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Li M, Sorensen M, Johnson MA, Ingram SL, Andresen MC, Habecker BA. Hypertension increases sympathetic neuron activity by enhancing intraganglionic cholinergic collateral connections. J Physiol 2024. [PMID: 39031543 DOI: 10.1113/jp286601] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2024] [Accepted: 06/06/2024] [Indexed: 07/22/2024] Open
Abstract
Autonomic dysregulation, including sympathetic hyperactivity, is a common feature of hypertension (HT) and other cardiovascular diseases. The CNS plays a role in driving chronic sympathetic activation in disease, but several lines of evidence suggest that neuroplasticity in the periphery may also contribute. The potential contribution of postganglionic sympathetic neurons to sustained sympathetic hyperactivity is not well understood. We recently discovered that noradrenergic sympathetic neurons in the stellate ganglion (SG) have excitatory cholinergic collateral connections to other neurons within the ganglion. We hypothesize that remodelling of these neurons and increased cholinergic collateral transmission contributes to sustained sympathetic hyperactivity in cardiovascular diseases, including HT. To test that hypothesis, we examined the activity of sympathetic neurons in isolated SG under control conditions and after 1 week of HT induced by peripheral angiotensin II infusion, using whole-cell patch clamp recordings. Despite the absence of central inputs, we observed elevated spontaneous activity and synaptic transmission in sympathetic SG neurons from hypertensive mice that required generation of action potentials. Genetically disrupting cholinergic transmission in noradrenergic neurons decreased basal neuronal activity and prevented angiotensin II-mediated enhancement of activity. Similar changes in activity, driven by increased collateral transmission, were identified in cardiac projecting neurons and neurons projecting to brown adipose tissue. These changes were not driven by altered A-type K+ currents. This suggests that HT stimulates increased activity throughout the intraganglionic network of collateral connections, contributing to the sustained sympathetic hyperactivity characteristic in cardiovascular disease. KEY POINTS: Sympathetic neurons in ganglia isolated from angiotensin II-treated hypertensive mice are more active than neurons from control mice despite the absence of central activation. The enhanced activity is the result of a ganglionic network of cholinergic collaterals, rather than altered intrinsic excitability. Increased neuronal activity was observed in both cardiac neurons and brown adipose tissue-projecting neurons, which are not involved in cardiovascular homeostasis.
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Affiliation(s)
- Minghua Li
- Department of Chemical Physiology and Biochemistry, Oregon Health and Science University, Portland, OR, USA
| | - Michelle Sorensen
- Department of Chemical Physiology and Biochemistry, Oregon Health and Science University, Portland, OR, USA
| | - Morgan A Johnson
- Department of Chemical Physiology and Biochemistry, Oregon Health and Science University, Portland, OR, USA
| | - Susan L Ingram
- Department of Anesthesiology, University of Colorado Anschutz Medical Campus, Aurora, CO, USA
| | - Michael C Andresen
- Department of Chemical Physiology and Biochemistry, Oregon Health and Science University, Portland, OR, USA
| | - Beth A Habecker
- Department of Chemical Physiology and Biochemistry, Oregon Health and Science University, Portland, OR, USA
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2
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Fan H, Yang JW, Wang LQ, Huang J, Lin LL, Wang Y, Zhang N, Liu CZ. The Hypotensive Role of Acupuncture in Hypertension: Clinical Study and Mechanistic Study. Front Aging Neurosci 2020; 12:138. [PMID: 32523527 PMCID: PMC7261879 DOI: 10.3389/fnagi.2020.00138] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2019] [Accepted: 04/23/2020] [Indexed: 01/03/2023] Open
Abstract
As a component of traditional Chinese medicine (TCM), acupuncture has the potential to lower blood pressure (BP) in patients with hypertension. Emerging evidence indicates that the acupuncture-induced inhibition of high BP occurs through the activation of the pathway in the afferent, central, and efferent pathways. An increasing number of studies have demonstrated that acupuncture not only activates distinct brain regions under conditions of hypertension caused by an imbalance between the sympathetic and parasympathetic systems but also modulates neurotransmitters in related brain regions to alleviate the autonomic response. The activity of these pathways can be assessed by injecting agonists or inhibitors or by performing neurotomy. This review focuses on the clinical and mechanistic studies of acupuncture in modulating BP, which might provide a neurobiological foundation for the effects of acupuncture. Although many mechanisms underlying the effects of acupuncture on cardiovascular function have been identified, further investigation is warranted.
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Affiliation(s)
- Hao Fan
- Acupuncture Research Center, School of Acupuncture-Moxibustion and Tuina, Beijing University of Chinese Medicine, Beijing, China.,Department of Acupuncture and Moxibustion, Beijing Hospital of Traditional Chinese Medicine Affiliated to Capital Medical University, Beijing, China
| | - Jing-Wen Yang
- Acupuncture Research Center, School of Acupuncture-Moxibustion and Tuina, Beijing University of Chinese Medicine, Beijing, China
| | - Li-Qiong Wang
- Acupuncture Research Center, School of Acupuncture-Moxibustion and Tuina, Beijing University of Chinese Medicine, Beijing, China
| | - Jin Huang
- Department of Acupuncture and Moxibustion, Beijing Hospital of Traditional Chinese Medicine Affiliated to Capital Medical University, Beijing, China
| | - Lu-Lu Lin
- Acupuncture Research Center, School of Acupuncture-Moxibustion and Tuina, Beijing University of Chinese Medicine, Beijing, China
| | - Yu Wang
- Department of Acupuncture and Moxibustion, Beijing Hospital of Traditional Chinese Medicine Affiliated to Capital Medical University, Beijing, China
| | - Na Zhang
- School of Acupuncture-Moxibustion and Tuina, Shandong University of Traditional Chinese Medicine, Jinan, China
| | - Cun-Zhi Liu
- Acupuncture Research Center, School of Acupuncture-Moxibustion and Tuina, Beijing University of Chinese Medicine, Beijing, China
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Hemodynamic and Electrocardiographic Aspects of Uncomplicated Singleton Pregnancy. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2018; 1065:413-431. [PMID: 30051399 DOI: 10.1007/978-3-319-77932-4_26] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Pregnancy is associated with significant changes in maternal hemodynamics, which are triggered by profound systemic vasodilation and mediated through the autonomic nervous system as well as the renin-angiotensin-aldosterone system. Vascular function changes to help accommodate an increase in intravascular volume due to blood volume expansion associated with pregnancy while maintaining the efficiency of ventricular-arterial coupling and diastolic perfusion pressure. The heart undergoes physiological (eccentric) hypertrophy due to increased volume load and cardiac stroke work, whereas the functional change of the left ventricle remains controversial. There are changes in cardiac electrical activity during pregnancy which can be detected in the electrocardiogram that are not related to disease. Sympathetic activation is a common phenomenon during uncomplicated pregnancy and may be a compensatory mechanism induced by profound systemic vasodilation and a decrease in mean arterial pressure. Despite marked sympathetic activation, vasoconstrictor responsiveness is blunted during uncomplicated pregnancy. There are race and ethnic differences in maternal hemodynamic adaptations to uncomplicated pregnancy, which may be attributed to differences in socioeconomic status or in prevalence rates of cardiovascular risk factors.
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Oyama Y, Iigaya K, Minoura Y, Okabe T, Izumizaki M, Onimaru H. An in vitro experimental model for analysis of central control of sympathetic nerve activity. J Physiol Sci 2017; 67:629-635. [PMID: 28601952 PMCID: PMC10717256 DOI: 10.1007/s12576-017-0549-5] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2017] [Accepted: 06/05/2017] [Indexed: 10/19/2022]
Abstract
Newborn rat brainstem-spinal cord preparations are useful for in vitro analysis of various brainstem functions including respiratory activity. When studying the central control of sympathetic nerve activity (SNA), it is important to record peripheral outputs of the SNA. We developed an in vitro preparation in which neuronal connections between the cardiovascular center in the medulla and SNA peripheral outputs are preserved. Zero- to 1-day-old rats were deeply anesthetized with isoflurane, and the brainstem and spinal cord were isolated with a partial right thoracic cage to record sympathetic nerve discharge from the right thoracic sympathetic nerve trunk (T9-T11). SNA in this preparation was strongly modulated by inspiratory activity. Single-shot electrical stimulation of the ipsilateral rostral ventrolateral medulla (RVLM) induced a transient increase of SNA. Bath application of angiotensin II induced an increase of SNA, and local ipsilateral microinjection of angiotensin II to the RVLM induced a transient increase of SNA. This preparation allows analysis of the central control of the SNA in vitro.
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Affiliation(s)
- Yuji Oyama
- Department of Physiology, Showa University School of Medicine, 1-5-8 Hatanodai, Shinagawa-ku, Tokyo, 142-8555, Japan
- Division of Cardiology and Cardiac Catheterization Laboratories, Showa University Northern Yokohama Hospital, 35-1 Chigasaki-Chuo, Tsuzuki, Yokohama, Kanagawa, 224-8503, Japan
| | - Kamon Iigaya
- Department of Internal Medicine, Hiratsuka City Hospital, 1-19-1 Minamihara, Hiratsuka, Kanagawa, 254-0065, Japan
| | - Yoshino Minoura
- Division of Cardiology, Department of Medicine, Showa University School of Medicine, 1-5-8 Hatanodai, Shinagawa-ku, Tokyo, 142-8555, Japan
| | - Toshitaka Okabe
- Division of Cardiology and Cardiac Catheterization Laboratories, Showa University Northern Yokohama Hospital, 35-1 Chigasaki-Chuo, Tsuzuki, Yokohama, Kanagawa, 224-8503, Japan
| | - Masahiko Izumizaki
- Department of Physiology, Showa University School of Medicine, 1-5-8 Hatanodai, Shinagawa-ku, Tokyo, 142-8555, Japan
| | - Hiroshi Onimaru
- Department of Physiology, Showa University School of Medicine, 1-5-8 Hatanodai, Shinagawa-ku, Tokyo, 142-8555, Japan.
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Kawada T, Akiyama T, Li M, Zheng C, Turner MJ, Shirai M, Sugimachi M. Acute arterial baroreflex-mediated changes in plasma catecholamine concentrations in a chronic rat model of myocardial infarction. Physiol Rep 2016; 4:4/15/e12880. [PMID: 27495297 PMCID: PMC4985546 DOI: 10.14814/phy2.12880] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2016] [Accepted: 06/23/2016] [Indexed: 11/24/2022] Open
Abstract
While it may be predictable that plasma norepinephrine (NE) concentration changes with efferent sympathetic nerve activity (SNA) in response to baroreceptor pressure inputs, an exact relationship between SNA and plasma NE concentration remains to be quantified in heart failure. We examined acute baroreflex-mediated changes in plasma NE and epinephrine (Epi) concentrations in normal control (NC) rats and rats with myocardial infarction (MI) (n = 6 each). Plasma NE concentration correlated linearly with SNA in the NC group (slope: 2.17 ± 0.26 pg mL(-1) %(-1), intercept: 20.0 ± 18.2 pg mL(-1)) and also in the MI group (slope: 19.20 ± 6.45 pg mL(-1) %(-1), intercept: -239.6 ± 200.0 pg mL(-1)). The slope was approximately nine times higher in the MI than in the NC group (P < 0.01). Plasma Epi concentration positively correlated with SNA in the NC group (slope: 1.65 ± 0.79 pg mL(-1) %(-1), intercept: 115.0 ± 69.5 pg mL(-1)) and also in the MI group (slope: 7.74 ± 2.20 pg mL(-1) %(-1), intercept: 24.7 ± 120.1 pg mL(-1)). The slope was approximately 4.5 times higher in the MI than in the NC group (P < 0.05). Intravenous administration of desipramine (1 mg kg(-1)) significantly increased plasma NE concentration but decreased plasma Epi concentration in both groups, suggesting that neuronal NE uptake had contributed to the reduction in plasma NE concentration. These results indicate that high levels of plasma catecholamine in MI rats were still under the influence of baroreflex-mediated changes in SNA, and may provide additional rationale for applying baroreflex activation therapy in patients with chronic heart failure.
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Affiliation(s)
- Toru Kawada
- Department of Cardiovascular Dynamics, National Cerebral and Cardiovascular Center, Osaka, Japan
| | - Tsuyoshi Akiyama
- Department of Cardiac Physiology, National Cerebral and Cardiovascular Center, Osaka, Japan
| | - Meihua Li
- Department of Cardiovascular Dynamics, National Cerebral and Cardiovascular Center, Osaka, Japan
| | - Can Zheng
- Department of Cardiovascular Dynamics, National Cerebral and Cardiovascular Center, Osaka, Japan
| | - Michael J Turner
- Department of Cardiovascular Dynamics, National Cerebral and Cardiovascular Center, Osaka, Japan
| | - Mikiyasu Shirai
- Department of Cardiac Physiology, National Cerebral and Cardiovascular Center, Osaka, Japan
| | - Masaru Sugimachi
- Department of Cardiovascular Dynamics, National Cerebral and Cardiovascular Center, Osaka, Japan
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Morgan DA, Despas F, Rahmouni K. Effects of leptin on sympathetic nerve activity in conscious mice. Physiol Rep 2015; 3:3/9/e12554. [PMID: 26381017 PMCID: PMC4600394 DOI: 10.14814/phy2.12554] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
Abstract
The adipocyte-derived hormone, leptin, has emerged as an important regulator of regional sympathetic nerve activity (SNA) with pathophysiological implications in obesity. Genetically engineered mice are useful to understand the molecular pathways underlying the SNA responses evoked by leptin. However, so far the effect of leptin on direct SNA in mice has been studied under general anesthesia. Here, we examined the sympathetic responses evoked by leptin in conscious mice. Mice were instrumented, under ketamine/xylazine anesthesia, with renal or lumbar SNA recordings using a thin (40 gauge) bipolar platinum-iridium wire. The electrodes were exteriorized at the nape of the neck and mice were allowed (5 h) to recover from anesthesia. Interestingly, the reflex increases in renal and lumbar SNA caused by sodium nitroprusside (SNP)-induced hypotension was higher in the conscious phase versus the anesthetized state, whereas the increase in both renal and lumbar SNA evoked by leptin did not differ between anesthetized or conscious mice. Next, we assessed whether isoflurane anesthesia would yield a better outcome. Again, the SNP-induced increase in renal SNA and baroreceptor-renal SNA reflex were significantly elevated in the conscious states relative to isoflurane-anesthetized phase, but the renal SNA response induced by leptin in the conscious states were qualitatively comparable to those evoked above. Thus, despite improvement in sympathetic reflexes in conscious mice the sympathetic responses evoked by leptin mimic those induced during anesthesia.
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Affiliation(s)
- Donald A Morgan
- Department of Pharmacology, University of Iowa Carver College of Medicine, Iowa City, Iowa
| | - Fabien Despas
- Department of Internal Medicine, University of Iowa Carver College of Medicine, Iowa City, Iowa
| | - Kamal Rahmouni
- Department of Pharmacology, University of Iowa Carver College of Medicine, Iowa City, Iowa Department of Internal Medicine, University of Iowa Carver College of Medicine, Iowa City, Iowa
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Okada Y, Best SA, Jarvis SS, Shibata S, Parker RS, Casey BM, Levine BD, Fu Q. Asian women have attenuated sympathetic activation but enhanced renal-adrenal responses during pregnancy compared to Caucasian women. J Physiol 2015; 593:1159-68. [PMID: 25545472 DOI: 10.1113/jphysiol.2014.282277] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2014] [Accepted: 12/24/2014] [Indexed: 12/15/2022] Open
Abstract
Asians have a lower prevalence of hypertensive disorders of pregnancy than Caucasians. Since sympathetic overactivity and dysregulation of the renal-adrenal system (e.g. low aldosterone levels) have been found in preeclamptic women, we hypothesized that Asians have lower muscle sympathetic nerve activity (MSNA) and greater aldosterone concentrations during normal pregnancy than Caucasians. In a prospective study, blood pressure (BP), heart rate (HR), and MSNA were measured during supine and upright tilt (30 deg and 60 deg for 5 min each) in 9 Asians (32 ± 1 years (mean ± SEM)) and 12 Caucasians (29 ± 1 years) during pre-, early (≤8 weeks of gestation) and late (32-36 weeks) pregnancy, and post-partum (6-10 weeks after delivery). Supine MSNA increased with pregnancy in both groups (P < 0.001); it was significantly lower in Asians than Caucasians (14 ± 3 vs. 23 ± 3 bursts min(-1) and 16 ± 5 vs. 30 ± 3 bursts min(-1) in early and late pregnancy, respectively; P = 0.023). BP decreased during early pregnancy (P < 0.001), but was restored during late pregnancy. HR increased during pregnancy (P < 0.001) with no racial difference (P = 0.758). MSNA increased during tilting and it was markedly lower in Asians than Caucasians in late pregnancy (31 ± 6 vs. 49 ± 3 bursts min(-1) at 60 deg tilt; P = 0.003). Upright BP was lower in Asians, even in pre-pregnancy (P = 0.006), and this racial difference persisted during pregnancy. Direct renin and aldosterone increased during pregnancy (both P < 0.001); these hormones were greater in Asians (P = 0.086 and P = 0.014). Thus, Asians have less sympathetic activation but more upregulated renal-adrenal responses than Caucasians during pregnancy. These results may explain, at least in part, why Asian women are at low risk of hypertensive disorders in pregnancy.
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Affiliation(s)
- Yoshiyuki Okada
- Institute for Exercise and Environmental Medicine, Texas Health Presbyterian Hospital Dallas, Dallas, TX, USA; University of Texas Southwestern Medical Center, Dallas, TX, USA
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Jancovski N, Carter DA, Connelly AA, Stevens E, Bassi JK, Menuet C, Allen AM. Angiotensin type 1A receptor expression in C1 neurons of the rostral ventrolateral medulla contributes to the development of angiotensin-dependent hypertension. Exp Physiol 2014; 99:1597-610. [DOI: 10.1113/expphysiol.2014.082073] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Affiliation(s)
- Nikola Jancovski
- Department of Physiology; University of Melbourne; Melbourne Victoria 3010 Australia
| | - David A. Carter
- Department of Physiology; University of Melbourne; Melbourne Victoria 3010 Australia
| | - Angela A. Connelly
- Department of Physiology; University of Melbourne; Melbourne Victoria 3010 Australia
| | - Elyse Stevens
- Department of Physiology; University of Melbourne; Melbourne Victoria 3010 Australia
| | - Jaspreet K. Bassi
- Department of Physiology; University of Melbourne; Melbourne Victoria 3010 Australia
| | - Clement Menuet
- Department of Physiology; University of Melbourne; Melbourne Victoria 3010 Australia
| | - Andrew M. Allen
- Department of Physiology; University of Melbourne; Melbourne Victoria 3010 Australia
- Florey Institute of Neuroscience and Mental Health; University of Melbourne; Melbourne Victoria 3010 Australia
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Jancovski N, Bassi JK, Carter DA, Choong YT, Connelly A, Nguyen TP, Chen D, Lukoshkova EV, Menuet C, Head GA, Allen AM. Stimulation of angiotensin type 1A receptors on catecholaminergic cells contributes to angiotensin-dependent hypertension. Hypertension 2013; 62:866-71. [PMID: 24001896 DOI: 10.1161/hypertensionaha.113.01474] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Hypertension contributes to multiple forms of cardiovascular disease and thus morbidity and mortality. The mechanisms inducing hypertension remain unclear although the involvement of homeostatic systems, such as the renin-angiotensin and sympathetic nervous systems, is established. A pivotal role of the angiotensin type 1 receptor in the proximal tubule of the kidney for the development of experimental hypertension is established. Yet, other systems are involved. This study tests whether the expression of angiotensin type 1A receptors in catecholaminergic cells contributes to hypertension development. Using a Cre-lox approach, we deleted the angiotensin type 1A receptor from all catecholaminergic cells. This deletion did not alter basal metabolism or blood pressure but delayed the onset of angiotensin-dependent hypertension and reduced the maximal response. Cardiac hypertrophy was also reduced. The knockout mice showed attenuated activation of the sympathetic nervous system during angiotensin II infusion as measured by spectral analysis of the blood pressure. Increased reactive oxygen species production was observed in forebrain regions, including the subfornical organ, of the knockout mouse but was markedly reduced in the rostral ventrolateral medulla. These studies demonstrate that stimulation of the angiotensin type 1A receptor on catecholaminergic cells is required for the full development of angiotensin-dependent hypertension and support an important role for the sympathetic nervous system in this model.
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Affiliation(s)
- Nikola Jancovski
- Department of Physiology, University of Melbourne, Victoria 3010, Australia.
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10
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Do high doses of AT(1)-receptor blockers attenuate central sympathetic outflow in humans with chronic heart failure? Clin Sci (Lond) 2013; 124:589-95. [PMID: 23163825 DOI: 10.1042/cs20120437] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
In patients with CHF (chronic heart failure) sympathetic activity increases as cardiac performance decreases and filling pressures increase. We hypothesized that in patients with mild-to-moderate CHF, higher than conventional doses of an AT1-receptor [AngII (angiotensin II) type 1 receptor] antagonist would achieve greater central AT1-receptor blockade, resulting in diminished MSNA (muscle sympathetic nerve activity) and augmented MSNA variability, two indices of central effects on sympathetic outflow. In total, 13 patients with ischaemic cardiomyopathy [NYHA (New York Heart Association) class II-III] were weaned off all pharmacological RAS (renin-angiotensin system) modifiers, and then randomized to receive a low (50 mg/day) or high (200 mg/day) dose of losartan. Central haemodynamics, MSNA and its variability, plasma catecholamines, AngI (angiotensin I) and AngII and aldosterone were assessed both before and 3 months after randomization. Neither dose altered BP (blood pressure), PCWP (pulmonary capillary wedge pressure) or CI (cardiac index) significantly. Compared with 50 mg daily, losartan 200 mg/day decreased MSNA significantly (P<0.05), by approximately 15 bursts/min, and increased MSNA variability within the 0.27-0.33 Hz high-frequency range by 0.11 units(2)/Hz (P=0.06). PNE [plasma noradrenaline (norepinephrine)] fell in parallel with changes in MSNA (r=0.62; P<0.05). These findings support the hypothesis that higher than conventional doses of lipophilic ARBs (AT1-receptor blockers) can modulate the intensity and variability of central sympathetic outflow in patients with CHF. The efficacy and safety of this conceptual change in the therapeutic approach to heart failure merits prospective testing in clinical trials.
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Markham DW, Fu Q, Palmer MD, Drazner MH, Meyer DM, Bethea BT, Hastings JL, Fujimoto N, Shibata S, Levine BD. Sympathetic neural and hemodynamic responses to upright tilt in patients with pulsatile and nonpulsatile left ventricular assist devices. Circ Heart Fail 2012; 6:293-9. [PMID: 23250982 DOI: 10.1161/circheartfailure.112.969873] [Citation(s) in RCA: 86] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
BACKGROUND Left ventricular assist devices (LVADs) are now widely accepted as an option for patients with advanced heart failure. First-generation devices were pulsatile, but they had poor longevity and durability. Newer generation devices are nonpulsatile and more durable, but remain associated with an increased risk of stroke and hypertension. Moreover, little is understood about the physiological effects of the chronic absence of pulsatile flow in humans. METHODS AND RESULTS We evaluated patients with pulsatile (n=6) and nonpulsatile (n=11) LVADs and healthy controls (n=9) during head-up tilt while measuring hemodynamics and muscle sympathetic nerve activity. Patients with nonpulsatile devices had markedly elevated supine and upright muscle sympathetic nerve activity (mean±SD, 43±15 supine and 60±21 bursts/min at 60° head-up tilt) compared with patients with pulsatile devices (24±7 and 35±8 bursts/min; P<0.01) and controls (11±6 and 31±6 bursts/min; P<0.01); however, muscle sympathetic nerve activity was not different between patients with pulsatile flow and controls (P=0.34). Heart rate, mean arterial pressure, and total peripheral resistance were greater, whereas cardiac output was smaller, in LVAD patients compared with controls in both supine and upright postures. However, these hemodynamic variables were not significantly different between patients with pulsatile and nonpulsatile flow. CONCLUSIONS Heart failure patients with continuous, nonpulsatile LVADs have marked sympathetic activation, which is likely due, at least in part, to baroreceptor unloading. We speculate that such chronic sympathetic activation may contribute to, or worsen end-organ diseases, and reduce the possibility of ventricular recovery. Strategies to provide some degree of arterial pulsatility, even in continuous flow LVADs may be necessary to achieve optimal outcomes in these patients.
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Affiliation(s)
- David W Markham
- University of Texas Southwestern Medical Center, Dallas, TX, USA
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12
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Jarvis SS, Shibata S, Bivens TB, Okada Y, Casey BM, Levine BD, Fu Q. Sympathetic activation during early pregnancy in humans. J Physiol 2012; 590:3535-43. [PMID: 22687610 DOI: 10.1113/jphysiol.2012.228262] [Citation(s) in RCA: 93] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023] Open
Abstract
Sympathetic activity has been reported to increase in normotensive pregnant women, and to be even greater in women with gestational hypertension and preeclampsia at term. Whether sympathetic overactivity develops early during pregnancy, remaining high throughout gestation, or whether it only occurs at term providing the substrate for hypertensive disorders is unknown. We tested the hypothesis that sympathetic activation occurs early during pregnancy in humans. Eleven healthy women (29 ± 3 (SD) years) without prior hypertensive pregnancies were tested during the mid-luteal phase (PRE) and early pregnancy (EARLY; 6.2 ± 1.2 weeks of gestation). Muscle sympathetic nerve activity (MSNA) and haemodynamics were measured supine, at 30 deg and 60 deg upright tilt for 5 min each. Blood samples were drawn for catecholamines, direct renin, and aldosterone. MSNA was significantly greater during EARLY than PRE (supine: 25 ± 8 vs. 14 ± 8 bursts min(-1), 60 deg tilt: 49 ± 14 vs. 40 ± 10 bursts min(-1); main effect, P < 0.05). Resting diastolic pressure trended lower (P = 0.09), heart rate was similar, total peripheral resistance decreased (2172 ± 364 vs. 2543 ± 352 dyne s cm(-5); P < 0.05), sympathetic vascular transduction was blunted (0.10 ± 0.05 vs. 0.36 ± 0.47 units a.u.(-1) min(-1); P < 0.01), and both renin (supine: 27.9 ± 6.2 vs. 14.2 ± 8.7 pg ml(-1), P < 0.01) and aldosterone (supine: 16.7 ± 14.1 vs. 7.7 ± 6.8 ng ml(-1), P = 0.05) were higher during EARLY than PRE. These results suggest that sympathetic activation is a common characteristic of early pregnancy in humans despite reduced diastolic pressure and total peripheral resistance. These observations challenge conventional thinking about blood pressure regulation during pregnancy, showing marked sympathetic activation occurring within the first few weeks of conception, and may provide the substrate for pregnancy induced cardiovascular complications.
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Affiliation(s)
- Sara S Jarvis
- Institute for Exercise and Environmental Medicine, 7232 Greenville Avenue, Suite 435, Dallas, TX 75231, USA
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13
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Young CN, Davisson RL. In vivo assessment of neurocardiovascular regulation in the mouse: principles, progress, and prospects. Am J Physiol Heart Circ Physiol 2011; 301:H654-62. [PMID: 21705676 DOI: 10.1152/ajpheart.00355.2011] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
A growing body of evidence indicates that a number of common complex diseases, including hypertension, heart failure, and obesity, are characterized by alterations in central neurocardiovascular regulation. However, our understanding of how changes within the central nervous system contribute to the development and progression of these and other diseases remains unclear. As with many areas of cardiovascular research, the mouse has emerged as a key species for investigations of neuroregulatory processes because of its amenability to highly specific genetic manipulations. In parallel with the development of increasingly sophisticated murine models has come the miniaturization and advancement in methodologies for in vivo assessment of neurocardiovascular end points in the mouse. The following brief review will focus on a number of key direct and indirect experimental approaches currently in use, including measurement of arterial blood pressure, assessment of cardiovascular autonomic control, and evaluation of arterial baroreflex function. The advantages and limitations of each methodology are highlighted to allow for a critical evaluation by the reader when considering these approaches.
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Affiliation(s)
- Colin N Young
- Biomedical Sciences, College of Veterinary Medicine, Cornell University, Ithaca, New York 14853-6401, USA.
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Davern PJ, Chen D, Head GA, Chavez CA, Walther T, Mayorov DN. Role of Angiotensin II Type 1A Receptors in Cardiovascular Reactivity and Neuronal Activation After Aversive Stress in Mice. Hypertension 2009; 54:1262-8. [DOI: 10.1161/hypertensionaha.109.139741] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
We determined whether genetic deficiency of angiotensin II Type 1A (AT
1A
) receptors in mice results in altered neuronal responsiveness and reduced cardiovascular reactivity to stress. Telemetry devices were used to measure mean arterial pressure, heart rate, and activity. Before stress, lower resting mean arterial pressure was recorded in AT
1A
−/−
(85±2 mm Hg) than in AT
1A
+/+
(112±2 mm Hg) mice; heart rate was not different between groups. Cage-switch stress for 90 minutes elevated blood pressure by +24±2 mm Hg in AT
1A
+/+
and +17±2 mm Hg in AT
1A
−/−
mice (
P
<0.01), and heart rate increased by +203±9 bpm in AT
1A
+/+
and +121±9 bpm in AT
1A
−/−
mice (
P
<0.001). Locomotor activation was less in AT
1A
−/−
(3.0±0.4 U) than in AT
1A
+/+
animals (6.0±0.4 U), but differences in blood pressure and heart rate persisted during nonactive periods. In contrast to wild-type mice, spontaneous baroreflex sensitivity was not inhibited by stress in AT
1A
−/−
mice. After cage-switch stress, c-Fos immunoreactivity was less in the paraventricular (
P
<0.001) and dorsomedial (
P
=0.001) nuclei of the hypothalamus and rostral ventrolateral medulla (
P
<0.001) in AT
1A
−/−
compared with AT
1A
+/+
mice. Conversely, greater c-Fos immunoreactivity was observed in the medial nucleus of the amygdala, caudal ventrolateral medulla, and nucleus of the solitary tract (
P
<0.001) of AT
1A
−/−
compared with AT
1A
+/+
mice. Greater activation of the amygdala suggests that AT
1A
receptors normally inhibit the degree of stress-induced anxiety, whereas the lesser activation of the hypothalamus and rostral ventrolateral medulla suggests that AT
1A
receptors play a key role in autonomic cardiovascular reactions to acute aversive stress, as well as for stress-induced inhibition of the baroreflex.
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Affiliation(s)
- Pamela J. Davern
- From the Baker IDI Heart and Diabetes Institute (P.J.D., G.A.H.), Melbourne, Victoria, Australia; Departments of Physiology (D.C.) and Pharmacology (C.A.C., D.N.M.), University of Melbourne, Victoria, Australia; Centre for Biomedical Sciences (T.W.), Hull York Medical School, University of Hull, Hull, United Kingdom; Excellence Cluster Cardio-Pulmonary System (T.W.), Justus-Liebig-Universität Giessen, Giessen, Germany
| | - Daian Chen
- From the Baker IDI Heart and Diabetes Institute (P.J.D., G.A.H.), Melbourne, Victoria, Australia; Departments of Physiology (D.C.) and Pharmacology (C.A.C., D.N.M.), University of Melbourne, Victoria, Australia; Centre for Biomedical Sciences (T.W.), Hull York Medical School, University of Hull, Hull, United Kingdom; Excellence Cluster Cardio-Pulmonary System (T.W.), Justus-Liebig-Universität Giessen, Giessen, Germany
| | - Geoffrey A. Head
- From the Baker IDI Heart and Diabetes Institute (P.J.D., G.A.H.), Melbourne, Victoria, Australia; Departments of Physiology (D.C.) and Pharmacology (C.A.C., D.N.M.), University of Melbourne, Victoria, Australia; Centre for Biomedical Sciences (T.W.), Hull York Medical School, University of Hull, Hull, United Kingdom; Excellence Cluster Cardio-Pulmonary System (T.W.), Justus-Liebig-Universität Giessen, Giessen, Germany
| | - Carolina A. Chavez
- From the Baker IDI Heart and Diabetes Institute (P.J.D., G.A.H.), Melbourne, Victoria, Australia; Departments of Physiology (D.C.) and Pharmacology (C.A.C., D.N.M.), University of Melbourne, Victoria, Australia; Centre for Biomedical Sciences (T.W.), Hull York Medical School, University of Hull, Hull, United Kingdom; Excellence Cluster Cardio-Pulmonary System (T.W.), Justus-Liebig-Universität Giessen, Giessen, Germany
| | - Thomas Walther
- From the Baker IDI Heart and Diabetes Institute (P.J.D., G.A.H.), Melbourne, Victoria, Australia; Departments of Physiology (D.C.) and Pharmacology (C.A.C., D.N.M.), University of Melbourne, Victoria, Australia; Centre for Biomedical Sciences (T.W.), Hull York Medical School, University of Hull, Hull, United Kingdom; Excellence Cluster Cardio-Pulmonary System (T.W.), Justus-Liebig-Universität Giessen, Giessen, Germany
| | - Dmitry N. Mayorov
- From the Baker IDI Heart and Diabetes Institute (P.J.D., G.A.H.), Melbourne, Victoria, Australia; Departments of Physiology (D.C.) and Pharmacology (C.A.C., D.N.M.), University of Melbourne, Victoria, Australia; Centre for Biomedical Sciences (T.W.), Hull York Medical School, University of Hull, Hull, United Kingdom; Excellence Cluster Cardio-Pulmonary System (T.W.), Justus-Liebig-Universität Giessen, Giessen, Germany
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15
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Xie C, Wang DH. Ablation of transient receptor potential vanilloid 1 abolishes endothelin-induced increases in afferent renal nerve activity: mechanisms and functional significance. Hypertension 2009; 54:1298-305. [PMID: 19858408 DOI: 10.1161/hypertensionaha.109.132167] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Endothelin 1 (ET-1) and its receptors, ETA and ETB, play important roles in regulating renal function and blood pressure, and these components are expressed in sensory nerves. Activation of transient receptor potential vanilloid (TRPV) 1 channels expressed in sensory nerves innervating the renal pelvis enhances afferent renal nerve activity (ARNA), diuresis, and natriuresis. We tested the hypothesis that ET-1 increases ARNA via activation of ETB, whereas ETA counterbalances ETB in wild-type (WT) but not TRPV1-null mutant mice. ET-1 alone or with BQ123, an ETA antagonist, perfused into the left renal pelvis increased ipsilateral ARNA in WT but not in TRPV1-null mutant mice, and ARNA increases were greater in the latter. [Ala1, 3,11,15]-endothelin 1, an ETB agonist, increased ARNA that was greater than that induced by ET-1 in WT mice only. [Ala1, 3,11,15]-endothelin 1-induced increases in ARNA were abolished by chelerythrine, a protein kinase C inhibitor, but not by H89, a protein kinase A inhibitor. Chelerythrine, H89, and BQ788, an ETB antagonist, did not affect ARNA triggered by capsaicin in WT mice. Substance P release from the renal pelvis was increased by [Ala1, 3,11,15]-endothelin 1 in WT mice only, and the increase was abolished by chelerythrine but not by H89. Chelerythrine, H89, and BQ788 did not affect capsaicin-induced substance P release. Our data show that ET1 increases ARNA via activation of ETB, whereas ETA counterbalances ETB in WT but not in TRPV1-null mutant mice, suggesting that TRPV1 mediates ETB-dependent increases in ARNA, diuresis, and natriuresis possibly via the protein kinase C pathway.
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Affiliation(s)
- Chaoqin Xie
- Department of Medicine, Michigan State University, B338 Clinical Center, East Lansing, MI 48823, USA
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16
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Gava AL, Peotta VA, Cabral AM, Vasquez EC, Meyrelles SS. Overexpression of eNOS prevents the development of renovascular hypertension in mice. Can J Physiol Pharmacol 2008; 86:458-64. [PMID: 18641695 DOI: 10.1139/y08-044] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Gene therapy has become an important tool for understanding several cardiovascular diseases. In the present study we investigated the effects of endothelial nitric oxide synthase (eNOS) overexpression on renovascular hypertension. Experiments were carried out in C57BL/6 mice randomly assigned to either a two-kidney one-clip (2K1C) hypertension group or a sham-operated group. At the same time surgery was carried out, both 2K1C and sham mice received an intravenous injection of recombinant adenovirus expressing the functional gene eNOS or the reporter gene beta-galactosidase (beta-gal). Fourteen days later, arterial pressure, baroreflex sensitivity, and cardiac sympathetic and parasympathetic tone were evaluated in conscious mice. Measurement of mean arterial pressure showed arterial hypertension in 2K1C-betagal mice compared with sham-betagal mice (121 +/- 3 vs. 96 +/- 2 mm Hg, p < 0.01), which was prevented by eNOS overexpression (2K1C-eNOS 100 +/- 4 vs. sham-eNOS 99 +/- 3 mm Hg). Linear regression analysis of the reflex tachycardia response to sodium nitroprusside-induced hypotension showed that baroreflex sensitivity was significantly attenuated in 2K1C-betagal mice (5.8 +/- 0.5 vs. sham-betagal 8.0 +/- 0.8 beats.min-1 x mm Hg-1, p < 0.05), but this decrease was not prevented by eNOS overexpression (2K1C-eNOS 7.2 +/- 0.5 vs. sham-eNOS 8.8 +/- 0.7 beats x min-1 x mm Hg-1, p < 0.05). The cardiac sympathetic tone was augmented and the vagal tone was reduced in 2K1C-betagal (152 +/- 17 and 45 +/- 12 beats.min-1, respectively) compared with sham-betagal mice (112 +/- 6 and 89 +/- 7 beats.min-1, respectively), and similar results were observed in 2K1C-eNOS mice compared with sham-eNOS. The data indicate that eNOS overexpression was able to prevent the development of 2K1C renovascular hypertension in mice, without affecting other characteristic cardiovascular dysfunctions.
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Affiliation(s)
- Agata L Gava
- Laboratory of Transgenes and Cardiovascular Control, Physiological Sciences Graduate Program, Health Sciences Center, Federal University of Espirito Santo, Avenida. Marechal Campos 1468, Vitoria, ES 29043-900, Brazil
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17
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Matsukawa T, Miyamoto T. Does infusion of ANG II increase muscle sympathetic nerve activity in patients with primary aldosteronism? Am J Physiol Regul Integr Comp Physiol 2008; 294:R1873-9. [PMID: 18367653 DOI: 10.1152/ajpregu.00471.2007] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Patients with primary aldosteronism (PA) were shown to have suppressed muscle sympathetic nerve activity (MSNA) in our previous study. Although baroreflex inhibition probably accounts in part for this reduced MSNA in PA, we hypothesized that the lowered activity of the renin-angiotensin system in PA may also contribute to the suppressed SNA. We recorded MSNA in 9 PA and 16 age-matched normotensive controls (NC). In PA, the resting mean blood pressure (MBP) and serum sodium concentrations were increased, and MSNA was reduced. We examined the effects of infusion of a high physiological dose of ANG II (5.0 ng.kg(-1).min(-1)) on MSNA in 6 of 9 PA and 9 of 16 NC. Infusion of ANG II caused a greater pressor response in PA than NC, but, in spite of the greater increase in pressure, MSNA increased in PA, whereas it decreased in NC. Simultaneous infusion of nitroprusside and ANG II, to maintain central venous pressure at the baseline level and reduce the elevation in MBP induced by ANG II, caused significantly greater increases in MSNA in PA than in NC. Baroreflex sensitivity of heart rate, estimated during phenylephrine infusions, was reduced in PA, but baroreflex sensitivity of MSNA was unchanged in PA compared with NC. All the abnormalities in PA were eliminated following unilateral adrenalectomy. In conclusion, the suppressed SNA in PA depends in part on the low level of ANG II in these patients.
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Affiliation(s)
- Toshiyoshi Matsukawa
- Laboratory of Behavioral Neuroscience, Department of Chemical and Biological Sciences, Faculty of Science, Japan Women's University, 2-8-1 Mejirodai, Bunkyoku, Tokyo.
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18
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Peotta VA, Gava AL, Vasquez EC, Meyrelles SS. Evaluation of baroreflex control of heart rate in renovascular hypertensive mice. Can J Physiol Pharmacol 2007; 85:761-6. [PMID: 17901885 DOI: 10.1139/y07-067] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The objective of the present study was to evaluate the baroreflex and the autonomic control of heart rate (HR) in renovascular hypertensive mice. Experiments were carried out in conscious C57BL/6 (n = 16) mice 28 days after a 2-kidney 1-clip procedure (2K1C mice) or a sham operation (sham mice). Baroreflex sensitivity was evaluated by measuring changes in heart rate (HR) in response to increases or decreases in mean arterial pressure (MAP) induced by phenylephrine or sodium nitroprusside. Cardiac autonomic tone was determined by use of atropine and atenolol. Basal HR and MAP were significantly higher in 2K1C mice than in sham mice. The reflex tachycardia induced by decreases in MAP was greatly attenuated in 2K1C mice compared with sham mice. Consequently, the baroreflex sensitivity was greatly decreased (2.2 +/- 0.4 vs. 4.4 +/- 0.3 beats x min(-1) x mmHg(-1)) in hypertensive mice compared with sham mice. The reflex bradycardia induced by increases in MAP and the baroreflex sensitivity were similar in both groups. Evaluation of autonomic control of HR showed an increased sympathetic tone and a tendency to a decreased vagal tone in 2K1C mice compared with that in sham mice. 2K1C hypertension in mice is accompanied by resting tachycardia, increased predominance of the cardiac sympathetic tone over the cardiac vagal tone, and impairment of baroreflex sensitivity.
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Affiliation(s)
- Veronica A Peotta
- Laboratory of Transgenes and Cardiovascular Control, Physiological Sciences Graduate Program, Health Sciences Center, Federal University of Espirito Santo, Avenida Marechal Campos 1468, Vitoria, ES 29042-755, Brazil
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19
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Hercule HC, Tank J, Plehm R, Wellner M, da Costa Goncalves AC, Gollasch M, Diedrich A, Jordan J, Luft FC, Gross V. Regulator of G protein signalling 2 ameliorates angiotensin II-induced hypertension in mice. Exp Physiol 2007; 92:1014-22. [PMID: 17644703 DOI: 10.1113/expphysiol.2007.038240] [Citation(s) in RCA: 55] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Angiotensin II (Ang II) activates signalling pathways predominantly through the G-protein-coupled Ang II type 1 receptor (AT(1)R). The regulator of G protein signalling 2 (RGS2) is a negative G protein regulator. We hypothesized that RGS2 deletion changes blood pressure regulation by increasing the response to Ang II. To address this issue, we infused Ang II (0.5 mg kg(-1) day(-1)) chronically into conscious RGS2-deleted (RGS2(-/-)) and wild-type (RGS2(+/+)) mice, measured mean arterial blood pressure and heart rate (HR) with telemetry and assessed vasoreactivity and gene expression of AT(1A), AT(1B) and AT(2) receptors. Angiotensin II infusion increased blood pressure more in RGS2(-/-) than in RGS2(+/+) mice, while HR was not different between the groups, indicating a resetting of the baroreceptor reflex. Urinary catecholamine excretion was similar in Ang II-infused RGS2(-/-) and RGS2(+/+) mice, indicating a minor role of sympathetic tone for blood pressure differences. Myogenic tone and vasoreactivity in response to Ang II, endothelin-1 and phenylephrine were increased in isolated renal interlobar arterioles of RGS2(-/-) mice compared with RGS2(+/+) mice. The AT(1A), AT(1B) and AT(2) receptor gene expression was not different between RGS2(-/-) and RGS2(+/+) mice. Our findings suggest that RGS2 deletion promotes Ang II-dependent hypertension primarily through an increase of myogenic tone and vasoreactivity, probably by sensitization of AT(1) receptors.
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MESH Headings
- Angiotensin II/physiology
- Animals
- Arterioles/drug effects
- Arterioles/physiology
- Baroreflex/drug effects
- Baroreflex/physiology
- Blood Pressure/drug effects
- Blood Pressure/genetics
- Blood Pressure/physiology
- Disease Models, Animal
- Endothelin-1/physiology
- Epinephrine/urine
- Heart Rate/drug effects
- Heart Rate/physiology
- Hypertension/physiopathology
- Male
- Mice
- Mice, Knockout
- Norepinephrine/urine
- Phenylephrine/pharmacology
- RGS Proteins/genetics
- RGS Proteins/physiology
- Receptor, Angiotensin, Type 1/genetics
- Receptor, Angiotensin, Type 1/physiology
- Receptor, Angiotensin, Type 2/genetics
- Receptor, Angiotensin, Type 2/physiology
- Vasoconstriction/drug effects
- Vasoconstriction/physiology
- Vasoconstrictor Agents/pharmacology
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20
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Chen Y, Oroszi TL, Morris M. Salt consumption increases blood pressure and abolishes the light/dark rhythm in angiotensin AT1a receptor deficient mice. Physiol Behav 2006; 88:95-100. [PMID: 16643970 DOI: 10.1016/j.physbeh.2006.03.008] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2005] [Revised: 02/23/2006] [Accepted: 03/08/2006] [Indexed: 11/20/2022]
Abstract
Experiments were performed to study the role of angiotensin (Ang) AT1a receptors in dietary sodium-induced changes in blood pressure (BP). We measured light/dark rhythms in BP, heart rate (HR) and drinking behavior in Ang AT1a deficient (AT1a -/-) and wild type (AT1a +/+) mice with arterial telemetric catheters. Mice were given ad libitum access to a high salt diet (8% NaCl, HSD for 8 days) and tap water. The major finding was that the Ang AT1a -/- mice showed enhanced sodium sensitivity. This was seen by a greater percentage increase in BP (+21% vs. +12%) and an earlier onset of BP change (increase on day 5 vs. day 8) in AT1a -/- vs. AT1a +/+. The normal light/dark BP rhythm was abolished in AT1a -/- after 5 days of HSD. HSD produced an increase in water intake (drinking activity and volume consumed) in both groups with no difference in the percentage increase or the light/dark drinking rhythm. HSD produced no changes in plasma osmolality, hematocrit or body weight in either group. Evidence shows that a deficiency of Ang AT1a receptors results in an enhancement in sodium sensitivity along with a disruption of the normal light/dark BP rhythm. The data combined with previous findings suggests that activation of other components of the renin angiotensin system and/or sympathetic pathways may be responsible for the cardiovascular changes in AT1a deficient mice.
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Affiliation(s)
- Yanfang Chen
- Department of Pharmacology and Toxicology, Boonshoft School of Medicine, Wright State University School, Dayton, OH 45450, USA.
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21
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Campos LA, Iliescu R, Fontes MAP, Schlegel WP, Bader M, Baltatu OC. Enhanced isoproterenol-induced cardiac hypertrophy in transgenic rats with low brain angiotensinogen. Am J Physiol Heart Circ Physiol 2006; 291:H2371-6. [PMID: 16731636 DOI: 10.1152/ajpheart.01145.2005] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
We have previously shown that a permanent deficiency in the brain renin-angiotensin system (RAS) may increase the sensitivity of the baroreflex control of heart rate. In this study we aimed at studying the involvement of the brain RAS in the cardiac reactivity to the beta-adrenoceptor (beta-AR) agonist isoproterenol (Iso). Transgenic rats with low brain angiotensinogen (TGR) were used. In isolated hearts, Iso induced a significantly greater increase in left ventricular (LV) pressure and maximal contraction (+dP/dt(max)) in the TGR than in the Sprague-Dawley (SD) rats. LV hypertrophy induced by Iso treatment was significantly higher in TGR than in SD rats (in g LV wt/100 g body wt, 0.28 +/- 0.004 vs. 0.24 +/- 0.004, respectively). The greater LV hypertrophy in TGR rats was associated with more pronounced downregulation of beta-AR and upregulation of LV beta-AR kinase-1 mRNA levels compared with those in SD rats. The decrease in the heart rate (HR) induced by the beta-AR antagonist metoprolol in conscious rats was significantly attenuated in TGR compared with SD rats (-9.9 +/- 1.7% vs. -18.1 +/- 1.5%), whereas the effect of parasympathetic blockade by atropine on HR was similar in both strains. These results indicate that TGR are more sensitive to beta-AR agonist-induced cardiac inotropic response and hypertrophy, possibly due to chronically low sympathetic outflow directed to the heart.
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Affiliation(s)
- Luciana A Campos
- Dept. of Physiology and Biophysics, The Center for Excellence in Cardiovascular-Renal Research, Univ. of Mississippi Medical Center, 2500 N. State St., Jackson, MS 39216-4505, USA
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22
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Ma X, Zhang HJ, Whiteis CA, Tian X, Davisson RL, Kregel KC, Abboud FM, Chapleau MW. NAD(P)H oxidase-induced oxidative stress in sympathetic ganglia of apolipoprotein E deficient mice. Auton Neurosci 2006; 126-127:285-91. [PMID: 16584925 DOI: 10.1016/j.autneu.2006.02.005] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2005] [Accepted: 02/03/2006] [Indexed: 10/24/2022]
Abstract
Superoxide anion (O2*-) is increased throughout the arterial wall in atherosclerosis. The oxidative stress contributes to lesion formation and vascular dysfunction. In the present study, we tested the hypothesis that NAD(P)H oxidase-derived O2*- is increased in nodose sensory ganglia and sympathetic ganglia of apolipoprotein E deficient (apoE-/-) mice, an established animal model of atherosclerosis. O2*- measured ex vivo by L-012-enhanced chemiluminescence was increased by 79+/-17% in whole sympathetic ganglia from apoE-/- mice (n=5) compared with sympathetic ganglia from control mice (n=5) (P<0.05). In contrast, O2*- was not elevated in nodose ganglia from apoE-/- mice. Dihydroethidium staining confirmed the selective increase in O2*- in sympathetic ganglia of apoE-/- mice, and revealed the contribution of both neurons and non-neuronal cells to the O2*- generation. We investigated the enzymatic source of increased O2*- in sympathetic ganglia of apoE-/- mice. The mRNA expression of gp91phox, p22phox, p67phox, and p47phox subunits of NAD(P)H oxidase measured by real time RT-PCR was increased approximately 3-4 fold in sympathetic ganglia of apoE-/- mice (n=5) compared with control ganglia (n=5). NADPH oxidase activity measured by lucigenin chemiluminescence was increased by 68+/-12% in homogenates of sympathetic ganglia from apoE-/- mice (n=7) compared with control ganglia (n=7) (P<0.05). The results identify sympathetic ganglia as a novel site of oxidative stress in atherosclerosis, and suggest that upregulation of NAD(P)H oxidase is the source of increased O2*- generation. We speculate that oxidative stress in sympathetic ganglia may contribute to impaired baroreflex control of sympathetic nerve activity.
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Affiliation(s)
- Xiuying Ma
- The Cardiovascular Center and Department of Internal Medicine, The University of Iowa, and The Veterans Affairs Medical Center, Iowa City, IA 52246, USA.
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23
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Zheng S, Noonan WT, Metreveli NS, Coventry S, Kralik PM, Carlson EC, Epstein PN. Development of late-stage diabetic nephropathy in OVE26 diabetic mice. Diabetes 2004; 53:3248-57. [PMID: 15561957 DOI: 10.2337/diabetes.53.12.3248] [Citation(s) in RCA: 129] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
OVE26 mice are a transgenic model of severe early-onset type 1 diabetes. These mice develop diabetes within the first weeks of life and can survive well over a year with no insulin treatment, and they maintain near normal body weight. To determine whether OVE26 mice provide a valuable model of chronic diabetic nephropathy (DN), OVE26 diabetic mice were compared with their nondiabetic littermates for functional and structural characteristics of DN. OVE26 mice exhibited pronounced polyuria and significant albuminuria by 2 months of age (305 microg/24 h in OVE26 vs. 20 microg/24 h in controls). Albumin excretion rate increased progressively with age and exceeded 15,000 microg/24 h at 9 months of age. The profound loss of albumin led to hypoalbuminemia in some diabetic animals. Albuminuria coincided with an elevation in blood pressure as measured by tail cuff. The glomerular filtration rate (GFR) in OVE26 mice measured using fluorescein isothiocynate inulin clearance demonstrated that GFR increased significantly from 2 to 3 months of age and then decreased significantly from 5 to 9 months. GFR in 9-month-old diabetic mice was significantly lower than that of 9-month-old control mice. The decline in GFR coincided with a significant increase in renal vascular resistance. Structural studies showed an almost twofold increase in kidney weight between 2 and 5 months. Diabetic mice also showed progressively enlarged glomeruli and expanded mesangium with diffuse and nodular expansion of mesangial matrix. Tubulointerstitial fibrosis was also observed in these mice. Glomerular basement membrane was thickened in OVE26 mice. In summary, OVE26 mice demonstrate that most of the characteristics of human DN can be produced by chronic hyperglycemia in a murine model. This model will be useful for improved understanding and treatment of DN.
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Affiliation(s)
- Shirong Zheng
- Department of Pediatrics, University of Louisville School of Medicine, Louisville, KY 40202, USA
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