Blockade of Endogenous Angiotensin-(1-7) in Hypothalamic Paraventricular Nucleus Attenuates High Salt-Induced Sympathoexcitation and Hypertension.

Angiotensin (Ang)-(1-7) is an important biologically-active peptide of the renin-angiotensin system. This study was designed to determine whether inhibition of Ang-(1-7) in the hypothalamic paraventricular nucleus (PVN) attenuates sympathetic activity and elevates blood pressure by modulating pro-inflammatory cytokines (PICs) and oxidative stress in the PVN in salt-induced hypertension. Rats were fed either a high-salt (8% NaCl) or a normal salt diet (0.3% NaCl) for 10 weeks, followed by bilateral microinjections of the Ang-(1-7) antagonist A-779 or vehicle into the PVN. We found that the mean arterial pressure (MAP), renal sympathetic nerve activity (RSNA), and plasma norepinephrine (NE) were significantly increased in salt-induced hypertensive rats. The high-salt diet also resulted in higher levels of the PICs interleukin-6, interleukin-1beta, tumor necrosis factor alpha, and monocyte chemotactic protein-1, as well as higher gp91phox expression and superoxide production in the PVN. Microinjection of A-779 (3 nmol/50 nL) into the bilateral PVN of hypertensive rats not only attenuated MAP, RSNA, and NE, but also decreased the PICs and oxidative stress in the PVN. These results suggest that the increased MAP and sympathetic activity in salt-induced hypertension can be suppressed by blockade of endogenous Ang-(1-7) in the PVN, through modulation of PICs and oxidative stress.

Alpha lipoic acid supplementation attenuates reactive oxygen species in hypothalamic paraventricular nucleus and sympathoexcitation in high salt-induced hypertension.

AIMS: High salt-induced oxidative stress plays an important role in the development of hypertension. Alpha lipoic acid (ALA) is extensively recognized as having a powerful superoxide inhibitory property. In this study, we determined whether ALA supplementation attenuates oxidative stress in hypothalamic paraventricular nucleus (PVN), decreases the sympathetic activity and arterial pressure in high salt-induced hypertension by cross-talking with renin-angiotensin system (RAS) and pro-inflammatory cytokines (PICs). METHODS: Male Wistar rats were administered a normal-salt diet (NS, 0.3% NaCl) or a high-salt diet (HS, 8.0% NaCl) for 8 weeks. These rats received ALA (60mg/kg) dissolved in vehicle (0.9% saline) or an equal voleme of vehicle, by gastric perfusion for 9 weeks. RESULTS: High salt intake resulted in higher renal sympathetic nerve activity (RSNA) and mean arterial pressure (MAP). These rats also had higher levels of superoxide, gp91(phox), gp47(phox) (subunits of NAD(P)H oxidase), angiotensin-converting enzyme (ACE), angiotensin II type1 receptor (AT1-R), interleukin-1beta (IL-1ß), interleukin-6 (IL-6), and lower levels of interleukin-10 (IL-10) and copper/zinc superoxide dismutase (Cu/Zn-SOD) than control animals. Treatment with ALA significantly attenuated the levels of superoxide, gp91(phox), gp47(phox), ACE, AT1-R, IL-1ß and IL-6, increased the levels of IL-10 and Cu/Zn-SOD, and decreased MAP and RSNA compared with high-salt induced hypertensive rats. The mRNA expression of gp47(phox) and gp91(phox) are in accordance with their protein expression. CONCLUSION: These findings suggest that supplementation of ALA obviously decreases the sympathetic activity and arterial pressure in high salt-induced hypertension by improving the superoxide inhibitory property, suppressing the activation of RAS and restoring the balance between pro- and anti-inflammatory cytokines in the PVN.

Salusin ß Within the Nucleus Tractus Solitarii Suppresses Blood Pressure Via Inhibiting the Activities of Presympathetic Neurons in the Rostral Ventrolateral Medulla in Spontaneously Hypertensive Rats.

Salusin ß is a newly identified bioactive peptide, which shows peripheral hypotensive, mitogenic and proatherosclerotic effects. The present study was undertaken to investigate the role of salusin ß within the nucleus tractus solitarii (NTS) and the underlying mechanism in regulating blood pressure and heart rate (HR) in spontaneously hypertensive rats (SHR). Our results showed that bilateral or unilateral microinjection of salusin ß (0.4-40 pmol) into the NTS in SHR decreased mean arterial pressure and HR in a dose-dependent manner. Bilateral microinjection of salusin ß (4 pmol) within NTS improved baroreflex sensitivity functions in SHR. Pretreatment with glutamate receptors antagonist kynurenic acid (5 nmol) into the NTS in SHR did not alter the salusin ß (4 pmol) induced hypotension and bradycardia. Likewise, bilateral vagotomy also did not alter the salusin ß (4 pmol) induced hypotension and bradycardia. However, pretreatment with GABAA receptors agonist muscimol (100 pmol) within the rostral ventrolateral medulla (RVLM) in SHR almost completely abolished the hypotension and bradycardia evoked by intra-NTS salusin ß (4 pmol). Our findings suggested that microinjection of salusin ß into the NTS produced hypotension and bradycardia, as well as improved baroreflex sensitivity functions, via inhibiting the activities of presympathetic neurons in the RVLM in SHR.

Central blockade of salusin ß attenuates hypertension and hypothalamic inflammation in spontaneously hypertensive rats.

Salusin ß is a multifunctional bioactive peptide and is considered as a promising candidate biomarker for predicting atherosclerotic cardiovascular diseases. The present study was designed to investigate the roles and mechanisms of salusin ß in the paraventricular nucleus (PVN) in attenuating hypertension and hypothalamic inflammation and whether central salusin ß blockade has protective effects in essential hypertension. Normotensive Wistar-Kyoto (WKY) rats and spontaneously hypertensive rats (SHR) were used in this study. The rats were chronic PVN infusion either specific salusin ß blocker, antisalusin ß IgG (SIgG), or control IgG (CIgG) for 2 weeks. Hypertensive rats had significantly increased salusin ß expression compared with normotensive rats. Central blockade of salusin ß attenuated hypertension, reduced circulating norepinephrine (NE) levels, and improved cardiac hypertrophy and function in hypertensive rats. Salusin ß blockade significantly reduced proinflammatory cytokines (PICs), nuclear factor-kappa B (NF-κB) activity, reactive oxygen species (ROS) levels, and altered renin-angiotensin system (RAS) components in the PVN of hypertensive rats. These findings suggest that the beneficial effects of salusin ß blockade in essential hypertension are possibly due to down-regulate of inflammatory molecules and ROS in the PVN.

Blockade of Salusin-ß in Hypothalamic Paraventricular Nucleus Attenuates Hypertension and Cardiac Hypertrophy in Salt-induced Hypertensive Rats.

Salusin-ß, a multifunctional bioactive peptide, is considered as a promising candidate biomarker for predicting cardiovascular diseases. This study was designed to determine whether inhibition of salusin-ß in the hypothalamic paraventricular nucleus (PVN) delays the progression of hypertension and attenuates cardiac hypertrophy by restoring neurotransmitters and cytokines. Male Sprague Dawley rats were fed with a normal salt diet (NS, 0.3%) or a high salt diet (HS, 8%) for 8 weeks to induce hypertension. Then, these rats received bilateral PVN infusion of a specific salusin-ß blocker, antisalusin-ß IgG (SIgG), or control IgG (CIgG) for 2 weeks. HS rats exhibited higher mean arterial pressure and cardiac hypertrophy as indicated by increased whole heart weight/bodyweight ratio, whole heart weight/tibia length ratio, left ventricular weight/tibia length ratio, and messenger RNA levels of cardiac atrial natriuretic peptide (ANP), and ß-myosin heavy chain. Compared with NS rats, HS rats had higher levels of glutamate, norepinephrine, tyrosine hydroxylase, proinflammatory cytokines, and lower levels of gamma-aminobutyric acid, interleukin 10, and the 67-kDa isoform of glutamate decarboxylase (GAD67) in the PVN, and higher plasma levels of proinflammatory cytokines. Chronic PVN infusion of SIgG attenuated all these changes in HS rats. Our findings suggest that HS rats have an imbalance between excitatory and inhibitory neurotransmitters, as well as an imbalance between proinflammatory and anti-inflammatory cytokines in the PVN; and chronic inhibition of salusin-ß in the PVN restores neurotransmitters and cytokines in the PVN, thereby attenuating hypertensive responses and cardiac hypertrophy.

Endogenous hydrogen peroxide in the hypothalamic paraventricular nucleus regulates neurohormonal excitation in high salt-induced hypertension.

Reactive oxygen species (ROS) in the brain plays an important role in the progression of hypertension and hydrogen peroxide (H2O2) is a major component of ROS. The aim of this study is to explore whether endogenous H2O2 changed by polyethylene glycol-catalase (PEG-CAT) and aminotriazole (ATZ) in the hypothalamic paraventricular nucleus (PVN) regulates neurotransmitters, renin-angiotensin system (RAS), and cytokines, and whether subsequently affects the renal sympathetic nerve activity (RSNA) and mean arterial pressure (MAP) in high salt-induced hypertension. Male Sprague-Dawley rats received a high-salt diet (HS, 8% NaCl) or a normal-salt diet (NS, 0.3% NaCl) for 10 weeks. Then rats were treated with bilateral PVN microinjection of PEG-CAT (0.2 i.u./50nl), an analog of endogenous catalase, the catalase inhibitor ATZ (10nmol/50nl) or vehicle. High salt-fed rats had significantly increased MAP, RSNA, plasma norepinephrine (NE) and pro-inflammatory cytokines (PICs). In addition, rats with high-salt diet had higher levels of NOX-2, NOX-4 (subunits of NAD(P)H oxidase), angiotensin-converting enzyme (ACE), interleukin-1beta (IL-1ß), glutamate and NE, and lower levels of gamma-aminobutyric acid (GABA) and interleukin-10 (IL-10) in the PVN than normal diet rats. Bilateral PVN microinjection of PEG-CAT attenuated the levels of RAS and restored the balance of neurotransmitters and cytokines, while microinjection of ATZ into the PVN augmented those changes occurring in hypertensive rats. Our findings demonstrate that ROS component H2O2 in the PVN regulating MAP and RSNA are partly due to modulate neurotransmitters, renin-angiotensin system, and cytokines within the PVN in salt-induced hypertension.

Chronic infusion of lisinopril into hypothalamic paraventricular nucleus modulates cytokines and attenuates oxidative stress in rostral ventrolateral medulla in hypertension.

The hypothalamic paraventricular nucleus (PVN) and rostral ventrolateral medulla (RVLM) play a critical role in the generation and maintenance of sympathetic nerve activity. The renin-angiotensin system (RAS) in the brain is involved in the pathogenesis of hypertension. This study was designed to determine whether inhibition of the angiotensin-converting enzyme (ACE) in the PVN modulates cytokines and attenuates oxidative stress (ROS) in the RVLM, and decreases the blood pressure and sympathetic activity in renovascular hypertensive rats. Renovascular hypertension was induced in male Sprague-Dawley rats by the two-kidney one-clip (2K1C) method. Renovascular hypertensive rats received bilateral PVN infusion with ACE inhibitor lisinopril (LSP, 10µg/h) or vehicle via osmotic minipump for 4weeks. Mean arterial pressure (MAP), renal sympathetic nerve activity (RSNA), and plasma proinflammatory cytokines (PICs) were significantly increased in renovascular hypertensive rats. The renovascular hypertensive rats also had higher levels of ACE in the PVN, and lower level of interleukin-10 (IL-10) in the RVLM. In addition, the levels of PICs, the chemokine MCP-1, the subunit of NAD(P)H oxidase (gp91(phox)) and ROS in the RVLM were increased in hypertensive rats. PVN treatment with LSP attenuated those changes occurring in renovascular hypertensive rats. Our findings suggest that the beneficial effects of ACE inhibition in the PVN in renovascular hypertension are partly due to modulation cytokines and attenuation oxidative stress in the RVLM.

Inhibition of reactive oxygen species in hypothalamic paraventricular nucleus attenuates the renin-angiotensin system and proinflammatory cytokines in hypertension.

AIMS: To explore whether reactive oxygen species (ROS) scavenger (tempol) in the hypothalamic paraventricular nucleus (PVN) attenuates renin-angiotensin system (RAS) and proinflammatory cytokines (PICs), and decreases the blood pressure and sympathetic activity in angiotensin II (ANG II)-induced hypertension. METHODS AND RESULTS: Male Sprague-Dawley rats were infused intravenously with ANG II (10 ng/kg per min) or normal saline (NS) for 4 weeks. These rats were treated with bilateral PVN infusion of oxygen free radical scavenger tempol (TEMP, 20 µg/h) or vehicle (artificial cerebrospinal fluid, aCSF) for 4 weeks. ANG II infusion resulted in increased mean arterial pressure (MAP) and renal sympathetic nerve activity (RSNA). These ANG II-infused rats also had higher levels of gp91(phox) (a subunit of NAD(P)H oxidase), angiotensin-converting enzyme (ACE), and interleukin-1 beta (IL-1ß) in the PVN than the control animals. Treatment with PVN infusion of TEMP attenuated the overexpression of gp91(phox), ACE and IL-1ß within the PVN, and decreased sympathetic activity and MAP in ANG II-infused rats. CONCLUSION: These findings suggest that ANG II infusion induces elevated PICs and oxidative stress in the PVN, which contribute to the sympathoexcitation in hypertension. Inhibition of reactive oxygen species in hypothalamic paraventricular nucleus attenuates the renin-angiotensin system, proinflammatory cytokines and oxidative stress in ANG II-induced hypertension.