Cited by 175Multiple Sclerosis Research StudiesNeuroinflammation and Neurodegeneration MechanismsPhagocytosis and Immune Regulation

MerTK Is a Functional Regulator of Myelin Phagocytosis by Human Myeloid Cells

Healy, Luke M, Perron, Gabrielle, Won, So-Yoon, Michell-Robinson, Mackenzie A, Rezk, Ayman, Ludwin, Samuel K, Moore, Craig S, Hall, Jeffery A +2 more·2016·The Journal of Immunology

Abstract

Multifocal inflammatory lesions featuring destruction of lipid-rich myelin are pathologic hallmarks of multiple sclerosis. Lesion activity is assessed by the extent and composition of myelin uptake by myeloid cells present in such lesions. In the inflamed CNS, myeloid cells are comprised of brain-resident microglia, an endogenous cell population, and monocyte-derived macrophages, which infiltrate from the systemic compartment. Using microglia isolated from the adult human brain, we demonstrate that myelin phagocytosis is dependent on the polarization state of the cells. Myelin ingestion is significantly enhanced in cells exposed to TGF-β compared with resting basal conditions and markedly reduced in classically activated polarized cells. Transcriptional analysis indicated that TGF-β–treated microglia closely resembled M0 cells. The tyrosine kinase phagocytic receptor MerTK was one of the most upregulated among a select number of differentially expressed genes in TGF-β–treated microglia. In contrast, MerTK and its known ligands, growth arrest-specific 6 and Protein S, were downregulated in classically activated cells. MerTK expression and myelin phagocytosis were higher in CNS-derived microglia than observed in monocyte-derived macrophages, both basally and under all tested polarization conditions. Specific MerTK inhibitors reduced myelin phagocytosis and the resultant anti-inflammatory biased cytokine responses for both cell types. Defining and modulating the mechanisms that regulate myelin phagocytosis has the potential to impact lesion and disease evolution in multiple sclerosis. Relevant effects would include enhancing myelin clearance, increasing anti-inflammatory molecule production by myeloid cells, and thereby permitting subsequent tissue repair.

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Crossref · 10.4049/jimmunol.1502562

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  • Housekeeping functions include synaptic remodeling, migration to sites of neuronal death for phagocytosis, and maintenance of myelin homeostasis.

    “Physiological housekeeping functions include synaptic remodeling (a function critical for CNS development, homeostasis, and neurodegeneration20–22), migration to sites of neuronal death to phagocytose dead or dying cells23,24 or debris, and maintaining myelin homeostasis25.”

    From Microglia in neurodegeneration (2018) · cites this paper as [25]

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Authors
Healy, L. M., Perron, G., Won, S.-Y., Michell-Robinson, M. A., Rezk, A., Ludwin, S. K., Moore, C. S., Hall, J. A., Bar-Or, A., & Antel, J. P.
Affiliations
  • Montreal Neurological Institute and Hospital (CA)
  • Neuroimmunology Unit, Montreal Neurological Institute, McGill University , Montreal, Quebec H3A 2B4 ,
  • Memorial University of Newfoundland (CA)
  • McGill University (CA)
Corresponding author
  • Perron, Gabrielle
  • Rezk, Ayman
Venue
The Journal of Immunology
Published
2016-04
Volume
196
Issue
8
Pages
3375-3384
ISSN
  • 0022-1767 (ISSN-L)
  • 1550-6606
OpenAlex
W2295670844
Cited by
174
References
47
Citations by year
2026: 10 · 2025: 6 · 2024: 29 · 2023: 27 · 2022: 26 · 2021: 20 · 2020: 18 · 2019: 14 · 2018: 13 · 2017: 7 · 2016: 4
FWCI
11.44
Type
journal article
Language
en
Open access
closed
Locations
  • The Journal of Immunology (publishedVersion)
  • PubMed (publishedVersion)
Topics
  • Health Sciences › Medicine › Pathology and Forensic Medicine › Multiple Sclerosis Research Studies
  • Life Sciences › Neuroscience › Neurology › Neuroinflammation and Neurodegeneration Mechanisms
  • Life Sciences › Immunology and Microbiology › Immunology › Phagocytosis and Immune Regulation
Keywords
MERTK, myelin phagocytosis, microglia, macrophages, multiple sclerosis, TGF-beta, microglial polarization, Gas6, protein S, myelin debris clearance, myeloid cells, anti-inflammatory cytokines, neuroinflammation
MeSH terms
c-Mer Tyrosine Kinase, Growth Arrest-Specific Protein 6, Adult, Brain, Cells, Cultured, Humans, Inflammation, Macrophages, Multiple Sclerosis, Myelin Sheath, Phagocytosis, Proto-Oncogene Proteins, Down-Regulation, Up-Regulation, Transforming Growth Factor beta, Cell Polarity, Protein S, Microglia, Receptor Protein-Tyrosine Kinases, Myeloid Cells, Intercellular Signaling Peptides and Proteins

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