Tachykinin NK3-receptor deficiency does not inhibit pulmonary eosinophilia in allergic mice.

Tachykinins are important in the development of pulmonary inflammation in mice but the tachykinin receptor subtype mediating this response has not been defined. To elucidate the role of tachykinin NK3-receptors on allergen-induced pulmonary inflammation, studies were performed on ovalbumin (OVA) sensitized and challenged mice with genetic disruption of the tachykinin NK3-receptor (NK3-/-). Aerosol OVA (0.5%) challenge produced eosinophil influx into the bronchoalveolar lavage fluid and lung tissue, goblet cell hyperplasia and damage to the airway epithelium of both NK3-/- mice and in wild type control mice (NK3+/+). There was no difference in the magnitude of these allergic inflammatory pulmonary responses between NK3-/- and NK3+/+ mice. These results find no role for tachykinin NK3-receptors on the pulmonary eosinophilia and lung damage after antigen challenge in mice.

Determination of plasma concentrations of SCH 44643 by a GC method and correlation of plasma concentration and anti-PAF activity in cynomolgus monkeys.

Inhibiting the action of platelet-activating factor (PAF) is a new therapeutic approach for the treatment of allergic disorders. SCH 44643 is a new orally-active antagonist of response to both PAF and histamine. This study was done to determine plasma drug concentrations using a GC method and to compare them to ex-vivo anti-PAF activity in the plasma of cynomolgus monkeys following a single oral (12.5 mg kg-1) administration. The GC method involved organic solvent extraction of monkey plasma followed by a GC analysis in a RTX-1 capillary column with a nitrogen/phosphorus detector. The method showed good precision (RSD < 8%) and accuracy (bias < 9%) with a limit of quantitation of 20 ng ml-1. The plasma profiles of SCH 44643 concentration and anti-PAF activity were very similar in each of the six monkeys. There was an excellent correlation (r = 0.9003) between anti-PAF activity and plasma concentration of SCH 44643, suggesting that the anti-PAF activity in cynomolgus monkeys was primarily due to unchanged SCH 44643, rather than its potential metabolite(s).

Interferon-alpha down-regulates the interleukin-6 receptor in a human multiple myeloma cell line, U266.

The effects of interferon-alpha (IFN-alpha) on the interleukin-6 (IL-6) receptor in a multiple myeloma cell line, U266, have been examined. IFN-alpha inhibits [3H]thymidine incorporation in U266 cells in a time- and dose-dependent manner. Furthermore, IFN-alpha inhibits the ability of IL-6 to induce increases in [3H]thymidine incorporation. While IFN-alpha suppresses the ability of 125I-IL-6 to bind to the IL-6 receptor on U266 cells, this effect is not due to competition of IFN-alpha with IL-6 for the IL-6 receptor. Although IFN-alpha induces IL-6 synthesis in the U266 cell, inhibition of IL-6 binding occurs when IL-6 synthesis is minimal. Furthermore, after pretreatment of U266 cells with neutralizing anti-IL-6 antibodies, IFN-alpha still inhibits 125I-IL-6 binding. These data suggest that IFN-alpha inhibition of 125I-IL-6 binding does not involve IL-6 synthesis. IFN-alpha reduces 125I-IL-6 binding without affecting its affinity, suggesting that IFN-alpha inhibits IL-6 receptor expression. Although pretreatment with cycloheximide inhibits 125I-IL-6 binding, IFN-alpha does not cause a selective decrease in the levels of gp130 or IL-6 receptor mRNA at times when 125I-IL-6 binding is inhibited. These observations indicate that IFN-alpha lowers IL-6 receptor density on U266 cells by mechanisms other than competitive binding or lowering IL-6 receptor mRNA production. Receptor down-regulation may be a mechanism of IFN-alpha-induced inhibition of growth in U266 cells.

Differential plasma duration of antiplatelet-activating factor and antihistamine activities of oral Sch 37370 in humans.

Preclinical studies have established that Sch 37370 (1-acetyl-4-(8-chloro-5,6-dihydro-11H-benzo[5,6]-cyclohepta [1,2-b]pyridin-11-ylidene)piperidine) is an orally active antagonist of platelet-activating factor (PAF) and histamine H1-receptors with potential therapeutic use in the treatment of asthma. To evaluate the efficacy and duration of anti-PAF and antihistamine actions of oral Sch 37370 in humans, a single dose (5 mg/kg) of Sch 37370 was given orally to each of 10 male subjects in a placebo-controlled, double-blind crossover study. Blood samples were drawn before and at various times (2 to 48 hours) after Sch 37370 or placebo. Plasma samples were analyzed for Sch 37370 by a gas chromatographic method, for the anti-PAF activity by measuring the aggregation of platelets stimulated with PAF, and for the antihistamine activity by measuring displacement of [3H]pyrilamine from rat brain membrane binding sites. The plasma anti-PAF activity declined from high levels at 2 hours to barely detectable levels at 24 hours; however, significant activity was still present at 12 hours. The plasma levels of Sch 37370 closely paralleled the anti-PAF profile. The plasma antihistamine activity reached a maximum within 2 to 8 hours and declined thereafter. However, 48 hours after Sch 37370, the antihistamine activity was still present at a significant level in most subjects. It is concluded that, in humans, oral Sch 37370 antagonizes both PAF and histamine with plasma antihistamine activity lasting longer than plasma anti-PAF activity.

Sch 37370: a potent, orally active, dual antagonist of platelet-activating factor and histamine.

Platelet-activating factor (PAF) and histamine are potent bronchospastic agents and possess additional properties such as induction of vasopermeability and activation of inflammatory cells that are consistent with their ability to mediate allergic and inflammatory responses. From a structural series with anticipated antihistamine activity, Sch 37370 (1-acetyl-4(8-chloro-5,6-dihydro-11H-benzo[5,6]cyclohepta[1,2- b]pyridine-11-ylidine)piperidine) has been identified as a dual antagonist of PAF and histamine in vitro and in vivo and has been compared with several selective antagonists of PAF and histamine. Sch 37370 selectively inhibits PAF-induced aggregation of human platelets (IC50 = 0.6 microM) and also competes with PAF binding to specific sites in membrane preparations from human lungs (IC50 = 1.2 microM). Sch 37370 blocks the binding of [3H]pyrilamine to histamine-H1 receptors in rat brain membranes. Administered i.v. to guinea pigs, Sch 37370 is an equipotent antagonist of PAF and histamine-induced bronchospasm (ED50 = 0.6-0.7 mg/kg). Orally in guinea pigs, Sch 37370 is somewhat more effective against bronchospasms to histamine (ED50 = 2.4 mg/kg) than against PAF (ED50 = 4.1-6.0 mg/kg) or serotonin (ED50 = 9.6 mg/kg). Sch 37370 only weakly antagonizes methacholine-induced bronchospasm (ED50 = 51 mg/kg) and is completely inactive at 50 mg/kg against leukotriene C4 or substance P. Sch 37370 blocks hypotension in rats and a cutaneous reaction in monkeys induced by either PAF or histamine, as well as PAF-induced lethality in mice.(ABSTRACT TRUNCATED AT 250 WORDS)

Edema formation and neutrophil mobilization in the neutropenic rat.

The relationship between leucocyte mobilization and edema formation was evaluated in the carrageenan pleurisy model. In normal rats carrageenan was able to mobilize between 80 and 100 million cells per ml of fluid. In neutropenic rats the concentration fell to between 20 and 50 million cells per ml, suggesting the edema formed after carrageenan injection is not directly correlated with cellular mobilization.