Aging is associated with a decline in T cell mediated functions, which contributes to a higher incidence of, and morbidity and mortality from, infectious diseases and tumors. The age-related defect in T cells has been shown to be due to intrinsic declines in T cell function, as well as increased production of prostaglandin (PG)E2, a T cell suppressive factor, by macrophages (Mphi). We demonstrated that the increased PGE2 production was due to ceramide mediated upregulation of cyclooxygenase 2 (COX-2) transcription, a key regulatory enzyme in PGE2 synthesis. The signaling mechanism through which ceramide upregulates COX 2 expression, however, is not known and needs to be investigated. We further showed that vitamin E (E) supplementation improves T cell mediated function by two distinct mechanisms: a) by decreasing PGE2 production, thus reducing macrophage Mphi mediated suppression, and b) by directly enhancing T cell function, independent of its effect on Mphi PGE2 production. E exerts its effect by improving the ability of naive T cells from old mice to produce IL-2 and progress through cell division cycles. The mechanism of E-induced enhancement of naive T cell function is not known and needs to be determined. Thus, the specific aims of this proposal are: 1) To determine the signaling pathway involved in ceramide-induced upregulation of COX-2 expression in old Mphi. To accomplish this goal, we will test the hypothesis that ceramide upregulates COX-2 expression in old macrophages through enhancing PKC-zeta activity, leading to increased IkappaB phosphorylation, and thus degradation. This in turn will increase NFkappaB activation and COX-2 expression. 2) To determine the mechanism of E-induced increase in the function of old naive T cells. To accomplish this goal, we will test the hypothesis that E enhances naive T cell function in old mice by increasing their ability to form an effective immune synapse at the site of T cell receptor (TCR) and antigen contact. This, in turn, will lead to improved TCR-associated signal transduction, and subsequent, IL-2 production in old mice. We propose that E induces its effect by changing the redistribution of key TCR associated signaling molecules in membrane lipid domains, known as lipid rafts, by one or both of the following mechanisms: a) increasing palmitoylation of key signaling molecules associated with TCR-mediated activation, and b) changing the structure of the lipid component of lipid rafts. These experiments will elucidate the mechanism of the age-related dysregulation of macrophages and T cells, as well as their normalization by E. This, in turn, will help in designing practical nutritional interventions to reverse and/or delay the age-associated dysregulation of immune and inflammatory responses as well as diseases associated with it.

Agency
National Institute of Health (NIH)
Institute
National Institute on Aging (NIA)
Type
Research Project (R01)
Project #
5R01AG009140-11
Application #
6805314
Study Section
Geriatrics and Rehabilitation Medicine (GRM)
Program Officer
Fuldner, Rebecca A
Project Start
2003-09-30
Project End
2008-08-31
Budget Start
2004-09-15
Budget End
2005-08-31
Support Year
11
Fiscal Year
2004
Total Cost
$280,000
Indirect Cost
Name
Tufts University
Department
Type
Organized Research Units
DUNS #
039318308
City
Boston
State
MA
Country
United States
Zip Code
02111
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Marko, Melissa G; Ahmed, Tanvir; Bunnell, Stephen C et al. (2007) Age-associated decline in effective immune synapse formation of CD4(+) T cells is reversed by vitamin E supplementation. J Immunol 178:1443-9

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