Endothelin is a downstream mediator of profibrotic responses to transforming growth factor beta in human lung fibroblasts

OBJECTIVE: Fibrosis is excessive scarring caused by the accumulation and contraction of extracellular matrix proteins and is a common end pathway in many chronic diseases, including scleroderma (systemic sclerosis SSc]). Indeed, pulmonary fibrosis is a major cause of death in SSc. Transforming growth factor beta (TGFbeta) induces endothelin 1 (ET-1) in human lung fibroblasts by a Smad-independent, JNK-dependent mechanism. The goal of this study was to assess whether ET-1 is a downstream mediator of the profibrotic effects of TGFbeta in lung fibroblasts. METHODS: We used a specific endothelin receptor antagonist to determine whether ET-1 is a downstream mediator of TGFbeta responses in lung fibroblasts, using microarray technology, real-time polymerase chain reaction, and Western blot analyses. RESULTS: The ability of TGFbeta to induce the expression of a cohort of profibrotic genes, including type I collagen, fibronectin, and CCN2, and to contract a collagen gel matrix, depends on ET-1. CONCLUSION: ET-1 contributes to the ability of TGFbeta to promote a profibrotic phenotype in human lung fibroblasts, consistent with the notion that endothelin receptor antagonism may be beneficial in controlling fibrogenic responses in lung fibroblasts.