Flavonoids from the leaves of Monanthotaxis filipes modulate PCSK9 and LDLR

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).