Abstract 1527: Hypoxia and Reoxygenation Induce Survivin Expression in Endothelial Cells Through P38 Pathway
Background: Survivin is a member of inhibitors of apoptosis protein (IAP) family and suppresses cell death. The purpose of this study was to determine the effects of hypoxia and reoxygenation on survivin expression in endothelial cells and investigate the underlying mechanisms.
Methods: Bovine aortic endothelial cells (BAECs) were exposed to hypoxia (2h to 72h) followed by reoxygenation for 24 h. Expression of survivin as well as PI3K, Akt, mTOR and VEGF levels were examined. Inhibitors of PI3K, PKC, P38, ERK1/2 delineated the signaling pathways involved. Adenoviral vectors containing dominant-negative [Ad-S (T34A)] or wild-type [Ad-S (WT)] survivin plus survivin siRNA were used to inactivate, overexpresss and knock down survivin in BAECs. Cell migration, proliferation, as well as ATP and glucose oxidase production were evaluated in the transfected cells. The apoptotic reaction was examined using Annexin V-FITC staining nucleosome.
Results: Survivin expression increased more than four-fold (p<0.05) after hypoxia for six hours followed by reoxygenation. Survivin expression is a dose-dependent manner in response to hypoxia from 2h to 72h with the peak at 6–12h (7–10 folds, p<0.05). PI3K inhibitor (LY 294002) blocked hypoxia-induced expression of Akt, mTOR and VEGF but not expression of survivin. P38 inhibitor (SB203580) significantly blocked hypoxia-induced survivin expression whereas PKC inhibitor (Staurosporin), ERK-1/2 inhibitor (U0126) did not. Flowing knock down of survivin with survivin siRNA, there were significantly increased apoptotic activity (5 folds, p<0.05). Over expression survivin increased cells migration and proliferation (3 fold, P<0.001) compared to control. Moreover, cytoplasmic ATP and glucose oxidase (1–1.5 fold, p<0.05) level were increased in over expressing survivin.
Conclusion: This study suggested that survivin plays an important role in inhibiting endothelial cell apoptosis in the setting of hypoxic preconditioning. In the presence of in hypoxic preconditioning, novel functions of survivin appear to emerge such as enhancement of endothelial cell metabolism, thereby suppressing cell death. These novel functions of survivin deserve further study to help uncover its role in endothelial cells.