Changes in serum thioredoxin among individuals chronically exposed to arsenic in drinking water

It is well known that oxidative damage plays a key role in the development of chronic arsenicosis. There is a complex set of mechanisms of redox cycling in vivo to protect cells from the damage. In this study, we examined the differences in the levels of serum thioredoxin1 (TRX1) among individuals exposed to different levels of arsenic in drinking water and detected early biomarkers of arsenic poisoning before the appearance of skin lesions. A total of 157 subjects from endemic regions of China were selected and divided into arsenicosis group with skin lesions (total intake of arsenic: 8.68-45.71 mg-year) and non-arsenicosis group without skin lesions, which further divided into low (0.00-1.06 mg-year), medium (1.37-3.55 mg-year), and high (4.26-48.13 mg-year) arsenic exposure groups. Concentrations of serum TRX1 were analyzed by an ELISA method. Levels of water arsenic and urinary speciated arsenics, including inorganic arsenic (iAs), monomethylated arsenic (MMA), and dimethylated arsenic (DMA), were determined by hydride generation atomic absorption spectrometry. Our results showed that the levels of serum TRX1 in arsenicosis patients were significantly higher than that of the subjects who were chronically exposed to arsenic, but without skin lesions. A positive correlation was seen between the levels of serum TRX1 and the total water arsenic intake or the levels of urinary arsenic species. The results of this study indicate that arsenic exposure could significantly change the levels of human serum TRX1, which can be detected before arsenic-specific dermatological symptoms occur. This study provides further evidence on revealing the mechanism of arsenic toxicity.     

Altered activity of heme biosynthesis pathway enzymes in individuals chronically exposed to arsenic in Mexico

Our objective was to evaluate the activities of some enzymes of the heme biosynthesis pathway and their relationship with the profile of urinary porphyrin excretion in individuals exposed chronically to arsenic (As) via drinking water in Region Lagunera, Mexico. We selected 17 individuals from each village studied: Benito Juarez, which has current exposure to 0.3 mg As/l; Santa Ana, where individuals have been exposed for more than 35 years to 0.4 mg As/l, but due to changes in the water supply (in 1992) exposure was reduced to its current level (0.1 mg As/l), and Nazareno, with 0.014 mg As/l. Average arsenic concentrations in urine were 2058, 398, and 88 μg As/g creatinine, respectively. The more evident alterations in heme metabolism observed in the highly exposed individuals were: (1) small but significant increases in porphobilinogen deaminase (PBG-D) and uroporphyrinogen decarboxylase (URO-D) activities in peripheral blood erythrocytes; (2) increases in the urinary excretion of total porphyrins, mainly due to coproporphyrin III (COPROIII) and uroporphyrin III (UROIII); and (3) increases in the COPRO/URO and COPROIII/COPROI ratios. No significant changes were observed in uroporphyrinogen III synthetase (UROIII-S) activity. The direct relationships between enzyme activities and urinary porphyrins, suggest that the increased porphyrin excretion was related to PBG-D, whereas the increased URO-D activity would enhance coproporphyrin synthesis and excretion at the expense of uroporphyrin. None of the human studies available have reported the marked porphyric response and enzyme inhibition observed in rodents. In conclusion, chronic As exposure alters human heme metabolism; however the severity of the effects appears to depend on characteristics of exposure not yet fully characterized. Received: 21 December 1998 / Accepted: 14 January 1999     

Randomized placebo-controlled trial of 2,3-dimercapto-1-propanesulfonate (DMPS) in therapy of chronic arsenicosis due to drinking arsenic-contaminated water.

BACKGROUND: Chronic arsenic toxicity, producing various clinical manifestations, is currently epidemic in West Bengal, India, Bangladesh, and other regions of the world. 2,3-Dimercapto-1-propanesulfonate, a chelating agent, increases excretion of arsenic in urine to several times the prechelation concentration but the therapeutic efficacy of 2,3-dimercapto-1-propanesulfonate in the management of chronic arsenic toxicity has been incompletely evaluated. We investigated the clinical use of 2,3-dmercapto-1-propanesulfonate in such patients. METHODS: Twenty-one consecutive patients with chronic arsenicosis were individually randomized into 2 groups: 11 patients (9 males and 2 females, age 30.63+/-11.4 years) received 2,3-dimercapto-1-propanesulfonate 100-mg capsules 4 times a day for 1 week and repeated in the 3rd, 5th, and 7th week with no drug during the intervening period. The other 10 patients (5 males and 5 females, age 34.4+/-14.41 years) were given placebo capsules (resembling 2,3-dimercapto-1-propanesulfonate) in the same schedule. The consumption of arsenic-contaminated water was terminated by all 21 subjects. Initial and posttreatment urinary arsenic excretion was determined in all cases. Sequential excretion of urinary arsenic was determined during the treatment of 2 drug- and 1 placebo-treated cases. The clinical features were evaluated by an objective scoring system before and after treatment. Routine investigation including liver function test and skin biopsy were also done before and after the treatment. Drug-associated toxicity was tabulated. RESULTS: Therapy with 2,3-dimercapto-1-propanesulfonate caused significant improvement in the clinical condition of chronic arsenicosis patients as evidenced by significant reduction of total clinical scores from 8.90+/-2.84 to 3.27+/-1.73; p < 0.0001. Exposure cessation alone with placebo treatment also reduced clinical scores (8.50+/-1.96 to 5.40+/-2.12; p < 0.003), but the posttreatment total clinical score of 2,3-dimercapto-1-propanesulfonate-treated patients (3.27+/-1.73) was significantly lower than that of placebo-treated patients (5.40+/-2.12; p < 0.01). The most significant improvement was noted in regard to the clinical scores of weakness, pigmentation, and lung disease. No difference was noted between groups in the hematological and biochemical parameters (which were normal) and skin histology before and after treatment. No 2,3-dimercapto-1-propanesulfonate-related adverse effects were noted. Total urinary excretion of arsenic in 2,3-dimercapto-1-propanesulfonate-treated cases increased significantly following drug therapy, with no increase in placebo-treated cases. CONCLUSION: 2,3-Dimercapto-1-propanesulfonate treatment caused significant improvement in the clinical score of patients suffering from chronic arsenic toxicity. Increased urinary excretion of arsenic during the period of therapy is the possible cause of this improvement.     

Urinary porphyrin profiles as biomarkers of trace metal exposure and toxicity: Studies on urinary porphyrin excretion patterns in rats during prolonged exposure to methyl mercury

Studies were conducted to define the specific changes in the urinary porphyrin excretion pattern (porphyrin profile) and the time course of those changes in rats exposed to mercury as methyl mercury hydroxide (MMH) at 5 or 10 ppm in the drinking water for up to 30 weeks. The urinary porphyrin profile elicited by MMH is uniquely characterized by highly elevated levels of 4- and 5-carboxyl porphyrins, and of a third atypical porphyrin with as yet undetermined chemical characteristics. Changes in the porphyrin profile were observed as early as 1 or 2 weeks following initiation of exposure to MMH at 10 or 5 ppm, respectively, and were sustained as long as 40 weeks following cessation of MMH treatment. The magnitude of the urinary porphyrin profile at either MMH dose level increased progressively during the course of mercury treatment and was highly correlated with the renal mercury concentration. A subsequent decline in the magnitude of the urinary porphyrin profile in animals exposed to 10 ppm MMH for more than 10 weeks was associated with the accumulation of high levels of Hg2+ in kidney cells and loss of renal functional status. These findings demonstrate that mercury elicits a unique change in the urinary porphyrin excretion pattern which is related to the dose and duration of mercury treatment. The association of urinary porphyrin excretion rates with renal mercury content and functional status suggests that urinary porphyrin profiles may serve as a useful biomarker of mercury accumulation and nephrotoxicity during prolonged mercury exposure.     

DNA hypermethylation of promoter of gene p53 and p16 in arsenic-exposed people with and without malignancy.

Chronic arsenic exposure is known to produce arsenicosis and cancer. To ascertain whether perturbation of methylation plays a role in such carcinogenesis, the degree of methylation of p53 and p16 gene in DNA obtained from blood samples of people chronically exposed to arsenic and skin cancer subjects was studied. Methylation-specific restriction endonuclease digestion followed by polymerase chain reaction (PCR) of gene p53 and bisulfite treatment followed by methylation-sensitive PCR of gene p16 have been carried out to analyze the methylation status of the samples studied. Significant DNA hypermethylation of promoter region of p53 gene was observed in DNA of arsenic-exposed people compared to control subjects. This hypermethylation showed a dose-response relationship. Further, hypermethylation of p53 gene was also observed in arsenic-induced skin cancer patients compared to subjects having skin cancer unrelated to arsenic, though not at significant level. However, a small subgroup of cases showed hypomethylation with high arsenic exposure. Significant hypermethylation of gene p16 was also observed in cases of arsenicosis exposed to high level of arsenic. In man, arsenic has the ability to alter DNA methylation patterns in gene p53 and p16, which are important in carcinogenesis.     

Arsenic contamination and arsenicosis in China

Arsenicosis is a serious environmental chemical disease in China mainly caused by drinking water from pump wells contaminated by high levels of arsenic. Chronic exposure of humans to high concentrations of arsenic in drinking water is associated with skin lesions, peripheral vascular disease, hypertension, blackfoot disease, and high risk of cancers. Lead by the Ministry of Health of China, we carried out a research about arsenicosis in China recently. Areas contaminated with arsenic from drinking water are determined by 10% pump well water sample method while areas from burning coal are determined by existing data. Two epidemic areas of Shanxi Province and Inner Mongolia are investigated for the distribution of pump wells containing high arsenic. Well water in all the investigated villages of Shanxi Province showed polluted by high arsenic, and the average rate of unsafe pump well water is 52%. In Inner Mongolia, the high percentage of pump wells containing elevated arsenic is found only in a few villages. The average rate of unsafe pump well water is 11%. From our research, we find that new endemic areas are continuously emerging in China. Up to now, epidemic areas of arsenicosis mainly involve eight provinces and 37 counties in China. In the affected areas, the discovery of wells and coal with high levels of arsenic is continuing sporadically, and a similar scattered distribution pattern of patients is also being observed.     

Quantitative evaluation of urinary porphyrins as a measure of kidney mercury content and mercury body burden during prolonged methylmercury exposure in rats.

Changes in urinary porphyrin excretion patterns (porphyrin profiles) during prolonged mercury exposure are attributable to mercury accumulation in the kidney and to consequent effects of Hg2+ on renal porphyrin metabolism. In the present study, we evaluated the quantitative relationship of urinary porphyrin concentrations to mobilizable renal mercury content, using the metal chelator 2,3-dimercapto-1-propanesulfonic acid (DMPS) to modulate kidney mercury levels. Rats exposed to methylmercury hydroxide (MMH) at 10 ppm in drinking water for 6 weeks were treated with up to 3 consecutive doses of DMPS (100mg/kg, ip) at 72-h intervals. Consistent with previous findings, the concentrations of pentacarboxyl- (5-) and copro- (4-) porphyrins and of an atypical porphyrin specific to mercury exposure, precoproporphyrin, were significantly elevated in urine of MMH-exposed rats, compared with that of rats exposed to distilled water (dH2O) for the same period. Consecutive DMPS treatments of MMH-exposed rats significantly decreased kidney concentrations of total, as well as Hg2+ and CH3Hg+ species, and promoted increased urinary mercury excretion. Concomitantly, DMPS treatment decreased both kidney and urinary porphyrin concentrations, consistent with depletion of renal mercury levels. Regression analyses demonstrated a high correlation (r approximately 0.9) between prechelation urinary porphyrins and postchelation urinary mercury levels and also between prechelation urinary porphyrins and prechelation kidney mercury concentrations. These findings demonstrate that urinary porphyrin concentrations relate quantitatively to DMPS-mobilizable mercury in the kidney and, therefore, serve as a biochemical measure of renal mercury content.     

Analysis of T-cell proliferation and cytokine secretion in the individuals exposed to arsenic

Over six million people in nine districts of West Bengal, India are exposed to very high levels of arsenic primarily through their drinking water. More than 300,000 people showed arsenic-induced skin lesions in these districts. This is regarded as the greatest arsenic calamity in the world. Chronic arsenicosis causes varied dermatological signs ranging from pigmentation changes, hyperkeratosis to non-melanocytic cancer of skin, and also malignancies in different internal organs. Higher incidences of opportunistic infections are found in the arsenic-exposed individuals, indicating that their immune systems may be impaired somehow. We have thus investigated the effect of arsenic on T-cell proliferation and cytokine secretion in 20 individuals with arsenic-induced skin lesions and compared the results with 18 arsenic-unexposed individuals. A marked dose-dependent suppression of Concanavalin A (Con A) induced T-cell proliferation was observed in the arsenic-exposed individuals compared with the unexposed (P < 0.001) individuals. This correlated with a significant decrease in the levels of secreted cytokines by the T cells (TNF-alpha, IFN-gamma, IL2, IL10, IL5, and IL4) in the exposed individuals (P < 0.001). Thus it can be inferred that arsenic exposure can cause immunosuppression in humans.     

High-dose vitamin E lowers urine porphyrin levels in patients affected by porphyria cutanea tarda.

Porphyria cutanea tarda (PCT) is a metabolic disorder of heme biosynthesis, characterized by reduced uroporphyrinogen decarboxylase (UROD) activity and increased urinary excretion of eight and seven carboxyl group porphyrins. Specific factors such as iron, alcohol and halogenated compounds further inhibit enzyme activity by generating reactive oxygen species. Antioxidant vitamin E has frequently been used to counteract oxidative stress in porphyria patients, but a number of studies have failed to detect any significant effect on porphyrin metabolism. Since the use of vitamin E in the treatment of porphyria is a debated question, it seemed of interest to administer high doses to five patients with PCT in order to evaluate the effects on urine porphyrin excretion. The patients had high urinary porphyrin excretion levels, but vitamin E significantly reduced the urinary excretion of eight carboxyl group porphyrins. This result is attributable to the increase in UROD activity caused by the vitamin, which is a known scavenger of the oxygen reactive species that interfere with the activity of the enzyme. In conclusion, this paper shows that vitamin E high doses significantly lowers the urine porphyrin excretion in studied patients affected by PCT.     

Oxidative DNA damage of peripheral blood polymorphonuclear leukocytes,selectively induced by chronic arsenic exposure,is associated with extent of arsenic-related skin lesions

There is increasing evidence that oxidative stress is an important risk factor for arsenic-related diseases. Peripheral blood leukocytes constitute an important defense against microorganisms or pathogens, while the research on the impact of chronic arsenic exposure on peripheral blood leukocytes is much more limited, especially at low level arsenic exposure. The purpose of the present study was to explore whether chronic arsenic exposure affects oxidative stress of peripheral blood leukocytes and possible linkages between oxidative stress and arsenic-induced skin lesions. 75 male inhabitants recruited from an As-endemic region of China were investigated in the present study. The classification of arsenicosis was based on the degree of skin lesions. Arsenic levels were measured in drinking water and urine by Atomic Fluorescence Spectroscopy. Urinary 8-hydroxy-2′-deoxyguanosine (8-OHdG) was tested by Enzyme-Linked Immunosorbent Assay. 8-OHdG of peripheral blood leukocytes was evaluated using immunocytochemical staining. 8-OHdG-positive reactions were only present in polymorphonuclear leukocytes (PMNs), but not in monocytes (MNs). The 8-OHdG staining of PMN cytoplasm was observed in all investigated populations, while the 8-OHdG staining of PMN nuclei was frequently found along with the elevated amounts of cell debris in individuals with skin lesion. Urinary arsenic levels were increased in the severe skin lesion group compared with the normal group. No relationship was observed between drinking water arsenic or urine 8-OHdG and the degree of skin lesions. These findings indicated that the target and persistent oxidative stress in peripheral blood PMNs may be employed as a sensitive biomarker directly to assess adverse health effects caused by chronic exposure to lower levels of arsenic.     

Clinical manifestations and arsenic methylation after a rare subacute arsenic poisoning accident

One hundred and four workers ingested excessive levels of arsenic in an accident caused by leakage of pipeline in a copper-smelting factory. Clinical examinations were performed by physicians in a local hospital. Excreted urinary arsenic species were determined by cold trap hydride generation atomic absorption spectrometry. In the initial toxic phase, gastrointestinal symptoms were predominant (83 people, 79.8%). Most patients showed leucopenia (72 people, 69.2%), and increased serum alanine aminotransferase (84 people, 80.8%) and aspartate aminotransferase (58 people, 55.8%). Thirty-five patients (33.6%) had elevated red blood cells in urine. After 17 days of admission, many subjects (45 people, 43.3%) developed peripheral neuropathy and 25 of these 45 patients (24.0%) showed a decrease in motor and sensory nerve conduction velocity. In the comparison of urinary arsenic metabolites among subacute arsenic-poisoned, chronic high arsenic-exposed and control subjects, we found that subacute arsenic-poisoned patients had significantly elevated proportions of urinary inorganic arsenic (iAs) and methylarsonic acid (MMA) but reduced proportion of urinary dimethylarsinic acid (DMA) compared with chronic high arsenic-exposed and control subjects. Chronic exposed subjects excreted higher proportions of iAs and MMA but lower proportions of DMA in urine compared with control subjects. These results suggest that gastrointestinal symptoms, leucopenia, and hepatic and urinary injury are predominant in the initial phase of subacute arsenic poisoning. Peripheral neuropathy is the most frequent manifestation after the initial phase. The biomethylation of arsenic decreases in a dose rate-dependent manner.     

Application of cDNA microarray to the study of arsenic-induced liver diseases in the population of Guizhou, China.

Arsenic is an environmental toxicant and a human carcinogen. Epidemiology studies link human arsenic exposure to various diseases and cancers, including liver diseases and hepatocellular carcinoma. However, the molecular mechanisms for arsenic toxicity and carcinogenicity are poorly understood. To better understand these mechanisms, we used the human cancer cDNA expression array to profile aberrant gene expression in arsenic-exposed populations in Guizhou, China. The selected patients had a history of exposure to environmental arsenic for at least 6-10 years, and had arsenic-induced skin lesions and hepatomegaly. Samples were obtained by liver needle biopsy. Histology showed degenerative liver lesions, such as chronic inflammation, vacuolation, and focal necrosis. The University of North Carolina Hospitals provided normal human liver tissues from surgical resection or rejected transplants. Microarray was performed with total RNA from liver samples, and signal intensities were analyzed with AtlasImage software and normalized with 9 housekeeping genes. Means and SEM were calculated for statistical analysis. Approximately 60 genes (10%) were differentially expressed in arsenic-exposed human livers compared to controls. The differentially expressed genes included those involved in cell-cycle regulation, apoptosis, DNA damage response, and intermediate filaments. The observed gene alterations appear to be reflective of hepatic degenerative lesions seen in the arsenic-exposed patients. This array analysis revealed important patterns of aberrant gene expression occurring with arsenic exposure in human livers. Aberrant expressions of several genes were consistent with the results of array analysis of chronic arsenic-exposed mouse livers and chronic arsenic-transformed rat liver cells. Clearly, a variety of gene expression changes may play an integral role in arsenic hepatotoxicity and possibly carcinogenesis.     

Structure-function alteration of hemoglobin in arsenicosis patients: a probable pathway to exert toxicity

Chronic arsenicosis, a major public health concern in India and Bangladesh, is mainly caused by ingestion of arsenic (As) contaminated ground water. Although this problem has been studied extensively, the mechanism of toxicity remains unknown. This paper investigates the process of trivalent arsenicals binding to hemoglobin (Hb) in chronic arsenicosis patients and consequent modification in the structure–function activity of Hb. In this work peroxidase activity, thermal denaturation profile, oxygen releasing capacity and hydrodynamic diameter have been evaluated for the Hb collected from subjects suffering with chronic arsenicosis. Increased peroxidative activity suggests altered oxidative status of Hb in the diseased state. The thermal denaturation profile indicates the Hb molecule to be more susceptible to unfolding in the pathologic state. The enhanced oxygen releasing capacity and significant reduction in hydrodynamic diameter of Hb is also observed in the diseased condition, suggesting conformational alterations in the Hb molecule. Finally, trivalent arsenic is found to bind with freshly isolated Hb from arsenicosis patients, binding affinity constant being 0.256 μM^?1. The binding is positively cooperative with a Hill coefficient of +2.961 and isosbestic points at specific wavelengths. Thus, our work explores the structure–function property of Hb in chronic arsenicosis subjects and reveals that the molecule is modified in such a way that comparatively weak binding with oxygen and strong binding with arsenic occur simultaneously. This association may play a crucial role in exerting the pathway for arsenic toxicity. Copyright © 2011 John Wiley & Sons, Ltd.     

Increased glycophorin A somatic cell variant frequency in arsenic-exposed patients of Guizhou, China

Exposure to arsenic through domestic burning arsenic-containing coal causes various tumors in a population of Guizhou, China. The glycophorin A (GPA) assay is a human mutation assay detecting somatic variation in erythrocytes expressing the MN blood type, and was used to assess genotoxicity of arsenic-exposed patients. Peripheral blood was collected from 18 adult healthy subjects and 40 arsenic-exposed patients in heparin-treated tubes. Erythrocytes were isolated, fixed in formalin and immuno-labeled with fluorescent antibodies against GPA, followed by flow cytometry analysis. Arsenic exposure increased the variant frequency (expressed as the number of variant red cells per 10(6) erythrocytes): NN, 3.7 in healthy subjects versus 21.2 in arsenic-exposed patients; N phi, 12.6 versus 33.1; MM, 13.1 versus 110; and M phi, 5.2 versus 20.3. The total GPA variant frequency was increased about five-fold (34.7 in healthy subjects versus 185 in arsenosis patients). Furthermore, the variant frequency was significantly higher in skin tumor-bearing patients: NN, 19.4 in arsenic-exposed non-tumor patients versus 31.5 in tumor-bearing patients; N phi, 29.5 versus 54.5; MM, 102 versus 159; M phi, 15.9 versus 45.1. Total GPA variant frequency in arsenic-exposed patients bearing skin tumors was significantly increased compared to patients without skin tumors (167 versus 290). The relationship between arsenic exposure history and GPA variant frequency was less evident. These data demonstrate that arsenic exposure is associated with mutations at the GPA locus, an effect exaggerated in patients bearing arsenic-induced skin tumors. The variant frequency of GPA could be a useful biomarker for arsenic exposure and arsenic carcinogenesis.     

A pilot study on the urinary excretion of porphyrins in human populations chronically exposed to arsenic in Mexico.

1 The aim of this pilot study was to investigate if the porphyrinuria produced by arsenic in rodents was present in humans chronically exposed to arsenic via drinking water. 2 The concentrations of uroporphyrin, coproporphyrin and total arsenic in urine were compared between 21 individuals exposed to arsenic in their drinking water (0.390 mg l-1) and 19 controls exposed to 0.012 mg l-1. 3 Arsenic-exposed individuals had significantly higher total arsenic concentrations in their urine than the control group. No increase in urinary porphyrin excretion was found in exposed individuals. However, an inversion of the coproporphyrin/uroporphyrin (COPRO/URO) ratio was observed in most exposed individuals. This inversion was caused both, by a decrease in coproporphyrin excretion and an increase in uroporphyrin excretion. 4 No demonstrable correlations between porphyrin excretion, the COPRO/URO ratio and total arsenic concentration in urine were found in exposed individuals.     

Arsenic methylation capacity and its correlation with skin lesions induced by contaminated drinking water consumption in residents of chronic arsenicosis area

Chronic exposure to excess level of arsenic through contaminated drinking water is associated with many injuries, among which skin lesions are the most prominent. In this study, we measured the concentrations of inorganic arsenic (iAs), monomethylarsonic acid (MMA), and dimethylarsinic acid (DMA) in the blood of the residents of arsenicosis area, who demonstrated different skin lesion grade from mild, moderate to advanced. We evaluated the individual methylation capacity by two indices of the first and secondary methylation ratio (FMR and SMR). We found that SMR of moderate and advanced groups were markedly lower than that of mild group. Significant negative correlation was found between SMR of all the subjects and the grade of skin lesion, with Spearman's correlation coefficient of ?0.429 (P = 0.016). Moreover, blood MMA proportion of moderate and advanced groups was found to be significantly higher than that of the mild group. These results suggest that low secondary arsenic methylation capacity and high MMA proportion are associated with the severity of arsenic‐related skin lesions. Our findings evaluated by blood speciation is consistent with that evaluated by the generally accepted urinary arsenic speciation in the relationship between arsenic methylation capacity and arsenic‐related lesions. © 2009 Wiley Periodicals, Inc. Environ Toxicol 26: 118–123, 2011.     

Urinary arsenic and porphyrin profile in C57BL/6J mice chronically exposed to monomethylarsonous acid (MMAIII) for two years

Arsenicals are proven carcinogens in humans and it imposes significant health impacts on both humans and animals. Recently monomethylarsonous acid (MMA(III)), the toxic metabolite of arsenic has been identified in human urine and believed to be more acutely toxic than arsenite and arsenate. Arsenic also affects the activity of a number of haem biosynthesis enzymes. As a part of 2-year arsenic carcinogenicity study, young female C57BL/6J mice were given drinking water containing 0, 100, 250 and 500 microg/L arsenic as MMA(III)ad libitum. 24 h urine samples were collected at 0, 1, 2, 4, 8 weeks and every 8 weeks for up to 104 weeks. Urinary arsenic speciation and porphyrins were measured using HPLC-ICP-MS and HPLC with fluorescence detection respectively. DMA(V) was a major urinary metabolite detected. Significant dose-response relationship was observed between control and treatment groups after 1, 4, 24, 32, 48, 56, 88, 96 and 104 weeks. The level of uroporphyrin in 250 and 500 microg As/L group is significantly different from the control group after 4, 8, 16, 32, 56, 72, 80, 96 and 104 weeks. Coproporphyrin I level in 500 microAs/L group is significantly different from control group after 8, 24, 32, 40, 56, 72, 80, 88 and 104 weeks. After 4 weeks the level of coproporphyrin III concentration significantly increased in all the treatment groups compared to the control except week 16 and 48. Our results show urinary DMA(V) and porphyrin profile can be used as an early warning biomarker for chronic MMA(III) exposure before the onset of cancer.     

Porphyrogenic effect of chronic treatment with 2,3,7,8-tetrachlorodibenzo-p-dioxin in female rats. Dose-effect relationship following urinary excretion of porphyrins

The porphyrogenic effect of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) was evaluated in female rats treated chronically for 45 weeks with 0.01, 0.10, and 1.00 μg/kg TCDD per week. The time course of the urinary porphyrin pattern was followed in order to determine the qualitative and quantitative composition in urine and to test the sensitivity of a parameter such as porphyrins in urine as an indication of exposure to TCDD. The results showed that the dose of 0.01 μg/kg/week resulted in significantly enhanced excretion of coproporphyrin from 6 months onward; with the dose of 0.10 μg/kg/week coproporphyrinuria was observed after 3 months and was associated at 10 months with a significant rise in uroporphyrin. The highest dose (1.00 μg/kg/week) caused enhanced excretion of coproporphyrin from 2 months onward. This effect was associated, at 6 months, with an increase in heptacarboxylic porphyrin and uroporphyrin excretion. A marked porphyric state was established in this group of animals from 8 months onward as indicated by massive enhancement of total urinary porphyrin excretion (about 70 times higher than the control group) with a large prevalence of porphyrins with a high number of carboxyl groups and reversal of the coproporphyrin/uroporphyrin ratio. Accumulation of porphyrins was also observed in liver, spleen, and kidneys of this group of animals. Terminal livers of rats treated with 0.01, 0.10, and 1.00 μg/kg/week contained 1050, 4740, and 30,700 ppt, respectively. Comparison of our data with the literature on the porphyrogenic effect of hexachlorobenzene indicated that TCDD can be considered 1400 times more potent.     

hOGG1 promoter methylation,hOGG1 genetic variants and their interactions for risk of coal-borne arsenicosis: A case-control study

To identify the effect of hOGG1 methylation, Ser326Cys polymorphism and their interactions on the risk of coal-borne arsenicosis, 113 coal-borne arsenicosis subjects and 55 reference subjects were recruited. Urinary arsenic contents were analyzed with ICP-MS. hOGG1 methylation and Ser326Cys polymorphism was measured by mehtylation-specific PCR and restriction fragment length polymorphism PCR in PBLCs, respectively. The results showed that the prevalence of methylated hOGG1 and variation genotype (326 ^Ser/Cys & 326 ^Cys/Cys) were increased with raised levels of urinary arsenic in arsenicosis subjects. Increased prevalence of methylated hOGG1 and variation genotype were associated with raised risk of arsenicosis. Moreover, the results revealed that variant genotype might increase the susceptibility to hOGG1 methylation. The interactions of methylated hOGG1 and variation genotype were also found to contribute to increased risk of arsenicosis. Taken together, hOGG1 hypermethylation, hOGG1 variants and their interactions might be potential biomarkers for evaluating risk of coal-borne arsenicosis.     

Pilot survey of urinary porphyrins from persons transiently exposed to a PCB transformer fire

In rats and humans chronically exposed to large amounts of PCB (polychlorinated biphenyls) and PCDF (polychlorinated dibenzofurans), the urinary excretion of uroporphyrin and coproporphyrin are altered. However, porphyrin excretion in humans after acute transient low level exposure has not been evaluated. Following such an exposure in which bystanders and firefighters were in contact with smoke from a PCB transformer fire, we surveyed 90 self-referred individuals by questionnaire and by determining single 24 hour urinary excretion of uroporphyrin and coproporphyrin 2-4 weeks after the fire. Questionnaire variables that assessed exposure were not associated with the magnitude of either uroporphyrin or coproporphyrin excretion. Uroporphyrin excretion was slightly elevated in nine subjects (range 66-106 micrograms/24 hours, normal less than 60), which is much less than in clinical cases of porphyria cutanea tarda. Uroporphyrin excretion was inversely correlated with coproporphyrin excretion (r = -0.3844, p = 0.0002). For 5 subjects (3 with elevated initial uroporphyrin excretion) retested at 3-4 weeks after the fire, all 5 showed increases in uroporphyrin and decreases in coproporphyrin excretion when compared to initial determinations. These two reciprocal relationships would be the expected result from inhibition of uroporphyrinogen decarboxylase, a known experimental effect of PCB and PCDF in mice. Overall, urinary porphyrin excretions were not altered or sensitive measures of exposure.