Alpha-synuclein activates microglia by inducing the expressions of matrix metalloproteinases and the subsequent activation of protease-activated receptor-1.
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.
Lee
Eun-Jung
EJ
Department of Molecular Medicine & Brain and Cognitive Sciences, Ewha Womans University, Korea.
Woo
Moon-Sook
MS
Moon
Pyong-Gon
PG
Baek
Moon-Chang
MC
Choi
In-Young
IY
Kim
Won-Ki
WK
Junn
Eunsung
E
Kim
Hee-Sun
HS
D000595:Amino Acid Sequence; D000818:Animals; D019898:Autocrine Communication / Q000276:immunology; D045744:Cell Line, Tumor; D002478:Cells, Cultured; D005786:Gene Expression Regulation / Q000276:immunology; D006801:Humans; D018836:Inflammation Mediators / Q000378:metabolism / Q000502:physiology; D008070:Lipopolysaccharides / Q000502:physiology; D061965:Matrix Metalloproteinase Inhibitors; D020782:Matrix Metalloproteinases / Q000096:biosynthesis* / Q000378:metabolism; D017628:Microglia / Q000201:enzymology / Q000378:metabolism* / Q000473:pathology; D008969:Molecular Sequence Data; D019899:Paracrine Communication / Q000276:immunology; D011499:Protein Processing, Post-Translational / Q000276:immunology; D051381:Rats; D017207:Rats, Sprague-Dawley; D044463:Receptor, PAR-1 / Q000819:agonists / Q000378:metabolism* / Q000502:physiology; D051844:alpha-Synuclein / Q000502:physiology*
D018836:Inflammation Mediators; D008070:Lipopolysaccharides; D061965:Matrix Metalloproteinase Inhibitors; D044463:Receptor, PAR-1; C497606:Snca protein, rat; D051844:alpha-Synuclein; D020782:Matrix Metalloproteinases