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Cardiovascular Research 2002 55(1):201-212; doi:10.1016/S0008-6363(02)00326-7
© 2002 by European Society of Cardiology
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Copyright © 2002, European Society of Cardiology

Effect of hypoxia and endothelial loss on vascular smooth muscle cell responsiveness to VEGF-A: role of flt-1/VEGF-receptor-1

Astrid Parentia, Laura Brogellia, Sandra Filippia, Sandra Donninib and Fabrizio Leddaa,*

aDepartment of Preclinical and Clinical Pharmacology, University of Florence, Viale G. Pieraccini 6, 50139 Florence, Italy
bInstitute of Pharmacological Science, University of Siena, Siena, Italy

* Corresponding author. Tel.: +39-55-427-1288; fax: +39-55-427-1280 ledda{at}ds.unifi.it

Objective: The influence of hypoxia and endothelial loss on the responsiveness of vascular smooth muscle cells (VSMCs) to vascular endothelial growth factor (VEGF-A) was tested. Methods and results: Exposure to hypoxia induced a potentiation of cultured cell proliferation in response to either the agonist for the VEGF receptor 1 (flt-1) placental growth factor (PlGF-1) or to VEGF-A. This effect was mediated by the mitogen activated protein kinase (MAPK) cascade, since it was inhibited by the MAPK kinase inhibitor PD98059 and by the farnesyl transferase inhibitor II. Accordingly, PlGF-1 activated extracellular signal-regulated kinase1/2. In rat aortic rings deprived of endothelium and cultured in three-dimensional fibrin gels, an increased sprouting of tubular structures in response to VEGF-A was observed only under hypoxia. Studies on rat aorta preparations revealed an endothelium-dependent vasorelaxation in response to either VEGF-A or PlGF1, which was reversed to a contractile response in endothelium-deprived preparations exposed to hypoxia. Western blot and immunohistochemistry of endothelium-deprived preparations exposed to hypoxia showed flt-1 receptor expression in all medial cells. Conversely, flt-1 mRNA, of endothelium-deprived aortic preparations and of tubular structures, was unchanged by hypoxia. Conclusion: These findings demonstrate that experimental conditions mimicking pathological vascular injury can make VSMCs responsive to VEGF-A through the induction of functional flt-1 receptors.

KEYWORDS Endothelial factors, hypoxia/anoxia; Remodeling; Smooth muscle; Vasoconstriction/dilation


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