Angiotensin (1-7) Attenuates the Chronotropic Response to Angiotensin II via Stimulation of PTEN in Spontaneously Hypertensive Rat Brain

• Main Author: Modgil, Amit
• Format: Others
• Published: North Dakota State University 2017
• Online Access: https://hdl.handle.net/10365/26797

The pathogenesis of hypertension and its mode of progression are complex, multifactorial and incompletely understood. Several studies have focused on the beneficial effects of peripheral Ang (1-7) in the regulation of cardiovascular functions, showing the counter-regulatory effects of Ang (1-7) against the actions of Ang II in the periphery. However, its actions in the central nervous system are not completely understood. In the present study, our main goal was to determine the central action of Ang (1-7) and its interaction with Ang II in the blood pressure control. Previous studies reported that Ang II produces a greater degree of activation of neuronal cells from brainstem/hypothalamus cultures of SHR versus WKY rats. Our present findings showed that this enhanced action of Ang II was attenuated in co-presence of either Ang (1-7) or PI3-kinase inhibitor. These counter-regulatory effects of Ang (1-7) on Ang II action in SHR neurons were abolished by co-treatment with either A-779, a Mas-R antagonist, or bisperoxovanadium (BPV), a PTEN inhibitor. In addition, incubation of WKY and SHR neurons with Ang (1-7) significantly increased PTEN activity. Chronic treatment with Ang (1-7) or chronic inhibition of PI3K using lentiviral vector significantly abolished the enhanced chronotroic response to Ang II in SHR neurons and significantly enhanced PTEN protein and mRNA expression levels in both WKY and SHR neuronal cultures. To further check the functional implications of our in vitro data, we further studied the interaction between Ang II and Ang (1-7) in the central control of cardiovascular functions. RVLM microinjection of Ang (1-7) or LY-294002 alone did not alter MAP, but reduced the pressor response to Ang II in SHR. Moreover, in compliance with our in vitro data, the inhibitory effect of Ang (1-7) on the pressor response to Ang II in SHR was abolished when co-administered together with A-779 or BPV. The data demonstrated that Ang (1-7) induce PTEN activity and expression via Mas-R, and depresses PI3-kinase-PKB/Akt signal transduction pathway, which lead to the counter-regulatory effect of Ang (1-7) on Ang II induced chronotropic and pressor effect on neuronal activity and cardiovascular functions including MAP and HR in SHR.