Takeshi Kawarabayashi

A chemical chaperone, sodium 4-phenylbutyric acid, attenuates the pathogenic potency in human α-synuclein A30P + A53T transgenic mice

Aggregation and cytotoxicity of misfolded alpha-synuclein are postulated to be crucial in the disease processes of Parkinsons disease (PD) and other synucleinopathies. Mutations in the alpha-synuclein gene in some pedigrees of familial PD have been reported. The mutant alpha-synuclein has been reported to form fibrillar aggregates resulting in biochemical abnormalities that are responsible for the onset of familial PD. Thus, any agent that effectively prevents the development of misfolded and aggregated alpha-synuclein would be a disease modifying therapeutic candidate. We examined the efficacy of sodium 4-phenylbutyric acid (PBA), one of the chemical chaperons, in transgenic (Tg) mice overexpressing human alpha-synuclein containing a double mutation (A30P + A53T). To evaluate the therapeutic efficacy, bradykinesia and motor coordination were assessed using a pole test and a rotarod treadmill task, respectively. After PBA treatment, these motor deteriorations gradually improved. In immunohistochemical examinations, both a loss of tyrosine hydroxylase-positive neurons and an increase of phosphorylated alpha-synuclein in the substantia nigra were inhibited, resulting in no depletion of the striatal dopamine content. These data suggest that PBA might be one of the therapeutic reagents for neurodegenerative disorders.

Microglial activation in brain lesions with tau deposits: comparison of human tauopathies and tau transgenic mice TgTauP301L.

The aim of this study is to clarify the relationship of microglia to phosphorylated tau accumulation and the characteristics of microglial activation in brain lesions of human tauopathies in comparison to mutant tau transgenic (TG) mice. We performed immunocytochemical analyses of brains from six patients with tauopathies, and 24 mice (18 TG mice expressing mutant tau P301L and six non-TG control mice, 11 to 27 months of age) using anti-tau antibodies and various microglial markers. In the tau TG, both semiquantitative severity ratings of microglial activation and an ultrastructural study were performed. In human tauopathies, Iba1- and major histocompatibility complex (MHC) class II-positive activated microglia increased in regions of phosphorylated tau (AT8) accumulation. The immunoreactivity of scavenger receptor class A (SRA) was present in some activated microglia, including phagocytic microglia in Alzheimers disease (AD). Double-immunofluorescent analysis under a confocal microscope showed activated microglia at the vicinity of AT8-positive cells. Semiquantitative data of the TG and control mice indicated that the immunopositivity of AT8 was closely associated with the number of Iba1-positive microglia in the cortical area. Tau-associated microglia showed rare immunoreactivity for MHC class II antigen and SRA in the TG mice. Ultrastructurally, activated microglia with enlarged cytoplasm were located near neurons containing abnormal cytoskeletons. This comparative study of human tauopathies and tau TG mice indicated that microglial activation was closely related to phosphorylated tau accumulation, and that activated microglia of the TG mice may have the low expression of MHC class II and SRA compared with those of human tauopathies.

Reuptake of L-DOPA-derived extracellular DA in the striatum of a rodent model of Parkinson's disease via norepinephrine transporter.

To determine the role of norepinephrine transporter in reuptake of L‐DOPA‐derived extracellular DA in the DA‐denervated Parkinsonian striatum, we examined extracellular DA levels in the striatum of 6‐hydroxyDA‐lesioned rats that received L‐DOPA (50 mg/kg with 12.5 mg/kg of benserazide) and L‐DOPA plus desipramine (25 mg/kg), a selective norepinephrine reuptake inhibitor, using in vivo microdialysis. The pretreatment with desipramine increased levels of extracellular DA derived from administrated L‐DOPA in the DA‐denervated striatum. This study provides evidence that L‐DOPA‐derived DA is taken up by the norepinephrine transporter, instead of the dopamine transporter, in the striatum with dopaminergic denervation. This result suggests that the norepinephrine transporter could be a promising target in the treatment for Parkinsons disease. Synapse 62:632–635, 2008.

Transthyretin Accelerates Vascular Aβ Deposition in a Mouse Model of Alzheimer's Disease

Transthyretin (TTR) binds amyloid‐β (Aβ) and prevents Aβ fibril formation in vitro. It was reported that the lack of neurodegeneration in a transgenic mouse model of Alzheimers disease (AD) (Tg2576 mouse) was associated with increased TTR level in the hippocampus, and that chronic infusion of anti‐TTR antibody into the hippocampus of Tg2576 mice led to increased local Aβ deposits, tau hyperphosphorylation and apoptosis. TTR is, therefore, speculated to prevent Aβ pathology in AD. However, a role for TTR in Aβ deposition is not yet known. To investigate the relationship between TTR and Aβ deposition, we generated a mouse line carrying a null mutation at the endogenous TTR locus and the human mutant amyloid precursor protein cDNA responsible for familial AD (Tg2576/TTR−/− mouse) by crossing Tg2576 mice with TTR‐deficient mice. We asked whether Aβ deposition was accelerated in Tg2576/TTR−/− mice relative to the heterozygous mutant Tg2576 (Tg2576/TTR+/−) mice. Contrary to our expectations, the degree of total and vascular Aβ burdens in the aged Tg2576/TTR−/− mice was significantly reduced relative to the age‐matched Tg2576/TTR+/− mice. Our experiments present, for the first time, compelling evidence that TTR does not suppress but rather accelerates vascular Aβ deposition in the mouse model of AD.

Plasma biomarkers of Alzheimer's disease.

Purpose of review The importance of biomarkers of Alzheimers disease is increasing. The present review aims to offer a general view of plasma biomarkers of Alzheimers disease and to discuss their relevance and limitations. Recent findings The broad overlap in the plasma amyloid β protein (Aβ) levels between patients with Alzheimers disease and control individuals indicates that the plasma Aβ level cannot differentiate cases of sporadic Alzheimers disease from control cases. Although the significance of Aβ for diagnosing Alzheimers disease is controversial, high plasma concentrations of Aβ40 and low plasma concentrations of Aβ42 indicate an increased risk of dementia. Summary The usefulness of biomarkers in cerebrospinal fluid has been shown by numerous studies; this test is not commonly used, however, and blood biomarkers are therefore preferred. Increasing evidence shows that the plasma Aβ concentration may be a premorbid marker for the risk of Alzheimers disease. It may be used for therapeutic monitoring, diagnosis of Aβ deposition in the brain, and also as a surrogate genetic marker to identify novel genetic determinants of Alzheimers disease. A potential role of plasma Aβ concentration as a marker of incipient dementia warrants further investigation.

A Japanese ALS6 family with mutation R521C in the FUS/TLS gene: A clinical, pathological and genetic report

Here we report a Japanese family with amyotrophic lateral sclerosis (ALS) characterized by very rapid progression, high penetrance and an autosomal dominant mode of inheritance. The phenotype includes atrophy of sternocleidomastoideus muscles, bulbar involvement, weakness of neck muscles and proximal muscle atrophy. These clinical symptoms are reminiscent of myopathy. All patients examined had similar clinical symptoms, age at onset and disease duration. The proband was found to have mutation R521C in the FUS/TLS gene, and was diagnosed as having ALS6. Autopsy material was available from the mother of the proband and FUS-immunoreactive neuronal and glial cytoplasmic inclusions were observed in the anterior horn of the spinal cord. While atrophy and weakness of the sternocleidomastoideus muscle is not emphasized in previous reports, this symptom may be a clinical hallmark of ALS6.

Extracellular and intraneuronal HMW-AbetaOs represent a molecular basis of memory loss in Alzheimer's disease model mouse.

BackgroundSeveral lines of evidence indicate that memory loss represents a synaptic failure caused by soluble amyloid β (Aβ) oligomers. However, the pathological relevance of Aβ oligomers (AβOs) as the trigger of synaptic or neuronal degeneration, and the possible mechanism underlying the neurotoxic action of endogenous AβOs remain to be determined.ResultsTo specifically target toxic AβOs in vivo, monoclonal antibodies (1A9 and 2C3) specific to them were generated using a novel design method. 1A9 and 2C3 specifically recognize soluble AβOs larger than 35-mers and pentamers on Blue native polyacrylamide gel electrophoresis, respectively. Biophysical and structural analysis by atomic force microscopy (AFM) revealed that neurotoxic 1A9 and 2C3 oligomeric conformers displayed non-fibrilar, relatively spherical structure. Of note, such AβOs were taken up by neuroblastoma (SH-SY5Y) cell, resulted in neuronal death. In humans, immunohistochemical analysis employing 1A9 or 2C3 revealed that 1A9 and 2C3 stain intraneuronal granules accumulated in the perikaryon of pyramidal neurons and some diffuse plaques. Fluoro Jade-B binding assay also revealed 1A9- or 2C3-stained neurons, indicating their impending degeneration. In a long-term low-dose prophylactic trial using active 1A9 or 2C3 antibody, we found that passive immunization protected a mouse model of Alzheimers disease (AD) from memory deficits, synaptic degeneration, promotion of intraneuronal AβOs, and neuronal degeneration. Because the primary antitoxic action of 1A9 and 2C3 occurs outside neurons, our results suggest that extracellular AβOs initiate the AD toxic process and intraneuronal AβOs may worsen neuronal degeneration and memory loss.ConclusionNow, we have evidence that HMW-AβOs are among the earliest manifestation of the AD toxic process in mice and humans. We are certain that our studies move us closer to our goal of finding a therapeutic target and/or confirming the relevance of our therapeutic strategy.

Plasma antibodies to Aβ40 and Aβ42 in patients with Alzheimer's disease and normal controls

Antibodies to amyloid beta protein (Abeta) are present naturally or after Abeta vaccine therapy in human plasma. To clarify their clinical role, we examined plasma samples from 113 patients with Alzheimers disease (AD) and 205 normal controls using the tissue amyloid plaque immunoreactivity (TAPIR) assay. A high positive rate of TAPIR was revealed in AD (45.1%) and age-matched controls (41.2%), however, no significance was observed. No significant difference was observed in the MMS score or disease duration between TAPIR-positive and negative samples. TAPIR-positive plasma reacted with the Abeta40 monomer and dimer, and the Abeta42 monomer weakly, but not with the Abeta42 dimer. TAPIR was even detected in samples from young normal subjects and young Tg2576 transgenic mice. Although the Abeta40 level and Abeta40/42 ratio increased, and Abeta42 was significantly decreased in plasma from AD groups when compared to controls, no significant correlations were revealed between plasma Abeta levels and TAPIR grading. Thus an immune response to Abeta40 and immune tolerance to Abeta42 occurred naturally in humans without a close relationship to the Abeta burden in the brain. Clarification of the mechanism of the immune response to Abeta42 is necessary for realization of an immunotherapy for AD.

Quantification of cystatin C in cerebrospinal fluid from various neurological disorders and correlation with G73A polymorphism in CST3

Cystatin C (CC) is a cysteine protease inhibitor abundantly expressed in the central nervous system. Bunina bodies, small eosinophilic intraneuronal inclusions, are stain positive for CC and are the most specific histological hallmark of amyotrophic lateral sclerosis (ALS). In this study, employing a latex turbidimetric immunoassay, levels of CC in cerebrospinal fluid (CSF) were quantified in 130 age-matched individuals with either a neurological disorder [ALS, Alzheimers disease (AD), Parkinsons disease (PD), tauopathy (TP), multiple system atrophy (MSA), chronic inflammatory demyelinating polyneuropathy (CIDP)] or no known neurological condition (normal control, NC). The CC level in CSF was found to be correlated with the age during the investigation but not the protein concentration. There was no difference in CC levels between NC and ALS or CIDP cases, whereas CC levels were significantly lower in MSA compared with NC. Of the 130 cases, 96 were genotyped, and G/A or A/A polymorphism at +73 within the CST3 gene was found in 28 individuals. The CC level was significantly lower in the combined group of G/A and A/A genotypes compared with G/G. The present data demonstrate that the level of CC in CSF should not be considered as a biomarker of ALS, but there is a correlation between CC levels and the CST3 genotype.

Motor impairment and aberrant production of neurochemicals in human α-synuclein A30P+A53T transgenic mice with α-synuclein pathology

Missense point mutations, duplication and triplication in the alpha-synuclein (alphaSYN) gene have been identified in familial Parkinsons disease (PD). Familial and sporadic PD show common pathological features of alphaSYN pathologies, e.g., Lewy bodies (LBs) and Lewy neurites (LNs), and a loss of dopaminergic neurons in the substantia nigra that leads to motor disturbances. To elucidate the mechanism of alphaSYN pathologies, we generated TgalphaSYN transgenic mice overexpressing human alphaSYN with double mutations in A30P and A53T. Human alphaSYN accumulated widely in neurons, processes and aberrant neuronal inclusion bodies. Sarcosyl-insoluble alphaSYN, as well as phosphorylated, ubiquitinated and nitrated alphaSYN, was accumulated in the brains. Significantly decreased levels of dopamine (DA) were recognized in the striatum. Motor impairment was revealed in a rotarod test. Thus, TgalphaSYN is a useful model for analyzing the pathological cascade from aggregated alphaSYN to motor disturbance, and may be useful for drug trials.