Environmental Factor, November 2011, National Institute of Environmental Health Sciences
Extramural papers of the month
By Nancy Lamontagne and Rebecca Wilson
- Smart management could mitigate risk of arsenic poisoning from wells
- Mutational signature for aristolochic acid
- Mechanism for green tea's health benefit
- Lead exposure and child development
Smart management could mitigate risk of arsenic poisoning from wells
A study from NIEHS Superfund Research Program-funded scientists shows that Bangladeshi citizens at risk of arsenic poisoning from their drinking water may be able to avoid illness by carefully managing deep-water wells. This research addresses a concern that pumping uncontaminated deep groundwater could lead to the intrusion of contaminated water from a shallower aquifer above.
The researchers injected arsenic-rich water into a deep aquifer in Bangladesh and monitored the change in concentration. They found that arsenic concentration had fallen by 70 percent after one day and continued to decline over the monitoring period. The decline was attributed to arsenic attaching to sediments in the deep aquifer.
The field results were applied to a hydrological model of the Bengal Basin. Water demand for household use was compared with demand for household use and irrigation water combined. They found that the risk of contamination increases significantly with increased demand.
The results from the study also illustrate how water demand influences groundwater vulnerability. Significantly increasing water demand, such as for irrigation purposes, means that the water that remains in the ground is more likely to become contaminated.
Citation: Radloff KA, Zheng Y, Michael HA, Stute M, Bostick BC, Mihajlov I, Bounds M, Huq MR, Choudhury I, Rahman MW, Schlosser P, Ahmed KM, van Geen A(http://www.nature.com/ngeo/journal/vaop/ncurrent/abs/ngeo1283.html) . 2011. Arsenic migration to deep groundwater in Bangladesh influenced by adsorption and water demand. Nat Geosci; doi:10.1038/ngeo1283 [Online 9 October 2011]. Story(www.niehs.nih.gov/2011/november/science-superfund/)
Mutational signature for aristolochic acid
NIEHS-supported researchers have identified the mutational signature for the environmental carcinogen aristolochic acid. This distinct mutational signature could be used as a biomarker to detect whether a person had prior exposure to aristolochic acid.
There is evidence that aristolochic acid causes endemic (Balkan) nephropathy, a chronic renal disease that affects residents of rural villages near tributaries of the Danube River. The disease is associated with upper urinary tract cancer. Aristolochic acid is found in Aristolochia herbs, which grow in fields cultivated for wheat in the Danube River basin. The herbs likely mix with the harvested wheat used to make bread.
The researchers analyzed tumor tissue from residents of areas where endemic nephropathy has been prevalent. Of the 97 tumors analyzed, 42 showed mutations in the tumor suppressor gene TP53, and the researchers identified a pattern of mutations unique to this group.
According to the study, the aristolochic acid mutational signature could be used to elucidate a suspected link between botanical products containing aristolochic acid and a high prevalence of upper urinary tract cancer and chronic renal disease in countries where Aristolochia herbal remedies have been used. For example, a third of the people in Taiwan have been prescribed Chinese herbal products known or suspected to contain aristolochic acid.
Citation: Moriya M, Slade N, Brdar B, Medverec Z, Tomic K, Jelakovic B, Wu L, Truong S, Fernandes A, Grollman AP(https://www.ncbi.nlm.nih.gov/pubmed/21413016) . 2011. TP53 Mutational signature for aristolochic acid: an environmental carcinogen. Int J Cancer 129(6):1532-1536. Story(https://factor.niehs.nih.gov/2011/november/science-grollman/)
Mechanism for green tea's health benefit
Researchers supported by NIEHS have shown that a component of green tea boosts the numbers of regulatory T cells, which are important for immune function and for suppressing autoimmune diseases.
Mice treated with epigallocatechin-3-gallate (EGCG), the major polyphenol in green tea, showed significantly increased numbers and frequencies of regulatory T cells in the spleen and lymph nodes and improved control of their immune response. Although the polyphenol didn't work as well as prescription drugs, the ability of dietary agents, such as EGCG, to target similar mechanisms, may allow for sustained and longer-term use with lower toxicity than prescription drugs.
Mice treated with epigallocatechin-3-gallate, the major polyphenol in green tea, showed significantly increased numbers and frequencies of regulatory T cells in the spleen and lymph nodes and improved control of their immune response. Although the polyphenol didn't work as well as prescription drugs, there are few concerns about its long-term use or toxicity.
The study also revealed that the polyphenol likely acts in part through an epigenetic mechanism. Although more research is needed to fully understand the mechanisms at work, the study provides a foundation for evaluating various dietary strategies for modulating immune function. The researchers say that dietary substances such as green tea could one day provide an easy and safe way to help control autoimmune problems and address various diseases.
Citation: Wong CP, Nguyen LP, Noh SK, Bray TM, Bruno RS, Ho E(https://www.ncbi.nlm.nih.gov/pubmed/21621552) . 2011. Induction of regulatory T cells by green tea polyphenol EGCG. Immunol Lett 139(1-2):7-13.
Lead exposure and child development
NIEHS grantees looking for gene-environment interactions that might modify the effect of lead exposure on cognitive development found that for the group of Mexican children they studied there was no evidence that polymorphisms in two dopamine neurotransmission genes alter the effect of lead exposure.
The researchers studied polymorphisms in the dopamine transporter (DAT1) and dopamine receptor D2 (DRD2) genes, because dopamine neurotransmission is thought to play a role in the cognitive problems associated with lead exposure.
Independent of postnatal lead exposure, the researchers found that prenatal lead exposure was adversely associated with development in children 24 months old, but this association was not apparent at 48 months. Children with a polymorphism in the DRD2 Taq1A gene scored higher on the Mental Development Index and the McCarthy memory scale. DRD2 regulates neurotransmission, and the Taq1A polymorphism is linked with a reduction in dopamine receptor-2 density and availability.
For the population studied, neither DAT1 nor DRD2 polymorphisms brought about gene-environmental interactions that modified the effects of prenatal or postnatal lead exposure on early childhood development. The study concluded that more studies are needed because of differing results found for other populations.
Citation: Kordas K, Ettinger AS, Bellinger DC, Schnaas L, Téllez Rojo MM, HernÁndez-Avila M, Hu H, Wright RO(https://www.ncbi.nlm.nih.gov/pubmed/21592505) . 2011. A Dopamine Receptor (DRD2) but Not Dopamine Transporter (DAT1) Gene Polymorphism is Associated with Neurocognitive Development of Mexican Preschool Children with Lead Exposure. J Pediatr 159 (4):638-643.
(Nancy Lamontagne is a science writer and Rebecca Wilson is an environmental health information specialist with MDB, Inc., a contractor for the NIEHS Division of Extramural Research and Training, Superfund Research Program, and Worker Education and Training Program.)