Background/Purpose: Activated myofibroblasts are the primary mediators of the excessive synthesis and deposition of collagens and other extracellular matrix (ECM) macromolecules during the pathogenesis of fibrotic diseases including Systemic Sclerosis (SSc). TGF-β signaling plays a pivotal role in the differentiation and activation of myofibrolasts.  Salinomycin, a polyether ionophore antibiotic isolated from Streptomyces albus has been shown to cause a selective inhibition of cancer stem cells. Recently, salinomycin has been reported to possess potent anti-myofibroblast properties, specifically targeting TGF-β-mediated myofibroblast activation and to inhibit TGF-β-induced collagen production, cell proliferation, contraction and migration in cultured primary normal human fibroblasts. The purpose of these studies was to perform a dose-response analysis of the effect of salinomycin on the expression of profibrotic genes in cultured dermal fibroblasts isolated from normal donors and donors with SSc to evaluate whether the reported inhibition of the profibrotic consequences of TGF-β signaling will produce an effect on dermal fibroblasts isolated from SSc donors.

Methods: Normal and SSc dermal fibroblasts were cultured in the presence of 100, 250 or 500 nM salinomycin alone or in combination with 10 ng/mL TGF-β1. After 72 hours, total RNA was isolated and the effects of salinomycin on the expression of profibrotic genes were assess by semiquantitative RT-PCR in triplicate on three replicates per normal and SSc cell line. Levels of ECM proteins in culture media and levels of α-SMA in cell lysates were evaluated by Western blot.

Results: Treatment of both cultured normal and SSc dermal fibroblasts with salinomycin induced a potent concentration-dependent decrease in the expression of several genes associated with fibrosis, including type I and type III collagens (COL1A1 and COL3A1), fibronectin 1 (FN1) and the FN-EDA splice variant as well as decreased expression of the myofibroblast marker  α-SMA. A similar effect was observed in TGF-β-treated normal and SSc fibroblasts. Remarkably, treatment of SSc fibroblasts with salinomycin caused a potent downregulation of the elevated levels of profibrotic gene transcripts in these cells.

Conclusion: The observed effects of salinomycin on cultured dermal fibroblasts from normal and SSc donors are consistent with its reported ability to suppress TGF-β-mediated myofibroblast differentiation and activation. Intriguingly, the ability of salinomycin to greatly reduce expression of COL1A1, COL3A1, FN1, FN-EDA and α-SMA was also seen in non-TGF-β treated cells from SSc donors, thus strongly supporting the concept that salinomycin may represent a potent and novel antifibrotic agent for the treatment of SSc.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/salinomycin-induces-potent-suppression-of-tgf-1-mediated-expression-of-profibrotic-genes-in-cultured-dermal-fibroblasts-from-normal-donors-and-from-donors-with-systemic-sclerosis-ssc-a-novel/