The cyclic AMP response element plays an essential role in the expression of the human prostaglandin-endoperoxide synthase 2 gene in differentiated U937 monocytic cells

Novel anti-cancer effect of 2-arachidonoylglycerol via processing body formation in HCA-7 human colon cancer cells

The endocannabinoid 2-arachidonoylglycerol (2-AG) has been reported to exhibit anticancer effects, including against colorectal cancer (CRC); however, the detailed mechanisms have not been clarified. Herein, we demonstrated that 2-AG suppressed cyclooxygenase-2 (COX-2) expression induced by prostaglandin E2 in human colon cancer HCA-7 cells. The suppression of COX-2 expression by 2-AG was through the acceleration of processing body (P-body) formation followed by COX-2 mRNA degradation. These effects were restored by TAK-715, a specific inhibitor of p38 MAPK. Therefore, the effect of 2-AG on COX-2 may be distinct from conventional non-steroidal anti-inflammatory drugs (NSAIDs). NSAIDs inhibit the function of COX-2, whereas 2-AG suppresses the protein expression of COX-2. Recently, the cardiovascular risks of NSAIDs were reported by the Food and Drug Administration in the United States. Therefore, elucidation of the effect of 2-AG is expected to contribute to the development of an alternative and novel therapeutic option that would have no or fewer risks regarding cardiovascular events.

Comparable Response Following Exposure to Biodiesel and Diesel Exhaust Particles in Advanced Multicellular Human Lung Models

Biodiesel is considered to be a sustainable alternative for fossil fuels such as petroleum-based diesel. However, we still lack knowledge about the impact of biodiesel emissions on humans, as airways and lungs are the primary target organs of inhaled toxicants. This study investigated the effect of exhaust particles from well-characterized rapeseed methyl ester (RME) biodiesel exhaust particles (BDEP) and petro-diesel exhaust particles (DEP) on primary bronchial epithelial cells (PBEC) and macrophages (MQ). The advanced multicellular physiologically relevant bronchial mucosa models were developed using human primary bronchial epithelial cells (PBEC) cultured at air-liquid interface (ALI) in the presence or absence of THP-1 cell-derived macrophages (MQ). The experimental set-up used for BDEP and DEP exposures (18 µg/cm² and 36 µg/cm²) as well as the corresponding control exposures were PBEC-ALI, MQ-ALI, and PBEC co-cultured with MQ (PBEC-ALI/MQ). Following exposure to both BDEP and DEP, reactive oxygen species as well as the stress protein heat shock protein 60 were upregulated in PBEC-ALI and MQ-ALI. Expression of both pro-inflammatory (M1: CD86) and repair (M2: CD206) macrophage polarization markers was increased in MQ-ALI after both BDEP and DEP exposures. Phagocytosis activity of MQ and the phagocytosis receptors CD35 and CD64 were downregulated, whereas CD36 was upregulated in MQ-ALI. Increased transcript and secreted protein levels of CXCL8, as well as IL-6 and TNF-α, were detected following both BDEP and DEP exposure at both doses in PBEC-ALI. Furthermore, the cyclooxygenase-2 (COX-2) pathway, COX-2-mediated histone phosphorylation and DNA damage were all increased in PBEC-ALI following exposure to both doses of BDEP and DEP. Valdecoxib, a COX-2 inhibitor, reduced the level of prostaglandin E2, histone phosphorylation, and DNA damage in PBEC-ALI following exposure to both concentrations of BDEP and DEP. Using physiologically relevant multicellular human lung mucosa models with human primary bronchial epithelial cells and macrophages, we found BDEP and DEP to induce comparable levels of oxidative stress, inflammatory response, and impairment of phagocytosis. The use of a renewable carbon-neutral biodiesel fuel does not appear to be more favorable than conventional petroleum-based alternative, as regards of its potential for adverse health effects.

Infectivity-Enhanced, Conditionally Replicative Adenovirus for COX-2-Expressing Castration-Resistant Prostate Cancer

BACKGROUND

The development of conditionally replicative adenoviruses (CRAds) for castration-resistant prostate cancer (CRPC), particularly neuroendocrine prostate cancer (NEPC), has two major obstacles: choice of control element and poor infectivity. We applied fiber-modification-based infectivity enhancement and an androgen-independent promoter (cyclooxynegase-2, COX-2) to overcome these issues.

METHODS

The properties of the COX-2 promoter and the effect of fiber modification were tested in two CRPC cell lines (Du-145 and PC3). Fiber-modified COX-2 CRAds were tested in vitro for cytocidal effect as well as in vivo for antitumor effect with subcutaneous CRPC xenografts.

RESULTS

In both CRPC cell lines, the COX-2 promoter showed high activity, and Ad5/Ad3 fiber modification significantly enhanced adenoviral infectivity. COX-2 CRAds showed a potent cytocidal effect in CRPC cells with remarkable augmentation by fiber modification. In vivo, COX-2 CRAds showed an antitumor effect in Du-145 while only Ad5/Ad3 CRAd showed the strongest antitumor effect in PC3.

CONCLUSION

COX-2 promoter-based, infectivity-enhanced CRAds showed a potent antitumor effect in CRPC/NEPC cells.

Regulation of Cyclooxygenase-2 Expression in Human T Cells by Glucocorticoid Receptor-Mediated Transrepression of Nuclear Factor of Activated T Cells

Cyclooxygenase (COX) is the key enzyme in prostanoid synthesis from arachidonic acid (AA). Two isoforms, named COX-1 and COX-2, are expressed in mammalian tissues. The expression of COX-2 isoform is induced by several stimuli including cytokines and mitogens, and this induction is inhibited by glucocorticoids (GCs). We have previously shown that the transcriptional induction of COX-2 occurs early after T cell receptor (TCR) triggering, suggesting functional implications of this enzyme in T cell activation. Here, we show that dexamethasone (Dex) inhibits nuclear factor of activated T cells (NFAT)-mediated COX-2 transcriptional induction upon T cell activation. This effect is dependent on the presence of the GC receptor (GR), but independent of a functional DNA binding domain, as the activation-deficient GRLS7 mutant was as effective as the wild-type GR in the repression of NFAT-dependent transcription. Dex treatment did not disturb NFAT dephosphorylation, but interfered with activation mediated by the N-terminal transactivation domain (TAD) of NFAT, thus pointing to a negative cross-talk between GR and NFAT at the nuclear level. These results unveil the ability of GCs to interfere with NFAT activation and the induction of pro-inflammatory genes such as COX-2, and explain some of their immunomodulatory properties in activated human T cells.

The Toxic Effects and Mechanisms of Nano-Cu on the Spleen of Rats

Research has shown that nano-copper (nano-Cu) can cause damage to the spleen and immune system yet their mechanisms of cytotoxicity are poorly understood. Our aim is to explore the potential immunotoxicity in the spleen of rats after nano-Cu exposure. The results of hematologic parameters, lymphocyte subsets, immunoglobulins, and histopathology indicated that copper obviously changed the immune function of the spleen. The levels of antioxidants (SOD, CAT, GSH-Px), oxidants (iNOS, NO, MDA), and anti-oxidative signalling pathway of Nrf2 (Nrf2 and HO-1) were strongly induced by nano-Cu. The expression of mRNA and protein of pro-/anti-inflammatory (IFN-γ, TNF-α, MIP-1α, MCP-1, MIF, IL-1/-2/-4/-6) cytokines were increased by nano-Cu. The expression of regulatory signal pathways, MAPKs and PI3-K/Akt were activated, which might be involved in the inflammatory responses and immunomodulatory processes of sub-acute nano-Cu exposure. The immune function of the spleen was repressed by nano-Cu induced oxidative stress and inflammation.

Lobohedleolide suppresses hepatitis C virus replication via JNK/c-Jun-C/EBP-mediated down-regulation of cyclooxygenase-2 expression

Hepatitis C virus (HCV) chronically infects 2–3% people of the global population, which leads to liver cirrhosis and hepatocellular carcinoma. Drug resistance remains a serious problem that limits the effectiveness of US Food and Drug Administration (FDA)-approved direct-acting antiviral (DAA) drugs against HCV proteins. The objective of our study was to discover new antivirals from natural products to supplement current therapeutics. We demonstrated that lobohedleolide, isolated from the Formosan soft coral Lobophytum crassum, significantly reduced HCV replication in replicon cells and JFH-1 infection system, with EC₅₀ values of 10 ± 0.56 and 22 ± 0.75 μM, respectively, at non-toxic concentrations. We further observed that the inhibitory effect of lobohedleolide on HCV replication is due to suppression of HCV-induced cyclooxygenase-2 (COX-2) expression. Based on deletion-mutant analysis of the COX-2 promoter, we identified CCAAT/enhancer-binding protein (C/EBP) as a key transcription factor for the down-regulation of COX-2 by lobohedleolide, through which lobohedleolide decreased the phosphorylation of c-Jun NH2-terminal protein kinase and c-Jun to suppress HCV-induced C/EBP expression. The combination treatment of lobohedleolide with clinically used HCV drugs synergistically reduced HCV RNA replication, indicating that lobohedleolide exhibited a high biomedical potential to be used as a supplementary therapeutic agent to control HCV infection.

The p53-S100A2 Positive Feedback Loop Negatively Regulates Epithelialization in Cutaneous Wound Healing

The S100A2 protein is an important regulator of keratinocyte differentiation, but its role in wound healing remains unknown. We establish epithelial-specific S100A2 transgenic (TG) mice and study its role in wound repair using punch biopsy wounding assays. In line with the observed increase in proliferation and migration of S100A2-depleted human keratinocytes, mice expressing human S100A2 exhibit delayed cutaneous wound repair. This was accompanied by the reduction of re-epithelialization as well as a slow, attenuated response of Mcp1, Il6, Il1β, Cox2, and Tnf mRNA expression in the early phase. We also observed delayed Vegfa mRNA induction, a delayed enhancement of the Tgfβ1-mediated alpha smooth muscle actin (α-Sma) axis and a differential expression of collagen type 1 and 3. The stress-activated p53 tumor suppressor protein plays an important role in cutaneous wound healing and is an S100A2 inducer. Notably, S100A2 complexes with p53, potentiates p53-mediated transcription and increases p53 expression both transcriptionally and posttranscriptionally. Consistent with a role of p53 in repressing NF-κB-mediated transcriptional activation, S100A2 enhanced p53-mediated promoter suppression of Cox2, an early inducible NF-κB target gene upon wound injury. Our study thus supports a model in which the p53-S100A2 positive feedback loop regulates wound repair process.

Prostaglandin terminal synthases as novel therapeutic targets

Non-steroidal anti-inflammatory drugs (NSAIDs) exert their anti-inflammatory and anti-tumor effects by reducing prostaglandin (PG) production via the inhibition of cyclooxygenase (COX). However, the gastrointestinal, renal and cardiovascular side effects associated with the pharmacological inhibition of the COX enzymes have focused renewed attention onto other potential targets for NSAIDs. PGH₂, a COX metabolite, is converted to each PG species by species-specific PG terminal synthases. Because of their potential for more selective modulation of PG production, PG terminal synthases are now being investigated as a novel target for NSAIDs. In this review, I summarize the current understanding of PG terminal synthases, with a focus on microsomal PGE synthase-1 (mPGES-1) and PGI synthase (PGIS). mPGES-1 and PGIS cooperatively exacerbate inflammatory reactions but have opposing effects on carcinogenesis. mPGES-1 and PGIS are expected to be attractive alternatives to COX as therapeutic targets for several diseases, including inflammatory diseases and cancer.

Response to tumor necrosis factor-α mediated inflammation involving activation of prostaglandin E2 and Wnt signaling in nucleus pulposus cells

The cyclooxygenase 2 (COX-2) product, prostaglandin E2 (PGE2 ), acts through a family of G protein-coupled receptors designated E-prostanoid (EP) receptors that mediate intracellular signaling by multiple pathways. However, it is not known whether crosstalk between tumor necrosis factor-α(TNF-α)-PGE2 -mediated signaling and Wnt signaling plays a role in the regulation of intervertebral disc (IVD) cells. In this study, we investigated the relationship between TNF-α-PGE2 signaling and Wnt signaling in IVD cells. TNF-α increased the expression of COX-2 in IVD cells. The EP receptors EP1, EP3, and EP4 were expressed in IVD cells, and TNF-α significantly increased PGE2 production. Stimulation with TNF-α also upregulated EP3 and EP4 mRNA and protein expression in IVD cells. The inductive effect of the EP3 and EP4 receptors on Topflash promoter activity was confirmed through gain- and loss-of-function studies using selective EP agonists and antagonists. PGE2 treatment activated Wnt-β-catenin signaling through activation of EP3. We conclude that TNF-α-induced COX-2 and PGE2 stimulate Wnt signaling and activate Wnt target genes. Suppression of the EP3 receptor via TNF-α-PGE2 signaling seems to suppress IVD degeneration by controlling the activation of Wnt signaling. These findings may help identify the underlying mechanism and role of Wnt signaling in IVD degeneration.

Nuclear factor-kappaB sensitizes to benzyl isothiocyanate-induced antiproliferation in p53-deficient colorectal cancer cells

Benzyl isothiocyanate (BITC), a dietary isothiocyanate derived from cruciferous vegetables, inhibits the proliferation of colorectal cancer cells, most of which overexpress β-catenin as a result of mutations in the genes for adenomatous polyposis coli or mutations in β-catenin itself. Because nuclear factor-κB (NF-κB) is a plausible target of BITC signaling in inflammatory cell models, we hypothesized that it is also involved in BITC-inhibited proliferation of colorectal cancer cells. siRNA-mediated knockdown of the NF-κB p65 subunit significantly decreased the BITC sensitivity of human colorectal cancer HT-29 cells with mutated p53 tumor suppressor protein. Treating HT-29 cells with BITC induced the phosphorylation of IκB kinase, IκB-α and p65, the degradation of IκB-α, the translocation of p65 to the nucleus and the upregulation of NF-κB transcriptional activity. BITC also decreased β-catenin binding to a positive cis element of the cyclin D1 promoter and thus inhibited β-catenin-dependent cyclin D1 transcription, possibly through a direct interaction between p65 and β-catenin. siRNA-mediated knockdown of p65 confirmed that p65 negatively affects cyclin D1 expression. On the other hand, when human colorectal cancer HCT-116 cells with wild-type p53 were treated with BITC, translocation of p65 to the nucleus was inhibited rather than enhanced. p53 knockout increased the BITC sensitivity of HCT-116 cells in a p65-dependent manner, suggesting that p53 negatively regulates p65-dependent effects. Together, these results identify BITC as a novel type of antiproliferative agent that regulates the NF-κB pathway in p53-deficient colorectal cancer cells.

Toxicological mechanisms of nanosized titanium dioxide-induced spleen injury in mice after repeated peroral application

Due to an increase in surface area per particle weight, nanosized titanium dioxide (nano-TiO2) has greatly increased its function as a catalyst and is used for whitening and brightening foods. However, concerns over the safety of nano-TiO2 have been raised. The purpose of this study was to determine whether the protein kinase MAPKs/PI3-K/Akt signaling pathways and transcription factors are activated prior to or concurrent with COX-2 up-regulation in mouse spleen following exposure to 10 mg/kg BW of pure anatase nano-TiO2 by the intragastric route for 15-90 days. The study clearly showed that nano-TiO2 was deposited in the spleen and resulted in reactive oxygen species production, time-dependent splenic inflammation, and necrosis, coupled with a 12.64-64.06% increase in COX-2 and prostaglandin E2 expression, respectively. Furthermore, nano-TiO2 elevated the expressions of ERK, AP-1, CRE, Akt, JNK2, MAPKs, PI3-K, c-Jun, and c-Fos in the spleen by 1.08-6-fold with increased exposure duration, respectively. These findings suggested that nano-TiO2-induced COX-2 expression may be mediated predominantly through the induction of AP-1 and CRE and that AP-1/CRE induction occurred via the MAPKs/PI3-K/Akt signaling pathways in the spleen. Therefore, the findings suggest the need for caution when using nanomaterials as food additives.

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.

Synaptic and extrasynaptic NMDA receptors differentially modulate neuronal cyclooxygenase-2 function, lipid peroxidation, and neuroprotection

Stimulation of synaptic NMDA receptors (NMDARs) induces neuroprotection, while extrasynaptic NMDARs promote excitotoxic cell death. Neuronal expression of cyclooxygenase-2 (COX-2) is enhanced by synaptic NMDARs, and although this enzyme mediates neuronal functions, COX-2 is also regarded as a key modulator of neuroinflammation and is thought to exacerbate excitotoxicity via overproduction of prostaglandins. This raises an apparent paradox: synaptic NMDARs are pro-survival yet are essential for robust neuronal COX-2 expression. We hypothesized that stimulation of extrasynaptic NMDARs converts COX-2 signaling from a physiological to a potentially pathological process. We combined HPLC-electrospray ionization-tandem MS-based mediator lipidomics and unbiased image analysis in mouse dissociated and organotypic cortical cultures to uncover that synaptic and extrasynaptic NMDARs differentially modulate neuronal COX-2 expression and activity. We show that synaptic NMDARs enhance neuronal COX-2 expression, while sustained synaptic stimulation limits COX-2 activity by suppressing cellular levels of the primary COX-2 substrate, arachidonic acid (AA). In contrast, extrasynaptic NMDARs suppress COX-2 expression while activating phospholipase A₂, which enhances AA levels by hydrolysis of membrane phospholipids. Thus, sequential activation of synaptic then extrasynaptic NMDARs maximizes COX-2-dependent prostaglandin synthesis. We also show that excitotoxic events only drive induction of COX-2 expression through abnormal synaptic network excitability. Finally, we show that nonenzymatic lipid peroxidation of arachidonic and other polyunsaturated fatty acids is a function of network activity history. A new paradigm emerges from our results suggesting that pathological COX-2 signaling associated with models of stroke, epilepsy, and neurodegeneration requires specific spatiotemporal NMDAR stimulation.

Regulation of bombesin-stimulated cyclooxygenase-2 expression in prostate cancer cells

Background

Cyclooxygenase-2 (COX-2) and the bombesin (BBS)-like peptide, gastrin-releasing peptide (GRP), have been implicated in the progression of hormone-refractory prostate cancer; however, a mechanistic link between the bioactive peptide and COX-2 expression in prostate cells has not been made.

Results

We report that BBS stimulates COX-2 mRNA and protein expression, and the release of prostaglandin E₂ from the GRP receptor (GRPR)-positive, androgen-insensitive prostate cancer cell line, PC-3. BBS-stimulated COX-2 expression is mediated, in part, by p38^MAPK and PI3 kinase (PI3K)/Akt pathways, and blocked by a GRPR antagonist. The PI3K/Akt pathway couples GRPR to the transcription factor, activator protein-1 (AP-1), and enhanced COX-2 promoter activity. Although BBS stimulates nuclear factor-kappaB (NF-κB) in PC-3, NF-κB does not regulate GRPR-mediated COX-2 expression. The p38^MAPK pathway increases BBS-stimulated COX-2 expression by slowing the degradation of COX-2 mRNA. Expression of recombinant GRPR in the androgen-sensitive cell line LNCaP is sufficient to confer BBS-stimulated COX-2 expression via the p38^MAPK and PI3K/Akt pathways.

Conclusions

Our study establishes a mechanistic link between GRPR activation and enhanced COX-2 expression in prostate cancer cell lines, and suggests that inhibiting GRPR may, in the future, provide an effective therapeutic alternative to non-steroidal anti-inflammatory drugs for inhibiting COX-2 in patients with recurrent prostate cancer.

Wnt/β-catenin signaling enhances cyclooxygenase-2 (COX2) transcriptional activity in gastric cancer cells

Background

Increased expression of the cyclooxygenase-2 enzyme (COX2) is one of the main characteristics of gastric cancer (GC), which is a leading cause of death in the world, particularly in Asia and South America. Although the Wnt/β-catenin signaling pathway has been involved in the transcriptional activation of the COX2 gene, the precise mechanism modulating this response is still unknown.

Methodology/Principal Findings

Here we studied the transcriptional regulation of the COX2 gene in GC cell lines and assessed whether this phenomenon is modulated by Wnt/β-catenin signaling. We first examined the expression of COX2 mRNA in GC cells and found that there is a differential expression pattern consistent with high levels of nuclear-localized β-catenin. Pharmacological treatment with either lithium or valproic acid and molecular induction with purified canonical Wnt3a significantly enhanced COX2 mRNA expression in a dose- and time-dependent manner. Serial deletion of a 1.6 Kbp COX2 promoter fragment and gain- or loss-of-function experiments allowed us to identify a minimal Wnt/β-catenin responsive region consisting of 0.8 Kbp of the COX2 promoter (pCOX2-0.8), which showed maximal response in gene-reporter assays. The activity of this pCOX2-0.8 promoter region was further confirmed by site-directed mutagenesis and DNA-protein binding assays.

Conclusions/Significance

We conclude that the pCOX2-0.8 minimal promoter contains a novel functional T-cell factor/lymphoid enhancer factor (TCF/LEF)-response element (TBE Site II; -689/-684) that responds directly to enhanced Wnt/β-catenin signaling and which may be important for the onset/progression of GC.

Techniques used to study regulation of cyclooxygenase-2 promoter sites

Cyclooxygenase-2 (COX-2), the rate-limiting enzyme for prostaglandin (PG) biosynthesis, plays a key role in inflammation, tumorigenesis, development and circulatory homeostasis. COX-2 expression is rapidly and sensitively regulated by various stimuli, and also its regulation is distinct among cell types at transcriptional and posttranscriptional levels. Therefore, it is important to consider these features of COX-2 expression in the reporter assays we describe in this chapter. Emphasis should be made with regard to two points. Firstly, COX-2 reporter assays should be evaluated by intrinsic COX-2 expression, such as RT-PCR, northern blotting, western blotting, or by PGE(2) measurement. Secondly, one must carefully choose several conditions in the reporter assays for experimental purposes.

Citral, a component of lemongrass oil, activates PPARα and γ and suppresses COX-2 expression

Lemongrass is a widely used herb as a food flavoring, as a perfume, and for its analgesic and anti-inflammatory purposes; however, the molecular mechanisms of these effects have not been elucidated. Previously, we identified carvacrol from the essential oil of thyme as a suppressor of cyclooxygenase (COX)-2, a key enzyme for prostaglandin synthesis, and also an activator of peroxisome proliferator-activated receptor (PPAR), a molecular target for "lifestyle-related" diseases. In this study, we evaluated the essential oil of lemongrass using our established assays for COX-2 and PPARs. We found that COX-2 promoter activity was suppressed by lemongrass oil in cell-based transfection assays, and we identified citral as a major component in the suppression of COX-2 expression and as an activator of PPARα and γ. PPARγ-dependent suppression of COX-2 promoter activity was observed in response to citral treatment. In human macrophage-like U937 cells, citral suppressed both LPS-induced COX-2 mRNA and protein expression, dose-dependently. Moreover, citral induced the mRNA expression of the PPARα-responsive carnitine palmitoyltransferase 1 gene and the PPARγ-responsive fatty acid binding protein 4 gene, suggesting that citral activates PPARα and γ, and regulates COX-2 expression. These results are important for understanding the anti-inflammatory and anti-lifestyle-related disease properties of lemongrass.

Carvacrol, a component of thyme oil, activates PPARalpha and gamma and suppresses COX-2 expression

Cyclooxygenase-2 (COX-2), the rate-limiting enzyme in prostaglandin biosynthesis, plays a key role in inflammation and circulatory homeostasis. Peroxisome proliferator-activated receptors (PPARs) are ligand-dependent transcription factors belonging to the nuclear receptor superfamily and are involved in the control of COX-2 expression, and vice versa. Here, we show that COX-2 promoter activity was suppressed by essential oils derived from thyme, clove, rose, eucalyptus, fennel, and bergamot in cell-based transfection assays using bovine arterial endothelial cells. Moreover, from thyme oil, we identified carvacrol as a major component of the suppressor of COX-2 expression and an activator of PPARalpha and gamma. PPARgamma-dependent suppression of COX-2 promoter activity was observed in response to carvacrol treatment. In human macrophage-like U937 cells, carvacrol suppressed lipopolysaccharide-induced COX-2 mRNA and protein expression, suggesting that carvacrol regulates COX-2 expression through its agonistic effect on PPARgamma. These results may be important in understanding the antiinflammatory and antilifestyle-related disease properties of carvacrol.

Suppression of lipopolysaccharide-induced inflammatory responses in RAW 264.7 murine macrophages by aqueous extract of Clinopodium vulgare L. (Lamiaceae)

ETHNOPHARMACOLOGICAL RELEVANCE

The wild basil Clinopodium vulgare L. is commonly used in Bulgarian folk medicine for treatment of irritated skin, mastitis- and prostatitis-related swelling, as well as for some disorders accompanied with significant degree of inflammation (e.g. gastric ulcers, diabetes, and cancer).

AIM OF STUDY

To determine the effect of aqueous extract of Clinopodium vulgare L. on LPS-induced inflammatory responses of murine RAW 264.7 macrophages.

MATERIALS AND METHODS

Cell cytotoxicity was evaluated by MTT assay. Protein expression levels were monitored by Western blot analysis. Production of NO and PGE(2) was measured by the Griess colorimetric method and enzyme immunoassay, respectively. Activation of MMP-9 was visualized by gelatin zymography. Cytokine levels were determined by BioPlex assay. Intracellular ROS and free radical scavenging potential were measured by DCFH-DA and DPPH method, respectively. Xanthine oxidase activity was evaluated spectrophotometrically.

RESULTS

The extract suppresses NF-kappaB activation by preventing I kappa-B phosphorylation and inhibits the phosphorylation of p38 and SAPK/JNK MAPKs. It down-regulates iNOS expression which manifests as a drastic decrease of NO production, inhibits MMP-9 activation, but does not affect COX-2 protein levels and reduces only slightly the released PGE(2). Secretion of IL-1 beta and Il-10 is greatly reduced, whereas suppression of TNF-alpha and GM-CSF production is less dramatic. The extract has strong free radical scavenging properties and exerts inhibitory effect on xanthine oxidase activity, which lowers the levels of intracellular ROS.

CONCLUSION

The study provides evidence for the anti-inflammatory potential of Clinopodium vulgare L. aqueous extract.

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

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

Genetic determination of the role of PU.1 in macrophage gene expression

PU.1, an Ets family transcription factor, mediates macrophage effector function in inflammation by regulating gene expression. But, the extent and nature of PU.1 function in gene expression has not been genetically determined because ablation of PU.1 gene abolishes macrophage development. Here, we epigenetically suppressed PU.1 by stably expressing PU.1 specific siRNA in macrophages, and determined the effect of PU.1 deficiency on expressions of key inflammatory genes: Toll-like receptor 4 (TLR4), cyclooxygenase-2 (COX-2), and macrophage inflammatory protein-1alpha (MIP-1alpha). PU.1-silenced cell lines expressed lower TLR4 mRNA and COX-2 protein, but higher MIP-1alpha protein, than controls. Over-expression of PU.1 suppressed lipopolysaccharide-induced MIP-1alpha production. PU.1 occupied proximal and distal cognate sites in the endogenous MIP-1alpha promoter, but dissociated only from the distal sites in response to lipopolysaccharide, suggesting a novel negative regulatory mechanism by PU.1. Together, our results defined PU.1 function in differentially regulating expressions of TLR4, COX-2, and MIP-1alpha.

Cross-Regulation of iNOS and COX-2 by its Products in Murine Macrophages Under Stress Conditions

Exposure of macrophages to heat shock induces rapid synthesis of heat shock proteins (HSPs) which are important for cell homeostasis. Prostaglandins (PGs) and nitric oxide (NO) are important cell regulatory molecules. We have therefore investigated the interactions between these molecules in the LPS-induced expression of iNOS and COX-2 and in the mitochondrial activity of macrophages. Cultures of the murine macrophage cell line, J774, were exposed to heat shock (43 degrees C, 30 min) and stimulated with LPS (1 microg/ml), concomitantly or after 8h of cell recovery. NO production was measured by Griess reaction; PGE(2) by ELISA; HSP70, iNOS and COX-2 by immunobloting; mitochondrial activity by MTT assay. Heat shock induced HSP70, but not iNOS or COX-2 whereas LPS induced iNOS and COX-2 but not HSP70. When heat shock and LPS were given concomitantly, iNOS but not COX-2 expression was reduced. When a period of 8h was given between heat shock and LPS stimulation, iNOS, COX-2, PGE(2) and NO levels were significantly increased. Under these conditions, the expression of COX-2 was reduced by L-NAME (NO-synthesis inhibitor) and of iNOS by nimesulide (PGs-synthesis inhibitor). Such cross-regulation was not observed in cells at 37 degrees C. These treatments significantly reduced MTT levels in cells at 37 degrees C but not in cells submitted to heat shock. These results suggest that HSPs and cross-regulation of iNOS and COX-2 by their products might be of relevance in the control of cell homeostasis during stress conditions.

HIV-1 envelope glycoprotein 120 induces cyclooxygenase-2 expression in astrocytoma cells through a nuclear factor-kappaB-dependent mechanism

Human immunodeficiency virus-1 gp120 alters astroglial function, which compromises the function of the nearby of neuronal cells contributing to the cognitive impairment in human immunodeficiency virus-1 infection. Cyclooxygenase (COX)-2 has been involved in this process, although the intracellular pathways and second messengers involved are yet unknown. We have investigated the role of gp120-induced COX-2 in the astrocytoma human cell line U-87, and the different pathways involved in this activation. COX-2 mRNA and protein expression were detected in gp120-stimulated cells. Moreover, gp120 induces COX-2 promoter transcription. The effect of gp120 was abrogated by a neutralizing antibody against the chemokine receptor CXCR4 neutralizing antibody. Analysis of the promoter show that deletion or mutation of a proximal nuclear factor (NF)-kappaB site completely abrogated gp120-dependent transcription. NF-kappaB but neither Activating protein-1 nor nuclear factor of activated T-cells-dependent transcription was induced by gp120, as shown by reporter and electrophoretic mobility shift assays. In addition, transfection assays with the NF-kappaB inhibitor, IkappaBalpha, prevented gp120-mediated COX-2 induction. In contrast, there was no inhibition of COX-2 promoter transcription by expressing a dominant negative c-Jun, or nuclear factor of activated T-cells constructs. The antioxidant pyrrolidine dithiocarbamate inhibited COX-2 protein expression and COX-2 transcriptional activity induced by gp120. Thus, our results indicate that gp120 induced COX-2 transcription through NF-kappaB activation in astrocytoma cells.

An upstream CRE-E-box element is essential for gastrin-dependent activation of the cyclooxygenase-2 gene in human colon cancer cells

Cyclooxygenase-2, the inducible enzyme of arachidonic acid metabolism and prostaglandin synthesis, is over expressed in colorectal cancer. Inhibition of COX-1/-2 by non-steroidal anti-inflammatory drugs is associated with a decreased risk for these malignancies, whereas high serum gastrin levels elevate this risk. As gastrin exhibits trophical effects on colonic epithelium we sought to explore whether it is capable to induce COX-2 expression in a human colon cancer cell line. The aim of this study is the description of the gastrin evoked effects on the transcriptional activity of the COX-2 gene in colorectal cancer cells and the identification of regulatory promoter elements. Reporter gene assays were performed with the gastrin-stimulated human colorectal cancer cell-line Colo-320, which was stable transfected with the human cholecystokinin-B/gastrin receptor cDNA and COX-2-promoter-luciferase constructs containing different segments of the 5'-region of the COX-2 gene or with mutated promoter constructs. Transcription factors were characterized with electrophoretic mobility shift assays. Gastrin-dependent induction of COX-2 mRNA was shown using "real-time" PCR. Resulting elevated Prostaglandin E2-levels were measured using ELISA. Gastrin stimulated the PGE2-generation and COX-2-mRNA expression in human Colo-320-B cells potently, obviously by transactivating the COX-2-promoter using a region between - 68 bp and + 70 bp. Further examinations identified a CRE-E-box element between - 56 bp and - 48 bp mediating the gastrin-effects on the COX-2 gene. Transcription factors binding to this promoter element were USF-1 und -2. These results show the necessity to perform succeeding studies, which could describe possible mechanisms in which gastrin and COX-2 contribute to the induction of colorectal carcinomas.

The High-Mobility Group A1 Gene Up-Regulates Cyclooxygenase 2 Expression in Uterine Tumorigenesis

Uterine cancer is the most common cancer of the female genital tract and is the fourth most frequent cause of cancer death in women in the U.S. Despite the high prevalence of uterine cancers, the molecular events that lead to neoplastic transformation in the uterus are poorly understood. Moreover, there are limited mouse models to study these malignancies. We generated transgenic mice with high-mobility group A1 gene (HMGA1a) expression targeted to uterine tissue and all female mice developed tumors by 9 months of age. Histopathologically, the tumors resemble human uterine adenosarcoma and are transplantable. To determine whether these findings are relevant to human disease, we evaluated primary human uterine neoplasms and found that HMGA1a mRNA and protein levels are increased in most high-grade neoplasms but not in normal uterine tissue, benign tumors, or most low-grade neoplasms. We also found that HMGA1a up-regulates cyclooxygenase 2 (COX-2) expression in transgenic tumors. Moreover, both HMGA1a and COX-2 expression are up-regulated in high-grade human leiomyosarcomas. Using chromatin immunoprecipitation, HMGA1a binds directly to the COX-2 promoter in human uterine cancer cells in vivo and activates its expression in transfection experiments. We also show that blocking either HMGA1a or COX-2 in high-grade human uterine cancer cells blocks anchorage-independent cell growth in methylcellulose. These findings show that HMGA1a functions as an oncogene when overexpressed in the uterus and contributes to the pathogenesis of human uterine cancer by activating COX-2 expression. Although a larger study is needed to confirm these results, HMGA1a may be a useful marker for aggressive human uterine cancers.

Yin Yang 1 enhances cyclooxygenase-2 gene expression in macrophages

Expression of cyclooxygenase-2 (COX-2) is associated with the pathogenesis of inflammation and various cancers, including lung cancer. Yin Yang 1 (YY1) is a zinc-finger transcription factor that interacts with histone acetyltransferases and deacetylases for its transcriptional activity and also is involved in inflammation and tumorigenesis. We investigated whether YY1 regulates COX-2 expression. We located a possible YY1 binding site proximal to the transcription initiation site of the COX-2 promoter. Electrophoretic mobility shift assays show that YY1 bound to the putative YY1 site in vitro. To show biological relevance, we performed chromatin immunoprecipitation assays showing that lipopolysaccharide (LPS) treatment induced YY1 binding to the cognate site in the endogenous COX-2 promoter. Overexpression of YY1 in macrophages treated with either LPS or live Pseudomonas aeruginosa increased COX-2 transcriptional activity. Furthermore, YY1 enhanced COX-2 protein expression and prostaglandin D2 production elicited by LPS treatment. Mechanistically, we observed that LPS treatment resulted in disruption of an interaction between YY1 and p300, a histone acetyltransferase, but did not affect the interaction between YY1 and histone deacetylase 1/2. These data suggest that in response to LPS, YY1 dissociates from p300 and binds to the COX-2 promoter, contributing to COX-2 expression in an inflammatory milieu.

COX-2 expression induced by diesel particles involves chromatin modification and degradation of HDAC1

Cyclooxygenase-2 (COX-2) plays an important role in the inflammatory response induced by physiologic and stress stimuli. Exposure to diesel exhaust particulate matter (DEP) has been shown to induce pulmonary inflammation and exacerbate asthma and chronic obstructive pulmonary disease. DEP is a potent inducer of inflammatory reponses in human airway epithelial cells. The mechanism through which DEP inhalation induces inflammatory mediator expression is not understood. In this report, we demonstrate that DEP can induce the expression of COX-2 gene in a human bronchial epithelial cell line (BEAS-2B) at both transcriptional and protein levels. The induction of COX-2 gene expression involves chromatin modification, in particular acetylation and deacetylation of histones. We show that exposure to DEP increases the acetylation of histone H4 associated with the COX-2 promoter and causes degradation of histone deacetylase 1 (HDAC1). Further, we establish that HDAC1 plays a pivotal role in mediating the transcriptional activation of the COX-2 gene in BEAS-2B cells exposed to DEP, supported by evidence that the down-regulation of HDAC1 using siRNA leads to activation of COX-2 gene expression, whereas overexpression of HDAC1 results in its repression. Finally, DEP exposure induced recruitment of histone acetyltransferase (HAT) p300 to the promoter of the COX-2 gene, suggesting that acetylation is also important in regulating its expression in response to DEP exposure. These results show for the first time acetylation via selective degradation of HDAC1, and that recruitment of HAT plays an important role in DEP-induced expression of the COX-2 gene.

n-3 and n-6 polyunsaturated fatty acids induce the expression of COX-2 via PPARgamma activation in human keratinocyte HaCaT cells

Polyunsaturated fatty acids (PUFA) n-3 inhibit inflammation, in vivo and in vitro in keratinocytes. We examined in HaCaT keratinocyte cell line whether eicosapentaenoic acid (EPA) a n-3 PUFA, gamma-linoleic acid (GLA) a n-6 PUFA, and arachidic acid a saturated fatty acid, modulate expression of cyclooxygenase-2 (COX-2), an enzyme pivotal to skin inflammation and reparation. We demonstrate that only treatment of HaCaT with GLA and EPA or a PPARgamma ligand (roziglitazone), induced COX-2 expression (protein and mRNA). Moreover stimulation of COX-2 promoter activity was increased by those PUFAs or rosiglitazone. The inhibitory effects of GW9662 and T0070907 (PPARgamma antagonists), on COX-2 expression and on stimulation of COX-2 promoter activity by EPA and GLA suggest that PPARgamma is implicated in COX-2 induction. Finally, PLA2 inhibitor methyl arachidonyl fluorophosphonate blocked the PUFA effects on COX-2 induction, promoter activity and arachidonic acid mobilization suggesting involvement of AA metabolites in PPAR activation. These findings demonstrate that n-3 and n-6 PUFA increased PPARgamma activity is necessary for the COX-2 induction in HaCaT human keratinocyte cells. Given the anti-inflammatory properties of EPA, we suggest that induction of COX-2 in keratinocytes may be important in the anti-inflammatory and protective mechanism of action of PUFAs n-3 or n-6.

Thalidomide destabilizes cyclooxygenase-2 mRNA by inhibiting p38 mitogen-activated protein kinase and cytoplasmic shuttling of HuR

We investigated the effect of thalidomide on transcriptional and post-transcriptional cyclooxygenase-2 (COX-2) expression, including a pathway leading to COX-2 mRNA destabilization. We found that thalidomide inhibited the interleukin-1beta (IL-1beta)-mediated induction of COX-2 protein and mRNA in Caco-2 cells. Transient transfection with a COX-2 promoter construct demonstrated that thalidomide did not affect IL-1beta-induced transcriptional activation of COX-2, although it did decrease the stability of COX-2 mRNA and suppress IL-1beta-induced cytoplasmic shuttling of an mRNA stabilizing protein, HuR. Thalidomide also suppressed IL-1beta-induced p38 mitogen-activated protein kinase (MAPK) activation, while a p38 MAPK inhibitor destabilized COX-2 mRNA and the cytoplasmic shuttling of HuR induced by IL-1beta. These data suggest that one of the molecular mechanisms of thalidomide may be destabilization of COX-2 mRNA through inhibition of cytoplasmic shuttling of HuR and p38 MAPK.

Green tea proanthocyanidins inhibit cyclooxygenase-2 expression in LPS-activated mouse macrophages: molecular mechanisms and structure-activity relationship

The inhibitory effects of green tea proanthocyanidins on cyclooxygenase-2 (COX-2) expression and prostaglandin E(2) (PGE(2)) release were investigated in lipopolysaccharide (LPS)-activated murine macrophage RAW264 cells. Prodelphinidin B2 3,3' di-O-gallate (PDGG) caused a dose-dependent inhibition of COX-2 at both mRNA and protein levels with the attendant release of PGE(2). Molecular evidence revealed that PDGG inhibited the degradation of Ikappa-B, nuclear translocation of p65 and CCAAT/enhancer-binding protein (C/EBP)delta, and phosphorylation of c-Jun, but not CRE-binding protein (CREB), which regulate COX-2 expression. Moreover, PDGG suppressed the activations of mitogen-activated protein kinase (MAPK) including c-Jun NH(2)-terminal kinase (JNK), extracellular signal-regulated kinase (ERK) and p38 kinase. The results demonstrated that PDGG suppressed COX-2 expression via blocking MAPK-mediated activation of nuclear factor-kappaB (NF-kappaB), activator protein-1 (AP-1) and C/EBPdelta. Furthermore, studies on structure-activity relationship using five kinds of proanthocyanidins revealed that the galloyl moiety of proanthocyanidins appeared important to their inhibitory actions. Thus, our findings provide the first molecular basis that green tea proanthocyanidins with the galloyl moiety might have anti-inflammatory properties through blocking MAPK-mediated COX-2 expression.

Regulation of intracellular cyclooxygenase levels by gene transcription and protein degradation

Cyclooxygenases-1 and -2 (COX-1 and -2) catalyze the committed step in prostaglandin formation. Each isozyme subserves different biological functions. This is, at least in part, a consequence of differences in patterns of COX-1 and COX-2 expression. COX-1 is induced during development, and COX-1 mRNA and COX-1 protein are very stable. These latter properties can explain why COX-1 protein levels usually remain constant in those cells that express this isozyme. COX-2 is usually expressed inducibly in association with cell replication or differentiation. Both COX-2 mRNA and COX-2 protein have short half-lives relative to those of COX-1. Therefore, COX-2 protein is typically present for only a few hours after its synthesis. Here we review and develop the concepts that (a) COX-2 gene transcription can involve at least six different cis-acting promoter elements interacting with trans-acting factors generated by multiple, different signaling pathways, (b) the relative contribution of each cis-acting COX-2 promoter element depends on the cell type, the stimulus and the time following the stimulus and (c) a unique 27 amino acid instability element located just upstream of the C-terminus of COX-2 targets this isoform to the ER-associated degradation system and proteolysis by the cytosolic 26S proteasome.

Proinsulin C-peptide stimulates a PKC/IkappaB/NF-kappaB signaling pathway to activate COX-2 gene transcription in Swiss 3T3 fibroblasts

Proinsulin C-peptide causes multiple molecular and physiological effects, and improves renal and neuronal dysfunction in patients with diabetes. However, whether C-peptide controls the inhibitor kappaB (IkappaB)/NF-kappaB-dependent transcription of genes, including inflammatory genes is unknown. Here we showed that 1 nM C-peptide increased the expression of cyclooxygenase-2 (COX-2) mRNA and its protein in Swiss 3T3 fibroblasts. Consistently, C-peptide enhanced COX-2 gene promoter-activity, which was inhibited by GF109203X and Go6976, specific PKC inhibitors, and BAY11-7082, a specific nuclear factor-kappaB (NF-kappaB) inhibitor, accompanied by increased phosphorylation and degradation of IkappaB. These results suggest that C-peptide stimulates the transcription of inflammatory genes via activation of a PKC/IkappaB/NF-kappaB signaling pathway.

Cox-2 is regulated by Toll-like receptor-4 (TLR4) signaling: Role in proliferation and apoptosis in the intestine

BACKGROUND & AIMS

We recently showed that mice deficient in Toll-like receptor 4 (TLR4) or its adapter molecule MyD88 have increased signs of colitis compared with wild-type (WT) mice after dextran sodium sulfate (DSS)-induced injury. We wished to test the hypothesis that cyclooxygenase 2 (Cox-2)-derived prostaglandin E2 (PGE2) is important in TLR4-related mucosal repair.

METHODS

Cox-2 expression was analyzed by real-time polymerase chain reaction, immunohistochemistry, Western blotting, and luciferase reporter constructs. Small interfering RNA was used to inhibit expression of MyD88. TLR4-/- or WT mice were given 2.5% DSS for 7 days. Proliferation and apoptosis were assessed using bromodeoxyuridine staining and terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate nick-end labeling assays, respectively. PGE2 was given orally to DSS-treated mice.

RESULTS

Intestinal epithelial cell lines up-regulated Cox-2 expression in a TLR4- and MyD88-dependent fashion. Lipopolysaccharide-mediated stimulation of PGE2 production was blocked by a selective Cox-2 inhibitor or small interfering RNA against MyD88. After DSS injury, Cox-2 expression increased only in WT mice. TLR4-/- mice have significantly reduced proliferation and increased apoptosis after DSS injury compared with WT mice. PGE2 supplementation of TLR4-/- mice resulted in improvement in clinical signs of colitis and restoration of proliferation and apoptosis to WT values. The mechanism for improved epithelial repair may be through PGE2-dependent activation of the epidermal growth factor receptor.

CONCLUSIONS

We describe an important link between TLR4 signaling and Cox-2 expression in the gut. TLR4 and MyD88 signaling are required for optimal proliferation and protection against apoptosis in the injured intestine. Although TLR4 signaling is beneficial in the short term, chronic signaling through TLR4 may lower the threshold for colitis-associated cancer.

Changes in antitumor response in C57BL/6J-Min/+ mice during long-term administration of a selective cyclooxygenase-2 inhibitor

Selective cyclooxygenase-2 (COX-2) inhibitors are widely prescribed for severe arthritis and are currently under study in human chemoprevention trials. Recently, long-term use of these agents has come under scrutiny due to reports of treatment-associated cardiovascular toxicity. On short-term administration, the selective COX-2 inhibitor celecoxib inhibits adenoma growth in animal tumor models, including the C57BL/6J-Min/+ (Min/+) mouse. With uninterrupted long-term celecoxib administration, intestinal tumors in Min/+ mice initially regressed and then recurred to levels comparable with untreated controls. Celecoxib treatment initially suppressed COX-2 and prostaglandin E2 (PGE2) expression, but long-term use produced significantly higher levels of these molecules and reactivated PGE2-associated growth factor signaling pathways in tumor and normal tissues. These results indicate that COX-2 is an important chemoprevention target and that inhibition of this enzyme alters a paracrine enterocyte regulatory pathway. Chronic uninterrupted celecoxib treatment, however, induces untoward effects that enhance early progression events in intestinal tumorigenesis and may contribute to treatment toxicity.

Up-regulation of cyclooxygenase-2 by interleukin-1β in colon carcinoma cells

Growing evidence shows that Interleukin (IL)-1beta and Cyclooxygenase 2 (COX-2) play a crucial role in the pathogenesis of inflammatory diseases and tumor growth, particularly in the gastrointestinal tract. Here, we have analyzed the regulation of COX-2 by IL-1beta in the human colon carcinoma cell line Caco-2, showing that COX-2 induction by this cytokine is due to both nuclear factor (NF)-kappaB-dependent transcriptional and p38 mitogen-activated protein kinase (MAPK)-mediated post-transcriptional mechanisms. Treatment of these cells with IL-1beta increased the levels of COX-2 mRNA and protein and hence the production of PGE2. IL-1beta induced NF-kappaB activation in Caco-2 cells, promoting the binding of this transcription factor to DNA and increasing NF-kappaB-dependent transcription. Inhibition of NF-kappaB activation diminished IL-1beta-mediated transcriptional activation of COX-2. Furthermore, mutation or deletion of a putative NF-kappaB binding site in the human COX-2 promoter greatly diminished its induction by IL-1beta. In addition, this cytokine induced a rapid increase in p38 MAPK activation. Interestingly, inhibition of p38 MAPK by SB203580 severely decreased induction of COX-2 expression by IL-1beta. p38 MAPK signalling was required for IL-1beta-dependent stabilization of COX-2 transcript. Given the importance of COX-2 expression in intestinal inflammation and colon carcinogenesis, these findings contribute to determine the key signalling pathways involved in the regulation of COX-2 expression in colorectal cells by inflammatory stimuli, such as IL-1beta.

IL-4 regulates COX-2 and PGE2 production in human non-small cell lung cancer

IL-4 is a type 2 cytokine that may mediate pleiotropic effects in the NSCLC microenvironment. Here, we investigated whether IL-4 regulates PGE(2) production in NSCLC cells. We found that IL-4 inhibited constitutive COX-2 expression and PGE(2) production in A427 and H2122 NSCLC cell lines, and also suppressed IL-1beta-induced COX-2 expression in A549 and RH2 NSCLC cell lines. COX-2 mRNA was decreased in response to IL-4, and promoter analysis indicated that IL-4 inhibited both constitutive and IL-1beta-induced COX-2 transcription. IL-4 inhibited IL-1beta-stimulated ERK phosphorylation, which may mediate the inhibition of IL-1beta-induced COX-2 by IL-4. IL-4 did not modulate additional arachidonic acid pathway enzymes mPGES-1 and 15-PGDH, which could potentially be responsible for regulating PGE(2) production. Overall, our studies demonstrate that IL-4 has the capacity to inhibit COX-2 mRNA transcription in NSCLC cells and the inhibition of PGE(2) appears to be predominately COX-2 dependent.

Glycogen synthase kinase-3 is a negative regulator of extracellular signal-regulated kinase

Glycogen-synthase kinase-3 (GSK-3) and extracellular signal-regulated kinase (ERK) are critical downstream signaling proteins for the PI3-kinase/Akt and Ras/Raf/MEK-1 pathway, respectively, and regulate diverse cellular processes including embryonic development, cell differentiation and apoptosis. Here, we show that inhibition of GSK-3 using GSK-3 inhibitors or RNA interference (RNAi) significantly induced the phosphorylation of ERK1/2 in human colon cancer cell lines HT29 and Caco-2. Pretreatment with the PKCdelta-selective inhibitor rottlerin or transfection with PKCdelta siRNA attenuated the phosphorylation of ERK1/2 induced by the GSK-3 inhibitor SB-216763 and, furthermore, treatment with SB-216763 or transfection with GSK-3alpha and GSK-3beta siRNA increased PKCdelta activity, thus identifying a role for PKCdelta in the induction of ERK1/2 phosphorylation by GSK-3 inhibition. Treatment with SB-216763 increased expression of cyclooxygenase-2 (COX-2) and IL-8, which are downstream targets of ERK1/2 activation; this induction was abolished by MEK/ERK inhibition, suggesting GSK-3 inhibition induced COX-2 and IL-8 through ERK1/2 activation. The transcriptional induction of COX-2 and IL-8 by GSK-3 inhibition was further demonstrated by the increased COX-2 and IL-8 promoter activity after SB-216763 treatment or transfection with GSK-3alpha or GSK-3beta siRNA. Importantly, our findings identify GSK-3, acting through PKCdelta, as a negative regulator of ERK1/2, thus revealing a novel crosstalk mechanism between these critical signaling pathways.

Epstein-Barr virus protein can upregulate cyclo-oxygenase-2 expression through association with the suppressor of metastasis Nm23-H1

Previous studies have demonstrated the interaction between the Epstein-Barr virus (EBV) nuclear antigen 3C (EBNA3C) and the metastatic suppressor Nm23-H1 both in vitro and in vivo (C. Subramanian, M. A. Cotter II, and E. S. Robertson, Nat. Med. 7:350-355, 2001). EBNA3C can reverse the ability of Nm23-H1 to suppress migration of Burkitt's lymphoma and breast carcinoma cell lines in vitro. EBNA3C contributes to EBV-associated human cancers by regulating transcription of a number of cellular and viral promoters and by targeting and altering the transcription activities of the metastasis suppressor Nm23-H1. Cyclo-oxygenase-2 (COX-2), an inducible enzyme important in inflammation, is overexpressed in a variety of cancers and can influence cell migration. In this report we show that Nm23-H1 and EBNA3C can modulate expression of COX-2 in the context of EBV infection and transformation. The levels of COX-2 were consistently higher in EBV-positive cells than in EBV-negative cells. Additionally, we show that Nm23-H1 can upregulate the COX-2 promoter element in luciferase reporter assays, whereas EBNA3C alone did not affect the level of response but clearly contributed to an additive increase when coexpressed with Nm23-H1. The downstream effect of COX-2 expression was also evaluated and showed that prostaglandin E(2) levels increased with Nm23-H1 and that there was some level of cooperativity in the presence of EBNA3C. The majority of this response was mediated through the cyclic AMP response element and NF-kappaB sites. These studies suggest a potential role for COX-2 in EBV-associated human cancers.

Heparanase Is Involved in Angiogenesis in Esophageal Cancer through Induction of Cyclooxygenase-2

PURPOSE

Both heparanase and cyclooxygenase-2 (COX-2) are thought to play critical roles for tumor malignancy, including angiogenesis, although it is unknown about their relationship with each other in cancer progression. We hypothesized that they may link to each other on tumor angiogenesis.

EXPERIMENTAL DESIGN

The expressions of heparanase and COX-2 in 77 primary human esophageal cancer tissues were assessed by immunohistochemistry to do statistical analysis for the correlation between their clinicopathologic features, microvessel density, and survival of those clinical cases. Human esophageal cancer cells were transduced with heparanase cDNA and used for reverse transcription-PCR and Western blot to determine the expression of heparanase and COX-2. COX-2 promoter vector and its deletion/mutation constructs were also used along with transduction of heparanase cDNA for luciferase assay.

RESULTS

Heparanase and COX-2 protein expression exhibited a similar pattern in esophageal tumor tissues, and their expression correlated with tumor malignancy and poor survival. Their expression also revealed a significant correlation with high intratumoral microvessel density. Up-regulation of COX-2 mRNA and protein was observed in esophageal cancer cells transfected with heparanase cDNA. COX-2 promoter was activated after heparanase cDNA was transduced and the deletion/mutation of three transcription factor (cyclic AMP response element, nuclear factor-kappaB, and nuclear factor-interleukin-6) binding elements in COX-2 promoter strongly suppressed its activity.

CONCLUSION

Our results suggest that heparanase may play a novel role for COX-2-mediated tumor angiogenesis.

Inhibition of lipopolysaccharide-induced cyclooxygenase-2 transcription by 6-(methylsulfinyl) hexyl isothiocyanate, a chemopreventive compound from Wasabia japonica (Miq.) Matsumura, in mouse macrophages

6-(Methylsulfinyl)hexyl isothiocyanate (6-MITC) is a chemopreventive compound occurring in Wasabi (Wasabia japonica (Miq.) Matsumura), which is a very popular pungent spice in Japan. We investigated the effects of 6-MITC on the expression of cyclooxygenase-2 (COX-2) in lipopolysaccharide (LPS)-activated murine macrophage RAW264 cells. Treatment with 6-MITC suppressed LPS-mediated induction of COX-2 protein in a dose-dependent manner. Transfections with various COX-2 promoter reporter constructs revealed that the inhibitory effects of 6-MITC on COX-2 gene expression were directed by the core promoter elements including nuclear factor kappaB (NF-kappaB), CCAAT/enhancer-binding protein (C/EBP) and cyclic AMP-response element (CRE) sites. Western blotting analysis showed that 6-MITC inhibited LPS-induced activation of MAPK (ERK, p38 kinase and JNK) and transcriptional factors (CREB, c-Jun and C/EBPdelta) binding the core elements of COX-2 promoter, substantiating the involvement of these signal transduction pathways in the regulation of COX-2 expression by 6-MITC. Moreover, Western blotting experiments with MAPK-specific inhibitors (U0126 for MEK1/2, SB203580 for p38 kinase and SP600125 for JNK) demonstrated that 6-MITC suppressed LPS-induced COX-2 expression by blocking the activation of JNK-mediated AP-1 and ERK/p38 kinase-mediated CREB or C/EBPdelta. Finally, the structure-activity study revealed that the inhibitory potency of methylsulfinyl isothiocyanates (MITCs) depended on the methyl chain length. These findings demonstrate for the first time that 6-MITC is an effective agent to attenuate COX-2 production, and enhance our understanding of the anti-inflammation properties of 6-MITC.

Anthocyanidins inhibit cyclooxygenase-2 expression in LPS-evoked macrophages: structure-activity relationship and molecular mechanisms involved

The effects of anthocyanidins, the aglycon nucleuses of anthocyanins widely occurring in reddish fruits and vegetables, on the expression of cyclooxygenase-2 (COX-2) were investigated in lipopolysaccharide (LPS)-activated murine macrophage RAW264 cells. Of five anthocyanidins, delphinidin and cyanidin inhibited LPS-induced COX-2 expression, but pelargonidin, peonidin and malvidin did not. The structure-activity relationship suggest that the ortho-dihydroxyphenyl structure of anthocyanidins on the B-ring appears to be related with the inhibitory actions. Delphinidin, the most potent inhibitor, caused a dose-dependent inhibition of COX-2 expression at both mRNA and protein levels. Western blotting analysis indicated that delphinidin inhibited the degradation of IkappaB-alpha, nuclear translocation of p65 and CCAAT/enhancer-binding protein (C/EBP)delta and phosphorylation of c-Jun, but not CRE-binding protein (CREB). Moreover, delphinidin suppressed the activations of mitogen-activated protein kinase (MAPK) including c-Jun N-terminal kinase (JNK), extracellular signal-regulated kinase (ERK) and p38 kinase. MAPK inhibitors (U0126 for MEK1/2, SB203580 for p38 kinase and SP600125 for JNK) specifically blocked LPS-induced COX-2 expression. Thus, our results demonstrated that LPS-induced COX-2 expression by activating MAPK pathways and delphinidin suppressed COX-2 by blocking MAPK-mediated pathways with the attendant activation of nuclear factor-kappaB (NF-kappaB), activator protein-1 (AP-1) and C/EBPdelta. These findings provide the first molecular basis that anthocyanidins with ortho-dihydroxyphenyl structure may have anti-inflammatory properties through the inhibition of MAPK-mediated COX-2 expression.

Induction of cyclooxygenase-2 by anandamide in cerebral microvascular endothelium

Anandamide (AEA), an endogenous cannabinoid receptor agonist, is a potent vasodilator in the cerebral microcirculation. AEA is converted to arachidonic acid (AA) by fatty acid amidohydrolase (FAAH), and the conversion of AA to prostaglandins has been proposed as a potential mechanism for the vasodilation. Although AEA stimulated prostaglandin production by mouse cerebral microvascular endothelial cells, no [(3)H]prostaglandins were produced when these cells were incubated with [3H]AEA. Incubation with R(+)-methanandamide (MAEA), a stable analogue of AEA that is not a substrate for FAAH, produced a similar increase in PGE2 production as AEA. The PGE2 production induced by either AEA or MAEA was completely inhibited by NS-398, a selective cyclooxygenase (COX)-2 inhibitor, suggesting that COX-2 was induced. AEA and MAEA increased the expression of COX-2 protein in a time-dependent manner. This increase occurred as early as 1 h and reached maximum at 2 h. Induction of COX-2 protein by AEA was partially inhibited by AM-251, a selective cannabinoid receptor-1 antagonist. Furthermore, AEA increased COX-2 promoter activity approximately twofold above baseline in a fragment ranging from -1432 to +59, the full-length of the COX-2 promoter, and the increase in COX-2 promoter activity produced by AEA was partially inhibited by AM-251. These results indicate that AEA increased COX-2 expression at the transcriptional level through, at least in part, a cannabinoid receptor-1-mediated mechanism in cerebral microvascular endothelium.

Hepatitis C virus core protein suppresses NF-kappaB activation and cyclooxygenase-2 expression by direct interaction with IkappaB kinase beta

In addition to hepatocytes, hepatitis C virus (HCV) infects immune cells, including macrophages. However, little is known concerning the impact of HCV infection on cellular functions of these immune effector cells. Lipopolysaccharide (LPS) activates IkappaB kinase (IKK) signalsome and NF-kappaB, which leads to the expression of cyclooxygenase-2 (COX-2), which catalyzes production of prostaglandins, potent effectors on inflammation and possibly hepatitis. Here, we examined whether expression of HCV core interferes with IKK signalsome activity and COX-2 expression in activated macrophages. In reporter assays, HCV core inhibited NF-kappaB activation in RAW 264.7 and MH-S murine macrophage cell lines treated with bacterial LPS. HCV core inhibited IKK signalsome and IKKbeta kinase activities induced by tumor necrosis factor alpha in HeLa cells and coexpressed IKKgamma in 293 cells, respectively. HCV core was coprecipitated with IKappaKappabeta and prevented nuclear translocation of IKKbeta. NF-kappaB activation by either LPS or overexpression of IKKbeta was sufficient to induce robust expression of COX-2, which was markedly suppressed by ectopic expression of HCV core. Together, these data indicate that HCV core suppresses IKK signalsome activity, which blunts COX-2 expression in macrophages. Additional studies are necessary to determine whether interrupted COX-2 expression by HCV core contributes to HCV pathogenesis.

Helicobacter pylori promote gastric cancer cells invasion through a NF-kB and COX-2-mediated pathway

AIM: To examine the effects of Helicobacter pylori (H pylori) infection on the invasiveness of gastric cancer cells, and to elucidate its mechanism.

METHODS: Gastric carcinoma cells, MKN-45, were incubated with CagA-positive H pylori, and cell invasion was determined by Matrigel analysis. The expression of matrix metallopr-oteinase-9 (MMP-9), vascular endothelial growth factor (VEGF), and cyclooxygenase-2 (COX-2) were assessed by Western-blot analysis, and transcriptional activation of the COX-2 promoter was examined by measuring luciferase and β-galactosidase activities. Lastly, the protein-DNA interaction was confirmed by an electrophoretic mobility shift assay.

RESULTS: The current studies showed that: (1) incubation of CagA-positive H pylori with MKN-45 cells significantly promotes gastric cancer cells invasion, and this effect is attenuated by pre-treatment with NS-398, a COX-2 inhibitor, or PDTC, a nuclear factor κB (NF-κB) inhibitor; (2) the induction of MKN-45 cells invasion by H pylori is associated with increases in COX-2, MMP-9, and VEGF protein expression, and co-incubation of NS-398 or PDTC significantly reduces these effects; (3) H pylori infection transactivates COX-2 promoter activity and increases the binding of NF-κB to this promoter.

CONCLUSION: Our data demonstrate that H pylori infection promotes gastric epithelial cells invasion by activating MMP-9 and VEGF expression. These effects appear to be mediated through a NF-κB and COX-2 mediated pathway, as COX-2 or NF-κB inhibitor significantly attenuate the invasiveness of gastric cancer cells and the expressions of MMP-9 and VEGF protein.