Settled house dust (SHD) may be a significant source of children's indoor exposure to hazardous substances including polycyclic aromatic hydrocarbons (PAHs). In this study, organic extracts of sieved vacuum cleaner dust from 51 homes were examined for the presence of 13 PAHs via GC/MS. PAHs were found in all samples with levels of total PAHs ranging between 1.5 and 325 µg g -1 . The PAH concentrations in the SHD were correlated with information contained in corresponding household questionnaires. Analyses showed levels of PAHs to be negatively associated with noncombustion activities such as vacuum cleaning frequency. A risk assessment was conducted to evaluate the excess lifetime cancer risks posed to preschool aged children who ingested PAHs in SHD. The assessment revealed that exposure to PAHs at levels found in 90% of the homes (<40 µg g -1 ) would result in excess cancer risks that are considered acceptable (i.e., 1-100 × 10 -6 ). However, exposure to higher levels of PAHs found in five homes yielded risks that could be higher than 1 × 10 -4 .

Per- and poly-fluoroalkyl substances (PFAS) are widely found in the environment because of their extensive use and persistence. Although several PFAS are well studied, most lack toxicity data to inform human health hazard and risk assessment. This study focussed on four model PFAS: perfluorooctanoic acid (PFOA; 8 carbon), perfluorobutane sulfonate (PFBS; 4 carbon), perfluorooctane sulfonate (PFOS; 8 carbon), and perfluorodecane sulfonate (PFDS; 10 carbon). Human primary liver cell spheroids (pooled from 10 donors) were exposed to 10 concentrations of each PFAS and analyzed at four time-points. The approach aimed to: (1) identify gene expression changes mediated by the PFAS; (2) identify similarities in biological responses; (3) compare PFAS potency through benchmark concentration analysis; and (4) derive bioactivity exposure ratios (ratio of the concentration at which biological responses occur, relative to daily human exposure). All PFAS induced transcriptional changes in cholesterol biosynthesis and lipid metabolism pathways, and predicted PPARα activation. PFOS exhibited the most transcriptional activity and had a highly similar gene expression profile to PFDS. PFBS induced the least transcriptional changes and the highest benchmark concentration (i.e., was the least potent). The data indicate that these PFAS may have common molecular targets and toxicities, but that PFOS and PFDS are the most similar. The transcriptomic bioactivity exposure ratios derived here for PFOA and PFOS were comparable to those derived using rodent apical endpoints in risk assessments. These data provide a baseline level of toxicity for comparison with other known PFAS using this testing strategy.

BackgroundThe transgenic rodent mutation reporter assay provides an efficient approach to identify mutagenic agents in vivo. A major advantage of this assay is that mutant reporter transgenes can be sequenced to provide information on the mode of action of a mutagen and to identify clonally expanded mutations. However, conventional DNA sequence analysis is laborious and expensive for long transgenes, such as lacZ (3096 bp), and is not normally implemented in routine screening.MethodsWe developed a high-throughput next-generation sequencing (NGS) approach to simultaneously sequence large numbers of barcoded mutant lacZ transgenes from different animals. We collected 3872 mutants derived from the bone marrow DNA of six Muta™Mouse males exposed to the well-established mutagen benzo[a]pyrene (BaP) and six solvent-exposed controls. Mutants within animal samples were pooled, barcoded, and then sequenced using NGS.ResultsWe identified 1652 mutant sequences from 1006 independent mutations that underwent clonal expansion. This deep sequencing analysis of mutation spectrum demonstrated that BaP causes primarily guanine transversions (e.g. G:C → T:A), which is highly consistent with previous studies employing Sanger sequencing. Furthermore, we identified novel mutational hotspots in the lacZ transgene that were previously uncharacterized by Sanger sequencing. Deep sequencing also allowed for an unprecedented ability to correct for clonal expansion events, improving the sensitivity of the mutation reporter assay by 50 %.ConclusionThese results demonstrate that the high-throughput nature and reduced costs offered by NGS provide a sensitive and fast approach for elucidating and comparing mutagenic mechanisms of various agents among tissues and enabling improved evaluation of genotoxins.Electronic supplementary materialThe online version of this article (doi:10.1186/s12864-015-2004-4) contains supplementary material, which is available to authorized users.

The global prevalence of depression is high during childbearing. Due to the associated risks to the mother and baby, the selective serotonin reuptake inhibitor fluoxetine (FLX) is often the first line of treatment. Given that FLX readily crosses the placenta, a fetus may be susceptible to the disruptive effects of FLX during this highly plastic stage of development. Here, we demonstrate that a 6-day FLX exposure to a fetus-relevant concentration at a critical developmental stage suppresses cortisol levels in the adult zebrafish (F0). This effect persists for three consecutive generations in the unexposed descendants (F1 to F3) without diminution and is more pronounced in males. We also show that the in vivo cortisol response of the interrenal (fish “adrenal”) to an i.p. injection of adrenocorticotropic hormone was also reduced in the males from the F0 and F3 FLX lineages. Transcriptomic profiling of the whole kidney containing the interrenal cells revealed that early FLX exposure significantly modified numerous pathways closely associated with cortisol synthesis in the male adults from the F0 and F3 generations. We also show that the low cortisol levels are linked to significantly reduced exploratory behaviors in adult males from the F0 to F2 FLX lineages. This may be a cause for concern given the high prescription rates of FLX to pregnant women and the potential long-term negative impacts on humans exposed to these therapeutic drugs.

Per- and polyfluoroalkyl substances (PFAS) are some of the most prominent organic contaminants in human blood. Although the toxicological implications of human exposure to perfluorooctane sulfonate (PFOS) and perfluorooctanoate (PFOA) are well established, data on lesser-understood PFAS are limited. New approach methodologies (NAMs) that apply bioinformatic tools to high-throughput data are being increasingly considered to inform risk assessment for data-poor chemicals. The aim of this study was to compare the potencies (i.e., benchmark concentrations: BMCs) of PFAS in primary human liver microtissues (3D spheroids) using high-throughput transcriptional profiling. Gene expression changes were measured using TempO-seq, a templated, multiplexed RNA-sequencing platform. Spheroids were exposed for 1 or 10 days to increasing concentrations of 23 PFAS in three subgroups: carboxylates (PFCAs), sulfonates (PFSAs), and fluorotelomers and sulfonamides. PFCAs and PFSAs exhibited trends toward increased transcriptional potency with carbon chain-length. Specifically, longer-chain compounds (7 to 10 carbons) were more likely to induce changes in gene expression and have lower transcriptional BMCs. The combined high-throughput transcriptomic and bioinformatic analyses support the capability of NAMs to efficiently assess the effects of PFAS in liver microtissues. The data enable potency ranking of PFAS for human liver cell spheroid cytotoxicity and transcriptional changes, and assessment of in vitro transcriptomic points of departure. These data improve our understanding of the possible health effects of PFAS and will be used to inform read-across for human health risk assessment.

Our results support the notion of a bone marrow microenvironment characterized by increased propensity toward adipogenesis in AML, which may negatively impact normal hematopoiesis. Larger confirmatory studies are needed to understand the impact of various clinical factors. Novel leukemia treatments aimed at normalizing bone marrow niches may enhance the competitive advantage of normal hematopoietic progenitors over leukemia cells.

Higher-throughput, mode-of-action-based assays provide a valuable approach to expedite chemical evaluation for human health risk assessment. In this study, we combined the high-throughput alkaline DNA damage-sensing CometChip® assay with the TGx-DDI transcriptomic biomarker (DDI = DNA damage-inducing) using high-throughput TempO-Seq®, as an integrated genotoxicity testing approach. We used metabolically competent differentiated human HepaRG™ cell cultures to enable the identification of chemicals that require bioactivation to cause genotoxicity. We studied 12 chemicals (nine DDI, three non-DDI) in increasing concentrations to measure and classify chemicals based on their ability to damage DNA. The CometChip® classified 10/12 test chemicals correctly, missing a positive DDI call for aflatoxin B1 and propyl gallate. The poor detection of aflatoxin B1 adducts is consistent with the insensitivity of the standard alkaline comet assay to bulky lesions (a shortcoming that can be overcome by trapping repair intermediates). The TGx-DDI biomarker accurately classified 10/12 agents. TGx-DDI correctly identified aflatoxin B1 as DDI, demonstrating efficacy for combined used of these complementary methodologies. Zidovudine, a known DDI chemical, was misclassified as it inhibits transcription, which prevents measurable changes in gene expression. Eugenol, a non-DDI chemical known to render misleading positive results at high concentrations, was classified as DDI at the highest concentration tested. When combined, the CometChip® assay and the TGx-DDI biomarker were 100% accurate in identifying chemicals that induce DNA damage. Quantitative benchmark concentration (BMC) modeling was applied to evaluate chemical potencies for both assays. The BMCs for the CometChip® assay and the TGx-DDI biomarker were highly concordant (within 4-fold) and resulted in identical potency rankings. These results demonstrate that these two assays can be integrated for efficient identification and potency ranking of DNA damaging agents in HepaRG™ cell cultures.

Many regulatory agencies are exploring ways to integrate toxicogenomic data into their chemical risk assessments. The major challenge lies in determining how to distill the complex data produced by high-content, multi-dose gene expression studies into quantitative information. It has been proposed that benchmark dose (BMD) values derived from toxicogenomics data be used as point of departure (PoD) values in chemical risk assessments. However, there is limited information regarding which genomics platforms are most suitable and how to select appropriate PoD values. In this study, we compared BMD values modeled from RNA sequencing-, microarray-, and qPCR-derived gene expression data from a single study, and explored multiple approaches for selecting a single PoD from these data. The strategies evaluated include several that do not require prior mechanistic knowledge of the compound for selection of the PoD, thus providing approaches for assessing data-poor chemicals. We used RNA extracted from the livers of female mice exposed to non-carcinogenic (0, 2 mg/kg/day, mkd) and carcinogenic (4, 8 mkd) doses of furan for 21 days. We show that transcriptional BMD values were consistent across technologies and highly predictive of the two-year cancer bioassay-based PoD. We also demonstrate that filtering data based on statistically significant changes in gene expression prior to BMD modeling creates more conservative BMD values. Taken together, this case study on mice exposed to furan demonstrates that high-content toxicogenomics studies produce robust data for BMD modelling that are minimally affected by inter-technology variability and highly predictive of cancer-based PoD doses.