Biomedical subjects

Martin G Sirois

Publications and source records attributed to Martin G Sirois.

At least 19 recordsLinked to original sources

PubMed2007

Vascular permeability induced by VEGF family members in vivo: role of endogenous PAF and NO synthesis.

We previously reported that vascular endothelial growth factor (VEGF) increases vascular permeability through the synthesis of endothelial platelet-activating factor (PAF), while others reported the contribution of nitric oxide (NO). Herein, we addressed the contribution of VEGF receptors and the role played by PAF and NO in VEGF-induced plasma protein extravasation. Using a modified Miles assay, intradermal injection in mice ears of VEGF-A(165), VEGF-A(121), and VEGF-C (1 microM) which activate VEGFR-2 (Flk-1) receptor increased vascular permeability, whereas a treatment with VEGFR-1 (Flt-1) analogs; PlGF and VEGF-B (1 microM) had no such effect. Pretreatment of mice with PAF receptor antagonist (LAU8080) or endothelial nitric oxide synthase (eNOS) inhibitor (L-NAME) abrogated protein extravasation mediated by VEGF-A(165). As opposed to PAF (0.01-1 microM), treatment with acetylcholine (ACh; up to 100 microM; inducer of NO synthesis) or sodium nitroprusside (SNP; up to 1 microM; NO donor) did not induce protein leakage. Simultaneous pretreatment of mice with eNOS and protein kinase A (PKA) inhibitors restored VEGF-A(165) vascular hyperpermeability suggesting that endogenous NO synthesis leads to PKA inhibition, which support maintenance of vascular integrity. Our data demonstrate that VEGF analogs increase vascular permeability through VEGFR-2 activation, and that both endogenous PAF and NO synthesis contribute to VEGF-A(165)-mediated vascular permeability. However, PAF but not NO directly increases vascular permeability per se, thereby, suggesting that PAF is a direct inflammatory mediator, whereas NO serves as a cofactor in VEGF-A(165) proinflammatory activities.

Animals↗

PubMed2007

Angiopoietin chemotactic activities on neutrophils are regulated by PI-3K activation.

Angiopoietins (Ang1 and Ang2) modulate blood vessel integrity during the angiogenic process through the activation of tyrosine kinase receptor (Tie2). We recently detected Tie2 expression on neutrophils and reported that angiopoietins induce acute proinflammatory events including neutrophil beta2-integrin activation and their adhesion onto endothelial cells. Herein, we investigated the effect of angiopoietins on neutrophil migration and their capacity to modulate CXCL8/IL-8 chemotactic properties. Using a Boyden chamber assay, we observed that Ang1 and Ang2 (up to 10 nM; 60 min) increased the migration of neutrophils, and the maximal effect was achieved at 1 nM (72% and 114% increase, respectively) as compared with untreated cells. Angiopoietins induce a rapid and transient Akt phosphorylation, and pretreatment of neutrophils with PI-3K inhibitors, wortmannin (100 nM) and LY294002 (500 nM), reduced Ang1-mediated neutrophil migration by 100% and 78% and Ang2 chemotactic activity by 100% and 71%, respectively. Treatment of neutrophils with CXCL8/IL-8 (up to 50 nM; 60 min) increased basal neutrophil migration by 257% at its optimal concentration (10 nM), and pretreatment of neutrophils with corresponding PI-3K inhibitors reduced CXCL8/IL-8 (1 nM) chemotactic effect. Pretreatment of neutrophils with Ang1 or Ang2 (10 nM; 15 min) potentiated neutrophil migration induced by CXCL8/IL-8 (1 or 10 nM; 60 min) by 263% and 238% and by 177% and 164%, respectively. Finally, both angiopoietins showed a synergistic effect on the induction of Akt phosphorylation mediated by CXCL8/IL-8. In summary, our data demonstrate that angiopoietins increase neutrophil migration through PI-3K activation and can enhance proinflammatory activities of other cytokines.

Angiopoietins↗

PubMed2006

Role of MSK1 in the signaling pathway leading to VEGF-mediated PAF synthesis in endothelial cells.

Vascular endothelial growth factor (VEGF) inflammatory effects require acute platelet-activating factor (PAF) synthesis by endothelial cells (EC). We previously reported that VEGF-mediated PAF synthesis involves the activation of VEGF receptor-2/Neuropilin-1 complex, which is leading to the activation of p38 and p42/44 mitogen-activated protein kinases (MAPKs) and group V secretory phospholipase A(2) (sPLA(2)-V). As the mechanisms regulating sPLA(2)-V remain unknown, we addressed the role of the mitogen- and stress-activated protein kinase-1 (MSK1), which can be rapidly and transiently activated by p38 or p42/44 MAPKs. In native bovine aortic endothelial cells (BAEC), we observed a constitutive protein interaction of MSK1 with p38, p42/44 MAPKs, and sPLA(2)-V. These protein interactions were maintained in BAEC transfected either with the empty vector pCDNA3.1, wild-type MSK1 (MSK1-WT) or N-terminal dead kinase MSK1 mutant (MSK1-D195A). However, in BAEC expressing C-terminal dead kinase MSK1 mutant (MSK1-D565A), the interaction between MSK1 and sPLA(2)-V was reduced by 82% and 90% under basal and VEGF-treated conditions as compared to native BAEC. Treatment with VEGF for 15 min increased basal PAF synthesis in native BAEC, pCDNA3.1, MSK1-WT, and MSK1-D195A by 166%, 139%, 125%, and 82%, respectively. In contrast, PAF synthesis was prevented in cells expressing MSK1-D565A mutant. These results demonstrate the essential role of the C-terminal domain of MSK1 for its constitutive interaction with sPLA(2)-V, which appears essential to support VEGF-mediated PAF synthesis.

Animals↗

PubMed2006

Estradiol blocks the induction of CD40 and CD40L expression on endothelial cells and prevents neutrophil adhesion: an ERalpha-mediated pathway.

OBJECTIVE: Interferon gamma (IFN-gamma) was shown to induce CD40 and CD40L expression on endothelial cells (ECs) and consequently to promote neutrophil adhesion. The pro- and anti-inflammatory effects of estrogens are well recognized but their role on the regulation of CD40 and CD40L expression on ECs remains undefined. METHODS AND RESULTS: Treatment of porcine aortic endothelial cells (PAEC) with IFN-gamma for 24 h enhanced CD40 and CD40L expression by 97% and 78%, respectively. Pretreatment of PAEC with 17-beta-estradiol (17betaE) for 24 h prevented the latter expression of CD40/CD40L. Treatment of PAEC with antisense oligomers targeting ERalpha mRNA attenuated the ability of 17betaE to inhibit the IFN-gamma-induced CD40 and CD40L protein expression. The IFN-gamma activation pathway of CD40 is known to involve the phosphorylation of the Janus activated kinase (JAK) and the signal transducer and activator of transcription 1 (Stat1). 17betaE, acting via the estrogen receptor alpha (ERalpha), abrogated IFN-gamma-mediated effects on Stat1 but failed to inhibit Jak1 and Jak2 phosphorylation. Furthermore, 17betaE prevented neutrophil adhesion induced by IFN-gamma. CONCLUSION: In summary, 17betaE binding to ERalpha blocked IFN-gamma-induced Stat1 phosphorylation, CD40 and CD40L protein expression, and neutrophil adhesion onto ECs.

Animals↗

PubMed2006

Angiopoietins-1 and -2 are both capable of mediating endothelial PAF synthesis: intracellular signalling pathways.

Vascular endothelial growth factor (VEGF) is the only angiogenic growth factor capable of inducing an inflammatory response and we have recently demonstrated that its inflammatory effect is mediated by the endothelial synthesis of platelet-activating factor (PAF). Recently discovered, Ang1 and Ang2, upon binding to Tie2 receptor, modulate vascular permeability and integrity, contributing to angiogenesis. Ang1 was initially identified as a Tie2 agonist whereas Ang2 can behave as a context-dependent Tie2 agonist or antagonist. We sought to determine if Ang1 and/or Ang2 could modulate PAF synthesis in bovine aortic endothelial cells (BAEC) and if so, through which intracellular signalling pathways. Herein, we report that Ang1 and Ang2 (1 nM) are both capable of mediating a rapid Tie2 phosphorylation and a rapid, progressive and sustained endothelial PAF synthesis maximal within 4 h (1695% and 851% increase, respectively). Angiopoietin-mediated endothelial PAF synthesis requires the activation of the p38 and p42/44 MAPKs, PI3K intracellular signalling pathways, and a secreted phospholipase A(2) (sPLA(2)-V). Furthermore, angiopoietin-mediated PAF synthesis is partly driven by a relocalization of endogenous VEGF to the cell surface membrane. Our results demonstrate that the angiopoietins constitute another class of angiogenic factors capable of mediating PAF synthesis which may contribute to proinflammatory activities.

Angiopoietin-1↗

PubMed2006

Endovascular cryotherapy accentuates the accumulation of the fibrillar collagen types I and III after percutaneous transluminal angioplasty in pigs.

PURPOSE: To investigate the effect of endovascular cryotherapy (Cryo) on the density of collagen types I (CI) and III (CIII), which are involved in the dynamic modulation of extracellular matrix (ECM) after percutaneous transluminal angioplasty (PTA). METHODS: Twenty-one juvenile farm swine and 10 miniswine underwent PTA of the femoral arteries with and without Cryo (-50 degrees C for 2 minutes). Quantitative angiography, histomorphometry, and quantification of CI and CIII were performed at 1 week (n=7), 1 month (n=7), 3 months (n=7), and 6 months (n=10). RESULTS: PTA decreased the minimal luminal diameter (MLD) (range 3.48+/-0.18 to 4.2+/-0.39 mm) compared to baseline values (range 3.67+/-0.15 to 4.59+/-0.23 mm), but the application of Cryo maintained the MLDs at preprocedural levels (range 3.88+/-0.31 to 4.58+/-0.21 mm). At the time of sacrifice, the MLDs were similar in PTA and Cryo-treated arteries, but the external elastic lamina was significantly greater after Cryo application (range 10.17+/-0.54 to 14.34+/-0.76 mm2) than after PTA (range 8.69+/-0.70 to 11.77+/-0.73 mm2, p<0.05). Cryo did not alter the luminal area or prevent neointimal growth. A time-dependent increase of both CI and CIII was observed as early as 1 week after PTA, peaking at 3 months, and declining thereafter. Cryo accentuated this increase at all time points. CONCLUSION: The application of Cryo accentuates the accumulation of CI and CIII in PTA-treated femoral arteries. This effect may be of clinical relevance in the stabilization of peripheral atherosclerotic plaque.

Angioplasty, Balloon↗

PubMed2005

EP 80317, a ligand of the CD36 scavenger receptor, protects apolipoprotein E-deficient mice from developing atherosclerotic lesions.

CD36, a type B scavenger receptor expressed on macrophages, appears to play a major role in fatty streak formation through scavenging oxidatively modified lipoproteins in the arterial wall. We tested the hypothesis that EP 80317, a novel CD36 ligand derived from the growth hormone (GH)-releasing peptide family but devoided of any GH releasing activity, exerts anti-atherosclerotic effects in apolipoprotein E-deficient (apoE-/-) mice fed an atherogenic diet from 6 wk of age. Daily subcutaneous injections of EP 80317 (300 microg/kg) or vehicle were initiated at 6, 10, 12, or 14 wk until death at 18 wk. En face analyses of the entire aortic tree revealed a striking reduction (up to 51%) of lesion areas in EP 80317-treated apoE-/- mice compared with controls. Chronic treatment with EP 80317 (12 wk) is also associated with a 30% decrease in total plasma cholesterol, suggesting potential effects of this drug on cholesterol metabolism at the intestine/hepatic levels. EP 80317 exerts both preventive and curative effects on atherosclerotic lesion progression that were shown to be reversible after cessation of treatment. At the macrophage level, EP 80317 reduced oxidized low density lipoproteins internalization and up-regulated genes involved in cholesterol efflux, including peroxisome proliferator-activated receptor gamma (PPARgamma), liver x receptor alpha (LXRalpha), and the ATP binding cassette (ABC) transporters ABCA1 and ABCG1, supporting a role in regulating peripheral cholesterol trafficking. Importantly, the effects of EP 80317 were shown to be CD36 dependent, inasmuch as no anti-atherosclerotic or hypocholesterolemic effects were observed in apoE/CD36 double-deficient mice. In addition, long-term treatment of apoE/CD36 double-deficient mice with EP 80317 did not modulate the expression of genes of the PPARgamma-LXRalpha-ABC transporters pathway. Our results suggest that EP 80317, as a CD36 ligand, might be a prototype for a novel class of anti-atherosclerotic agents.

ATP Binding Cassette Transporter 1↗

PubMed2005

Vascular endothelial growth factor (VEGF)-A165-induced prostacyclin synthesis requires the activation of VEGF receptor-1 and -2 heterodimer.

We previously reported that vascular endothelial growth factor (VEGF)-A(165) inflammatory effect is mediated by acute platelet-activating factor synthesis from endothelial cells upon the activation of VEGF receptor-2 (VEGFR-2) and its coreceptor, neuropilin-1 (NRP-1). In addition, VEGF-A(165) promotes the release of other endothelial mediators including nitric oxide and prostacyclin (PGI(2)). However, it is unknown whether VEGF-A(165) is mediating PGI(2) synthesis through VEGF receptor-1 (VEGFR-1) and/or VEGF receptor-2 (VEGFR-2) activation and whether the coreceptor NRP-1 potentiates VEGF-A(165) activity. In this study, PGI(2) synthesis in bovine aortic endothelial cells (BAEC) was assessed by quantifying its stable metabolite (6-keto prostaglandin F(1alpha), 6-keto PGF(1alpha)) by enzyme-linked immunosorbent assay. Treatment of BAEC with VEGF analogs, VEGF-A(165) (VEGFR-1, VEGFR-2 and NRP-1 agonist) and VEGF-A(121) (VEGFR-1 and VEGFR-2 agonist) (up to 10(-9) m), increased PGI(2) synthesis by 70- and 40-fold within 15 min. Treatment with VEGFR-1 (placental growth factor and VEGF-B) or VEGFR-2 (VEGF-C) agonist did not increase PGI(2) synthesis. The combination of VEGFR-1 and VEGFR-2 agonists did not increase PGI(2) release. Pretreatment with a VEGFR-2 inhibitor abrogated PGI(2) release mediated by VEGF-A(165) and VEGF-A(121), and pretreatment of BAEC with antisense oligomers targeting VEGFR-1 or VEGFR-2 mRNA reduced PGI(2) synthesis mediated by VEGF-A(165) and VEGF-A(121) up to 79%. In summary, our data demonstrate that the activation of VEGFR-1 and VEGFR-2 heterodimer (VEGFR-1/R-2) is essential for PGI(2) synthesis mediated by VEGF-A(165) and VEGF-A(121), which cannot be reproduced by the parallel activation of VEGFR-1 and VEGFR-2 homodimers with corresponding agonists. In addition, the binding of VEGF-A(165) to NRP-1 potentiates its capacity to promote PGI(2) synthesis.

Animals↗

PubMed2005

Local delivery of 17beta-estradiol improves reendothelialization and decreases inflammation after coronary stenting in a porcine model.

In the current study, we investigated the effect of local intravascular delivery of 17beta-estradiol (17beta-E) on subsequent in-stent neointimal hyperplasia. Twenty-seven stents were implanted in coronary arteries of juvenile swine. Coronary arteries were randomized to local treatment with 17beta-E or no drug therapy (control-vehicle treated). Twenty-eight days post-treatment, angiographic images revealed an improved minimal lumen diameter (2.2 +/- 0.2 vs. 1.3 +/- 0.2 mm, P < 0.005) and a reduction of late lumen loss (1.7 +/- 0.2 vs. 2.3 +/- 0.1 mm, P < 0.01) in 17beta-E-treated vessels compared to control-vehicle treated. Histological analyses showed a reduction of stenosis (51.49 +/- 6.75 vs. 70.86 +/- 6.24%, P < 0.05), mean neointimal thickness (0.51 +/- 0.07 vs. 0.83 +/- 0.14 mm, P < 0.05) and inflammation score (1.29 +/- 0.28 vs. 2.85 +/- 0.40, P < 0.05) in 17beta-E-treated arteries compared to control-vehicle treated arteries. Immunohistochemistry analyses revealed a reduction of proliferating smooth muscle cells and increased in-stent reendothelialization in 17beta-E-treated arteries. Finally, we observed a correlation between neointimal hyperplasia and inflammation score, which in turn, was inversely related to reendothelialization. Locally delivered, 17beta-E is inhibiting the inflammatory response and smooth muscle cells proliferation and improving vascular reendothelialization which together are contributing to reduce in-stent restenosis in a porcine coronary injury model. Together, these data demonstrate the potential clinical application of 17beta-estradiol to improve vascular healing and prevent in-stent restenosis.

Angioplasty, Balloon, Coronary↗

PubMed2004

Angiopoietins can directly activate endothelial cells and neutrophils to promote proinflammatory responses.

Angiopoietin-1 (Ang1) and -2 (Ang2) are endothelial growth factors that bind to the tyrosine kinase receptor Tie2 and contribute to orchestrate blood vessel formation during angiogenesis. Ang1 mediates vessel maturation and integrity by the recruitment of pericytes. In contrast, Ang2 is classically considered as a Tie2 antagonist, counteracting the stabilizing action of Ang1. Inflammation exists in a mutually dependent association with angiogenesis and we have therefore studied the capacity of angiopoietins to modulate proinflammatory activities, namely P-selectin translocation and neutrophil adhesion onto endothelial cells. We observed that both Ang1 and Ang2 increased these biologic activities. Furthermore, combination of Ang1/Ang2 induced an additive effect on neutrophil adhesion but not on P-selectin translocation. In an attempt to clarify this phenomenon, we found that angiopoietins can directly activate neutrophils through Tie2 signaling as well as modulate platelet-activating factor (PAF) synthesis and beta(2) integrin functional up-regulation. Together, our data demonstrate that angiopoietins could promote acute recruitment of leukocytes, which might contribute to facilitate vascular remodeling and angiogenesis.

Angiopoietin-1↗

PubMed2004

VEGF-mediated endothelial P-selectin translocation: role of VEGF receptors and endogenous PAF synthesis.

The acute increase in vascular permeability produced by vascular endothelial growth factor (VEGF-A(165)) requires activation of endothelial Flk-1 receptors (VEGFR-2) and stimulation of platelet-activating factor (PAF) synthesis. Like PAF, VEGF-A(165) promotes translocation of P-selectin to the endothelial cell (EC) surface. However, the mechanisms involved remain unknown. By treating human umbilical vein endothelial cells (HUVECs) with VEGF analogs, we show that activation of VEGFR-1 or VEGFR-2 or both induced a rapid and transient translocation of endothelial P-selectin and neutrophil adhesion to activated ECs. The effects mediated by VEGF-A(165) and VEGF-A(121) (VEGFR-1/VEGFR-2 agonists) were blocked by a selective VEGFR-2 inhibitor, SU1498. VEGF-A(165) was twice as potent as VEGF-A(121), which can be explained by the binding capacity of VEGF-A(165) to its coreceptor neuropilin-1 (NRP-1). Indeed, treatment with NRP-1 antagonist (GST-Ex7) reduced the effect of VEGF-A(165) to the levels observed upon stimulation with VEGF-A(121). Finally, the use of selective PAF receptor antagonists reduced VEGF-A(165)-mediated P-selectin translocation. Together, these data show that maximal P-selectin translocation and subsequent neutrophil adhesion was mediated by VEGF-A(165) on the activation of VEGFR-2/NRP-1 complex and required PAF synthesis.

Cell Adhesion↗

PubMed2004

Effect of chronic exercise and Angiotensin-converting enzyme inhibition on rodent thoracic aorta.

Vascular reactivity can be modulated by local physical factors as well as pharmacologic manipulations. The aim of this study was to evaluate the effects of chronic exercise (EX) with or without the ACEI captopril (CAP) on vascular reactivity. Sixty-four Sprague-Dawley male rats were randomized into 4 groups (n = 16): group 1, control; group 2, captopril; group 3, exercise; and group 4, exercise and captopril. After 10 weeks of treatment, rats were killed, and their thoracic aortas harvested. Vascular reactivity was studied in an organ chamber (n = 12). Aortic endothelium constitutive nitric oxyde synthase (NOS3) expression was determined by Western blot analysis (n = 4). Endothelial-dependent relaxation was increased in both CAP and EX rats relative to the control group. Maximal aortic relaxations were enhanced in the CAP group, and potencies of these mediators were enhanced in the EX group (P < 0.05 versus control). Combined treatment did not result in a synergistic effect. NOS3 relative expressions were: group 1, 100%; group 2, 241%; group 3, 64%; and group 4, 108%. Exercise enhanced both potencies and efficacies of the mediators studied, whereas CAP increased mainly their efficacies. NOS3 protein expression was up-regulated in CAP-treated rats but not in exercised rats. These findings suggest different mechanisms for the observed increased vascular reactivity.

Acetylcholine↗

PubMed2004

Prevention of in-stent restenosis via reduction of thrombo-inflammatory reactions with recombinant P-selectin glycoprotein ligand-1.

The binding of leukocyte P-selectin glycoprotein ligand-1 (PSGL-1) to platelet P-selectin is central to post-angioplasty restenosis. Although intracoronary stents limit the mechanical component of restenosis, they cause marked thrombo-inflammation and neointimal proliferation leading to greater late luminal loss. We sought to demonstrate that P-selectin antagonism, using recombinant PSGL-1 (rPSGL-Ig), is effective in reducing platelet-leukocyte reactions and in-stent restenosis in double-injured porcine coronary arteries. Two weeks after initial injury by angioplasty to the coronary arteries, stents were implanted at the injury-induced lesion site, 15 min after an i.v. bolus administration of a vehicle or rPSGL-Ig (1 mg/kg). Four weeks later, adhesion of (51)Cr-platelets and (111)In-neutrophils and histomorphometric analyses were performed. In-stent residual lumen was almost 3 fold larger in rPSGL-Ig-treated arteries (3.1 +/- 0.4 mm(2)) as compared to control (1.1 +/- 0.2 mm(2)), which correspond to 64% vascular stenosis in control with no change in rPSGL-Ig animals. For a similar injury score, in-stent neointima was significantly reduced by 30 to 40% in the rPSGL-Ig group and quantitative coronary angiography showed a significant 35% reduction in late lumen loss. These effects of rPSGL-Ig were associated with a respective 70% and 53% reduction in platelet and neutrophil adhesion. In conclusion, pretreatment with rPSGL-Ig reduces thrombo-inflammatory responses, neointimal proliferation, and in-stent restenosis. P-selectin antagonism offers a promising therapy to improve clinical outcomes of coronary stenting.

Angioplasty↗

PubMed2004

Percutaneous endoluminal arterial cryoenergy improves vascular remodelling after angioplasty.

This study aimed to investigate the effect of percutaneous endoluminal arterial cryoenergy immediately after balloon angioplasty on vascular remodeling. Restenosis, the main complication after coronary artery angioplasty, is a complex phenomenon in which vascular remodeling plays a prominent role. Observations of reduced scarring in freeze-induced wounds suggest potential value for cryoenergy in the prevention of restenosis. Juvenile swine underwent a first oversized balloon injury in both carotid arteries (CA) (3 injury sites/artery) and a second injury at day 14. At that time, one CA was randomly assigned to endoluminal cryoenergy of the sequential segments (proximal, medial, distal) at -15 degrees C, -30 degrees C, and -50 degrees C for 120 sec, and the other CA was used as control. Animals were sacrificed 28 days after the second procedure. Compared with intact reference segments, angioplasty reduced both the luminal (LA) and the external elastic lamina (EEL) areas from 6.66+/-0.59 to 3.13+/-0.54 mm(2) (p<0.05) and from 8.81+/-0.81 to 6.48+/-0.52 mm(2) (p<0.05), respectively. Cryoenergy, at the temperature with maximal benefits (-50 degrees C), caused a temperature-related protection, as the LA was maintained (6.79+/-0.89 versus 7.18+/-0.78 mm(2) for reference) and the EEL area increased from 9.12+/-0.78 to 12.98+/-1.07 mm(2), p<0.05. Moreover, cryoenergy increased the density of collagen III (p<0.05) which correlated with the maintenance of the LA (r=0.8045, p<0.009). Cryoenergy prevents late luminal loss after double-injury angioplasty by improving vascular remodeling, and is an interesting new therapeutic approach for the prevention of restenosis after angioplasty. The increased synthesis of collagen III appears to be involved in this phenomenon and could be a potential method of stabilizing the vulnerable plaque.

Angioplasty, Balloon↗

PubMed2003

Sphingosine 1-phosphate effect on endothelial cell PAF synthesis: role in cellular migration.

Sphingosine 1-phosphate (S1P) and vascular endothelial growth factor (VEGF) are two inflammatory mediators capable of promoting endothelial cell (EC) migration and angiogenesis. As VEGF inflammatory effect is mediated by the synthesis of endothelial platelet-activating factor (PAF) which is also contributing to VEGF chemotactic activity, we wanted to assess if S1P can trigger PAF synthesis in EC and if S1P-induced migration is PAF-dependent. Treatment of bovine aortic EC (BAEC) with S1P (10(-10)-10(-6) M) increased dose- and time-dependently the synthesis of PAF by up to 3.3-fold above the basal level, with a maximal amount of PAF detected at 20 min post-stimulation. This biological response was attenuated by inhibiting p38 mitogen-activated protein kinase (MAPK), cytosolic or secreted phospholipase A(2) (cPLA(2), sPLA(2)) activity, suggesting that p38 MAPK activation by S1P promotes the conversion of membrane phospholipids into PAF through the combined activation of cPLA(2) and sPLA(2). Interestingly, pretreatment of BAEC with extracellular PAF receptor antagonists (BN52021, 10(-5) M and CV3988, 10(-6) M) reduced by up to 42% the cellular migration induced by S1P (10(-6) M). These data demonstrate the capacity of S1P to induce PAF synthesis, which contributes in part to S1P chemotactic activity.

Animals↗

PubMed2003

Specific contribution of estrogen receptors on mitogen-activated protein kinase pathways and vascular cell activation.

Randomized clinical trials have not provided conclusive data that hormone replacement therapy confers cardioprotection against coronary artery disease in postmenopausal women. However, other studies have shown that estrogens can induce beneficial effects on the vasculature. Nevertheless, the specific contribution of estrogen receptors (ERs) alpha and beta on vascular cells is not well characterized. Therefore, we used an antisense gene therapy approach to investigate the contribution of ERalpha and ERbeta on p38 and p42/44 mitogen-activated protein kinase (MAPK) activation and on vascular cell responsiveness. Treatment of porcine smooth muscle cells (PSMCs) with platelet-derived growth factor-BB induced p38 and p42/44 MAPK activation and their migration and proliferation. These effects were prevented by pretreatment with 17beta-estradiol (17betaE). The inhibitory effects of 17betaE on PSMCs were abrogated by the downregulation of ERbeta protein expression with selective ERbeta mRNA antisense oligomers, whereas the downregulation of ERalpha had no effect. However, treatment of porcine aortic endothelial cells with 17betaE promoted p38 and p42/44 MAPK phosphorylation and their migration and proliferation. These effects were ERalpha dependent, as defined by antisense gene therapy. These results suggest that in PSMCs, 17betaE reduces p42/44 and p38 MAPK activity through ERbeta stimulation, whereas in contrast, in porcine aortic endothelial cells, 17betaE induces p42/44 and p38 MAPK through ERalpha activation. 17betaE may contribute to the vascular healing process and to the prevention of restenosis by improving reendothelialization through ERalpha activation and by decreasing smooth muscle cell migration and proliferation through ERbeta stimulation.

Animals↗

PubMed2003

Lower incidence of thrombus formation with cryoenergy versus radiofrequency catheter ablation.

BACKGROUND: Radiofrequency (RF) catheter ablation is limited by thromboembolic complications. The objective of this study was to compare the incidence and characteristics of thrombi complicating RF and cryoenergy ablation, a novel technology for the catheter-based treatment of arrhythmias. METHODS AND RESULTS: Ablation lesions (n=197) were performed in 22 mongrel dogs at right atrial, right ventricular, and left ventricular sites preselected by a randomized factorial design devised to compare RF ablation with cryocatheter configurations of varying sizes (7F and 9F), cooling rates (-1 degrees C/s, -5 degrees C/s, and -20 degrees C/s) and target temperatures (-55 degrees C and -75 degrees C). Animals were pretreated with acetylsalicylic acid and received intraprocedural intravenous unfractionated heparin. Seven days after ablation, the incidence of thrombus formation was significantly higher with RF than with cryoablation (75.8% versus 30.1%, P=0.0005). In a multiple regression model, RF energy remained an independent predictor of thrombus formation compared with cryoenergy (OR, 5.6; 95% CI, 1.7, 18.1; P=0.0042). Thrombus volume was also significantly greater with RF than with cryoablation (median, 2.8 versus 0.0 mm3; P<0.0001). More voluminous thrombi were associated with larger RF lesions, but cryolesion dimensions were not predictive of thrombus size. CONCLUSIONS: RF energy is significantly more thrombogenic than cryoenergy, with a higher incidence of thrombus formation and larger thrombus volumes. The extent of hyperthermic tissue injury is positively correlated with thrombus bulk, whereas cryoenergy lesion size does not predict thrombus volume, most likely reflecting intact tissue ultrastructure with endothelial cell preservation.

Animals↗

PubMed2003

Effects of acute rejection on L-arginine/iNOS pathway in canine heart transplantation.

BACKGROUND: The inflammatory process resulting from ischemia-reperfusion and acute rejection is a strong modulator of the endothelial nitric oxide synthase expression of both constitutive and inducible isoforms. OBJECTIVE: To assess the expression of the endothelial constitutive nitric oxide synthase (ecNOS) and inducible nitric oxide synthase (iNOS) activity in conductance coronary arteries after reperfusion and acute rejection in the canine heart transplantation setting. METHODS: Expression of ecNOS and iNOS was evaluated in two groups of mongrel dogs (n=7) that underwent heterotopic heart transplantation without immunosuppression. The first group was studied after 24 h of reperfusion and the second after five days of acute untreated rejection. A third group (n=7) consisting of normal unoperated dogs was used as control. Functional vascular status of iNOS isoforms was studied in organ chambers, and tissue enzyme expression by histological and immunohistochemical studies. RESULTS: At harvest, vonWillebrand factor was present on the coronary endothelium of all groups. Both transplanted groups displayed iNOS and ecNOS expression by immunohistochemical study. The control group only displayed ecNOS expression. L-arginine induced endothelium-dependent relaxations in group 1 and group 2 but not in the control group. This was inhibited by the iNOS inhibitor aminoguanidine. Endothelium-independent contractility and relaxation were unaffected. CONCLUSIONS: In this experimental setting, a specific endothelial expression of iNOS was observed early on after acute rejection. The functional aspect of this endothelial iNOS expression was reversible with aminoguanidine.

Animals↗