We investigated the participation of prostaglandin (PG) E2 in the regulation of the alpha 1(I) procollagen gene expression by tumor necrosis factor alpha (TNF alpha), and interleukin-1 beta (IL-1 beta) in normal adult human lung fibroblasts. TNF alpha (100 units/ml) and IL-1 beta (100 units/ml) stimulated the production of PGE2 and caused a dose-dependent inhibition of up to 54 and 66%, respectively, of the production of type I procollagen. Preincubation of cultures with indomethacin partially reversed the inhibition of procollagen production induced by the cytokines. Cytokine-stimulated endogenous fibroblast PG accounted for 35 and 68% of the inhibition induced by TNF alpha and IL-1 beta, respectively. Steady-state mRNA levels for alpha 1(I) procollagen paralleled the changes in collagen production. The transcription rate of the alpha 1(I) procollagen gene was reduced by 58% by TNF alpha and by 43% by IL-1 beta. Cytokine-stimulated endogenous PG production accounted for half of these effects. These results indicate that TNF alpha and IL-1 beta inhibit the expression of the alpha 1(I) procollagen gene in human lung fibroblasts at the transcriptional level by a PGE2-independent effect as well as through the effect of endogenous fibroblast PGE2 released under the stimulus of the cytokines.
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Diaz et al. (1993) studied this question.