TREM2 Deficiency Aggravates NLRP3 Inflammasome Activation and Pyroptosis in MPTP-Induced Parkinson's Disease Mice and LPS-Induced BV2 Cells.

Microglia-mediated neuroinflammation plays a crucial role in the pathogenesis of Parkinson's disease (PD). Triggering receptor expressed on myeloid cells 2 (TREM2) confers strong neuroprotective effects in PD by regulating the phenotype of microglia. Recent studies suggest that TREM2 regulates high glucose-induced microglial inflammation through the NLRP3 signaling pathway. This study aimed to investigate the effect of TREM2 on NLRP3 inflammasome activation and neuroinflammation in PD. Mice were injected with AAV-TREM2-shRNA into both sides of the substantia nigra using a stereotactic injection method, followed by intraperitoneal injection of MPTP to establish chronic PD mouse model. Behavioral assessments including the pole test and rotarod test were conducted to evaluate the effects of TREM2 deficiency on MPTP-induced motor dysfunction. Immunohistochemistry of TREM2 and tyrosine hydroxylase (TH), immunohistochemistry and immunofluorescence Iba1, Western blot of NLRP3 inflammasome and its downstream inflammatory factors IL-1β and IL-18, and the key pyroptosis factors GSDMD and GSDMD-N were performed to explore the effect of TREM2 on NLRP3 inflammasome and neuroinflammation. In an in vitro experiment, lentivirus was used to interfere with the expression of TREM2 in BV2 microglia, and then lipopolysaccharide (LPS) and adenopterin nucleoside triphosphate (ATP) were used to stimulate inflammation to construct a cellular inflammation model. The expression differences of NLRP3 inflammasome and its components were detected by qPCR and Western blot. In vivo, TREM2 knockdown aggravated the loss of dopaminergic neuron and the decline of motor function. After TREM2 knockdown, the number of activated microglia was significantly increased, and the expression of cleaved caspase-1, NLRP3 inflammasome, IL-1β, GSDMD, and GSDMD-N was increased. In vitro, TREM2 knockdown aggravated the inflammatory response of BV2 cells stimulated by LPS and promoted the activation of NLRP3 inflammasome through the NF-κB pathway. In addition, TREM2 knockdown also promoted the expression of TLR4/MyD88, an upstream factor of the NF-κB pathway. Our vivo and vitro data showed that TREM2 knockdown promoted NLRP3 inflammasome activation and downstream inflammatory response, promoted pyroptosis, and aggravated dopaminergic neuron loss. TREM2 acts as an anti-inflammatory in PD through the TLR4/MyD88/NF-κB pathway, which extends previous findings and supports the notion that TREM2 ameliorates neuroinflammation in PD.

Huang P ，Zhang Z ，Zhang P ，Feng J ，Xie J ，Zheng Y ，Liang X ，Zhu B ，Chen Z ，Feng S ，Wang L ，Lu J ，Liu Y ，Zhang Y ... -  《-》

[Macrophage migration inhibitory factor meditates MPP+/MPTP-induced NLRP3 inflammasome activation in microglia cells].

Huang H ，Gao Y ，Nie K ，Wang L ... -  《-》

Wuzi Yanzong Pill relieves MPTP-induced motor dysfunction and neuron loss by inhibiting NLRP3 inflammasome-mediated neuroinflammation.

Parkinson disease (PD) is an age-related neurodegenerative disease, which is associated with the loss of dopaminergic neurons (DA neurons) in the substantia nigra pars compacta (SNpc), and neuroinflammation may lead to the occurrence of PD. Wuzi Yanzong Pill (WYP) has demonstrated neuroprotective and anti-inflammatory properties, but its molecular mechanism of action is still unclear. In this study, we used 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-induced PD mice and LPS-mediated BV2 microglia to explore WYP intervention, anti-inflammatory effect and molecular mechanism in vivo and in vitro. The results showed that oral administration of WYP in MPTP-induced PD mice for 2 weeks ameliorated abnormal motor dysfunction, attenuated the loss of TH + neurons in SNpc, protected dopaminergic neurons, and inhibited the activation of microglia in MPTP-induced PD mice and LPS-stimulated BV2 cell. Meanwhile, WYP intervention inhibited the expression of IL-6, TNF-α, Pro-IL-1β, IL-1β, Pro-IL-18, IL-18 and enhanced the expression of IL-10 in the SNpc of PD mice. Simultaneously, WYP intervention inhibited the expression of NLRP3 inflammasome, accompanied by the decrease of the TLR4/MyD88/NF-κB pathway. However, the exact target and interaction of WYP on NLRP3 inflammasome and TLR4/MyD88/NF-κB pathway still needs to be further investigated.

Pan T ，Xiao Q ，Fan HJ ，Xu L ，Qin SC ，Yang LX ，Jin XM ，Xiao BG ，Zhang B ，Ma CG ，Chai Z ... -  《-》

Baohuoside I suppresses the NLRP3 inflammasome activation via targeting GPER to fight against Parkinson's disease.

Accumulating evidence indicates the crucial role of microglia-mediated inflammation and the NLR family pyrin domain containing 3 (NLRP3) inflammasome-mediated pyroptosis in the pathogenesis of Parkinson's disease (PD). Baohuoside I, a natural flavonoid extracted from Herba Epimedii, has been shown to possess anti-inflammatory effects, but its potential neuroprotective effects and mechanism against PD have not been documented. The anti-inflammatory effects of Baohuoside I were evaluated by LPS-induced BV2 cells or primary microglia isolated from wide type or G protein-coupled estrogen receptor (GPER) gene knockout mice. The underlying mechanism related to GPER-mediated NLRP3 inflammasome inhibition was further explored using LPS-induced GPER+/+ or GPER-/- mouse models of PD. The neuroprotective effects of Baohuoside I were detected through western blot analysis, real-time PCR, molecular docking, mouse behavioral tests, immunofluorescence, and immunohistochemistry. Baohuoside I significantly alleviated LPS-induced neuroinflammation by inhibiting the activation of NF-κB signal and the increase of pyroptosis levels as evidenced by the downregulated expression of pyroptosis-related proteins (NLRP3, ASC, pro-Caspase-1, IL-1β) in microglia cells. Intragastric administration of Baohuoside I protected against LPS-induced motor dysfunction and loss of dopaminergic neurons, reduced pro-inflammatory cytokines expressions, and inhibited microglial (Iba-1) and astrocyte (GFAP) activation in the nigrostriatal pathway in LPS-induced mouse model of PD. Pretreatment with GPER antagonist G15 in microglia cells or GPER gene deletion in mice significantly blocked the inhibitory effects of Baohuoside I on LPS-induced neuroinflammation and activation of the NLRP3/ASC/Caspase-1 pathway. Molecular docking further indicated that Baohuoside I might bind to GPER directly with a binding energy of -10.4 kcal/mol. Baohuoside I provides neuroprotective effects against PD by inhibiting the activation of the NF-κB signal and NLRP3/ASC/Caspase-1 pathway. The molecular target for its anti-inflammatory effects is proved to be GPER in the PD mouse model. Baohuoside I may be a valuable anti-neuroinflammatory agent and a drug with well-defined target for the treatment of PD.

Gu Y ，Hu ZF ，Zheng DW ，Yang YQ ，Dong XL ，Chen WF ... -  《-》

Echinacoside protects dopaminergic neurons by inhibiting NLRP3/Caspase-1/IL-1β signaling pathway in MPTP-induced Parkinson's disease model.

Persistent microglia-mediated neuroinflammation contributes to the progressive loss of dopaminergic (DA) neurons in Parkinson's disease (PD). Recently, NOD-like receptor protein 3 (NLRP3) inflammasome-mediated neuroinflammation is considered to influence the pathogenesis of PD profoundly. Promoting DA neuron survival and/or inhibiting neuroinflammation may offer neuroprotection for PD. In the present study, we found that echinacoside (ECH), a phenylethanoid glycoside derived from Cistanche Deserticola, ameliorated motor deficit induced by 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) in a mouse PD model, characterized as decreased mobility distance in open field test and average time in rotarod test, as well as increased turn time and total time in pole test. ECH administration promoted the reduction of tyrosine hydroxylase (TH) expression and the number of TH-positive neurons in the substantia nigra (SN) under MPTP injury as the molecular docking simulation predicted that ECH would interact with TH. Moreover, ECH improved cell viability in MPP+-damaged SH-SY5Y cell, a cell line for DA neuron, in vitro. Furthermore, ECH administration alleviated MPTP-triggered microglial activation, thus downregulated the expression and activation of NLRP3 inflammasomes in mice SN, along with the involved proteins including Caspase (CASP)-1 and interleukin-1β (IL-1β). The inhibition of NLRP3/CASP-1/IL-1β neuroinflammatory signaling was further confirmed in murine N9 microglia activated by MPP+ insult after ECH treatment in vitro. Furthermore, MCC950, a selective inhibitor for NLRP3 activation, reduced the enhancive expression of NLRP3/CASP-1/IL-1β in MPP+-insulted N9, and also facilitated the inhibition of inflammation synergistically mediated by ECH treatment. All the collected data revealed that ECH ameliorated PD mice neuroethology through promoting DA neuron survival and inhibiting the activated microglia-mediated NLRP3/CASP-1/IL-1β inflammatory signaling. These findings highlight the crucial roles of NLRP3 inflammasome involved in PD neuropathology and ECH exertes neuroprotection for PD as double-targeting neuroinflammation and DA neuronal survival.

Gao MR ，Wang M ，Jia YY ，Tian DD ，Liu A ，Wang WJ ，Yang L ，Chen JY ，Yang Q ，Liu R ，Wu YM ... -  《-》