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Biomedical subjects

A Brunet

Publications and source records attributed to A Brunet.

At least 37 records · Page 2Linked to original sources
PubMed2000

Influence of SIN-1 on platelet Ca2+ handling in patients with suspected coronary artery disease: ex vivo and in vitro studies.

The 3-morpholinosydnonimine (SIN-1) generates both nitric oxide (NO) and superoxide anion (O2-). It elicits dose-dependent vasodilation in vivo, in spite of the opposite effects of its breakdown products on vascular tone and platelet aggregation. This study was designed to investigate the influence of intravenous SIN-1 injection on platelet Ca2+ handling in patients undergoing coronary angiography. SIN-1 administration reduced cytosolic [Ca2+] in unstimulated platelets by decreasing Ca2+ influx. It attenuated Ca2+ mobilization from internal stores evoked by thrombin or thapsigargin. In vitro studies were used as an approach to investigate how simultaneous productions of NO and O2- from SIN-1 modify thrombin- or thapsigargin-induced platelet Ca2+ mobilization. Superoxide dismutase, the O2- scavenger, enhanced the capacity of SIN-1 to inhibit Ca2+ mobilization but catalase had no effect. This suggests that the effects of SIN-1 on platelet Ca2+ handling resemble those of NO, but are modulated by simultaneous O2- release, independently of H2O2 formation.

Angina Pectoris↗
PubMed1999

Cell survival promoted by the Ras-MAPK signaling pathway by transcription-dependent and -independent mechanisms.

A mechanism by which the Ras-mitogen-activated protein kinase (MAPK) signaling pathway mediates growth factor-dependent cell survival was characterized. The MAPK-activated kinases, the Rsks, catalyzed the phosphorylation of the pro-apoptotic protein BAD at serine 112 both in vitro and in vivo. The Rsk-induced phosphorylation of BAD at serine 112 suppressed BAD-mediated apoptosis in neurons. Rsks also are known to phosphorylate the transcription factor CREB (cAMP response element-binding protein) at serine 133. Activated CREB promoted cell survival, and inhibition of CREB phosphorylation at serine 133 triggered apoptosis. These findings suggest that the MAPK signaling pathway promotes cell survival by a dual mechanism comprising the posttranslational modification and inactivation of a component of the cell death machinery and the increased transcription of pro-survival genes.

Animals↗
PubMed1999

Akt promotes cell survival by phosphorylating and inhibiting a Forkhead transcription factor.

Survival factors can suppress apoptosis in a transcription-independent manner by activating the serine/ threonine kinase Akt, which then phosphorylates and inactivates components of the apoptotic machinery, including BAD and Caspase 9. In this study, we demonstrate that Akt also regulates the activity of FKHRL1, a member of the Forkhead family of transcription factors. In the presence of survival factors, Akt phosphorylates FKHRL1, leading to FKHRL1's association with 14-3-3 proteins and FKHRL1's retention in the cytoplasm. Survival factor withdrawal leads to FKHRL1 dephosphorylation, nuclear translocation, and target gene activation. Within the nucleus, FKHRL1 triggers apoptosis most likely by inducing the expression of genes that are critical for cell death, such as the Fas ligand gene.

14-3-3 Proteins↗
PubMed1999

Nuclear translocation of p42/p44 mitogen-activated protein kinase is required for growth factor-induced gene expression and cell cycle entry.

Mitogen-activated protein kinase (MAPK) modules, composed of three protein kinases activated by successive phosphorylation, are involved in the signal transduction of a wide range of extracellular agents. In mammalian cells, mitogenic stimulation triggers the translocation of p42/p44MAPK from the cytoplasm to the nucleus, whereas the other protein kinases of the module remain cytosolic. Since MAPK has been shown to phosphorylate and activate nuclear targets, such as the transcription factor Elk1, it has been proposed, but not yet demonstrated, that MAPK nuclear translocation could represent a critical step in signal transduction. In this study, we sequestered p42/p44MAPK in the cytoplasm by the expression of a catalytically inactive form of cytoplasmic MAP kinase phosphatase (MKP-3/Pyst-1). Sequestering MAPK in the cytoplasm did not alter its activation or its ability to phosphorylate cytoplasmic substrates of MAPK (p90RSK1 or an engineered cytoplasmic form of Elk1). In contrast, prevention of MAPK nuclear translocation strongly inhibited Elk1-dependent gene transcription and the ability of cells to reinitiate DNA replication in response to growth factors. Thus the relocalization of MAPK to the nucleus appears to be an important regulatory step for mitogen-induced gene expression and cell cycle re-entry.

Animals↗
PubMed1999

Superoxide release from interleukin-1B-stimulated human vascular cells: in situ electrochemical measurement.

Release of superoxide anion by cultured vascular cells was investigated with the use of selective microelectrodes. Local concentration of superoxide anion (O2*-) was followed by differential pulse amperometry on a carbon microfiber at 0.1 V/SCE. The oxidation current allows O2*- detection in the 10(-8) M concentration range without interference of the other major oxygen species. Interleukin-1beta-stimulated O2*- release that progressively increased to reach local concentrations at the cell membrane level of 76 +/- 11 nm 40-60 min after stimulation in human cord vein endothelial cells, and 131 +/- 18 nm 1-2 h after stimulation in internal mammary artery smooth muscle cells. In the two types of cells, the O2*- oxidation signal was suppressed in the presence of superoxide dismutase. Spontaneous O2*-release from unstimulated cells was undetectable. These results demonstrate that selective microelectrodes allow direct and real-time monitoring of local O2*- released from vascular endothelial as well as from smooth muscle cells submitted to an inflammatory stimulus.

Cells, Cultured↗
PubMed1998

Growth factor-induced p42/p44 MAPK nuclear translocation and retention requires both MAPK activation and neosynthesis of nuclear anchoring proteins.

Mitogen-activated protein kinases (p42/p44 MAPK, also called Erk2 and Erk1) are key mediators of signal transduction from the cell surface to the nucleus. We have previously shown that the activation of p42/p44 MAPK required for transduction of mitogenic signaling is associated with a rapid nuclear translocation of these kinases. However, the means by which p42 and p44 MAPK translocate into the nucleus after cytoplasmic activation is still not understood and cannot simply be deduced from their protein sequences. In this study, we have demonstrated that activation of the p42/ p44 MAPK pathway was necessary and sufficient for triggering nuclear translocation of p42 and p44 MAPK. First, addition of the MEK inhibitor PD 98059, which blocks activation of the p42/p44 MAPK pathway, impedes the nuclear accumulation, whereas direct activation of the p42/p44 MAPK pathway by the chimera DeltaRaf-1:ER is sufficient to promote nuclear accumulation of p42/p44 MAPK. In addition, we have shown that this nuclear accumulation of p42/p44 MAPK required the neosynthesis of short-lived proteins. Indeed, inhibitors of protein synthesis abrogate nuclear accumulation in response to serum and accelerate p42/p44 MAPK nuclear efflux under conditions of persistent p42/p44 MAPK activation. In contrast, inhibition of targeted proteolysis by the proteasome synergistically potentiated p42/p44 MAPK nuclear localization by nonmitogenic agonists and markedly prolonged nuclear localization of p42/p44 MAPK after mitogenic stimulation. We therefore conclude that the MAPK nuclear translocation requires both activation of the p42/p44 MAPK module and neosynthesis of short-lived proteins that we postulate to be nuclear anchors.

Animals↗
PubMed1998

Inhibition of the mitogen-activated protein kinase pathway triggers B16 melanoma cell differentiation.

In B16 melanoma cells, mitogen-activated protein (MAP) kinases are activated during cAMP-induced melanogenesis (Englaro, W., Rezzonico, R., Durand-Clément, M., Lallemand, D., Ortonne, J. P., and Ballotti, R. (1995) J. Biol. Chem. 270, 24315-24320). To establish the role of the MAP kinases in melanogenesis, we studied the effects of a specific MAP kinase kinase (MEK) inhibitor PD 98059 on different melanogenic parameters. We showed that PD 98059 inhibits the activation of MAP kinase extracellular signal-regulated kinase 1 by cAMP, but does not impair the effects of cAMP either on the morphological differentiation, characterized by an increase in dendrite outgrowth, or on the up-regulation of tyrosinase that is the key enzyme in melanogenesis. On the contrary, PD 98059 promotes by itself cell dendricity and increases the tyrosinase amount and activity. Moreover, down-regulation of the MAP kinase pathway by PD 98059, or with dominant negative mutants of p21(ras) and MEK, triggers a stimulation of the tyrosinase promoter activity and enhances the effect of cAMP on this parameter. Conversely, activation of the MAP kinase pathway, using constitutive active mutants of p21(ras) and MEK, leads to an inhibition of basal and cAMP-induced tyrosinase gene transcription. These results demonstrate that the MAP kinase pathway activation is not required for cAMP-induced melanogenesis. Furthermore, the inhibition of this pathway induces B16 melanoma cell differentiation, while a sustained activation impairs the melanogenic effect of cAMP-elevating agents.

Animals↗
PubMed1998

Involvement of extracellular signal-regulated kinase module in HIV-mediated CD4 signals controlling activation of nuclear factor-kappa B and AP-1 transcription factors.

Although the molecular mechanisms by which the HIV-1 triggers either T cell activation, anergy, or apoptosis remain poorly understood, it is well established that the interaction of HIV-1 envelope glycoproteins with cell surface CD4 delivers signals to the target cell, resulting in activation of transcription factors such as NF-kappa B and AP-1. In this study, we report the first evidence indicating that kinases MEK-1 (MAP kinase/Erk kinase) and ERK-1 (extracellular signal-regulated kinase) act as intermediates in the cascade of events that regulate NF-kappa B and AP-1 activation upon HIV-1 binding to cell surface CD4. We found that CEM cells transfected with dominant negative forms of MEK-1 or ERK-1 do not display NF-kappa B activation after HIV-1 binding to CD4. In contrast, NF-kappa B activation was observed in these cells after PMA stimulation. Although the different cell lines studied expressed similar amounts of CD4 and p56(lck), HIV-1 replication and HIV-1-induced apoptosis were slightly delayed in cells expressing dominant negative forms of MEK-1 or ERK-1 compared with parental CEM cells and cells expressing a constitutively active mutant form of MEK-1 or wild-type ERK-1. In light of recently published data, we propose that a positive signal initiated following oligomerization of CD4 by the virus is likely to involve a recruitment of active forms of p56(lck), Raf-1, MEK-1, and ERK-1, before AP-1 and NF-kappa B activation.

Apoptosis↗
PubMed1998

High mobility group 1 (HMG1) protein in mouse preimplantation embryos.

High mobility group 1 protein (HMG1) has traditionally been considered a structural component of chromatin, possibly similar in function to histone H1. In fact, at the onset of Xenopus and Drosophila development, HMG1 appears to substitute for histone H1: HMG1 is abundant when histone H1 is absent after the midblastula transition histone H1 largely replaces HMG1. We show that in early mouse embryos the expression patterns of HMG1 and histone H1 are not complementary. Instead, HMG1 content increases after zygotic genome activation at the same time as histone H1. HMG1 does not remain associated to mitotic chromosomes either in embryos or somatic cells. These results argue against a shared structural role for HMG1 and histone H1 in mammalian chromatin.

Amino Acid Sequence↗
PubMed1998

MMPI scales for diagnosing acute and chronic PTSD in civilians. Minnesota Multiphasic Personality Inventory.

To develop new Minnesota Multiphasic Personality Inventory (MMPI) scales for diagnosing acute and chronic posttraumatic stress disorder (PTSD), 237 civilians with PTSD or panic disorder (controls) completed the MMPI-R. All 399 items were submitted to chi-square analysis to select those differentiating acute or chronic PTSD from controls. The analyses yielded an MMPI Acute PTSD scale (32 items) and a MMPI Chronic PTSD scale (41 items). Discriminating between acute PTSD and controls, the MMPI Acute PTSD scale had a hit rate of 83% and the MMPI Chronic PTSD scale produced a hit rate of 75% to 80%. Cross-validation produced similar hit rates. These scales scores were not substantially influenced by gender or types of traumatic events, and only the MMPI Acute PTSD scale seemed to not be sensitive to co-morbidity.

Acute Disease↗
PubMed1998

Inhibition by cholesterol oxides of NO release from human vascular endothelial cells.

Recent studies have demonstrated that, unlike cholesterol, cholesterol oxidized at position 7 can reduce the maximal endothelium-dependent relaxation of isolated rabbit aortas (Circulation. 1997;95:723-731). The aim of the current study was to determine whether cholesterol oxides reduce the release of nitric oxide (NO) from human umbilical vein endothelial cells (HUVECs). The amount of NO released by histamine-stimulated HUVECs was determined by differential pulse amperometry using a nickel porphyrin- and Nafion-coated carbon microfiber electrode. The effects of cholesterol (preserved from oxidation by butylated hydroxytoluene), 7-ketocholesterol, 7beta-hydroxycholesterol, 5alpha,6alpha-epoxycholesterol, 19-hydroxycholesterol (60 microg/mL), and alpha-lysophosphatidylcholine (10 microg/mL) were compared. Pretreatment of HUVECs with cholesterol, 5alpha,6alpha-epoxycholesterol, or 19-hydroxycholesterol did not alter histamine-activated NO production. In contrast, pretreatment with 7-ketocholesterol or 7beta-hydroxycholesterol significantly decreased NO release. The inhibitory effect of 7-ketocholesterol was time and dose dependent and was maintained in the presence of L-arginine. In the absence of serum, lysophosphatidylcholine also reduced NO production. In ionomycin-stimulated cells, pretreatment with 7-ketocholesterol did not inhibit NO release. These results demonstrate that cholesterol derivatives oxidized at the 7 position, the main products of low density lipoprotein oxidation, reduce histamine-activated NO release in HUVECs. Such an inhibitory effect of cholesterol oxides may account, at least in part, for the ability of oxidized low density lipoprotein to reduce the endothelium-dependent relaxation of arteries.

Arginine↗
PubMed1998

Lifetime exposure to traumatic events among a sample of city bus drivers.

Lifetime exposure to traumatic events was assessed retrospectively among a representative sample of city bus drivers (228 men and 54 women) from Montréal, Canada. Among them, 68.1% reported at least one exposure to a traumatic event of any type. Among the 68% exposed. 70.4% reported multiple traumatic exposures (M = 2.6, SD = 1.67), with ratings ranging from 0 to 12. This report underlines the fact that the prevalence of traumatic events is not yet well known. Epidemiological research should devote more effort to assess fully the lifetime prevalence of traumatic events and not only cases of PTSD.

Adult↗
PubMed1998

Relations of platelet Ca2+ handling and membrane microviscosity to vascular tone and restenosis after angioplasty in human coronary artery.

This study was designed to assess whether platelet Ca2+ handling or membrane microviscosity could be considered as indexes of vascular tone, or could help to predict an increased risk of restenosis after coronary angioplasty. Vascular tone was quantified in 21 patients with stable angina by the vasodilator response to sin-1 intracoronary injection in the reference coronary segment and by the importance of the acute recoil after angioplasty in the narrowed segment. The degree of restenosis was quantified by coronary angiography 6 months later. Individual values of relative sin-1-induced changes in the reference coronary diameter were positively correlated with cytosolic Ca2+ concentration in unstimulated platelets, irrespective of the extracellular Ca2+ concentration (p < 0.01). This relationship was also observed with the thrombin-evoked Ca2+ changes, measured in the absence of a Ca2+ influx (p = 0.01). No relationship was found between sin-1-induced coronary changes and membrane microviscosity evaluated by TMA-DPH and DPH anisotropies or platelet volume, or between degree of acute recoil and platelet characteristics. In conclusion, platelet Ca2+ reflects the vasodilating efficacy in response to sin-1, but cannot help to predict restenosis after coronary angioplasty.

Adult↗
PubMed1998

[Signal transduction from the membrane to the nucleus: variations on common themes].

During their life, cells are exposed to a wide variety of extracellular stimuli and have to develop appropriate biological responses. Signal transduction from the plasma membrane, which is in contact with the extracellular environment, to the nucleus, where gene expression is achieved, thus represents a fundamental process for the development and maintenance of life in organisms. Signalling pathways are extremely diverse and range from direct strategies, such as the steroid hormone receptor and JAK/STAT (signal transducers and activators of transcription) pathways, to multi-step strategies, such as the NF-kappa B (nuclear factor kappa B), PKA (protein kinase A) and Ras/MAPK (mitogen-activated protein kinase) pathways. In order to modulate gene expression, all these pathways must ultimately achieve nuclear localization. The mechanisms by which these varied signalling components cross the nuclear envelope are equally as diverse. However, despite the variety of the means used, cells have adopted several common themes for signal transduction, particularly interaction between proteins as a mean to transport the signal and phosphorylation as a post-translational modification carrying information. Finally, all signalling pathways have been conserved throughout evolution, inghlighting their advantage for cells. In mammals, proteins that participate in signal transmission represent a frequent target for mutations leading to tumor development. Unraveling signalling pathways thus represents an important step in the fight against cancer.

Cell Membrane↗
PubMed1997

The dual specificity mitogen-activated protein kinase phosphatase-1 and -2 are induced by the p42/p44MAPK cascade.

Mitogen-activated protein (MAP) kinase phosphatase-1 (MKP-1) and MKP-2 are two members of a recently described family of dual specificity phosphatases that are capable of dephosphorylating p42/p44MAPK. Overexpression of MKP-1 or MKP-2 inhibits MAP kinase-dependent intracellular signaling events and fibroblast proliferation. By using specific antibodies that recognize endogenous MKP-1 and MKP-2 in CCL39 cells, we show that MKP-1 and MKP-2 are not expressed in quiescent cells, but are rapidly induced following serum addition, with protein detectable as early as 30 min (MKP-1) or 60 min (MKP-2). Serum induction of MKP-1 and MKP-2 is sustained, with protein detectable up to 14 h after serum addition. Induction of MKP-1 and, to a lesser extent, MKP-2 temporally correlates with p42/p44MAPK inactivation. To analyze the contribution of the MAP kinase cascade to MKP-1 and MKP-2 induction, we examined CCL39 cells transformed with either v-ras or a constitutively active direct upstream activator of MAP kinase, mitogen-activated protein kinase kinase-1 (MKK-1; MKK-1(SD/SD) mutant). In both cell models, MKP-1 and MKP-2 are constitutively expressed, with MKP-2 being prevalent. In addition, in CCL39 cells expressing an estradiol-inducible deltaRaf-1::ER chimera, activation of Raf alone is sufficient to induce MKP-1 and MKP-2. The role of the MAP kinase cascade in MKP induction was highlighted by the MKK-1 inhibitor PD 098059, which blunted both the activation of p42/p44MAPK and the induction of MKP-1 and MKP-2. However, the MAP kinase cascade is not absolutely required for the induction of MKP-1, as this phosphatase, but not MKP-2, was induced to detectable levels by agents that stimulate protein kinases A and C. Thus, activation of the p42/p44MAPK cascade promotes the induction of MKP-1 and MKP-2, which may then attenuate p42/p44MAPK-dependent events in an inhibitory feedback loop.

Animals↗
PubMed1997

Identification of maternal transcripts that progressively disappear during the cleavage period of rabbit embryos.

In order to characterize the changes that occur in the population of maternally inherited transcripts before the transition from maternal to zygotic control of embryonic development (MZT) in mammals, we used rabbit embryos where zygotic transcription becomes necessary only after the fourth cleavage division, during the second day that follows fertilization. In the present work we have associated mRNA differential display and an RT-PCR based-method that allows amplification of the whole population of messengers to identify and characterize maternal transcripts which are degraded throughout this early period of development. While there is no major degradation of the polyA RNA population before MZT we identify 4 transcripts which progressively disappear up until the 8-16 cell stage. We also show that the degradation of one of these maternal messengers is controlled by zygotic transcription, which is not the case for the three others. This messenger shows homology with the human FGF9 gene and is potentially a good candidate to address the question of the molecular control of maternal to zygotic transition in early mammalian embryogenesis.

Animals↗
PubMed1997

Vinorelbine and ifosfamide for unresectable non-small cell lung cancer.

PURPOSE: The study assessed the efficacy of combination therapy with vinorelbine and ifosfamide in patients with unresectable non-small cell lung cancer. PATIENTS AND METHODS: Forty patients with non-small cell lung cancer whose tumour was unresectable by virtue of the extent of disease or severity of impairment of lung function and who were considered unsuitable for treatment with a cisplatin based treatment were entered onto the study. Thirty-four patients received two cycles of treatment and were considered to be evaluable for response. The treatment schedule consisted of vinorelbine (Navelbine, Pierre Fabre Medicament) 25 mg/m2 on days 1 and 8, and ifosfamide 2 g/m2 per day with mesna 0.5 g/m2 three times daily given on days 1 to 3; cycles were repeated every 21 days and treatment continued in responding patients until progression occurred. RESULTS: Objective responses were observed in 12 patients (30%; CI95, 16-44) with one completed response (CR) and 11 partial response (PR). CONCLUSION: This schedule achieves good levels of response without the use of cisplatin so it is suitable for patients whose performance status or concomitant medical condition precludes the use of platinum based chemotherapy.

Aged↗