IL-36 has proinflammatory effects on human endothelial cells

Interleukin-36 cytokines are predominantly expressed by epithelial cells. Significant upregulation of epidermal IL-36 is now a recognised characteristic of psoriatic skin inflammation. IL-36 is known to induce inflammatory responses in dendritic cells, fibroblasts and epithelial cells. Although vascular alterations are a hallmark of psoriatic lesions and dermal endothelial cells are well known to play a critical role in skin inflammation, the effects of IL-36 on endothelial cells are unexplored. We here show that endothelial cells including dermal microvascular cells express a functionally active IL-36 receptor. Adhesion molecules VCAM-1 and ICAM-1 are upregulated by IL-36 stimulation, and this is reversed by the presence of the endogenous IL-36 receptor antagonist. IL-36-stimulated endothelial cells secrete the proinflammatory chemokines IL-8, CCL2 and CCL20. Chemotaxis assays showed increased migration of T-cells following IL-36 stimulation of endothelial cells. These results suggest a role for IL-36 in the dermal vascular compartment, and it is likely to enhance psoriatic skin inflammation by activating endothelial cells and promoting leucocyte recruitment.