ABSTRACT
Atrial fibrillation (AF), one of the most common types of arrhythmias, is associated with high morbidity and mortality, seriously endangering human health. Inflammation is closely associated with AF development. Activation of the nucleotide-binding domain-like receptor protein 3 (NLRP3) inflammasome in cardiomyocytes has been shown to promote AF progression. Here, we demonstrate the effect of miR-135 on NLRP3 inflammasome and study the cardioprotective role of miR-135 in AF. We observed that overexpression of miR-135 in mice reduced the AF incidence and duration, and inhibited both excessive activation of NLRP3 inflammasome and the increased intracellular calcium release during AF. However, the inhibitory effect of miR-135 on AF was partly abolished in the presence of a specific agonist of the calcium-sensing receptor (CaSR). We showed in the present study that miR-135 has a protective effect against AF by suppressing intracellular calcium-mediated NLRP3 inflammasome activation, suggesting the potential of miR-135 as a therapeutic agent in the treatment of AF.
ABSTRACT
Myocardial infarction (MI)-induced the activation of NLRP3 inflammasome has been well known to aggravate myocardial injury and cardiac dysfunction by causing inflammation and pyroptosis in the heart. Circular RNAs (circRNAs) have been demonstrated to play critical roles in cardiovascular diseases. However, the functions and mechanisms of circRNAs in modulating cardiac inflammatory response and cardiomyocyte pyroptosis remain largely unknown. We revealed that circHelz, a novel circRNA transcribed from the helicase with zinc finger (Helz) gene, was significantly upregulated in both the ischemic myocardium of MI mouse and neonatal mouse ventricular cardiomyocytes (NMVCs) exposed to hypoxia. Overexpression of circHelz caused cardiomyocyte injury in NMVCs by activating the NLRP3 inflammasome and inducing pyroptosis, while circHelz silencing reduced these effects induced by hypoxia. Furthermore, knockdown of circHelz remarkably attenuated NLRP3 expression, decreased myocardial infarct size, pyroptosis, inflammation, and increased cardiac function in vivo after MI. Overexpression of miR-133a-3p in cardiomyocytes greatly prevented pyroptosis in the presence of hypoxia or circHelz by targeting NLRP3 in NMVCs. Mechanistically, circHelz functioned as an endogenous sponge for miR-133a-3p via suppressing its activity. Overall, our results demonstrate that circHelz causes myocardial injury by triggering the NLRP3 inflammasome-mediated pro-inflammatory response and subsequent pyroptosis in cardiomyocytes by inhibiting miR-133a-3p function. Therefore, interfering with circHelz/miR-133a-3p/NLRP3 axis might be a promising therapeutic approach for ischemic cardiac diseases.
Subject(s)
Gene Silencing , Inflammasomes/metabolism , MicroRNAs/metabolism , Myocardial Infarction/metabolism , NLR Family, Pyrin Domain-Containing 3 Protein/metabolism , RNA Helicases/genetics , RNA, Circular/metabolism , Signal Transduction/genetics , Animals , Animals, Newborn , Cell Hypoxia , Disease Models, Animal , Male , Mice , Mice, Inbred C57BL , MicroRNAs/genetics , Myocardial Infarction/genetics , Myocytes, Cardiac/metabolism , Pyroptosis/genetics , RNA, Circular/genetics , Transfection , Up-RegulationABSTRACT
N6-methyladenosine (m6A) methylation in RNA is a dynamic and reversible modification regulated by methyltransferases and demethylases, which has been reported to participate in many pathological processes of various diseases, including cardiac disorders. This study was designed to investigate an m6A writer Mettl14 on cardiac ischemia-reperfusion (I/R) injury and uncover the underlying mechanism. The m6A and Mettl14 protein levels were increased in I/R hearts and neonatal mouse cardiomyocytes upon oxidative stress. Mettl14 knockout (Mettl14+/-) mice showed pronounced increases in cardiac infarct size and LDH release and aggravation in cardiac dysfunction post-I/R. Conversely, adenovirus-mediated overexpression of Mettl14 markedly reduced infarct size and apoptosis and improved cardiac function during I/R injury. Silencing of Mettl14 alone significantly caused a decrease in cell viability and an increase in LDH release and further exacerbated these effects in the presence of H2O2, while overexpression of Mettl14 ameliorated cardiomyocyte injury in vitro. Mettl14 resulted in enhanced levels of Wnt1 m6A modification and Wnt1 protein but not its transcript level. Furthermore, Mettl14 overexpression blocked I/R-induced downregulation of Wnt1 and ß-catenin proteins, whereas Mettl14+/- hearts exhibited the opposite results. Knockdown of Wnt1 abrogated Mettl14-mediated upregulation of ß-catenin and protection against injury upon H2O2. Our study demonstrates that Mettl14 attenuates cardiac I/R injury by activating Wnt/ß-catenin in an m6A-dependent manner, providing a novel therapeutic target for ischemic heart disease.
