Kerry Cormier

The spectrum of disease in chronic traumatic encephalopathy

Chronic traumatic encephalopathy is a progressive tauopathy that occurs as a consequence of repetitive mild traumatic brain injury. We analysed post-mortem brains obtained from a cohort of 85 subjects with histories of repetitive mild traumatic brain injury and found evidence of chronic traumatic encephalopathy in 68 subjects: all males, ranging in age from 17 to 98 years (mean 59.5 years), including 64 athletes, 21 military veterans (86% of whom were also athletes) and one individual who engaged in self-injurious head banging behaviour. Eighteen age- and gender-matched individuals without a history of repetitive mild traumatic brain injury served as control subjects. In chronic traumatic encephalopathy, the spectrum of hyperphosphorylated tau pathology ranged in severity from focal perivascular epicentres of neurofibrillary tangles in the frontal neocortex to severe tauopathy affecting widespread brain regions, including the medial temporal lobe, thereby allowing a progressive staging of pathology from stages I-IV. Multifocal axonal varicosities and axonal loss were found in deep cortex and subcortical white matter at all stages of chronic traumatic encephalopathy. TAR DNA-binding protein 43 immunoreactive inclusions and neurites were also found in 85% of cases, ranging from focal pathology in stages I-III to widespread inclusions and neurites in stage IV. Symptoms in stage I chronic traumatic encephalopathy included headache and loss of attention and concentration. Additional symptoms in stage II included depression, explosivity and short-term memory loss. In stage III, executive dysfunction and cognitive impairment were found, and in stage IV, dementia, word-finding difficulty and aggression were characteristic. Data on athletic exposure were available for 34 American football players; the stage of chronic traumatic encephalopathy correlated with increased duration of football play, survival after football and age at death. Chronic traumatic encephalopathy was the sole diagnosis in 43 cases (63%); eight were also diagnosed with motor neuron disease (12%), seven with Alzheimers disease (11%), 11 with Lewy body disease (16%) and four with frontotemporal lobar degeneration (6%). There is an ordered and predictable progression of hyperphosphorylated tau abnormalities through the nervous system in chronic traumatic encephalopathy that occurs in conjunction with widespread axonal disruption and loss. The frequent association of chronic traumatic encephalopathy with other neurodegenerative disorders suggests that repetitive brain trauma and hyperphosphorylated tau protein deposition promote the accumulation of other abnormally aggregated proteins including TAR DNA-binding protein 43, amyloid beta protein and alpha-synuclein.

Sodium phenylbutyrate prolongs survival and regulates expression of anti-apoptotic genes in transgenic amyotrophic lateral sclerosis mice

Multiple molecular defects trigger cell death in amyotrophic lateral sclerosis (ALS). Among these, altered transcriptional activity may perturb many cellular functions, leading to a cascade of secondary pathological effects. We showed that pharmacological treatment, using the histone deacetylase inhibitor sodium phenylbutyrate, significantly extended survival and improved both the clinical and neuropathological phenotypes in G93A transgenic ALS mice. Phenylbutyrate administration ameliorated histone hypoacetylation observed in G93A mice and induced expression of nuclear factor‐κB (NF‐κB) p50, the phosphorylated inhibitory subunit of NF‐κB (pIκB) and beta cell lymphoma 2 (bcl‐2), but reduced cytochrome c and caspase expression. Curcumin, an NF‐κB inhibitor, and mutation of the NF‐κB responsive element in the bcl‐2 promoter, blocked butyrate‐induced bcl‐2 promoter activity. We provide evidence that the pharmacological induction of NF‐κB‐dependent transcription and bcl‐2 gene expression is neuroprotective in ALS mice by inhibiting programmed cell death. Phenylbutyrate acts to phosphorylate IκB, translocating NF‐κB p50 to the nucleus, or to directly acetylate NF‐κB p50. NF‐κB p50 transactivates bcl‐2 gene expression. Up‐regulated bcl‐2 blocks cytochrome c release and subsequent caspase activation, slowing motor neuron death. These transcriptional and post‐translational pathways ultimately promote motor neuron survival and ameliorate disease progression in ALS mice. Phenylbutyrate may therefore provide a novel therapeutic approach for the treatment of patients with ALS.

ESET/SETDB1 gene expression and histone H3 (K9) trimethylation in Huntington's disease

Chromatin remodeling and transcription regulation are tightly controlled under physiological conditions. It has been suggested that altered chromatin modulation and transcription dysfunction may play a role in the pathogenesis of Huntingtons disease (HD). Increased histone methylation, a well established mechanism of gene silencing, results in transcriptional repression. ERG-associated protein with SET domain (ESET), a histone H3 (K9) methyltransferase, mediates histone methylation. We show that ESET expression is markedly increased in HD patients and in transgenic R6/2 HD mice. Similarly, the protein level of trimethylated histone H3 (K9) was also elevated in HD patients and in R6/2 mice. We further demonstrate that both specificity protein 1 (Sp1) and specificity protein 3 (Sp3) act as transcriptional activators of the ESET promoter in neurons and that mithramycin, a clinically approved guanosine–cytosine-rich DNA binding antitumor antibiotic, interferes with the DNA binding of these Sp family transcription factors, suppressing basal ESET promoter activity in a dose dependent manner. The combined pharmacological treatment with mithramycin and cystamine down-regulates ESET gene expression and reduces hypertrimethylation of histone H3 (K9). This polytherapy significantly ameliorated the behavioral and neuropathological phenotype in the R6/2 mice and extended survival over 40%, well beyond any existing reported treatment in HD mice. Our data suggest that modulation of gene silencing mechanisms, through regulation of the ESET gene is important to neuronal survival and, as such, may be a promising treatment in HD patients.

Chronology of behavioral symptoms and neuropathological sequela in R6/2 Huntington's disease transgenic mice.

Genetic murine models play an important role in the study of human neurological disorders by providing accurate and experimentally accessible systems to study pathogenesis and to test potential therapeutic treatments. One of the most widely employed models of Huntingtons disease (HD) is the R6/2 transgenic mouse. To characterize this model further, we have performed behavioral and neuropathological analyses that provide a foundation for the use of R6/2 mice in preclinical therapeutic trials. Behavioral analyses of the R6/2 mouse reveal age‐related impairments in dystonic movements, motor performance, grip strength, and body weight that progressively worsen until death. Significant neuropathological sequela, identified as increasing marked reductions in brain weight, are present from 30 days, whereas decreased brain volume is present from 60 days and decreased neostriatal volume and striatal neuron area, with a concomitant reduction in striatal neuron number, are present at 90 days of age. Huntingtin‐positive aggregates are present at postnatal day 1 and increase in number and size with age. Our findings suggest that the R6/2 HD model exhibits a progressive HD‐like behavioral and neuropathological phenotype that more closely corresponds to human HD than previously believed, providing further assurance that the R6/2 mouse is an appropriate model for testing potential therapies for HD. J. Comp. Neurol. 490:354–370, 2005.

Mitochondrial loss, dysfunction, and altered dynamics in Huntington’s disease

Although a direct causative pathway from the gene mutation to the selective neostriatal neurodegeneration remains unclear in Huntingtons disease (HD), one putative pathological mechanism reported to play a prominent role in the pathogenesis of this neurological disorder is mitochondrial dysfunction. We examined mitochondria in preferentially vulnerable striatal calbindin-positive neurons in moderate-to-severe grade HD patients, using antisera against mitochondrial markers of COX2, SOD2 and cytochrome c. Combined calbindin and mitochondrial marker immunofluorescence showed a significant and progressive grade-dependent reduction in the number of mitochondria in spiny striatal neurons, with marked alteration in size. Consistent with mitochondrial loss, there was a reduction in COX2 protein levels using western analysis that corresponded with disease severity. In addition, both mitochondrial transcription factor A, a regulator of mtDNA, and peroxisome proliferator-activated receptor-co-activator gamma-1 alpha, a key transcriptional regulator of energy metabolism and mitochondrial biogenesis, were also significantly reduced with increasing disease severity. Abnormalities in mitochondrial dynamics were observed, showing a significant increase in the fission protein Drp1 and a reduction in the expression of the fusion protein mitofusin 1. Lastly, mitochondrial PCR array profiling in HD caudate nucleus specimens showed increased mRNA expression of proteins involved in mitochondrial localization, membrane translocation and polarization and transport that paralleled mitochondrial derangement. These findings reveal that there are both mitochondrial loss and altered mitochondrial morphogenesis with increased mitochondrial fission and reduced fusion in HD. These findings provide further evidence that mitochondrial dysfunction plays a critical role in the pathogenesis of HD.

Combination therapy with Coenzyme Q10 and creatine produces additive neuroprotective effects in models of Parkinson’s and Huntington’s Diseases

Coenzyme Q10 (CoQ10) and creatine are promising agents for neuroprotection in neurodegenerative diseases via their effects on improving mitochondrial function and cellular bioenergetics and their properties as antioxidants. We examined whether a combination of CoQ10 with creatine can exert additive neuroprotective effects in a MPTP mouse model of Parkinson’s disease, a 3‐NP rat model of Huntington’s disease (HD) and the R6/2 transgenic mouse model of HD. The combination of the two agents produced additive neuroprotective effects against dopamine depletion in the striatum and loss of tyrosine hydroxylase neurons in the substantia nigra pars compacta (SNpc) following chronic subcutaneous administration of MPTP. The combination treatment resulted in significant reduction in lipid peroxidation and pathologic α‐synuclein accumulation in the SNpc neurons of the MPTP‐treated mice. We also observed additive neuroprotective effects in reducing striatal lesion volumes produced by chronic subcutaneous administration of 3‐NP to rats. The combination treatment showed significant effects on blocking 3‐NP‐induced impairment of glutathione homeostasis and reducing lipid peroxidation and DNA oxidative damage in the striatum. Lastly, the combination of CoQ10 and creatine produced additive neuroprotective effects on improving motor performance and extending survival in the transgenic R6/2 HD mice. These findings suggest that combination therapy using CoQ10 and creatine may be useful in the treatment of neurodegenerative diseases such as Parkinson’s disease and HD.

In vivo expression of polyglutamine-expanded huntingtin by mouse striatal astrocytes impairs glutamate transport: a correlation with Huntington's disease subjects

Huntingtons disease (HD) is a neurodegenerative disorder previously thought to be of primary neuronal origin, despite ubiquitous expression of mutant huntingtin (mHtt). We tested the hypothesis that mHtt expressed in astrocytes may contribute to the pathogenesis of HD. To better understand the contribution of astrocytes in HD in vivo, we developed a novel mouse model using lentiviral vectors that results in selective expression of mHtt into striatal astrocytes. Astrocytes expressing mHtt developed a progressive phenotype of reactive astrocytes that was characterized by a marked decreased expression of both glutamate transporters, GLAST and GLT-1, and of glutamate uptake. These effects were associated with neuronal dysfunction, as observed by a reduction in DARPP-32 and NR2B expression. Parallel studies in brain samples from HD subjects revealed early glial fibrillary acidic protein expression in striatal astrocytes from Grade 0 HD cases. Astrogliosis was associated with morphological changes that increased with severity of disease, from Grades 0 through 4 and was more prominent in the putamen. Combined immunofluorescence showed co-localization of mHtt in astrocytes in all striatal HD specimens, inclusive of Grade 0 HD. Consistent with the findings from experimental mice, there was a significant grade-dependent decrease in striatal GLT-1 expression from HD subjects. These findings suggest that the presence of mHtt in astrocytes alters glial glutamate transport capacity early in the disease process and may contribute to HD pathogenesis.

Magnetic resonance spectroscopic analysis of Alzheimer's disease mouse brain that express mutant human APP shows altered neurochemical profile

Transgenic mice that express mutant human amyloid precursor protein (APPTg2576) develop beta-amyloid (Abeta) plaques throughout the cortex starting at 10-12 months of age. We examined the neurochemical profile of APPTg2576 mice using in vitro and in vivo magnetic resonance spectroscopy (MRS); gross abnormalities using magnetic resonance imaging (MRI) and plaque distribution; size and number using immunohistochemistry. Transgenic mice were anesthetized with halothane and scanned at 4.7 T using T2-weighted imaging and in vivo MRS of frontal cortex. In vitro MRS was run from brain extracts of frontal cortex in both APP and wild-type mice. Mice were also perfused and brains were collected and cut for immunohistochemistry. We found that N-acetylaspartate (NAA), glutamate and glutathione were decreased by 17%, 22% and 36%, respectively, in the cerebral cortex of APP transgenic mice at 19 months of age when Abeta deposits are widespread. Taurine was increased 21% compared to wild-type. Decreased levels of NAA and increased levels of taurine are consistent with decreased neuronal viability and increased glial volume, and are similar to findings of decreased NAA and increased myo-inositol in human Alzheimers disease (AD) brains. Correlation between the severity of Abeta deposition and altered neurochemical profile remains to be studied. Nevertheless, the altered neurochemical profile may be a valuable marker to test therapeutics in this mouse model.

Clinicopathological evaluation of chronic traumatic encephalopathy in players of American football

Importance Players of American football may be at increased risk of long-term neurological conditions, particularly chronic traumatic encephalopathy (CTE). Objective To determine the neuropathological and clinical features of deceased football players with CTE. Design, Setting, and Participants Case series of 202 football players whose brains were donated for research. Neuropathological evaluations and retrospective telephone clinical assessments (including head trauma history) with informants were performed blinded. Online questionnaires ascertained athletic and military history. Exposures Participation in American football at any level of play. Main Outcomes and Measures Neuropathological diagnoses of neurodegenerative diseases, including CTE, based on defined diagnostic criteria; CTE neuropathological severity (stages I to IV or dichotomized into mild [stages I and II] and severe [stages III and IV]); informant-reported athletic history and, for players who died in 2014 or later, clinical presentation, including behavior, mood, and cognitive symptoms and dementia. Results Among 202 deceased former football players (median age at death, 66 years [interquartile range, 47-76 years]), CTE was neuropathologically diagnosed in 177 players (87%; median age at death, 67 years [interquartile range, 52-77 years]; mean years of football participation, 15.1 [SD, 5.2]), including 0 of 2 pre–high school, 3 of 14 high school (21%), 48 of 53 college (91%), 9 of 14 semiprofessional (64%), 7 of 8 Canadian Football League (88%), and 110 of 111 National Football League (99%) players. Neuropathological severity of CTE was distributed across the highest level of play, with all 3 former high school players having mild pathology and the majority of former college (27 [56%]), semiprofessional (5 [56%]), and professional (101 [86%]) players having severe pathology. Among 27 participants with mild CTE pathology, 26 (96%) had behavioral or mood symptoms or both, 23 (85%) had cognitive symptoms, and 9 (33%) had signs of dementia. Among 84 participants with severe CTE pathology, 75 (89%) had behavioral or mood symptoms or both, 80 (95%) had cognitive symptoms, and 71 (85%) had signs of dementia. Conclusions and Relevance In a convenience sample of deceased football players who donated their brains for research, a high proportion had neuropathological evidence of CTE, suggesting that CTE may be related to prior participation in football.

Chronic traumatic encephalopathy pathology in a neurodegenerative disorders brain bank

Chronic traumatic encephalopathy (CTE) is a progressive neurodegenerative disorder linked to repetitive traumatic brain injury (TBI) and characterized by deposition of hyperphosphorylated tau at the depths of sulci. We sought to determine the presence of CTE pathology in a brain bank for neurodegenerative disorders for individuals with and without a history of contact sports participation. Available medical records of 1721 men were reviewed for evidence of past history of injury or participation in contact sports. Subsequently, cerebral cortical samples were processed for tau immunohistochemistry in cases with a documented history of sports exposure as well as age- and disease-matched men and women without such exposure. For cases with available frozen tissue, genetic analysis was performed for variants in APOE, MAPT, and TMEM106B. Immunohistochemistry revealed 21 of 66 former athletes had cortical tau pathology consistent with CTE. CTE pathology was not detected in 198 individuals without exposure to contact sports, including 33 individuals with documented single-incident TBI sustained from falls, motor vehicle accidents, domestic violence, or assaults. Among those exposed to contact sports, those with CTE pathology did not differ from those without CTE pathology with respect to noted clinicopathologic features. There were no significant differences in genetic variants for those with CTE pathology, but we observed a slight increase in MAPT H1 haplotype, and there tended to be fewer homozygous carriers of the protective TMEM106B rs3173615 minor allele in those with sports exposure and CTE pathology compared to those without CTE pathology. In conclusion, this study has identified a small, yet significant, subset of individuals with neurodegenerative disorders and concomitant CTE pathology. CTE pathology was only detected in individuals with documented participation in contact sports. Exposure to contact sports was the greatest risk factor for CTE pathology. Future studies addressing clinical correlates of CTE pathology are needed.