Endothelin 1 contributes to the effect of transforming growth factor β1 on wound repair and skin fibrosis

Objective To characterize the pathways induced by transforming growth factor β1 (TGFβ1) that lead to the expression of endothelin 1 (ET‐1) in human dermal fibroblasts, and to study the effects of TGFβ1 and ET‐1 on the acquisition of a profibrotic phenotype and assess the contribution of the TGFβ1/ET‐1 axis to skin wound healing and fibrosis in vivo. Methods The mechanism of induction of ET‐1 expression by TGFβ1 and its effect on the expression of α‐smooth muscle actin and type I collagen were studied in human dermal fibroblasts, in experiments involving the TGFβ receptor inhibitor GW788388 and the ET receptor antagonist bosentan, by real‐time reverse transcription–polymerase chain reaction (RT‐PCR), enzyme‐linked immunosorbent assay, immunofluorescence, Western blotting, and promoter/reporter transient transfection analyses. Experiments assessing dermal wound healing in mice were performed with adenovirus‐driven overexpression of active TGFβ1 and ET‐1, with or without treatment with bosentan. The contributions of TGFβ1 and ET‐1 to the fibrotic response were also assessed in a mouse model of bleomycin‐induced skin fibrosis, by histologic, immunohistochemical, RT‐PCR, and protein analyses. Results TGFβ1 induced ET‐1 expression in human dermal fibroblasts through Smad‐ and activator protein 1/JNK–dependent signaling. The ability of TGFβ1 to induce the expression of profibrotic genes was dependent on ET‐1. Adenovirus‐mediated overexpression of TGFβ1 and ET‐1 in mouse skin was associated with accelerated wound closure, increased fibrogenesis, and excessive scarring. Treatment with bosentan prevented the effects of TGFβ1. In the bleomycin‐induced fibrosis model, treatment with GW788388 and bosentan prevented the fibrotic response. Conclusion Our results strongly support the notion that the TGFβ1/ET‐1 axis has a role in wound repair and skin fibrosis. ET‐1 receptor antagonists, such as bosentan, may represent a useful therapeutic tool in the treatment of excessive scarring and fibrosis‐related diseases.