BRG1 regulates endothelial-derived IL-33 to promote ischemia-reperfusion induced renal injury and fibrosis in mice.

Endothelial-derived factors regulate a wide range of pathophysiological events. It has been reported previously that IL-33 promotes acute kidney injury (AKI) in mice although the underlying epigenetic mechanism is unclear. In the present study we investigated the role of BRG1, a chromatin remodeling protein, in AKI with a focus on its regulation of IL-33 expression in endothelial cells. Smarca4-flox mice were crossbred with Cdh5-Cre mice to achieve endothelial-specific deletion of BRG1. AKI was induced by unilateral renal ischemia followed by reperfusion. Compared to wild type (WT) littermates, endothelial conditional BRG1 knockout (CKO) mice were protected from ischemia-reperfusion induced AKI as evidenced by decreased plasma creatinine levels, attenuated caste and tubular necrosis, and diminished immune infiltrates. CKO mice also developed less severe renal fibrosis as indicated by expression levels of extracellular matrix proteins, picrosirius red staining of collagenous tissues, and quantification of renal hydroxylproline levels. Of interest, renal expression of IL-33 was down-regulated as result of endothelial BRG1 deficiency. In cultured endothelial cells, BRG1 directly bound to the IL-33 promoter to activate transcription. Endothelial cell-derived conditioned media promoted the synthesis of pro-fibrogenic proteins in renal tubular epithelial cells. Knockdown of either BRG1 or IL-33 in endothelial cells blunted the pro-fibrogenic response in renal tubular epithelial cells. In conclusion, we propose that BRG1 may contribute to ischemia-reperfusion induced renal injury and fibrosis by promoting IL-33 transcription in endothelial cells.