Effect of vascular endothelial growth factor on cultured endothelial cell monolayer transport properties

Vascular endothelial growth factor (VEGF) is a potent enhancer of microvasc ular permeability in vivo. To date, its effects on hydraulic conductivity ( L-p) and diffusive albumin permeability (P-e) of endothelial monolayers hav e not been thoroughly assessed in vitro. We hypothesized that VEGF affects endothelial transport properties differently depending on vessel location a nd endothelial phenotype. Using three well-established endothelial cell cul ture models-human umbilical vein endothelial cells (HUVECs), bovine aortic endothelial cells (BAECs), and bovine retinal microvascular cells (BRECs)-g rown on porous, polycarbonate filters we were able to produce baseline tran sport properties characteristic of restrictive barriers. Our results show 3 .1-fold and 5.7-fold increases in endothelial L-p for BAEC and BREC monolay ers, respectively, at the end of 3 h of VEGF (100 ng/ml) exposure. HUVECs, however, showed no significant alteration in L-p after 3 h (100 ng/ml) or 2 4 h (25 ng/ml) of incubation with VEGF even though they were responsive to the inflammatory mediators, thrombin (1 U/ml; 27-fold increase in L-p in 25 min) and bradykinin (10 mu M; 4-fold increase in L-p in 20 min). Protein k inase C (PKC) and nitric oxide (NO) are downstream effecters of VEGF signal ing. BAEC L-p was responsive to activation of NO (SNAP) and PKC (PMA), wher eas these agents had no effect in altering HWEC L-p. Moreover, BAECs expose d to the PKC inhibitor, staurosporine (50 ng/ml), exhibited significant att enuation of VEGF-induced increase in L-p, but inhibition of nitric oxide sy nthase (NOS) with L-NMMA (100 mu M) had no effect in altering the VEGF-indu ced increase in L-p. These data provide strong evidence that in BAECs, the VEGF-induced increase in L-p is mediated by a PKC-dependent mechanism. Rega rding diffusive albumin P-e, at the end of 3 h, BAECs and BRECs showed 6.0- fold and 9.9-fold increases in P-e in response to VEGF (100 ng/ml), whereas VEGF had no significant effect after 3 h (100 ng/ml) or 24 h (25 ng/ml) in changing HWEC P-e. In summary, these data indicate that VEGF affects endot helial transport properties differently depending on the vessel type and th at differences in cell signaling pathways underlie the differences in VEGF responsiveness. (C) 2000 Academic Press.