ARF6 controls VSMC phenotypic switching upon lipid stimulation to promote inflammatory signaling contributing to the progression of atherosclerosis.

Vascular smooth muscle cells (VSMCs) play a pivotal role in the development and progression of atherosclerosis. Traditionally viewed as contractile cells that maintain vascular tone and structure, VSMCs undergo phenotypic switching in response to atherogenic stimuli, such as high circulating levels of LDL, thus adopting synthetic, osteogenic, or macrophage-like phenotypes. This plasticity contributes to plaque formation, extracellular matrix remodeling, and inflammatory signaling. We have previously shown that ADP-ribosylation factor 1, a small GTP-binding protein, regulates the expression and function of actin, which is important for maintaining the contractile phenotype of VSMCs. However, the role of ARF6 in phenotypic switching remains to be elucidated. Here, we demonstrate that ARF6 knockdown in human aortic smooth muscle cells reduced lipid uptake through alterations in the expression of scavenger receptors (lectin-like oxidized low-density lipoprotein receptor-1, macrophage scaverger receptor 1), cytokine production (IL-6) as well as the modulation of inflammatory markers and pathways (adhesion molecules, PI3K, NF-kB, p38). To confirm our findings in an in vivo setting, we engineered a novel conditional smooth muscle cell-specific ARF6 KO mouse in an atheroprone background (Acta2-Cre-ERT2(+/-)/Apoee(-/-)/Arf6(f/f) mice). Mice were fed a high-fat diet to accelerate plaque formation. ARF6 knockout resulted in a significant reduction of atherosclerotic lesions in the aortic arch, which was associated with a reduction of collagen and foam cells. Furthermore, we observed that ARF6 regulates the expression of inflammatory markers. These findings highlight the importance of ARF6 expression in VSMCs and its role in the pathogenesis of atherosclerosis.