Vascular endothelial growth factor is an important vasodilator and effector of permeability in systemic blood vessels. Molecular and tissue culture techniques have provided evidence for its placental synthesis and release. Using an in vitro dual perfusion model of the term placental lobule from normal pregnancy, we report here the relative secretion of total VEGF, sVEGFR-1 and free VEGF into the maternal and fetoplacental circulations of the placenta. We tested the hypothesis that VEGF has vasomotor and permeability effects in the fetoplacental circulation of the human placenta and we examined the broad intracellular pathways involved in the vasodilatory effect which we found. We show that total VEGF is released into the fetal and maternal circulations in a bipolar fashion, with a bias towards maternal side output. Soluble VEGFR-1 was also secreted into both circulations with bias towards the maternal side. Consequently, free VEGF (12.8 +/- 2.4 pg / ml, mean +/- SE) was only found in the fetoplacental circulation. VEGF-165 was found to be a potent vasodilator of the fetoplacental circulation (maximum response: 77% of previous steady state fetal-side inflow hydrostatic pressure following preconstriction with U46619; EC50 = 71 pM). This vasodilatory effect was mediated by the VEGFR-2 receptor and nitric oxide in a manner independent of the involvement of prostacyclin and the src-family tyrosine kinases. However, nitric oxide could only explain 50% of the vasodilatory effect. Finally, we measured the permeability of the perfused placenta to inert hydrophilic tracers and found no difference in the presence and absence of VEGF.

Reactive oxygen species (ROS) have been implicated in the cellular membrane damage and postoperative morbidity associated with obligatory ischemia-reperfusion (I-R) during vascular surgery. Thus, a clinical study was undertaken to evaluate the effects of ascorbate prophylaxis on ROS exchange kinetics in 22 patients scheduled for elective abdominal aortic aneurysm (AAA) or infra-inguinal bypass (IIB) repair. Patients were assigned double-blind to receive intravenous sodium ascorbate (2 g vitamin C, n = 10) or placebo (0.9% saline, n = 12) administered 2 h prior to surgery. Blood samples were obtained from the arterial and venous circulation proximal to the respective sites of surgical repair (local) and from an antecubital vein (peripheral) during cross-clamping (ischemia) and within 60 s of clamp release (reperfusion). Ascorbate supplementation increased the venoarterial concentration difference (v-a(diff)) of lipid hydroperoxides (LH), interleukin (IL)-6 and vascular endothelial growth factor (VEGF) protein during ischemia. This increased the peripheral concentration of LH, total creatine phosphokinase (CPK), and VEGF protein during reperfusion (P < 0.05 vs placebo). Electron paramagnetic resonance (EPR) spectroscopy confirmed that free iron was available for oxidative catalysis in the local ischemic venous blood of supplemented patients. An increased concentration of the ascorbate radical (A(-)) and alpha-phenyl-tert-butylnitrone (PBN) adducts assigned as lipid-derived alkoxyl (LO()) and alkyl (LC()) species were also detected in the peripheral blood of supplemented patients during reperfusion (P < 0.05 vs ischemia). In conclusion, these findings suggest that ascorbate prophylaxis may have promoted iron-induced oxidative lipid damage via a Fenton-type reaction initiated during the ischemic phase of surgery. The subsequent release of LH into the systemic circulation may have catalyzed formation of second-generation radicals implicated in the regulation of vascular permeability and angiogenesis.

PURPOSE: The aim of this case-control study was to investigate the relationship between homocysteine (tHcy), 5,10 methylene tetrahydrofolate reductase (MTHFR) C677T genotype, folate and vitamin B12 status, and retinal vein occlusion (RVO). METHODS: Subjects with RVO (n = 106) were recruited from outpatient and inpatient sources. Controls (n = 98) were selected to achieve a similar age and sex distribution. Full ocular examination was performed and medical history was taken for each study participant. Plasma and serum samples were analyzed for tHcy level and folate and vitamin B12 status, and extracted DNA was assessed for the MTHFR C677T genotype. RESULTS: There was no significant difference in plasma tHcy level or thermolabile MTHFR allele frequency between subjects and controls. Similarly, there was no significant difference in folate or vitamin B12 status between subjects and controls. MTHFR genotype did not affect folate or vitamin B12 concentrations in subjects or controls. However, tHcy was significantly higher in thermolabile homozygotes than in nonthermolabile homozygotes (ratio of geometric means, 1.35; 95% confidence interval [CI], 1.04-1.74; P = 0.024). CONCLUSIONS: Hyperhomocysteinemia, the MTHFR C677T mutation, and folate and vitamin B12 status are not important risk factors for RVO in this population.

OBJECTIVE: This study was undertaken to analyze prospectively circulating vascular endothelial growth factor (VEGF) and its soluble receptor,(s) Flt-1, throughout normotensive and preeclamptic pregnancies and to assess the importance of these proteins in the development of preeclampsia. STUDY DESIGN: In this longitudinal cohort study, serum samples were collected from recruited subjects throughout pregnancy at 12, 20, 30, and 37 weeks and in the 24 hours before and after delivery. Subjects were divided retrospectively into normotensive and preeclamptic groups. Circulating VEGF and sFlt-1 concentrations were analyzed by radioimmunoassay and enzyme-linked immunosorbent assay, respectively. RESULTS: Circulating sFlt-1 and VEGF significantly increased as gestation progressed and both were further elevated in preeclampsia compared with normotensive pregnancy. Soluble Flt-1 concentrations were elevated early in gestation and were significantly increased at 30 weeks' gestation in those who subsequently developed preeclampsia. CONCLUSION: These results indicate a definite association between elevated sFlt-1 concentrations and the onset of preeclampsia suggesting that sFlt-1 is linked with disease pathogenesis.