TLR2 deficiency is beneficial at the late phase in MPTP-induced Parkinson' disease mice

Abstract

Aims: Parkinson's disease (PD) is a progressive neurodegenerative disorder. The etiology of PD is still elusive but neuroinflammation is proved to be an important contributor. Toll-like receptor 2 (TLR2) involves in the release of several inflammatory cytokines. Whether TLR2 serves as a mediator contributing to the damage of DA system in PD remain unclear.

Main methods: Tlr2 knockout (Tlr2^-/-) and wild-type (WT) mice were treated with a subacute regimen of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP). At 3, 7 and 14 days after MPTP injection, the behavioral performance, including the Pole test, the Rotarod test, the Rearing test and the Wire hang test was evaluated. Moreover, the PD-like phenotypes, including dopaminergic degeneration, the activation of glial cells and the α-Syn expression were systematically analyzed in the nigrostriatal pathway. Finally, the composition of gut microbiota in the MPTP-treated groups were assessed.

Key findings: TLR2 deficiency had no obvious impact on the dopaminergic injury at 3 and 7 days following MPTP administration. On the contrary, at 14 days post injection, TLR2 deficiency not only significantly attenuated motor deficits in the Pole test and the Rotarod test, and the nigrostriatal dopaminergic degeneration, but also mitigated α-Syn abnormality, astrocyte activation and neuroinflammation through the suppressed TLR2/MyD88/TRAF6/NF-κB signaling pathways. Additionally, the alteration of gut microbiota was also detected in the mutant mice.

Significance: These findings highlight the neuroprotective effect of TLR2-pathways at the late phase in the MPTP-induced PD mouse model.

Keywords: Microbiota-gut-brain axis; Neuroinflammation; Parkinson's disease; TLR2/MyD88/TRAF6/NF-κB signaling pathway; Toll-like receptor 2.