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Accumulating evidence suggests that phosphatidylinositol (PI) pathways have been involved in the secretion of dopamine (DA) and the regulation of DA transporter, which is a target of methamphetamine (METH). A recent large-scale gene-association study in a Dutch population demonstrated that the PIK4CA gene was closely linked to schizophrenia [Jungerius et al. (2007); Mol Psychiatry]. Here, we conducted a case (N = 232)-control (N = 233) study of the PIK4CA gene on Japanese METH abusers, which can manifest severe psychosis similar to schizophrenia. The genotype and allelic distributions of all four single nucleotide polymorphisms (SNPs) did not differ significantly between the METH abusers and the controls. The comparisons based on the classification of the psychosis as transient or prolonged and on the presence or absence of spontaneous relapse revealed no significant distribution of the four SNPs compared to the controls. Furthermore, haplotype analyses showed almost the same frequencies between the METH abusers and the controls. The present study suggests that the PIK4CA gene does not play a significant role in the vulnerability to METH use disorder in the Japanese population., (2008 Wiley-Liss, Inc.)

Accumulating evidence suggests that oxidative stress plays a role in the mechanisms of action of methamphetamine (METH) in the brain. In the present study, we investigated the association between the genetic polymorphisms among glutathione (GSH)-related enzymes; glutathione S-transferases (GSTs) such as GSTT1 (Non-deletion/Null), GSTT2 (Met139Ile), GSTA1 (-69C/T), and GSTO1 (Ala140Asp); glutathione peroxidase 1 (GPX1) (Pro198Leu); and glutamate-cysteine ligase modifier (GCLM) subunit and METH use disorder in a Japanese population. Two hundred eighteen METH abusers and 233 healthy controls were enrolled in the study. There was a significant difference in GSTT1 genotype frequency between patients with METH psychosis and controls (P = 0.039, odds ratio: 1.52, 95% CI 1.03-2.24). Furthermore, the frequency (66.0%) of the GSTT1 null genotype among prolonged-type METH psychotic patients with spontaneous relapse was significantly higher (P = 0.025, odds ratio: 2.43, 95% CI 1.13-5.23) than that (44.4%) of transient-type METH psychotic patients without spontaneous relapse. However, there were no associations between the polymorphisms of other genes and METH abuse. The present study suggests that the polymorphism of the GSTT1 gene might be a genetic risk factor of the development of METH psychosis in a Japanese population.

The mesolimbic system is thought to be involved in the reinforcing action of many addictive drugs and the release of dopamine modulated by neuronal nicotine cholinergic receptors (nAChRs). Several investigations suggested that nAChRs on dopaminergic terminals play an important role in the development of some long-lasting adaptations associated with drug abuse. A majority of high-affinity nicotine binding sites in the brain have been showed in heteropentameric alpha4 (alpha4) and beta2 subunit (beta2) of nAChRs. Therefore, we conducted a genetic association analysis of the alpha4 gene (CHRNA4) and beta2 gene (CHRNB2) with methamphetamine (METH)-use disorder (191 cases and 753 controls). We first evaluated the linkage disequilibrium (LD) structure of these genes and selected 7 and 5 tagging SNPs (tag SNPs) on CHRNA4 and CHRNB2, respectively. Some tag SNPs were significantly associated with total METH-use disorder and METH-induced psychosis; however, these associations were no longer statistically significant after Bonferroni's correction for multiple testing. In conclusion, our results suggest that neither CHRNA4 nor CHRNB2 plays a major role in Japanese METH-use disorder.

Casein kinase 1 epsilon (CKIepsilon) is a component of the DARPP-32 in second-messenger pathway. CKIepsilon phosphorylates and activates DARPP-32, a key molecule in various complex signaling pathways, including dopamine and glutamine signaling, which have both been demonstrated to be main pathways in substance dependence. A recent clinical study showed that rs135745, a noncoding single nucleotide polymorphism of the 3'-untranslated region of the CSNK1E gene, was associated with the intensity of the subjective response to an oral amphetamine dose in normal volunteers. Differences in sensitivity to the drug should affect development of dependence to it. Hence, we genotyped rs135745 of the CSNK1E (MIM 600863) gene in 215 patients with methamphetamine dependence and 274 age- and gender-matched normal controls. No significant differences in genotype and allele frequencies were observed between the patients with methamphetamine dependence and controls. There was also no significant association between rs135745 and the clinical characteristics of methamphetamine dependence and co-morbid methamphetamine psychosis (e.g., age of first consumption, latency of psychosis, prognosis of psychosis after therapy, spontaneous relapse of psychotic symptoms, and poly-substance abuse status). The present findings suggest that having a genetic variant of the CSNK1E gene did not affect susceptibility to methamphetamine dependence or psychosis, at least in a Japanese population.

Abnormal intracellular signaling molecules in dopamine signal transduction are thought to be associated with the pathophysiology of methamphetamine (METH)-use disorder. A recent study reported that a new intracellular protein, prostate apoptosis response 4 (Par-4), plays a critical role in dopamine 2 receptor signaling. We therefore analyzed the association between the Par-4 gene (PAWR) and METH-use disorder in a Japanese population (191 patients with METH-use disorder and 466 healthy controls). Using the recommended "gene-based" association analysis, we selected five tagging SNPs in PAWR from the HapMap database. No significant allele/genotype-wise or haplotype-wise association was found between PAWR and METH-use disorder. These results suggest that PAWR does not play a major role in METH-use disorders in the Japanese population.

A recent study showed a significant association between schizophrenia in European samples and the glutamate cysteine ligase modifier (GCLM) subunit gene, which is the key glutathione (GSH)-synthesizing enzyme. Since the symptoms of methamphetamine (METH)-induced psychosis are similar to those of schizophrenia, the GCLM gene is thought to be a good candidate gene for METH-use disorder or related disorders. To evaluate the association between the GCLM gene and METH-use disorder and schizophrenia, we conducted a case-control study of Japanese subjects (METH-use disorder, 185 cases; schizophrenia, 742 cases; and controls, 819). Four SNPs (2 SNPs from an original report and JSNP database, and 2 "tagging SNPs" from HapMap database) in the GCLM gene were examined in this association analysis; one SNP showed an association with both METH-use disorder and METH-induced psychosis. After Bonferroni's correction for multiple testing, however, this significance disappeared. No significant association was found with schizophrenia. Our findings suggest that a common genetic variation in the GCLM gene might not contribute to the risk of METH-use disorder and schizophrenia in the Japanese population.

Several lines of evidence from animal and genetic analyses showed that the calcineurin A gamma subunit gene (PPP3CC) plays an important role in the pathogenesis of schizophrenia. Moreover, a recent large Japanese case-control study confirmed the genetic association of PPP3CC with schizophrenia. The symptoms of methamphetamine (MAP)-induced psychosis are similar to those of schizophrenia, suggesting that PPP3CC is an attractive candidate gene not only for schizophrenia, but also for METH-related disorders. In this study, we carried out a genetic association study of PPP3CC with MAP-use disorder in a Japanese population. We selected five haplotype-tagging SNPs from the aforementioned replication study and genotyped 393 samples (MAP abuse, 128; control, 265). We could not detect a significant association of all tagging SNPs with each condition. In conclusion, our data suggest that PPP3CC does not elevate the risk of MAP-use disorder in the Japanese population.

Because methamphetamine (METH) is metabolized by CYP2D6 at the first step of hydroxylation and demethylation, it is possible that functional variants of CYP2D6 alter susceptibility to methamphetamine-induced dependence. We genotyped CYP2D6*1, *4, *5, *10, and *14 for 202 patients with METH dependence and 337 controls in a Japanese population and found a significant association of the CYP2D6 gene with METH dependence (p=0.0299). The patients had fewer *10 and *14 alleles, which are hypofunction alleles, than the controls. CYP2D6 genotypes were divided into three phenotypes: extensive metabolizers, intermediate metabolizers, and poor metabolizers. There was no poor metabolizer among our Japanese subjects, and intermediate metabolizers of CYP2D6 were significantly fewer in methamphetamine-dependent subjects than in controls (p=0.0212), with an odds ratio of 0.62 (95% confidence interval: 0.51-0.76). The present study demonstrated that reduced CYP2D6 activity was a negative risk factor for methamphetamine dependence.

Context: We can improve understanding of human methamphetamine dependence, and possibly our abilities to prevent and treat this devastating disorder, by identifying genes whose allelic variants predispose to methamphetamine dependence., Objective: To find "methamphetamine dependence" genes identified by each of 2 genome-wide association (GWA) studies of independent samples of methamphetamine-dependent individuals and matched controls., Design: Replicated GWA results in each of 2 case-control studies., Setting: Japan and Taiwan., Participants: Individuals with methamphetamine dependence and matched control subjects free from psychiatric, substance abuse, or substance dependence diagnoses (N = 580)., Main Outcome Measures: "Methamphetamine dependence" genes that were reproducibly identified by clusters of nominally positive single-nucleotide polymorphisms (SNPs) in both samples in ways that were unlikely to represent chance observations, based on Monte Carlo simulations that corrected for multiple comparisons, and subsets of "methamphetamine dependence" genes that were also identified by GWA studies of dependence on other addictive substances, success in quitting smoking, and memory., Results: Genes identified by clustered nominally positive SNPs from both samples were unlikely to represent chance observations (Monte Carlo P < .00001). Variants in these "methamphetamine dependence" genes are likely to alter cell adhesion, enzymatic functions, transcription, cell structure, and DNA, RNA, and/or protein handling or modification. Cell adhesion genes CSMD1 and CDH13 displayed the largest numbers of clustered nominally positive SNPs. "Methamphetamine dependence" genes overlapped, to extents much greater than chance, with genes identified in GWA studies of dependence on other addictive substances, success in quitting smoking, and memory (Monte Carlo P range < .04 to < .00001)., Conclusion: These data support polygenic contributions to methamphetamine dependence from genes that include those whose variants contribute to dependence on several addictive substances, success in quitting smoking, and mnemonic processes.

Glycine transporter (GlyT)-1 plays a pivotal role in maintaining the glycine level at the glutamatergic synapse. Glycine is an allosteric agonist of N-methyl-D-aspartate (NMDA) receptors. Because activation of NMDA receptors is an essential step for induction of methamphetamine dependence and psychosis, differences in the functioning of GlyT-1 due to genetic variants of the GlyT-1 gene (GLYT1) may influence susceptibility. A case-control genetic association study of the GLYT1 gene examined 204 patients with methamphetamine-use disorder and 210 healthy controls. We examined three single nucleotide polymorphisms (SNPs), SNP1, IVS3 + 411C > T, rs2486001; SNP2, 1056G > A, rs2248829; and SNP3, IVS11 + 22G > A, rs2248632, of the GLYT1 gene and found that SNP1 showed a significant association in both genotype (P = 0.0086) and allele (P = 0.0019) with methamphetamine-use disorder. The T-G haplotype at SNP1 and SNP2 was a significant risk factor for the disorder (P = 0.000039, odds ratio: 2.04). The present findings indicate that genetic variation of the GLYT1 gene may contribute to individual vulnerability to methamphetamine dependence and psychosis., ((c) 2007 Wiley-Liss, Inc.)

Objective: Protein interacting with C-kinase-1 (PICK1) plays a role in the targeting and clustering of dopamine transporter, which is the primary target site for the abused drug methamphetamine. Based on the interaction of PICK1 with dopamine transporter, it is of particular interest to investigate the association between the PICK1 gene and methamphetamine abusers., Method: The authors studied the association between PICK1 gene polymorphisms and methamphetamine abusers in a Japanese group. Two hundred and eight methamphetamine abusers and 218 healthy comparison subjects were enrolled in the study. Furthermore, the authors also examined the effects of single nucleotide polymorphisms (SNPs) in the promoter and 5'-untranslated region on transcription levels of PICK1., Results: The authors identified four highly frequent SNPs, rs737622 (-332 C/G) and rs3026682 (-205 G/A) in the promoter region and rs713729 (T/A) in intron3 and rs2076369 (T/G) in intron4. Of these SNPs, rs713729 was significantly associated with methamphetamine abusers in general, and rs713729 and rs2076369 were significantly associated with those with spontaneous relapse of psychosis. Furthermore, haplotype analysis revealed that specific haplotypes of these SNPs were associated with methamphetamine abusers. A gene reporter assay revealed that the two SNPs in the promoter region significantly altered transcriptional activity., Conclusions: Our findings suggest that the PICK1 gene may be implicated in the susceptibility to spontaneous relapse of methamphetamine psychosis and that, as an intracellular adapter protein, PICK1 may play a role in the pathophysiology of methamphetamine psychosis.

Recent investigations suggest that the AKT/glycogen synthase kinase 3 (GSK3) signaling cascade may be associated with the pathophysiology of schizophrenia and methamphetamine (METH) use disorder. One important molecule related to this cascade is beta-arrestin 2 (ARRB2). We therefore conducted a genetic case-control association analysis of the gene for ARRB2 with schizophrenia and METH use disorder in a Japanese population (547 people with schizophrenia, 177 with METH use disorder and 546 controls). A possible association of 'tag single nucleotide polymorphisms (SNPs)' was found in METH use disorder (rs1045280: P(genotype) = 0.0118, P(allele) = 0.00351; rs2036657: P(allele) = 0.0431; rs4790694: P(genotype) = 0.0167, P(allele) = 0.0202), but no association was found with schizophrenia. We also evaluated the gene-gene interactions among ARRB2, AKT1, and GSK3B, which we previously reported for each of these diseases. However, no interaction was seen in our samples. This is the first association analysis of ARRB2, and our results indicate that ARRB2 may play a role in the pathophysiology of METH use disorder.

Background: Methamphetamine (MAP) is one of the most frequently used illegal substances in Japan, and family and twin studies have suggested that genetic factors contribute to psychostimulant dependence, including MAP dependence. Organic cation transporter 3 (OCT3) has been reported to be involved in the disposition of MAP as well as MAP-induced behavioral changes in animals. Moreover, SLC22A3 (which encodes OCT3) is a candidate gene for MAP dependence because it is located within a chromosomal region associated with substance dependence., Methods: Using 96 healthy control subjects, linkage disequilibrium (LD) within the SLC22A3 was investigated, and 5 single-nucleotide polymorphisms (SNPs) were selected as haplotype tag SNPs to search for an association with MAP dependence. Single-marker analyses and haplotype analyses of these SNPs were performed in 213 subjects with MAP dependence and 443 healthy controls., Results: SLC22A3 polymorphisms were not significantly associated with MAP dependence in any of the single-marker and haplotype analyses. When subjects with MAP dependence were divided into polysubstance and single-MAP users, genotype and allele frequency of SNP2 (p=0.024, p=0.011, respectively), allele frequency of SNP3 (p=0.037), and haplotypic frequencies for these 2 SNPs (p=0.0438) differed significantly between groups., Conclusions: These results suggest that polymorphisms of SLC22A3 are related to the development of polysubstance use in Japanese patients with MAP dependence.

SOD2 (superoxide dismutase 2) plays a crucial role in protecting the cells against damage caused by free radicals, by catalyzing their detoxification. On the other hand, cell damage caused by free radical generation following methamphetamine administration has been postulated as one of the possible pathophysiological mechanisms for methamphetamine psychosis. Hence, we investigated the association of SOD2 polymorphisms with the development of methamphetamine psychosis, in two independent populations of Japan and Taiwan. We recruited 116 patients with methamphetamine psychosis and 189 controls in Japan, and 135 patients with methamphetamine psychosis and 204 controls in Taiwan. The methamphetamine group was divided into two clinical subtypes: a transient type of psychosis (i.e., good prognosis) and a prolonged type of psychosis (i.e., poor prognosis), according to the course of the manifestation of psychosis. With reference to the genotypic and allelic frequencies of Ala/Val functional polymorphism in exon 2, we found significant differences between individuals with prolonged methamphetamine psychosis and control samples from Japan and Taiwan in the genotypic (P value 0.014 and 0.016, respectively) and in the allelic (P value 0.004 and 0.047, respectively) frequencies. Our results suggest that Ala/Val polymorphism of the SOD2 gene could be associated with the risk of developing methamphetamine psychosis.

Dihydropyrimidinase-related protein 2 (DRP-2 or DPYSL-2)mediates the intracellular response to collapsin, a repulsive extracellular guidance cue or axonal outgrowth. DRP-2 is also referred to as collapsin response mediator protein 2 (CRMP-2). We have previously demonstrated that the DRP-2 gene is associated with susceptibility to schizophrenia, but not to bipolar disorders. In addition, a genetic association was observed with paranoid-type schizophrenia, but not with hebephrenic-type schizophrenia. It has been well documented that repeated abuse of methamphetamine (METH) for a long period frequently produces psychotic symptoms, such as auditory hallucinations and delusions that are hardly distinguishable from those of paranoid-type schizophrenia. Therefore, we hypothesized that a certain genetic variant of the DRP-2 gene may affect individual vulnerability to the development of METH-induced psychosis. We examined the genetic association by a case-control method. The polymorphism *2236T>C in the 3' untranslated region of the DRP-2 gene, which has been shown to be a negative genetic risk factor for paranoid-type schizophrenia, was analyzed in 198 patients with METH psychosis and 221 corresponding healthy controls in a Japanese population. No significant association of the DRP-2 gene with METH psychosis was found. Neither did we find an association with the clinical phenotype of METH psychosis, such as the age of first consumption of METH, latency to development of psychosis after METH abuse, prognosis of psychosis after detoxification from METH use, complication of spontaneous relapse of psychosis without reconsumption of the drug, or multisubstance abuse status. These findings indicate that a genetic variant of the DRP-2 gene may not affect the risk of METH psychosis or any clinical phenotype of the disorder.

Recent preclinical findings that repeated treatment with methamphetamine (METH) induced an increase in tumor necrosis factor-alpha (TNF-alpha) mRNA in some brain regions and that TNF-alpha blocked METH neurotoxicity and rewarding effects suggest TNF-alpha, a multifunctional pro-inflammatory cytokine, may be involved in METH dependence. We hypothesized that genetic polymorphisms of the TNF-alpha gene and its receptor genes may be associated with vulnerability to METH dependence. Genetic association of -308G>A and -857C>T in the promotor region of the TNF-alpha gene, and 36A>G in exon 1 of the TNF receptor 1A gene (TNFR-SF1A), were analyzed in patients with METH dependence (n = 185) and healthy controls (n = 221) in a Japanese population. No significant association of alleles or haplotypes of the TNF-alpha or TNFR-SF1A genes with METH dependence was found. Neither was any significant association of clinical phenotype with METH dependence found. These results suggest that genetic variations in the TNF-alpha gene and its receptor genes may not be involved in individual vulnerability to METH dependence.

Cocaine- and amphetamine-regulated transcript (CART) was originally discovered as a peptide that increased in the rat striatum after injection of a psychostimulant drug, such as cocaine or amphetamine, and is suggested to play potential roles in drug dependence. We tested the genetic association between the CART gene and methamphetamine (METH) dependence and/or psychosis. The subjects were 203 patients with METH dependence and 239 age- and gender-matched healthy controls. Two single nucleotide polymorphisms (SNPs) of the CART gene, -156A>G and IVS1 + 224G>A, were examined . There were no significant differences in genotype and allele distributions of the polymorphisms between patients with METH dependence and/or psychosis and controls. Neither were significant differences in subgroups of clinical phenotypes, for example, age at first consumption of METH, latency to onset of psychotic symptoms after the first consumption of METH, prognosis of psychosis after therapy, complication of spontaneous relapse to a psychotic state, or multisubstance abuse status, observed. The present findings suggest that the CART gene may not play a pivotal role in the development of METH dependence and psychosis, at least in a Japanese population.

Previous studies have indicated that genetic factors substantially affect development of substance use disorders, including methamphetamine dependence. Prodynorphin (PDYN) is an opioid peptide precursor that yields dynorphins, endogenous kappa opioid-receptor agonists that play important roles in substance abuse. A physiologically active polymorphism of 1-4 repeats of a 68-bp element in the promoter region of the PDYN gene has been identified. We analyzed this polymorphism of the PDYN gene by a case-control association study in 143 patients with methamphetamine dependence and 209 healthy controls in the Japanese population. A 3- or 4-repeat allele in the PDYN gene promoter was found significantly more frequently in patients with methamphetamine dependence than in controls (chi(2)=9.45, p=0.0021). A 3- or 4-repeat allele in the PDYN gene promoter, which was shown to produce significantly higher transcription activity of the PDYN gene than a 1- or 2-repeat allele, is a genetic risk factor for development of methamphetamine dependence (odds ratio: 1.83, 95% CI=1.24-2.68).

Several studies indicate that the mu-opioid receptor plays a role in addiction not only to opiate drugs but also to alcohol and non-opiate addictive drugs. Our studies aim to reveal the associations between gene polymorphisms and methamphetamine (MAP) dependence/psychosis. We newly identified several polymorphisms and four substantial linkage disequilibrium (LD) blocks in the mu-opioid receptor (OPRM1) gene. We found significant differences in both genotype and allele frequencies of the single-nucleotide polymorphism (SNP) IVS2+G691C between control (n=232) and MAP-dependent/psychotic patients (n=128). There was also a significant association between IVS2+G691C and patients with transient psychosis. These results suggest that the OPRM1 gene variations may be a factor in development and prognosis of MAP psychosis.

Recent evidence suggests that the AKT1-GSK3beta signalling cascade partially mediates dopamine-dependent behaviours. In relation to the pathophysiology of schizophrenia or methamphetamine (Meth) use disorder, AKT1 is a good candidate gene for such conditions. For schizophrenia, positive associations of SNPs and AKT1 haplotypes were reported in US and Japanese samples. To evaluate the association between AKT1 and Meth-use disorder, we conducted a case-control study of Japanese samples (182 patients and 437 controls). A positive association between a SNP and haplotypes was found, and the 'signal' SNP was the same SNP found to be associated with US schizophrenia, but not with Japanese schizophrenia. Our results indicate that AKT1 may play a possible role in the development of Meth-use disorder. Further investigation of these associations, together with evidence from previous animal studies, may open the way to elucidation of the pathophysiology of this condition.

Bipolar disorder has known as a high risk factor for substance abuse and dependence such as alcohol and illegal drugs. Recently, Kakiuchi et al. reported that the -116C/G polymorphism in the promoter region of the X-box binding protein 1 (XBP-1) gene, which translates a transcription factor specific for endoplasmic reticulum stress caused by misfolded proteins, was associated with bipolar disorders and schizophrenia in a Japanese population. Abuse of methamphetamine often produces affective disorders such as manic state, depressive state, and psychosis resembling paranoid-type schizophrenia. To clarify a possible involvement of XBP-1 in the etiology of methamphetamine dependence, we examined the genetic association of the -116C/G polymorphism of the XBP-1 gene by a case-control study. We found no significant association in allele and genotype frequencies of the polymorphism either with methamphetamine dependence or any clinical phenotype of dependence. Because the polymorphism is located in the promoter region of the XBP-1 gene and affects transcription activity of the gene, it is unlikely that dysfunction of XBP-1 may induces susceptibility to methamphetamine dependence.

Several lines of evidence suggest that oxidative stress plays a role in the mechanisms of action of methamphetamine (MAP) in the human brain. Given the role of glutathione S-transferases (GSTs) in the protection against oxidative stress, genes encoding the GSTs have been considered as candidates for association studies of MAP abuse. This study was undertaken to investigate the role of the functional polymorphism of GSTP1 gene exon 5 (Ile105Val) in the pathogenesis of MAP abuse. Genotyping for GSTP1 gene polymorphism exon 5 (Ile105Val) in 189 MAP abusers and 199 normal controls was performed by polymerase chain reaction (PCR)-restriction fragment length polymorphism (RFLP). Association between GSTP1 gene polymorphism and clinical features (prognosis of psychosis (transient-type and prolonged-type), spontaneous relapse (positive and negative), and poly-substance abuse) of MAP abusers was evaluated. Significant differences in the frequency of both alleles (P = 0.026, odds ratio: 1.70, 95% confidence intervals (CI) 1.06-2.72) and genotypes (P = 0.029) between MAP abusers and controls were detected. In particular, a significant difference in both genotype frequency (P = 0.013) and allele frequency (P = 0.014, odds ratio: 1.84, 95% CI 1.13-2.97) between MAP abusers with psychosis (transient-type and prolonged-type) and controls was detected. Our findings suggest that the polymorphism (Ile105Val) on exon 5 of the GSTP1 gene may contribute to a vulnerability to psychosis associated with MAP abuse in Japanese population., (Copyright 2005 Wiley-Liss, Inc.)

Genetic contributions to the etiology of substance abuse and dependence are topics of major interest. Acute and chronic cannabis use can produce drug-induced psychosis resembling schizophrenia and worsen positive symptoms of schizophrenia. The endocannabinoid system is one of the most important neural signaling pathways implicated in substance abuse and dependence. The fatty acid amide hydrolase (FAAH) is a primary catabolic enzyme of endocannabinoids. To clarify a possible involvement of FAAH in the etiology of methamphetamine dependence/psychosis or schizophrenia, we examined the genetic association of a nonsynonymous polymorphism of the FAAH gene (Pro129Thr) by a case-control study. We found no significant association in allele and genotype frequencies of the polymorphism with either disorder. Because the Pro129Thr polymorphism reduces enzyme instability, it is unlikely that dysfunction of FAAH and enhanced endocannabinoid system induce susceptibility to either methamphetamine dependence/psychosis or schizophrenia.

Several lines of evidence suggest that genetic factors might contribute to drug abuse vulnerability. Recent genomic scans for association demonstrated that the brain-derived neurotrophic factor (BDNF) gene was associated with drug abuse vulnerability. In this study, we analyzed association of two BDNF gene single nucleotide polymorphisms (SNPs), 132C > T (C270T named formerly) in the noncoding region of exon V and 196G > A (val66met) in the coding region of exon XIIIA, with methamphetamine (MAP) abuse in Japan. No significant differences were found in the frequency of the genotype or allele in these two SNPs between MAP abusers and controls (132C > T in exon V: genotype, P = 0.586, allele, P = 0.594; 196G > A (val66met) in exon XIIIA: genotype, P = 0.889, allele, P = 0.713). Furthermore, there was no difference between clinical parameters (e.g., prognosis psychosis, spontaneous relapse, or poly-substance abuse) and the two SNPs of BDNF gene. These results suggest that the two SNPs (132C > T in exon V and 196G > A (val66met) in exon XIIIA) of the BDNF gene may not be associated with Japanese MAP abusers. This article contains supplementary material, which may be viewed at the American Journal of Medical Genetics website at http://www.interscience.wiley.com/jpages/0148-7299:1/suppmat/index.html., (Copyright 2004 Wiley-Liss, Inc.)

Psychostimulant use disorder and schizophrenia have a substantial genetic basis. Evidence from human and animal studies on the involvement of the gamma-aminobutyric acid (GABA) system in methamphetamine (METH) use disorder and schizophrenia is mounting. As we tested for the association of the human GABA(A) receptor gamma 2 subunit gene (GABRG2) with each diagnostic group, we used a case-control design with a set of 178 subjects with METH use disorder, 288 schizophrenics and 288 controls. First, we screened 96 controls and identified six SNPs in GABRG2, three of whom we newly reported. Next, we selected two SNPs, 315C>T and 1128+99C>A, as representatives of the linkage disequilibrium blocks for further case-control association analysis. Although no associations were found in either allelic or genotypic frequencies, we detected a haplotypic association in GABRG2 with METH use disorder, but not with schizophrenia. This finding partly replicates a recent case-control study of GABRG2 in METH use disorder, and thus indicates that GABRG2 may be one of the susceptibility genes of METH use disorder.

Methamphetamine (MAP) dissipates proton gradients across the membranes of synaptic vesicles, enhances cytoplasmic dopamine (DA) concentrations, and causes calcium-independent, nonvesicular DA release into synapses. MAP is taken into the cytosol by the dopamine transporter (DAT) on the synaptic terminals of DA neurons, and endogenous DA is concurrently released through the transporter by carrier exchange mechanisms, resulting in a robust increase in DA concentration in the synaptic clefts. The enhanced DA release through DAT by MAP is the main mechanism for the reinforcing effects of MAP. The complexes of alpha-synuclein and DAT facilitate membrane clustering of the DAT, thereby accelerating DA uptake in vitro. alpha-Synuclein has been shown to be overexpressed in the midbrain DA neurons of chronic cocaine abusers. The present study was performed to study the association between the alpha-synuclein gene polymorphisms and MAP psychosis/dependence in Japanese population. Since the T10A7 polymorphic site at the 5' end of the noncoding exon 1' in the alpha-synuclein gene is highly polymorphic, we analyzed the noncoding exon 1' and intron 1, including this polymorphic site by sequencing. We confirmed four single nucleotide polymorphisms (SNPs) within 1.38 kbp of the T10A7 polymorphic site. No significant difference was found in genotype or allele frequencies in the T10A7 polymorphic site between MAP psychotic/dependent and control subjects. We found significant association between three SNPs in the vicinity of this polymorphic site in intron 1 and MAP psychosis/dependence in female subjects, but not in males. These results suggest an association of the alpha-synuclein gene polymorphisms with MAP psychosis/dependence in our female subjects. Further analyses are necessary to clarify the gender difference, by using a larger sample size and/or different ethnic groups, as well as functional variations in the alpha-synuclein gene.

It has been suggested that individual genetic factors are involved in susceptibility to drug dependence and the manifestation of drug-induced psychosis. The aim of this study was to examine the relation between methamphetamine abusers/psychosis and the type 1 sigma receptor gene polymorphisms. Subjects comprised 143 MAP abusers and 181 healthy controls. Two polymorphisms in the type 1 sigma receptor gene, GC-241-240TT and A61C (Gln2Pro), were examined in the present study. No significant differences were observed in either polymorphism between healthy controls and MAP abusers/psychosis. In the subgroup analyses, the rate of CC genotype of A61C tended to be higher in MAP patients who had experienced spontaneous relapse without MAP use than in those who had not (P = .06, OR = 3.02 95%CI = 0.92-9.92). However, the level of this significant trend did not remain after the Bonferroni's multiple correction. This study suggests that type 1 sigma receptor gene is unlikely to play a major role in substance abuse liability and/or the development of MAP psychosis.

In drug addiction, the opioid system is thought to mediate motivational effects through dopamine-independent mechanisms. We have investigated associations of the mu-opioid receptor gene (OPRM) variations with methamphetamine (MAP) dependence/psychosis. The allelic frequency of A118G (Asn40Asp) in exon 1 of ORPM was 45.3% in our control subjects, but only 7.5-25.8% in the Caucasian or African-American population of previous studies. We have identified several novel polymorphisms in intron 1 and the 5' untranslated region (5'UTR) of OPRM. Polymorphisms in the functionally relevant 5' regulatory region of OPRM were different in our Japanese population from Caucasian or African-American populations. No significant differences between controls and MAP abusers were found in either genotype or allele frequency at any single nucleotide polymorphism (SNP) or (AC)n dinucleotide repeat in intron 1. A subdivision of our MAP group revealed that A118G of OPRM shows a significant association with MAP psychosis having latency less than three years. Further analysis should be capable of identifying associations between the OPRM variations and MAP dependence/psychosis.

In the central nervous system, tissue-plasminogen activator (t-PA)/plasmin system is involved in long-term synaptic plasticity and remodeling, and participates in rewarding effects of methamphetamine (MAP), by acutely regulating MAP-induced dopamine release in the nucleus accumbens. The aim of this study was to examine the relationships between the patients with MAP abusers/psychosis and the t-PA/plasminogen system genes. Subjects comprised 185 MAP abusers and 288 healthy controls. Four polymorphisms in the t-PA, plasminogen activator inhibitor, and plasminogen genes were examined in the present study. No significant differences were observed in each polymorphism between healthy controls and MAP abusers/psychosis. This study suggests that t-PA/plasminogen system is unlikely to be a major contributor to the substance abuse liability and/or the development of MAP psychosis.

Several lines of evidence suggest that increased generation of auto-oxidized dopamine (DA) o-quinone is associated with the neurotoxicity of methamphetamine (MAP) in the brain, and that, as a cellular defenses against DA-derived quinines, glutathione S-transferase (GST) detoxifies auto-oxidized DA o-quinone in the brain. Glutathione S-transferase M1 (GSTM1) of the mu-class of GSTs catalyzes reaction between glutathione and catecholamine o-quinones under physiological conditions. This study was undertaken to investigate the role of the GSTM1 gene deletion polymorphism in the neuropathology of MAP abuse. One hundred fifty-seven MAP abusers and 200 healthy comparison subjects were tested for a genetic polymorphism of GSTM1. The difference in the frequency of deletion (D)/non-deletion (N) alleles between the female abusers and female controls was close to statistical significance (P = 0.071), although there was no statistical difference (P = 0.651) between male abusers and male controls. Furthermore, the number of female abusers with deletion alleles was significantly (P = 0.007, odds ratio: 2.77, 95% CI 1.30-5.89) higher than that of male abusers with deletion alleles. These findings suggest that GSTM1 gene deletion may contribute to a vulnerability to MAP abuse in female subjects, but not in male subjects., (Copyright 2003 Wiley-Liss, Inc.)

Susceptibility to drug dependence and drug-induced psychoses is influenced not only by the pharmacological effects of the drug but also by the genetic factors of the individual. To clarify the latter, we investigated the association between methamphetamine (METH) dependence/psychosis and the hDAT1 gene (SLC6A3) encoding the dopamine transporter, which is the primary site of METH activity in the brain. Four exonic polymorphisms of the hDAT1 gene, 242C/T (exon 2), 1342A/G (exon 9), 2319G/A (3'UTR), and VNTR (3'UTR) were examined. Although there was no significant difference in genotypic and allelic distribution of the four polymorphisms between all METH dependence/psychosis patients (N=124) and controls (N=160), the patients with METH psychosis lasting for 1 month or more after discontinuance of METH consumption showed a significant excess of nine- or fewer repeat alleles of the VNTR in 3'UTR of the hDAT1 gene (P=0.0054, OR=4.24, 95% CI=2.46-7.31). The present study demonstrated that the presence of nine- or fewer repeat alleles of hDAT1 is a strong risk factor for a worse prognosis of METH psychosis.