Paper Title
Expressions of DNA Methylation And hydroxymethylation in Isoniazid-Induced Injury Liver in Rats

Abstract
This study analyzed whether there is a link between DNA methylation and hydroxymethylation and isoniazid-induced rat liver injury. Glutathione S-Transferase P1 (GSTP1), Cytochrome P450 1A1 (CYP1A1) and Cytochrome P450 2E1 (CYP2E1), and TETIprotein, their regulatory protein, were selected as target genes and protein.Ninety six rats were randomly divided into the isoniazid (INH) group and control group. In the INH group, 48 rats were randomly divided into 6 groups which received INH 50mg•kg-1•d-1 on 3, 7, 10, 14, 21, 28 d respectively. In the control group, 48 rats were randomly divided into 6 groups, which received saline at same volume and time as that of INH group. The extent of liver injury was identified by estimating the alanine transaminase (ALT), aspartate transaminase (AST) levels and observing the pathological alter during the observation period. The expressions of DNA methylation and hydroxymethylation were analyzed using 5mC-5hmC analysis kits. The changes in TETI protein were analyzed via enzyme-linked immunosorbent assay (ELISA). The mRNA level of TETI was tested by RT-PCR.Experimental dose of INH could cause rats’ liver injury gradually. In INH group, the cytosine content in GSTP1 and CYP2E1showed thedownward trend. The contents of DNA methylation indicated the increasing trends in GSTP1 and CYP1A1 genes. The content of DNA hydroxymethylation showed the overall downward trend but with the marginal rise at the end in three target genes. The expressions of TETI protein and gene’s mRNAfall to the lowest at 21d (P<0.05). Changing of DNA methylation, hydroxymethylation in GSTP1 and CYP1A1 genes, and even their regulator protein, TETI, showed a certain regularity in isoniazid-induced rat liver injury. They might need the further validation to be used as early maker in the future. Keyword - DNA methylation status; 5-methylcytosine; 5-hydroxymethylcytosine; Ten-eleven translocation protein; Isoniazid; Rat hepatotoxicity