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Biomedical subjects

C Jacquemin

Publications and source records attributed to C Jacquemin.

At least 19 recordsLinked to original sources
PubMed1997

Mediation by arachidonic acid metabolites of the H2O2-induced stimulation of mitogen-activated protein kinases (extracellular-signal-regulated kinase and c-Jun NH2-terminal kinase).

Reactive oxygen species modulate major cellular functions by mechanisms which are still poorly understood. Recently, H2O2 has been reported to stimulate the activity of the mitogen-activated protein kinases (MAPKs) ERK and JNK, and the expression of the proto-oncogenes c-fos and c-jun. As their expression is enhanced by H2O2 in astrocytes, we studied whether these MAPKs were stimulated by H2O2 in primary cultured astrocytes. The result was positive, a maximum of stimulation being reached with 200 microM H2O2 (0.3 pmol H2O2/cell) for both ERK and JNK. ERK was previously reported to stimulate cytosolic phospholipase A2 phosphorylation and activity. H2O2 stimulated the release of arachidonic acid in astrocytes, as already reported in other cell types. We found also that cPLA2 phosphorylation was increased by H2O2. Moreover, the stimulation by H2O2 of ERK and JNK was decreased by phospholipase A2 activity inhibitors. When astrocytes were incubated first with eicosatetraynoic acid, a structural analogue competing in arachidonic acid metabolism, the stimulation of JNK by H2O was also inhibited, suggesting the involvement of arachidonic acid metabolites. Cyclooxygenase or cytochrome P450 monooxygenase inhibitors failed in decreasing the MAPK stimulation by H2O2, whereas lipoxygenase inhibitors completely abolished that of JNK. Mitogenicity has been reported to be stimulated by H2O2 in other cell types. Although ERK was strongly and durably stimulated by 200 microM H2O2 in astrocytes, at the same extent as by mitogenic growth factors, basal thymidine incorporation rate was decreased by more than 80% after 12-15 h. Moreover, the stimulation of thymidine incorporation induced by basic fibroblast growth factor was transiently abolished by H2O2. Furthermore, H2O2 likely induced the expression of CL100/PAC1/MKP-1, a dual specificity phosphatase which has been implicated in ERK and JNK inactivation in the nucleus. Finally, the prior treatment of astrocytes with MK886, a 5-lipoxygenase-activating protein inhibitor, prevented JNK from stimulation, but did not prevent thymidine incorporation from inhibition, both induced by H2O2. These results strongly suggest an involvement of arachidonic acid and/or its metabolites in the stimulation of both ERK and JNK following the oxidative stress evoked by H2O2, which induced a cell cycle arrest probably independent of the stimulation of JNK.

Animals↗
PubMed1997

Snaring of the target vessel in less invasive bypass operations does not cause endothelial dysfunction.

BACKGROUND: Minimally invasive coronary artery bypass grafting aims to achieve less patient discomfort and a more rapid return to active life. Most approaches have used maintenance of the beating heart and control of the target coronary vessel by different hemostatic devices. The purpose of this study was to assess the effects of commonly used coronary artery snares and of the occlusion of the coronary vessel necessary for minimally invasive coronary artery operations on coronary endothelial function. METHODS: Coronary artery bypass grafting with an internal mammary artery to left anterior descending artery anastomosis was performed in a porcine model with a 30-minute period of ischemia and a subsequent 30-minute period of reperfusion, using snares on either side of the anastomotic site to achieve hemostasis of the operative field. Endothelium-dependent relaxation to serotonin was studied in conventional organ chamber experiments with rings taken from the left anterior descending artery at the proximal snare site, the anastomotic site in the segment that underwent the ischemia-reperfusion cycle, the distal snare site, and at a control segment. Responses to potassium chloride and bradykinin were also compared. RESULTS: There were no significant differences in endothelium-dependent relaxation values among the four sites studied. CONCLUSIONS: These results confirm that snaring of the coronary artery for achieving hemostasis at the anastomotic site when performing coronary artery bypass grafting on the beating heart does not cause endothelial dysfunction.

Animals↗
PubMed1996

Evidence for cAMP-dependent platelet ectoprotein kinase activity that phosphorylates platelet glycoprotein IV (CD36).

The dephosphorylating enzyme alkaline phosphatase, by removing phosphate groups from the external platelet membrane proteins, modulates platelet activation (Hatmi, M., Haye, B., Gavaret, J. M., Vargaftig, B. B., and Jacquemin, C. (1991) Br. J. Pharmacol. 104, 554-558). This observation, together with findings reported by others (Ehrlich, Y. H., Davis, T. B., Bock, E., Kornecki, E., and Lenox, R. H. (1986) Nature 320, 67-70; Dusenbery, K. E., Mendiola, J. R., and Skubitz, K. M. (1988) Biochem. Biophys. Res. Commun. 153, 7-13), indicate the existence of ectoprotein kinase activity on the blood platelet surface. In this study, we demonstrate that washed human platelets phosphorylate the synthetic heptapeptide kemptide in a cAMP-dependent mode. The intensity of the phosphorylation was concentration-dependent for kemptide. In addition, incubation of platelets with [gamma-32P]ATP resulted in a rapid incorporation of [32P] phosphate into proteins at the outer membrane surface that was sensitive to alkaline phosphatase treatment. When cAMP was added to the medium, major phosphorylation of an 88-kDa ectoprotein occurred. Its isoelectric point determined by isoelectric focusing SDS-polyacrylamide gel electrophoresis was around pH 6.2. Phosphorylations of this 88-kDa polypeptide and of the exogenous kemptide substrate were both prevented by the specific protein kinase A inhibitor peptide. When platelets were preincubated with [32P]inorganic phosphate to label intracellular proteins, the protein phosphorylation pattern was different from that obtained with [gamma-32P]ATP, indicating that the latter occurred at the outer surface of the cells. Prostacyclin, which induces the increase of intracellular cAMP levels and, consequently, its liberation into the extracellular medium, increased phosphorylation of both kemptide and platelet 88-kDa polypeptide. The major protein of 88-kDa, which was phosphorylated in the presence of cAMP and external [gamma-32P]ATP, was identified by immunoprecipitation to GPIV (CD36), one of thrombospondin and collagen binding sites on platelets. The phosphorylation of CD36 also occurred in platelet-rich plasma, suggesting a physiological role for this ectoenzyme. In the present study, we clearly demonstrate the presence of an ectoprotein kinase A activity at the surface of intact human platelets, and we revealed its principal endogenous substrate as being CD36.

Blood Platelets↗
PubMed1996

Endothelial effects of hemostatic devices for continuous cardioplegia or minimally invasive operations.

BACKGROUND: Improvements in myocardial protection may include the continuous delivery of normothermic blood cardioplegia. Technical aids are required for optimal visualization of the operative field during the performance of coronary anastomoses if cardioplegia is to be given continuously or during minimally invasive operations. However, the effects of the different hemostatic devices on coronary endothelial function are unknown. METHODS: We compared the effects on endothelial function of two commonly used hemostatic techniques, coronary clamping and gas jet insufflation, with those of a technique using extravascular balloon occlusion to mimic systolic luminal closure by the surrounding myocardium. The three techniques were applied for 15 minutes on porcine epicardial coronary arteries from explanted hearts. For coronary clamping, standard bulldog clamps were used. Gas jet insufflation was applied by blowing oxygen (12 L/min) tangentially at a 45-degree angle 1 cm away from a 3-mm arteriotomy. Extravascular balloon occlusion was achieved with a needle-tipped silicone loop, the midportion of which, once positioned beneath the coronary artery, was inflated to push a myocardial "cushion" against the back of the vessel until its occlusion. Control rings were taken from the same coronary artery. The endothelial function of control and instrumented arterial rings was then studied in organ chambers filled with modified Krebs-Ringer bicarbonate solution. RESULTS: Contractions to potassium chloride and prostaglandin F2 alpha and endothelium-independent relaxation to sin-1, a nitric oxide donor, were unaffected in all groups. Endothelium-dependent relaxation to serotonin was impaired after clamping and preserved after gas jet insufflation and extravascular balloon occlusion. Maximal endothelium-dependent relaxation to serotonin was as follows: for coronary clamping, 63% +/- 6% versus 87% +/- 3% in controls; for gas jet insufflation, 67% +/- 12% versus 88% +/- 7%; and for extraluminal balloon occlusion, 79% +/- 6% versus 85% +/- 5%. CONCLUSIONS: Whereas commonly used hemostatic devices may impair endothelial function, extravascular balloon occlusion appears to achieve effective hemostasis while preserving endothelial integrity.

Animals↗
PubMed1996

Long-term effect of forskolin on the activation of adenylyl cyclase in astrocytes.

Long-term (48-h) forskolin treatment of rat astroglial cells led to a slight decrease (30-40%) in the response to isoproterenol, vasoactive-intestinal peptide, guanyl 5'-(beta gamma-imido)diphosphate, guanosine 5'-O-(3-thiotriphosphate) [GTP(S)], and AIF4- in crude membrane fractions. In contrast, the acute stimulatory effect of forskolin was increased by 1.25-1.5-fold. These two opposite effects of forskolin were mediated by a cyclic AMP-dependent mechanism. No changes in Gs alpha, Gi alpha, or G beta protein levels could be determined by immunoblotting using specific antisera. No significant differences were observed in the ability of G proteins extracted from control and forskolin-treated cells to reconstitute a full adenylyl cyclase activity in membranes from S49 cyc- cells, lacking Gs alpha protein. Gs alpha proteins were detected in two pools of membranes, one in the heavy sucrose fractions and the other in light sucrose fractions. Forskolin treatment of the cells shifted Gs alpha protein toward the light-density membranes. We did not find any significant change in the distribution of adenylyl cyclase. In contrast to the decreased stimulation of adenylyl cyclase activity by agonists acting via Gs alpha, observed in the crude membrane fraction, the responses of adenylyl cyclase to forskolin as well as to GTP(S) were increased in the purified plasma membrane fractions. These results may indicate that sensitization of the catalyst appears to be the dominant component in the astroglial cell response to long-term treatment by forskolin.

Adenylyl Cyclases↗
PubMed1995

Stimulation of mitogen-activated protein kinase by thyrotropin in primary cultured human thyroid follicles.

In the thyroid, thyrotropin (TSH) stimulates both growth and function, and stimulates the production of cAMP which reproduces most of the effects of TSH. Here, we report evidence that TSH stimulates the mitogen-activated protein (MAP) kinase cascade through a cAMP-independent pathway, in human thyroid. TSH stimulated MAP kinase activity (4-9-fold the basal level) measured in the cytosolic fractions of primary cultured thyroid follicles. Maximal activity was reached after 20 min and remained sustained for 1-3 h, TSH being as potent as EGF; EC50 was 1.5 nM TSH. Only a single isoform of MAP kinase (p42) was detected in the follicles. p42 was phosphorylated on tyrosine residues and showed a reduced electrophoretic mobility in follicles stimulated by TSH. All these effects on MAP kinase were decreased by preincubation of the follicles with human anti-TSH receptor antibodies. The stimulation of MAP kinase by TSH was neither blocked by pertussis toxin nor reproduced by forskolin, cholera toxin, or 8-bromo-cAMP. In conclusion, in human thyroid cells, in contrast with previous observations on dog thyroid cells, TSH stimulates strongly MAP kinase through a pertussis toxin-insensitive and cAMP-independent pathway.

Amino Acid Sequence↗
PubMed1995

Stimulation of mitogen-activated protein kinase by thyrotropin in astrocytes.

We have recently reported the expression of the thyrotropin (TSH) receptor and the stimulation by TSH of type-II iodothyronine 5'-deiodinase in astrocytes. In these cells, TSH stimulated arachidonate release, but neither cAMP production, nor phosphatidylinositolbisphosphate hydrolysis, as described in the human thyroid gland. Here we report, in contrast to a recent observation made in dog thyroid cells, that TSH stimulates mitogen-activated protein kinase (MAP kinase) in astrocytes. Indeed, TSH increases the tyrosine phosphorylation of the two isoforms of MAP kinase expressed in these cells, in correlation with both a slower electrophoretic migration of the tyrosine phosphorylated species and an enhanced enzymic activity measured on a specific substrate peptide. This stimulation of MAP kinase by TSH was specifically inhibited by incubation of astrocytes in the presence of human blocking anti-(TSH receptor) IgG, and by immunoprecipitation of TSH with monoclonal anti-TSH IgG. In astrocytes, TSH was neither mitogenic by itself, nor modified significantly the basic-fibroblast-growth-factor-induced mitogenesis. The stimulation of MAP kinase by TSH was not affected by treatment with pertussis toxin, suggesting guanine-nucleotide-binding-regulatory protein i/o was not implicated in this TSH effect. Our model will allow the study of the stimulation of MAP kinase by TSH without interference either from cAMP or from phosphoinositide signalling pathways.

Animals↗
PubMed1995

Monohydroperoxidized fatty acids but not 4-hydroxynonenal induced acute cardiac cell damage.

Unsaturated fatty acids constitutive of cardiac membranal lipid matrix are one of the primary targets for reactive oxygen species generated during ischemia-reperfusion cycle. Lipid peroxidation is a cascade of intricate reactions involving the successive formations of fatty acids hydroperoxides and aldehydic compounds such as alkenals derived from the oxidative fragmentation of these hydroperoxides. The potential deleterious effects of different classes of lipid peroxidation products on cardiac cells were compared using three in vitro approaches: (i) cardiomyocyte integrity, (ii) electromechanical activity of papillary muscle, and (iii) atrial contractility. The following products of lipid peroxidation were tested: (i) photoperoxidized arachidonic acid pooling hydroperoxidized derivatives and aldehydic compounds, (ii) fatty acids hydroperoxides, and (iii) 4-hydroxynonenal, a characteristic alkenal derived from the oxidative fragmentation of hydroperoxidized n-6 fatty acids. Only fatty acids hydroperoxides induced drastic loss of cellular integrity and severe disturbances in electromechanical activity of cardiomyocytes. 4-hydroxynonenal induced only a slight leak of lactate dehydrogenase at high concentrations and did not modify the electromechanical behavior of cardiac preparations. Under our conditions, monohydroperoxidized fatty acids but not 4-hydroxynonenal induced acute cardiac cell damages. In conclusion, lipid hydroperoxides can be considered both as markers of oxidative injury and relay sources of oxidative stress.

Aldehydes↗
PubMed1994

Cyclic AMP regulation of messenger RNA level of the stimulatory GTP-binding protein Gs alpha. Isoproterenol, forskolin and 8-bromoadenosine 3':5'-cyclic monophosphate increase the level of Gs alpha mRNA in cultured astroglial cells.

The existence of a cAMP-dependent regulation of the expression of the alpha-subunit of the stimulatory guanine nucleotide-binding protein (Gs) in a well characterized astroglial cells culture was established. The culture of astroglial cells for 3-6 h with isoproterenol (10 microM) or forskolin (10 microM) (a cAMP-inducing agent) increased (200-400%) the response of adenylylcyclase to agents which bypass the receptor; GTP, GTP[S] or forskolin. For prolonged exposure times (15 h or more) to isoproterenol or forskolin, the adenylycyclase activity decreased to the value observed in control cells. The same biphasic response of adenylylcyclase to isoproterenol (10 microM) plus GTP (10 microM) occurred in membrane fractions from cells cultured with forskolin, whereas a diminished response to isoproterenol was observed in isoproterenol-treated cells, indicating that the beta-adrenergic receptor was desensitized. To understand the molecular mechanism of these phenomena, we measured the levels of the alpha subunits of the guanine-nucleotide binding protein (Gs and Gi) by Western-blot analysis. The culture of astroglial cells with isoproterenol or forskolin (3-24 h) resulted in a transient increase of both the Gs alpha and the Gi alpha protein levels, while the level of G beta subunits was unaffected. We also identified Gs alpha protein (about 40% of the total cellular protein) in the supernatant fraction of astroglial cells but its level was not modified by the stimulation of cells by forskolin. The level of Gs alpha mRNA measured by Northern-blot analysis was transiently increased (200%) after stimulation of astroglial cells with isoproterenol or forskolin for an incubation period of 6-9 h, then returned to that of control cells for longer period of time. In addition, the Gs alpha mRNA level was threefold increased when cells were cultured for 2-6 h with 8-bromoadenosine 3':5'-cyclic monophosphate (10 microM), a permeant analogue of cAMP. These results indicate that cAMP induces a time-dependent increase of Gs alpha mRNA. The half-life of Gs alpha protein and Gs alpha mRNA were determined. Pulse-chase studies revealed that the decay of Gs alpha protein was clearly biphasic with an early phase (5-6 h) and a slower second phase (20-25 h) but the treatment of cells with forskolin did not accelerate or slow down the turnover of Gs alpha protein.(ABSTRACT TRUNCATED AT 400 WORDS)

8-Bromo Cyclic Adenosine Monophosphate↗
PubMed1994

12-O-tetradecanoyl-phorbol-13-acetate (TPA) counteracts the cAMP up-regulation of the expression of the stimulatory guanine nucleotide binding protein (Gs alpha) and Gs alpha messenger RNA in cultured pig thyroid cells.

In this study, we examined whether the protein kinase C (PKC) pathway could interfere with the regulation of Gs protein in porcine thyroid cells. The two days culture of cells with 12-O-tetradecanoylphorbol 13-acetate (TPA) (0.1 microM) alone neither affected adenylyl cyclase activity, nor the level of Gs alpha protein in membranes when compared with control cells. The co-addition of TPA with thyrotropin (TSH) (1 mU/ml) or forskolin (fk) (10 microM) in the culture medium, abolished the stimulatory effects of either agonists on the activation of adenylyl cyclase by fk or [AlF4]- and on the increase of Gs alpha protein. By contrast, TPA had effects neither on the Gi-dependent inhibition of adenylyl cyclase nor on Gi alpha proteins levels. The level of Gs alpha mRNA measured by Northern blot analysis was increased (200%) in TSH- or fk-treated cells and this increase was counteracted by TPA. The effects of TPA observed after 6-9 h of contact with cells were mimicked by mezerezin, a non-phorbol protein kinase C activator and blocked by bisindolylmaleimide a specific protein kinase C inhibitor (GF 109203X). These results suggest that the activation of the PKC pathway prevents the cAMP-dependent up-regulation of Gs alpha protein and Gs alpha mRNA expression.

Adenylyl Cyclases↗
PubMed1994

[Agenesis of the corpus callosum, heterotopia of the gray cortex and interhemispheric cyst. Late radiologic diagnosis in an asymptomatic adult].

Agenesis of the corpus callosum may occur as an isolated finding; most often, it is present in association with other cerebral malformations such as cortical heterotopias. Computerized tomography and magnetic resonance imaging are methods of choice to detect these cerebral prenatal abnormalities, especially asymptomatic forms. We report the case of an asymptomatic young adult with complete callosal agenesis, cortical heterotopia and interhemispheric cyst, on CT and MR imaging.

Adult↗
PubMed1993

Evidence for cAMP-independent thyrotropin effects on astroglial cells.

Thyroid hormones are essential for normal brain development and function. Brain astroglial cells express type II iodothyronine 5'-deiodinase which converts thyroxine into 3,5,3'-triiodothyronine. This type II deiodinase is regulated through various signalling pathways, allowing probably for the local adaptation of the level of 3,5,3'-triiodothyronine. Our results demonstrated that thyrotropin was able to induce type II deiodinase activity in astrocytes. A thyrotropin receptor was demonstrated. It was not coupled, as in thyroid, to adenylyl cyclase and phospholipase C, but it stimulated cytosolic phospholipase A2. The stimulation by thyrotropin of both thyroxine synthesis in thyroid and its local activation in astrocytes, could protect the brain from variations in the level of 3,5,3'-triiodothyronine.

Adenylyl Cyclases↗
PubMed1993

[Central pontine myelinolysis with cerebellar ataxia and dystonia].

A 46-year-old alcoholic woman presented with dementia, chronic cerebellar ataxia and diffuse dystonia. Neurological examination also demonstrated emotional lability and a pyramidal signs on the four limbs. CT showed mild cerebellar and frontal atrophy. The diagnosis of central pontine myelinolysis was confirmed by MRI. The centropontine lesion gave an hyposignal on T1-weighted sequences and a hypersignal on T2-weighted sequences. It was shaped as a trident and symmetrical, sparing the tegmentum and the ventro-lateral regions of the pons. Cerebellar ataxia was related to cerebellar atrophy and extension of myelinolysis to the middle cerebellar peduncles. Dystonia, rarely reported in central pontine myelinolysis, was not associated with striatal lesions on MRI. The pathophysiology of these movement disorders in central pontine myelinolysis remains unclear. This case shows that central pontine myelinolysis is a rare cause of dystonia and can be diagnosed by MRI.

Alcoholism↗
PubMed1992

Autocrine biological effects of glycosyl inositol phosphate produced by reconstituted pig thyroid follicles: role of pertussis toxin sensitive G proteins.

We examine the autocrine activity of glycosyl inositol phosphate (InP-gly) on thyroid metabolism. The cAMP accumulation promoted by thyrotropin (TSH) or forskolin was modulated by InP-gly, stimulated by the lowest tested concentration (10(-8) M) and progressively inhibited by higher concentrations. Iodide uptake and iodine organification were decreased in a concentration-dependent manner by InP-gly alone, or in the presence of TSH. The IAP component of pertussis toxin blocked the inhibitory action of InP-gly on cAMP accumulation by reconstituted thyroid follicles (RTF), suggesting the participation of Gi protein. But the same treatment with IAP was without effect on iodine metabolism, suggesting that there is a second target for InP-gly, more distal than Gi protein, or coupled to another G protein which is insensitive to the toxin.

Animals↗