Graciela Gudiño-Cabrera

Role of p38 MAPK and pro-inflammatory cytokines expression in glutamate-induced neuronal death of neonatal rats.

Pro‐inflammatory cytokines TNF‐α, IL‐1β and IL‐6 rises significantly during neuronal damage and activate the signaling p38 MAPK pathway, which is involved in the apoptotic (AP) neuronal death. Systemic administration of glutamate as monosodium salt (MSG) to newborn animals induces neuronal death, however whether neurons die by AP or necrosis through MAPK p38 pathway activation it is unknown. In this study, TNF‐α, IL‐1β and IL‐6 expression levels, AP neuronal death and cellular type that produces TNF‐α was also identified in the cerebral cortex (CC) and striatum (St) of rats at 8, 10, and 14 days of age after neonatal exposure to MSG. TNF‐α production and AP neuronal death was significantly increased in the CC at PD8–10, and in the St in all ages studied by excitotoxicity effect induced with MSG. This effect was completely inhibited by SB203580 (p38 inhibitor) in both regions studied. TNF‐α, IL‐1β and IL‐6 RNAm increased after MSG administration, whereas SB203580 did not modify their expression. These data indicates that neuronal death induced by excitotoxicity appears to be mediated through p38 signaling pathway activated by TNF‐α and their inhibition may have an important neuroprotective role as part of anti‐inflammatory therapeutic strategy.

P38 MAPK Inhibition Protects Against Glutamate Neurotoxicity and Modifies NMDA and AMPA Receptor Subunit Expression

NMDA and AMPA receptors are thought to be responsible for Ca++ influx during glutamate-induced excitotoxicity and, therefore, hippocampal neuronal death. We assessed whether excitotoxicity induced by neonatal treatment with monosodium glutamate in rats at postnatal age of 1, 3, 5, and 7 modifies the hippocampal expression of the NMDAR subunit NR1 and the AMPAR subunits GluR1/GluR2 at postnatal days 8, 10, 12, and 14. We also assessed the involvement of MAPK signaling by using the p38 inhibitor SB203580. Our results showed that monosodium glutamate induces neuronal death and alters the expression of the subunits evaluated in the hippocampus at all ages studied, which could be prevented by SB203580 treatment.Furthermore, expression of the NRSF gene silencing factor also increased in response to excitotoxicity, suggesting a relationship in suppressing GluR2-expression, which was regulated by the p38-MAPK pathway inhibitor SB203580. This result suggests that selectively blocking the pro-death signaling pathway may reduce neuronal death in some neurodegenerative diseases in which these neurotoxic processes are present and produce major clinical benefits in the treatment of these pathologies.

Microarray analysis of rat hippocampus exposed to excitotoxicity: Reversal Na+/Ca2+ exchanger NCX3 is overexpressed in glial cells

Multiple factors are involved in the glutamate‐induced excitotoxicity phenomenon, such as overload of ionotropic and metabotropic receptors, excess Ca2+ influx, nitric oxide synthase activation, oxidative damage due to increase in free radicals, and release of endogenous polyamine, among others. In order to attempt a more integrated approach to address this issue, we established, by microarray analysis, the hippocampus gene expression profiles under glutamate‐induced excitotoxicity conditions. Increased gene expression is mainly related to excitotoxicity (CaMKII, glypican 2, GFAP, NCX3, IL‐2, and Gmeb2) or with cell damage response (dynactin and Ecel1). Several genes that augmented their expression are related to glutamatergic system modulation, in particular with NMDA receptor modulation and calcium homeostasis (IL‐2, CaMKII, acrosin, Gmeb2, hAChE, Slc83a, and SP1 factor). Conversely, among genes that diminished their expression, we found the Syngap 1, which is downregulated by CaMKII, and the MHC II, which is downregulated by glutamate. Changes observed in gene expression induced by monosodium glutamate (MSG) neonatal treatment in the hippocampus are consistent with the activation of the mechanisms that modulate NMDA receptor function as well as with the implementation of plastic response to cell damage and intracellular calcium homeostasis. Regarding this aspect, we report here that NCX3/Slc8a3, a Na+/Ca2+ membrane exchanger, is highly expressed in astrocytes, both in vitro and in vivo, in response to glutamate‐induced excitotoxicity. Hence, the results of this analysis present a broad view of the expression profile elicited by MSG neonatal treatment, and lead us to suggest the possible molecular pathways of action and reaction involved under this experimental model of excitotoxicity.

Excitotoxicity Triggered by Neonatal Monosodium Glutamate Treatment and Blood–Brain Barrier Function

It is likely that monosodium glutamate (MSG) is the excitotoxin that has been most commonly employed to characterize the process of excitotoxicity and to improve understanding of the ways that this process is related to several pathological conditions of the central nervous system. Excitotoxicity triggered by neonatal MSG treatment produces a significant pathophysiological impact on adulthood, which could be due to modifications in the blood-brain barrier (BBB) permeability and vice versa. This mini-review analyzes this topic through brief descriptions about excitotoxicity, BBB structure and function, role of the BBB in the regulation of Glu extracellular levels, conditions that promote breakdown of the BBB, and modifications induced by neonatal MSG treatment that could alter the behavior of the BBB. In conclusion, additional studies to better characterize the effects of neonatal MSG treatment on excitatory amino acids transporters, ionic exchangers, and efflux transporters, as well as the role of the signaling pathways mediated by erythropoietin and vascular endothelial growth factor in the cellular elements of the BBB, should be performed to identify the mechanisms underlying the increase in neurovascular permeability associated with excitotoxicity observed in several diseases and studied using neonatal MSG treatment.

Subtractive hybridization identifies genes differentially expressed by olfactory ensheathing cells and neural stem cells

The in vitro differentiation of embryonic stem cells into glia has received relatively limited attention to date when compared with the interest in the generation of neurons. We are interested in a particular glial phenotype, the aldynoglia, and their differentiation from multipotential neural precursors (MNP), since this type of glia can promote neuronal regeneration. We constructed cDNA libraries from cultures of purified olfactory ensheathing cells (OEC), an aldynoglia cell type, and MNP to perform subtractive hybridization. As a result, we isolated four genes from the OEC: one tenascin C (Tn‐C) isoform, Insulin‐like growth factor binding protein 5 (Igfbp‐5), cytochrome oxidase subunit I (COX1) and a phosphodiesterase for cyclic nucleotides (CNPase). With the exception of CNPase, these genes are expressed more strongly in the OEC than in the MNP and moreover, the expression of all four is induced when MNP were exposed to OEC conditioned media. The data suggest a role for these genes in MNP differentiation, and their products appear to represent characteristic proteins of the aldynoglia phenotype.

Neural stem cells in the adult brain: From benchside to clinic

Increasing evidence indicates that neural stem cells (NSCs) play an important role in sustaining cellular homeostasis and brain tissue restoration. The study of all mechanisms that control and modulate the function of NSC is a crucial step for the design of therapies against chronic neurodegenerative processes. In this special issue of the journal, we had the pleasure to edit the topic entitled “Neural Stem Cells in the Adult Brain: From Benchside to Clinic.” This special compilation of paper was aimed to provide a global forum for publications of original peer-reviewed manuscripts that reported original research findings in the field of adult neural stem cell, including short communications, full-length research, and review articles. Below, we briefly discuss the papers you may find in this issue. K. Nakaguchi et al., in their paper entitled “Growth factors released from gelatin hydrogel microspheres increase new neurons in the adult mouse brain”, suggest that new neurons born in the subventricular zone (SVZ) may be able to replace neurons lost in degenerative disease or injury and improve or repair neurological deficits. In this excellent paper, they tested whether delivering growth factors via gelatin hydrogel microspheres can support neurogenesis in the SVZ. Their findings indicated that hepatocyte growth factor-containing microspheres increased the number of new neurons migrating from the SVZ towards the injured striatum in a stroke model in mouse. Therefore, they propose that gelatin hydrogel microspheres may be a good delivery tool for the sustained release of growth factors to promote neural regeneration of damaged brain tissues. J. Tu and S. O. Ugoya discuss that traumatic brain injury (TBI) is one of the leading causes of major disability and death worldwide. Neural stem cells (NSCs) have recently been shown to contribute to the cellular remodeling and may represent a possible therapy for TBI. In their work the authors nicely summarized a critical assessment of recent data and developed a view comprising of six points to possible quality translation of NSCs in TBI. B. P. Carreira et al., in their paper entitled “Regulation of injury-induced neurogenesis by nitric oxide”, sustain that nitric oxide (NO), a pleiotropic signaling molecule in the central nervous system, is able to modulate neurogenesis, acting as a pro- or antineurogenic agent. In their interesting review, they discussed the relevance of the NO system for the treatment of neurodegenerative diseases or several pathological conditions that affect the brain. J. Namiki et al. analyzed the phosphorylation of nestin, an intermediate filament protein commonly used as a neural stem/progenitor cell marker. Nestin is required for the survival and self-renewal of neural stem cells. In this study, the authors nicely reported CNS-specific phosphorylation sites in nestin that allow distinguishing vascular expression of nestin from other intermediate filament protein subtypes. Hormonal signals from the pancreatic islets influence the energy homeostasis of the brain and vice versa. In an excellent review, M. Machida and coworkers explain the correlation between the insulin-mediated regulatory system of the CNS and the pancreatic endocrine system. Remarkably, adult neurogenesis from undifferentiated neural stem cells is greatly decreased in diabetic patients, and as a result their learning and memory functions decline. In their paper, the authors summarized latest research regarding this endocrinal and neurological relationship. L. Calatrava-Ferreras et al. explained that cerebellar ataxias, a heterogeneous group of diseases characterized by motor incoordination, may be treated using cell transplantations. Specifically they propose the use of human umbilical cord blood mononuclear cells as a promising approach for restoration of cerebellar function S. Martinez-Herrero et al. discuss that adrenomedullin (AM) acts as a growth and cell fate regulatory factor for adult neural stem cells. AM regulates the proliferation rate and the differentiation of stem/progenitor cells into neurons, astrocytes, and oligodendrocytes, probably through the PI3K/Akt pathway. AM gene is also able to regulate the cytoskeleton rearrangements, which is important for cellular morphogenesis. In addition, AM appears to contribute to neural stem cell growth regulation by allowing cells to pass through mitosis. Consequently, AM may contribute to program stem cells for future clinical uses. Finally, R. Ramos-Zuniga et al. discussed the ethical implications on the use of stem cells. They explain that every clinical project should take that into account, along with potential clinical applications, the principle of “primum non nocere” (first, do no harm). The authors also indicate the importance of keeping a close clinical surveillance to establish the possible risks in the use of stem-cell-based therapies. With this compendium of cutting-edge review articles and original articles written for experts in the stem-cell field, we hope these in the field of adult neural stem cells will help be helpful and educational for readers. Oscar Gonzalez-Perez Jose M. Garcia-Verdugo Alfredo Quinones-Hinojosa Sonia Luquin Graciela Gudino-Cabrera Rocio E. Gonzalez-Castaneda

Changes in the expression level of MAPK pathway components induced by monosodium glutamate-administration produce neuronal death in the hippocampus from neonatal rats

Excessive Glutamate (Glu) release may trigger excitotoxic cellular death by the activation of intracellular signaling pathways that transduce extracellular signals to the cell nucleus, which determines the onset of a death program. One such signaling pathway is the mitogen-activated protein kinases (MAPK), which is involved in both survival and cell death. Experimental evidences from the use of specific inhibitors supports the participation of some MAPK pathway components in the excitotoxicity mechanism, but the complete process of this activation, which terminates in cell damage and death, is not clearly understood. The present work, we investigated the changes in the expression level of some MAPK-pathway components in hippocampal excitotoxic cell death in the neonatal rats using an experimental model of subcutaneous monosodium glutamate (MSG) administration on postnatal days (PD) 1, 3, 5 and 7. Data were collected at different ages through PD 14. Cell viability was evaluated using fluorescein diacetate mixed with propidium iodide (FDA-PI), and the Nissl-staining technique was used to evaluate histological damage. Transcriptional changes were also investigated in 98 components of the MAPK pathway that are associated with cell damage. These results are an evidence of that repetitive use of MSG, in neonatal rats, induces cell damage-associated transcriptional changes of MAPK components, that might reflect a differential stage of both biochemical and molecular brain maturation. This work also suggests that some of the proteins evaluated such as phosphorylated retinoblastoma (pRb) protein, which was up-regulated, could regulate the response to excitotoxic through modulation of the process of re-entry into the cell cycle in the hippocampus of rats treated with MSG.

Modifications in the Seizures Susceptibility by Excitotoxic Neuronal Damage and Its Possible Relationship with the Pharmacoresistance

The neuronal damage and seizures are two processes closely related not only as cause and effect in reciprocal way but also through the cellular mechanisms and signaling pathways that they share. Therefore, increments in extracellular levels of the glutamate excitatory neurotransmitter, the over-activation of its receptors and the excessive neuronal excitation, have been described as events associated to both processes. In general, if neurons are not able to recover from its excessive excitation, then they die by excitotoxicity. Our group has showed that the excitotoxicity induced by monosodium glutamate in early developmental stages is able to produce significant modifications in glutamatergic and GABAergic neurotransmission systems. Moreover, preliminary results indicate that those modifications are able to increase the seizure susceptibility in the adulthood, particularly when the convulsive drug 4-aminopyridine and the GABA antagonists are employed to induce the seizures, but not when NMDA agonists are used. Through this chapter the topics mentioned above and the hypothesis about the excitotoxic neonatal damage is able to induce a kind of pharmacoresistance to NMDA analogs will be discussed with in detail.

Effect of short-term carbon tetrachloride administration on blood lactic acid levels.

1. A short-term CCl4 administration was used in vivo as a model to produce a rise in lactic acid levels and to explain the probable interaction of CCl4 and lactic acid elevation with hepatic fibrogenesis. 2. A single dose of CCl4 produced an increase in lactic acid levels from 16.6 +/- 3.57 to 24.2 +/- 4.2 mg/dl. Three consecutive doses produced an elevation to 33.28 +/- 10.07 mg/dl, thus describing a direct relationship between lactic acid levels and CCl4 administration in a short-term fashion. 3. A morphological evaluation was performed to show hepatic changes caused by CCl4 administration. No clue of fibrogenesis was found. However, we conclude that an elevation in lactic acid exists, prior to cirrhosis. Therefore, chronic presence of lactic acid may lead to cirrhosis.