Lychee seed polyphenol protects the blood-brain barrier through inhibiting Aβ(25-35)-induced NLRP3 inflammasome activation via the AMPK/mTOR/ULK1-mediated autophagy in bEnd.3 cells and APP/PS1 mice.

Blood-brain barrier (BBB) dysfunction has been implicated in Alzheimer's disease (AD) and is closely linked to the release of proinflammatory cytokines in brain capillary endothelial cells. We have previously reported that lychee seed polyphenols (LSP) exerted anti-neuroinflammatory effect. In this study, we aimed to explore the protective effect of LSP on BBB integrity. The monolayer permeability of bEnd.3 cells, and the mRNA level and protein expression of tight junction proteins (TJs), including Claudin 5, Occludin, and ZO-1, were examined. In addition, the inhibition of Aβ(25-35)-induced NLRP3 inflammasome activation, and the autophagy induced by LSP were investigated by detecting the expression of NLRP3, caspase-1, ASC, LC3, AMPK, mTOR, and ULK1. Furthermore, the cognitive function and the expression of TJs, NLRP3, caspase-1, IL-1β, and p62 were determined in APP/PS1 mice. The results showed that LSP significantly decreased the monolayer permeability and inhibited the NLRP3 inflammasome in Aβ(25-35)-induced bEnd3 cells. In addition, LSP induced autophagy via the AMPK/mTOR/ULK1 pathway in bEnd.3 cells, and improved the spatial learning and memory function, increased the TJs expression, and inhibited the expression of NLRP3, caspase-1, IL-1β, and p62 in APP/PS1 mice. Therefore, LSP protects BBB integrity in AD through inhibiting Aβ(25-35)-induced NLRP3 inflammasome activation via the AMPK/mTOR/ULK1-mediated autophagy.

Xiong R ，Zhou XG ，Tang Y ，Wu JM ，Sun YS ，Teng JF ，Pan R ，Law BY ，Zhao Y ，Qiu WQ ，Wang XL ，Liu S ，Wang YL ，Yu L ，Yu CL ，Mei QB ，Qin DL ，Wu AG ... -  《-》

Lychee seed polyphenol inhibits Aβ-induced activation of NLRP3 inflammasome via the LRP1/AMPK mediated autophagy induction.

Emerging evidence indicates that the enhancement of microglial autophagy inhibits the NLRP3 inflammasome mediated neuroinflammation in Alzheimer's disease (AD). Meanwhile, low density lipoprotein receptor-related protein 1 (LRP1) highly expressed in microglia is able to negatively regulate neuroinflammation and positively regulate autophagy. In addition, we have previously reported that an active lychee seed fraction enriching polyphenol (LSP) exhibits anti-neuroinflammation in Aβ-induced BV-2 cells. However, its molecular mechanism of action is still unclear. In this study, we aim to investigate whether LSP inhibits the NLRP3 inflammasome mediated neuroinflammation and clarify its molecular mechanism in Aβ-induced BV-2 cells and APP/PS1 mice. The results showed that LSP dose- and time-dependently activated autophagy by increasing the expression of Beclin 1 and LC3II in BV-2 cells, which was regulated by the upregulation of LRP1 and its mediated AMPK signaling pathway. In addition, both the Western blotting and fluorescence microscopic results demonstrated that LSP could significantly suppress the activation of NLRP3 inflammasome by inhibiting the expression of NLRP3, ASC, the cleavage of caspase-1, and the release of IL-1β in Aβ(1-42)-induced BV-2 cells. In addition, the siRNA LRP1 successfully abolished the effect of LSP on the activation of AMPK and its mediated autophagy, as well as the inhibition of NLRP3 inflammasome. Furthermore, LSP rescued PC-12 cells which were induced by the conditioned medium from Aβ(1-42)-treated BV-2 cells. Moreover, LSP improved the cognitive function and inhibited the NLRP3 inflammasome in APP/PS1 mice. Taken together, LSP inhibited the NLRP3 inflammasome-mediated neuroinflammation in the in vitro and in vivo models of AD, which was closely associated with the LRP1/AMPK-mediated autophagy. Thus, the findings from this study further provide evidences for LSP serving as a potential drug for the treatment of AD in the future.

Qiu WQ ，Pan R ，Tang Y ，Zhou XG ，Wu JM ，Yu L ，Law BY ，Ai W ，Yu CL ，Qin DL ，Wu AG ... -  《-》

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》

Pien-Tze-Huang, a Chinese patent formula, attenuates NLRP3 inflammasome-related neuroinflammation by enhancing autophagy via the AMPK/mTOR/ULK1 signaling pathway.

NLRP3 inflammasome is a key mediator in ischemic stroke-induced neuroinflammation and subsequent brain injury. Our previous study demonstrated the potent activity of Pien-Tze-Huang (PTH), a well-known Chinese patent formula, in reducing mitochondria-mediated neuronal apoptosis in cerebral ischemia/reperfusion impaired rats. This study aims to elucidate the mechanistic action of PTH related to neuroinflammation in LPS-induced BV2 microglial cells and cerebral ischemia/reperfusion impaired rats. BV2 cells were stimulated with LPS for 12 h and treated with PTH with various concentrations. Modulation by PTH of relevant genes (IL-6, IL-1β, IL-18, TNF-α, COX-2 and iNOS mRNA) and proteins (NLRP3 inflammasome, autophagy and AMPK/mTOR/ULK signaling) was analyzed by real-time PCR and western blot, respectively. Similar analyses were conducted in middle cerebral artery occlusion rat model including neurological deficit, infarct volume, microglial activation, and key genes and proteins in modulating autophagy and NLRP3. Our results showed that PTH significantly inhibited the production of key proinflammatory mediators and protein expressions of NLRP3 and caspase-1 p20 in LPS induced BV2 cells. It also enhanced the autophagy response by modulating the key autophagy proteins via AMPK/mTOR/ULK related pathway. The reduced inflammatory responses and NLRP3 expressions by PTH were partially blocked by the autophagy inhibitor (3-MA) and AMPK blocker (compound C). In rats, PTH significantly reduced infarct size, suppressed microglial activation, and improved neuron deficit. It also promoted autophagy and reduced NLRP3 activity. Our study demonstrated that PTH inhibited NLRP3 inflammasome-mediated neuroinflammation, which was associated with enhanced autophagy via AMPK/mTOR/ULK1 pathway in vitro and in vivo.

Huang Z ，Zhou X ，Zhang X ，Huang L ，Sun Y ，Cheng Z ，Xu W ，Li CG ，Zheng Y ，Huang M ... -  《-》

Dihydromyricetin inhibits microglial activation and neuroinflammation by suppressing NLRP3 inflammasome activation in APP/PS1 transgenic mice.

Activated microglia-mediated inflammation plays a key role in the pathogenesis of Alzheimer's disease (AD). In addition, chronic activation of NLRP3 inflammasomes triggered by amyloid β peptide (Aβ) in microglia contributes to persistent neuroinflammation. Here, the primary goal was to assess whether Dihydromyricetin (DHM), a plant flavonoid compound, is effective therapies for AD; it is crucial to know whether DHM will affect microglial activation and neuroinflammation in APP/PS1 transgenic mice. After DHM was intraperitoneally injected in APP/PS1 double-transgenic mice, we assessed the effect of DHM on microglial activation, the expression of NLRP3 inflammasome components, and the production of inflammatory cytokine IL-1β by immunofluorescence and Western blot. To determine whether DHM play roles in the Aβ production and deposition, amyloid β protein precursor (APP) and β-site APP cleaving enzyme1 (BACE1), as well as neprilysin (NEP), were detected by Western blot. Finally, behavior was tested by Morris Water Maze to illustrate whether DHM treatment has a significantly positive effect on ameliorating the memory and cognition deficits in AD. Dihydromyricetin treatment significantly ameliorated memory and cognition deficits and decreased the number of activated microglia in the hippocampus and cortex of APP/PS1 mice. In addition, APP/PS1 mice show reduced activation of NLRP3 inflammasomes and reduced expression of NLRP3 inflammasome components. Furthermore, DHM could promote clearance of Aβ, a trigger for NLRP3 inflammasome activation, by increasing levels of NEP and shift microglial conversion to the M2-specific agrinase-1-positive cell phenotype, which enhances microglial clearance of Aβ and its aggregates but not production of Aβ. Taken together, our findings suggest that DHM prevents progression of AD-like pathology through inhibition of NLRP3 inflammasome-based microglia-mediated neuroinflammation and may be a promising therapeutic drug for treating AD.

Feng J ，Wang JX ，Du YH ，Liu Y ，Zhang W ，Chen JF ，Liu YJ ，Zheng M ，Wang KJ ，He GQ ... -  《-》