Angiotensin-(1-7) attenuates angiotensin II-induced signalling associated with activation of a tyrosine phosphatase in Sprague-Dawley rats cardiac fibroblasts.

BACKGROUND INFORMATION: Angiotensin-(1-7) [ANG-(1-7)] mediates vasodilation, antiproliferation, anti-apoptosis and antifibrosis, therefore, it opposes the effects of angiotensin II (ANG II). However, the detailed signal transduction mechanism following the Mas receptor activated by ANG-(1-7) is still poorly understood. Src homology2-containing inositol phosphatase 1 (SHP-1), a redoxsensitive protein tyrosine phosphatase, negatively influences downstream signalling molecules, such as mitogen-activated protein kinases (MAPKs), through dephosphorylation, thereby inhibiting proliferative and profibrotic signalling induced by ANG II. Therefore, we hypothesised that SHP-1 may mediate the antiproliferative signalling of ANG-(1-7) through the regulation of the dynamic balance of MAPKs and SHP-1 in isolated cardiac fibroblasts. Primary culture of neonatal Sprague-Dawley rats cardiac fibroblasts was treated separately with different interventions to investigate this issue.

RESULTS: Our data revealed that ANG II increased the phosphorylation of extracellular signal-related kinase (p-ERK1/2) and the ratio of (p-ERK1/2)/(ERK1/2), but ANG-(1-7) decreased them. The effects of ANG-(1-7) on the phosphorylation p-ERK1/2 were blocked by the Mas receptor antagonist A-779. Unlike ANG II, which decreased the activity of SHP-1, ANG-(1-7) increased its activity. Overexpression of SHP-1 attenuated the ANG II-stimulated phosphorylation of c-Src, its downstream molecules ERK1/2, α-smooth muscle actin and transforming growth factor-β1 (TGF-β1). These effects were also inhibited by the specific inhibitor of SHP-1, sodium stibogluconate. ANG-(1-7) had no significant effects on the gene expression of TGF-β1, collagen I or collagen III, but was found to antagonise the stimulatory effects of ANG II on them.

CONCLUSIONS: ANG-(1-7), through Mas receptor, activates SHP-1 in cardiac fibroblasts, which can negatively modulate ANG II-induced phosphorylation of c-Src and MAPKs, and inhibits profibrotic factors TGF-β1 and collagen production. ANG-(1-7) can thereby serve as a protective role by counteracting the effects of ANG II.