RESUMO
Recent studies have demonstrated that activated microglia play an important role in dopamine (DA) neuronal degeneration in Parkinson disease (PD) by generating NADPH-oxidase (NADPHO)-derived superoxide. However, the molecular mechanisms that underlie microglial activation in DA cell death are still disputed. We report here that matrix metalloproteinase-3 (MMP-3) was newly induced and activated in stressed DA cells, and the active form of MMP-3 (actMMP-3) was released into the medium. The released actMMP-3, as well as catalytically active recombinant MMP-3 (cMMP-3) led to microglial activation and superoxide generation in microglia and enhanced DA cell death. cMMP-3 caused DA cell death in mesencephalic neuron-glia mixed culture of wild-type (WT) mice, but this was attenuated in the culture of NADPHO subunit null mice (gp91(phox-/-)), suggesting that NADPHO mediated the cMMP-3-induced microglial production of superoxide and DA cell death. Furthermore, in the N-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-injected animal model of PD, nigrostriatal DA neuronal degeneration, microglial activation, and superoxide generation were largely attenuated in MMP-3-/- mice. These results indicate that actMMP-3 released from stressed DA neurons is responsible for microglial activation and generation of NADPHO-derived superoxide and eventually enhances nigrostriatal DA neuronal degeneration. Our results could lead to a novel therapeutic approach to PD.
