Increased production of reactive oxygen species (ROS) significantly contributed to the pathogenesis of acute myocardial infarction (AMI). Recent studies suggest that hypoxia upregulated the long noncoding RNA taurine upregulated gene 1 (TUG1). In this study, we explored the functional significance and molecular mechanisms of TUG1/miR-132-3p axis in ischemia-challenged cardiomyocytes. In primary cardiomyocytes challenged with H2O2, expressions of miR-132-3p, TUG1, and other target proteins were measured by RT quantitative PCR or Western blot analysis; cell viability by 3-(4,5-dimethylthiazolyl-2)-2,5-diphenyltetrazolium bromide assay; apoptosis by annexin V and propidium iodide staining; the abundance of acetylated H3K9 or histone deacetylase 3 (HDAC3) within the promoter of target genes by chromatin immunoprecipitation; the direct interaction between miR-132-3p and HDAC3 or TUG1 by luciferase reporter assay. The biological significance of miR-132-3p, TUG1, and HDAC3 was assessed using miR-132-3p mimic, siRNA-targeting TUG1 and HDAC3 inhibitor RGF966, respectively, in H2O2-challenged cells in vitro or ischemia-reperfusion (I/R)-induced AMI in vivo. miR-132-3p was downregulated, whereas TUG1 upregulated in H2O2-challenged cardiomyocytes. Overexpressing miR-132-3p or knocking down TUG1 significantly improved viability, inhibited apoptosis, and reduced ROS production in H2O2-stressed cardiomyocytes in vitro and alleviated I/R-induced AMI in vivo. Mechanistically, TUG1 sponged miR-132-3p and upregulated HDAC3, which reduced the acetylation of H3K9 and epigenetically inhibited expressions of antioxidative genes, including Bcl-xL, Prdx2, and Hsp70. The TUG1/miR-132-3p/HDAC3 axis critically regulates ROS production and the pathogenic development of AMI. Targeting TUG1, upregulating miR-132-3p, or inhibiting HDAC3 may benefit AMI treatment. NEW & NOTEWORTHY Increased production of reactive oxygen species (ROS) significantly contributed to the pathogenesis of acute myocardial infarction (AMI). Recent studies suggest that hypoxia upregulated the long noncoding RNA taurine upregulated gene 1 (TUG1). However, the underlying mechanisms remain elusive. In the present study, we reported for the first time that H2O2 or ischemia-reperfusion-induced TUG1, by sponging microRNA 132-3p, activated histone deacetylase 3, which in turn targeted multiple protective genes, stimulated intracellular ROS accumulation, and aggravated the injury of AMI. Our findings might provide some insight to seek new targets for AMI treatment.

In this study, we aim to investigate the regulation of specific long non-coding RNAs (lncRNAs) on the progression of ischemia/reperfusion (I/R) injury. We identified and characterized the exosomes derived from mouse primary aortic endothelial cells. Subsequently, we found that these exosomes expressed typical exosomal markers and high levels of LINC00174, which significantly ameliorated I/R-induced myocardial damage and suppressed the apoptosis, vacuolation, and autophagy of myocardial cells. Mechanistic approaches revealed that LINC00174 directly interacted with SRSF1 to suppress the expression of p53, thus restraining the transcription of myocardin and repressing the activation of the Akt/AMPK pathway that was crucial for autophagy initiation in I/R-induced myocardial damage. Moreover, this molecular mechanism was verified by in vivo study. In summary, exosomal LINC00174 generated from vascular endothelial cells repressed p53-mediated autophagy and apoptosis to mitigate I/R-induced myocardial damage, suggesting that targeting LINC00174 may be a novel strategy to treat I/R-induced myocardial infarction.

We determined the effect of atorvastatin on myocardial apoptosis and caspase-8 activation following coronary microembolization (CME) in a rat model. For this, 50 rats were randomly and equally divided into CME; sham-operated (control); atorvastatin lavage; gastric lavage control; and caspase-8 inhibitor (CHO) groups. In CME animals, a microembolization ball was injected through the left ventricle. Sham animals were injected with normal saline (NS). Atorvastatin group received atorvastatin gastric lavage once-a-day, 1 week before surgery. Gastric lavage controls had similar lavage with NS. CHO group was i.p-injected (CHO: 10 mg/kg) 30 min before surgery. Cardiac indices in each group were determined by echocardiography 6-h postoperatively. TUNEL assay and western blot were used for myocardial apoptosis and expression of caspases-3/-8, respectively. Echocardiography data show that left ventricular ejection fraction (LVEF) in CME group was significantly decreased (P < 0.05) compared with sham controls. Besides, left ventricular fractional shortening (FS) and cardiac output (CO) were also decreased with an increase in left ventricular end-diastolic dimension (LVEDd). Atorvastatin and CHO animals had significantly improved (P < 0.05) cardiac function compared with CME group. Myocardial apoptosis and activation levels of caspases-3/-8 were significantly increased (P < 0.05) compared with sham; myocardial apoptosis and activation levels of caspases-3/-8 were significantly decreased (P < 0.05) in atorvastatin and CHO groups compared with CME group. In conclusion, atorvastatin pretreatment suppressed post-CME myocardial apoptosis and improved cardiac function through the blockade of a myocardial death receptor-mediated apoptotic pathway.

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Increasing evidence suggests that mitochondrial microRNAs (miRNAs) are implicated in the pathogenesis of cardiovascular diseases; however, their roles in ischemic heart disease remain unclear. Herein, we demonstrate that miR-146a is enriched in the mitochondrial fraction of cardiomyocytes, and its level significantly decreases after ischemic reperfusion (I/ R) challenge. Cardiomyocyte-specific knockout of miR-146a aggravated myocardial infarction, apoptosis, and cardiac dysfunction induced by the I/R injury. Overexpression of miR-146a suppressed anoxia/reoxygenation-induced cardiomyocyte apoptosis by inhibiting the mitochondria-dependent apoptotic pathway and increasing the Bcl-2/Bax ratio. miR-146a overexpression also blocked mitochondrial permeability transition pore opening and attenuated the loss of mitochondrial membrane potential and cytochrome c leakage; meanwhile, miR-146a knockdown elicited the opposite effects. Additionally, miR-146a overexpression decreased cyclophilin D protein, not mRNA, expression. The luciferase reporter assay revealed that miR-146a binds to the coding sequence of the cyclophilin D gene. Restoration of cyclophilin D reversed the inhibitory action of miR-146a on cardiomyocyte apoptosis. Furthermore, cardiomyocyte-specific cyclophilin D deletion completely abolished the exacerbation of myocardial infarction and apoptosis observed in miR-146a cardiomyocyte-deficient mice. Collectively, these findings demonstrate that nuclear miR-146a translocates into the mitochondria and regulates mitochondrial function and cardiomyocyte apoptosis. Our study unveils a novel role for miR-146a in ischemic heart disease.

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