Cyclopiazonic Acid-Induced Ca(2+) Store Depletion Initiates Endothelium-Dependent Hyperpolarization-Mediated Vasorelaxation of Mesenteric Arteries in Healthy and Colitis Mice

Purposes: Since the role of store-operated calcium entry (SOCE) in endothelium-dependent hyperpolarization (EDH)-mediated vasorelaxation of mesenteric arteries in health and colitis is not fully understood, cyclopiazonic acid (CPA), a specific inhibitor of the sarco(endo) plasmic reticulum calcium-ATPases (SERCA), was used as a SOCE activator to investigate its role in normal mice and its alteration in colitis mice. Methods: The changes in Ca(2+) signaling in vascular endothelial cells (VEC) were examined by single cell Ca(2+) imaging and tension of mesenteric arteries in response to CPA were examined using Danish DMT520A microvascular measuring system. Results: CPA activated the SOCE through depletion of the endoplasmic reticulum (ER) Ca(2+) in endothelial cells. CPA had a concentration-dependent vasorelaxing effect in endothelium-intact mesenteric arteries, which was lost after endothelial removal. Both nitric oxide (NO) and prostacyclin (PGI(2)) inhibitors did not affect CPA-induced vasorelaxation; however, after both NO and PGI(2) were inhibited, K(Ca) channel blocker [10 mM tetraethylammonium chloride (TEA)] inhibited CPA-induced vasorelaxation while K(Ca) channel activator (0.3 μM SKA-31) promoted it. Two SOCE blockers [30 μM SKF96365 and 100 μM flufenamic acid (FFA)], and an Orai channel blocker (30 μM GSK-7975A) inhibited this vasorelaxation. The inhibition of both Na(+)/K(+)-ATPase (NKA) and Na(+)/Ca(2+)-exchange (NCX) also inhibited CPA-induced vasorelaxation. Finally, the CPA involved in EDH-induced vasorelaxation by the depletion of ER Ca(2+) of mesenteric arteries was impaired in colitis mice. Conclusion: Depletion of ER Ca(2+) by CPA induces a vasorelaxation of mesenteric arteries that is mediated through EDH mechanism and invokes the activation of SOCE. The CPA-induced endothelium-dependent dilation is impaired in colitis which may limit blood perfusion to the intestinal mucosa.