Exosomal circ_HIPK3 reduces apoptosis in H2O2-induced AC16 cardiomyocytes through miR-33a-5p/IRS1 axis.

BACKGROUND: Exosomal circular RNAs (circRNAs) has been revealed to participate in the processes of cellular angiogenesis, growth and metastasis. Herein, the goal of this work was to investigate the role of exosomal circ_HIPK3 in cardiomyocyte apoptosis.

METHODS: Exosomes were isolated using ultracentrifugation method and observed by transmission electron microscopy (TEM). Western blot was used to detect exosomes markers. The experimental group AC16 cells were exposed to hydrogen peroxide (H2O2). Levels of genes and proteins was detected by qRT-PCR and Western blot. EdU assay, CCK8 assay, flow cytometry, and Western blot were utilized to detect the function of exosomal circ_HIPK3 in proliferation, and apoptosis. The target relationship between miR-33a-5p and circ_HIPK3 or IRS1 (insulin receptor substrate 1).

RESULTS: Circ_HIPK3 was packaged into exosomes and derived from AC16 cells. The expression of circ_HIPK3 was decreased by H2O2 treatment in AC16 cells, which also led to the decrease of circ_HIPK3 in exosomes. Functional analysis showed exosomal circ_HIPK3 promoted AC16 cell proliferation and reduced cell apoptosis under H2O2 treatment. Mechanistically, circ_HIPK3 acted as a sponge of miR-33a-5p to up-regulate the expression of its target IRS1. Functionally, forced expression of miR-33a-5p reversed the reduction of exosomal circ_HIPK3 in apoptosis of H2O2-stimulated AC16 cells. Moreover, miR-33a-5p inhibition contributed to the proliferation of H2O2-stimulated AC16 cells, which was abolished by IRS1 silencing.

CONCLUSION: Exosomal circ_HIPK3 reduced H2O2-induced AC16 cardiomyocyte apoptosis through miR-33a-5p/IRS1 axis, suggesting a novel insight into the pathology of myocardial infarction.