Delaney, P. | bioRxiv Science

bioRxiv2023

Sustained Effects of Developmental Exposure to Inorganic Arsenic on Hepatic Gene Expression and Mating Success in Zebrafish

The impacts of exposure to the pervasive environmental toxicant, inorganic arsenic (iAs), on human and fish health are well characterized and several lines of evidence suggest that some impacts can manifest years after exposure cessation. Using a developmental exposure protocol whereby zebrafish embryos were exposed to 0.5 and 1.5 mM iAs from 4-120 hours post fertilization (hpf) and then was removed, we investigated the sustained effects of iAs on gene expression in the liver, survival, reproductive success, and susceptibility to iAs toxicity in the subsequent generation. Developmental exposure to iAs has massive effects on the hepatic transcriptome, with 23% of genes differentially expressed at the end of exposure at 120 hpf, and some of these genes remain deregulated in the liver 9 months after iAs was removed. Developmental exposure to 1.5 mM iAs, but not 0.5 mM, increased mortality through 3 months by over 50%. Adults that were developmentally exposed to 0.5 mM iAs had reduced mating success, but their offspring had no differences in observable aspects of development or their susceptibility to iAs toxicity. This demonstrates that developmental exposure of zebrafish to iAs reduces long-term survival, reproductive success and causes sustained changes to gene expression in the liver. SUMMARY STATEMENTThis work investigates the long-term effects of developmental exposure to inorganic arsenic (iAs) using zebrafish. Months after iAs-exposure was terminated, we found increased mortality, changes in gene expression in the liver and decreased mating success.

pharmacology and toxicology↗

bioRxiv2020

Rearing medium dictates variability across replicates in untreated and arsenic challenged zebrafish larvae

Reproducibility and consistency are hallmarks of scientific integrity. Biological systems are inherently noisy, posing a challenge to reproducibility. This is particularly relevant to the field of environmental toxicology, where many unaccounted experimental parameters can have a marked influence on the biological response to exposure. Here, we extend the use of zebrafish as a robust toxicological model for studying the effects of inorganic arsenic (iAs) on liver biology. We observed that iAs toxicity in this system is not influenced by important parameters including genetic background, rearing container material or rearing volume but the dose response to iAs is influenced by the rearing medium. We compared mortality as a measure of iAs toxicity to embryos cultured in two standard rearing media: egg water made from dehydrated ocean salts dissolved in water and a defined embryo medium which is a pH adjusted, buffered salt solution. Larvae reared in egg water were more susceptible to iAs compared to those reared in embryo medium. This effect was independent of the pH differences between these solutions. These culture conditions did not cause any difference in the global hepatic transcriptome of control zebrafish. Further, no difference in the expression of genes involved in the unfolded protein response (UPR) in larvae exposed to iAs treatment or in a stress independent system to activate UPR genes by transgenic overexpression of activating transcription factor 6 (nAtf6) in hepatocytes was observed. However, the clutch-to-clutch variation in gene expression was significantly greater in larvae reared in egg water compared to those in embryo medium. These data demonstrate that egg water affects reproducibility across replicates in terms of gene expression and exacerbates iAs mediated toxic response. This highlights the importance of rigorous evaluation of experimental conditions to assure reproducibility.

pharmacology and toxicology↗