Regulation of human lung fibroblast collagen production by recombinant interleukin-1, tumor necrosis factor, and interferon-gamma.

Several cytokines have been shown to modulate the synthesis of matrix molecules, but few reports have defined how the cytokines interact with one another in mediating these regulatory effects. To define the cytokine network regulating collagen production, we have studied the effects of interferon-gamma, interleukin-1, and tumor necrosis factor on collagen synthesis by cultured human lung fibroblasts. Confluent cells were treated with cytokines for 24 h in the absence of serum or in media containing 1% serum. In the absence of serum, IL-1 and TNF each dose-dependently stimulated types I and III collagen production, with a maximal 2-4-fold increase in collagen accumulation being observed. Cells treated with IL-1 and TNF in combination showed less stimulation than with either cytokine alone. IFN-gamma also diminished the stimulatory effects of both IL-1 and TNF. In contrast, in 1% serum IL-1 and TNF individually had relatively minor effects, while IFN-gamma inhibited collagen production. However, the combination of IL-1 and TNF inhibited collagen production. Generally, these effects were achieved through control of mRNA levels. These studies demonstrate the existence of a cytokine network regulating fibroblast collagen production and suggest that cytokine effects in vivo may vary depending upon the constellation of factors present in the tissue.