Byssinosis: Thromboxane Release From Human Platelets by Cotton Dust and Bract Extracts

ABSTRACT

Extracts of cotton dust and bract induced in vitro release of arachidonic acid metabolite thromboxane A₂ (TxA₂), a potent bronchoconstricting agent, from human platelets. TxA₂ release, determined by radioimmunoassay of the stabile metabolite TxB₂, was both time- and dose-dependent. Cotton green bract extract was significantly more potent in releasing TxA₂ from human platelets than cotton dust extract or cotton brown bract (field-dried bract) extract, while brown bract extract was least active, which suggests that the etiological agent(s) is of plant origin and not microbial in nature. TxA₂ release was shown to be enzyme-dependent by inhibition of the reaction by indomethacin (cydooxygenase inhibitor) and 7-(1-imidazolyl) heptanoic acid (thromboxane synthetase inhibitor). This study is the first to show in vitro platelet TxA₂ release by cotton extracts and may provide an explanation for increased concentrations of TxB₂, a metabolite of TxA₂, in the bronchoalveolar spaces of rabbits exposed to aerosolized cotton dust extract. Platelet aggregation and production of TxA₂ may prove to be an important mechanism in the pathogenesis of bronchoconstriction in byssinosis.