Age-associated alterations in the time-dependent profile of pro- and anti-inflammatory proteins within the hippocampus in response to acute exposure to interleukin-1β

The pro-inflammatory cytokine IL-1β is known to play a role in several models of aging, neuroinflammation, and neurodegenerative diseases. Here, we document a detailed time- and age-dependent pattern of pro- and anti-inflammatory biomarkers following bilateral intrahippocampal injection of interleukin-1β. During the first 12. h several pro- and anti-inflammatory cytokines increased in the aged (24. mo old) rats, some of which returned to baseline levels by 24. h post-injection while others remained elevated for 72. h post-injection. In contrast, no such increases were observed in the young (3. mo old) rats. Interestingly, young rats up-regulated mRNA of two pro-inflammatory cytokines, interleukin-1β and tumor necrosis factor-α, but did not translate these transcripts into functional proteins, which may be related to expression of suppressor of cytokine signaling type-2. These results contribute to our understanding of how neuroinflammation may contribute to the pathogenesis of age-related neurodegenerative disorders due to an age-related bias towards a hyper-reactive immune response that is not selective for a pro- or anti-inflammatory phenotype following an inflammatory stimulus.