Differential downregulation of vascular endothelial growth factor by dexamethasone in normoxic and hypoxic rat glioma cells
| Autor: | Annette Damert, Georg Breier, Volker Rönicke, W. Risau, M R Machein, Karl H. Plate, J. Kullmer, U Machein, M Krieg |
|---|---|
| Rok vydání: | 1999 |
| Předmět: |
Vascular Endothelial Growth Factor A
medicine.medical_specialty Umbilical Veins Histology Endothelium Angiogenesis Down-Regulation Vascular permeability Endothelial Growth Factors Dexamethasone Pathology and Forensic Medicine Cell Line chemistry.chemical_compound Downregulation and upregulation Physiology (medical) Glioma Internal medicine medicine Tumor Cells Cultured Animals Humans RNA Messenger Glucocorticoids Progesterone Lymphokines Estradiol business.industry Vascular Endothelial Growth Factors medicine.disease Cell Hypoxia Rats Vascular endothelial growth factor Vascular endothelial growth factor A Endocrinology medicine.anatomical_structure Neurology chemistry Neurology (clinical) Endothelium Vascular business medicine.drug |
| Zdroj: | ResearcherID |
| ISSN: | 0305-1846 |
| Popis: | Vascular endothelial growth factor/vascular permeability factor (VEGF/VPF) is a mitogen and chemotactic factor for endothelial cells in vitro and an angiogenesis and vascular permeability factor in vivo. Due to its properties, VEGF is a candidate for both angiogenesis and vascular permeability/oedema induction which typically occur in glioblastomas. In this study we test the hypothesis that the antioedema effect of dexamethasone is mediated by downregulation of VEGF or VEGF receptor expression. VEGF mRNA and protein levels of two rat glioma cells lines, C6 and GS-9L, were determined after incubation with dexamethasone under normoxic and hypoxic conditions. In normoxic C6 and GS9L cells, we observed 50-60% downregulation of VEGF mRNA by dexamethasone (P=0.015 and P=0. 01, respectively). This effect was dependent on glucocorticoid-receptor (GR) function. The inhibitory effect of dexamethasone on VEGF gene expression by tumour cells was markedly reduced by hypoxia which suggests that the upregulation of VEGF driven by hypoxia overcomes the effect of the dexamethasone. Dexamethasone did not alter VEGFR-2 mRNA levels in human umbilical endothelial cells. In a subcutaneous glioma tumour model, we observed only a 15% decrease in VEGF mRNA expression in dexamethasone treated animals (n = 12) compared with controls animals (P = 0.24). We conclude that dexamethasone may decrease brain tumour-associated oedema by reduction of VEGF expression in tumour cells. However, the highly reduced activity on hypoxic tumour cells suggests that dexamethasone efficacy may be limited by hypoxia in rapidly growing tumours. |
| Databáze: | OpenAIRE |
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