Effects of atrazine and chlorpyrifos on DNA methylation in the liver, kidney and gill of the common carp (Cyprinus carpio L.)

• DNA methylation of common carp was investigated by ATR, CPF and their mixture.
• Decrease of DNMTs expression involves in the low DNA methylation in ATR and CPF treated carp.
• In our study, the level of DNA methylation altered significantly in most of treated groups.
• The first report on DNA methylation in carp tissues by ATR, CPF and their mixture.

Pesticide exposure has repeatedly been associated with cancers, although the molecular mechanisms behind this association are largely undetermined. Abnormal DNA methylation plays a key role in the process of some disease. However, little was known about the effect of pesticides on DNA methylation in the common carp. In this study, we investigated the mRNA levels of DNA methyltransferases (DNMTs) and methyl-CpG-binding protein DNA-binding domain protein 2 (MBD2) as well as the DNA methylation levels in the liver, kidney and gill of the common carp (Cyprinus carpio L.) after 40-d exposure to atrazine (ATR) and chlorpyrifos (CPF) alone or in combination, and a 40-d recovery period. Juvenile common carp were exposed to various concentrations of ATR (at concentrations of 4.28, 42.8 and 428 μg/L), CPF (1.16, 11.6 and 116 μg/L), and an ATR/CPF mixture (at concentrations of 1.13, 11.3 and 113 μg/L). The results revealed that the levels of genomic DNA methylation decreased in all tissues after 40 d of exposure to ATR and CPF either individually or in combination. Moreover, the mRNA expression of DNMTs was down-regulated in all treatment groups. In contrast, the mRNA expression of MBD2 was up-regulated. These results demonstrated that long-term exposure to ATR, CPF and ATR/CPF mixtures could disrupt genomic DNA. It might imply that DNA methylation is involved in the toxicity caused by ATR and CPF in the common carp.