Effects of silica on human lung fibroblast in culture

Silica has been reported to directly stimulate cellular proliferation of hu man lung fibroblasts, and silica-treated macrophage supernatants induce fib roblast proliferation and some of their biosynthetic activities. Alveolar m acrophages produce increased amount of tumour necrosis factor alpha (TNF-al pha) and transforming growth factor beta (TGF-beta). Lung fibroblasts are p roducers of interleukin-6 (IL-6). We investigated the capacity of lung fibr oblasts obtained from normal and silicosis subjects to elaborate IL-6 in re sponse to TNF-alpha and to TGF-beta. Our data show that TNF-alpha and TGF-b eta are able to stimulate the proliferation of human lung fibroblasts in cu lture, to increase the collagen production of the cells and are both able t cs increase IL-6 production by lung fibroblasts of patients with silicosis. We hypothesise that silica is able to stimulate lung fibroblast both direc tly, increasing the cell proliferation, and indirectly stimulating the rele ase of factors las TNF-alpha and TGF-beta) from activated alveolar macropha ges, that are able to increase proliferative and biosynthetic activities of fibroblast. (C) 2001 Elsevier Science B.V. All rights reserved.