Secretory products of alveolar macrophages : stimulation by cotton bract extracts and possible roles in byssinosis

Abstract

Byssinosis, an occupational respiratory disease of cotton workers, is characterized by chest tightness, bronchoconstriction, and neutrophil influx into the airways following inhalation of cotton dust or extracts of cotton dust. The alveolar macrophage (AM) has been shown to be a central cell in inflammatory and immune reactions in the lung. Therefore the in vitro release of inflammatory mediators by cotton bract extract-stimulated rabbit and mouse alveolar macrophages was studied to determine if these cells can contribute to the etiology of byssinosis. It was shown that AM release prostaglandins E and F(,2(alpha)) in a dose-dependent fashion when stimulated with ether-soluble material from aqueous extracts of cotton bract (EECB). Bacterial endotoxin, a contaminant of bract and of aqueous extracts of bract, was not the stimulating agent in EECB, because endotoxin-unresponsive C3H/HeJ mouse AM also release prostaglandins when stimulated by EECB. Rabbit AM also release chemotactic factors (AMCF) for neutrophils and monocytes after in vitro exposure to aqueous bract extract. The release of AMCF began within 4 hours after exposure to aqueous extracts and continued for at least 48 hours. A concentration gradient was necessary for increased migration of target cells through the filter, thus indicating the presence of chemotactic factors rather than chemokinetic factors. Platelet activating factor was released from rabbit AM after stimulation by bract extracts in two of five experiments. Bract extracts did not stimulate AM to release elastase or thromboxane B(,2) in vitro. ...