3-Acetylpyridine-induced ataxic-like motor impairments are associated with plastic changes in the Purkinje cells of the rat cerebellum.

Ataxias are characterized by aberrant movement patterns closely related to cerebellar dysfunction. Purkinje cell axons are the sole outputs from the cerebellar cortex, and dysfunctional activity of Purkinje cells has been associated with ataxic movements. However, the synaptic characteristics of Purkinje cells in cases of ataxia are not yet well understood. The nicotinamide antagonist 3-acethylpyridine (3-AP) selectively destroys inferior olivary nucleus neurons so it is widely used to induce cerebellar ataxia. Five days after 3-AP treatment (65mg/kg) in adult male Sprague-Dawley rats, motor incoordination was revealed through BBB and Rotarod testing. In addition, in Purkinje cells from lobules V-VII of the cerebellar vermis studied by the Golgi method, the density of dendritic spines decreased, especially the thin and mushroom types. Western blot analysis showed a decrease in AMPA and PSD-95 content with an increase of the α-catenin protein, while GAD-67 and synaptophysin were unchanged. Findings suggest a limited capacity of Purkinje cells to acquire and consolidate afferent excitatory inputs and an aberrant, rigid profile in the movement-related output patterns of Purkinje neurons that likely contributes to the motor-related impairments characteristic of cerebellar ataxias.

Chronic Inhibition of FAAH Reduces Depressive-Like Behavior and Improves Dentate Gyrus Proliferation after Chronic Unpredictable Stress Exposure.

Symptoms of depressive disorders such as anhedonia and despair can be a product of an aberrant adaptation to stress conditions. Chronic unpredictable stress model (CUS) can generate an increase in the activity of the hypothalamic-pituitary-adrenal axis (HPA) and induce a reduction of neurotrophin signaling and the proliferation of neural progenitors in the adult dentate gyrus, together with increased oxidative stress. Levels of the endocannabinoid anandamide (AEA) seem to affect these depression-by-stress-related features and could be modulated by fatty acid amide hydrolase (FAAH). We aimed to evaluate the effects of FAAH inhibitor, URB597, on depressive-like behavior and neural proliferation of mice subjected to a model of CUS. URB597 was administered intraperitoneally at a dose of 0.2 mg/kg for 14 days after CUS. Depressive-like behaviors, anhedonia, and despair were evaluated in the splash and forced swimming tests, respectively. Alterations at the HPA axis level were analyzed using the relative weight of adrenal glands and serum corticosterone levels. Oxidative stress and brain-derived neurotrophic factor (BDNF) were also evaluated. Fluorescence immunohistochemistry tests were performed for the immunoreactivity of BrdU and Sox2 colabeling for comparison of neural precursors. The administration of URB597 was able to reverse the depressive-like behavior generated in mice after the model. Likewise, other physiological responses associated with CUS were reduced in the treated group, among them, increase in the relative weight of the adrenal glands, increased oxidative stress, and decreased BDNF and number of neural precursors. Most of these auspicious responses to enzyme inhibitor administration were blocked by employing a cannabinoid receptor antagonist. In conclusion, the chronic inhibition of FAAH generated an antidepressant effect, promoting neural progenitor proliferation and BDNF expression, while reducing adrenal gland weight and oxidative stress in mice under the CUS model.

ß-Caryophyllene exerts protective antioxidant effects through the activation of NQO1 in the MPTP model of Parkinson's disease.

Parkinson's disease (PD) is a neurodegenerative disorder, caused by the selective death of dopaminergic neurons in the substantia nigra pars compacta. ß-caryophyllene (BCP) is a phytocannabinoid with several pharmacological properties, producing anti-inflammatory and antihypertensive effects. In addition, BCP protects dopaminergic neurons from neuronal death induced by 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP), yet it remains unclear if this effect is due to its antioxidant activity. To assess whether this is the case, the effect of BCP on the expression and activity of NAD(P)H quinone oxidoreductase (NQO1) was evaluated in mice after the administration of MPTP. Male C57BL/6 J mice were divided into four groups, the first of which received saline solution i.p. in equivalent volume and served as a control group. The second group received MPTP. The second group received MPTP hydrochloride (5 mg/kg, i.p.) daily for seven consecutive days. The third group received BCP (10 mg/kg) for seven days, administered orally and finally, the fourth group received MPTP as described above and BCP for 7 days from the fourth day of MPTP administration. The results showed that BCP inhibits oxidative stress-induced cell death of dopaminergic neurons exposed to MPTP at the same time as it enhances the expression and enzymatic activity of NQO1. Also, the BCP treatment ameliorated motor dysfunction and protected the dopaminergic cells of the SNpc from damage induced by MPTP. Hence, BCP appears to achieve at least some of its antioxidant effects by augmenting NQO1 activity, which protects cells from MPTP toxicity. Accordingly, this phytocannabinoid may represent a promising pharmacological option to safeguard dopaminergic neurons and prevent the progression of PD.

HIF-1α expression in the hippocampus and peripheral macrophages after glutamate-induced excitotoxicity.

Hypoxia-inducible factor-1 alpha (HIF-1α) is a master transcription factor that regulates the response to hypoxia and ischemia and induces the expression of various genes, including vascular endothelial growth factor (VEGF) and erythropoietin (EPO). This study shows the systemic response of increased HIF-1α, EPO, and VEGF mRNA and protein. In addition, VEGF expression was increased in neurons and over-expressed in glial cells in a model of neuroexcitotoxicity in the hippocampus, in which rats were neonatally exposed to high glutamate concentrations. Simultaneous increases in HIF-1α, EPO and VEGF mRNA in peritoneal macrophages were also observed. Our study is consistent with the hypothesis that these genes exert a protective effect in response to neurotoxicity.

Expression of HIF-1 alpha, VEGF and EPO in peripheral blood from patients with two cardiac abnormalities associated with hypoxia.

OBJECTIVES: HIF-1 alpha (hypoxia-inducible factor-1 alpha) mediates the responses of mammalian cells to hypoxia/ischemia by inducing the expression of adaptive gene products (e.g., vascular endothelial growth factor (VEGF) and erythropoietin (EPO)). Persistent pulmonary hypertension of the newborn (PPHN) and cyanotic congenital heart disease (CCHD) are common neonatal diseases considered as paradigms of hypoxemia. Since the expression HIF-1 alpha, VEGF and EPO in newborns diagnosed with these diseases has yet to be studied, we set out to define the expression of these genes in peripheral blood from newborn infants diagnosed with PPHN and CCHD. DESIGN AND METHODS: The mRNA transcripts encoding HIF-1 alpha, VEGF and EPO were measured by RT-PCR in healthy newborn infants and infants diagnosed with PPHN and CCHD. RESULTS: An important increase in HIF-1 alpha expression was observed in both pathological conditions, accompanied by significant increases in VEGF and EPO expression when compared to healthy infants. CONCLUSIONS: HIF-1 alpha mRNA expression increases in newborn infants with PPHN or CCHD, as does the expression of its target genes VEGF and EPO.

Changes in hippocampal NMDA-R subunit composition induced by exposure of neonatal rats to L-glutamate.

Overactivation of NMDA-Rs may mediate excitotoxic cell death associated with epileptic seizures, and hypoxic-ischemic conditions. We assessed whether repeated subcutaneous administration of l-glutamate to neonatal rats affects the subunit composition of NMDA-Rs. Accordingly, cortical and hippocampal tissue from 14-day-old rats was analyzed by Western blotting and RT-PCR to quantify the protein and mRNA expression of different NMDA-R subunits. In addition, tissue sections were Nissl stained to assess the cell damage in this tissue. Early exposure of neonatal rats to L-glutamate differentially affects the expression of mRNA transcripts for NMDA-R subunits in the cerebral cortex and hippocampus. In the cerebral cortex, a decrease in NR2B subunit mRNA expression was observed, as well as a loss of NR1 and NR2A protein. By contrast, neonatal L-glutamate administration augmented the transcripts encoding the NR1, NR2B, and NR2C subunits in the hippocampal formation. The expression of mRNA encoding the NR2A subunit was not affected by neonatal L-glutamate administration in either of the brain regions examined. This differential expression of NMDA-R subunits following neonatal exposure to L-glutamate may represent an adaptive response of the glutamate receptors to overactivation in order to reduce the effect of high L-glutamate during the early period of life when the animal is more vulnerable to excitotoxicity.

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

Pro-inflammatory cytokines TNF-alpha, IL-1beta 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-alpha, IL-1beta and IL-6 expression levels, AP neuronal death and cellular type that produces TNF-alpha 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-alpha 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-alpha, IL-1beta 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-alpha and their inhibition may have an important neuroprotective role as part of anti-inflammatory therapeutic strategy.

The expression and binding of kainate receptors is modified in different brain regions by glutamate neurotoxicity during postnatal rat development.

Kainic acid receptor (KA-R) subunits are differentially expressed during brain development, and they modulate both neural growth and survival. High concentrations of glutamate in the brain can induce neuronal injury through these receptors, altering normal development. However, it is unclear whether KAR subunit expression itself is also modified by neonatal exposure to high glutamate. To analyze this, monosodium glutamate (4mg/g of body weight) was subcutaneously administered on postnatal days 1, 3, 5 and 7, and the expression of GluR5, GluR6, KA1 and KA2, as well as [(3)H]-kainic acid (KA-R) binding, was evaluated on postnatal days 14, 21, 30 and 60 in different regions of rat brain. As a result, high levels of GluR5 expression associated with strong [(3)H]-kainic acid binding were observed on postnatal days 30 and 60 in the cerebral cortex of rats exposed to glutamate. Similarly, the changes induced by glutamate administration in the expression of the KA1 and KA2 subunits were paralleled by those of [(3)H]-kainic acid binding in the striatum at postnatal days 21 and 30. In contrast, while KAR subunits were over expressed in the hippocampus, no changes were observed in [(3)H]-kainic acid binding in adult rats that had been exposed to glutamate. Therefore, glutamate modifies both the expression of kainic acid receptor subunits and kainic acid binding in a determined spatial and temporal manner, which may be indicative of a regional susceptibility to glutamate neurotoxicity.

Neuronal damage and changes in the expression of muscarinic acetylcholine receptor subtypes in the neonatal rat cerebral cortical upon exposure to sparteine, a quinolizidine alkaloid.

Sparteine is a quinolizidine alkaloid (QA) produced by Lupine species that has generated much interest due to its anti-hypertensive, anti-pyretic, and anti-inflammatory properties. In the nervous system, sparteine has been shown to display anti-cholinergic and depressive activity, although how sparteine exerts its toxic effects in the brain remains unclear. We have addressed this issue by administering subcutaneous injections of sparteine (25 mg/kg of body weight) to rats on postnatal days 1 and 3, and then examining the expression of the muscarinic acetylcholine receptor (mAChR) subunits m1-m4 in the brains of the neonatal rats 14-60 days later. Administration of sparteine to neonatal rats caused neuronal damage in the cerebral motor cortex accompanied by transient changes in the expression of m1-m4 mAChR subunits as revealed by both RT-PCR and Western blotting. This effect could be prevented by pre-treatment with atropine (10 mg/kg) 1 h prior to the injection of sparteine, suggesting that the cytotoxic activity of sparteine is mediated through mAChRs.

Neuronal cell death due to glutamate excitotocity is mediated by p38 activation in the rat cerebral cortex.

Excitotoxic neuronal death occurs through the activation of NMDA and non-NMDA glutamatergic receptors in the CNS. Glutamate also induces strong activation of p38 and indeed, cell death can be prevented by inhibitors of the p38 pathway. Furthermore, intracellular signals generated by AMPA receptors activate the stress sensitive MAP kinases implicated in apoptotic neuronal death, such as JNK and p38. To investigate the relationship between these elements, we have used immunohistochemistry to analyze the expression of GluR2 in the cerebral cortex of postnatal rats (postnatal Day [PD] 8 and 14) after administering them with monosodium glutamate (MSG; 4 mg/g body weight on PD1, 3, 5, and 7). Similarly, the expression of REST, Fas-L and Bcl-2 mRNA transcripts in animals exposed to a p38 inhibitor, SB203580 (0.42 microg/g body weight, administered subcutaneously) was determined by reverse transcriptase-PCR. The enhanced GluR2-expression in the cerebral cortex at PD8 and the down regulation of this receptor at PD14 was correlated with neuronal damage induced by excitotoxicity. In addition, the enhanced expression of REST at PD8 and PD14 suggests that the induction of REST transcription contributes to glutamate-induced excitotoxic neurodegeneration, possibly by modulating GluR2 expression. Fas-L and Bcl-2 over expression at PD8 and their subsequent down regulation at PD14 also suggests that Fas-L could be the direct effector of apoptosis in the cerebral cortex. On the other hand, the presence of Bcl-2 at PD8 could attenuate certain survival signals in neurons under these neurotoxic conditions. Thus, a change in glutamate receptor composition, and enhanced Fas-L and Bcl-2 expression, coupled with activation of the p38/SAPK pathway appear to be events involved in the neuronal apoptosis induced under neurotoxic conditions.

NR1, NR2A and NR2C subunits expression after cervical spinal cord transplant and section in dogs.

This paper served to evaluate the expression levels of subunits NR1, NR2A and NR2C which are implicated in neuronal plasticity events. A 50% (right half) 4 mm longitudinal resection of the spinal cord was done at the C5-C6 level with preservation of the anterior spinal artery. This was effected in a dog model after either a homologous transplant or a pure spinal cord section. In this study we used two groups of dogs with four individuals each, as well as a control group. The transplant group (n=4) was analyzed at days 3 and 28 post surgery. The section group (n=4) was also analyzed at days 3 and 28 post op. All three groups (transplant, section and control) were evaluated as to the subunit expression in each of the segments corresponding to the transplanted or sectioned sites, the site contralateral to the transplanted or sectioned sites at levels half a centimeter both proximal and distal to the site of transplant and section. The results showed a variety of changes in each of the subunits depending on the group, the segment and the time of evaluation (acute versus chronic). This could be closely related to mechanisms which participate in regeneration and functional recuperation.

NMDAR-2C and 2D subunits gene expression is induced in brain by neonatal exposure of monosodium L-glutamate to adult rats.

Monosodium glutamate (MSG) was administered subcutaneously to male neonate rats, and the effects on N-methyl-D-asparatate (NMDA) subunit receptor types NR2C and NR2D from different brain regions were studied. A semi-quantitative reverse transcription-polymerase chain reaction was used to measure NR2C and NR2D expression levels in the cerebral cortex, hippocampus and striatum. MSG treatment (4 mg/g body weight, on postnatal days 1, 3, 5, and 7) produced an important increase of NR2C and NR2D subunit gene expression levels in the hippocampus and striatum of adults rats. No change was observed in the cerebral cortex. We propose that an early excessive activation of glutamate receptors could modify NMDA subunit expression and its structural composition on postnatal development. This, as part of a compensatory response by an altered neuronal circuitry, mainly in the hippocampus and striatum, suggests that the NMDA receptor could be a determinant factor to modulate the dendritic arrangement and the synaptogenesis.