O Pré-Condicionamento com Dexmedetomidina Atenua a Lesão de Isquemia/Reperfusão Miocárdica em Ratos, Suprimindo a Mitofagia Via Ativação do Receptor Α2-Adrenérgico

Background: Dexmedetomidine (DEX), a specific alpha 2-adrenergic receptor agonist, is protective against myocardial ischemia/reperfusion injury (MIRI). However, the association between DEX preconditioning-induced cardioprotection and mitophagy suppression remains unclear.Objective: Hence, we aimed to investigate whether DEX preconditioning alleviates MIRI by suppressing mitophagy via alpha 2-adrenergic receptor activation.Method: Sixty isolated rat hearts were treated with or without DEX before inducing ischemia and reperfusion; an alpha 2-adrenergic receptor antagonist, yohimbine (YOH), was also administered before ischemia, alone or with DEX. The heart rate (HR), left ventricular diastolic pressure (LVDP), left ventricular end-diastolic pressure (LVEDP), maximal and minimal rate of left ventricular pressure development (+/- dp/dtmax), and myocardial infarction size were measured. The mitochondrial ultrastructure and autophagosomes were assessed using transmission electron microscopy. Mitochondrial membrane potential and reactive oxygen species (ROS) levels were measured using JC-1 and dichloride hydrofluorescein diacetate assays, respectively. The expression levels of the mitophagy-associated proteins Beclin1, LC3II/I ratio, p62, PINK1, and Parkin were detected by western blotting.Results: Compared with the control group, in the ischemia/reperfusion group, the HR, LVDP, and +/- dp/dtmax were remarkably decreased (p< 0.05), whereas LVEDP and infarct sizes were significantly increased (p< 0.05). DEX preconditioning significantly improved cardiac dysfunction reduced myocardial infarction size, maintained mitochondrial structural integrity, increased mitochondrial membrane potential, inhibited autophagosomes formation, and decreased ROS production and Beclin1, LC3II/I ratio, PINK1, Parkin, and p62 expression(p< 0.05). When DEX and YOH were combined, YOH canceled the effect of DEX, whereas the use of YOH alone had no effect.Conclusion: Therefore, DEX preconditioning was cardioprotective against MIRI in rats by suppressing mitophagy via alpha 2-adrenergic receptor activation.

Automated summary

The study found that dexmedetomidine, through the activation of alpha 2-adrenergic receptors, suppresses mitophagy and provides cardioprotection against myocardial ischemia/reperfusion injury in rats.