Kenji Ikeda

Fas antigen expression in brains of patients with Alzheimer-type dementia.

Fas antigen (CD95) is a cell surface protein that mediates apoptosis. We have investigated the immunohistochemical localization of Fas antigen in postmortem brain tissue from control subjects, patients with Alzheimer-type dementia (ATD), and from a few patients with diffuse Lewy body disease, progressive supranuclear palsy and adrenoleukodystrophy. In all brains, including controls, vascular endothelial cells and residual blood plasma were weakly stained. In ATD brains, senile plaques and a small number of star-like cells were brains of patients with neurological diseases other than ATD. In double immunostaining for Fas and glial fibrillary acidic protein (GFAP), a small number of cells were positive for both antigens. The majority of Fas-positive astrocytes were, however, negative for GFAP. This implies the downregulation of GFAP production in these cells. Doubly labeled astrocytes were also found around senile plaques, suggesting that the Fas immunoreactivity in senile plaques was derived from astrocytic membranes. The results of this study indicate that Fas antigen is expressed by a subset of reactive astrocytes in degenerative neurological diseases. Such astrocytes may undergo the Fas-mediated apoptotic process.

Early response of brain resident microglia to kainic acid-induced hippocampal lesions.

We investigated the early response of microglia with complement and other proteins in well controlled rat central nervous system lesions. A selective neuronal degeneration in the hippocampal CA3 region was induced without direct tissue damage by an intraventricular injection of a small amount of kainic acid. As early as 1 h post injection, complement proteins C1q, C4, and C3 and immunoglobulin(Ig)G were found in the lesioned area. After 2 h, non-specific leakage of other plasma proteins occurred. By 3 h, reactive microglia gathered around the injured pyramidal neurons. Areas surrounding the lesions were depleted, on the other hand, indicating that these reactive microglia had originally resided in and migrated from such vacant areas. Upregulation of ICAM-1 expression by vascular endothelial cells commenced after 6 h. LFA-1-positive leucocytes were, then, accumulated in the vasculature, which was followed by an infiltration of leucocytes into the lesioned brain parenchyma. These results indicate that, following an acute neuronal injury, the response of the humoral factors such as complement proteins and IgG precedes the microglial reaction. Activation of vascular endothelial cells and subsequent infiltration of blood leucocytes occurs much later than the activation and migration of brain resident microglia. The origin of complement proteins and IgG in the lesioned brain parenchyma remains to be determined, although the production of complement proteins by microglia is suggested.

Argyrophilic thread-like structure in corticobasal degeneration and supranuclear palsy.

Massive argyrophilic thread-like structures (ATS) are observed in corticobasal degeneration and, in varied degrees, in some cases of progressive supranuclear palsy. Immunohistochemically, ATS has a full length of phosphorylated tau epitopes without ubiquitin. Gallyas- and immuno-electron microscopic observation revealed that ATS is a cytoskeletal abnormality occurred in both the inner and outer loop of the oligodendroglia. tau-Positive oligodendroglial tangles were distributed in the same region as ATS.

Expression of the receptor for macrophage colony stimulating factor by brain microglia and its upregulation in brains of patients with Alzheimer's disease and amyotrophic lateral sclerosis

The receptor for macrophage colony stimulating factor (CSF-1) was localized immunohistochemically in postmortem human brain tissue. Microglia constitutively expressed the receptor for CSF-1 and its expression was upregulated in lesions of Alzheimers disease and amyotrophic lateral sclerosis. The CSF-1 mediated pathway appears to be involved in the response and activation of microglia in the central nervous system lesions.

Immunohistochemical study of brain-derived neurotrophic factor and its receptor, TrkB, in the hippocampal formation of schizophrenic brains.

Recently, the pathogenesis of schizophrenia has been investigated from the perspective of neurodevelopmental dysfunction theory. On the other hand, it has been indicated that neurotrophic factors, such as nerve growth factors, brain-derived neurotrophic factor (BDNF), and neurotrophin-3, are significantly involved in the development and functional differences of central nervous system (CNS). Some reports proposed that the dysfunction of these factors could explain the pathogenesis of schizophrenia possibly. In this study, the authors investigated immunohistochemically the distribution and/or morphology of BDNF and TrkB, its peculiar receptor, in the hippocampal formation of schizophrenic brain. As a result, BDNF-positive pyramidal cells in the CA2 and neurons in the CA3 and the field of the CA4 were intensely stained compared to those of normal control. Staining of TrkB-positive neurons showed a signet-ring like shape in the hippocampus of normal control brains. Such figures were not observed on staining of those neurons from schizophrenic brains. In the control cases, TrkB-immunopositive varicose fibers were frequently seen. Those observed differences between schizophrenic and normal cases may indicate the existence of dysfunction of BDNF and TrkB in schizophrenic brain, and this dysfunction may be one of the factors involved in the pathogenesis of schizophrenia.

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.

Activated microglial cells are colocalized with perivascular deposits of amyloid-β protein in Alzheimer's disease brain

BACKGROUND AND PURPOSE Microglial cells are present in the center of senile plaques (SPs) in Alzheimers disease (AD) brain. Such a localization of microglial cells suggests that they are involved in the deposition or the clearance of amyloid-beta protein (A beta) in the brain. We examined their association with another type of parenchymal A beta deposit, which is termed the perivascular deposits of A beta (PA beta). METHODS Thick sections from AD brain were stained with a three-color immunofluorescence method that labeled A beta, activated microglial cells, and vascular endothelial cells simultaneously. RESULTS Three-dimensional observation under a laser scanning microscope confirmed that perivascular aggregates of activated microglial cells were colocalized with PA beta. CONCLUSIONS Microglia occur in association with both SPs and PA beta, suggesting that they play important roles in the metabolism of A beta in AD brain.

Phenotypic down-regulation of glutamate receptor subunit GluR1 in Alzheimer's disease.

Glutamate receptors play crucial roles in cognition and memory. We have quantitated the protein levels of alpha-amino-isoxazolepropionic acid (AMPA)-type (GluR1) and N-methyl-D-aspartate-type (NMDAR1) glutamate receptors in postmortem brain tissues of patients with Alzheimers disease and age-matched controls using western blotting. The bolts carrying fully denatured proteins were probed with antibodies specific to their carboxyl terminus of these receptors. In Alzheimers disease, GluR1 levels were significantly decreased in the entorhinal cortex and dentate gyrus, but not in the motor cortex. In contrast, levels of NMDAR1 were not altered in the dentate gyrus, suggesting that GluR1 expression was specifically diminished in this structure that is known to be preserved histologically in patients. However, the results of immunocytochemical examination confirmed a previous controversial report: GluR1-immunoreactive structures were labeled rather intensely in the molecular layer of the dentate gyrus of Alzheimers patients. Interestingly, levels of a postsynaptic density protein named SAP97, which recognizes and potentially masks the epitope region of GluR1, was positively correlated with those of GluR1 protein in the control group, but not in the patient group. Thus, the enhanced GluR1-like staining in Alzheimers disease might be ascribed to the hampered interaction between SAP97 and GluR1 leading to epitope unmasking of GluR1 on tissue sections. These findings indicate that abnormal expressions of the AMPA receptor and its interacting PSD molecule are associated with Alzheimers disease and implicated in pathophysiology of this disease.

Morphological diversities of CD44 positive astrocytes in the cerebral cortex of normal subjects and patients with Alzheimer's disease.

The localization of CD44 was investigated immunohistochemically in postmortem human brain tissue of control subjects and patients with Alzheimers disease. CD44 is a multifunctional cell surface glycoprotein that serves as a receptor for hyaluronic acid, collagen types I and VI, and mucosal vascular addressin. In gray matter, it was found to be associated with some astrocytes of both protoplasmic and fibrous morphology. These positively stained astrocytes were most frequently observed in association with blood vessels, and had morphologies that were highly comparable to those described with the Golgi technique. Double immunostaining for CD44 and glial fibrillary acidic protein (GFAP) revealed that a significant number of these astrocytes were positive for both antigens. However, GFAP staining was mostly confined to the cell somata and proximal processes, while CD44 staining extended to a rich and extensive array of processes. Occasional CD44 positive cells of spherical morphology with a few thin varicose processes were observed. Their processes formed thick terminations on blood vessels, suggesting that these cells are a special class of astrocyte. In Alzheimers disease brain, the number of CD44 positive astrocytes increased dramatically. These data suggest that astrocytes have very extensive branching patterns, which are reflected by CD44 staining patterns. CD44 may be an important adhesion molecule for these astrocytic processes.

Differences in a dinucleotide repeat polymorphism in the tau gene between Caucasian and Japanese populations: implication for progressive supranuclear palsy

Previous studies of a tau polymorphism in Caucasian subjects with progressive supranuclear palsy (PSP) showed an over-representation of one genotype, A0/A0, versus normal control subjects. This result suggested that tau may be playing a genetic role in the progression of PSP. This study examines whether the over-representation of A0/A0 is Caucasian-specific or universal to PSP. Unfortunately, we found this dinucleotide repeat was relatively non-polymorphic in Japanese subjects. As a result, the genotypes were virtually the same, A0/A0, between Japanese PSP and control subjects. However, this outcome, albeit negative, does suggest two possible roles of the tau gene in PSP pathogenesis: (1) the role of this dinucleotide repeat in PSP may be different between Caucasian and Japanese populations or (2) this repeat may not be causal for PSP but represents a marker for other molecular genetic risk factors within or close to the tau gene on chromosome 17.