Kuniaki Tsuchiya

Phosphorylated TDP-43 in frontotemporal lobar degeneration and amyotrophic lateral sclerosis.

TAR DNA‐binding protein of 43kDa (TDP‐43) is deposited as cytoplasmic and intranuclear inclusions in brains of patients with frontotemporal lobar degeneration with ubiquitinated inclusions (FTLD‐U) and amyotrophic lateral sclerosis (ALS). Previous studies reported that abnormal phosphorylation takes place in deposited TDP‐43. The aim of this study was to identify the phosphorylation sites and responsible kinases, and to clarify the pathological significance of phosphorylation of TDP‐43.

Phosphorylated TDP-43 in Alzheimer’s disease and dementia with Lewy bodies

Phosphorylated and proteolytically cleaved TDP-43 is a major component of the ubiquitin-positive inclusions in the most common pathological subtype of frontotemporal lobar degeneration (FTLD-U). Intracellular accumulation of TDP-43 is observed in a subpopulation of patients with other dementia disorders, including Alzheimer’s disease (AD) and dementia with Lewy bodies (DLB). However, the pathological significance of TDP-43 pathology in these disorders is unknown, since biochemical features of the TDP-43 accumulated in AD and DLB brains, especially its phosphorylation sites and pattern of fragmentation, are still unclear. To address these issues, we performed immunohistochemical and biochemical analyses of AD and DLB cases, using phosphorylation-dependent anti-TDP-43 antibodies. We found a higher frequency of pathological TDP-43 in AD (36–56%) and in DLB (53–60%) than previously reported. Of the TDP-43-positive cases, about 20–30% showed neocortical TDP-43 pathology resembling the FTLD-U subtype associated with progranulin gene (PGRN) mutations. Immunoblot analyses of the sarkosyl-insoluble fraction from cases with neocortical TDP-43 pathology showed intense staining of several low-molecular-weight bands, corresponding to C-terminal fragments of TDP-43. Interestingly, the band pattern of these C-terminal fragments in AD and DLB also corresponds to that previously observed in the FTLD-U subtype associated with PGRN mutations. These results suggest that the morphological and biochemical features of TDP-43 pathology are common between AD or DLB and a specific subtype of FTLD-U. There may be genetic factors, such as mutations or genetic variants of PGRN underlying the co-occurrence of abnormal deposition of TDP-43, tau and α-synuclein.

Occurrence of T cells in the brain of Alzheimer's disease and other neurological diseases

We investigated the occurrence of T cells in the brain parenchyma of Alzheimers disease (AD), non-AD degenerative dementias and controls by semi-quantitative analysis of immunohistochemically stained tissue sections. In all cases, we found at least some T cells. The number of T cells was increased in the majority of AD cases compared with other cases. The phenotype of T cells in the AD brain indicates that they are activated but are not fully differentiated. Antigen-triggered clonal expansion is not likely to take place. Local inflammatory conditions might cause accumulation and activation of T cells in the AD brain.

Distinct isoforms of tau aggregated in neurons and glial cells in brains of patients with Pick's disease, corticobasal degeneration and progressive supranuclear palsy

Abstract. We investigated isoform composition of aggregated tau protein in brains with Picks disease (PiD), corticobasal degeneration (CBD) and progressive supranuclear palsy (PSP) by immunoblot analysis of sarkosyl-insoluble fractions of brain homogenates. We also examined the adjacent brain tissues immunohistochemically with a rabbit antibody, Ex10, which specifically recognizes exon 10 of tau. The Ex10 recognizes tau isoforms with four microtubule-binding repeats (4Rtau) but not those with three microtubule-binding repeats (3Rtau). Sarkosyl-insoluble tau from the brains of patients with CBD and PSP consisted of 4Rtau. Insoluble tau from the PiD brains contained both 3Rtau and 4Rtau, where 3Rtau predominated over 4Rtau. In brain tissues of CBD and PSP, Ex10 immunostained all neuronal and glial tau-positive structures. They included pre-tangles, astrocytic plaques, tuft-shaped astrocytes, and oligodendroglial coiled bodies. In PiD brains, astrocytic inclusions were also positive for 4Rtau. However, the majority of, if not all, Pick bodies and oligodendroglial tau inclusions were negative for 4Rtau. Such results suggest that, in neurons and oligodendroglia, tau isoforms involved in the pathological processes differ between CBD/PSP and PiD, and are thus disease specific. This contrasts with the astrocytic tau isoforms that accumulate similarly in all three disorders.

Sympathetic cardiac denervation in Parkinson's disease and pure autonomic failure but not in multiple system atrophy.

Three neurodegenerative diseases causing primary autonomic failure are pure autonomic failure (PAF), Parkinsons disease (PD), and multiple system atrophy (MSA). Differential diagnoses among these diseases are often difficult especially in early disease stage. For example, it may be difficult to determine whether a patient with parkinsonism and autonomic failure has PD or MSA. Recently, a decrease in myocardial uptake of meta-iodobenzylguanidine (MIBG), an analogue of norepinephrine, has been reported in PD but not in MSA using [123I]MIBG myocardial scintigraphy.1 This new imaging approach is thought to be of significance in the diagnosis and characterisation of akinetic rigid syndromes, especially PD. After that, we reported severe loss of cardiac sympathetic nerves in one patient with PD but not in one patient with MSA, which accounts for a difference in myocardial uptake of MIBG between PD and MSA.2 However, our observation was based on the study in only a single patient of each disease. In this study, we immunohistochemically examined the heart tissues from four patients with PD, three patients with MSA, and one patient with PAF, and showed the involvement of postganglionic cardiac sympathetic nerves in PD and PAF …

Identification of amino‐terminally cleaved tau fragments that distinguish progressive supranuclear palsy from corticobasal degeneration

Progressive supranuclear palsy (PSP) and corticobasal degeneration (CBD) are neurodegenerative diseases that are characterized by intracytoplasmic aggregates of hyperphosphorylated tau with four microtubule‐binding repeats. Although PSP and CBD have distinctive pathological features, no biochemical difference in aggregated tau has been identified. In this study, we examined the brains of eight patients with PSP, six patients with CBD, and one atypical case with pathological features of both CBD and PSP. On immunoblots of sarkosyl‐insoluble brain extracts, a 33kDa band predominated in the low molecular weight tau fragments in PSP, whereas two closely related bands of approximately 37kDa predominated in CBD. Immunoblots of the atypical case showed both the 33kDa band and the 37kDa doublet. Protein sequencing and immunochemical analyses showed that the 33kDa band and the 37kDa doublet consisted of the carboxyl half of tau with different amino termini. These results suggest that, despite the identical composition of tau isoforms, different proteolytic processing of abnormal tau takes place in these two diseases. Such a biochemical divergence may be related to the neuropathological features of these diseases.

The Role of G-Protein-Coupled Receptor Kinase 5 in Pathogenesis of Sporadic Parkinson's Disease

Sporadic Parkinsons disease (sPD) is a common neurodegenerative disorder, characterized by selective degeneration of dopaminergic neurons in the substantia nigra. Although the pathogenesis of the disease remains undetermined, phosphorylation of α-synuclein and its oligomer formation seem to play a key role. However, the protein kinase(s) involved in the phosphorylation in the pathogenesis of sPD has not been identified. Here, we found that G-protein-coupled receptor kinase 5 (GRK5) accumulated in Lewy bodies and colocalized with α-synuclein in the pathological structures of the brains of sPD patients. In cotransfected cells, GRK5 phosphorylated Ser-129 of α-synuclein at the plasma membrane and induced translocation of phosphorylated α-synuclein to the perikaryal area. GRK5-catalyzed phosphorylation also promoted the formation of soluble oligomers and aggregates of α-synuclein. Genetic association study revealed haplotypic association of the GRK5 gene with susceptibility to sPD. The haplotype contained two functional single-nucleotide polymorphisms, m22.1 and m24, in introns of the GRK5 gene, which bound to YY1 (Yin Yang-1) and CREB-1 (cAMP response element-binding protein 1), respectively, and increased transcriptional activity of the reporter gene. The results suggest that phosphorylation of α-synuclein by GRK5 plays a crucial role in the pathogenesis of sPD.

Enhanced expression of aquaporin 4 in human brain with infarction

A series of human brains with cerebral infarction obtained at autopsy were investigated to clarify the possible contribution of aquaporin 4 (AQP4) to the development of brain edema. Cellular localization of AQP4 and its relation to ischemic foci were examined with double-labeling immunohistochemistry. AQP4 immunoreactivity (IR) was more intense at the periphery of ischemic foci than at their center. Double-labeling study demonstrated that AQP4 IR was restricted to astrocytes and was localized to their entire processes, including their end feet facing the outer surface of capillaries. Moreover, AQP4 IR, detectable in the subpial and subependymal zone in the normal condition, was more intense in the vicinity of ischemic foci. Accumulation of AQP4 IR may reflect its participation in the development of brain edema in human brains by playing a role in the transport of water not only through blood vessel walls but also through pial and ependymal surface of the brain.

Different histopathology accounting for a decrease in myocardial MIBG uptake in PD and MSA

Differential diagnosis between PD and multiple-system atrophy (MSA) is often difficult, especially in early disease stages. Recent studies have shown that [123I]metaiodobenzylguanidine (MIBG) myocardial scintigraphy is useful to separate PD from MSA; MIBG uptake in PD is significantly lower than in MSA.1-3⇓⇓ However, a pathophysiologic mechanism for the decrease in myocardial MIBG uptake in PD and MSA remains to be elucidated. We describe a patient with PD and a patient with MSA. Postmortem examination revealed a severe loss of myocardial sympathetic nerve fibers in the former but not in the latter. ### Patient 1. An 80-year-old woman developed bradykinesia and gait disturbance, followed by right dominant resting hand tremor and rigidity, postural instability, severe constipation, and orthostatic hypotension. Dopaminergic therapy such as levodopa/carbidopa was given and effective for bradykinesia, rigidity, and tremor. She was diagnosed as having PD at the age of 82 years. Her condition deteriorated; she occasionally experienced syncope. She died of bronchopneumonia at 84 years old. MIBG myocardial scintigraphy, at the age of 83 years, showed …

Argyrophilic glial inclusions in the midbrain of patients with Parkinson's disease and diffuse Lewy body disease are immunopositive for NACP/α-synuclein

Argyrophilic glial inclusions occur in the midbrain of patients with Parkinsons disease (PD) and diffuse Lewy body disease (DLBD). These inclusions are immunohistochemically positive for NACP/alpha-synuclein but negative for tau protein. The results of the present study suggest that a primary degenerative process involves NACP/alpha-synuclein in PD and DLBD and that the process takes place not only in neurons but also in glial cells. Argyrophilic cytoplasmic inclusions, both glial and neuronal, in a variety of degenerative diseases may be grouped into two major categories; one related to aggregates of abnormally phosphorylated tau protein and the other to unusual accumulations of NACP/alpha-synuclein.