N,N,N',N'-Tetrakis(2-pyridylmethyl)ethylenediamine induces endothelium-dependent hyperpolarization-mediated vasorelaxation via store-operated calcium entry mechanism in healthy and intestinal inflammatory mice.

Although the store-operated Ca entry (SOCE) plays a critical role in maintaining Ca homeostasis in vascular endothelial cells (VECs), its role in regulating endothelium-dependent hyperpolarization (EDH)-mediated vasorelaxation is largely unknown. Inflammatory bowel disease (IBD) and irritable bowel syndrome (IBS) are the most common gastrointestinal disorders with no effective cures. The present study applied N,N,N',N'-tetrakis (2-pyridylmethyl)ethylenediamine (TPEN) as a Ca chelator in the endoplasmic reticulum (ER) to study the SOCE/EDH-mediated vasorelaxation of micro-arteries and their involvements in the pathogenesis of IBD and IBS. Human submucosal arterioles and the second-order branch of 6-8 weeks male C57BL/6 mouse mesenteric arterioles were used, and TPEN-induced vasorelaxation was recorded by Danish DMT520A microvascular measuring system. The mice were fed water with 2.5 % dextran sulfate sodium for 7 days to induce mouse model of ulcerative colitis, and water avoidance stress was used to induce mouse model of IBS. The statistical significance of differences in the means of experimental groups was determined using a -test for two groups or one-way ANOVA for more than two groups. TPEN concentration-dependently induced vasorelaxation of human colonic submucosal arterioles and the second-order branch of murine mesenteric arteries in endothelium-dependent manner. TPEN-induced vasorelaxation was much greater in the arteries pre-constricted by noradrenaline than those by high K. While TPEN-induced vasorelaxation was unaffected by inhibitors of NO and PGI, it was significantly inhibited by the selective inhibitors of IK and SK channels but was potentiated by their activator. Moreover, TPEN-induced vasorelaxation was attenuated by selective inhibitors of NCX, NKA, SOCE, STIM translocation and Orai transportation. Finally, TPEN-induced vasorelaxation via SOCE/EDH was impaired in colitic mice but remained intact in IBS mice. Interestingly, TPEN could rescue vagus neurotransmitter ACh-induced vasorelaxation that was impaired in IBS mice. Therefore, since TPEN-induced SOCE/EDH-mediated vasorelaxation of mesenteric arteries is well-preserved to be able to rescue ACh-induced vasorelaxation impaired in IBS, TPEN has therapeutic potentials for IBS.