Aging but not dietary restriction alters the activation-induced apoptosis in rat T cells

The aim of this study was to determine if aging or dietary restriction (DR) alters activation-induced cell death, which is known to regulate cell prol iferation and eliminate the high number of activated cells during an immune response, Splenic T cells were isolated from young (4-6 months) and old (2 5-26 months) Fischer 344 rats that had free access to food, ad libitum (AL) , and from dietary-restricted (DR) old (25-26 months) rats that beginning a t 6 weeks of age mere fed 60% (40% food-restricted) of the diet consume by the AL rats, T cells were incubated with anti-CD3 antibody, or staphylococc al enterotoxin B (primary stimulus) for 72-96 h, followed by restimulation with anti-CD3 (secondary stimulus) for 72 h, Activation-induced apoptosis w as assessed by DNA fragmentation and the expression of Fas/CD95 receptor an d Fas ligand (Fas-L) was measured by flow cytometry, We found that the amou nt of DNA fragmentation was significantly (P < 0.05) higher in the stimulat ed and restimulated T cells from AL old rats and DR old rats compared to yo ung rats. The increase in DNA fragmentation with age was paralleled by an i ncrease in the proportion of the cells expressing Fas and Fas-L, However, D R had no significant effect on the age-related increase in DNA fragmentatio n or the expression of Fas or Fas-L, We also measured the levels of Bcl-2 a nd Bas protein and found that the level of Bcl-2 decreased and Pax increase d with age and that DR had no effect on the age-related changes in the leve l of Bcl-2 or Bax protein. These results demonstrate that aging but not DR alters activation-induced apoptosis in rat T cells. (C) 2001 Federation of European Biochemical Societies, Published by Elsevier Science B.V. All righ ts reserved.