Nicorandil, an ATP-sensitive potassium channel activation, attenuates myocardial injury in rats with ischemic cardiomyopathy

Role of Mitochondrial Dynamics in Heart Diseases

Mitochondrial dynamics, including fission and fusion processes, are essential for heart health. Mitochondria, the powerhouses of cells, maintain their integrity through continuous cycles of biogenesis, fission, fusion, and degradation. Mitochondria are relatively immobile in the adult heart, but their morphological changes due to mitochondrial morphology factors are critical for cellular functions such as energy production, organelle integrity, and stress response. Mitochondrial fusion proteins, particularly Mfn1/2 and Opa1, play multiple roles beyond their pro-fusion effects, such as endoplasmic reticulum tethering, mitophagy, cristae remodeling, and apoptosis regulation. On the other hand, the fission process, regulated by proteins such as Drp1, Fis1, Mff and MiD49/51, is essential to eliminate damaged mitochondria via mitophagy and to ensure proper cell division. In the cardiac system, dysregulation of mitochondrial dynamics has been shown to cause cardiac hypertrophy, heart failure, ischemia/reperfusion injury, and various cardiac diseases, including metabolic and inherited cardiomyopathies. In addition, mitochondrial dysfunction associated with oxidative stress has been implicated in atherosclerosis, hypertension and pulmonary hypertension. Therefore, understanding and regulating mitochondrial dynamics is a promising therapeutic tool in cardiac diseases. This review summarizes the role of mitochondrial morphology in heart diseases for each mitochondrial morphology regulatory gene, and their potential as therapeutic targets to heart diseases.

Effect of the selective mitochondrial KATP channel opener nicorandil on the QT prolongation and myocardial damage induced by amitriptyline in rats

OBJECTIVES

The aim of this study is to evaluate the protective effect of nicorandil, a selective mitochondrial KATP channel opener, on QT prolongation and myocardial damage induced by amitriptyline.

METHODS

The dose of amitriptyline (intraperitoneal, i.p.) that prolong the QT interval was found 75 mg/kg. Rats were randomized into five groups the control group, amitriptyline group, nicorandil (selective mitochondrial KATP channel opener, 3 mg/kg i.p.) + amitriptyline group, 5-hdyroxydecanoate (5-HD, selective mitochondrial KATP channel blocker, 10 mg/kg i.p.) + amitriptyline group and 5-HD + nicorandil + amitriptyline group. Cardiac parameters, biochemical and histomorphological/immunohistochemical examinations were evaluated. p < 0.05 was accepted as statistically significant.

KEY FINDINGS

Amitriptyline caused statistically significant prolongation of QRS duration, QT interval and QTc interval (p < 0.05). It also caused changes in tissue oxidant (increase in malondialdehyde)/anti-oxidant (decrease in glutathione peroxidase) parameters (p < 0.05), myocardial damage and apoptosis (p < 0.01 and p < 0.001). While nicorandil administration prevented amitriptyline-induced QRS, QT, QTc prolongation (p < 0.05), myocardial damage and apoptosis (p < 0.05), it did not affect the changes in oxidative parameters (p > 0.05).

CONCLUSIONS

Our results suggest that nicorandil, a selective mitochondrial KATP channel opener, plays a protective role in amitriptyline-induced QT prolongation and myocardial damage. Mitochondrial KATP channel opening and anti-apoptotic effects may play a role in the cardioprotective effect of nicorandil.

Current Understanding of the Pivotal Role of Mitochondrial Dynamics in Cardiovascular Diseases and Senescence

The heart is dependent on ATP production in mitochondria, which is closely associated with cardiovascular disease because of the oxidative stress produced by mitochondria. Mitochondria are highly dynamic organelles that constantly change their morphology to elongated (fusion) or small and spherical (fission). These mitochondrial dynamics are regulated by various small GTPases, Drp1, Fis1, Mitofusin, and Opa1. Mitochondrial fission and fusion are essential to maintain a balance between mitochondrial biogenesis and mitochondrial turnover. Recent studies have demonstrated that mitochondrial dynamics play a crucial role in the development of cardiovascular diseases and senescence. Disruptions in mitochondrial dynamics affect mitochondrial dysfunction and cardiomyocyte survival leading to cardiac ischemia/reperfusion injury, cardiomyopathy, and heart failure. Mitochondrial dynamics and reactive oxygen species production have been associated with endothelial dysfunction, which in turn causes the development of atherosclerosis, hypertension, and even pulmonary hypertension, including pulmonary arterial hypertension and chronic thromboembolic pulmonary hypertension. Here, we review the association between cardiovascular diseases and mitochondrial dynamics, which may represent a potential therapeutic target.