Biomedical subjects

M Bardoul

Publications and source records attributed to M Bardoul.

5 recordsLinked to original sources

PubMed2001

Blockade of AMPA/kainate receptors can either decrease or increase the survival of cultured neocortical cells depending on the stage of maturation.

Neurotoxicity has often been associated with glutamate receptor stimulation and neuroprotection with glutamate receptor blockade. However, the relationship may be much more complex. We dissociated cells from the rat neocortical anlage at an early stage of prenatal development (embryonic day 14). The cells were exposed in vitro to agonists and antagonists of alpha-amino-3-hydroxy-5-methyl-4-isoxazole-propionate (AMPA)/kainate and N-methyl-D-aspartate (NMDA) receptors and the effects on differentiation and survival have been quantitatively and qualitatively evaluated. NMDA and the non-competitive antagonist (5R,10S)-(+)-5-methyl-10,11-dihydro-5H-dibenzo[a,d]-cyclohepten-5,10-imine hydrogen maleate (MK-801) had the expected effects (the agonist decreasing and the antagonist increasing neuronal survival) when applied at a relatively advanced stage of in vitro maturation, but no significant effect in either direction at earlier stages. Kainate also had an effect on cell survival only at an advanced stage (where it decreased the number of cells). However, this cannot be attributed to the absence of functional AMPA/kainate receptors at earlier stages, since: (1) cells could be loaded with cobalt; and (2) early application of kainate dramatically reduced the number of cobalt-positive cells. Furthermore, exposure at early stages to 6,7-dinitroquinoxaline-2,3-dione (DNQX), or GYKI 53655, (competitive and non-competitive AMPA receptor antagonists, respectively) strongly reduced cell survival. The effects were concentration- and time-dependent with a complex time--curve. The decrease in cell number was maximal after antagonist application from 2 to 5 days in vitro. The effects of DNQX could be cancelled by co-application of kainate. When exposed to an antagonist at later stages of development, the number of surviving cells gradually approached control values and finally became significantly higher. Our results suggest that cells of the developing neocortex (and perhaps newly generated cells in the adult brain) require at different stages of their development, an appropriate level of AMPA/kainate receptor activation.

Animals↗

PubMed1998

Functional AMPA/kainate receptors in human embryonic and foetal central nervous system.

Here, functional AMPA/kainate receptors in human embryonic (5.5-7.5 gestational weeks) and foetal (8-10 gestational weeks) central nervous system tissue, shown by the cobalt labeling method, are reported. Specific agonist-induced cobalt incorporation was detected in brainstem and spinal cord cells, even in the youngest embryo studied. T-AMPA or kainate, but also vegetal toxins such as L-BOAA or acromelate, induced accumulation of cobalt. In contrast, no labeling was observed after exposure to KCl or NMDA. Cobalt labeled cells were particularly prominent in motor regions of brainstem and spinal cord. Co-application of the diuretic agent cyclothiazide, a desensitization blocker at AMPA receptors, dramatically increased the number of stained cells, which was particularly obvious in sensory regions, suggesting different receptor properties in motor versus sensory regions. This is the first study providing evidence for functional AMPA/kainate receptors, permeable to divalent cations, in brainstem and spinal cord at an early stage of human central nervous system development. Since many developmental processes are influenced by the modulation of cytosolic calcium, exposure at critical stages of embryogenesis to food or drug substances modifying the activity of AMPA/kainate receptors may alter brain development.

Amino Acids, Diamino↗

PubMed1998

Modulation of intracellular calcium in early neural cells by non-NMDA ionotropic glutamate receptors.

Non-NMDA ionotropic receptor channels were longtime thought to be impermeable to calcium. There is now increasing evidence that this is not a general feature. Neural cells bearing non-NMDA receptors permeable to divalent cations can be found not only in the adult CNS, but also at surprisingly early stages of development (well before the onset of synaptogenesis). Since modulation of cytosolic calcium is known to trigger numerous transcription, translation, and post-translation mechanisms, molecules acting at non-NMDA ionotropic receptors may profoundly affect the fate of individual cells, brain regions, and finally the whole nervous system. However, present knowledge of transduction mechanisms and possible roles (ranging from transcription of immediate early genes to regulation of cell survival) is still very fragmentary. These receptors can be activated and modulated by endogenous molecules, but also by exogenous naturally occurring or pharmaceutical substances. If significant amounts of these substances can pass the human placental barrier, their consumption or accidental intake during pregnancy may constitute a risk for the developing embryonic and foetal CNS.

Animals↗

PubMed1997

AMPA/kainate receptors modulate the survival in vitro of embryonic brainstem cells.

This study aimed at analyzing the involvement of (RS)-alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid/kainate (AMPA/kainate) receptors in the survival of cultured rat embryonic brainstem cells, dissociated on embryonic day 14. The cell number was estimated after pharmacological manipulation of the receptors by exposure to agonists or antagonists. The developmental stage at the moment of drug application was critical for cell survival. We observed after 8 days in vitro a much stronger decrease in the number of gamma-enolase-positive cells when the cultures were treated for 3 days with the antagonist 6,7-dinitroquinoxaline-2,3-dione (DNQX) starting on the day of plating than when DNQX was added after 5 days in vitro. Conversely, exposure to the agonists (RS)-2-amino-3-(3-hydroxy-5-tri-fluoromethyl-4-isoxazolyl)-propion ic acid (T-AMPA) or kainate for 3 days significantly reduced cell survival only when the treatment was initiated after 5 days in vitro. Survival of S-100-positive cells was not affected after exposure to either agonists or antagonists. Neither agonist nor antagonist treatment modified cell proliferation, as assessed by 5-bromo-2'-deoxyuridine (BrdU) staining, suggesting that the decrease in the number of gamma-enolase-positive cells is essentially due to cell death. If some of the processes we observed in vitro correspond to analogous events in vivo, then exposure to excitatory amino acid receptor agonists or antagonists at critical stages of embryogenesis may alter the development of the central nervous system.

Animals↗

PubMed1996

Functional expression of P-glycoprotein in an immortalised cell line of rat brain endothelial cells, RBE4.

The presence of P-glycoprotein in the cell plasma membrane limits the penetration of many cytotoxic substances into cells that express the gene product. There is considerable evidence also to indicate that P-glycoprotein is expressed as part of the normal blood-brain barrier in the luminal membranes of the cerebral capillary endothelial cells, where it presumably performs a protective function for the brain. This report describes the functional expression of P-glycoprotein in an immortalised cell line, RBE4, derived from rat cerebral capillary endothelial cells. The expression of P-glycoprotein is demonstrated by western immunoblotting and by immunogold and fluorescent staining with monoclonal antibodies. The cellular accumulation of [3H]colchicine and [3H]-vinblastine is investigated and shown to be enhanced by the presence of azidothymidine, chlorpromazine, verapamil, cyclosporin A, and PSC 833 ([3'-keto-Bmt1]-[Val2]-cyclosporin) at 50 or 100 microM concentration. It is concluded that the RBE4 cell line is a valuable tool for investigating the mechanisms of P-glycoprotein activity both in the blood-brain barrier and in multidrug resistance in general.

ATP Binding Cassette Transporter, Subfamily B, Mem↗