title: Inhibition of NADPH oxidase alleviates experimental diabetes-induced myocardial contractile dysfunction.
abstract: OBJECTIVE
  O(2) (-) production is implicated in cardiac dysfunction for a number of diseases including diabetes. Activation of the O(2) (-)-producing enzyme NADPH oxidase is seen in diabetes, although its role in diabetic cardiomyopathy is unclear. This study was designed to evaluate the effect of NADPH oxidase inhibition on cardiac function in diabetes.
  
  
  METHODS
  Experimental diabetes was induced in adult C57 mice using streptozotocin (STZ, 150 mg/kg, i.p.) prior to the administration of the NADPH oxidase inhibitor apocynin (4 mg/kg/day) for 2 weeks. Left ventricular (LV) and myocyte contractile functions were evaluated using echocardiography and edge-detection, respectively.
  
  
  RESULTS
  STZ elicited hyperglycaemia and reduced body weight gain, which was unaffected by apocynin. STZ significantly reduced fractional shortening, LV wall thickness, peak shortening, maximal velocity and duration of shortening or relengthening, the effects of which - with the exception of wall thickness - were significantly attenuated or ablated by apocynin. Western blot analysis revealed that the effects of comparable Akt phosphorylation, reduced AMPK phosphorylation, downregulation of sarco(endo)plasmic reticulum Ca(2+)-ATPase and lessened phosphorylation of phospholamban in diabetic myocardium were unaffected by apocynin. Both apocynin and the nitric oxide synthase (NOS) inhibitor l-arginine methyl ester (L-NAME) inhibited elevated O(2) (-) production in diabetes without any additive effect between the two, indicating the presence of endothelial nitric oxide synthase (eNOS) uncoupling. However, neither diabetes nor apocynin altered the expression of heat shock protein 90 and eNOS phosphorylation (Ser(1177)). In addition, apocynin mitigated elevated levels of nitrotyrosine and nitric oxide in diabetes.
  
  
  CONCLUSIONS
  Taken together, these data indicate the beneficial role of NADPH oxidase inhibition in diabetes-induced myocardial contractile dysfunction.
authors.affiliation: Division of Pharmaceutical Sciences & Center for Cardiovascular Research and Alternative Medicine, University of Wyoming, Laramie, USA.
authors.forename: N D
authors.initials: ND
authors.lastname: Roe
authors.forename: D P
authors.initials: DP
authors.lastname: Thomas
authors.forename: J
authors.initials: J
authors.lastname: Ren
mesh_terms: D000098:Acetophenones / Q000494:pharmacology*; D000818:Animals; D015153:Blotting, Western; D003921:Diabetes Mellitus, Experimental / Q000503:physiopathology; D004452:Echocardiography; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D006329:Heart Conduction System / Q000187:drug effects* / Q000503:physiopathology; D006352:Heart Ventricles / Q000187:drug effects* / Q000503:physiopathology; D008297:Male; D051379:Mice; D009119:Muscle Contraction / Q000187:drug effects*; D032383:Myocytes, Cardiac / Q000187:drug effects*; D019255:NADPH Oxidases / Q000037:antagonists & inhibitors*; D009569:Nitric Oxide / Q000494:pharmacology*
chemical_list: D000098:Acetophenones; D004791:Enzyme Inhibitors; D009569:Nitric Oxide; C056165:acetovanillone; D019255:NADPH Oxidases