Heart sensitivity to ischemia-reperfusion and exercise-induced cardioprotection : involvement of myocardial eNOS
Exercise training is recognized as an efficient way to protect the myocardium against ischemiareperfusion(IR). However, mechanisms responsible for such cardioprotection remain still unclear. Theaims of this work were then i) to evaluate the preventive effect of exercise on a model highly sensitiveto myocardial IR, and ii) to investigate the role of eNOS in exercise-induced cardioprotection. In a firstpart we showed that regular boots of exercise, by its beneficial effects on calcium handling andenzymatic antioxidant status, prevents the highly sensitive phenotypical remodeling of the heart andthen normalized heart vulnerability to IR. Then, in a second part of this work, we showed that exerciseinducedcardioprotection was associated with a decrease of eNOS phosphorylation at Ser1177 andespecially its uncoupling during early reperfusion. Such phenomenon, associated with increased heartantioxidant capacity was responsible for reduced nitro-oxidative stress. Indeed, reduced NOSdependentNO synthesis associated with the improved capacity to scavenge O2.- contribute to preventthe formation of ONOO-. Altogether, these results showed that exercise-induced cardioprotection is acomplex mechanism requiring interactions between antioxidant capacity improvement, eNOSuncoupling during reperfusion and intracellular calcium homeostasis. Finally, this work opens newperspectives regarding the role of NO synthesis modulation to impact heart sensitivity to IR