The mixed-lineage kinase 3 inhibitor URMC-099 facilitates microglial amyloid-β degradation

Weiguo Dong, Christine M. Embury, Yaman Lu, Sarah M. Whitmire, Bhagyalaxmi Dyavarshetty, Harris A. Gelbard, Howard Eliot Gendelman, Tomomi Kiyota

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Abstract

Background: Amyloid-β (Aβ)-stimulated microglial inflammatory responses engage mitogen-activated protein kinase (MAPK) pathways in Alzheimer's disease (AD). Mixed-lineage kinases (MLKs) regulate upstream MAPK signaling that include p38 MAPK and c-Jun amino-terminal kinase (JNK). However, whether MLK-MAPK pathways affect Aβ-mediated neuroinflammation is unknown. To this end, we investigated if URMC-099, a brain-penetrant small-molecule MLK type 3 inhibitor, can modulate Aβ trafficking and processing required for generating AD-associated microglial inflammatory responses. Methods: Aβ1-42 (Aβ42) and/or URMC-099-treated murine microglia were investigated for phosphorylated mitogen-activated protein kinase kinase (MKK)3, MKK4 (p-MKK3, p-MKK4), p38 (p-p38), and JNK (p-JNK). These pathways were studied in tandem with the expression of the pro-inflammatory cytokines interleukin (IL)-1β, IL-6, and tumor necrosis factor (TNF)-α. Gene expression of the anti-inflammatory cytokines, IL-4 and IL-13, was evaluated by real-time quantitative polymerase chain reaction. Aβ uptake and expression of scavenger receptors were measured. Protein trafficking was assessed by measures of endolysosomal markers using confocal microscopy. Results: Aβ42-mediated microglial activation pathways were shown by phosphorylation of MKK3, MKK4, p38, and JNK and by expression of IL-1β, IL-6, and TNF-α. URMC-099 modulated microglial inflammatory responses with induction of IL-4 and IL-13. Phagocytosis of Aβ42 was facilitated by URMC-099 with up-regulation of scavenger receptors. Co-localization of Aβ and endolysosomal markers associated with enhanced Aβ42 degradation was observed. Conclusions: URMC-099 reduced microglial inflammatory responses and facilitated phagolysosomal trafficking with associated Aβ degradation. These data demonstrate a new immunomodulatory role for URMC-099 to inhibit MLK and to induce microglial anti-inflammatory responses. Thus, URMC-099 may be developed further as a novel disease-modifying AD therapy.

Original languageEnglish (US)
Article number184
JournalJournal of Neuroinflammation
Volume13
Issue number1
DOIs
StatePublished - Jul 11 2016

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Keywords

  • Alzheimer's disease
  • Amyloid-β
  • Endolysosomal pathway
  • Microglia
  • Mixed-lineage kinase 3
  • Phagocytosis

ASJC Scopus subject areas

  • Neuroscience(all)
  • Immunology
  • Neurology
  • Cellular and Molecular Neuroscience

Cite this

Dong, W., Embury, C. M., Lu, Y., Whitmire, S. M., Dyavarshetty, B., Gelbard, H. A., Gendelman, H. E., & Kiyota, T. (2016). The mixed-lineage kinase 3 inhibitor URMC-099 facilitates microglial amyloid-β degradation. Journal of Neuroinflammation, 13(1), [184]. https://doi.org/10.1186/s12974-016-0646-z