Alpha-synuclein activates microglia by inducing the expressions of matrix metalloproteinases and the subsequent activation of protease-activated receptor-1

J Immunol. 2010 Jul 1;185(1):615-23. doi: 10.4049/jimmunol.0903480. Epub 2010 May 28.


The mutation or overexpression of alpha-synuclein protein plays a pivotal role in the pathogenesis of Parkinson's disease. In our preliminary experiments, we found that alpha-synuclein induced the expression of matrix metalloproteinases (MMPs) (MMP-1, -3, -8, and -9) in rat primary cultured microglia. Thus, the current study was undertaken to determine the roles of MMPs in alpha-synuclein-induced microglial activation. The inhibition of MMP-3, -8, or -9 significantly reduced NO and reactive oxygen species levels and suppressed the expression of TNF-alpha and IL-1beta. Notably, MMP-8 inhibitor suppressed TNF-alpha production more efficaciously than MMP-3 or MMP-9 inhibitors. Inhibition of MMP-3 or -9 also suppressed the activities of MAPK, NF-kappaB, and AP-1. Previously, protease-activated receptor-1 (PAR-1) has been associated with the actions of MMPs, and thus, we further investigated the role of PAR-1 in alpha-synuclein-induced inflammatory reactions. A PAR-1-specific inhibitor and a PAR-1 antagonist significantly suppressed cytokine levels, and NO and reactive oxygen species production in alpha-synuclein-treated microglia. Subsequent PAR-1 cleavage assay revealed that MMP-3, -8, and -9, but not alpha-synuclein, cleaved the synthetic peptide containing conventional PAR-1 cleavage sites. These results suggest that MMPs secreted by alpha-synuclein-stimulated microglia activate PAR-1 and amplify microglial inflammatory signals in an autocrine or paracrine manner. Furthermore, our findings suggest that modulation of the activities of MMPs and/or PAR-1 may provide a new therapeutic strategy for Parkinson's disease.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Acid Sequence
  • Animals
  • Autocrine Communication / immunology
  • Cell Line, Tumor
  • Cells, Cultured
  • Gene Expression Regulation / immunology
  • Humans
  • Inflammation Mediators / metabolism
  • Inflammation Mediators / physiology
  • Lipopolysaccharides / physiology
  • Matrix Metalloproteinase Inhibitors
  • Matrix Metalloproteinases / biosynthesis*
  • Matrix Metalloproteinases / metabolism
  • Microglia / enzymology
  • Microglia / metabolism*
  • Microglia / pathology
  • Molecular Sequence Data
  • Paracrine Communication / immunology
  • Protein Processing, Post-Translational / immunology
  • Rats
  • Rats, Sprague-Dawley
  • Receptor, PAR-1 / agonists
  • Receptor, PAR-1 / metabolism*
  • Receptor, PAR-1 / physiology
  • alpha-Synuclein / physiology*


  • Inflammation Mediators
  • Lipopolysaccharides
  • Matrix Metalloproteinase Inhibitors
  • Receptor, PAR-1
  • Snca protein, rat
  • alpha-Synuclein
  • Matrix Metalloproteinases