ABSTRACT
OBJECTIVE: To explore the correlation between intermittent hypoxia (IH)-induced apoptosis of human umbilical vein endothelial cells (HUVECs) and release of cytochrome C (cytC) from mitochondria. METHODS: HUVECs in IH groups were exposed to repetitive cycles (1% O2 5 min alternating with 21% O2 5 min, 37 â, 5% CO2) for different exposure time (8, 16 and 24 h, respectively), while the control group were placed in an ordinary incubator (21% O2, 37 â, 5% CO2) for 24 h. Apoptosis rate of HUVECs were determined by using Annexin V-FITC/PI apoptosis detection kit. The mitochondria ultrastructure was observed under transmission electron microscope (TEM). The mitochondria and cytoplasm of HUVECs were isolated by differential centrifugation, and the expression cytC in two separations were detected by Western blot. The correlation between the release of cytC and apoptosis rate was analyzed. RESULTS: TEM showed that mitochondria in HUVECs treated with IH appeared significant swelling, cristae rupture and vacuolization, compared with intact mitochondria in control group. Apoptosis rates in IH groups of 8, 16 and 24 h were significantly higher than control group[(6.710±0.599)%, (8.863±1.190)% and (9.607±1.266)% vs (2.450±0.795)%]in a time-dependent manner (all P<0.05). Apoptosis rates in IH groups positively correlated with cytC expression in cytoplasm (r=0.741, P=0.022). CONCLUSION: IH-induced cytC release from mitochondria promotes apoptosis of HUVECs, which participates in IH-induced endothelial injury.
