IM-412 inhibits transforming growth factor β-induced fibroblast differentiation in human lung fibroblast cells

Abstract

Pulmonary fibrosis is a type of interstitial lung disease that causes progressive scarring in lung tissues. Although there have been many studies on fibrosis, there is no standard treatment for fibrotic disease. Thus, there is an urgent need for the development of effective anti-fibrotic drugs. Transforming growth factor β (TGF-β) is a major fibrotic mediator known to stimulate fibrosis. To identify small molecules that inhibit TGF-β responses, we performed cell-based chemical screening using genetically engineered HEK293 reporter cells. Among 8000 chemical compounds containing biologically active natural products and synthetic or clinically used compounds, we found that 3-(2-chlorobenzyl)-1,7-dimethyl-1H-imidazo[2,1-f]purine-2,4(3H,8H)-dione (IM-412) significantly decreased TGF-β stimulated reporter activity in a dose-dependent manner. In addition, IM-412 inhibited TGF-β-induced expression of the fibrotic markers α-smooth muscle actin (α-SMA) and fibronectin, and collagen accumulation in CCD-18Lu human normal lung fibroblasts without cell cytotoxicity. IM-412 decreased Smad2 and -3 phosphorylation as well as JNK and ERK activity. Moreover, expression levels of TGF-β receptor I (TβRI) and receptor II (TβRII) were down-regulated by IM-412 in a dose-dependent manner. Thus, our findings indicate that the small molecule IM-412 attenuated TGF-β-mediated fibroblast differentiation through inhibition of the overall TGF-β response and may be a promising novel agent for the treatment of pathological fibrotic conditions.