Apremilast Interferes With The Tgf Beta 1-Induced Transition Of Human Skin Fibroblasts Into Profibrotic Myofibroblasts: In Vitro Study

Objectives. Fibroblast-to-myofibroblast transition and extracellular matrix overproduction represent progressive events in chronic inflammatory and fibrotic diseases, in which TGF beta 1 is one of the key mediators. Phosphodiesterase 4 (PDE4) acts as a proinflammatory enzyme through the degradation of cyclic adenosine monophosphate and it is overexpressed in skin fibroblasts. The study investigated how apremilast (a PDE4 inhibitor) interferes with the intracellular signalling pathways responsible for the TGF beta 1-induced fibroblast-to-myofibroblast transition and profibrotic extracellular matrix protein synthesis.Methods. Cultured human skin fibroblasts were stimulated with TGF beta 1 (10 ng/ml) alone or combined with apremilast (1 and 10 mu M) for 4, 16 and 24h. Other aliquots of the same cells were previously stimulated with TGF beta 1 and then treated with apremilast (1 and 10 mu M) for 4, 16 and 24h, always under stimulation with TGF beta 1. Gene and protein expression of aSMA, type I collagen (COL1) and fibronectin were evaluated, together with the activation of small mothers against decapentaplegic 2 and 3 (Smad2/3) and extracellular signal-regulated kinase (Erk1/2) proteins.Results. Apremilast reduced the TGF beta 1-induced increase in alpha SMA, COL1 and fibronectin gene expression at 4 and 16 h, and protein synthesis at 24 h of treatment in cultured fibroblasts, even for cells already differentiated into myofibroblasts by way of a previous stimulation with TGF beta 1. Apremilast inhibited the TGF beta 1-induced Smad2/3 and Erk1/2 phosphorylation at 15 and 30 min.Conclusion. Apremilast seems to inhibit in vitro the fibroblast-to-myofibroblast transition and the profibrotic activity induced by TGF beta 1 in cultured human skin fibroblasts by downregulating Smad2/3 and Erk1/2 intracellular signalling pathways.