Figure 5.

Effect of sunitinib on cardiac structure, mitochondrial function and apoptosis.

A. TEM of cardiac tissue from mice treated with control (left panel) or sunitinib (center and right panels) at 40 mg/kg/d for 10 days. Images from treated animals are notable for swollen mitochondria with disrupted cristae (M). Higher magnification image (right panel) illustrates membrane whorls (arrow) within the mitochondria of myocytes from sunitinib-treated mice.

B. Sunitinib induces cytochrome c release from mitochondria. Neonatal rat ventricular myocytes (NRVMs) in culture were incubated in media (control) or media containing sunitinib (1 μM) for the times shown. Cells were then stained for cytochrome c. The punctate staining in the control is consistent with mitochondrial-localized cytochrome c, while the diffuse staining in the sunitinib-treated cells reflects release of cytochrome c from the mitochondria into the cytosol.

C. Sunitinib activates Capase-9 and induces apoptosis.

Top: NRVMs were treated with vehicle (DMSO) or sunitinib at the concentrations noted for 40 hours. Caspase-9 activity was examined. Sunitinib resulted in significant increases in caspase-9 activity at 1 μM (** P=,0·02) and 10 μM (* P=0·006). Data are mean ± SD.

Bottom: Cardiomyocytes were treated with vehicle (control) or sunitinib (1 μM) for 44 hours, followed by TUNEL staining to detect apoptotic cells. * P=0·01 vs. control.

D. Sunitinib induces apoptosis in vivo in the setting of increased blood pressure. Mice were fed normal chow (control) or chow containing sunitinib (10mg/kg/d) for 2 weeks. During the second week, phenylephrine (PE; 30 mg/kg/d) vs. vehicle was administered via subcutaneous mini-pump. Heart sections were then stained for TUNEL. Graph depicts percent TUNEL positive cells for the various treatments. * P=0·02 vs. control + vehicle; # P = 0·002 vs. control + PE; n = 4 for control + vehicle; n = 6 for control + PE; n = 3 for sunitinib + PE.