Mycophenolic acid may delay allograft fibrosis by inhibiting transforming growth factor-beta1-induced activation of Nox-2 through the nuclear factor-kappaB pathway.
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.
Djamali
Arjang
A
Department of Medicine, University of Wisconsin Madison SMPH, Madison, WI, USA. axd@medicine.wisc.edu
Vidyasagar
Aparna
A
Yagci
Gokhan
G
Huang
Ling-Jin
LJ
Reese
Shannon
S
D000328:Adult; D000818:Animals; D000900:Anti-Bacterial Agents / Q000627:therapeutic use; D001284:Atrophy; D001706:Biopsy; D003404:Creatinine / Q000097:blood; D004195:Disease Models, Animal; D005355:Fibrosis / Q000517:prevention & control*; D006801:Humans; D007166:Immunosuppressive Agents / Q000627:therapeutic use; D007678:Kidney Glomerulus / Q000473:pathology; D016030:Kidney Transplantation / Q000276:immunology / Q000473:pathology*; D007684:Kidney Tubules / Q000473:pathology; D009173:Mycophenolic Acid / Q000627:therapeutic use*; D016328:NF-kappa B / Q000502:physiology*; D018384:Oxidative Stress; D051381:Rats; D011917:Rats, Inbred Lew; D017382:Reactive Oxygen Species / Q000378:metabolism; D053773:Transforming Growth Factor beta1 / Q000037:antagonists & inhibitors* / Q000378:metabolism; D014184:Transplantation, Homologous / Q000473:pathology*
D000900:Anti-Bacterial Agents; D007166:Immunosuppressive Agents; D016328:NF-kappa B; D017382:Reactive Oxygen Species; D053773:Transforming Growth Factor beta1; D003404:Creatinine; D009173:Mycophenolic Acid