WNT signaling in activated microglia is proinflammatory.
Microglia activation is central to the neuroinflammation associated with neurological and neurodegenerative diseases, particularly because activated microglia are often a source of proinflammatory cytokines. Despite decade-long research, the molecular cascade of proinflammatory transformation of microglia in vivo remains largely elusive. Here, we report increased β-catenin expression, a central intracellular component of WNT signaling, in microglia undergoing a proinflammatory morphogenic transformation under pathogenic conditions associated with neuroinflammation such as Alzheimer's disease. We substantiate disease-associated β-catenin signaling in microglia in vivo by showing age-dependent β-catenin accumulation in mice with Alzheimer's-like pathology (APdE9). In cultured mouse microglia expressing the WNT receptors Frizzled FZD(4,5,7,8) and LDL receptor-related protein 5/6 (LRP5/6), we find that WNT-3A can stabilize β-catenin. WNT-3A dose dependently induces LRP6 phosphorylation with downstream activation of disheveled, β-catenin stabilization, and nuclear import. Gene-expression profiling reveals that WNT-3A stimulation specifically increases the expression of proinflammatory immune response genes in microglia and exacerbates the release of de novo IL-6, IL-12, and tumor necrosis factor α. In summary, our data suggest that the WNT family of lipoglycoproteins can instruct proinflammatory microglia transformation and emphasize the pathogenic significance of β-catenin-signaling networks in this cell type.
Halleskog
Carina
C
Department of Physiology and Pharmacology, Karolinska Institutet, Stockholm, Sweden.
Mulder
Jan
J
Dahlström
Jenny
J
Mackie
Ken
K
Hortobágyi
Tibor
T
Tanila
Heikki
H
Kumar Puli
Lakshman
L
Färber
Katrin
K
Harkany
Tibor
T
Schulte
Gunnar
G
D000544:Alzheimer Disease / Q000378:metabolism*; D000704:Analysis of Variance; D000818:Animals; D015153:Blotting, Western; D001921:Brain / Q000378:metabolism*; D002478:Cells, Cultured; D016207:Cytokines / Q000235:genetics / Q000378:metabolism; D004797:Enzyme-Linked Immunosorbent Assay; D051157:Frizzled Receptors / Q000235:genetics / Q000378:metabolism; D020869:Gene Expression Profiling; D006801:Humans; D007150:Immunohistochemistry; D007249:Inflammation / Q000235:genetics / Q000378:metabolism*; D051379:Mice; D017628:Microglia / Q000187:drug effects / Q000378:metabolism*; D010766:Phosphorylation / Q000187:drug effects; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015398:Signal Transduction / Q000187:drug effects / Q000502:physiology*; D051153:Wnt Proteins / Q000235:genetics / Q000378:metabolism* / Q000494:pharmacology; D051176:beta Catenin / Q000235:genetics / Q000378:metabolism
D016207:Cytokines; D051157:Frizzled Receptors; D012333:RNA, Messenger; D051153:Wnt Proteins; D051176:beta Catenin