ABSTRACT
Cardiovascular disease (CVD) occurs globally and has a high mortality rate. The highest risk factor for developing CVD is high blood pressure. Currently, natural products are emerging for the treatment of hypertension to avoid the side effects of drugs. Among existing natural products, lupeol is known to be effective against hypertension in animal experiments. However, there exists no study regarding the molecular physiological evidence against the effects of lupeol. Consequently, we investigated the interaction of lupeol with α3ß4 nicotinic acetylcholine receptors (nAChRs). In this study, we performed a two-electrode voltage-clamp technique to investigate the effect of lupeol on the α3ß4 nicotine acetylcholine receptor using the oocytes of Xenopus laevis. Coapplication of acetylcholine and lupeol inhibited the activity of α3ß4 nAChRs in a concentration-dependent, voltage-independent, and reversible manner. We also conducted a mutational experiment to investigate the influence of residues of the α3 and ß4 subunits on lupeol binding with nAChRs. Double mutants of α3ß4 (I37A/N132A), nAChRs significantly attenuated the inhibitory effects of lupeol compared to wild-type α3ß4 nAChRs. A characteristic of α3ß4 nAChRs is their effect on transmission in the cardiac sympathetic ganglion. Overall, it is hypothesized that lupeol lowers hypertension by mediating its effects on α3ß4 nAChRs. The interaction between lupeol and α3ß4 nAChRs provides evidence against its effect on hypertension at the molecular-cell level. In conclusion, the inhibitory effect of lupeol is proposed as a novel therapeutic approach involving the antihypertensive targeting of α3ß4 nAChRs. Furthermore, it is proposed that the molecular basis of the interaction between lupeol and α3ß4 nAChRs would be helpful in cardiac-pharmacology research and therapeutics.
