To study the influence of radiation on autophagy and its protective effect on radiation injury of hepatic cells.
MethodsAutophagy in mouse liver tissues was examined by GFP-LC3 staining and Western blot. Radiation-induced hepatic injury was evaluated by ALT and AST in mouse serum, protein expressions, and H & E and TUNEL staining of liver tissue. L02 cells were used for in vitro study. Chloroquine and rapamycin were used to manipulate the level of autophagy.
ResultsTotal body irradiation (TBI) of 8 Gy caused an increase of autophagy in mouse liver tissue and AST level in serum(t＝－7.47, P<0.05) at 12 h after irradiation. Irradiation significantly increased the apoptotic level in liver tissue as well. Inhibition of autophagy by chloroquine caused a further increases of AST [IR: (345.42±35.25)U/L vs. IR＋CQ: (433.42±40.07)U/L, t＝－2.86, P<0.05] and ALT [IR: (35.67±8.08)U/L vs. IR＋CQ: (98.5±26.67)U/L, t＝－3.09, P<0.05] in the serum, and it also promoted apoptosis in live tissue. However, rapamycin as an autophagy promoter showed protective effect for radiation-induced hepatic injury [AST: IR: (345.42±35.25)U/L vs. IR＋Rap: (278.42±20.09)U/L, t＝－2.86, P<0.05]. Similar changes of autophagy and apoptosis in L02 cells were also observed in the cells treated with chloroquine and rapamycin. Inhibition of autophagy by CQ caused an increase of ROS in vitro and in vivo and further increased ALT and AST levels in serum, reduced L02 cell viability. Activation of autophagy by Rap effectively reversed those changes.
ConclusionsAutophagy protects hepatic cells from radiation injury by decreasing ROS induction, which provides a potential target for the development of new clinical regimens against radiation induced liver injury.