Heat shock factor-1 knockout enhances cholesterol 7α-hydroxylase (CYP7A1) and multidrug transporter (MDR1) gene expressions to attenuate atherosclerosis

Abstract

Aims: Stress response, in terms of activation of stress factors, is known to cause obesity and coronary heart disease such as atherosclerosis in human. However, the underlying mechanism(s) of these pathways are not known. Here, we investigated the effect of heat shock factor-1 (HSF-1) on atherosclerosis. Methods and results: HSF-1 and low-density lipoprotein receptor (LDLr) double knockout (HSF-1-/-/LDLr-/-) and LDLr knockout (LDLr-/-) mice were fed with atherogenic western diet (WD) for 12 weeks. WD-induced weight gain and atherosclerotic lesion in aortic arch and carotid regions were reduced in HSF-1-/-/LDLr-/- mice, compared with LDLr-/- mice. Also, repression of PPAR-g2 and AMPKa expression in adipose tissue, low hepatic steatosis, and lessened plasma adiponectins and lipoproteins were observed. In HSF-1-/-/LDLr-/- liver, higher cholesterol 7α-hydroxylase (CYP7A1) and multidrug transporter [MDR1/P-glycoprotein (P-gp)] gene expressions were observed, consistent with higher bile acid transport and larger hepatic bile ducts. Luciferase reporter gene assays with wild-type CYP7A1 and MDR1 promoters showed lesser luminescence than with mutant promoters (HSF-1 binding site deleted), indicating that HSF-1 binding is repressive of CYP7A1 and MDR1 gene expressions. Conclusion: HSF-1 ablation not only eliminates heat shock response, but it also transcriptionally up-regulates CYP7A1 and MDR1/Pgp axis in WD-diet fed HSF-1-/-/LDLr-/- mice to reduce atherosclerosis.