Pharmacological and biochemical demonstration of the role of cyclooxygenase 2 in inflammation and pain

Pharmacological and pharmacokinetic evaluation of celecoxib prodrugs in rats

This study demonstrates the utility of an in vitro - in vivo correlative approach in the selection and optimization of a prodrug candidate of celecoxib (CBX), a COX(2) inhibitor. As an initial screening step, a comparative single oral dose pharmacokinetic study was conducted in rats for CBX and its three aliphatic acyl water-soluble prodrugs viz., CBX-acetyl (CBX-AC), CBX-propionyl (CBX-PR) and CBX-butyryl (CBX-BU) at high equimolar dose, 100 mg/kg. Only CBX-BU and CBX-PR converted rapidly to CBX and yielded approximately five-fold greater systemic exposure of CBX than CBX alone or CBX-AC. Rank order of systemic exposure of prodrugs in its intact form was CBX-AC >CBX-PR >CBX-BU. Further in vitro hydrolysis studies of CBX prodrugs in intestinal mucosal suspensions and liver homogenates indicated that CBX-BU is rapidly and completely converted to CBX, whereas CBX-PR and CBX-AC require longer incubation period for complete conversion to CBX. There was a very good correlation of the in vitro and in vivo data supporting CBX-BU as the prodrug of choice. Further in vitro pharmacological studies showed that COX(2) selective inhibition is improved for CBX-BU as compared to CBX-AC and CBX-PR. Dose proportionality in pharmacokinetic studies of CBX-BU and CBX at equimolar oral doses confirmed that relative oral bioavailability of CBX was improved following CBX-BU administration and there was linearity in pharmacokinetics of CBX over a wide dose range (10-100 mg/kg), whereas CBX in its conventional form showed poor bioavailability and lack of dose linearity in pharmacokinetics. The oral bioavailability of CBX from CBX-BU was dose independent and was in the range 78-96%. At a 50% reduced molar dose, CBX-BU showed an equivalent efficacy to that of CBX in the in vivo carrageenan model. Based on the study, water-soluble CBX-BU prodrug can be considered for clinical development in view of its potential advantages.

Cyclooxygenase-2 inhibitors: promise or peril?

The discovery of two isoforms of the cyclooxygenase enzyme, COX-1 and COX-2, and the development of COX-2-specific inhibitors as anti-inflammatories and analgesics have offered great promise that the therapeutic benefits of NSAIDs could be optimized through inhibition of COX-2, while minimizing their adverse side effect profile associated with inhibition of COX-1. While COX-2 specific inhibitors have proven to be efficacious in a variety of inflammatory conditions, exposure of large numbers of patients to these drugs in postmarketing studies have uncovered potential safety concerns that raise questions about the benefit/risk ratio of COX-2-specific NSAIDs compared to conventional NSAIDs. This article reviews the efficacy and safety profiles of COX-2-specific inhibitors, comparing them with conventional NSDAIDs.

Synthesis of isotopically labeled arachidonic acids to probe the reaction mechanism of prostaglandin H synthase

Prostaglandin H synthase (PGHS) catalyzes the conversion of arachidonic acid to prostaglandin G(2) in the cyclooxygenase reaction. The first step of the mechanism has been proposed to involve abstraction of the pro-S hydrogen atom from C13 to generate a pentadienyl radical spanning C11-C15. We report here the synthesis of six site-specifically deuterated arachidonic acids to investigate the structure of the radical intermediate. The preparation of these compounds was achieved using a divergent scheme that involved one advanced intermediate for all targets. The synthetic design introduced the label late in the routes and allowed the utilization of common synthetic intermediates in the preparation of various targets. Both 13(R)- and 13(S)-deuterium-labeled arachidonic acids were synthesized in high enantiomeric purity as deduced from soybean lipoxygenase assays and mass spectrometric analysis of the resulting enzymatic products. Each synthetic compound was reacted under anaerobic conditions with the wide singlet tyrosyl radical of PGHS-2 to generate a radical intermediate that was analyzed by EPR. Deuterium substitution at positions 11, 13(S), and 15 resulted in the loss of one hyperfine interaction, indicating that the protons at these positions interact with the unpaired electron. Simulation of the spectra was achieved with one set of parameters that are consistent with the assignment of a pentadienyl radical. Use of 16-[(2)H(2)]-arachidonic acid indicated that only one of the protons at C16 gives rise to a strong hyperfine interaction. The findings are discussed in the context of two proposed mechanisms for the cyclooxygenase reaction.

Pharmacology of celecoxib in rat brain after kainate administration

Prostaglandin E(2) (PGE(2)) is the major prostaglandin produced both centrally and in the periphery in models of acute and chronic inflammation, and its formation in both locations is blocked by cyclooxygenase-2 (COX-2) inhibitors such as celecoxib. In animal models of inflammation, PGE(2) inhibition in the brain may occur secondarily to a peripheral action by inhibiting local PG formation that elicits increased firing of pain fibers and consequent activation of PG synthesis in the central nervous system (CNS). Celecoxib was studied in the kainate-induced seizure model in the rat, a model of direct central prostaglandin induction, to determine whether it can act directly in the CNS. In the kainate-treated rat brain there was increased PGE(2), PGF(2alpha), and PGD(2) production, with COX activity and PGE(2) formation increased about 7-fold over normal. We quantitated mRNA levels for enzymes involved in the prostaglandin biosynthetic pathways and found that both COX-2 and PGE synthase (PGEs) mRNA levels were increased in the brain; no changes were found for expression of COX-1 or PGD synthase mRNA. By Western blot analysis, COX-2 and PGEs were induced in total brain, hippocampus, and cortex, but not in the spinal cord. Immunohistological studies showed that COX-2 protein expression was enhanced in neurons. Dexamethasone treatment reduced the expression of both COX-2 and PGEs in kainate-treated animals. Celecoxib reduced the elevated PGE(2) levels in brain of kainate-treated rats and inhibited induced COX activity, demonstrating the ability of this compound to act on COX-2 in CNS. Doses of celecoxib that inhibited brain COX-2 were lower than those needed for anti-inflammatory activity in adjuvant arthritis, demonstrating a potent direct central action of the compound.

Effect of misoprostol and indomethacin on cyclooxygenase induction and eicosanoid production in carrageenan-induced air pouch inflammation in rats

Effects of misoprostol, a synthetic prostaglandin E1 (PGE1) analogue, on cyclooxygenase-2 (COX-2) protein level and exudate prostaglandin E2 (PGE2) and thromboxane B2 (TXB2) level were investigated in acute carrageenan-induced air pouch inflammation in rats. Treatment with misoprostol (12.5, 25, and 50 microg/kg) has been started in separated groups, 30 min and 2 days before carrageenan injection and it was given twice a day (total of five doses) by orogastric route. Indomethacin, in doses of 0.5 and 5 mg/kg, and specific COX-2 inhibitor SC-58236, in doses of 5, 10, and 20 mg/kg were given 1 h before carrageenan injection by the orogastric route. Misoprostol increased the levels of PGE2 and COX-2 protein at all doses applied. Despite indomethacin and SC-58236 increased the level of COX-2 protein when they used alone, these drugs partially inhibited misoprostol-induced increase in the level of COX-2 protein. Partial inhibition of misoprostol-induced increase in the level of COX-2 protein by indomethacin or SC-58236 may indicate the modulatory roles of endogenous prostaglandins (PGs, especially, PGE2) on the COX-2 expression.

Anti-inflammatory potency of FR167653, a p38 mitogen-activated protein kinase inhibitor, in mouse models of acute inflammation

The anti-inflammatory effect of FR167653 (1-[7-(4-fluorophenyl)-1,2,3,4-tetrahydro-8-(4-pyridyl)pyrazolo[5,1-c][1,2,4]triazin-2-yl]-2-phenylethanedione sulfate monohydrate), a p38 mitogen-activated protein (MAP) kinase inhibitor, was examined in two mouse models of acute inflammation. Carrageenan-induced paw edema was inhibited by pretreatment with FR167653, anti-tumor necrosis factor (TNF)-alpha antibody, and NS-398 (N-(2-cyclohexyloxy-4-nitrophenyl) methanesulfonamide), a selective cyclooxygenase-2 inhibitor. Carrageenan increased TNF-alpha and prostaglandin E(2) levels in the paw, both of which were suppressed by FR167653. Subcutaneous injection of lipopolysaccharide at the back of mouse caused local increase in vascular permeability determined by leakage of Pontamine sky blue. FR167653 dose-dependently inhibited the lipopolysaccharide-induced plasma leakage. FR167653 also inhibited lipopolysaccharide-induced increases in serum TNF-alpha level, and skin TNF-alpha and prostaglandin E(2) levels at the injection site. On the other hand, FR167653 did not reduce arachidonic acid-induced plasma leakage which is not mediated by cyclooxygenase-2. FR167653 exhibits anti-inflammatory effects against both carrageenan-induced paw edema and lipopolysaccharide-induced plasma leakage through inhibiting the synthesis of inflammatory mediators that are regulated by p38 MAP kinase.

Purification and characterization of a cyclooxygenase-2 and angiogenesis suppressing factor produced by human fibroblasts

Cyclooxygenase-2 (COX-2) is an inducible enzyme that plays an important role in several pathophysiological processes, including inflammation, angiogenesis, and tumorigenesis. We have recently observed that COX-2 induction is restrained in proliferating fibroblasts. The mechanism by which this occurs is unclear. Here, we report the detection and isolation from the conditioned medium of proliferating fibroblasts a factor that suppressed COX-2 expression. This factor, which was named cytoguardin, suppressed COX-2 protein levels induced by phorbol 12-myristate 13-acetate, interleukin-1beta, tumor necrosis factor alpha, and lipopolysaccharide (LPS) in fibroblasts and LPS-induced COX-2 protein levels and promoter activities in human endothelial cells and murine RAW 264.7 cells in a comparable concentration-dependent manner. It inhibited COX-2 expression induced by angiogenic factors and endothelial tube formation induced by angiogenic factors and colon cancer cell medium. These findings provide evidence for the control of COX-2 transcription by an endogenous cellular factor.

Chemopreventive effect of celecoxib and expression of cyclooxygenase-1 and cyclooxygenase-2 on chemically-induced rat mammary tumours

We investigated the chemopreventive effect of celecoxib on 7,12-dimethylbenz[a]anthracene (DMBA)-induced rat mammary tumours and also the expression and immunolocalization of cyclooxygenase-1 (COX-1) and COX-2 in the various stages of rat mammary carcinogenesis. Rats were divided into normal control group, DMBA-control group, 500 p.p.m. celecoxib-treated group, and 1500 p.p.m. celecoxib-treated group. Both incidence and multiplicity values of tumour for rats treated with celecoxib were less than those in rats of the DMBA-control group. The level of prostaglandin E2 was higher in tumours of the DMBA-control and both celecoxib-treated groups compared to normal mammary glands of each group. In Western blot analysis, all tumours of the DMBA-control group expressed COX-1, whereas normal mammary glands showed insignificant expression. COX-2 expression was observed in 67% of the DMBA-control group and 20% of both celecoxib-treated groups and was absent in normal mammary glands. COX-1 protein was localized in the nuclear membrane and cytoplasm of epithelial tumour cells abutting on glandular lumen, stromal cells, and endothelial cells. COX-2 protein was detected in the perinuclear cytoplasm of tumour cells bordering on glandular lumen and surrounding stroma, stromal cells, and vascular smooth muscle. In the DMBA-control group, invasive carcinoma cells showed higher positive immunoreactivity of COX-2 than carcinomas in situ and atypical tumours. Tumours displayed an increased number of mast-like cells with COX-2 expression in comparison to carcinomas in situ. Our results suggest that COX-1 and COX-2 expression in tumour cells and stromal cells play an important role in the various stages of DMBA-induced rat mammary carcinogenesis. In addition, we reconfirm that celecoxib reduces the growth of DMBA-induced rat mammary tumours.

Indomethacin attenuates the immunosuppressive and tumor-promoting effects of surgery

We have previously shown in rats that both intrathecal and systemic analgesia regimens attenuate surgery-induced increases in tumor susceptibility. The current study used indomethacin to assess the role of prostaglandins and inflammation-associated pain in mediating the deleterious effects of surgery on immunity and tumor susceptibility. Male and female Fischer 344 rats were anesthetized with halothane and were either subjected or not to experimental laparotomy, followed by the administration of indomethacin or vehicle. Tumor susceptibility was assessed by the lung retention assay using the syngeneic MADB106 mammary adenocarcinoma cell line, a natural killer (NK)-sensitive tumor that colonizes only in the lungs. Surgery resulted in a 2- to 3.5-fold increase in lung tumor retention, and indomethacin administration significantly reduced this effect in both sexes without affecting unoperated animals. Indomethacin also attenuated the reductions in rearing behavior evident after surgery, suggesting that it relieved abdominal discomfort. Surgery increased interleukin-6 levels and suppressed NK activity per milliliter blood. Indomethacin restored NK activity in both male and female rats but attenuated surgery-induced interleukin-6 increases only in the male rats. These findings further support our previous work implicating pain in mediating the tumor-enhancing effects of surgery and implicate prostaglandins in mediating this effect. If similar relationships occur in humans, controlling postoperative pain and inflammation must become a priority in the management of cancer patients undergoing surgery.

Rofecoxib inhibits cyclooxygenase 2 expression and activity and reduces cell proliferation in Barrett's esophagus

BACKGROUND & AIMS

Cyclooxygenase 2 (COX-2) is overexpressed in Barrett's esophagus and adenocarcinoma and up-regulated by acid or bile salt exposure. COX-2 inhibition with the selective inhibitor rofecoxib may be important in chemoprevention of esophageal adenocarcinoma by decreasing cell proliferation.

METHODS

Biopsy specimens of esophagus, Barrett's esophagus, and duodenum were obtained at baseline from 12 patients and were compared with biopsy specimens obtained after 10 days of therapy with rofecoxib 25 mg orally daily. All patients were maintained asymptomatic on their proton pump inhibitor therapy throughout the study. COX-2 expression, proliferating cell nuclear antigen (PCNA) expression (proliferation marker), and prostaglandin E2 (PGE2) biopsy content (marker of COX activity) were assessed by immunoblotting and enzyme immunoabsorbence assays.

RESULTS

At baseline, COX-2 expression was 3-fold higher in Barrett's esophagus than esophagus and duodenum (P < 0.05). After rofecoxib therapy, COX-2 expression in Barrett's esophagus decreased by 77% (P < 0.005). Similarly at baseline, PGE2 content was 2-fold higher in Barrett's esophagus than esophagus or duodenum. After rofecoxib therapy, PGE2 content decreased in Barrett's esophagus by 59% (P < 0.005). At baseline, PCNA expression was also 2-fold higher in Barrett's esophagus than squamous esophagus and duodenum (P < 0.005). After rofecoxib therapy, PCNA expression in Barrett's esophagus decreased by 62.5% (P < 0.005).

CONCLUSIONS

Rofecoxib 25 mg orally once daily reduces COX-2 expression, PGE2 release, and cell proliferation in Barrett's esophagus. Together with acid suppressive therapy, rofecoxib may be a promising chemoprevention agent against dysplasia and esophageal adenocarcinoma.

Opposite effects of cyclooxygenase-1 and -2 activity on the pressor response to angiotensin II

Therapeutic use of cyclooxygenase-inhibiting (COX-inhibiting) nonsteroidal antiinflammatory drugs (NSAIDs) is often complicated by renal side effects including hypertension and edema. The present studies were undertaken to elucidate the roles of COX1 and COX2 in regulating blood pressure and renal function. COX2 inhibitors or gene knockout dramatically augment the pressor effect of angiotensin II (Ang II). Unexpectedly, after a brief increase, the pressor effect of Ang II was abolished by COX1 deficiency (either inhibitor or knockout). Ang II infusion also reduced medullary blood flow in COX2-deficient but not in control or COX1-deficient animals, suggesting synthesis of COX2-dependent vasodilators in the renal medulla. Consistent with this, Ang II failed to stimulate renal medullary prostaglandin E(2) and prostaglandin I(2) production in COX2-deficient animals. Ang II infusion normally promotes natriuresis and diuresis, but COX2 deficiency blocked this effect. Thus, COX1 and COX2 exert opposite effects on systemic blood pressure and renal function. COX2 inhibitors reduce renal medullary blood flow, decrease urine flow, and enhance the pressor effect of Ang II. In contrast, the pressor effect of Ang II is blunted by COX1 inhibition. These results suggest that, rather than having similar cardiovascular effects, the activities of COX1 and COX2 are functionally antagonistic.

Obligatory role of cyclic adenosine monophosphate response element in cyclooxygenase-2 promoter induction and feedback regulation by inflammatory mediators

BACKGROUND

Cyclooxygenase-2 (COX-2) plays a key role in human inflammatory disorders such as vascular inflammation. COX-2 promoter activity is induced by proinflammatory mediators, but the role of cyclic adenosine monophosphate response element (CRE) in promoter stimulation remains unclear.

METHODS AND RESULTS

Transient transfection of a 0.9-kb COX-2 promoter fragment bearing CRE mutation abrogated COX-2 promoter activity induced by proinflammatory mediators in human endothelial cells and fibroblasts. Dual mutations of CRE and an upstream CCAAT/enhancer binding protein (C/EBP) site did not have an additional effect. Binding of CREB-2, ATF-2, USF-2, and c-Jun transactivators to a wild-type and CRE-mutated oligonucleotide was analyzed by a novel DNA-binding assay. CREB-2 and ATF-2 in nuclear extracts of unstimulated endothelial cells bound to CRE, whereas USF-2 and c-Jun or c-Fos bound to non-CRE sites. CREB-2 and c-Fos binding was increased by phorbol 12-myristate 13-acetate but not tumor necrosis factor-alpha. The binding assay and chromatin immunoprecipitation revealed binding of P300 coactivator to the COX-2 promoter region.

CONCLUSIONS

CRE plays an obligatory role in COX-2 promoter activation by diverse stimuli. CREB-2 and ATF-2 bound to CRE serve as an anchor for P300 interaction with upstream transactivators and downstream transcription machinery.

NSAID inhibition of RGM1 gastric monolayer wound re-epithelialization: comparison of selective Cox-2 versus non-selective Cox inhibitors

Clinical studies indicate that specific cyclooxygenase-2 (Cox-2) inhibitors are less ulcerogenic than their non-selective predecessors (e.g. indomethacin). However, Cox-2 inhibitors may also interfere with ulcer healing. Re-epithelialization is a crucial factor in both gastrointestinal mucosal injury and ulcer healing. This study was aimed to compare the effects of selective Cox-2 inhibitor (NS398) versus non-selective Cox inhibitor (indomethacin) on basal and basic fibroblast growth factor (bFGF) - stimulated gastric wound re-epithelialization. In-vitro epithelial wounds were created in confluent monolayers of RGM1 rat gastric epithelial cells by a razor blade scrape. Following wounding there was a significant re-epithelialization by 24 hrs. Indomethacin (0.25 mM and 0.5 mM) significantly inhibited basal wound re-epithelialization in a dose dependent manner. In contrast, selective Cox-2 inhibitor NS398 did not inhibit the basal re-epithelialization process. Basic FGF treatment produced significant enhancement of wound re-epitheliazation at the various concentrations [10, 20, 30, 40, 50 and 70 ng/ml] studied. Both indomethacin and NS398 inhibited bFGF stimulated wound re-epithelialization, with indomethacin having a greater inhibitory effect. The extent of NS398 inhibition was limited to the bFGF-stimulated component, whereas indomethacin inhibition extended to both the bFGF-stimulated and the basal re-epithelialization components. These findings indicate that specific Cox-2 inhibitor (NS398) does not interfere with the basal re-epithelialization but significantly inhibits the bFGF - stimulated re-epithelialization, whereas indomethacin interferes with both the basal as well as the bFGF-stimulated wound re-epithelialization.

Alteration of gastric ulcerogenic and healing responses in rats with adjuvant-induced arthritis

Gastroenteropathy is the most common among patients who use non-steroidal anti-inflammatory drugs (NSAIDs) for treatment of inflammatory disorders. It is known that rheumatoid arthritic patients are more susceptible to NSAID-induced gastropathy than other NSAID users. This article reviewed our recent studies concerning the influence of arthritic conditions on gastric ulcerogenic response to NSAID and healing response of chronic gastric ulcers in rats. Gastric lesions induced by indomethacin, one of the conventional NSAIDs, were markedly aggravated in arthritic rats. This increased ulcerogenic response in arthritic rats was attributable to nitric oxide production due to up-regulation of inducible nitric oxide synthase. In arthritic rat stomachs, cyclooxygenase (COX)-2 was also up-regulated, where COX-2 selective inhibitors such as rofecoxib or celecoxib provoked gross lesions, although they caused no damage in normal rats. In addition, the healing of chronic gastric ulcers was also delayed in arthritic rats because of less expression of various growth factors such as basic fibroblast growth factors or insulin-like growth factors. Based on these findings, it is concluded that arthritic conditions alter the mucosal ulcerogenic and healing responses in the stomach. Especially, caution should be paid on the use of COX-2 selective inhibitors in rheumatoid arthritic patients.

Cyclooxygenase-2: a therapeutic target

Cyclooxygenase (COX), also known as prostaglandin endoperoxide synthase, is the key enzyme required for the conversion of arachidonic acid to prostaglandins. Two COX isoforms have been identified, COX-1 and COX-2. In many situations, the COX-1 enzyme is produced constitutively (e.g., in gastric mucosa), whereas COX-2 is highly inducible (e.g., at sites of inflammation and cancer). Traditional nonsteroidal anti-inflammatory drugs (NSAIDs) inhibit both enzymes, and a new class of COX-2 selective inhibitors (COXIBs) preferentially inhibit the COX-2 enzyme. This review summarizes our current understanding of the role of COX-1 and COX-2 in normal physiology and disease.

Dendritic cells produce eicosanoids, which modulate generation and functions of antigen-presenting cells

Eicosanoids have been shown to be potent immunoregulatory arachidonic acid (AA) metabolites. AA is the precursor of prostaglandin E(2) (PGE(2)) and leukotriene B(4) (LTB(4)) which are able to modulate both inflammation and the immune response. Dendritic cells process and present antigens to T lymphocytes. They are highly specialized antigen-presenting cells (APC) and usually considered as 'professional APC'. In the present paper, we report some data on the biosynthetic capacity of murine APC from the bone marrow (BM-DCs) to produce AA metabolites. Using an ELISA we have observed that BM-DCs spontaneously produce both PGE(2) and LTB(4) whose production increased in response to bacterial lipopolysaccharides (LPS). In addition we found that LTB(4) production was twice as high when both COX pathways were blocked with selective COX-inhibitors. We have also investigated the effect of PGE(2) and LTB(4) on the in vitro generation of the so-called BM-DCs. Exogenous PGE(2) and LTB(4) added to bone marrow cultures inhibit and promote, respectively, BM-DC generation. PGE(2) added to the maturing BM-DCs reduces their MHC class-II expression.

Effects of carprofen on renal function and results of serum biochemical and hematologic analyses in anesthetized dogs that had low blood pressure during anesthesia

OBJECTIVE

To investigate effects of IV administered carprofen on indices of renal function and results of serum biochemical and hematologic analyses in dogs anesthetized with acepromazine-thiopentone-isoflurane that had low blood pressure during anesthesia.

ANIMALS

6 healthy Beagles.

PROCEDURE

A randomized crossover study was conducted, using the following treatments: saline (0.9% NaCl solution)-saline, saline-carprofen, and carprofen-saline. Saline (0.08 ml/kg) and carprofen (4 mg/kg) were administered IV. The first treatment was administered 30 minutes before induction of anesthesia and immediately before administration of acepromazine (0.1 mg/kg, IM). Anesthesia was induced with thiopentone (25 mg/ml, IV) and maintained with inspired isoflurane (2% in oxygen). The second treatment was administered 30 minutes after onset of inhalation anesthesia. Blood gases, circulation, and ventilation were monitored. Renal function was assessed by glomerular filtration rate (GFR), using scintigraphy, serum biochemical analyses, and urinalysis. Hematologic analysis was performed. Statistical analysis was conducted, using ANOVA or Friedman ANOVA.

RESULTS

Values did not differ significantly among the 3 treatments. For all treatments, sedation and anesthesia caused changes in results of serum biochemical and hematologic analyses, a decrease in mean arterial blood pressure to 65 mm Hg, an increase of 115 pmol/L in angiotensin II concentration, and an increase of 100 seconds in time required to reach maximum activity counts during scintigraphy.

CONCLUSIONS AND CLINICAL RELEVANCE

Carprofen administered IV before or during anesthesia did not cause detectable significant adverse effects on renal function or results of serum biochemical and hematologic analyses in healthy Beagles with low blood pressure during anesthesia.

Protective role of cyclooxygenase (COX) inhibitors in burn-induced intestinal and liver damage

The aim of this study was to investigate the role of cyclooxygenase (COX) inhibition in intestinal motility and in the extent of tissue injury of the small intestine and liver with the use of various COX inhibitors. Wistar albino rats were exposed to 90 degrees C water bath for 10s. The intestinal transit index decreased compared to control group and treatment with nimesulide (NIM; 10mg/kg, subcutaneously) or piroxicam (Pir; 5mg/kg, orogastrically) reversed this effect significantly. The intestinal and liver glutathione levels showed a significant decrease in the burn group compared to sham (P<0.001 and P<0.05, respectively). Decrease in intestinal glutathione level was reversed by NIM or Pir treatment (P<0.01 and P<0.01, respectively), whereas all drugs tested were effective in reversing low liver glutathione level. The MPO activity in intestinal segments were significantly high in burned animals compared to sham. All test drugs reversed this effect but ketorolac (Ket; 3mg/kg, orogastrically) was the most effective one. The liver samples characterized by sinusoidal dilatation and pericentral atrophy in burn group were protected by treatment with Ket or Pir (P<0.05). Plasma ALT and AST activities were markedly high in this burn group compared to sham (P<0.0001 and P<0.001, respectively). None of the agents reversed these high enzyme activities. These data suggest that not only COX-2 but also COX-1 inhibition is required for protection against inflammatory changes in liver and small intestine following burn injury.

Effects of cyclooxygenase and lipoxygenase inhibition on basal- and serotonin-induced ion transport in rat colon

The purpose of this study was to determine the effect of a selective cyclooxygenase (COX)-2 inhibitor as compared to non-selective COX and lipoxygenase (LOX) inhibitors in rat colon. Basal- and serotonin (5-hydroxytryptamine, 5-HT)-induced electrogenic ion transport (short circuit current, SCC), prostaglandin E2 (PGE2) release and histological characteristics were measured. Muscle-stripped mucosal sheets of the proximal and distal segment of rat colon were investigated by employing the Ussing chamber technique, radioimmunoassays for PGE2 and light microscopy examinations for control of tissue integrity. 5-HT and PGE2 both induced a concentration-dependent increase in SCC by activation of multiple receptors. The response to 5-HT was bumetanide-sensitive. Neither the non-selective COX inhibitor piroxicam, nor the selective COX-2 inhibitor SC-'236, altered basal- SCC or 5-HT-induced SCC. Indomethacin reduced both basal- and 5-HT-induced SCC in both segments. Nordihydroguaiaretic acid reduced the 5-HT-induced increase in SCC, but did not change basal SCC. 5-HT-induced a concentration-dependent release of PGE2. Only high concentrations of piroxicam and indomethacin reduced basal PGE2 release and 5-HT-induced PGE2 release. Histological examination of the specimens demonstrated only minor changes following mounting in chambers. There were no apparent differences in the morphology following treatment with COX or LOX inhibitors. These results suggest that in rat colon only the COX-1 enzyme is expressed under basal conditions. Furthermore, data suggest neither the COX-1 nor the COX-2 enzyme to be of major importance for 5-HT-induced ion transport in rat colon in vitro. In conclusion, this study supports 5-HT as a mediator of chloride secretion by activating several receptor subtypes and the LOX enzyme, releasing mediators such as leucotrienes.

Dermal application of jet fuel suppresses secondary immune reactions

Applying military jet fuel (JP-8) to the skin of mice activates systemic immune suppression. In all of our previous experiments, JP-8 was applied to immunologically naïve mice. The effect of jet fuels on established immune reactions, such as immunological memory, is unknown. The focus of the experiments presented here was to test the hypothesis that jet fuel exposure [both JP-8 and commercial jet fuel (Jet-A)] suppresses established immune reactions. Mice were immunized with the opportunistic fungal pathogen Candida albicans and, at different times after immunization (10 to 30 days), various doses of undiluted JP-8 or Jet-A were applied to their skin. Both the elicitation of delayed-type hypersensitivity (DTH) (mice challenged 10 days after immunization) and immunological memory (mice challenged 30 days after immunization) were significantly suppressed in a dose-dependent manner. Dermal exposure to either multiple small doses (50 microl over 4 days) or a single large dose (approximately 200-300 microl) of JP-8 and/or Jet-A suppressed DTH to C. albicans. The mechanism by which dermal application of JP-8 and Jet-A suppresses immunological memory involves the release of immune biologic response modifiers. Blocking the production of prostaglandin E(2) by a selective cyclooxygenase-2 inhibitor (SC 236) significantly reversed jet fuel-induced suppression of immunologic memory. These findings indicate, for the first time, that dermal exposure to commercial jet fuel (Jet-A) suppresses the immune response. In addition, the data reported here expand on previous findings by suggesting that jet fuel exposure may depress the protective effect of prior vaccination.

Up-regulation of COX-2 by inhibition of COX-1 in the rat: a key to NSAID-induced gastric injury

BACKGROUND

A recent study demonstrated that inhibition of both cyclooxygenase (COX)-1 and COX-2 is required for the development of nonsteroidal anti-inflammatory drug (NSAID)-induced gastric lesions. However, the role of COX-1 or COX-2 inhibition in the pathogenisis of these lesions remains unclear.

AIM

To examine the gastric ulcerogenic properties of selective COX-1 and COX-2 inhibitors in rats and to investigate further the relationship of COX inhibition to various events involved in the process of NSAID-induced gastric lesions.

METHODS

Animals were given various COX inhibitors p.o., either alone or in combination, and killed 8 h later. Under the treatment, gastric damage, prostaglandin (PG) E2 content, mucosal permeability, myeloperoxidase (MPO) activity as well as gastric motility were examined.

RESULTS

The nonselective COX inhibitor indomethacin inhibited PGE2 production, enhanced gastric motility, and provoked severe lesions in the stomach, with an increase in mucosal permeability and MPO activity. In contrast, the selective COX-2 inhibitor rofecoxib did not induce any damage in the stomach and had no effect on mucosal PGE2 content. Similarly, the selective COX-1 inhibitor SC-560 also caused no gastric damage, despite inhibiting PGE2 production. The combined administration of SC-560 and rofecoxib, however, provoked gross damage in the gastric mucosa, in a dose-dependent manner for each drug. SC-560, but not rofecoxib, caused marked gastric hypermotility and an increase in mucosal permeability, although an increase in MPO activity was observed only when rofecoxib was coadministered. The normal gastric mucosa expressed COX-1 mRNA and not COX-2 mRNA, but COX-2 mRNA was expressed in the stomach after administration of SC-560 as well as indomethacin but not rofecoxib.

CONCLUSION

These results suggest that the gastric ulcerogenic properties of NSAIDs are not accounted for solely by COX-1 inhibition, but require the inhibition of both COX-1 and COX-2. The inhibition of COX-1 up- regulates COX-2 expression, and COX-2/PGs may, in turn, counteract the deleterious affects of gastric hypermotility due to COX-1 inhibition.

In vitro antiinflammatory activity of kalopanaxsaponin A isolated from Kalopanax pictus in murine macrophage RAW 264.7 cells

In the present study, effects of various hederagenin monodesmosides isolated from the stem bark of Kalopanax pictus Nakai, such as hederagenin, 5-hederin, kalopanaxsaponin A, kalopanaxsaponin 1, and sapindoside C, have been evaluated on lipopolysaccharide (LPS)-induced nitric oxide (NO), prostaglandin E2 (PGE2) and tumor necrosis factor-alpha (TNF-alpha) release by the macrophage cell line RAW 264.7. Among the tested monodesmosides, kalopanxsaponin A was the most potent inhibitor of NO production, and it also significantly decreased PGE2 and TNF-alpha release. Consistent with these observations, the expression level of inducible NO synthase (iNOS) and cyclooxygenase (COX)-2 enzyme was inhibited by kalopanxsaponin A in a concentration-dependent manner. Thus, this study suggests that kalopanaxsaponin A-mediated inhibition of iNOS, COX-2 expression, and TNF-alpha release may be one of the mechanisms responsible for the anti-inflammatory effects of the stem bark of Kalopanax pictus Nakai.

Chemoprevention of esophageal adenocarcinoma by COX-2 inhibitors in an animal model of Barrett's esophagus

BACKGROUND & AIMS

Carcinogenesis in Barrett's esophagus (BE) is associated with an increased expression of cyclooxygenase (COX) 2. However, there has been no direct evidence that inhibition of COX-2 prevents cancer in BE. We studied the effect of MF-Tricyclic, a selective COX-2 inhibitor, on the development of BE and adenocarcinoma in a rat model.

METHODS

Four weeks after esophagojejunostomy, 105 Sprague-Dawley rats were randomized to a chow containing MF-Tricyclic or Sulindac, or a placebo. Ninety-six (92%) rats completed the study and were sacrificed at 28 +/- 2 weeks. The animals were assessed for the presence of cancer, tumor volume, BE, degree of inflammation, and COX-2 expression and activity.

RESULTS

MF-Tricyclic and Sulindac reduced the relative risk of development of esophageal cancer by 55% (95% confidence interval [CI] = 43%-66%, P < 0.008) and by 79% (95% CI = 68%-87%, P < 0.001), respectively, compared with controls. No significant differences were noted in the risk of esophageal cancer between the MF-Tricyclic and the Sulindac group (P = 0.34). The median tumor volume was not significantly different among the 3 groups (P = 0.081). Moderate to severe degree of inflammation was significantly more common (P = 0.005) in the control compared with the MF-Tricyclic and the Sulindac group; however, the prevalence of BE was not significantly different between groups (P = 0.98). Rats in the control group had higher tissue PGE2 level compared with the MF-Tricyclic and Sulindac groups (P = 0.038).

CONCLUSIONS

Selective and nonselective COX-2 inhibitors can inhibit inflammation, COX-2 activity, and development of adenocarcinoma induced by reflux. This provides direct evidence that COX-2 inhibitors may have chemopreventive potential in BE.

Pharmacology of cyclooxygenase-2 inhibition in the kidney

Cyclooxygenase (COX) exists as two unique isoforms (that is, COX-1 and COX-2) which are poorly understood with regard to their roles in renal function. The renal effects of conventional non-steroidal anti-inflammatory drugs (NSAIDs) are believed to result from the inhibition of one or both isoforms. Drugs that selectively inhibit COX-2 provide useful pharmacological tools for discerning the effects associated with the inhibition of the individual isoforms, and may help clarify the renal roles of COX-1 and COX-2. This review summarizes the current data on the renal expression of COX isoforms and their potential roles in renal function, and reviews the studies that have attempted to correlate renal functional changes with selective isoform inhibition. Since there are significant differences in the expression of COX isoforms in the kidneys of laboratory animals and humans, this review also examines the correlation of the results of COX inhibition in experimental studies in laboratory animals with clinical data. Because of potential interspecies differences in the roles of COX isoforms in renal function, animal models may have limited predictive value for patients, particularly those with renal risk factors. Accordingly, any uncertainty concerning the safety or therapeutic benefit of COX-2-specific drugs in these patient populations will need to be resolved with clinical investigations.

Efficacy and safety of the COX-2 specific inhibitor valdecoxib in the management of osteoarthritis of the hip: a randomized, double-blind, placebo-controlled comparison with naproxen

OBJECTIVE

Non-steroidal antiinflammatory agents are commonly used to treat pain and inflammation associated with osteoarthritis (OA), but have poor gastrointestinal (GI) tolerability. This study compared the efficacy of the COX-2 specific inhibitor valdecoxib with naproxen and placebo, in treating symptomatic OA of the hip.

DESIGN

This multicenter, randomized, double-blind 12-week study compared the efficacy and tolerability of single daily doses of valdecoxib 5 mg and 10 mg with placebo or naproxen 500 mg BID. Efficacy was assessed by Patient's and Physician's Global Assessment of Arthritis, and the WOMAC (Western Ontario and McMasters) OA Individual and Composite Indices. The incidence of adverse events was monitored throughout the study.

RESULTS

Valdecoxib was clinically and statistically superior to placebo for Patient's and Physician's Global Assessment of Arthritis and for all WOMAC OA Indices over the 12 week study period (P<or= 0.05). Valdecoxib 10 mg was similar to naproxen in terms of efficacy, and demonstrated greater numerical improvements compared with valdecoxib 5 mg. Valdecoxib 5 mg and 10 mg demonstrated similar tolerability compared to placebo and a lower incidence of GI-related adverse effects compared with naproxen.

CONCLUSIONS

Single daily doses of valdecoxib 5 mg and 10 mg were similar to naproxen and superior to placebo, in treating symptomatic OA of the hip. Both doses of valdecoxib were well tolerated and demonstrated improved GI tolerability compared to naproxen.

Cardiovascular pharmacology of nonselective nonsteroidal anti-inflammatory drugs and coxibs: clinical considerations

Cyclooxygenase (COX)-2 inhibitors have been developed with the goal of providing similar efficacy and greater safety compared with traditional nonsteroidal anti-inflammatory drugs. Development was based on the hypothesis that COX-1 is the housekeeping enzyme necessary for production of prostaglandins (PGs) with homeostatic functions, whereas COX-2 is a mediator of pathophysiologic processes. However, later research has demonstrated a role of COX-2 in production of PGs that have functions under normal physiologic conditions. In the vasculature, COX-2 seems to be the main enzyme responsible for the production of prostacyclin. Increased synthesis of this vasodilatory and antithrombotic PG represents a homeostatic response during periods of accelerated platelet-vessel wall interactions and counteracts increased synthesis of COX-1-derived prothrombotic prostanoid thromboxane A(2) (TXA(2)). The clinical sequelae of inhibiting prostacyclin activity in the absence of concomitant inhibition of TXA(2) are not currently clear. Animal studies show that inhibition of prostacyclin activity does not lead to spontaneous thrombosis but may increase response to thrombotic stimuli. Therefore, prostacyclin synthesis may be important for limiting thrombotic events in patients who are at an increased cardiovascular risk. Overviews of clinical studies in arthritis and Alzheimer's disease have not demonstrated increased cardiovascular risk associated with specific COX-2 inhibition in most patients. However, data from 1 clinical trial revealed a 5-fold divergence in rates of myocardial infarction between a coxib and a nonsteroidal anti-inflammatory drug comparitor. Credible explanations for the results of this trial have been proposed and further studies are necessary to clarify the relative risk-to-benefit ratio of COX-2 inhibition in patients at increased risk for cardiovascular events, and the effects of concomitant aspirin therapy.

An evidence-based evaluation of the gastrointestinal safety of coxibs

Nonsteroidal anti-inflammatory drugs (NSAIDs) are nonselective inhibitors of cyclooxygenase (COX) isoforms COX-1 and COX-2. NSAIDs have analgesic and anti-inflammatory properties that are proven, and they are extensively used in the treatment of arthritis, pain, and headache. Despite their good efficacy, NSAIDs are associated with significant gastrointestinal (GI) toxicity, which appears to be related to the inhibition of the cytoprotective function of COX-1. Thus, selective COX-2 inhibitors, or coxibs, were designed to inhibit only the production of COX-2-dependent inflammatory prostaglandins, without any effect on COX-1 and its gastroprotective function. This article reviews important evidence on the GI safety of coxibs. Endoscopic studies demonstrated that coxibs, such as celecoxib and rofecoxib, induced significantly fewer ulcers than nonspecific NSAIDs. To analyze whether the incidence of clinical GI events is also lower with coxibs, 2 large controlled clinical trials, the Celecoxib Long-term Arthritis Safety Study (CLASS) and Vioxx Gastrointestinal Outcomes Research (VIGOR), evaluated the GI safety of celecoxib and rofecoxib, respectively. Based on evidence from the VIGOR trial, it was demonstrated that rofecoxib has already fulfilled the promise and significantly decreases the risk of clinically important and complicated GI events compared with a nonselective NSAID, naproxen. In contrast, the CLASS trial showed that the incidence of ulcer complications in patients treated with celecoxib was similar in patients treated with nonspecific NSAIDs.

Differential regulation of interleukin-6 and inducible cyclooxygenase gene expression by cytokines through prostaglandin-dependent and -independent mechanisms in human dental pulp fibroblasts

Increased levels of interleukin-1 (IL)-1, tumor necrosis factor-alpha (TNF-alpha), IL-6, and prostaglandin E2 (PGE2) have been detected in inflamed pulp tissue. To gain further insight into the molecular pathogenesis of pulpitis, we investigated the effects of IL-1alpha or TNF-alpha and PGE2, either alone or in combination on IL-6 and cyclooxygenase (COX)-2 messenger RNA (mRNA) production in cultured human dental pulp (HDP) fibroblasts. Exposure of HDP fibroblasts to IL-1alpha or TNF-alpha resulted in elevated levels of IL-6 (approximately 3.4 to approximately 10.4-fold) and COX-2 (approximately 5 to approximately 6.2-fold) mRNA. Simultaneous addition of IL-1alpha and PGE2 or TNF-alpha and PGE2 to the cultures significantly reduced the cytokine-induced IL-6 mRNA synthesis ranging from 45% to 65%. However, indomethacin enhanced the cytokine-stimulated IL-6 mRNA synthesis by approximately 1.7 to approximately 3.4-fold. This action could be reversed by exogenous PGE2. In contrast, PGE2 or indomethacin failed to modify the stimulatory effect of IL-1alpha or TNF-alpha on COX-2 gene expression. Because excessive levels of IL-6 and prostaglandins have been connected with the pathogenesis of several inflammatory diseases, our results suggest the involvement of HDP fibroblasts in the development of pulpitis via producing IL-6 and COX-2. Furthermore, expression of IL-6 and COX-2 genes in this cell seems to be differentially regulated by cytokines through prostaglandin-dependent and -independent pathways.

Up-regulation of cyclooxygenase-2 by inhibition of cyclooxygenase-1: a key to nonsteroidal anti-inflammatory drug-induced intestinal damage

Nonsteroidal anti-inflammatory drugs (NSAIDs) induce gastrointestinal ulceration as the adverse reaction. This effect of NSAIDs is attributable to endogenous prostaglandin (PG) deficiency caused by inhibition of cyclooxygenase (COX), yet the relation between COX inhibition and the gastrointestinal ulcerogenic property of NSAIDs remains controversial. Using selective COX inhibitors, we examined whether inhibition of COX-1 or COX-2 alone is sufficient for induction of intestinal damage in rats. Various COX inhibitors were administered p.o. in rats, and the animals were killed 24 h later. Mucosal PGE2 levels were determined by enzyme immunoassay, whereas the gene expression of COX isozymes was examined by reverse transcription-polymerase chain reaction. Nonselective COX inhibitors such as indomethacin inhibited PGE2 production and caused damage in the small intestine. Selective COX-2 inhibitors (rofecoxib or celecoxib) had no effect on the generation of PG, resulting in no damage. A selective COX-1 inhibitor (SC-560) did not cause damage, despite reducing PGE2 content. However, the combined administration of COX-1 and COX-2 inhibitors provoked intestinal damage with an incidence of 100%. COX-2 was up-regulated in the small intestine after administration of SC-560, and the PGE2 content was restored 6 h later, in a rofecoxib-dependent manner. The intestinal lesions induced by SC-560 plus rofecoxib were significantly prevented by later administration of 16,16-dimethyl PGE2. These results suggest that the intestinal ulcerogenic property of NSAID is not accounted for solely by inhibition of COX-1 and requires inhibition of COX-2 as well. The inhibition of COX-1 up-regulates COX-2 expression, and this may be a key to NSAID-induced intestinal damage.

Cyclooxygenase-2-issued prostaglandin e(2) enhances the production of endogenous IL-10, which down-regulates dendritic cell functions

PGE(2) is a well-known immunomodulator produced in the immune response by APCs, such as dendritic cells (DCs), the most potent APC of the immune system. We investigated the PGE(2) biosynthetic capacity of bone marrow-derived DC (BM-DC) and the effects of PG on the APC. We observed that BM-DC produce PGE(2) and other proinflammatory mediators, such as leukotriene B(4) and NO, after LPS exposure. Constitutively present in BM-DC, cyclooxygenase (COX)-1 did not contribute significantly to the total pool of PGE(2) compared with the LPS-induced COX-2-produced PGE(2). Treatment of BM-DC with exogenous PGE(2) induced the production of large amounts of IL-10 and less IL-12p70. In addition, selective inhibition of COX-2, but not COX-1, was followed by significant decrements in PGE(2) and IL-10, a concomitant restoration of IL-12 production, and an enhancement of DC stimulatory potential. In contrast, we found no demonstrable role for leukotriene B(4) or NO. In view of the potential of PGE(2) to stimulate IL-10, we examined the possibility that the suppressive effect of PGE(2) is mediated via IL-10. We found that exogenous IL-10 inhibits IL-12p70 production in the presence of NS-398, a COX-2 selective inhibitor, while the inhibitory effects of PGE(2) were totally reversed by anti-IL-10. We conclude that COX-2-mediated PGE(2) up-regulates IL-10, which down-regulates IL-12 production and the APC function of BM-DC.

Valdecoxib is more efficacious than rofecoxib in relieving pain associated with oral surgery

Inhibition of the cyclooxygenase (COX)-2 enzyme has been shown previously to reduce pain and inflammation. Valdecoxib is a new highly selective COX-2 inhibitor with a rapid onset of action and significant analgesic properties. This study compared the analgesic efficacy of valdecoxib and rofecoxib in treating postoperative pain in patients undergoing oral surgery. This randomized, double-blind, placebo-controlled study compared the efficacy of 40 mg valdecoxib with that of 50 mg rofecoxib and placebo. Efficacy was assessed by the onset of analgesia, pain intensity levels, and pain relief over 24 hours, time-weighted sum of total pain, sum of pain intensity difference, the percentage of patients requiring rescue medication and experiencing regimen failure, and patients' global evaluation. Patients receiving valdecoxib experienced a significantly quicker onset of analgesia, significantly improved pain relief, and lower pain intensity compared with patients receiving rofecoxib and greater satisfaction with their study medication after a single dose. Valdecoxib also demonstrated efficacy that was superior to that of rofecoxib with respect to the percentage of patients requiring rescue medication or experiencing regimen failure (p < or =.05). Valdecoxib, rofecoxib, and placebo were equally well tolerated. This study demonstrates that valdecoxib provides significantly greater analgesic efficacy than rofecoxib in the management of pain after oral surgery.

Dynamic regulation of cyclooxygenase-2 promoter activity by isoforms of CCAAT/enhancer-binding proteins

To elucidate the mechanism by which isoforms of CCAAT/enhancer-binding proteins regulate cyclooxygenase-2 expression, we determined by a novel technique binding of six isoforms of this transactivator to two sequence-specific CCAAT/enhancer-binding protein (-132/-125) and cyclic AMP (-59/-53) regulatory elements in human foreskin fibroblasts treated with phorbol 12-myristate 13-acetate for 4 h. The delta isoform bound to these two elements at basal state, which was displaced by full-length as well as two truncated beta isoforms, a 41-kDa liver-enriched activating protein and a 16-kDa liver-enriched inhibitory protein, after phorbol ester stimulation. Kinetic analysis shows time-dependent changes in beta and delta binding that were concordant with time-dependent increase in cyclooxygenase-2 induction. Overexpression of the 16-kDa beta isoform blocked the promoter activity and protein level induced by phorbol ester. Paradoxically, it increased binding of beta isoforms to the sequence-specific promoter DNA but suppressed cyclooxygenase-2 promoter activation by p300 cotransfection. These findings provide new insight into the regulation of cyclooxygenase-2 promoter by an interplay between two opposite beta isoforms and p300 co-activator.

Involvement of peripheral cyclooxygenase-1 and cyclooxygenase-2 in inflammatory pain

Pain-induced functional impairment in the rat (PIFIR) is a model of inflammatory and arthritic pain similar to that of clinical gout. Nociception is induced by the intra-articular injection of uric acid into the right hind limb, inducing its dysfunction. Animals then receive analgesic drugs and the recovery of functionality over time is assessed as an expression of antinociception. We have examined the role of peripheral prostaglandins synthesized by cyclooxygenase-1 (COX-1) and cyclooxygenase-2 (COX-2) in inflammatory pain using the PIFIR model. Rofecoxib (a selective COX-2 inhibitor) and SC-560 (a selective COX-1 inhibitor) both produced dose-dependent effects. When the inhibitors were administered before uric acid, they showed similar potency, but the antinociceptive efficacy of SC-560 was lower than rofecoxib; the best antinociceptive effects were obtained with the dose of 100 microg/articulation of each inhibitor (pre-treatment). In post-treatment (inhibitors administered after the uric acid), rofecoxib showed the least antinociceptive effect and SC-560 was more potent than rofecoxib. The inhibition of both COX-1 and COX-2 produced a more profound analgesic effect than the inhibition of either COX-1 or COX-2 alone. The present data support the idea that both COX isoforms contribute to the development and maintenance of local inflammatory nociception. Thus, it could be expected that inhibition of both COX-1 and COX-2 is required for non-steroidal anti-inflammatory drugs (NSAID)-induced antinociception in the rat. These findings suggest that the therapeutic effects of NSAIDs may involve, at least in part, inhibition of COX-1 and COX-2.

Differential binding mode of diverse cyclooxygenase inhibitors

Non-steroidal anti-inflammatory drugs (NSAIDs) are competitive inhibitors of cyclooxygenase (COX), the enzyme that mediates biosynthesis of prostaglandins and thromboxanes from arachidonic acid. There are at least two different isoforms of the enzyme known as COX-1 and -2. Site directed mutagenesis studies suggest that non-selective COX inhibitors of diverse chemical families exhibit differential binding modes to the two isozymes. These results cannot clearly be explained from the sole analysis of the crystal structures of COX available from X-ray diffraction studies. With the aim to elucidate the structural features governing the differential inhibitory binding behavior of these inhibitors, molecular modeling studies were undertaken to generate atomic models compatible with the experimental data available. Accordingly, docking of different COX inhibitors, including selective and non-selective ligands: rofecoxib, ketoprofen, suprofen, carprofen, zomepirac, indomethacin, diclofenac and meclofenamic acid were undertaken using the AMBER program. The results of the present study provide new insights into a better understanding of the differential binding mode of diverse families of COX inhibitors, and are expected to contribute to the design of new selective compounds.

Comparison of the antinociceptive effect of celecoxib, diclofenac and resveratrol in the formalin test

The peripheral antinociceptive effect of the selective COX-2 inhibitor celecoxib in the formalin-induced inflammatory pain was compared with that of resveratrol (COX-1 inhibitor) and diclofenac (non-selective COX inhibitor). Rats received local pretreatment with saline, celecoxib, diclofenac or resveratrol followed by 50 microl of either 1% or 5% formalin. Peripheral administration of celecoxib did not produce antinociception at either formalin concentration. In contrast, diclofenac and resveratrol produced a dose-dependent antinociceptive effect in the second phase of both 1% and 5% formalin test. The peripheral antinociception produced by diclofenac or resveratrol was due to a local action, as drug administration in the contralateral paw was ineffective. Results indicate that the selective COX-2 inhibitor celecoxib does not produce peripheral antinociception in formalin-induced inflammatory pain. In contrast, selective COX-1 and non-selective COX inhibitors (resveratrol and diclofenac, respectively) are effective drugs in this model of pain.

Protective effects of Celecoxib on lung injury and red blood cells modification induced by carrageenan in the rat

In the present study, we evaluated the effect of Celecoxib, a selective COX-2 inhibitor, in an acute model of lung injury induced by carrageenan administration in the rats. Injection of carrageenan into the pleural cavity of rats elicited an acute inflammatory response characterized by: fluid accumulation in the pleural cavity which contained a large number of polymorphonuclear neutrophils (PMNs) as well as an infiltration of PMNs in lung tissues and subsequent lipid peroxidation, and increased production of prostaglandin E(2) (PGE(2)), tumor necrosis factor alpha (TNFalpha), and interleukin-1beta. All parameters of inflammation were attenuated by Celecoxib. Furthermore, carrageenan induced an upregulation of the adhesion molecules ICAM-1 and P-selectin, as well as nitrotyrosine and poly(ADP-ribose) synthetase (PARS) as determined by immunohistochemical analysis of lung tissues. The degree of staining for the ICAM-1, P-selectin, nitrotyrosine and PARS was reduced by Celecoxib. These results clearly confirmed that COX-2 plays a critical role in the development of the inflammatory response by altering key components of the inflammatory cascade. Therefore, selective inhibitor of COX-2 such as Celecoxib, offers a therapeutic approach for the management of various inflammatory diseases.

Effects of a selective cyclooxygenase-2 inhibitor, celecoxib, on bone resorption and osteoclastogenesis in vitro

The effects of an important new anti-inflammatory agent, the selective cyclooxygenase-2 inhibitor celecoxib, on bone resorption and osteoclastogenesis elicited by the inflammatory cytokines interleukin-1beta (IL-1beta) and tumor necrosis factor-alpha (TNF-alpha), the endotoxin lipopolysaccharide (LPS), and the systemic hormones 1alpha,25-dihydroxyvitamin D(3) and parathyroid hormone were examined in vitro. Bone resorption was evaluated by measuring calcium released into the culture medium in a neonatal mouse calvarial bone organ culture. Osteoclastogenesis was evaluated by measuring tartrate-resistant acid phosphatase activity in the cells in cocultures of bone marrow cells and osteoblastic cells and in macrophage-colony-stimulating factor-dependent bone marrow cell cultures. Celecoxib (0.1 microM) completely inhibited the calcium release induced by IL-1beta, TNF-alpha, and LPS. The resorptive effect of 1alpha,25-dihydroxyvitamin D(3) was inhibited partially by celecoxib. In contrast, celecoxib did not inhibit the calcium release elicited by parathyroid hormone or prostaglandin E(2). Celecoxib (0.1 microM) also markedly inhibited osteoclastogenesis induced by these stimulators of bone resorption except for PGE(2) in the coculture system, whereas it failed to inhibit osteoclastogenesis in macrophage-colony-stimulating factor-dependent bone marrow cell cultures. These results indicate that, under certain conditions, cyclooxygenase-2-dependent prostaglandin synthesis is critical for the bone resorption induced by IL-1beta, TNF-alpha, and LPS, and for the osteoclastogenesis induced by these pro-inflammatory molecules and calciotropic hormones. The prevention of prostaglandin synthesis by inflammatory cytokines in bone cells could contribute to the efficacy of celecoxib in preventing bone loss in rheumatoid arthritis.

Cyclooxygenase-1 derived prostaglandins are involved in the maintenance of renal function in rats with cirrhosis and ascites

1. The maintenance of renal function in decompensated cirrhosis is highly dependent on prostaglandins (PGs). Since PG synthesis is mediated by cyclooxygenase-1 and -2 (COX-1 and COX-2), the present study was designed to examine which COX isoform is involved in this phenomenon. 2. Renal COX-1 and COX-2 protein expression and distribution were analysed by Western blot and immunohistochemistry in nine rats with carbon tetrachloride-induced cirrhosis and ascites and 10 control animals. The effects of placebo and selective COX-1 (SC-560) and COX-2 (celecoxib) inhibitors on urine flow (V), urinary excretion of sodium (U(Na)V) and PGE(2) (U(PGE2)V), glomerular filtration rate (GFR), renal plasma flow (RPF), the diuretic and natriuretic responses to furosemide and renal water metabolism were assessed in 88 rats with cirrhosis and ascites. 3. COX-1 protein levels were found to be unchanged in kidneys from cirrhotic rats. In contrast, these animals showed enhanced renal COX-2 protein expression which was focally increased in the corticomedullary region. Although U(PGE2)V was equally reduced by SC-560 and celecoxib, only SC-560 produced a significant decrease in U(Na)V, GFR and RPF and a pronounced impairment in the diuretic and natriuretic responses to furosemide in rats with cirrhosis and ascites. Neither SC-560 nor celecoxib affected renal water metabolism in cirrhotic rats. 4. These results indicate that despite abundant renal COX-2 protein expression, the maintenance of renal function in cirrhotic rats is mainly dependent on COX-1-derived prostaglandins.

Effects of selective cyclooxygenase-2 inhibitor and non-selective NSAIDs on Helicobacter pylori-induced gastritis in Mongolian gerbils

BACKGROUND

It is still a point of controversy whether Helicobacter pylori-infected patients are more likely to develop mucosal damage while taking NSAIDs. Selective cyclooxygenase (COX-2) inhibitors may be associated with less severe gastric mucosal damage than conventional NSAIDs, but this association is undefined in H. pylori-induced gastritis. The aim of this study was to evaluate the effects of selective COX-2 and nonselective NSAIDs on H. pylori-induced gastritis.

METHODS

After intragastric administration of indomethacin, NS-398 or vehicle alone, once daily for 5 days in H. pylori-infected and uninfected Mongolian gerbils, we evaluated gastric mucosal damage, inflammatory cell infiltration and prostaglandin E2 (PGE2) concentration. We investigated whether H. pylori infection induced the COX-2 expression.

RESULTS

In H. pylori-uninfected groups, the indomethacin-treated group showed the highest mucosal damage score and the lowest PGE2 concentration. There was no difference in mucosal damage scores and PGE2 concentration between NS-398 and vehicle-alone treated group. In H. pylori-infected groups, there was no difference in mucosal damage scores, irrespective of the type of drugs administered. The indomethacin-treated group showed the lowest PGE2 concentration, similar to that of the NS-398 and vehicle-alone treated groups, both without H. pylori infection. Gastric neutrophil and monocyte infiltration scores were higher in H. pylori-infected groups than in uninfected groups. However, there was no difference in these scores according to the type of drugs administered, within H. pylori-infected or uninfected groups. COX-2 protein expression was observed in H. pylori-infected Mongolian gerbils but not in uninfected ones.

CONCLUSIONS

Our animal study showed that H. pylori infection induced COX-2 expression and increased prostaglandin concentration. Administration of NSAIDs decreased the prostaglandin concentration, but did not increase mucosal damage in H. pylori-induced gastritis. Selective COX-2 inhibitors, instead of conventional NSAIDs, had no beneficial effect on preventing mucosal damage in H. pylori-induced gastritis.

Effects of lornoxicam, piroxicam, and meloxicam in a model of thermal hindpaw hyperalgesia induced by formalin injection in rat tail

Non-steroidal anti-inflammatory drugs (NSAIDs) are frequently used as analgesics. Although the results of clinical studies indicate considerable disparity in the analgesic efficacy of NSAIDs, the pre-clinical models generally used for the study of nociception do not allow a clear distinction to be made between the analgesic properties of agents belonging to this family. As clinical pain is characterized by hyperalgesia, we evaluated the effects of NSAIDs with similar chemical structures but different selectivities for cyclo-oxygenase (COX)-1 and COX-2 in a new behavioural model of central hyperalgesia in rats. We assessed the effects of lornoxicam, piroxicam, and meloxicam on the reduction of hindpaw nociceptive thresholds to thermal stimulation produced by a 10% formaldehyde (formalin) injection into rat tail. Each drug was administered intraperitoneally (i.p.) at its ED(50)for the anti-inflammatory effect (namely the inhibition of carrageenan-induced hindpaw oedema). At this dose (1.3 mg kg(-1), 1.0 mg kg(-1), and 5.8 mg kg(-1), respectively), lornoxicam, piroxicam, and meloxicam produced the same anti-inflammatory effect, did not modify thermal nociceptive thresholds, and significantly reduced the hyperalgesia. However, only lornoxicam was fully effective for prevention of hyperalgesia. Our results indicate a dissociation between the anti-inflammatory and the anti-hyperalgesic activity of NSAIDs, where the latter seems to be more evident after the block of both COX-1 and COX-2. Finally, they suggest that our experimental model of thermal hindpaw hyperalgesia can be effectively utilized to assess the ability of different drugs to reduce central sensitization, and thus hyperalgesia.

Central nociceptive role of prostacyclin (IP) receptor induced by peripheral inflammation

Prostacyclin (PGI2) is well known to play crucial roles in induction of edema and pain behavior in the periphery. In the present study, we investigated the central role of PGI2 in inflammatory pain. Intraplantar injection of carrageenan markedly induced the expression of prostacyclin receptor (IP receptor) mRNA with the maximum at 6 h, coincidently induction of the inducible form of cyclooxygenase (COX-2), although IP receptor mRNA was weakly expressed in the spinal cord of naive mice. Intrathecal administration of the IP agonist cicaprost induced mechanical hyperalgesia 6 h after carrageenan injection. These results suggest that PGI2 is involved in pain transmission at the spinal cord following expression of IP receptor mRNA induced by peripheral inflammation.

A pyrroloquinazoline derivative with anti-inflammatory and analgesic activity by dual inhibition of cyclo-oxygenase-2 and 5-lipoxygenase

In a previous study, we reported a new pyrroloquinazoline derivative, 3-(4'-acetoxy-3',5'-dimethoxy)benzylidene-1,2-dihydropyrrolo[2,1-b]quinazoline-9-one (PQ), which inhibited human purified 5-lipoxygenase activity and prostaglandin E2 release in lipopolysaccharide-stimulated RAW 264.7 cells. In the present work, we show that PQ inhibits cyclo-oxygenase-2 activity in intact cell assays (human monocytes) and purified enzyme preparations (ovine isoenzymes) without affecting cyclo-oxygenase-1 activity. This behaviour was confirmed in vivo by using the zymosan-injected mouse air pouch model, where PQ caused a marked reduction in cell migration and leukotriene B4 levels at 4 h, as well as inhibition of prostaglandin E2 levels without affecting cyclo-oxygenase-2 expression at 24 h after zymosan stimulation. In addition, oral administration of this compound significantly reduced carrageenan-induced mouse paw oedema and phenyl-p-benzoquinone-induced writhings in mice. These results indicate that oral PQ exerts analgesic and anti-inflammatory effects, which are related to dual inhibition of cyclo-oxygenase-2 and 5-lipoxygenase activities.

Clinical potential of cyclo-oxygenase-2 inhibitors

On the basis of their reduced potential to cause injury to the gastroduodenal mucosa, cyclo-oxygenase (COX)-2-selective inhibitors were developed and marketed as a safer alternative to traditional nonsteroidal anti-inflammatory drugs (NSAIDs). This manuscript reviews the major steps leading to the introduction of COX-2-selective inhibitors into clinical practice, from the identification of the COX isoenzymes to their various roles in physiological and pathological processes. The available data show that COX-2 inhibitors have a favourable safety profile and are at least as effective as traditional NSAIDs for the treatment of pain and inflammatory conditions with a reduced incidence of gastrointestinal complications. Emerging evidence points to new and unanticipated effects from these agents. COX-2 inhibition appears to play an important role in the modulation of intestinal polyposis and colorectal carcinogenesis. Additionally, COX-2 expression may be associated with inflammatory responses leading to the occurrence of Alzheimer's disease and potentially, COX-2 inhibitors could be used to retard the progression of this condition. However, by decreasing prostacyclin production, COX-2 inhibitors may lead to increased prothrombotic activity and increase the risk of cardiovascular events. Until further large-scale prospective studies are performed, and the magnitude of these potential risks is quantified, COX-2 inhibitors should be used with caution in patients at risk for cardiovascular morbidity.

Therapeutic uses of non-steroidal anti-inflammatory drugs in dentistry

The non-steroidal anti-inflammatory drugs (NSAIDs) are among the most widely used classes of drugs for the management of acute and chronic pain in dentistry. Their therapeutic efficacy and toxicity are well-documented and provide evidence that NSAIDs generally provide an acceptable therapeutic ratio of pain relief with fewer adverse effects than the opioid-mild analgesic combination drugs that they have largely replaced for most dental applications. The great many studies done with the oral surgery model of acute pain indicate that a single dose of an NSAID is more effective than combinations of aspirin or acetaminophen plus an opioid, with fewer side-effects, thus making it preferable for ambulatory patients. The combination of an NSAID with an opioid generally results in marginal analgesic activity but with an increased incidence of side-effects, which limits its use to patients in whom the NSAID alone results in inadequate analgesia. The selective COX-2 inhibitors hold promise for clinical efficacy with less toxicity from chronic administration and may prove advantageous for the relief of chronic orofacial pain. The use of repeated doses of NSAIDs for chronic orofacial pain should be re-evaluated in light of a lack of documented efficacy and the potential for serious gastrointestinal and renal toxicity with repeated dosing.

Diverse effects of ethanol on the pathway of inducible prostaglandin E2 production in macrophages

The effects of ethanol on inducible prostaglandin production in RAW macrophages were investigated. Indomethacin (1 microM) or cycloheximide (1 microM) abolished prostaglandin E2 (PGE2) production induced by lipopolysaccharide (LPS, 1 microg/ml). Ethanol at concentrations from 100 mM to 600 mM concentration-dependently inhibited inducible PGE2 production, while ethanol only at higher concentrations (400 mM or more) showed cytotoxity to the cells. Cyclooxygenase-2 (COX-2) activity, estimated by transformation of exogenous arachidonic acid into PGE2, was not affected by ethanol (100-400 mM). LPS-induced expression of COX-2 mRNA was inhibited by ethanol (50-400 mM). On the other hand, protein expression of COX-2 by LPS was significantly increased by ethanol (100-400 mM). Ethanol alone at concentrations up to 600 mM did not induce expression of COX-2 protein. In a medium containing arachidonic acid (1 microM), ethanol at a low concentration (100 mM) did not significantly affect LPS-induced PGE2 production. These results suggest that ethanol shows diverse effects on the pathway of inducible PGE2 production in macrophages. Finally, ethanol may suppress utilization of arachidonic acid, resulting in reduction of inducible PGE2 production. Further study is needed to elucidate the mechanism of dissociation of ethanol effects on protein and mRNA expression.