Prolonged neuroinflammation after lipopolysaccharide exposure in aged rats

PLoS One. 2014 Aug 29;9(8):e106331. doi: 10.1371/journal.pone.0106331. eCollection 2014.

Abstract

Inflammation is a hallmark of several disease states ranging from neurodegeneration to sepsis but is also implicated in physiological processes like ageing. Non-resolving inflammation and prolonged neuroinflammation are unclear processes implicated in several conditions, including ageing. In this study we studied the long-term effects of endotoxemia, as systemic lipopolysaccharide (LPS) injection, focusing on the role of astrocyte activation and cytokine release in the brain of aged rats. A single dose of LPS (2 mg/kg) or 0.9% saline was injected intraperitoneally in aged rats. Levels of pro-inflammatory cytokines (TNFα and IL-1β) and NF-κB p65 activation were measured systemically and in hippocampal tissue. Astrocytes and cytokines release in the CNS were detected via double immunofluorescence staining at different time-points up to day 30. Serum levels of TNFα and IL-1β were significantly increased acutely after 30 minutes (p<0.001) and up to 6 hours (p<0.001) following LPS-injection. Centrally, LPS-treated rats showed up-regulated mRNA expression and protein levels of pro-inflammatory cytokines in the hippocampus. These changes associated with astrogliosis in the hippocampus dentate gyrus (DG), IL-1β immunoreactivity and elevated NF-κB p65 expression up to day 30 post LPS exposure. Overall, these data demonstrate that LPS induces prolonged neuroinflammation and astrocyte activation in the hippocampus of aged rats. Hippocampal NF-κB p65 and excessive astrocytes-derived IL-1β release may play a pivotal role in regulating long-lasting neuroinflammation.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Aging / genetics
  • Aging / metabolism*
  • Animals
  • Astrocytes / pathology*
  • Gene Expression Regulation / drug effects
  • Hippocampus / metabolism
  • Hippocampus / pathology
  • Inflammation / chemically induced*
  • Inflammation / metabolism
  • Inflammation / pathology
  • Interleukin-1beta / genetics
  • Interleukin-1beta / metabolism*
  • Lipopolysaccharides / administration & dosage*
  • Male
  • Rats
  • Rats, Wistar
  • Signal Transduction / drug effects
  • Transcription Factor RelA / genetics
  • Transcription Factor RelA / metabolism*

Substances

  • IL1B protein, mouse
  • Interleukin-1beta
  • Lipopolysaccharides
  • Rela protein, mouse
  • Transcription Factor RelA

Grants and funding

This work was supported by the National Natural Science Foundation of China (81241096). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.