Stress level of glucocorticoid exacerbates neuronal damage and Aβ production through activating NLRP1 inflammasome in primary cultured hippocampal neurons of APP-PS1 mice

Glucocorticoid (GC), secreted by adrenal cortex, plays important roles in regulating many physiological functions, while chronic stress level of GC exposure has many adverse effects on the structure and function of hippocampal neurons, and is closely implicated to the deterioration of Alzheimer's disease (AD). Oxidative stress and neuroinflammation play an important role in the occurrence and development of AD. However, it is still unclear whether chronic GC exposure promotes beta-amyloid (Aβ) accumulation and neuronal injury by increasing oxidative stress and neuroinflammation. In this study, we investigated the effects of chronic GC exposure on NOX2-NLRP1 inflammasome activation and the protective effects of NLRP1-siRNA against GC-induced neuronal injury in primary hippocampal neurons of APP/PS1 mice. The results showed that chronic dexamethasone (DEX, 1 µM) exposure 72 h had no significant effect on the primary hippocampal neurons of WT mice, but significantly increased Aβ_1-42 accumulation (2.17 ± 0.19 fold in APP group and 3.06 ± 0.49 fold in APP + DEX group over WT group) and neuronal injury in primary hippocampal neurons of APP/PS1 mice. Meanwhile, chronic DEX exposure significantly increased the levels of reactive oxygen species (ROS) production and IL-1β, and significantly up-regulated the expressions of NOX2- and NLRP1-related proteins and mRNAs in primary hippocampal neurons of APP/PS1 mice but not in WT mice. Moreover, inhibition of NLRP1 by NLRP1-siRNA treatment also significantly alleviated neuronal injury and Aβ_1-42 accumulation (1.96 ± 0.11 fold in APP + DEX group and 0.25 ± 0.01 fold in APP + NLRP1-siRNA + DEX group over APP group), and down-regulated the expressions of APP, BACE1, NCSTN and p-TAU/TAU in chronic DEX-induced hippocampal neurons of APP/PS1 mice. The results suggest that chronic GC exposure can accelerate neuronal damage and Aβ production by activating oxidative stress and NLRP1 inflammasome in primary hippocampal neurons of APP/PS1 mice, resulting in deterioration of AD.And inhibition of NLRP1 inflammasome may be an important strategy in improving chronic GC-induced neuronal injury.