Influence of cholesterol synthesis and absorption on expression of proteins of the cholesterol reverse transport in HepG2 and CACO-2 cells

Abstract

Inhibitors of cholesterol synthesis (statins) and intestinal absorption (ezetimibe) are potent lowering-cholesterol drugs that reduce the risk for coronary events mainly due to the reduction of plasma low-density lipoprotein (LDL) cholesterol. Statins may also affect the concentration of high-density lipoprotein (HDL) cholesterol, known as atheroprotective, mainly due to its role on cholesterol reverse transport (CRT). However, the response to HDL cholesterol to treatment with statins is highly variable. Therefore, it is of interest to study the regulatory mechanism of proteins involved in CRT, such as ATP-binding cassette transporter A1 e G1 (ABCA1 e ABCG1), apolipoprotein E (ApoE) and scavenger receptor BI (SRBI), mediated by lowering-cholesterol drugs. This study aims to investigate the effects of statins and ezetimibe on expression of ABCA1, ABCG1, ApoE e SRBI in human hepatocyte (HepG2) and enterocyte (Caco-2) cell lines. The cells will be incubated with different concentrations of lowering-cholesterol drugs to evaluate cellular viability and fragmentation by optic microscopy and flow citometry. The mRNA expression of ABCA1, ABCG1, ApoE and SRBI will be measured by quantitative real time PCR (PCRq) and the protein expression will be evaluated by Western blotting and flow citometry. The activity of transcription factors involved in regulation of these genes, such as LXR±, LXR² and SREBP2, will be analyzed by electrophoresis mobility shift assay (EMSA) that allows to situdy the DNA-proteins interactions. The effects of lowering-lipid drugs on transcript stability will be measured by PCRq. The results of this study will contribute to the knowledge of the mechanisms involved on modulation of proteins of the CRT by lowering-lipid drugs. This knowledge would aid the development of new pharmacological strategies that increase HDL in plasma and reduce coronary events in individuals with cardiovascular risk. (AU)