Expression of selected pathway-marker genes in human urothelial cells exposed chronically to a non-cytotoxic concentration of monomethylarsonous acid

AbstractBladder cancer has been associated with chronic arsenic exposure. Monomethylarsonous acid [MMA(III)] is a metabolite of inorganic arsenic and has been shown to transform an immortalized urothelial cell line (UROtsa) at concentrations 20-fold less than arsenite. MMA(III) was used as a model arsenical to examine the mechanisms of arsenical-induced transformation of urothelium. A previous microarray analysis revealed only minor changes in gene expression at 1 and 2 months of chronic exposure to MMA(III), contrasting with substantial changes observed at 3 months of exposure. To address the lack of information between 2 and 3 months of exposure (the critical period of transformation), the expression of select pathway marker genes was measured by PCR array analysis on a weekly basis. Cell proliferation rate, anchorage-independent growth, and tumorigenicity in SCID mice were also assessed to determine the early, persistent phenotypic changes and their association with the changes in expression of these selected marker genes. A very similar pattern of alterations in these genes was observed when compared to the microarray results, and suggested that early perturbations in cell signaling cascades, immunological pathways, cytokine expression, and MAPK pathway are particularly important in driving malignant transformation. These results showed a strong association between the acquired phenotypic changes that occurred as early as 1–2 months of chronic MMA(III) exposure, and the observed gene expression pattern that is indicative of the earliest stages in carcinogenesis

Developmentally Restricted Genetic Determinants of Human Arsenic Metabolism: Association between Urinary Methylated Arsenic and CYT19 Polymorphisms in Children

We report the results of a screen for genetic association with urinary arsenic metabolite levels in three arsenic metabolism candidate genes, PNP, GSTO, and CYT19, in 135 arsenic-exposed subjects from the Yaqui Valley in Sonora, Mexico, who were exposed to drinking water concentrations ranging from 5.5 to 43.3 ppb. We chose 23 polymorphic sites to test in the arsenic-exposed population. Initial phenotypes evaluated included the ratio of urinary inorganic arsenic(III) to inorganic arsenic(V) and the ratio of urinary dimethylarsenic(V) to monomethylarsenic(V) (D:M). In the initial association screening, three polymorphic sites in the CYT19 gene were significantly associated with D:M ratios in the total population. Subsequent analysis of this association revealed that the association signal for the entire population was actually caused by an extremely strong association in only the children (7–11 years of age) between CYT19 genotype and D:M levels. With children removed from the analysis, no significant genetic association was observed in adults (18–79 years). The existence of a strong, developmentally regulated genetic association between CYT19 and arsenic metabolism carries import for both arsenic pharmacogenetics and arsenic toxicology, as well as for public health and governmental regulatory officials

Differential Susceptibility of Human Peripheral Blood T Cells to Suppression by Environmental Levels of Sodium Arsenite and Monomethylarsonous Acid

Human exposure to arsenic in drinking water is known to contribute to many different health outcomes such as cancer, diabetes, and cardiopulmonary disease. Several epidemiological studies suggest that T cell function is also altered by drinking water arsenic exposure. However, it is unclear how individual responses differ to various levels of exposure to arsenic. Our laboratory has recently identified differential responses of human peripheral blood mononuclear cell (HPMBC) T cells as measured by polyclonal T cell activation by mitogens during sodium arsenite exposure. T cells from certain healthy individuals exposed to various concentrations (1–100 nM) of arsenite in vitro showed a dose-dependent suppression at these extremely low concentrations (∼0.1–10 ppb) of arsenite, whereas other individuals were not suppressed at low concentrations. In a series of more than 30 normal donors, two individuals were found to be sensitive to low concentration (10 nM equivalent ∼1 ppb drinking water exposure) to sodium arsenite-induced inhibition of T cell proliferation produced by phytohemagglutinin (PHA) and anti-CD3/anti-CD28. In an arsenite-susceptible individual, arsenite suppressed the activation of Th1 (Tbet) cells, and decreased the percentage of cells in the double positive Th17 (RORγt) and Treg (FoxP3) population. While the majority of normal blood donors tested were not susceptible to inhibition of proliferation at the 1–100 nM concentrations of As+3, it was found that all donors were sensitive to suppression by 100 nM monomethylarsonous acid (MMA+3), a key metabolite of arsenite. Thus, our studies demonstrate for the first time that low ppb-equivalent concentrations of As+3 are immunosuppressive to HPBMC T cells in some individuals, but that most donor HPBMC are sensitive to suppression by MMA+3 at environmentally relevant exposure levels

A Population-Based Case–Control Study of Urinary Arsenic Species and Squamous Cell Carcinoma in New Hampshire, USA

Background: Chronic high arsenic exposure is associated with squamous cell carcinoma (SCC) of the skin, and inorganic arsenic (iAs) metabolites may play an important role in this association. However, little is known about the carcinogenicity of arsenic at levels commonly observed in the United States. Objective: We estimated associations between total urinary arsenic and arsenic species and SCC in a U.S. population. Methods: We conducted a population-based case–control SCC study (470 cases, 447 controls) in a U.S. region with moderate arsenic exposure through private well water and diet. We measured urinary iAs, monomethylarsonic acid (MMA), and dimethylarsinic acid (DMA), and summed these arsenic species (ΣAs). Because seafood contains arsenolipids and arsenosugars that metabolize into DMA through alternate pathways, participants who reported seafood consumption within 2 days before urine collection were excluded from the analyses. Results: In adjusted logistic regression analyses (323 cases, 319 controls), the SCC odds ratio (OR) was 1.37 for each ln-transformed microgram per liter increase in ln-transformed ΣAs concentration [ln(ΣAs)] (95% CI: 1.04, 1.80). Urinary ln(MMA) and ln(DMA) also were positively associated with SCC (OR = 1.34; 95% CI: 1.04, 1.71 and OR = 1.34; 95% CI: 1.03, 1.74, respectively). A similar trend was observed for ln(iAs) (OR = 1.20; 95% CI: 0.97, 1.49). Percent iAs, MMA, and DMA were not associated with SCC. Conclusions: These results suggest that arsenic exposure at levels common in the United States relates to SCC and that arsenic metabolism ability does not modify the association

Estimated Exposure to Arsenic in Breastfed and Formula-Fed Infants in a United States Cohort

Background: Previous studies indicate that concentrations of arsenic in breast milk are relatively low even in areas with high drinking-water arsenic. However, it is uncertain whether breastfeeding leads to reduced infant exposure to arsenic in regions with lower arsenic concentrations. Objective: We estimated the relative contributions of breast milk and formula to arsenic exposure during early infancy in a U.S. population. Methods: We measured arsenic in home tap water (n = 874), urine from 6-week-old infants (n = 72), and breast milk from mothers (n = 9) enrolled in the New Hampshire Birth Cohort Study (NHBCS) using inductively coupled plasma mass spectrometry. Using data from a 3-day food diary, we compared urinary arsenic across infant feeding types and developed predictive exposure models to estimate daily arsenic intake from breast milk and formula. Results: Urinary arsenic concentrations were generally low (median, 0.17 μg/L; maximum, 2.9 μg/L) but 7.5 times higher for infants fed exclusively with formula than for infants fed exclusively with breast milk (β = 2.02; 95% CI: 1.21, 2.83; p \u3c 0.0001, adjusted for specific gravity). Similarly, the median estimated daily arsenic intake by NHBCS infants was 5.5 times higher for formula-fed infants (0.22 μg/kg/day) than for breastfed infants (0.04 μg/kg/day). Given median arsenic concentrations measured in NHBCS tap water and previously published for formula powder, formula powder was estimated to account for ~ 70% of median exposure among formula-fed NHBCS infants. Conclusions: Our findings suggest that breastfed infants have lower arsenic exposure than formula-fed infants, and that both formula powder and drinking water can be sources of exposure for U.S. infants

Dietary flavonoids improve urinary arsenic elimination among Mexican women

Inorganic arsenic (iAs) exposure increases risk of several diseases, including cancer. Some nutrients such as flavonoids enhance glutathione activity, which in turn play a key role in iAs elimination. Our objective was to explore whether dietary non-soy flavonoids are associated with iAs metabolism. We hypothesized that the intake of flavonoids belonging to the following groups, flavan-3-ols, flavone, flavonol, flavanone, and anthocyanidin, is positively associated with urinary dimethylarsinic acid (DMA), which is the most soluble iAs metabolite excreted. We performed a cross-sectional study that included 1027 women living in an arsenic-contaminated area of northern Mexico. Flavonoid intake was estimated using a validated food frequency questionnaire. Concentration of urinary iAs and its metabolites (monomethylarsonic acid and DMA) were determined by high performance liquid chromatography ICP-MS. Results showed positive significant associations between DMA and the flavonoid groups flava-3-ols (beta= 0.0112) and flavones (beta= 0.0144), as well as the individual intake of apigenin (beta= 0.0115), luteolin (beta= 0.0138), and eriodictyol (beta= 0.0026). Our findings suggest that certain non-soy flavonoids may improve iAs elimination; however, there is still very limited information available regarding the consumption of flavonoids and iAs metabolism. (C) 2018 Elsevier Inc. All rights reserved.CONACYT Fondo Sectorial de Investigacion en Salud y Seguridad Social [2005-2-14373, 2009-1-111384, 2010-1-140962, POCPN 2013-01-215464, FOSISS 272632]; National Center on Minority Health and Health Disparities of the National Institutes of Health [MD 001452]12 month embargo; available online 21 April 2018.This item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at [email protected]

Gas6 Downregulation Impaired Cytoplasmic Maturation and Pronuclear Formation Independent to the MPF Activity

Previously, we found that the growth arrest-specific gene 6 (Gas6) is more highly expressed in germinal vesicle (GV) oocytes than in metaphase II (MII) oocytes using annealing control primer (ACP)-PCR technology. The current study was undertaken to investigate the role of Gas6 in oocyte maturation and fertilization using RNA interference (RNAi). Interestingly, despite the specific and marked decrease in Gas6 mRNA and protein expression in GVs after Gas6 RNAi, nuclear maturation including spindle structures and chromosome segregation was not affected. The only discernible effect induced by Gas6 RNAi was a change in maturation promoting factor (MPF) activity. After parthenogenetic activation, Gas6 RNAi-treated oocytes at the MII stage had not developed further and arrested at MII (90.0%). After stimulation with Sr2+, Gas6-silenced MII oocytes had markedly reduced Ca2+ oscillation and exhibited no exocytosis of cortical granules. In these oocytes, sperm penetration occurred during fertilization but not pronucleus (PN) formation. By roscovitine and colcemid treatment, we found that the Gas6 knockdown affected cytoplasmic maturation directly, independent to the changed MPF activity. These results strongly suggest that 1) the Gas6 signaling itself is important to the cytoplasmic maturation, but not nuclear maturation, and 2) the decreased Gas6 expression and decreased MPF activity separately or mutually influence sperm head decondensation and PN formation