Acetaminophen exposure alters the DNA methylation pattern of Mugilogobius chulae, along with the changes in the Nrf2-Keap1 signaling pathway

DNA methylation can dynamically regulate multiple physiological processes in organisms in response to changes of the external environment. The effects of acetaminophen (APAP) on DNA methylation in aquatic organisms and its toxic mechanisms is an interesting issue. In the present study, Mugilogobius chulae (Approximately 225 individual), a small benthic native fish, were employed to assess the toxic effects of APAP-exposure on non-target organisms. First, under APAP exposure (0.5 μg/L and 500 μg/L) for 168 h, 17,488 and 14,458 differentially methylated regions (DMRs) were identified in liver of M. chulae, respectively, which were involved in energy metabolism, signaling transduction, and cellular processes etc. The modification of lipid metabolism by DNA methylation was particularly prominent and the increased fat vacuoles in the sections were observed. Some key nodes associated with oxidative stress and detoxification such as Kelch-1ike ECH-associated protein l (Keap1) and fumarate hydratase (FH) were modified by DNA methylation. Meanwhile, changes in DNA methyltransferase and Nrf2-Keap1 signaling pathways at different concentrations of APAP (0.5 μg/L, 5 μg/L, 50 μg/L and 500 μg/L) for different time (24 h and 168 h) were addressed at the transcriptional level. Results showed that ten eleven translocation enzymes 2 (TET2) transcript expression was upregulated 5.7-folds after being exposed to 500 μg/L APAP for 168 h, indicating the urgent need for active demethylation in the exposed organism. The elevated DNA methylation levels of Keap1 led to repression of its transcriptional expression so as to promote recovery or reactivation of Nrf2, which displayed negatively relationship with Keap1 gene. Meanwhile, P62 was significantly positively correlated with Nrf2. Downstream genes in the Nrf2 signaling pathway changed synergistically except for Trx2, in which GST and UGT were highly significantly upregulated. This work illustrated that APAP exposure altered the DNA methylation processes, together with the Nrf2-Keap1 signaling pathway, and affected the stress responses of M. chulae to pharmaceuticals exposure.