Transforming Growth Factor (TGF)-β Type I Receptor Kinase (ALK5) Inhibitor Alleviates Profibrotic TGF-β1 Responses in Fibroblasts Derived from Peyronie's Plaque

Abstract

Transforming growth factor-β1 (TGF-β1) has been identified as an important fibrogenic cytokine associated with Peyronie's disease (PD). The aim of this study was to study the differential expression of the TGF-β1 and Smad transcription factors in plaque tissue from PD patients and to determine the antifibrotic effect of SKI2162 (SK Chemicals, Seoul, South Korea), a novel small-molecule inhibitor of activin receptor-like kinase 5 (ALK5), a type I receptor of TGF-β, in primary fibroblasts derived from human PD plaque. Plaque tissue was isolated from five PD patients, and tunica albuginea tissue was obtained from four control patients. Plaque tissues from a patient with PD were used for primary fibroblast culture. Fibroblasts were pretreated with SKI2162 (10 µM) and then stimulated with TGF-β1 (10ng/mL). The plaque or tunica albuginea tissue was stained with Masson's trichrome or antibody to TGF-β1, phospho-Smad2 (P-Smad2), and P-Smad3. Protein was extracted from treated fibroblasts for Western blotting, and the membranes were probed with antibody to P-Smad2/Smad2, P-Smad3/Smad3, plasminogen activator inhibitor-1, fibronectin, collagen I, and collagen IV. We also determined the inhibitory effect of SKI2162 on TGF-β1-induced nuclear translocation of Smad2/3 in fibroblasts. The plaque tissue from PD patients showed higher TGF-β1, P-Smad2, and P-Smad3 immunoreactivity than did the tunica albuginea tissue from control patients. SKI2162 not only blocked TGF-β1-induced phosphorylation and nuclear translocation of Smad2 and Smad3, but also inhibited the production of extracellular matrix markers in fibroblasts derived from human PD plaque. In light of the pivotal role of TGF-β and Smads in the pathogenesis of PD, pharmacologic inhibition of ALK5 may represent a novel targeted approach to treating PD.