P102	Inhibition of VEGF-induced NO production by FGF-2 in endothelial cells.
1Chr.Klarskov, 2F.Krötz, 1U.Pohl, 1T.Gloe
1Institute of Physiology, LMU, München, DE; 2Klinikum Innenstadt, LMU, München, DE.

There is growing evidence that nitric oxide (NO) plays a significant modulator role in angiogenesis and vascular remodelling by opposed interactions with growth factors. We investigated therefore the interplay of NO with FGF-2 and VEGF, both cytokines are known for their potency in vascular remodelling and angiogenesis, and additionally investigated possible modulator effects of both, FGF-2 and VEGF, on NO synthesis as possible feedback loop. Primary endothelial cells (HUVEC) were used throughout the study. VEGF (5-10ng/ml) or histamine (1µg/ml), the latter used here as independent control, induced NO production significantly after 6h (measured as nitrite 3-fold vs. control, n=8, p<0.05), whereas FGF-2 (3ng/ml) had no inductor effect. Furthermore, FGF-2 even inhibited NO production when it was combined with VEGF or histamine. These FGF-2 effects were abolished by a FGF-2 receptor antagonist or wortmannin, indicating a PI3Kinase-dependent signalling pathway. Similarly, in shear stress experiments (16dyn/cm2) HUVEC increased NO production only within the first 2h. However, the addition of FGF-2 receptor blockers led to an exponential increase in shear stress induced NO formation even beyond 2h indicating, again, a FGF-2-dependent inhibition of mechanically induced NO-formation. The inhibitory effects of FGF-2 and the inductive effects of VEGF on the NO production were also reflected by their individual interplay with NO. Exogenously added NO (SNAP, 1µM,) inhibited FGF-2-induced migration by 50% but not those of VEGF-induced (n=4x10, p<0.05). Accordingly, FGF-2 induced differentiation (capillary like structure formation out of aortic rings) was increased twofold if basal NO production was inhibited (L-NA, L-nitro-arginine, 30µM) whereas the effect of VEGF on vessel sprouting was reduced by twofold. Similar effects were found in proliferation; VEGF- but not FGF-2-induced cell growth was reduced by L-NA (14% after 72h, n=8, p<0.05). The results identify NO as a significant modulator of vascular remodelling and angiogenesis by affecting the efficiency of both angiogenic growth factors VEGF and FGF-2 in an oppositional manner. Moreover, FGF-2 dependent inhibition of NO production might be a set back mechanism for flow induced NO production. By that, FGF-2 might be part of a negative feed back loop preventing an overshoot in dilatation and may participate in local blood pressure regulation.

Copyright © 2005 S. Karger AG, Basel. Any further use of this abstract requires written permission from the publisher.