TY - JOUR
T1 - Microglia priming by interleukin-6 signaling is enhanced in aged mice
AU - Garner, Katherine M.
AU - Amin, Ravi
AU - Johnson, Rodney W.
AU - Scarlett, Emily J.
AU - Burton, Michael D.
N1 - Funding Information:
This work was supported by NIH grant: K22NS096030 (MDB) and The University of Texas STARS program research support grant (MDB).
Publisher Copyright:
© 2018
PY - 2018/11/15
Y1 - 2018/11/15
N2 - During peripheral infection, excessive production of pro-inflammatory cytokines in the aged brain from primed microglia induces exaggerated behavioral pathologies. While the pro-inflammatory cytokine IL-6 increases in the brain with age, its role in microglia priming is not known. This study examined the functional role of IL-6 signaling on microglia priming. Our hypothesis is that IL-6 signaling mediates primed states of microglia in the aged. An initial study assessed age-related alteration in IL-6 signaling molecules; sIL-6R and sgp130 were measured in cerebrospinal fluid of young and aged wild-type animals. Subsequent studies of isolated microglia from C57BL6/J (IL-6+/+) and IL-6 knock-out (IL-6−/−) mice showed significantly less MHC-II expression in aged IL-6−/− compared to IL-6+/+ counterparts. Additionally, adult and aged IL-6+/+ and IL-6−/− animals were administered lipopolysaccharide (LPS) to simulate a peripheral infection; sickness behaviors and hippocampal cytokine gene expression were measured over a 24 h period. Aged IL-6−/− animals were resilient to LPS-induced sickness behaviors and recovered more quickly than IL-6+/+ animals. The age-associated baseline increase of IL-1β gene expression was ablated in aged IL-6−/− mice, suggesting IL-6 is a key driver of cytokine activity from primed microglia in the aged brain. We employed in vitro studies to understand molecular mechanisms in priming factors. MHC-II and pro-inflammatory gene expression (IL-1β, IL-10, IL-6) were measured after treating BV.2 microglia with sIL-6R and IL-6 or IL-6 alone. sIL-6R enhanced expression of both pro-inflammatory genes and MHC-II. Taken together, these data suggest IL-6 expression throughout life is involved in microglia priming and increased amounts of IL-6 following peripheral LPS challenge are involved in exaggerated sickness behaviors in the aged.
AB - During peripheral infection, excessive production of pro-inflammatory cytokines in the aged brain from primed microglia induces exaggerated behavioral pathologies. While the pro-inflammatory cytokine IL-6 increases in the brain with age, its role in microglia priming is not known. This study examined the functional role of IL-6 signaling on microglia priming. Our hypothesis is that IL-6 signaling mediates primed states of microglia in the aged. An initial study assessed age-related alteration in IL-6 signaling molecules; sIL-6R and sgp130 were measured in cerebrospinal fluid of young and aged wild-type animals. Subsequent studies of isolated microglia from C57BL6/J (IL-6+/+) and IL-6 knock-out (IL-6−/−) mice showed significantly less MHC-II expression in aged IL-6−/− compared to IL-6+/+ counterparts. Additionally, adult and aged IL-6+/+ and IL-6−/− animals were administered lipopolysaccharide (LPS) to simulate a peripheral infection; sickness behaviors and hippocampal cytokine gene expression were measured over a 24 h period. Aged IL-6−/− animals were resilient to LPS-induced sickness behaviors and recovered more quickly than IL-6+/+ animals. The age-associated baseline increase of IL-1β gene expression was ablated in aged IL-6−/− mice, suggesting IL-6 is a key driver of cytokine activity from primed microglia in the aged brain. We employed in vitro studies to understand molecular mechanisms in priming factors. MHC-II and pro-inflammatory gene expression (IL-1β, IL-10, IL-6) were measured after treating BV.2 microglia with sIL-6R and IL-6 or IL-6 alone. sIL-6R enhanced expression of both pro-inflammatory genes and MHC-II. Taken together, these data suggest IL-6 expression throughout life is involved in microglia priming and increased amounts of IL-6 following peripheral LPS challenge are involved in exaggerated sickness behaviors in the aged.
KW - IL-6 trans signaling
KW - Inflammation
KW - MHC-II
KW - Neuroimmunology
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U2 - 10.1016/j.jneuroim.2018.09.002
DO - 10.1016/j.jneuroim.2018.09.002
M3 - Article
C2 - 30261355
AN - SCOPUS:85053789040
SN - 0165-5728
VL - 324
SP - 90
EP - 99
JO - Advances in Neuroimmunology
JF - Advances in Neuroimmunology
ER -