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Lansdell TA, Chambers LC, Dorrance AM. Endothelial Cells and the Cerebral Circulation. Compr Physiol 2022; 12:3449-3508. [PMID: 35766836 DOI: 10.1002/cphy.c210015] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Endothelial cells form the innermost layer of all blood vessels and are the only vascular component that remains throughout all vascular segments. The cerebral vasculature has several unique properties not found in the peripheral circulation; this requires that the cerebral endothelium be considered as a unique entity. Cerebral endothelial cells perform several functions vital for brain health. The cerebral vasculature is responsible for protecting the brain from external threats carried in the blood. The endothelial cells are central to this requirement as they form the basis of the blood-brain barrier. The endothelium also regulates fibrinolysis, thrombosis, platelet activation, vascular permeability, metabolism, catabolism, inflammation, and white cell trafficking. Endothelial cells regulate the changes in vascular structure caused by angiogenesis and artery remodeling. Further, the endothelium contributes to vascular tone, allowing proper perfusion of the brain which has high energy demands and no energy stores. In this article, we discuss the basic anatomy and physiology of the cerebral endothelium. Where appropriate, we discuss the detrimental effects of high blood pressure on the cerebral endothelium and the contribution of cerebrovascular disease endothelial dysfunction and dementia. © 2022 American Physiological Society. Compr Physiol 12:3449-3508, 2022.
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Affiliation(s)
- Theresa A Lansdell
- Department of Pharmacology and Toxicology, College of Osteopathic Medicine, Michigan State University, East Lansing, MI, 48824, USA
| | - Laura C Chambers
- Department of Pharmacology and Toxicology, College of Osteopathic Medicine, Michigan State University, East Lansing, MI, 48824, USA
| | - Anne M Dorrance
- Department of Pharmacology and Toxicology, College of Osteopathic Medicine, Michigan State University, East Lansing, MI, 48824, USA
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2
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Mowry FE, Peaden SC, Stern JE, Biancardi VC. TLR4 and AT1R mediate blood-brain barrier disruption, neuroinflammation, and autonomic dysfunction in spontaneously hypertensive rats. Pharmacol Res 2021; 174:105877. [PMID: 34610452 PMCID: PMC8648989 DOI: 10.1016/j.phrs.2021.105877] [Citation(s) in RCA: 30] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/28/2021] [Revised: 09/03/2021] [Accepted: 09/05/2021] [Indexed: 01/23/2023]
Abstract
Angiotensin II (AngII) is implicated in neuroinflammation, blood-brain barrier (BBB) disruption, and autonomic dysfunction in hypertension. We have previously shown that exogenous AngII stimulates Toll-like receptor 4 (TLR4) via AngII type 1 receptor (AT1R), inducing activation of hypothalamic microglia ex vivo, and that AngII-AT1R signaling is necessary for the loss of BBB integrity in spontaneously hypertensive rats (SHRs). Herein, we hypothesized that microglial TLR4 and AT1R signaling interactions represent a crucial mechanistic link between AngII-mediated neuroinflammation and BBB disruption, thereby contributing to sympathoexcitation in SHRs. Male SHRs were treated with TAK-242 (TLR4 inhibitor; 2 weeks), Losartan (AT1R inhibitor; 4 weeks), or vehicle, and age-matched to control Wistar Kyoto rats (WKYs). TLR4 and AT1R inhibitions normalized increased TLR4, interleukin-6, and tumor necrosis factor-α protein densities in SHR cardioregulatory nuclei (hypothalamic paraventricular nucleus [PVN], rostral ventrolateral medulla [RVLM], and nucleus tractus solitarius [NTS]), and abolished enhanced microglial activation. PVN, RVLM, and NTS BBB permeability analyses revealed complete restoration after TAK-242 treatment, whereas SHRs presented with elevated dye leakage. Mean arterial pressure was normalized in Losartan-treated SHRs, and attenuated with TLR4 inhibition. In conscious assessments, TLR4 blockade rescued SHR baroreflex sensitivity to vasoactive drugs, and reduced the SHR pressor response to ganglionic blockade to normal levels. These data suggest that TLR4 activation plays a substantial role in mediating a feed-forward pro-hypertensive cycle involving BBB disruption, neuroinflammation, and autonomic dysfunction, and that TLR4-specific therapeutic interventions may represent viable alternatives in the treatment of hypertension.
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Affiliation(s)
- Francesca E Mowry
- Department of Anatomy, Physiology & Pharmacology, College of Veterinary Medicine, Auburn University, Auburn, AL, USA; Center for Neurosciences Initiative, Auburn University, Auburn, AL, USA
| | - Sarah C Peaden
- Department of Anatomy, Physiology & Pharmacology, College of Veterinary Medicine, Auburn University, Auburn, AL, USA
| | - Javier E Stern
- Center for Neuroinflammation, Georgia State University, Atlanta, GA, USA
| | - Vinicia C Biancardi
- Department of Anatomy, Physiology & Pharmacology, College of Veterinary Medicine, Auburn University, Auburn, AL, USA; Center for Neurosciences Initiative, Auburn University, Auburn, AL, USA.
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3
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Angiotensin II and the Cardiac Parasympathetic Nervous System in Hypertension. Int J Mol Sci 2021; 22:ijms222212305. [PMID: 34830184 PMCID: PMC8624735 DOI: 10.3390/ijms222212305] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2021] [Revised: 11/09/2021] [Accepted: 11/10/2021] [Indexed: 01/08/2023] Open
Abstract
The renin-angiotensin-aldosterone system (RAAS) impacts cardiovascular homeostasis via direct actions on peripheral blood vessels and via modulation of the autonomic nervous system. To date, research has primarily focused on the actions of the RAAS on the sympathetic nervous system. Here, we review the critical role of the RAAS on parasympathetic nerve function during normal physiology and its role in cardiovascular disease, focusing on hypertension. Angiotensin (Ang) II receptors are present throughout the parasympathetic nerves and can modulate vagal activity via actions at the level of the nerve endings as well as via the circumventricular organs and as a neuromodulator acting within brain regions. There is tonic inhibition of cardiac vagal tone by endogenous Ang II. We review the actions of Ang II via peripheral nerve endings as well as via central actions on brain regions. We review the evidence that Ang II modulates arterial baroreflex function and examine the pathways via which Ang II can modulate baroreflex control of cardiac vagal drive. Although there is evidence that Ang II can modulate parasympathetic activity and has the potential to contribute to impaired baseline levels and impaired baroreflex control during hypertension, the exact central regions where Ang II acts need further investigation. The beneficial actions of angiotensin receptor blockers in hypertension may be mediated in part via actions on the parasympathetic nervous system. We highlight important unknown questions about the interaction between the RAAS and the parasympathetic nervous system and conclude that this remains an important area where future research is needed.
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Li J, Liang M, Zeng T, Qiu M, Zhang M, Jiang S, Tan L, Li A. Silencing of Central (Pro)renin Receptor Ameliorates Salt-Induced Renal Injury in Chronic Kidney Disease. Antioxid Redox Signal 2021; 35:93-112. [PMID: 32757619 DOI: 10.1089/ars.2019.7840] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
Aims: A high-salt diet can aggravate oxidative stress, and renal fibrosis via the brain and renal renin-angiotensin system (RAS) axis in chronic kidney disease (CKD) rats. (Pro)renin receptor (PRR) plays a role in regulating RAS and oxidative stress locally. However, whether central PRR regulates salt-induced renal injury in CKD remains undefined. Here, we hypothesized that the reduction of central PRR expression could ameliorate central lesions and thereby ameliorate renal injury in high-salt-load CKD rats. Results: We investigated RAS, sympathetic nerve activity, oxidative stress, inflammation, and tissue injury in subfornical organs and kidneys in high-salt-load 5/6 nephrectomy CKD rats after the silencing of central PRR expression by intracerebroventricular lentivirus-RNAi. We found that the sympathetic nerve activity was reduced, and the levels of inflammation and oxidative stress were decreased in both brain and kidney. Renal injury and fibrosis were ameliorated. To explore the mechanism by which central inhibition of PRR expression ameliorates kidney damage, we blocked central MAPK/ERK1/2 and PI3K/Akt signaling pathways as well as angiotensin converting enzyme 1-angiotensin II-angiotensin type 1 receptors (ACE1-Ang II-AT1R) axis. Salt-induced overexpression of renal RAS, inflammation, oxidative stress, and fibrosis in CKD rats were prevented by central blockade of the pathways. Innovation: This study provides new insights into the mechanisms underlying salt-induced kidney damage. Targeting central PRR or PRR-mediated signaling pathway may be a novel strategy for the treatment of CKD. Conclusions: These results suggested that the silencing of central PRR expression ameliorates salt-induced renal injury in CKD through Ang II-dependent and -independent pathways.
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Affiliation(s)
- Jiawen Li
- Guangdong Provincial Key Laboratory of Renal Failure Research, State Key Laboratory of Organ Failure Research, National Clinical Research Center for Kidney Disease, Nanfang Hospital, Southern Medical University, Guangzhou, China
| | - Min Liang
- Guangdong Provincial Key Laboratory of Renal Failure Research, State Key Laboratory of Organ Failure Research, National Clinical Research Center for Kidney Disease, Nanfang Hospital, Southern Medical University, Guangzhou, China
| | - Tao Zeng
- Guangdong Provincial Key Laboratory of Renal Failure Research, State Key Laboratory of Organ Failure Research, National Clinical Research Center for Kidney Disease, Nanfang Hospital, Southern Medical University, Guangzhou, China
| | - Minzi Qiu
- Department of Nephrology, The Second Affiliated Hospital of Nanchang University, Nanchang, China
| | - Mengbi Zhang
- Guangdong Provincial Key Laboratory of Renal Failure Research, State Key Laboratory of Organ Failure Research, National Clinical Research Center for Kidney Disease, Nanfang Hospital, Southern Medical University, Guangzhou, China
| | - Shaoling Jiang
- Department of Nephrology, The People's Hospital of Nanhai District of Foshan City, Foshan, China
| | - Lishan Tan
- Guangdong Provincial Key Laboratory of Renal Failure Research, State Key Laboratory of Organ Failure Research, National Clinical Research Center for Kidney Disease, Nanfang Hospital, Southern Medical University, Guangzhou, China
| | - Aiqing Li
- Guangdong Provincial Key Laboratory of Renal Failure Research, State Key Laboratory of Organ Failure Research, National Clinical Research Center for Kidney Disease, Nanfang Hospital, Southern Medical University, Guangzhou, China
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Fernandes MV, Rosso Melo M, Mowry FE, Lucera GM, Lauar MR, Frigieri G, Biancardi VC, Menani JV, Colombari DSA, Colombari E. Intracranial Pressure During the Development of Renovascular Hypertension. Hypertension 2021; 77:1311-1322. [PMID: 33689460 DOI: 10.1161/hypertensionaha.120.16217] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
[Figure: see text].
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Affiliation(s)
- Marcos Vinicius Fernandes
- From the Department of Physiology and Pathology, School of Dentistry of Araraquara, São Paulo State University, Araraquara, Brazil (M.V.F.S., M.R.M., G.M.L., M.R.L., G.F., J.V.M., D.S.A.C., E.C.)
| | - Mariana Rosso Melo
- From the Department of Physiology and Pathology, School of Dentistry of Araraquara, São Paulo State University, Araraquara, Brazil (M.V.F.S., M.R.M., G.M.L., M.R.L., G.F., J.V.M., D.S.A.C., E.C.)
| | - Francesca Elisabeth Mowry
- Department of Anatomy, Physiology, and Pharmacology, College of Veterinary Medicine (F.E.M., V.C.B.), Auburn University, AL.,Center for Neurosciences Research Initiative (F.E.M., V.C.B.), Auburn University, AL
| | - Gabriela Maria Lucera
- From the Department of Physiology and Pathology, School of Dentistry of Araraquara, São Paulo State University, Araraquara, Brazil (M.V.F.S., M.R.M., G.M.L., M.R.L., G.F., J.V.M., D.S.A.C., E.C.)
| | - Mariana Ruiz Lauar
- From the Department of Physiology and Pathology, School of Dentistry of Araraquara, São Paulo State University, Araraquara, Brazil (M.V.F.S., M.R.M., G.M.L., M.R.L., G.F., J.V.M., D.S.A.C., E.C.)
| | - Gustavo Frigieri
- From the Department of Physiology and Pathology, School of Dentistry of Araraquara, São Paulo State University, Araraquara, Brazil (M.V.F.S., M.R.M., G.M.L., M.R.L., G.F., J.V.M., D.S.A.C., E.C.)
| | - Vinicia Campana Biancardi
- Department of Anatomy, Physiology, and Pharmacology, College of Veterinary Medicine (F.E.M., V.C.B.), Auburn University, AL.,Center for Neurosciences Research Initiative (F.E.M., V.C.B.), Auburn University, AL
| | - Jose V Menani
- From the Department of Physiology and Pathology, School of Dentistry of Araraquara, São Paulo State University, Araraquara, Brazil (M.V.F.S., M.R.M., G.M.L., M.R.L., G.F., J.V.M., D.S.A.C., E.C.)
| | - Débora Simões Almeida Colombari
- From the Department of Physiology and Pathology, School of Dentistry of Araraquara, São Paulo State University, Araraquara, Brazil (M.V.F.S., M.R.M., G.M.L., M.R.L., G.F., J.V.M., D.S.A.C., E.C.)
| | - Eduardo Colombari
- From the Department of Physiology and Pathology, School of Dentistry of Araraquara, São Paulo State University, Araraquara, Brazil (M.V.F.S., M.R.M., G.M.L., M.R.L., G.F., J.V.M., D.S.A.C., E.C.)
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6
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Falquetto B, Thieme K, Malta MB, e Rocha KC, Tuppy M, Potje SR, Antoniali C, Rodrigues AC, Munhoz CD, Moreira TS, Takakura AC. Oxidative stress in the medullary respiratory neurons contributes to respiratory dysfunction in the 6‐OHDA model of Parkinson's disease. J Physiol 2020; 598:5271-5293. [DOI: 10.1113/jp279791] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2020] [Accepted: 08/14/2020] [Indexed: 11/08/2022] Open
Affiliation(s)
- Bárbara Falquetto
- Department of Pharmacology Institute de Ciencias Biomedicas Universidade de Sao Paulo São Paulo SP 05508‐000 Brazil
| | - Karina Thieme
- Department of Physiology and Biophysics Instituto de Ciencias Biomedicas Universidade de Sao Paulo São Paulo SP 05508‐000 Brazil
| | - Marília B. Malta
- Department of Pharmacology Institute de Ciencias Biomedicas Universidade de Sao Paulo São Paulo SP 05508‐000 Brazil
| | - Karina C. e Rocha
- Department of Pharmacology Institute de Ciencias Biomedicas Universidade de Sao Paulo São Paulo SP 05508‐000 Brazil
| | - Marina Tuppy
- Department of Pharmacology Institute de Ciencias Biomedicas Universidade de Sao Paulo São Paulo SP 05508‐000 Brazil
| | - Simone R. Potje
- Department of Basic Sciences School of Dentistry São Paulo State University (UNESP) Araçatuba SP 16015‐050 Brazil
| | - Cristina Antoniali
- Department of Basic Sciences School of Dentistry São Paulo State University (UNESP) Araçatuba SP 16015‐050 Brazil
| | - Alice C. Rodrigues
- Department of Pharmacology Institute de Ciencias Biomedicas Universidade de Sao Paulo São Paulo SP 05508‐000 Brazil
| | - Carolina D. Munhoz
- Department of Pharmacology Institute de Ciencias Biomedicas Universidade de Sao Paulo São Paulo SP 05508‐000 Brazil
| | - Thiago S. Moreira
- Department of Physiology and Biophysics Instituto de Ciencias Biomedicas Universidade de Sao Paulo São Paulo SP 05508‐000 Brazil
| | - Ana C. Takakura
- Department of Pharmacology Institute de Ciencias Biomedicas Universidade de Sao Paulo São Paulo SP 05508‐000 Brazil
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7
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Blood-brain barrier dysfunction: the undervalued frontier of hypertension. J Hum Hypertens 2020; 34:682-691. [PMID: 32424144 DOI: 10.1038/s41371-020-0352-2] [Citation(s) in RCA: 26] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/24/2019] [Revised: 04/29/2020] [Accepted: 05/01/2020] [Indexed: 02/06/2023]
Abstract
The blood-brain barrier (BBB) constitutes the complex anatomic and physiologic interface between the intravascular compartment and the central nervous system, and its integrity is paramount for the maintenance of the very sensitive homeostasis of the central nervous system. Arterial hypertension is a leading cause of morbidity and mortality. The BBB has been shown to be disrupted in essential hypertension. BBB integrity is important for central autonomic control and this may be implicated in the pathophysiology of hypertension. On the other hand, evidence from experimental studies indicates that BBB disruption can be present in both hypertensive disease and dementia syndromes, suggesting a possibly key position of loss of BBB integrity in the pathophysiological pathways linking arterial hypertension with cognitive decline. Although much still remains to be elucidated with respect to the exact underlying mechanisms, the discovery of novel pathological pathways has changed our understanding of adult dementia and central nervous system disease overall, pointing out-in parallel-new potential therapeutic targets. The aim of this review is to summarize current scientific knowledge relevant to the pathophysiologic pathways that are involved in the disruption of the BBB function and potentially mediate hypertension-induced cognitive impairment. In parallel, we underline the differential cognition-preserving effect of several antihypertensive agents of similar blood pressure-lowering capacity, highlighting the presence of previously under-recognized BBB-protective actions of these drugs.
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8
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Nunes KP, de Oliveira AA, Lima VV, Webb RC. Toll-Like Receptor 4 and Blood Pressure: Lessons From Animal Studies. Front Physiol 2019; 10:655. [PMID: 31191352 PMCID: PMC6549540 DOI: 10.3389/fphys.2019.00655] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2019] [Accepted: 05/09/2019] [Indexed: 11/13/2022] Open
Affiliation(s)
- Kenia Pedrosa Nunes
- Department of Biomedical and Chemical Engineering and Sciences, Florida Institute of Technology, Melbourne, FL, United States
| | - Amanda Almeida de Oliveira
- Department of Biomedical and Chemical Engineering and Sciences, Florida Institute of Technology, Melbourne, FL, United States
| | - Victor Vitorino Lima
- Institute of Biological and Health Sciences, Federal University of Mato Grosso, Barra do Garças, Brazil
| | - R. Clinton Webb
- Department of Physiology, Medical College of Georgia at Augusta University, Augusta, GA, United States
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9
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Buttler L, Jordão MT, Fragas MG, Ruggeri A, Ceroni A, Michelini LC. Maintenance of Blood-Brain Barrier Integrity in Hypertension: A Novel Benefit of Exercise Training for Autonomic Control. Front Physiol 2017; 8:1048. [PMID: 29311978 PMCID: PMC5733101 DOI: 10.3389/fphys.2017.01048] [Citation(s) in RCA: 43] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2017] [Accepted: 11/30/2017] [Indexed: 12/27/2022] Open
Abstract
The blood-brain barrier (BBB) is a complex multicellular structure acting as selective barrier controlling the transport of substances between these compartments. Accumulating evidence has shown that chronic hypertension is accompanied by BBB dysfunction, deficient local perfusion and plasma angiotensin II (Ang II) access into the parenchyma of brain areas related to autonomic circulatory control. Knowing that spontaneously hypertensive rats (SHR) exhibit deficient autonomic control and brain Ang II hyperactivity and that exercise training is highly effective in correcting both, we hypothesized that training, by reducing Ang II content, could improve BBB function within autonomic brain areas of the SHR. After confirming the absence of BBB lesion in the pre-hypertensive SHR, but marked fluorescein isothiocyanate dextran (FITC, 10 kD) leakage into the brain parenchyma of the hypothalamic paraventricular nucleus (PVN), nucleus of the solitary tract, and rostral ventrolateral medulla during the established phase of hypertension, adult SHR, and age-matched WKY were submitted to a treadmill training (T) or kept sedentary (S) for 8 weeks. The robust FITC leakage within autonomic areas of the SHR-S was largely reduced and almost normalized since the 2nd week of training (T2). BBB leakage reduction occurred simultaneously and showed strong correlations with both decreased LF/HF ratio to the heart and reduced vasomotor sympathetic activity (power spectral analysis), these effects preceding the appearance of resting bradycardia (T4) and partial pressure fall (T8). In other groups of SHR-T simultaneously infused with icv Ang II or saline (osmotic mini-pumps connected to a lateral ventricle cannula) we proved that decreased local availability of this peptide and reduced microglia activation (IBA1 staining) are crucial mechanisms conditioning the restoration of BBB integrity. Our data also revealed that Ang II-induced BBB lesion was faster within the PVN (T2), suggesting the prominent role of this nucleus in driven hypertension-induced deficits. These original set of data suggest that reduced local Ang II content (and decreased activation of its downstream pathways) is an essential and early-activated mechanism to maintain BBB integrity in trained SHR and uncovers a novel beneficial effect of exercise training to improve autonomic control even in the presence of hypertension.
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Affiliation(s)
- Leila Buttler
- Department Physiology and Biophysics, Institute of Biomedical Sciences, University of São Paulo, São Paulo, Brazil
| | - Maria T Jordão
- Department Physiology and Biophysics, Institute of Biomedical Sciences, University of São Paulo, São Paulo, Brazil
| | - Matheus G Fragas
- Department Physiology and Biophysics, Institute of Biomedical Sciences, University of São Paulo, São Paulo, Brazil
| | - Adriana Ruggeri
- Department Physiology and Biophysics, Institute of Biomedical Sciences, University of São Paulo, São Paulo, Brazil
| | - Alexandre Ceroni
- Department Physiology and Biophysics, Institute of Biomedical Sciences, University of São Paulo, São Paulo, Brazil
| | - Lisete C Michelini
- Department Physiology and Biophysics, Institute of Biomedical Sciences, University of São Paulo, São Paulo, Brazil
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10
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Carter DA, Guo H, Connelly AA, Bassi JK, Fong AY, Allen AM, McDougall SJ. Viscerosensory input drives angiotensin II type 1A receptor-expressing neurons in the solitary tract nucleus. Am J Physiol Regul Integr Comp Physiol 2017; 314:R282-R293. [PMID: 29118020 DOI: 10.1152/ajpregu.00290.2017] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
Homeostatic regulation of visceral organ function requires integrated processing of neural and neurohormonal sensory signals. The nucleus of the solitary tract (NTS) is the primary sensory nucleus for cranial visceral sensory afferents. Angiotensin II (ANG II) is known to modulate peripheral visceral reflexes, in part, by activating ANG II type 1A receptors (AT1AR) in the NTS. AT1AR-expressing NTS neurons occur throughout the NTS with a defined subnuclear distribution, and most of these neurons are depolarized by ANG II. In this study we determined whether AT1AR-expressing NTS neurons receive direct visceral sensory input, and whether this input is modulated by ANG II. Using AT1AR-GFP mice to make targeted whole cell recordings from AT1AR-expressing NTS neurons, we demonstrate that two-thirds (37 of 56) of AT1AR-expressing neurons receive direct excitatory, visceral sensory input. In half of the neurons tested (4 of 8) the excitatory visceral sensory input was significantly reduced by application of the transient receptor potential vallinoid type 1 receptor agonist, capsaicin, indicating AT1AR-expressing neurons can receive either C- or A-fiber-mediated input. Application of ANG II to a subset of second-order AT1AR-expressing neurons did not affect spontaneous, evoked, or asynchronous glutamate release from visceral sensory afferents. Thus it is unlikely that AT1AR-expressing viscerosensory neurons terminate on AT1AR-expressing NTS neurons. Our data suggest that ANG II is likely to modulate multiple visceral sensory modalities by altering the excitability of second-order AT1AR-expressing NTS neurons.
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Affiliation(s)
- D A Carter
- Department of Physiology, The University of Melbourne , Victoria , Australia
| | - H Guo
- Florey Institute of Neuroscience and Mental Health, The University of Melbourne , Victoria , Australia
| | - A A Connelly
- Department of Physiology, The University of Melbourne , Victoria , Australia
| | - J K Bassi
- Department of Physiology, The University of Melbourne , Victoria , Australia
| | - A Y Fong
- Department of Physiology, The University of Melbourne , Victoria , Australia
| | - A M Allen
- Department of Physiology, The University of Melbourne , Victoria , Australia.,Florey Institute of Neuroscience and Mental Health, The University of Melbourne , Victoria , Australia
| | - S J McDougall
- Florey Institute of Neuroscience and Mental Health, The University of Melbourne , Victoria , Australia
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11
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Setiadi A, Korim WS, Elsaafien K, Yao ST. The role of the blood-brain barrier in hypertension. Exp Physiol 2017; 103:337-342. [PMID: 28986948 DOI: 10.1113/ep086434] [Citation(s) in RCA: 64] [Impact Index Per Article: 9.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2017] [Accepted: 10/05/2017] [Indexed: 12/22/2022]
Abstract
NEW FINDINGS What is the topic of this review? This review highlights the importance of the blood-brain barrier in the context of diseases involving autonomic dysfunction, such as hypertension and heart failure. What advances does it highlight? It highlights the potential role of pro-inflammatory cytokines, leucocytes and angiotensin II in disrupting the blood-brain barrier in cardiovascular diseases. Advances are highlighted in our understanding of neurovascular unit cells, astrocytes and microglia, with a specific emphasis on their pathogenic roles within the brain. The blood-brain barrier (BBB) is a crucial barrier that provides both metabolic and physical protection to an immune-privileged CNS. The BBB has been shown to be disrupted in hypertension. This review addresses the importance of the BBB in maintaining homeostasis in the context of diseases related to autonomic dysfunction, such as hypertension. We highlight the potentially important roles of the immune system and neurovascular unit in the maintenance of the BBB, whereby dysregulation may lead to autonomic dysfunction in diseases such as heart failure and hypertension. Circulating leucocytes and factors such as angiotensin II and pro-inflammatory cytokines are thought ultimately to downregulate endothelial tight junction proteins that are a crucial component of the BBB. The specific mechanisms underlying BBB disruption and their role in contributing to autonomic dysfunction are not yet fully understood but are a growing area of interest. A greater understanding of these systems and advances in our knowledge of the molecular mechanisms causing BBB disruption will allow for the development of future therapeutic interventions in the treatment of autonomic imbalance associated with diseases such as heart failure and hypertension.
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Affiliation(s)
- Anthony Setiadi
- Florey Institute of Neuroscience and Mental Health, University of Melbourne, Victoria, Australia
| | - Willian S Korim
- Florey Institute of Neuroscience and Mental Health, University of Melbourne, Victoria, Australia
| | - Khalid Elsaafien
- Florey Institute of Neuroscience and Mental Health, University of Melbourne, Victoria, Australia
| | - Song T Yao
- Florey Institute of Neuroscience and Mental Health, University of Melbourne, Victoria, Australia.,Florey Department of Neuroscience and Mental Health, University of Melbourne, Victoria, Australia
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12
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Cao W, Li A, Li J, Wu C, Cui S, Zhou Z, Liu Y, Wilcox CS, Hou FF. Reno-Cerebral Reflex Activates the Renin-Angiotensin System, Promoting Oxidative Stress and Renal Damage After Ischemia-Reperfusion Injury. Antioxid Redox Signal 2017; 27:415-432. [PMID: 28030955 PMCID: PMC5549812 DOI: 10.1089/ars.2016.6827] [Citation(s) in RCA: 70] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
AIMS A kidney-brain interaction has been described in acute kidney injury, but the mechanisms are uncertain. Since we recently described a reno-cerebral reflex, we tested the hypothesis that renal ischemia-reperfusion injury (IRI) activates a sympathetic reflex that interlinks the renal and cerebral renin-angiotensin axis to promote oxidative stress and progression of the injury. RESULTS Bilateral ischemia-reperfusion activated the intrarenal and cerebral, but not the circulating, renin-angiotensin system (RAS), increased sympathetic activity in the kidney and the cerebral sympathetic regulatory regions, and induced brain inflammation and kidney injury. Selective renal afferent denervation with capsaicin or renal denervation significantly attenuated IRI-induced activation of central RAS and brain inflammation. Central blockade of RAS or oxidative stress by intracerebroventricular (ICV) losartan or tempol reduced the renal ischemic injury score by 65% or 58%, respectively, and selective renal afferent denervation or reduction of sympathetic tone by ICV clonidine decreased the score by 42% or 52%, respectively (all p < 0.05). Ischemia-reperfusion-induced renal damage and dysfunction persisted after controlling blood pressure with hydralazine. INNOVATION This study uncovered a novel reflex pathway between ischemic kidney and the brain that sustains renal oxidative stress and local RAS activation to promote ongoing renal damage. CONCLUSIONS These data suggest that the renal and cerebral renin-angiotensin axes are interlinked by a reno-cerebral sympathetic reflex that is activated by ischemia-reperfusion, which contributes to ischemia-reperfusion-induced brain inflammation and worsening of the acute renal injury. Antioxid. Redox Signal. 27, 415-432.
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Affiliation(s)
- Wei Cao
- 1 Division of Nephrology, Nanfang Hospital, Southern Medical University , State Key Laboratory of Organ Failure Research, National Clinical Research Center of Kidney Disease, Guangzhou, P.R. China
| | - Aiqing Li
- 1 Division of Nephrology, Nanfang Hospital, Southern Medical University , State Key Laboratory of Organ Failure Research, National Clinical Research Center of Kidney Disease, Guangzhou, P.R. China
| | - Jiawen Li
- 1 Division of Nephrology, Nanfang Hospital, Southern Medical University , State Key Laboratory of Organ Failure Research, National Clinical Research Center of Kidney Disease, Guangzhou, P.R. China
| | - Chunyi Wu
- 1 Division of Nephrology, Nanfang Hospital, Southern Medical University , State Key Laboratory of Organ Failure Research, National Clinical Research Center of Kidney Disease, Guangzhou, P.R. China
| | - Shuang Cui
- 1 Division of Nephrology, Nanfang Hospital, Southern Medical University , State Key Laboratory of Organ Failure Research, National Clinical Research Center of Kidney Disease, Guangzhou, P.R. China
| | - Zhanmei Zhou
- 1 Division of Nephrology, Nanfang Hospital, Southern Medical University , State Key Laboratory of Organ Failure Research, National Clinical Research Center of Kidney Disease, Guangzhou, P.R. China
| | - Youhua Liu
- 1 Division of Nephrology, Nanfang Hospital, Southern Medical University , State Key Laboratory of Organ Failure Research, National Clinical Research Center of Kidney Disease, Guangzhou, P.R. China
| | - Christopher S Wilcox
- 2 Hypertension, Kidney and Vascular Research Center, Georgetown University , Washington, District of Columbia
| | - Fan Fan Hou
- 1 Division of Nephrology, Nanfang Hospital, Southern Medical University , State Key Laboratory of Organ Failure Research, National Clinical Research Center of Kidney Disease, Guangzhou, P.R. China
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Ferreira-Neto H, Ribeiro I, Moreira T, Yao S, Antunes V. Purinergic P2 receptors in the paraventricular nucleus of the hypothalamus are involved in hyperosmotic-induced sympathoexcitation. Neuroscience 2017; 349:253-263. [DOI: 10.1016/j.neuroscience.2017.02.054] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2016] [Revised: 02/23/2017] [Accepted: 02/24/2017] [Indexed: 11/16/2022]
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14
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Underwood CF, Hildreth CM, Wyse BF, Boyd R, Goodchild AK, Phillips JK. Uraemia: an unrecognized driver of central neurohumoral dysfunction in chronic kidney disease? Acta Physiol (Oxf) 2017; 219:305-323. [PMID: 27247097 DOI: 10.1111/apha.12727] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2015] [Revised: 01/21/2016] [Accepted: 05/31/2016] [Indexed: 12/12/2022]
Abstract
Chronic kidney disease (CKD) carries a large cardiovascular burden in part due to hypertension and neurohumoral dysfunction - manifesting as sympathetic overactivity, baroreflex dysfunction and chronically elevated circulating vasopressin. Alterations within the central nervous system (CNS) are necessary for the expression of neurohumoral dysfunction in CKD; however, the underlying mechanisms are poorly defined. Uraemic toxins are a diverse group of compounds that accumulate as a direct result of renal disease and drive dysfunction in multiple organs, including the brain. Intensive haemodialysis improves both sympathetic overactivity and cardiac baroreflex sensitivity in renal failure patients, indicating that uraemic toxins participate in the maintenance of autonomic dysfunction in CKD. In rodents exposed to uraemia, immediate early gene expression analysis suggests upregulated activity of not only pre-sympathetic but also vasopressin-secretory nuclei. We outline several potential mechanisms by which uraemia might drive neurohumoral dysfunction in CKD. These include superoxide-dependent effects on neural activity, depletion of nitric oxide and induction of low-grade systemic inflammation. Recent evidence has highlighted superoxide production as an intermediate for the depolarizing effect of some uraemic toxins on neuronal cells. We provide preliminary data indicating augmented superoxide production within the hypothalamic paraventricular nucleus in the Lewis polycystic kidney rat, which might be important for mediating the neurohumoral dysfunction exhibited in this CKD model. We speculate that the uraemic state might serve to sensitize the central actions of other sympathoexcitatory factors, including renal afferent nerve inputs to the CNS and angiotensin II, by way of recruiting convergent superoxide-dependent and pro-inflammatory pathways.
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Affiliation(s)
- C. F. Underwood
- Department of Biomedical Sciences; Macquarie University; Sydney NSW Australia
| | - C. M. Hildreth
- Department of Biomedical Sciences; Macquarie University; Sydney NSW Australia
| | - B. F. Wyse
- Department of Biomedical Sciences; Macquarie University; Sydney NSW Australia
| | - R. Boyd
- Department of Biomedical Sciences; Macquarie University; Sydney NSW Australia
| | - A. K. Goodchild
- Department of Biomedical Sciences; Macquarie University; Sydney NSW Australia
| | - J. K. Phillips
- Department of Biomedical Sciences; Macquarie University; Sydney NSW Australia
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15
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Concepts, technologies, and practices for drug delivery past the blood–brain barrier to the central nervous system. J Control Release 2016; 240:251-266. [DOI: 10.1016/j.jconrel.2015.12.041] [Citation(s) in RCA: 38] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2015] [Revised: 12/21/2015] [Accepted: 12/23/2015] [Indexed: 12/29/2022]
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16
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Biancardi VC, Stern JE. Compromised blood-brain barrier permeability: novel mechanism by which circulating angiotensin II signals to sympathoexcitatory centres during hypertension. J Physiol 2016; 594:1591-600. [PMID: 26580484 PMCID: PMC4799983 DOI: 10.1113/jp271584] [Citation(s) in RCA: 78] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2015] [Accepted: 10/23/2015] [Indexed: 12/14/2022] Open
Abstract
Angiotensin II (AngII) is a pivotal peptide implicated in the regulation of blood pressure. In addition to its systemic vascular and renal effects, AngII acts centrally to modulate the activities of neuroendocrine and sympathetic neuronal networks, influencing in turn sympatho-humoral outflows to the circulation. Moreover, a large body of evidence supports AngII signalling dysregulation as a key mechanism contributing to exacerbated sympathoexcitation during hypertension. Due to its hydrophilic actions, circulating AngII does not cross the blood-brain barrier (BBB), signalling to the brain via the circumventricular organs which lack a tight BBB. In this review, we present and discuss recent studies from our laboratory showing that elevated circulating levels of AngII during hypertension result in disruption of the BBB integrity, allowing access of circulating AngII to critical sympathoexcitatory brain centres such as the paraventricular nucleus of the hypothalamus and the rostral ventrolateral medulla. We propose the novel hypothesis that AngII-driven BBB breakdown constitutes a complementary mechanism by which circulating AngII, working in tandem with the central renin-angiotensin system, further exacerbates sympatho-humoral activation during hypertension. These results are discussed within the context of a growing body of evidence in the literature supporting AngII as a pro-inflammatory signal, and brain microglia as key cell targets mediating central AngII actions during hypertension.
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Affiliation(s)
- V C Biancardi
- Department of Physiology, Georgia Regents University, Augusta, GA, USA
| | - J E Stern
- Department of Physiology, Georgia Regents University, Augusta, GA, USA
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17
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Gromnicova R, Yilmaz CU, Orhan N, Kaya M, Davies H, Williams P, Romero IA, Sharrack B, Male D. Localization and mobility of glucose-coated gold nanoparticles within the brain. Nanomedicine (Lond) 2016; 11:617-25. [DOI: 10.2217/nnm.15.215] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
Aim: To identify the localization of glucose-coated gold nanoparticles within cells of the brain after intravascular infusion which may point to the mechanism by which they cross the blood–brain barrier. Materials & methods: Tissue distribution of the nanoparticles was measured by inductively-coupled-mass spectrometry and localization within the brain by histochemistry and electron microscopy. Results & conclusion: Nanoparticles were identified within neurons and glial cells more than 10 μm from the nearest microvessel within 10 min of intracarotid infusion. Their distribution indicated movement across the endothelial cytosol, and direct transfer between cells of the brain. The rapid movement of this class of nanoparticle (<5 nm) into the brain demonstrates their potential to carry therapeutic biomolecules or imaging reagents.
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Affiliation(s)
- Radka Gromnicova
- Department of Life, Health & Chemical Sciences, The Open University, Milton Keynes, MK7 6AA, UK
| | - Canan Ugur Yilmaz
- Department of Laboratory Animal Science, Institute of Experimental Medicine, Istanbul University, Istanbul, Turkey
| | - Nurcan Orhan
- Department of Neuroscience, Institute of Experimental Medicine, Istanbul University, Istanbul, Turkey
| | - Mehmet Kaya
- Department of Physiology, Istanbul Faculty of Medicine, Istanbul University, Istanbul, Turkey
| | - Heather Davies
- Department of Life, Health & Chemical Sciences, The Open University, Milton Keynes, MK7 6AA, UK
| | | | - Ignacio A Romero
- Department of Life, Health & Chemical Sciences, The Open University, Milton Keynes, MK7 6AA, UK
| | - Basil Sharrack
- Department of Neurology, University of Sheffield, Sheffield, UK
| | - David Male
- Department of Life, Health & Chemical Sciences, The Open University, Milton Keynes, MK7 6AA, UK
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Zawada WM, Mrak RE, Biedermann J, Palmer QD, Gentleman SM, Aboud O, Griffin WST. Loss of angiotensin II receptor expression in dopamine neurons in Parkinson's disease correlates with pathological progression and is accompanied by increases in Nox4- and 8-OH guanosine-related nucleic acid oxidation and caspase-3 activation. Acta Neuropathol Commun 2015; 3:9. [PMID: 25645462 PMCID: PMC4359535 DOI: 10.1186/s40478-015-0189-z] [Citation(s) in RCA: 47] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2014] [Accepted: 01/20/2015] [Indexed: 12/22/2022] Open
Abstract
Background In rodent models of Parkinson’s disease (PD), dopamine neuron loss is accompanied by increased expression of angiotensin II (AngII), its type 1 receptor (AT1), and NADPH oxidase (Nox) in the nigral dopamine neurons and microglia. AT1 blockers (ARBs) stymie such oxidative damage and neuron loss. Whether changes in the AngII/AT1/Nox4 axis contribute to Parkinson neuropathogenesis is unknown. Here, we studied the distribution of AT1 and Nox4 in dopamine neurons in two nigral subregions: the less affected calbindin-rich matrix and the first-affected calbindin-poor nigrosome 1 of three patients, who were clinically asymptomatic, but had nigral dopamine cell loss and Braak stages consistent with a neuropathological diagnosis of PD (prePD). For comparison, five clinically- and neuropathologically-confirmed PD patients and seven age-matched control patients (AMC) were examined. Results AT1 and Nox4 immunoreactivity was noted in dopamine neurons in both the matrix and the nigrosome 1. The total cellular levels of AT1 in surviving dopamine neurons in the matrix and nigrosome 1 declined from AMC>prePD>PD, suggesting that an AngII/AT1/Nox4 axis orders neurodegenerative progression. In this vein, the loss of dopamine neurons was paralleled by a decline in total AT1 per surviving dopamine neuron. Similarly, AT1 in the nuclei of surviving neurons in the nigral matrix declined with disease progression, i.e., AMC>prePD>PD. In contrast, in nigrosome 1, the expression of nuclear AT1 was unaffected and similar in all groups. The ratio of nuclear AT1 to total AT1 (nuclear + cytoplasmic + membrane) in dopamine neurons increased stepwise from AMC to prePD to PD. The proportional increase in nuclear AT1 in dopamine neurons in nigrosome 1 of prePD and PD patients was accompanied by elevated nuclear expression of Nox4, oxidative damage to DNA, and caspase-3-mediated cell loss. Conclusions Our observations are consistent with the idea that AngII/AT1/Nox4 axis-mediated oxidative stress gives rise to the dopamine neuron dysfunction and loss characteristic of the neuropathological and clinical manifestations of PD and suggest that the chance for a neuron to survive increases in association with lower total as well as nuclear AT1 expression. Our results support the need for further evaluation of ARBs as disease-modifying agents in PD.
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Cao W, Li A, Wang L, Zhou Z, Su Z, Bin W, Wilcox CS, Hou FF. A Salt-Induced Reno-Cerebral Reflex Activates Renin-Angiotensin Systems and Promotes CKD Progression. J Am Soc Nephrol 2015; 26:1619-33. [PMID: 25635129 DOI: 10.1681/asn.2014050518] [Citation(s) in RCA: 77] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2014] [Accepted: 09/10/2014] [Indexed: 12/30/2022] Open
Abstract
Salt intake promotes progression of CKD by uncertain mechanisms. We hypothesized that a salt-induced reno-cerebral reflex activates a renin-angiotensin axis to promote CKD. Sham-operated and 5/6-nephrectomized rats received a normal-salt (0.4%), low-salt (0.02%), or high-salt (4%) diet for 2 weeks. High salt in 5/6-nephrectomized rats increased renal NADPH oxidase, inflammation, BP, and albuminuria. Furthermore, high salt activated the intrarenal and cerebral, but not the systemic, renin-angiotensin axes and increased the activity of renal sympathetic nerves and neurons in the forebrain of these rats. Renal fibrosis was increased 2.2-fold by high versus low salt, but intracerebroventricular tempol, losartan, or clonidine reduced this fibrosis by 65%, 69%, or 59%, respectively, and renal denervation or deafferentation reduced this fibrosis by 43% or 38%, respectively (all P<0.05). Salt-induced fibrosis persisted after normalization of BP with hydralazine. These data suggest that the renal and cerebral renin-angiotensin axes are interlinked by a reno-cerebral reflex that is activated by salt and promotes oxidative stress, fibrosis, and progression of CKD independent of BP.
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Affiliation(s)
- Wei Cao
- State Key Laboratory of Organ Failure Research, National Clinical Research Center for Kidney Disease, Nanfang Hospital, Southern Medical University, Guangzhou, People's Republic of China; and
| | - Aiqing Li
- State Key Laboratory of Organ Failure Research, National Clinical Research Center for Kidney Disease, Nanfang Hospital, Southern Medical University, Guangzhou, People's Republic of China; and
| | - Liangliang Wang
- State Key Laboratory of Organ Failure Research, National Clinical Research Center for Kidney Disease, Nanfang Hospital, Southern Medical University, Guangzhou, People's Republic of China; and
| | - Zhanmei Zhou
- State Key Laboratory of Organ Failure Research, National Clinical Research Center for Kidney Disease, Nanfang Hospital, Southern Medical University, Guangzhou, People's Republic of China; and
| | - Zhengxiu Su
- State Key Laboratory of Organ Failure Research, National Clinical Research Center for Kidney Disease, Nanfang Hospital, Southern Medical University, Guangzhou, People's Republic of China; and
| | - Wei Bin
- State Key Laboratory of Organ Failure Research, National Clinical Research Center for Kidney Disease, Nanfang Hospital, Southern Medical University, Guangzhou, People's Republic of China; and
| | - Christopher S Wilcox
- Center for Hypertension, Kidney, and Vascular Research, Georgetown University, Washington, DC
| | - Fan Fan Hou
- State Key Laboratory of Organ Failure Research, National Clinical Research Center for Kidney Disease, Nanfang Hospital, Southern Medical University, Guangzhou, People's Republic of China; and
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Biancardi VC, Son SJ, Ahmadi S, Filosa JA, Stern JE. Circulating angiotensin II gains access to the hypothalamus and brain stem during hypertension via breakdown of the blood-brain barrier. Hypertension 2013; 63:572-9. [PMID: 24343120 DOI: 10.1161/hypertensionaha.113.01743] [Citation(s) in RCA: 182] [Impact Index Per Article: 16.5] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Angiotensin II-mediated vascular brain inflammation emerged as a novel pathophysiological mechanism in neurogenic hypertension. However, the precise underlying mechanisms and functional consequences in relation to blood-brain barrier (BBB) integrity and central angiotensin II actions mediating neurohumoral activation in hypertension are poorly understood. Here, we aimed to determine whether BBB permeability within critical hypothalamic and brain stem regions involved in neurohumoral regulation was altered during hypertension. Using digital imaging quantification after intravascularly injected fluorescent dyes and immunohistochemistry, we found increased BBB permeability, along with altered key BBB protein constituents, in spontaneously hypertensive rats within the hypothalamic paraventricular nucleus, the nucleus of the solitary tract, and the rostral ventrolateral medulla, all critical brain regions known to contribute to neurohumoral activation during hypertension. BBB disruption, including increased permeability and downregulation of constituent proteins, was prevented in spontaneously hypertensive rats treated with the AT1 receptor antagonist losartan, but not with hydralazine, a direct vasodilator. Importantly, we found circulating angiotensin II to extravasate into these brain regions, colocalizing with neurons and microglial cells. Taken together, our studies reveal a novel angiotensin II-mediated feed-forward mechanism during hypertension, by which circulating angiotensin II evokes increased BBB permeability, facilitating in turn its access to critical brain regions known to participate in blood pressure regulation.
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Ramchandra R, Yao ST, May CN. Organ Selective Regulation of Sympathetic Outflow by the Brain Angiotensin System. Curr Hypertens Rep 2013; 15:401-8. [DOI: 10.1007/s11906-013-0355-2] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
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