Depolarization of mitochondria in endothelial cells promotes cerebral artery vasodilation by activation of nitric oxide synthase

Prasad V.G. Katakam, Edina A. Wappler, Paige S. Katz, Ibolya Rutkai, Adam Institoris, Ferenc Domoki, Tamás Gáspár, Samuel M. Grovenburg, James A. Snipes, David W. Busija

Research output: Contribution to journalArticle

43 Citations (Scopus)

Abstract

OBJECTIVE: Mitochondrial depolarization after ATP-sensitive potassium channel activation has been shown to induce cerebral vasodilation by the generation of calcium sparks in smooth muscle. It is unclear, however, whether mitochondrial depolarization in endothelial cells is capable of promoting vasodilation by releasing vasoactive factors. Therefore, we studied the effect of endothelial mitochondrial depolarization by mitochondrial ATP-sensitive potassium channel activators, BMS-191095 (BMS) and diazoxide, on endothelium-dependent vasodilation. APPROACH AND RESULTS: Diameter studies in isolated rat cerebral arteries showed BMS- and diazoxide-induced vasodilations that were diminished by endothelial denudation. Mitochondrial depolarization-induced vasodilation was reduced by inhibition of mitochondrial ATP-sensitive potassium channels, phosphoinositide-3 kinase, or nitric oxide synthase. Scavenging of reactive oxygen species, however, diminished vasodilation induced by diazoxide, but not by BMS. Fluorescence studies in cultured rat brain microvascular endothelial cells showed that BMS elicited mitochondrial depolarization and enhanced nitric oxide production; diazoxide exhibited largely similar effects, but unlike BMS, increased mitochondrial reactive oxygen species production. Measurements of intracellular calcium ([Ca]i) in cultured rat brain microvascular endothelial cells and arteries showed that both diazoxide and BMS increased endothelial [Ca]i. Western blot analyses revealed increased phosphorylation of protein kinase B and endothelial nitric oxide synthase (eNOS) by BMS and diazoxide. Increased phosphorylation of eNOS by diazoxide was abolished by phosphoinositide-3 kinase inhibition. Electron spin resonance spectroscopy confirmed vascular nitric oxide generation in response to diazoxide and BMS. CONCLUSIONS: Pharmacological depolarization of endothelial mitochondria promotes activation of eNOS by dual pathways involving increased [Ca]i as well as by phosphoinositide-3 kinase-protein kinase B-induced eNOS phosphorylation. Both mitochondrial reactive oxygen species-dependent and -independent mechanisms mediate activation of eNOS by endothelial mitochondrial depolarization.

Original languageEnglish
Pages (from-to)752-759
Number of pages8
JournalArteriosclerosis, thrombosis, and vascular biology
Volume33
Issue number4
DOIs
Publication statusPublished - Apr 1 2013

Keywords

  • BMS-191095
  • diazoxide
  • intracellular calcium
  • membrane potential
  • mitochondrial ATP-sensitive potassium channels
  • superoxide

ASJC Scopus subject areas

  • Cardiology and Cardiovascular Medicine

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    Katakam, P. V. G., Wappler, E. A., Katz, P. S., Rutkai, I., Institoris, A., Domoki, F., Gáspár, T., Grovenburg, S. M., Snipes, J. A., & Busija, D. W. (2013). Depolarization of mitochondria in endothelial cells promotes cerebral artery vasodilation by activation of nitric oxide synthase. Arteriosclerosis, thrombosis, and vascular biology, 33(4), 752-759. https://doi.org/10.1161/ATVBAHA.112.300560