Effects in vitro of several antioxidants on the natural killer function ofaging mice

The aim of the present work is to study the change with aging in the effect in vitro of several antioxidants: thiazolidine-4-carboxylic acid or thiopr oline, N-acetylcysteine (NAC), ascorbic acid (AA), and alpha-tocopherol (vi tamin E, VE) on the natural killer (NK) activity in mononuclear cells from axillary nodes, spleen, thymus and peritoneal leukocytes from BALB/c male m ice. Young (8 +/- 2 weeks), adult (24 +/- 2 weeks), mature (48 +/- 2 weeks) , and old (72 +/- 2 weeks) animals were studied. A nonradioactive cytotoxic assay with cells from the murine lymphoma YAC-1 as target cells and a rela tion effector cells/target cells of 10/1 were used. The concentrations of t he different antioxidants were: 1 mM for thioproline and N-acetylcysteine a nd 5 mu M for ascorbic acid and alpha-tocopherol, which induced a maximum e ffect in our previous dose-response experiments. The results show that, in general, the above antioxidants cause an enhancement of the NK activity at all ages studied, this stimulation being higher with thioproline and N-acet ylcysteine than with ascorbic: acid and alpha-tocopherol. The effects were similar for the three lymphoid organs and the peritoneum. This stimulation of the NK activity by antioxidants is an important favorable response, espe cially in old mice, in which age results in a decrease in NK function and, therefore, in a higher incidence of neoplasia. (C) 1999 Elsevier Science In c. All rights reserved.