Angiotensin-(1-7) through Mas receptor up-regulates neuronal norepinephrine transporter via Akt and Erk1/2-dependent pathways

As angiotensin (Ang) (17) decreases norepinephrine (NE) content in the synaptic cleft, we investigated the effect of Ang-(17) on NE neuronal uptake in spontaneously hypertensive rats. [3H]-NE neuronal uptake was measured in isolated hypothalami. NE transporter (NET) expression was evaluated in hypothalamic neuronal cultures by western-blot. Ang-(17) lacked an acute effect on neuronal NE uptake. Conversely, Ang-(17) caused an increase in NET expression after 3 h incubation (40 +/- 7%), which was blocked by the Mas receptor antagonist, a PI3-kinase inhibitor or a MEK1/2 inhibitor suggesting the involvement of Mas receptor and the PI3-kinase/Akt and MEK1/2-ERK1/2 pathways in the Ang-(17)-stimulated NET expression. Ang-(17) through Mas receptors stimulated Akt and ERK1/2 activities in spontaneously hypertensive rat neurons. Cycloheximide attenuated Ang-(17) stimulation of NET expression suggesting that Ang-(17) stimulates NET synthesis. In fact, Ang-(17) increased NET mRNA levels. Thus, we evaluated the long-term effect of Ang-(17) on neuronal NE uptake after 3 h incubation. Under this condition, Ang-(17) increased neuronal NE uptake by 60 +/- 14% which was blocked by cycloheximide and the Mas receptor antagonist. Neuronal NE uptake and NET expression were decreased after 3 h incubation with an anti-Ang-(17) antibody. Ang-(17) induces a chronic stimulatory effect on NET expression. In this way, Ang-(17) may regulate a pre-synaptic mechanism in maintaining appropriate synaptic NE levels during hypertensive conditions.