Clock-Bmal1 mediates MMP9 induction in acrolein-promoted atherosclerosis associated with gut microbiota regulation

Circadian rhythm is believed to play important roles in atherosclerosis. The gut microbiota is found to be closely related to atherogenesis, and shows compositional and functional circadian oscillation. However, it's still unclarified whether circadian clock and intestinal microbiota are involved in the progression of atherosclerosis induced by environmental pollutant acrolein. Herein, patients with atherosclerosis showed higher MMP9, a promising biomarker for atherosclerosis, and lower Bmal1 and Clock expression in the plasma. Interestingly, acrolein exposure contributed to the increased MMP9, decreased Clock and Bmal1, and activated MAPK pathways in human umbilical vein endothelial cells (HUVECs). We found that knockdown of Clock or Bmal1 lead to upregulation of MMP9 in HUVECs, and that Clock and Bmal1 expression was elevated while MAPK pathways were blocked. Atherosclerotic apolipoproteinE-deficient mice consumed a high-fat diet were used and treated with acrolein (3 mg/kg/day) in the drinking water for 12 weeks. Upregulation of MMP9, and downregulation of Clock and Bmal1 were also observed in plasma of the mice. Besides, acrolein feeding altered gut microbiota composition at a phylum level especially for an increased Firmicutes and a decreased Bacteroidetes. Additionally, gut microbiota showed correlation with atherosclerotic plaque, MMP9 and Bmal1 levels. Therefore, our findings indicated that acrolein increased the expression of MMP9 through MAPK regulating circadian clock, which was associated with gut microbiota regulation in atherosclerosis. Circadian rhythms and gut microbiota might be promising targets in the prevention of cardiovascular disease caused by environmental pollutants.