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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

Effect of Ang-(1–7) on high glucose-stimulated TGF-β1. Graph depicts the effect of Ang-(1–7) (10−7 M) on TGF-β1 in normal glucose (NG, 5 mM) and high glucose (HG, 25 mM) for 72 h, with or without A-779 (10−5 M). TGF-β1 synthesis was measured by ELISA. *P < 0.05 versus NG control; n = 5.
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Figure 7: Effect of Ang-(1–7) on high glucose-stimulated TGF-β1. Graph depicts the effect of Ang-(1–7) (10−7 M) on TGF-β1 in normal glucose (NG, 5 mM) and high glucose (HG, 25 mM) for 72 h, with or without A-779 (10−5 M). TGF-β1 synthesis was measured by ELISA. *P < 0.05 versus NG control; n = 5.

Mentions: Diabetic nephropathy is associated with high glucose-induced synthesis of intrarenal TGF-β1, and extracellular matrix proteins [1]. Incubation of LLC-PK1 cells in high glucose for 72 h caused a small but significant stimulation of TGF-β1 production (Figure 7). This effect was partly inhibited by Ang-(1–7) (10−7 M), in a receptor Mas-dependent manner. In contrast, Ang-(1–7) had no significant effect on high glucose-stimulated production of fibronectin, either cell-associated or secreted into the media (Figure 8), and did not inhibit high glucose-stimulated synthesis of collagen IV (Figure 9). In normal glucose, Ang-(1–7) had no significant effect on TGF-β1, fibronectin or collagen IV (Figures 7–9).


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 Ang-(1–7) on high glucose-stimulated TGF-β1. Graph depicts the effect of Ang-(1–7) (10−7 M) on TGF-β1 in normal glucose (NG, 5 mM) and high glucose (HG, 25 mM) for 72 h, with or without A-779 (10−5 M). TGF-β1 synthesis was measured by ELISA. *P < 0.05 versus NG control; n = 5.
© Copyright Policy - creative-commons
Related In: Results  -  Collection

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

Figure 7: Effect of Ang-(1–7) on high glucose-stimulated TGF-β1. Graph depicts the effect of Ang-(1–7) (10−7 M) on TGF-β1 in normal glucose (NG, 5 mM) and high glucose (HG, 25 mM) for 72 h, with or without A-779 (10−5 M). TGF-β1 synthesis was measured by ELISA. *P < 0.05 versus NG control; n = 5.
Mentions: Diabetic nephropathy is associated with high glucose-induced synthesis of intrarenal TGF-β1, and extracellular matrix proteins [1]. Incubation of LLC-PK1 cells in high glucose for 72 h caused a small but significant stimulation of TGF-β1 production (Figure 7). This effect was partly inhibited by Ang-(1–7) (10−7 M), in a receptor Mas-dependent manner. In contrast, Ang-(1–7) had no significant effect on high glucose-stimulated production of fibronectin, either cell-associated or secreted into the media (Figure 8), and did not inhibit high glucose-stimulated synthesis of collagen IV (Figure 9). In normal glucose, Ang-(1–7) had no significant effect on TGF-β1, fibronectin or collagen IV (Figures 7–9).

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