How do NSAIDs cause ulcer disease?

Gastroduodenal ulceration and bleeding are the major limitations to the use of non-steroidal anti-inflammatory drugs (NSAIDs). The development of safer NSAIDs or of effective therapies for the prevention of the adverse effects of existing NSAIDs requires a better understanding of the pathogenesis of NSAID-induced ulcer disease. NSAIDs can cause damage to the gastroduodenal mucosa via several mechanisms, including the topical irritant effect of these drugs on the epithelium, impairment of the barrier properties of the mucosa, suppression of gastric prostaglandin synthesis, reduction of gastric mucosal blood flow and interference with the repair of superficial injury. The presence of acid in the lumen of the stomach also contributes to the pathogenesis of NSAID-induced ulcers and bleeding, by impairing the restitution process, interfering with haemostasis and inactivating several growth factors that are important in mucosal defence and repair. In recent years, a fuller understanding of the pathogenesis of NSAID-induced ulcer disease has facilitated some new, very promising approaches to the development of stomach-sparing NSAIDs.

Cyclooxygenase 2 inhibitors: discovery, selectivity and the future

The recent marketing of two selective cyclooxygenase 2 (COX-2) inhibitors climaxes the first phase of an exciting and fast-paced effort to exploit a novel molecular target for nonsteroidal anti-inflammatory drugs (NSAIDs). Much has been written in the lay and scientific press about the potential of COX-2 inhibitors as anti-inflammatory and analgesic agents that lack the gastrointestinal side-effects of traditional NSAIDs. Although research on COX-2 inhibitors has focussed mainly on inflammation and pain, experimental and epidemiological data suggest that COX-2 inhibitors could be used in the treatment or prevention of a broader range of diseases. In this review, some key points and unresolved issues related to the discovery of COX-2 inhibitors, the kinetic and structural basis for their selectivity, and possible complications in their development and use will be discussed.

Inducible types of cyclooxygenase and nitric oxide synthase in adaptive cytoprotection in rat stomachs

Roles of cyclooxygenases (COX-1 and COX-2) and nitric oxide (NO) synthases (nNOS and iNOS) in adaptive cytoprotection induced by 20 mM taurocholate dissolved in 50 mM HCl (TC) were investigated in rat stomachs. Intragastric administration of 0.6 N HCl caused haemorrhagic damage in the stomach. These lesions were prevented by pretreatment of the animals with TC p.o. 0.5 h before 0.6 N HCl, and a significant protection persisted for more than 5 h. The protection afforded by TC given 0.5 h before HCl was almost totally reversed by indomethacin and slightly mitigated by N(G)-nitro-L-arginine methyl ester (L-NAME) but not affected by NS-398 or aminoguanidine. By contrast, the mucosal protective action of TC given 5 h before HCl was significantly reversed by NS-398, L-NAME and aminoguanidine as well as indomethacin. Mucosal prostaglandin E2 (PGE2) contents were significantly increased for over 5 h after TC, while luminal NOx output tended to elevate at 0.5 h and be significantly increased at 5 h after TC. The increased PGE2 generation observed 0.5 h after TC was attenuated only by indomethacin, while that observed 5 h after TC was inhibited by NS-398 as well as indomethacin. On the other hand, the NOx output determined at 5 h after TC was significantly reduced by both L-NAME and aminoguanidine. The expression of mRNA for both COX-2 and iNOS was apparently detected in the stomach from 3 h after TC treatment. These results suggest that TC induced adaptive cytoprotection in the rat stomach against 0.6 N HCl, the effect lasting for over 5 h, and the underlying mechanism differs depending on the period after the irritation. The early phase is mediated mainly by COX-1/PGs, while the later phase is mediated by iNOS/NO, in addition to prostaglandins (PGs) produced by both COX-1 and COX-2.

Cyclooxygenase knockout mice: models for elucidating isoform-specific functions

The development of cyclooxygenase (COX) deficient mice has allowed investigation into the individual physiological roles of the COX-1 and COX-2 isoforms. In the following article, the phenotypes of the two Ptgs (genes coding for COX-1 and COX-2) knockouts are summarized, and recent studies to investigate the effects of COX deficiency on cancer susceptibility, inflammatory response, gastric ulceration, and female reproductive processes are discussed. Also, the development and potential uses of mice deficient in both COX isoforms and mice containing only a single copy of one isoform are discussed. Additionally, when the data permit, the effects of genetic ablation of COX activity are compared with those of pharmacological inhibition of COX activity by nonsteroidal anti-inflammatory drugs. The data suggest that prostaglandins derived via the individual COX isoforms have separate as well as common functions. However, for the maintenance of normal physiology, it appears that deficiency of COX-2 has more profound effects than deficiency of COX-1.

Non-steroidal anti-inflammatory drugs (NSAIDs) and gastro-intestinal toxicity: current issues

Non-steroidal anti-inflammatory drugs (NSAIDs) are among the most widely used drugs and their widespread use is associated with increased gastro-intestinal toxic effects such as ulceration, haemorrhage, perforation and death. They result in these complications mainly by reducing cytoprotective prostaglandins (PGE2 and PGI2) in the stomach, through the inhibition of cyclo-oxygenase (COX) enzyme. The increased morbidity and mortality, in addition to enormous cost, associated with NSAID-associated side effects, necessitates a need for safer GI-friendly NSAID. Various approaches have been used to counteract NSAID associated side effects with varying degrees of success and acceptance. These include the use of alternative analgesia, anti-acid secretory agents like proton pump inhibitors, sucralfate and prostaglandin analogues. In addition, new types of NSAIDs are being developed, based on new understanding of their mechanism of action and the pathogenesis of inflammation. These include a new class of NSAIDs called "selective Cox-2 inhibitors". These agents preserve the COX-1 that is responsible for the production of cytoprotective prostaglandins in the stomach and selectively inhibit COX-2 induced at the sites of inflammation. Selective COX-2 inhibitors exert the same analgesic and anti-inflammatory effects as the existing NSAIDs but may be less toxic to the stomach. In this review the background development and well-structured clinical trials on this new generation NSAIDs are discussed.

The cyclooxygenase-2 inhibitors: safety and effectiveness

OBJECTIVE

To review the development of cyclooxygenase-2 (COX-2) inhibitors and discuss specific agents that are currently under investigation or have been marketed.

DATA SOURCES

Primary literature on selective COX inhibitors was identified from a comprehensive MEDLINE, English-literature search from January 1966 through September 1998, with additional studies selected by review of the references. Abstracts from recent meetings and package insert literature from approved agents were also used as source material. Indexing terms included COX-2 inhibitors, meloxicam, celecoxib, rofecoxib, flosulide, SC-58635, and MK-966.

STUDY SELECTION

Human clinical, pharmacokinetic, and dose-ranging trials performed in Europe and the US and randomized comparative trials were reviewed.

DATA SYNTHESIS

With the discovery of at least two COX isoforms, a better understanding of the mechanism of action and gastrointestinal toxicity of nonsteroidal antiinflammatory drugs (NSAIDs) has been realized. While COX-1 is involved in physiologic maintenance, COX-2 seems to be involved in inflammation, mitogenesis, and specialized signal transductions. Selective COX-2 inhibitors may allow maximum antiinflammatory activity while improving the safety profile associated with NSAID therapy. Celecoxib and rofecoxib have been approved by the Food and Drug Administration for the treatment of osteo- and rheumatoid arthritis; meloxicam is undergoing Phase III clinical trials. Preliminary data indicate that the selective COX-2 inhibitors provide analgesic and antiinflammatory efficacy comparable with older NSAIDs, with fewer adverse gastrointestinal effects.

CONCLUSIONS

Specific COX-2 inhibitors offer promising benefits over older NSAIDs with regard to gastrointestinal safety while maintaining analgesic and antiinflammatory efficacy. Further study is required to determine long-term efficacy and safety in clinical use.

Synthesis and biological acitivity of annulated pyrazoles as selective COX-2 inhibitors. I

A series of disubstituted 4,5-polymethylenepyrazoles were synthesized and evaluated their inhibitory activities against COX-2. Some compounds showed strong (0.3 nM) inhibitory activity on COX-2 and were found somewhat selective (up to 16) on COX-2 over COX-1.

Ex vivo assay to determine the cyclooxygenase selectivity of non-steroidal anti-inflammatory drugs

1. In this study we describe experiments to establish ex vivo the selectivity of non-steroidal anti-inflammatory drugs (NSAIDs) given in vivo. 2. Anaesthetised (Inactin, 120 mg kg(-1)) male Wistar rats (220-250 g) received an i.v. dose of one of the following compounds (dose mg kg(-1)): aspirin (20), diclofenac (3), L-745,337 (30), nimesulide (15), salicylate (20), sulindac (10). Blood samples were taken before and up to 6 h after dosing and the plasma obtained from it was tested for its ability to inhibit prostanoid formation in IL-1beta-treated A549 cells (COX-2 system) and human washed platelets (COX-1 system). For control the same compounds were also added directly to the assay systems. 3. All drugs, except sodium salicylate, inhibited COX-1 and COX-2 when added directly to the test systems. Plasma from aspirin-treated rats was without effect on either COX-1 or COX-2, consistent with the rapid in vivo metabolism to salicylate. Conversely, plasma from sulindac-treated rats inhibited COX-1 and COX-2 with potencies according with in vivo metabolism to sulindac sulphide. Diclofenac was COX-1/2 non-selective when tested in vitro, but a slightly preferential inhibitor of COX-2 when tested ex vivo. Nimesulide was confirmed as preferential inhibitor of COX-2 both in vitro and ex vivo. L-745,337 was a selective COX-2 inhibitor when tested in vitro or ex vivo. 4. In conclusion, our experiments show clearly (a) NSAIDs inactivation, (b) activation of prodrugs, and (c) NSAIDs selectivity. Our assay provides useful information about the selectivity of NSAIDs that could be extended by the analysis of plasma samples taken from humans similarly treated with test drugs.

Effect of a novel non-steroidal anti-inflammatory drug (M-5011) on cytokine levels in rats with monosodium urate crystal- induced pleurisy

We evaluated the effects of a new non-steroidal anti-inflammatory drug (NSAID), d-2-[4-(3-methyl-2-thienyl)phenyl]propionic acid (M-5011), and indomethacin on the production of arachidonate metabolites and pro-inflammatory cytokines in male Sprague-Dawley rats with monosodium urate crystal (MSU)-induced pleurisy. Levels of tumor necrosis factor (TNF), interleukin (IL)-1 and IL-6 in the pleural exudate were determined by biological assays, while prostaglandin E2 (PGE2), leukotriene B4 (LTB4) and cytokine-induced chemoattractant-1 (CINC-1) levels were quantified by enzyme immunoassays. Orally administered M-5011 (5 mg/kg) decreased the pleural exudate volume at 3 and 4 hr after MSU injection. Indomethacin (10 mg/kg) decreased the volume at 3-5 hr. These drugs reduced the number of leukocytes in the pleural cavity at 6 hr. Both NSAIDs also reduced the content of PGE2 in the exudate without affecting LTB4 levels. Increased productions of both IL-6 and CINC-1 in the exudate were reduced by pretreatment with M-5011 or indomethacin, and TNF levels in the exudate were increased by pretreatment of these drugs. Thus, M-5011 inhibits the production of both IL-6 and CINC-1 at lower doses than those of indomethacin, and the inhibitory effect of M-5011 on CINC-1, but not IL-6, may partly contribute to the inhibition of leukocyte infiltration in rats with MSU-induced pleurisy.

Cyclooxygenase-dependent signalling: molecular events and consequences

Non-steroidal anti-inflammatory drugs (NSAIDs) currently attract large interest. Next to pain relief, NSAIDs have important anti-thrombotic and anti-oncogenic effects. NSAIDs exert their action by inhibition of cyclooxygenase, the enzyme responsible for the production of prostanoids. Prostanoid signal transduction is still poorly understood, but it has become clear that these inflammatory lipids influence cellular physiology at three different levels: (1) activation of a 7 x transmembrane receptor coupled to heterotrimeric G proteins, (2) the inhibition of inflammation by activating corticosteroid-like receptors, (3) participation in receptor protein tyrosine kinase signal transduction. In this review prostanoid signalling at these three different levels will be reviewed and the relevance in (patho)physiological processes will be evaluated.

The use of analgesics in the management of pain in rheumatic diseases

Pain is the most common complaint of patients who see rheumatologists. In this article, the current treatment options for pain are reviewed; these include acetaminophen, nonsteroidal anti-inflammatory drugs, new specific cyclooxygenase-2 inhibitors, opioid analgesics, centrally acting muscle relaxants, antidepressants, and topical analgesics and counterirritants. The doses of medication and known adverse effects of these medications are highlighted.

Regulation of cyclooxygenase-2 expression in human mesangial cells--transcriptional inhibition by IL-13

Activated mesangial cells may play an important part in glomerulonephritis. Cytokines can modulate the release of prostanoids by human mesangial cells (HMC). We have investigated the effects of pro-inflammatory stimuli on COX-2 expression in HMC and its potential modulation by interleukin (IL)-13. HMC released increased amounts of prostaglandin E2 (PGE2) after treatment with several combinations of IL-1 beta, tumor necrosis factor (TNF)-alpha and/or lipopolysaccharide. Increases in PGE2 correlated with the induction of COX-2 protein expression. The accumulation of PGE2 elicited by a combination of IL-1 beta/TNF-alpha correlated closely with the temporal pattern of COX-2 protein expression, which reflected the induction of COX-2 mRNA. IL-13 inhibited IL-1 beta/TNF-alpha-elicited PGE2 production, as well as COX-2 protein and mRNA expression in a concentration-dependent fashion. With 50 ng.mL-1 IL-13 these parameters were inhibited by 90, 80 and 84%, respectively. In HMC transfected with the 5' regulatory region of the COX-2 gene, IL-13 suppressed cytokine-induced promoter activation. Our results suggest that COX-2 expression is a major target for IL-13-mediated abrogation of prostaglandin release by HMC and support that this process takes place by transcriptional inhibition of the COX-2 gene.

Anti-inflammatory and analgesic effects of a novel pyrazole derivative, FR140423

The pharmacological profile of a novel and newly discovered non-steroidal anti-inflammatory and analgesic compound, 3-(difluoromethyl)-1-(4-methoxyphenyl)-5-[4-(methylsulfinyl)phenyl]pyraz ole (FR140423), was investigated. In recombinant human cyclooxygenase enzyme assays, the inhibition of prostaglandin E2 formation by FR140423 was 150 times more selective for cyclooxygenase-2 than cyclooxygenase-1. Oral administration of FR140423 dose dependently reduced carrageenin-induced paw edema and adjuvant arthritis. These effects were two- to three-fold more potent than those of indomethacin. Unlike indomethacin, FR140423 did not induce mucosal lesions in the stomach. FR140423 showed dose-dependent anti-hyperalgesic effects in the yeast-induced hyperalgesic model. This effect was five-fold more potent than that of indomethacin. Furthermore, FR140423 increased the pain threshold in non-inflamed paws and, unlike indomethacin, it produced an analgesic effect in the tail-flick test. These analgesic effects were blocked by the mu-opioid antagonist naloxone. These results suggest that FR140423, a selective cyclooxygenase-2 inhibitor, is a potent non-steroidal anti-inflammatory drug (NSAID) without gastrointestinal side effects and is a unique compound having morphine-like analgesic effects.

Selective inhibitors of cyclooxygenase-2: are they really effective, selective, and GI-safe?

Selective inhibitors of the "inducible" isoform of cyclooxygenase (COX-2) have been suggested to be effective analgesic and anti-inflammatory drugs while sparing the gastrointestinal (GI) tract of injury. There is some experimental and early clinical evidence to support this hypothesis. However, some important questions remain regarding the utility of selective COX-2 inhibitors. For example, estimates of the selectivity of COX-2 inhibitors based on in vitro studies are likely to be poor predictors of selectivity in vivo. Efficacy with selective blockade of COX-2 may be inferior to that achieved with combined inhibition of COX-1 and COX-2. Furthermore, in situations in which there is inflammation or ulceration in the GI tract, COX-2 produces prostaglandins that are essential for repair. In these circumstances, inhibition of COX-2 leads to delay of ulcer healing and exacerbation of inflammation. Some caution should therefore be exercised before the theory is fully accepted that selective COX-2 inhibitors are effective anti-inflammatory drugs that spare the GI tract of injury.

Expression of prostaglandin H synthase isoforms in human myometrium at parturition

OBJECTIVE

The purpose of this study was to identify the isoforms and splicing patterns of prostaglandin H synthase present in pregnant human lower-segment myometrium and determine whether there is differential expression of the isoforms or splice variants with respect to gestational age or parturition.

STUDY DESIGN

Lower-segment myometrium was collected at cesarean section at term (>37 weeks) or preterm (<37 weeks) from patients who were or were not in labor. Total messenger ribonucleic acid was isolated and reverse transcribed. Polymerase chain reaction for prostaglandin H synthase isoforms 1 and 2 and calponin were performed. Primers designed to characterize the splicing patterns of exon 9 of prostaglandin H synthase-1 were used.

RESULTS

The predominant polymerase chain reaction product in all samples corresponds to prostaglandin H synthase-1 messenger ribonucleic acid spliced to include exon 9, but a less-abundant polymerase chain reaction product corresponding to prostaglandin H synthase-1 messenger ribonucleic acid spliced at the internal donor site of exon 9 was also detected. Prostaglandin H synthase-2 messenger ribonucleic acid was detected in human myometrium at a lower abundance than prostaglandin H synthase-1, and neither prostaglandin H synthase-1 or prostaglandin H synthase-2 messenger ribonucleic acid expression changed significantly with gestational age or labor.

CONCLUSION

Both prostaglandin H synthase-1 and prostaglandin H synthase-2 isoforms are present in human myometrium. The prostaglandin H synthase-1 messenger ribonucleic acid that includes all of exon 9 encodes the predominant prostaglandin H synthase-1 isoform present in human myometrium. No significant alterations in the expression or splicing patterns for prostaglandin H synthase-1 were detected with respect to gestational age or the onset of labor; but prostaglandin H synthase-1 expression appeared higher at term in anticipation of labor. Although prostaglandin H synthase-2 is present in human myometrium, induction of prostaglandin H synthase-2 does not occur in lower-segment myometrium at parturition.

Prostaglandins prevent inducible nitric oxide synthase protein expression by inhibiting nuclear factor-kappaB activation in J774 macrophages

We investigated the effect of PGE2 and iloprost (a prostacyclin analogue) on inducible nitric oxide synthase (iNOS) protein expression and nuclear factor-kappaB (NF-kappaB) activation in lipopolysaccharide (LPS)-stimulated J774 macrophages. Incubation of J774 cells with LPS (10 microg/ml) caused an increase of iNOS protein expression which was prevented in a concentration-dependent fashion by PGE2 (0.1, 1, 10 microM) and iloprost (0.01, 0.1, 1 microM). Electrophoretic mobility shift assay indicated that both prostanoids blocked the activation of NF-kappaB, a transcription factor necessary for NO synthase induction. PGE2 and iloprost also blocked disappearance of I kappaB-alpha from cytosolic fraction and nuclear translocation of NF-kappaB subunits p50 and p65. These results show for the first time that PGE2 and iloprost down-regulate iNOS protein expression by inhibiting NF-kappaB activation and suggest a negative feed-back mechanism that may be important for limiting excessive or prolonged NO production in pathological events.

Profile of JTE-522 as a human cyclooxygenase-2 inhibitor

Inhibitory activity and the mechanism of action of JTE-522 (4-(4-cyclohexyl-2-methyloxazol-5-yl)-2-fluorobenzenesulfonamid e), a novel selective cyclooxygenase (COX)-2 inhibitor, on human COX-1 and COX-2 were investigated and compared with those of reference compounds. In an enzyme assay, JTE-522 inhibited yeast-expressed human recombinant COX-2 with an IC50 value of 0.085 microM. In contrast, JTE-522 did not inhibit human COX-1 prepared from human platelets at concentrations up to 100 microM. In a cell-based assay, JTE-522 diminished lipopolysaccharide-induced prostaglandin E2 production in human peripheral blood mononuclear cells (COX-2) (IC50 value = 15.1 nM). On the other hand, JTE-522 was less potent at inhibiting calcium ionophore-induced thromboxane B2 production in washed human platelets (COX-1) (IC50 value = 6210 nM). JTE-522 showed highly selective inhibition of human COX-2, and its activity was more selective than that of other COX-2 inhibitors (NS-398 and SC-58635). Human recombinant COX-2 activity was attenuated by JTE-522 in a dose-dependent and time-dependent manner. In contrast, the inhibitory activity of JTE-522 on human COX-1 was not affected by preincubation time. COX-2 inhibition by JTE-522 could not be recovered by gel filtration. These results indicate that JTE-522 is a highly selective, time-dependent and irreversible inhibitor of human COX-2.

Cyclooxygenase-2 inhibitors in tumorigenesis (part I)

The rate-limiting enzyme in arachidonate metabolism is mediated by enzymes known as cyclooxygenases (COXs). These enzymes catalyze the biosynthesis of prostaglandin H2, the precursor of molecules, such as prostaglandins, prostacyclin, and thromboxanes. The COX enzyme family consists of the classical COX-1 enzyme, which is constitutively expressed in many tissues, and a second enzyme, i.e., COX-2, which is induced by various stimuli, such as mitogens and cytokines, and is involved in many inflammatory reactions. Because nonsteroidal anti-inflammatory drugs inhibit both COX-1 and COX-2, these drugs also cause unwanted side effects, exemplified by gastrointestinal bleeding. Accumulating evidence indicates that nonsteroidal anti-inflammatory drugs can reduce the incidence of colorectal cancers in human and experimental animals and can reduce the polyp number and size in patients with familial adenomatous polyposis. This Part I (of a two-part review) focuses on the discovery of the COXs; their biochemical, molecular, and structural properties; and on the discovery of isozyme-specific inhibitors of COX activity.

Effects of compounds extracted from Santolina oblongifolia on TXB2 release in human platelets

A group of compounds isolated from the medicinal plant, Santolina oblongifolia, have been investigated for their effects on the release of platelet cyclo-oxygenase metabolite thromboxane A(2) (measured as thromboxane B(2)) from ionophore-stimulated human platelets. These compounds, which are dual inhibitors of cyclo-oxygenase (prostaglandin E(2)) and lipoxygenase (leukotriene C(4)) activity in vitro, are: apigenin, luteolin, quercetin, herniarin, scopoletin, scopolin and aesculetin. All compounds assayed presented a dose-related response to thromboxane B(2) release, with the percentages of inhibition being slightly lower than the reference drug, ibuprofen. Inhibition was more evident with the flavonoids. Our data support the inhibition of arachidonic acid metabolism as one of the mechanisms for which flavonoids and coumarins from S. oblongifolia exert their anti-inflammatory effect.

Design of selective inhibitors of cyclooxygenase-2 as nonulcerogenic anti-inflammatory agents

The discovery of a second isoform of cyclooxygenase (cyclooxygenase-2) that is expressed in inflammatory cells and the central nervous system, but not in the gastric mucosa, offers the possibility of developing anti-inflammatory and analgesic agents that lack the gastrointestinal side effects of currently available nonsteroidal anti-inflammatory drugs. Lead compounds from several different structural classes have been identified and shown to be slow, tight-binding inhibitors that express their selectivity for cyclooxygenase-2 in the time-dependent step. The determination of structures of enzyme-inhibitor co-crystals along with site-directed mutagenesis experiments reveal the molecular basis for selectivity of some, but not all, inhibitors. Preclinical and clinical studies suggest cyclooxygenase-2 inhibitors are highly promising new agents for the treatment of pain and inflammation, and for the prevention of cancer.

Cyclooxygenase 1 contributes to inflammatory responses in rats and mice: implications for gastrointestinal toxicity

BACKGROUND & AIMS

Selective inhibitors of cyclooxygenase (COX)-2 are being developed as gastrointestinal-sparing anti-inflammatory drugs based on the premise that this isoform is solely responsible for prostaglandin synthesis at sites of inflammation, whereas COX-1 produces prostaglandins important for maintenance of mucosal integrity. We investigated the relationship between suppression of inflammation by COX-2 inhibitors (NS-398, nimesulide, DuP697, and etodolac) and their effects on gastric prostaglandin synthesis.

METHODS

Effects of pretreatment of rats with drugs with a range of in vitro selectivity for COX-2 vs. COX-1 on carrageenan-induced paw inflammation were assessed, along with extent of suppression of COX-1 and COX-2. The role of COX-1 in inflammation was also assessed in COX-2-deficient mice.

RESULTS

Significant anti-inflammatory effects were only observed at doses of the drugs that inhibited COX-1. At these doses, the drugs also significantly suppressed gastric prostaglandin synthesis and elicited gastric mucosal erosions. The degree of suppression of prostaglandin synthesis at the site of inflammation correlated significantly with inhibition of COX-1 but not COX-2.

CONCLUSIONS

COX-1 makes an important contribution to inflammatory responses. To achieve desirable anti-inflammatory effects, COX-2 inhibitors needed to be given at doses in which selectivity was lost, leading to suppression of gastric prostaglandin synthesis and to mucosal injury.

Systematic pharmacological approach to the characterization of NSAIDs

Non-steroidal anti-inflammatory drugs (NSAIDs) are widely used for the treatment of inflammatory diseases. NSAIDs inhibit cyclooxygenase (COX), the rate limiting enzyme responsible for the conversion of arachidonic acid into prostaglandins. Recent studies have shown the existence of two isoforms of cyclooxygenase: COX-1, now often referred to as the constitutive form, and COX-2, an inducible form which is the major isoenzyme involved in prostaglandin synthesis in inflammation and other pathological situations. Since inhibition of prostaglandin production in tissues where they play a physiological role leads to important side effects, a COX-2 preferential inhibitor would present therapeutical advantages. In the present study, we evaluated the inhibitory properties of cyclooxygenase inhibitors on human COX-1 and COX-2 using a heterologous expression system. We investigated instantaneous inhibition and pre-incubation inhibition as well as time recovery of cyclooxygenase activity assays with the aid of four NSAIDs: mefenamic acid, indomethacin, aspirin and NS-398. Our results demonstrate that instantaneous inhibition assays have little correlation with clinical results. Inhibition assays using pre-incubation with the drugs tested, however, more closely resemble the data from in vivo studies. Cyclooxygenase recovery assays enabled better characterization of simple competitive inhibitors, competitive reversible time-dependent inhibitors and irreversible time-dependent inhibitors. The data illustrate the usefulness of our system in allowing a better determination of the pharmacological characteristics of NSAIDs as well as permitting a comparison among different drugs.

Effects of inhibitors of the activity of cyclo-oxygenase-2 on the hypotension and multiple organ dysfunction caused by endotoxin: a comparison with dexamethasone

1. Endotoxaemia is associated with the expression of the inducible isoform of cyclo-oxygenase, cyclo-oxygenase-2 (COX-2), and an overproduction of arachidonic acid (AA) metabolites. The role of the AA metabolites generated by COX-2 in the circulatory failure and multiple organ dysfunction caused by endotoxin is unclear. Dexamethasone prevents the expression of COX-2 and exerts beneficial effects in animal models of shock. 2. Here we compare the effects of two inhibitors of COX-2 activity, namely NS-398 (5 mg kg(-1), i.p., n=7) and SC-58635 (3 mg kg(-1), i.p., n=9) with those of dexamethasone (3 mg kg(-1), i.p., n=9) on the circulatory failure and organ dysfunction caused by lipopolysaccharide (LPS, E. coli, 6 mg kg(-1), i.v., n=11) in the rat. 3. Endotoxaemia for 6 h caused hypotension, acute renal dysfunction, hepatocellular injury, pancreatic injury and an increase in the plasma levels of 6-keto-PGF1alpha (indicator of the induction of COX-2) and nitrite/nitrate (indicator of the induction of iNOS). 4. Pretreatment of rats with dexamethasone attenuated the hypotension, the renal dysfunction, the hepatocellular and pancreatic injury and the induction of COX-2 and iNOS caused by LPS. In contrast, inhibition of COX-2 activity with SC-58635 or NS-398 neither attenuated the circulatory failure nor the multiple organ failure caused by endotoxin. 5. Thus, the prevention of the circulatory failure and the multiple organ injury/dysfunction caused by dexamethasone in the rat is not due to inhibition of the activity of COX-2. Our results suggest that an enhanced formation of eicosanoids by COX-2 does not contribute to the development of organ injury and/or dysfunction in rats with endotoxaemia.

Induction of cyclooxygenase-2 by the activated MEKK1 --> SEK1/MKK4 --> p38 mitogen-activated protein kinase pathway

The mitogen-activated protein kinase (MAPK) cascade is believed to function as an important regulator of prostaglandin biosynthesis. Previously we reported that interleukin-1beta induces activation of JNK/SAPK and p38 MAPK with concomitant up-regulation of cyclooxygenase (Cox)-2 expression and prostaglandin E2 (PGE2) synthesis. Our experiments demonstrate that overexpression of DeltaMEKK1 (a constitutively active truncation mutant of MEKK1 containing the C-terminal 324 amino acids) increases Cox-2 expression and PGE2 production which is completely blocked by SC68376, a pharmacologic inhibitor of p38 MAPK. DeltaMEKK1 overexpression results in activation of both c-Jun N-terminal kinases/extracellular signal-regulated kinases (JNK/SAPK) and p38 MAPK. Furthermore, activation of MEKK1 increases SEK1/MKK4 but not MKK3 or MKK6 activity. These findings suggest that MEKK1 --> SEK1/MKK4 may function as an upstream kinase capable of activating both p38 MAPK and JNK/SAPK with subsequent induction of Cox-2 expression and PGE2 production. We also found that overexpression of the constitutively active form of SEK1 (SEK1-ED) increases both p38 MAPK and JNK/SAPK phosphorylation, and increases PGE2 production and Cox-2 expression. By comparison, overexpression of the dominant negative form of SEK1 (SEK1-AL) decreases the phosphorylation of both p38 MAPK and JNK/SAPK and reduces Cox-2 expression. Together, this data suggests a potential role for the MEKK1 --> SEK1/MKK4 --> p38 MAPK -->--> Cox-2 cascade linking members of the MAPK pathway with prostaglandin biosynthesis.

Mechanism of action of nonsteroidal anti-inflammatory drugs

Salicylic acid and salicylates, obtained from natural sources, have long been used as medicaments. Salicylic acid was chemically synthesized in 1860 and was used as an antiseptic, an antipyretic, and an antirheumatic. Almost 40 years later, aspirin was developed as a more palatable form of salicylate. Soon after, other drugs having similar actions to aspirin were discovered, and the group was termed the "aspirin-like drugs" (also now termed the nonsteroidal anti-inflammatory drugs [NSAIDs]). Twenty-five years ago, it was proposed that the mechanism of action of NSAIDs was through their inhibition of prostaglandin biosynthesis. Since then, there has been general acceptance of the concept that these drugs work by inhibition of the enzyme cyclo-oxygenase (COX), which we now know to have at least two distinct isoforms: the constitutive isoform, COX-1, and the inducible isoform, COX-2. COX-1 has clear physiologic functions. Its activation leads, for instance, to the production of prostacyclin, which when released by the endothelium is antithrombogenic and when released by the gastric mucosa is cytoprotective. COX-2, discovered 6 years ago, is induced by inflammatory stimuli and cytokines in migratory and other cells. It is therefore attractive to suggest that the anti-inflammatory actions of NSAIDs are due to inhibition of COX-2, whereas the unwanted side-effects, such as irritation of the stomach lining, are due to inhibition of COX-1. Drugs that have the highest COX-2 activity and a more favorable COX-2: COX-1 activity ratio will have a potent anti-inflammatory activity with fewer side-effects than drugs with a less favorable COX-2: COX-1 activity ratio. The identification of selective inhibitors of COX-2 will therefore lead to advances in therapy.

Regulation of prostaglandin H2 synthase-2 expression in primary human amnion cells by tyrosine kinase dependent mechanisms

Prostaglandin H2 synthase (PGHS)-1 and PGHS-2 expression was examined in primary cultures of human amnion cells, an in vitro model of amnion tissue. Epidermal growth factor (EGF), the protein kinase C (PKC) activating phorbol ester TPA, and the protein phosphatase inhibitor, okadaic acid (OA), stimulated PGHS activity and the level of PGHS-2 mRNA, but did not affect the level of PGHS-1 mRNA. In situ hybridization suggested that the same population of cells responded to EGF, TPA and OA. Okadaic acid promoted PGHS activity independently of PKC. EGF stimulated the activity of extracellular signal-regulated protein kinase (Erk) and N-terminal c-Jun kinase (Jnk). OA increased Jnk activity but had no effect on Erk activity, while TPA had no influence on either Erk or Jnk activity. PD098059, a selective inhibitor of the Erk-activating kinase MEK, blocked the stimulation of PGHS expression by EGF, but did not decrease stimulation in response to OA. Herbimycin A, a tyrosine kinase inhibitor, suppressed the stimulation of PGHS activity and PGHS-2 mRNA abundance by all three stimulants, and blocked signalling via the Erk and Jnk mitogen-activated protein kinase pathways. Thus, growth factor stimulation, PKC activation and protein phosphatase inhibition induced the expression of PGHS-2 in primary amnion cells by distinct regulatory mechanisms involving tyrosine kinase(s). Tyrosine kinase inhibitors may constitute a new category of PGHS-2 inhibitors that act by blocking the expression of the enzyme.

Selective cyclo-oxygenase-2 inhibitors and their influence on the protective effect of a mild irritant in the rat stomach

1. The effects of the non-selective cyclo-oxygenase (COX) inhibitor indomethacin and the selective COX-2 inhibitors, N-[2-(cyclohexyloxy)-4-nitrophenyl] methanesulphonamide (NS-398), 5-methanesulphonamido-6-(2,4-difluorothio-phenyl)-1-indan one (L-745,337) and 5,5-dimethyl-3-(3-fluorophenyl)-4-(4-methylsulphonyl) phenyl-2(5H)-furanone (DFU), on the protection induced by the mild irritant 20% ethanol were investigated in the rat stomach. 2. Instillation of 20% ethanol (1 ml, p.o.) effectively protected against gastric mucosal injury induced by subsequent instillation of 70% or 96% ethanol (1 ml, p.o.). 3. Oral administration of indomethacin (1.25-20 mg kg[-1]) dose-dependently counteracted the protective effect of 20% ethanol (ID50: 3.5 mg kg[-1]). 4. Likewise, NS-398 (0.1-1 mg kg[-1]), L-745,337 (0.2-2 mg kg[-1]) and DFU (0.02-0.2 mg kg[-1]) inhibited the protective effect of 20% ethanol in a dose-dependent manner with ID50 values of 0.3 mg kg(-1), 0.4 mg kg(-1) and 0.06 mg kg(-1), respectively. 5. Inhibition of mild irritant-induced protection was also found when NS-398 (1 mg kg[-1]) was administered s.c. or when 96% ethanol was used to damage the mucosa. 6. Pretreatment with 16,16-dimethyl-prostaglandin (PG)E2 at 4 ng kg(-1), a dose that did not protect against ethanol (70%)-induced mucosal damage when given alone, completely reversed the effect of the selective COX-2 inhibitors on the mild irritant-induced protection. 7. Pretreatment with dexamethasone (3 mg kg(-1), 24 and 2 h before instillation of 20% ethanol) did not affect the protective activity of the mild irritant, indicating that enzyme induction is not involved. 8. Indomethacin (20 mg kg(-1), p.o.) did not prevent the protection conferred by sodium salicylate (100 mg kg[-1]), dimercaprol (30 microg kg[-1]), iodoacetamide (50 mg kg[-1]) and lithium (20 mg kg[-1]). Likewise, the protective effect of these agents was not counteracted by NS-398 (1 mg kg(-1), p.o.). 9. Whereas indomethacin (20 mg kg(-1), p.o.) near-maximally inhibited gastric mucosal formation of PGE2, 6-keto-PGF1alpha and thromboxane (TX) B2 as well as platelet TXB2 release, the selective COX-2 inhibitors were ineffective. 10. The findings show that selective COX-2 inhibitors, although lacking in ulcerogenic activity, prevent the protection conferred by a mild irritant. Prostaglandis generated by a constitutive COX-2 could thus contribute to physiological functions involved in gastric homeostasis, although at present a non-COX-2-related mechanism underlying the effect of the selective COX-2 inhibitors tested on mild irritant-induced protection cannot be completely excluded.

In vitro and in vivo localization of prostaglandin H synthase in fetal sheep neurons

Immunoreactive (IR) prostaglandin H synthase (PGHS) was evident in primary cortical cultures as early as day 2 after seeding. Labeling did not increase with time in culture, nor was there an apparent difference in IR intensity between 2 and 10% serum cultures or between glial and neuronal figures. PGHS-1 IR appeared as a homogeneous cytoplasmic fluorescence compared with PGHS-2 IR which tended to be more intense, particulate and exclusively perinuclear. PGHS-2(+) IR in both neurons and glia increased with time in culture. Immunofluorescence varied in intensity, but no significant degree of variation was seen between cell types. Neuronal PGHS-2 IR extended into processes and amassed in growth cones and at the leading edge processes of astrocytes. Novel rosette formations, possibly lipid bodies, were common in cultured neurons, but not astrocytes.

Pregnancy increases ovine uterine artery endothelial cyclooxygenase-1 expression

During normal pregnancy, and especially in the third trimester, both uterine blood flow and prostacyclin production by ovine uterine arteries are dramatically increased. We sought to determine if this is due, in part, to an increase in cyclooxygenase (COX) expression in the uterine artery endothelium. In this study we compared COX expression in uterine artery endothelium from nonpregnant and third-trimester pregnant (110-142 days' gestation) ewes. COX-2 expression was not detectable by Western blotting in uterine artery endothelium or vascular smooth muscle (VSM). In contrast, COX-1 expression was clearly observed in uterine artery. Immunohistochemical localization of COX-1 was endothelium > VSM, with both cell types showing an increase in COX-1 during the third trimester of pregnancy. COX-1 protein and messenger RNA (mRNA) levels were also detectable in collagenase dispersed endothelial cells, with expression of COX-1 in uterine artery endothelial cells dramatically increased during the third trimester of pregnancy at both the level of protein (346.4 +/- 28% of nonpregnant controls, P < 0.0005) and mRNA (51.04 +/- 7.98-fold of nonpregnant controls, P < 0.001). We conclude that the pregnancy-induced increases in prostacyclin production by uterine arteries is largely due to a dramatic increase in expression of COX-1 mRNA and associated protein predominantly occurring in the uterine artery endothelium and, to a lesser extent, in the VSM.

Multiple controls in inflammation. Extracellular and intracellular phospholipase A2, inducible and constitutive cyclooxygenase, and inducible nitric oxide synthase

Inflammation occurs as a defensive response to invasion of the host by foreign material, often of microbial nature. This response is normally a localized protective response that at the microscopic level involves a complex series of events including dilatation of arterioles, venules, and capillaries with increased vascular permeability, exudation of fluids including plasma proteins, and leukocyte migration into the inflammatory area. Since disease characterized by inflammation is an important cause of morbidity and mortality in humans, the processes involved in the host defense in inflammation have been and continue to be the object of several experimental studies. The role of several mediators such as histamine, serotonin, bradykinin, prostaglandins, and, more recently, cytokines and nitric oxide has been evaluated, and a contribution for each one of these mediators has been proposed. With the development of powerful molecular biology tools, it has become possible to study enzymes involved in this complex phenomenon by measuring the expression or evaluating the signaling pathways following a specific stimulus. These techniques have generated a proliferation of studies on the role of several enzymes and cytokines in inflammation. Most of these studies have been conducted in vitro on cell lines, and not many of the results have been confirmed by in vivo studies. This commentary does not pretend to analyze all of the studies and their possible in congruences, but endeavors to provoke in the reader a critical review of dogmas and current beliefs that most of the time are built on unilateral interpretation of the data.

Anti-inflammatory, analgesic and anti-pyretic effects of d-2-[4-(3-methyl-2-thienyl)phenyl]propionic acid (M-5011), a new non-steroidal anti-inflammatory drug, in rats and guinea pigs

Anti-inflammatory, analgesic and anti-pyretic effects of d-2-[4-(3-methyl-2-thienyl)phenyl]propionic acid (M-5011), a new non-steroidal anti-inflammatory drug (NSAID), were compared with those of indomethacin, diclofenac sodium and ketoprofen in rats and guinea pigs. Anti-inflammatory effect of M-5011 on ultraviolet-induced erythema in guinea pigs was 11.7 and 1.8 times more potent than that of indomethacin and ketoprofen, respectively. Inhibitory effect of M-5011 on carrageenin-induced paw edema was 2 and 1.5 times more potent than that of indomethacin and diclofenac sodium, respectively. Analgesic effect of M-5011 on dry yeast-induced hyperalgesia or adjuvant-induced arthritic pain was equipotent to that of indomethacin, diclofenac sodium or ketoprofen. Anti-pyretic effect of M-5011 on yeast-induced pyrexia in rats was 4.2 and 4.6 times more potent than that of indomethacin and ketoprofen, respectively. Inhibitory effect of M-5011 on prostaglandin E2 production in the exudate of air-pouch inflammation induced by carrageenin was 1.75 times more potent than that in the non-inflamed site (stomach). As a result, gastric ulcerogenic activity of M-5011 was half that of indomethacin in rat. These results suggest that M-5011 shows more potent anti-inflammatory and anti-pyretic effects and equipotent analgesic effect with low gastro-ulcerogenic activity compared with classical NSAIDs.

The effects of a newly developed nonsteroidal anti-inflammatory drug (M-5011) on arachidonic acid metabolism in rheumatoid synovial fibroblasts

M-5011 (d-2-[4-(3-methyl-2-thienyl)phenyl]propionic acid) is a newly developed nonsteroidal anti-inflammatory drug (NSAID) that displays potent anti-inflammatory and analgesic properties with low ulcerogenic activities in animal models. In this study, the effects of M-5011 on arachidonic acid (AA) metabolism in synovial fibroblasts from patients with rheumatoid arthritis were evaluated and compared with those of other NSAIDs in vitro. Either M-5011 or ketoprofen potently inhibited prostaglandin (PG) E2 production by cyclooxygenase (COX)-2 from exogenous AA in interleukin-1beta (IL-1beta)-stimulated cells. The IC50 values of M-5011 and ketoprofen were 4.4 x 10(-7) and 5.9 x 10(-7) M, respectively. However, diclofenac and indomethacin were one order less potent. Although the latter two drugs exhibited time-dependent and irreversible inhibition on COX-2 in IL-1beta-stimulated cells, the inhibitory effects of M-5011 and ketoprofen were reversible. PGE2 production by COX-1 from exogenous AA in non-stimulated cells was also inhibited by M-5011 with a potency less than that of ketoprofen. In addition, M-5011 inhibited [14C]AA release from prelabeled synovial cells stimulated with bradykinin. However, ketoprofen hardly affected the [14C]AA release. It is likely that the effects of M-5011 on AA metabolism are, in part, responsible for its in vivo efficacy and safety profile.

Involvement of NF-kappaB in the regulation of cyclooxygenase-2 protein expression in LPS-stimulated J774 macrophages

We investigated the involvement of NF-kappaB in the regulation of COX-2 protein expression and prostaglandin production in LPS-stimulated J774 macrophages. Incubation of J774 cells with LPS (1 microg/ml) for 24 h caused an increase of COX-2 protein expression and accumulation of both PGE2 and 6-keto-PGF1alpha in the cell culture medium. Ammonium pyrrolidinedithiocarbamate (APDC, 0.1, 1, 10 microM) and N-alpha-p-tosyl-L-lysine chloromethylketone (TLCK, 1, 10, 100 microM), two inhibitors of NF-kappaB activation, suppressed in a concentration-dependent manner both LPS-induced COX-2 protein expression and prostanoid generation. Moreover, APDC and TLCK both inhibited the LPS-induced increase of NF-kappaB DNA binding activity and prevented IkappaB-alpha degradation. Our results show for the first time that NF-kappaB is involved in COX-2 protein expression in LPS-stimulated J774 macrophages and suggest that inhibitors of NF-kappaB activation may represent a useful tool for the pharmacological control of inflammation.

Effects of selective cyclooxygenase-2 inhibitors on alkaline secretory and mucosal ulcerogenic responses in rat duodenum

Effects of the selective cyclooxygenase-2 (COX-2) inhibitors such as NS-398 and nimesulide on duodenal HCO3- secretory and ulcerogenic responses to mucosal acidification were examined in rats, in comparison with indomethacin, a nonselective COX inhibitor. Duodenal HCO3- secretion in anesthetized rats was increased in response to mucosal acidification. The increased HCO3- response to acid was significantly suppressed by pretreatment with indomethacin (10 mg kg(-1), s.c.), while both NS-398 and nimesulide (10 mg kg(-1), s.c.) had no effect on this response. The luminal release of prostaglandin E2 (PGE2) was increased during and after mucosal acidification, and this response was significantly inhibited by indomethacin but not NS-398 or nimesulide. Indomethacin provoked hemorrhagic lesions in the duodenum when acid hypersecretion was concomitantly induced by histamine (8 mg kg(-1) hr(-1), i.v.), while either NS-398 or nimesulide did not cause damage in the duodenum. Either of these drugs had no effect on histamine-induced acid secretion. On the other hand, both NS-398 and nimesulide showed a significant suppression against carrageenan-induced rat paw edema, similar to indomethacin. The present study supports a mediator role for endogenous PGs in duodenal HCO3- secretion in response to mucosal acidification and suggests that COX-1 but not COX-2 is a key enzyme in regulating this process and maintaining the mucosal integrity against acid in the duodenum.

Effect of azelastine on PGE2 production in fibroblasts in normal skin. The possibility of inhibition of inducible cyclooxygenase by azelastine

The effects of azelastine on prostaglandin E2 (PGE2) production were investigated by using cultured normal dermal fibroblasts obtained from the same traumatic region of 3 patients and the CRL-1475 cell line. Interleukin-1beta (IL-1) enhanced PGE2 production in cultured normal fibroblasts and CRL-1475 cells. 10(-6) M azelastine inhibited PGE2 production in these IL-1-stimulated fibroblasts. However, the drug did not influence spontaneous PGE2 production in cultured CRL-1475 fibroblasts not stimulated with IL-1 but slightly it increased in cultured normal dermal fibroblasts under the same conditions. These results suggest that azelastine either regulates synthesis of an inducible cyclooxygenose protein or inhibits PGE2 production as an inducible cyclooxygenase inhibitor.

Cyclo-oxygenase isozymes in mucosal ulcergenic and functional responses following barrier disruption in rat stomachs

1. We examined the effects of selective and nonselective cyclo-oxygenase (COX) inhibitors on various functional changes in the rat stomach induced by topical application of taurocholate (TC) and investigated the preferential role of COX isozymes in these responses. 2. Rat stomachs mounted in ex vivo chambers were perfused with 50 mM HCl and transmucosal potential difference (p.d.), mucosal blood flow (GMBF), luminal acid loss and luminal levels of prostaglandin E2 (PGE2) were measured before, during and after exposure to 20 mM TC. 3. Mucosal application of TC in control rats caused a reduction in p.d., followed by an increase of luminal acid loss and GMBF, and produced only minimal damage in the mucosa 2 h later. Pretreatment with indomethacin (10 mg kg[-1], s.c.), a nonselective COX-1 and COX-2 inhibitor, attenuated the gastric hyperaemic response caused by TC without affecting p.d. and acid loss, resulting in haemorrhagic lesions in the mucosa. In contrast, selective COX-2 inhibitors, such as NS-398 and nimesulide (10 mg kg[-1], s.c.), had no effect on any of the responses induced by TC and did not cause gross damage in the mucosa. 4. Luminal PGE2 levels were markedly increased during and after exposure to TC and this response was significantly inhibited by indomethacin but not by either NS-398 or nimesulide. The expression of COX-1-mRNA was consistently detected in the gastric mucosa before and after TC treatment, while a faint expression of COX-2-mRNA was detected only 2 h after TC treatment. 5. Both NS-398 and nimesulide significantly suppressed carrageenan-induced rat paw oedema, similar to indomethacin. 6. These results confirmed a mediator role for prostaglandins in the gastric hyperaemic response following TC-induced barrier disruption, and suggest that COX-1 but not COX-2 is a key enzyme in maintaining 'housekeeping' functions in the gastric mucosa under both normal and adverse conditions.

NSAID-induced apoptosis in Rous sarcoma virus-transformed chicken embryo fibroblasts is dependent on v-src and c-myc and is inhibited by bcl-2

Mounting epidemiological and experimental evidence implicates non-steroidal antiinflammatory drugs as anti-tumorigenic agents. Our previous work showed that nonsteroidal antiinflammatory drug treatment of src-transformed chicken embryo fibroblasts caused apoptosis--a mechanism by which these drugs might exert their anti-tumorigenic effect. The present studies employ a sensitive technique for detecting single- and double-stranded DNA cleavage (the comet assay) to quantitate apoptosis. By this method pp60v-src, which antagonizes apoptosis in many cell systems, was found to induce apoptosis in 11-23% of serum-starved fibroblasts. However, treatment with diclofenac following pp60v-src activation produced a much stronger response beginning within 6 hours of treatment that resulted in 100% lethality. During cell death, cyclooxygenase-2 but not cyclooxygenase-1 mRNA was found to be uniformly increased by all apoptotic drugs tested. Examination of the expression of apoptosis-associated genes showed that c-rel and p53 (found in normal or v-src-transformed chicken embryo fibroblasts at moderate levels), and bcl-2 (present at an extremely low level) were largely unchanged by treatment with eight different nonsteroidal antiinflammatory drugs. However, overexpression of human bcl-2 inhibited diclofenac-mediated apoptosis by 90%, demonstrating directly that bcl-2 expression can regulate nonsteroidal antiinflammatory drug induction of cell death. The proto-oncogene c-myc is known to cause apoptosis in chicken embryo fibroblasts when artificially overexpressed in cells deprived of trophic factors. We found that nonsteroidal antiinflammatory drug treatment following pp60v-src activation persistently induced myc protein and mRNA by more than 20-fold above that evoked by pp60v-src activation alone. Moreover, transfection of antisense c-myc oligonucleotides reduced drug-induced myc expression by 80% and caused a concomitant 50% reduction in cell death. These findings suggest that nonsteroidal antiinflammatory drug-induced apoptosis proceeds through a src/myc dependent pathway which is negatively regulated by bcl-2.

Suppressive effects of tranilast on the expression of inducible cyclooxygenase (COX2) in interleukin-1beta-stimulated fibroblasts

We investigated the effects of tranilast on inducible cyclooxygenase (COX2)-mediated prostaglandin E2 (PGE2) production and enzyme induction in interleukin-lbeta (IL-1beta)-stimulated cultured dermal fibroblasts. IL-1beta enhanced PGE2 production in cultured fibroblasts. Tranilast did not affect constitutive cyclooxygenase (COX1) or COX2 activity in non-stimulated or IL-lbeta-stimulated fibroblasts. However, the COX2 expression induced by IL-1beta was inhibited by tranilast. This result, that IL-1beta-induced COX2 expression was suppressed by tranilast, was confirmed by immunohistochemical analysis. Thus, it is possible for tranilast to regulate PGE2 production by inhibiting COX2 induction.

Effect of calpain inhibitor I, an inhibitor of the proteolysis of I kappa B, on the circulatory failure and multiple organ dysfunction caused by endotoxin in the rat

1. We compared the effects of calpain inhibitor I (inhibitor of the proteolysis of I kappa B and, hence, of the activation of nuclear factor kappa B (NF kappa B) and dexamethasone on (i) the circulatory failure, (ii) multiple organ dysfunction and (iii) induction of the inducible isoforms of nitric oxide (NO) synthase (iNOS) and cyclo-oxygenase (COX-2) in anaesthetized rats with endotoxic shock. 2. Injection of lipopolysaccharide (LPS, E. coli, 10 mg kg-1, i.v.) resulted in hypotension and a reduction of the pressor responses elicited by noradrenaline. This circulatory dysfunction was attenuated by pretreatment of LPS-rats with calpain inhibitor I (10 mg kg-1, i.v., 2 h before LPS) or dexamethasone (1 mg kg-1, i.v.). 3. Endotoxaemia also caused rises in the serum levels of (i) urea and creatinine (renal dysfunction), (ii) alanine aminotransferase (ALT), aspartate aminotransferase (AST) (hepatocellular injury), bilirubin and gamma-glutamyl transferase (gamma GT) (liver dysfunction), (iii) lipase (pancreatic injury) and (iv) lactate. Calpain inhibitor I and dexamethasone attenuated the liver injury, the pancreatic injury, the lactic acidosis as well as the hypoglycaemia caused by LPS. Dexamethasone, but not calpain inhibitor I, reduced the renal dysfunction caused by LPS. 4. Endotoxaemia for 6 h resulted in a substantial increase in iNOS and COX-2 protein and activity in lung and liver, which was attenuated in LPS-rats pretreated with calpain inhibitor I or dexamethasone. 5. Thus, calpain inhibitor I and dexamethasone attenuate (i) the circulatory failure, (ii) the multiple organ dysfunction (liver and pancreatic dysfunction/injury, lactic acidosis, hypoglycaemia), as well as (iii) the induction of iNOS and COX-2 protein and activity in rats with endotoxic shock. We propose that prevention of the activation of NF-kappa B in vivo may be useful in the therapy of circulatory shock or of disorders associated with local or systemic inflammation.

Mechanism of action of aspirin-like drugs

Nonsteroid antiinflammatory drugs (NSAIDs) or aspirin-like drugs act by inhibiting the activity of the cyclooxygenase (COX) enzyme. Two isoforms of COX exist, COX-1, which is constitutively expressed, and COX-2, which is an inducible isoform. Prostaglandins synthesized by the constitutively expressed COX-1 are implicated in the maintenance of normal physiological function and have a 'cytoprotective' action in the stomach. COX-2 expression is normally low but is induced by inflammatory stimuli and cytokines. It is thought that the antiinflammatory actions of NSAIDs are caused by the inhibition of COX-2, whereas the unwanted side effects, such as gastrointestinal and renal toxicity, are caused by the inhibition of the constitutively expressed COX-1. Individual NSAIDs show different selectivities against the COX-1 and COX-2 isoforms. NSAIDs that are selective towards COX-2, such as meloxicam, may have an improved side-effect profile over current NSAIDs. In addition to their use as antiinflammatory agents in the treatment of rheumatoid arthritis and osteoarthritis, selective COX-2 inhibitors may also be beneficial in inhibiting colorectal tumor cell growth and in delaying premature labor.

Expression of recombinant human cyclooxygenase isoenzymes in transfected COS-7 cells in vitro and inhibition by tenoxicam, indomethacin and aspirin

The recent discovery of cyclooxygenase-2 (COX-2), an isoenzyme associated mainly with inflammation created the need to reevaluate cyclooxygenase inhibitors with reliable screening methods. In the present study we standardized a technique to determine the IC50S of cyclooxygenase inhibitors on recombinant human COX-1 and COX-2 expressed in mammalian cells and used it to study the compounds tenoxicam, aspirin and indomethacin. The IC50S of aspirin, indomethacin and tenoxicam for human COX-1 were 0.41 +/- 0.07 microgram/ml, 0.008 +/- 0.003 microgram/ml, and 7.94 +/- 3.28 micrograms/ml, respectively, and for human COX-20.64 +/- 0.16 microgram/ml, 0.09 +/- 0.05 microgram/ml, and 10.61 +/- 1.50 micrograms/ml, for aspirin, indomethacin, and tenoxicam. Tenoxicam had the lowest IC50hCOX-2/IC50hCOX-1 ratio (1.34), followed by aspirin (1.53) and indomethacin (10.82). The system described in the present study provides a simple and efficient way to determine the specificity of NSAID inhibition for each of the human cyclooxygenase isoenzymes separately.

Activation of cytoprotective prostaglandin synthase-1 by minoxidil as a possible explanation for its hair growth-stimulating effect

Data from the literature indicate that nonsteroidal anti-inflammatory drugs (NSAIDs), such as indomethacin, naproxen, piroxicam, or ibuprofen, induce hair loss in vivo. These NSAIDs are well-known inhibitors of both the cytoprotective isoform of prostaglandin endoperoxide synthase-1 (PGHS-1) and of the inducible form (PGHS-2). By immunohistochemical staining, we found that PGHS-1 is the main isoform present in the dermal papilla from normal human hair follicle (either anagen or catagen), whereas PGHS-2 was only faintly and exclusively expressed in anagen dermal papilla. Thus, PGHS-1 might be the primary target of the hair growth-inhibitory effects of NSAIDs. We thus speculated that activation of PGHS-1 might be a mechanism by which minoxidil (2,4-diamino-6-piperidinopyrimidine-3-oxyde) stimulates hair growth in vivo. We demonstrate here that minoxidil is a potent activator of purified PGHS-1 (AC50 = 80 microM), as assayed by oxygen consumption and PGE2 production. This activation was also evidenced by increased PGE2 production by BALB/c 3T3 fibroblasts and by human dermal papilla fibroblasts in culture. Our findings suggest that minoxidil and its derivatives may have a cytoprotective activity in vivo and that more potent second-generation hair growth-promoting drugs might be designed, based on this mechanism.