Nicorandil activates lkb1-ampk signaling pathway to ameliorate cardiac remodeling after myocardial ischemia/reperfusion injury by upregulating mt2
Authors: An Y L , Fu P , Li Z Z , Zhang Y L , Lin Q Y , Zhang B 
Published: October 2024

Abstract

Background
Cardiomyocyte apoptosis is a crucial event underlying the development of cardiac abnormalities and dysfunction after myocardial ischemia reperfusion (MI/R) injury. A better understanding of the cell signaling pathways involved in cardiac remodeling may support the development of new therapeutic strategies for the treatment of heart failure (HF) after MI/R. Nicorandil, an ATP-sensitive potassium channel opener, could improve mitochondrial damage and reduce oxidative stress，which reduce cardiomyocyte apoptosis. Metallothionein (Mt), reactive oxygen species (ROS) scavenger, which can reduce oxidative stress, also attenuated MI/R-induced autophagy and cell apoptosis. Except as a potassium channel opener, nicorandil may play a cardioprotective role by regulating metallothionein, and its specific mechanism remains to be elucidated.

Objective
To clarify the protective effect of nicorandil in myocardial ischemia/reperfusion injury, and elucidate the specific mechanism which nicorandil regulate the expression of metallothiosin to reduce myocardial ischemia/reperfusion injury, so as to provide new drug targets or new measures for clinical prevention and treatment of MI/R.

Methods
A cardiac MI/R injury model was constructed by the ligation of the left anterior descending coronary artery to investigate the underlying molecular mechanisms. The apoptosis of myocardial tissue cells was detected by TUNEL staining. The ultrastructural changes of myocardial tissue were observed by transmission electron microscopy. The expressions of Mt family, mitochondrial dynamics and Glucose metabolism-associated genes were measured by Western blotting and qPCR. The content of ATP was determined by ELISA in heart tissue. AutodockVina was used to evaluate binding energy and interaction patterns between drug candidates and their targets. The protein-protein interaction model was predicted by ZDOCK software.

Results
Treatment with nicorandil mitigated left ventricular enlargement, improved cardiac dysfunction,reduced myocardial infarcation area and decreased cardiomyocyte apoptosis after I/R. Nicorandil up-regulated the expression of Mt2 and decreased the expressions of Drp-1,p-Drp-1(ser616), while enhanced the expression of Mfn1/2,GLUT4,HK II and MPC II in myocardium. Knockdown of Mt2 decreased the effects of nicorandil on apoptosis and mitochondrial dysfunction after I/R. Mechanistically, nicorandil significantly upregulated the expression of Mt2, which could bound to LKB1 and cause phosphorylation of LKB1, resulting in AMPK-dependent activation.

Conclusions
Nicorandil significantly upregulated the expression of Mt2, which interacted with LKB1 to promote LKB1 protein phosphorylation, resulting in AMPK-dependent activation and subsequently alleviating I/R-induced mitochondrial dysfunction and energy metabolism disorder, and thereby reducing cardiomyocyte apoptosis, eventually improving I/ R-induced cardiac remodeling and dysfunction.