<p>Hypertrophic scarring of the skin is a cause of pain, disfigurement, and restricted mobility. Excessive TGF-β1 signalling leads to SMAD3 phosphorylation, which is implicated in hypertrophic scarring. In this study, we examined the mechanism of action of tomentosenol A, a small compound that we isolated from the propolis of the Australian stingless bee <i>Tetragonula carbonaria</i>. Cultured adult human dermal fibroblasts and HEK293 cells were stimulated with TGF-β1, with or without tomentosenol A, and were assessed for phosphorylation of SMADs 2/3 (Western blot, AlphaLISA assay), SMAD signalling (HEK293 cells expressing a SMAD3 reporter gene), and profibrotic gene transcription using RTqPCR for <i>ACTA2</i> (smooth muscle α-actin), <i>COL1A1</i> and <i>COL3A</i> (collagens), <i>CCN2</i> (connective tissue growth factor) and <i>FN1</i> (fibronectin). Protein expression was measured using ELISA (fibronectin) and visualised via confocal microscopy (smooth muscle α-actin). TGF-β1 increased SMAD3 phosphorylation by 44.3-fold above baseline levels, and this effect was inhibited by tomentosenol A in a concentration-dependent manner (IC<sub>50</sub>, 99.0&#xa0;nM). TGF-β1 stimulated SMAD3 reporter gene expression and upregulated <i>ACTA2, COL1A1</i>, <i>COL3A1</i>, <i>FN1</i> and <i>CCN2</i> transcription; fibronectin protein expression; and smooth muscle α-actin filament formation in fibroblasts. These responses were inhibited by 6.25&#xa0;μM tomentosenol A. These findings indicate that tomentosenol A inhibits TGF-β1/SMAD3 signalling and downstream profibrotic gene transcription and protein expression. As this pathway is implicated in hypertrophic scarring of the skin, tomentosenol A can be developed as a novel therapy for the management of scars caused by deep dermal injuries that are associated with surgery, trauma and burns.</p>

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Propolis compound inhibits profibrotic TGF-β1/SMAD signalling in human fibroblasts

  • Lisa J. Randall,
  • Sarah Bajan,
  • Trong D. Tran,
  • Robert J. Harvey,
  • Fraser D. Russell

摘要

Hypertrophic scarring of the skin is a cause of pain, disfigurement, and restricted mobility. Excessive TGF-β1 signalling leads to SMAD3 phosphorylation, which is implicated in hypertrophic scarring. In this study, we examined the mechanism of action of tomentosenol A, a small compound that we isolated from the propolis of the Australian stingless bee Tetragonula carbonaria. Cultured adult human dermal fibroblasts and HEK293 cells were stimulated with TGF-β1, with or without tomentosenol A, and were assessed for phosphorylation of SMADs 2/3 (Western blot, AlphaLISA assay), SMAD signalling (HEK293 cells expressing a SMAD3 reporter gene), and profibrotic gene transcription using RTqPCR for ACTA2 (smooth muscle α-actin), COL1A1 and COL3A (collagens), CCN2 (connective tissue growth factor) and FN1 (fibronectin). Protein expression was measured using ELISA (fibronectin) and visualised via confocal microscopy (smooth muscle α-actin). TGF-β1 increased SMAD3 phosphorylation by 44.3-fold above baseline levels, and this effect was inhibited by tomentosenol A in a concentration-dependent manner (IC50, 99.0 nM). TGF-β1 stimulated SMAD3 reporter gene expression and upregulated ACTA2, COL1A1, COL3A1, FN1 and CCN2 transcription; fibronectin protein expression; and smooth muscle α-actin filament formation in fibroblasts. These responses were inhibited by 6.25 μM tomentosenol A. These findings indicate that tomentosenol A inhibits TGF-β1/SMAD3 signalling and downstream profibrotic gene transcription and protein expression. As this pathway is implicated in hypertrophic scarring of the skin, tomentosenol A can be developed as a novel therapy for the management of scars caused by deep dermal injuries that are associated with surgery, trauma and burns.