Influence of Renal Sympathetic Denervation on Cardiac Extracellular Matrix Turnover and Cardiac Fibrosis

Possible Role of Gut Microbiota Alterations in Myocardial Fibrosis and Burden of Heart Failure in Hypertensive Heart Disease

Epidemiological studies have revealed that hypertensive heart disease is a major risk factor for heart failure, and its heart failure burden is growing rapidly. The need to act in the face of this threat requires first an understanding of the multifactorial origin of hypertensive heart disease and second an exploration of new mechanistic pathways involved in myocardial alterations critically involved in cardiac dysfunction and failure (eg, myocardial interstitial fibrosis). Increasing evidence shows that alterations of gut microbiota composition and function (ie, dysbiosis) leading to changes in microbiota-derived metabolites and impairment of the gut barrier and immune functions may be involved in blood pressure elevation and hypertensive organ damage. In this review, we highlight recent advances in the potential contribution of gut microbiota alterations to myocardial interstitial fibrosis in hypertensive heart disease through blood pressure-dependent and blood pressure-independent mechanisms. Achievements in this field should open a new path for more comprehensive treatment of myocardial interstitial fibrosis in hypertensive heart disease and, thus, for the prevention of heart failure.

Vagotomy associated with splenectomy reduces lipid accumulation and causes kidneys histological changes in rats with hypothalamic obesity

Purpose

To evaluate the influence of autonomic vagal and splenic activities on renal histomorphometric aspects in obese rats.

Methods

Thirty male Wistar rats were used, of which, 24 received subcutaneous injections of monosodium glutamate (MSG) during the first 5 days of life (4 g/kg body weight) and six control animals received injections of saline solution (CON). Five experimental groups were organized (n = 6/group): falsely-operated control (CON-FO); falsely-operated obese (MSG-FO); vagotomized obese (MSG-VAG); splenectomized obese (MSG-SPL); vagotomized and splenectomized obese (MSG-VAG-SPL).

Results

The MSG-FO group animals showed a significant reduction in body weight and nasal-anal length when compared to CON-FO group animals (p < 0.05). The MSG-VAG-SPL group showed significant reduced in most biometric parameters associated with obesity. Falsely-operated obese animals showed a significant reduction in renal weight, glomerular diameters, glomerular tuff and capsule areas and Bowman’s space compared to CON-FO group animals (p < 0.05). There was a significant reduction in diameter, glomerular tuft and capsule areas, and Bowman’s space in MSG-VAG, MSG-SPL, MSG-VAG-SPL groups when compared to the MSG-FO group.

Conclusions

Vagotomy associated with splenectomy induces a reduction in the adiposity and causes histological changes in the kidney of obese rats.

Sympathetic Activation in Hypertensive Chronic Kidney Disease - A Stimulus for Cardiac Arrhythmias and Sudden Cardiac Death?

Studies have revealed a robust and independent correlation between chronic kidney disease (CKD) and cardiovascular (CV) events, including death, heart failure, and myocardial infarction. Recent clinical trials extend this range of adverse CV events, including malignant ventricular arrhythmias and sudden cardiac death (SCD). Moreover, other studies point out that cardiac structural and electrophysiological changes are a common occurrence in this population. These processes are likely contributors to the heightened hazard of arrhythmias in CKD population and may be useful indicators to detect patients who are at a higher SCD risk. Sympathetic overactivity is associated with increased CV risk, specifically in the population with CKD, and it is a central feature of the hypertensive state, occurring early in its clinical course. Sympathetic hyperactivity is already evident at the earliest clinical stage of CKD and is directly related to the progression of renal failure, being most pronounced in those with end-stage renal disease. Sympathetic efferent and afferent neural activity in kidney failure is a crucial facilitator for the perpetuation and evolvement of the disease. Here, we will revisit the role of the feedback loop of the sympathetic neural cycle in the context of CKD and how it may aggravate several of the risk factors responsible for causing SCD. Targeting the overactive sympathetic nervous system therapeutically, either pharmacologically or with newly available device-based approaches, may prove to be a pivotal intervention to curb the substantial burden of cardiac arrhythmias and SCD in the high-risk population of patients with CKD.

New Approaches in the Management of Sudden Cardiac Death in Patients with Heart Failure-Targeting the Sympathetic Nervous System

Cardiovascular diseases (CVDs) have been considered the most predominant cause of death and one of the most critical public health issues worldwide. In the past two decades, cardiovascular (CV) mortality has declined in high-income countries owing to preventive measures that resulted in the reduced burden of coronary artery disease (CAD) and heart failure (HF). In spite of these promising results, CVDs are responsible for ~17 million deaths per year globally with ~25% of these attributable to sudden cardiac death (SCD). Pre-clinical data demonstrated that renal denervation (RDN) decreases sympathetic activation as evaluated by decreased renal catecholamine concentrations. RDN is successful in reducing ventricular arrhythmias (VAs) triggering and its outcome was not found inferior to metoprolol in rat myocardial infarction model. Registry clinical data also suggest an advantageous effect of RDN to prevent VAs in HF patients and electrical storm. An in-depth investigation of how RDN, a minimally invasive and safe method, reduces the burden of HF is urgently needed. Myocardial systolic dysfunction is correlated to neuro-hormonal overactivity as a compensatory mechanism to keep cardiac output in the face of declining cardiac function. Sympathetic nervous system (SNS) overactivity is supported by a rise in plasma noradrenaline (NA) and adrenaline levels, raised central sympathetic outflow, and increased organ-specific spillover of NA into plasma. Cardiac NA spillover in untreated HF individuals can reach ~50-fold higher levels compared to those of healthy individuals under maximal exercise conditions. Increased sympathetic outflow to the renal vascular bed can contribute to the anomalies of renal function commonly associated with HF and feed into a vicious cycle of elevated BP, the progression of renal disease and worsening HF. Increased sympathetic activity, amongst other factors, contribute to the progress of cardiac arrhythmias, which can lead to SCD due to sustained ventricular tachycardia. Targeted therapies to avoid these detrimental consequences comprise antiarrhythmic drugs, surgical resection, endocardial catheter ablation and use of the implantable electronic cardiac devices. Analogous NA agents have been reported for single photon-emission-computed-tomography (SPECT) scans usage, specially the 123I-metaiodobenzylguanidine (123I-MIBG). Currently, HF prognosis assessment has been improved by this tool. Nevertheless, this radiotracer is costly, which makes the use of this diagnostic method limited. Comparatively, positron-emission-tomography (PET) overshadows SPECT imaging, because of its increased spatial definition and broader reckonable methodologies. Numerous ANS radiotracers have been created for cardiac PET imaging. However, so far, [11C]-meta-hydroxyephedrine (HED) has been the most significant PET radiotracer used in the clinical scenario. Growing data has shown the usefulness of [11C]-HED in important clinical situations, such as predicting lethal arrhythmias, SCD, and all-cause of mortality in reduced ejection fraction HF patients. In this article, we discussed the role and relevance of novel tools targeting the SNS, such as the [11C]-HED PET cardiac imaging and RDN to manage patients under of SCD risk.

Effects of Renal Denervation on Cardiac Structural and Functional Abnormalities in Patients with Resistant Hypertension or Diastolic Dysfunction

The aim of the present study is to systematically evaluate the impact of RDN on cardiac structure and function in patients with resistant hypertension (RH) or diastolic dysfunction. We retrieved Pubmed, Embase and Cocharane Library databases, from inception to April 1^st, 2016. Studies reporting left ventricular mass (LVMI) or left ventricular (LV) diastolic function (reflected by the ratio of mitral inflow velocity to annular relaxation velocity [E/e’]) responses to RDN were included. Two randomized controlled trials (RCTs), 3 controlled studies and 11 uncontrolled studies were finally identified. In observational studies, there was a reduction in LVMI, E/e’ and N-terminal pro B-type natriuretic peptide (BNP) at 6 months, compared with pre-RDN values. LV ejection fraction (LVEF) elevated at 6 months following RDN. In RCTs, however, no significant change in LVMI, E/e’, BNP, left atrial volume index or LVEF was observed at 12 months, compared with pharmaceutical therapy. In summary, both LV hypertrophy and cardiac function improved at 6 months after RDN. Nonetheless, current evidence failed to show that RDN was superior to intensive (optimal) drug therapy in improving cardiac remodeling and function.

Renal sympathetic denervation in therapy resistant hypertension - pathophysiological aspects and predictors for treatment success

Many forms of human hypertension are associated with an increased systemic sympathetic activity. Especially the renal sympathetic nervous system has been found to play a prominent role in this context. Therefore, catheter-interventional renal sympathetic denervation (RDN) has been established as a treatment for patients suffering from therapy resistant hypertension in the past decade. The initial enthusiasm for this treatment was markedly dampened by the results of the Symplicity-HTN-3 trial, although the transferability of the results into clinical practice to date appears to be questionable. In contrast to the extensive use of RDN in treating hypertensive patients within or without clinical trial settings over the past years, its effects on the complex pathophysiological mechanisms underlying therapy resistant hypertension are only partly understood and are part of ongoing research. Effects of RDN have been described on many levels in human trials: From altered systemic sympathetic activity across cardiac and metabolic alterations down to changes in renal function. Most of these changes could sustainably change long-term morbidity and mortality of the treated patients, even if blood pressure remains unchanged. Furthermore, a number of promising predictors for a successful treatment with RDN have been identified recently and further trials are ongoing. This will certainly help to improve the preselection of potential candidates for RDN and thereby optimize treatment outcomes. This review summarizes important pathophysiologic effects of renal denervation and illustrates the currently known predictors for therapy success.

Effect of Renal Sympathetic Denervation on Specific MicroRNAs as an Indicator of Reverse Remodeling Processes in Hypertensive Heart Disease

A total of 90 consecutive patients undergoing renal sympathetic denervation (RSD) were included in this study. A significant reduction in office systolic blood pressure (SBP) of 21.1 mm Hg (P<.001) was documented 6 months after RSD. At this time point, circulating concentrations of microRNA (miR)-133a were significantly increased (sevenfold; P<.001) compared with baseline values. Correlation analysis showed a significant relationship between baseline SBP values and SBP reduction (P<.001) as well as between miR-133a baseline levels and the increase in miR-133a expression (P<.001) after the 6-month follow-up. The effect of RSD on miR-133a expression was significantly greater in patients at high risk for hypertensive heart disease. In addition to the effective blood pressure reduction in response to RSD, this study demonstrates an effect of RSD on miR reflecting cardiovascular reverse remodeling processes. Thus, these results provide information on a beneficial effect of RSD on cardiac recovery in patients at high risk for hypertensive heart disease.

Renal denervation significantly attenuates cardiorenal fibrosis in rats with sustained pressure overload

To investigate the effects of renal denervation (RDN) on comprehensive cardiac and renal fibrosis in cardiomyopathy. Five weeks after successful transverse aortic constriction (TAC)-induced cardiomyopathy model building, Sprague-Dawley rats were randomly assigned to three groups: (1) RDN, (2) sham, and (3) losartan. Sham TAC rats served as control group. Compared with control, TAC groups showed a significant decrease in left ventricle ejection fraction and increase in ventricular septum thickness and left atrium diameter on echocardiography after 5 weeks. At 10 weeks post-TAC, venous blood samples were collected for fibrosis biochemical assay. Heart and kidney samples were also harvested for fibrosis pathophysiological detection. Cardiac and renal fibrosis quantity results showed that, compared with sham group, collagen volume fraction was significantly decreased in RDN group more than in losartan group. Biochemical parameters such as tumor necrosis factor α, aldosterone, and B-type natriuretic peptide levels as well as biomarkers for fibrosis such as procollagen type I N-terminal propeptide and procollagen type III N-terminal propeptide concentrations were significantly decreased in RDN group in comparison with sham. In addition, compared with sham group, left ventricle tissue protein expression of transforming growth factor-β1 and angiotensin II type I receptor was downregulated, and angiotensin-converting enzyme 2 was upregulated in RDN but not in losartan group. RDN significantly attenuates cardiac and renal fibrosis in cardiomyopathy. Differing from losartan, which only has angiotensin II type I receptor inhibition effects, RDN comprehensively suppresses cardiac and renal fibrogenesis through multiple pathways.

A Novel Swine Model of Spontaneous Hypertension With Sympathetic Hyperactivity Responds Well to Renal Denervation

BACKGROUND

The large animal model of arterial hypertension is very valuable to test the antihypertensive drugs and devices. We characterized a novel swine model of spontaneous hypertension and investigated its response to renal denervation (RDN).

METHODS

The blood pressure (BP), levels of plasma catecholamines and urine vanillylmandelic acid, and the protein expressions of angiotensin-converting enzyme (ACE) and angiotensin II type 1 (AT1), and type 2 (AT2) receptors in the rostral ventrolateral medulla (RVLM) were compared between domestic pigs and Guizhou mini-pigs. Twelve-month-old Guizhou mini-pigs were divided into sham (n = 7) and ablation (n = 7) groups. The mini-pigs in ablation group received bilateral percutaneous RDN with a saline-irrigated Sniper ablation catheter. Three months after the procedure, the BP was measured and the histology of renal nerves and arteries was analyzed.

RESULTS

The mini-pigs spontaneously developed hypertension by the age of 6 months and the BP (162.2 ± 11.4/111.8 ± 9.2mm Hg) was significantly higher than age-matched domestic pigs (137.5 ± 1.9/80.2 ± 4.1mm Hg, P < 0.05). The levels of plasma catecholamines and urine vanillylmandelic acid were higher in mini-pigs than domestic pigs. The expressions of ACE and AT1 were increased, but the AT2 was decreased, in RVLM from mini-pigs compared with domestic pigs. Three months after the procedure, the BP was sharply reduced in ablation group (113.8 ± 14.4/79.4 ± 11.7 mm Hg) compared with sham group (192.4 ± 10.5/141.2 ± 5.9 mm Hg, P < 0.01). Renal nerves were substantially destroyed, while renal arteries and function were not significantly affected by ablation.

CONCLUSIONS

The Guizhou mini-pig is a novel spontaneous hypertensive animal model with sympathetic hyperactivity and responds well to RDN.

Renal Denervation Findings on Cardiac and Renal Fibrosis in Rats with Isoproterenol Induced Cardiomyopathy

Cardio-renal fibrosis plays key roles in heart failure and chronic kidney disease. We sought to determine the effects of renal denervation (RDN) on cardiac and renal fibrosis in rats with isoproterenol induced cardiomyopathy. Sixty male Sprague Dawley rats were randomly assigned to Control (n = 10) and isoproterenol (ISO)-induced cardiomyopathy group (n = 50). At week 5, 31 survival ISO-induced cardiomyopathy rats were randomized to RDN (n = 15) and Sham group (n = 16). Compared with Control group, ejection fraction was decreased, diastolic interventricular septal thickness and left atrial dimension were increased in ISO-induced cardiomyopathy group at 5 week. After 10 weeks, cardio-renal pathophysiologic results demonstrated that the collagen volume fraction of left atrio-ventricular and kidney tissues reduced significantly in RDN group compared with Sham group. Moreover the pro-fibrosis factors (TGF-β1, MMP2 and Collagen I), inflammatory cytokines (CRP and TNF-α), and collagen synthesis biomarkers (PICP, PINP and PIIINP) concentration significantly decreased in RDN group. Compared with Sham group, RDN group showed that release of noradrenaline and aldosterone were reduced, angiotensin-converting enzyme (ACE)/angiotensin II (Ang II)/angiotensin II type-1 receptor (AT₁R) axis was downregulated. Meanwhile, angiotensin-converting enzyme 2 (ACE2)/angiotensin-1-7 (Ang-(1-7))/mas receptor (Mas-R) axis was upregulated. RDN inhibits cardio-renal fibrogenesis through multiple pathways, including reducing SNS over-activity, rebalancing RAAS axis.

Chronic kidney disease and risk factors responsible for sudden cardiac death: a whiff of hope?

Several studies have shown a strong independent association between chronic kidney disease (CKD) and cardiovascular events, including death, heart failure, and myocardial infarction. Recent clinical trials extend this range of adverse cardiovascular events, also including ventricular arrhythmias and sudden cardiac death. Furthermore, other studies suggest structural remodeling of the heart and electrophysiological alterations in this population. These processes may explain the increased risk of arrhythmia in kidney disease and help to identify patients who are at increased risk of sudden cardiac death. Sympathetic hyperactivity is well known to increase cardiovascular risk in CKD patients and is a hallmark of essential hypertensive state that occurs early in the clinical course of the disease. In CKD, the sympathetic hyperactivity seems to be expressed at the earliest clinical stage of the disease, showing a direct relationship with the severity of the condition of renal failure, being more pronounced in the terminal stage of CKD. The sympathetic efferent and afferent neural activity in kidney failure is a key mediator for the maintenance and progression of the disease. The aim of this review was to show that the feedback loop of this cycle, due to adrenergic hyperactivity, also aggravates many of the risk factors responsible for causing sudden cardiac death and may be a potential target modifiable by percutaneous renal sympathetic denervation. If it is feasible and effective in end-stage renal disease, little is known.

Renal denervation attenuates NADPH oxidase-mediated oxidative stress and hypertension in rats with hydronephrosis

Hydronephrosis is associated with the development of salt-sensitive hypertension. Studies have suggested that increased sympathetic nerve activity and oxidative stress play important roles in hypertension and the modulation of salt sensitivity. The present study primarily aimed to examine the role of renal sympathetic nerve activity in the development of hypertension in rats with hydronephrosis. In addition, we aimed to investigate if NADPH oxidase (NOX) function could be affected by renal denervation. Partial unilateral ureteral obstruction (PUUO) was created in 3-wk-old rats to induce hydronephrosis. Sham surgery or renal denervation was performed at the same time. Blood pressure was measured during normal, high-, and low-salt diets. The renal excretion pattern, NOX activity, and expression as well as components of the renin-angiotensin-aldosterone system were characterized after treatment with the normal salt diet. On the normal salt diet, rats in the PUUO group had elevated blood pressure compared with control rats (115 ± 3 vs. 87 ± 1 mmHg, P < 0.05) and displayed increased urine production and lower urine osmolality. The blood pressure change in response to salt loading (salt sensitivity) was more pronounced in the PUUO group compared with the control group (15 ± 2 vs. 5 ± 1 mmHg, P < 0.05). Renal denervation in PUUO rats attenuated both hypertension (97 ± 3 mmHg) and salt sensitivity (5 ± 1 mmHg, P < 0.05) and normalized the renal excretion pattern, whereas the degree of renal fibrosis and inflammation was not changed. NOX activity and expression as well as renin and ANG II type 1A receptor expression were increased in the renal cortex from PUUO rats and normalized by denervation. Plasma Na(+) and K(+) levels were elevated in PUUO rats and normalized after renal denervation. Finally, denervation in PUUO rats was also associated with reduced NOX expression, superoxide production, and fibrosis in the heart. In conclusion, renal denervation attenuates hypertension and restores the renal excretion pattern, which is associated with reduced renal NOX and components of the renin-angiotensin-aldosterone system. This study emphasizes a link between renal nerves, the development of hypertension, and modulation of NOX function.