title: The role of phase II antioxidant enzymes in protecting memory T cells from spontaneous apoptosis in young and old mice.
abstract: Aging is associated with a functional decline and change in the phenotypic distribution of T cell subsets. The free radical theory of aging is widely promoted as the mechanistic basis for cellular senescence, including the immune system. Although the exact molecular explanation for the role of oxidative stress in cellular senescence is unclear, there is a connection to altered mitochondrial function, both as a contributor and as a target of oxidative stress. In this study we demonstrate that splenic T lymphocytes from old C57BL/6 mice exhibit a significant decline in mitochondrial membrane potential (deltapsi(m)). However, despite this change, there is a lower rate of withdrawal apoptosis in the memory CD4+ and CD8+ T cells. To explain the survival of these long-lived cells against a background of increased oxidative stress, we demonstrate increased glutathione production and phase II enzyme expression, which combine to protect memory T cells against oxidative stress, mitochondrial dysfunction, and cell death. The accumulation of memory T cells with aging explains higher phase II enzyme expression in CD4+ and CD8+ T cells from old mice. Compared with wild-type mice, mice lacking the expression of NF-E2-related factor-2, the transcription factor that regulates phase II enzyme expression, had a significantly enhanced rate of apoptosis in the presence of an oxidative stress stimulus. NF-E2-related factor-2-deficient T cells exhibit a bigger decline in deltapsi(m) and increased reactive oxygen species production than cells from wild-type animals. Taken together, we suggest that phase II enzyme expression and the accompanying increase in intracellular thiol levels protect memory T cells from mitochondrial dysfunction and spontaneous apoptosis.
authors.affiliation: Division of Clinical Immunology and Allergy, Department of Medicine, University of California, Los Angeles, CA 90095, USA.
authors.forename: Hyon-Jeen
authors.initials: HJ
authors.lastname: Kim
authors.forename: Andre E
authors.initials: AE
authors.lastname: Nel
mesh_terms: D000375:Aging / Q000276:immunology*; D000818:Animals; D000975:Antioxidants / Q000502:physiology*; D017209:Apoptosis; D004268:DNA-Binding Proteins / Q000235:genetics / Q000502:physiology; D005978:Glutathione / Q000378:metabolism; D005979:Glutathione Peroxidase / Q000502:physiology; D005982:Glutathione Transferase / Q000502:physiology; D006419:Heme Oxygenase (Decyclizing) / Q000502:physiology; D051547:Heme Oxygenase-1; D007156:Immunologic Memory; D008297:Male; D008564:Membrane Potentials; D008565:Membrane Proteins; D051379:Mice; D008810:Mice, Inbred C57BL; D008928:Mitochondria / Q000502:physiology; D016660:NAD(P)H Dehydrogenase (Quinone); D009252:NADPH Dehydrogenase / Q000502:physiology; D051267:NF-E2-Related Factor 2; D018384:Oxidative Stress; D012333:RNA, Messenger / Q000032:analysis; D013601:T-Lymphocytes / Q000502:physiology*; D015534:Trans-Activators / Q000235:genetics / Q000502:physiology
chemical_list: D000975:Antioxidants; D004268:DNA-Binding Proteins; D008565:Membrane Proteins; D051267:NF-E2-Related Factor 2; C495636:Nfe2l2 protein, mouse; D012333:RNA, Messenger; D015534:Trans-Activators; D005979:Glutathione Peroxidase; D006419:Heme Oxygenase (Decyclizing); D051547:Heme Oxygenase-1; C496542:Hmox1 protein, mouse; D016660:NAD(P)H Dehydrogenase (Quinone); C491732:Nqo1 protein, mouse; D009252:NADPH Dehydrogenase; D005982:Glutathione Transferase; D005978:Glutathione