Absence of the G Protein–Coupled Receptor G2A in Mice Promotes Monocyte/Endothelial Interactions in Aorta

Abstract—The G protein–coupled receptor G2A is highly expressed on macrophages and lymphocytes and has been localized to atherosclerotic plaques. We examined the role of G2A in modulating monocyte/endothelial interactions in the vessel wall. We measured adhesion of WEHI 78/24 monocytes to aortas of C57BL/6 (B6) and G2A-deficient (G2A/) mice using an ex vivo adhesion assay. G2A/ mice had 10-fold elevations in adhesion of monocytes to aortas. Injection of GFP-expressing wild-type macrophages into B6 and G2A/ mice in vivo showed increased macrophage accumulation in the aortic wall of G2A/ mice. We isolated aortic endothelial cells (ECs) from B6 and G2A/ mice and found a 2-fold increase in intercellular adhesion molecule-1 and E-selectin surface expression on G2A/ ECs using flow cytometry. Using ELISA, we found a 3-fold increase in interleukin-6 and monocyte chemoattractant protein-1 production by G2A/ ECs compared with B6 ECs. We found a dramatic increase in nuclear localization of the p65 subunit of nuclear factor B in G2A/ ECs. Transfection of G2A into G2A/ ECs to restore normal expression levels reduced p65 nuclear localization to 35%. Restoration of G2A expression in G2A/ ECs significantly reduced intercellular adhesion molecule-1 and endothelial selectin surface expression and reduced monocyte chemoattractant protein-1 and interleukin-6 production. Restoring G2A to G2A/ ECs reduced monocyte adhesion by 80 % compared with G2A/ ECs in a flow chamber assay. Absence of G2A in endothelium results in proinflammatory signaling and increased monocyte/endothelial interactions in the aortic wall. Thus, endothelial G2A expression may aid in preventio