Schwarzinicine A inhibits transient receptor potential canonical channels and exhibits overt vasorelaxation effects

Abstract

This study investigated the vasorelaxant effects of schwarzinicine A, an alkaloid recently reported from Ficus schwarzii Koord. Regulation of calcium homeostasis in vascular smooth muscle cells (VSMC) is viewed as one of the main mechanisms for controlling blood pressure. L‐type voltage‐gated calcium channel (VGCC) blockers are commonly used for controlling hypertension. Recently, the transient receptor potential canonical (TRPC) channels were found in blood vessels of different animal species with evidence of their roles in the regulation of vascular contractility. In this study, we studied the mechanism of actions of schwarzinicine A focusing on its regulation of L‐type VGCC and TRPC channels. Schwarzinicine A exhibited the highest vasorelaxant effect (123.1%) compared to other calcium channel blockers. It also overtly attenuated calcium‐induced contractions of the rat isolated aortae in a calcium‐free environment showing its mechanism to inhibit calcium influx. Fluorometric intracellular calcium recordings confirmed its inhibition of hTRPC3‐, hTRPC4‐, hTRPC5‐ and hTRPC6‐mediated calcium influx into HEK cells with IC50 values of 3, 17, 19 and 7 μM, respectively. The evidence gathered in this study suggests that schwarzinicine A blocks multiple TRPC channels and L‐type VGCC to exert a significant vascular relaxation response.

Preparation and Preliminary Structure–Activity Relationship Studies of Schwarzinicine A Analogs as Vasorelaxant Agents

“…To gain deeper insights into the potential mode of action of selected schwarzinicine A analogs, we conducted a preliminary MD simulation involving a 44 -bound TRPC complex. In our previous study, we showed that 1 inhibited TRPC3- and TRPC6-mediated calcium entry into cells . Due to the absence of an inhibitor-bound TRPC3, we chose to pursue our computational investigation based on a closed conformation of the antagonist AM-1473-bound TRPC6 structure, previously resolved through cryo-EM (PDB ID: 6UZA).…”

“…Following method A, compound 7 was prepared from 64b and propylamine in 49% yield (light yellow oil): 1 N-Phenethyl-1-phenylpentan-3-amine (8). Following method A, compound 8 was prepared from 64e and phenethylamine in 72% yield (yellow oil): 1 N-Phenethyl-1-phenylpentan-2-amine (9). Following method A, compound 9 was prepared from 64c and phenethylamine in 26% yield (yellow oil): 1 28).…”

“…Further investigation into the mechanism of action suggested that schwarzinicine A (1) exerts its significant vasorelaxant effect by inhibiting calcium influx through the blockade of multiple transient receptor potential canonical (TRPC) channels (TRPC3, -4, -5, and -6) and L-type voltage-gated calcium (Ca 2+ ) channels (VGCC). 9 Building on this exciting discovery, a concise synthesis of schwarzinicines A (1) and B (2) has been reported, providing a viable and sustainable source of these alkaloids for further investigations into their biological properties. 10 Based on the structures and vasorelaxant activities of schwarzinicines A−D (1−4), we previously suggested that the chirality at C-2 and minor variations in the methoxy/methylenedioxy substitution pattern in the phenyl ring C of the schwarzinicine scaffold appeared to have no effect on the vasorelaxant activity (Figure 1).…”

“…In our previous study, we showed that 1 inhibited TRPC3-and TRPC6-mediated calcium entry into cells. 9 Due to the absence of an inhibitor-bound TRPC3, we chose to pursue our computational investigation based on a closed conformation of the antagonist AM-1473-bound TRPC6 structure, previously resolved through cryo-EM (PDB ID: 6UZA). 12 Although the chemical structure of the antagonist AM-1473 is grossly different from that of analog 44, both compounds share the characteristic of being small molecules with molecular weights below 350 amu (333 amu for AM-1473, 283 amu for 44).…”

“…Schwarzinicines A–D ( 1 – 4 ) were found to exhibit pronounced vasorelaxant activities in rat isolated aorta (Figure ). Further investigation into the mechanism of action suggested that schwarzinicine A ( 1 ) exerts its significant vasorelaxant effect by inhibiting calcium influx through the blockade of multiple transient receptor potential canonical (TRPC) channels (TRPC3, -4, -5, and -6) and L-type voltage-gated calcium (Ca 2+ ) channels (VGCC) . Building on this exciting discovery, a concise synthesis of schwarzinicines A ( 1 ) and B ( 2 ) has been reported, providing a viable and sustainable source of these alkaloids for further investigations into their biological properties .…”