Involvement of a AS3MT/c-Fos/p53 signaling axis in arsenic-induced tumor in human lung cells.

Arsenite methyltransferase (AS3MT) is an enzyme that catalyzes the dimethylation of arsenite (+3 oxidation state). At present, the studies on arsenic carcinogenicity mainly focus on studying the polymorphisms of AS3MT and measuring their catalytic activities. We recently showed that AS3MT was overexpressed in lung cancer patients who had not been exposed to arsenic. However, little is known about the molecular mechanisms of AS3MT in arsenite-induced tumorigenesis. In this study, we showed that AS3MT protein expression was higher in the arsenic-exposed population compared to the unexposed population. AS3MT was also overexpressed in human lung adenocarcinoma (A549) and human bronchial epithelial (16HBE) cells exposed to arsenic (A549: 20-60 µmol/L; 16HBE: 2-6 µmol/L) for 48 h. Furthermore, we investigated the effects of AS3MT on cell proliferation and apoptosis using siRNA. The downregulation of AS3MT inhibited the proliferation and promoted the apoptosis of cells. Mechanistically, AS3MT was found to specifically bind to c-Fos, thereby inhibiting the binding of c-Fos to c-Jun. Additionally, the siRNA-mediated knockdown of AS3MT enhanced the phosphorylation of Ser392 in p53 by upregulating p38 MAPK expression. This led to the activation of p53 signaling and the upregulated expression of downstream targets, such as p21, Fas, PUMA, and Bax. Together, these studies revealed that the inorganic arsenic-mediated upregulation of AS3MT expression directly affected the proliferation and apoptosis of cells, leading to arsenic-induced toxicity or carcinogenicity.

Inorganic arsenic-mediated upregulation of TUG1 promotes apoptosis in human bronchial epithelial cells by activating the p53 signaling pathway.

Exposure to arsenic, an environmental contaminant, is known to cause arsenicosis and cancer. Although considerable research has been conducted to understand the underlying mechanism responsible for arsenic-induced cancers, the precise molecular mechanisms remain unknown, especially at the epigenetic regulation level. Long non-coding RNAs (LncRNAs) that have been shown to mediate various biological processes, including proliferation, apoptosis, necrosis, and mutagenesis. There are few studies on LncRNAs and biological damage caused by environmental pollutants. The LncRNAs taurine upregulated gene 1 (TUG1) regulates cell growth both in vitro and in vivo, and contributes its oncogenic role. However, the precise roles and related mechanisms of arsenic-induced cell apoptosis are still not fully understood owing to controversial findings in the literature. In this study, quantitative real-time polymerase chain reaction (qRT-PCR) analysis revealed higher expression levels of TUG1 in people occupationally exposed to arsenic than in individuals living away from the source of arsenic exosure (N = 25). In addition, the results suggested that TUG1 was involved in arsenic-induced apoptosis. Furthermore, knockdown experiments showed that silencing of TUG1 markedly inhibited proliferation, whereas depletion of TUG1 led to increased apoptosis. The TUG1-small interfering RNA (siRNA) combination with arsenic (3 µM/L) slightly increased apoptosis compared with the TUG1-siRNA. Additionally, the knockdown experiments showed that the silencing of TUG1 by siRNA inhibited proliferation and promoted apoptosis by inducing p53, p-p53 (ser392), FAS, BCL2, MDM2, cleaved-caspase7 proteins in 16HBE cells. These results indicated that arsenic mediates the upregulation of TUG1 and induces cell apoptosis via activating the p53 signaling pathway.

Inorganic arsenic-mediated upregulation of AS3MT promotes proliferation of nonsmall cell lung cancer cells by regulating cell cycle genes.

Long-term arsenic exposure can promote cancer through epigenetic mechanisms, and arsenite methyltransferase (AS3MT) plays an important role in this process. However, the expression patterns and mechanisms of AS3MT in arsenic carcinogenesis remain unclear. In this study, we found that the AS3MT was overexpressed in arsenic exposed population, non-small cell lung cancer (NSCLC) tissues, and A549 cells with sodium arsenite (NaAsO2 ) treatment for 48 hours. Besides, the level of AS3MT expression was positively correlated with the concentrations of urinary total arsenic (tAs), inorganic arsenic (iAs), methanearsonic acid (MMA), and dimethylarsinic acid (DMA) in all subjects. Functional experiments demonstrated that siRNA-mediated knockdown of AS3MT significantly inhibited proliferation of A549 cells. Mechanism investigation revealed that silencing of AS3MT inhibited proliferation by increasing mRNA expression levels of p21 and E2F1, and inhibiting CDK1, CDK2, CDK4, CDK6, Cyclin A2, Cyclin E1, Cyclin E2, and PCNA mRNA expression. Therefore, arsenic increased AS3MT expression in vivo and in vitro, which could directly act on the cell and affect the progression of NSCLC by regulating cell cycle genes.

[Expression changes of tumor-related gene mRNA in workers who smelt arsenic].

OBJECTIVE: To explore the changes and influencing factors about expressions of tumor-related gene mRNA in workers who smelt arsenic. METHODS: There were 37 workers who smelt arsenic, 43 workers who stopped exposure to arsenic for 85 days, and 51 individuals as control group which selected by random cluster sampling. Arsenic species( iAs, MMA, and DMA) in urine were determined by atomic absorption spectrophotometer with an As speciation pretreatment system. Real time PCR( RT-PCR)was performed to detect the expressions of 4 tumor-related gene mRNAs. RESULTS: The concentrations of iAs, MMA and DMA in urine of workers who smelt arsenic, stopped exposure to arsenic for 85 days, and control group were( 133. 97 ± 109. 53), ( 208. 93 ±171. 43) and( 820. 35 ± 487. 39) µg/( g·creatinine)( workers who smelt arsenic), ( 123. 31 ± 112. 72), ( 176. 21 ± 157. 19) and( 467. 73 ± 392. 17) µg/( g·creatinine)( workers who stopped exposure to arsenic), ( 1. 55 ±1. 49), ( 0. 10 ±0. 09) and( 10. 47 ±7. 85) µg/( g·creatinine)( control group). Compared to control group, the concentrations of 3 arsenic species were all higher in worker came from arsenic smelting. Compared to workers who were smelting arsenic, DMA are lower in workers who stopped exposure to arsenic for 85 days( P < 0. 05). The relative mRNA expressions of Lin28, Bax, Bcl-2 and Fas in 3 groups were( 8. 88 ± 2. 42), ( 6. 87 ± 1. 10), ( 7. 24 ± 2. 31) and( 8. 23 ±2. 90)( workers who smelt arsenic), ( 6. 21 ± 2. 94), ( 5. 81 ± 1. 72), ( 4. 50 ± 1. 59)and( 6. 89 ± 2. 35)( workers who stopped exposure to arsenic), ( 5. 60 ± 1. 43), ( 5. 56 ±0. 98), ( 4. 88 ± 1. 39) and( 6. 92 ± 1. 87)( control group). Compared to control group, relative mRNA expressions of Lin28, Bax, Bcl-2 and Fas were all higher in worker who were smelting arsenic( P < 0. 05). CONCLUSION: The expressions of tumor-related gene mRNAs are high in workers who smelt arsenic, and the methylation metabolism of arsenic play great role in the process of relative mRNAs expresses.

[Changes in mRNA expression of p53 and related downstream genes in peripheral blood lymphocytes in workers occupationally exposed to arsenic].

OBJECTIVE: To investigate the changes in mRNA expression of p53 and related downstream genes in peripheral blood lymphocytes in workers occupationally exposed to arsenic as well as its influencing factors, and to analyze the mechanism of genetic toxicity of arsenic. METHODS: With cluster random sampling, 79 workers from an arsenic smelting plant were selected as exposure group, and another 24 people without occupational exposure to arsenic were selected as control group. The relative mRNA expression of p53 and related downstream genes in the peripheral blood lymphocytes of the two groups was determined by quantitative realtime PCR. The levels of inorganic arsenic (iAs), monomethylarsonic acid (MMA), and dimethylarsinic acid (DMA) in urine were determined by hydride generation-atomic absorption spectrometry. RESULTS: The exposure group had significantly higher levels of iAs, MMA, and DMA than the control group (P<0.01); the exposure group had significantly higher relative mRNA expression (2(-ΔΔCt)) of p53 and four related downstream genes in peripheral blood lymphocytes than the control group (P<0.05); the relative mRNA expression of p53 and related downstream genes was positively correlated with each other (P<0.01), with a correlation coefficient greater than 0.4; the levels of arsenic compounds in urine were positively correlated with the relative mRNA expression of p53 and some of its downstream genes (P<0.05). CONCLUSION: The changes in mRNA expression of p53 and related downstream genes are closely related to the metabolic transformation of inorganic arsenic in workers occupationally exposed to arsenic, and it also plays an important role in genetic toxicity and carcinogenic effect in people exposed to arsenic.

Research progress on the regulatory mechanism of cell senescence in arsenic toxicity: a systematic review.

As an element with metalloid properties, arsenic is pervasively present in the environment and is recognized as a potent carcinogen. Consequently, the issue of human arsenic exposure has become a significant concern within the global public health sector. Numerous studies have indicated that arsenic induces cellular senescence through various mechanisms, including triggering epigenetic alterations, inducing the senescence-associated secretory phenotype (SASP), promoting telomere shortening, and causing mitochondrial dysfunction. This article collates and summarizes the latest research advancements on the involvement of cellular senescence in arsenic toxicity and explores the mechanisms of arsenic-induced toxicity. This study aims to provide new perspectives and directions for future research on arsenic toxicity and the development of prevention and treatment strategies.

As3MT is related to relative RNAs and base modifications of p53 in workers exposed to arsenic.

As3MT is the key enzyme involved in the methylation metabolism of arsenic. It is associated with DNA methylation closely also. This study is to explore the relationships between As3MT and epigenetic changes, and how p53 and relative ncRNAs and mRNAs play roles in the process. In this study, workers from four arsenic plants and individuals who resided in villages far away from the four plants were recruited. Arsenic compounds, relative indices, 28 relative RNAs, and base modifications of exons 5-8 of p53 were detected separately. Several methods were used to analyze the associations between them. Results shown that As3MT RNA was closely associated with all selected lncRNAs, miRNAs, and mRNAs related to miRNA production and maturation, tumorigenesis, and base modifications of p53. There probably exists causal relationship. Base modifications of exons 7 and 8 of p53 had significant synergistic effects on the expression of As3MT RNA and a series of genetic indices. But miR-190, miR-548, and base modifications of exon 5 of p53 had substantial inhibitory effects. Arsenic compounds and relative indices of metabolic transformation may have limited roles. The main novel finding in the present study is that As3MT play special and significant roles in the genotoxicity and carcinogenesis which could be coordinated operation with p53, and influenced by epigenetic factors largely, such as lncRNAs and miRNAs. P53 and relative ncRNAs and mRNAs may regulate the process by interacting with As3MT. The changes may initiate by arsenic, but probability through indirect relationship.

A Three-Monoclonal Antibody Combination Potently Neutralizes BoNT/G Toxin in Mice.

Equine-derived antitoxin (BAT®) is the only treatment for botulism from botulinum neurotoxin serotype G (BoNT/G). BAT® is a foreign protein with potentially severe adverse effects and is not renewable. To develop a safe, more potent, and renewable antitoxin, humanized monoclonal antibodies (mAbs) were generated. Yeast displayed single chain Fv (scFv) libraries were prepared from mice immunized with BoNT/G and BoNT/G domains and screened with BoNT/G using fluorescence-activated cell sorting (FACS). Fourteen scFv-binding BoNT/G were isolated with KD values ranging from 3.86 nM to 103 nM (median KD 20.9 nM). Five mAb-binding non-overlapping epitopes were humanized and affinity matured to create antibodies hu6G6.2, hu6G7.2, hu6G9.1, hu6G10, and hu6G11.2, with IgG KD values ranging from 51 pM to 8 pM. Three IgG combinations completely protected mice challenged with 10,000 LD50s of BoNT/G at a total mAb dose of 6.25 µg per mouse. The mAb combinations have the potential for use in the diagnosis and treatment of botulism due to serotype G and, along with antibody combinations to BoNT/A, B, C, D, E, and F, provide the basis for a fully recombinant heptavalent botulinum antitoxin to replace the legacy equine product.

Wearable tesla valve-based sweat collection device for sweat colorimetric analysis.

Sweat sensor has become one of the most important developing directions of in vitro wearable diagnostic device in recent years. Stable sweat collecting device is the key to realize sweat component analysis. In order to ensure that the collected sweat is not subject to component analysis errors caused by evaporation or environmental pollution, mechanical micro-valves were adopted for microfluidic sweat collection devices to realize sealed storage of sweat. However, this poses a challenge to the stability of machining and reusability of the acquisition device. In this work, the Tesla valve without any mechanical structure were introduced into the design of sweat collection chip. And made full use of its diodicity to improve the collection to a certain extent, prevent backflow at the entrance, and restrain the flow at the exit to contact with the outside world. In addition, through optimizing the shunt angle, branch channel parameters of Tesla valve, boosted its diodicity under low flow rate. Furthermore, a sweat storage chamber with baffle structure that can achieve maximum static storage area was adopted to form a whole sweat collection chip. The design was verified through the flow experiment of methylene blue and methyl red indicators on the chip. Through modification of the filter paper fixed in the collection chamber, the colorimetric analysis of glucose and pH was realized. This device may provide new inspirations for the development of wearable sweat sensor.

Multicolor fluorescence activated cell sorting to generate humanized monoclonal antibody binding seven subtypes of BoNT/F.

Generating specific monoclonal antibodies (mAbs) that neutralize multiple antigen variants is challenging. Here, we present a strategy to generate mAbs that bind seven subtypes of botulinum neurotoxin serotype F (BoNT/F) that differ from each other in amino acid sequence by up to 36%. Previously, we identified 28H4, a mouse mAb with poor cross-reactivity to BoNT/F1, F3, F4, and F6 and with no detectable binding to BoNT/F2, F5, or F7. Using multicolor labeling of the different BoNT/F subtypes and fluorescence-activated cell sorting (FACS) of yeast displayed single-chain Fv (scFv) mutant libraries, 28H4 was evolved to a humanized mAb hu6F15.4 that bound each of seven BoNT/F subtypes with high affinity (KD 5.81 pM to 659.78 pM). In contrast, using single antigen FACS sorting, affinity was increased to the subtype used for sorting but with a decrease in affinity for other subtypes. None of the mAb variants showed any binding to other BoNT serotypes or to HEK293 or CHO cell lysates by flow cytometry, thus demonstrating stringent BoNT/F specificity. Multicolor FACS-mediated antibody library screening is thus proposed as a general method to generate multi-specific antibodies to protein subtypes such as toxins or species variants.

Metabolites of arsenic and increased DNA damage of p53 gene in arsenic plant workers.

Recent studies have shown that monomethylarsonous acid is more cytotoxic and genotoxic than arsenate and arsenite, which may attribute to the increased levels of reactive oxygen species. In this study, we used hydride generation-atomic absorption spectrometry to determine three arsenic species in urine of workers who had been working in arsenic plants,and calculated primary and secondary methylation indexes. The damages of exon 5, 6, 8 of p53 gene were determined by the method developed by Sikorsky, et al. Results show that the concentrations of each urinary arsenic species,and damage indexes of exon 5 and 8 of p53 gene in the exposed population were significantly higher, but SMI was significantly lower than in the control group. The closely positive correlation between the damage index of exon 5 and PMI,MMA, DMA were found, but there was closely negative correlation between the damage index of exon 5 and SMI. Those findings suggested that DNA damage of exon 5 and 8 of p53 gene existed in the population occupationally exposed to arsenic. For exon 5, the important factors may include the model of arsenic metabolic transformation, the concentrations of MMA and DMA, and the MMA may be of great importance.

A Four-Monoclonal Antibody Combination Potently Neutralizes Multiple Botulinum Neurotoxin Serotypes C and D.

Human botulism can be caused by botulinum neurotoxin (BoNT) serotypes A to G. Here, we present an antibody-based antitoxin composed of four human monoclonal antibodies (mAbs) against BoNT/C, BoNT/D, and their mosaic toxins. This work built on our success in generating protective mAbs to BoNT /A, B and E serotypes. We generated mAbs from human immune single-chain Fv (scFv) yeast-display libraries and isolated scFvs with high affinity for BoNT/C, BoNT/CD, BoNT/DC and BoNT/D serotypes. We identified four mAbs that bound non-overlapping epitopes on multiple serotypes and mosaic BoNTs. Three of the mAbs underwent molecular evolution to increase affinity. A four-mAb combination provided high-affinity binding and BoNT neutralization of both serotypes and their mosaic toxins. The mAbs have potential utility as therapeutics and as diagnostics capable of recognizing and neutralizing BoNT/C and BoNT/D serotypes and their mosaic toxins. A derivative of the four-antibody combination (NTM-1634) completed a Phase 1 clinical trial (Snow et al., Antimicrobial Agents and Chemotherapy, 2019) with no drug-related serious adverse events.

A novel photostable near-infrared-to-near-infrared fluorescent nanoparticle for in vivo imaging.

Water-soluble K5 HoLi2 F10 (KHLF) nanoprobes with the excitation and emission both in the near-infrared (NIR) region were developed and first demonstrated for in vivo imaging of living mice. The PEG400 coating endows the nanoprobes with good water solubility and biocompatibility. Doping with Ho3+ ions is capable of emitting NIR fluorescence with two peaks centered, respectively, at 887 and 1,180 nm once excited by a 808 nm laser; meanwhile, it also possess good photothermal conversion performance. The KHLF matrix with specifically structure of large ion-distance and low photon energy imparts the nanoprobes low quenching effect and excellent photostability (fluorescence decrease <5% upon 120 min illumination of 808 nm continuous laser with a power density of 1 W/cm2 ). The nanoparticles (NPs) were tested for in vitro bioimaging with living mice. The results show the NPs have low biotoxicity, rapid metabolism, normal biodistribution, together with the photothermal imaging performance and a high-contrast fluorescence images (signal-to-background ratio of 14:1). The superior performances of these nanoprobes in vivo imaging of mice proclaim the great potential of this type of probe for high-contrast imaging and photothermal treatment in practical applications.

Oxidative damage of the extracts of condensate, particulate and semivolatile organic compounds from gasoline engine exhausts on testicles of rats.

Oxidative damage induced by extracts of condensate, particulate matters and semivolatile organic compounds from gasoline engine exhausts were investigated in testicles of adult Sprague-Dawley rats. The results showed that gasoline engine exhaust could increase the contents of malondialdehyde and carbonyl protein, decrease activities of superoxide dismutase and glutathione peroxidase, and induce DNA damage in testicle of rat. Taking together, the gasoline engine exhaust could promote oxidative damage of bio-macromolecular in testicles of rat and oxidative stress might be an alternative mechanism for male reproductive function of male mammals.

Increased damage of exon 5 of p53 gene in workers from an arsenic plant.

Mutagenesis is a multistage process. Substitution mutations can be induced by base modified through alteration of pairing property. Mutations of exon 5 and 8 of p53 gene have been found in most arsenicosis patients with precarcinomas and carcinomas, but never in arsenicosis individuals without precarcinomas and carcinomas. This study investigates whether base modification exists in exon 5 and 8 of p53 gene, and explores the dose-effect relationship between damage of exon 5 of p53 gene and urinary arsenic. Concentrations of urinary 8-hydroxydeoxyguanine (8-OHdG) are analyzed to identify the occurrence of DNA damage. The real-time PCR developed by Sikorsky et al. is applied to detect base modification in exon 5 and 8 of p53 gene for apparently healthy participants. Our results show that the mean total arsenic concentrations of two exposed groups from an arsenic plant are significantly elevated compared with the control group, and the damage level of exon 5 of the high-exposed group is significantly higher than that of the control group, but which does not happen in exon 8. The closely correlation between the damage index of exon 5 and urinary organic arsenic concentration are found. Concentration of 8-OHdG of the high-exposed group is significantly higher than that of the control group. These results imply that base modification in exon 5 of p53 gene can be induced by arsenic. In addition, our study suggests that the damage level of exon 5 is a useful biomarker to assess adverse health effect levels caused by chronic exposure to arsenic.

Relative miRNA and mRNA expression involved in arsenic methylation.

Three arsenic species in urine are measured using an atomic absorption spectrophotometer. RT-PCR is performed to detect the expression levels of AS3MT, 3 miRNAs, and 17 relative mRNAs in 43 workers producing arsenic trioxide, 36 workers who stopped exposure to arsenic for 85 days, and 24 individuals as the control group. The concentrations of urinary arsenic are very high in workers. A negative correlation between AS3MT and MiR-548c-3p is found. There exist significant changes for most selected miRNAs and mRNAs in workers. There are no significant differences between workers who stopped exposure to arsenic and the control group for most miRNAs and mRNAs, but the MiR-548c-3p levels show significant changes. Similar positive correlations between the expression of AS3MT and all selected mRNAs are found. Negative correlations between the expression of MiR-548c-3p and many relative mRNAs are found as well. AS3MT and MiR-548c-3p may regulate arsenic methylation jointly, which when involved in a group of relative mRNAs may play roles in arsenic metabolism and epigenetic changes caused by this metabolism.

Modulation of Cellular Response to Arsenic Trioxide Toxicity by Resveratrol.

Arsenic trioxide (As2O3) is an environmental carcinogen and a putative endocrine disruptor. Resveratrol has been shown to reverse As2O3-induced oxidative damage. In immortalized but nontransformed estrogen receptor α-negative human breast cells (MCF10A), we observed that 25 µM resveratrol ameliorated As2O3-induced cytotoxicity. As2O3, in the presence or absence of 25 µM resveratrol, induced quinone reductase (NAD(P)H quinone dehydrogenase 1), via the induction of NFE2-related factor 2. As2O3 caused a repression of cytochrome P450 (CYP)1B1, but the addition of 25 µM resveratrol rescued the expression of cytochrome P450 1B1 and kept it at a constant level. Therefore, 25 µM resveratrol can modulate the effects of As2O3 on enzymes involved in estrogen metabolism.

A Single Tri-Epitopic Antibody Virtually Recapitulates the Potency of a Combination of Three Monoclonal Antibodies in Neutralization of Botulinum Neurotoxin Serotype A.

The standard of treatment for botulism, equine antitoxin, is a foreign protein with associated safety issues and a short serum half-life which excludes its use as a prophylactic antitoxin and makes it a less-than-optimal therapeutic. Due to these limitations, a recombinant monoclonal antibody (mAb) product is preferable. It has been shown that combining three mAbs that bind non-overlapping epitopes leads to highly potent botulinum neurotoxin (BoNT) neutralization. Recently, a triple human antibody combination for BoNT/A has demonstrated potent toxin neutralization in mouse models with no serious adverse events when tested in a Phase I clinical trial. However, a triple antibody therapeutic poses unique development and manufacturing challenges. Thus, potentially to streamline development of BoNT antitoxins, we sought to achieve the potency of multiple mAb combinations in a single IgG-based molecule that has a long serum half-life. The design, production, and testing of a single tri-epitopic IgG1-based mAb (TeAb) containing the binding sites of each of the three parental BoNT/A mAbs yielded an antibody of nearly equal potency to the combination. The approach taken here could be applied to the design and creation of other multivalent antibodies that could be used for a variety of applications, including toxin elimination.

A Three Monoclonal Antibody Combination Potently Neutralizes Multiple Botulinum Neurotoxin Serotype E Subtypes.

Human botulism is most commonly caused by botulinum neurotoxin (BoNT) serotypes A, B, and E. For this work, we sought to develop a human monoclonal antibody (mAb)-based antitoxin capable of binding and neutralizing multiple subtypes of BoNT/E. Libraries of yeast-displayed single chain Fv (scFv) antibodies were created from the heavy and light chain variable region genes of humans immunized with pentavalent-toxoid- and BoNT/E-binding scFv isolated by Fluorescence-Activated Cell Sorting (FACS). A total of 10 scFv were isolated that bound one or more BoNT/E subtypes with nanomolar-level equilibrium dissociation constants (KD). By diversifying the V-regions of the lead mAbs and selecting for cross-reactivity, we generated three scFv that bound all four BoNT/E subtypes tested at three non-overlapping epitopes. The scFvs were converted to IgG that had KD values for the different BoNT/E subtypes ranging from 9.7 nM to 2.28 pM. An equimolar combination of the three mAbs was able to potently neutralize BoNT/E1, BoNT/E3, and BoNT/E4 in a mouse neutralization assay. The mAbs have potential utility as therapeutics and as diagnostics capable of recognizing multiple BoNT/E subtypes. A derivative of the three-antibody combination (NTM-1633) is in pre-clinical development with an investigational new drug (IND) application filing expected in 2018.

[Study on the association between urinary organic arsenic and 8-hydroxydeoxyguanine in workers exposed to arsenic].

OBJECTIVE: To evaluate the association between metabolism of arsenic and DNA oxidative damage in workers in a arsenic mill. METHODS: Urinary organic arsenic and 8-hydroxydeoxyguanine were detected in 37 workers highly exposed to arsenic and 16 administrative and logistic staff with mild exposure in a arsenic mill in Yunnan province, and also 28 local people who did not have the exposure in the near past time. The correlation between metabolism of arsenic and DNA oxidative damage was evaluated. RESULTS: The urinary organic arsenic concentration was respectively (0.48 +/- 0.37) mg/L and (0.08 +/- 0.05) mg/L for men with high and low exposure, and was respectively 0.11 mg/L and (0.30 +/- 0.24) mg/ L for women with high and low exposure, while it was lower than 0.02 mg/L in the controls. Urinary 8-hydroxydeoxyguanine concentration was (18.07 +/- 11.68) micromol/mol creatinine, (11.79 +/- 8.25) micromol/mol creatinine, (10.07 +/- 3.04) micromol/mol creatinine for the males with high and low exposure and of controls, respectively, (P < 0.05), and it was 84.35 micromol/mol creatinine, (21.27 +/- 5.89) micromol/mol creatinine, (14.43 +/- 2.58) micromol/mol creatinine for females with high and low exposure and of controls, respectively. The female workers exposed to arsenic had higher urinary 8-hydroxydeoxyguanine levels than males did (P < 0.05). The increased tendencies of urinary 8-hydroxydeoxyguanine levels with the organic arsenic concentration were found in workers (r(s) = 0.279, P = 0.019). CONCLUSION: Occupational individuals exposed to arsenic have obvious DNA oxidative damage, which is more severe in females. The difference of metabolism of arsenic may play a key role.