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Matrix metalloproteinase-3: a novel signaling proteinase from apoptotic neuronal cells that activates microglia

Yoon Seong Kim1, Sung Soo Kim, Jeong Je Cho

  • 1Burke Medical Research Institute, Weill Medical College and Graduate School of Medical Sciences of Cornell University, White Plains, New York 10605, USA.

The Journal of Neuroscience : the Official Journal of the Society for Neuroscience
|April 9, 2005
PubMed

Insights

Matrix metalloproteinase-3 (MMP-3) released by dying neurons activates microglia, driving inflammation and further neuronal death. This MMP-3 signaling may worsen neurodegenerative diseases like Parkinson's.

Area of Science:

  • Neuroscience
  • Molecular Biology
  • Immunology

Background:

  • Microglial activation and inflammation are hallmarks of neurodegenerative diseases, contributing to neuronal cell death.
  • Understanding the molecular triggers for microglial activation in this context is crucial for developing therapeutic strategies.

Purpose of the Study:

  • To investigate the molecular signaling mechanisms by which apoptotic neurons activate microglia.
  • To identify specific molecules released by dying neurons that mediate microglial responses.

Main Methods:

  • Utilized serum-deprived media (SDM) from apoptotic PC12 cells and recombinant matrix metalloproteinase-3 (MMP-3) to activate primary microglia and BV2 cell lines.
  • Analyzed cytokine and chemokine release profiles (e.g., TNF-alpha, IL-6, IL-1beta) using specific assays.
  • Investigated intracellular signaling pathways, including NF-kappaB and MAPK pathways (ERK, JNK, p38).
  • Assessed the effect of an MMP-3 inhibitor (NNGH) on microglial activation.
  • Evaluated the impact of activated microglia on neuronal apoptosis.

Main Results:

  • Active MMP-3 was released from apoptotic neuronal cells.
  • Both SDM and catalytic domain of recombinant MMP-3 (cMMP-3) activated microglia, inducing specific pro-inflammatory cytokines (TNF-alpha, IL-6, IL-1beta) but not others (IL-12, iNOS).
  • MMP-3-induced microglial activation involved the nuclear factor-kappaB pathway and ERK phosphorylation.
  • Preincubation with an MMP-3 inhibitor abolished these microglial responses.
  • Conditioned media from activated microglia induced further neuronal apoptosis.

Conclusions:

  • The release of active MMP-3 from apoptotic neurons serves as a distinct signal that activates microglia.
  • MMP-3-mediated microglial activation contributes to a cycle of inflammation and neuronal degeneration.
  • MMP-3 signaling represents a potential therapeutic target for neurodegenerative disorders such as Parkinson's disease.

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