Saucerneol F, a new lignan, inhibits iNOS expression via MAPKs, NF-κB and AP-1 inactivation in LPS-induced RAW264.7 cells

Saucerneol F (SF), a new tetrahydrofuran-type sesquilignan isolated from Saururus chinensis, dose-dependently inhibited nitric oxide (NO) production, with concomitant reduction of inducible nitric oxide synthase (iNOS) protein and mRNA expression in lipopolysaccharide (LPS)-stimulated murine macrophage RAW264.7 cells. To elucidate the molecular mechanism underlying the inhibition of iNOS expression by SF, we assessed the effects of SF on nuclear factor-κB (NF-κB) DNA-binding activity, NF-κB-dependent reporter gene activity, inhibitory factor-κB (IκB) phosphorylation and degradation, and p65 nuclear translocation. Treatment with SF decreased the luciferase activities of NF-κB reporter promoters in a dose-dependent manner and translocation of NF-κB p65. In addition, pretreatment of SF reduced LPS-stimulated activation of mitogen-activated protein kinases (MAPKs) including extracellular signal-regulated kinase 1/2 (ERK1/2), p38 MAPK, and c-Jun NH(2)-terminal kinase (JNK). Furthermore, SF attenuated the luciferase activities of AP-1 reporter promoters and the DNA-binding capacity of AP-1. Taken together, the present results indicate that SF attenuates NO production and iNOS expression by blocking LPS-induced activation of NF-κB, MAPKs, and AP-1, suggesting that SF is potentially applicable as an anti-inflammatory drug.     

Differential effects of LY294002 and wortmannin on inducible nitric oxide synthase expression in glomerular mesangial cells

Nitric oxide (NO) that is produced by inducible nitric oxide synthase (iNOS) is associated with the pathophysiology of glomerulonephritis. Numerous studies have focused on the regulation of NO production by iNOS to reduce NO-mediated cytotoxicity. In the present study, we demonstrated the differential effects of two phosphatidylinositol 3-kinase (PI3K) inhibitors, LY294002 and wortmannin, on lipopolysaccharide- (LPS) and interferon (IFN)-γ-induced NO production in a glomerular mesangial cell line, MES-13 cells. At dosages without affecting cell viability of MES-13 cells, 5μM LY294002 showed a more-significant inhibitory effect on LPS/IFN-γ-induced NO production, and iNOS protein and gene expressions than did 1μM wortmannin. Akt phosphorylation in MES-13 cells declined upon the addition of wortmannin, but not upon treatment with LY294002. Suppression of PI3K expression by small interfering (si)RNA exhibited no effect on LPS/IFN-γ-stimulated NO production or iNOS protein expression in MES-13 cells. Neither LY294002 nor wortmannin reduced IFN-γ-induced STAT-1α phosphorylation. LY294002 exhibited a more-significant inhibitory effect on NF-κB luciferase activities than wortmannin in LPS/IFN-γ-stimulated MES-13 cells. Moreover, LY294002, but not wortmannin, accelerated iNOS protein degradation and reduced the iNOS dimer/monomer ratio in MES-13 cells. Although both LY294002 and wortmannin are known as PI3K inhibitors, their differential effects on iNOS expression in MES-13 cells indicate that the effects of LY294002 on inhibiting NF-κB activation and accelerating iNOS protein degradation are through a mechanism independent of PI3K.     

Lectin purified from Musca domestica pupa up-regulates NO and iNOS production via TLR4/NF-κB signaling pathway in macrophages

The present study reported that nitric oxide (NO) was up-regulated by the induction of lectin purified from Musca domestica pupa (MPL) in macrophages without cytotoxicity. The mRNA expression and protein secretion of inducible nitric oxide synthase (iNOS) were strongly induced by MPL treatments. Subsequent investigation revealed that the nuclear factor-κB (NF-κB) inhibitory κB (IκB) in endochylema was inhibited and NF-κB translocated into the nucleus after MPL treatment. Meanwhile, the IKKβ was strongly induced and the production of the toll-like receptor 4 (TLR4) was significantly up-regulated. Moreover, MPL increased NO production via inducing the expression of iNOS through the activation of NF-κB, which suggested that MPL probably acted as an activating agent of the NF-κB activation.     

Inhibition of lipopolysaccharide-induced expression of inducible nitric oxide synthase by phenolic (3E)-4-(2-hydroxyphenyl)but-3-en-2-one in RAW 264.7 macrophages

The large amount of nitric oxide (NO) produced by inducible NO synthase (iNOS) contributes to cellular injury in inflammatory disease. In the present study, a novel synthetic compound (3E)-4-(2-hydroxyphenyl)but-3-en-2-one (HPB) was found to inhibit lipopolysaccharide (LPS)-induced NO generation, but not through the inhibition of iNOS activity, in RAW 264.7 macrophages. Administration of HPB into mice also inhibited the LPS-induced increase in serum nitrite/nitrate levels. To evaluate the underlying mechanisms of HPB inhibition of NO generation, the expression of the iNOS gene in RAW 264.7 macrophages was examined. HPB abolished the LPS-induced expression of iNOS protein, iNOS mRNA and iNOS promoter activity in a similar concentration-dependent manner. LPS-induced nuclear factor-κB (NF-κB) DNA binding and NF-κB-dependent reporter gene activity were both significantly inhibited by HPB. This effect was mediated through the inhibition of inhibitory factor-κBα (IκBα) phosphorylation and degradation, and of p65 nuclear translocation. HPB had no effect on the LPS-induced phosphorylation of extracellular signal-regulated kinase (ERK), p38 mitogen-activated protein kinases (MAPK), and c-Jun NH₂-terminal kinase (JNK). However, HPB suppressed the LPS-induced intracellular reactive oxygen species (ROS) production. These results indicate that HPB down-regulates iNOS gene expression probably through the inhibition of LPS-induced intracellular ROS production, which has been implicated in the activation of NF-κB.     

3‑Bromo‑5‑(ethoxymethyl)‑1,2‑benzenediol inhibits LPS-induced pro-inflammatory responses by preventing ROS production and downregulating NF-κB in vitro and in a zebrafish model

The anti-inflammatory effects of 3‑bromo‑5‑(ethoxymethyl)‑1,2‑benzenediol (BEMB) from Polysiphonia morrowii were evaluated in lipopolysaccharide (LPS)-induced RAW264.7 cells and zebrafish embryo. BEMB showed anti-inflammatory effects by inhibiting the production of nitric oxide (NO) and reactive oxygen species (ROS), and the expression of inducible NO synthase (iNOS) and cyclooxygenase-2 (COX-2) in the LPS-activated RAW264.7 cells and zebrafish embryo without cytotoxicity. Moreover, BEMB suppressed the protein and mRNA expression levels of nuclear factor (NF)-κB (p65 and inhibitor of NF-κB [IκB]-A) in RAW264.7 cells and zebrafish embryo, respectively. Collectively, the results of this study indicate that BEMB suppressed the production of pro-inflammatory mediators such as NO, iNOS, and COX-2 as well as their regulation in LPS-induced RAW264.7 cells and zebrafish embryos by inhibiting ROS production and NF-κB expression. Therefore, this study suggests that BEMB could be a potential anti-inflammatory agent for the treatment of inflammatory diseases.     

Psoralidin inhibits LPS-induced iNOS expression via repressing Syk-mediated activation of PI3K-IKK-IκB signaling pathways

Psoralidin has been reported to inhibit lipopolysaccharide (LPS)-induced nitric oxide (NO) production, but the mechanisms of the action remain unclear. Thus, the impact of psoralidin on signaling pathways known to be implicated in NO synthesis was explored in LPS-activated RAW264.7 macrophages by using RT-PCR and Western blotting. Consistent with NO inhibition, psoralidin suppressed LPS-induced expression of inducible NO synthase (iNOS) by abolishing IκB kinase (IKK) phosphorylation, IκB degradation and nuclear factor κB (NF-κB) nuclear translocation without effecting mitogen-activated protein kinases (MAPKs) phosphorylation. Exposure to wortmannin abrogated IKK/IκB/NF-κB-mediated iNOS expression, suggesting activation of such a signal pathway might also be phosphoinositide-3-kinase (PI3K) dependent. By using Src inhibitor PP2, Janus kinase 2 (JAK-2) inhibitor AG490, Bruton's tyrosine kinase (Btk) inhibitor LFM-A13 and spleen tyrosine kinase (Syk) inhibitor piceatannol, the results showed that piceatannol clearly repressed NO production more potently than the other inhibitors. Furthermore, piceatannol significantly repressed LPS-induced PI3K/Akt phosphorylation and the downstream IKK/IκB activation, suggesting that Syk is an upstream key regulator in the activation of PI3K/Akt-mediated signaling. In fact, transfection with siRNA targeting Syk obviously reduced iNOS expression. Interestingly, LPS-induced phosphorylations of Syk and PI3K-p85 were both significantly blunted by psoralidin treatment. The present results show that interfering with Syk-mediated PI3K phosphorylation might contribute to the NO inhibitory effect of psoralidin via blocking IKK/IκB signaling propagation in LPS-stimulated RAW 264.7 macrophages.     

Ampelopsin reduces endotoxic inflammation via repressing ROS-mediated activation of PI3K/Akt/NF-κB signaling pathways

Ampelopsin (AMP), a plant flavonoid, has potent anti-inflammatory properties in vitro and in vivo. The molecular mechanisms of ampelopsin on pharmacological and biochemical actions of RAW264.7 macrophages in inflammation have not been clearly elucidated yet. In the present study, non-cytotoxic level of ampelopsin significantly inhibited the release of nitric oxide (NO) and pro-inflammatory cytokines such as interleukin (IL)-1β, IL-6 and tumor necrosis factor (TNF)-α in a dose-dependent manner. Consistent with NO inhibition, ampelopsin suppressed lipopolysaccharide (LPS)-induced expression of inducible NO synthase (iNOS) by inhibiting nuclear factor κB (NF-κB) activation, which highly correlated with its inhibitory effect on IκB kinase (IKK) phosphorylation, IκB phosphorylation and NF-κB nuclear translocation. Further study demonstrated that ampelopsin suppressed LPS-induced activation of Akt without effecting mitogen-activated protein kinases (MAPKs) phosphorylation. A pharmacological inhibitor of the phosphoinositide 3-kinase (PI3K)-Akt pathway, LY294002, abrogated IKK/IκB/NF-κB-mediated iNOS gene expression. Finally, we certificated that ampelopsin reduced reactive oxygen species (ROS) accumulation and an anti-oxidant N-acetyl-L-cysteine (NAC) significantly repressed LPS-induced PI3K/Akt phosphorylation and the downstream IKK/IκB activation. NAC thereby inhibited LPS-induced iNOS expression and NO production. The present results suggest that the anti-inflammatory effect of ampelopsin is due to inhibiting the interconnected ROS/Akt/IKK/NF-κB signaling pathways.     

Hydrangenol inhibits lipopolysaccharide-induced nitric oxide production in BV2 microglial cells by suppressing the NF-κB pathway and activating the Nrf2-mediated HO-1 pathway

We previously demonstrated the anti-inflammatory effect of water extract of Hydrangea macrophylla in lipopolysaccharide (LPS)-stimulated macrophage cells. Here, we investigated whether hydrangenol, a bioactive component of H. macrophylla, attenuates the expression of nitric oxide (NO) and its associated gene, inducible NO synthase (iNOS), in LPS-stimulated BV2 microglial cells. Our data showed that low dosages of hydrangenol inhibited LPS-stimulated NO release and iNOS expression without any accompanying cytotoxicity. Hydrangenol also suppressed LPS-induced nuclear translocation of nuclear factor-κB (NF-κB) subunits, consequently inhibiting DNA-binding activity of NF-κB. Additionally, the NF-κB inhibitors, pyrrolidine dithiocarbamate (PDTC) and PS-1145, significantly attenuated LPS-induced iNOS expression, indicating that hydrangenol-induced NF-κB inhibition might be a key regulator of iNOS expression. Furthermore, our data showed that hydrangenol suppresses NO production by inducing heme oxygenase-1 (HO-1). The presence of cobalt protoporphyrin, a specific HO-1 inducer, potently suppressed LPS-induced NO production. Hydrangenol also promoted nuclear translocation of nuclear factor erythroid 2-related factor 2 (Nrf2) and subsequently increased its binding activity at the specific antioxidant response element sites. Additionally, transient knockdown of Nrf2 significantly downregulated hydrangenol-induced HO-1 expression, indicating that hydrangenol-induced Nrf2 is an upstream regulator of HO-1. Taken together, these data suggest that hydrangenol attenuates NO production and iNOS expression in LPS-stimulated BV2 microglial cells by inhibiting NF-κB activation and by stimulating the Nrf2-mediated HO-1 signaling pathway. Therefore, hydrangenol is a promising therapeutic agent for treatment of LPS-mediated inflammatory diseases.     

Ampelopsin attenuates lipopolysaccharide-induced inflammatory response through the inhibition of the NF-κB and JAK2/STAT3 signaling pathways in microglia

Increasing evidence suggests that microglia are a major cellular contributor to neuroinflammation. The present study investigated whether Ampelopsin (Amp), a type of flavanonol derivative from Ampelopsis grossedentata, may exert an anti-inflammatory effect on lipopolysaccharide (LPS)-induced BV2 and primary microglia cells. We found that pre-treatment of microglia cells with Amp before LPS with a non-cytotoxic concentration range decreased the production of nitric oxide (NO) and prostaglandin E2 (PGE2). Amp also suppressed the expression of inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2) at the mRNA and protein levels. In addition, LPS-induced production of pro-inflammatory cytokines such as interleukin (IL)-1β, IL-6, and tumor necrosis factor-α (TNF-α) was obviously reduced by Amp. Our mechanistic study indicated that Amp suppressed LPS-induced activation of the IκB/NF-κB inflammation pathway without affecting changes in the phosphorylation levels of mitogen-activated protein kinases (MAPKs) in BV2 cells. Further studies revealed that Amp markedly reduced the phosphorylation levels of JAK2-STAT3 and STAT3 nuclear translocation. Overall, our data suggest that Amp can suppress the LPS-induced inflammatory response of microglial cells, indicating that Amp has potential for the treatment of inflammation-mediated neurodegenerative diseases.     

Protective effects of probiotic Lactobacillus casei Zhang against endotoxin- and d-galactosamine-induced liver injury in rats via anti-oxidative and anti-inflammatory capacities

Lactobacillus casei Zhang (LcZ) has been recently isolated from the traditional Mongolian beverage koumiss and has a set of favorable probiotic properties, including aciduricity, bile resistance and ability to colonize the gastrointestinal tract. We have previously reported the anti-oxidative properties of LcZ in the hyperlipidemic rats. In this study, the hepatoprotective effects of LcZ against lipopolysaccharide (LPS) and d-galactosamine (D-GalN)-induced liver injury were investigated. We found that pretreatment with LcZ significantly improved survival of rats challenged with LPS/D-GalN. In addition, pretreatment with LcZ significantly decreased alanine transaminase (ALT) and aspartate aminotransferase (AST) levels in LPS/D-GalN-challenged rats, which were accompanied by diminished liver injuries, reduced malondialdehyde (MDA) content and increased superoxide dismutase (SOD) activity in liver homogenates. Pretreatment with LcZ also markedly reduced LPS/D-GalN-induced production of hepatic nitric oxide (NO), activation of inducible nitric oxide synthase (iNOS) and expression of tumor necrosis factor-α (TNF-α). Furthermore, hepatic toll-like receptor 4 (TLR4) mRNA and protein levels, the phosphorylation of I-κB and translocation of nuclear factor κB (NF-κB) were significantly down-regulated by pretreatment with LcZ. These results suggest that pretreatment with LcZ protects against LPS/D-GalN-induced liver injury in rats via its anti-oxidative and anti-inflammatory capacities. The hepatoprotective effects of LcZ are associated with an inhibition of TLR4 expression and TLR4 signaling.     

Salvianic acid A inhibits induction of inflammatory mediators by blocking Nuclear Factor-κB activation in macrophages

Objective To investigate the anti-inflammation effect and possible mechanism of Salvianic acid A(SAA)in mouse peritoneal macrophages.Methods Peritoneal macrophages were obtained from BALB/c mice.LPS induced nitric oxide(NO),tumor necrosis factor-alpha(TNF-α)and interleukin-6(IL-6)in supernatant,protein expression of inducible nitric oxide synthase(iNOS),matrix metalloproteinase-9(MMP-9)and activation of nuclear factor-kappa B(NF-κB)in the extract were measured.Results SAA strongly inhibited the excessive production of NO,TNF-α and IL-6 in LPS-induced peritoneal macrophages in a concentration-dependent manner and blocked the expression of iNOS and MMP-9.Treatment with LPS alone increased the translocation of NF-κB(p65)from cytosol to the nucleus,but the SAA inhibited the translocation of NF-κB(p65).Conclusions The results showed that SAA had strong anti-inflammatory effects in LPS-stimulated peritoneal macrophages.The important mechanism is due to its inhibition of NF-κB activation.     

Downregulation of NO and PGE2 in LPS-stimulated BV2 microglial cells by trans-isoferulic acid via suppression of PI3K/Akt-dependent NF-κB and activation of Nrf2-mediated HO-1

Little is known about whether trans-isoferulic acid (TIA) regulates the production of lipopolysaccharide (LPS)-induced proinflammatory mediators. Therefore, we examined the effect of TIA isolated from Clematis mandshurica on LPS-induced nitric oxide (NO) and prostaglandin E₂ (PGE₂) production in BV2 microglial cells. We found that TIA inhibited the production of LPS-induced NO and PGE₂ without accompanying cytotoxicity in BV2 microglial cells. TIA also downregulated the expression levels of specific regulatory genes such as inducible NO synthase (iNOS) and cyclooxygenase-2 (COX-2) by suppressing LPS-induced NF-κB activity via dephosphorylation of PI3K/Akt. In addition, we demonstrated that a specific NF-κB inhibitor PDTC and a selective PI3K/Akt inhibitor, LY294002 effectively attenuated the expression of LPS-stimulated iNOS and COX-2 mRNA, while LY294002 suppressed LPS-induced NF-κB activity, suggesting that TIA attenuates the expression of these proinflammatory genes by suppressing PI3K/Akt-mediated NF-κB activity. Our results showed that TIA suppressed NO and PGE₂ production through the induction of nuclear factor erythroid 2-related factor 2 (Nrf2)-dependent heme oxygenase-1 (HO-1). Taken together, our data indicate that TIA suppresses the production of proinflammatory mediators such as NO and PGE₂, as well as their regulatory genes, in LPS-stimulated BV2 microglial cells, by inhibiting PI3K/Akt-dependent NF-κB activity and enhancing Nrf2-mediated HO-1 expression.     

Biochanin-A, an isoflavon, showed anti-proliferative and anti-inflammatory activities through the inhibition of iNOS expression, p38-MAPK and ATF-2 phosphorylation and blocking NFκB nuclear translocation

Biochanin-A, an isoflavone, existing in red clover, cabbage and alfalfa, has an inhibitory and apoptogenic effect on certain cancer cells. However, the actual mechanism by which this compound inhibits proliferation and induces apoptosis in cancer cells and the mechanism of its anti-inflammatory activities have not been well characterized. In this study, we have investigated the anti-inflammatory and anti-proliferative activity of Biochanin-A. The effects of Biochanin-A on RAW 264.7, HT-29 cell lines and mouse peritoneal macrophages have been investigated in vitro. Cell proliferation and anti-inflammatory effects were analyzed by 3-(4-5-dimethylthiozol-2-yl)2-5-diphenyl-tetrazolium bromide (MTT) assay, (3)H-thymidine incorporation assay, Western blot, cytokines estimation, Luciferase assay, Electrophoretic mobility shift assay (EMSA) and Kinase assay. Present investigation demonstrated that, Biochanin-A inhibited lipopolysacharide (LPS)-induced nitric oxide(NO) production in macrophage and showed dose dependent inhibition of inducible nitric oxide synthase (iNOS) expression. The induction of NF-κB binding activity by LPS was inhibited markedly by co-incubation with different doses of Biochanin-A. Biochanin-A inhibited the LPS-induced IkB kinase (IKK) activity and nuclear factor kappa beta (NF-κB) activation associated with the inhibition of iNOS expression. LPS-induced phosphorylation of IκBα and p38 MAPK was blocked by Biochanin-A and it inhibited IL-6, IL-1β and TNF-α production in RAW264.7 cells indicating its anti-inflammatory activity in association with anti-proliferation. Biochanin-A is important for the prevention of phosphorylation and degradation of IκBα, thereby blocking NF-κB activation, which in turn leads to decreased expression of the iNOS, thus preventing proliferation and inflammation.     

8,8′-Bieckol,isolated from edible brown algae,exerts its anti-inflammatory effects through inhibition of NF-κB signaling and ROS production in LPS-stimulated macrophages

Ecklonia cava (E. cava) is an abundant brown alga that contains high levels of phlorotannins, which are unique marine polyphenolic compounds. It has been suggested that E. cava phlorotannins exert anti-inflammatory effects. However, the anti-inflammatory effects and underlying molecular mechanism exerted by 8,8′-bieckol isolated from E. cava have not been reported. Thus, in this study, we examined the anti-inflammatory effects of 8,8′-bieckol on lipopolysaccharide (LPS)-stimulated primary macrophages and RAW 264.7 macrophages. We found that 8,8′-bieckol suppressed key inflammatory mediator [i.e., nitric oxide (NO) and prostaglandin E₂ (PGE₂)] production in both primary and RAW 264.7 macrophages. 8,8′-Bieckol inhibited NO by suppressing LPS-induced expression of inducible nitric oxide synthase (iNOS) at the mRNA and protein levels in primary macrophages and RAW 264.7 cells. In addition, 8,8′-bieckol decreased the production and mRNA expression of the inflammatory cytokine interleukin-6 (IL-6), but not tumor necrosis factor (TNF)-α, in RAW 264.7 cells. Moreover, 8,8′-bieckol treatment diminished transactivation of nuclear factor-kappa B (NF-κB) and nuclear translocation of the NF-κB p65 subunit and suppressed LPS-induced intracellular reactive oxygen species (ROS) production in macrophages. Furthermore, 8,8′-bieckol markedly reduced mortality in LPS-induced septic mice. Taken together, these data indicate that the anti-inflammatory properties of 8,8′-bieckol are associated with the suppression of NO, PGE₂, and IL-6 via negative regulation of the NF-κB pathway and ROS production in LPS-stimulated RAW 264.7 cells. Moreover, 8,8′-bieckol protects mice from endotoxin shock.     

Vitisin A suppresses LPS-induced NO production by inhibiting ERK,p38, and NF-κB activation in RAW 264.7 cells

Vitisin A, a resveratrol tetramer isolated from Vitis vinifera roots, exhibits antioxidative, anticancer, antiapoptotic, and anti-inflammatory effects. It also inhibits nitric oxide (NO) production. Here, we examined the mechanism by which vitisin A inhibits NO production in lipopolysaccharide (LPS)-induced RAW 264.7 macrophage cells. Vitisin A dose dependently inhibited LPS-induced NO production and inducible NO synthase (iNOS) expression. In contrast, the production of proinflammatory cytokines such as tumor necrosis factor-α (TNF-α) and interleukin-6 (IL-6) was not altered by vitisin A. To investigate the signaling pathway for NO inhibition by vitisin A, we examined nuclear factor-κB (NF-κB) activation in the mitogen-activated protein kinase (MAPK) pathway, an inflammation-induced signal pathway in RAW 264.7 cells. Vitisin A inhibited LPS-induced extracellular signal-regulated kinase 1/2 (ERK1/2) and p38 phosphorylation and suppressed LPS-induced NF-κB activation in RAW 264.7 cells. This suggests that vitisin A decreased NO production via downregulation of ERK1/2 and p38 and the NF-κB signal pathway in RAW 264.7 cells.     

Heme oxygenase-1-mediated anti-inflammatory effects of tussilagonone on macrophages and 12-O-tetradecanoylphorbol-13-acetate-induced skin inflammation in mice

The dried flower buds of Tussilago farfara L. have been used in traditional medicine, mainly as an antitussive in the treatment of cough and other respiratory problems. In the present study, we investigated the anti-inflammatory signaling pathway via the upregulation of heme oxygenase-1 (HO-1) in response to tussilagonone (TGN), a sesquiterpene compound isolated from T. farfara. TGN induced HO-1 expression and nuclear factor-E2-related factor 2 (Nrf2) activation in RAW 264.7 cells. Nuclear translocation of Nrf2 by TGN also increased in a time- and dose-dependent manner, indicating that TGN induced HO-1 via the Nrf2 pathway. Consistent with the notion that HO-1 has anti-inflammatory properties, TGN suppressed inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2) expression and reduced the mRNA expression of proinflammatory cytokines, as well as nitric oxide (NO) and prostaglandin E₂ (PGE₂) production in lipopolysaccharide (LPS)-stimulated RAW 264.7 cells. TGN inhibited the phosphorylation and degradation of inhibitory κB-α (IκB-α) and the nuclear translocation of nuclear factor (NF)-κB. However, a specific inhibitor of HO-1 reversed the TGN-mediated suppression of NO production and knockdown of HO-1 by small interfering RNA abrogated inhibitory effects of TGN on iNOS and COX-2 protein expression and NF-κB nuclear translocation. Furthermore, TGN reduced iNOS and COX-2 expression in a 12-O-tetradecanoylphorbol-13-acetate (TPA)-induced skin inflammation mouse model. Taken together, these findings suggest an important role for TGN-induced HO-1 activation in regulating inflammatory responses. Moreover, TGN is a potent therapeutic candidate for targeting the crosstalk between Nrf2/HO-1 and the NF-κB signaling pathway in the prevention or treatment of inflammation-associated diseases.     

Tormentic acid, a triterpenoid saponin, isolated from Rosa rugosa, inhibited LPS-induced iNOS, COX-2, and TNF-α expression through inactivation of the nuclear factor-κb pathway in RAW 264.7 macrophages

We previously reported that extract of Rosa rugosa root and its active triterpenoids constituents exhibit anti-nociceptive and anti-inflammatory effects in animal models. However, little is known about the effects and the molecular mechanism of the 19α-hydroxyursane-type triterpenoids. Among the tested 19α-hydroxyursane-type triterpenoids (kaji-ichigoside F(1), rosamultin, euscaphic acid, tormentic acid (TA)), TA was found to most potently inhibit the production of nitric oxide (NO) in RAW 264.7 cells. We investigated the anti-inflammatory effects and its underlying molecular mechanisms of TA in lipopolysaccaride (LPS)-stimulated RAW 264.7 cells. TA dose-dependently reduced the productions of NO, prostaglandin E(2) (PGE(2)), and tumor necrosis factor-α (TNF-α) induced by LPS. In addition, TA significantly suppressed the LPS-induced expressions of inducible nitric oxide synthase (iNOS), cyclooxygenase-2 (COX-2), and TNF-α at the mRNA and protein levels. Moreover, treatment with TA decreased LPS-induced DNA binding of nuclear factor-kappa B (NF-κB) and nuclear translocation of p65 and p50 subunits of NF-κB. Consistent with these findings, TA also suppressed the LPS-stimulated degradation and phosphorylation of inhibitor of kappa B-α (IκB-α). Taken together, these results suggest that the anti-inflammatory activity of TA is associated with the down-regulation of iNOS, COX-2, and TNF-α through the negative regulation of the NF-κB pathway in RAW 264.7 cells.