Reduced neuronal nitric oxide synthase expression contributes to cardiac oxidative stress and nitroso-redox imbalance in ob/ob mice.
Disruption of leptin signaling in the heart may contribute to obesity-related cardiac disease, as leptin deficient (oblob) mice display cardiac hypertrophy, increased cardiac apoptosis and reduced survival. Since leptin maintains a tonic level of neuronal nitric oxide synthase (NOS1) expression in the brain, we hypothesized that leptin deficiency would decrease NOS1 cardiac expression, in turn activating xanthine oxidoreductase (XOR) and creating nitroso-redox imbalance. We studied 2- to 6-month-old oblob (n=26) and C57Bl/6 controls (n=27). Cardiac NOS1 protein abundance (P<0.01) and mRNA expression (P=0.03) were reduced in oblob (n=10 and 6, respectively), while NOS3 protein abundance and mRNA expression were unaltered. Importantly, cardiac NOS1 protein abundance was restored towards normal in oblob mice after leptin treatment (n=3; P<0.05 vs leptin untreated oblob mice). NO metabolite (nitrite and nitrate) production within the myocardium was also reduced in oblob mice (n=5; P=0.02). Furthermore, oxidative stress was increased in oblob mice as GSH/GSSG ratio was decreased (n=4; P=0.02). Whereas XOR activity measured by Amplex Red fluorescence was increased (n=8; P=0.04), XOR and NADPH oxidase subunits protein abundance were not changed in oblob mice (n=6). Leptin deficiency did not disrupt NOS1 subcellular localization, as NOS1 co-localized with ryanodine receptor but not with caveolin-3. In conclusion, leptin deficiency is linked to decreased cardiac expression of NOS1 and NO production, with a concomitant increase in XOR activity and oxidative stress, resulting in nitroso-redox imbalance. These data offer novel insights into potential mechanisms of myocardial dysfunction in obesity.
Saraiva
Roberto M
RM
Cardiology Division, Department of Medicine, Johns Hopkins Medical Institutions, Baltimore, MD 21205, USA.
Minhas
Khalid M
KM
Zheng
Meizi
M
Pitz
Eleanor
E
Treuer
Adriana
A
Gonzalez
Daniel
D
Schuleri
Karl H
KH
Vandegaer
Koenraad M
KM
Barouch
Lili A
LA
Hare
Joshua M
JM
D000818:Animals; D005978:Glutathione / Q000378:metabolism; D020738:Leptin / Q000008:administration & dosage / Q000378:metabolism*; D051379:Mice; D008810:Mice, Inbred C57BL; D008820:Mice, Obese; D009206:Myocardium / Q000166:cytology / Q000201:enzymology*; D019255:NADPH Oxidases / Q000235:genetics / Q000378:metabolism; D009566:Nitrates / Q000378:metabolism; D009569:Nitric Oxide / Q000378:metabolism; D052248:Nitric Oxide Synthase Type I / Q000235:genetics / Q000378:metabolism*; D052247:Nitric Oxide Synthase Type II / Q000235:genetics / Q000378:metabolism; D052250:Nitric Oxide Synthase Type III; D009573:Nitrites / Q000378:metabolism; D009765:Obesity / Q000378:metabolism*; D010084:Oxidation-Reduction; D018384:Oxidative Stress; D017382:Reactive Oxygen Species / Q000378:metabolism; D015398:Signal Transduction / Q000502:physiology; D014969:Xanthine Oxidase / Q000235:genetics / Q000378:metabolism
D020738:Leptin; D009566:Nitrates; D009573:Nitrites; D017382:Reactive Oxygen Species; D009569:Nitric Oxide; D052248:Nitric Oxide Synthase Type I; D052247:Nitric Oxide Synthase Type II; D052250:Nitric Oxide Synthase Type III; C496321:Nos1 protein, mouse; C496315:Nos3 protein, mouse; D014969:Xanthine Oxidase; D019255:NADPH Oxidases; D005978:Glutathione