Induction of heme oxygenas-1 attenuates NLRP3 inflammasome activation in lipopolysaccharide-induced mastitis in mice

Mastitis is one of most prevalent production disease in dairy herds worldwide, and is responsible for enormous economic losses. Heme oxygenase-1 (HO-1) is a cytoprotective enzyme, which is involved in the response to oxidative stress and inflammatory response. The purpose of this study was to detect the protective effect of HO-1 on LPS-induced mastitis in mice. BALB/c mice were pretreated with hemin (HO-1 inducer) and zinc protoporphyrin (ZnPP; HO-1 inhibitor) at 2 h before LPS stimulation. The results showed that the mammary gland damage, production of inflammatory cytokines IL-1β, and MPO activity in mammary gland tissues were significantly reduced after pretreated with hemin compared with the group of LPS stimulation only. However, ZnPP reversed the effects of hemin. Furthermore, we found that the levels of ROS and NLRP3 inflammasome were increased after LPS stimulation. The increases were inhibited by hemin and the inhibition of hemin on ROS production and NLRP3 inflammasome activation were blocked by ZnPP. In addition, the results showed that hemin reduced the expression of thioredoxin-interacting protein (TXNIP) induced by LPS, and ZnPP attenuated these changes. In conclusion, the results suggested that overproduction of HO-1 may inhibit the activation of NLRP3 inflammasome and the expression of TXNIP. Induction of HO-1 may be served as a promising method against mastitis induced by LPS.     

热打击通过活化NLRP3炎性小体增加肺毛细血管的通透性

目的 验证热打击通过活化 NLRP3炎性小体增加肺毛细血管通透性的机制。方法 C57BL/6小鼠和肺微血管内皮细胞,用 42 ℃热打击。体内实验分组包括：对照组和热打击组,每组 12只小鼠;体外实验分组包括：对照组、热打击组、热打击+2,2,6,6-四甲基哌啶氧化物（TEMPO）组、热打击+半胱氨酸的天冬氨酸蛋白水解酶（caspase）抑制剂（Z-VAD-FMK）组、热打击+白细胞介素-1受体拮抗剂（IL-1Ra）组,每组 4例。检测肺组织和肺微血管内皮细胞活性氧（ROS）表达;Western blot 和（或）免疫荧光检测 caspase-1、白细胞介素-1β（IL-1β）、紧密连接蛋白 ZO-1、occludin、claudin-5的表达;用伊文氏蓝检测小鼠肺毛细血管的通透性。结果 体内实验结果显示,与对照组比较,热打击组小鼠肺组织伊文氏蓝浓度明显升高、ROS表达上调、NLRP3炎性小体活化、IL-1β表达上调和紧密连接蛋白的表达下调（P＜0.01）。体外实验结果显示,用 TEMPO 清除 ROS 后,NLRP3炎性小体活化被抑制（P＜0.01）;用 ZVAD-FMK抑制 caspase-1作用后,IL-1β表达显著下调（P＜0.01）;用 IL-1Ra阻断 IL-1β作用后,紧密连接蛋白表达显著上调（P＜0.01）。结论 热打击可通过活化 NLRP3炎性小体促进 IL-1β的表达,进而下调紧密连接蛋白的表达,导致肺微血管通透性增加。     

Biochanin A protects lipopolysaccharide/D-galactosamine-induced acute liver injury in mice by activating the Nrf2 pathway and inhibiting NLRP3 inflammasome activation

Biochanin A, an isoflavone existed in red clover and peanuts, has been reported to possess a wide spectrum of pharmacological activities, such as anti-inflammatory and antioxidant effects. However, the protective effects and mechanism of biochanin A on liver injury have not been reported. In this study, acute liver injury was induced by intraperitoneal injection of lipopolysaccharide (LPS) and d-galactosamine (D-GalN). Biochanin A was administrated 1 h prior to LPS/D-GalN challenge. Serum ALT, AST, IL-1β, and TNF-α levels, hepatic malondialdehyde (MDA), GPx, SOD, and Catalase contents, tissue histology, IL-1β, TNF-α, NLRP3, and Nrf2 expression were detected. The results showed that serum ALT, AST, IL-1β, and TNF-α levels and hepatic MDA content increased after LPS/GalN treatment. These changes were attenuated by biochanin A. Meanwhile, biochanin A dose-dependently up-regulated the expression of Nrf2 and HO-1. Biochanin A also inhibited hepatic IL-1β and TNF-α expression in a dose-dependent manner. Biochanin A did not inhibit LPS/D-GalN-induced hepatic NLRP3, ASC, and caspase-1 expression. However, the interaction of NLRP3 with ASC and caspase-1 were inhibited by biochanin A. In addition, LPS/D-GalN-induced up-regulation of thioredoxin-interacting protein (TXNIP) and interaction between TXNIP and NLRP3 were also inhibited by biochanin A. In conclusion, biochanin A protected against LPS/GalN-induced liver injury by activating the Nrf2 pathway and inhibiting NLRP3 inflammasome activation.     

NecroX-5 alleviate lipopolysaccharide-induced acute respiratory distress syndrome by inhibiting TXNIP/NLRP3 and NF-κB

The activation of NLRP3 inflammasome and NF-κB pathway, associating with oxidative stress, have been implicated in the development of acute lung injury (ALI) and acute respiratory distress syndrome (ARDS). NecroX-5 has been reported to exhibit the effects of anti-oxidation and anti-stress in various diseases. However, the role of NecroX-5 in ALI has not been explicitly demonstrated. The aim of this study was to explore the therapeutic effects and potential mechanism action of NecroX-5 on ALI. Here, we found that NecroX-5 pretreatment dramatically diminished the levels of IL-1β, IL-18 and ROS in in RAW264.7 cells challenged with LPS and ATP. Furthermore, NecroX-5 suppressed the activation of NLRP3 inflammasome and NF-κB signal pathway. In addition, NecroX-5 also inhibited the thioredoxin-interacting protein (TXNIP) expression. In vivo, NecroX-5 reduced the LPS-induced lung histopathological injury, the number of TUNEL-positive cells, lung wet/dry (W/D) ratio, levels of total protein and inflammatory cytokines in the bronchoalveolar lavage fluid (BALF) in mice. Additionally, LPS-induced upregulation of myeloperoxidase (MPO), ROS production and malondialdehyde (MDA) were inhibited by NecroX-5 administration. Thus, our results demonstrate that NecroX-5 protects against LPS-induced ALI by inhibiting TXNIP/NLRP3 and NF-κB.     

Inhibition of GSK-3β alleviates cerebral ischemia/reperfusion injury in rats by suppressing NLRP3 inflammasome activation through autophagy

The nod-like receptor protein 3 (NLRP3) inflammasome has a critical role in cerebral ischemic injury, and autophagy is related to activation of the inflammasome under oxidative stress conditions. However, it is unclear how NLRP3 inflammasome activation is regulated. Glycogen synthase kinase 3β (GSK-3β) emerged as an important risk factor for brain ischemia reperfusion injury, and GSK-3β inhibits autophagic activity in many diseases. In this study, we examined whether NLRP3 inflammasome-derived inflammation could be ameliorated by GSK-3β inhibition in a cerebral ischemia reperfusion injury model and assessed whether autophagy is involved in this process. To establish ischemic reperfusion injury, we used a middle cerebral artery occlusion-reperfusion (MCAO/R) model in rats. A chemical inhibitor (SB216763) and GSK-3β siRNA were used to suppress GSK-3β activation and GSK-3β expression in vivo. The results demonstrated that SB216763 and GSK-3β siRNA improved neurological scores, reduced cerebral infarct volume, and decreased the levels of NLRP3 inflammasome, cleaved-caspase-1, IL-1β, and IL-18. Inhibiting GSK-3β activation enhanced autophagic activity (ratio of LC3B-II/LC3B-I and p62/SQSTM1), whereas treating with an autophagy inhibitor (3-MA) abrogated the inhibitory effect on NLRP3 inflammasome activation after GSK-3β inhibition. These results suggest that inhibiting GSK-3β downregulates NLRP3 inflammasome expression by increasing autophagic activity in cerebral ischemia reperfusion injury. GSK-3β might be an attractive specific target and that it functions by regulating the NLRP3 inflammasome.     

Pinellia pedatisecta lectin exerts a proinflammatory activity correlated with ROS-MAPKs/NF-κB pathways and the NLRP3 inflammasome in RAW264.7 cells accompanied by cell pyroptosis

Pinellia pedatisecta, a widely used herb in Chinese medicine, has proinflammatory toxicity related to its Pinellia pedatisecta lectin (PPL), but the mechanism is still unknown. However, for safer use, it is necessary to clarify its proinflammatory mechanism. Herein, we studied the mechanism in RAW264.7 cells. PPL decreased the mitochondrial membrane potential (MMP) and increased the outflow of calcium, accompanied by the overproduction of reactive oxygen species (ROS), which resulted in the activation of the MAPK and NF-κB pathways and the release of IL-1β. The maturation of IL-1β relied on caspase-1 p20, the active caspase-1, as demonstrated by adding caspase-1 inhibitor. While caspase-1 was associated with the activation of the NLRP3 inflammasome, we further found that the stimulation of PPL also contributed to the activation. In addition, TXNIP was downregulated, whereas NLRP3/caspase-1 p20/ASC was upregulated, and there was binding of TXNIP with NLRP3. There was also binding of NLRP3 with ASC and caspase-1. Further, we found that N-acetylcysteine (NAC), an ROS scavenger, could inhibit the PPL-stimulated activation of these pathways and the release of IL-1β. Moreover, PPL led to cell pyroptosis with pyknotic nuclei and plasma membrane rupture, which could be inhibited by NAC. All of these findings demonstrated an important role of ROS in the inflammation caused by PPL. Taken together, our data provide new mechanistic insights into the possible endogenous signaling pathways involved in the inflammation of RAW264.7 cells, stimulated by PPL.     

Quercetin and allopurinol reduce liver thioredoxin-interacting protein to alleviate inflammation and lipid accumulation in diabetic rats

Background and Purpose

Thioredoxin-interacting protein (TXNIP), a regulator of cellular oxidative stress, has been associated with activation of NOD-like receptor 3 (NLRP3) inflammasome, inflammation and lipid metabolism, suggesting it has a role in the pathogenesis of non-alcoholic fatty liver disease (NAFLD) in diabetes. In this study we investigated whether TXNIP is involved in type 1 diabetes-associated NAFLD and whether antioxidants, quercetin and allopurinol, alleviate NAFLD by targeting TXNIP.

Experimental Approach

Diabetes was induced in male Sprague-Dawley rats by a single i.p. injection of 55 mg·kg⁻¹ streptozotocin. Quercetin and allopurinol were given p.o. to diabetic rats for 7 weeks. Hepatic function, oxidative stress, inflammation and lipid levels were determined. Rat BRL-3A and human HepG2 cells were exposed to high glucose (30 mM) in the presence and absence of antioxidants, TXNIP siRNA transfection or caspase-1 inhibitor, Ac-YVAD-CMK.

Key Results

Quercetin and allopurinol significantly inhibited the TXNIP overexpression, activation of NLRP3 inflammasome, down-regulation of PPARα and up-regulation of sterol regulatory element binding protein-1c (SREBP-1c), SREBP-2, fatty acid synthase and liver X receptor α, as well as elevation of ROS and IL-1β in diabetic rat liver. These effects were confirmed in hepatocytes in vitro and it was further shown that TXNIP down-regulation contributed to the suppression of NLRP3 inflammasome activation, inflammation and changes in PPARα and SREBPs.

Conclusions and Implications

Inhibition of hepatic TXNIP by quercetin and allopurinol contributes to the reduction in liver inflammation and lipid accumulation under hyperglycaemic conditions. The targeting of hepatic TXNIP by quercetin and allopurinol may have therapeutic implications for prevention of type 1 diabetes-associated NAFLD.     

白藜芦醇抑制大肠埃希菌O104∶H4诱导的结肠上皮细胞NLRP3炎症小体活化

目的:研究白藜芦醇(RES)对大肠埃希菌O104∶H4感染的结肠上皮Caco-2细胞线粒体和氧化应激损伤及NLRP3炎症小体活化的影响。方法:RES(200μmol/L)预处理Caco-2细胞12 h,然后107 CFU/mL的大肠埃希菌O104∶H4(MOI 10∶1)感染细胞4 h。CCK-8法检测细胞活力,qRT-PCR法分析过氧化物酶体增殖物激活受体γ共激活因子1α(PGC1α)、细胞色素氧化酶4(COX-4)、核呼吸因子1(NRF1)、线粒体转录因子1(TFAM)、超氧化物歧化酶1(SOD1)和血红素加氧酶1(HO-1)mRNA表达水平,Western blot检测炎症小体NLRP3、半胱氨酸天冬氨酸蛋白水解酶-1活化亚基p20(CASP1 p20)、半胱氨酸天冬氨酸蛋白水解酶-1活化亚基p10(CASP1 p10)、pro-IL-1β和IL-1β蛋白表达水平,并对Caco-2细胞线粒体膜电位、氧耗量和活性氧(ROS)水平进行检测。结果:大肠埃希菌O104∶H4感染可明显诱导NLRP3、CASP1 p20、CASP1 p10、IL-1β蛋白和PGC1α、COX-4和NRF1 mRNA表达,促使氧消耗量和ROS水平增高,而细胞活力、TFAM mRNA表达和线粒体膜电位降低(P<0.05);RES处理后能明显抑制NLRP3、CASP1 p20、CASP1 p10、IL-1β蛋白和PGC1α、COX-4和NRF1 mRNA表达,降低氧消耗量和ROS水平,而细胞活力、TFAM mRNA表达和线粒体膜电位增高(P<0.05);另外,ROS抑制剂N-乙酰半胱氨酸(NAC)也能显著抑制NLRP3炎症小体和IL-1β表达水平。结论:大肠埃希菌O104∶H4感染诱导Caco-2细胞线粒体释放ROS和NLRP3炎症小体活化,而RES可部分改善Caco-2细胞损伤,降低NLRP3炎症小体和ROS水平。     

益母草碱抑制NLRP3炎症小体过度激活调控巨噬细胞M1/M2表型分化

目的 研究益母草碱对脂多糖(LPS)诱导小鼠腹腔巨噬细胞免疫应答影响及相关机制.方法 分离小鼠腹腔巨噬细胞,用脂多糖和益母草碱预处理24 h,MMT法检测巨噬细胞活性;Griess法检测NO释放量;ELISA法检测IL-1β、IL-18、IL-6、TNF-α的释放量;RT-PCR法检测NLRP3、ASC、caspase...     

HIV-1 Viral Protein R Activates NLRP3 Inflammasome in Microglia: implications for HIV-1 Associated Neuroinflammation

Human Immunodeficiency virus (HIV) enters the brain soon after seroconversion and induces chronic neuroinflammation by infecting and activating brain macrophages. Inflammasomes are cytosolic protein complexes that mediate caspase-1 activation and ensuing cleavage and release of IL-1β and ?18 by macrophages. Our group recently showed that HIV-1 infection of human microglia induced inflammasome activation in NLRP3-dependent manner. The HIV-1 viral protein R (Vpr) is an accessory protein that is released from HIV-infected cells, although its effects on neuroinflammation are undefined. Infection of human microglia with Vpr-deficient HIV-1 resulted in reduced caspase-1 activation and IL-1β production, compared to cells infected with a Vpr-encoding HIV-1 virus. Vpr was detected at low nanomolar concentrations in cerebrospinal fluid from HIV-infected patients and in supernatants from HIV-infected primary human microglia. Exposure of human macrophages to Vpr caused caspase-1 cleavage and IL-1β release with reduced cell viability, which was dependent on NLRP3 expression. Increased NLRP3, caspase-1, and IL-1β expression was evident in HIV-1 Vpr transgenic mice compared to wild-type littermates, following systemic immune stimulation. Treatment with the caspase-1 inhibitor, VX-765, suppressed NLRP3 expression with reduced IL-1β expression and associated neuroinflammation. Neurobehavioral deficits showed improvement in Vpr transgenic animals treated with VX-765. Thus, Vpr-induced NLRP3 inflammasome activation, which contributed to neuroinflammation and was abrogated by caspase-1 inhibition. This study provides a new therapeutic perspective for HIV-associated neuropsychiatric disease.     

Nicotinic acid inhibits NLRP3 inflammasome activation via SIRT1 in vascular endothelial cells

Emerging evidences indicated that NLRP3 inflammasome initiates inflammatory response involved in cardiovascular disease. Nicotinic acid (NA) has been known to possess potential anti-inflammatory property. The aim of this study was to investigate the effect of NA on the activation of NLRP3 inflammasome and the underlying mechanisms. It was found that lipopolysaccharide (LPS) and adenosine triphosphate (ATP) triggered the activation of NLRP3 inflammasome in human umbilical vein endothelial cells (HUVECs). NA inhibited NLRP3 inflammasome activation and subsequent caspase-1 cleavage as well as interleukin (IL)-1β secretion. Moreover, NA administration up-regulated SIRT1 expression in HUVECs stimulated with LPS plus ATP. Importantly, knockdown of SIRT1 reversed the inhibitory effect of NA on the activation of NLRP3 inflammasome. Further study revealed that NA also decreased the generation of reactive oxygen species (ROS) in HUVECs. In addition, NA inhibited NLRP3 inflammasome activation partly through suppression of ROS. Taken together, these findings indicate that NA is able to regulate the activation of NLRP3 inflammasome in HUVECs, which may be partly mediated by SIRT1 and ROS.     

NLRP3 inflammasome and glia maturation factor coordinately regulate neuroinflammation and neuronal loss in MPTP mouse model of Parkinson’s disease

Neuroinflammation plays an active role in the pathogenesis of several neurodegenerative diseases, including Parkinson’s disease (PD). Earlier studies from this laboratory showed that glia maturation factor (GMF), a proinflammatory mediator; is up-regulated in the brain in neurodegenerative diseases and that deficiency of GMF showed decreased production of IL-1β and improved behavioral abnormalities in mouse model of PD. However, the mechanisms linking GMF and dopaminergic neuronal death have not been completely explored. In the present study, we have investigated the expression of NLRP3 inflammasome and caspase-1 in the substantia nigra (SN) of human PD and non-PD brains by immunohistochemistry. Wild-type (WT) and GMF^−/− (GMF knock-out) mice were treated with 1-methyl-4-phenyl-1,2,3,6-tetrahydro pyridine (MPTP) and the brains were isolated for neurochemical and morphological examinations. NLRP3 and caspase-1 positive cells were found significantly increased in PD when compared to non-PD control brains. Moreover, GMF co-localized with α-Synuclein within reactive astrocytes in the midbrain of PD. Mice treated with MPTP exhibit glial activation-induced inflammation, and nigrostriatal dopaminergic neurodegeneration. Interestingly, increased expression of the inflammasome components in astrocytes and microglia observed in the SN of MPTP-treated WT mice were significantly reduced in GMF^−/− mice. Additionally, we show that NLRP3 activation in microglia leads to translocation of GMF and NLRP3 to the mitochondria. We conclude that downregulation of GMF may have beneficial effects in prevention of PD by modulating the cytotoxic functions of microglia and astrocytes through reduced activation of the NLRP3 inflammasome; a major contributor of neuroinflammation in the CNS.     

Piezo1 activates the NLRP3 inflammasome in nucleus pulposus cell-mediated by Ca2+/NF-κB pathway

Studying and understanding the mechanism of inflammation in nucleus pulposus is the key to understand and prevent intervertebral disc degeneration. We propose a model of mechanical sensitive ion channel Piezo1 mediated inflammation of nucleus pulposus cells. Piezo1 can up-regulate the level of interleukin-1β (IL-1β) in nucleus pulposus cells once it is activated. It is suggested that Piezo1 may mediate inflammation by activating Nod-like receptor protein 3 (NLRP3) inflammasome to accelerate the production and maturation of IL-1β. The primary objective of this study was to explore whether Piezo1 activates NLRP3 inflammasome in nucleus pulposus cells. Piezo1 sensitization was induced by mechanical stretch following which we analyzed the priming and assembly of NLRP3 inflammasome and also studied if the downstream Ca²⁺/NF-κB pathway mediated this activation in nucleus pulposus cells. The expression of Piezo1 and NLRP3 inflammasome increased in a time-dependent manner upon mechanical stretch. Piezo1 activation promoted NLRP3 inflammasome assembly, which was demonstrated by the upregulation of caspase-1 activation and IL-1β production. Transfection of Piezo1-siRNA reversed this process. The inhibition of Ca²⁺/NF-κB pathway reduced Piezo1-dependent activation of NLRP3 inflammasome. Thus, we propose that activation of NLRP3 inflammasome in nucleus pulposus cells mediated by Piezo1 through the Ca²⁺/NF-κB pathway is a novel pathogenesis for the progress of intervertebral disc degeneration. As per our knowledge this is the first study which has provided evidence linking Piezo1-mediated inflammation in nucleus pulposus cells with the production of NLRP3 inflammasome.     

MicroRNA-152 attenuates neuroinflammation in intracerebral hemorrhage by inhibiting thioredoxin interacting protein (TXNIP)-mediated NLRP3 inflammasome activation

Neuroinflammation significantly contributes to brain injury and neurological deterioration following intracerebral hemorrhage (ICH). MicroRNA-152(miR-152) was reported to be downregulated in ICH patients and to possess anti-inflammatory properties in other diseases. In this study, we aimed to explore the role of miR-152 in ICH, and the underlying mechanisms, using a collagenase-induced rat ICH model and hemin-exposure as a cell model. We first confirmed that miR-152 was consistently downregulated in both models. Overexpression of miR-152 in microglial BV2 cells reduced hemin-induced inflammatory response and reactive oxygen species (ROS) generation, thus protecting co-cultured neuronal HT22 cells. Moreover, overexpression of miR-152 by intracerebroventricular lentivirus injection in ICH rats significantly alleviated neurodecifits, brain edema, and hematoma. These changes were associated with a marked reduction in ICH-induced neuronal death, as detected by co-staining of NeuN and TUNEL, and ICH-induced neuroinflammation, as revealed by inflammatory cytokine levels as well as by the number of Iba1 positive-stained cells in the perihematomal region. Mechanistically, miR-152 significantly inhibited ICH-induced TXNIP expression, and its overexpression blocked the interaction between TXNIP and NOD-like receptor pyrin domain containing 3(NLRP3), thus inhibiting NLRP3-driven inflammasome activation to attenuate neuroinflammation in vivo and in vitro. Moreover, the results of si-TXNIP transfection further confirmed that TXNIP inhibition was involved in the reduction of NLRP3 inflammasome activation by the overexpression of miR-152. Collectively, the present study demonstrates that miR-152 confers protection against ICH-induced neuroinflammation and brain injury by inhibiting TXNIP-mediated NLRP3 inflammasome activation, indicating a potential strategy for ICH treatment.     

TRPM2 dependence of ROS-induced NLRP3 activation in Alzheimer's disease

Recent studies have shown that neuroinflammation plays an important role in Alzheimer's disease (AD). Microglial cells are responsible for the phagocytosis of Amyloid-β (Aβ). However, it has been demonstrated that in AD patients the efficiency of phagocytosis decreases due to proinflammatory cytokines, such as Interleukin-1β (IL-1β), which is produced through the activation of NLRP3 inflammasome. In this study, we aimed at deciphering the mechanism underlying the NLRP3 activation. The results showed that Aβ induces an increase in the level of reactive oxygen species (ROS). According to this study, ROS produced from both mitochondria and NADPH oxidase was responsible for NLRP3 activation. In addition, it was observed that this high level of ROS activated the transient receptor potential melastatin 2 (TRPM2) channel, which causes an increase in the level of intracellular calcium. The results demonstrated that in the absence of intracellular calcium, caspase-1 cannot be activated and therefore the level of IL-1β decreases. Altogether, our findings supported the role of TRPM2 channel in ROS-induced NLRP3 activation in microglial cells through the exposure to Aβ.     

Panax notoginseng saponin Rl attenuates allergic rhinitis through AMPK/DRP1 mediated mitochondrial fission北大核心CSCD

目的探讨三七皂苷(notoginsenoside R1,PNS-R1)是否通过AMP激活蛋白激酶(AMP-activated protein kinase,AMPK)/线粒体裂变关键蛋白(dynamin-related protein 1,DRP1)介导的线粒体裂变减轻过敏性鼻炎(allergic rhinitis,AR)。方法利用不同剂量PNS-R1治疗卵清蛋白(Ovalbumin,OVA)诱导的AR小鼠,通过观察擦鼻、打喷嚏的过敏症状和鼻组织的HE染色探索PNS-R1在AR中的抑制作用。通过酶联免疫吸附法(ELISA)检测血清IgE水平和鼻灌洗液(nasal lavage fluid,NLF)炎性细胞因子水平,Western blot检测凋亡相关蛋白。在体外,利用IL-13刺激人鼻黏膜上皮细胞(human nasal epithelial cells,HNEpC),观察细胞凋亡、线粒体膜电位、细胞活性氧(reactive oxygen species,ROS)和线粒体ROS(mtROS)生成、AMPK/DRP1,TXNIP/NLRP3炎症小体的表达水平以及DRP1易位情况。结果PNS-R1减轻了AR小鼠的过敏症状,HE染色炎性细胞减少,降低血清OVA特异性IgE水平以及NLF中IL-4、IL-6和IL-8的水平。在体外,PNS-R1上调IL-13刺激后的线粒体膜电位,降低ROS和mtROS生成、减少cleaved-caspase-3、Bax和上调Bcl-2表达,以AMPK依赖性方式下调DRP1磷酸化(Ser 616)和DRP1在线粒体膜上的易位,减少TXNIP/NLRP3表达。结论PNS-R1通过抑制AMPK/DRP1信号轴及随后的TXNIP/NLRP3信号轴保护线粒体的完整性,缓解AR。     

The Ketone Body β-Hydroxybutyrate Does Not Inhibit Synuclein Mediated Inflammasome Activation in Microglia

Parkinson's disease (PD) is recognized as the most common neurodegenerative movement disorder and results in debilitating motor deficits. The accumulation and spread of neurotoxic synuclein aggregates in the form of Lewy bodies is a key pathological feature of PD. Chronic activation of the NLRP3 inflammasome by protein aggregates is emerging as a major pathogenic mechanism in progressive neurodegenerative disorders and is considered an important therapeutic target. Recently the ketone body, β-hydroxy butyrate (BHB), was shown to efficiently inhibit the NLRP3 inflammasome in macrophages, and in vivo models of inflammatory disease. Furthermore, BHB can readily cross the blood brain barrier suggesting that it could have therapeutic benefits for the management of PD. In this study, we evaluated if BHB could inhibit chronic microglial inflammasome activation induced by pathological fibrillar synuclein aggregates. Interestingly, we found that BHB treatment almost completely blocked all aspects of inflammasome activation and pyroptosis induced by ATP and monosodium urate (MSU) crystals, consistent with previously published reports in macrophages. Surprisingly however, BHB did not inhibit inflammasome activation and release of IL-1β or caspase-1 induced by synuclein fibrils. Our results demonstrate that BHB does not block the upstream pathways regulating inflammasome activation by synuclein fibrils and suggest that synuclein mediated inflammasome activation proceeds via distinct mechanisms compared to traditional NLRP3 activators such as ATP and MSU.     

Mitochondrial dysfunction and neuroinflammation in Parkinson disease

Parkinson disease(PD) is an age-related neurodegenerative disease. Wide spread α-synuclein aggregation and progressive loss of dopaminergic(DA) neurons in the substantia nigra are major neuropathological hallmarks of PD. The molecular mechanisms are not well understood. In recent years, mitochondrial dysfunctionis considered to play a central role in pathogenesis and progression of PD. The parkinsonian toxins(MPTP/MPP+and rotenone)have been reported to inhibit mitochondrial complex I and lead to disturbed oxidative phosphorylation and mitochondrial dynamics, increased reactive oxygen species(ROS) production and reduced mitochondrial membrane potential, thus causing DA neuron degeneration. Mitochondrial dysfunction was also shown to elicit the aggregation of α-synuclein, which in turn interfered with mitochondrial function in a vicious cycle. In sensitive neurons, all these intracellular changes may be devastating for cell survival. On the other hand, inflammasome activation is identified as pivotal inflammatory mechanism that drives progressive DA neuropathology. Inflammasome is intracellular multiprotein complex that can be activated to trigger caspase-1 cleavage in response to neurotoxic insults. Cleaved caspase-1 further promotes the maturation of the proinflammatory cytokines, and thereby results in neuroinflammation and neuronal death. Patients with PD and preclinical PD models showed extensive activation of microglial NLRP3 inflammasome. Targeting NLRP3 inflammasome has been regarded as a potential therapeutic strategy in PD. Moreover, α-synuclein is strongly linked to inflammasome activation. NLRP3 inflammasome activation by pathological α-synuclein fibrils in mouse microglia resulted in a delayed but substantial release of cleaved IL-1β, but not IL-18. NLRP3 inhibitor abolished fibrillar α-synuclein-induced NLRP3 inflammasome activation in vitro. Inhibition of inflammasome by NLRP3 inhibitor significantly ameliorated nigrostriatalα-synuclein pathology, DA neoron degeneration and motor deficits in multiple rodent PD models. These findings suggest a bi-directional relationship between microglial inflammation and neuronal α-synuclein pathology. Roles of caspase-1 and inflammasome in α-synuclein aggregation and cell death were also reported in neuronal M17-a Syn cells. Furthermore, accumulating experimental evidence supports a complex association between mitochondria and neuroinflammation in PD. In complex I inhibitory pesticides-related PD, mitochondrial dysfunction and oxidative stress induced neuroinflammation via microglial NLRP3-dependent pathways. Mitochondria-targeted antioxidant ameliorated both mitochondrial oxidative stress and NLRP3 inflammasome activation, suggesting probable upstream role of mitochondria in inflammasome activation. This result is confirmed by two in vivo studies indicating mitochondrion-driven activation of NLRP3 inflammasome and neurotoxicity in rotenone and Mito Park mouse models of PD. Conversely, inflammatory mediators produced by activated microglia can strongly affect mitochondrial oxidative phosphorylation and ROS production, eventually leading to neurodegeneration. Additionally,functional mitophagy was shown to be vital for mitochondrial quality control. When mitophagy was impaired due to some reasons such as mutation in PD-associated genes PINK1 and parkin, accumulation of dysfunctional or damaged mitochondriamay be responsible for neuroinflammation and neurodegeneration. Collectively, the available data highlight the roles of mitochondria dysfunction and neuroinflammation in neurodegeneration of PD.Identifying crosstalk and interaction among mitochondria impairment, neuroinflammation and neurodegeneration may provide insights into the pathogenesis and eventually develop novel therapeutic approaches against PD.