The Spectrum of Mild to Severe Psoriasis Vulgaris Is Defined by a Common Activation of IL-17 Pathway Genes, but with Key Differences in Immune Regulatory Genes
JOURNAL OF INVESTIGATIVE DERMATOLOGY
Authors: Kim, Jaehwan; Bissonnette, Robert; Lee, Jongmi; da Rosa, Joel Correa; Suarez-Farinas, Mayte; Lowes, Michelle A.; Krueger, James G.
Abstract
Mild versus severe psoriasis is often distinguished by clinical measures such as the extent of skin involvement or Psoriasis Area and Severity Index score, both of which use arbitrary boundaries. It is widely assumed that severe psoriasis involves higher levels of skin inflammation, but comparative molecular profiles of mild versus severe disease have not been performed. In this study, we used immunohistochemistry, reverse transcription PCR, and gene arrays to determine the phenotype of North American patients with mild psoriasis (n = 34, mean PASI score = 5.5) versus severe psoriasis (n = 23, mean PASI score = 23.2). Overall, skin inflammation, defined as the sum of T-cell infiltration/activation and IL-17-mediated epidermal responses, was not higher in severe psoriasis lesions. Surprisingly, mild psoriasis was characterized by higher numbers of T cells in skin lesions, higher IL-17A expression, and stronger expression of the core psoriasis transcriptome. In contrast, severe psoriasis was characterized by stronger expression of some epidermal response genes (TGFA, CALM1, SMPD3, and IL1RL2). However, a key molecular distinction was higher expression of negative immune regulatory genes (CTLA4, CD69 and PD-L1) in mild lesions compared with severe psoriasis lesions. These data have important implications for treating psoriasis across the spectrum of disease, as well as for potential mechanisms that allow psoriasis to progress to more extensive cutaneous disease.
An analysis of IL-36 signature genes and individuals with IL1RL2 knockout mutations validates IL-36 as a psoriasis therapeutic target
SCIENCE TRANSLATIONAL MEDICINE
Authors: Mahil, Satveer K.; Catapano, Marika; Di Meglio, Paola; Dand, Nick; Ahlfors, Helena; Carr, Ian M.; Smith, Catherine H.; Trembath, Richard C.; Peakman, Mark; Wright, John; Ciccarelli, Francesca D.; Barker, Jonathan N.; Capon, Francesca
Abstract
Interleukin (IL)-36a, IL-36b, and IL-36g are innate mediators of acute epithelial inflammation. We sought to demonstrate that these cytokines are also required for the pathogenesis of plaque psoriasis, a common and chronic skin disorder, caused by abnormal T helper 17 (T(H)17) cell activation. To investigate this possibility, we first defined the genes that are induced by IL-36 cytokines in primary human keratinocytes. This enabled us to demonstrate a significant IL-36 signature among the transcripts that are up-regulated in plaque psoriasis and the susceptibility loci associated with the disease in genome-wide studies. Next, we investigated the impact of in vivo and ex vivo IL-36 receptor blockade using a neutralizing antibody or a recombinant antagonist. Both inhibitors had marked anti-inflammatory effects on psoriatic skin, demonstrated by statistically significant reductions in IL-17 expression, keratinocyte activation, and leukocyte infiltration. Finally, we explored the potential safety profile associated with IL-36 blockade by phenotyping 12 individuals carrying knockout mutations of the IL-36 receptor gene. We found that normal immune function was broadly preserved in these individuals, suggesting that IL-36 signaling inhibition would not substantially compromise host defenses. These observations, which integrate the results of transcriptomics and model system analysis, pave the way for early-stage clinical trials of IL-36 antagonists.