References of "Malgrange, Brigitte"
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See detailAn atypical cell during development of the auditory organ : the inner pillar cell
Thelen, Nicolas ULg; Malgrange, Brigitte ULg; Thiry, Marc ULg

Poster (2007, September)

Although the structure of the auditory organ in mature mammals, the organ of Corti, is clearly established, its development is far to be elucidated. Using cytochemical and immunohistochemical methods at ... [more ▼]

Although the structure of the auditory organ in mature mammals, the organ of Corti, is clearly established, its development is far to be elucidated. Using cytochemical and immunohistochemical methods at the light and electron microscope levels, we examined its spatiotemporal development in rats from embryonic day 16 (E16) to E19. <br />At E16, whatever the region of the cochlear studied (base, middle, apex), the organ of Corti is not present. We demonstrate that the organ of Corti develops from a non-proliferative cell zone that is located in the junctional region between the greater epithelial ridge and the lesser epithelial ridge of the cochlear duct and that is characterized by the presence of numerous microvilli. Using the periodic acid-thiocarbohydrazide-silver proteinate method, we reveal that the first cells to develop in this zone are the inner pillar cells, a particular type of nonsensory supporting cells; they arise in the base of the cochlear duct at the boundary between the two ridges at E16. The cell differentiation in this prosensory region continues according to a base-to-apex gradient, the inner hair cells appear in the greater epithelial ridge at E17 and the outer hair cells in the lesser epithelial ridge at E18. At E19, all the different cell types of the organ of Corti are well in place. We also show that the development of the inner pillar cells within the prosensory region does not involve Notch1 signaling. These results highlight the central role that cells could play the inner pillar in the organ of Corti development. [less ▲]

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See detailVector-mediated delivery of bcl-2 prevents degeneration of auditory hair cells and neurons after injury.
Staecker, Hinrich; Liu, Wei; Malgrange, Brigitte ULg et al

in ORL (2007), 69(1), 43-50

OBJECTIVE: To test the hypothesis that bcl-2 prevents oxidative stress-induced apoptosis of auditory sensory cells in explants of the organ of Corti and dissociated cell cultures of the spiral ganglion ... [more ▼]

OBJECTIVE: To test the hypothesis that bcl-2 prevents oxidative stress-induced apoptosis of auditory sensory cells in explants of the organ of Corti and dissociated cell cultures of the spiral ganglion. METHODS: Organ of Corti explants and dissociated spiral ganglion cell cultures obtained from 3-day-old (P3) rats or adult spiral ganglion cell cultures from 28-day-old (P28) rats were transduced with vectors containing a human bcl-2 gene. Cultures were then exposed to neomycin, cisplatin or subjected to withdrawal of neurotrophin supplementation. Outcome measures included hair cell and neuron counts, mitochondrial membrane potential and a histological measure of apoptosis. RESULTS: Expression of bcl-2 in the organ of Corti explants and neuronal cell cultures provided a significant level of protection against cell death. Bcl-2 expression in the organ of Corti explants also protected mitochondria from loss of membrane potential and blocked an early step in the commitment of hair cells to apoptosis. CONCLUSION: Expression of bcl-2 in cochlear tissues protects sensory cells from a variety of insults that have been demonstrated to damage the inner ear. [less ▲]

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See detailPrenatal development study of rat corti organ at the morphological level
Thelen, Nicolas ULg; Malgrange, Brigitte ULg; Thiry, Marc ULg

Poster (2006, September)

Although the structural organization of the mature Corti organ is generally well defined, little is known about its prenatal development. Here, we have examined by photonic and electron transmission ... [more ▼]

Although the structural organization of the mature Corti organ is generally well defined, little is known about its prenatal development. Here, we have examined by photonic and electron transmission microscopies the morphological changes occurring in the cochlear epithelium from the embryonic day 16 to 19 in rat. Moreover, we have used the periodic acid-thiocarbohydrazide-silver proteinate method to detect the glycogen particles on semithin and ultrathin sections of the cochlear duct. <br />At the embryonic day 16 (E16), whatever the region of the cochlear studied (base, medium, apex), the organ of Corti is not present. The cochlear epithelium appears as a pseudostratified epithelium formed formed by two distinct regions according to the presence or the absence of microvilli at the apical surface of cells. The region with the microvilli is on the modiolar side and the presence of microvilli is a characteristic of cells in the greater epithelial ridge (GER). In basal part of the cochlear duct, glycogen particles are visible on ultrathin sections in only one cell. On both sides of this cell, apical part of the epithelium shows microvilli. At E17, on semithin sections of basal and medium parts of cochlear duct, one cell visible on the whole height of the epithelium shows rich content in glycogen . At E18, in the majority of sections realized at the base and medium of the cochlear canal, the organ of Corti is relatively well recognizable. We distinguish principally the inner hair cells but also to a lesser extent the outer hair cells as well as the supporting cells (pillar, phalengeal and Deiters cells).We show that only the pillar cells have a rich content in glycogen. At E19, the organ of Corti is clearly recognizable in all the basal and medium parts of the cochlear duct. By contrast, it is yet differenciated in the apex. <br />These data seem to indicate that the Corti organ in rat develops from base to apex in the greater epithelial ridge starting by the pillar cells. [less ▲]

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See detailDelayed GM-CSF treatment stimulates axonal regeneration and functional recovery in paraplegic rats via an increased BDNF expression by endogenous macrophages
Bouhy, Delphine; Malgrange, Brigitte ULg; Multon, Sylvie ULg et al

in FASEB Journal (2006), 20(8), 12391241

Macrophages (monocytes/microglia) could play a critical role in central nervous system repair. We have previously found a synchronism between the regression of spontaneous axonal regeneration and the ... [more ▼]

Macrophages (monocytes/microglia) could play a critical role in central nervous system repair. We have previously found a synchronism between the regression of spontaneous axonal regeneration and the deactivation of macrophages 3-4 wk after a compression-injury of rat spinal cord. To explore whether reactivation of endogenous macrophages might be beneficial for spinal cord repair, we have studied the effects of granulocyte-macrophage colony stimulating factor (GM-CSF) in the same paraplegia model and in cell cultures. There was a significant, though transient, improvement of locomotor recovery after a single delayed intraperitoneal injection of 2 mu g GM-CSF, which also increased significantly the expression of Cr3 and brain-derived neurotrophic factor ( BDNF) by macrophages at the lesion site. At longer survival delays, axonal regeneration was significantly enhanced in GMCSF-treated rats. In vitro, BV2 microglial cells expressed higher levels of BDNF in the presence of GM-CSF and neurons cocultured with microglial cells activated by GM-CSF generated more neurites, an effect blocked by a BDNF antibody. These experiments suggest that GM-CSF could be an interesting treatment option for spinal cord injury and that its beneficial effects might be mediated by BDNF.-Bouhy, D., Malgrange, B., Multon, S., Poirrier, A. L., Scholtes, F., Schoenen, J., Franzen, R. Delayed GM-CSF treatment stimulates axonal regeneration and functional recovery in paraplegic rats via an increased BDNF expression by endogenous macrophages. [less ▲]

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See detailThe Yin and Yang of cell cycle progression and differentiation in the oligodendroglial lineage
Nguyen, Laurent ULg; Borgs, Laurence ULg; Vandenbosch, Renaud ULg et al

in Mental Retardation & Developmental Disabilities Research Reviews (2006), 12(2), 85-96

In white matter disorders such as leukodystrophies (LD), periventricular leucomalacia (PVL), or multiple sclerosis (MS), the hypomyelination or the remyelination failure by oligodendrocyte progenitor ... [more ▼]

In white matter disorders such as leukodystrophies (LD), periventricular leucomalacia (PVL), or multiple sclerosis (MS), the hypomyelination or the remyelination failure by oligodendrocyte progenitor cells involves errors in the sequence of events that normally occur during development when progenitors proliferate, migrate through the white matter, contact the axon, and differentiate into myelin-forming oligodendrocytes. Multiple mechanisms underlie the eventual progressive deterioration that typifies the natural history of developmental demyelination in LID and PVL and of adult-onset demyelination in MS. Over the past few years, pathophysiological studies have mostly focused on seeking abnormalities that impede oligodendroglial maturation at the level of migration, myelination, and survival. In contrast, there has been a strikingly lower interest for early proliferative and differentiation events that are likely to be equally critical for white matter development and myelin repair. This review highlights the Yin and Yang principles of interactions between intrinsic factors that coordinately regulate progenitor cell division and the onset of differentiation, i.e. the initial steps of oligodendrocyte lineage progression that are obviously crucial in health and diseases. (C) 2006 Wiley-Liss, Inc. [less ▲]

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See detailActivation of protein kinase CbetaI constitutes a new neurotrophic pathway for deafferented spiral ganglion neurons
Lallemend, François; Hadjab, Saida; Hans, Grégory ULg et al

in Journal of Cell Science (2005), 118(19), 4511-4525

In mammals, degeneration of peripheral auditory neurons constitutes one of the main causes of sensorineural hearing loss. Unfortunately, to date, pharmacological interventions aimed at counteracting this ... [more ▼]

In mammals, degeneration of peripheral auditory neurons constitutes one of the main causes of sensorineural hearing loss. Unfortunately, to date, pharmacological interventions aimed at counteracting this condition have not presented complete effectiveness in protecting the integrity of cochlear neural elements. In this context, the protein kinase C (PKC) family of enzymes are important signalling molecules that play a role in preventing neurodegeneration after nervous system injury. The present study demonstrates, for the first time, that the PKC signalling pathway is directly neurotrophic to axotomised spiral ganglion neurons (SGNs). We found that PKC beta I was strictly expressed by postnatal and adult SGNs both in situ and in vitro. In cultures of SGNs, we observed that activators of PKC, such as phorbol esters and bryostatin 1, induced neuronal survival and neurite regrowth in a manner dependent on the activation of PKC beta I. The neuroprotective effects of PKC activators were suppressed by pre-treatment with LY294002 (a PI3K inhibitor) and with U0126 (a MEK inhibitor), indicating that PKC activators promote the survival and neurite outgrowth of SGNs by both PI3K/Akt and MEK/ERK-dependent mechanisms. In addition, whereas combining the neurotrophins brain-derived neurotrophic factor (BDNF) and neurotrophin-3 (NT3) was shown to provide only an additive effect on SGN survival, the interaction between PKC and neurotrophin signalling gave rise to a synergistic increase in SGN survival. Taken together, the data indicate that PKC beta I activation represents a key factor for the protection of the integrity of neural elements in the cochlea. [less ▲]

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See detailPeripheral benzodiazepine receptor (PBR) ligand cytotoxicity unrelated to PBR expression
Hans, Grégory ULg; Wislet, Sabine ULg; Lallemend, François et al

in Biochemical Pharmacology (2005), 69(5), 819-830

Some synthetic ligands of the peripheral-type benzodiazepine receptor (PBR), an 18 kDa protein of the outer mitochondrial membrane, are cytotoxic for several tumor cell lines and arise as promising ... [more ▼]

Some synthetic ligands of the peripheral-type benzodiazepine receptor (PBR), an 18 kDa protein of the outer mitochondrial membrane, are cytotoxic for several tumor cell lines and arise as promising chemotherapeutic candidates. However, conflicting results were reported regarding the actual effect of these drugs on cellular survival ranging from protection to toxicity. Moreover, the concentrations needed to observe such a toxicity were usually high, far above the affinity range for their receptor, hence questioning its specificity. In the present study, we have shown that micromolar concentrations of FGIN-1-27 And Ro 5-4864, two chemically unrelated PBR ligands are toxic for both PBR-expressing SK-N-BE neuroblastoma cells and PBR-deficient Jurkat lymphoma cells. We have thereby demonstrated that the cytotoxicity of these drugs is unrelated to their PBR-binding activity. Moreover, Ro 54864-induced cell death differed strikingly between both cell types, being apoptotic in Jurkat cells while necrotic in SK-N-BE cells. Again, this did not seem to be related to PBR expression since Ro 5-4864-induced death of PBR-transfected Jurkat cells remained apoptotic. Taken together, our results show that PBR is unlikely to mediate all the effects of these PBR ligands. They however confirm that some of these ligands are very effective cytotoxic drugs towards various cancer cells, even for reputed chemoresistant tumors such as neuroblastoma, and, surprisingly, also for PBR-lacking tumor cells. (C) 2004 Elsevier Inc. All rights reserved. [less ▲]

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See detailbeta-carbolines induce apoptosis in cultured cerebellar granule neurons via the mitochondrial pathway
Hans, Grégory ULg; Malgrange, Brigitte ULg; Lallemend, François et al

in Neuropharmacology (2005), 48(1), 105-117

N-Butyl-beta-carboline-3-carboxylate (betaCCB) is, together with 2-methyl-norharmanium and 2,9-dimethylnorharmanium ions, an endogenously occurring beta-carboline. Due to their structural similarities ... [more ▼]

N-Butyl-beta-carboline-3-carboxylate (betaCCB) is, together with 2-methyl-norharmanium and 2,9-dimethylnorharmanium ions, an endogenously occurring beta-carboline. Due to their structural similarities with the synthetic neurotoxin 1-methy14-phenyl-1,2,3,6-tetrahydropyridine (MPTP), harman and norharman compounds have been proposed to be involved in the pathogenesis of Parkinson's disease. While also structurally related, betaCCB has received much less interest in that respect although we had previously demonstrated that it induces the apoptotic cell death of cultured cerebellar granule neurons (CGNs). Herein, we have investigated the molecular events leading to CGN apoptosis upon betaCCB treatment. We first demonstrated that betaCCB-induced apoptosis occurs in neurons only, most likely as a consequence of a specific neuronal uptake as shown using binding/uptake experiments. Then we observed that, in betaCCB-treated CGNs, caspases 9, 3 and 8 were successively activated, suegesing an activation of the mitochondrial pathway. Consistently, betaCCB also induced the release from the mitochondrial intermembrane space of two pro-apoptotic factors. i.e. cytochrome c and apotptosis inducing factor (AIF). Interestingly, no mitochondrial membrane depolarisation was associated with this release. suggesting a mitochondrial permeability transition pore-independent mechanism. The absence of any neuroprotective effect provided by two mPTP inhibitors. i.e. cyclosporine A and bongkrekic acid. further supported this hypothesis. Together. these results show that betaCCB is specifically taken up by neuronal cells where it triggers a specific permeabilization of the outer mitochondrial membrane and a subsequent apoptotic cell death. (C) 2004 Elsevier Ltd. All rights reserved. [less ▲]

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See detailActivation of protein kinase C$\beta$I constitutes a new neurotrophic pathway for deafferented spiral ganglion neurons
Lallemend, François; Hadjab, Sa Ida; HANS, Grégory ULg et al

in Journal of cell science (2005), 118(19), 4511--4525

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See detailMolecular pathways involved in apoptotic cell death in the injured cochlea: Cues to novel therapeutic strategies
Lallemend, François; Lefèbvre, Philippe ULg; Hans, Grégory ULg et al

in Current Pharmaceutical Design (2005), 11(17), 2257-2275

Most hearing loss results from lesions of the sensory cells and/or neurons of the auditory portion of the inner ear. To date, only the cochlear implantation offers long-term hearing-aid benefit, but still ... [more ▼]

Most hearing loss results from lesions of the sensory cells and/or neurons of the auditory portion of the inner ear. To date, only the cochlear implantation offers long-term hearing-aid benefit, but still with limited performance and expensive cost. While the underlying causes of deafness are not clear, the death or hair cells and/or neurons and the loss of neuronal contacts are key pathological features. Pinpointing molecular events that control cell death in the cochlea is critical for the development of new strategies to prevent and treat deafness, whether in combination or not with cochlear implant therapy. [less ▲]

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See detailNOX3, a superoxide-generating NADPH oxidase of the inner ear
Banfi, Botond; Malgrange, Brigitte ULg; Knisz, Judit et al

in Journal of Biological Chemistry (2004), 279(44), 46065-46072

Reactive oxygen species (ROS) play a major role in drug-, noise-, and age-dependent hearing loss, but the source of ROS in the inner ear remains largely unknown. Herein, we demonstrate that NADPH oxidase ... [more ▼]

Reactive oxygen species (ROS) play a major role in drug-, noise-, and age-dependent hearing loss, but the source of ROS in the inner ear remains largely unknown. Herein, we demonstrate that NADPH oxidase (NOX) 3, a member of the NOX/dual domain oxidase family of NADPH oxidases, is highly expressed in specific portions of the inner ear. As assessed by real-time PCR, NOX3 mRNA expression in the inner ear is at least 50-fold higher than in any other tissues where its expression has been observed ( e. g. fetal kidney, brain, skull). Microdissection and in situ hybridization studies demonstrated that NOX3 is localized to the vestibular and cochlear sensory epithelia and to the spiral ganglions. Transfection of human embryonic kidney 293 cells with NOX3 revealed that it generates low levels of ROS on its own but produces high levels of ROS upon co-expression with cytoplasmic NOX subunits. NOX3-dependent superoxide production required a stimulus in the absence of subunits and upon co-expression with phagocyte NADPH oxidase subunits p47(phox) and p67(phox), but it was stimulus-independent upon co-expression with colon NADPH oxidase subunits NOX organizer 1 and NOX activator 1. Pre-incubation of NOX3-transfected human embryonic kidney 293 cells with the ototoxic drug cisplatin markedly enhanced superoxide production, in both the presence and the absence of subunits. Our data suggest that NOX3 is a relevant source of ROS generation in the cochlear and vestibular systems and that NOX3-dependent ROS generation might contribute to hearing loss and balance problems in response to ototoxic drugs. [less ▲]

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See detailCaspases, the enemy within, and their role in oxidative stress-induced apoptosis of inner ear sensory cells
Van De Water, T. R.; Lallemend, François; Eshraghi, A. A. et al

in Otology & Neurotology (2004), 25(4), 627-632

This review covers the general roles of members of the cysteine protease family of caspases in the process of apoptosis (programmed cell death) looking at their participation in both the "extrinsic" cell ... [more ▼]

This review covers the general roles of members of the cysteine protease family of caspases in the process of apoptosis (programmed cell death) looking at their participation in both the "extrinsic" cell death receptor and the "intrinsic" mitochondrial cell death pathways. It defines the difference between initiator and effector caspases and shows the progression of caspase activations that ends up in the apoptotic cell death and elimination of a damaged cell. The review then presents what is currently know about the participation of caspases in the programmed cell death of inner ear sensory cells during the process of normal development and maturation of the inner ear and their importance in this process as illustrated by the results of caspase-3 gene knockout experiments. The participation of specific caspases and the sequence of their activation in the elimination (apoptosis) of damaged sensory cells from adult inner ears after an injury that generates oxidative stress are reviewed. Both the possibility and the potential efficacy of caspase inhibition with a broad-spectrum pancaspase inhibitor as an interventional therapy to treat and rescue oxidative stress-damaged inner ear sensory cells from apoptosis are presented and discussed. [less ▲]

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See detailStriatal PSA-NCAM(+) precursor cells from the newborn rat express functional glycine receptors
Nguyen, Laurent ULg; Malgrange, Brigitte ULg; Breuskin, Ingrid ULg et al

in Neuroreport (2004), 15(4), 583-587

Immunocytochemical analysis showed that ionotropic glycine receptors are expressed in neurogenic progenitors purified from the newborn rat striatum and expressing the polysialylated form of the neural ... [more ▼]

Immunocytochemical analysis showed that ionotropic glycine receptors are expressed in neurogenic progenitors purified from the newborn rat striatum and expressing the polysialylated form of the neural cell adhesion molecule, both in vitro and in situ. To ascertain whether glycine receptors were functional in vitro, whole-cell patch-clamp recordings demonstrated that glycine triggers inward strychnine-sensitive currents in the majority of these cells. Moreover, we found that glycine receptors expressed by these neurogenic progenitors display intermediate electrophysiological characteristics between those of glycine receptors expressed by neural stem cells and by mature interneurons from the rat striatum. Altogether, the present data show that functional strychnine-sensitive glycine receptors are expressed in neurogenic progenitors purified from the newborn rat striatum. [less ▲]

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See detailModulation of the HSV-TK/ganciclovir bystander effect by n-butyrate in glioblastoma: correlation with gap-junction intercellular communication.
Robe, Pierre ULg; Jolois, Olivier ULg; Nguyen Khac, Minh-Tuan ULg et al

in International Journal of Oncology (2004), 25(1), 187-92

The efficacy of HSV-TK/ganciclovir gene therapy largely relies on the bystander effect, i.e. the ability of transfected cells to kill the adjacent, untrasfected cells. This mechanism itself depends ... [more ▼]

The efficacy of HSV-TK/ganciclovir gene therapy largely relies on the bystander effect, i.e. the ability of transfected cells to kill the adjacent, untrasfected cells. This mechanism itself depends chiefly on the transfer via gap junctions of phosphorylated ganciclovir between cells, and is often deficient in glioblastomas. In this report, we demonstrate that n-butyrate markedly enhances the gap junction intercellular communication of GJIC-deficient glioma cells, and significantly increases the bystander effect in such cells. This effect of n-butyrate appears to be independent from its HDAC inhibitory effect, since trichostatin A does not reproduce it. [less ▲]

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See detailThe Inhibition of Cyclin-Dependent Kinases Induces Differentiation of Supernumerary Hair Cells and Deiters' Cells in the Developing Organ of Corti
Malgrange, Brigitte ULg; Knockaert, Marie; Belachew, Shibeshih ULg et al

in FASEB Journal (2003), 17(14), 2136-8

In the embryonic day 19 organs of Corti, we showed that roscovitine, a chemical inhibitor of cyclin-dependent kinases (CDKs), significantly increased the number of hair cells (HCs) and corresponding ... [more ▼]

In the embryonic day 19 organs of Corti, we showed that roscovitine, a chemical inhibitor of cyclin-dependent kinases (CDKs), significantly increased the number of hair cells (HCs) and corresponding supporting cells (SCs) by triggering differentiation of precursor cells without interacting with cell proliferation. The effect of roscovitine was mimicked by other CDK1, 2, 5, and 7 inhibitors but not by CDK4/6 and mitogen-activated protein kinase pathway antagonists. Immunohistochemical analysis indicated that roscovitine-specific intracellular targets, CDK1, 2, 5, and 7, were expressed in the organ of Corti and especially in Hensen's cells. Affinity chromatography studies showed a tight correlation between the protein levels of CDK1/2 and 5 and the rate of roscovitine-induced supernumerary cells in the organ of Corti. In addition, we demonstrated that basal CDK activity was higher and more roscovitine-sensitive at developmental stages that are selectively permissive for the emergence of supernumerary cells. These results suggest that CDKs are involved in the normal development of the organ of Corti and that, at least in E19 embryos, inhibition of CDKs is sufficient to trigger the differentiation of HCs and corresponding SCs, presumably from the Hensen's cell progenitors and/or from progenitors located in the greater epithelial ridge area. [less ▲]

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See detailSubstance P protects spiral ganglion neurons from apoptosis via PKC-Ca2+-MAPK/ERK pathways
Lallemend, François; Lefèbvre, Philippe ULg; Hans, Grégory ULg et al

in Journal of Neurochemistry (2003), 87(2), 508-521

In the current study, we have investigated the ability of substance P (SP) to protect 3-day-old (P3) rat spiral ganglion neurons (SGNs) from trophic factor deprivation (TFD)-induced cell death. The ... [more ▼]

In the current study, we have investigated the ability of substance P (SP) to protect 3-day-old (P3) rat spiral ganglion neurons (SGNs) from trophic factor deprivation (TFD)-induced cell death. The presence of SP high affinity neurokinin-1 receptor (NK1) transcripts was detected in the spiral ganglion and the NK1 protein localized to SGNs both ex vivo and in vitro. Treatment with SP increased cytoplasmic Ca2+ in SGNs, further arguing for the presence of functional NK1 on these neurons. Both SP and the agonist [Sar(9), Met(O-2)(11)]-SP significantly decreased SGN cell death induced by TFD, with no effect on neurite outgrowth. The survival promoting effect of SP was blocked by the NK1 antagonist, WIN51708. Both pan-caspase inhibitor BOC-D-FMK and SP treatments markedly reduced activation of caspases and DNA fragmentation in trophic factor deprived-neurons. The neuroprotective action of SP was antagonised by specific inhibitors of second messengers, including 1.2-bis-(O-aminophenoxy)-ethane-N,N,N',N'-tetraacetic acid (BAPTA-AM) to chelate cytosolic Ca2+, the protein kinase C (PKC) inhibitors bisindolylmaleimide I, Go6976 and LY333531 and the MAPK/ERK inhibitor U0126. In contrast, nifedipine, a specific inhibitor of L-type Ca2+ channel, and LY294002, a phosphatidylinositol-3-OH kinase (PI3K) inhibitor, had no effect on SP trophic support of SGNs. Moreover, activation of endogenous PKC by 4beta-phorbol 12-myristate 13-acetate (PMA) also reduced the loss of trophic factor-deprived SGNs. Thus, NK1 expressed by SGNs transmit a survival-promoting regulatory signal during TFD-induced SGN cell death via pathways involving PKC activation, Ca2+ signalling and MAPK/ERK activation, which can be accounted for by an inhibition of caspase activation. [less ▲]

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See detailChemical inhibitors of cyclin-dependent kinases control proliferation, apoptosis and differentiation of oligodendroglial cells
Nguyen, Laurent ULg; Malgrange, Brigitte ULg; Rocher, Véronique et al

in International Journal of Developmental Neuroscience (2003), 21(6), 321-326

Since cyclin-dependent kinases (Cdks) and their endogenous inhibitors (Cdkis) play an essential role as regulators of cell cycle withdrawal and onset of differentiation within oligodendroglial cells, we ... [more ▼]

Since cyclin-dependent kinases (Cdks) and their endogenous inhibitors (Cdkis) play an essential role as regulators of cell cycle withdrawal and onset of differentiation within oligodendroglial cells, we assessed here the effects of exogenous chemical Cdk inhibitors (CKIs) on cultured rat cortical oligodendrocyte progenitor cells (OPCs). We showed that purine derivatives and especially roscovitine strongly inhibited OPCs proliferation. In the presence of mitogenic signals, roscovitine synergized with thyroid hormone to stimulate oligodendrocyte differentiation. Roscovitine also prevented oligodendroglial apoptosis induced by growth factor deprivation. We thus demonstrated that small molecular weight chemical CKIs have important effects on crucial events of oligodendroglial development in vitro. This might open prospects for using these apparently well tolerated agents in remyelination strategies. (C) 2003 ISDN. Published by Elsevier Ltd. All rights reserved. [less ▲]

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See detailUntangling the functional potential of PSA-NCAM-expressing cells in CNS development and brain repair strategies
Nguyen, Laurent ULg; Rigo, Jean-Michel; Malgrange, Brigitte ULg et al

in Current Medicinal Chemistry (2003), 10(20), 2185-2196

Central nervous system (CNS) neural stem cells (NSCs), which are mostly defined by their ability to self-renew and to generate the three main cell lineages of the CNS, were isolated from discrete regions ... [more ▼]

Central nervous system (CNS) neural stem cells (NSCs), which are mostly defined by their ability to self-renew and to generate the three main cell lineages of the CNS, were isolated from discrete regions of the adult mammalian CNS including the subventricular zone (SVZ) of the lateral ventricle and the dentate gyrus in the hippocampus. At early stages of CNS cell fate determination, NSCs give rise to progenitors that express the polysialylated form of the neural cell adhesion molecule (PSA-NCAM). PSA-NCAM(+) cells persist in adult brain regions where neuronal plasticity and sustained formation of new neurons occur. PSA-NCAM, has been shown to be involved in the regulation of CNS myelination as well as in changes of cell morphology that are necessary for motility, axonal guidance, synapse formation, and functional plasticity in the CNS. Although being preferentially committed to a restricted either glial or neuronal fate, cultured PSA-NCAM(+) progenitors do preserve a relative degree of multipotentiality. Considering that PSA-NCAM(+) cells can be neatly used for brain repair purposes, there is much interest for studying signaling factors regulating their development. With this regard, it is noteworthy that neurotransmitters, which belong to the micro-environment of neural cells in vivo, regulate morphogenetic events preceding synaptogenesis such as cell proliferation, migration, differentiation and death. Consistently, several ionotropic but also G-protein-coupled neurotransmitter receptors were found to be expressed in CNS embryonic and postnatal progenitors. In the present review, we outlined the ins and outs of PSA-NCAM(+) cells addressing to what extent our understanding of extrinsic and in particular neurotransmitter-mediated signaling in these CNS precursor cells might represent a new leading track to develop alternative strategies to stimulate brain repair. [less ▲]

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See detailArrest of apoptosis in auditory neurons: Implications for sensorineural preservation in cochlear implantation
Scarpidis, U.; Madnani, D.; Shoemaker, C. et al

in Otology & Neurotology (2003), 24(3), 409-417

Hypothesis: The JNK/c-Jun cell death pathway is a major pathway responsible for the loss of oxidative stress-damaged auditory neurons. Background: Implantation of patients with residual hearing ... [more ▼]

Hypothesis: The JNK/c-Jun cell death pathway is a major pathway responsible for the loss of oxidative stress-damaged auditory neurons. Background: Implantation of patients with residual hearing accentuates the need to preserve functioning sensorineural elements. Although some auditory function may survive electrode insertion, the probability of initiating an ongoing loss of auditory neurons and hair cells is unknown. Cochlear implantation can potentially generate oxidative stress, which can initiate the cell death of both auditory neurons and hair cells. Methods: Dissociated cell cultures of P4 rat auditory neurons identified the apoptotic pathway initiated by oxidative stress insults (e.g., loss of trophic factor support) and characterized this pathway by arresting translation of pathway-specific mRNA with antisense oligonucleotide treatment and with the use of pathway specific inhibitors. The presence or absence of apoptosis-specific protein and changes in the level of neuronal survival measured the efficacy of these interventional strategies. Results: These in vitro studies identified the JNK/c-Jun cascade as a major initiator of apoptosis of auditory neurons in response to oxidative stress. Neurons pretreated with c-jun antisense oligonucleotide and exposed to high levels of oxidative stress were rescued from apoptosis, whereas neurons in treatment control cultures died. Treatment of oxidative-stressed cultures with either curcumin, a MAPKKK pathway inhibitor, or PD-098059, a MEK1 inhibitor, blocked loss of neurons via the JNK/c-Jun apoptotic pathway. Conclusion: Blocking the JNK/c-Jun cell death pathway is a feasible approach to treating oxidative stress-induced apoptosis within the cochlea and may have application as an otoprotective strategy during cochlear implantation. [less ▲]

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