Styrene trimer may increase thyroid hormone levels via down-regulation of the aryl hydrocarbon receptor (AhR) target gene UDP-glucuronosyltransferase

Developmental toxicity and mechanism of polychlorinated biphenyls 126 and nano-polystyrene combined exposure to zebrafish larvae

3,3',4,4',5-Pentachlorobiphenyl (PCB126) is the most toxic congener of dioxin-like polychlorinated biphenyls (DL PCBs), while nanoplastics (NPs) have recently emerged as significant marine pollutants, both posing threats to aquatic organisms and human health. They coexist in the environment, but their comprehensive toxicological effects remain unclear. In this study, zebrafish embryos were simultaneously exposed to PCB126 and 80-nanometer nanoplastyrene (NPS). Researchers utilized fluorescence microscopy, qPCR, histopathological examination, and transcriptomic sequencing to investigate the developmental toxicity of different concentrations of PCB126 and NPS individually or in combination on zebrafish embryos and larvae. Results indicate that the chorion significantly impedes the accumulation of NPS (p < 0.05). It is noteworthy that this barrier effect diminishes upon simultaneous exposure to PCB126. In this experiment, the semi-lethal concentration of PCB126 for larvae was determined to be 6.33 μg/L. Exposure to PCB126 induces various deformities, primarily mediated through the aryl hydrocarbon receptor (AHR). Similarly, exposure to NPS also activates AHR, leading to developmental impairments. Furthermore, transcriptomic sequencing revealed similar effects of PCB126 and NPS on the gene expression trends in zebrafish larvae, but combined exposure to both exacerbates the risk of cancer and induces more severe cardiac toxicity. At this level, co-exposure to PCB126 and NPS adversely affects the development of zebrafish larvae. This study contributes to a deeper understanding of the in vivo accumulation of DL polychlorinated biphenyls and microplastics in actual aquatic environments and their impact on fish development.

Prevalence and implications of microplastics in potable water system: An update

Synthetic plastics, which are lightweight, durable, elastic, mouldable, cheap, and hydrophobic, were originally invented for human convenience. However, their non-biodegradability and continuous accumulation at an alarming rate as well as subsequent conversion into micro/nano plastic scale structures via mechanical and physio-chemical degradation pose significant threats to living beings, organisms, and the environment. Various minuscule forms of plastics detected in water, soil, and air are making their passage into living cells. High temperature and ambient humidity increase the degradation potential of plastic polymers photo-catalytically under sunlight or UV-B radiations. Microplastics (MPs) of polyethylene terephthalate, polyethylene, polystyrene, polypropylene, and polyvinyl chloride have been detected in bottled water. These microplastics are entering into the food chain cycle, causing serious harm to all living organisms. MPs entering into the food chain are usually inert in nature, possessing different sizes and shapes. Once they enter a cell or tissue, it causes mechanical damage, induces inflammation, disturbs metabolism, and even lead to necrosis. Various generation routes, types, impacts, identification, and treatment of microplastics entering the water bodies and getting associated with various pollutants are discussed in this review. It emphasizes potential detection techniques like pyrolysis, gas chromatography-mass spectrometry (GC-MS), micro-Raman spectroscopy, and fourier transform infrared spectroscopy (FT IR) spectroscopy for microplastics from water samples.

Migration of styrene oligomers from food contact materials: in silico prediction of possible genotoxicity

Styrene oligomers (SO) are well-known side products formed during styrene polymerization. They consist mainly of dimers (SD) and trimers (ST) that have been shown to be still residual in polystyrene (PS) materials. In this study migration of SO from PS into sunflower oil at temperatures between 5 and 70 °C and contact times between 0.5 h and 10 days was investigated. In addition, the contents of SD and ST in the fatty foodstuffs créme fraiche and coffee cream, which are typically enwrapped in PS, were measured and the amounts detected (of up to 0.123 mg/kg food) were compared to literature data. From this comparison, it became evident, that the levels of SO migrating from PS packaging into real food call for a comprehensive risk assessment. As a first step towards this direction, possible genotoxicity has to be addressed. Due to technical and experimental limitations, however, the few existing in vitro tests available are unsuited to provide a clear picture. In order to reduce uncertainty of these in vitro tests, four different knowledge and statistics-based in silico tools were applied to such SO that are known to migrate into food. Except for SD4 all evaluated SD and ST showed no alert for genotoxicity. For SD4, either the predictions were inconclusive or the substance was assigned as being out of the chemical space (out of domain) of the respective in silico tool. Therefore, the absence of genotoxicity of SD4 requires additional experimental proof. Apart from SD4, in silico studies supported the limited in vitro data that indicated the absence of genotoxicity of SO. In conclusion, the overall migration of all SO together into food of up to 50 µg/kg does not raise any health concerns, given the currently available in silico and in vitro data.

Plastic/Natural Fiber Composite Based on Recycled Expanded Polystyrene Foam Waste

A novel reinforced recycled expanded polystyrene (r-EPS) foam/natural fiber composite was successfully developed. EPS was recycled by means of the dissolution method using an accessible commercial mixed organic solvent, while natural fibers, i.e., coconut husk fiber (coir) and banana stem fiber (BSF) were used as reinforcement materials. The treatment of natural fibers with 5% (w/v) sodium hydroxide solution reduces the number of –OH groups and non-cellulose components in the fibers, more so with longer treatments. The natural fibers treated for 6 h showed rough surfaces that provided good adhesion and interlocking with the polymer matrix for mechanical reinforcement. The tensile strength and impact strength of r-EPS foam composites with treated fibers were higher than for non-filled r-EPS foam, whereas their flexural strengths were lower. Thus, this study has demonstrated an alternative way to produce recycled polymer/natural fiber composites via the dissolution method, with promising enhanced mechanical properties.

Environmental Distribution of Styrene Oligomers (SOs) Coupled with Their Source Characteristics: Tracing the Origin of SOs in the Environment

Despite growing concerns regarding plastic additives, their environmental fate coupled with leaching from source materials are not well known. Styrene oligomers (SOs), which are unintended additives in expanded polystyrene (EPS), are estrogenic micropollutants. Here, we identified the effects of their potential sources (i.e., EPS buoy and its leachate) and environmental dilution on SO distribution within coastal sediments. SO content in fresh EPS particles was 0.1% (w/w), dominated by 2,4,6-triphenyl-hexene (ST-1), while 2,4-diphenyl-1-butene (SD-2) accounted for most of the SOs in EPS leachate, indicating its faster leachability. In lake and offshore environments, the SO composition profiles from their terrestrial inputs and inner sites were similar to those of EPS leachate; meanwhile, the exponentially decreasing SO concentration and increasing styrene trimers (STs) fraction with distance from the inner to outer sites were evident. These profiles indicated continuous SO leaching from their potential sources in the inland, followed by a change in SOs due to environmental dilution. SOs in beach sediment implied the presence of micro-sized EPS particles. We suggest the ST-1 to SD-2 ratio as an index to differentiate among freshly leached SOs (∼0.02), environmentally diluted SOs after leaching (∼0.1), SOs in fresh EPS (∼1.2), and SOs in aged EPS (> 2).

Albumin is a secret factor involved in multidirectional interactions among the serotoninergic, immune and endocrine systems that supervises the mechanism of CYP1A and CYP3A regulation in the liver

This review focuses on albumin, which is involved in multidirectional interactions among the immune, endocrine and serotoninergic systems and supervises the regulation of cytochrome P450 (CYP) isoforms under conditions of both normal liver function and liver insufficiency. Special attention is paid to albumin, thyroid hormones, testosterone and tryptophan hydroxylase in these interactions as well as their potential roles in liver regeneration. The association of these factors with inflammation and the modification of the mechanism of hepatic drug-metabolizing CYP isoform regulation are also presented because changes in the expression of CYP isoforms in the liver may result in subsequent changes to a marker substance used for testing CYP activity, thus providing a simple way to control the liver regeneration process or the dangerous stimulation of hepatocarcinogenesis.

Marine microplastics bound dioxin-like chemicals: Model explanation and risk assessment

Microplastics have become one of the most pervasive emerging pollutants in the marine environment because of their wide occurrence and high sorption ability for hydrophobic organic contaminants (HOCs). Among the associated HOCs, dioxin-like chemicals (DLCs) can pose severe health risks; however, information on effects of microplastics bound DLCs is lacking. To fill this knowledge gap, this study integrated chemical analysis and in vitro bioassays to elucidate the potential dioxin-like effects of microplastics bound DLCs. Chemical analysis results demonstrated that styrofoams possessed significantly greater DLCs than other coastal or open ocean plastic particles. This was probably due to the presence of additives and greater sorption ability of expanded polystyrene. However, styrofoams did not show as strong dioxin-like effects as predicted by the bioanalysis equivalent model in bioassays. This could be attributed to the decreased DLC bioavailability and increased competition with the presence of styrene oligomers. Besides, bioassay results also demonstrated that aging increased the associated DLC concentrations, since extra sorption from surrounding environment occurred during prolonged retention periods. Finally, it was estimated that the leaching of DLCs could induce dioxin-like effects in marine organisms under 100% (11/11) and 18% (2/11) scenarios for aged pellets and styrofoams through aqueous or dietary exposures.

The body burden and thyroid disruption in lizards (Eremias argus) living in benzoylurea pesticides-contaminated soil

Dermal exposure is regarded as a potentially significant but understudied route for pesticides uptake in terrestrial reptiles. In this study, a native Chinese lizard was exposed to control, diflubenzuron or flufenoxuron contaminated soil (1.5 mg kg^-1) for 35 days. Tissue distribution, liver lesions, thyroid hormone levels and transcription of most target genes were examined. The half-lives of diflubenzuron and flufenoxuron in the soil were 118.9 and 231.8 days, respectively. The accumulation of flufenoxuron in the liver, brain, kidney, heart, plasma and skin (1.4-35.4 mg kg^-1) were higher than that of diflubenzuron (0-1.7 mg kg^-1) at all time points. The skin permeability factor of flufenoxuron was more than 20-fold greater than that of diflubenzuron at the end of exposure. However, the liver was more vulnerable in the diflubenzuron exposure group. The alterations of triiodothyronine (T3) and thyroxine (T4) level after diflubenzuron or flufenoxuron exposure were accompanied with the changes in the transcription of target genes involved not only in hypothalamus-pituitary-thyroid (HPT) axis (sult, dio2, trα and udp) but also in metabolism system (cyp1a and ahr). These results indicated that flufenoxuron produced greater body burdens to lizards through dermal exposure, whereas both diflubenzuron and flufenoxuron have the potential to disturb metabolism and thyroid endocrine system.

Long-term changes in distributions of dioxin-like and estrogenic compounds in sediments of Lake Sihwa, Korea: Revisited mass balance

In the late 1990s, severe pollution by persistent organic contaminants (POCs) was observed in Lake Sihwa by use of a combination of instrumental analyses and in vitro bioassays. To determine long-term changes (>15-year gaps) in distributions of POCs and their potential toxic potencies in the given region, sediment assessments were reconducted. Target chemicals include polycyclic aromatic hydrocarbons (PAHs), alkylphenols (APs), and recently reported emerging chemicals, styrene oligomers (SOs). We employed in vitro bioassays (such as H4IIE-luc and MVLN) to determine potential sediment toxicities. The reduction rates of mean concentrations of APs and SOs in sediments between the two sampling years (1998 vs. 2015) were estimated to be 99% and 67%, respectively. Although APs and SOs significantly declined over the 15-year period, concentrations of PAHs were consistent. Results of the bioassays were consistent with the instrumental data, with relatively great concentrations of all target compounds being detected, particularly in inland creeks. Compositions of all target compounds exhibited changes in homologue patterns over the 15 years considered. This result indicated varying and/or continuing sources in this region. In particular, PAHs were dominated by higher-molecular-weight PAHs (e.g., benzo[g,h,i]perylene and benzo[b]fluoranthene) in recent years. This result might indicate consumption of oil-related fuels. Quantitative potency balance analysis revealed that concentrations of instrumentally-derived equivalents accounted for as little as 18.5% of bioassay-derived equivalents, which indicated significant amounts of unknown and/or unmeasured compounds were present. The present study documented the continuing severe pollution by selected POCs in the Lake Sihwa region over the last 15 years, indicating a lack of management in the area studied.

Hazardous or not - Are adult and juvenile individuals of Potamopyrgus antipodarum affected by non-buoyant microplastic particles?

Microplastic has been ubiquitously detected in freshwater ecosystems. A variety of freshwater organisms were shown to ingest microplastic particles, while a high potential for adverse effects are expected. However, studies addressing the effect of microplastic in freshwater species are still scarce compared to studies on marine organisms. In order to gain further insights into possible adverse effects of microplastic particles on freshwater invertebrates and to set the base for further experiments we exposed the mud snail (Potampoyrgus antipodarum) to a large range of common and environmentally relevant non-buoyant polymers (polyamide, polyethylene terephthalate, polycarbonate, polystyrene, polyvinylchloride). The impact of these polymers was tested by performing two exposure experiments with irregular shaped microplastic particles with a broad size distribution in a low (30%) and a high microplastic dose (70%) in the food. First, possible effects on adult P. antipodarum were assessed by morphological and life-history parameters. Second, the effect of the same mixture on the development of juvenile P. antipodarum until maturity was analyzed. Adult P. antipodarum showed no morphological changes after the exposure to the microplastic particles, even if supplied in a high dose. Moreover, although P. antipodarum is an established model organism and reacts especially sensitive to endocrine active substances no effects on embryogenesis were detected. Similarly, the juvenile development until maturity was not affected. Considering, that most studies showing effects on marine and freshwater invertebrates mostly exposed their experimental organisms to very small (≤20 μm) polystyrene microbeads, we anticipate that these effects may be highly dependent on the chemical composition of the polymer itself and the size and shape of the particles. Therefore, more studies are necessary to enable the identification of harmful synthetic polymers as some of them may be problematic and should be declared as hazardous whereas others may have relatively moderate or no effects.

Are styrene oligomers in coastal sediments of an industrial area aryl hydrocarbon-receptor agonists?

Effect-directed analysis (EDA) was performed to identify the major aryl hydrocarbon receptor (AhR) agonists in sediments collected from a highly industrialized area (Lake Shihwa, Korea). Great AhR-mediated potencies were found in fractions containing aromatic compounds with log Kow values of 5-8, and relatively great concentrations of styrene oligomers (SOs) and polycyclic aromatic hydrocarbons (PAHs) were detected in those fractions. Until now, there was little information on occurrences and toxic relative potencies (RePs) of SOs in coastal environments. In the present study; i) distributions and compositions, ii) AhR binding affinities, and iii) contributions of SOs to total AhR-mediated potencies were determined in coastal sediments. Elevated concentrations of 10 SOs were detected in sediments of inland creeks ranging from 61 to 740 ng g(-1) dry mass (dm), while lesser concentrations were found in inner (mean = 33 ng g(-1) dm) and outer regions (mean = 25 ng g(-1) dm) of the lake. Concentrations of PAHs in sediments were comparable to those of SOs. 2,4-diphenyl-1-butene (SD3) was the predominant SO analogue in sediments. SOs and PAHs were accumulated in sediments near sources, and could not be transported to remote regions due to their hydrophobicity. RePs of 3 SOs could be derived, which were 1000- to 10,000-fold less than that of one representative potent AhR active PAH, benzo[a]pyrene. Although concentrations of SOs in sediments were comparable to those of PAHs, the collective contribution of SOs to total AhR-mediated potencies were rather small (<1%), primarily due to their smaller RePs. Overall, the present study provides information on distributions and AhR binding affinities for SOs as baseline data for degradation products of polystyrene plastic in the coastal environment.

Global styrene oligomers monitoring as new chemical contamination from polystyrene plastic marine pollution

Polystyrene (PS) plastic marine pollution is an environmental concern. However, a reliable and objective assessment of the scope of this problem, which can lead to persistent organic contaminants, has yet to be performed. Here, we show that anthropogenic styrene oligomers (SOs), a possible indicator of PS pollution in the ocean, are found globally at concentrations that are higher than those expected based on the stability of PS. SOs appear to persist to varying degrees in the seawater and sand samples collected from beaches around the world. The most persistent forms are styrene monomer, styrene dimer, and styrene trimer. Sand samples from beaches, which are commonly recreation sites, are particularly polluted with these high SOs concentrations. This finding is of interest from both scientific and public perspectives because SOs may pose potential long-term risks to the environment in combination with other endocrine disrupting chemicals. From SOs monitoring results, this study proposes a flow diagram for SOs leaching from PS cycle. Using this flow diagram, we conclude that SOs are global contaminants in sandy beaches around the world due to their broad spatial distribution.

Diastereoisomer-specific effects of hexabromocyclododecanes on hepatic aryl hydrocarbon receptors and cytochrome P450s in zebrafish (Danio rerio)

In order to elucidate the mechanism for diastereoisomer-specific toxicity and metabolism of hexabromocyclododecanes (HBCDs) in biota, zebrafish (Danio rerio) were exposed to different concentrations of individual HBCD diastereoisomers (α-, β- and γ-HBCD) in water for 7 and 21d. We examined the gene expression of aryl hydrocarbon receptor (AHR) and cytochrome P450 (CYP), as well as ethoxyresorufin-O-deethylase (EROD) activity in zebrafish livers. Exposure to different HBCD diastereoisomers caused different expression of AHRs in zebrafish livers. For instance, 10 and 100μgL(-1) of α- and β-HBCD up-regulated the expressions of ahr1a and ahr1b in zebrafish liver, whereas 10 and 100μgL(-)(1) of γ-HBCD down-regulated them after 7d exposure. α-HBCD showed the most significant up-regulation of ahr1a and ahr1b expression, whereas γ-HBCD showed the most significant down-regulation of their expression among three HBCD diastereoisomers. Moreover, HBCDs could affect the expression of CYP1s as well as EROD activity in a gene-specific and diastereoisomer-specific manner. α-, β- and γ-HBCD inhibited cyp1a expression but enhanced the expression of cyp1b1 and cyp1c1. α-, β- and γ-HBCD showed different degrees of effect on the same CYP1 gene in a concentration-dependent way. The different effects of HBCD diastereoisomers on these genes we examined and EROD activity not only indicate diastereoisomer-specific toxic effect, but also in turn explain diastereoisomer-specific accumulation of HBCDs in zebrafish.

Regional distribution of styrene analogues generated from polystyrene degradation along the coastlines of the North-East Pacific Ocean and Hawaii

Beach sand and seawater taken from the coastlines of the North-East Pacific Ocean and Hawaii State were investigated to determine the causes of global chemical contamination from polystyrene (PS). All samples were found to contain styrene monomer (SM), styrene dimers (SD), and styrene trimers (ST) with a concentration distribution of styrene analogues in the order of ST > SD > SM. The contamination by styrene analogues along the West Coast proved more severe than in Alaska and other regions. The Western Coastlines of the USA seem be affected by both land- and ocean-based pollution sources, which might result from it being a heavily populated area as the data suggest a possible proportional relationship between PS pollution and population. Our results suggest the presence of new global chemical contaminants derived from PS in the ocean, and along coasts.

Tanshinone I increases CYP1A2 protein expression and enzyme activity in primary rat hepatocytes

This study investigated the effects of Danshen and its active ingredients on the protein expression and enzymatic activity of CYP1A2 in primary rat hepatocytes. The ethanolic extract of Danshen roots (containing mainly tanshinones) inhibited CYP1A2-catalyzed phenacetin O-deethylation (IC(50)=24.6 μg/ml) in primary rat hepatocytes while the water extract containing mainly salvianolic acid B and danshenshu had no effect. Individual tanshinones such as cryptotanshinone, dihydrotanshinone, tanshinone IIA inhibited the CYP1A2-mediated metabolism with IC(50) values at 12.9, 17.4 and 31.9 μM, respectively. After 4-day treatment of the rat hepatocytes, the ethanolic extract of Danshen and tanshinone I increased rat CYP1A2 activity by 6.8- and 5.2-fold, respectively, with a concomitant up-regulation of CYP1A2 protein level by 13.5- and 6.5-fold, respectively. CYP1A2 induction correlated with the up-regulation of mRNA level of aryl hydrocarbon receptor (AhR), which suggested a positive feedback mechanism of tanshinone I-mediated CYP1A2 induction. A formulated Danshen pill (containing mainly danshensu and salvianolic acid B and the tanshinones) up-regulated CYP1A2 protein expression and enzyme activity, but danshensu and salvianolic acid B, when used individually, did not affect CYP1A2 activity. This study was the first report on the Janus action of the tanshinones on rat CYP1A2 activity.

Increased plasma thyroid hormone concentrations in LDL receptor deficient mice may be explained by inhibition of aryl hydrocarbon receptor-dependent expression of hepatic UDP-glucuronosyltransferases

BACKGROUND

Overexpression of SREBP-1 causes a repression of hepatic genes involved in phase II metabolism. In LDL receptor deficient (LDLR(-/-)) mice, active levels of SREBP-1 in the liver are increased. We investigated the hypothesis that LDLR(-/-) mice have increased concentrations of thyroid hormones in plasma due to a reduced hepatic glucuronidation.

METHODS

Female LDLR(-/-) and wild-type mice were used to study the effect of the LDLR(-/-) genotype on thyroid hormone metabolism.

RESULTS

LDLR(-/-) mice had a higher concentration of nuclear SREBP-1, higher concentrations of thyroxine and triiodothyronine in plasma, a lower expression of relevant UGT1A isoforms, reduced activities of pNP-UGT, T(3)-UGT and T(4)-UGT and a lower mRNA and protein concentration of AhR in the liver than wild-type mice (P<0.05). Plasma concentration of TSH, mRNA concentrations of various genes involved in thyroid hormone synthesis in the thyroid, activity of deiodinase and mRNA concentrations of two thyroid hormone responsive genes, CYP7A1 and Na(+)/K(+)-ATPase, in the liver did not differ between both genotypes.

CONCLUSIONS

This study shows that LDLR(-/-) mice have increased concentrations of thyroid hormones in plasma. This effect is probably due to an inhibition of thyroid hormone glucuronidation, which might be caused by down-regulation of UGT genes due to a reduced expression of AhR. However, with respect to plasma TSH concentration and expression of thyroid hormone responsive genes no overt hyperthyroidism was detected.

GENERAL SIGNIFICANCE

LDL receptor deficiency leads to a reduced glucuronidation of thyroid hormones in the liver which causes a moderate increase of plasma thyroid hormone concentrations.

Upregulation of Ugt1a genes in placentas and fetal livers in a murine model of assisted reproduction

Genes from Ugt1a family in placenta and fetal liver are responsible for hormone, nutrient and chemical balance during pregnancy. Assisted reproduction technologies (ART) i.e. intracytoplasmic sperm injection (ICSI) and in vitro fertilization (IVF) alter steroid homeostasis in pregnancy through increased glucuronidation. Here we show that ART (particularly ICSI) upregulates Ugt1a1, 1a2, 1a6 and 1a9 expression in murine placentas and fetal livers with higher mRNA related to lower progesterone (1a1) and cholesterol (1a2, 1a6) in placentas. Greater steroid clearance in ART through transcriptional upregulation of Ugt1a in the placental-fetal unit may decrease the availability of essential molecules, mediating negative reproductive outcomes.

Correlation of dysfunction of nonmuscle myosin IIA with increased induction of Cyp1a1 in Hepa-1 cells

The aryl hydrocarbon receptor (AhR) is one of the best known ligand-activated transcription factors and it induces Cyp1a1 transcription by binding with 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD). Recent focus has been on the relationship of AhR with signaling pathways that modulate cell shape and migration. In nonmuscle cells, nonmuscle myosin II is one of the key determinants of cell morphology, but it has not been investigated whether its function is related to Cyp1a1 induction. In this study, we observed that (-)-blebbistatin, which is a specific inhibitor of nonmuscle myosin II, increased the level of CYP1A1-mRNA in Hepa-1 cells. Comparison of (-)-blebbistatin with (+)-blebbistatin, which is an inactive enantiomer, indicated that the increase of CYP1A1-mRNA was due to nonmuscle myosin II inhibition. Subsequent knockdown experiments observed that reduction of nonmuscle myosin IIA, which is only an isoform of nonmuscle myosin II expressed in Hepa-1 cells, was related to the enhancement of TCDD-dependent Cyp1a1 induction. Moreover, chromatin immunoprecipitation assay indicated that the increase of Cyp1a1 induction was the result of transcriptional activation due to increased binding of AhR and RNA polymerase II to the enhancer and proximal promoter regions of Cyp1a1, respectively. These findings provide a new insight into the correlation between the function of nonmuscle myosin II and gene induction.

Use of transgenic mice in UDP-glucuronosyltransferase (UGT) studies

Transgenic mouse models are useful to understand the function and regulation of drug-metabolizing enzymes in vivo. This article is intended to describe the general strategies and to discuss specific examples on how to use transgenic, gene knockout, and humanized mice to study the function as well as genetic and pharmacological regulation of UDP-glucuronosyltransferases (UGTs). The physiological and pharmacological implications of transcription factor-mediated UGT regulation will also be discussed. The UGT-regulating transcription factors to be discussed in this article include nuclear hormone receptors (NRs), aryl hydrocarbon receptor (AhR), and nuclear factor erythroid 2-related factor 2 (Nrf2).

Exposure to endocrine disrupting compounds via the food chain: Is packaging a relevant source?

Contamination of foodstuffs by environmental pollutants (e.g. dioxins, metals) receives much attention. Until recently, food packaging as a source of xenobiotics, especially those with endocrine disrupting properties, has received little awareness despite its ubiquitous use. This article reviews the regulations and use of endocrine disrupting compounds (EDCs) in food packaging and discusses their presence within the context of new toxicology paradigms. I focused on substances known to be legally used in food packaging that have been shown to exhibit endocrine disruptive effects in biological systems. I compiled a list of 50 known or potential EDCs used in food contact materials and examined data of EDCs leaching from packaging into food, with a focus on nonylphenol. I included recent advances in toxicology: mixture effects, the developmental origins of adult disease hypothesis, low-dose effects, and epigenetics. I especially considered the case of bisphenol A. The core hypothesis of this review is that chemicals leaching from packaging into food contribute to human EDCs exposure and might lead to chronic disease in light of the current knowledge. Food contact materials are a major source of food contaminants. Many migrating compounds, possibly with endocrine disruptive properties, remain unidentified. There is a need for information on identity/quantity of chemicals leaching into food, human exposure, and long-term impact on health. Especially EDCs in food packaging are of concern. Even at low concentrations, chronic exposure to EDCs is toxicologically relevant. Concerns increase when humans are exposed to mixtures of similar acting EDCs and/or during sensitive windows of development. In particular, non-intentionally added substances (NIAS) migrating from food contact materials need toxicological characterization; the overall migrate of the finished packaging could be evaluated for biological effects using bioassays. The widespread legal use of EDCs in food packaging requires dedicated assessment and should be updated according to contemporary scientific knowledge.