Interaction of nitric oxide synthase and mitochondrial ATP-sensitive potassium channels in protective impacts of combination therapy with irisin-preconditioning and melatonin-postconditioning in myocardial ischemia/reperfusion in aging

[Display omitted] •Aging negatively affects cardioprotection in patients with ischemia/reperfusion damage.•Pre- and post-conditioning with irisin and melatonin induced potent cardioprotection in aged hearts.•Irisin/melatonin has anti-inflammatory, anti-apoptotic, and mitochondrial boosting effects.•Activation of mitoKATP channels is the main contributor to this conditioning effect.•eNOS/NO signaling pathway is only partially involved in this protection. The main challenge for cardioprotection in patients with cardiac ischemia–reperfusion (I/R) damage is the existence of negatively-acting multiple risk factors such as aging. This work aimed to evaluate the efficacy of combined therapy with irisin and melatonin on cardiac I/R injury in aged rats by focusing on the involvement of mitochondrial ATP-sensitive potassium (mitoKATP) channels, and the eNOS/NO pathway. Male aged Wistar rats (78 rats, 400–450 g) were experienced LAD ligation for 30 min followed by 3 h or 2 weeks reperfusion. Irisin (0.5 mg/kg/day) was administered for one week before ischemic insult. Melatonin (20 mg/kg) was administered 10 min before the onset of reperfusion. The releases of CK and LDH, mitochondrial function, inflammatory and apoptosis responses, the expression of eNOS, the levels of NO, cardiac function, and infarct size (IS) were evaluated. Combined therapy with irisin and melatonin significantly improved heart function, reduced IS, and limited the releases of CK and LDH (P