Interference of circRNA HIPK3 alleviates cardiac dysfunction in lipopolysaccharide-induced mice models and apoptosis in H9C2 cardiomyocytes

Background: Circular RNAs (circRNAs) have been deemed to be microRNA (miRNA) sponges that are involved in multiple biological processes. It has not yet been corroborated whether the regulation of circular RNA HIPK3 (circHIPK3) can be used for the treatment of myocardial dysfunction. Methods: In this study, we aimed to investigate the cardioprotective effects and apoptosis inhibition of circHIPK3 regulation on lipopolysaccharide (LPS)-induced myocarditis in vivo and vitro. C57BL/6 mice were exposed to LPS with or without knockdown of circHIPK3. Reverse transcription polymerase chain reaction (RT-PCR) testing was used to evaluate the expression of circHIPK3. Hematoxylin and eosin (HE) staining, immunohistochemistry (IHC), Cell Counting Kit-8 (CCK8), flow cytometry, terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) assay, enzyme-linked immunosorbent assay (ELISA), and western blotting were used to evaluate histopathology, proliferation, apoptosis, oxidative stress, and inflammatory response, respectively. Cardiac function and myocardial damage were also evaluated. Results: It was proven that short hairpin RNA1 (shRNA1) was a superior interference of circHIPK3. The results revealed that knockdown of circHIPK3 effectively alleviated myocardial tissue damage, improved cardiac function, and suppressed cardiomyocyte apoptosis in the animal model of LPS-induced myocarditis. Furthermore, LPS-induced oxidative injuries and inflammation in the myocardium were also partly reversed after circHIPK3 knockdown. In vitro, being LPS-induced enhanced the levels of heart damage markers, simultaneously inhibited proliferation, promoted apoptosis, and stimulated oxidative stress and inflammation of H9C2 cells. Fortunately, the abnormalities mentioned were partly reversed following circHIPK3 knockdown. Conclusions: In this study, we characterized the expression and regulation of circHIPK3 in LPS-induced myocarditis in the animal model and H9c2 cells. The results demonstrated that circHIPK3 expression is significantly upregulated when exposed to LPS in vivo and in vitro. Knockdown of circHIPK3 effectively alleviated LPS-induced myocarditis.