Kazuhiro Niizato

Abnormal expression of epidermal growth factor and its receptor in the forebrain and serum of schizophrenic patients

Epidermal growth factor (EGF) comprises a structurally related family of proteins containing heparin-binding EGF-like growth factor (HB-EGF) and transforming growth factor alpha (TGFα) that regulates the development of dopaminergic neurons as well as monoamine metabolism. We assessed the contribution of EGF to schizophrenia by measuring EGF family protein levels in postmortem brains and in fresh serum of schizophrenic patients and control subjects. EGF protein levels were decreased in the prefrontal cortex and striatum of schizophrenic patients, whereas the levels of HB-EGF and TGFα were not significantly different in any of the regions examined. Conversely, EGF receptor expression was elevated in the prefrontal cortex. Serum EGF levels were markedly reduced in schizophrenic patients, even in young, drug-free patients. Chronic treatment of animals with the antipsychotic drug haloperidol had no influence on EGF levels in the brain or serum. These findings suggest that there is abnormal EGF production in various central and peripheral tissues of patients with both acute and chronic schizophrenia. EGF might thus provide a molecular substrate for the pathologic manifestation of the illness, although additional studies are required to determine a potential link between impaired EGF signaling and the pathology/etiology of schizophrenia.

Brain Cannabinoid CB2 Receptor in Schizophrenia

BACKGROUND Neural endocannabinoid function appears to be involved in schizophrenia. Two endocannabinoid receptors, CB1 and CB2, are found in the brain and elsewhere in the body. We investigated roles of CB2 in schizophrenia. MATERIALS AND METHODS An association study was performed between tag single nucleotide polymorphisms (SNPs) in the CNR2 gene encoding the CB2 receptor and schizophrenia in two independent case-control populations. Allelic differences of associated SNPs were analyzed in human postmortem brain tissues and in cultured cells. Prepulse inhibition and locomotor activity in C57BL/6JJmsSlc mice with CB2 receptor antagonist AM630 administration was examined. RESULTS The analysis in the first population revealed nominally significant associations between schizophrenia and two SNPs, and the associations were replicated in the second population. The R63 allele of rs2501432 (R63Q) (p = .001), the C allele of rs12744386 (p = .005) and the haplotype of the R63-C allele (p = 5 x 10(-6)) were significantly increased among 1920 patients with schizophrenia compared with 1920 control subjects in the combined population. A significantly lower response to CB2 ligands in cultured CHO cells transfected with the R63 allele compared with those with Q63, and significantly lower CB2 receptor mRNA and protein levels found in human brain with the CC and CT genotypes of rs12744386 compared with TT genotype were observed. AM630 exacerbated MK-801- or methamphetamine-induced disturbance of prepulse inhibition and hyperactivity in C57BL/6JJmsSlc mice. CONCLUSIONS These findings indicate an increased risk of schizophrenia for people with low CB2 receptor function.

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.

Selective reduction of a PDZ protein, SAP-97, in the prefrontal cortex of patients with chronic schizophrenia

Many postsynaptic density proteins carrying postsynaptic density‐95/discs large/zone occludens‐1 (PDZ) domain(s) interact with glutamate receptors to control receptor dynamics and synaptic plasticity. Here we examined the expression of PDZ proteins, synapse‐associated protein (SAP) 97, postsynaptic density (PSD)‐95, chapsyn‐110, GRIP1 and SAP102, in post‐mortem brains of schizophrenic patients and control subjects, and evaluated their contribution to schizophrenic pathology. Among these PDZ proteins, SAP97 exhibited the most marked change: SAP97 protein levels were decreased to less than half that of the control levels specifically in the prefrontal cortex of schizophrenic patients. In parallel, its binding partner, GluR1, similarly decreased in the same brain region. The correlation between SAP97 and GluR1 levels in control subjects was, however, altered in schizophrenic patients. SAP102 levels were also significantly reduced in the hippocampus of schizophrenic patients, but this reduction was correlated with sample storage time and post‐mortem interval. There were no changes in the levels of the other PDZ proteins in any of the regions examined. In addition, neuroleptic treatment failed to mimic the SAP97 change. These findings suggest that a phenotypic loss of SAP97 is associated with the postsynaptic impairment in prefrontal excitatory circuits of schizophrenic patients.

Enhanced carbonyl stress in a subpopulation of schizophrenia.

CONTEXT Various factors are involved in the pathogenesis of schizophrenia. Accumulation of advanced glycation end products, including pentosidine, results from carbonyl stress, a state featuring an increase in reactive carbonyl compounds (RCOs) and their attendant protein modifications. Vitamin B(6) is known to detoxify RCOs, including advanced glycation end products. Glyoxalase I (GLO1) is one of the enzymes required for the cellular detoxification of RCOs. OBJECTIVES To examine whether plasma levels of pentosidine and serum vitamin B(6) are altered in patients with schizophrenia and to evaluate the functionality of GLO1 variations linked to concomitant carbonyl stress. DESIGN An observational biochemical and genetic analysis study. SETTING Multiple centers in Japan. PARTICIPANTS One hundred six individuals (45 schizophrenic patients and 61 control subjects) were recruited for biochemical measurements. Deep resequencing of GLO1 derived from peripheral blood or postmortem brain tissue was performed in 1761 patients with schizophrenia and 1921 control subjects. MAIN OUTCOME MEASURES Pentosidine and vitamin B(6) concentrations were determined by high-performance liquid chromatographic assay. Protein expression and enzymatic activity were quantified in red blood cells and lymphoblastoid cells using Western blot and spectrophotometric techniques. RESULTS We found that a subpopulation of individuals with schizophrenia exhibit high plasma pentosidine and low serum pyridoxal (vitamin B(6)) levels. We also detected genetic and functional alterations in GLO1. Marked reductions in enzymatic activity were associated with pentosidine accumulation and vitamin B(6) depletion, except in some healthy subjects. Most patients with schizophrenia who carried the genetic defects exhibited high pentosidine and low vitamin B(6) levels in contrast with control subjects with the genetic defects, suggesting the existence of compensatory mechanisms. CONCLUSIONS Our findings suggest that GLO1 deficits and carbonyl stress are linked to the development of a certain subtype of schizophrenia. Elevated plasma pentosidine and concomitant low vitamin B(6) levels could be the most cogent and easily measurable biomarkers in schizophrenia and should be helpful for classifying heterogeneous types of schizophrenia on the basis of their biological causes.

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.

Corticobasal degeneration with primary progressive aphasia and accentuated cortical lesion in superior temporal gyrus: case report and review

Abstract A 57-year-old woman showed progressive sensory aphasia as an initial symptom, and then developed total aphasia within 6 years and, finally, severe dementia. Neuropathologically, the cerebral cortex was most severely affected in the superior and transverse temporal gyri, and subsequently in the inferior frontal gyrus, especially in the pars opercularis. The degeneration in the subcortical grey matter was most severe in the substantia nigra, and it was moderate to mild in the ventral part of thalamus, globus pallidus and striatum. Cytopathologically, in addition to achromatic ballooned neurons, massive tau-positive types of cytosekeletal abnormalities were observed both in neurons and glia, mainly in the degenerating region. This cytoskeletal pathology coincided with that reported in corticobasal degeneration (CBD). On Bodian staining, only a few neurofibrillary tangles were found in the entorhinal pre-alpha layer and substantia nigra. Pick’s bodies and senile plaques could not be found. This case is thought to represent a type of CBD, but with its cortical lesion focus located in the speech area instead of the frontoparietal region. A survey of 28 pathologically evaluated cases of CBD revealed two similar cases, both of which began with progressive aphasia and presented cortical degeneration in the superior temporal gyrus. An overview of CBD cases clarified the features in another group of cases, in which the cerebral accentuated focus was shifted forward from the central region, clinically resembling Pick’s disease. The clinical manifestations in CBD seem to be the expression of these diverse cortical lesions. Primary progressive aphasia may include cases of CBD with involvement of the language center.

Phosphorylated and cleaved TDP-43 in ALS, FTLD and other neurodegenerative disorders and in cellular models of TDP-43 proteinopathy.

Transactivation response (TAR) DNA‐binding protein of Mr 43 kDa (TDP‐43) is a major component of the tau‐negative and ubiquitin‐positive inclusions that characterize amyotrophic lateral sclerosis (ALS) and frontotemporal lobar degeneration which is now referred to as FTLD‐TDP. Concurrent TDP‐43 pathology has been reported in a variety of other neurodegenerative disorders such as Alzheimers disease, forming a group of TDP‐43 proteinopathy. Accumulated TDP‐43 is characterized by phosphorylation and fragmentation. There is a close relationship between the pathological subtypes of FTLD‐TDP and the immunoblot pattern of the C‐terminal fragments of phosphorylated TDP‐43. These results suggest that proteolytic processing of accumulated TDP‐43 may play an important role for the pathological process. In cultured cells, transfected C‐terminal fragments of TDP‐43 are more prone to form aggregates than full‐length TDP‐43. Transfecting the C‐terminal fragment of TDP‐43 harboring pathogenic mutations of TDP‐43 gene identified in familial and sporadic ALS cases into cells enhanced the aggregate formation. Furthermore, we found that methylene blue and dimebon inhibit aggregation of TDP‐43 in these cellular models. Understanding the mechanism of phosphorylation and truncation of TDP‐43 and aggregate formation may be crucial for clarifying the pathogenesis of TDP‐43 proteinopathy and for developing useful therapeutics.

Involvement of SMARCA2/BRM in the SWI/SNF chromatin-remodeling complex in schizophrenia

Chromatin remodeling may play a role in the neurobiology of schizophrenia and the process, therefore, may be considered as a therapeutic target. The SMARCA2 gene encodes BRM in the SWI/SNF chromatin-remodeling complex, and associations of single nucleotide polymorphisms (SNPs) to schizophrenia were found in two linkage disequilibrium blocks in the SMARCA2 gene after screening of 11 883 SNPs (rs2296212; overall allelic P = 5.8 x 10(-5)) and subsequent screening of 22 genes involved in chromatin remodeling (rs3793490; overall allelic P = 2.0 x 10(-6)) in a Japanese population. A risk allele of a missense polymorphism (rs2296212) induced a lower nuclear localization efficiency of BRM, and risk alleles of intronic polymorphisms (rs3763627 and rs3793490) were associated with low SMARCA2 expression levels in the postmortem prefrontal cortex. A significant correlation in the fold changes of gene expression from schizophrenic prefrontal cortex (from the Stanley Medical Research Institute online genomics database) was seen with suppression of SMARCA2 in transfected human cells by specific siRNA, and of orthologous genes in the prefrontal cortex of Smarca2 knockout mice. Smarca2 knockout mice showed impaired social interaction and prepulse inhibition. Psychotogenic drugs lowered Smarca2 expression while antipsychotic drugs increased it in the mouse brain. These findings support the existence of a role for BRM in the pathophysiology of schizophrenia.