O17	Isoprostanes inhibit in vitro migration and tube formation of endothelial cells via the thromboxane A2 receptor.
A.Gnann, R.A.Benndorf, E.Schwedhelm, G.D.Kom, R.H.Böger
Institut für Experimentelle und Klinische Pharmakologie, Hamburg, DE.

Background: Isoprostanes are generated from non-enzymatic free radical-induced lipid peroxidation of arachidonic acid. Furthermore, they are markers of oxidative stress and independent risk markers of coronary heart disease (CHD). However, their physiological and pathophysiological properties as well as signalling of isoprostanes have remained elusive. In CHD patients, impaired angiogenesis may exacerbate insufficient blood supply of ischemic myocardium. We therefore hypothesized that isoprostanes might exert detrimental cardiovascular effects by inhibiting angiogenesis. Methods: Endothelial cell migration and tube formation represent essential steps in the process of angiogenesis. We examined the effect of iPF2alpha and iPA2 on basal and VEGF-induced migration (Boyden chamber) and on VEGF-induced tube formation on extracellular matrix (Matrigel Assay) of human coronary artery endothelial cells (HCAECs). Results: The isoprostanes iPF2alphaα and iPA2 inhibited VEGF-induced migration and tube formation of HCAECs. VEGF as positive control induced migration of HCAECs ((mean+/-SD 160+/-14.1%; P<0.05). Both iPF2alpha (134.5+/-14.1%; P<0.05 vs. VEGF) and iPA2 (127.1+/-18.4; P<0.05 vs. VEGF) significantly reduced VEGF-mediated cell migration. Concomitant incubation with the TXA2 receptor antagonist SQ-29548 blocked the observed effect of iPF2alpha (156.3+/-13.3 SD; P<0.05 vs. VEGF+iPF2alpha) and iPA2 (163.0+/-8.5 SD; P<0.05 vs. VEGF+iPA2). In contrast, the TXA2 receptor agonist U-46619 mimicked the inhibitory effect of isoprostanes (106.7+/-17.8%; P<0.05 vs. VEGF). The effects of iPF2alphaα and iPA2 on basal migration were concentration-dependent. At concentrations <1µM, iPA2 and iPF2alpha activated the migration of HCAECs (P<0.01 vs. vehicle, P<0.001 vs. vehicle, respectively), whereas in higher concentrations (>1µM), they inhibited migration. Conclusions: We demonstrate for the first time that isoprostanes negatively regulate in vitro angiogenesis via activation of the TXA2 receptor. By this mechanism, isoprostanes might contribute directly to the exacerbation of CHD.

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