Heart can usually survive a short period of ischemia, but when this period is too long, damages of the cardiac tissue became irreversible and are possibly exacerbated by blood reperfusion. Loss of cardiac myocytes via apoptosis is believed to contribute to the continuous decline of ventricular function described in heart failure. Limiting theses deleterious responses is of major importance in cardiac surgery and for the treatment of coronary thrombosis. The purpose of this study was to assess the short and long term cardioprotective effects of the long lasting effect erythropoietin analogue darbepoetin-⍺ (DA) in a myocardial ischemia-reperfusion model in rat and ; to investigate the signaling pathway through which DA potentially limits apoptosis of cardiomyocytes.
Rat were subjected to 40 min left coronary artery ligation followed by 3h, 72h or 4 weeks reperfusion and they received either DA (3 or 30 μg/kg) or vehicle i.v. prior ischemia. Left ventricle (LV) function was assessed by echocardiography prior surgery and after reperfusion. Hearts were collected for histological analysis, protein analysis and reactive oxygen species (ROS) production.
In DA3 and DA30 72hrs groups, both LV shortening fraction and LV ejection fraction were higher vs. control (P<0.05), matching with histological analysis revealing a relative LV infarct size 72h post ischemia of 40±5 % in control vs. 27±3 and 17±2 % in DA3 and DA30, respectively. DA treatment lowered ROS production, the activity of caspase 3 in 3 h and 72 h reperfusion groups, and activated the JAK2/AkT signaling pathway and then increased both phosphorylated Bad and GSk3β proteins. This was consistent with the decrease of Bad-Bcl-Xl in DA30 group, suggesting an increased level of Bcl-Xl protein. Similar results were obtained in DA-treated rats reperfused 4 weeks ; in which cardiac fibrosis was significantly lower than that in control group.
DA pre-treatment limited in a dose dependent manner the early and late I/R-induced heart injury in rat. Anti-apoptotic effects mediated through the activation the survival kinase Akt that regulates the Bcl-2 family proteins and activates GSK-3β is central in the DA cardioprotective mechanism.Le texte complet de cet article est disponible en PDF.