Fluoro-Jade C can specifically stain the degenerative neurons in the substantia nigra of the 1-methy-4-phenyl-1,2,3,6-tetrahydro pyrindine-treated C57BL/6 mice

Pyroptosis-mediator GSDMD promotes Parkinson's disease pathology via microglial activation and dopaminergic neuronal death

GSDMD-mediated pyroptosis occurs in the nigrostriatal pathway in Parkinson's disease animals, yet the role of GSDMD in neuroinflammation and death of dopaminergic neurons in Parkinson's disease remains elusive. Here, our in vivo and in vitro studies demonstrated that GSDMD, as a pyroptosis executor, contributed to glial reaction and death of dopaminergic neurons across different Parkinson's disease models. The ablation of the Gsdmd attenuated Parkinson's disease damage by reducing dopaminergic neuronal death, microglial activation, and detrimental transformation. Disulfiram, an inhibitor blocking GSDMD pore formation, efficiently curtailed pyroptosis, thereby lessening the pathology of Parkinson's disease. Additionally, a modification in GSDMD was identified in the blood of Parkinson's disease patients in contrast to healthy subjects. Therefore, the detected alteration in GSDMD within the blood of Parkinson's disease patients and the protective impact of disulfiram could be promising for the diagnostic and therapeutic approaches against Parkinson's disease.

Peroxiredoxin 2 deletion impairs hippocampal-dependent memory via exacerbating transient ischemia-induced oxidative damage

Peroxiredoxin 2 (Prx2) regulates oxidative stress response in neuronal injury. The present study examined the effects of Prx2 deletion on transient global ischemia-induced hippocampal-dependent memory impairment. First, 20-min bilateral common carotid artery occlusion (BCCAO)-reperfusion and sham-operated control procedures were conducted in 6- or 7-month-old Prx2 knockout and wild-type mice. The cognitive status of these mice was assessed using the Morris water maze task with a hidden platform and a novel object recognition task 7 days after the 20-min BCCAO. Next, to evaluate neuronal degeneration and oxidative stress in the CA1 subregion of the hippocampus critical for learning and memory, we measured immunoreactive Fluro-jade C (FJC)-positive signals and 4-hydroxy-2-trans-nonenal (4-HNE) levels, respectively. The 20-min BCCAO induced cognitive impairments and increased the intensity of FJC-positive signals and 4-HNE levels of CA1 in Prx2 knockout mice but not in wild-type mice. These results suggest that Prx2 deficiency reduces resilience to transient global ischemia.

Programmed Death-1 Deficiency Aggravates Motor Dysfunction in MPTP Model of Parkinson's Disease by Inducing Microglial Activation and Neuroinflammation in Mice

Abundant reactive gliosis and neuroinflammation are typical pathogenetic hallmarks of brains in Parkinson's disease (PD) patients, but regulation mechanisms are poorly understood. We are interested in role of programmed death-1 (PD-1) in glial reaction, neuroinflammation and neuronal injury in PD pathogenesis. Using PD mouse model and PD-1 knockout (KO) mice, we designed wild-type-control (WT-CON), WT-1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (WT-MPTP), PD-1-KO-control (KO-CON) and PD-1-KO-MPTP (KO-MPTP), and observed motor dysfunction of animal, morphological distribution of PD-1-positive cells, dopaminergic neuronal injury, glial activation and generation of inflammatory cytokines in midbrains by motor behavior detection, immunohistochemistry and western blot. WT-MPTP mouse model exhibited decrease of PD-1/Iba1-positive microglial cells in the substantia nigra compared with WT-CON mice. By comparison of four groups, PD-1 deficiency showed exacerbation in motor dysfunction of animals, decreased expression of TH protein and TH-positive neuronal protrusions. PD-1 deficiency enhanced microglial activation, production of proinflammatory cytokines like inducible nitric oxide synthase, tumor necrosis factor-α, interleukin-1β and interleukin-6, and expression and phosphorylation of AKT and ERK1/2 in the substantia nigra of MPTP model. We concluded that PD-1 deficiency could aggravate motor dysfunction of MPTP mouse model by inducing microglial activation and neuroinflammation in midbrains, suggesting that PD-1 signaling abnormality might be possibly involved in PD pathogenesis.

NADPH Oxidase: a Possible Therapeutic Target for Cognitive Impairment in Experimental Cerebral Malaria

Long-term cognitive impairment associated with seizure-induced hippocampal damage is the key feature of cerebral malaria (CM) pathogenesis. One-fourth of child survivors of CM suffer from long-lasting neurological deficits and behavioral anomalies. However, mechanisms on hippocampal dysfunction are unclear. In this study, we elucidated whether gp91^phox isoform of nicotinamide adenine dinucleotide phosphate oxidase 2 (NOX2) (a potent marker of oxidative stress) mediates hippocampal neuronal abnormalities and cognitive dysfunction in experimental CM (ECM). Mice symptomatic to CM were rescue treated with artemether monotherapy (ARM) and in combination with apocynin (ARM + APO) adjunctive based on scores of Rapid Murine Come behavior Scale (RMCBS). After a 30-day survivability period, we performed Barnes maze, T-maze, and novel object recognition cognitive tests to evaluate working and reference memory in all the experimental groups except CM. Sensorimotor tests were conducted in all the cohorts to assess motor coordination. We performed Golgi-Cox staining to illustrate cornu ammonis-1 (CA1) pyramidal neuronal morphology and study overall hippocampal neuronal density changes. Further, expression of NOX2, NeuN (neuronal marker) in hippocampal CA1 and dentate gyrus was determined using double immunofluorescence experiments in all the experimental groups. Mice administered with ARM monotherapy and APO adjunctive treatment exhibited similar survivability. The latter showed better locomotor and cognitive functions, reduced ROS levels, and hippocampal NOX2 immunoreactivity in ECM. Our results show a substantial increase in hippocampal NeuN immunoreactivity and dendritic arborization in ARM + APO cohorts compared to ARM-treated brain samples. Overall, our study suggests that overexpression of NOX2 could result in loss of hippocampal neuronal density and dendritic spines of CA1 neurons affecting the spatial working and reference memory during ECM. Notably, ARM + APO adjunctive therapy reversed the altered neuronal morphology and oxidative damage in hippocampal neurons restoring long-term cognitive functions after CM.

Synthesis of human amyloid restricted to liver results in an Alzheimer disease-like neurodegenerative phenotype

Several lines of study suggest that peripheral metabolism of amyloid beta (Aß) is associated with risk for Alzheimer disease (AD). In blood, greater than 90% of Aß is complexed as an apolipoprotein, raising the possibility of a lipoprotein-mediated axis for AD risk. In this study, we report that genetic modification of C57BL/6J mice engineered to synthesise human Aß only in liver (hepatocyte-specific human amyloid (HSHA) strain) has marked neurodegeneration concomitant with capillary dysfunction, parenchymal extravasation of lipoprotein-Aß, and neurovascular inflammation. Moreover, the HSHA mice showed impaired performance in the passive avoidance test, suggesting impairment in hippocampal-dependent learning. Transmission electron microscopy shows marked neurovascular disruption in HSHA mice. This study provides causal evidence of a lipoprotein-Aß /capillary axis for onset and progression of a neurodegenerative process.

It has been suggested that peripheral metabolism of amyloid-beta is associated with risk for Alzheimer’s disease. This study reveals that the expression of human amyloid exclusively in the liver induces Alzheimer’s disease-like pathologies in mice, potentially indicating a completely novel pathway of Alzheimer’s disease aetiology and therapies.

Restricted Sensitivity of FJ-C Staining to Assess Neuronal Degeneration and Death in Preclinical Mouse Studies

Fluorescein-derived fluorochromes and anionic dyes such as Fluoro-Jade (FJ) stains have been introduced to facilitate recognition of dying neurons in tissue sections. However, the definition of what is really detected by FJ-based stains and its sensitivity in the detection of neuronal cell death is unclear. In our work, we evaluated the outcome of FJ-C staining in mouse brains from 4 different well-characterized models of neurodegeneration. Neuronal degeneration and loss were highlighted with high sensitivity by FJ-C stain in mice with dysfunctional γ-secretase in the glutamatergic neurons and in mice affected by acute cerebral ischemia. Histopathologically, acute eosinophilic necrosis or "red dead" neurons were associated with FJ-C staining in both settings. Conversely, in mice affected by chronic cerebral microinfarcts due to tumor lysis syndrome as well as in a model of mitochondrial encephalopathy, FJ-C staining failed to detect neuronal death. Histopathologically, these models were characterized by extensive neuronal vacuolation associated with fading neurons ("ghost cells"). Therefore, contrary to the widespread belief that FJ-C stain has high affinity for all degenerating neurons regardless of the underlying cell death mechanism, we observed restricted sensitivity of the technique to specific conditions of neuronal cell death. As such, complementary techniques are essential to evaluate the presence of neurodegeneration in the absence of a positive FJ-C signal.

Early Adolescence Prefrontal Cortex Alterations in Female Rats Lacking Dopamine Transporter

Monoamine dysfunctions in the prefrontal cortex (PFC) can contribute to diverse neuropsychiatric disorders, including ADHD, bipolar disorder, PTSD and depression. Disrupted dopamine (DA) homeostasis, and more specifically dopamine transporter (DAT) alterations, have been reported in a variety of psychiatric and neurodegenerative disorders. Recent studies using female adult rats heterozygous (DAT+/-) and homozygous (DAT-/-) for DAT gene, showed the utility of those rats in the study of PTSD and ADHD. Currently, a gap in the knowledge of these disorders affecting adolescent females still represents a major limit for the development of appropriate treatments. The present work focuses on the characterization of the PFC function under conditions of heterozygous and homozygous ablation of DAT during early adolescence based on the known implication of DAT and PFC DA in psychopathology during adolescence. We report herein that genetic ablation of DAT in the early adolescent PFC of female rats leads to changes in neuronal and glial cell homeostasis. In brief, we observed a concurrent hyperactive phenotype, accompanied by PFC alterations in glutamatergic neurotransmission, signs of neurodegeneration and glial activation in DAT-ablated rats. The present study provides further understanding of underlying neuroinflammatory pathological processes that occur in DAT-ablated female rats, what can provide novel investigational approaches in human diseases.

Loss of Endothelial Laminin α5 Exacerbates Hemorrhagic Brain Injury

Endothelial cells make laminin-411 and laminin-511. Although laminin-411 is well studied, the role of laminin-511 remains largely unknown due to the embryonic lethality of lama5-/- mutants. In this study, we generated endothelium-specific lama5 conditional knockout (α5-TKO) mice and investigated the biological functions of endothelial lama5 in blood-brain barrier (BBB) maintenance under homeostatic conditions and the pathogenesis of intracerebral hemorrhage (ICH). First, the BBB integrity of α5-TKO mice was measured under homeostatic conditions. Next, ICH was induced in α5-TKO mice and their littermate controls using the collagenase model. Various parameters, including injury volume, neuronal death, neurological score, brain edema, BBB integrity, inflammatory cell infiltration, and gliosis, were examined at various time points after injury. Under homeostatic conditions, comparable levels of IgG or exogenous tracers were detected in α5-TKO and control mice. Additionally, no differences in tight junction expression, pericyte coverage, and astrocyte polarity were found in these mice. After ICH, α5-TKO mice displayed enlarged injury volume, increased neuronal death, elevated BBB permeability, exacerbated infiltration of inflammatory cells (leukocytes, neutrophils, and mononuclear cells), aggravated gliosis, unchanged brain edema, and worse neurological function, compared to the controls. These findings suggest that endothelial lama5 is dispensable for BBB maintenance under homeostatic conditions but plays a beneficial role in ICH.

Cerebral dopamine neurotrophic factor-deficiency leads to degeneration of enteric neurons and altered brain dopamine neuronal function in mice

Cerebral dopamine neurotrophic factor (CDNF) is neuroprotective for nigrostriatal dopamine neurons and restores dopaminergic function in animal models of Parkinson’s disease (PD). To understand the role of CDNF in mammals, we generated CDNF knockout mice (Cdnf^−/−), which are viable, fertile, and have a normal life-span. Surprisingly, an age-dependent loss of enteric neurons occurs selectively in the submucosal but not in the myenteric plexus. This neuronal loss is a consequence not of increased apoptosis but of neurodegeneration and autophagy. Quantitatively, the neurodegeneration and autophagy found in the submucosal plexus in duodenum, ileum and colon of the Cdnf^−/− mouse are much greater than in those of Cdnf^+/+ mice. The selective vulnerability of submucosal neurons to the absence of CDNF is reminiscent of the tendency of pathological abnormalities to occur in the submucosal plexus in biopsies of patients with PD. In contrast, the number of substantia nigra dopamine neurons and dopamine and its metabolite concentrations in the striatum are unaltered in Cdnf^−/− mice; however, there is an age-dependent deficit in the function of the dopamine system in Cdnf^−/− male mice analyzed. This is observed as D-amphetamine-induced hyperactivity, aberrant dopamine transporter function, and as increased D-amphetamine-induced dopamine release demonstrating that dopaminergic axon terminal function in the striatum of the Cdnf^−/− mouse brain is altered. The deficiencies of Cdnf^−/− mice, therefore, are reminiscent of those seen in early stages of Parkinson’s disease.

Genetic Association Between NGFR, ADAM17 Gene Polymorphism, and Parkinson's Disease in the Chinese Han Population

Parkinson's disease (PD) is a common neurodegenerative disease characterized by neuronal loss in the substantia nigra. The p75 neurotrophin receptor (p75NTR, encoded by NGFR) was found to play an important role in the selective neuronal death of dopamine neurons in the substantia nigra, as well as the pathogenesis and development of PD. To assess the association between NGFR gene polymorphism and the susceptibility of PD, this case-control study consisting of 414 PD patients and 623 age- and sex-matched controls in a Chinese Han cohort was conducted. Twelve tag-single nucleotide polymorphisms (tag-SNPs) were selected from the NGFR gene through the construction of linkage disequilibrium blocks. One tag-SNP from the ADAM17 gene was also selected owing to its function of encoding tumor necrosis factor α-converting enzyme, which is responsible for the shedding of the extracellular domain of p75NTR. A multiplex polymerase chain reaction-ligase detection reaction (PCR-LDR) method was applied for genotyping. The associations between tag-SNPs and the risk of PD with the adjustment for age and sex were analyzed by unconditional logistic regression, and five genetic models including codominant, dominant, recessive, over-dominant, and additive models were applied. The results showed that among the 13 tag-SNPs, rs741073 was associated with a reduced risk of PD in the codominant (OR = 0.71, 95% CI = 0.54-0.93, P = 0.037), dominant (OR = 0.76, 95% CI = 0.58-0.98, P = 0.033), and over-dominant models (OR = 0.71, 95% CI = 0.54-0.92, P = 0.010), and rs1804011 was also associated with a reduced risk of PD in the codominant (OR = 0.69, 95% CI = 0.50-0.95, P = 0.049), dominant (OR = 0.69, 95% CI = 0.50-0.93, P = 0.014), over-dominant (OR = 0.70, 95% CI = 0.51-0.96, P = 0.025), and additive models (OR = 0.72, 95% CI = 0.54-0.94, P = 0.016). However, these associations did not retain after Bonferroni correction. Conclusively, our study failed to reveal the association between the selected tag-SNPs within NGFR, ADAM17, and the susceptibility of PD. The role of p75NTR and its gene polymorphisms in the pathogenesis of PD needs to be further studied.

Mural cell-derived laminin-α5 plays a detrimental role in ischemic stroke

At the blood-brain barrier (BBB), laminin-α5 is predominantly synthesized by endothelial cells and mural cells. Endothelial laminin-α5 is dispensable for BBB maintenance under homeostatic conditions but inhibits inflammatory cell extravasation in pathological conditions. Whether mural cell-derived laminin-α5 is involved in vascular integrity regulation, however, remains unknown. To answer this question, we generated transgenic mice with laminin-α5 deficiency in mural cells (α5-PKO). Under homeostatic conditions, no defects in BBB integrity and cerebral blood flow (CBF) were observed in α5-PKO mice, suggesting that mural cell-derived laminin-α5 is dispensable for BBB maintenance and CBF regulation under homeostatic conditions. After ischemia-reperfusion (MCAO) injury, however, α5-PKO mice displayed less severe neuronal injury, including reduced infarct volume, decreased neuronal death, and improved neurological function. In addition, α5-PKO mice also showed attenuated vascular damage (milder BBB disruption, reduced inflammatory cell infiltration, decreased brain edema, and diminished hemorrhagic transformation). Mechanistic studies revealed less severe tight junction protein (TJP) loss and pericyte coverage reduction in α5-PKO mice after ischemia-reperfusion injury, indicating that the attenuated ischemic injury in α5-PKO mice is possibly due to less severe vascular damage. These findings suggest that mural cell-derived laminin-α5 plays a detrimental role in ischemic stroke and that inhibiting its signaling may have a neuroprotective effect.

TAT-Ngn2 Enhances Cognitive Function Recovery and Regulates Caspase-Dependent and Mitochondrial Apoptotic Pathways After Experimental Stroke

Neurogenin-2 (Ngn2) is a basic helix-loop-helix (bHLH) transcription factor that contributes to the identification and specification of neuronal fate during neurogenesis. In our previous study, we found that Ngn2 plays an important role in alleviating neuronal apoptosis, which may be viewed as an attractive candidate target for the treatment of cerebral ischemia. However, novel strategies require an understanding of the function and mechanism of Ngn2 in mature hippocampal neurons after global cerebral ischemic injury. Here, we found that the expression of Ngn2 decreased in the hippocampus after global cerebral ischemic injury in mice and in primary hippocampal neurons after oxygen glucose deprivation (OGD) injury. Then, transactivator of transcription (TAT)-Ngn2, which was constructed by fusing a TAT domain to Ngn2, was effectively transported and incorporated into hippocampal neurons after intraperitoneal (i.p.) injection and enhanced cognitive functional recovery in the acute stage after reperfusion. Furthermore, TAT-Ngn2 alleviated hippocampal neuronal damage and apoptosis, and inhibited the cytochrome C (CytC) leak from the mitochondria to the cytoplasm through regulating the expression levels of brain-derived neurotrophic factor (BDNF), phosphorylation tropomyosin-related kinase B (pTrkB), Bcl-2, Bax and cleaved caspase-3 after reperfusion injury in vivo and in vitro. These findings suggest that the downregulation of Ngn2 expression may have an important role in triggering brain injury after ischemic stroke and that the neuroprotection of TAT-Ngn2 against stroke might involve the modulation of BDNF-TrkB signaling that regulates caspase-dependent and mitochondrial apoptotic pathways, which may be an attractive therapeutic strategy for cerebral ischemic injury.

Wnt3a, a Protein Secreted by Mesenchymal Stem Cells Is Neuroprotective and Promotes Neurocognitive Recovery Following Traumatic Brain Injury

Intravenous administration of bone marrow derived mesenchymal stem cells (MSCs) has been shown to reduce blood brain barrier compromise and improve neurocognition following traumatic brain injury (TBI). These effects occur in the absence of engraftment and differentiation of these cells in the injured brain. Recent studies have shown that soluble factors produced by MSCs mediate a number of the therapeutic effects. In this study, we sought to determine if intravenous administration of MSCs (IV-MSCs) could enhance hippocampal neurogenesis following TBI. Our results demonstrate that IV-MSC treatment attenuates loss of neural stem cells and promotes hippocampal neurogenesis in TBI injured mice. As Wnt signaling has been implicated in neurogenesis, we measured circulating Wnt3a levels in serum following IV-MSC administration and found a significant increase in Wnt3a. Concurrent with this increase, we detected increased activation of the Wnt/β-catenin signaling pathway in hippocampal neurons. Furthermore, IV recombinant Wnt3a treatment provided neuroprotection, promoted neurogenesis, and improved neurocognitive function in TBI injured mice. Taken together, our results demonstrate a role for Wnt3a in the therapeutic potential of MSCs and identify Wnt3a as a potential stand-alone therapy or as part of a combination therapeutic strategy for the treatment of TBI. Stem Cells 2016;34:1263-1272.

Blood-Brain Barrier Dysfunction Precedes Cognitive Decline and Neurodegeneration in Diabetic Insulin Resistant Mouse Model: An Implication for Causal Link

Diabetic insulin resistance and pro-diabetic diet are reported to increase dementia risk through unknown mechanisms. Emerging evidence suggests that the integrity of blood-brain barrier (BBB) is central to the onset and progression of neurodegeneration and cognitive impairment. Therefore, the current study investigated the effect of pro-diabetic diets on cognitive dysfunction in association to BBB integrity and its putative mechanisms. In C57BL/6J mice chronically ingested with a diet enriched in fat and fructose (HFF), Morris Water Maze (MWM) test indicated no significant cognitive decline after 4 weeks of HFF feeding compared to low-fat (LF) fed control. However, at this stage, BBB dysfunction accompanied by heightened neuroinflammation in cortex and hippocampal regions was already evident. After 24 weeks, HFF fed mice showed significantly deteriorated cognitive function concomitant with substantial neurodegeneration, which both showed significant associations with increased BBB permeability. In addition, the data indicated that the loss of BBB tight junctions was significantly associated with heightened inflammation and leukocyte infiltration. The data collectively suggest that in mice maintained on pro-diabetic diet, the dysfunctional BBB associated to inflammation and leukocyte recruitment precedes the neurodegeneration and cognitive decline, possibly indicating causal association.

Antihypertensive agents do not prevent blood-brain barrier dysfunction and cognitive deficits in dietary-induced obese mice

BACKGROUND

While vascular risk factors including Western-styled diet and obesity are reported to induce cognitive decline and increase dementia risk, recent reports consistently suggest that compromised integrity of cerebrovascular blood-brain barrier (BBB) may have an important role in neurodegeneration and cognitive deficits. A number of studies report that elevated blood pressure increases the permeability of BBB.

METHODS

In this study, we investigated the effects of antihypertensive agents, candesartan or ursodeoxycholic acid (UDCA), on BBB dysfunction and cognitive decline in wild-type mice maintained on high fat and fructose (HFF) diet for 24 weeks.

RESULTS

In HFF-fed mice, significantly increased body weight with elevated blood pressure, plasma insulin and glucose compared with mice fed with low-fat control chow was observed. Concomitantly, significant disruption of BBB and cognitive decline were evident in the HFF-fed obese mice. Hypertension was completely prevented by the coprovision of candesartan or UDCA in mice maintained on HFF diet, while only candesartan significantly reduced the body weight compared with HFF-fed mice. Nevertheless, BBB dysfunction and cognitive decline remained unaffected by candesartan or UDCA.

CONCLUSIONS

These data conclusively indicate that modulation of blood pressure and/or body weight may not be directly associated with BBB dysfunction and cognitive deficits in Western diet-induced obese mice, and hence antihypertensive agents may not be effective in preventing BBB disruption and cognitive decline. The findings may provide important mechanistical insights to obesity-associated cognitive decline and its therapy.

Time course of neuronal death following endothelin-1 induced focal ischemia in rats

BACKGROUND

Endothelin-1 (ET-1) induced focal ischemia is increasingly being used as a preclinical model of stroke. Here, we described for the first time, the time course of neuronal death and infarct evolution during the first 7 days following ischemia.

NEW METHOD

We used hematoxylin and eosin (H&E) staining to evaluate infarct progression and Fluoro-Jade C (FJC) to quantify neuronal degeneration at 24, 48, 72h and 7 days after ET-1 injection to the forelimb motor cortex in Sprague-Dawley rats.

RESULTS

We found that infarct volume and neuronal degeneration are maximal at 24h post-stroke. Neuronal degeneration is also significantly reduced within 7 days of stroke induction.

COMPARISON WITH EXISTING METHOD

This study is the first to provide a direct evaluation of both infarct volume evolution and neuronal death time course following ET-1 induced focal ischemia in the forelimb motor cortex.

CONCLUSION

This study describes the short-term time course of neuronal death and brain injury in the ET-1 stroke model, which provides a significant reference when determining the appropriate time to commence neuroprotective or recovery promoting strategies.

Rgs6 is required for adult maintenance of dopaminergic neurons in the ventral substantia nigra

Parkinson disease (PD) is characterized by the preferential, but poorly understood, vulnerability to degeneration of midbrain dopaminergic (mDA) neurons in the ventral substantia nigra compacta (vSNc). These sensitive mDA neurons express Pitx3, a transcription factor that is critical for their survival during development. We used this dependence to identify, by flow cytometry and expression profiling, the negative regulator of G-protein signaling Rgs6 for its restricted expression in these neurons. In contrast to Pitx3^−/− mDA neurons that die during fetal (vSNc) or post-natal (VTA) period, the vSNc mDA neurons of Rgs6^−/− mutant mice begin to exhibit unilateral signs of degeneration at around 6 months of age, and by one year cell loss is observed in a fraction of mice. Unilateral cell loss is accompanied by contralateral degenerating neurons that exhibit smaller cell size, altered morphology and reduced dendritic network. The degenerating neurons have low levels of tyrosine hydroxylase (TH) and decreased nuclear Pitx3; accordingly, expression of many Pitx3 target gene products is altered, including Vmat2, Bdnf, Aldh1a1 (Adh2) and Fgf10. These low TH neurons also express markers of increased dopamine signaling, namely increased DAT and phospho-Erk1/2 expression. The late onset degeneration may reflect the protective action of Rgs6 against excessive DA signaling throughout life. Rgs6-dependent protection is thus critical for adult survival and maintenance of the vSNc mDA neurons that are most affected in PD.

The locomotor deficits associated with Parkinson disease result from the death of a specific subset of dopamine neurons in the ventral part of the midbrain. The reason for the greater sensitivity to degeneration of those, relative to other, neurons is not clear. Prior work showed that the Pitx3 transcription factor is specifically expressed in these neurons where it has a survival role during development. The present work identified a cell signaling component, Rgs6, that is also restricted to the sensitive neurons in the midbrain and that exerts a protective function, particularly late in life. While the loss of Rgs6 function may predispose or contribute to Parkinson disease, its stimulation may provide a novel therapeutic avenue to treat Parkinson disease.

A role for Apolipoprotein A-I in the pathogenesis of multiple sclerosis

Apolipoprotein A1 (Apo A-I), the most abundant component of high-density lipoprotein (HDL), is an anti-inflammatory molecule, yet its potential role in the pathogenesis of multiple sclerosis (MS) has not been fully investigated. In this study, Western blot analyses of human plasma showed differential Apo A-I expression in healthy controls compared to MS patients. Further, primary progressive MS patients had less plasma Apo A-I than other forms of MS. Using experimental allergic encephalomyelitis (EAE) as a model for MS, Apo A-I deficient mice exhibited worse clinical disease and more neurodegeneration concurrent with increased levels of pro-inflammatory cytokines compared to wild-type animals. These data suggest that Apo A-I plays a role in the pathogenesis of EAE, a model for MS, creating the possibility for agents that increase Apo A-I levels as potential therapies for MS.

The pro-inflammatory cytokine interferon-gamma is an important driver of neuropathology and behavioural sequelae in experimental pneumococcal meningitis

Interferon-gamma is known to play a complex modulatory role in immune defence during microbial infections. Its actions in pneumococcal meningitis, however, remain ill-defined. Here, a pathological role for IFN-γ was demonstrated using a murine model of pneumococcal meningitis, in that C57BL/6J mice deficient in this pro-inflammatory cytokine (IFN-γ(-/-)) showed less severe acute and long-term neuropathology following intracerebral challenge with Streptococcus pneumoniae. The absence of IFN-γ significantly lengthened the survival of mice that otherwise would have developed fatal clinical signs within two days of CNS infection. Compared to their wild-type counterparts, IFN-γ(-/-) mice showed a diminished inflammatory response (attenuated levels of pro-inflammatory cytokines in the cerebrospinal fluid) and milder brain pathologies (less BBB permeability to protein and brain haemorrhage) during the acute phase of disease. Following a full regime of antibiotic treatment, we found substantial brain injuries in the wild-type mice 10days after infection. IFN-γ(-/-) mice, however, showed decreased neuronal damage in both hippocampus and cortex. In the longer term (≈10weeks p.i.), the wild-type mice that had survived meningitis due to antibiotic treatment had neurobehavioural abnormalities including diurnal hypoactivity, nocturnal hyperactivity and impaired performance in a discrimination reversal task. IFN-γ(-/-) mice, concomitantly tested in the automated IntelliCage platform, had reduced behavioural and cognitive disorders compared to wild-type mice. Both IFN-γ(-/-) and wild-type survivors of pneumococcal meningitis showed impaired working memory in the IntelliCage-based complex patrolling task. These observations indicate an association between IFN-γ-driven acute brain pathology and the long-term neurological sequelae resulting from pneumococcal meningitis.

Neuroprotective effects of sevoflurane against electromagnetic pulse-induced brain injury through inhibition of neuronal oxidative stress and apoptosis

Electromagnetic pulse (EMP) causes central nervous system damage and neurobehavioral disorders, and sevoflurane protects the brain from ischemic injury. We investigated the effects of sevoflurane on EMP-induced brain injury. Rats were exposed to EMP and immediately treated with sevoflurane. The protective effects of sevoflurane were assessed by Nissl staining, Fluoro-Jade C staining and electron microscopy. The neurobehavioral effects were assessed using the open-field test and the Morris water maze. Finally, primary cerebral cortical neurons were exposed to EMP and incubated with different concentration of sevoflurane. The cellular viability, lactate dehydrogenase (LDH) release, superoxide dismutase (SOD) activity and malondialdehyde (MDA) level were assayed. TUNEL staining was performed, and the expression of apoptotic markers was determined. The cerebral cortexes of EMP-exposed rats presented neuronal abnormalities. Sevoflurane alleviated these effects, as well as the learning and memory deficits caused by EMP exposure. In vitro, cell viability was reduced and LDH release was increased after EMP exposure; treatment with sevoflurane ameliorated these effects. Additionally, sevoflurane increased SOD activity, decreased MDA levels and alleviated neuronal apoptosis by regulating the expression of cleaved caspase-3, Bax and Bcl-2. These findings demonstrate that Sevoflurane conferred neuroprotective effects against EMP radiation-induced brain damage by inhibiting neuronal oxidative stress and apoptosis.

Measurement of viscoelastic properties in multiple anatomical regions of acute rat brain tissue slices

Mechanical property data for brain tissue are needed to understand the biomechanics of neurological disorders and response of the brain to different mechanical and surgical forces. Most studies have characterized mechanical behavior of brain tissues over large regions or classified tissue properties for either gray or white matter regions only. In this study, spatially heterogeneous viscoelastic properties of ex vivo rat brain tissue slices were measured in different anatomical regions including the cerebral cortex, caudate/putamen, and hippocampus using an optical coherence tomography (OCT) indentation system. Cell viability was also tested to observe neuronal degeneration and morphological changes in tissue slices and provide a proper timeline for mechanical tests. Shear modulus was estimated by fitting normalized deformation data (D/ti), which was defined as the ratio of deformation depth (D) to initial thickness of the tissue slice (ti), to a viscoelastic finite element model. The estimated shear modulus decayed nonlinearly over 10min in each anatomical region, and the range of instantaneous to equilibrium shear modulus was 3.8-0.54kPa in the cerebral cortex, 1.4-0.27kPa in the hippocampus and 1.0-0.17kPa in the caudate/putamen. Although these regions are all gray matter structures, their measured mechanical properties were significantly different. Accurate measurement of inter-regional variations in mechanical properties will contribute to improved understanding organ-level structural parameters and regional differential susceptibility to deformation injury within CNS tissues.

Targeted delivery of neurogenin-2 protein in the treatment for cerebral ischemia-reperfusion injury

Neurogenin-2 (Ngn2), as a proneural gene that promotes the survival and differentiation of neural precursor cells, is an attractive candidate for therapy against cerebral ischemia-reperfusion injury. However, the delivery approach limits its clinical application. To deliver Ngn2 protein into the cerebral ischemic region and exert a therapeutic effect on injured neurons after ischemia, we here reported that the fusion protein TAT-LBD-Ngn2 was constructed by fusing a transactivator of transcription (TAT) domain and a laminin-binding domain (LBD) to Ngn2. TAT-LBD-Ngn2 promoted the outgrowth of neuronal neurite, increased the survival rate and alleviated apoptosis of hippocampal neurons exposed to oxygen glucose deprivation in vitro. Furthermore, a focal cerebral ischemia model in C57BL/6 mice showed that TAT-LBD-Ngn2 efficiently crossed the blood brain barrier, aggregated in the ischemic zone and was consistently incorporated into neurons. Moreover, TAT-LBD-Ngn2 transduced into brains attenuated neuronal degeneration and apoptosis in the ischemic zone. TAT-LBD-Ngn2 treatment resulted in a reduction of infarct volume that was associated with a parallel improvement in neurological functional outcomes after reperfusion. In conclusion, the targeted delivery of TAT-LBD-Ngn2 into the ischemic zone attenuated cerebral ischemia-reperfusion injury through the inhibition of neuronal degeneration and apoptosis, suggesting that TAT-LBD-Ngn2 is a promising target candidate for the treatment of ischemic stroke.

The proform of glia cell line-derived neurotrophic factor: a potentially biologically active protein

Growing evidences have revealed that the proforms of several neurotrophins including nerve growth factor (NGF), brain-derived neurotrophic factor (BDNF), and neurotrophin-3 (NT3), by binding to p75 neurotrophin receptor and sortilin, could induce neuronal apoptosis and are implicated in the pathogenesis of various neurodegenerative diseases. The glial cell line-derived neurotrophic factor (GDNF), one of the most potent useful neurotrophic factors for the treatment of Parkinson's disease (PD), is firstly synthesized as the proform (proGDNF) like other neurotrophin NGF, BDNF, and NT3. However, little is known about proGDNF expression and secretion under physiological as well as pathological states in vivo or in vitro. In this study, we investigated the expression profile and dynamic changes of proGDNF in brains of aging and PD animal models, with the interesting finding that proGDNF was a predominant form of GDNF with molecular weight of about 36 kDa by reducing and nonreducing immunoblots in adult brains and was unregulated in the aging, lipopolysaccharide (LPS), and 1-methyl-4-phenyl- 1,2,3,6-tetrahydropyridine (MPTP) insult. We further provided direct evidence that accompanied activation of primary astrocytes as well as C6 cell line induced by LPS stimulation, proGDNF was increasingly synthesized and released as the uncleaved form in cell culture. Taken together, our results strongly suggest that proGDNF may be a biologically active protein and has specific effects on the cells close to its secreting site, and a potentially important role of proGDNF signaling in the brains, in the glia-neuronal interaction or in the pathogenesis of PD, should merit further investigation.

Laforin prevents stress-induced polyglucosan body formation and Lafora disease progression in neurons

Glycogen, the largest cytosolic macromolecule, is soluble because of intricate construction generating perfect hydrophilic-surfaced spheres. Little is known about neuronal glycogen function and metabolism, though progress is accruing through the neurodegenerative epilepsy Lafora disease (LD) proteins laforin and malin. Neurons in LD exhibit Lafora bodies (LBs), large accumulations of malconstructed insoluble glycogen (polyglucosans). We demonstrated that the laforin-malin complex reduces LBs and protects neuronal cells against endoplasmic reticulum stress-induced apoptosis. We now show that stress induces polyglucosan formation in normal neurons in culture and in the brain. This is mediated by increased glucose-6-phosphate allosterically hyperactivating muscle glycogen synthase (GS1) and is followed by activation of the glycogen digesting enzyme glycogen phosphorylase. In the absence of laforin, stress-induced polyglucosans are undigested and accumulate into massive LBs, and in laforin-deficient mice, stress drastically accelerates LB accumulation and LD. The mechanism through which laforin-malin mediates polyglucosan degradation remains unclear but involves GS1 dephosphorylation by laforin. Our work uncovers the presence of rapid polyglucosan metabolism as part of the normal physiology of neuroprotection. We propose that deficiency in the degradative phase of this metabolism, leading to LB accumulation and resultant seizure predisposition and neurodegeneration, underlies LD.

Differential vulnerability of substantia nigra and corpus striatum to oxidative insult induced by reduced dietary levels of essential fatty acids

Oxidative stress (OS) has been implicated in the etiology of certain neurodegenerative disorders. Some of these disorders have been associated with unbalanced levels of essential fatty acids (EFA). The response of certain brain regions to OS, however, is not uniform and a selective vulnerability or resilience can occur. In our previous study on rat brains, we observed that a two-generation EFA dietary restriction reduced the number and size of dopaminergic neurons in the substantia nigra (SN) rostro-dorso-medial. To understand whether OS contributes to this effect, we assessed the status of lipid peroxidation (LP) and anti-oxidant markers in both SN and corpus striatum (CS) of rats submitted to this dietary treatment for one (F1) or two (F2) generations. Wistar rats were raised from conception on control or experimental diets containing adequate or reduced levels of linoleic and α-linolenic fatty acids, respectively. LP was measured using the thiobarbituric acid reaction method (TBARS) and the total superoxide dismutase (t-SOD) and catalase (CAT) enzymatic activities were assessed. The experimental diet significantly reduced the docosahexaenoic acid (DHA) levels of SN phospholipids in the F1 (~28%) and F2 (~50%) groups. In F1 adult animals of the experimental group there was no LP in both SN and CS. Consistently, there was a significant increase in the t-SOD activity (p < 0.01) in both regions. In EF2 young animals, degeneration in dopaminergic and non-dopaminergic neurons and a significant increase in LP (p < 0.01) and decrease in the CAT activity (p < 0.001) were detected in the SN, while no inter-group difference was found for these parameters in the CS. Conversely, a significant increase in t-SOD activity (p < 0.05) was detected in the CS of the experimental group compared to the control. The results show that unbalanced EFA dietary levels reduce the redox balance in the SN and reveal mechanisms of resilience in the CS under this stressful condition.

The CCL2-CCR2 system affects the progression and clearance of intracerebral hemorrhage

Intracerebral hemorrhage (ICH) has been associated with inflammation and apoptosis. The CCL2-CCR2 chemotactic system is one of the major signaling pathways that induce inflammation and apoptosis. However, its role on ICH has not been investigated. We subjected wild-type, CCL2(-/-) , and CCR2(-/-) mice to collagenase-induced ICH, and assessed histological and behavioral outcomes. Lack of CCL2 or CCR2 decreased the hematoma volume early after collagenase-induced ICH but delayed its recovery. The hematoma size was accompanied by brain edema, neuronal death, and neurological scores. Although microglia activation/migration was attenuated in CCL2(-/-) or CCR2(-/-) mice 1 day after injury, more microglia were present at later time points, suggesting that alternative signaling pathways had been activated to recruit them. On the contrary, leukocyte and neutrophil infiltration were decreased in these mice, suggesting a tighter/recovered blood-brain barrier. In addition, we also found that FL- and K104Stop-CCL2 were able to restore the changes found in CCL2(-/-) mice, but K104A-CCL2 failed to do so. These results suggest that plasmin-mediated truncation of CCL2 may be an indispensable step to fully activate the chemokine in vivo. The data also indicate that CCL2-CCR2 signaling pathway may be a molecular target for the treatment of ICH.

Fluorophilia: fluorophore-containing compounds adhere non-specifically to injured neurons

Ionic (free) zinc (Zn(2+)) is implicated in apoptotic neuronal degeneration and death. In our attempt to examine the effects of Zn(2+) in neurodegeneration following brain injury, we serendipitously discovered that injured neurons bind fluorescein moieties, either alone or as part of an indicator dye, in histologic sections. This phenomenon, that we have termed "fluorophilia", is analogous to the ability of degenerating neuronal somata and axons to bind silver ions (argyrophilia - the basis of silver degeneration stains). To provide evidence that fluorophilia occurs in sections of brain tissue, we used a wide variety of indicators such as Fluoro-Jade (FJ), a slightly modified fluorescein sold as a marker for degenerating neurons; Newport Green, a fluorescein-containing Zn(2+) probe; Rhod-5N, a rhodamine-containing Ca(2+) probe; and plain fluorescein. All yielded remarkably similar staining of degenerating neurons in the traumatic brain-injured tissue with the absence of staining in our sham-injured brains. Staining of presumptive injured neurons by these agents was not modified when Zn(2+) in the brain section was removed by prior chelation with EDTA or TPEN, whereas staining by a non-fluorescein containing Zn(2+) probe, N-(6-methoxy-8-quinolyl)-p-toluenesulfonamide (TSQ), was suppressed by prior chelation. Thus, certain fluorophore-containing compounds nonspecifically stain degenerating neuronal tissue in histologic sections and may not reflect the presence of Zn(2+). This may be of concern to researchers using indicator dyes to detect metals in brain tissue sections. Further experiments may be advised to clarify whether Zn(2+)-binding dyes bind more specifically in intact neurons in culture or organotypic slices.

High-strain-rate brain injury model using submerged acute rat brain tissue slices

Blast-induced traumatic brain injury (bTBI) has received increasing attention in recent years due to ongoing military operations in Iraq and Afghanistan. Sudden impacts or explosive blasts generate stress and pressure waves that propagate at high velocities and affect sensitive neurological tissues. The immediate soft tissue response to these stress waves is difficult to assess using current in vivo imaging technologies. However, these stress waves and resultant stretching and shearing of tissue within the nano- to microsecond time scale of blast and impact are likely to cause initial injury. To visualize the effects of stress wave loading, we have developed a new ex vivo model in which living tissue slices from rat brain, attached to a ballistic gelatin substrate, were subjected to high-strain-rate loads using a polymer split Hopkinson pressure bar (PSHPB) with real-time high-speed imaging. In this study, average peak fluid pressure within the test chamber reached a value of 1584±63.3 psi. Cavitation due to a trailing underpressure wave was also observed. Time-resolved images of tissue deformation were collected and large maximum eigenstrains (0.03-0.42), minimum eigenstrains (-0.33 to -0.03), maximum shear strains (0.09-0.45), and strain rates (8.4×10³/sec) were estimated using digital image correlation (DIC). Injury at 4 and 6 h was quantified using Fluoro-Jade C. Neuronal injury due to PSHPB testing was found to be significantly greater than injury associated with the tissue slice paradigm alone. While large pressures and strains were encountered for these tests, this system provides a controllable test environment to study injury to submerged brain slices over a range of strain rate, pressure, and strain loads.

Assessment of α-synuclein secretion in mouse and human brain parenchyma

Genetic, biochemical, and animal model studies strongly suggest a central role for α-synuclein in the pathogenesis of Parkinson's disease. α-synuclein lacks a signal peptide sequence and has thus been considered a cytosolic protein. Recent data has suggested that the protein may be released from cells via a non-classical secretory pathway and may therefore exert paracrine effects in the extracellular environment. However, proof that α-synuclein is actually secreted into the brain extracellular space in vivo has not been obtained. We developed a novel highly sensitive ELISA in conjugation with an in vivo microdialysis technique to measure α-synuclein in brain interstitial fluid. We show for the first time that α-synuclein is readily detected in the interstitial fluid of both α-synuclein transgenic mice and human patients with traumatic brain injury. Our data suggest that α-synuclein is physiologically secreted by neurons in vivo. This interstitial fluid pool of the protein may have a role in the propagation of synuclein pathology and progression of Parkinson's disease.

The TrkB-positive dopaminergic neurons are less sensitive to MPTP insult in the substantia nigra of adult C57/BL mice

Tyrosine kinase receptors TrkB and TrkC mediate neuroprotective effects of the brain-derived neurotrophic factor (BDNF) and neurotrophins in the dopaminergic nigro-striatal system, but it is obscure about their responses or expression changes in the injured substantia nigra under Parkinson's disease. In present study, immunofluorescence, Fluoro-Jade staining and laser scanning confocal microscopy were applied to investigate distribution and changes of TrkB and TrkC in the dopamine neurons of the substantia nigra by comparison of control and 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) mouse model. It revealed that TrkB and TrkC-immunoreactivities were substantially localized in cytoplasm and cell membrane of the substantia nigra neurons of control adults. While neurons double-labeled with tyrosine hydroxylase (TH)/TrkB, or TH/TrkC were distributed in a large numbers in the substantia nigra of controls, they apparently went down at 36.2-65.7% of normal level, respectively following MPTP insult. In MPTP model, cell apoptosis or degeneration of nigral neurons were confirmed by caspase-3 and Fluoro-Jade staining. More interestingly, TH/TrkB-positive neurons survived more in cell numbers in comparison with that of TH/TrkC-positive ones in the MPTP model. This study has indicated that TrkB-containing dopamine neurons are less sensitive in the substantia nigra of MPTP mouse model, suggesting that specific organization of Trks may be involved in neuronal vulnerability to MPTP insult, and BDNF-TrkB signaling may play more important role in protecting dopamine neurons and exhibit therapeutic potential for Parkinson's disease.

Optically based-indentation technique for acute rat brain tissue slices and thin biomaterials

Currently, micro-indentation testing of soft biological materials is limited in its capability to test over long time scales due to accumulated instrumental drift errors. As a result, there is a paucity of measures for mechanical properties such as the equilibrium modulus. In this study, indentation combined with optical coherence tomography (OCT) was used for mechanical testing of thin tissue slices. OCT was used to measure the surface deformation profiles after placing spherical beads onto submerged test samples. Agarose-based hydrogels at low-concentrations (w/v, 0.3-0.6%) and acute rat brain tissue slices were tested using this technique over a 30-min time window. To establish that tissue slices maintained cell viability, allowable testing times were determined by measuring neuronal death or degeneration as a function of incubation time with Fluor-Jade C (FJC) staining. Since large deformations at equilibrium were measured, displacements of surface beads were compared with finite element elastic contact simulations to predict the equilibrium modulus, μ(∞) . Values of μ(∞) for the low-concentration hydrogels ranged from 0.07 to 1.8 kPa, and μ(∞) for acute rat brain tissue slices was 0.13 ± 0.04 kPa for the cortex and 0.09 ± 0.015 kPa for the hippocampus (for Poisson ratio = 0.35). This indentation technique offers a localized, real-time, and high resolution method for long-time scale mechanical testing of very soft materials. This test method may also be adapted for viscoelasticity, for testing of different tissues and biomaterials, and for analyzing changes in internal structures with loading.

Fluoro jade-C staining in the assessment of brain injury after deep hypothermia circulatory arrest

OBJECTIVE

To evaluate the efficacy of Fluoro Jade-C staining (FJC) in the assessment of brain injury after deep hypothermia circulatory arrest (DHCA).

METHODS

Six healthy adult miniature male pigs underwent DHCA, the rectal temperature was down to 18°C, circulation was stopped , circulatory arrest was maintained for 60 minutes. On postoperative day 1, perfusion-fixation was performed on brain tissue. Cerebral cortex, hippocampus, cerebellum were taken for sampling. FJC, hematoxylin-eosin staining (HE), nissl staining (NISSL), terminal deoxynucleotidyl transferase biotin-dUTP nick end labeling (TUNEL) were performed to detect the histological and pathological changes. Histological scores of all slices were ranked. Comparison between the FJC and other techniques was done by analysis of variance (ANOVA) according to histological scores.

RESULTS

All animals survived the operation. On the cerebral cortex, in comparison of FJC between HE, NISSL and TUNEL, the p value was 0.90, 0.40, 0.16 respectively (p>0.05). On the hippocampus, the comparison of FJC with HE, NISSL and TUNEL had a p value of 0.12, 0.23, 0.62 respectively (p>0.05). On the cerebellum, in comparing FJC with HE, NISSL and TUNEL, the p value was 0.96, 0.77, 0.96 respectively (p>0.05). On representative regions, the results of FJC were in accordance with that of TUNEL, NISSL and HE. Furthermore, ascertainment of brain injury is easier with FJC.

CONCLUSION

FJC is a reliable and convenient method to assess brain injury after DHCA.

Depletion of Beclin-1 due to proteolytic cleavage by caspases in the Alzheimer's disease brain

The Beclin-1 protein is essential for the initiation of autophagy, and recent studies suggest this function may be compromised in Alzheimer's disease (AD). In addition, in vitro studies have supported a loss of function of Beclin-1 due to proteolytic modification by caspases. In the present study, we examined whether caspase-cleavage of Beclin-1 occurs in the AD brain by designing a site-directed caspase-cleavage antibody based upon a known cleavage site within the protein at position D149. We confirmed that Beclin-1 is an excellent substrate for caspase-3 and demonstrates cleavage led to the formation of a 35-kDa C-terminal fragment labeled by our novel antibody following Western blot analysis. Application of this antibody termed Beclin-1 caspase-cleavage product antibody or BeclinCCP in frontal cortex tissue sections revealed strong immunolabeling within astrocytes that localized with plaque regions and along blood vessels in all AD cases examined. In addition, weaker, more variable BeclinCCP labeling was also observed within neurofibrillary tangles that colocalized with the early tau conformational marker, MC-1 as well as the late tangle marker, PHF-1. Collectively, these data support a depletion of Beclin-1 in AD following caspase-cleavage. This article is part of a Special Issue entitled "Autophagy and protein degradation in neurological diseases."

Neurodegeneration in an Abeta-induced model of Alzheimer's disease: the role of Cdk5

Cdk5 dysregulation is a major event in the neurodegenerative process of Alzheimer's disease (AD). In vitro studies using differentiated neurons exposed to Abeta exhibit Cdk5-mediated tau hyperphosphorylation, cell cycle re-entry and neuronal loss. In this study we aimed to determine the role of Cdk5 in neuronal injury occurring in an AD mouse model obtained through the intracerebroventricular (icv) injection of the Abeta(1-40) synthetic peptide. In mice icv-injected with Abeta, Cdk5 activator p35 is cleaved by calpains, leading to p25 formation and Cdk5 overactivation. Subsequently, there was an increase in tau hyperphosphorylation, as well as decreased levels of synaptic markers. Cell cycle reactivation and a significant neuronal loss were also observed. These neurotoxic events in Abeta-injected mice were prevented by blocking calpain activation with MDL28170, which was administered intraperitoneally (ip). As MDL prevents p35 cleavage and subsequent Cdk5 overactivation, it is likely that this kinase is involved in tau hyperphosphorylation, cell cycle re-entry, synaptic loss and neuronal death triggered by Abeta. Altogether, these data demonstrate that Cdk5 plays a pivotal role in tau phosphorylation, cell cycle induction, synaptotoxicity, and apoptotic death in postmitotic neurons exposed to Abeta peptides in vivo, acting as a link between diverse neurotoxic pathways of AD.

Application of Fluoro-Jade C in acute and chronic neurodegeneration models: utilities and staining differences

Recent neuropathological studies have shown that Fluoro-Jade C (FJC), an anionic fluorescent dye, is a good marker of degenerating neurons. However, those studies have mostly examined acute rather than chronic models of neurodegeneration. We therefore compared FJC staining using the intrastriatal 6-hydroxydopamine (6-OHDA)-injected rat as an acute model and the zitter rat as a chronic model, as both show dopaminergic (DA) neurodegeneration. In the 6-OHDA-injected rat, FJC-positive neurons were found in the substantia nigra pars compacta (SNc) before the loss of tyrosine hydroxylase (TH)-positive DA neurons. In the zitter rat, FJC-labeled fibers were first detected at 1 month old (1M) and were considerably increased in the striatum at 4M, whereas FJC-labeled cell bodies were found at 4M, but not at 1M in the SNc. Furthermore, FJC-labeled neurons of the zitter rat showed TH-immunoreactivity in fibers, but little in cell bodies, while those from the 6-OHDA-injected rat showed TH-immunoreactivity even in the cell bodies. These results demonstrate that FJC is a useful tool for detecting chronically degenerating neurons, and suggest that intracellular substances bound to FJC may accumulate in the cell bodies from fibers at a slower rate in the chronic model than in the acute model.

Cytosolic labile zinc accumulation in degenerating dopaminergic neurons of mouse brain after MPTP treatment

High levels of labile zinc accumulate in degenerating neurons after brain injury, such as ischemic stroke, trauma, epilepsy, and hypoglycemia. Cytosolic zinc accumulation is also found in brain neurons undergoing apoptosis during development or after neuronal target ablation. Thus, staining with zinc-specific probes can be used to identify neuronal death in the brain. In this study, mice were intraperitoneally given four 20 mg/kg doses of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) at 2-hour intervals, and dopaminergic neurons were then evaluated for zinc accumulation and apoptosis. In the substantia nigra pars compacta, zinc-specific fluorescent dyes revealed that all degenerating neurons, identified by terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick-end labeling (TUNEL), or acid fuchsin or Fluoro-Jade C staining, contained high levels of cytosolic labile zinc. Nuclear condensation/fragmentation was noted in dopaminergic neurons with cytosolic zinc accumulation, indicating apoptotic cell death. These findings support the supposition that cytosolic labile zinc accumulation is an indicator of degenerating dopaminergic neurons in animal models of Parkinson's disease.

Influence of chronic exercise on the amphetamine-induced dopamine release and neurodegeneration in the striatum of the rat

The aim of this study was to verify the effect of chronic exercise on the striatal dopamine (DA) outflow induced by low and high single doses of amphetamine (AMPH), and verify the existence of an exercise protective role on neurodegeneration. Adult male Sprague-Dawley rats were randomly separated into six groups: chronic exercise, saline; chronic exercise, 5 mg kg(-1) AMPH; chronic exercise, 30 mg kg(-1) AMPH; without exercise, saline; without exercise, 5 mg kg(-1) AMPH; without exercise, 30 mg kg(-1) AMPH. Chronic exercise consisted of an 8-week running program on a treadmill, with increasing intensity. Animals were anesthetized, placed into a stereotaxic frame and an intracerebral guide cannula implanted into the caudate-putamen. When indicated, microdialysis was performed. Dialysate samples were collected during 30-min intervals for 6 h, before and after the intraperitonial administration of AMPH or saline solution. HPLC with electrochemical detection was used to quantify DA. Chronic exercise did not significantly change the extracellular DA basal values. Regarding the maximal DA levels in the dialysates, in the rats treated with 5 mg kg(-1) AMPH, there was no significant difference between groups with and without chronic exercise; on the contrary, in animals treated with 30 mg kg(-1) AMPH, the DA release was lower in the group with chronic exercise. Moreover, the maintenance of higher levels of DA along time in the training group suggests a diminished reuptake of DA. By using the Fluoro-Jade C staining technique, we did not find neuronal death in any of the groups. In conclusion, these results suggest that chronic exercise leads to a diminished release and reuptake of DA after administration of a high dose of AMPH, whereas neither chronic exercise nor AMPH seems to induce neurodegeneration.

Evaluation of Fluoro-Jade C as a marker of degenerating neurons in the rat retina and optic nerve

Detection of neuronal death is an essential requirement for researchers investigating retinal degeneration. Fluoro-Jade C (FJC) is a novel, fluorescent dye that has been successfully used to label degenerating neurons in the brain, but its effectiveness in the eye has not been ascertained. In the current study, we determined the efficacy of FJC for detection of neuronal degeneration in the retina and optic nerve in various paradigms of injury. N-methyl-D-aspartate (NMDA) and kainic acid-induced excitotoxicity, optic nerve transection, and bilateral occlusion of the common carotid arteries (BCCAO) were performed using standard techniques. Rats were killed at various time points and the retinas with optic nerves attached were removed for tissue processing prior to labelling for FJC, for DNA fragmentation by TUNEL or for immunohistochemical analysis. Retinas from RCS rats of different ages were also analysed. After excitotoxicity-induced injury, cell bodies and dendrites within the ganglion cell and inner plexiform layers were specifically labelled by FJC within 6h, a time point comparable to the appearance of TUNEL-positive nuclei and to reductions in mRNA levels of retinal ganglion cell-specific proteins, but in advance of alterations in some immunohistochemical markers. The number of FJC-labelled cell bodies in the retina declined over time as cell loss proceeded, although dendritic staining remained prominent. Colocalisation of FJC with TUNEL and with immunohistochemical neuronal markers was achieved. FJC was successful at identifying somato-dendritic degeneration following ischemia induced by BCCAO, but surprisingly, not after optic nerve transection. FJC visualised photoreceptor degeneration in the RCS rat, albeit less effectively than with the TUNEL assay, and was also effective for imaging and quantifying degenerating axons in the optic nerve after multiple injuries. In addition to labelling degenerating neurons, however, FJC also bound non-specifically to astrocytes and to blood cells in unperfused rats. Since the ganglion cell layer is adjacent to astrocytes within the nerve fibre layer, caution is needed when using FJC as a quantitative tool for detecting ganglion cell death.

Temporal neuropathologic and behavioral phenotype of 6neo/6neo Pompe disease mice

Pompe disease (glycogen storage disease II) is caused by mutations in the acid alpha-glucosidase gene. The most common form is rapidly progressive with glycogen storage, particularly in muscle, which leads to profound weakness, cardiac failure, and death by the age of 2 years. Although usually considered a muscle disease, glycogen storage also occurs in the CNS. We evaluated the progression of neuropathologic and behavioral abnormalities in a Pompe disease mouse model (6neo/6neo) that displays many features of the human disease. Homozygous mutant mice store excess glycogen within large neurons of hindbrain, spinal cord, and sensory ganglia by the age of 1 month; accumulations then spread progressively within many CNS cell types. "Silver degeneration" and Fluoro-Jade C stains revealed severe degeneration in axon terminals of primary sensory neurons at 3 to 9 months. These abnormalities were accompanied by progressive behavioral impairment on rotorod, wire hanging, and foot fault tests. The extensive neuropathologic alterations in this model suggest that therapy of skeletal and cardiac muscle disorders by systemic enzyme replacement therapy may not be sufficient to reverse functional deficits due to CNS glycogen storage, particularly early-onset, rapidly progressive disease. A better understanding of the basis for clinical manifestations is needed to correlate CNS pathology with Pompe disease manifestations.

Time-course of neuronal death in the mouse pilocarpine model of chronic epilepsy using Fluoro-Jade C staining

Epilepsy is a serious neurological disorder in human beings and the long-term pathological events remain largely obscure. We are interested in elucidating long-term brain injury that may occur in the temporal lobe epilepsy, and time-course of neuronal death was examined in a mouse pilocarpine model of chronic epilepsy by Fluoro-Jade C (FJC) dye that can specifically stain the degenerative neurons in the central nervous system. The FJC stain combined with immunohistochemistry to neuronal nuclear specific protein revealed that pilocarpine-induced status epilepticus (SE) resulted in massive degenerative death of neuronal cells in brains with their dense distribution in the cerebral cortex and hippocampus. The FJC-positive degenerating neurons, most of them also expressed apoptosis signaling molecules such as caspase-9 and activated caspase-3, occurred at 4h, increased into peak levels at 12h-3d, and then gradually went down at 7d-14d after onset of SE. More interestingly, a large percentage (about 88%) of FJC-positive degenerative neurons were GABAergic as indicated with their immunoreactivity to glutamic acid decarboxylase-67, implying that inhibitory function of GABAergic neural system might by seriously damaged in brains subject to SE attack in this mouse pilocarpine model. Taken together with previous studies, time-course of degenerative neurons in the mouse pilocarpine model by Fluoro-Jade C staining further benefits understanding of long-term brain pathological changes and recurrent seizure mechanism, and may also result in finding the most suitable time-window in therapeutic manipulation of the chronic epilepsy in human beings.

Identification and kainic acid-induced up-regulation of low-affinity p75 neurotrophin receptor (p75NTR) in the nigral dopamine neurons of adult rats

Parkinson's disease is a common and severe debilitating neurological disease that results from massive and progressive degenerative death of dopamine neurons in the substantia nigra, but the mechanisms of neuronal degeneration and disease progression remains largely obscure. We are interested in possible implications of low-affinity p75 neurotrophin receptor (p75NTR), which may mediate neuronal apoptosis in the central nervous system, in triggering cell death of the nigral dopamine neurons. The RT-PCR and immunohistochemistry were carried out to detect if p75NTR is expressed in these nigral neurons and up-regulated by kainic acid (KA) insult in adult rats. It revealed p75NTR-positive immunoreactivity in the substantia nigra, and co-localization of p75NTR and tyrosine hydroxylase (TH) was found in a large number of substantia nigra neurons beside confirmation of p75NTR in the choline acetyltransferase (ChAT)-positive forebrain neurons. Cell count data further indicated that about 47-100% of TH-positive nigral neurons and 98-100% of ChAT-positive forebrain neurons express p75NTR. More interestingly, significant increasing in both p75NTR mRNA and p75NTR-positive neurons occurred rapidly following KA insult in the substantia nigra of animal model. The present study has provided first evidence on p75NTR expression and KA-inducing p75NTR up-regulation in substantia nigra neurons in rodent animals. Taken together with previous data on p75NTR functions in neuronal apoptosis, this study also suggests that p75NTR may play important roles in neuronal cell survival or excitotoxic degeneration of dopamine neurons in the substantia nigra in pathogenesis of Parkinson's disease in human beings.

Lack of pathology in a triple transgenic mouse model of Alzheimer's disease after overexpression of the anti-apoptotic protein Bcl-2

Alzheimer's disease (AD) is characterized by the accumulation of plaques containing beta-amyloid (Abeta) and neurofibrillary tangles (NFTs) consisting of modified tau. Although Abeta deposition is thought to precede the formation of NFTs in AD, the molecular steps connecting these two pathologies is not known. Previous studies have suggested that caspase activation plays an important role in promoting the pathology associated with AD. To further understand the contribution of caspases in disease progression, a triple transgenic Alzheimer's mouse model overexpressing the anti-apoptotic protein Bcl-2 was generated. Here we show that overexpression of Bcl-2 limited caspase-9 activation and reduced the caspase cleavage of tau. Moreover, overexpression of Bcl-2 attenuated the processing of APP (amyloid precursor protein) and tau and reduced the number of NFTs and extracellular deposits of Abeta associated with these animals. In addition, overexpression of Bcl-2 in 3xTg-AD mice improved place recognition memory. These findings suggest that the activation of apoptotic pathways may be an early event in AD and contributes to the pathological processes that promote the disease mechanisms underlying AD.

Neurokinin-3 peptide instead of neurokinin-1 synergistically exacerbates kainic acid-inducing degeneration of neurons in the substantia nigra of mice

Neurokinin peptides neurokinin-1 (NK1), neurokinin-3 (NK3), and related receptors are abundantly distributed in the substantia nigra (SN) and evidenced by their possible roles in the Parkinson's disease. Differential intervention roles of NK3 on kainic acid (KA)-induced neuronal injury in the SN of mice were thus in vitro and in vivo studied by Fluoro-Jade C (FJC) staining, immunohistochemistry to tyrosine hydroxylase (TH) or phospho-NMDA receptor, and 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay. It revealed that (i) in contrast to protective effect of NK1 agonist septide that reduced FJC-positive degenerative neurons and lesion volume insulted by KA, NK3 agonist senktide significantly increased FJC-positive ones and lesion volume, and this effect was sufficiently reversed by NK3 antagonist SB218795; (ii) similarly, senktide reduced TH-positive neurons and this effect was antagonized by SB218795, but septide increased TH-positive ones; (iii) mechanistic observation showed differential influences of NK1 and NK3 agonists on phosphorylated-NMDA receptor subunit 1 (phospho-NMDAR1) and glial fibrillary acidic protein-expressing astrocytes, i.e. senktide enhanced of NMDA receptor phosphorylation and astrocyte activity, while septide reduced NMDA receptor phosphorylation and astrocytic response; (iv) cell culture further confirmed the exacerbating effect of NK3 agonist on KA-induced lesion of nigral cells or dopaminergic neurons, in which administration of senktide alone did not show significant cell toxicity. This study presents new evidence that neurokinin NK3 instead of NK1 synergistically exacerbate excitotoxic neuronal degeneration in the SN in a dose-dependent manner and possibly through modulation of NMDA receptor phosphorylation and astrocyte activity, suggesting their potential significance in novel pharmaceutical therapy against Parkinson's disease.