title: Hyperhomocysteinemia, a cardiac metabolic disease: role of nitric oxide and the p22phox subunit of NADPH oxidase.
abstract: BACKGROUND
  Hyperhomocysteinemia (HHcy) is a reliable indicator of cardiovascular disease, in part because of the production of superoxide and scavenging of nitric oxide (NO). The present study assessed the impact of HHcy on the NO-dependent control of cardiac O2 consumption and examined enzymatic sources of superoxide.
  
  
  RESULTS
  Rats and mice were fed methionine in drinking water for 5 to 9 weeks to increase plasma homocysteine, a process that did not cause significant changes in hemodynamic function. The ability of the NO agonists bradykinin and carbachol to reduce myocardial O2 consumption in vitro was impaired by approximately 40% in methionine-fed rats, and this impairment was proportional to their individual plasma homocysteine concentration. However, responses were restored in the presence of ascorbic acid, tempol, and apocynin, which inhibits NADPH oxidase assembly. Western blots showed no difference in Cu/Zn or Mn superoxide dismutase, endothelial NO synthase, or inducible NO synthase protein, but HHcy caused a 100% increase in the p22phox subunit of NADPH oxidase. Western blots with plasma membrane-enriched fractions of cell lysate detected elevated levels of p22phox, p67phox, and rac-1, which indicates increased oxidase assembly. Finally, mice lacking a functional gp91phox subunit of NADPH oxidase demonstrated normal NO-dependent regulation of myocardial O2 consumption after methionine feeding.
  
  
  CONCLUSIONS
  In HHcy, superoxide produced by NADPH oxidase reduces the ability of NO to regulate mitochondrial function in the myocardium. The severity of this effect is proportional to the increase in homocysteine.
authors.affiliation: Department of Physiology, New York Medical College, Valhalla, NY 10595, USA.
authors.forename: Justin S
authors.initials: JS
authors.lastname: Becker
authors.forename: Alexandra
authors.initials: A
authors.lastname: Adler
authors.forename: Aaron
authors.initials: A
authors.lastname: Schneeberger
authors.forename: Harer
authors.initials: H
authors.lastname: Huang
authors.forename: Zipping
authors.initials: Z
authors.lastname: Wang
authors.forename: Erin
authors.initials: E
authors.lastname: Walsh
authors.forename: Akos
authors.initials: A
authors.lastname: Koller
authors.forename: Thomas H
authors.initials: TH
authors.lastname: Hintze
mesh_terms: D000818:Animals; D006331:Heart Diseases / Q000378:metabolism*; D020138:Hyperhomocysteinemia / Q000139:chemically induced / Q000201:enzymology / Q000378:metabolism*; D008297:Male; D026901:Membrane Transport Proteins / Q000096:biosynthesis*; D008715:Methionine; D051379:Mice; D018345:Mice, Knockout; D009206:Myocardium / Q000201:enzymology / Q000378:metabolism; D019255:NADPH Oxidases / Q000096:biosynthesis* / Q000378:metabolism; D009569:Nitric Oxide / Q000378:metabolism*; D010101:Oxygen Consumption; D010750:Phosphoproteins / Q000096:biosynthesis*; D051381:Rats; D017208:Rats, Wistar; D013481:Superoxides / Q000378:metabolism; D015854:Up-Regulation
chemical_list: D026901:Membrane Transport Proteins; D010750:Phosphoproteins; D013481:Superoxides; D009569:Nitric Oxide; D008715:Methionine; D019255:NADPH Oxidases; C086986:CYBA protein, human