ALVEOLAR MACROPHAGES MODULATE THE EPITHELIAL-CELL RESPONSE TO COAL-DUST IN-VITRO

The response of the alveolar epithelium to coal dust exposure is poorl y understood. Coal or other dusts may act on the epithelium directly o r indirectly through nearby alveolar macrophages (AM) that produce cyt okines and other soluble products. AM and type II pneumocytes (T2P) we re thus exposed to dust in coculture to evaluate their possible intera ctions. Anthracite coal dust PSOC 867 increased synthesis of extracell ular matrix (ECM) components by T2P. AM alone did not produce ECM. Sim ilarly, coculture of T2P with AM (3.75:1) had little effect on epithel ial ECM synthesis. In contrast, coculture of T2P with AM significantly increased PSOC 867 effects on T2P rates of ECM synthesis, ECM fibrone ctin content, and T2P levels of fibronectin mRNA. AM-conditioned mediu m did not change the PSOC 867 effect on T2P. Neither control nor PSOC 867-treated AM on Falcon culture inserts (0.45-mu m pore size) over T2 P stimulated ECM synthesis by either untreated or dust-exposed epithel ium. Thus AM-mediated changes in ECM synthesis by PSOC 867-treated T2P require close cell-cell interactions, suggesting a role for cell-cell contact or for short-lived soluble mediators of the AM effects.