Modulation of antioxidant enzymes and apoptosis in mice by dietary lipids and treadmill exercise

The current experiments were designed to study the effect of dietary n-6 an d n-3 polyunsaturated fatty acids on antioxidant enzyme activity and dexame thasone (DEX)-induced apoptosis in spleen cells of sedentary (Sed) and trea dmill-exercised (Ex) ICR male mice. Two-month-old mice maintained on AIN 76 formula diet, supplemented with either 5% corn oil (CO) or 5% fish oil (FO ) diets, were trained on a treadmill to run from 45 to 50 min 1 km/day, 6 d ays a week for 12 weeks. After 12 weeks of exercise? both Sed and Ex groups were sacrificed. Blood and various tissues, including spleen, were collect ed asceptically. Increased serum and spleen homogenate peroxide [malondiald ehyde (MDA)] levels were observed in mice fed FO (n-3 PUFA) diets, compared to mice fed CO (n-6 PUFA). However, exercise did not alter MDA levels in e ither CO- or FO-fed mice. Feeding n-3 PUFA significantly increased superoxi de dismutase (SOD), catalase, and glutathione peroxidase activity of spleen homogenates. Exercise also significantly increased SOD and peroxidase in G O-fed animals, whereas catalase, glutathione peroxidase, and glutathione tr ansferase were higher in FO-fed mice, compared to the Sed group. Apoptosis and necrosis were quantitated in splenocytes incubated with or without 1 mu M Dex in RPMI medium for 8 and 24 hr. Cells were stained with Annexin V an d propidium iodide (PI) for apoptotic and necrotic cells. FO-fed mice showe d higher apoptosis (64 vs 50%) and necrosis (40 vs 22%) in spleen cells tha n GO-fed mice. Cells from FO-fed mice, incubated in medium alone, showed in creased apoptosis (112%) 24 hr after incubation, and necrosis (37 and 70%) at 8 and 24 hr of incubation, compared to GO-fed mice. In Ex group, apoptos is was increased in both CO- and FO-fed mice only at 24 hr after incubation . In summary, these results indicate that FO (n-3 PUFA-enriched) diets incr ease apoptosis and antioxidant enzyme activity in spleen cells, probably du e to elevated lipid peroxides.