Constitutive activation of NF-kappa B in an animal model of aging.

The pathophysiology of many disease states observed in aged individuals has been linked to the dysregulated production of several pleiotropic cytokines. We have demonstrated that NF-kappa B, a major transcriptional regulator of these aberrantly expressed cytokines, exists in a constitutively activated state in cells obtained from the major lymphoid organs of aged animals. Therapeutic treatment with dietary antioxidants or with agents capable of activating the peroxisome proliferator-activated receptor (PPAR)-alpha was able to correct the abnormal nuclear NF-kappa B activity, reduce lipid peroxide levels, and eliminate the dysregulated expression of cytokines and other genes under NF-kappa B control. These results suggest that abnormal activation of NF-kappa B in aging contributes to the dysregulated expression of certain pleiotropic cytokines. Effective therapeutic regimens for aging and other inflammatory disease states might benefit from the administration of antioxidants or other agents which specifically activate PPAR-alpha.

IL-12 directly stimulates expression of IL-10 by CD5+ B cells and IL-6 by both CD5+ and CD5- B cells: possible involvement in age-associated cytokine dysregulation.

Constitutive expression of p35 and p40 IL-12 mRNA was detected in splenic macrophages isolated from aged mice. Macrophages were also implicated as the cell type responsible for the dysregulated IL-6 and tumor necrosis factor (TNF)-alpha commonly observed to be constitutively produced by lymphoid cells from aged donors. A role for IL-12 in the aging process was suggested when it was found that recombinant IL-12 (rIL-12) directly stimulated splenic CD5+ B cells to secrete IL-10, and both CD5+ and CD5- B cells could be directly induced to produce IL-6 in response to rIL-12. Furthermore, splenocytes from aged animals cultured in the presence of anti-IL-12 antibodies demonstrated a significant reduction in spontaneous IL-6, IL-10 and IFN-gamma production. Based on these observations it was concluded that IL-12 might be responsible for the dysregulated production of IL-10 and IFN-gamma known to occur in aged animals. Treatment of aged animals with low doses of dehydroepiandrosterone sulfate, previously established to be immunocorrective in immunosenescent animals, reduced the age-associated alterations in IL-12 mRNA and protein expression. The mechanisms responsible for the abnormal constitutive expression of inflammatory cytokines by the macrophages of aged animals may play an important afferent role in establishing the immunosenescent phenotype.

Dysregulation of IL-10 production with aging: possible linkage to the age-associated decline in DHEA and its sulfated derivative.

Peripheral lymphoid cells isolated from the spleens and peritoneal cavities of aged mice were found to constitutively secrete the multifunctional cytokine interleukin (IL)-10 when cultured in vitro. B-Lymphocytes were implicated as the cell type responsible. Abnormal expression of this cytokine was also detected in vivo because high levels of mRNA for IL-10 were present in splenocytes freshly isolated from aged animals. In addition to the spontaneous secretion of IL-10, lymphoid cells from aged donors were hyperresponsive to exogenous stimulation with endotoxin, producing exaggerated quantities of both IL-10 and IL-6 in culture. Treatment of aged animals with dehydroepiandrosterone sulfate (DHEAS), a natural steroid, reversed the age-associated alterations in cytokine production, rendering the treated mice quite similar to mature adult controls. DHEAS treatment of aged mice also resulted in a lowering in the number of B1 cells present in the peritoneal cavity and also reduced the titers of circulating autoantibodies specific for phosphatidylcholine (PtC). Based on its wide range of biologic activities, a dysregulation in the mechanisms that control IL-10 production could be a major contributor to immunosenescence. The ability of DHEAS treatment to restore normal control over the expression of IL-10 may explain how this steroid enhances immunocompetence in aged animals.