Long non-coding RNA nuclear-enriched abundant transcript 1 inhibition blunts myocardial ischemia reperfusion injury via autophagic flux arrest and apoptosis in streptozotocin-induced diabetic rats.

BACKGROUND AND AIMS

This study aimed to investigate the effects of long non-coding RNA (lncRNA)-nuclear-enriched abundant transcript (Neat1) on myocardial ischemia reperfusion injury in diabetic rats ex vivo and in vivo.

METHODS

Screening for LncRNA Neat1 expression was performed in rat myocardial tissues using microarray analysis and verified by qRT-PCR. Cell viability of rat cardiomyocytes was analyzed by MTT assay. Levels of autophagy-related proteins Atg7, Atg5, LC3-II/LC3-I and p62 were determined by Western blot assay. Left ventricular end diastolic diameter (LVEDD), left ventricular end systolic diameter (LVESD), left ventricular ejection fraction (LVEF) and fractioning shortening were obtained by transthoracic echocardiography. Left ventricular end systolic pressure (LVESP), left ventricular end diastolic pressure (LVEDP), maximum rate of increase or decrease of left ventricular pressure (±dp/dtmax) and heart rate were obtained by computer algorithms and an interactive videographics programme. Myocardial infarct size was determined by Evans blue and triphenyltetrazolium chloride (TTC) staining. Myocardial apoptotic index was analyzed by TUNEL assay and immunohistochemical staining. Autophagic flux was examined by evaluating fluorescent LC3 puncta.

RESULTS

Neat1 was highly expressed in ischemia reperfusion-treated diabetic rat myocardial tissues. Overexpression of Neat1 promoted the production of lactate dehydrogenase, inhibited superoxide dismutase content and cardiomyocyte viability. Neat1 overexpression also promoted the production of serum myocardial enzymes, including creatine kinase and creatine kinase-MB, and increased infarct size. By promoting myocardial apoptosis and autophagy, Neat1 aggravated myocardial ischemia reperfusion (I/R) injury in diabetic rats. Neat1 promoted cardiomyocyte autophagy by up-regulating Foxo1 expression to increase hypoxia-reoxygenation injury.

CONCLUSIONS

I/R treatment caused more injuries in diabetic rats compared with normal rats. Elevated Neat1 expression aggravates myocardial ischemia reperfusion injury via activation of apoptosis and autophagy in diabetic rats. Foxo1 is one of the molecular mechanisms underlying Neat1-induced autophagy.