Ligand-induced prostaglandin synthesis requires expression of the TIS10/PGS-2 prostaglandin synthase gene in murine fibroblasts and macrophages

Tetrahydrocurcumin Derivatives Enhanced the Anti-Inflammatory Activity of Curcumin: Synthesis, Biological Evaluation, and Structure-Activity Relationship Analysis

Tetrahydrocurcumin, the most abundant curcumin transformation product in biological systems, can potentially be a new alternative therapeutic agent with improved anti-inflammatory activity and higher bioavailability than curcumin. In this article, we describe the synthesis and evaluation of the anti-inflammatory activities of tetrahydrocurcumin derivatives. Eleven tetrahydrocurcumin derivatives were synthesized via Steglich esterification on both sides of the phenolic rings of tetrahydrocurcumin with the aim of improving the anti-inflammatory activity of this compound. We showed that tetrahydrocurcumin (2) inhibited TNF-α and IL-6 production but not PGE2 production. Three tetrahydrocurcumin derivatives inhibited TNF-α production, five inhibited IL-6 production, and three inhibited PGE2 production. The structure-activity relationship analysis suggested that two factors could contribute to the biological activities of these compounds: the presence or absence of planarity and their structural differences. Among the tetrahydrocurcumin derivatives, cyclic compound 13 was the most active in terms of TNF-α production, showing even better activity than tetrahydrocurcumin. Acyclic compound 11 was the most effective in terms of IL-6 production and retained the same effect as tetrahydrocurcumin. Moreover, acyclic compound 12 was the most active in terms of PGE2 production, displaying better inhibition than tetrahydrocurcumin. A 3D-QSAR analysis suggested that the anti-inflammatory activities of tetrahydrocurcumin derivatives could be increased by adding bulky groups at the ends of compounds 2, 11, and 12.

Polyphenols with Anti-Inflammatory Properties: Synthesis and Biological Activity of Novel Curcumin Derivatives

Herein, we describe the synthesis and evaluation of anti-inflammatory activities of new curcumin derivatives. The thirteen curcumin derivatives were synthesized by Steglich esterification on one or both of the phenolic rings of curcumin with the aim of providing improved anti-inflammatory activity. Monofunctionalized compounds showed better bioactivity than the difunctionalized derivatives in terms of inhibiting IL-6 production, and known compound 2 presented the highest activity. Additionally, this compound showed strong activity against PGE₂. Structure-activity relationship studies were carried out for both IL-6 and PGE₂, and it was found that the activity of this series of compounds increases when a free hydroxyl group or aromatic ligands are present on the curcumin ring and a linker moiety is absent. Compound 2 remained the highest activity in modulating IL-6 production and showed strong activity against PGE₂ synthesis.

Inflammation and JNK's Role in Niacin-GPR109A Diminished Flushed Effect in Microglial and Neuronal Cells With Relevance to Schizophrenia

Schizophrenia is a neuropsychiatric illness with no single definitive aetiology, making its treatment difficult. Antipsychotics are not fully effective because they treat psychosis rather than the cognitive or negative symptoms. Antipsychotics fail to alleviate symptoms when patients enter the chronic stage of illness. Topical application of niacin showed diminished skin flush in the majority of patients with schizophrenia compared to the general population who showed flushing. The niacin skin flush test is useful for identifying patients with schizophrenia at their ultra-high-risk stage, and understanding this pathology may introduce an effective treatment. This review aims to understand the pathology behind the diminished skin flush response, while linking it back to neurons and microglia. First, it suggests that there are altered proteins in the GPR109A-COX-prostaglandin pathway, inflammatory imbalance, and kinase signalling pathway, c-Jun N-terminal kinase (JNK), which are associated with diminished flush. Second, genes from the GPR109A-COX-prostaglandin pathway were matched against the 128-loci genome wide association study (GWAS) for schizophrenia using GeneCards, suggesting that G-coupled receptor-109A (GPR109A) may have a genetic mutation, resulting in diminished flush. This review also suggests that there may be increased pro-inflammatory mediators in the GPR109A-COX-prostaglandin pathway, which contributes to the diminished flush pathology. Increased levels of pro-inflammatory markers may induce microglial-activated neuronal death. Lastly, this review explores the role of JNK on pro-inflammatory mediators, proteins in the GPR109A-COX-prostaglandin pathway, microglial activation, and neuronal death. Inhibiting JNK may reverse the changes observed in the diminished flush response, which might make it a good therapeutic target.

Flipping the cyclooxygenase (Ptgs) genes reveals isoform-specific compensatory functions

Two prostaglandin (PG) H synthases encoded by Ptgs genes, colloquially known as cyclooxygenase (COX)-1 and COX-2, catalyze the formation of PG endoperoxide H₂, the precursor of the major prostanoids. To address the functional interchangeability of these two isoforms and their distinct roles, we have generated COX-2>COX-1 mice whereby Ptgs2 is knocked in to the Ptgs1 locus. We then "flipped" Ptgs genes to successfully create the Reversa mouse strain, where knock-in COX-2 is expressed constitutively and knock-in COX-1 is lipopolysaccharide (LPS) inducible. In macrophages, flipping the two Ptgs genes has no obvious impact on COX protein subcellular localization. COX-1 was shown to compensate for PG synthesis at high concentrations of substrate, whereas elevated LPS-induced PG production was only observed for cells expressing endogenous COX-2. Differential tissue-specific patterns of expression of the knock-in proteins were evident. Thus, platelets from COX-2>COX-1 and Reversa mice failed to express knock-in COX-2 and, therefore, thromboxane (Tx) production in vitro and urinary Tx metabolite formation in COX-2>COX-1 and Reversa mice in vivo were substantially decreased relative to WT and COX-1>COX-2 mice. Manipulation of COXs revealed isoform-specific compensatory functions and variable degrees of interchangeability for PG biosynthesis in cells/tissues.

Different Fatty Acids Compete with Arachidonic Acid for Binding to the Allosteric or Catalytic Subunits of Cyclooxygenases to Regulate Prostanoid Synthesis

Prostaglandin endoperoxide H synthases (PGHSs), also called cyclooxygenases (COXs), convert arachidonic acid (AA) to PGH2. PGHS-1 and PGHS-2 are conformational heterodimers, each composed of an (Eallo) and a catalytic (Ecat) monomer. Previous studies suggested that the binding to Eallo of saturated or monounsaturated fatty acids (FAs) that are not COX substrates differentially regulate PGHS-1 versus PGHS-2. Here, we substantiate and expand this concept to include polyunsaturated FAs known to modulate COX activities. Non-substrate FAs like palmitic acid bind Eallo of PGHSs stimulating human (hu) PGHS-2 but inhibiting huPGHS-1. We find the maximal effects of non-substrate FAs on both huPGHSs occurring at the same physiologically relevant FA/AA ratio of ∼20. This inverse allosteric regulation likely underlies the ability of PGHS-2 to operate at low AA concentrations, when PGHS-1 is effectively latent. Unlike FAs tested previously, we observe that C-22 FAs, including ω-3 fish oil FAs, have higher affinities for Ecat than Eallo subunits of PGHSs. Curiously, C-20 ω-3 eicosapentaenoate preferentially binds Ecat of huPGHS-1 but Eallo of huPGHS-2. PGE2 production decreases 50% when fish oil consumption produces tissue EPA/AA ratios of ≥0.2. However, 50% inhibition of huPGHS-1 itself is only seen with ω-3 FA/AA ratios of ≥5.0. This suggests that fish oil-enriched diets disfavor AA oxygenation by altering the composition of the FA pool in which PGHS-1 functions. The distinctive binding specificities of PGHS subunits permit different combinations of non-esterified FAs, which can be manipulated dietarily, to regulate AA binding to Eallo and/or Ecat thereby controlling COX activities.

Cellular sources of cyclooxygenase-1 and -2 up-regulation in the spinal dorsal horn after spinal nerve ligation

AIMS

Recent studies suggested that the development of neuropathic pain associated with neural injury may be partly due to up-regulation of cyclooxygenase (COX) in the central nervous system. However, the cellular sources of COX-1 and COX-2 up-regulation following nerve injury are unclear.

METHODS

We investigated the spinal cellular sources of COX-1 and COX-2 in association with allodynia following L5 spinal nerve ligation (SNL).

RESULTS

Post-SNL pain-related behaviour was shown by increased sensitivity to mechanical stimulation. There was a significant increase in both COX-1 and COX-2 immunoreactivity (P < 0.01) on the ipsilateral side of spinal dorsal horn. Double immunofluorescence labelling demonstrated that COX-1 immunoreactive cells colocalized chiefly with dorsal horn neuronal nuclei and microglia, whereas COX-2 was expressed in neuronal cytoplasm.

CONCLUSION

These findings demonstrate that while spinal dorsal horn neurones are important source of COX-1 and COX-2 after nerve injury, microglia also contribute to the pathogenesis of neuropathic pain, partly by producing additional COX-1.

A cyclooxygenase-2-dependent prostaglandin E2 biosynthetic system in the Golgi apparatus

Cyclooxygenases (COXs) catalyze the committed step in prostaglandin (PG) biosynthesis. COX-1 is constitutively expressed and stable, whereas COX-2 is inducible and short lived. COX-2 is degraded via endoplasmic reticulum (ER)-associated degradation (ERAD) following post-translational glycosylation of Asn-594. COX-1 and COX-2 are found in abundance on the luminal surfaces of the ER and inner membrane of the nuclear envelope. Using confocal immunocytofluorescence, we detected both COX-2 and microsomal PGE synthase-1 (mPGES-1) but not COX-1 in the Golgi apparatus. Inhibition of trafficking between the ER and Golgi retarded COX-2 ERAD. COX-2 has a C-terminal STEL sequence, which is an inefficient ER retention signal. Substituting this sequence with KDEL, a robust ER retention signal, concentrated COX-2 in the ER where it was stable and slowly glycosylated on Asn-594. Native COX-2 and a recombinant COX-2 having a Golgi targeting signal but not native COX-1 exhibited efficient catalytic coupling to mPGES-1. We conclude that N-glycosylation of Asn-594 of COX-2 occurs in the ER, leading to anterograde movement of COX-2 to the Golgi where the Asn-594-linked glycan is trimmed prior to retrograde COX-2 transport to the ER for ERAD. Having an inefficient ER retention signal leads to sluggish Golgi to ER transit of COX-2. This permits significant Golgi residence time during which COX-2 can function catalytically. Cytosolic phospholipase A2α, which mobilizes arachidonic acid for PG synthesis, preferentially translocates to the Golgi in response to physiologic Ca(2+) mobilization. We propose that cytosolic phospholipase A2α, COX-2, and mPGES-1 in the Golgi comprise a dedicated system for COX-2-dependent PGE2 biosynthesis.

Methanol Extract of Artemisia apiacea Hance Attenuates the Expression of Inflammatory Mediators via NF- κ B Inactivation

Artemisia apiacea Hance is one of the most widely used herbs for the treatment of malaria, jaundice, and dyspeptic complaint in oriental medicine. This study investigated the effects of methanol extracts of A. apiacea Hance (MEAH) on the induction of inducible nitric oxide synthase (iNOS) and proinflammatory mediators by lipopolysaccharide (LPS) in Raw264.7 macrophage cells and also evaluated the in vivo effect of MEAH on carrageenan-induced paw edema in rats. MEAH treatment in Raw264.7 cells significantly decreased LPS-inducible nitric oxide production and the expression of iNOS in a concentration-dependent manner, while MEAH (up to 100 μg/mL) had no cytotoxic activity. Results from immunoblot analyses and ELISA revealed that MEAH significantly inhibited the expression of cyclooxygenase-2, tumor necrosis factor-α, interleukin-1β, and interleukin-6 in LPS-activated cells. As a plausible molecular mechanism, increased degradation and phosphorylation of inhibitory-κBα and nuclear factor-κB accumulation in the nucleus by LPS were partly blocked by MEAH treatment. Finally, MEAH treatment decreased the carrageenan-induced formation of paw edema and infiltration of inflammatory cells in rats. These results demonstrate that MEAH has an anti-inflammatory therapeutic potential that may result from the inhibition of nuclear factor-κB activation, subsequently decreasing the expression of proinflammatory mediators.

Differential COX-2 induction by viral and bacterial PAMPs: Consequences for cytokine and interferon responses and implications for anti-viral COX-2 directed therapies

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We report interactions of Toll-like receptors (TLRs) with COX enzymes in vivo.

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COX-2 was broadly induced by LPS (TLR4) but more locally by poly(I:C) (TLR3).

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COX-1/2 deletion modified the response to TLR activation in a TLR-specific manner.

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COX-2 deletion enhanced interferon responses to viral-type TLR3/7/9 ligands.

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COX-2 inhibition could provide a novel anti-viral therapeutic strategy.

Cyclooxygenase 2 (COX)-2 is induced by bacterial and viral infections and has complex, poorly understood roles in anti-pathogen immunity. Here, we use a knock-in luciferase reporter model to image Cox2 expression across a range of tissues in mice following treatment with the either the prototypical bacterial pathogen-associated molecular pattern (PAMP), LPS, which activates Toll-like receptor (TLR)4, or with poly(I:C), a viral PAMP, which activates TLR3. LPS induced Cox2 expression in all tissues examined. In contrast, poly(I:C) elicited a milder response, limited to a subset of tissues. A panel of cytokines and interferons was measured in plasma of wild-type, Cox1^−/− and Cox2^−/− mice treated with LPS, poly(I:C), MALP2 (TLR2/6), Pam3CSK4 (TLR2/1), R-848 (TLR7/8) or CpG ODN (TLR9), to establish whether/how each COX isoform modulates specific PAMP/TLR responses. Only LPS induced notable loss of condition in mice (inactivity, hunching, piloerection). However, all TLR agonists produced cytokine responses, many of which were modulated in specific fashions by Cox1 or Cox2 gene deletion. Notably we observed opposing effects of Cox2 gene deletion on the responses to the bacterial PAMP, LPS, and the viral PAMP, poly(I:C), consistent with the differing abilities of the PAMPs to induce Cox2 expression. Cox2 gene deletion limited the plasma IL-1β and interferon-γ responses and hypothermia produced by LPS. In contrast, in response to poly(I:C), Cox2^−/− mice exhibited enhanced plasma interferon (IFNα,β,γ,λ) and related cytokine responses (IP-10, IL-12). These observations suggest that a COX-2 selective inhibitor, given early in infection, may enhance and/or prolong endogenous interferon responses, and thereby increase anti-viral immunity.

Cyclooxygenase-2, prostaglandin E2 glycerol ester and nitric oxide are involved in muscarine-induced presynaptic enhancement at the vertebrate neuromuscular junction

Previous work has demonstrated that activation of muscarinic acetylcholine receptors at the lizard neuromuscular junction (NMJ) induces a biphasic modulation of evoked neurotransmitter release: an initial depression followed by a delayed enhancement. The depression is mediated by the release of the endocannabinoid 2-arachidonylglycerol (2-AG) from the muscle and its binding to cannabinoid type 1 receptors on the motor nerve terminal. The work presented here suggests that the delayed enhancement of neurotransmitter release is mediated by cyclooxygenase-2 (COX-2) as it converts 2-AG to the glycerol ester of prostaglandin E2 (PGE2-G). Using immunofluorescence, COX-2 was detected in the perisynaptic Schwann cells (PSCs) surrounding the NMJ. Pretreatment with either of the selective COX-2 inhibitors, nimesulide or DuP 697, prevents the delayed increase in endplate potential (EPP) amplitude normally produced by muscarine. In keeping with its putative role as a mediator of the delayed muscarinic effect, PGE2-G enhances evoked neurotransmitter release. Specifically, PGE2-G increases the amplitude of EPPs without altering that of spontaneous miniature EPPs. As shown previously for the muscarinic effect, the enhancement of evoked neurotransmitter release by PGE2-G depends on nitric oxide (NO) as the response is abolished by application of either N(G)-nitro-l-arginine methyl ester (l-NAME), an inhibitor of NO synthesis, or carboxy-PTIO, a chelator of NO. Intriguingly, the enhancement is not prevented by AH6809, a prostaglandin receptor antagonist, but is blocked by capsazepine, a TRPV1 and TRPM8 receptor antagonist. Taken together, these results suggest that the conversion of 2-AG to PGE2-G by COX-2 underlies the muscarine-induced enhancement of neurotransmitter release at the vertebrate NMJ.

Cytokine gene expression and prostaglandin production in head kidney leukocytes isolated from Atlantic cod (Gadus morhua) added different levels of arachidonic acid and eicosapentaenoic acid

Primary head kidney leukocytes from Atlantic cod were isolated to evaluate the use of arachidonic acid and eicosapentaenoic acid by cyclooxygenases and the production of prostaglandins E₂ and E₃. The expression of cyclooxygenase genes and selected interleukin genes like Interleukin 1β, Interleukin 6, interleukin 8 and interleukin 10 were monitored. Increasing concentrations of eicosapentaenoic acid and arachidonic acid in equal amounts increased cyclooxygenase2 transcription as well as cell secretion of prostaglandin E₂. Even though the ratio of the two fatty acids was 1:1, the ratio between prostaglandin E₂ and E₃ was 50:1. The addition of arachidonic acid alone increased prostaglandin E₂ secretion but did not induce cyclooxygenase2 transcription. However, when the concentration of eicosapentaenoic acid was increased, maintaining arachidonic acid constant, both prostaglandin E₃ and prostaglandin E₂ production was induced and the prostaglandin E₂ production was higher than in cell cultures only added arachidonic acid. An up-regulation of cyclooxygenase2 transcription was also observed. The addition of the two fatty acids also affected the immune response by alteration of leukocytic cytokines gene expression. According to our results the Cyclooxygenase in cod seem to prefer arachidonic acid as substrate. Therefore, we suggest that the shift from marine oils (rich in n-3 fatty acids) to plant oils (higher in n-6 fatty acids) in the diet of commercially reared Atlantic cod could have negative effects on the whole organism through the increase in the production of prostaglandins belonging to those derived from n-6 fatty acids.

The absence of myocardial calcium-independent phospholipase A2γ results in impaired prostaglandin E2 production and decreased survival in mice with acute Trypanosoma cruzi infection

Cardiomyopathy is a serious complication of Chagas' disease, caused by the protozoan parasite Trypanosoma cruzi. The parasite often infects cardiac myocytes, causing the release of inflammatory mediators, including eicosanoids. A recent study from our laboratory demonstrated that calcium-independent phospholipase A2γ (iPLA2γ) accounts for the majority of PLA2 activity in rabbit ventricular myocytes and is responsible for arachidonic acid (AA) and prostaglandin E2 (PGE2) release. Thus, we hypothesized that cardiac iPLA2γ contributes to eicosanoid production in T. cruzi infection. Inhibition of the isoform iPLA2γ or iPLA2β, with the R or S enantiomer of bromoenol lactone (BEL), respectively, demonstrated that iPLA2γ is the predominant isoform in immortalized mouse cardiac myocytes (HL-1 cells). Stimulation of HL-1 cells with thrombin, a serine protease associated with microthrombus formation in Chagas' disease and a known activator of iPLA2, increased AA and PGE2 release, accompanied by platelet-activating factor (PAF) production. Similarly, T. cruzi infection resulted in increased AA and PGE2 release over time that was inhibited by pretreatment with (R)-BEL. Further, T. cruzi-infected iPLA2γ-knockout (KO) mice had lower survival rates and increased tissue parasitism compared to wild-type (WT) mice, suggesting that iPLA2γ-KO mice were more susceptible to infection than WT mice. A significant increase in iPLA2 activity was observed in WT mice following infection, whereas iPLA2γ-KO mice showed no alteration in cardiac iPLA2 activity and produced less PGE2. In summary, these studies demonstrate that T. cruzi infection activates cardiac myocyte iPLA2γ, resulting in increased AA and PGE2 release, mediators that may be essential for host survival during acute infection. Thus, these studies suggest that iPLA2γ plays a cardioprotective role during the acute stage of Chagas' disease.

Anti-inflammatory effects of glyceollins derived from soybean by elicitation with Aspergillus sojae

OBJECTIVE

Given the preventive effect of soy intake against several chronic diseases, this study was conducted to investigate the inhibitory activity against inflammatory response of phytoalexins glyceollins derived from soybean isoflavones by treatment with a biotic elicitor.

METHODS

Using RAW264.7 cells, we examined the effects of glyceollins on production of nitric oxide (NO) and inflammatory cytokines, expression of inducible nitric oxide synthase (iNOS) and cyclo-oxygenase (COX)-2, and activation of NF-кB, induced by lipopolysaccharide (LPS).

RESULTS

Our data showed that glyceollins effectively inhibited NO production, IL-6 release, and expression of iNOS and COX-2 induced by LPS. In particular, glyceollins suppressed the LPS-induced phosphorylation of NF-кB p65, suggesting that the compounds inhibit the production of NO and transcriptional activation of COX-2 by regulating NF-кB activity. In another experiment we found that glyceollins enhanced the expression of heme oxygenase 1 in LPS-treated RAW264.7 cells. Glyceollins also reduced TPA-induced skin inflammation in a mouse model, confirming the anti-inflammatory activity of glyceollins in an in-vivo system as well as in a cell culture system.

CONCLUSION

Glyceollins exert an anti-inflammatory effect, which is mediated through the inhibition of NF-κB activation in LPS-activated murine RAW264.7 cells. Glyceollins merit further study as potential therapeutic agents for inflammatory disorders.

Non-Steroidal Anti-Inflammatory Drugs in the Carcinogenesis of the Gastrointestinal Tract

It is estimated that underlying infections and inflammatory responses are linked to 15–20% of all deaths from cancer worldwide. Inflammation is a physiologic process in response to tissue damage resulting from microbial pathogen infection, chemical irritation, and/or wounding. Tissues injured throughout the recruitment of inflammatory cells such as macrophages and neutrophils, generate a great amount of growth factors, cytokines, and reactive oxygen and nitrogen species that may cause DNA damage that in turn predisposes to the transformation from chronic inflammation to neoplasia. Cyclooxygenase (COX), playing a key role in cell homeostasis, angiogenesis and tumourigenesis, may represent the link between inflammation and cancer. Currently COX is becoming a pharmacological target for cancer prevention and treatment.

Anti-inflammatory effects of ethyl acetate fraction from Melilotus suaveolens Ledeb on LPS-stimulated RAW 264.7 cells

AIM OF THE STUDY

This paper aimed to elucidate the anti-inflammatory effects of EtOAc fraction prepared from Melilotus suaveolens Ledeb ethanol extract with a cellular model of LPS-stimulated RAW 264.7 cell.

MATERIALS AND METHODS

Some key pro-inflammatory cytokines and mediators including IL-1 beta, IL-6, NO, iNOS, COX-2 and TNF-alpha, two important anti-inflammatory cytokines and mediators IL-10 and HO-1, I-kappaB and NF-kappaB were studied by sandwich ELISA, real-time PCR, western blot analysis and immunocytochemistry. At last a HPLC fingerprint was taken to evaluate the fraction.

RESULTS

The EtOAc fraction could significantly inhibit the production of IL-1 beta, IL-6, NO, TNF-alpha, COX-2 in LPS-stimulated cell than that of single LPS-stimulated cell (p<0.01 or p<0.05), and the extract could increase the production of IL-10 and HO-1 than that of single LPS intervention cell (p<0.01 or p<0.05). Meanwhile, the extract also could inhibit the production of NF-kappaB compared to single LPS-stimulated cell. All the results showed that the extract had a good anti-inflammatory effect on LPS-stimulated RAW264.7 cell.

CONCLUSIONS

Taken together, the anti-inflammatory actions of M. suaveolens Ledeb EtOAc fraction might be due to the down-regulation of IL-1 beta, IL-6, NO, TNF-alpha and COX-2 via the suppression of NF-kappaB activation, and another pathway was up regulating the production of IL-10 and HO-1. Meanwhile, the EtOAc fraction might be further studied to isolate the active anti-inflammatory ingredients besides coumarin.

Cyclooxygenase Allosterism, Fatty Acid-mediated Cross-talk between Monomers of Cyclooxygenase Homodimers

Prostaglandin endoperoxide H synthases (PGHSs) 1 and 2, also known as cyclooxygenases (COXs), catalyze the oxygenation of arachidonic acid (AA) in the committed step in prostaglandin (PG) biosynthesis. PGHSs are homodimers that display half of sites COX activity with AA; thus, PGHSs function as conformational heterodimers. Here we show that, during catalysis, fatty acids (FAs) are bound at both COX sites of a PGHS-2 dimer. Initially, an FA binds with high affinity to one COX site of an unoccupied homodimer. This monomer becomes an allosteric monomer, and it causes the partner monomer to become the catalytic monomer that oxygenates AA. A variety of FAs can bind with high affinity to the COX site of the monomer that becomes the allosteric monomer. Importantly, the efficiency of AA oxygenation is determined by the nature of the FA bound to the allosteric monomer. When tested with low concentrations of saturated and monounsaturated FAs (e.g. oleic acid), the rates of AA oxygenation are typically 1.5-2 times higher with PGHS-2 than with PGHS-1. These different kinetic behaviors of PGHSs may account for the ability of PGHS-2 but not PGHS-1 to efficiently oxygenate AA in intact cells when AA is a small fraction of the FA pool such as during "late phase" PG synthesis.

Effects of Bothrops asper snake venom on the expression of cyclooxygenases and production of prostaglandins by peritoneal leukocytes in vivo, and by isolated neutrophils and macrophages in vitro

In this study, the ability of Bothrops asper snake venom (BaV) to increase the production of prostaglandins PGE(2) and PGD(2) was assessed in a mouse model in vivo and in inflammatory cells in vitro. In addition, the expressions of COX-1 and COX-2 were assessed. BaV induced an increment in the in vivo synthesis of PGE(2) and PGD(2), together with an enhanced expression of COX-2, but not of COX-1. However, enzymatic activities of COX-1 and COX-2 were increased. Incubation of isolated macrophages and neutrophils with a sub-cytotoxic concentration of BaV in vitro resulted in increased release of PGE(2) and PGD(2) by macrophages and PGE(2) by neutrophils, concomitantly with an increment in the expression of COX-2, but not of COX-1 by both cell types. Our results demonstrate the ability of BaV to promote the expression of COX-2 and to induce the synthesis of proinflammatory prostaglandins. Macrophages and neutrophils may be important targets for this venom under in vivo situation.

A novel mitogen-activated protein kinase phosphatase-1 and glucocorticoid receptor (GR) interacting protein-1-dependent combinatorial mechanism of gene transrepression by GR

Glucocorticoids have major antiinflammatory effects. Because COX-2 is the rate-limiting enzyme for proinflammatory prostaglandins, this study investigated the combinatorial inhibitory role of glucocorticoid receptor (GR) in COX-2 gene induction in macrophages and sought to identify the molecular mechanisms for that inhibition. Glucocorticoid-activated GR repressed COX-2 gene induction by lipopolysaccharide (LPS). Activated GR inhibited LPS-induced activator protein 1 activity, which in turn decreased activating transcription factor 2/c-Jun phosphorylation. The inhibition of MAPK-dependent activating transcription factor 2/c-Jun phosphorylation by GR in COX-2 repression was a result of MAPK phosphatase-1 (MKP-1) induction. Although GR did not inhibit LPS-induced p65 phosphorylation or nuclear factor-kappaB DNA binding activity, deletion of the nuclear factor-kappaB binding site in the COX-2 gene suppressed the ability of glucocorticoid to attenuate COX-2 induction. Chromatin immunoprecipitation and transfection assays revealed that a p65 DNA complex involving GR-bound GR-interacting protein 1 (GRIP1) also contributed to COX-2 repression. Additional knockdown and transfection assays identified other inflammatory genes coordinately regulated by MKP-1 and GRIP1. In summary, activated GR was found to antagonize the LPS-dependent induction of the COX-2 gene via a novel combinatorial mechanism involving MKP-1-mediated activator protein 1 inhibition and GR/GRIP1 recruitment to the p65 DNA complex; moreover, this work facilitated the identification of other GR-responding MKP-1/GRIP1-regulated genes.

Targeting mRNA stability arrests inflammatory bone loss

Many proinflammatory cytokines contain adenylate-uridylate-rich elements (AREs) within the 3'-untranslated region (UTR) that confer rapid mRNA destabilization. During the inflammatory response, cytokine mRNA are stabilized via complex interactions with RNA-binding proteins controlled by phosphorylation via multiple signaling pathways including the mitogen-activated protein kinases (MAPKs). In the absence of inflammation, a key cytokine-regulating RNA-binding protein, tristetraprolin (TTP), shuttles mRNA transcripts to degradation machinery in order to maintain low levels of inflammatory cytokines. Using this general model of mRNA decay, over expression of TTP was evaluated in an experimental model of inflammatory bone loss to determine whether altering cytokine mRNA stability has an impact in pathological bone resorption. Using adenoviral-delivered TTP, significant reductions of interleukin-6 (IL-6), tumor necrosis factor-alpha (TNF-alpha), and prostaglandin (PG)E(2) were observed in vitro through a mechanism consistent with targeting mRNA stability. In vivo analysis indicates a significant protective effect from inflammation-induced bone loss and inflammatory infiltrate in animals overexpressing TTP compared with reporter controls. These findings provide experimental evidence that mRNA stability is a valid therapeutic target in inflammatory bone loss.

Predominance of cyclooxygenase 1 over cyclooxygenase 2 in the generation of proinflammatory prostaglandins in autoantibody-driven K/BxN serum-transfer arthritis

OBJECTIVE

Prostaglandins (PGs) are found in high levels in the synovial fluid of patients with rheumatoid arthritis, and nonsteroidal blockade of these bioactive lipids plays a role in patient care. The aim of this study was to explore the relative contribution of cyclooxygenase (COX) isoforms and PG species in the autoantibody-driven K/BxN serum-transfer arthritis.

METHODS

The prostanoid content of arthritic ankles was assessed in ankle homogenates, and the importance of this pathway was confirmed with pharmacologic blockade. The presence of COX isoforms was assessed by Western blotting and their functional contribution was compared using COX-1-/- and COX-2-/- mice as well as isoform-specific inhibitors. The relative importance of PGE2 and PGI2 (prostacyclin) was determined using mice deficient in microsomal PGE synthase 1 (mPGES-1) and in the receptors for PGI2.

RESULTS

High levels of PGE2 and 6-keto-PGF1alpha (a stable metabolite of PGI2) were detected in arthritic joint tissues, correlating strongly with the intensity of synovitis. Pharmacologic inhibition of PG synthesis prevented arthritis and ameliorated active disease. While both COX isoforms were found in inflamed joint tissues, only COX-1 contributed substantially to clinical disease; COX-1-/- mice were fully resistant to disease, whereas COX-2-/- mice remained susceptible. These findings were confirmed by isoform-specific pharmacologic inhibition. Mice lacking mPGES-1 (and therefore PGE2) developed arthritis normally, whereas mice incapable of responding to PGI2 exhibited a significantly attenuated arthritis course, confirming a role of PGI2 in this arthritis model.

CONCLUSION

These findings challenge previous paradigms of distinct "housekeeping" versus inflammatory functions of the COX isoforms and highlight the potential pathogenic contribution of prostanoids synthesized via COX-1, in particular PGI2, to inflammatory arthritis.

Two distinct pathways for cyclooxygenase-2 protein degradation

Cyclooxygenases (COX-1 and COX-2) are N-glycosylated, endoplasmic reticulum-resident, integral membrane proteins that catalyze the committed step in prostanoid synthesis. COX-1 is constitutively expressed in many types of cells, whereas COX-2 is usually expressed inducibly and transiently. The control of COX-2 protein expression occurs at several levels, and overexpression of COX-2 is associated with pathologies such as colon cancer. Here we have investigated COX-2 protein degradation and demonstrate that it can occur through two independent pathways. One pathway is initiated by post-translational N-glycosylation at Asn-594. The N-glycosyl group is then processed, and the protein is translocated to the cytoplasm, where it undergoes proteasomal degradation. We provide evidence from site-directed mutagenesis that a 27-amino acid instability motif (27-IM) regulates posttranslational N-glycosylation of Asn-594. This motif begins with Glu-586 8 residues upstream of the N-glycosylation site and ends with Lys-612 near the C terminus at Leu-618. Key elements of the 27-IM include a helix involving residues Glu-586 to Ser-596 with Asn-594 near the end of this helix and residues Leu-610 and Leu-611, which are located in an apparently unstructured downstream region of the 27-IM. The last 16 residues of the 27-IM, including Leu-610 and Leu-611, appear to promote N-glycosylation of Asn-594 perhaps by causing this residue to become exposed to appropriate glycosyl transferases. A second pathway for COX-2 protein degradation is initiated by substrate-dependent suicide inactivation. Suicide-inactivated protein is then degraded. The biochemical steps have not been resolved, but substrate-dependent degradation is not inhibited by proteasome inhibitors or inhibitors of lysosomal proteases. The pathway involving the 27-IM occurs at a constant rate, whereas degradation through the substrate-dependent process is coupled to the rate of substrate turnover.

Nutritionally essential fatty acids and biologically indispensable cyclooxygenases

The study of cyclooxygenases (COXs), targets of aspirin and related drugs, is rooted in the discovery of essential fatty acids (EFAs). There are two COXs that convert EFAs, primarily arachidonic acid, to prostaglandins. Each COX is involved with distinct biologies. COX-1 expression is constitutive while COX-2 is inducible. The two COXs might have evolved partly to permit prostaglandin formation at different tissue sites. However, COX-2 is sometimes induced in cells already expressing COX-1, and in these instances, COX-2 functions while COX-1 is latent. This can occur because of unique biochemical properties of COX-2 that enable cells to form prostaglandins when arachidonic acid comprises a small fraction of available fatty acids and the concentrations of peroxides that are necessary for COX to function are low.

Prostaglandin Endoperoxide H Synthases

The cyclooxygenase (COX) activity of prostaglandin endoperoxide H synthases (PGHSs) converts arachidonic acid and O2 to prostaglandin G2 (PGG2). PGHS peroxidase (POX) activity reduces PGG2 to PGH2. The first step in POX catalysis is formation of an oxyferryl heme radical cation (Compound I), which undergoes intramolecular electron transfer forming Intermediate II having an oxyferryl heme and a Tyr-385 radical required for COX catalysis. PGHS POX catalyzes heterolytic cleavage of primary and secondary hydroperoxides much more readily than H2O2, but the basis for this specificity has been unresolved. Several large amino acids form a hydrophobic "dome" over part of the heme, but when these residues were mutated to alanines there was little effect on Compound I formation from H2O2 or 15-hydroperoxyeicosatetraenoic acid, a surrogate substrate for PGG2. Ab initio calculations of heterolytic bond dissociation energies of the peroxyl groups of small peroxides indicated that they are almost the same. Molecular Dynamics simulations suggest that PGG2 binds the POX site through a peroxyl-iron bond, a hydrogen bond with His-207 and van der Waals interactions involving methylene groups adjoining the carbon bearing the peroxyl group and the protoporphyrin IX. We speculate that these latter interactions, which are not possible with H2O2, are major contributors to PGHS POX specificity. The distal Gln-203 four residues removed from His-207 have been thought to be essential for Compound I formation. However, Q203V PGHS-1 and PGHS-2 mutants catalyzed heterolytic cleavage of peroxides and exhibited native COX activity. PGHSs are homodimers with each monomer having a POX site and COX site. Cross-talk occurs between the COX sites of adjoining monomers. However, no cross-talk between the POX and COX sites of monomers was detected in a PGHS-2 heterodimer comprised of a Q203R monomer having an inactive POX site and a G533A monomer with an inactive COX site.

Enzymes and receptors of prostaglandin pathways with arachidonic acid-derived versus eicosapentaenoic acid-derived substrates and products

Dietary fish oil containing omega 3 highly unsaturated fatty acids has cardioprotective and anti-inflammatory effects. Prostaglandins (PGs) and thromboxanes are produced in vivo both from the omega 6 fatty acid arachidonic acid (AA) and the omega 3 fatty acid eicosapentaenoic acid (EPA). Certain beneficial effects of fish oil may result from altered PG metabolism resulting from increases in the EPA/AA ratios of precursor phospholipids. Here we report in vitro specificities of prostanoid enzymes and receptors toward EPA-derived, 3-series versus AA-derived, 2-series prostanoid substrates and products. The largest difference was seen with PG endoperoxide H synthase (PGHS)-1. Under optimal conditions purified PGHS-1 oxygenates EPA with only 10% of the efficiency of AA, and EPA significantly inhibits AA oxygenation by PGHS-1. Two- to 3-fold higher activities or potencies with 2-series versus 3-series compounds were observed with PGHS-2, PGD synthases, microsomal PGE synthase-1 and EP1, EP2, EP3, and FP receptors. Our most surprising observation was that AA oxygenation by PGHS-2 is only modestly inhibited by EPA (i.e. PGHS-2 exhibits a marked preference for AA when EPA and AA are tested together). Also unexpectedly, TxA(3) is about equipotent to TxA(2) at the TP alpha receptor. Our biochemical data predict that increasing phospholipid EPA/AA ratios in cells would dampen prostanoid signaling with the largest effects being on PGHS-1 pathways involving PGD, PGE, and PGF. Production of 2-series prostanoids from AA by PGHS-2 would be expected to decrease in proportion to the compensatory decrease in the AA content of phospholipids that would result from increased incorporation of omega 3 fatty acids such as EPA.

Induction of prostaglandin E synthase by gastroesophageal reflux contents in normal esophageal epithelial cells and esophageal cancer cells

The synthesis of prostaglandin E2 (PGE2) requires cyclooxygenase (COX) and prostaglandin E synthase (PGES). There are two forms of PGES: cytosolic PGES (cPGES) and microsomal PGES (mPGES)-1. In this study, we investigated the effects of gastroesophageal reflux (GER) contents on PGES and COX-2 in esophageal cells. We incubated a human normal esophageal cell line, two esophageal squamous cell carcinoma (SCC) cell lines, and two esophageal adenocarcinoma (ADC) cell lines with GER contents. The production of PGE2 by these cells was assayed with an enzyme immunoassay kit. The protein expression of COX-2, cPGES, and mPGES-1 was confirmed by immunoblot analysis. The following results were obtained: GER contents induced the expression of COX-2 in all five cell lines. In normal esophageal cells, cPGES, but not mPGES-1, was detected in the cytosolic fraction. GER contents induced the expression of cPGES in the microsomal fraction. In SCC cells, cPGES was expressed in the cytosolic fraction, and mPGES-1 was expressed in the microsomal fraction. GER contents induced the expression of mPGES-1 in the microsomal fraction. In ADC cells, cPGES was expressed in both the cytosolic and microsomal fractions. GER contents induced the expression of both cPGES and mPGES-1 in the microsomal fraction. In conclusion, our results suggest that GER contents induce PGE2 production in esophageal cells. However, there are different isoforms of PGES in normal cells, SCC cells, and ADC cells.

Dual ligand stimulation of RAW 264.7 cells uncovers feedback mechanisms that regulate TLR-mediated gene expression

To characterize how signaling by TLR ligands can be modulated by non-TLR ligands, murine RAW 264.7 cells were treated with LPS, IFN-gamma, 2-methyl-thio-ATP (2MA), PGE(2), and isoproterenol (ISO). Ligands were applied individually and in combination with LPS, for 1, 2, and 4 h, and transcriptional changes were measured using customized oligo arrays. We used nonadditive transcriptional responses to dual ligands (responses that were reproducibly greater or less than the expected additive responses) as a measure of pathway interaction. Our analysis suggests that cross-talk is limited; <24% of the features with significant responses to the single ligands responded nonadditively to a dual ligand pair. PGE(2) and ISO mainly attenuated, while 2MA enhanced, LPS-induced transcriptional changes. IFN-gamma and LPS cross-regulated the transcriptional response induced by each other: while LPS preferentially enhanced IFN-gamma-induced changes in gene expression at 1 h, IFN-gamma signaling primarily attenuated LPS-induced changes at 4 h. Our data suggest specific cross-talk mechanisms: 1) LPS enhances the expression of IFN-gamma-response genes by augmenting STAT1 activity and by activating NF-kappaB, which synergizes with IFN-gamma-induced transcriptional factors; 2) IFN-gamma attenuates the late LPS transcriptional response by increasing the expression of suppressor of cytokine signaling 1 and cytokine-inducible SH2-containing protein expression; 3) 2MA modulates LPS secondary transcriptional response by increasing IFN-beta and inhibiting IL-10 gene expression; 4) PGE(2) and ISO similarly regulate the LPS transcriptional response. They increase IL-10 transcription, resulting in attenuated expression of known IL-10-suppressed genes.

Effect of arachidonic and eicosapentaenoic acid metabolism on RAW 264.7 macrophage proliferation

Prostaglandins (PGs) and leukotrienes (LTs) derived from arachidonic acid (AA) are potent mediators of inflammation and cell proliferation. Dietary intake of eicosapentaenoic acid (EPA) appears beneficial to both inflammatory processes and cell proliferation. However, there is no clear mechanism explaining these effects. In this study, we investigated the effect of EPA on the AA incorporation in phospholipid membranes, on AA release and metabolism, and consequently, on PG synthesis. Our results showed not only that [(3)H]AA and [(14)C]EPA were similar incorporated into RAW 264.7 macrophage membranes, but also that the redistribution pattern between phospholipids was alike. [(3)H]AA or [(14)C]EPA release was induced by fetal bovine serum (FBS) in a similar fashion with AA metabolizing 3-fold more than EPA. In this way, we observed that AA could be metabolized by cyclooxygenase (COX)-1, COX-2 and 5-lipoxygenase (5-LOX) whereas EPA was metabolized by COX-2 and 5-LOX pathways. Moreover, both fatty acids were able to induce COX-2 expression. When we incubated [(3)H]AA labeled cells with exogenous EPA, we observed that EPA did not modify FBS-induced [(3)H]AA release but that the presence of EPA decreased [(3)H]AA metabolism and therefore PGE(2) synthesis. Moreover, we studied the effect of AA and EPA metabolites on macrophage proliferation. Our results showed that PGE(3) stimulated cell growth with a potency similar to that of PGE(2), whereas LTB(5) was less effective than LTB(4). These data suggest that the effects of EPA on cell growth might be attributable, at least in part, to the marked decrease of eicosanoid release.

Divergent cyclooxygenase responses to fatty acid structure and peroxide level in fish and mammalian prostaglandin H synthases

Prostanoid synthesis in mammalian tissues is regulated at the level of prostaglandin H synthase (PGHS) cyclooxygenase catalysis by the availability and structure of substrate fatty acid and the availability of peroxide activator. Two major PGHS isoforms, with distinct pathophysiological functions and catalytic regulation, have been characterized in mammals; a functionally homologous PGHS isoform pair has been cloned from an evolutionarily distant vertebrate, brook trout. The cyclooxygenase activities of recombinant brook trout PGHS-1 and -2 were characterized to test the generality of mammalian regulatory paradigms for substrate specificity, peroxide activation, and product shifting by aspirin. Both trout cyclooxygenases had much more restrictive substrate specificities than their mammalian counterparts, with pronounced discrimination toward arachidonate (20:4n-6) and against eicosapentaenoate (20:5n-3) and docosahexaenoate (22:6n-3), the latter two prominent in trout tissue lipids. Aspirin treatment did not increase lipoxygenase-type catalysis by either trout enzyme. Both trout enzymes had higher requirements for peroxide activator than their mammalian counterparts, though the preferential peroxide activation of PGHS-2 over PGHS-1 seen in mammals was conserved in the fish enzymes. The divergence in cyclooxygenase characteristics between the trout and mammalian PGHS proteins may reflect accomodations to differences among vertebrates in tissue lipid composition and general redox state.

Positioning prostanoids of the D and J series in the immunopathogenic scheme

Prostaglandin D(2) (PGD(2)) is produced by a variety of immune and non-hematopoietic cells and appears to function in both an inflammatory and homeostatic capacity. Two genetically distinct PGD(2)-synthesizing enzymes have been identified to date, including hematopoietic- and lipocalin-type PGD synthases (H-PGDS and L-PGDS, respectively). Though the inter-species expression profiles of these two enzymes vary widely, H-PGDS is generally localized to the cytosolic aspect of immune and inflammatory cells, whereas L-PGDS is more resigned to tissue-based expression. PGD(2) activity is principally mediated through two unique G protein-coupled receptors (GPCR), designated DP(1) and DP(2). These receptors exhibit overlapping binding profiles, yet their respective agonists elicit generally distinctive responses. Additional to DP receptors, the PGD(2) metabolite 15-deoxy-Delta(12,14)-PGJ(2) (15d-PGJ(2)) binds the nuclear peroxisome proliferator-activated receptor gamma (PPARgamma) and has the facility to initiate a variety of anti-inflammatory phenotypes either through or independent of PPARgamma association. This review highlights the collective relevance of PGD(2) and its respective synthases, receptors, and metabolites in immunopathologic responses.

Differentiation-dependent regulation of the cyclooxygenase cascade during adipogenesis suggests a complex role for prostaglandins

AIM

A thorough understanding of the mechanisms of adipocyte differentiation and metabolism is important for the prevention and/or treatment of obesity and its complications, including type 2 diabetes mellitus. A complex role for prostaglandins (PGs) in adipogenesis is suggested. We examined the expression and cellular localization of enzymes in the cyclooxygenase (COX) cascade that synthesize PGs as well as the PG profile as a function of differentiation status in 3T3-L1 cells.

METHODS

Murine 3T3-L1 preadipocytes were used as a model for studies of adipocyte differentiation induced by a hormone cocktail and compared with the parental fibroblastic line NIH 3T3. Both cell lines were incubated in maintenance medium or differentiation medium. Nine days after differentiation, the expression of enzymes in the COX cascade was evaluated by immunoblot analysis, reverse transcriptase-polymerase chain reaction (RT-PCR) and immunocytochemistry, and PG formation was examined using enzyme immunoassay.

RESULTS

A differentiation-dependent diminution of COX-1 and COX-2 mRNA and cognate proteins in 3T3-L1 cells was observed. PG release, including PGE(2), 6-keto PGF(1alpha), PGD(2) and 15d-PGJ(2), significantly decreased following differentiation in 3T3-L1 cells (anova/Tukey, p < 0.05). However, microsomal PGE synthase (mPGES) and lipocalin-type PGD synthase (L-PGDS) were selectively upregulated. Immunocytochemistry revealed that COX-1 and COX-2 became intracellularly more diffuse upon differentiation, whereas mPGES was redistributed to the nuclear compartment.

CONCLUSIONS

Regulation of PG formation and COX-2 expression in 3T3-L1 cells is differentiation-dependent and involves changes in the levels of gene expression of the individual isoforms as well as redistribution of the enzymes within cellular compartments.

Synthesis of 4-(5-[18F]fluoromethyl-3-phenylisoxazol-4-yl)benzenesulfonamide, a new [18F]fluorinated analogue of valdecoxib, as a potential radiotracer for imaging cyclooxygenase-2 with positron emission tomography

Fluoroalkyl and fluoroaryl analogues of valdecoxib were found to possess potent inhibitory activities against cyclooxygenase-2 comparable to that of the parent valdecoxib. Among them, the fluoromethyl analogue was chosen for 18F-labeling. Thus, 4-(5-[18F]fluoromethyl-3-phenylisoxazol-4-yl)benzenesulfonamide (approximately 2000 Ci/mmol at end of synthesis) was synthesized by [18F]fluoride-ion displacement of the corresponding tosylate in approximately 40% decay-corrected radiochemical yield within approximately 120 min from end of bombardment.

Cyclooxygenase-2: how good is it as a target for cancer chemoprevention?

There is now substantial evidence for a role for cyclooxygenase-2 (COX-2)-mediated prostaglandin (PG) signalling during carcinogenesis in a number of tissues and selective COX-2 inhibitors (coxibs) were considered attractive candidate chemoprevention agents. However, recent concerns over the toxicity of systemic selective COX-2 inhibition and the realisation that COX-1 may also contribute to carcinogenesis have cast some doubt on COX-2 inhibition as a safe and effective chemoprevention strategy. This review will describe the available evidence relating to the known benefits (preventive efficacy in rodent tumorigenesis models and limited human data from small randomised, controlled trials and epidemiological studies) and risks (cardiovascular and renal toxicity) of coxib therapy for cancer chemoprevention. Potential, alternative strategies for inhibition of COX-PG signalling that minimise or avoid systemic selective COX-2 inhibition will also be discussed.

The role of cyclooxygenase in gastric mucosal protection

COX-1 and COX-2 are two cyclooxygenase enzymes responsible for prostanoid production. COX-2 is expressed in inflammatory cells and fibroblasts of the gastric mucosa, and through the production of various growth factors including hepatocyte growth factor (HGF) and vascular endothelial growth factor (VEGF), plays a key role in the tissue repair process. Aspirin induces and acetylates COX-2 to produce 15-(R)-epi-lipoxinA4, an anti-inflammatory mediator thought to protect the gastric mucosa against aspirin-induced injury. Recently, three different PGE synthases have been identified, that convert COX-2 metabolites into PGE2. mPGE synthase (mPGES)-1 has been shown to be inducible, and to colocalize with COX-2 in fibroblasts and macrophages infiltrating the gastric ulcer bed. cPGES and mPGES-2 have been found expressed in normal gastric mucosa, with no change in expression levels seen in gastritis or gastric ulcer tissue. Finally, this review discusses the role of these enzymes in the pathophysiology of the gastric mucosa, as well as the biologcal significance of their inhibition.

Depletion of iNOS-derived nitric oxide by prostaglandin H synthase-2 in inflammation-activated J774.2 macrophages through lipohydroperoxidase turnover

PGHS-2 (prostaglandin H synthase-2) is induced in mammalian cells by pro-inflammatory cytokines in tandem with iNOS [high-output ('inducible') nitric oxide synthase], and is co-localized with iNOS and nitrotyrosine in human atheroma macrophages. Herein, murine J774.2 macrophages incubated with lipopolysaccharide and interferon gamma showed induction of PGHS-2 and generated NO using iNOS that could be completely depleted by 12(S)-HPETE [12(S)-hydroperoxyeicosatetraenoic acid; 2.4 muM] or hydrogen peroxide (500 microM) (0.42+/-0.084 and 0.38+/-0.02 nmol x min(-1) x 10(6) cells(-1) for HPETE and H2O2 respectively). COS-7 cells transiently transfected with human PGHS-2 also showed HPETE- or H2O2-dependent NO decay (0.44+/-0.016 and 0.20+/-0.04 nmol x min(-1) x 10(6) cells(-1) for 2.4 microM HPETE and 500 microM H2O2 respectively). Finally, purified PGHS-2 consumed NO in the presence of HPETE or H2O2 (168 and 140 microM x min(-1) x microM enzyme(-1) for HPETE and H2O2 respectively), in a haem-dependent manner, with 20 nM enzyme consuming up to 4 microM NO. K(m) (app) values for NO and 15(S)-HPETE were 1.7+/-0.2 and 0.45+/-0.16 microM respectively. These data indicate that PGHS-2 catalytically consumes NO during peroxidase turnover and that pro-inflammatory cytokines simultaneously upregulate NO synthesis and degradation pathways in murine macrophages. Catalytic NO consumption by PGHS-2 represents a novel interaction between NO and PGHS-2 that may impact on the biological effects of NO in vascular signalling and inflammation.

A common polymorphism in the 3'UTR of cyclooxygenase 2/prostaglandin synthase 2 gene and risk of lung cancer in a Chinese population

Cyclooxygenases (COXs) are key enzymes that convert arachidonic acid to prostaglandins. Overexpression of COX-2, one of the COX isozymes, has been shown to be an early event in lung carcinogenesis and may play an important role in lung cancer development. A common single nucleotide polymorphism, T8473C, located within a potential functional region in the 3'UTR of COX-2 gene was identified and we hypothesized that this COX-2 variant is associated with lung cancer risk. To test this hypothesis, we genotyped this variant in a case-control study of 322 histologically-confirmed lung cancer patients and 323 age and sex frequency-matched cancer-free controls in a Chinese population. The results showed that the frequencies of variant genotypes 8473CT/CC were significantly less common in the cases (27.3%) than in the controls (35.3%) (P=0.034), suggesting that the 8473C allele was protective against lung cancer. Multivariate logistic regression analyses revealed that the COX-2 variant genotypes (8473CT/CC) were associated with a significantly decreased risk of lung cancer compared with the 8473TT wild-type homozygotes (OR=0.64, 95% CI=0.45-0.92). When we defined the reference group as non-smokers having the 8473CT/CC variant genotypes, the smokers with the 8473TT wild-type genotype had the greatest risk (adjusted OR=5.28, 95% CI=3.10-9.00). These findings indicate that the COX-2 T8473C polymorphism may contribute to lung cancer susceptibility in the Chinese population. Further larger molecular epidemiological studies are warranted to confirm these findings.

Role of reactive oxygen species in gynecologic diseases

Free radicals derived from molecular oxygen and nitrogen are highly reactive metabolites called reactive oxygen species (ROS). Cells continuously produce free radicals and ROS as part of the metabolic process. They are involved in the various functions of the reproductive system. Antioxidants are enzymes or compounds that scavenge and reduce the presence of free radicals. Normally, a balance exists between concentrations of reactive oxygen species and antioxidant scavenging systems. The disruption of the delicate balance between pro- and antioxidants results in oxidative stress. Oxidative stress has been implicated in embryo fragmentation, DNA damage, apoptosis and poor pregnancy outcome. It has also been implicated in a large number of gynecologic diseases, such as endometriosis, pre-eclampsia and maternal diabetes. The use of antioxidants may be beneficial in combating the harmful effects of oxidative stress in many of these diseases. The present review outlines the importance of these species in the pathology of various gynecologic diseases. (Reprod Med Biol 2004; 3: 177 - 199).

Electron microscope immunocytochemical localization of cyclooxygenase-1 and -2 in pseudopregnant rat corpus luteum during luteolysis

Prostaglandins converted from arachidonic acid by cyclooxygenases play an important regulatory role in regression of the corpus luteum. To reveal luteal distribution of cyclooxygenase isoforms during luteolysis, an electron microscope immunocytochemical study was performed. Cyclooxygenase-1 and -2 were found both in luteal steroid-producing and interstitial cells on days 13, 15 and 18 of the adult pseudopregnant rat. Cyclooxygenase-2 immunolabelling was predominantly seen in non-luteal cells. The two enzymes were localized in similar fashion to the plasma membrane, rough and smooth endoplasmic reticulum, lipid bodies and mitochondria, but differently in the nuclear compartment. Cyclooxygenase-1 labelling was found only in the perinuclear region, while cyclooxygenase-2 was localized to the nuclear envelope, region of condensed heterochromatin as well as at the perimeter of the heterochromatin. Nuclear residence may indicate additional roles for cyclooxygenase-2 in regulating gene expression. Identification of both enzymes on lipid bodies suggests that these inclusions may be involved in luteal prostanoid production.

Induction of cyclooxygenase-2 by bovine type I collagen in macrophages via C/EBP and CREB activation by multiple cell signaling pathways

Bovine type I collagen (Col-I) is utilized for medical purposes such as cosmetic surgery and wrinkle removal. Cyclooxygenase-2 (COX-2) plays roles in pathophysiological processes including inflammation and tumorigenesis. This study examines the effects of Col-I on the COX-2 expression and the signaling pathways in macrophages. Col-I increased the levels of COX-2 protein and mRNA in serum-stimulated Raw264.7 cells in a time- and concentration-dependent manner. Treatment of cells with Col-I increased CCAAT/enhancer binding protein (C/EBP) DNA binding. Antibody supershift experiments revealed that C/EBP DNA binding activity induced by Col-I depended largely on C/EBPbeta and C/EBPdelta. Immunocytochemistry showed that Col-I induced nuclear translocation of C/EBPbeta and C/EBPdelta, whose activation contributes to COX-2 induction. Overexpression of the dominant-negative mutant form of C/EBP abolished COX-2 induction by Col-I. Col-I also increased cyclic-AMP response element binding protein (CREB) binding to DNA. Inhibition of focal adhesion kinase (FAK) or downstream phosphoinositide 3-kinase and p70S6 kinase by specific chemical inhibitors prevented COX-2 induction by Col-I, and C/EBP and CREB from binding to their consensus DNA oligonucleotides. Experiments using chemical inhibitors or dominant-negative mutant vectors showed that the mitogen-activated protein (MAP) kinase pathways including p38-kinase and extracellular signal-regulated kinase (ERK1/2), but not c-Jun N-terminal kinase (JNK1), simultaneously regulated COX-2 induction by Col-I. This was in agreement with inhibition of Col-I-inducible C/EBP and CREB DNA binding by concomitant treatment with SB203580 and PD98059. These results provide evidence that Col-I induces COX-2 in serum-stimulated macrophages and that the multiple cell signaling pathways involving Src-focal adhesion kinase, phosphoinositide 3-kinase, and MAP kinases regulate COX-2 induction by Col-I via C/EBP and CREB activation.

Cyclooxygenase-1-dependent prostaglandin synthesis modulates tumor necrosis factor-alpha secretion in lipopolysaccharide-challenged murine resident peritoneal macrophages

Comprehensive studies of prostaglandin (PG) synthesis in murine resident peritoneal macrophages (RPM) responding to bacterial lipopolysaccharide (LPS) revealed that the primary PGs produced by RPM were prostacyclin and PGE(2). Detectable increases in net PG formation occurred within the first hour, and maximal PG formation had occurred by 6-10 h after LPS addition. Free arachidonic acid levels rose and peaked at 1-2 h after LPS addition and then returned to baseline. Cyclooxygenase-2 (COX-2) and microsomal PGE synthase levels markedly increased upon exposure of RPM to LPS, with the most rapid increases in protein expression occurring 2-6 h after addition of the stimulus. RPM constitutively expressed high levels of COX-1. Studies using isoform-selective inhibitors and RPM from mice bearing targeted deletions of ptgs-1 and ptgs-2 demonstrated that COX-1 contributes significantly to PG synthesis in RPM, especially during the initial 1-2 h after LPS addition. Selective inhibition of either COX isoform resulted in increased secretion of tumor necrosis factor-alpha (TNF-alpha); however, this effect was much greater with the COX-1 than with the COX-2 inhibitor. These results demonstrate autocrine regulation of TNF-alpha secretion by endogenous PGs synthesized primarily by COX-1 in RPM and suggest that COX-1 may play a significant role in the regulation of the early response to endotoxemia.

Human lupus T cells resist inactivation and escape death by upregulating COX-2

Autoimmune T-helper cells drive pathogenic autoantibody production in systemic lupus erythematosus (SLE), but the mechanisms maintaining those T cells are unknown. Autoreactive T cells are normally eliminated by functional inactivation (anergy) and activation-induced cell death (AICD) or apoptosis through death receptor (Fas) signaling. However, mutations in the genes encoding Fas and its ligand (FasL) are rare in classical SLE. By gene microarray profiling, validated by functional and biochemical studies, we establish here that activated T cells of lupus patients resist anergy and apoptosis by markedly upregulating and sustaining cyclooxygenase-2 (COX-2) expression. Inhibition of COX-2 caused apoptosis of the anergy-resistant lupus T cells by augmenting Fas signaling and markedly decreasing the survival molecule c-FLIP (cellular homolog of viral FLICE inhibitory protein). Studies with COX-2 inhibitors and Cox-2-deficient mice confirmed that this COX-2/FLIP antiapoptosis program is used selectively by anergy-resistant lupus T cells, and not by cancer cells or other autoimmune T cells. Notably, the gene encoding COX-2 is located in a lupus-susceptibility region on chromosome 1. We also found that only some COX-2 inhibitors were able to suppress the production of pathogenic autoantibodies to DNA by causing autoimmune T-cell apoptosis, an effect that was independent of prostaglandin E(2) (PGE(2)). These findings could be useful in the design of lupus therapies.

Studies on the anti-inflammatory effects ofclerodendron trichotomum thunberg leaves

Clerodendron trichotomum Thunberg Leaves (CTL) have been used for centuries in Chinese folk medicine for their anti-inflammatory properties. We have studied the anti-inflammatory effects of CTL extracts in rats, mice and in Raw 264.7 cells. 1 mg/kg solutions of the 30% and 60% methanol extracts of CTL were used and a 1 mg/kg of indomethacin was used as a positive anti-inflammatory standard; these were then administrated to rats. Carrageenan was injected subcutaneously to induce hind paw edema in rats. The result of carrageenan-induced rat paw oedema showed that a 1 mg/kg of the 30%, and 60% methanol fraction of CTL and 1 mg/kg of indomethacin inhibited the hind paw edema by 19.5%, 23.0%, and 20.5% respectively. The effect of CTL on inflammation in mice by a capillary permeability assay was examined by detecting Evans blue leakage from capillaries after the intraperitoneal injection of acetic acid, a potent inflammatory stimulus. The 60% methanol fraction of CTL inhibited Evans blue dye leakage by 47.0%, which was 10% higher than that of the inhibition of 1 mg/kg of indomethacin. Also, the 60% methanol fraction of CTL suppressed the prostaglandin E2 (PGE2) generation in RAW 264.7 macrophage cells after treatment with lipopolysaccharide (LPS) by as much as the inhibition of 1 mg/kg of indomethacin and this led to the synthesis of PGE2 by COX-2 induction. The inhibition of the carrageenan-induced rat paw oedema, vascular permeability and the PGE2 generation demonstrates that the 60% methanol fraction of CTL contains a potent anti-inflammatory activity.

Cyclooxygenase 2 in infiltrating inflammatory cells in injured nerve is universally up-regulated following various types of peripheral nerve injury

We previously reported the up-regulation of cyclooxygenase 2 (COX2) in injured sciatic nerve of rats with partial sciatic nerve ligation (PSNL) and the reversal of PSNL-elicited tactile allodynia by local injection of the COX inhibitor ketorolac [Eur J Neurosci 15 (2002) 1037]. We further asked whether COX2 up-regulation in injured nerve is a universal phenomenon following various types of nerve injury. In the current study, we observed that abundant COX2 immunoreactive (IR) cell profiles appeared in injured nerves of rats following spinal nerve ligation (SNL), chronic constriction injury (CCI) and complete sciatic nerve transection. Most COX2-IR cells were identified as infiltrating macrophages. Partial injury induced greater COX2 up-regulation than complete injury. COX2 up-regulation reached a peak at 2-4 weeks, evidently declined by 3 months and disappeared by 7 months postlesion. These findings suggest that up-regulation of COX2 in injured nerve is a common event during the initial several months after nerve injury. We observed that local ketorolac-elicited anti-allodynia was closely associated with the abundance of COX2-IR cells in injured nerve, varying with the type of injury and time after injury. The anti-allodynia lasted the longest when local ketorolac was given 2-4 weeks after PSNL, CCI and SNL. The duration of local ketorolac's anti-allodynia was the longest in CCI rats, which also exhibited the most abundant COX2 up-regulation. Local ketorolac's anti-allodynia lasted much shorter when given 2-3 months after lesion. Local ketorolac failed to induce anti-allodynia 7 months after lesion, a time when COX2-IR cells completely disappeared from the injured nerve except a few cells at the injury site. Our data strongly suggest that during the initial several months after nerve injury, peripherally over-produced prostaglandins play an important role in the maintenance of neuropathic pain.

COX-2 induction during murine gammaherpesvirus 68 infection leads to enhancement of viral gene expression

The murine gammaherpesvirus 68 (MHV-68 or gammaHV-68) model provides many advantages for studying virus-host interactions involved in gammaherpesvirus replication, including the role of cellular responses to infection. We examined the effects of cellular cyclooxygenase-2 (COX-2) and its by-product prostaglandin E(2) (PGE(2)) on MHV-68 gene expression and protein production following de novo infection of cultured cells. Western blot analyses revealed an induction of COX-2 protein in MHV-68-infected cells but not in cells infected with UV-irradiated MHV-68. Luciferase reporter assays demonstrated activation of the COX-2 promoter during MHV-68 replication. Two nonsteroidal anti-inflammatory drugs, a COX-2-specific inhibitor (NS-398) and a COX-1-COX-2 inhibitor (indomethacin), substantially reduced MHV-68 protein production in infected cells. Inhibition of viral protein expression and virion production by NS-398 was reversed in the presence of exogenous PGE(2). Global gene expression analysis using an MHV-68 DNA array showed that PGE(2) increased production of multiple viral gene products, and NS-398 inhibited production of many of the same genes. These studies suggest that COX-2 activity and PGE(2) production may play significant roles during MHV-68 de novo infection.