273-LB: Leukocyte-Endothelial Interaction Is Reduced by Insulin-Induced Downregulation of Endothelial CXCR4

Abstract

An activated, pro-inflammatory endothelium is a key feature of obesity and type 2 diabetes and may contribute to adipose tissue inflammation, atherosclerosis and tumor formation. We have previously published a striking 4-fold increase in leukocyte adhesion to endothelium in mice with endothelial cell knockout of the insulin receptor. Here, we searched for insulin-regulated genes involved in leukocyte-endothelial cell interaction by performing RNA sequencing in primary human endothelial cells. Among genes with the largest change in expression after insulin treatment was C-X-C motif chemokine receptor 4 (CXCR4), which was downregulated by 54%. This reduction was completely prevented by pretreatment with wortmannin but not by U0126, an inhibitor of MAPK signaling. In CD31+ cells isolated by fluorescence-activated cell sorting of enzymatically dissociated tissue, CXCR4 mRNA in was 77% higher in mice with diet-induced obesity compared to lean controls and 37% higher in db/db mice compared to db/+ controls, consistent with upregulation of CXCR4 in endothelial cell insulin resistance. Stromal-derived factor-1 (SDF-1), the ligand for CXCR4, increased leukocyte adhesion to cultured endothelial cells. Insulin treatment of endothelial cells prevented 80% of this increase which in turn was abrogated by plerixafor, a clinically approved CXCR4 antagonist, or deletion of CXCR4 by gene editing. To study gain of endothelial cell insulin signaling in vivo, we examined transgenic mice with endothelial overexpression of insulin receptor substrate-1 (IRS-1). In vivo microscopy of mesenteric venules showed an increase in leukocyte rolling and adhesion after intravenous injection of SDF-1 in wildtype mice which was reduced by 83% in transgenic mice. We conclude that endothelial cell insulin signaling limits leukocyte-endothelial cell interaction through downregulation of CXCR4 and that targeting endothelial CXCR4 may protect against inflammation in insulin resistant states. Disclosure B. Kunkemoeller: None. T. Rathjen: Employee; Self; Bayer AG. J.C. Patti: None. Q. Li: None. K. Park: None. G.L. King: Research Support; Self; Sanofi. C. Rask-Madsen: None.