MicroRNA-7 Enhances Subventricular Zone Neurogenesis by Inhibiting NLRP3/Caspase-1 Axis in Adult Neural Stem Cells.

α-Synuclein (α-syn) has been recognized to induce neuroinflammation and to disturb nerve repair process in Parkinson's disease. However, the potential mechanisms underlying α-syn-induced impairment of adult neurogenesis remain unclear. In the present study, A53T mutant α--synuclein transgenic (A53T ^tg/tg ) mice, caspase-1 knockout mice, and A53T ^tg/tg ;caspase-1 ^-/- double transgenic mice were used to prepare adult neural stem cells (ANSCs) and to investigate inflammasome-related mechanism for α-syn-impaired neurogenesis in mouse subventricular zone (SVZ). We showed that α-syn inhibited neurogenesis in the SVZ of A53T ^tg/tg mice and impaired proliferation and differentiation in ANSCs cultured in vitro, accompanied by reduced microRNA-7 (miR-7) expression levels. We further found that ANSC expressed NLRP3-containing inflammasome and α-syn activated both TLR4/NF-κB and NLRP3/caspase-1 signals in ANSCs. Either Nlrp3 knockdown or Caspase-1 knockout could attenuate the inhibition of proliferation in ANSCs induced by α-syn. Furthermore, we demonstrated that miR-7 post-transcriptionally controlled Nlrp3 expression besides targeting α-syn. Most notably, stereotactic injection of miR-7 mimics into lateral ventricles significantly inhibited NLRP3 inflammasome activation and improved adult neurogenesis in mouse SVZ. Our study provides a direct link between NLRP3 inflammasome activation and α-syn-impaired neurogenesis in the pathogenesis of α-synucleinopathies.