Curcumin Vasorelaxation in Uterine Artery of Goat (Capra hircus) is Mediated by Differential Activation of Nitric Oxide, Prostaglandin I2, Soluble Guanylyl Cyclase, and Gap Junction Communication

Background: Curcumin is a principal active constituent of Curcuma longa and has potential therapeutic application in various disease states. In this study, we investigated the mechanism of vasorelaxatory effects of curcumin in middle uterine artery (MUA) of both pregnant (P) and nonpregnant (NP) Capra hircus (Ch). Materials and Methods: The middle uterine arterial rings (MUA) were mounted in an automatic organ bath attached to a PowerLab data acquisition system. We analyzed the effect of curcumin on signaling mediators of endothelium‑derived hyperpolarizing factor: nitric oxide (NO), soluble guanylyl cyclase (sGC), prostaglandin I2 (PGI2), and myoendothelial gap junctions (MEGJs). Results: The maximal vasorelaxation response to curcumin (1 ρM–100 µM) induced in phenylephrine- precontracted endothelium intact and denuded MUA rings were 42.58%, 25.12% in NP and 55.49%, 12.66%, in P Ch. In the presence of 1H-(1,2,4) oxadiazolo (4,3,-a) quinoxalin-1-one, the maximal curcumin- induced vasorelaxation (CVR) was inhibited to 20.65%, and 15.81% in MUA of NP and P Ch. In the presence of N.-nitro-L-arginine methyl, indomethacin and combination of both CVR were decreased to 20.49%, 12.47%, 12.82% in MUA ring of NP and to 40.60%, 52.55%, 46.53% in MUA ring of P Ch, respectively. The sensitivity of curcumin to MEGJ blockers carbenoxolone, 18β‑glycyrrhetinic acid in causing vasorelaxation was 33.18%, 22.61% in MUA rings of NP, and to 15.76%, 18.54% in P Ch. Conclusion: In P Ch, endothelium‑dependent vasorelaxation to curcumin is augmented by two‑fold as that of MUA of NP. Endothelial vasorelaxation in MUA of NP is mediated through the activation of cyclooxygenase‑PGI2‑cyclic adenosine monophosphate and endothelial NO synthase (eNOS)‑sGC‑cyclic guanosine monophosphate (cGMP) signaling with low activation of sGC and MEGJ. In contrast, vasorelaxation to curcumin is mediated through increased activity of sGC and MEGJ with major involvement of eNOS‑NO‑sGC‑cGMP in MUA of P Ch. These studies have strong implications in the therapeutic targeting for hypertensive disorders.