Effects of Chronic Endurance Exercise on Doxorubicin-Induced Thymic Damage

The use of prior exercise training has shown promise in minimizing doxorubicin (DOX)-induced physical impairments. The purpose of this study was to compare changes in thymus mass, thymocyte (T-cell) number, and tissue peroxidation following chronic endurance exercise and DOX treatment in the rat. The thymus mass, number of viable T-cells, and levels of malondialdehyde and 4-hydroxyalkenals (MDA+4-HAE) were compared 3 days post-injection between rats assigned to the following treatment conditions: (a) 10 weeks of endurance training, followed by a saline injection 24 hours after the last training session (TM+SAL); (b) treadmill training as above, followed by a single, bolus 10-mg/kg injection of DOX (TM+10); (c) treadmill training with 12.5 mg/kg of DOX (TM+12.5); (d) sedentary (without exercise) and a saline injection (SED+SAL); (e) sedentary with 10 mg/kg of DOX (SED+10); and (f) sedentary with 12.5 mg/kg (SED+12.5). Thymic mass and T-cell numbers significantly decreased following DOX injections. TM rats exhibited significantly less lipid peroxidation compared with paired-dose SED groups. TM+10 did not significantly differ from SED+SAL in thymic levels of lipid peroxidation. We conclude that chronic endurance exercise decreases levels of lipid peroxidation in the thymus seen with acute DOX treatment.