Biomedical subjects

Jacques Bonnet

Publications and source records attributed to Jacques Bonnet.

29 records · Page 2Linked to original sources

PubMed2003

The -308 G/A tumor necrosis factor-alpha gene dimorphism: a risk factor for unstable angina.

Since the inflammatory cytokine tumor necrosis factor-alpha (TNF-alpha) may play a major role in the pathophysiology of acute coronary syndromes, 299 consecutive male patients hospitalized for coronary artery disease (i.e., lumen lost > or = 50%) were genotyped for the functional -308G/A TNF-alpha polymorphism using restriction fragment length polymorphism method, in order to evaluate its potential association with the risk of unstable angina and/or myocardial infarction. A higher frequency of carriers of the A allele was observed in patients with unstable angina (n = 58) when compared to control patients with stable angina (n = 95) (39.66% vs. 23.16% respectively, p = 0.029, odds ratio = 2.2) but not in patients with myocardial infarction (n = 146) (23.97% vs. 23.16%, p = NS). Furthermore, we evidenced an interaction of the polymorphism studied with body mass index in patients with unstable angina. Thus, when stratified analysis was performed, results in patients with a body mass index < or = 27 showed a more striking association between A allele carriage frequency and unstable angina (p = 0.012, odds ratio = 3.0). These results suggest the crucial role of TNF-alpha in the mechanisms responsible for unstable angina in accordance with the concept of vulnerable plaque. On the other hand, mechanisms controlling myocardial infarction appear more complex and heterogeneous.

Aged↗

PubMed2002

The radioprotective effect of the 24 kDa FGF-2 isoform in HeLa cells is related to an increased expression and activity of the DNA dependent protein kinase (DNA-PK) catalytic subunit.

We previously reported that overexpression of the 24 kDa basic fibroblast factor (or FGF-2) isoform provides protection from the cytotoxic effect of ionizing radiation (IR). DNA double-strand breaks (DSB), the IR-induced lethal lesions, are mainly repaired in human cells by non-homologous end joining system (NHEJ). NHEJ reaction is dependent on the DNA-PK holoenzyme (composed of a regulatory sub-unit, Ku, and a catalytic sub-unit, DNA-PKcs) that assembles at sites of DNA damage. We demonstrated here that the activity of DNA-PK was increased by twofold in two independent radioresistant cell lines, HeLa 3A and CAPAN A3, over expressing the 24 kDa FGF-2. This increase was associated with an overexpression of the DNA-PKcs without modification of Ku expression or activity. This overexpression was due to an up-regulation of the DNA-PKcs gene transcription by the 24 kDa FGF-2 isoform. Finally, HeLa 3A cells exhibited the hallmarks of phenotypic changes associated with the overexpression of an active DNA-PKcs. Indeed, a faster repair rate of DSB and sensitization to IR by wortmannin was observed in these cells. Our results represent the characterization of a new mechanism of control of DNA repair and radioresistance in human tumor cells dependent on the overproduction of the 24 kDa FGF-2 isoform.

Androstadienes↗

PubMed2002

RhoB controls the 24 kDa FGF-2-induced radioresistance in HeLa cells by preventing post-mitotic cell death.

Farnesylated Ras oncoprotein induces a cellular resistance to ionizing radiation that can be reversed by farnesyltransferase inhibitors (FTI). We previously demonstrated that, expression of the 24 kDa FGF2 isoform in wild type ras bearing HeLa cells, induced radioresistance which was also reversed by FTI. We tested the hypothesis that wild type Ras or RhoB, which has been proposed as a potential FTI target, could control the FGF-2-induced radioresistance mechanisms. For this, we expressed inducible dominant negative forms of Ras (RasN17) and Rho (RhoBN19) in 24 kDa FGF2 transfected HeLa cells and analysed their survival after irradiation. While no cell survival modification was observed after RasN17 induction, the expression of RhoBN19 induced a radiosensitization of FGF2 radioresistant HeLa cells in the same range as the one observed after a 48 h treatment with the specific FTI, R115777. Moreover, we showed that activated RhoB but not RhoA induced radioresistance in NIH3T3 cells. The radiosensitizer effect of RhoBN19 expression was due to the induction of the radiation induced post-mitotic cell death. Taken together, these data demonstrate that 24 kDa FGF-2-induced radioresistance is controlled by Rho pathways and suggest that RhoB should be a major determinant in cellular resistance to ionizing radiation.

Alkyl and Aryl Transferases↗

PubMed2002

Farnesyltransferase inhibitor, R115777, reverses the resistance of human glioma cell lines to ionizing radiation.

We investigated for the first time the ability of farnesyltransferase inhibitors (FTI) to radiosensitize human glioma. For this, human glioma cell lines were treated with the specific FTI, R115777, 48 hr prior to a 2Gy irradiation. The treatment with R115777 decreased by 45% the SF2 value of the more radioresistant glioma cell lines (SF763 and U87) without any significant effect on the radioresistance of the radiosensitive ones (SF767 and U251-MG). This radiosensitizer effect was due to the induction of post-mitotic necrotic cell death. We then tested the hypothesis that wild-type Ras or RhoB, which has been proposed as potential FTI target, could control the glioma radioresistance. For this, we expressed inducible dominant negative forms of Ras (RasN17) and RhoB (RhoBN19) in radioresistant U87 glioma cell line and analyzed the survival after irradiation of the obtained clones. While blocking Ras pathways by expression of RasN17 did not affect the SF2 value of the U87 glioma cell line, the expression of RhoBN19 dramatically reduced the cell survival after irradiation of these cells. Taken together, these data demonstrated that RhoB, but not Ras, is implicated in glioma radioresistance. Furthermore, the R115777 differential radiosensitizer effect underlines the potential therapeutic interest of using this drug as a radiosensitizer of human glioma.

Alkyl and Aryl Transferases↗

PubMed2002

Vitronectin is up-regulated after vascular injury and vitronectin blockade prevents neointima formation.

OBJECTIVE: Smooth muscle cell (SMC) migration involves interactions with extracellular matrix (ECM) and is an important process in response to arterial wall injury. We investigated the expression and the functional role of vitronectin (VN) in the response after vascular injury. METHODS: VN and alpha v beta 3/beta 5 integrin expressions were investigated after balloon carotid injury of Sprague-Dawley rats. Adventitial delivery of blocking antibodies to VN, alpha v beta 5 and beta 3 integrins were performed to assess their roles in neointima formation. In vitro, migration assays were carried out on human SMC. RESULTS: Immunohistochemistry and in situ hybridization for VN showed an upregulation of VN during the early time points of intima formation. alpha v beta 3/beta 5 integrins expression correlated with VN expression. After 7 days, blocking antibodies to VN, alpha v beta 5 and beta 3 induced a significant decrease on intimal area associated with a decrease in intimal cell counts. A slight decrease in intimal cell proliferation without any effect on apoptosis was observed after VN blockade. In vitro, migrating SMC strongly expressed VN after injury and neutralizing anti-VN antibody inhibited SMC migration. Blocking experiment with anti-alpha v beta 5 and -alpha v beta 3 integrin antibodies showed that not only VN-alpha v beta 3 but also VN-alpha v beta 5 interactions are required for SMC migration. CONCLUSION: This study characterizes the VN-ECM interaction in SMC and supports the role of VN in mediating SMC migration and neointimal formation in response to injury.

Adult↗

PubMed2002

Mycophenolic acid antagonizes the activation of cultured human mesangial cells.

BACKGROUND: Activation of mesangial cells is observed in several forms of chronic renal disease, and in culture conditions upon stimulation by fetal calf serum (FCS), or agonists such as transforming growth factor beta (TGF-beta). Mycophenolate mofetil (MMF), the precursor of mycophenolic acid (MPA), is currently used in organ transplantation and has been shown to be protective in clinical and experimental glomerulonephritis. This study assessed the effects of MPA on markers of human mesangial cells (HMC) activation. METHODS: Primary cultures of HMC and of an immortalized HMC clone (IP15 cells characterized in this report) were stimulated either by FCS or by TGF-beta, and treated by MPA at clinically relevant concentrations (1 to 10 micromol/L) for 24 hours to 14 days. HMC proliferation, smooth muscle alpha-actin (SMA), collagen type I alpha-1 chain (coll I) and fibronectin synthesis were used as markers of HMC phenotypic activation. RESULTS: Exposure of HMC to MPA inhibited proliferation induced by FCS without cytotoxicity. MPA counteracted the stimulatory effects of FCS and TGF-beta on coll I mRNA and protein and fibronectin protein. SMA expression was increased upon exposure to MPA, without cell hypertrophy. CONCLUSION: Treatment of cultured HMC with MPA inhibited mesangial cell proliferation and matrix production induced by stimulation with either FCS or TGF-beta. Such mechanisms may contribute to the favorable effects of treatment using mycophenolate mofetil in chronic fibrotic kidney diseases, including chronic allograft rejection.

Actins↗

PubMed1996

Significance of "Strands" on Mitral Mechanical Prostheses During Late Follow-Up After Surgery.

The presence of "strands" on mitral mechanical prostheses (MMP) has been described, although their significance has yet to be established. The aim of this study was to determine the incidence and clinical implications of "strands" on MMP in late follow-up by a retrospective analysis of 320 consecutive patients who had undergone a transesophageal echocardiographic (TEE) examination under standardized conditions 7 +/- 6 years after mitral surgery. Twenty patients (6.25%) with "strands," defined as highly mobile linear echogenic densities, were identified. This group was compared with a control group of 38 patients, matched for age, sex, and interval between surgery and TEE study, selected at random from this population. Patients with MMP dysfunction were excluded. Type of prosthesis, echographic characteristics (left atrial diameter, spontaneous echo contrast, ejection fraction), and anticoagulant status were not found to bear any relationship to the presence of strands. However, the prevalence of previous embolic events was significantly higher in the "strand" group (10/20 [50%]) than in the control group (7/38 [18.4%]) (P < 0.05). The "strand" group also contained more patients with a prior history of mitral prosthesis thrombosis (7/20 [35%] vs 1/30 [2.6%]; P < 0.05). However, long-term follow-up (1-4 years) was uneventful. These results suggest that: (1) in late follow-up, strands are rare in patients with MMP (6%); and (2) strands were related to previous thromboembolic episodes. (ECHOCARDIOGRAPHY, Volume 13, May 1996)

Journal Article↗

PubMed1996

Relationship Between Intravascular Hemolysis and Bright Sparkling Echoes Detected by TEE in the Vicinity of Mechanical Mitral Prosthesis.

The significance of abnormal bright and sparkling echoes in patients with mechanical mitral prosthetic valves (MMPV) has yet to be established. In the present study, the incidence of this phenomenon and its relationship with hemolysis was evaluated. Thirty-five consecutive patients with MMPV, each examined by transesophageal echocardiography (TEE), were divided into four groups: (1) no bright echoes (n = 11 patients); (2) minor echoes (+) (n = 11 patients); (3) moderate echoes (++) (n = 7 patients); and (4) numerous echoes (+++) (n = 6 patients). Hemolysis was evaluated from assays of serum haptoglobin, serum lactic dehydrogenase (LDH) and hydrobutyric dehydrogenase (HDH), plasma hemoglobin, indirect bilirubin, and LDH1 and LDH2 isoenzymes. Serum haptoglobin was significantly lower in the patients with bright echoes (0.17 vs 0.63; P < 0.05). In patients with (++) and (+++) bright echoes, the plasma hemoglobin levels and indirect bilirubin levels were significantly higher than the levels found in those patients with minor echoes or with no echoes. These results suggest that bright echoes in patients with MMPV are related to intravascular hemolysis, and the more intense the echo the more severe the hemolysis. Furthermore, there was a higher incidence of bright echoes in the patients with bileaflet prosthetic valves than in those fitted with the Björk valve (84.6% vs 22%). (ECHOCARDIOGRAPHY, Volume 13, July 1996)

Journal Article↗

PubMedDate not supplied

Early activation of internal medial smooth muscle cells in the rabbit aorta after mechanical injury: relationship with intimal thickening and pharmacological applications.

1. Smooth muscle cells (SMC) participate in both inflammatory and dedifferentiation processes during atherosclerosis, as well as during mechanical injury following angioplasty. In the latter, we studied medial SMC differentiation and inflammation processes implicated early after de-endothelialization in relation to mechanical stresses. We hypothesized that activation of a subpopulation of SMC within the media plays a crucial role in the early phase of neointimal formation. 2. For this purpose, we used a rabbit model of balloon injury to study activation and differentiation of medial SMC in the early time after denudation and just before neointima thickening. Inflammation was evaluated by the expression of vascular cell adhesion molecule (VCAM)-1, integrin alpha4beta1 and nuclear factor (NF)-kB. Myosin isoforms and 2P1A2 antigen, a membrane protein expressed by rabbit dedifferentiated SMC, were used as markers of differentiation. 3. On day 2 after de-endothelialization, VCAM-1, alpha4beta1 and NF-kB were coexpressed by a well-defined subpopulation of SMC of the internal part of the media, in the vicinity of the blood stream. At the same time, the majority of SMC throughout the media expressed non-muscle myosin heavy chain-B (nm-MHC-B) and 2P1A2 antigen. On day 7, when intimal thickening appeared, SMC of the media were no longer activated, whereas some intimal SMC expressed the activation markers. Thus, after de-endothelialization, early dedifferentiation occurs in most of the medial SMC, whereas activation concerned only a subpopulation of SMC located in the internal media. Using the T-type voltage-operated calcium channel blocker mibefradil (0.1-1 micromol/L) in SMC culture, we showed that this agent exhibited an antiproliferative effect in a dose-dependent manner only on undifferentiated cells. 4. In conclusion, the results suggest that the activated SMC represent cells that are potentially able to migrate and participate in the intimal thickening process. Thus, the medial SMC inflammatory process, without any contribution of inflammatory cells, may represent a major mechanism underlying the development of intimal thickening following mechanical stress. In humans, inhibition of T-type calcium channels may be a tool to prevent the early proliferation step leading to neointimal formation.

Animals↗

PubMedDate not supplied

Validation of a new method of detecting peripheral artery disease by determination of ankle-brachial index using an automatic blood pressure device.

Peripheral artery disease (PAD) is a predictor of total and cardiovascular mortality; its most valuable simple index is the ankle-brachial index (ABI). The present study was designed to assess whether a commercially available automatic device could be used to determine ABI in comparison with the classical Doppler method. The ABI was defined as the ratio of systolic blood pressure at each ankle to the maximal brachial systolic pressure, a pathological index being defined for a ratio <0.90. The ABI were calculated in 219 consecutive patients (aged 55 +/-19 years) with systolic blood pressure measured either by using a mercury sphygmo-manometer and a continuous-wave Doppler probe or an automatic manometer Omron M4. This device has been validated for measurements in upper limbs, and so the authors undertook validation in the lower limbs versus intraarterial measurements. There was an excellent correlation between intraarterial measurements and automatic readings in the range of 70-220 mm Hg, r=0.99, p<0.001. The systolic pressures measured in upper limbs correlated well in the right (r=0.87, p<0.001) and the left (r=0.89, p<0.001) upper limbs; and in the left (r=0.72, p<0.001) and the right (r=0.68, p<0.001) lower limbs. Correlations between ABI in both methods were good in the left (r=0.66, p<0.001) and the right (r=0.61, p<0.001) lower limbs. The sensitivity (76%), specificity (95%), positive predictive value (86%), negative predictive value (90%), and global accuracy (89%) of a pathological automatic index to predict an abnormal Doppler index were good. The use of a simple, automatic blood pressure device to determine ABI appears feasible, easy, and precise. It would provide a practical tool for physicians not trained in Doppler to detect PAD.

Adult↗

PubMedDate not supplied

Quantification of the expression of multidrug resistance-related genes in human tumour cell lines grown with free doxorubicin or doxorubicin encapsulated in polyisohexylcyanoacrylate nanospheres.

Doxorubicin (dox) encapsulated in polyisohexylcyanoacrylate nanospheres (PIHCA-dox) can circumvent P-glycoprotein-mediated multidrug resistance (MDR). In order to investigate whether this drug formulation is able to select MDR cells in culture in the same way as free doxorubicin does, two human tumour cell lines, K562 and MCF7, were grown with increasing concentrations of either free dox or PIHCA-dox. For both drug formulations and for each selection level, the cell lines were more resistant to free dox than to PIHCA-dox. The MCF7 sublines selected with PIHCA-dox exhibited a higher level of resistance to both doxorubicin formulations than those selected with free doxorubicin. Different levels of overexpression of several genes involved in drug resistance (MDR1, MRP1, BCRP and TOP2alpha) occurred in the resistant variants. MDR1 gene overexpression was consistently higher in free dox-selected cells than in PIHCA-dox-selected cells, while this was the reverse for the BCRP gene. Overexpression of the MRP1 and TOP2alpha genes was also observed in the selected variants. Our results show that several mechanisms may be involved in the acquisition of drug resistance and that drug encapsulation markedly alters or delays these processes.

ATP Binding Cassette Transporter, Subfamily G, Mem↗