Peripheral benzodiazepine receptor (PBR) ligand cytotoxicity unrelated to PBR expression

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 ▲]

Plasticity of cultured mesenchymal stem cells: switch from nestin-positive to excitable neuron-like phenotype.

in Stem Cells (2005), 23(3), 392-402

Bone marrow mesenchymal stem cells (MSCs) can differentiate into several types of mesenchymal cells, including osteocytes, chondrocytes, and adipocytes, but, under appropriate experimental conditions, can ... [more ▼]

Bone marrow mesenchymal stem cells (MSCs) can differentiate into several types of mesenchymal cells, including osteocytes, chondrocytes, and adipocytes, but, under appropriate experimental conditions, can also differentiate into nonmesenchymal cells--for instance, neural cells. These observations have raised interest in the possible use of MSCs in cell therapy strategies for various neurological disorders. In the study reported here, we addressed the question of in vitro differentiation of MSCs into functional neurons. First, we demonstrate that when they are co-cultured with cerebellar granule neurons, adult MSCs can express neuronal markers. Two factors are needed for the emergence of neuronal differentiation of the MSCs: the first one is nestin expression by MSCs (nestin is a marker for the responsive character of MSCs to extrinsic signals), and the second one is a direct cell-cell interaction between neural cells and MSCs that allows the integration of these extrinsic signals. Three different approaches suggest that neural phenotypes arise from MSCs by a differentiation rather than a cell fusion process, although this last phenomenon can also coexist. The expression of several genes--including sox, pax, notch, delta, frizzled, and erbB--was analyzed by quantitative reverse transcription polymerase chain reaction (RT-PCR) in order to further characterize the nestin-positive phenotype compared to the nestin-negative one. An overexpression of sox2, sox10, pax6, fzd, erbB2, and erbB4 is found in nestin-positive MSCs. Finally, electrophysiological analyses demonstrate that MSC-derived neuron-like cells can fire single-action potentials and respond to several neurotransmitters such as GABA, glycine, and glutamate. We conclude that nestin-positive MSCs can differentiate in vitro into excitable neuron-like cells. [less ▲]

Striatal PSA-NCAM(+) precursor cells from the newborn rat express functional glycine receptors

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 ▲]

Substance P protects spiral ganglion neurons from apoptosis via PKC-Ca2+-MAPK/ERK pathways

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 ▲]

Identification of factors that maintain mammalian outer hair cells in adult organ of Corti explants

in Hearing Research (2002), 170(1-2), 48-58

Both outer hair cells (OHCs) and inner hair cells (IHCs) survive and mature in 3 days old rat organ of Corti explants cultured for I month in a minimal essential medium. In contrast. under the same ... [more ▼]

Both outer hair cells (OHCs) and inner hair cells (IHCs) survive and mature in 3 days old rat organ of Corti explants cultured for I month in a minimal essential medium. In contrast. under the same culture conditions, only IHCs survive in explants from adult guinea pig organ of Corti while many of the OHCs are lost within the first 48 It. Hair cell Count,, show OHCs loss to be greater in the lower portion (i.e. middle turn) of the cochlea than Lit the apex. Terminal deoxynucleotidyl transferase-mediated dUTP nick end labelling (TUNEL) indicates that there is DNA damage in adult OHCs, within 8 h of explantation. Treatment of the adult organ of Corti explants with either actinomycin D (10(-7) M) or cycloheximide (10(-6) M) prevents most OHC losses . According to these results apoptosis may be the mechanism of OHC loss in adult organ of Corti explants, Stable membrane potentials recorded from the OHCs in both uncultured and actinomycin D-treated organ of Corti explants cultured for 72 h demonstrate the functional integrity of these hair cells. OHC losses in the adult guinea pig, organ of Corti cultures can also be prevented by treatment with several of the growth factors tested. i.e. acidic fibroblast growth factor (aFGF), insulin-like growth factor-1 (IGF-1), epidermal growth factor (EGF), transforming growth factor-beta1 (TGF-beta1). and glial cell-derived neurotrophic factor (GDNF). The results of this study suggest that growth factor therapy may be applicable to the treatment of some hearing disorders. (C) 2002 Elsevier Science B.V. All rights reserved. [less ▲]

Glycine Triggers an Intracellular Calcium Influx in Oligodendrocyte Progenitor Cells Which Is Mediated by the Activation of Both the Ionotropic Glycine Receptor and Na+-Dependent Transporters

in European Journal of Neuroscience (2000), 12(6), 1924-30

Using fluo-3 calcium imaging, we demonstrate that glycine induces an increase in intracellular calcium concentration ([Ca2+]i) in cortical oligodendrocyte progenitor (OP) cells. This effect results from a ... [more ▼]

Using fluo-3 calcium imaging, we demonstrate that glycine induces an increase in intracellular calcium concentration ([Ca2+]i) in cortical oligodendrocyte progenitor (OP) cells. This effect results from a calcium entry through voltage-gated calcium channels (VGCC), as it is observed only in OP cells expressing such channels, and it is abolished either by removal of calcium from the extracellular medium or by application of an L-type VGCC blocker. Glycine-triggered Ca2+ influx in OP cells actually results from an initial depolarization that is the consequence of the activation of both the ionotropic glycine receptor (GlyR) and Na+-dependent transporters, most probably the glycine transporters 1 (GLYT1) and/or 2 (GLYT2) which are colocalized in these cells. Through this GlyR- and transporter-mediated effect on OP intrcellular calcium concentration [Ca2+]i, glycine released by neurons may, as well as other neurotransmitters, serve as a signal between neurons and OP during development. [less ▲]