Angiotensin-(1-7) in Paraventricular Nucleus Contributes to the Enhanced Cardiac Sympathetic Afferent Reflex and Sympathetic Activity in Chronic Heart Failure Rats

Background/Aims: Cardiac sympathetic afferent reflex (CSAR) enhancement contributes to exaggerated sympathetic activation in chronic heart failure (CHF). The current study aimed to investigate the roles of angiotensin (Ang)-(1-7) in CSAR modulation and sympathetic activation and Ang-(1-7) signaling pathway in paraventricular nucleus of CHF rats. Methods: CHF was induced by coronary artery ligation. Responses of renal sympathetic nerve activity (RSNA) and mean arterial pressure (MAP) to epicardial application of capsaicin were used to evaluate CSAR in rats with anesthesia. Results: Ang-(1-7) increased RSNA, MAP, CSAR activity, cAMP level, NAD(P)H oxidase activity and superoxide anion level more significantly in CHF than in sham-operated rats, while Mas receptor antagonist A-779 had the opposite effects. Moreover, Ang-(1-7) augmented effects of Ang II in CHF rats. The effects of Ang-(1-7) were blocked by A-779, adenylyl cyclase inhibitor SQ22536, protein kinase A inhibitor Rp-cAMP, superoxide anion scavenger tempol and NAD(P)H oxidase inhibitor apocynin. Mas and AT1 receptor protein expressions, Ang-(1-7) and Ang II levels in CHF increased. Conclusions: These results indicate that Ang-(1-7) in paraventricular nucleus enhances CSAR and sympathetic output not only by exerting its own effects but also by augmenting the effects of Ang II through Mas receptor in CHF. Endogenous Ang-(1-7)/Mas receptor activity contributes to CSAR enhancement and sympathetic activation in CHF, and NAD(P)H oxidase-derived superoxide anions and the cAMP-PKA signaling pathway are involved in mediating the effects of Ang-(1-7) in CHF.

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Abstract 15532: Altered Ubiquitination and Stability of Protein Inhibitor of Neuronal Nitric Oxide Synthase in the Paraventricular Nucleus of Chronic Heart Failure Rats: Role of Angiotensin II

Circulation ◽

10.1161/circ.130.suppl_2.15532 ◽

2014 ◽

Vol 130 (suppl_2) ◽

Author(s):

Neeru Sharma ◽

Xuefei Liu ◽

Hong Zheng ◽

Kaushik Patel

Keyword(s):

Nitric Oxide ◽

Heart Failure ◽

Angiotensin Ii ◽

Chronic Heart Failure ◽

Paraventricular Nucleus ◽

Neuronal Nitric Oxide Synthase ◽

Ang Ii ◽

Protein Inhibitor ◽

Ubiquitin Proteasome ◽

Oxide Synthase

Introduction and Hypothesis: Expression of neuronal nitric oxide synthase (nNOS) is decreased in the paraventricular nucleus (PVN) of rats with chronic heart failure (CHF), however the underlying molecular mechanism/s remain unclear. Recently, we demonstrated, Angiotensin II (Ang II) mediated increase in PIN: protein inhibitor of nNOS (0.76±0.10 Sham vs 1.12±0.09* CHF) which is known to down-regulate nNOS through disruption of active dimers (~60% decrease in dimer/monomer ratio) in the PVN of rats with CHF. Functionally impeded monomeric enzyme is degraded by ubiquitin proteasome system. Interestingly, PIN transcript levels remain unchanged in the PVN in CHF (1.00±0.23 Sham vs. 1.1±0.28 CHF). This observation prompted us to elucidate the molecular mechanism for the accumulation of PIN post-transcriptionally in the PVN in CHF Methods and Results: We used coronary artery ligation model of CHF in rats (6-8 weeks past ligation) and neuronal NG108-15 hybrid cell line. PIN translation was inhibited using cyclohexamide (CHX) for 0-4h after 20h of pretreatment with Ang II in NG108 cells. CHX mediated decrease in PIN expression was ameliorated with Ang II (0.19±0.04 vs 0.41±0.06* 4h). Proteasome inhibitor lactacystin (LC) treatment dramatically elevates PIN level suggesting the involvement of proteasome system in PIN regulation. Immunoprecipitation with ubiquitin antibody showed decrease PIN-Ub conjugates in Ang II-treated cells (1.04 ± 0.05 LC vs. 0.62 ± 0.07* LC AngII). In vitro ubiquitination assay in cells transfected with pCMV-(HA-Ub)8 vector revealed reduction of HA-Ub-PIN conjugates after Ang II treatment (9.2 ± 2.2 LC vs. 4.5 ± 0.6* LC Ang II). Furthermore, there was decreased accumulation of PIN-Ub conjugates in the PVN of CHF rats compared to Sham as revealed by immunohistochemistry. Conclusions: Taken together, our studies revealed that PIN is targeted for rapid degradation by the ubiquitin-proteasome pathway and Ang II delays the rate of degradation resulting in accumulation of PIN. We conclude that post-translational accumulation of PIN, mediated by Ang II, leads to a decrease in the dimeric active form of nNOS as well as protein levels of nNOS, which may lead to reduced nitric oxide resulting in over-activation of sympathetic drive during CHF.

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ANG II in the paraventricular nucleus potentiates the cardiac sympathetic afferent reflex in rats with heart failure

Journal of Applied Physiology ◽

10.1152/japplphysiol.00573.2004 ◽

2004 ◽

Vol 97 (5) ◽

pp. 1746-1754 ◽

Cited By ~ 67

Author(s):

Guo-Qing Zhu ◽

Lie Gao ◽

Kuashik P. Patel ◽

Irving H. Zucker ◽

Wei Wang

Keyword(s):

Heart Failure ◽

Electrical Stimulation ◽

Paraventricular Nucleus ◽

Sham Group ◽

Ang Ii ◽

Renal Sympathetic Nerve Activity ◽

Afferent Nerves ◽

Coronary Ligation ◽

Cardiac Sympathetic Afferent Reflex ◽

Renal Sympathetic

Chronic heart failure (CHF) is characterized by sympathoexcitation, and the cardiac sympathetic afferent reflex (CSAR) is a sympathoexcitatory reflex. Our previous studies have shown that the CSAR was enhanced in CHF. In addition, central angiotensin II (ANG II) is an important modulator of this reflex. This study was performed to determine whether the CSAR evoked by stimulation of cardiac sympathetic afferent nerves (CSAN) in rats with coronary ligation-induced CHF is enhanced by ANG II in the paraventricular nucleus (PVN). Under α-chloralose and urethane anesthesia, renal sympathetic nerve activity (RSNA) was recorded. The RSNA responses to electrical stimulation (5, 10, 20, and 30 Hz) of the CSAN were evaluated. Bilateral microinjection of the AT1-receptor antagonist losartan (50 nmol) into the PVN had no significant effects in the sham group, but it abolished the enhanced RSNA response to stimulation in the CHF group. Unilateral microinjection of three doses of ANG II (0.03, 0.3, and 3 nmol) into the PVN resulted in dose-related increases in the RSNA responses to stimulation. Although ANG II also potentiated the RSNA response to electrical stimulation in sham rats, the RSNA responses to stimulation after ANG II into the PVN in rats with CHF were much greater than in sham rats. The effects of ANG II were prevented by pretreatment with losartan into the PVN in CHF rats. These results suggest that the central gain of the CSAR is enhanced in rats with coronary ligation-induced CHF and that ANG II in the PVN augments the CSAR evoked by CSAN, which is mediated by the central angiotensin AT1 receptors in rats with CHF.

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AT1 receptor mRNA antisense normalizes enhanced cardiac sympathetic afferent reflex in rats with chronic heart failure

AJP Heart and Circulatory Physiology ◽

10.1152/ajpheart.01245.2003 ◽

2004 ◽

Vol 287 (4) ◽

pp. H1828-H1835 ◽

Cited By ~ 68

Author(s):

Guo-Qing Zhu ◽

Lie Gao ◽

Yifan Li ◽

Kaushik P. Patel ◽

Irving H. Zucker ◽

...

Keyword(s):

Heart Failure ◽

Chronic Heart Failure ◽

Paraventricular Nucleus ◽

Genetic Manipulation ◽

Intracerebroventricular Administration ◽

Renal Sympathetic Nerve Activity ◽

Protein Levels ◽

Coronary Ligation ◽

Cardiac Sympathetic Afferent Reflex

Previous studies showed that the cardiac sympathetic afferent reflex (CSAR) is enhanced in dogs and rats with chronic heart failure (CHF) and that central ANG II type 1 receptors (AT1R) are involved in this augmented reflex. The aim of this study was to determine whether intracerebroventricular administration and microinjection of antisense oligodeoxynucleotides targeted to AT1R mRNA would attenuate the enhanced CSAR and decrease resting renal sympathetic nerve activity (RSNA) in rats with coronary ligation-induced CHF. The CSAR was elicited by application of bradykinin to the epicardial surface of the left ventricle. Reflex responses to epicardial administration of bradykinin were enhanced in rats with CHF. The response to bradykinin was determined every 50 min after intracerebroventricular administration (lateral ventricle) or microinjection (into paraventricular nucleus) of antisense or scrambled oligonucleotides to AT1R mRNA. AT1R mRNA and protein levels in the paraventricular nucleus were significantly reduced 5 h after administration of antisense. Antisense significantly decreased resting RSNA and normalized the enhanced CSAR responses to bradykinin in rats with CHF. Scrambled oligonucleotides did not alter resting RSNA or the enhanced responses to bradykinin in rats with CHF. No significant effects were found in sham-operated rats after administration of either antisense or scrambled oligonucleotides. These results strongly suggest that central AT1R mRNA antisense reduces expression of AT1R protein and normalizes the augmentation of this excitatory sympathetic reflex and that genetic manipulation of protein expression can be used to normalize the sympathetic enhancement in CHF.

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Exercise training normalizes enhanced sympathetic activation from the paraventricular nucleus in chronic heart failure: role of angiotensin II

AJP Regulatory Integrative and Comparative Physiology ◽

10.1152/ajpregu.00046.2012 ◽

2012 ◽

Vol 303 (4) ◽

pp. R387-R394 ◽

Cited By ~ 31

Author(s):

Hong Zheng ◽

Neeru M. Sharma ◽

Xuefei Liu ◽

Kaushik P. Patel

Keyword(s):

Heart Failure ◽

Exercise Training ◽

Protein Expression ◽

Paraventricular Nucleus ◽

Treadmill Running ◽

Receptor Protein ◽

Coronary Artery Ligation ◽

Sympathetic Outflow ◽

Ang Ii ◽

Ext Groups

Exercise training (ExT) normalizes the increased sympathetic outflow in heart failure (HF), but the underlying mechanisms are not known. We hypothesized ExT would normalize the augmented activation of the paraventricular nucleus (PVN) via an angiotensinergic mechanism during HF. Four groups of rats used were the following: 1) sham-sedentary (Sed); 2) sham-ExT; 3) HF-Sed, and 4) HF-ExT. HF was induced by left coronary artery ligation. Four weeks after surgery, 3 wk of treadmill running was performed in ExT groups. The number of FosB-positive cells in the PVN was significantly increased in HF-Sed group compared with the sham-Sed group. ExT normalized (negated) this increase in the rats with HF. In anesthetized condition, the increases in renal sympathetic nerve activity (RSNA), mean arterial pressure (MAP), and heart rate (HR) in response to microinjection of angiotensin (ANG) II (50∼200 pmol) in the PVN of HF-Sed group were significantly greater than of the sham-Sed group. In the HF-ExT group the responses to microinjection of ANG II were not different from sham-Sed or sham-ExT groups. Blockade of ANG II type 1 (AT1) receptors with losartan in the PVN produced a significantly greater decrease in RSNA, MAP, and HR in HF-Sed group compared with sham-Sed group. ExT prevented the difference between HF and sham groups. AT1 receptor protein expression was increased 50% in HF-Sed group compared with sham-Sed group. In the HF-ExT group, AT1 receptor protein expression was not significantly different from sham-Sed or sham-ExT groups. In conclusion, one mechanism by which ExT alleviates elevated sympathetic outflow in HF may be through normalization of angiotensinergic mechanisms within the PVN.

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Superoxide anions in the paraventricular nucleus mediate the enhanced cardiac sympathetic afferent reflex and sympathetic activity in renovascular hypertensive rats

Journal of Applied Physiology ◽

10.1152/japplphysiol.00908.2010 ◽

2011 ◽

Vol 110 (3) ◽

pp. 646-652 ◽

Cited By ~ 39

Author(s):

Ying Han ◽

Zhi-Dan Fan ◽

Ning Yuan ◽

Gui-Qin Xie ◽

Juan Gao ◽

...

Keyword(s):

Renovascular Hypertension ◽

Paraventricular Nucleus ◽

Superoxide Anion ◽

Sympathetic Activity ◽

Oxidase Inhibitor ◽

Ang Ii ◽

Superoxide Anions ◽

Diethyldithiocarbamic Acid ◽

Cardiac Sympathetic Afferent Reflex

An enhanced cardiac sympathetic afferent reflex (CSAR) is involved in the sympathetic activation in renovascular hypertension. The present study was designed to determine the role of superoxide anions in the paraventricular nucleus (PVN) in mediating the enhanced CSAR and sympathetic activity in renovascular hypertension in the two-kidney, one-clip (2K1C) model. Sinoaortic denervation and vagotomy were carried out, and renal sympathetic nerve activity (RSNA) and mean arterial pressure (MAP) were recorded under anesthesia. The CSAR was evaluated by the response of RSNA to the epicardial application of capsaicin. Superoxide anion levels and NAD(P)H oxidase activity in the PVN increased in 2K1C rats and were much higher in 2K1C rats than in sham-operated (sham) rats after the epicardial application of capsaicin or PVN microinjection of ANG II. In both 2K1C and sham rats, PVN microinjection of the superoxide anion scavenger tempol or the NAD(P)H oxidase inhibitor apocynin abolished the CSAR, whereas the SOD inhibitor diethyldithiocarbamic acid (DETC) potentiated the CSAR. Tempol and apocynin decreased but DETC increased baseline RSNA and MAP. ANG II in the PVN caused larger responses of the CSAR, baseline RSNA, and baseline MAP in 2K1C rats than in sham rats. The effects of ANG II were abolished by pretreatment with tempol or apocynin in both 2K1C and sham rats and augmented by DETC in the PVN in 2K1C rats. These results indicate that superoxide anions in the PVN mediate the CSAR and the effects of ANG II in the PVN. Increased superoxide anions in the PVN contribute to the enhanced CSAR and sympathetic activity in renovascular hypertension.

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