Zhang Xiaoning, Li Hui, Qiu Qian, Qi Yongmei, Huang Dejun, Zhang Yingmei
School of Life Sciences, Lanzhou University, Lanzhou 730000, China.
School of Life Sciences, Lanzhou University, Lanzhou 730000, China.
Comp Biochem Physiol C Toxicol Pharmacol. 2014 Mar;160:54-9. doi: 10.1016/j.cbpc.2013.11.008. Epub 2013 Dec 4.
Altered DNA methylation is associated with changes in gene expression, signal transduction and stress response after exposure to a wide range of exogenous compounds, and abnormal methylation is a major toxic effect induced by chemicals such as benzene and phenols. 2,4-Dichlorophenol (2,4-DCP), a derivative of phenol, has been classified as a priority pollutant by the US EPA due to its toxic effects on aquatic organisms. However, the effect of 2,4-DCP on DNA methylation and its potential mechanism in fish are rarely understood. The present study aims to figure out whether 2,4-DCP could impact DNA methylation and explore its potential mechanisms by measuring the global DNA methylation levels, S-adenosylmethionine (SAM) and S-adenosylhomocysteine (SAH) contents, the mRNA expression of DNA methyltransferase1 (DNMT1) and DNA methyltransferase3 (DNMT3) in the liver of goldfish Carassius auratus. DNA methylation levels were analyzed using high performance liquid chromatography (HPLC) and MspI/HpaII ethidium bromide assay, SAM and SAH contents were determined by HPLC, the mRNA expression of DNMT1 and DNMT3 was measured by quantitative-PCR (qPCR). The results showed that 2,4-DCP caused global DNA hypermethylation, elevated the methylation levels of CpG islands, increased the SAM and SAH contents, decreased the SAM/SAH ratio, and upregulated the mRNA expression of DNMT1 and DNMT3, while depletion of SAM with Na2SeO3 and inhibition of DNMTs activity with 5-aza-2'-deoxycytidine (5AdC) impaired 2,4-DCP-induced global DNA hypermethylation, suggesting that the increase of SAM contents and upregulation of the mRNA expression of DNMT1 and DNMT3 may play important roles in 2,4-DCP-induced global DNA hypermethylation process. Our report is the first one to show that short-term 2,4-DCP exposure caused the global DNA hypermethylation via altered SAM level and DNMTs expression in fish.
DNA甲基化改变与接触多种外源性化合物后的基因表达、信号转导及应激反应变化相关，异常甲基化是苯和酚类等化学物质诱导产生的主要毒性效应。2,4 -二氯苯酚（2,4 - DCP）是苯酚的衍生物，因其对水生生物的毒性作用被美国环境保护局列为优先污染物。然而，2,4 - DCP对鱼类DNA甲基化的影响及其潜在机制鲜为人知。本研究旨在通过检测金鱼肝脏中整体DNA甲基化水平、S -腺苷甲硫氨酸（SAM）和S -腺苷同型半胱氨酸（SAH）含量、DNA甲基转移酶1（DNMT1）和DNA甲基转移酶3（DNMT3）的mRNA表达，来确定2,4 - DCP是否会影响DNA甲基化并探索其潜在机制。采用高效液相色谱法（HPLC）和MspI/HpaII溴化乙锭分析法分析DNA甲基化水平，用HPLC测定SAM和SAH含量，通过定量聚合酶链反应（qPCR）检测DNMT1和DNMT3的mRNA表达。结果表明，2,4 - DCP导致整体DNA高甲基化，提高了CpG岛的甲基化水平，增加了SAM和SAH含量，降低了SAM/SAH比值，并上调了DNMT1和DNMT3的mRNA表达，而用亚硒酸钠消耗SAM以及用5 -氮杂- 2'-脱氧胞苷（5AdC）抑制DNA甲基转移酶活性削弱了2,4 - DCP诱导的整体DNA高甲基化，这表明SAM含量的增加以及DNMT1和DNMT3的mRNA表达上调可能在2,4 - DCP诱导的整体DNA高甲基化过程中起重要作用。我们的报告首次表明，短期接触2,4 - DCP通过改变鱼类体内SAM水平和DNA甲基转移酶表达导致整体DNA高甲基化。
