Environmental Factor, July 2011, National Institute of Environmental Health Sciences
Extramural papers of the month
By Jerry Phelps
- Prenatal PAH exposure linked to behavioral problems in kids
- Breakfast helps to reduce childhood lead poisoning
- Endoplasmic reticulum stress in obesity
- Astrocytes and microglia display distinct sensitivities to methylmercury
Prenatal PAH exposure linked to behavioral problems in kids
Children of expectant mothers who are exposed during pregnancy to polycyclic aromatic hydrocarbons (PAH) are more likely to have behavioral problems as they grow and develop. A new study, funded by NIEHS at the Columbia Center for Children's Environmental Health, examined 215 children enrolled at birth. Children with high levels of PAH-DNA adducts, a biomarker of exposure, had more symptoms of attention problems and anxiety at ages 5 and 7 than did children with lower exposure.
PAH exposure occurs as a result of the incomplete combustion of fossil fuels and other organic material. These pollutants cross the placenta during pregnancy and bind to the DNA of the fetus. The researchers measured PAH-DNA adducts in white blood cells from umbilical cord blood samples taken at birth. A few years later, their mothers completed a detailed behavioral assessment of each child.
This study is the first to link behavioral effects with prenatal exposure to air pollution. The results are concerning since attention problems and anxiety may affect subsequent academic performance and social wellbeing.
Citation: Perera FP, Wang S, Vishnevetsky J, Zhang B, Cole KJ, Tang D, Rauh V, Phillips DH. 2011. PAH/Aromatic DNA Adducts in Cord Blood and Behavior Scores in New York City Children. Environ Health Perspect [Online 4 April 2011].
Breakfast helps to reduce childhood lead poisoning
A first-of-its-kind study of 1,344 children in Jintan, China reports that children who eat breakfast regularly have a blood lead content about 15 percent lower than children who do not. These results are consistent with previous studies in adults, which demonstrated that fasting increases lead absorption from the gut.
The participants took part in the China Jintan Child Cohort Study, which is funded by a grant from NIEHS to the University of Pennsylvania. Children were enrolled in the study in 2004-2005 when they were three to five years old. Their parents filled out questionnaires regarding their eating habits and foods they frequently ate.
The study compared blood lead levels to social factors, eating patterns, and intake of trace minerals and other micronutrients. There were no gender or age differences in breakfast consumption, but there was a marked decrease in blood lead concentration for children who ate breakfast regularly, which was defined as 5 days per week. The children who ate breakfast regularly had an average blood lead level of 6.1 micrograms/deciliter as compared to 7.2 micrograms/deciliter for those that ate breakfast irregularly.
Citation: Liu J, McCauley L, Compher C, Yan C, Shen X, Needleman H, Pinto-Martin JA. (https://www.ncbi.nlm.nih.gov/pubmed/21457535) 2011. Regular breakfast and blood lead levels among preschool children. Environ Health 10:28.
Endoplasmic reticulum stress in obesity
NIEHS-supported scientists at the Harvard School of Public Health report in Naturethat abnormal lipid and calcium metabolism are important contributors to endoplasmic reticulum (ER) stress accompanying obesity. These findings suggest that interventions that modulate lipid synthesis or calcium homeostasis might offer new opportunities for treating obesity, insulin resistance, and diabetes.
The ER is the main site of a variety of cellular processes, including protein and lipid synthesis, xenobiotic metabolism, and calcium storage. Disturbances in ER homeostasis can lead to stress and the subsequent activation of the unfolded protein response. Chronic ER stress is known to be important in the development of insulin resistance and diabetes in obese individuals; however, the mechanisms responsible are not well understood.
These investigators compared the proteomic and lipidomic signatures of endoplasmic reticuli purified from the livers of obese and normal sized mice. They observed suppression of protein synthesis and stimulation of lipid synthesis in the ER from the obese mice. Alterations in the fatty acid and fat composition resulted in changes in calcium ATPase activity. They also discovered that correcting the obesity-induced changes in ER phospholipid makeup reduced chronic ER stress and improved glucose homeostasis.
Citation: Fu S, Yang L, Li P, Hofmann O, Dicker L, Hide W, Lin X, Watkins SM, Ivanov AR, Hotamisligil GS. (https://www.ncbi.nlm.nih.gov/pubmed/21532591) 2011. Aberrant lipid metabolism disrupts calcium homeostasis causing liver endoplasmic reticulum stress in obesity. Nature 473(7348):528-531.
Astrocytes and microglia display distinct sensitivities to methylmercury
In the first study to compare responses in microglia and astrocytes, the two major forms of glial cells that provide support for neurons in the central nervous system, NIEHS-supported scientists have determined that they react very differently to methylmercury exposure. These findings could be important in the identification and development of therapies to reduce methyl mercury-induced damage to the central nervous system.
Microglia and astrocytes have both been identified as primary targets for the damaging effects of methylmercury. This study was carried out in primary cell cultures of the two cell types to determine their responses to methylmercury exposure with particular attention paid to cell viability, the generation of reactive oxygen species, mercury uptake, and glutathione levels.
The experimental results show that microglia are more sensitive to methylmercury than astrocytes, and they have higher uptake of mercury and lower glutathione levels, which are important in detoxifying reactive oxygen species. Microglia exhibited greater oxidative stress responses to methylmercury exposure than did astrocytes. This study furthers our understanding of how these cell types respond to environmental insults.
Citation: Ni M, Li X, Yin Z, Sidoryk-Węgrzynowicz M, Jiang H, Farina M, Rocha JB, Syversen T, Aschner M.( https://www.ncbi.nlm.nih.gov/pubmed/21351162) 2011. Comparative study on the response of rat primary astrocytes and microglia to methylmercury toxicity. Glia 59(5):810-820.
(Jerry Phelps is a program analyst in the NIEHS Division of Extramural Research and Training.)