Characterization of the effect of histone deacetylation inhibitors on CD8 + T cells in the context of aging

Background Posttranslational protein modifications regulate essential cellular processes, including the immune cell activation. Despite known age-related alterations of the phenotype, composition and cytokine profiles of immune cells, the role of acetylation in the aging process of the immune system was not broadly investigated. Therefore, in the current study the effect of acetylation on the protein expression profiles and function of CD8 + T cells from donors of distinct age was analyzed using histone deacetylase inhibitors (HDACi). Methods CD8 + T cells isolated from peripheral blood mononuclear cells of 30 young (< 30 years) and 30 old (> 60 years) healthy donors were activated with anti-CD3/anti-CD28 antibodies in the presence and absence of a cocktail of HDACi. The protein expression profiles of untreated and HDACi-treated CD8 + T cells were analyzed using two-dimensional gel electrophoresis. Proteins with a differential expression level (less than 0.66-fold decrease or more than 1.5-fold increase) between CD8 + T cells of young and old donors were identified by matrix-associated laser desorption ionization—time of flight mass spectrometry. Functional enrichment analysis of proteins identified was performed using the online tool STRING. The function of CD8 + T cells was assessed by analyses of cytokine secretion, surface expression of activation markers, proliferative capacity and apoptosis rate. Results The HDACi treatment of CD8 + T cells increased in an age-independent manner the intracellular acetylation of proteins, in particular cytoskeleton components and chaperones. Despite a strong similarity between the protein expression profiles of both age groups, the functional activity of CD8 + T cells significantly differed with an age-dependent increase in cytokine secretion and expression of activation markers for CD8 + T cells from old donors, which was maintained after HDACi treatment. The proliferation and apoptosis rate of CD8 + T cells after HDACi treatment was equal between both age groups. Conclusions Despite a comparable effect of HDACi treatment on the protein signature of CD8 + T cells from donors of different ages, an initial higher functionality of CD8 + T cells from old donors when compared to CD8 + T cells from young donors was detected, which might have clinical relevance.