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European Journal of Heart Failure 2007 9(10):967-973; doi:10.1016/j.ejheart.2007.07.004
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© 2007 European Society of Cardiology

Reactive oxygen species in the paraventricular nucleus mediate the cardiac sympathetic afferent reflex in chronic heart failure rats

Ying Hana, Zhen Shia, Feng Zhanga, Yang Yua, Ming-Kui Zhonga, Xing-Ya Gaoa, Wei Wanga,b and Guo-Qing Zhua,*

a Department of Physiology, Nanjing Medical University Nanjing 210029, China
b Department of Cellular and Integrative Physiology, University of Nebraska College of Medicine Omaha, Nebraska 68198-5850, United States

* Corresponding author. Tel./fax: +86 25 86862885. E-mail address: gqzhucn{at}njmu.edu.cn (G.-Q. Zhu).


   Abstract
Top
 Abstract
1. Introduction
 2. Methods
 3. Results
 4. Discussion
 Acknowledgment
 References
 
The aim of this study was to determine whether reactive oxygen species (ROS) in the paraventricular nucleus (PVN) mediate both the cardiac sympathetic afferent reflex (CSAR) and angiotensin II-induced CSAR enhancement in chronic heart failure (CHF) rats. CSAR was evaluated from the responses of renal sympathetic nerve activity (RSNA) to epicardial application of bradykinin. In both CHF and sham-operated rats, PVN microinjection of the superoxide anion scavengers tempol or tiron almost abolished the CSAR, but the superoxide dismutase inhibitor DETC potentiated the CSAR. PVN pretreatment with tempol or tiron abolished, whereas DETC augmented, the angiotensin II-induced CSAR enhancement. In CHF rats, superoxide anion and malondialdehyde (MDA) levels in the PVN were increased, but were normalized by the AT1 receptor antagonist losartan. PVN microinjection of tempol decreased superoxide anion and MDA levels, but epicardial application of bradykinin or PVN microinjection of angiotensin II increased superoxide anion and MDA to higher levels in CHF rats than in sham-operated rats. These results indicate that ROS in the PVN mediates the CSAR and the effect of angiotensin II in the PVN on the CSAR in both CHF and sham-operated rats. Increased ROS in the PVN are involved in the enhanced CSAR in CHF.

Key Words: Reactive oxygen species • Angiotensin • Paraventricular nucleus • Cardiac sympathetic afferent reflex • sympathetic activity

Received February 13, 2007; Revised May 28, 2007; Accepted July 11, 2007


   1. Introduction
Top
 Abstract
 1. Introduction
2. Methods
 3. Results
 4. Discussion
 Acknowledgment
 References
 
It is well known that sympathetic activity is enhanced in chronic heart failure (CHF). This enhanced sympathetic activity contributes to further haemodynamic deterioration and the degree of sympathoexcitation is prognostic for survival in this disease [1,2]. In CHF, the cardiac sympathetic afferent reflex (CSAR) is over-activated and contributes to the increases in sympathetic outflow [3-5]. Inhibition of this enhanced CSAR to reduce the over-excitation of the sympathetic nervous system may be beneficial in CHF.

The paraventricular nucleus (PVN) is an important integrative centre for the control of cardiovascular activity and sympathetic outflow. In a previous study we reported that Ang II and AT1 receptors in the PVN play an important role in the central modulation of CSAR, and contribute to the pathogenesis of enhanced CSAR in CHF [5-10]. Furthermore, microinjection of the GABAA receptor agonist muscimol into the PVN has been shown to attenuate the CSAR induced by epicardial application of bradykinin (BK) [11]. Another study reported an increase in c-Fos immunoreactive cells in the PVN after epicardial application of BK in cats [12].

It has been reported that reactive oxygen species (ROS) are novel molecules involved in the intracellular signalling mechanisms of Ang II in the brain [13,14]. We found that NAD(P)H oxidase-derived ROS in the PVN modulated the CSAR and contributed to the effect of Ang II in the PVN on the CSAR in normal rats [6,7]. The present study was designed to investigate whether ROS in the PVN is involved in the pathogenesis of enhanced CSAR in CHF rats, and whether ROS in the PVN mediates the Ang II-induced CSAR enhancement in CHF rats.


   2. Methods
Top
 Abstract
 1. Introduction
 2. Methods
3. Results
 4. Discussion
 Acknowledgment
 References
 
Experiments were carried out on 228 male Sprague-Dawley rats weighing between 300 and 400 g. The procedures were approved by the Experimental Animal Care and Use Committee of Nanjing Medical University and complied with the Guide for the Care and Use of Laboratory Animals (NIH Publication No. 85-23, revised 1985).

2.1. CHF model
CHF was induced by coronary artery ligation as previously described [15]. Briefly, all rats were anesthetized with phenobarbital (50 mg/kg, i.p.) and instrumented using sterile techniques. The left coronary artery was ligated near its branch point from the aorta. The sham-operated rats underwent the same operative procedure, but their coronary arteries were not ligated. Laboratory chow and tap water were available ad libitum. Mortality was about 30% in the rats with coronary ligation, and death occurred primarily during the first day after ligation.

The final experiment was carried out 6-8 weeks after coronary ligation or sham surgery. The criteria for CHF were an elevated left ventricular end-diastolic pressure (LVEDP, >13 mm Hg), and a 40% decrease in maximum of the first differentiation of left ventricular pressure (+dp/dtmax).

2.2. Acute experimental procedure
Each rat was anesthetized with urethane (800 mg/kg, ip) and {alpha}-chloralose (40 mg/kg, ip). Supplemental anesthesia was administered at 1/10 of the initial dose per hour. The trachea and right carotid artery were cannulated for mechanical ventilation and measurement of arterial pressure respectively. Baroreceptor denervation and vagotomy were carried out and confirmed as previously reported [7,10]. Baroreceptor denervation was assumed to be complete if HR changed by less than 5 beats/min in response to an intravenous injection of phenylephrine (20 µg/kg).

Rats were placed in a stereotaxic instrument (Stoelting, Chicago). The location of the PVN was determined according to the Paxinos and Watson rat atlas (1.8 mm caudal from bregma, 0.4 mm lateral to the midline, and 7.9 mm ventral to the dorsal surface). The PVN microinjection volume was 100 nl and administration was completed within 1 min. A representative photograph of microinjection sites in the PVN is shown in Fig. 1.


Figure 01
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  		Fig. 1 A representative coronal photograph of brain section showing bilateral microinjection sites in the PVN of a rat. The arrows show the microinjection sites.

 
Renal sympathetic nerve activity (RSNA) was recorded as previously described [7]. The signal was amplified with an AC/DC differential amplifier (Model 3000, A-M System Inc.) with a low-frequency cut-off at 60 Hz and a high-frequency cut-off at 3 kHz. The amplified and filtered signals were integrated at time constant of 10 ms. The background noise was determined after section of the central end of the renal nerve at the end of the experiment and subtracted from all the integrated values of the RSNA. The RSNA and arterial pressure were recorded with PowerLab data acquisition system (8SP, ADInstruments). The RSNA was expressed as the percent change from control.

The CSAR was elicited by application of a piece of filter paper (3x3 mm) containing bradykinin (BK, 0.4 µg in 2.0 µl) to the non-infarcted area of the epicardial surface of the left ventricle. Each piece of paper was applied for 1 min, and then removed. The epicardium was rinsed three times with 10 ml of warm normal saline (38 °C). The CSAR was evaluated by the response of the RSNA to epicardial application of BK.

At the end of the experiment, 100 nl of Evans blue (2%) was injected into the microinjection site for histological identification. Only the data from rats whose microinjection sites were within the boundaries of the PVN were used for analysis.

2.3. Measurement of superoxide anion and malondialdehyde (MDA) levels
The rat brain was removed quickly, flash-frozen in liquid nitrogen and stored at –70 °C. Coronal sections of the brain were made using a cryostat microtome (CM1900, Leica LTD), and the PVN area was punched out with a 15-gauge needle. The punched PVN tissue was homogenized and then centrifuged. Protein concentrations in the supernatant were measured with the Bradford assay [16].

Malondialdehyde (MDA) was used as an indirect marker of ROS level and was determined by the thiobarbituric acid spectrometric method of Ohkawa et al. [17]. The pink-coloured chromogen formed by the reaction of thiobarbituric acid with the MDA in an acidic medium was read at 532 nm. 1,1,3,3-tetraethoxypropane was used as the external standard. The MDA level was expressed as nanomoles per milligram of tissue protein.

Lucigenin-derived chemiluminescence is a valid probe for detecting superoxide anion [18-22]. The lucigenin reacts with the superoxide anion in the sample to yield an unstable dioxetane intermediate. The lucigenin dioxetane breaks down into two molecules of N-methylacridone, one of which is in an electronically excited state, which becomes the ground state by emitting a photon. The superoxide anion level is determined by measuring the photon emission. The reaction was started by addition of dark-adapted lucigenin (5 µM). Light emission was measured with a luminometer (20/20n, Turner, CA), and values were expressed as mean light unit (MLU) per minute per milligram of protein, which represents the superoxide anion level. Background chemiluminescence in the buffer containing lucigenin (5 µM) was measured. Specificity for superoxide anion was determined by adding superoxide dismutase (SOD, 350 U/ml) to the incubation medium.

2.4. Drugs
BK, Ang II, tempol, tiron, diethyldithio-carbamic acid (DETC) and lucigenin were obtained from Sigma Chemical Co. Losartan was a gift from Merck.

2.5. Protocols
First, the effects of PVN microinjection of saline, tempol (0.2, 2 and 20 nmol), tiron (10 nmol) and diethyldithio-carbamic acid (DETC, 10 nmol) on the CSAR, baseline RSNA and MAP were determined in 6 groups of CHF rats and 6 groups of sham-operated rats (n=6 for each). CSAR was determined 10 min after the PVN microinjection.

Secondly, the effect of pretreatment with PVN microinjection of saline, tempol (0.2, 2 and 20 nmol), tiron (10 nmol) and DETC (10 nmol) on the CSAR, RSNA and MAP responses to PVN microinjection of Ang II (0.3 nmol) were investigated in 6 groups of CHF rats and 6 groups of sham-operated rats (n=6 for each). The PVN microinjection of Ang II was carried out 8 minutes after pretreatment, and the CSAR was determined 2 min after Ang II.

Thirdly, the effects of epicardial application of saline and BK (0.4 µg) on MDA and superoxide anion levels in the PVN were determined in 2 groups of CHF rats and 2 groups of sham-operated rats (n=6 for each).

Fourthly, the effects of microinjection of saline, Ang II (0.3 nmol), losartan (10 nmol) and tempol (20 nmol) on MDA and superoxide anion levels in the PVN were determined in 4 groups of CHF rats and 4 groups of sham-operated rats (n=6 for each).

Finally, to exclude the possibility that the effects of tempol were caused by diffusion into other areas of the brain, the effects of microinjection of tempol (20 nmol) into the anterior hypothalamic area, which is adjacent to the PVN, on the CSAR and Ang II-induced responses were determined in CHF and sham-operated rats (n=3 for each).

2.6. Statistics
Comparisons between two observations (before and after administration) in the same animal were assessed by Student's paired t test. One-way ANOVA, followed by the Student's t test, was used when multiple comparisons were made. All data were expressed as mean±SE. P<0.05 was considered statistically significant.


   3. Results
Top
 Abstract
 1. Introduction
 2. Methods
 3. Results
4. Discussion
 Acknowledgment
 References
 
3.1. Anatomic and haemodynamic data in CHF and sham-operated rats
The mean infarct area was about 34% of the left ventricle in CHF rats, no obvious infarcts were found in sham-operated rats. The heart weight and the heart-to-body weight ratio were increased in CHF rats, suggesting myocardial hypertrophy in the non-infarcted region of the myocardium. The systolic arterial pressure, pulse pressure, left ventricle peak systolic pressure, developed pressure and +dP/dtmax decreased, while LVEDP increased in CHF rats. Table 1 shows anatomic and haemodynamic data for a representative group of CHF rats and sham-operated rats. There were no significant differences between each group of sham-operated rats or each group of CHF rats. These haemodynamic and anatomical data indicate the presence of myocardial damage and suggest decreased contractile function in CHF rats.


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  		Table 1 Heart weight, infarcted area and baseline haemodynamics in a representative group of sham-operated and CHF rats

 
3.2. Effects of tempol, tiron and DETC on baseline RSNA and MAP
Microinjection of the superoxide anion scavengers, tempol or tiron, into the PVN decreased baseline RSNA and MAP in both CHF and sham-operated rats, but the superoxide dismutase inhibitor DETC showed opposite effects. In addition, the RSNA change caused by DETC in CHF rats was greater than that in sham-operated rats (Fig. 2).


Figure 02
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  		Fig. 2 Effects of PVN microinjection of saline, tempol (20 nmol), tiron (10 nmol) and DETC (10 nmol) on baseline RSNA and MAP. Values are mean±SE. *P<0.05 compared with saline, {dagger}P<0.05 compared with sham-operated rats, n=6 for each group.

 
3.3. Effects of tempol, tiron and DETC on CSAR
Microinjection of tempol into the PVN dose-dependently inhibited the CSAR (data not shown). Representative recordings in Fig. 3 show that CSAR was enhanced in the CHF rat, and that microinjection of high dose of tempol into the PVN abolished the CSAR in both CHF and sham-operated rats. Microinjection of a high dose of tempol or tiron into the PVN inhibited the CSAR, but DETC enhanced the CSAR in both CHF and sham-operated rats (Fig. 4). Microinjection of a high dose of tempol into the anterior hypothalamic area (adjacent to the PVN) failed to abolish the CSAR.


Figure 03
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  		Fig. 3 Tracing showing the effect of microinjection of the superoxide anion scavenger tempol (20 nmol) or saline into the PVN on the CSAR in CHF rats (upper panel) and sham-operated rats (lower panel). CSAR was evaluated by the RSNA response to epicardial application of BK. The CSAR in CHF rats was enhanced compared with sham-operated rats. Tempol abolished the CSAR in both CHF rats and sham-operated rats.

 


Figure 04
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  		Fig. 4 Effects of PVN microinjection of saline, tempol (20 nmol), tiron (10 nmol) and DETC (10 nmol) on the CSAR evoked by epicardial application of BK. Values were mean±SE. *P<0.05 compared with the value before microinjection, {dagger}P<0.05 compared with sham-operated rats, {ddagger}P<0.05 compared with saline, n=6 for each group.

 
3.4. Effects of pretreatment with tempol, tiron and DETC on RSNA and MAP responses to Ang II
Microinjection of Ang II into the PVN increased RSNA and MAP in both CHF rats and sham-operated rats. Pretreatment with a high dose of tempol or tiron abolished the effects of Ang II on the RSNA and MAP in both CHF rats and sham-operated rats. However, DETC did not further potentiate the effects of Ang II on RSNA and MAP (Fig. 5).


Figure 05
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  		Fig. 5 Effects of pretreatment with PVN microinjection of saline, tempol (20 nmol), tiron (10 nmol) and DETC (10 nmol) on RSNA and MAP responses induced by microinjection of 0.3 nmol of Ang II into the PVN. Values are mean±SE. *P<0.05 compared with saline, {dagger}P<0.05 compared with Sham-operated rats, n=6 for each group.

 
3.5. Effects of pretreatment with tempol, tiron and DETC on enhanced CSAR responses to Ang II
Microinjection of Ang II into the PVN significantly potentiated the CSAR in both sham-operated and CHF rats, which is similar to our previous report [9]. Microinjection of tempol into the PVN dose-dependently inhibited the enhanced CSAR response induced by Ang II (data not shown). Pretreatment with microinjection of tiron or a high dose of tempol into the PVN almost abolished the enhanced CSAR response induced by Ang II in both CHF and sham-operated rats. DETC augmented the enhanced CSAR response induced by Ang II only in CHF rats (Fig. 6). Microinjection of a high dose of tempol into the anterior hypothalamic area (adjacent to the PVN) failed to abolish the enhanced CSAR response induced by Ang II.


Figure 06
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  		Fig. 6 Effects of pretreatment with PVN microinjection of saline, tempol (20 nmol), tiron (10 nmol) and DETC (10 nmol) on the enhanced CSAR response induced by PVN microinjection of 0.3 nmol of Ang II. Values are mean±SE. *P<0.05 compared with the value before Ang II, {dagger}P<0.05 compared with sham-operated rats, {ddagger}P<0.05 compared with saline. n=6 for each group.

 
3.6. Superoxide anion and MDA levels in CHF rats and sham-operated rats
The superoxide anion and MDA levels in the PVN were higher in CHF rats than in sham-operated rats (Superoxide anion, 9.07±0.89 vs. 3.37±1.01 MLU/min/mg protein, P<0.05; MDA, 2.12±0.11 vs. 1.59±0.16 nmol/mg protein, P<0.05).

3.7. Effects of epicardial application of BK on superoxide anion and MDA levels
Epicardial application of BK increased MDA and superoxide anions levels in the PVN in both sham-operated and CHF rats. The MDA and superoxide anion levels in CHF rats were much higher than in sham-operated rats after administration of BK (Fig. 7).


Figure 07
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  		Fig. 7 Effects of epicardial application (Epi) of saline and BK (0.4 µg) as well as PVN microinjection of saline, Ang II (0.3 nmol), losartan (10 nmol) and tempol (20 nmol) on superoxide anion and MDA levels in the PVN. Values are mean±SE. *P<0.05 compared with saline, {dagger}P<0.05 compared with sham-operated rats. n=6 for each group.

 
3.8. Effects of microinjection of Ang II, losartan and tempol into the PVN on superoxide anion and MDA levels
Microinjection of Ang II into the PVN increased superoxide anion and MDA levels in the PVN in both CHF and sham-operated rats. The superoxide anion and MDA levels in CHF rats were higher than those in sham-operated rats after administration of Ang II. Tempol had opposite effects to Ang II. However, the AT1 receptor antagonist losartan only normalized the elevated superoxide anion and MDA levels in CHF rats without significant effects in sham-operated rats (Fig. 7).


   4. Discussion
Top
 Abstract
 1. Introduction
 2. Methods
 3. Results
 4. Discussion
Acknowledgment
 References
 
Our previous studies have indicated that CSAR is enhanced in rats and dogs with CHF [15,23]. AT1 receptors in the PVN have been shown to be involved in the enhanced CSAR in CHF rats [5,8-10]. ROS in the PVN mediates the CSAR in normal rats [6,7]. We have now shown that scavenging superoxide anions in the PVN abolish the CSAR, and block the Ang II-induced CSAR enhancement in CHF rats. These results suggest that the enhanced CSAR in CHF rats is mediated by the ROS in PVN, and that the augmented effect of Ang II in the PVN on the CSAR is also mediated by the ROS in the PVN.

Tempol (4-hydroxy-2,2,6,6-tetramethylpiperidine 1-oxyl) and tiron (4,5-dihydroxy-1,3-benzenedisulfonic acid) are stable membrane-permeable superoxide anion scavengers which mimic superoxide dismutase to scavenge superoxide anions [24-27]. It has been reported that intracerebroventricular infusion of tempol decrease arterial pressure and inhibit RSNA in rats [28]. Kishi et al found that bilateral microinjection of tempol into the rostral ventrolateral medulla decreased blood pressure; and that superoxide dismutase over-expression in the rostral ventrolateral medulla decreased blood pressure and inhibited sympathetic nerve activity in stroke-prone spontaneously hypertensive rats [29]. These results suggest that central ROS is involved in regulating arterial pressure and sympathetic activity. The present study found that microinjection of tempol or tiron into the PVN abolished CSAR, inhibited RSNA, and decreased MAP, but the superoxide dismutase inhibitor DETC showed opposite effects in both CHF and sham-operated rats. Furthermore, epicardial chemical stimulation of the cardiac afferents with BK increased, but microinjection of tempol into the PVN decreased the superoxide anion and MDA levels in the PVN in both CHF and sham-operated rats. These results indicate that ROS in the PVN mediates the CSAR in both CHF and sham-operated rats. It is interesting that superoxide anion scavengers abolished not only normal CSAR, but also the enhanced CSAR in CHF rats. On the other hand, DETC further potentiated the enhanced CSAR in CHF rats although the CSAR was already enhanced. Furthermore, superoxide anion and MDA levels in the PVN increased in CHF rats. Epicardial application of BK in CHF rats resulted in much higher levels of the superoxide anion and MDA in the PVN with enhanced CSAR compared with sham-operated rats. These results suggest that the generation of ROS in the PVN could be involved in the pathogenesis of enhanced CSAR in CHF.

Our previous study showed that the enhanced CSAR in CHF rats was normalized by microinjection of the AT1 receptor antagonist losartan, AT1 receptor mRNA antisense or the angiotensin-converting enzyme inhibitor captopril, into the PVN. Furthermore, AT1 receptor protein in the PVN was up-regulated in CHF rats [5,8,9]. It was reported that the changes in blood pressure, heart rate and drinking elicited by intracerebroventricular injection of Ang II were abolished by prior treatment with AdSOD in the brain in mice [30]. Gao et al found that intracerebroventricular administration of tempol or apocynin (a NAD(P)H oxidase inhibitor) inhibited the increased RSNA responses induced by intracerebroventricular administration of Ang II, and decreased the baseline RSNA in rabbits with heart failure, suggesting a close relationship between Ang II and ROS in the brain in contributing to sympathoexcitation in heart failure [18]. However, the location of the central sites in which the ROS is involved in sympathoexcitation in CHF, and whether central ROS contributes to the enhanced CSAR in CHF rats, is not known. Recently, we found that ROS in the PVN mediated the Ang II-induced CSAR enhancement in normal rats [6,7]. In the present study, microinjection of Ang II into the PVN potentiated the CSAR, and increased RSNA as well as MAP. The effects of Ang II in CHF rats were much greater than those in sham-operated rats. Pretreatment with microinjection of tempol or tiron into the PVN almost abolished the effect of Ang II on the CSAR, RSNA and MAP in both CHF rats and sham-operated rats. Microinjection of Ang II into the PVN significantly increased the MDA and superoxide anion levels in the PVN. However, DETC augmented the effect of Ang II only in CHF rats. Microinjection of Ang II into the PVN in CHF rats resulted in much higher levels of superoxide anion and MDA in the PVN and larger CSAR than sham-operated rats. The AT1 receptor antagonist losartan normalized the increased superoxide anion and MDA levels in CHF rats without significant effects in sham-operated rats. This is consistent with our previous findings that losartan normalized the enhanced CSAR in CHF rats without significant effects on the CSAR in normal rats [9]. Combining the present study with our previous findings, that increased activity of AT1 receptors in the PVN contributed to the enhanced CSAR [5,8,9], we concluded that the augmented effect of Ang II on the CSAR in CHF rats was mediated by ROS in the PVN in CHF rats.

It is interesting to compare the present study with our previous studies. Both blockade of AT1 receptors and decreased Ang II in the PVN, normalized the enhanced CSAR, but did not completely abolish the CSAR in CHF rats. Also, In addition, there were no significant effects on the CSAR in normal rats [5,8,9]. However, scavenging superoxide anions in the PVN almost completely abolished CSAR in both CHF rats and sham rats, although the CSAR in CHF rats was much greater than that in sham rats. We therefore conclude that ROS in the PVN mediate the CSAR in either normal or CHF rats, but the AT1 receptor activity in the PVN only partially mediates or modulates the CSAR. The ROS in the PVN mediate the effects of Ang II in the PVN on CSAR in both sham-operated rats and CHF rats. It is possible that the enhanced AT1 receptor activity in the PVN in CHF increases the generation of ROS and then contributes to the enhanced CSAR and sympathetic activity in CHF rats.

One limitation to the present study is that the neurotransmitter which mediates the CSAR upstream of the ROS in the PVN is unknown. We plan to investigate the possible neurotransmitters which mediate the CSAR in the near future.

In summary, ROS in the PVN mediate the CSAR and the effect of Ang II in the PVN on the CSAR in both CHF and sham-operated rats. Increased ROS in the PVN is involved in the enhanced CSAR in CHF.


   Acknowledgment
Top
 Abstract
 1. Introduction
 2. Methods
 3. Results
 4. Discussion
 Acknowledgment
References
 
This study was supported by National Natural Science Foundation of China (30470632 & 30670768).


   References
Top
 Abstract
 1. Introduction
 2. Methods
 3. Results
 4. Discussion
 Acknowledgment
 References
 

  1. Cohn J.N., Levine T.B., Olivari M.T., et al. Plasma norepinephrine as a guide to prognosis in patients with chronic congestive heart failure. N Engl J Med (1984) 311:819–823.[Abstract]
  2. Ferguson D.W., Berg W.J., Sanders J.S. Clinical and hemodynamic correlates of sympathetic nerve activity in normal humans and patients with heart failure: evidence from direct microneurographic recordings. J Am Coll Cardiol (1990) 16:1125–1134.[Abstract]
  3. Gao L., Schultz H.D., Patel K.P., Zucker I.H., Wang W. Augmented input from cardiac sympathetic afferents inhibits baroreflex in rats with heart failure. Hypertension (2005) 45:1173–1181.[Abstract/Free Full Text]
  4. Malliani A., Pagani M. The role of the sympathetic nervous system in congestive heart failure. Eur Heart J (1983) 4(Suppl_A):49–54.[Abstract]
  5. Zhu G.Q., Gao L., Li Y., Patel K.P., Zucker I.H., Wang W. AT1 receptor mRNA antisense normalizes enhanced cardiac sympathetic afferent reflex in rats with chronic heart failure. Am J Physiol Heart Circ Physiol (2004) 287:H1828–H1835.[Abstract/Free Full Text]
  6. Zhang Y., Yu Y., Zhang F., et al. NAD(P)H oxidase in paraventricular nucleus contributes to the effect of angiotensin II on cardiac sympathetic afferent reflex. Brain Res (2006) 1082:132–141.[CrossRef][Web of Science][Medline]
  7. Han Y., Zhang Y., Wang H.J., Gao X.Y., Wang W., Zhu G.Q. Reactive oxygen species in paraventricular nucleus modulates cardiac sympathetic afferent reflex in rats. Brain Res (2005) 1058:82–90.[CrossRef][Web of Science][Medline]
  8. Wang H.J., Zhang F., Zhang Y., Gao X.Y., Wang W., Zhu G.Q. AT1 receptor in paraventricular nucleus mediates the enhanced cardiac sympathetic afferent reflex in rats with chronic heart failure. Auton Neurosci (2005) 121:56–63.[CrossRef][Web of Science][Medline]
  9. Zhu G.Q., Gao L., Patel K.P., Zucker I.H., Wang W. ANG II in the paraventricular nucleus potentiates the cardiac sympathetic afferent reflex in rats with heart failure. J Appl Physiol (2004) 97:1746–1754.[Abstract/Free Full Text]
  10. Zhu G.Q., Patel K.P., Zucker I.H., Wang W. Microinjection of ANG II into paraventricular nucleus enhances cardiac sympathetic afferent reflex in rats. Am J Physiol Heart Circ Physiol (2002) 282:H2039–H2045.[Abstract/Free Full Text]
  11. Zahner M.R., Pan H.L. Role of paraventricular nucleus in the cardiogenic sympathetic reflex in rats. Am J Physiol Regul Integr Comp Physiol (2005) 288:R420–R426.[Abstract/Free Full Text]
  12. Guo Z.L., Moazzami A.R. Involvement of nuclei in the hypothalamus in cardiac sympathoexcitatory reflexes in cats. Brain Res (2004) 1006:36–148.[CrossRef][Web of Science][Medline]
  13. Zimmerman M.C., Davisson R.L. Redox signaling in central neural regulation of cardiovascular function. Prog Biophys Mol Biol (2004) 84:125–149.[CrossRef][Web of Science][Medline]
  14. Griendling K.K., Ushio-Fukai M. Reactive oxygen species as mediators of angiotensin II signaling. Regul Pept (2000) 91:21–27.[CrossRef][Web of Science][Medline]
  15. Zhu G.Q., Zucker I.H., Wang W. Central AT1 receptors are involved in the enhanced cardiac sympathetic afferent reflex in rats with chronic heart failure. Basic Res Cardiol (2002) 97:320–326.[CrossRef][Web of Science][Medline]
  16. Bradford M.M. A rapid and sensitive method for the quantitation of microgram quantities of protein utilizing the principle of protein-dye binding. Anal Biochem (1976) 72:248–254.[CrossRef][Web of Science][Medline]
  17. Ohkawa H., Ohishi N., Yagi K. Assay for lipid peroxides in animal tissues by thiobarbituric acid reaction. Anal Biochem (1979) 95:351–358.[CrossRef][Web of Science][Medline]
  18. Gao L., Wang W., Li Y.L., et al. Superoxide mediates sympathoexcitation in heart failure: roles of angiotensin II and NAD(P)H oxidase. Circ Res (2004) 95:937–944.[Abstract/Free Full Text]
  19. Latini A., Scussiato K., Rosa R.B., et al. Induction of oxidative stress by L-2-hydroxyglutaric acid in rat brain. J Neurosci Res (2003) 74:103–110.[CrossRef][Web of Science][Medline]
  20. Li Y., Zhu H., Kuppusamy P., Roubaud V., Zweier J.L., Trush M.A. Validation of lucigenin (bis-N-methylacridinium) as a chemilumigenic probe for detecting superoxide anion radical production by enzymatic and cellular systems. J Biol Chem (1998) 273:2015–2023.[Abstract/Free Full Text]
  21. Tai M.H., Wang L.L., Wu K.L., Chan J.Y. Increased superoxide anion in rostral ventrolateral medulla contributes to hypertension in spontaneously hypertensive rats via interactions with nitric oxide. Free Radic Biol Med (2005) 38:450–462.[CrossRef][Web of Science][Medline]
  22. Meimaridou E., Jacobson J., Seddon A.M., Noronha-Dutra A.A., Robertson W.G., Hothersall J.S. Crystal and microparticle effects on MDCK cell superoxide production: oxalate-specific mitochondrial membrane potential changes. Free Radic Biol Med (2005) 38:1553–1564.[CrossRef][Web of Science][Medline]
  23. Wang W., Zucker I.H. Cardiac sympathetic afferent reflex in dogs with congestive heart failure. Am J Physiol (1996) 271:R751–R756.[Web of Science][Medline]
  24. Reddan J.R., Sevilla M.D., Giblin F.J., et al. The superoxide dismutase mimic TEMPOL protects cultured rabbit lens epithelial cells from hydrogen peroxide insult. Exp Eye Res (1993) 56:543–554.[CrossRef][Web of Science][Medline]
  25. Yamada J., Yoshimura S., Yamakawa H., et al. Cell permeable ROS scavengers, Tiron and Tempol, rescue PC12 cell death caused by pyrogallol or hypoxia/reoxygenation. Neurosci Res (2003) 45:1–8.[CrossRef][Web of Science][Medline]
  26. Greenstock C.L., Miller R.W. The oxidation of tiron by superoxide anion. Kinetics of the reaction in aqueous solution in chloroplasts. Biochim Biophys Acta (1975) 396:11–16.[Medline]
  27. Krishna C.M., Liebmann J.E., Kaufman D., et al. The catecholic metal sequestering agent 1,2-dihydroxybenzene-3,5-disulfonate confers protection against oxidative cell damage. Arch Biochem Biophys (1992) 294:98–106.[CrossRef][Web of Science][Medline]
  28. Campese V.M., Ye S., Zhong H., Yanamadala V., Ye Z., Chiu J. Reactive oxygen species stimulate central and peripheral sympathetic nervous system activity. Am J Physiol Heart Circ Physiol (2004) 287:H695–H703.[Abstract/Free Full Text]
  29. Kishi T., Hirooka Y., Kimura Y., Ito K., Shimokawa H., Takeshita A. Increased reactive oxygen species in rostral ventrolateral medulla contribute to neural mechanisms of hypertension in stroke-prone spontaneously hypertensive rats. Circulation (2004) 109:2357–2362.[Abstract/Free Full Text]
  30. Zimmerman M.C., Lazartigues E., Lang J.A., et al. Superoxide mediates the actions of angiotensin II in the central nervous system. Circ Res (2002) 91:1038–1045.[Abstract/Free Full Text]

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