Effect of in vitro generation of oxygen free radicals on T cell function in young and old rats.
T cells from young (6 months) and old (24 months) male Fischer 344 rats were isolated and exposed to three different oxidative stress conditions: (a) reactive oxygen species generated by xanthine-xanthine oxidase (X/XO), (b) hydrogen peroxide (H2O2), and (c) hyperthermia (43 degrees C for 1 h). After oxidative stress treatment, the induction of proliferation and IL-2 production by concanavalin A (Con A) was measured. Exposure of T cells to X/XO or H2O2 resulted in suppression of proliferation and IL-2 expression, and the suppressive effect was more pronounced in T cells from young rats than in T cells from old rats. Similarly, hyperthermia caused inhibition of proliferation and IL-2 expression in T cells from young and old rats. Addition of antioxidant to cultured cells only slightly attenuated the effects of X/XO and H2O2 on T cell function; however, antioxidant had no effect on heat shock-mediated inhibition of proliferation in young or old rats. Because IL-2 plays a crucial role in T cell proliferation and because the transcription factor NFAT (nuclear factor of activated T cell) plays a major role in the regulation of IL-2 transcription, the induction of NFAT as well as NF-KB and AP-1 DNA binding activities in nuclear extracts of the X/XO-treated and untreated control cells was measured using a gel shift assay. The ability of nuclear extracts to bind NFAT or NF-KB oligonucleotide decreased in the X/XO-treated cells from young and old rats compared to the untreated controls. Therefore, these data imply that reactive oxygen species generated by the X/XO system alter the distal step of mitogen-mediated signal transduction, i.e., transcription factors that regulate IL-2 transcription.
Pahlavani
M A
MA
Geriatric Research, Education and Clinical Center, South Texas Veterans Health Care System and Department of Physiology, University of Texas Health Science Center, San Antonio, USA. Pahlavani@uthscsa.edu
Harris
M D
MD
D000375:Aging; D000818:Animals; D000975:Antioxidants / Q000494:pharmacology; D002478:Cells, Cultured; D003208:Concanavalin A / Q000494:pharmacology; D005609:Free Radicals; D006358:Hot Temperature; D006861:Hydrogen Peroxide / Q000494:pharmacology; D007376:Interleukin-2 / Q000096:biosynthesis; D008213:Lymphocyte Activation / Q000187:drug effects; D008297:Male; D051381:Rats; D011916:Rats, Inbred F344; D017382:Reactive Oxygen Species / Q000378:metabolism*; D013601:T-Lymphocytes / Q000502:physiology*; D014157:Transcription Factors / Q000378:metabolism; D019820:Xanthine / Q000378:metabolism; D014969:Xanthine Oxidase / Q000378:metabolism
D000975:Antioxidants; D005609:Free Radicals; D007376:Interleukin-2; D017382:Reactive Oxygen Species; D014157:Transcription Factors; D003208:Concanavalin A; D019820:Xanthine; D006861:Hydrogen Peroxide; D014969:Xanthine Oxidase