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Expression of vascular permeability factor/vascular endothelial growth factor in pig cerebral microvascular
S Fischer1, H S Sharma, G F Karliczek
1Max-Planck Institute for Physiological and Clinical Research, Bad Nauheim, Germany.
Abstract:
Porcine brain-derived microvascular endothelial cells (BMEC) express the mRNA of the polypeptide mitogen vascular permeability factor/vascular endothelial growth factor (VPF/VEGF). The VEGF mRNA expression in BMEC could be upregulated 2.5 fold after 6 h of treatment with 5 microM adenosine and adenosine agonists. Adenosine A1 and A2 receptor antagonists completely abolished the upregulation of the VEGF mRNA caused by adenosine. Agents like forskolin and cAMP phosphodiesterase inhibitors which are known to increase the cAMP level decreased the VEGF mRNA expression slightly whereas agents like phorbolester which activate the proteinkinase C (PKC) pathway enhanced the VEGF mRNA expression 3.2 fold. The specific inhibitor of the PKC bisindolymaleimide (BIM) abolished the upregulation of the VEGF mRNA by adenosine completely. The BMEC conditioned medium stimulated the proliferation of BMEC itself and Western blot analysis of the BMEC conditioned medium using a polyclonal antibody to human VEGF showed one band at 18 kDa which was slightly upregulated after treatment with adenosine. Results suggest that the effect of adenosine on the VEGF mRNA expression is mediated via the A1 receptor and that an activation of the PKC may be involved in the observed effects of adenosine on the VEGF mRNA expression. VEGF produced by BMEC and which is inducible by adenosine may function via the autocrine pathway and may be involved in repair reactions of brain blood vessels and/or the maintenance of these cells.
Insights
Adenosine increases vascular endothelial growth factor (VEGF) mRNA in brain microvascular endothelial cells (BMEC), potentially via A1 receptors and protein kinase C (PKC). This suggests a role for VEGF in brain blood vessel repair.
Area of Science:
- Neuroscience
- Molecular Biology
- Cell Biology
Background:
- Porcine brain-derived microvascular endothelial cells (BMEC) express vascular permeability factor/vascular endothelial growth factor (VPF/VEGF) mRNA.
- VEGF plays a crucial role in angiogenesis and vascular maintenance.
Purpose of the Study:
- To investigate the effect of adenosine on VEGF mRNA expression in BMEC.
- To elucidate the signaling pathways involved in adenosine-mediated VEGF regulation.
Main Methods:
- Treatment of BMEC with adenosine, adenosine agonists, and antagonists.
- Analysis of VEGF mRNA expression using quantitative methods.
- Investigation of protein kinase C (PKC) and cAMP signaling pathways.
- Western blot analysis of VEGF protein levels.
Main Results:
- Adenosine significantly upregulated VEGF mRNA expression in BMEC.
- Adenosine A1 and A2 receptor antagonists blocked this upregulation.
- PKC activation enhanced VEGF mRNA expression, while PKC inhibition abolished adenosine's effect.
- BMEC-conditioned medium promoted BMEC proliferation, and VEGF protein levels were slightly increased by adenosine.
Conclusions:
- Adenosine upregulates VEGF mRNA expression in BMEC, primarily mediated via the A1 receptor.
- Activation of the PKC pathway is involved in adenosine's effect on VEGF mRNA expression.
- Adenosine-induced VEGF production by BMEC may act through an autocrine pathway, potentially contributing to brain blood vessel repair and maintenance.