RESUMEN
BACKGROUND: A powder formulation of salmeterol has been shown to prevent exercise-induced bronchospasm (EIB) in asthmatic children and adults; however, the delivery device (Diskhaler; Glaxo Wellcome Inc, Research Triangle Park, NC) must be reloaded after 4 doses. A new multidose powder inhaler (Diskus) provides 60 doses of salmeterol in a blister pack presentation with a dose counter. OBJECTIVE: To evaluate the safety and efficacy of 50-microg salmeterol powder via two different delivery systems (Diskhaler and Diskus) in preventing EIB in asthmatic children. STUDY DESIGN: A randomized, double-blind, double-dummy, single-dose, placebo-controlled, three-way crossover study was conducted in 24 children 4 to 11 years of age demonstrating EIB and mild to moderate asthma. Serial forced expiratory volume in 1 second (FEV(1)) was measured before and after treadmill exercise challenges conducted at 1, 6, and 12 hours after study drug administration. Adverse events were also assessed. RESULTS: During all exercise challenges, EIB-mediated reductions in FEV(1) were minimized or prevented in patients receiving single doses of salmeterol powder compared with placebo. Single doses of salmeterol powder delivered via either system were equally effective in preventing EIB. There were no drug-related adverse events, cardiovascular, or other clinically relevant safety concerns. CONCLUSIONS: Single doses of salmeterol powder delivered by either delivery system are safe and effective in preventing EIB for >/=12 hours in asthmatic children.
Asunto(s)
Agonistas Adrenérgicos beta/administración & dosificación , Albuterol/análogos & derivados , Asma Inducida por Ejercicio/tratamiento farmacológico , Espasmo Bronquial/prevención & control , Nebulizadores y Vaporizadores , Administración por Inhalación , Agonistas Adrenérgicos beta/uso terapéutico , Albuterol/administración & dosificación , Albuterol/uso terapéutico , Asma Inducida por Ejercicio/fisiopatología , Niño , Preescolar , Estudios Cruzados , Método Doble Ciego , Prueba de Esfuerzo , Femenino , Humanos , Masculino , Polvos , Xinafoato de Salmeterol , Factores de TiempoRESUMEN
Cytokines active on eosinophils are important in the pathogenesis of allergic diseases. A study was conducted to determine if nasal eosinophilia in allergic rhinitis is associated with an increase in eosinophil-active cytokines in nasal secretions and to compare the effects of fluticasone propionate aqueous nasal spray with astemizole and placebo on the levels of these cytokines. Forty-five patients with moderately severe ragweed allergic rhinitis were randomly assigned to receive 2 weeks of treatment with fluticasone propionate aqueous nasal spray 200 micrograms once daily, astemizole 10 mg once daily, or placebo. Nasal lavage was performed in July (preseason), August (peak season), September (after 2 weeks of treatment), and October (postseason). The number of eosinophils, the amount of eosinophil-derived neurotoxin (EDN), and the amount of eosinophil survival-enhancing activity were measured. Total mean nasal symptom scores, concentrations of nasal eosinophils and EDN, and eosinophil survival-enhancing cytokine activity in nasal secretions were significantly lower after 2 weeks of treatment with fluticasone propionate compared with astemizole or placebo. Survival-enhancing activity was detected in the nasal secretions of 25 patients. By blocking activity with monoclonal antibodies, specific cytokines were identified (granulocyte macrophage-colony stimulating factor, 3 samples; interleukin-3, 2 samples; interleukin-5, 5 samples). In conclusion, eosinophil-active cytokine concentrations parallel the nasal symptoms of patients with ragweed allergic rhinitis. Unlike astemizole, fluticasone propionate significantly lowers cytokine activity in nasal tissue, which may contribute to the therapeutic efficacy of the drug.
Asunto(s)
Androstadienos/administración & dosificación , Antialérgicos/administración & dosificación , Eosinófilos/efectos de los fármacos , Mucosa Nasal/efectos de los fármacos , Rinitis Alérgica Estacional/tratamiento farmacológico , Ribonucleasas , Adulto , Aerosoles , Astemizol/administración & dosificación , Citocinas/efectos de los fármacos , Citocinas/metabolismo , Neurotoxina Derivada del Eosinófilo , Femenino , Fluticasona , Humanos , Masculino , Mucosa Nasal/metabolismo , Neurotoxinas/aislamiento & purificaciónRESUMEN
Angiotensin II can inhibit hormone-stimulated adenylyl cyclase in intact hepatocytes or in hepatic membrane preparations. Because the response can be blocked by pertussis toxin, the object of the present study was to determine which of the known variants of Gi can couple angiotensin II receptors to inhibition of adenylyl cyclase. The potential candidates were identified by probing RNA isolated from rat hepatocytes with cDNAs specific for the alpha subunits of known toxin-sensitive guanine nucleotide-binding regulatory proteins (G proteins). Hepatocytes contained no detectable RNA for the Go or Gi1 alpha subunits and similar levels of RNA coding for the Gi2 and Gi3 alpha subunits. To determine whether Gi3 could couple angiotensin receptors to inhibition of cyclase, membranes were prepared from hepatocytes whose G proteins were fully ADP-ribosylated with pertussis toxin, and the Gi3 holoprotein purified from rabbit liver was reconstituted into the membranes. The nature of the Gi3 reconstituted into the membrane was assessed by immunoblotting with antibodies specific for the Gi alpha subunits. Reconstitution of 6-10 pmol of Gi3/mg of membrane protein into the toxin-treated membranes restored the ability of 10 nM angiotensin II to inhibit adenylyl cyclase. Because pertussis toxin has nonspecific effects, an assay was developed to measure the interaction of the angiotensin receptor with reconstituted G proteins in normal membranes. In the presence of Mg2+, guanosine 5'-O-(3-thiotriphosphate) (GTP gamma S) caused a reduction of the affinity of the angiotensin II receptor for 125I-angiotensin II that was stable to washing and the detergents used to reconstitute G proteins into the membranes. Using this protocol to activate G proteins and "uncouple" receptors, the ability of the GDP-liganded form of Gi to restore high affinity binding was examined. Reconstitution of about 10-15 pmol of oligomeric Gi3/mg of membrane protein restored both the high affinity state of the angiotensin II receptor and the ability of GTP gamma S to shift the affinity to a lower state. The same shift in receptor affinity could be accomplished by reconstituting the Gi3 alpha subunit, resolved free of beta gamma subunits, into the membranes. Reconstitution of up to 50 pmol of Gs/mg of membrane protein had no effect on angiotensin II receptor affinity. The results suggest that a major form of Gi in hepatocytes is Gi3 and that it can couple angiotensin receptors to inhibition of adenylyl cyclase.
Asunto(s)
Inhibidores de Adenilato Ciclasa , Angiotensina II/metabolismo , Proteínas de Unión al GTP/fisiología , Hígado/enzimología , Receptores de Angiotensina/fisiología , Angiotensina II/farmacología , Animales , Proteínas de Unión al GTP/análisis , Proteínas de Unión al GTP/genética , Guanosina 5'-O-(3-Tiotrifosfato)/farmacología , Magnesio/farmacología , Masculino , ARN Mensajero/análisis , Ratas , Ratas EndogámicasRESUMEN
Epidermal growth factor (EGF) causes rapid increases in free intracellular Ca2+ and stimulates the phosphorylation of 11 cytosolic proteins in hepatocytes. Ten of the 11 cytosolic proteins altered by EGF are identical to those affected by angiotensin II, a hormone that stimulates the breakdown of phosphatidylinositol 4,5-bisphosphate. An increase in the phosphorylation of the other protein, spot c (Mr = 36,000, pI = 5.5), is observed only with EGF. Treatment of intact rats with pertussis toxin to ADP-ribosylate Ni, the inhibitory GTP-binding protein of the adenylate cyclase complex, abolished the effect of EGF on Ca2+ mobilization and on the phosphorylation of the 10 proteins affected in common with angiotensin II. This treatment had minimal effects on the ability of EGF to stimulate the phosphorylation of its unique substrate, spot c. In marked contrast, modification of Ni did not block the ability of angiotensin II to stimulate Ca2+ mobilization or protein phosphorylation. Pretreatment of normal hepatocytes with 4 beta-phorbol 12-myristate 13-acetate blocked all responses to EGF, including the increased phosphorylation of spot c, but had no effect on the responses to angiotensin II. These results imply that Ni or a similar pertussis toxin substrate may mediate the apparent effects of EGF on phosphatidylinositol breakdown and that protein kinase C may regulate a site in the transduction pathway. Angiotensin II appears to use a different signal transduction mechanism to stimulate phosphatidylinositol metabolism in hepatocytes.
Asunto(s)
Toxina de Adenilato Ciclasa , Angiotensina II/farmacología , Calcio/metabolismo , Diglicéridos/metabolismo , Factor de Crecimiento Epidérmico/farmacología , Glicéridos/metabolismo , Fosfatos de Inositol/metabolismo , Hígado/fisiología , Toxina del Pertussis , Forboles/farmacología , Fosfatos de Azúcar/metabolismo , Acetato de Tetradecanoilforbol/farmacología , Factores de Virulencia de Bordetella/farmacología , Aminoquinolinas , Animales , Proteínas de Unión al GTP/metabolismo , Punto Isoeléctrico , Masculino , Peso Molecular , Fosfoproteínas/metabolismo , RatasRESUMEN
Pertussis toxin catalyzes the ADP-ribosylation of the inhibitory subunit (Ni) of adenylate cyclase. Despite several studies which demonstrate that pertussis toxin influences cyclic AMP accumulation and hormone secretion in normal anterior pituitary cells, the target protein(s) for this toxin in these cells has not been identified. We have examined pertussis toxin mediated ADP-ribosylation in membrane preparations of tumor-derived (235-1, GH4C1, GH3) and normal anterior pituitary cells. Autoradiograms of SDS gels reveal that in the presence of [32P]NAD and pertussis toxin, a 40 kilodalton protein band was labeled in membrane preparations from cells cultured with vehicle. Such labeling was diminished when the cells were exposed to pertussis toxin (35 ng/ml) for 18 hours. Similar results were found in both tumor-derived and normal (monkey and rat) anterior pituitary cells. The pertussis toxin specific band was further resolved into two bands of approximately 39 and 41 kilodaltons. Autoradiograms of two dimensional gels revealed two ADP-ribosylated spots with isoelectric points of 5.7 and 6.2, although the molecular weights appeared identical (approx. 40 kilodaltons). Cholera toxin, which catalyzes the ADP-ribosylation of a 45 kilodalton protein did not prevent labeling of the pertussis toxin-specific band(s) in cells pretreated with cholera toxin. These results suggest that pertussis toxin specifically mediates ADP-ribosylation of the Ni protein in normal anterior pituitary cells.
Asunto(s)
Adenosina Difosfato Ribosa/metabolismo , Toxina de Adenilato Ciclasa , Proteínas de la Membrana/metabolismo , Azúcares de Nucleósido Difosfato/metabolismo , Toxina del Pertussis , Adenohipófisis/metabolismo , Factores de Virulencia de Bordetella/farmacología , Adenilil Ciclasas/metabolismo , Animales , Línea Celular , Membrana Celular/metabolismo , Toxina del Cólera/farmacología , Electroforesis en Gel de Poliacrilamida , Femenino , Macaca fascicularis , Masculino , Peso Molecular , Adenohipófisis/enzimología , Ratas , Ratas Endogámicas , Factores de TiempoRESUMEN
Angiotensin II can inhibit glucagon-stimulated cyclic AMP production in hepatocytes and adenylate cyclase activity in hepatic membranes. Pertussis toxin, an exotoxin produced by Bordetella pertussis, was used to investigate the role of the inhibitory guanine nucleotide-binding regulatory protein of adenylate cyclase (Ni) in coupling angiotensin receptors to the adenylate cyclase system. An assay was developed using [32P] NAD+ to quantitate the amount of Ni protein in the membrane and the extent of its ADP-ribosylation catalyzed by toxin. The ability of angiotensin to inhibit adenylate cyclase and interact with its receptor was compared with the degree of modification of Ni in membranes prepared from isolated hepatocytes. In control membranes angiotensin II inhibited basal adenylate cyclase by 35%. When all of the Ni molecules in the membrane were ADP-ribosylated, angiotensin did not inhibit adenylate cyclase. However, the attenuation of angiotensin's effect on cyclase was not linearly correlated with the degree of modification of Ni; ADP-ribosylation of greater than 80% of the Ni was required before a reduction of the angiotensin effect was observed. A possible explanation for this finding is an excess of Ni molecules in the membrane (approximately 3.4 pmol/mg of membrane protein) over angiotensin II receptors (approximately 1.2 pmol/mg of membrane protein). 125I-angiotensin bound to sites in the membrane with two affinities. Computer fitting of the binding isotherms yielded parameters of N1 = 279 fmol/mg protein, Kd1 = 0.2 nM; N2 = 904 fmol/mg protein, Kd2 = 1.4 nM. When all of the Ni molecules in the membrane were ADP-ribosylated, angiotensin bound to only one site with binding parameters of N = 349 fmol/mg protein, Kd = 0.4 nM. GTP-gamma-S caused a 7-fold increase in the Kd of this site to 2.7 nM. Overall, the data indicate that the Ni protein mediates the effect of angiotensin on adenylate cyclase. The observation that GTP-gamma-S can markedly decrease the affinity of angiotensin receptors when all Ni molecules are ADP-ribosylated suggests that angiotensin receptors may couple to other GTP-binding proteins which may mediate the effects of angiotensin in other signal transduction systems.