title: Nox4 contributes to the hypoxia-mediated regulation of actin cytoskeleton in cerebrovascular smooth muscle.
abstract: Ischemia/reperfusion and the resulting oxidative/nitrative stress impair cerebral myogenic tone via actin depolymerization. While it is known that NADPH oxidase (Nox) family is a major source of vascular oxidative stress; the extent and mechanisms by which Nox activation contributes to actin depolymerization, and equally important, the relative role of Nox isoforms in this response is not clear.
  
  
  OBJECTIVE
  To determine the role of Nox4 in hypoxia-mediated actin depolymerization and myogenic-tone impairment in cerebral vascular smooth muscle.
  
  
  METHODS
  Control and Nox4 deficient (siRNA knock-down) human brain vascular smooth muscle cells (HBVSMC) were exposed to 30-min hypoxia/45-min reoxygenation. Nox2, Nox4, inducible and neuronal nitric oxide synthase (iNOS and nNOS) and nitrotyrosine levels as well as F:G actin were determined. Myogenic-tone was measured using pressurized arteriography in middle cerebral artery isolated from rats subjected to sham, 30-min ischemia/45-min reperfusion or ex-vivo oxygen glucose deprivation in the presence and absence of Nox inhibitors.
  
  
  RESULTS
  Nox4 and iNOS expression were significantly upregulated following hypoxia or ischemia/reperfusion. Hypoxia augmented nitrotyrosine levels while reducing F actin. These effects were nullified by inhibiting nitration with epicatechin or pharmacological or molecular inhibition of Nox4. Ischemia/reperfusion impaired myogenic-tone, which was restored by the selective inhibition of Nox4.
  
  
  CONCLUSIONS
  Nox4 activation in VSMCs contributes to actin depolymerization after hypoxia, which could be the underlying mechanism for myogenic-tone impairment following ischemia/reperfusion.
authors: Charlie Norwood VA Medical Center, Augusta University, United States; Departments of Physiology, Augusta University, United States; Program in Clinical and Experimental Therapeutics, University of Georgia College of Pharmacy, Augusta, GA, United States.
authors: Maha
authors: M
authors: Coucha
authors: Charlie Norwood VA Medical Center, Augusta University, United States; Departments of Physiology, Augusta University, United States.
authors: Mohammed
authors: M
authors: Abdelsaid
authors: Charlie Norwood VA Medical Center, Augusta University, United States; Departments of Physiology, Augusta University, United States.
authors: Weiguo
authors: W
authors: Li
authors: Departments of Biostatistics, Augusta University, United States.
authors: Maribeth H
authors: MH
authors: Johnson
authors: Vichem Chemie, Ltd., Budapest, Hungary.
authors: Laszlo
authors: L
authors: Orfi
authors: Charlie Norwood VA Medical Center, Augusta University, United States; Program in Clinical and Experimental Therapeutics, University of Georgia College of Pharmacy, Augusta, GA, United States.
authors: Azza B
authors: AB
authors: El-Remessy
authors: Charlie Norwood VA Medical Center, Augusta University, United States; Departments of Neurology, Augusta University, United States; Program in Clinical and Experimental Therapeutics, University of Georgia College of Pharmacy, Augusta, GA, United States.
authors: Susan C
authors: SC
authors: Fagan
authors: Charlie Norwood VA Medical Center, Augusta University, United States; Departments of Physiology, Augusta University, United States; Program in Clinical and Experimental Therapeutics, University of Georgia College of Pharmacy, Augusta, GA, United States. Electronic address: aergul@augusta.edu.
authors: Adviye
authors: A
authors: Ergul
mesh_terms: D008841:Actin Cytoskeleton / Q000378:metabolism*; D000199:Actins / Q000378:metabolism; D000818:Animals; D002478:Cells, Cultured; D006801:Humans; D000860:Hypoxia / Q000378:metabolism*; D008562:Membrane Glycoproteins / Q000378:metabolism; D020768:Middle Cerebral Artery / Q000502:physiology; D009131:Muscle, Smooth, Vascular / Q000378:metabolism*; D000074662:NADPH Oxidase 2; D000074663:NADPH Oxidase 4; D019255:NADPH Oxidases / Q000096:biosynthesis / Q000378:metabolism*; D052248:Nitric Oxide Synthase Type I / Q000378:metabolism; D052247:Nitric Oxide Synthase Type II / Q000378:metabolism; D034741:RNA, Small Interfering / Q000494:pharmacology; D051381:Rats; D015427:Reperfusion Injury / Q000378:metabolism; D014443:Tyrosine / Q000031:analogs & derivatives / Q000378:metabolism; D015854:Up-Regulation
chemical_list: D000199:Actins; D008562:Membrane Glycoproteins; D034741:RNA, Small Interfering; C002744:3-nitrotyrosine; D014443:Tyrosine; D052248:Nitric Oxide Synthase Type I; D052247:Nitric Oxide Synthase Type II; C496318:Nos2 protein, rat; C500593:Cybb protein, rat; D000074662:NADPH Oxidase 2; D000074663:NADPH Oxidase 4; D019255:NADPH Oxidases; C498911:Nox4 protein, rat
keywords: Actin polymerization; Hypoxia; Ischemia/reperfusion; Myogenic tone; NADPH oxidase; Nox4; Oxidative stress