Vascular endothelial growth factor/vascular permeability factor augments nitric oxide release from quiescent rabbit and human vascular endothelium

Actions of a nitric oxide donor on prostaglandin production and angiogenic activity in the equine endometrium

Nitric oxide (NO) plays an important role in prostaglandin secretion and angiogenesis in the reproductive system. In the present study, the roles of the NO donor spermine NONOate and tumour necrosis factor-α (TNF; as a positive control) in prostaglandin production and angiogenic activity of equine endometria during the oestrous cycle were evaluated. In addition, the correlation between NO production and the expression of key prostaglandin synthase proteins was determined. The protein expression of prostaglandin F synthase (PGFS) increased in early and mid-luteal stages, whereas that of prostaglandin E synthase (PGES) was increased in the early luteal stage. The in vitro release of NO was highest after ovulation. There was a high correlation between NO production and PGES expression, as well as NO release and PGFS expression. There were no differences detected in prostaglandin H synthase 2 (PTGS-2) throughout the oestrous cycle and there was no correlation between PTGS-2 expression and NO. In TNF- or spermine-treated endometria, the expression of prostaglandin (PG) E2 increased in the early and mid-luteal phases, whereas that of PGF2α increased in the follicular and late luteal phases. Bovine aortic endothelial cell (BAEC) proliferation was stimulated in TNF-treated follicular-phase endometria. However, in spermine-treated endometria, NO delivered from its donor had no effect, or even an inhibitory effect, on BAEC proliferation. In conclusion, despite no change in PTGS-2 expression throughout the oestrous cycle in equine endometrial tissue, there were changes observed in the expression of PGES and PGFS, as well as in the production of PGE2 and PGF2α. In the mare, NO is involved in the secretory function of the endometrium, modulating PGE2 and PGF2α production. Even though TNF caused an increase in the production of angiogenic factors and prostaglandins, its complex action in mare uterus should be elucidated.

Effect of maternal administration of betamethasone on peripheral arterial development in fetal rabbit lungs

OBJECTIVES

Glucocorticoids promote lung maturation and reduce the incidence of respiratory distress syndrome in premature newborns. We hypothesized that betamethasone (BM), which is known to induce thinning of the alveolar walls, would also thin the arterial media and adventitia of intra-parenchymatic vessels in developing rabbit lungs.

STUDY DESIGN

112 fetuses from 21 time-mated, pregnant, giant white rabbits received maternal injections of BM at either 0.05 or 0.1 mg/kg/day on days 25-26 of gestational age. Controls received either saline (10 does, 56 fetuses) or no injection (10 does, 59 fetuses). Fetuses were harvested from day 27 onwards until term (day 31). 44 additional fetuses (8 does) were harvested between days 23 and 26. Endpoints were wet lung-to-body weight ratio, vascular morphometric indices and immunohistochemistry staining for alpha-smooth muscle actin, Flk-1, vascular endothelial growth factor (VEGF) and endothelial nitric oxide synthase (eNOS). ANOVA (Tukey's test) and independent t test (p < 0.05) were used for comparison between BM and saline groups.

RESULTS

Maternal BM injected on days 25-26 to pregnant rabbits induced a significant decrease in fetal body and lung weight and the lung-to-body weight ratio in the preterm pups shortly after injection. BM led to a dose-dependent thinning of the arterial media and adventitia (pulmonary arteries with an external diameter (ED) of <100 microm), to an increase in the percentage of non-muscularized peripheral vessels (ED <60 microm), in eNOS and VEGF immunoreactivity of the endothelial and smooth muscle cells in the pulmonary vessels and to an increase in Flk-1-positive pulmonary epithelial cell density.

CONCLUSIONS

Maternal administration of BM caused thinning of the arterial wall of pulmonary vessels (ED <100 microm) and a decrease in muscularization in peripheral vessels (ED <60 microm). This coincided with increased expression of Flk-1 in the endothelium and smooth muscle cells of the pulmonary arteries. All the effects studied were dose-dependent.

Growth factors and cell therapy in myocardial regeneration

Despite significant advances in myocardial revascularization and reperfusion, coronary artery disease and subsequently myocardial infarction, are the leading cause of morbidity and mortality in the US. Thus one of the main goals in the treatment of myocardial ischemia is the development of effective therapy for angiogenesis. The first evidence is the demonstration of alleviation of myocardial ischemia and increased number of collateral blood vessels in the early 1990s following intra-coronary administration of basic fibroblast growth factor protein in dog. Multiple animal studies, has confirmed the concept of stimulation of collateral development by pharmacological and molecular means. This includes direct delivery of growth factors into the ischemic target tissues, or of genes that encode for synthesis of growth factors by target tissues. Both cell therapy and gene therapy have proven to be effective to promote neovascularization in various animal models. Cell therapy alone is proven to be beneficial however the combination of cell and gene therapy (growth factors) may enhance therapeutic neovascularization. Thus clinically relevant, combined strategy could be an excellent strategy for treating patients with myocardial infarction.

Secoisolariciresinol diglucoside induces neovascularization-mediated cardioprotection against ischemia-reperfusion injury in hypercholesterolemic myocardium

Hypercholesterolemia (HC) induced endothelial cell dysfunction and decreased endothelial nitric oxide formation results in impaired angiogenesis and subsequent cardiovascular disorders. Therapeutic angiogenesis is known to be a novel strategy for treatment of patients with ischemic heart disease. We have shown that secoisolariciresinol diglucoside (SDG) is angiogenic as well as cardioprotective against myocardial ischemia. In the present study, we examined the efficacy of SDG in a hypercholesterolemic myocardial infarction (MI) model. The rats were maintained on a normal and high cholesterol diet (2%) for 8 weeks followed by oral administration of SDG (20 mg/kg) for 2 weeks. The rats were divided into four groups (n=24 in each): Control (C); SDG control (SDG); HC; and HC+SDG (HSDG). Isolated hearts subjected to 30 min of global ischemia followed by 120 min of reperfusion were used to measure the cardiac functions, infarct size and to examine the protein expression profile. After treatment, MI was induced by ligating the left anterior descending artery. Echocardiographic parameters were examined 30 days after MI. Significant reduction in total cholesterol, LDL-cholesterol, triglycerides and an increase in HDL-cholesterol levels were observed in HSDG as compared to the HC. Decreased infarct size was observed in the HSDG group (43%) compared to the HC (54%). Increased phosphorylation of endothelial nitric oxide synthase (p-eNOS) (3.1-fold), vascular endothelial growth factor (1.9-fold) and heme oxygenase-1 (2.3-fold) was observed in the HSDG group as compared to the HC group. Significant improvement in left ventricular functions was also observed in the HSDG group as evidenced by increased ejection fraction (55% vs. 45%), fractional shortening (28% vs. 22%) and decreased left ventricular inner diameter in systole (8 vs. 6 mm) in HSDG compared to HC. Moreover, MI model has shown increased capillary density (2531 vs. 1901) and arteriolar density (2.6 vs. 1.8) in SDG-treated rats as compared to the HC. The increased capillary and arteriolar density along with increased left ventricular functions on SDG treatment might be due to increased HO-1, VEGF and p-eNOS expression. In conclusion, our study demonstrates for the first time that SDG treatment reduces ventricular remodeling by neovascularization of the infarcted HC myocardium.

Chronic alcohol-induced oxidative endothelial injury relates to angiotensin II levels in the rat

The link between chronic alcohol consumption and cardiovascular injury including hypertension is well known. However, molecular mediators implicated with alcohol-induced elevation in blood pressure (BP) remain elusive. The aim of this study was to investigate the relationship of chronic ethanol-induced endothelial injury and elevation in BP with angiotensin II levels in rats. Male Fisher rats were divided into two groups of seven animals each and treated as follows: (1) Control (5% sucrose, orally) daily for 12 weeks and (2) ethanol (4 g kg(-1), orally) daily for 12 weeks. The BP (systolic, diastolic, and mean) was recorded every week. The animals were anesthetized with pentobarbital after 12 weeks; blood and thoracic aorta were isolated and analyzed for aortic reactivity response, angiotensin II levels, and oxidative endothelial injury. The results show that the systolic, diastolic, and mean BP were significantly elevated 12 weeks after ethanol ingestion. The increased BP was related to elevated angiotensin II levels in the plasma and aorta of alcohol treated group compared to control. The aortic NADPH oxidase activity, ratio of oxidized to reduced glutathione (GSSG/GSH) and lipid peroxidation significantly increased, whereas nitric oxide (NO), endothelial NO synthase (eNOS), and vascular endothelial growth factor (VEGF) protein expressions were depressed in alcohol group compared to control. The phenylephrine-mediated vasoconstriction response was not altered, while acetylcholine-mediated vasorelaxation response was depressed in the aorta of ethanol treated rats compared to control. It is concluded that chronic ethanol ingestion induces hypertension which is correlated with elevated tissue angiotensin II levels, activation of NADPH oxidase activity causing endothelial injury, depletion of endothelial NO generating system, and impaired vascular relaxation in rats.

Down regulation of aortic nitric oxide and antioxidant systems in chronic alcohol-induced hypertension in rats

The aim of this study was to investigate the relationship between chronic ethanol-induced increase in blood pressure (BP) and alterations in the aortic nitric oxide (NO) and the antioxidant systems in rats. Male Fisher rats (200-250 g) were divided into two groups of six animals each and treated as follows: 1) control (5% sucrose, orally) daily for 12 weeks and 2) 20% ethanol (4 g/kg, orally) daily for 12 weeks. The BP (systolic, diastolic and mean) was recorded every week through tail-cuff method. The animals were sacrificed 12 weeks after treatments and thoracic aorta was collected and analysed. The results show that systolic, diastolic and mean BP was significantly elevated 12 weeks after ethanol ingestion in rats compared to control. The endothelial nitric oxide synthase (eNOS) and vascular endothelial growth factor (VEGF) expressions were down-regulated (50-55% of control) leading to depletion of aortic NO levels (69% of control) in ethanol treated rats compared to control. The ratio of reduced to oxidized glutathione (GSH/GSSG) was significantly depleted (58% of control) in the aorta of ethanol-treated rats compared to control. The decrease in aortic GSH/GSSG ratio was good correlated with increase in BP (r = 0.69). The antioxidant enzymes: copper/zinc-superoxide dismutase (CuZn-SOD) and manganese (Mn)-SOD, catalase (CAT) and glutathione peroxidase (GSH-Px) activities were significantly depressed (36-53% of control) in the aorta of ethanol-treated rats compared to control. The study concluded that chronic ethanol ingestion induces hypertension which relates to the vascular endothelial dysfunction on account of the down-regulation of aortic endothelial antioxidants and NO generating system in rats.

Drugs, gene transfer, signaling factors: a bench to bedside approach to myocardial stem cell therapy

In the past few years, the dogma that the heart is a terminally differentiated organ has been challenged. Evidence from preclinical investigations emerged that there are cells, even in the heart itself, that may be able to restore impaired cardiac function after myocardial infarction. Although the exact mechanisms by which the infarcted heart can be repaired by stem cells are not yet fully defined, there is a new optimism among cardiologists that this treatment will prove successful in addressing the cause of heart failure after myocardial infarction-myocyte loss. Despite the promising preliminary data of human myocardial stem cell trials, scientists have also focused on the possibility of enhancing the underlying mechanisms of stem cell repair to gain healthier myocardial tissue. Attempts to induce neo-angiogenesis by transfecting stem cells with signaling factors (such as VEGF), to raise the number of endothelial progenitor cells with medical treatments (such as statins), to transfect stem cells with heat shock protein 70 (as a cardioprotective agent against ischemia) and to enhance the healing process after myocardial infarction with the use of various forms of stimulating factors (G-CSF, SCF, GM-CSF) have been made with notable results. In this article, we summarize the evidence from preclinical and clinical myocardial stem cell studies that have addressed the possibility of enhancing the regenerative capacity of cells used after myocardial infarction.

Functional interplay between endothelial nitric oxide synthase and membrane type 1 matrix metalloproteinase in migrating endothelial cells

Nitric oxide (NO) is essential for vascular homeostasis and is also a critical modulator of angiogenesis; however, the molecular mechanisms of NO action during angiogenesis remain elusive. We have investigated the potential relationship between NO and membrane type 1-matrix metalloproteinase (MT1-MMP) during endothelial migration and capillary tube formation. Endothelial NO synthase (eNOS) colocalizes with MT1-MMP at motility-associated structures in migratory human endothelial cells (ECs); moreover, NO is produced at these structures and is released into the medium during EC migration. We have therefore addressed 2 questions: (1) the putative regulation of MT1-MMP by NO in migratory ECs; and (2) the requirement for MT1-MMP in NO-induced EC migration and tube formation. NO upregulates MT1-MMP membrane clustering on migratory human ECs, and this is accompanied by increased degradation of type I collagen substrate. MT1-MMP membrane expression and localization are impaired in lung ECs from eNOS-deficient mice, and these cells also show impaired migration and tube formation in vitro. Inhibition of MT1-MMP with a neutralizing antibody impairs NOinduced tube formation by human ECs, and NO-induced endothelial migration and tube formation are impaired in lung ECs from mice deficient in MT1-MMP. MT1-MMP thus appears to be a key molecular effector of NO during the EC migration and angiogenic processes, and is a potential therapeutic target for NO-associated vascular disorders.

Evaluation of tissue-engineered vascular autografts

This study evaluated the endothelial function and mechanical properties of tissue-engineered vascular autografts (TEVAs) constructed with autologous mononuclear bone marrow cells (MN-BMCs) and a biodegradable scaffold using a canine inferior vena cava (IVC) model. MN-BMCs were obtained from a dog and seeded onto a biodegradable tubular scaffold consisting of polyglycolide fiber and poly(L-lactide-co-epsilon-caprolactone) sponge. This scaffold was implanted in the IVC of the same dog on the day of surgery. TEVAs were analyzed biochemically, biomechanically, and histologically after implantation. When TEVAs were explanted and stimulated with acetylcholine at 1 month, they produced nitrates and nitrites dose dependently. N(G)-nitro-L-arginine methylester significantly inhibited these reactions. With stimulation by acetylcholine, factor VIII-positive cells of TEVAs produced endothelial nitric oxide synthase proteins, and the ratio of endothelial nitric oxide synthase/s17 mRNA was similar among native IVC and TEVAs 1 and 3 months after implantation. TEVAs had biochemical properties and wall thickness similar to those of native IVC at 6 months after implantation, and tolerated venous pressure well without any problems such as calcification. The number of inflammatory cells in TEVAs and the ratio of CD4/s17 mRNA decreased significantly with time. These results indicate that TEVAs are a biocompatible material with functional endothelial cells and biomechanical properties and do not have unwanted side effects.

VEGFR1 (Flt-1+/-) gene knockout leads to the disruption of VEGF-mediated signaling through the nitric oxide/heme oxygenase pathway in ischemic preconditioned myocardium

This report demonstrates that mice deficient in Flt-1 failed to establish ischemic preconditioning (PC)-mediated cardioprotection in isolated working buffer-perfused ischemic/reperfused (I/R) hearts compared to wild type (WT) subjected to the same PC protocol. WT and Flt-1+/- mice were divided into four groups: (1) WT I/R, (2) WT + PC, (3) Flt-1+/- I/R, and (4) Flt-1+/- + PC. Group 1 and 3 mice were subjected to 30 min of ischemia followed by 2 h of reperfusion and group 2 and 4 mice were subjected to four episodes of 4-min global ischemia followed by 6 min of reperfusion before ischemia/reperfusion. For both wild-type and Flt-1+/- mice, the postischemic functional recovery for the hearts was lower than the baseline, but the recovery for the knockout mice was less compared to the WT mice even in preconditioning. The myocardial infarction and apoptosis were higher in Flt-1+/- compared to wild-type I/R. Flt-1+/- KO mice demonstrated pronounced inhibition of the expression of iNOS, p-AKT & p-eNOS. Significant inhibition of STAT3 & CREB were also observed along with the inhibition of HO-1 mRNA. Results demonstrate that Flt-1+/- mouse hearts are more susceptible to ischemia/reperfusion injury and also document that preconditioning is not as effective as found in WT and therefore suggest the importance of VEGF/Flt-1 signaling in ischemic/reperfused myocardium.

Pharmacogenomics and the Yin/Yang actions of ginseng: anti-tumor, angiomodulating and steroid-like activities of ginsenosides

In Chinese medicine, ginseng (Panax ginseng C.A. Meyer) has long been used as a general tonic or an adaptogen to promote longevity and enhance bodily functions. It has also been claimed to be effective in combating stress, fatigue, oxidants, cancer and diabetes mellitus. Most of the pharmacological actions of ginseng are attributed to one type of its constituents, namely the ginsenosides. In this review, we focus on the recent advances in the study of ginsenosides on angiogenesis which is related to many pathological conditions including tumor progression and cardiovascular dysfunctions. Angiogenesis in the human body is regulated by two sets of counteracting factors, angiogenic stimulators and inhibitors. The 'Yin and Yang' action of ginseng on angiomodulation was paralleled by the experimental data showing angiogenesis was indeed related to the compositional ratio between ginsenosides Rg1 and Rb1. Rg1 was later found to stimulate angiogenesis through augmenting the production of nitric oxide (NO) and vascular endothelial growth factor (VEGF). Mechanistic studies revealed that such responses were mediated through the PI3K-->Akt pathway. By means of DNA microarray, a group of genes related to cell adhesion, migration and cytoskeleton were found to be up-regulated in endothelial cells. These gene products may interact in a hierarchical cascade pattern to modulate cell architectural dynamics which is concomitant to the observed phenomena in angiogenesis. By contrast, the anti-tumor and anti-angiogenic effects of ginsenosides (e.g. Rg3 and Rh2) have been demonstrated in various models of tumor and endothelial cells, indicating that ginsenosides with opposing activities are present in ginseng. Ginsenosides and Panax ginseng extracts have been shown to exert protective effects on vascular dysfunctions, such as hypertension, atherosclerotic disorders and ischemic injury. Recent work has demonstrates the target molecules of ginsenosides to be a group of nuclear steroid hormone receptors. These lines of evidence support that the interaction between ginsenosides and various nuclear steroid hormone receptors may explain the diverse pharmacological activities of ginseng. These findings may also lead to development of more efficacious ginseng-derived therapeutics for angiogenesis-related diseases.

Endometrial nitric oxide production and nitric oxide synthases in the equine endometrium: Relationship with microvascular density during the estrous cycle

Nitric oxide (NO) plays an important role in angiogenesis and in the regulation of the blood flow. This study was carried out to investigate (i) the effects of endogenous estrogens and progestins and exogenous progesterone (P(4)) (5 ng/ml or 1 microg/ml) or estradiol 17beta (E(2)beta) (50 pg/ml or 1 microg/ml) on in vitro endometrial NO synthesis; (ii) the presence of different isoforms of NO synthase; (iii) and their relationship to microvascular density in the equine endometrium during the estrous cycle. NOS expression was also evaluated in the myometrium. Expression of endothelial and inducible forms of NOS in the uterus was assessed by Western blot and immunocytochemistry. Vascular density in endometrial tissue was determined on histologic sections. In the luteal phase, compared to the follicular phase, endometrial NO production increased without exogenous hormones and with exogenous E(2)beta (1 microg/ml). Although immunocytochemistry revealed iNOS and eNOS expression in the endometrium, no positive signal for iNOS was detected by Western blot. Endothelial NOS was observed in endometrial glands, endothelial cells, fibroblasts, blood and lymphatic vessels. Endometrial eNOS expression was the highest in the follicular and mid-luteal phases while it was found to be the lowest in the early luteal phase. In the follicular phase, hyperplasia of endometrial tissue with respect to myometrium was detected. No difference in vascular density was present between phases. All together, NO may play some roles in both proliferative and secretory phases of endometrial development in the mare.

Beneficial effects of thiazolidinediones on diabetic nephropathy in OLETF rats

PURPOSE

Diabetic nephropathy is the most serious of complications in diabetes mellitus. Thiazolidinedione (TZD) is thought to ameliorate diabetic nephropathy; however, the mechanism underlying this effect has not been elucidated. We hypothesized that the vascular endothelial growth factor (VEGF) participates in the pathogenesis of diabetic nephropathy and that TZD may be beneficial for the treatment of diabetic nephropathy because of the effect it has on VEGF.

MATERIALS AND METHODS

23 Otsuka- Long-Evans-Tokushima-Fatty (OLETF) rats and eight control Long-Evans-Tokushima-Otsuka (LETO) rats were divided into the following four groups: LETO group, control OLETF group, pioglitazone treated group (10mg/ kg/day), and rosiglitazone treated group (3mg/kg/day).

RESULTS

A progressive increase in urinary protein excretion was observed in the diabetic rats. Glomerular VEGF expression in the control OLETF rats was significantly higher than in the control LETO rats. However, there was a significant reduction in both the glomerular VEGF expression and the VEGF mRNA levels after treatment with pioglitazone and rosiglitazone. The twenty-four hour urine protein levels were significantly decreased in both groups of the treated OLETF rats.

CONCLUSION

These results suggest that TZD may have beneficial effects on diabetic nephropathy by reducing the VEGF expression.

Vasorelaxation induced by vascular endothelial growth factor in the human internal mammary artery and radial artery

OBJECTIVES

Due to potential therapeutic value of vascular endothelial growth factor (VEGF) in coronary artery disease, the effect and mechanism of VEGF in human arteries used as coronary bypass grafts become important but not fully understood. VEGF-mediated endothelial regulation in vasorelaxation was studied in internal mammary artery (IMA) and radial artery (RA), compared with that of the classical agent-acetylcholine (ACh). The role of nitric oxide (NO), prostacyclin (PGI2), and endothelium-derived hyperpolarizing factor (EDHF) was investigated.

METHODS

VEGF- and ACh-induced responses were measured in RA and IMA with or without endothelium and in the absence or presence of inhibitors of nitric oxide synthase or prostacyclin. In addition, the VEGF-induced PGI2 was measured by enzyme immunoassay.

RESULTS

VEGF induced similar relaxation in RA (59.2+/-9.3%) and IMA (56.1+/-6.4%) that was significantly inhibited by N(omega)-nitro-L-arginine (L-NNA) plus oxyhemoglobin (HbO) (IMA: 24.9+/-4.3%, P=0.03 vs. RA: 25.0+/-8.6%, P=0.01) or by indomethacin (INDO) (IMA: 21.8+/-2.5%, P=0.000 vs. RA: 30.0+/-6.6%, P=0.04) with more inhibition in IMA than RA (P<0.05). In addition, the VEGF-induced PGI2 was significantly higher in IMA than RA (11.5+/-2.1 vs. 4.9+/-1.1 pg/ml/mg, P=0.002). INDO+L-NNA+HbO reduced the VEGF-induced relaxation to 20.8+/-4.6% in RA vs. 4.8+/-1.6% in IMA (P=0.01). In contrast, the maximal relaxation induced by ACh in RA (55.9+/-6.0%) and IMA (48.5+/-5.3%) was largely inhibited by L-NNA in IMA and RA (14.7+/-3.0%, P=0.000 vs. 15.2+/-3.2%, P=0.004) but little affected by INDO.

CONCLUSIONS

VEGF induces similar relaxation in IMA and RA with significantly more PGI2-mediated relaxation and higher stimulated PGI2 level in IMA but more EDHF-mediated relaxation in RA. In comparison, ACh-induced relaxation mainly depends on NO. Thus, our study reveals a significant difference in the mechanism of the endothelium-dependent relaxation induced by VEGF and ACh.

Evidence against the involvement of nitric oxide in the modulation of telomerase activity or replicative capacity of human endothelial cells

Telomerase, a reverse transcriptase involved in the maintenance of telomere function and cellular replicative capacity, is thought to be regulated by nitric oxide (NO). Here, we have used pharmacological tools and RNA interference to re-assess the role of NO in the regulation of telomerase and senescence of human umbilical vein endothelial cells. Acute or chronic treatment of these cells with the NO donors diethylenetriamine/NO (DETA-NO) or S-nitroso-N-acetylpenicillamine (SNAP) at concentrations which generated NO in the 1-300 nM range did not modulate telomerase activity. Similarly these agents did not affect cellular replicative capacity during long-term sub-cultivation. The NO synthase (NOS) inhibitor N(G)-monomethyl-L-arginine (1 mM) reduced basal levels of c-GMP by 50% but had no effect on telomerase activity or replicative capacity. Withdrawal of ascorbic acid increased the intracellular pro-oxidant capacity, reduced telomerase activity and increased the accumulation of senescent cells upon serial passage in culture. However, this shift to a more oxidative redox state did not unmask the putative capacity of NO to modulate telomerase or senescence. Infection of cells with a lentiviral vector expressing a small hairpin RNA targeted against endothelial NOS inhibited endogenous NO production completely but failed to affect the decrease of telomerase activity or the accumulation of senescent cells observed with passage in culture. Our findings suggest that physiological concentrations of NO do not modulate telomerase levels or replicative capacity of endothelial cells, regardless of their cellular oxidative status.

Biological fate and clinical implications of arginine metabolism in tissue healing

Since its discovery in 1987, many biological roles (including wound healing) have been identified for nitric oxide (NO). The gas is produced by NO synthase using the dibasic amino acid L-arginine as a substrate. It has been established that a lack of dietary L-arginine delays experimental wound healing. Arginine can also be metabolized to urea and ornithine by arginase-1, a pathway that generates L-proline, a substrate for collagen synthesis, and polyamines, which stimulate cellular proliferation. Herein, we review subjects of interest in arginine metabolism, with emphasis on the biochemistry of wound NO production, relative NO synthase isoform activity in healing wounds, cellular contributions to NO production, and NO effects and mechanisms of action in wound healing.

Combined Treatment With Sustained-Release Basic Fibroblast Growth Factor and Heparin Enhances Neovascularization in Hypercholesterolemic Mouse Hindlimb Ischemia

BACKGROUND

Whether the combined treatment with sustained-release basic fibroblast growth factor (bFGF) and heparin enhances neovascularization in hypercholesterolemic mouse hindlimb ischemia was investigated.

METHODS AND RESULTS

Wild-type C57BL/6 and low density lipoprotein receptor-deficient mice were assigned to 1 of the following 4 experimental groups and treated for 2 weeks after femoral artery extraction: group N, no treatment; group H, daily subcutaneous injection of heparin calcium; group F, single intramuscular injection of the sustained-release bFGF microspheres; and group FH, combined treatment with sustained-release bFGF and heparin. Among the wild-type mice at 4 weeks after femoral artery extraction, the laser Doppler perfusion image index (LDPII) in groups H, F, and FH was significantly higher than that in group N. The vascular density in group FH was the highest among the 4 groups. The maturation index in the 3 treated groups was significantly higher than that in group N. Among the hypercholesterolemic mice, the LDPII in group FH was significantly higher than that in the other 3 groups. The vascular density and maturation index in group FH were the highest among the 4 groups.

CONCLUSIONS

Combined treatment with sustained-release bFGF and heparin enhanced neovascularization in the hypercholesterolemic hindlimb ischemia model.

Caveolin-1 is important for nitric oxide-mediated angiogenesis in fibrin gels with human umbilical vein endothelial cells

AIM

The role of caveolin-1 (Cav-1) in angiogenesis remains poorly understood. The endothelial nitric oxide (NO) synthase (eNOS), a caveolin-interacting protein, was demonstrated to play a predominant role in vascular endothelial growth factor (VEGF) -induced angiogenesis. The purpose of our study was to examine the role of Cav-1 and the eNOS complex in NO-mediated angiogenesis.

METHODS

Human umbilical vein endothelial cells (HUVEC) were isolated and cultured in 3-D fibrin gels to form capillary-like tubules by VEGF stimulation. The expression of Cav-1 and eNOS was detected by semiquantitative RT-PCR. The HUVEC were treated with antisense oligonucleotides to downregulate Cav-1 expression. Both transduced and non-infected HUVEC were cultured in fibrin gels in the presence or absence of VEGF (20 ng/mL) and NG-nitro-L-arginine methyl ester (L-NAME; 5 mmol/L). NO was measured using a NO assay kit and capillary-like tubules were quantified by tubule formation index using the Image J program.

RESULTS

RT-PCR analysis revealed that Cav-1 levels steadily increased in a time-dependent manner and reached their maximum after 5 d of incubation, but there were no obvious changes in eNOS mRNA expression in response to VEGF in the fibrin gel model. VEGF (20 ng/mL) can promote NO production and the formation of capillary-like tubules, and this promoting effect of VEGF was blocked by the addition of L-NAME (5 mmol/L). When transduced HUVEC with the antisense Cav-1 oligonucleotides were plated in the fibrin gels, the capillary-like tubules were significantly fewer than those of the non-infected cells. The capillary-like tubules formation and NO production of transduced HUVEC with the antisense Cav-1 oligonucleotides cultured in fibrin gels showed no responses to the addition of VEGF (20 ng/mL) and L-NAME (5.0 mmol/L).

CONCLUSION

NO was a critical angiogenic mediator in this model. Cav-1 was essential for NO-mediated angiogenesis and may be an important target of anti-angiogenesis therapy.

Secoisolariciresinol diglucoside: relevance to angiogenesis and cardioprotection against ischemia-reperfusion injury

Therapeutic angiogenesis represents a novel approach for the prevention and treatment of ischemic heart disease. This study examined a novel method of stimulating myocardial angiogenesis using secoisolariciresinol diglucoside (SDG), a plant lignan isolated from flaxseed. SDG has been shown to decrease serum cholesterol and reduce the extent of atherosclerosis. In the present study, the angiogenic properties of SDG were investigated in three different models. First, in the in vitro model, human coronary arteriolar endothelial cells (HCAEC) treated with SDG (50 and 100 microM) showed a significant increase in tubular morphogenesis compared with control. Western blot analysis indicated an increased expression of vascular endothelial growth factor (VEGF), kinase insert domain-containing receptor (KDR), Flt-1, angiopoietin-1 (Ang-1), Tie-1, and phosphorylated endothelial nitric oxide synthase (p-eNOS) in the SDG-treated cells. Second, in the ex vivo ischemia/reperfusion model, SDG-treated rats (20 mg/kg b.wt./day for 2 weeks orally) showed an increased level of aortic flow and functional recovery after 2 h of reperfusion following 30 min of ischemia compared with the control group [dP/dt (mm Hg/s) of 2110 +/- 35 versus 1752 +/- 62]. SDG reduced infarct size compared with the control group by 32% (38 versus 26%) and also decreased cardiomyocyte apoptosis. Increased protein expression of VEGF, Ang-1, and p-eNOS was also observed in the SDG-treated group. Third, in the in vivo myocardial infarction model, SDG increased capillary density and myocardial function as evidenced by increased fractional shortening and ejection fraction. In conclusion, these results suggest that SDG has potent angiogenic and antiapoptotic properties that may contribute to its cardioprotective effect in ischemic models.

Hypoxia-targeted bioreductive tyrosine kinase inhibitors with glutathione-depleting function

Tyrosine kinase inhibitors may serve as ligands for kinases that are involved in normal cell differentiation or repair, thereby leading to toxicity. It may be possible to target such inhibitors to tumor cells by coupling them to hypoxia-activated bioreductive molecules. Such coupling can utilize or incorporate bonds that have a propensity to be preferentially oxidized by thiols such as intracellular glutathione (GSH). The resulting depletion of GSH may increase redox-mediated apoptosis. The resultant molecule is hence projected to act via multiple cell killing mechanisms: (i) inhibition of tumor kinases, (ii) tumor DNA disruption and (iii) causing increased redox-mediated apoptosis.

Serum vascular endothelial growth factor as a possible indicator of arterial reactivity in postmenopausal women

OBJECTIVE

To determine whether serum vascular endothelial growth factor (VEGF) concentration is correlated with arterial reactivity in postmenopausal women.

METHODS

An observational study was conducted on 24 postmenopausal women who did not receive any hormone therapy in the 6 months preceding the study and had no pre-existing cardiovascular diseases or cardiovascular risk factors. Serum samples were obtained from all participants and analyzed for VEGF concentrations. Arterial reactivity was assessed by the measurement of endothelium-dependent dilatation and endothelium-independent dilatation of the brachial artery, using color duplex Doppler ultrasound.

RESULTS

The study population was aged 50.8 years on average, with about 2 years of menopause. Serum VEGF concentration in postmenopausal women was significantly correlated with both endothelium-dependent dilatation (r = -0.66, p < 0.01) and endothelium-independent dilatation (r = -0.65, p < 0.01) of the brachial artery.

CONCLUSIONS

Serum VEGF level may be a potential indicator of arterial reactivity in postmenopausal women.

The Basic Science of Wound Healing

Understanding wound healing today involves much more than simply stating that there are three phases: "inflammation, proliferation, and maturation." Wound healing is a complex series of reactions and interactions among cells and "mediators." Each year, new mediators are discovered and our understanding of inflammatory mediators and cellular interactions grows. This article will attempt to provide a concise report of the current literature on wound healing by first reviewing the phases of wound healing followed by "the players" of wound healing: inflammatory mediators (cytokines, growth factors, proteases, eicosanoids, kinins, and more), nitric oxide, and the cellular elements. The discussion will end with a pictorial essay summarizing the wound-healing process.

VEGF-induced relaxation of pulmonary arteries is mediated by endothelial cytochrome P-450 hydroxylase

The cytochrome P-450 metabolite 20-HETE induces calcium-, endothelial-, and nitric oxide (NO)-dependent relaxation of bovine pulmonary arteries (PA). VEGF is an NO-dependent dilator of systemic arteries and plays a key role in maintaining the integrity of the pulmonary vasculature. We tested the effect of VEGF on PA diameter and tone and the contribution of cytochrome P-450 family 4 (CYP4) to vasoactive effects of VEGF. Bovine PA rings (1 mm in diameter) relaxed with VEGF (0.1-10 nM) in an endothelial- and eNOS-dependent manner. This response was blunted by pretreatment with the CYP4 inhibitor dibromododecynyl methyl sulfonamide (DDMS) as well as a mechanistically different CYP4 inhibitor N-hydroxy-N'-(4-butyl-2-methylphenyl)formamidine. PAs also increased in diameter by 6-12% in the presence of VEGF (10 nM), and this increase was attenuated by DDMS. In contrast to that shown in PAs, 20-HETE constricted bovine renal arteries and did not increase intracellular Ca(2+) in renal artery endothelial cells as observed in bovine pulmonary artery endothelial cells (BPAECs). VEGF-evoked increases in intracellular Ca(2+) concentration ([Ca(2+)](i)) in BPAECs were blunted by treatment with DDMS. Both VEGF (10 nM) and 20-HETE (1-5 microM) stimulated NO release from cultured BPAECs, and once again VEGF-induced increases were attenuated by pretreating the cells with DDMS. We conclude that CYP4/20-HETE contributes to VEGF-stimulated NO release and vasodilation in bovine PAs. Given the unique expression of 20-HETE-forming CYP4 in BPAECs vs. systemic arterial endothelial cells, CYP4 may be an important mediator of endothelial-dependent vasoreactivity in PAs.

Endogenous production of nitric oxide contributes to proliferation effect of vascular endothelial growth factor-induced malignant melanoma cell

The objectives of this study were to observe the effect of overexpression of vascular endothelial growth factor (VEGF) on the proliferation of the malignant melanoma (MM) cell line A375, and to study the role of nitric oxide (NO) in this process and the mechanism of VEGF induced-A375 cell proliferation. The VEGF(165) cDNA was transfected into A375 cells by electroporation. VEGF mRNA and protein in A375 cells were detected by RT-PCR and ELISA. The proliferation of A375 cells was assessed by cell counting and MTT assay. Protein expression of iNOS, eNOS and nNOS was detected by Western blotting. NO production in A375 cell supernatant was measured by the nitrate reductase method. VEGF mRNA in A375 cells was significantly increased 72 h and 96 h after transfection of VEGF(165) cDNA, as were VEGF protein, NO and iNOS levels. However, protein expression of eNOS and nNOS was not detected in either transfected or untransfected cells. Proliferation of A375 cells transfected with VEGF(165) cDNA was enhanced. The nitric oxide synthase inhibitor l-NAME could dose-dependently inhibit the proliferation of A375 cells evoked by VEGF. These results indicate that VEGF enhances the expression of iNOS in A375 cells and results in an increase in NO formation, which may be important in the process of VEGF-induced proliferation of A375 cells.

Vascular endothelial growth factor modulates contractile response in microvascular lung pericytes

BACKGROUND

Pericytes are capillary support cells that may play a role in regulating permeability by their contractile responses. Vascular endothelial growth factor (VEGF) may play a role in the increased permeability found in sepsis and other inflammatory conditions. The purpose of this study was to evaluate the role of VEGF in regulating pericyte contraction.

METHODS

Rat microvascular lung pericytes were isolated according to previously described methods and cultured on collagen gel matrices. Cells were exposed to VEGF (10, 100, and 1000 pg/mL) for varying time periods (0, 10, 30, 60, and 120 minutes). The gels were released and their contractile responses digitally quantified.

RESULTS

At all doses, VEGF induced initial pericyte relaxation (contraction 85% to 90% of controls; P < .001). This was followed-up by increased and sustained contraction (107% to 120% of controls; P < .01).

CONCLUSIONS

VEGF modifies the contractile response of microvascular lung pericytes. This mechanism may play a role in the increased permeability demonstrated in inflammatory states.

Vascular endothelial growth factor antagonist modulates leukocyte trafficking and protects mouse livers against ischemia/reperfusion injury

Although hypoxia stimulates the expression of vascular endothelial growth factor (VEGF), little is known of the role or mechanism by which VEGF functions after ischemia and reperfusion (I/R) injury. In this report, we first evaluated the expression of VEGF in a mouse model of liver warm ischemia. We found that the expression of VEGF increased after ischemia but peaked between 2 and 6 hours after reperfusion. Mice were treated with a neutralizing anti-mouse VEGF antiserum (anti-VEGF) or control serum daily from day -1 (1 day before the initiation of ischemia). Treatment with anti-VEGF significantly reduced serum glutaminic pyruvic transaminase levels and reduced histological evidence of hepatocellular damage compared with controls. Anti-VEGF also markedly decreased T-cell, macrophage, and neutrophil accumulation within livers and reduced the frequency of intrahepatic apoptotic terminal deoxynucleotidyl transferase-mediated dUTP nick end-labeling-positive cells. Moreover, there was a reduction in the expression of pro-inflammatory cytokines (tumor necrosis factor-alpha and interferon-gamma), chemokines (interferon-inducible protein-10 and monocyte chemoattractant protein-1) and adhesion molecules (E-selectin) in parallel with enhanced expression of anti-apoptotic genes (Bcl-2/Bcl-xl and heme oxygenase-1) in anti-VEGF-treated animals. In conclusion, hypoxia-inducible VEGF expression by hepatocytes modulates leukocyte trafficking and leukocyte-induced injury in a mouse liver model of warm I/R injury, demonstrating the importance of endogenous VEGF production in the pathophysiology of hepatic I/R injury.

Serum level of lipoprotein (a) is inversely associated with the development of coronary collateral circulation

BACKGROUND

This study sought to determine the relationship between serum lipoprotein (a) levels and angiographically visible coronary collateral circulation and to evaluate whether lipoprotein (a) exerts any effect on vascular endothelial cell growth factor.

METHODS

The study population included 60 patients (39 men, mean age 59+/-13 years) with angiographically documented total occlusion in one of the major coronary arteries. Development of collaterals was classified by Rentrop's method. Patients were defined as having poorly developed collaterals for grades 0 and 1 (group 1), or well-developed collaterals for grades 2 and 3 (group 2). Serum lipoprotein (a) and vascular endothelial cell growth factor levels were determined by enzyme-linked immunosorbent assay.

RESULTS

In group 1, lipoprotein (a) levels were significantly higher and vascular endothelial cell growth factor levels were significantly lower than in group 2 (34+/-19 vs. 20+/-12 mg/dl, P<0.001, and 2.5+/-0.7 vs. 3.4+/-0.8 ng/dl, P<0.001, respectively). Poorly developed collaterals were significantly more frequent in patients with lipoprotein (a) levels >or=30 mg/dl than in patients with levels <30 mg/dl (72 vs. 37%, P=0.008). A strong negative correlation was observed between lipoprotein (a) and vascular endothelial cell growth, factor (r=-0.708, P<0.0001). Multivariate analysis revealed that a high level of lipoprotein (a) negatively affected the development of collaterals, whereas the duration of angina had a positive effect.

CONCLUSION

This study demonstrated for the first time that the high level of lipoprotein (a) negatively affects the formation of coronary collateral vessels in human beings. Reduced production or bioactivity of vascular endothelial cell growth factor caused by high levels of lipoprotein (a) may be the possible responsible mechanisms of hyperlipoprotein (a)-related poor collateral formation.

Anti-angiogenic treatment of gastrointestinal malignancies

The scientific rationale to block angiogenesis as a treatment strategy for human cancer has been developed over the last 30 years, but is only now entering the clinical arena. Preclinical studies have demonstrated the importance of the vascular endothelial growth factor (VEGF) pathways in both physiologic and pathologic angiogenesis, and have led to the development of approaches to block its role in tumor angiogenesis. Bevacizumab is an antibody to VEGF and has been shown to prolong survival when given with chemotherapy in the treatment of metastatic colorectal cancer (CRC). Although this is the first anti-angiogenic treatment to be approved for the treatment of human epithelial malignancy, a number of other approaches currently are in development. Soluble chimeric receptors to sequester serum VEGF and monoclonal antibodies against VEGF receptors have both shown considerable promise in the laboratory and are being brought into clinical investigation. A number of small-molecule tyrosine kinase inhibitors that have activity against VEGF receptors also are in clinical trials. Although these novel treatments are being pioneered in CRC, anti-angiogenic approaches also are being tested in the treatment of other gastrointestinal malignancies. Anti-VEGF therapy has shown promise in such traditionally resistant tumors as pancreatic cancer and hepatocellular carcinoma. This review will examine the preclinical foundation and then focus on the clinical studies of anti-VEGF therapy in gastrointestinal cancers.

Nitric oxide and the vascular endothelium

The vascular endothelium synthesises the vasodilator and anti-aggregatory mediator nitric oxide (NO) from L-arginine. This action is catalysed by the action of NO synthases, of which two forms are present in the endothelium. Endothelial (e)NOS is highly regulated, constitutively active and generates NO in response to shear stress and other physiological stimuli. Inducible (i)NOS is expressed in response to immunological stimuli, is transcriptionally regulated and, once activated, generates large amounts of NO that contribute to pathological conditions. The physiological actions of NO include the regulation of vascular tone and blood pressure, prevention of platelet aggregation and inhibition of vascular smooth muscle proliferation. Many of these actions are a result of the activation by NO of the soluble guanylate cyclase and consequent generation of cyclic guanosine monophosphate (cGMP). An additional target of NO is the cytochrome c oxidase, the terminal enzyme in the electron transport chain, which is inhibited by NO in a manner that is reversible and competitive with oxygen. The consequent reduction of cytochrome c oxidase leads to the release of superoxide anion. This may be an NO-regulated cell signalling system which, under certain circumstances, may lead to the formation of the powerful oxidant species, peroxynitrite, that is associated with a variety of vascular diseases.

Repeated Thermal Therapy Up-Regulates Endothelial Nitric Oxide Synthase and Augments Angiogenesis in a Mouse Model of Hindlimb Ischemia

BACKGROUND

Nitric oxide (NO), constitutively produced by endothelial NO synthase (eNOS), plays roles in angiogenesis. Having reported that thermal therapy up-regulated the expression of arterial eNOS in hamsters, we investigated whether this therapy increased angiogenesis in mice with hindlimb ischemia.

METHODS AND RESULTS

Unilateral hindlimb ischemia was induced in apolipoprotein E-deficient mice, which were divided into control and thermal therapy groups. The latter mice were placed in a far-infrared dry sauna at 41 degrees C for 15 min and then at 34 degrees C for 20 min once daily for 5 weeks. Laser Doppler perfusion imaging demonstrated that the ischemic limb/normal side blood perfusion ratio in the thermal therapy group was significantly increased beyond that in controls (0.79+/-0.04 vs 0.54+/-0.08, p<0.001). Significantly greater capillary density was seen in thermal therapy group (757+/-123 /mm2 vs 416+/-20 /mm2, p<0.01). Western blotting showed thermal therapy markedly increased hindlimb eNOS expression. To study possible involvement of eNOS in thermally induced angiogenesis, thermal therapy was given to mice with hindlimb ischemia with or without N(G)-nitro-L-arginine methyl ester (L-NAME) administration for 5 weeks. L-NAME treatment eliminated angiogenesis induced using thermal therapy. Thermal therapy did not increase angiogenesis in eNOS-deficient mice.

CONCLUSION

Angiogenesis was induced via eNOS using thermal therapy in mice with hindlimb ischemia.

Regulation of noncapacitative calcium entry by arachidonic acid and nitric oxide in endothelial cells

Several peptides, including vascular endothelial growth factor (VEGF) and basic fibroblast growth factor (bFGF), activate the release of arachidonic acid (AA) and nitric oxide (NO) in endothelial cells (ECs). Both messengers are involved in EC proliferation and vascular permeability and control calcium homeostasis in different ways. Interestingly, it has been recently suggested that NO acts as a downstream mediator of AA-induced calcium entry in smooth muscle cells and isolated mouse parotid cells. In this paper, we have investigated the complex relationships that link intracellular calcium, AA, and NO in cultured endothelial cells. Using different experimental approaches, mainly simultaneous Ca2+ and NO fluorimetric confocal imaging, we provide evidence for a complex pathway leading to noncapacitative calcium entry (NCCE) in bovine aortic endothelial cells (BAECs). In particular, AA is able to induce NCCE through two different pathways: one dependent on eNOS recruitment and NO release, the other NO-independent. Finally, we show that NO increase is involved in the control of BAEC proliferation.

Troglitazone reverses the inhibition of nitric oxide production by high glucose in cultured bovine retinal pericytes

In the retinal microcirculation, there is a basal release of nitric oxide (NO) which maintains the retinal blood flow. The proportions of endothelial cells and pericytes in the retinal capillaries are almost equal, so pericytes appear to play a important role in the regulation of microcirculatory hemodynamics in the retina. It has been suggested that the pathogenesis of early diabetic retinopathy may involve a reduced bioavailability or diminished production of NO. In this study, we investigated the role of troglitazone, a potent agonist of peroxisome proliferator activated receptor-gamma (PPARgamma) used for the treatment of diabetes, on the NO release and the effect of exposure to high glucose on the production of NO in cultured bovine retinal pericytes. Troglitazone significantly increased NO production and iNOS expression after 24hr in a dose-and PPARgamma-dependent manner. Elevation of D-glucose, but not L-glucose, from 5.5 to 30 mm for 24 hr decreased NO production, but co-treatment with troglitazone reversed high glucose-induced inhibition of NO production as well as iNOS expression. In conclusion, high glucose inhibits iNOS expression and subsequently NO synthesis in cultured bovine retinal pericytes, and troglitazone restores the NO production.

Quantitative multi-gene transcriptional profiling using real-time PCR with a master template

We previously reported a method for quantitative multi-gene transcriptional profiling with gene-specific standard curves using real-time PCR. Here, we report an approach that increases experimental throughput by using a master template to generate a single standard curve for the estimation of mRNA copy numbers from all genes. We prepared fifty-nine different templates and measured eNOS mRNA copy numbers in Matrigel VEGF-transfectant samples. The copy numbers obtained using each of the fifty-nine templates were within 50% of the copy number obtained using the previously reported method. Analysis of primer design parameters, and subsequent tests, showed that eliminating complementarities between the first nucleotides at the 5'-ends of the forward and reverse primers reduces the influence of saturation effects and produces copy numbers similar to those generated with gene-specific templates-generally, within 20%. Measurements on a panel consisting of eNOS, iNOS, and nNOS further validated the master-template approach. The master-template approach enables rapid quantification of mRNA abundances from panels of hundreds of genes, and will be a valuable tool for screening large numbers of genes as part of a search for biomarkers, the validation of DNA-microarray data, or research into the dynamics of the gene-protein network.

Application of angiogenic factors for therapy of erectile dysfunction: Protein and DNA transfer of VEGF 165 into the rat penis

OBJECTIVES

To establish a laboratory animal model for vascular endothelial growth factor (VEGF) transfer in the rat penis to invent a curative therapy for erectile dysfunction (ED). Vascular insufficiency is a common pathomechanism of ED. Previous investigations have shown neovascularization of ischemic organs after gene transfer of VEGF.

METHODS

For VEGF-protein transfer, osmotic pumps were connected to the renal arteries of rats. The pumps were filled with human VEGF 165 protein (n = 20) or sterile saline (n = 20). After 28 days, a VEGF serum immunoassay was performed to document successful delivery. For VEGF-DNA transfer, liposome complexes containing VEGF 165 expression vectors were injected into rat corpora cavernosa. After immunostaining, computerized image analysis was performed to quantify the percentage of area (within the corpora cavernosa) covered by smooth muscle or endothelial cells.

RESULTS

The immunoassay of the VEGF-protein transfer showed a 10-fold greater VEGF concentration in the serum of rats carrying VEGF pumps than in the control group. In the VEGF-DNA transfer, the penes transfected with VEGF 165 vectors showed a 283-bp polymerase chain reaction product according to specific primers for human VEGF. Although statistical trends were measured in the VEGF protein-treated group, no statistically significant difference in smooth muscle or endothelial cell content was found between the control and VEGF-treated rats.

CONCLUSIONS

Our findings have established proof of principle for successful delivery of VEGF protein and VEGF-DNA transfer in the rat penis. This study was a prelude to attempt to manipulate genetically expression of angiogenic factors in insufficient erectile tissue as a curative therapy for ED.

Margatoxin inhibits VEGF-induced hyperpolarization, proliferation and nitric oxide production of human endothelial cells

BACKGROUND

Vascular endothelial growth factor (VEGF) induces proliferation of endothelial cells (EC) in vitro and angiogenesis in vivo. Furthermore, a role of VEGF in K(+) channel, nitric oxide (NO) and Ca(2+) signaling was reported. We examined whether the K(+) channel blocker margatoxin (MTX) influences VEGF-induced signaling in human EC.

METHODS

Fluorescence imaging was used to analyze changes in the membrane potential (DiBAC), intracellular Ca(2+) (FURA-2) and NO (DAF) levels in cultured human EC derived from human umbilical vein EC (HUVEC). Proliferation of HUVEC was examined by cell counts (CC) and [(3)H]-thymidine incorporation (TI).

RESULTS

VEGF (5--50 ng/ml) caused a dose-dependent hyperpolarization of EC, with a maximum at 30 ng/ml (n=30, p<0.05). This effect was completely blocked by MTX (5 micromol/l). VEGF caused an increase in transmembrane Ca(2+) influx (n=30, p<0.05) that was sensitive to MTX and the blocker of transmembrane Ca(2+) entry 2-aminoethoxydiphenyl borate (APB, 100 micromol/l). VEGF-induced NO production was significantly reduced by MTX, APB and a reduction in extracellular Ca(2+) (n=30, p<0.05). HUVEC proliferation, examined by CC and TI, was significantly increased by VEGF and inhibited by MTX (CC: -58%, TI --121%); APB (CC --99%, TI--187%); N-monomethyl-L-arginine (300 micromol/l: CC: -86%, TI --164%).

CONCLUSIONS

VEGF caused an MTX-sensitive hyperpolarization which results in an increased transmembrane Ca(2+) entry that is responsible for the effects on endothelial proliferation and NO production.

Dual role of vascular endothelial growth factor in hepatic ischemia-reperfusion injury

BACKGROUND

Vascular endothelial growth factor (VEGF), a major angiogenic factor, mediates a variety of disease conditions through promotion of angiogenesis. It also plays a critical role as a potent proinflammatory cytokine in a variety of physiologic and pathologic immune responses. In the present study, we evaluated the expression of VEGF in hepatic warm ischemia-reperfusion (I/R) injury and examined the effect of recombinant human (rh)VEGF administration in an established murine model.

METHOD

The expression of VEGF in the liver was assessed by quantitative real-time polymerase chain reaction and immunohistochemistry during I/R injury using 70% partial hepatic ischemia model. The effect of rhVEGF administration on I/R injury was evaluated by measuring liver function and histology. In addition, local inducible nitric oxide synthase (iNOS) and endothelial NO synthase expressions were examined to address the underlying mechanisms.

RESULTS

The local expression of VEGF was significantly up-regulated at 2 hours after reperfusion after 60 minutes of ischemia compared with that in the naive liver. VEGF was expressed predominantly in CD11b+ cells infiltrating into the ischemic liver. The administration of rhVEGF had a significant protective effect on ischemic injury in the liver. This effect was associated with the up-regulation of iNOS expression in the rhVEGF-treated liver.

CONCLUSION

We demonstrate a dual role of VEGF in hepatic warm I/R injury. Although endogenous VEGF is expressed and functional to initiate hepatic I/R injury, exogenous rhVEGF has a beneficial effect on the ischemic liver. These data may provide new insights into the role of VEGF as well as pathophysiology of hepatic I/R injury.

Dual Role of Vascular Endothelial Growth Factor in Experimental Obliterative Bronchiolitis

Obliterative bronchiolitis (OB) is the major limitation for long-term survival of lung allograft recipients. We investigated the role of vascular endothelial growth factor (VEGF) in the development of OB in rat tracheal allografts. In nonimmunosuppressed allografts, VEGF mRNA and protein expression vanished in the epithelium and increased in smooth muscle cells and mononuclear inflammatory cells with progressive loss of epithelium and airway occlusion compared with syngeneic grafts. Intragraft VEGF overexpression by adenoviral transfer of a mouse VEGF(164) gene increased early epithelial cell proliferation and regeneration but increased microvascular remodeling and lymphangiogenesis and luminal occlusion by more than 50% compared with AdlacZ-treated allografts. Although VEGF receptor inhibition decreased early epithelial regeneration in noninfected allografts, it reduced microvascular remodeling, lymphangiogenesis, intragraft traffic of CD4(+) and CD8(+) T cells, and the degree of luminal occlusion. Simultaneous VEGF gene transfer and platelet-derived growth factor receptor inhibition with imatinib preserved respiratory epithelium and totally prevented luminal occlusion. In conclusion, our findings indicate that VEGF has a dual role in transplant OB. Our results suggest that VEGF may protect epithelial integrity. On the other hand, VEGF may enhance luminal occlusion by increasing the recruitment of mononuclear inflammatory cells with platelet-derived growth factor acting as a final effector molecule in this process.

NO mediates mural cell recruitment and vessel morphogenesis in murine melanomas and tissue-engineered blood vessels

NO has been shown to mediate angiogenesis; however, its role in vessel morphogenesis and maturation is not known. Using intravital microscopy, histological analysis, alpha-smooth muscle actin and chondroitin sulfate proteoglycan 4 staining, microsensor NO measurements, and an NO synthase (NOS) inhibitor, we found that NO mediates mural cell coverage as well as vessel branching and longitudinal extension but not the circumferential growth of blood vessels in B16 murine melanomas. NO-sensitive fluorescent probe 4,5-diaminofluorescein imaging, NOS immunostaining, and the use of NOS-deficient mice revealed that eNOS in vascular endothelial cells is the predominant source of NO and induces these effects. To further dissect the role of NO in mural cell recruitment and vascular morphogenesis, we performed a series of independent analyses. Transwell and under-agarose migration assays demonstrated that endothelial cell-derived NO induces directional migration of mural cell precursors toward endothelial cells. An in vivo tissue-engineered blood vessel model revealed that NO mediates endothelial-mural cell interaction prior to vessel perfusion and also induces recruitment of mural cells to angiogenic vessels, vessel branching, and longitudinal extension and subsequent stabilization of the vessels. These data indicate that endothelial cell-derived NO induces mural cell recruitment as well as subsequent morphogenesis and stabilization of angiogenic vessels.

Endostatin induces acute endothelial nitric oxide and prostacyclin release

Chronic exposure to endostatin (ES) blocks endothelial cell (EC) proliferation, and migration and induces EC apoptosis thereby inhibiting angiogenesis. Nitric oxide (NO) and prostacyclin (PGI(2)), in contrast, play important roles in promoting angiogenesis. In this study, we examined the acute effects of ES on endothelial NO and PGI(2) production. Unexpectedly, a cGMP reporter cell assay showed that ES-induced acute endothelial NO release in cultured bovine aortic endothelial cells (BAECs). Enzyme immunoassay showed that ES also induced an acute increase in PGI(2) production in BAECs. These results were confirmed by ex vivo vascular ring studies that showed vascular relaxation in response to ES. Immunoblot analysis showed that ES stimulated acute phosphorylation of endothelial nitric oxide synthase (eNOS) at Ser116, Ser617, Ser635, and Ser1179, and dephosphorylation at Thr497 in BAECs, events associated with eNOS activation. Short-term exposure of EC to ES, therefore, unlike long-term exposure which is anti-angiogenic, may be pro-angiogenic.

Circulating levels of nitric oxide and vascular endothelial growth factor throughout ovine pregnancy

Nitric oxide (NO) production has been shown to increase uterine blood flow and be elevated in ewes carrying multiple fetuses during late gestation. Vascular endothelial growth factor (VEGF) has been reported to increase eNOS expression and NO production in endothelial cell cultures. As angiogenesis and vasodilatation of the uterine and placental vascular beds are important at all stages of pregnancy, it is important to understand how VEGF and NO change throughout gestation in circulation. Therefore the objectives of the current study were to evaluate the systemic levels of VEGF and NO metabolite (NOx) throughout ovine gestation and to determine if there was an effect of sheep carrying singletons versus multiple fetuses. NOx and VEGF concentrations were analysed in systemic blood from pregnant ewes starting on day 27 of pregnancy and at multiple intermittent intervals throughout pregnancy until term. Blood samples from non-pregnant and postpartum ewes were also analysed. NOx concentrations in maternal blood expressed a biphasic pattern with NOx concentrations increasing (P < 0.05) over non-pregnant values on days 40-69 of gestation, returning to non-pregnant concentrations from days 70-100, and again increasing (P < 0.05) until term. Postpartum NOx concentrations were similar to non-pregnant values. While ewes carrying multiple fetuses had increased (P < 0.05) concentrations of NOx on days 60-69, there were no differences in NOx concentrations in ewes carrying singletons or multiples from day 70-99 of gestation. Starting on day 100 and continuing throughout the duration of pregnancy, ewes carrying multiple fetuses had increased (P < 0.05) concentrations of NOx compared to ewes carrying singletons. Concentrations of VEGF showed a different pattern from NOx with VEGF decreasing (P < 0.05) from day 20-69 of pregnancy compared to non-pregnant ewes. Concentrations of VEGF returned to non-pregnant levels by day 70 and remained constant throughout the duration of pregnancy. On days 20-39, ewes carrying singleton fetuses had an increased VEGF concentration (P < 0.05), whereas ewes carrying multiple fetuses demonstrated elevated VEGF concentrations from day 90-109 of gestation. Concentrations from non-pregnant and postpartum ewes did not differ (P > 0.1). While there was no effect of fetal number on circulating VEGF concentrations, circulating levels of NOx were substantially increased (P < 0.05) in ewes carrying multiple fetuses, compared to ewes carrying singletons. The pattern of the rise in NOx in circulating plasma was not directly associated with changes in VEGF regardless of the number of fetuses present. However, circulating concentrations of NOx and VEGF appear to, respectively, follow patterns of uterine blood flow and angiogenesis of the uterus. An understanding of these circulatory patterns may have important implications for fetal size, birth weight and fetal/developmental origins of adult disease.

Angiogenic signal during cardiac repair

Despite significant advances in myocardial revascularization and reperfusion, coronary artery disease and subsequently myocardial infarction, are the leading causes of morbidity and mortality in the United States. Strategies which improve the myocardial substrate during and following a myocardial infarction-such as the regrowth of functional blood vessels to the ischemic myocardium would be of great clinical importance. This review article attempts to address this important clinical issue through identifying potential signalling mechanisms by various mode of preconditioning that cause angiogenesis.

Activation and translocation of PKCdelta is necessary for VEGF-induced ERK activation through KDR in HEK293T cells

VEGF-KDR/Flk-1 signal utilizes the phospholipase C-gamma-protein kinase C (PKC)-Raf-MEK-ERK pathway as the major signaling pathway to induce gene expression and cPLA2 phosphorylation. However, the spatio-temporal activation of a specific PKC isoform induced by VEGF-KDR signal has not been clarified. We used HEK293T (human embryonic kidney) cells expressing transiently KDR to examine the activation mechanism of PKC. PKC specific inhibitors and human PKCdelta knock-down using siRNA method showed that PKCdelta played an important role in VEGF-KDR-induced ERK activation. Myristoylated alanine-rich C-kinase substrate (MARCKS) translocates from the plasma membrane to the cytoplasm depending upon phosphorylation by PKC. Translocation of MARCKS-GFP induced by VEGF-KDR stimulus was blocked by rottlerin, a PKCdelta specific inhibitor, or human PKCdelta siRNA. VEGF-KDR stimulation did not induce ERK phosphorylation in human PKCdelta-knockdown HEK293T cells, but co-expression of rat PKCdelta-GFP recovered the ERK phosphorylation. Y311/332F mutant of rat PKCdelta-GFP which cannot be activated by tyrosine-phosphorylation but activated by DAG recovered the ERK phosphorylation, while C1B-deletion mutant of rat PKCdelta-GFP, which can be activated by tyrosine-phosphorylation but not by DAG, failed to recover the ERK phosphorylation in human PKCdelta-knockdown HEK293T cell. These results indicate that PKCdelta is involved in VEGF-KDR-induced ERK activation via C1B domain.

Non‐Viral Vectors for Gene Therapy: Clinical Trials in Cardiovascular Disease

The population of patients with end-stage symptomatic coronary and peripheral vascular disease is ever-expanding. Many of these patients no longer have options for mechanical revascularization, and despite maximal medical therapy, they remain physically limited due to angina or critical limb ischemia. The fundamental problem in these patients is insufficient blood supply to muscle due to severely diseased conduit vessels to the target tissue. Therefore, it seems logical that increasing the blood supply to ischemic tissue will relieve symptoms. One potential means to achieving this goal is via therapeutic angiogenesis. The molecular mechanisms behind vascular development are being elucidated, and animal models have shown that mediators of vascular development can be harnessed to produce new capillaries in ischemic tissue. These mediators include cytokines such as vascular endothelial growth factor (VEGF) and fibroblast growth factor (FGF). Angiogenic cytokines can be delivered in several forms including recombinant protein or via gene delivery as a naked plasmid or via viral vector. This chapter will describe the clinical trial experience to date with delivery of non-viral gene therapy for therapeutic angiogenesis in humans with disabling myocardial ischemia and peripheral vascular disease.

Follicular blood flow is a better predictor of the outcome of in vitro fertilization-embryo transfer than follicular fluid vascular endothelial growth factor and nitric oxide concentrations

OBJECTIVE

To investigate the relationship between follicular blood flow and the follicular fluid vascular endothelial growth factor (VEGF) and nitric oxide (NO) concentrations and to determine which factor might be a better predictor of the outcome of IVF-ET.

DESIGN

Prospective study.

SETTING

Academic research laboratory.

PATIENT(S)

Forty-seven cycles of IVF (tubal factor, 25 cycles; male factor, 22 cycles) at the infertility clinic of Pusan National University Hospital from February 2002 to June 2002.

INTERVENTION(S)

Follicular blood flow was estimated on the day of hCG administration. Each follicular fluid sample was collected at oocyte retrieval, and follicular fluid VEGF and NO concentrations were assessed.

MAIN OUTCOME MEASURE(S)

Follicular blood flow and follicular fluid VEGF and NO concentrations according to the age of patients, the cause of infertility, and pregnancy rate.

RESULT(S)

Of 47 cycles, 18 (38.3%) cycles resulted in a pregnancy. Follicular blood flow was significantly higher in the pregnant group compared with the nonpregnant group, but there was no statistically significant difference in age and infertility cause. Follicular fluid concentrations of VEGF and NO did not show statistically significant differences in age, infertility cause, or pregnancy outcome. As the follicle size increases, the follicular blood flow and follicular fluid VEGF concentrations increased significantly but the follicular fluid NO concentrations decreased. There was no correlation between VEGF and NO concentrations in the follicular fluid by linear regression analysis.

CONCLUSION(S)

Our study showed that follicular blood flow was positively associated with the outcome of pregnancy. This is the first study to investigate the direct association of the follicular blood flow with pregnancy outcome after IVF-ET. These results suggest that follicular blood flow might be a more effective prognostic marker of the pregnancy outcome of IVF than follicular fluid VEGF or NO concentrations.