PubMed Health⌕ Search

Biomedical subjects

F Bayard

Publications and source records attributed to F Bayard.

At least 19 recordsLinked to original sources
PubMed2006

IRES-dependent regulation of FGF-2 mRNA translation in pathophysiological conditions in the mouse.

The mRNA coding for FGF-2 (fibroblast growth factor 2), a major angiogenic factor, is translated by an IRES (internal ribosome entry site)-dependent mechanism. We have studied the role of the IRES in the regulation of FGF-2 expression in vivo, under pathophysiological conditions, by creating transgenic mice lines expressing bioluminescent bicistronic transgenes. Analysis of FGF-2 IRES activity indicates strong tissue specificity in adult brain and testis, suggesting a role of the IRES in the activation of FGF-2 expression in testis maturation and brain function. We have explored translational control of FGF-2 mRNA under diabetic hyperglycaemic conditions, as FGF-2 is implied in diabetes-related vascular complications. FGF-2 IRES is specifically activated in the aorta wall in streptozotocin-induced diabetic mice, in correlation with increased expression of endogenous FGF-2. Thus, under hyperglycaemic conditions, where cap-dependent translation is blocked, IRES activation participates in FGF-2 overexpression, which is one of the keys of diabetes-linked atherosclerosis aggravation. IRES activation under such pathophysiological conditions may involve ITAFs (IRES trans-acting factors), such as p53 or hnRNP AI (heterogeneous nuclear ribonucleoprotein AI), recently identified as inhibitory or activatory ITAFs respectively for FGF-2 IRES.

Animals↗
PubMed2004

Role of fibroblast growth factor-2 isoforms in the effect of estradiol on endothelial cell migration and proliferation.

Both 17beta-estradiol (E2) and fibroblast growth factor-2 (FGF2) stimulate angiogenesis and endothelial cell migration and proliferation. The first goal of this study was to explore the potential link between this hormone and this growth factor. E2-stimulated angiogenesis in SC Matrigel plugs in Fgf2+/+ mice, but not in Fgf2-/- mice. Cell cultures from subcutaneous Matrigel plugs demonstrated that E2 increased both migration and proliferation in endothelial cells from Fgf2+/+ mice, but not from in Fgf2-/- mice. Several isoforms of fibroblast growth factor-2 (FGF2) are expressed: the low molecular weight 18-kDa protein (FGF2lmw) is secreted and activates tyrosine kinase receptors (FGFRs), whereas the high molecular weight (21 and 22 kDa) isoforms (FGF2hmw) remains intranuclear, but their role is mainly unknown. The second goal of this study was to explore the respective roles of FGF2 isoforms in the effects of E2. We thus generated mice deficient only in the FGF2lmw (Fgf2lmw-/-). E2 stimulated in vivo angiogenesis and in vitro migration in endothelial cells from Fgf2lmw-/- as it did in Fgf2+/+ mice. E2 increased FGF2hmw protein abundance in endothelial cell cultures from Fgf2+/+ and Fgf2lmw-/- mice. As shown using siRNA transfection, these effects were FGFR independent but involved FGF2-Interacting Factor, an intracellular FGF2hmw partner. This is the first report for a physiological role for the intracellular FGF2hmw found to mediate the effect of E2 on endothelial cell migration via an intracrine action.

Animals↗
PubMed2004

Estrogens and atherosclerosis.

Numerous epidemiological as well as experimental studies have suggested that estradiol (E2) prevents atherosclerosis development. However two controlled prospective and randomized studies in women using hormone replacement therapy (HRT) did not confirm this beneficial effect. We then decided to use mouse models of atherosclerosis to define the possible mechanisms involved and the reasons for the discrepancy. We have shown that, although serum cholesterol decreases, this influence on lipid metabolism is negligible. Surprisingly, E2 induces an inflammatory-immune response towards a T helper cell (Th1) profile with increasing interferon-gamma production that could destabilize atheromatous plaques, and could account for the increase in the frequency of cardiovascular events in women undergoing HRT. At the level of the endothelium, E2 induces an increase in nitric oxide (NO) biodisponibility, but this phenomenon does not concern the development of fatty streaks. Nevertheless, the atheroprotective effect is apparently mediated at the level of the endothelium by a mechanism that has still to be characterized in molecular terms. These new acquisitions constitute a basis for new pharmacological developments allowing the prevention of deleterious effects and preserving the beneficial ones.

Animals↗
PubMed2003

The atheroprotective effect of 17 beta-estradiol is not altered in P-selectin- or ICAM-1-deficient hypercholesterolemic mice.

The mechanisms that mediate the atheroprotective properties of estrogens remain obscure. In the present study, we evaluated the involvement of the adhesion molecule P-selectin, intercellular adhesion molecule (ICAM-1) and vascular cell adhesion molecule (VCAM-1) in the atheroprotective effect of estrogens in murine models evaluating early steps of atherosclerosis. First, we studied the effect of 17 beta-estradiol (E2) administration for 12 weeks on fatty streak constitution at the root aorta of ovariectomized female mice deficient in apolipoprotein E (apoE) alone or deficient in both apoE and either P-selectin or ICAM-1. Compared with respective placebo groups, E2 significantly prevented the development of fatty streak, to a similar extent in all three genotypes (-70.0% in apoE(-/-), -77.4% in apoE(-/-) P-selectin(-/-), and -77.1% in apoE(-/-) ICAM-1(-/-)). Second, the endothelial expression of VCAM-1 at the root aorta was assessed by immunohistochemistry in either placebo or E2-treated ovariectomized C57BL/6 female mice fed an atherogenic diet. Compared with placebo, E2 treatment resulted in a 31.8% decrease of VCAM-1 endothelial expression at this lesion-prone site (P=0.03). These results demonstrate that P-selectin and ICAM-1 are not involved in the atheroprotective effect of estrogens, and suggest that VCAM-1 could play a role in this process.

Animals↗
PubMed2002

Estradiol alters nitric oxide production in the mouse aorta through the alpha-, but not beta-, estrogen receptor.

Although estradiol (E(2)) has been recognized to exert several vasculoprotective effects in several species, its effects in mouse vasomotion are unknown, and consequently, so is the estrogen receptor subtype mediating these effects. We investigated the effect of E(2) (80 microg/kg/day for 15 days) on NO production in the thoracic aorta of ovariectomized C57Bl/6 mice compared with those given placebo. E(2) increased basal NO production. In contrast, the relaxation in response to ATP, to the calcium ionophore A23187, and to sodium nitroprusside was unaltered by E(2), whereas acetylcholine-elicited relaxation was decreased. The abundance of NO synthase I, II, and III immunoreactive proteins (using Western blot) in thoracic aorta homogenates was unchanged by E(2). To determine the estrogen receptor (ER) subtype involved in these effects, transgenic mice in which either the ERalpha or ERbeta has been disrupted were ovariectomized and treated, or not, with E(2). Basal NO production was increased and the sensitivity to acetylcholine decreased in ERbeta knockout mice in response to E(2), whereas this effect was abolished in ERalpha knockout mice. Finally, these effects of E(2) on vasomotion required long-term and/or in vivo exposure, as short-term incubation of aortic rings with 10 nmol/L E(2) in the isolated organ chamber did not elicit any vasoactive effects. In conclusion, this study demonstrates that ERalpha, but not ERbeta, mediates the beneficial effect of E(2) on basal NO production.

Adenosine Triphosphate↗
PubMed2002

The AF-1 activation-function of ERalpha may be dispensable to mediate the effect of estradiol on endothelial NO production in mice.

Two isoforms of estrogen receptor (ER) have been described: ERalpha and ERbeta. The initial gene targeting of ERalpha, consisting in the introduction of a Neo cassette in exon 1 [alphaERKO, hereafter called ERalpha-Neo KO (knockout)], was reported in 1993. More recently, another mouse deficient in ERalpha because of the deletion of exon 2 (ERalphaKO, hereafter called ERalpha-delta2 KO) was generated. In ovariectomized ERalpha-wild-type mice, estradiol (E(2)) increases uterine weight and basal production of endothelial nitric oxide (NO). Both of these effects are abolished in ERalpha-delta2 KO mice. In contrast, we show here that both of these effects of E(2) are partially (uterine weight) or totally (endothelial NO production) preserved in ERalpha-Neo KO. We also confirm the presence of two ERalpha mRNA splice variants in uterus and aorta from ERalpha-Neo KO mice. One of them encodes a chimeric ERalpha protein (ERalpha55), partially deleted in the A/B domain, that was detected in both uterus and aorta by Western blot analysis. The other ERalpha mRNA splice variant codes for an isoform deleted for the A/B domain (ERalpha46), which was detected in uterus of ERalpha-Neo KO, and wild-type mice. This protein isoform was not detected in aorta. The identification of these two N-terminal modified isoforms in uterus, and at least one of them in aorta, probably explains the persistence of the E(2) effects in ERalpha-Neo KO mice. Furthermore, ERalpha-Neo KO mice may help in the elucidation of the specific functions of full-length ERalpha (ERalpha66) and ERalpha46, both shown to be physiologically generated in vivo.

Alternative Splicing↗
PubMed2001

Supported metallocene catalysts by surface organometallic chemistry. Synthesis, characterization, and reactivity in ethylene polymerization of oxide-supported mono- and biscyclopentadienyl zirconium alkyl complexes: establishment of structure/reactivity relationships.

The reactions of CpZr(CH(3))(3), 1, and Cp(2)Zr(CH(3))(2), 2, with partially dehydroxylated silica, silica-alumina, and alumina surfaces have been carried out with careful identification of the resulting surface organometallic complexes in order to probe the relationship between catalyst structure and polymerization activity. The characterization of the supported complexes has been achieved in most cases by in situ infrared spectroscopy, surface microanalysis, qualitative and quantitative analysis of evolved gases during surface reactions with labeled surface, solid state (1)H and (13)C NMR using (13)C-enriched compounds, and EXAFS. 1 and 2 react with silica(500) and silica-alumina(500) by simple protonolysis of one Zr-Me bond by surface silanols with formation of a single well-defined neutral compound. In the case of silica-alumina, a fraction of the supported complexes exhibits some interactions with electronically unsaturated surface aluminum sites. 1 and 2 also react with the hydroxyl groups of gamma-alumina(500), leading to several surface structures. Correlation between EXAFS and (13)C NMR data suggests, in short, two main surface structures having different environments for the methyl group: [Al](3)-OZrCp(CH(3))(2) and [Al](2)-OZrCp(CH(3))(mu-CH(3))-[Al] for the monoCp series and [Al](2)-OZrCp(2)(CH(3)) and [Al]-OZrCp(2)(mu-CH(3))-[Al] for the bisCp series. Ethylene polymerization has been carried out with all the supported complexes under various reaction conditions. Silica-supported catalysts in the absence of any cocatalyst exhibited no activity whatsoever for ethylene polymerization. When the oxide contained Lewis acidic sites, the resulting surface species were active. The activity, although improved by the presence of additional cocatalysts, remained very low by comparison with that of the homogeneous metallocene systems. This trend has been interpreted on the basis of various possible parameters, including the (p-pi)-(d-pi) back-donation of surface oxygen atoms to the zirconium center.

Journal Article↗
PubMed2001

Estradiol accelerates reendothelialization in mouse carotid artery through estrogen receptor-alpha but not estrogen receptor-beta.

BACKGROUND: The atheroprotective effect of 17beta-estradiol (E(2)) has been suggested in women and clearly demonstrated in animals through both an effect on lipid metabolism and a direct effect on the cells of the arterial wall. It has been shown, for example, that E(2) promotes endothelium-dependent relaxation and accelerates reendothelialization in rats. Similar studies have been undertaken in mice to appreciate the molecular mechanism of this process. METHODS AND RESULTS: We report here a model of electric carotid injury adapted from that described by Carmeliet et al (1997) that allows us to precisely evaluate the reendothelialization process. We demonstrate that E(2) accelerates endothelial regeneration in castrated female wild-type mice. In ovariectomized transgenic mice in which either the estrogen receptor (ER)-alpha or ERbeta gene has been disrupted, E(2) accelerated reendothelialization in female ERbeta knockout mice, whereas this effect was abolished in female ERalpha knockout mice. CONCLUSIONS: This study demonstrates that ERalpha but not ERbeta mediates the beneficial effect of E(2) on reendothelialization and potentially the prevention of atherosclerosis.

Animals↗
PubMed2001

Alteration of plasmalemmal caveolae mimics endothelial dysfunction observed in atheromatous rabbit aorta.

OBJECTIVE: In endothelial cells, nitric oxide (NO) is produced by the endothelial isoform of nitric oxide synthase (eNOS), which is localized in the cholesterol-rich plasmalemmal microdomains involved in signal transduction, known as caveolae. The present study was undertaken to evaluate the effect of hypercholesterolemia and fatty streak formation on the endothelial caveolae and on endothelial function, and attempted to determine to what extent the caveolae were involved in endothelium-derived NO production. METHODS AND RESULTS: We first studied the effect of atheroma on endothelial NO production. Fatty streak infiltrated aorta of cholesterol-fed New Zealand White rabbits demonstrated an impairment of acetylcholine-induced relaxation and nearly normal calcium ionophore A23187-induced maximal relaxation. The abundance of caveolae in the endothelium covering the fatty streak, as well as their 'grape-like' clustering, appeared to be decreased. We therefore investigated the effect, on endothelial NO production, of the cholesterol-binding agents 2-hydroxypropyl-beta-cyclodextrin (hp-beta-CD) and filipin, known to alter caveolae structure and/or function. Treatment with either hp-beta-CD (2%) or filipin (4 microg/ml) did not affect contraction to phenylephrine or relaxant responses to A23187 or to the NO donor sodium nitroprusside. In contrast, both treatments impaired acetylcholine-induced relaxation. Cultured bovine aortic endothelial cells (BAEC) similarly treated with hp-beta-CD demonstrated a 50% decrease of total cellular cholesterol and a decreased abundance of caveolae as well as their 'grape-like' clustering. Cholesterol depletion decreased the bradykinin-induced transient peak of free intracellular calcium and subsequent receptor-stimulated NO production (assessed using reporter cells rich in soluble guanylyl cyclase), whereas that elicited by A23187 remained unaltered. CONCLUSION: Fatty streak deposit is associated with a decrease in caveolae 'transductosomes' abundance which appears to represent a novel mechanism of endothelial dysfunction.

2-Hydroxypropyl-beta-cyclodextrin↗
PubMed2001

Omapatrilat, a dual angiotensin-converting enzyme and neutral endopeptidase inhibitor, prevents fatty streak deposit in apolipoprotein E-deficient mice.

Angiotensin-converting enzyme (ACE) is mainly responsible for converting angiotensin I (AI) to angiotensin II (AII), and ACE inhibitors prevent atherosclerosis in animal models. Neutral endopeptidase 24.11 (NEP) degrades substance P, kinins and atrial natriuretic peptide (ANP), and aortic wall NEP activity was found to be increased in atherosclerosis. In the present study, we have evaluated the effect of candoxatril, a NEP inhibitor, and of omapatrilat, a dual ACE and NEP inhibitor, on the development of fatty streak in apolipoprotein E (apoE)-deficient mice. Groups of ten male apoE-deficient mice were given either placebo, candoxatril 50 mg/kg per day, or omapatrilat 10, or 100 mg/kg per day for 4 months. None of the treatments influenced body weight, serum total or HDL-cholesterol. Compared with the placebo, candoxatril did not protect the mice from fatty streak deposit. In contrast, omapatrilat dose dependently inhibited the constitution of fatty streak in apoE-deficient mice. The precise advantages of the dual ACE and NEP inhibition versus the inhibition of only ACE should now be considered in the prevention of atherosclerosis as well as in the occurrence of its complications.

Angiotensin-Converting Enzyme Inhibitors↗
PubMed2001

Involvement of interleukin-6 in atherosclerosis but not in the prevention of fatty streak formation by 17beta-estradiol in apolipoprotein E-deficient mice.

Interleukin-6 (IL-6) gene expressed in bone marrow-derived stromal cells and osteoblasts contributes to the state of mineralization and its control by estradiol may be involved in the development of post-menopausal osteoporosis. Since IL-6 is also expressed in the different cell populations of the arterial wall, the purpose of this study was to gain more insight into its involvement in the atherosclerotic process and the atheroprotective effect of estradiol by studying double deficient mice at the apolipoprotein E and IL-6 loci (IL-6(-/-)/E(-/-)). At 1 year of age, IL-6(-/-)/E(-/-) mice showed similar hypercholesterolemia to IL-6(+/+)/E(-/-) mice but presented significantly larger and more calcified lesions. In younger mice (sixteen weeks of age), no significant difference in fatty streaks could be detected in IL-6(+/+)/E(-/-), IL-6(+/-)/E(-/-) and IL-6(-/-)/E(-/-) mice on a normal chow diet. Estrogen supplementation at this age induced a decrease of fatty streak formation in all three genotypes. The combined data indicate that IL-6 expression is involved at the fibrous plaque stage of the atherosclerotic process but does not constitute a direct target for estradiol to prevent fatty streak formation.

Analysis of Variance↗
PubMed2001

Vasculoprotective effects of oestrogens.

1. The rationale for preclinical research on the atheroprotective effect of oestrogens is based on the epidemiological evidence that women are protected against the clinical complications of atherosclerosis until menopause. However, this protection, probably due to sex hormones, is progressively lost within the years following menopause. 2. In addition, numerous studies have clearly demonstrated the atheroprotective effect of oestrogens in all animal models. 3. In the present paper, we first summarize our understanding of the pathophysiology of atherosclerosis. We then focus on the recognized target of oestradiol (E2) in the vessel wall: the classical target, namely the endothelium, and a recently characterized target, namely cells of the inflammatory-immune system. Finally, we discuss how unknown mechanisms in atherosclerosis could be responsible for the absence of effect of hormone-replacement therapy in the Heart and Estrogen/ progestin Replacement Study (HERS).

Arteriosclerosis↗
PubMed2000

Detection of superoxide anion released extracellularly by endothelial cells using cytochrome c reduction, ESR, fluorescence and lucigenin-enhanced chemiluminescence techniques.

Endothelium produces oxygen-derived free radicals (nitric oxide, NO&z.rad;; superoxide anion, O(2)(*-)) which play a major role in physiology and pathology of the vessel wall. However, little is known about endothelium-derived O(2)(*-) production, particularly due to the difficulty in assessing O(2)(*-) when its production is low and to controversies recently raised about the use of lucigenin-enhanced chemiluminescence. We compared four techniques of O(2)(*-) assessment when its production is low. In the present study, we have compared ferricytochrome c reduction, electron spin resonance (ESR) spectroscopy using DMPO as spin trap, hydroethidine fluorescence, and lucigenin-enhanced chemiluminescence to assess O(2)(*-) production in cultured bovine aortic endothelial cells (BAEC). We focused our study on extracellular O(2)(*-) production because the specificity of the signal is provided by the use of superoxide dismutase, and this control cannot be obtained intracellularly. We found that the calcium ionophore A23187 dose-dependently stimulated O(2)(*-) production, with a good correlation between all four techniques. The signals evoked by postconfluent BAEC were increased 2- to 7-fold in comparison to just-confluent BAEC, according to the technique used. Ferricytochrome c 20 microm rather than at 100 microm appears more suitable to detect O(2)(*-). However, in the presence of electron donors such as NADH or NADPH, lucigenin-enhanced chemiluminescence generated high amounts of O(2)(*-). Thus, ferricytochrome c reduction, electron spin resonance (ESR), and hydroethidine fluorescence appear as adequate tools for the detection of extracellular endothelium-derived O(2)(*-) production, whereas lucigenin may be artifactual, even when a low concentration of lucigenin is employed.

Acridines↗
PubMed2000

IL-6 promoter is modulated by the 24 kDa FGF-2 isoform fused to the hormone binding domain of the oestrogen receptor.

Fusion proteins consisting of the 24 kDa nuclear form of basic fibroblast growth factor (FGF-2), associated with the hormone binding domain of oestrogen receptor (HBD), convey oestrogen inducibility to FGF-2. When stable HBD-FGF-2 HeLa cell lines were transiently transfected with an interleukin 6 (IL-6) construct, the IL-6 promoter activity was downregulated by the addition of oestradiol. Moreover, in these cell lines, the function of the FGF-2 nuclear localisation sequence was abolished by its fusion to HBD, while addition of oestradiol restored the location of the chimera to the nucleus.

Binding Sites↗