2-methyl-6-(4-methoxyphenyl)-3-7-dihydroimidazo(1-2-alpha)pyrazin-3-one and Asthma

Blood was drawn from healthy human volunteers and a 30-year-old woman with severe bronchial asthma (atopic and perennial type), whose peripheral blood platelets counts were continuously higher than 60 x 10(4)/mm3. Neutrophils were purified on a Conray-Ficoll gradient and platelets were isolated by a gel filtration method with Sepharose 2B. Superoxide anion (O2-) generation from the cells was measured by 2-methyl-6-[p-methoxyphenyl]-3,7-dihydroimidazo [1,2-a]purazin-3-one (MCLA)-dependent luminescence. Addition of 0.5 microM MCLA and 10(-8) M N-formyl-methionyl-leucyl-phenylalanine (fMLP) or 10 ng/ml phorbol myristate acetate (PMA) to a suspension of platelets obtained from the healthy controls and the patient caused no significant MCLA-dependent luminescence, 02- generation by neutrophils from healthy human volunteers, activated by 10(-8) M fMLP or 10 ng/ml PMA, was inhibited by their platelets in a concentration-dependent manner. Platelets from the patient failed to inhibit O2- generation from neutrophils activated by 10(-8)M fMLP. Cu-Zn superoxide dismutase concentrations in platelets from healthy human volunteers were not higher than the patient's. These data suggest that the absence of inhibition of superoxide generation from activated neutrophils by platelets might be involved in the pathogenesis of bronchial asthma.

Topics: Adult; Asthma; Blood Platelets; Cell Communication; Chromatography, Gel; Female; Humans; Imidazoles; Luminescent Measurements; Neutrophils; Platelet Count; Pyrazines; Superoxide Dismutase; Superoxides

Airway inflammation with polymorphonuclear leukocytes (PMN) may play an important role in bronchial hyperresponsiveness (BHR). PMN generate superoxide anion (O2-) and other oxygen radicals that can damage lung tissue. We investigated the ability of peripheral PMN of children with bronchial asthma and control subjects to generate O2- and other active oxygen species using a 2-methyl-6-(p-methoxyphenyl)-3,7-dihydroimidazo[1,2-a]pyrazin++ +-3-one, a highly sensitive and specific chemiluminescence (CL) probe for O2-, and luminol-dependent CL. The ability of PMN of subjects with asthma to generate O2- and other active oxygen species was significantly greater than that of PMN of control subjects when stimulated with opsonized zymosan (OZ), phorbol myristate acetate or N-formyl-methionyl-leucyl-phenylalanine. Furthermore, in the same asthmatic children, the generation of O2- and other active oxygen species was significantly higher with attacks than without attacks when PMN were stimulated with OZ. We also demonstrated that O2- generation correlated with the degree of BHR to inhaled histamine. These results suggest that PMN of asthmatic children, especially those with attacks, generate more active oxygen species than that of control subjects and that airway inflammation caused by O2- may be closely related to BHR in subjects with bronchial asthma.

Topics: Adolescent; Adult; Asthma; Bronchial Hyperreactivity; Bronchial Provocation Tests; Child; Child, Preschool; Female; Humans; Imidazoles; Luminol; Lymphocyte Activation; Male; Neutrophils; Pyrazines; Superoxides