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

J. Neurochem. (2012) 120, 46–55. As angiotensin (Ang) (1–7) decreases norepinephrine (NE) content in the synaptic cleft, we investigated the effect of Ang‐(1–7) 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‐(1–7) lacked an acute effect on neuronal NE uptake. Conversely, Ang‐(1–7) 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‐(1–7)‐stimulated NET expression. Ang‐(1–7) through Mas receptors stimulated Akt and ERK1/2 activities in spontaneously hypertensive rat neurons. Cycloheximide attenuated Ang‐(1–7) stimulation of NET expression suggesting that Ang‐(1–7) stimulates NET synthesis. In fact, Ang‐(1–7) increased NET mRNA levels. Thus, we evaluated the long‐term effect of Ang‐(1–7) on neuronal NE uptake after 3 h incubation. Under this condition, Ang‐(1–7) 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‐(1–7) antibody. Ang‐(1–7) induces a chronic stimulatory effect on NET expression. In this way, Ang‐(1–7) may regulate a pre‐synaptic mechanism in maintaining appropriate synaptic NE levels during hypertensive conditions. Central NET upregulation by angiotensin‐(1‐7) in hypertension As angiotensin (Ang) (1–7) decreases norepinephrine (NE) content in the synaptic cleft, we investigated the effect of Ang‐(1–7) on centrally NE neuronal uptake, the main mechanism for NE removal from the synaptic cleft, in hypothalamic neurons from hypertensive rats. We showed that Ang‐(1–7) causes a long‐term stimulatory effect on NE neuronal uptake by increasing NE transporter expression. This effect is coupled to Mas receptor activation acting through both MEK1/2‐ERK1/2 and PI3‐kinase/Akt‐dependent pathways. In this way, Ang‐(1–7) may regulate a pre‐synaptic mechanism in maintaining appropriate synaptic NE levels during hypertensive conditions, thus contributing to the modulation of NE homeostasis and blood pressure regulation.