ATP-Binding Pocket-Targeted Suppression of Src and Syk by Luteolin Contributes to Its Anti-Inflammatory Action

Luteolin: A promising multifunctional natural flavonoid for human diseases

Natural products are closely associated with human health. Luteolin (LUT), a flavonoid polyphenolic compound, is widely found in fruits, vegetables, flowers, and herbs. It is noteworthy that LUT exhibits a variety of beneficial pharmacological properties and holds significant potential for clinical applications, particularly in antitumor, anti-convulsion, diabetes control, anti-inflammatory, neuroprotection, anti-oxidation, anti-cardiovascular, and other aspects. The potential mechanism of action has been partially elucidated, including the mediation of NF-κB, toll-like receptor, MAPK, Wnt/β-catenin, PI3K/Akt, AMPK/mTOR, and Nrf-2, among others. The review that aimed to comprehensively consolidate essential information on natural sources, pharmacological effects, therapeutic and preventive potential, as well as potential mechanisms of LUT. The objective is to establish a theoretical basis for the continued development and application of LUT.

Comprehensive and critical view on the anti-inflammatory and immunomodulatory role of natural phenolic antioxidants

The immune response encompasses innate and adaptive immunity, each with distinct and specific activities. The innate immune system is constituted by phagocytic cells, macrophages, monocytes and neutrophils, the cascade system, and different classes of receptors such as toll-like receptors that are exploited by the innate immune cells. The adaptive immune system is antigen-specific, encompassing memory lymphocytes and the corresponding specific receptors. Inflammation is understood as an activation of different signaling pathways such as toll-like receptors or nuclear factor kappa-light-chain-enhancer of activated B cells, with an increase in nitric oxide, inflammatory cytokines and chemokines. Increased oxidative stress has been identified as main source of chronic inflammation. Phenolic antioxidants modulate the activities of lymphocytes and macrophages by impacting cytokines and nitric oxide release, exerting anti-inflammatory effect. The nuclear-factor kappa-light-chain-enhancer of activated B cells signaling pathway and the mitogen-activated protein kinase pathway are targeted, alongside an increase in nuclear factor erythroid 2-related factor mediated antioxidant response, triggering the activity of antioxidant enzymes. The inhibitive potential on phospholipase A2, cyclooxygenase and lipoxygenase in the arachidonic acid pathway, and the subsequent reduction in prostaglandin and leukotriene generation, reveals the potential of phenolics as inflammation antagonists. The immunomodulative potential encompasses the capacity to interfere with proinflammatory cytokine synthesis and with the expression of the corresponding genes. A diet rich in antioxidants can result in prevention of inflammation-related pathologies. More investigations are necessary to establish the role of these antioxidants in therapy. The appropriate delivery system and the prooxidant effects exhibited at large doses, or in the presence of heavy metal cations should be regarded.

A NETWORK PHARMACOLOGY-BASED TREATMENT ANALYSIS OF LUTEOLIN FOR REGULATING PYROPTOSIS IN ACUTE LUNG INJURY

ABSTRACT

Background: Acute lung injury (ALI) and its severe manifestation, acute respiratory distress syndrome, are complicated pulmonary inflammatory conditions for which standard therapeutics are still not well established. Although increasing research has indicated the anti-inflammatory, anticancer, and antioxidant effects of luteolin, especially in lung diseases, the molecular mechanisms underlying luteolin treatment remain largely unclear. Methods: The potential targets of luteolin in ALI were explored using a network pharmacology-based strategy and further validated in a clinical database. The relevant targets of luteolin and ALI were first obtained, and the key target genes were analyzed using a protein-protein interaction network, Gene Ontology, and Kyoto Encyclopedia of Genes and Genomes pathway enrichment analyses. The targets of luteolin and ALI were then combined to ascertain the relevant pyroptosis targets, followed by Gene Ontology analysis of core genes and molecular docking of key active compounds to the antipyroptosis targets of luteolin in resolving ALI. The expression of the obtained genes was verified using the Gene Expression Omnibus database. In vivo and in vitro experiments were performed to explore the potential therapeutic effects and mechanisms of action of luteolin against ALI. Results: Fifty key genes and 109 luteolin pathways for ALI treatment were identified through network pharmacology. Key target genes of luteolin for treating ALI via pyroptosis were identified. The most significant target genes of luteolin in ALI resolution included AKT1, NOS2, and CTSG. Compared with controls, patients with ALI had lower AKT1 expression and higher CTSG expression. Luteolin simply reduced systemic inflammation and lung tissue damage in septic mice. Furthermore, we blocked AKT1 expression and found luteolin reduced the degree of lung injury and affected NOS2 levels. Conclusions: As demonstrated by a network pharmacology approach, luteolin may exert an antipyroptosis effect on ALI via AKT1, NOS2, and CTSG.

Antioxidant and Anti-Inflammatory Effects of 6,3',4´- and 7,3´,4´-Trihydroxyflavone on 2D and 3D RAW264.7 Models

Dietary flavones 6,3´,4´-trihydroxyflavone (6,3´,4´-HOFL) and 7,3´,4´-trihydroxyflavone (7,3´,4´-HOFL) showed preliminary antioxidant and anti-inflammatory activities in a two-dimensional (2D) cell culture model. However, their action mechanisms remain unclear, and the anti-inflammatory activities have not been studied in a reliable three-dimensional (3D) cell model. Therefore, in the current study, the antioxidant potency was examined by their scavenging ability of cellular reactive oxygen species. Anti-inflammatory activities were examined via their inhibitory effects on inflammatory mediators in vitro on 2D and 3D macrophage models, and their mechanisms were determined through transcriptome. In the 3D macrophages, two flavones were less bioactive than they were in 2D macrophages, but they both significantly suppressed the overexpression of proinflammatory mediators in two cell models. The divergent position of the hydroxyl group on the A ring resulted in activity differences. Compared to 6,3´,4´-HOFL, 7,3´,4´-HOFL showed lower activity on NO, IL-1β suppression, and c-Src binding (IC₅₀: 12.0 and 20.9 µM) but higher ROS-scavenging capacity (IC₅₀: 3.20 and 2.71 µM) and less cytotoxicity. In addition to the IL-17 and TNF pathways of 6,3´,4´-HOFL, 7,3´,4´-HOFL also exerted anti-inflammatory activity through JAK-STAT, as indicated by the RNA-sequencing results. Two flavones showed prominent antioxidant and anti-inflammatory activities on 2D and 3D models.

Structure-Activity Relationship (SAR) of Flavones on Their Anti-Inflammatory Activity in Murine Macrophages in Culture through the NF-κB Pathway and c-Src Kinase Receptor

Flavones benefit human health through their anti-inflammatory activity; however, their structure-activity relationship is unclear. Herein, we selected 15 flavones with the same backbone but different substituents and systematically assessed their anti-inflammatory activities in RAW 264.7 regarding cellular-Src kinase (c-Src) affinity, suppression of IκBα phosphorylation, inhibition of nitric oxide (NO) and inducible nitric oxidase (iNOS) production, and downregulation of genes of proinflammatory cytokines interleukin 6 (IL-6), interleukin 1β (IL-1β), and tumor necrosis factor α (TNF-α). Overall, our results showed that the double bond between C2-C3 and C3'- and C4'-OH promoted anti-inflammatory activity, while C8- and C5'-OH and the methoxy group on C4' attenuated the overall anti-inflammatory and antioxidant activities. The hydroxyl groups at other positions exhibited more complicated functions. The two most effective flavones are 3',4'-dihydroxyflavone and luteolin with inhibitory concentration (IC₅₀) values for inhibiting the LPS-induced nitric oxide level are 9.61 ± 1.36 and 16.90 ± 0.74 μM, respectively. Furthermore, they suppressed the production of iNOS by approximately 90% and inhibited IL-1β and IL-6 by more than 95%. Taken together, our results established a relationship between the flavone structure and anti-inflammatory activity in vitro.

New Approaches and advancement in drug development from phenolic p-coumaric acid

P-coumaric acid occurs as a common dietary polyphenol distributed in fruits, vegetables, and cereals in associated and free form. The toxicity profile of the drug is very low and it exhibits many pharmacological actions (antihypertensive, anti-inflammatory, anticancer, antimicrobial activity, antidiabetic, anticancer, and antioxidant effect). P-coumaric acid also acts as a free radical scavenger and inhibits various enzymes which generate free radicals. It is also used as the raw material for the preparation of preservatives, vanillin, sports foods, skin defense agents, and as a cross-linker for the formation of edible films and food gels. The current study is based upon biological effectiveness, molecular docking, SAR, sources of p-coumaric acid, and related derivatives.

A Newly Synthesized Flavone from Luteolin Escapes from COMT-Catalyzed Methylation and Inhibits Lipopolysaccharide-Induced Inflammation in RAW264.7 Macrophages via JNK, p38 and NF-κB Signaling Pathways

Luteolin is a common dietary flavone possessing potent anti-inflammatory activities. However, when administrated in vivo, luteolin becomes methylated by catechol-O-methyltransferases (COMT) owing to the catechol ring in the chemical structure, which largely diminishes its anti-inflammatory effect. In this study, we made a modification on luteolin, named LUA, which was generated by the chemical reaction between luteolin and 2,2'-azobis(2-amidinopropane) dihydrochloride (AAPH). Without a catechol ring in the chemical structure, this new flavone could escape from the COMT-catalyzed methylation, thus affording the potential to exert its functions in the original form when administrated in the organism. Moreover, an LPS-stimulated RAW cell model was applied to detect the anti-inflammatory properties. LUA showed much more superior inhibitory effect on LPS-induced production of NO than diosmetin (a major methylated form of luteolin) and significantly suppressed upregulation of iNOS and COX-2 in macrophages. LUA treatment dramatically reduced LPS-stimulated reactive oxygen species (ROS) and mRNA levels of pro-inflammatory mediators such as IL-1β, IL-6, IL-8 and IFN-β. Furthermore, LUA significantly reduced the phosphorylation of JNK and p38 without affecting that of ERK. LUA also inhibited the activation of NF-κB through suppression of p65 phosphorylation and nuclear translocation.

Anti-Inflammation Activity of Flavones and Their Structure-Activity Relationship

Flavones are an important class of bioactive constituents in foods, and their structural diversity enables them to interact with different targets. In particular, flavones are known for their anti-inflammatory activity. Herein, we summarized commonly applied in vitro, in vivo, and clinical models in testing anti-inflammatory activity of flavones. The anti-inflammatory structure-activity relationship of flavones was systematically mapped and supported with cross comparisons of that with flavanones, flavanols, and isoflavones. Hydroxyl groups (-OH) are indispensable for the anti-inflammatory function of flavones, and -OH at the C-5 and C-4' positions enhance while -OH at the C-6, C-7, C-8, and C-3' positions attenuate their activity. Moreover, the C2-C3 single bond, -OH at the C-3 and B-ring positions undermine flavone aglycones' activity. Most of the flavone aglycones function through NF-κB, MAPK, and JNK-STAT pathways, and their possible cell binding targets are kinase, aryl hydrocarbon receptor (AhR), G-protein coupled receptors, and estrogen receptors. However, the structure and anti-inflammatory activity relationship of flavones were unclear, and further research shall be conducted to close the gap in order to guide development of evidence-based functional foods.

Luteolin inhibits NLRP3 inflammasome activation via blocking ASC oligomerization

The NLRP3 inflammasome is a caspase-1 containing multi-protein complex that controls the release of IL-1β and plays important roles in the innate immune response. Since NLRP3 inflammasome is implicated in the pathogenesis of a variety of diseases, it has become an increasingly interested target in developing therapies for multiple diseases. We reported the current study to determine how luteolin, a natural phenolic compound found in many vegetables and medicinal herbs, would modulate NLRP3 inflammasome in both the in vivo and in vitro settings. First, we found that a high-fat diet upregulated mRNA expression of NLRP3 inflammasome components Asc and Casp1 in adipose tissue of ovariectomized mice, which were greatly reduced by dietary supplementation with luteolin. Of note, Asc and Casp1 expression in adipose tissue correlated with mRNA levels of Adgre1 encoding F4/80, an established marker for mature macrophages. We also demonstrated that luteolin inhibited NLRP3 inflammasome-derived caspase-1 activation and IL-1β secretion in J774A.1 macrophages upon diverse stimuli including ATP, nigericin, or silica crystals. Luteolin inhibited the activation step of NLRP3 inflammasome by interfering with ASC oligomerization. Taken together, these findings suggest that luteolin supplementation may suppress NLRP3 induction and activation process and thus potentially would be protective against NLRP3-mediated inflammatory diseases.

Flavonoids in adipose tissue inflammation and atherosclerosis: one arrow, two targets

Flavonoids are polyphenolic compounds naturally occurring in fruits and vegetables, in addition to beverages such as tea and coffee. Flavonoids are emerging as potent therapeutic agents for cardiovascular as well as metabolic diseases. Several studies corroborated an inverse relationship between flavonoid consumption and cardiovascular disease (CVD) or adipose tissue inflammation (ATI). Flavonoids exert their anti-atherogenic effects by increasing nitric oxide (NO), reducing reactive oxygen species (ROS), and decreasing pro-inflammatory cytokines. In addition, flavonoids alleviate ATI by decreasing triglyceride and cholesterol levels, as well as by attenuating inflammatory mediators. Furthermore, flavonoids inhibit synthesis of fatty acids and promote their oxidation. In this review, we discuss the effect of the main classes of flavonoids, namely flavones, flavonols, flavanols, flavanones, anthocyanins, and isoflavones, on atherosclerosis and ATI. In addition, we dissect the underlying molecular and cellular mechanisms of action for these flavonoids. We conclude by supporting the potential benefit for flavonoids in the management or treatment of CVD; yet, we call for more robust clinical studies for safety and pharmacokinetic values.

Loratadine, an antihistamine drug, exhibits anti-inflammatory activity through suppression of the NF-kB pathway

Loratadine is an antihistamine drug that shows promise as an anti-inflammatory drug, but supportive studies are lacking. We elucidated the effects and mechanisms by which loratadine inhibits inflammatory responses. Molecular components were evaluated in macrophages by nitric oxide assay, polymerase chain reaction, luciferase assay, immunoblotting, overexpression strategies and cellular thermal shift assay. At the molecular level, loratadine reduced the levels of nitric oxide, iNOS, IL-1β, TNF-α, IL-6, and COX-2 in RAW264.7 cells treated with lipopolysaccharide. Loratadine also specifically inhibited the NF-_kB pathway, targeting the Syk and Src proteins. Furthermore, loratadine bound Src in the bridge between SH2 and SH3, and bound Syk in the protein tyrosine kinase domain. The NF-_kB signaling pathway was assessed along with putative binding sites through a docking approach. The anti-inflammatory effect of loratadine was tested using mouse models of gastritis, hepatitis, colitis, and peritonitis. Stomach tissue histopathology, liver morphology, and colon length in the loratadine group were improved over the group without loratadine treatment. Taken together, loratadine inhibited the inflammatory response through the NF-_kB pathway by binding with the Syk and Src proteins.

Tamarind: A diet-based strategy against lifestyle maladies

The modern-day review article is an exquisite attempt to demonstrate the extreme therapeutic potential of tamarind fruit (Tamarindus indica), particularly its pulp, seed, and leaf extract, against lifestyle-related chronic disorders. The rapid transition in the diet patterns and also the varying lifestyle of the people has made its way forth, a momentous upsurge in a number of chronic as well as degenerative diseases. An excess of foods having functional and nutraceutical significance has come into view recently. These foods have emerged as effective therapeutical remedies against these disorders owing to their natural phytochemical constituents present in them, in abundance. Tamarindus indica serves as a proverbial herbal medicine in each and every part of the world that is known to mankind. Also, the tamarind kernel powder (TKP) is of immense commercial significance in some of the major, leading industries of the World. The derivation of an important gel-forming substance (polysaccharide), named as "jellose," from the decorticated seed kernels of tamarind fruit has led to the manufacture of pectin. It is used in industrial scale in the preparation of various products like jams, jellies, and most important in the preparation of cheese. It plays an evident role as a stabilizer of commercial significance, and it has also been greatly recommend by the scientists to be used as a potent ingredient in a range of pharmaceutical products. The leaves of tamarind plant are also used as part of the daily diet in several countries where they are readily consumed in fresh form and especially during drought season.

Natural flavonoids inhibit the plasma membrane Ca2+-ATPase

Research on flavonoids from plant sources has recently sparked increasing interest because of their beneficial health properties. Different studies have shown that flavonoids change the intracellular Ca²⁺ homeostasis linked to alterations in the function of mitochondria, Ca²⁺ channels and Ca²⁺ pumps. These findings hint at plasma membrane Ca²⁺-ATPase (PMCA) involvement, as it transports Ca²⁺ actively to the extracellular medium coupled to ATP hydrolysis, thus maintaining ion cellular homeostasis. The present study aims to investigate the effect of several natural flavonoids on PMCA both in isolated protein systems and in living cells, and to establish the relationship between flavonoid structure and inhibitory activity on PMCA. Our results show that natural flavonoids inhibited purified and membranous PMCA with different effectiveness: quercetin and gossypin were the most potent and their inhibition mechanisms seem to be different, as quercetin does not prevent ATP binding whereas gossypin does. Moreover, PMCA activity was inhibited in human embryonic kidney cells which transiently overexpress PMCA, suggesting that the effects observed on isolated systems could occur in a complex structure like a living cell. In conclusion, this work reveals a novel molecular mechanism through which flavonoids inhibit PMCA, which leads to Ca²⁺ homeostasis and signaling alterations in the cell.

Phosphatidylinositide 3-Kinase Contributes to the Anti-Inflammatory Effect of Abutilon crispum L. Medik Methanol Extract

Abutilon crispum L. Medik, better known as bladdermallow, is used as a traditional remedy in India, for its anti-inflammatory effect due to its high content of flavonoids. However, research about its anti-inflammatory effect at the molecular level has not been performed. In this study, we aimed to investigate the mechanism of Abutilon crispum methanol extract (Ac-ME) in inhibiting the inflammatory response by conducting several experiments including cellular and molecular assays. Ac-ME inhibited the production of nitric oxide (NO) in RAW264.7 cells during treatment of LPS and Pam3CSK4 without exhibiting cytotoxicity. Ac-ME also suppressed the mRNA expression of inducible nitric oxide (iNOS) and proinflammatory cytokines such as interleukin (IL)-1β and IL-6. Moreover, Ac-ME was shown to inhibit the NF-κB pathway, according to the luciferase reporter gene assay performed with a NF-κB-Luc construct containing NF-κB-binding promoter regions under MyD88 and TRIF overexpression conditions, and immunoblotting analysis by determining the phospho-form levels of IκBα, IKKα/β, and p85, a regulatory domain of phosphatidylinositide 3-kinase (PI3K). Finally, we observed that the level of phospho-p85 induced by the overexpression of spleen tyrosine kinase (Syk) and Src was decreased by Ac-ME at 200 μg/ml. Therefore, these results suggest that Ac-ME has an anti-inflammatory effect by targeting PI3K in the NF-κB signaling pathway.

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.

Ethanol Extract of Lilium Bulbs Plays an Anti-Inflammatory Role by Targeting the IKK[Formula: see text]/[Formula: see text]-Mediated NF-[Formula: see text]B Pathway in Macrophages

Lilium bulbs have long been used as Chinese traditional medicines to alleviate the symptoms of various human inflammatory diseases. However, mechanisms of Lilium bulb-mediated anti-inflammatory activity and the bioactive components in Lilium bulbs remain unknown. In the present study, the anti-inflammatory activity of Lilium bulbs and the underlying mechanism of action were investigated in macrophages using Lilium bulb ethanol extracts (Lb-EE). In a dose-dependent manner, Lb-EE inhibited nitric oxide (NO) production in lipopolysaccharide (LPS)-stimulated RAW264.7 cells and bone marrow-derived macrophages (BMDMs) without causing significant cytotoxicity. Lb-EE also down-regulated mRNA expression of inflammatory genes in LPS-stimulated RAW264.7 cells, which included inducuble nitric oxide synthase (iNOS), cyclooxygenase-2 (COX2), and tumor necrosis factor-[Formula: see text] (TNF-[Formula: see text]). Furthermore, Lb-EE markedly restored LPS-induced morphological changes in RAW264.7 cells to a normal morphology. HPLC analysis identified quercetin, luteolin, and kaempferol as bioactive components contained in Lb-EE. Mechanistic studies in LPS-stimulated RAW264.7 cells revealed that Lb-EE suppressed MyD88- and TRIF-induced NF-[Formula: see text]B transcriptional activation and the nuclear translocation of NF-[Formula: see text]B transcription factors. Moreover, Lb-EE inhibited IKK[Formula: see text]/[Formula: see text]-induced activation of the NF-[Formula: see text]B signaling pathway and IKK inhibition significantly reduced NO production in LPS-stimulated RAW264.7 cells. Taken together, these results suggest that Lb-EE plays an anti-inflammatory role by targeting IKK[Formula: see text]/[Formula: see text]-mediated activation of the NF-[Formula: see text]B signaling pathway during macrophage-mediated inflammatory responses.

Ethnopharmacological properties of Artemisia asiatica: A comprehensive review

ETHNOPHARMACOLOGICAL RELEVANCE

Artemisia asiatica Nakai (Compositae) has a long history as a traditional remedy. Preparation from various parts of the plant (aerial parts and leaves) are used to treat a wide range of diseases including gastric trouble, liver dysfunction, and skin inflammation.

AIMS OF THIS REVIEW

The aims of this review were: 1) to provide an overview of recent studies and progress on A. asiatica-derived ethnopharmacological compounds and their pharmacological activities; and 2) to summarize existing evidence and provide insight for future studies.

MATERIALS AND METHODS

This investigation was carried out by analyzing published books and research papers via scientific databases, namely Science Direct, PubMed ACS Publication, Wiley Online Library, CNKI and information obtained online. The keywords "Artemisia asiatica traditional uses," "Compounds isolated and studied in Artemisia asiatica," and "Pharmacological advances in Artemisia asiatica" were used and articles published between 1995 and 2017 were considered. In total, 500 works related to biological activities of A. asiatica were identified, and only materials published in English were included in the review.

RESULTS

Comparative analysis of literature searched through sources available confirmed that the ethnopharmacological use of A. asiatica was recorded in Korea, China, and Japan. Phytochemical studies revealed the presence of flavonoids, sesquiterpene lactones, monoterpenes, and steroids in A. asiatica. Of these, flavonoids have been shown to exhibit significant pharmacological effects such as gastroprotective, anti-inflammatory, anti-tumor, and anti-microbial actions.

CONCLUSIONS

Phytochemical and pharmacological studies of Artemisia asiatica have proven that this plant is one of valuable medicinal sources with neuroprotective, gastroprotective, anti-oxidative, anti-inflammatory, and anti-cancer effects. Although ethanol extract of this plant is now being prescribed as gastroprotective and anti-ulcerative medicine, it is now time to expand its application to other human inflammatory diseases such as pancreatitis and hepatitis and further extensive study on toxicity in human. Therefore, the present review will encourage further studies of A. asiatica in the pursuit of wide range of therapeutic remedy.

Alisma canaliculatum ethanol extract suppresses inflammatory responses in LPS-stimulated macrophages, HCl/EtOH-induced gastritis, and DSS-triggered colitis by targeting Src/Syk and TAK1 activities

ETHNOPHARMACOLOGICAL RELEVANCE

Alisma canaliculatum A.Braun & C.D.Bouché, distributed in Korea, Japan, China, and Taiwan, is a traditional medicine. In particular, the stem and root of Alisma canaliculatum A.Braun & C.D.Bouché are prescribed to relieve various inflammatory symptoms resulting from nephritis, cystitis, urethritis, and dropsy.

AIM OF STUDY

However, the curative mechanism of Alisma canaliculatum A.Braun & C.D.Bouché with respect to inflammatory symptoms is poorly understood. In this study, the curative roles of this plant in various inflammatory conditions as well as its inhibitory mechanism were aimed to examine using an ethanol extract (Ac-EE).

MATERIALS AND METHODS

Anti-inflammatory effects of Ac-EE were evaluated in lipopolysaccharide (LPS)-induced macrophages in vitro and HCl/EtOH-stimulated mouse model of gastritis and DSS-treated mouse model of colitis. To determine the potentially active anti-inflammatory components in this extracts, we employed HPLC. We also used kinase assays, reporter gene assay, immunoprecipitation analysis and target enzyme overexpressing cell analysis to analyze the molecular mechanisms and the target molecules.

RESULTS

This extract dose-dependently inhibited the production of nitric oxide (NO) and prostaglandin E₂ (PGE₂) from RAW264.7 cells and peritoneal macrophages activated by lipopolysaccharide (LPS). Additionally, Ac-EE ameliorated inflammatory symptoms resulting from gastritis and colitis. Ac-EE down-regulated the mRNA levels of inducible NO synthase (iNOS), tumor necrosis factor (TNF)-α, and cyclooxygenase-2 (COX-2). Ac-EE also blocked the nuclear translocation of nuclear factor (NF)-κB and activator protein (AP)- 1 in LPS-stimulated RAW264.7 cells. By analyzing the target signaling molecules activating these transcription factors, we found that Src and Syk, as well as molecular association between TAK1 and mitogen-activated protein kinase kinase 4/7 (MKK4/7), were targeted by Ac-EE.

CONCLUSIONS

Our data suggest that the Ac-EE NF-κB/AP-1-targeted anti-inflammatory potential is mediated by suppression of Src and Syk as well as the complex formation between TAK1 and its substrate proteins MKK4/7.

Src Is a Prime Target Inhibited by Celtis choseniana Methanol Extract in Its Anti-Inflammatory Action

Celtis choseniana is the traditional plant used at Korea as a herbal medicine to ameliorate inflammatory responses. Although Celtis choseniana has been traditionally used as a herbal medicine at Korea, no systemic research has been conducted on its anti-inflammatory activity. Therefore, the present study explored an anti-inflammatory effect and its underlying molecular mechanism using Celtis choseniana methanol extract (Cc-ME) in macrophage-mediated inflammatory responses. In vitro anti-inflammatory activity of Cc-ME was evaluated using RAW264.7 cells and peritoneal macrophages stimulated by lipopolysaccharide (LPS), pam3CSK4 (Pam3), or poly(I:C). In vivo anti-inflammatory activity of Cc-ME was investigated using acute inflammatory disease mouse models, such as LPS-induced peritonitis and HCl/EtOH-induced gastritis. The molecular mechanism of Cc-ME-mediated anti-inflammatory activity was examined by Western blot analysis and immunoprecipitation using whole cell and nuclear fraction prepared from the LPS-stimulated RAW264.7 cells and HEK293 cells. Cc-ME inhibited NO production and mRNA expression of inducible nitric oxide synthase (iNOS), cyclooxygenase (COX-2), and tumor necrosis factor-alpha (TNF-α) in the RAW264.7 cells and peritoneal macrophages induced by LPS, pam3, or poly(I:C) without cytotoxicity. High-performance liquid chromatography (HPLC) analysis showed that Cc-ME contained anti-inflammatory flavonoids quercetin, luteolin, and kaempferol. Among those, the content of luteolin, which showed an inhibitory effect on NO production, was highest. Cc-ME suppressed the NF-κB signaling pathway by targeting Src and interrupting molecular interactions between Src and p85, its downstream kinase. Moreover, Cc-ME ameliorated the morphological finding of peritonitis and gastritis in the mouse disease models. Therefore, these results suggest that Cc-ME exerted in vitro and in vivo anti-inflammatory activity in LPS-stimulated macrophages and mouse models of acute inflammatory diseases. This anti-inflammatory activity of Cc-ME was dominantly mediated by targeting Src in NF-κB signaling pathway during macrophage-mediated inflammatory responses.

Tulobuterol patch alleviates allergic asthmic inflammation by blockade of Syk and NF-κB activation in mice

Background

Tulobuterol patch, one of strongest bronchodilators, was recently shown to improve bronchial hyperresponsiveness and significantly decrease the sputum eosinophil counts by combining with nonspecific anti-inflammatory drugs on patients with asthma. However, there is limited study on the anti-inflammatory activities of tulobuterol patch and its potential machenism.

Results

The tulobuterol patch significantly ameliorated inflammatory cell infiltration in the lung tissue, reduced the number of total leukocytes and its differential count, markedly reduced the production of IL-1β, TNF-α, IL-6, CCL-11 and IL-4 in bronchial alveolar lavage fluid, as well as a reduction in IL-4/IFN-γ ratio. Tulobuterol patch exhibited the best effect on allergic inflammation compared with formoterol and salbutamol. Furthermore, tulobuterol patch treatment significantly suppressed the expression and activation of Syk and its downdream signaling NF-κB and p-NF-κB.

Conclusions

The present studies revealed that tulobuterol patch effectively ameliorated airway inflammatory responses in allergic asthma, and its mechanisms, at least partially, via down-regulating Syk/NF-κB pathway.

Methods

An ovalbumin induced allergic asthma mouse model were used, and the effects of tulobuterol patch on allergic airway inflammation were evaluated. Also, its anti-airway inflammatory potential was compared with two other β₂-agonists, salbutamol and formoterol. Its possible anti-inflammatory mechanisms were identified by using western blotting and immunohistochemistry.

Src is the primary target of aripiprazole, an atypical antipsychotic drug, in its anti-tumor action

Aripiprazole (ARP) is an atypical anti-psychotic drug widely used to treat schizophrenia and bipolar disorder. The pharmacological effects of ARP on cancer cells are still poorly understood. In this study, anti-cancer effects of ARP on various malignant tumor cells and its molecular mechanism were further carefully examined by using cell proliferation assay, xenograft mouse model, immunoblotting analysis, migration assay, luciferase reporter gene assay, kinase assay, and overexpression strategy. Treatment with ARP induced cytotoxicity in U251 glioma cells, MKN-1 gastric adenosquamous carcinoma cells, and CT26 colon carcinoma cells. ARP suppressed cell proliferation of LN428, MDA-MB-231, and HEK293 cells. Pro-apoptotic factors active caspase-3, -8, and -9, as well as p53, were upregulated, whereas the protein and mRNA levels of anti-apoptotic factor B-cell lymphoma 2 (Bcl-2) decreased. In agreement with the in vitro results, ARP compound also significantly suppressed the growth of tumor masses formed by injecting CT26 colon cancer cells into mice. ARP treatment also effectively decreased the migratory ability of U251 glioma cells by downregulating metalloproteinase-9. Levels of phosphorylated Src, phosphorylated phosphatidylinositide 3-kinase (PI3K), and phosphorylated signal transducer and activator of transcription 3 (STAT3) were significantly decreased following ARP treatment. ARP compound reduced the kinase activity of Src. Our studies suggest that Src may be an important target molecule linked to the antitumor effects of ARP.

Anti-inflammatory effect of torilidis fructus ethanol extract through inhibition of Src

CONTEXT

Torilidis fructus, fruits of Torilis japonica Decadolle (Umbelliferae), is a medicinal herb traditionally used as a pesticide, an astrictive, or a medicine for various inflammatory diseases.

OBJECTIVES

Due to the lack of pharmacological studies on this herbal medicine, we explored the inhibitory activity of torilidis fructus on the macrophage-mediated inflammatory response using its ethanol extract (Tf-EE).

MATERIAL AND METHODS

The Griess assay and prostaglandin (PGE₂) ELISA assay were conducted with Tf-EE (0-75 µg/mL) and LPS (1 µg/mL) treated RAW264.7 cells in cultured media. Tf-EE pretreated RAW264.7 cells were incubated with LPS for 6 h and semi-quantitative PCR was performed. Reporter gene assays, overexpression of target enzymes and immunoblotting were performed on macrophages to determine the molecular targets of Tf-EE.

RESULTS

Tf-EE markedly suppressed the inflammatory response of macrophages, such as lipopolysaccharide (LPS)-induced nitric oxide (NO) and PGE₂ production with IC₅₀ values of 35.66 and 62.47 µg/mL, respectively. It was also found that Tf-EE reduced the expression of inducible NO synthase (iNOS) and cyclooxygenase (COX)-2 by 80%. Nuclear translocation and activation of nuclear factor (NF)-κB (p65 and p50) were declined by 60% and 30% respectively, and their regulatory events including the phosphorylation of AKT, IκBα, Src, and the formation of complexes between Src and p-p85 were also recognized to be diminished.

CONCLUSIONS

The signalling events managed by Src and p85 complex seemed to be critically involved in Tf-EE-mediated anti-inflammatory response. This might suggest that Tf-EE exhibited anti-inflammatory effects through Src-targeted inhibition of NF-κB.

Luteolin: A Flavonoid that Has Multiple Cardio-Protective Effects and Its Molecular Mechanisms

Cardiovascular disease (CVD) has become the leading cause of morbidity and mortality worldwide. A well-monitored diet with a sufficient intake of fruits and vegetables has been confirmed as a primary prevention of CVD. Plant constituents such as flavonoids have been shown to confer healthy benefits. Luteolin (Lut), a kind of flavonoid, possesses anti-oxidative, anti-tumor, and anti-inflammatory properties. Recent scientific literature has reported the cardiac protective effects of Lut in vitro and in vivo. Therefore, the aim of this review is to provide an update and detailed overview with cardio-protective molecular mechanisms of Lut with a focus on multiple intrinsic and extrinsic effectors. We further explore how these mechanisms participate in ischemia/reperfusion (I/R) injury, heart failure (HF) and atherosclerosis (AS). A proper understanding of the cardiovascular protective effects and the relative mechanisms of Lut may provide the possibility of new drug design and development for CVD. With the previous studies mainly focused on basic research, we need to advance the prospects of its further clinical utilization against CVD, large prospective clinical trials of Lut are needed to observe its therapeutic effects on patients with I/R injury, HF and AS, especially on the effective therapeutic dosage, and safety of long-term administration.

Anti-Inflammatory Effect of Piper attenuatum Methanol Extract in LPS-Stimulated Inflammatory Responses

Piper attenuatum is used as a traditional medicinal plant in India. One of the substances in P. attenuatum has been suggested to have anti-inflammatory effects. However, there is insufficient research about the anti-inflammatory mechanisms of action of P. attenuatum. The effects of P. attenuatum methanol extract (Pa-ME) on the production of inflammatory mediators nitric oxide (NO) and prostaglandin E₂ (PGE₂), the expression of proinflammatory genes, the translocation level of transcription factors, and intracellular signaling activities were investigated using macrophages. Pa-ME suppressed the production of NO and PGE₂ in lipopolysaccharide- (LPS-), pam3CSK4-, and poly(I:C)-stimulated RAW264.7 cells without displaying cytotoxicity. The mRNA expression levels of inducible NO synthase (iNOS) and cyclooxygenase 2 (COX-2) were decreased by Pa-ME. P-ME reduced the translocation of p50/NF-κB and AP-1 (c-Jun and c-Fos), as well as the activity of their upstream enzymes Src, Syk, and TAK1. Immunoprecipitation analysis showed failure of binding between their substrates, phospho- (p-) p85 and p-MKK3/6. p-p85 and p-MKK3/6, which were induced by overexpression of Src, Syk, and TAK1, were also reduced by Pa-ME. Therefore, these results suggest that Pa-ME exerts its anti-inflammatory effects by targeting Src and Syk in the NF-κB signaling pathway and TAK1 in the AP-1 signaling pathway.

Src and Syk contribute to the anti-inflammatory activities of Achyranthes aspera ethanolic extract

ETHNOPHARMACOLOGICAL RELEVANCE

Nuclear factor-kappa B (NF-κB) plays pivotal roles in inflammation. Src and Syk are two tyrosine kinases that act upstream of NF-κB signaling. Although Achyranthes aspera L. (A. aspera) has been used as a traditional medicine to treat fevers and inflammatory ailments and heal wounds, the molecular mechanisms of its anti-inflammatory actions are not yet fully understood.

MATERIALS AND METHODS

In this study, we evaluated the anti-inflammatory effect of A. aspera ethanol extract (Aa-EE). To determine the mechanism by which Aa-EE dampens the inflammatory response, nitric oxide (NO) production and the mRNA expression levels of tumor necrosis factor (TNF)-α and inducible nitric oxide synthase (iNOS) were examined by Griess assay and RT-PCR. Luciferase assays and immunoblotting were also conducted to examine how Aa-EE regulates the NF-κB pathway.

RESULTS

Aa-EE reduced NO production up to 60% without any cytotoxicity. This extract was found to downregulate the mRNA expression levels of inflammatory genes. Aa-EE blocked NF-κB promoter activity induced by both TNF-α and adaptor molecule MyD88 (about 70% and 40%, respectively). Moreover, nuclear translocation of p65 and IκBα phosphorylation were also inhibited. Furthermore, Aa-EE inactivated two upstream signaling molecules, the Src and Syk kinases. In accordance with these data, the kinase activities of Src and Syk were decreased by 50% and 80%, respectively. The anti-inflammatory action of Aa-EE was also confirmed in a gastritis model.

CONCLUSION

Our data suggest that Aa-EE targets NF-κB to exert its anti-inflammatory properties by suppressing Src and Syk. Therefore, our study raises the possibility that this extract can be developed as a novel natural anti-inflammatory remedy.

AKT-targeted anti-inflammatory activity of the methanol extract of Chrysanthemum indicum var. albescens

ETHNOPHARMACOLOGICAL RELEVANCE

Wild chrysanthemum (Chrysanthemum indicum) is one of well-known medicinal plants traditionally used in Korea and China. As a variant of wild chrysanthemum, white wild chrysanthemum (Chrysanthemum indicum var. albescens) is also ethnopharmacologically applied to treat various symptoms such as inflammatory diseases.

AIM OF STUDY

Although the anti-inflammatory activity of Chrysanthemum indicum has been reported, the anti-inflammatory activity and underlying molecular mechanism of white wild chrysanthemum are poorly understood.

MATERIALS AND METHODS

The effects of Chrysanthemum indicum var. albescens methanol extract (Civ-ME) on the production of inflammatory mediators, expression of pro-inflammatory genes, cell viability, and the activities of intracellular signaling molecules and transcription factors were investigated in lipopolysaccharide (LPS)-stimulated RAW264.7 cells.

RESULTS

Civ-ME suppressed the production of both nitric oxide (NO) and prostaglandin E₂ (PGE₂) without cytotoxicity in LPS-stimulated RAW264.7 cells. Civ-ME was found to reduce the mRNA levels of inflammatory genes such as inducible NO synthase (iNOS) and tumor necrosis factor (TNF)-α and reduced NF-κB-mediated transcriptional activation. Civ-ME inhibited the nuclear translocation of NF-κB (p65 and p50), and its upstream signaling composed of IκBα and IKKα/β. An NF-κB luciferase reporter gene assay and an in vitro kinase assay confirmed that AKT1 and AKT2 might be direct pharmacological targets of Civ-ME. In addition, luteolin was identified by HPLC analysis as the main active pharmacological components of Civ-ME.

CONCLUSION

Civ-ME exerts an anti-inflammatory effect by targeting AKT1 and AKT2 in the NF-κB signaling pathway in macrophage-mediated inflammatory responses.

Expression of typical osteoclast markers by PBMCs after PEG-induced fusion as a model for studying osteoclast differentiation

Bone is a metabolically active organ subjected to continuous remodeling process that involves resorption by osteoclast and subsequent formation by osteoblasts. Osteoclast involvement in this physiological event is regulated by macrophage colony-stimulating factor (M-CSF) and receptor activator of nuclear factor κB ligand (RANKL). Fusion of mono-nuclear pre-osteoclasts is a critical event for osteoclast differentiation and for bone resorption. Here we show that PBMCs can be successfully fused with polyethylenglicol (PEG) in order to generated viable osteoclast-like cells that exhibit tartrate-resistant acid phosphatase (TRAP) and bone resorptive activities. PEG-fused PBMCs expressed additional markers compatible with osteoclastogenic differentiation such as carbonic anhydrase II (CAII), calcitonin receptor (CR), cathepsin K (Cat K), vacuolar ATPase (V-ATPase) subunit C1 (V-ATPase), integrin β3, RANK and cell surface aminopeptidase N/CD13. Actin redistribution in PEG-fused cells was found to be affected by cell cycle synchronization at G0/G1 or G2/M phases. PEG-induced fusion also led to expression of tyrosine kinases c-Src and Syk in their phosphorylated state. Scanning electron microscopy images showed morphological features typical of osteoclast-like cells. The results here shown allow concluding that PEG-induced fusion of PBMCs provides a suitable model system for understanding the mechanisms involved in osteoclastogenesis and for assaying new therapeutic strategies.

1-(2,3-Dibenzimidazol-2-ylpropyl)-2-methoxybenzene Is a Syk Inhibitor with Anti-Inflammatory Properties

Inflammation is the protective action of our bodies against external pathogens by recognition of pathogen-associated molecular patterns (PAMPs) via pattern recognition receptors (PRRs). Proper regulation of inflammatory responses is required to maintain our body’s homeostasis, as well as there are demands to develop proper acute or chronic inflammation. In this study, we elucidated the regulatory mechanism of NF-κB-mediated inflammatory responses by a novel compound, 1-(2,3-dibenzimidazol-2-ylpropyl)-2-methoxybenzene (DBMB). We found that DBMB suppressed inflammatory mediators, nitric oxide (NO) and prostaglandin E₂ (PGE₂), reacted to exposure to a number of toll like receptor (TLR) ligands. Such observations occurred following to decreased mRNA expression of several pro-inflammatory mediators, and such diminished mRNA levels were caused by inhibited transcriptional factor nuclear factor (NF)-κB, as evaluated by luciferase reporter assay and molecular biological approaches. To find the potential targets of DBMB, we screened phosphorylated forms of NF-κB signal molecules: inhibitor of κBα (IκBα), IκB kinase (IKK)α/β, Akt, 3-phosphoinositide dependent protein kinase-1 (PDK1), p85, and spleen tyrosine kinase (Syk). We found that DBMB treatment could suppress signal transduction through these molecules. Additionally, we conducted in vitro kinase assays using immunoprecipitated Syk and its substrate, p85. Consequently, we could say that DBMB clearly suppressed the kinase activity of Syk kinase activity. Together, our results demonstrate that synthetic DBMB has an effect on the inflammatory NF-κB signaling pathway and suggest the potential for clinical use in the treatment of inflammatory diseases.

(E)-3-(3-methoxyphenyl)-1-(2-pyrrolyl)-2-propenone displays suppression of inflammatory responses via inhibition of Src, Syk, and NF-κB

(E)-3-(3-methoxyphenyl)-1-(2-pyrrolyl)-2-propenone (MPP) is an aldol condensation product resulting from pyrrole-2-carbaldehyde and m- and p- substituted acetophenones. However, its biological activity has not yet been evaluated. Since it has been reported that some propenone-type compounds display anti-inflammatory activity, we investigated whether MPP could negatively modulate inflammatory responses. To do this, we employed lipopolysaccharide (LPS)-stimulated macrophage-like RAW264.7 cells and examined the inhibitory levels of nitric oxide (NO) production and transcriptional activation, as well as the target proteins involved in the inflammatory signaling cascade. Interestingly, MPP was found to reduce the production of NO in LPS-treated RAW264.7 cells, without causing cytotoxicity. Moreover, this compound suppressed the mRNA levels of inflammatory genes, such as inducible NO synthase (iNOS) and tumor necrosis factor (TNF)-α. Using luciferase reporter gene assays performed in HEK293 cells and immunoblotting analysis with nuclear protein fractions, we determined that MPP reduced the transcriptional activation of nuclear factor (NF)-κB. Furthermore, the activation of a series of upstream signals for NF-κB activation, composed of Src, Syk, Akt, and IκBα, were also blocked by this compound. It was confirmed that MPP was able to suppress autophosphorylation of overexpressed Src and Syk in HEK293 cells. Therefore, these results suggest that MPP can function as an anti-inflammatory drug with NF-κB inhibitory properties via the suppression of Src and Syk.

4-Isopropyl-2,6-bis(1-phenylethyl)aniline 1, an Analogue of KTH-13 Isolated from Cordyceps bassiana, Inhibits the NF-κB-Mediated Inflammatory Response

The Cordyceps species has been a good source of compounds with anticancer and anti-inflammatory activities. Recently, we reported a novel compound (4-isopropyl-2,6-bis(1-phenylethyl)phenol, KTH-13) with anticancer activity isolated from Cordyceps bassiana and created several derivatives to increase its pharmacological activity. In this study, we tested one of the KTH-013 derivatives, 4-isopropyl-2,6-bis(1-phenylethyl)aniline 1 (KTH-13-AD1), with regard to anti-inflammatory activity under macrophage-mediated inflammatory conditions. KTH-13-AD1 clearly suppressed the production of nitric oxide (NO) and reactive oxygen species (ROS) in lipopolysaccharide (LPS) and sodium nitroprusside- (SNP-) treated macrophage-like cells (RAW264.7 cells). Similarly, this compound also reduced mRNA expression of inducible NO synthase (iNOS) and tumor necrosis factor-α (TNF-α), as analyzed by RT-PCR and real-time PCR. Interestingly, KTH-13-AD1 strongly diminished NF-κB-mediated luciferase activities and nuclear translocation of NF-κB family proteins. In accordance, KTH-13-AD1 suppressed the upstream signaling pathway of NF-κB activation, including IκBα, IKKα/β, AKT, p85/PI3K, and Src in a time- and dose-dependent manner. The autophosphorylation of Src and NF-κB observed during the overexpression of Src was also suppressed by KTH-13-AD1. These results strongly suggest that KTH-13-AD1 has strong anti-inflammatory features mediated by suppression of the Src/NF-κB regulatory loop.