Effect of arsenic exposure on alveolar macrophage function. I. Effect of soluble as(III) and as(V)

In vitro assessment of arsenic mobility in historical mine waste dust using simulated lung fluid

Exposure studies have linked arsenic (As) ingestion with disease in mining-affected populations; however, inhalation of mine waste dust as a pathway for pulmonary toxicity and systemic absorption has received limited attention. A biologically relevant extractant was used to assess the 24-h lung bioaccessibility of As in dust isolated from four distinct types of historical gold mine wastes common to regional Victoria, Australia. Mine waste particles less than 20 µm in size (PM₂₀) were incubated in a simulated lung fluid containing a major surface-active component found in mammalian lungs, dipalmitoylphosphatidylcholine. The supernatants were extracted, and their As contents measured after 1, 2, 4, 8 and 24 h. The resultant As solubility profiles show rapid dissolution followed by a more modest increasing trend, with between 75 and 82% of the total 24-h bioaccessible As released within the first 8 h. These profiles are consistent with the solubility profile of scorodite, a secondary As-bearing phase detected by X-ray diffraction in one of the investigated waste materials. Compared with similar studies, the cumulative As concentrations released at the 24-h time point were extremely low (range 297 ± 6-3983 ± 396 µg L^-1), representing between 0.020 ± 0.002 and 0.036 ± 0.003% of the total As in the PM₂₀.

Imbalanced immune responses involving inflammatory molecules and immune-related pathways in the lung of acute and subchronic arsenic-exposed mice

Inorganic arsenic has been claimed to increase the risk of pulmonary diseases through ingestion, as opposed to inhalation, which makes it a unique and intriguing environmental toxicant. However, the immunotoxic effects of lung, one of the targets of arsenic exposure, have not been extensively investigated in vivo. In the present study, we first confirmed that 2.5, 5 and 10mg/kg NaAsO₂ orally for 24h dose-dependently triggered the infiltration of neutrophils, lymphocytes and macrophages in BALF. Not only the transcription activity, but also the secretion of proinflammatory cytokines IL-1β, IL-6 and TNF-α were consistently raised in the lung and BALF of acute arsenic-exposed mice. Acute oral administration of NaAsO₂ also raised pulmonary MPO activity and mRNA levels of chemokine Mip-2 and Mcp-1. Meanwhile, obvious histopathological damages with inflammatory cells infiltration and erythrocyte aggregation around the capillaries were verified in the lung of mice drank arsenic-rich water freely for 3 months. Furthermore, we affirmed notable disturbance of CD4⁺ T-cell differentiation in the lung of acute arsenic-exposed mice, as demonstrated by up-regulated mRNA levels of regulator Gata3 and cytokine Il-4 of Th2, enhanced Foxp3 and Il-10 of Treg, down-regulated T-bet and Ifn-γ of Th1, as well as lessened Ror-γt and Il-23 of Th17. However, impressive elevation of cytokine Ifn-γ and Il-23, as well as moderate enhancement of Il-4 and Il-10 were found in the lung by subchronic arsenic administration. Finally, our present study demonstrated that both a single and sustained arsenic exposure prominently increased the expression of immune-related p38, JNK, ERK1/2 and NF-κB proteins in the lung tissue. While disrupting the pulmonary redox homeostasis by increasing MDA levels, exhausting GSH and impaired enzyme activities of CAT and GSH-Px, antioxidant regulator NRF2 and its downstream targets HO-1 and GSTO1/2 were also up-regulated by both acute and subchronic arsenic treatment. Conclusively, our present study demonstrated both acute and subchronic oral administration of arsenic triggers multiple pulmonary immune responses involving inflammatory molecules and T-cell differentiation, which might be closely associated with the imbalanced redox status and activation of immune-related MAPKs, NF-κB and anti-inflammatory NRF2 pathways.

Arsenic and Immune Response to Infection During Pregnancy and Early Life

PURPOSE OF REVIEW

Arsenic, a known carcinogen and developmental toxicant, is a major threat to global health. While the contribution of arsenic exposure to chronic diseases and adverse pregnancy and birth outcomes is recognized, its ability to impair critical functions of humoral and cell-mediated immunity-including the specific mechanisms in humans-is not well understood. Arsenic has been shown to increase risk of infectious diseases that have significant health implications during pregnancy and early life. Here, we review the latest research on the mechanisms of arsenic-related immune response alterations that could underlie arsenic-associated increased risk of infection during the vulnerable periods of pregnancy and early life.

RECENT FINDINGS

The latest evidence points to alteration of antibody production and transplacental transfer as well as failure of T helper cells to produce IL-2 and proliferate. Critical areas for future research include the effects of arsenic exposure during pregnancy and early life on immune responses to natural infection and the immunogenicity and efficacy of vaccines.

Monomethylarsonous Acid (MMAIII) Has an Adverse Effect on the Innate Immune Response of Human Bronchial Epithelial Cells to Pseudomonas aeruginosa

Arsenic is the number one contaminant of concern with regard to human health according to the World Health Organization. Epidemiological studies on Asian and South American populations have linked arsenic exposure with an increased incidence of lung disease, including pneumonia, and chronic obstructive pulmonary disease, both of which are associated with bacterial infection. However, little is known about the effects of low dose arsenic exposure, or the contributions of organic arsenic to the innate immune response to bacterial infection. This study examined the effects on Pseudomonas aeruginosa (P. aeruginosa) induced cytokine secretion by human bronchial epithelial cells (HBEC) by inorganic sodium arsenite (iAs^III) and two major metabolites, monomethylarsonous acid (MMA^III) and dimethylarsenic acid (DMA^V), at concentrations relevant to the U.S. population. Neither iAs^III nor DMA^V altered P. aeruginosa induced cytokine secretion. By contrast, MMA^III increased P. aeruginosa induced secretion of IL-8, IL-6 and CXCL2. A combination of iAs^III, MMA^III and DMA^V (10 pbb total) reduced IL-8 and CXCL1 secretion. These data demonstrate for the first time that exposure to MMA^III alone, and a combination of iAs^III, MMA^III and DMA^V at levels relevant to the U.S. may have negative effects on the innate immune response of human bronchial epithelial cells to P. aeruginosa.

Early life arsenic exposure and acute and long-term responses to influenza A infection in mice

BACKGROUND

Arsenic is a significant global environmental health problem. Exposure to arsenic in early life has been shown to increase the rate of respiratory infections during infancy, reduce childhood lung function, and increase the rates of bronchiectasis in early adulthood.

OBJECTIVE

We aimed to determine if early life exposure to arsenic exacerbates the response to early life influenza infection in mice.

METHODS

C57BL/6 mice were exposed to arsenic in utero and throughout postnatal life. At 1 week of age, a subgroup of mice were infected with influenza A. We then assessed the acute and long-term effects of arsenic exposure on viral clearance, inflammation, lung structure, and lung function.

RESULTS

Early life arsenic exposure reduced the clearance of and exacerbated the inflammatory response to influenza A, and resulted in acute and long-term changes in lung mechanics and airway structure.

CONCLUSIONS

Increased susceptibility to respiratory infections combined with exaggerated inflammatory responses throughout early life may contribute to the development of bronchiectasis in arsenic-exposed populations.

Arsenic immunotoxicity: a review

Exposure to arsenic (As) is a global public health problem because of its association with various cancers and numerous other pathological effects, and millions of people worldwide are exposed to As on a regular basis. Increasing lines of evidence indicate that As may adversely affect the immune system, but its specific effects on immune function are poorly understood. Therefore, we conducted a literature search of non-cancer immune-related effects associated with As exposure and summarized the known immunotoxicological effects of As in humans, animals and in vitro models. Overall, the data show that chronic exposure to As has the potential to impair vital immune responses which could lead to increased risk of infections and chronic diseases, including various cancers. Although animal and in vitro models provide some insight into potential mechanisms of the As-related immunotoxicity observed in human populations, further investigation, particularly in humans, is needed to better understand the relationship between As exposure and the development of disease.

Speciated arsenic in air: measurement methodology and risk assessment considerations

Accurate measurement of arsenic (As) in air is critical to providing a more robust understanding of arsenic exposures and associated human health risks. Although there is extensive information available on total arsenic in air, less is known on the relative contribution of each arsenic species. To address this data gap, the authors conducted an in-depth review of available information on speciated arsenic in air. The evaluation included the type of species measured and the relative abundance, as well as an analysis of the limitations of current analytical methods. Despite inherent differences in the procedures, most techniques effectively separated arsenic species in the air samples. Common analytical techniques such as inductively coupled plasma mass spectrometry (ICP-MS) and/or hydride generation (HG)- or quartz furnace (GF)-atomic absorption spectrometry (AAS) were used for arsenic measurement in the extracts, and provided some of the most sensitive detection limits. The current analysis demonstrated that, despite limited comparability among studies due to differences in seasonal factors, study duration, sample collection methods, and analytical methods, research conducted to date is adequate to show that arsenic in air is mainly in the inorganic form. Reported average concentrations of As(III) and As(V) ranged up to 7.4 and 10.4 ng/m3, respectively, with As(V) being more prevalent than As(III) in most studies. Concentrations of the organic methylated arsenic compounds are negligible (in the pg/m3 range). However because of the variability in study methods and measurement methodology, the authors were unable to determine the variation in arsenic composition as a function of source or particulate matter (PM) fraction. In this work, the authors include the implications of arsenic speciation in air on potential exposure and risks. The authors conclude that it is important to synchronize sample collection, preparation, and analytical techniques in order to generate data more useful for arsenic inhalation risk assessment, and a more robust documentation of quality assurance/quality control (QA/QC) protocols is necessary to ensure accuracy, precision, representativeness, and comparability.

Arsenic toxicology: translating between experimental models and human pathology

BACKGROUND

Chronic arsenic exposure is a worldwide health problem. How arsenic exposure promotes a variety of diseases is poorly understood, and specific relationships between experimental and human exposures are not established. We propose phenotypic anchoring as a means to unify experimental observations and disease outcomes.

OBJECTIVES

We examined the use of phenotypic anchors to translate experimental data to human pathology and investigated research needs for which phenotypic anchors need to be developed.

METHODS

During a workshop, we discussed experimental systems investigating arsenic dose/exposure and phenotypic expression relationships and human disease responses to chronic arsenic exposure and identified knowledge gaps. In a literature review, we identified areas where data exist to support phenotypic anchoring of experimental results to pathologies from specific human exposures.

DISCUSSION

Disease outcome is likely dependent on cell-type-specific responses and interaction with individual genetics, other toxicants, and infectious agents. Potential phenotypic anchors include target tissue dosimetry, gene expression and epigenetic profiles, and tissue biomarkers.

CONCLUSIONS

Translation to human populations requires more extensive profiling of human samples along with high-quality dosimetry. Anchoring results by gene expression and epigenetic profiling has great promise for data unification. Genetic predisposition of individuals affects disease outcome. Interactions with infectious agents, particularly viruses, may explain some species-specific differences between human pathologies and experimental animal pathologies. Invertebrate systems amenable to genetic manipulation offer potential for elaborating impacts of specific biochemical pathways. Anchoring experimental results to specific human exposures will accelerate understanding of mechanisms of arsenic-induced human disease.

Effects of 5-chloro-2-methyl-4-isothiazolin-3-one and other candidate biodiesel biocides on rat alveolar macrophages and NR8383 cells

Biocides are added to biodiesels to inhibit and remove microbial growth. The effects of 5-chloro-2-methyl-4-isothiazolin-3-one (CMIT), a candidate biodiesel biocide, were studied using freshly isolated rat alveolar macrophages (AM) and NR8383 cell line. CMIT markedly inhibited phagocytic oxidative burst as measured by zymosan-induced chemiluminescence, and cellular cytokine secretion as measured by zymosan-induced TNF-α secretion. The 50% inhibition concentration (LC(50)) for CMIT was 0.002-0.004 mM for both cellular functions. AM exposed to CMIT for as little as 2 min showed markedly inhibited functions that persisted for at least 5 h. Sodium metabisulfite was able to partially neutralize the inhibitory activity of CMIT. Cysteine and glutathione, when present at a molar ratio of 2-1 or higher against CMIT, were effective neutralizers, while serine, histidine, alanine, and albumin were without effect. When the AM testing system was used to compare the toxicity of CMIT against three other candidate biodiesel biocides, methylene dithiocyanate (MDC) was found to be of comparable toxicity to CMIT, 2-methyl-4-isothiazolin-3-one (MIT) was much less toxic, and dimethyl acetylenedicarboxylate (DMAD) was non-toxic. Because AM is among the first cell-type exposed to inhaled biodiesel aerosols, the result suggested that CMIT present in biodiesel may produce respiratory effects, and further investigations including animal studies are warranted.

Lipoic acid ameliorates arsenic trioxide-induced HO-1 expression and oxidative stress in THP-1 monocytes and macrophages

Inorganic arsenic is a common environmental contaminant; chronic exposure to arsenic can alter the physiology of various key immune cells, particularly macrophages. The aim of this research is to elucidate the key parameters associated with arsenic-induced toxicity and investigate the potential and mechanism of α-lipoic acid (LA), a potent thioreducant, for reducing the toxicity in human promonocytic THP-1 cells. We found that a non-lethal concentration of arsenic trioxide (1 μM) significantly induced the expression of heme oxygenase-1 (HO-1), a response biomarker to arsenic, without stimulating measurable superoxide production. Co-treatment of cells with the HO-1 competitive inhibitor zinc protoporphyrin (Znpp) potentiated arsenic-induced cytotoxicity, indicating that HO-1 confers a cytoprotective effect against arsenic toxicity. In addition, low concentrations of arsenic trioxide (1 and 2.5 μM) markedly inhibited monocyte-to-macrophage differentiation and expression of macrophage markers. Treatment of cells with LA attenuated arsenic trioxide-induced cytotoxicity and HO-1 over-expression and restored the redox state. In addition, LA neutralized arsenic trioxide-inhibition of monocyte maturation into macrophages and reversed the expression and activity of scavenger receptors. In conclusion, the cytotoxicity of arsenic trioxide is associated with an imbalance of the cellular redox state, and LA can protect cells from arsenic-induced malfunctions either through its reducing activity, direct interacting with arsenic or stimulating other unidentified signaling pathways.

Removal of Cr(VI) and As(V) from aqueous solutions by HDTMA-modified zeolite Y

The synthesized zeolite NaY from rice husk ash (RHA) and the commercial zeolite NaY both modified with surfactants in amounts equal to 50%, 100% and 200% of their external cation exchange capacity (ECEC) were used to remove chromate and arsenate anions from aqueous solutions. While the unmodified zeolite Y had little or no affinity for the Cr(VI) and As(V) anionic species, the surfactant-modified zeolite Y (SMZY) showed significant ability to remove of these anions from the aqueous solutions. The highest chromates and arsenates adsorption efficiency was observed from solutions of pH values 3 and 8, respectively because of the dominance of the univalent species of both anions. The adsorption equilibrium data were best fitted with the Langmuir isotherm model with the highest removal capacities observed for the SMZY initially prepared considering the hexadecyltrimethyl ammonium (HDTMA) amount equal to the 100% of the ECEC of zeolite Y. Synthesized SMZY remove Cr(VI) and As(V) more than the corresponding commercial one due to its lower silica to alumina ratio. Thus, the HDTMA-covered modified zeolite Y synthesized using RHA can be used to remove Cr(VI) and As(V) from water.

Modulation of Murine Peritoneal Macrophage Function by Chronic Exposure to Arsenate in Drinking Water

Exposure of humans to arsenic is associated with various adverse health effects including immunotoxicity and elevated risk of cancer development. Specific mechanisms of these effects are not well understood. In the present study we investigated some functional parameters of peritoneal macrophages isolated from mice exposed for 12 weeks to sodium arsenate in drinking water at 0.5, 5, and 50 mgAs/l. The experimental conditions were matched with the environmental conditions of arsenic exposure in humans. To characterize function of the macrophages, we assessed their ability to release nitric oxide (NO), reactive oxygen species (ROS), and tumor necrosis factor-alpha (TNF-alpha) in response to common stimulants. To this end the isolated cells were stimulated with lipopolysaccharide (1 microg/ml) to assess NO and TNF-alpha production (the WEHI-164 bioassay) or with phorbol myristate acetate (5 microg/ml) to assess superoxide production (NBT reduction test). As a result, in mice exposed to 0.5, 5, and 50 mgAs/l we observed decreased production of NO (9 +/- 2, 8 +/- 2, 11 +/- 5 microM NO2-, respectively, versus 27 +/- 7 microM in control) and superoxide (41.3 +/- 18.2%, 52.8 +/- 15.1% and 55.9 +/- 12.9%, respectively, less than in control). Despite reduced NO production, expression of iNOS mRNA in RT-PCR, showed similar levels in exposed and control animals. We did not see any significant influence of the exposure on TNF-alpha release and mRNA expression. The potential consequences of decreased production of NO and superoxide by peritoneal macrophages as observed in exposed mice may suggest impaired response of the cells against infection or developing tumor cells.

Arsenite-induced cytotoxicity in dorsal root ganglion explants

Peripheral neuropathy is common in people chronically overexposed to arsenic. We studied sodium arsenite (arsenite)-induced cytotoxicity in dorsal root ganglion (DRG) explants. Incubation with arsenite concentration- and time-dependently increased the expression of stress proteins, heat shock protein 70, and heme oxygenase-1 in DRG explants. Furthermore, apoptosis was involved in the arsenite-induced cytotoxicity in the treated DRG. Elevation in cytosolic cytochrome c levels and reduction in procaspase 3 levels suggested an involvement of the mitochondrial pathway in arsenite-induced apoptosis in this preparation. At the same time, increases in the activating transcription factor-4 and C/EBP homologous protein and reduction in procaspase 12 levels indicated activation of the endoplasmic reticulum (ER) pathway in the arsenite-induced cytotoxicity in DRG explants. Salubrinal (30 microM), an ER inhibitor, was found to attenuate arsenite-induced DNA fragmentation and reduction in procaspase 12 in DRG explants. Cytotoxic effects by arsenite, sodium arsenate (arsenate), monomethylarsonic acid (MMA), and dimethylarsinic acid (DMA) were compared, and the potency was as follows: arsenite >>> arsenate>MMA and DMA. Recombinant adenovirus vectors encoding glial-cell-derived neurotrophic factor (AdGDNF) genes allowed a stable delivery of GDNF genes to the infected cells in DRG explants. Applied in this manner, AdGDNF was found to inhibit arsenite-induced DNA fragmentation in DRG explants. Moreover, AdGDNF attenuated the arsenite-induced reduction in procaspases 3 and 12 levels. Taken together, our study demonstrates that arsenite is capable of inducing cytotoxicity in DRG explants. Both ER and mitochondria pathways are involved in the arsenite-induced apoptosis in DRG explants. Glial-cell-derived neurotrophic factor appears to be protective against arsenite-induced peripheral neuropathy.

Association of respiratory complications and elevated serum immunoglobulins with drinking water arsenic toxicity in human

We assessed the relationship between chronic arsenic exposure through drinking water with respiratory complications and humoral immune response by measuring serum immunoglobulin profiles in the affected subjects (arsenicosis patients) living in the arsenic endemic rural villages of Bangladesh. The duration of exposure was determined through detailed history of the patients (n=125) and the levels of arsenic in the drinking water and urine samples were determined. The mean duration of exposure in the patients was 7.4+/-5.3 y, and the levels of arsenic in the drinking water and urine samples were 216+/-211 and 223+/-302 micro g/L, respectively, compared to 11+/-20 and 29+/-19 microg/L, respectively, in the unexposed subjects. There was high prevalence of respiratory complications like breathing problems including chest sound, asthma, bronchitis and cough associated with drinking water arsenic toxicity. Arsenicosis patients had significantly elevated levels of IgG (P<0.001) and IgE (P<0.001) while the levels of IgA were also significantly higher (P<0.005) but IgM were similar to that of the control subjects. Analysis of the clinical symptoms based on skin manifestations showed the levels of both IgG and IgE were significantly elevated during the initial stages while IgE were further elevated with the duration of arsenic exposure. Arsenicosis patients with respiratory complications had mean serum IgE levels of 706+/-211 IU/mL compared to 542+/-241 IU/mL in patients without apparent involvement with the respiratory system (P<0.01). The eosinophil counts in the patients did not differ significantly from the unexposed subjects indicating that elevated levels of serum IgE might not be due to allergic diseases, rather it could be due to direct effects of arsenic. We found significant linear relationships between the levels of serum IgE and inorganic phosphorus (P<0.05), and serum IgA levels with urinary excretion of arsenic (P<0.001). These observations suggested that arsenic toxicity caused respiratory complications, induced changes in the humoral as well as mucosal immune responses.

Role of oxidative stress in arsenic-induced toxicity

Arsenic is recognized as a carcinogen for human skin, bladder, and lung, following either ingestion or inhalation; however the exact mode of action of environmentally relevant exposure has not been determined. Because arsenic in the environment exists in several oxidative states and can interact with thiols, it is thought that arsenic toxicity is mediated through oxidative stress. Production of oxygen radicals following acute in vitro exposures has been demonstrated. However, our research has chosen to focus on the role of oxidative stress following whole animal exposure to environmentally relevant doses of arsenic. Following a 28-d inhalation of arsenic or cigarette smoke or both, there was a significant decrease in both the reduced and total glutathione levels in the combined arsenic and smoke group compared to groups exposed to arsenic or smoke alone. This correlated with a 5-fold increase in DNA oxidation. Lungs processed for immunohistochemistry localization of 8-oxo-dG showed increased staining in nuclei of airway epithelium and subadjacent interstitial cells. Increases in DNA oxidation were not due to increased inflammation. Although inhalation of arsenic is an important occupational exposure, the majority of human exposures occurs through ingestion of arsenic. Our recent work has been devoted to the identification of altered pulmonary gene and protein expression following ingestion of environmentally relevant levels of arsenic in drinking water. We have found that, following chronic exposure, arsenic leads to misregulation of a number of genes and proteins in the lung. A large percentage of the altered genes and proteins are known to be regulated by redox-sensitive transcription factors, (SP1, NF kappaB, AP-1), suggesting that, at environmentally relevant levels of chronic exposure, arsenic may be acting through alteration of cellular redox status. Validation of the alterations seen in animal models of exposure is being carried out in humans.

Invasive aspergillosis in association with criminal arsenic poisoning

A 26-year-old man suffered acute arsenic poisoning after a poisoning attempt. He developed multiple organ failure including encephalopathy, bleeding disorders, pancreatitis, renal and hepatocellular impairment. Generalized erythroderma also developed within one week after admission. The developed acute respiratory distress syndrome and Aspergillus fumigatus was isolated from the endotracheal aspirate. Despite intensive care support, antidote administration and various epuration techniques, the patient died on day 26 from subarachnoid bleeding. An autopsy was obtained and the concentration of arsenic was determined in different tissues. Multiple abscesses due to Aspergillus fumigatus were seen in the lungs, myocardium and kidneys. This uncommon complication in a previously immunocompetent patient could be related to impaired immunity directly caused by arsenic poisoning.

Arsenic and cigarette smoke synergistically increase DNA oxidation in the lung

Epidemiological evidence has indicated that arsenic and cigarette smoking exposure act synergistically to increase the incidence of lung cancer. Since oxidative damage of DNA has been linked to cancer, our hypothesis is that aerosolized arsenic and cigarette smoke work synergistically to increase oxidative stress and increase DNA oxidation in the lung. To test this hypothesis male Syrian golden hamsters were exposed to room air (control), aerosolized arsenic compounds (3.2 mg/m3 for 30 minutes), cigarette smoke (5 mg/m3 for 30 minutes), or both smoke and arsenic. Exposures were for 5 days/week for 5 or 28-days. Animals were sacrificed one day after the last exposure. In the 28-day group, glutathione levels and DNA oxidation (8-oxo-2'-deoxyguanosine (8-oxo-dG)) were determined. Our results show that in the 28-day arsenic/smoke group there was a significant decrease in both the reduced and total glutathione levels compared with arsenic or smoke alone. This correlated with a 5-fold increase in DNA oxidation as shown by HPLC. Immunohistochemical localization of 8-oxo-dG showed increase staining in nuclei of airway epithelium and subadjacent interstitial cells. These results show that dual exposure of arsenic and cigarette smoke at environmentally relevant levels can act synergistically to cause DNA damage.

Spatial dependency of Buruli ulcer prevalence on arsenic-enriched domains in Amansie West District, Ghana: implications for arsenic mediation in Mycobacterium ulcerans infection

BACKGROUND: In 1998, the World Health Organization recognized Buruli ulcer (BU), a human skin disease caused by Mycobacterium ulcerans (MU), as the third most prevalent mycobacterial disease. In Ghana, there have been more than 2000 reported cases in the last ten years; outbreaks have occurred in at least 90 of its 110 administrative districts. In one of the worst affected districts, Amansie West, there are arsenic-enriched surface environments resulting from the oxidation of arsenic-bearing minerals, occurring naturally in mineral deposits. RESULTS: Proximity analysis, carried out to determine spatial relationships between BU-affected areas and arsenic-enriched farmlands and arsenic-enriched drainage channels in the Amansie West District, showed that mean BU prevalence in settlements along arsenic-enriched drainages and within arsenic-enriched farmlands is greater than elsewhere. Furthermore, mean BU prevalence is greater along arsenic-enriched drainages than within arsenic-enriched farmlands. CONCLUSION: The results suggest that arsenic in the environment may play a contributory role in MU infection.

Arsenite pretreatment attenuates benzo[a]pyrene cytotoxicity in a human lung adenocarcinoma cell line by decreasing cyclooxygenase-2 levels

Both simultaneous and sequential exposure to arsenite and benzo[a]pyrene (BaP) potentially occur in human populations drinking arsenic-contaminated water or burning arsenic-contaminated coal. Although arsenite and BaP are both well-documented hazardous substances and human carcinogens, interactions between these two agents have not been well defined. In this study, we demonstrated that posttreatment with arsenite synergistically enhanced the cytotoxicity of BaP for a human lung adenocarcinoma cell line, CL3. In contrast, pretreatment of CL3 cells with arsenite attenuated BaP cytotoxicity. Involvement of heat-shock protein 70 and heme oxygenase-1 in this arsenite-mediated attenuation of BaP cytotoxicity was ruled out. Our data also indicated that arsenite pretreatment did not affect the BaP-mediated induction of CYP1A1, the initial enzyme involved in its metabolic activation, but did result in a significant decrease in mRNA and protein levels of cyclooxygenase-2 (COX-2), which is required to convert the BaP metabolite BaP 7,8-dihydrodiol to the ultimate epoxide. In contrast to the high susceptibility of CL3 cells to BaP, the human lung carcinoma cells, H460, and CL3R15 cells (arsenic-resistant CL3 cells) showed normal CYP1A1 inducibility by BaP, had negligible amounts of COX-2, and were highly resistant to BaP. The involvement of COX-2 in BaP activation was confirmed by transfection of H460 cells with a recombinant adenovirus, Ad-pgk-Cox2, coding for COX-2, which resulted in a significant increase in the levels of the COX-2 product prostaglandin E2 in the medium and in the susceptibility of H460 cells to BaP. The present study confirms the importance of COX-2 in BaP activation and demonstrates that the arsenite-mediated attenuation of BaP cytotoxicity is mediated by a reduction in COX-2 levels.

Chronic Fatigue Syndrome (CFS) in 15 dogs and cats with specific biochemical and microbiological anomalies

A great deal of controversy and speculation surrounds the etiology of Chronic Fatigue Syndrome (CFS) in human patients and the existence of a similar illness in animals. To evaluate the association with a presumptive staphylococcal infection and bacteremia, seven dogs and eight cats diagnosed with CFS (two meeting the CDC working case definition) were submitted to rapid blood cultures and fresh blood smears investigations. Nine out of 15 blood cultures proved Staph-positive and four isolates were specified as S. xilosus (3) and S. intermedius (1). The presence of micrococci-like organisms in the blood was of common observation among these subjects, in association with fatigue/pain-related symptoms and biochemical abnormalities suggestive of a myopathy. Following treatment with a low dosage arsenical drug (thiacetarsamide sodium, Caparsolate, i.v., 0.1 ml/kg/day) all patients experienced complete remission. Micrococci disappeared from the blood at post-treatment controls made 10-30 days later. The outcomes were compared with those of five healthy controls and five 'sick with other illness' patients showing significant difference.

Immunosuppression by arsenic: a comparison of cathepsin L inhibition and apoptosis

Arsenicals are toxicants and carcinogens to which large numbers of people risk exposure by contaminated water, air pollution or industrial contact. Several animal studies have determined that inorganic arsenicals are immunotoxic, but the mechanism of immune suppression is not clear. In this study, we show that trivalent arsenic inhibits enzymatic activity of the lysosomal protease cathepsin L (CathL) in the murine antigen-presenting B cell line TA3. CathL plays an important role in antigen processing, the mechanism by which antigen-presenting cells cleave foreign protein antigens to peptides for stimulating a T cell response. Deficient proteolysis may lead to diminished immune responses. Arsenite suppressed enzymatic activity within TA3 cells after 4 h exposure without affecting cell viability. Kinetic analyses revealed that the chemical was a reversible, partially noncompetitive inhibitor of CathL with a Ki of 120 microM. However, an 18 h arsenite exposure triggered massive cell death at concentrations that were substantially lower than those required for enzymatic inhibition. Morphological analysis and annexin V staining showed that arsenite-exposed TA3 cells underwent apoptosis within 18 h, and early stages of apoptosis began by 4 h. These findings suggest that apoptosis may be an important mechanism for arsenic-induced immunosuppression.

Diversity of inorganic arsenite biotransformation

Biotransformation of inorganic arsenic in mammals is catalyzed by three serial enzyme activities: arsenate reductase, arsenite methyltransferase, and monomethylarsonate methyltransferase. Our laboratory has purified and characterized these enzymes in order to understand the mechanisms and elucidate the variations of the responses to arsenate/arsenite challenge. Our results indicate a marked deficiency and diversity of these enzyme activities in various animal species.

Clearance of [125I]-tumor necrosis factor-alpha from the brain into the blood after intracerebroventricular injection in rats

To test the hypothesis that brain to blood clearance is a mechanism by which brain inflammation and damage can increase circulating acute phase cytokines, rate of transfer of [125I]-tumor necrosis factor-alpha ([125I]-TNF) from brain to blood was determined. Acid precipitable [125I]-TNF appeared in peripheral blood within 5 min of intracerebroventricular (i.c.v.) injection and was cleared from brain to blood following first order kinetics at a fractional rate of 0.01123 +/- 0.0030/min, a value virtually identical with a previously determined clearance rate of [125I]-IL-6. Area under blood concentration curve compared with that after intravenous injection shows that 31.6 +/- 5.8% of the intracerebral dose reached peripheral blood in 4 h. Elevated ratios of superior sagittal sinus to aortic blood radioactivity concentration at 1 and 3 h (1.48 +/- 0. 26, p = 0.042; 1.95 +/- 0.39, p = 0.026, respectively) indicate that TNF-alpha drains from brain at least in part via the sagittal sinus. Escherichia coli lipopolysaccharide i.c.v. injection increased the rate of brain efflux of TNF-alpha.

Enzymatic methylation of arsenic compounds. V. Arsenite methyltransferase activity in tissues of mice

With the development of a rapid assay for arsenite methyltransferase (Zakharyan et al., 1995), the specific activity of this critical enzyme for arsenite biotransformation was determined by incubating liver, testis, kidney, or lung cytosol of male B6C3F1 mice with sodium arsenite and S-[methyl-3H]adenosyl-L-methionine and measuring the formation of [methyl-3H]monomethylarsonate. The mean arsenite methyltransferase specific activities (U/mg +/- SEM) measured in these organs were liver, 0.40 +/- 0.06; testis, 1.45 +/- 0.08; kidney, 0.70 +/- 0.06; and lung, 0.22 +/- 0.01. Heretofore, the enzymatic methylation of arsenite has been regarded primarily as a hepatic function. The arsenite methyltransferase specific activity of the testis was 3.6 times greater than that of the liver (p < 0.01) and the specific activity of the kidney was 1.8 times greater than that of the liver (p < 0.05). Additionally, when mice were given arsenate in drinking water for 32 or 91 days at concentrations of 25 or 2500 micrograms As/L, the arsenite methyltransferase activities of liver, testis, kidney, and lung cytosol were not significantly increased in animals receiving either dose of arsenic for either 32 or 91 days compared to controls. No evidence for the induction of arsenite methyltransferase was found under these experimental conditions.

Reduction of the ex vivo production of tumor necrosis factor alpha by alveolar phagocytes after administration of coal fly ash and copper smelter dust

We investigated the effect of intratracheally instilled coal fly ash (FA) and copper smelter dust (CU) on the lung integrity and on the ex vivo release of tumor necrosis factor alpha (TNF-alpha) by alveolar phagocytes. Groups of female NMRI mice received a single intratracheal administration of different particles normalized for the arsenic content (20 micrograms/kg body weight, i.e., 600 ng arsenic/mouse) and the particle load (100 mg/kg body weight, i.e., 3 mg/mouse). Mice received tungsten carbide (WC) alone (100 mg/kg), FA alone (100 mg/kg, i.e., 20 micrograms arsenic/kg), CU mixed with WC (CU, 13.6 mg/kg, i.e., 20 micrograms arsenic/kg; WC, 86.4 mg/kg) and Ca3(AsO4)2 mixed with WC (20 micrograms arsenic/kg; WC, 100 mg/kg). Animals were sacrificed at 1, 6, or 30 d posttreatment and analyzed by bronchoalveolar lavage for total protein (TP) content, inflammatory cell number and type, and TNF-alpha production. Additional mice were studied to evaluate particle retention by measuring total arsenic retention in the lung at appropriate times. Instillation of WC induced a mild and transient (d 1) inflammatory reaction characterized by an increase of TP and an influx of polymorphonuclear leukocytes in the alveolar compartment. Compared to WC, Ca3(AsO4)2 produced a significant increase of TP content in BALF. CU particles caused a severe but transient inflammatory reaction, while a persisting alveolitis (30 d) was observed after treatment with FA. Compared to control saline, a marked inhibition of TNF-alpha release was observed in response to LPS in all groups at d 1. Cytokine production was upregulated in WC- and Ca3(AsO4)1-treated animals after 6 and 30 d, respectively. However, a 90% inhibition of TNF-alpha production was still observed at d 30 after administration of CU and FA. Although arsenic was cleared from the lung tissue 6 d after Ca3(AsO4)2 administration, a significant fraction persisted (10-15% of the arsenic administered) in the lung of CU- and FA-treated mice at d 30. We hypothetize that suppression of TNF-alpha production is dependent upon the slow elimination of the particles and their metal content from the lung.

Toxicity to alveolar macrophages in rats following parenteral injection of mercuric chloride

Alveolar macrophages collected by pulmonary lavage from male Fisher-344 rats at intervals (24-72 h) after HgCl2 injection (1-5 mg/kg, s.c.) were analyzed by several techniques. Within 24-72 h, the macrophages showed morphological signs of activation (hypertrophy and ruffled plasma membrane). Lipid peroxidation (increased malondialdehyde concentration) was not detected until 48 h. Dose- and time-related effects of HgCl2 on malondialdehyde concentration and mercury content of alveolar macrophages were observed 24-72 h postinjection. Diminished cell viability occurred only at 72 h after the highest dosage of HgCl2. This study demonstrates that the alveolar macrophage was a cellular target for mercury toxicity following parenteral exposure to HgCl2.