Environmental Factor

Environmental Factor

Your Online Source for NIEHS News

January 2017

2016 Papers of the Year

Research funded by grants

Phthalates may negatively affect in vitro fertilization

Higher concentrations of phthalate metabolites in urine are associated with a negative impact on in vitro fertilization (IVF) outcomes in women. The findings link exposure to phthalates in women undergoing IVF to lower levels of ovary cells necessary for reproduction, and fewer successful pregnancies and live births.

The analysis included 256 women enrolled in the Environment and Reproductive Health (EARTH) study, 2004-2012. Researchers measured 11 urinary phthalate metabolites, an indicator of phthalate exposure, and evaluated the association of metabolite concentrations with IVF outcomes.

Women with the highest concentrations of metabolites had a lower number of oocytes, or number of egg cells in the ovary, compared with women with the lowest levels of phthalate metabolites. The group with the lowest levels of phthalate metabolites had more women who became pregnant and gave birth than the group with the highest urinary metabolite concentrations.

Citation: Hauser R, Gaskins AJ, Souter I, Smith KW, Dodge LE, Ehrlich S, Meeker JD, Calafat AM, Williams PL; Earth Study Team. 2015. Urinary phthalate metabolite concentrations and reproductive outcomes among women undergoing in vitro fertilization: results from the EARTH study. Environ Health Perspect 124(6):831–839. (Synopsis) (https://www.niehs.nih.gov/news/newsletter/2016/1/papers/dert/index.htm#a1)

Chronic arsenic exposure may impair muscle healing after injury

Researchers found that chronic exposure to arsenic might alter the ability of muscles to regenerate after injury, and that NF kappa B, a protein involved in tissue repair, might play a role.

The researchers exposed mice to arsenic-laced drinking water for 5 weeks, then injured muscle, and next compared outcomes in exposed and unexposed mice. In addition to finding a significant decrease in muscle regeneration in arsenic-exposed mice, they observed structural differences in muscle tissue surrounding muscle cells, or the extracellular matrix.

When the scientists seeded the arsenic-exposed extracellular matrix with human muscle stem cells, they found that the extracellular matrix lowered the ability of the stem cells to form new muscle fibers. After blocking NF kappa B activation, the arsenic-exposed muscle recovered normally, suggesting that NF kappa B might play a role in arsenic’s negative effects on muscle regeneration.

Citation: Zhang C, Ferrari R, Beezhold K, Stearns-Reider K, D'Amore A, Haschak M, Stolz D, Robbins PD, Barchowsky A, Ambrosio F. 2015. Arsenic promotes NF-kB-mediated fibroblast dysfunction and matrix remodeling to impair muscle stem cell function. Stem Cells 34(3):732–742. (Synopsis) (https://www.niehs.nih.gov/news/newsletter/2016/1/papers/dert/index.htm#a3)

Natural food additive prevents UV skin damage in mice

NIEHS grantees discovered that a compound found in the natural food additive annatto prevents the formation of cancer cells and skin damage from ultraviolet (UV) radiation in mice. They also found that this protection is dependent on the nuclear factor-E2-related factor 2 (NRF2).

The researchers studied bixin, the bright reddish-orange compound found in annatto. After injecting mice with bixin and exposing them and a control group to UV radiation, they found that the bixin mice experienced far less severe sun damage than the control mice. Because previous studies suggested NRF2 might be involved in protection from sun damage, the researchers examined bixin’s effects in mice with and without NRF2. Bixin showed its protective effects only in mice with NRF2. Similar studies in cultured human skin cells also demonstrated that bixin activates a NRF2-dependent protective response in cells.

Citation: Tao S, Park SL, de la Vega MR, Zhang DD, Wondrak GT. 2015. Systemic administration of the apocarotenoid bixin protects skin against solar UV-induced damage through activation of NRF2. Free Radic Biol Med 89:690–700. (Synopsis) (https://www.niehs.nih.gov/news/newsletter/2016/3/papers/dert/index.htm#a3)

Seafood consumption and Alzheimer’s disease

An NIEHS grantee and colleagues reported that people with a higher risk of developing Alzheimer’s disease, who also consumed more seafood, showed fewer brain changes tied to the disease. The protective effects of eating seafood were only observed among people with the apolipoprotein 4 (APOE4) allele, a gene variant linked with increased risk of Alzheimer’s disease.

The researchers examined deceased participants in the Memory and Aging Project who had reported seafood consumption annually, before their deaths. Among 286 autopsied brains, the team found that higher levels of mercury were linked with eating more meals containing seafood each week. After adjusting for age, sex, education, and total energy intake, eating seafood one or more times a week was significantly correlated with fewer brain changes related to Alzheimer’s, including amyloid plaques and neurofibrillary tangles, but only among APOE4 carriers.

Citation: Morris MC, Brockman J, Schneider JA, Wang Y, Bennett DA, Tangney CC, van de Rest O. 2016. Association of seafood consumption, brain mercury level, and APOE epsilon4 status with brain neuropathology in older adults. JAMA 315(5):489–497. (Synopsis) (https://www.niehs.nih.gov/news/newsletter/2016/4/papers/dert/index.htm#a1)

Effects of low arsenic levels during pregnancy and fetal growth

According to NIEHS grantee research, consuming water and food with low levels of arsenic while pregnant may affect fetal growth. The study is one of the first to report an association between low-level exposure to arsenic during pregnancy and birth outcomes.

Unlike the majority of epidemiological studies on arsenic exposure, this population-based, prospective study explored exposures at levels common in the U.S. Researchers analyzed 706 mother-infant pairs exposed through drinking water and diet. They measured urinary arsenic from each mother and compared it to the birth weight of her baby, adjusting for maternal prepregnancy weight.

Researchers found that decreased head circumference at birth was associated with higher levels of arsenic in the mother’s urine during her second trimester. They also found associations with changes in birth weight and length, with mixed effects based on the sex of the newborn and maternal weight status.

Citation: Gilbert-Diamond D, Emond JA, Baker ER, Korrick SA, Karagas MR. 2016. Relation between in utero arsenic exposure and birth outcomes in a cohort of mothers and their newborns from New Hampshire. Environ Health Perspect 124(8):1299–1307. (Synopsis) (https://www.niehs.nih.gov/news/newsletter/2016/5/papers/dert/index.htm#a1)

Children’s lung health improves with decreasing air pollution

Research, supported in part by NIEHS, showed that decreases in ambient air pollution in Southern California were associated with significant reductions in respiratory symptoms in children with and without asthma.

Since 1992, air pollution reduction policies and strategies have significantly improved air quality across Southern California. To find out how these improvements affected lung health, the researchers examined data from a total of 4,602 children in the Southern California Children’s Health Study.

The authors reported that decreases in ambient concentrations of nitrogen dioxide, ozone, and two sizes of particulate matter — less than 10 microns and less than 2.5 microns — were associated with significant decreases in bronchitic symptoms in children with and without asthma. Children with asthma showed proportionally larger symptom reductions, which remained persistent through age 15 years. Communities with the highest improvements in air quality exhibited the largest reductions in bronchitic symptoms.

Citation: Berhane K, Chang CC, McConnell R, Gauderman WJ, Avol E, Rapapport E, Urman R, Lurmann F, Gilliland F. 2016. Association of changes in air quality with bronchitic symptoms in children in California, 1993-2012. JAMA 315(14):1491–1501. (Synopsis) (https://www.niehs.nih.gov/news/newsletter/2016/6/papers/dert/index.htm#a1)

Air pollution’s effect on the heart

Results from a 2000 to 2010 study showed that long-term exposure to air pollution speeds up calcification in arteries that supply blood to the heart. Using data from the Multi-Ethnic Study of Atherosclerosis and Air Pollution, researchers used home addresses of more than 6,795 people from six U.S. states to assess exposure to air pollutants, including particulate matter smaller than 2.5 microns (PM2.5), nitrogen oxides, and black carbon. Researchers used computed tomography, or CT, scans to measure calcium deposits in the coronary arteries of each participant.

The analysis showed that air pollution sped up calcification of the arteries, which was consistent with acceleration of atherosclerosis, a condition associated with heart disease. Study participants showed a 20 percent acceleration in the rate of calcium deposits for every 5 micrograms per cubic meter increase in PM2.5, or 35 parts per billion increase in concentration of nitrogen oxides.

Citation: Kaufman JD, Adar SD, Barr RG, Budoff M, Burke GL, Curl CL, Daviglus ML, Roux AV, Gassett AJ, Jacobs DR Jr, Kronmal R, Larson TV, Navas-Acien A, Olives C, Sampson PD, Sheppard L, Siscovick DS, Stein JH, Szpiro AA, Watson KE. 2016. Association between air pollution and coronary artery calcification within six metropolitan areas in the USA (the Multi-Ethnic Study of Atherosclerosis and Air Pollution): a longitudinal cohort study. Lancet 388(10045):696–704. (Synopsis) (https://www.niehs.nih.gov/news/newsletter/2016/7/papers/dert/index.htm#a1)

Researchers discover new diet-toxicant interaction

An NIEHS grantee and colleagues identified a new interaction that may link exposure to polychlorinated biphenyls (PCBs) with cardiovascular disease. The researchers examined whether exposure to PCBs could lead to increased levels of trimethylamine N-oxide (TMAO), a compound produced when the body metabolizes certain foods, especially those derived from animals. Several large studies in humans have linked high levels of circulating TMAO with an increased risk of heart disease.

The researchers found that several types of PCBs in mice led to increased levels of a liver enzyme that generates TMAO. In addition, feeding dietary precursors of TMAO to mice that had been exposed to PCBs increased blood levels of TMAO.

The findings identified environmental pollutants as previously unknown modulators of blood TMAO levels and raised the possibility that exposure to environmental pollutants, like PCBs, might contribute to variability in TMAO levels among people.

Citation: Petriello MC, Hoffman JB, Sunkara M, Wahlang B, Perkins JT, Morris AJ, Hennig B. 2016. Dioxin-like pollutants increase hepatic flavin containing monooxygenase (FMO3) expression to promote synthesis of the pro-atherogenic nutrient biomarker trimethylamine N-oxide from dietary precursors. J Nutr Biochem 33:145–153. (Synopsis) (https://www.niehs.nih.gov/news/newsletter/2016/9/papers/dert/index.htm#a1)

Device improves detection of pollutants in water and sediment

NIEHS-supported researchers have developed and tested a new device for detecting and analyzing pollution in water and sediment. The instrument provides information about the presence and relative risk of chemicals of concern, while offering better accuracy, cost, and versatility than existing methods.

Called the in situ sampler for biphasic water monitoring (IS2B), the device directly determines pollutant bioavailability in samples collected over time periods ranging from days to weeks. It can analyze contaminants that are either fully dissolved or suspended as particulates in free-flowing surface water, and those in the stagnant water in sediment.

The researchers tested IS2B in an engineered wetland to monitor the pesticide fipronil and its transformation products. They detected fipronil and its products at concentrations as low as 0.040 nanograms per liter. Their measurements were statistically indistinguishable from those determined by conventional, more laborious techniques.

Citation: Supowit SD, Roll IB, Dang VD, Kroll KJ, Denslow ND, Halden RU. 2016. Active sampling device for determining pollutants in surface and pore water — the in situ sampler for biphasic water monitoring. Sci Rep 6:21886. (Synopsis) (https://www.niehs.nih.gov/news/newsletter/2016/4/papers/dert/index.htm#a4)

In-house research

Study links glucocorticoid signaling to female fertility

Scientists at NIEHS are the first to provide compelling evidence that glucocorticoid signaling plays a central role in regulating female fertility. Characterization of glucocorticoid signaling in the uterus has significant clinical relevance and may lead to strategies to improve pregnancy rates.

Using a uterine-specific GR knockout mouse, investigators found that glucocorticoid signaling is involved in establishing uterine receptivity for the fertilized egg. Researchers further demonstrated that the absence of uterine GR signaling causes critical deficiencies in the cellular programming required for a healthy pregnancy. The loss of uterine GR signaling resulted in an exaggerated inflammatory response and altered immune cell abundance in response to maternal hormones.

These findings provide direct evidence that GR signaling is required to establish the necessary cellular context for maintaining normal uterine biology and fertility, and they may lead to strategies to improve pregnancy rates.

Citation: Whirledge SD, Oakley RH, Myers PH, Lydon JP, DeMayo F, Cidlowski JA. 2015. Uterine glucocorticoid receptors are critical for fertility in mice through control of embryo implantation and decidualization. Proc Natl Acad Sci U S A 112(49):15166–15171. (Synopsis) (https://www.niehs.nih.gov/news/newsletter/2016/2/papers/dir/index.htm#a2)

How CA2 hippocampal neurons respond to changes in the environment

NIEHS scientists and their collaborators established a possible mechanism for how the brain creates memories of novel and social information. The research could eventually help people with altered social capacities, such as those with schizophrenia and autism.

The researchers looked at neuronal activity in the CA2 portion of the hippocampus and found that, like other areas of the hippocampus, CA2 used groups of cells, called place cells, to represent spatial information. However, CA2 place cell properties changed in response to other animals and novel objects in the environment.

The researchers used fluorescent in situ hybridization to examine genes that switch on when neurons are active, as well as recordings of individual neurons in rats, to see whether CA2 neurons became more active during social conditions. Rather than becoming more active in response to changes in the environment, CA2 neurons updated their maps where place cells were active.

Citation: Alexander GM, Farris S, Pirone JR, Zheng C, Colgin LL, Dudek SM. 2016. Social and novel contexts modify hippocampal CA2 representations of space. Nat Commun 7:10300. (Synopsis) (https://www.niehs.nih.gov/news/newsletter/2016/4/papers/dir/index.htm#a4) (Story)

Maternal folate levels linked to altered DNA methylation in newborns

NIEHS researchers found that higher levels of maternal folate, an essential vitamin for fetal development, are associated with altered newborn DNA methylation, an epigenetic mark that controls gene expression. Because folate is central to a cellular pathway that provides methyl groups for DNA methylation, the scientists studied the connection between maternal folate and newborn DNA methylation.

The researchers examined the blood folate levels in mothers during pregnancy, and methylation of cytosine and guanine nucleotide pairings, or CpG sites, in DNA from newborn cord blood. After combining results from two European population groups, the scientists concluded that higher levels of maternal folate were associated with methylation of 443 CpGs, which localized to 320 genes. Many of these genes were not previously associated with folate and are involved in neurological functions, developmental diseases, and tumor progression. Identification of these genes provides possible clues to the mechanistic effects of folate supplementation on human health.

Citation: Joubert BR, den Dekker HT, Felix JF, Bohlin J, Lighthart S, Beckett E, Tiemeier H, van Meurs JB, Uitterlinden AG, Hofman A, Haberg SE, Reese SE, Peters MJ, Kulle Andreassen B, Steegers EA, Nilsen RM, Vollset SE, Midttun O, Ueland PM, Franco OH, Dehghan A, de Jongste JC, Wu MC, Wang T, Peddada SD, Jaddoe VW, Nystad W, Duijts L, London SJ. 2016. Maternal plasma folate impacts differential DNA methylation in an epigenome-wide meta-analysis of newborns. Nat Commun 7:10577. (Synopsis) (https://www.niehs.nih.gov/news/newsletter/2016/4/papers/dir/index.htm#a2)

Protein may protect mice from inflammatory diseases

Increased levels of endogenous tristetraprolin (TTP), a protein that facilitates turnover of specific mRNA transcripts, protects against inflammatory diseases, according to NIEHS researchers.

Previous studies have shown that mice deficient in TTP developed a chronic inflammatory syndrome caused by overproduction of a proinflammatory protein called tumor necrosis factor. After generating a new mouse model in which an instability sequence within the TTP transcript was deleted, researchers observed a marked increase in TTP transcript half-life and protein levels throughout the body.

As a result of enhanced TTP availability, these mice were protected from collagen antibody-induced arthritis, showed reduced inflammation in imiquimod-induced dermatitis, and resisted experimental autoimmune encephalomyelitis induction compared to normal mice. These treatment conditions modeled rheumatoid arthritis, psoriasis, and multiple sclerosis. The work demonstrated that increasing levels of an endogenous molecule by genetic means could point to novel therapeutic approaches for these diseases.

Citation: Patial S, Curtis AD 2nd, Lai WS, Stumpo DJ, Hill GD, Flake GP, Mannie MD, Blackshear PJ. 2016. Enhanced stability of tristetraprolin mRNA protects mice against immune-mediated inflammatory pathologies. Proc Natl Acad Sci U S A 113(7):1865–1870. (Synopsis) (https://www.niehs.nih.gov/news/newsletter/2016/4/papers/dir/index.htm#a3) (Story)

GDNF is needed for undifferentiated spermatogonial cell development

Scientists at NIEHS were the first to provide genetic evidence that glial cell line-derived neurotrophic factor (GDNF) produced by peritubular myoid (PM) cells is required for development of undifferentiated spermatogonial cells.

The absence of GDNF resulted in a decrease in fertility in male mice, by a reduction in sperm count and a defect in spermatogenesis. Testes of mice lacking PM cell GDNF exhibited a marker for undifferentiated spermatogonia. The scientists showed there was a decrease in undifferentiated spermatogonia, but not in the level of differentiated spermatogonia, in the testes of one-week-old mice or of spermatocytes in four-week-old mice lacking PM cell GDNF.

The results showed the importance of PM cell GDNF in undifferentiated spermatogonial cell development in vivo, and supported the hypothesis of its importance in spermatogonial stem cell maintenance. These results are a step toward determining one underlying cause of male infertility.

Citation: Chen LY, Willis WD, Eddy EM. 2016. Targeting the Gdnf gene in peritubular myoid cells disrupts undifferentiated spermatogonial cell development. Proc Natl Acad Sci U S A 113(7):1829–1834. (Synopsis) (https://www.niehs.nih.gov/news/newsletter/2016/4/papers/dir/index.htm#a5)

GATA3 directs chromatin remodeling during MET

A team of NIEHS researchers characterized how the GATA3 protein mediated chromatin remodeling during mesenchymal-to-epithelial transition (MET). The scientists identified GATA3-binding sites that overlapped with MET-associated gene loci. They further demonstrated that GATA3 binding at closed sites could open chromatin and make it accessible to other transcription factors. 

Using high-throughput sequencing, the scientists discovered that, at certain loci, binding by GATA3 resulted in the formation of an open chromatin structure, as indicated by increased levels of histone modifications associated with active chromatin. Furthermore, results showed that GATA3 could target nucleosomal DNA, leading to nucleosome eviction during the formation of accessible chromatin. 

Additional experiments determined that GATA3 required its N-terminal transactivation domain for chromatin remodeling. Together, these results suggest how GATA3 can pioneer binding sites in previously inaccessible chromatin and offer possible insights into how GATA3 mutations affect breast cancer. 

Citation: Takaku M, Grimm SA, Shimbo T, Perera L, Menafra R, Stunnenberg HG, Archer TK, Machida S, Kurumizaka H, Wade PA. 2016. GATA3-dependent cellular reprogramming requires activation-domain dependent recruitment of a chromatin remodeler. Genome Biol 17(1):36. (Synopsis) (https://www.niehs.nih.gov/news/newsletter/2016/5/papers/dir/index.htm#a4)

Maternal smoking during pregnancy leads to epigenetic changes in newborns

As part of the Pregnancy and Childhood Epigenetics (PACE) consortium, NIEHS scientists shed new light on the links between maternal smoking during pregnancy and epigenetic modifications in newborns. 

Researchers combined epidemiologic and epigenetic data from 13 different studies and used a statistical method called meta-analysis to determine associations between maternal smoking during pregnancy and genome-wide changes in DNA methylation in newborn blood. 

Using the Illumina450K platform, researchers measured DNA methylation at more than 450,000 cytosine and guanine nucleotide pairings, or CpG sites, along the DNA sequence to determine the epigenetic modification. More than 6,000 of these CpG sites were differentially methylated relative to maternal smoking during pregnancy. Although many were linked to genes that had already been related to maternal smoking, nearly 3,000 had never been associated with smoking in either children or adults before this study. 

Citation: Joubert BR, Felix JF, Yousefi P, Bakulski KM, Just AC, Breton C, Reese S, Markunas CA, Richmond RC, Xu C-J, Kupers LK, Oh SS, Hoyo C, Gruzieva O, Soderhall C, Salas LA, Baiz N, Zhang H, Lepeule J, Ruiz C, Ligthart S, Wang T, Taylor JA, Duijts L, Sharp GC, Jankipersadsing SA, Nilsen RM, Vaez A, Fallin MD, Hu D, Litonjua AA, Fuemmeler BF, Huen K, Kere J, Kull I, Munthe-Kaas MC, Gehring U, Bustamante M, Saurel-Coubizolles MJ, Quraishi BM, Ren J, Tost J, Gonzalez JR, Peters MJ, Haberg SE, Xu Z, van Meurs JB, Gaunt TR, Kerkhof M, Corpeleijn E, Feinberg AP, Eng C, Baccarelli AA, Neelon SEB, Bradman A, Merid K, Bergstrom A, Herceg Z, Hernandez-Vargas H, Brunekreef B, Pinart M, Heude B, Ewart S, Yao J, Lemonnier N, Franco OH Wu MC, Hofman A, McArdle W, Van der Vlies P, Falahi F, Gillman MW, Barcellos LF, Kumar A, Wickman M, Guerra S, Charles M-A, Holloway J, Auffray C, Tiemeier HW, Smith GD, Postma D, Hivert M-F, Eskenazi B, Vrijheid M, Arshad H, Anto JM, Dehghan A, Karmaus W, Annesi-Maesano I, Sunyer J, Ghantous A, Pershagen G, Holland N, Murphy SK, DeMeo DL, Burchard EG, Ladd-Acosta C, Snieder H, Nystad W, Koppelman GH, Relton CL, Jaddoe VWV, Wilcox A, Melen E, London SJ. 2016. DNA methylation in newborns and maternal smoking in pregnancy: genome-wide consortium meta-analysis. Am J Hum Genet 98(4):680–696. (Synopsis) (https://www.niehs.nih.gov/news/newsletter/2016/6/papers/dir/index.htm#a3) (Story)

Deficiency in LC3-associated phagocytosis linked with autoinflammatory symptoms

An NIEHS scientist was part of a team that found a link between LC3-associated phagocytosis (LAP) and autoinflammatory disease. The findings showed that animals deficient in LAP manifest symptoms of systemic lupus erythematosus (SLE).

Once a cell dies, it must be removed from the body. Other studies have associated SLE with improper clearance of dying cells. In this paper, LAP-deficient mice displayed similar defects in clearance. Dying cells injected into LAP-deficient mice were engulfed by immune cells, but not degraded. Continuous injection of dying cells accelerated the progression of SLE symptoms. Serum collected from LAP-deficient mice showed many characteristics associated with SLE, such as elevated levels of inflammatory cytokines, autoantibodies, type I interferon-regulated genes, and markers of kidney injury. The research suggests that LAP is essential for the digestion of dying cells and the subsequent suppression of inflammatory responses by macrophages in a lupus-like disease.

Citation: Martinez J, Cunha LD, Park S, Yang M, Lu Q, Orchard R, Li QZ, Yan M, Janke L, Guy C, Linkermann A, Virgin HW, Green DR. 2016. Noncanonical autophagy inhibits the autoinflammatory, lupus-like responses to dying cells. Nature 533(7601):115–119. (Synopsis) (https://www.niehs.nih.gov/news/newsletter/2016/7/papers/dir/index.htm#a2)

INO80 role in melanoma

According to NIEHS researchers and their collaborators, the chromatin remodeling complex INO80 regulates superenhancers (SEs) and oncogenic transcription in melanoma, a commonly diagnosed cancer. SEs are large stretches of DNA containing high numbers of enhancer marks. The approach of disrupting SEs could provide a novel strategy for treating melanoma.

The investigators found that the expression of INO80, the SWI/SNF ATPase in the complex, is elevated in melanoma cell lines and primary melanomas, compared with normal primary melanocytes. INO80 occupies SEs near genes that are important for tumor progression in melanoma cells. Its occupancy results in reduced nucleosomes and increased chromatin accessibility at enhancers, which facilitates the recruitment of Med1 and oncogenic transcription. Finally, driver mutations, the abnormally activated signaling pathways and transcription factors involved in melanoma, can hijack INO80 to rewire the transcription circuity in normal cells to a pathological state that supports tumorigenesis.

Citation: Zhou B, Wang L, Zhang S, Bennett BD, He F, Zhang Y, Xiong C, Han L, Diao L, Li P, Fargo DC, Cox AD, Hu G. 2016. INO80 governs superenhancer-mediated oncogenic transcription and tumor growth in melanoma. Genes Dev 30(12):1440–1453. (Synopsis) (https://www.niehs.nih.gov/news/newsletter/2016/8/papers/dir/index.htm#a4)

Advances in nanotechnology could lead to improved pulmonary safety

An NIEHS-led research team revealed a novel methodology for reducing the lung toxicity caused by multiwalled carbon nanotubes (MWCNTs), cylindrical carbon molecules used in a variety of applications, including structural engineering, optics, and biosensors. This report is the first to show that adding a natural sugar molecule, hyaluronic acid (HA), to MWCNTs reduces their potential for injuring lungs.

The scientists functionalized or attached HA to MWCNTs, then added the complexes to cultures of lung cells from both mice and humans. From monitoring the cells for proinflammatory and profibrotic changes, they observed significantly decreased lung fibrosis and mucous cell metaplasia, which are hallmarks of chronic airway disorders, and reduced inflammation in primary human cells, compared with nonfunctionalized MWCNTs. These findings provide insights into the beneficial impacts of HA functionalization on MWCNT toxicity and may pave the way for advances in pulmonary chemotherapy and occupational safety.

Citation: Hussain S, Ji Z, Taylor AJ, DeGraff LM, George M, Tucker CJ, Chang CH, Li R, Bonner JC, Garantziotis S. 2016. Multiwalled carbon nanotube functionalization with high molecular weight hyaluronan significantly reduces pulmonary injury. ACS Nano 10(8):7675−7688. (Synopsis) (https://www.niehs.nih.gov/news/newsletter/2016/11/papers/dir/index.htm#a5)

X-ray crystal structure of a ribosomal biogenesis protein

NIEHS researchers and their collaborators solved the crystal structure of Nop9, an RNA-binding protein involved in the production of ribosomes, or the free or membrane-bound protein factories of the cell. They also discovered that Nop9 played a crucial role in timing the steps that lead to synthesis of ribosomes. Defects in the manufacture of ribosomes or their function could lead to ribosomopathies, a collection of rare genetic disorders characterized by developmental abnormalities in humans.

The researchers performed X-ray crystallography studies on proteins generated in yeast to identify the structure of Nop9. Because Nop9 is known to interact with ribosomal RNA, the precise site where Nop9 and the target RNA bind each other was determined by biochemical and molecular methods. Using in vivo studies, the authors discovered that Nop9 prevents precocious maturation of pre-ribosomal RNAs by the timely blocking of their access to certain nucleases.

Citation: Zhang J, McCann KL, Qiu C, Gonzalez LE, Baserga SJ, Hall TM. 2016. Nop9 is a PUF-like protein that prevents premature cleavage to correctly process pre-18S rRNA. Nat Commun 7:13085. (Synopsis) (https://www.niehs.nih.gov/news/newsletter/2016/12/papers/dir/index.htm#a2)

Surplus folate during pregnancy may increase child asthma risk

Collaborating with an international team of researchers, NIEHS scientists found a direct link between elevated maternal folate intake and an increased risk of asthma during childhood.

Total folate intake included both dietary and supplemental folate consumption that was validated against plasma folate levels at 18 weeks of gestation. By combining data from the Norwegian Mother and Child Cohort Study and Norwegian Prescription Database, researchers achieved robust follow-up. Risk of childhood asthma increased by approximately 20 percent between the highest and lowest quintiles of total folate intake.

Because adequate folate intake is important for preventing neural tube defects, the World Health Organization recommends supplemental folate intake during pregnancy. The scientists determined that supplemental intake at or above the recommended dosage, in combination with a folate-rich diet, achieves a total folate intake level associated with a slightly increased risk of pediatric asthma.

Citation: Parr CL, Magnus MC, Karlstad O, Haugen M, Refsum H, Ueland PM, McCann A, Nafstad P, Haberg SE, Nystad W, London SJ. 2016. Maternal folate intake during pregnancy and childhood asthma in a population based cohort. Am J Respir Crit Care Med; doi:10.1164/rccm.201604-0788OC [Online 12 August 2016]. (Synopsis) (https://www.niehs.nih.gov/news/newsletter/2016/10/papers/dir/index.htm#a3)

National Toxicology Program (NTP) research

New NTP assay for chemicals that affect neurological development

NTP researchers led a collaborative team that, for the first time, screened 80 compounds with a high-throughput, high-content assay using human neurons derived from induced pluripotent stem cells. The screened compounds ranged from those associated with developmental neurotoxicity and neurotoxicity, to those with unknown potential, such as polycyclic aromatic hydrocarbons and flame retardants.

The scientists treated neurons for 72 hours in 384-well plates, using six different concentrations of each compound. They evaluated compound-specific effects on neurite growth by quantifying total outgrowth, branches, and processes. Simultaneously, they quantified cell viability as a marker of nonspecific cell toxicity.

Among the 80 compounds tested, 38 decreased neurite outgrowth or cell viability, with 16 specifically inhibiting neurite outgrowth. Twelve of the 16 compounds were associated with developmental neurotoxicity or neurotoxicity. Three were polycyclic aromatic hydrocarbons, and one was a flame retardant.

Citation: Ryan KR, Sirenko O, Parham F, Hsieh JH, Cromwell EF, Tice RR, Behl M. 2016. Neurite outgrowth in human induced pluripotent stem cell-derived neurons as a high-throughput screen for developmental neurotoxicity or neurotoxicity. Neurotoxicology 53:271–281. (Synopsis) (https://www.niehs.nih.gov/news/newsletter/2016/4/papers/dir/index.htm#a1)

New resource for studying developing mouse vasculature

An NTP-led research team created a comprehensive histology atlas of the developing mouse blood and lymphatic vasculature using hematoxylin and eosin and immunohistochemical stains. The atlas specifically focused on the hepatobiliary vascular system in CD1 mice embryos 11.5–18.5 days old and in the early postnatal period.

The atlas displays low- and high-magnification color images of the developing embryonic mouse hepatobiliary vascular system and an accompanying 3-dimensional (3D) video representation of the E18.5 mouse venous vasculature. The work correctly identified the portal sinus, a structure that was previously misinterpreted as the ductus venosus. The digital images and 3D video can be viewed online at https://niehsimages.epl-inc.com, with the username “ToxPathLiver” and password “embryolivers.” To view the video, select Projects, then Embryo Hepatobiliary Vascular System, click on the brain symbol associated with the “3D Video,” and open Primary Slide Attachments.

Citation: Swartley OM, Foley JF, Livingston DP 3rd, Cullen JM, Elmore SA. 2016. Histology atlas of the developing mouse hepatobiliary hemolymphatic vascular system with emphasis on embryonic days 11.5-18.5 and early postnatal development. Toxicol Pathol 44(5):705–725. (Synopsis) (https://www.niehs.nih.gov/news/newsletter/2016/5/papers/dir/index.htm#a1)

NTP reduces animal use, one assay at a time — skin sensitization testing

Researchers at the NTP Interagency Center for the Evaluation of Alternative Methods have advanced the integration of nonanimal models to predict chemical skin sensitization. Skin sensitization testing is currently the most common use of animals in chemical safety assessment, and these new approaches will help eliminate animal use.

The researchers used a database of 120 chemicals to train and evaluate six computer models, each with six sets of variables, to optimize accuracy of predictions while minimizing inputs. The variables included in vitro assays, in silico modeling, and chemical properties. Model accuracy was determined based on results in the in vivo local lymph node assay, a gold standard for skin sensitization testing. Using this approach, the researchers identified seven models for predicting skin sensitization that have higher accuracy than currently recommended nonanimal test methods.

Citation: Strickland J, Zang Q, Kleinstreuer N, Paris M, Lehmann DM, Choksi N, Matheson J, Jacobs A, Lowit A, Allen D, Casey W. 2016. Integrated decision strategies for skin sensitization hazard. J Appl Toxicol 36(9):1150–1162. (Synopsis) (https://www.niehs.nih.gov/news/newsletter/2016/10/papers/dir/index.htm#a1)

NTP involved in identifying characteristics of carcinogenicity

An NTP researcher participated in an international working group that identified 10 key characteristics of cancer-causing compounds. Hosted by the International Agency for Research on Cancer, the working group concluded these characteristics might be used to mechanistically identify and evaluate human carcinogenic agents.

Scientists identified features common to many known human carcinogens, such as the ability to affect DNA repair, cause epigenetic changes, and alter cell proliferation, cell death, or nutrient supplies. They then performed a systematic literature review, using the 10 key characteristics to organize information for benzene and polychlorinated biphenyls (PCBs), two Group 1 carcinogens. Their analysis indicated that eight of the 10 proposed characteristics were associated with benzene carcinogenicity, whereas seven of the 10 characteristics were associated with PCBs. The continued development of this model will help assess the potential human cancer risk of newly available compounds.

Citation: Smith MT, Guyton KZ, Gibbons CF, Fritz JM, Portier CJ, Rusyn I, DeMarini DM, Caldwell JC, Kavlock RJ, Lambert PF, Hecht SS, Bucher JR, Stewart BW, Baan RA, Cogliano VJ, Straif K. 2016. Key characteristics of carcinogens as a basis for organizing data on mechanisms of carcinogenesis. Environ Health Perspect 124(6):713–721. (Synopsis) (https://www.niehs.nih.gov/news/newsletter/2016/8/papers/dir/index.htm#a1)


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