Yu Feng1, Qingchu Li2, Yinxiang Wu3, Nana Zhao3, Lu Li3, Li Li4, Liming Zhao5. 1. Department of Respiratory Medicine, Shanghai East Hospital, Tongji University School of Medicine, Pudong, Shanghai, 200120, China. 2. Department of Radiology, Secondary Affiliated Hospital of the Second Military Medical University, Shanghai, 200001, China. 3. Department of Respiratory Medicine, Third Affiliated Hospital of Second Military Medical University, Shanghai, 200438, China. 4. Department of Teaching Support, Second Military Medical University, Shanghai, 200433, China. czjwlili@163.com. 5. Department of Respiratory Medicine, Shanghai East Hospital, Tongji University School of Medicine, Pudong, Shanghai, 200120, China. zhao.liming@hotmail.com.
Abstract
BACKGROUND: Intermittent hypoxia (IH) can damage endothelial cells and lead to apoptosis in obstructive sleep apnea-hypopnea syndrome (OSAHS). Hypoxia induces apoptosis in endothelial cells via upregulation of endothelin-1 (ET-1) and hypoxia inducible factor-1 alpha (HIF-1α) plays a key role in the hypoxic stress response. PURPOSE: We investigated an approach to diminish the negative effect of HIF-1α while maintaining its protective effect. METHODS: Human umbilical vein endothelial cells (HUVECs) were subjected to sustained hypoxia (SH) or IH for 24 h, and the responses of HIF-1α, CCAAT/enhancer binding protein beta (C/EBP β), and endothelin-1 (ET-1) were assessed by western blotting. A luciferase reporter system was employed to verify the potential binding site (transcription factor binding site, TFBS) for C/EBP β in the ET-1 promoter. The specificity of regulation of ET-1 by HIF-1α via C/EBP β was evaluated by a lentiviral system. The effects of silencing of C/EBP β on IH-induced apoptosis, vascular endothelial growth factor (VEGF) protein levels, proliferation, and in vitro tube formation were studied. RESULTS: We found that IH significantly increased HIF-1α, C/EBP β, and ET-1 in HUVECs. Knockdown of HIF-1α or C/EBP β inhibited the upregulation of ET-1 induced by IH. Blocking C/EBP β impaired IH-induced apoptosis but did not affect VEGF expression, proliferation, or in vitro tube formation. C/EBP β was shown to mediate increased ET-1 transcription by HIF-1α through the TFBS, 5'-GTTGCCTGTTG-3', in ET-1 promoter. CONCLUSION: Silencing of C/EBP β can suppress apoptosis but does not affect the protective role of HIF-1α in the hypoxic stress response.
BACKGROUND: Intermittent hypoxia (IH) can damage endothelial cells and lead to apoptosis in obstructive sleep apnea-hypopnea syndrome (OSAHS). Hypoxia induces apoptosis in endothelial cells via upregulation of endothelin-1 (ET-1) and hypoxia inducible factor-1 alpha (HIF-1α) plays a key role in the hypoxic stress response. PURPOSE: We investigated an approach to diminish the negative effect of HIF-1α while maintaining its protective effect. METHODS: Human umbilical vein endothelial cells (HUVECs) were subjected to sustained hypoxia (SH) or IH for 24 h, and the responses of HIF-1α, CCAAT/enhancer binding protein beta (C/EBP β), and endothelin-1 (ET-1) were assessed by western blotting. A luciferase reporter system was employed to verify the potential binding site (transcription factor binding site, TFBS) for C/EBP β in the ET-1 promoter. The specificity of regulation of ET-1 by HIF-1α via C/EBP β was evaluated by a lentiviral system. The effects of silencing of C/EBP β on IH-induced apoptosis, vascular endothelial growth factor (VEGF) protein levels, proliferation, and in vitro tube formation were studied. RESULTS: We found that IH significantly increased HIF-1α, C/EBP β, and ET-1 in HUVECs. Knockdown of HIF-1α or C/EBP β inhibited the upregulation of ET-1 induced by IH. Blocking C/EBP β impaired IH-induced apoptosis but did not affect VEGF expression, proliferation, or in vitro tube formation. C/EBP β was shown to mediate increased ET-1 transcription by HIF-1α through the TFBS, 5'-GTTGCCTGTTG-3', in ET-1 promoter. CONCLUSION: Silencing of C/EBP β can suppress apoptosis but does not affect the protective role of HIF-1α in the hypoxic stress response.
Authors: Carlos Zamarrón-Sanz; Jorge Ricoy-Galbaldon; Francisco Gude-Sampedro; Alberto Riveiro-Riveiro Journal: Arch Med Res Date: 2006-05 Impact factor: 2.235
Authors: P Quehenberger; A Bierhaus; P Fasching; C Muellner; M Klevesath; M Hong; G Stier; M Sattler; E Schleicher; W Speiser; P P Nawroth Journal: Diabetes Date: 2000-09 Impact factor: 9.461