The Brain Renin-Angiotensin System: Localization and General Significance

1992 ◽  
Vol 19 ◽  
pp. S51-S62 ◽  
Author(s):  
Bernd Bunnemann ◽  
Kjell Fuxe ◽  
Detlev Ganten
2012 ◽  
Vol 302 (3) ◽  
pp. R313-R320 ◽  
Author(s):  
Curt D. Sigmund

The purpose of this review is two-fold. First, I will highlight recent advances in our understanding of the mechanisms regulating angiotensin II (ANG II) synthesis in the brain, focusing on evidence that renin is expressed in the brain and is expressed in two forms: a secreted form, which may catalyze extracellular ANG I generation from glial or neuronal angiotensinogen (AGT), and an intracellular form, which may generate intracellular ANG in neurons that may act as a neurotransmitter. Second, I will discuss recent studies that advance the concept that the renin-angiotensin system (RAS) in the brain not only is a potent regulator of blood pressure and fluid intake but may also regulate metabolism. The efferent pathways regulating the blood pressure/dipsogenic effects and the metabolic effects of elevated central RAS activity appear different, with the former being dependent upon the hypothalamic-pituitary-adrenal axis, and the latter being dependent upon an interaction between the brain and the systemic (or adipose) RAS.


Author(s):  
Thomas Unger ◽  
Detlev Ganten ◽  
Gerald Ludwig ◽  
Rudolf E. Lang

2017 ◽  
Vol 46 ◽  
pp. 1-8 ◽  
Author(s):  
Ehab Farag ◽  
Daniel I. Sessler ◽  
Zeyd Ebrahim ◽  
Andrea Kurz ◽  
Joseph Morgan ◽  
...  

1999 ◽  
Vol 276 (5) ◽  
pp. H1608-H1615 ◽  
Author(s):  
Weiguo Zhang ◽  
Bing S. Huang ◽  
Frans H. H. Leenen

Blockade of brain “ouabain” prevents the sympathetic hyperactivity and impairment of baroreflex function in rats with congestive heart failure (CHF). Because brain “ouabain” may act by activating the brain renin-angiotensin system (RAS), the aim of the present study was to assess whether chronic treatment with the AT1-receptor blocker losartan given centrally normalizes the sympathetic hyperactivity and impairment of baroreflex function in Wistar rats with CHF postmyocardial infarction (MI). After left coronary artery ligation (2 or 6 wk), rats received either intracerebroventricular losartan (1 mg ⋅ kg−1 ⋅ day−1, CHF-Los) or vehicle (CHF-Veh) by osmotic minipumps. To assess possible peripheral effects of intracerebroventricular losartan, one set of CHF rats received the same rate of losartan subcutaneously. Sham-operated rats served as control. After 2 wk of treatment, mean arterial pressure (MAP), heart rate (HR), and renal sympathetic nerve activity (RSNA) at rest and in response to air-jet stress and intracerebroventricular injection of the α2-adrenoceptor-agonist guanabenz were measured in conscious animals. Arterial baroreflex function was evaluated by ramp changes in MAP. Compared with sham groups, CHF-Veh groups showed impaired arterial baroreflex control of HR and RSNA, increased sympathoexcitatory and pressor responses to air-jet stress, and increased sympathoinhibitory and hypotensive responses to guanabenz. The latter is consistent with decreased activity in sympathoinhibitory pathways. Chronic intracerebroventricular infusion of losartan largely normalized these abnormalities. In CHF rats, the same rate of infusion of losartan subcutaneously was ineffective. In sham-operated rats, losartan intracerebroventricularly or subcutaneously did not affect sympathetic activity. We conclude that the chronic increase in sympathoexcitation, decrease in sympathoinhibition, and desensitized baroreflex function in CHF all appear to depend on the brain RAS, since this whole pattern of changes can be normalized by chronic central AT1-receptor blockade with losartan.


Circulation ◽  
2007 ◽  
Vol 116 (suppl_16) ◽  
Author(s):  
Ying Ma ◽  
Yu-Ming Kang* ◽  
Zhi-Ming Yang ◽  
Joseph Francis*

Introduction: Neurohumoral mechanisms play an important role in the pathophysiology of congestive heart failure (HF). Recent studies suggest that the brain renin angiotensin system (RAS) plays an important role in regulating body fluids and sympathetic drive in HF. In addition, it has been shown that there is cross talk between cytokines and RAS in cardiovascular disease. In this study we determined whether blockade of brain RAS attenuate inflammatory cytokines and oxidative stress in HF rats. Methods and Results: Adult male Sprague-Dawley rats were implanted with intracerebroventricular (ICV) cannulae and subjected to coronary artery ligation to induce HF and confirmed by echocardiography. Rats were treated with an angiotensin type 1 receptors (AT1-R) antagonist losartan (LOS, 20 μg/hr, ICV) or vehicle (VEH) for 4 weeks. At the end of the study, left ventricular (LV) function was measured by echocardiography and rats were sacrificed, and brain and plasma samples were collected for measurements of cytokines and superoxide using immunohistochemistry, Western blot and real time RT-PCR. HF rats induced significant increases in Nuclear Factor-kappaB (NF-κB) p50-positive neurons and activated microglia in the paraventricular nucleus (PVN) of hypothalamus, and TNF-α, IL-1β, IL-6 and NF-κB p50 in hypothalamus when compared with sham rats. These animals also had increased staining for dihydroethidium (DHE) and plasma levels of norepinephrine (NE), an indirect indicator of sympathetic activity. In contrast, ICV treatment with LOS attenuated cytokine expression and oxidative stress in the PVN and hypothalamus when compared with VEH treated HF rats. ICV treatment with LOS also reduced plasma NE levels, and proinflammatory cytokine, heart weight to body weight ratio with decreased LV end-diastolic pressure. Conclusions : These findings suggest the cross talk between the cytokines and renin angiotensin system within the brain contribute to sympatho-excitation in HF.


Stroke ◽  
2013 ◽  
Vol 44 (suppl_1) ◽  
Author(s):  
Douglas M Bennion ◽  
Lauren Donnangelo ◽  
David Pioquinto ◽  
Robert Regenhardt ◽  
Mohan K Raizada ◽  
...  

Background: Toward discovering novel stroke therapies, recent research has shown that activation of the newly-discovered angiotensin converting enzyme 2/angiotensin-(1-7)/mas (ACE2/Ang-(1-7)/Mas) pathway, a counter-regulatory axis of the brain renin-angiotensin system, is neuroprotective in ischemic stroke in rats. Specifically, intraventricular administration of the novel ACE2 activator diminazine aceturate (DIZE) before and during an ischemic stroke decreases cerebral infarct and neurologic deficits. Efficacy must now be demonstrated using minimally-invasive methods if this therapy is to be translated to the care of human patients. In this study, we assessed the hypothesis that systemic administration of DIZE post ischemic stroke would be neuroprotective. Methods: Adult male Sprague-Dawley rats underwent ischemic stroke by endothelin-1 induced middle cerebral artery occlusion and were randomly divided into 2 groups (n=9-10/set): 1) intraperitoneal (IP) administrations of DIZE (7.5 mg/kg) at 4, 24, and 48 h after stroke; 2) IP administrations of 0.9% saline vehicle at the same time points. At 24 and 72 h after stroke, rats underwent blinded neurologic assessments. Immediately following the 72 h tests, animals were sacrificed, cerebral infarct volumes assessed by TTC staining, and IL-1β expression in the stroke region analyzed by rt-PCR. Data are expressed as mean ± SEM with significance inferred at p<0.05. Results: Mean infarct volume was significantly decreased by IP injections of DIZE (9.4% ± 4.35) as compared to control (22.8%±3.6, p=0.039). At 24 h post stroke, neurologic deficits (Garcia Scale) were significantly improved in the DIZE treated group (16.7±0.40) versus the saline group (15.22±0.57, p=0.037). Although DIZE tended to improve neurologic deficits 72 h post stroke, this trend was not significant. Finally, DIZE treatment significantly reduced mRNA expression of IL-1β (0.43 ± 0.14) in the cerebral cortical stroke region as compared to saline treatment (1.47±0.08, p=0.001). Conclusions: Our findings suggest that targeting the ACE2/Ang-(1-7)/Mas axis post stroke can improve function, decrease inflammation, and reduce infarct volume - a significant translational step in brain renin-angiotensin system research.


1999 ◽  
Vol 277 (5) ◽  
pp. H1786-H1792 ◽  
Author(s):  
Frans H. H. Leenen ◽  
Baoxue Yuan ◽  
Bing S. Huang

In chronic heart failure (CHF), sympathetic activity increases in parallel with the impairment of left ventricle (LV) function, and sympathetic hyperactivity has been postulated to contribute to the progression of heart failure. In the brain, compounds with ouabain-like activity (“ouabain,” for brevity) and the renin-angiotensin system contribute to sympathetic hyperactivity in rats with CHF after myocardial infarction (MI). In the present studies, we assessed whether, in rats, chronic blockade of brain “ouabain” or the brain renin-angiotensin system inhibits the post-MI LV dysfunction. In rats, an MI was induced by acute coronary artery ligation. At either 0.5 or 4 wk post-MI, chronic treatment with Fab fragments for blocking brain “ouabain” or with losartan for blocking brain AT1 receptors was started and continued until 8 wk post-MI using osmotic minipumps connected to intracerebroventricular cannulas. At 8 wk post-MI, in conscious rats, LV pressures were measured at rest and in response to volume and pressure overload, followed by LV passive pressure-volume curves in vitro. At 8 wk post-MI, control MI rats exhibited clear increases in LV end-diastolic pressure (LVEDP) at rest and in response to pressure and volume overload. LV pressure-volume curves in vitro showed a marked shift to the right. Intravenous administration of the Fab fragments or losartan at rates used for central blockade did not affect these parameters. In contrast, chronic central blockade with either Fab fragments or losartan significantly lowered LVEDP at rest (only in 0.5- to 8-wk groups) and particularly in response to pressure or volume overload. LV dilation, as assessed from LV pressure-volume curves, was also significantly inhibited. These results indicate that chronic blockade of brain “ouabain” or brain AT1 receptors substantially inhibits development of LV dilation and dysfunction in rats post-MI.


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