Angiotensin-(1–7) stimulates the phosphorylation of JAK2, IRS-1 and Akt in rat heart in vivo: role of the AT₁ and Mas receptors

Abstract

Angiotensin (ANG) II exerts a negative modulation on insulin signal transduction that might be involved in the pathogenesis of hypertension and insulin resistance. ANG-(1-7), an endogenous heptapeptide hormone formed by cleavage of ANG I and ANG II, counteracts many actions of ANG II. In the current study, we have explored the role of ANG-(1-7) in the signaling crosstalk that exists between ANG II and insulin. We demonstrated that ANG-(1-7) stimulates the phosphorylation of Janus kinase 2 (JAK2) and insulin receptor substrate (IRS)-1 in rat heart in vivo. This stimulating effect was blocked by administration of the selective ANG type 1 (AT(1)) receptor blocker losartan. In contrast to ANG II, ANG-(1-7) stimulated cardiac Akt phosphorylation, and this stimulation was blunted in presence of the receptor Mas antagonist A-779 or the phosphatidylinositol 3-kinase (PI3K) inhibitor wortmannin. The specific JAK2 inhibitor AG-490 blocked ANG-(1-7)-induced JAK2 and IRS-1 phosphorylation but had no effect on ANG-(1-7)-induced phosphorylation of Akt, indicating that activation of cardiac Akt by ANG-(1-7) appears not to involve the recruitment of JAK2 but proceeds through the receptor Mas and involves PI3K. Acute in vivo insulin-induced cardiac Akt phosphorylation was inhibited by ANG II. Interestingly, coadministration of insulin with an equimolar mixture of ANG II and ANG-(1-7) reverted this inhibitory effect. On the basis of our present results, we postulate that ANG-(1-7) could be a positive physiological contributor to the actions of insulin in heart and that the balance between ANG II and ANG-(1-7) could be relevant for the association among insulin resistance, hypertension, and cardiovascular disease.

Angiotensin-converting enzyme 2, angiotensin-(1–7) and Mas: new players of the renin–angiotensin system

“…It has been reported that Ang-(1-7) and insulin have some common downstream signaling effectors in HAEC (Sampaio et al 2007b) and in the hearts (Giani et al 2007). Ang-(1-7) induces the phosphorylation of the insulin downstream effectors PI3K and AKT via Mas in HAEC (Giani et al 2007, Sampaio et al 2007b) and IRS-1 and JAK2 via AT 1 receptor in hearts (Giani et al 2007). Moreover, Ang-(1-7)/Mas negatively regulates Ang II/AT 1 signaling in HAEC by promoting dephosphorylation of c-Src and ERK1/2 and inhibition of NADPH oxidase activity (Sampaio et al 2007a).…”

Chronic infusion of angiotensin-(1–7) improves insulin resistance and hypertension induced by a high-fructose diet in rats

“…Tissue samples were homogenized in solubilization buffer containing 1% Triton together with phosphatase and protease inhibitors, as described previously (17,33). Tissue extracts were centrifuged at 100,000 g for 1 h at 4°C to eliminate insoluble material, and protein concentration in the supernatants was measured using the Bradford method, as described previously (17,33). Equal amounts of solubilized protein (2 mg) were incubated at 4°C overnight with anti-IR or anti-IRS-1 antibodies at a final concentration of 4 g/ml.…”

“…Equal amounts of solubilized protein (2 mg) were incubated at 4°C overnight with anti-IR or anti-IRS-1 antibodies at a final concentration of 4 g/ml. Immune complexes were collected by incubation with protein A-Sepharose 6 MB, as described previously (17,33). SDS-PAGE and Western transfer of proteins to PVDF membranes were performed as described previously (17,33).…”

“…In a previous work, we demonstrated that Ang-(1-7) is able to modulate the insulinsignaling pathway by inducing Akt phosphorylation via the Mas receptor (17). In addition, it was shown that Ang-(1-7) overcomes the inhibition of insulin-induced phosphorylation of Akt phosphorylation by Ang II (17).…”

ANG II, ANG-(1-7), ALDO and AVP biphasic effects on Na+/H+ transport: the role of cellular calcium

“…Also in agreement with findings showing the cardioprotective effects of ANG-(1-7), a genetic deletion of the Mas receptor impaired heart function and changed the extracellular matrix to a profibrotic state [140]. After the activation of the Mas receptor, the intracellular signal transduction mechanisms that are involved in the following processes or tissues are poorly understood: i) in vivo, in the rat heart, ANG-(1-7) stimulated the phosphorylation of Janus kinase 2 (JAK2), insulin receptor substrate (IRS)-1 and Akt [141], ii) Mas receptor activation led to an increase in NO production via the phosphorylation of eNOS, a process that involves the activation of phosphatidylinositol 3-kinase-dependent Akt phosphorylation [142,143], and iii) upon the activation of the Mas receptor, MAPK phosphorylation is inhibited [144,145].…”