Abstract 3305: Deficiency of Dimethylarginine Dimethylaminotransferase-1 Exacerbates Myocardial Ischemia-Reperfusion Injury in Mice
Ischemic heart disease is a leading cause of mortality and morbidity in the Western world. Nitric oxide (NO) protects from myocardial ischemia-reperfusion (I/R) injury. Dimethylarginine dimethylaminohydrolase-1 (DDAH1) is a key enzyme responsible for degradation of asymmetric dimethylarginine (ADMA), an endogenous competitive inhibitor of NO synthases. We tested the hypothesis that a relative deficiency of endogenous DDAH1 elevates cardiac ADMA levels, lowers NO production in the heart, and exacerbates myocardial I/R injury in mice. Male heterozygous DDAH1-deficient (DDAH1+/−) mice and their wild-type (WT) littermates on a C57BL/6 background were studied at 11 weeks of age. ADMA levels in plasma and the heart were determined by liquid chromatography/mass spectrometry. NO oxidation products (NOx) in the heart were analyzed by gas-phase luminescence. Regional I/R injury was produced by 30 minutes of left coronary artery ligation followed by 2 hours of reperfusion. The area at risk and infarct size were determined by injection of Evans blue and staining with triphenyltetrazolium chloride, respectively. Myocardial injury also was assessed by measurement of plasma levels of troponin T and heart fatty-acid binding protein (H-FABP). Myocardial superoxide production was measured by enhanced chemiluminescence with 5 μM lucigenin one minute after reperfusion. Levels of ADMA were elevated by 30% in the plasma and 50% in the heart in DDAH1+/− mice compared with WT mice (P<0.05). Cardiac levels of NOx were significantly decreased in DDAH1+/− mice compared with WT mice (P<0.01). The area of myocardial infarction was larger in DDAH1+/− mice (67±7% of area at risk) than in WT mice (43±7%; P<0.05). In agreement with the infarct size data, plasma levels of troponin T and H-FABP were elevated in DDAH1+/− mice compared with WT mice (P<0.01). There were strong correlations between plasma troponin T, H-FABP, and infarct size (P<0.001). No differences in cardiac superoxide generation were detected between DDAH1+/− and WT mice. We conclude that heterozygous deficiency of endogenous DDAH1 results in changes in ADMA and NO metabolism in the heart and exacerbates myocardial I/R injury through a mechanism that is independent of the reperfusion-induced oxidative burst.