Abstract
The present study provides evidence that inducible nitric-oxide synthase (iNOS)-mediated nitrative stress plays a pivotal role in chronic β-adrenergic receptor (AR) stimulation-induced cardiac damage. In mice, 14 days of isoproterenol (ISO) stimulation via an osmotic minipump induced an up-regulation of iNOS as evidenced by increases in mRNA, protein expression, and immunochemical staining of myocardial iNOS. Serum level of C-reactive protein, an inflammatory mediator, was also markedly increased. Under chronic ISO stimulation, the up-regulated iNOS produced a significantly increased amount of nitric oxide (NO) and its byproduct, peroxynitrite, in the circulation and heart and subsequently resulted in an accelerated myocardial apoptosis. Forty-minute myocardial ischemia (MI) and 24-h reperfusion (R) further increased NO production and peroxynitrite formation and resulted in an enlarged infarct size in mice receiving chronic ISO stimulation. However, the treatment with a selective iNOS inhibitor [N-(3-(aminomethyl) benzyl)acetamidine] (1400W) or the use of a genetic modified animal (iNOS-knockout mice) markedly reduced iNOS-mediated production of NO and formation of peroxynitrite and consequently significantly decreased myocardial apoptosis and infarct size, showing a crucial link between iNOS-mediated nitrative stress and myocardial injury. In conclusion, chronic β-AR stimulation up-regulates iNOS expression and increases NO production in the heart, which subsequently markedly enhances formation of reactive nitrogen species/peroxynitrite in the heart, thereby eliciting myocardial apoptosis and potentiating MI/R injury.
Footnotes
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This study was supported in part by National Institutes of Health Grant RO1 HL-63828 (X.L.M.) and a FAER (Foundation for Anesthesia Education and Research) grant (J.Z.S.).
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Article, publication date, and citation information can be found at http://jpet.aspetjournals.org.
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doi:10.1124/jpet.106.102160.
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ABBREVIATIONS: MI, myocardial ischemia; AR, adrenergic receptor; iNOS, inducible nitric-oxide synthase; NO, nitric oxide; RNS, reactive nitrogen species; eNOS, endothelial nitric-oxide synthase; nNOS, neuronal nitric-oxide synthase; R, reperfusion; ISO, isoproterenol; 1400W, N-(3-(aminomethyl) benzyl)acetamidine; KO, knockout; PCR, polymerase chain reaction; LV, left ventricular; ELISA, enzyme-linked immunosorbent assay; TUNEL, terminal deoxynucleotidyl transferase dUTP nick-end labeling; CRP, C-reactive protein; TTC, 2,3,5-triphenyltetrazolium chloride; AAR, area at risk; IL, interleukin.
- Received February 1, 2006.
- Accepted March 28, 2006.
- The American Society for Pharmacology and Experimental Therapeutics