In utero exposure to benzo(a)pyrene predisposes offspring to cardiovascular dysfunction in later-life

The Impact of the Aryl Hydrocarbon Receptor on Antenatal Chemical Exposure-Induced Cardiovascular-Kidney-Metabolic Programming

Early life exposure lays the groundwork for the risk of developing cardiovascular-kidney-metabolic (CKM) syndrome in adulthood. Various environmental chemicals to which pregnant mothers are commonly exposed can disrupt fetal programming, leading to a wide range of CKM phenotypes. The aryl hydrocarbon receptor (AHR) has a key role as a ligand-activated transcription factor in sensing these environmental chemicals. Activating AHR through exposure to environmental chemicals has been documented for its adverse impacts on cardiovascular diseases, hypertension, diabetes, obesity, kidney disease, and non-alcoholic fatty liver disease, as evidenced by both epidemiological and animal studies. In this review, we compile current human evidence and findings from animal models that support the connection between antenatal chemical exposures and CKM programming, focusing particularly on AHR signaling. Additionally, we explore potential AHR modulators aimed at preventing CKM syndrome. As the pioneering review to present evidence advocating for the avoidance of toxic chemical exposure during pregnancy and deepening our understanding of AHR signaling, this has the potential to mitigate the global burden of CKM syndrome in the future.

AHR-mediated DNA damage contributes to BaP-induced cardiac malformations in zebrafish

Benzo[a]pyrene (BaP) is a representative polycyclic aromatic hydrocarbon widely present in the environment. We previously reported that the aryl hydrocarbon receptor (AHR) mediates BaP-induced apoptosis and cardiac malformations in zebrafish embryos, but the underlying molecular mechanisms were unclear. Since BaP is a mutagenetic compound, we hypothesize that BaP induces apoptosis and heart defects via AHR-mediated DNA damage. In this study, zebrafish embryos were exposed to BaP at a concentration of 0.1 μM from 2 to 72 h post fertilization, either with or without inhibitors/agonists. AHR activity and levels of reactive oxygen species (ROS) were examined under a fluorescence microscope. mRNA expression levels were quantified by qPCR. DNA damage and apoptosis were detected by immunofluorescence. Our findings revealed that BaP exposure significantly increased BPDE-DNA adducts, mitochondrial damage, apoptosis and heart defects in zebrafish embryos. These effects were counteracted by inhibiting AHR/cyp1a1 using pharmaceutical inhibitors or genetic knockdown. Furthermore, we observed that spironolactone, an antagonist of nucleotide excision repair (NER), significantly enhanced BaP-induced BPDE-DNA adducts, mitochondrial damage, apoptosis and heart malformation rates. Conversely, SRT1720, a SIRT1 agonist, reduced the adverse effects of BaP. Supplementation with spironolactone also enhanced γ-H2AX signals in the heart of zebrafish embryos exposed to BaP. Additional experiments demonstrated that BaP suppressed the expression of SIRT1. We further established that AHR, when activated by BaP, directly inhibited SIRT1 transcription, leading to downregulation of XPC and XPA, which are essential NER genes involved in the recognition and verification steps of the NER process. Taken together, our results indicate that AHR mediates BaP-induced DNA damage in the heart of zebrafish embryos by inducing BPDE-DNA adduct formation via the AHR/Cyp1a1 signalling pathway, as well as suppressing NER via AHR-mediated inhibition of SIRT1.

Disease burden and health risk to rural communities of northeastern India from indoor cooking-related exposure to parent, oxygenated and alkylated PAHs

Exposure to a total of 51 targeted and non-targeted polycyclic aromatic hydrocarbons (PAHs) and their oxygenated and alkylated derivatives associated with size-segregated aerosol was investigated in rural kitchens using liquefied petroleum gas (LPG), mixed biomass (MB) and firewood (FW) fuels in northeastern India. The averaged PM10-associated parent-, alkylated-, and oxygenated-PAHs concentrations increased notably from LPG (257, 54, and 116 ng m-3) to MB (838, 119, and 272 ng m-3) to FW-using kitchens (2762, 225, and 554 ng m-3), respectively. PAHs were preferentially associated with the PM1 fraction with contributions increasing from 80 % in LPG to 86 % in MB and 90 % in FW-using kitchens, which in turn was dominated by <0.25 μm particles (54-75 % of the total). A clear profile of enrichment of low-molecular weight PAHs in cleaner fuels (LPG) and a contrasting enrichment of high-molecular weight PAHs in biomass-based fuels was noted. The averaged internal dose of Benzo[a]pyrene equivalent was the lowest in the case of LPG (19 ng m-3), followed by MB (161 ng m-3) and the highest in FW users (782 ng m-3). Estimation of incremental lifetime cancer risk (ILCR) from PAH exposure revealed extremely high cancer risk in biomass users (factors of 8-40) compared to LPG. The potential years of life lost (PYLL) and PYLL rate averaged across kitchen categories was higher for lung cancer (PYLL: 10.55 ± 1.04 years; PYLL rate: 204 ± 426) compared to upper respiratory tract cancer (PYLL: 10.02 ± 0.05 years; PYLL rate: 4 ± 7), and the PYLL rates for biomass users were higher by factors of 9-56 as compared to LPG users. These findings stress the need for accelerated governmental intervention to ensure a quick transition from traditional biomass-based fuels to cleaner alternatives for the rural population of northeastern India.

Melatonin attenuates cardiopulmonary toxicity induced by benzo(a)pyrene in mice focusing on apoptosis and autophagy pathways

Benzo(a)pyrene (BaP) is a polycyclic aromatic hydrocarbon and a serious environmental pollutant. BaP is formed by the incomplete combustion of organic matter at high temperatures. In addition, tobacco smoke and many foods, especially charbroiled food and grilled meats, contain BaP and can cause it to enter human body. Melatonin, a pineal gland hormone, has antioxidant, anti-apoptosis, and autophagy regulatory properties. The possible protective impact of melatonin on cardiopulmonary toxicity induced by BaP was investigated by examining the antioxidant effects and the apoptosis and autophagy properties of melatonin. Thirty male mice were divided into 5 groups and treated for 28 days as follows: (I) control (BaP and melatonin solvent), (II) BaP (75 mg/kg, oral gavage), (III and IV) BaP (75 mg/kg) + melatonin (10 and 20 mg/kg, intraperitoneally), (V) melatonin (20 mg/kg). The oxidative stress factors (MDA and GSH content) were assessed in the heart and lung tissues. The levels of apoptotic (Caspase-3 and the Bax/Bcl-2 ratio) and autophagic (the LC3 ӀӀ/Ӏ, Beclin-1, and Sirt1) proteins were examined by using western blot analysis. Following the administration of BaP, MDA, the Bax/Bcl-2 ratio, and the Caspase-3 proteins increased in the heart and lung tissues, while GSH, Sirt1, Beclin-1, and the LC3 II/I ratio diminished. The coadministration of melatonin along with BaP, MDA, and apoptotic proteins returned to the control values, while GSH and the autophagy proteins were enhanced in both the heart and lungs. Melatonin exhibited a protective effect against BaP-induced heart and lung injury through the suppression of oxidative stress and apoptosis and the induction of the Sirt1/autophagy pathway.

Benzo(a)pyrene and cardiovascular diseases: An overview of pre-clinical studies focused on the underlying molecular mechanism

Benzo(a)pyrene (BaP) is a highly toxic and carcinogenic polycyclic aromatic hydrocarbon (PAH) whose toxicological effects in the vessel-wall cells have been recognized. Many lines of evidence suggest that tobacco smoking and foodborne BaP exposure play a pivotal role in the dysfunctions of vessel-wall cells, such as vascular endothelial cell and vascular smooth muscle cells, which contribute to the formation and worsening of cardiovascular diseases (CVDs). To clarify the underlying molecular mechanism of BaP-evoked CVDs, the present study mainly focused on both cellular and animal reports whose keywords include BaP and atherosclerosis, abdominal aortic aneurysm, hypertension, or myocardial injury. This review demonstrated the aryl hydrocarbon receptor (AhR) and its relative signal transduction pathway exert a dominant role in the oxidative stress, inflammation response, and genetic toxicity of vessel-wall cells. Furthermore, antagonists and synergists of BaP are also discussed to better understand its mechanism of action on toxic pathways.

Gestational Benzo[a]pyrene Exposure Destroys F1 Ovarian Germ Cells Through Mitochondrial Apoptosis Pathway and Diminishes Surviving Oocyte Quality

Polycyclic aromatic hydrocarbons, including benzo[a]pyrene (BaP), are products of incomplete combustion. In female mouse embryos primordial germ cells proliferate before and after arriving at the gonadal ridge around embryonic (E) 10 and begin entering meiosis at E13.5. Now oocytes, they arrest in the first meiotic prophase beginning at E17.5. We previously reported dose-dependent depletion of ovarian follicles in female mice exposed to 2 or 10 mg/kg-day BaP E6.5-15.5. We hypothesized that embryonic ovaries are more sensitive to gestational BaP exposure during the mitotic developmental window, and that this exposure results in persistent oxidative stress in ovaries and oocytes of exposed F1 female offspring. We orally dosed timed-pregnant female mice with 0 or 2 mg/kg-day BaP in oil from E6.5-11.5 (mitotic window) or E12.5-17.5 (meiotic window). Cultured E13.5 ovaries were utilized to investigate the mechanism of BaP-induced germ cell death. We observed statistically significant follicle depletion and increased ovarian lipid peroxidation in F1 pubertal ovaries following BaP exposure during either prenatal window. Culture of E13.5 ovaries with BaP induced germ cell DNA damage and release of cytochrome c from the mitochondria in oocytes, confirming that BaP exposure induced apoptosis via the mitochondrial pathway. Mitochondrial membrane potential, oocyte lipid droplet (LD) volume, and mitochondrial-LD colocalization were decreased and mitochondrial superoxide levels were increased in the MII oocytes of F1 females exposed gestationally to BaP. Results demonstrate similar sensitivity to germ cell depletion and persistent oxidative stress in F1 ovaries and oocytes following gestational BaP exposure during mitotic or meiotic windows.

Polycyclic aromatic hydrocarbon and its effects on human health: An overeview

Polycyclic aromatic hydrocarbons (PAHs) are a class of chemicals of considerable environmental significance. PAHs are chemical contaminants of fused carbon and hydrogen aromatic rings, basically white, light-yellow, or solid compounds without color. Natural sources of pollution are marginal or less significant, such as volcanic eruptions, natural forest fires, and moorland fires that trigger lightning bursts. The significant determinants of PAH pollution are anthropogenic pollution sources, classified into four groups, i.e., industrial, mobile, domestic, and agricultural pollution sources. Humans can consume PAHs via different routes, such as inhalation, dermal touch, and ingestion. The Effect of PAHs on human health is primarily based on the duration and route of exposure, the volume or concentration of PAHs to which one is exposed, and the relative toxicity of PAHs. Many PAHs are widely referred to as carcinogens, mutagens, and teratogens and thus pose a significant danger to human health and the well-being of humans. Skin, lung, pancreas, esophagus, bladder, colon, and female breast are numerous organs prone to tumor development due to long-term PAH exposure. PAH exposure may increase the risk of lung cancer as well as cardiovascular disease (CVD), including atherosclerosis, thrombosis, hypertension, and myocardial infarction (MI). Preclinical studies have found a relationship between PAH exposure, oxidative stress, and atherosclerosis. In addition, investigations have discovered a relationship between PAH exposure at work and CVD illness and mortality development. This review aims to explain PAH briefly, its transportation, its effects on human health, and a relationship between environmental exposures to PAHs and CVD risk in humans.

Association of maternal dietary habits and ADIPOQ gene polymorphisms with the risk of congenital heart defects in offspring: a hospital-based case-control study

OBJECTIVES

To estimate the association of maternal ADIPOQ gene, dietary habits in early pregnancy, and their interactions with the risk of congenital heart defects (CHDs) in offspring.

METHODS

A case-control study of 464 mothers of CHDs children and 504 mothers of healthy children was included. Maternal dietary habits and genetic polymorphisms of ADIPOQ were the main exposure of interest. Their independent effects and interactions in the development of CHDs were analyzed in our study.

RESULTS

The excessive consumption of pickled vegetables (aOR = 1.58, 95%CI: 1.17-2.12), smoked foods (aOR = 1.84, 95%CI:1.34-2.52), barbecued foods (aOR = 1.62, 95%CI: 1.09-2.39), fish and shrimp (aOR = 0.37, 95%CI: 0.27-50), and milk products (aOR = 0.64, 95%CI: 0.51-80) had a significant association with total CHDs risk. The polymorphisms of ADIPOQ gene at rs1501299 (T/T vs G/G: aOR = 0.27, 95%CI: 0.14-50; G/T vs G/G: aOR = 0.67, 95%CI: 0.46-98) and rs2241766 (G/G vs T/T: aOR = 4.35, 95%CI: 2.23-8.51; T/G vs T/T: aOR = 2.23, 95%CI: 1.51-3.28) showed a significant association with total CHDs risk. Likewise, our results found that maternal dietary habits and ADIPOQ genetic variants also were significantly related to the risk of specific CHDs phenotypes. In addition, gene-diet interaction revealed significant associations between the ADIPOQ gene and maternal dietary habits with total CHDs.

CONCLUSIONS

Maternal dietary habits, ADIPOQ gene, and their interactions show a significant association with the risk of CHDs. However, our study has some limitations, thus our findings need to be taken with caution, which highlights that more studies are required to further corroborate our findings.

Sex Differences in Embryonic Gonad Transcriptomes and Benzo[a]pyrene Metabolite Levels After Transplacental Exposure

Polycyclic aromatic hydrocarbons like benzo[a]pyrene (BaP) are generated during incomplete combustion of organic materials. Prior research has demonstrated that BaP is a prenatal ovarian toxicant and carcinogen. However, the metabolic pathways active in the embryo and its developing gonads and the mechanisms by which prenatal exposure to BaP predisposes to ovarian tumors later in life remain to be fully elucidated. To address these data gaps, we orally dosed pregnant female mice with BaP from embryonic day (E) 6.5 to E11.5 (0, 0.2, or 2 mg/kg/day) for metabolite measurement or E9.5 to E11.5 (0 or 3.33 mg/kg/day) for embryonic gonad RNA sequencing. Embryos were harvested at E13.5 for both experiments. The sum of BaP metabolite concentrations increased significantly with dose in the embryos and placentas, and concentrations were significantly higher in female than male embryos and in embryos than placentas. RNA sequencing revealed that enzymes involved in metabolic activation of BaP are expressed at moderate to high levels in embryonic gonads and that greater transcriptomic changes occurred in the ovaries in response to BaP than in the testes. We identified 490 differentially expressed genes (DEGs) with false discovery rate P-values < 0.05 when comparing BaP-exposed to control ovaries but no statistically significant DEGs between BaP-exposed and control testes. Genes related to monocyte/macrophage recruitment and activity, prolactin family genes, and several keratin genes were among the most upregulated genes in the BaP-exposed ovaries. Results show that developing ovaries are more sensitive than testes to prenatal BaP exposure, which may be related to higher concentrations of BaP metabolites in female embryos.

In utero exposure to mixed PAHs causes heart mass reduction in adult male mice

Polycyclic aromatic hydrocarbons (PAHs) are a risk factor for the occurrence of cardiac diseases. The present study was conducted to investigate the influence of prenatal exposure to a mixed PAHs on heart and the underlying mechanism. Pregnant mice were orally administered with a mixture of 8 kinds of PAHs (0, 5, 50, 500 μg/kg body weight) once every 2 days for a total of 8 dosages. The mixed PAHs contained naphthalene, acenaphthylene, phenanthrene, fluoranthene, pyrene, benzo[a]pyrene, dibenzo[a,h]anthracene and benzo[g,h,i]perylene at a weight ratio of 10: 10: 10: 10: 10: 1: 1: 1. The adult males, not females, showed significantly decreased heart/body weight ratio, which was attributed to the loss of cardiac fiber and the increase of cell apoptosis. The protein expression of transforming growth factor β1 and its downstream transcription factors, Smad3 and Smad4, was significantly downregulated, which caused the loss of cardiac fiber. The downregulated phosphatidylinositol 3-kinase and AKT led to increased expression of caspase3, caspase9, BAX and reduced expression of Bcl-2, which was responsible for the increased cell apoptosis. Different levels of aromatic hydrocarbon receptor and sex hormone receptors between males and females were associated with the distinct effect on heart.

Adverse Impact of Environmental Chemicals on Developmental Origins of Kidney Disease and Hypertension

Chronic kidney disease (CKD) and hypertension are becoming a global health challenge, despite developments in pharmacotherapy. Both diseases can begin in early life by so-called "developmental origins of health and disease" (DOHaD). Environmental chemical exposure during pregnancy can affect kidney development, resulting in renal programming. Here, we focus on environmental chemicals that pregnant mothers are likely to be exposed, including dioxins, bisphenol A (BPA), phthalates, per- and polyfluoroalkyl substances (PFAS), polycyclic aromatic hydrocarbons (PAH), heavy metals, and air pollution. We summarize current human evidence and animal models that supports the link between prenatal exposure to environmental chemicals and developmental origins of kidney disease and hypertension, with an emphasis on common mechanisms. These include oxidative stress, renin-angiotensin system, reduced nephron numbers, and aryl hydrocarbon receptor signaling pathway. Urgent action is required to identify toxic chemicals in the environment, avoid harmful chemicals exposure during pregnancy and lactation, and continue to discover other potentially harmful chemicals. Innovation is also needed to identify kidney disease and hypertension in the earliest stage, as well as translating effective reprogramming interventions from animal studies into clinical practice. Toward DOHaD approach, prohibiting toxic chemical exposure and better understanding of underlying mechanisms, we have the potential to reduce global burden of kidney disease and hypertension.

AHR/ROS-mediated mitochondria apoptosis contributes to benzo[a]pyrene-induced heart defects and the protective effects of resveratrol

Benzo[a]pyrene (BaP), a prototypical polycyclic aromatic hydrocarbon, is widely present in the environment. BaP-induced heart defects have been frequently reported, but the underlying molecular mechanisms remain elusive. Here, we found that BaP increased heart malformations in zebrafish embryos in a concentration-dependent manner, which were attenuated by supplementation with either CH223191 (CH), an aryl hydrocarbon receptor (AHR) inhibitor, or N-acetyl-l-cysteine (NAC), a reactive oxygen species (ROS) scavenger. While CH and NAC both inhibited BaP-induced ROS generation, NAC had no effect on BaP-induced AHR activation. We further demonstrated that BaP increased mitochondrial ROS, decreased mitochondrial membrane potential, and caused endogenous apoptosis, with all these effects being counteracted by supplementation with either CH or NAC. Resveratrol (RSV), a natural AHR antagonist and ROS scavenger, also counteracted the heart malformations caused by BaP. Further experiments showed that RSV attenuated BaP-induced oxidative stress, mitochondrial damage and apoptosis, but had no significant effect on AHR activation. In conclusion, our findings show that BaP induces oxidative stress via AHR activation, which causes mitochondria-mediated intrinsic apoptosis, resulting in heart malformations in zebrafish embryos, and that RSV had a protective effect against BaP-induced heart defects mainly by inhibiting oxidative stress rather than through antagonism of AHR activity.

Benzo(a)pyrene exposure in utero exacerbates Parkinson's Disease (PD)-like α-synucleinopathy in A53T human alpha-synuclein transgenic mice

BACKGROUND

Previous work indicated that benzo[a]pyrene (B(a)P) exposure in utero might adversely affect neurodevelopment and cause Parkinson's Disease (PD)-like symptoms. However, the effect of utero exposure to B(a)P on PD-like α-synucleinopathy and the mechanism under are unclear.

OBJECTIVE

The A53T human alpha-synuclein (α-syn) transgenic mice (M83^+/-) were used in this study to gain insights into the role of B(a)P exposure in utero in the onset of α-syn pathology and neuronal damage.

METHOD

Timed-pregnant M83^+/- dams were exposed to 1) corn oil (vehicle) or 2) 5 mg/kg bw/d B(a)P or 3) 20 mg/kg bw/d B(a)P at gestational day 10-17 by oral gavage and then the SNCA transcription, α-syn accumulation and aggregation, neuroinflammation and nigral dopaminergic neurodegeneration of 60-day-old pups were evaluated.

RESULT

SNCA mRNA and α-syn protein expression in the midbrain of 60 days adult mice were found to be remarkably elevated after B(a)P exposure in utero, the protein degradation capacity was injured (in 20 mg/kg dose group) and α-syn aggregation could be observed in the substantia nigra (SN); Enhanced Iba1 expression in the midbrain and microglial activation (in 20 mg/kg dose group) in the SN were also figured out; Besides, dopaminergic neurons in the SN of 60 days adult mice were significantly decreased.

CONCLUSIONS

Our findings demonstrated that B(a)P exposure in utero could exacerbate α-syn pathology and induce activation of microglia which might further lead to dopaminergic neuronal loss in the SN.

Association and interaction effect of UCP2 gene polymorphisms and dietary factors with congenital heart diseases in Chinese Han population

Congenital heart diseases (CHDs) are the most common birth defects and the leading cause of non-infectious deaths in infants, with an unknown etiology. We aimed to assess the association of genetic variations in UCP2 gene, dietary factors, and their interactions with the risk of CHDs in offspring. The hospital-based case–control study included 464 mothers of children with CHDs and 504 mothers of healthy children. The exposures of interest were maternal dietary factors in early pregnancy and UCP2 genetic variants. Logistic regression analyses were used to assess the association and interaction of UCP2 gene and dietary factors with CHDs. Our results found that the polymorphisms of UCP2 gene at rs659366 and rs660339, together with maternal dietary factors including excessive intake of pickled vegetables and smoked foods were associated with increased risks of CHDs in offspring. Regular intake of fresh meat, fish and shrimp, and milk products were associated with lower risks of CHDs in offspring. Besides, positive interaction between the dominant model of rs659366 and excessive intake of pickled vegetables was found in the additive interaction model (RERI = 1.19, P = 0.044). These findings provide the theoretical basis for gene screening and a new clue for the prevention of CHDs in offspring.

AHR canonical pathway: in vivo findings to support novel antihypertensive strategies

Essential hypertension (HTN) is a disease where genetic and environmental factors interact to produce a high prevalent set of almost indistinguishable phenotypes. The weak definition of what is under the umbrella of HTN is a consequence of the lack of knowledge on the players involved in environment-gene interaction and their impact on blood pressure (BP) and mechanisms. The disclosure of these mechanisms that sense and (mal)adapt to toxic-environmental stimuli might at least determine some phenotypes of essential HTN and will have important therapeutic implications. In the present manuscript, we looked closer to the environmental sensor aryl hydrocarbon receptor (AHR), a ligand-activated transcription factor involved in cardiovascular physiology, but better known by its involvement in biotransformation of xenobiotics through its canonical pathway. This review aims to disclose the contribution of the AHR-canonical pathway to HTN. For better mirror the complexity of the mechanisms involved in BP regulation, we privileged evidence from in vivo studies. Here we ascertained the level of available evidence and a comprehensive characterization of the AHR-related phenotype of HTN. We reviewed clinical and rodent studies on AHR-HTN genetic association and on AHR ligands and their impact on BP. We concluded that AHR is a druggable mechanistic linker of environmental exposure to HTN. We conclude that is worth to investigate the canonical pathway of AHR and the expression/polymorphisms of its related genes and/or other biomarkers (e.g. tryptophan-related ligands), in order to identify patients that may benefit from an AHR-centered antihypertensive treatment.

Association of maternal dietary intakes and CBS gene polymorphisms with congenital heart disease in offspring

BACKGROUND

Although it is generally acknowledged that genetic and environmental factors are associated with risk of congenital heart disease (CHD), the causes are not fully understood. This study aimed at assessing the association of maternal dietary intakes, genetic variants of cystathionine beta synthase (CBS) gene and their interactions with risk of CHDs in offspring.

METHOD

A hospital-based case-control study of 464 mothers with CHD infants and 504 control mothers of health infant was performed. The exposures of interest were maternal dietary intakes in early pregnancy, single nucleotide polymorphisms (SNPs) of CBS gene.

RESULTS

More frequent intake of pickled vegetables (adjusted odds ratio[aOR] = 1.81; 95% confidence interval[CI]: 1.38-2.37), smoked foods (aOR = 2.00; 95%CI: 1.53-2.60), barbecued foods (aOR = 1.63; 95%CI: 1.19-2.25) and fried foods (aOR = 1.57; 95%CI: 1.22-2.03) were associated with higher risk of CHD, while salted eggs (aOR = 0.20; 95%CI: 0.12-0.33), fish and shrimp (aOR = 0.34; 95%CI: 0.27-0.44), fresh fruits (aOR = 0.49; 95%CI: 0.37-0.66), and milk products (aOR = 0.54; 95%CI: 0.45-0.65) were associated with lower risk of CHD. The SNPs of CBS gene at rs2851391 (T/T vs C/C: aOR = 1.91, 95%CI: 1.15-3.15) and rs234714 (T/T vs C/C: aOR = 2.22, 95%CI: 1.32-3.73) significantly increased the risk of CHD. Additionally, significant interaction effects between maternal dietary intakes and CBS genetic variants on CHD risks were observed.

CONCLUSIONS

Maternal dietary factors, CBS genetic variants and their interactions were significantly associated with risk of CHD in offspring. However, it is still unclear how these factors jointly work in the development of CHD, and more studies with larger samples and prospective design are required.

Potential role of polycyclic aromatic hydrocarbons as mediators of cardiovascular effects from combustion particles

Air pollution is the most important environmental risk factor for disease and premature death, and exposure to combustion particles from vehicles is a major contributor. Human epidemiological studies combined with experimental studies strongly suggest that exposure to combustion particles may enhance the risk of cardiovascular disease (CVD), including atherosclerosis, hypertension, thrombosis and myocardial infarction.In this review we hypothesize that adhered organic chemicals like polycyclic aromatic hydrocarbons (PAHs), contribute to development or exacerbation of CVD from combustion particles exposure. We summarize present knowledge from existing human epidemiological and clinical studies as well as experimental studies in animals and relevant in vitro studies. The available evidence suggests that organic compounds attached to these particles are significant triggers of CVD. Furthermore, their effects seem to be mediated at least in part by the aryl hydrocarbon receptor (AhR). The mechanisms include AhR-induced changes in gene expression as well as formation of reactive oxygen species (ROS) and/or reactive electrophilic metabolites. This is in accordance with a role of PAHs, as they seem to be the major chemical group on combustion particles, which bind AhR and/or is metabolically activated by CYP-enzymes. In some experimental models however, it seems as PAHs may induce an inflammatory atherosclerotic plaque phenotype irrespective of DNA- and/or AhR-ligand binding properties. Thus, various components and several signalling mechanisms/pathways are likely involved in CVD induced by combustion particles.We still need to expand our knowledge about the role of PAHs in CVD and in particular the relative importance of the different PAH species. This warrants further studies as enhanced knowledge on this issue may amend risk assessment of CVD caused by combustion particles and selection of efficient measures to reduce the health effects of particular matters (PM).

In Utero Exposure to Benzo[a]pyrene Induces Ovarian Mutations at Doses That Deplete Ovarian Follicles in Mice

Polycyclic aromatic hydrocarbons like benzo[a]pyrene (BaP) are ubiquitous environmental contaminants formed during incomplete combustion of organic materials. Our prior work showed that transplacental exposure to BaP depletes ovarian follicles and increases prevalence of epithelial ovarian tumors later in life. We used the MutaMouse transgenic rodent model to address the hypothesis that ovarian mutations play a role in tumorigenesis caused by prenatal exposure to BaP. Pregnant MutaMouse females were treated with 0, 10, 20, or 40 mg/(kg day) BaP orally on gestational days 7-16, covering critical windows of ovarian development. Female offspring were euthanized at 10 weeks of age; some ovaries with oviducts were processed for follicle counting; other ovaries/oviducts and bone marrow were processed for determination of lacZ mutant frequency (MF). Mutant plaques were pooled within dose groups and sequenced to determine the mutation spectrum. BaP exposure caused highly significant dose-related decreases in ovarian follicles and increases in ovarian/oviductal and bone marrow mutant frequencies at all doses. Absence of follicles, cell packets, and epithelial tubular structures were observed with 20 and 40 mg/(kg day) BaP. Depletion of ovarian germ cells was inversely associated with ovarian MF. BaP induced primarily G > T and G > C transversions and deletions in ovaries/oviducts and bone marrow cells and produced a mutation signature highly consistent with that of tobacco smoking in human cancers. Overall, our results show that prenatal BaP exposure significantly depletes ovarian germ cells, causes histopathological abnormalities, and increases the burden of ovarian/oviductal mutations, which may be involved in pathogenesis of epithelial ovarian tumors. Environ. Mol. Mutagen. 60:410-420, 2019. © 2018 Her Majesty the Queen in Right of Canada.

Maternal exposure to ambient PM2.5 exaggerates fetal cardiovascular maldevelopment induced by homocysteine in rats

Maternal exposure to airborne particulate matter with aerodynamic diameter <2.5 µm (PM_2.5 ) during pregnancy and lactation periods is associated with filial congenital cardiovascular diseases. This study aimed to investigate the toxic effects of maternal exposure to ambient levels of PM_2.5 on filial cardiovascular maldevelopment induced by homocysteine. Using a 2 × 2 factorial design, rats were randomized into four groups and were exposed to ambient PM_2.5 or filtered air (FA) throughout the pregnancy and lactation periods coupled with the administration of either homocysteine (HCY) or normal saline (NS) daily from gestation days 8-10. Morphological changes in the heart, myocardial apoptosis, expressions of cardiac progenitor transcriptional factors, and levels of cytokines were investigated in the offspring. The apoptosis-like changes in the myocardium were seen in the FA plus HCY-treated group and more obviously in the PM_2.5 plus HCY-treated group, which was in accordance with an increased myocardial apoptosis rate in the two groups. PM_2.5 exposure resulted in significantly decreased Nkx2-5 protein level and GATA4 and Nkx2-5 mRNA expressions, and significantly increased TNF-α and IL-1β levels. There were significant interactions between PM_2.5 exposure and HCY-treatment that PM_2.5 exposure reduced Nkx2-5 protein levels and GATA4 and Nkx2-5 mRNA expressions in the HCY-treated groups. These results suggest that maternal exposure to PM_2.5 , even at the ambient levels in urban regions in China, exaggerates filial cardiovascular maldevelopment induced by HCY in a murine model, exacerbating structural abnormalities in the filial cardiac tissue, which is possibly associated with oxidative stress and reduced GATA4 and Nkx2-5 transcription factor expressions. © 2016 Wiley Periodicals, Inc. Environ Toxicol 32: 877-889, 2017.

Effects of coke oven emissions and benzo[a]pyrene on blood pressure and electrocardiogram in coke oven workers

Objective:

To evaluate the effects of occupational exposures to coke oven emissions (COEs) and benzo[a]pyrene (B[a]P) on the prevalence of hypertension and abnormal electrocardiogram (ECG) in coke oven workers.

Methods:

We included 880 coke oven workers and 710 oxygen employees in the exposed and control groups, respectively. Blood pressure (BP), ECG, blood lipid levels, and glucose levels of all subjects were measured. COE and B[a]P concentrations at the bottom, side, and top of the oven and control plants were estimated by weighing and high-performance liquid chromatography.

Results:

The COE concentration at the top and side was higher than that at the bottom (P < 0.05). The levels of B[a]P at the top and side significantly exceeded the limit value. Abnormal BP, ECG, the detection ratio of hypertension and left ventricular high voltage were significantly greater in the exposed group than in the control group (P < 0.05). The logistic regression analysis results revealed that age and B[a]P exposure were risk factors for hypertension in coke oven workers (P < 0.05) and both were risk factors for abnormal ECG (P < 0.05). Moreover, B[a]P exposure, age, and gender were risk factors for impaired fasting glucose in coke oven workers (P < 0.05).

Conclusions:

B[a]P and COE exposures are risk factors for hypertension and abnormal ECG in coke oven workers.

The Nrf2-ARE pathway is associated with Schisandrin b attenuating benzo(a)pyrene-Induced HTR cells damages in vitro

As is ubiquitous in the environmental sources, benzo(a)pyrene (BaP) has been reported to induce reprotoxicity in previous studies. Toxicity to trophoblast cells may be one key factor, but evidences were absent. We speculated that BaP can induce cytotoxicity in human trophoblast HTR-8/SVneo (HTR) cells, and Schisandrin B (Sch B) as a potential protector can inhibit the cytotoxicity. MTS assay identified that BaP induced HTR cells death while Sch B played a cytoprotective role. And after Nrf2 interference, the ability of Sch B-induced cytoprotection was declined. Furthermore, PCR, western blot, ELISA, and SOD assays were found that Sch B significantly increased the mRNA and protein expression of Nrf2, HO1, NQO1, and SOD in the Nrf2-ARE pathway, and the extents of increase were declined after Nrf2 interference. These results demonstrated that the Nrf2-ARE pathway plays an important role in Sch B attenuating BaP-induced HTR cells damages in vitro. © 2015 Wiley Periodicals, Inc. Environ Toxicol 31: 1439-1449, 2016.

Phenanthrene exposure induces cardiac hypertrophy via reducing miR-133a expression by DNA methylation

Growing evidence indicates that there is an emerging link between environmental pollution and cardiac hypertrophy, while the mechanism is unclear. The objective of this study was to examine whether phenanthrene (Phe) could cause cardiac hypertrophy, and elucidate the molecular mechanisms involved. We found that: 1) Phe exposure increased the heart weight and cardiomyocyte size of rats; 2) Phe exposure led to enlarged cell size, and increased protein synthesis in H9C2 cells; 3) Phe exposure induced important markers of cardiac hypertrophy, such as atrial natriuretic peptide, B-type natriuretic peptide, and c-Myc in H9C2 cells and rat hearts; 4) Phe exposure perturbed miR-133a, CdC42 and RhoA, which were key regulators of cardiac hypertrophy, in H9C2 cells and rat hearts; 5) Phe exposure induced DNA methyltransferases (DNMTs) in H9C2 cells and rat hearts; 6) Phe exposure led to methylation of CpG sites within the miR-133a locus and reduced miR-133a expression in H9C2 cells; 7) DNMT inhibition and miR-133a overexpression could both alleviate the enlargement of cell size and perturbation of CdC42 and RhoA caused by Phe exposure. These results indicated that Phe could induce cardiomyocyte hypertrophy in the rat and H9C2 cells. The mechanism might involve reducing miR-133a expression by DNA methylation.

Comparison of toxicogenomics and traditional approaches to inform mode of action and points of departure in human health risk assessment of benzo[a]pyrene in drinking water

Toxicogenomics is proposed to be a useful tool in human health risk assessment. However, a systematic comparison of traditional risk assessment approaches with those applying toxicogenomics has never been done. We conducted a case study to evaluate the utility of toxicogenomics in the risk assessment of benzo[a]pyrene (BaP), a well-studied carcinogen, for drinking water exposures. Our study was intended to compare methodologies, not to evaluate drinking water safety. We compared traditional (RA1), genomics-informed (RA2) and genomics-only (RA3) approaches. RA2 and RA3 applied toxicogenomics data from human cell cultures and mice exposed to BaP to determine if these data could provide insight into BaP's mode of action (MOA) and derive tissue-specific points of departure (POD). Our global gene expression analysis supported that BaP is genotoxic in mice and allowed the development of a detailed MOA. Toxicogenomics analysis in human lymphoblastoid TK6 cells demonstrated a high degree of consistency in perturbed pathways with animal tissues. Quantitatively, the PODs for traditional and transcriptional approaches were similar (liver 1.2 vs. 1.0 mg/kg-bw/day; lungs 0.8 vs. 3.7 mg/kg-bw/day; forestomach 0.5 vs. 7.4 mg/kg-bw/day). RA3, which applied toxicogenomics in the absence of apical toxicology data, demonstrates that this approach provides useful information in data-poor situations. Overall, our study supports the use of toxicogenomics as a relatively fast and cost-effective tool for hazard identification, preliminary evaluation of potential carcinogens, and carcinogenic potency, in addition to identifying current limitations and practical questions for future work.

Metabolomic analysis to define and compare the effects of PAHs and oxygenated PAHs in developing zebrafish

Polycyclic aromatic hydrocarbons (PAHs) and their oxygenated derivatives are ubiquitously present in diesel exhaust, atmospheric particulate matter and soils sampled in urban areas. Therefore, inhalation or non-dietary ingestion of both PAHs and oxy-PAHs are major routes of exposure for people; especially young children living in these localities. While there has been extensive research on the parent PAHs, limited studies exist on the biological effects of oxy-PAHs which have been shown to be more soluble and more mobile in the environment. Additionally, investigations comparing the metabolic responses resulting from parent PAHs and oxy-PAHs exposures have not been reported. To address these current gaps, an untargeted metabolomics approach was conducted to examine the in vivo metabolomic profiles of developing zebrafish (Danio rerio) exposed to 4 µM of benz[a]anthracene (BAA) or benz[a]anthracene-7,12-dione (BAQ). By integrating multivariate, univariate and pathway analyses, a total of 63 metabolites were significantly altered after 5 days of exposure. The marked perturbations revealed that both BAA and BAQ affect protein biosynthesis, mitochondrial function, neural development, vascular development and cardiac function. Our previous transcriptomic and genomic data were incorporated in this metabolomics study to provide a more comprehensive view of the relationship between PAH and oxy-PAH exposures on vertebrate development.

A cross-sectional analysis of polycyclic aromatic hydrocarbons and diesel particulate matter exposures and hypertension among individuals of Mexican origin

BACKGROUND

Epidemiological studies have found that particulate matter is associated with increases in blood pressure. Yet, less is known about the effects of specific sources or constituents of particulate matter, such as diesel particulate matter or polycyclic aromatic hydrocarbons (PAHs). We evaluated associations between self-reported hypertension and residential air levels of diesel particulate matter and PAHs among individuals of Mexican origin living in a large inner city.

METHODS

The Mano a Mano cohort (established in 2001 by the University of Texas MD Anderson Cancer Center) is comprised of individuals of Mexican origin residing in Houston, Texas. Using geographical information systems, we linked modeled annual estimates of PAHs and diesel particulate matter at the census tract level from the 2002 and 2005 U.S. Environmental Protection Agency's National-Scale Air Toxics Assessment to baseline residential addresses of cohort members who enrolled from 2001 to 2003 or 2004 to 2006, respectively. For each enrollment period, we applied mixed-effects logistic regression models to determine associations between diesel particulate matter and PAHs, separately, and self-reported hypertension while adjusting for confounders and the clustering of observations within census tracts and households.

RESULTS

The study population consisted of 11218 participants of which 77% were women. The mean participant age at baseline was 41 years. Following adjustment for age, there was a dose-dependent, positive association between PAHs and hypertension (medium exposure, adjusted odds ratio (OR) = 1.09, 95% CI: 0.88-1.36; high exposure, OR = 1.40, 95% CI: 1.01-1.94) for individuals enrolled during 2001-2003; associations were generally similar in magnitude, but less precise, following adjustment for age, gender, smoking, and BMI. No association was detected for the later period. There was no evidence of an association between residential levels of diesel particulate matter and hypertension.

CONCLUSIONS

This study builds on a limited number of prior investigations of the association between ambient air levels of PAHs or diesel particulate matter and hypertension by focusing on a relatively young cohort of predominantly adult women of Mexican origin. Future analyses are warranted to explore associations in the cohort using incident hypertension when sufficient data become available and to further examine associations between specific chemical constituents of particulate matter and hypertension in this and other populations.

Transcriptomic Changes in Zebrafish Embryos and Larvae Following Benzo[a]pyrene Exposure

Benzo[a]pyrene (BaP) is an environmentally relevant carcinogenic and endocrine disrupting compound that causes immediate, long-term, and multigenerational health deficits in mammals and fish. Previously, we found that BaP alters DNA methylation patterns in developing zebrafish, which may affect gene expression. Herein, we performed a genome-wide transcriptional analysis and discovered differential gene expression and splicing in developing zebrafish. Adult zebrafish were exposed to control or 42.0 ± 1.9 µg/l BaP for 7 days. Eggs were collected and raised in control conditions or continuously exposed to BaP until 3.3 and 96 h post-fertilization (hpf). RNA sequencing (RNA-Seq) was conducted on zebrafish embryos and larvae. Data were analyzed to identify differentially expressed (DE) genes (changed at the gene or transcript variant level) and genes with differential exon usage (DEU; changed at the exon level). At 3.3 hpf, BaP exposure resulted in 8 DE genes and 51 DEU genes. At 96 hpf, BaP exposure altered expression in 1153 DE genes and 159 DEU genes. Functional ontology analysis by Ingenuity Pathway Analysis revealed that many disease pathways, including organismal death, growth failure, abnormal morphology of embryonic tissue, congenital heart disease, and adverse neuritogenesis, were significantly enriched for the DE and DEU genes, providing novel insights on the mechanisms of action of BaP-induced developmental toxicities. Collectively, we discovered substantial transcriptomic changes at the gene, transcript variant, and exon levels in developing zebrafish after early life BaP waterborne exposure, and these changes may lead to long-term adverse physiological consequences.

Cotinine and polycyclic aromatic hydrocarbons levels in the amniotic fluid and fetal cord at birth and in the urine from pregnant smokers

Cigarette smoking during pregnancy has several impacts on fetal development, including teratogenic effects. The objective of this study was to assess whether the toxic substances (cotinine and polycyclic aromatic hydrocarbons) found in pregnant smokers are transmitted to their fetuses. The outcomes were analyzed measuring cotinine and 1-hydroxypyrene in the amniotic fluid and maternal urine, benzopyrene and cotinine in the umbilical cord blood. Through a controlled cross-sectional design, 125 pregnant women were selected and classified according to their smoking status: 37 current smokers, 25 passive smokers and 63 non-smokers (controls). We performed high-performance liquid chromatography to measure substances’ concentrations. A post-hoc Tukey’s test was used to analyze the differences between the groups. All variables were significantly different between controls and smokers. The mean ratios between the concentration of cotinine in smokers compared to controls were as follows: 5.9 [2.5–13.5], p<0.001 in the urine; 25 [11.9–52.9], p<0.001 in the amniotic fluid; and 2.6 [1.0–6.8], p = 0.044 in the umbilical cord blood. The mean ratios of 1-hydroxypyrene concentration between smokers and controls were 7.3 [1.6–29.6], p = 0.003 in the urine and 1.3 [1.0–1.7], p = 0.012 in the amniotic fluid, and of benzopyrene in umbilical cord blood was 2.9 [1.7–4.7], p<0.001. There were no significant differences between controls and passive smokers. When comparing the three groups together, there were statistical differences between all variables. Thus, the fetuses of pregnant smokers are exposed to toxic and carcinogens substances. To our knowledge, this is the first study to measure 1-hydroxypyrene in the amniotic fluid and benzopyrene in umbilical cord blood by high-performance liquid chromatography when considering pregnant women in relation to smoking exposure only.

Exposure to low dose benzo[a]pyrene during early life stages causes symptoms similar to cardiac hypertrophy in adult zebrafish

Growing evidence indicates that polycyclic aromatic hydrocarbons (PAHs) can lead to cardiac hypertrophy and recent research indicates that exposure to low dose crude oil during early embryonic development may lead to impacts on heart health at later life stages. The aim of this study was to evaluate whether exposure during early life stages to low dose benzo[a]pyrene (BaP), as a high-ring PAH, would lead to cardiac hypertrophy at later life stages. Zebrafish were exposed to low dose BaP until 96 hpf, then transferred to clean water and maintained for a year before histological and molecular biological analysis. Our results showed that exposure to low level BaP during early life stages increased heart weight to body weight ratios and deposited collagen in the heart of adult zebrafish. ANP, BNP and c-Myc were also induced in the heart of adult zebrafish by BaP. These results proved that low level BaP exposure during early life stages caused symptoms similar to cardiac hypertrophy in adult zebrafish. Our results displayed an elevated expression of CdC42, RhoA, p-ERK1, 2 and Rac1. Therefore, the mechanism of the cardiac hypertrophy caused by BaP exposure during early life stages may be through inducing the expression of CdC42, RhoA and Rac1, together with activating ERK1, 2.

Increased susceptibility to hyperoxic lung injury and alveolar simplification in newborn rats by prenatal administration of benzo[a]pyrene

Maternal smoking is one of the risk factors for preterm birth and for the development of bronchopulmonary dysplasia (BPD). In this study, we tested the hypothesis that prenatal exposure of rats to benzo[a]pyrene (BP), a component of cigarette smoke, will result in increased susceptibility of newborns to oxygen-mediated lung injury and alveolar simplification, and that cytochrome P450 (CYP)1A and 1B1 enzymes and oxidative stress mechanistically contribute to this phenomenon. Timed pregnant Fisher 344 rats were administered BP (25 mg/kg) or the vehicle corn oil (CO) on gestational days 18, 19 and 20, and newborn rats were either maintained in room air or exposed to hyperoxia (85% O2) for 7 or 14 days. Hyperoxic newborn rats prenatally exposed to the vehicle CO showed lung injury and alveolar simplification, and inflammation, and these effects were potentiated in rats that were prenatally exposed to BP. Prenatal exposure to BP, followed by hyperoxia, also resulted in significant modulation of hepatic and pulmonary cytochrome P450 (CYP)1A and 1B1 enzymes at PND 7-14. These rats displayed significant oxidative stress in lungs at postnatal day (PND) 14, as evidenced by increased levels of the F2-isoprostane 8-iso-PGF2α. Furthermore, these animals showed BP-derived DNA adducts and oxidative DNA adducts in the lung. In conclusion, our results show increased susceptibility of newborns to oxygen-mediated lung injury and alveolar simplification following maternal exposure to BP, and our results suggest that modulation of CYP1A/1B1 enzymes, increases in oxidative stress, and BP-DNA adducts contributed to this phenomenon.

Influence of dietary fat type on benzo(a)pyrene [B(a)P] biotransformation in a B(a)P-induced mouse model of colon cancer

In the US alone, around 60,000 lives/year are lost due to colon cancer. Diet and environment have been implicated in the development of sporadic colon tumors. The objective of this study was to determine how dietary fat potentiates the development of colon tumors through altered B(a)P biotransformation, using the Adenomatous polyposis coli with Multiple intestinal neoplasia mouse model. Benzo(a)pyrene was administered to mice through tricaprylin, and unsaturated (USF; peanut oil) and saturated (SF; coconut oil) fats at doses of 50 and 100 μg/kg via oral gavage over a 60-day period. Blood, colon, and liver were collected at the end of exposure period. The expression of B(a)P biotransformation enzymes [cytochrome P450 (CYP)1A1, CYP1B1 and glutathione-S-transferase] in liver and colon were assayed at the level of protein, mRNA and activities. Plasma and tissue samples were analyzed by reverse phase high-performance liquid chromatography for B(a)P metabolites. Additionally, DNA isolated from colon and liver tissues was analyzed for B(a)P-induced DNA adducts by the (32)P-postlabeling method using a thin-layer chromatography system. Benzo(a)pyrene exposure through dietary fat altered its metabolic fate in a dose-dependent manner, with 100 μg/kg dose group registering an elevated expression of B(a)P biotransformation enzymes, and greater concentration of B(a)P metabolites, compared to the 50 μg/kg dose group (P<.05). This effect was more pronounced for SF group compared to USF group (P<.05). These findings establish that SF causes sustained induction of B(a)P biotransformation enzymes and extensive metabolism of this toxicant. As a consequence, B(a)P metabolites were generated to a greater extent in colon and liver, whose concentrations also registered a dose-dependent increase. These metabolites were found to bind with DNA and form B(a)P-DNA adducts, which may have contributed to colon tumors in a subchronic exposure regimen.

Benzo[a]pyrene decreases global and gene specific DNA methylation during zebrafish development

DNA methylation is important for gene regulation and is vulnerable to early-life exposure to environmental contaminants. We found that direct waterborne benzo[a]pyrene (BaP) exposure at 24μg/L from 2.5 to 96hpf to zebrafish embryos significantly decreased global cytosine methylation by 44.8% and promoter methylation in vasa by 17%. Consequently, vasa expression was significantly increased by 33%. In contrast, BaP exposure at environmentally relevant concentrations did not change CpG island methylation or gene expression in cancer genes such as ras-association domain family member 1 (rassf1), telomerase reverse transcriptase (tert), c-jun, and c-myca. Similarly, BaP did not change gene expression of DNA methyltransferase 1 (dnmt1) and glycine N-methyltransferase (gnmt). While total DNMT activity was not affected, GNMT enzyme activity was moderately increased. In summary, BaP is an epigenetic modifier for global and gene specific DNA methylation status in zebrafish larvae.

Structurally distinct polycyclic aromatic hydrocarbons induce differential transcriptional responses in developing zebrafish

Polycyclic aromatic hydrocarbons (PAHs) are ubiquitous in the environment as components of fossil fuels and by-products of combustion. These multi-ring chemicals differentially activate the aryl hydrocarbon receptor (AHR) in a structurally dependent manner, and induce toxicity via both AHR-dependent and -independent mechanisms. PAH exposure is known to induce developmental malformations in zebrafish embryos, and recent studies have shown cardiac toxicity induced by compounds with low AHR affinity. Unraveling the potentially diverse molecular mechanisms of PAH toxicity is essential for understanding the hazard posed by complex PAH mixtures present in the environment. We analyzed transcriptional responses to PAH exposure in zebrafish embryos exposed to benz(a)anthracene (BAA), dibenzothiophene (DBT) and pyrene (PYR) at concentrations that induced developmental malformations by 120 h post-fertilization (hpf). Whole genome microarray analysis of mRNA expression at 24 and 48 hpf identified genes that were differentially regulated over time and in response to the three PAH structures. PAH body burdens were analyzed at both time points using GC-MS, and demonstrated differences in PAH uptake into the embryos. This was important for discerning dose-related differences from those that represented unique molecular mechanisms. While BAA misregulated the least number of transcripts, it caused strong induction of cyp1a and other genes known to be downstream of the AHR, which were not induced by the other two PAHs. Analysis of functional roles of misregulated genes and their predicted regulatory transcription factors also distinguished the BAA response from regulatory networks disrupted by DBT and PYR exposure. These results indicate that systems approaches can be used to classify the toxicity of PAHs based on the networks perturbed following exposure, and may provide a path for unraveling the toxicity of complex PAH mixtures.