TLR4 absence reduces neuroinflammation and inflammasome activation in Parkinson's diseases in vivo model.

Parkinson's disease (PD) is a progressive, disabling neurodegenerative disorder. It has been shown Toll like receptor (TLR) 4-deficient mice protect against MPTP toxicity, suggesting that dopaminergic cell death is TLR4-dependent. The aim of this study was to demonstrate, in an in vivo model of PD, how TLR4 plays its important role in the pathogenesis of PD by using MPTP neurotoxin model (4 × 20 mg/kg, 2 h apart, i.p). Our experiments have demonstrated that the absence of TLR4 prevented dopamine depletion, increased tyrosine hydroxylase and dopamine transporter activities and reduced the number of α-synuclein-positive neurons. The absence of TLR4 also had an impact on inflammatory processes, modulating the transcription factors NF-κB p65 and AP-1, and reducing astrogliosis. Importantly, we demonstrated that the absence of TLR4 modulated inflammosome pathway. Moreover, it has been shown that TLR4 modulated motor and non-motor symptoms typical of PD. Our results clearly demonstrated that absence of TLR4 reduces the development of neuroinflammation associated with PD through NF-κB, AP-1 and inflammasome pathways modulation; therefore, TLR4 could be considered as an encouraging therapeutic target in neurodegenerative disorders.