Involvement of mitogen-activated protein kinase homologues in the regulation of lipopolysaccharide-mediated induction of cyclo-oxygenase-2 but not nitric oxide synthase in RAW 264.7 macrophages

Potential mechanisms underlying the protective effects of Tricholoma matsutake singer peptides against LPS-induced inflammation in RAW264.7 macrophages

This study aimed to investigate the protective effects of a < 3 kDa Tricholoma matsutake Singer peptide (TMWP) on lipopolysaccharide (LPS)-induced inflammation in RAW264.7 macrophages. The results showed that TMWP significantly upregulated superoxide dismutase (SOD) activity and reduced reactive oxygen species (ROS) generation in RAW264.7 macrophages. Western blotting and immunofluorescence analysis indicated that TMWP inhibited the activation of the mitogen-activated protein kinase (MAPK) and nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) pathways, thereby reducing the secretion of IL-1β and IL-6 and the expression of TNF-α, COX-2, and iNOS. Additionally, TMWP improved mitochondrial respiration in LPS-stressed macrophages, counteracting the harmful effects of LPS treatment on mitochondrial function. Three peptides (SDIKHFPF, SDLKHFPF, and WFNNAGP) with the highest predicted scores for potential anti-inflammatory activity were identified using nano-HPLC-MS/MS. These data indicated that T. matsutake peptides could be an attractive natural ingredient for developing novel functional foods.

Aristolochia trilobata: Identification of the Anti-Inflammatory and Antinociceptive Effects

Aristolochia trilobata, popularly known as “mil-homens,” is widely used for treatment of stomach aches, colic, asthma, pulmonary diseases, diabetes, and skin affection. We evaluated the antinociceptive and anti-inflammatory activities of the essential oil (EO) and the main constituent, 6-methyl-5-hepten-2-yl acetate (sulcatyl acetate, SA). EO and SA (1, 10, and 100 mg/kg, p.o.) were evaluated using chemical (formalin-induced licking) and thermal (hot-plate) models of nociception or inflammation (carrageenan-induced cell migration into the subcutaneous air pouch, SAP). The mechanism of antinociceptive activity was evaluated using opioid, cholinergic receptor antagonists (naloxone and atropine), or nitric oxide synthase inhibitor (L-NAME). EO and SA presented a central antinociceptive effect (the hot-plate model). In formalin-induced licking response, higher doses of EO and SA also reduced 1st and 2nd phases. None of the antagonists and enzyme inhibitor reversed antinociceptive effects. EO and SA reduced the leukocyte migration into the SAP, and the cytokines tumor necrosis factor and interleukin-1 (TNF-α and IL-1β, respectively) produced in the exudate. Our results are indicative that EO and SA present peripheral and central antinociceptive and anti-inflammatory effects.

Antinociceptive and Anti-Inflammatory Effects of Nypa fruticans Wurmb by Suppressing TRPV1 in the Sciatic Neuropathies

Neuropathic pain is generally characterized by sensory abnormalities such as sensory disorders, hyperalgesia, and allodynia. Recent studies have reported that TRPV1 activation is essential for establishing of inflammation in the neuropathy pain models, showing that the expression of this receptor is increased, and contributing to enhanced thermal sensitivity. Nypa fruticans Wurmb (NF), which was used as a folk remedy, is a plant that is gaining attention due to its various effects. In this study, we investigated the antinociceptive and anti-inflammatory effects of NFE (Nypa fruticans Wurmb extracts) by controlling the neurological function of TRPV1. In sciatic crush injury rat models, a significant level of antinociceptive effect was observed in the thermal hyperalgesia test in which NF extracts (NFE 500 mg/kg) were orally administered, daily. Protein quantification of the sciatic nerve and the of the L4-L6 spinal cord showed a decrease of the TRPV1 expression, the inflammatory expression factor, COX2, and proinflammatory factors in the NFE treated groups. Our results indicate that NFE affects antinociceptive and anti-inflammatory by controlling TRPV1 in sciatic neuropathic pain models.

An ethyl-acetate fraction of Holothuria scabra modulates inflammation in vitro through inhibiting the production of nitric oxide and pro-inflammatory cytokines via NF-κB and JNK pathways

Sea cucumber, Holothuria scabra, is an echinoderm marine animal that has long been used as a traditional therapeutic in various diseases due to its chemical composition and protein enrichment. Many researchers have extensively studied the efficacy of sea cucumber extracts for many health benefits in recent years. Inflammation is a complex process involved in pro-/anti-inflammatory cytokine products. However, the role of the H. scabra extracts in anti-inflammation and its molecular regulations has not been apparently elucidated yet. In this study, we investigated the anti-inflammatory effect of H. scabra extracts by using lipopolysaccharide (LPS) from E. coli to induce an inflammatory response in RAW264.7 macrophage. It was found that ethyl acetate fraction of H. scabra extracts (EAHS) inhibited pro-inflammatory cytokines synthesis at both the transcriptional and translational levels, notably nitric oxide (NO), inducible nitric oxide synthase (iNOS), interleukin-1β (IL-1β), tumor necrosis factor-α (TNF-α), and prostaglandin E₂ (PGE₂). In addition, EAHS was able to downregulate IκB/NF-κB, and JNK expressions. These effects may be influenced by high contents of phenolic compound and triterpene glycosides in EAHS. Therefore, EAHS might have the potential to be developed as a natural anti-inflammatory agent.

Arterial Thrombosis Is Accompanied by Elevated Mitogen-Activated Protein Kinase (MAPK) and Cyclooxygenase-2 (COX-2) Expression via Toll-Like Receptor 4 (TLR-4) Activation by S100A8/A9

BACKGROUND The aim of this study was to determine the involvement of S100A8/A9 in the development of arterial thrombosis. MATERIAL AND METHODS A total of 303 patients were enrolled in this study, with 110 having acute coronary syndrome (ACS) and 110 having coronary heart disease (CHD), and 83 subjects served as healthy blood donors. The concentrations of Toll-like receptor 4 (TLR-4), cyclooxygenase-2 (COX-2), and S100A8/A9 protein were determined in the sera of the participants and in peripheral blood mononuclear cells (PBMCs) derived from a rat carotid artery thrombosis model and in human aortic endothelial cells (HAECs). The mitogen-activated protein kinase (MAPK) inhibitor SB203580 and the TLR-4 blocker CLI-095 were used to investigate the role of the TLR-4-MAPK-COX2 signaling axis in thrombosis. RESULTS The levels of COX-2, TLR-4, and S100A8/A9 in the sera of patients with ACS and CHD were significantly higher than in healthy controls (P<0.05). S100A8/A9 expression was significantly correlated with TLR-4 and COX-2 in the ACS group and with TLR-4 in the CHD group. In the rat carotid thrombosis model, the expressions of TLR-4, COX-2, and p-p38 MAPK significantly increased until 14 days after thrombosis induction, whereas S100A8/A9 expression increased until day 7, but then decreased. Administration of SB203580 to rats reduced COX-2 expression in PBMCs after thrombosis induction, and incubation of HAECs with CLI-095 reduced their p-p38 MAPK and COX-2 response to S100A8/A9 stimulation. CONCLUSIONS S100A8/A9 is upregulated after blood vessel injury and is enhanced in combination with TLR-4 COX-2 induction via p38 MAPK activation.

Alliin, a garlic organosulfur compound, ameliorates gut inflammation through MAPK-NF-κB/AP-1/STAT-1 inactivation and PPAR-γ activation

SCOPE

In this study, the anti-inflammatory effects and the molecular mechanism of alliin were analyzed in dextran sulfate sodium (DSS)-induced colitis mice and lipopolysaccharide-stimulated RAW264.7 cell model.

METHODS

The phenotype of mice was recorded in the DSS-induced and/or alliin (500 mg/kg) groups. Histopathological alterations were analyzed by H&E staining. MPO and MDA of colon tissues were measured. The mRNA expression levels of inflammatory factors were determined by qRT-PCR, and protein expressions of inflammatory factors or activation of kinases were determined by Western blotting.

RESULTS

Oral administration of alliin significantly inhibited the decrease of body weight, improved the DAI and decreased the infiltration of inflammatory cells in colonic tissues. The content of NO, MDA, and MPO, the expression of iNOS and inflammatory factors as well as MAPK and the phosphorylation of PPAR-γ were inhibited in alliin-treated group. Treatment with alliin significantly repressed the expression of inflammatory factors in LPS-stimulated RAW264.7 cells. Further research demonstrated that alliin repressed LPS-induced AP-1/NF-κB/STAT-1 activation by inhibiting the phosphorylations of p38, JNK, and ERK1/2-regulated PPAR-γ activation.

CONCLUSION

Our results show that alliin ameliorates DSS-induced ulcerative colitis and inhibits the inflammatory responses in LPS-stimulated RAW264.7 cells partly through inhibiting ERK1/2-, JNK-/PPAR-γ-stimulated NF-κB/AP-1/STAT-1 activations.

Anti-inflammatory effects of 6'-O-acetyl mangiferin from Iris rossii Baker via NF-κb signal blocking in lipopolysaccharide-stimulated RAW 264.7 cells

A series of acylated xanthone C-glucosides were identified from the methanolic extract of whole Iris rossii Baker. The major constituent was characterized as 6'-O-acetyl mangiferin (OAM), and complete structure elucidation was carried out using 2D NMR (COSY, HSQC, and HMBC) and LC-IT-TOF-MS analyses. The present study is the first to report the anti-inflammatory effects of 6'-O-acetyl mangiferin from Iris rossii Baker on the lipopolysaccharide (LPS)-induced inflammatory response in RAW264.7 macrophage cells. OAM strongly suppressed protein expression of inducible nitric oxide (iNOS) and cyclooxygenase-2 (COX-2), thereby inhibiting the production of nitric oxide (NO), prostaglandin E2 (PGE2), and cytokines such as tumor necrosis factor-α (TNF-α), interleukin-1β (IL-1β), and interleukin-6 (IL-6). Furthermore, OAM inhibited the LPS-induced phosphorylation of ERK, JNK, and p38, which led to the blockade of nuclear factor-kappa B (NF-κB) and inhibitor kappa B (IκB)-α activation. These results suggest that the anti-inflammatory effects of OAM may be attributed to the downregulation of COX-2 and iNOS via the suppression of NF-κB and the MAPK signaling pathway in RAW264.7 macrophages.

Flavonoids of Polygonum hydropiper L. attenuates lipopolysaccharide-induced inflammatory injury via suppressing phosphorylation in MAPKs pathways

Background

Polygonum hydropiper L. is widely used as a traditional remedy for the treatment of dysentery, gastroenteritis. It has been used to relieve swelling and pain, dispel wind and remove dampness, eliminate abundant phlegm and inflammatory for a long time. Previous study showed that antioxidants especially flavonoids pretreatment alleviated sepsis-induced injury in vitro and in vivo. In the present study, the possible anti-inflammatory effect of flavonoids from normal butanol fraction of Polygonum hydropiper L. extract (FNP) against inflammation induced by lipopolysaccharide (LPS) was evaluated in vivo and in vitro.

Methods

The content of total flavonoid of FNP was determined by the aluminum colorimetric method. The content of rutin, quercetin and quercitrin was determined by HPLC method. Mice received FNP orally 3 days before an intra-peritoneal (i.p.) injection of lipopolysaccharide (LPS). Total superoxidase dismutase (T-SOD), total antioxidant capacity (T-AOC), glutathione peroxidase (GSH-PX), glutathione (GSH), myeloperoxidase (MPO) and malondialdehyde (MDA) levels were measured. Tumor necrosis factor-α levels in serum and tissue was measured. mRNA expressions of pro-inflammatory cytokines in lung were assessed by Real-Time PCR. Histopathological changes were evaluated in lung, ileum and colon. We also investigated FNP on reactive oxygen species (ROS), nitric oxide (NO) and pro-inflammatory cytokines (TNF-α, IL-1β, IL-6 and IL-8) production, inducible nitric oxide synthase (iNOS), Cyclooxygenase-2 (COX-2) protein expression, phosphorylation of MAPKs and AMPK in LPS-stimulated RAW264.7 cells.

Results

FNP increased the levels of T-SOD, T-AOC, GSH-PX and GSH, decreased the levels of TNF-α, MPO and MDA, attenuate the histopathological lesion in LPS-stimulated mice. FNP inhibited production of inflammatory cytokines, ROS and NO, protein expressions of iNOS and COX-2, phosphorylation of ERK, JNK and c-JUN in MAPKs, promoted phosphorylation of AMPKα suppressed by LPS.

Conclusion

These results suggested in vivo anti-inflammatory activities of FNP might contributed to its enhancement in antioxidant capacity, its inhibitory effects may be mediated by inhibiting the phosphorylation of JNK, ERK and c-JUN in MAPKs signaling pathways.

c-Jun N-terminal kinase-mediated anti-inflammatory effects of Garcinia subelliptica in macrophages

Garcinia plants have been traditionally used to treat inflammatory diseases, such as skin infections and pain, in many regions including South‑East Asia. Garcinia subelliptica, a plant of the Garcinia species widely distributed from Japan to Thailand, has been reported to contain components similar to other Garcinia plants that exhibit anti‑inflammatory effects. The present study aimed to explore the anti‑inflammatory effects of ethanol extracts of Garcinia subelliptica (EGS) in macrophages, as there are no previous systemic studies that have investigated the effects of Garcinia subelliptica on inflammation. Non‑cytotoxic concentrations of EGS (≤200 µg/ml) were observed to reduce nitric oxide production by modulating iNOS expression in lipopolysaccharide (LPS)‑stimulated RAW 264.7 macrophages. The expression of cyclooxygenase‑2, the enzyme responsible for the production of prostaglandin E2, was notably reduced by EGS. EGS treatment inhibited the production of pro‑inflammatory cytokines, including IL‑6 and IL‑1β, however, not TNF‑α. Reduced production of inflammatory mediators by EGS was followed by reduced phosphorylation of c‑Jun N‑terminal kinase (JNK) however, not of other mitogen‑activated protein kinases and nuclear factor‑κB. These results indicate that EGS selectively inhibits the excessive production of inflammatory mediators in LPS‑stimulated murine macrophages by reducing the activation of JNK, suggesting that EGS is a candidate for modulating severe inflammation.

Mechanisms Underlying the Anti-Inflammatory Effects of Clinacanthus nutans Lindau Extracts: Inhibition of Cytokine Production and Toll-Like Receptor-4 Activation

Clinacanthus nutans has had a long history of use in folk medicine in Malaysia and Southeast Asia; mostly in the relief of inflammatory conditions. In this study, we investigated the effects of different extracts of C. nutans upon lipopolysaccharide (LPS) induced inflammation in order to identify its mechanism of action. Extracts of leaves and stem bark of C. nutans were prepared using polar and non-polar solvents to produce four extracts, namely polar leaf extract (LP), non-polar leaf extract (LN), polar stem extract (SP), and non-polar stem extracts (SN). The extracts were standardized by determining its total phenolic and total flavonoid contents. Its anti-inflammatory effects were assessed on LPS induced nitrite release in RAW264.7 macrophages and Toll-like receptor (TLR-4) activation in TLR-4 transfected human embryonic kidney cells (HEK-Blue(TM)-hTLR4 cells). The levels of inflammatory cytokines (TNF-α, IFN-γ, IL-1β, IL-6, IL-12p40, and IL-17) in treated RAW264.7 macrophages were quantified to verify its anti-inflammatory effects. Western blotting was used to investigate the effect of the most potent extract (LP) on TLR-4 related inflammatory proteins (p65, p38, ERK, JNK, IRF3) in RAW264.7 macrophages. All four extracts produced a significant, concentration-dependent reduction in LPS-stimulated nitric oxide, LPS-induced TLR-4 activation in HEK-Blue(TM)-hTLR4 cells and LPS-stimulated cytokines production in RAW264.7 macrophages. The most potent extract, LP, also inhibited all LPS-induced TLR-4 inflammatory proteins. These results provide a basis for understanding the mechanisms underlying the previously demonstrated anti-inflammatory activity of C. nutans extracts.

Xanthii fructus inhibits inflammatory responses in LPS-stimulated RAW 264.7 macrophages through suppressing NF-κB and JNK/p38 MAPK

ETHNOPHARMACOLOGICAL RELEVANCE

Xanthii fructus (XF) has long been used to treat a variety of inflammatory conditions in Korean traditional medicine, but the underlying mechanisms that could explain the anti-inflammatory actions of XF remain largely unknown.

AIM OF THE STUDY

This study aimed to elucidate the anti-inflammatory effects of X. fructus (XF) and to examine its underlying molecular mechanisms in lipopolysaccharide (LPS)-stimulated RAW 264.7 macrophages.

MATERIALS AND METHODS

The effect of XF on LPS-induced mRNA and protein expressions of inflammatory mediators and cytokines were determined. Moreover, the activation of the nuclear factor-κB (NF-κB) and mitogen-activated protein kinase (MAPK) signaling pathways and the expression of heme oxygenase-1 (HO-1) were explored to elucidate the anti-inflammatory mechanisms.

RESULTS

XF significantly inhibited LPS-induced production of inflammatory mediators, interleukin-6 (IL-6), nitric oxide (NO), and prostaglandin E2 (PGE2), without any cytotoxicity. However, it did not affect tissue necrosis factor (TNF)-α or IL-1β production in LPS-stimulated RAW 264.7 cells. Expression levels of inducible nitric oxide synthase (iNOS) mRNA and protein were inhibited dose-dependently by XF in LPS-stimulated RAW 264.7 cells, but there were no changes in cyclooxygenase-2 (COX-2) mRNA and protein. XF significantly attenuated LPS-induced phosphorylation and degradation of inhibitory kappa Bα (IκBα) and consequently reduced the nuclear translocation of p65 NF-κB. Pretreatment with XF also strongly inhibited the LPS-induced phosphorylation of p38 kinase and JNK, whereas the phosphorylation of ERK1/2 was not affected. In addition, XF led to an increase in HO-1 expression.

CONCLUSION

Taken together, our findings support that XF inhibits LPS-induced inflammatory responses by blocking NF-κB activation, inhibiting JNK/p38 MAPK phosphorylation, and enhancing HO-1 expression in macrophages, suggesting that it could be an attractive therapeutic candidate for various inflammatory diseases.

Effects of taraxasterol on iNOS and COX-2 expression in LPS-induced RAW 264.7 macrophages

ETHNOPHARMACOLOGICAL RELEVANCE

Taraxasterol was isolated from the Chinese medicinal herb Taraxacum officinale which has been frequently used as a remedy for inflammatory diseases. Our previous study has shown that taraxasterol inhibited lipopolysaccharide (LPS)-induced nitric oxide (NO) and prostaglandin E2 (PGE2) production in RAW 264.7 macrophages. To elucidate the underlying mechanism responsible for these effects, in the present study, we investigated the effects of taraxasterol on inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2) expression, and mitogen-activated protein kinases (MAPKs) signaling pathway in LPS-induced RAW 264.7 macrophages.

MATERIALS AND METHODS

RAW 264.7 cells were pretreated with 2.5, 5 and 12.5 μg/ml of taraxasterol 1 h prior to treatment with 1 μg/ml of LPS. The mRNA expression levels of iNOS and COX-2 were examined by RT-PCR. The protein expression levels of iNOS and COX-2, and the phosphorylation of extracellular signal-regulated kinase 1/2 (ERK1/2), p38 and c-Jun N-terminal kinase (JNK) MAPKs were measured by Western blot.

RESULTS

The mRNA and protein expression levels of iNOS and COX-2 were inhibited by taraxasterol in a concentration-dependent manner. Further studies revealed that taraxasterol suppressed the phosphorylation of ERK1/2 and p38 in LPS-induced RAW 264.7 macrophages.

CONCLUSIONS

These results indicate that taraxasterol inhibits iNOS and COX-2 expression by blocking ERK1/2 and p38 MAPKs signaling pathway.

Anti-inflammatory effect of methanol extract from Erigeron Canadensis L. may be involved with upregulation of heme oxygenase-1 expression and suppression of NFκB and MAPKs activation in macrophages

BACKGROUND/OBJECTIVES

In this study, we determined the anti-inflammatory activities and the underlying molecular mechanisms of the methanol extract from Erigeron Canadensis L. (ECM) in LPS-stimulated RAW264.7 macrophage cells.

MATERIALS/METHODS

The potential anti-inflammatory properties of ECM were investigated by using RAW264.7 macrophages. We used western blot assays and real time quantitative polymerase chain reaction to detect protein and mRNA expression, respectively. Luciferase assays were performed to determine the transactivity of transcription factors.

RESULTS

ECM significantly inhibited inducible nitric oxide synthase (iNOS)-derived NO and cyclooxygenase-2 (COX-2) derived PGE2 production in LPS-stimulated RAW264.7 macrophages. These inhibitory effects of ECM were accompanied by decreases in LPS-induced nuclear translocations and transactivities of NFκB. Moreover, phosphorylation of mitogen-activated protein kinase (MAPKs) including extracellular signal-related kinase (ERK1/2), p38, and c-jun N-terminal kinase (JNK) was significantly suppressed by ECM in LPS-stimulated RAW264.7 macrophages. Further studies demonstrated that ECM by itself induced heme oxygenase-1 (HO-1) protein expression at the protein levels in dose-dependent manner. However, zinc protoporphyrin (ZnPP), a selective HO-1 inhibitor, abolished the ECM-induced suppression of NO production.

CONCLUSIONS

These results suggested that ECM-induced HO-1 expression was partly responsible for the resulting anti-inflammatory effects. These findings suggest that ECM exerts anti-inflammatory actions and help to elucidate the mechanisms underlying the potential therapeutic values of Erigeron Canadensis L.

Lysimachia clethroides Duby extract attenuates inflammatory response in Raw 264.7 macrophages stimulated with lipopolysaccharide and in acute lung injury mouse model

ETHNOPHARMACOLOGICAL RELEVANCE

Lysimachia clethroides Duby (LC) is a traditional medicinal herb used to treat edema, hepatitis and inflammatory diseases in China and other Asian countries. In this study, the anti-inflammatory effects of LC extract and the mechanisms underlying were explored in both in vitro cell lines and acute lung injury (ALI) animal model of inflammation in vivo.

MATERIALS AND METHODS

Lipopolysaccharide (LPS)-stimulated Raw 264.7 murine macrophages were used to study the regulatory effects of LC extract on inflammatory mediators such as nitric oxide (NO) and proinflammatory cytokine expression. Western blotting or ELISA techniques were employed to estimate protein levels. RT-PCR was used for analyzing the interferon (IFN)-β production. LPS-induced ALI mouse model in vivo was employed to study the effect of LC extract. Further high-performance liquid chromatography (HPLC) fingerprinting technique was used to evaluate the active constituents present in LC extract, compared with reference standards.

RESULTS

Pre-treatment with LC extract inhibited the LPS-stimulated NO release, interleukin (IL)-1β and IL-6 production in Raw 264.7 cells dose dependently. LC extract inhibited the LPS-stimulated IRF3 and STAT1 phosphorylation. Further, in vivo experiments revealed that LC extract suppressed the infiltration of immune cells into the lung and proinflammatory cytokine production in broncho-alveolar lavage fluid (BALF) in the LPS-induced ALI mouse model.

CONCLUSIONS

Our results indicate that LC extract attenuates LPS-stimulated inflammatory responses in macrophages via regulating the key inflammatory mechanisms, providing a scientific support for its traditional use in treating various inflammatory diseases.

Genipin induces cyclooxygenase-2 expression via NADPH oxidase, MAPKs, AP-1, and NF-κB in RAW 264.7 cells

Genipin is a compound found in gardenia fruit extract with diverse pharmacological activities. However, the mechanism underlying genipin-induced cyclooxygenase-2 (COX-2) expression remains unknown. In this study, we investigated the effects of genipin on COX-2 expression and determined that exposure to genipin dose-dependently enhanced the production of prostaglandin E2 (PGE2), a major COX-2 metabolite, in RAW 264.7 cells. These effects were mediated by genipin-induced activation of the COX-2 promoter, as well as AP-1 and NF-κB luciferase constructs. Phosphatidylinositol-3-kinase/Akt and MAPKs were also significantly activated by genipin, and Akt and MAPKs inhibitors (PD98059, SB20358, SP600125, and LY294002) inhibited genipin-induced COX-2 expression. Moreover, genipin increased production of the ROS and the ROS-producing NAPDH-oxidase (NOX) family oxidases, NOX2 and NOX3. Inhibition of NADPH with diphenyleneiodonium attenuated ROS production, COX-2 expression and NF-κB and AP-1 activation. These results suggest that the molecular mechanism mediating ROS-dependent COX-2 up-regulation and PGE2 production by genipin involves activation of Akt, MAPKs and AP-1/NF-κB.

Mitogen-activated protein kinases in innate immunity

Following pathogen infection or tissue damage, the stimulation of pattern recognition receptors on the cell surface and in the cytoplasm of innate immune cells activates members of each of the major mitogen-activated protein kinase (MAPK) subfamilies--the extracellular signal-regulated kinase (ERK), p38 and Jun N-terminal kinase (JNK) subfamilies. In conjunction with the activation of nuclear factor-κB and interferon-regulatory factor transcription factors, MAPK activation induces the expression of multiple genes that together regulate the inflammatory response. In this Review, we discuss our current knowledge about the regulation and the function of MAPKs in innate immunity, as well as the importance of negative feedback loops in limiting MAPK activity to prevent host tissue damage. We also examine how pathogens have evolved complex mechanisms to manipulate MAPK activation to increase their virulence. Finally, we consider the potential of the pharmacological targeting of MAPK pathways to treat autoimmune and inflammatory diseases.

Inhibitory effects of sulfated 20(S)-ginsenoside Rh2 on the release of pro-inflammatory mediators in LPS-induced RAW 264.7 cells

Ginsenoside Rh2 is one of the most important ginsenosides in ginseng with anti-inflammatory and antitumor effects. However, the extremely poor oral bioavailability induced by its low water solubility greatly limits the potency of Rh2 in vivo. In the previous study, we sulfated 20(S)-ginsenoside Rh2 with chlorosulfonic acid and pyridine method, and got one novel derivative, Rh2-B1, with higher water solubility and greater immunologic enhancement than Rh2. However, the anti-inflammatory effect of Rh2-B1 remains unclear. We therefore investigated the effects of Rh2-B1 on lipopolysaccharide (LPS)-induced proinflammatory mediators in RAW 264.7 macrophages. We found that Rh2-B1 dramatically inhibited LPS-induced overproduction of nitric oxide, prostaglandin E2, tumor necrosis factor (TNF)-α, interleukin (IL)-1β, and IL-6. Consistently, the protein and mRNA expression levels of inducible nitric oxide synthase and cyclooxygenase-2 were remarkably decreased by Rh2-B1. In addition, Rh2-B1 significantly suppressed the phosphorylations of p38, c-Jun N-terminal kinase, and extracellular signal receptor-activated kinase 1/2 induced by LPS. Rh2-B1 was further shown to inhibit NF-κB p65 translocation into the nucleus by suppressing IκBα degradation. In conclusion, we demonstrate that Rh2-B1 inhibits the release of LPS-induced pro-inflammatory mediators through blocking mitogen-activated protein kinases and NF-κB signaling pathways, suggesting that sulfated ginsenosides could be potential agents for anti-inflammatory therapies.

MSK1 and MSK2 inhibit lipopolysaccharide-induced prostaglandin production via an interleukin-10 feedback loop

Prostaglandin production is catalyzed by cyclooxygenase 2 (cox-2). We demonstrate here that MSK1 and MSK2 (MSK1/2) can exert control on the induction of cox-2 mRNA by Toll-like receptor (TLR) agonists. In the initial phase of cox-2 induction, MSK1/2 knockout macrophages confirmed a role for MSK in the positive regulation of transcription. However, at later time points both lipopolysaccharide (LPS)-induced prostaglandin and cox-2 protein levels were increased in MSK1/2 knockout. Further analysis found that while MSKs promoted cox-2 mRNA transcription, following longer LPS stimulation MSKs also promoted degradation of cox-2 mRNA. This was found to be the result of an interleukin 10 (IL-10) feedback mechanism, with endogenously produced IL-10 promoting cox-2 degradation. The ability of IL-10 to do this was dependent on the mRNA binding protein TTP through a p38/MK2-mediated mechanism. As MSKs regulate IL-10 production in response to LPS, MSK1/2 knockout results in reduced IL-10 secretion and therefore reduced feedback from IL-10 on cox-2 mRNA stability. Following LPS stimulation, this increased mRNA stability correlated to an elevated induction of both of cox-2 protein and prostaglandin secretion in MSK1/2 knockout macrophages relative to that in wild-type cells. This was not restricted to isolated macrophages, as a similar effect of MSK1/2 knockout was seen on plasma prostaglandin E2 (PGE2) levels following intraperitoneal injection of LPS.

Sargaquinoic acid isolated from Sargassum siliquastrum inhibits lipopolysaccharide-induced nitric oxide production in macrophages via modulation of nuclear factor-κB and c-Jun N-terminal kinase pathways

Nitric oxide (NO) is a crucial molecule in inflammatory diseases and is synthesized from L-arginine by a specific enzyme, NO synthase (NOS). The expression of inducible NOS (iNOS) is activated in macrophages by various stimuli, such as lipopolysaccharide (LPS), a wall component of gram-negative bacteria. LPS binds to toll-like receptor 4 (TLR4) on the macrophage surface and activates several downstream signaling pathways, including mitogen-activated protein kinase (MAPK) and nuclear factor (NF)-κB pathways. This study investigated whether sargaquinoic acid isolated from Sargassum siliquastrum might have anti-inflammatory activity and interfere with NO production in macrophages by disrupting LPS-induced signaling. This study was conducted in vitro using RAW264.7 murine macrophages. LPS-stimulated cells were treated with sargaquinoic acid, and the effects on NO production, iNOS expression, and involvement of the NF-κB signaling pathway were investigated by Griess assay, western blotting, and confocal microscopy. The results demonstrated that sargaquinoic acid inhibited the production of NO and the expression of the iNOS protein in LPS-stimulated RAW264.7 macrophages. Moreover, sargaquinoic acid inhibited the degradation of inhibitory-κB protein (IκB)-α and the nuclear translocation of NF-κB, a key transcription factor for the regulation of iNOS expression. Also, sargaquinoic acid influenced the phosphorylation of JNK1/2 MAPK, except ERK1/2 and p38 MAPKs, stimulated by LPS. These results suggest that sargaquinoic acid specifically prevents NO production in macrophages via the blockade of NF-κB activation and may thus have therapeutic applications in various inflammatory diseases.

Ethyl pyruvate induces heme oxygenase-1 through p38 mitogen-activated protein kinase activation by depletion of glutathione in RAW 264.7 cells and improves survival in septic animals

AIMS

We investigated the molecular mechanism by which ethyl pyruvate (EP) induces heme oxygenase-1 (HO-1) in RAW 264.7 cells and its effect on survival rate in cecal ligation and puncture (CLP)-induced wild-type (WT) and HO-1 knockout (HO-1(-/-)) septic mice.

RESULTS

EP induced HO-1 in a dose- and time-dependent manner, which was mediated through p38 mitogen-activated protein kinase (MAPK) and NF-E2-related factor 2 (Nrf2) signaling cascade in RAW 264.7 cells. EP significantly inhibited the lipopolysaccharide (LPS)-stimulated inducible nitric oxide synthase (iNOS) expression and high-mobility group box 1 (HMGB1) release in RAW 264.7 cells. The inhibitory effect of EP on LPS-stimulated iNOS expression and HMGB1 release was reversed by transfection with siHO-1RNA in RAW 264.7 cells, but EP failed to reduce them in HO-1(-/-) peritoneal macrophages treated with LPS. Moreover, treatment of cells with glutathione ethyl ester (GSH-Et), SB203580 (p38 MAPK inhibitor), siHO-1, or p38-siRNA transfection inhibited anti-inflammatory effect of EP. Interestingly, both HO-1 induction and phosphorylation of p38 by EP were reversed by GSH-Et, and antioxidant redox element-luciferase activity by EP was reversed by SB203580 in LPS-activated cells. EP increased survival and decreased serum HMGB1 in CLP-WT mice, whereas it did not increase survival or decrease circulating HMGB1 in HO-1(-/-) CLP-mice.

INNOVATION AND CONCLUSION

Our work provides new insights into the understanding the molecular mechanism by showing that EP induces HO-1 through a p38 MAPK- and NRF2-dependent pathway by decreasing GSH cellular levels. We conclude that EP inhibits proinflammatory response to LPS in macrophages and increases survival in CLP-induced septic mice by upregulation of HO-1 level, in which p38 MAPK and Nrf2 play an important role.

Anti-inflammatory Effect of Perilla frutescens (L.) Britton var. frutescens Extract in LPS-stimulated RAW 264.7 Macrophages

This study was designed to investigate the inhibitory effects of Perilla frutescens (L.) Britton var. frutescens extract on the production of inflammation-related mediators (NO, ROS, NF-κB, iNOS and COX-2) and pro-inflammatory cytokines (TNF-α, IL-1β, IL-6) in lipopolysaccharide-stimulated RAW 264.7 macrophages. Perilla frutescents (L.) Britton var. frutescens was air-dried and extracted with ethanol. The extract dose-dependently decreased the generation of intracellular reactive oxygen species and dose-dependently increased antioxidant enzyme activities, such as superoxide dismutase, catalase and glutathione peroxidase in lipopolysaccharide stimulated RAW 264.7 macrophages. Also, Perilla frutescens (L.) Britton var. frutescens extract suppressed NO production in lipopolysaccharide-stimulated RAW 264.7 cells. The expressions of pro-inflammatory cytokines (TNF-α, IL-1β and IL-6), NF-κB, iNOS and COX-2 were inhibited by the treatment with the extract. Thus, this study shows the Perilla frutescens (L.) Britton var. frutescens extract could be useful for inhibition of the inflammatory process.

The Chloroform Fraction of Solanum nigrum Suppresses Nitric Oxide and Tumor Necrosis Factor-α in LPS-Stimulated Mouse Peritoneal Macrophages Through Inhibition of p38, JNK and ERK1/2

Solanum nigrum L., commonly known as black nightshade, is used worldwide for the treatment of skin and mucosal ulcers, liver cirrhosis and edema. We aimed to determine the anti-inflammatory active fraction of S. nigrum by serial extractions. S. nigrum was first extracted with methanol, then fractionated with chloroform and water. The effects of S. nigrum fractions, diosgenin and α-solanine on LPS/interferon-gamma-induced nitric oxide (NO) and inducible NO synthase (iNOS), or LPS-induced tumor necrosis factor-α (TNF-α) and interleukin (IL)-6, in mouse peritoneal macrophages were determined. Western blotting analysis was used to detect LPS-induced phosphorylation of p38, JNK and ERK1/2. The chloroform fraction of S. nigrum was cytotoxic in a time and concentration dependent manner; however, the methanol and water fractions were not. The chloroform fraction reduced NO through inhibition of iNOS synthesis and inhibited TNF-α and IL-6 at the level of protein secretion; the methanol and water fractions showed a weak or no effect. The chloroform fraction also suppressed p38, JNK and ERK1/2. Diosgenin and α-solanine were cytotoxic at a high concentration. In particular, diosgenin was able to inhibit TNF-α and IL-6, but both compounds did not affect LPS-induced iNOS expression. These results indicate that the anti-inflammatory compounds of S. nigrum exist preferentially in the nonpolar fraction, ruling out the possibility that diosgenin and α-solanine are the likely candidates. The inhibition of iNOS, TNF-α and IL-6 by the chloroform fraction may be partly due to the suppression of p38, JNK and ERK1/2. Further study is required to identify the active compounds of S. nigrum.

Anti-inflammatory and anti-allergic effects of Agrimonia pilosa Ledeb extract on murine cell lines and OVA-induced airway inflammation

ETHNOPHARMACOLOGICAL EVIDENCE

Agrimonia pilosa Ledeb (Rosaceae, AP) has long been used as a traditional medicine in Korea and other Asian countries to treat various diseases.

AIM OF THE STUDY

In the present study, the anti-inflammatory and anti-allergic effects of AP extract in in vitro cell lines and in vivo mouse model of inflammation and the molecular mechanisms involved were reported.

MATERIALS AND METHODS

Using Raw 264.7 murine macrophages the effects of methanol extract of AP in lipopolysaccharide (LPS)-induced production of inflammatory mediators were measured. Further IgE-DNP-induced interleukin (IL)-4 production and degranulation in RBL-2H3 rat basophilic cell lines was also estimated. To investigate the anti-asthmatic effect of AP in vivo, airway inflammation in ovalbumin (OVA)-induced mouse model was used.

RESULTS

AP attenuated the production of inflammatory mediators such as NO, PGE(2) and pro-inflammatory cytokines in LPS-induced Raw 264.7 cells. Further, AP inhibited IL-4 production and degranulation in IgE-DNP-induced RBL-2H3 cells. Furthermore, AP attenuated the infiltration of immune cells into lung, cytokines production in broncho-alveolar lavage fluid (BALF) and airway-hyperresponsiveness (AHR) on OVA-induced mouse model of inflammation.

CONCLUSION

Our results showed that AP attenuated the activation of macrophages, basophils, and inhibited the OVA-induced airway inflammation. The molecular mechanisms leading to AP's potent anti-inflammatory and anti-allergic effects might be through regulation of TRIF-dependent and Syk-PLCγ/AKT signaling pathways, suggesting that AP may provide a valuable therapeutic strategy in treating various inflammatory diseases including asthma.

Hericium erinaceus suppresses LPS-induced pro-inflammation gene activation in RAW264.7 macrophages

The aim of this study was to investigate the anti-inflammatory properties of each fraction of Hericium erinaceus (HE). The ethanol extract from HE was partitioned with different solvents in the order of increasing polarity. The treatment with 10-100 μg/mL of each fraction did not reduce RAW 264.7 cell viability except ethyl acetate fraction. Among the various extracts, the chloroform fraction showed the most potent activity against nitric oxide (NO), prostaglandin E(2) (PGE(2)) and reactive oxygen species (ROS). The western blotting and reverse transcriptase polymerase chain reaction (RT-PCR) analyses revealed that chloroform fraction from HE (CHE) significantly reduced the protein level of iNOS and cyclooxygenase-2 (COX-2) or mRNA levels of iNOS in lipopolysaccharide-induced macrophages. Furthermore, CHE inhibited the translocation of nuclear factor (NF)-κB p65 subunit, phsophorylation of I-κB, extracellular signal-regulated kinase (ERK), and c-Jun N-terminal kinase (JNK) in a dose-dependent manner. Furthermore, the activation of both activator protein-1 (AP-1) and NF κB in the nucleus were abrogated by CHE with luciferase assay. In conclusion, these results indicate that CHE may provide an anti-inflammatory effect by attenuating the generation of excessive NO, PGE(2), and ROS and by suppressing the expression of pro-inflammatory genes through the inhibition of NF-κB and JNK activity.

Anti-inflammatory effects of glyceollins derived from soybean by elicitation with Aspergillus sojae

OBJECTIVE

Given the preventive effect of soy intake against several chronic diseases, this study was conducted to investigate the inhibitory activity against inflammatory response of phytoalexins glyceollins derived from soybean isoflavones by treatment with a biotic elicitor.

METHODS

Using RAW264.7 cells, we examined the effects of glyceollins on production of nitric oxide (NO) and inflammatory cytokines, expression of inducible nitric oxide synthase (iNOS) and cyclo-oxygenase (COX)-2, and activation of NF-кB, induced by lipopolysaccharide (LPS).

RESULTS

Our data showed that glyceollins effectively inhibited NO production, IL-6 release, and expression of iNOS and COX-2 induced by LPS. In particular, glyceollins suppressed the LPS-induced phosphorylation of NF-кB p65, suggesting that the compounds inhibit the production of NO and transcriptional activation of COX-2 by regulating NF-кB activity. In another experiment we found that glyceollins enhanced the expression of heme oxygenase 1 in LPS-treated RAW264.7 cells. Glyceollins also reduced TPA-induced skin inflammation in a mouse model, confirming the anti-inflammatory activity of glyceollins in an in-vivo system as well as in a cell culture system.

CONCLUSION

Glyceollins exert an anti-inflammatory effect, which is mediated through the inhibition of NF-κB activation in LPS-activated murine RAW264.7 cells. Glyceollins merit further study as potential therapeutic agents for inflammatory disorders.

Lipopolysaccharide induced protection against sulfur mustard cytotoxicity in RAW264.7 cells through generation of TNF-alpha

Sulfur mustard (HD), a very potent alkylating agent and lipopolysacchride (LPS), are both well characterized inflammatory factors. We have found that concomitant exposure of murine macrophage cells (RAW264.7) to LPS and HD induced protection against HD induced cytotoxicity. Both HD and LPS induce release of inflammatory markers in RAW264.7 cells. However, there are marked differences in the repertoire of inflammatory factors released by the two toxins: While exposure to HD, induced a dose-dependant death of these cells, no significant change in survival rate was observed following LPS (1-100 ng/ml) exposure. Additionally, LPS elicited a robust nitric oxide (NO) and TNF-alpha secretion whereas HD was practically ineffective. Both toxins increased PGE(2) secretion in a concentration dependent manner. Treatment of HD-exposed RAW264.7 cells with anti-inflammatory drugs such as dexamethazone (5 muM), voltaren (diclofenac) (8 muM) or doxycycline (5 muM), decreased the release of cytokines but had no effect on cell viability. Simultaneous application of LPS (100 ng/ml) and HD (20-100 muM) resulted in an amelioration of HD cytotoxicity. Adding the NO generator S-nitrosoglutathione (GSNO) or inhibiting NO production using L-N(G)-monomethyl Arginine, had no effect on cell viability. Moreover, addition of PGE(2) (20 ng/ml) failed to induce any changes in cell viability under basal or HD-induced toxicity. In contrast, TNF-alpha (20 ng/ml) provided remarkable protection against HD-induced cell death. These findings strongly suggest that LPS exerts its protective action against HD toxicity through the generation of TNF-alpha and may provide better understanding of the mechanism of cytoprotection.

Quaternary alkaloid, pseudocoptisine isolated from tubers of Corydalis turtschaninovi inhibits LPS-induced nitric oxide, PGE(2), and pro-inflammatory cytokines production via the down-regulation of NF-kappaB in RAW 264.7 murine macrophage cells

It is well known that pro-inflammatory mediators like nitric oxide (NO), prostaglandin E(2) (PGE(2)), tumor necrosis factor-alpha (TNF-alpha), and interleukin-6 (IL-6) contribute to the courses of many inflammatory diseases. In the present study, the authors investigated the anti-inflammatory effects of pseudocoptisine, a quaternary alkaloid with a benzylisoquinoline skeleton, which was isolated from the tubers of Corydalis turtschaninovii by examining its inhibitory effects on pro-inflammatory mediators in lipopolysaccharide (LPS)-stimulated murine macrophage RAW 264.7 cells. Pseudocoptisine caused dose-dependent reductions in the levels of inducible nitric oxide (iNOS) and cyclooxygenase-2 (COX-2) at both protein and mRNA levels and concomitant decreases in PGE(2) and NO production. In addition, it was found that pseudocoptisine suppressed the production and mRNA expressions of inflammatory cytokines, such as, TNF-alpha and IL-6. Furthermore, molecular data revealed that pseudocoptisine inhibited the LPS-stimulated DNA binding activity and the transcription activity of nuclear factor-kappa B (NF-kappaB). Moreover, this effect was accompanied by decreases in the phosphorylation of inhibitory kappaB (IkappaB)-alpha and in the subsequent blocking of p65 subunit of NF-kappaB translocation to the nucleus. In addition, pseudocoptisine dose-dependently inhibited the phosphorylations of ERK and p38. Taken together, these results suggest that pseudocoptisine reduces levels of the pro-inflammatory mediators, such as, iNOS, COX-2, TNF-alpha, and IL-6 through the inhibition of NF-kappaB activation via the suppression of ERK and p38 phosphorylation in RAW 264.7 cells. These findings reveal in part the molecular basis for the anti-inflammatory properties of pseudocoptisine.

Chrysanthemum indicum Linné extract inhibits the inflammatory response by suppressing NF-kappaB and MAPKs activation in lipopolysaccharide-induced RAW 264.7 macrophages

AIMS OF STUDY

Although the flowers of Chrysanthemum indicum Linné (Asteraceae) have long been used in traditional Korean and Chinese medicine to treat inflammatory diseases, the underlying mechanism(s) by which these effects are induced remains to be defined. We investigated the effects of a 70% ethanolic extract of C. indicum (CIE) on the activities of cellular signaling molecules that mediate inflammatory responses.

MATERIALS AND METHODS

Production of NO, PGE(2), TNF-alpha, and IL-1beta by ELISA, mRNA and protein expression of iNOS and COX-2, phosphorylation of MAPKs, and activation of NF-kappaB by RT-PCR and Western blotting were examined in LPS-induced RAW 264.7 macrophages.

RESULTS

The CIE strongly inhibited NO, PGE(2), TNF-alpha, and IL-1beta production, and also significantly inhibited mRNA and protein expression of iNOS and COX-2 in LPS-induced RAW 264.7 macrophages, in a dose-dependent manner. Furthermore, the CIE clearly suppressed nuclear translocation of NF-kappaB p65 subunits, which correlated with an inhibitory effect on IkappaBalpha phosphorylation. The CIE also attenuated the activation of ERK1/2 and JNK in a dose-dependent manner.

CONCLUSION

Our results suggest that the anti-inflammatory properties of CIE might result from the inhibition of inflammatory mediators, such as NO, PGE(2), TNF-alpha, and IL-1beta, via suppression of MAPKs and NF-kappaB-dependent pathways.

Inhibitory effects of ivermectin on nitric oxide and prostaglandin E2 production in LPS-stimulated RAW 264.7 macrophages

We have previously shown that ivermectin inhibits LPS-induced production of inflammatory cytokines. In the present study, we investigated the effect of ivermectin on lipopolysaccharide (LPS)-induced nitric oxide (NO) and prostaglandin E(2) (PGE(2)) production in RAW 264.7 macrophages. Ivermectin inhibited LPS-induced NO and PGE(2) production. Consistent with these observations, the protein and mRNA expression levels of inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2) enzymes were inhibited by ivermectin in a concentration-dependent manner. Furthermore, the phosphorylation of p38, ERK1/2, and JNK in LPS-stimulated RAW 264.7 cells was suppressed by ivermectin in a dose-dependent manner. These results suggest that ivermectin suppresses NO and PGE(2) production, as well as iNOS and COX-2 expression, by inhibiting phosphorylation of mitogen-activated protein kinases (MAPK) (p38, ERK1/2, and JNK) in LPS-stimulated RAW 264.7 cells.

Risk assessment of tetrabromobisphenol A on cyclooxygenase-2 expression via MAP kinase/NF-kappaB/AP-1 signaling pathways in murine macrophages

Tetrabromobisphenol A [2,2-bis-(3,5-dibromo-4-hydroxyphenyl)propane; TBBPA] is used worldwide as a flame retardant in numerous products. In the present study, the effects of TBBPA were examined on the expression of cyclooxygenase-2 (COX-2), inflammation-related cytokines, transcription factors, and signaling pathways responsible for transcriptional activation of the COX-2 gene in murine RAW 264.7 macrophages. Exposure to TBBPA markedly enhanced the production of prostaglandin E(2), a major COX-2 metabolite, in macrophages. TBBPA concentration-dependently increased the levels of COX-2 protein and mRNA. In addition, TBBPA increased the secretion and mRNA levels of proinflammatory cytokines such as tumor necrosis factor (TNF)-alpha, interleukin (IL)-6, and IL-1beta. Transfection of a human COX-2 promoter construct demonstrated that TBBPA induced COX-2 promoter activity. Furthermore, transfection with pNF-kappaB-Luc and pAP-1-Luc plasmid revealed that TBBPA activated the NF-kappaB and AP-1 sites. Phosphatidylinositol 3 (PI3) kinase, its downstream signaling molecule, Akt, and mitogen-activated protein kinases (MAPK) were also significantly activated by TBBPA. Our data demonstrate TBBPA-induced COX-2 and proinflammatory cytokine expression occurs through the PI3-kinase/Akt/MAP kinase/NF-kappaB/AP-1 pathways.

Quantitative proteomics analysis of macrophage rafts reveals compartmentalized activation of the proteasome and of proteasome-mediated ERK activation in response to lipopolysaccharide

Lipopolysaccharide (LPS), a glycolipid component of the outer membrane of Gram-negative bacteria, is a potent initiator of the innate immune response of the macrophage. LPS triggers downstream signaling by selectively recruiting and activating proteins in cholesterol-rich membrane microdomains called lipid rafts. We applied proteomics analysis to macrophage detergent-resistant membranes (DRMs) during an LPS exposure time course in an effort to identify and validate novel events occurring in macrophage rafts. Following metabolic incorporation in cell culture of heavy isotopes of amino acids arginine and lysine ([(13)C(6)]Arg and [(13)C(6)]Lys) or their light counterparts, a SILAC (stable isotope labeling with amino acids in cell culture)-based quantitative, liquid chromatography-tandem mass spectrometry proteomics approach was used to profile LPS-induced changes in the lipid raft proteome of RAW 264.7 macrophages. Unsupervised network analysis of the proteomics data set revealed a marked representation of the ubiquitin-proteasome system as well as changes in proteasome subunit composition following LPS challenge. Functional analysis of DRMs confirmed that LPS causes selective activation of the proteasome in macrophage rafts and proteasome inactivation outside of rafts. Given previous reports of an essential role for proteasomal degradation of IkappaB kinase-phosphorylated p105 in LPS activation of ERK mitogen-activated protein kinase, we tested for a role of rafts in compartmentalization of these events. Immunoblotting of DRMs revealed proteasome-dependent activation of MEK and ERK specifically occurring in lipid rafts as well as proteasomal activity upon raft-localized p105 that was enhanced by LPS. Cholesterol extraction from the intact macrophage with methyl-beta-cyclodextrin was sufficient to activate ERK, recapitulating the LPS-IkappaB kinase-p105-MEK-ERK cascade, whereas both it and the alternate raft-disrupting agent nystatin blocked subsequent LPS activation of the ERK cascade. Taken together, our findings indicate a critical, selective role for raft compartmentalization and regulation of proteasome activity in activation of the MEK-ERK pathway.

Miyabenol A inhibits LPS-induced NO production via IKK/IkappaB inactivation in RAW 264.7 macrophages: possible involvement of the p38 and PI3K pathways

The anti-inflammatory effect of miyabenol A, a stilbene isolated from Vitis thunbergii, on lipopolysaccaride (LPS)-induced nitric oxide (NO) production in RAW264.7 macrophages was studied. Miyabenol A inhibited NO production (EC 50: 2.7 muM) and iNOS protein and mRNA expression in a parallel concentration-dependent manner. LPS-evoked NF-kappaB nuclear translocation and associated IkappaB degradation were abrogated by miyabenol A treatment. Phosphorylations of IKKalpha/beta, ERK1/2, JNK p38 MAPK, and Akt were observed in LPS-stimulated cells; nevertheless, miyabenol A selectively blocked IKKalpha/beta, p38, and Akt phosphorylation. Furthermore, LPS-stimulated IKKalpha/beta and Akt phosphorylation was abolished by p38 inhibitor SB203580. Wortmannin (a PI3K inhibitor) also attenuated LPS-induced IKKalpha/beta phosphorylation, although to a less extent than SB203580, but failed to affect p38 phosphorylation. These observations suggested that PI3K/Akt might lie downstream of p38 MAPK to coregulate LPS-induced IKKalpha/beta phosphorylation. Taken together, miyabenol A acted via interfering with p38 MAPK-related signal pathways to down-regulate IKK/IkappaB activation and NO production.

Intracellular signaling in primary sensory neurons and persistent pain

During evolution, living organisms develop a specialized apparatus called nociceptors to sense their environment and avoid hazardous situations. Intense stimulation of high threshold C- and Adelta-fibers of nociceptive primary sensory neurons will elicit pain, which is acute and protective under normal conditions. A further evolution of the early pain system results in the development of nociceptor sensitization under injury or disease conditions, leading to enhanced pain states. This sensitization in the peripheral nervous system is also called peripheral sensitization, as compared to its counterpart, central sensitization. Inflammatory mediators such as proinflammatory cytokines (TNF-alpha, IL-1beta), PGE(2), bradykinin, and NGF increase the sensitivity and excitability of nociceptors by enhancing the activity of pronociceptive receptors and ion channels (e.g., TRPV1 and Na(v)1.8). We will review the evidence demonstrating that activation of multiple intracellular signal pathways such as MAPK pathways in primary sensory neurons results in the induction and maintenance of peripheral sensitization and produces persistent pain. Targeting the critical signaling pathways in the periphery will tackle pain at the source.

Phellinus linteus inhibits inflammatory mediators by suppressing redox-based NF-kappaB and MAPKs activation in lipopolysaccharide-induced RAW 264.7 macrophage

The mushroom Phellinus linteus has been known to exhibit potent biological activity. In contrast to the immuno-potentiating properties of Phellinus linteus, the anti-inflammatory properties of Phellinus linteus have rarely been investigated. Recently, ethanol extract and n-BuOH fractions from Phellinus linteus were deemed most effective in anti-inflammatory activity in RAW 264.7 macrophages. The regulatory mechanisms of Phellinus linteus butanol fractions (PLBF) on the pharmacological and biochemical actions of macrophages involved in inflammation have not been clearly defined yet. In the present study, we tested the role of PLBF on anti-inflammation patterns in lipopolysaccharide (LPS)-stimulated RAW 264.7 macrophage cells. To investigate the mechanism by which PLBF inhibits NO and PGE2 production as well as inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2) expression, we examined the activation of IkappaB and MAPKs in LPS-activated macrophages. PLBF clearly inhibited nuclear translocation of NF-kappaB p65 subunits, which correlated with PLBF's inhibitory effects on IkappaBalpha phosphorylation and degradation. PLBF also suppressed the activation of mitogen-activated protein (MAP) kinases including p38 and stress-activated protein kinase/c-Jun NH2-terminal kinase (SAPK/JNK). Furthermore, macrophages stimulated with LPS generated ROS via activation of membrane-bound NADPH oxidase, and ROS played an important role in the activation of nuclear factor-kappaB (NF-kappaB) and MAPKs. We demonstrated that PLBF directly blocked intracellular accumulation of reactive oxygen species in RAW 264.7 cells stimulated with LPS much as the NADPH oxidase inhibitors, diphenylene iodonium, and antioxidant pyrrolidine dithiocarbamate did. The suppression of NADPH oxidase also inhibited NO production and iNOS protein expression. Cumulatively, these results suggest that PLBF inhibits the production of NO and PGE2 through the down-regulation of iNOS and COX-2 gene expression via ROS-based NF-kappaB and MAPKs activation. Thus, PLBF may provide a potential therapeutic approach for inflammation-associated disorders.

Modulation of LPS stimulated NF-kappaB mediated Nitric Oxide production by PKCepsilon and JAK2 in RAW macrophages

BACKGROUND

Nuclear factor kappa B (NF-kappaB) has been shown to play an important role in regulating the expression of many genes involved in cell survival, immunity and in the inflammatory processes. NF-kappaB activation upregulates inducible nitric oxide synthase leading to enhanced nitric oxide production during an inflammatory response. NF-kappaB activation is regulated by distinct kinase pathways independent of inhibitor of kappaB kinase (IKK). Here, we examine the role of protein kinase C isoforms and janus activated kinase 2 (JAK2) activation in NF-kappaB activation and LPS-stimulated NO production.

METHODS

Murine RAW 264.7 macrophages were treated with lipopolysaccharide (LPS), Phorbol 12-myristate 13-acetate (PMA) and a combination of LPS and PMA in the presence or absence of various inhibitors of PKC isoforms and JAK2. Nuclear translocation of the NF-kappaB p65 subunit, was assessed by Western blot analysis whilst NO levels were assessed by Greiss assay.

RESULTS

LPS-stimulated NO production was attenuated by PMA whilst PMA alone did not affect NO release. These effects were associated with changes in p65 nuclear translocation. The PKCalpha, beta, gamma, delta and zeta inhibitor Gö 6983 (Go) had no effect on LPS-induced NO release. In contrast, Bisindolymalemide I (Bis), a PKC alpha, betaI, betaII, gamma, delta and epsilon isoform inhibitors completely inhibited LPS-stimulated NO production without affecting p65 nuclear translocation. Furthermore, a partial inhibitory effect on LPS-induced NO release was seen with the JAK2 inhibitor AG-490 and the p38 MAPK inhibitor SB 203850.

CONCLUSION

The results further define the role of NF-kappaB in LPS stimulated NO production in RAW macrophages. The data support a function for PKCepsilon, JAK2 and p38 MAPK in NF-kappaB activation following p65 nuclear import.