Susceptibility to neurofibrillary tangles: role of the PTPRD locus and limited pleiotropy with other neuropathologies.

Tauopathies, including Alzheimer's disease (AD) and other neurodegenerative conditions, are defined by a pathological hallmark: neurofibrillary tangles (NFTs). NFT accumulation is thought to be closely linked to cognitive decline in AD. Here, we perform a genome-wide association study for NFT pathologic burden and report the association of the PTPRD locus (rs560380, P=3.8 × 10-8) in 909 prospective autopsies. The association is replicated in an independent data set of 369 autopsies. The association of PTPRD with NFT is not dependent on the accumulation of amyloid pathology. In contrast, we found that the ZCWPW1 AD susceptibility variant influences NFT accumulation and that this effect is mediated by an accumulation of amyloid ß plaques. We also performed complementary analyses to identify common pathways that influence multiple neuropathologies that coexist with NFT and found suggestive evidence that certain loci may influence multiple different neuropathological traits, including tau, amyloid ß plaques, vascular injury and Lewy bodies. Overall, these analyses offer an evaluation of genetic susceptibility to NFT, a common end point for multiple different pathologic processes.

Characterization of cognitive impairments and neurotransmitter changes in a novel transgenic mouse lacking Slc10a4.

An orphan member of the solute carrier (SLC) family SLC10, SLC10A4 has been found to be enriched in midbrain and brainstem neurons and has been found to co-localize with and to affect dopamine (DA) homeostasis. We generated an SLC10A4 knockout mouse (Slc10a4(Δ/Δ)) using Cre-targeted recombination, and characterized behavioral measures of motor and cognitive function as well as DA and acetylcholine (ACh) levels in midbrain and brainstem. In agreement with previous studies, Slc10a4 mRNA was preferentially expressed in neurons in the brains of wild-type (Slc10a4(+/+)) mice and was enriched in dopaminergic and cholinergic regions. Slc10a4(Δ/Δ) mice had no impairment in motor function or novelty-induced exploratory behaviors but performed significantly worse in measures of spatial memory and cognitive flexibility. Slc10a4(Δ/Δ) mice also did not differ from Slc10a4(+/+) in measures of anxiety. High-performance liquid chromatography (HPLC) measures on tissue punches taken from the dorsal and ventral striatum reveal a decrease in DA content and a corresponding increase in the metabolite 3,4-dihydroxyphenylacetic acid (DOPAC), indicating an increase in DA turnover. Punches taken from the brainstem revealed a decrease in ACh as compared with Slc10a4(+/+) littermates. Together, these data indicate that loss of SLC10A4 protein results in neurotransmitter imbalance and cognitive impairment.

Association of cognitive domains with postural instability/gait disturbance in Parkinson's disease.

INTRODUCTION: Research suggests an association between global cognition and postural instability/gait disturbance (PIGD) in Parkinson disease (PD), but the relationship between specific cognitive domains and PIGD symptoms is not clear. This study examined the association of cognition (global and specific cognitive domains) with PIGD symptoms in a large, well-characterized sample of individuals with PD. METHODS: Cognitive function was measured with a detailed neuropsychological assessment, including global cognition, executive function, memory, visuospatial function, and language. PIGD symptoms were measured using the Movement Disorder Society Unified Parkinson's Disease Rating Scale (MDS-UPDRS) Part III, Motor Examination subscale. Multiple linear regression analyses were performed to assess the relationship between cognition and PIGD symptoms with models adjusting for age, sex, education, enrollment site, disease duration, and motor symptom severity. RESULTS: The analysis included 783 participants, with mean (standard deviation) age of 67.3 (9.7) years and median (interquartile range) MDS-UPDRS Motor Subscale score of 26 (17, 35). Deficits in global cognition, executive function, memory, and phonemic fluency were associated with more severe PIGD symptoms. Deficits in executive function were associated with impairments in gait, freezing, and postural stability, while visuospatial impairments were associated only with more severe freezing, and poorer memory function was associated only with greater postural instability. DISCUSSION: While impairments in global cognition and aspects of executive functioning were associated with more severe PIGD symptoms, specific cognitive domains were differentially related to distinct PIGD components, suggesting the presence of multiple neural pathways contributing to associations between cognition and PIGD symptoms in persons with PD.

Nonsteroidal anti-inflammatory drugs are associated with increased neuritic plaques.

OBJECTIVES: Observational and experimental studies suggest that nonsteroidal anti-inflammatory drugs (NSAIDs) may protect against Alzheimer disease (AD); however, clinical trials and other observational studies, including the Adult Changes in Thought (ACT) study, show no protection or promotion of AD. The objective of this study is to determine the relationship between common dementia-associated pathologies and mid- to late-life NSAID exposure. METHODS: We examined the association of mid- to late-life NSAID use with neuropathologic findings on 257 autopsies from ACT, a population-based study of brain aging and incident dementia. Cumulative standard daily doses (SDD) of nonselective NSAIDs were determined from ≥10 years of computerized pharmacy dispensing data. Analyses were adjusted for selection bias to broaden generalizability of results to 3,026 eligible participants in the ACT cohort. Seven pathologic indices were evaluated: intermediate or frequent score for neuritic plaques, Braak stages V or VI for neurofibrillary tangles, >2 cerebral microinfarcts, the presence of any neocortical Lewy bodies, any macroscopic infarcts, any amyloid angiopathy, and moderate or severe atherosclerosis. RESULTS: Of the neuropathologic indices evaluated, only neuritic plaque score was significantly increased in participants with greater use of nonselective NSAIDs (p = 0.065), specifically in those with high levels of cumulative use: 1,000-2,000 SDD (adjusted relative risk [RR] 2.16, 95% confidence interval [CI] 1.02-4.25, compared to light/nonuse [<60 SDD]) and >2,000 SDD (adjusted RR 2.37, 95% CI 1.24-4.67). CONCLUSIONS: Increased neuritic plaque accumulation may explain the association between heavy use of nonselective NSAIDs and increased risk of dementia among ACT participants.

Impaired cognition, sensorimotor gating, and hippocampal long-term depression in mice lacking the prostaglandin E2 EP2 receptor.

Cyclooxygenase-2 (COX-2) is a neuronal immediate early gene that is regulated by N-methyl d aspartate (NMDA) receptor activity. COX-2 enzymatic activity catalyzes the first committed step in prostaglandin synthesis. Recent studies demonstrate an emerging role for the downstream PGE(2) EP2 receptor in diverse models of activity-dependent synaptic plasticity and a significant function in models of neurological disease including cerebral ischemia, Familial Alzheimer's disease, and Familial amyotrophic lateral sclerosis. Little is known, however, about the normal function of the EP2 receptor in behavior and cognition. Here we report that deletion of the EP2 receptor leads to significant cognitive deficits in standard tests of fear and social memory. EP2-/- mice also demonstrated impaired prepulse inhibition (PPI) and heightened anxiety, but normal startle reactivity, exploratory behavior, and spatial reference memory. This complex behavioral phenotype of EP2-/- mice was associated with a deficit in long-term depression (LTD) in hippocampus. Our findings suggest that PGE(2) signaling via the EP2 receptors plays an important role in cognitive and emotional behaviors that recapitulate some aspects of human psychopathology related to schizophrenia.

CSF tau/Abeta42 ratio for increased risk of mild cognitive impairment: a follow-up study.

BACKGROUND: Processes of Alzheimer disease (AD) likely begin years prior to the onset of cognitive impairment (latent AD), progress though a prodromal phase of mild cognitive impairment (MCI), and culminate in dementia. While many studies have evaluated CSF tau and Abeta(42) as biomarkers of the dementia or prodromal stages of AD, we are unaware of any study to evaluate these potential CSF biomarkers of latent AD. METHODS: We determined the ratio of CSF tau/Abeta(42) (T/Abeta) using Luminex reagents in 129 control individuals that spanned from 21 to 100 years of age; for comparison we included patients with MCI (n = 12), probable AD (n = 21), or other neurodegenerative diseases (n = 12). RESULTS: We identified 16% of the control group with abnormally elevated CSF T/Abeta; all were 53 years or older. Using age-matched controls with normal CSF T/Abeta we showed that the high CSF T/Abeta subgroup of controls had significantly increased frequency of the epsilon4 allele of the apolipoprotein E gene and significantly increased risk of conversion to MCI during follow-up of up to 42 months suggesting that they had latent AD at the time of lumbar puncture. CONCLUSIONS: These generally applicable methods establish cutoff values to identify control individuals at increased risk of conversion to mild cognitive impairment which may be useful to people weighing the risk-benefit ratio of new preventive therapeutics and to researchers striving to enrich clinical trial populations with people with latent Alzheimer disease.

Statin therapy is associated with reduced neuropathologic changes of Alzheimer disease.

BACKGROUND: Treatment with 3-hydroxy-3-methylglutaryl-coenzyme-A reductase inhibitors ("statins") has been associated in some epidemiologic studies with reduced risk of Alzheimer disease (AD). However, direct evidence of statin effects on neuropathologic markers of AD is lacking. We investigated whether antecedent statin exposure is associated with neuritic plaque (NP) or neurofibrillary tangle (NFT) burden in a population-based sample of human subjects. METHODS: Brain autopsies were performed on 110 subjects, ages 65 to 79 years, who were cognitively normal at enrollment into the Adult Changes in Thought Study. Neuropathologic findings were compared between statin users with > or =3 prescriptions of > or =15 pills of simvastatin, pravastatin, lovastatin, or atorvastatin vs nonusers, based on pharmacy dispensing records. RESULTS: After controlling for age at death, gender, cognitive function at study entry, brain weight, and presence of cerebral microvascular lesions, the odds ratio (OR) for each unit increase in Braak NFT stage in statin users vs nonusers was 0.44 (95% CI: 0.20 to 0.95). The OR for each unit increase in Consortium to Establish a Registry for Alzheimer's Disease (CERAD) staging of NPs did not deviate significantly from unity (OR 0.69; 95% CI: 0.32 to 1.52). However, the risk for typical AD pathology (Braak stage > or = IV and CERAD rating > or = moderate) was reduced in statin users (OR 0.20; 95% CI: 0.05 to 0.86). CONCLUSIONS: These findings demonstrate an association between antecedent statin use and neurofibrillary tangle burden at autopsy. Additional study is needed to examine whether statin use may be causally related to decreased development of Alzheimer disease-related neuropathologic changes.

Neural transplantation in Huntington disease: long-term grafts in two patients.

OBJECTIVE: Clinical trials of fetal neural tissue transplantation for Huntington disease (HD) have been conducted with variable clinical results. However, no long-term analysis of graft survival and integration has been published. Here, we report the pathologic findings in two patients with HD who died 74 and 79 months after transplantation. METHODS: Methods used were pathologic examination, histochemistry, and immunohistochemistry. RESULTS: Neostriatum from both patients showed typical neuropathologic changes of advanced HD. Surviving grafts were identified in both patients (6/6 sites and 7/8 sites, respectively) as well-demarcated nests within host neostriatum with associated needle tracts. Grafted neurons adopted either dominant calbindin/parvalbumin or calretinin immunoreactivity (IR). Few neurofilament, MAP-2, DARPP-32, tyrosine hydroxylase, or calbindin IR processes traversed the host parenchyma-graft interface despite minimal junctional gliosis. Immunohistochemistry for CD68 showed microgliosis that was more pronounced in host striatum than graft. Scattered CD45 and CD3 IR cells were present within grafts and host parenchyma. No ubiquitin IR neuronal intranuclear inclusions were identified in graft neurons, although these were prevalent in host cells. CONCLUSIONS: These two autopsies confirm previous findings of neuronal differentiation and survival of transplanted fetal tissue from the ganglionic eminence and also demonstrate viability of neurons from fetal transplants in human neostriatum for more than 6 years. Despite prolonged survival, these grafts had poor integration with host striatum that is likely responsible for lack of clear clinical improvement in these patients.

A novel progranulin mutation associated with variable clinical presentation and tau, TDP43 and alpha-synuclein pathology.

Mutations in the progranulin (GRN) gene have recently been reported as a cause of the frontotemporal dementia (FTD) syndrome. We performed a clinical, neuropathological and molecular genetic study of two families with FTD and the same novel mutation in GRN. Age of onset ranged from 35 to 75 years and all individuals progressed to a severe dementia syndrome with a mean disease duration of approximately 6-10 years. Variable clinical presentations included language impairment, behaviour change or parkinsonism. Seven total autopsies in the families (five in Family 1, two in Family 2) showed gross and microscopic evidence of neuronal loss in the neocortex, striatum, hippocampus and substantia nigra. All cases with material available for immunohistochemistry had cytoplasmic and intranuclear ubiquitin positive, tau negative inclusions that stained best with an antibody to the TDP43 protein. In addition, all but one had evidence of distinctive tau pathology. Two cases in Family 1 also had alpha-synuclein (SNCA) pathology, one with diffuse neocortical inclusions and neurites and unusual striatal cytoplasmic inclusions. Affected persons in both families had the same mutation in GRN (c.709-2A>G). A minigene construct showed that this mutation alters splicing of exon 7 and results in reduced mRNA message in brain. A single GRN mutation in these two families was associated with variable clinical presentations consistent with the FTD syndrome. All cases had ubiquitin/TDP43 immuno-positive inclusions and most had additional tau pathology. Two cases had SNCA pathology. These findings suggest a link between mutations in GRN and aggregation of tau, TDP43 and SNCA.

Selective dendritic degeneration of medium spiny neurons in dementia with Lewy bodies.

Dementia with Lewy bodies (DLB) is the second most common form of dementia and shows more severely impaired performance on tests of executive functions compared to Alzheimer disease. Here the authors demonstrate selective spinodendritic degeneration of medium spiny neurons in regions of the caudate nucleus that subserve executive functions and propose that this may underlie, at least in part, the heightened executive dysfunction observed in patients with DLB.

Dendritic degeneration in neostriatal medium spiny neurons in Parkinson disease.

Dysfunction of neostriatal medium spiny neurons (MSNs) is hypothesized to underlie late-stage motor complications of Parkinson disease (PD). The authors demonstrate shortened dendrite length of MSNs that was similar in four regions of neostriatum in late-stage PD. In contrast, MSN dendrite spine degeneration was unevenly distributed with the greatest loss in caudal putamen. The authors propose that these structural changes in MSN may contribute to late-stage motor complications of PD.

Fragile X gene premutation in multiple system atrophy.

Previous reports have suggested that expansion of the CGG repeat located in the fragile X mental retardation 1 (FMR1) gene might be responsible for a significant number of patients with the multiple system atrophy (MSA) phenotype. Analysis of 65 MSA patients found only 4.6% displayed CGG expansions in the suspected range. This is similar to the frequency reported in the normal population, suggesting that this expansion does not play a major role in the MSA phenotype.

Proteasomal inhibition induced by manganese ethylene-bis-dithiocarbamate: relevance to Parkinson's disease.

Maneb, a widely used fungicide, has been associated with Parkinsonism in humans. In experimental models, maneb and its major active element, manganese ethylene-bis-dithiocarbamate (Mn-EBDC) cause selective nigrostriatal neurodegeneration in mice and in rats, respectively. To investigate the mechanisms underlying this neurodegeneration, we studied the effects of Mn-EBDC on proteasomal function, which is decreased in patients with Parkinson's disease (PD), in a dopaminergic neuronal cell line (MES 23.5 or MES). The results demonstrated that exposure of MES cells to 6 microM Mn-EBDC for 7 days produced not only significant neurotoxicity but also inhibition of proteasomal chymotrypsin-like and postglutamyl peptidase activities. Proteasomal dysfunction was accompanied by formation of cytoplasmic inclusions that were positive for alpha-synuclein immunostaining and significantly increased sodium dodecyl sulfate-insoluble alpha-synuclein aggregation seen by Western blot analysis. In addition, there was a significant increase in oxidative stress, evidenced by elevated total protein carbonyl content, in cells treated with Mn-EBDC. Manipulation of intracellular reduced glutathione levels with N-acetyl-L-cysteine or L-buthionine sulfoximine pretreatment to modulate Mn-EBDC-mediated oxidative stress altered Mn-EBDC-mediated neurotoxicity, proteasomal dysfunction, and alpha-synuclein aggregation in these cells. These data suggest that neurotoxicity-induced by Mn-EBDC is at least partially attributable to Mn-EBDC-mediated proteasomal inhibition, and that the proteasome may be an important target by which environmental exposure modifies the risk for developing PD in vulnerable populations.

Lipoproteins and lipid peroxidation in Alzheimer's disease.

Alzheimer's Disease (AD) is a clinical-pathological entity that probably derives from different causes. Mounting evidence strongly implicates regionally increased oxidative damage to brain beyond what occurs with aging as one of the processes that may contribute to AD progression. While several different classes of molecules may be affected, lipid peroxidation is thought to be a prominent and especially deleterious form of oxidative damage in brain due to this organ's relative enrichment in polyunsaturated fatty acids. Our laboratory recently has demonstrated that lipoproteins in AD brain extracellular fluid are more vulnerable to oxidation than lipoproteins in control brain extracellular fluid. Apolipoprotein E (apoE) is the principal apolipoprotein in the central nervous system (CNS), and it serves as the major apolipoprotein that is capable of lipid transport and regulation of lipid metabolism through known receptor-mediated processes. Moreover, inheritance of the APOE4 allele represents the strongest genetic risk factor for sporadic AD. Evidence suggests that apoE isoforms may specifically influence the cellular distribution of lipid peroxidation products in brain and may therefore contribute to the stratification of risk for AD associated with APOE. Here, we review possible mechanisms whereby lipoprotein trafficking and lipid peroxidation converge to contribute to neurodegeneration in AD brain.

CSF lipoproteins and Alzheimer's disease.

Alterations in lipid homeostasis have been suggested to play a role in the pathogenesis of Alzheimer's disease (AD). This hypothesis is supported by the observed changes in lipid content and composition of AD brains when compared to age-matched control brains. The association between the e4 allele of the apolipoprotein E gene and increased risk of AD implicates lipoproteins in the pathogenesis. Lipoproteins are macromolecular particles responsible for lipid trafficking and metabolism. CNS lipoproteins are different from their plasma counter parts. We review the current understanding of the structure and functions of CNS lipoproteins. In addition to mediating lipid trafficking and metabolism, there is increasing evidence that apoE-containing lipoproteins are also involved in dendritic remodeling and synaptogensis and maintenance of the synapto-dendritic complexity during aging. Interestingly, these functions have been shown to be apoE-isoform specific with apoE4 lacking the activities of apoE3 and apoE2. In addition to the association between apoE4 and an increased risk of AD, oxidative stress is believed to play a role in the pathogenesis of this disease. Indeed evidence of lipid peroxidation in cerebral spinal fluid (CSF) lipoproteins from AD patients has been observed. Oxidation of lipoproteins not only eliminates their supportive roles in neurite outgrowth and synaptogenesis, but actually transforms them into neurotoxic agents. The elucidation of the pathways and mechanisms by which apoE-isoform and oxidation affect lipoprotein function in the CNS remains a challenge for scientist in the field of neurodegenerative disease.

The mitochondrial common deletion in Parkinson's disease and related movement disorders.

The mitochondrial 4977-bp common deletion has been reported in some studies to occur exclusively or with increased frequency in the midbrain of patients with Parkinson's disease (PD). Other studies could not confirm these results; rather, it was suggested that the mitochondrial common deletion is associated with aging in the midbrain and not PD. One possible explanation for these conflicting results is the difficulty in quantifying mitochondrial DNA deletions or mutations in the whole midbrain or substantia nigra (SN) while only a subset of midbrain neurons degenerate in PD. In addition, none of the studies has addressed the cell types with the common deletion within the midbrain. In this study we used in situ hybridization to detect the common deletion in sections of midbrain from patients with PD, multiple system atrophy-parkinsonian type (MSA-P), progressive supranuclear palsy (PSP), dementia with Lewy bodies (DLB), age-matched controls, and individuals of different ages. The results demonstrated that the mitochondrial common deletion accumulated primarily in neurons but not glia in both the SN and other midbrain regions. There was no significant difference in the number or distribution of neurons with the common deletion or the average of the mean densities (AMD) of staining with the common deletion in nigral neurons among patients with PD, MSA-P, PSP, DLB, or age-matched controls. In addition, there was no difference in the number or distribution of neurons with the common deletion in nigral neurons between any age group, although there was a tendency for the common deletion to increase in the non-nigral neurons in older patients. These data indicate that accumulation of the 4977-bp common deletion in mitochondrial DNA in midbrain occurred primarily in neurons, and by this cytological approach, it was not associated with nigral neurodegeneration in the common movement disorders or aging.

Cysteine and mercapturate conjugates of oxidized dopamine are in human striatum but only the cysteine conjugate impedes dopamine trafficking in vitro and in vivo.

Recent results have suggested that some products of mercapturic acid pathway (MAP) metabolism of oxidized dopamine (DA) may contribute to mesostriatal dopaminergic neurodegeneration, and that at least one product, 5-S-cysteinyldopamine (Cys-DA), is elevated in patients with advanced Parkinson's disease (PD) who have been treated with L-DOPA. Here we investigated MAP enzymes and products in the midbrain and striatum of control individuals and patients with dementia with Lewy bodies (DLB) who had less severe dopaminergic degeneration than PD patients and who were not treated with L-DOPA. We also determined the biological activity of MAP metabolites of oxidized DA using primary rat mesencephalic cultures, rat cerebral synaptosomes, and rat striatum in vivo microdialysis. Our results showed that the human mesostriatal dopaminergic pathway generates Cys-DA but has limited enzymatic capacity for mercapturate formation, that striatal levels of MAP products of oxidized DA are not elevated in DLB patients compared with controls, and that Cys-DA interferes with trafficking of DA in vitro and in vivo. These results indicate that while Cys-DA is not increased in striatum of patients with mild dopaminergic neurodegeneration, it may interfere with uptake of DA in patients with advanced PD.

Improved assay for the quantification of the major urinary metabolite of the isoprostane 15-F(2t)-Isoprostane (8-iso-PGF(2alpha)) by a stable isotope dilution mass spectrometric assay.

BACKGROUND: The F(2)-isoprostanes (IsoPs) are a series of novel prostaglandin (PG)-like compounds generated from the free radical catalyzed peroxidation of arachidonic acid. One IsoP, 15-F(2t)-IsoP (8-iso-PGF(2alpha)), has been shown to be formed in abundance in vivo and to exert potent biological activity. METHODS: As a means to assess the endogenous production of this compound, we previously developed a method to quantify the major urinary metabolite of 15-F(2t)-IsoP, 2,3-dinor-5,6-dihydro-15-F(2t)-IsoP (2,3-dinor-5,6-dihydro-8-iso-PGF(2alpha), 15-F(2t)-IsoP-M ), by gas chromotography (GC)/negative ion chemical ionization mass spectrometry (MS) employing stable isotope dilution methodology. While useful, we found that the assay occasionally suffered from the presence of impurities that co-elute on GC with 15-F(2t)-IsoP-M, making the measurement of this compound difficult. We now report a modified assay for the quantification of 15-F(2t)-IsoP-M employing GC/MS that alleviates this problem. RESULTS: Precision of the assay is +/-7% and the accuracy is 96%. The lower limit of sensitivity is approximately 8 pg. Normal concentrations of this metabolite in urine were found to be 0.46+/-0.09 ng/mg creatinine (mean+/-1 S.D.) Urinary excretion of 15-F(2t)-IsoP-M is markedly altered in situations associated with increased or decreased oxidant stress in vivo. CONCLUSIONS: This assay provided a sensitive and accurate method to assess endogenous IsoP generation and can be used to further explore the role of oxidant injury in human disease.

Elevation of AKR7A2 (succinic semialdehyde reductase) in neurodegenerative disease.

Elevated levels of oxidative stress or decreased antioxidant defense mechanisms may underlie the regionally increased oxidative damage to brain observed in many neurodegenerative disorders. Phase I detoxification pathways for reactive aldehydes generated from lipid peroxidation include aldehyde dehydrogenases, alcohol dehydrogenases and aldo-keto reductases (AKR). In the present study, we examined the cellular expression of AKR family member, succinic semialdehyde reductase (AKR7A2) that reduces toxic aldehydes as well as catalyzing the biosynthesis of the neuromodulator gamma-hydroxybutyrate (GHB). Our results show that in the cerebral cortex and hippocampus, AKR7A2 is primarily localized to glial cells, astrocytes and microglia. In the midbrain, AKR7A2 was found in glia and neuromelanin-containing neurons of the substantia nigra, and the periaqueductal gray. In sections of cerebral cortex and hippocampus from patients with AD and DLB, AKR7A2 immunoreactivity was elevated in reactive astrocytes and microglial cells. Furthermore, total AKR7A2 protein levels were elevated in the cerebral cortex of patients with AD versus control individuals. Our data suggest that reactive gliosis, as a response to injury, may affect GHB neuromodulatory pathways in neurodegenerative disease and elevate aldehyde detoxification pathways.