Macrophage EP4 Deficiency Drives Atherosclerosis Progression via CD36-Mediated Lipid Uptake and M1 Polarization.

Atherosclerosis is a chronic inflammatory disease and a major pathological basis of numerous cardiovascular conditions, with a high global mortality rate. Macrophages play a pivotal role in its pathogenesis through phenotypic switching and foam cell formation. Prostaglandin E2 receptor subtype 4 (EP4) highly expressed on the macrophage surface, is involved in various pathophysiological processes, such as inflammation and lipid metabolism. However, the role of macrophage EP4 in the progression of atherosclerosis remains unclear. To determine whether macrophage EP4 affects the progression of atherosclerosis by regulating foam cell formation and macrophage polarization. Myeloid-specific EP4 knockout mice with an ApoE-deficient background were fed a Western diet for 16 weeks. Our results showed that EP4 expression was significantly downregulated during atherosclerosis. EP4 deficiency was found to exacerbate atherosclerotic plaque formation and destabilizes plaques. In vitro studies further demonstrated that loss of EP4 in myeloid cells promoted foam cell formation and M1 macrophage polarization. Both transcriptomic and proteomic analysis showed that EP4 may regulate these processes by regulating CD36 expression in macrophage, which was further confirmed by Western blot and qPCR. In summary, deficiency of EP4 receptor in macrophages enhance foam cell formation and M1 polarization by upregulating CD36 expression, thereby accelerating the progression of atherosclerosis.