Effects of Lithium and 2,4-Dichlorophenol on Zebrafish: Circadian Rhythm Disorder and Molecular Effects

The aim of this study was to investigate lithium and 2,4-dichlorophenol (2,4-DCP)-induced circadian rhythm disorder and their genome-wide effects in zebrafish. Zebrafish larvae were exposed to 250 ppm LiCl (n = 40) or 20 ppm 2,4-DCP. RNA was subsequently extracted and determined quantitatively. The mRNA levels of circadian clock-related genes, including clock1a, bmal1b, per2, and per1b, were determined. Microarray datasets were generated and the differentially expressed genes (DEGs) were identified. The mRNA levels of some upregulated and downregulated DEGs were examined by quantitative real-time polymerase chain reaction (RT-PCR). Finally, gene ontology (GO) enrichment analysis was applied to determine the roles of the DEGs. The mRNA expression levels of circadian rhythm-related genes in the daily cycle were significantly affected after incubation of zebrafish with LiCl and 2,4-DCP. Many genes were differentially expressed during the light phase (97 h) and RT-PCR validation tests revealed that the expression patterns of DEGs were in accordance with those obtained by microarray analysis. GO functional enrichment analysis showed that the DEGs in LiCl- and 2,4-DCP-treated groups were associated with signal transduction and development. Collectively, our findings indicate that LiCl and 2,4-DCP could affect signal transduction pathways and immune response, thereby inducing circadian rhythm disorder.