Nox-2 is a modulator of fibrogenesis in kidney allografts.
We studied the role of classical phagocytic NADPH oxidase (Nox) in the pathogenesis of kidney allograft tubulointerstitial fibrosis. Immunofluorescence studies showed that Nox-2 and p22phox (electron transfer subunits of Nox) colocalized in the tubulointerstitium of human kidney allografts. Tubular Nox-2 also colocalized with alpha-SMA in areas of injury, suggestive of epithelial-to-mesenchymal transition (EMT). Interstitial macrophages (CD68(+)) and myofibroblasts (alpha-SMA(+)) expressed Nox-2 while graft infiltrating T cells (CD3(+)) and mature fibroblasts (S100A4(+)) were Nox-2(-). These results were confirmed in the Fisher-to-Lewis rat kidney transplant model. Areas of tubulitis were associated with Nox-2 and alpha-SMA, suggestive of EMT. Immunoblot analyses showed that Nox-2 upregulation was associated with oxidative stress (nitrotyrosine) and fibrogenesis (alpha-SMA and phospho-Smad2) at 3 weeks and 6 months. Allografts treated with Nox inhibitors (DPI or apocynin) for 1 week showed reduced fibronectin and phospho-Smad2 and increased E-cadherin levels. Cyclosporine A, TGF-beta1 and angiotensin II increased Nox-2 mRNA levels 2- to 7-fold in vitro (NRK52E cells). Treatment with specific Nox inhibitors (DPI or apocynin) prevented the downregulation of E-cadherin and upregulation of fibronectin transcripts. In aggregate, these studies suggest that Nox-2 is involved in the pathogenesis of allograft tubulointerstitial fibrosis via activation transcription factor Smad2, EMT and myofibroblasts.
Djamali
A
A
Nephrology Section, Department of Medicine, University of Wisconsin Madison School of Medicine and Public Health, Madison, WI, USA. axd@medicine.wisc.edu
Vidyasagar
A
A
Adulla
M
M
Hullett
D
D
Reese
S
S
D000199:Actins / Q000378:metabolism; D000328:Adult; D000368:Aged; D000818:Animals; D005260:Female; D005355:Fibrosis; D006801:Humans; D007150:Immunohistochemistry; D016030:Kidney Transplantation; D008297:Male; D008562:Membrane Glycoproteins / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D008875:Middle Aged; D000074662:NADPH Oxidase 2; D019255:NADPH Oxidases / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D009395:Nephritis, Interstitial / Q000503:physiopathology*; D018384:Oxidative Stress; D012333:RNA, Messenger / Q000235:genetics; D051381:Rats; D011916:Rats, Inbred F344; D011917:Rats, Inbred Lew; D014184:Transplantation, Homologous
C541116:ACTA2 protein, human; D000199:Actins; D008562:Membrane Glycoproteins; D012333:RNA, Messenger; C056558:CYBB protein, human; D000074662:NADPH Oxidase 2; D019255:NADPH Oxidases