Francesca De Rosa, Francesco Pettini, Ottavia Spiga, Atanas G Atanasov, Fabio Fusi
Calebin A, a naturally occurring polyphenol isolated from Curcuma longa, has attracted attention for its diverse pharmacological activities, although its vascular effects remain poorly defined. The present study investigated the vasorelaxant properties of calebin A in isolated rat blood vessels and explored the underlying molecular mechanisms using electrophysiological, functional, and computational approaches. Whole-cell patch-clamp recordings in rat tail artery smooth muscle cells showed that calebin A reduced Ba2+ currents through CaV1.2 channels in a concentration-dependent manner, accelerating current decay without significantly affecting voltage-dependent activation. Under experimental conditions favouring KCa1.1 current recording, calebin A also enhanced TEA-sensitive outward currents and modified spontaneous transient KCa1.1 current activity. Computational docking analyses identified plausible binding sites for calebin A on both CaV1.2 and KCa1.1 channels. Functional studies demonstrated concentration-dependent, endothelium-independent relaxation of phenylephrine-contracted thoracic aorta rings. Vasorelaxation was reduced under high extracellular K+ conditions, consistent with a contribution of K+ channel-dependent mechanisms. Moreover, calebin A significantly attenuated the contractile response elicited by restoration of extracellular Ca2+ influx under Ca2+-free conditions, whereas it did not significantly modify the contraction attributed to phenylephrine-induced intracellular Ca2+ release. Together, these findings support inhibition of CaV1.2 channels as a major mechanism underlying calebin A-induced vasorelaxation and support a contributory role for KCa1.1-dependent pathways, whose precise molecular basis requires further investigation. This dual pharmacological profile identifies calebin A as a promising template for the development of innovative vasorelaxant compounds acting through complementary mechanisms.