Release of prostaglandin E(2) and leukotriene B-4 by alveolar macrophages from patients with sarcoidosis

Background - Mediators released by alveolar macrophages, as well as by T cells, play an important part in modulating local immune processes in sarcoidosis. Among alveolar macrophage secretory products, arachidonic acid metabolites are known to regulate inflammatory and immune reactions. It has been suggested that cyclooxygenase and lipoxygenase pathway metabolites of arachidonic acid modulate the evolution of the granulomatous inflammatory response in the lung differently. Methods - Alveolar macrophages recovered from the bronchoalveolar lavage (BAL) fluid of 32 patients with sarcoidosis in different states of disease activity and 10 normal subjects were evaluated for their ability to release prostaglandin E(2) (PGE(2)) and leukotriene B-4 (LTB(4)). Alveolar macrophages were cultured in the presence or absence of opsonised zymosan (500 mu g/ml), and PGE(2) and LTB(4) levels in the culture supernatants were determined by enzyme immunoassay (EIA). Results - Stimulated alveolar macrophages from patients with active sarcoidosis released higher LTB(4) levels than those from normal subjects, but no differences in PGE(2) release were observed between the two groups. The time course of LTB(4) release by activated alveolar macrophages showed that normal cells produced similar levels of the hydroxyacid during the early and late times of culture while LTB(4) release by activated cells from patients with sarcoidosis increased markedly after 60 minutes of culture, remaining elevated until 24 hours. Indomethacin (3 x 10(-6) M) caused the expected inhibition of PGE(2) formation without affecting LTB(4) release. Conclusions - These results suggest that alveolar macrophages from the BAL fluid of patients with active sarcoidosis are primed to release LTB(4), which may contribute to the locally heightened immune response.