Genistein increased hepatic cholesterol uptake via a JNK mediated activation of SREBP‐2 and LDLR expression

Abstract

Genistein has been implicated for its anti‐atherogenic effects. To understand the anti‐atherogenic mechanism of action genistein was investigated its impact on hepatic cholesterol uptake, the expression of LDLR which is the receptor for LDL‐cholesterol, and related signaling pathways in human hepatoma HepG2 cells. the The addition of 40 μM genistein increased cholesterol uptake into HepG2cells. Genistein increased mRNA and protein levels of LDLR in a time‐dependent manner. The addition of cholesterol up to 5 μg/mL for 24 hours did not significantly affect the effect of genistein towards LDLR protein expression. Genistein increased the transcriptional activity of LDLR promoter containing reporter gene (pLDLR‐luc, −805 to +50). But sterol‐regulatory element (SRE) deletion mutant construct was failed to be activated by genistein. Genistein increased the nuclear fraction of SREBP‐2 and DNA binding activity of SREBP‐2 to LDLR promoter as assessed by chromatin immunoprecipitation assay (CHIP). Genistein phosphorylated JNKs. JNK inhibitor (SP600126) abolished genistein‐stimulated levels of LDLR and nuclear SREBP‐2. To minimize the effects of c‐Jun, a transcription factor activated by JNK signals, a truncated LDLR luciferase construct that was contained SRE but lacked the c‐jun putative binding site was constructed. Genistein was still able to boost the transcriptional activity of the truncated LDLR construct. In conclusion, our data supports that genistein may have the anti‐atherogenic effects by increasing hepatic LDL cholesterol uptake via activating JNK signals and SREBP‐2 processing, which is followed by up‐regulation of LDLR.