Attenuation of the hypoxia-induced miR-34a protects cardiomyocytes through maintenance of glucose metabolism.

Ischemic injury in the heart is associated with death of cardiomyocytes and even after decades of research there is no appropriate therapeutic intervention to treat ischemic injury. The microRNA miR-34a is known to be induced in cardiomyocytes following ischemic injury. Another hallmark of ischemic injury is impaired glycolysis. The objective of the current study was to investigate the effects of short- and long-term exposure to hypoxia on miR-34a expression on apoptosis and regulation of key glycolysis metabolic enzymes. Both repeated short-term (30 min) burst of hypoxia with intermittent reoxygenation (30 min) as well as long-term (4 h) exposure to hypoxia followed by 6 h of reoxygenation robustly induced miR-34a levels. Hypoxia induced changes in cardiac permeability and localization of the channel protein connexin 34 as well as induced apoptosis as evident by levels of cleaved-caspase 3/7 and impaired cell proliferation. Hypoxia was also associated with decreased expression of key glycolytic enzymes hexokinase-1, hexokinase-2, glucose-6-phosphate-isomerase, and pyruvate dehydrogenase kinase 1. Attenuation of hypoxia-induced miR-34a by anti-miR-34a antagomir, but not a control antagomir, decreased miR-34a levels to those observed under normoxia and also inhibited apoptosis, potentially by rescuing expression of the key glycolytic enzymes. Cumulatively, our results establish that therapeutic targeting of miR-34a via antagomir might be a potent therapeutic mechanism to treat ischemic injury in the heart.

Wang ZC ，Wang ZZ ，Ma HJ ，Wang CC ，Wang HT ... -  《-》

Attenuation of miR-34a protects cardiomyocytes against hypoxic stress through maintenance of glycolysis.

MiRNAs are a class of endogenous, short, single-stranded, non-coding RNAs, which are tightly linked to cardiac disorders such as myocardial ischemia/reperfusion (I/R) injury. MiR-34a is known to be involved in the hypoxia-induced cardiomyocytes apoptosis. However, the molecular mechanisms are unclear. In the present study, we demonstrate that under low glucose supply, rat cardiomyocytes are susceptible to hypoxia. Under short-time hypoxia, cellular glucose uptake and lactate product are induced but under long-time hypoxia, the cellular glucose metabolism is suppressed. Interestingly, an adaptive up-regulation of miR-34a by long-time hypoxia was observed both in vitro and in vivo, leading to suppression of glycolysis in cardiomyocytes. We identified lactate dehydrogenase-A (LDHA) as a direct target of miR-34a, which binds to the 3'-UTR region of LDHA mRNA in cardiomyocytes. Moreover, inhibition of miR-34a attenuated hypoxia-induced cardiomyocytes dysfunction through restoration of glycolysis. The present study illustrates roles of miR-34a in the hypoxia-induced cardiomyocytes dysfunction and proposes restoration of glycolysis of dysfunctional cardiomyocytes by inhibiting miR-34a during I/R might be an effectively therapeutic approach against I/R injury.

Zhang Y ，Liu G ，Gao X 《-》

Hydrogen Sulfide Protects Cardiomyocytes against Apoptosis in Ischemia/Reperfusion through MiR-1-Regulated Histone Deacetylase 4 Pathway.

Hydrogen sulfide (H<Sub>2</Sub>S) is a powerful inhibitor of cardiomyocytes apoptosis following ischemia/reperfusion (IR) injury, but the underlying mechanism remains unclear. Our previous study showed that microRNA-1 (miR-1) was upregulated by 2.21 fold in the IR group compared with that in the H<Sub>2</Sub>S preconditioned group. MiR-206 affected the process of cardiomyocytes hypertrophy by regulating histone deacetylase 4 (HDAC4). HDAC4 is also known to play an anti-apoptotic role in tumor cells, but its role in the myocardium has not been reported. The aim of this study was to test whether H<Sub>2</Sub>S could inhibit apoptosis of cardiomyocytes through HDAC4 regulation by miR-1 in IR. Cardiomyocytes of neonatal rats were subjected to hypoxia/reoxygenation (HR) injury with or without H<Sub>2</Sub>S pretreatment to simulate IR injury Cardiomyocytes were transfected with miR-1 mimic or HDAC4 siRNA to evaluate whether the miR-1-HDAC4 signaling pathway was involved in the protective effect of H<Sub>2</Sub>S. HR increased cell apoptosis and caspase-3 cleavage, upregulated miR-1, and downregulated HDAC4. H<Sub>2</Sub>S preconditioning attenuated the apoptosis of cardiomyocytes, caspase-3 cleavage and LDH release, and enhanced cell viability In addition, H<Sub>2</Sub>S downregulated miR-1, and preserved HDAC4 expression. HDAC4 protein was down-regulated by miR-1 mimic. Transfection of cardiomyocytes with miR-1 mimic partially reduced the protective effect of H<Sub>2</Sub>S. Meanwhile, transfection of cardiomyocytes with siRNA to HDAC4 partially abrogated the protective effect of H<Sub>2</Sub>S. The miR-1-HDAC4 signaling pathway is involved in the protective effect of H<Sub>2</Sub>S against the apoptosis of cardiomyocytes during the IR injury process.

Kang B ，Li W ，Xi W ，Yi Y ，Ciren Y ，Shen H ，Zhang Y ，Jiang H ，Xiao J ，Wang Z ... -  《-》

MiR-93 inhibition ameliorates OGD/R induced cardiomyocyte apoptosis by targeting Nrf2.

Yan LJ ，Fan XW ，Yang HT ，Wu JT ，Wang SL ，Qiu CG ... -  《-》

MiR-34a-5p mediates sevoflurane preconditioning induced inhibition of hypoxia/reoxygenation injury through STX1A in cardiomyocytes.

Anesthetic preconditioning is a cellular protective approach whereby exposure to a volatile anesthetic renders cardio injury. Sevoflurane preconditioning has been shown to exhibit cardio protective effect on hypoxia/reoxygenation (H/R) injury, but the underlying mechanism is unclear. Syntaxin 1A (STX1A), an important regulator in cardio disease, was predicted to be the target gene of microRNA-34a-5p (miR-34a-5p). The current research was designed to delineate the role of miR-34a-5p in regulating sevoflurane preconditioning in cardiomyocytes injury. In this study, the results demonstrated that the expression of STX1A was significantly increased, while miR-34a-5p was dramatically decreased in sev-preconditioning H9c2 cells as compared with cells only under H/R stimulation. Moreover, miR-34a-5p regulated the protective effect of sev-preconditioning in injured H9c2 cells by mediating cell proliferation and cell apoptosis. Additionally, the luciferase report confirmed the targeting reaction between STX1A and miR-34a-5p. Taken together, our study suggested that miR-34a-5p regulated sev-preconditioning induced inhibition of hypoxia/reoxygenation injury through mediating STX1A, provided a potential therapeutic target for anesthetic protection in cardio disease.

Wenlan L ，Zhongyuan X ，Shaoqing L ，Liying Z ，Bo Z ，Min L ... -  《-》