Expression of c-fos and hsp70 mRNA in neonatal rat cerebrocortical slices during NMDA-induced necrosis and apoptosis

Fos expression following activation of the ventral pallidum in normal rats and in a model of Parkinson's Disease: implications for limbic system and basal ganglia interactions

The circuit-related consequences of activating the ventral pallidum (VP) are not well known, and lacking in particular is how these effects are altered in various neuropathological states. To help to address these paucities, this study investigated the brain regions affected by VP activation by quantifying neurons that stain for Fos-like immunoreactivity (ir). Fos-ir was assessed after intra-pallidal injections of the excitatory amino acid agonist, NMDA, or the GABA(A) antagonist, bicuculline in normal rats and in those rendered Parkinsonian-like by lesioning dopaminergic neurons with the neurotoxin, 6-OHDA. We hypothesized that activation of the VP will alter the activity state of brain regions associated with both the basal ganglia and limbic system, and that this influence would be modified in the Parkinsonian state. Blocking tonically activated GABA(A) receptors with bicuculline (50 ng/0.5 microl) elevated Fos-ir in the VP to 423% above the contralateral, vehicle-injected side. Likewise, intra-VP NMDA (0.23 microg or 0.45 microg/0.5 microl), dose-dependently increased the number of pallidal neurons expressing Fos-ir by 224 and 526%, respectively. At higher NMDA doses, the density of Fos-ir neurons was not elevated above control levels. This inverted U-shaped profile was mirrored by a VP output structure, the medial subthalamic nucleus (mSTN). The mSTN showed a 289% increase in Fos-ir neurons with intra-VP injections of 0.45 microg NMDA, and this response was halved following intra-VP injections of 0.9 microg NMDA. Of the 12 other brain regions measured, three showed VP NMDA-induced enhancements in Fos-ir: the frontal cortex, entopeduncular nucleus and substantia nigra pars reticulata, all regions associated with the basal ganglia. In a second study, we evaluated the NMDA activation profile in a rat model of Parkinson's Disease (PD) which was created by a unilateral injection of 6-OHDA into the rostral substantia nigra pars compacta. Comparisons of responses to intra-VP NMDA between the hemispheres ipsilateral and contralateral to the lesion revealed that Fos-ir cells in the pedunculopontine nucleus was reduced by 62%, whereas Fos-ir for the basolateral amygdala and STN was reduced by 32 and 42%, respectively. These findings support the concept that the VP can influence both the basal ganglia and the limbic system, and that that the nature of this influence is modified in an animal model of PD. As the VP regulates motivation and cognition, adaptations in this system may contribute to the mood and mnemonic disorders that can accompany PD.

Prognostic significance of loss of c-fos protein in gastric carcinoma

c-fos was first identified as a viral oncoprotein, and has been studied in terms of its oncogenic function in tumorigenesis. Many experimental and clinical data indicated that c-fos expression plays a role in the progression of several types of carcinomas. However, some recent studies challenge this view as they indicate that c-fos has tumor suppressor activity. In the present study, we assessed c-fos protein expression in 625 consecutive gastric cancers immunohistochemically, and analyzed its relationship with clinicopathologic factors and survival. We found that a loss of c-fos expression is correlated with a more advanced stage, lymph node metastasis, lymphatic invasion and shorter survival, indicating that c-fos expression in gastric cancer cells is lost during progression and that this loss is associated with a poor prognosis. The above findings suggest that loss of c-fos expression has tumor suppressor activity in gastric cancer and we suspect that this suppressor activity might be related to the pro-apoptotic function of c-fos.

Effects of edaravone on N-methyl-D-aspartate (NMDA)-mediated cytochrome c release and apoptosis in neonatal rat cerebrocortical slices

N-Methyl-D-aspartate-mediated neurotoxicity is known to involve nitric oxide production and to be augmented in an environment of reactive oxygen species. We used TUNEL staining and homogenous cytosolic immunoreactivity of cytochrome c in an acute brain slice preparation to investigate the influence of edaravone (3-methyl-1-phenyl-2-pyrazolin-5-one), a free radical scavenger, on N-methyl-D-aspartate-induced apoptosis. Cerebrocortical slices were obtained from parietal lobes of 7-day-old Sprague-Dawley rats, superfused with well-oxygenated artificial cerebrospinal fluid, and metabolically recovered. Subsequent 30-min exposures to 10 microM N-methyl-D-aspartate in treated and untreated slices were followed by 4 h of recovery superfusion with oxygenated artificial cerebrospinal fluid. Outcomes were compared for three groups of slices: "the N-methyl-D-aspartate-only group"; "the edaravone treatment group", which had 20 microM edaravone present throughout and subsequent to N-methyl-D-aspartate exposure; the "control group", in which slices were superfused only with oxygenated artificial cerebrospinal fluid. At the conclusion of recovery (t = 4 h), the percentage of TUNEL-positive cells in the edaravone treatment group (7.0+/-3.3%) was significantly reduced from the percentage for the N-methyl-D-aspartate-only group (21.9+/-4.1%), and insignificantly greater than the percentage for the control group (3.4+/-2.1%). Percentages of cytochrome c positive cells at t = 1 h were significantly increased (p < 0.01) in the N-methyl-d-aspartate-only group (30.6+/-1.9%) compared to percentages for both the control group (11.4+/-2.6%) and the edaravone treatment group (15.2+/-2.1%). Edaravone's reduction in TUNEL staining and cytochrome c release provides evidence of reactive oxygen species mechanisms and antioxidant benefits in cytochrome c-mediated apoptosis during N-methyl-D-aspartate excitotoxicity.

Oxidative metabolism, apoptosis and perinatal brain injury

Perinatal hypoxic-ischaemic injury (HII) is a significant cause of neurodevelopmental impairment and disability. Studies employing 31P magnetic resonance spectroscopy to measure phosphorus metabolites in situ in the brains of newborn infants and animals have demonstrated that transient hypoxia-ischaemia leads to a delayed disruption in cerebral energy metabolism, the magnitude of which correlates with the subsequent neurodevelopmental impairment. Prominent among the biochemical features of HII is the loss of cellular ATP, resulting in increased intracellular Na+ and Ca2+, and decreased intracellular K+. These ionic imbalances, together with a breakdown in cellular defence systems following HII, can contribute to oxidative stress with a net increase in reactive oxygen species. Subsequent damage to lipids, proteins, and DNA and inactivation of key cellular enzymes leads ultimately to cell death. Although the precise mechanisms of neuronal loss are unclear, it is now clear both apoptosis and necrosis are the significant components of cell death following HII. A number of different factors influence whether a cell will undergo apoptosis or necrosis, including the stage of development, cell type, severity of mitochondrial injury and the availability of ATP for apoptotic execution. This review will focus on some pathological mechanisms of cell death in which there is a disruption to oxidative metabolism. The first sections will discuss the process of damage to oxidative metabolism, covering the data collected both from human infants and from animal models. Following sections will deal with the molecular mechanisms that may underlie cerebral energy failure and cell death in this form of brain injury, with a particular emphasis on the role of apoptosis and mitochondria.

Neuroprotection mediated by subtoxic dose of NMDA in SH-SY5Y neuroblastoma cultures: activity-dependent regulation of PSA-NCAM expression

The NMDA class of glutamate receptors plays a critical role in CNS, such as synaptic plasticity, axonal sprouting, growth, and migration. NMDA receptor stimulation has been shown to regulate polysialylated neural cell adhesion molecule (PSA-NCAM) expression in glial cell cultures and in hippocampal slice cultures. There is also growing evidence that molecular chaperons and ROS are related to the synaptic plasticity phenomena. We have examined the neuroprotective effect of subtoxic dose of NMDA in retinoic acid differentiated SH-SY5Y neuroblastoma cells. SH-SY5Y cell line differentiated with retinoic acid (10 muM) was exposed to NMDA (100 microM) or to antagonist MK-801 (200 nM) + NMDA and cells harvested after 24 h of treatment for PSA-NCAM, NCAM, and HSP70 expression study and for biochemical analysis. A significant increase was observed in PSA-NCAM, NCAM-180, NCAM-140, and HSP70 expression as seen by Western blotting and immunocytofluorescent studies in NMDA-treated cultures. Biochemical analysis revealed a significant increase in the activities of glutathione peroxidase (GPx) and copper zinc-superoxide dismutase (CuZnSOD) upon exposure to NMDA. No significant change was observed in the level of lipid peroxidation. All the changes observed reverted back to the control values upon pretreatment of cultures with MK-801, a non-competitive NMDA receptor antagonist, prior to NMDA exposure indicating the involvement of NMDA receptor in these changes. These results illustrate the neuroprotective role of subtoxic dose of NMDA in SH-SY5Y neuroblastoma cells.

Crush injury induces NMDA-receptor-dependent delayed nerve cell death in rat entorhinal-hippocampal slice cultures

The aim of the present study was to develop an in vitro model that produces an injury-induced delayed nerve cell death. We used entorhinal-hippocampal slices from 12-day-old rats, which were cultured for 14 days before experiments prior to a crush injury in the middle layers of the entorhinal cortex. Crush injury increased specific propidium iodide (PI) fluorescence at the site of primary injury at day 1. Specific PI fluorescence decreased over the following days, with a slower decrease taking place at days 4-7. At days 4-7, PI fluorescence increased in CA1 and CA3. Treatment with 30 microM MK-801 for 2 h at the time of crush injury prevented the increase in PI fluorescence at days 4-7 at the site of injury, in CA1, and in CA3. Crush injury induced TUNEL-positive cells at the site of injury at days 1 and 5. MK-801 markedly reduced the number of TUNEL-positive cells observed at day 5, but had no effect on the number of TUNEL-positive cells at day 1. The present data indicate that crush injury may induce two types of secondary cell death. The first, early, type of cell death is induced quickly and is maximal at day 1, after which the dead cells are gradually removed. The second, delayed, type of cell death appears at day 4. NMDA receptor antagonism prevents the induction of the delayed cell death but has no effect on the early cell death.

Profound molecular changes following hippocampal slice preparation: loss of AMPA receptor subunits and uncoupled mRNA/protein expression

The acute hippocampal slice preparation is a convenient, in vitro model widely used to study the biological basis of synaptic plasticity. Although slices may preserve their electrophysiological properties for several hours, profound molecular changes in response to the injury caused by the slicing procedure are likely to occur. To determine the magnitude and duration of these changes we examined the post-slicing expression kinetics of three classes of genes known to be implicated in long-term synaptic plasticity: glutamate AMPA receptors (GluR), transcription factors and neurotrophins. Slicing resulted in a striking loss of GluR1 and GluR3, but not of GluR2 proteins suggesting that rapid changes in the composition of major neurotransmitter receptors may occur. Slicing caused a significant induction of the transcription factors c-fos, zif268, CCAAT enhancer binding protein (C/EBP ) beta and delta mRNAs and of the neurotrophin brain-derived neurothophic factor (BDNF ) mRNA. In contrast, there was no augmentation, and sometimes a decline, in the levels of the corresponding proteins. These data reveal that significant discrepancies exist between the slice preparation and the intact hippocampus in terms of the metabolism of molecular components known to be involved in synaptic plasticity.

Laminar variation in neuronal viability and trophic dependence in neocortical slices

Organotypic slices are used frequently in studies of central nervous system development and function because they provide excellent experimental access with significant preservation of cellular context and relationships. Within a slice, however, a variety of factors may cause individual classes of neurons to respond differently to the culture environment. Differences in deafferentation, cellular maturation, trophic dependence and ongoing naturally occurring cell death may produce changes in the neuronal population that are transparent to the experimenter but that could affect experimental results significantly. In this study, we examined the distribution and prevalence of cell death among neurons in each cortical layer in organotypic slices. In addition, we assessed the ability of several neurotrophic factors to ameliorate neuronal death in each cortical layer. Within the first 24 hr in culture, there was striking laminar variation in the extent of neuronal death in culture, which could not be accounted for by the pattern of programmed cell death in vivo. In addition, neurons in the six layers of the neocortex differed in the degree to which they could be rescued by neurotrophic factors. These data suggest that differential neuronal death and rescue are important considerations in studies utilizing organotypic slices and may represent particularly confounding variables in studies of effects of trophic factors in such preparations.

Ceramide-induced apoptosis in cortical neurons is mediated by an increase in p38 phosphorylation and not by the decrease in ERK phosphorylation

Ceramide, the central molecule of the sphingomyelin pathway, serves as a second messenger for cellular functions ranging from proliferation and differentiation to growth arrest and apoptosis. In this study we show that c2-ceramide induces apoptosis in primary cortical neuron cultures and that this effect correlates with differential modulation of mitogen-activated protein kinase (MAPK) cascades. Phosphorylation of extracellular signal-regulated kinases (ERKs) and their upstream activators MAPK kinases (MEKs), as measured by immunoblotting is rapidly decreased by c2-ceramide. However, the MEK inhibitor PD98059 alone does not induce apoptosis and in combination with c2-ceramide it does not modify c2-ceramide-induced apoptosis. Treatment with c2-ceramide increases p38 and c-Jun N-terminal kinase (JNK) phosphorylation before and during caspase-3 activation. The p38 inhibitor SB203580 partially protects cortical neurons against c2-ceramide-induced apoptosis, implicating the p38 pathway in this process. The c2-ceramide treatment also increases levels of c-jun, c-fos and p53 mRNA in primary cortical neuron cultures, but this is independent of p38 activation. Our study further elucidates the time-courses of MAPK cascade modulation, and of c-jun, c-fos and p53 activation during c2-ceramide-induced neuronal apoptosis. It reveals that one of the activated kinases, p38, is necessary for this apoptosis.

Hippocampal apoptosis in major depression is a minor event and absent from subareas at risk for glucocorticoid overexposure

Glucocorticoid (GC) overexposure in animals has been implicated in hippocampal dysfunctioning and neuronal loss. In major depression, hypercortisolemia, hypothalamic-pituitary-adrenocortical-axis alterations, and reduced hippocampal volumes are commonly observed; hence, hippocampal neurodegeneration is also expected. To study possible GC-related pathology, we investigated hippocampal tissue of 15 major-depressed patients, 16 matched controls, and 9 steroid-treated patients, using in situ-end-labeling for DNA fragmentation and apoptosis, and heat-shock protein 70 and nuclear transcription factor kappaB immunocytochemistry for damage-related responses. No obvious massive cell loss was observed in any group. In 11 of 15 depressed patients, rare, but convincing apoptosis was found in entorhinal cortex, subiculum, dentate gyrus, CA1, and CA4. Also in three steroid-treated patients, apoptosis was found. Except for several steroid-treated patients, heat-shock protein 70 staining was generally absent, nor was nuclear transcription factor-kappaB activation found. The detection in 11 of 15 depressed patients, in three steroid-treated, and in one control patient, demonstrates for the first time that apoptosis is involved in steroid-related changes in the human hippocampus. However, in absence of major pyramidal loss, its rare occurrence, that notably was absent from areas at risk for GC damage such as CA3, indicates that apoptosis probably only contributes to a minor extent to the volume changes in depression.

Expression and changes of HSP70 in the rat forebrain subjected to gamma knife (100Gy) irradiation targeted on the caudate putamen and survived for different times

Forebrain heat shock protein 70 (HSP70) immunohistochemical reactivity was investigated in rats subjected to gamma knife irradiation focusing on the right caudate putamen nucleus. The forebrain sections of all experimental animals were processed with anti-HSP70 antiserum and then by avidin-biotin peroxidase complex immunohistochemistry after gamma ray irradiation with a dose of 100Gy and they each survived for different times (from 30 min to 30 days). Some neurons, glial cells, and endothelial cells were HSP70-like immunoreactivity (HSP70-LI) positive. HSP70-LI was mainly distributed in the target area of irradiation, as well as in non-target regions, e.g. the cortex, hippocampus, and hypothalamus, etc. The expression and change of HSP70-LI from 3 h to 30 days after irradiation followed the following rules: (1) Within 3 to 24 h, the dilated vessels with HSP70-LI endothelial cells were found at first, and a few lightly stained HSP70-LI neurons and glias were observed in the target and non-target regions; (2) In 3-7 days, darkly stained HSP70-LI neurons and glias were apparently increased and formed an expression peak. From 14 to 30 days, HSP70-LI cells were distinctly decreased and became weakly stained or negative. These results suggested that although the irradiation target of the gamma knife was localized, the response to irradiation occurred extensively.

BDNF protects the neonatal brain from hypoxic-ischemic injury in vivo via the ERK pathway

Neurotrophins activate several different intracellular signaling pathways that in some way exert neuroprotective effects. In vitro studies of sympathetic and cerebellar granule neurons have demonstrated that the survival effects of neurotrophins can be mediated via activation of the phosphatidylinositol 3-kinase (PI3-kinase) pathway. Neurotrophin-mediated protection of other neuronal types in vitro can be mediated via the extracellular signal-related protein kinase (ERK) pathway. Whether either of these pathways contributes to the neuroprotective effects of neurotrophins in the brain in vivo has not been determined. Brain-derived neurotrophic factor (BDNF) is markedly neuroprotective against neonatal hypoxic-ischemic (H-I) brain injury in vivo. We assessed the role of the ERK and PI3-kinase pathways in neonatal H-I brain injury in the presence and absence of BDNF. Intracerebroventricular administration of BDNF to postnatal day 7 rats resulted in phosphorylation of ERK1/2 and the PI3-kinase substrate AKT within minutes. Effects were greater on ERK activation and occurred in neurons. Pharmacological inhibition of ERK, but not the PI3-kinase pathway, inhibited the ability of BDNF to block H-I-induced caspase-3 activation and tissue loss. These findings suggest that neuronal ERK activation in the neonatal brain mediates neuroprotection against H-I brain injury, a model of cerebral palsy.

Induction by synaptic zinc of heat shock protein-70 in hippocampus after kainate seizures

Following seizures, heat shock protein (HSP)-70 is induced in various brain regions. Since zinc that can induce HSP-70 in various cell systems is enriched in certain glutamatergic terminals and translocates to postsynaptic neurons with seizures, we examined the possibility that HSP-70 induction in the epileptic brain is mediated by synaptic zinc. Adult rats were injected intraperitoneally with kainate to induce seizures. Seizures were halted 3 h after the kainate administration by the injection of phenytoin. Staining of brain sections with zinc-specific fluorescent dye TFL at 24 h after the kainate injection revealed a one-to-one correlation between dense TFL fluorescence and acidophilic neuronal degeneration in the hippocampus. Subsequent staining with anti-HSP-70 antibody, however, revealed that more numerous neurons than degenerating neurons exhibited HSP-70 immunoreactivity. Most of the HSP-70(+) neurons were not stained with acid fuchsin but exhibited mild zinc fluorescence in the cytoplasm. Intraventricular injection of CaEDTA attenuated neuronal death as well as the HSP-70 induction in a dose-dependent manner. Supporting the specificity of zinc rather than calcium as the inducer of HSP-70 in neurons, exposure to zinc but not to a calcium ionophore or excitotoxins increased expression of HSP-70 mRNA and protein in cultured cortical neurons. The present results suggest that not only selective neuronal death, but also HSP-70 induction in neurons after seizures, is mediated by the translocation of endogenous synaptic zinc.

Immunohistochemical nitrotyrosine distribution in neonatal rat cerebrocortical slices during and after hypoxia

The peroxynitrite contributions to hypoxic damage in brain slices that arise from N-methyl-D-aspartate (NMDA) receptor activation were studied by following the temporal-spatial course of nitrotyrosine (NT) formation during six conditions: hypoxia (pO(2)<5 mmHg) with or without 10 microM MK-801 treatment; with exposure to 10, 100 and 1000 microM NMDA; and no treatment (control). In each experiment, twenty 350-micrometer thick cerebrocortical slices, obtained from the parietal lobes of ten 7-day-old Sprague-Dawley rats, were metabolically recovered and allowed to respire in a well-oxygenated perfusion system. Thirty minutes exposures to hypoxia or NMDA were followed by 2 h of oxygenated reperfusion. MK-801 administration began 15 min prior to hypoxia and was discontinued during reperfusion. Anti-NT serum immunohistochemistry stains in 20-micrometer frozen sections of slices taken during oxygenated reperfusion, after hypoxia or NMDA exposure, were positive in both neurons and endothelial cells. NT-positive neurons were detected sooner after hypoxia than after NMDA exposure, suggesting that mechanisms of superoxide generation were different in both groups. After hypoxia and even more so after NMDA exposure, more intense NT-positive staining was observed in endothelial cells than in neurons. Cell damage after hypoxia was attenuated by MK-801. MK-801 decreased post-hypoxia counts of NT-stained endothelial cells by 78.5% (p<0. 001) and NT-stained neurons by 54.1% (p<0.05). Our findings suggest that NMDA receptor activation in hypoxic brain slices is associated with increased post-hypoxic peroxynitrite production that contributes to acute neuronal death and endothelial cell injury. Peroxynitrite injury to endothelial cells, caused either by increased peroxynitrite from within or from increased vulnerability to peroxynitrite from without, might play an important role in hypoxic-ischemic brain injury and NMDA-induced brain injury.

c-fos expression in brains of patients with Down syndrome

c-fos is a protooncogene serving in multiple physiological processes in brain from signalling to proliferation and synaptic plasticity. We therefore decided to determine this transcription factor in control and Down Syndrome (DS) brain with the Rationale that c-fos may be linked to brain damage in DS. We determined mRNA steady state levels in frontal, parietal, occipital, temporal cortex and cerebellum of 9 patients with DS and 9 controls using RT-PCT. Significantly increased levels of mRNA c-fos normalized versus the housekeeping gene beta-actin mRNA were found in frontal, parietal and temporal cortex of DS brain. c-fox mRNA levels comparable to controls were found in occipital cortex and cerebellum. Deteriorated c-fos expression in the individual brain regions may be linked to increased apoptosis and neurodegeneration, overexcitation by excitatory amino acids of reactive oxygen species.