Hiroko Hori

Manganese superoxide dismutase gene polymorphism and schizophrenia : Relation to tardive dyskinesia

There has been increasing evidence that deranged superoxide dismutase (SOD) activities might be a risk factor for schizophrenia and/or tardive dyskinesia (TD). In the present study, we investigated the genetic association between a functional polymorphism (Ala−9Val) in the human manganese (Mn) SOD gene and schizophrenia or TD (192 schizophrenics : 39 with TD and 153 without TD; 141 controls). No significant differences in the allelic or genotypic distribution between schizophrenics and controls were observed. However, we did find a significant difference in genotypic distribution between schizophrenics with and those without TD (p = .03). Moreover, decreased −9Ala (mutant) allele was found among patients with TD (p = .02; odds ratio = 0.29; 95% confidence interval = 0.10–0.83). In conjunction with previous findings of increased free radicals and decreased SOD activities in TD subjects, these results suggest that the−9Ala (high activity) MnSOD allele may play a role in protecting against susceptibility to TD in schizophrenics.

No association between the brain-derived neurotrophic factor (BDNF) Val66Met polymorphism and schizophrenia in Asian populations: Evidence from a case-control study and meta-analysis.

Brain-derived neurotrophic factor (BDNF) is a nerve growth factor that plays an important role in the development and maintenance of adult neurons and is important regulator of synaptic plasticity in human brain. It has been reported that there are alterations in BDNF levels in the brains of patients with schizophrenia. It has also been reported that transneuronal transfer of BDNF is dependent on neuronal activity, suggesting that BDNF plays an important role in neurotransmission. A single nucleotide polymorphism (SNP) in the BDNF gene that causes a valine to methionine substitution at codon 66 (Val66Met) has been demonstrated to affect human memory and hippocampal function. A possible positive association between the BDNF Val66Met polymorphism and schizophrenia has also been shown in Scottish and Spanish populations. Furthermore, the BDNF Val66Met polymorphism has been implicated in the age of onset of schizophrenia. In the present study, we attempted to replicate these findings in a Japanese case-control sample (211 patients with schizophrenia and 205 controls). We did not find an association between the BDNF Val66Met polymorphism and schizophrenia. An association between the Val66Met polymorphism and age of onset was not observed either. Furthermore, a meta-analysis including the present and previous Asian studies comparing 2059 patients with schizophrenia and 2765 controls also revealed no significant association between the BDNF Val66Met polymorphism and schizophrenia. Our results do not support a significant role for the BDNF Val66Met polymorphism in the development of schizophrenia in Asian populations.

Polymorphisms of dopamine degradation enzyme (COMT and MAO) genes and tardive dyskinesia in patients with schizophrenia.

Several lines of evidence suggest that tardive dyskinesia (TD) may be associated with altered dopaminergic neurotransmission. We hypothesized that deranged dopamine degradation enzyme activities might be related to the susceptibility to TD through altered dopaminergic neurotransmission in the central nervous system. In the present study, we investigated the relationship between the gene polymorphisms of three dopamine degradation enzymes and TD. We genotyped the valine/methionine polymorphism of codon 108/158 in the catechol-O-methyltransferase (COMT) gene, the 30-bp repeat polymorphism in the promoter of the monoamine oxidase A (MAOA) gene, and the A/G polymorphism in intron 13 of the monoamine oxidase B (MAOB) gene in 206 Japanese patients with schizophrenia. No significant difference was found in total scores on the Abnormal Involuntary Movement Scale (AIMS) among the subject groups, sorted according to the COMT, MAOA and MAOB genotypes. Moreover, no significant difference was found in allele frequencies between patients with TD and patients without TD for any of the polymorphisms. As both COMT and MAO genes are involved in degrading catecholamines, we also sought evidence for additive and epistatic effects, but none was observed. Our data, therefore, do not support the hypothesis that polymorphisms in COMT, MAOA, and MAOB genes are involved individually or in combination in the predisposition to TD.

Association analyses of the DAOA/G30 and D-amino-acid oxidase genes in schizophrenia: further evidence for a role in schizophrenia.

A number of linkage studies have previously implicated the region of chromosome 13q34 in schizophrenia. Chumakov and colleagues (2002) identified a gene complex called G72 (now termed d-amino acid oxidase activator: DAOA)/G30 in this region and performed association analyses of the DAOA/G30 as well as the d-amino-acid oxidase (DAAO) gene with schizophrenia. DAAO oxidizes d-serine, a potent activator of the N-methyl-d-aspartate (NMDA) type glutamate receptor in the human brain whereas the DAOA protein is considered an activator of DAAO. The interaction of these two genes has thus been implicated in the NMDA receptor regulation pathway in schizophrenia. To date, several studies have shown a relatively consistent positive association between schizophrenia and DAOA/G30, but not with DAAO. The aim of our study was to further evaluate the contributions of these genes to the susceptibility to schizophrenia using two different sample sets. Our sample consisted of 168 matched case-control pairs as well as a family-based sample (n=113) for transmission disequilibrium test. Significant associations between the DAOA/G30 M-7 and M-18 polymorphisms and schizophrenia were observed in our case-control sample whereas no associations were observed for DAAO markers. We also observed significant or suggestive transmission disequilibrium for DAOA/G30 M-7, M-23, and M-24 to probands with schizophrenia in our family-based sample. Subsequent analysis of haplotypes made up of four DAOA/G30 markers, one marker selected from each of two linkage disequilibrium blocks that were observed in our sample as well as both ends (M-7 and M-25), were also associated with schizophrenia. Our data provide further evidence that the DAOA/G30 locus may play a role in the pathophysiology of schizophrenia. Although no direct link to genetic polymorphism in these genes and NMDA receptor function has been revealed, the present findings support previous reports implicating DAOA/G30 as susceptibility genes for schizophrenia. Further research is warranted to determine the functional variation underlying these findings and to relate this to the pathophysiology of schizophrenia.

Treatment of Charles Bonnet syndrome with valproate

Charles Bonnet syndrome (CBS), as described in the psychiatric literature, refers to pseudohallucinations in elderly people who frequently suffer from reduced visual acuity. There is no established treatment for CBS. We report two cases involving elderly women with CBS who were successfully treated with valproate. The present results suggest that valproate can be useful for CBS in some patients.

Genetic association analysis of functional polymorphisms in the cytochrome P450 1A2 (CYP1A2) gene with tardive dyskinesia in Japanese patients with schizophrenia.

Objective Recent studies have revealed positive associations between tardive dyskinesia (TD) and genetic polymorphisms of several cytochrome P450 (CYP) subfamilies that are involved in pharmacokinetic process of antipsychotic drugs. In the present study, we analyzed the relationship between TD and two polymorphisms of the CYP1A2 gene, 734C/A and −2964G/A, in a sample of Japanese patients with schizophrenia. Methods We studied 199 Japanese patients with schizophrenia. We used the Abnormal Involuntary Movement Scale to evaluate TD. Two polymorphisms of the CYP1A2 gene, 734C/A and −2964 G/A were genotyped by means of polymerase chain reaction and restriction fragment length polymorphism analysis. Results Neither the 734C/A nor the −2964G/A polymorphism was associated with TD [734C/A genotype: χ2=0.02, degrees of freedom (df)=2, P=1.00; allele: χ2=0.02, df=1, P=0.89; −2964G/A genotype: χ2=0.21, df=2, P=0.90; allele: χ2=0.15, df=1, P=0.70]. In addition, CYP1A2 haplotype was associated with TD (χ2=0.24, df=3, P=0.97). Furthermore, in both the subgroup of smokers and the subgroup of patients receiving high-dosage antipsychotics (chlorpromazine equivalent >1000 mg), neither the 734C/A nor the −2964G/A polymorphism was associated with TD. Conclusions We did not find significant associations between the 734C/A and −2964G/A polymorphisms of CYP1A2 gene and TD in Japanese patients with schizophrenia. Our results suggest that these CYP1A2 gene polymorphisms may not contribute to TD susceptibility.

Charles Bonnet Syndrome with Auditory Hallucinations: A Diagnostic Dilemma

Charles Bonnet syndrome (CBS) appears to be commoner in elderly people than was previously thought. Nonetheless, as yet, no firm diagnostic criteria have been established for CBS, leaving the need for well-defined diagnostic criteria describing this syndrome unfulfilled. Two recently proposed diagnostic criteria for CBS insist on an absence of hallucinations in modalities other than visual. However, we experienced 2 cases suffering from probable CBS who experienced auditory hallucinations. In this report, we recommend that even if CBS coexists with other hallucinations, we should not exclude CBS as a probable diagnosis when the patients recognize their hallucinations as unreal. We believe that this modification of CBS diagnostic criteria will contribute to psychiatric epidemiology by correcting the current underestimation of CBS prevalence.

Genetic association analysis of the glutathione peroxidase (GPX1) gene polymorphism (Pro197Leu) with tardive dyskinesia.

A possible involvement of oxidative stress in the pathophysiology of tardive dyskinesia (TD) has previously been proposed (reviewed in [Andreassen, O.A., Jorgensen, H.A., 2000. Neurotoxicity associated with neuroleptic-induced oral dyskinesias in rats. Implications for tardive dyskinesia? Progress in Neurobiology 61, 525-541.]). Long-term administration of neuroleptics alters dopaminergic turnover, which results in increased formation of reactive oxygen species (ROS). This is hypothesized to lead to TD through neuronal toxicity as a consequence of oxidative stress. In the present study, the relationship between TD and a possible functional polymorphism of the human glutathione peroxidase (GPX1) gene (an important antioxidant enzyme) was studied in 68 chronic treatment-refractory patients with schizophrenia. A proline (Pro) to leucine (Leu) substitution at codon 197 (Pro197Leu) in the GPX1 gene was genotyped. No significant difference in total Abnormal Involuntary Movements Scale (AIMS) scores was observed among patients in the three genotype groups. Moreover, no significant differences in genotype or allele frequencies were observed between subjects with and without TD. Our results suggest that the GPX1 gene polymorphism does not confer increased susceptibility to TD, although further studies are warranted before a conclusion can be drawn.

Genetic association analysis of 5-HT6 receptor gene polymorphism (267C/T) with tardive dyskinesia

Possible involvement of serotonergic (5-hydroxytryptamine: 5-HT) receptors in the pathophysiology of tardive dyskinesia (TD) has been suggested. In the present study, the relationship between the 5-HT(6) receptor gene (HTR6) polymorphisms and TD was studied in 173 Japanese patients with schizophrenia. The 267C/T allele of HTR6 was genotyped using PCR amplification followed by endonuclease digestion. The patients with the three 267C/T genotypes showed no significant difference in gender, age, duration of illness, or current antipsychotic dose. In addition, there were no significant differences in total AIMS scores among patients with the three genotypes. Moreover, no significant differences in genotypes and allele frequencies were observed between subjects with and without TD. These results suggest that the 267C/T polymorphism of HTR6 does not confer increased susceptibility to TD.

Genetic association analysis of neuronal nitric oxide synthase gene polymorphism with tardive dyskinesia.

Possible involvement of oxidative stress in the pathophysiology of tardive dyskinesia (TD) has been proposed (reviewed in Andreassen and Jorgensen, 2000). Long-term administration of neuroleptics alters dopaminergic turnover, yielding the increase of the formation of reactive oxygen species (ROS), which may lead to TD through neuronal toxicity as a consequence of oxidative stress. In the present study, the relationship between TD and a polymorphism of the neuronal nitric oxide synthase (NOS1) gene whose reaction product, nitric oxide (NO), is involved in oxidative stress was studied in 171 Japanese patients with schizophrenia, including 41 patients meeting TD criteria. The C/T polymorphism in exon 29 of the NOS1 gene was genotyped using polymerase chain reaction (PCR) amplification followed by restriction enzyme digestion. No significant difference in genotype frequencies was detected between subjects with and without TD (X2=1.54, df=2, p=0.46). In addition, there was no difference in allele frequencies (X2=0.42, df=1, p=0.51). These results suggest that the NOS1 gene polymorphism may not confer increased susceptibility to TD, although more investigations on other populations are warranted.