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Abstract: FR-PO1003

Mycophenolic Acid Decreases TGF-β1 Induced Fibronectin Expression Through Inhibition of F-actin Polymerization and Downregulation of SMAD3 Phosphorylation in Human Proximal Tubular Epithelial Cells

Session Information

  • CKD: Pathobiology - I
    November 04, 2022 | Location: Exhibit Hall, Orange County Convention Center‚ West Building
    Abstract Time: 10:00 AM - 12:00 PM

Category: CKD (Non-Dialysis)

  • 2203 CKD (Non-Dialysis): Mechanisms


  • Tam, Tsz Wai, The University of Hong Kong Li Ka Shing Faculty of Medicine, Hong Kong, Hong Kong
  • Yung, Susan, The University of Hong Kong Li Ka Shing Faculty of Medicine, Hong Kong, Hong Kong
  • Chan, Tak Mao Daniel, The University of Hong Kong Li Ka Shing Faculty of Medicine, Hong Kong, Hong Kong

Despite advances in immunosuppressive treatment, many patients with lupus nephritis (LN) develop chronic kidney disease (CKD) characterized by increased TGF-β1 expression and accumulation of matrix proteins in the tubulo-interstitium leading to progressive kidney failure. Fibronectin serves as a scaffold for the deposition of other matrix proteins. We previously reported that mycophenolic acid (MPA) inhibited fibronectin expression in proximal tubular epithelial cells (PTEC) in murine LN. This study investigated the mechanism through which TGF-β1 induced fibronectin expression in PTEC and how MPA exerted its anti-fibrotic effect.


Confluent growth arrested PTEC were stimulated with TGF-β1 (1 ng/ml) in the presence or absence of MPA (5 µg/ml), LY2109761 (specific inhibitor of TFβRI/II activity, 1 µM), SIS3 (specific SMAD3 inhibitor, 7µM), PD98059 (specific ERK inhibitor, 50 µM) or cytochalasin B (inhibitor of actin polymerization, 2 µM), for up to 48 h, and cells were harvested for qPCR, Western blot and immunohistochemistry.


TGF-β1 induced fibronectin expression in a time-dependent manner, accompanied by increased SMAD2, SMAD3, TGFβRI and TGF-βRII expression and F-actin polymerization with the formation of thick stress fibres that traversed the cells. Constitutive fibronectin expression was mediated through ERK phosphorylation, whereas fibronectin induced by TGF-β1 was mediated through SMAD2, SMAD3 and ERK phosphorylation. MPA inhibited fibronectin expression through suppression of F-actin polymerization, decreased TGF-βRII expression and phosphorylation of SMAD3 and ERK, but had no effect on SMAD2 phosphorylation.


MPA inhibits fibronectin synthesis in PTEC by targeting TGF-β1 canonical and non-canonical signaling pathways and F-actin reorganization. The results could have implications on the intervention of CKD due to LN or other causes.


  • Government Support – Non-U.S.