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NDT Advance Access published online on January 14, 2009
Nephrology Dialysis Transplantation, doi:10.1093/ndt/gfn736
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© The Author [2009].
The online version of this article has been published under an open access model. Users are entitled to use, reproduce, disseminate, or display the open access version of this article for non-commercial purposes provided that: the original authorship is properly and fully attributed; the Journal and Oxford University Press are attributed as the original place of publication with the correct citation details given; if an article is subsequently reproduced or disseminated not in its entirety but only in part or as a derivative work this must be clearly indicated. For commercial re-use, please contact journals.permissions@oxfordjournals.org


Angiotensin-(1–7) activates a tyrosine phosphatase and inhibits glucose-induced signalling in proximal tubular cells

Elisandra Gava1, Arman Samad-Zadeh1, Joseph Zimpelmann1, Nasim Bahramifarid1, Gregory T. Kitten2, Robson A. Santos3, Rhian M. Touyz1 and Kevin D. Burns1

1 Division of Nephrology, Department of Medicine, Kidney Research Centre, Ottawa Health Research Institute, University of Ottawa, Ottawa, Ontario, Canada 2 The Department of Morphology 3 The Department of Physiology and Biophysics, Institute of Biological Sciences, Federal University of Minas Gerais, Belo Horizonte, Brazil

Correspondence and offprint requests to: Kevin D. Burns, Kidney Research Centre, 1967 Riverside Drive, Room. 535, Ottawa, ON, K1H 7W9, Canada. Tel: +1-613-738-8400-82580; Fax: +1-613-738-8337; E-mail: kburns{at}ottawahospital.on.ca



  Abstract

Background. In the diabetic kidney, stimulation of mitogen-activated protein kinases (MAPKs) leads to extracellular matrix protein synthesis. In the proximal tubule, angiotensin-(1–7) [Ang-(1–7)] blocks activation of MAPKs by angiotensin II. We studied the effect of Ang-(1–7) on signalling responses in LLC-PK1 cells in normal (5 mM) or high (25 mM) glucose.

Methods. The p38 MAPK was assayed by immunoblot, Src homology 2-containing protein-tyrosine phosphatase-1 (SHP-1) activity was measured after immunoprecipitation, cell protein synthesis was determined by [3H]-leucine incorporation and transforming growth factor-β1 (TGF-β1), fibronectin and collagen IV were assayed by immunoblots and/or ELISA.

Results. High glucose stimulated p38 MAPK. This response was inhibited by Ang-(1–7) in a concentration-dependent fashion, an effect reversed by the receptor Mas antagonist A-779. Ang-(1–7) increased SHP-1 activity, via the receptor Mas. An inhibitor of tyrosine phosphatase, phenylarsine oxide, reversed the inhibitory effect of Ang-(1–7) on high glucose-stimulated p38 MAPK. Ang-(1–7) inhibited high glucose-stimulated protein synthesis, and blocked the stimulatory effect of glucose on TGF-β1. Conversely, Ang-(1–7) had no effect on glucose-stimulated synthesis of fibronectin or collagen IV.

Conclusions. These data indicate that in proximal tubular cells, binding of Ang-(1–7) to the receptor Mas stimulates SHP-1, associated with the inhibition of glucose-stimulated p38 MAPK. Ang-(1–7) selectively inhibits glucose-stimulated protein synthesis and TGF-β1. In diabetic nephropathy, Ang-(1–7) may partly counteract the profibrotic effects of high glucose.

Keywords: angiotensin; diabetic nephropathy; proximal tubule; receptor Mas; renin–angiotensin system

Received for publication: 4. 7.08
Accepted in revised form: 9.12.08


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