Anti-inflammatory mechanisms of N-adamantyl-4-methylthiazol-2-amine in lipopolysaccharide-stimulated BV-2 microglial cells

Irisin Attenuates Neuroinflammation Targeting the NLRP3 Inflammasome

Neuroinflammation is defined as an immune response involving various cell types, particularly microglia, which monitor the neuroimmune axis. Microglia activate in two distinct ways: M1, which is pro-inflammatory and capable of inducing phagocytosis and releasing pro-inflammatory factors, and M2, which has anti-inflammatory properties. Inflammasomes are large protein complexes that form in response to internal danger signals, activating caspase-1 and leading to the release of pro-inflammatory cytokines such as interleukin 1β. Irisin, a peptide primarily released by muscles during exercise, was examined for its effects on BV2 microglial cells in vitro. Even at low concentrations, irisin was observed to influence the NLRP3 inflammasome, showing potential as a neuroprotective and anti-inflammatory agent after stimulation with lipopolysaccharides (LPSs). Irisin helped maintain microglia in their typical physiological state and reduced their migratory capacity. Irisin also increased Arg-1 protein expression, a marker of M2 polarization, while downregulating NLRP3, Pycard, caspase-1, IL-1β, and CD14. The results of this study indicate that irisin may serve as a crucial mediator of neuroprotection, thus representing an innovative tool for the prevention of neurodegenerative diseases.

LC-QToF chemical profiling of Euphorbia grantii Oliv. and its potential to inhibit LPS-induced lung inflammation in rats via the NF-κB, CY450P2E1, and P38 MAPK14 pathways

Acute lung injury (ALI) is a life-threatening syndrome that causes high morbidity and mortality worldwide. The aerial parts of Euphorbia grantii Oliv. were extracted with methanol to give a total methanolic extract (TME), which was further fractionated into dichloromethane (DCMF) and the remaining mother liquor (MLF) fractions. Biological guided anti-inflammatory assays in vitro revealed that the DCMF showed the highest activity (IC50 6.9 ± 0.2 μg/mL and 0.29 ± 0.01 μg/mL) compared to. celecoxib (IC50 of 88.0 ± 1 μg/mL and 0.30 ± 0.01 μg/mL) on COX-1 and COX-2, respectively. Additionally, anti-LOX activity was IC50 = 24.0 ± 2.5 μg/mL vs. zileuton with IC50 of 40.0 ± 0.5 μg/mL. LC-DAD-QToF analysis of TME and the active DCMF resulted in the tentative identification and characterization of 56 phytochemical compounds, where the diterpenes were the dominated metabolites. An LPS-induced inflammatory model of ALI (10 mg/kg i.p) was used to assess the anti-inflammatory potential of DCMF in vivo at dose of 200 mg/kg and 300 mg/kg compared to dexamethasone (5 mg/kg i.p). Our treatments significantly reduced the pro-inflammatory cytokines (TNF-α, IL-1, IL-6, and MPO), increased the activity of antioxidant enzymes (SOD, CAT, and GSH), decreased the activity of oxidative stress enzyme (MDA), and reduced the expression of inflammatory genes (p38.MAPK14 and CY450P2E1). The western blotting of NF-κB p65 in lung tissues was inhibited after orally administration of the DCMF. Histopathological study of the lung tissues, scoring, and immunohistochemistry of transforming growth factor-beta 1 (TGF-β1) were also assessed. In both dose regimens, DCMF of E. grantii prevented further lung damage and reduced the side effects of LPS on acute lung tissue injury.

A2BR facilitates the pathogenesis of H. pylori-associated GU by inducing oxidative stress through p38 MAPK phosphorylation

Gastric ulcers significantly impact the quality of life of patients, the pathogenesis of which is closely associated with Helicobacter pylori (HP) infection. Oxidative stress is involved in the pathological mechanism of gastric ulcers. Recently, adenosine A2B Receptor (A2BR) was reported to activate the p38MAPK pathway. However, the role of A2BR in gastric ulcers remains unknown. In the present study, the biological function of A2BR in HP-induced gastric ulcers was investigated to explore novel targets for gastric ulcers. GES-1 cells were infected with HP, followed by incubation with 10 μM BAY60-6583 (A2BR agonist) and 25 nM PSB1115 (A2BR antagonist). In HP-infected GES-1 cells, an increased apoptotic rate, enhanced migration ability, excessive release of reactive oxygen species (ROS), increased malondialdehyde (MDA) levels, and decreased superoxide dismutase (SOD) activity were observed, accompanied by the activation of p38MAPK signaling, which were dramatically aggravated by BAY60-6583 and alleviated by PSB1115. In animal experiments, rats were treated with 2 mg/kg BAY60-6583 and 10 mg/kg PSB1115, followed by gastric ulcer modeling 30 min later. In HP-infected rats, increased ulcer area, elevated pepsin activity, increased hematoxylin and eosin (HE) pathological scores, increased MDA levels, and decreased SOD activity were observed, which were further aggravated by BAY60-6583 and ameliorated by PSB1115. Finally, the effects of A2BR activation on apoptosis, migration, oxidative stress, and p38MAPK signaling in HP-infected GES-1 cells were reversed by an inhibitor of the p38MAPK pathway. Collectively, A2BR facilitated the pathogenesis of HP-induced gastric ulcers by inducing oxidative stress through p38MAPK activation.

Nicotinamide Mononucleotide Attenuates LPS-Induced Acute Lung Injury With Anti-Inflammatory, Anti-Oxidative and Anti-Apoptotic Effects

INTRODUCTION

Nicotinamide mononucleotide (NMN) is a nucleotide that is commonly recognized for its role as an intermediate of nicotinamide adenine dinucleotide (NAD⁺) biosynthesis with multiple pharmacological effects. The purpose of this study was to evaluate the protective effect of nicotinamide mononucleotide (NMN) against lipopolysaccharide (LPS)-induced acute lung injury (ALI).

METHODS

We investigated the effect of NMN on ALI-induced inflammatory response, oxidative stress, and cell apoptosis. The ALI mouse model was performed by injecting LPS intratracheally at a dose of 10 mg/kg in 50 μL saline. Flow cytometry was used to detect neutrophil infiltration in bronchoalveolar lavage fluid (BALF), and ELISA was used to detect the contents of inflammatory cytokines TNF-α, IL-1β and IL-6 in BALF. Oxidative stress was evaluated by determining the superoxide dismutase (SOD) activity and malondialdehyde (MDA) content in lung tissue. ROS formation was analyzed by immunofluorescence. Western blotting was performed to detect apoptotic levels and p38MAPK/NF-κB phosphorylation levels in lung tissue.

RESULTS

In the ALI mouse model, NMN showed a significant therapeutic effect compared to the LPS group. NMN attenuated the pathological damage and cell apoptosis in lung tissue, decreased the levels of TNF-α, IL-1β, and IL-6 in BALF, and reduced the number of total cells and neutrophils in BALF. In addition, NMN attenuated the LPS-induced elevation of dry-to-wet ratio, MDA content, p38 MAPK and p65 NF-κB phosphorylation levels, and the SOD activity was increased by NMN treatment.

CONCLUSIONS

In conclusion, the present study showed that NMN exerted a protective effect on LPS-induced ALI with anti-inflammatory, antioxidative, and antiapoptotic effects.

Anti-inflammatory effects of N-cyclooctyl-5-methylthiazol-2-amine hydrobromide on lipopolysaccharide-induced inflammatory response through attenuation of NLRP3 activation in microglial cells

Microglial activation is closely associated with neuroinflammatory pathologies. The nucleotide-binding and oligomerization domain-like receptor containing a pyrin domain 3 (NLRP3) inflammasomes are highly organized intracellular sensors of neuronal alarm signaling. NLRP3 inflammasomes activate nuclear factor kappa-B (NF-κB) and reactive oxygen species (ROS), which induce inflammatory responses. Moreover, NLRP3 dysfunction is a common feature of chronic inflammatory diseases. The present study investigated the effect of a novel thiazol derivative, N-cyclooctyl-5-methylthiazol-2-amine hydrobromide (KHG26700), on inflammatory responses in lipopolysaccharide (LPS)-treated BV-2 microglial cells. KHG26700 significantly attenuated the expression of several pro-inflammatory cytokines, including tumor necrosis factor-α, interleukin-1β, and interleukin-6, in these cells, as well as the LPS-induced increases in NLRP3, NF-κB, and phospho-IkBα levels. KHG26700 also suppressed the LPS-induced increases in protein levels of autophagy protein 5 (ATG5), microtubule-associated protein 1 light chain 3 (LC3), and beclin-1, as well as downregulating the LPS-enhanced levels of ROS, lipid peroxidation, and nitric oxide. These results suggest that the anti-inflammatory effects of KHG26700 may be due, at least in part, to the regulation of the NLRP3-mediated signaling pathway during microglial activation.

Ficus deltoidea: Potential inhibitor of pro-inflammatory mediators in lipopolysaccharide-induced activation of microglial cells

ETHNOPHARMACOLOGICAL RELEVANCE

Ficus deltoidea Jack (FD) is widely consumed in traditional medicine as a treatment for various diseases in Malaysia. Each part of the plant such as its leave, stem, fruit and root are used traditionally to treat different types of diseases. Vitexin and isovitexin are bioactive compounds abundantly found in the leaves of FD that possessed many pharmacological properties including neuroprotection. Nonetheless, its effects on key events in neuroinflammation are unknown.

AIM OF THE STUDY

To determine the inhibitory properties of FD aqueous extract on pro-inflammatory mediators involved in lipopolysaccharide (LPS)-induced microglial cells.

METHODS

Vitexin and isovitexin in the extract were quantified via high performance liquid chromatography (HPLC). The extract was evaluated for its cytotoxicity activity via 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. Pre-treatment with the extract on LPS-induced microglial cells was done to determine its antioxidant and anti-neuroinflammatory properties by measuring the level of reactive oxygen species (ROS), nitric oxide (NO), tumour necrosis factor alpha (TNF-α), interleukin-1β (IL-1β) and interleukin-6 (IL-6) via 2'-7'-dichlorofluorescin diacetate (DCFDA) assay, Griess assay and Western blot respectively.

RESULTS

The extract at all tested concentrations (0.1 μg/mL, 1 μg/mL, 10 μg/mL, 100 μg/mL) were not cytotoxic as the percentage viability of microglial cells were all above ~80%. At the highest concentration (100 μg/mL), the extract significantly reduced the formation of ROS, NO, TNF-α, IL-1β and IL-6 in microglial cells induced by LPS.

CONCLUSION

The extract showed neuroprotective effects by attenuating the levels of pro-inflammatory and cytotoxic factors in LPS-induced microglial cells, possibly by mediating the nuclear factor-kappa B (NF-κB) signalling pathway.

Protective effects of sulfated polysaccharides from Lentinula edodes on the lung and liver of MODS mice

In this work, the effects of sulfated polysaccharides from Lentinula edodes (SPLE) on zymosan (ZYM)-induced multiple organ dysfunction syndrome (MODS) mice were investigated. Using the MODS mice model, biochemical works have already shown that in mice treated with SPLE, the lung parameters of GGT, C3 and hs-CRP were down-regulated and the hepatic parameters of TC, TG, ALT and AST, HDLC, LDL-C and VLDL-C were improved, the serum levels of CK, Cr and Amy were decreased, and the levels of inflammatory factors such as TNF-α, IL-1β, IL-6 and IL-10 were also reduced, the activity of antioxidant enzymes SOD and CAT enhanced, and the content of MDA was reduced. In addition, histopathology of the lung and liver confirmed the beneficial effects of SPLE on MODS mice, indicating that SPLE played a role in protecting the organ function of MODS mice. In addition, SPLE was characterized as a sulfated β-glucan linked by β-type glycosidic bonds. These conclusions indicated that SPLE had effective antioxidant and anti-inflammatory activities, and could be used as a functional food and medicine to prevent MODS.

N-Adamantyl-4-methylthiazol-2-amine suppresses glutamate-induced autophagic cell death via PI3K/Akt/mTOR signaling pathways in cortical neurons

We recently reported that N-adamantyl-4-methylthiazol-2-amine (KHG26693) attenuates glutamate-induced oxidative stress and inflammation in the brain. In this study, we investigated KHG 26693 as a therapeutic agent against glutamate-induced autophagic death of cortical neurons. Treatment with KHG26693 alone did not affect the viability of cultured cortical neurons but was protective against glutamate-induced cytotoxicity in a concentration-dependent manner. KHG26693 attenuated the glutamate-induced increase in protein levels of LC3, beclin-1, and p62. Whereas glutamate decreased the phosphorylation of PI3K, Akt, and mTOR, these levels were restored by treatment with KHG26693. These results suggest that KHG26693 inhibits glutamate-induced autophagy by regulating PI3K/Akt/mTOR signaling. Finally, KHG26693 treatment also attenuated glutamate-induced increases in reactive oxygen species, glutathione, glutathione peroxidase, and superoxide dismutase levels in cortical neurons, indicating that KHG26693 also protects cortical neurons against glutamate-induced autophagy by regulating the reactive oxygen species scavenging system.

Beta-naphthoflavone inhibits LPS-induced inflammation in BV-2 cells via AKT/Nrf-2/HO-1-NF-κB signaling axis

Numerous studies have shown that over-activation of microglia could cause neuroinflammation and release pro-inflammatory mediators, which could result in neurodegenerative diseases, like Parkinson's disease, Alzheimer's disease etc. Beta-naphthoflavone (BNF) has anti-oxidant and anti-inflammatory effects in borderline tissues, but BNF has not been reported the effect associated with neuroinflammation. Therefore, the purpose of this experiment is to inquiry the impact and mechanism of BNF on neuroinflammation. The results indicated that BNF significantly inhibited the production of pro-inflammatory mediators (inducible nitric-oxide synthase (iNOS), Cyclooxygenase-2 (COX-2), tumor necrosis factor-α (TNF-α) andinterleukin-6 (IL-6)) in LPS-exposed BV-2 cells. Analysis of western blot results found that BNF accelerated the activation of AKT/Nrf-2/HO-1 signaling pathway and suppressed NF-κB pathway activation. Further study showed that BNF inhibited activation of NF-κB pathway via promoting HO-1, and SnPP IX (a HO-1 inhibitor) could inhibit anti-inflammatory function of BNF. We also found that BNF reduced the apoptosis rate of Human neuroblastoma cells (SHSY5Y) and mouse hippocampal neuron cell line (HT22) by inhibiting release of inflammatory mediators in LPS-exposed BV2 cells. In a word, our results suggested that BNF could inhibit inflammatory response via AKT/Nrf-2/HO-1-NF-κB signaling axis in BV-2 cells and exerts neuroprotective impact via inhibiting the activation of BV2 cells.

Effects of α-lipoic acid on LPS-induced neuroinflammation and NLRP3 inflammasome activation through the regulation of BV-2 microglial cells activation

Microglial cells are known as the main immune cells in the central nervous system, both regulating its immune response and maintaining its homeostasis. Furthermore, the antioxidant α-lipoic acid (LA) is a recognized therapeutic drug for diabetes because it can easily invade the blood–brain barrier. This study investigated the effect of α-LA on the inflammatory response in lipopolysaccharide (LPS)-treated BV-2 microglial cells. Our results revealed that α-LA significantly attenuated several inflammatory responses in BV-2 microglial cells, including pro-inflammatory cytokines, such as tumor necrosis factor-α and interleukin (IL)-6, and other cytotoxic molecules, such as nitric oxide and reactive oxygen species. In addition, α-LA inhibited the LPS-induced phosphorylation of ERK and p38 and its pharmacological properties were facilitated via the inhibition of the nuclear factor kappa B signaling pathway. Moreover, α-LA suppressed the activation of NOD-like receptor pyrin domain containing 3 (NLRP3) inflammasomes, multiprotein complexes consisting of NLRP3 and caspase-1, which are involved in the innate immune response. Finally, α-LA decreased the genes accountable for the M1 phenotype, IL-1β and ICAM1, whereas it increased the genes responsible for the M2 phenotype, MRC1 and ARG1. These findings suggest that α-LA alleviates the neuroinflammatory response by regulating microglial polarization.

The roles played by TLR4 in the pathogenesis of multiple sclerosis; A systematic review article

Multiple sclerosis (MS) is a world-wide pro-inflammatory based disease, which is prevalent among young individuals. The etiology of the disease and its related complications are yet to be clarified. It has been hypothesized that environmental factors, including pathogen-associated molecular patterns (PAMPs) and the internal factors such as damage-associated molecular patterns (DAMPs), may be the most important inducers/stimulators of the disorder and its related complications. Previous investigations proved that pathogen recognition receptors (PRRs) are the main sensors for the PAMPs and DAMPs. Therefore, it seems that the PRRs have been considered to be the plausible molecules participating in the etiology of MS. Toll-like receptors (TLRs) have been the widely studied PRRs and their roles have been documented in human-related diseases. TLR4 is the main PRR expressed on the cell surface of several immune cells including macrophages and dendritic cells. Several investigations reported that TLR4 to be the main molecule involved in the pathogenesis of pro-inflammatory based diseases. Thus, it has been hypothesized that TLR4 may be a part of the MS puzzle. This review article discusses the role of TLR4 in the MS pathogenesis using recent in vitro and in vivo investigations.

Effects of α-lipoic acid on LPS-induced neuroinflammation and NLRP3 inflammasome activation through the regulation of BV-2 microglial cells activation

Microglial cells are known as the main immune cells in the central nervous system, both regulating its immune response and maintaining its homeostasis. Furthermore, the antioxidant α-lipoic acid (LA) is a recognized therapeutic drug for diabetes because it can easily invade the blood-brain barrier. This study investigated the effect of α-LA on the inflammatory response in lipopolysaccharide (LPS)-treated BV-2 microglial cells. Our results revealed that α-LA significantly attenuated several inflammatory responses in BV-2 microglial cells, including pro-inflammatory cytokines, such as tumor necrosis factor-α and interleukin (IL)-6, and other cytotoxic molecules, such as nitric oxide and reactive oxygen species. In addition, α-LA inhibited the LPS-induced phosphorylation of ERK and p38 and its pharmacological properties were facilitated via the inhibition of the nuclear factor kappa B signaling pathway. Moreover, α-LA suppressed the activation of NOD-like receptor pyrin domain containing 3 (NLRP3) inflammasomes, multiprotein complexes consisting of NLRP3 and caspase-1, which are involved in the innate immune response. Finally, α-LA decreased the genes accountable for the M1 phenotype, IL-1β and ICAM1, whereas it increased the genes responsible for the M2 phenotype, MRC1 and ARG1. These findings suggest that α-LA alleviates the neuroinflammatory response by regulating microglial polarization. [BMB Reports 2019; 52(10): 613-618].

Piperlongumine Improves Lipopolysaccharide-Induced Amyloidogenesis by Suppressing NF-KappaB Pathway

Amyloidogenesis is known to cause Alzheimer's disease. Our previous studies have found that lipopolysaccharide (LPS) causes neuroinflammation and amyloidogenesis through activation of nuclear factor kappaB (NF-κB). Piperlongumine (PL) is an alkaloid amide found naturally in long pepper (Piper longum) isolates; it was reported to have inhibitory effects on NF-κB activity. We therefore investigated whether PL exhibits anti-inflammatory and anti-amyloidogenic effects by inhibiting NF-κB. A murine model of LPS-induced memory impairment was made via the intraperitoneal (i.p.) injection of LPS (0.25 mg/kg/day, i.p.). We then injected PL (1.5 or 3.0 mg/kg/day, i.p.) for 7 days in three groups of mice to observe effects on memory. We also conducted an in vitro study with astrocytes and microglial BV-2 cells, which were treated with LPS (1 µg/mL) or PL (0.5 or 1.0 or 2.5 µM). Results from our behavioral tests showed that PL inhibited LPS-induced memory. PL also prevented LPS-induced beta-amyloid (Aβ) accumulation and inhibited the activities of β- and γ-secretases. The expression of inflammatory proteins also was decreased in PL-treated mice, cultured BV-2, and primary astrocyte cells. These effects were associated with the inhibition of NF-κB activity. A docking model analysis and pull-down assay showed that PL binds to p50. Taken together, our findings suggest that PL diminishes LPS-induced amyloidogenesis and neuroinflammation by inhibiting NF-κB signaling; PL therefore demonstrates potential for the treatment of Alzheimer's disease.

The Liver Protection Effects of Maltol, a Flavoring Agent, on Carbon Tetrachloride-Induced Acute Liver Injury in Mice via Inhibiting Apoptosis and Inflammatory Response

The purpose of this research was to evaluate whether maltol could protect from hepatic injury induced by carbon tetrachloride (CCl₄) in vivo by inhibition of apoptosis and inflammatory responses. In this work, maltol was administered at a level of 100 mg/kg for 15 days prior to exposure to a single injection of CCl₄ (0.25%, i.p.). The results clearly indicated that the intrapulmonary injection of CCl₄ resulted in a sharp increase in serum aspartate transaminase (AST) and alanine transaminase (ALT) activities, tumor necrosis factor-α (TNF-α), irreducible nitric oxide synthase (iNOS), nuclear factor-kappa B (NF-κB) and interleukin-1β (IL-1β) levels. Histopathological examination demonstrated severe hepatocyte necrosis and the destruction of architecture in liver lesions. Immunohistochemical staining and western blot analysis suggested an accumulation of iNOS, NF-κB, IL-1β and TNF-α expression. Maltol, when administered to mice for 15 days, can significantly improve these deleterious changes. In addition, TUNEL and Hoechst 33258 staining showed that a liver cell nucleus of a model group diffused uniform fluorescence following CCl₄ injection. Maltol pretreatment groups did not show significant cell nuclear condensation and fragmentation, indicating that maltol inhibited CCl₄-induced cell apoptosis. By evaluating the liver catalase (CAT), glutathione (GSH), superoxide dismutase (SOD) activity, and further using a single agent to evaluate the oxidative stress in CCl₄-induced hepatotoxicity by immunofluorescence staining, maltol dramatically attenuated the reduction levels of hepatic CAT, GSH and SOD, and the over-expression levels of CYP2E1 and HO-1. In the mouse model of CCl₄-induced liver injury, we have demonstrated that the inflammatory responses were inhibited, the serum levels of ALT and AST were reduced, cell apoptosis was suppressed, and liver injury caused by CCl₄ was alleviated by maltol, demonstrating that maltol may be an efficient hepatoprotective agent.

The Anti-neuroinflammatory Activity of Tectorigenin Pretreatment via Downregulated NF-κB and ERK/JNK Pathways in BV-2 Microglial and Microglia Inactivation in Mice With Lipopolysaccharide

The activation of microglia is decisively involved with the neurodegeneration observed in many neuroinflammatory pathologies, such as multiple sclerosis, Parkinson’s disease, and Alzheimer’s disease. Tectorigenin (TEC) is an isoflavone isolated from various medicinal plants, such as Pueraria thunbergiana Benth, Belamcanda chinensis, and Iris unguicularis. In the present study, the neuroinflammatory effects of TEC were evaluated in both lipopolysaccharide (LPS)-treated BV-2 microglial and mouse models. TEC remarkably inhibited reactive oxygen species (ROS) generation. TEC also inhibits the production and expression of nitric oxide (NO), prostaglandin E₂ (PGE₂), tumor necrosis factor-α (TNF-α), and interleukin-6 (IL-6) in LPS-stimulated BV-2 cells. In addition, TEC suppressed the LPS-induced activation of nuclear factor-κB (NF-κB), phosphorylation of extracellular signal-regulated kinase (ERK), and c-Jun N-terminal kinase (JNK) to regulate the inflammatory mediators, such as inducible NO synthase (iNOS), cyclooxygenase-2 (COX-2), TNF-α, and IL-6. These results indicate that TEC may inhibit neuronal inflammation through the downregulation of inflammatory mediators, including iNOS, COX-2, TNF-α, and IL-6 by suppressing NF-κB/ERK/JNK-related signaling pathways. Furthermore, cotreatment with TEC and ERK inhibitor SCH772984 or JNK inhibitor SP600125 suppressed the overproduction of LPS-induced NO production in BV-2 cells. Consistent with the results of in vitro experiments, an LPS-induced brain inflammation mouse model, administration of TEC effectively decrease the levels of malondialdehyde, iNOS in hippocampus, and prevented increases in the levels of TNF-α and IL-6 in the serum. TEC showed marked attenuation of microglial activation. Finally, TEC inhibited protein expression of toll-like receptor 4 and myeloid differentiation factor 88 in LPS-activated BV-2 microglia and mouse models. Taken altogether, the cumulative findings suggested that TEC holds the potential to develop as a neuroprotective drug for the intervention of neuroinflammatory disorders.

Pristimerin Inhibits LPS-Triggered Neurotoxicity in BV-2 Microglia Cells Through Modulating IRAK1/TRAF6/TAK1-Mediated NF-κB and AP-1 Signaling Pathways In Vitro

Microglia plays a prominent role in the brain's inflammatory response to injury or infection by migrating to affected locations and secreting inflammatory molecules. However, hyperactivated microglial is neurotoxic and plays critical roles in the pathogenesis of neurodegenerative diseases. Pristimerin, a naturally occurring triterpenoid, possesses antitumor, antioxidant, and anti-inflammatory activities. However, the effect and the molecular mechanism of pristimerin against lipopolysaccharide (LPS)-induced neurotoxicity in microglia remain to be revealed. In the present study, using BV-2 microglial cultures, we investigated whether pristimerin modifies neurotoxicity after LPS stimulation and which intracellular pathways are involved in the effect of pristimerin. Here we show that pristimerin markedly suppressed the release of Regulated on Activation, Normal T Expressed and Secreted (RANTES), transforming growth factor-β1 (TGF-β1), IL-6, tumor necrosis factor-α (TNF-α), and nitric oxide (NO). Pristimerin also significantly inhibited migration of BV-2 microglia and alleviated the death of neuron-like PC12 cell induced by the conditioned medium from LPS-activated BV-2 microglial cells. Moreover, pristimerin reduced the expression and interaction of TNF Receptor-Associated Factor 6 (TRAF6) and Interleukin-1 Receptor-Associated Kinases (IRAK1), limiting TGF-beta activating kinase 1 (TAK1) activation, and resulting in an inhibition of IKKα/β/NF-κB and MKK7/JNK/AP-1 signaling pathway in LPS-activated BV-2 microglia. Taken together, the anti-neurotoxicity action of pristimerin is mediated through the inhibition of TRAF6/IRAK1/TAK1 interaction as well as the related pathways: IKKα/β/NF-κB and MKK7/JNK/AP-1 signaling pathways. These findings may suggest that pristimerin might serve as a new therapeutic agent for treating hyperactivated microglial induced neurodegenerative diseases.

N-Adamantyl-4-Methylthiazol-2-Amine Attenuates Glutamate-Induced Oxidative Stress and Inflammation in the Brain

In this study, we explored the possible mechanisms underlying the neuroprotective and anti-oxidative effects of N-adamantyl-4-methylthiazol-2-amine (KHG26693) against in vivo glutamate-induced toxicity in the rat cerebral cortex. Our results showed that pretreatment with KHG26693 significantly attenuated glutamate-induced elevation of lipid peroxidation, tumor necrosis factor-α, interferon gamma, IFN-γ, interleukin-1β, nitric oxide, reactive oxygen species, NADPH oxidase, caspase-3, calpain activity, and Bax. Furthermore, KHG26693 pretreatment attenuated key antioxidant parameters such as levels of superoxide dismutase, catalase, glutathione, and glutathione reductase. KHG26693 also attenuated the protein levels of inducible nitric oxide synthase, neuronal nitric oxide synthase, nuclear factor erythroid 2-related factor 2, heme oxygenase-1, and glutamate cysteine ligase catalytic subunit caused by glutamate toxicity. Finally, KHG26693 mitigated glutamate-induced changes in mitochondrial ATP level and cytochrome oxidase c. Thus, KHG26693 functions as neuroprotective and anti-oxidative agent against glutamate-induced toxicity through its antioxidant and anti-inflammatory activities in rat brain at least in part.

TLR4 is a link between diabetes and Alzheimer's disease

Recently, more and more studies have shown that there is an essential link between diabetes mellitus (DM) and Alzheimer's disease (AD). In addition, innate immunity plays an important role in the occurrence and development of DM and AD, which increase the risk of developing type 2 diabetes (T2D) and AD. Although the pathogenesis of those diseases is still a matter of debate, the important role of Toll-like receptor 4 (TLR4) in the two diseases has been receiving much attention at present. TLR4 and insulin resistance do have close ties, and chronic TLR4 activation may contribute to the insulin resistance. Aside from this, TLR4-mediated chronic inflammation also causes many DM complications such as diabetic nephropathy, diabetic retinopathy and diabetic neuropathy and has a profound impact on the internal environment of the body and brain's microenvironment. In parallel, TLR4 is widely distributed in the brain and also has an important role in the central nervous system (CNS) via regulation of neuroinflammation. The cerebrum under the circumstances of insulin resistance may lead to mitochondrial dysfunction in neurons. Interestingly, in the initial stage, the activation of TLR4 has a useful scavenging effect on amyloid beta (Aβ), but chronic long-term activation leads to Aβ deposition in the brain. Therefore we speculate that the TLR4 signaling pathway may be a potential link between DM and AD.

Tat-PRAS40 prevent hippocampal HT-22 cell death and oxidative stress induced animal brain ischemic insults

Proline rich Akt substrate (PRAS40) is a component of mammalian target of rapamycin complex 1 (mTORC1) and is known to play an important role against reactive oxygen species-induced cell death. However, the precise function of PRAS40 in ischemia remains unclear. Thus, we investigated whether Tat-PRAS40, a cell-permeable fusion protein, has a protective function against oxidative stress-induced hippocampal neuronal (HT-22) cell death in an animal model of ischemia. We showed that Tat-PRAS40 transduced into HT-22 cells, and significantly protected against cell death by reducing the levels of H2O2 and derived reactive species, and DNA fragmentation as well as via the regulation of Bcl-2, Bax, and caspase 3 expression levels in H2O2 treated cells. Also, we showed that transduced Tat-PARS40 protein markedly increased phosphorylated RRAS40 expression levels and 14-3-3σ complex via the Akt signaling pathway. In an animal ischemia model, Tat-PRAS40 effectively transduced into the hippocampus in animal brain and significantly protected against neuronal cell death in the CA1 region. We showed that Tat-PRAS40 protein effectively transduced into hippocampal neuronal cells and markedly protected against neuronal cell damage. Therefore, we suggest that Tat-PRAS40 protein may be used as a therapeutic protein for ischemia and oxidative stress-induced brain disorders.

N-Adamantyl-4-methylthiazol-2-amine suppresses amyloid β-induced neuronal oxidative damage in cortical neurons

Recently, we have reported that N-adamantyl-4-methylthiazol-2-amine (KHG26693) successfully reduced the production of oxidative stress in streptozotocin-induced diabetic rats and lipopolysaccharide-induced BV-2 microglial cells by increasing their antioxidant capacity. However, antioxidative effects of KHG26693 against Aβ (Aβ)-induced oxidative stress have not yet been reported. In the present study, we further investigated the antioxidative function of KHG26693 in Aβ-mediated primary cultured cortical neurons. We showed here that KHG26693 attenuated Aβ-induced cytotoxicity, increase of Bax/Bcl-2 ratio, elevation of caspase-3 expression, and impairment of mitochondrial membrane potential in cultured primary cortical neurons. KHG26693 also decreases the Aβ-mediated formation of malondialdehyde, reactive oxygen species, and NO production by decreasing nitric oxide synthase (iNOS) and NADPH oxidase level. Moreover, KHG26693 suppress the Aβ-induced oxidative stress through a possible mechanism involving attenuation of GSH and antioxidant enzyme activities such as glutathione reductase and glutathione peroxidase (GPx). Finally, pretreatment of cortical neurons with KHG26693 significantly reduced the Aβ-induced protein oxidation and nitration. To our knowledge, this is the first report, showing that KHG26693 significantly attenuates Aβ-induced oxidative stress in primary cortical neurons, and may prove attractive strategies to reduce Aβ-induced neural cell death.

The ethyl acetate fraction from Physalis alkekengi inhibits LPS-induced pro-inflammatory mediators in BV2 cells and inflammatory pain in mice

ETHNOPHARMACOLOGICAL RELEVANCE

Physalis alkekengi is an edible herb whose fruit and calyx are traditionally used to treat a wide range of diseases including inflammation, toothache, and rheumatism. However, the effects of Physalis alkekengi fruit along with its calyx (PAF) on neuroinflammation and inflammatory pain behavior have not been reported yet.

AIM OF THE STUDY

This study evaluated the anti-inflammatory effect of PAF on lipopolysaccharide (LPS)-induced neuroinflammation and several in vivo model of inflammatory pain in mice.

MATERIALS AND METHODS

Here, first we studied the effects of PAF fractions on the production of pro-inflammatory mediators in LPS-treated BV2 microglial cells using enzyme-linked immunosorbent assay. The translocation of nuclear factor-kappa B (NF-κB) and the involvements of Akt and mitogen-activated protein (MAP) kinases in ethyl acetate fraction of PAF (PAF-EA)-mediated anti-inflammatory effect were measured using Western blotting. In in vivo experiments, the efficacy of PAF-EA was evaluated at the doses of 100 and 200mg/kg using several chemical-induced models of inflammatory pain such as acetic acid-induced writhing, formalin-induced paw licking and edema.

RESULTS

We found that compared to other fractions, the PAF-EA more potently inhibited the LPS-induced generation of nitric oxide, tumor necrosis factor-α, interleukin-6 and reactive oxygen species. It also inhibited LPS-induced nuclear translocation of NF-κB. These actions of EA fraction were found to be associated with a disruption of Akt and MAP kinases signaling pathways. The EA fraction also significantly inhibited acetic acid-induced writhing, formalin-induced licking time and edema in mice.

CONCLUSIONS

Our findings support the ethnopharmacological use of P. alkekengi fruit along with its calyx as an anti-inflammatory agent and suggest that the EA fraction of PAF may serve as a potential candidate to treat different neurological disorders and pain associated with inflammation.

Characterization of a novel adult murine immortalized microglial cell line and its activation by amyloid-beta

BACKGROUND

Alzheimer's disease is associated with amyloid-beta (Aβ)-induced microglia activation. This pro-inflammatory response promotes neuronal damage, and therapies are sought to limit microglial activation. Screening efforts to develop new pharmacological inhibitors require a robust in vitro cell system. Current models lack significant responses to Aβ, and their use in examining age-related neurodegenerative diseases is questionable. For example, the commonly used BV-2 microglial line was derived from embryonic mononuclear cells and its activation by various stimuli is limited. To this end, we have established a new immortalized microglial (IMG) cell line from adult murine brain. The objective of this study was to characterize Aβ-induced activation of IMG cells, and here, we demonstrate the ability of cannabinoids to significantly reduce this inflammatory response.

METHODS

Microglial cells derived from adult murine brain were immortalized via infection with the v-raf/v-myc retrovirus under conditions that selectively promote microglia growth. The presence or absence of markers CD11b and F4/80 (microglial), NeuN (neuronal), and GFAP (astrocytic) was assessed by immunofluorescence microscopy and western blotting. Using IMG and BV-2 cells, levels of pro- and anti-inflammatory transcripts in response to extracellular stimuli were determined by quantitative PCR (qPCR). Phagocytosis of fluorescent beads and fluorescein isothiocyanate (FITC)-labeled Aβ oligomers was assessed using flow cytometry and fluorescence microscopy. FITC-Aβ uptake was quantified using a fluorescence plate reader. The ability of cannabinoids to mitigate Aβ-induced expression of inducible nitric oxide synthase (iNOS) was evaluated.

RESULTS

IMG cells express the microglial markers CD11b and F4/80 but not NeuN or GFAP. Relative to BV-2 cells, IMG cells increased iNOS (>200-fold) and Arg-1 (>100-fold) in response to pro- and anti-inflammatory stimuli. IMG cells phagocytose foreign particles and Aβ oligomers, with the latter trafficked to phagolysosomes. Aβ-induced activation of IMG cells was suppressed by delta-9-tetrahydrocannabinol and the CB2-selective agonist JWH-015 in a time- and concentration-dependent manner.

CONCLUSIONS

IMG cells recapitulate key features of microglial cell activation. As an example of their potential pharmacological use, cannabinoids were shown to reduce activation of Aβ-induced iNOS gene expression. IMG cells hold promising potential for drug screening, mechanistic studies, and functional investigations directed towards understanding how Aβ interacts with microglia.

Anti-inflammatory effects and antioxidant activity of dihydroasparagusic acid in lipopolysaccharide-activated microglial cells

The activation of microglia and subsequent release of toxic pro-inflammatory factors are crucially associated with neurodegenerative disease, characterized by increased oxidative stress and neuroinflammation, including Alzheimer and Parkinson diseases and multiple sclerosis. Dihydroasparagusic acid is the reduced form of asparagusic acid, a sulfur-containing flavor component produced by Asparagus plants. It has two thiolic functions able to coordinate the metal ions, and a carboxylic moiety, a polar function, which may enhance excretion of the complexes. Thiol functions are also present in several biomolecules with important physiological antioxidant role as glutathione. The aim of this study is to evaluate the anti-inflammatory and antioxidant potential effect of dihydroasparagusic acid on microglial activation in an in vitro model of neuroinflammation. We have used lipopolysaccharide to induce an inflammatory response in primary rat microglial cultures. Our results suggest that dihydroasparagusic acid significantly prevented lipopolysaccharide-induced production of pro-inflammatory and neurotoxic mediators such as nitric oxide, tumor necrosis factor-α, prostaglandin E2, as well as inducible nitric oxide synthase and cyclooxygenase-2 protein expression and lipoxygenase activity in microglia cells. Moreover it effectively suppressed the level of reactive oxygen species and affected lipopolysaccharide-stimulated activation of mitogen activated protein kinase, including p38, and nuclear factor-kB pathway. These results suggest that dihydroasparagusic acid's neuroprotective properties may be due to its ability to dampen induction of microglial activation. It is a compound that can effectively inhibit inflammatory and oxidative processes that are important factors of the etiopathogenesis of neurodegenerative diseases.

The azetidine derivative, KHG26792 protects against ATP-induced activation of NFAT and MAPK pathways through P2X7 receptor in microglia

Azetidine derivatives are of interest for drug development because they may be useful therapeutic agents. However, their mechanisms of action remain to be completely elucidated. Here, we have investigated the effects of 3-(naphthalen-2-yl(propoxy)methyl)azetidine hydrochloride (KHG26792) on ATP-induced activation of NFAT and MAPK through P2X7 receptor in the BV-2 mouse microglial cell line. KHG26792 decreased ATP-induced TNF-α release from BV-2 microglia by suppressing, at least partly, P2X7 receptor stimulation. KHG26792 also inhibited the ATP-induced increase in IL-6, PGE2, NO, ROS, CXCL2, and CCL3. ATP induced NFAT activation through P2X7 receptor, with KHG26792 reducing the ATP-induced NFAT activation. KHG26792 inhibited an ATP-induced increase in iNOS protein and ERK phosphorylation. KHG26792 prevented an ATP-induced increase in MMP-9 activity through the P2X7 receptor as a result of degradation of TIMP-1 by cathepsin B. Our data provide mechanistic insights into the role of KHG26792 in the inhibition of TNF-α produced via P2X7 receptor-mediated activation of NFAT and MAPK pathways in ATP-treated BV-2 cells. This study highlights the potential use of KHG26792 as a therapeutic agent for the many diseases of the CNS related to activated microglia.

N-adamantyl-4-methylthiazol-2-amine suppresses lipopolysaccharide-induced brain inflammation by regulating NF-κB signaling in mice

We report that N-adamantyl-4-methylthiazol-2-amine (KHG26693), a novel thiazole derivative, can prevent lipopolysaccharide (LPS)-induced brain inflammation in mice. In this LPS-induced model of brain inflammation, administration of KHG26693 effectively prevented increases in the levels of IL-1β, TNF-α, prostaglandin E2, malondialdehyde, and nitric oxide, and mitigated reductions in the levels of superoxide dismutase in the hippocampus. KHG26693 also prevented reductions in the levels of hippocampal brain-derived neurotrophic factors. Furthermore, pretreatment with KHG26693 prior to LPS treatment dramatically attenuated the elevation of inducible nitric oxide synthase and cyclooxygenase-2 protein levels. Moreover, pretreatment with KHG26693 significantly suppressed LPS-induced phosphorylation of NF-κB and IκBα through the inactivation of IKKβ. Additionally, KHG26693 caused the downregulation of LPS-induced cystathionine-b-synthase gene expression in the brain. Although the clinical relevance of our findings remains to be determined, our data suggest that KHG26693 might prevent neuronal cell injury via the reduction of inflammation and oxidative stress in the brain.

The protective effect of Trillin LPS-induced acute lung injury by the regulations of inflammation and oxidative state

Inflammation response and oxidative stress have been reported to be involved in the pathogenesis of acute lung injury (ALI). Accordingly, anti-inflammatory treatment is proposed to be a possible efficient therapeutic strategy for ALI. The purpose of our present study was to evaluate the anti-inflammatory efficacy of trillin (Tr) on ALI induced by lipopolysaccharide (LPS) in mice and explore the underlying mechanism. BALB/c mice received Tr (50, 100 mg/kg) intraperitoneally 1 h prior to the intratracheal instillation of lipopolysaccharide (LPS) challenge. Pretreatment with Tr at the dose of 50, 100 mg/kg markedly ameliorated lung wet-to-dry weight (W/D) ratio, myeloperoxidase (MPO) activity and pulmonary histopathological conditions. In addition, the protective efficacy of Tr might be attributed to the down-regulations of neutrophil infiltration, malondialdehyde (MDA), inflammatory cytokines and the up-regulations of super-oxide dismutase (SOD), catalase(CAT), glutathione(GSH), Glutathione Peroxidase(GSH-Px) in bronchoalveolar lavage fluid (BALF). Meanwhile, our study revealed some correlations between (NF-E2-related factor 2) Nrf2/heme oxygenase (HO)-1/nuclear factor-kappa B (NF-κB) pathways and the beneficial effect of Tr, as evidenced by the significant up-regulations of HO-1 and Nrf2 protein expressions as well as the down-regulations of p-NF-κB and p-inhibitor of NF-κB (IκB) in lung tissues. Taken together, our results indicated that Tr exhibited protective effect on LPS-induced ALI by the regulations of related inflammatory events via the activations of Nrf2, HO-1 and NF-κB pathway. The current study indicated that Tr could be a potentially effective candidate medicine for the treatment of ALI.

Beneficial effects of evodiamine on P2X(4)-mediated inflammatory injury of human umbilical vein endothelial cells due to high glucose

Evodiamine has been reported to exhibit anti-inflammatory and anti-nociceptive effects, but the underlying mechanisms remain to be defined. P2X4 receptor (P2X4R) is a subtype of ATP receptors and plays important roles in pain, inflammatory and immune responses. We aimed to investigate whether evodiamine has beneficial effects on endothelial inflammatory injury mediated by chronic high glucose condition. We found that culturing human umbilical vein endothelial cells (HUVECs) with high glucose significantly increased the expression of P2X4 receptor in HUVECs, cytosolic Ca(2+) concentrations and intracellular reactive oxygen species (ROS) while decreasing nitric oxide (NO); these effects could be reversed by evodiamine. High glucose also significantly increased the expression of the pro-inflammatory activators (NF-κB) and TNFR-ɑ, which was accompanied by the elevation of P2X4R levels. Evodiamine was able to down-regulate the elevated NF-κB, TNFR-ɑ, P2X4R and ROS, and up-regulate the decreased NO. Thus the evodiamine may exert the anti-inflammation activity on high-glucose challenge HUVEC via suppressing the P2X4R signaling pathway, exhibiting beneficial ability to protect HUVECs from glucotoxicity.

Rapidly activated epidermal growth factor receptor mediates lipopolysaccharide-triggered migration of microglia

Previous reports have suggested that epidermal growth factor receptor (EGFR) is involved in microglia activation characterized by cell morphology changes, cytokine production and cell migration; and the biochemical regulation of the microglia migration is a potential therapeutic target following CNS inflammatory damages. However, the role of EGFR in microglia motility after inflammatory stimulation remains unknown. In the present study, lipopolysaccharide (LPS) was found to trigger rapid EGFR phosphorylation within 10 min, which was sustained during long-term stimulation in both primary microglial cells and the cultured BV2 microglial cells, furthermore, blocking EGFR phosphorylation by AG1478 significantly attenuated the LPS-induced chemotactic and chemokinetic migration of microglia. In addition, LPS could initiate calcium oscillation in microglia during live-cell recording, however, an intracellular calcium chelator and a selective inhibitor of calcium/calmodulin-dependent protein kinase II, but not an extracellular calcium chelator, remarkably suppressed the LPS-induced EGFR phosphorylation in BV2 microglia cells. As EGFR is not a traditional receptor for LPS, these findings suggest that the rapid phosphorylation of EGFR is attributed to the LPS-triggered intracellular calcium mobilization. By examining the downstream signals of EGFR, we further proved that extracellular signal-regulated kinase (ERK) is essential for EGFR-mediated microglia migration, because ERK inhibition attenuated the chemotactic and chemokinetic migration of microglia that had been induced by either LPS or EGF. Collectively, these results suggest that LPS could trigger the rapid phosphorylation of EGFR and subsequent ERK activation through mobilizing calcium activity, which underlies the microglia migration in an inflammatory condition.

Bee venom ameliorates lipopolysaccharide-induced memory loss by preventing NF-kappaB pathway

Background

Accumulation of beta-amyloid and neuroinflammation trigger Alzheimer’s disease. We previously found that lipopolysaccharide (LPS) caused neuroinflammation with concomitant accumulation of beta-amyloid peptides leading to memory loss. A variety of anti-inflammatory compounds inhibiting nuclear factor kappaB (NF-κB) activation have showed efficacy to hinder neuroinflammation and amyloidogenesis. We also found that bee venom (BV) inhibits NF-κB.

Methods

A mouse model of LPS-induced memory loss used administration of BV (0.8 and 1.6 μg/kg/day, i.p.) to ICR mice for 7 days before injection of LPS (2.5 mg/kg/day, i.p.). Memory loss was assessed using a Morris water maze test and passive avoidance test. For in vitro study, we treated BV (0.5, 1, and 2 μg/mL) to astrocytes and microglial BV-2 cells with LPS (1 μg/mL).

Results

We found that BV inhibited LPS-induced memory loss determined by behavioral tests as well as cell death. BV also inhibited LPS-induced increases in the level of beta-amyloid (Aβ), β-and γ-secretases activities, NF-κB and its DNA-binding activity and expression of APP, and BACE1 and neuroinflammation proteins (COX-2, iNOS, GFAP and IBA-1) in the brain and cultured cells. In addition, pull-down assay and molecular modeling showed that BV binds to NF-κB.

Conclusions

BV attenuates LPS-induced amyloidogenesis, neuroinflammation, and therefore memory loss via inhibiting NF-κB signaling pathway. Thus, BV could be useful for treatment of Alzheimer’s disease.

Paeoniflorin attenuates Aβ1-42-induced inflammation and chemotaxis of microglia in vitro and inhibits NF-κB- and VEGF/Flt-1 signaling pathways

Alzheimer׳s disease (AD) is a neurodegenerative disease with elusive pathogenesis, which accounts for most cases of dementia in the aged population. It has been reported that persistent inflammatory responses and excessive chemotaxis of microglia stimulated by beta-amyloid (Aβ) oligomers in the brain may accelerate the progression of AD. The present study was conducted to explore whether paeoniflorin (PF), a water-soluble monoterpene glycoside isolated from the root of Paeonia lactiflora Pallas, could attenuate Aβ1-42-induced toxic effects on primary and BV-2 microglial cells in vitro. Our data showed that PF pretreatment inhibited Aβ1-42-induced production of tumor necrosis factor (TNF)-α, interleukin (IL)-1β and IL-6 in rodent microglia. Also, the nuclear translocation of nuclear factor kappa B (NF-κB) subunit p65 and the phosphorylation of NF-κB inhibitor alpha (IκBα) in Aβ1-42-stimulated microglial cells were suppressed by PF administration. Moreover, PF treatment reduced the release of chemokine (C-X-C motif) ligand 1 (CXCL1) and chemokine (C-C motif) ligand 2 (CCL-2) from Aβ1-42-stimulated microglia. Additionally, application of PF inhibited the increases in vascular endothelial growth factor (VEGF) and VEGF receptor 1 (Flt-1) triggered by Aβ1-42, and resulted in a concomitant reduction in microglial chemotaxis. Restoration of VEGF was noted to counteract the inhibitory effect of PF, suggesting that PF mitigated Aβ1-42-elicited microglial migration at least partly by suppressing the VEGF/Flt-1 axis. In summary, in presence of Aβ1-42, PF pretreatment inhibited the excessive microglial activation and chemotaxis.