CELLULAR IMMUNOLOGY 180, 10–19 (1997) ARTICLE NO. CI971155 The Increase in the Induction of IL-2 Expression with Caloric Restriction Is Correlated to Changes in the Transcription Factor NFAT Mohammad A. Pahlavani, Melissa D. Harris, and Arlan Richardson Geriatric Research, Education, and Clinical Center, South Texas Veterans Health Care System, and Department of Physiology, University of Texas Health Science Center, San Antonio, Texas 78284 Received February 10, 1997; accepted June 5, 1997 increases the survival of laboratory rodents by re- tarding aging (1 – 3). In addition, caloric restriction has The objective of this study was to determine if the been found to delay the incidence of most age-related increase in the induction of interleukin-2 (IL-2) ex- diseases and retard a wide variety of age-sensitive im- pression with caloric restriction correlates with munological parameters (4, 5). Because the immune changes in binding activity of the IL-2-specific tran- scription factor NFAT (nuclear factor of activated T system is one of the major physiological systems that cells) and/or the ubiquitous transcription factor AP-1 perceives and responds to a variety of environmental in T cells from male Fischer 344 rats. Splenic T cells challenges such as pathogenic microorganisms and were isolated from young (6-month) and old (24- cancerous cells and because a decline in the immunode- month) rats fed ad libitum and from old (24-month) fense system has been implicated in aging (6, 7), it has rats fed a restricted diet (40% caloric restriction) that been suggested that alterations in the immunologic began at 6 weeks of age. T cells were stimulated with function of rodents after caloric restriction are im- concanavalin A (Con A) and the expression of IL-2 and portant in the life-extending action of caloric restriction the DNA binding activity of the transcription factors (4 – 6, 8, 9). The initial observation by Walford’s labora- NFAT and AP-1 were measured in these cells. We found tory (6) showed that mitogen-induced lymphocyte pro- that the induction of IL-2 activity and mRNA levels liferation was greater for mice fed a caloric-restricted decreased with age and that caloric restriction sig- diet compared to that of mice fed ad libitum. Subse- nificantly (P õ 0.05) reduced the age-related decline in quent studies from other laboratories (4, 5, 8), includ- IL-2 expression. The ability of nuclear extracts from T ing our laboratory (9), confirmed this initial observa- cells isolated from old rats fed ad libitum and re- tion and showed that mitogen-induced lymphocyte pro- stricted old rats to bind to the NFAT oligonucleotide liferation is enhanced in caloric-restricted animals. or AP-1 oligonucleotide decreased with age. Caloric Although a number of studies demonstrate that lym- restriction significantly (P õ 0.05) reduced the age-re- phocytes isolated from caloric-restricted rodents show lated decline in NFAT but had no significant effect on higher proliferative response to activating agents than AP-1 binding activity. We also measured the induction lymphocytes from rodents fed ad libitum, there is cur- of c-fos and c-jun expression by Con A in T cells from rently very little information on the mechanism respon- young and old rats fed ad libitum or caloric-restricted diet. The induction of c-fos protein and mRNA levels sible for the increased proliferative capacity of lympho- but not c-jun protein or mRNA levels decreased sig- cytes in caloric-restricted rodents. Interleukin-2 (IL-2) nificantly with age. Caloric restriction significantly (P has been shown to play an essential role in lymphocyte õ 0.05) reduced the age-related decline in c-fos expres- proliferation. IL-2 is a lymphokine/cytokine produced sion but had no significant effect on c-jun expression. primarily by the helper subset of T cells, and its inter- Therefore, the increase in IL-2 expression with caloric action with IL-2 receptor (IL-2R) on the surface of T restriction correlates with an increase in binding ac- cells drives the cells to proliferate (10, 11). The effect tivity of transcription factor NFAT and an increase in of IL-2 is not restricted only to the proliferation of T the expression of c-fos, which is a component of the cells, but it affects the growth and function of a variety NFAT – protein complex.  1997 Academic Press of different immune cells, e.g., B cells, cytotoxic T cells, natural killer cells, lymphokine-activated killer cells (10–13). The expression of IL-2 has been found to de- INTRODUCTION crease with age in mice, rats, and humans, and a num- ber of laboratories have shown that caloric restriction Research over the past two decades has shown that caloric restriction (i.e., 40% restriction in food intake) retards the age-related decline in IL-2 expression (re- 10 0008-8749/97 $25.00 Copyright  1997 by Academic Press All rights of reproduction in any form reserved. AID CI 1155 / 6c26$$$181 09-05-97 23:33:46 cias