Altered regulation of IL-6 production with normal aging. Possible linkage to the age-associated decline in dehydroepiandrosterone and its sulfated derivative.

Normal aging in humans has been recently shown to be accompanied by reduced control over production of the multifunctional cytokine IL-6. This cytokine was reported to be quantitatively elevated in most serum samples obtained from "normal" elderly humans. In the present investigation, we report that IL-6 levels are elevated in serum samples obtained from aged mice, and its spontaneous production could also be easily detected in culture supernatants of unstimulated lymphoid cells obtained from aged, but not mature, adult donors. Spontaneous production of IL-6 was consistently observed in culture supernatants of lymphoid cells from both the spleen and mesenteric lymph nodes from aged donors, but was absent from supernatants derived from their peripheral lymph nodes. In aged mice, the reduced regulation of IL-6 production could be effectively prevented and/or reversed by supplementing aging animals with dehydroepiandrosterone sulfate, a steroid hormone whose endogenous production is known to decline with advancing age in all species tested. It was also established that serum obtained from old dehydroepiandrosterone sulfate-treated mice contained lower (normal) levels of serum amyloid P substance (an acute phase reactant), reduced levels of serum Ig (all classes and isotypes) and lower titers of tissue-specific autoantibodies than untreated aged controls. Therefore, a number of well described, age-related conditions, some of which could be contributing to the pathologic phenotype of old age, may actually represent secondary effects to this age-associated change in IL-6 production.