FIGURE 5.

BTG2^/TIS21 enhanced expression of MnSOD and its activity, but not other antioxidant enzymes. A, Western blot analysis showing the expressions of antioxidant enzymes in HeLa cells treated with the indicated concentrations of DOXO for 12 h. Note the induction of MnSOD and CuZnSOD in response to DOXO treatment, but not GPx and catalase. B, Ad-TIS21 enhanced DOXO-induced MnSOD expression without other antioxidant enzymes. In addition to that, Ad-TIS21 alone induced MnSOD, but not CuZnSOD, expression. HeLa cells infected with 50 m.o.i. of Ad-TIS21 or Ad-β-Gal were exposed to DOXO (1.0 μg/ml) for 12 h, and then the expressions of antioxidant enzymes were examined by Western blotting. C, increase of MnSOD activity by Ad-TIS21 with or without DOXO treatment. HeLa cells were subjected to the analyses of MnSOD activity, after infection with Ad-TIS21 (50 m.o.i.) virus and then with DOXO (1.0 μg/ml) for 12 h. Note accordant increase of MnSOD activity with the level of MnSOD expression. ⋆, p < 0.05 versus without Ad-TIS21. D, inhibition of MnSOD expression by sh-BTG2 infection, but not GPx and catalase. HeLa cells were infected with sh-BTG2 H4 and H5 or empty vector (Con) and then treated with DOXO (1.0 μg/ml) for 12 h. Expression of antioxidant enzymes was examined by Western blotting. Note inhibition of MnSOD expression in the H4, H5-infected cells. E, inhibition of DOXO-induced lamina A/C cleavage by membrane-permeable catalase (PEG-catalase). HeLa cells were pretreated with indicated concentrations of PEG-catalase for 12 h and then treated with DOXO (1.0 μg/ml) for 24 h. The cleavage of lamin A/C was determined by Western blotting. Note the inhibition of DOXO-induced cell death by increasing the concentration of PEG-catalase. The data represent a typical result from three independent experiments.