Studies On The Correlation Between DNA Methylation And As₂O₃ Against Marek's Disease

Marek's disease (MD) is a kind of infective disease that has harmed the poultry industryseverely, it is also the first kind ofphymatosis that can be precluded by vaccine. But with the virusvariation and appearance of Marek's disease herpesvirus (MDV) with stronger toxicity, traditionalvaccine can not protect chicken commendably. Etiopathogenesis of MD must be studied deeply inorder to prevent and cure it efficiently. Investigation indicates that oncogene and anti-oncogenechange with methylation during the development of tumor. There is no report about the mechanismof methylation in MD tumor at home and abroad. The experiment investigated the metabolismkinetics process of arsenic trioxide(As₂O₃) in chicken by new silver salt method, meanwhile HPLC,MS-PCR and semiquantitative RT-PCR were used to detect the changes of oncogene DNAmethylation level, anti-oncogene p15 methylation as well as mRNA expression of methylationtransfering enzyme and anti-oncogene p53 between MD chicken and As₂O₃ treated MDchicken. The experiment provided a new approach for studying the anti-tumor mechanism of As₂O₃and deepened the cognition of the pathogenetic of MD.Results were described as follows:1. The metabolism kinetic equations of As₂O₃ in chicken are: C_blood=1.62916e^-0.22733t+0.15327e^-0.02024t-1.78243e^-1.36943t, C_liver=10.8896e^-0.5307t+0.8389e^-0.0676t-11.7285e^-16.5388t,C_kidney=18.4888e^-0.7156t+1.5501e^-0.0536t-20.0388e^-10.0238t, C_{pectoral muscle}=0.7300 (e^-0.0195t-e^-6.6288t).The metabolism kinetic equations in blood, liver and kidney are consistent with two-compartmentmodel with one-stage, the metabolism kinetic equation in pectoral muscles is consistent withone-compartment model with one-stage.2. The level of DNA methylation in tumor tissue decreased with the development of diseaseand the level of DNA methylation increased gradually after using As₂O₃.3. The incidence rate of p15 methylation in normal chicken liver was fairly low (1/120), butthat in tumor tissue was quite high (liver 56.7%, kidney 61.7%), after using As₂O₃ the incidencerate of p15 methylation decreased4. The mRNA expression of DNA methyltransferase in tumor tissue increased visibly, themRNA expression of anti-oncogene p53 decreased gradually. As₂O₃ could reverse the mRNAexpression of DNA methyltransferase and p53, decrease the mRNA expression of DNAmethyltransferase, while increase the mRNA expression of p53.