Molecular basis of age-associated cytokine dysregulation in LPS-stimulated macrophages

Abstract: Aged humans and rodents are suscepti-ble to infection with Streptococcus pneumoniae bacteria as a result of an inability to make antibod-ies to capsular polysaccharides. This is partly a result of decreased production of proinflammatory cytokines and increased production of interleukin (IL)-10 by macrophages (M) from aged mice [1]. To understand the molecular basis of cytokine dys-regulation in aged mouse M, a microarray anal-ysis was performed on RNA from resting and lipo-polysaccharide (LPS)-stimulated M from aged and control mice using the Affymetrix Mouse Ge-nome 430 2.0 gene chip. Two-way ANOVA analy-sis demonstrated that at an overall P < 0.01 level, 853 genes were regulated by LPS (169 in only the young, 184 in only the aged, and 500 in both). Expression analysis of systematic explorer re-vealed that immune response (proinflammatory chemokines, cytokines, and their receptors) and signal transduction genes were specifically reduced in aged mouse M. Accordingly, expression of Il1 and Il6 was reduced, and Il10 was increased, con-firming our previous results. There was also de-creased expression of interferon-. Genes in the Toll-like receptor-signaling pathway leading to nu-clear factor-B activation were also down-regu-lated but IL-1 receptor-associated kinase 3, a neg-ative regulator of this pathway, was increased in aged mice. An increase in expression of the gene for p38 mitogen-activated protein kinase (MAPK) was observed with a corresponding increase in pro-tein expression and enzyme activity confirmed by Western blotting. Low doses of a p38 MAPK inhib-itor (SB203580) enhanced proinflammatory cyto-kine production by M and reduced IL-10 levels, indicating that increased p38 MAPK activity has a role in cytokine dysregulation in the aged mous