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Published on: August 13, 2017
Mycophenolic acid may delay allograft fibrosis by inhibiting transforming growth factor-beta1-induced activation of
Arjang Djamali1, Aparna Vidyasagar, Gokhan Yagci
1Department of Medicine, University of Wisconsin Madison SMPH, Madison, WI, USA. axd@medicine.wisc.edu
Background:
We evaluated the role of renal tubular Nox-2 in the pathogenesis of epithelial-to-mesenchymal transition (EMT) in kidney allografts.
Methods:
We examined this question in the human kidney allografts with interstitial fibrosis and tubular atrophy not otherwise specified (IFTANOS), in the Fisher to Lewis rat transplant model, and in the in vitro model of transforming growth factor-beta1-induced EMT in normal rat kidney epithelial cells (NRK52E).
Results:
We first demonstrated that Nox-2 and alpha-smooth muscle actin (SMA) were increased in renal tubules from kidney transplant recipients on calcineurin inhibitors, mycophenolic acid (MPA), and prednisone with IFTANOS, suggestive of EMT (n=6). Next, we examined Nox-2 expression and fibrogenesis in syngeneic transplants, allogeneic transplants treated with MPA 40 mg/kg per 24 hr, and untreated allogeneic transplants for 6 months (n=14 in each group). Immunofluorescent and immunohistochemical studies for Nox-2, alpha-SMA, and E-cadherin showed that similar to patients with IFTANOS, rat allografts had greater tubulointerstitial staining for Nox-2 and alpha-SMA. MPA therapy prevented these changes. Immunoblot analyses examining Nox-2 signaling (phospho-nuclear factor [NF]-kappaB), redox signaling (phospho-smad2), and fibrosis (alpha-SMA and fibronectin) demonstrated that MPA treatment prevented the up-regulation of Nox-2, inhibited p-NF-kappaB and p-smad2, and down-regulated alpha-SMA and fibronectin levels. Finally, we examined Nox-2 signaling in vitro and confirmed that MPA inhibited phospho-NF-kappaB, Nox-2, phospho-smad2, and alpha-SMA during transforming growth factor-beta1-induced EMT of NRK52E cells while reducing Nox-2, vimentin, and fibronectin mRNA levels.
Conclusions:
MPA may down-regulate Nox-2 activation and EMT through the NF-kappaB pathway in the tubular epithelial cells, suggesting a novel role for this drug independent of its immunosuppressive properties.
Insights
Mycophenolic acid (MPA) may prevent kidney allograft fibrosis by inhibiting Nox-2 activation and epithelial-to-mesenchymal transition (EMT) via the NF-kappaB pathway. This suggests a novel, non-immunosuppressive role for MPA in kidney transplant outcomes.
Area of Science:
- Nephrology
- Immunology
- Molecular Biology
Background:
- Renal tubular NADPH oxidase 2 (Nox-2) plays a role in kidney allograft fibrosis.
- Epithelial-to-mesenchymal transition (EMT) is a key process in kidney allograft interstitial fibrosis and tubular atrophy (IFTANOS).
Purpose of the Study:
- To evaluate the role of renal tubular Nox-2 in EMT pathogenesis within kidney allografts.
- To investigate the potential of mycophenolic acid (MPA) in modulating Nox-2 activation and EMT.
Main Methods:
- Examined human kidney allografts with IFTANOS.
- Utilized a Fisher to Lewis rat kidney transplant model.
- Employed an in vitro model of transforming growth factor-beta1-induced EMT in normal rat kidney epithelial cells (NRK52E).
- Assessed Nox-2, alpha-smooth muscle actin (SMA), E-cadherin, phospho-nuclear factor kappaB (NF-kappaB), and phospho-smad2 expression via immunofluorescence, immunohistochemistry, and immunoblot analyses.
Main Results:
- Nox-2 and alpha-SMA were elevated in human and rat kidney allografts with IFTANOS, indicating EMT.
- MPA treatment in rats prevented Nox-2 and alpha-SMA upregulation, and inhibited NF-kappaB and smad2 phosphorylation.
- In vitro, MPA inhibited Nox-2, NF-kappaB, smad2 phosphorylation, and alpha-SMA expression during TGF-beta1-induced EMT.
Conclusions:
- MPA may attenuate kidney allograft fibrosis by down-regulating Nox-2 activation and EMT.
- The mechanism involves the NF-kappaB pathway in tubular epithelial cells.
- MPA demonstrates a potential therapeutic role independent of its immunosuppressive effects.
