-
Views
-
Cite
Cite
Attila Sebe, Suvi-Katri Leivonen, Attila Fintha, Andras Masszi, Laszlo Rosivall, Veli-Matti Kähäri, Istvan Mucsi, Transforming growth factor-β-induced alpha-smooth muscle cell actin expression in renal proximal tubular cells is regulated by p38β mitogen-activated protein kinase, extracellular signal-regulated protein kinase1,2 and the Smad signalling during epithelial–myofibroblast transdifferentiation, Nephrology Dialysis Transplantation, Volume 23, Issue 5, May 2008, Pages 1537–1545, https://doi.org/10.1093/ndt/gfm789
Close - Share Icon Share
Abstract
Background. Transforming growth factor-β (TGFβ)-induced epithelial–myofibroblast transdifferentiation is a central mechanism contributing to the pathogenesis of progressive tubulo-interstitial fibrosis. We wanted to dissect the role of extracellular signal-regulated protein kinase (ERK1,2), p38 mitogen-activated protein kinase (p38 MAPK) and the receptor-regulated Smad proteins in the regulation of α-smooth muscle cell actin (αSMA) expression, a hallmark of myofibroblast formation, induced by TGFβ in renal proximal tubular cells.
Methods. Activation of signalling molecules was assessed by western blotting using phospho-specific antibodies. To specifically interfere with signalling cascades, porcine proximal tubular cells (LLC-PK/AT1) were infected with recombinant replication-deficient adenoviruses. In other experiments, specific kinase inhibitors were used. The αSMA synthesis was assessed by western blotting or immunofluorescent staining of cellular αSMA. To assess the regulation of the αSMA promoter, tubular cells were transiently transfected with a 785 bp αSMA promoter–luciferase reporter construct and vectors interfering with the Smad pathway.
Results. Blocking ERK1,2 activation with PD98059 or p38 MAPK with SB 203580 potently inhibited the TGFβ-induced αSMA synthesis in renal tubular cells. Adenoviral expression of dominant negative (DN) p38β but not of p38α potently inhibited αSMA expression. Furthermore, adenoviral expression of DN MKK6b but not of DN MKK3b caused a substantial inhibition of the TGFβ effect, confirming the role of p38β in the regulation of TGFβ-induced αSMA expression. Finally, inhibiting the Smad pathway with adenovirally delivered Smad7 and DN Smad3 also blocked TGFβ-induced αSMA synthesis.
Conclusion. TGFβ-induced αSMA expression is regulated by the coordinated activation of a complex system of parallel MAPK and Smad signalling pathways in renal proximal tubular cells during epithelial–mesenchymal transdifferentiation.
Comments