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Ryu S, Kolozsvary A, Jenrow KA, Brown SL, Kim JH. Mitigation of radiation-induced optic neuropathy in rats by ACE inhibitor ramipril: importance of ramipril dose and treatment time. J Neurooncol 2006; 82:119-24. [PMID: 17004100 DOI: 10.1007/s11060-006-9256-4] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2006] [Accepted: 08/25/2006] [Indexed: 12/01/2022]
Abstract
PURPOSE Radiation-induced optic nerve damage was reduced by ramipril, a prodrug angiotensin-converting enzyme inhibitor (ACEI). This study was to determine the optimum dose and administration time of ramipril for mitigating radiation-induced optic neuropathy. MATERIALS AND METHOD Adult Fischer 344 male rats were treated with a single dose radiation 30 Gy by using radiosurgical technique. After irradiation, the animals were randomly assigned into groups of different ramipril doses and administration time; control (no treatment), radiation alone, radiation+ramipril in different doses and starting times of drug. Ramipril was given 0.5-1.5 mg/kg/day and AT1R blocker Losartan 20 mg/kg/day in drinking water for 180 days. Functional endpoint with visual evoked potential (VEP) and anatomical endpoint with gross and histological analysis with immunohistochemical (IHC) stain were used. RESULTS Normal VEP measurements in un-irradiated rats were 46.2+/-7.9 ms. There was no change of VEP value until 4 months, but was lengthened to 188.1+/-58.7 ms at 6 months after radiation. By ramipril treatment with the dose of 1.5 mg starting at 2 weeks after radiation, VEP was significantly shortened to 105.7+/-88.5 ms at 6 months. Gross and microscopic structure of the irradiated optic nerve was well preserved in the ramipril-treated group. CONCLUSION Ramipril can mitigate the radiation-induced optic nerve damage and preserve the functional integrity of the nerve. The results support early treatment with a high dose of ramipril after radiation.
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Affiliation(s)
- Samuel Ryu
- Department of Radiation Oncology and Neurosurgery, Henry Ford Hospital, 2799 West Grand Boulevard, Detroit, Michigan 48202, USA.
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202
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Shekhar A, Johnson PL, Sajdyk TJ, Fitz SD, Keim SR, Kelley PE, Gehlert DR, DiMicco JA. Angiotensin-II is a putative neurotransmitter in lactate-induced panic-like responses in rats with disruption of GABAergic inhibition in the dorsomedial hypothalamus. J Neurosci 2006; 26:9205-15. [PMID: 16957077 PMCID: PMC6674511 DOI: 10.1523/jneurosci.2491-06.2006] [Citation(s) in RCA: 68] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2006] [Revised: 07/15/2006] [Accepted: 07/17/2006] [Indexed: 11/21/2022] Open
Abstract
Intravenous sodium lactate infusions or the noradrenergic agent yohimbine reliably induce panic attacks in humans with panic disorder but not in healthy controls. However, the exact mechanism of lactate eliciting a panic attack is still unknown. In rats with chronic disruption of GABA-mediated inhibition in the dorsomedial hypothalamus (DMH), achieved by chronic microinfusion of the glutamic acid decarboxylase inhibitor L-allylglycine, sodium lactate infusions or yohimbine elicits panic-like responses (i.e., anxiety, tachycardia, hypertension, and tachypnea). In the present study, previous injections of the angiotensin-II (A-II) type 1 receptor antagonist losartan and the nonspecific A-II receptor antagonist saralasin into the DMH of "panic-prone" rats blocked the anxiety-like and physiological components of lactate-induced panic-like responses. In addition, direct injections of A-II into the DMH of these panic-prone rats also elicited panic-like responses that were blocked by pretreatment with saralasin. Microinjections of saralasin into the DMH did not block the panic-like responses elicited by intravenous infusions of the noradrenergic agent yohimbine or by direct injections of NMDA into the DMH. The presence of the A-II type 1 receptors in the region of the DMH was demonstrated using immunohistochemistry. Thus, these results implicate A-II pathways and the A-II receptors in the hypothalamus as putative substrates for sodium lactate-induced panic-like responses in vulnerable subjects.
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Affiliation(s)
- Anantha Shekhar
- Department of Psychiatry, Institute of Psychiatric Research, Indiana University School of Medicine, Indianapolis, Indiana 46202, USA.
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203
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Shi L, Mao C, Wu J, Morrissey P, Lee J, Xu Z. Effects of i.c.v. losartan on the angiotensin II-mediated vasopressin release and hypothalamic fos expression in near-term ovine fetuses. Peptides 2006; 27:2230-8. [PMID: 16677737 DOI: 10.1016/j.peptides.2006.03.013] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/16/2006] [Revised: 03/14/2006] [Accepted: 03/14/2006] [Indexed: 11/28/2022]
Abstract
Our previous studies have shown that central administration of angiotensin (ANG II) causes arginine vasopressin (AVP) release in the fetus at 70-90% gestation. This is evidence that the hypothalamic-neurohypophysial system is relatively mature before birth. However, few data exist regarding central ANG receptor mechanisms-mediated AVP response during fetal life. To determine roles of brain ANG receptor subtypes in this response, AT1 and AT2 receptor antagonists, losartan and PD123319, were investigated in the brain in chronically prepared ovine fetuses at the last third of gestation. Application of losartan intracerebroventricularly (i.c.v.) at 0.5 mg/kg suppressed central ANG II-stimulated plasma AVP release. Losartan at 5 mg/kg (i.c.v.) demonstrated a significant enhancement of AVP increase to i.c.v. ANG II. Associated with the increase of plasma vasopressin levels, c-fos expression in the hypothalamic neurons was significantly different between the low and high doses of losartan. The low dose losartan markedly reduced the dual immunoreactivity for FOS and AVP in the supraoptic nuclei and paraventricular nuclei after i.c.v. ANG II, whereas the high dose losartan together with ANG II, significantly increased the co-localization of positive FOS in the AVP-containing neurons than that induced by i.c.v. ANG II alone. Central ANG II induced fetal plasma vasopressin increase was not altered by PD123319. The data suggest that losartan in the fetal brain has remarkably different effects based on the doses administrated on central ANG II-related neuroendocrine effects at the late gestation, and that the AT1 mechanism is critical in the regulation of fetal body fluid homeostasis related to plasma AVP levels.
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Affiliation(s)
- Lijun Shi
- Department of Human Sport Science, Beijing Sport University, Beijing 100084, China
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204
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Wang G, Anrather J, Glass MJ, Tarsitano MJ, Zhou P, Frys KA, Pickel VM, Iadecola C. Nox2, Ca2+, and protein kinase C play a role in angiotensin II-induced free radical production in nucleus tractus solitarius. Hypertension 2006; 48:482-9. [PMID: 16894058 DOI: 10.1161/01.hyp.0000236647.55200.07] [Citation(s) in RCA: 90] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
The dorsomedial portion of the nucleus tractus solitarius (dmNTS) is the site of termination of baroreceptor and cardiorespiratory vagal afferents and plays a critical role in cardiovascular regulation. Angiotensin II (Ang II) is a powerful signaling molecule in dmNTS neurons and exerts some of its biological effects by modulating Ca(2+) currents via reactive oxygen species (ROS) derived from reduced nicotinamide-adenine dinucleotide phosphate (NADPH) oxidase. We investigated whether a Nox2-containing NADPH oxidase is the source of the Ang II-induced ROS production and whether the signaling mechanisms of its activation require intracellular Ca(2+) or protein kinase C (PKC). Second-order dmNTS neurons were anterogradely labeled with 4-(4-[didecylamino]styryl)-N-methylpyridinium iodide transported from the vagus and isolated from the brain stem. ROS production was assessed in 4-(4-[didecylamino]styryl)-N-methylpyridinium iodide-positive dmNTS neurons using the fluorescent dye 6-carboxy-2',7'-dichlorodihydro-fluorescein di(acetoxymethyl ester). Ang II (3 to 2000 nmol/L) increased ROS production in dmNTS neurons (EC(50)=38.3 nmol/L). The effect was abolished by the ROS scavenger Mn (III) porphyrin 5,10,20-tetrakis (benzoic acid) porphyrin manganese (III), the Ang II type 1 receptor antagonist losartan, or the NADPH oxidase inhibitors apocynin or gp91ds-tat. Ang II failed to increase ROS production or to potentiate L-type Ca(2+) currents in dmNTS neurons of mice lacking Nox2. The PKC inhibitor GF109203X or depletion of intracellular Ca(2+) attenuated Ang II-elicited ROS production. We conclude that the powerful effects of Ang II on Ca(2+) currents in dmNTS neurons are mediated by PKC activation leading to ROS production via Nox2. Thus, a Nox2-containing NADPH oxidase is the critical link between Ang II and the enhancement of Ca(2+) currents that underlie the actions of Ang II on central autonomic regulation.
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Affiliation(s)
- Gang Wang
- Division of Neurobiology, Weill Medical College of Cornell University, 411 East 69th St, New York, NY 10021, USA.
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205
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Stragier B, Clinckers R, Meurs A, De Bundel D, Sarre S, Ebinger G, Michotte Y, Smolders I. Involvement of the somatostatin-2 receptor in the anti-convulsant effect of angiotensin IV against pilocarpine-induced limbic seizures in rats. J Neurochem 2006; 98:1100-13. [PMID: 16771832 DOI: 10.1111/j.1471-4159.2006.03942.x] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The anti-convulsant properties of angiotensin IV (Ang IV), an inhibitor of insulin-regulated aminopeptidase (IRAP) and somatostatin-14, a substrate of IRAP, were evaluated in the acute pilocarpine rat seizure model. Simultaneously, the neurochemical changes in the hippocampus were monitored using in vivo microdialysis. Intracerebroventricularly (i.c.v.) administered Ang IV or somatostatin-14 caused a significant increase in the hippocampal extracellular dopamine and serotonin levels and protected rats against pilocarpine-induced seizures. These effects of Ang IV were both blocked by concomitant i.c.v. administration of the somatostatin receptor-2 antagonist cyanamid 154806. These results reveal a possible role for dopamine and serotonin in the anti-convulsant effect of Ang IV and somatostatin-14. Our study suggests that the ability of Ang IV to inhibit pilocarpine-induced convulsions is dependent on somatostatin receptor-2 activation, and is possibly mediated via the inhibition of IRAP resulting in an elevated concentration of somatostatin-14 in the brain.
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Affiliation(s)
- Bart Stragier
- Department of Pharmaceutical Chemistry, Drug Analysis and Drug Information, Research Group Experimental Pharmacology, Vrije Universiteit Brussel, Brussels, Belgium
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206
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Callewaere C, Banisadr G, Desarménien MG, Mechighel P, Kitabgi P, Rostène WH, Mélik Parsadaniantz S. The chemokine SDF-1/CXCL12 modulates the firing pattern of vasopressin neurons and counteracts induced vasopressin release through CXCR4. Proc Natl Acad Sci U S A 2006; 103:8221-6. [PMID: 16702540 PMCID: PMC1570101 DOI: 10.1073/pnas.0602620103] [Citation(s) in RCA: 60] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2005] [Indexed: 11/18/2022] Open
Abstract
Chemokines play a key role in inflammation. They are expressed not only in neuroinflammatory conditions, but also constitutively by different cell types, including neurons in the normal brain, suggesting that they may act as modulators of neuronal functions. Here, we investigated a possible neuroendocrine role of the chemokine stromal cell-derived factor 1 (SDF-1)/CXCL12. We demonstrated the colocalization of SDF-1 and its receptor CXCR4 with arginine vasopressin (AVP) in the magnocellular neurons of the supraoptic nucleus (SON) and the paraventricular hypothalamic nucleus and on AVP projections to the neurohypophysis. Electrophysiological recordings of SON neurons demonstrated that SDF-1 affects the electrical activity of AVP neurons through CXCR4, resulting in changes in AVP release. We observed that SDF-1 can blunt the autoregulation of AVP release in vitro and counteract angiotensin II-induced plasma AVP release in vivo. Furthermore, a short-term physiological increase in AVP release induced by enhanced plasma osmolarity, which was produced by the administration of 1 M NaCl i.p., was similarly blocked by central injection of SDF-1 through CXCR4. A change in water balance by long-term salt loading induced a decrease in both SDF-1 and CXCR4 parallel to that of AVP immunostaining in SON. From these data, we demonstrate that chemokine actions in the brain are not restricted to inflammatory processes. We propose to add to the known autoregulation of AVP on its own neurons, a second autocrine system induced by SDF-1 able to modulate central AVP neuronal activity and release.
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Affiliation(s)
- Céline Callewaere
- *Institut National de la Santé et de la Recherche Médicale, Unité 732, F-75012 Paris, France
- Université Pierre et Marie Curie-Paris 6, Hôpital Saint-Antoine, 184 Rue du Faubourg Saint-Antoine, F-75571 Paris Cedex 12, France
| | - Ghazal Banisadr
- *Institut National de la Santé et de la Recherche Médicale, Unité 732, F-75012 Paris, France
- Université Pierre et Marie Curie-Paris 6, Hôpital Saint-Antoine, 184 Rue du Faubourg Saint-Antoine, F-75571 Paris Cedex 12, France
| | - Michel G. Desarménien
- Institut de Génomique Fonctionnelle, Université Montpellier, Faculté de Médecine, F-34094 Montepellier, France
- Institut National de la Santé et de la Recherche Médicale, Unité 661, F-34094 Montpellier, France; and
- Centre National de la Recherche Scientifique, Unité Mixte de Recherche 5203, F-34094 Montpellier, France
| | - Patricia Mechighel
- *Institut National de la Santé et de la Recherche Médicale, Unité 732, F-75012 Paris, France
- Université Pierre et Marie Curie-Paris 6, Hôpital Saint-Antoine, 184 Rue du Faubourg Saint-Antoine, F-75571 Paris Cedex 12, France
| | - Patrick Kitabgi
- *Institut National de la Santé et de la Recherche Médicale, Unité 732, F-75012 Paris, France
- Université Pierre et Marie Curie-Paris 6, Hôpital Saint-Antoine, 184 Rue du Faubourg Saint-Antoine, F-75571 Paris Cedex 12, France
| | - William H. Rostène
- *Institut National de la Santé et de la Recherche Médicale, Unité 732, F-75012 Paris, France
- Université Pierre et Marie Curie-Paris 6, Hôpital Saint-Antoine, 184 Rue du Faubourg Saint-Antoine, F-75571 Paris Cedex 12, France
| | - Stéphane Mélik Parsadaniantz
- *Institut National de la Santé et de la Recherche Médicale, Unité 732, F-75012 Paris, France
- Université Pierre et Marie Curie-Paris 6, Hôpital Saint-Antoine, 184 Rue du Faubourg Saint-Antoine, F-75571 Paris Cedex 12, France
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207
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Rey P, Lopez-Real A, Sanchez-Iglesias S, Muñoz A, Soto-Otero R, Labandeira-Garcia JL. Angiotensin type-1-receptor antagonists reduce 6-hydroxydopamine toxicity for dopaminergic neurons. Neurobiol Aging 2006; 28:555-67. [PMID: 16621167 DOI: 10.1016/j.neurobiolaging.2006.02.018] [Citation(s) in RCA: 83] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2005] [Revised: 02/20/2006] [Accepted: 02/27/2006] [Indexed: 02/07/2023]
Abstract
Angiotensin II activates (via type 1 receptors) NAD(P)H-dependent oxidases, which are a major source of superoxide, and is relevant in the pathogenesis of several cardiovascular diseases and certain degenerative changes associated with ageing. Given that there is a brain renin-angiotensin system and that oxidative stress is a key contributor to Parkinson's disease, we investigated the effects of angiotensin II and angiotensin type 1 (AT(1)) receptor antagonists in the 6-hydroxydopamine model of Parkinson's disease. Rats subjected to intraventricular injection of 6-hydroxydopamine showed bilateral reduction in the number of dopaminergic neurons and terminals. Injection of angiotensin alone did not induce any significant effect. However, angiotensin increased the toxic effect of 6-hydroxydopamine. Rats treated with the AT(1) receptor antagonist ZD 7155 and then 6-hydroxydopamine (with or without exogenous administration of angiotensin) showed a significant reduction in 6-hydroxydopamine-induced oxidative stress (lipid peroxidation and protein oxidation) and dopaminergic degeneration. Dopaminergic degeneration was also reduced by the NAD(P)H inhibitor apocynin. Angiotensin may play a pivotal role, via AT(1) receptors, in increasing the oxidative damage of dopaminergic cells, and treatment with AT(1) antagonists may reduce the progression of Parkinson's disease.
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Affiliation(s)
- P Rey
- Laboratory of Neuroanatomy and Experimental Neurology, Department of Morphological Sciences, Faculty of Medicine, University of Santiago de Compostela, Santiago de Compostela, Spain
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208
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Donadio MVF, Gomes CM, Sagae SC, Franci CR, Anselmo-Franci JA, Lucion AB, Sanvitto GL. Estradiol and progesterone modulation of angiotensin II receptors in the arcuate nucleus of ovariectomized and lactating rats. Brain Res 2006; 1083:103-9. [PMID: 16566904 DOI: 10.1016/j.brainres.2006.02.018] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2005] [Revised: 02/01/2006] [Accepted: 02/07/2006] [Indexed: 10/24/2022]
Abstract
The expression of angiotensin II (Ang II) receptors in the brain is modulated by estradiol and progesterone. Considering that Ang II plays a critical role in controlling prolactin secretion and that neurons in the arcuate nucleus (ARC) are the main regulator of this function, the present study aimed to evaluate ARC Ang II receptor binding in 2 experimental models with different estradiol and progesterone plasma levels. Animals were divided into 4 groups: ovariectomy (OVX) plus oil vehicle, OVX plus estradiol and progesterone replacement, lactating rats on day 7 postpartum, and lactating rats on day 20. Animals were killed by decapitation, and the brains were removed. Ang II receptors were quantified by autoradiography in ARC. Trunk blood samples were collected, and plasma estradiol and progesterone were measured by radioimmunoassay. Treatment of OVX rats with estradiol and progesterone increased Ang II receptor binding when compared to OVX vehicle-treated animals. Plasma estradiol (r = +0.77) and progesterone (r = +0.87) were highly correlated with Ang II receptors in ovariectomized animals. Lactating rats (day 20) showed a significant decrease in Ang II receptor binding and plasma progesterone when compared to lactating rats (day 7), however, no difference was seen in plasma estradiol. Plasma levels of progesterone (r = +0.81), but not estradiol (r = +0.32), were highly correlated with Ang II receptors in lactating rats. In conclusion, present results show that ARC Ang II receptors decreases on day 20 of lactation compared to day 7 and are highly correlated with plasma progesterone, indicating a pivotal role for progesterone in this regulation.
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Affiliation(s)
- Márcio Vinícius Fagundes Donadio
- Departamento de Fisiologia, Instituto de Ciências Básicas da Saúde (ICBS), Universidade Federal do Rio Grande do Sul (UFRGS), Sarmento Leite 500, Porto Alegre, RS 90050-170, Brazil
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209
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Erdös B, Broxson CS, King MA, Scarpace PJ, Tümer N. Acute pressor effect of central angiotensin II is mediated by NAD(P)H-oxidase-dependent production of superoxide in the hypothalamic cardiovascular regulatory nuclei. J Hypertens 2006; 24:109-16. [PMID: 16331108 DOI: 10.1097/01.hjh.0000198026.99600.59] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
BACKGROUND Centrally applied angiotensin II (Ang II) increases sympathetic nervous activity and mean arterial blood pressure (MAP), but the mediation of these effects is not fully understood. OBJECTIVE To test the hypothesis that central effects of Ang II are mediated by reduced nicotinamide adenine dinucleotide phosphate [NAD(P)H]-oxidase-dependent production of superoxide in the hypothalamus. METHODS Under isoflurane anesthesia, male Sprague-Dawley rats were given an intracerebroventricular infusion of either artificial cerebrospinal fluid or apocynin (4 microg/kg per min), a selective inhibitor for NAD(P)H oxidase, for 30 min, followed by Ang II (20 ng) or carbachol (200 ng), while MAP and heart rate were measured at the femoral artery. At the end of the experiments, hydroethidine, a superoxide-sensitive fluorescent dye, was infused intravenously for 10 min, and superoxide production was assessed in the vasoregulatory hypothalamic nuclei using confocal microscopy. RESULTS Ang II elicited a rapid 11 +/- 2-mmHg increase in MAP and a 16 +/- 2-beats/min decrease in heart rate. Apocynin abolished these effects of Ang II in a specific manner, as carbachol-induced increases in MAP were unaffected by the inhibition of NAD(P)H oxidase (MAP increased by 9 +/- 2 and 8 +/- 1 mmHg in the absence and presence of apocynin, respectively). In response to Ang II, apocynin-sensitive production of superoxide increased significantly in the nuclei of the anterior hypothalamus, in the subfornical organ, and in the paraventricular nucleus of the hypothalamus. CONCLUSION These findings demonstrate that acute pressor responses of central Ang II are mediated by NAD(P)H-oxidase-dependent production of superoxide in the hypothalamus.
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Affiliation(s)
- Benedek Erdös
- Geriatric Research, Education and Clinical Center, Department of Veterans Affairs Medical Center, Gainesville, Florida, USA.
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210
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Donadio MVF, Gomes CM, Sagae SC, Franci CR, Anselmo-Franci JA, Lucion AB, Sanvitto GL. Angiotensin II receptors are upregulated by estradiol and progesterone in the locus coeruleus, median preoptic nucleus and subfornical organ of ovariectomized rats. Brain Res 2005; 1065:47-52. [PMID: 16297888 DOI: 10.1016/j.brainres.2005.10.019] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2005] [Revised: 10/03/2005] [Accepted: 10/11/2005] [Indexed: 11/20/2022]
Abstract
Angiotensin II (Ang II) receptors in specific brain areas and in the anterior pituitary are controlled by reproductive hormones. Since Ang II also plays a role in controlling reproductive functions, such as luteinizing hormone and prolactin secretion, the objective of the present study was to evaluate the regulation of Ang II receptors by estradiol (E(2)) and progesterone (P) in areas of the brain involved in homeostatic and reproductive functions, such as the locus coeruleus (LC), median preoptic nucleus (MnPO) and subfornical organ (SFO). Adult female rats were ovariectomized under anesthesia and divided into 2 groups after 2 weeks: OVX plus E(2)/P replacement (OVXE(2)P) and OVX plus oil vehicle (OVX). E(2) was injected for 3 consecutive days followed by an injection of P on the 4th day. Animals were killed by decapitation and the brains were removed and frozen. Consecutive coronal brain sections were cut in a cryostat and Ang II receptors were quantified by autoradiography in the MnPO, LC and SFO. Treatment of OVX rats with E(2) and P induced a significant increase in the Ang II receptor binding (fmol/mg protein) in the MnPO (OVX: 4.48 +/- 0.58 and OVXE(2)P: 9.89 +/- 1.65), LC (OVX: 2.72 +/- 0.37 and OVXE(2)P: 8.03 +/- 0.9) and SFO (OVX: 5.45 +/- 0.66 and OVXE(2)P: 10.73 +/- 1.79) compared to OVX animals treated with the vehicle, P < 0.05. In conclusion, these results show that Ang II receptors are upregulated by E(2) and P in the LC, MnPO and SFO of ovariectomized rats.
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Affiliation(s)
- Márcio Vinícius Fagundes Donadio
- Departamento de Fisiologia, Instituto de Ciências Básicas da Saúde, ICBS, Universidade Federal do Rio Grande do Sul, UFRGS, Sarmento Leite 500, Porto Alegre, RS 90050-170, Brazil
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211
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Blume A, Undeutsch C, Zhao Y, Kaschina E, Culman J, Unger T. ANG III induces expression of inducible transcription factors of AP-1 and Krox families in rat brain. Am J Physiol Regul Integr Comp Physiol 2005; 289:R845-50. [PMID: 15879055 DOI: 10.1152/ajpregu.00672.2004] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
In addition to rapid responses comprising increases in blood pressure, drinking, and stimulation of natriuresis, ANG II induces the expression of transcription factors (TF) in the central nervous system. The ANG II metabolite ANG III (ANG 2–8) has been demonstrated to exert physiological effects similar to those of ANG II. We aimed to determine 1) whether ANG III induces TF expression in the brain, 2) which ANG II (AT) receptor subtype is involved, and 3) whether the two peptides, ANG II and ANG III, differ in their efficacy to stimulate TF expression. ANG II (100 pmol), ANG III (100 pmol), or vehicle was injected into the lateral brain ventricle of conscious rats alone or in combination with the AT1 receptor antagonist losartan (10 nmol), the AT2 receptor antagonist PD-123319 (5 nmol), or the aminopeptidase inhibitor amastatin (10 nmol). Similar to ANG II, ANG III induced the expression of c-Fos, c-Jun, and Krox-24 in four brain regions, subfornical organ, median preoptic area, paraventricular nucleus, and supraoptic nucleus of the hypothalamus, with the same efficacy. This effect was AT1 receptor mediated. Pretreatment with amastatin reduced the expression of TF in response to ANG II, indicating that this expression is partly mediated by ANG III. Interestingly, the AT2 receptor antagonist PD-123319 alone slightly enhanced the expression of c-Fos, c-Jun, and Krox-24 in different populations of neurons of the paraventricular nucleus. These data indicate that different populations of neurons in the paraventricular nucleus are tonically inhibited by AT2 receptors under physiological conditions.
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Affiliation(s)
- Annegret Blume
- Institute of Zoology, University of Regensburg, Universitätsstrasse 31, 93053 Regensburg, Germany.
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212
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Abstract
In 1989, the development of specific angiotensin receptor antagonists which distinguish between two angiotensin receptor subtypes (AT1 and AT2) led to a breakthrough in angiotensin research. It turned out, that the AT1 receptor was almost entirely responsible for the "classical" actions of angiotensin II related to the regulation of blood pressure as well as volume and electrolyte balance. However, actions and signal transduction mechanisms coupled to the AT2 receptor remained enigmatic for a long time. The present review summarizes the current knowledge of AT2 receptor distribution, signaling and function with an emphasis on growth/anti-growth, differentiation and the regeneration of neuronal tissue.
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Affiliation(s)
- U M Steckelings
- Center for Cardiovascular Research, Institut für Pharmakologie und Toxikologie, Charité-Universitätsmedizin Berlin, Hessische Strasse 3-4, 10115 Berlin, Germany.
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213
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Pelegrini-da-Silva A, Martins AR, Prado WA. A new role for the renin-angiotensin system in the rat periaqueductal gray matter: angiotensin receptor-mediated modulation of nociception. Neuroscience 2005; 132:453-63. [PMID: 15802196 DOI: 10.1016/j.neuroscience.2004.12.046] [Citation(s) in RCA: 52] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 12/21/2004] [Indexed: 10/25/2022]
Abstract
Renin-angiotensin (Ang) system (RAS) peptides injected into the periaqueductal gray matter (PAG) elicit antinociception. Saralasin blocks Ang II-elicited antinociception. Thus, it is possible that endogenous RAS peptides could participate on the modulation of nociception in the PAG. This possibility was tested here injecting, in the PAG, the specific Ang type 1 and type 2 receptor (AT1 receptor and AT(2 receptor) antagonists losartan and CGP42,112A, respectively, either alone or before Ang II. The effects of Ang II, losartan and CGP42,112A on nociception were measured using the tail flick test and the model of incision allodynia. Ang II increased tail-flick latency, an effect inhibited by both losartan and CGP42,112A. Ang II reduced incisional allodynia. Either losartan or CGP42,112A alone increased incision allodynia, suggesting that endogenous Ang II and/or an Ang-peptide participates in the control of allodynia by the PAG. AT1 and AT2 receptors were immunolocalized in neuronal cell bodies and processes in the ventrolateral PAG. Taken together, the antinociceptive effect of Ang II injection into the ventrolateral PAG, the increase of allodynia elicited by injecting either losartan or CGP42,112A alone in the PAG, and the presence of AT1 and AT2 receptors in neurons and neuronal processes in the same region, represent the first evidence that part of the tonic nociceptive control mediated by the PAG is carried out locally by endogenous Ang II and/or an Ang-peptide acting on AT1 and AT2 receptors.
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Affiliation(s)
- A Pelegrini-da-Silva
- Department of Pharmacology, Faculty of Medicine of Ribeirão Preto, University of São Paulo, Avenida Bandeirantes 3900, 14049-900 Ribeirão Preto, São Paulo, Brazil
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214
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Alponti RF, Zambotti-Villela L, Murena-Nunes C, Marinho CE, do Amaral Olivo R, Silveira PF. Cystyl aminopeptidase activity in the plasma, viscera and brain of the snake Bothrops jararaca. Comp Biochem Physiol A Mol Integr Physiol 2005; 141:336-52. [PMID: 16006161 DOI: 10.1016/j.cbpb.2005.06.005] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2004] [Revised: 06/10/2005] [Accepted: 06/13/2005] [Indexed: 11/28/2022]
Abstract
The relationship between plasma osmolality and cystyl aminopeptidase was characterized in the snake Bothrops jararaca and comparisons were made with the emerging picture of this relationship in rats. The profile of cystyl aminopeptidase activity under basal conditions was determined in the soluble and membrane-bound forms in visceral organs and in the central nervous system in comparison with that of alanyl aminopeptidase. The regional localization of cystyl and alanyl aminopeptidase activities was studied in the central nervous system. The basal level of plasma cystyl aminopeptidase, four- to six-fold higher than in rats, suggests its importance to help regulate circulating levels of neurohypophysial peptides in B. jararaca snake. The osmotic sensitivity of this plasma enzyme, undetectable in male, but about three-fold higher in female snakes than in rats, reveals a sexual dimorphism. In marked contrast to those observed in rats, low levels of soluble and particulate forms in the kidney indicate that cystyl aminopeptidase plays a minor metabolizing role at this anatomical location in B. jararaca. Despite of the regional-specific divergence between the levels of rat and snake enzymes, the bilaterally symmetric pattern of the diencephalic distribution of alanyl aminopeptidase reflects functional homologies between these two distantly related species.
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215
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Ramchandra R, Barrett CJ, Malpas SC. NITRIC OXIDE and SYMPATHETIC NERVE ACTIVITY IN THE CONTROL OF BLOOD PRESSURE. Clin Exp Pharmacol Physiol 2005; 32:440-6. [PMID: 15854155 DOI: 10.1111/j.1440-1681.2005.04208.x] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
1. Endothelial dysfunction marked by impairment in the release of nitric oxide (NO) is seen very early in the development of hypertension and is considered important in mediating the impaired vascular tone evident in essential hypertensive patients. 2. Recently, a hypothesis has emerged that NO acting as a neurotransmitter in the brain can modulate levels of sympathetic nerve activity and thereby blood pressure. The NO inhibition model of hypertension has been used to explore the possibility that a decrease in levels of NO can cause an increase in levels of sympathetic nerve activity that can mediate the hypertension. 3. In the present review, we examine the literature regarding the role of NO in setting the mean level of sympathetic nerve activity and blood pressure. Although the acute effects of NO inhibition are well understood, the chronic interaction between the sympathetic nervous system and NO has only been investigated using indirect measures of sympathetic nerve activity, such as ganglionic blockade. This has led to inconsistent results regarding the role of NO in modulating sympathetic nerve activity chronically. 4. Some of the conflicting results may be explained by differences in the 'background' levels of angiotensin (Ang) II. Evidence suggests that NO may interact with AngII and baroreceptor afferent inputs in the central nervous system to set the mean level of sympathetic nerve activity. 5. We suggest chronic NO inhibition can increase sympathetic nerve activity if baroreceptor input is intact and AngII levels are elevated. Although studies exploring the actions of NO or AngII in isolation are useful for gathering initial information, future studies should focus on their interactions and their role in setting the long-term levels of sympathetic activity and blood pressure.
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Affiliation(s)
- Rohit Ramchandra
- Circulatory Control Laboratory, Department of Physiology, University of Auckland, New Zealand
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216
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Latchford KJ, Ferguson AV. Angiotensin depolarizes parvocellular neurons in paraventricular nucleus through modulation of putative nonselective cationic and potassium conductances. Am J Physiol Regul Integr Comp Physiol 2005; 289:R52-8. [PMID: 15831764 DOI: 10.1152/ajpregu.00549.2004] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Neurosecretory parvocellular neurons in the hypothalamic paraventricular nucleus (PVN) exercise considerable influence over the adenohypophysis and thus play a critical role in neuroendocrine regulation. ANG II has been demonstrated to act as a neurotransmitter in PVN, exerting significant impact on neuronal excitability and also influencing corticotrophin-releasing hormone secretion from the median eminence and, therefore, release of ACTH from the pituitary. We have used whole cell patch-clamp techniques in hypothalamic slices to examine the effects of ANG II on the excitability of neurosecretory parvocellular neurons. ANG II application resulted in a dose-dependent depolarization of neurosecretory neurons, a response that was maintained in tetrodotoxin (TTX), suggesting a direct mechanism of action. The depolarizing actions of this peptide were abolished by losartan, demonstrating these effects are AT(1) receptor mediated. Voltage-clamp analysis using slow voltage ramps revealed that ANG II activates a voltage-independent conductance with a reversal potential of -37.8 +/- 3.8 mV, suggesting ANG II effects on a nonselective cationic current. Further, a sustained potassium current characteristic of I(K) was significantly reduced (29.1 +/- 4.7%) by ANG II. These studies identify multiple postsynaptic modulatory sites through which ANG II can influence the excitability of neurosecretory parvocellular PVN neurons and, as a consequence of such actions, control hormonal secretion from the anterior pituitary.
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Affiliation(s)
- Kevin J Latchford
- Department of Physiology, Queen's University, Kingston, Ontario, Canada K7L 3N6
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217
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Banegas I, Prieto I, Alba F, Vives F, Araque A, Segarra AB, Durán R, de Gasparo M, Ramírez M. Angiotensinase activity is asymmetrically distributed in the amygdala, hippocampus and prefrontal cortex of the rat. Behav Brain Res 2005; 156:321-6. [PMID: 15582118 DOI: 10.1016/j.bbr.2004.06.002] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2004] [Accepted: 06/02/2004] [Indexed: 11/21/2022]
Abstract
There are important asymmetries in brain functions such as emotional processing and stress response in humans and animals. Knowledge of the bilateral distribution of brain neurotransmitters is important to appropriately understand its functions. Some peptides such as those included in the renin-angiotensin system (RAS) and cholecystokinin (CCK) are related to modulation of behavior and stress. However, although angiotensin AT1 and CCK type 2 receptors were found in adult rat brain, there are no studies of their bilateral distribution in stress-related areas. The function of angiotensin peptides is depending on the action of several aminopeptidases (AP) called angiotensinases, some of them being also involved in the metabolism of CCK. We have studied the bilateral distribution of soluble (SOL) and membrane-bound (MEM) alanyl- (AlaAP), cystinyl- (CysAP), glutamyl- (GluAP) and aspartyl- (AspAP) AP activities in stress-related areas such as amygdala, hippocampus and medial prefrontal cortex of adult male rats in resting conditions. These enzymes are involved in the metabolism of angiotensins (AlaAP, CysAP, GluAP, AspAP) and CCK (GluAP, AspAP). In the amygdala, all the activities studied showed a right predominance with a significant difference ranging from 30% for SOL CysAP to 125% for SOL GluAP. In the hippocampus, there was a left predominance for SOL AlaAP, SOL and MEM CysAP and MEM AspAP activities (100, 80, 300 and 100% higher, respectively). In contrast, GluAP predominated remarkably in the right hippocampus (eight-fold for SOL and three-fold for MEM). In the prefrontal cortex, SOL and MEM CysAP and SOL AspAP predominated in the left hemisphere (40, 100 and 40% higher, respectively). These results demonstrated a heterogeneous bilateral pattern of angiotensinase activities in motivation and stress-related areas. This may reflect an uneven asymmetrical distribution of their endogenous substrates depending on the brain location and consequently, it would be also a reflect of the asymmetries in the functions they are involved in.
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Affiliation(s)
- I Banegas
- Unit of Physiology, University of Jaén, Building B-3, 23071 Jaén, Spain
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218
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Reaux-Le Goazigo A, Iturrioz X, Fassot C, Claperon C, Roques BP, Llorens-Cortes C. Role of angiotensin III in hypertension. Curr Hypertens Rep 2005; 7:128-34. [PMID: 15748538 DOI: 10.1007/s11906-005-0087-z] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
Abstract
The hyperactivity of the brain renin-angiotensin system (RAS) has been implicated in the development and maintenance of hypertension in several types of experimental and genetic hypertension animal models. Among the main bioactive peptides of the brain RAS, angiotensin (Ang) II and Ang III display the same affinity for type 1 and type 2 Ang II receptors. Both peptides, injected intracerebroventricularly, similarly increase blood pressure (BP); however, because Ang II is converted in vivo to Ang III, the identity of the true effector is unknown. In this article, we review new insights into the predominant role of brain Ang III in the control of BP, underlining the fact that brain aminopeptidase A (APA), the enzyme-forming central Ang III, could constitute a putative central therapeutic target for the treatment of hypertension. This justifies the development of potent systemically active APA inhibitors, such as RB150, as prototypes of a new class of antihypertensive agents for the treatment of certain forms of hypertension.
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219
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Xu Z, Hu F, Shi L, Sun W, Wu J, Morrissey P, Yao J. Angiotensin-induced vasopressin release and activation of hypothalamic neuron in pre-term fetuses. Peptides 2005; 26:307-14. [PMID: 15629543 DOI: 10.1016/j.peptides.2004.09.004] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/28/2004] [Revised: 09/07/2004] [Accepted: 09/09/2004] [Indexed: 10/26/2022]
Abstract
Our previous studies have shown that central administration of angiotensin II (ANG II) causes vasopressin release in the near-term fetus in utero as evidence that the hypothalamic-neurohypophysial system has relatively matured before birth. However, it is still unknown whether the vasopressin controlling centers have been functionally developed in younger fetuses. This study determined fetal plasma vasopressin levels and hypothalamic vasopressin neuron activity in the chronically instrumented pre-term ovine fetuses. Introcerebroventricular (i.c.v.) administration of ANG II did not affect fetal plasma osmolality and sodium concentrations. However, fetal plasma vasopressin levels were significantly increased ( approximately 3-fold) in response to central injection of ANG II. Central ANG II also induced vasopressin-neuron activity marked with c-fos expression in the fetal hypothalamus at pre-term. In addition, the fetal organum vasculosum of the lamina terminalis and the subfornical organ were activated. The results suggest that hypothalamic-neurohypophysial system has been relatively intact and functional at 70% gestational age, and that central angiotensin is important in inducing fetal vasopressin release in utero.
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Affiliation(s)
- Zhice Xu
- Soochaw University School of Medicine, Suzhou 215007, China.
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220
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Li J, Culman J, Hörtnagl H, Zhao Y, Gerova N, Timm M, Blume A, Zimmermann M, Seidel K, Dirnagl U, Unger T. Angiotensin AT2 receptor protects against cerebral ischemia-induced neuronal injury. FASEB J 2005; 19:617-9. [PMID: 15665034 DOI: 10.1096/fj.04-2960fje] [Citation(s) in RCA: 201] [Impact Index Per Article: 10.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Several lines of clinical and experimental evidence suggest an important role of the renin-angiotensin system in ischemic brain injury although the cellular regulation of the angiotensin AT1 and AT2 receptors and their potential relevance in this condition have not yet been clearly defined. We first assessed the regulation of brain AT1 and AT2 receptors in response to transient unilateral medial cerebral artery occlusion in rats by real-time RT-PCR, Western blot, and immunofluorescence labeling. AT2 receptors in the peri-infarct zone were significantly upregulated 2 days after transient focal cerebral ischemia. Increased AT2 receptors, which were abundantly distributed in a large number of brain regions adjacent to the infarct area including cerebral frontal cortex, piriform cortex, striatum, and hippocampus, were exclusively expressed in neurons. By contrast, AT1 receptors, which remained unaltered, were mainly expressed in astrocytes. In neurons of ischemic striatum, increased AT2 receptors were associated with intense neurite outgrowth. Blockade of central AT2 receptors with PD123177 abolished the neuroprotective effects of central AT1 receptor blockade with irbesartan on infarct size and neurological outcome. In primary cortical neurons, stimulation of AT2 receptors supported neuronal survival and neurite outgrowth. Our data indicate that cerebral AT2 receptors exert neuroprotective actions in response to ischemia-induced neuronal injury, possibly by supporting neuronal survival and neurite outgrowth in peri-ischemic brain areas.
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MESH Headings
- Angiotensin II/pharmacology
- Angiotensin II Type 1 Receptor Blockers/pharmacology
- Angiotensin II Type 2 Receptor Blockers
- Animals
- Astrocytes/chemistry
- Blotting, Western
- Brain Diseases/etiology
- Brain Diseases/prevention & control
- Brain Ischemia/complications
- Cell Survival/drug effects
- Cell Survival/physiology
- Cells, Cultured
- Cerebral Cortex/cytology
- Cerebral Infarction/pathology
- Fluorescent Antibody Technique
- Gene Expression
- Male
- Neurites/physiology
- Neurons/chemistry
- Neurons/cytology
- Neurons/physiology
- Rats
- Rats, Wistar
- Receptor, Angiotensin, Type 1/analysis
- Receptor, Angiotensin, Type 1/genetics
- Receptor, Angiotensin, Type 1/physiology
- Receptor, Angiotensin, Type 2/genetics
- Receptor, Angiotensin, Type 2/physiology
- Reverse Transcriptase Polymerase Chain Reaction
- Tissue Distribution
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Affiliation(s)
- Jun Li
- Center for Cardiovascular Research/Institute of Pharmacology and Toxicology, Charité-University Medicine Berlin, Germany
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221
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Chen Y, Ross BM, Currie RW. Heat shock treatment protects against angiotensin II-induced hypertension and inflammation in aorta. Cell Stress Chaperones 2005; 9:99-107. [PMID: 15270082 PMCID: PMC1065311 DOI: 10.1379/csc-1r.1] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
Angiotensin II (Ang II) is a potent vasoconstrictor and induces inflammation and end-organ injury through its activation of the proinflammatory transcription factor, nuclear factor-kappaB (NF-kappaB). Heat shock (HS) treatment with subsequent expression of heat shock proteins (Hsps) is an effective strategy for tissue protection against oxidative injuries. Recently, HS and Hsps have been shown to interact with NF-kappaB in tissue injury. In this study, we investigated whether HS could protect against Ang II-induced hypertension and inflammation by inhibiting NF-kappaB. Sprague-Dawley rats were divided into control and HS groups. Control and 24-hour post-heat shocked rats were treated with Ang II. At days 1, 3, 5, 7, 11, and 14 after Ang II administration, systolic blood pressures were measured by tail-cuff plethysmography, and aorta tissues were collected. Aorta NF-kappaB deoxyribonucleic acid-binding activity was measured by electrophoretic mobility shift assay, and NF-kappaB p65 subunit, Hsp70, Hsp27, and interleukin-6 (IL-6) expressions were measured by Western analysis. HS treatment significantly decreased Ang II-induced hypertension. The activation of NF-kappaB in aorta by Ang II was suppressed by HS treatment. The elevated expression of IL-6 induced by Ang II treatment was also decreased by HS treatment. Although Ang II treatment induced an increase in Hsp70 and Hsp27, HS treatment induced a greater elevation of Hsp70 and Hsp27 expression. HS treatment protects against Ang II-induced hypertension and inflammation. This protection may relate to the interaction of Hsps and the NF-kappaB pathway.
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Affiliation(s)
- Yu Chen
- Department of Anatomy & Neurobiology, Dalhousie University, 5850 College Street, Halifax, Nova Scotia, Canada B3H 1X5
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222
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Wan Y, Wallinder C, Plouffe B, Beaudry H, Mahalingam AK, Wu X, Johansson B, Holm M, Botoros M, Karlén A, Pettersson A, Nyberg F, Fändriks L, Gallo-Payet N, Hallberg A, Alterman M. Design, synthesis, and biological evaluation of the first selective nonpeptide AT2 receptor agonist. J Med Chem 2005; 47:5995-6008. [PMID: 15537354 DOI: 10.1021/jm049715t] [Citation(s) in RCA: 269] [Impact Index Per Article: 14.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
The first druglike selective angiotensin II AT(2) receptor agonist (21) with a K(i) value of 0.4 nM for the AT(2) receptor and a K(i) > 10 microM for the AT(1) receptor is reported. Compound 21, with a bioavailability of 20-30% after oral administration and a half-life estimated to 4 h in rat, induces outgrowth of neurite cells, stimulates p42/p44(mapk), enhances in vivo duodenal alkaline secretion in Sprague-Dawley rats, and lowers the mean arterial blood pressure in anesthetized, spontaneously hypertensive rats. Thus, the peptidomimetic 21 exerts a similar biological response as the endogenous peptide angiotensin II after selective activation of the AT(2) receptor. Compound 21, derived from the prototype nonselective AT(1)/AT(2) receptor agonist L-162,313 will serve as a valuable research tool, enabling studies of the function of the AT(2) receptor in more detail.
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Affiliation(s)
- Yiqian Wan
- Department of Medicinal Chemistry, BMC, Uppsala University, P.O. Box 574, SE-751 23 Uppsala, Sweden
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223
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El-Haddad MA, Ismail Y, Gayle D, Ross MG. Central angiotensin II AT1 receptors mediate fetal swallowing and pressor responses in the near-term ovine fetus. Am J Physiol Regul Integr Comp Physiol 2004; 288:R1014-20. [PMID: 15550618 DOI: 10.1152/ajpregu.00479.2003] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Swallowed volumes in the fetus are greater than adult values (per body weight) and serve to regulate amniotic fluid volume. Central ANG II stimulates swallowing, and nonspecific ANG II receptor antagonists inhibit both spontaneous and ANG II-stimulated swallowing. In the adult rat, AT1 receptors mediate both stimulated drinking and pressor activities, while the role of AT2 receptors is controversial. As fetal brain contains increased ANG II receptors compared with the adult brain, we sought to investigate the role of both AT1 and AT2 receptors in mediating fetal swallowing and pressor activities. Five pregnant ewes with singleton fetuses (130 +/- 1 days) were prepared with fetal vascular and lateral ventricle (LV) catheters and electrocorticogram and esophageal electromyogram electrodes and received three studies over 5 days. On day 1 (ANG II), following a 2-h basal period, 1 ml artificial cerebrospinal fluid (aCSF) was injected in the LV. At time 4 h, ANG II (6.4 microg) was injected in the LV, and the fetus was monitored for a final 2 h. On day 3, AT1 receptor blocker (losartan 0.5 mg) was administered at 2 h, and ANG II plus losartan was administered at 4 h. On day 5, AT2 receptor blocker (PD-123319; 0.8 mg was administered at 2 h and ANG II plus PD-123319 at 4 h. In the ANG II study, LV injection of ANG II significantly increased fetal swallowing (0.9 +/- 0.1 to 1.4 +/- 0.1 swallows/min; P < 0.05). In the losartan study, basal fetal swallowing significantly decreased in response to blockade of AT1 receptors (0.9 +/- 0.1 to 0.4 +/- 0.1 swallows/min; P < 0.05), while central injection of ANG II in the presence of AT1 receptor antagonism did not increase fetal swallowing (0.6 +/- 0.1 swallows/min). In the PD-123319 study, basal fetal swallowing did not change in response to blockade of AT2 receptor (0.9 +/- 0.1 swallows/min), while central injection of ANG II in the presence of AT2 blockade significantly increased fetal swallowing (1.5 +/- 0.1 swallows/min; P < 0.05). ANG II caused significant pressor responses in the control and PD-123319 studies but no pressor response in the presence of AT1 blockade. These data demonstrate that in the near-term ovine fetus, AT1 receptor but not AT2 receptors accessible via CSF contribute to dipsogenic and pressor responses.
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Affiliation(s)
- Mostafa A El-Haddad
- David Geffen UCLA Medical School, Research and Educational Institute, Harbor/UCLA Medical Center, 1124 W. Carson St., RB-1, Torrance, CA 90502, USA.
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224
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Crowley SD, Tharaux PL, Audoly LP, Coffman TM. Exploring type I angiotensin (AT1) receptor functions through gene targeting. ACTA ACUST UNITED AC 2004; 181:561-70. [PMID: 15283771 DOI: 10.1111/j.1365-201x.2004.01331.x] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
The renin-angiotensin system (RAS) modulates a diverse set of physiological processes including development, blood pressure, renal function and inflammation. The principal effector molecule of this system, angiotensin II, mediates most of these actions. The classically recognized functions of the RAS are triggered via the type 1 (AT(1)) class of angiotensin receptors. Pharmacological blockade of the AT(1) receptor lowers blood pressure and slows the progression of cardiovascular and renal diseases. Gene-targeting technology provides an experimental approach for precisely dissecting the physiological functions of the RAS. Here, we review how gene-targeting experiments have elucidated AT(1) receptor functions.
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Affiliation(s)
- S D Crowley
- Division of Nephrology, Duke University and Durham VA Medical Centers, Durham, NC 27705, USA
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225
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de Lucca Junior W, Franci CR. Angiotensinergic pathway through the median preoptic nucleus in the control of oxytocin secretion and water and sodium intake. Brain Res 2004; 1014:236-43. [PMID: 15213008 DOI: 10.1016/j.brainres.2004.03.077] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 03/31/2004] [Indexed: 11/27/2022]
Abstract
Our objective was to study in which situations the median preoptic nucleus (MnPO) interferes with the control of oxytocin secretion and salt intake and the possible mediation of angiotensin II (AII) through their AT1 receptors. Lesion of the MnPO by ibotenic acid in male rats did not change water and NaCl intake in conditions of ad libitum offer, water deprivation or salt load, but it did cause significant decrease of NaCl intake in sodium depleted animals. These animals presented higher water intake or lower NaCl intake after microinjection of AII or losartan into the MnPO, respectively. They decreased plasma oxytocin after microinjection of losartan into the MnPO, but not of AII or isotonic saline. Oxytocin secretion induced by hypertonic saline i.p. was reduced by microinjection of AII, but not losartan into the MnPO. On the other hand, microinjection of losartan in this area, but not AII, reduced plasma oxytocin in animals submitted to the isotonic saline i.p. Thus, it seems that the sodium intake control is performed by MnPO neurons through the stimulatory action of angiotensin II on AT1 receptors under sodium depletion, but not water deprivation or salt overload neither of ad libitum water and salt intake condition. On the other hand, in the high-sodium condition, endogenous angiotensin did not act on MnPO neurons to the control of oxytocin secretion while exogenous angiotensin inhibited oxytocin secretion. These results indicate two possible angiotensinergic neural circuits: one is stimulating and the other is inhibiting oxytocin secretion, depending on sodium balance.
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Affiliation(s)
- Waldecy de Lucca Junior
- Departamento de Fisiologia, Faculdade de Medicina de Ribeirão Preto, Universidade de São Paulo, Avenida bandeirantes, 3900. CEP: 14049-900 Ribeirão Preto-SP, Brazil
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226
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Chen Y, Liu-Stratton Y, Hassanain H, Cool DR, Morris M. Dietary sodium regulates angiotensin AT1a and AT1b mRNA expression in mouse brain. Exp Neurol 2004; 188:238-45. [PMID: 15246823 DOI: 10.1016/j.expneurol.2004.04.005] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2003] [Revised: 04/01/2004] [Accepted: 04/07/2004] [Indexed: 10/26/2022]
Abstract
Previous results showed that angiotensin (Ang) AT1a and AT1b receptor mRNA are expressed in mouse hypothalamus (HYP), brainstem (BS) and anterior pituitary (PIT). To extend these findings, we developed a real-time polymerase chain reaction (PCR) method to differentiate and quantify Ang AT1a and AT1b mRNA in mouse brain. An experiment was conducted in male C57Bl/6J mice to determine the effects of low and high dietary salt (0.04 or 8% NaCl for 2 weeks) on mRNA expression. Physiological measurements showed that high salt increased water intake (15.1 +/- 0.6 ml/day), whereas low salt decreased water intake (3.2 +/- 0.1 ml/day). There were no significant changes in body weight, hematocrit or plasma osmolality. Real-time PCR was effective in distinguishing AT1a and AT1b receptor mRNA. The PCR efficiencies for AT1a, AT1b and 18S ribosome were tested to be identical, making it possible to quantify mRNA levels. There were differences in angiotensin receptor expression, related to diet and brain region. In hypothalamus, both the high salt and low salt diet decreased AT1a expression (to 63 +/- 4% and 62 +/- 1%), although there were no changes in AT1b. In brainstem, there was a marked increase in AT1a (to 365 +/- 60%) and AT1b (to 372 +/- 23%) after high salt, although there was only a marked decrease for AT1b (to 23 +/- 5%) after low salt. In anterior pituitary, both high salt and low salt diet increased AT1a expression (to 152 +/- 8% and 123 +/- 9%), although there were no changes in AT1b. Results document that both AT1 receptor subtypes are present in mouse hypothalamus, brainstem and anterior pituitary, and that there is differential regulation of expression in response to changes in dietary salt.
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Affiliation(s)
- Yanfang Chen
- Department of Pharmacology and Toxicology, Wright State University School of Medicine, Dayton, OH 45435-0001, USA.
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227
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Thöne-Reineke C, Zimmermann M, Neumann C, Krikov M, Li J, Gerova N, Unger T. Are angiotensin receptor blockers neuroprotective? Curr Hypertens Rep 2004; 6:257-66. [PMID: 15257859 DOI: 10.1007/s11906-004-0019-3] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
Abstract
Stroke is one of the leading causes of invalidism and death in the industrialized world. Among others, the renin- angiotensin system (RAS) has been implicated in the pathogenesis and outcome of ischemic events, including stroke. Angiotensin II (Ang II), the major effector peptide of the RAS, exerts most of its well-defined physiologic and pathophysiologic actions, including those on the central and peripheral nervous system, through its Ang II type 1 (AT1) receptor subtype. This receptor not only contributes to stroke-related pathologic mechanisms (eg, hypertension, atherothrombosis, and cardiac hypertrophy) but also may be involved in postischemic damage to the brain. However, it has also been demonstrated that Ang II, via its AT2 receptor subtype, accelerates neuronal tissue regeneration after injury. In this article, we review the experimental evidence supporting the notion that blockade of brain AT1 receptors can be beneficial with respect to stroke incidence and outcome. We further delineate how AT2 receptors could be involved in neuronal regeneration following brain injury, such as stroke. In doing so, we also attempt to shed some light on the mechanisms by which AT1 receptor blockers, which leave the AT2 receptor unopposed, might exert protective actions in brain ischemia.
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Affiliation(s)
- Christa Thöne-Reineke
- Center for Cardiovascular Research (CCR)/Institut für Pharmakologie und Toxikologie, Campus Charité Mitte Charité--Universitätsmedizin Berlin, Hessische Strasse 3-4, 10115 Berlin, Germany
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228
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Speth RC. Sarcosine1,glycine8 angiotensin II is an AT1 angiotensin II receptor subtype selective antagonist. ACTA ACUST UNITED AC 2004; 115:203-9. [PMID: 14556962 DOI: 10.1016/s0167-0115(03)00172-1] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Studies predating the discovery of the two major subtypes of angiotensin II (Ang II) receptors, AT1 and AT2, revealed anomalous characteristics of sarcosine1,glycine8 Ang II (Sar1,Gly8 Ang II). It competed poorly for 125I-Ang II binding in bovine brain but potently antagonized dipsogenic responses to intracerebroventricularly administered Ang II. Subsequent recognition that bovine brain contains AT(2) receptors, while dipsogenic responses to Ang II are mediated by AT1 receptors, suggests that Sar1,Gly(8) Ang II is AT1 selective. Sar1,Gly8 Ang II competed for 125I-sarcosine1,isoleucine8 Ang II binding to AT1 receptors in pituitary, liver and adrenal (the latter with the AT2 selective antagonist PD 123,319) with Ki's of 0.66, 1.40 and 1.36 nM, respectively. In contrast, the Ki of Sar1,Gly8 Ang II for AT2 receptors in rat adrenal (with the selective AT1 antagonist losartan) was 52 nM. 125I-Sar1,Gly8 Ang II (0.5-3 nM) bound to AT1 receptors in pituitary, liver, heart, adrenal, and hypothalamic membranes with high affinity (Kd=0.43, 1.6, 2.3, 0.96 and 1.8 nM, respectively), but showed no saturable binding to the adrenal AT2 receptor. 125I-Sar1,Gly8 Ang II selectively labeled AT1 receptors in sections of adrenal using receptor autoradiography. Thus, binding studies reveal Sar1,Gly8 Ang II to be the first angiotensin peptide analog to show AT1 receptor selectivity. 125I-Sar1,Gly8 Ang II offers a new means to selectively radiolabel AT1 receptors and may help to characterize ligand docking sites and agonist switches for AT1 versus AT2 receptors.
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Affiliation(s)
- Robert C Speth
- Department of Veterinary and Comparative Anatomy, Pharmacology and Physiology, Washington State University, Pullman, WA 99164-6520, USA.
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229
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Donadio MVF, Sagae SC, Franci CR, Anselmo-Franci JA, Lucion AB, Sanvitto GL. Angiotensin II receptors in the arcuate nucleus mediate stress-induced reduction of prolactin secretion in steroid-primed ovariectomized and lactating rats. Brain Res 2004; 1006:59-65. [PMID: 15047024 DOI: 10.1016/j.brainres.2004.01.052] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 01/27/2004] [Indexed: 11/24/2022]
Abstract
Angiotensin II (Ang II) is a peptide that exerts an inhibitory effect upon pituitary prolactin (PRL) release through the hypothalamic arcuate nucleus (ARC). Since both PRL and Ang II are known to be affected by stress, the experiments reported here were conducted to investigate the possible participation of Ang II in the stress-induced response of PRL in situations in which pre-stress PRL levels are high, as during the PRL surge induced by estradiol (E(2)) and progesterone (P) in ovariectomized rats (OVXE(2)P) and lactating females on day 7 post-partum. Adult female rats were stereotactically implanted with bilateral guide-cannulae in the ARC; 3 days later, they were microinjected with saline or losartan and, after a 15-min interval, they were submitted to stress by ether inhalation during 1 min. Five minutes after stress, trunk blood samples were collected. Plasma PRL was measured by radioimmunoassay (RIA). In OVXE(2)P and lactating rats, a significant reduction in PRL levels was detected after stress compared to non-stressed animals. The microinjection of losartan in the ARC before stress blocked the reduction of PRL in both OVXE(2)P and lactating females. In conclusion, the stress-induced reduction of plasma PRL in OVXE(2)P and lactating rats is mediated by Ang II through AT(1) receptors in the ARC.
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Affiliation(s)
- Márcio Vinícius Fagundes Donadio
- Departamento de Fisiologia, Instituto de Ciências Básicas da Saúde (ICBS), Universidade Federal do Rio Grande do Sul (UFRGS), Sarmento Leite 500, Porto Alegre, RS 90050-170, Brazil
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230
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Pladys P, Lahaie I, Cambonie G, Thibault G, Lê NLO, Abran D, Nuyt AM. Role of brain and peripheral angiotensin II in hypertension and altered arterial baroreflex programmed during fetal life in rat. Pediatr Res 2004; 55:1042-9. [PMID: 15071169 DOI: 10.1203/01.pdr.0000127012.37315.36] [Citation(s) in RCA: 85] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
Intrauterine programming of hypertension is associated with evidence of increased renin-angiotensin system (RAS) activity. The current study was undertaken to investigate whether arterial baroreflex and blood pressure variability are altered in a model of in utero programming of hypertension secondary to isocaloric protein deprivation and whether activation of the RAS plays a role in this alteration. Pregnant Wistar rats were fed a normal-protein (18%) or low-protein (9%) diet during gestation, which had no effect on litter size, birth weight, or pup survival. Mean arterial blood pressure (MABP; 126 +/- 3 mm Hg 9% versus 108 +/- 4 mm Hg 18%; p < 0.05) and blood pressure variability were significantly greater in the adult offspring of the 9% protein-fed mothers. Arterial baroreflex control of heart rate, generated by graded i.v. infusion of phenylephrine and nitroprusside, was significantly shifted toward higher pressure; i.v. angiotensin-converting enzyme inhibitor normalized MABP and shifted the arterial baroreflex curve of the 9% offspring toward lower pressure without affecting the 18% offspring. For examining whether brain RAS is also involved in programming of hypertension, angiotensin-converting enzyme inhibitor and losartan (specific AT(1) receptor antagonist) were administered intracerebroventricularly; both significantly reduced MABP of the 9% but not the 18% offspring. Autoradiographic receptor binding studies demonstrated an increase in brain AT(1) expression in the subfornical organ and the vascular organ of the lamina terminalis in the 9% offspring. These data demonstrate a major tonic role of brain and peripheral RAS on hypertension associated with antenatal nutrient deprivation.
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Affiliation(s)
- Patrick Pladys
- Research Center, Hôpital Sainte-Justine, Department of Pediatrics, University of Montreal, 3175 Côte Sainte-Catherine, Montreal, Quebec, Canada, H3T 1C5
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231
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Hu F, Morrissey P, Yao J, Xu Z. Development of AT(1) and AT(2) receptors in the ovine fetal brain. BRAIN RESEARCH. DEVELOPMENTAL BRAIN RESEARCH 2004; 150:51-61. [PMID: 15126038 DOI: 10.1016/j.devbrainres.2004.02.007] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Accepted: 02/23/2004] [Indexed: 11/30/2022]
Abstract
This study determined the development of AT(1) and AT(2) receptors in the ovine fetal brain from preterm to term by utilizing Western blot for the receptor expression at the protein level, RT-PCR for the receptor mRNA, and immunostaining for the specific receptor immunoreactivity. The results demonstrated that AT(1) and AT(2) receptors developed in an increasing pattern from preterm to term gestational periods in the fetal sheep brain. Both AT(1) and AT(2) receptors have appeared in the major structures in the angiotensin-related central cardiovascular and body fluid controlling pathways at the 0.7 of the gestational age. Importantly, AT(1) receptors have been discovered in the supraoptic nuclei in the fetal hypothalamus, and in the lateral parabrachial nuclei and the ventrolateral medulla in the fetal hindbrain. This provides evidence of the anatomical existence of the angiotensin receptors in the brain areas that are critical for cardiovascular and fluid regulatory functions in utero. In addition, although the results demonstrated the predominance of AT(2) receptors in several regions such as the cerebellum in the ovine fetal brain, dominant occupation of AT(1) receptors in the hypothalamus have appeared early in the life of sheep animals before birth. Together, the data support the hypothesis that the central angiotensin receptors are well developed and established in the last third trimester of gestation. The brain receptors provide a pharmacological basis for the action of angiotensin in the maintenance of in utero fetal physiological functions, including cardiovascular and body fluid balance.
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Affiliation(s)
- Fang Hu
- Harbor-UCLA Medical Center and Research and Education Institute, Torrance, CA 90502, USA
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232
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Schwimmer H, Gerstberger R, Horowitz M. Nitric oxide and angiotensin II: neuromodulation of thermoregulation during combined heat and hypohydration stress. Brain Res 2004; 1006:177-89. [PMID: 15051521 DOI: 10.1016/j.brainres.2004.01.064] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 01/07/2004] [Indexed: 11/22/2022]
Abstract
We investigated the central role of nitric oxide and AngII on thermoregulation in rats (Rattus norvegicus, Sabra strain,) undergoing heat-stress in euhydration or hypohydration (water deprivation, -10% b.wgt). Experimental rats received AngII (100 pm), 7-nitroindazole-an antagonist of neuronal nitric oxide synthase (7NI-100 nm), or AngII+7NI in a 5-microl bolus intracerebroventricularly (i.c.v.) under light chloroform anesthesia; untreated control rats received saline or DMSO (5%). We used three experimental paradigms: (1) heat defense responses [salivation (STsh), vasodilatation (VTsh) temperature thresholds and heat-endurance] in conscious, heat-stressed (39 degrees C) rats; (2) Western immunoblotting to detect AngII AT(1) and AT(2) receptors and nNOS protein expression; (3) real-time PCR to measure gene transcripts. In the in vivo experiment, 7NI decreased thermoregulatory thresholds, namely, NO had a reciprocal effect that was more pronounced during hypohydration (e.g. euhydration: STsh: -0.7+/-0.01 degrees C, hypohydration: -0.9+/-0.18 degrees C, p<0.05). AngII decreased STsh by 0.9+/-0.18 degrees C (p<0.05) upon euhydration but increased it in hypohydration (+1.7+/-0.28 degrees C, p<0.05). A novel finding was the involvement of AT(2) receptors in thermoregulation, which was more pronounced upon hypohydration. The response to NO was mediated via AT(1) and AT(2) receptors signaling, as well as independently. A synthesis of the results from all experimental paradigms suggests (1) a dominant influence (decrease) of NO on AT(1) receptors, thereby changing AT(1)/AT(2) receptor ratio and their signaling pathway; primarily upon hypohydration; (2) an influence of AngII (increase) on receptor density, more pronounced during hypohydration, at both gene transcription and translation levels; and (3) an effect of AngII on nNOS protein levels, implying a mutual effect of AngII and NO.
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MESH Headings
- Analysis of Variance
- Angiotensin II/antagonists & inhibitors
- Angiotensin II/physiology
- Angiotensin II Type 1 Receptor Blockers
- Angiotensin II Type 2 Receptor Blockers
- Animals
- Blotting, Western/methods
- Body Temperature/drug effects
- Body Temperature Regulation/drug effects
- Body Temperature Regulation/physiology
- Body Weight/drug effects
- Cell Membrane/drug effects
- Cell Membrane/metabolism
- Cell Nucleus/drug effects
- Cell Nucleus/metabolism
- Dehydration/physiopathology
- Drug Interactions
- Enzyme Inhibitors/pharmacology
- Heat Stress Disorders/physiopathology
- Indazoles/pharmacology
- Injections, Intraventricular/methods
- Losartan/pharmacology
- Male
- Nitric Oxide/physiology
- RNA, Messenger/biosynthesis
- Rats
- Receptor, Angiotensin, Type 1/genetics
- Receptor, Angiotensin, Type 1/metabolism
- Receptor, Angiotensin, Type 2/genetics
- Receptor, Angiotensin, Type 2/metabolism
- Reverse Transcriptase Polymerase Chain Reaction/methods
- Salivation/drug effects
- Salivation/physiology
- Vasodilation/drug effects
- Vasodilation/physiology
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Affiliation(s)
- H Schwimmer
- Division of Physiology, Hadassah School of Dental Medicine, The Hebrew University, POB 12272, Jerusalem 91120, Israel.
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233
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Thomas MA, Fleissner G, Stöhr M, Hauptfleisch S, Lemmer B. Localization of components of the renin–angiotensin system in the suprachiasmatic nucleus of normotensive Sprague–Dawley rats. Brain Res 2004; 1008:224-35. [PMID: 15145760 DOI: 10.1016/j.brainres.2004.01.085] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 01/27/2004] [Indexed: 11/25/2022]
Abstract
The dominant pacemaker of the mammalian circadian clock, located in the suprachiasmatic nucleus (SCN), is of special interest for many pharmacological, physiological and immunohistological studies on angiotensins and their receptors. Based on its role in the circadian modulation of blood pressure and vasopressin release, the distribution and function of the neuropeptide angiotensin II (ANG II) and its AT1-receptors (AT1) in the SCN became a target for several immunohistological studies. Though the distribution of ANG II and vasopressin in the SCN is well known at light microscopic level, detailed data concerning the AT1-receptor distribution in the SCN is missing. To confirm the mechanisms by which ANG II exerts its actions in the SCN, it is vital to understand how the brain renin-angiotensin system is organized at the cellular level, including the distribution of ANG II and the ANG II (AT1)-receptors as well as the protein-receptor complex. The current paper presents a light- and electron microscopic study on AT1-receptor-immunolabeling in the suprachiasmatic nucleus of normotensive Sprague-Dawley rats.
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Affiliation(s)
- Martin Alexander Thomas
- Institute of Pharmacology and Toxicology, Ruprecht-Karls University Heidelberg, Maybachstr. 14-16, 68169 Mannheim, Germany.
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234
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Zimmerman MC, Davisson RL. Redox signaling in central neural regulation of cardiovascular function. PROGRESS IN BIOPHYSICS AND MOLECULAR BIOLOGY 2004; 84:125-49. [PMID: 14769433 DOI: 10.1016/j.pbiomolbio.2003.11.009] [Citation(s) in RCA: 101] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
One of the most prominent concepts to emerge in cardiovascular research over the past decade, especially in areas focused on angiotensin II (AngII), is that reactive oxygen species (ROS) are critical signaling molecules in a wide range of cellular processes. Many of the physiological effects of AngII are mediated by ROS, and alterations in AngII-mediated redox mechanisms are implicated in cardiovascular diseases such as hypertension and atherosclerosis. Although most investigations to date have focused on the vasculature as a key player, the nervous system has recently begun to gain attention in this field. Accumulating evidence suggests that ROS have important effects on central neural mechanisms involved in blood pressure regulation, volume homeostasis, and autonomic function, particularly those that involve AngII signaling. Furthermore, oxidant stress in the central nervous system is implicated in the neuro-dysregulation associated with some forms of hypertension and heart failure. The main objective of this review is to discuss the recent progress and prospects for this new field of central redox signaling in cardiovascular regulation, while also addressing the molecular tools that have spurred it forward.
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Affiliation(s)
- Matthew C Zimmerman
- Department of Anatomy and Cell Biology, Roy J and Lucille A Carver College of Medicine, The University of Iowa, Iowa City 52245, USA
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235
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Huang J, Hara Y, Anrather J, Speth RC, Iadecola C, Pickel VM. Angiotensin II subtype 1A (AT1A) receptors in the rat sensory vagal complex: subcellular localization and association with endogenous angiotensin. Neuroscience 2004; 122:21-36. [PMID: 14596846 DOI: 10.1016/s0306-4522(03)00606-7] [Citation(s) in RCA: 58] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Angiotensin II (Ang II) type 1 (AT1) receptors are prevalent in the sensory vagal complex including the nucleus tractus solitarii (NTS) and area postrema, each of which has been implicated in the central cardiovascular effects produced by Ang II. In rodents, these actions prominently involve the AT1A receptor. Thus, we examined the electron microscopic dual immunolabeling of antisera recognizing the AT1A receptor and Ang II to determine interactive sites in the sensory vagal complex of rat brain. In both the area postrema and adjacent dorsomedial NTS, many somatodendritic profiles were dually labeled for the AT1A receptor and Ang II. In these profiles, AT1A receptor-immunoreactivity was often seen in the cytoplasm beneath labeled portions of the plasma membrane and in endosome-like granules as well as Golgi lamellae and outer nuclear membranes. In addition, AT1A receptor labeling was detected on the plasma membrane and in association with cytoplasmic membranes in many small axons and axon terminals. These terminals were morphologically heterogeneous containing multiple types of vesicles and forming either inhibitory- or excitatory-type synapses. In the area postrema, AT1A receptor labeling also was detected in many non-neuronal cells including glia, capillary endothelial cells and perivascular fibroblasts that were less prevalent in the NTS. We conclude that in the rat sensory vagal complex, AT1A receptors are strategically positioned for involvement in modulation of the postsynaptic excitability and intracrine hormone-like effects of Ang II. In addition, these receptors have distributions consistent with diverse roles in regulation of transmitter release, regional blood flow and/or vascular permeability.
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Affiliation(s)
- J Huang
- Department of Neurology and Neuroscience, Cornell University Medical College, 411 East 69th Street, Room KB-410, New York, NY 10021, USA
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236
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Antunes-Rodrigues J, de Castro M, Elias LLK, Valença MM, McCann SM. Neuroendocrine control of body fluid metabolism. Physiol Rev 2004; 84:169-208. [PMID: 14715914 DOI: 10.1152/physrev.00017.2003] [Citation(s) in RCA: 311] [Impact Index Per Article: 15.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023] Open
Abstract
Mammals control the volume and osmolality of their body fluids from stimuli that arise from both the intracellular and extracellular fluid compartments. These stimuli are sensed by two kinds of receptors: osmoreceptor-Na+ receptors and volume or pressure receptors. This information is conveyed to specific areas of the central nervous system responsible for an integrated response, which depends on the integrity of the anteroventral region of the third ventricle, e.g., organum vasculosum of the lamina terminalis, median preoptic nucleus, and subfornical organ. The hypothalamo-neurohypophysial system plays a fundamental role in the maintenance of body fluid homeostasis by secreting vasopressin and oxytocin in response to osmotic and nonosmotic stimuli. Since the discovery of the atrial natriuretic peptide (ANP), a large number of publications have demonstrated that this peptide provides a potent defense mechanism against volume overload in mammals, including humans. ANP is mostly localized in the heart, but ANP and its receptor are also found in hypothalamic and brain stem areas involved in body fluid volume and blood pressure regulation. Blood volume expansion acts not only directly on the heart, by stretch of atrial myocytes to increase the release of ANP, but also on the brain ANPergic neurons through afferent inputs from baroreceptors. Angiotensin II also plays an important role in the regulation of body fluids, being a potent inducer of thirst and, in general, antagonizes the actions of ANP. This review emphasizes the role played by brain ANP and its interaction with neurohypophysial hormones in the control of body fluid homeostasis.
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Affiliation(s)
- José Antunes-Rodrigues
- Department of Physiology, School of Medicine of Ribeirao Preto, University of São Paulo, Ribeirao Preto, São Paulo, Brazil.
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237
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Sangaleti CT, Crescenzi A, Michelini LC. Endogenous angiotensin and pressure modulate brain angiotensinogen and AT1A mRNA expression. Hypertension 2004; 43:317-23. [PMID: 14732738 DOI: 10.1161/01.hyp.0000112030.79692.21] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
In the coarctation hypertension model, we showed both dissociation of plasma renin activity from cardiovascular-induced effects and the reversal of hypertension-induced responses by losartan. In this study, we investigated the effects of hypertension on the expression of brain renin-angiotensin system components and the simultaneous functional responses and effects of long-term angiotensin II (AT) receptor blockade on these responses. Rats were given vehicle or losartan for 9 days and subjected to subdiaphragmatic aortic constriction or sham surgery after 4 days of treatment. On the fifth postsurgical day, pressure and heart rate were measured in the conscious state; the brain was perfused and removed afterward. Sequential slices of brainstem were hybridized with 35S-oligodeoxynucleotide probes for angiotensinogen, AT1A, and AT1B receptors and processed for autoradiography and densitometry. In vehicle-treated rats, hypertension was accompanied by tachycardia and marked increments in angiotensinogen and AT1A mRNA expression in the cardiovascular system-controlling brainstem areas. In the nucleus tractus solitarii, AT1A density was correlated with both pressure and heart rate values (P<0.01), whereas angiotensinogen levels were correlated with pressure only (P<0.05). Losartan did not change the pressure of hypertensive rats (142+/-4 versus 146+/-2 mm Hg, losartan versus vehicle) and the hypertension-induced angiotensinogen mRNA expression but did block both tachycardic response and hypertension-induced AT1A mRNA expression. Hypertension and losartan did not change AT1B mRNA expression. The hypertension-induced positive feedback on angiotensinogen and AT1A mRNA expression supports the concept of a permissive role for brain angiotensin II in orchestrating circulatory responses during the development of hypertension. These data also explain the efficacy of long-term AT1 receptor blockade to reverse hypertension-induced effects.
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Affiliation(s)
- Carine T Sangaleti
- Department of Physiology and Biophysics, Institute of Biomedical Sciences, Universidade de Sao Paulo, Sao Paulo, SP, Brazil
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238
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Chen Y, Ross BM, William Currie R. Heat shock treatment protects against angiotensin II–induced hypertension and inflammation in aorta. Cell Stress Chaperones 2004. [DOI: 10.1379/1466-1268(2004)009<0099:hstpaa>2.0.co;2] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
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239
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Jain P, Armando I, Juorio AV, Barden N, Benicky J, Saavedra JM. Decreased hypothalamic and adrenal angiotensin II receptor expression and adrenomedullary catecholamines in transgenic mice with impaired glucocorticoid receptor function. Neuroendocrinology 2004; 80:171-80. [PMID: 15583474 DOI: 10.1159/000082358] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/24/2004] [Accepted: 09/14/2004] [Indexed: 11/19/2022]
Abstract
In transgenic mice expressing an antisense mRNA against the glucocorticoid receptor (GR), which partially blocks GR expression, impaired glucocorticoid feedback efficacy is accompanied by reduced hypothalamic corticotropin-releasing hormone (CRH) and vasopressin (AVP) activity and reduced peripheral sympathetic tone, indications of a shift in the balance of hypothalamic CRH and sympathetic regulation. As angiotensin II (Ang II) regulates CRH, AVP and sympathetic activity, we studied the expression of Ang II receptors in the hypothalamus and adrenal gland of GR transgenic and wild-type mice, adrenal catecholamines and mRNA for their rate-limiting enzyme, tyrosine hydroxylase (TH). We found that transgenic mice expressed significantly less numbers of Ang II AT(1) receptors in the hypothalamic paraventricular nucleus and median eminence, lower numbers of AT(2) receptors in supraoptic and paraventricular nuclei and lower numbers of AT(2) receptors in the adrenal medulla when compared with wild-type controls. The expression of TH mRNA and the concentration of adrenomedullary epinephrine and norepinephrine were also lower in transgenic mice when compared with wild-type controls. Decreased hypothalamic and adrenal Ang II receptor stimulation as a result of decreased GR expression may explain the decreased hypothalamic CRH and AVP and decreased adrenomedullary and sympathetic activities in this model.
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Affiliation(s)
- Paul Jain
- Division of Intramural Research Programs, National Institute of Mental Health, National Institutes of Health, Department of Health and Human Services, Bethesda, MD 20892, USA
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240
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Xu Z, Shi L, Yao J. Central angiotensin II-induced pressor responses and neural activity in utero and hypothalamic angiotensin receptors in preterm ovine fetus. Am J Physiol Heart Circ Physiol 2003; 286:H1507-14. [PMID: 14684369 DOI: 10.1152/ajpheart.00764.2003] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The central renin-angiotensin system is important in the control of blood pressure in the adult. However, few data exist about the in utero development of central angiotensin-mediated pressor responses. Our recent studies have shown that the application of ANG II into the fetal brain can increase blood pressure at near term. The present study determined fetal blood pressure and heart rate in response to a central application of ANG II in the chronically prepared preterm ovine fetus, determined the action sites marked by c-Fos expression in the fetal central pathways after intracerebroventricular injection of ANG II in utero, and determined angiotensin subtype 1 receptors in the fetal hypothalamus. Central injection of ANG II significantly increased fetal mean arterial pressure (MAP). Adjusted fetal MAP against amniotic pressure was also increased by ANG II. Fetal heart rate was subsequently decreased after the central administration of ANG II and/or the increase of blood pressure. ANG II induced c-Fos expression in the central putative cardiovascular area, the paraventricular nuclei in the brain sympathetic pathway. Application of ANG II also caused intense Fos immunoreactivity in the tractus solitarius nuclei in the hindbrain. In addition, intense angiotensin subtype 1 receptors were expressed in the hypothalamus at preterm. These data demonstrate that central ANG II-related pressor centers start to function as early as at preterm and suggest that the central angiotensin-related sympathetic pathway is likely intact in the control of blood pressure in utero.
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Affiliation(s)
- Zhice Xu
- Harbor-University of California Los Angeles Medical Center, (UCLA), Harbor-UCLA Medical Center, Torrance, CA 90502, USA.
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241
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Davisson RL. Physiological genomic analysis of the brain renin-angiotensin system. Am J Physiol Regul Integr Comp Physiol 2003; 285:R498-511. [PMID: 12909574 DOI: 10.1152/ajpregu.00190.2003] [Citation(s) in RCA: 71] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Abstract
The brain renin-angiotensin system (RAS) has long been considered pivotal in cardiovascular regulation and important in the pathogenesis of hypertension and heart failure. However, despite more than 30 years of study, the brain RAS continues to defy explanation. Our lack of understanding of how the brain RAS is organized at the cellular and regional levels has made it difficult to resolve long-sought questions of how ANG II is produced in the brain and the precise mechanisms by which it exerts its actions. A major reason for this is the difficulty in experimentally dissecting the brain RAS at the regional, cellular, and whole organism levels. Recently, we and others developed a series of molecular tools for selective manipulation of the murine brain RAS, in parallel with technologies for integrative analysis of cardiovascular and volume homeostasis in the conscious mouse. This review, based in part on a lecture given in conjunction with the American Physiological Society Young Investigator Award in Regulatory and Integrative Physiology (Water and Electrolyte Homeostasis Section), outlines the physiological genomics strategy that we have taken in an effort to unravel some of the complexities of this system. It also summarizes the principles, progress, and prospects for a better understanding of the brain RAS in health and disease.
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Affiliation(s)
- Robin L Davisson
- Dept. of Anatomy and Cell Biology, 1-251 Bowen Science Bldg., The Univ. of Iowa Roy J. and Lucille A. Carver College of Medicine, Iowa City, IA 52242, USA.
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242
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Fleegal MA, Sumners C. Drinking behavior elicited by central injection of angiotensin II: roles for protein kinase C and Ca2+/calmodulin-dependent protein kinase II. Am J Physiol Regul Integr Comp Physiol 2003; 285:R632-40. [PMID: 12738610 DOI: 10.1152/ajpregu.00151.2003] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Prior studies utilizing neurons cultured from the hypothalamus and brain stem of newborn rats have demonstrated that ANG II-induced modulation of neuronal firing involves activation of both protein kinase C (PKC) and Ca2+/calmodulin-dependent protein kinase II (CaMKII). The present studies were performed to determine whether these signaling molecules are also involved in physiological responses elicited by ANG II in the brain in vivo. Central injection of ANG II (10 ng/2 microl) into the lateral cerebroventricle (icv) of Sprague-Dawley rats increased water intake in a time-dependent manner. This ANG II-mediated dipsogenic response was attenuated by central injection of the PKC inhibitors chelerythrine chloride (0.5-50 microM, 2 microl) and Go-6976 (2.3 nM, 2 microl) and by the CaMKII inhibitor KN-93 (10 microM, 2 microl). Conversely, icv injection of chelerythrine chloride (50 microM, 2 microl) and KN-93 (10 microM, 2 microl) had no effect on the dipsogenic response elicited by central injection of carbachol (200 ng/2 microl). Furthermore, injection of ANG II (10 ng/2 microl) icv increases the activity of both PKC-alpha and CaMKII in rat septum and hypothalamus. These data suggest that signaling molecules involved in ANG II-induced responses in vitro are also relevant in physiological responses elicited by ANG II in the whole animal model.
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Affiliation(s)
- Melissa A Fleegal
- Dept. of Physiology and Functional Genomics, P.O. Box 100274, Univ. of Florida, Gainesville, FL 32610, USA
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243
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Sunn N, McKinley MJ, Oldfield BJ. Circulating angiotensin II activates neurones in circumventricular organs of the lamina terminalis that project to the bed nucleus of the stria terminalis. J Neuroendocrinol 2003; 15:725-31. [PMID: 12834432 DOI: 10.1046/j.1365-2826.2003.00969.x] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
The aim of this study was to determine, in conscious rats, whether elevated concentrations of circulating angiotensin II activate neurones in both the subfornical organ and organum vasculosum of the lamina terminalis (OVLT) that project to the bed nucleus of the stria terminalis (BNST). The strategy employed was to colocalize retrogradely transported cholera toxin B subunit (CTB) from the BNST, with elevated levels of Fos protein in response to angiotensin II. Circulating angiotensin II concentrations were increased by either intravenous infusion of angiotensin II or subcutaneous injection of isoproterenol. Neurones exhibiting Fos in response to angiotensin II were present in the subfornical organ, predominantly in its central core but with some also seen in its peripheral aspect, the dorsal and lateral margins of the OVLT, the supraoptic nucleus and the parvo- and magnocellular divisions of the paraventricular nucleus. Fos-labelling was not apparent in control rats infused with isotonic saline intravenously or injected with either CTB or CTB conjugated to gold particles (CTB-gold) only. Of the neurones in the subfornical organ that were shown by retrograde labelling to project to BNST, approximately 50% expressed Fos in response to isoproterenol. This stimulus also increased Fos in 33% of neurones in the OVLT that project to BNST. Double-labelled neurones were concentrated in the central core of the subfornical organ and lateral margins of the OVLT in response to increased circulating angiotensin II resulting from isoproterenol treatment. These data support a role for circulating angiotensin II acting either directly or indirectly on neurones in subfornical organ and OVLT that project to the BNST and provide further evidence of functional regionalization within the subfornical organ and the OVLT. The function of these pathways is yet to be determined; however, a role in body fluid homeostasis is possible.
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Affiliation(s)
- N Sunn
- Howard Florey Institute of Experimental Physiology and Medicine, University of Melbourne, Melbourne, Victoria, Australia
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244
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García MJ, Martínez-Martos JM, Mayas MD, Carrera MP, Ramírez-Expósito MJ. Hormonal status modifies renin-angiotensin system-regulating aminopeptidases and vasopressin-degrading activity in the hypothalamus-pituitary-adrenal axis of male mice. Life Sci 2003; 73:525-38. [PMID: 12770609 DOI: 10.1016/s0024-3205(03)00294-7] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
Local renin-angiotensin systems (RAS) have been postulated in brain, pituitary and adrenal glands. These local RAS have been implicated, respectively, in the central regulation of the cardiovascular system and body water balance, the secretion of pituitary hormones and the secretion of aldosterone by adrenal glands. By other hand, it is known that the hypothalamus-pituitary-adrenal (HPA) axis is involved in blood pressure regulation, and is affected by sex hormones. The aim of the present work is to analyze the influence of testosterone on RAS-regulating aminopeptidase A, B and M activities and vasopressin-degrading activity in the HPA axis, measuring these activities in their soluble and membrane-bound forms in the hypothalamus, pituitary and adrenal glands of orchidectomized males and orchidectomized males treated subcutaneously with several doses of testosterone. The present data suggest that in male mice, testosterone influences the RAS- and vasopressin-degrading activities at all levels of the HPA axis.
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Affiliation(s)
- María Jesús García
- Unit of Physiology, Department of Health Sciences, Faculty of Experimental and Health Sciences, University of Jaén, Paraje Las Lagunillas s/n, E-23071 Jaén, Spain
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McKinley MJ, Albiston AL, Allen AM, Mathai ML, May CN, McAllen RM, Oldfield BJ, Mendelsohn FAO, Chai SY. The brain renin-angiotensin system: location and physiological roles. Int J Biochem Cell Biol 2003; 35:901-18. [PMID: 12676175 DOI: 10.1016/s1357-2725(02)00306-0] [Citation(s) in RCA: 391] [Impact Index Per Article: 18.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Angiotensinogen, the precursor molecule for angiotensins I, II and III, and the enzymes renin, angiotensin-converting enzyme (ACE), and aminopeptidases A and N may all be synthesised within the brain. Angiotensin (Ang) AT(1), AT(2) and AT(4) receptors are also plentiful in the brain. AT(1) receptors are found in several brain regions, such as the hypothalamic paraventricular and supraoptic nuclei, the lamina terminalis, lateral parabrachial nucleus, ventrolateral medulla and nucleus of the solitary tract (NTS), which are known to have roles in the regulation of the cardiovascular system and/or body fluid and electrolyte balance. Immunohistochemical and neuropharmacological studies suggest that angiotensinergic neural pathways utilise Ang II and/or Ang III as a neurotransmitter or neuromodulator in the aforementioned brain regions. Angiotensinogen is synthesised predominantly in astrocytes, but the processes by which Ang II is generated or incorporated in neurons for utilisation as a neurotransmitter is unknown. Centrally administered AT(1) receptor antagonists or angiotensinogen antisense oligonucleotides inhibit sympathetic activity and reduce arterial blood pressure in certain physiological or pathophysiological conditions, as well as disrupting water drinking and sodium appetite, vasopressin secretion, sodium excretion, renin release and thermoregulation. The AT(4) receptor is identical to insulin-regulated aminopeptidase (IRAP) and plays a role in memory mechanisms. In conclusion, angiotensinergic neural pathways and angiotensin peptides are important in neural function and may have important homeostatic roles, particularly related to cardiovascular function, osmoregulation and thermoregulation.
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Affiliation(s)
- M J McKinley
- Howard Florey Institute of Experimental Physiology and Medicine, University of Melbourne, Melbourne 3010, Vic., Australia.
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246
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Abstract
Fear is an adaptive component of the acute "stress" response to potentially-dangerous (external and internal) stimuli which threaten to perturb homeostasis. However, when disproportional in intensity, chronic and/or irreversible, or not associated with any genuine risk, it may be symptomatic of a debilitating anxious state: for example, social phobia, panic attacks or generalized anxiety disorder. In view of the importance of guaranteeing an appropriate emotional response to aversive events, it is not surprising that a diversity of mechanisms are involved in the induction and inhibition of anxious states. Apart from conventional neurotransmitters, such as monoamines, gamma-amino-butyric acid (GABA) and glutamate, many other modulators have been implicated, including: adenosine, cannabinoids, numerous neuropeptides, hormones, neurotrophins, cytokines and several cellular mediators. Accordingly, though benzodiazepines (which reinforce transmission at GABA(A) receptors), serotonin (5-HT)(1A) receptor agonists and 5-HT reuptake inhibitors are currently the principle drugs employed in the management of anxiety disorders, there is considerable scope for the development of alternative therapies. In addition to cellular, anatomical and neurochemical strategies, behavioral models are indispensable for the characterization of anxious states and their modulation. Amongst diverse paradigms, conflict procedures--in which subjects experience opposing impulses of desire and fear--are of especial conceptual and therapeutic pertinence. For example, in the Vogel Conflict Test (VCT), the ability of drugs to release punishment-suppressed drinking behavior is evaluated. In reviewing the neurobiology of anxious states, the present article focuses in particular upon: the multifarious and complex roles of individual modulators, often as a function of the specific receptor type and neuronal substrate involved in their actions; novel targets for the management of anxiety disorders; the influence of neurotransmitters and other agents upon performance in the VCT; data acquired from complementary pharmacological and genetic strategies and, finally, several open questions likely to orientate future experimental- and clinical-research. In view of the recent proliferation of mechanisms implicated in the pathogenesis, modulation and, potentially, treatment of anxiety disorders, this is an opportune moment to survey their functional and pathophysiological significance, and to assess their influence upon performance in the VCT and other models of potential anxiolytic properties.
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Affiliation(s)
- Mark J Millan
- Psychopharmacology Department, Centre de Rescherches de Croissy, Institut de Recherches (IDR) Servier, 125 Chemin de Ronde, 78290 Croissy-sur-Seine, Paris, France.
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247
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Barnes KL, DeWeese DM, Andresen MC. Angiotensin potentiates excitatory sensory synaptic transmission to medial solitary tract nucleus neurons. Am J Physiol Regul Integr Comp Physiol 2003; 284:R1340-53. [PMID: 12531785 DOI: 10.1152/ajpregu.00505.2002] [Citation(s) in RCA: 39] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Femtomole doses of angiotensin (ANG) II microinjected into nucleus tractus solitarii (nTS) decrease blood pressure and heart rate, mimicking activation of the baroreflex, whereas higher doses depress this reflex. ANG II might generate cardioinhibitory responses by augmenting cardiovascular afferent synaptic transmission onto nTS neurons. Intracellular recordings were obtained from 99 dorsal medial nTS region neurons in rat medulla horizontal slices to investigate whether ANG II modulated short-latency excitatory postsynaptic potentials (EPSPs) evoked by solitary tract (TS) stimulation. ANG II (200 fmol) increased TS-evoked EPSP amplitudes 20-200% with minimal membrane depolarization in 12 neurons excited by ANG II and glutamate, but not substance P (group A). Blockade of non-N-methyl-d-aspartate receptors eliminated TS-evoked EPSPs and responses to ANG II. ANG II did not alter TS-evoked EPSPs in 14 other neurons depolarized substantially by ANG II and substance P (group B). ANG II appeared to selectively augment presynaptic sensory transmission in one class of nTS neurons but had only postsynaptic effects on another group of cells. Thus ANG II is likely to modulate cardiovascular function by more than one nTS neuronal pathway.
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Affiliation(s)
- Karen L Barnes
- Lerner Research Institute, Cleveland Clinic Foundation, Cleveland, Ohio 44195, USA.
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Veerasingham SJ, Raizada MK. Brain renin-angiotensin system dysfunction in hypertension: recent advances and perspectives. Br J Pharmacol 2003; 139:191-202. [PMID: 12770924 PMCID: PMC1573858 DOI: 10.1038/sj.bjp.0705262] [Citation(s) in RCA: 207] [Impact Index Per Article: 9.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2003] [Accepted: 02/27/2003] [Indexed: 11/08/2022] Open
Abstract
This review focuses on the dysfunction of the intrinsic brain renin-angiotensin system (RAS) in the pathogenesis of hypertension. Hyperactivity of the brain RAS plays a critical role in mediating hypertension in both humans and animal models of hypertension, including the spontaneously hypertensive rat (SHR). The specific mechanisms by which increased brain RAS activity results in hypertension are not well understood but include increases in sympathetic vasomotor tone and impaired arterial baroreflex function. We discuss the contribution of endogenous angiotensin (Ang) II actions on presympathetic vasomotor rostral ventrolateral medulla neurons to enhance sympathetic activity and maintain hypertension. In addition, we discuss Ang II-induced attenuation of afferent baroreceptor feedback within the nucleus tractus solitarius and its relevance to the development of hypertension. We also outline the cellular and molecular mechanisms of Ang II signal transduction that may be critical for the initiation and establishment of hypertension. In particular, we present evidence for a phosphoinositide-3-kinase-dependent signaling pathway that appears to contribute to hypertension in the SHR, possibly via augmented Ang II-induced increases in neuronal firing rate and enhanced transcriptional noradrenaline neuromodulation. Finally, we outline future directions in utilizing our understanding of the brain RAS dysfunction in hypertension for the development of improved therapeutic intervention in hypertension.
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Affiliation(s)
| | - Mohan K Raizada
- Department of Physiology and Functional Genomics, University of Florida, U.S.A
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249
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Abstract
Experiments were performed to study angiotensin (Ang) AT1a and AT1b mRNA expression in mice, including, examination of brain distribution and the effect of salt loading. In situ hybridization (ISH) methods showed that the pattern of mRNA expression was identical for AT1a and AT1b, with cellular labeling in rostral forebrain, hypothalamus and brainstem. Receptor mRNAs were concentrated in brain regions involved in the regulation of electrolyte and cardiovascular balance. Immunocytochemistry with AT1 specific antisera showed a pattern that was consistent with the ISH. Reverse transcriptase-polymerase chain reaction (RT-PCR) of hypothalamus and pituitary verified the presence of both AT1a and AT1b mRNA. Using quantitative ISH, we found that AT1a mRNA expression was significantly increased after 5 days of 2% NaCl consumption in anterior third ventricle (AV3V), paraventricular hypothalamus (PVN) and subfornical organ (SFO), but unchanged in anterior pituitary. There were no significant changes in AT1b mRNA. These results document the utility of ISH coupled with quantitative imaging techniques for the study of subtype specific expression. Using ISH and RT-PCR, we verified that AT1a and AT1b receptors are expressed in mouse brain and pituitary and show a similar pattern of distribution. Salt loading produced a specific increase in AT1a mRNA in osmosensitive regions, suggesting that this receptor subtype is regulated by sodium/osmolar input.
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Affiliation(s)
- Yanfang Chen
- Department of Pharmacology and Toxicology, Wright State University School of Medicine, 3640 Colonel Glenn Highway, Dayton, OH 45401-0001, USA
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250
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Wright JW, Tamura-Myers E, Wilson WL, Roques BP, Llorens-Cortes C, Speth RC, Harding JW. Conversion of brain angiotensin II to angiotensin III is critical for pressor response in rats. Am J Physiol Regul Integr Comp Physiol 2003; 284:R725-33. [PMID: 12433674 DOI: 10.1152/ajpregu.00326.2002] [Citation(s) in RCA: 62] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The present investigation measured the relative pressor potencies of intracerebroventricularly infused ANG II, ANG III, and the metabolically resistant analogs d-Asp(1)ANG II and d-Arg(1)ANG III in alert freely moving rats. The stability of these analogs was further facilitated by pretreatment with the specific aminopeptidase A inhibitor EC33 or the aminopeptidase N inhibitor PC18. The results indicate that the maximum elevations in mean arterial pressure (MAP) were very similar for each of these compounds across the dose range 1, 10, and 100 pmol/min during a 5-min infusion period. However, d-Asp(1)ANG II revealed significantly extended durations of pressor effects before return to base level MAP. Pretreatment intracerebroventricular infusion with EC33 blocked the pressor activity induced by the subsequent infusion of d-Asp(1)ANG II, whereas EC33 had no effect on the pressor response to subsequent infusion of d-Arg(1)ANG III. In contrast, pretreatment infusion with PC18 extended the duration of the d-Asp(1)ANG II pressor effect by about two to three times and the duration of d-Arg(1)ANG III's effect by approximately 10 to 15 times. Pretreatment with the specific AT(1) receptor antagonist losartan blocked the pressor responses induced by the subsequent infusion of both analogs indicating that they act via the AT(1) receptor subtype. These results suggest that the brain AT(1) receptor may be designed to preferentially respond to ANG III, and ANG III's importance as a centrally active ligand has been underestimated.
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Affiliation(s)
- John W Wright
- Department of Psychology, Washington State University, Pullman, Washington 99164-4820, USA.
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