Sex- and Developmental Stage-Related Differences in the Hepatic Transcriptome of Japanese Quail (Coturnix japonica) Exposed to 17ß-Trenbolone.

Endocrine-disrupting chemicals can cause transcriptomic changes that may disrupt biological processes associated with reproductive function including metabolism, transport, and cell growth. We investigated effects from in ovo and dietary exposure to 17ß-trenbolone (at 0, 1, and 10 ppm) on the Japanese quail (Coturnix japonica) hepatic transcriptome. Our objectives were to identify differentially expressed hepatic genes, assess perturbations of biological pathways, and examine sex- and developmental stage-related differences. The number of significantly differentially expressed genes was higher in embryos than in adults. Male embryos exhibited greater differential gene expression than female embryos, whereas in adults, males and females exhibited similar numbers of differentially expressed genes (>2-fold). Vitellogenin and apovitellenin-1 were up-regulated in male adults exposed to 10 ppm 17ß-trenbolone, and these birds also exhibited indications of immunomodulation. Functional grouping of differentially expressed genes identified processes including metabolism and transport of biomolecules, enzyme activity, and extracellular matrix interactions. Pathway enrichment analyses identified as perturbed peroxisome proliferator-activated receptor pathway, cardiac muscle contraction, gluconeogenesis, growth factor signaling, focal adhesion, and bile acid biosynthesis. One of the primary uses of 17ß-trenbolone is that of a growth promoter, and these results identify effects on mechanistic pathways related to steroidogenesis, cell proliferation, differentiation, growth, and metabolism of lipids and proteins. Environ Toxicol Chem 2021;40:2559-2570. © 2021 SETAC. This article has been contributed to by US Government employees and their work is in the public domain in the USA.

Thyroid disruption and oxidative stress in American kestrels following embryonic exposure to the alternative flame retardants, EHTBB and TBPH.

Brominated flame retardant chemicals, such as 2-ethylhexyl-2,3,4,5-tetrabromobenzoate (EHTBB) (CAS #: 183658-27-7) and bis(2-ethylhexyl)-2,3,4,5-tetrabromophthalate (TBPH) (CAS #: 26040-51-7), have been detected in avian tissues and eggs from remote regions. Exposure to EHTBB and TBPH has been shown to cause oxidative stress and altered thyroid function in rodents and fish, yet no controlled studies have examined potential adverse effects of exposure in birds. Because flame retardants have been detected in wild raptors, we used American kestrels (Falco sparverius) as a model raptor to determine whether in ovo exposure to EHTBB or TBPH affected growth, hatching success, oxidative stress, or thyroid function. We exposed kestrel embryos to nominal concentrations (10, 50, or 100 ng g-1 egg weight) of EHTBB and TBPH via egg-injection on embryonic day 5. Embryonic exposure (~23 d) to EHTBB increased thyroid gland mass, reduced glandular colloid and total thyroxine (T4) in hatchling males and females, whereas deiodinase enzyme activity increased in males but decreased in females. Hatchlings exposed to TBPH in ovo exhibited reduced colloid and increased oxidative stress. Although exposure to EHTBB and TBPH caused several physiological effects (e.g., heart and brain mass), only exposure to 50 ng g-1 EHTBB appeared to reduce hatching success. Our results suggest these flame retardants may be hazardous for predatory birds. Future research should evaluate long-term survival and fitness consequences in birds exposed to these chemicals.

Mutagenicity of 3-methylcholanthrene, pcb3, and 4-oh-pcb3 in the lung of transgenic bigblue rats.

Recent findings of high levels of predominantly lower chlorinated biphenyls in indoor and outdoor air open the question of possible health consequences. Lower chlorinated biphenyls are more readily metabolized to reactive and potentially harmful intermediates, acting as mutagens and cancer initiators. The goal of this study was to assess the mutagenicity of PCB3 in the lungs of rats. Male BigBlue® 334 Fisher transgenic rats, which carry the bacterial lacI gene as a target of mutagenicity, were given intraperitoneal injections of corn oil, 3-methylcholanthrene (3-MC, positive control), 4-monochlorobiphenyl (PCB3) or its metabolite 4-hydroxy-PCB3 (4-OH-PCB3) weekly for 4 weeks. Lungs tissue was harvested to determine mutant frequencies, mutation spectra, and pathological changes. 3-MC caused a 15-fold increase in mutant frequency and an increase in transversion type mutations; a very early occurrence of this type of mutation in lung tissue was previously identified in Ki-ras oncogenes of lung tumors from 3-MC exposed mice. The 2-fold increase in the mutant frequency after treatment with PCB3 and 4-OH-PCB3 was not statistically significant, but a shift in the mutation spectra, especially with PCB3, and an increase in mutations outside of the hotspot region for spontaneous mutations (bp 1-400), suggest that PCB3 and possibly 4-OH-PCB3 are mutagenic in the rat lung.

Effects on Circulating Steroid Hormones and Gene Expression along the Hypothalamus-Pituitary-Gonadal Axis in Adult Japanese Quail Exposed to 17ß-Trenbolone across Multiple Generations.

We investigated the effects of the androgenic growth promoter 17ß-trenbolone (17ßTB) on adult Japanese quail (Coturnix japonica) exposed across three generations. The F0 generation was exposed after sexual maturity to 0, 1, 5, 10, 20, and 40 ppm through feed. The F1 generation was exposed in ovo by maternal transfer and through feed at the same doses as their parents. The F2 generation was exposed in ovo only. Levels of plasma sex steroids, gonadal Cytochrome P450 aromatase (CYP19A1) mRNA and select brain neuroendocrine peptide mRNAs were measured. In males, testosterone levels did not differ in any generation from those in controls. Estradiol was significantly elevated in 17ßTB treated F0 and F1 males. In F0 and F1 females, testosterone was suppressed by 17ßTB, whereas estradiol was significantly higher at 40 ppm in F0 and at 10 ppm in F1 females. CYP19A1 expression in F1 males and females increased suggesting a compensatory response to the androgenic effects of 17ßTB. Few significant effects were observed in the F2 birds indicating that in ovo exposure had limited effects on the monitored endpoints. Overall, our results confirmed endocrine disrupting effects of dietary 17ßTB in Japanese quail but the response was dependent on sex, developmental stage at initiation of exposure, and dose.