1-O-Tigloyl-1-O-deacetyl-nimbolinin B Inhibits LPS-Stimulated Inflammatory Responses by Suppressing NF-κB and JNK Activation in Microglia Cells

Research on the signaling pathways related to the intervention of traditional Chinese medicine in Parkinson's disease:A literature review

ETHNOPHARMACOLOGICAL RELEVANCE

Parkinson's disease (PD) is the most common progressive neurodegenerative disorder affecting more than 10 million people worldwide and is characterized by the progressive loss of Daergic (DA) neurons in the substantia nigra pars compacta. It has been reported that signaling pathways play a crucial role in the pathogenesis of PD, while the active ingredients of traditional Chinese medicine (TCM) have been found to possess a protective effect against PD. TCM has demonstrated significant potential in mitigating oxidative stress (OS), neuroinflammation, and apoptosis of DA neurons via the regulation of signaling pathways associated with PD.

AIM OF THE REVIEW

This study discussed and analyzed the signaling pathways involved in the occurrence and development of PD and the mechanism of active ingredients of TCM regulating PD via signaling pathways, with the aim of providing a basis for the development and clinical application of therapeutic strategies for TCM in PD.

MATERIALS AND METHODS

With "Parkinson's disease", "Idiopathic Parkinson's Disease", "Lewy Body Parkinson's Disease", "Parkinson's Disease, Idiopathic", "Parkinson Disease, Idiopathic", "Parkinson's disorders", "Parkinsonism syndrome", "Traditional Chinese medicine", "Chinese herbal medicine", "active ingredients", "medicinal plants" as the main keywords, PubMed, Web of Science and other online search engines were used for literature retrieval.

RESULTS

PD exhibits a close association with various signaling pathways, including but not limited to MAPKs, NF-κB, PI3K/Akt, Nrf2/ARE, Wnt/β-catenin, TLR/TRIF, NLRP3, Notch. The therapeutic potential of TCM lies in its ability to regulate these signaling pathways. In addition, the active ingredients of TCM have shown significant effects in improving OS, neuroinflammation, and DA neuron apoptosis in PD.

CONCLUSION

The active ingredients of TCM have unique advantages in regulating PD-related signaling pathways. It is suggested to combine network pharmacology and bioinformatics to study the specific targets of TCM. This not only provides a new way for the prevention and treatment of PD with the active ingredients of TCM, but also provides a scientific basis for the selection and development of TCM preparations.

Potential Role of Oxidative Stress in the Pathophysiology of Neurodegenerative Disorders

Neurodegeneration causes premature death in the peripheral and central nervous system. Neurodegeneration leads to the accumulation of oxidative stress, inflammatory responses, and the generation of free radicals responsible for nervous disorders like amyotrophic lateral sclerosis, Alzheimer's disease, Parkinson's disease, and Huntington's disorders. Therefore, focus must be diverted towards treating and managing these disorders, as it is very challenging. Furthermore, effective therapies are also lacking, so the growing interest of the global market must be inclined towards developing newer therapeutic approaches that can intercept the progression of neurodegeneration. Emerging evidences of research findings suggest that antioxidant therapy has significant potential in modulating disease phenotypes. This makes them promising candidates for further investigation. This review focuses on the role of oxidative stress and reactive oxygen species in the pathological mechanisms of various neurodegenerative diseases, amyotrophic lateral sclerosis, Alzheimer's disease, Parkinson's disease, and Huntington's disorders and their neuroprotection. Additionally, it highlights the potential of antioxidant-based therapeutics in mitigating disease severity in humans and improving patient compliance. Ongoing extensive global research further sheds light on exploring new therapeutic targets for a deeper understanding of disease mechanisms in the field of medicine and biology targeting neurogenerative disorders.

An overview of Fructus Meliae Toosendan: Botany, traditional uses, phytochemistry, pharmacology and toxicology

Fructus Meliae Toosendan (FMT) is the dried and mature fruit of MeLia toosendan Sieb.et Zucc. It contains a variety of chemical constituents and reported to possess a variety of pharmacological activities. This review aims to provide a thorough and organized summary of botany, traditional uses, chemical ingredients, pharmacological actions, toxicity, quality control, and uses. In this review, we have compiled the data regarding FMT from 1994 to 2022 in the databases: Web of Science, PubMed, Google Scholar, CNKI, and Baidu Scholar. The keywords: "Fructus Meliae Toosendan", "botany", "traditional uses","chemical components", "pharmacological activity", "toxicity", "quality control" and "clinical application" have been used to collected the literature published in the online bibliographic databases. Based on the correlation of these documents and FMT, 126 articles were finally selected as references. This paper provides a reasonable summary of the 190 chemical components of FMT and its pharmacological effects and toxicity. Moreover, this paper also compiled the quality control studies and clinical applications. In the future, more experimental studies on FMT are needed to achieve the purpose of toxicity reducing and efficacy enhancing. This comprehensive review of FMT can provide a reference for subsequent relevant studies.

Limonoids with anti-inflammatory activity: A review

The natural limonoids distributed mainly in the Meliaceae and Rutaceae plants are known for their unique and complex structure with high degree oxidation and cyclic rearrangement. However, these compounds exhibit a broad range of biological activities such as insecticidal, antibacterial, antifungal, antimalarial, antioxidant, anticancer, antiviral, and anti-inflammatory. There is still limited report about the biological activity of the anti-inflammatory effect of limonoids isolated from plants. Therefore, this study aimed to examine the effect of intact, deformed and rearranged limonoids as anti-inflammatory agents. The majority of anti-inflammatory investigations were evaluated by in vitro and in vivo assays of the isolated pure compounds and their derivatives. For the in vitro study, intact and C-ring seco limonoids showed a potent inhibitory effect against NO production. The in vivo analysis of Intact, C-seco, and AD-seco limonoids showed a potent effect based on the inhibition of pro-inflammatory cytokines expression, indicating their potency as anti-inflammatory agents.

Discovery of novel MIF inhibitors that attenuate microglial inflammatory activation by structures-based virtual screening and in vitro bioassays

Macrophage migration inhibitory factor (MIF) is a pluripotent pro-inflammatory cytokine and is related to acute and chronic inflammatory responses, immune disorders, tumors, and other diseases. In this study, an integrated virtual screening strategy and bioassays were used to search for potent MIF inhibitors. Twelve compounds with better bioactivity than the prototypical MIF-inhibitor ISO-1 (IC₅₀ = 14.41 μM) were identified by an in vitro enzymatic activity assay. Structural analysis revealed that these inhibitors have novel structural scaffolds. Compound 11 was then chosen for further characterization in vitro, and it exhibited marked anti-inflammatory efficacy in LPS-activated BV-2 microglial cells by suppressing the activation of nuclear factor kappa B (NF-κB) and mitogen-activated protein kinases (MAPKs). Our findings suggest that MIF may be involved in the regulation of microglial inflammatory activation and that small-molecule MIF inhibitors may serve as promising therapeutic agents for neuroinflammatory diseases.

Activation of UCP2 by anethole trithione suppresses neuroinflammation after intracerebral hemorrhage

Intracerebral hemorrhage (ICH) is a devastating disease, in which neuroinflammation substantially contributes to brain injury. Uncoupling protein 2 (UCP2) is a member of the mitochondrial anion carrier family, which uncouples oxidative phosphorylation from ATP synthesis by facilitating proton leak across the mitochondrial inner membrane. UCP2 has been reported to modulate inflammation. In this study we investigated whether and how UCP2 modulated neuroinflammation through microglia/macrophages following ICH in vitro and in vivo. We used an in vitro neuroinflammation model in murine BV2 microglia to mimic microglial activation following ICH. ICH in vivo model was established in mice through collagenase infusion into the left striatum. ICH mice were treated with anetholetrithione (ADT, 50 mg· kg^-1 ·d^-1, ip) or the classical protonophoric uncoupler FCCP (injected into hemorrhagic striatum). We showed that the expression and mitochondrial location of microglial UCP2 were not changed in both in vitro and in vivo ICH models. Knockdown of UCP2 exacerbated neuroinflammation in BV2 microglia and mouse ICH models, suggesting that endogenous UCP2 inhibited neuroinflammation and therefore played a protective role following ICH. ADT enhanced mitochondrial ROS production thus inducing mitochondrial uncoupling and activating UCP2 in microglia. ADT robustly suppressed neuroinflammation, attenuated brain edema and improved neurological deficits following ICH, and these effects were countered by striatal knockdown of UCP2. ADT enhanced AMP-activated protein kinase (AMPK) activation in the hemorrhagic brain, which was abrogated by striatal knockdown of UCP2. Moreover, striatal knockdown of AMPK abolished the suppression of neuroinflammation by ADT following ICH. On the other hand, FCCP-induced mitochondrial uncoupling was independent of UCP2 in microglia; and striatal knockdown of UCP2 did not abrogate the suppression of neuroinflammation by FCCP in ICH mice. In conclusion, the uncoupling activity is essential for suppression of neuroinflammation by UCP2. We prove for the first time the concept that activators of endogenous UCP2 such as anetholetrithione are a new class of uncouplers with translational significance.

Ethanol Extract of Elaeagnus glabra f. oxyphylla Branches Alleviates the Inflammatory Response Through Suppression of Cyclin D3/Cyclin-Dependent Kinase 11p58 Coupled to Lipopolysaccharide-Activated BV-2 Microglia

Neuroinflammation plays a pivotal role in the pathogenesis of neurodegenerative diseases and is characterized by microglial dysregulation. Here, we explored the beneficial effects of a leaf extract of Elaeagnus glabra f. oxyphylla (EGFO), a native medicinal plant to Korea, South China, Japan, and Taiwan, on neuroinflammation using lipopolysaccharide (LPS)-stimulated BV-2 microglia. Levels of the inflammatory mediators were determined by enzyme-linked immunosorbent assays and reverse transcription–polymerase chain reaction. The phospho levels of mitogen-activated protein kinases, which are key kinase molecules in the inflammatory signaling pathway in microglia, were analyzed by Western blotting. Treatment with EGFO significantly suppressed the LPS-mediated induction of nitric oxide and prostaglandin E2. Consistently, EGFO treatment in LPS-stimulated BV-2 cells markedly reduced the inflammatory cytokines tumor necrosis factor-alpha (TNF-α) and interleukin-6 (IL-6) levels. The best concentration of EGFO that could reduce TNF-α and IL-6 was 100 μg/mL. EGFO relatively reduced the messenger RNA expression of TNF-α and IL-6 by 0.36 and 0.32-fold ratio, respectively, compared to LPS treatment. Moreover, EGFO markedly reduced the phospho levels of p38 and the c-jun N-terminal kinase. Furthermore, antibody microarray and immunoblotting data revealed that the pharmacological mechanisms driving the antineuroinflammatory action of EGFO involve prevention of the cyclin D3/cyclin-dependent kinase 11p58 (CDK11p58) interaction. In conclusion, our results demonstrate that EGFO alleviates the inflammatory response through the suppression of cyclin D3/CDK11p58 coupling in LPS-activated BV-2 microglia. We propose the potential of EGFO as a novel drug candidate for neurodegenerative diseases by targeting neuroinflammation.

Limonoids From the Genus Melia (Meliaceae): Phytochemistry, Synthesis, Bioactivities, Pharmacokinetics, and Toxicology

Limonoids, as the vital bioactive chemical compounds in genus Melia plants, have attracted significant attention owing to their exclusive structural characteristics and remarkable biological activity. These compounds can be usually classified into two categories, including the ring-intact group and the ring-C-seco group. Benefiting from the development of separation and analysis technology, more than 200 limonoids have been isolated and identified from this genus. There is growing evidence that limonoids from genus Melia possess diverse pharmacological activities, especially anti-cancer effects, insecticidal activities, and anti-botulism effects. Toosendanin, one of the paramount limonoids, was considered as the pivotal bioactive marker in two medicinal herbs, including Melia toosendan Sieb. et Zucc and Melia azedarach L. In particular, limonoids are found to exhibit non-negligible toxic effects, a finding which needs further research. Besides this, the lack of clinical research data seriously hinders its further development and utilization, and necessary clinical trials should be taken into consideration. In this review, we systematically summarized the phytochemical compounds and their synthesis methods, pharmacological activities, and the structure–activity relationship, pharmacokinetics, and toxicology of genus Melia-derived limonoids. We believe that this up-to-date review could provide scientific evidence for the application of limonoids as agents beneficial to health in future clinical practice.

Natural Terpenoids as Neuroinflammatory Inhibitors in LPS-stimulated BV-2 Microglia

Neuroinflammation is a typical feature of many neurodegenerative diseases, including Alzheimer's disease and Parkinson's disease. Microglia, the resident immune cells of the brain, readily become activated in response to an infection or an injury. Uncontrolled and overactivated microglia can release pro-inflammatory and cytotoxic factors and are the major culprits in neuroinflammation. Hence, research on novel neuroinflammatory inhibitors is of paramount importance for the treatment of neurodegenerative diseases. Bacterial lipopolysaccharide, widely used in the studies of brain inflammation, initiates several major cellular activities that critically contribute to the pathogenesis of neuroinflammation. This review will highlight the progress on terpenoids, an important and structurally diverse group of natural compounds, as neuroinflammatory inhibitors in lipopolysaccharidestimulated BV-2 microglial cells over the last 20 years.

Pretreatment with kaempferol attenuates microglia-mediate neuroinflammation by inhibiting MAPKs-NF-κB signaling pathway and pyroptosis after secondary spinal cord injury

Spinal cord injury (SCI) is a devastating injury that characterized by oxidative stress and inflammatory response. Kaempferol is reported to be an anti-neuroinflammation in neurologic disorders. Nevertheless, the role and mechanism of kaempferol in SCI remains unclear. The present study aims to investigate effects of kaempferol on SCI and its possible underlying mechanisms in in vivo and in vitro models. A C5 hemi-contusion injury was induced in Sprague-Dawley rats to investigate the neuroprotective effects of kaempferol after SCI. For in vitro study, the BV2 microglia cell lines were pretreated with or without kaempferol. A combination of molecular and histological methods was used to clarify the mechanism and explore the signaling pathway both in vivo and in vitro. One-way analysis of variance (ANOVA) was conducted with Bonferroni post hoc tests to examine the differences between groups. The in vivo studies showed that kaempferol could improve the recovery of hindlimb motor function and ameliorate tissue damage in the spinal cord after SCI. Moreover, administration of kaempferol reduced microglia activation and oxidative stress level in the spinal cord. The in vitro studies showed that kaempferol suppressed the microglia activation resulting from the administration of LPS with ATP to BV-2 cells. Pretreated BV2 cells with kaempferol reduced the generation of reactive oxygen species (ROS) by inhibiting NADPH oxidase 4, and then, suppressed the phosphorylation of p38 MAPK and JNK, which subsequently inhibited nuclear translocation of NF-κB p65 to express pro-inflammatory factors. We also observed that kaempferol could inhibite the pyroptosis related proteins (NLRP3 Caspase-1 p10 ASC N-GSDMD) and reduce the release of IL-18 and IL-1β. In conclusion, kaempferol was able to reduce oxidative stress and inflammatory response through down-regulation of ROS dependent MAPKs- NF-κB and pyroptosis signaling pathway, which suggested that kaempferol might be a novel promising therapeutic agent for SCI.

Knockdown of milk-fat globule EGF factor-8 suppresses glioma progression in GL261 glioma cells by repressing microglial M2 polarization

Tumor-associated microglial cells promote glioma growth, invasion, and chemoresistance by releasing inflammatory factors. Milk fat globule EGF factor 8 protein (MFG-E8), a secreted glycoprotein, is closely related to tissue homeostasis and anti-inflammation. In the present study, we investigated the role of MFG-E8 in microglial polarization and glioma progression in vitro and in vivo. We found that glioma cells secrete comparable amounts of MFG-E8 in culture media to astrocytes. Recombinant MFG-E8 triggered microglia to express the M2 polarization markers, such as arginase-1 (ARG-1), macrophage galactose-type C-type lectin-2 (MGL-2), and macrophage mannose receptor (CD206). Forced expression of MFG-E8 in BV-2 microglia cells not only promoted IL-4-induced M2 polarization but also inhibited lipopolysaccharide (LPS)-induced M1 microglial polarization. Mechanistic studies demonstrated that recombinant MFG-E8 markedly induced signal transducer and activator of transcription 3 (STAT3) phosphorylation, and the STAT3 inhibitor stattic significantly blocked MFG-E8-induced ARG-1 expression. Administration of antibody against MFG-E8 and knockdown of its receptor, integrin β3, significantly attenuated MFG-E8-induced ARG-1 expression. Similarly, knockdown of MFG-E8 also markedly reduced IL-4-induced M2 marker expression and increased LPS-induced M1 marker expression in microglia cells. Moreover, the knockdown of MFG-E8 in GL261 glioma cells inhibited cell proliferation and enhanced chemosensitivity to 1,3-bis(2-chloroethyl)-1-nitrosourea (BCNU), which was likely associated with the downregulation of FAK/AKT activation and STAT3/cyclin D1 signaling. The murine GL261 glioma experimental model demonstrated that knockdown of MFG-E8 significantly reduced tumor size and extended survival times. Additionally, attenuated CD11b⁺ cell infiltration and reduced CD206⁺ expression in CD11b⁺ cells were also observed in an MFG-E8 knockdown GL261 murine glioma model. These results suggested that inhibition of MFG-E8 might hamper the immunosuppressive microenvironment in gliomas and therefore ameliorate tumor progression.

Advanced oxidation protein products induce microglia-mediated neuroinflammation via MAPKs-NF-κB signaling pathway and pyroptosis after secondary spinal cord injury

Background

Inflammatory response mediated by oxidative stress is considered as an important pathogenesis of spinal cord injury (SCI). Advanced oxidation protein products (AOPPs) are novel markers of oxidative stress and their role in inflammatory response after SCI remained unclear. This study aimed to investigate the role of AOPPs in SCI pathogenesis and explore the possible underlying mechanisms.

Methods

A C5 hemi-contusion injury was induced in Sprague-Dawley rats to confirm the involvement of AOPPs after SCI. For in vivo study, apocynin, the NADPH oxidase inhibitor was used to study the neuroprotective effects after SCI. For in vitro study, the BV2 microglia cell lines were pretreated with or without the inhibitor or transfected with or without small interference RNA (siRNA) and then stimulated with AOPPs. A combination of molecular and histological methods was used to clarify the mechanism and explore the signaling pathway both in vivo and in vitro. One-way analysis of variance (ANOVA) was conducted with Bonferroni post hoc tests to examine the differences between groups.

Results

The levels of AOPPs in plasma and cerebrospinal fluid as well as the contents in the spinal cord showed significant increase after SCI. Meanwhile, apocynin ameliorated tissue damage in the spinal cord after SCI, improving the functional recovery. Immunofluorescence staining and western blot analysis showed activation of microglia after SCI, which was in turn inhibited by apocynin. Pretreated BV2 cells with AOPPs triggered excessive generation of reactive oxygen species (ROS) by activating NADPH oxidase. Increased ROS induced p38 MAPK and JNK phosphorylation, subsequently triggering nuclear translocation of NF-κB p65 to express pro-inflammatory cytokines. Also, treatment of BV2 cells with AOPPs induced NLRP3 inflammasome activation and cleavage of Gasdermin-d (GSDMD), causing pyroptosis. This was confirmed by cleavage of caspase-1, production of downstream mature interleukin (IL)-1β and IL-18 as well as rupture of rapid cell membrane.

Conclusions

Collectively, these data indicated AOPPs as biomarkers of oxidative stress, modulating inflammatory response in SCI by multiple signaling pathways, which also included the induction of NADPH oxidase dependent ROS, and NLRP3-mediated pyroptosis, and activation of MAPKs and NF-κB.

Pathophysiology and Therapeutic Perspectives of Oxidative Stress and Neurodegenerative Diseases: A Narrative Review

Introduction

Neurodegeneration is the term describing the death of neurons both in the central nervous system and periphery. When affecting the central nervous system, it is responsible for diseases like Alzheimer’s disease, Parkinson’s disease, Huntington’s disorders, amyotrophic lateral sclerosis, and other less frequent pathologies. There are several common pathophysiological elements that are shared in the neurodegenerative diseases. The common denominators are oxidative stress (OS) and inflammatory responses. Unluckily, these conditions are difficult to treat. Because of the burden caused by the progression of these diseases and the simultaneous lack of efficacious treatment, therapeutic approaches that could target the interception of development of the neurodegeneration are being widely investigated. This review aims to highlight the most recent proposed novelties, as most of the previous approaches have failed. Therefore, older approaches may currently be used by healthcare professionals and are not being presented.

Methods

This review was based on an electronic search of existing literature, using PubMed as primary source for important review articles, and important randomized clinical trials, published in the last 5 years. Reference lists from the most recent reviews, as well as additional sources of primary literature and references cited by relevant articles, were used.

Results

Eighteen natural pharmaceutical substances and 24 extracted or recombinant products, and artificial agents that can be used against OS, inflammation, and neurodegeneration were identified. After presenting the most common neurodegenerative diseases and mentioning some of the basic mechanisms that lead to neuronal loss, this paper presents up to date information that could encourage the development of better therapeutic strategies.

Conclusions

This review shares the new potential pharmaceutical and not pharmaceutical options that have been recently introduced regarding OS and inflammatory responses in neurodegenerative diseases.

The oncometabolite 2-hydroxyglutarate inhibits microglial activation via the AMPK/mTOR/NF-κB pathway

Microglia, the brain-resident macrophage, is known as the innate immune cell type in the central nervous system. Microglia is also the major cellular component of tumor mass of gliomas that plays a key role in glioma development. Mutations of isocitrate dehydrogenases 1 and 2 (IDH1/2) frequently occur in gliomas, which leads to accumulation of oncometabolic product 2-hydroxyglutarate (2HG). Moreover, IDH1/2 mutations were found to correlate with better prognosis in glioma patients. In the present study, we investigated the effects of the 2HG on microglial inflammatory activation. We showed that the conditioned media (CM) from GL261 glioma cells stimulated the activation of BV-2 microglia cells, evidenced by markedly increased expression of interleukin-6 (IL-6), IL-1β, tumor necrosis factor-α (TNF-α), CCL2 (C-C motif chemokine ligand 2) and CXCL10 (C-X-C motif chemokine 10). CM-induced expression of proinflammatory genes was significantly suppressed by pretreatment with a synthetic cell-permeable 2HG (1 mM) or a nuclear factor-κB (NF-κB) inhibitor BAY11-7082 (10 μM). In lipopolysaccharide (LPS)- or TNF-α-stimulated BV-2 microglia cells and primary microglia, pretreatment with 2HG (0.25-1 mM) dose-dependently suppressed the expression of proinflammatory genes. We further demonstrated that 2HG significantly suppressed LPS-induced phosphorylation of IκB kinase α/β (IKKα/β), IκBα and p65, IκB degradation, and nuclear translocation of p65 subunit of NF-κB, as well as NF-κB transcriptional activity. Similarly, ectopic expression of mutant isocitrate dehydrogenase 1 (IDH1) (R132H) significantly decreased TNF-α-induced activation of NF-κB signaling pathway. Finally, we revealed that activation of adenosine 5'-monophosphate-activated protein kinase (AMPK) and subsequent inhibition of mammalian target of rapamycin (mTOR) signaling contributed to the inhibitory effect of 2HG on NF-κB signaling pathway in BV-2 cells. Taken together, these results, for the first time, show that oncometabolite 2HG inhibits microglial activation through affecting AMPK/mTOR/NF-κB signaling pathway and provide evidence that oncometabolite 2HG may regulate glioma development via modulating microglial activation in tumor microenvironment.

Natural CAC chemopreventive agents from Ilex rotunda Thunb

Colitis-associated cancer (CAC) is one of the most serious complications of inflammatory bowel disease. The pathogenesis of CAC is complicated and so far elusive, and the anti-inflammatory effect does not assure CAC preventive activity, making it difficult to discover CAC preventive drugs. In this study, we report the CAC preventive effect of the ethyl acetate (EIR) of Ilex rotunda Thunb., a traditional Chinese herbal medicine being clinically used to treat intestinal disease. We also report the results of screening for CAC preventive agents from EIR via a nuclear factor-kappa B (NF-κB) translocation model in Caco2 cells, since activated NF-κB can be used by tumor cells at the early stage of tumorigenesis. Twenty-four components were isolated from EIR and identified by multiple chromatography and spectral analysis. MTT experiments in IEC-6 and RAW264.7 cells showed that all 24 compounds were toxic-free to normal cell lines. Furthermore, compound rotundic acid (RA) (19) exhibited an inhibitory effect on LPS-induced NF-κB translocation in Caco2 cells. Moreover, RA did not induce apoptosis in Caco2 tumor cells while possessing an anti-inflammatory effect both in immune and intestinal epithelium cells (RAW264.7 and IEC-6 cells, respectively). Removing RA (19) and its 28-O-glucopyranoside (17) from EIR definitely undermined the in vivo CAC preventive activity of EIR. Therefore, the current study suggested that RA (19) could be a potential therapeutic agent against CAC.

Role of Mitogen Activated Protein Kinase Signaling in Parkinson's Disease

Parkinson's disease (PD) is a neurodegenerative disorder caused by insufficient dopamine production due to the loss of 50% to 70% of dopaminergic neurons. A shortage of dopamine, which is predominantly produced by the dopaminergic neurons within the substantia nigra, causes clinical symptoms such as reduction of muscle mass, impaired body balance, akinesia, bradykinesia, tremors, postural instability, etc. Lastly, this can lead to a total loss of physical movement and death. Since no cure for PD has been developed up to now, researchers using cell cultures and animal models focus their work on searching for potential therapeutic targets in order to develop effective treatments. In recent years, genetic studies have prominently advocated for the role of improper protein phosphorylation caused by a dysfunction in kinases and/or phosphatases as an important player in progression and pathogenesis of PD. Thus, in this review, we focus on the role of selected MAP kinases such as JNKs, ERK1/2, and p38 MAP kinases in PD pathology.

Andrographolide Alleviates Acute Brain Injury in a Rat Model of Traumatic Brain Injury: Possible Involvement of Inflammatory Signaling

Neuroinflammation plays an important role in secondary injury after traumatic brain injury (TBI). Andrographolide (Andro), a diterpenoid lactone isolated from Andrographis paniculata, has been demonstrated to exhibit anti-inflammatory activity in neurodegenerative disorders. This study therefore aimed to investigate the potential neuroprotective effects of Andro after TBI and explore the underlying mechanisms. In our study, we used a weight-dropped model to induce TBI in Sprague–Dawley rats, the neurological deficits were assessed using modified neurological severity scores, Fluoro-Jade B (FJB) and terminal deoxynucleotidyl transferase (TdT) dUTP Nick-End Labeling (TUNEL) staining were employed to examine neuronal degeneration and apoptosis after TBI, immunofluorescence was designed to investigate microglial activation. Quantitative Real-time PCR and ELISA were conducted to detect the expression levels of pro-inflammatory cytokines, Western blot was used to examine the expression level of proteins of relative signaling pathway. Our results showed that after Andro administration, the neurological deficit was attenuated, and the cerebral edema and apoptosis in brain tissues were also decreased following TBI. Both microglial activation and the expression of pro-inflammatory cytokines were significantly inhibited by Andro after TBI. Moreover, Andro inhibited NF-κB p65 subunit translocation and decreased the expression levels of phosphorylated extracellular signal regulated kinase (ERK) and p38 MAPK after TBI. Altogether, this study suggests that Andro could improve neurobehavioral function by inhibiting NF-κB and MAPK signaling pathway in TBI, which might provide a new approach for treating brain injury.

Neuroprotective effects of metformin on traumatic brain injury in rats associated with NF-κB and MAPK signaling pathway

Traumatic brain injury (TBI) triggers a complex sequence of inflammatory responses that contribute to secondary injury. Metformin, a first-line drug used to treat type 2 diabetes, is reported to exhibit potent anti-inflammatory activity on diseases associated with the central nervous system (CNS). The aim of this study is to investigate the potential neuroprotective effects of metformin on acute brain injury after TBI and explore the underlying mechanisms. Male Sprague-Dawley (SD) rats were divided into four groups: sham group, TBI group, TBI + saline (NS) group and TBI + metformin group. A weight-dropping model was employed to induce TBI in rats. Modified neurological severity scores (mNSS) were employed to assess the short-term neurological deficits, neuronal degeneration and apoptosis in the brain tissues were assayed with Fluoro-Jade B and TUNEL staining, immunofluorescence was designed to investigate microglial activation. The mRNA and protein expression levels of pro-inflammatory cytokines such as necrosis factor-alpha (TNF-α), interleukin-beta (IL-1β) and nterleukin-6 (IL-6) were evaluated by real-time quantitative reverse transcriptase polymerase chain reaction (QPCR) and enzyme-linked immunosorbent assay (ELISA). Western blotting analysis was engaged to examine the expression of NF-κB p65 and phosphorylation of ERK1/2 and p38 MAPK. Our results showed that metformin significantly ameliorated neurological deficit, cerebral edema and neuronal apoptosis in rats following TBI. Moreover, metformin administration inhibited microglial activation and decreased the production of pro-inflammatory cytokines including TNF-α, IL-1β and IL-6. In addition, metformin inhibited the translocation of NF-κB p65 from cytoplasm into the nucleus, as well as the phosphorylation of ERK1/2 and p38 MAPK. This study suggests that metformin administration inhibits microglia activation-mediated inflammation via NF-κB and MAPK signaling pathway to improve neurobehavioral function following TBI, which provide a potential therapeutic benefit in treating brain injury.

Macrophage migration inhibitory factor (MIF) inhibitor, Z-590 suppresses cartilage destruction in adjuvant-induced arthritis via inhibition of macrophage inflammatory activation

BACKGROUND

Macrophage migration inhibitory factor (MIF) is a pleiotropic pro-inflammatory mediator that is involved in the progression of rheumatoid arthritis (RA). Previously, we demonstrated a small molecule compound 3-[(biphenyl-4-ylcarbonyl) carbamothioyl] amino benzoic acid (Z-590) could inhibit MIF activity with docking-based virtual screening and experimental evaluation.

METHODS

The LPS activated RAW264.7 macrophage cells were used to determine the anti-inflammatory effects of Z-590 in vitro. A rat adjuvant-induced arthritis (AIA) model was used to determine the anti-arthritic effects of Z-590 in vivo.

RESULTS

MIF inhibitor Z-590 significantly inhibited the production of NO, TNF-α and IL-6 in LPS-activated RAW 264.7 macrophage cells and markedly inhibited LPS-induced expression of TNF-α, IL-6, inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2). Z-590 also significantly reduced paw edema, serum level of TNF-α, IL-6 and spleen index in the adjuvant-induced arthritis (AIA) rat model. Furthermore, Z-590 markedly ameliorated joint inflammation and articular cartilage damage in AIA rat model.

CONCLUSION

MIF inhibitor Z-590 possesses potent anti-arthritic activity through suppression of macrophage activation, and could be a potential therapeutic treatment for RA.

Petasites japonicus bakkenolide B inhibits lipopolysaccharide‑induced pro‑inflammatory cytokines via AMPK/Nrf2 induction in microglia

Abnormal neuroinflammatory responses have diverse roles in neuronal death, oxidative stress and neurodegenerative diseases, such as Alzheimer's and Parkinson's disease. Microglia regulate these responses via molecular signaling cascades that involve inflammatory cytokines and complement proteins. Bakkenolide B from Petasites japonicus exhibits significant anti‑inflammatory and anti‑allergic bioactivities. The present study investigated the anti‑neuroinflammatory effects and underlying molecular mechanisms of bakkenolide B on the lipopolysaccharide (LPS)‑mediated neuroinflammatory response in microglia. The results indicated that bakkenolide B pretreatment significantly reduced microglial production of interleukin (IL)‑1β, IL‑6, IL‑12, and tumor necrosis factor (TNF)‑α. Furthermore, this effect was associated with reduced production of reactive oxygen species. The role of bakkenolide B was then evaluated in the upregulation of nuclear factor erythroid 2‑related factor 2 (Nrf2)/antioxidant response element (ARE) signaling pathways. The results suggested that bakkenolide B significantly upregulated Nrf2/ARE pathway‑related downstream factors, such as NADPH dehydrogenase quinone‑1 (NQO‑1) and heme oxygenase‑1 (HO‑1). Silencing of Nrf2, HO‑1 and NQO‑1 diminished the anti‑neuroinflammatory properties of bakkenolide B. AMP‑activated protein kinase (AMPK) activates the Nrf2/ARE signaling pathway, and the results of the present study demonstrated that bakkenolide B increased AMPK phosphorylation in microglia. In addition, an AMPK inhibitor abolished the bakkenolide B‑induced increase in nuclear Nrf2, NQO‑1 and HO‑1 protein expression. Finally, an AMPK inhibitor diminished the bakkenolide B‑mediated inhibition of LPS‑stimulated TNF‑α production. Taken together, the present results demonstrate that bakkenolide B may be an effective and therapeutically relevant AMPK/Nrf2 pathway activator for suppressing abnormal neuro-inflammation in neurodegenerative diseases.

Dietary teasaponin ameliorates alteration of gut microbiota and cognitive decline in diet-induced obese mice

A high-fat (HF) diet alters gut microbiota and promotes obesity related inflammation and cognitive impairment. Teasaponin is the major active component of tea, and has been associated with anti-inflammatory effects and improved microbiota composition. However, the potential protective effects of teasaponin, against HF diet-induced obesity and its associated alteration of gut microbiota, inflammation and cognitive decline have not been studied. In this study, obesity was induced in C57BL/6 J male mice by feeding a HF diet for 8 weeks, followed by treatment with oral teasaponin (0.5%) mixed in HF diet for a further 6 weeks. Teasaponin treatment prevented the HF diet-induced recognition memory impairment and improved neuroinflammation, gliosis and brain-derived neurotrophic factor (BDNF) deficits in the hippocampus. Furthermore, teasaponin attenuated the HF diet-induced endotoxemia, pro-inflammatory macrophage accumulation in the colon and gut microbiota alterations. Teasaponin also improved glucose tolerance and reduced body weight gain in HF diet-induced obese mice. The behavioral and neurochemical improvements suggest that teasaponin could limit unfavorable gut microbiota alterations and cognitive decline in HF diet-induced obesity.

Activation of Nur77 in microglia attenuates proinflammatory mediators production and protects dopaminergic neurons from inflammation-induced cell death

Microglia-mediated neuroinflammation plays a critical role in the pathological development of Parkinson's disease (PD). Orphan nuclear receptor Nur77 (Nur77) is abundant in neurons, while its role in microglia-mediated neuroinflammation remains unclear. The present data demonstrated that the expression of Nur77 in microglia was reduced accompanied by microglia activation in response to lipopolysaccharide (LPS) in vitro and in experimental 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine-PD mouse model. Nur77 over-expression or application of Nur77 agonist cytosporone B suppressed the expression of proinflammatory genes, such as inducible nitric oxide NOS, cyclooxygenase-2, IL-1β, and tumor necrosis factor-α in the activated microglia, while silenced Nur77 exaggerated the inflammatory responses in microglia. Moreover, activation of Nur77 suppressed the LPS-induced NF-κB activation which was partly dependent on p38 MAPK activity, since inhibition of p38 MAPK by SB203580 abolished the LPS-activated NF-κB in microglia. On the other hand, inhibition of p38 MAPK attenuated LPS-induced Nur77 reduction. Furthermore, in a microglia-conditioned cultured media system, Nur77 ameliorated the cytotoxicity to MN9D dopaminergic cells. Lastly, cytosporone B attenuated microglia activation and loss of dopaminergic neuron in the substantia nigra pars compacta (SNpc) of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine-PD mouse model. Taken together, these findings revealed the first evidence that Nur77 was an important modulator in microglia function that associated with microglia-mediated dopaminergic neurotoxicity, and thus modulation of Nur77 may represent a potential novel target for treatment for neurodegenerative disease.

Accessible Method for the Development of Novel Sterol Analogues with Dipeptide-like Side Chains That Act as Neuroinflammation Inhibitors

A number of novel sterol derivatives with dipeptide-like side chains were synthesized using an Ugi four-component condensation method and assayed to test their anti-inflammatory effects in activated microglial cells. Compound 18b ((3S,10R,13S)-N-((R)-1-(tert-butylamino)-1-oxo-3-phenylpropan-2-yl)-3-hydroxy-N,10,13-trimethyl-2,3,4,7,8,9,10,11,12,13,14,15-dodecahydro-1H-cyclopenta[a]phenanthrene-17-carboxamide) was identified as the most potent anti-inflammatory agent in the series of compounds analyzed. Compound 18b markedly inhibited the expression of proinflammatory factors, including inducible nitric oxide synthase, interleukin (IL)-6, IL-1β, tumor necrosis factor-α, and cyclooxygenase-2 in lipopolysaccharide-stimulated microglial cells. Further studies showed that compound 18b significantly suppressed the transcriptional activity of AP-1 and NF-κB in activated microglial cells, which was likely mediated by the inhibition of the p38 MAPK and JNK signal transduction pathways. In addition, compound 18b displayed neuroprotective effects in a microglial-conditioned medium/neuron coculture and an experimental focal ischemic mouse model.

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.

MicroRNA let-7c-5p protects against cerebral ischemia injury via mechanisms involving the inhibition of microglia activation

The present study was designed to reveal the potential role of let-7c-5p, a highly conserved miRNA in stroke. We found that the content of let-7c-5p was significantly decreased in the plasma of patients with ischemic stroke as well as in experimental animals. Moreover, we also observed a significant decrease of let-7c-5p in ipsilateral cortex and striatum in mice that were subjected to middle cerebral artery occlusion (MCAO) at 24h reperfusion. Overexpression of let-7c-5p via ICV injection decreased the infarction volume and attenuated the neurological deficits, and most interestingly, inhibited microglial activation. To further explore the mechanism, we checked let-7c-5p expression in BV2 cells and primary microglia in an OGD condition and in LPS-induced microglial activation. The results indicated that decreased let-7c-5p was evidenced in the activated microglia. Overexpression of let-7c-5p in BV2 cells remarkably inhibited the microglial activation. The inhibition of microglial activation by overexpression of let-7c-5p was also observed in mice with experimental stroke, which is in line with the decreased infarction volume and improved neurological deficits. We identified that let-7c-5p directly targeted to the 3'-untranslated region of the caspase 3 mRNA to reduce caspase 3 levels, which may underline the miRNA - modulated microglial activity. The present study revealed that suppression of microglia activation by let-7c-5p overexpression may be involved in the protection effects of ischemic damage. The mechanism may include the miRNA-mediated caspase 3 pathway.

Allosteric modulation of sigma-1 receptors by SKF83959 inhibits microglia-mediated inflammation

Recent studies have shown that sigma-1 receptor orthodox agonists can inhibit neuroinflammation. SKF83959 (3-methyl-6-chloro-7,8-hydroxy-1-[3-methylphenyl]-2,3,4,5-tetrahydro-1H-3-benzazepine), an atypical dopamine receptor-1 agonist, has been recently identified as a potent allosteric modulator of sigma-1 receptor. Here, we investigated the anti-inflammatory effects of SKF83959 in lipopolysaccharide (LPS)-stimulated BV2 microglia. Our results indicated that SKF83959 significantly suppressed the expression/release of the pro-inflammatory mediators, such as tumor necrosis factor-α (TNF-α), interleukin-1β (IL-1β), inducible nitric oxide synthase (iNOS), and inhibited the generation of reactive oxygen species. All of these responses were blocked by selective sigma-1 receptor antagonists (BD1047 or BD1063) and by ketoconazole (an inhibitor of enzyme cytochrome c17 to inhibit the synthesis of endogenous dehydroepiandrosterone, DHEA). Additionally, we found that SKF83959 promoted the binding activity of DHEA with sigma-1 receptors, and enhanced the inhibitory effects of DHEA on LPS-induced microglia activation in a synergic manner. Furthermore, in a microglia-conditioned media system, SKF83959 inhibited the cytotoxicity of conditioned medium generated by LPS-activated microglia toward HT-22 neuroblastoma cells. Taken together, our study provides the first evidence that allosteric modulation of sigma-1 receptors by SKF83959 inhibits microglia-mediated inflammation. SKF83959 is a potent allosteric modulator of sigma-1 receptor. Our results indicated that SKF83959 enhanced the activity of endogenous dehydroepiandrosterone (DHEA) in a synergic manner, and inhibited the activation of BV2 microglia and the expression/release of the pro-inflammatory mediators, such as tumor necrosis factor-α (TNF-α), interleukin-1β (IL-1β), inducible nitric oxide synthase (iNOS).

Structure-Activity Relationships and Anti-inflammatory Activities of N-Carbamothioylformamide Analogues as MIF Tautomerase Inhibitors

Macrophage migration inhibitory factor (MIF), a proinflammatory cytokine, is an attractive therapeutic target for the treatment of inflammatory diseases. In our previous study, 3-[(biphenyl-4-ylcarbonyl)carbamothioyl]amino benzoic acid (compound 1) was discovered as a potent inhibitor of MIF by docking-based virtual screening and bioassays. Here, a series of analogues of compound 1 derived from similarity search and chemical synthesis were evaluated for their MIF tautomerase activities, and their structure-activity relationships were then analyzed. The most potent inhibitor (compound 5) with an IC50 of 370 nM strongly suppressed lipopolysaccharide (LPS)-induced production of TNF-α and IL-6 in a dose-dependent manner and significantly enhanced the survival rate of mice with LPS-induced endotoxic shock from 0 to 35% at 0.5 mg/kg and to 45% at 1 mg/kg, highlighting the therapeutic potential of the MIF tautomerase inhibition in inflammatory diseases.

Anti-inflammatory effects of glaucocalyxin B in microglia cells

Over-activated microglia is involved in various kinds of neurodegenerative process including Parkinson, Alzheimer and HIV dementia. Suppression of microglial over activation has emerged as a novel strategy for treatment of neuroinflammation-based neurodegeneration. In the current study, anti-inflammatory and neuroprotective effects of the ent-kauranoid diterpenoids, which were isolated from the aerial parts of Rabdosia japonica (Burm. f.) var. glaucocalyx (Maxim.) Hara, were investigated in cultured microglia cells. Glaucocalyxin B (GLB), one of five ent-kauranoid diterpenoids, significantly decreased the generation of nitric oxide (NO), tumor necrosis factor (TNF)-α, interleukin (IL)-1β, cyclooxygenase (COX)-2 and inducible nitric oxide synthase (iNOS) in the lipopolysaccharide (LPS)-activated microglia cells. In addition, GLB inhibited activation of nuclear factor-κB (NF-κB), p38 mitogen-activated protein kinase (MAPK) and generation of reactive oxygen species (ROS) in LPS-activated microglia cells. Furthermore, GLB strongly induced the expression of heme oxygenase (HO)-1 in BV-2 microglia cells. Finally, GLB exhibited neuroprotective effect by preventing over-activated microglia induced neurotoxicity in a microglia/neuron co-culture model. Taken together, the present study demonstrated that the GLB possesses anti-nueroinflammatory activity, and might serve as a potential therapeutic agent for treating neuroinflammatory diseases.

Induction of COX-2-PGE2 synthesis by activation of the MAPK/ERK pathway contributes to neuronal death triggered by TDP-43-depleted microglia

Neuroinflammation is a striking hallmark of amyotrophic lateral sclerosis (ALS) and other neurodegenerative disorders. Previous studies have shown the contribution of glial cells such as astrocytes in TDP-43-linked ALS. However, the role of microglia in TDP-43-mediated motor neuron degeneration remains poorly understood. In this study, we show that depletion of TDP-43 in microglia, but not in astrocytes, strikingly upregulates cyclooxygenase-2 (COX-2) expression and prostaglandin E2 (PGE2) production through the activation of MAPK/ERK signaling and initiates neurotoxicity. Moreover, we find that administration of celecoxib, a specific COX-2 inhibitor, greatly diminishes the neurotoxicity triggered by TDP-43-depleted microglia. Taken together, our results reveal a previously unrecognized non-cell-autonomous mechanism in TDP-43-mediated neurodegeneration, identifying COX-2-PGE2 as the molecular events of microglia- but not astrocyte-initiated neurotoxicity and identifying celecoxib as a novel potential therapy for TDP-43-linked ALS and possibly other types of ALS.

Design, synthesis and evaluation of a series of non-steroidal anti-inflammatory drug conjugates as novel neuroinflammatory inhibitors

Neuroinflammation is involved in the process of several central nervous system (CNS) diseases such as Parkinson's disease, Alzheimer's disease, ischemia and multiple sclerosis. As the macrophages in the central nervous system, microglial cell function in the innate immunity of the brain and are largely responsible for the inflammation-mediated neurotoxicity. Prevention of microglia activation might alleviate neuronal damage and degeneration under the inflammatory conditions, and therefore, represents a possible therapeutic approach to the aforementioned CNS diseases. Here we report the synthesis of a number of non-steroidal anti-inflammatory drug (NSAID) conjugates, and the evaluation of their anti-inflammatory effects in lipopolysaccharide (LPS)-stimulated BV-2 microglial cells and primary mouse microglial cells. Among the tested analogues, compounds 8 and 11 demonstrated potent inhibition of nitric oxide production with no or weak cell toxicity. Compound 8 also significantly suppressed the expression of tumor necrosis factor (TNF)-α, interleukin (IL)-6, cyclooxygenase (COX)-2 as well as inducible nitric oxide synthase (iNOS) in LPS-stimulated BV-2 microglial cells. Further mechanistic studies indicated that compound 8 significantly suppressed phosphorylation of mitogen-activated protein kinases (MAPKs) and subsequent activation of activator of transcription 1 (AP-1). Furthermore, in a co-culture system, compound 8 inhibited the cytotoxicity generated by LPS-activated microglia toward HT-22 neuroblastoma cells. Collectively, these experimental results demonstrated that compound 8 possessed potent anti-neuroinflammatory activity via inhibition of microglia activation, and might serve as a potential lead for the therapeutic treatment of neuroinflammatory diseases.

Inhibition of neuroinflammation by synthetic androstene derivatives incorporating amino acid methyl esters on activated BV-2 microglia

Androstene derivatives incorporating amino acid methyl esters were prepared, and their anti-inflammatory effects were evaluated in lipopolysaccharide (LPS)-activated BV-2 microglial cells. Several compounds exhibited dose-dependent inhibition. The most active compound, methyl ((3S,10R,13S)-3-hydroxy-10,13-dimethyl-2,3,4,7,8,9,10,11,12,13,14,15,16,17-tetradecahydro-1H-cyclopenta[a]phenanthrene-17-carbonyl)-L-phenylalaninate (10) significantly suppressed LPS-induced expression of inducible nitric oxide synthase (iNOS), cyclooxygenase-2 (COX-2), interleukin-6 (IL-6), and tumor necrosis factor-α (TNF-α). Mechanistic studies revealed that compound 10 markedly inhibits phosphorylation of p38 mitogen-activated protein kinases (MAPKs) and subsequent transcription factor (NF-κB) and activator protein-1 (AP-1) activation. Furthermore, compound 10 decreased LPS-activated microglial neurotoxicity in a condition medium/HT-22 neuroblastoma co-culture model. Taken together, these results suggest 10 is a potential lead compound for the development of a novel therapeutic agent for neurodegenerative diseases.