A combined FSTRA-shotgun proteomics approach to identify molecular changes in zebrafish upon chemical exposure

Abstract

The fish short-term reproduction assay (FSTRA) is a common in vivo screening assay for assessing endocrine effects of chemicals on reproduction in fish. However, the current reliance on measures such as egg number, plasma vitellogenin concentration and morphological changes to determine endocrine effects can lead to false labelling of chemicals with non-endocrine modes- of-action. Here, we integrated quantitative liver and gonad shotgun proteomics into the FSTRA in order to investigate the causal link between an endocrine mode-of-action and adverse effects assigned to the endocrine axis. Therefore, we analyzed the molecular effects of fadrozole-induced aromatase inhibition in zebrafish ( Danio rerio) . We observed a concentration-dependent decrease in fecundity, a reduction in plasma vitellogenin concentrations and a mild oocyte atresia with oocyte membrane folding in females. Consistent with these apical measures, proteomics revealed a significant dysregulation of proteins involved in steroid hormone secretion and estrogen stimulus in the female liver. In the ovary, the deregulation of estrogen synthesis and binding of sperm to zona pellucida were among the most significantly perturbed pathways. A significant deregulation of proteins targeting the transcriptional activity of estrogen receptor ( esr1 ) was observed in male liver and testis. Our results support that organ- and sex-specific quantitative proteomics represent a promising tool for identifying early gene expression changes preceding chemical-induced adverse outcomes. These data can help to establish consistency in chemical classification and labelling.

Development of a Comprehensive Toxicity Pathway Model for 17α-Ethinylestradiol in Early Life Stage Fathead Minnows (Pimephales promelas)

“…Furthermore, the induction of Vtg protein synthesis may not have immediately occurred at the early embryonic stage, but rather at the later stages when the yolk sac was almost absorbed; thus, at 4 dph, larvae may have just actively started producing Vtg protein. The abundance of Vtg proteins in larval fish exposed to xenoestrogens has been rarely reported, unlike in their adult counterparts; moreover, recent studies showed organ- and sex-specific proteomic responses of adult fish exposed to endocrine disrupting compounds. , Thus, the use of pooled whole embryos might have diluted the relative abundance levels, resulting in lower DAP. Other dysregulated proteins associated with EE2 exposure are involved in cellular growth, organization and transport, metabolic processes, biosynthetic processes, and development; however, most of these proteins had low differential abundance and are not functionally specific, which may suggest that there was a delayed onset of responses at the proteome level.…”

Mutation of brain aromatase disrupts spawning behavior and reproductive health in female zebrafish

“…These findings represent an important difference from the observed impairment of female fertility in chemical inhibitor studies in which both aromatase isoforms are inhibited in the body. For example, total aromatase inhibition reduced female fathead minnow ( Pimephales promelas ; 6 ), medaka ( Oryzias latipes ; 7 ) and zebrafish ( 8 ) fecundity. These differences are likely due to the contribution of circulating estrogens produced by the ovaries via Cyp19a1a that function to maintain the integrity of the ovarian state and the reproductive capacity (i.e., fertility) of female zebrafish ( 10 ).…”

Short-Term Test for Toxicogenomic Analysis of Ecotoxic Modes of Action in Lemna minor

“…Eluted peptides were analyzed on a Thermo Fisher Q Exactive mass spectrometer (Thermo Fisher, Waltham, USA) as described previously. 29 , 30 …”

“…For quantitative proteomics, 500 ng combined TMT-labeled peptides were injected replicate wise onto a nanoACQUITY UPLC C18 Trap Column, before being separated on a nanoACQUITY reversed-phase analytical column (Waters, Massachusetts, USA) using a linear gradient from 3 to 97% (v/v) of 90% (v/v) acetonitrile in 0.1% (v/v) formic acid for 170 min with a flow rate of 300 nL/min. Eluted peptides were analyzed on a Thermo Fisher Q Exactive mass spectrometer (Thermo Fisher, Waltham, USA) as described previously. , …”