Apoptosis of Murine T-Cell Lymphoma EL4 Cells Induced by Murine Cytomegalovirus and Its Mechanism

Abstract

To detect whether the murine T-cell lymphoma cell line EL4 could be infected by murine cytomegalovirus (MCMV), and to observe the morphological changes and apoptosis of El4 cells before and after infection. EL4 cells were infected with MCMV smith strain with 1, 10 and 100 multiplicity of infection (MOI) respectively. The morphology of the cells was observed by light microscopy and Wright's-Giemsa staining. The survival rate was calculated by trypan blue staining. RT-PCR-based assay was used to detect the copy number of MCMV-DNA in the infected ELA cells. Flow cytometry was used to detect apoptosis. RT-qPCR was used to detect the mRNA expression levels of P53, P21, cFlip and Caspase 8. The protein expression levels of Caspase8, P53, BAX, BCL-2 and Cleaved Caspase3 proteins were detected by Western blot. After Wright-Giemsa staining, it was found that the infected EL4 cells displayed larger volume, irregular nuclei and the folded twist under light microscopy. Compared with the normal control group, the survival rate of EL4 cells decreased, and the apoptosis rate statistically significantly (P<0.05) increased with the increasing MOI and the infected time in each group. While, the level of apoptosis protein P53, BAX/BCL-2, Cleaved-caspase3 and Caspase8 were up-regulated. And the survival rate, apoptosis rate and the apoptosis protein level of infected EL4 cells with MOI=10 were the most obvious at the 5thday. Compared with MCMV infection group (MOI=60), the content of MCMV DNA in EL4 cells was decreased in MCMV+GGV group ［MOI=60, GCV 25 (g/ml)］, and the cell apoptosis rate and apoptosis protein expression of P53, Caspase8, BAX/BCL-2 were decreased (P<0.05). Murine T-cell lymphoma cell line EL4 can be infected by MCMV and displayes an obvious apoptosis phenomenon. MCMV may up-regulate the expression levels of apoptosis protein P53, BAX-BCL-2, Cleaved-caspase3 and Caspase8 in EL4 cells. The drug ganciclovir reduces the copy mumber of MCMV DNA in infected EL4 cells and inhibited the killing effect of MCMV on EL4 cells.