Inhibitory effects of voluntary wheel exercise on apoptosis in splenic lymphocyte subsets of C57BL/6 mice

Two-month-old mice were placed in cages with (Ex) or without exercise running wheels with free access to the wheel 24 h/day for 10 mo. An equal amount of food for both groups was provided daily. Ex mice ran an average of 33.67 km/wk initially, and exercise decreased gradually with age. Ex mice had gained an average of 43.5% less body weight at the end of the experiment. Although serum lipid peroxides were not altered by exercise, superoxide dismutase and glutathione peroxidase activities in serum were significantly increased. Flow cytometric analysis of spleen cells revealed an increased percentage of CD8⁺ T cells and a decreased percentage of CD19⁺ B cells in Ex mice (P < 0.05). Exercise decreased apoptosis in total splenocytes and CD4⁺ cells incubated with medium alone or with H₂O₂, dexamethasone, tumor necrosis factor-α (TNF-α), or anti-CD3 monoclonal antibody (P < 0.05) and CD8⁺ cells with medium alone or with TNF-α (P < 0.05). Even though exercise did not alter the intracellular cytokines (TNF-α and interleukin-2) or Fas ligand, it did significantly lower interferon-γ in CD4⁺ and CD8⁺ cells (P < 0.05). In summary, voluntary wheel exercise appears to decrease H₂O₂-induced apoptosis in immune cells as well as decrease interferon-γ production.