RESUMEN
This manuscript reports the results of preclinical studies in the rat with robenacoxib, a novel selective cyclooxygenase (COX)-2 inhibitor. Robenacoxib selectively inhibited COX-2 in vitro as evidenced from COX-1:COX-2 IC50 ratios of 27:1 in purified enzyme preparations and >967:1 in isolated cell assays. Binding to COX-1 was rapid and readily reversible (dissociation t(1/2) << 1 min), whilst COX-2 binding was slowly reversible (t(1/2) = 25 min). In vivo, robenacoxib inhibited PGE2 production (an index of COX-2 inhibition) in lipopolysaccharide (LPS)-stimulated air pouches (ID50 0.3 mg/kg) and for at least 24 h in zymosan-induced inflammatory exudate (at 2 mg/kg). Robenacoxib was COX-1 sparing, as it inhibited serum TxB2 synthesis ex vivo (an index of COX-1 inhibition) only at very high doses (100 mg/kg but not at 2-30 mg/kg). Robenacoxib inhibited carrageenan-induced paw oedema (ID50 0.40-0.48 mg/kg), LPS-induced fever (ID50 1.1 mg/kg) and Randall-Selitto pain (10 mg/kg). Robenacoxib was highly bound to plasma protein (99.9% at 50 ng/mL in vitro). After intravenous dosing, clearance was 2.4 mL/min/kg and volume of distribution at steady-state was 306 mL/kg. Robenacoxib was preferentially distributed into inflammatory exudate; the AUC for exudate was 2.9 times higher than for blood and the MRT in exudate (15.9 h) was three times longer than in blood (5.3 h). Robenacoxib produced significantly less gastric ulceration and intestinal permeability as compared with the reference nonsteroidal anti-inflammatory drug (NSAID), diclofenac, and did not inhibit PGE2 or 6-keto PGF(1alpha) concentrations in the stomach and ileum at 30 mg/kg. Robenacoxib also had no relevant effects on kidney function at 30 mg/kg. In summary, results of preclinical studies in rats studies suggest that robenacoxib has an attractive pharmacological profile for potential use in the intended target species, cats and dogs.
Asunto(s)
Antiinflamatorios no Esteroideos/farmacología , Inhibidores de la Ciclooxigenasa 2/farmacología , Ciclooxigenasa 2/efectos de los fármacos , Difenilamina/análogos & derivados , Fenilacetatos/farmacología , Animales , Antiinflamatorios no Esteroideos/efectos adversos , Antiinflamatorios no Esteroideos/farmacocinética , Área Bajo la Curva , Línea Celular , Ciclooxigenasa 1/efectos de los fármacos , Ciclooxigenasa 1/metabolismo , Ciclooxigenasa 2/metabolismo , Inhibidores de la Ciclooxigenasa 2/efectos adversos , Inhibidores de la Ciclooxigenasa 2/farmacocinética , Inhibidores de la Ciclooxigenasa/efectos adversos , Inhibidores de la Ciclooxigenasa/farmacocinética , Inhibidores de la Ciclooxigenasa/farmacología , Difenilamina/efectos adversos , Difenilamina/farmacocinética , Difenilamina/farmacología , Modelos Animales de Enfermedad , Edema/inducido químicamente , Edema/patología , Fiebre/inducido químicamente , Fiebre/patología , Humanos , Isoenzimas , Masculino , Dolor/inducido químicamente , Dolor/patología , Fenilacetatos/efectos adversos , Fenilacetatos/farmacocinética , Unión Proteica , Distribución Aleatoria , Ratas , Ratas Endogámicas Lew , Ratas Sprague-Dawley , Ratas WistarRESUMEN
Cardiac measures of heart period and high-frequency heart period variability are increasingly employed as dependent variables in studies of social and emotional development in infancy and childhood. This study describes significant developmental increases in these measures in a longitudinal sample assessed at 4, 9, 14, 24, and 48 months of age. In addition, developmental changes in the characteristics of the heart period power spectra are described. These changes have implications for the quantification of high-frequency heart period variability in infancy and childhood. First, shorter analysis epoch lengths may be used for younger infants. Second, the commonly used high-frequency band for infants (0.24-1.04 Hz) appears to reach its practical limit at an age of around four years. Findings are discussed in relation to the design of developmental psychophysiological studies.
Asunto(s)
Desarrollo Infantil/fisiología , Electrocardiografía , Frecuencia Cardíaca/fisiología , Factores de Edad , Preescolar , Femenino , Humanos , Lactante , Masculino , Estudios Prospectivos , Valores de Referencia , Fenómenos Fisiológicos RespiratoriosRESUMEN
This study shows that relations between behavioral inhibition and cardiac activity may be clarified by identifying attachment status, whereas relations between security of attachment and cardiac activity may be clarified by identifying inhibition status. Assessments at 4.5 years (N = 126) included heart period (HP), respiratory sinus arrhythmia (RSA), behavioral inhibition (BI), and security of attachment. There was no main effect of BI status (Low, Medium, High) on either HP or RSA. Instead, it was only the Secure children who showed the predicted relation between low BI and high HP or RSA, with the Low BI-Secure group having significantly higher HP than either the High BI-Secure or the Low BI-Insecure groups. Turning to attachment, both HP and RSA increased significantly from an assessment during separation from mother to an assessment 3 min after reunion. The only subgroups showing a significant increase in HP, however, were those with both secure attachment and an absence of high BI.
Asunto(s)
Arritmias Cardíacas/diagnóstico , Conducta Infantil/psicología , Frecuencia Cardíaca/fisiología , Inhibición Psicológica , Apego a Objetos , Trastornos Respiratorios/diagnóstico , Arritmias Cardíacas/complicaciones , Preescolar , Electrocardiografía , Femenino , Humanos , Masculino , Relaciones Madre-Hijo , Trastornos Respiratorios/complicaciones , Factores de Tiempo , Grabación en VideoRESUMEN
Hydroperoxide-induced tyrosyl radicals are putative intermediates in cyclooxygenase catalysis by prostaglandin H synthase (PGHS)-1 and -2. Rapid-freeze EPR and stopped-flow were used to characterize tyrosyl radical kinetics in PGHS-1 and -2 reacted with ethyl hydrogen peroxide. In PGHS-1, a wide doublet tyrosyl radical (34-35 G) was formed by 4 ms, followed by transition to a wide singlet (33-34 G); changes in total radical intensity paralleled those of Intermediate II absorbance during both formation and decay phases. In PGHS-2, some wide doublet (30 G) was present at early time points, but transition to wide singlet (29 G) was complete by 50 ms. In contrast to PGHS-1, only the formation kinetics of the PGHS-2 tyrosyl radical matched the Intermediate II absorbance kinetics. Indomethacin-treated PGHS-1 and nimesulide-treated PGHS-2 rapidly formed narrow singlet EPR (25-26 G in PGHS-1; 21 G in PGHS-2), and the same line shapes persisted throughout the reactions. Radical intensity paralleled Intermediate II absorbance throughout the indomethacin-treated PGHS-1 reaction. For nimesulide-treated PGHS-2, radical formed in concert with Intermediate II, but later persisted while Intermediate II relaxed. These results substantiate the kinetic competence of a tyrosyl radical as the catalytic intermediate for both PGHS isoforms and also indicate that the heme redox state becomes uncoupled from the tyrosyl radical in PGHS-2.
Asunto(s)
Hemo/metabolismo , Isoenzimas/metabolismo , Prostaglandina-Endoperóxido Sintasas/metabolismo , Tirosina/análogos & derivados , Tirosina/metabolismo , Animales , Apoenzimas/química , Apoenzimas/metabolismo , Ciclooxigenasa 1 , Ciclooxigenasa 2 , Espectroscopía de Resonancia por Spin del Electrón , Radicales Libres/metabolismo , Humanos , Isoenzimas/química , Cinética , Masculino , Proteínas de la Membrana , Oxidación-Reducción , Prostaglandina-Endoperóxido Sintasas/química , Conformación Proteica , Proteínas Recombinantes/química , Proteínas Recombinantes/metabolismo , Vesículas Seminales/enzimología , OvinosRESUMEN
A series of carboxy-substituted cinnamides were investigated as antagonists of the human cell surface leukotriene B4 (LTB4) receptor. Binding was determined through measurement of [3H]LTB4 displacement from human neutrophils. Receptor antagonism was confirmed through a functional assay, which measures inhibition of Ca2+ release in human neutrophils. Potent antagonists were discovered through optimization of a random screening hit, a p-(alpha-methylbenzyloxy)cinnamide, having low-micromolar activity. Substantial improvement of in vitro potency was realized by the attachment of a carboxylic acid moiety to the cinnamide phenyl ring through a flexible tether, leading to identification of compounds with low-nanomolar potency. Modification of the benzyloxy substituent, either through ortho-substitution on the benzyloxy phenyl group or through replacement of the ether oxygen with a methylene or sulfur atom, produced achiral antagonists of equal or greater potency. The most potent compounds in vitro were assayed for oral activity using the arachidonic acid-induced mouse ear edema model of inflammation. Several compounds in this series were found to significantly inhibit edema formation and myeloperoxidase activity in this model up to 17 h after oral administration. Representatives of this series have been shown to be potent and long-acting orally active inhibitors of the LTB4 receptor.
Asunto(s)
Amidas/síntesis química , Cinamatos/síntesis química , Receptores de Leucotrieno B4/antagonistas & inhibidores , Administración Oral , Amidas/química , Amidas/metabolismo , Amidas/farmacología , Animales , Calcio/metabolismo , Cinamatos/química , Cinamatos/metabolismo , Cinamatos/farmacología , Evaluación Preclínica de Medicamentos , Oído , Edema/tratamiento farmacológico , Femenino , Humanos , Técnicas In Vitro , Ratones , Neutrófilos/efectos de los fármacos , Neutrófilos/metabolismo , Relación Estructura-ActividadRESUMEN
Children were selected according to criteria for high or low behavioral inhibition (BI) on the basis of both a maternal questionnaire and interviewer ratings at home. Subsequent laboratory assessments involved further BI ratings as well as heart period (HP) and respiratory sinus arrhythmia (RSA). BI, HP, and RSA were all moderately stable from 4.5 to 7 years. HP and RSA changed in meaningful ways according to the context of different laboratory episodes. No significant relations emerged between BI and HP or RSA over the whole sample. However, HP predicted which of the children in the high inhibition group would remain inhibited at 7 years: HP at 4.5 years was significantly lower for children with high BI ratings at 4.5 who remained high at 7 years compared with children with high BI at 4.5 years who were less inhibited at 7 years.
Asunto(s)
Sistema Nervioso Autónomo/crecimiento & desarrollo , Desarrollo Infantil/fisiología , Frecuencia Cardíaca/fisiología , Personalidad/fisiología , Timidez , Temperamento/fisiología , Factores de Edad , Análisis de Varianza , Arritmias Cardíacas/psicología , Biomarcadores , Niño , Preescolar , Electrocardiografía , Femenino , Humanos , Inhibición Psicológica , Estudios Longitudinales , Masculino , Reproducibilidad de los ResultadosRESUMEN
Cartilage specimens from osteoarthritis (OA)-affected patients spontaneously released PGE2 at 48 h in ex vivo culture at levels at least 50-fold higher than in normal cartilage and 18-fold higher than in normal cartilage + cytokines + endotoxin. The superinduction of PGE2 production coincides with the upregulation of cyclooxygenase-2 (COX-2) in OA-affected cartilage. Production of both nitric oxide (NO) and PGE2 by OA cartilage explants is regulated at the level of transcription and translation. Dexamethasone inhibited only the spontaneously released PGE2 production, and not NO, in OA-affected cartilage. The NO synthase inhibitor HN(G)-monomethyl-L-arginine monoacetate inhibited OA cartilage NO production by > 90%, but augmented significantly (twofold) the spontaneous production of PGE2 in the same explants. Similarly, addition of exogenous NO donors to OA cartilage significantly inhibited PGE2 production. Cytokine + endotoxin stimulation of OA explants increased PGE2 production above the spontaneous release. Addition of L-NMMA further augmented cytokine-induced PGE2 production by at least fourfold. Inhibition of PGE2 by COX-2 inhibitors (dexamethasone or indomethacin) or addition of exogenous PGE2 did not significantly affect the spontaneous NO production. These data indicate that human OA-affected cartilage in ex vivo conditions shows (a) superinduction of PGE2 due to upregulation of COX-2, and (b) spontaneous release of NO that acts as an autacoid to attenuate the production of the COX-2 products such as PGE2. These studies, together with others, also suggest that PGE2 may be differentially regulated in normal and OA-affected chondrocytes.
Asunto(s)
Cartílago Articular/enzimología , Isoenzimas/biosíntesis , Óxido Nítrico/fisiología , Osteoartritis/enzimología , Prostaglandina-Endoperóxido Sintasas/biosíntesis , Adulto , Anciano , Secuencia de Bases , Ciclooxigenasa 2 , Dinoprostona/antagonistas & inhibidores , Dinoprostona/biosíntesis , Dinoprostona/metabolismo , Inducción Enzimática/efectos de los fármacos , Humanos , Isoenzimas/genética , Proteínas de la Membrana , Persona de Mediana Edad , Datos de Secuencia Molecular , Óxido Nítrico/metabolismo , Prostaglandina-Endoperóxido Sintasas/genética , ARN Mensajero/biosíntesisRESUMEN
A hydroperoxide-induced tyrosyl radical has been proposed as a key cyclooxygenase intermediate for the "basal" isoform of prostaglandin H synthase (PGHS-1). In the present study with the "inducible" isoform (PGHS-2), hydroperoxide was also found to generate a radical in high yield, a wide singlet at g = 2.0058 (29 G peak to trough). Reaction of PGHS-2 with a tyrosine-modifying reagent, tetranitromethane (TNM), resulted in cyclooxygenase inactivation and a much narrower radical EPR signal (22 G peak to trough). Addition of a cyclooxygenase inhibitor, nimesulide, similarly resulted in a narrow PGHS-2 radical. In PGHS-1, cyclooxygenase inhibition by tyrosine nitration with TNM or by active site ligands leads to generation of a narrow EPR instead of a wide EPR, with both signals originating from authentic tyrosyl radicals, indicating that the hydroperoxide-induced radicals in PGHS-2 are also tyrosyl radicals. Treatment of PGHS-2 with aspirin (acetyl salicylic acid, ASA) was previously shown to result in acetylation of a specific serine residue, cyclooxygenase inhibition, and increased lipoxygenase activity. Acetylation of PGHS-1 by ASA, in contrast, inhibited both lipoxygenase and cyclooxygenase activity. We now have found the ASA-treated PGHS-2 radical to be indistinguishable from that in control PGHS-2. Addition of nimesulide to ASA-treated PGHS-2 inhibited the lipoxygenase and resulted in a narrow radical EPR like that seen in PGHS-2 treated with TNM or nimesulide alone. Retention of PGHS-2 oxygenase activity was thus associated with retention of the native radical, and loss of activity was associated with alteration of the radical. Both native and ASA-treated PGHS-2 produced only the R stereoisomer of 11- and 15-HETE, demonstrating that the lipoxygenase stereochemistry was not changed by ASA. Native and ASA-treated PGHS-2 had lipoxygenase K(m) values considerably higher than that of the control PGHS-2 cyclooxygenase. Taken together, these results suggest that the same PGHS-2 tyrosyl radical serves as the oxidant for both cyclooxygenase and lipoxygenase catalysis and that acetylation of PGHS-2 by ASA favors arachidonate binding in an altered conformation which results in abstraction of the pro-R hydrogen from C13 and formation of 11(R)- and 15(R)-HETE.
Asunto(s)
Aspirina/farmacología , Peróxido de Hidrógeno/farmacología , Isoenzimas/química , Isoenzimas/efectos de los fármacos , Lipooxigenasa/metabolismo , Prostaglandina-Endoperóxido Sintasas/química , Prostaglandina-Endoperóxido Sintasas/efectos de los fármacos , Tirosina/análogos & derivados , Tirosina/efectos de los fármacos , Ácido Araquidónico/metabolismo , Ciclooxigenasa 2 , Espectroscopía de Resonancia por Spin del Electrón , Activación Enzimática/efectos de los fármacos , Radicales Libres/química , Humanos , Isoenzimas/metabolismo , Cinética , Proteínas de la Membrana , Prostaglandina-Endoperóxido Sintasas/metabolismo , Estereoisomerismo , Tetranitrometano/farmacología , Tirosina/químicaRESUMEN
Alzheimer's disease (AD) pathology is characterized by plaques, tangles, and neuronal cell loss. The main constituent of plaques is beta-amyloid peptide (A beta), a 39-42 residue peptide which has been linked to disruption of calcium homeostasis and neurotoxicity in vitro. We demonstrate that a neurotoxic fragment of A beta, A beta (25-35) spontaneously inserted into planar lipid membranes to form weakly selective, voltage dependent, ion-permeable channels. We suggest that channel formation may be involved in the pathogenesis of AD and that A beta (25-35) may be the active channel forming segment.
Asunto(s)
Péptidos beta-Amiloides/metabolismo , Canales Iónicos/metabolismo , Membrana Dobles de Lípidos/metabolismo , Fragmentos de Péptidos/metabolismo , Secuencia de Aminoácidos , Péptidos beta-Amiloides/química , Calcio/metabolismo , Cloruros/metabolismo , Humanos , Potenciales de la Membrana , Datos de Secuencia Molecular , Fragmentos de Péptidos/química , Potasio/metabolismo , Sodio/metabolismoRESUMEN
The open reading frame of human cyclooxygenase-2 was cloned by pcr amplification of IL-1 beta stimulated human dermal fibroblast cDNA. The coding region was used to construct a recombinant baculovirus which when used to infect Sf9 cells directed the expression of recombinant human cyclooxygenase-2. The heterologously expressed enzyme was characterized and found to display all salient features of cyclooxygenase. Large-scale microsomal preparations of infected cells yielded more than 20 units of enzyme with a specific activity of 240 nmoles prostaglandin product/mg protein.
Asunto(s)
Prostaglandina-Endoperóxido Sintasas/genética , Animales , Secuencia de Bases , Compartimento Celular , Clonación Molecular , Inhibidores de la Ciclooxigenasa/farmacología , Cartilla de ADN/química , Expresión Génica , Humanos , Datos de Secuencia Molecular , Mariposas Nocturnas , Prostaglandina-Endoperóxido Sintasas/metabolismo , Prostaglandinas/biosíntesis , ARN Mensajero/genética , Proteínas RecombinantesRESUMEN
The antiinflammatory activity of rolipram, a selective inhibitor of the cyclic AMP-specific phosphodiesterase (PDE IV), was studied. Rolipram did not inhibit 5-lipoxygenase activity but did inhibit human monocyte production of leukotriene B4 (LTB4, IC50 3.5 microM). Likewise, murine mast cell release of leukotriene C4 and histamine was inhibited. In vivo, rolipram inhibited arachidonic acid-induced inflammation in the mouse, while the low Km-cyclic-GMP PDE inhibitor, zaprinast, did not inhibit. Rolipram had a modest effect on LTB4 production in the mouse, but markedly reduced LTB4-induced PMN infiltration. Beta-adrenergic receptor activation of adenylate cyclase was important for rolipram antiinflammatory activity since beta blockade abrogated arachidonic acid-induced inflammation. Thus, the antiinflammatory profile of rolipram is novel and may result from inhibition of PMN function and perhaps vasoactive amine release and leukotriene biosynthesis. These actions may be dependent upon endogenous beta-adrenergic activity and are likely mediated through inhibition of PDE IV.
Asunto(s)
3',5'-AMP Cíclico Fosfodiesterasas , Antiinflamatorios no Esteroideos/farmacología , Inflamación/metabolismo , Mastocitos/efectos de los fármacos , Neutrófilos/efectos de los fármacos , Inhibidores de Fosfodiesterasa/farmacología , Hidrolasas Diéster Fosfóricas , Pirrolidinonas/farmacología , Animales , Ácido Araquidónico/toxicidad , Calcimicina/farmacología , Células Cultivadas , Colforsina/farmacología , Fosfodiesterasas de Nucleótidos Cíclicos Tipo 4 , Oído Externo , Eicosanoides/metabolismo , Liberación de Histamina/efectos de los fármacos , Humanos , Imidazoles/farmacología , Inflamación/inducido químicamente , Leucotrieno B4/biosíntesis , Masculino , Ratones , Ratones Endogámicos BALB C , Monocitos/efectos de los fármacos , Nadolol/farmacología , Naproxeno/farmacología , Hidrolasas Diéster Fosfóricas/fisiología , Purinonas/farmacología , Pirazoles/farmacología , Receptores Adrenérgicos beta/efectos de los fármacos , Receptores Adrenérgicos beta/fisiología , Rolipram , SRS-A/metabolismo , Tiazoles/farmacologíaRESUMEN
SK&F 105809 [2-(4-methylsulfinylphenyl)-3-(4-pyridyl)- 6,7-dihydro-[5H]-pyrrolo[1,2,a] imidazole] demonstrated unique antiinflammatory activities in murine models that are resistant to selective cyclooxygenase (CO) inhibitors. Both edema and inflammatory cell infiltration induced by the topical application of arachidonic acid to the mouse ear were decreased by SK&F 105809 (ED50 values of 44 mg/kg, p.o.). Polymorphonuclear leukocyte (PMN) infiltration following the intraperitoneal injection of either monosodium urate crystal or carrageenan was inhibited with ED50 values of 64 and 72 mg/kg, p.o., respectively. These inflammatory responses were unaffected by the selective cyclooxygenase inhibitor naproxen. SK&F 105809 also inhibited leukotriene B4 (LTB4) and prostaglandin E2 production in vivo in arachidonic acid-induced inflammatory exudates (ED50 values of 41 and 15 mg/kg, p.o., respectively). The inhibition of LTB4 production preceded the inhibition of PMN infiltration. The impact of inhibition of both 5-lipoxygenase (5-LO) and CO was seen with platelet-activating factor-induced vascular permeability which was inhibited markedly by SK&F 105809. However, the 5-LO inhibitor, phenidone, only strongly inhibited when coadministered with the selective CO inhibitor, indomethacin. In spite of a short half-life (14-18 min) for both SK&F 105809 and the active metabolite SK&F 105561 [2-(4- methylthiophenyl)-3-(4-pyridyl)-6,7-dihydro-[5H]-pyrrolo[1,2-a] imidazole], the pharmacological activity lasted at least 1.5 hr. The biochemical evidence of inhibition of interleukin-1 (IL-1) production and 5-LO and CO activity, in vitro, by the metabolite (SK&F 105561) seen in the companion paper (Marshall PJ, Griswold DE, Breton J. Webb EF, Hillegass LM, Sarau HM, Newton J Jr, Lee JC, Bender PE and Hanna N, Pharmacology of the pyrroloimidazole, SK&F 105809--I. Inhibition of inflammatory cytokine production and of 5-lipoxygenase- and cyclooxygenase-mediated metabolism of arachidonic acid. Biochem Pharmacol 42: 813-824, 1991) and inhibition of the fluid and cellular phases of the inflammatory response, in vivo, by SK&F 105809 suggest that this compound possesses a unique profile of activity.
Asunto(s)
Antiinflamatorios no Esteroideos/farmacología , Imidazoles/farmacología , Profármacos/farmacología , Animales , Antiinflamatorios no Esteroideos/farmacocinética , Ácido Araquidónico , Ácidos Araquidónicos/toxicidad , Dermatitis por Contacto/tratamiento farmacológico , Dermatitis por Contacto/metabolismo , Edema/tratamiento farmacológico , Eicosanoides/biosíntesis , Imidazoles/farmacocinética , Inflamación/inducido químicamente , Inflamación/tratamiento farmacológico , Inflamación/metabolismo , Masculino , Ratones , Ratones Endogámicos BALB C , Profármacos/farmacocinéticaRESUMEN
SK&F 105809 [2-(4- methylsulfinylphenyl)-3-(4-pyridyl)-6,7-dihydro-[5H]-pyrrolo[1,2- a] imidazole] was determined to be a prodrug for the sulfide metabolite SK&F 105561 [2-(4- methylthiophenyl)-3-(4-pyridyl)-6,7-dihydro-[5H]-pyrrolo[1,2-a] imidazole] which inhibited interleukin-1 (IL-1) production in vitro and both 5-lipoxygenase (5-LO) and prostaglandin H (PGH) synthase activities in vitro and ex vivo. SK&F 105561 inhibited partially purified 5-LO with a half-maximal concentration (IC50) of 3 microM. This inhibition was reversible, independent of preincubation time, and dependent on the concentration of the substrate arachidonic acid. SK&F 105561 also inhibited purified PGH synthase with the potency dependent on the level of peroxidase activity. The IC50 was 100 microM in the absence of peroxidase activity, whereas an IC50 of 3 microM was observed in the presence of peroxidase activity. Using human monocytes, SK&F 105561 inhibited A23187-stimulated prostaglandin E2 (PGE2) and leukotriene B4 (LTB4) production with IC50 values of 0.1 and 2 microM, respectively. In addition, IL-1 production by lipopolysaccharide-stimulated human monocytes was also inhibited (IC50 2 microM). Oral administration of SK&F 105809 to rats resulted in a dose-related generation of SK&F 105561 and in the inhibition of thromboxane B2 and LTB4 production ex vivo with a half-maximal dose (ED50) of 15 and 60 mg/kg, respectively. SK&F 105561 showed weak inhibitory activity on 12-lipoxygenase with an IC50 of greater than 200 microM. Neither SK&F 105561 nor SK&F 105809 inhibited the stimulated-turnover of arachidonic acid-containing phospholipids in human monocytes or the activity of cell-free phospholipases A2 and C. Moreover, neither SK&F 105561 nor SK&F 105809 antagonized the binding of LTB4 or leukotriene D4 to membrane receptors. From these results, SK&F 105561, the active principle of SK&F 105809, acts as an inhibitor of both inflammatory cytokine and eicosanoid production.
Asunto(s)
Ácidos Araquidónicos/metabolismo , Inhibidores de la Ciclooxigenasa , Citocinas/biosíntesis , Eicosanoides/biosíntesis , Imidazoles/farmacología , Inhibidores de la Lipooxigenasa , Profármacos/farmacología , Animales , Araquidonato 5-Lipooxigenasa/metabolismo , Ácido Araquidónico , Eicosanoides/sangre , Humanos , Inflamación/metabolismo , Interleucina-1/biosíntesis , Leucotrienos/metabolismo , Masculino , Fosfolipasas/metabolismo , Fosfolípidos/metabolismo , Prostaglandina-Endoperóxido Sintasas/metabolismo , Ratas , Ratas Endogámicas LewRESUMEN
The effects of SK&F 105809, 6,7,-dihydro-2-[4(methylsulfinyl) phenyl]-3-(4-pyridyl) -5[H]-pyrrolo[1,2-a] imidazole, on eicosanoid metabolism, inflammatory responses, algesia and ulcer formation are described. SK&F 105809 was determined to be a prodrug for the sulfide metabolite SK&F 105561 which is an inhibitor of 5-lipoxygenase (5-LO) and prostaglandin H (PGH) synthase activities seen with both the isolated enzyme (IC50S 3 microM) and human monocyte production of the eicosanoids leukotriene B4 (LTB4, IC50 1.0 microM) and prostaglandin E2 (PGE2, IC50 0.1 microM). In-vivo conversion of SK&F 105809 to the active principle SK&F 105561 was observed in both mice and rats. SK&F 105809 inhibited LTB4 and PGE2 production in vivo in inflammatory exudates as well as the production of LTB4 and thromboxane B2 (TxB2) ex vivo in rat blood. SK&F 105809 inhibited oedema and inflammatory-cell infiltration in arachidonic acid-induced inflammation in the mouse ear and rat paw as well as in carrageenan- and monosodium urate crystal-induced peritonitis. SK&F 105809 was also effective in inhibiting mouse collagen-induced arthritis and associated acute-phase reactant protein. At the same time, these acute and chronic models of inflammation were found to be resistant to the action of selective cyclooxygenase inhibitors such as naproxen. In addition, SK&F 105809 possessed analgesic activity in phenylquinone-induced abdominal constriction assay and inhibited indomethacin-induced ulcers.
Asunto(s)
Ácidos Araquidónicos/metabolismo , Administración Oral , Analgésicos/farmacología , Animales , Ácido Araquidónico , Artritis Experimental/tratamiento farmacológico , Colágeno , Inhibidores de la Ciclooxigenasa , Eicosanoides/biosíntesis , Mucosa Gástrica/efectos de los fármacos , Humanos , Imidazoles/aislamiento & purificación , Imidazoles/metabolismo , Indometacina , Inhibidores de la Lipooxigenasa , Masculino , Ratones , Ratones Endogámicos , Otitis Externa/inducido químicamente , Otitis Externa/tratamiento farmacológico , Otitis Externa/metabolismo , Peritonitis/tratamiento farmacológico , Ratas , Ratas Endogámicas Lew , Úlcera Gástrica/inducido químicamente , Úlcera Gástrica/tratamiento farmacológicoRESUMEN
The mode of action of the dual inhibitors of eicosanoid metabolism, SK&F 86002 and SK&F 104493 was evaluated on inflammatory cell infiltration induced in mice by carrageenan, monosodium urate crystals, and arachidonic acid. The results were compared to those seen with standard antiinflammatory compounds. Inflammatory cell infiltration was inhibited by SK&F 86002. SK&F 104493, colchicine, and phenidone but not naproxen. In vivo, PMN infiltration induced by LTB4 was inhibited by colchicine but not by SK&F 86002, SK&F 104493, or phenidone treatment. Similarly, in vitro chemotaxis to LTB4 was not inhibited by SK&F 86002. The 5-lipoxygenase inhibitors, SK&F 86002, SK&F 104493, and phenidone inhibited LTB4 production in vivo as well as inflammatory cell infiltration induced by arachidonic acid. The data are consistent with the suggestion that the bicyclic imidazoles inhibit PMN infiltration by virtue of inhibition of LTB4 production.
Asunto(s)
Imidazoles/farmacología , Inflamación/patología , Piridinas/farmacología , Tiazoles/farmacología , Animales , Antiinflamatorios no Esteroideos/farmacología , Quimiotaxis de Leucocito/efectos de los fármacos , Ciclofosfamida/farmacología , Dinoprostona/biosíntesis , Enfermedades del Oído/etiología , Enfermedades del Oído/patología , Edema/etiología , Edema/patología , Eicosanoides/antagonistas & inhibidores , Eicosanoides/biosíntesis , Inflamación/metabolismo , Leucotrieno B4/antagonistas & inhibidores , Leucotrieno B4/farmacología , Masculino , Ratones , Ratones Endogámicos BALB C , Neutrófilos/fisiología , Peritonitis/patología , Peritonitis/fisiopatologíaAsunto(s)
Daño por Reperfusión Miocárdica/prevención & control , Fenilacetatos/farmacología , Sulfonamidas/farmacología , Ácido 15-Hidroxi-11 alfa,9 alfa-(epoximetano)prosta-5,13-dienoico , Animales , Enfermedad Coronaria/tratamiento farmacológico , Enfermedad Coronaria/patología , Masculino , Infarto del Miocardio/patología , Infarto del Miocardio/prevención & control , Daño por Reperfusión Miocárdica/patología , Neutrófilos/efectos de los fármacos , Neutrófilos/patología , Endoperóxidos de Prostaglandinas Sintéticos/antagonistas & inhibidores , Ratas , Ratas Endogámicas , Receptores de Prostaglandina , Receptores de TromboxanosRESUMEN
Prostaglandin H synthase has two distinct catalytic activities: a cyclooxygenase activity that forms prostaglandin G2 from arachidonic acid; and a peroxidase activity that reduces prostaglandin G2 to prostaglandin H2. Lipid hydroperoxides, such as prostaglandin G2, also initiate the cyclooxygenase reaction, probably via peroxidase reaction cycle enzyme intermediates. The relation between the binding sites for lipid substrates of the two activities was investigated with an analysis of the effects of arachidonic and docosahexaenoic acids on the reaction kinetics of the peroxidase activity, and their effects on the ability of a lipid hydroperoxide to initiate the cyclooxygenase reaction. The cyclooxygenase activity of pure ovine synthase was found to have an apparent Km value for arachidonate of 5.3 microM and a Ki value (competetive inhibitor) for docosahexaenoate of 5.2 microM. When present at 20 microM neither fatty acid had a significant effect on the apparent Km value of the peroxidase for 15-hydroperoxyeicosatetraenoic acid: the values were 7.6 microM in the absence of docosahexaenoic acid and 5.9 microM in its presence, and (using aspirin-treated synthase) 13.7 microM in the absence of arachidonic acid and 15.7 microM in its presence. Over a range of 1 to 110 microM the level of arachidonate had no significant effect on the initiation of the cyclooxygenase reaction by 15-hydroperoxyeicosatetraenoic acid. The inability of either arachidonic acid or docosahexaenoic acid to interfere with the interaction between the peroxidase and lipid hydroperoxides indicates that the cyclooxygenase and peroxidase activities of prostaglandin H synthase have distinct binding sites for their lipid substrates.
Asunto(s)
Ácidos Grasos/metabolismo , Leucotrienos/metabolismo , Peróxidos Lipídicos/metabolismo , Prostaglandina-Endoperóxido Sintasas/metabolismo , Animales , Ácido Araquidónico , Ácidos Araquidónicos/farmacología , Aspirina/farmacología , Ácidos Grasos Insaturados/farmacología , Cinética , Peroxidasas/metabolismo , OvinosRESUMEN
The effects of SK&F 86002 [5-(4-pyridyl)-6 (4-fluorophenyl)-2,3-dihydroimidazo (2,1-b) thiazole] on the generation of eicosanoids in vitro and on inflammatory responses in vivo are described and compared to other non-steroidal anti-inflammatory drugs. SK&F 86002 inhibited prostaglandin H2 (PGH2) synthase activity (IC50 120 microM) as well as prostanoid production by rat basophilic leukemia (RBL-1) cells (IC50 70 microM) and its sonicate (IC50 100 microM) and human monocytes (IC50 1 microM). In addition, SK&F 86002 inhibited the generation of dihydroxyeicosatetraenoic acid (diHETE) and 5-hydroxyeicosatetraenoic acid (5-HETE) by a high speed supernatant fraction of RBL-1 cells (IC50 10 microM). Cellular production of 5-lipoxygenase products was inhibited by SK&F 86002 as measured by leukotriene B4 (LTB4) generation from human neutrophils (IC50 20 microM), leukotriene C4 (LTC4) generation by human monocytes (IC50 20 microM), and 5-HETE production by RBL-1 cells (IC50 40 microM). The in vivo profile of anti-inflammatory activity of SK&F 86002 supports the dual inhibition of arachidonate metabolism as indicated by its activity in inflammation models that are insensitive to selective cyclooxygenase inhibitors. The responses of arachidonic-acid-induced edema in the mouse ear and rat paw, as well as the cell infiltration induced by carrageenan in the mouse peritoneum and by arachidonic acid in the rat air pouch, were inhibited by SK&F 86002 and phenidone but not by the selective cyclooxygenase inhibitors naproxen and indomethacin.
Asunto(s)
Antiinflamatorios/farmacología , Araquidonato Lipooxigenasas/antagonistas & inhibidores , Ácidos Araquidónicos/metabolismo , Inhibidores de la Ciclooxigenasa , Imidazoles/farmacología , Inhibidores de la Lipooxigenasa , Tiazoles/farmacología , Animales , Ácido Araquidónico , Humanos , Inflamación/metabolismo , Leucocitos/metabolismo , Leucotrieno B4/metabolismo , Ratones , Pirazoles/farmacología , Ratas , SRS-A/metabolismoRESUMEN
The formation of prostaglandins by prostaglandin H synthase can be limited by the availability of the fatty acid substrate or the hydroperoxide activator and also by a self-catalyzed inactivation associated with the oxygenation reaction. Each pmol of synthase appeared able to form only about 1300 pmol of prostaglandin from arachidonate before it was inactivated. This extent of synthesis was not diminished when substrate fatty acid was complexed with cytosolic proteins even though the velocity of the oxygenation reaction was greatly decreased by the lower availability of substrate acid. When the availability of hydroperoxide activator was decreased by added glutathione peroxidase, the extent of oxygenation per mol of synthase was decreased irrespective of the amount of cytosolic protein present. Approximately 65% of the total prostaglandin synthesis by homogenates was suppressed with a glutathione peroxidase to prostaglandin H synthase ratio of about 90. The remaining prostaglandin synthetic activity was more resistant, being completely suppressed only when the ratio of peroxidase to synthase exceeded 750. The overall ratio of glutathione peroxidase (peroxide-removing) capacity to prostaglandin synthetic (peroxide-forming) capacity in selected tissues ranged from over 1800 in rat liver to less than 30 in leukocytes. A comparison between the daily urinary output of prostaglandin metabolites and tissue prostaglandin synthetic capacity suggested that prostaglandin H synthase inactivation along with glutathione peroxidase suppression of the extent of prostaglandin synthase may be important in limiting prostaglandin biosynthesis within cells.