Endothelial IL-36 receptor activation promotes vascular stability to limit pathological microvessel permeability in the CNS

Pathological increases in vascular permeability lead to edema and swelling, causing a host of retinal and neurological disorders. Few barrier-enhancing factors have been discovered to specifically promote barrier integrity and make blood vessels resistant to fluid leakage. In this study, we explore the effects of IL-36 receptor (IL-36R) activation on vascular permeability in vivo in adult mice, ex vivo in tissue explant and in vitro in primary mouse and human microvascular endothelial cells. Using a highly soluble and biologically active DEVD- modified recombinant IL-36ß cytokine, we find that processed DEVDIL-36ß enhances endothelial barrier function, reducing vascular leakage and thus limiting pathology. Specific knockdown of IL-36R on endothelial cells using the Cre/Lox system demonstrates it is IL-36R signaling in endothelial cells that is responsible for DEVDIL-36ß's barrier-promoting property. Analysis of IL-36R expression and localization on endothelial cells implies IL-36R is mobilized to the plasma membrane in response to loss of endothelial cell-cell contact, in keeping with the IL-1 family role in responding to tissue stress. Mechanistically, IL-36R signaling increases adherens and tight junctions and induces vasculoprotective processes that result in vessel remodeling and stabilization. These functional assays are further supported by RNA sequencing data. In summary, our data present IL-36R signaling as a novel regulator of vascular integrity, with barrier-enhancing properties that prevent pathological vascular leakage. Overall design: RNA-Seq profiling of primary mouse brain microvascular endothelial cells (BMVECs) treated with DEVD mIL-36ß (100 ng/ml) for either 24 hours or untreated.