Grantee Research Project Results

Project 1 (R834599C001)

Project 2 (R834599C002)

1. To begin evaluating how increased infant consumption of solid foods affects arsenic exposure for infants aged 4-12 months
2. To test the feasibility of measuring urinary metabolites of arsenic in infants at 4 months of age, and determine the relationships among urinary arsenic, arsenic ingestion estimated from food and water, and toenail arsenic levels.

Project 3 (R834599C003) In this pilot project, our multidisciplinary team will: (1) establish a methodology integrating geospatial and Project 4 (R834599C004) A number of limited studies have shown a statistically significant increase in birth defects of children exposed to arsenic (As) in utero. This number is probably an underestimate of the prevalence of As induced birth defects, as the majority of early developmental abnormalities result in spontaneous abortion. Based on our unpublished results, we hypothesize that As exerts some of its teratogenic effects through modulation of Sonic Hedgehog (Shh) signaling. This hypothesis is consistent with the pivotal role Shh plays in the development of numerous structures, including those that are consistently malformed in children exposed to As in utero. Our identification of As as a modulator of Shh signaling may be particularly relevant to human development, as humans are much more sensitive to modulation of Shh activity than various animal models. Interestingly, although As exhibits teratogenic activity in mice, the concentrations of As required to elicit these effects are higher than those that are relevant to human exposure. Thus, similar to the increased sensitivity of humans to Shh levels, it has also been argued that humans are more sensitive to the teratogenic effects of As. Here we propose to (1) determine the mechanism by which As modulates Shh signaling, and (2) begin to develop the reagents and protocols necessary to analyze human maternal and embryonic derived tissues for biomarkers of Shh activity. In future work, such reagents will be used to correlate in utero As exposure to modulation of Shh signaling, and ultimately to correlate this modulation of Shh signaling with various human developmental defects. This latter analysis of human samples will be particularly important because of the relative insensitivity of animal models to the in utero perturbation of Shh signaling. Our experience in the dissection of the HH signaling pathway will provide us a unique position from which to elucidate how As is able to modulate this pathway and to determine whether such modulation is important from a human health perspective, and will help to inform GIS/epidemiologic Project 3 on birth defects. The knowledge gained as a result of this work could be used to design preventative strategies for the various human developmental disorders that result from a deregulated HH pathway.

Project 1 (R834599C001)
This project extends the work of The New Hampshire Birth Cohort Study, an ongoing longitudinal study of women and infants who obtain household water from wells that are a potential source of As exposure. As part of Project 1, we are prospectively following infants enrolled in our cohort through: (1) interval phone interviews with the mothers at 4, 8 and 12 months of age; (2) screening infant pediatric records covering in the first year of life; (3) reviewing prenatal records for information on maternal infections and collecting data regarding infections on the post-partum questionnaire self-administered to women through the parent study. Project 1 further collaborates with Pilot Project 2, Food borne exposure to arsenic during the first year of life to obtain pilot feeding practices (e.g., breast or bottle feeding) and other dietary information and Pilot Project 4, entitled Determining How Arsenic Modulates Hedgehog Signaling During Development by providing placenta biopsies from our cohort. Project 2 (R834599C002) Primary Aim: To determine how infant consumption of breast milk and formula contributes to exposure to arsenic during the first 4 months of life. We have made substantial progress on this aim and look forward to preparing a paper on our findings during spring-summer 2013.

1. For the data of arsenic concentration in groundwater, we acquired three most updated (unpublished) new GIS data layers from USGS NH-VT Water Science Center, representing the probabilities of arsenic concentration > 1, 5, and 10 ug/L, respectively, at each location (represented by 30 m pixel) in New Hampshire.
2. For the public water supply coverage in NH, we acquired public water supply pipeline data from the NH Department of Environmental Service.
3. We further compiled the birth defect data of NH for geospatial analysis. Besides the filtering processes reported last time (unique infant, plurality, mother’s age, etc), we did literature research and had extensive discussions on identifying non-environmental birth defect types. Therefore, we excluded fetal alcohol syndrome and chromosomal defects (i.e., Down syndrome, Trisomy 13, and Trisomy 18, accounting for about 8% of all the records) because these conditions result from known causes.
4. We have compiled data for studies of low birth weight (LBW), high birth weight (HBW), and small for gestational age (SGA) in NH.
5. We further developed and improved the sophisticated geocomputational approach to disease mapping and have named it the RCMC-UCMC approach (restricted-and-controlled-Monte-Carlo and unrestricted-and-controlled-Monte-Carlo). We applied it to NH birth defect mapping and created high- resolution risk maps of birth defects in NH, along with quantified evaluation of spatial uncertainty of the results. A paper of this work has been submitted to the American Journal of Epidemiology. We have established collaboration with the National Center for Supercomputing Applications (NCSA), located at the University of Illinois at Urbana-Champaign, to migrate the software we developed for this method to the Center’s supercomputing environment, so as to enhance its computational capability and public accessibility.

• We conducted a fairly exhaustive exploration for detecting spatial association between groundwater arsenic and birth defects in NH.
• On the arsenic side, we tested the well data collected by the Dartmouth researchers (led by Margaret Karagas, the PI of this Center), and four different USGS datasets (raster layers of probabilities for different arsenic concentration levels).
• For the public water coverage, using the best available public water supply pipeline data from the NH DES, we tested a number of different buffer distances around the pipelines to define the public water supply coverage.
• For confounding factors, besides mother's age, we tested land use (different degrees of urbanization), household medium income, and total population.
• For the geographic scale, we conducted analyses at both the town level and very detailed pixel level (30 m).

6. For NH, we are conducting town-level analysis on spatial association between low birth weight (LBW) and groundwater arsenic, and a paper is under preparation.
7. The analyses for high birth weight (HBW) and small for gestational age (SGA) in NH are ongoing.
8. We have also acquired data of state Maine. The compilation of Maine data is largely done, and the analysis has started.

 

We have now analyzed approximately 150 different placentas with about 50 nanostring probes—targeted to a series of arsenic target genes—that were activated in cell lines in vitro. These data allow us to derive a dependence model linking in utero arsenic exposure to birth outcomes (e.g., lower birth weight) of the exposed children. We have also begun to analyze the modulation of key developmental signaling pathways in these placenta samples, including target genes of the Shh, Wnt and Notch signaling pathways.

Project 2 (R834599C002)

We will continue to collect data on infant consumption of breast milk and formula via telephone and collect food diaries and urine samples at 6 weeks as additional infants are enrolled in this study. In addition, we will begin to collect food diaries, urine samples, and toenail clippings at 12 months. Project 3 (R834599C003) For Aim 1, We will include more data in the analysis, including mother’s smoking status, percentage of public water use at Census tract level, and other socioeconomic and healthcare data. Some of these data have been acquired, and some are expected to be available in the near future. We will conduct a “darting” method, which is a version of the RCMC-UCMC method for detecting spatial association, to further investigate local variation, at the pixel level, in the spatial associations between ground water arsenic and birth defects, LBW, HBW, and SGA in NH. We will continue the collaboration with NCSA to make the software more versatile, capable, and accessible. We will continue the data compilation and analyses with the Maine data.

Project 4: (R834599C004)

1. “Publish our manuscript on arsenic-related genes in the placenta in relation to birth outcomes.
2. Submit a manuscript on the modulation of key developmental signaling target genes by arsenic.
3. Continue to develop the chick embryo explant system, as a relevant developmental model system.