Increased inducible nitric oxide synthase (iNOS) expression has been reported in heart failure, cardiomyopathies, and arteriosclerosis. iNOS is expressed in the heart upon inflammatory stimuli and produces excessive amounts of nitric oxide (NO). The overproduction of NO is cytotoxic and involved in cardiovascular diseases. Furthermore, iNOS produces superoxide anion which proceeds with NO to the harmful oxidant peroxynitrite, causing oxidative stress in the heart. The aim of the study was to gain new insights into the role of iNOS in human myocardial infarction (MI) and its contribution to oxidative stress in the heart. Furthermore, we investigated the unaffected myocardium of the infarction hearts, to study if iNOS expression is increased, probably as an indicator for oxidative stress. Our results show a significant increase (p = 0.013) of the iNOS expression in the affected regions of MI hearts (n = 9) in comparison with healthy control hearts (n = 4). In the unaffected regions of MI hearts, an increase in the iNOS expression in some samples was found as well. Our study demonstrated the direct detection of iNOS mRNA in human myocardial tissue. The balance between beneficial and deleterious effects of iNOS may be particularly influenced by the presence or absence of concurrent oxidative stress.
Keywords: Inducible nitric oxide synthase (iNOS); Myocardial infarction (MI); Oxidative stress; Reactive oxygen species (ROS).