Effects of Enterovirus 71 on Mitochondrial Dynamics in Human Glioma U251 Cells

Abstract

To investigate the effects of enterovirus 71 (EV71) on mitochondrial dynamics in human Glioma U251 cells. The EV71 was replicated in Vero cells and the 50% tissue culture infective dose (TCID 50) was calculated based on the Reed-Muench formula. After the U251 cells were infected with EV71, the cellular morphology was assessed through the light microscope. The mitochondrial morphology was detected by MitoTracker Deep Red staining under laser confocal microscopy and the mitochondrial ultrastructure was visualized by transmission electron microscopy. The expressions of mitochondrial fission proteins Drp1, p-Drp1 and fusion protein Opa1 were examined by Western blot. The level of ATP was measured by a commercial ATP assay kit. The generation of mitochondrial superoxide was detected by MitoSOX staining. The TCID 50 of EV71 was 10 －5.4/0.1 mL. Twenty-four or 48 h after EV71 infection, the U251 cells appeared shrunken, round and dead. The laser confocal microscopy and transmission electron microscopy images showed that the EV71 infection induced mitochondrial elongation and cristae damage. Moreover, Western blot analysis demonstrated that the protein expressions of Drp1 and Opa1 were downregulated at both 24 and 48 h after EV71 infection in U251 cells, companied with a significant increase in Drp1 phosphorylation at 48 h after infection ( P<0.05). In addition, a decreased ATP level and elevated mitochondrial superoxide generation were observed in the EV71 infected group, as compared to the control group. Our study demonstrated that infection with EV71 led to changes of mitochondrial morphology and dynamics in U251 cells, which may impair mitochondrial function and contribute to nervous system dysfunction.