Crocetin exerts hypocholesterolemic effect by inducing LDLR and inhibiting PCSK9 and Sortilin in HepG2 cells

Abstract

Proprotein convertase subtilisin/kexin type 9 (PCSK9) is an important post-transcriptional regulator of plasma levels of low-density lipoprotein cholesterol (LDL-C). Inhibition of PCSK9 has emerged as an attractive strategy in recent years to combat hypercholesterolemia stimulating the search for PCSK9 inhibitors. The carotenoid crocetin exhibits hypocholesterolemic effect. However, it is unknown whether the beneficial effect is mediated through PCSK9 modulation. We hypothesized that crocetin inhibits PCSK9 and therefore, in our quest for natural and safe PCSK9 inhibitors, we investigated crocetin on PCSK9 expression and other key molecular targets involved in hepatic cholesterol metabolism using the human hepatoma cell line HepG2 as a model system. We demonstrate for the first time that crocetin treatment significantly decreases PCSK9 and sterol regulatory element binding proteins (SREBP) expression in a dose-dependent manner, accompanied by a concomitant increase in the hepatic low-density lipoprotein receptor (LDLR) expression. Additionally, crocetin significantly downregulates the levels of both mRNA and protein expression of sortilin, a key sorting receptor that facilitates PCSK9 transport in the trans Golgi network in a dose dependent manner. Overall, our results suggest that crocetin is a LDLR inducer, and an inhibitor of PCSK9, sortilin and SREBPs, thus making it an effective natural anti-cholesterol agent.