The PI3K/Akt pathway is required for LPS activation of microglial cells

Upregulation of inflammatory responses in the brain is associated with a number of neurodegenerative diseases. Microglia are activated in neurodegenerative diseases, producing pro-inflammatory mediators. Critically, lipopolysaccharide (LPS)-induced microglial activation causes dopaminergic neurodegeneration in vitro and in vivo. The signaling mechanisms triggered by LPS to stimulate the release of pro-inflammatory mediators in microglial cells are still incompletely understood. To further explore the mechanisms of LPS-mediated inflammatory response of microglial cells, we studied the role of phosphatidylinositol 3-kinase (PI3K)/Akt signal transduction pathways known to be activated by toll-like receptor-4 signaling through LPS. In the current study, we report that the activation profile of LPS-induced pAkt activation preceded those of LPS-induced NF-κB activation, suggesting a role for PI3K/Akt in the pathway activation of NF-κB-dependent inflammatory responses of activated microglia. These results, providing the first evidence that PI3K dependent signaling is involved in the inflammatory responses of microglial cells following LPS stimulation, may be useful in preventing inflammatory based neurodegenerative processes.     

Activation of adenosine A3 receptor suppresses lipopolysaccharide-induced TNF-α production through inhibition of PI 3-kinase/Akt and NF-κB activation in murine BV2 microglial cells

Adenosine is an endogenous nucleoside that regulates many processes, including inflammatory responses, through activation of its receptors. Adenosine receptors have been reported to be expressed in microglia, which are major immune cells of brain, yet little is known about the role of adenosine receptors in microglial cytokine production. Thus, we investigated the effect of adenosine and adenosine A₃ receptor ligands on LPS-induced tumor necrosis factor (TNF-α) production and its molecular mechanism in mouse BV2 microglial cells. Adenosine and Cl-IB-MECA, a specific adenosine A₃ receptor agonist, suppressed LPS-induced TNF-α protein and mRNA levels. Moreover, MRS1523, a selective A₃ receptor antagonist, blocked suppressive effects of both adenosine and Cl-IB-MECA on TNF-α. We further examined the effect of adenosine on signaling molecules, such as PI 3-kinase, Akt, p38, ERK1/2, and NF-κB, which are involved in the regulation of inflammatory responses. Adenosine inhibited LPS-induced phosphatidylinositol (PI) 3-kinase activation and Akt phosphorylation, whereas it had no effect on the phosphorylation of p38 and ERK1/2. We also found that adenosine as well as Cl-IB-MECA inhibited LPS-induced NF-κB DNA binding and luciferase reporter activity. Taken together, these results suggest that adenosine A₃ receptor activation suppresses TNF-α production by inhibiting PI 3-kinase/Akt and NF-κB activation in LPS-treated BV2 microglial cells.     

Plantamajoside Inhibits Lipopolysaccharide-Induced MUC5AC Expression and Inflammation through Suppressing the PI3K/Akt and NF-κB Signaling Pathways in Human Airway Epithelial Cells

It has been reported that plantamajoside (PMS), a major natural compound isolated from Plantago asiatica, has anti-inflammatory activities. However, the effect of PMS on respiratory inflammatory diseases has not yet been studied. The present study aimed to evaluate the effect of PMS on lipopolysaccharide (LPS)-induced airway inflammation and the underlying mechanism. The results showed that PMS did not affect the cell viability of 16-HBE cells. PMS (20 and 40 μg/ml) decreased the expression levels of MUC5AC, IL-6, and IL-1β, which were induced by LPS treatment. PMS inhibited the LPS-induced phosphorylation of Akt and p65. In addition, inhibitors of the PI3K/Akt and NF-κB pathways attenuated the effect of LPS on 16-HBE cells. In conclusion, PMS inhibits LPS-induced MUC5AC expression and inflammation through suppressing the PI3K/Akt and NF-κB signaling pathways, indicating that PMS may be a potential therapy for the treatment of respiratory inflammatory diseases.     

Phlorofucofuroeckol A Suppresses Expression of Inducible Nitric Oxide Synthase, Cyclooxygenase-2, and Pro-inflammatory Cytokines via Inhibition of Nuclear Factor-κB, c-Jun NH2-Terminal Kinases, and Akt in Microglial Cells

Microglial activation has been implicated in many neurological disorders for its inflammatory and neurotrophic effects. In this study, we investigated the effects of phlorofucofuroeckol A isolated from Ecklonia stolonifera Okamura on the production of inflammatory mediators in lipopolysaccharide (LPS)-stimulated microglia. Pre-treatment of phlorofucofuroeckol A attenuated the productions of nitric oxide, prostaglandin E₂, and pro-inflammatory cytokines in LPS-stimulated microglia. Profoundly, phlorofucofuroeckol A treatment showed inactivation of nuclear factor-κB (NF-κB) by preventing the degradation of inhibitor κB-α and the nuclear translocation of p65 NF-κB subunit. Moreover, phlorofucofuroeckol A inhibited the activation of c-Jun NH₂-terminal kinases (JNKs), p38 mitogen-activated protein kinase (MAPK), and Akt, but not that of extracellular signal-regulated kinase. These results indicate that phlorofucofuroeckol A inhibits the LPS-induced expression of inflammatory mediators through inactivation of NF-κB, JNKs, p38 MAPK, and Akt pathways. These findings suggest that phlorofucofuroeckol A can be considered as a nutraceutical candidate for the treatment of neuroinflammation in neurodegenerative diseases.     

RNF11 modulates microglia activation through NF-κB signalling cascade

Microglia are resident macrophages in the central nervous system (CNS) that play a major role in neuroinflammation and pathogenesis of several neurodegenerative diseases. Upon activation, microglia releases a multitude of pro-inflammatory factors that initiate and sustain an inflammatory response by activating various signalling pathways, including the NF-κB pathway in a feed forward cycle. In microglial cells, activation of NF-κB signalling is normally transient, while sustained NF-κB activation is associated with persistent neuroinflammation. RING finger protein 11 (RNF11), in association with A20 ubiquitin-editing complex, is one of the key negative regulators of NF-κB signalling pathway in neurons. In this study, we have demonstrated and confirmed this role of RNF11 in microglia, the immune cells of the CNS. Coimmunoprecipitation experiments showed that RNF11 and A20 interact in a microglial cell line, suggesting the presence of A20 ubiquitin-editing protein complex in microglial cells. Next, using targeted short hairpin RNA (shRNA) knockdown and over-expression of RNF11, we established that RNF11 expression levels are inversely related to NF-κB activation, as evident from altered expression of NF-κB transcribed genes. Moreover our studies, illustrated that RNF11 confers protection against LPS-induced cell cytotoxicity. Thus our investigations clearly demonstrated that microglial RNF11 is a negative regulator of NF-κB signalling pathway and could be a strong potential target for modulating inflammatory responses in neurodegenerative diseases.     

Effect of sevoflurane treatment on microglia activation,NF-kB and MAPK activities

Microglia activation has been implicated in neurodegenerative disease. Sevoflurane is fluorinated methyl isopropyl ether with anti-inflammatory activity. In this study, we evaluated the potential effects of sevoflurane on lipopolysaccharides (LPS)-induced microglia activation. We treated primary microglia cells with sevoflurane prior to LPS treatment and tested the microglia migration, the productions of pro-inflammatory cytokines including tumor necrosis factor-α, interleukin-6 and interleukin-8. We also explored the effects of sevoflurane on NF-κB and p38 MAPK activation. Finally, we examined the effect of sevoflurane on cytokines production in rat brain. Sevoflurane significantly reduced LPS-induced microglial migration. Sevoflurane significantly decreased the production of pro-inflammatory cytokines both in vitro and in vivo. Sevoflurane attenuated activations of NF-κB and MAPK signaling pathways. Sevoflurane treatment decreased microglia activation by suppressing NF-kB and MAPK signaling pathways.     

Novel strategies for opposing murine microglial activation

Pathologic microglial activation is believed to contribute to progressive neuronal damage in neurodegenerative diseases by the release of potentially neurotoxic agents, such as pro-inflammatory cytokines including tumor necrosis factor alpha (TNF-alpha). Using cultured N9 microglial cells, we have examined the regulation of TNF-alpha following endotoxic insult with lipopolysacharide (LPS), focusing on the role of the pro-inflammatory phospholipase A2/mitogen activated protein kinase/arachidonic acid/cyclo-oxygenase-2 cascade and the nitric oxide/cGMP pathway. Data show that various inhibitors of the PLA2 cascade markedly inhibit LPS-induced TNF-alpha release, supporting a key role of this pathway in the regulation of microglial activation. We also investigated the putative effects of cGMP-elevating agents on blocking microglial activation induced by LPS. Data show that each member of this class of cGMP-elevating compounds that we employed opposed microglial TNF-alpha release, suggesting that strengthening intracellular cGMP signaling mitigates against microglial activation. Taken together, our results suggest novel strategies for reducing microglial activation.     

PI3Kγ activation is required for LPS-induced reactive oxygen species generation in respiratory epithelial cells

Objective

In this study, we investigated the molecular basis of reactive oxygen species (ROS) generation induced by lipopolysaccharide (LPS) in A549 cells—an alveolar epithelial cell line.

Experimental design

A549 cells or normal human bronchial epithelial (NHBE) cells were stimulated with LPS. ROS generation was measured in A549 cells or NHBE cells pre-treated with a selective inhibitor of phosphatidylinositol 3-kinase γ (PI3Kγ), AS 605240, PI3Kγ siRNA, or a ROS scavenger, pyridoxamine (PM).

Results

Treatment of A549 cells or NHBE cells with LPS caused a significant increase in intracellular ROS generation. Pretreatment with the PI3Kγ inhibitor, AS 605240 decreased the LPS-induced increase of ROS generation, phosphorylation of Akt, and production of phosphatidyl 3,4,5-trisphosphate in A549 cells. In addition, interference with siRNA for PI3Kγ significantly reduced LPS-induced ROS generation in A549 cells. Treatment of A549 cells with LPS or hydrogen peroxide increased the nuclear factor-κB (NF-κB) in the nucleus, accompanying an increase in phosphorylation of inhibitory κB-α, degradation of the protein, and reduction of cytosolic NF-κB. Pretreatment with AS 605240 reduced these LPS-induced changes. In addition, pretreatment with PM or N-acetyl cysteine resulted in inhibition of nuclear NF-κB activation.

Conclusion

These results suggest that PI3Kγ plays a key role in LPS-induced ROS generation in alveolar epithelial cells, thereby activating NF-κB.     

Oleic acid reduces lipopolysaccharide-induced expression of iNOS and COX-2 in BV2 murine microglial cells: Possible involvement of reactive oxygen species,p38 MAPK,and IKK/NF-κB signaling pathways

Microglia are the major cells involved in neuroinflammation resulting in brain tissue damage during infection and neurodegenerative diseases. In this study, we examined the effects of the monounsaturated fatty acid oleic acid (OA) on LPS-induced proinflammatory mediators production and the mechanisms involved in BV2 microglia. OA inhibited LPS-induced expression of iNOS and COX-2 as well as production of NO and prostaglandin E2. We showed that OA blocked LPS-induced NF-κB activation and phosphorylation of inhibitor κB kinase (IKK). We also showed that OA inhibited LPS-induced phosphorylation of Akt and p38 MAPK, but not that of ERK. Finally, we showed that OA reduced reactive oxygen species (ROS) accumulation and an anti-oxidant N-acetylcysteine inhibited NF-κB transactivation and phosphorylation of IKK and Akt in LPS-stimulated BV2 cells. Taken together, our results suggest that OA shows an anti-inflammatory effect by inhibiting ROS, p38 MAPK, and Akt/IKK/NF-κB signaling pathways in LPS-stimulated BV2 microglia.     

Oleamide suppresses lipopolysaccharide-induced expression of iNOS and COX-2 through inhibition of NF-κB activation in BV2 murine microglial cells

Oleamide (cis-9-octadecenamide) is an endogenous sleep-inducing fatty acid amide that accumulates in the cerebrospinal fluid of the sleep-deprived animals. Microglia are the major immune cells involved in neuroinflammation causing brain damage during infection, ischemia, and neurodegenerative disease. In this study, we examined the effects of oleamide on LPS-induced production of proinflammatory mediators and the mechanisms involved in BV2 microglia. Oleamide inhibited LPS-induced production of NO and prostaglandin E2 as well as expression of iNOS and COX-2. We showed that oleamide blocked LPS-induced NF-κB activation and phosphorylation of inhibitor κB kinase (IKK). We also showed that oleamide inhibited LPS-induced phosphorylation of Akt, p38 MAPK, and ERK, activation of PI 3-kinase, and accumulation of reactive oxygen species (ROS). Finally, we showed that a specific antagonist of the CB2 receptor, AM630, blocked the inhibitory effects of oleamide on LPS-induced production of proinflammatory mediators and activation of NF-κB. Taken together, our results suggest that oleamide shows an anti-inflammatory effect through inhibition of NF-κB activation in LPS-stimulated BV2 microglia.     

Aspirin Inhibits LPS-Induced Expression of PI3K/Akt,ERK, NF-κB,CX3CL1, and MMPs in Human Bronchial Epithelial Cells

This study focused on the effects of aspirin on lipopolysaccharide (LPS)-induced expression of phosphoinositide 3 kinase (PI3K)/protein kinase B (Akt), extracellular signal-regulated protein kinase (ERK), nuclear factor-κB (NF-κB), CX3CL1, and MMPs in human bronchial epithelial cells. Human bronchial epithelial cells were seeded in six-well plates. After 24 h, the cells were classified into six groups: control blank (CK) group; LPS group; PD98059 (ERK inhibitor) (PD) group, treated with LPS + ERK inhibitor; LY294002(PI3K/Akt inhibitor) (LY) group, treated with LPS + PI3K/Akt inhibitor; Aspirin (Asp) group, treated with LPS + aspirin; and Pyrrolidinedithiocarbamic acid (PDTC) group, treated with LPS + NF-κB inhibitor. After 4-h treatment, the cells were harvested. Western blot analysis was performed to detect the expression of PI3K/Akt, ERK, NF-κB, and CX3CL1. Real-time quantitative PCR (RT-qPCR) was used to determine the gene expression of MMP-7, MMP-9, and MMP-12. Compared to the CK group, expression of PI3K/Akt, ERK, NF-κB, and CX3CL1 was significantly increased in the LPS group (P?<?0.05). When compared to the LPS group, expression of PI3K/Akt, ERK, NF-κB, and CX3CL1 was significantly decreased in the PD group, PDTC group, and Asp group (P?<?0.05). In addition, expression of NF-κB in the LY group was significantly reduced by comparison with the LPS group (P?<?0.05). RT-qPCR: When compared to the LPS group, expression of MMP-7 and MMP-12 was significantly decreased in Asp group (P?<?0.05). Expression of MMP-12 was significantly reduced in LY group (P?<?0.05). LPS-ERK, NF-κB-PI3K/Akt, and CX3CL1 signal pathways exist in human bronchial epithelial cells. The PI3K/Akt inhibitor repressed expression of MMP-12. Aspirin inhibited LPS-induced expression of PI3K, Akt, ERK, NF-κB, CX3CL1, MMP-7, and MMP-12 in human bronchial epithelial cells.     

Nardosinone-Type Sesquiterpenes from the Hexane Fraction of <Emphasis Type="Italic">Nardostachys jatamansi</Emphasis> Attenuate NF-κB and MAPK Signaling Pathways in Lipopolysaccharide-Stimulated BV2 Microglial Cells

Four nardosinone-type sesquiterpenes, nardosinone, isonardosinone, kanshone E, and kanshone B, were isolated from the hexane fraction of Nardostachys jatamansi (Valerianaceae) methanol extract. The structures of these compounds were mainly established by analyzing the data obtained from nuclear magnetic resonance (NMR) spectroscopy and mass spectrometry (MS). In this study, we investigated their anti-neuroinflammatory effects in lipopolysaccharide (LPS)-induced BV2 microglial cells. The results showed that nardosinone-type sesquiterpenes inhibited the production of pro-inflammatory mediators, such as nitric oxide (NO) and prostaglandin E₂ (PGE₂) in LPS-induced BV2 microglial cells. These inhibitory effects were correlated with the downregulation of inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2). Moreover, these sesquiterpenes also attenuated the mRNA expression of pro-inflammatory cytokines including interleukin-1β (IL-1β), IL-6, and tumor necrosis factor-α (TNF-α) in LPS-induced BV2 microglial cells. During the evaluation of the signaling pathways involved in these anti-neuroinflammatory effects, western blot analysis and DNA-binding activity assay revealed that the suppression of inflammatory reaction by these sesquiterpenes was mediated by the inactivation of nuclear factor-kappa B (NF-κB) pathway. These sesquiterpenes also suppressed the phosphorylation of extracellular signal-regulated kinase (ERK), c-Jun N-terminal kinase (JNK), and p38 mitogen-activated protein kinase (MAPK) signaling pathways in LPS-stimulated BV2 microglial cells. Taken together, these four nardosinone-type sesquiterpenes inhibited NF-κB- and MAPK-mediated inflammatory pathways, demonstrating their potential role in the treatment of neuroinflammation conditions.     

Glycogen synthase kinase-3 beta inhibitor suppresses Porphyromonas gingivalis lipopolysaccharide-induced CD40 expression by inhibiting nuclear factor-kappa B activation in mouse osteoblasts

Bone-forming osteoblasts have been recently reported capable of expressing the critical co-stimulatory molecule CD40 upon exposure to bacterial infection, which supports the unappreciated role of osteoblasts in modulating bone inflammation. Recent studies highlight the anti-inflammatory potential of glycogen synthase kinase-3β (GSK-3β) inhibitors; however, their effect on osteoblasts remains largely unclear. In the present study, we showed that treatment with SB216763, a highly specific GSK-3β inhibitor, resulted in a dose-dependent decrease in the mRNA and protein expression of CD40, as well as production of pro-inflammatory cytokines IL-6, TNF-α and IL-1β, in the Porphyromonas gingivalis-lipopolysaccharide (LPS)-stimulated murine osteoblastic-like MC3T3-E1 cells. Furthermore, inhibition of GSK-3β remarkably represses the LPS-induced activation of the nuclear factor kappa B (NF-κB) signaling pathway by suppressing IκBα phosphorylation, NF-κBp65 nuclear translocation, and NF-κBp65 DNA binding activity. Closer investigation by immunoprecipitation assay revealed that β-catenin can physically interact with NF-κBp65. The negative regulation effect of GSK-3β inhibitor on CD40 expression is mediated through β-catenin, for siRNA of β-catenin attenuated the GSK-3β inhibitor-induced repression of NF-κB activation and, consequently, the expression of CD40 and production of pro-inflammatory cytokines in LPS-stimulated MC3T3-E1 cells. Thus our results elucidate the molecular mechanisms whereby GSK-3β inhibitor prevents the LPS-induced CD40 expression on osteoblasts and provide supportive evidence of the potential role of GSK-3β inhibitors in suppressing the immune function of osteoblasts in inflammatory bone diseases.     

三七皂苷Rg1抑制脂多糖诱导的小胶质细胞激活

目的 探讨三七皂苷Rg1(Rg1)对脂多糖(LPS)诱导的小胶质细胞系BV-2细胞炎性因子释放的抑制作用.方法 用LPS刺激BV-2细胞构建炎症模型,采用四甲基偶氮唑盐比色法检测Rg1对BV-2细胞活力的影响,免疫荧光染色和反转录PCR方法检测不同浓度Rg1(10、20、40μmol/L)对细胞炎性蛋白酶诱导型一氧化氮合酶(iNOS)和环氧合酶-2 (COX-2)、细胞炎性因子肿瘤坏死因子-α(TNF-α)和白细胞介素-1β(IL-1β)、炎性信号分子NF-κB蛋白与mRNA的表达变化.结果 不同浓度的Rg1在转录水平和翻译水平上明显抑制了LPS诱导的细胞炎性蛋白酶iNOS和COX-2、细胞炎性因子TNF-α和IL-1β与炎性信号分子NF-κB的上调,并且iNOS、COX-2和NF-κB的表达呈剂量依赖性.结论 Rg1可通过调控LPS诱导的小胶质细胞系BV-2细胞炎性因子释放从而抑制小胶质细胞激活,发挥抗神经炎症的作用.     

Inhibiting Mer receptor tyrosine kinase suppresses STAT1, SOCS1/3, and NF-κB activation and enhances inflammatory responses in lipopolysaccharide-induced acute lung injury

Mer signaling participates in a novel inhibitory pathway in TLR activation. The purpose of the present study was to examine the role of Mer signaling in the down-regulation of TLR4 activation-driven immune responses in mice, i.t.-treated with LPS, using the specific Mer-blocking antibody. At 4 h and 24 h after LPS treatment, expression of Mer protein in alveolar macrophages and lung tissue decreased, sMer in BALF increased significantly, and Mer activation increased. Pretreatment with anti-Mer antibody did not influence the protein levels of Mer and sMer levels. Anti-Mer antibody significantly reduced LPS-induced Mer activation, phosphorylation of Akt and FAK, STAT1 activation, and expression of SOCS1 and -3. Anti-Mer antibody enhanced LPS-induced inflammatory responses, including activation of the NF-κB pathway; the production of TNF-α, IL-1β, and MIP-2 and MMP-9 activity; and accumulation of inflammatory cells and the total protein levels in BALF. These results indicate that Mer plays as an intrinsic feedback inhibitor of the TLR4- and inflammatory mediator-driven immune responses during acute lung injury.     

Upregulation of heme oxygenase-1 via PI3K/Akt and Nrf-2 signaling pathways mediates the anti-inflammatory activity of Schisandrin in Porphyromonas gingivalis LPS-stimulated macrophages

The lipopolysaccharide (LPS) of Porphyromonas gingivalis is thought to induce periodontitis. In this study, we isolated Schisandrin from the dried fruits of Schisandra chinensis and examined the anti-inflammatory effect of Schisandrin in macrophages stimulated with LPS from P. gingivalis. First, Schisandrin inhibited LPS-induced pro-inflammatory cytokines, including TNF-α, IL-1β, and IL-6. And Schisandrin suppressed the nuclear translocation and activity of NF-κB and phosphorylation of IκBα in LPS-stimulated RAW 264.7 cells. Next, the presence of a selective inhibitor of HO-1 (SnPP) and a siRNA specific for HO-1 inhibited Schisandrin-mediated anti-inflammatory activity. Furthermore, Schisandrin induced HO-1 expression of RAW 264.7 cells through Nrf-2, PI3K/Akt, and ERK activation. Therefore, these results suggest that the anti-inflammatory effects of Schisandrin on P. gingivalis LPS-stimulated RAW 264.7 cells may be due to a reduction of NF-κB activity and induction of the expression of HO-1, leading to TNF-α, IL-1β, and IL-6 down-regulation.     

肾上腺素对小鼠巨噬细胞中促炎／抗炎介质比值的影响

目的：研究肾上腺素对脂多糖（LPS）诱导的小鼠单核巨噬细胞株RAW264.7中促炎介质［肿瘤坏死因子（TNF-α）、一氧化氮（NO）、环加氧酶-2（COX-2）］和抗炎介质［血红素氧化酶-1（HO-1）、白介素10（IL-10）］表达及NF-κB活化的影响。 方法： 以10 μg/L的LPS刺激体外培养的RAW264.7细胞作为炎症模型，加入不同浓度的肾上腺素（1、5、10、50 μmol/L）孵育24 h后，收集培养上清并提取细胞总蛋白，酶联免疫法测定上清中TNF-α、IL-10浓度，Griess法检测上清NO含量(以NO2-/NO3-表示)，免疫印迹法检测细胞总蛋白中COX-2、HO-1、IκB-α的含量。 结果： 10 μg/L的LPS明显诱导TNF-α、NO(NO2-/NO3-)、COX-2、IL-10及HO-1的产生；LPS+肾上腺素组与LPS单独作用组相比促炎介质TNF-α、NO(NO2-/NO3-)、COX-2的表达量显著下降，而抗炎介质IL-10、HO-1的表达却明显增强；肾上腺素与LPS共同作用组中IκB-α的含量与单独LPS作用组相比无明显差异。 结论： 肾上腺素下调LPS诱导的巨噬细胞中促炎介质的表达同时促进抗炎介质的表达，这种效应并不通过影响NF-κB的活化来实现。     

MD-2 regulates LPS-induced NLRP3 inflammasome activation and IL-1beta secretion by a MyD88/NF-κB-dependent pathway in alveolar macrophages cell line

Myeloid differentiation protein 2 (MD-2) is required in the recognition of lipopolysaccharide (LPS) by toll-like receptor 4 (TLR4), and participates in LPS-induced alveolar macrophage (AM) inflammation during acute lung injury (ALI). Activation of the NOD-like receptor family, pyrin domain containing 3 (NLRP3) inflammasome aggravates inflammation in LPS-induced ALI. However, there is currently little known about the relationship between MD-2 signaling and the NLRP3 inflammasome. This study showed that NLRP3 expression, IL-1beta (IL-1β) secretion, and pyroptosis were up-regulated after LPS stimulation in the NR8383 AM cell-line. MD-2 gene knock-down reduced LPS-induced mRNA and protein expression of NLRP3 and IL-1β secretion in NR8383 cells, and inhibited the MyD88/NF-κB signaling pathway. Conversely, over-expression of MD-2 not only heightened NLRP3, MyD88, and NF-κB p65 protein expression, it also aggravated the LPS-induced inflammatory response. Furthermore, the NF-κB inhibitor SN50 had a beneficial role in decreasing NLRP3 and caspase-1 mRNA and protein expression. The observations suggest that MD-2 helps to regulate LPS-induced NLRP3 inflammasome activation and the inflammatory response in NR8383 cells, and likely does so by affecting MyD88/NF-κB signaling.     

Celastrol attenuates impairments associated with lipopolysaccharide-induced acute respiratory distress syndrome (ARDS) in rats

Celastrol, a constituent from a traditional Chinese medicinal herb belonging to the family Celastraceae, has been shown to impart anti-inflammatory properties, in part, by inhibiting NF-κB activity and related induction of pro-inflammatory cytokine formation/release. The present study investigated the effects of celastrol in an animal model of acute respiratory distress syndrome (ARDS) induced by intratracheal administration of lipopolysaccharides (LPSs). Celastrol pre-treatment groups received celastrol by intraperitoneal injection on seven consecutive days before LPS treatment. In rats evaluated 24?h after LPS administration, oxygenation indices and lung injury were measured, as were levels of inflammatory cells and cytokines in isolated bronchoalveolar lavage fluid (BALF). Lung tissue expression of proteins involved in NF-κB and ERK/MAPK pathways were measured by Western blot analyses. Celastrol pre-treatments appeared to attenuate LPS-induced lung injury and inflammatory responses in the rats, including decreases in inducible aggregation\infiltration of inflammatory cells and production/release of pro-inflammatory cytokines into the lung airways. Celastrol appeared to also inhibit NF-κB activation, but had no effect on ERK/MAPK pathways in the LPS-induced ARDS. The results here thus indicated that celastrol pre-treatment could impart protective effects against LPS-induced ARDS, and that these effects may be occurring through an inhibition of induction of NF-κB signaling pathways.