The role of reactive oxygen species in the vascular pathology asiated with atherosclerosis was examined by testing the hypothesis that impaired vascular reactivity results from the reaction of nitric oxide (NO) with superoxide (O2), yielding the oxidant peroynitrite (ONOO-). Contractility studies were performed on femoral arteries from rabbits fed a cholesterol-supplemented diet Endothelium-dependent relaxation is impaired in vessels from atherosclerotic patients (1, 2) and hypercholesterolemic animal models (3-6), suggesting the functional modification of endothelium-derived relaxing factor (EDRF) in hyperlipidemia. The dynamic role ofthe endothelium in the regulation of vascular tone was established when it was observed that relaxation of isolated blood vessels by vasoactive agents, such as acetylcholine (ACh) and the calcium ionophore A23187, was dependent on an intact endothelium and a diffusible factor (EDRF) that stimulated cGMP-dependent relaxation of vascular smooth muscle cells (VSMCs; ref. 7).Nitric oxide (-NO) and EDRF share similar chemical and pharmacological properties (8) and are derived from the oxidation of a terminal guanidino group of L-arginine (9, 10).Numerous mechanisms have been suggested for the defect in vascular relaxation in atherosclerosis and hypercholesterolemic animal models. They include an increased diffusional barrier for 'NO due to intimal cell proliferation and lipid deposition (11), L-argifine depletion (3,12,13) Vessel Contraction Studies. New Zealand White rabbits (2.5-3.0 kg) were maintained on rabbit chow containing 1% cholesterol (Ralston Purina) for 6 months prior to study [cholesterol-fed (Chol-fed) group]. Age-and weight-matched controls were fed a standard diet. After exsanguination under ketamine/rompun anesthesia, vessels were isolated and changes in tension were measured in femoral artery ring segments as described (28). After maximal contraction with 70 mM KCl and recovery, phenylephrine was added to achieve 30% of maximal tone. Rings were then exposed to increasing doses of ACh; relaxation is reported as the percentage decrease in preexisting tone. After the generation of cumulative ACh dose-response curves, rings were exposed to 30 ,uM papaverine. In some experiments, rings from control and Chol-fed rabbits were incubated with 3 mM L-arginine for 30 min prior to administration of ACh. In other studies, vessels were treated with native bovine SOD (200 units/ml) before measuring ACh-induced relaxation. All studies were performed in the presence of 5 !uM indomethacin.

Hypervascularity, focal necrosis, persistent cerebral edema, and rapid cellular proliferation are key histopathologic features of glioblastoma multiforme (GBM), the most common and malignant of human brain tumors. By immunoperoxidase and immunofluorescence, we definitively have demonstrated the presence of vascular endothelial growth factor (VEGF) and epidermal growth factor receptor (EGFr) in five out of five human glioma cell lines (U-251MG, U-105MG, D-65MG, D-54MG, and CH-235MG) and in eight human GBM tumor surgical specimens. In vitro experiments with glioma cell lines revealed a consistent and reliable relation between EGFr activation and VEGF production; namely, EGF (1-20 ng/ml) stimulation of glioma cells resulted in a 25-125% increase in secretion of bioactive VEGF. Conditioned media (CM) prepared from EGF-stimulated glioma cell lines produced significant increases in cytosolic free intracellular concentrations of Ca2+ ([Ca2+]i) in human umbilical vein endothelial cells (HUVECs). Neither EGF alone or CM from glioma cultures prepared in the absence of EGF induced [Ca2+]i increases in HUVECs. Preincubation of glioma CM with A4.6.1, a monoclonal antibody to VEGF, completely abolished VEGF-mediated [Ca2+]i transients in HUVECs. Likewise, induction by glioma-derived CM of von Willebrand factor release from HUVECs was completely blocked by A4.6.1 pretreatment. These observations provide a key link in understanding the basic cellular pathophysiology of GBM tumor angiogenesis, increased vascular permeability, and cellular proliferation. Specifically, EGF activation of EGFr expressed on glioma cells leads to enhanced secretion of VEGF by glioma cells. VEGF released by glioma cells in situ most likely accounts for pathognomonic histopathologic and clinical features of GBM tumors in patients, including striking tumor angiogenesis, increased cerebral edema and hypercoagulability manifesting as focal tumor necrosis, deep vein thrombosis, or pulmonary embolism.

Vascular endothelial growth factor (VEGF), also known as vascular permeability factor (VPF), has recently been shown to increase cytosolic free calcium in endothelial cells. In the present study, we investigated the coronary vascular effects of recombinant human and native guinea pig VEGF/VPF in isolated canine coronary arteries in the presence and absence of intimal endothelium, indomethacin, and NG-monomethyl-L-arginine, a competitive nitric oxide synthase inhibitor. Addition of recombinant VEGF/VPF (1-660 pM) in coronary arteries that had been previously contracted with prostaglandin F2 alpha induced a slow, dose-dependent relaxation, reaching a maximum of -59.1 +/- 6.7% (mean +/- SE, n = 19). Mechanical disruption of the intimal endothelium completely abolished the observed relaxation. No direct vascular effect of recombinant VEGF/VPF on the endothelium-disrupted coronary arteries was noted. Pretreatment of endothelium-intact coronary arteries with 5 microM of indomethacin did not alter the observed relaxation (-57.3 +/- 7.0%, n = 18), whereas pretreatment with either NG-monomethyl-L-arginine or 10 microM of genistein, a known inhibitor of tyrosine kinase, significantly inhibited the relaxation. Addition of native VEGF/VPF (1-100 pM) also induced an endothelium-dependent relaxation in the isolated coronary arteries. Heating of recombinant VEGF/VPF (70 degrees C, 25 min) or prior incubation with a specific antibody raised against a VEGF/VPF peptide completely abolished the relaxation. Finally, recombinant VEGF/VPF stimulated a slow rise in cytosolic free calcium in cultured human endothelial cells that was qualitatively similar to that of native VEGF/VPF.(ABSTRACT TRUNCATED AT 250 WORDS)

We have identified a third member of the junctional adhesion molecule (JAM) family. At the protein level JAM3 displays 36 and 32% identity to JAM2 and JAM1, respectively. The coding region is distributed over 9 exons and maps to chromosome 11q25. The gene shows widespread tissue expression with higher levels apparent in the kidney, brain, and placenta. At the cellular level we show expression of JAM3 transcript within endothelial cells. Our major finding is that JAM3 and JAM2 are binding partners. Thus, JAM3 ectodomain binds firmly to JAM2-Fc. This heterotypic interaction is maintained when JAM3-Fc is used to capture Chinese hamster ovary cells expressing full-length JAM2. In static adhesion assays we show that JAM3 is unable to bind to leukocyte cell lines. This is consistent with the lack of JAM2 expression. However, using JAM2-Fc pulldown experiments in combination with polyclonal anti-JAM3 serum, we demonstrate that JAM3 is the previously uncharacterized 43-kDa counter-receptor that mediates JAM2 adhesion to T cells. Most significantly we demonstrate up-regulation of JAM3 protein on peripheral blood lymphocytes following activation. Finally we show the utility of JAM3 ectodomain as an inhibitor of JAM2 adhesion.

The purpose of these experiments was to investigate a potential role for vascular endothelial growth factor (VEGF) in mediating vascular dysfunction induced by increased glucose flux via the sorbitol pathway. Skin chambers were mounted on the backs of Sprague-Dawley rats and 1 wk later, granulation tissue in the chamber was exposed twice daily for 7 d to 5 mM glucose, 30 mM glucose, or 1 mM sorbitol in the presence and absence of neutralizing VEGF antibodies. Albumin permeation and blood flow were increased two-to three-fold by 30 mM glucose and 1 mM sorbitol; these increases were prevented by coadministration of neutralizing VEGF antibodies. Blood flow and albumin permeation were increased ‫ف‬ 2.5-fold 1 h after topical application of recombinant human VEGF and these effects were prevented by nitric oxide synthase (NOS) inhibitors (aminoguanidine and N G -monomethyl L -arginine). Topical application of a superoxide generating system increased albumin permeation and blood flow and these changes were markedly attenuated by VEGF antibody and NOS inhibitors. Application of sodium nitroprusside for 7 d or the single application of a calcium ionophore, A23187, mimicked effects of glucose, sorbitol, and VEGF on vascular dysfunction and the ionophore effect was prevented by coadministration of aminoguanidine. These observations suggest a potentially important role for VEGF in mediating vascular dysfunction induced by "hypoxia-like" cytosolic metabolic imbalances (reductive stress, increased superoxide, and nitric oxide production) linked to increased flux of glucose via the sorbitol pathway. ( J. Clin. Invest. 1997. 99:2192-2202.)