Renal denervation attenuates aldosterone expression and associated cardiovascular pathophysiology in angiotensin II-induced hypertension

The role of Mas receptor on renal hemodynamic responses to angiotensin II administration in chronic renal sympathectomized male and female rats

Background and purpose

Renal hemodynamics is influenced by renal sympathetic nerves and the renin-angiotensin system. On the other hand, renal sympathetic denervation impacts kidney weight by affecting renal hemodynamics. The current study evaluated the role of the Mas receptor on renal hemodynamic responses under basal conditions and in response to angiotensin II (Ang II) in chronic renal sympathectomy in female and male rats.

Experimental approach

Forty-eight nephrectomized female and male rats were anesthetized and cannulated. Afterward, the effect of chronic renal sympathectomy was investigated on hemodynamic parameters such as renal vascular resistance (RVR), mean arterial pressure (MAP), and renal blood flow (RBF). In addition, the effect of chronic sympathectomy on kidney weight was examined.

Findings/Results

Chronic renal sympathectomy increased RVR and subsequently decreased RBF in both sexes. Renal perfusion pressure also increased after sympathectomy in male and female rats, while MAP did not change, significantly. In response to the Ang II injection, renal sympathectomy caused a greater decrease in RBF in all experimental groups, while it did not affect the MAP response. In addition, chronic sympathectomy increased left kidney weight in right nephrectomized rats.

Conclusion and implications

Chronic renal sympathectomy changed systemic/renal hemodynamics in baseline conditions and only renal hemodynamics in response to Ang II administration. Moreover, chronic sympathectomy increased compensatory hypertrophy in nephrectomized rats. These changes are unaffected by gender difference and Mas receptor blocker.

Plasma renin and aldosterone concentrations related to endovascular ultrasound renal denervation in the RADIANCE-HTN SOLO trial

OBJECTIVE

The RADIANCE-HTN SOLO trial demonstrated a greater reduction in daytime ambulatory SBP at 2 months by endovascular ultrasound renal denervation than sham procedure. We hypothesized that plasma renin and aldosterone concentrations would be associated with the SBP response to renal denervation.

METHODS

Hypertensive patients were randomized to renal denervation (n = 74) or sham (n = 72) after a 4-week washout of antihypertensive medications. In a 53-patient subset, 2-month and 6-month plasma renin and aldosterone concentration were measured. Dietary sodium was not controlled.

RESULTS

Mean age of the 29 treatment and 24 sham patients was 54 years; 62% were men; 17% black. Daytime ambulatory SBP fell in the denervation but not the sham group at 2 months (-7.8 ± 10.7 vs. -0.1 ± 10.1 mmHg; P = 0.048). Baseline plasma renin and aldosterone concentrations were in the low-normal range, did not change significantly at 2 months in either group and did not predict response to renal denervation. At 6 months, after the addition of antihypertensive medications, there was a significant rise in renin in the sham but not the denervation group.

CONCLUSION

Although renal denervation but not sham resulted in a decrease in daytime ambulatory SBP at 2 months, renin and aldosterone concentrations did neither predict the BP response to renal denervation; nor did they fall after denervation. A rise in renin at 6 months in the sham group likely represents confounding from antihypertensive medications. Whether the BP-lowering effect of renal denervation depends on reducing local intrarenal renin release requires further study.

Renal denervation inhibits the renin-angiotensin-aldosterone system in spontaneously hypertensive rats

This study was conducted to explore the effect of renal denervation (RDN) on the renin-angiotensin-aldosterone system (RAAS) in spontaneously hypertensive rats (SHRs). Our experimental rats were randomly divided into the RDN group conducted by painting 10% phenol on the bilateral renal nerves (RDNX), the shamoperation group simply painting with saline (Sham), and the normotension control group (WKY) following all the animal blood and tissues of kidney, hypothalamus, and adrenal gland collected and examined 2 weeks after RDN operation. We found that the aldosterone (ALD) levels in serum and tissues all decreased in the RDNX group compared with the Sham group (p < .05). Meantime, the expression of angiotensin II type1 receptor (AT1R) mRNA also exhibited significantly reduced by 2.22-fold in the RDNX group compared to the Sham group identical to the expression of AT1R protein in the renal cortex and outer stripe of the outer medulla (OSOM) subjected to denervation surgery, which manifested the lower ATIR protein expression than the Sham group (p < .05). Besides, the expression of angiotensin II (Ang II) protein in the cortex , OSOM, and inner stripe of the outer medulla were all attenuated by RDN in comparison with the Sham group (p < .05). RDN reduced intrarenal RAAS and circulating RAAS to lower blood pressure and repair renal function.

LncRNA MIAT promotes hypoxia-induced H9C2 cell pyroptosis via binding to SF1 to inhibit CGRP transcription

NEW FINDINGS

What is the central question of this study? How does long non-coding RNA myocardial infarction-associated transcript (lncRNA MIAT) function in hypoxia-induced H9C2 cells? What is the main finding and its importance? LncRNA MIAT inhibited transcription of calcitonin gene-related peptide by binding to splicing factor 1, thereby promoting hypoxia-induced H9C2 cell pyroptosis. This study provides a new theoretical basis for the treatment of acute myocardial infarction by using lncRNA MIAT as a molecular target to mediate cardiomyocyte pyrodeath.

ABSTRACT

Hypoxia induces severe cardiomyocyte pyroptosis, contributing to acute myocardial infarction. The aim of this study was to analyse the molecular mechanism of long non-coding RNA myocardial infarction-associated transcript (lncRNA MIAT) in hypoxia-induced H9C2 cell pyroptosis. A hypoxic H9C2 cell model was established. Cell viability was detected via the Cell Counting Kit-8 method. Levels of lactate dehydrogenase, malondialdehyde and superoxide dismutase and expressions of pyroptotic markers, lncRNA MIAT, splicing factor 1 (SF1) and calcitonin gene-related peptide (CGRP) were detected via qRT-PCR. The subcellular localization of lncRNA MIAT was predicted and confirmed via LncATLAS and nuclear/cytosol fractionation assay. The binding relationships between lncRNA MIAT and SF1 and between SF1 and the CGRP promotor were verified via RNA immunoprecipitation. Rescue experiments were designed to confirm the role of lncRNA MIAT/SF1/CGRP in H9C2 cell pyroptosis. LncRNA MIAT was overexpressed in hypoxia-induced H9C2 cells. Hypoxia induced pyroptosis in H9C2 cells. Silencing of lncRNA MIAT enhanced cell viability and alleviated pyroptosis. LncRNA MIAT inhibited CGRP transcription via binding to SF1. Overexpression of SF1 promoted CGRP transcription and relieved H9C2 cell pyroptosis. Downregulation of CGRP reversed the role of silencing lncRNA MIAT in H9C2 cell pyroptosis. Overall, lncRNA MIAT inhibited CGRP transcription via binding to SF1, thereby promoting hypoxia-induced H9C2 cell pyroptosis.

Retroperitoneal adipose tissue denervation improves cardiometabolic and autonomic dysfunction in a high fat diet model

Sympathetic vasomotor overactivity is a major feature leading to the cardiovascular dysfunction related to obesity. Considering that the retroperitoneal white adipose tissue (rWAT) is an important fat visceral depot and receives intense sympathetic and afferent innervations, the present study aimed to evaluate the effects evoked by bilateral rWAT denervation in obese rats. Male Wistar rats were fed with HFD for 8 consecutive weeks and rWAT denervation was performed at the 6th week. Arterial pressure, splanchnic and renal sympathetic vasomotor nerve activities were assessed and inflammation and the components of the renin -angiotensin system were evaluated in different white adipose tissue depots. HFD animals presented higher serum levels of leptin and glucose, an increase in arterial pressure and splanchnic sympathetic nerve activity; rWAT denervation, normalized these parameters. Pro-inflammatory cytokines levels were significantly increased, as well as RAAS gene expression in WAT of HFD animals; rWAT denervation significantly attenuated these changes. In conclusion, HFD promotes vasomotor sympathetic overactivation and inflammation with repercussions on the cardiovascular system. In conclusion, the neural communication between WAT and the brain is fundamental to trigger sympathetic vasomotor activation and this pathway is a possible new therapeutic target to treat obesity-associated cardiovascular dysfunction.

Effect of renal denervation on catecholamines and the renin-angiotensin-aldosterone system

Introduction:

The effect of renal sympathetic denervation (RDN) on neurohormonal responses is largely unknown. We aimed to assess the effect of RDN on the renin–angiotensin–aldosterone system (RAAS) and endogenous catecholamines.

Methods:

A total of 60 patients with hypertension underwent RDN and remained on a stable antihypertensive drug regimen. Samples for plasma aldosterone, plasma renin and urine (nor)metanephrine were collected at baseline and at 6 months post procedure. Ambulatory blood pressure (BP) recordings were obtained at baseline and at 6 months post procedure.

Results:

Mean age was 64±9 years, and 30/60 patients were male. At 6 months, average daytime systolic and diastolic ambulatory BP decreased by 10 and 6 mmHg, respectively (p<0.001). No significant change was observed in plasma aldosterone (median=248.0 pmol/L (interquartile range (IQR) 113.3–369.5 pmol/L) vs. median=233.0 pmol/L (IQR 110.3–360.8 pmol/L); p=0.66); renin (median=19.5 µIU/mL (IQR 6.8–119.5 µIU/mL) vs. median=14.3 µIU/mL (IQR 7.2–58.0 µIU/mL); p=0.32), urine metanephrine (median=0.46 µmol/L (IQR 0.24–0.77 µmol/L) vs. median=0.46 µmol/L (IQR 0.22–0.88 µmol/L); p=0.75) and normetanephrine (median=1.41 µmol/L (IQR 0.93–2.00 µmol/L vs. median =1.56 (IQR 0.74–2.50 µmol/L); p=0.58) between baseline and 6 months, respectively. No correlation was found between the decrease in mean systolic daytime BP and changes in RAAS hormones or endogenous catecholamines.

Conclusion:

Despite significant reductions in ambulatory BP, RDN did not result in a significant change in endogenous catecholamines or in RAAS hormones at 6 months.

Mesenchymal Stem Cells Therapies on Fibrotic Heart Diseases

Stem cell therapy is a promising alternative approach to heart diseases. The most prevalent source of multipotent stem cells, usually called somatic or adult stem cells (mesenchymal stromal/stem cells, MSCs) used in clinical trials is bone marrow (BM-MSCs), adipose tissue (AT-MSCs), umbilical cord (UC-MSCs) and placenta. Therapeutic use of MSCs in cardiovascular diseases is based on the benefits in reducing cardiac fibrosis and inflammation that compose the cardiac remodeling responsible for the maintenance of normal function, something which may end up causing progressive and irreversible dysfunction. Many factors lead to cardiac fibrosis and failure, and an effective therapy is lacking to reverse or attenuate this condition. Different approaches have been shown to be promising in surpassing the poor survival of transplanted cells in cardiac tissue to provide cardioprotection and prevent cardiac remodeling. This review includes the description of pre-clinical and clinical investigation of the therapeutic potential of MSCs in improving ventricular dysfunction consequent to diverse cardiac diseases.

Changes in Plasma Renin Activity After Renal Artery Sympathetic Denervation

BACKGROUND

The renin-angiotensin-aldosterone system plays a key role in blood pressure (BP) regulation and is the target of several antihypertensive medications. Renal denervation (RDN) is thought to interrupt the sympathetic-mediated neurohormonal pathway as part of its mechanism of action to reduce BP.

OBJECTIVES

The purpose of this study was to evaluate plasma renin activity (PRA) and aldosterone before and after RDN and to assess whether these baseline neuroendocrine markers predict response to RDN.

METHODS

Analyses were conducted in patients with confirmed absence of antihypertensive medication. Aldosterone and PRA levels were compared at baseline and 3 months post-procedure for RDN and sham control groups. Patients in the SPYRAL HTN-OFF MED Pivotal trial were separated into 2 groups, those with baseline PRA ≥0.65 ng/ml/h (n = 110) versus <0.65 ng/ml/h (n = 116). Follow-up treatment differences between RDN and sham control groups were adjusted for baseline values using multivariable linear regression models.

RESULTS

Baseline PRA was similar between RDN and control groups (1.0 ± 1.1 ng/ml/h vs. 1.1 ± 1.1 ng/ml/h; p = 0.37). Change in PRA at 3 months from baseline was significantly greater for RDN compared with control subjects (-0.2 ± 1.0 ng/ml/h; p = 0.019 vs. 0.1 ± 0.9 ng/ml/h; p = 0.14), p = 0.001 for RDN versus control subjects, and similar differences were seen for aldosterone: RDN compared with control subjects (-1.2 ± 6.4 ng/dl; p = 0.04 vs. 0.4 ± 5.4 ng/dl; p = 0.40), p = 0.011. Treatment differences at 3 months in 24-h and office systolic blood pressure (SBP) for RDN versus control patients were significantly greater for patients with baseline PRA ≥0.65 ng/ml/h versus <0.65 ng/ml/h, despite similar baseline BP. Differences in office SBP changes according to baseline PRA were also observed earlier at 2 weeks post-RDN.

CONCLUSIONS

Plasma renin activity and aldosterone levels for RDN patients were significantly reduced at 3 months when compared with baseline as well as when compared with sham control. Higher baseline PRA levels were associated with a significantly greater reduction in office and 24-h SBP. (SPYRAL PIVOTAL - SPYRAL HTN-OFF MED Study; NCT02439749).

Efficacy and safety of renal denervation in addition to pulmonary vein isolation for atrial fibrillation and hypertension-Systematic review and meta-analysis of randomized controlled trials

Introduction

This systematic review and meta‐analysis aimed to assess the latest evidence on the use of renal denervation (RDN) + pulmonary vein isolation (PVI) compared to PVI alone for treating atrial fibrillation (AF) with hypertension.

Methods

A systematic literature search from several electronic databases was performed up until January 2020. The primary outcome was AF recurrence defined as AF/atrial flutter (AFL)/atrial tachycardia (AT) ≥30 seconds at 12‐month follow‐up and the secondary outcome was procedure‐related complications.

Results

There were 568 subjects from five studies. AF recurrence was 90/280 (32.1%) in the RDN + PVI group and 142/274 (51.8%) in the PVI group. RDN + PVI was associated with a lower incidence of AF recurrence (RR 0.62 [0.51, 076], P < .001; I²: 0%). Pooled analysis of HR showed that RDN + PVI was associated with reduced AF recurrence (HR 0.51 [0.38, 0.70], P < .001; I²: 0%). Complications were 7/241 (2.9%) in the RDN + PVI group and 8/237 (3.4%) in the PVI group. The rate of complications between the groups was similar (RR 0.87 [0.33, 2.29], P = .77; I²: 0%). In the subgroup analysis of paroxysmal AF, RDN + PVI was shown to reduce AF recurrence (RR 0.64 [0.49, 0.82], P < .001; I²: 0% and HR 0.56 [0.38, 0.82], P = .003; I²: 0%) compared to PVI alone. RDN + PVI has a moderate certainty of evidence in the reducing AF recurrence with an absolute reduction of 197 fewer per 1000 (from 254 fewer to 124 fewer).

Conclusion

RDN in addition to PVI, is associated with reduced 12‐month AF recurrence and similar procedure‐related complications compared to PVI alone.

Relationship Between 25-Hydroxyvitamin D, Renin, and Collagen Remodeling Biomarkers in Atrial Fibrillation

The interplay between vitamin D, the renin-angiotensin system (RAS), and collagen remodeling has been implicated in the pathogenesis of various cardiovascular diseases. This study sought to explore this relationship in atrial fibrillation (AF) by profiling plasma levels of 25-hydroxyvitamin D, RAS biomarkers, and collagen remodeling biomarkers using the enzyme-linked immunosorbent assay method. We hypothesized that 25-hydroxyvitamin D levels would inversely correlate with RAS biomarkers and that levels of RAS and collagen remodeling biomarkers would positively correlate with each other. Although our AF cohort (n = 37) did not exhibit decreased 25-hydroxyvitamin D levels compared to normal controls (n = 26), these levels inversely correlated with renin (Spearman r = -0.57, P = 0.005). Renin levels were elevated in patients with AF compared to normal controls (1233 ± 238 ng/mL vs 401 ± 27 ng/mL, P = 0.0002) and positively correlated with levels of matrix metalloproteinase 1 (MMP-1; Spearman r = 0.89, P = 0.01) and MMP-2 (Spearman r = 0.82, P = 0.03). These data suggest that 25-hydroxyvitamin D may influence RAS activation, and renin may help mediate the collagen remodeling process in AF. Understanding mediators of RAS dysregulation in AF may elucidate targets for therapeutic intervention to prevent collagen remodeling.

Steroidogenic acute regulatory protein/aldosterone synthase mediates angiotensin II-induced cardiac fibrosis and hypertrophy

Aldosterone produced in adrenal glands by angiotensin II (Ang II) is known to elicit myocardial fibrosis and hypertrophy. This study was designed to test the hypothesis that Ang II causes cardiac morphological changes through the steroidogenic acute regulatory protein (StAR)/aldosterone synthase (AS)-dependent aldosterone synthesis primarily initiated in the heart. Sprague-Dawley rats were randomized to following groups: Ang II infusion for a 4-week period, treatment with telmisartan, spironolactone or adrenalectomy during Ang II infusion. Sham-operated rats served as control. Relative to Sham rats, Ang II infusion significantly increased the protein levels of AT1 receptor, StAR, AS and their tissue expression in the adrenal glands and heart. In coincidence with reduced aldosterone level in the heart, telmisartan, an AT1 receptor blocker, significantly down-regulated the protein level and expression of StAR and AS. Ang II induced changes in the expression of AT1/StAR/AS were not altered by an aldosterone receptor antagonist spironolactone. Furthermore, Ang II augmented migration of macrophages, protein level of TGFβ1, phosphorylation of Smad2/3 and proliferation of myofibroblasts, accompanied by enhanced perivascular/interstitial collagen deposition and cardiomyocyte hypertrophy, which all were significantly abrogated by telmisartan or spironolactone. However, adrenalectomy did not fully suppress Ang II-induced cell migration/proliferation and fibrosis/hypertrophy, indicating a role of aldosterone synthesized within the heart in pathogenesis of Ang II induced injury. These results indicate that myocardial fibrosis and hypertrophy stimulated by Ang II is associated with tissue-specific activation of aldosterone synthesis, primarily mediated by AT1/StAR/AS signaling pathways.

Adventitial fibroblast-derived vascular endothelial growth factor promotes vasa vasorum-associated neointima formation and macrophage recruitment

Aims

Adventitial vasa vasorum provides oxygen and nourishment to the vascular wall, but whether it regulates vascular disease remains unclear. We have previously shown that an increased expression of VEGF (vascular endothelial growth factor) is associated with macrophage infiltration. This study aims to determine whether adventitial fibroblast (AF)-derived VEGF increases the number of vasa vasorum contributing to neointima formation through macrophage recruitment.

Methods and results

In rat balloon injury model, vasa vasorum count was increased particularly in the adventitia accompanied by cell proliferation and VEGF expression. Both endogenous and PKH26-labelled exogenous macrophages were mainly distributed in adventitia around vasa vasorum. Interestingly, perivascular delivery of Ranibizumab preferentially concentrated in adventitia resulted in a decrease of neointima formation with concurrent reduction of vasa vasorum count and macrophage infiltration. AFs with adenovirus-mediated VEGF over-expression delivered to the adventitia significantly enhanced these pathological changes after injury. In Tie2-cre/Rosa-LoxP-RFP mice, endothelial cells were increased in the adventitia after wire injury. By using multiphoton laser scanning microscopy, macrophage rolling, adhesion and transmigration were observed in vasa vasorum. Moreover, adoptive transfer of macrophages accelerated injury-induced neointima formation. VEGF-neutralizing antibody administration also attenuated wire injury-induced neointima formation and macrophage infiltration. In primary cultured AFs, exogenous VEGF increased VEGF expression and secretion in a time- and dose-dependent manner. AF-conditioned medium promoted endothelial cell angiogenesis, vascular cell adhesion molecule-1 expression and macrophage adhesion was blocked by VEGF-neutralizing antibody and VEGFR2 inhibitor ZM323881, which also inhibited activation of VEGFR2/ERK1/2 pathway.

Conclusion

These results demonstrate that AF-derived VEGF plays a significant role in the increase of vasa vasorum count which is involved in macrophage recruitment and neointima formation.

Renal denervation and CD161a immune ablation prevent cholinergic hypertension and renal sodium retention

Cholinergic receptor activation leads to premature development of hypertension and infiltration of proinflammatory CD161a⁺/CD68⁺ M1 macrophages into the renal medulla. Renal inflammation is implicated in renal sodium retention and the development of hypertension. Renal denervation is known to decrease renal inflammation. The objective of this study was to determine the role of CD161a⁺/CD68⁺ macrophages and renal sympathetic nerves in cholinergic-hypertension and renal sodium retention. Bilateral renal nerve denervation (RND) and immune ablation of CD161a⁺ immune cells were performed in young prehypertensive spontaneously hypertensive rat (SHR) followed by infusion of either saline or nicotine (15 mg·kg^-1·day^-1) for 2 wk. Immune ablation was conducted by injection of unconjugated azide-free antibody targeting rat CD161a⁺. Blood pressure was monitored by tail cuff plethysmography. Tissues were harvested at the end of infusion. Nicotine induced premature hypertension, renal expression of the sodium-potassium chloride cotransporter (NKCC2), increases in renal sodium retention, and infiltration of CD161a⁺/CD68⁺ macrophages into the renal medulla. All of these effects were abrogated by RND and ablation of CD161a⁺ immune cells. Cholinergic activation of CD161a⁺ immune cells with nicotine leads to the premature development of hypertension in SHR. The effects of renal sympathetic nerves on chemotaxis of CD161a⁺ macrophages to the renal medulla, increased renal expression of NKCC2, and renal sodium retention contribute to cholinergic hypertension. The CD161a⁺ immune cells are necessary and essential for this prohypertensive nicotine-mediated inflammatory response.NEW & NOTEWORTHY This is the first study that describes a novel integrative physiological interaction between the adrenergic, cholinergic, and renal systems in the development of hypertension, describing data for the role of each in a genetic model of essential hypertension. Noteworthy findings include the prevention of nicotine-mediated hypertension following successful immune ablation of CD161a⁺ immune cells and the necessary role these cells play in the overexpression of the sodium-potassium-chloride cotransporter (NKCC2) in the renal medulla and renal sodium retention. Renal infiltration of these cells is demonstrated to be dependent on the presence of renal adrenergic innervation. These data offer a fertile ground of therapeutic potential for the treatment of hypertension as well as open the door for further investigation into the mechanism involved in inflammation-mediated renal sodium transporter expression. Taken together, these findings suggest immune therapy, renal denervation, and, possibly, other new molecular targets as having a potential role in the development and maintenance of essential hypertension.

Membrane raft redox signalling contributes to endothelial dysfunction and vascular remodelling of thoracic aorta in angiotensin II-infused rats

NEW FINDINGS

What is the central question of this study? Is the membrane raft redox signalling pathway involved in blood pressure increase, endothelial dysfunction and vascular remodelling in an angiotensin II-induced hypertensive animal model? What is the main finding and its importance? The membrane raft redox signalling pathway was involved in endothelial dysfunction and medial remodelling in angiotensin II-induced hypertension.

ABSTRACT

The membrane raft (MR) redox pathway is characterized by NADPH oxidase activation via the clustering of its subunits through lysosome fusion and the activation of acid sphingomyelinase (ASMase). Our previous study shows that the MR redox signalling pathway is associated with angiontensin II (AngII)-induced production of reactive oxygen species (ROS) and endothelial dysfunction in rat mesenteric arteries. In the present study, we hypothesized that this signalling pathway is involved in blood pressure increase, endothelial dysfunction and vascular remodelling in an AngII-induced hypertensive animal model. Sixteen-week-old male Sprague-Dawley rats were subjected to AngII infusion for 2 weeks with or without treatment with the lysosome fusion inhibitor bafilomycin A1 and ASMase inhibitor amitriptyline. After treatments, aortas were harvested for further study. The results showed that the MR redox signalling pathway was activated as indicated by the increase of MR formation, ASMase activity and ROS production in aorta from AngII-infused rats compared with that from control rats. MR formation and ROS production were significantly inhibited in thoracic aorta from AngII-induced rats treated with bafilomycin A1 and amitriptyline. Both treatments significantly attenuated blood pressure increase, endothelial dysfunction and vascular remodelling including medial hypertrophy, and increased collagen and fibronectin deposition in thoracic aortas from AngII-infused rats. Finally, both treatments significantly prevented the increase of inflammatory factors including monocyte chemotactic protein 1, intercellular adhesion molecule 1 and tumour necrosis factor α in thoracic aorta from AngII-infused rats. In conclusion, the present study demonstrates that the MR redox signalling pathway was involved in endothelial dysfunction and medial remodelling in AngII-induced hypertension.

Chronic intermittent hypoxia-mediated renal sympathetic nerve activation in hypertension and cardiovascular disease

In sleep apnea syndrome (SAS), chronic intermittent hypoxia (CIH) is believed to activate the sympathetic nerve system, and is thus involved in cardiovascular diseases (CVD). However, since patients with SAS are often already obese, and have diabetes and/or hypertension (HT), the effects of CIH alone on sympathetic nerve activation and its impacts on CVD are largely unknown. We, therefore, examined the effects of CIH on sympathetic nerve activation in non-obese mice to determine whether renal sympathetic nerve denervation (RD) could ameliorate CIH-mediated cardiovascular effects. Male C57BL/6 (WT) mice were exposed to normal (FiO₂ 21%) or CIH (10% O₂, 12 times/h, 8 h/day) conditions for 4 weeks with or without RD treatment. Increased urinary norepinephrine (NE), 8-OHdG, and angiotensinogen levels and elevated serum asymmetric dimethyl arginine levels were observed in the CIH model. Concomitant with these changes, blood pressure levels were significantly elevated by CIH treatment. However, these deleterious effects by CIH were completely blocked by RD treatment. The present study demonstrated that CIH-mediated renal sympathetic nerve activation is involved in increased systemic oxidative stress, endothelial dysfunction, and renin-angiotensin system activation, thereby contributing to the development of HT and CVD, thus could be an important therapeutic target in patients with SAS.

The renin-angiotensin system in cardiovascular autonomic control: recent developments and clinical implications

Complex and bidirectional interactions between the renin-angiotensin system (RAS) and autonomic nervous system have been well established for cardiovascular regulation under both physiological and pathophysiological conditions. Most research to date has focused on deleterious effects of components of the vasoconstrictor arm of the RAS on cardiovascular autonomic control, such as renin, angiotensin II, and aldosterone. The recent discovery of prorenin and the prorenin receptor have further increased our understanding of RAS interactions in autonomic brain regions. Therapies targeting these RAS components, such as angiotensin-converting enzyme (ACE) inhibitors and angiotensin receptor blockers, are commonly used for treatment of hypertension and cardiovascular diseases, with blood pressure-lowering effects attributed in part to sympathetic inhibition and parasympathetic facilitation. In addition, a vasodilatory arm of the RAS has emerged that includes angiotensin-(1-7), ACE2, and alamandine, and promotes beneficial effects on blood pressure in part by reducing sympathetic activity and improving arterial baroreceptor reflex function in animal models. The role of the vasodilatory arm of the RAS in cardiovascular autonomic regulation in clinical populations, however, has yet to be determined. This review will summarize recent developments in autonomic mechanisms involved in the effects of the RAS on cardiovascular regulation, with a focus on newly discovered pathways and therapeutic targets for this hormone system.

Relationship between obstructive sleep apnoea syndrome and essential hypertension: a dose-response meta-analysis

OBJECTIVE

The objective of this study was to summarize the evidence regarding the relationship between obstructive sleep apnoea syndrome (OSAS) and the risk of essential hypertension.

METHODS

The study was a dose-response meta-analysis of observational studies. The PubMed, Embase, CNKI, VIP and CBM databases were searched to collect relative studies examining the relationship between OSAS and the risk of essential hypertension. Studies were retrieved from database establishment through September 2016, and new literature published between September 2016 and May 2017 was later supplemented. Linear and non-linear dose-response models were used to assess the relationship between apnoea-hypopnea index (AHI), which was used to reflect the severity of OSAS, and the risk of essential hypertension. Stata 13.0 was used for the meta-analysis.

RESULTS

Six prospective cohort studies and one case-control study were included, for a total sample size of 6098. The dose-response meta-analysis showed that a high AHI significantly increased the risk of essential hypertension compared with a low AHI (odds ratio (OR) = 1.77, 95% confidence interval (CI) (1.30, 2.41), p = 0.001). The linear dose-response meta-analysis showed that the risk of essential hypertension increased by 17% for every 10 events/h increase in the AHI (OR = 1.17, 95% CI (1.07, 1.27), p = 0.001), and the results of the non-linear dose-response meta-analysis showed that the risk of essential hypertension increased with increasing AHI value.

CONCLUSION

A potential dose-response relationship exists between the severity of OSAS and the risk of essential hypertension. This relationship should be considered when developing prevention measures for essential hypertension.

Association between echocardiographic structural parameters and body weight in Wistar rats

BACKGROUND

The association between echocardiographic structural parameters and body weight (BW) during rat development has been poorly addressed. We evaluated echocardiographic variables: left ventricular (LV) end-diastolic (LVDD) and end-systolic (LVSD) diameters, LV diastolic posterior wall thickness (PWT), left atrial diameter (LA), and aortic diameter (AO) in function of BW during development.Results/Materials and Methods: Male Wistar rats (n = 328, BW: 302-702 g) were retrospectively used to construct regression models and 95% confidence intervals relating to cardiac structural parameters and BW. Adjusted indexes were significant to all relationships; the regression model for predicting LVDD (R2 = 0.678; p < 0.001) and AO (R2 = 0.567; p < 0.001) had the highest prediction coefficients and LA function the lowest prediction coefficient (R2 = 0.274; p < 0.01). These relationships underwent validation by performing echocardiograms on additional rats (n = 43, BW: 300-600 g) and testing whether results were within confidence intervals of our regressions. Prediction models for AO and LA correctly allocated 38 (88.4%) and 39 rats (90.7%), respectively, within the 95% confidence intervals. Regression models for LVDD, LVSD, and PWT included 27 (62.7%), 30 (69.8%), and 19 (44.2%) animals, respectively, within the 95% confidence intervals.

CONCLUSIONS

Increase in cardiac structures is associated with BW gain during rat growth. LA and AO can be correctly predicted using regression models; prediction of PWT and LV diameters is not accurate.

A promoter polymorphism in APJ gene is significantly associated with blood pressure changes and hypertension risk in Chinese women

The aim of this study was to interrogate the gender-specific association of 5 well-defined polymorphisms in apelin/APJ system with both blood pressure changes and hypertension risk in a northeastern Chinese population. This is a population-based case-control study, including 650 hypertensive patients and 645 normotensive controls. Data were analyzed by STATA and Haplo.Stats. The genotype distributions of 5 study polymorphisms were in Hardy-Weinberg equilibrium in both genders. The rs7119375 and rs10501367 were completely linked. The genotypes (P = 0.001) and alleles (P < 0.001) of rs7119375 differed significantly between patients and controls in women. Carriers of rs7119375-AA genotype had significant higher systolic blood pressure (SBP) than carriers of rs7119375-GG genotype in both patients and controls of female gender (P < 0.01). Moreover, carriers of rs7119375-A allele were 1.80 times more likely to develop hypertension relative to carriers of rs7119375-GG genotype after adjusting for age, body mass index and glucose (odds ratio: 1.80; 95% confidence interval: 1.03–3.16; P = 0.040). Further allele combination analysis supported the leading contribution of rs7119375 to hypertension risk. Our findings demonstrated that the mutation of promoter polymorphism rs7119375 in APJ gene was significantly associated with elevated SBP and increased hypertension risk in Chinese women.