Browsing by Author "Ardiles, Nicolas M."

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    Ca2+-activated K+ channels of small and intermediate conductance control eNOS activation through NAD(P)H oxidase
    (ELSEVIER SCIENCE INC, 2012) Gaete, Pablo S.; Lillo, Mauricio A.; Ardiles, Nicolas M.; Perez, Francisco R.; Figueroa, Xavier F.
    Ca2+-activated K+ channels (K-Ca) and NO play a central role in the endothelium-dependent control of vasomotor tone. We evaluated the interaction of K-Ca with NO production in isolated arterial mesenteric beds of the rat. In phenylephrine-contracted mesenteries, acetylcholine (ACh)-induced vasodilation was reduced by NO synthase (NOS) inhibition with N-omega-nitro-L-arginine (L-NA), but in the presence of tetraethylammonium, L-NA did not further affect the response. In KCl-contracted mesenteries, the relaxation elicited by 100 nM ACh or 1 mu M ionomycin was abolished by L-NA, tetraethylammonium, or simultaneous blockade of small-conductance K-Ca (SKCa) channels with apamin and intermediate-conductance K-Ca (IKCa) channels with triarylmethane-34 (TRAM-34). Apamin-TRAM-34 treatment also abolished 100 nM ACh-activated NO production, which was associated with an increase in superoxide formation. Endothelial cell Ca2+ buffering with BAPTA elicited a similar increment in superoxide. Apamin-TRAM-34 treatment increased endothelial NOS phosphorylation at threonine 495 (P-eNOS(Thr495)). Blockade of NAD(P)H oxidase with apocynin or superoxide dismutation with PEG-SOD prevented the increment in superoxide and changes in P-eNOS(Thr495) observed during apamin and TRAM-34 application. Our results indicate that blockade of SKCa and IKCa activates NAD(P)H oxidase-dependent superoxide formation, which leads to inhibition of NO release through P-eNOS(Thr495). These findings disclose a novel mechanism involved in the control of NO production. (C) 2011 Elsevier Inc. All rights reserved.
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    Critical contribution of Na+-Ca2+ exchanger to the Ca2+-mediated vasodilation activated in endothelial cells of resistance arteries
    (2018) Lillo, Mauricio A.; Gaete, Pablo S.; Puebla, Mariela; Ardiles, Nicolas M.; Poblete, Ines; Becerra, Alvaro; Simon, Felipe; Figueroa, Xavier
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    Critical contribution of Na+-Ca2+ exchanger to the Ca2+-mediated vasodilation activated in endothelial cells of resistance arteries
    (2018) Lillo, Mauricio A.; Gaete, Pablo S.; Puebla, Mariela; Ardiles, Nicolas M.; Poblete, Ines; Becerra, Alvaro; Simon, Felipe; Figueroa, Xavier F.
    Na+-Ca2+ exchanger (NCX) contributes to control the intracellular free Ca2+ concentration ([Ca2+](i)), but the functional activation of NCX reverse mode (NCXrm) in endothelial cells is controversial. We evaluated the participation of NCXrm-mediated Ca2+ uptake in the endothelium-dependent vasodilation of rat isolated mesenteric arterial beds. In phenylephrine-contracted mesenteries, the acetylcholine (ACh)-induced vasodilation was abolished by treatment with the NCXrm blockers SEA0400, KB-R7943, or SN-6. Consistent with that, the ACh-induced hyperpolarization observed in primary cultures of mesenteric endothelial cells and in smooth muscle of isolated mesenteric resistance arteries was attenuated by KB-R7943 and SEA0400, respectively. In addition, both blockers abolished the NO production activated by ACh in intact mesenteric arteries. In contrast, the inhibition of NCXrm did not affect the vasodilator responses induced by the Ca2+ ionophore, ionomycin, and the NO donor, S-nitroso-N-acetylpenicillamine. Furthermore, SEA0400, KB-R7943, and a small interference RNA directed against NCX1 blunted the increase in [Ca2+](i) induced by ACh or ATP in cultured endothelial cells. The analysis by proximity ligation assay showed that the NO-synthesizing enzyme, eNOS, and NCX1 were associated in endothelial cell caveolae of intact mesenteric resistance arteries. These results indicate that the activation of NCXrm has a central role in Ca2+-mediated vasodilation initiated by ACh in endothelial cells of resistance arteries.