Coptidis rhizoma extract protects against cytokine-induced death of pancreatic beta-cells through suppression of NF-kappaB activation

We demonstrated previously that Coptidis rhizoma extract (CRE) prevented S-nitroso-N-acetylpenicillamine-induced apoptotic cell death via the inhibition of mitochondrial membrane potential disruption and cytochrome c release in RINm5F (RIN) rat insulinoma cells. In this study, the preventive effects of CRE against cytokine-induced beta-cell death was assessed. Cytokines generated by immune cells infiltrating pancreatic islets are crucial mediators of beta-cell destruction in insulin-dependent diabetes mellitus. The treatment of RIN cells with IL-1beta and IFN-gamma resulted in a reduction of cell viability. CRE completely protected IL-1beta and IFN-gamma-mediated cell death in a concentration-dependent manner. Incubation with CRE induced a significant suppression of IL-1beta and IFN-gamma-induced nitric oxide (NO) production, a finding which correlated well with reduced levels of the iNOS mRNA and protein. The molecular mechanism by which CRE inhibited iNOS gene expression appeared to involve the inhibition of NF-kappaB activation. The IL-1beta and IFN-gamma-stimulated RIN cells showed increases in NF-kappaB binding activity and p65 subunit levels in nucleus, and IkappaB alpha degradation in cytosol compared to unstimulated cells. Furthermore, the protective effects of CRE were verified via the observation of reduced NO generation and iNOS expression, and normal insulin-secretion responses to glucose in IL-1beta and IFN-gamma-treated islets.     

Epigallocatechin gallate,a constituent of green tea,suppresses cytokine-induced pancreatic beta-cell damage

Cytokines produced by immune cells infiltrating pancreatic islets have been implicated as one of the important mediators of beta-cell destruction in insulin-dependent diabetes mellitus. In this study, the protective effects of epigallocatechin gallate (EGCG) on cytokine-induced beta-cell destruction were investigated. EGCG effectively protected IL-1beta and IFN-gamma-mediated cytotoxicity in insulinoma cell line (RINm5F). EGCG induced a significant reduction in IL-1beta and IFN-gamma-induced nitric oxide (NO) production and reduced levels of the inducible form of NO synthase (iNOS) mRNA and protein levels on RINm5F cells. The molecular mechanism by which EGCG inhibited iNOS gene expression appeared to involve the inhibition of NF-kappaB activation. These findings revealed EGCG as a possible therapeutic agent for the prevention of diabetes mellitus progression.     

Induction of nitric oxide synthase (NOS) by soluble glucocorticoid induced tumor necrosis factor receptor (sGITR) is modulated by IFN-gamma in murine macrophage

Earlier study showed that glucocorticoid induced tumor necrosis factor receptor (GITR), a new TNFR family, activated murine macrophages to express inducible nitric oxide synthase (iNOS) and to generate nitric oxide (NO). A possible involvement of pro-inflammatory cytokines on NO production by GITR was investigated in vitro systems and signaling molecules contributing to sGITR-induced iNOS production are determined in Raw 264.7 cells, a murine macrophage cell line. The result showed that the synergy was afforded by the combination of GITR with IFN-g in a dose-dependent manner but IFN-gamma alone was not able to induce NOS. No effects were observed with TNF-alpha, IL-1beta, or IL-6 co-treated with GITR. To determine signaling molecules contributing to sGITR-induced iNOS production, a specific inhibitor for signal pathway proteins tested showed that PDTC (NF-kappaB) and genistein (tyrosine kinase) inhibited NOS induction significantly, while sodium orthovanadate (tyrosine phosphatase) potentiated NOS expression. These results suggest that activations of NF-kappaB were involved in induction of iNOS by GITR and IFN-gamma priming caused earlier and stronger NF-kappaB activation.     

Rapid upregulation of cytoprotective nitric oxide in breast tumor cells subjected to a photodynamic therapy-like oxidative challenge

Many tumor cells produce nitric oxide (NO) as an antiapoptotic/progrowth molecule which also promotes antiogenesis and tumor expansion. This study was designed to examine possible antagonistic effects of endogenous NO on tumor eradication by photodynamic therapy (PDT). Using COH-BR1 breast cancer cells sensitized in mitochondria with 5-aminolevulinic acid (ALA)-generated protoporphyrin IX as a model for ALA-based PDT, we found that caspase-9 activation and apoptotic death following irradiation were strongly enhanced by 1400W, an inhibitor of inducible nitric oxide synthase (iNOS). RT-PCR and Western analyses revealed a substantial upregulation of both iNOS mRNA and protein, beginning ca 4 h after irradiation and persisting for at least 20 h. Accompanying this was a strong 1400W-inhibitable increase in intracellular NO, as detected with the NO probe, DAF-2-DA. Short hairpin RNA-based iNOS knockdown in COH-BR1 cells dramatically reduced NO production under photostress while enhancing caspase-9 activation and apoptosis. These findings suggest that cytoprotective iNOS/NO induction in PDT-treated tumor cells could reduce treatment efficacy, and point to pharmacologic intervention with iNOS inhibitors for counteracting this.     

Protein kinase A mediates microglial activation induced by plasminogen and gangliosides

In the injured brain, microglia is known to be activated and produce proinflammatory mediators such as interleukin-1beta (IL-1beta), tumor necrosis factor-alpha (TNF-alpha) and inducible nitric oxide synthase (iNOS). We investigated the role of protein kinase A (PKA) in microglial activation by both plasminogen and gangliosides in rat primary microglia and in the BV2 immortalized murine microglial cell line. Both plasminogen and gangliosides induced IL-1beta, TNF-alpha and iNOS mRNA expression, and that this expression was inhibited by the addition of the PKA inhibitors, KT5720 and H89. Both plasminogen and gangliosides activated PKA and increased the DNA binding activity of the cAMP response element- binding protein (CREB). Furthermore, KT5720 and H89 reduced the DNA binding activities of CREB and NF-kappaB in plasminogen-treated cells. These results suggest that PKA plays an important role in plasminogen and gangliosides- induced microglial activation.     

Polyphenols isolated from Broussonetia kazinoki prevent cytokine-induced β-cell damage and the development of type 1 diabetes

The axis of nuclear factor κB (NF-κB)-inducible NO synthase (iNOS)-nitric oxide plays a key role in cytokine- and streptozotocin-mediated pancreatic β-cell damage. In this study, we investigated the effects of kazinol C and isokazinol D isolated from Broussonetia kazinoki on the β-cell viability and function. RINm5F cells and primary islets were used for in vitro and ex vivo cytokine toxicity experiments, respectively. For type 1 diabetes induction, mice were injected with multiple low-dose streptozotocin (MLDS). Cytokine-induced toxicity was completely abolished in both RINm5F cells and islets that were pretreated with either kazinol C or isokazinol D. Both kazinols inhibited the NF-κB signaling pathway, thereby inhibiting cytokine-mediated iNOS induction, nitric oxide production, apoptotic cell death and defects in insulin secretion. Moreover, the occurrence of diabetes in MLDS-treated mice was efficiently attenuated in kazinol-pretreated mice. Immunohistochemical analysis revealed that the numbers of terminal deoxynucleotidyl transferase dUTP nick end labeling-positive apoptotic cells and nuclear p65-positive cells were significantly decreased in kazinol-pretreated mice. Our results suggest that kazinol C and isokazinol D block the NF-κB pathway, thus reducing the extent of β-cell damage. Therefore, kazinol C and isokazinol D may have therapeutic value in delaying pancreatic β-cell damage in type 1 diabetes.     

Sulfuretin protects against cytokine-induced ��-cell damage and prevents streptozotocin-induced diabetes

NF-κB activation has been implicated as a key signaling mechanism for pancreatic β-cell damage. Sulfuretin is one of the main flavonoids produced by Rhus verniciflua, which is reported to inhibit the inflammatory response by suppressing the NF-κB pathway. Therefore, we isolated sulfuretin from Rhus verniciflua and evaluated if sulfuretin could inhibit cytokine- or streptozotocin-induced β-cell damage. Rat insulinoma RINm5F cells and isolated rat islets were treated with IL-1β and IFN-γ to induce cytotoxicity. Incubation of cells and islets with sulfuretin resulted in a significant reduction of cytokine-induced NF-κB activation and its downstream events, iNOS expression, and nitric oxide production. The cytotoxic effects of cytokines were completely abolished when cells or islets were pretreated with sulfuretin. The protective effect of sulfuretin was further demonstrated by normal insulin secretion of cytokine-treated islets in response to glucose. Treatment of mice with streptozotocin resulted in hyperglycemia and hypoinsulinemia, which was further evidenced by immunohistochemical staining of islets. However, the diabetogenic effects of streptozotocin were completely prevented when mice were pretreated with sulfuretin. The anti-diabetogenic effects of sulfuretin were also mediated by suppression of NF-κB activation. Collectively, these results indicate that sulfuretin may have therapeutic value in preventing β-cell damage.     

Anti-inflammatory and free radial scavenging activities of the constituents isolated from Machilus zuihoensis

A new biflavonol glycoside, quercetin-3-O-β-D-glucopyranoside-(3'→O-3')-quercetin-3-O-β-D-galactopyranoside (9), together with eight known compounds was isolated for the first time from the leaves of Machilus zuihoensis Hayata (Lauraceae). The structure of compound 9 was elucidated by various types of spectroscopic data analysis. Analysis of the biological activity assay found that compound 9 showed significant superoxide anion scavenging activity (IC?? is 30.4 μM) and markedly suppressed LPS-induced high mobility group box 1 (HMGB-1) protein secretion in RAW264.7 cells. In addition, the HMGB-1 protein secretion was also inhibited by quercitrin (3), ethyl caffeate (6), and ethyl 3-O-caffeoylquinate (7) treatment. In the LPS-stimulated inducible nitric oxide synthase (iNOS) activation analysis, two known compounds, quercetin (1) and ethyl caffeate (6), were found to markedly suppress nitric oxide (NO) production (IC?? value, 27.6 and 42.9 μM, respectively) in RAW264.7 cells. Additionally, it was determined that ethyl caffeate (6) down-regulated mRNA expressions of iNOS, IL-1β, and IL-10 in the LPS-treatment of RAW264.7 cells via a suppressed NF-kB pathway. These results suggested for the first time that the new compound 9 and other constituents isolated from M. zuihoensis have potential anti-inflammatory and superoxide anion scavenging effects. These constituents may be useful for treating various inflammatory diseases.     

beta-Carotene inhibits inflammatory gene expression in lipopolysaccharide-stimulated macrophages by suppressing redox-based NF-kappaB activation

beta-Carotene has shown antioxidant and anti-inflammatory activities; however, its molecular mechanism has not been clearly defined. We examined in vitro and in vivo regulatory function of beta-carotene on the production of nitric oxide (NO) and PGE(2) as well as expression of inducible NO synthase (iNOS), cyclooxygenase-2, TNF-alpha, and IL-1beta. beta-Carotene inhibited the expression and production of these inflammatory mediators in both LPS-stimulated RAW264.7 cells and primary macrophages in a dose-dependent fashion as well as in LPS-administrated mice. Furthermore, this compound suppressed NF-kappaB activation and iNOS promoter activity in RAW264.7 cells stimulated with LPS. beta-Carotene blocked nuclear translocation of NF-kappaB p65 subunit, which correlated with its inhibitory effect on IkappaBalpha phosphorylation and degradation. This compound directly blocked the intracellular accumulation of reactive oxygen species in RAW264.7 cells stimulated with LPS as both the NADPH oxidase inhibitor diphenylene iodonium and antioxidant pyrrolidine dithiocarbamate did. The inhibition of NADPH oxidase also inhibited NO production, iNOS expression, and iNOS promoter activity. These results suggest that beta-carotene possesses anti-inflammatory activity by functioning as a potential inhibitor for redox-based NF-kappaB activation, probably due to its antioxidant activity.     

In vitro anti-inflammatory activity of 4-arylcoumarins from endophytic Streptomyces aureofaciens CMUAc130 in murine macrophage RAW 264.7 cells

This research was undertaken to find the in vitro inflammatory action of 5,7-dimethoxy-4-p-methoxylphenylcoumarin and 5,7-dimethoxy-4-phenylcoumarin produced by Streptomyces aureofaciens CMUAc130. We investigated the effects of 5,7-dimethoxy-4-p-methoxylphenylcoumarin and 5,7-dimethoxy-4-phenylcoumarin not only on the formation of nitric oxide (NO), PGE(2), TNF-alpha, IL-6 and IL-1beta, but also on inducible NO synthase and cyclooxygenase-2 (COX-2) in lipopolysaccharide (LPS)-induced murine macrophage RAW 264.7 cells. The data obtained were consistent with the modulation of iNOS enzyme expression. A similar fashion was also observed when LPS-induced PGE(2) release and COX-2 expression were tested. The significant inhibitory effects were shown in concentration-dependent manners. In addition, 5,7-dimethoxy-4-p-methoxylphenylcoumarin and 5,7-dimethoxy-4-phenylcoumarin also mildly but significantly reduced the formation of TNF-alpha. These findings support the application of 5,7-dimethoxy-4-p-methoxylphenylcoumarin and 5,7-dimethoxy-4-phenylcoumarin as anti-inflammatory agents.     

Effect of sildenafil citrate on interleukin-1beta-induced nitric oxide synthesis and iNOS expression in SW982 cells

The purpose of this study was to identify the effect of sildenafil citrate on IL-1β-induced nitric oxide (NO) synthesis and iNOS expression in human synovial sarcoma SW982 cells. IL-1β stimulated the cells to generate NO in both dose- and time-dependent manners. The IL-1β-induced NO synthesis was inhibited by guanylate cyclase (GC) inhibitor, LY83583. When the cells were treated with 8-bromo-cGMP, a hydrolyzable analog of cGMP, NO synthesis was increased upto 5-fold without IL-1β treatment suggesting that cGMP is an essential component for increasing the NO synthesis. Synoviocytes and chondrocytes contain strong cGMP phosphodiesterase (PDE) activity, which has biochemical features of PDE5. When SW982 cells were pretreated with sildenafil citrate (Viagra), a PDE5 specific inhibitor, sildenafil citrate significantly inhibited IL-1β-induced NO synthesis and iNOS expressions. From this result, we noticed that PDE5 activity is required for IL-1β-induced NO synthesis and iNOS expressions in human synovial sarcoma cells, and sildenafil citrate may be able to suppress an inflammatory reaction of synovium through inhibition of NO synthesis and iNOS expression by cytokines.     

Antiallergic agents from natural sources 9. Inhibition of nitric oxide production by novel chalcone derivatives from Mallotus philippinensis (Euphorbiaceae)

Three novel chalcone derivatives, mallotophilippens C (1), D (2) and E (3) were isolated from the fruits of Mallotus philippinensis MUELL. ARG. These compounds were identified, using chemical and spectral data, as 1-[6-(3,7-dimethyl-octa-2,6-dienyl)-5,7-dihydroxy-2,2-dimethyl-2H-chromen-8-yl]-3-(4-hydroxy-phenyl)-propenone, 3-(3,4-dihydroxy-phenyl)-1-[6-(3,7-dimethyl-octa-2,6-dienyl)-5,7-dihydroxy-2,2-dimethyl-2H-chromen-8-yl]-propenone and 1-[5,7-dihydroxy-2-methyl-6-(3-methyl-but-2-enyl)-2-(4-methyl-pent-3-enyl)-2H-chromen-8-yl]-3-(3,4-dihydroxy-phenyl)-propenone, respectively. They inhibited nitric oxide (NO) production and inducible NO synthase (iNOS) gene expression by a murine macrophage-like cell line (RAW 264.7), which was activated by lipopolysaccharide (LPS) and recombinant mouse interferon-gamma (IFN-gamma). Furthermore, they downregulated cyclooxygenase-2 (COX-2) gene, interleukin-6 (IL-6) gene and interleukin-1beta (IL-1beta) gene expression. These results suggest that they have anti-inflammatory and immunoregulatory effects.     

Celastrol inhibits production of nitric oxide and proinflammatory cytokines through MAPK signal transduction and NF-kappaB in LPS-stimulated BV-2 microglial cells

Excessive production of nitric oxide (NO) and proinflammatory cytokines from activated microglia play an important role in human neurodegenerative disorders. Here, we investigated whether celastrol, which has been used as a potent anti-inflammatory and anti-oxidative agent in Chinese medicine, attenuates excessive production of NO and proinflammatory cytokines such as TNF-alpha and IL-1betal in LPS-stimulated BV-2 cells, a mouse microglial cell line. We report here that the LPS-elicited excessive production of NO, TNF-alpha, and IL-1beta in BV-2 cells was largely inhibited in the presence of celastrol, and the attenuation of inducible iNOS and these cytokines resulted from the reduced expression of mRNAs of iNOS and these cytokines, respectively. The molecular mechanisms that underlie celastrol-mediated attenuation were the inhibition of LPS-induced phosphorylation of MAPK/ERK1/2 and the DNA binding activity of NF-kappaB in BV-2 cells. The results indicate that celastrol effectively attenuated NO and proinflammatory cytokine production via the inhibition of ERK1/2 phosphorylation and NF-kappaB activation in LPS-activated microglia. Thus, celastrol may be an effective therapeutic candidate for use in the treatment of neurodegenerative human brain disorders.     

Antagonistic Effects of Endogenous Nitric Oxide in a Glioblastoma Photodynamic Therapy Model

Gliomas are aggressive brain tumors that are resistant to conventional chemotherapy and radiotherapy. Much of this resistance is attributed to endogenous nitric oxide (NO). Recent studies revealed that 5‐aminolevulinic acid (ALA)‐based photodynamic therapy (PDT) has advantages over conventional treatments for glioblastoma. In this study, we used an in vitro model to assess whether NO from glioblastoma cells can interfere with ALA‐PDT. Human U87 and U251 cells expressed significant basal levels of neuronal NO synthase (nNOS) and its inducible counterpart (iNOS). After an ALA/light challenge, iNOS level increased three‐ to fourfold over 24 h, whereas nNOS remained unchanged. Elevated iNOS resulted in a large increase in intracellular NO. Extent of ALA/light‐induced apoptosis increased substantially when an iNOS inhibitor or NO scavenger was present, implying that iNOS/NO was acting cytoprotectively. Moreover, cells surviving a photochallenge exhibited a striking increase in proliferation, migration and invasion rates, iNOS/NO again playing a dominant role. Also observed was a large iNOS/NO‐dependent increase in matrix metalloproteinase‐9 activity, decrease in tissue inhibitor of metalloproteinase‐1 expression and increase in survivin and S100A4 expression, each effect being consistent with accelerated migration/invasion as a prelude to metastasis. Our findings suggest introduction of iNOS inhibitors as pharmacologic adjuvants for glioblastoma PDT.     

Nitric oxide agents impair insulin-mediated signal transduction in rat skeletal muscle

Background  

Evidence demonstrates that exogenously administered nitric oxide (NO) can induce insulin resistance in skeletal muscle. We have investigated the modulatory effects of two NO donors, S-nitroso-N-acetyl-D, L-penicillamine (SNAP) and S-nitrosoglutathione (GSNO) on the early events in insulin signaling in rat skeletal myocytes.     

A simple HPLC-fluorescence detection of nitric oxide in cultivated plant cells by in situ derivatization with 2,3-diaminonaphthalene.

An HPLC method with fluorescence detection for the determination of nitric oxide (NO) in cultivated plant cells (Agave pacifica, Agavaceae) was developed. NO was derivatized in situ with 2,3-diaminonaphthalene (DAN) as a labeling reagent and converted to 1(H)-naphthotriazole. The maximum peak height of the derivative was observed by incubation for 3 h at 25 degrees C with 0.2 mM DAN. Excess reagent in cells was removed by washing 3 times with 5 ml of water. The calibration curve for authentic standard of DAN-NO spiked to cultivated plant cells showed a good linearity (r = 0.995) in the range of 5.0 to 50 pmol/g cell. The detection limit at a signal-to-noise ratio of 3 was 3.4 pmol/g cells. The proposed method was successfully applied to the monitoring of NO concentration with cell growth. The effect of thermal treatment on the concentration of NO in plant cells was also examined. The concentration of NO in cells treated at 5 degrees C for 1 h was significantly higher than that treated at 25 degrees C and 35 degrees C for 1 h (n = 3, p < 0.05).