Pulmonary biomarkers based on alterations in protein expression after exposure to arsenic

Study on the Mechanism of Arsenic-Induced Lung Injury Based on SWATH Proteomics Technology

Chronic arsenic poisoning is a global health problem that affects millions of people, and studies have found that long-term ingestion of arsenic-containing compounds can lead to lung damage, but the exact mechanism is unknown. In this study, Sprague-Dawley (SD) rats were used as the research object, and the proteomic analysis method based on sequential window acquisition of all theoretical fragment ions (SWATH) was used to detect the changes in the expression levels of related proteins in the lung tissue of arsenic-exposed rats, and to explore the mechanism of arsenic compound-induced lung injury. The results showed that arsenic exposure resulted in the abnormal expression of collagen type III and proteins involved in metabolic, immune, and cellular processes, leading to the dysfunction of important pathways associated with these proteins, resulting in lung injury. It suggested that the underlying mechanism of arsenic-induced lung injury may be related to oxidative stress, immune injury, cell junction, and collagen type III. This result provides a new research idea for revealing the mechanism of lung injury caused by arsenic exposure.

Zinc supplementation prevents mitotic accumulation in human keratinocyte cell lines upon environmentally relevant arsenic exposure

Disrupted cell cycle progression underlies the molecular pathogenesis of multiple diseases. Chronic exposure to inorganic arsenic (iAs) is a global health issue leading to multi-organ cancerous and non-cancerous diseases. Exposure to supratherapeutic concentrations of iAs causes cellular accumulation in G2 or M phase of the cell cycle in multiple cell lines by inducing cyclin B1 expression. It is not clear if iAs exposure at doses corresponding to serum levels of chronically exposed populations (∼100 nM) has any effect on cell cycle distribution. In the present study we investigated if environmentally relevant iAs exposure induced cell cycle disruption and mechanisms thereof employing two human keratinocyte cell lines (HaCaT and Ker-CT), flow cytometry, immunoblots and quantitative real-time PCR (qRT-PCR). iAs exposure (100 nM; 24 h) led to mitotic accumulation of cells in both cell lines, along with the stabilization of ANAPC11 ubiquitination targets cyclin B1 and securin, without affecting their steady state mRNA levels. This result suggested that induction of cyclin B1 and securin is modulated at the level of protein degradation. Moreover, zinc supplementation successfully prevented iAs-induced mitotic accumulation and stabilization of cyclin B1 and securin without affecting their mRNA levels. Together, these data suggest that environmentally relevant iAs exposure leads to mitotic accumulation possibly by displacing zinc from the RING finger subunit of anaphase promoting complex/cyclosome (ANAPC11), the cell cycle regulating E3 ubiquitin ligase. This early cell cycle disruptive effect of environmentally relevant iAs concentration could underpin the molecular pathogenesis of multiple diseases associated with chronic iAs exposure.

Temporal Modulation of Differential Alternative Splicing in HaCaT Human Keratinocyte Cell Line Chronically Exposed to Arsenic for up to 28 Wk

BACKGROUND

Chronic arsenic exposure via drinking water is associated with an increased risk of developing cancer and noncancer chronic diseases. Pre-mRNAs are often subject to alternative splicing, generating mRNA isoforms encoding functionally distinct protein isoforms. The resulting imbalance in isoform species can result in pathogenic changes in critical signaling pathways. Alternative splicing as a mechanism of arsenic-induced toxicity and carcinogenicity is understudied.

OBJECTIVE

This study aimed to accurately profile differential alternative splicing events in human keratinocytes induced by chronic arsenic exposure that might play a role in carcinogenesis.

METHODS

Independent quadruplicate cultures of immortalized human keratinocytes (HaCaT) were maintained continuously for 28 wk with 0 or 100  nM sodium arsenite. RNA-sequencing (RNA-Seq) was performed with poly(A) RNA isolated from cells harvested at 7, 19, and 28 wk with subsequent replicate multivariate analysis of transcript splicing (rMATS) analysis to detect and quantify differential alternative splicing events. Reverse transcriptase-polymerase chain reaction (RT-PCR) for selected alternative splicing events was performed to validate RNA-Seq predictions. Functional enrichment was performed by gene ontology (GO) analysis of the differential alternative splicing event data set at each time point.

RESULTS

At least 600 differential alternative splicing events were detected at each time point tested, comprising all the five main types of alternative splicing and occurring in both open reading frames (ORFs) and untranslated regions (UTRs). Based on functional relevance ELK4, SHC1, and XRRA1 were selected for validation of predicted alternative splicing events at 7 wk by RT-PCR. Densitometric analysis of RT-PCR data corroborated the rMATS predicted alternative splicing for all three events. Protein expression validation of the selected alternative splicing events was challenging given that very few isoform-specific antibodies are available. GO analysis demonstrated that the enriched terms in differential alternatively spliced mRNAs changed dynamically with the time of exposure. Notably, RNA metabolism and splicing regulation pathways were enriched at the 7-wk time point, when the greatest number of differentially alternatively spliced mRNAs are detected. Our preliminary proteomic analysis demonstrated that the expression of the canonical isoforms of the splice regulators DDX42, RMB25, and SRRM2 were induced upon chronic arsenic exposure, corroborating the splicing predictions.

DISCUSSION

These results using cultures of HaCaT cells suggest that arsenic exposure disrupted an alternative splice factor network and induced time-dependent genome-wide differential alternative splicing that likely contributed to the changing proteomic landscape in arsenic-induced carcinogenesis. However, significant challenges remain in corroborating alternative splicing data at the proteomic level. https://doi.org/10.1289/EHP9676.

Arsenic-induced lung inflammation and fibrosis in a rat model: Contribution of the HMGB1/RAGE, PI3K/AKT, and TGF-β1/SMAD pathways

An increasing number of studies have shown that arsenic exposure increases the risk of lung cancer as well as a variety of non-malignant respiratory diseases, including bronchitis and tracheobronchitis. HMGB1 is widely expressed in a variety of tissues and cells and is involved in the pathological processes of many lung diseases through binding to the corresponding receptors and activating the downstream signaling pathways. However, the exact role of HMGB1/RAGE in arsenic-induced lung injury remains unknown. The aim of this study was to investigate whether HMGB1/RAGE and its activated downstream pathways are involved in the process of arsenic exposure-induced lung injury in rats. In this study, an animal model of oral exposure to arsenic was induced using 2.5, 5 and 10 mg/kg NaAsO2. The results showed that capillary permeability (LDH, TP, ACP, and AKP) was increased in the arsenic exposure groups, resulting in cell damage; this was accompanied by acute inflammation marked by significant neutrophil infiltration. Meanwhile, obvious histopathological damage, including thickening of the lung epithelium, increased infiltration of inflammatory cells, rupture of the alveolar wall, swelling of the mitochondria, and chromatin agglutination was observed by H&E staining and transmission electron microscopy. Furthermore, the results confirmed that the expressions of HMGB1 and RAGE in lung tissue were enhanced, and protein expression of PI3K, p-AKT, IL-1β, IL-18, and MMP-9 was increased in lung homogenates from the arsenic-exposed groups compared to the control group. Finally, Masson's staining results revealed arsenic-induced fibrosis and collagen deposition. Moreover, a significant increase in key fibrosis factors, including TGF-β1, p-SMAD2, p-SMAD3, and SMAD4 was observed in the lung homogenates in arsenic-exposed groups. In conclusion, the current study demonstrates that sub-chronic arsenic exposure triggers the inflammatory response and collagen fiber deposition in rat lung tissue. The potential mechanism may be closely related to activation of the pro-inflammatory-related HMGB1/RAGE pathway and initiation of the PI3K/AKT and TGF-β1/SMAD pathways.

Inflammation biomarkers associated with arsenic exposure by drinking water and respiratory outcomes in indigenous children from three Yaqui villages in southern Sonora, México

Environmental arsenic exposure in adults and children has been associated with a reduction in the expression of club cell secretory protein (CC16) and an increase in the expression of matrix metalloproteinase-9 (MMP-9), both biomarkers of lung inflammation and negative respiratory outcomes. The objectives of this study were to determine if the levels of serum CC16 and MMP-9 and subsequent respiratory infections in children are associated with the ingestion of arsenic by drinking water. This cross-sectional study included 216 children from three Yaqui villages, Potam, Vicam, and Cocorit, with levels of arsenic in their ground water of 70.01 ± 21.85, 23.3 ± 9.99, and 11.8 ± 4.42 μg/L respectively. Total arsenic in water and urine samples was determined by inductively coupled plasma/optical emission spectrometry. Serum was analyzed for CC16 and MMP-9 using ELISA. The children had an average urinary arsenic of 79.39 μg/L and 46.8 % had levels above of the national concern value of 50 μg/L. Increased arsenic concentrations in drinking water and average daily arsenic intake by water were associated with decreased serum CC16 levels (β = - 0.12, 95% CI - 0.20, - 0.04 and β = - 0.10, 95% CI - 0.18, - 0.03), and increased serum MMP-9 levels (β = 0.35, 95% CI 0.22, 0.48 and β = 0.29, 95% CI 0.18, 0.40) at significant levels (P < 0.05). However, no association was found between levels of these serum biomarkers and urinary arsenic concentrations. In these children, reduced serum CC16 levels were significantly associated with increased risk of respiratory infections (OR = 0.34, 95% CI 0.13, 0.90). In conclusion, altered levels of serum CC16 and MMP-9 in the children may be due to the toxic effects of arsenic exposure through drinking water.

Receptor for advanced glycation end products in relation to exposure to metal fumes and polycyclic aromatic hydrocarbon in shipyard welders

Advanced glycation end products (AGE) and the receptor for AGE (RAGE) have been found to be pivotal biomarkers to predict the risk of inflammation and oxidative stress. Limited evidence focuses on the influence of occupational exposure to polycyclic aromatic hydrocarbon (PAH) and metal fumes on AGE and RAGE in shipyard welders. Our aim was to determine the relationships among PAH, metal exposure, and inflammatory biomarkers. From September 1 to December 31, 2017, 53 welding workers (exposed group) and 29 office workers (control group) were enrolled in the study. Comprehensive workups included demographic characteristics, laboratory data, AGE, RAGE, Interleukin-6 (IL-6), tumor necrosis factor-α, PAH, and urinary metal concentrations. RAGE levels were measured by flow cytometric analysis. Urinary 1-hydroxypyrene (1-OHP) was used as a biomarker of exposure to PAH. Several metals were elevated in the personal fine particulate matter (PM_2.5) samples, including Mn, Fe, V, Co, Zn, and Cu. The exposed group had significantly higher exposure to PM_2.5 (p = 0.015), RAGE (p = 0.020), IL-6 (p = 0.008) than the control group. After adjusting for pertinent variables, there was still a significant and positive association between Ni level and AGE (β = 0.101; 95% CI, 0.031-0.172). Significant relationship between Cr and Cd levels and RAGE was observed (β = 0.173; 95% CI, 0.017-0.329; β = 0.084; 95% CI, 0.011-0.157, respectively). Participants with elevated 1-OHP level had higher odds of high RAGE level in the model 1 (OR = 3.466, 95% CI, 1.053-11.412) and model 2 (OR = 3.454, 95% CI, 1.034-11.536). The RAGE expression of participants was significantly associated with IL-6 levels in the fully adjusted model (β = 0.294; 95% CI, 0.083-0.732). Our findings highlighted that urinary metal levels and PAH were associated with increased AGE and RAGE formation in shipyard workers. Elevated serum RAGE might induce the production of proinflammatory cytokines and trigger ensuing inflammatory cascades.

Arsenic represses airway epithelial mucin expression by affecting retinoic acid signaling pathway

Arsenic is a ubiquitous environmental toxicant, found in high concentrations worldwide. Although abundant research has dealt with arsenic-induced cancers, studies on mechanisms of non-malignant lung diseases have not been complete. In addition, decades of research have mostly concentrated on high-dose arsenic exposure, which has very limited use in modeling the biological effects of today's low-dose exposures. Indeed, accumulated evidence has shown that low-dose arsenic exposure (i.e. ≤100 ppb) may also alter lung homeostasis by causing host susceptibility to viral infection. However, the underlying mechanism of this alteration is unknown. In this study, we found that low-dose sodium arsenite (As (III)) repressed major airway mucins-MUC5AC and MUC5B at both mRNA and protein levels. We further demonstrated that this repression was not caused by cellular toxicity or mediated by the reduction of a common mucin-inducing pathway-EGFR. Other established mucin activators- dsRNA, IL1β or IL17 were not able to override As (III)-induced mucin repression. Interestingly, the suppressing effect of As (III) appeared to be partially reversible, and supplementation of all trans retinoic acid (t-RA) doses dependently restored mucin gene expression. Further analyses indicated that As (III) treatment significantly reduced the protein level of retinoic acid receptors (RARα, γ and RXRα) as well as RARE promoter reporter activity. Therefore, our study fills in an important knowledge gap in the field of low-dose arsenic exposure. The interference of RA signaling, and mucin gene expression may be important pathogenic factors in low-dose arsenic induced lung toxicity.

Cutaneous lewisite exposure causes acute lung injury

Lewisite is a strong vesicating and chemical warfare agent. Because of the rapid transdermal absorption, cutaneous exposure to lewisite can also elicit severe systemic injury. Lewisite (2.5, 5.0, and 7.5 mg/kg) was applied to the skin of Ptch1^+/- /SKH-1 mice and acute lung injury (ALI) was assessed after 24 hours. Arterial blood gas measurements showed hypercapnia and hypoxemia in the lewisite-exposed group. Histological evaluation of lung tissue revealed increased levels of proinflammatory neutrophils and a dose-dependent increase in structural changes indicative of injury. Increased inflammation was also confirmed by altered expression of cytokines, including increased IL-33, and a dose-dependent elevation of CXCL1, CXCL5, and GCSF was observed in the lung tissue. In the bronchoalveolar lavage fluid of lewisite-exposed animals, there was a significant increase in HMGB1, a damage-associated molecular pattern molecule, as well as elevated CXCL1 and CXCL5, which coincided with an influx of neutrophils to the lungs. Complete blood cell analysis revealed eosinophilia and altered neutrophil-lymphocyte ratios as a consequence of lewisite exposure. Mean platelet volume and RBC distribution width, which are predictors of lung injury, were also increased in the lewisite group. These data demonstrate that cutaneous lewisite exposure causes ALI and may contribute to mortality in exposed populations.

Inhibitory effect of metals on animal and plant glutathione transferases

Glutathione transferases (GSTs) represent a widespread enzyme superfamily in eukaryotes and prokaryotes catalyzing different reactions with endogenous and xenobiotic substrates such as organic pollutants. The latter are often found together with metal contamination in the environment. Besides performing of essential functions, GSTs protect cells by conjugation of glutathione with various reactive electrophiles. The interference of toxic metals with this functionality of GSTs may have unpredictable toxicological consequences for the organisms. In this review results from the recent literature are summarized and discussed describing the ability of metals to inhibit intracellular detoxification processes in animals and plants.

Serum Proteomic Profiling Analysis of Rats Chronically Exposed to Arsenic

Background

Arsenic (As) is an environmental contaminant, and As pollution in water and soil is a public health issue worldwide. As exposure is associated with the incidence of many disorders, such as arteriosclerosis, diabetes, neurodegenerative diseases, and renal dysfunction. However, the mechanism of As toxicity remains unclear.

Material/Methods

We investigated the changes in serum protein profiles of rats chronically exposed to As. Twenty healthy rats were randomly divided into 4 groups, and sodium arsenite of varying final concentrations (0, 2, 10, and 50 mg/L, respectively) was add into the drinking water for each group. The administration lasted for 3 months. Two proteomic strategies, isobaric tags for relative and absolute quantitation (iTRAQ), and 2-dimensional gel electrophoresis (2-DE), were employed to screen the differential serum proteins between control and arsenite exposure groups.

Results

We identified a total of 27 differentially-expressed proteins, among which 9 proteins were significantly upregulated and 18 were downregulated by As exposure. Many of the differentially-expressed proteins were related to fat digestion and absorption, including 5 apolipoproteins, which indicated lipid metabolism may be the most affected by As exposure.

Conclusions

This study revealed the influence of As on lipid metabolism, suggesting an increased potential risk of relevant diseases in subjects chronically exposed to As.

Low-moderate arsenic exposure and respiratory in American Indian communities in the Strong Heart Study

BACKGROUND

Arsenic exposure through drinking water is an established lung carcinogen. Evidence on non-malignant lung outcomes is less conclusive and suggests arsenic is associated with lower lung function. Studies examining low-moderate arsenic (< 50 μg/L), the level relevant for most populations, are limited. We evaluated the association of arsenic exposure with respiratory health in American Indians from the Northern Plains, the Southern Plains and the Southwest United States, communities with environmental exposure to inorganic arsenic through drinking water.

METHODS

The Strong Heart Study is a prospective study of American Indian adults. This analysis used urinary arsenic measurements at baseline (1989-1991) and spirometry at Visit 2 (1993-1995) from 2132 participants to evaluate associations of arsenic exposure with airflow obstruction, restrictive pattern, self-reported respiratory disease, and symptoms.

RESULTS

Airflow obstruction was present in 21.5% and restrictive pattern was present in 14.4%. The odds ratio (95% confidence interval) for obstruction and restrictive patterns, based on the fixed ratio definition, comparing the 75th to 25th percentile of arsenic, was 1.17 (0.99, 1.38) and 1.27 (1.01, 1.60), respectively, after adjustments, and 1.28 (1.02, 1.60) and 1.33 (0.90, 1.50), respectively, based on the lower limit of normal definition. Arsenic was associated with lower percent predicted FEV1 and FVC, self-reported emphysema and stopping for breath.

CONCLUSION

Low-moderate arsenic exposure was positively associated with restrictive pattern, airflow obstruction, lower lung function, self-reported emphysema and stopping for breath, independent of smoking and other lung disease risk factors. Findings suggest that low-moderate arsenic exposure may contribute to restrictive lung disease.

Health effects inflicted by chronic low-level arsenic contamination in groundwater: A global public health challenge

Groundwater arsenic (As) contamination is a global public health concern. The high level of As exposure (100-1000 μg/L or even higher) through groundwater has been frequently associated with serious public health hazards, e.g., skin disorders, cardiovascular diseases, respiratory problems, complications of gastrointestinal tract, liver and splenic ailments, kidney and bladder disorders, reproductive failure, neurotoxicity and cancer. However, reviews on low-level As exposure and the imperative health effects are far less documented. The World Health Organization (WHO) and the United States Environmental Protection Agency (USEPA) has set the permissible standard of As in drinking water at 10 μg/L. Considering the WHO and USEPA guidelines, most of the developed countries have established standards at or below this guideline. Worldwide many countries including India have millions of aquifers with low-level As contamination (≤50 μg/L). The exposed population of these areas might not show any As-related skin lesions (hallmark of As toxicity particularly in a population consuming As contaminated groundwater >300 μg/L) but might be subclinically affected. This review has attempted to encompass the wide range of health effects associated with chronic low-level As exposure ≤50 μg/L and the probable mechanisms that might provide a better insight regarding the underlying cause of these clinical manifestations. Therefore, there is an urgent need to create mass awareness about the health effects of chronic low-level As exposure and planning of proper mitigation strategies.

Metal-Induced Pulmonary Fibrosis

PURPOSE OF REVIEW

The incidence of pulmonary fibrosis is increasing worldwide and may, in part, be due to occupational and environmental exposures. Secondary fibrotic interstitial lung diseases may be mistaken for idiopathic pulmonary fibrosis with important implications for both disease management and prognosis. The purposes of this review are to shed light on possible underlying causes of interstitial pulmonary fibrosis and to encourage dialogue on the importance of acquiring a thorough patient history of occupational and environmental exposures.

RECENT FINDINGS

A recent appreciation for various occupational and environmental metals inducing both antigen-specific immune reactions in the lung and nonspecific "innate" immune system responses has emerged and with it a growing awareness of the potential hazards to the lung caused by low-level metal exposures. Advancements in the contrast and quality of high-resolution CT scans and identification of histopathological patterns of interstitial pulmonary fibrosis have improved clinical diagnostics. Moreover, recent findings indicate specific hotspots of pulmonary fibrosis within the USA. Increased prevalence of lung disease in these areas appears to be linked to occupational/environmental metal exposure and ethnic susceptibility/vulnerability. A systematic overview of possible occupational and environmental metals causing interstitial pulmonary fibrosis and a detailed evaluation of vulnerable/susceptible populations may facilitate a broader understanding of potential underlying causes and highlight risks of disease predisposition.

Impact of prenatal arsenic exposure on chronic adult diseases

Exposure to environmental stressors during susceptible windows of development can result in negative health outcomes later in life, a concept known as the Developmental Origins of Health and Disease (DOHaD). There is a growing body of evidence that exposures to metals early in life (in utero and postnatal) increase the risk of developing adult diseases such as cancer, cardiovascular disease, non-alcoholic fatty liver disease, and diabetes. Of particular concern is exposure to the metalloid arsenic, a drinking water contaminant and worldwide health concern. Epidemiological studies of areas with high levels of arsenic in the drinking water, such as some regions in Chile and Bangladesh, indicate an association between in utero arsenic exposure and the development of adult diseases. Therefore, the need for experimental models to address the mechanism underlining early onset of adult diseases have emerged including the in utero and whole-life exposure models. This review will highlight the epidemiological events and subsequent novel experimental models implemented to study the impact of early life exposure to arsenic on the development of adult diseases. In addition, current research using these models will be discussed as well as possible underlying mechanism for the early onset of disease. Abbreviations: ALT: alanine aminotransferase; AMI: acute myocardial infarction; AST: aspartate aminotransferase; ATSDR: Agency for Toxic Substances and Disease Registry; CVD: cardiovascular disease; DMA: dimethylarsinate; DOHaD: Developmental Origins of Health and Disease; EPA: U.S. Environmental Protection Agency; ER-α: estrogen receptor alpha; HDL: high-density lipoprotein; HOMA-IR: homeostatic model assessment of insulin resistance; iAs: inorganic arsenic; LDL: low-density lipoprotein; MetS: metabolic syndrome; MMA: monomethylarsonate; NAFLD: non-alcoholic fatty liver disease; PND: postnatal day; ppb: parts per billion; ppm: parts per million; SAM: S-adenosylmethionine; USFDA: United States Food and Drug Administration.

C. elegans-An Emerging Model to Study Metal-Induced RAGE-Related Pathologies

The receptor for advanced glycation end products (RAGE), a multi-ligand receptor, is mostly associated with promoting inflammation and oxidative stress. In addition to advanced glycation end products (AGEs), its ligands include High mobility group box 1 protein (HMGB-1), S-100 proteins and beta-sheet fibrils. The effects of several metals and metalloids on RAGE expression and activation have been recently studied: in vivo and in vitro exposure to methylmercury, selenium, zinc, manganese, and arsenic was associated with a variety of RAGE-related alterations and behavioral impairments, which are mostly dependent upon the administration procedure (local vs. systemic) and age during exposure. Recently, C. elegans has been proposed as a potential novel model for studying RAGE-related pathologies; preliminary data regarding such model and its potential contribution to the study of metal-induced RAGE-related pathologies are discussed.

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.

DNA methylation of extracellular matrix remodeling genes in children exposed to arsenic

Several novel mechanistic findings regarding to arsenic's pathogenesis has been reported and some of them suggest that the etiology of some arsenic induced diseases are due in part to heritable changes to the genome via epigenetic processes such as DNA methylation, histone maintenance, and mRNA expression. Recently, we reported that arsenic exposure during in utero and early life was associated with impairment in the lung function and abnormal receptor for advanced glycation endproducts (RAGE), matrix metalloproteinase-9 (MMP-9) and tissue inhibitor of matrix metalloproteinase-1 (TIMP-1) sputum levels. Based on our results and the reported arsenic impacts on DNA methylation, we designed this study in our cohort of children exposed in utero and early childhood to arsenic with the aim to associate DNA methylation of MMP9, TIMP1 and RAGE genes with its protein sputum levels and with urinary and toenail arsenic levels. The results disclosed hypermethylation in MMP9 promotor region in the most exposed children; and an increase in the RAGE sputum levels among children with the mid methylation level; there were also positive associations between MMP9 DNA methylation with arsenic toenail concentrations; RAGE DNA methylation with iAs, and %DMA; and finally between TIMP1 DNA methylation with the first arsenic methylation. A negative correlation between MMP9 sputum levels with its DNA methylation was registered. In conclusion, arsenic levels were positive associated with the DNA methylation of extracellular matrix remodeling genes;, which in turn could modifies the biological process in which they are involved causing or predisposing to lung diseases.

Structure, function and disease relevance of Omega-class glutathione transferases

The Omega-class cytosolic glutathione transferases (GSTs) have distinct structural and functional attributes that allow them to perform novel roles unrelated to the functions of other GSTs. Mammalian GSTO1-1 has been found to play a previously unappreciated role in the glutathionylation cycle that is emerging as significant mechanism regulating protein function. GSTO1-1-catalyzed glutathionylation or deglutathionylation of a key signaling protein may explain the requirement for catalytically active GSTO1-1 in LPS-stimulated pro-inflammatory signaling through the TLR4 receptor. The observation that ML175 a specific GSTO1-1 inhibitor can block LPS-stimulated inflammatory signaling has opened a new avenue for the development of novel anti-inflammatory drugs that could be useful in the treatment of toxic shock and other inflammatory disorders. The role of GSTO2-2 remains unclear. As a dehydroascorbate reductase, it could contribute to the maintenance of cellular redox balance and it is interesting to note that the GSTO2 N142D polymorphism has been associated with multiple diseases including Alzheimer's disease, Parkinson's disease, familial amyotrophic lateral sclerosis, chronic obstructive pulmonary disease, age-related cataract and breast cancer.

Differential expression of serum proteins in rats subchronically exposed to arsenic identified by iTRAQ-based proteomic technology-14-3-3 ζ protein to serve as a potential biomarker

Arsenic is a multi-system toxicant. However, the mechanism of arsenic toxicity is not fully clarified and few effective protein biomarkers could be used for arsenic poisoning. This study was to investigate the differentially expressed proteins in the serum of rats subchronically exposed to arsenic. Sixty male rats were randomly divided into four groups, and the dose of sodium arsenite in drinking water for each group was 0, 2, 10, and 50 mg L^-1, respectively. The exposure lasted for 12 weeks. An Isobaric tags for relative and absolute quantitation (iTRAQ)-based proteomic approach was used to identify the differentially expressed proteins in serum between control and 50 mg L^-1 groups. A total of 201 serum proteins were identified by iTRAQ, of which 12 were significantly changed by arsenic exposure with two up-regulated and ten down-regulated proteins. One down-regulated protein 14-3-3 ζ, an abundant protein expressed in the brain, was verified by ELISA using serum samples and by immunohistochemical, real time PCR, and western blot methods using brain tissues in four groups. Our work provided valuable insight into the serum protein changes in rats exposed to arsenic, and indicated that 14-3-3 ζ may serve as a useful biomarker for nervous damage caused by arsenic poisoning.

Lung inflammation biomarkers and lung function in children chronically exposed to arsenic

Evidence suggests that exposure to arsenic in drinking water during early childhood or in utero has been associated with an increase in respiratory symptoms or diseases in the adulthood, however only a few studies have been carried out during those sensitive windows of exposure. Recently our group demonstrated that the exposure to arsenic during early childhood or in utero in children was associated with impairment in the lung function and suggested that this adverse effect could be due to a chronic inflammation response to the metalloid. Therefore, we designed this cross-sectional study in a cohort of children associating lung inflammatory biomarkers and lung function with urinary As levels. A total of 275 healthy children were partitioned into four study groups according with their arsenic urinary levels. Inflammation biomarkers were measured in sputum by ELISA and the lung function was evaluated by spirometry. Fifty eight percent of the studied children were found to have a restrictive spirometric pattern. In the two highest exposed groups, the soluble receptor for advanced glycation end products' (sRAGE) sputum level was significantly lower and matrix metalloproteinase-9 (MMP-9) concentration was higher. When the biomarkers were correlated to the urinary arsenic species, negative associations were found between dimethylarsinic (DMA), monomethylarsonic percentage (%MMA) and dimethylarsinic percentage (%DMA) with sRAGE and positive associations between %DMA with MMP-9 and with the MMP-9/tissue inhibitor of metalloproteinase (TIMP-1) ratio. In conclusion, chronic arsenic exposure of children negatively correlates with sRAGE, and positively correlated with MMP-9 and MMP-9/TIMP-1 levels, and increases the frequency of an abnormal spirometric pattern. Arsenic-induced alterations in inflammatory biomarkers may contribute to the development of restrictive lung diseases.

Environmental arsenic exposure, selenium and sputum alpha-1 antitrypsin

Exposure to arsenic in drinking water is associated with increased respiratory disease. Alpha-1 antitrypsin (AAT) protects the lung against tissue destruction. The objective of this study was to determine whether arsenic exposure is associated with changes in airway AAT concentration and whether this relationship is modified by selenium. A total of 55 subjects were evaluated in Ajo and Tucson, Arizona. Tap water and first morning void urine were analyzed for arsenic species, induced sputum for AAT and toenails for selenium and arsenic. Household tap-water arsenic, toenail arsenic and urinary inorganic arsenic and metabolites were significantly higher in Ajo (20.6±3.5 μg/l, 0.54±0.77 μg/g and 27.7±21.2 μg/l, respectively) than in Tucson (3.9±2.5 μg/l, 0.16±0.20 μg/g and 13.0±13.8 μg/l, respectively). In multivariable models, urinary monomethylarsonic acid (MMA) was negatively, and toenail selenium positively associated with sputum AAT (P=0.004 and P=0.002, respectively). In analyses stratified by town, these relationships remained significant only in Ajo, with the higher arsenic exposure. Reduction in AAT may be a means by which arsenic induces respiratory disease, and selenium may protect against this adverse effect.

Environmental arsenic exposure and microbiota in induced sputum

Arsenic exposure from drinking water is associated with adverse respiratory outcomes, but it is unknown whether arsenic affects pulmonary microbiota. This exploratory study assessed the effect of exposure to arsenic in drinking water on bacterial diversity in the respiratory tract of non-smokers. Induced sputum was collected from 10 subjects with moderate mean household water arsenic concentration (21.1 ± 6.4 ppb) and 10 subjects with low household water arsenic (2.4 ± 0.8 ppb). To assess microbiota in sputum, the V6 hypervariable region amplicons of bacterial 16s rRNA genes were sequenced using the Ion Torrent Personal Genome Machine. Microbial community differences between arsenic exposure groups were evaluated using QIIME and Metastats. A total of 3,920,441 sequence reads, ranging from 37,935 to 508,787 per sample for 316 chips after QIIME quality filtering, were taxonomically classified into 142 individual genera and five phyla. Firmicutes (22%), Proteobacteria (17%) and Bacteriodetes (12%) were the main phyla in all samples, with Neisseriaceae (15%), Prevotellaceae (12%) and Veillonellacea (7%) being most common at the genus level. Some genera, including Gemella, Lactobacillales, Streptococcus, Neisseria and Pasteurellaceae were elevated in the moderate arsenic exposure group, while Rothia, Prevotella, Prevotellaceae Fusobacterium and Neisseriaceae were decreased, although none of these differences was statistically significant. Future studies with more participants and a greater range of arsenic exposure are needed to further elucidate the effects of drinking water arsenic consumption on respiratory microbiota.

Alterations in apoptotic caspases and antioxidant enzymes in arsenic exposed rat brain regions: reversal effect of essential metals and a chelating agent

Arsenic (As) widely studied for its effects as a neurotoxicant. The present study was designed to evaluate the protective effect of calcium, zinc or monoisoamyl dimercaptosuccinic acid (MiADMSA), either individually or in combination on As induced oxidative stress and apoptosis in brain regions (cerebral cortex, hippocampus and cerebellum) of postnatal day (PND) 21, 28 and 3 months old rats. Arsenic exposure significantly decreased the activities of superoxide dismutase (SOD) isoforms, catalase (CAT), glutathione peroxidase (GPx) and glutathione reductase (GR) with increase in glutathione s transferase (GST) while lipid peroxidation (LPx), arsenic levels, mRNA expression of caspase 3 and 9 were significantly increased in different brain regions. Arsenic induced alterations in these parameters were greater in PND 28 and more pronounced in cerebral cortex. From the results it is evident that combined supplementation of calcium and zinc along with MiADMSA would be most effective compared to individual administration in reducing arsenic induced neurotoxicity.

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.

Health risk from As contaminated fish consumption by population living around River Chenab, Pakistan

We analyzed six edible fish species (Securicola gora; Cirrhinus reba; Rita rita; Sperata sarvari; Culpisoma naziri and Labeo kalbasu) to evaluation As contamination. These species were caught from the River Chenab of Pakistan. The aim of this study was to determine the concentration of arsenic (As) and the antioxidant response in the muscle, liver and gills. The sampling sites were divided into agricultural, industrial and urban land uses. Although, the highest concentration of As, and the antioxidant activity was found in the liver, but the muscles also had a high concentration of As than that of gills. The range of As detected in these tissues was in the following order: Liver (0.009-3.95μgg(-1))>muscles (0.006-3.5μgg(-1))>gills (0.002-2.96μgg(-1)). Furthermore, the R. rita showed the highest concentration of As (2.18μgg(-1)) followed by S. sarvari (1.98μgg(-1)). The median concentrations of As, in the liver and muscles were also above the FAO/WHO, EPA permissible limits. The LPO activity was significantly related to As, which showed a possibility of cell membrane damage in these species. The human health risk assessment revealed that higher than normal concentration of As in muscle was particularly hazardous for the younger population.

Mass spectrometric immunoassay and MRM as targeted MS-based quantitative approaches in biomarker development: potential applications to cardiovascular disease and diabetes

Type 2 diabetes mellitus (T2DM) is an important risk factor for cardiovascular disease (CVD)--the leading cause of death in the United States. Yet not all subjects with T2DM are at equal risk for CVD complications; the challenge lies in identifying those at greatest risk. Therapies directed toward treating conventional risk factors have failed to significantly reduce this residual risk in T2DM patients. Thus newer targets and markers are needed for the development and testing of novel therapies. Herein we review two complementary MS-based approaches--mass spectrometric immunoassay (MSIA) and MS/MS as MRM--for the analysis of plasma proteins and PTMs of relevance to T2DM and CVD. Together, these complementary approaches allow for high-throughput monitoring of many PTMs and the absolute quantification of proteins near the low picomolar range. In this review article, we discuss the clinical relevance of the high density lipoprotein (HDL) proteome and Apolipoprotein A-I PTMs to T2DM and CVD as well as provide illustrative MSIA and MRM data on HDL proteins from T2DM patients to provide examples of how these MS approaches can be applied to gain new insight regarding cardiovascular risk factors. Also discussed are the reproducibility, interpretation, and limitations of each technique with an emphasis on their capacities to facilitate the translation of new biomarkers into clinical practice.

The impact of pre-analytical conditions on the serum proteome: heat-stabilization versus nitrogen storage

CONTEXT

Biological material reflecting the in vivo composition of markers provides a high potential for biomarker discovery.

OBJECTIVE

We compared the serum proteome following heat- and nitrogen-preservation, with and without subsequent storage at room temperature.

MATERIALS AND METHODS

Serum samples were collected, treated and analysed by two-dimensional gel electrophoresis. Protein spots were identified and confirmed by two mass spectrometry approaches (MALDI & ESI) and subjected to Ingenuity Pathway Analysis.

RESULTS

We revealed 24 differentially expressed proteins (p ≤ 0.05) between nitrogen and heat preservation, and 87 between nitrogen and heat preservation with subsequent storage for 120 h at room-temperature. Mass spectrometry identified 25 polypeptides. Pathway analysis resulted in networks maintaining Cellular Assembly and Organization, Movement and Maintenance.

CONCLUSION

Heat-stabilization does not substantially change the short-term proteome composition of serum compared with nitrogen treatment. However, heat-stabilization alone seems insufficient for long-term sample preservation for serum samples. We identified transthyretin and apolipoprotein A-IV as sample quality markers.

Environmental arsenic exposure and serum matrix metalloproteinase-9

The objective of this study was to evaluate the relationship between environmental arsenic exposure and serum matrix metalloproteinase (MMP)-9, a biomarker associated with cardiovascular disease and cancer. In a cross-sectional study of residents of Arizona, USA (n=215) and Sonora, Mexico (n=163), drinking water was assayed for total arsenic, and daily drinking water arsenic intake was estimated. Urine was speciated for arsenic, and concentrations were adjusted for specific gravity. Serum was analyzed for MMP-9 using ELISA. Mixed model linear regression was used to assess the relation among drinking water arsenic concentration, drinking water arsenic intake, urinary arsenic sum of species (the sum of arsenite, arsenate, monomethylarsonic acid and dimethylarsinic acid), and MMP-9, controlling for autocorrelation within households. Drinking water arsenic concentration and intake were positively associated with MMP-9, both in crude analysis and after adjustment for gender, country/ethnicity, age, body mass index, current smoking, and diabetes. Urinary arsenic sum of species was positively associated with MMP-9 in multivariable analysis only. Using Akaike's Information Criterion, arsenic concentration in drinking water provided a better fitting model of MMP-9 than either urinary arsenic or drinking water arsenic intake. In conclusion, arsenic exposure evaluated using all three exposure metrics was positively associated with MMP-9.

The broad scope of health effects from chronic arsenic exposure: update on a worldwide public health problem

BACKGROUND

Concerns for arsenic exposure are not limited to toxic waste sites and massive poisoning events. Chronic exposure continues to be a major public health problem worldwide, affecting hundreds of millions of persons.

OBJECTIVES

We reviewed recent information on worldwide concerns for arsenic exposures and public health to heighten awareness of the current scope of arsenic exposure and health outcomes and the importance of reducing exposure, particularly during pregnancy and early life.

METHODS

We synthesized the large body of current research pertaining to arsenic exposure and health outcomes with an emphasis on recent publications.

DISCUSSION

Locations of high arsenic exposure via drinking water span from Bangladesh, Chile, and Taiwan to the United States. The U.S. Environmental Protection Agency maximum contaminant level (MCL) in drinking water is 10 µg/L; however, concentrations of > 3,000 µg/L have been found in wells in the United States. In addition, exposure through diet is of growing concern. Knowledge of the scope of arsenic-associated health effects has broadened; arsenic leaves essentially no bodily system untouched. Arsenic is a known carcinogen associated with skin, lung, bladder, kidney, and liver cancer. Dermatological, developmental, neurological, respiratory, cardiovascular, immunological, and endocrine effects are also evident. Most remarkably, early-life exposure may be related to increased risks for several types of cancer and other diseases during adulthood.

CONCLUSIONS

These data call for heightened awareness of arsenic-related pathologies in broader contexts than previously perceived. Testing foods and drinking water for arsenic, including individual private wells, should be a top priority to reduce exposure, particularly for pregnant women and children, given the potential for life-long effects of developmental exposure.

Chronic arsenic exposure in nanomolar concentrations compromises wound response and intercellular signaling in airway epithelial cells

Paracrine ATP signaling in the lung epithelium participates in a variety of innate immune functions, including mucociliary clearance, bactericide production, and as an initiating signal in wound repair. We evaluated the effects of chronic low-dose arsenic relevant to U.S. drinking water standards (i.e., 10 ppb [130nM]) on airway epithelial cells. Immortalized human bronchial epithelial cells (16HBE14o-) were exposed to 0, 130, or 330nM arsenic (as Na-arsenite) for 4-5 weeks and examined for wound repair efficiency and ATP-mediated Ca(2+) signaling. We found that chronic arsenic exposure at these low doses slows wound repair and reduces ATP-mediated Ca(2+) signaling. We further show that arsenic compromises ATP-mediated Ca(2+) signaling by altering both Ca(2+) release from intracellular stores (via metabotropic P2Y receptors) and Ca(2+) influx mechanisms (via ionotropic P2X receptors). To better model the effects of arsenic on ATP-mediated Ca(2+) signaling under conditions of natural exposure, we cultured tracheal epithelial cells obtained from mice exposed to control or 50 ppb Na-arsenite supplemented drinking water for 4 weeks. Tracheal epithelial cells from arsenic-exposed mice displayed reduced ATP-mediated Ca(2+) signaling dynamics similar to our in vitro chronic exposure. Our findings demonstrate that chronic arsenic exposure at levels that are commonly found in drinking water (i.e., 10-50 ppb) alters cellular mechanisms critical to airway innate immunity.

Global liver proteome analysis using iTRAQ labeling quantitative proteomic technology to reveal biomarkers in mice exposed to perfluorooctane sulfonate (PFOS)

Proteomic analysis allows detection of changes of proteins expression in organisms exposed to environmental pollutants, leading to the discovery of biomarkers of exposure and understanding of the action mechanism of toxicity. In the present study, we applied iTRAQ labeling quantitative proteomic technology for global characterization of the liver proteome in mice exposed to perfluorooctane sulfonate (PFOS). This successfully identified and quantified 1038 unique proteins. Seventy-one proteins showed a significant expression change in the treated groups (1.0, 2.5, 5.0 mg/kg of body weight) compared with the control group, and 16 proteins displayed strong dose-dependent changes. Gene ontology analysis showed that these differential proteins were significantly enriched and mainly involved in lipid metabolism, transport, biosynthetic processes, and response to stimulus. We detected significantly increased expression levels of enzymes regulating peroxisomal β-oxidation-including long-chain acyl-CoA synthetase, acyl-CoA oxidase 1, bifunctional enzyme, and 3-ketoacyl-CoA thiolase A. PFOS also significantly induced cytochrome P450s and glutathione S-transferases that are responsible for the metabolism of xenobiotic compounds. The expressions of several proteins with important biological functions-such as cysteine sulfinic acid decarboxylase, aldehyde dehydrogenase, and apolipoprotein A-I, also correlated with PFOS exposure. Together, the present results provide insight into the molecular mechanism and biomarkers for PFOS-induced effects.

Proteomics-based investigations of animal models of disease

Cells contain a large yet, constant genome, which contains all the coding information necessary to sustain cellular physiology. However, proteins are the end products of genes, and hence dictate the phenotype of cells and tissues. Therefore, proteomics can provide key information for the elucidation of physiological and pathophysiological mechanisms by identifying the protein profile from cells and tissues. The relatively novel techniques used for the study of proteomics thus have the potential to improve diagnostic, prognostic, as well as therapeutic avenues. In this review, we first discuss the benefits of animal models over the use of human samples for the proteomic analysis of human disease. Next, we aim to demonstrate the potential of proteomics in the elucidation of disease mechanisms that may not be possible by other conventional technologies. Following this, we describe the use of proteomics for the analysis of PTM and protein interactions in animal models and their relevance to the study of human disease. Finally, we discuss the development of clinical biomarkers for the early diagnosis of disease via proteomic analysis of animal models. We also discuss the development of standard proteomes and relate how this data will benefit future proteomic research. A comprehensive review of all animal models used in conjunction with proteomics is beyond the scope of this manuscript. Therefore, we aimed to cover a large breadth of topics, which together, demonstrate the potential of proteomics as a powerful tool in biomedical research.

Characterization of the role of protein-cysteine residues in the binding with sodium arsenite

To better characterize the interaction of protein-cysteines with sodium arsenite, arsenic-binding proteins were identified from the arsenic-resistant Chinese hamster ovary cell line SA7 using a p-aminophenylarsine oxide (PAO)-agarose matrix in combination with proteomic techniques. Twenty of the isolated arsenic-binding proteins were further peptide-mapped by MALDI-Q-TOF-MS. The binding capacity of PAO-agarose-retained proteins was then verified by re-applying Escherichia coli overexpressed recombinant proteins with various numbers of cysteine residues onto the PAO-agarose matrix. The results showed that recombinant heat shock protein 27 (HSP27, with one cysteine residue), reticulocalbin-3 (RCN3, with no cysteine residue), galectin-1 (GAL1, with six cysteine residues), but not peroxiredoxin 6 (Prdx6, with one cysteine residue but not retained by the PAO-agarose matrix), were bound to the PAO-agarose matrix. The six free cysteine residues in GAL1 were individually or double-mutated to alanine by means of site-directed mutagenesis and subjected to CD and ICP-MS analysis. The binding capacity of GAL1 for sodium arsenite was significantly attenuated in C16A, C88A and all double mutant clones. Taken together, our current data suggest that the cysteine residues in GAL1 may play a critical role in the binding of arsenic, but that in the case of RCN3 and Prdx6, this interaction may be mediated by other factors.

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.

Arsenic-induced oxidative stress and its reversibility

This review summarizes the literature describing the molecular mechanisms of arsenic-induced oxidative stress, its relevant biomarkers, and its relation to various diseases, including preventive and therapeutic strategies. Arsenic alters multiple cellular pathways including expression of growth factors, suppression of cell cycle checkpoint proteins, promotion of and resistance to apoptosis, inhibition of DNA repair, alterations in DNA methylation, decreased immunosurveillance, and increased oxidative stress, by disturbing the pro/antioxidant balance. These alterations play prominent roles in disease manifestation, such as carcinogenicity, genotoxicity, diabetes, cardiovascular and nervous systems disorders. The exact molecular and cellular mechanisms involved in arsenic toxicity are rather unrevealed. Arsenic alters cellular glutathione levels either by utilizing this electron donor for the conversion of pentavalent to trivalent arsenicals or directly binding with it or by oxidizing glutathione via arsenic-induced free radical generation. Arsenic forms oxygen-based radicals (OH(•), O(2)(•-)) under physiological conditions by directly binding with critical thiols. As a carcinogen, it acts through epigenetic mechanisms rather than as a classical mutagen. The carcinogenic potential of arsenic may be attributed to activation of redox-sensitive transcription factors and other signaling pathways involving nuclear factor κB, activator protein-1, and p53. Modulation of cellular thiols for protection against reactive oxygen species has been used as a therapeutic strategy against arsenic. N-acetylcysteine, α-lipoic acid, vitamin E, quercetin, and a few herbal extracts show prophylactic activity against the majority of arsenic-mediated injuries in both in vitro and in vivo models. This review also updates the reader on recent advances in chelation therapy and newer therapeutic strategies suggested to treat arsenic-induced oxidative damage.

Lung function decrement with arsenic exposure to drinking groundwater along River Indus: a comparative cross-sectional study

This study was designed to determine the association between chronic arsenic exposure through drinking groundwater and decrement in lung function, particularly among individuals who do not have signs of arsenic lesions, among an adult population. This was a comparative cross-sectional study conducted during the months of January to March 2009. One hundred participants ≥15 years of age in each group, i.e. exposed (≥100 μg/l) and unexposed (≤10 μg/l) to arsenic, determined by testing drinking water samples (using portable kits), were compared for effects on lung function using spirometry. A structured and validated questionnaire was administered. Examination for arsenic skin lesions was also done. There was a decline in the mean adjusted FEV1 of 154.3 ml (95% CI: -324.7, 16.0; p = 0.076), in mean adjusted FVC of 221.9 ml (95% CI: -419.5, -24.3; p = 0.028), and in FEV1/FVC ratio of 2.0 (95% CI: -25.3, 29.4; p = 0.884) among participants who were exposed to arsenic compared to those unexposed. A separate model comprising a total of 160 participants, 60 exposed to arsenic concentrations ≥250 μg/l and 100 unexposed at arsenic concentrations of ≤10 μg/l, showed a decrement in mean adjusted FEV1 of 226.4 ml (95% CI: -430.4, -22.4; p = 0.030), in mean adjusted FVC of 354.8 ml (95% CI: -583.6, -126.0; p = 0.003), and in FEV1/FVC ratio of 9.9 (95% CI: -21.8, 41.6; p = 0.539) among participants who were exposed to arsenic in drinking groundwater. This study demonstrated that decrement in lung function is associated with chronic exposure to arsenic in drinking groundwater, occurring independently, and even before any manifestation, of arsenic skin lesions or respiratory symptoms. The study also demonstrated a dose-response effect of arsenic exposure and lung function decrement.

Arsenic alters ATP-dependent Ca²+ signaling in human airway epithelial cell wound response

Arsenic is a natural metalloid toxicant that is associated with occupational inhalation injury and contaminates drinking water worldwide. Both inhalation of arsenic and consumption of arsenic-tainted water are correlated with malignant and nonmalignant lung diseases. Despite strong links between arsenic and respiratory illness, underlying cell responses to arsenic remain unclear. We hypothesized that arsenic may elicit some of its detrimental effects on the airway through limitation of innate immune function and, specifically, through alteration of paracrine ATP (purinergic) Ca²+ signaling in the airway epithelium. We examined the effects of acute (24 h) exposure with environmentally relevant levels of arsenic (i.e., < 4 μM as Na-arsenite) on wound-induced Ca²+ signaling pathways in human bronchial epithelial cell line (16HBE14o-). We found that arsenic reduces purinergic Ca²+ signaling in a dose-dependent manner and results in a reshaping of the Ca²+ signaling response to localized wounds. We next examined arsenic effects on two purinergic receptor types: the metabotropic P2Y and ionotropic P2X receptors. Arsenic inhibited both P2Y- and P2X-mediated Ca²+ signaling responses to ATP. Both inhaled and ingested arsenic can rapidly reach the airway epithelium where purinergic signaling is essential in innate immune functions (e.g., ciliary beat, salt and water transport, bactericide production, and wound repair). Arsenic-induced compromise of such airway defense mechanisms may be an underlying contributor to chronic lung disease.

Identification of chemical-adducted proteins in urine by multi-dimensional protein identification technology (LC/LC-MS/MS)

Recent technological advancements in mass spectrometry facilitate the detection of chemical-induced posttranslational modifications (PTMs) that may alter cell signaling pathways or alter the structure and function of the modified proteins. To identify such protein adducts (Kleiner et al., Chem Res Toxicol 11:1283-1290, 1998), multi-dimensional protein identification technology (MuDPIT) has been utilized. MuDPIT was first described by Link et al. as a new technique useful for protein identification from a complex mixture of proteins (Link et al., Nat Biotechnol 17:676-682, 1999). MuDPIT utilizes two different HPLC columns to further enhance peptide separation, increasing the number of peptide hits and protein coverage. The technology is extremely useful for proteomes, such as the urine proteome, samples from immunoprecipitations, and 1D gel bands resolved from a tissue homogenate or lysate. In particular, MuDPIT has enhanced the field of adduct hunting for adducted peptides, since it is more capable of identifying lesser abundant peptides, such as those that are adducted, than the more standard LC-MS/MS. The site-specific identification of covalently adducted proteins is a prerequisite for understanding the biological significance of chemical-induced PTMs and the subsequent toxicological response they elicit.

Proteomic analysis of serum of workers occupationally exposed to arsenic, cadmium, and lead for biomarker research: a preliminary study

The main factor of environmental contamination is the presence of the heavy metals lead, cadmium, and arsenic. The aim of serum protein profile analysis of people chronically exposed to heavy metals is to find protein markers of early pathological changes. The study was conducted in a group of 389 healthy men working in copper foundry and 45 age-matched non-exposed healthy men. Toxicological test samples included whole blood, serum, and urine. Thirty-seven clinical parameters were measured. Based on the parameters values of the healthy volunteers, the centroid in 37-dimensional space was calculated. The individuals in the metal-exposed and control groups were ordered based on the Euclidean distance from the centroid defined by the first component according to Principal Component Analysis (PCA). Serum samples of two individuals, one from the control and one from the metal-exposed group, were chosen for proteomic analysis. In optimized conditions of two-dimensional gel electrophoresis (2-DE), two protein maps were obtained representing both groups. Twenty-eight corresponding protein spots from both protein maps were chosen and identified based on PDQuest analysis and the SWISS-2DPAGE database. From a panel of six proteins with differences in expression greater than a factor of two, three potential markers with the highest differences were selected: hemoglobin-spot 26 (pI 7.05, Mw 10.53), unidentified protein-spot 27 (pI 6.73, Mw 10.17), and unidentified protein-spot 25 (pI 5.75, Mw 12.07). Further studies are required to prove so far obtained results. Identified proteins could serve as potential markers of preclinical changes and could be in the future included in biomonitoring of people exposed to heavy metals.

Dcp2 phosphorylation by Ste20 modulates stress granule assembly and mRNA decay in Saccharomyces cerevisiae

The Ste20 kinase targets the decapping enzyme Dcp2 during stress responses, allowing accumulation of Dcp2 in P-bodies and the formation of stress granules.

Translation and messenger RNA (mRNA) degradation are important sites of gene regulation, particularly during stress where translation and mRNA degradation are reprogrammed to stabilize bulk mRNAs and to preferentially translate mRNAs required for the stress response. During stress, untranslating mRNAs accumulate both in processing bodies (P-bodies), which contain some translation repressors and the mRNA degradation machinery, and in stress granules, which contain mRNAs stalled in translation initiation. How signal transduction pathways impinge on proteins modulating P-body and stress granule formation and function is unknown. We show that during stress in Saccharomyces cerevisiae, Dcp2 is phosphorylated on serine 137 by the Ste20 kinase. Phosphorylation of Dcp2 affects the decay of some mRNAs and is required for Dcp2 accumulation in P-bodies and specific protein interactions of Dcp2 and for efficient formation of stress granules. These results demonstrate that Ste20 has an unexpected role in the modulation of mRNA decay and translation and that phosphorylation of Dcp2 is an important control point for mRNA decapping.

Multidimensional protein identification technology for clinical proteomic analysis

Proteomics technologies demonstrate enormous data-gathering capabilities to discover disease-specific biomarkers in serum, plasma, urine, tissue and other biological samples. The traditional way to achieve this consists of protein separation performed using two-dimensional polyacrylamide gel electrophoresis (2DE). However, the 2DE approach has its drawbacks with respect to automation, sensitivity, and throughput. Considerable efforts have been devoted to the development of non-gel-based proteome separation technologies able to resolve complex protein and peptide mixtures prior to mass spectrometric (MS) analysis. This review discusses some of the most recent advances in multidimensional peptide separation techniques compatible with MS analysis, including gel electrophoresis, isoelectric focusing, capillary electrophoresis and liquid chromatography techniques. Based on future perspectives and our experiences, special attention is given to the application of two-dimensional chromatographic separation coupled to MS, the so-called multidimensional protein identification technology approach.

Low-dose arsenic compromises the immune response to influenza A infection in vivo

BACKGROUND

Arsenic exposure is a significant worldwide environmental health concern. We recently reported that 5-week exposure to environmentally relevant levels (10 and 100 ppb) of As in drinking water significantly altered components of the innate immune response in mouse lung, which we hypothesize is an important contributor to the increased risk of lung disease in exposed human populations.

OBJECTIVES

We investigated the effects of As exposure on respiratory influenza A (H1N1) virus infection, a common and potentially fatal disease.

METHODS

In this study, we exposed C57BL/6J mice to 100 ppb As in drinking water for 5 weeks, followed by intranasal inoculation with a sub lethal dose of influenza A/PuertoRico/8/34 (H1N1) virus. Multiple end points were assessed postinfection.

RESULTS

Arsenic was associated with a number of significant changes in response to influenza, including an increase in morbidity and higher pulmonary influenza virus titers on day 7 post-infection. We also found many alterations in the immune response relative to As-unexposed controls, including a decrease in the number of dendritic cells in the mediastinal lymph nodes early in the course of infection.

CONCLUSIONS

Our data indicate that chronic As exposure significantly compromises the immune response to infection. Alterations in response to repeated lung infection may also contribute to other chronic illnesses, such as bronchiectasis, which is elevated by As exposure in epidemiology studies.

Pre-analytical factors in clinical proteomics investigations: impact of ex vivo protein modifications for multiple sclerosis biomarker discovery

Serum proteome investigations have raised an incredible interest in the research of novel molecular biomarker, nevertheless few of the proposed evidences have been translated to the clinical practice. One of the limiting factors has been the lack of generally accepted guidelines for clinical proteomics studies and the lack of a robust analytical and pre-analytical ground for the proposed classification models. Pre-analytical issues may results in a deep impact for biomarker discovery campaign. In this study we present a systematic evaluation of sample storage and sampling conditions for clinical proteomics investigations. We have developed and validated a linear MALDI-TOF-MS protein profiling method to explore the low protein molecular weight region (5-20 kDa) of serum samples. Data normalization and processing was performed using optimise peak detection routine (LIMPIC) able to describe each group under investigation. Data were acquired either from healthy volunteers and from multiple sclerosis patients in order to highlight ex vivo protein profile alteration related to different physio-pathological conditions. Our data showed critical conditions for serum protein profiles depending on storage times and temperatures: 23 degrees C, 4 degrees C, -20 degrees C and -80 degrees C. We demonstrated that upon a -20 degrees C short term storage, characteristic degradation profiles are associated with different clinical groups. Protein signals were further identified after preparative HPLC separation by peptide sequencing on a nanoLC-Q-TOF TANDEM mass spectrometer. Apolipoprotein A-IV and complement C3 protein fragments, transthyretin and the oxidized isoforms in different apolipoprotein species represent the major molecular features of such a degradation pattern.

Chronic exposure to arsenic in the drinking water alters the expression of immune response genes in mouse lung

BACKGROUND

Chronic exposure to drinking water arsenic is a significant worldwide environmental health concern. Exposure to As is associated with an increased risk of lung disease, which may make it a unique toxicant, because lung toxicity is usually associated with inhalation rather than ingestion.

OBJECTIVES

The goal of this study was to examine mRNA and protein expression changes in the lungs of mice exposed chronically to environmentally relevant concentrations of As in the food or drinking water, specifically examining the hypothesis that As may preferentially affect gene and protein expression related to immune function as part of its mechanism of toxicant action.

METHODS

C57BL/6J mice fed a casein-based AIN-76A defined diet were exposed to 10 or 100 ppb As in drinking water or food for 5-6 weeks.

RESULTS

Whole genome transcriptome profiling of animal lungs revealed significant alterations in the expression of many genes with functions in cell adhesion and migration, channels, receptors, differentiation and proliferation, and, most strikingly, aspects of the innate immune response. Confirmation of mRNA and protein expression changes in key genes of this response revealed that genes for interleukin 1beta, interleukin 1 receptor, a number of toll-like receptors, and several cytokines and cytokine receptors were significantly altered in the lungs of As-exposed mice.

CONCLUSIONS

These findings indicate that chronic low-dose As exposure at the current U.S. drinking-water standard can elicit effects on the regulation of innate immunity, which may contribute to altered disease risk, particularly in lung.

On the acquisition of +1 charge states during high-throughput proteomics: Implications on reproducibility, number and confidence of protein identifications

Modern high-throughput methods for the proteome analysis are gradually replacing more traditional 2D gel-based techniques. Almost immediately after the introduction of high-throughput proteomics techniques in 2001, reproducibility of the results became an issue. Extensive discussion in the literature led to the conclusion that certain "undersampling" exhibited during measurements could be due to the stochastic nature of the data-dependent sampling, routinely used with current mass spectrometry equipment. At the same time, the effect of the acquisition of different charge states on the reproducibility and confidence of protein identifications, to the best of our knowledge, has never been properly evaluated. There exists the frequently voiced yet hardly documented opinion that +1 charge states should be rejected during data-dependent acquisition. The work presented here shows that inclusion of the +1 charge state in the data-dependent acquisition protocols can indeed lead to improved proteome coverage, reproducibility, and the confidence of protein identifications by high-throughput proteomics. It was also shown that contrary to the established opinion, gas-phase dissociation of singly charged peptide species results in rich fragmentation patterns containing both b- and y-ions allowing for successful and confident peptide identification.

Analysis of environmental stress response on the proteome level

Thousands of man-made chemicals are annually released into the environment by agriculture, transport, industries, and other human activities. In general, chemical analysis of environmental samples used to assess the pollution status of a specific ecosystem is complicated by the complexity of the mixture, and in some cases by the very low toxicity thresholds of chemicals present. In that sense, a proteomics approach, capable of detecting subtle changes in the level and structure of individual proteins within the whole proteome in response to the altered surroundings, has obvious applications in the field of ecotoxicology. In addition to identifying new protein biomarkers, it can also help to provide an insight into underlying mechanisms of toxicity. Despite being a comparatively new field with a number of caveats, proteomics applications have spread from microorganisms and plants to invertebrates and vertebrates, gradually becoming an established technology used in environmental research. This review article highlights recent advances in the field of environmental proteomics, mainly focusing on experimental approaches with a potential to understand toxic modes of action and to identify novel ecotoxicological biomarkers.