title: Differential effects of an anti-oxidant intervention on cardiomyocyte expression of adrenomedullin and intermedin and their receptor components in chronic nitric oxide deficiency.
abstract: BACKGROUND
  Chronic inhibition of nitric oxide (NO) synthesis is associated with hypertension, myocardial oxidative stress and hypertrophic remodeling. Up-regulation of the cardiomyocyte adrenomedullin (AM) / intermedin (IMD) receptor signaling cascade is also apparent in NO-deficient cardiomyocytes: augmented expression of AM and receptor activity modifying proteins RAMP2 and RAMP3 is prevented by blood pressure normalization while that of RAMP1 and intermedin (IMD) is not, indicating that the latter is regulated by a pressure-independent mechanism.
  
  
  OBJECTIVE
  to verify the ability of an anti-oxidant intervention to normalize cardiomyocyte oxidant status and to investigate the influence of such an intervention on expression of AM, IMD and their receptor components in NO-deficient cardiomyocytes.
  
  
  METHODS
  NO synthesis inhibitor, N(G)-nitro-L-arginine methyl ester (L-NAME, 35 mg/kg/day) was given to rats for 8 weeks, with/without con-current administration of antioxidants (Vitamin C (25mg/kg/day) and Tempol (25mg/kg/day)).
  
  
  RESULTS
  In left ventricular cardiomyocytes isolated from L-NAME treated rats, increased oxidative stress was indicated by augmented (3.6 fold) membrane protein oxidation, enhanced expression of catalytic and regulatory subunits of pro-oxidant NADPH oxidases (NOX1, NOX2) and compensatory increases in expression of anti-oxidant glutathione peroxidase and Cu/Zn superoxide dismutases (SOD1, SOD3). Vitamin C plus Tempol did not reduce systolic blood pressure but normalized augmented plasma levels of IMD, but not of AM, and in cardiomyocytes: (i) abolished increased membrane protein oxidation; (ii) normalized augmented expression of prepro-IMD and RAMP1, but not prepro-AM, RAMP2 and RAMP3; (iii) attenuated (by 42%) increased width and normalized expression of hypertrophic markers, skeletal-alpha-actin and prepro-endothelin-1 similarly to blood pressure normalization but in contrast to blood pressure normalization did not attenuate augmented brain natriuretic peptide (BNP) expression.
  
  
  CONCLUSIONS
  normalization specifically of augmented IMD/RAMP1 expression in NO-deficient cardiomyocytes by antioxidant intervention in the absence of blood pressure reduction indicates that these genes are likely to be induced directly by myocardial oxidative stress. Although oxidative stress contributed to cardiomyocyte hypertrophy, induction of IMD and RAMP1 is unlikely to be secondary to cardiomyocyte hypertrophy.
authors.affiliation: Cardiovascular Research Group, School of Medicine and Dentistry, Queen's University Belfast, Whitla Medical Building, Northern Ireland. d.bell@qub.ac.uk
authors.forename: David
authors.initials: D
authors.lastname: Bell
authors.forename: YouYou
authors.initials: Y
authors.lastname: Zhao
authors.forename: Francis P G
authors.initials: FP
authors.lastname: McCoy
authors.forename: Adrian B
authors.initials: AB
authors.lastname: Devine
authors.forename: Barbara J
authors.initials: BJ
authors.lastname: McDermott
mesh_terms: D053607:Adrenomedullin / Q000378:metabolism*; D000818:Animals; D000975:Antioxidants / Q000494:pharmacology*; D001794:Blood Pressure / Q000187:drug effects; D006332:Cardiomegaly / Q000139:chemically induced / Q000503:physiopathology; D006973:Hypertension / Q000139:chemically induced / Q000503:physiopathology; D008297:Male; D032383:Myocytes, Cardiac / Q000187:drug effects* / Q000378:metabolism*; D009479:Neuropeptides / Q000378:metabolism*; D009569:Nitric Oxide / Q000378:metabolism*; D018384:Oxidative Stress; D051381:Rats; D017207:Rats, Sprague-Dawley; D018000:Receptors, Peptide / Q000737:chemistry / Q000378:metabolism*
chemical_list: C499411:Adm2 protein, rat; D000975:Antioxidants; D009479:Neuropeptides; D018000:Receptors, Peptide; D053607:Adrenomedullin; D009569:Nitric Oxide