A comparison of the therapeutic efficacy and tolerability of etoricoxib and diclofenac in patients with osteoarthritis.

OBJECTIVE: To evaluate and compare the efficacy and tolerability of etoricoxib and diclofenac in patients with osteoarthritis of the knee or hip. METHODS: In this 6-week double-blind, active comparator controlled, parallel-group study eligible osteoarthritis patients were randomised to receive either etoricoxib 60 mg once daily (n = 256) or diclofenac 50 mg three times daily (n = 260). The primary study endpoint was the Western Ontario McMaster osteoarthritis index (WOMAC) pain subscale. Other endpoints included were the WOMAC stiffness and physical function subscales, and the Patient's Global Assessment of Response to Therapy (PGART) questionnaire. Early efficacy was evaluated using WOMAC first question (pain walking on a flat surface) and PGART 4 h after the morning dose of each drug on days 1 and 2. Rescue medication (paracetamol) used was also recorded. The study was designed to show comparable efficacy between etoricoxib 60 mg once daily and diclofenac 50 mg three times daily with respect to the primary endpoint and was conducted outside the United States at 67 centres in 29 countries. RESULTS: Etoricoxib (60 mg once daily) was comparable in efficacy to diclofenac (150 mg daily) on all the above parameters. The one exception was in the assessment of early efficacy where etoricoxib demonstrated significantly greater benefit within 4 h of taking the first dose on the first day of therapy (p = 0.007) as evaluated by the percentage of patients with good or excellent (PGART) responses. The treatment effects of both drugs were similar by the time day 2 was reached and were sustained throughout the 6 weeks of therapy. Both treatments were generally well tolerated. CONCLUSIONS: Etoricoxib is clinically effective in the therapy of osteoarthritis providing a magnitude of effect comparable to that of the maximum recommended daily dose of diclofenac. The onset of clinical benefit with etoricoxib on day one is more rapid than that of diclofenac. Both drugs were generally well tolerated.

Etoricoxib (MK-0663): preclinical profile and comparison with other agents that selectively inhibit cyclooxygenase-2.

We report here the preclinical profile of etoricoxib (MK-0663) [5-chloro-2-(6-methylpyridin-3-yl)-3-(4-methylsulfonylphenyl) pyridine], a novel orally active agent that selectively inhibits cyclooxygenase-2 (COX-2), that has been developed for high selectivity in vitro using whole blood assays and sensitive COX-1 enzyme assays at low substrate concentration. Etoricoxib selectively inhibited COX-2 in human whole blood assays in vitro, with an IC(50) value of 1.1 +/- 0.1 microM for COX-2 (LPS-induced prostaglandin E2 synthesis), compared with an IC(50) value of 116 +/- 8 microM for COX-1 (serum thromboxane B2 generation after clotting of the blood). Using the ratio of IC(50) values (COX-1/COX-2), the selectivity ratio for the inhibition of COX-2 by etoricoxib in the human whole blood assay was 106, compared with values of 35, 30, 7.6, 7.3, 2.4, and 2.0 for rofecoxib, valdecoxib, celecoxib, nimesulide, etodolac, and meloxicam, respectively. Etoricoxib did not inhibit platelet or human recombinant COX-1 under most assay conditions (IC(50) > 100 microM). In a highly sensitive assay for COX-1 with U937 microsomes where the arachidonic acid concentration was lowered to 0.1 microM, IC(50) values of 12, 2, 0.25, and 0.05 microM were obtained for etoricoxib, rofecoxib, valdecoxib, and celecoxib, respectively. These differences in potency were in agreement with the dissociation constants (K(i)) for binding to COX-1 as estimated from an assay based on the ability of the compounds to delay the time-dependent inhibition by indomethacin. Etoricoxib was a potent inhibitor in models of carrageenan-induced paw edema (ID(50) = 0.64 mg/kg), carrageenan-induced paw hyperalgesia (ID(50) = 0.34 mg/kg), LPS-induced pyresis (ID(50) = 0.88 mg/kg), and adjuvant-induced arthritis (ID(50) = 0.6 mg/kg/day) in rats, without effects on gastrointestinal permeability up to a dose of 200 mg/kg/day for 10 days. In squirrel monkeys, etoricoxib reversed LPS-induced pyresis by 81% within 2 h of administration at a dose of 3 mg/kg and showed no effect in a fecal 51Cr excretion model of gastropathy at 100 mg/kg/day for 5 days, in contrast to lower doses of diclofenac or naproxen. In summary, etoricoxib represents a novel agent that selectively inhibits COX-2 with 106-fold selectivity in human whole blood assays in vitro and with the lowest potency of inhibition of COX-1 compared with other reported selective agents.

Selective potentiating effect of RS14203 on a serotoninergic pathway in anesthetized rats.

The usefulness of selective inhibitors of type 4 phosphodiesterase (PDE4) in the treatment of inflammation and pulmonary diseases is limited by their side effects: nausea and vomiting. We studied the effect of three structurally diverse PDE4 inhibitors on the vagal nerve afferent and efferent fibers in anesthetized rats. The effects of RS14203, (R)-rolipram, and CT-2450 were evaluated on the von Bezold-Jarisch reflex (vagal afferent fibers) and in a model of vagal electrical stimulation (vagal efferent fibers). All three PDE4 inhibitors were administered at 1, 10, or 100 microg/kg (iv) 15 min prior to the induction of bradycardia by an iv injection of 2-methyl-5-HT (von Bezold-Jarisch reflex) or by vagal electrical stimulation. At 100 microg/kg, RS14203 significantly potentiated the 2-methyl-5-HT response. No statistically significant effects were observed with (R)-rolipram or CT-2450 at the doses studied. RS14203, (R)-rolipram, or CT-2450 (1-100 microg/kg iv) did not affect the bradycardia induced by vagal electrical stimulation. Consequently, our results show that RS14203 selectively facilitates serotoninergic neurotransmission in vagal afferent fibers. The emetic action of RS14203 may be mediated by this mechanism.

Inhibition of cyclooxygenase-2 improves cardiac function in myocardial infarction.

Induction of cyclooxygenase-2 (COX-2) in ischemic myocardium is thought to increase the production of proinflammatory prostanoids and contribute significantly to the ischemic inflammation. Left ventricular myocardial infarction (MI) was created by ligating the left coronary artery in Lewis rats. Hemodynamic measurements at 4 weeks showed better cardiac function in the group treated with a selective COX-2 inhibitor (DFU; 5 mg/kg/day) for 2 weeks after induction of MI compared to the vehicle treated group. These results suggest that induction of COX-2 contributes to myocardial dysfunction, and that selective inhibition of COX-2 could constitute an important therapeutic target for the treatment of MI.

Prostaglandin H synthase 2 expression in airway cells from patients with asthma and chronic obstructive pulmonary disease.

Products of the prostaglandin H synthase (PGHS) metabolic pathway are thought to play a role in the pathogenesis of asthma. We determined the level of expression of the constitutive (PGHS-1) and inducible (PGHS-2) isoforms of the enzyme in induced sputum and bronchial biopsies of patients with asthma, patients with chronic obstructive pulmonary disease (COPD), and unaffected control subjects by immunocyto- and immunohistochemistry. Immunoreactivity for PGHS-2 was significantly greater in the induced sputum of patients with asthma and patients with COPD compared with unaffected control subjects. The level of PGHS-2 was greater in asthma than in COPD. Immunoreactivity for PGHS-1 increased in cells in the induced sputum of patients with asthma and patients with COPD compared with that of unaffected control subjects. Immunostained cells included macrophages, eosinophils, and neutrophils. Greater PGHS-2 immunoreactivity was seen in the submucosal inflammatory infiltrate and in the airway epithelium of patients with asthma compared with unaffected control subjects. In summary, we demonstrate an induction of PGHS-2 in asthma, suggesting increased formation of prostanoids, which may contribute to the inflammatory process.

The effects of phosphodiesterase type 4 inhibitors on tumour necrosis factor-alpha and leukotriene B4 in a novel human whole blood assay.

1. The aim of this study was to assess the inhibitory activities of phosphodiesterase type 4 (PDE4) inhibitors on tumour necrosis factor-alpha (TNF-alpha) and leukotriene B4 (LTB4) production in a novel human whole blood assay. 2. Lipopolysaccharide (LPS) stimulation of human whole blood caused a time dependent increase in TNF-alpha and prostaglandin E2 (PGE2) plasma levels. Inhibition of LPS-induced TNF-alpha by the selective PDE4 inhibitor RP73401 was proportionally enhanced with endogenous PGE2 (maximal after 24 h). In contrast, blocking endogenous PGE2 production with indomethacin in blood stimulated with LPS for 24 h decreased the potency of RP73401 to that observed with a 4 h LPS incubation. 3. Non-selective and selective PDE4 inhibitors showed greater inhibition of LPS-induced TNF-alpha after 24 h compared to 4 h. Stereoselectivity was only achieved in the 24 h method. 4. LPS-stimulation of whole blood for either 30 min or 24 h followed by N-formyl-Met-Leu-Phe (fMLP) activation resulted in low plasma LTB4 levels. Combination of both treatments resulted in a greater than 7 fold increase in plasma LTB4 levels. Inhibition of the double LPS and fMLP-activated LTB4 production was observed with non-selective and PDE4-selective inhibitors. Their LTB4 inhibitory potencies were similar to that observed in the 24 h LPS-induced TNF-alpha assay. Thus, stimulation of human whole blood with two LPS stimulations followed by fMLP gives rise to both TNF-alpha and LTB4 and their inhibition by various compounds can be assessed in the same blood sample. 5. Calcium ionophore (A23187) stimulation of whole blood resulted in plasma LTB4 levels similar to the double LPS and fMLP method. Inhibition of A23187-induced LTB4 biosynthesis was also achieved by PDE4-selective inhibitors as well as the direct 5-lipoxygenase (5-LO) inhibitor L-739,010. 6. These results confirm the anti-inflammatory properties of PDE4 inhibitors. Thus, this novel human whole blood can be used to assess the biochemical efficacy of PDE4 inhibitors in human subjects.

Emesis induced by inhibitors of type IV cyclic nucleotide phosphodiesterase (PDE IV) in the ferret.

Emesis induced by inhibitors of type IV cyclic nucleotide phosphodiesterase (PDE IV) has been investigated in the ferret. The PDE IV inhibitors studied were: RS14203, R-rolipram and CT-2450 (i.e. (R)-N-[4-[1-(3-cyclopentyloxy-4-methoxyphenyl)-2-(4-pyridyl)ethyl]phenyl ]N'-ethylurea), in addition to the less active enantiomers S-rolipram and CT-3405. Following oral administrations, different emetic profiles were observed with time. Emesis induced by RS14203 exhibited a dose-response relationship but no such relationship was seen for R-rolipram or CT-2450. The incidence of emesis was positively influenced by the dose of PDE IV inhibitors administered, allowing a rank order of potency: RS14203 > R-rolipram > S-rolipram > CT-2450 > CT-3405. PDE IV inhibitor-induced emesis was abolished by the tachykinin NK1 receptor antagonist, CP-99,994. No peripheral release of substance P by PDE IV inhibitors seems to be involved in triggering the emetic reflex since L-743,310, which only has peripheral NK1 receptor antagonist activity, was without effect. The implication of 5-HT3 receptors in PDE IV inhibitor-induced emesis was variable. Our results suggest that the PDE IV inhibitors studied are mixed peripheral-central emetogens. PDE IV inhibition itself could be plausible mechanism of action of these agents. However, whether emesis is mediated via a specific isoform of PDE IV remains to be established.

Differential effect of a selective cyclooxygenase-2 inhibitor versus indomethacin on renal blood flow in conscious volume-depleted dogs.

Renal effects of a selective cyclooxygenase-2 (COX-2) inhibitor [MF-Tricyclic; 3-(3,4-difluorophenyl)-4-(4-(methylsulfonyl)phenyl)-2-(5H)-furanone] were studied in control and volume-depleted conscious dogs. MF-Tricyclic was compared with the nonselective COX-1/COX-2 inhibitor indomethacin. Six instrumented male dogs were randomly selected to receive MF-Tricyclic or indomethacin at 10 mg/kg. Volume depletion was effected by a sodium-restricted diet (14 days) with administration of furosemide (7.5 mg/kg, i.v.) the day before the experiment. Indomethacin ablated systemic COX-1 activity (p < 0.05), whereas MF-Tricyclic did not affect this activity. Each compound achieved plasma concentrations in excess of their respective median inhibitory concentrations (IC50 values) against canine COX-2. In controls, neither compound affected mean arterial pressure (MAP), heart rate (HR), renal blood flow (RBF), fractional excretion (FE) Na+, or FE K+. In volume-depleted dogs, indomethacin reduced RBF (p < 0.05), whereas MF-Tricyclic did not affect this parameter. Indices of renal function in volume-depleted dogs were not affected. These data are consistent with the view that the effects of indomethacin on RBF are a consequence of inhibition of COX-1 activity. Furthermore, in these studies, short-term administration of a selective COX-2 inhibitor was without deleterious effects on renal function.

Characterization of CHO-K1 cells stably expressing PDE-IV enzymes. Whole-cell cAMP determinations vs broken-cell enzymatic assays.

A CHO-K1 cell line stably expressing a recombinant full-length human PDE-IVa (HSPDE4A4B) enzyme was established under hygromycin B selection. Full-length expression of the protein was determined by Western blot analysis, which revealed the presence of a 125-kDa immunoreactive band using rabbit anti-PDE-IVa antibodies. The potency of inhibitor compounds was examined by their ability to increase cAMP in the whole-cell, and by their ability to inhibit cAMP hydrolysis in a 100,000 g supernatant (soluble enzyme preparation) obtained from the same cell line. Inhibition of the expressed PDE-IVa activity by selective PDE-IV inhibitors--(R) and (S)-rolipram, RS 14203, and CDP 840--at 100 nM substrate demonstrated that RS 14203 and CDP 840 were the most potent with IC50 = 9 nM, followed by (R)-rolipram (IC50 = 110 nM) and (S)-rolipram (IC50 = 420 nM). The rank order of potencies of the inhibitors in elevating cAMP in the whole-cell assay was quite different from that on the soluble enzyme. RS 14203 was still the most potent compound in elevating cAMP. Moreover, the relative rank order of potencies between CDP 840 and (R)-rolipram changed dramatically, such that (R)-rolipram was more potent than CDP 840 = (S)-rolipram. An apparent 30-fold stereoselectivity between (R)- and (S)-rolipram was also noted. The whole-cell rank order of potencies was also maintained when PKA activity ratios were measured in place of cAMP levels. The ability of the compounds to elevate cAMP in the stable CHO-K1 cells appeared to track better with the potency of the compounds against the high-affinity (Sr) conformer of the enzyme rather than the low-affinity catalytic state.

Effects of a selective phosphodiesterase IV inhibitor (CDP-840) in a leukotriene-dependent non-human primate model of allergic asthma.

The activity of CDP-840, a novel, selective phosphodiesterase IV inhibitor was determined in a leukotriene-dependent non-human primate model of allergic asthma. Measurements of specific airway resistance (sRaw) were recorded in a dual chamber plethysmograph for 1 h and 3-5 h after challenge of allergic conscious squirrel monkeys with an aerosol of ascaris antigen. Orally administered CDP-840 (10 mg/kg; 1 h before challenge) produced partial inhibition (41 and 45%, respectively) of both the acute (1 h post antigen) response and the late (3-5 h post antigen) response to antigen but failed to alter the response to an aerosol of leukotriene D4. In a second series of experiments, intravenous CDP-840 (5 mg/kg; 30 min before challenge) showed improved potency, producing 82% inhibition of the early and 51% inhibition of the late phase response. CDP-840 was inactive when tested intravenously at 1 mg/kg and was inactive against the 3-5 h response when administered after the early phase response (5 mg/kg; i.v. 60 min post antigen challenge). The novel phosphodiesterase IV inhibitor CDP-840 selectively inhibited antigen-induced bronchoconstriction in conscious squirrel monkeys. This effect appears to be independent of any direct bronchodilator action. It is concluded that the activity of CDP-840 in this model may be due to an inhibitory effect on mediator (e.g., leukotriene) release.

Co-localization of the cysteine protease caspase-3 with apoptotic myocytes after in vivo myocardial ischemia and reperfusion in the rat.

The aim of our study was to characterize the temporal relationship of apoptosis to regional myocardial ischemia and reperfusion and we aimed to determine the effect of ischemia and reperfusion on the distribution of the pro-apoptotic cysteine protease caspase-3 (CPP 32, apopain, Yama) in an in vivo rat model. Male Sprague-Dawley rats (250-400 g) were anesthetized with sodium pentobarbital (65 mg/kg, i.p.), the left external carotid artery was isolated to monitor arterial pressure and a left thoracotomy was performed. Regional myocardial ischemia was induced by occluding the left main coronary artery for 45 min. The heart was reperfused for 0, 60, 120 or 180 min. TUNEL staining of formalin-fixed, paraffin-embedded left ventricle, and DNA fragmentation analysis, showed that apoptosis occurred during 45 min of ischemia alone, but further developed during the 3-h reperfusion period. Immunohistochemical analysis of ischemic/reperfused left ventricle showed caspase-3 levels were substantially elevated and localized in the ischemic/reperfused region, and that caspase-3 co-localized to TUNEL positive myocytes. Therefore, regional myocardial ischemia serves as a stimulus for myocyte apoptosis, and this form of cell death progresses time-dependently after the onset of reperfusion. Our studies implicate caspase-3 to be involved in apoptotic cell death in ischemic/reperfused rat heart.

Cardiovascular and renal actions of the endothelin(B) receptor in pigs.

Previously we showed that blocking the endothelin (ET)A receptor subtype with BQ-153 inhibited the vasoconstrictor effects of intravenously administered ET-1. In the presence of the ET(A) antagonist, ET-1 produced marked reductions in myocardial contractility and renal blood flow. We postulated that either the ET(B) receptor, or some other, as yet unidentified, ET-receptor subtype mediated the observed hemodynamic changes. In anesthetized pigs, this hypothesis was tested by using a recently developed selective, high-affinity antagonist to the ET(B) receptor, BQ-788, and sarafotoxin S6c, a selective ET(B) agonist, to determine the contribution of this receptor subtype to cardiovascular function. Endothelin-1 (0.4 nmol/kg, i.v.) produced the characteristic biphasic hemodynamic responses, consisting of an initial transient reduction in mean arterial pressure (MAP; 83 +/- 3 to 72 +/- 4 mm Hg; n = 9) followed by a prolonged increase (112 +/- 4 mm Hg; p < 0.01). As well, cardiac output (-58%; p < 0.05), myocardial contractility (-19%; p < 0.01), and renal blood flow (63%; p < 0.05) decreased. Sarafotoxin S6c produced marked but transient reductions in MAP (p < 0.001), cardiac output (p < 0.01), myocardial contractility (p < 0.001), and renal blood flow (p < 0.05). BQ-788 (1.0 mg/kg, i.v.), administered 3 min before sarafotoxin S6c, inhibited its effects. BQ-788 also inhibited the initial transient reduction in MAP seen after the injection of ET-1, but the subsequent sustained pressor responses were enhanced as reflected in the greater increases in left ventricular pressure (p < 0.02), myocardial contractility (p < 0.05), MAP (p < 0.01), and a larger reduction in cardiac output (p < 0.05). The heart rate was not changed after the initial ET injection, but it increased 54% when the peptide was administered in the presence of BQ-788. The reduction in renal blood flow was still evident, and its magnitude (64%) remained the same (p < 0.01) after treatment with BQ-788. Only the combined administration of both the ET(A) (BQ-123) and ET(B) (BQ-788) receptor antagonists blocked the effects of ET-1 on renal blood flow (p < 0.05). These data confirm that BQ-788 is a selective and effective antagonist of the ET(B) receptor and show that activation of this receptor subtype is involved in the transient vasodilation provoked by ET-1. Additionally, the ET(B) receptor appears to oppose the vasoconstrictor effects of the ET(A) receptor, which clearly mediates vasoconstriction. Combined treatment with BQ-123 and BQ-788 attenuated the reductions in renal blood flow produced by ET-1. Furthermore, some actions of ET-1 were not blocked by these antagonists and cannot be attributed to either the ET(A) or ET(B) receptors. We hypothesize the existence of an additional ET receptor or a subtype of the ET(B) receptor that is insensitive to BQ-788.

Biochemical and pharmacological profile of a tetrasubstituted furanone as a highly selective COX-2 inhibitor.

1. DFU (5,5-dimethyl-3-(3-fluorophenyl)-4-(4-methylsulphonyl)phenyl-2(5H)-furan one) was identified as a novel orally active and highly selective cyclo-oxygenase-2 (COX-2) inhibitor. 2. In CHO cells stably transfected with human COX isozymes, DFU inhibited the arachidonic acid-dependent production of prostaglandin E2 (PGE2) with at least a 1,000 fold selectivity for COX-2 (IC50 = 41 +/- 14 nM) over COX-1 (IC50 > 50 microM). Indomethacin was a potent inhibitor of both COX-1 (IC50 = 18 +/- 3 nM) and COX-2 (IC50 = 26 +/- 6 nM) under the same assay conditions. The large increase in selectivity of DFU over indomethacin was also observed in COX-1 mediated production of thromboxane B2 (TXB2) by Ca2+ ionophore-challenged human platelets (IC50 > 50 microM and 4.1 +/- 1.7 nM, respectively). 3. DFU caused a time-dependent inhibition of purified recombinant human COX-2 with a Ki, value of 140 +/- 68 microM for the initial reversible binding to enzyme and a kappa 2 value of 0.11 +/- 0.06 s-1 for the first order rate constant for formation of a tightly bound enzyme-inhibitor complex. Comparable values of 62 +/- 26 microM and 0.06 +/- 0.01 s-1, respectively, were obtained for indomethacin. The enzyme-inhibitor complex was found to have a 1:1 stoichiometry and to dissociate only very slowly (t1/2 = 1-3 h) with recovery of intact inhibitor and active enzyme. The time-dependent inhibition by DFU was decreased by co-incubation with arachidonic acid under non-turnover conditions, consistent with reversible competitive inhibition at the COX active site. 4. Inhibition of purified recombinant human COX-1 by DFU was very weak and observed only at low concentrations of substrate (IC50 = 63 +/- 5 microM at 0.1 microM arachidonic acid). In contrast to COX-2, inhibition was time-independent and rapidly reversible. These data are consistent with a reversible competitive inhibition of COX-1. 5. DFU inhibited lipopolysaccharide (LPS)-induced PGE2 production (COX-2) in a human whole blood assay with a potency (IC50 = 0.28 +/- 0.04 microM) similar to indomethacin (IC50 = 0.68 +/- 0.17 microM). In contrast, DFU was at least 500 times less potent (IC50 > 97 microM) than indomethacin at inhibiting coagulation-induced TXB2 production (COX-1) (IC50 = 0.19 +/- 0.02 microM). 6. In a sensitive assay with U937 cell microsomes at a low arachidonic acid concentration (0.1 microM), DFU inhibited COX-1 with an IC50 value of 13 +/- 2 microM as compared to 20 +/- 1 nM for indomethacin. CGP 28238, etodolac and SC-58125 were about 10 times more potent inhibitors of COX-1 than DFU. The order of potency of various inhibitors was diclofenac > indomethacin approximately naproxen > nimesulide approximately meloxicam approximately piroxicam > NS-398 approximately SC-57666 > SC-58125 > CGP 28238 approximately etodolac > L-745,337 > DFU. 7. DFU inhibited dose-dependently both the carrageenan-induced rat paw oedema (ED50 of 1.1 mg kg-1 vs 2.0 mg kg-1 for indomethacin) and hyperalgesia (ED50 of 0.95 mg kg-1 vs 1.5 mg kg-1 for indomethacin). The compound was also effective at reversing LPS-induced pyrexia in rats (ED50 = 0.76 mg kg-1 vs 1.1 mg kg-1 for indomethacin). 8. In a sensitive model in which 51Cr faecal excretion was used to assess the integrity of the gastrointestinal tract in rats, no significant effect was detected after oral administration of DFU (100 mg kg-1, b.i.d.) for 5 days, whereas chromium leakage was observed with lower doses of diclofenac (3 mg kg-1), meloxicam (3 mg kg-1) or etodolac (10-30 mg kg-1). A 5 day administration of DFU in squirrel monkeys (100 mg kg-1) did not affect chromium leakage in contrast to diclofenac (1 mg kg-1) or naproxen (5 mg kg-1). 9. The results indicate that COX-1 inhibitory effects can be detected for all selective COX-2 inhibitors tested by use of a sensitive assay at low substrate concentration. The novel inhibitor DFU shows the lowest inhibitory potency against COX-1, a consistent high selectivity of inhibition of COX-2 over COX-1 (>300 fold) with enzyme, whole cell and whole blood assays, with no detectable loss of integrity of the gastrointestinal tract at doses >200 fold higher than efficacious doses in models of inflammation, pyresis and hyperalgesia. These results provide further evidence that prostanoids derived from COX-1 activity are not important in acute inflammatory responses and that a high therapeutic index of anti-inflammatory effect to gastropathy can be achieved with a selective COX-2 inhibitor.

A selective inhibitor of cyclooxygenase-2 reverses endotoxin-induced pyretic responses in non-human primates.

The anti-pyretic effect of a selective cyclooxygenase-2 inhibitor, DFU (5,5-dimethyl-3-(3-fluorophenyl)-4-(4-methylsulfonyl)phenyl-2(5H)-furano ne), was examined in conscious, un-restrained squirrel monkeys (Saimiri sciureus) using a radio telemetric system. Injection of bacterial endotoxin (lipopolysaccharide, 6 microg kg(-1), i.v.) in squirrel monkeys caused a gradual increase in core body temperature reaching a plateau of 2.07 +/- 0.17 degrees C above baseline at 2 h post-injection. Oral administration of DFU (1 mg kg(-1)) reduced, and DFU (3 mg kg(-1)) completely reversed the lipopolysaccharide-induced pyretic responses. The onset of action of DFU (about 30 min) is in good agreement with the pharmacokinetic profile of this compound in squirrel monkeys. The effect of DFU is comparable to that of a conventional non-selective non-steroidal anti-inflammatory drug (NSAID), diclofenac (3 mg kg(-1)). Since the plasma levels achieved for DFU at the dose employed in the present study are below the threshold required for inhibition of cyclooxygenase-1, it is concluded that the anti-pyretic effect of DFU can be attributed predominantly to an inhibitory action on cyclooxygenase-2. Thus, lipopolysaccharide-induced pyresis in squirrel monkeys can be used as a model for evaluation of anti-pyretic activity of cyclooxygenase inhibitors.

One-month exposure to inhaled endotoxin produces a dose-dependent increase in stored mucosubstances in rat intrapulmonary airways.

This study examined the production of stored mucosubtances in rats after repeated exposure to aerosolized endotoxin, a common contaminant of bioaerosols. Male Fischer 344 rats were exposed to aerosolized saline (sham control) or endotoxin (target concentrations of 0.05, 0.5, and 5.0 micrograms/m3) for 3 h/day, 5 days/week for 4 weeks. Following the final exposure, the left lung of each animal was lavaged and the right lung and nasal cavity were fixed with buffered formalin. Morphometric examination of Alcian blue/Periodic acid Schiffs-stained (AB/PAS) lung sections demonstrated dose-dependent increases in stored intraepithelial mucosubstances in the intrapulmonary airways of endotoxin-exposed rats. Threefold and eightfold increases in stored mucosubstances were observed in generation 5 airways of animals exposed to 0.5 or 5.0 microgram/m3 endotoxin, respectively (p < .05). This mucous cell metaplasia in the intrapulmonary airways was not accompanied by evidence of lung inflammation or increased AB/PAS-staining high molecular weight material in lavage fluid. Furthermore, despite significant deposition of endotoxin aerosols (mass median aerodynamic diameter of 1.9 microns) in the nasal cavity, no significant changes in stored mucosubstances were observed in the nasal septum. In animals repeatedly exposed to 5.0 micrograms/m3 endotoxin and allowed to recover for 1 month, stored mucosubstances in the intrapulmonary airway were still more than fivefold greater than control values. Thus, in rats, repeated exposure to inhaled endotoxin produced a persistent mucous cell metaplasia only in the intrapulmonary airways.