Skip to main page content
U.S. flag

An official website of the United States government

Dot gov

The .gov means it’s official.
Federal government websites often end in .gov or .mil. Before sharing sensitive information, make sure you’re on a federal government site.

Https

The site is secure.
The https:// ensures that you are connecting to the official website and that any information you provide is encrypted and transmitted securely.

Access keys NCBI Homepage MyNCBI Homepage Main Content Main Navigation
. 2013 Oct 12;113(9):1087-1096.
doi: 10.1161/CIRCRESAHA.113.301811. Epub 2013 Sep 6.

Brain angiotensin-converting enzyme type 2 shedding contributes to the development of neurogenic hypertension

Huijing Xia #  1 , Srinivas Sriramula #  1 , Kavaljit H Chhabra  1 , Eric Lazartigues  1
Affiliations

Brain angiotensin-converting enzyme type 2 shedding contributes to the development of neurogenic hypertension

Huijing Xia et al. Circ Res. .

Abstract

Rationale: Overactivity of the brain renin-angiotensin system is a major contributor to neurogenic hypertension. Although overexpression of angiotensin-converting enzyme type 2 (ACE2) has been shown to be beneficial in reducing hypertension by transforming angiotensin II into angiotensin-(1-7), several groups have reported decreased brain ACE2 expression and activity during the development of hypertension.

Objective: We hypothesized that ADAM17-mediated ACE2 shedding results in decreased membrane-bound ACE2 in the brain, thus promoting the development of neurogenic hypertension.

Methods and results: To test this hypothesis, we used the deoxycorticosterone acetate-salt model of neurogenic hypertension in nontransgenic and syn-hACE2 mice overexpressing ACE2 in neurons. Deoxycorticosterone acetate-salt treatment in nontransgenic mice led to significant increases in blood pressure, hypothalamic angiotensin II levels, inflammation, impaired baroreflex sensitivity, and autonomic dysfunction, as well as decreased hypothalamic ACE2 activity and expression, although these changes were blunted or prevented in syn-hACE2 mice. In addition, reduction of ACE2 expression and activity in the brain paralleled an increase in ACE2 activity in the cerebrospinal fluid of nontransgenic mice after deoxycorticosterone acetate-salt treatment and were accompanied by enhanced ADAM17 expression and activity in the hypothalamus. Chronic knockdown of ADAM17 in the brain blunted the development of hypertension and restored ACE2 activity and baroreflex function.

Conclusions: Our data provide the first evidence that ADAM17-mediated shedding impairs brain ACE2 compensatory activity, thus contributing to the development of neurogenic hypertension.

Keywords: angiotensin; autonomic dysfunction; baroreflex; central nervous system; gene therapy; hypertension; inflammation.

PubMed Disclaimer

Figures

Figure 1
Figure 1. Neuron-targeted ACE2 over-expression attenuates DOCA-salt hypertension
Deoxycorticosterone acetate (DOCA) implanted subcutaneously and combined with 1% saline drinking solution induced a progressive rise of mean arterial pressure (MAP, A) in uni-nephrectomized (n=12 mice/group) non-transgenic (NT) and syn-hACE2 (SA) mice with neuron-specific expression of human ACE2. After 21 days of DOCA-salt treatment, Spontaneous Baroreceptor Reflex Sensitivity (SBRS, B) was calculated using the sequence method and autonomic function was assessed pharmacologically by determining the changes in MAP (ΔMAP) and heart rate (ΔHR) following ip injections of a β-blocker (propranolol: 4 mg/kg, C), ganglionic blocker (chlorisondamine: 5 mg/kg, D) and muscarinic antagonist (atropine: 1 mg/kg, E). At the end of the protocol, hypothalamic Ang-II (F), plasma AVP (G) and urinary norepinephrine (H) were determined using ELISA kits (n=3-6 mice/group). *P<0.05 vs. sham and †P<0.05 vs. NT+DOCA.
Figure 2
Figure 2. ACE2 overexpression reduces DOCA-salt induced inflammation
Quantitative real time RT-PCR measurements of pro-inflammatory cytokines (IL-1β, IL-6, and TNF) and chemokine (MCP-1) in hypothalamic paraventricular nucleus samples isolated from non-transgenic (NT) and syn-hACE2 (SA) mice following a 3-week DOCA-salt, or sham, treatment. Data are means ±SEM (n=3/group). *P<0.05 vs. sham, †P<0.05 vs. NT+DOCA.
Figure 3
Figure 3. Neuron-specific ACE2 over-expression reverses the DOCA-salt induced changes in angiotensin receptors
Quantitative real time RT-PCR measurements of mRNA expression for AT1R (A) and MasR (B) in the hypothalamic paraventricular nucleus (PVN) of DOCA-salt-, or sham-, treated non-transgenic (NT) and syn-hACE2 (SA) mice. Representative western blots and densitometric analysis of group data for AT1R (C) and MasR (D) protein expression in the PVN. Data are means ±SEM (n=6 mice/group). *P<0.05 vs. sham and †P<0.05 vs. NT+DOCA.
Figure 4
Figure 4. ADAM17-mediated shedding impairs ACE2 expression and activity in DOCA-salt hypertension
(A) ACE2 activity assay from hypothalami isolated after 3 weeks of DOCA-salt or sham treatment in NT and SA mice (n=5-7/group). (B) Representative Western blot and quantitative data for mACE2 in 2 independent hypothalamus homogenates per group. (n=6 mice/treatment group). (C) ACE2 activity assay from microdialyzed CSF samples (n=4-6/group). (D) ADAM17 activity assay from hypothalami isolated after 3 weeks of DOCA-salt or sham treatment in NT and SA mice (n=5-7/group). (E) Representative Western blot showing both pro (upper band) and mature (lower band) forms and quantitative data for ADAM17 (n=6 mice/treatment group). (F) Representative immunoblotting for mACE2 following immunoprecipitation of calmodulin in 3 independent hypothalamus homogenates. (n=6 mice/treatment group). *P<0.05 vs. NT+sham and †P<0.05 vs. NT+DOCA. Abbreviations: AFU, arbitrary fluorescence units; AU, arbitrary units; mACE2, mouse ACE2.
Figure 5
Figure 5. Brain ADAM17 knockdown reduces BP and restores baroreflex sensitivity in DOCA-salt hypertension
MAP recording (A) and changes in SBRS (B) after 3 weeks of DOCA-salt or sham treatment in NT mice compared to baseline recordings obtained before treatment (n=5-7/group). (C) Representative Western blot and quantitative data for ADAM17 in hypothalamus homogenates. (n=3-6 mice/group). (D) ACE2 activity assay in the hypothalamus and CSF of NT mice following DOCA-salt or sham treatment in the presence or absence of ADAM17 siRNA (n=4/group). *P<0.05 vs. NT+sham and †P<0.05 vs. NT+DOCA.
Figure 6
Figure 6. Brain RAS, ADAM17 and neurogenic hypertension
On baseline, Angiotensin(Ang)-II is formed from Ang-I by the angiotensin converting enzyme (ACE) and can bind Ang-II type 1 (AT1R) and type 2 (AT2R) receptors. Ang-II can be cleaved by ACE2 to form Ang-(1-7) which then interacts with the Mas receptor (MasR). RAS overactivity under DOCA-salt stimulation results in increased levels of Ang-II and AT1R expression, leading to increased expression of ADAM17 which in turn cleaves ACE2, resulting in decreased membrane ACE2 levels, thereby decreasing Ang-(1-7) formation, reducing MasR activation and ultimately contributing to the development of neurogenic hypertension. Overexpression of ACE2 in the brain results in enhanced conversion of DOCA-salt-induced increase in Ang-II levels, thereby promoting enhanced formation of Ang-(1-7) levels while inhibiting ADAM17 up-regulation.
See this image and copyright information in PMC

Similar articles

See all similar articles

Cited by

See all "Cited by" articles

References

    1. Xu P, Sriramula S, Lazartigues E. ACE2/Ang-(1-7)/Mas pathway in the brain: The Axis of Good. Am J Physiology - Regul Integr Comp Physiol. 2011;300:R804–817. - PMC - PubMed
    1. O’Callaghan EL, Choong Y-T, Jancovski N, Allen AM. Central angiotensinergic mechanisms associated with hypertension. Auton Neurosci. 2013;175:85–92. - PubMed
    1. Werner C, Baumhäkel M, Teo KK, Schmieder R, Mann J, Unger T, Yusuf S, Böhm M. RAS blockade with ARB and ACE inhibitors: current perspective on rationale and patient selection. Clin Res Cardiol. 2008;97:418–431. - PubMed
    1. Ferrario CM. ACE2: more of Ang-(1-7) or less Ang II? Curr Opin Nephrol Hypertens. 2011;20:1–6. - PMC - PubMed
    1. Marian AJ. The Discovery of the ACE2 Gene. Circ Res. 2013;112:1307–1309. - PubMed

Publication types

MeSH terms

-