Psoriasis
A Framework for Multi-Omic Prediction of Treatment Response to Biologic Therapy for Psoriasis
Biologic therapies have shown high efficacy in psoriasis, but individual response varies and is poorly understood. To inform biomarker discovery in the Psoriasis Stratification to Optimise Relevant Therapy (i.e., PSORT) study, we evaluated a comprehensive array of omics platforms across three time points and multiple tissues in a pilot investigation of 10 patients with severe psoriasis, treated with the tumor necrosis factor (TNF) inhibitor, etanercept. We used RNA sequencing to analyze mRNA and small RNA transcriptome in blood, lesional and nonlesional skin, and the SOMAscan platform to investigate the serum proteome.Genome-Wide DNA Methylation Profiling Identifies Differential Methylation in Uninvolved Psoriatic Epidermis
Psoriasis is a chronic inflammatory skin disease with both local and systemic components. Genome-wide approaches have identified more than 60 psoriasis-susceptibility loci, but genes are estimated to explain only one-third of the heritability in psoriasis, suggesting additional, yet unidentified, sources of heritability. Epigenetic modifications have been linked to psoriasis and altered DNA methylation patterns in psoriatic versus healthy skin have been reported in whole-skin biopsies. In this study, focusing on epigenetic modifications in the psoriatic uninvolved skin, we compared the lesional and non-lesional epidermis from psoriasis patients with epidermis from healthy controls.Psoriasis-Associated Late Cornified Envelope (LCE) Proteins Have Antibacterial Activity
Terminally differentiating epidermal keratinocytes express a large number of structural and antimicrobial proteins that are involved in the physical barrier function of the stratum corneum and provide innate cutaneous host defense. Late cornified envelope (LCE) genes, located in the epidermal differentiation complex on chromosome 1, encode a family of 18 proteins of unknown function, whose expression is largely restricted to epidermis. Deletion of two members, LCE3B and LCE3C (LCE3B/C-del), is a widely-replicated psoriasis risk factor that interacts with the major psoriasis-psoriasis risk gene HLA-C*06.Endogenous Glucocorticoid Deficiency in Psoriasis Promotes Inflammation and Abnormal Differentiation
The factors involved in maintaining a localized inflammatory state in psoriatic skin remain poorly understood. Here, we demonstrate through metabolomic and transcriptomic profiling marked suppression of glucocorticoid biosynthesis in the epidermis of psoriatic skin leading to localized deficiency of cortisol. Utilizing a 3D human epidermis model, we demonstrate that glucocorticoid biosynthesis is suppressed by proinflammatory cytokines and that glucocorticoid deficiency promotes inflammatory responses in keratinocytes.Induction of Alternative Proinflammatory Cytokines Accounts for Sustained Psoriasiform Skin Inflammation in IL-17C+IL-6KO Mice
IL-6 inhibition has been unsuccessful in treating psoriasis, despite high levels of tissue and serum IL-6 in patients. In addition, de novo psoriasis onset has been reported after IL-6 blockade in patients with rheumatoid arthritis. To explore mechanisms underlying these clinical observations, we backcrossed an established psoriasiform mouse model (IL-17C+ mice) with IL-6-deficient mice (IL-17C+KO) and examined the cutaneous phenotype. IL-17C+KO mice initially exhibited decreased skin inflammation; however, this decrease was transient and reversed rapidly, concomitant with increases in skin Tnf, Il36α/β/γ, Il24, Epgn, and S100a8/a9 to levels higher than those found in IL-17C+ mice.Keratinocyte-Derived IL-17E Contributes to Inflammation in Psoriasis
Psoriasis is a chronic inflammatory skin disorder effectively treated by blocking IL-17RA, a receptor chain used by several IL-17 family members, including IL-17E. Although IL-17A is critically involved in the pathogenesis of psoriasis, the contribution of IL-17E remains unknown. Here we show that IL-17E+ cells are more abundant than IL-17A+ cells in lesional psoriatic skin. IL-17E synthesis is increased in keratinocytes within psoriatic plaques, and macrophages having a mixed M1/M2 phenotype represent an important proportion of the IL-17E+ cells infiltrating the dermis.Sebaceous Gland Atrophy in Psoriasis: An Explanation for Psoriatic Alopecia?
In a transcriptome study of lesional psoriatic skin (PP) versus normal skin, we found a coexpressed gene module (N5) enriched 11.5-fold for lipid biosynthetic genes. We also observed fewer visible hairs in PP skin, compared with uninvolved nonlesional psoriatic skin or normal skin (P < 0.0001). To ask whether these findings might be due to abnormalities of the pilosebaceous unit, we carried out three-dimensional morphometric analysis of paired PP and nonlesional psoriatic skin biopsies. Sebaceous glands were markedly atrophic in PP versus nonlesional psoriatic skin (91% average reduction in volume, P = 0.031).Cross-Disease Transcriptomics: Unique IL-17A Signaling in Psoriasis Lesions and an Autoimmune PBMC Signature
Transcriptome studies of psoriasis have identified robust changes in mRNA expression through large-scale analysis of patient cohorts. These studies, however, have analyzed all mRNA changes in aggregate, without distinguishing between disease-specific and nonspecific differentially expressed genes (DEGs). In this study, RNA-seq meta-analysis was used to identify (1) psoriasis-specific DEGs altered in few diseases besides psoriasis and (2) nonspecific DEGs similarly altered in many other skin conditions.
