Dementia with Lewy bodies (DLB) is the second most common type of neurodegenerative dementia after Alzheimer's disease (AD). Neuroinflammation plays an important role in neurodegenerative diseases. It is urgent to unravel the pathogenesis of DLB and find potential therapeutic drugs. Here, we investigated the pharmacological effects of the NLRP3 inflammasome inhibitor MCC950 in A53T α-synuclein transgenic line M83 mice aged 4 months. The behavioral tests including Y-maze, Barnes maze, nest building and Rotarod showed that MCC950 significantly improved the cognitive dysfunction symptom without affecting the motor coordination after consecutive intragastric administration every day for 5 weeks. Furthermore, immunostaining or immunoblotting experiments on the hippocampal tissue were performed, and the results suggested that MCC950 not only inhibited the expression of NLRP3, and suppressed the activation of astrocytes and microglia, but also promoted the mTOR-mediated autophagy pathway to reduce human α-synuclein accumulation. Our findings further demonstrate that line M83 mice may be used as an animal model for DLB research, and can provide preclinical evidences for the development of MCC950 as a promising therapeutic drug. • MCC950 improved dementia symptom in line M83 mice aged 5 months. • MCC950 promoted degradation of human A53T α-synuclein in the hippocampus. • MCC950 activated mTOR-mediated autophagy in the hippocampus. • MCC950 inhibited the activation of astrocytes and microglia in the hippocampus. [ABSTRACT FROM AUTHOR]