Search

Polycyclic aromatic hydrocarbons (PAHs) impaired pre-migratory fueling in 49 orally dosed Sanderling (Calidris alba). In the present study, 8 genes related to fat deposition and PAH exposure were measured in liver subsamples from these same shorebirds. At the highest dose (1260 µg total PAH [tPAH]/kg body wt/day), PAH exposure decreased liver basic fatty acid binding protein 1 (Lbfabp) and hepatic lipase (Lipc) expression. The present study reveals candidate molecular-level pathways for observed avian pre-migratory refueling impairment. Environ Toxicol Chem 2021;40:1983-1991. © 2021 SETAC.

Environmental risk assessment is often challenged by a lack of toxicity data for ecological species. The overall goal of the present study was to employ an avian early-life stage toxicity test to determine the effects of 4 chemicals (benzo[a]pyrene [BaP], chlorpyrifos, fluoxetine hydrochloride [FLX], and ethinyl estradiol [EE2]) on an ecologically relevant avian species, the double-crested cormorant (Phalacrocorax auritus), and to compare our results with those we previously reported for a laboratory model species, Japanese quail. Chemicals were dissolved in dimethyl sulfoxide and administered via air cell injection to fertilized, unincubated double-crested cormorant eggs at 3 nominal concentrations, the highest selected to approximate the 20% lethal dose. Of the 4 chemicals, only chlorpyrifos and FLX were detected in liver tissue of embryos at midincubation (day 14) and termination (day 26; 1-2 d prior to hatch); EE2 and BaP were not detectable, suggesting embryonic clearance/metabolism. No apical effects were observed in double-crested cormorant embryos up to the highest concentrations of chlorpyrifos (no-observed-effect level [NOEL] = 25 µg/g) or FLX (NOEL = 18 µg/g). Exposure to EE2 reduced embryonic viability and increased deformities at a concentration of 2.3 µg/g (NOEL = 0.18 µg/g), and BaP decreased embryonic viability (median lethal dose = 0.015 µg/g; NOEL = 0.0027 µg/g). Compared with Japanese quail, double-crested cormorant were more sensitive with regard to embryolethality and deformities for EE2 and embryolethality for BaP, whereas they were less sensitive to embryonic deformities associated with chlorpyrifos exposure. These data reinforce the idea that standardized toxicity tests using a laboratory model species may not always be protective of wild birds, and thus they stress the importance of developing such alternative testing strategies (e.g., the EcoToxChip Project) for ecologically relevant species to augment risk assessment efforts. Environ Toxicol Chem 2021;40:390-401. © 2020 SETAC.

As the number of chemicals developed and used by industry increases, the inherent limitations of traditional toxicology approaches become an unavoidable issue. To help meet the demand for toxicity evaluation, new methods, such as high-throughput toxicity screening, are currently being developed to permit rapid determination of toxic, molecular, and/or biochemical effects of a wide range of chemicals. In the present study, we demonstrate the utility of an avian in vitro toxicogenomics screening approach to determine the cytotoxic and transcriptomic effects of 10 organic flame retardants (OFRs) currently of international priority for ecological risk evaluation to prioritize and inform future toxicological studies. Hepatocytes from 2 avian species, chicken and double-crested cormorant, were prepared and exposed for 24 h to various concentrations (0-300 μM) of the following 10 OFRs: Chemical Abstracts Service registration numbers 29761-21-5, 56803-37-3 (p-tert-butylphenyl diphenyl phosphate [BPDP]), 65652-41-7, 68937-41-7 (phenol, isopropylated, phosphate [3:1] [IPPP]), 95906-11-9, 19186-97-1, 26040-51-7, 35948-25-5, 21850-44-2, and 25713-60-4. Cell viability, the 7-ethoxyresorufin-O-deethylase assay, and transcriptomic analysis using species-specific ToxChip polymerase chain reaction arrays were performed to evaluate the in vitro effect of these OFRs. Of the 10 OFRs assessed, BPDP and IPPP elicited the strongest cytotoxic and transcriptomic responses in both chicken and double-crested cormorant hepatocytes and are therefore recommended as priority candidates for further wildlife toxicological investigations. Environ Toxicol Chem 2018;37:3134-3144. © 2018 Crown in the right of Canada. Published by Wiley Periodicals Inc. on behalf of SETAC.

Interference with endogenous developmental processes that are regulated by the aryl hydrocarbon receptor (AHR), through sustained exogenous activation, causes molecular, structural, and functional cardiac abnormalities in avian, mammalian and piscine embryos; this cardiotoxicity ultimately leads to severe oedema and embryo death in birds and fish and some strains of rat. There have been numerous proposed mechanisms of action for this toxicity profile, many of which include the dysregulation of vascular endothelial growth factor (VEGF). This AOP describes the indirect suppression of VEGF expression through the sequestration of the aryl hydrocarbon receptor nuclear translocator (ARNT) by AHR. ARNT is common dimerization partner for both AHR and hypoxia inducible factor alpha (HIF-1α), which stimulates angiogenesis through the transcriptional regulation of VEGF. The suppression of VEGF thereby reduces cardiomyocyte and endothelial cell proliferation, altering cardiovascular morphology and reducing cardiac output, which ultimately leads to congestive heart failure and death.

Hepatic uroporphyria is a disorder where the disturbance of heme biosynthesis results in accumulation and excretion of uroporphyrin, heptacarboxyl- and hexacarboxyl porphyrin: collectively referred to as highly carboxylated porphyrins (HCPs). The disorder is due to a homozygous mutation in uroporphyrinogen decarboxylase (UROD), an enzyme involved in the heme biosynthesis pathway, or may be chemically induced, which involves the inhibition of UROD. This AOP describes the linkages leading to chemically induced porphyria through the activation of the aryl hydrocarbon receptor (AHR), a ligand-activated transcription factor. AHR activation leads to the induction of cytochrome P450 1A2, a phase I metabolising enzyme, which in turn results in excessive oxidation of uroporphyrinogen. This oxidation produces a UROD inhibitor, preventing the conversion of uroporphyrinogen to coprouroporphyrinogen and increasing the synthesis of the UROD inhibitor in a positive feedback loop. The accumulation of uroporphyrinogen leads to its preferential oxidation and accumulation of HCP in various organs (Uroporphyria).

Early-life stage (ELS) toxicity tests are recognized as an advancement over current testing methodologies in terms of cost, animal use, and biological relevance. However, standardized ELS tests are not presently available for some vertebrate taxa, including birds. The present study describes a Japanese quail (Coturnix japonica) ELS test that is a promising candidate for standardization and applies it to test 8 environmental chemicals (ethinylestradiol, benzo[a]pyrene, chlorpyrifos, fluoxetine, lead(II)nitrate, trenbolone, seleno-L-methionine, hexabromocyclododecane). Individual chemicals were injected into the air cell of unincubated Japanese quail eggs at 3 concentrations, all predicted to cause ≤20% mortality. Survival to embryonic day 16 was consistently high (>90%) among the vehicle-injected controls. All chemicals, except ethinylestradiol, were detected in liver tissue, most at concentrations suggestive of embryonic clearance. Adverse effects were observed for 5 of the 8 chemicals; chlorpyrifos (41.1 µg/g) significantly increased developmental abnormalities and decreased embryo and gallbladder mass. Ethinylestradiol (54.2 µg/g) and hexabromocyclododecane (0.02 µg/g) decreased embryo mass and tarsus length, respectively. Benzo[a]pyrene (0.83 µg/g) and fluoxetine hydrochloride (32.7 µg/g) exceeded the 20% mortality cutoff. No effects were observed following lead(II)nitrate, seleno-L-methionine, or trenbolone exposure up to 10.7, 0.07, and 4.4 µg/g, respectively. Overall, our ELS approach was time- and cost-effective, caused minimal mortality in controls, effectively delivered diverse chemicals to the embryo, and permitted identification of apical outcomes, all of which provide support toward standardization. Environ Toxicol Chem 2019;39:141-154. © 2019 SETAC.

In vitro screening tools and 'omics methods are increasingly being incorporated into toxicity studies to determine mechanistic effects of chemicals and mixtures. To date, the majority of these studies have been conducted with well-characterized laboratory animal models. In the present study, well-established methods developed for chicken embryonic hepatocyte (CEH) studies were extended to a wild avian species, the double-crested cormorant (DCCO; Phalacrocorax auritus), in order to compare the effects of several environmental contaminants on cytotoxicity, ethoxyresorufin O-deethylase (EROD) activity, and mRNA expression. Five organic flame retardants and one plasticizer decreased cormorant hepatocyte viability in a similar manner to that observed in previous studies with CEH. EROD activity was induced in a concentration-dependent manner following exposure to two dioxin-like chemicals and the calculated EC50 values were concordant with domestic avian species from similar species sensitivity categories. Transcriptomic effects were determined using a novel DCCO PCR array, which was designed, constructed and validated in our laboratory based on a commercially available chicken PCR array. The DCCO array has 27 target genes covering a wide range of toxicity pathways. Gene profiles were variable among the 10 chemicals screened; however, good directional concordance was observed with regard to results previously obtained in CEH. Overall, the application of well-established methods (i.e., CEH and chicken PCR array) to the double-crested cormorant demonstrated the portability of the techniques to an indicator species of ecological relevance.

As the number of chemicals developed and used by industry increases, the inherent limitations of traditional toxicology approaches become an unavoidable issue. To help meet the demand for toxicity evaluation, new methods, such as high-throughput toxicity screening, are currently being developed to permit rapid determination of toxic, molecular, and/or biochemical effects of a wide range of chemicals. In the present study, we demonstrate the utility of an avian in vitro toxicogenomics screening approach to determine the cytotoxic and transcriptomic effects of 10 organic flame retardants (OFRs) currently of international priority for ecological risk evaluation to prioritize and inform future toxicological studies. Hepatocytes from 2 avian species, chicken and double-crested cormorant, were prepared and exposed for 24 h to various concentrations (0-300 μM) of the following 10 OFRs: Chemical Abstracts Service registration numbers 29761-21-5, 56803-37-3 (p-tert-butylphenyl diphenyl phosphate [BPDP]), 65652-41-7, 68937-41-7 (phenol, isopropylated, phosphate [3:1] [IPPP]), 95906-11-9, 19186-97-1, 26040-51-7, 35948-25-5, 21850-44-2, and 25713-60-4. Cell viability, the 7-ethoxyresorufin-O-deethylase assay, and transcriptomic analysis using species-specific ToxChip polymerase chain reaction arrays were performed to evaluate the in vitro effect of these OFRs. Of the 10 OFRs assessed, BPDP and IPPP elicited the strongest cytotoxic and transcriptomic responses in both chicken and double-crested cormorant hepatocytes and are therefore recommended as priority candidates for further wildlife toxicological investigations. Environ Toxicol Chem 2018;37:3134-3144. © 2018 Crown in the right of Canada. Published by Wiley Periodicals Inc. on behalf of SETAC.

The flame retardant, tris(1,3-dichloro-2-propyl) phosphate (TDCPP), was previously shown to affect chicken embryo growth, gallbladder size, and lipid homeostasis. A microarray study, however, revealed only modest transcriptional alterations in liver tissue of pipping embryos (days 20–21), which was attributed to the rapid metabolism of TDCPP throughout incubation. To identify the most appropriate sampling time for rapidly metabolized compounds, the present study assessed the time-dependent effects of TDCPP on 27 genes, in ovo (50 µg [116 nmol] TDCPP/g egg) and in vitro (10 µM), using a chicken ToxChip polymerase chain reaction array. The greatest magnitude in dysregulation (up to 362-fold) occurred on day 8 of incubation (in ovo) with alterations of genes involved in phase I, II, and III metabolism, among others. Gallbladder hypotrophy was observed by embryonic day 12, corroborating the finding in pipping embryos from our previous study. From days 12 to 19, genes involved in lipid homeostasis, steroid hormone metabolism, and oxidative stress were affected. In chicken embryonic hepatoctyes (CEHs), TDCPP was completely metabolized to bis(1,3-dichloro-2-propyl) phosphate (BDCPP) within 36 h, but transcriptional changes remained significant up to 36 h. These changes were not attributed to BDCPP exposure as it only altered 1 gene (CYP1A4). An 18-h exposure in CEHs altered the greatest number of genes, making it an appropriate time point for high-throughput chemical screening; however, depending on the biological pathways of interest, shorter or longer incubation times may be more informative. Overall, TDCPP elicits the transcriptional and phenotypic alterations observed in vitro and in ovo, whereas its major metabolite, BDCPP, is far less biologically active. Environ Toxicol Chem 2014;33:2842–2849. © 2014 SETAC

Tris(1-chloro-2-propyl) phosphate (TCPP) and tris(1,3-dichloro-2-propyl) phosphate (TDCPP) are organic flame retardants detected in the environment and biota for which avian toxicological data are limited. In this study, domestic chicken eggs were injected with TCPP or TDCPP (maximum dose = 51,600 and 45,000ng/g egg, respectively) to determine dose-dependent effects on pipping success, development, hepatic messenger RNA (mRNA) expression levels of genes associated with xenobiotic metabolism and the thyroid hormone (TH) pathway, and TH levels following 20-22 days of incubation. Neither compound reduced pipping success; however, TCPP significantly delayed pipping at 9240 and 51,600ng/g and reduced tarsus length at 51,600ng/g. TDCPP exposure resulted in significant decreases in head plus bill length, embryo mass, and gallbladder size at 45,000ng/g and reduced plasma free T4 levels at 7640ng/g. Type I deiodinase, liver fatty acid-binding protein, and cytochrome P450 (CYP) 3A37 mRNA levels were significantly induced by TCPP, whereas TDCPP induced CYP3A37 and CYP2H1. Chemical analysis of egg contents at incubation days 0, 5, 11, 18, and 19 revealed that > 92% of the injected TCPP or TDCPP concentration was detectable up to day 5; however, < 1% was detected by day 19. The observed phenotypic responses to TCPP and TDCPP exposure may be associated with disruption of the TH axis, which is critical for normal growth and development in birds. The effects of TDCPP on the gallbladder indicate that the disturbance of lipid metabolism is a likely mechanism of toxicity.

Photochromic dithienylethenes that possess elements of lipid complementarity, and undergo large, photoinduced changes in molecular geometry have been prepared. Further, a regioselective approach has been developed for the preparation of dithienylethenes containing phenylethynyl and various aryl substituents at C2 and C5 of the thiophene moieties, respectively. The prepared photochromic compounds were observed to undergo reversible photoisomerization. Their absorption properties, reaction quantum yields, and photoconversions were determined in n-hexane.

The flame retardant, tris(1,3-dichloro-2-propyl) phosphate (TDCPP), was previously shown to affect chicken embryo growth, gallbladder size, and lipid homeostasis. A microarray study, however, revealed only modest transcriptional alterations in liver tissue of pipping embryos (days 20-21), which was attributed to the rapid metabolism of TDCPP throughout incubation. To identify the most appropriate sampling time for rapidly metabolized compounds, the present study assessed the time-dependent effects of TDCPP on 27 genes, in ovo (50 µg [116 nmol] TDCPP/g egg) and in vitro (10 µM), using a chicken ToxChip polymerase chain reaction array. The greatest magnitude in dysregulation (up to 362-fold) occurred on day 8 of incubation (in ovo) with alterations of genes involved in phase I, II, and III metabolism, among others. Gallbladder hypotrophy was observed by embryonic day 12, corroborating the finding in pipping embryos from our previous study. From days 12 to 19, genes involved in lipid homeostasis, steroid hormone metabolism, and oxidative stress were affected. In chicken embryonic hepatoctyes (CEHs), TDCPP was completely metabolized to bis(1,3-dichloro-2-propyl) phosphate (BDCPP) within 36 h, but transcriptional changes remained significant up to 36 h. These changes were not attributed to BDCPP exposure as it only altered 1 gene (CYP1A4). An 18-h exposure in CEHs altered the greatest number of genes, making it an appropriate time point for high-throughput chemical screening; however, depending on the biological pathways of interest, shorter or longer incubation times may be more informative. Overall, TDCPP elicits the transcriptional and phenotypic alterations observed in vitro and in ovo, whereas its major metabolite, BDCPP, is far less biologically active.