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Objective:The aim of the study was to investigate the role of microRNA-21 (miR-21) in cardiomyocyte apoptosis and to determine a possible mechanism.Methods:H9c2 embryonic rat heart-derived cells were used in the study. Cell viability was determined using the 3-(4.5-dimethyl-2-thiazolyl)-2,5-diphenyl-2-H-tetrazolium bromide (MTT) assay, and flow cytometry was used to evaluate cell apoptosis. Reverse transcription-polymerase chain reaction and western blot assays were used to detect mRNA and protein expression of the apoptosis-related proteins and miR-21. ELISA was used to detect reactive oxygen species (ROS).Results:Palmitate exposure greatly reduced miR-21 expression in cardiomyocytes. Apoptosis increased when miR-21 was inhibited with or without palmitate exposure. Consistently, reduced apoptosis was observed when miR-21 was overexpressed in cardiomyocytes. Caspase-3 activity was reduced after palmitate exposure. Bcl-2 protein expression was increased in H9c2 cells when transfected with the miR-21 mimic. MiR-21 overexpression alone did not induce ROS or DNA fragmentation; however, in conjunction with palmitate exposure, miR-21 mimic reduced ROS and DNA fragmentation. Moreover, palmitate administration overcame the antioxidant effect of 3 mM N-acetylcysteine to significantly inhibit apoptosis, DNA fragmentation, and caspase-3 activity. The exposure to palmitate greatly reduced p65 and p-p38 expression in the nucleus. A p38 inhibitor had no effect on the expression of Bcl-2 and cleaved caspase-3 in H9c2 cells alone; however, when combined with exposure to palmitate the p38 inhibitor induced Bcl-2 expression and inhibited caspase-3 activity. The p38 inhibitor by itself did not induce apoptosis, ROS production, or DNA fragmentation in H9c2 cells, but when palmitate was included with the p38 inhibitor, apoptosis, ROS production, and DNA fragmentation were reduced.Conclusion:miR-21 protects cardiomyocytes from apoptosis that is induced by palmitate through the caspase-3/NF-κB signal pathways.

Excessive fat ectopically deposited in the non-adipose tissues is considered as one of the leading causes of myopathy. The aim of this study was to investigate the role of Dihydroartemisinin (DHA) in palmitate (PAL)incubated H9c2 cells (lipotoxicity-induced cell injury model). Cell viability of PAL-treated cells was determined by MTT assay, and apoptotic regulators were examined by qRT-PCR and western blot analysis, in the absence or in the presence of DHA, respectively. Expression levels of miR-133b and Sirt1 were also evaluated by qRT-PCR and western blotting examination. PAL decreased the viability of H9c2 cells and enhanced the expression of apoptotic genes. DHA reversed the effect of PAL on cell viability and lowed the level of Caspase3 and Bax. It also lowered the expression of miR-133b, while enhanced the expression of Bcl-2. Sirt1 was revealed as target of miR-133b through transcriptional regulation and the process was affected by DHA. DHA partially protected against the PAL-induced lipotoxicity by influencing the expression of miR-133b that hindered the activity of Sirt1. DHA may be used as a potential treatment in clinical management for lipotoxicity induced heart complications.