Suppression of the TRIF-dependent signaling pathway of Toll-like receptors by luteolin

Luteolin inhibits herpes simplex virus 1 infection by activating cyclic guanosine monophosphate-adenosine monophosphate synthase-mediated antiviral innate immunity

BACKGROUND

The successive outbreaks of large-scale infectious diseases due to virus infection have been a major threat to human health in recent decades. Herpes simplex virus I (HSV-1) is a widely-disseminated DNA virus that infects the central nervous system to cause herpes labialis, keratitis and herpes simplex virus encephalitis (HSE), resulting in recurrent lifelong clinical or subclinical episodes. Luteolin is a plant flavone that has been extensively used in the treatment of various human diseases, including carcinogenesis, inflammation and chronic degenerative diseases.

PURPOSE

The aim of this study was to investigate the antiviral molecular mechanism of luteolin against HSV-1 infection in vitro and in vivo.

METHODS

The antiviral effect of luteolin in cell lines was examined by viral plaque assay, RT-qPCR, Western blot and time-of-addition assay. The interaction between luteolin and cyclic guanosine monophosphate-adenosine monophosphate synthase (cGAS) was evaluated by molecular modeling and semi-denaturing detergent agarose gel electrophoresis. The efficacy of luteolin on HSE was evaluated in the HSE mouse model by analyzing weight loss, neurodegenerative symptoms and histopathological scores. Cytokine expression and protein levels were examined by RT-qPCR, Western blot and ELISA.

RESULTS

Luteolin inhibited the early process of HSV-1 infection, without affecting the infection of acyclovir-resistant HSV-1 strains. In addition, luteolin enhanced antiviral type I interferon production and activated the cytoplasmic DNA-sensing cGAS-stimulator of interferon gene (STING) pathway. Luteolin directly bound the active substrate binding site and promoted the oligomerization of cGAS. Luteolin also inhibited HSE-related weight loss, neurodegeneration and neuroinflammation in mice caused by HSV-1 infection. Furthermore, luteolin enhanced type I interferon expression and stimulated the cGAS-STING signaling pathway in vivo.

CONCLUSION

Luteolin inhibited the post-entry process of HSV-1 by activating the cGAS-STING pathway to promote antiviral interferon production. These results provided the rationale for luteolin as a potent cGAS activator and antiviral agent.

Neuroprotective Agents with Therapeutic Potential for COVID-19

COVID-19 patients can exhibit a wide range of clinical manifestations affecting various organs and systems. Neurological symptoms have been reported in COVID-19 patients, both during the acute phase of the illness and in cases of long-term COVID. Moderate symptoms include ageusia, anosmia, altered mental status, and cognitive impairment, and in more severe cases can manifest as ischemic cerebrovascular disease and encephalitis. In this narrative review, we delve into the reported neurological symptoms associated with COVID-19, as well as the underlying mechanisms contributing to them. These mechanisms include direct damage to neurons, inflammation, oxidative stress, and protein misfolding. We further investigate the potential of small molecules from natural products to offer neuroprotection in models of neurodegenerative diseases. Through our analysis, we discovered that flavonoids, alkaloids, terpenoids, and other natural compounds exhibit neuroprotective effects by modulating signaling pathways known to be impacted by COVID-19. Some of these compounds also directly target SARS-CoV-2 viral replication. Therefore, molecules of natural origin show promise as potential agents to prevent or mitigate nervous system damage in COVID-19 patients. Further research and the evaluation of different stages of the disease are warranted to explore their potential benefits.

Foodomics-Based Approaches Shed Light on the Potential Protective Effects of Polyphenols in Inflammatory Bowel Disease

Inflammatory bowel disease (IBD) is a chronic and progressive inflammatory disorder affecting the gastrointestinal tract (GT) caused by a wide range of genetic, microbial, and environmental factors. IBD is characterized by chronic inflammation and decreased gut microbial diversity, dysbiosis, with a lower number of beneficial bacteria and a concomitant increase in pathogenic species. It is well known that dysbiosis is closely related to the induction of inflammation and oxidative stress, the latter caused by an imbalance between reactive oxygen species (ROS) production and cellular antioxidant capacity, leading to cellular ROS accumulation. ROS are responsible for intestinal epithelium oxidative damage and the increased intestinal permeability found in IBD patients, and their reduction could represent a potential therapeutic strategy to limit IBD progression and alleviate its symptoms. Recent evidence has highlighted that dietary polyphenols, the natural antioxidants, can maintain redox equilibrium in the GT, preventing gut dysbiosis, intestinal epithelium damage, and radical inflammatory responses. Here, we suggest that the relatively new foodomics approaches, together with new technologies for promoting the antioxidative properties of dietary polyphenols, including novel delivery systems, chemical modifications, and combination strategies, may provide critical insights to determine the clinical value of polyphenols for IBD therapy and a comprehensive perspective for implementing natural antioxidants as potential IBD candidate treatment.

Oxidative stress, hormones, and effects of natural antioxidants on intestinal inflammation in inflammatory bowel disease

Inflammatory bowel disease (IBD) is a chronic, relapsing gastrointestinal (GI) disorder characterized by intestinal inflammation. The etiology of IBD is multifactorial and results from a complex interplay between mucosal immunity, environmental factors, and host genetics. Future therapeutics for GI disorders, including IBD, that are driven by oxidative stress require a greater understanding of the cellular and molecular mechanisms mediated by reactive oxygen species (ROS). In the GI tract, oxidative stressors include infections and pro-inflammatory responses, which boost ROS generation by promoting the production of pro-inflammatory cytokines. Nuclear factor kappa B (NF-κB) and nuclear factor erythroid 2-related factor 2 (Nrf2) represent two important signaling pathways in intestinal immune cells that regulate numerous physiological processes, including anti-inflammatory and antioxidant activities. Natural antioxidant compounds exhibit ROS scavenging and increase antioxidant defense capacity to inhibit pro-oxidative enzymes, which may be useful in IBD treatment. In this review, we discuss various polyphenolic substances (such as resveratrol, curcumin, quercetin, green tea flavonoids, caffeic acid phenethyl ester, luteolin, xanthohumol, genistein, alpinetin, proanthocyanidins, anthocyanins, silymarin), phenolic compounds including thymol, alkaloids such as berberine, storage polysaccharides such as tamarind xyloglucan, and other phytochemicals represented by isothiocyanate sulforaphane and food/spices (such as ginger, flaxseed oil), as well as antioxidant hormones like melatonin that target cellular signaling pathways to reduce intestinal inflammation occurring with IBD.

Beyond DNA sensing: expanding the role of cGAS/STING in immunity and diseases

Cyclic guanosine monophosphate-adenosine monophosphate (cGAMP) synthase (cGAS) is a DNA sensor that elicits a robust type I interferon response by recognizing ubiquitous danger-associated molecules. The cGAS/stimulator of interferon genes (cGAS/STING) is activated by endogenous DNA, including DNA released from mitochondria and extranuclear chromatin, as well as exogenous DNA derived from pathogenic microorganisms. cGAS/STING is positioned as a key axis of autoimmunity, the inflammatory response, and cancer progression, suggesting that the cGAS/STING signaling pathway represents an efficient therapeutic target. Based on the accumulated evidence, we present insights into the prevention and treatment of cGAS/STING-related chronic immune and inflammatory diseases. This review presents the current state of clinical and nonclinical development of modulators targeting cGAS/STING, providing useful information on the design of therapeutic strategies.

Dietary (poly)phenols mitigate inflammatory bowel disease: Therapeutic targets, mechanisms of action, and clinical observations

Inflammatory bowel diseases (IBD), which include Crohn's disease and ulcerative colitis, are a rapidly growing public health concern worldwide. These diseases are heterogeneous at the clinical, immunological, molecular, genetic, and microbial level, but characteristically involve a disrupted immune-microbiome axis. Shortcomings in conventional treatment options warrant the need for novel therapeutic strategies to mitigate these life-long and relapsing disorders of the gastrointestinal tract. Polyphenols, a diverse group of phytochemicals, have gained attention as candidate treatments due to their array of biological effects. Polyphenols exert broad anti-inflammatory and antioxidant effects through the modulation of cellular signaling pathways and transcription factors important in IBD progression. Polyphenols also bidirectionally modulate the gut microbiome, supporting commensals and inhibiting pathogens. One of the primary means by which gut microbiota interface with the host is through the production of metabolites, which are small molecules produced as intermediate or end products of metabolism. There is growing evidence to support that modulation of the gut microbiome by polyphenols restores microbially derived metabolites critical to the maintenance of intestinal homeostasis that are adversely disrupted in IBD. This review aims to define the therapeutic targets of polyphenols that may be important for mitigation of IBD symptoms, as well as to collate evidence for their clinical use from randomized clinical trials.

Identification of Protosappanoside D from Caesalpinia decapetala and Evaluation of Its Pharmacokinetic, Metabolism and Pharmacological Activity

Protosappanoside D (PTD) is a new component isolated from the extract of Caesalpinia decapetala for the first time. Its structure was identified as protosappanin B-3-O-β-D-glucoside by ¹H-NMR, ¹³C-NMR, 2D-NMR and MS techniques. To date, the pharmacological activities, metabolism or pharmacokinetics of PTD has not been reported. Therefore, this research to study the anti-inflammatory activity of PTD was investigated via the LPS-induced RAW264.7 cells model. At the same time, we also used the UHPLC/Q Exactive Plus MS and UPLC-MS/MS methods to study the metabolites and pharmacokinetics of PTD, to calculate its bioavailability for the first time. The results showed that PTD could downregulate secretion of the pro-inflammatory cytokines. In the metabolic study, four metabolites were identified, and the primary degradative pathways in vivo involved the desaturation, oxidation, methylation, alkylation, dehydration, degradation and desugarization. In the pharmacokinetic study, PTD and its main metabolite protosappanin B (PTB) were measured after oral and intravenous administration. After oral administration of PTD, its T_max was 0.49 h, t_1/2z and MRT_(0–t) were 3.47 ± 0.78 h and 3.06 ± 0.63 h, respectively. It shows that PTD was quickly absorbed into plasma and it may be eliminated quickly in the body, and its bioavailability is about 0.65%.

Luteolin is an Effective Component of Platycodon grandiflorus in Promoting Wound Healing in Rats with Cutaneous Scald Injury

Background

Platycodon grandiflorus could significantly improve the pathological results of cutaneous scald injury, reduce the release of inflammatory factors and promote angiogenesis. This study investigated the wound healing effect of luteolin, an active component of P. grandiflorus, on induced cutaneous scald injury in Sprague-Dawley (SD) rats.

Methods

The protein expression levels of TNF-α and IL-6 were detected by ELISA. QRT-PCR was adopted to detect the expression of TGF-β1 and VEGF. Histopathological changes of scald wounds were analyzed by hematoxylin-eosin staining. Cell viability and migration ability were detected by CCK-8 assay and scratch assay.

Results

Both in vivo and in vitro experiments showed that luteolin promoted wound healing of cutaneous scald injury. Gene Oncology (GO) functional analysis and rescue experiments showed that endothelial nitric oxide synthase 3 (NOS3) was the critical target of luteolin in treating cutaneous scald.

Conclusion

This study demonstrated that luteolin is an effective component of P. grandiflorus and is effective in the treatment of cutaneous scald injury.

Anti-Inflammatory Activity of Glabralactone, a Coumarin Compound from Angelica sinensis, via Suppression of TRIF-Dependent IRF-3 Signaling and NF-κB Pathways

The dried root of Angelica sinensis (A. sinensis) has been widely used in Chinese traditional medicine for various diseases such as inflammation, osteoarthritis, infections, mild anemia, fatigue, and high blood pressure. Searching for the secondary metabolites of A. sinensis has been mainly conducted. However, the bioactivity of coumarins in the plant remains unexplored. Therefore, this study was designed to evaluate the anti-inflammatory activity of glabralactone, a coumarin compound from A. sinensis, using in vitro and in vivo models, and to elucidate the underlying molecular mechanisms of action. Glabralactone effectively inhibited nitric oxide production in lipopolysaccharide- (LPS-) stimulated RAW264.7 macrophage cells. The downregulation of LPS-induced mRNA and protein expression of iNOS, TNF-α, IL-1β, and miR-155 was found by glabralactone. The activation of NF-κB and TRIF-dependent IRF-3 pathway was also effectively suppressed by glabralactone in LPS-stimulated macrophages. Glabralactone (5 and 10 mg/kg) exhibited an in vivo anti-inflammatory activity with the reduction of paw edema volume in carrageenan-induced rat model, and the expressions of iNOS and IL-1β proteins were suppressed by glabralactone in the paw soft tissues of the animal model. Taken together, glabralactone exhibited an anti-inflammatory activity in in vitro and in vivo models. These findings reveal that glabralactone might be one of the potential components for the anti-inflammatory activity of A. sinensis and may be prioritized in the development of a chemotherapeutic agent for the treatment of inflammatory diseases.

The Role of Natural Products in Treatment of Depressive Disorder

Depressive disorder is one of the most common psychiatric syndromes that, if left untreated, can cause many disturbances in a person's life. Numerous factors are involved in depression, including inflammation, brain-derived neurotrophic factor (BDNF), GABAergic system, hypothalamic- pituitary-adrenal (HPA) Axis, monoamine neurotransmitters (serotonin (5-HT), noradrenaline, and dopamine). Common treatments for depression are selective serotonin reuptake inhibitors, tricyclic antidepressants, and monoamine oxidase inhibitors, but these drugs have several side effects such as anxiety, diarrhea, constipation, weight loss, and sexual dysfunctions. These agents only reduce the symptoms and temporarily reduce the rate of cognitive impairment associated with depression. As a result, extensive research has recently been conducted on the potential use of antidepressant and sedative herbs. According to the available data, herbs used in traditional medicine can be significantly effective in reducing depression, depressive symptoms and improving patients' performance. The present study provides a summary of biomarkers and therapeutic goals of depression and shows that natural products such as saffron or genipin have antidepressant effects. Some of the useful natural products and their mechanisms were evaluated. Data on various herbs and natural isolated compounds reported to prevent and reduce depressive symptoms is also discussed.

Anti-Inflammatory and Active Biological Properties of the Plant-Derived Bioactive Compounds Luteolin and Luteolin 7-Glucoside

Flavonoids are interesting molecules synthetized by plants. They can be found abundantly in seeds and fruits, determining the color, flavor, and other organoleptic characteristics, as well as contributing to important nutritional aspects. Beyond these characteristics, due to their biochemical properties and characteristics, they can be considered bioactive compounds. Several interesting studies have demonstrated their biological activity in different cellular and physiological processes in high-order organisms including humans. The flavonoid molecular structure confers the capability of reacting with and neutralizing reactive oxygen species (ROS), behaving as scavengers in all processes generating this class of molecules, such as UV irradiation, a process widely present in plant physiology. Importantly, the recent scientific literature has demonstrated that flavonoids, in human physiology, are active compounds acting not only as scavengers but also with the important role of counteracting the inflammation process. Among the wide variety of flavonoid molecules, significant results have been shown by investigating the role of the flavones luteolin and luteolin-7-O-glucoside (LUT-7G). For these compounds, experimental results demonstrated an interesting anti-inflammatory action, both in vitro and in vivo, in the interaction with JAK/STAT3, NF-κB, and other pathways described in this review. We also describe the effects in metabolic pathways connected with inflammation, such as cellular glycolysis, diabetes, lipid peroxidation, and effects in cancer cells. Moreover, the inhibition of inflammatory pathway in endothelial tissue, as well as the NLRP3 inflammasome assembly, demonstrates a key role in the progression of such phenomena. Since these micronutrient molecules can be obtained from food, their biochemical properties open new perspectives with respect to the long-term health status of healthy individuals, as well as their use as a coadjutant treatment in specific diseases.

Lactobacillus plantarum FNCC 0137 fermented red Moringa oleifera exhibits protective effects in mice challenged with Salmonella typhi via TLR3/TLR4 inhibition and down-regulation of proinflammatory cytokines

Background

Salmonella typhi is a foodborne pathogenic bacterium that threatens health. S. typhi infection exacerbated the antibiotic resistance problem that needs alternative strategies. Moringa oleifera possesses anti-inflammatory and antimicrobial effects. However, there is a lack of information about the pharmacological value of red M. oleifera. The fermentation of red M. oleifera leaves extract (RMOL) is expected to add to its nutritional value.

Objective

The present study aimed to evaluate non-fermented RMOL (NRMOL) and fermented RMOL (FRMOL) effects on S. typhi infection in mice.

Materials and methods

Female Balb/C mice were randomly divided into eight groups. The treatment groups were orally administered with NRMOL or FRMOL at doses 14, 42, and 84 mg/kg BW during the 28 days experimental period. Then S. typhi was introduced to mice through intraperitoneal injection except in the healthy groups. The NRMOL or FRMOL administration was continued for the next seven days. Cells that expressed CD11b⁺ TLR3⁺, CD11b⁺TLR4⁺, CD11b⁺IL-6⁺, CD11b⁺IL-17⁺, CD11b⁺TNF-a⁺, and CD4⁺CD25⁺CD62L⁺ were assessed by flow cytometry.

Results

Our result suggested that NRMOL and FRMOL extracts significantly reduced (p < 0.05) the expression of CD11b⁺TLR3⁺, CD11b⁺TLR4⁺, CD11b⁺IL-6⁺, CD11b⁺IL-17⁺, and CD11b⁺TNF-α⁺ subsets. In contrast, NRMOL and FRMOL extracts significantly increased (p < 0.05) the expression of CD4⁺CD25⁺CD62L⁺ subsets. NRMOL at dose 14 and 42 mg/kg BW was more effective compared to FRMOL in reducing the expression of CD11b⁺TLR3⁺, CD11b⁺TLR4⁺, and CD11b⁺TNF-α⁺ subsets.

Conclusion

Our findings demonstrated that NRMOL and FRMOL extracts could be promising agents for protection against S. typhi infection via modulation of TLR3/TLR4, regulatory T cells, and proinflammatory cytokines.

Luteolin as a modulator of skin aging and inflammation

Luteolin belongs to the group of flavonoids and can be found in flowers, herbs, vegetables and spices. It plays an important role in defending plants, for example against UV radiation by partially absorbing UVA and UVB radiation. Thus, luteolin can also decrease adverse photobiological effects in the skin by acting as a first line of defense. Furthermore, anti-oxidative and anti-inflammatory activities of luteolin were described on keratinocytes and fibroblasts as well as on several immune cells (e.g., macrophages, mast cell, neutrophils, dendritic cells and T cells). Luteolin can suppress proinflammatory mediators (e.g., IL-1β, IL-6, IL-8, IL-17, IL-22, TNF-α and COX-2) and regulate various signaling pathway (e.g., the NF-κB, JAK-STAT as well as TLR signaling pathway). In this way, luteolin modulates many inflammatory processes of the skin. The present review summarizes the recent in vitro and in vivo research on luteolin in the field of skin aging and skin cancer, wound healing as well as inflammatory skin diseases, including psoriasis, contact dermatitis and atopic dermatitis. In conclusion, luteolin might be a promising molecule for the development of topic formulations and systemic agents against inflammatory skin diseases.

A novel chrysin thiazole derivative polarizes macrophages to an M1 phenotype via targeting TLR4

Tumor-associated macrophages (TAMs) are an important cause of tumorigenesis and tumor development. M2 macrophages can promote tumor growth while M1 macrophages kill tumor cells, therefore, polarizing macrophages to achieve a functional M1 phenotype could effectively play its anti-tumor role. In the current study, we synthesized a novel chrysin derivative which is termed as ChR-TD. And we found ChR-TD might be a ligand of TLR4 that polarized the TAMs towards M1 phenotype and played its anti-tumor role. Further study indicated that ChR-TD reprogrammed the macrophages into an M1 phenotype via TLR4 activation. Moreover, ChR-TD activated TLR4/NF-κB signaling pathway and promoted the NF-κB/p65 translocated into the nuclear, leading to the activation of NF-κB and proinflammatory cytokines release. In addition, type I interferon signaling was also activated by ChR-TD, leading to the expressions of IFN-α and IFN-β and its targeted genes NOS2, MCP-1 and IP-10 were significantly increased in macrophages. Importantly, these effects were disturbed in TLR4^-/- macrophages, which are constructed by using CRISPR/Cas9 system. And the molecule docking simulation further indicated that ChR-TD could bind to TLR4 and might be a ligand of TLR4. Hence, these findings suggested that ChR-TD might be a ligand of TLR4 and can be used as a potential lead compound for tumors treatment.

Canine atopic dermatitis: Role of luteolin as new natural treatment

Background

Luteolin has been demonstrated to possess numerous biological effects. However, the effect of luteolin on LPS (Lipopolysaccharides) stimulation in CPEK cells has not been investigated.

Hypothesis/Objectives

An in vitro model of atopic canine dermatitis was used to identify the antioxidant effect of luteolin as a new treatment that is capable of improving the conditions of veterinary patients.

Methods

CPEK cells were treated with or without luteolin in the presence or absence of LPS. A cell viability assay was performed to test luteolin toxicity and the protective effect of luteolin after LPS stimulation. Additionally, enzyme‐linked immunosorbent assay (ELISA) kits were used to detect the levels of IL‐33, IL‐1β, IL‐6, and IL‐8.

Results

Luteolin was capable to significantly decrease levels expression of IL‐33, IL 1β, IL‐6, and IL‐8.

Conclusions and clinical importance

Luteolin could be a new pharmacological treatment for canine atopic dermatitis.

An Update of Palmitoylethanolamide and Luteolin Effects in Preclinical and Clinical Studies of Neuroinflammatory Events

The inflammation process represents of a dynamic series of phenomena that manifest themselves with an intense vascular reaction. Neuroinflammation is a reply from the central nervous system (CNS) and the peripheral nervous system (PNS) to a changed homeostasis. There are two cell systems that mediate this process: the glia of the CNS and the lymphocites, monocytes, and macrophages of the hematopoietic system. In both the peripheral and central nervous systems, neuroinflammation plays an important role in the pathogenesis of neurodegenerative diseases, such as Parkinson’s and Alzheimer’s diseases, and in neuropsychiatric illnesses, such as depression and autism spectrum disorders. The resolution of neuroinflammation is a process that allows for inflamed tissues to return to homeostasis. In this process the important players are represented by lipid mediators. Among the naturally occurring lipid signaling molecules, a prominent role is played by the N-acylethanolamines, namely N-arachidonoylethanolamine and its congener N-palmitoylethanolamine, which is also named palmitoylethanolamide or PEA. PEA possesses a powerful neuroprotective and anti-inflammatory power but has no antioxidant effects per se. For this reason, its co-ultramicronization with the flavonoid luteolin is more efficacious than either molecule alone. Inhibiting or modulating the enzymatic breakdown of PEA represents a complementary therapeutic approach to treating neuroinflammation. The aim of this review is to discuss the role of ultramicronized PEA and co-ultramicronized PEA with luteolin in several neurological diseases using preclinical and clinical approaches.

Anti-inflammatory effects of nobiletin on TLR4/TRIF/IRF3 and TLR9/IRF7 signaling pathways in prostate cancer cells

Background: Toll-like receptors (TLRs) are often expressed in natural immune cells as well as in tumor cells. TLR4 exhibits both tumor promoting and tumor-suppressing roles and higher TLR9 expression is an important marker of poor prognosis in prostate cancer (PCa). Nobiletin (NOB) is an O-methylated flavonoid and NOB has been proven to have anti-cancer effect in PCa cells. However, there is no study in the literature investigating the potential anti-inflammatory effects of NOB on the TLR signaling pathways in cancer. Therefore, we aimed to explore the potential anti-inflammatory effects of NOB on the TLR4/TRIF/IRF3 and TLR9/IRF7 signaling pathways in different types of PCa cell lines, for the first time.Material and methods: In the current study, the cytotoxic effect of NOB PC-3 (hormone-independent and metastatic) and LNCaP cells (hormone-dependent) was evaluated by WST-1 assay. Furthermore, the inhibitory effects of NOB on TLR4/TRIF/IRF3 and TLR9/IRF7signaling pathway were determined by RT-PCR, western blotting and ELISA analysis.Results: NOB demonstrated an inhibitory effect on PCa cell growth and LNCaP cells were more sensitive to NOB than PC-3 cells due to androjen receptor status. Furthermore, NOB alone could suppress TLR4/TRIF/IRF3 and TLR9/IRF7 signaling pathways through the downregulation of their associated pathways (mRNA and related protein levels) and the release of IFN-α and IFN-β compared to LPS or CpG-ODN stimulated PCa cells.Conclusions: NOB potentially inhibited TLR4 and TL9-dependent signaling pathway in PCa cells. However, the efficacy of NOB was different in PCa cells due to the hormone status and aggressive features.

Anti-inflammatory effect of synthesized indole-based chalcone (2E)-3-(4-bromophenyl)-1-(1H-indol-3-yl) prop-2-en-1-one: an in vitro and in vivo studies

Purpose: Chalcones are precursors of flavonoids with a wide range of pharmacological activities. This study evaluates the anti-inflammatory effect of indole based chalcone derivative (2E)-3-(4-bromophenyl)-1-(1H-indol-3-yl) prop-2-en-1-one (IC9) on lipopolysaccharide (LPS) activated murine macrophages RAW264.7 cells and carrageenan-induced acute model in rats.Materials and methods: LPS-treated RAW264.7 cell lines and carrageenan-induced animal model were employed to evaluate the anti-inflammatory activity of IC9. The cell cytotoxicity studies were carried out by MTT assay. Reactive oxygen species (ROS) production and other inflammatory markers such as prostaglandin E2 (PGE2), nitric oxide (NO) as well as cyclooxygenase-2 (COX-2) activity were determined using ELISA. The RT-PCR was performed to determine mRNA expressions in the case of inducible nitric oxide synthase (iNOS), COX-2, Toll-like receptor-4 (TLR-4) and also nuclear translocation of NF-κB activity.Results: LPS-activated RAW264.7 cells showed an increased level of ROS generation and other inflammatory markers such as PGE2, NO level and COX-2 activity. Expression of iNOS, COX- 2 and TLR-4 mRNA expression were also up-regulated along with nuclear translocation of NF-κB. On IC9 supplementation, all the above parameters of LPS-activated cells were found to be reversed, resembling the control group. Moreover, IC9 significantly inhibited paw swelling and exhibited maximum inhibition of 78.45% at low dose of 7.5 mg/kg.bwt.Conclusions: The targeting anti-inflammatory efficacy and profound NF-κB sensitive transcriptional regulatory mechanism of IC9 accounts for its effective anti-inflammatory action.

Regulation of Toll-Like Receptor (TLR) Signaling Pathway by Polyphenols in the Treatment of Age-Linked Neurodegenerative Diseases: Focus on TLR4 Signaling

Neuronal dysfunction initiates several intracellular signaling cascades to release different proinflammatory cytokines and chemokines, as well as various reactive oxygen species. In addition to neurons, microglia, and astrocytes are also affected by this signaling cascade. This release can either be helpful, neutral or detrimental for cell survival. Toll-like receptors (TLRs) activate and signal their downstream pathway to activate NF-κB and pro-IL-1β, both of which are responsible for neuroinflammation and linked to the pathogenesis of different age-related neurological conditions. However, herein, recent aspects of polyphenols in the treatment of neurodegenerative diseases are assessed, with a focus on TLR regulation by polyphenols. Different polyphenol classes, including flavonoids, phenolic acids, phenolic alcohols, stilbenes, and lignans can potentially target TLR signaling in a distinct pathway. Further, some polyphenols can suppress overexpression of inflammatory mediators through TLR4/NF-κB/STAT signaling intervention, while others can reduce neuronal apoptosis via modulating the TLR4/MyD88/NF-κB-pathway in microglia/macrophages. Indeed, neurodegeneration etiology is complex and yet to be completely understood, it may be that targeting TLRs could reveal a number of molecular and pharmacological aspects related to neurodegenerative diseases. Thus, activating TLR signaling modulation via natural resources could provide new therapeutic potentiality in the treatment of neurodegeneration.

Anti-Inflammatory Effects of Catalpalactone Isolated from Catalpa ovata in LPS-Induced RAW264.7 Cells

Catalpa ovata (Bignoniaceae) is widely distributed throughout Korea, China, and Japan. This study investigated the anti-inflammatory effects of catalpalactone isolated from C. ovata in lipopolysaccharide (LPS)-induced RAW264.7 cells. Catalpalactone significantly inhibited nitric oxide (NO) production and inducible NO synthase (iNOS) expression in LPS-induced RAW264.7 cells. The levels of cytokines such as interleukin-6 and tumor necrosis factor-α were reduced under catalpalactone exposure in LPS-induced RAW264.7 cells. Additionally, catalpalactone suppressed signal transducer and activator of transcription 1 (STAT-1) protein expression and interferon-β (IFN-β) production. Treatment with catalpalactone prevented interferon regulatory factor 3 (IRF3) and nuclear factor-κB (NF-κB) activation. Taken together, these results suggest that the anti-inflammatory effects of catalpalactone are associated with the suppression of NO production and iNOS expression through the inhibition of IRF3, NF-κB, and IFN-β/STAT-1 activation.

Binding aspects of dietary flavone, luteolin, with polymorphic forms of natural DNA: a spectroscopic and molecular docking approach

Physicochemical studies on the interactions of small molecules with different polymorphs of DNA are relevant for elucidation at the molecular level of the processes occurringin vivo.

Anti-inflammatory effects of luteolin: A review of in vitro, in vivo, and in silico studies

ETHNOPHARMACOLOGICAL RELEVANCE

Luteolin (3', 4', 5,7-tetrahydroxyflavone) has been identified as commonly present in plants. Plants with a high luteolin content have been used ethnopharmacologically to treat inflammation-related symptoms. Both isolated luteolin and extracts from luteolin-rich plants have been studied using various models and exhibited anti-inflammatory activity.

AIM OF THE REVIEW

This paper uses recent research findings with a broad range of study models to describe the anti-inflammatory activity of luteolin, particularly its mechanisms at the molecular level; provide guidance for future research; and evaluate the feasibility of developing luteolin into an anti-inflammatory drug.

MATERIALS AND METHODS

We summarize reports about the anti-inflammatory activity of luteolin published since 2009, which we found in MEDLINE/PubMed, Scopus, Web of Knowledge, and Google Scholar. To acquire broad information, we extended our search to online FDA documents.

RESULTS

Luteolin is a flavonoid commonly found in medicinal plants and has strong anti-inflammatory activity in vitro and in vivo. Some of its derivatives, such as luteolin-7-O-glucoside, have also shown anti-inflammatory activity. The action mechanism of luteolin varies, but Src in the nuclear factor (NF)-κB pathway, MAPK in the activator protein (AP)- 1 pathway, and SOCS3 in the signal transducer and activator of transcription 3 (STAT3) pathway are its major target transcription factors. A clinical trial with a formulation containing luteolin showed excellent therapeutic effect against inflammation-associated diseases.

CONCLUSION

In silico, in vitro, in vivo, and clinical studies strongly suggest that the major pharmacological mechanism of luteolin is its anti-inflammatory activity, which derives from its regulation of transcription factors such as STAT3, NF-κB, and AP-1. Much work remains to ensure the safety, quality, and efficacy of luteolin before it can be used to treat inflammation-related diseases in humans.

The Cancer Prevention, Anti-Inflammatory and Anti-Oxidation of Bioactive Phytochemicals Targeting the TLR4 Signaling Pathway

Toll-like receptors (TLRs) are a well-known family of pattern recognition receptors that play an important role in a host immune system. TLR triggering leads to the induction of pro-inflammatory cytokines and chemokines, driving the activation of both innate and adaptive immunity. Recently, an increasing number studies have shown the link between TLRs and cancer. Among them, the toll-like receptor 4 (TLR4) signaling pathway is associated with inflammatory response and cancer progression. Dietary phytochemicals are potential modulators of immunological status with various pharmacological properties including anti-cancer, anti-oxidant and anti-inflammatory. Curcumin, 6-gingerol, 6-shogaol, 1-dehydro-10-gingerdione, epigallocatechin gallate (EGCG), luteolin, quercetin, resveratrol, caffeic acid phenethyl ester, xanthohumol, genistein, berberine, and sulforaphane can inhibit TLR4 activation. The aim of the present review is to describe the role of the TLR4 signaling pathway between inflammatory response and cancer progression. We further introduce bioactive phytochemicals with potential anti-inflammation and chemoprevention by inhibiting TLR activation.

The Anti-Inflammatory Effects of Shinbaro3 Is Mediated by Downregulation of the TLR4 Signalling Pathway in LPS-Stimulated RAW 264.7 Macrophages

Shinbaro3, a formulation derived from the hydrolysed roots of Harpagophytum procumbens var. sublobatum (Engl.) Stapf, has been clinically used in the pharamacopuncture treatment of arthritis in Korea. In the present study, Shinbaro3 inhibited NO generation in LPS-induced RAW 264.7 cells in a dose-dependent manner. Shinbaro3 also downregulated the mRNA and protein expression of inflammatory mediators in a dose-dependent manner. Three mechanisms explaining the effects of Shinbaro3 in RAW 264.7 cells were identified as follows: (1) inhibition of the extracellular signal-regulated kinase 1 and 2 (ERK1/2), stress-activated protein kinase (SAPK)/c-Jun N-terminal protein kinase (JNK), and p38 mitogen-activated protein kinase (MAPK) pathways; (2) suppression of IκB kinase-α/β (IKK-α/β) phosphorylation and nuclear factor-kappa B (NF-κB) subunits in the NF-κB pathway, which are involved in MyD88-dependent signalling; and (3) downregulation of IFN-β mRNA expression via inhibition of interferon regulatory factor 3 (IRF3) and Janus-activated kinase 1 (JAK1)/signal transducer and activator of transcription 1 (STAT1) phosphorylation, which is involved in TRIF-dependent signalling. Shinbaro3 exerted anti-inflammatory effects in LPS-stimulated RAW 264.7 macrophage cells through modulation of the TLR4/MyD88 pathways, suggesting that Shinbaro3 is a novel anti-inflammatory therapeutic candidate in the field of pharmacopuncture.

Luteolin reduces inflammation in Staphylococcus aureus-induced mastitis by inhibiting NF-kB activation and MMPs expression

Mastitis is a serious and prevalent disease caused by infection by pathogens such as Staphylococcus aureus. We evaluated the anti-inflammatory effects and mechanism of luteolin, a natural flavonoid with a wide range of pharmacological activities, in a mouse model of S. aureus mastitis. We also treated cultured mouse mammary epithelial cells (mMECs) with S. aureus and luteolin. Histopathological changes were examined by H&E staining and the levels of inflammatory cytokine proteins were analyzed using ELISAs. We determined mRNA levels with qPCR and the level of NF-κB and matrix metalloproteinase (MMP) proteins by Western blotting. The observed histopathological changes showed that luteolin protected mammary glands with S. aureus infection from tissue destruction and inflammatory cell infiltration. Luteolin inhibited the expression of TNF-α, IL-1β, and IL-6, all of which were increased with S. aureus infection of mammary tissues and mMECs. S. aureus-induced TLR2 and TLR4 was suppressed by luteolin, as were levels of IκBα and NF-κB p65 phosphorylation and expression of MMP-2 and MMP-9. Levels of tissue inhibitor of metalloproteinases (TIMP)-1 and TIMP-2 were enhanced. These findings suggest luteolin is a potentially effective new treatment to reduce tissue damage and inflammation from S. aureus-induced mastitis.

Crosstalk between signals initiated from TLR4 and cell surface BAFF results in synergistic induction of proinflammatory mediators in THP-1 cells

Cellular response to stimulation is mediated by meshwork of signaling pathways that may share common signaling adaptors. Here, we present data demonstrating that signaling pathways initiated from the membrane-bound form of B-cell activating factor (BAFF) can crosstalk with lipopolysaccharide (LPS)-induced signaling for synergistic expression of proinflammatory mediators in the human macrophage-like cell line THP-1. Co-treatment of the cells with BAFF-specific monoclonal antibody and LPS resulted in enhanced mitogen-activated protein kinase (MAPK)/mitogen- and stress-activated protein kinase (MSK)-mediated phosphorylation of nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) p65 subunit (Ser276), which then interacts with CREB binding protein (CBP) for subsequent acetylation. Simultaneously, the phosphorylation of cyclic AMP-response element binding protein (CREB) was enhanced through the combined action of phosphatidylinositol-3-kinase (PI3K)/AKT and MAPK/MSK pathways, and the resulting phospho-CREB interacted with the NF-κB/CBP complex. Transfection of CREB-specific siRNA inhibited the BAFF-mediated enhancing effect indicating that the formation of the CREB/NF-κB/CBP complex is required for the synergistic induction of the proinflammatory genes. These findings indicate that BAFF-mediated reverse signaling can modulate LPS-induced inflammatory activation through regulation of NF-κB and CREB activity and point out the necessity to re-evaluate the role of BAFF in diseases where its expression is high in macrophages.

IinQ attenuates systemic inflammatory responses via selectively impairing the Myddosome complex formation upon TLR4 ligation

A specific small-molecule inhibitor of the TLR4 signaling complex upstream of the IKK would likely provide therapeutic benefit for NF-κB-mediated inflammatory disease. We previously identified brazilin as a selective upstream IKK inhibitor targeting the Myddosome complex. In this study, using a cell-based ubiquitination assay for IRAK1 and a chemical library comprising a series of structural analogues of brazilin, a novel small molecule, 2-hydroxy-5,6-dihydroisoindolo[1,2-a]isoquinoline-3,8-dione (IinQ), was identified as a selective and potent inhibitor of IRAK1-dependent NF-κB activation upon TLR4 ligation. In RAW264.7 macrophages, IinQ drastically suppressed activation of upstream IKK signaling events including membrane-bound IRAK1 ubiquitination and IKK phosphorylation by the TLR4 ligand, resulting in reduced expression of proinflammatory mediators including IL-6, TNF-α, and nitric oxide. Interestingly, IinQ did not suppress NF-κB activation via the TLR3 ligand, DNA damaging agents, or a protein kinase C activator, indicating IinQ is specific for TLR4 signaling. Analysis of upstream signaling events further confirmed that IinQ disrupts the MyD88-IRAK1-TRAF6 complex formation induced by LPS treatment, without affecting TLR4 oligomerization. Moreover, intravenous administration of IinQ significantly reduced lethality and attenuated systemic inflammatory responses in an in vivo mouse model of endotoxin shock following LPS challenge. Thus, IinQ represents a novel class of brazilin analogues with improved potency and specificity toward disruption of Myddosome complex formation in TLR4 signaling, indicating that IinQ may be a promising therapeutic candidate for the treatment of systemic inflammatory diseases.

Potential therapeutic targets for inflammation in toll-like receptor 4 (TLR4)-mediated signaling pathways

Inflammation is set off when innate immune cells detect infection or tissue injury. Tight control of the severity, duration, and location of inflammation is an absolute requirement for an appropriate balance between clearance of injured tissue and pathogens versus damage to host cells. Impeding the risk associated with the imbalance in the inflammatory response requires precise identification of potential therapeutic targets involved in provoking the inflammation. Toll-like receptors (TLRs) primarily known for the pathogen recognition and subsequent immune responses are being investigated for their pathogenic role in various chronic diseases. A mammalian homologue of Drosophila Toll receptor 4 (TLR4) was shown to induce the expression of genes involved in inflammatory responses. Signaling pathways via TLR4 activate various transcription factors like Nuclear factor kappa-light-chain-enhancer (NF-κB), activator protein 1 (AP1), Signal Transducers and Activators of Transcription family of transcription factors (STAT1) and Interferon regulatory factors (IRF's), which are the key players regulating the inflammatory response. Inhibition of these targets and their upstream signaling molecules provides a potential therapeutic approach to treat inflammatory diseases. Here we review the therapeutic targets involved in TLR-4 signaling pathways that are critical for suppressing chronic inflammatory disorders.

Sesquiterpenoids from the Rhizomes of Curcuma phaeocaulis and Their Inhibitory Effects on LPS-Induced TLR4 Activation

Two new guaiane-type (2, 6) and one new furanogermacrane-type (11) sesquiterpenoids have been isolated along with twelve known compounds from an EtOAc-soluble extract of Curcuma phaeocaulis rhizomes. The structures of the isolated compounds were elucidated using a combination of NMR, MS, and circular dichroism (CD) spectra. The inhibitory effects of each compound on lipopolysaccharide (LPS)-induced Toll-like receptor 4 (TLR4) activation in THP-1-Blue cells were assessed, and compound 4 showed more potent inhibitory activity against LPS-stimulated TLR4 activation.

Postprandial Inflammatory Responses and Free Fatty Acids in Plasma of Adults Who Consumed a Moderately High-Fat Breakfast with and without Blueberry Powder in a Randomized Placebo-Controlled Trial

BACKGROUND

Saturated fatty acids (FAs) released from triglyceride-rich lipoproteins (TGRLs) activate Toll-like receptor 2 (TLR-2) and induce the expression of proinflammatory cytokines in monocytes. Certain plant polyphenols inhibit TLR-mediated signaling pathways.

OBJECTIVE

We determined whether plasma free FAs (FFAs) after a moderately high-fat (MHF, 40% kcal from fat) breakfast modulate the inflammatory status of postprandial blood, and whether blueberry intake suppresses FFA-induced inflammatory responses in healthy humans.

METHODS

Twenty-three volunteers with a mean ± SEM age and body mass index (in kg/m(2)) of 30 ± 3 y and 21.9 ± 0.4, respectively, consumed an MHF breakfast with either a placebo powder or 2 or 4 servings of blueberry powder in a randomized crossover design. The placebo powder was provided on the first test day and the blueberry powder doses were randomized with a 2-wk washout period. Plasma concentrations of lipids, glucose, and cytokines were determined. To determine whether FFAs derived from TGRL stimulate monocyte activation, and whether this is inhibited by blueberry intake, whole blood was treated with lipoprotein lipase (LPL).

RESULTS

The median concentrations of FFAs and cytokines [tumor necrosis factor-α, interleukin (IL)-6 and IL-8] in postprandial plasma (3.5 h) decreased compared with fasting plasma regardless of the blueberry intake (P < 0.001 for FFAs and P < 0.05 for cytokines). However, concentrations of FFAs and cytokines including IL-1β increased in LPL-treated whole blood compared with untreated blood samples from participants who consumed the placebo powder. Blueberry intake suppressed IL-1β and IL-6 production in LPL-treated postprandial blood compared with the placebo control when fasting changes were used as a covariate.

CONCLUSIONS

The plasma FFA concentration may be an important determinant affecting inflammatory cytokine production in blood. Supplementation with blueberry powder did not affect plasma FFA and cytokine concentrations; however, it attenuated the cytokine production induced by ex vivo treatment of whole blood with LPL. This trial was registered at clinicaltrials.gov as NCT01594008.

Mutational analysis of TBK1 in Taiwanese patients with amyotrophic lateral sclerosis

Mutations in the TBK1 gene were just recently identified to cause amyotrophic lateral sclerosis (ALS), and their role in ALS in various populations remains unclear. The aim of this study was to determine the frequency and spectrum of mutations in TBK1 in a Taiwanese ALS cohort of Han Chinese origin. Mutational analyses of TBK1 were carried out by direct nucleotide sequencing in a cohort of 207 unrelated patients with ALS. Among them, the genetic diagnoses of 168 patients remained elusive after mutations in SOD1, C9ORF72, TARDBP, FUS, ATXN2, OPTN, VCP, UBQLN2, SQSTM1, PFN1, HNRNPA1, HNRNPA2B1, MATR3, CHCHD10, and TUBA4A had been excluded. We identified one nonsense mutation, p.R444X (c.1330C>T), in one patient with apparently sporadic ALS-frontotemporal dementia. In vitro functional study demonstrated the p.R444X mutation resulting in a truncated TANK-binding kinase 1 (TBK1) protein product, low protein expression, and loss of kinase function and interaction with optineurin. The frequency of TBK1 mutations in ALS patients in Taiwan is, therefore, approximately 0.5% (1/207). This study reports a novel TBK1 mutation and stresses on the importance to consider TBK1 mutation as a possible etiology of ALS.

Pedilanthus tithymaloides Inhibits HSV Infection by Modulating NF-κB Signaling

Pedilanthus tithymaloides (PT), a widely used ethnomedicinal plant, has been employed to treat a number of skin conditions. To extend its utility and to fully exploit its medicinal potential, we have evaluated the in vitro antiviral activity of a methanolic extract of PT leaves and its isolated compounds against Herpes Simplex Virus type 2 (HSV-2). Bioactivity-guided studies revealed that the extract and one of its constituents, luteolin, had potent antiviral activity against wild-type and clinical isolates of HSV-2 (EC₅₀ 48.5–52.6 and 22.4–27.5 μg/ml, respectively), with nearly complete inhibition at 86.5–101.8 and 40.2–49.6 μg/ml, respectively. The inhibitory effect was significant (p<0.001) when the drug was added 2 h prior to infection, and was effective up to 4 h post-infection. As viral replication requires NF-κB activation, we examined whether the observed extract-induced inhibition of HSV-2 was related to NF-κB inhibition. Interestingly, we observed that treatment of HSV-2-infected cells with extract or luteolin suppressed NF-κB activation. Although NF-κB, JNK and MAPK activation was compromised during HSV replication, neither the extract nor luteolin affected HSV-2-induced JNK1/2 and MAPK activation. Moreover, the PT leaf extract and luteolin potently down-regulated the expression of tumor necrosis factor (TNF)-α, Interleukin (IL)-1β, IL-6, NO and iNOS and the production of gamma interferon (IFN-γ), which are directly involved in controlling the NF-κB signaling pathway. Thus, our results indicate that both PT leaf extract and luteolin modulate the NF-κB signaling pathway, resulting in the inhibition of HSV-2 replication.

Luteolin as an anti-inflammatory and neuroprotective agent: A brief review

According to the World Health Organization, two billion people will be aged 60 years or older by 2050. Aging is a major risk factor for a number of neurodegenerative disorders. These age-related disorders currently represent one of the most important and challenging health problems worldwide. Therefore, much attention has been directed towards the design and development of neuroprotective agents derived from natural sources. These phytochemicals have demonstrated high efficacy and low adverse effects in multiple in vitro and in vivo studies. Among these phytochemicals, dietary flavonoids are an important and common chemical class of bioactive products, found in several fruits and vegetables. Luteolin is an important flavone, which is found in several plant products, including broccoli, pepper, thyme, and celery. Numerous studies have shown that luteolin possesses beneficial neuroprotective effects both in vitro and in vivo. Despite this, an overview of the neuroprotective effects of luteolin has not yet been accomplished. Therefore, the aim of this paper is to provide a review of the available literature regarding the neuroprotective effects of luteolin and its molecular mechanisms of action. Herein, we also review the available literature regarding the chemistry of luteolin, its herbal sources, and bioavailability as a pharmacological agent for the treatment and management of age-related neurodegenerative disorders.

Chrysin suppresses human CD14(+) monocyte-derived dendritic cells and ameliorates experimental autoimmune encephalomyelitis

Chrysin, a naturally flavonoid of plant, has various biological activities. However, the effects of chrysin on dendritic cells (DCs) and multiple sclerosis (MS) remain unknown. In this study, we demonstrate that chrysin inhibited human DC differentiation, maturation, function and the expression of the Th1 cells polarizing cytokines IFN-γ and IL-12p35 form DCs. In addition, chrysin ameliorated experimental autoimmune encephalomyelitis (EAE), an animal model of MS, by reducing CNS inflammation and demyelination. Furthermore, chrysin suppressed DCs and Th1 cells in the EAE mice. Taken together, chrysin exerts anti-inflammatory and immune suppressive effects, and suggests a possible therapeutic application of chrysin in MS.

Celastrol blocks binding of lipopolysaccharides to a Toll-like receptor4/myeloid differentiation factor2 complex in a thiol-dependent manner

ETHNOPHARMACOLOGICAL RELEVANCE

Tripterygium wilfordii (lei gong teng; Thunder of God Vine), which belongs to the Celastraceae family, has long been used in traditional Chinese medicine to treat inflammation and rheumatoid arthritis. Celastrol is a bioactive compound isolated from T. wilfordii.

AIM OF THE STUDY

We investigated whether celastrol suppressed binding of lipopolysaccharides (LPS) to myeloid differentiation factor 2 (MD2), thereby downregulating Toll-like receptor4 (TLR4) activation in mouse primary macrophages.

MATERIALS AND METHODS

Cytokine expression was determined by polymerase chain reaction analysis and enzyme-linked immunosorbent assay in bone marrow-derived primary macrophages (BMDMs). The kinase activity of tank-binding kinase 1 (TBK1) was examined by a luciferase reporter assay and an in vitro kinase assay. LPS binding to MD2 was examined by an in vitro binding assay and confocal microscopy analysis.

RESULTS

Celastrol reduced LPS-induced expression of inflammatory cytokines, such as tumor necrosis factor (TNF)-α, interleukin (IL)-6, IL-12, and IL-1β, at both the mRNA and protein levels in BMDMs. Celastrol suppressed LPS binding to MD2, as shown by the in vitro binding assay, whereas it did not inhibit TBK1. In addition, co-localization of LPS with MD2 in BMDMs was blocked by celastrol. The inhibitory effects of celastrol on LPS binding to MD2 were reversed by thiol donors (N-acetyl-L-cysteine and dithiothreitol), suggesting that the thiol reactivity of celastrol contributes to its inhibitory effects on TLR4 activation in macrophages.

CONCLUSION

Our results demonstrate that celastrol suppresses TLR4 activation through the inhibition of LPS binding to the TLR4/MD2 complex. These results provide a novel mechanism of action by which celastrol contributes to the anti-inflammatory activity of T. wilfordii.

TANK-binding kinase 1 (TBK1) modulates inflammatory hyperalgesia by regulating MAP kinases and NF-κB dependent genes

BACKGROUND

TANK-binding kinase (TBK1) is a non-canonical IκB kinase (IKK) involved in the regulation of type I interferons and of NF-κB signal transduction. It is activated by viral infections and inflammatory mediators and has therefore been associated with viral diseases, obesity, and rheumatoid arthritis. Its role in pain has not been investigated so far. Due to the important roles of NF-κB, classical IκB Kinases and the IKK-related kinase, IKKε, in inflammatory nociception, we hypothesized that TBK1, which is suggested to form a complex with IKKε under certain conditions, might also alter the inflammatory nociceptive response.

METHODS

We investigated TBK1 expression and regulation in "pain-relevant" tissues of C57BL/6 mice by immunofluorescence, quantitative PCR, and Western blot analysis. Furthermore, nociceptive responses and the underlying signal transduction pathways were assessed using TBK1(-/-) mice in two models of inflammatory nociception.

RESULTS

Our data show that TBK1 is expressed and regulated in the spinal cord after peripheral nociceptive stimulation and that a deletion of TBK1 alleviated the inflammatory hyperalgesia in mice while motor function and acute nociception were not altered. TBK1-mediated effects are at least partially mediated by regulation of NF-κB dependent COX-2 induction but also by alteration of expression of c-fos via modulation of MAP kinases as shown in the spinal cord of mice and in cell culture experiments.

CONCLUSION

We suggest that TBK1 exerts pronociceptive effects in inflammatory nociception which are due to both modulation of NF-κB dependent genes and regulation of MAPKs and c-fos. Inhibition of TBK1 might therefore constitute a novel effective tool for analgesic therapy.

Gambogic Acid Disrupts Toll-like Receptor4 Activation by Blocking Lipopolysaccharides Binding to Myeloid Differentiation Factor 2

Our body's immune system has defense mechanisms against pathogens such as viruses and bacteria. Immune responses are primarily initiated by the activation of toll-like receptors (TLRs). In particular, TLR4 is well-characterized and is known to be activated by gram-negative bacteria and tissue damage signals. TLR4 requires myeloid differentiation factor 2 (MD2) as a co-receptor to recognize its ligand, lipopolysaccharides (LPS), which is an extracellular membrane component of gram-negative bacteria. Gambogic acid is a xanthonoid isolated from brownish or orange resin extracted from Garcinia hanburyi. Its primary effect is tumor suppression. Since inflammatory responses are related to the development of cancer, we hypothesized that gambogic acid may regulate TLR4 activation. Our results demonstrated that gambogic acid decreased the expression of pro-inflammatory cytokines (TNF-α, IL-6, IL-12, and IL-1β) in both mRNA and protein levels in bone marrow-derived primary macrophages after stimulation with LPS. Gambogic acid did not inhibit the activation of Interferon regulatory factor 3 (IRF3) induced by TBK1 overexpression in a luciferase reporter gene assay using IFN-β-PRD III-I-luc. An in vitro kinase assay using recombinant TBK1 revealed that gambogic acid did not directly inhibit TBK1 kinase activity, and instead suppressed the binding of LPS to MD2, as determined by an in vitro binding assay and confocal microscopy analysis. Together, our results demonstrate that gambogic acid disrupts LPS interaction with the TLR4/MD2 complex, the novel mechanism by which it suppresses TLR4 activation.

Fascin regulates TLR4/PKC-mediated translational activation through miR-155 and miR-125b, which targets the 3' untranslated region of TNF-α mRNA

Fascin is a well-known cytoskeletal regulatory protein that, as a substrate of protein kinase C (PKC), is involved in PKC-mediated translational regulation of TNF-α in macrophages stimulated with lipopolysaccharide (LPS). The regulatory effects of fascin targeted the 3'-untraslated region (UTR) of the TNF-α mRNA, and suppression of PKC activity or fascin expression resulted in specific blockage of the LPS-induced translational activation of the mRNA. In an effort to identify the molecular mechanism of this fascin-mediated translational regulation, the expression levels of micro-RNA (miRNA) after stimulation of the toll-like receptor 4 (TLR4) signaling pathways were analyzed in cells with down-regulation of fascin. The LPS-induced translation of TNF-α is known to be regulated by miR-155 and miR-125b, which have positive and negative effects, respectively. Interestingly, suppression of fascin expression reversed LPS-induced down-regulation of miR-125b and abolished the LPS-induced increase in miR-155. Furthermore, introduction of miR-155 precursor, blocking of miR-125b activity, or introduction of a mutation into the miR-125b binding site of the TNF-α 3'-UTR restored translational activation in cells with suppressed fascin expression. These data indicate that fascin regulates translation through miR-155 and miR-125b, which target 3' UTR in TNF-α mRNA.

Trif-dependent induction of Th17 immunity by lung dendritic cells

Allergic asthma is thought to stem largely from maladaptive T helper 2 (Th2) responses to inhaled allergens, which in turn lead to airway eosinophilia and airway hyperresponsiveness (AHR). However, many individuals with asthma have airway inflammation that is predominantly neutrophilic and resistant to treatment with inhaled glucocorticoids. An improved understanding of the molecular basis of this form of asthma might lead to improved strategies for its treatment. Here, we identify novel roles of the adaptor protein, TRIF (TIR-domain-containing adapter-inducing interferon-β), in neutrophilic responses to inhaled allergens. In different mouse models of asthma, Trif-deficient animals had marked reductions in interleukin (IL)-17, airway neutrophils, and AHR compared with wild-type (WT) mice, whereas airway eosinophils were generally similar in these two strains. Compared with lung dendritic cells (DCs) from WT mice, lung DCs from Trif-deficient mice displayed impaired lipopolysaccharide (LPS)-induced migration to regional lymph nodes, lower levels of the costimulatory molecule, CD40, and produced smaller amounts of the T helper 17 (Th17)-promoting cytokines, IL-6, and IL-1β. When cultured with allergen-specific, naive T cells, Trif-deficient lung DCs stimulated robust Th2 cell differentiation but very weak Th1 and Th17 cell differentiation. Together, these findings reveal a TRIF-CD40-Th17 axis in the development of IL-17-associated neutrophilic asthma.

Flavonoids Affect Host-Microbiota Crosstalk through TLR Modulation

Interaction between host cells and microbes is known as crosstalk. Among other mechanisms, this takes place when certain molecules of the micro-organisms are recognized by the toll-like receptors (TLRs) in the body cells, mainly in the intestinal epithelial cells and in the immune cells. TLRs belong to the pattern-recognition receptors and represent the first line of defense against pathogens, playing a pivotal role in both innate and adaptive immunity. Dysregulation in the activity of such receptors can lead to the development of chronic and severe inflammation as well as immunological disorders. Among components present in the diet, flavonoids have been suggested as antioxidant dietary factors able to modulate TLR-mediated signaling pathways. This review focuses on the molecular targets involved in the modulatory action of flavonoids on TLR-mediated signaling pathways, providing an overview of the mechanisms involved in such action. Particular flavonoids have been able to modify the composition of the microbiota, to modulate TLR gene and protein expression, and to regulate the downstream signaling molecules involved in the TLR pathway. These synergistic mechanisms suggest the role of some flavonoids in the preventive effect on certain chronic diseases.