The effect of cotton bract extract on respiratory glycoconjugate secretion from human airways in vitro

In vivo and in vitro studies with a water-soluble extract of cotton bracts (CBE) suggest that CBE may be responsible for some of the clinical manifestations of byssinosis. Since chronic bronchitis has been repeatedly documented as a major feature of byssinosis, we studied the effect of CBE on respiratory glycoconjugate (RGC) release from human airways (HAs) in vitro. HAs were incubated with [3H]glucosamine to label RGC molecules. CBE in increasing concentrations was added to radiolabeled HAs, and the release of 3H-RGC, histamine, and other mediators was measured. CBE in concentrations of 1 to 7 mg/ml caused a dose-related increase in RGC, as well as histamine release (RGC, 14% to 45% increase above control; histamine, 12 to 70 ng/ml released concurrently). Additionally, CBE in a dose of 5 mg/ml caused a more than threefold increase in peptidoleukotriene production above baseline. The effect of histamine H1 and H2 (pyrilamine and cimetidine), cyclooxygenase pathway inhibitor (indomethacin), leukotriene (LY 171883 and FPL 55712), and lipoxygenase pathway (BW nordihydroguaiarectic acid) blocking agents on CBE-induced RCG secretion was studied. In addition to histamine-H1 blockers, lipoxygenase inhibitors (nordihydroguaiarectic acid and BW 755C) and leukotriene blockers (FPL 55712 and LY 171883) are also potent inhibitors of CBE-induced RGC secretion. This suggests that CBE may act via the release of several mediators (histamine and leukotrienes), possibly from airway cells, such as mast cells, macrophages, or epithelial cells, to stimulate RGC secretion.