Effects of silica on human lung fibroblast in culture

Silica has been reported to directly stimulate cellular proliferation of human lung fibroblasts, and silica-treated macrophage supernatants induce fibroblast proliferation and some of their biosynthetic activities. Alveolar macrophages produce increased amount of tumour necrosis factor alpha ŽTNF- . and transforming growth factor beta ŽTGF- .. Lung fibroblasts are producers of interleukin-6 ŽIL-6.. We investigated the capacity of lung fibroblasts obtained from normal and silicosis subjects to elaborate IL-6 in response to TNF- and to TGF- . Our data show that TNF- and TGF- are able to stimulate the proliferation of human lung fibroblasts in culture, to increase the collagen production of the cells and are both able to increase IL-6 production by lung fibroblasts of patients with silicosis. We hypothesise that silica is able to stimulate lung fibroblast both directly, increasing the cell proliferation, and indirectly stimulating the release of factors Žas TNF- and TGF- . from activated alveolar macrophages, that are able to increase proliferative and biosynthetic activities of fibroblast