Journal Article

DZNE-2026-00119

http://join2-wiki.gsi.de/foswiki/pub/Main/Artwork/join2_logo100x88.png MicroRNA-29a-5p contributes to neuroinflammation through TLR7.

McGurran, H. ; Graceffo, E. ; Kumbol, V. ; Jendrach, M. ; Hinkelmann, L. ; Brehm, M. ; Ravatt, L.DZNE* ; Krüger, C. ; Wallach, T. ; Haake, A.DZNE* ; Wegmann, S.DZNE* ; Heppner, F. L.DZNE* ; Schülke, M. ; Lehnardt, S.

2026
BioMed Central London

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Please use a persistent id in citations: doi:10.1186/s12974-025-03680-4

Abstract: MicroRNAs (miRNAs) canonically regulate post-transcriptional gene expression, but they can also serve as ligands for Toll-like receptors (TLRs). These receptors and their associated signalling pathways contribute to inflammatory responses involved in various central nervous system (CNS) diseases, including Alzheimer's disease (AD). Here, we investigated the effects of extracellularly delivered miRNA in the context of neuroinflammation. We identified several miRNAs specifically dysregulated in AD and/or neuroinflammatory states, which directly activate the single-stranded RNA sensors mouse TLR7 and human TLR7/8. Among them, extracellular miR-29a-5p induced cytokine and chemokine release from murine primary microglia, altered expression of TLR signalling elements, and enhanced Aβ phagocytosis. Furthermore, this miRNA induced neuronal injury dependent on microglial TLR7 expression, but also in a cell-autonomous fashion, in vitro. Intrathecal injection of miR-29a-5p into mice led to microglial accumulation and neuronal injury in the cerebral cortex through TLR7 after 3 days. Brains of wild-type and APP/PS1 mice, an established AD mouse model, treated with multiple intrathecal miR-29a-5p injections over 120 days exhibited changes in cytokine/chemokine expression and neuronal injury. RNAseq analysis of the cerebral cortex of both miRNA-treated genotypes revealed downregulation of MAPK-associated pathways.Our study establishes AD-associated miRNAs such as miR-29a-5p as TLR7 agonists and signalling molecules for microglia, thereby altering the neuroinflammatory response.

Keyword(s): Animals (MeSH) ; MicroRNAs: metabolism (MeSH) ; MicroRNAs: genetics (MeSH) ; MicroRNAs: administration & dosage (MeSH) ; Toll-Like Receptor 7: metabolism (MeSH) ; Toll-Like Receptor 7: genetics (MeSH) ; Mice (MeSH) ; Neuroinflammatory Diseases: metabolism (MeSH) ; Neuroinflammatory Diseases: genetics (MeSH) ; Neuroinflammatory Diseases: pathology (MeSH) ; Humans (MeSH) ; Microglia: metabolism (MeSH) ; Mice, Transgenic (MeSH) ; Mice, Inbred C57BL (MeSH) ; Alzheimer Disease: metabolism (MeSH) ; Alzheimer Disease: pathology (MeSH) ; Alzheimer Disease: genetics (MeSH) ; Membrane Glycoproteins: metabolism (MeSH) ; Membrane Glycoproteins: genetics (MeSH) ; Cells, Cultured (MeSH) ; Male (MeSH) ; Alzheimer’s disease ; Cytokine expression ; MicroRNA ; Microglia ; Neuroinflammation ; Toll-like receptors ; MicroRNAs ; Toll-Like Receptor 7 ; Tlr7 protein, mouse ; MIRN29 microRNA, mouse ; Membrane Glycoproteins ; MIRN29a microRNA, human

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Contributing Institute(s):

1. Protein Actions in Neurodegeneration (AG Wegmann)
2. Neuroimmunology (AG Heppner)

Research Program(s):

1. 352 - Disease Mechanisms (POF4-352) (POF4-352)
2. 353 - Clinical and Health Care Research (POF4-353) (POF4-353)

Appears in the scientific report 2026

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Database coverage:
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