Akihisa Hata

A ubiquitin ligase HRD1 promotes the degradation of Pael receptor, a substrate of Parkin

It has been proposed that in autosomal recessive juvenile parkinsonism (AR‐JP), a ubiquitin ligase (E3) Parkin, which is involved in endoplasmic reticulum‐associated degradation (ERAD), lacks E3 activity. The resulting accumulation of Parkin‐associated endothelin receptor‐like receptor (Pael‐R), a substrate of Parkin, leads to endoplasmic reticulum stress, causing neuronal death. We previously reported that human E3 HRD1 in the endoplasmic reticulum protects against endoplasmic reticulum stress‐induced apoptosis. This study shows that HRD1 was expressed in substantia nigra pars compacta (SNC) dopaminergic neurons and interacted with Pael‐R through the HRD1 proline‐rich region, promoting the ubiquitylation and degradation of Pael‐R. Furthermore, the disruption of endogenous HRD1 by small interfering RNA (siRNA) induced Pael‐R accumulation and caspase‐3 activation. We also found that ATF6 overexpression, which induced HRD1, accelerated and caused Pael‐R degradation; the suppression of HRD1 expression by siRNA partially prevents this degradation. These results suggest that in addition to Parkin, HRD1 is also involved in the degradation of Pael‐R.

HPLC-ICP-MS Speciation Analysis of Arsenic in Urine of Japanese Subjects without Occupational Exposure

HPLC‐ICP‐MS Speciation Analysis of Arsenic in Urine of Japanese Subjects without Occupational Exposure: Akihisa Hata, et al. Department of Preventive Medicine and Environmental Health, Graduate School of Medicine, Osaka City University—The toxicity and carcinogenicity of arsenic depend on its species. Individuals living in Japan consume much seafood that contains high levels of organoarsenics. Speciation analysis of urinary arsenic is required to clarify the health risks of arsenic intake. There has been no report of urinary arsenic analysis in Japan using high performance liquid chromatography with inductively coupled plasma mass spectrometry (HPLC‐ICP‐MS). We performed speciation analysis of urinary arsenic for 210 Japanese male subjects without occupational exposure using HPLC‐ICP‐MS. The median values of urinary arsenics were as follows: sodium arsenite (AsIII), 3.5; sodium arsenate (AsV), 0.1; monomethylarsonic acid (MMA), 3.1; dimethylarsinic acid (DMA), 42.6; arsenobetaine (AsBe), 61.3; arsenocholine, trimethylarsine oxide, and unidentified arsenics (others), 5.2; and total arsenic (total As), 141.3 µgAs/l. The median creatinine‐adjusted values were as follows: AsIII, 3.0; AsV, 0.1; MMA, 2.6; DMA, 35.9; AsBe, 52.1; others 3.5; and total As, 114.9 µgAs/g creatinine. Our findings indicate that DMA and AsBe levels in Japan are much higher than those found in Italian and American studies. It appears that the high levels of DMA and AsBe observed in Japan may be due in part to seafood intake. ACGIH and DFG set the BEI and BAT values for occupational arsenic exposure as 35 µgAs/l and 50 µgAs/l, respectively, using the sum of inorganic arsenic (iAs), MMA, and DMA. In the general Japanese population, the sums of these were above 50 µgAs/l in 115 (55%) samples. We therefore recommend excluding DMA concentration in monitoring of iAs exposure.

Rapid and Effective Speciation Analysis of Arsenic Compounds in Human Urine using Anion-Exchange Columns in HPLC-ICP-MS

Received Jan 29, 2009; Accepted May 14, 2009Published online in J-STAGE Jun 18, 2009Correspondence to: Y. Suzuki, Research Center for OccupationalPoisoning, Tokyo Rosai Hospital, Japan Labour Health and WelfareOrganization, 4–13–21 Ohmori-minami, Ohta-ku, Tokyo 143-0013,Japan (e-mail: suzy@tokyoh.rofuku.go.jp)

A novel metabolic activation associated with glutathione in dimethylmonothioarsinic acid (DMMTAV)-induced toxicity obtained from in vitro reaction of DMMTAV with glutathione

The purpose of the present study was to elucidate the metabolic processing of dimethylmonothioarsinic acid (DMMTA(V)), which is a metabolite of inorganic arsenic and has received a great deal of attention recently due to its high toxicity. The metabolites produced from an in vitro reaction with GSH were analyzed by high performance liquid chromatography-time of flight mass spectrometer (HPLC-TOFMS), HPLC with a photodiode array detector (PDA), and also gas chromatography-mass spectrometry (GC-MS) and GC with a flame photometric detector (FPD). The reaction of dimethylarsinic acid (DMA(V)) with GSH did not generate DMA(V)-SG but did generate dimethylarsinous acid (DMA(III)) or DMA(III)-SG. On the contrary, we confirmed that the reaction of DMMTA(V) with GSH directly produced the stable complex of DMMTA(V)-SG without reduction through a trivalent dimethylated arsenic such as DMA(III) and DMA(III)-SG. Furthermore, the present study suggests the production of hydrogen sulfide (H2S) and dimethylmercaptoarsine (DMA(III)-SH), a trivalent dimethylated arsenic, as well as DMA(III) and DMA(III)-SG in the decomposition process of DMMTA(V)-SG. These results indicate that the toxicity of DMMTA(V) depends not only on the formation of DMA(III) but also on at least those of H2S and DMA(III)-SH.

A biological indicator of inorganic arsenic exposure using the sum of urinary inorganic arsenic and monomethylarsonic acid concentrations.

The sum of urinary inorganic arsenic (iAs), monomethylarsonic acid (MMA), and dimethylarsinic acid (DMA) concentrations is used for the biological monitoring of occupational iAs exposure. Although DMA is a major metabolite of iAs, it is an inadequate index because high DMA levels are present in urine after seafood consumption. We estimated the urinary iAs+MMA concentration corresponding to iAs exposure.

Possible production of arsenic hemoglobin adducts via exposure to arsine.

Possible production of arsenic hemoglobin adducts via exposure to arsine: Takenori YAMAU‐CHI, et al. Department of Public Health Faculty of Medicine, University of Miyazaki

Comprehensive analysis of prokaryotes in environmental water using DNA microarray analysis and whole genome amplification.

The microflora in environmental water consists of a high density and diversity of bacterial species that form the foundation of the water ecosystem. Because the majority of these species cannot be cultured in vitro, a different approach is needed to identify prokaryotes in environmental water. A novel DNA microarray was developed as a simplified detection protocol. Multiple DNA probes were designed against each of the 97,927 sequences in the DNA Data Bank of Japan and mounted on a glass chip in duplicate. Evaluation of the microarray was performed using the DNA extracted from one liter of environmental water samples collected from seven sites in Japan. The extracted DNA was uniformly amplified using whole genome amplification (WGA), labeled with Cy3-conjugated 16S rRNA specific primers and hybridized to the microarray. The microarray successfully identified soil bacteria and environment-specific bacteria clusters. The DNA microarray described herein can be a useful tool in evaluating the diversity of prokaryotes and assessing environmental changes such as global warming.

Differences in apoptotic signaling and toxicity between dimethylmonothioarsinic acid (DMMTAV) and its active metabolite, dimethylarsinous acid (DMAIII), in HepaRG cells: Possibility of apoptosis cascade based on diversity of active metabolites of DMMTAV

Dimethylmonothioarsinical acid (DMMTAV), a metabolite of arsenosugars (AsSug) and arsenolipids (AsLP), which are major organoarsenicals contained in seafoods, has been a focus of our attention due to its toxicity. It has been reported that the toxicity of DMMTAV differs according to the host cell type and that dimethylarsinous acid (DMAIII), which is a higher active metabolite of inorganic and organo arsenic compounds, may be the ultimate substance. To further elucidate the details of the mechanisms of DMMTAV, we carried out toxicological characterization by comparing DMMTAV and DMAIII using HepaRG cells, which are terminally differentiated hepatic cells derived from a human hepatic progenitor cell line that retains many characteristics, e.g, primary human hepatocytes including the morphology and expression of key metabolic enzymes (P450 s and GSTs, etc.) and complete expression of all nuclear receptors. HepaRG cells were induced to undergo differentiation by DMSO, which result red in increased levels of metabolic enzymes such as P450 and GST, in non-differentiated cells the cellular toxicities of DMMTAV and DMAIII were reduced and the induction of toxicity by DMMTAV was increased by GSH but not by DMAIII. Both DMAIII and DMMTAV induce apoptosis and increase caspase 3/7 activity. DMAIII exposure increased the activity of caspase-9. On the contrary, DMMTAV exposure resulted in markedly elevated activity of caspase-8 as well as caspase-9. These results suggest there are differences between the signaling pathways of apoptosis in DMAIII and DMMTAV and that between their active metabolites. Consequently, the ultimate metabolic substance of toxicity induction of DMMTAV may not only be DMAIII, but may also be partly due to other metabolic substances produced through the activation mechanism by GSH.