Young Sun Song

Luteolin and chicoric acid synergistically inhibited inflammatory responses via inactivation of PI3K-Akt pathway and impairment of NF-κB translocation in LPS stimulated RAW 264.7 cells

Synergistic anti-inflammatory effects of luteolin and chicoric acid, two abundant constituents of the common dandelion (Taraxacum officinale Weber), were investigated in lipopolysaccharide (LPS) stimulated RAW 264.7 cells. Co-treatment with luteolin and chicoric acid synergistically reduced cellular concentrations of nitric oxide (NO) and prostaglandin E2 (PGE2) and also inhibited expression of inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2). In addition, co-treatment reduced the levels of proinflammatory cytokines, tumor necrosis factor (TNF)-α, and interleukin (IL)-1β. Both luteolin and chicoric acid suppressed oxidative stress, but they did not exhibit any synergistic activity. Luteolin and chicoric acid co-treatment inhibited phosphorylation of NF-κB and Akt, but had no effect on extracellular signal-regulated kinase (ERK), c-Jun NH2-terminal kinase (JNK), and p38. This anti-inflammatory signaling cascade coincides with that affected by luteolin treatment alone. These results suggest that luteolin plays a central role in ameliorating LPS-induced inflammatory cascades via inactivation of the NF-κB and Akt pathways, and that chicoric acid strengthens the anti-inflammatory activity of luteolin through NF-κB attenuation.

Taraxacum officinale Weber extracts inhibit LPS-induced oxidative stress and nitric oxide production via the NF-κB modulation in RAW 264.7 cells.

ETHNOPHARMACOLOGICAL RELEVANCEnThe common dandelion (Taraxacum officinale G.H. Weber ex Wiggers, Asteraceae) has been widely used in folklore medicine to treat dyspepsia, heartburn, and spleen and liver disorders.nnnAIM OF THE STUDYnTo compare the antioxidative and anti-inflammatory activities of Taraxacum officinale methanol extract (TOME) and water extract (TOWE) in lipopolysaccharide (LPS)-stimulated RAW 264.7 cells and assess their constitutional differences, including luteolin, chicoric acid, and total phenol content.nnnMATERIALS AND METHODSnAntioxidative enzyme activities, nitric oxide (NO) production, and inducible NO synthase (iNOS) and nuclear factor (NF)-κB expression were estimated by biochemical analysis, the Griess reaction, reverse transcription-polymerase chain reaction, western hybridization, and electrophoretic mobility shift assay. High-performance liquid chromatography and the Folin-Ciocalteau method were used to analyze functional phytochemicals and total phenol content.nnnRESULTSnTOME and TOWE significantly reduced NO production with an IC(50) of 79.9 and 157.5 μg/mL, respectively, without cytotoxicity. Depleted glutathione (GSH) and antioxidative enzyme activities, including superoxide dismutase, catalase, GSH-peroxidase, and GSH-reductase, were restored by dandelion extracts. Both extracts inhibited LPS-stimulated iNOS gene expression and that of its transcription factor, NF-κB, in parallel with nitrite reduction. TOME showed more potent antioxidative and anti-inflammatory capacities than TOWE, which was attributable to its high total phenol, luteolin, and chicoric acid content.nnnCONCLUSIONSnThese results indicate that TOME and TOWE inhibit oxidative stress and inflammatory responses through elevated de novo synthesis of antioxidative enzymes and suppression of iNOS expression by NF-κB inactivation.

TOP1 and 2, polysaccharides from Taraxacum officinale, attenuate CCl4-induced hepatic damage through the modulation of NF-κB and its regulatory mediators.

In this work, we estimate the inhibitory effect of two polysaccharides from Taraxacum officinale (TOP) on CCl(4)-induced oxidative stress and inflammation in Sprague-Dawley rats. TOP1 and 2 (304, 92 mg/kg bw) were administered for 7 days via a stomach sonde, and hepatitis was induced by a single dose of CCl(4) (50% CCl(4)/olive oil; 0.5 mL/kg bw) administration. CCl(4) significantly elevated serum aspartate aminotransferase (AST) and alanine aminotransferase (ALT) activities. Histopathological observation further revealed that CCl(4)-induced moderate levels of inflammatory cell infiltration, centrilobular fatty change, apoptosis, and necrosis. However, TOPs pretreatment markedly decreased AST and ALT activities as well as hepatic lesions. TOPs also increased free radical scavenging activity, as exhibited by a lowered TBARS concentration. TOPs pretreatment also reversed other hepatitis-associated symptoms, including GSH depletion, inhibited anti-oxidative enzyme activities, up-regulation of NF-kappaB and increased expression of its regulatory inflammatory mediators, such as inducible nitric oxide synthase (iNOS), cyclooxygenase (COX)-2, tumor necrosis factor (TNF)-alpha, and interleukin (IL)-1beta. These results suggest that TOPs have a hepatoprotective effect by modulating inflammatory responses and ameliorating oxidative stress.

Amelioration of oxidative stress by dandelion extract through CYP2E1 suppression against acute liver injury induced by carbon tetrachloride in Sprague-Dawley rats.

The protective effects of common dandelion leaf water extract (DLWE) were investigated by carbon tetrachloride (CCl4) induced hepatitis in Sprague‐Dawley rats. The animals were divided into five groups: normal control, DLWE control, CCl4 control, and two DLWE groups (0.5 and 2u2009g/kg bw). After 1 week of administering corresponding vehicle or DLWE, a single dose of CCl4 (50% CCl4/olive oil; 0.5u2009mL/kg bw) was administered 24u2009h before killing in order to produce acute liver injury. The DLWE treatment significantly decreased CCl4‐induced hepatic enzyme activities (AST, ALT and LDH) in a dose dependent manner. Also, the obstructed release of TG and cholesterol into the serum was repaired by DLWE administration. Hepatic lipid peroxidation was elevated while the GSH content and antioxidative enzyme activities were reduced in the liver as a result of CCl4 administration, which were counteracted by DLWE administration. Furthermore, the hepatocytotoxic effects of CCl4 were confirmed by significantly elevated Fas and TNF‐? mRNA expression levels, but DLWE down‐regulated these expressions to the levels of the normal control. Highly up‐regulated cytochrome P450 2E1 was also lowered significantly in the DLWE groups. These results indicate that DLWE has a protective effect against CCl4‐induced hepatic damage with at least part of its effect being attributable to the attenuation of oxidative stress and inflammatory processes resulting from cytochrome P450 activation by CCl4. Copyright

Luteolin and luteolin-7-O-glucoside strengthen antioxidative potential through the modulation of Nrf2/MAPK mediated HO-1 signaling cascade in RAW 264.7 cells

It has been understood that glycosidic forms of flavonoids were hydrolyzed by gut bacteria and absorbed as aglycones. However, several reports suggested that glycosides were partly absorbed without hydrolysis and remained biologically active. In this study, we evaluated the antioxidative potential of luteolin and luteolin-7-O-glucoside, glycosidic form of luteolin, against the oxidative damage and compared their antioxidative mechanisms in RAW 264.7 cells. Heme oxygenase-1 (HO-1), one of the phase II enzymes showing an antioxidative activity, was potently induced by luteolin and luteolin-7-O-glucoside treatment, which was in accordance with the translocated nuclear factor-erythroid 2 p45-related factor 2 (Nrf2) into nucleus. Moreover, luteolin and the luteolin-7-O-glucoside activated HO-1 expression by p38 and c-Jun NH2-terminal kinase (JNK) regulation. In order to identify the antioxidation potential by HO-1, tert-butyl hydroperoxide (t-BHP)-induced oxidative damage was applied and ameliorated by luteolin and the luteolin-7-O-glucoside treatment in a dose dependent manner, which was confirmed by HO-1 selective inhibitor and inducer, tin protoporphyrin (SnPP) and cobalt protoporphyrin (CoPP), respectively. Consequently, luteolin and luteolin-7-O-glucoside potently strengthen the HO-1-mediated antioxidative potential through the modulation of the Nrf2/MAPK signaling pathways.

Methionine Supplementation Accelerates Oxidative Stress and Nuclear Factor κB Activation in Livers of C57BL/6 Mice

The present study was designed to investigate whether hyperhomocysteinemia (HHcy) induced by methionine supplementation promotes oxidative stress and nuclear factor kappaB (NFkappaB) activation in livers of C57BL/6 mice when fed a 2% methionine and low folate (1 mg/kg) diet for 12 weeks. Plasma homocysteine concentrations of mice fed methionine were found to be 49 micromol/L by 12 weeks of feeding, which was five times higher than that of controls. HHcy induced by methionine feeding significantly increased oxidative stress, as measured by thiobarbituric acid-reactive substances (P < .05) in livers. This was further confirmed by lower levels of hepatic glutathione (P < .05) and elevated mRNA expressions of hepatic antioxidative enzymes, such as Cu,Zn-superoxide dismutase, catalase, glutathione reductase, and L-gulonolactone oxidase in methionine-fed animals (P < .05). Hepatic function of mice fed methionine seems to be normal, while hepatic triglyceride concentration was lowered by methionine feeding. NFkappaB nuclear binding activities of livers were higher in the methionine group than in the control group. The above results suggest that HHcy induced by methionine may promote disturbances in lipid peroxidation and antioxidant processes and be a pro-inflammatory mediator in livers of C57BL/6 mice.

TOP 1 and 2, polysaccharides from Taraxacum officinale, inhibit NFκB-mediated inflammation and accelerate Nrf2-induced antioxidative potential through the modulation of PI3K-Akt signaling pathway in RAW 264.7 cells

Anti-inflammatory and anti-oxidative activities of polysaccharides from Taraxacum officinale (TOP 1 and 2) were analyzed in RAW 264.7 cells. First, lipopolysaccharide (LPS) was applied to identify anti-inflammatory activity of TOPs, which reduced expression of inducible nitric oxide synthase (iNOS) and tumor necrosis factor (TNF)-α. TOPs treatment inhibited phosphorylation of inflammatory transcription factor, nuclear factor (NF)κB, and its upstream signaling molecule, PI3K/Akt. Second, cytoprotective potential of TOPs against oxidative stress was investigated via heme oxygenase (HO)-1 induction. HO-1, one of phase II enzymes shows antioxidative activity, was potently induced by TOPs treatment, which was in accordance with the nuclear translocation of nuclear factor-erythroid 2 p45-related factor 2 (Nrf2). In addition, TOPs treatment phosphorylated PI3K/Akt with slight activation of c-Jun NH2-terminal kinase (JNK). TOPs-mediated HO-1 induction protected macrophage cells from oxidative stress-induced cell death, which was confirmed by SnPP and CoPP (HO-1 inhibitor and inducer, respectively). Consequently, TOPs potently inhibited NFκB-mediated inflammation and accelerated Nrf2-mediated antioxidative potential through the modulation of PI3K/Akt pathway, which would contribute to their promising strategy for novel anti-inflammatory and anti-oxidative agents.

Comparative effect of genistein and daidzein on the expression of MCP-1, eNOS, and cell adhesion molecules in TNF-α-stimulated HUVECs

We compared the effects of genistein and daidzein on the expression of chemokines, cell adhesion molecules (CAMs), and endothelial nitric oxide synthase (eNOS) in tumor necrosis factor (TNF)-α-stimulated human umbilical vascular endothelial cells (HUVECs). TNF-α exposure significantly increased expression of monocyte chemoattractant protein (MCP)-1, vascular adhesion molecule (VCAM)-1, and intercellular adhesion molecule-1. Genistein significantly decreased MCP-1 and VCAM-1 production in a dose-dependent manner, whereas CAM expression was not significantly lowered by genistein treatment. However, daidzein slightly decreased MCP-1 production. The effects of genistein and daidzein on MCP-1 secretion coincided with mRNA expression. Pre-treatment with either genistein or daidzein elevated eNOS expression and nitric oxide production disturbed by TNF-α exposure. A low concentration of isoflavones significantly inhibited nuclear factor (NF)κB activation, whereas a high dose slightly ameliorated these inhibitive effects. These results suggest that genistein had a stronger effect on MCP-1 and eNOS expression than that of daidzein. Additionally, NFκB transactivation might be partially related to the down-regulation of these mRNAs in TNF-α-stimulated HUVECs.

Identification and characterization of highly expressed genes in suspension-cultured cells of sweet potato

Cultured plant cells have high potential in providing efficient and low-cost molecular farming systems for the large-scale production of commercially valuable recombinant proteins. As an initial aim at establishing an efficient expression system for suspension-cultured cells of food crops, we first obtained 1411 expressed sequence tags from a sweet potato cDNA library of exponential phase cells, and assembled them into 156 contigs and 1039 singletons. Five ESTs were selected as the most significantly abundant genes. These were transcripts for a cell wall development protein (cinnamyl alcohol dehydrogenase), a carbohydrate metabolite protein (glyceraldehyde-3-phosphate dehydrogenase), and a cell cycle regulator protein (small GTP binding protein Ran), as well as inorganic pyrophosphatase and cyclophilin. Comparisons were then made with the root and leaf EST libraries of sweet potato. Northern blot and RT-PCR analyses revealed that these five genes were strongly expressed in the suspension cells but not in the roots and leaves, thereby supporting the data obtained from the comparative analysis. This is the first reported comparison of the various EST libraries isolated from different cell types of the same plant species. These genes can now contribute to an applicable promoter for devising an efficient expression system from suspension-cultured cells.

Luteolin inhibits inflammatory responses by downregulating the JNK, NF-κB, and AP-1 pathways in TNF-α activated HepG2 cells

The inhibitory mechanism of luteolin on tumor necrosis factor (TNF)-α-induced inflammation was investigated in HepG2 cells. Luteolin significantly suppressed TNF-α-stimulated inducible nitric oxide synthase (iNOS) expression in a dose-dependent manner without cytotoxicity. Phosphorylation and nuclear translocation of both transcription factors, nuclear factor (NF)-κB and activator protein (AP)-1, were also inhibited by luteolin treatment. Additionally, luteolin suppressed TNF-α-induced c-Jun N-terminal kinase (JNK) phosphorylation, which is crucially related to regulating inflammation. SP600125, a JNK selective inhibitor, abolished the TNF-α triggered inflammatory signaling cascade. These results suggest that luteolin attenuates inflammatory responses by blocking NF-κB and AP-1 activation through suppressed JNK phosphorylation in TNF-α-stimulated HepG2 cells.