Inhibition of Nitric Oxide Production by Ethyl Digallates Isolated from Galla Rhois in RAW 264.7 Macrophages

Isolation of phenolic acids and tannin acids from Mangifera indica L. kernels as inhibitors of lipid accumulation in 3T3-L1 cells

Mango (Mangifera indica L.) kernels are usually discarded as waste, but they contain many pharmacological properties and bioactivities. In this study, we isolated antiobesity agents from mango kernels that inhibit intracellular lipid formation in 3T3-L1 adipocytes. Two phenolic acids, ethyl gallate and ethyl digallate, and 2 tannin acids, 1,2,3,4,6-penta-O-galloyl-β-d-glucose (PGG) and 3-O-digalloyl-1,2,4,6-tetra-O-β-d-glucose (HGG), were identified from mango kernels and were found to be suppressed lipid accumulation as evidenced by Oil Red O staining. Furthermore, ethyl digallate, PGG, and HGG significantly downregulated the mRNA expression of adipogenic transcription factors such as C/EBPα and PPARγ. However, ethyl gallate did not affect the expression of these transcription factors. Our findings reveal the presence of antiobesity compounds in mango kernels, implying its therapeutic role against obesity.

Pathophysiological Role of S-Nitrosylation and Transnitrosylation Depending on S-Nitrosoglutathione Levels Regulated by S-Nitrosoglutathione Reductase

Nitric oxide (NO) mediates various physiological and pathological processes, including cell proliferation, differentiation, and inflammation. Protein S-nitrosylation (SNO), a NO-mediated reversible protein modification, leads to changes in the activity and function of target proteins. Recent findings on protein-protein transnitrosylation reactions (transfer of an NO group from one protein to another) have unveiled the mechanism of NO modulation of specific signaling pathways. The intracellular level of S-nitrosoglutathione (GSNO), a major reactive NO species, is controlled by GSNO reductase (GSNOR), a major regulator of NO/SNO signaling. Increasing number of GSNOR-related studies have shown the important role that denitrosylation plays in cellular NO/SNO homeostasis and human pathophysiology. This review introduces recent evidence of GSNO-mediated NO/SNO signaling depending on GSNOR expression or activity. In addition, the applicability of GSNOR as a target for drug therapy will be discussed in this review.

TANK-binding kinase 1 and Janus kinase 2 play important roles in the regulation of mitogen-activated protein kinase phosphatase-1 expression after toll-like receptor 4 activation

Inflammation is a response that protects the body from pathogens. Through several inflammatory signaling pathways mediated by various families of transcription factors, such as nuclear factor-κB (NF-κB), activator protein-1 (AP-1), interferon regulatory factors (IRFs), and signal transducers and activators of transcription (STATs), various inflammatory cytokines and chemokines are induced and inflammatory responses are boosted. Simultaneously, inhibitory systems are activated and provide negative feedback. A typical mechanism by which this process occurs is that inflammatory signaling molecules upregulate mitogen-activated protein kinase phosphatase-1 (MKP1) expression. Here, we investigated how kinases regulate MKP1 expression in lipopolysaccharide-triggered cascades. We found that p38 and c-Jun N-terminal kinase (JNK) inhibitors decreased MKP1 expression. Using specific inhibitors, gene knockouts, and gene knockdowns, we also found that tumor necrosis factor receptor-associated factor family member-associated nuclear factor κB activator (TANK)-binding kinase 1 (TBK1) and Janus kinase 2 (JAK2) are involved in the induction of MKP1 expression. By analyzing JAK2-induced activation of STATs, STAT3-specific inhibitors, promoter binding sites, and STAT3^-/- cells, we found that STAT3 is directly linked to TBK1-mediated and JAK2-mediated induction of MKP1 expression. Our data suggest that MKP1 expression can be differentially regulated by p38, JNK, and the TBK1-JAK2-STAT3 pathway after activation of toll-like receptor 4 (TLR4). These data also imply crosstalk between the AP-1 pathway and the IRF3 and STAT3 pathways.

ATF-2/CREB/IRF-3-targeted anti-inflammatory activity of Korean red ginseng water extract

ETHNOPHARMACOLOGICAL RELEVANCE

Korean Red Ginseng (KRG) is one of the representative traditional herbal medicines prepared from Panax ginseng Meyer (Araliaceae) in Korea. It has been reported that KRG exhibits a lot of different biological actions such as anti-aging, anti-fatigue, anti-stress, anti-atherosclerosis, anti-diabetic, anti-cancer, and anti-inflammatory activities. Although systematic studies have investigated how KRG is able to ameliorate various inflammatory diseases, its molecular inhibitory mechanisms had not been carried out prior to this study.

MATERIALS AND METHODS

In order to investigate these mechanisms, we evaluated the effects of a water extract of Korean Red Ginseng (KRG-WE) on the in vitro inflammatory responses of activated RAW264.7 cells, and on in vivo gastritis and peritonitis models by analyzing the activation events of inflammation-inducing transcription factors and their upstream kinases.

RESULTS

KRG-WE reduced the production of nitric oxide (NO), protected cells against NO-induced apoptosis, suppressed mRNA levels of inducible NO synthase (iNOS), cyclooxygenase (COX)-2, and interferon (IFN)-β, ameliorated EtOH/HCl-induced gastritis, and downregulated peritoneal exudate-derived NO production from lipopolysaccharide (LPS)-injected mice. The inhibition of these inflammatory responses by KRG-WE was regulated through the suppression of p38, c-Jun N-terminal kinase (JNK), and TANK-binding kinase 1 (TBK1) and by subsequent inhibition of activating transcription factor (ATF)-2, cAMP response element-binding protein (CREB), and IRF-3 activation. Of ginsensides included in this extract, interestingly, G-Rc showed the highest inhibitory potency on IRF-3-mediated luciferase activity.

CONCLUSION

These results strongly suggest that the anti-inflammatory activities of KRG-WE could be due to its inhibition of the p38/JNK/TBK1 activation pathway.

(5-Hydroxy-4-oxo-4H-pyran-2-yl)methyl 6-hydroxynaphthalene-2-carboxylate, a kojic acid derivative, inhibits inflammatory mediator production via the suppression of Syk/Src and NF-κB activation

Numerous derivatives of kojic acid have been synthesised to expand its immunopharmacological uses. Kojic acid is known to have anti-cancer, anti-inflammatory, and anti-melanogenesis effects. We found that (5-hydroxy-4-oxo-4H-pyran-2-yl)methyl 6-hydroxynaphthalene-2-carboxylate (MHNC) strongly suppressed the production of nitric oxide (NO) in an initial screening experiment. In this study, we explored the in vitro and in vivo anti-inflammatory activity of MHNC and its inhibitory mechanisms using lipopolysaccharide (LPS)-treated RAW264.7 cells and HCl/EtOH-treated ICR mice. MHNC dose-dependently diminished the secretion of nitric oxide (NO) and prostaglandin (PG)E2 in LPS-treated RAW264.7 cells. This compound also suppressed the upregulation of mRNA levels for the inducible NO synthase (iNOS) and cyclooxygenase (COX)-2 genes. Additionally, the transcriptional activation of these genes was inhibited by MHNC through the suppression of the nuclear translocation of nuclear factor (NF)-κB subunits (p65 and p50), as determined by a luciferase reporter assay. Interestingly, MHNC treatment was found to suppress a series of upstream signalling cascades consisting of IκBα, AKT, PDK1, Src, and Syk for NF-κB activation. Furthermore, a direct enzyme assay with purified Src and Syk and luciferase assays using Src and Syk overexpression indicated that these enzymes were directly inhibited by MHNC. Finally, MHNC (20mg/kg) prevented inflammatory symptoms of the stomach in mice treated with HCl/EtOH by reducing phospho-IκBα levels. Taken together, our data suggest that MHNC may negatively modulate in vitro and in vivo inflammatory responses via the direct suppression of Syk/Src and NF-κB.

Syk and Src are major pharmacological targets of a Cerbera manghas methanol extract with kaempferol-based anti-inflammatory activity

ETHNOPHARMACOLOGICAL RELEVANCE

Cerbera manghas L. (Apocynaceae), a semi-mangrove medicinal plant distributed throughout tropical and subtropical countries, is traditionally known to possess analgesic, anti-inflammatory, anti-convulsant, cardiotonic, and hypotensive activity. In vitro and in vivo anti-inflammatory activities of a methanol extract of the leaves of Cerbera manghas and the underlying molecular mechanisms were investigated to validate the ethnopharmacological use of this plant.

MATERIALS AND METHODS

The effect of Cerbera manghas methanol extract (Cm-ME) on the production of inflammatory mediators and the induction of HCl/EtOH-treated gastritis was explored using macrophages, HEK293 cells, and ICR mice. The molecular targets of this extract and potential active components in Cm-ME were also investigated.

RESULTS

Cm-ME inhibited the production of nitric oxide (NO) in lipopolysaccharide (LPS)-treated RAW264.7 cells and peritoneal macrophages in a dose-dependent manner. This extract also suppressed the expression of NO synthase (iNOS) and cyclooxygenase (COX)-2. NF-κB-mediated enhancement of luciferase activity, nuclear translocation of p50 and p65, and phosphorylation of IκBα were markedly reduced by Cm-ME treatment. Direct enzyme assays, reporter gene assays, and immunoprecipitation analysis of kinases revealed Syk and Src as immunopharmacological targets of Cm-ME. Moreover, this extract strongly ameliorated the gastric symptoms induced by HCl/EtOH treatment of mice. Finally, HPLC analysis and pharmacological tests identified kaempferol as an active component of the extract with Src/Syk inhibitory activities.

CONCLUSION

Inhibition of Syk/Src and the NF-κB pathway by kaempferol could play a key role in the anti-inflammatory pharmacological action of Cerbera manghas.

20S-dihydroprotopanaxadiol, a ginsenoside derivative, boosts innate immune responses of monocytes and macrophages

20S-dihydroprotopanaxadiol (2H-PPD) is a derivative of protopanaxadiol, a glycone of ginsenosides prepared from Panax ginseng. Although ginsenosides and acidic polysaccharides are known to be major active ingredients in ginseng, the immunopharmacological activities of their metabolites and derivatives have not been fully explored. In this study, we aimed to elucidate the regulatory action of 2H-PPD on the function of monocytes and macrophages in innate immune responses. 2H-PPD was able to boost the phagocytic uptake of fluorescein isothiocyanate-dextran in macrophages and enhance the generation of radicals (reactive oxygen species) in sodium nitroprusside-treated RAW264.7 cells. The surface levels of the costimulatory molecules such as CD80 and CD86 were also increased during 2H-PPD treatment. In addition, this compound boosted U937 cellcell aggregation induced by CD29 and CD43 antibodies, but not by cell-extracellular matrix (fibronectin) adhesion. Similarly, the surface levels of CD29 and CD43 were increased by 2H-PPD exposure. Therefore, our results strongly suggest that 2H-PPD has the pharmacological capability to upregulate the functional role of macrophages/monocytes in innate immunity.

Methanol extract of Evodia lepta displays Syk/Src-targeted anti-inflammatory activity

ETHNOPHARMACOLOGICAL RELEVANCE

Evodia lepta (Spreng.) Merr., in the Rutaceae family, is a medicinal plant traditionally used to treat inflammatory symptoms such as in meningitis and hepatitis. However, no study has systematically investigated its anti-inflammatory activities including its molecular mechanism.

MATERIALS AND METHODS

The effects of a methanol extract from the roots Evodia lepta (El-ME) were evaluated using lipopolysaccharide (LPS)-treated RAW264.7 cells producing nitric oxide (NO) and prostaglandin E2 (PGE2), and an HCl/ethanol-induced mouse gastritis model. Target molecules were identified by analyzing the activation of transcription factors and their upstream kinases.

RESULTS

El-ME reduced the production of NO and PGE2 from LPS-activated RAW264.7 cells in a dose-dependent manner. El-ME also ameliorated the gastritis symptoms of EtOH/HCl-treated mice. The extract suppressed production of mRNA for the inducible NO synthase (iNOS) and cyclooxygenase (COX)-2; the nuclear translocation of nuclear factor (NF)-κB; the phosphorylation of upstream kinases that activate NF-κB; and the kinase activities of Syk and Src.

CONCLUSION

The anti-inflammatory effects of El-ME might be due to its suppression of Syk/Src and NF-κB. Considering the in vitro and in vivo efficacy of El-ME, Evodia lepta could be developed into an anti-inflammatory herbal remedy.

Dipterocarpus tuberculatus ethanol extract strongly suppresses in vitro macrophage-mediated inflammatory responses and in vivo acute gastritis

ETHNOPHARMACOLOGICAL RELEVANCE

Dipterocarpus tuberculatus Roxb. (Dipterocarpaceae) has been traditionally used to treat various inflammatory symptoms. However, no mechanistic studies on the anti-inflammatory actions of D. tuberculatus have been reported. This study is therefore aimed at exploring the anti-inflammatory effects of 95% ethanol extracts (Dt-EE) of this plant.

MATERIALS AND METHODS

The regulatory activity of Dt-EE and its molecular mechanism on the release of nitric oxide (NO) and prostaglandin (PG)E2 in lipopolysaccharide (LPS)-treated macrophage-like RAW264.7 cells were elucidated by evaluating the activation of transcription factors and their upstream signals and by analyzing the kinase activities of target enzymes. Furthermore, to confirm its availability for oral use, an EtOH/HCl-induced acute gastritis model was tested with this extract.

RESULTS

Dt-EE effectively suppressed LPS-mediated inflammatory responses such as the production of NO and PGE2 from macrophages in a dose-dependent manner. In particular, Dt-EE clearly blocked the activation of NF-κB by blocking the phosphorylation of its upstream enzymes IKK and Akt. Using a direct enzyme assay, Dt-EE was shown to block the enzyme activity of PDK1. Finally, this extract also remarkably ameliorated inflammatory lesions in the stomach induced by EtOH/HCl.

CONCLUSION

Our data strongly suggest that Dt-EE can be considered as a novel anti-inflammatory remedy with PDK1/NF-κB inhibitory properties and can also be used to treat gastritis symptoms. In addition, our findings can serve as a basis for further phytochemical and pharmacological studies in the future.

In vitro and in vivo anti-inflammatory effect of Rhodomyrtus tomentosa methanol extract

ETHNOPHARMACOLOGICAL RELEVANCE

Rhodomyrtus tomentosa (Aiton) Hassk. is a representative Thai medicinal plant traditionally used in South Asian countries to relieve various inflammatory symptoms. However, no systematic studies on its anti-inflammatory activity and mechanisms have been reported.

MATERIALS AND METHODS

The effect of the methanol extract from the leaves of this plant (Rt-ME) on the production of inflammatory mediators [nitric oxide (NO) and prostaglandin E2 (PGE2)] and the molecular mechanism of Rt-ME-mediated inhibition, including target enzymes, were studied with RAW264.7, peritoneal macrophage, and HEK293 cells. Additionally, the in vivo anti-inflammatory activity of this extract was evaluated with mouse gastritis and colitis models.

RESULTS

Rt-ME clearly inhibited the production of NO and PGE2 in lipopolysaccharide (LPS)-activated RAW264.7 cells and peritoneal macrophages in a dose-dependent manner. According to RT-PCR, immunoblotting and immunoprecipitation analyses and a kinase assay with mRNA, whole cell extract, and nucleus lysates from RAW264.7 cells and mice, it was revealed that Rt-ME was capable of suppressing the activation of both nuclear factor (NF)-κB and activator protein (AP)-1 pathways by directly targeting Syk/Src and IRAK1/IRAK4.

CONCLUSION

Rt-ME could have anti-inflammatory properties by suppressing Syk/Src/NF-kB and IRAK1/IRAK4/AP-1 pathways and will be further developed as a herbal remedy for preventive and/or curative purposes in various inflammatory diseases.

Src and Syk are targeted to an anti-inflammatory ethanol extract of Aralia continentalis

ETHNOPHARMACOLOGICAL RELEVANCE

Aralia continentalis Kitagawa (Araliaceae) is a representative ethnomedicinal herbal plant traditionally prescribed in Korea to relieve various inflammatory symptoms. However, the exact molecular mechanism of its anti-inflammatory activity has not been fully investigated.

MATERIALS AND METHODS

The effect of the ethanol extract from the roots of this plant (Ac-EE) on the production of the inflammatory mediator nitric oxide (NO) was studied in RAW264.7 cells. Its effect on inflammatory symptoms (gastritis and hepatitis) in mice was also examined. In particular, the molecular inhibitory mechanism was analysed by measuring the activation of transcription factors and their upstream signalling and the kinase activity of target enzymes.

RESULTS

Ac-EE dose-dependently suppressed NO production in lipopolysaccharide (LPS)-activated RAW264.7 cells. This extract also displayed curative activity against EtOH/HCl-induced gastritis and LPS-induced hepatitis in mice. Ac-EE-mediated anti-inflammatory activity was found to be at the transcriptional level, as it blocked the activation of the nuclear factor (NF)-κB pathway composed of Syk and Src, according to immunoblotting and immunoprecipitation analyses and a kinase assay with whole and nucleus lysates from RAW264.7 cells and mice.

CONCLUSION

Ac-EE may be developed as a functional herbal remedy targeting Syk- and Src-mediated anti-inflammatory mechanisms. Future work using pre-clinical studies will be needed to investigate this possibility.