Berberine inhibits excessive autophagy and protects myocardium against ischemia/reperfusion injury via the RhoE/AMPK pathway

Several studies have shown that berberine (BBR) is effective in protecting against myocardial ischemia-reperfusion injury (MI/RI). However, the precise molecular mechanism remains elusive. The present study observed the mechanism and the safeguarding effect of BBR against hypoxia/reoxygenation (H/R) myocardial injury in H9c2 cells. BBR pretreatment significantly improved the decrease of cell viability, P62 protein, Rho Family GTPase 3 (RhoE) protein, ubiquinone subunit B8 protein, ubiquinol-cytochrome c reductase core protein U, the Bcl-2-associated X protein/B-cell lymphoma 2 ratio, glutathione (GSH) and the GSH/glutathione disulphide (GSSG) ratio induced by H/R, while reducing the increase in lactate dehydrogenase, microtubule-associated protein 1 light 3 protein, caspase-3 activity, reactive oxygen species, GSSG and malonaldehyde caused by H/R. Transmission electron microscopy and LysoTracker Red DND-99 staining results showed that BBR pretreatment inhibited H/R-induced excessive autophagy by mediating RhoE. BBR also inhibited mitochondrial permeability transition, maintained the stability of the mitochondrial membrane potential, reduced the apoptotic rate, and increased the level of caspase-3. However, the protective effects of BBR were attenuated by pAD/RhoE-small hairpin RNA, rapamycin (an autophagy activator) and compound C (an AMP-activated protein kinase inhibitor). These new findings suggested that BBR protects the myocardium from MI/RI by inhibiting excessive autophagy, maintaining mitochondrial function, improving the energy supply and redox homeostasis, and attenuating apoptosis through the RhoE/AMP-activated protein kinase pathway.