A Possible Cardio-Protective Role of Early Remote Ischemia Preconditioning Against Ischemia Reperfusion Injury I’m Isolated Hearts of Adult Albino Rats: Possible Involvement of Hypoxia Inducible Factor

Background Inspite of the claimed cardio-protective effects of ischemic preconditioning (IPC), it is invasive and so using remote ischemic preconditioning (RIPC) may offer an alternative. Meanwhile, RIPC cardioprotective role is controversial, with an equivocal underlying mechanism. The hypoxia inducible factor 1 alpha (HIF-1-alpha) which is increased following ischemic insults is claimed as a humoral mediator for RIPC. Objective To investigate the effect of remote ischemic pre-conditioning on myocardial ischemia/reperfusion injury in rats, and to elucidate the possible role of hypoxia inducible factor in this protection. Materials and Methods The present study was performed on 28 adult female albino rats in the same estrus cycle evaluated by vaginal smear, and they were allocated into 3 groups: Group I: control rats subjected to ischemic/reperfusion injury (I/R) only, group II: early RIPC rats (RIPC 2 hours prior to I/R), group III: acriflavine-treated early RIPC rats. Acriflavine is a drug that binds directly to HIF-1 alpha and HIF-2 alpha subunits, thus inhibiting its dimerization and transcriptional activity, and it was injected IP 10 days prior to RIPC. On sacrifice day, ECG was recorded and isolated heart studies were performed. Later, cardiac chambers weight, serum HIF-1-alpha, myocardial perfusate lactate dehydrogenase, and cardiac oxidative markers: Malonaldehyde and glutathione perioxidase were measured. Results Compared to the control group, the early RIPC group showed significant increase in the heart rate (HR), QTc interval in the ECG recording, glutathione peroxidase and the HIF 1α levels together with reduction in the percent of decrease in PT and PT/LV, in the percent of prolongation in time to peak tension (TPT), perfusate lactate dehydrogenase and MDA levels, while no significant changes were recorded in the heart chronotropic activity, in the percent of half relaxation time (HRT) prolongation, or in the percent of decrease of MFR. Following acriflavine treatment, the effects of RIPC were abolished highlighting the role of HIF-1-alpha in mediating RIPC protective effects. Conclusion The non-invasive and non-pharmological remote ischemic preconditioning technique can ameliorate the cardiac ischemic reperfusion injury with an obvious role of HIF-1α in mediating these protective effects.