Junko Fujihara

Genetic polymorphisms in glutathione S-transferase (GST) superfamily and arsenic metabolism in residents of the Red River Delta, Vietnam

To elucidate the role of genetic factors in arsenic metabolism, we investigated associations of genetic polymorphisms in the members of glutathione S-transferase (GST) superfamily with the arsenic concentrations in hair and urine, and urinary arsenic profile in residents in the Red River Delta, Vietnam. Genotyping was conducted for GST omega1 (GSTO1) Ala140Asp, Glu155del, Glu208Lys, Thr217Asn, and Ala236Val, GST omega2 (GSTO2) Asn142Asp, GST pi1 (GSTP1) Ile105Val, GST mu1 (GSTM1) wild/null, and GST theta1 (GSTT1) wild/null. There were no mutation alleles for GSTO1 Glu208Lys, Thr217Asn, and Ala236Val in this population. GSTO1 Glu155del hetero type showed higher urinary concentration of As(V) than the wild homo type. Higher percentage of DMA(V) in urine of GSTM1 wild type was observed compared with that of the null type. Strong correlations between GSTP1 Ile105Val and arsenic exposure level and profile were observed in this study. Especially, heterozygote of GSTP1 Ile105Val had a higher metabolic capacity from inorganic arsenic to monomethyl arsenic, while the opposite trend was observed for ability of metabolism from As(V) to As(III). Furthermore, other factors including sex, age, body mass index, arsenic level in drinking water, and genotypes of As (+3 oxidation state) methyltransferase (AS3MT) were also significantly co-associated with arsenic level and profile in the Vietnamese. To our knowledge, this is the first study indicating the associations of genetic factors of GST superfamily with arsenic metabolism in a Vietnamese population.

Genetic polymorphisms in AS3MT and arsenic metabolism in residents of the Red River Delta, Vietnam

To elucidate the role of genetic factors in arsenic (As) metabolism, we studied associations of single nucleotide polymorphisms (SNPs) in As (+3 oxidation state) methyltransferase (AS3MT) with the As concentrations in hair and urine, and urinary As profile in residents in the Red River Delta, Vietnam. Concentrations of total As in groundwater were 0.7-502 mug/l. Total As levels in groundwater drastically decreased by using sand filter, indicating that the filter could be effective to remove As from raw groundwater. Concentrations of inorganic As (IAs) in urine and total As in hair of males were higher than those of females. A significant positive correlation between monomethylarsonic acid (MMA)/IAs and age in females indicates that older females have higher methylation capacity from IAs to MMA. Body mass index negatively correlated with urinary As concentrations in males. Homozygote for SNPs 4602AA, 35991GG, and 37853GG, which showed strong linkage disequilibrium (LD), had higher percentage (%) of dimethylarsinic acid (DMA) in urine. SNPs 4740 and 12590 had strong LD and associated with urinary %DMA. Although SNPs 6144, 12390, 14215, and 35587 comprised LD cluster, homozygotes in SNPs 12390GG and 35587CC had lower DMA/MMA in urine, suggesting low methylation capacity from MMA to DMA in homo types for these SNPs. SNPs 5913 and 8973 correlated with %MMA and %DMA, respectively. Heterozygote for SNP 14458TC had higher MMA/IAs in urine than TT homozygote, indicating that the heterozygote may have stronger methylation ability of IAs. To our knowledge, this is the first study on the association of genetic factors with As metabolism in Vietnamese.

Arsenic in Marine Mammals, Seabirds, and Sea Turtles

Although there have been numerous studies on arsenic in low-trophic-level marine organisms, few studies exist on arsenic in marine mammals, seabirds, and sea turtles. Studies on arsenic species and their concentrations in these animals are needed to evaluate their possible health effects and to deepen our understanding of how arsenic behaves and cycles in marine ecosystems. Most arsenic in the livers of marine mammals, seabirds, and sea turtles is AB, but this form is absent or occurs at surprisingly low levels in the dugong. Although arsenic levels were low in marine mammals, some seabirds, and some sea turtles, the black-footed albatross and hawksbill and loggerhead turtles showed high concentrations, comparable to those in marine organisms at low trophic levels. Hence, these animals may have a specific mechanism for accumulating arsenic. Osmoregulation in these animals may play a role in the high accumulation of AB. Highly toxic inorganic arsenic is found in some seabirds and sea turtles, and some evidence suggests it may act as an endocrine disruptor, requiring new and more detailed studies for confirmation. Furthermore, DMA(V) and arsenosugars, which are commonly found in marine animals and marine algae, respectively, might pose risks to highly exposed animals because of their tendency to form reactive oxygen species. In marine mammals, arsenic is thought to be mainly stored in blubber as lipid-soluble arsenicals. Because marine mammals occupy the top levels of their food chain, work to characterize the lipid-soluble arsenicals and how they cycle in marine ecosystems is needed. These lipid-soluble arsenicals have DMA precursors, the exact structures of which remain to be determined. Because many more arsenicals are assumed to be present in the marine environment, further advances in analytical capabilities can and will provide useful future information on the transformation and cycling of arsenic in the marine environment.

Individual Variations in Inorganic Arsenic Metabolism Associated with AS3MT Genetic Polymorphisms

Individual variations in inorganic arsenic metabolism may influence the toxic effects. Arsenic (+3 oxidation state) methyltransferase (AS3MT) that can catalyze the transfer of a methyl group from S-adenosyl-l-methionine (AdoMet) to trivalent arsenical, may play a role in arsenic metabolism in humans. Since the genetic polymorphisms of AS3MT gene may be associated with the susceptibility to inorganic arsenic toxicity, relationships of several single nucleotide polymorphisms (SNPs) in AS3MT with inorganic arsenic metabolism have been investigated. Here, we summarize our recent findings and other previous studies on the inorganic arsenic metabolism and AS3MT genetic polymorphisms in humans. Results of genotype dependent differences in arsenic metabolism for most of SNPs in AS3MT were Inconsistent throughout the studies. Nevertheless, two SNPs, AS3MT 12390 (rs3740393) and 14458 (rs11191439) were consistently related to arsenic methylation regardless of the populations examined for the analysis. Thus, these SNPs may be useful indicators to predict the arsenic metabolism via methylation pathways.

Exposure, metabolism, and health effects of arsenic in residents from arsenic-contaminated groundwater areas of Vietnam and Cambodia: a review.

In this review, we summarize the current knowledge on exposure, metabolism, and health effects of arsenic (As) in residents from As-contaminated groundwater areas of Vietnam and Cambodia based on our findings from 2000 and other studies. The health effects of As in humans include severe gastrointestinal disorders, hepatic and renal failure, cardiovascular disturbances, skin pigmentation, hyperkeratosis, and cancers in the lung, bladder, liver, kidney, and skin. Arsenic contamination in groundwater is widely present at Vietnam and Cambodia and the highest As levels are frequently found in groundwater from Cambodia. Sand filter system can reduce As concentration in raw groundwater. The results of hair and urine analyses indicate that residents from these As-contaminated areas are exposed to As. In general, sex, age, body mass index, and As exposure level are significantly associated with As metabolism. Genetic polymorphisms in arsenic (+III) methyltransferase and glutathione-S-transferase isoforms may be influenced As metabolism and accumulation in a Vietnamese population. It is suggested oxidative DNA damage is caused by exposure to As in groundwater from residents in Cambodia. An epidemiologic study on an association of As exposure with human health effects is required in these areas.

Ethnic differences in five intronic polymorphisms associated with arsenic metabolism within human arsenic (+3 oxidation state) methyltransferase (AS3MT) gene.

Human arsenic (+3 oxidation state) methyltransferase (AS3MT) is known to catalyze the methylation of arsenite, and intronic single-nucleotide polymorphisms (SNPs: G7395A, G12390C, T14215C, T35587C, and G35991A) in the AS3MT gene were shown to be related to inter-individual variation in the arsenic metabolism. In the present study, the genotyping for these SNPs was developed using the polymerase chain reaction and restriction fragment length polymorphism technique. Applying this method, the genotype distribution among the Ovambo, Turkish, Mongolian, Korean, and Japanese populations was investigated, and our results were compared with those from other studies. G7395, G12390, T35587, and A35991 were predominant among the five populations in our study. However, a previous study in Argentina, C12390 and G35991 showed the highest allele frequency among the eight populations studied in other studies. The dominant allele of T14215C differed among populations: the T14215 allele was predominant in Argentina, the allele frequency of C14215 was higher than that of T14215 among Turks, Mongolians, Europeans, and American ancestry. In Korea and Japan, similar allele frequencies were observed in T14215 and C14215. Higher allele frequencies were observed in haplotype G7395/G12390/C14215/T35587 with frequencies of 0.40 (Turks), 0.28 (Mongolians), and 0.23 (Koreans). On the other hand, the allele frequency for G7395/G14215/T35587/A35991 was the highest among the Ovambos (0.32), and the frequency for G7395/G12390/C35587/G35991 was the highest among the Japanese (0.27). It is noteworthy that the Japanese haplotype differs from that of the Koreans and Mongolians, which indicates the importance of investigating other intronic polymorphisms in AS3MT, especially in Asians.

Lipid-soluble and water-soluble arsenic compounds in blubber of ringed seal (Pusa hispida)

High concentrations of arsenic were observed in the blubber of ringed seals (Pusa hispida) in our previous study. To better understand the arsenic accumulation in blubber of marine mammals, arsenicals in the blubber of ringed seal were characterized using high performance liquid chromatography-inductively coupled plasma mass spectrometry (HPLC-ICPMS). The most predominant water-soluble arsenical in the blubber was dimethylarsinic acid (DMA), in spite of the predominance of arsenobetaine in other tissues. Lipid-soluble fraction was hydrolyzed under mild (tetraethylammonium hydroxide (TEAH) hydrolysis) and strong (NaOH hydrolysis) conditions, and then an aliquot of hydrolysate was injected onto HPLC-ICPMS. Both TEAH-labile and TEAH-stable/NaOH-labile lipid-soluble fractions contained precursors of DMA. These results suggest that the blubber might be the pool of DMA and DMA-containing precursors in ringed seals.

A biochemical and genetic study on all non-synonymous single nucleotide polymorphisms of the gene encoding human deoxyribonuclease I potentially relevant to autoimmunity

A reduction of deoxyribonuclease I (DNase I) activity levels in the serum of patients with autoimmune diseases has been reported. The objectives of this study were to clarify genetic and biochemical aspects of 12 non-synonymous SNPs in the human gene (DNASE1), potentially giving rise to an alteration in the in vivo DNase I activity levels. Genotyping of all the non-synonymous SNPs was performed in healthy subjects of three ethnic groups including 15 populations using newly developed methods. Among them, only four SNPs, R-21S, Y95S, G105R, and Q222R were polymorphic in all or some populations; Asian group showed a relatively low genetic diversity of these SNPs. Furthermore, the distribution pattern of the common SNP Q222R was classified into three ethnic groups. The activity levels of the amino acid-substituted DNase I forms derived from SNPs R-21S, G105R, P132A, and P197S were significantly high compared with that of the wild-type; the polymorphic SNPs R-21S and G105R gave rise to a high activity-harboring DNase I isoform. On the other hand, activity levels from Q35H, R85G, V89M, C209Y, Q222R, and A224P were significantly low, but these SNPs, except Q222R, were not distributed in any of the populations. However, since these SNPs may produce potentially low levels of in vivo DNase I activity, a minor allele in each SNP will be served as a genetic risk factor for autoimmune diseases. These findings on non-synonymous SNPs in DNASE1 may provide a biochemical-genetic basis for the clarification of a possible relationship between DNase I and the diseases.

Caucasian-specific allele in non-synonymous single nucleotide polymorphisms of the gene encoding deoxyribonuclease I-like 3, potentially relevant to autoimmunity, produces an inactive enzyme

BACKGROUND Deoxyribonuclease I-like 3 (DNase Il3), a member of human DNase I family, is postulated to be involved in the genesis of autoimmune diseases. In the DNase Il3 gene, 2 non-synonymous SNPs, R178H and R206C, have been identified, however relevant population data are not available. METHODS Genotyping of the SNPs was performed in healthy subjects belonging to 3 ethnic groups (n=1708), including nine different populations, using an amplification refractory mutation system and the PCR-RFLP technique. RESULTS All of the 9 populations were typed as a single genotype in R178H. All Asian and African populations exhibited only a homozygous C686 allele in R206C, whereas a heterozygote, C686/T686, was found (frequency of 3.5-15.4%) in three Caucasian populations (Turk, German and Mexican); Caucasian-specific allele T686 was identified. The substitution of Arg by Cys corresponding to R206C resulted in elimination of DNase Il3 activity. CONCLUSION A Caucasian-specific allele in SNP R206C produces an inactive form of DNase Il3. It seems plausible that levels of DNase Il3 activity in Caucasian subjects with the heterozygote in R206C are lower than those in individuals with the predominant homozygote. Our results may have clinical implications in relation to the prevalence of autoimmune diseases.

DIVERSITY OF GLUTATHIONE S-TRANSFERASE OMEGA 1 (A140D) AND 2 (N142D) GENE POLYMORPHISMS IN WORLDWIDE POPULATIONS

1 Glutathione S‐transferase class omega (GSTO) 1 and 2 are members of the glutathione‐S‐transferase family, which uses glutathione in the process of the biotransformation of drugs, xenobiotics and oxidative stress. Associations with the age‐at‐onset of Alzheimers and Parkinsons diseases have been shown in the genetic polymorphism of GSTO1 and GSTO2. 2 In the present study, the frequencies of GSTO1*A140D and GSTO2*N142D in Ovambos (n = 163), Turks (n = 194), Mongolians (n = 243) and Japanese (n = 102) were investigated and compared with findings from other studies. Detection of these single nucleotide polymorphisms was performed by polymerase chain reaction–restriction fragment length polymorphism analysis. 3 The allele frequencies of these polymorphisms in Ovambos, Turks, Mongolians and Japanese were 0.040, 0.085, 0.128 and 0.108, respectively, for GSTO1*A140D and 0.583, 0.219, 0.173 and 0.216, respectively, for GSTO2*N142D. Ovambos showed the lowest allele frequency of GSTO1*A140D. Conversely, Africans, including Ovambos, showed higher allele frequencies of GSTO2*N142D than Caucasians and Asians. 4 The existence of a certain genetic heterogeneity in the worldwide distribution of these two polymorphisms is revealed in the present study.