Induction of in vitro angiogenesis in the endothelial-derived cell line, EA hy926, by ethanol is mediated through PKC and MAPK

Histamine promotes angiogenesis through a histamine H1 receptor-PKC-VEGF-mediated pathway in human endothelial cells

Histamine is a well-known inflammatory mediator, but how histamine induces angiogenesis remains poorly understood. In the present study, we demonstrated a dose-dependent dynamic tube formation in the human endothelial cell line EA.hy926 in the presence of histamine that was completely blocked by histamine H1 receptor (H1R) and protein kinase C (PKC) inhibitors. However, histamine H2, H3, and H4 receptor inhibitors did not inhibit tube formation, suggesting that H1R-PKC signaling is involved in histamine-induced tube formation. Moreover, we found an H1-specific induction of vascular endothelial growth factor (VEGF) expression. Inhibition of VEGF receptor 2 (VEGFR2) suppressed the histamine-induced tube formation, indicating that VEGF is downstream of histamine signaling. Additionally, we demonstrated that histamine stimulation induces the expression of critical regulators of angiogenesis such as matrix metalloproteinase (MMP)-9 and MMP-14 metalloproteases, as histamine-induced tube formation is blocked by MMP inhibitors. In summary, our study indicates that histamine can activate the H1R in human endothelial cells and thereby promote tube formation through the PKC, MMP, and VEGF signaling pathways.

Chronic Low-Dose Alcohol Consumption Promotes Cerebral Angiogenesis in Mice

Chronic alcohol consumption dose-dependently affects the incidence and prognosis of ischemic stroke. We determined the influence of chronic alcohol consumption on cerebral angiogenesis under physiological conditions and following ischemic stroke. In in vitro studies, acute exposure to low-concentration ethanol significantly increased angiogenic capability and upregulated vascular endothelial growth factor A (VEGF-A) and vascular endothelial growth factor receptor 2 (VEGFR2) in C57BL/6J mouse brain microvascular endothelial cells (MBMVECs). The increased angiogenic capability was abolished in the presence of a VEGFR2 inhibitor. In addition, the increased angiogenic capability and upregulated VEGF-A and VEGFR2 remained in chronically low-concentration ethanol-exposed MBMVECs. In in vivo studies, 8-week gavage feeding with low-dose ethanol significantly increased vessel density and vessel branches and upregulated VEGF-A and VEGFR2 in the cerebral cortex under physiological conditions. Furthermore, vessel density, vessel branches, and expression of VEGF-A and VEGFR2 in the peri-infarct cortex were significantly greater in low-dose ethanol-fed mice at 72 h of reperfusion. Although low-dose ethanol did not alter cerebral vasoreactivity and regional cerebral blood flow (rCBF) either before or during ischemia, it significantly augmented post-ischemic hyperemia during reperfusion. In contrast, exposure to high-concentration ethanol and 8-week gavage feeding with high-dose ethanol only had a mild inhibitory effect on angiogenic capability and cerebral angiogenesis, respectively. We conclude that heavy alcohol consumption may not dramatically alter cerebral angiogenesis, whereas light alcohol consumption significantly promotes cerebral angiogenesis.

Therapeutic approach of adipose-derived mesenchymal stem cells in refractory peptic ulcer

Peptic ulcer is one of the most common gastrointestinal tract disorders worldwide, associated with challenges such as refractory morbidity, bleeding, interference with use of anticoagulants, and potential side effects associated with long-term use of proton pump inhibitors. A peptic ulcer is a defect in gastric or duodenal mucosa extending from muscularis mucosa to deeper layers of the stomach wall. In most cases, ulcers respond to standard treatments. However, in some people, peptic ulcer becomes resistant to conventional treatment or recurs after initially successful therapy. Therefore, new and safe treatments, including the use of stem cells, are highly favored for these patients. Adipose-derived mesenchymal stem cells are readily available in large quantities with minimal invasive intervention, and isolation of adipose-derived mesenchymal stromal stem cells (ASC) produces large amounts of stem cells, which are essential for cell-based and restorative therapies. These cells have high flexibility and can differentiate into several types of cells in vitro. This article will investigate the effects and possible mechanisms and signaling pathways of adipose tissue-derived mesenchymal stem cells in patients with refractory peptic ulcers.

Mesenchymal stem cells promote healing of nonsteroidal anti-inflammatory drug-related peptic ulcer through paracrine actions in pigs

Nonsteroidal anti-inflammatory drugs (NSAIDs) are among the most important causes of peptic ulcer disease in high-income countries. Proton pump inhibitors are the current standard treatment; however, safety and long-term adverse effects of using these drugs are attracting more and more concerns in recent years. Using a porcine model of NSAID-related gastric ulcer, we herein show that adipose-derived mesenchymal stem cells (ADMSCs) delivered by endoscopic submucosal injection promoted ulcer healing with less inflammatory infiltration and enhanced reepithelization and neovascularization at day 7 and day 21 when compared with the controls (saline injection). However, only few engrafted ADMSCs showed myofibroblast and epithelial cell phenotype in vivo, suggesting the ulcer healing process might be much less dependent on the stem cell transdifferentiation. Further experiment with submucosal injection of MSC-derived secretome revealed a therapeutic efficacy comparable to that of stem cell transplantation. Profiling analysis showed up-regulation of genes associated with inflammation, granulation formation, and extracellular matrix remodeling at day 7 after injection of MSC-derived secretome. In addition, the extracellular signal-regulated kinase/mitogen-activated protein kinase and the phosphoinositide-3-kinase/protein kinase B pathways were activated after injection of ADMSCs or MSC-derived secretome. Both signaling pathways were involved in mediating the major events critical to gastric ulcer healing, including cell survival, migration, and angiogenesis. Our data suggest that endoscopic submucosal injection of ADMSCs serves as a promising approach to promote healing of NSAID-related peptic ulcer, and the paracrine effectors released from stem cells play a crucial role in this process.

Ethanol Induces Enhanced Vascularization Bioactivity of Endothelial Cell-Derived Extracellular Vesicles via Regulation of MicroRNAs and Long Non-Coding RNAs

Extracellular vesicles (EVs), such as exosomes, have been identified as regulators of vascular remodeling and have promise as therapeutics for vascularization applications. Towards development of EVs as therapeutics, it has been demonstrated that physiological stimuli of angiogenic phenotypes in EV-producing cells can enhance the potency of EVs for vascularization. The goal of this study was to assess whether ethanol, which induces angiogenic phenotypes in endothelial cells, could be employed to enhance endothelial-derived EV vascularization bioactivity. The results indicate that ethanol conditioning of endothelial cells increases the ability of endothelial EVs to induce a pro-vascularization response. This response is due in part to increased CD34 expression in recipient endothelial cells that may result from downregulation of microRNA-106b in EVs isolated from ethanol-conditioned producer endothelial cells. Further, ethanol-induced upregulation of long non-coding RNAs (lncRNAs) HOTAIR and MALAT1 in endothelial EVs was observed to play a significant role in mediating pro-angiogenic effects of these vesicles. Overall, these studies validate ethanol conditioning as a method to enhance the bioactivity of endothelial EVs via regulation of EV-associated microRNAs (miRNAs) and, especially, lncRNAs. Further, the results suggest that alcohol consumption may activate endothelial EVs towards a pro-vascularization phenotype, which could have implications for alcohol-induced tumor angiogenesis.

CCM2-CCM3 interaction stabilizes their protein expression and permits endothelial network formation

CCM2–CCM3 interactions protect CCM2 and CCM3 from proteasomal degradation, and both CCM2 and CCM3 are required for normal endothelial cell network formation.

Mutations in the essential adaptor proteins CCM2 or CCM3 lead to cerebral cavernous malformations (CCM), vascular lesions that most frequently occur in the brain and are strongly associated with hemorrhagic stroke, seizures, and other neurological disorders. CCM2 binds CCM3, but the molecular basis of this interaction, and its functional significance, have not been elucidated. Here, we used x-ray crystallography and structure-guided mutagenesis to show that an α-helical LD-like motif within CCM2 binds the highly conserved “HP1” pocket of the CCM3 focal adhesion targeting (FAT) homology domain. By knocking down CCM2 or CCM3 and rescuing with binding-deficient mutants, we establish that CCM2–CCM3 interactions protect CCM2 and CCM3 proteins from proteasomal degradation and show that both CCM2 and CCM3 are required for normal endothelial cell network formation. However, CCM3 expression in the absence of CCM2 is sufficient to support normal cell growth, revealing complex-independent roles for CCM3.

Impaired fetoplacental angiogenesis in growth-restricted fetuses with abnormal umbilical artery doppler velocimetry is mediated by aryl hydrocarbon receptor nuclear translocator (ARNT)

CONTEXT

Fetal growth restriction with abnormal umbilical artery Doppler velocimetry (FGRadv), reflective of elevated fetoplacental vascular resistance, is associated with increased risks of fetal morbidity and mortality even in comparison to those of growth-restricted fetuses with normal placental blood flow. One major cause of this abnormally elevated fetoplacental vascular resistance is the aberrantly formed, thin, elongated villous vessels that are seen in FGRadv placentas.

OBJECTIVE

The purpose of this study was to determine the role of fetoplacental endothelial cells (ECs) in angiogenesis in normal pregnancies and in those complicated by FGRadv.

DESIGN AND PARTICIPANTS

Human placental specimens were obtained from FGRadv and gestational age-matched, appropriately grown control pregnancies for EC isolation/culture and for immunohistochemical studies. Additional mechanistic studies were performed on ECs isolated from subjects with term, uncomplicated pregnancies.

MAIN OUTCOME MEASURES

We evaluated tube formation and differential angiogenic gene expression in FGRadv and control ECs, and we used ECs from uncomplicated pregnancies to further elucidate the molecular mechanisms by which angiogenesis is impaired in FGRadv pregnancies.

RESULTS

Tube formation assays showed that FGRadv ECs demonstrate fewer branch points and total length compared with those from gestational age-matched controls, and this defect was not rescued by exposure to hypoxia. FGRadv ECs also demonstrated lower aryl hydrocarbon receptor nuclear translocator (ARNT) expression. ARNT knockdown resulted in suppression of key angiogenic genes including vascular endothelial growth factor A expression and led to deficient tube formation.

CONCLUSIONS

ARNT expression in the placental vasculature mediates key angiogenic expression and fetoplacental EC angiogenesis, and low ARNT expression in FGRadv ECs appears to be a key factor in deficient angiogenesis. This, in turn, results in malformed thin villous vessels that structurally contribute to the abnormally elevated fetoplacental vascular resistance that is associated with high morbidity and mortality in fetal growth restriction.

Flk-1/KDR mediates ethanol-stimulated endothelial cell Notch signaling and angiogenic activity

We previously reported that ethanol (EtOH) stimulates endothelial angiogenic activity mediated via a notch- and angiopoietin-1 (Ang-1) pathway. As crosstalk exists between notch and vascular endothelial growth factor (VEGF) signaling, we examined whether the VEGF receptor (VEGFR) Flk-1 (fetal liver kinase 1) mediates EtOH-stimulated notch signaling and angiogenic activity.

METHODS AND RESULTS

Treatment of human coronary artery endothelial cells (HCAECs) with EtOH (1-50 mM, 24 h) dose-dependently increased Flk-1 expression with a maximum increase observed at 25 mM EtOH. Ethanol treatment activated both Flk-1 and Flt-1 (FMS-like tyrosine kinase 1) as indicated by their phosphorylation, and subsequent stimulation of Akt. EtOH activation of Flk-1 was inhibited by the VEGFR inhibitor SU5416. Gene silencing of Flk-1 using small interfering RNA inhibited the EtOH-induced increase in notch receptors 1 and 4 and notch target gene (hairy enhancer of split-related transcription factor 1) mRNA. Knockdown of Flk-1 inhibited EtOH-induced Ang-1/Tie-2 mRNA expression and blocked EtOH-induced HCAEC network formation on Matrigel, a response that was restored by notch ligand, notch ligand delta-like ligand 4, treatment. In vivo, moderate alcohol feeding increased vascular remodeling in mouse ischemic hindlimbs.

CONCLUSIONS

These data demonstrate that EtOH activates Flk-1 and Flt-1 receptors in HCAECs and promotes angiogenic activity via an Flk-1/notch pathway. These effects of EtOH may be relevant to the influence of moderate alcohol consumption on cardiovascular health.

Novel VEGFR-2 kinase inhibitors identified by the back-to-front approach

We report a novel VEGFR-2 inhibitor, developed by the back-to-front approach. Docking experiments indicated that the 3-chloromethylphenylurea motif of the lead compound occupied the back pocket of VEGFR-2 kinase. An attempt was made to enhance the binding affinity of 1 by expanding the structure to access the front pocket using a triazole linker. A library of 1,4-(disubstituted)-1H-1,2,3-triazoles were screened in silico, and one compound (VH02) was identified with an IC50 against VEGFR-2 of 0.56μM. VH02 showed antiangiogenic effects, inhibiting tube formation in HUVEC cells (EA.hy926) at 0.3μM, 13 times lower than its cytotoxic dose. These enzymatic and cellular activities suggest that VH02 has potential as a lead for further optimization.

Antioxidant and anti-inflammatory effects of Astragalus polysaccharide on EA.hy926 cells

The aim of this study was to explore the role of astragalus polysaccharide (APS) in the pathogenesis of bronchopulmonary dysplasia (BPD) in preterm children using an established BPD cell model. EA.hy926 cell cultures were divided into three groups: the air group as the blank control, the hyperoxia group as the experimental control and the APS group (2.5 mg/ml). The production of superoxide dismutase (SOD), malondialdehyde (MDA) and reactive oxygen species (ROS) were analyzed by biochemical assays. Real-time reverse transcription-polymerase chain reaction (RT-PCR) and western blotting were used to detect the RNA and protein expression levels of inflammatory cytokines, including interleukin (IL)-8, intercellular adhesion molecule 1 (ICAM-1) and nuclear factor (NF)-κB p65. Compared with the hyperoxia group, the ROS and MDA levels of the APS group were significantly reduced. By contrast, SOD production was significantly increased. The expression of IL-8, ICAM-1 and NF-κB p65 in the APS group was downregulated. APS acts as an antioxidant by stimulating SOD production while inhibiting lipid peroxidation in the EA.hy926 cells. Furthermore, this study demonstrated that APS retards the inflammatory response, as shown by the reduced expression of NF-κB p65, IL-8 and ICAM-1 when APS was added.

Ethanol protects from injury due to ischemia and reperfusion by increasing vascularity via vascular endothelial growth factor

The cardioprotective effects of moderate ethanol consumption have been known for years and have generally been ascribed to long-term effects of alcohol on blood lipids. However, other mechanisms, particularly ethanol-induced increase in blood vessel density, may also be involved. Our goal was to understand the relationship between ethanol consumption, new blood vessel formation in vivo and protection from injury due to ischemia and ischemia/reperfusion. Using paired ethanol fed and control rats, we assessed capillary density in the heart, brain and skeletal muscle by immunostaining and quantified expression of vascular endothelial growth factor (VEGF) by Western blot analysis and immunocytochemistry. Numbers of vessels were significantly increased in the brain, heart and skeletal muscle of animals fed ethanol-rich diets. VEGF (and its receptors) were upregulated in these organs. These effects were very rapid: highly significantly increased vascularization was seen within 2 weeks of commencing alcohol feeding. A neutralizing VEGF antibody, bevacizumab, inhibited new blood vessel formation induced by moderate doses of ethanol. Ethanol consumption increased vascularization and promoted skeletal muscle regeneration following hindlimb ischemia; these effects were prevented by bevacizumab. Finally, ethanol consumption protected myocardium following experimental ischemia/reperfusion.

CONCLUSION

Experimental ethanol ingestion rapidly increases VEGF production, significantly increasing the capillary bed in the heart, brain, and skeletal muscle. Moreover, the ethanol-induced increase of blood vessel density is protective against ischemic events (i.e., hindlimb ischemia and myocardium ischemia/reperfusion) and promotes skeletal muscle regeneration.

Alcohol and cardiovascular disease--modulation of vascular cell function

Alcohol is a commonly used drug worldwide. Epidemiological studies have identified alcohol consumption as a factor that may either positively or negatively influence many diseases including cardiovascular disease, certain cancers and dementia. Often there seems to be a differential effect of various drinking patterns, with frequent moderate consumption of alcohol being salutary and binge drinking or chronic abuse being deleterious to one’s health. A better understanding of the cellular and molecular mechanisms mediating the many effects of alcohol consumption is beginning to emerge, as well as a clearer picture as to whether these effects are due to the direct actions of alcohol itself, or caused in part by its metabolites, e.g., acetaldehyde, or by incidental components present in the alcoholic beverage (e.g., polyphenols in red wine). This review will discuss evidence to date as to how alcohol (ethanol) might affect atherosclerosis that underlies cardiovascular and cerebrovascular disease, and the putative mechanisms involved, focusing on vascular endothelial and smooth muscle cell effects.

Brewing complications: the effect of acute ethanol exposure on wound healing

Ethanol consumption is linked to a higher incidence of traumatic wounds and increases the risk for morbidity and mortality following surgical or traumatic injury. One of the most profound effects of acute ethanol exposure on wound healing occurs during the inflammatory response, and altered cytokine production is a primary component. Acute ethanol exposure also impairs the proliferative response during healing, causing delays in epithelial coverage, collagen synthesis, and blood vessel regrowth. The accumulated data support the paradigm that acute ethanol intoxication prior to injury significantly diminishes a patient's ability to heal efficiently.

Phosphatidylethanol mediates its effects on the vascular endothelial growth factor via HDL receptor in endothelial cells

BACKGROUND

Previous epidemiological studies have shown that light to moderate alcohol consumption has protective effects against coronary heart disease but the mechanisms of the beneficial effect of alcohol are not known. Ethanol may increase high density lipoprotein (HDL) cholesterol concentration, augment the reverse cholesterol transport, or regulate growth factors or adhesion molecules. To study whether qualitative changes in HDL phospholipids mediate part of the beneficial effects of alcohol on atherosclerosis by HDL receptor, we investigated whether phosphatidylethanol (PEth) in HDL particles affects the secretion of vascular endothelial growth factor (VEGF) by a human scavenger receptor CD36 and LIMPII analog-I (CLA-1)-mediated pathway.

METHODS

Human EA.hy 926 endothelial cells were incubated in the presence of native HDL or PEth-HDL. VEGF concentration and CLA-1 protein expression were measured. Human CLA-1 receptor-mediated mechanisms in endothelial cells were studied using CLA-1 blocking antibody and protein kinase inhibitors.

RESULTS

Phosphatidylethanol-containing HDL particles caused a 6-fold increase in the expression of CLA-1 in endothelial cells compared with the effect of native HDL. That emergent effect was mediated mainly through protein kinase C and p44/42 mitogen-activated protein kinase pathways. PEth increased the secretion of VEGF and that increase could be abolished by a CLA-1 blocking antibody.

CONCLUSIONS

High density lipoprotein particles containing PEth bind to CLA-1 receptor and thereby increase the secretion of VEGF from endothelial cells. Ethanol-induced protective effects against coronary heart disease may be explained, at least partly, by the effects of PEth-modified HDL particles on VEGF via CLA-1-mediated mechanisms in endothelial cells.

Acute ethanol exposure disrupts VEGF receptor cell signaling in endothelial cells

Physiological angiogenesis is regulated by various factors, including signaling through vascular endothelial growth factor (VEGF) receptors. We previously reported that a single dose of ethanol (1.4 g/kg), yielding a blood alcohol concentration of 100 mg/dl, significantly impairs angiogenesis in murine wounds, despite adequate levels of VEGF, suggesting direct effects of ethanol on endothelial cell signaling (40). To examine the mechanism by which ethanol influences angiogenesis in wounds, we employed two different in vitro angiogenesis assays to determine whether acute ethanol exposure (100 mg/dl) would have long-lasting effects on VEGF-induced capillary network formation. Ethanol exposure resulted in reduced VEGF-induced cord formation on collagen and reduced capillary network structure on Matrigel in vitro. In addition, ethanol exposure decreased expression of endothelial VEGF receptor-2, as well as VEGF receptor-2 phosphorylation in vitro. Inhibition of ethanol metabolism by 4-methylpyrazole partially abrogated the effect of ethanol on endothelial cell cord formation. However, mice treated with t-butanol, an alcohol not metabolized by alcohol dehydrogenase, exhibited no change in wound vascularity. These results suggest that products of ethanol metabolism are important factors in the development of ethanol-induced changes in endothelial cell responsiveness to VEGF. In vivo, ethanol exposure caused both decreased angiogenesis and increased hypoxia in wounds. Moreover, in vitro experiments demonstrated a direct effect of ethanol on the response to hypoxia in endothelial cells, as ethanol diminished nuclear hypoxia-inducible factor-1alpha protein levels. Together, the data establish that acute ethanol exposure significantly impairs angiogenesis and suggest that this effect is mediated by changes in endothelial cell responsiveness to both VEGF and hypoxia.

Ethanol stimulates endothelial cell angiogenic activity via a Notch- and angiopoietin-1-dependent pathway

AIMS

Our aims were to determine the effect of alcohol (EtOH) on endothelial angiogenic activity and to delineate the cell signalling mechanisms involved.

METHODS AND RESULTS

Treatment of human umbilical vein endothelial cells (HUVECs) with EtOH (1-100 mM, 24 h) dose-dependently increased their network formation on Matrigel (an index of angiogenesis) with a maximum response (2.5- to 3-fold increase) at 25 mM. Ethanol also stimulated the proliferation (by cell count and proliferating cell nuclear antigen expression) and migration (by scratch wound assay) of HUVECs. In parallel cultures, EtOH stimulated Notch receptor (1 and 4) and Notch target gene (hrt-1, -2, and -3) mRNA and protein expression and enhanced CBF-1/RBP-Jk promoter activity. EtOH also stimulated, at the mRNA and protein level, the expression of angiopoietin-1 (Ang1) and its Tie2 receptor in these cells. Knockdown of Notch 1 or 4 by siRNA or inhibition of Notch-mediated, CBF-1/RBP-Jk-regulated gene expression by the Epstein-Barr virus-encoded protein RPMS-1 inhibited both ethanol-induced Ang1/Tie2 expression in HUVECs and their network formation on Matrigel. Moreover, knockdown of Ang1 or Tie2 by siRNA inhibited ethanol-induced endothelial network formation.

CONCLUSION

These data demonstrate that ethanol, at levels consistent with moderate consumption, enhances endothelial angiogenic activity in vitro by stimulating a novel Notch/CBF-1/RBP-JK-Ang1/Tie2-dependent pathway. These actions of ethanol may be relevant to the cardiovascular effects of alcohol consumption purported by epidemiological studies.

Effects of ethanol on lipids and atherosclerosis

Moderate alcohol consumption is associated with an increase in plasma high density lipoprotein (HDL) cholesterol concentration and a decrease in low density lipoprotein (LDL) cholesterol concentration. Changes in the concentration and composition of lipoproteins are estimated to account for more than half of alcohol's protective effect for coronary heart disease. Alcohol intake also affects plasma proteins involved in lipoprotein metabolism: cholesteryl ester transfer protein, phospholipid transfer protein, lecithin:cholesterol acyltransferase, lipoprotein lipase, hepatic lipase, and phospholipases. In addition, alcohol intake may result in acetaldehyde modification of apolipoproteins. Furthermore, "abnormal" lipids, phosphatidylethanol and fatty acid ethyl esters are formed in the presence of ethanol and are associated with lipoproteins in plasma. Ethanol and ethanol-induced modifications of lipids may modulate the effects of lipoproteins on the cells in the arterial wall. The molecular mechanisms involved in these processes are complex, requiring further study to better understand the specific effects of ethanol in the pathogenesis of atherosclerosis. This review discusses the effects of ethanol on lipoproteins and lipoprotein metabolism, as well as the novel effects of lipoproteins on vascular wall cells.

Phosphatidylethanol in high density lipoproteins increases the vascular endothelial growth factor in smooth muscle cells

To study whether qualitative changes in high density lipoprotein (HDL) phospholipids mediate part of the advantageous effects of ethanol on atherosclerosis, we investigated whether HDL associated phosphatidylethanol (PEth) affects the secretion of vascular endothelial growth factor (VEGF) from cultured human smooth muscle cells. Serum-starved human umbilical vein HUVS-112D smooth muscle cells were incubated in the presence of PEth-HDL, HDL, or buffer. The phosphorylation of protein kinase C (PKC) and mitogen activated protein kinase (p44/42 MAPK) was determined by specific antibodies against phosphorylated and total proteins. VEGF concentrations were measured from cell culture medium of the cells. PEth increased the secretion of VEGF into the culture medium of HUVS cells. PEth-HDL increased the PKC phosphorylation by 2.1-fold and p44/42 MAPK phosphorylation by 3.3-fold compared with HDL, indicating that PEth-containing HDL particles influence vascular smooth muscle cells by PKC and p44/42 MAPK signalling. This may mediate the effects of ethanol on vascular wall by increasing the VEGF secretion from smooth muscle cells. The secreted VEGF may inhibit the formation of neointima and in doing so helps prevent atherosclerosis.

Gene transfer using the mature form of VEGF-D reduces neointimal thickening through nitric oxide-dependent mechanism

Gene transfer to the vessel wall using vascular endothelial growth factors (VEGFs) has shown therapeutic potential for the treatment of restenosis. In this study, we evaluated the effect of catheter-mediated adenoviral (Ad) gene transfer of the mature form of VEGF-D (VEGF-D(DeltaNDeltaC)) in balloon-denuded cholesterol-fed rabbit aorta. AdLacZ was used as a control. Transduced VEGF-D(DeltaNDeltaC) mRNA was detectable in the arterial wall with RT-PCR at 6, 14 and 28 days. Gene transfer efficiency as detected with X-gal staining 6 days after the AdLacZ transduction was 1.91 +/- 1.32% in intima. AdVEGF-D(DeltaNDeltaC) gene transfer led to 52% reduction in intima/media ratio (I/M) as compared to the AdLacZ controls at 14 days time point. At 6 days there were no differences in I/M, but the number of macrophages in the vessel wall was 85% lower in the AdVEGF-D(DeltaNDeltaC) group as compared to the controls. The therapeutic effect was no longer detectable 28 days after the gene transfer. The therapeutic effect of VEGF-D(DeltaNDeltaC) was nitric oxide (NO)-dependent as the feeding of NO synthase inhibitor, L-NAME, blocked the reduction in intimal thickening. It is concluded that AdVEGF-D(DeltaNDeltaC) gene transfer reduces intimal thickening and macrophage influx into the vessel wall in balloon-denuded rabbit aortas.

Lipoprotein-Associated Phosphatidylethanol Increases the Plasma Concentration of Vascular Endothelial Growth Factor

OBJECTIVE

To study whether qualitative changes in high-density lipoprotein (HDL) phospholipids mediate part of the beneficial effects of alcohol on atherosclerosis, we investigated whether phosphatidylethanol (PEth) in HDL particles affects the secretion of vascular endothelial growth factor (VEGF) from endothelial cells.

METHODS AND RESULTS

PEth increased the secretion of VEGF into the culture medium of EA.hy 926 endothelial cells. The mitogen-activated protein kinase (MAPK) phosphorylation increased by 3.3-fold and protein kinase C (PKC) by 2.2-fold by PEth-containing HDL. Moreover, we showed that intravenous injection of PEth incorporated into HDL particles increased plasma concentration of VEGF by 2.4-fold in rats in vivo. Similar effect was observed when the rats were injected with HDL particles isolated from alcohol drinkers.

CONCLUSIONS

HDL particles containing PEth affect endothelial cells by MAPK and PKC signaling. This may mediate the effects of ethanol on the arterial wall by increasing VEGF secretion from endothelial vascular cells. That may explain, at least in part, the beneficial effect of moderate alcohol consumption on atherosclerosis.

Dual actions of nitric oxide on angiogenesis: possible roles of PKC, ERK, and AP-1

Regulation of angiogenesis by nitric oxide (NO) is controversial since NO has been shown to have both pro- and anti-angiogenic effects. In this study, we examined the effect of the NO donor, S-nitro-N-acetyl-penicillamine (SNAP), on in vitro angiogenesis, and the mechanisms involved: PKC activity, ERK and c-Jun phosphorylation, and AP-1 DNA binding activity, in microvascular endothelial cells. SNAP, at 0.5-4 mM, significantly and dose-dependently inhibited angiogenesis, PKC activity, and ERK and c-Jun phosphorylation up to 80%, 83%, and 63% and 73%, respectively. SNAP at concentrations > 2mM also abolished AP-1 binding activity. Lower concentrations of SNAP (0.1-0.3 mM) significantly increased angiogenesis, PKC activity, and ERK and c-Jun phosphorylation up to 46%, 60%, and 61% and 180%, respectively. These findings indicate that the dual pro- and anti-angiogenic actions of NO are dose-dependent and suggest that they are mediated by PKC and ERK acting on AP-1.

Aspirin and salicylate inhibit colon cancer medium- and VEGF-induced endothelial tube formation: correlation with suppression of cyclooxygenase-2 expression

To determine whether aspirin and salicylate suppress colon cancer cell-mediated angiogenesis, we evaluated the effects of aspirin and sodium salicylate on endothelial tube formation on Matrigel. Aspirin and sodium salicylate concentration-dependently inhibited human endothelial cell (EC) tube formation induced by conditioned medium collected from DLD-1, HT-29 or HCT-116 colon cancer cells. Aspirin and sodium salicylate at pharmacological concentrations were equally effective in blocking tube formation. Neutralizing antivascular endothelial growth factor (VEGF) antibodies blocked colon cancer medium-induced tube formation. VEGF receptor 2 but not receptor 1 antibodies inhibited tube formation to a similar extent as anti-VEGF antibodies. These results indicate that VEGF interaction with VEGF receptor 2 is the primary mechanism underlying colon cancer-induced angiogenesis. Aspirin or sodium salicylate inhibited VEGF-induced tube formation in a concentration-dependent manner comparable to that of inhibition of colon cancer medium-induced endothelial tube formation. It has been shown that cyclooxygenase-2 (COX-2) is pivotal in cancer angiogenesis. We found that colon cancer medium-induced COX-2 protein expression in EC and aspirin or sodium salicylate suppressed the cancer-induced COX-2 protein levels at concentrations correlated with those that suppressed endothelial tube formation. Furthermore, aspirin and sodium salicylate inhibited COX-2 expression stimulated by VEGF. These findings indicate that aspirin and other salicylate drugs at pharmacological concentrations inhibit colon cancer-induced angiogenesis which is correlated with COX-2 suppression.

Inhibition of angiogenesis by NSAIDs: molecular mechanisms and clinical implications

Angiogenesis, the formation of new capillary blood vessels, is a fundamental process essential for reproduction and embryonic development. It is crucial to the healing of tissue injury because it provides essential oxygen and nutrients to the healing site. Angiogenesis is also required for cancer growth and progression since tumor growth requires an increased nutrient and oxygen supply. Nonsteroidal anti-inflammatory drugs (NSAIDs) are the most widely used drugs worldwide for treating pain, arthritis, cardiovascular diseases, and more recently for colon cancer prevention. However, NSAIDs produce gastrointestinal ulcers and delay ulcer healing. Recently NSAIDs have been demonstrated to inhibit angiogenesis, but the underlying mechanisms are only beginning to be elucidated. The inhibition of angiogenesis by NSAIDs is a causal factor in the delay of ulcer healing, and it is becoming clear that this is also likely to be one of the mechanisms by which NSAIDs can reduce or prevent cancer growth. Based on the experimental data and the literature, the mechanisms by which NSAIDs inhibit angiogenesis appear to be multifactorial and likely include local changes in angiogenic growth factor expression, alteration in key regulators and mediators of vascular endothelial growth factor (VEGF), increased endothelial cell apoptosis, inhibition of endothelial cell migration, recruitment of inflammatory cells and platelets, and/or thromboxane A2 mediated effects. Some of these mechanisms include: inhibition of mitogen-activated protein (Erk2) kinase activity; suppression of cell cycle proteins; inhibition of early growth response (Egr-1) gene activation; interference with hypoxia inducible factor 1 and VEGF gene activation; increased production of the angiogenesis inhibitor, endostatin; inhibition of endothelial cell proliferation, migration, and spreading; and induction of endothelial apoptosis.

Angiogenesis in collagen I requires alpha2beta1 ligation of a GFP*GER sequence and possibly p38 MAPK activation and focal adhesion disassembly

Angiogenesis depends on proper collagen biosynthesis and cross-linking, and type I collagen is an ideal angiogenic scaffold, although its mechanism is unknown. We examined angiogenesis using an assay wherein confluent monolayers of human umbilical vein endothelial cells were overlain with collagen in a serum-free defined medium. Small spaces formed in the cell layer by 2 h, and cells formed net-like arrays by 6-8 h and capillary-like lumens by 24 h. Blocking of alpha2beta1, but not alpha1 or alpha(v)beta3 integrin function halted morphogenesis. We found that a triple-helical, homotrimeric peptide mimetic of a putative alpha2beta1 binding site: alpha1(I)496-507 GARGERGFP*GER (where single-letter amino acid nomenclature is used, P* = hydroxyproline) inhibited tube formation, whereas a peptide carrying another putative site: alpha1(I)127-138 GLP*GERGRP*GAP* or control peptides did not. A chemical inhibitor of p38 mitogen-activated protein kinase (p38 MAPK), SB202190, blocked tube formation, and p38 MAPK activity was increased in collagen-treated cultures, whereas targeting MAPK kinase (MEK), focal adhesion kinase (FAK), or phosphatidylinositol 3-kinase (PI3K) had little effect. Collagen-treated cells had fewer focal adhesions and 3- to 5-fold less activated FAK. Thus capillary morphogenesis requires endothelial alpha2beta1 integrin engagement of a single type I collagen integrin-binding site, possibly signaling via p38 MAPK and focal adhesion disassembly/FAK inactivation.

Hydrogen peroxide formation and actin filament reorganization by Cdc42 are essential for ethanol-induced in vitro angiogenesis

This report focuses on the identification of the molecular mechanisms of ethanol-induced in vitro angiogenesis. The manipulation of angiogenesis is an important therapeutic approach for the treatment of cancer, cardiovascular diseases, and chronic inflammation. Our results showed that ethanol stimulation altered the integrity of actin filaments and increased the formation of lamellipodia and filopodia in SVEC4-10 cells. Further experiments demonstrated that ethanol stimulation increased cell migration and invasion and induced in vitro angiogenesis in SVEC4-10 cells. Mechanistically, ethanol stimulation activated Cdc42 and produced H(2)O(2) a reactive oxygen species intermediate in SVEC4-10 cells. Measuring the time course of Cdc42 activation and H(2)O(2) production upon ethanol stimulation revealed that the Cdc42 activation and the increase of H(2)O(2) lasted more than 3 h, which indicates the mechanisms of the long duration effects of ethanol on the cells. Furthermore, either overexpression of a constitutive dominant negative Cdc42 or inhibition of H(2)O(2) production abrogated the effects of ethanol on SVEC4-10 cells, indicating that both the activation of Cdc42 and the production of H(2)O(2) are essential for the actions of ethanol. Interestingly, we also found that overexpression of a constitutive dominant positive Cdc42 itself was sufficient to produce H(2)O(2) and to induce in vitro angiogenesis. Taken together, our results suggest that ethanol stimulation can induce H(2)O(2) production through the activation of Cdc42, which results in reorganizing actin filaments and increasing cell motility and in vitro angiogenesis.

Delphinidin inhibits endothelial cell proliferation and cell cycle progression through a transient activation of ERK-1/-2

Epidemiological studies have shown that a diet rich in fruits and vegetables might reduce the risk of cardiovascular diseases and protect against cancer by mechanisms that have not been elucidated yet. This study was aimed to define the effect of delphinidin, a vasoactive polyphenol belonging to the class of anthocyanin, on bovine aortic endothelial cells (BAECs) proliferation. Delphinidin inhibited serum- and vascular endothelium growth factor-induced BAECs proliferation. This antiproliferative effect of delphinidin, is triggered by ERK-1/-2 activation, independent of nitric oxide pathway and is correlated with suppression of cell progression by blocking the cell cycle in G(0)/G(1) phase. Furthermore, suppression of cell cycle progression is associated with the modulation of the mitogenic signaling transduction cascade. This includes over-expression of caveolin-1 and p21(WAF1/Cip1) and down-expression of Ras and cyclin D1. In conclusion, the antiproliferative effect of delphinidin may be of importance in preventing both plaque development and stability in atherosclerosis and tumor dissemination in cancer.

Alprostadil suppresses angiogenesis in vitro and in vivo in the murine Matrigel plug assay

1. Prostaglandin E(1) (PGE(1), alprostadil) is used as a vasodilator for the treatment of peripheral vascular diseases. 2. Previous reports suggested a pro-angiogenic effect for PGE(1). 3. We studied the in vitro and in vivo effect of PGE(1), complexed with alpha-cyclodextrin, on the angiogenic process. Contrary to what was expected, we found that, in human umbilical vein endothelial cells (HUVECs), PGE(1) inhibited proliferation, migration and capillary-like structure formation in Matrigel. 4. By RT-PCR studies, the expression of the EP(2) and EP(3) subtypes of the PG receptor was detected in HUVECs. 5. PGE(1) alone stimulated adenylate cyclase activity at micromolar concentrations, while at nanomolar concentrations potentiated the forskolin-induced cAMP accumulation. 6. 8-Bromoadenosine-3':5'-cyclic monophosphate (Br-cAMP) mimicked the inhibitory effect of PGE(1) on endothelial cell growth, motility and tube formation. 7. Sulprostone, an agonist at the EP(3) subtype of PG receptors, mimicked the in vitro anti-angiogenic effects of PGE(1), while butaprost, an EP(2) receptor agonist, had no effect. 8. Finally, in the plug assay model of angiogenesis in mice, PGE(1) showed a strong inhibitory effect on Matrigel neovascularization. 9. Thus, PGE(1) possesses strong anti-angiogenic activity in vitro and in vivo.

Ethanol modulates the growth of human breast cancer cells in vitro

The role of ethanol or its metabolites on breast neoplasm has not been characterized. We hypothesized that ethanol may alter the growth rate of human breast tumor epithelial cells by modulating putative growth-promoting signaling pathways such as p44/42 mitogen-activated protein kinases (MAPKs). The MCF-7 cell line, considered a suitable model, was used in these studies to investigate the effects of ethanol on [(3)H]thymidine incorporation, cell number, and p44/42 MAPK activities in the presence or absence of a MAPK or extracellular signal-regulated kinase ERK-1, and (MEK1) inhibitor (PD098059). Treatment of MCF-7 cells with a physiologically relevant concentration of ethanol (0.3% or 65 mM) increased p44/42 activities by an average of 400% (P < 0.02), and subsequent cell growth by 200% (P < 0.05) in a MEK1 inhibitor (PD098059)-sensitive fashion, thus suggesting that the Ras/MEK/MAPK signaling pathways are crucial for ethanol-induced MCF-7 cell growth.

Acute ethanol increases angiogenic growth factor gene expression in rat skeletal muscle

Moderate ethanol consumption demonstrates a protective effect against cardiovascular disease and improves insulin sensitivity, possibly through angiogenesis. We investigated whether 1) ethanol would increase skeletal muscle growth factor gene expression and 2) the effects of ethanol on skeletal muscle growth factor gene expression were independent of exercise-induced growth factor gene expression. Female Wistar rats were used. Four groups (saline + rest; saline + exercise; 17 mmol/kg ethanol + rest; and 17 mmol/kg ethanol + exercise) were used to measure the growth factor response to acute exercise and ethanol administration. Vascular endothelial growth factor (VEGF), transforming growth factor-beta(1) (TGF-beta(1)), basic fibroblast growth factor (bFGF), Flt-1, and Flk-1 mRNA were analyzed from the left gastrocnemius by quantitative Northern blot. Ethanol increased VEGF, TGF-beta(1), bFGF, and Flt-1 mRNA at rest and after acute exercise. Ethanol increased resting Flk-1 mRNA. Ethanol increased bFGF mRNA independently of exercise. These findings suggest that 1) ethanol can increase skeletal muscle angiogenic growth factor gene expression and 2) the mechanisms responsible for the ethanol-induced increases in VEGF, TGF-beta(1), and Flt-1 mRNA appear to be different from those responsible for exercise-induced regulation. Therefore, these results provide evidence in adult rat tissue that the protective cardiovascular effects of moderate ethanol consumption may result in part through the increase of angiogenic growth factors.

Angioprevention': angiogenesis is a common and key target for cancer chemopreventive agents

The potential to block tumor growth by inhibition of the neoangiogenic process represents an intriguing approach to the treatment of solid tumors. The high proliferation rate in the tumor deprived of proper vascularization would be balanced by cell death due to lack of diffusion of nutrients and oxygen. Matrix metalloproteinases (MMPs), angiogenic growth factors, and their receptors are the main targets of an increasing number of clinical trials approved to test the tolerance and therapeutic efficacy of antiangiogenic agents. We observed that a series of substances proposed as possible cancer chemopreventive agents show antiangiogenic properties when tested in in vitro and in vivo angiogenesis models. We demonstrated that N-acetyl-l-cysteine is able to reduce the invasive and metastatic potential of melanoma cells, and to inhibit endothelial cell invasion by direct inhibition of MMP activity. We also showed that epigallocatechin gallate (EGCG), a flavonoid from green tea that possesses chemopreventive activity in experimental and epidemiological studies, is a potent inhibitor of MMP-2 and MMP-9. Angiogenesis has also been demonstrated to be a target for nonsteroidal anti-inflammatory drug chemopreventive activity. Based on these data, we hypothesize that other chemopreventive agents, including natural or synthetic retinoids, steroid hormone antagonists, peroxisome proliferator-activated receptor gamma ligands, vitamin D, and protease inhibitors, might have antiangiogenesis as an important mechanism of action, a novel concept we will term 'angioprevention'. We analyze the mechanisms on how and why chemopreventive agents could exert antiangiogenic effects aimed at controlling tumor growth, and their potential use in the clinic.

[Moderate alcohol consumption and cardiovascular diseases]

While excessive ethanol consumption can result in higher rate of morbidity and mortality resulting from several diseases including cancer and cirrhosis, epidemiological studies suggest that moderate alcohol ingestion reduces the risk of cardiovascular diseases. However, the precise mechanisms by which moderate alcohol consumption protects against coronary heart disease (CHD) is not fully understood. Epidemiological studies suggest that alcohol consumption influences several risk factors for CHD including blood pressure, plasma cholesterol levels, platelet function, and fibrinolytic parameters, preventing both vascular thrombosis and occlusion. Turning to molecular and cellular levels, ethanol has been shown to act on several signal transduction mechanisms involve in the inhibition of smooth muscle cells proliferation and migration and in the activation of the release of vasoactive factors from vascular cells such as nitric oxide (NO). The latter is of importance since NO has been shown to possess antioxidant, antiaggregant properties, to regulate vascular tone and to inhibit both proliferation of smooth muscle cells and adhesion of leukocytes. Altogether, the above mentioned beneficial properties of moderate concentration of ethanol might help to explain the cardio- and vascular protection induced by ethanol. This review compels several bibliographic data concerning the cardiovascular effect of moderate alcohol consumption.

Mechanical strain and estrogen activate estrogen receptor alpha in bone cells

Bone cells' early responses to estrogen and mechanical strain were investigated in the ROS 17/2.8 cell line. Immunoblotting with antiphosphorylated estrogen receptor a (ER-alpha) antibody showed that when these cells were exposed for 10 minutes to estrogen (10(-8) M) or a single period of cyclic dynamic strain (peak 3400 microepsilon, 1 Hz, 600 cycles), there was an increase in the intensity of a 66-kDa band, indicating phosphorylation of ser122 in the amino terminus of ER-alpha. Increased phosphorylation was detected within 5 minutes of exposure to estrogen and 5 minutes after the end of the period of strain. Estrogen and strain also activated the mitogen-activated protein kinase (MAPK) family member extracellular regulated kinase-1 (ERK-1). Increases in ERK activation coincided with increased ER-alpha phosphorylation. Activation of ERK-1 and the phosphorylation of ER-alpha, by both estrogen and strain, were prevented by the MAP kinase kinase (MEK) inhibitor U0126 and the protein kinase A (PKA) inhibitor (PKI). These data support previous suggestions that resident bone cells' early responses to strain and estrogen share a common pathway, which involves ER-alpha. This pathway also appears to involve PKA and ERK-mediated phosphorylation of ser122 within the amino terminus of ER-alpha. Reduced availability of this pathway when estrogen levels are reduced could explain diminished effectiveness of mechanically related control of bone architecture after the menopause.

Effects of prolonged exposure to hypoxia on morphological changes of endothelial cells plated on fibrin gel

Since tissue oxygenation has a profound effect on capillary growth, the effect of pO2 on endothelial cell functions was studied. Under normoxic conditions, EA.hy926 endothelial cells and HUVEC plated onto fibrin gels in low-serum culture medium underwent rapid and profound morphological changes within 12 to 48 hours depending on the cell line used. Their characteristic cobblestone organisation was transformed into a network of cord-like or tube-like structures. We showed that when exposed to low oxygen concentrations for 3 days, HUVEC and EA.hy926 have their ability to rearrange reduced to around 50 %. With EA.hy926 this effect was amplified by 79% after 9 days of hypoxia. The altered behaviour of hypoxia-adapted cells was not caused by a loss in their fibrinolytic activity. In fact, the fibrin degradation rate and the generated fibrin fragments appeared identical in normoxia and hypoxia. Confocal microscopy and gel densitometry showed that in normoxia the remaining undegraded fibrin gel underwent a dynamic remodeling whereas in hypoxia it remained undisturbed. It is likely that hypoxia induces modification in the factors that integrate matrix information and cytoskeletal organisation in order to contract fibrin.

RACK1 is up-regulated in angiogenesis and human carcinomas

Angiogenesis is crucial for many biological and pathological processes including the ovarian cycle and tumor growth. To identify molecules relevant for angiogenesis, we performed mRNA fingerprinting and subsequent Northern blot analysis using bovine cord-forming vs. monolayer-forming endothelial cells (EC) in vitro and staged bovine corpora lutea in vivo. We detected the receptor for activated C kinase 1 (RACK1), the specific receptor for activated protein kinase C beta (PKC beta), to be up-regulated in bovine cord-forming EC in vitro and in angiogenically active stages of bovine corpora lutea in vivo. Thereafter we established and determined the complete bovine RACK1 cDNA sequence. RACK1 was massively induced in subconfluent vs. contact-inhibited bovine EC, during angiogenesis in vitro, active phases of the murine ovarian cycle, human tumor angiogenesis, and in cancer cells in vivo as assessed by quantitative PCR and in situ hybridization. RACK1 transcripts were localized to proliferating EC in vitro and the endothelium of tumor neovascularizations in vivo by in situ hybridization. PKC beta plays an important role in angiogenesis and cancer growth. Our data suggest that downstream signaling of PKC beta in angiogenically active vs. inactive tissues and endothelium is affected by the availability of RACK1.

Intravascular adenovirus-mediated VEGF-C gene transfer reduces neointima formation in balloon-denuded rabbit aorta

BACKGROUND

Gene transfer to the vessel wall may provide new possibilities for the treatment of vascular disorders, such as postangioplasty restenosis. In this study, we analyzed the effects of adenovirus-mediated vascular endothelial growth factor (VEGF)-C gene transfer on neointima formation after endothelial denudation in rabbits. For comparison, a second group was treated with VEGF-A adenovirus and a third group with lacZ adenovirus. Clinical-grade adenoviruses were used for the study.

METHODS AND RESULTS

Aortas of cholesterol-fed New Zealand White rabbits were balloon-denuded, and gene transfer was performed 3 days later. Animals were euthanized 2 and 4 weeks after the gene transfer, and intima/media ratio (I/M), histology, and cell proliferation were analyzed. Two weeks after the gene transfer, I/M in the lacZ-transfected control group was 0. 57+/-0.04. VEGF-C gene transfer reduced I/M to 0.38+/-0.02 (P:<0.05 versus lacZ group). I/M in VEGF-A-treated animals was 0.49+/-0.17 (P:=NS). The tendency that both VEGF groups had smaller I/M persisted at the 4-week time point, when the lacZ group had an I/M of 0.73+/-0.16, the VEGF-C group 0.44+/-0.14, and the VEGF-A group 0. 63+/-0.21 (P:=NS). Expression of VEGF receptors 1, 2, and 3 was detected in the vessel wall by immunocytochemistry and in situ hybridization. As an additional control, the effect of adenovirus on cell proliferation was analyzed by performing gene transfer to intact aorta without endothelial denudation. No differences were seen in smooth muscle cell proliferation or I/M between lacZ adenovirus and 0.9% saline-treated animals.

CONCLUSIONS

Adenovirus-mediated VEGF-C gene transfer may be useful for the treatment of postangioplasty restenosis and vessel wall thickening after vascular manipulations.

Tumor angiogenesis in chronic pancreatitis and pancreatic adenocarcinoma: impact of K-ras mutations

Chronic pancreatitis (CP) is one condition in which epidemiologic studies have demonstrated a definite association with pancreatic adenocarcinoma (PAC). The pathophysiologic and molecular events that either predispose to the development of, or potentiate the growth of, PAC are unknown. Mutation of the codon 12 K-ras gene is one genetic aberration commonly associated with development of PAC. Tumor angiogenesis, or microvascular proliferation of new capillaries, is another pathophysiologic alteration associated with PAC. Although activated ras oncogenes modulate tumor angiogenesis/neovascularization in some tumors, the importance of tumor angiogenesis and the role of K-ras mutation in regulating angiogenesis in CP and PAC are unknown. The aim of this study was to elucidate the relationship between angiogenesis and K-ras mutations in CP and PAC. Tumor angiogenesis and K-ras mutations were evaluated in resected specimens from 25 CP (23 CP plus two CP with PAC) and 16 PAC patients. Tumor angiogenesis was determined using immunohistochemistry of factor VIII-related antigen (FVIIIRAg) and ras mutations were identified by enriched-nested polymerase chain reaction. The mean number of FVIIIRAg-positive blood vessels was significantly (p < 0.005) higher in PAC (23.0 +/- 7.5), CP with a mutant K-ras genome (17.7 +/- 2.8) and CP with a normal K-ras genome (6.5 +/- 3.8), compared to unaffected areas. Codon 12 K-ras mutations were detected in three of 25 CP specimens (12%) and in 15 of 16 PAC specimens (94%). In CP patients with mutant K-ras in their genome, microvessel density was significantly (p < 0.01) elevated, compared to patients with a normal K-ras genome. Statistical analyses (Spearman rank-difference correlation coefficient, Student t test, and chi2 analysis) indicated a significant association between codon 12 K-ras mutations and tumor angiogenesis in both CP and PAC. This study demonstrates a significant association between angiogenesis and K-ras mutation in both PAC and CP. At a minimum, K-ras mutation is associated with the events that increase angiogenesis and it may potentiate or promote tumor angiogenesis.

Inhibition of endothelial cell migration, intercellular communication, and vascular tube formation by thromboxane A(2)

The eicosanoid thromboxane A(2) (TXA(2)) is released by activated platelets, monocytes, and the vessel wall and interacts with high affinity receptors expressed in several tissues including endothelium. Whether TXA(2) might alter endothelial migration and tube formation, two determinants of angiogenesis, is unknown. Thus, we investigated the effect of the TXA(2) mimetic [1S-(1alpha, 2beta(5Z),3alpha(1E,3R), 4alpha]-7-[3-(3-hydroxy-4-(4'-iodophenoxy)-1-butenyl)-7-o xab icyclo- [2.2.1]heptan-2-yl]-5'-heptenoic acid (IBOP) on human endothelial cell (HEC) migration and angiogenesis in vitro. IBOP stimulation inhibited HEC migration by 50% and in vitro capillary formation by 75%. These effects of IBOP were time- and concentration-dependent with an IC(50) of 25 nM. IBOP did not affect integrin expression or cytoskeletal morphology of HEC. Since gap junction-mediated intercellular communication increases in migrating HEC, we determined whether IBOP might inhibit coupling or connexin expression in HEC. IBOP reduced the passage of microinjected dyes between HEC by 50%, and the effects of IBOP on migration and tube formation were mimicked by the gap junction inhibitor 18beta-glycyrrhetinic acid (1 microM) with a similar time course and efficacy. IBOP (24 h) did not affect the expression or phosphorylation of connexin 43 in whole HEC lysates. Immunohistologic examination of HEC suggested that IBOP may impair functional coupling by altering the cellular distribution of gap junctions, leading to increased connexin 43 internalization. Thus, this finding that TXA(2) mimetics can prevent HEC migration and tube formation, possibly by impairing intercellular communication, suggests that antagonizing TXA(2) signaling might enhance vascularization of ischemic tissue.

Inhibition of angiogenesis by nonsteroidal anti-inflammatory drugs: insight into mechanisms and implications for cancer growth and ulcer healing

Angiogenesis, the formation of new capillary blood vessels, is essential not only for the growth and metastasis of solid tumors, but also for wound and ulcer healing, because without the restoration of blood flow, oxygen and nutrients cannot be delivered to the healing site. Nonsteroidal anti-inflammatory drugs (NSAIDs) such as aspirin, indomethacin and ibuprofen are the most widely used drugs for pain, arthritis, cardiovascular diseases and, more recently, the prevention of colon cancer and Alzheimer disease. However, NSAIDs produce gastroduodenal ulcers in about 25% of users (often with bleeding and/or perforations) and delay ulcer healing, presumably by blocking prostaglandin synthesis from cyclooxygenase (COX)-1 and COX-2 (ref. 10). The hypothesis that the gastrointestinal side effects of NSAIDs result from inhibition of COX-1, but not COX-2 (ref. 11), prompted the development of NSAIDs that selectively inhibit only COX-2 (such as celecoxib and rofecoxib). Our study demonstrates that both selective and nonselective NSAIDs inhibit angiogenesis through direct effects on endothelial cells. We also show that this action involves inhibition of mitogen-activated protein (MAP) kinase (ERK2) activity, interference with ERK nuclear translocation, is independent of protein kinase C and has prostaglandin-dependent and prostaglandin-independent components. Finally, we show that both COX-1 and COX-2 are important for the regulation of angiogenesis. These findings challenge the premise that selective COX-2 inhibitors will not affect the gastrointestinal tract and ulcer/wound healing.

Activation of Raf-1 during experimental gastric ulcer healing is Ras-mediated and protein kinase C-independent

Our previous study demonstrated increases in epidermal growth factor receptor (EGF-R) phosphorylation and receptor tyrosine kinase and extracellular signal-regulated kinase (ERK1 and ERK2) activities in the ulcer margin of experimental gastric ulcer during healing. However, the intermediate steps linking activated receptor tyrosine kinase to ERKs during ulcer healing are as yet unknown. Raf-1 is upstream of mitogen-activated protein kinases (MAPK/ERK) and can be activated by Ras-dependent and/or Ras-independent mechanisms. Therefore, we studied Raf-1 activity, its potential activators protein kinase C (PKC) and Ras, and expression and associations of adapter proteins Shc, Grb2, and Sos during experimental gastric ulcer healing. To investigate if Raf-1-ERK activation is attributable to the epithelial component of ulcer margins, we studied the effect of EGF on PKC, Ras, and ERK activities in a rat gastric epithelial cell line (RGM1). Our results demonstrate that gastric ulceration significantly increases Raf-1 kinase activity, Grb2 and Ras protein, and Shc-Grb2 and Grb2-Sos complex levels. In contrast, PKC activity and protein level were significantly decreased in the ulcer margins. In RGM1 cells, EGF significantly increased Ras and ERK2 activities without affecting PKC activity. These findings indicate that Raf-1 activation during gastric ulcer healing is Ras mediated, involves Shc-Grb2-Sos, and is PKC-independent.

Angiogenesis activators and inhibitors differentially regulate caveolin-1 expression and caveolae formation in vascular endothelial cells. Angiogenesis inhibitors block vascular endothelial growth factor-induced down-regulation of caveolin-1

Angiogenesis is the process by which new blood vessels are formed via proliferation of vascular endothelial cells. A variety of angiogenesis inhibitors that antagonize the effects of vascular endothelial growth factor (VEGF) and basic fibroblast growth factor (bFGF) have recently been identified. However, the mechanism by which these diverse angiogenesis inhibitors exert their common effects remains largely unknown. Caveolin-1 and -2 are known to be highly expressed in vascular endothelial cells both in vitro and in vivo. Here, we examine the potential role of caveolins in the angiogenic response. For this purpose, we used the well established human umbilical vein endothelial cell line, ECV 304. Treatment of ECV 304 cells with known angiogenic growth factors (VEGF, bFGF, or hepatocyte growth factor/scatter factor), resulted in a dramatic reduction in the expression of caveolin-1. This down-regulation event was selective for caveolin-1, as caveolin-2 levels remained constant under these conditions of growth factor stimulation. VEGF-induced down-regulation of caveolin-1 expression also resulted in the morphological loss of cell surface caveolae organelles as seen by transmission electron microscopy. A variety of well characterized angiogenesis inhibitors (including angiostatin, fumagillin, 2-methoxy estradiol, transforming growth factor-beta, and thalidomide) effectively blocked VEGF-induced down-regulation of caveolin-1 as seen by immunoblotting and immunofluorescence microscopy. However, treatment with angiogenesis inhibitors alone did not significantly affect the expression of caveolin-1. PD98059, a specific inhibitor of mitogen-activated protein kinase and a known angiogenesis inhibitor, also blocked the observed VEGF-induced down-regulation of caveolin-1. Furthermore, we show that caveolin-1 can function as a negative regulator of VEGF-R (KDR) signal transduction in vivo. Thus, down-regulation of caveolin-1 may be an important step along the pathway toward endothelial cell proliferation.