Flavonoids from the leaves of Monanthotaxis filipes modulate PCSK9 and LDLR

Abstract

Proprotein convertase subtilisin/kexin type 9 (PCSK9) plays a crucial role in the regulation of blood cholesterol levels. Its inhibition attenuates hypercholesterolemia and hence is a viable approach for the management of atherosclerotic cardiovascular disease (ASCVD). We evaluated the flavonoids of the leaves of Monanthotaxis filipes P.H. Hoekstra (Annonaceae) for their effect on PCSK9 and low-density lipoprotein receptor (LDLR) expression at the mRNA level in HepG2 cells using quantitative real-time PCR analysis and for their influence on protein expression by ELISA. Six flavonoids, including two chalcones (1, 5), three flavones (2–4), and one flavanone (6), were isolated by chromatographic techniques and identified by spectroscopic (NMR, IR, UV, MS) analyses. 2′,3′,4′,6′-Tetramethoxychalcone (1) reduced the PCSK9 protein amount and altered LDLR both on mRNA and protein levels, 6,7,8-trimethoxyflavone (2) inhibited PCSK9 both on mRNA and protein levels but did not change the amount of LDLR in HepG2 cells, whereas 2ʹ,4ʹ-dihydroxy-6ʹ-methoxy-3ʹ,5ʹ-dimethylchalcone (5) decreased PCSK9 and upregulated LDLR protein expression. Thus, chalcones 1 and 5, flavones 2–4, and flavanone 6 were shown to be promising compounds for the management of cardiovascular disease. Molecular dynamics simulations suggest that an allosteric mechanism underlies the inhibitory effect of 2 on PCSK9. In contrast, the pronounced activity of 5 is due to the interaction of its benzene ring with the Cys358, Pro438, Val460 and Trp461 residues of the catalytic site, as proposed by Molecular Mechanics Poisson Boltzmann surface area (MM-PBSA) analyses. Our results showed that chalcone 5 might be studied further for the management of atherosclerotic cardiovascular disease (ASCVD).