RasGRP3 Promotes RAP1B Activity to Inhibit Endothelial Inflammation and Alleviate Atherosclerosis in High-Fat Diet-Fed ApoE−/− Mice

Atherosclerosis (AS) is a cardiovascular disorder accompanied by endothelial dysfunction and vascular inflammation. We aim to investigate the effects of Ras guanine nucleotide-releasing protein 3 (RasGRP3), a guanine nucleotide exchange factor in AS. Decreased RasGRP3 protein expression was observed in the endothelium of high-fat diet-fed ApoE−/− mice and oxidized low-density lipoprotein (ox-LDL)-induced human primary aortic endothelial cells. RasGRP3 overexpression decreased the mRNA expressions and productions of pro-inflammatory cytokines IL-1β, IL-6, and TNF-α, VCAM-1 protein expression, and THP-1 cell adhesion in vitro. RasGRP3 overexpression inhibited NF-κB pathway activation and THP-1 cell adhesion in vitro by activating Ras-related protein 1 (RAP1) without altering its protein expression. In endothelial cell-specific RasGRP3 overexpression ApoE−/− mice, the RAP1B activity was elevated. RasGRP3 overexpression inhibited atherosclerotic plaque formation in the aortic root and reduced lipid deposition in the entire aorta. Additionally, the concentration of IL-1β, IL-6, and TNF-α in vivo was reduced by the RasGRP3 overexpression. Ubiquitin-like containing PHD and RING finger domain 1 (UHRF1), a member of the E3 ubiquitin ligase family, is one of the RasGRP3 binding proteins. A previous study reported that UHRF1 inhibition alleviated ox-LDL-induced endothelial injury. We found that by inhibiting ubiquitination and degradation of RasGRP3, UHRF1 knockdown promoted RasGRP3 protein expression in vitro. In conclusion, RasGRP3 overexpression alleviated endothelial dysfunction and vascular inflammation in AS mice through activation of RAP1B, a process that may be mediated by UHRF1 regulation of RasGRP3 ubiquitination.