Effect of a leukotriene B4 receptor antagonist, LY293111, on allergen induced responses in asthma.

BACKGROUND: Leukotriene (LT) B4 is a potent neutrophil chemoattractant and also stimulates eosinophils in vitro, but its role in asthmatic inflammation is unknown. METHODS: The effect of the novel LTB4 receptor antagonist, LY293111, was examined using allergen challenge as a model for asthmatic inflammation in 12 atopic asthmatic subjects in a double blind placebo controlled crossover trial. Subjects with an established early (EAR) and late asthmatic response (LAR) to allergen at screening received oral LY293111 in a dose of 112 mg three times daily for seven days or placebo before further allergen challenge. Each treatment was separated by a washout period of 28 days. Individuals underwent histamine challenge one hour before and three hours after allergen challenge. Bronchoalveolar lavage (BAL) fluid was obtained at bronchoscopy 24 hours after allergen challenge. RESULTS: There was no difference in baseline lung function, EAR, LAR, or in airway responsiveness to histamine before and after allergen between placebo and LY293111. By contrast, treatment with LY293111 significantly reduced the number of neutrophils in BAL fluid expressed as both absolute cell numbers and percentage cell differential counts: absolute cell counts, median (range) 0.04 (0.02-0.15) x 10(6) after LY293111, 0.09 (0.02-0.43) x 10(6) after placebo; percentage differential cell counts 0.35 (0.1-2.0) after LY293111, 0.80 (0.1-3.6) after placebo (p < 0.05). Eosinophils, macrophages, and lymphocytes in BAL fluid did not differ between treatments. There was a significant reduction in the concentration of myeloperoxidase (MPO) with both placebo (16 (6.6) ng/ml) and LY293111 (3.5 (1.8) ng/ml) and of LTB4 (placebo 4.6 (1.2) pg/ml, LY293111 2.2 (0.2) pg/ml). Concentrations of LTC4 and interleukin 8 were reduced, although not significantly, whereas concentrations of interleukin 6, GM-CSF, and TNF-alpha were unchanged by LY293111. CONCLUSIONS: These results demonstrate an influence of LTB4 on neutrophil influx and activation in the airway following allergen challenge. Despite this anti-inflammatory effect, there was no measured physiological benefit and this questions the functional role of the neutrophil in the pathophysiology of allergen induced asthma.

Evidence of a novel association of unsaturated fatty acids with Gc (vitamin D-binding protein).

The strong sequence homology described recently between Gc (Vitamin D-binding protein) and albumin, and the ability of the latter, to bind 2-p-toluidinylnaphthylene sulfonate (TNS) promoted similar binding studies with Gc. TNS bound to native Gc as demonstrated by fluorescence, but chloroform:methanol extraction of Gc and gas chromatography revealed that large amounts of unsaturated fatty acids - 16:1, 18:1, 18:2 and 20:4 were also associated with Gc. In addition, TNS fluorescence was abolished by delipidation of Gc, and restored upon subsequent reconstitution with fatty acid. Finally, 70-80% of [3H]-arachidonic acid added to whole serum bound to Gc. These results demonstrated that TNS fluorescence of the native molecule reflects associated lipid, and suggest a novel role for Gc as a reservoir for a circulating pool of unsaturated fatty acids.

Group-specific component (vitamin D binding protein) prevents the interaction between G-actin and profilin.

Profilin purified from human platelets formed a 1:1 molar ratio complex with rabbit skeletal muscle G-actin but was displaced by purified serum Gc (vitamin D binding protein) in a dose-dependent fashion as assessed by chromatography and ultrafiltration. This suggested that Gc and profilin competed for the same binding area on G-actin, with Gc-G-actin complexes being more stable than profilin-G-actin complexes in vitro. The binding domain for Gc on G-actin was localized to a 16,000-Da C-terminal fragment of G-actin generated by Staphylococcus aureus V8 protease, as judged by comigration on two-dimensional electrophoresis and also by overlaying electrophoresis gels with 125I-Gc. Previous studies have reported that residues 374 and 375 of G-actin are essential for binding of profilin. In this study, experiments involving tryptic removal of Cys-374 labeled with the fluorescent probe N-(iodoacetyl)-N'-(5-sulfo-1-naphthyl)-ethylenediamine showed that these C-terminal amino acids were not necessary for interaction with Gc.

The effect of thermal injury on plasma carnitine in rats.

The plasma concentration of L-carnitine in scalded rats was determined to be greater (p less than or equal to 0.05) than that of control rats at 6 h following the administration of a 20% body surface, full-thickness burn produced by scalding in a 100 degrees C water bath for 15 sec.