Glial fibrillary acidic protein and related glial proteins as biomarkers of neurotoxicity

Berberine ameliorate oxidative stress and astrogliosis in the hippocampus of STZ-induced diabetic rats

Diabetes mellitus increases the risk of central nervous system (CNS) disorders such as stroke, seizures, dementia, and cognitive impairment. Berberine, a natural isoquinoline alkaloid, is reported to exhibit beneficial effect in various neurodegenerative and neuropsychiatric disorders. Moreover, astrocytes are proving critical for normal CNS function, and alterations in their activity and impaired oxidative stress could contribute to diabetes-related cognitive dysfunction. Metabolic and oxidative insults often cause rapid changes in glial cells. Key indicators of this response are increased synthesis of glial fibrillary acidic protein (GFAP) as an astrocytic marker. Therefore, we examined the effects of berberine on glial reactivity of hippocampus in streptozotocin (STZ)-induced diabetic rats, using GFAP immunohistochemistry. Lipid peroxidation, superoxide dismutase (SOD) activity, and nitrite levels were assessed as the parameters of oxidative stress. Eight weeks after diabetes induction, we observed increased numbers of GFAP(+) astrocytes immunostaining associated with increased lipid peroxidation, decreased superoxide dismutase activity, and elevated nitrite levels in the hippocampus of STZ-diabetic rats. In contrast, chronic treatment with berberine (50 and 100 mg/kg p.o. once daily) lowered hyperglycemia, reduced oxidative stress, and prevented the upregulation of GFAP in the brain of diabetic rats. In conclusion, the present study demonstrated that the treatment with berberine resulted in an obvious reduction of oxidative stress and GFAP-immunoreactive astrocytes in the hippocampus of STZ-induced diabetic rats.

MPTP-induced dopamine neuron degeneration and glia activation is potentiated in MDMA-pretreated mice

Clinical observations report a greater propensity to develop Parkinson's disease (PD) in amphetamine users. 3,4-Methylenedioxymethamphetamine (MDMA; "ecstasy") is an amphetamine-related drug that is largely consumed by adolescents and young adults, which may have neuroinflammatory and neurotoxic effects. Here, the objective was to evaluate in mice whether consumption of MDMA during adolescence might influence the neuroinflammatory and neurotoxic effects of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP), a toxin known to induce PD in humans. The activation of astroglia and microglia by glial fibrillary acidic protein (GFAP) and complement receptor type 3 (CD11b) immunohistochemistry and the degeneration of dopaminergic neurons by tyrosine hydroxylase (TH) immunohistochemistry were evaluated. MPTP (20 mg/kg × 4) was administered to mice treated from ages 8 weeks to 17 weeks with MDMA (10 mg/kg twice daily, two times a week). In mice that were chronically treated with MDMA, administration of MPTP induced a higher microglial and astroglial response in both the striatum and the substantia nigra pars compacta (SNc) compared with vehicle-treated or vehicle + MPTP-treated mice. Inflammatory changes were associated with a decrease in TH immunoreactivity in the SNc of MDMA-treated mice and with a further decrease in the striatum and the SNc of MDMA + MPTP-treated mice compared with vehicle-treated, MDMA-treated, and MPTP-treated mice. The results demonstrate that chronic administration of MDMA during late adolescence in mice exacerbates the neurodegeneration and neuroinflammation caused by MPTP, suggesting that MDMA may constitute a risk factor for dopaminergic neuron degeneration.

In vivo molecular markers for pro-inflammatory cytokine M1 stage and resident microglia in trimethyltin-induced hippocampal injury

Microglia polarization to the classical M1 activation state is characterized by elevated pro-inflammatory cytokines; however, a full profile has not been generated in the early stages of a sterile inflammatory response recruiting only resident microglia. We characterized the initial M1 state in a hippocampal injury model dependent upon tumor necrosis factor (TNF) receptor signaling for dentate granule cell death. Twenty-one-day-old CD1 male mice were injected with trimethyltin (TMT 2.3 mg/kg, i.p.) and the hippocampus was examined at an early stage (24-h post-dosing) of neuronal death. Glia activation was assessed using a custom quantitative nuclease protection assay. We report elevated mRNA levels for glia response such as ionizing calcium-binding adapter molecule-1 and glial fibrillary acidic protein (Gfap); Fas, hypoxia inducible factor alpha, complement component 1qb, TNF-related genes (Tnf, Tnfaip3, Tnfrsfla); interleukin-1 alpha, Cd44, chemokine (C-C motif) ligand (Ccl)2, Cc14, integrin alpha M, lipocalin (Lcn2), and secreted phosphoprotein 1 (Spp1). These changes occurred in the absence of changes in matrix metalloproteinase 9 and 12, neural cell adhesion molecule, metabotropic glutamate receptor (Grm)3, and Ly6/neurotoxin 1 (Lynx1), as well as, a decrease in neurotrophin 3, glutamate receptor subunit epsilon (Grin)-2b, and neurotrophic tyrosine kinase receptor, type 3. The M2 anti-inflammatory marker, transforming growth factor beta-1 (Tgfb1) was elevated. mRNAs associated with early stage of injury-induced neurogenesis including fibroblast growth factor 21 and Mki67 were elevated. In the "non-injured" temporal cortex receiving projections from the hippocampus, Lynx1, Grm3, and Grin2b were decreased and Gfap increased. Formalin fixed-paraffin-embedded tissue did not generate a comparable profile.

Amniotic fluid glial fibrillary acidic protein (AF-GFAP), a biomarker of open neural tube defects

OBJECTIVE

Neural tube defects (NTDs) are usually identified by ultrasonography and confirmed by alpha-fetoprotein (AFP) assay and acetylcholinesterase (AchE) electrophoresis in amniotic fluid. Yet, both of these biomarkers can be found positive in other etiologies. Here, amniotic fluid glial fibrillary acidic protein (AF-GFAP), which was identified by a proteomic study, is shown to be a useful biomarker for NTD diagnosis.

METHOD

Amniotic fluid glial fibrillary acidic protein was measured by an ELISA assay in 138 cases of NTDs. Seventy samples from normal pregnancies used as controls and 27 samples giving false positive or false negative results either for AchE or AFP and corresponding to fetal death (n = 8), gastroschisis (n = 8), and unexplained etiologies (n = 11) were also tested.

RESULTS

Whatever the gestational age, GFAP was below 0.2 ng/mL in control samples, whereas 99.1% of open NTDs (29/29 in the anterior NTD group and 80/81 in the spina bifida group) were above this threshold. Closed NTDs were all negative (28/28). None of the other samples tested were positive, except in case of fetal death (8/8).

CONCLUSIONS

Amniotic fluid glial fibrillary acidic protein is a sensitive biomarker for open NTD diagnosis with a good negative predictive value for closed NTD. Compared with AFP and AchE, our results indicate that AF-GFAP alone is more efficient than this classical association.

Attenuation of neurological injury with early baicalein treatment following subarachnoid hemorrhage in rats

OBJECT

Baicalein has been shown to offer neuroprotection in the ischemic brain, but its effect in subarachnoid hemorrhage (SAH) is unknown. The authors used a double-hemorrhage model to study the role of early baicalein treatment in SAH.

METHODS

Subarachnoid hemorrhage was induced in male Wistar rats through a repeat injection of autologous blood at a 48-hour interval. Rats subjected or not subjected to SAH received a 30-mg/kg baicalein injection 3 hours after SAH and daily for 6 consecutive days, and results were compared with those obtained in vehicle-treated control rats. Mortality of the rats was recorded. Neurological outcome was assessed daily. Cerebrospinal fluid dialysates were collected and examined for glutamate concentrations. Cerebral vasospasm (CVS), brain water content, neuron variability, expression of glutamate transporter-1 (GLT-1), immunoreactivity of astrocyte, and level of malondialdehyde, activities of superoxide dismutase (SOD), and catalase in brain tissues content were determined on post-SAH Day 7.

RESULTS

Mortality rate, neuronal degeneration, brain water content, and CVS were decreased and neurological function improved in the baicalein-treated rats. Baicalein increased astrocyte activity and preserved GLT-1, which attenuated the glutamate surge after SAH. Baicalein also provided antioxidative stress by preserving activities of SOD and catalase and decreased malondialdehydelevel after SAH. The glutamate, body weight, neurological scores, and glial fibrillary acidic protein activity were significantly correlated. The CVS was correlated with neuronal degeneration, and GLT-1 was correlated with oxidative stress.

CONCLUSIONS

Early baicalein treatment attenuated CVS and limited neurological injury following SAH. These data may indicate clinical utility for baicalein as an adjunct therapy to reduce brain injury and improve patient outcomes.

Astrocyte plasticity revealed by adaptations to severe proteotoxic stress

Neurodegeneration is characterized by an accumulation of misfolded proteins in neurons. It is less well appreciated that glia often also accumulate misfolded proteins. However, glia are highly plastic and may adapt to stress readily. Endogenous adaptations to stress can be measured by challenging stressed cells with a second hit and then measuring viability. For example, subtoxic stress can elicit preconditioning or tolerance against second hits. However, it is not known if severe stress that kills half the population can elicit endogenous adaptations in the remaining survivors. Glia, with their resilient nature, offer an ideal model in which to test this new hypothesis. The present study is the first demonstration that astrocytes surviving one LC50 hit of the proteasome inhibitor MG132 were protected against a second MG132 hit. ATP loss in response to the second hit was also prevented. MG132 caused compensatory rises in stress-sensitive heat shock proteins. However, stressed astrocytes exhibited an even greater rise in ubiquitin-conjugated proteins upon the second hit, illustrating the severity of the proteotoxicity and verifying the continued impact of MG132. Despite this stress, MG132-pretreated astrocytes were completely prevented from losing glutathione with the second hit. Furthermore, inhibiting glutathione synthesis rendered astrocytes sensitive to the second hit, unmasking the cumulative impact of two hits by removal of an endogenous adaptation. These findings suggest that stressed astrocytes become progressively harder to kill by virtue of antioxidant defenses. Such plasticity may permit astrocytes under severe stress to better support neurons and help explain the protracted nature of neurodegeneration.

NOX2 deficiency attenuates markers of adiposopathy and brain injury induced by high-fat diet

The consumption of high-fat/calorie diets in modern societies is likely a major contributor to the obesity epidemic, which can increase the prevalence of cancer, cardiovascular disease, and neurological impairment. Obesity may precipitate decline via inflammatory and oxidative signaling, and one factor linking inflammation to oxidative stress is the proinflammatory, pro-oxidant enzyme NADPH oxidase. To reveal the role of NADPH oxidase in the metabolic and neurological consequences of obesity, the effects of high-fat diet were compared in wild-type C57Bl/6 (WT) mice and in mice deficient in the NAPDH oxidase subunit NOX2 (NOX2KO). While diet-induced weight gains in WT and NOX2KO mice were similar, NOX2KO mice had smaller visceral adipose deposits, attenuated visceral adipocyte hypertrophy, and diminished visceral adipose macrophage infiltration. Moreover, the detrimental effects of HFD on markers of adipocyte function and injury were attenuated in NOX2KO mice; NOX2KO mice had improved glucose regulation, and evaluation of NOX2 expression identified macrophages as the primary population of NOX2-positive cells in visceral adipose. Finally, brain injury was assessed using markers of cerebrovascular integrity, synaptic density, and reactive gliosis, and data show that high-fat diet disrupted marker expression in WT but not NOX2KO mice. Collectively, these data indicate that NOX2 is a significant contributor to the pathogenic effects of high-fat diet and reinforce a key role for visceral adipose inflammation in metabolic and neurological decline. Development of NOX-based therapies could accordingly preserve metabolic and neurological function in the context of metabolic syndrome.

Chronic exposure to corticosterone enhances the neuroinflammatory and neurotoxic responses to methamphetamine

Up-regulation of proinflammatory cytokines and chemokines in brain ("neuroinflammation") accompanies neurological disease and neurotoxicity. Previously, we documented a striatal neuroinflammatory response to acute administration of a neurotoxic dose of methamphetamine (METH), i.e. one associated with evidence of dopaminergic terminal damage and activation of microglia and astroglia. When we used minocycline to suppress METH-induced neuroinflammation, indices of dopaminergic neurotoxicity were not affected, but suppression of neuroinflammation was incomplete. Here, we administered the classic anti-inflammatory glucocorticoid, corticosterone (CORT), in an attempt to completely suppress METH-related neuroinflammation. METH alone caused large increases in striatal proinflammatory cytokine/chemokine mRNA and subsequent astrocytic hypertrophy, microglial activation, and dopaminergic nerve terminal damage. Pre-treatment of mice with acute CORT failed to prevent neuroinflammatory responses to METH. Surprisingly, when mice were pre-treated with chronic CORT in the drinking water, an enhanced striatal neuroinflammatory response to METH was observed, an effect that was accompanied by enhanced METH-induced astrogliosis and dopaminergic neurotoxicity. Chronic CORT pre-treatment also sensitized frontal cortex and hippocampus to mount a neuroinflammatory response to METH. Because the levels of chronic CORT used are associated with high physiological stress, our data suggest that chronic CORT therapy or sustained physiological stress may sensitize the neuroinflammatory and neurotoxicity responses to METH.

Nervous system autoantibodies and vitamin D receptor gene polymorphisms in hemodialysis patients

Cognitive deficits are prevalent in hemodialysis (HD) patients. Vitamin D deficiency and vitamin D receptor (VDR) gene single nucleotide polymorphism (SNPs) have been linked to both neurodegeneration (ND) and neuroprotection, respectively. Autoantibodies (Ab) to myelin basic protein (MBP), glial fibrillary acidic protein (GFAP), and neurofilament (NF) triplet proteins arise secondary to nervous system (NS) damage providing a means to assess neurological injury. Characterization of Ab biomarkers of NS damage in HD patients, their association with VDR SNPs, and nutritional vitamin D (NVD) therapy was performed. VDR genotypes, cytokines, and Ab biomarkers to NS proteins in HD subjects receiving ergocalciferol (n = 40) were compared with nonusers (n = 71). Interleukin-6 (IL-6), tumor necrosis factor-α (TNF-α), and immunoglobulin G (IgG) titers against NFs, GFAP, and MBP were measured by immunoassay. Subjects were genotyped for VDR SNPs BsmI (rs1544410) and FokI (rs2228570). Subjects (age 63.3 ± 16.1 years, 66% male) who were C allele carriers of BsmI had higher values of NF-68 antibody titers (p = 0.027). Ergocalciferol users (n = 40) compared with nonusers (n = 71) had lower Ab titers to NS proteins; however, only anti-NF-160 and anti-MBP titers were significantly (p < 0.05) higher. IgG against NS proteins in HD patients suggests neuronal and glial insult and a relationship with VDR alleles. NVD may provide some neuroprotection, indicated by anti-NF-160 and anti-MBP, which was markedly lowered in ergocalciferol patients. This preliminary study suggests that Ab detection may be useful in monitoring ND and the potential of NVD for neuroprotection in HD patients.

Cerebrospinal fluid protein biomarker panel for assessment of neurotoxicity induced by kainic acid in rats

Glutamate excitotoxicity plays a key role in the etiology of a variety of neurological, psychiatric, and neurodegenerative disorders. The goal of this study was to investigate spatiotemporal distribution in the brain and cerebrospinal fluid (CSF) concentrations of ubiquitin C-terminal hydrolase-1 (UCH-L1), glial fibrillary acidic protein (GFAP), αII-spectrin breakdown products (SBDP150, SBDP145, and SBDP120), and their relationship to neuropathology in an animal model of kainic acid (KA) excitotoxicity. Triple fluorescent labeling and Fluoro-Jade C staining revealed a reactive gliosis in brain and specific localization of degenerating neurons in hippocampus and entorhinal cortex of KA-treated rats. Immunohistochemistry showed upregulation of GFAP expression in hippocampus and cortex beginning 24h post KA injection and peaking at 48h. At these time points concurrent with extensive neurodegeneration all SBDPs were observed throughout the brain. At 24h post KA injection, a loss of structural integrity was observed in cellular distribution of UCH-L1 that correlated with an increase in immunopositive material in the extracellular matrix. CSF levels of UCH-L1, GFAP, and SBDPs were significantly increased in KA-treated animals compared with controls. The temporal increase in CSF biomarkers correlated with brain tissue distribution and neurodegeneration. This study provided evidence supporting the use of CSF levels of glial and neuronal protein biomarkers to assess neurotoxic damage in preclinical animal models that could prove potentially translational to the clinic. The molecular nature of these biomarkers can provide critical information on the underlying mechanisms of neurotoxicity that might facilitate the development of novel drugs and allow physicians to monitor drug safety.

Brain injury caused by HIV protease inhibitors: role of lipodystrophy and insulin resistance

HIV-associated neurocognitive disorders (HAND) remain prevalent even with widespread use of combination antiretroviral therapy (ART), suggesting a potential role for co-morbidities in neurologic decline. Indeed, it is well established that ART drugs, particularly HIV protease inhibitors, can induce hyperlipidemia, lipodystrophy, and insulin resistance; all of which are associated with neurologic impairment. This study was designed to determine how metabolic dysfunction might contribute to cognitive impairment and to reveal specific metabolic co-morbidities that could be targeted to preserve brain function. Adult male C57BL/6 mice were thus treated with clinically relevant doses of lopinavir/ritonavir for 4 weeks, and subjected to thorough metabolic, neurobehavioral, and biochemical analyses. Data show that lopinavir/ritonavir resulted in manifestations of lipodystrophy, insulin resistance, and hyperlipidemia. Evaluation of neurologic function revealed cognitive impairment and increased learned helplessness, but not motor impairment following treatment with lopinavir/ritonavir. Further analyses revealed a significant linear relationship between cognitive performance and specific markers of lipodystrophy and insulin resistance. Finally, analysis of brain injury indicated that lopinavir/ritonavir treatment resulted in cerebrovascular injury associated with decreased synaptic markers and increased inflammation, and that the cerebral cortex was more vulnerable than the cerebellum or hippocampus. Collectively, these data reveal an intimate link between metabolic co-morbidities and cognitive impairment, and suggest that remediation of selective aspects of metabolic syndrome could potentially reduce the prevalence or severity HIV-associated neurocognitive disorders.

Particulate matter (PM10) exposure induces endothelial dysfunction and inflammation in rat brain

Epidemiological studies suggest that particulate matter (PM(10)) inhalation was associated with adverse effects on brain-related health, however, existing experimental data lacked relevant evidences. In this study, we treated Wistar rats with PM(10) at different concentrations (0.3, 1, 3 and 10 mg/kg body weight (bw)), and investigated endothelial dysfunction and inflammatory responses in the brain. The results indicate that mild pathological abnormal occurred after 15-day exposure (five times with 3 days each), followed by the changes of endothelial mediators (ET-1 and eNOS) and inflammatory markers (IL-1β, TNF-α, COX-2, iNOS and ICAM-1). Also, the sample up-regulated bax/bcl-2 ratio and p53 expression, and induced neuronal apoptosis. It implicates that PM(10) exerted injuries to mammals' brain, and the mechanisms might be involved in endothelial dysfunction and inflammatory responses.

Astrogliosis: a target for intervention in intracerebral hemorrhage?

Intracerebral hemorrhage (ICH) is a debilitating neurological injury, accounting for 10-15 % of all strokes. Despite neurosurgical intervention and supportive care, the 30-day mortality rate remains ~50 %, with ICH survivors frequently displaying neurological impairments and requiring long-term assisted care. Unfortunately, the lack of medical interventions to improve clinical outcomes has led to the notion that ICH is the least treatable form of stroke. Hence, additional studies are warranted to better understand the pathophysiology of ICH. Astrogliosis is an underlying astrocytic response to a wide range of brain injuries and postulated to have both beneficial and detrimental effects. However, the molecular mechanisms and functional roles of astrogliosis remain least characterized following ICH. Herein, we review the functional roles of astrogliosis in brain injuries and raise the prospects of therapeutically targeting astrogliosis after ICH.

Effects of chronic guanosine treatment on hippocampal damage and cognitive impairment of rats submitted to chronic cerebral hypoperfusion

Chronic cerebral hypoperfusion contributes to a cognitive decline related to brain disorders. Its experimental model in rats is a permanent bilateral common carotid artery occlusion (2VO). Overstimulation of the glutamatergic system excitotoxicity due to brain energetic disturbance in 2VO animals seems to play a pivotal role as a mechanism of cerebral damage. The nucleoside guanosine (GUO) exerts extracellular effects including antagonism of glutamatergic activity. Accordingly, our group demonstrated several neuroprotective effects of GUO against glutamatergic excitotoxicity. Therefore, in this study, we evaluated a chronic GUO treatment effects in rats submitted to 2VO. We evaluated the animals performance in the Morris water maze and hippocampal damage by neurons and astrocytes immunohistochemistry. In addition, we investigated the cerebrospinal fluid (CSF) brain derived neurotrophic factor (BDNF) and serum S100B levels. Additionally, the purine CSF and plasma levels were determined. GUO treatment did not prevent the cognitive impairment promoted by 2VO. However, none of the 2VO animals treated with GUO showed differences in the hippocampal regions compared to control, while 20% of 2VO rats not treated with GUO presented loss of pyramidal neurons and increased glial labeling cells in CA1 hippocampal region. In addition, we did not observe differences in CSF BDNF nor serum S100B levels among the groups. Of note, both the 2VO surgery and GUO treatment changed the purine CSF and plasma profile. In conclusion, GUO treatment did not prevent the cognitive impairment observed in 2VO animals, but our data suggest that GUO could be neuroprotective against hippocampal damage induced by 2VO.

Trimethyltin-induced neurotoxicity: gene expression pathway analysis, q-RT-PCR and immunoblotting reveal early effects associated with hippocampal damage and gliosis

Damage to the CNS results in a complex series of molecular and cellular changes involving the affected targets and the ensuing glial reaction. The initial gene expression events that underlie these cellular responses may serve as early biomarkers of neurotoxicity. Here, we examined gene expression profiles during the initial phase of hippocampal damage resulting from systemic exposure of rats to the organometallic neurotoxicant, trimethyltin (TMT, 8.0 mg/kg, i.p.). Using TMT as a neurodegeneration tool confers several advantages for evaluating molecular events associated with neural damage: 1) regional and cellular targets and time course of damage are known, 2) the blood-brain barrier is not compromised, which limits the contribution of blood-borne factors, e.g. immune, to neural injury responses and 3) known protein and mRNA signatures of TMT-induced neurotoxicity can be used as positive controls to validate novel expression events associated with exposure to this neurotoxicant. Using Affymetrix Gene Chip® to assess gene expression after TMT, combined with Ingenuity Pathway Analysis®, we observed changes consistent for genes known to be affected in hippocampus, while corresponding changes were not detected in cerebellum, a non-target region. In agreement with previous observations, limited changes in expression of inflammation-related genes were observed. Correlated expression profiles were found after exposure to TMT, including changes in gene ontologies associated with neurological disease, cellular assembly and maintenance, as well as signaling pathways associated with cellular stress, energy metabolism and glial activation. Selected gene changes were confirmed from each category by q-RT-PCR and immunoblot analysis. The canonical relationships identified implicate molecular pathways and processes relevant to detection of early stages of hippocampal damage in the TMT model. These observations provide new insight into early events associated with neuronal degeneration and associated glial activation that may serve as the basis for discovery and development of biomarkers of neurotoxicity.

Chronic brain hypoperfusion causes early glial activation and neuronal death, and subsequent long-term memory impairment

Reduction of cerebral blood flow is an important risk factor for dementia states and other brain dysfunctions. In present study, the effects of permanent occlusion of common carotid arteries (2VO), a well established experimental model of brain ischemia, on memory function were investigated, as assessed by reference and working spatial memory protocols and the object recognition task; cell damage to the hippocampus, as measured through changes in immunoreactivity for GFAP and the neuronal marker NeuN was also studied. The working hypothesis is that metabolic impairment following hypoperfusion will affect neuron and glial function and result in functional damage. Adult male Wistar rats were submitted to the modified 2VO method, with the right common carotid artery being occluded first and the left one week later, and tested seven days, three and six months after the ischemic event. A significant cognitive deficit was found in both reference and working spatial memory, as well as in the object recognition task, three and six months after surgery. Neuronal death and reactive astrogliosis were already present at 7 days and continued for up to 3 months after the occlusion; interestingly, there was no significant reduction in hippocampal volume. Present data suggests that cognitive impairment caused by brain hypoperfusion is long - lasting and persists beyond the time point of recovery from glial activation and neuronal loss.

Effects of dietary methylmercury on the zebrafish brain: histological, mitochondrial, and gene transcription analyses

The neurotoxic compound methylmercury (MeHg) is a commonly encountered pollutant in the environment, and constitutes a hazard for wildlife and human health through fish consumption. To study the neurotoxic impact of MeHg on piscivorous fish, we contaminated the model fish species Danio rerio for 25 and 50 days with food containing 13.5 μg/g dry weight (dw) of MeHg (0.6 μg MeHg/fish/day), an environmentally relevant dose leading to brain mercury concentrations of 30 ± 4 μg of Hg g(-1) (dw) after 25 days of exposure and 46 ± 7 μg of Hg g(-1) (dw) after 50 days. Brain mitochondrial respiration was not modified by exposure to MeHg, contrary to what happens in skeletal muscles. A 6-fold increase in the expression of the sdh gene encoding the succinate dehydrogenase Fe/S protein subunit was detected in the contaminated brain after 50 days of exposure. An up regulation of 3 genes, atp2b3a, atp2b3b, and slc8a2b, encoding for calcium transporters was noticed after 25 days of exposure but the atp2b3a and atp2b3b were repressed and the slc8a2b gene expression returned to its basal level after 50 days, suggesting a perturbation of calcium homeostasis. After 50 days, we detected the up regulation of glial fibrillary acidic protein and glutathione S-transferase genes (gfap and gst), along with a repression of the glutathione peroxidase gene gpx1. These results match well with a MeHg-induced onset of oxidative stress and inflammation. A transmission electron microscopic observation confirmed an impairment of the optical tectum integrity, with a decrease of the nucleal area in contaminated granular cells compared to control cells, and a lower density of cells in the contaminated tissue. A potential functional significance of such changes observed in optical tectum when considering wild fish contaminated in their natural habitat might be an impaired vision and therefore a lowered adaptability to their environment.

Moderate exercise training and chronic caloric restriction modulate redox status in rat hippocampus

Physical activity has been related to antioxidant adaptations, which is associated with health benefits, including those to the nervous system. Additionally, available data suggest exercise and a caloric restriction regimen may reduce both the incidence and severity of neurological disorders. Therefore, our aim was to compare hippocampal redox status and glial parameters among sedentary, trained, caloric-restricted sedentary and caloric-restricted trained rats. Forty male adult rats were divided into 4 groups: ad libitum-fed sedentary (AS), ad libitum-fed exercise training (AE), calorie-restricted sedentary (RS) and calorie-restricted exercise training (RE). The caloric restriction (decrease of 30% in food intake) and exercise training (moderate in a treadmill) were carried out for 3 months. Thereafter hippocampus was surgically removed, and then redox and glial parameters were assessed. Increases in reduced glutathione (GSH) levels and total antioxidant reactivity (TAR) were observed in AE, RS and RE. The nitrite/nitrate levels decreased only in RE. We found a decrease in carbonyl content in AE, RS and RE, while no modifications were detected in thiobarbituric acid reactive substances (TBARS). Total reactive antioxidant potential (TRAP), superoxide dismutase (SOD) activity, S100B and glial fibrilary acid protein (GFAP) content did not change, but caloric restriction was able to increase glutamine synthetase (GS) activity in RS and glutamate uptake in RS and RE. Exercise training, caloric restriction and both combined can decrease oxidative damage in the hippocampus, possibly involving modulation of astroglial function, and could be used as a strategy for the prevention of neurodegenerative diseases.

Gypenoside attenuates white matter lesions induced by chronic cerebral hypoperfusion in rats

Cerebral white matter lesions (WMLs) are frequently observed in vascular dementia and Alzheimer's disease and are believed to be responsible for cognitive dysfunction. The cerebral WMLs are most likely caused by chronic cerebral hypoperfusion and can be experimentally induced by permanent bilateral common carotid artery occlusion (BCCAO) in rats. Previous studies found the involvement of oxidative stress and astrocytic activation in the cerebral WMLs of BCCAO rats. Gypenoside (GP), a pure component extracted from the Gyrostemma pentaphyllum Makino, a widely reputed medicinal plants in China, has been reported to have some neuroprotective effects via anti-oxidative stress and anti-inflammatory mechanisms. In the present study, we investigated the protective effect of GP against cerebral WMLs and the underlying mechanisms for its inhibition of cognitive decline in BCCAO rats. Adult male Sprague-Dawley rats were orally administered daily doses of 200 and 400mg/kg GP for 33 days after BCCAO, and spatial learning and memory were assessed using the Morris water maze. Following behavioral testing, oxygen free radical levels and antioxidative capability were measured biochemically. The levels of lipid peroxidation and oxidative DNA damage were also assessed by immunohistochemical staining for 4-hydroxynonenal and 8-hydroxy-2'-deoxyguanosine, respectively. Activated astrocytes were also assessed by immunohistochemical staining and Western blotting with GFAP antibodies. The morphological changes were stained with Klüver-Barrera. Rats receiving 400mg/kg GP per day performed significantly better in tests for spatial learning and memory than saline-treated rats. GP 400mg/kg per day were found to markedly scavenge oxygen free radicals, enhance antioxidant abilities, decrease lipid peroxide production and oxidative DNA damage, and inhibit the astrocytic activation in corpus callosum and optic tract in BCCAO rats. However, GP 200mg/kg per day had no significant effects. GP may have therapeutic potential for treating dementia induced by chronic cerebral hypoperfusion and further evaluation is warranted.

Quantitative assessment of neurons and neuroglia with computer morphometry

The morphology of neural and glial cells in different cerebral areas and in various experimental models was quantitatively studied by methods of computer morphometry combined with video image analysis systems. The following parameters were obtained: density of neurons and glial cells per 1 mm(2), number of satellite perineuronal glial cells, aspect ratio for neural and glial cells, the area occupied by neuroglial projections, etc. The tested computer morphometry methods can be efficient in quantitative assessment of pathological and regenerative processes in the nervous tissue.

NOX activity in brain aging: exacerbation by high fat diet

This study describes how age and high fat diet affect the profile of NADPH oxidase (NOX). Specifically, NOX activity and subunit expression were evaluated in the frontal cerebral cortex of 7-, 16-, and 24-month old mice following a 4-month exposure to either Western diet (WD, 41% calories from fat) or very high fat lard diet (VHFD, 60% calories from fat). Data reveal a significant effect of age in on NOX activity, and show that NOX activity was only increased by VHFD, and only in 24-month old mice. NOX subunit expression was also increased by diet only in older mice. Quantification of protein carbonyls revealed significant age-related increases in protein oxidation, and indicate that only aged mice respond to high fat diet with enhanced protein oxidation. Histological analyses indicate prominent neuronal localization of both NOX subunits and protein carbonylation. Finally, data indicate that changes in reactive microgliosis, but not astrocytosis, mirror the pattern of diet-induced NOX activation and protein oxidation. Collectively, these data show that both age and dietary fat drive NOX activation, and further indicate that aged mice are preferentially sensitive to the effects of high fat diet. These data also suggest that high fat diets might exacerbate age-related oxidative stress in the brain via increased NOX.

Single-cell ELISA and flow cytometry as methods for highlighting potential neuronal and astrocytic toxicant specificity

The timeline imposed by recent worldwide chemical legislation is not amenable to conventional in vivo toxicity testing, requiring the development of rapid, economical in vitro screening strategies which have acceptable predictive capacities. When acquiring regulatory neurotoxicity data, distinction on whether a toxic agent affects neurons and/or astrocytes is essential. This study evaluated neurofilament (NF) and glial fibrillary acidic protein (GFAP) directed single-cell (S-C) ELISA and flow cytometry as methods for distinguishing cell-specific cytoskeletal responses, using the established human NT2 neuronal/astrocytic (NT2.N/A) co-culture model and a range of neurotoxic (acrylamide, atropine, caffeine, chloroquine, nicotine) and non-neurotoxic (chloramphenicol, rifampicin, verapamil) test chemicals. NF and GFAP directed flow cytometry was able to identify several of the test chemicals as being specifically neurotoxic (chloroquine, nicotine) or astrocytoxic (atropine, chloramphenicol) via quantification of cell death in the NT2.N/A model at cytotoxic concentrations using the resazurin cytotoxicity assay. Those neurotoxicants with low associated cytotoxicity are the most significant in terms of potential hazard to the human nervous system. The NF and GFAP directed S-C ELISA data predominantly demonstrated the known neurotoxicants only to affect the neuronal and/or astrocytic cytoskeleton in the NT2.N/A cell model at concentrations below those affecting cell viability. This report concluded that NF and GFAP directed S-C ELISA and flow cytometric methods may prove to be valuable additions to an in vitro screening strategy for differentiating cytotoxicity from specific neuronal and/or astrocytic toxicity. Further work using the NT2.N/A model and a broader array of toxicants is appropriate in order to confirm the applicability of these methods.

Astrogliosis in CNS pathologies: is there a role for microglia?

Astrogliosis, a cellular reaction with specific structural and functional characteristics, represents a remarkably homotypic response of astrocytes to all kinds of central nervous system (CNS) pathologies. Astrocytes play diverse functions in the brain, both harmful and beneficial. Mounting evidence indicates that astrogliosis is an underlying component of a diverse range of diseases and associated neuropathologies. The mechanisms that lead to astrogliosis are not fully understood, nevertheless, damaged neurons have long been reported to induce astrogliosis and astrogliosis has been used as an index for underlying neuronal damage. As the predominant source of proinflammatory factors in the CNS, microglia are readily activated under certain pathological conditions. An increasing body of evidence suggests that release of cytokines and other soluble products by activated microglia can significantly influence the subsequent development of astrogliosis and scar formation in CNS. It is well known that damaged neurons activate microglia very quickly, therefore, it is possible that activated microglia contribute factors/mediators through which damaged neuron induce astrogliosis. The hypothesis that activated microglia initiate and maintain astrogliosis suggests that suppression of microglial overactivation might effectively attenuate reactive astrogliosis. Development of targeted anti-microglial activation therapies might slow or halt the progression of astrogliosis and, therefore, help achieve a more beneficial environment in various CNS pathologies.

Cognitive impairment following high fat diet consumption is associated with brain inflammation

C57Bl/6 mice were administered a high fat, Western diet (WD, 41% fat) or a very high fat lard diet (HFL, 60% fat), and evaluated for cognitive ability using the Stone T-maze and for biochemical markers of brain inflammation. WD consumption resulted in significantly increased body weight and astrocyte reactivity, but not impaired cognition, microglial reactivity, or heightened cytokine levels. HFL increased body weight, and impaired cognition, increased brain inflammation, and decreased BDNF. Collectively, these data suggest that while different diet formulations can increase body weight, the ability of high fat diets to disrupt cognition is linked to brain inflammation.

The impact of age and gender on the striatal astrocytes activation in murine model of Parkinson's disease

OBJECTIVE

The aim of the present study was to determine how aging and gender influence the response of astrocytes to 1-methyl-4-phenyl-1,2,3,6-tetrahydropiridine (MPTP) intoxication.

MATERIALS AND METHODS

To asses the MPTP-induced astrocytes activation in nigro-striatal system, we measured the temporal changes in mRNA and protein expression of the specific astrocytic marker, glial fibrillary acidic protein (GFAP; by RT-PCR and Western blot), in the striatum of male and female C57BL/6 mice (2 and 12-month old) after 6 h and 1, 3, 7, 14 and 21 days post-intoxication.

RESULTS

We observed the increases of GFAP mRNA level post-MPTP intoxication in both young and aging males only at early time points, whereas in females (both ages) also at later time points. We noticed maximal increase of GFAP protein content on the 3rd day post-intoxication in young and aged males, whereas in females at the 7-daytime point.

CONCLUSIONS

The present results provide additional information of potential relevance to understand the mechanisms of gender and age-related difference in susceptibility of nigro-striatal system to MPTP insult.

Prenatal exposure to lipopolysaccharide results in cognitive deficits in age-increasing offspring rats

Studies have suggested that maternal infection/inflammation maybe a major risk factor for neurodevelopmental brain damage. In the present study, we evaluated the effects of prenatal exposure to a low level of inflammatory stimulation lipopolysaccharide (LPS) repeatedly on spatial learning and memory performances in rat offspring's lifetime. Sixteen pregnant Sprague-Dawley rats were randomly divided into two groups. The rats in the LPS group were treated i.p. with LPS (0.79 mg/kg) at gestation day 8, 10 and 12; meanwhile the rats in the control group were treated with saline. After delivery, the rat offspring at 3- (young), 10- (adult) and 20-mon-old (aged) were allocated. Spatial learning and memory abilities were tested by Morris water maze. The structure of hippocampal CA1 region was observed by light microscopy. The expression of synaptophysin (SYP) and glial fibrillary acidic protein (GFAP) in hippocampal CA1 region were measured by immunohistochemistry. Results showed that the rat offspring of LPS group needed longer escape latency and path-length in the Morris water maze and presented a significant neuron loss, decreased expression of SYP, increased expression of GFAP in CA1 region in histological studies. All these changes were more significant with the age increasing. These findings support the hypothesis that maternal systemic inflammation may alter the state of astrocytes in rat offspring for a long time, the alteration may affect neurons and synapse development in neural system, increase the neurons' vulnerability to environment especially as the age increasing, at last result in distinct learning and memory impairment.

Indirubins deplete striatal monoamines in the Intact and MPTP-treated mouse brain and block kainate-induced striatal astrogliosis

The indirubins long have been used in Chinese medicine for treatment of myelocytic leukemia. Among the many more recently described biological activities of the indirubins, attention has been directed toward the ability of these compounds to inhibit GSK-3 and CDKs, kinases implicated in neurodegenerative conditions. Little information is available on effects of indirubins on chemically-induced neurodegeneration. Here we examined the influence of three indirubins on 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)- and kainic acid (KA)-induced neurotoxicity in the mouse. The three indirubins examined were 6-bromoindirubin-3'-oxime (6BIO), 5-bromoindirubin-3'-oxime (5BIO) and 5-amino-6-bromoindirubin (5A6BI). The first two derivatives were previously described indirubins with low nanomolar inhibitory activity against GSK-3 and CDKs. The third compound was synthesized by the dimerization of 5-amino-6-bromoisatin with 3-acetoxyindol. The synthesis of the key compound 5-amino-6-bromoisatin was based on the bromination of the ketal of 5-amino-isatin. All indirubins examined decreased various measures associated with dopaminergic neurotransmission in striatum. These effects occurred alone or over and above the decrements seen following administration of the dopaminergic neurotoxicant, MPTP. Striatal serotonin and serotonin turnover were decreased by the indirubins in MPTP-treated mice. None of these striatal effects of the indirubins alone were associated with evidence of astrogliosis, an indicator of underlying neuropathology, nor did they potentiate the astrogliosis accompanying administration of MPTP. In general, the indirubins reduced KA-associated mortality and striatal but not hippocampal astrogliosis due to this toxicant. The data suggest that indirubins affect striatal biogenic amine levels and turnover in intact mice. The data do not indicate a neuroprotective action of indirubins in mice treated with MPTP but that they do suggest that they may be neuroprotective against KA-induced injury of the neostriatum.

Effects of environmental tobacco smoke on adult rat brain biochemistry

Environmental tobacco smoke (ETS) has been linked to deleterious health effects, particularly pulmonary and cardiac disease; yet, the general public considers ETS benign to brain function in adults. In contrast, epidemiological data have suggested that ETS impacts the brain and potentially modulates neurodegenerative disease. The present study begins to examine yet unknown biochemical effects of ETS on the adult mammalian brain. In the developed animal model, adult male rats were exposed to ETS 3 h a day for 3 weeks. Biochemical data showed altered glial fibrillary acid protein levels as a main treatment effect of ETS, suggestive of reactive astrogliosis. Yet, markers of oxidative and cell stress were unaffected by ETS exposure in the brain regions examined. Increased proteolytic degradation of alphaII-spectrin by caspase-3 and the dephosphorylation of serine(116) on PEA-15 indicated greater apoptotic cell death modulated by the extrinsic pathway in the brains of ETS-exposed animals. Further, beta-synuclein was upregulated by ETS, a neuroprotective protein previously reported to exhibit anti-apoptotic and anti-fibrillogenic properties. These findings demonstrate that ETS exposure alters the neuroproteome of the adult rat brain, and suggest modulation of inflammatory and cell death processes.

A neuronal and astrocyte co-culture assay for high content analysis of neurotoxicity

High Content Analysis (HCA) assays combine cells and detection reagents with automated imaging and powerful image analysis algorithms, allowing measurement of multiple cellular phenotypes within a single assay. In this study, we utilized HCA to develop a novel assay for neurotoxicity. Neurotoxicity assessment represents an important part of drug safety evaluation, as well as being a significant focus of environmental protection efforts. Additionally, neurotoxicity is also a well-accepted in vitro marker of the development of neurodegenerative diseases such as Alzheimer's and Parkinson's diseases. Recently, the application of HCA to neuronal screening has been reported. By labeling neuronal cells with betaIII-tubulin, HCA assays can provide high-throughput, non-subjective, quantitative measurements of parameters such as neuronal number, neurite count and neurite length, all of which can indicate neurotoxic effects. However, the role of astrocytes remains unexplored in these models. Astrocytes have an integral role in the maintenance of central nervous system (CNS) homeostasis, and are associated with both neuroprotection and neurodegradation when they are activated in response to toxic substances or disease states. GFAP is an intermediate filament protein expressed predominantly in the astrocytes of the CNS. Astrocytic activation (gliosis) leads to the upregulation of GFAP, commonly accompanied by astrocyte proliferation and hypertrophy. This process of reactive gliosis has been proposed as an early marker of damage to the nervous system. The traditional method for GFAP quantitation is by immunoassay. This approach is limited by an inability to provide information on cellular localization, morphology and cell number. We determined that HCA could be used to overcome these limitations and to simultaneously measure multiple features associated with gliosis - changes in GFAP expression, astrocyte hypertrophy, and astrocyte proliferation - within a single assay. In co-culture studies, astrocytes have been shown to protect neurons against several types of toxic insult and to critically influence neuronal survival. Recent studies have suggested that the use of astrocytes in an in vitro neurotoxicity test system may prove more relevant to human CNS structure and function than neuronal cells alone. Accordingly, we have developed an HCA assay for co-culture of neurons and astrocytes, comprised of protocols and validated, target-specific detection reagents for profiling betaIII-tubulin and glial fibrillary acidic protein (GFAP). This assay enables simultaneous analysis of neurotoxicity, neurite outgrowth, gliosis, neuronal and astrocytic morphology and neuronal and astrocytic development in a wide variety of cellular models, representing a novel, non-subjective, high-throughput assay for neurotoxicity assessment. The assay holds great potential for enhanced detection of neurotoxicity and improved productivity in neuroscience research and drug discovery.

Prostaglandin E2 released from activated microglia enhances astrocyte proliferation in vitro

Microglial activation has been implicated in many astrogliosis-related pathological conditions including astroglioma; however, the detailed mechanism is not clear. In this study, we used primary enriched microglia and astrocyte cultures to determine the role of microglial prostaglandin E(2) (PGE(2)) in the proliferation of astrocytes. The proliferation of astrocytes was measured by BrdU incorporation. The level of PGE(2) was measured by ELISA method. Pharmacological inhibition or genetic ablation of COX-2 in microglia were also applied in this study. We found that proliferation of astrocytes increased following lipopolysaccharide (LPS) treatment in the presence of microglia. Furthermore, increased proliferation of astrocytes was observed in the presence of conditioned media from LPS-treated microglia. The potential involvement of microglial PGE(2) in enhanced astrocyte proliferation was suggested by the findings that PGE(2) production and COX-2 expression in microglia were increased by LPS treatment. In addition, activated microglia-induced increases in astrocyte proliferation were blocked by the PGE(2) antagonist AH6809, COX-2 selective inhibitor DuP-697 or by genetic knockout of microglial COX-2. These findings were further supported by the finding that addition of PGE(2) to the media significantly induced astrocyte proliferation. These results indicate that microglial PGE(2) plays an important role in astrocyte proliferation, identifying PGE(2) as a key neuroinflammatory molecule that triggers the pathological response related to uncontrollable astrocyte proliferation. These findings are important in elucidating the role of activated microglia and PGE(2) in astrocyte proliferation and in suggesting a potential avenue in the use of anti-inflammatory agents for the therapy of astroglioma.

Effects of high fat diet on Morris maze performance, oxidative stress, and inflammation in rats: contributions of maternal diet

This study was undertaken to investigate the effects of prenatal and postnatal exposure to high fat diet on the brain. Female rats were divided into high fat diet (HFD) and control diet (CD) groups 4 weeks prior to breeding and throughout gestation and lactation. After weaning, male progeny were placed on a chow diet until 8 weeks old, and then segregated into HFD or CD groups. At 20 weeks old, rats were evaluated in the Morris water maze, and markers of oxidative stress and inflammation were documented in the brain. In comparison to rats fed CD, cognitive decline in HFD progeny from HFD dams manifested as a decline in retention, but not acquisition, in the water maze. HFD was also associated with significant increases in 3-nitrotyrosine, inducible nitric oxide synthase, IL-6, and glial markers Iba-1 and GFAP, with the largest increases frequently observed in HFD animals born to HFD dams. Thus, these data collectively suggest that HFD increases oxidative and inflammatory signaling in the brain, and further indicate that maternal HFD consumption might sensitize offspring to the detrimental effects of HFD.

Pyrethroid and organophosphate insecticide exposure in the 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine mouse model of Parkinson’s disease: an immunohistochemical analysis of tyrosine hydroxylase and glial fibrillary acidic protein in dorsolateral striatum

The pyrethroid insecticide permethrin and the organophosphate insecticide chlorpyrifos can experimentally produce Parkinson’s disease (PD)-associated changes in the dopaminergic nigrostriatal pathway, short of frank degeneration, although at doses considerably higher than from a likely environmental exposure. The ability of permethrin (200 mg/kg), chlorpyrifos (50 mg/kg), or combined permethrin + chlorpyrifos to facilitate nigrostriatal damage in the 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) (30 mg/kg) C57BL/6 mouse model of PD was investigated in three separate experiments. Tyrosine hydroxylase (TH) and glial fibrillary acidic protein (GFAP) immunohistochemistry assessed nigrostriatal degeneration or nigrostriatal damage more subtle than frank degeneration. Four fields in the dorsolateral caudate-putamen were examined at two rostrocaudal locations. The dopaminergic neurotoxin MPTP decreased striatal TH immunopositive neuropil and increased GFAP immunopositive neuropil. Neither permethrin nor chlorpyrifos, alone or in combination, altered the effects of MPTP upon TH or GFAP immunostaining. Permethrin alone increased striatal GFAP immunopositive neuropil but not when combined with chlorpyrifos treatment. Therefore, combined administration of the two insecticides appeared to protect against an increase in a neuropathological indicator of striatal damage seen with permethrin treatment alone. Differences compared with analysis of entire striatum emphasize the value of varying the topographic focus used to assess nigrostriatal degeneration in studies of insecticides in PD.

Molecular bases of methamphetamine-induced neurodegeneration

Methamphetamine (METH) is a highly addictive psychostimulant drug, whose abuse has reached epidemic proportions worldwide. The addiction to METH is a major public concern because its chronic abuse is associated with serious health complications including deficits in attention, memory, and executive functions in humans. These neuropsychiatric complications might, in part, be related to drug-induced neurotoxic effects, which include damage to dopaminergic and serotonergic terminals, neuronal apoptosis, as well as activated astroglial and microglial cells in the brain. Thus, the purpose of the present paper is to review cellular and molecular mechanisms that might be responsible for METH neurotoxicity. These include oxidative stress, activation of transcription factors, DNA damage, excitotoxicity, blood-brain barrier breakdown, microglial activation, and various apoptotic pathways. Several approaches that allow protection against METH-induced neurotoxic effects are also discussed. Better understanding of the cellular and molecular mechanisms involved in METH toxicity should help to generate modern therapeutic approaches to prevent or attenuate the long-term consequences of psychostimulant use disorders in humans.

Defining "neuroinflammation"

Neuroinflammation is a hot topic in contemporary neuroscience. A relatively new open-access journal, the Journal of Neuroinflammation, focuses on this field. As another example, abstracts to the 2007 Annual Meeting of the Society for Neuroscience could be submitted in several subcategories of neuroinflammation, a strong signal of growth in this research area. While it is becoming clear that activation of microglia and astroglia and the attendant expression of proinflammatory cytokines and chemokines often are associated with disease-, trauma-, and toxicant-induced damage to the CNS, it is by no means clear that a cause-and-effect relationship exists between the presence of a neuroinflammatory process and neural damage. We have explored this issue with two models of dopaminergic neurotoxicity. We used a single low-dose regimen of MPTP or METH, a paradigm that causes selective degeneration of striatal dopaminergic nerve terminals without affecting the cell body in the substantia nigra. Both compounds increased the expression of the microglia-associated factors, Il-1alpha, Il6, Ccl2, and Tnf-alpha, and also elicited morphologic evidence of microglial activation prior to induction of astrogliosis. Pharmacologic antagonism of MPTP and METH neurotoxicity prevented these proinflammatory responses, findings suggestive of a link between neuroinflammation and the observed neurotoxic outcomes. Nevertheless, when we used minocycline to suppress the expression of all these mediators, with the exception of Tnf-alpha, we failed to see neuroprotection. Likewise, when we examined the effects of MPTP or METH in transgenic mice lacking Il6, Ccl2, or Tnfr1/2 genes, deficiency of either Il6 or Ccl2 did not alter neurotoxicity, whereas deficiency in Tnfr1/2 was neuroprotective. Although these observations pointed to a role of the proinflammatory cytokine, TNF-alpha, in the neurotoxic effects of MPTP and METH, other observations did not support this supposition. For example, activation of NF-kappaB or induction of iNOS, known components of inflammatory responses and free radical formation, were not observed. Moreover, immunosuppressive regimens of glucocorticoids failed to suppress TNF-alpha or attenuate neurotoxicity. Taken together, our observations suggest that MPTP and METH neurotoxicity are associated with the elaboration of a "neuroinflammatory" response, yet this response lacks key features of inflammation and, with the exception of TNF-alpha, neurotoxicity appears to be the cause rather than the consequence of proinflammatory signals.

Astroglial and cognitive effects of chronic cerebral hypoperfusion in the rat

The permanent occlusion of common carotid arteries (2VO) causes a significant reduction of cerebral blood flow (hypoperfusion) in rats and constitutes a well established experimental model to investigate neuronal damage and cognitive impairment that occurs in human ageing and Alzheimer's disease. In the present study, we evaluated two astroglial proteins--S100B and glial fibrillary acidic protein (GFAP)--in cerebral cortex and hippocampus tissue, glutamate uptake and glutamine synthetase activity in hippocampus tissue, as well as S100B in cerebrospinal fluid. Cognition, as assessed by reference and working spatial memory protocols, was also investigated. Adult male Wistar rats were submitted to 10 weeks of chronic cerebral hypoperfusion by the 2VO method. A significant increase of S100B and GFAP in hippocampus tissue was observed, as well a significant decrease in glutamate uptake. Interestingly, we observed a decrease in S100B in cerebrospinal fluid. As for the cognitive outcome, there was an impairment of both reference and working spatial memory in the water maze; positive correlation between cognitive impairment and glutamate uptake decrease was evidenced in hypoperfused rats. These data support the hypothesis that astrocytes play a crucial role in the mechanisms of experimental neurodegeneration and that hippocampal pathology arising after chronic hypoperfusion gives rise to memory deficits.

The role of oxidative stress, metabolic compromise, and inflammation in neuronal injury produced by amphetamine-related drugs of abuse

Methamphetamine (METH) and 3,4-methylenedioxymethamphetamine (MDMA, ecstasy) are amphetamine derivatives with high abuse liability. These amphetamine-related drugs of abuse mediate their effects through the acute activation of both dopaminergic and serotonergic neurons. Long-term abuse of these amphetamine derivatives, however, results in damage to both dopaminergic and serotonergic terminals throughout the brain. This toxicity is mediated in part by oxidative stress, metabolic compromise, and inflammation. The overall objective of this review is to highlight experimental evidence that METH and MDMA increase oxidative stress, produce mitochondrial dysfunction, and increase inflammation that converge and culminate in the long-term toxicity to dopaminergic and serotonergic neurons.

“Current Pathology Techniques” Symposium Review: Advances and Issues in Neuropathology

Our understanding of the mechanisms that incite neurological diseases has progressed rapidly in recent years, mainly owing to the advent of new research instruments and our increasingly facile ability to assemble large, complex data sets acquired across several disciplines into an integrated representation of neural function at the molecular, cellular, and systemic levels. This mini-review has been designed to communicate the principal technical advances and current issues of importance in neuropathology research today in the context of our traditional neuropathology practices. Specific topics briefly addressed in this paper include correlative biology of the many facets of the nervous system; conventional and novel methods for investigating neural structure and function; theoretical and technical issues associated with investigating neuropathology end points in emerging areas of concern (developmental neurotoxicity, neurodegenerative conditions); and challenges and opportunities that will face pathologists in this field in the foreseeable future. We have organized this information in a manner that we hope will be of interest not only to professionals with a career focus in neuropathology, but also to general pathologists who occasionally face neuropathology questions.

Low-level human equivalent gestational lead exposure produces supernormal scotopic electroretinograms, increased retinal neurogenesis, and decreased retinal dopamine utilization in rats

BACKGROUND

Postnatal lead exposure in children and animals produces alterations in the visual system primarily characterized by decreases in the rod-mediated (scotopic) electroretinogram (ERG) amplitude (subnormality). In contrast, low-level gestational Pb exposure (GLE) increases the amplitude of scotopic ERGs in children (supernormality).

OBJECTIVES

The goal of this study was to establish a rat model of human equivalent GLE and to determine dose-response effects on scotopic ERGs and on retinal morphology, biochemistry, and dopamine metabolism in adult offspring.

METHODS

We exposed female Long-Evans hooded rats to water containing 0, 27 (low), 55 (moderate), or 109 (high) ppm of Pb beginning 2 weeks before mating, throughout gestation, and until postnatal day (PND) 10. We measured maternal and litter indices, blood Pb concentrations (BPb), retinal Pb concentrations, zinc concentrations, and body weights. On PND90, we performed the retinal experiments.

RESULTS

Peak BPb concentrations were < 1, 12, 24, and 46 microg/dL in control, low-, moderate- and high-level GLE groups, respectively, at PNDs 0-10. ERG supernormality and an increased rod photoreceptor and rod bipolar cell neurogenesis occurred with low- and moderate-level GLE. In contrast, high-level GLE produced ERG subnormality, rod cell loss, and decreased retinal Zn levels. GLE produced dose-dependent decreases in dopamine and its utilization.

CONCLUSIONS

Low- and moderate-level GLE produced persistent scotopic ERG supernormality due to an increased neurogenesis of cells in the rod signaling pathway and/or decreased dopamine utilization, whereas high-level GLE produced rod-selective toxicity characterized by ERG subnormality. The ERG is a differential and noninvasive biomarker of GLE. The inverted U-shaped dose-response curves reveal the sensitivity and vulnerability of the developing retina to GLE.

Zebrafish: a predictive model for assessing drug-induced toxicity

The zebrafish model organism is increasingly used for assessing drug toxicity and safety and numerous studies confirm that mammalian and zebrafish toxicity profiles are strikingly similar. This transparent vertebrate offers several compelling experimental advantages, including convenient drug delivery and low cost. Although full validation will require assessment of a large number of compounds from diverse classes, zebrafish can be used to eliminate potentially unsafe compounds rapidly in the early stages of drug development and to prioritize compounds for further preclinical and clinical studies. Adaptation of conventional instrumentation combined with new nanotechnology developments will continue to expand use of zebrafish for drug screening.

Biological and methodological features of the measurement of S100B, a putative marker of brain injury

The S100B astroglial protein is widely used as a parameter of glial activation and/or death in several conditions of brain injury. Cerebrospinal fluid and serum S100B variations have been proposed to evaluate clinical outcomes in these situations. Here, we briefly broach some aspects, commonly not sufficiently valorized, concerning the biology and measurements of this protein. S100B has molecular targets and activities in and outside of astrocytes, and variations of intra and extracellular content are not necessarily coupled. We discuss the extracellular origin of this protein in brain tissue, as well as extracerebral sources of this protein in serum, comparing it with other available protein markers of brain damage. The superestimation of the heterodimer S100A1-B in the current clinical literature is also analyzed. We affirm that poor dualistic views that consider S100B elevation as "bad" or "good" simplify clinical practice and delay our comprehension of the role of this protein, both in physiological conditions and in brain disorders.

Chronic and acute melatonin effects in gerbil global forebrain ischemia: long-term neural and behavioral outcome

Melatonin attenuates the short-term consequences of brain ischemia in several animal models. However, there is scant information regarding its efficacy for improving the long-term outcome. To further address that issue, we subjected gerbils to 5-min bilateral carotid occlusion. Some gerbils received acute peri-surgical administration of melatonin while others received continuous melatonin in their water. The gerbils' brains were histologically assessed at 20 wk postsurgery. Chronic but not acute melatonin attenuated ischemia-induced hyperactivity at 3 days postsurgery. Twenty weeks postsurgery, the ischemic gerbils showed varying degrees of bilateral loss of hippocampal CA1 pyramidal cells and elevation of glial fibrillary acidic protein immunoreactivity there. Both the cell loss and the immunoreactivity were markedly asymmetrical for some gerbils. Neither acute nor chronic melatonin altered this pattern of CA1 cell loss and glial immunoreactivity increase. Ischemia increased the number of CA1 cells that were immunoreactive for doublecortin (DCX), a marker for newborn neurons. This increase in CA1 DCX expression was not affected by either melatonin treatment. However, both acute and chronic melatonin reduced the number of DCX immunoreactive neurons in the dentate gyrus. Thus, neither acute nor chronic melatonin altered the long-term neural outcome of forebrain ischemia, although chronic administration seemed to attenuate the short-term behavioral effect. It is suggested that persistently high brain levels of melatonin may be essential for long-term neuroprotection against ischemia. The possibility that melatonin may modulate hippocampal neurogenesis merits further exploration both in normal animals and in models of brain insult.

Changes in visual fields and lateral geniculate nucleus in monkey laser-induced high intraocular pressure model

Monkey eyes are useful for ophthalmologic research into eye diseases because their histological and functional properties are very similar to those of humans. The monkey laser-induced high intraocular pressure (IOP) model is a common model for ophthalmologic research, especially into glaucoma. Although several studies using this model have focused on changes in visual field, retinal ganglion cells (RGC), and lateral geniculate nucleus (LGN), clear relationships among these changes in one and the same monkey have not been established. We therefore examined visual field changes, RGC and LGN numbers, and glial fibrous acidic protein (GFAP) immunohistochemistry in the LGN in each of two monkeys. Visual field sensitivity, RGC number, and neuronal density of LGN were all decreased by high IOP. The relationship between loss of RGC and decrease in visual field sensitivity depended on the eccentricity from the fovea. Moreover, LGN immunohistochemistry revealed greater increases in GFAP expression in the layers receiving a neuronal input from the high IOP eye than in those receiving a neuronal input from the contralateral untreated eye. From these results, we suggest that glaucoma may lead to changes in glial function not only in the retina, but also in the visual pathway, and that such central nervous system changes may be a hallmark of neuropathy in glaucoma, as in other neurodegenerative diseases.