Characterization of a cellular model for studing the effect of HDACs silencing on cholesterol homeostasis

Cholesterol 7α-hydroxylase, CYP7A1, is the rate-limiting enzyme in the conversion of cholesterol to bile acids (BA). Excretion of BA is mediated by the bile salt export pump, BSEP, CYP7A1 and BZEP expression is regulated by e negative feedback and positive feed-forward mechanism, respectively, through BA-mediated activation of farnesoid X receptor, FXR. Histone deacetylases, HDACs, and fibroblast growth factor 19, FGF19, play a key role in the regulation of CYP7A1 gene transcription. FGF19 signals from intestine to liver to repress CYP7A1 via a JNK-dependent pathway. The aim of this work is to characterize a cellular model to investigate the effect of HDACs silencing on cholesterol homeostasis. In human and murine hepatic cell cultures, siRNAs targeting specific HDACs and SMRT/N-CoR have been identified. In four hepatic cell lines, treated with BA and FGF19, gene expression of HDACs, CYP7A1, SHP and BSEP has been determined. Preliminary results suggest Hep3B as a possible cellular model for further investigations. (Funded by CARIPLO Foundation 2008.2511)