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Depletion of [Ca2+]i inhibits hypoxia-induced vascular permeability factor (vascular endothelial growth factor) gene
1Department of Pathology, Beth Israel Deaconess Medical Center and Harvard Medical School, Boston, Massachusetts, 02215, USA. dmukhopa@bih.harvard.edu
Abstract:
We have investigated the role of ion channels and intracellular Ca2+ in the regulation of hypoxia-mediated VPF/VEGF activation. Known channel activator and blockers like lemakalim, glibenclamide, tetraethylammonium, 4-aminopyridine and nifedipine do not inhibit VPF/VEGF induction due to hypoxia. Whereas, 5 mM caffeine pretreatment of the 293 cells exhibits a complete inhibition of hypoxia inducted VPF/VEGF expression. Moreover, the cells treated with BAPTA-AM prior to hypoxia also show a dramatic decrease in the VPF/VEGF message level, which suggests an important role of intracellular Ca2+ in this signaling pathway. Caffeine pretreatment also inhibits hypoxia-mediated c-Src kinase activity. These findings demonstrate the importance of intracellular Ca2+ in the event of hypoxia-induced VPF/VEGF expression.
Insights
Hypoxia-induced vascular permeability factor/vascular endothelial growth factor (VPF/VEGF) expression is regulated by intracellular calcium (Ca2+). Caffeine and BAPTA-AM inhibited this expression, highlighting Ca2+ as a key signaling molecule.
Area of Science:
- Cellular signaling
- Molecular biology
- Physiology
Background:
- Hypoxia, a state of low oxygen, triggers cellular responses.
- Vascular permeability factor/vascular endothelial growth factor (VPF/VEGF) plays a crucial role in angiogenesis and vascularization.
- The precise mechanisms regulating hypoxia-mediated VPF/VEGF activation are not fully understood.
Purpose of the Study:
- To investigate the role of ion channels and intracellular calcium (Ca2+) in regulating hypoxia-induced VPF/VEGF activation.
- To identify specific signaling pathways involved in this process.
Main Methods:
- Utilized 293 cells for experiments.
- Administered known ion channel modulators (lemakalim, glibenclamide, tetraethylammonium, 4-aminopyridine, nifedipine).
- Applied caffeine and BAPTA-AM (a Ca2+ chelator) pretreatment before inducing hypoxia.
- Assessed VPF/VEGF expression levels.
- Measured c-Src kinase activity.
Main Results:
- Ion channel modulators did not inhibit hypoxia-induced VPF/VEGF.
- Caffeine pretreatment completely inhibited hypoxia-induced VPF/VEGF expression.
- BAPTA-AM treatment significantly decreased VPF/VEGF message levels.
- Caffeine also inhibited hypoxia-mediated c-Src kinase activity.
Conclusions:
- Intracellular Ca2+ plays a critical role in hypoxia-induced VPF/VEGF expression.
- Caffeine and BAPTA-AM effectively block this signaling pathway.
- The findings suggest a signaling cascade involving intracellular Ca2+ and c-Src kinase in response to hypoxia.