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      Role of the Sympathetic Nervous System and Its Modulation in Renal Hypertension

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          Abstract

          The kidneys are densely innervated with renal efferent and afferent nerves to communicate with the central nervous system. Innervation of major structural components of the kidneys, such as blood vessels, tubules, the pelvis, and glomeruli, forms a bidirectional neural network to relay sensory and sympathetic signals to and from the brain. Renal efferent nerves regulate renal blood flow, glomerular filtration rate, tubular reabsorption of sodium and water, as well as release of renin and prostaglandins, all of which contribute to cardiovascular and renal regulation. Renal afferent nerves complete the feedback loop via central autonomic nuclei where the signals are integrated and modulate central sympathetic outflow; thus both types of nerves form integral parts of the self-regulated renorenal reflex loop. Renal sympathetic nerve activity (RSNA) is commonly increased in pathophysiological conditions such as hypertension and chronic- and end-stage renal disease. Increased RSNA raises blood pressure and can contribute to the deterioration of renal function. Attempts have been made to eliminate or interfere with this important link between the brain and the kidneys as a neuromodulatory treatment for these conditions. Catheter-based renal sympathetic denervation has been successfully applied in patients with resistant hypertension and was associated with significant falls in blood pressure and renal protection in most studies performed. The focus of this review is the neural contribution to the control of renal and cardiovascular hemodynamics and renal function in the setting of hypertension and chronic kidney disease, as well as the specific roles of renal efferent and afferent nerves in this scenario and their utility as a therapeutic target.

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          Most cited references 56

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          Catheter-based renal sympathetic denervation for resistant hypertension: a multicentre safety and proof-of-principle cohort study.

          Renal sympathetic hyperactivity is associated with hypertension and its progression, chronic kidney disease, and heart failure. We did a proof-of-principle trial of therapeutic renal sympathetic denervation in patients with resistant hypertension (ie, systolic blood pressure >/=160 mm Hg on three or more antihypertensive medications, including a diuretic) to assess safety and blood-pressure reduction effectiveness. We enrolled 50 patients at five Australian and European centres; 5 patients were excluded for anatomical reasons (mainly on the basis of dual renal artery systems). Patients received percutaneous radiofrequency catheter-based treatment between June, 2007, and November, 2008, with subsequent follow-up to 1 year. We assessed the effectiveness of renal sympathetic denervation with renal noradrenaline spillover in a subgroup of patients. Primary endpoints were office blood pressure and safety data before and at 1, 3, 6, 9, and 12 months after procedure. Renal angiography was done before, immediately after, and 14-30 days after procedure, and magnetic resonance angiogram 6 months after procedure. We assessed blood-pressure lowering effectiveness by repeated measures ANOVA. This study is registered in Australia and Europe with ClinicalTrials.gov, numbers NCT 00483808 and NCT 00664638. In treated patients, baseline mean office blood pressure was 177/101 mm Hg (SD 20/15), (mean 4.7 antihypertensive medications); estimated glomerular filtration rate was 81 mL/min/1.73m(2) (SD 23); and mean reduction in renal noradrenaline spillover was 47% (95% CI 28-65%). Office blood pressures after procedure were reduced by -14/-10, -21/-10, -22/-11, -24/-11, and -27/-17 mm Hg at 1, 3, 6, 9, and 12 months, respectively. In the five non-treated patients, mean rise in office blood pressure was +3/-2, +2/+3, +14/+9, and +26/+17 mm Hg at 1, 3, 6, and 9 months, respectively. One intraprocedural renal artery dissection occurred before radiofrequency energy delivery, without further sequelae. There were no other renovascular complications. Catheter-based renal denervation causes substantial and sustained blood-pressure reduction, without serious adverse events, in patients with resistant hypertension. Prospective randomised clinical trials are needed to investigate the usefulness of this procedure in the management of this condition.
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            Sympathetic overactivity in patients with chronic renal failure.

            Hypertension is a frequent complication of chronic renal failure, but its causes are not fully understood. There is indirect evidence that increased activity of the sympathetic nervous system might contribute to hypertension in patients with end-stage renal disease, but sympathetic-nerve discharge has not been measured directly in patients or animals with chronic renal failure. We recorded the rate of postganglionic sympathetic-nerve discharge to the blood vessels in skeletal muscle by means of microelectrodes inserted into the peroneal nerve in 18 patients with native kidneys who were undergoing long-term treatment with hemodialysis (of whom 14 had hypertension), 5 patients receiving hemodialysis who had undergone bilateral nephrectomy (of whom 1 had hypertension), and 11 normal subjects. RESULTS. The mean (+/- SE) rate of sympathetic-nerve discharge was 2.5 times higher in the patients receiving hemodialysis who had not undergone nephrectomy than in the normal subjects (58 +/- 3 vs. 23 +/- 3 bursts per minute, P < 0.01). In contrast, the rate of sympathetic-nerve discharge was similar in the patients receiving hemodialysis who had undergone bilateral nephrectomy (21 +/- 6 bursts per minute) and the normal subjects. The rate of sympathetic-nerve discharge in the patients receiving hemodialysis who had not undergone nephrectomy was also significantly higher (P < 0.01) than that in the patients with bilateral nephrectomy, and it was accompanied in the former group by higher values for vascular resistance in the calf (45 +/- 4 vs. 22 +/- 4 units, P < 0.05) and mean arterial pressure (106 +/- 4 vs. 76 +/- 14 mm Hg, P < 0.05). The rate of sympathetic-nerve discharge was not correlated with either plasma norepinephrine concentrations or plasma renin activity. Chronic renal failure may be accompanied by reversible sympathetic activation, which appears to be mediated by an afferent signal arising in the failing kidneys.
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              Nitric oxide signaling in the central nervous system.

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                Author and article information

                Contributors
                Journal
                Front Med (Lausanne)
                Front Med (Lausanne)
                Front. Med.
                Frontiers in Medicine
                Frontiers Media S.A.
                2296-858X
                29 March 2018
                2018
                : 5
                Affiliations
                1Neurovascular Hypertension and Kidney Disease Laboratory, Baker Heart and Diabetes Institute , Melbourne, VIC, Australia
                2Faculty of Medicine, Nursing and Health Sciences, Central Clinical School, Monash University , Melbourne, VIC, Australia
                3Neuropharmacology Laboratory, Baker Heart and Diabetes Institute , Melbourne, VIC, Australia
                4Cardiovascular Program, Department of Physiology, Monash Biomedicine Discovery Institute, Monash University , Melbourne, VIC, Australia
                5Preclinical Critical Care Unit, The Florey Institute of Neuroscience and Mental Health, The University of Melbourne , Parkville, VIC, Australia
                6Dobney Hypertension Centre, School of Medicine – Royal Perth Hospital Unit, University of Western Australia , Perth, WA, Australia
                Author notes

                Edited by: Maik Gollasch, Charité Universitätsmedizin Berlin, Germany

                Reviewed by: Swapnil Hiremath, University of Ottawa, Canada; Bassam G. Abu Jawdeh, University of Cincinnati, United States

                *Correspondence: Markus P. Schlaich, markus.schlaich@ 123456uwa.edu.au

                Specialty section: This article was submitted to Nephrology, a section of the journal Frontiers in Medicine

                Article
                10.3389/fmed.2018.00082
                5884873
                Copyright © 2018 Sata, Head, Denton, May and Schlaich.

                This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) and the copyright owner are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.

                Page count
                Figures: 3, Tables: 1, Equations: 0, References: 70, Pages: 10, Words: 7691
                Categories
                Medicine
                Review

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