Exercise Inhibits Doxorubicin-Induced Damage to Cardiac Vessels and Activation of Hippo/YAP-Mediated Apoptosis

SIMPLE SUMMARY: We developed a juvenile mouse cardiotoxicity model and demonstrated that doxorubicin treatment led to cardiac vascular damage involving a decrease in vascular endothelial cells and pericytes. By contrast, cardiac vessels in mice treated with exercise (Ex) during Dox treatment had no change in vascular endothelial cells or pericyte coverage. Here we show that exercise during Dox induced the migration of bone marrow (BM) stem cells into the heart with their differentiation into vascular endothelial cells and pericytes. These data define a new mechanism of Dox-induced cardiotoxicity and suggest that Ex inhibits vascular damage by promoting bone marrow (BM) stem cell-mediated cardiac vessel repair. We also show that Ex inhibits Hippo-YAP signaling-mediated apoptosis in cardiomyocytes. Ex may be an effective intervention strategy. Targeting Hippo-YAP signaling may also offer another novel therapeutic option to protect the heart. ABSTRACT: Dose-related cardiomyopathy is a major side effect following doxorubicin (Dox). To investigate whether exercise (Ex)-induced vasculogenesis plays a role in reducing Dox-induced cardiotoxicity, GFP(+) bone marrow (BM) cells from GFP transgenic mice were transplanted into wild-type mice. Transplanted mice were treated with Dox, Ex, Dox+Ex, or control. We found Dox therapy resulted in decreased systolic and diastolic blood flow, decreased ejection fraction and fractional shortening, and decreased vascular endothelial cells and pericytes. These abnormalities were not seen in Dox+Ex hearts. Heart tissues from control-, Ex-, or Dox-treated mice showed a small number of GFP(+) cells. By contrast, the Dox+Ex-treated hearts had a significant increase in GFP(+) cells. Further analyses demonstrated these GFP(+) BM cells had differentiated into vascular endothelial cells (GFP(+)CD31(+)) and pericytes (GFP(+)NG2(+)). Decreased cardiomyocytes were also seen in Dox-treated but not Dox+Ex-treated hearts. Ex induced an increase in GFP(+)c-Kit(+) cells. However, these c-Kit(+) BM stem cells had not differentiated into cardiomyocytes. Dox therapy induced phosphorylation of MST1/2, LATS1, and YAP; a decrease in total YAP; and cleavage of caspase-3 and PARP in the heart tissues. Dox+Ex prevented these effects. Our data demonstrated Dox-induced cardiotoxicity is mediated by vascular damage resulting in decreased cardiac blood flow and through activation of Hippo-YAP signaling resulting in cardiomyocyte apoptosis. Furthermore, Ex inhibited these effects by promoting migration of BM stem cells into the heart to repair the cardiac vessels damaged by Dox and through inhibiting Dox-induced Hippo-YAP signaling-mediated apoptosis. These data support the concept of using exercise as an intervention to decrease Dox-induced cardiotoxicity.