In:
Immunity & Ageing, Springer Science and Business Media LLC, Vol. 6, No. 1 ( 2009-12)
Kurzfassung:
Immunosenescence is an age-associated disorder occurring primarily in T cell compartments, including altered subset composition, functions, and activation. In women, evidence implicates diminished estrogen in the postmenopausal period as a contributing factor to diminished T cell responsiveness. Since hypoestrogenism is present in postmenopausal women, our objective focused on whether T cell activation, defined as signalling molecule expressions and activation, and function, identified as IL-2 production, were affected by low estrogen. Methods Using Jurkat 6.1 T cells, consequences of 4 pg/ml (corresponding to postmenopausal levels) or 40 pg/ml (premenopausal levels) of estradiol (E 2 ) were analyzed on signalling proteins, CD3-zeta, JAK2, and JAK3, determined by Western immunoblotting. These consequences were correlated with corresponding gene expressions, quantified by real time-polymerase chain reaction. Tyrosine phosphorylation of CD3-zeta was defined by immunoprecipitation and western immunoblotting following activation by T cell receptor (TcR) cross-linking. CD3-zeta expression and modulation was also confirmed in T cells from pre- and postmenopausal women. To assess functional consequences, IL-2 production, induced by PMA and ionomycin, was determined using enzyme-linked immunosorbent spot assay (ELISpot). Results At 40 pg/ml E 2 , the level of signalling protein CD3-zeta was elevated 1.57-fold, compared with cells exposed to 4 pg/ml E 2 . The CD3-zeta proteins also exhibited altered levels of activation-induced phosphorylation in the presence of 40 pg/ml E 2 versus 4 pg/ml: 23 kD phosphorylated form increased 2.64-fold and the 21 kD form was elevated 2.95-fold. Examination of kinases associated with activation signalling also demonstrated that, in the presence of 40 pg/ml E 2 , JAK2 protein expression was increased 1.64-fold (p 〈 0.001) and JAK3 enhanced 1.79-fold (p 〈 0.001) compared to 4 pg/ml. mRNA levels for CD3-zeta, JAK2, and JAK3 were significantly increased following exposure to 40 pg/ml E 2 (2.39, 2.01, and 2.21 fold, respectively) versus 4 pg/ml. These findings were confirmed in vivo, since T cells from postmenopausal women exhibited 7.2-fold diminished CD3-zeta expression, compared to pre-menopausal controls and this expression was elevated 3.8-fold by addition of 40 pg/ml E 2 . Functionally, Jurkat cells exposed to 40 pg/ml E 2 and activated exhibited significantly elevated numbers of IL-2 producing colonies compared to 4 pg/ml (75.3 ± 2.2 versus 55.7 ± 2.1 colonies, p 〈 0.0001). Conclusion Jurkat T cells exposed to 4 pg/ml E 2 expressed significantly diminished activation signalling proteins, correlating with reduced IL-2 production. Lower signalling protein levels appear to result from decreased CD3-zeta, JAK2, and JAK3 gene expressions. These findings may provide a molecular basis for immunosenescence associated with the postmenopausal state.
Materialart:
Online-Ressource
ISSN:
1742-4933
DOI:
10.1186/1742-4933-6-1
Sprache:
Englisch
Verlag:
Springer Science and Business Media LLC
Publikationsdatum:
2009
ZDB Id:
2168941-6
