Cytokine-mediated transcriptional induction of the human inducible nitric oxide synthase gene requires both activator protein 1 and nuclear factor kappaB-binding sites

Anti-inflammatory and chondroprotective activity of (+)-α-pinene: structural and enantiomeric selectivity

Previous studies have suggested that α-pinene, a common volatile plant metabolite, may have anti-inflammatory effects in human chondrocytes, thus exhibiting potential antiosteoarthritic activity. The objective of this study was to further characterize the potential antiosteoarthritic activity of selected pinene derivatives by evaluating their ability to modulate inflammation and extracellular matrix remodeling in human chondrocytes and to correlate the biological and chemical properties by determining whether the effects are isomer- and/or enantiomer-selective. To further elucidate chemicopharmacological interactions, the activities of other naturally occurring monoterpenes with the pinane nucleus were also investigated. At noncytotoxic concentrations, (+)-α-pinene (1) elicited the most potent inhibition of the IL-1β-induced inflammatory and catabolic pathways, namely, NF-κB and JNK activation and the expression of the inflammatory (iNOS) and catabolic (MMP-1 and -13) genes. (-)-α-Pinene (2) was less active than the (+)-enantiomer (1), and β-pinene (3) was inactive. E-Pinane (4) and oxygenated pinane-derived compounds, pinocarveol (5), myrtenal (6), (E)-myrtanol (7), myrtenol (8), and (Z)-verbenol (9), were less effective or even completely inactive and more cytotoxic than the pinenes tested (1-3). The data obtained show isomer- and enantiomer-selective anti-inflammatory and anticatabolic effects of α-pinene in human chondrocytes, (+)-α-pinene (1) being the most promising for further studies to determine its potential value as an antiosteoarthritic drug.

Anti-inflammatory activity of a methanol extract from Ardisia tinctoria on mouse macrophages and paw edema

Ardisia tinctoria (AT) is a plant of the Myrsinaceae family. No studies on its anti-inflammatory effects have yet been reported. This study investigated the anti-inflammatory activity of AT. A non-cytotoxic methanol extract of AT inhibited the expression of inducible NO synthase (iNOS) and cyclooxygenase-2 (COX-2), leading to significantly reduced levels of nitric oxide (NO) and prostaglandin E2 (PGE2) and of two proteins regulated by these, interleukin-1β (IL-1β) and IL-6, in lipopolysaccharide (LPS)-stimulated RAW 264.7 macrophage cells. The thickness of paw edema induced in vivo in mice by carrageenan administration was effectively reduced by the AT extract. Translocation of the nuclear factor-κB (NF-κB) subunit 65 (p65) into the nucleus and phosphorylation of mitogen-activated protein kinase kinase (MEK) and extracellular signal-related kinase (ERK) were inhibited by the AT extract. Our results indicated that a methanol extract of AT downregulates the inflammatory response by blocking phosphorylation of MEK and ERK and activation of NF-κB. To the best of our knowledge, this is the first study of anti-inflammatory effects of an AT extract, and demonstrates its potential in the treatment of inflammatory diseases.

microRNA and human inducible nitric oxide synthase

Regulation of human inducible nitric oxide synthase (iNOS) expression involves both transcriptional and posttranscriptional mechanisms. Human iNOS gene transcription is controlled in a cell type-specific manner by extracellular cytokines. Transcriptional regulation of human iNOS gene involves transcription factors NF-κB, Stat-1, AP-1, C/EBPβ, KLF6, Oct 1, and NRF. Important posttranscriptional mechanisms also regulate human iNOS mRNA stability through RNA binding proteins HuR, TTP, KSRP, and PABP. Recently, there are several miRNAs that were validated to regulate human and rodent iNOS gene expression. Among them, miR-939 and miR-26a were identified to bind with the human iNOS 3'-UTR and exert a translational blockade of human iNOS protein synthesis.

Extra virgin olive oil polyphenolic extracts downregulate inflammatory responses in LPS-activated murine peritoneal macrophages suppressing NFκB and MAPK signalling pathways

Extra virgin olive oil (EVOO) is obtained from the fruit of the olive treeOlea europaeaL. Phenolic compounds present in EVOO have recognized anti-oxidant and anti-inflammatory properties.

Abarema cochliacarpos reduces LPS-induced inflammatory response in murine peritoneal macrophages regulating ROS-MAPK signal pathway

ETHNOPHARMACOLOGICAL RELEVANCE

Abarema cochliacarpos (Gomes) Barneby and Grimes (Fabaceae), known by the vulgar name of Babatenã, has been traditionally used in Northeast Brazil, as an anti-inflammatory remedy. Previous studies have demonstrated its anti-inflammatory and antiulcer effects in skin lesion, alcohol gastric ulcer and acute and chronic colitis.

AIMS

The present study was designed to evaluate the antioxidant and anti-inflammatory effects of the butanolic fraction from A. cochliacarpos (BFAC) and its major flavonoid, (+)-catechin, in LPS-stimulated murine peritoneal macrophages. Moreover, we studied the role of mitogen-activated protein kinase (MAPK)s and NF-kB signaling pathways possibly involved in the beneficial effects.

MATERIALS AND METHODS

The quantification of the extract was carried out by ultra-performance liquid chromatography analysis. Cell viability was determined using SRB assay. Nitric oxide (NO) production was analyzed by Griess method and intracellular reactive oxygen species (ROS) by fluorescence analysis. In addition, cyclooxygenase (COX-2) and inducible nitric oxide synthase (iNOS) expression, MAPK activation and IkappaBalpha (IKBα) degradation, were determined by Western blot.

RESULTS

After BFAC characterization, (+)-catechin was revealed as its major constituent. Both BFAC and (+)-catechin, exerted significant anti-oxidant and anti-inflammatory effects inhibiting LPS-induced intracellular ROS and NO production in peritoneal macrophages. Additionally, the extract but also its major component reduced pro-inflammatory proteins expression probably through c-Jun N-terminal kinase and p38 MAPK signaling pathways.

CONCLUSION

These data suggest that the beneficial effects of BFAC might be mediated, at least in part, by the presence of (+)-catechin. Conclusively our findings confirm the potential of A. cochliacarpos as a new therapeutic strategy for the management of inflammatory and oxidative stress-related diseases.

Salidroside attenuates LPS-stimulated activation of THP-1 cell-derived macrophages through down-regulation of MAPK/NF-kB signaling pathways

Excessive activation of macrophages is implicated in various inflammatory injuries. Salidroside (Sal), one of the main bioactive components of Rhodiola Sachalinensis, has been reported to possess anti-inflammatory activities. This study aimed to examine the effect of Sal on the activation of macrophages and the possible mechanism. The lipopolysaccharide (LPS)-stimulated phrobol 12-myristate 13-acetate (PMA)-differentiated THP-1 macrophage models were established. The changes in the inflammatory profiles of THP-1-derived macrophages were determined. The results showed that Sal significantly decreased the expression of inducible nitric oxide synthase (iNOS), cyclooxygenase-2 (COX2), interleukin-1beta (IL-1β), interleukin-6 (IL-6) and tumor necrosis factor-α (TNF-α) at both mRNA and protein levels in THP-1-derived macrophages, and the effect was dose-depedent. Moreover, NF-κB activation was significantly suppressed and the phosphorylation of ERK, p38 and JNK was substantially down-regulated after Sal treatment. The findings suggested that Sal can suppress the activation of LPS-stimulated PMA-differetiated THP-1 cells, as evidenced by the decreased expression of iNOS, COX2, IL-1β, IL-6 and TNF-α, and the mechanism involves the inhibition of NF-κB activation and the phosphorylation of the MAPK signal pathway.

Modulation of ENaC, CFTR, and iNOS expression in bronchial epithelial cells after stimulation with Staphylococcus epidermidis (94B080) and Staphylococcus aureus (90B083)

Bacteria affect the respiratory epithelium, which is covered by airway surface liquid (ASL) and mucus. Ion concentrations in the ASL are determined by the cystic fibrosis transmembrane conductance regulator (CFTR) and the epithelial Na(+) channel (ENaC). Neonatal sepsis is a major risk factor for subsequent pulmonary disease in preterm newborns. Predominating are coagulase-negative staphylococci (e.g., Staphylococccus epidermidis and Staphylococccus aureus). The aim of this study was to investigate modulation of CFTR, ENaC, mucins, proinflammatory cytokines, and inducible nitric oxide synthase (iNOS) in respiratory epithelial cells after S. epidermidis 94B080 and S. aureus 90B083 exposure. Bronchial epithelial cells were incubated with S. epidermidis 94B080 and S. aureus 90B083 (neonatal blood isolates) for 1-36 h. Expression of CFTR, ENaC, iNOS, and mucins was analyzed by real-time PCR and Western blotting. Release of cytokines was analyzed by ELISA, and production of NO by the Griess assay. Expression of CFTR significantly decreased after 36 h incubation with S. epidermidis and more prominently with S. aureus, whereas S. epidermidis caused a significant increase in the expression of β- and γ-ENaC. Expression of iNOS increased, but NO was not detected. Both staphylococci caused a decrease in the intracellular Ca(2+) concentration. S. aureus induced increased secretion of IL-6, IL-8, and transforming nuclear factor (TNF)-α in a time-dependent manner as compared with S. epidermidis. In conclusion, expression of ENaC, CFTR, and iNOS is modulated by exposure to S. aureus 90B083 and S. epidermidis 94B080. S. aureus is more potent in causing release of IL-6, IL-8, and TNF-α by bronchial epithelial cells as compared with S. epidermidis. The mRNA expression for the mucus proteins MUC2, MUC5AC, and MUC5B could not be measured, neither in the presence nor in the absence of bacteria.

Regulation of nitrogen monoxide production in human malaria

The production of nitrogen monoxide (NO(*)) contributes to defence mechanisms of the immune system to fight infectious agents like bacteria and protozoa. The respective gene producing the NO(*) has to be carefully regulated so that an overwhelming response kills the pathogen but does not harm the host. A strong increase in the NO(*) production for efficient anti-microbial activity is achieved by the transcriptional up-regulation of the nitric oxide synthase 2 gene (NOS2 or inducible nitric oxide synthase, iNOS), which is regulated by a number of transcription factors that are vital in the regulation of many genes involved in the immune response. Binding sites for members of the nuclear factor-kappaB (NF-kappaB) and activator protein 1 (AP1) families have been detected and seem to fulfil their function in vitro. Genetic variants of the iNOS genes have been identified that are linked to NO(*) production and to the outcome of malaria in humans.

Competitive metabolism of L-arginine: arginase as a therapeutic target in asthma

Exhaled breath nitric oxide (NO) is an accepted asthma biomarker. Lung concentrations of NO and its amino acid precursor, L-arginine, are regulated by the relative expressions of the NO synthase (NOS) and arginase isoforms. Increased expression of arginase I and NOS2 occurs in murine models of allergic asthma and in biopsies of asthmatic airways. Although clinical trials involving the inhibition of NO-producing enzymes have shown mixed results, small molecule arginase inhibitors have shown potential as a therapeutic intervention in animal and cell culture models. Their transition to clinical trials is hampered by concerns regarding their safety and potential toxicity. In this review, we discuss the paradigm of arginase and NOS competition for their substrate L-arginine in the asthmatic airway. We address the functional role of L-arginine in inflammation and the potential role of arginase inhibitors as therapeutics.

Phlorofucofuroeckol A suppresses expression of inducible nitric oxide synthase, cyclooxygenase-2, and pro-inflammatory cytokines via inhibition of nuclear factor-κB, c-Jun NH2-terminal kinases, and Akt in microglial cells

Microglial activation has been implicated in many neurological disorders for its inflammatory and neurotrophic effects. In this study, we investigated the effects of phlorofucofuroeckol A isolated from Ecklonia stolonifera Okamura on the production of inflammatory mediators in lipopolysaccharide (LPS)-stimulated microglia. Pre-treatment of phlorofucofuroeckol A attenuated the productions of nitric oxide, prostaglandin E2, and pro-inflammatory cytokines in LPS-stimulated microglia. Profoundly, phlorofucofuroeckol A treatment showed inactivation of nuclear factor-κB (NF-κB) by preventing the degradation of inhibitor κB-α and the nuclear translocation of p65 NF-κB subunit. Moreover, phlorofucofuroeckol A inhibited the activation of c-Jun NH2-terminal kinases (JNKs), p38 mitogen-activated protein kinase (MAPK), and Akt, but not that of extracellular signal-regulated kinase. These results indicate that phlorofucofuroeckol A inhibits the LPS-induced expression of inflammatory mediators through inactivation of NF-κB, JNKs, p38 MAPK, and Akt pathways. These findings suggest that phlorofucofuroeckol A can be considered as a nutraceutical candidate for the treatment of neuroinflammation in neurodegenerative diseases.

Anti-inflammatory effect of hexane fraction from Myagropsis myagroides ethanolic extract in lipopolysaccharide-stimulated BV-2 microglial cells

OBJECTIVES

Microglial activation has been implicated in neurological disorders for its inflammatory and neurotrophic effects. We investigated the anti-inflammatory effect of the hexane fraction from Myagropsis myagroides (Mertens ex Turner) Fensholt ethanolic extract and its underlying molecular mechanism in lipopolysaccharide-stimulated microglia.

METHODS

Various solvent fractions prepared from the ethanolic extract of M. myagroides were analysed for total phenolic content, 2,2-diphenyl-1-picrylhydrazyl radical-scavenging activity and inhibitory effect on nitric oxide (NO) production in activated BV-2 microglia. We measured prostaglandin E2 (PGE2 ) and pro-inflammatory cytokine levels by enzyme-linked immunosorbent assay. Expression of inflammatory enzymes was analysed by Western blot. Nuclear translocation and activation of nuclear factor-kappaB (NF-κB) were determined by immunofluorescence and reporter gene assay, respectively.

KEY FINDINGS

Among the fractions, the hexane fraction (MMH), rich in fatty acid, showed the highest inhibitory activity on NO generation. Pretreatment with MMH decreased mRNA and protein levels of inducible NO synthase and cyclooxygenase-2, resulting in a decrease in NO and PGE2 in LPS-stimulated BV-2 cells. Furthermore, MMH inhibited the production of inducible pro-inflammatory cytokines at their transcriptional level via inactivation of NF-κB. MMH inhibited the activation of extracellular signal-regulated kinase and c-Jun N-terminal kinase.

CONCLUSIONS

These results indicate that MMH has a strong anti-inflammatory activity in LPS-stimulated microglia, suggesting that MMH can be used as a therapeutic agent against neuroinflammatory diseases.

Water extract of processed Hydrangea macrophylla (Thunb.) Ser. leaf attenuates the expression of pro-inflammatory mediators by suppressing Akt-mediated NF-κB activation

Although Hydrangea macrophylla is native to Northeast Asia and widely cultivated in many parts of the world, no studies on its anti-inflammatory effects have been reported. In this study, we evaluated the anti-inflammatory effect of a water extract of processed H. macrophylla leaf (WH) in lipopolysaccharide (LPS)-stimulated RAW264.7 macrophage cells. WH inhibited the expression of LPS-stimulated pro-inflammatory mediators such as nitric oxide (NO), prostaglandin E2 (PGE2), and tumor necrosis factor-α (TNF-α), as well as their regulatory genes inducible NO synthase (iNOS), cyclooxygenase-2 (COX-2), and TNF-α without any accompanying cytotoxicity. Moreover, WH significantly suppressed the LPS-induced DNA-binding activity of nuclear factor-κB (NF-κB), as well as the nuclear translocation of the NF-κB subunits, p65 and p50 by suppressing of IκBα phosphorylation and degradation. WH also increased Akt dephosphorylation, leading to the suppression of the DNA-binding activity of NF-κB in LPS-stimulated RAW264.7 macrophage cells. Our results indicate that WH downregulates the expression of pro-inflammatory mediators such as NO, PGE2, and TNF-α by suppressing the Akt-mediated NF-κB activity in LPS-stimulated RAW264.7 macrophage cells.

Hexane fraction from Laminaria japonica exerts anti-inflammatory effects on lipopolysaccharide-stimulated RAW 264.7 macrophages via inhibiting NF-kappaB pathway

PURPOSE

Laminaria japonica is a representative marine brown alga used as a culinary item in East Asia. L. japonica extract was shown to exert various biological activities; however, its anti-inflammatory activity has not been reported. The aim of this study is to investigate the molecular mechanisms underlying its anti-inflammatory action.

METHODS

Anti-inflammatory mechanisms of L. japonica n-hexane fraction (LHF) were assessed using lipopolysaccharide (LPS)-stimulated RAW 264.7 macrophages. An anti-inflammatory compound isolated from LHF by reverse-phase chromatography was identified using nuclear magnetic resonance (NMR) spectroscopy.

RESULTS

Our results indicate that LHF significantly inhibited LPS-stimulated nitric oxide (NO) and prostaglandin E(2) (PGE(2)) secretion in a dose-dependent manner and suppressed the expression of inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2) with no cytotoxicity. As results, levels of pro-inflammatory cytokines were significantly reduced by pretreatment of LHF in LPS-stimulated RAW 264.7 cells. Treatment of LHF strongly suppressed nuclear factor-κB (NF-κB) promoter-driven expression and nuclear translocation of NF-κB by preventing proteolytic degradation of inhibitor of κB (IκB)-α in LPS-stimulated RAW 264.7 cells. Moreover, LHF inhibited the phosphorylation of Akt and mitogen-activated protein kinase (MAPK) in LPS-stimulated RAW 264.7 cells. One of the anti-inflammatory compounds was isolated from LHF and identified as fucoxanthin.

CONCLUSIONS

These results indicate that the LHF-mediated inhibition of NO and PGE(2) secretion in LPS-stimulated macrophages is regulated by NF-κB inactivation through inhibition of IκB-α, MAPKs, and Akt phosphorylation. LHF may be considered as a functional food candidate for the prevention or treatment of inflammatory diseases.

Hexane fraction from Sargassum fulvellum inhibits lipopolysaccharide-induced inducible nitric oxide synthase expression in RAW 264.7 cells via NF-κB pathways

Sargassum fulvellum (Turner) C. Agardh has been used to treat various inflammatory diseases, including lump, dropsy, swollen and painful scrotum, and urination problems for several centuries with no side effects. This study aims to investigate the anti-inflammatory effect of the hexane fraction of S. fulvellum (HFS) in lipopolysaccharide (LPS)-stimulated RAW 264.7 cells and phorbol 12-myristate 13-acetate (PMA)-induced mouse-ear edema. The anti-inflammatory activity of HFS in LPS-stimulated RAW 264.7 cells was investigated by assessing the inhibition of nitric oxide (NO) and pro-inflammatory cytokine production during Griess reaction and enzyme-linked immunosorbent assay (ELISA), respectively. The molecular mechanisms that underlie the anti-inflammatory action of HFS were investigated by analyzing the activation of transcription factor and its upstream signaling proteins. Additionally, an in vivo study of the anti-inflammatory effect of HFS was carried out using PMA-induced mouse-ear edema. HFS inhibited LPS-induced NO production in a dose-dependent manner and suppressed the expression of inducible NO synthase (iNOS) in the RAW 264.7 cells. Further, HFS reduced the production of pro-inflammatory cytokines in the LPS-stimulated RAW 264.7 cells. HFS significantly inhibited LPS-induced nuclear factor kappa B (NF-κB) transcriptional activity and NF-κB translocation into the nucleus by preventing degradation of inhibitor κB-α. Moreover, HFS inhibited the activation of Akt and mitogen-activated protein kinases (MAPKs) in the LPS-stimulated RAW 264.7 cells. Furthermore, HFS suppressed PMA-induced mouse-ear edema. The above data indicate that the anti-inflammatory effects of HFS on LPS-stimulated cells are associated with the suppression of NF-κB through the inhibition of MAPKs and Akt phosphorylation.

β-Ionone attenuates LPS-induced pro-inflammatory mediators such as NO, PGE2 and TNF-α in BV2 microglial cells via suppression of the NF-κB and MAPK pathway

β-Ionone, a precursor of carotenoids, possesses a variety of biological properties such as anti-cancerous, anti-mutagenic and anti-microbial activity. Nevertheless, anti-inflammatory effects of β-ionone remain unknown. In this study, we investigated whether ION attenuates the expression of lipopolysaccharide (LPS)-induced pro-inflammatory mediators such as nitric oxide (NO), prostaglandin E2 (PGE2) and tumor necrosis factor-α (TNF-α) in BV2 microglia cells. Our data showed that β-ionone significantly inhibits secretion of NO, PGE2 and TNF-α. β-Ionone also inhibits the expression of inducible NO synthesis (iNOS), cyclooxygenase-2 (COX-2) and TNF-α protein and their mRNA in LPS-stimulated BV2 microglia cells. In addition, β-ionone significantly reduced DNA-binding activity of nuclear factor-κB (NF-κB) through suppression of nuclear translocation of p50 and p65. We showed that NF-κB inhibitor N-acetyl-L-cysteine (NAC) effectively attenuates the expression of LPS-stimulated iNOS, COX-2 and TNF-α. We also found that LPS-induced NF-κB activation is significantly regulated through inhibition of Akt phosphorylation in the presence of β-ionone. Finally, we showed that β-ionone substantially inhibits the phosphorylation of mitogen-activated protein kinases (MAPKs), including ERK1/2, p38 and JNK, which are closely related to regulation of pro-inflammatory mediator secretion. Taken together, these data imply that β-ionone regulates LPS-induced NF-κB-dependent inflammatory pathways through suppression of Akt and MAPK activation.

Modulation of Asthma Pathogenesis by Nitric Oxide Pathways and Therapeutic Opportunities

Asthma, a chronic airway inflammatory disease is typically associated with high levels of exhaled nitric oxide (NO). Over the past decades, extensive research has revealed that NO participates in a number of metabolic pathways that contribute to animal models of asthma and human asthma. In asthmatic airway, high levels of NO lead to greater formation of reactive nitrogen species (RNS), which modify proteins adversely affecting functional activities. In contrast, high levels of NO are associated with lower than normal levels of S-nitrosothiols, which serve a bronchodilator function in the airway. Detailed mechanistic studies have enabled the development of compounds that target NO metabolic pathways, and provide opportunities for novel asthma therapy. This review discusses the role of NO in asthma with the primary focus on therapeutic opportunities developed in recent years.

Anti-inflammatory effects of phlorofucofuroeckol B-rich ethyl acetate fraction obtained from Myagropsis myagroides on lipopolysaccharide-stimulated RAW 264.7 cells and mouse edema

Myagropsis myagroides has been used as a Chinese medicine and its extract has shown various biological activities, however, its anti-inflammatory mechanism remains unknown. In this study, we investigated the inhibitory effects of the ethyl acetate fraction of M. myagroides (EFM) on the production of inflammatory mediators and pro-inflammatory cytokines in lipopolysaccharides (LPS)-stimulated RAW 264.7 cells. EFM significantly inhibited LPS-induced production of nitric oxide (NO), prostaglandin E(2), and pro-inflammatory cytokines in a dose-dependent manner and suppressed the production of inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 in RAW 264.7 cells. Inhibitory effect of EFM on iNOS expression and NO production was further confirmed using LPS-activated mouse peritoneal macrophages. EFM treatment strongly suppressed the activation of nuclear factor-kappa B (NF-κB) by suppressing phosphorylation of Akt and extracellular signal-regulated kinases (ERKs). EFM as well as phlorofucofuroeckol B (PFF-B), a major compound isolated from EFM, reduced ear edema induced by phorbol 12-myristate 13-acetate in mice. These results indicate that the anti-inflammatory effect of EFM, rich in PFF-B, on LPS-stimulated macrophages is regulated by the inhibition of NF-κB pathway through the inhibition of ERKs and Akt phosphorylation in LPS-stimulated macrophage cells.

High mobility group box 1 protein synergizes with lipopolysaccharide and peptidoglycan for nitric oxide production in mouse peritoneal macrophages in vitro

Extracellular high mobility group box 1 (HMGB1) protein and nitric oxide (NO) has been credited with multiple inflammatory functions using in vivo and in vitro systems. Therefore, delineating their regulation may be an important therapeutic strategy for the treatment of sepsis. In the present study, it is demonstrated that recombinant HMGB1 (rHMGB1) synergizes with sub threshold concentration of TLR2 agonist (PGN; 1 μg/ml) as well as with TLR4 agonist (LPS; 1 ng/ml) to induce NO release in mouse peritoneal macrophages. The enhanced iNOS expression was also observed at the transcription and translational level. Co-incubation of macrophages with rHMGB1 with either PGN or LPS showed enhanced expression of TLR2, TLR4 and RAGE. TLR2, TLR4 or RAGE knockdown macrophages effectively inhibited the rHMGB1+PGN or LPS induced NO synergy. It was further observed that the JNK MAPK inhibitor SP600125 attenuated the PGN+rHMGB1 induced iNOS/NO synergy whereas p38 MAPK inhibitor SB908912 inhibited iNOS/NO synergy induced by LPS+rHMGB1. It was also observed that the activation of NF-κB is essential for the synergy as the pharmacological inhibition or siRNA knockdown of NF-κB (cRel) significantly reduced the rHMGB1+PGN or rHMGB1+LPS induced enhanced iNOS/NO expression. Altogether, the data suggests that the co-incubation of macrophages with rHMGB1 with either LPS or PGN induces the synergistic effect on iNOS expression and NO release by the upregulation of surface receptors (TLR2, TLR4 and RAGE) which in turn amplifies the MAPKs (p38 and JNK) and NF-κB activation and results in enhanced iNOS expression and NO production.

Anti-inflammatory effect of ethanolic extract from Myagropsis myagroides on murine macrophages and mouse ear edema

BACKGROUND

This study aims to investigate anti-inflammatory effect of ethanolic extract of Myagropsis myagroides (EMM) in the lipopolysaccharide (LPS)-stimulated RAW 264.7 macrophages and the phorbol 12-myristate 13-acetate (PMA)-induced ear edema in mice, and to clarify its underlying molecular mechanisms.

METHODS

The levels of nitric oxide (NO), prostaglandin E2 (PGE2), and pro-inflammatory cytokines were measured by Griess assay and enzyme linked immunosorbent assay. The expressions of inducible nitric oxide synthase (iNOS), cyclooxygenase-2 (COX-2), mitogen-activated protein kinases (MAPKs), and Akt were measured using Western blotting. Nuclear translocation and transcriptional activation of nuclear factor-κB (NF-κB) were determined by immunocytochemistry and reporter gene assay, respectively. PMA-induced mouse ear edema was used as the animal model of inflammation. Anti-inflammatory compounds in EMM were isolated using high-performance liquid chromatography and identified by nuclear magnetic resonance.

RESULTS

EMM significantly inhibited the production of NO, PGE2, and pro-inflammatory cytokines in a dose-dependent manner and suppressed the expression of iNOS and COX-2 in LPS-stimulated RAW 264.7 cells. EMM strongly suppressed nuclear translocation of NF-κB by preventing degradation of inhibitor of κB-α as well as by inhibiting phosphorylation of Akt and MAPKs. EMM reduced ear edema in PMA-induced mice. One of the anti-inflammatory compounds in EMM was identified as 6,6'-bieckol.

CONCLUSIONS

These results suggest that the anti-inflammatory properties of EMM are associated with the down-regulation of iNOS, COX-2, and pro-inflammatory cytokines through the inhibition of NF-κB pathway in LPS-stimulated macrophages.

Dichloromethane fraction of Laminaria japonica ethanolic extract inhibits lipopolysaccharide-induced nitric oxide synthase and cyclooxygenase-2 expression in RAW 264.7 cells via NF-κB pathway

Strong anti-inflammatory activity has been found in Laminaria japonica dichloromethane fraction (LDF); however, the molecular mechanisms underlying its anti-inflammatory activity are not reported. Our results indicated that LDF inhibited LPS-induced nitric oxide and prostaglandin E(2) production in a dose-dependent manner and suppressed the expression of inducible nitric oxide synthase (iNOS) and cyclooxygenase 2 (COX-2) in RAW 264.7 cells. Also, levels of pro-inflammatory cytokines such as tumor necrosis factor-α, interleukin (IL)-1β and IL-6 were remarkably reduced by LDF in LPS-treated RAW 264.7 cells. LDF greatly inhibited promoter activity of nuclear factor-κB (NF-κB) and translocation of NF-κB subunits by prevention of the degradation of inhibitor κB-α in LPS-treated RAW 264.7 cells (p < 0.05). Moreover, LDF inhibited activation of mitogen-activated protein kinases and AKT in LPS-treated RAW 264.7 cells. These results indicate that the LDF downregulates iNOS and COX-2 expressions through the suppression of NF-κB pathway associated with inhibition of multiple signaling proteins.

Anti-inflammatory activities of an ethanol extract of Ecklonia stolonifera in lipopolysaccharide-stimulated RAW 264.7 murine macrophage cells

Ecklonia stolonifera is a brown alga that was shown to have antioxidant, anti-inflammatory, tyrosinase inhibitory, and chemopreventive activities. However, the molecular mechanisms underlying its anti-inflammatory activity remain unclear. In this study, we investigated the molecular mechanism of the anti-inflammatory action of E. stolonifera ethanolic extracts (ESE) using lipopolysaccharide (LPS)-stimulated RAW 264.7 cells. ESE inhibited LPS-induced nitric oxide (IC(50) = 72 ± 1.9 μg/mL) and prostaglandin E(2) (IC(50) = 98 ± 5.3 μg/mL) production in a dose-dependent manner and suppressed the expression of inducible nitric oxide synthase and cyclooxygenase-2 in RAW 264.7 cells. ESE also reduced the production of pro-inflammatory cytokines in LPS-stimulated RAW 264.7 cells. LPS-induced nuclear factor-κB (NF-κB) transcriptional activity and NF-κB translocation into the nucleus were significantly inhibited by ESE treatment through the prevention of the degradation of inhibitor κB-α. Moreover, ESE inhibited the activation of Akt, ERK, JNK1/2, and p38 MAPK in LPS-stimulated RAW 264.7 cells. The main components with anti-inflammatory activity in ESE were identified as phlorofucofuroeckol A and B based on the inhibition of NO production. Our results indicate that ESE can be considered as a potential source of therapeutic agents for inflammatory diseases.

Molecular Mechanisms Underlying Anti-Inflammatory Actions of 6-(Methylsulfinyl)hexyl Isothiocyanate Derived from Wasabi (Wasabia japonica)

6-(Methylsulfinyl)hexyl isothiocyanate (6-MSITC) is a major bioactive compound in wasabi (Wasabia japonica), which is a typical Japanese pungent spice. Recently, in vivo and in vitro studies demonstrated that 6-MSITC has several biological properties, including anti-inflammatory, antimicrobial, antiplatelet, and anticancer effects. We previously reported that 6-MSITC strongly suppresses cyclooxygenase-2 (COX-2), inducible nitric oxide synthase (iNOS), and cytokines, which are important factors that mediate inflammatory processes. Moreover, molecular analysis demonstrated that 6-MSITC blocks the expressions of these factors by suppressing multiple signal transduction pathways to attenuate the activation of transcriptional factors. Structure-activity relationships of 6-MSITC and its analogues containing an isothiocyanate group revealed that methylsulfinyl group and the length of alkyl chain of 6-MSITC might be related to high inhibitory potency. In this paper, we review the anti-inflammatory properties of 6-MSITC and discuss potential molecular mechanisms focusing on inflammatory responses by macrophages.

Role of AP-1 family proteins in regulation of inducible nitric oxide synthase (iNOS) in human neutrophils

The aim of the study was to assess the activity of AP-1 family proteins, e.g. Fra-1, Fra-2, JunB, JunD, and FosB, engaged in the regulation of inducible nitric oxide synthase (iNOS) expression and the production of NO by neutrophils (PMN) exposed to N-nitrosodimethylamine (NDMA) xenobiotic. Isolated human PMN were incubated in the presence of NDMA. iNOS mRNA expression was then analyzed using Northern blot and the expression of other proteins in the cytoplasmic and nuclear fractions were assessed using Western blot. The obtained results indicate that NDMA increased iNOS mRNA and protein expression in human PMN. Furthermore, it increased the expression of Fra-1, Fra-2, JunB, and JunD in the cytoplasmic fraction, and FosB expression in the fractions of analyzed cells. As a consequence of inhibiting p38 pathway and JNK, reduced iNOS expression and NO production was noted in PMN exposed to NDMA. Inhibition of the p38 pathway resulted in reduced expression of all analyzed proteins in the cytoplasmic fraction of PMN exposed to NDMA. Furthermore, increased Fra-2 expression and reduced FosB expression were found in the nuclear fraction of those cells. Inhibiting ERK5 pathway resulted in increased JunB expression in both fractions of the analyzed cells. Therefore, no changes in the expression of analyzed proteins in the presence of NDMA were observed in PMN pre-incubated with JNK pathway inhibitor. In conclusion, the results here indicate a role of Fra-1, Fra-2, JunB, JunD, and FosB transcription factors in the regulation of iNOS expression and NO production by human neutrophils exposed to NDMA.

Involvement of the RNA-binding protein ARE/poly(U)-binding factor 1 (AUF1) in the cytotoxic effects of proinflammatory cytokines on pancreatic beta cells

AIMS/HYPOTHESIS

Chronic exposure of pancreatic beta cells to proinflammatory cytokines leads to impaired insulin secretion and apoptosis. ARE/poly(U)-binding factor 1 (AUF1) belongs to a protein family that controls mRNA stability and translation by associating with adenosine- and uridine-rich regions of target messengers. We investigated the involvement of AUF1 in cytokine-induced beta cell dysfunction.

METHODS

Production and subcellular distribution of AUF1 isoforms were analysed by western blotting. To test for their role in the control of beta cell functions, each isoform was overproduced individually in insulin-secreting cells. The contribution to cytokine-mediated beta cell dysfunction was evaluated by preventing the production of AUF1 isoforms by RNA interference. The effect of AUF1 on the production of potential targets was assessed by western blotting.

RESULTS

MIN6 cells and human pancreatic islets were found to produce four AUF1 isoforms (p42>p45>p37>p40). AUF1 isoforms were mainly localised in the nucleus but were partially translocated to the cytoplasm upon exposure of beta cells to cytokines and activation of the ERK pathway. Overproduction of AUF1 did not affect glucose-induced insulin secretion but promoted apoptosis. This effect was associated with a decrease in the production of the anti-apoptotic proteins, B cell leukaemia/lymphoma 2 (BCL2) and myeloid cell leukaemia sequence 1 (MCL1). Silencing of AUF1 isoforms restored the levels of the anti-apoptotic proteins, attenuated the activation of the nuclear factor-κB (NFκB) pathway, and protected the beta cells from cytokine-induced apoptosis.

CONCLUSIONS/INTERPRETATION

Our findings point to a contribution of AUF1 to the deleterious effects of cytokines on beta cell functions and suggest a role for this RNA-binding protein in the early phases of type 1 diabetes.

Identification of hamster inducible nitric oxide synthase (iNOS) promoter sequences that influence basal and inducible iNOS expression

IFN-γ/LPS-activated hamster (Mesocricetus auratus) macrophages express significantly less iNOS (NOS2) than activated mouse macrophages, which contributes to the hamster's susceptibility to intracellular pathogens. We determined a mechanism responsible for differences in iNOS promoter activity in hamsters and mice. The HtPP (1.2 kb) showed low basal and inducible promoter activity when compared with the mouse, and sequences within a 100-bp region (-233 to -133) of the mouse and hamster promoters influenced this activity. Moreover, within this 100 bp, we identified a smaller region (44 bp) in the mouse promoter, which recovered basal promoter activity when swapped into the hamster promoter. The mouse homolog (100-bp region) contained a cis-element for NF-IL-6 (-153/-142), which was absent in the hamster counterpart. EMSA and supershift assays revealed that the hamster sequence did not support the binding of NF-IL-6. Introduction of a functional NF-IL-6 binding sequence into the hamster promoter or its alteration in the mouse promoter revealed the critical importance of this transcription factor for full iNOS promoter activity. Furthermore, the binding of NF-IL-6 to the iNOS promoter (-153/-142) in vivo was increased in mouse cells but was reduced in hamster cells after IFN-γ/LPS stimulation. Differences in the activity of the iNOS promoters were evident in mouse and hamster cells, so they were not merely a result of species-specific differences in transcription factors. Thus, we have identified unique DNA sequences and a critical transcription factor, NF-IL-6, which contribute to the overall basal and inducible expression of hamster iNOS.

Activation of Akt leading to NF-κB up-regulation in chondrocytes stimulated with fibronectin fragment

Increased fibronectin fragments are thought to contribute to joint destruction in osteoarthritis (OA). However, the mechanism whereby fibronectin fragments cause catabolic activities is not totally understood. While COOH-terminal heparin-binding fibronectin fragment (HBFN-f) has been shown to activate nuclear factor (NF)-κB pathway, intracellular upstream events that cause NF-κB up-regulation in response to HBFN-f remain unclear. Thus, this study was aimed to elucidate the involvement of phosphoinositide-3-OH kinase (PI3K)/Akt pathway in NF-κB activation by HBFN-f in OA chondrocytes. In chondrocyte monolayer cultures, HBFN-f stimulated nitric oxide (NO) production in association with phosphorylation of NF-κB and Akt. Inhibition studies using LY294002 revealed the requirement of PI3K/Akt pathway for NO production and NF-κB activation by HBFN-f. Anti-CD44 treatment with anti-CD44 antibody and hyaluronan resulted in significant inhibition of HBFN-f actions on NO, NF-κB, and Akt. Herein, we provided the first evidence that HBFN-f activates PI3K/Akt pathway leading to up-regulation of NF-κB through interaction with CD44.

Phlorofucofuroeckol A inhibits the LPS-stimulated iNOS and COX-2 expressions in macrophages via inhibition of NF-κB, Akt, and p38 MAPK

We have recently reported that phlorofucofuroeckol A isolated from the edible brown algae Ecklonia stolonifera showed potential antioxidative and anti-inflammatory properties in macrophage stimulated by LPS treatments. In this study, we further investigated the pharmacological characteristic of phlorofucofuroeckol A in regulations of inducible nitric oxide synthase (iNOS) and cyclooxygenase (COX)-2 through regulatory and signaling pathways using LPS-treated RAW 264.7 cells. Treatment with 20 μM of phlorofucofuroeckol A significantly decreased levels of iNOS and COX-2 mRNA induced by LPS stimulation. As results, levels of pro-inflammatory cytokines such as interleukin (IL)-1β, IL-6 and tumor necrosis factor (TNF)-α were significantly reduced by treatments of phlorofucofuroeckol A in LPS-stimulated RAW 264.7 cells. Phlorofucofuroeckol A inhibited promoter activities of inflammatory-mediators (iNOS and COX-2) and transcriptional factors (nuclear factor-κB, NF-κB, and AP-1) in LPS-treated RAW 264.7 cells. Moreover, phlorofucofuroeckol A inhibited activation of Akt and p38 MAPK in LPS-treated RAW 264.7 cells. These results indicate that the phlorofucofuroeckol A regulates iNOS and COX-2 expressions through the NF-κB-dependent transcriptional control associated with inhibition of multiple signaling proteins, suggesting potential candidates of phloroglucinol derivatives for treatments of inflammatory diseases.

Helicobacter pylori attenuates lipopolysaccharide-induced nitric oxide production by murine macrophages

Intragastric growth of Helicobacter pylori and non-Helicobacter microorganisms is thought to be associated with elevated levels of pro-inflammatory cytokines and the production of NO these effects can lead to chronic inflammation. Microorganisms can activate the expression of iNOS and the production of NO by macrophages through stimulation with bacterial LPS. Helicobacter pylori can evade these vigorous immune responses, but the underlying mechanism remains unknown. In this study, we used a murine model of macrophage infection to demonstrate that H. pylori inhibits LPS-induced expression of iNOS and production of NO by macrophages. Suppression of LPS-induced NO production by macrophages led to elevated survival of H. pylori in a trans-well system. This effect was abrogated in macrophages from iNOS(-/-) mice. Analysis of iNOS mRNA and protein levels revealed that H. pylori inhibits iNOS expression at both transcriptional and post-transcriptional levels, and that these effects occurred with live bacteria. Furthermore, the effect of H. pylori involved down-regulation of the mitogen-activated protein kinase pathway and the translocation of active NF-κB into the nucleus. Taken together, our results reveal a new mechanism by which H. pylori modulates the innate immune responses of the host and maintains a persistent infection within the stomach.

Nitric oxide metabolism in asthma pathophysiology

BACKGROUND

Asthma, a chronic inflammatory disease is typically characterized by bronchoconstriction and airway hyper-reactivity.

SCOPE OF REVIEW

A wealth of studies applying chemistry, molecular and cell biology to animal model systems and human asthma over the last decade has revealed that asthma is associated with increased synthesis of the gaseous molecule nitric oxide (NO).

MAJOR CONCLUSION

The high NO levels in the oxidative environment of the asthmatic airway lead to greater formation of reactive nitrogen species (RNS) and subsequent oxidation and nitration of proteins, which adversely affect protein functions that are biologically relevant to chronic inflammation. In contrast to the high levels of NO and nitrated products, there are lower levels of beneficial S-nitrosothiols (RSNO), which mediate bronchodilation, due to greater enzymatic catabolism of RSNO in the asthmatic airways.

GENERAL SIGNIFICANCE

This review discusses the rapidly accruing data linking metabolic products of NO as critical determinants in the chronic inflammation and airway reactivity of asthma. This article is part of a Special Issue entitled Biochemistry of Asthma.

Role of mitogen-activated protein kinases in peptidoglycan-induced expression of inducible nitric oxide synthase and nitric oxide in mouse peritoneal macrophages: extracellular signal-related kinase, a negative regulator

The expression of inducible nitric oxide synthase (iNOS) and the production of nitric oxide (NO) are important host defense mechanisms against pathogens in mononuclear phagocytes. The objectives of this study were to examine the roles of mitogen-activated protein kinases (MAPKs) and transcription factors (nuclear factor-κB [NF-κB] and activating protein 1 [AP-1]) in peptidoglycan (PGN)-induced iNOS expression and NO production in macrophages. PGN is a cell wall component of Gram-positive bacteria that stimulates inflammatory responses both ex vivo and in vivo. PGN stimulates the activation of all three classes of MAPKs, extracellular signal-related kinase (ERK), c-Jun N-terminal kinase (JNK), and p38(mapk) in macrophages, albeit with differential activation kinetics. Using a selective inhibitor of JNK (SP600125) and JNK1/2 small interfering RNA (siRNA) knocked-down macrophages, it was observed that PGN-induced iNOS and NO expression is significantly inhibited. This suggested that JNK MAPK plays an essential role in PGN-induced iNOS expression and NO production. In contrast, inhibition of the ERK pathway using PD98059 dose dependently enhanced PGN-induced iNOS expression and NO production. PGN-induced ERK activation was attenuated in ERK1/2 siRNA knocked-down macrophages; however, NO and iNOS expression were significantly enhanced. An electrophoretic mobility shift assay showed that SP600125 inhibited PGN-induced NF-κB and AP-1 activation, whereas inhibition of the ERK pathway enhanced NF-κB activation, but with no effect on AP-1. These results indicate that the JNK MAPK positively regulate PGN-induced iNOS and NO expression by activating NF-κB and AP-1 transcription factors, whereas the ERK pathway plays a negative regulatory role via affecting NF-κB activity.

ANTI-INFLAMMATORY AND STRUCTURE PROTECTIVE EFFECTS OF HYALURONANS: ARE THESE EFFECTS MOLECULAR WEIGHT DEPENDENT?

Although hyaluronans (HA) has been proved to be effective in the treatment of patients with osteoarthritis and rheumatoid arthritis, the correlations between these effects and the molecular weight (MW) of HA have not been systematically followed. Many different HA preparations are now applied worldwide in clinical usage. Their MWs are very wide ranged (500–6,000 kDa). No systematic review especially addresses the role of HA's MW in the effects of anti-inflammation and structure protection. This study evaluates the literature of the basic and clinical studies on biological, pathological, and clinical effects of different MW HA. Databases were searched through PubMed (period 1978–2009), using the terms hyaluronan, hyaluronic acid, arthritis, and MW. Reference lists of relevant articles were controlled for additional references. We define the "high" MW (HMW) as MW greater than 2,000 kDa and define the "low" MW (LMW) as MW less than 2,000 kDa in the current study. Most data that support the structure protective effect of HA are from the studies with LMW HA. On the other hand, the majority of data that recommend the anti-inflammatory effect of HA are from the reports of HMW HA. In conclusion, we suggest that the effects of LMW HA were more structure protective and those of HMW HA were more anti-inflammatory.

Apocynin restores endothelial dysfunction in streptozotocin diabetic rats through regulation of nitric oxide synthase and NADPH oxidase expressions

AIM

Increased production of reactive oxygen species (ROS) in the diabetic vasculature results in the impairment of nitric oxide (NO)-mediated relaxations leading to impaired endothelium-dependent vasodilation. An important source of ROS is nicotinamide adenine dinucleotide phosphate (NADPH) oxidase, and the inhibition of this enzyme is an active area of interest. This study aimed to investigate the effects of apocynin, an NADPH oxidase inhibitor, on endothelial dysfunction and on the expression of NO synthase (NOS) and NADPH oxidase in thoracic aorta of diabetic rats.

METHOD

Streptozotocin (STZ)-diabetic rats received apocynin (16 mg/kg per day) for 4 weeks. Endothelium-dependent and -independent relaxations were determined in thoracic aortic rings. Western blotting and RT-PCR analysis were performed for NOSs and NADPH oxidase in the aortic tissue.

RESULTS

Acetylcholine-induced relaxations and l-NAME-induced contractions were decreased in diabetic aorta. The decrease in acetylcholine and l-NAME responses were prevented by apocynin treatment without a significant change in plasma glucose levels. Endothelial NOS (eNOS) protein and mRNA expression exhibited significant decrease in diabetes, while protein and/or mRNA expressions of inducible NOS (iNOS) as well as p22(phox) and gp91(phox) subunits of NADPH oxidase were increased, and these alterations were markedly prevented by apocynin treatment.

CONCLUSION

NADPH oxidase expression is increased in diabetic rat aorta. NADPH oxidase-mediated oxidative stress is accompanied by the decreased eNOS and increased iNOS expressions, contributing to endothelial dysfunction. Apocynin effectively prevents the increased NADPH oxidase expression in diabetic aorta and restores the alterations in NOS expression, blocking the vicious cycle leading to diabetes-associated endothelial dysfunction.

Akt-mediated signaling is induced by cytokines and cyclic adenosine monophosphate and suppresses hepatocyte inducible nitric oxide synthase expression independent of MAPK P44/42

Cyclic AMP inhibits the expression of nitric oxide synthase (Harbrecht et al., 1995 [1]) in hepatocytes but the mechanism for this effect is incompletely understood. Cyclic AMP can activate several intracellular signaling pathways in hepatocytes including Protein Kinase A (PKA), cAMP regulated guanine nucleotide exchange factors (cAMP-GEFs), and calcium-mediated Protein Kinases. There is considerable overlap and cross-talk between many of these signaling pathways, however, and how these cascades regulate hepatocyte iNOS is not known. We hypothesized that Akt mediates the effect of cAMP on hepatocyte iNOS expression. Hepatocytes cultured with cytokines and dbcAMP increased Akt phosphorylation up to 2h of culture. Akt phosphorylation was inhibited by the PI3K inhibitor LY294002 (10μM), farnyltranferase inhibitor FTI-276, or transfection with a dominant negative Akt. The cyclic AMP-induced suppression of cytokine-stimulated iNOS was partially reversed by LY294002 and FTI-276. LY294002 also increased NFκB nucleus translocation by Western blot analysis in nuclear extracts. Cyclic AMP increased phosphorylation of Raf1 at serine 259 which was blocked by LY294002 and associated with decreased MAPK P44/42 phosphorylation. However, inhibition of MAPK P44/42 signaling with PD98059 failed to suppress cytokine-induced hepatocyte iNOS expression and did not enhance the inhibitory effect of dbcAMP on iNOS production. A constitutively active MAPK P44/42 plasmid had no effect on cytokine-stimulated NO production. These data demonstrate that dbcAMP regulates hepatocyte iNOS expression through an Akt-mediated signaling mechanism that is independent of MAPK P44/42.

Abnormal modulation of cell protective systems in response to ischemic/reperfusion injury is important in the development of mouse sickle cell hepatopathy

BACKGROUND

Sickle cell disease, a genetic red cell disorder inherited in an autosomal recessive manner, occurs throughout the world. Hepatic dysfunction and liver damage may be present in sickle cell disease, but the pathogenesis of these conditions is only partially understood.

DESIGN AND METHODS

Transgenic mice with sickle cell disease (SAD mice) and wild-type mice were exposed to an ischemic/reperfusion stress. The following parameters were evaluated: hematologic profile, transaminase and bilirubin levels, liver histopathology, and mRNA levels of nuclear factor-κB p65, endothelial nitric oxide synthase, inducible nitric oxide synthase, heme oxygenase-1 and phosphodiesterase-1, -2, -3, and -4 genes in hepatocytes obtained by laser-capture microdissection. Immunoblotting was used to analyze the expression of the following proteins: nuclear factor-κB p65 and phospho-nuclear factor-κB p65, heme oxygenase-1, biliverdin reductase, heat shock protein-70, heat shock protein-27 and peroxiredoxin-6. A subgroup of SAD mice was treated with the phosphodiesterase-4 inhibitor rolipram (30 mg/Kg/day by gavage) during the ischemic/reperfusion protocol.

RESULTS

In SAD mice the ischemic/reperfusion stress induced liver damage compatible with sickle cell disease hepatopathy, which was associated with: (i) lack of hypoxia-induced nuclear factor-κB p65 activation; (ii) imbalance in the endothelial/inducible nitric oxide synthase response to ischemic/reperfusion stress; (iii) lack of hypoxia-induced increased expression of heme oxygenase-1/biliverdin reductase paralleled by a compensatory increased expression of heat shock proteins 70 and 27 and peroxiredoxin-6; and (iv) up-regulation of the phosphodiesterase-1, -2, -3, and -4 genes. In SAD mice the phosphodiesterase-4 inhibitor rolipram attenuated the ischemic/reperfusion-related microcirculatory dysfunction, reduced the inflammatory cell infiltration and induced the heme oxygenase-1/biliverdin reductase cytoprotective systems.

CONCLUSIONS

In SAD mice, sickle cell hepatopathy is associated with perturbed nuclear factor-κB p65 signaling with an imbalance of endothelial/inducible nitric oxide synthase levels, lack of heme oxygenase-1/biliverdin reductase expression and up-regulation of two novel cytoprotective systems: heat shock protein-27 and peroxiredoxin-6.

Effects of low protein intake on the development of the remaining kidney in subtotally nephrectomized immature rats: expression of inducible and endothelial NO synthase

We examined the effects of low protein intake on the development of the remaining kidney in subtotally (5/6) nephrectomized immature rats. Three-week-old rats were kept on a diet containing either 12% protein (Lp rats) or 18% protein (Np rats) for 4 or 8 weeks after subtotal nephrectomy (SUNx). In Western blot analysis, the endothelial NO synthase (eNOS) protein expression of the Lp rats was significantly higher than that of the Np rats at 4 weeks after SUNx. Immunohistochemically, more inducible NO synthase (iNOS)-positive cells were observed in the Np rats than in the Lp rats 4 weeks after SUNx in the distal tubules. In semiquantitative RT-PCR, the expression of renin mRNA was significantly lower in the Lp rats than in the Np rats at 4 and 8 weeks after SUNx. These findings reveal that protein restriction is effective in preventing renal failure of immature rats and that the changes in the expression levels of renin, eNOS, and iNOS is involved in the process of this prevention.

Regulation of NF-kappaB activity and inducible nitric oxide synthase by regulatory particle non-ATPase subunit 13 (Rpn13)

Human Rpn13, also known as adhesion regulating molecule 1 (ADRM1), was recently identified as a novel 19S proteasome cap-associated protein, which recruits the deubiquitinating enzyme UCH37 to the 26S proteasome. Knockdown of Rpn13 by siRNA does not lead to global accumulation of ubiquitinated cellular proteins or changes in proteasome expression, suggesting that Rpn13 must have a specialized role in proteasome function. Thus, Rpn13 participation in protein degradation, by recruiting UCH37, is rather selective to specific proteins whose degradation critically depends on UCH37 deubiquitination activity. The specific substrates for the Rpn13/UCH37 complex have not been determined. Because of a previous discovery of an interaction between Rpn13 and inducible nitric oxide synthase (iNOS), we hypothesized that iNOS is one of the substrates for the Rpn13/UCH37 complex. In this study, we show that Rpn13 is involved in iNOS degradation and is required for iNOS interaction with the deubiquitination protein UCH37. Furthermore, we discovered that IkappaB-alpha, a protein whose proteasomal degradation activates the transcription factor NF-kappaB, is also a substrate for the Rpn13/UCH37 complex. Thus, this study defines two substrates, with important roles in inflammation and host defense for the Rpn13/UCH37 pathway.

XBP1U inhibits the XBP1S-mediated upregulation of the iNOS gene expression in mammalian ER stress response

Upregulation of the inducible nitric oxide synthase (iNOS) gene is associated with many pathological conditions such as endoplasmic reticulum (ER) stress, and X-box binding protein 1 (XBP1) is critical in mediating ER-stress responsive genes, including iNOS. Nonetheless, the mechanism by which XBP1 regulates iNOS during ER stress remains unexplored. Here we show that the active/spliced form of XBP1 protein, XBP1S, directly binds to the AABS (A-activator-binding site) in the iNOS promoter in vitro and in living cells. XBP1S exhibits dose-dependent activation of iNOS-specific reporter gene activity and endogenous iNOS expression. XBP1S is elevated whereas the unspliced form of XBP1, XBP1U, reduced in ER stress in HepG2 cells. In addition, XBP1U binds to XBP1S and this complex is associated with the iNOS promoter in response to ER stress. Furthermore, XBP1U acts as a negative mediator and suppresses XBP1S-mediated induction of iNOS. Collectively, we present the first evidence demonstrating the regulation of iNOS gene induction by the interaction between the spliced and unspliced forms of XBP1 in response to ER stress.

Regulation of the expression of inducible nitric oxide synthase

Nitric oxide (NO) generated by the inducible isoform of nitric oxide synthase (iNOS) is involved in complex immunomodulatory and antitumoral mechanisms and has been described to have multiple beneficial microbicidal, antiviral and antiparasital effects. However, dysfunctional induction of iNOS expression seems to be involved in the pathophysiology of several human diseases. Therefore iNOS has to be regulated very tightly. Modulation of expression, on both the transcriptional and post-transcriptional level, is the major regulation mechanism for iNOS. Pathways resulting in the induction of iNOS expression vary in different cells or species. Activation of the transcription factors NF-kappaB and STAT-1alpha and thereby activation of the iNOS promoter seems to be an essential step for the iNOS induction in most human cells. However, at least in the human system, also post-transcriptional mechanisms involving a complex network of RNA-binding proteins build up by AUF1, HuR, KSRP, PTB and TTP is critically involved in the regulation of iNOS expression. Recent data also implicate regulation of iNOS expression by non-coding RNAs (ncRNAs).

Toll-like receptor 4 and inducible nitric oxide synthase gene polymorphisms are associated with Type 2 diabetes

BACKGROUND

The toll-like receptor 4 (TLR4) and inducible nitric oxide synthase are proteins from the innate immune system that, when activated, can induce insulin resistance. Polymorphisms in these genes, TLR4 and NOS2, respectively, could affect the immune response, as well as the prevalence of Type 2 diabetes (T2DM).

OBJECTIVE

The aim of the present study was to investigate the contribution of four polymorphisms (two from TLR4 and two from NOS2) to susceptibility to T2DM in a southeast Brazilian population.

DESIGN

A total of 211 patients with T2DM and 200 unrelated controls were genotyped for the Asp299Gly and Thr399Ile polymorphisms of the TLR4 gene and for the insertion (I)/deletion (D) AAAT and (CCTTT)n polymorphisms of the NOS2 promoter gene.

RESULTS

With regard to the NOS2 promoter region, the data showed that the I allele of the I/D AAAT polymorphism was more prevalent in the T2DM group and that the L/L genotype of the (CCTTT)n polymorphism was also more frequent in the same group. In contrast, the 299Gly allele and the 399Ile allele from the Asp299Gly and Thr399Ile TLR4 gene polymorphisms, respectively, were associated with protection of T2DM. It is believed that the persistence of these genetic variations in human populations may be indicative of a selective advantage in the face of different environmental pressures.

CONCLUSIONS

Genetic variations in the NOS2 gene promoter and TLR4 coding sequence may lead to deleterious and protective effects, respectively, arising from altered function of the innate immune system in patients with T2DM.

GREEN TEA POLYPHENOLS MEDIATED APOPTOSIS IN INTESTINAL EPITHELIAL CELLS BY A FADD-DEPENDENT PATHWAY

Colorectal cancer is the most common malignant complication in patients with chronic inflammatory bowel disease (IBD). In addition, these patients are at risk for developing painful complications during chemotherapy due to cytotoxic effects of drugs currently in use. Past studies have suggested a protective effect of tea consumption on gastrointestinal (GI) malignancies. Green tea polyphenols (GrTP) inhibited carcinogen-induced GI tumors in rodents and induced apoptosis in various carcinoma cell lines. We hypothesized that GrTP and its polyphenolic compounds regulate apoptosis in the intestinal epithelia. In this study, the effects of GrTP and its polyphenolics on apoptosis was evaluated in intestinal epithelial, IEC-6, cells grown to 85% confluency. GrTP (400-800 mg/ml) induced DNA fragmentation in a dose dependent fashion. Higher concentrations (>800 mg/ml) induced a mixed apoptosis and cytolysis. Epithelial cells exposed to GrTP and a major polyphenol, EGCG, but not EGC or EC, increased caspase activities in a time and dose dependent manner. The caspase inhibitors rescued cells from GrTP and EGCG-induced cell death. Concomitantly, GrTP resulted in activation of fatty acid synthase (Fas)-associated protein with death domain (FADD) and recruitment to Fas/CD95 domain 30 minutes following treatment. While GrTP also blocked NF-κB activation, an NFκ-B inhibitor (MG132) only promoted cytolysis. In conclusion, these data demonstrated GrTP and EGCG induced apoptosis in intestinal epithelia mediated by caspase-8 through a FADD dependent pathway. Future investigation may warrant preventive as well as therapeutic strategies for GrTP in GI malignancy.

Redox control of asthma: molecular mechanisms and therapeutic opportunities

An imbalance in reducing and oxidizing (redox) systems favoring a more oxidative environment is present in asthma and linked to the pathophysiology of the defining symptoms and signs including airflow limitation, hyper-reactivity, and airway remodeling. High levels of hydrogen peroxide, nitric oxide ((*)NO), and 15-F(2t)-isoprostane in exhaled breath, and excessive oxidative protein products in lung epithelial lining fluid, peripheral blood, and urine provide abundant evidence for pathologic oxidizing processes in asthma. Parallel studies document loss of reducing potential by nonenzymatic and enzymatic antioxidants. The essential first line antioxidant enzymes superoxide dismutases (SOD) and catalase are reduced in asthma as compared to healthy individuals, with lowest levels in those patients with the most severe asthma. Loss of SOD and catalase activity is related to oxidative modifications of the enzymes, while other antioxidant gene polymorphisms are linked to susceptibility to develop asthma. Monitoring of exhaled (*)NO has entered clinical practice because it is useful to optimize asthma care, and a wide array of other biochemical oxidative and nitrative biomarkers are currently being evaluated for asthma monitoring and phenotyping. Novel therapeutic strategies that target correction of redox abnormalities show promise for the treatment of asthma.

NOS2A, TLR4, and IFNGR1 interactions influence pulmonary tuberculosis susceptibility in African-Americans

Tuberculosis (TB) has substantial mortality worldwide with 5-10% of those exposed progressing to active TB disease. Studies in mice and humans indicate that the inducible nitric oxide synthase (iNOS) molecule plays an important role in immune response to TB. A mixed case-control association study of individuals with TB, relatives, or close contact controls was performed in 726 individuals (279 case and 166 control African-Americans; 198 case and 123 control Caucasians). Thirty-nine single nucleotide polymorphisms (SNPs) were selected from the NOS2A gene for single SNP, haplotype, and multilocus interaction analyses with other typed candidate genes using generalized estimating equations. In African-Americans, ten NOS2A SNPs were associated with TB. The strongest associations were observed at rs2274894 (odds ratio (OR) = 1.84, 95% confidence interval (CI) [1.23-2.77], p = 0.003) and rs7215373 (OR = 1.67, 95% CI [1.17-2.37], p = 0.004), both of which passed a false discovery rate correction for multiple comparisons (q* = 0.20). The strongest gene-gene interactions were observed between NOS2A rs2248814 and IFNGR1 rs1327474 (p = 0.0004) and NOS2A rs944722 and IFNGR1 rs1327474 (p = 0.0006). Three other SNPs in NOS2A interacted with TLR4 rs5030729 and five other NOS2A SNPs interacted with IFNGR1 rs1327474. No significant associations were observed in Caucasians. These results suggest that NOS2A variants may contribute to TB susceptibility, particularly in individuals of African descent, and may act synergistically with SNPs in TLR4 and IFNGR1.

Malaria severity and human nitric oxide synthase type 2 (NOS2) promoter haplotypes

Nitric oxide (NO) mediates host resistance to severe malaria and other infectious diseases. NO production and mononuclear cell expression of the NO producing enzyme-inducible nitric oxide synthase (NOS2) have been associated with protection from severe falciparum malaria. The purpose of this study was to identify single nucleotide polymorphisms (SNPs) and haplotypes in the NOS2 promoter, to identify associations of these haplotypes with malaria severity and to test the effects of these polymorphisms on promoter activity. We identified 34 SNPs in the proximal 7.3 kb region of the NOS2 promoter and inferred NOS2 promoter haplotypes based on genotyping 24 of these SNPs in a population of Tanzanian children with and without cerebral malaria. We identified 71 haplotypes; 24 of these haplotypes comprised 82% of the alleles. We determined whether NOS2 promoter haplotypes were associated with malaria severity in two groups of subjects from Dar es Salaam (N = 185 and N = 250) and in an inception cohort of children from Muheza-Tanga, Tanzania (N = 883). We did not find consistent associations of NOS2 promoter haplotypes with malaria severity or malarial anemia, although interpretation of these results was potentially limited by the sample size of each group. Furthermore, cytokine-induced NOS2 promoter activity determined using luciferase reporter constructs containing the proximal 7.3 kb region of the NOS2 promoter and the G-954C or C-1173T SNPs did not differ from NOS2 promoter constructs that lacked these polymorphisms. Taken together, these studies suggest that the relationship between NOS2 promoter polymorphisms and malaria severity is more complex than previously described.

Dynamic compression alters NFkappaB activation and IkappaB-alpha expression in IL-1beta-stimulated chondrocyte/agarose constructs

OBJECTIVE AND DESIGN

Determine the effect of IL-1beta and dynamic compression on NFkappaB activation and IkappaB-alpha gene expression in chondrocyte/agarose constructs.

METHODS

Constructs were cultured under free-swelling conditions or subjected to dynamic compression for up to 360 min with IL-1beta and/or PDTC (inhibits NFkappaB activation). Nuclear translocation of NFkappaB-p65 was analysed by immunofluoresence microscopy. Gene expression of IkappaB-alpha, iNOS, IL-1beta and IL-4 was assessed by real-time qPCR.

RESULTS

Nuclear translocation of NFkappaB-p65 was concomitant with an increase in nuclear fluorescence intensity which reached maximum values at 60 min with IL-1beta (p < 0.001). Dynamic compression or PDTC reduced nuclear fluorescence and NFkappaB nuclear translocation in cytokine-treated constructs (p < 0.001 and p < 0.01 respectively). IL-1beta increased IkappaB-alpha expression (p < 0.001) at 60 min and either induced iNOS (p < 0.001) and IL-1beta (p < 0.01) or inhibited IL-4 (p < 0.05) expression at 360 min. These time-dependent events were partially reversed by dynamic compression or PDTC (p < 0.01) with IL-1beta. Co-stimulation by dynamic compression and PDTC favoured suppression (IkappaB-alpha, iNOS, IL-1beta) or induction (IL-4) of gene expression.

CONCLUSIONS

NFkappaB is one of the key players in the mechanical and inflammatory pathways, and its inhibition by a biophysical/therapeutic approach could be a strategy for attenuating the catabolic response in osteoarthritis.