Chemerin, a chemoattractant ligand for chemokine-like receptor 1 (CMKLR1) is predicted to share similar tertiary structure with antibacterial cathelicidins. Recombinant chemerin has antimicrobial activity. Here we show that endogenous chemerin is abundant in human epidermis, and that inhibition of bacteria growth by exudates from organ cultures of primary human skin keratinocytes is largely chemerin-dependent. Using a panel of overlapping chemerin-derived synthetic peptides, we demonstrate that the antibacterial activity of chemerin is primarily mediated by Val66-Pro85, which causes direct bacterial lysis. Therefore, chemerin is an antimicrobial agent in human skin.

No abstract

IL-17E (IL-25) is a member of the IL-17 cytokine family involved in the promotion of type 2 immune responses. Recently, IL-17E has been reported to be up-regulated in distinct skin inflammatory diseases such as psoriasis and atopic and contact dermatitis. We assessed the role played by IL-17E in skin inflammation. Here, we show that IL-17E induces skin inflammation in vivo, characterized by the expression of innate immune response genes and the recruitment of innate immune cells, particularly neutrophils. Genetic deletion or IL-17E neutralization ameliorated skin inflammation induced by imiquimod application or tape stripping, with reductions in neutrophil and macrophage infiltration as assessed by t-distributed stochastic neighbor embeddingeguided multiparameter flow cytometry analysis, in mice. In humans, IL-17E promotes the recruitment of neutrophils via activation of macrophages in a p38-dependent mechanism. In addition, IL-17E is up-regulated in neutrophil-rich inflammatory skin diseases, such as pyoderma gangrenosum and acute generalized exanthematous pustulosis. Our data show a role for IL-17E in skin inflammation that is unrelated to the development of type 2 immune reactions. We propose that IL-17E is an important common denominator of chronic skin inflammation, promoting innate immune cell recruitment and activation.

Our group has recently shown that keratinocyte-derived IL-17E (IL-25), one of six members of the IL-17 family, is overexpressed in lesional psoriatic skin and is involved in its pathophysiology. We show here that IL-22 enhances IL-17E production in human keratinocytes and that these cells display a complete IL-17E receptor at their surface, the expression of which is further induced by IL-17A, indicating a potential autocrine effect of IL-17E. Therefore, we addressed the impact of IL-17E on the function of human primary keratinocytes. IL-17E promoted the proliferation of keratinocytes in two-dimensional and three-dimensional cultures and caused the concomitant upregulation of differentiation-associated gene transcripts (e.g., keratin 10), whereas their expression was either inhibited or not changed by IL-17A. Contrary to IL-17A, IL-17E was not involved in the induction of antimicrobial proteins. Time-lapse analysis of cell movement showed that IL-17E influences cell motility, increasing both cell speed and displacement. This was associated with specific changes in the actin cytoskeleton organization and the cell-substrate adhesion. No such effects were observed upon IL-17A stimulation. In summary, we identified effects of IL-17E clearly distinct from IL-17A, pointing toward an important role of IL-17E in the physiology and pathophysiology of the epidermis.

(2015) Fenofibrate enhances barrier function of endothelial continuum within the metastatic niche of prostate cancer cells, Expert