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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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Related in: MedlinePlus

Ang-(1–7) inhibits high glucose-stimulated cell protein synthesis. Graph depicts the effect of Ang-(1–7) (10−7 M) in normal glucose (NG, 5 mM) and high glucose (HG, 25 mM) for 48 h, with or without A-779 (10−5 M) on cell protein synthesis, measured by [3H]-leucine incorporation. *P < 0.001 versus NG control, **P < 0.001 versus A-779 + Ang-(1–7), P < 0.010 versus HG control, and P < 0.030 versus HG + A-779; n = 5–11.
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Figure 6: Ang-(1–7) inhibits high glucose-stimulated cell protein synthesis. Graph depicts the effect of Ang-(1–7) (10−7 M) in normal glucose (NG, 5 mM) and high glucose (HG, 25 mM) for 48 h, with or without A-779 (10−5 M) on cell protein synthesis, measured by [3H]-leucine incorporation. *P < 0.001 versus NG control, **P < 0.001 versus A-779 + Ang-(1–7), P < 0.010 versus HG control, and P < 0.030 versus HG + A-779; n = 5–11.

Mentions: To determine the functional impact of the inhibitory effect of Ang-(1–7) on high glucose-stimulated p38 MAPK, we examined the effects on cell protein synthesis, measured by [3H]-leucine incorporation. Incubation of cells for 48 h in high glucose caused a significant stimulation of leucine incorporation, compared to normal glucose, and this was blocked by 48 h incubation with Ang-(1–7) (10−7 M) (Figure 6). The inhibitory effect of Ang-(1–7) was completely prevented by co-incubation with A-779 (10−5 M).


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)

Ang-(1–7) inhibits high glucose-stimulated cell protein synthesis. Graph depicts the effect of Ang-(1–7) (10−7 M) in normal glucose (NG, 5 mM) and high glucose (HG, 25 mM) for 48 h, with or without A-779 (10−5 M) on cell protein synthesis, measured by [3H]-leucine incorporation. *P < 0.001 versus NG control, **P < 0.001 versus A-779 + Ang-(1–7), P < 0.010 versus HG control, and P < 0.030 versus HG + A-779; n = 5–11.
© Copyright Policy - creative-commons
Related In: Results  -  Collection

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

Figure 6: Ang-(1–7) inhibits high glucose-stimulated cell protein synthesis. Graph depicts the effect of Ang-(1–7) (10−7 M) in normal glucose (NG, 5 mM) and high glucose (HG, 25 mM) for 48 h, with or without A-779 (10−5 M) on cell protein synthesis, measured by [3H]-leucine incorporation. *P < 0.001 versus NG control, **P < 0.001 versus A-779 + Ang-(1–7), P < 0.010 versus HG control, and P < 0.030 versus HG + A-779; n = 5–11.
Mentions: To determine the functional impact of the inhibitory effect of Ang-(1–7) on high glucose-stimulated p38 MAPK, we examined the effects on cell protein synthesis, measured by [3H]-leucine incorporation. Incubation of cells for 48 h in high glucose caused a significant stimulation of leucine incorporation, compared to normal glucose, and this was blocked by 48 h incubation with Ang-(1–7) (10−7 M) (Figure 6). The inhibitory effect of Ang-(1–7) was completely prevented by co-incubation with A-779 (10−5 M).

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