Edaravone dexborneol promotes M2 microglia polarization against lipopolysaccharide-induced inflammation via suppressing TLR4/MyD88/NF-κB pathway

Edaravone dexborneol (ED) is a novel neuroprotective compound that consists of two active ingredients, edaravone and ( +)-borneol in a 4:1 ratio, which has been shown the anti-inflammatory properties in animal models of ischemic stroke, cerebral hemorrhage, and autoimmune encephalomyelitis. However, the effect of ED on the polarization of microglia in neuroinflammation has not been elucidated. This study was to investigate the effects of ED on the polarization of microglia induced by lipopolysaccharide (LPS) and potential mechanisms. BV-2 microglial cells were incubated with ED (100, 200, and 400 µM) for 2 h, followed by lipopolysaccharide (LPS, 1 µg/ml) for 12 h. The researchers used the Griess method, western blot, immunocytochemistry, and subcellular fractionation to assess the effects and potential mechanisms of ED on neuroinflammatory reactions. The expression of ROS and the activities of antioxidant enzymes (SOD, GPx, and CAT) in LPS-induced BV-2 cells were also measured using the DCFH-DA fluorescent probe and colorimetric methods, respectively. It was observed that ED significantly declined the levels of TLR4/NF-κB pathway-associated proteins (TLR4, MyD88, p65, p-p65, IκBα, p-IκBα, IKKβ, p-IKKβ) and therefore inhibited LPS-induced production of NO, IL-1β, and TNF-α. Moreover, ED markedly downregulated the M1 marker (iNOS) and upregulated the M2 marker (Arginase-1, Ym-1). In addition, ED also reduced ROS generation and enhanced GPx activity. ED induced the polarization of LPS-stimulated microglia from M1 to M2 against inflammation by negatively regulating the TLR4/MyD88/NF-κB signaling pathway. Additionally, ED performed antioxidative function by depleting the intracellular excessive ROS caused by LPS through the enhancement of the enzymatic activity of GPx. ED may be a potential agent to attenuate neuroinflammation via regulating the polarization of microglia.

gingivalis LPS-Induced IL-1β Production by BV-2 Microglia through Suppression of Cathepsins B and L

Cathepsin B (CatB) is thought to be essential for the induction of Porphyromonas gingivalis lipopolysaccharide (Pg LPS)-induced Alzheimer's disease-like pathologies in mice, including interleukin-1β (IL-1β) production and cognitive decline. However, little is known about the role of CatB in Pg virulence factor-induced IL-1β production by microglia. We first subjected IL-1β-luciferase reporter BV-2 microglia to inhibitors of Toll-like receptors (TLRs), IκB kinase, and the NLRP3 inflammasome following stimulation with Pg LPS and outer membrane vesicles (OMVs). To clarify the involvement of CatB, we used several known CatB inhibitors, including CA-074Me, ZRLR, and human β-defensin 3 (hBD3). IL-1β production in BV-2 microglia induced by Pg LPS and OMVs was significantly inhibited by the TLR2 inhibitor C29 and the IκB kinase inhibitor wedelolactonne, but not by the NLRPs inhibitor MCC950. Both hBD3 and CA-074Me significantly inhibited Pg LPS-induced IL-1β production in BV-2 microglia. Although CA-074Me also suppressed OMV-induced IL-1β production, hBD3 did not inhibit it. Furthermore, both hBD3 and CA-074Me significantly blocked Pg LPS-induced nuclear NF-κB p65 translocation and IκBα degradation. In contrast, hBD3 and CA-074Me did not block OMV-induced nuclear NF-κB p65 translocation or IκBα degradation. Furthermore, neither ZRLR, a specific CatB inhibitor, nor shRNA-mediated knockdown of CatB expression had any effect on Pg virulence factor-induced IL-1β production. Interestingly, phagocytosis of OMVs by BV-2 microglia induced IL-1β production. Finally, the structural models generated by AlphaFold indicated that hBD3 can bind to the substrate-binding pocket of CatB, and possibly CatL as well. These results suggest that Pg LPS induces CatB/CatL-dependent synthesis and processing of pro-IL-1β without activation of the NLRP3 inflammasome. In contrast, OMVs promote the synthesis and processing of pro-IL-1β through CatB/CatL-independent phagocytic mechanisms. Thus, hBD3 can improve the IL-1β-associated vicious inflammatory cycle induced by microglia through inhibition of CatB/CatL.

Sesquiterpene coumarins isolated from Ferula bungeana and their anti-neuroinflammatory activities

This is the first study to profile natural sesquiterpene coumarins (SCs) in Ferula bungeana, a medicinal plant of the genus Ferula in China. Eight undescribed sesquiterpene coumarins (1-8), along with six known ones (9-14) were obtained from the whole plant of F. bungeana. These unreported SCs (1-8) enriched the structural diversity of natural SCs, especially these with the hydroxy or carbonyl group at C-7' and a hydroperoxy group at C-7' or C-8'. Compounds (9-14) were reported for the first time from this plant. The in vitro anti-neuroinflammatory activity assay showed that compounds 2 and 9 showed stronger inhibitory effect on nitric oxide (NO) production in lipopolysaccharide (LPS)-induced BV-2 microglia, compared with positive control minocycline, and compounds 5 and 10 showed moderate inhibitory effects.

Paraquat mediates BV-2 microglia activation by raising intracellular ROS and inhibiting Akt1 phosphorylation

Microglia is the innate immune cell in central nervous system (CNS) and plays an important role in neuroinflammation. Microglia mediated neuroinflammation is the key factor affecting the development of neurodegenerative diseases. Although there was evidence that paraquat (PQ) could induce inflammatory response, its mechanism was not clear. The present study investigated the mechanisms of PQ-induced inflammatory responses in BV-2 microglia cells, and tried to reveal the role of ROS/Akt1 pathway. The results showed that the cell activation markers (iNOS and CD206) of BV-2 cells were increased after PQ treatment, suggesting that BV-2 microglia were activated. PQ induced the reactive oxygen species (ROS) and inhibited the AKT1 phosphorylation in BV-2 cells. Besides, the M1 markers expression (IL-6, TNF-α and IL-1β) were significantly increased after PQ treatment, which suggested that PQ induced the increase of M1 phenotype of BV-2 microglia. Pre-treated with NAC (ROS scavenger), the M1 phenotype was decreased while the p-Akt1 was restored compared to PQ stimulation. Furthermore, we built an Akt1(S473E)-overexpression BV-2 cell line. The Akt1 (S473E) partially attenuated the PQ induced increase in M1 phenotype, while ROS did not significantly change. These results indicated that PQ induced BV-2 microglia activation by increased ROS mediated Akt1 activation inhibition, leading to neuroinflammation.

Omp31 of Brucella Inhibits NF-κB p65 Signaling Pathway by Inducing Autophagy in BV-2 Microglia

Neurobrucellosis is a serious central nervous system (CNS) inflammatory disorder caused by Brucella, and outer membrane protein-31 (Omp31) plays an important role in Brucella infection. This study aims to determine whether Omp31 can induce autophagy in BV-2 microglia. Another goal of the study is to further examine the effect of autophagy on the nuclear transcription factor κB (NF-κB) p65 signaling pathway. We observed that Omp31 stimulated autophagy by increasing microtubule-associated protein 1 light chain 3B (LC3B-II) levels and inducing autophagosome formation at 6 h and 12 h. Concomitantly, Omp31 induced tumor necrosis factor-alpha (TNF-α) and interleukin-6 (IL-6) expression in a time-dependent manner but reduced the expression of TNF-α at 6 h. We utilized Omp31 with or without rapamycin or 3-methyladenine (3-MA) to treat BV-2 microglia, and it demonstrated further that Omp31 induced autophagy by promoting LC3B-II, Beclin-1 proteins expression and inhibiting the p62 protein levels. Furthermore, we explored the effects of autophagy on the NF-κB p65 pathway through western blot analysis, RT-qPCR assay, enzyme-linked immunosorbent assay (ELISA) and immunofluorescence. The data suggest that Omp31 as well as rapamycin, the autophagy inducer, can decrease TNF-α levels through the inhibition of the NF-κB p65 signaling pathway. Taken together, Omp31 can function as a catalyst in both autophagy induction and NF-κB p65 signal inhibition. Furthermore, Omp31-induced autophagy may inhibit the expression of TNF-α by negatively regulating NF-κB p65 signaling pathway.

Walnut peptide WEKPPVSH in alleviating oxidative stress and inflammation in lipopolysaccharide-activated BV-2 microglia via the Nrf2/HO-1 and NF-κB/p38 MAPK pathways

The peptide WEKPPVSH from walnut protein hydrolyzate was used to evaluate the antioxidant and anti-inflammatory protective effect on lipopolysaccharide (LPS)-activated BV-2 microglia and its possible mechanism. The results indicated that WEKPPVSH significantly decreased nitric oxide (NO) and reactive oxygen species (ROS) generation in a dose-dependent manner, and significantly up-regulated superoxide dismutase and catalase activities (P < 0.01). Results of enzyme-linked immunosorbent assay (ELISA) showed that WEKPPVSH significantly mitigated the secretion of tumor necrosis factor-α (TNF-α), interleukin-1β (IL-1β) and interleukin-6 (IL-6) (P < 0.01). Immunofluorescence analysis exhibited that WEKPPVSH down-regulated p65 translocation to the cell nucleus. Western blotting showed that WEKPPVSH up-regulated the expression of nuclear factor erythroid 2-related factor (Nrf2) and heme oxygenase-1 (HO-1), and down-regulated the expression of inducible nitric oxide synthase (iNOS), cyclooxygenase-2 (COX-2), p-IκB/IκB, p-p65/p65 and p-p38/p38. In summary, WEKPPVSH might protect against oxidative stress and inflammation in LPS-stimulated BV-2 microglia by enhancing the Nrf2/HO-1 signaling pathway and blocking the nuclear factor-κB/p38 mitogen - activated protein kinase (NF-κB/p38 MAPK) signaling pathway. The results provided an experimental basis for the research and development of walnut peptide products.

Immunometabolic Modulatory Role of Naltrexone in BV-2 Microglia Cells

Background: Naltrexone is an opioid receptor antagonist commonly used to treat opioid and alcohol dependence. The use of low dose naltrexone (LDN) was found to have anti-inflammatory properties for treatment of diseases such as fibromyalgia, Crohn’s disease, multiple sclerosis and regional pain syndromes. Related to its anti-neuroinflammatory properties, the mechanism of action is possibly mediated via Toll-like receptor 4 antagonism, which is widely expressed on microglial cells. The aim of the present study was to assess the immunometabolic effects of naltrexone on microglia cells in in vitro conditions. Methods: All experiments were performed in the BV-2 microglial cell line. The cells were treated with naltrexone at 100 μM concentrations corresponding to low dose for 24 h. Cell viability was assessed for every drug dose. To induce additional activation, the cells were pretreated with LPS and IFN-γ. Immunofluorescence was used to analyse the classical microglial activation markers iNOS and CD206, while Seahorse was used for real-time cellular metabolic assessments. mTOR activity measured over the expression of a major direct downstream target S6K was assessed using western blot. Results: LDN induced a shift from highly activated pro-inflammatory phenotype (iNOS^highCD206^low) to quiescent anti-inflammatory M2 phenotype (iNOS^lowCD206^high) in BV-2 microglia cells. Changes in the inflammatory profile were accompanied by cellular metabolic switching based on the transition from high glycolysis to mitochondrial oxidative phosphorylation (OXPHOS). LDN-treated cells were able to maintain a metabolically suppressive phenotype by supporting OXPHOS with high oxygen consumption, and also maintain a lower energetic state due to lower lactate production. The metabolic shift induced by transition from glycolysis to mitochondrial oxidative metabolism was more prominent in cells pretreated with immunometabolic modulators such as LPS and IFN-γ. In a dose-dependent manner, naltrexone also modulated mTOR/S6K expression, which underlies the cell metabolic phenotype regulating microglia immune properties and adaptation. Conclusion: By modulating the phenotypic features by metabolic switching of activated microglia, naltrexone was found to be an effective and powerful tool for immunometabolic reprogramming and could be a promising novel treatment for various neuroinflammatory conditions.

Role of Militarine in PM2.5-Induced BV-2 Cell Damage

A growing number of studies have shown that air fine particulate matter (PM_2.5) pollution is closely associated with neuroinflammation in humans. Militarine, a glucosyloxybenzyl 2-isobutylmalate compound isolated from Bletilla striata, has been found to exert significant neuroprotective effects. However, the anti-inflammatory, antioxidant and antiapoptotic effects of militarine on PM_2.5-stimulated BV-2 microglial cells have not been reported. This study aimed to investigate the protective effects of militarine against PM_2.5-induced cytotoxicity and its mechanism in BV-2 microglial cells. Our results revealed that pretreatment with 0.31-1.25 μg/mL militarine reversed the morphological changes caused by PM_2.5 and decreased proinflammatory cytokine generation and gene expression in PM_2.5-treated BV-2 cells. In particular, tumor necrosis factor-α and interleukin-6 expression was inhibited in a dose-dependent manner. Notably, militarine markedly inhibited the upregulation of Toll-like receptor 4, Toll-like receptor 2, and cyclo-oxygenase-2 expression at both the mRNA and protein levels and reduced NF-κB pathway-associated protein expression. Immunofluorescence analysis showed that militarine suppressed NF-κB activity through inhibiting p65 nuclear translocation. Our data suggested that militarine alleviated neuroinflammation in BV-2 microglial cells, possibly by inhibiting the expression of neuroinflammatory cytokines through the TLR/NF-κB signaling pathway. Additionally, militarine significantly reduced PM_2.5-mediated reactive oxygen species (ROS) generation and cell apoptosis and restored the mitochondrial membrane potential (MMP; ΔΨm). Collectively, these findings demonstrate that militarine played a protective role against PM_2.5-induced damage in BV-2 cells by exerting anti-inflammatory, antioxidant, and antiapoptotic effects.

Two New Phomaligols from the Marine-Derived Fungus Aspergillus flocculosus and Their Anti-Neuroinflammatory Activity in BV-2 Microglial Cells

Two new phomaligols, deketo-phomaligol A (1) and phomaligol E (2), together with six known compounds (3-8) were isolated from the culture broth of the marine-derived fungus Aspergillus flocculosus. Compound 1 was first isolated as a phomaligol derivative possessing a five-membered ring. The structures and absolute configurations of the new phomaligols were determined by detailed analyses of mass spectrometry (MS), nuclear magnetic resonance (NMR) data, optical rotation values and electronic circular dichroism (ECD). In addition, the absolute configurations of the known compounds 3 and 4 were confirmed by chemical oxidation and comparison of optical rotation values. Isolated compounds at a concentration of 100 μM were screened for inhibition of nitric oxide (NO) production in lipopolysaccharide (LPS)-induced BV-2 microglial cells. Among the compounds, 4 showed moderate anti-neuroinflammatory effects with an IC50 value of 56.6 μM by suppressing the production of pro-inflammatory mediators in activated microglial cells without cytotoxicity.

The protective effect of 5-O-methylvisammioside on LPS-induced depression in mice by inhibiting the over activation of BV-2 microglia through Nf-κB/IκB-α pathway

BACKGROUND

5-O-methylvisammioside (MeV), also known as 4'-O-β-D-glucosyl-5-O-methylvisamminol, is a conventional marker compound for quality control of roots of Saposhnikovia diviaricata (Radix Saposhnikoviae), which exhibits anti-inflammatory and neuroprotective activities.

PURPOSE

According to the activity of MeV, we speculated that MeV may have antidepressant effect on LPS induced depression, and further explored its mechanism.

STUDY DESIGN

First, to explore the effect and mechanism of MeV on LPS-induced depression in mice, and then to further explore the effect and mechanism of MeV on LPS-activated BV-2 microglia.

METHODS

By the OFT, EPM, TST and FST behavioral tests, to explore the effect of MeV pretreatment on the behavior of LPS-induced depression mice. ELISA and Griess method were used to detect the changes of the serum TNF-α and IL-6 levels, the hippocampus SOD and MDA levels, and the NO, SOD, MDA, TNF-α and IL-6 levels in the culture medium of LPS-stimulated BV-2 microglia. Western blot was used to analyze the protein expression in the Nf-κB/IκB-α and BDNF/TrkB pathway in the hippocampus of mice and BV-2 microglia.

RESULTS

MeV (4 mg/kg, i.p.) pretreatment significantly improves the activity and exploration ability of LPS-induced depression mice, and reduces the immobility time. MeV inhibited the production of pro-inflammatory cytokines in the serum of mice induced by LPS, such as IL-6 and TNF-α. MeV also increased the levels of SOD and reduces the expression of MDA in the hippocampus, thus promoting the alleviation of depressive symptoms in mice. Western blotting analysis showed that the antidepressant activity of MeV was related to the decrease of Nf-κB nuclear transport, the inhibition of IκB-α phosphorylation, and the increase of BDNF and TrkB expression. MeV (40 μM) significantly reduced the contents of NO, MDA, TNF-α and IL-6 in the culture medium of LPS-stimulated BV-2 microglia, and increased the content of SOD.

CONCLUSION

MeV can regulate the neurotrophic factors in the mouse brain, reduce the content of inflammatory factors by the Nf-κB/IκB-α pathway, improve oxidative stress, and inhibit the excessive activation of LPS-stimulated BV -2 microglia. It effectively reversed the depression-like behAavior induced by LPS in mice.

Semisynthetic quercetin-quinone mitigates BV-2 microglia activation through modulation of Nrf2 pathway

During brain ageing, microglia, the resident immune cells of the CNS, are immunologically activated and contribute to neuroinflammation, a vicious cycle that supports development of neurological disorders. Therapeutic approaches focus mainly on downregulation of their pro-inflammatory activated state that is associated with health benefits. Electrophilic compounds, such as natural quinones and their reduced pro-electrophilic precursors, flavonoids, represent a wide group of diverse substances with important biological effects. They can cause considerable cytotoxicity when used at higher dosages, but on the other hand, they have versatile health benefits at lower dosages. In this study, we investigated the cytotoxicity and prooxidant profile of synthetic conjugate of two electrophilic compounds, quercetin and 1,4-naphthoquinone, 4'-O-(2-chloro-1,4-naphthoquinone-3-yloxy) quercetin (CHNQ), and its attenuation of inflammatory responses and modulation of Nrf2 pathway in BV-2 microglial cells. CHNQ showed higher cytotoxicity than its precursors, accompanied by promotion of production of reactive oxygen species along with G2/M cell cycle arrest at higher concentrations tested. Nevertheless, at a lower non-toxic concentration, CHNQ, more significantly than did its precursors, downregulated LPS-stimulated microglia cells as documented by decreased iNOS, COX-2 and TNFα protein levels. Moreover, CHNQ most effectively upregulated expression of phase II antioxidant enzyme HO-1 and β5 subunit of constitutive proteasome. The enhanced anti-inflammatory effect of CHNQ was accompanied by prominent increase in cytosolic expression of Nrf2 and c-Jun, however, induction effect on nuclear Nrf2 translocation was comparable to QUER. Moreover, a conditioned medium from activated BV-2 cells co-treated with quercetin and CHNQ maintained viability of neuron-like PC12 cells. The compounds tested did not show any disturbance of phagocytosis of live or dead PC12 cells. The present experimental data predict a preventive and therapeutic potential of semisynthetic derivative CHNQ in ageing and related pathologies, mediated by activation of proteins of the antioxidant response.

Combined Cyclosporin A and Hypothermia Treatment Inhibits Activation of BV-2 Microglia but Induces an Inflammatory Response in an Ischemia/Reperfusion Hippocampal Slice Culture Model

Introduction

Hypothermia attenuates cerebral ischemia-induced neuronal cell death associated with neuroinflammation. The calcineurin inhibitor cyclosporin A (CsA) has been shown to be neuroprotective by minimizing activation of inflammatory pathways. Therefore, we investigated whether the combination of hypothermia and treatment with CsA has neuroprotective effects in an oxygen-glucose deprivation/reperfusion (OGD/R) injury model in neuronal and BV-2 microglia monocultures, as well as in an organotypic hippocampal slice culture (OHSC).

Methods

Murine primary neurons, BV-2 microglia, and OHSC were pretreated with CsA and exposed to 1 h OGD (0.2% O₂) followed by reperfusion at normothermia (37°C) or hypothermia (33.5°C). Cytotoxicity was measured by lactate dehydrogenase and glutamate releases. Damage-associated molecular patterns (DAMPs) high mobility group box 1 (HMGB1), heat shock protein 70 (Hsp70), and cold-inducible RNA-binding protein (CIRBP) were detected in cultured supernatant by western blot analysis. Interleukin-6 (IL-6), Interleukin-1α and -1β (IL-1α/IL1-β), tumor necrosis factor-α (TNF-α), monocyte chemotactic protein 1 (MCP1), inducible nitric oxide synthase (iNOS), glia activation factors ionized calcium-binding adapter molecule 1 (Iba1), and transforming growth factor β1 (TGF-β1) gene expressions were analyzed by RT-qPCR.

Results

Exposure to OGD plus 10 μM CsA was sufficient to induce necrotic cell death and subsequent release of DAMPs in neurons but not BV-2 microglia. Moreover, OGD/R-induced secondary injury was also observed only in the neurons, which was not attenuated by cooling and no increased toxicity by CsA was observed. BV-2 microglia were not sensitive to OGD/R-induced injury but were susceptible to CsA-induced toxicity in a dose dependent manner, which was minimized by hypothermia. CsA attenuated IL-1β and Iba1 expressions in BV-2 microglia exposed to OGD/R. Hypothermia reduced IL-1β and iNOS expressions but induced TNF-α and Iba1 expressions in the microglia. However, these observations did not translate to the ex vivo OHCS model, as general high expressions of most cytokines investigated were observed.

Conclusion

Treatment with CsA has neurotoxic effects on primary neurons exposed to OGD but could inhibit BV-2 microglia activation. However, CsA and hypothermia treatment after ischemia/reperfusion injury results in cytotoxic neuroinflammation in the complex ex vivo OHSC.

Multi-Target Anti-Alzheimer Activities of Four Prenylated Compounds from Psoralea Fructus

Alzheimer’s disease (AD) is an age-related neurodegenerative disease that is mediated by multiple signaling pathways. In recent years, the components of Psoralea Fructus (PF) have demonstrated some anti-Alzheimer effects both in vitro and in vivo. To further reveal the active compounds of PF and their mechanisms regulating key targets of AD, in this study, we identified four prenylated compounds from the 70% ethanolic aqueous extract of PF, namely bavachin, bavachinin, bavachalcone, and isobavachalcone. Multi-target bioactivity analysis showed that these compounds could differentially inhibit neuroinflammation, oxidative damage, and key AD-related protein targets, such as amyloid β-peptide 42, β-secretase, glycogen synthase kinase 3β, and acetylcholinesterase. These compounds may generate beneficial effects in AD prevention and treatment.

Immunoglobulins G from Sera of Amyotrophic Lateral Sclerosis Patients Induce Oxidative Stress and Upregulation of Antioxidative System in BV-2 Microglial Cell Line

Amyotrophic lateral sclerosis (ALS) is a neurodegenerative disorder with a very fast progression, no diagnostic tool for the presymptomatic phase, and still no effective treatment of the disease. Although ALS affects motor neurons, the overall pathophysiological condition points out to the non-cell autonomous mechanisms, where astrocytes and microglia play crucial roles in the disease progression. We have already shown that IgG from sera of ALS patients (ALS IgG) induce calcium transients and an increase in the mobility of acidic vesicles in cultured rat astrocytes. Having in mind the role of microglia in neurodegeneration, and a well-documented fact that oxidative stress is one of the many components contributing to the disease, we decided to examine the effect of ALS IgG on activation, oxidative stress and antioxidative system of BV-2 microglia, and to evaluate their acute effect on cytosolic peroxide, pH, and on reactive oxygen species (ROS) generation. All tested ALS IgGs (compared to control IgG) induced oxidative stress (rise in nitric oxide and the index of lipid peroxidation) followed by release of TNF-α and higher antioxidative defense (elevation of Mn- and CuZn-superoxide dismutase, catalase, and glutathione reductase with a decrease of glutathione peroxidase and glutathione) after 24 h treatment. Both ALS IgG and control IgG showed same localization on the membrane of BV-2 cells following 24 h treatment. Cytosolic peroxide and pH alteration were evaluated with fluorescent probes HyPer and SypHer, respectively, having in mind that HyPer also reacts to pH changes. Out of 11 tested IgGs from ALS patients, 4 induced slow exponential rise of HyPer signal, with maximal normalized fluorescence in the range 0.2–0.5, also inducing similar increase of SypHer intensity, but of a lower amplitude. None of the control IgGs induced changes with neither of the indicators. Acute ROS generation was detected in one out of three tested ALS samples with carboxy-H2DCFDA. The observed phenomena demonstrate the potential role of inflammatory humoral factors, IgGs, as potential triggers of the activation in microglia, known to occur in later stages of ALS. Therefore, revealing the ALS IgG signaling cascade in microglial cells could offer a valuable molecular biomarker and/or a potential therapeutic target.

NF-κB dependent up-regulation of TRPC6 by Aβ in BV-2 microglia cells increases COX-2 expression and contributes to hippocampus neuron damage

The deposition of amyloid β-protein (Aβ) has been involved in neurodegeneration of Alzheimer's disease (AD). Besides Aβ plaques and neuronal loss, microglia activation is also common in AD patient brains, suggesting its important role in the pathogenesis of AD. Although activation of microglia by Aβ plaques has been demonstrated, the mechanism underlying it is still largely unclear. Here, we found that TRPC6 has a crucial role in microglia activation by Aβ. Aβ up-regulates the level of TRPC6 via NF-κB in BV-2 microglia and increases the expression of pro-inflammatory factors and oxidative enzyme, COX-2. Knock-down of TRPC6 reduces the Aβ-induced expression of pro-inflammatory factors and COX-2 and the damage of hippocampus neurons. Furthermore, inhibition of COX-2 also protects hippocampus neurons from Aβ-induced inflammatory damage. Collectively, our studies suggest that Aβ increase the expression of TRPC6 via NF-κB in BV-2 microglia and promotes the production of COX-2, which induces hippocampus neuron damage.

Bioassay-guided fractionation of ethyl acetate extract from Armillaria mellea attenuates inflammatory response in lipopolysaccharide (LPS) stimulated BV-2 microglia

BACKGROUND

Armillaria mellea (A. mellea) is a traditional Chinese medicinal and edible mushroom, which is proved to possess a lot of biological activities, including anti-oxidation, immunopotentiation, anti-vertigo and anti-aging activities. However, little information is available in regard to its neuroprotection activity in inflammation-mediated neurodegenerative diseases.

PURPOSE

We have found that A. mellea has an anti-inflammatory activity in LPS-induced RAW264.7 cells in our previous study. The objective of this study is to investigate the anti-neuroinflammatory mechanism of a bioassay-guided fractionation (Fr.2) and its active components/compounds.

METHODS

Compounds were isolated by preparative high performance liquid chromatography (pre-HPLC) and their structures were established by mass spectrometry (MS) and nuclear magnetic resonance (NMR) spectroscopic analyses. The anti-neuroinflammatory effect of Fr.2 and each compounds were investigated in lipopolysaccharide (LPS)-stimulated murine microglia cell lineBV-2.

RESULTS

We demonstrated that Fr.2 significantly decreased the production of inflammation mediator nitric oxide (NO) and inflammatory cytokines tumor necrosis factor alpha (TNF-α), interleukin-6 (IL-6) and interleukin-1beta (IL-1β) in a dose-dependent manner (10, 30, 100µg/ml). In addition, Fr.2 markedly down-regulated the phosphorylation levels of nuclear factor kappa B p65 (NF-κB p65), inhibitory κB-α (IκB-α) and c-Jun N-terminal kinases (JNKs) pathways. Sevens compounds were isolated from Fr.2, among them, three compounds, 5-hydroxymethylfurfural (CP1), vanillic acid (CP4) and syringate (CP5) were reported for the first time in A. mellea. NO and inflammatory cytokines (TNF-α, IL-6, IL-1β) secretion indicated that daidzein (CP6) and genistein (CP7) showed a more outstanding anti-inflammation potential at non-toxic concentrations (10, 30, 100µM) than the other five compounds.

CONCLUSIONS

In conclusion, Fr.2 may have therapeutic potential for neurodegenerative diseases by inhibiting inflammatory mediators and suppress inflammation pathway in activated microglia. Daidzein and genistein may serve as the effective anti-inflammation compounds of Fr.2.

Anti-Neuroinflammatory ent-Kaurane Diterpenoids from Pteris multifida Roots

Activated microglia are known to be a major source of cellular neuroinflammation which causes various neurodegenerative diseases, including Alzheimer’s disease. In our continuing efforts to search for new bioactive phytochemicals against neuroinflammatory diseases, the 80% methanolic extract of Pteris multifida (Pteridaceae) roots was found to exhibit significant NO inhibitory activity in lipopolysaccharide (LPS)-activated BV-2 microglia cells. Three new ent-kaurane diterpenoids, pterokaurane M₁ 2-O-β-d-glucopyranoside (4), 2β,16α-dihydroxy-ent-kaurane 2,16-di-O-β-d-glucopyranoside (10), and 2β,16α,17-trihydroxy-ent-kaurane 2-O-β-d-glucopyranoside (12), were isolated along with nine other known compounds from P. multifida roots. The chemical structures of the new compounds were determined by 1D- and 2D-NMR, HR-ESI-MS, and CD spectroscopic data analysis. Among the isolates, compounds 1 and 7 significantly inhibited NO production in LPS-stimulated BV-2 cells reducing the expression of the cyclooxygenase-2 (COX-2) protein and the level of pro-inflammatory mediators such as prostaglandin E₂ (PGE₂), tumor necrosis factor (TNF)-α, interleukin (IL)-1β, and IL-6. These results suggest that ent-kaurane diterpenes from P. multifida could be potential lead compounds that act as anti-neuroinflammatory agents.

Regulation of Microglial Phagocytosis by RhoA/ROCK-Inhibiting Drugs

Inflammation within the central nervous system (CNS) is a major component of many neurodegenerative diseases. The underlying mechanisms of neuronal loss are not fully understood, but the activation of CNS resident phagocytic microglia seems to be a significant element contributing to neurodegeneration. At the onset of inflammation, high levels of microglial phagocytosis may serve as an essential prerequisite for creating a favorable environment for neuronal regeneration. However, the excessive and long-lasting activation of microglia and the augmented engulfment of neurons have been suggested to eventually govern widespread neurodegeneration. Here, we investigated in a functional assay of acute inflammation how the small GTPase RhoA and its main target the Rho kinase (ROCK) influence microglial phagocytosis of neuronal debris. Using BV-2 microglia and human NT2 model neurons, we demonstrate that the pain reliever Ibuprofen decreases RhoA activation and microglial phagocytosis of neuronal cell fragments. Inhibition of the downstream effector ROCK with the small-molecule agents Y-27632 and Fasudil reduces the engulfment of neuronal debris and attenuates the production of the inflammatory mediator nitric oxide during stimulation with lipopolysaccharide. Our results support a therapeutic potential for RhoA/ROCK-inhibiting agents as an effective treatment of excessive inflammation and the resulting progression of microglia-mediated neurodegeneration in the CNS.

Anesthetic isoflurane attenuates activated microglial cytokine-induced VSC4.1 motoneuronal apoptosis

Isoflurane (ISO) exhibits neuroprotective effects against inflammation and apoptosis. However, the role of ISO in motoneuronal apoptosis induced by activated microglia remains poorly studied. We investigated the protective effects of ISO on the apoptosis of ventral spinal cord 4.1 (VSC4.1) motoneurons induced by lipopolysaccharide (LPS)-activated BV-2 microglia. Results indicated that ISO inhibited NF-κB activation and pro-inflammatory cytokine release in LPS-treated BV-2 microglia. Conditioned medium (CM) from activated BV-2 cells treated by ISO directly prevented VSC4.1 motoneurons from LPS-CM-induced neuronal apoptosis, as determined by the following: reductions in caspase-8, caspase-9, and caspase-3 activities; downregulation of pro-apoptotic procaspase-8, cleaved (cl)-caspase-8, procaspase-9, cl-caspase-9, caspase-3, cl-caspase-3, Bid, Bax, and cytochrome c expression; and upregulation of anti-apoptotic Bcl-2 expression in LPS-CM-cultured VSC4.1 motoneurons. Findings demonstrated that ISO inhibits BV-2 microglia activation and alleviates VSC4.1 motoneuronal apoptosis induced by microglial activation. These effects suggest that ISO can be used as an alternative agent for reducing neuronal apoptosis.

Modulation of BV-2 microglia functions by novel quercetin pivaloyl ester

Chronic inflammation in brain plays a critical role in major neurodegenerative diseases such as Alzheimer's, Parkinson's disease, stroke or multiple sclerosis. Microglia, resident macrophages and intristinc components of CNS, appear to be main effectors in this pathological process. Quercetin, a naturally occurring flavonoid, was proven to downregulate inflammatory genes in microglia. Synthetically modified quercetin, 3'-O-(3-chloropivaloyl) quercetin (CPQ), is assumed to possess better biological availability and enhanced antioxidant properties. In the present study, antineuroinflammatory capability of the novel compound CPQ was assessed in BV-2 microglial cells. Our data show that treatment with CPQ attenuated the production of the inflammatory mediators, nitric oxide (NO) and tumour necrosis factor-α (TNF-α), in LPS-stimulated microglia somewhat more efficiently than did quercetin (p > 0.05 for CPQ vs. quercetin-treated group). Also, protein level of inducible NO synthase (iNOS) in LPS-activated BV-2 microglia was to some extent more effectively supressed by CPQ than by unmodified flavonoid. In consistence with the extent of their effects on pro-inflammatory markers, CPQ and quercetin showed down-regulation of NFκB activation. This quercetin analogue caused also a decline in BV-2 microglia proliferation with interfering with cell cycle progression (p < 0.001 for CPQ vs. quercetin-treated group). However, CPQ did not remarkably affect cell viability. In addition, CPQ showed a minor better suppression of PMA-induced generation of superoxide than did quercetin. Neither CPQ nor quercetin influenced phagocytosis of BV-2 cells. These results point to the therapeutic potential of 3'-O-(3-chloropivaloyl)quercetin (CPQ) as a novel antiinflammatory drug in neurodegenerative diseases, mediating favourable modulation of pro-inflammatory functions of microglia.

Nitric oxide regulates antagonistically phagocytic and neurite outgrowth inhibiting capacities of microglia

Traumatic injury or the pathogenesis of some neurological disorders is accompanied by inflammatory cellular mechanisms, mainly resulting from the activation of central nervous system (CNS) resident microglia. Under inflammatory conditions, microglia up-regulate the inducible isoform of NOS (iNOS), leading to the production of high concentrations of the radical molecule nitric oxide (NO). At the onset of inflammation, high levels of microglial-derived NO may serve as a cellular defense mechanism helping to clear the damaged tissue and combat infection of the CNS by invading pathogens. However, the excessive overproduction of NO by activated microglia has been suggested to govern the inflammation-mediated neuronal loss causing eventually complete neurodegeneration. Here, we investigated how NO influences phagocytosis of neuronal debris by BV-2 microglia, and how neurite outgrowth of human NT2 model neurons is affected by microglial-derived NO. The presence of NO greatly increased microglial phagocytic capacity in a model of acute inflammation comprising lipopolysaccharide (LPS)-activated microglia and apoptotic neurons. Chemical manipulations suggested that NO up-regulates phagocytosis independently of the sGC/cGMP pathway. Using a transwell system, we showed that reactive microglia inhibit neurite outgrowth of human neurons via the generation of large amounts of NO over effective distances in the millimeter range. Application of a NOS blocker prevented the LPS-induced NO production, totally reversed the inhibitory effect of microglia on neurite outgrowth, but reduced the engulfment of neuronal debris. Our results indicate that a rather simple notion of treating excessive inflammation in the CNS by NO synthesis blocking agents has to consider functionally antagonistic microglial cell responses during pharmaceutic therapy.