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 Aβ1-42 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 Aβ1-42 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.

Yang L ，Zhou H ，Huang L ，Su Y ，Kong L ，Ji P ，Sun R ，Wang C ，Li W ，Li W ... -  《-》

Chronic glucocorticoid exposure accelerates Aβ generation and neurotoxicity by activating calcium-mediated CN-NFAT1 signaling in hippocampal neurons in APP/PS1 mice.

Glucocorticoid (GC) exposure can lead to deterioration of the structure and function of hippocampal neurons and is closely involved in Alzheimer's disease (AD). Amyloid-β (Aβ) overproduction is an important aspect of AD pathogenesis. Our study mainly investigated the mechanism of chronic GC exposure in accelerating Aβ production in primary cultured hippocampal neurons from APP/PS1 mice. The results indicated that chronic dexamethasone (DEX, 1 μM) significantly accelerated neuronal damage and Aβ accumulation in hippocampal neurons from APP/PS1 mice. Meanwhile, DEX exposure markedly upregulated APP, NCSTN, BACE1 and p-Tau/Tau expression in hippocampal neurons from APP/PS1 mice. Our study also indicated that chronic DEX exposure significantly increased intracellular Ca2+ ([Ca2+]i) levels and the expressions of p-PLC, CN and NFAT1 in hippocampal neurons from APP/PS1 mice. We further found that stabilizing intracellular calcium homeostasis with 2-APB (50 μM) and SKF-96365 (10 μM) significantly alleviated neuronal damage and Aβ accumulation in chronic DEX-induced hippocampal neurons from APP/PS1 mice. Additionally, dual luciferase assays showed that NFAT1 upregulated NCSTN transactivation, which was further increased upon DEX treatment. This study suggests that chronic DEX exposure accelerates Aβ accumulation by activating calcium-mediated CN-NFAT1 signaling in hippocampal neurons from APP/PS1 mice, which may be closely related to the acceleration of AD.

Ding S ，Yang L ，Huang L ，Kong L ，Chen M ，Su Y ，Li X ，Dong X ，Han Y ，Li W ，Li W ... -  《-》

Inhibition of NLRP1 inflammasome improves autophagy dysfunction and Aβ disposition in APP/PS1 mice.

Increasing evidence has shown that the NOD-like receptor protein 1 (NLRP1) inflammasome is associated with Aβ generation and deposition, which contributes to neuronal damage and neuronal-inflammation in Alzheimer's disease (AD). However, the specific mechanism of NLRP1 inflammasome in the pathogenesis of AD is still unclear. It has been reported that autophagy dysfunction can aggravate the pathological symptoms of AD and plays an important role in regulating Aβ generation and clearance. We hypothesized that NLRP1 inflammasome activation may induce autophagy dysfunction contributing to the progression of AD. In the present study, we observed the relationship between Aβ generation and NLRP1 inflammasome activation, as well as AMPK/mTOR mediated-autophagy dysfunction in WT 9-month-old (M) mice, APP/PS1 6 M and APP/PS1 9 M mice. Additionally, we further studied the effect of NLRP1 knockdown on cognitive function, Aβ generation, neuroinflammation and AMPK/mTOR mediated autophagy in APP/PS1 9 M mice. Our results indicated that NLRP1 inflammasome activation and AMPK/mTOR mediated-autophagy dysfunction are closely implicated in Aβ generation and deposition in APP/PS1 9 M mice, but not in APP/PS1 6 M mice. Meanwhile, we found that knockdown of NLRP1 significantly improved learning and memory impairments, decreased the expressions of NLRP1, ASC, caspase-1, p-NF-κB, IL-1β, APP, CTF-β, BACE1 and Aβ1-42, and decreased the level of p-AMPK, Beclin 1 and LC3 II, and increased the level of p-mTOR and P62 in APP/PS1 9 M mice. Our study suggested that inhibition of NLRP1 inflammasome activation improves AMPK/mTOR mediated-autophagy dysfunction, resulting in the decrease of Aβ generation, and NLRP1 and autophagy might be important targets to delay the progression of AD.

Li X ，Zhang H ，Yang L ，Dong X ，Han Y ，Su Y ，Li W ，Li W ... -  《Behavioral and Brain Functions》

Inhibition of NOX2-NLRP1 signaling pathway protects against chronic glucocorticoids exposure-induced hippocampal neuronal damage.

Glucocorticoids (GCs) exposure has deleterious alteration on the structure and function in hippocampal neurons. NADPH oxidase 2 (NOX2) is a major contributor to oxidative stress in neurological diseases, and NLRP1 inflammasome can be activated in response to oxidative stress. We hypothesize that inhibition of NOX2-mediated NLRP1 inflammasome activation may protect against chronic GCs exposure-induced neuronal injury. In this study, the lentivirus with NLRP1-siRNA was injected into the hippocampus of male mice which were then treated with dexamethasone (DEX, 5 mg/kg) for 28 d. The data indicated that NLRP1-siRNA treatment down-regulated the NLRP1 expression and significantly improved the exploratory behavior and spatial memory deficits in open field tests and Morris water maze which were deteriorated by chronic DEX treatment in mice. Additionally, inhibition of NLRP1 expression significantly alleviated neuronal degeneration and increased MAP2 expression in the hippocampus in mice. Meanwhile, the results showed that DEX exposure increased NOX2, p22phox and p47phox expression in hippocampus tissue in mice. We further examined the effect of tempol (ROS scavenger) and apocynin (NOX inhibitor) treatment on NLRP1 inflammasome activation in chronic DEX-treated hippocampal neurons. The results revealed that the tempol (50 μM) and apocynin (50 μM) treatment significantly decreased generation of ROS, expression of NOX2 and NLRP1-related protein in DEX-treated hippocampal neurons. These data indicate that NOX2-mediated NLRP1 activation involves in chronic GCs exposure-induced neuronal injury and inhibition of NOX2-NLRP1 signaling pathway protects against GCs-induced neuronal damage.

Sun L ，Chen Y ，Shen X ，Xu T ，Yin Y ，Zhang H ，Ding S ，Zhao Y ，Zhang Y ，Guan Y ，Li W ... -  《-》

GEPT extract reduces Abeta deposition by regulating the balance between production and degradation of Abeta in APPV717I transgenic mice.

Tian J ，Shi J ，Zhang L ，Yin J ，Hu Q ，Xu Y ，Sheng S ，Wang P ，Ren Y ，Wang R ，Wang Y ... -  《-》