Bcl-xL is Required for the Protective Effects of Low-dose Berberine Against Doxorubicin-induced Cardiotoxicity Through Blocking Apoptosis and Activating Mitophagy-mediated ROS Elimination

Background: Doxorubicin (DOX)-induced cardiotoxicity is related to abnormal autophagy and apoptosis in the heart. Berberine (BBR) is a well-known natural compound with potential cardioprotective and autophagic modulatory properties.

Hypothesis: We hypothesized that BBR ameliorates DOX-induced cardiotoxicity by balancing cardiomyocyte autophagy and apoptosis.

Study Design/methods: DOX was used to generate in vivo and in vitro cardiotoxic models. Larval and adult zebrafish and human AC16 cells were used to study (i) the effects of BBR on autophagy and apoptosis upon DOX challenge and (ii) the underlying mechanisms.

Results: BBR protected AC16 cells and zebrafish hearts from DOX-induced cytotoxicity and apoptosis. Bcl-xL knockdown in AC16 cells and zebrafish demonstrated that Bcl-xL is required for BBR's anti-apoptotic activity. DOX treatment promoted Beclin1 binding to Bcl-xL, disrupted mitophagy, and increased ROS accumulation in AC16 cells. In AC16 cells and zebrafish hearts, pretreatment with BBR enhanced mitophagy via dissociation of the Bcl-xL-Beclin1 complex and decreased ROS accumulation. Inhibition of autophagy attenuated this effect of BBR. Intriguingly, BBR increased Bcl-xL binding to Bnip3, sequestration, and mitophagy, indicating that Bcl-xL may play a beneficial role in BBR-induced mitophagy. Additionally, BBR significantly ameliorated DOX-induced cardiac dysfunction in zebrafish, whereas Bcl-xL knockdown abolished this effect. Notably, we discovered that BBR exerts biphasic dose-response effects in response to DOX; the cardioprotective properties were observed upon treatment with low-dose BBR (≤ 1 μM in cells, ≤ 10 μM in zebrafish), but not with relatively high-dose BBR.

Conclusion: These findings indicate that the protective effects of low-dose BBR against DOX-induced cardiotoxicity are mediated by Bcl-xL.