Chronic Unpredictable Mild Stress Accelerates Lipopolysaccharide- Induced Microglia Activation and Damage of Dopaminergic Neurons in Rats

Parkinson's disease (PD) is a neurodegenerative disorder, which is characterized by microglia activation and dopaminergic neurons affected by inflammatory processes. Inflammation has been recognized to be necessary for initiation and progress of PD. Emerging evidence indicates that NLRP3 inflammasome complex is involved in the recognition and execution of host inflammatory response. Stress is acknowledged to be a predisposing and precipitating factor in some neurodegenerative diseases. However, it is unknown whether chronic unpredictable mild stress (CUMS) sensitized microglia to pro-inflammatory stimuli. In this study, in vivo experiments are used to evaluate the effects of CUMS on lipopolysaccharide (LPS)-induced microglia activation and NLRP3 inflammasome activation. The results showed that CUMS pretreatment for 14 days significantly aggravated the behavioral dysfunction of PD rats, increased the activation of microglia. Pretreatment with CUMS for 14 days increased the levels of interleukin-1β (IL-1β), interleukin-6 (IL-6), and tumor necrosis factor-a (TNF-a) in the serum, and increased the expression of NLRP-3, ASC, Casepase-1 in the substantia nigra of PD rats. Our data showed that pretreatment with CUMS for 14 days increased the microglia activation and the DA neurons damage, and the mechanisms may be associated with the acceleration of the inflammatory response and activation of NLRP3 inflammasome.