Lipopolysaccharide potentiates dopaminergic neuronal dysfunction in α-synuclein transgenic mice

Parkinson's disease (PD) is the most prevalent neurodegenerative disorder, with several risk factors contributing to the onset, such as aging, genetics, oxidative stress and neuroinflammation. There are several PD animals that mimics different risk factor. α-Synuclein mutation mice and systemic lipopolysaccharide (LPS) injection mice are two kinds of most common animal models that replicate genetic mutation and neuroinflammation, respectively. However, in these two animal models, the pathogenesis occurred after a long period of stimulation. In the present study, four-month-old α-synucleintransgenic mice (A53T) were intraperitoneally injected with LPS once a week for continuous 8 weeks to simulate the inflammatory response. The behavioral results showed that the time of mice staying on the rod and the performance score were markedly decreased, indicating motor dysfunction. Dopaminergic neuronal function also decreased. It was noted that the movement dysfunction and pathological changes were aggravated in LPS plus α-synuclein challenged mice compared with LPS or α-synuclein stimulated alone, suggesting that the double attack had synergistic effects. Mechanistic study demonstrated that LPS and α-synuclein combined challenge led to obvious neuroinflammatory response and apoptosis, which might contribute to motor and dopaminergic neuronal dysfunction. In addition, differential proteomic study showed that the expression of CD99L2 and COX7RP significantly increased in the midbrain of LPS plus α-synuclein challenged mice, which were closely related to inflammation and apoptosis, and might be involved in the pathogenesis of PD. In conclusion, the present study demonstrated that LPS could potentiate dopaminergic neuronal function in α-synuclein transgenic mice, which might be an ideal method to develop PD animal model.