Epigenetic regulation of PCSK9 expression by statins

Abstract Background Statins are lipid-lowering drugs widely used to reduce the risk of cardiovascular diseases. Although they inhibit HMG-CoA, statins are known to induce the expression of PCSK9, a key regulator of plasma LDL-cholesterol. However, the underlying epigenetic mechanisms remain unknown. Objective This study aimed at investigating the histone modification-mediate epigenetic regulation of PCSK9 and the underlying mechanisms during statin treatment. Methods Using immunoblotting, qPCR, and immunofluorescence techniques we assessed various histone modifications and expression levels of PCSK9 and other cholesterol-regulating candidates upon statin treatment. Further, 4-6 weeks old C57BL/6 mice were subjected to high-fat diet in combination with atorvastatin for 10 weeks. We then performed ChIP-qPCR to evaluate the fold enrichment of targeted histone marks at the gene promoter regions of PCSK9 and SREBP. Results Atorvastatin and cholesterol-treated HepG2 cells were reported to have an increased transcript and protein expression of PCSK9. Further, screening of different histone methylation and acetylation marks under atorvastatin treatment revealed significant enrichment in the levels of the activating H3K4me3 and H3K9ac marks. ChIP-qPCR analysis suggested significantly higher enrichment of H3K4me3 and H3K9ac at the gene promoter region of PCSK9 and SREBP2 (Figure 1&2). In vitro pharmacological intervention against these histone modifications not only significantly lowered their activation but also attenuated statin-induced PCSK9 expression. Conclusion Together, these findings suggest that statins modulate the expression of PCSK9 by regulating H3K4me3 and H3K9ac levels at the PCSK9 gene promoter. Inhibition of these activating histone modifications repressed statin-dependent PCSK9 expression. Thus, targeting chromatin remodeling may help negate the adverse effects of statin treatment, primarily of increasing PCSK9 during hypercholesterolemia.