Selective contribution of interleukin-6 and leptin to brain inflammatory signals induced by systemic LPS injection in mice

J Comp Neurol. 2008 Nov 20;511(3):373-95. doi: 10.1002/cne.21850.


This study aimed to address the relative contributions of the proinflammatory cytokine interleukin-6 (IL-6) and the cytokine-like hormone leptin to the genomic activation of brain cells during lipopolysaccharide (LPS)-induced systemic inflammation. Wildtype and IL-6KO mice were injected with LPS (50 microg/kg, intraperitoneally) and the brains analyzed by immunohistochemistry and reverse-transcriptase polymerase chain reaction (RT-PCR). LPS induced a pronounced nuclear translocation of the signal transducer and activator of transcription (STAT3) throughout the brains of wildtype mice, an effect that was significantly diminished, but not abolished, in the IL-6KOs. The remnant STAT3-activation, although still observed within some of the same areas activated by IL-6, was most intense in ependymal and meningial cells and along distinct blood vessels throughout the brain. This expression was almost totally abolished in the presence of an anti-leptin antiserum. Interestingly, the induction of cyclooxygenase 2 and microsomal prostaglandin E synthase (mPGES), the rate-limiting enzymes for synthesis of PGE2 by LPS, was diminished to a degree that correlated with the absence of IL-6 but not entirely with leptin. These results demonstrate that the induction of the inflammatory pathway in the brain is mediated by both IL-6 and leptin, which appear to work in tandem. Unlike IL-6, however, the contribution of leptin to this response was limited to distinct cell types/brain areas and STAT3-responsive target genes implicated in the brain-controlled sickness-type response. The physiological significance of leptin's action on meningeal and endothelial cells remains to be clarified but might reflect a role in LPS-induced immune cell infiltration into the brain.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Brain* / anatomy & histology
  • Brain* / immunology
  • Cyclooxygenase 2 / genetics
  • Cyclooxygenase 2 / metabolism
  • I-kappa B Proteins / genetics
  • I-kappa B Proteins / metabolism
  • Inflammation / metabolism*
  • Interleukin-1beta / genetics
  • Interleukin-1beta / immunology
  • Interleukin-6 / genetics
  • Interleukin-6 / immunology*
  • Leptin / immunology*
  • Lipopolysaccharides* / immunology
  • Lipopolysaccharides* / pharmacology
  • Male
  • Mice
  • Mice, Inbred C57BL
  • Mice, Knockout
  • NF-KappaB Inhibitor alpha
  • Prostaglandin-Endoperoxide Synthases / genetics
  • Prostaglandin-Endoperoxide Synthases / metabolism
  • Receptors, Leptin / genetics
  • Receptors, Leptin / metabolism
  • STAT3 Transcription Factor / metabolism
  • von Willebrand Factor / metabolism


  • I-kappa B Proteins
  • Interleukin-1beta
  • Interleukin-6
  • Leptin
  • Lipopolysaccharides
  • Nfkbia protein, mouse
  • Receptors, Leptin
  • STAT3 Transcription Factor
  • Stat3 protein, mouse
  • von Willebrand Factor
  • NF-KappaB Inhibitor alpha
  • Ptgs2 protein, mouse
  • Cyclooxygenase 2
  • Prostaglandin-Endoperoxide Synthases