Homocysteine accelerates atherosclerosis via inhibiting LXRα–mediated ABCA1/ABCG1–dependent cholesterol efflux from macrophages

Aims: Macrophage-derived foam-cell formation plays a crucial role in the development of atherosclerosis, and liver X receptor alpha (LXRα) is a key regulator of lipid metabolism in macrophages. Homocysteine (Hcy) is an independent risk factor of atherosclerosis; however, the regulation of lipid metabolism and role of LXRα induced by Hcy in macrophages is still unknown. The present study aimed to investigate the potential role of Hcy in disordered lipid metabolism and atherosclerotic lesions, especially the effects of Hcy on cholesterol efflux in macrophages and the possible mechanisms. Main methods: In vitro, lipid accumulation and cholesterol efflux were evaluated in THP-1 macrophages with Hcy intervention. Real-time quantitative PCR and western blot analyses were used to assess mRNA and protein levels. In vivo, atherosclerotic lesions and lipid profiles were evaluated by methionine diet-induced hyperhomocysteinemia (HHcy) in ApoE^−/− mice. The LXRα agonist T0901317 was used to verify the role of LXRα in HHcy-accelerated atherosclerosis. Key findings: Hcy promoted lipid accumulation and inhibited cholesterol efflux in THP-1 macrophages. HHcy mice showed increased lesion area and lipid accumulation in plaque. Both studies in vitro and in vivo showed decreased expression of ATP binding cassette transporter A1 (ABCA1) and G1 (ABCG1). T0901317 treatment increased ABCA1 and ABCG1 levels; reversed macrophage-derived foam-cell formation in THP-1 macrophages and reduced atherosclerotic lesions in ApoE^−/− mice. Significance: Inhibition of LXRα-mediated ABCA1/ABCG1-dependent cholesterol efflux from macrophages is a novel mechanism in Hcy-accelerated atherosclerosis.