Central inhibition of interleukin-6 trans-signaling during peripheral infection reduced neuroinflammation and sickness in aged mice.
During systemic infection, inflammatory cytokines such as interleukin (IL)-6 are produced in excess in the brain of aged mice and induce severe behavioral deficits. However, no studies have examined how pro-inflammatory IL-6 trans-signaling is involved in the exaggerated production of IL-6 in the aged brain, nor the extent to which IL-6 trans-signaling affects other markers of neuroinflammation, adhesion molecules, and behavior. Therefore, this study investigated in aged mice the presence of IL-6 signaling subunits in microglia; the central effects of soluble gp130 (sgp130)-a natural inhibitor of the IL-6 trans-signaling pathway-on IL-6 production in microglia; and the effects of sgp130 given intracerebroventricularly (ICV) on neuroinflammation and sickness behavior caused by i.p. injection of lipopolysaccharide (LPS). Here we show that microglia isolated from aged mice have higher expression of IL-6 receptor (IL-6R) compared to microglia from adults; and the level of mRNA for ADAM17, the enzyme responsible for shedding membrane-bound IL-6R in trans-signaling, is higher in the hippocampus of aged mice compared to adults. Additionally, we show in aged mice that peripheral LPS challenge elicits a hyperactive IL-6 response in microglia, and selective blockade of trans-signaling by ICV injection of sgp130 mitigates this. The sgp130-associated inhibition of IL-6 was paralleled by amelioration of exaggerated and protracted sickness behavior in aged mice. Taken together, the results show that microglia are important regulators of the IL-6 trans-signaling response in the aged brain and sgp130 exerts an anti-inflammatory effect by inhibiting the pro-inflammatory arm of IL-6 signaling.
Laboratory of Integrative Immunology and Behavior, Animal Science Department, University of Illinois at Urbana-Champaign, Urbana, 7 Animal Sciences Laboratory, 1207 W. Gregory Dr., Urbana, IL 61801, USA.
Michael D
MD
Burton
Jennifer L
JL
Rytych
Gregory G
GG
Freund
Rodney W
RW
Johnson
D051722:ADAM Proteins / Q000235:genetics / Q000378:metabolism; D000072198:ADAM17 Protein; D000818:Animals; D000893:Anti-Inflammatory Agents / Q000494:pharmacology*; D001522:Behavior, Animal / Q000187:drug effects / Q000502:physiology; D001921:Brain / Q000187:drug effects* / Q000276:immunology / Q000378:metabolism; D050822:Cytokine Receptor gp130 / Q000494:pharmacology*; D004660:Encephalitis / Q000276:immunology* / Q000378:metabolism; D006624:Hippocampus / Q000187:drug effects / Q000276:immunology / Q000378:metabolism; D055809:Illness Behavior / Q000187:drug effects* / Q000502:physiology; D007249:Inflammation / Q000276:immunology / Q000378:metabolism; D015850:Interleukin-6 / Q000235:genetics / Q000378:metabolism; D008297:Male; D051379:Mice; D017628:Microglia / Q000187:drug effects / Q000276:immunology / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects* / Q000276:immunology; D000093242:Interleukin-6 Inhibitors
D051722:ADAM Proteins; D000072198:ADAM17 Protein; D000893:Anti-Inflammatory Agents; D050822:Cytokine Receptor gp130; D015850:Interleukin-6; D000093242:Interleukin-6 Inhibitors; C000606463:Adam17 protein, mouse