Rofecoxib [Vioxx, MK-0966; 4-(4'-methylsulfonylphenyl)-3-phenyl-2-(5H)-furanone]: a potent and orally active cyclooxygenase-2 inhibitor. Pharmacological and biochemical profiles.
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The discoveries that cyclooxygenase (COX)-2 is an inducible form of COX involved in inflammation and that COX-1 is the major isoform responsible for the production of prostaglandins (PGs) in the gastrointestinal tract have provided a rationale for the development of specific COX-2 inhibitors as a new class of anti-inflammatory agents with improved gastrointestinal tolerability. In the present study, the preclinical pharmacological and biochemical profiles of rofecoxib [Vioxx, also known as MK-0966, 4-(4'-methylsulfonylphenyl)-3-phenyl-2-(5H)-furanone], an orally active COX-2 inhibitor, are described. Rofecoxib is a potent inhibitor of the COX-2-dependent production of PGE(2) in human osteosarcoma cells (IC(50) = 26 +/- 10 nM) and Chinese hamster ovary cells expressing human COX-2 (IC(50) = 18 +/- 7 nM) with a 1000-fold selectivity for the inhibition of COX-2 compared with the inhibition of COX-1 activity (IC(50) > 50 microM in U937 cells and IC(50) > 15 microM in Chinese hamster ovary cells expressing human COX-1). Rofecoxib is a time-dependent inhibitor of purified human recombinant COX-2 (IC(50) = 0.34 microM) but caused inhibition of purified human COX-1 in a non-time-dependent manner that could only be observed at a very low substrate concentration (IC(50) = 26 microM at 0.1 microM arachidonic acid concentration). In an in vitro human whole blood assay, rofecoxib selectively inhibited lipopolysaccharide-induced, COX-2-derived PGE(2) synthesis with an IC(50) value of 0.53 +/- 0.02 microM compared with an IC(50) value of 18.8 +/- 0.9 microM for the inhibition of COX-1-derived thromboxane B(2) synthesis after blood coagulation. Using the ratio of the COX-1 IC(50) values over the COX-2 IC(50) values in the human whole blood assay, selectivity ratios for the inhibition of COX-2 of 36, 6.6, 2, 3, and 0.4 were obtained for rofecoxib, celecoxib, meloxicam, diclofenac, and indomethacin, respectively. In several in vivo rodent models, rofecoxib is a potent inhibitor of carrageenan-induced paw edema (ID(50) = 1.5 mg/kg), carrageenan-induced paw hyperalgesia (ID(50) = 1.0 mg/kg), lipopolysaccharide-induced pyresis (ID(50) = 0.24 mg/kg), and adjuvant-induced arthritis (ID(50) = 0.74 mg/kg/day). Rofecoxib also has a protective effect on adjuvant-induced destruction of cartilage and bone structures in rats. In a (51)Cr excretion assay for detection of gastrointestinal integrity in either rats or squirrel monkeys, rofecoxib has no effect at doses up to 200 mg/kg/day for 5 days. Rofecoxib is a novel COX-2 inhibitor with a biochemical and pharmacological profile clearly distinct from that of current nonsteroidal anti-inflammatory drugs and represents a new therapeutic class of anti-inflammatory agents for the treatment of the symptoms of osteoarthritis and rheumatoid arthritis with improved gastrointestinal tolerability. (+info)
NF-kappa B is a central regulator of the intestinal epithelial cell innate immune response induced by infection with enteroinvasive bacteria.
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Human intestinal epithelial cells up-regulate the expression of an inflammatory gene program in response to infection with a spectrum of different strains of enteroinvasive bacteria. The conserved nature of this program suggested that diverse signals, which are activated by enteroinvasive bacteria, can be integrated into a common signaling pathway that activates a set of proinflammatory genes in infected host cells. Human intestinal epithelial cell lines, HT-29, Caco-2, and T84, were infected with invasive bacteria that use different strategies to induce their uptake and have different intracellular localizations (i.e., Salmonella dublin, enteroinvasive Escherichia coli, or Yersinia enterocolitica). Infection with each of these bacteria resulted in the activation of TNF receptor associated factors, two recently described serine kinases, I kappa B kinase (IKK) alpha and IKK beta, and increased NF-kappa B DNA binding activity. This was paralleled by partial degradation of I kappa B alpha and I kappa B epsilon in bacteria-infected Caco-2 cells. Mutant proteins that act as superrepressors of IKK beta and I kappa B alpha inhibited the up-regulated transcription and expression of downstream targets genes of NF-kappa B that are key components of the epithelial inflammatory gene program (i.e., IL-8, growth-related oncogene-alpha, monocyte chemoattractant protein-1, TNF-alpha, cyclooxygenase-2, nitric oxide synthase-2, ICAM-1) activated by those enteroinvasive bacteria. These studies position NF-kappa B as a central regulator of the epithelial cell innate immune response to infection with enteroinvasive bacteria. (+info)
Up-regulation of ICAM-1 by cytokines in human tracheal smooth muscle cells involves an NF-kappa B-dependent signaling pathway that is only partially sensitive to dexamethasone.
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Although the precise mechanisms by which steroids mediate their therapeutic effects remain unknown, steroids have been reported to abrogate cytokine-induced activation of the transcription factor NF-kappa B. In some cell types, NF-kappa B activation is necessary to regulate cytokine-mediated cellular functions. However, compelling evidence suggests that the steroid inhibition of NF-kappa B is complex and cell specific. Using EMSA, we show that stimulation with TNF-alpha or IL-1 beta induces NF-kappa B DNA-binding activity in human airway smooth muscle cells. TNF-alpha and IL-1 beta also increased luciferase activity in airway smooth muscle cells transfected with a reporter plasmid containing kappa B enhancer elements. Cytokines activated NF-kappa B by rapidly degrading its cytosolic inhibitor I kappa B alpha, which was then regenerated after 60 min. Cytokine-mediated I kappa B alpha reappearance was completely blocked by the protein synthesis inhibitor cycloheximide. Inhibition of cytokine-mediated I kappa B alpha proteolysis using the protease inhibitors N-tosyl-L -phenylalanine chloromethyl ketone and N-acetyl-L -leucinyl-L -leucinyl-norleucinal also inhibited cytokine-mediated early expression of ICAM-1. Although dexamethasone partially inhibited IL-1 beta- and TNF-alpha-induced up-regulation of ICAM-1 at 4 h, dexamethasone had no effect on cytokine-induced ICAM-1 expression at 18-24 h. In addition, neither cytokine-induced degradation or resynthesis of I kappa B alpha nor NF-kappa B DNA-binding activity were affected by dexamethasone. In cells transfected with the luciferase reporter, dexamethasone did not affect TNF-alpha-induced NF-kappa B-dependent transcription. Interestingly, cytokine-mediated expression of cyclooxygenase-2 was completely abrogated by dexamethasone at 6 h. Together, these data demonstrate that cytokine-mediated NF-kappa B activation and ICAM-1 expression involve activation of a steroid-insensitive pathway. (+info)
Aberrant prostaglandin synthase 2 expression defines an antigen-presenting cell defect for insulin-dependent diabetes mellitus.
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Prostaglandins (PGs) are lipid molecules that profoundly affect cellular processes including inflammation and immune response. Pathways contributing to PG output are highly regulated in antigen-presenting cells such as macrophages and monocytes, which produce large quantities of these molecules upon activation. In this report, we demonstrate aberrant constitutive expression of the normally inducible cyclooxygenase PG synthase 2 (PGS(2)/ COX-2) in nonactivated monocytes of humans with insulin-dependent diabetes mellitus (IDDM) and those with islet autoantibodies at increased risk of developing this disease. Constitutive PGS(2) appears to characterize a high risk for diabetes as it correlates with and predicts a low first-phase insulin response in autoantibody-positive subjects. Abnormal PGS(2) expression in at-risk subjects affected immune response in vitro, as the presence of a specific PGS(2) inhibitor, NS398, significantly increased IL-2 receptor alpha-chain (CD25) expression on phytohemagglutinin-stimulated T cells. The effect of PGS(2) on CD25 expression was most profound in subjects expressing both DR04 and DQbeta0302 high-risk alleles, suggesting that this cyclooxygenase interacts with diabetes-associated MHC class II antigens to limit T-cell activation. These results indicate that constitutive PGS(2) expression in monocytes defines an antigen-presenting cell defect affecting immune response, and that this expression is a novel cell-associated risk marker for IDDM. (+info)
Calcium antagonistic properties of the cyclooxygenase-2 inhibitor nimesulide in human myometrial myocytes.
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The non-steroidal anti-inflammatory drug nimesulide is a selective inhibitor of cyclooxygenase-2 which relaxes spontaneously contracting human myometrium in vivo and is potentially a useful tocolytic drug. Part of the relaxant action of nimesulide may be via block of myometrial Ca2+ channels. Here, we describe the Ca2+ channel blocking properties of nimesulide in freshly dispersed human term-pregnant myometrial smooth muscle cells (HMSMCs). Both L- and T-components of the whole cell Ca2+ channel current were inhibited by 100 microM nimesulide (38+/-3 and 35+/-1% block, respectively). At physiological pH inside and outside the cell (pHo/pHi = 7.4/7.2), this block did not depend on the holding or test potential, although a degree of use-dependence was observed during high frequency stimulation at a higher concentration of drug (300 microM). At pHo/pHi = 6.8, under which condition the concentration of the non-ionized form of the drug is increased 3 fold compared to pH 7.4, nimesulide blocked the L-type current more potently (58+/-3% inhibition at 100 microM, P<0.01) compared to physiological pH. Nimesulide caused a 7 mV leftward shift in the availability curve of the current at pH 6.8, suggesting that the affinity of the drug for the inactivated channel is approximately 4 fold higher than its affinity for the closed channel. We speculate that acidification and depolarization of the myometrium during the intense and prolonged contractions of labour might increase the potency of nimesulide as a Ca2+ channel antagonist, promoting its action as a tocolytic agent. (+info)
A771726, the active metabolite of leflunomide, directly inhibits the activity of cyclo-oxygenase-2 in vitro and in vivo in a substrate-sensitive manner.
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1. The immunosuppressive and anti-inflammatory drug leflunomide has several sites of action, although its precise mode of action is unknown. 2. Here we show in vitro and in vivo that leflunomide and/or its active metabolite A771726, inhibit the activity of cyclo-oxygenase (COX) at doses below those that affect protein expression. 3. In J774.2 macrophages treated with endotoxin for 24 h to induce COX-2 and iNOS, leflunomide and A771726 inhibited more potently the accumulation of PGE2 (A771726, IC50 3.5 microg ml-1) than of NO2 (A771726, IC50 380 microg ml-1). At high concentrations (>300 microg ml-1) A771726 also exhibited the expression of COX-2 and iNOS proteins. 4. In A549 cells treated for 24 h with interleukin-1beta, to induce COX-2, A771726 potently inhibited PGE2 synthesis (IC50 0.13 microg ml-1). In the same cells, A771726 was notably less active (IC50, 52 microg ml-1) at inhibiting the formation of PGE2 stimulated by exposure to 30 microM arachidonic acid. 5. In a human whole blood assay, measuring the accumulation of TxB2 in response to calcium ionophore as a measure of COX-1 activity and in response to incubation with bacterial endotoxin as a measure of COX-2 activity, leflunomide inhibited COX-1 and COX-2 with IC50 values of 31 and 185 microg ml-1; for A771726 the corresponding values were 40 and 69 microg ml-1. 6. Pre-treatment of rats with leflunomide or A771726 (10 mg kg-1, i.p.) inhibited the plasma accumulation of 6-keto-PGF1alpha but not NO2/NO3 following infusion of endotoxin. Injection of a bolus of arachidonic acid following 6 h infusion of endotoxin caused a marked acute rise in plasma 6-keto-PGF1alpha which was inhibited only by higher doses of A771726 (50 mg kg-1, i.p.). 7. In conclusion, leflunomide via A771726 can directly inhibit the activity of COX, an effect that appears blunted both by increases in substrate supply and possibly by plasma binding. Only at much higher drug levels does leflunomide and/or A771726 inhibit the induction of COX-2 or iNOS proteins. (+info)
Interleukin-1beta induces interleukin-6 production through the production of prostaglandin E(2) in human osteoblasts, MG-63 cells.
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This study was conducted to investigate the mechanism of interleukin-1beta (IL-1beta)-induced IL-6 production in human osteoblasts (MG-63 cells). Stimulation with IL-1beta resulted in the production of IL-6 and prostaglandin E(2) (PGE(2)). IL-6 production gradually increased and peaked 96 h after stimulation. IL-6 mRNA was detected between 4 and 72 h after IL-1beta stimulation. The patterns of PGE(2) production and the expression of cyclooxygenase-2 (COX-2) mRNA were biphasic after stimulation. Actinomycin D, cycloheximide, indomethacin, and NS-398 (COX-2 inhibitor) suppressed the production of IL-6 and PGE(2). Anti-PGE(2) antibody markedly reduced the production of IL-6. In addition, stimulation with 17-phenyl-PGE(2), a PGE receptor-1 (EP-1 receptor) agonist, led to the expression of IL-6 mRNA after pretreatment with IL-1beta. These findings indicate that IL-1beta-induced IL-6 production in MG-63 cells involves the following sequence of steps: IL-1beta-induced COX-2 activation, PGE(2) production, and EP-1 receptor signaling prior to IL-6 production. (+info)
Selective COX-2 inhibitors and human inflammatory bowel disease.
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BACKGROUND: Much recent effort has been made to produce selective inhibitors of cyclo-oxygenase-2 (COX-2) in the belief that these will lack the gastrointestinal damaging effects of traditional non-steroidal anti-inflammatory drugs (NSAIDs). Inflammatory bowel disease is associated with increased local production of prostanoids. These prostanoids, particularly PGE2 and PGI2, may well be protective as inflammatory bowel disease is aggravated by NSAID use. AIM: To examine the effects of a traditional NSAID and a highly selective COX-2 inhibitor on the production of these prostanoids in human inflammatory bowel disease. METHODS: Colonic mucosal biopsies were obtained from patients undergoing routine colonoscopy and biopsy for diagnostic or surveillance purposes. Biopsies were incubated in culture medium containing 10% foetal calf serum and antibiotics, plus test drugs or vehicle for 24 h, after which time the medium was removed and the content of PGE2, PGI2 (measured as 6 keto-PGF1alpha) and thromboxane (Tx) A2 (measured as TxB2) determined. RESULTS: Biopsies obtained from diseased colonic mucosa produced significantly more PGE2, PGI2 and thromboxane A2 than did controls (for example, PGE2: ulcerative colitis, 4.17+/-1.06; Crohn's disease, 3.97+/-1.66; control, 0.12 +/-0.13 ng/mL, n = 8-12). These increases were inhibited to a similar extent by either a highly selective COX-2 inhibitor (L-745,337) or a traditional non-selective NSAID (indomethacin). CONCLUSIONS: Until selective COX-2 inhibitors have been assessed adequately in human inflammatory bowel disease, these compounds should not be assumed to be safe for the gastrointestinal tract in inflammatory bowel disease. (+info)