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

Gava E, Samad-Zadeh A, Zimpelmann J, Bahramifarid N, Kitten GT, Santos RA, Touyz RM, Burns KD - Nephrol. Dial. Transplant. (2009)

Bottom Line: Ang-(1-7) inhibited high glucose-stimulated protein synthesis, and blocked the stimulatory effect of glucose on TGF-beta1.Conversely, Ang-(1-7) had no effect on glucose-stimulated synthesis of fibronectin or collagen IV.In diabetic nephropathy, Ang-(1-7) may partly counteract the profibrotic effects of high glucose.

View Article: PubMed Central - PubMed

Affiliation: Division of Nephrology, Department of Medicine, Kidney Research Centre, Ottawa Health Research Institute, University of Ottawa, Ottawa, Ontario, Canada.

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-PK(1) 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 [(3)H]-leucine incorporation and transforming growth factor-beta1 (TGF-beta1), 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-beta1. 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-beta1. In diabetic nephropathy, Ang-(1-7) may partly counteract the profibrotic effects of high glucose.

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Effect of phenylarsine oxide (PAO) on SHP-1 activity in normal glucose or high glucose. (A) The effect of Ang-(1–7) (10−7 M) on SHP-1 activity in normal glucose is depicted (NG, 5 mM) with or without PAO (10−7 M). *P < 0.001 versus control, **P < 0.001 versus Ang-(1–7); n = 3. (B) The effect of Ang-(1–7) (10−7 M) on SHP-1 activity in high glucose is depicted (HG, 25 mM) with or without PAO (10−7 M). *P < 0.01 versus control, **P < 0.05 versus Ang-(1–7); n = 5. Results are presented in arbitrary units.
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Figure 4: Effect of phenylarsine oxide (PAO) on SHP-1 activity in normal glucose or high glucose. (A) The effect of Ang-(1–7) (10−7 M) on SHP-1 activity in normal glucose is depicted (NG, 5 mM) with or without PAO (10−7 M). *P < 0.001 versus control, **P < 0.001 versus Ang-(1–7); n = 3. (B) The effect of Ang-(1–7) (10−7 M) on SHP-1 activity in high glucose is depicted (HG, 25 mM) with or without PAO (10−7 M). *P < 0.01 versus control, **P < 0.05 versus Ang-(1–7); n = 5. Results are presented in arbitrary units.

Mentions: To determine the role of Ang-(1–7)-stimulated SHP-1 activation in mediating the inhibition of p38 phosphorylation in high glucose, the cells were preincubated for 15 min with the inhibitor of phosphotyrosine phosphatase PAO [21]. PAO completely inhibited activation of SHP-1 activity under both normal and high glucose conditions (Figure 4), and it also reversed the inhibitory effect of Ang-(1–7) on high glucose-stimulated p38 phosphorylation (Figure 5).


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

Gava E, Samad-Zadeh A, Zimpelmann J, Bahramifarid N, Kitten GT, Santos RA, Touyz RM, Burns KD - Nephrol. Dial. Transplant. (2009)

Effect of phenylarsine oxide (PAO) on SHP-1 activity in normal glucose or high glucose. (A) The effect of Ang-(1–7) (10−7 M) on SHP-1 activity in normal glucose is depicted (NG, 5 mM) with or without PAO (10−7 M). *P < 0.001 versus control, **P < 0.001 versus Ang-(1–7); n = 3. (B) The effect of Ang-(1–7) (10−7 M) on SHP-1 activity in high glucose is depicted (HG, 25 mM) with or without PAO (10−7 M). *P < 0.01 versus control, **P < 0.05 versus Ang-(1–7); n = 5. Results are presented in arbitrary units.
© Copyright Policy - creative-commons
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC2684752&req=5

Figure 4: Effect of phenylarsine oxide (PAO) on SHP-1 activity in normal glucose or high glucose. (A) The effect of Ang-(1–7) (10−7 M) on SHP-1 activity in normal glucose is depicted (NG, 5 mM) with or without PAO (10−7 M). *P < 0.001 versus control, **P < 0.001 versus Ang-(1–7); n = 3. (B) The effect of Ang-(1–7) (10−7 M) on SHP-1 activity in high glucose is depicted (HG, 25 mM) with or without PAO (10−7 M). *P < 0.01 versus control, **P < 0.05 versus Ang-(1–7); n = 5. Results are presented in arbitrary units.
Mentions: To determine the role of Ang-(1–7)-stimulated SHP-1 activation in mediating the inhibition of p38 phosphorylation in high glucose, the cells were preincubated for 15 min with the inhibitor of phosphotyrosine phosphatase PAO [21]. PAO completely inhibited activation of SHP-1 activity under both normal and high glucose conditions (Figure 4), and it also reversed the inhibitory effect of Ang-(1–7) on high glucose-stimulated p38 phosphorylation (Figure 5).

Bottom Line: Ang-(1-7) inhibited high glucose-stimulated protein synthesis, and blocked the stimulatory effect of glucose on TGF-beta1.Conversely, Ang-(1-7) had no effect on glucose-stimulated synthesis of fibronectin or collagen IV.In diabetic nephropathy, Ang-(1-7) may partly counteract the profibrotic effects of high glucose.

View Article: PubMed Central - PubMed

Affiliation: Division of Nephrology, Department of Medicine, Kidney Research Centre, Ottawa Health Research Institute, University of Ottawa, Ottawa, Ontario, Canada.

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-PK(1) 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 [(3)H]-leucine incorporation and transforming growth factor-beta1 (TGF-beta1), 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-beta1. 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-beta1. In diabetic nephropathy, Ang-(1-7) may partly counteract the profibrotic effects of high glucose.

Show MeSH
Related in: MedlinePlus