Figure 4.

TLR4 accelerates atherosclerotic plaque formation and VSMC foam cell formation by upregulating the ACAT1 expression. (a) ACAT1 expression in aortas detected by western blot. HF diet induced ACAT1 expression in ApoE^−/− mice but not in ApoE/TLR4^−/− mice (*P<0.05 versus ApoE^−/− mice with NC diet). (b) Primary VSMCs from WT and TLR4^−/− mice were treated with oxLDL (80 μg/ml) for 24 h in the presence of LPS (100 ng/ml) or eritoran (Erit) (10 ng/ml). OxLDL significantly increased the level of ACAT1 in VSMCs from WT mice. LPS further increased, whereas eritoran significantly impeded, the oxLDL-induced ACAT1 expression. In contrast, VSMCs from TLR4^−/− mice failed to regulate the ACAT1 expression in response to oxLDL, LPS or eritoran exposure (*P<0.05 versus control WT-VSMCs; ^#P<0.05 versus WT-VSMCs with oxLDL challenge). (c–e) Primary VSMCs from WT and ACAT1^−/− mice were treated with oxLDL for 24 h in the presence of LPS or eritoran. OxLDL significantly increased the level of TLR4 in VSMCs from WT and ACAT1^−/− mice, which were reverted by eritoran and further enhanced by LPS (c). LPS significantly increased oxLDL-induced lipid droplet accumulation (d) and intracellular cholesterol elevation (e) in VSMCs from WT mice, whereas eritoran exposure exerted the opposite effect. In contrast, oxLDL failed to increase lipid droplet accumulation (d) and intracellular cholesterol level (e) in VSMCs from ACAT1^−/− mice. Neither LPS nor eritoran exerted detectable impact on lipid droplet accumulation (d) and intracellular cholesterol level (e) in VSMCs from ACAT1^−/− mice (*P<0.05 versus control WT-VSMCs; ^#P<0.05 versus control WT-VSMCs with oxLDL challenge). Results were presented as mean±S.D. (error bars) of three independent experiments