PHLPP1 deficiency alleviates dopaminergic neurodegeneration and represses neuroinflammation in Parkinson's disease.

Background: Pleckstrin homology (PH) domain leucine-rich repeat protein phosphatases (PHLPP) has been associated with several neurodegenerative diseases, however, few studies have investigated the role of PHLPP in Parkinson's disease (PD). The present study aimed to answer this question through establishing a Parkinson's disease (PD) model using the Phlpp1-/- and wild-type (WT) mice and testing their behavioral as well as molecular changes.

Methods: MPTP was intraperitoneal injected into mice to generate a PD model. Neurobehavioral parameters, protein expression and inflammatory cytokines release were measured by the open filed test, the pole test, immunohistochemistry, immunoblotting, immunoprecipitation, and quantitative reverse transcription PCR.

Results: MPTP-induced neurobehavioral deficits were more significantly ameliorated in PHLPP-KO-MPTP mice compared to WT-MPTP mice. The survival rate of TH⁺ neurons in the PHLPP-KO-MPTP group was higher than that in the WT-MPTP group (66% vs. 38%). Additionally, PHLPP1 knockout in KO-MPTP mice markedly reduced levels of IL-1β, IL-6, TNF-α, and iNOS, and increased levels of TGF-β compared to those of WT-MPTP mice. Furthermore, PHLPP1 was found to bind to NLRP3 and that PHLPP1 knockout inhibited MPTP-induced expression of IL-1β and caspase-1 in substantia nigra of PD model mice.

Conclusion: Our results demonstrates that PHLPP1 knockout in PD model is positively associated with the survival of TH + neurons by suppressing inflammatory response in substantia nigra, suggesting that PHLPP1 plays a critical role in the development of PD.