Embryonic Atrazine Exposure Causes Behavioral, Transcriptomic, Epigenetic, and Pathological Alterations in Adult Zebrafish Brain [male]

According to the developmental origins of health and disease (DOHaD) hypothesis, exposure to environmental stressors during early development can cause genetic, epigenetic, or functional changes in tissues that increase disease risk later in life. Atrazine (ATZ) is a commonly used pesticide that frequently contaminates rural and urban water sources at levels above the 3 ppb maximum contaminant level set by the US Environmental Protection Agency. Exposure to ATZ is linked to endocrine disruption, cancer, changes in genome methylation, and alterations in neurochemistry and behavior. This study tests the hypothesis that embryonic exposure to ATZ results in sex-specific changes in behavior, the adult brain transcriptome, and adult body and brain pathology, according to the DOHaD hypothesis. Zebrafish (Danio rerio) embryos were exposed to 0, 0.3, 3, or 30 ppb (ppb; µg/L) ATZ during the period from fertilization through 72 hours post fertilization (hpf), and then were rinsed and raised to maturity with no further exposure. At 9 months post fertilization (mpf), a novel tank test, a light-dark box, and an open field test evaluated adult behavior. Transcriptomic analysis investigated ATZ related differences in gene expression and the brain was evaluated histopathologically for morphometric alterations in the area of the dorsal telencephalon, posterior tuberculum, and raphe populations. At 14 mpf, the body length, weight, and brain weight was measured to evaluate effects of ATZ on mature body and brain size. The 9 mpf adult behavioral tests found non-monotonic, sex-specific behavior changes, with male zebrafish having decreased activity and female zebrafish having increased signs of anxiety. Transcriptomic analysis identified sex-specific alterations, with females having altered expression of genes in pathways related to cancer and organismal injury and males having altered gene expression in organismal development and reproductive system development and function pathways. Morphometric analysis identified a decreased number of cells in male raphe populations and adult zebrafish also had non-monotonic, sex-specific alterations in body length, body weight, and brain weight. This results suggests that developmental exposure to ATZ does cause sex-specific alterations in adult neural function. We treated zebrafish embryos from approximately 1 hour post fertilization through 72 hours post fertilization (embryogenesis) with 0, 0.3, 3, or 30 ppb atrazine. Following the 72 hour exposure period, larvae were rinsed and reared to 9 months post fertilization. After zebrafish were euthanized, the brains were removed and processed for transcriptomic analysis.