-κB inhibitors, ABIN1 and A20, increase risk for psoriasis. While critical for hematopoietic immune cell function, these genes are believed to additionally inhibit psoriasis by dampening inflammatory signaling in keratinocytes. We dissected ABIN1 and A20s regulatory role in human keratinocyte inflammation using an RNA sequencing-based comparative genomic approach. Here we show subsets of the IL-17 and tumor necrosis factor-α signaling pathways are robustly restricted by A20 overexpression. In contrast, ABIN1 overexpression inhibits these genes more modestly for IL-17, and weakly for tumor necrosis factor-α. Our genome-scale analysis also indicates that inflammatory program suppression appears to be the major transcriptional influence of A20/ABIN1 overexpression, without obvious influence on keratinocyte viability genes. Our findings thus enable dissection of the differing anti-inflammatory mechanisms of two distinct psoriasis modifiers, which may be directly exploited for therapeutic purposes. Importantly, we report that IL-17-induced targets of A20 show similar aberrant epidermal layer-specific transcriptional upregulation in keratinocytes from diseases as diverse as psoriasis, atopic dermatitis, and erythrokeratodermia variabilis, suggesting a contributory role for epidermal inflammation in a broad spectrum of rashes.

This 12-month, pragmatic, randomized controlled equivalency trial evaluated whether an online, collaborative connected-health model results in equivalent improvements in quality of life compared with in-person care for psoriasis. Overall, 296 adults with physician-diagnosed psoriasis from ambulatory clinics were randomly assigned to either online or in-person care; all were analyzed for outcomes. In the online group, patients and primary care providers sought dermatologists' care directly and asynchronously online. The in-person group sought care face to face. Interventions did not allow blinding of participants; investigators were blinded during analysis. Across 12 months, for the online group, the mean ± standard deviation decline in Skindex-16 from baseline across follow-up visits was 9.02 ± 20.67 compared with 10.55 ± 23.50 for the in-person group. The difference in Skindex-16 between the two groups was -0.83 (95% confidence interval = -5.18 to 3.51), and this was within the equivalence margin (±7.0). For the online group, the mean ± standard deviation decline in Dermatology Life Quality Index was 1.64 ± 4.34 compared with 1.18 ± 4.77 for the in-person group. The difference in Dermatology Life Quality Index between the two groups was -0.45 (95% confidence interval = -1.29 to 0.38) and was within the equivalence margin (±2.5). In conclusion, the online model was as effective as in-person care in improving quality of life among psoriasis patients. This study was funded by the Patient-Centered Outcomes Research Institute and is registered on clinicaltrials.gov (NCT02358135).

As medicine advances, cures are being found for diseases that were previously considered incurable, as is the case for some types of cancer. Traditionally, the term cure is reserved for resolution of disease, both at a clinical and a molecular level, which continues after cessation of treatment. Biologic therapies have revolutionized the definition of remission in severe psoriasis, with some patients achieving long-lasting disease suppression, but the disease nearly always relapses on withdrawal of the drug. Our improved understanding of the pathomechanisms of psoriasis, coupled with anecdotal reports of long-term clearance of the disease after cell-based therapies, leads us to the hypothesis that psoriasis is curable. We propose that cure of psoriasis can be achieved by restoring immune homeostasis through a combinatorial, personalized medicine approach encompassing early intervention to include biologics, advanced therapeutics, and lifestyle modification., (Copyright © 2024 The Authors. Published by Elsevier Inc. All rights reserved.)

Imaging mass cytometry is a technology that enables comprehensive analysis of cellular phenotypes at the tissue level. We performed a multiparameter characterization of structural and immune cell populations in psoriatic skin and synovial tissue samples aimed at characterizing immune cell differences in patients with psoriasis and psoriatic arthritis. A panel of 33 antibodies was used to stain selected immune and structural cell populations. Imaging mass cytometry data were segmented into single cells on the basis of combinations of antibody stains. Single cells were then clustered into cell categories on the basis of prespecified markers. The spatial relationships of different cell populations were assessed using neighborhood analysis. Among all cell types in the skin and synovium, lymphoid cells accounted for the most prevalent cell type. T cells and macrophages were the most prevalent immune cell type in the synovium, and B cells and NK cells were also identified. Neighborhood analysis showed high correlation between synovial T cells, B cells, macrophages, dendritic cells, and neutrophils, suggesting spatial organization. Innate and adaptive immune cells can be reliably identified using imaging mass cytometry in the skin and synovium. Interpatient heterogeneity exists in tissue cell populations. Imaging mass cytometry provides opportunities for exploring in depth the underlying immunological mechanisms driving psoriasis and psoriatic arthritis., (Copyright © 2024 The Authors. Published by Elsevier Inc. All rights reserved.)

The expressions of long noncoding RNAs (lncRNAs) and their roles in epidermal differentiation have been previously defined using bulk RNA sequencing. Despite their tissue-specific expression profiles, most lncRNAs are not well-annotated at the single-cell level. In this study, we evaluated the use of single-cell RNA sequencing to profile and characterize lncRNAs using data from 6 patients with psoriasis with paired uninvolved and lesional psoriatic skin. Despite their overall lower expression, we were able to detect >7000 skin-expressing lncRNAs and their cellular sources. Differential gene expression analysis revealed 137 differentially expressed lncRNAs in lesional psoriasis skin and identified 169 cell-type-specific lncRNAs. Keratinocytes had the highest number of differentially expressed lncRNA in psoriatic skin, which we validated using spatial transcriptomic data. We further showed that expression of the keratinocyte-specific lncRNA, AC020916.1, upregulated in lesional skin, is significantly correlated with expressions of genes participating in cell proliferation/epidermal differentiation, including SPRR2E and transcription factor ZFP36, particularly in the psoriatic skin. Our study highlights the potential for using single-cell RNA sequencing to profile skin-expressing lncRNA transcripts and to infer their cellular origins, providing a crucial approach that can be applied to the study of other inflammatory skin conditions., (Copyright © 2024. Published by Elsevier Inc.)

A precise regulation of gene expression depends on the accuracy of the 3-dimensional (3D) structure of chromatin; however, the effects of the 3D genome on gene expression in psoriasis remain unknown. In this study, we conducted Hi-C and RNA sequencing on CD4+ T cells collected from 5 patients with psoriasis and 3 healthy controls and constructed a comprehensive 3D chromatin interaction map to delineate the genomic hierarchies, including A/B compartments, topologically associated domains, and chromatin loops. Then, the specific superenhancers related to psoriasis were identified by Hi-C and H3K27ac chromatin immunoprecipitation sequencing data. Subsequently, comprehensive analyses were carried out on the differentially expressed genes that are associated with altered topologically associated domains, loops, and superenhancers in psoriasis. Finally, we screened the candidate target genes and examined the potential functional SNP in psoriasis affected by disruptions of the spatial organization. This study provides a comprehensive reference for examining the 3D genome interactions in psoriasis and elucidating the interplay between spatial organization disruption and gene regulation. We hope that our findings can help clarify the mechanisms underlying the pathogenesis of psoriasis and shed light on the role of 3D genomic structure, therefore informing potential therapeutic approaches., (Copyright © 2024 The Authors. Published by Elsevier Inc. All rights reserved.)

Systemic inflammation or insulin resistance drive atherosclerosis. However, they are difficult to capture for assessing cardiovascular risk in clinical settings. The monocyte-to-high-density lipoprotein ratio (MHR) is an accessible biomarker that integrates inflammatory and metabolic information and has been associated with poorer cardiovascular outcomes. Our aim was to evaluate the association of MHR with the presence of subclinical atherosclerosis in patients with psoriasis. The study involved a European and an American cohort including 405 patients with the disease. Subclinical atherosclerosis was assessed by coronary computed tomography angiography. First, MHR correlated with insulin resistance through homeostatic model assessment for insulin resistance, with high-sensitivity CRP and with 18 F-fluorodeoxyglucose uptake in spleen, liver, and bone marrow by positron emission tomography/computed tomography. MHR was associated with both the presence of coronary plaques >50% of the artery lumen and noncalcified coronary burden, beyond traditional cardiovascular risk factors (P < .05). In a noncalcified coronary burden prediction model accounting for cardiovascular risk factors, statins, and biologic treatment, MHR added value (area under the curve base model = 0.72 vs area under the curve base model plus MHR = 0.76, P = .04) within the American cohort. These results suggests that MHR may detect patients with psoriasis who have subclinical burden of cardiovascular disease and warrant more aggressive measures to reduce lifetime adverse cardiovascular outcomes., (Copyright © 2024 The Authors. Published by Elsevier Inc. All rights reserved.)

Vascular endothelial cells (ECs), the inner layer of blood vessels, were previously considered to be a passive lining that facilitates cellular and molecular exchange. However, recent studies have revealed that ECs can respond to various stimuli and actively regulate vascular function and skin inflammation. Specific subtypes of ECs are known to have significant roles in a diverse range of physiological and pathological processes in the skin. This review suggests that EC dysfunction is both causal and consequential in the pathogenesis of psoriasis. Further investigations into dysregulated pathways in EC dysfunction may provide new insights for the treatment of psoriasis., (Copyright © 2024 The Authors. Published by Elsevier Inc. All rights reserved.)

Monocytes play a critical role in the inflammation associated with psoriasis, and their abnormalities have been reported as biomarkers of cardiovascular event risk, a psoriasis comorbidity. Monocytic cells in chronic inflammatory disorders express elevated levels of cAMP phosphodiesterase. Restoring cAMP levels using the oral cAMP phosphodiesterase-4 inhibitor, apremilast, improves clinical outcomes for a subset of patients with psoriasis. We asked whether aberrant monocyte subsets or transcriptomic pathways can function as biomarkers of psoriasis endotypes that can predict enhanced clinical responses to cAMP phosphodiesterase inhibition. A 16-week open-label study of 22 patients with monocyte flow cytometric and transcriptomic analysis was performed. Subjects with elevated hyperadhesive monocyte doublets at baseline were more likely to be responders to apremilast (P < .0001); 82% of subjects with elevated hyperadhesive monocyte doublets achieved 50% reduction in PASI compared with 46% in those without elevated doublets. We observed a significant reduction in hyperadhesive monocyte-containing doublets and monocyte-platelet aggregates, suggesting an effect of apremilast on the adhesiveness of blood monocytes during chronic inflammation. Monocyte differentially expressed gene transcripts predictive of clinical response uncovered pharmacoendotypes with distinct patterns of nucleotide metabolism, energetics, and differentiation. Further study to understand the basis of drug responsiveness and to develop an apremilast psoriasis treatment algorithm using monocyte-refined gene expression is required to validate and become practical in clinical use, offering patients a test that personalizes their likelihood of clinical response., (Copyright © 2024 The Authors. Published by Elsevier Inc. All rights reserved.)

We used RNA sequencing to study and characterize the long noncoding RNA (lncRNA) transcriptome in lesional skin from psoriasis patients before (PP) and after treatment (PT) with adalimumab and in normal skin from healthy individuals (NN). To this end, we sequenced total RNA from 18 psoriasis patients and 16 healthy controls. We merged three lncRNA reference datasets to create a single combined reference of 67,157 lncRNA transcripts with no overlaps. We identified differential expression of 971 lncRNAs between PP and NN, 157 between PP and PT, and 377 between PT and NN. Using differentially expressed lncRNAs between PP and NN, we identified a molecular lncRNA signature that distinguishes psoriatic skin from healthy skin. Furthermore, we performed an unsupervised hierarchical analysis that revealed distinct clustering of PP samples from NN. A coding noncoding network analysis revealed a large network of highly correlated lncRNA and protein coding transcripts that provided insight into the potential functions of unannotated lncRNAs. To the best of our knowledge, this description of both polyadenylated as well as nonpolyadenylated lncRNA transcripts in psoriasis has not been previously reported. Our findings highlight the potential importance of lncRNAs in the biology of psoriasis and response to treatment.

Hidradenitis suppurativa (HS) is a chronic inflammatory disease that is difficult to control, and its mechanism remains unclear. Hepatocyte GF (HGF) has been reported to be significantly upregulated in the serum and skin of patients with HS, especially in the lesions with tunnels. In this study, we examined the transcriptome of HGF-treated keratinocytes and compared it with genetic profiling of HS lesions. HGF was highly expressed in HS skin, especially in the deep dermis, compared with that in healthy controls, and its source was mainly fibroblasts. HGF upregulated more genes in keratinocytes than IL-17A or TNF-a, and these genes included multiple epithelial-mesenchymal transition-related genes. Differentially expressed genes in HGF-stimulated keratinocytes were involved in activation of epithelial-mesenchymal transition-related pathways. These HGF-induced genes were significantly upregulated in HS lesions compared with those in healthy skin and nonlesions and were more strongly associated with HS tunnels. In summary, HGF was highly expressed in HS and induced epithelial-mesenchymal transition-related genes in keratinocytes; HGF-induced genes were highly associated with gene profiling of HS with tunnels, suggesting that HGF may be involved in HS tunnel formation through epithelial-mesenchymal transition., (Copyright © 2024 The Authors. Published by Elsevier Inc. All rights reserved.)

Psoriasis is a chronic and relapsing inflammatory skin disorder characterized by keratinocyte hyperproliferation and immune cell infiltration. LPCAT1 has been identified as a cancer promoter in cutaneous squamous cell carcinoma by us, yet its role in psoriasis remains elusive. In this study, we report that LPCAT1 is highly expressed in psoriatic skin lesions. LPCAT1 promotes keratinocyte hyperproliferation and enhances the secretion of IL-1β, IL-6, CXCL10, CCL20, S100A9, and platelet-activating factor. In psoriasiform keratinocytes, LPCAT1 promotes proliferation and inflammatory mediator production by activating protein kinase B/NF-κB and signal transducer and activator of transcription 3 signaling pathways. Furthermore, LPCAT1 inhibition attenuated epidermal hyperplasia and relieved skin inflammation in imiquimod-treated mice. Importantly, we identify the glucose transporter GLUT3, a recently reported promising target to mitigate T helper 17 cell-mediated inflammatory diseases, as a critical downstream effector of LPCAT1. GLUT3 deficiency impaired the proliferation and inflammation of psoriatic keratinocytes. LPCAT1 regulates GLUT3 in keratinocytes through NF-κB/signal transducer and activator of transcription 3 signaling, enhancing keratinocyte glycolysis and promoting proproliferative and proinflammatory effects. In addition, suppressing GLUT3 in mice alleviated imiquimod-induced dermatitis. Taken together, our study indicates the critical role of the LPCAT1-GLUT3 axis in psoriasis pathogenesis and proposes LPCAT1 or GLUT3 as a potential therapeutic target for psoriasis., (Copyright © 2024 The Authors. Published by Elsevier Inc. All rights reserved.)

The migration of γδ T lymphocytes toward skin lesions and their concomitant pathogenic IL-17A production play a crucial role in the pathogenesis of psoriasis. However, the regulatory mechanisms of IL-17A production by γδ T cells and their migration remain to be fully explored. Intracellular GRP78 is a molecular chaperone that regulates endoplasmic reticulum stress, whereas secretory GRP78, as a member of the resolution-associated molecular patterns, exerts immunoregulatory effects. In this study, we reported that both the intracellular GRP78 in skin lesions and secretory GRP78 in the serum were significantly decreased in patients with psoriasis. A GRP78 knockdown exacerbated imiquimod-induced skin inflammation, whereas the application of recombinant GRP78 protein or BIP inducer X (a GRP78 inducer) attenuated the dermatitis. Mechanistically, the GRP78 knockdown in keratinocytes enhanced the production of chemokines, specifically CCL20, which regulates γδ T-cell migration. Moreover, recombinant GRP78 was found to directly bind to γδ T cells to suppress its migration ability and proinflammatory capacities by downregulating the CCR6 and IL-17A expression. Collectively, our results uncovered a pivotal role of GRP78 in the pathogenesis of psoriasis, which was mainly exerted by regulating the interaction between keratinocytes and γδ T cells, and might provide a promising target for psoriasis therapy., (Copyright © 2024 The Authors. Published by Elsevier Inc. All rights reserved.)

AP-2 transcription factors regulate ectodermal development, but their roles in epidermal homeostasis in adult skin are unknown. We find that AP-2α is the predominant AP-2 family member in adult epidermis, followed by AP-2β. Through inactivation of AP-2α, AP-2β, or both in keratinocytes, we assessed the effects of a gradient of epidermal AP-2 activity on skin function. We find that (i) loss of AP-2β in keratinocytes is compensated for by AP-2α, (ii) loss of AP-2α impairs terminal keratinocyte differentiation and hair morphogenesis, and (iii) the combined loss of AP-2α/AP-2β results in more severe skin and hair abnormalities. Keratinocyte differentiation defects precede progressive neutrophilic skin inflammation. Inducible inactivation of AP-2α/AP-2β in the adult phenocopies these manifestations. Transcriptomic analyses of epidermis lacking AP-2α or AP-2α/AP-2β in keratinocytes demonstrate a terminal keratinocyte differentiation defect with upregulation of alarmin keratins and of several immune pathway regulators. Moreover, our analyses suggest a key role of reduced AP-2α-dependent gene expression of CXCL14 and the keratin 15 gene K15 as an early pathogenic event toward the manifestation of skin inflammation. Thus, AP-2α and AP-2β are critical regulators of epidermal homeostasis in adult skin., (Copyright © 2024 The Authors. Published by Elsevier Inc. All rights reserved.)

Although a peak incidence of psoriasis in women aged around 60 years has been observed, the link between reproductive lifespan and late-onset psoriatic diseases is underexplored. This study aims to elucidate the association between reproductive lifespan and the risk of late-onset psoriasis and psoriatic arthritis (PsA). Utilizing the UK Biobank data, we conducted a prospective cohort study in postmenopausal women without baseline psoriatic diseases. The exposure variables included age at natural menopause (ANM) and duration from menarche to menopause, termed reproductive years. The outcome variables were incident psoriasis and PsA. We employed Cox regression analysis, factoring in polygenic risk scores for psoriatic diseases and recognized risk factors. We found that later ANM and longer reproductive years were significantly associated with decreased risks of late-onset psoriasis and PsA in a dose-dependent manner (P<.05). ANM after age 55 years led to a 34 and 46% risk reduction in late-onset psoriasis and PsA, respectively, compared with ANM before age 45 years (P<.001). The population-attributable risks of ANM were 17.4% for late-onset psoriasis and 21.6% for PsA. In conclusion, reproductive lifespan, with its inherent homeostasis, plays a pivotal yet overlooked role in late-onset psoriatic diseases. Investigations into estrogen-centric causes and sex-specific interventions are imperative., (Copyright © 2023 The Authors. Published by Elsevier Inc. All rights reserved.)

Psoriasis is a chronic inflammatory skin disease driven by aberrant signals from the immune system. In this issue, Li et al. present the first large RNA-seq analysis of gene expression in normal skin and psoriasis lesions, providing a more comprehensive view of mRNA expression than earlier microarray studies. This study's size enables gene co-expression analysis, a method illustrating which pathways are altered by the presence of disease.

Psoriasis is an inflammatory skin disease with an estimated heritability of around 70%. Previous GWASs have detected several risk loci for psoriasis. To further improve the understanding of the genetic risk factors impacting the disease, we conducted a discovery GWAS in FinnGen and a subsequent replication and meta-analysis with data from the Estonian Biobank and the UK Biobank; the study sample included 925,649 individuals (22,659 cases and 902,990 controls), the largest sample for psoriasis yet. In addition, we conducted downstream analyses to find out more about psoriasis' cross-trait genetic correlations and causal relationships. We report 6 risk loci, which, to our knowledge, are previously unreported, most of which harbor genes related to NF-κB signaling pathway and overall immunity. Genetic correlations highlight the relationship between psoriasis and smoking, higher body weight, and lower education level. In addition, we report causal relationships between psoriasis and mood symptoms as well as 2-directioned causal relationship between psoriasis and lower education level. Our results provide further knowledge on psoriasis risk factors, which may be useful in the development of future treatment strategies., (Copyright © 2024 The Authors. Published by Elsevier Inc. All rights reserved.)

Psoriasis and rosacea are both chronic inflammatory skin disorders resulted from aberrant keratinocyte-immune cell crosstalk, but the common molecular foundations for these 2 conditions are poorly understood. In this study, we reveal that both patients with psoriasis and those with rosacea as well as their mouse models have significantly elevated expressions of SERPINB3/B4 (members of serine protease inhibitor) in the lesional skin. Skin inflammation in mice that resembles both psoriasis and rosacea is prevented by SERPINB3/B4 deficiency. Mechanistically, we demonstrate that SERPINB3/B4 positively induces NF-κB signaling activation, thereby stimulating disease-characteristic inflammatory chemokines and cytokines production in keratinocytes and promoting the chemotaxis of CD4 + T cells. Our results suggest that in keratinocytes, SERPINB3/B4 may be involved in the pathogenesis of both psoriasis and rosacea by stimulating NF-κB signaling, and they indicate a possible treatment overlap between these 2 diseases., (Copyright © 2024 The Authors. Published by Elsevier Inc. All rights reserved.)

Whether childhood obesity or weight gain leads to the development of pediatric immune-mediated skin diseases remains unclear. We aimed to determine the associations between body mass index or body mass index changes and the development of 3 main immune-mediated skin diseases-alopecia areata, atopic dermatitis (AD), and psoriasis-by analyzing a longitudinal cohort of 2,161,900 Korean children from 2009 to 2020. The findings indicated that children who were obese had a higher risk of pediatric immune-mediated skin diseases than those with normal weight (P for trend < .01). An increase in body mass index was associated with a higher risk of AD, whereas a decrease in body mass index was correlated with a reduced risk of AD. Children who gained weight, transitioning from normal to overweight, exhibited a higher AD risk than those who maintained a normal weight (adjusted hazard ratio = 1.15, 95% confidence interval = 1.11-1.20). However, those who shifted from being overweight to achieving a normal weight (adjusted hazard ratio = 0.87, 95% confidence interval = 0.81-0.94) had a lower AD risk than children who were overweight who maintained their weight. In summary, early childhood obesity may increase the risk of pediatric immune-mediated skin diseases. Weight gain may increase AD risk, whereas weight loss may lower the risk., (Copyright © 2024 The Authors. Published by Elsevier Inc. All rights reserved.)

Previously, we showed that the combination of methotrexate and adalimumab treatment leads to less antidrug antibody development. In this study, we quantify the pharmacokinetics/pharmacodynamics (PK/PD) of adalimumab and evaluate the influence of methotrexate cotreatment. A population PK-PD model was developed using prospective data from 59 patients with psoriasis (baseline PASI = 12.6) receiving adalimumab over 49 weeks. Typical PK and PD parameters and their corresponding interpatient variability were estimated. We performed a covariate analysis to assess whether interpatient variability could be explained by addition of methotrexate and other covariates. In total, 330 PASIs, 252 adalimumab serum concentrations, and 247 antidrug antibody titers were available. Presence of antidrug antibodies (adalimumab group = 46.7%, adalimumab + methotrexate group = 38.7%; P = .031) was correlated with increased adalimumab apparent clearance (P < .001). In the PD model, the use of concomitant methotrexate was borderline to significantly correlated with a decreased half-maximal inhibitory concentration (adalimumab concentration for which clinical response score is reduced by half; P < .10). On the basis of our PK-PD model, concomitant use of methotrexate indirectly increases adalimumab concentration, partially through less antidrug antibodies formation, which may result in better efficacy., (Copyright © 2023 The Authors. Published by Elsevier Inc. All rights reserved.)

Psoriasis is characterized by excessive keratinocyte proliferation and immunocyte infiltration, but the underlying pathogenesis remains unclear. Aminoacyl-tRNA synthetases are universally expressed enzymes that catalyze the first step of protein synthesis. Glycyl-tRNA synthetase (GARS) is a member of the aminoacyl-tRNA synthetase family. In addition to its canonical function, we found that GARS was overexpressed in the serum and skin lesions of patients with psoriasis. Moreover, GARS was highly expressed in human skin keratinocytes, and GARS knockdown in keratinocytes suppressed cell proliferation and promoted apoptosis through NF-κB/MAPK signaling pathway. Moreover, intradermal injection of recombinant GARS protein caused skin thickening, angiogenesis, and IFN/TNF-driven skin inflammation. Intriguingly, the reported functional receptor for GARS, cadherin 6 (CDH6), was specifically expressed in vascular endothelial cells, and we found that keratinocyte-derived GARS promotes inflammation and angiogenesis of vascular endothelial cells through CDH6. In addition, intradermal injection of GARS aggravated the phenotype and angiogenesis in imiquimod-induced psoriasiform dermatitis models, whereas the psoriatic phenotype and angiogenesis were relieved after knockdown of GARS by adeno-associated virus. Taken together, the results of this study identify the critical role of GARS in the pathogenesis of psoriasis and suggest that blocking GARS may be a therapeutic approach for alleviating psoriasis., (Copyright © 2023 The Authors. Published by Elsevier Inc. All rights reserved.)

Psoriasis is an inflammatory skin disorder that is characterized by keratinocyte hyperproliferation in response to immune cell infiltration and cytokine secretion in the dermis. γδ T cells expressing the Vγ4 TCR chain are among the highest contributors of IL-17A, which is a major cytokine that drives a psoriasis flare, making Vγ4 + γδ T cells a suitable target to restrict psoriasis progression. In this study, we demonstrate that mitochondrial translation inhibition within Vγ4 + γδ T cells effectively reduced erythema, scaling, and skin thickening in a murine model of psoriatic disease. The antibiotic linezolid, which blocks mitochondrial translation, inhibited the production of mitochondrial-encoded protein cytochrome c oxidase in Vγ4 + γδ T cells and systemically reduced the frequencies of IL-17A + Vγ4 + γδ T cells, effectively resolving IL-17A-dependent inflammation. Inhibiting mitochondrial translation could be a novel metabolic approach to interrupt IL-17A signaling in Vγ4 + T cells and reduce psoriasis-like skin pathophysiology., (Copyright © 2023 The Authors. Published by Elsevier Inc. All rights reserved.)

Loss-of-function sequence variations in the IL36RN gene encoding IL-36 receptor antagonist cause familial generalized pustular psoriasis, which begins shortly after birth and is difficult to treat, and its effects on the epidermis are unclear. This study investigated the involvement of IL-36 receptor agonists in the epidermal formation of generalized pustular psoriasis. We found that the IL-36 receptor agonists, especially mature IL-36γ, stimulated IL-8 and pro-IL-36γ production in the epidermis while downregulating the genes encoding epidermal cornified envelope-related proteins, for example, corneodesmosin. IL-36 receptor antagonist and monoclonal anti-IL-36γ antibodies counteracted the effect of mature IL-36γ on corneodesmosin in keratinocytes in a dose-dependent manner. In the epidermis of patients with generalized pustular psoriasis with IL36RN loss-of-function sequence variations, pro-IL-36γ was overproduced in the epidermis, and corneodesmosin protein expression was markedly decreased in the region of giant subcorneal pustules (Kogoj's spongiform pustules), with high neutrophil infiltration. IL-8 induced by mature IL-36γ stimulated the infiltration of several neutrophils in the epidermis. The newly produced pro-IL-36γ is cleaved to the mature form by neutrophil proteases. This newly produced mature IL-36γ was predicted to further suppress the gene expression of corneodesmosin, leading to significant stratum corneum exfoliation and formation of the pustules. Overall, our results elucidate the mechanism underlying the formation of Kogoj's spongiform pustules in generalized pustular psoriasis., (Copyright © 2023 The Authors. Published by Elsevier Inc. All rights reserved.)

Psoriasis is a chronic inflammatory immune-mediated disorder affecting the skin and other organs including joints. Over 1,300 transcripts are altered in psoriatic involved skin compared with normal skin. However, to our knowledge, global epigenetic profiling of psoriatic skin is previously unreported. Here, we describe a genome-wide study of altered CpG methylation in psoriatic skin. We determined the methylation levels at 27,578 CpG sites in skin samples from individuals with psoriasis (12 involved, 8 uninvolved) and 10 unaffected individuals. CpG methylation of involved skin differed from normal skin at 1,108 sites. Twelve mapped to the epidermal differentiation complex, upstream or within genes that are highly upregulated in psoriasis. Hierarchical clustering of 50 of the top differentially methylated (DM) sites separated psoriatic from normal skin samples with uninvolved skin exhibiting intermediate methylation. CpG sites where methylation was correlated with gene expression are reported. Sites with inverse correlations between methylation and nearby gene expression include those of KYNU, OAS2, S100A12, and SERPINB3, whose strong transcriptional upregulation is an important discriminator of psoriasis. Pyrosequencing of bisulfite-treated DNA from skin biopsies at three DM loci confirmed earlier findings and revealed reversion of methylation levels toward the non-psoriatic state after 1 month of anti-TNF-α therapy.

IL-36 is a most recent member of the IL-1 cytokine family, primarily expressed at barrier sites of the body such as the skin, lungs, and intestine. It plays a vital role in inflammation and is implicated in the development of various cutaneous; intestinal; and pulmonary disorders, including psoriasis, inflammatory bowel disease, and chronic obstructive pulmonary disease. IL-36 comprises 4 isoforms: the proinflammatory IL-36α, IL-36β, and IL-36γ and the anti-inflammatory IL-36R antagonist. An imbalance between proinflammatory and anti-inflammatory IL-36 isoforms can contribute to the inflammatory fate of cells and tissues. IL-36 cytokines signal through an IL-36R heterodimer mediating their function through canonical signaling cacade, including the NF-B pathway. Prominent for its role in psoriasis, IL-36 has recently been associated with disease mechanisms in atopic dermatitis, hidradenitis suppurativa, neutrophilic dermatoses, autoimmune blistering disease, and Netherton syndrome. The major cutaneous source of IL-36 cytokines is keratinocytes, pointing to its role in the communication between the epidermis, innate (neutrophils, dendritic cells) immune system, and adaptive (T helper [Th]1 cells, Th17) immune system. Thus, cutaneous IL-36 signaling is crucial for the immunopathological outcome of various skin diseases. Consequently, the IL-36/IL-36R axis has recently been recognized as a promising drug target for the treatment of inflammatory disorders beyond psoriasis. This review summarizes the current update on IL-36 cytokines in inflammatory skin diseases., (Copyright © 2023 The Authors. Published by Elsevier Inc. All rights reserved.)