Activation of melatonin receptor 2 but not melatonin receptor 1 mediates melatonin‐conferred cardioprotection against myocardial ischemia/reperfusion injury

Abstract

Accumulated pieces of evidence have proved the beneficial effects of melatonin on myocardial ischemia/reperfusion (MI/R) injury, and these effects were largely dependent on melatonin membrane receptor activation. In humans and other mammals, there are two types of melatonin receptors, including the melatonin receptor 1 (MT1, melatonin receptor 1a or MTNR1A) and melatonin receptor 1 (MT2, melatonin receptor 1b or MTNR1B) receptor subtypes. However, which receptor mediates melatonin‐conferred cardioprotection remains unclear. In this study, we employed both loss‐of‐function and gain‐of‐function approaches to reveal the answer. Mice (wild‐type; MT1 or MT2 silencing by in vivo minicircle vector; and those overexpressing MT1 or MT2 by in vivo AAV9 vector) were exposed to MI/R injury. Both MT1 and MT2 were present in wild‐type myocardium. MT2, but not MT1, was essentially upregulated after MI/R Melatonin administration significantly reduced myocardial injury and improved cardiac function after MI/R Mechanistically, melatonin treatment suppressed MI/R‐initiated myocardial oxidative stress and nitrative stress, alleviated endoplasmic reticulum stress and mitochondrial injury, and inhibited myocardial apoptosis. These beneficial actions of melatonin were absent in MT2‐silenced heart, but not the MT1 subtype. Furthermore, AAV9‐mediated cardiomyocyte‐specific overexpression of MT2, but not MT1, mitigated MI/R injury and improved cardiac dysfunction, which was accompanied by significant amelioration of oxidative stress, endoplasmic reticulum stress, and mitochondrial dysfunction. Mechanistically, MT2 protected primary cardiomyocytes against hypoxia/reoxygenation injury via MT2/Notch1/Hes1/RORα signaling. Our study presents the first direct evidence that the MT2 subtype, but not MT1, is a novel endogenous cardiac protective receptor against MI/R injury. Medications specifically targeting MT2 may hold promise in fighting ischemic heart disease.

New Insights Into the Evolutionary History of Melatonin Receptors in Vertebrates, With Particular Focus on Teleosts

“…Melatonin plays a critical role in major anti-aging-related cardiovascular diseases including heart failure [for review see (108,109)]. In rat both MTNR1A (MT1) and MTNR1B (MT2) are expressed in myocardium, and MTNR1B was upregulated after myocardial ischemia/reperfusion in mice (110).…”

High plasma levels of pro-inflammatory factors interleukin-17 and interleukin-23 are associated with poor outcome of cardiac-arrest patients: a single center experience

“…Bro-Jeppesen et al reported baseline plasma IL-6 and IL-10 levels were significantly higher in non-survivors compared with survivors [11,12]. Melatonin, an anti-oxidant and anti-inflammatory agent, improves neurological outcomes and preserves hippocampal mitochondrial function in cardiac arrest [36], which may be associated with its protection against inflammation [22,[37][38][39], myocardial ischemia-reperfusion injury [40][41][42][43], ventricular fibrillation [44], cardiac hypertrophy [45], dilated cardiomyopathy [46], and mitochondria-related disorders [47,48]. As neutralization of IL-17 rescues neuroinflammation [49], melatonin may contribute to the complex role of IL-17 signaling in ROSC [50].…”

Exenatide inhibits NF-κB and attenuates ER stress in diabetic cardiomyocyte models

“…These results identified ER stress as a downstream target of Exenatide treatment. Indeed, protection of the ER against abnormal protein modifications promotes cardiomyocyte viability [40,41].…”