Global gene expression analysis reveals evidence for decreased lipid biosynthesis and increased innate immunity in uninvolved psoriatic skin. J Invest Dermatol. 2009;129:2795-2804. [PMID: 19571819 DOI: 10.1038/jid.2009.173]

Factor XII and prekallikrein promote microvascular inflammation and psoriasis in mice

BACKGROUND AND PURPOSE

Psoriasis is an autoimmune inflammatory skin disease, featuring microvascular abnormalities and elevated levels of bradykinin. Contact activation of Factor XII can initiate the plasma kallikrein-kinin cascade, producing inflammation and angioedema. The role of Factor XII in psoriasis is unknown.

EXPERIMENTAL APPROACH

The effects of deficiency of Factor XII or its enzymatic substrate, prekallikrein, were examined in the imiquimod-induced mouse model of psoriasis. Skin microcirculation was assessed using intravital confocal microscopy and laser Doppler flowmeter. A novel antibody blocking Factor XII activation was evaluated for psoriasis prevention.

KEY RESULTS

Expression of Factor XII was markedly up-regulated in human and mouse psoriatic skin. Genetic deletion of Factor XII or prekallikrein, attenuated imiquimod-induced psoriatic lesions in mice. Psoriatic induction increased skin microvascular blood perfusion, causing vasodilation, hyperpermeability and angiogenesis. It also promoted neutrophil-vascular interaction, inflammatory cytokine release and enhanced Factor XII / prekallikrein enzymatic activity with elevated bradykinin. Factor XII or prekallikrein deficiency ameliorated these microvascular abnormalities and abolished bradykinin increase. Antagonism of bradykinin B2 receptors reproduced the microvascular protection of Factor XII / prekallikrein deficiency, attenuated psoriatic lesions, and prevented protection by Factor XII / prekallikrein deficiency against psoriasis. Furthermore, treatment of mice with Factor XII antibody alleviated experimentally induced psoriasis and suppressed microvascular inflammation.

CONCLUSION AND IMPLICATIONS

Activation of Factor XII promoted psoriasis via prekallikrein-dependent formation of bradykinin, which critically mediated psoriatic microvascular inflammation. Inhibition of contact activation represents a novel therapeutic strategy for psoriasis.

Murine Alox8 versus the human ALOX15B ortholog: differences and similarities

Human arachidonate 15-lipoxygenase type B is a lipoxygenase that catalyzes the peroxidation of arachidonic acid at carbon-15. The corresponding murine ortholog however has 8-lipoxygenase activity. Both enzymes oxygenate polyunsaturated fatty acids in S-chirality with singular reaction specificity, although they generate a different product pattern. Furthermore, while both enzymes utilize both esterified fatty acids and fatty acid hydro(pero)xides as substrates, they differ with respect to the orientation of the fatty acid in their substrate-binding pocket. While ALOX15B accepts the fatty acid "tail-first," Alox8 oxygenates the free fatty acid with its "head-first." These differences in substrate orientation and thus in regio- and stereospecificity are thought to be determined by distinct amino acid residues. Towards their biological function, both enzymes share a commonality in regulating cholesterol homeostasis in macrophages, and Alox8 knockdown is associated with reduced atherosclerosis in mice. Additional roles have been linked to lung inflammation along with tumor suppressor activity. This review focuses on the current knowledge of the enzymatic activity of human ALOX15B and murine Alox8, along with their association with diseases.

Resolved Psoriasis with Abundant Oleic Acid in Stratum Corneum Exhibits Lower T-Cell-Driven IL-17 Signature

Relapses of psoriasis involve T cells that stem and survive in the skin. Inherited from previous flares, the tissue-resident memory T cells are epidermal IL-17-producing CD8+ and IL-22-producing CD4+ T cells. Because the capacity of resident memory T cells to take in fatty acids is essential for their residence and function, the surface composition of fatty acids may affect underlying T-cell populations. In patients treated with biologics, we used gas chromatography/mass spectrometry to decipher the fatty acid composition in both resolved and nonlesional sites. Skin T cells were activated by OKT-3 in explants from the same body sites to perform bulk transcriptomic analysis (Nanostring). The fatty acid composition differed between skin from healthy donors and normal-looking skin of patients with psoriasis but not further between nonlesional and resolved skin. Patients in whom the resolved skin was rich in oleic acid had lower T-cell-driven IL-17 epidermal transcriptomic signature upon activation of T cells in skin explants. The skin lipid composition is linked with the functions of the underlying epidermal T cells. Testing the modulating effect of custom fatty acids on skin resident T cells could help with coming closer to disease oblivion in inflammatory skin diseases.

Histone and Histone Acetylation-Related Alterations of Gene Expression in Uninvolved Psoriatic Skin and Their Effects on Cell Proliferation, Differentiation, and Immune Responses

Psoriasis is a chronic immune-mediated skin disease in which the symptom-free, uninvolved skin carries alterations in gene expression, serving as a basis for lesion formation. Histones and histone acetylation-related processes are key regulators of gene expression, controlling cell proliferation and immune responses. Dysregulation of these processes is likely to play an important role in the pathogenesis of psoriasis. To gain a complete overview of these potential alterations, we performed a meta-analysis of a psoriatic uninvolved skin dataset containing differentially expressed transcripts from nearly 300 individuals and screened for histones and histone acetylation-related molecules. We identified altered expression of the replication-dependent histones HIST2H2AA3 and HIST2H4A and the replication-independent histones H2AFY, H2AFZ, and H3F3A/B. Eight histone chaperones were also identified. Among the histone acetyltransferases, ELP3 and KAT5 and members of the ATAC, NSL, and SAGA acetyltransferase complexes are affected in uninvolved skin. Histone deacetylation-related alterations were found to affect eight HDACs and members of the NCOR/SMRT, NURD, SIN3, and SHIP HDAC complexes. In this article, we discuss how histone and histone acetylation-related expression changes may affect proliferation and differentiation, as well as innate, macrophage-mediated, and T cell-mediated pro- and anti-inflammatory responses, which are known to play a central role in the development of psoriasis.

IL17A Blockade with Ixekizumab Suppresses MuvB Signaling in Clinical Psoriasis

Unbiased informatics approaches have the potential to generate insights into uncharacterized signaling pathways in human disease. In this study, we generated longitudinal transcriptomic profiles of plaque psoriasis lesions from patients enrolled in a clinical trial of the anti-IL17A antibody ixekizumab (IXE). This dataset was then computed against a curated matrix of over 700 million data points derived from published psoriasis and signaling node perturbation transcriptomic and chromatin immunoprecipitation-sequencing datasets. We observed substantive enrichment within both psoriasis-induced and IXE-repressed gene sets of transcriptional targets of members of the MuvB complex, a master regulator of the mitotic cell cycle. These gene sets were similarly enriched for pathways involved in the regulation of the G2/M transition of the cell cycle. Moreover, transcriptional targets for MuvB nodes were strongly enriched within IXE-repressed genes whose expression levels correlated strongly with the extent and severity of the psoriatic disease. In models of human keratinocyte proliferation, genes encoding MuvB nodes were transcriptionally repressed by IXE, and depletion of MuvB nodes reduced cell proliferation. Finally, we made the expression and regulatory networks that supported this study available as a freely accessible, cloud-based hypothesis generation platform. Our study positions inhibition of MuvB signaling as an important determinant of the therapeutic impact of IXE in psoriasis.

Emerging roles of a chemoattractant receptor GPR15 and ligands in pathophysiology

Chemokine receptors play a central role in the maintenance of immune homeostasis and development of inflammation by directing leukocyte migration to tissues. GPR15 is a G protein-coupled receptor (GPCR) that was initially known as a co-receptor for human immunodeficiency virus (HIV) and simian immunodeficiency virus (SIV), with structural similarity to other members of the chemoattractant receptor family. Since the discovery of its novel function as a colon-homing receptor of T cells in mice a decade ago, GPR15 has been rapidly gaining attention for its involvement in a variety of inflammatory and immune disorders. The recent identification of its natural ligand C10orf99, a chemokine-like polypeptide strongly expressed in gastrointestinal tissues, has established that GPR15-C10orf99 is a novel signaling axis that controls intestinal homeostasis and inflammation through the migration of immune cells. In addition, it has been demonstrated that C10orf99-independent functions of GPR15 and GPR15-independent activities of C10orf99 also play significant roles in the pathophysiology. Therefore, GPR15 and its ligands are potential therapeutic targets. To provide a basis for the future development of GPR15- or GPR15 ligand-targeted therapeutics, we have summarized the latest advances in the role of GPR15 and its ligands in human diseases as well as the molecular mechanisms that regulate GPR15 expression and functions.

Cutaneous lesions in psoriatic arthritis are enriched in chemokine transcriptomic pathways

OBJECTIVES

Skin from people with psoriasis has been extensively studied and is assumed to be identical to skin from those with psoriatic arthritis (PsA). Chemokines and the CC chemokine scavenger receptor ACKR2 are upregulated in uninvolved psoriasis. ACKR2 has been proposed as a regulator of cutaneous inflammation in psoriasis. The aim of this study was to compare the transcriptome of PsA skin to healthy control (HC) skin and evaluate ACKR2 expression in PsA skin.

METHODS

Full-thickness skin biopsies from HC, lesional and uninvolved skin from participants with PsA were sequenced on NovaSeq 6000. Findings were validated using qPCR and RNAscope.

RESULTS

Nine HC and nine paired PsA skin samples were sequenced. PsA uninvolved skin was transcriptionally similar to HC skin, and lesional PsA skin was enriched in epidermal and inflammatory genes. Lesional PsA skin was enriched in chemokine-mediated signalling pathways, but uninvolved skin was not. ACKR2 was upregulated in lesional PsA skin but had unchanged expression in uninvolved compared with HC skin. The expression of ACKR2 was confirmed by qPCR, and RNAscope demonstrated strong expression of ACKR2 in the suprabasal layer of the epidermis in PsA lesions.

CONCLUSION

Chemokines and their receptors are upregulated in lesional PsA skin but relatively unchanged in uninvolved PsA skin. In contrast to previous psoriasis studies, ACKR2 was not upregulated in uninvolved PsA skin. Further understanding of the chemokine system in PsA may help to explain why inflammation spreads from the skin to the joints in some people with psoriasis.

Preclinical study models of psoriasis: State-of-the-art techniques for testing pharmaceutical products in animal and nonanimal models

Local and systemic treatments exist for psoriasis, but none can do more than control its symptoms because of its numerous unknown mechanisms. The lack of validated testing models or a defined psoriatic phenotypic profile hinders antipsoriatic drug development. Despite their intricacy, immune-mediated diseases have no improved and precise treatment. The treatment actions may now be predicted for psoriasis and other chronic hyperproliferative skin illnesses using animal models. Their findings confirmed that a psoriasis animal model could mimic a few disease conditions. However, their ethical approval concerns and inability to resemble human psoriasis rightly offer to look for more alternatives. Hence, in this article, we have reported various cutting-edge techniques for the preclinical testing of pharmaceutical products for the treatment of psoriasis.

Association of Lipid-Lowering Drugs With Risk of Psoriasis: A Mendelian Randomization Study

Importance

Lipid pathways have been implicated in the pathogenesis of psoriasis, and some lipid-lowering drugs, such as statins, are hypothesized to have disease-modifying properties. However, large population-level studies are scarce, and causal interpretation of results from traditional observational designs is limited by confounding.

Objective

To investigate the causal association between genetically proxied lipid-lowering drugs and psoriasis risk.

Design, Setting, and Participants

This 2-sample mendelian randomization study was performed from August to October 2022 and included population-level genome-wide association studies of psoriasis in the UK Biobank and FinnGen studies and low-density lipoprotein (LDL) by the Global Lipids Genetics Consortium. The inverse variance-weighted method was used with pleiotropy robust methods and colocalization as sensitivity analyses.

Exposures

Genetically proxied inhibition of 3-hydroxy-3-methylglutaryl CoA reductase (HMGCR, targeted by statins), Niemann-Pick C1-like 1 (NPC1L1, targeted by ezetimibe), and proprotein convertase subtilisin/kexin type 9 (PCSK9, targeted by, eg, alirocumab), using LDL as the biomarker.

Main Outcomes and Measures

Risk of psoriasis.

Results

Data from 12 116 patients with psoriasis and approximately 1.3 million individuals with LDL measurement were analyzed. Genetically proxied PCSK9 inhibition was associated with reduced risk of psoriasis (odds ratio, 0.69 per standard deviation reduction in LDL; 95% CI, 0.55-0.88; P = .003), which was replicated in FinnGen (odds ratio, 0.71; 95% CI, 0.57-0.88; P = .002). Sensitivity analyses did not provide statistical evidence of bias from pleiotropy or genetic confounding. No robust association was found for HMGCR or NPC1L1 inhibition.

Conclusions and Relevance

This mendelian randomization study suggests that PCSK9 is implicated in psoriasis pathogenesis, and its inhibition is associated with reduced psoriasis risk. These findings potentially pave the way for future studies that may allow personalized selection of lipid-lowering drugs for those at risk of psoriasis.

The proteome of hand eczema assessed by tape stripping

Hand eczema (HE) is a prevalent skin disease. However, classification of HE into different subtypes remains challenging. Limited number of prior studies have employed invasive biopsy-based strategies; yet, studies of the HE proteome using non-invasive tape stripping methodology have not been reported. In this study, we wanted to assess whether global proteomic analysis of skin tape strip samples can be used for sub-classification of HE patients. Tape strips were collected from patients with HE and healthy skin. Liquid chromatography-mass spectrometry (LC/MS) proteomics was performed, and the global protein expression was analyzed. We identified 2,919 proteins in stratum corneum-derived skin cells from tape strip samples. Compared to healthy skin, the lesional samples from HE patients exhibited increased expression of immune-related markers and a decreased expression of structural barrier proteins. The difference between HE subtypes was restricted to the lesional skin areas, and included an increased expression of skin barrier-related proteins independently of the concurrent AD. In conclusion we found, that the non-invasive tape strip method used in combination with LC/MS proteomics can be used for analysis of skin protein expression in HE patients. Thus, the method shows potential for assessing the proteomic differences between subtypes of HE, and biomarker discovery.

Skin-associated adipocytes in skin barrier immunity: A mini-review

The skin contributes critically to health via its role as a barrier tissue against a multitude of external pathogens. The barrier function of the skin largely depends on the uppermost epidermal layer which is reinforced by skin barrier immunity. The integrity and effectiveness of skin barrier immunity strongly depends on the close interplay and communication between immune cells and the skin environment. Skin-associated adipocytes have been recognized to play a significant role in modulating skin immune responses and infection by secreting cytokines, adipokines, and antimicrobial peptides. This review summarizes the recent understanding of the interactions between skin-associated adipocytes and other skin cells in maintaining the integrity and effectiveness of skin barrier immunity.

Arachidonate 15-lipoxygenase type B: Regulation, function, and its role in pathophysiology

As a lipoxygenase (LOX), arachidonate 15-lipoxygenase type B (ALOX15B) peroxidizes polyenoic fatty acids (PUFAs) including arachidonic acid (AA), eicosapentaenoic acid (EPA), docosahexaenoic acid (DHA), and linoleic acid (LA) to their corresponding fatty acid hydroperoxides. Distinctive to ALOX15B, fatty acid oxygenation occurs with positional specificity, catalyzed by the non-heme iron containing active site, and in addition to free PUFAs, membrane-esterified fatty acids serve as substrates for ALOX15B. Like other LOX enzymes, ALOX15B is linked to the formation of specialized pro-resolving lipid mediators (SPMs), and altered expression is apparent in various inflammatory diseases such as asthma, psoriasis, and atherosclerosis. In primary human macrophages, ALOX15B expression is associated with cellular cholesterol homeostasis and is induced by hypoxia. Like in inflammation, the role of ALOX15B in cancer is inconclusive. In prostate and breast carcinomas, ALOX15B is attributed a tumor-suppressive role, whereas in colorectal cancer, ALOX15B expression is associated with a poorer prognosis. As the biological function of ALOX15B remains an open question, this review aims to provide a comprehensive overview of the current state of research related to ALOX15B.

Molecular and cellular regulation of psoriatic inflammation

This review highlights the molecular and cellular mechanisms underlying psoriatic inflammation with an emphasis on recent developments which may impact on treatment approaches for this chronic disease. We consider both the skin and the musculoskeletal compartment and how different manifestations of psoriatic inflammation are linked. This review brings a focus to the importance of inflammatory feedback loops that exist in the initiation and chronic stages of the condition, and how close interaction between the epidermis and both innate and adaptive immune compartments drives psoriatic inflammation. Furthermore, we highlight work done on biomarkers to predict the outcome of therapy as well as the transition from psoriasis to psoriatic arthritis.

Full-Length Transcriptome Sequencing Analysis of Differentially Expressed Genes and Pathways After Treatment of Psoriasis With Oxymatrine

Psoriasis is a recurrent chronic inflammatory skin disease. Unlike many of the latest psoriasis treatments that only confer limited curative effects and have certain side effects, oxymatrine effectively improves severe plaque psoriasis with mild adverse reactions. Here, we explored the genes and pathways underlying the effects of oxymatrine on psoriasis. Briefly, patients with severe plaque psoriasis were treated with oxymatrine and their lesioned skin samples were sequenced by full-length transcriptomics. Next, the differentially expressed genes (DEGs) in psoriatic lesions were identified and compared in oxymatrine-treated patients and healthy controls, their genes were functionally annotated, and protein–protein interaction network analysis and immunohistochemistry were performed. Both Psoriasis Area and Severity Index (PASI) and Body Surface Area (BSA) scores were recovered significantly from all 16 patients (all p < 0.001). The number of DEGs in patients before and after oxymatrine treatment was 4232, and 4105 DEGs were found between the psoriasis group (before oxymatrine treatment) and the normal control group [p < 0.01, |log₂ fold change, (FC)| >1.5]. While most of the DEGs recovered significantly after oxymatrine treatment, only 650 DEGs were observed between the psoriasis group (after oxymatrine treatment) and the normal control group (p < 0.01, |log₂FC|> 1.5). Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analysis showed that 64 pathways were significantly activated after oxymatrine treatment (p < 0.05). Only 12 pathways were statistically significant between after oxymatrine treatment and the normal control group (p < 0 .05). Among all the restored pathways, the improvement of the IL-17 signaling pathway was the most significant (p = 1.18E-06). Gene loci of oxymatrine action was assessed by protein interaction analysis on 205 DEGs that were co-expressed in 5 patients before and after oxymatrine treatment (p < 0.05, FC > 1.5). After oxymatrine treatment, the expression of two mitosis-related genes namely, cyclin dependent kinase 1 (CDK1) and cyclin B1 (CCNB1), that affect cell proliferation recovered significantly. In light of these results, we conclude that oxymatrine likely alters the abnormal expression of some genes and pathways in psoriasis patients. Multipathway and multitarget therapy can greatly ameliorate abnormalities in genes and pathways and effectively treat psoriasis. Importantly, among the DEGs, the proliferation-related genes, such as CDK1 and CCNB1, are likely important targets for treating psoriasis by oxymatrine. We believe that these findings may lead to a new treatment strategy for psoriasis.

Estrogen Acts Through Estrogen Receptor-β to Promote Mannan-Induced Psoriasis-Like Skin Inflammation

Sex-bias is more obvious in several autoimmune disorders, but not in psoriasis. However, estrogen levels fluctuate during puberty, menstrual cycle, pregnancy, and menopause, which are related to variations in psoriasis symptoms observed in female patients. Estrogen has disease promoting or ameliorating functions based on the type of immune responses and tissues involved. To investigate the effects of estrogen on psoriasis, at first, we developed an innate immunity dependent mannan-induced psoriasis model, which showed a clear female preponderance in disease severity in several mouse strains. Next, we investigated the effects of endogenous and exogenous estrogen using ovariectomy and sham operated mice. 17-β-estradiol (E2) alone promoted the skin inflammation and it also significantly enhanced mannan-induced skin inflammation. We also observed a prominent estrogen receptor-β (ER-β) expression in the skin samples, especially on keratinocytes. Subsequently, we confirmed the effects of E2 on psoriasis using ER-β antagonist (PHTPP) and agonist (DPN). In addition, estrogen was found to affect the expression of certain genes (vgll3 and cebpb), microRNAs (miR146a and miR21), and immune cells (DCs and γδ T cells) as well as chemokines (CCL5 and CXCL10) and cytokines (TNF-α, IL-6, IL-22, IL-23, and IL-17 family), which promoted the skin inflammation. Thus, we demonstrate a pathogenic role for 17-β-estradiol in promoting skin inflammation, which should be considered while designing new treatment strategies for psoriasis patients.

Noninvasive Tape-Stripping with High-Resolution RNA Profiling Effectively Captures a Preinflammatory State in Nonlesional Psoriatic Skin

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.

Transcriptional Basis of Psoriasis from Large Scale Gene Expression Studies: The Importance of Moving towards a Precision Medicine Approach

Transcriptome profiling techniques, such as microarrays and RNA sequencing (RNA-seq), are valuable tools for deciphering the regulatory network underlying psoriasis and have revealed large number of differentially expressed genes in lesional and non-lesional skin. Such approaches provide a more precise measurement of transcript levels and their isoforms than any other methods. Large cohort transcriptomic analyses have greatly improved our understanding of the physiological and molecular mechanisms underlying disease pathogenesis and progression. Here, we mostly review the findings of some important large scale psoriatic transcriptomic studies, and the benefits of such studies in elucidating potential therapeutic targets and biomarkers for psoriasis treatment. We also emphasised the importance of looking into the alternatively spliced RNA isoforms/transcripts in psoriasis, rather than focussing only on the gene-level annotation. The neutrophil and blood transcriptome signature in psoriasis is also briefly reviewed, as it provides the immune status information of patients and is a less invasive platform. The application of precision medicine in current management of psoriasis, by combining transcriptomic data, improves the clinical response outcome in individual patients. Drugs tailored to individual patient's genetic profile will greatly improve patient outcome and cost savings for the healthcare system.

Proteomic Studies of Psoriasis

In this review paper, we discuss the contribution of proteomic studies to the discovery of disease-specific biomarkers to monitor the disease and evaluate available treatment options for psoriasis. Psoriasis is one of the most prevalent skin disorders driven by a Th17-specific immune response. Although potential patients have a genetic predisposition to psoriasis, the etiology of the disease remains unknown. During the last two decades, proteomics became deeply integrated with psoriatic research. The data obtained in proteomic studies facilitated the discovery of novel mechanisms and the verification of many experimental hypotheses of the disease pathogenesis. The detailed data analysis revealed multiple differentially expressed proteins and significant changes in proteome associated with the disease and drug efficacy. In this respect, there is a need for proteomic studies to characterize the role of the disease-specific biomarkers in the pathogenesis of psoriasis, develop clinical applications to choose the most efficient treatment options and monitor the therapeutic response.

Cytokine responses in nonlesional psoriatic skin as clinical predictor to anti-TNF agents

BACKGROUND

A major issue with the current management of psoriasis is our inability to predict treatment response.

OBJECTIVE

Our aim was to evaluate the ability to use baseline molecular expression profiling to assess treatment outcome for patients with psoriasis.

METHODS

We conducted a longitudinal study of 46 patients with chronic plaque psoriasis treated with anti-TNF agent etanercept, and molecular profiles were assessed in more than 200 RNA-seq samples.

RESULTS

We demonstrated correlation between clinical response and molecular changes during the course of the treatment, particularly for genes responding to IL-17A/TNF in keratinocytes. Intriguingly, baseline gene expressions in nonlesional, but not lesional, skin were the best marker of treatment response at week 12. We identified USP18, a known regulator of IFN responses, as positively correlated with Psoriasis Area and Severity Index (PASI) improvement (P = 9.8 × 10^-4) and demonstrate its role in regulating IFN/TNF responses in keratinocytes. Consistently, cytokine gene signatures enriched in baseline nonlesional skin expression profiles had strong correlations with PASI improvement. Using this information, we developed a statistical model for predicting PASI75 (ie, 75% of PASI improvement) at week 12, achieving area under the receiver-operating characteristic curve value of 0.75 and up to 80% accurate PASI75 prediction among the top predicted responders.

CONCLUSIONS

Our results illustrate feasibility of assessing drug response in psoriasis using nonlesional skin and implicate involvement of IFN regulators in anti-TNF responses.

Transcriptional Analysis-Based Alterations Affecting Neuritogenesis of the Peripheral Nervous System in Psoriasis

An increasing amount of evidence indicates the critical role of the cutaneous nervous system in the initiation and maintenance of psoriatic skin lesions by neurogenic inflammation. However, molecular mechanisms affecting cutaneous neurons are largely uncharacterized. Therefore, we reanalyzed a psoriatic RNA sequencing dataset from published transcriptome experiments of nearly 300 individuals. Using the Ingenuity Pathway Analysis software, we associated several hundreds of differentially expressed transcripts (DETs) to nervous system development and functions. Since neuronal projections were previously reported to be affected in psoriasis, we performed an in-depth analysis of neurite formation-related process. Our in silico analysis suggests that SEMA-PLXN and ROBO-DCC-UNC5 regulating axonal growth and repulsion are differentially affected in non-lesional and lesional skin samples. We identified opposing expressional alterations in secreted ligands for axonal guidance signaling (RTN4/NOGOA, NTNs, SEMAs, SLITs) and non-conventional axon guidance regulating ligands, including WNT5A and their receptors, modulating axon formation. These differences in neuritogenesis may explain the abnormal cutaneous nerve filament formation described in psoriatic skin. The processes also influence T-cell activation and infiltration, thus highlighting an additional angle of the crosstalk between the cutaneous nervous system and the immune responses in psoriasis pathogenesis, in addition to the known neurogenic pro-inflammatory mediators.

Use of Cytokine Mix-, Imiquimod-, and Serum-Induced Monoculture and Lipopolysaccharide- and Interferon Gamma-Treated Co-Culture to Establish In Vitro Psoriasis-like Inflammation Models

Psoriasis (Ps), commonly perceived as a skin and joint disorder, has a complex basis and results from disturbances in the sophisticated network between skin and the immune system. This makes it difficult to properly depict the complete pathomechanism on an in vitro scale. Deciphering the complicated or even subtle modulation of intra- and intercellular factors, assisted by the implementation of in vitro human skin models, may provide the opportunity to dissect the disease background step by step. In addition to reconstructed artificial skin substitutes, which mimic the native physiological context, in vitro models are conducive to the broad "3 Rs" philosophy (reduce, refine, and replace) and represent important tools for basic and applied skin research. To meet the need for a more comprehensive in vitro Ps model, a set of various experimental conditions was applied in this study. The selection of in vitro treatment that mimicked the Ps phenotype was illustrated by analyses of discriminating biomarker genes involved in the pathogenesis of the disease, i.e., keratinocyte differentiation markers, antimicrobial peptides, chemokines, and proliferation markers. This resulted in a reproducible protocol for the use of the primary skin keratinocyte (pKC) monoculture treated with a cytokine cocktail (5MIX, i.e., interleukin (IL) 1 alpha (IL-1α), IL-17A, IL-22, oncostatin M (OSM), and tumour necrosis factor alpha (TNF-α)) at a calcium (Ca2+) concentration (i.e., 2 mM) in an applied medium, which best mirrored the in vitro Ps-like inflammatory model. In addition, based on waste skin material, the method has the potential for extensive experimentation, both in detailed molecular studies and preclinical tests.

PI3Kδ Sustains Keratinocyte Hyperproliferation and Epithelial Inflammation: Implications for a Topically Druggable Target in Psoriasis

The phosphatidylinositol 3-kinase (PI3K)-dependent signaling pathway is aberrantly activated in psoriatic lesions and contributes to disease pathogenesis. Among PI3Ks enzymes, PI3Kα, β, and δ isoforms are known to bind the p85 regulatory subunit and mediate activation of AKT and other downstream effectors. In this study, we deepened our understanding of the expression and function of PI3Kδ in skin lesions of patients affected by psoriasis. For the first time, we found that PI3Kδ is overexpressed in psoriatic plaques, and its expression is not only confined to infiltrating immune cells but also accumulates in proliferating keratinocytes of the epidermal basal layer. We investigated the function of PI3Kδ in psoriatic skin by evaluating the impact of seletalisib, a newly developed selective PI3Kδ inhibitor, in both in vitro and in vivo experimental models of psoriasis. Of note, we found that PI3Kδ sustains keratinocyte hyperproliferation and impaired terminal differentiation induced by IL-22, as well as induces epithelial inflammation and resistance to apoptosis mediated by TNF-α in human keratinocytes. Mechanistically, PI3Kδ promotes PDK1 phosphorylation and signals through AKT-dependent or -independent pathways. It is worth mentioning that PI3Kδ inhibition by seletalisib attenuates the severity of psoriasiform phenotype induced in the Imiquimod-induced mouse model of psoriasis by restoring the physiological proliferation and differentiation programs in epidermal keratinocytes and contrasting the cutaneous inflammatory responses. Therefore, we suggest PI3Kδ as a potential topically druggable target in psoriasis and skin diseases characterized by epidermal hyperproliferation and skin inflammation.

Application of Genetic Algorithm-Based Support Vector Machine in Identification of Gene Expression Signatures for Psoriasis Classification: A Hybrid Model

BACKGROUND

Psoriasis is a chronic autoimmune disease impairing significantly the quality of life of the patient. The diagnosis of the disease is done via a visual inspection of the lesional skin by dermatologists. Classification of psoriasis using gene expression is an important issue for the early and effective treatment of the disease. Therefore, gene expression data and selection of suitable gene signatures are effective sources of information.

METHODS

We aimed to develop a hybrid classifier for the diagnosis of psoriasis based on two machine learning models of the genetic algorithm and support vector machine (SVM). The method also conducts gene signature selection. A publically available gene expression dataset was used to test the model.

RESULTS

A number of 181 probe sets were selected among the original 54,675 probes using the hybrid model with a prediction accuracy of 100% over the test set. A number of 10 hub genes were identified using the protein-protein interaction network. Nine out of 10 identified genes were found in significant modules.

CONCLUSIONS

The results showed that the genetic algorithm improved the SVM classifier performance significantly implying the ability of the proposed model in terms of detecting relevant gene expression signatures as the best features.

SIGIRR Negatively Regulates IL-36-Driven Psoriasiform Inflammation and Neutrophil Infiltration in the Skin

SIGIRR has been described as a negative regulator of several IL-1R/TLR family members and has been implicated in several inflammatory disease conditions. However, it is unknown whether it can suppress IL-36 family cytokines, which are members of the broader IL-1 superfamily that have emerged as critical orchestrators of psoriatic inflammation in both humans and mice. In this study, we demonstrate that SIGIRR is downregulated in psoriatic lesions in humans and mice, and this correlates with increased expression of IL-36 family cytokines. Using Sigirr ^-/- mice, we identify, for the first time (to our knowledge), SIGIRR as a negative regulator of IL-36 responses in the skin. Mechanistically, we identify dendritic cells and keratinocytes as the primary cell subsets in which IL-36 proinflammatory responses are regulated by SIGIRR. Both cell types displayed elevated IL-36 responsiveness in absence of SIGIRR activity, characterized by enhanced expression of neutrophil chemoattractants, leading to increased neutrophil infiltration to the inflamed skin. Blockade of IL-36R signaling ameliorated exacerbated psoriasiform inflammation in Sigirr^-/- mice and inhibited neutrophil infiltration. These data identify SIGIRR activity as an important regulatory node in suppressing IL-36-dependent psoriatic inflammation in humans and mice.

Lipidomic and transcriptional analysis of the linoleoyl-omega-hydroxyceramide biosynthetic pathway in human psoriatic lesions

A complex assembly of lipids including fatty acids, cholesterol, and ceramides is vital to the integrity of the mammalian epidermal barrier. The formation of this barrier requires oxidation of the substrate fatty acid, linoleic acid (LA), which is initiated by the enzyme 12R-lipoxygenase (LOX). In the epidermis, unoxidized LA is primarily found in long-chain acylceramides termed esterified omega-hydroxy sphingosine (EOS)/phytosphingosine/hydroxysphingosine (collectively EOx). The precise structure and localization of LOX-oxidized EOx in the human epidermis is unknown, as is their regulation in diseases such as psoriasis, one of the most common inflammatory diseases affecting the skin. Here, using precursor LC/MS/MS, we characterized multiple intermediates of EOx, including 9-HODE, 9,10-epoxy-13-HOME, and 9,10,13-TriHOME, in healthy human epidermis likely to be formed via the epidermal LOX pathways. The top layers of the skin contained more LA, 9-HODE, and 9,10,13-TriHOME EOSs, whereas 9,10-epoxy-13-HOME EOS was more prevalent deeper in the stratum corneum. In psoriatic lesions, levels of native EOx and free HODEs and HOMEs were significantly elevated, whereas oxidized species were generally reduced. A transcriptional network analysis of human psoriatic lesions identified significantly elevated expression of the entire biosynthetic/metabolic pathway for oxygenated ceramides, suggesting a regulatory function for EOx lipids in reconstituting epidermal integrity. The role of these new lipids in progression or resolution of psoriasis is currently unknown. We also discovered the central coordinated role of the zinc finger protein transcription factor, ZIC1, in driving the phenotype of this disease. In summary, long-chain oxygenated ceramide metabolism is dysregulated at the lipidomic level in psoriasis, likely driven by the transcriptional differences also observed, and we identified ZIC1 as a potential regulatory target for future therapeutic interventions.

Is Galanin a Promising Therapeutic Resource for Neural and Nonneural Diseases?

BACKGROUND

Galanin (GAL) constitutes a family of neuropeptides composed of four peptides: (i) galanin (GAL), (ii) galanin-message associated peptide (GAMP), (iii) galanin-like peptide (GALP), and (iv) alarin. GAL contains 29/30 amino acids, and its biological action occurs through the interactions with its various receptors (GALR1, GALR2, and GALR3). The neuropeptide GAL regulates several physiological and pathophysiological functions in the central nervous system, the peripheral nervous system, and the peripheral organs. GAL is secreted mainly by oligodendrocytes, astrocytes, and the gastrointestinal tract, and its effect depends on the interaction with its different receptors. These receptors are expressed mainly in the central, peripheral nervous systems and the intestines.

OBJECTIVE

The present review evaluates the role of GAL family in inflammatory diseases. An overview is given of the signaling and pharmacological effects due to the interaction between GAL and GALR in different cell types. The potential use of GAL as a therapeutic resource is critically discussed.

CONCLUSION

GAL is suggested to have an anti-inflammatory function in some situations and a proinflammatory function in others. The literature on GAL is controversial and currently not conclusive. This could be due to the complexity of the metabolic network signaling induced by the interactions between GAL and GALR. In the next future, GAL might be a promising therapeutic resource for several diseases, but its practical use for disease control is presently not advisable.

Therapeutic wavelengths of ultraviolet B radiation activate apoptotic, circadian rhythm, redox signalling and key canonical pathways in psoriatic epidermis

Ultraviolet B radiation (UVB) exerts pleiotropic effects on human skin. DNA damage response and repair pathways are activated by UVB; if damage cannot be repaired, apoptosis ensues. Although cumulative UVB exposure predisposes to skin cancer, UVB phototherapy is widely used as an effective treatment for psoriasis. Previous studies defined the therapeutic action spectrum of UVB and showed that psoriasis is resistant to apoptosis. This study aimed to investigate early molecular responses within psoriasis plaques following irradiation with single equi-erythemogenic doses of clinically-effective (311 nm, narrow-band) compared to clinically-ineffective (290 nm) UVB. Forty-eight micro-dissected epidermal samples from 20 psoriatic patients were analyzed using microarrays. Our bioinformatic analysis compared gene expression between 311 nm irradiated, 290 nm irradiated and control psoriasis epidermis to specifically identify 311 nm UVB differentially expressed genes (DEGs) and their upstream regulatory pathways. Key DEGs and pathways were validated by immunohistochemical analysis. There was a dynamic induction and repression of 311 nm UVB DEGs between 6 h and 18 h, only a limited number of DEGs maintained their designated expression status between time-points. Key disease and function pathways included apoptosis, cell death, cell migration and leucocyte chemotaxis. DNA damage response pathways, NRF2-mediated oxidative stress response and P53 signalling were key nodes, interconnecting apoptosis and cell cycle arrest. Interferon signalling, dendritic cell maturation, granulocyte adhesion and atherosclerotic pathways were also differentially regulated. Consistent with these findings, top transcriptional regulators of 311 nm UVB DEGs related to: a) apoptosis, DNA damage response and cell cycle control; b) innate/acquired immune regulation and inflammation; c) hypoxia/redox response and angiogenesis; d) circadian rhythmicity; f) EGR/AP1 signalling and keratinocyte differentiation; and g) mitochondrial biogenesis. This research provides important insights into the molecular targets of 311 nm UVB, underscoring key roles for apoptosis and cell death. These and the other key pathways delineated may be central to the therapeutic effects of 311 nm in psoriasis.

Causal Relationship and Shared Genetic Loci between Psoriasis and Type 2 Diabetes through Trans-Disease Meta-Analysis

Psoriasis and type 2 diabetes (T2D) are complex conditions with significant impacts on health. Patients with psoriasis have a higher risk of T2D (∼1.5 OR) and vice versa, controlling for body mass index; yet, there has been a limited study comparing their genetic architecture. We hypothesized that there are shared genetic components between psoriasis and T2D. Trans-disease meta-analysis was applied to 8,016,731 well-imputed genetic markers from large-scale meta-analyses of psoriasis (11,024 cases and 16,336 controls) and T2D (74,124 cases and 824,006 controls), adjusted for body mass index. We confirmed our findings in a hospital-based study (42,112 patients) and tested for causal relationships with multivariable Mendelian randomization. Mendelian randomization identified a causal relationship between psoriasis and T2D (P = 1.6 × 10^‒4, OR = 1.01) and highlighted the impact of body mass index. Trans-disease meta-analysis further revealed four genome-wide significant loci (P < 5 × 10^‒8) with evidence of colocalization and shared directions of effect between psoriasis and T2D not present in body mass index. The proteins coded by genes in these loci (ACTR2, ERLIN1, TRMT112, and BECN1) are connected through NF-κB signaling. Our results provide insight into the immunological components that connect immune-mediated skin conditions and metabolic diseases, independent of confounding factors.

An assembly of galanin-galanin receptor signaling network

The galanin receptor family of proteins is present throughout the central nervous system and endocrine system. It comprises of three subtypes-GalR1, GalR2, and GalR3; all of which are G-protein-coupled receptors. Galanin predominantly acts as an inhibitory, hyper-polarizing neuromodulator, which has several physiological as well as pathological functions. Galanin has a role in mediating food intake, memory, sexual behavior, nociception and is also associated with diseases such as Alzheimer's disease, epilepsy, diabetes mellitus, and chronic pain. However, the understanding of signaling mechanisms of the galanin family of neuropeptides is limited and an organized pathway map is not yet available. Therefore, a detailed literature mining of the publicly available articles pertaining to the galanin receptor was followed by manual curation of the reactions and their integration into a map. This resulted in the cataloging of molecular reactions involving 64 molecules into five categories such as molecular association, activation/inhibition, catalysis, transport, and gene regulation. For enabling easy access of biomedical researchers, the galanin-galanin receptor signaling pathway data was uploaded to WikiPathways ( https://www.wikipathways.org/index.php/Pathway:WP4970 ), a freely available database of biological pathways.

Transcriptome Profiling Analyses in Psoriasis: A Dynamic Contribution of Keratinocytes to the Pathogenesis

Psoriasis is an immune-mediated inflammatory skin disease with a complex etiology involving environmental and genetic factors. A better insight into related genomic alteration helps design precise therapies leading to better treatment outcome. Gene expression in psoriasis can provide relevant information about the altered expression of mRNA transcripts, thus giving new insights into the disease onset. Techniques for transcriptome analyses, such as microarray and RNA sequencing (RNA-seq), are relevant tools for the discovery of new biomarkers as well as new therapeutic targets. This review summarizes the findings related to the contribution of keratinocytes in the pathogenesis of psoriasis by an in-depth review of studies that have examined psoriatic transcriptomes in the past years. It also provides valuable information on reconstructed 3D psoriatic skin models using cells isolated from psoriatic patients for transcriptomic studies.

Tolerance and efficacy of a new celastrol-containing balm as adjunct care in psoriasis

BACKGROUND

In patients with psoriasis, the non-lesional skin also presents abnormalities, requiring emollient application on the whole body.

OBJECTIVES

To evaluate the tolerance of a new emollient balm containing celastrol, an active ingredient with anti-Th17 immunomodulatory properties used alone or in association with topical or systemic drug treatments or phototherapy, and its efficacy when used alone.

METHODS

Adults with body plaque psoriasis applied the product over the whole body once a day for 4 weeks (balm used alone in 41 patients and with ongoing treatment in 50 patients). At D1, D8 ('balm alone' study) or D15 ('balm in association' study) and D29, the dermatologist rated physical and functional signs and assessed pruritus and body global lesion score (evaluating erythema, induration/thickness, scaling and dryness) in the 'balm alone' study.

RESULTS

No reaction related to the product was reported, and the tolerance was deemed excellent. In the 'balm alone' study, mean pruritus intensity score significantly decreased at D8 (-39%, P < 0.001) and D29 (-60%, P < 0.001) compared with D1, together with the body global lesion score (-24% at D8 and -26% at D29, P < 0.001). In parallel, quality of life improved, as evidenced by a patient-reported outcome questionnaire. Cosmetic acceptability was good.

CONCLUSION

This new emollient balm was very well tolerated by patients with body plaque psoriasis either alone or in association with drug treatment or phototherapy, which is important to ensure long-term compliance. Daily application during one month improved pruritus, physical signs and quality of life.

Vascular Endothelial Growth Factor Blockade Induces Dermal Endothelial Cell Apoptosis in a Clinically Relevant Skin Organ Culture Model

BACKGROUND/AIMS

Vascular endothelial growth factor (VEGF), a key mediator of angiogenesis, plays a key role in physiological processes and is a major contributor to several diseases including cancer and psoriasis. Anti-VEGF therapies are widely used as cancer and ophthalmological treatments. There is some evidence that VEGF blockade may have utility in the management of psoriasis, although their potential has been largely unexplored. We hypothesized that a human skin organ culture could provide a stable ex vivo model in which the cutaneous microvascular network could be studied and experimentally manipulated.

METHODS

Punch biopsies (3 mm) of skin, donated by healthy individuals (39-72 years old, n = 5), were incubated with monoclonal antibody (mAb) to human VEGF (bevacizumab) at doses based on data from animal and clinical studies. After 3-day culture, cell death and proliferation as well as vascular endothelial cell changes were assessed using quantitative immunohistomorphometry.

RESULTS

Anti-VEGF mAb at 0.8 mg/mL induced a significant increase in cleaved caspase-3 expression in CD31+ cells (p < 0.05). None of the doses tested increased TUNEL or decreased Ki-67 expression in the basal layer of the epidermis, confirming the model's viability. In addition, the lactate dehydrogenase (LDH) assay showed no increase in LDH activity in treated samples compared to untreated control. The highest anti-VEGF mAb dose (0.8 mg/mL) induced an increase in TUNEL expression in the upper epidermis, which did not correlate with caspase-3 immunoreactivity. Further investigation revealed that anti-VEGF mAb did not change the expression of markers of terminal differentiation such as keratin 10, filaggrin, and involucrin, suggesting that VEGF depletion does not affect keratinocyte terminal differentiation. In contrast to the control group, levels of VEGF protein were undetectable in the culture supernatant of samples treated with 0.8 mg/mL of anti-VEGF mAb, suggesting sufficient dose.

CONCLUSION

Our pilot study provides the first evidence that anti-VEGF therapy promotes endothelial cell apoptosis in human skin ex vivo. Our pragmatic human skin organ culture assay offers a valuable tool for future preclinical endothelial cell and translational microvascular network/anti-angiogenesis research in human skin.

Genomic DNA methylation in HLA-Cw*0602 carriers and non-carriers of psoriasis

BACKGROUND

HLA-Cw*0602 has long been established as one of the most important genetic biomarkers in psoriasis. However, the epigenetic and gene expression differences between HLA-Cw*0602 carriers and non-carriers has not yet been investigated.

OBJECTIVE

We aim to explore the whole-genome methylation and gene expression differences between HLA-Cw*0602 carriers and non-carriers.

METHODS

HLA imputation was performed to get landscape of variants in this region. Genome-wide DNA methylation was compared between positive and negative HLA-Cw*0602 groups. Eleven methylation loci were selected for further validation in additional 43 cases. For differentially methylated genes, GO and KEGG were used to annotate gene functions.

RESULTS

We imputed 29,948 variants based on the constructed HLA reference panels, and obtained 42 HLA-Cw*0602 carriers and 72 non-carriers. Significant methylation differences were detected at 4321 sites (811 hypo- and 3510 hypermethylated). The cg02607779 (KLF7, P = 0.001), cg06936779 (PIP5K1A, P = 0.002), cg03860400 (BTBD10, P = 0.017) and cg26112390 (GOLGA2P5, P = 0.019) were identified and validated to be the significant CpGs contributed to different HLA-C*0602 groups. Among the hypo- and hypermethylated sites, the top CpGs were in gene body and CpG island.

CONCLUSION

We performed the first whole-genome study on methylation differences between psoriatic individuals with or without HLA-Cw*0602, and found the key methylation sites which may contribute to the carrying status of HLA-Cw*0602. Methylation loci located in gene body and CpG island are more likely to affect the methylation levels in HLA-Cw*0602 carriers. This integrated analysis shed light on novel insights into the pathogenic mechanisms of genomic methylation in different HLA genotypes of psoriasis.

The miR-155/GATA3/IL37 axis modulates the production of proinflammatory cytokines upon TNF-α stimulation to affect psoriasis development

Psoriasis is a recrudescent chronic immune-mediated inflammatory dermatosis; the production and release of proinflammatory cytokines/chemokines such as TNF-α has been regarded as critical issues during psoriasis pathogenesis. Based on online microarray profiles, the expression of the transcription factor GATA3 was downregulated in psoriasis lesion tissues. In the present study, we searched for miRNAs that might be related to TNF-α and GATA3 to investigate an in-depth understanding of psoriasis pathogenesis. Herein, higher TNF-α and GATA3 protein levels were observed in psoriasis lesion tissues and that GATA3 overexpression significantly reverses TNF-α-induced increases within the production of IL-6 and CXCL8 in keratinocytes. TNF-α stimulation increases miR-155 expression dose-independently, and the miR-155 inhibitor significantly reverses TNF-α-induced suppression of GATA3 protein levels and increases IL-6 and CXCL8 production. miR-155 could suppress the expression of GATA3 by targeting its 3'UTR, while GATA3 could activate the transcription of IL37 by targeting its promoter region. miR-155 overexpression reduces IL37 protein and increases CXCL8 production; GATA3 overexpression might significantly attenuate the effects of miR-155 overexpression. In contrast to GATA3, miR-155 expression is significantly upregulated in psoriasis lesion tissue and is negatively correlated with GATA3 and IL37. In summary, the miR-155/GATA3/IL37 axis modulates the production of IL-6 and CXCL8 upon TNF-α stimulation to affect psoriasis development. Thus, miR-155/GATA3/IL37 may be potent targets for psoriasis treatment, which needs further in vivo and clinical investigation.

Gentiana lutea Extract Modulates Ceramide Synthesis in Primary and Psoriasis-Like Keratinocytes

Gentiana lutea is a bitter herb that is traditionally used to improve gastric disorders. Recently, we have shown that Gentiana lutea extract (GE) also modulates the lipid metabolism of human keratinocytes in vitro and in vivo. In the present study, we investigated the role of GE on ceramide synthesis in human primary keratinocytes (HPKs) and psoriasis-like keratinocytes. We could demonstrate that GE increased the concentrations of glucosylceramides and the ceramide AS/AdS subclass without affecting the overall ceramide content in HPKs. The expression of ceramide synthase 3 (CERS3) and elongases (ELOVL1 and 4) was reduced in psoriasis lesions compared to healthy skin. Psoriasis-like HPKs, generated by stimulating HPKs with cytokines that are involved in the pathogenesis of psoriasis (IL-17, TNF-α, IL-22 and IFN-γ) showed increased levels of IL-6, IL-8 and increased expression of DEFB4A, as well as decreased expression of ELOVL4. The treatment with GE partly rescued the reduced expression of ELOVL4 in psoriasis-like HPKs and augmented CERS3 expression. This study has shown that GE modulates ceramide synthesis in keratinocytes. Therefore, GE might be a novel topical treatment for skin diseases with an altered lipid composition such as psoriasis.

Keratinocytes Derived from Patient-Specific Induced Pluripotent Stem Cells Recapitulate the Genetic Signature of Psoriasis Disease

Psoriasis is characterized by hyperproliferation and defective differentiation of keratinocytes (KCs). Patients with psoriasis are at a high risk of developing diabetes and cardiovascular diseases. The debate on the genetic origin of psoriasis pathogenesis remains unresolved due to lack of suitable in vitro human models mimicking the disease phenotypes. In this study, we provide the first human induced pluripotent stem cell (iPSC) model for psoriasis carrying the genetic signature of the patients. iPSCs were generated from patients with psoriasis (PsO-iPSCs) and healthy donors (Ctr-iPSCs) and were efficiently differentiated into mature KCs. RNA sequencing of KCs derived from Ctr-iPSCs and PsO-iPSCs identified 361 commonly upregulated and 412 commonly downregulated genes. KCs derived from PsO-iPSCs showed dysregulated transcripts associated with psoriasis and KC differentiation, such as HLA-C, KLF4, chemokines, type I interferon-inducible genes, solute carrier family, IVL, DSG1, and HLA-DQA1, as well as transcripts associated with insulin resistance, such as IRS2, GDF15, GLUT10, and GLUT14. Our data suggest that the KC abnormalities are the main driver triggering psoriasis pathology and highlights the substantial contribution of genetic predisposition in the development of psoriasis and insulin resistance.

Integrated microRNA/mRNA expression profiling of the skin of psoriasis patients

BACKGROUND

Psoriasis is a chronic inflammatory disease characterized by demarcated, raised, and scaling skin lesions. It often serves as a model for immune-mediated disorders. Gene expression profiling of affected skin has allowed insights into psoriasis pathogenesis. However, the mechanisms leading to specific mRNA expression alterations in psoriasis are barely understood.

OBJECTIVES

To perform integrated microRNA-mRNA expression studies of non-lesional, peri-lesional, and lesional skin from psoriasis patients.

METHODS

Cutaneous microRNA and mRNA expression profiles of 14 patients using Nanostring nCounter-technology and RNA sequencing as well as in vitro keratinocyte stimulation and qPCR studies.

RESULTS

Only 3.5 % of microRNAs manifested a robust gradual expression trend from non-lesional to paired lesional skin, with 61 % being upregulated and 39 % being downregulated. Relevance of these microRNA regulations was supported by their inverse association with 57 % of the mRNA species found to be regulated during psoriatic lesion development. Many of the involved mRNAs were downregulated and functionally related to keratinocyte metabolism, barrier function, and neuronal signaling, and were already regulated in peri-lesional skin. An integrated correlation analysis revealed a robust interaction for 134 microRNAs/mRNAs pairs. In vitro keratinocyte studies of selected microRNAs/mRNAs revealed regulations of all analyzed microRNAs in a psoriasis-like manner by IL-17A/TNF-α (e.g. hsa-miR-23a-3p), IFN-γ (e.g. hsa-miR-106a-5p/miR-17-5p), or IL-24 (e.g. hsa-miR-203a-3p). Moreover, most of their predicted target mRNAs (e.g. ID4, EPHB2) were respectively altered by the same cytokines.

CONCLUSION

Our study suggests that, during development of psoriatic lesions, defined aspects of psoriasis pathogenesis are regulated by the action of microRNAs.

Comprehensive Proteomic Analysis Reveals Intermediate Stage of Non-Lesional Psoriatic Skin and Points out the Importance of Proteins Outside this Trend

To better understand the pathomechanism of psoriasis, a comparative proteomic analysis was performed with non-lesional and lesional skin from psoriasis patients and skin from healthy individuals. Strikingly, 79.9% of the proteins that were differentially expressed in lesional and healthy skin exhibited expression levels in non-lesional skin that were within twofold of the levels observed in healthy and lesional skin, suggesting that non-lesional skin represents an intermediate stage. Proteins outside this trend were categorized into three groups: I. proteins in non-lesional skin exhibiting expression similar to lesional skin, which might be predisposing factors (i.e., CSE1L, GART, MYO18A and UGDH); II. proteins that were differentially expressed in non-lesional and lesional skin but not in healthy and lesional skin, which might be non-lesional characteristic alteration (i.e., CHCHD6, CHMP5, FLOT2, ITGA7, LEMD2, NOP56, PLVAP and RRAS); and III. proteins with contrasting differential expression in non-lesional and lesional skin compared to healthy skin, which might contribute to maintaining the non-lesional state (i.e., ITGA7, ITGA8, PLVAP, PSAPL1, SMARCA5 and XP32). Finally, proteins differentially expressed in lesions may indicate increased sensitivity to stimuli, peripheral nervous system alterations, furthermore MYBBP1A and PRKDC were identified as potential regulators of key pathomechanisms, including stress and immune response, proliferation and differentiation.

IL-17A inhibition by secukinumab induces early clinical, histopathologic, and molecular resolution of psoriasis

BACKGROUND

Hyperactivity of the IL-23/IL-17 axis is central to plaque psoriasis pathogenesis. Secukinumab, a fully human mAb that selectively inhibits IL-17A, is approved for treatment of psoriasis, psoriatic arthritis, and ankylosing spondylitis. Secukinumab improves the complete spectrum of psoriasis manifestations, with durable clinical responses beyond 5 years of treatment. In the feed-forward model of plaque chronicity, IL-17A has been hypothesized as the key driver of pathogenic gene expression by lesional keratinocytes, but in vivo evidence in human subjects is lacking.

METHODS

We performed a randomized, double-blind, placebo-controlled study (NCT01537432) of patients receiving secukinumab at the clinically approved dose up to 12 weeks. We then correlated plaque and nonlesional skin transcriptomic profiles with histopathologic and clinical measures of efficacy.

RESULTS

After 12 weeks of treatment, secukinumab reversed plaque histopathology in the majority of patients and modulated thousands of transcripts. Suppression of the IL-23/IL-17 axis by secukinumab was evident at week 1 and continued through week 12, including reductions in levels of the upstream cytokine IL-23, the drug target IL-17A, and downstream targets, including β-defensin 2. Suppression of the IL-23/IL-17 axis by secukinumab at week 4 was associated with clinical and histologic responses at week 12. Secukinumab did not affect ex vivo T-cell activation, which is consistent with its favorable long-term safety profile.

CONCLUSION

Our data suggest that IL-17A is the critical node within the multidimensional pathogenic immune circuits that maintain psoriasis plaques and that early reduction of IL-17A-dependent feed-forward transcripts synthesized by hyperplastic keratinocytes favors plaque resolution.

Phenotypic changes of lymphocyte populations in psoriasiform dermatitis animal model

Psoriasis is a T cell mediated, chronic inflammatory autoimmune skin disease that affects up to 2-3% of the global population and leads to a decrease in quality of life. Experimental data accumulated in recent years highlighted the important role played by the immune system in the pathogenesis of this disease. Non-human psoriasis models are an important research tool that attempts to reproduce the clinical features of the disease in order to explain the pathogenesis of psoriasis and to identify possible therapeutic targets. Imiquimod-based murine model of psoriatic dermatitis is an alternative to traditional models of experimental psoriasis in mice and the induced dermatitis closely mimics the pathologic changes in human psoriasis. In order to emphasize changes in immune cell populations involved in lesion pathogenesis, we performed a murine model of psoriasiform dermatitis model by topical IMQ application. The progress and the severity of IMQ-induced skin inflammation were clinically (PASI score) and histopathologically evaluated. The immunological changes induced by IMQ treatment in lymphocyte populations from peripheral blood and spleen were evaluated by flow cytometry. The main changes observed in peripheral blood were the significantly increased T-CD8a⁺ lymphocyte and NK1.1⁺ cell percentages and the decreased T-CD4⁺ and B lymphocyte percentages in IMQ-treated mice. In spleen samples, lymphocytes showed the same tendency of variation as in peripheral blood, but without statistical significance. A significant decrease of B cells percentages was observed in spleen suspensions. Data obtained in skin samples may suggest the involvement of CD3ε⁺, CD4⁺ and CD8a⁺ cells in the lesional process. This murine model was analyzed by performing a basic cellular profile at three levels: peripheral blood, spleen and skin. The evaluation aimed to establish the immune framework of this experimental model that could further be used for etipathogenic mechanism identification and/or for studies regarding targeted therapies.

A skewed pool of resident T cells triggers psoriasis-associated tissue responses in never-lesional skin from patients with psoriasis

BACKGROUND

Resident T cells are implicated in the maintenance and recurrence of psoriatic lesions. Whether skin that has not yet experienced psoriasis in patients with established disease harbors pathogenic T cells is less investigated.

OBJECTIVE

We sought to analyze the composition of resident T cells and T cell-driven tissue responses in skin never affected by psoriasis from patients with mild disease.

METHODS

Never-lesional skin from patients with psoriasis (NLP) was collected from those with mild disease. T-cell profiles were assessed by using confocal imaging and flow cytometry. Tissue responses to T-cell stimulation were measured by using multiplex and NanoString technology.

RESULTS

T-cell activation ex vivo triggered psoriasiform and type I interferon tissue responses in NLP psoriasis. Accordingly, keratinocytes from NLP responded to IFN-γ stimulation with myxovirus 1 (MX1) expression and IFN-α release. Additionally, CCR6-expressing resident T cells poised to produce IFN-γ and IL-17 were enriched in epidermis from NLP, whereas dermal tissue responses and T-cell compositions were similar to those in healthy skin. Finally, keratinocytes from NLP exposed to IL-17 and skin explants exposed to common fungal antigens responded with upregulation of the CCR6 ligand CCL20.

CONCLUSION

Epidermal resident T cells capable of triggering psoriasiform tissue responses accumulate in epidermis from NLP. Our global analysis of NLP reveals that microbial interplay with genetically predisposed keratinocytes might shape the local pool of resident T cells.

Noninvasive profiling of sweat-derived lipid mediators for cutaneous research

BACKGROUND AND OBJECTIVE

Recent increases in the use of noninvasive matrices for biomedical analysis has led to interest in the evaluation of sweat for both clinical and research applications. However, despite being one of the two main cutaneous secretions, until very recently, only one study actually analyzed sweat in the context of cutaneous disease. This review attempts to make the case for increased use of sweat in cutaneous research, and discusses lipid mediators as potential analytical targets in sweat.

METHODS

Sweat composition and its relationship with the skin and systemic circulation are discussed, as are practical considerations for sweat sampling and analysis. Previous analyses of lipid mediators in skin biopsies are provided to show that lipid mediators can regulate cutaneous processes and disease pathways. Summaries of recent studies involving the analysis of sweat lipid mediators are provided to demonstrate the utility of sweat lipid mediator testing to support future cutaneous research studies.

RESULTS

Sweat has the potential to reflect both local and systemic biochemical changes in response to disease or intervention, and two recent studies of sweat lipid mediators confirm this ability. Additionally, sweat lipid mediators appear to be temporally stable with individual variability comparable to other matrices, suggesting that these analytes could be useful biomarkers.

CONCLUSIONS

Sweat metabolites may be capable of reporting changes in cutaneous biochemical pathways, thereby providing insight into the immunomodulatory biochemistry of the skin. Lipid mediator analysis of sweat appears to be a non invasive approach that could enhance existing cutaneous research and diagnostic methodologies.

Signatures of photo-aging and intrinsic aging in skin were revealed by transcriptome network analysis

There are various factors that alter physiological characteristics in skin. Elucidating the underlying mechanism of transcriptional alterations by intrinsic and extrinsic factors may lead us to understand the aging process of skin. To identify the transcriptomic changes of the aging skin, we analyzed publicly available RNA sequencing data from Genotype-Tissue Expression (GTEx) project. GTEx provided RNA sequencing data of suprapubic (n=228) and lower leg (n=349) skins, which are photo-protected and photo-damaged. Using differentially expressed gene analysis and weighted gene co-expression network analysis, we characterized transcriptomic changes due to UV exposure and aging. Genes involved in skin development such as epidermal differentiation complex component (SPRR and LCE families), vasculature development (TGFBR1, TGFBR2, TGFBR3, KDR, FGF2, and VEGFC), and matrix metalloproteinase (MMP2, MMP3, MMP8, MMP10, and MMP13) were up-regulated by UV exposure. Also, down-regulated lipid metabolism and mitochondrial biogenesis were observed in photo-damaged skin. Moreover, wound healing process was universally down-regulated in suprapubic and lower leg with aging and further down-regulation of lipid metabolism and up-regulation of vasculature development were found as photo-aging signatures. In this study, dynamic transcriptomic alterations were observed in aged skin. Hence, our findings may help to discover a potential therapeutic target for skin rejuvenation.

Molecular action of isoflavone genistein in the human epithelial cell line HaCaT

Due to its strong proliferation-reducing effects on keratinocytes, and also anti-inflammatory properties, the isoflavone genistein has already been proposed as a possible antipsoriatic compound. As there is still no detailed information on this topic, we examined the effects of genistein by using an in vitro model of both, normal and "psoriasis-like" keratinocytes at this stage of our work exhaustively testing the selected flavonoid in a mono-treated experimental design. Gene expression studies revealed transcriptional changes that confirms known disease-associated pathways and highlights many psoriasis-related genes. Our results suggested that aberrant expression of genes contributing to the progress of psoriasis could be improved by the action of genistein. Genistein prevented "cytokine mix" as well as TNF-α-induced NF-κB nuclear translocation, with no effect on the PI3K signaling cascade, indicating the luck of turning this pathway into NF-κB activation. It could have attenuated TNF-α and LPS-induced inflammatory responses by suppressing ROS activation. Regardless of the type of keratinocyte stimulation used, reduction of cytokine IL-8, IL-20 and CCL2 production (both at RNA and protein level) following genistein treatment was visible. Because investigations of other groups supported our commentary on potential administration of genistein as a potential weapon in the armamentarium against psoriasis, it is believed that this paper should serve to encourage researchers to conduct further studies on this subject.