Transcriptomic analysis of adult zebrafish brain exposed developmentally to 2 concentrations of a persistent organic pollutants (POP) mixture or 2 concentrations of PFOS (0.3, 2.06 mg/L)

Complex mixtures of persistent organic pollutants (POPs) are regularly detected in the environment and animal tissues. Often these chemicals are associated with latent effects following early-life exposures, following the developmental origin of health and disease paradigm. We investigated the long-term effects of a human relevant mixture of 29 POPs on adult zebrafish following a developmental exposure, in addition to a single PFOS exposure for comparison, as it was the compound with the highest concentration within the mixture. Zebrafish embryos were exposed from 6 to 96 hours post fertilization to x10 and x70 the level of POP mixture or PFOS found in human blood before being transferred to clean water. We measured growth, swimming performance, and reproductive output at different life stages. In addition, we assessed anxiety behavior of the adults and their offspring, as well as performing a transcriptomic analysis on the adult zebrafish brain, as the POP mixture and PFOS concentrations used are known to affect larval behavior. Exposure to POP mixture and PFOS reduced swimming performance and increased length and weight, compared to controls. No effect of developmental exposure was observed on reproductive output or anxiety behavior. Additionally, RNA-seq did not reveal pathways related to anxiety although pathways related to synapse biology were affected at the x10 PFOS level. Furthermore, pathway analysis of the brain transcriptome of adults exposed as larvae to the low concentration of PFOS revealed enrichment in pathways such as calcium, MAPK, and GABA signaling, all of which are important for learning and memory. Based on our results we can conclude that some effects on the endpoints measured were apparent, but if these effects lead to adversities at population levels remains elusive. Overall design: The POPs mixture used in this study was base on average leves of chemicals found in blood of the Scandinavian population. The low concentration of POP (POP10) reflected levels x 10 higher of what is found in human blood and the high concentration (POP70) reflected levels x 70. PFOS10 and PFOS70 single exposure were based on the levels of PFOS in the POPs mixture. Zebrafish larvae were exposed from 6 hpf until 96 hpf to either POP10, POP70, PFOS10 or PFOS70 in 4 replicates. We also included a control condition of zebrafish larvae exposed only to the solvent (0.1% DMSO) in 4 replicates. Zebrafish were transferred to clean water and left to grow until adulthood. Sampling of adults was performed at ages 219-240 dpf. Whole brain tissue from 2 females and 2 males per condition and replicate (total 8 females and 8 males per condition) were collected individually.