Glial-derived arginine, the nitric oxide precursor, protects neurons from NMDA-induced excitotoxicity

Excitotoxic neuronal cell death is characterized by an overactivation of glutamate receptors, in particular of the NMDA subtype, and the stimulation of the neuronal nitric oxide synthase (nNOS), which catalyses the formation of nitric oxide (NO) from l-arginine (L-Arg). At low L-Arg concentrations, nNOS generates NO and superoxide (O2(.)(-)), favouring the production of the toxin peroxynitrite (ONOO-). Here we report that NMDA application for five minutes in the absence of added L-Arg induces neuronal cell death, and that the presence of L-Arg during NMDA application prevents cell loss by blocking O2(.)(-) and ONOO- formation and by inhibiting mitochondrial depolarization. Because L-Arg is transferred from glial cells to neurons upon activation of glial glutamate receptors, we hypothesized that glial cells play an important modulator role in excitotoxicity by releasing L-Arg. Indeed, as we further show, glial-derived L-Arg inhibits NMDA-induced toxic radical formation, mitochondrial dysfunction and cell death. Glial cells thus may protect neurons from excitotoxicity by supplying L-Arg. This potential neuroprotective mechanism may lead to an alternative approach for the treatment of neurodegenerative diseases involving excitotoxic processes, such as ischemia.     

Phenotype of CD4+ T cell subsets that develop following mouse facial nerve axotomy

We have previously shown that CD4(+) T helper (Th) 2 cells, but not Th1 cells, participate in the rescue of mouse facial motoneurons (FMN) from axotomy-induced cell death. Recently, a number of other CD4(+) T cell subsets have been identified in addition to the Th1 and Th2 effector subsets, including Th17, inducible T regulatory type 1 (Tr1), and naturally thymus-born Foxp3(+) regulatory (Foxp3(+) Treg) cells. These subsets regulate the nature of a T cell-mediated immune response. Th1 and Th17 cells are pro-inflammatory subsets, while Th2, Tr1, and Foxp3(+) Treg cells are anti-inflammatory subsets. Pro-inflammatory responses in the central nervous system are thought to be neurodestructive, while anti-inflammatory responses are considered neuroprotective. However, it remains to be determined if another CD4(+) T cell subset, other than the Th2 cell, develops after peripheral nerve injury and participates in FMN survival. In the present study, we used FACS analysis to determine the temporal frequency of Th1, Th17, Th2, Tr1 and Foxp3(+) Treg CD4(+) T cell subset development in C57BL/6 wild type mice after facial nerve transection at the stylomastoid foramen in the mouse. The results indicate that all of the known CD4(+) T cell subsets develop and expand in number within the draining lymph node, with a peak in number primarily at 7 days postoperative (dpo), followed by a decline at 9 dpo. In addition to the increase in subset frequency over time, FACS analysis of individual cells showed that the level of cytokine expressed per cell also increased for interferon-gamma (IFN-gamma), interleukin (IL)-10 and IL-17, but not IL-4. Additional control double-cytokine labeling experiments were done which indicate that, at 7dpo, the majority of cells indeed have committed to a specific phenotype and express only 1 cytokine. Collectively, our findings indicate for the first time that there is no preferential activation and expansion of any single CD4(+) T cell subset after peripheral nerve injury but, rather, that both pro-inflammatory and anti-inflammatory CD4(+) T cells develop.     

VX-765 reduces neuroinflammation after spinal cord injury in mice

Inflammation is a major cause of neuronal injury after spinal cord injury. We hypothesized that inhibiting caspase-1 activation may reduce neuroinflammation after spinal cord injury, thus producing a protective effect in the injured spinal cord. A mouse model of T9 contusive spinal cord injury was established using an Infinite Horizon Impactor, and VX-765, a selective inhibitor of caspase-1, was administered for 7 successive days after spinal cord injury. The results showed that: (1) VX-765 inhibited spinal cord injury-induced caspase-1 activation and interleukin-1β and interleukin-18 secretion. (2) After spinal cord injury, an increase in M1 cells mainly came from local microglia rather than infiltrating macrophages. (3) Pro-inflammatory Th1Th17 cells were predominant in the Th subsets. VX-765 suppressed total macrophage infiltration, M1 macrophages/microglia, Th1 and Th1Th17 subset differentiation, and cytotoxic T cells activation; increased M2 microglia; and promoted Th2 and Treg differentiation. (4) VX-765 reduced the fibrotic area, promoted white matter myelination, alleviated motor neuron injury, and improved functional recovery. These findings suggest that VX-765 can reduce neuroinflammation and improve nerve function recovery after spinal cord injury by inhibiting caspase-1/interleukin-1β/interleukin-18. This may be a potential strategy for treating spinal cord injury. This study was approved by the Animal Care Ethics Committee of Bengbu Medical College (approval No. 2017-037) on February 23, 2017.

Chinese Library Classification No. R453; R392.3; R744     

Delta 9-Tetrahydrocannabinol regulates Th1/Th2 cytokine balance in activated human T cells

Human leukocytes express cannabinoid (CB) receptors, suggesting a role for both endogenous ligands and Delta 9-tetrahydrocannabinol (THC) as immune modulators. To evaluate this, human T cells were stimulated with allogeneic dendritic cells (DC) in the presence or absence of THC (0.625-5 microg/ml). THC suppressed T cell proliferation, inhibited the production of interferon-gamma and shifted the balance of T helper 1 (Th1)/T helper 2 (Th2) cytokines. Intracellular cytokine staining demonstrated that THC reduced both the percentage and mean fluorescence intensity of activated T cells capable of producing interferon-gamma, with variable effects on the number of T cells capable of producing interleukin-4. Exposure to THC also decreased steady-state levels of mRNA encoding for Th1 cytokines, while increasing mRNA levels for Th2 cytokines. The CB2 receptor antagonist, SR144528, abrogated the majority of these effects. We conclude that cannabinoids have the potential to regulate the activation and balance of human Th1/Th2 cells by a CB2 receptor-dependent pathway.     

Transfection of C6 glioma cells with glia maturation factor upregulates brain-derived neurotrophic factor and nerve growth factor: trophic effects and protection against ethanol toxicity in cerebellar granule cells

Glial cells play active roles in neuronal survival, as well as neuroprotection against toxic insult. Recent studies suggest that the brain protein glia maturation factor (GMF) is involved in intracellular signaling in glia. This study investigated whether or not GMF plays a role in the survival-promoting and neuroprotective functions of glia. C6 glioma cells were transfected in vitro with GMF utilizing an adenovirus vector. The transfected cells overexpressed GMF intracellularly, but did not secrete the protein. The conditioned medium (CM) was obtained from the GMF-transfected cells (CM-GMF) and tested on primary neuronal cultures, consisting of cerebellar granule cells (CGC). The CGC cultures were utilized because these cultures have a background level of cell death, and the survival-promoting, i.e. neurotrophic effect, of the CM could be tested. In addition, since CGC cultures are ethanol-sensitive (ethanol enhances neuronal death), the neuroprotective effect of the CM against ethanol-induced cell death was tested also. We demonstrated that the CM-GMF had an enhanced neurotrophic effect as well as an increased neuroprotective effect against ethanol-induced cell death compared to control CM obtained from untransfected C6 cells (CM-Mock) or CM obtained from cells transfected with an unrelated gene (CM-LacZ). Because neurotrophins have trophic and protective effects, we investigated whether GMF-transfection upregulated the expression of neurotrophins in C6 cells. RT-PCR verified that GMF-transfected C6 cells had increased mRNA levels for BDNF and NGF. Immunoblotting corroborated the RT-PCR results and indicated that CM-GMF contained greater concentrations of BDNF and NGF protein compared to CM-Mock and CM-LacZ. A soluble TrkB-IgG fusion protein, which selectively binds BDNF and prevents its binding to the neuronal TrkB receptor, eliminated the neurotrophic effect of CM-GMF; whereas anti-NGF antibody was ineffective in preventing this effect, suggesting that the neurotrophic effect was due to BDNF. On the other hand, both the TrkB-IgG fusion protein and anti-NGF reduced neuroprotection, suggesting that BDNF and NGF both contribute to the neuroprotective effect of CM-GMF. In conclusion, GMF upregulates the expression of BDNF and NGF in C6 cells, and these factors exert neurotrophic and neuroprotective functions on primary neurons.     

Selective blockade of the mGluR1 receptor reduces traumatic neuronal injury in vitro and improvesoOutcome after brain trauma

The effects of selective blockade of group I metabotropic glutamate receptor subtype 1 (mGluR1) on neuronal cell survival and post-traumatic recovery was examined using rat in vitro and in vivo trauma models. The selective mGluR1 antagonists (RS)-1-aminoindan-1,5-dicarboxylic acid (AIDA), 7-(hydroxyimino)cyclopropa[b]chromen-1a-carboxylate ethyl ester (CPCCOEt), and (S)-(+)-alpha-amino-4-carboxy-2-methylbezeneacetic acid (LY367385) provided significant neuroprotection in rat cortical neuronal cultures subjected to mechanical injury, in both pretreatment or posttreatment paradigms. Administration of the antagonists also attenuated glutamate-induced neuronal cell death in the cultures. Coapplication of these antagonists with the N-methyl-d-aspartate (NMDA) receptor antagonist (5R,10S)-(+)-5-methyl-10,11-dihydro-5H-dibenzo[a,d]cyclohepten-5,10-imine (MK-801) had additive neuroprotective effects in glutamate injured cultures. Intracerebroventricular administration of AIDA to rats markedly improved recovery from motor dysfunction after lateral fluid percussion induced traumatic brain injury (TBI). Treatment with mGluR1 antagonists also significantly reduced lesion volumes in rats after TBI, as evaluated by MRI. It appears that these compounds mediate their neuroprotective effect through an mGluR1 antagonist action, as demonstrated by inhibition of agonist induced phosphoinositide hydrolysis in our in vitro system. Moreover, AIDA, CPCCOEt, and LY367385, at concentrations shown to be neuroprotective, had no significant effects on the steady state NMDA evoked whole cell current. Taken together, these data suggest that modulation of mGluR1 activity may have substantial therapeutic potential in brain injury.     

Relationship between the increased cell surface alpha7 nicotinic receptor expression and neuroprotection induced by several nicotinic receptor agonists.

Nicotine and other nicotinic acetylcholine receptor agonists have been shown to exert neuroprotective actions in vivo and in vitro by an as yet unknown mechanism. Even the identification of the subtype of nicotinic receptor(s) mediating this action has not been determined. In neural cell lines, the induction of cytoprotection often requires exposure to nicotine for up to 24 hr to produce a full protective effect. One phenomenon associated with chronic exposure of neural cells to nAChR agonists is the increased expression of nAChRs (upregulation), possibly as a response to desensitization. Because nicotinic receptors desensitize rapidly in the continuous presence of agonist, we investigated whether the neuroprotective actions produced by different nicotinic receptor agonists was related to their ability to induce nicotinic receptor upregulation. Differentiated PC12 cells were preincubated for 24 hr with various nAChR ligands, and the cells were subsequently deprived of both NGF and serum to induce cytotoxicity. Under control conditions cell viability was reduced to 66.5 +/- 5.4% of control by trophic factor withdrawal. For those cells pretreated with nicotine (1 nM-100 microM) cell viability increased from 74.2 +/- 1.5 to 97.3 +/- 4%. The neuroprotective action of nicotine was blocked by co-treatment with either 5 microM mecamylamine or 10 nM methyllycaconitine (MLA). The high potency blockade by MLA suggested that neuroprotection was mediated through the alpha7 nicotinic receptor subtype. For the seven agonists examined for neuroprotective activity, only nicotine was capable of evoking a near maximal (near 100% cell viability) neuroprotective action. The next most effective group included epibatidine, 4OHGTS-21, methycarbamylcholine, and 1,1-dimethyl-4-phenyl-piperazinium iodide. These least effective group included cytisine and tetraethylammonium. Incubation of differentiated PC12 cells with 10 microM nicotine increased the number of [(125)I]alpha bungarotoxin ([(125)I]alphaBGTbinding sites by 41% from 82.6 +/- 3.67 to 117 +/- 10.3 fmol/mg protein). Under similar conditions of incubation, the nicotinic receptor agonist cytisine (that was least effective in terms of neuroprotection) failed to increase the number of [(125)I]alphaBGT binding sites. Cells expressing increased levels of cell surface [(125)I]alphaBGT binding sites received added neuroprotective benefit from nicotine. Thus the induced upregulation of the alpha7 subtype of nicotinic receptors during chronic exposure to nicotine may be responsible for the drug's neuroprotective action.     

Tat-NR2B9c prevents excitotoxic neuronal superoxide production

The Tat-NR2B9c peptide has shown clinical efficacy as a neuroprotective agent in acute stroke. Tat-NR2B9c is designed to prevent nitric oxide (NO) production by preventing postsynaptic density protein 95 (PSD-95) binding to N-methyl-D-aspartate (NMDA) receptors and neuronal nitric oxide synthase; however, PSD-95 is a scaffolding protein that also couples NMDA receptors to other downstream effects. Here, using neuronal cultures, we show that Tat-NR2B9c also prevents NMDA-induced activation of neuronal NADPH oxidase, thereby blocking superoxide production. Given that both superoxide and NO are required for excitotoxic injury, the neuroprotective effect of Tat-NR2B9c may alternatively be attributable to uncoupling neuronal NADPH oxidase from NMDA receptor activation.     

Nicotinic receptor stimulation protects nigral dopaminergic neurons in rotenone-induced Parkinson's disease models

Parkinson's disease (PD) is the second most common neurodegenerative disease and is characterized by dopaminergic (DA) neuronal cell loss in the substantia nigra. Although the entire pathogenesis of PD is still unclear, both environmental and genetic factors contribute to neurodegeneration. Epidemiologic studies show that prevalence of PD is lower in smokers than in nonsmokers. Nicotine, a releaser of dopamine from DA neurons, is one of the candidates of antiparkinson agents in tobacco. To assess the protective effect of nicotine against rotenone-induced DA neuronal cell toxicity, we examined the neuroprotective effects of nicotine in rotenone-induced PD models in vivo and in vitro. We observed that simultaneous subcutaneous administration of nicotine inhibited both motor deficits and DA neuronal cell loss in the substantia nigra of rotenone-treated mice. Next, we analyzed the molecular mechanisms of DA neuroprotective effect of nicotine against rotenone-induced toxicity with primary DA neuronal culture. We found that DA neuroprotective effects of nicotine were inhibited by dihydro-beta-erythroidine (DHbetaE), alpha-bungarotoxin (alphaBuTx), and/or PI3K-Akt/PKB (protein serine/threonine kinase B) inhibitors, demonstrating that rotenone-toxicity on DA neurons are inhibited via activation of alpha4beta2 or alpha7 nAChRs-PI3K-Akt/PKB pathway or pathways. These results suggest that the rotenone mouse model may be useful for assessing candidate antiparkinson agents, and that nAChR (nicotinic acetylcholine receptor) stimulation can protect DA neurons against degeneration.     

Pituitary adenylate cyclase-activating polypeptide protects rat-cultured cortical neurons from glutamate-induced cytotoxicity

We have investigated the effects of pituitary adenylate cyclase-activating polypeptide with 38 residues (PACAP38) on glutamate-induced neuronal cell death in rat-cultured cortical neurons. The rat-cultured neurons were obtained from E17 day-old embryos and cultured in a chemically defined medium without serum for 10 days, after which more than 95% of the cells were stained by a specific antibody against MAP-2, a specific marker for neurons. The number of viable neurons was identified by the mitochondria) conversion of 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide (MTT) to formazan, which was detected by the associated change in optical density at 570 nm. Glutamate-induced neuronal cell death was suppressed by PACAP38 at concentrations as low as 10⁻¹³ M, and at 10⁻¹¹ M maximally suppressed half of the amount of glutamate-induced cell death seen in a control situation (no PACAP38). The dose-response curve was bell-shaped. Dibutyryl cAMP (dbcAMP) also increased the number of neurons that were protected from damage with a bell-shaped dose-response curve suggesting that PACAP exerts its neuroprotective effect through the activation of a cAMP signal transduction system. However, cAMP accumulation in the media of neurons was stimulated by PACAP38 at concentrations as low as 10⁻¹¹ M, a much higher concentration than the minimal effective dose of PACAP38 required for protection against glutamate-induced neuronal cell death. Among the three neuropeptides of PACAP38, arginine vasopressin (AVP) and C-type natriuretic peptide (CNP), only PACAP38 exhibited a neurotrophic effect in the glutamate-induced neuronal cell death at the indicated concentrations. These data indicate that PACAP38 is one of the more important neuroprotective factors. The kind of intracellular signal transduction system involved in the neuroprotective effect of PACAP38 still remains to be established.     

N-methyl-D-aspartate and TrkB receptors protect neurons against glutamate excitotoxicity through an extracellular signal-regulated kinase pathway

N-Methyl-D-aspartate (NMDA) at a subtoxic concentration (100 microM) promotes neuronal survival against glutamate-mediated excitotoxicity via a brain-derived neurotrophic factor (BDNF) autocrine loop in cultured cerebellar granule cells. The signal transduction mechanism(s) underlying NMDA neuroprotection, however, remains elusive. The mitogen-activated protein kinase (MAPK) and phosphatidylinositol-3 kinase (PI3-K) pathways alter gene expression and are involved in synaptic plasticity and neuronal survival. This study tested whether neuroprotective activation of NMDA receptors, together with TrkB receptors, coactivated the MAPK or PI3-K pathways to protect rat cerebellar neurons. NMDA receptor activation caused a concentration- and time-dependent activation of MAPK lasting 24 hr. This activation was blocked by the NMDA receptor antagonist MK-801 but was attenuated only partially by the tyrosine kinase inhibitor k252a, suggesting that activation of both NMDA and TrkB receptors are required for maximal neuroprotection. The MAPK kinase (MEK) inhibitor U0126 (10 microM) partially blocked NMDA neuroprotection, whereas LY294002, a selective inhibitor of the PI3-K pathway, did not affect the neuroprotective activity of NMDA. Glutamate excitotoxicity decreased bcl-2, bcl-X(L), and bax mRNA levels,. NMDA increases Bcl-2 and Bcl-X(L) protein levels and decreases Bax protein levels. NMDA and TrkB receptor activation thus converge on the extracellular signal-regulated kinase (ERK) 1/2 signaling pathway to protect neurons against glutamate-mediated excitotoxicity. By increasing antiapoptotic proteins of the Bcl-2 family, NMDA receptor activation may also promote neuronal survival by preventing apoptosis.     

Caffeine Modulates Tau Phosphorylation and Affects Akt Signaling in Postmitotic Neurons

Neuronal cell cycle reentry, which is associated with aberrant tau phosphorylation, is thought to be a mechanism of neurodegeneration in AD. Caffeine is a neuroprotective drug known to inhibit the cell cycle, suggesting that its neuroprotective nature may rely, at least in part, on preventing tau abnormalities secondary to its inhibitory effect on neuronal cell cycle-related pathways. Accordingly, we have explored in the present study the impact of caffeine on cell cycle-linked parameters and tau phosphorylation patterns in an attempt to identify molecular clues to its neuroprotective effect. We show that caffeine blocks the cell cycle at G1 phase in neuroblastoma cells and leads to a decrease in tau phosphorylation; similarly, exposure of postmitotic neurons to caffeine led to changes in tau phosphorylation concomitantly with downregulation of Akt signaling. Taken together, our results show a unique impact of caffeine on tau phosphorylation and warrant further investigation to address whether caffeine may help prevent neuronal death by preventing tau abnormalities secondary to aberrant entry into the cell cycle.     

Role of mammalian target of rapamycin in hypoxic or ischemic brain injury: potential neuroprotection and limitations

Hypoxic or ischemic stress causes serious brain injury via various pathologic mechanisms including suppressed protein synthesis, neuronal apoptosis, and the release of neurotoxic substances. Many neuroprotective treatments of hypoxic or ischemic brain injury rely on these pathologic mechanisms. The mammalian target of rapamycin (mTOR), an atypical Ser/Thr protein kinase, could be a novel therapeutic target. mTOR plays a critical role in regulating many activities such as protein synthesis, cell growth, and cell death. Furthermore, mTOR could promote angiogenesis, neuronal regeneration, and synaptic plasticity, reduce neuronal apoptosis, and remove neurotoxic substances, which are all closely associated with the repair and survival mechanisms of hypoxic or ischemic brain injury. Although there is currently controversy with regard to regulating the activation of mTOR, the effective neuroprotective functions resulting from mTOR activation have been confirmed by various studies. Considering the potential capability for mTOR in regulating the repair and survival mechanisms of hypoxic or ischemic brain injury, mTOR may be a novel target for neuroprotective treatment.     

Dendritic cells in experimental allergic encephalomyelitis and multiple sclerosis

The mechanisms by which autoimmune diseases are triggered and by which the activation of autoreactive T cells is initiated and maintained are not yet fully understood. As the most potent antigen presenting cells (APC), and also being responsible for antigen transport as well as primary sensitisation of T cells, dendritic cells (DC) are capable of breaking the state of self-ignorance and inducing aggressive autoreactive T cells. In the development of autoimmune diseases, different types of DC exhibit distinct properties for inducing Th1/Th2 cell responses. Appropriate cytokines can convert immunogenic DC to tolerogenic DC. Utilizing the possibility to promote the tolerogenic effects of DC, a new therapeutic tool might soon become available to treat multiple sclerosis and other autoimmune diseases.     

Nicotinic receptor agonists as neuroprotective/neurotrophic drugs. Progress in molecular mechanisms

Summary. In the present work we reviewed recent advances concerning neuroprotective/neurotrophic effects of acute or chronic nicotine exposure, and the signalling pathways mediating these effects, including mechanisms implicated in nicotine addiction and nAChR desensitization. Experimental and clinical data largely indicate long-lasting effects of nicotine and nicotinic agonists that imply a neuroprotective/neurotrophic role of nAChR activation, involving mainly α7 and α4β2 nAChR subtypes, as evidenced using selective nAChR agonists. Compounds interacting with neuronal nAChRs have the potential to be neuroprotective and treatment with nAChR agonists elicits long-lasting neurotrophic effects, e.g. improvement of cognitive performance in a variety of behavioural tests in rats, monkeys and humans. Nicotine addiction, which is mediated by interaction with nACh receptors, is believed to involve the modification of signalling cascades that modulate synaptic plasticity and gene expression. Desensitization, in addition to protecting cells from uncontrolled excitation, is recently considered as a form of signal plasticity. nAChR can generate these longe-lasting effects by elaboration of complex intracellular signals that mediate medium to long-term events crucial for neuronal maintenance, survival and regeneration. Although a comprehensive survey of the gene-based molecular mechanisms that underlie nicotine effects has yet not been performed a growing amount of data is beginning to improve our understanding of signalling mechanisms that lead to neurotrophic/neuroprotective responses. Evidence for an involvement of the fibroblast growth factor-2 gene in nAChR mechanisms mediating neuronal survival, trophism and plasticity has been obtained. However, more work is needed to establish the mechanisms involved in the effects of nicotinic receptor subtype activation from cognition-enhancing and neurotrophic effects to smoking behaviour and to determine more precisely the therapeutic objectives in potential nicotinic drug treatments of neurodegenerative diseases.     

The Predominant Protective Effect of Tianeptine Over Other Antidepressants in Models of Neuronal Apoptosis: The Effect Blocked by Inhibitors of MAPK/ERK1/2 and PI3-K/Akt Pathways

Tianeptine (Tian) possesses neuroprotective potential, however, little is known about the effect of this drug in models of neuronal apoptosis. In the present study, we aimed (1) to compare the neuroprotective capacities of some antidepressants (ADs) in the models of staurosporine (St)- and doxorubicin (Dox)-evoked cell death, activating the intracellular and the extracellular apoptotic pathway, respectively; (2) to identify the Tian-modulated steps underlying its neuroprotective action; (3) to test the effect of various ADs against Dox-evoked cell damage in glia cells. Primary neuronal and glia cell cultures and retinoic acid-differentiated human neuroblastoma SH-SY5Y (RA-SH-SY5Y) cells were co-treated with imipramine, fluoxetine, citalopram, reboxetine, mirtazapine or Tian and St or Dox. The data showed the predominant neuroprotective effect of Tian over other tested ADs against St- and Dox-induced cell damage in primary neurons and in RA-SH-SY5Y cells. This effect was shown to be caspase-3-independent but connected with attenuation of DNA fragmentation. Moreover, neuroprotection elicited by Tian was blocked by pharmacological inhibitors of MAPK/ERK1/2 and PI3-K/Akt signaling pathways as well by inhibitor of necroptosis, necrostatin-1. Interestingly, the protective effects of all tested ADs were demonstrated in primary glia cells against the Dox-evoked cell damage. The obtained data suggests the glial cells as a common target for protective action of various ADs whereas in relation to neuronal cells only Tian possesses such properties, at least against St- and Dox-induced cell damage. Moreover, this neuroprotective effect of Tian is caspase-3-independent and engages the regulation of survival pathways (MAPK/ERK1/2 and PI3-K/Akt).     

Selective Blockade of the mGluR1 Receptor Reduces Traumatic Neuronal Injury in Vitro and Improves Outcome after Brain Trauma

The effects of selective blockade of group I metabotropic glutamate receptor subtype 1 (mGluR1) on neuronal cell survival and post-traumatic recovery was examined using rat in vitro and in vivo trauma models. The selective mGluR1 antagonists (RS)-1-aminoindan-1,5-dicarboxylic acid (AIDA), 7-(hydroxyimino)cyclopropa[b]chromen-1a-carboxylate ethyl ester (CPCCOEt), and (S)-(+)-α-amino-4-carboxy-2-methylbezeneacetic acid (LY367385) provided significant neuroprotection in rat cortical neuronal cultures subjected to mechanical injury, in both pretreatment or posttreatment paradigms. Administration of the antagonists also attenuated glutamate-induced neuronal cell death in the cultures. Coapplication of these antagonists with the N-methyl- -aspartate (NMDA) receptor antagonist (5R,10S)-(+)-5-methyl-10,11-dihydro-5H-dibenzo[a,d]cyclohepten-5,10-imine (MK-801) had additive neuroprotective effects in glutamate injured cultures. Intracerebroventricular administration of AIDA to rats markedly improved recovery from motor dysfunction after lateral fluid percussion induced traumatic brain injury (TBI). Treatment with mGluR1 antagonists also significantly reduced lesion volumes in rats after TBI, as evaluated by MRI. It appears that these compounds mediate their neuroprotective effect through an mGluR1 antagonist action, as demonstrated by inhibition of agonist induced phosphoinositide hydrolysis in our in vitro system. Moreover, AIDA, CPCCOEt, and LY367385, at concentrations shown to be neuroprotective, had no significant effects on the steady state NMDA evoked whole cell current. Taken together, these data suggest that modulation of mGluR1 activity may have substantial therapeutic potential in brain injury.     

Neuroprotection by nicotine in hippocampal slices subjected to oxygen-glucose deprivation

Nicotine (NIC) is neuroprotective against glutamate and hypoxia-induced neurotoxicity, preventing neuronal death and apoptosis in primary neuronal cultures. This effect is mediated by activation of both alpha7 and alpha4beta2 subtypes of nicotinic receptors for acetylcholine (nAChR) (Kaneko et al., 1997; Hejmadi et al., 2003). Furthermore, it seems that activation of alpha7 nAChR is the mechanism by which galantamine protects against thapsigargin and beta-amyloid-induced cell death (Arias et al., 2004), as well as in neuroprotection exerted by NIC against tumor necrosis factor alpha (Gahring et al., 2003). In this context we studied possible protection produced by NIC in an oxygen-glucose deprivation (OGD) model of rat and mouse hippocampal slices. The involvement of alpha7 nAChR in neuroprotection was proved by using wild-type and alpha7 knockout (KO) mice.