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Yang H, Tenorio Lopes L, Barioni NO, Roeske J, Incognito AV, Baker J, Raj SR, Wilson RJA. The molecular makeup of peripheral and central baroreceptors: stretching a role for Transient Receptor Potential (TRP), Epithelial Sodium Channel (ENaC), Acid Sensing Ion Channel (ASIC), and Piezo channels. Cardiovasc Res 2022; 118:3052-3070. [PMID: 34734981 DOI: 10.1093/cvr/cvab334] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/18/2021] [Revised: 09/27/2021] [Accepted: 10/29/2021] [Indexed: 12/16/2022] Open
Abstract
The autonomic nervous system maintains homeostasis of cardiovascular, respiratory, gastrointestinal, urinary, immune, and thermoregulatory function. Homeostasis involves a variety of feedback mechanisms involving peripheral afferents, many of which contain molecular receptors sensitive to mechanical deformation, termed mechanosensors. Here, we focus on the molecular identity of mechanosensors involved in the baroreflex control of the cardiovascular system. Located within the walls of the aortic arch and carotid sinuses, and/or astrocytes in the brain, these mechanosensors are essential for the rapid moment-to-moment feedback regulation of blood pressure (BP). Growing evidence suggests that these mechanosensors form a co-existing system of peripheral and central baroreflexes. Despite the importance of these molecules in cardiovascular disease and decades of research, their precise molecular identity remains elusive. The uncertainty surrounding the identity of these mechanosensors presents a major challenge in understanding basic baroreceptor function and has hindered the development of novel therapeutic targets for conditions with known arterial baroreflex impairments. Therefore, the purpose of this review is to (i) provide a brief overview of arterial and central baroreflex control of BP, (ii) review classes of ion channels currently proposed as the baroreflex mechanosensor, namely Transient Receptor Potential (TRP), Epithelial Sodium Channel (ENaC), Acid Sensing Ion Channel (ASIC), and Piezo, along with additional molecular candidates that serve mechanotransduction in other organ systems, and (iii) summarize the potential clinical implications of impaired baroreceptor function in the pathophysiology of cardiovascular disease.
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Affiliation(s)
- Hannah Yang
- Department of Physiology and Pharmacology, Cumming School of Medicine, University of Calgary, 3330 Hospital Dr. N.W., Calgary, AB T2N4N1, Canada.,Hotchkiss Brain Institute, Cumming School of Medicine, University of Calgary, 3330 Hospital Dr. N.W., Calgary, AB T2N4N1, Canada.,Alberta Children's Hospital Research Institute, Cumming School of Medicine, University of Calgary, 3330 Hospital Dr. N.W., Calgary, AB T2N4N1, Canada
| | - Luana Tenorio Lopes
- Department of Physiology and Pharmacology, Cumming School of Medicine, University of Calgary, 3330 Hospital Dr. N.W., Calgary, AB T2N4N1, Canada.,Hotchkiss Brain Institute, Cumming School of Medicine, University of Calgary, 3330 Hospital Dr. N.W., Calgary, AB T2N4N1, Canada.,Alberta Children's Hospital Research Institute, Cumming School of Medicine, University of Calgary, 3330 Hospital Dr. N.W., Calgary, AB T2N4N1, Canada
| | - Nicole O Barioni
- Department of Physiology and Pharmacology, Cumming School of Medicine, University of Calgary, 3330 Hospital Dr. N.W., Calgary, AB T2N4N1, Canada.,Hotchkiss Brain Institute, Cumming School of Medicine, University of Calgary, 3330 Hospital Dr. N.W., Calgary, AB T2N4N1, Canada.,Alberta Children's Hospital Research Institute, Cumming School of Medicine, University of Calgary, 3330 Hospital Dr. N.W., Calgary, AB T2N4N1, Canada
| | - Jamie Roeske
- Department of Physiology and Pharmacology, Cumming School of Medicine, University of Calgary, 3330 Hospital Dr. N.W., Calgary, AB T2N4N1, Canada.,Hotchkiss Brain Institute, Cumming School of Medicine, University of Calgary, 3330 Hospital Dr. N.W., Calgary, AB T2N4N1, Canada.,Alberta Children's Hospital Research Institute, Cumming School of Medicine, University of Calgary, 3330 Hospital Dr. N.W., Calgary, AB T2N4N1, Canada
| | - Anthony V Incognito
- Department of Physiology and Pharmacology, Cumming School of Medicine, University of Calgary, 3330 Hospital Dr. N.W., Calgary, AB T2N4N1, Canada.,Hotchkiss Brain Institute, Cumming School of Medicine, University of Calgary, 3330 Hospital Dr. N.W., Calgary, AB T2N4N1, Canada.,Alberta Children's Hospital Research Institute, Cumming School of Medicine, University of Calgary, 3330 Hospital Dr. N.W., Calgary, AB T2N4N1, Canada
| | - Jacquie Baker
- Department of Cardiac Sciences, Libin Cardiovascular Institute, Cumming School of Medicine, University of Calgary, 3330 Hospital Dr. N.W., Calgary, AB T2N4N1, Canada
| | - Satish R Raj
- Department of Cardiac Sciences, Libin Cardiovascular Institute, Cumming School of Medicine, University of Calgary, 3330 Hospital Dr. N.W., Calgary, AB T2N4N1, Canada
| | - Richard J A Wilson
- Department of Physiology and Pharmacology, Cumming School of Medicine, University of Calgary, 3330 Hospital Dr. N.W., Calgary, AB T2N4N1, Canada.,Hotchkiss Brain Institute, Cumming School of Medicine, University of Calgary, 3330 Hospital Dr. N.W., Calgary, AB T2N4N1, Canada.,Alberta Children's Hospital Research Institute, Cumming School of Medicine, University of Calgary, 3330 Hospital Dr. N.W., Calgary, AB T2N4N1, Canada
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Hong J, Adam RJ, Gao L, Hahka T, Xia Z, Wang D, Nicholas TA, Zucker IH, Lisco SJ, Wang H. Macrophage activation in stellate ganglia contributes to lung injury-induced arrhythmogenesis in male rats. Acta Physiol (Oxf) 2021; 232:e13657. [PMID: 33817984 DOI: 10.1111/apha.13657] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2021] [Revised: 02/21/2021] [Accepted: 04/01/2021] [Indexed: 12/21/2022]
Abstract
AIM Patients suffering from acute lung injury (ALI) are at high risk of developing cardiac arrhythmias. We hypothesized that stellate ganglia (SG) neural inflammation contributes to ALI-induced arrhythmia. METHODS We created an ALI rat model using a single tracheal instillation of bleomycin (2.5 mg/kg), with saline as a sham control. We recorded ECGs by implanted radiotelemetry in male bleomycin and sham rats treated with and without oral minocycline (20 mg/kg/d), an anti-inflammatory drug that inhibits microglia/macrophage activation. The SG neuronal excitability was assessed by electrophysiology experiments. RESULTS ECG data showed that bleomycin-exposed rats exhibited significantly more spontaneous premature ventricular contractions (PVCs) from 1- to 3-week post-induction compared with sham rats, which was mitigated by chronic oral administration of minocycline. The bleomycin-exposed rats displayed a robust increase in both the number of Iba1-positive macrophages and protein expression of interferon regulatory factor 8 in the SG starting as early at 1-week post-exposure and lasted for at least 4 weeks, which was largely attenuated by minocycline. Heart rate variability analysis indicated autonomic imbalance during the first 2-week post-bleomycin, which was significantly attenuated by minocycline. Electrical stimulation of the decentralized SG triggered more PVCs in bleomycin-exposed rats than sham and bleomycin + minocycline rats. Patch-clamp data demonstrated enhanced SG neuronal excitability in the bleomycin-exposed rats, which was attenuated by minocycline. Co-culture of lipopolysaccharide (LPS)-pretreated macrophages with normal SG neurons enhanced SG neuronal excitability. CONCLUSION Macrophage activation in the SG contributes to arrhythmogenesis in bleomycin-induced ALI in male rats.
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Affiliation(s)
- Juan Hong
- Department of Anesthesiology University of Nebraska Medical Center Omaha NE USA
| | - Ryan J. Adam
- Department of Anesthesiology University of Nebraska Medical Center Omaha NE USA
- Department of Cellular and Integrative Physiology University of Nebraska Medical Center Omaha NE USA
| | - Lie Gao
- Department of Cellular and Integrative Physiology University of Nebraska Medical Center Omaha NE USA
| | - Taija Hahka
- Department of Anesthesiology University of Nebraska Medical Center Omaha NE USA
| | - Zhiqiu Xia
- Department of Anesthesiology University of Nebraska Medical Center Omaha NE USA
| | - Dong Wang
- Department of Pharmaceutical Sciences University of Nebraska Medical Center Omaha NE USA
| | - Thomas A. Nicholas
- Department of Anesthesiology University of Nebraska Medical Center Omaha NE USA
| | - Irving H. Zucker
- Department of Cellular and Integrative Physiology University of Nebraska Medical Center Omaha NE USA
| | - Steven J. Lisco
- Department of Anesthesiology University of Nebraska Medical Center Omaha NE USA
| | - Han‐Jun Wang
- Department of Anesthesiology University of Nebraska Medical Center Omaha NE USA
- Department of Cellular and Integrative Physiology University of Nebraska Medical Center Omaha NE USA
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Wang R, Lu Y, Gunasekar S, Zhang Y, Benson CJ, Chapleau MW, Sah R, Abboud FM. The volume-regulated anion channel (LRRC8) in nodose neurons is sensitive to acidic pH. JCI Insight 2017; 2:e90632. [PMID: 28289711 DOI: 10.1172/jci.insight.90632] [Citation(s) in RCA: 34] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
Abstract
The leucine rich repeat containing protein 8A (LRRC8A), or SWELL1, is an essential component of the volume-regulated anion channel (VRAC) that is activated by cell swelling and ionic strength. We report here for the first time to our knowledge its expression in a primary cell culture of nodose ganglia neurons and its localization in the soma, neurites, and neuronal membrane. We show that this neuronal VRAC/SWELL1 senses low external pH (pHo) in addition to hypoosmolarity. A robust sustained chloride current is seen in 77% of isolated nodose neurons following brief exposures to extracellular acid pH. Its activation involves proton efflux, intracellular alkalinity, and an increase in NOX-derived H2O2. The molecular identity of both the hypoosmolarity-induced and acid pHo-conditioned VRAC as LRRC8A (SWELL1) was confirmed by Cre-flox-mediated KO, shRNA-mediated knockdown, and CRISPR/Cas9-mediated LRRC8A deletion in HEK cells and in primary nodose neuronal cultures. Activation of VRAC by low pHo reduces neuronal injury during simulated ischemia and N-methyl-D-aspartate-induced (NMDA-induced) apoptosis. These results identify the VRAC (LRRC8A) as a dual sensor of hypoosmolarity and low pHo in vagal afferent neurons and define the mechanisms of its activation and its neuroprotective potential.
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Affiliation(s)
- Runping Wang
- Department of Internal Medicine.,Abboud Cardiovascular Research Center, University of Iowa, Iowa City, Iowa, USA
| | - Yongjun Lu
- Department of Internal Medicine.,Abboud Cardiovascular Research Center, University of Iowa, Iowa City, Iowa, USA
| | - Susheel Gunasekar
- Department of Internal Medicine.,Abboud Cardiovascular Research Center, University of Iowa, Iowa City, Iowa, USA
| | - Yanhui Zhang
- Department of Internal Medicine.,Abboud Cardiovascular Research Center, University of Iowa, Iowa City, Iowa, USA
| | - Christopher J Benson
- Department of Internal Medicine.,Abboud Cardiovascular Research Center, University of Iowa, Iowa City, Iowa, USA.,Veterans Affairs Medical Center, Iowa City, Iowa, USA
| | - Mark W Chapleau
- Department of Internal Medicine.,Abboud Cardiovascular Research Center, University of Iowa, Iowa City, Iowa, USA.,Veterans Affairs Medical Center, Iowa City, Iowa, USA.,Department of Molecular Physiology and Biophysics, University of Iowa, Iowa City, Iowa, USA
| | - Rajan Sah
- Department of Internal Medicine.,Abboud Cardiovascular Research Center, University of Iowa, Iowa City, Iowa, USA.,Department of Molecular Physiology and Biophysics, University of Iowa, Iowa City, Iowa, USA
| | - François M Abboud
- Department of Internal Medicine.,Abboud Cardiovascular Research Center, University of Iowa, Iowa City, Iowa, USA.,Department of Molecular Physiology and Biophysics, University of Iowa, Iowa City, Iowa, USA
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Lau OC, Shen B, Wong CO, Tjong YW, Lo CY, Wang HC, Huang Y, Yung WH, Chen YC, Fung ML, Rudd JA, Yao X. TRPC5 channels participate in pressure-sensing in aortic baroreceptors. Nat Commun 2016; 7:11947. [PMID: 27411851 PMCID: PMC4947175 DOI: 10.1038/ncomms11947] [Citation(s) in RCA: 56] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2015] [Accepted: 05/13/2016] [Indexed: 11/25/2022] Open
Abstract
Blood pressure is maintained within a normal physiological range by a sophisticated regulatory mechanism. Baroreceptors serve as a frontline sensor to detect the change in blood pressure. Nerve signals are then sent to the cardiovascular control centre in the brain in order to stimulate baroreflex responses. Here, we identify TRPC5 channels as a mechanical sensor in aortic baroreceptors. In Trpc5 knockout mice, the pressure-induced action potential firings in the afferent nerve and the baroreflex-mediated heart rate reduction are attenuated. Telemetric measurements of blood pressure demonstrate that Trpc5 knockout mice display severe daily blood pressure fluctuation. Our results suggest that TRPC5 channels represent a key pressure transducer in the baroreceptors and play an important role in maintaining blood pressure stability. Because baroreceptor dysfunction contributes to a variety of cardiovascular diseases including hypertension, heart failure and myocardial infarction, our findings may have important future clinical implications. The identity of mechanosensors within aortic baroreceptors that sense fluctuations in blood pressure is unclear. Here, Lau et al. show that a cation channel TRPC5 acts as a transducer of mechanical stimuli in aortic baroreceptor neurons in rodents.
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Affiliation(s)
- On-Chai Lau
- Li Ka Shing Institute of Health Sciences, Faculty of Medicine, The Chinese University of Hong Kong, Hong Kong, China.,School of Biomedical Sciences, Faculty of Medicine, The Chinese University of Hong Kong, Hong Kong, China
| | - Bing Shen
- Li Ka Shing Institute of Health Sciences, Faculty of Medicine, The Chinese University of Hong Kong, Hong Kong, China.,School of Biomedical Sciences, Faculty of Medicine, The Chinese University of Hong Kong, Hong Kong, China.,Department of Physiology, Anhui Medical University, Hefei 230032, China
| | - Ching-On Wong
- Li Ka Shing Institute of Health Sciences, Faculty of Medicine, The Chinese University of Hong Kong, Hong Kong, China.,School of Biomedical Sciences, Faculty of Medicine, The Chinese University of Hong Kong, Hong Kong, China
| | - Yung-Wui Tjong
- Li Ka Shing Institute of Health Sciences, Faculty of Medicine, The Chinese University of Hong Kong, Hong Kong, China.,School of Biomedical Sciences, Faculty of Medicine, The Chinese University of Hong Kong, Hong Kong, China
| | - Chun-Yin Lo
- Li Ka Shing Institute of Health Sciences, Faculty of Medicine, The Chinese University of Hong Kong, Hong Kong, China.,School of Biomedical Sciences, Faculty of Medicine, The Chinese University of Hong Kong, Hong Kong, China
| | - Hui-Chuan Wang
- School of Biomedical Sciences, Faculty of Medicine, The Chinese University of Hong Kong, Hong Kong, China
| | - Yu Huang
- Li Ka Shing Institute of Health Sciences, Faculty of Medicine, The Chinese University of Hong Kong, Hong Kong, China.,School of Biomedical Sciences, Faculty of Medicine, The Chinese University of Hong Kong, Hong Kong, China
| | - Wing-Ho Yung
- School of Biomedical Sciences, Faculty of Medicine, The Chinese University of Hong Kong, Hong Kong, China
| | - Yang-Chao Chen
- School of Biomedical Sciences, Faculty of Medicine, The Chinese University of Hong Kong, Hong Kong, China
| | - Man-Lung Fung
- Department of Physiology, University of Hong Kong, Hong Kong, China
| | - John Anthony Rudd
- School of Biomedical Sciences, Faculty of Medicine, The Chinese University of Hong Kong, Hong Kong, China
| | - Xiaoqiang Yao
- Li Ka Shing Institute of Health Sciences, Faculty of Medicine, The Chinese University of Hong Kong, Hong Kong, China.,School of Biomedical Sciences, Faculty of Medicine, The Chinese University of Hong Kong, Hong Kong, China
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5
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Mutolo D, Cinelli E, Iovino L, Pantaleo T, Bongianni F. Downregulation of the cough reflex by aclidinium and tiotropium in awake and anesthetized rabbits. Pulm Pharmacol Ther 2016; 38:1-9. [DOI: 10.1016/j.pupt.2016.04.001] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/26/2016] [Revised: 04/08/2016] [Accepted: 04/10/2016] [Indexed: 01/23/2023]
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6
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Meng Q, Fang P, Hu Z, Ling Y, Liu H. Mechanotransduction of trigeminal ganglion neurons innervating inner walls of rat anterior eye chambers. Am J Physiol Cell Physiol 2015; 309:C1-10. [PMID: 25904679 DOI: 10.1152/ajpcell.00028.2015] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2015] [Accepted: 04/20/2015] [Indexed: 11/22/2022]
Abstract
To address mechanoreceptive roles of trigeminal ganglion (TG) nerve endings in the inner walls of rat anterior eye chambers, we investigated the mechanotransduction process and mechanosensitive (MS) channel on somata of TG neurons innervating this area in vitro. Rat TG neurons innervating inner walls of anterior chambers were labeled by anterior chamber injection of 1,1'-dilinoleyl-3,3,3',3'-tetramethylindocarbocyanine, 4-chlorobenzenesulfonate (FAST DiI). The neuronal cell bodies were voltage clamped using a whole cell patch-clamp technique, while it was deformed by ejection of bath solution to verify mechanotransduction. Immunofluorescence staining was performed on sections of TG ganglia to determine the specific MS channel proteins. Mechanical stimuli induced MS currents in 55 out of 96 FAST DiI-labeled TG neurons. The MS currents exhibited mechanical intensity-dependent and clamp voltage-dependent characteristics. Mechanical stimulation further enhanced the membrane potential and increased the frequency of action potentials. Transient receptor potential ankyrin 1 (TRPA1), TRP vanilloid 4 (TRPV4), acid-sensing ion channel (ASIC) 2 and ASIC3 channel proteins were expressed in FAST DiI-labeled TG neurons. The inhibitory effect of HC-030031, a specific inhibitor of TRPA1, on MS currents demonstrated that TRPA1 was an essential MS channel protein. Taken together, our results show that mechanical stimuli induce MS currents via MS channels such as TRPA1 to trigger mechanotransduction in TG neurons innervating inner walls of anterior chambers. Our results indicate the existence of mechanoreceptive TG nerve endings in inner walls of anterior chambers. Whether the mechanoreceptive TG nerve endings play a role in intraocular pressure sensation warrants further investigation.
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Affiliation(s)
- Qingli Meng
- Department of Ophthalmology, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Hubei, China; and
| | - Peng Fang
- Department of Pharmacology, Tongji Medical College, Huazhong University of Science and Technology, Hubei, China
| | - Zhuangli Hu
- Department of Pharmacology, Tongji Medical College, Huazhong University of Science and Technology, Hubei, China
| | - Yun Ling
- Department of Ophthalmology, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Hubei, China; and
| | - Haixia Liu
- Department of Ophthalmology, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Hubei, China; and
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7
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Santana-Filho VJ, Davis GJ, Castania JA, Ma X, Salgado HC, Abboud FM, Fazan R, Chapleau MW. Autocrine/paracrine modulation of baroreceptor activity after antidromic stimulation of aortic depressor nerve in vivo. Auton Neurosci 2014; 180:24-31. [PMID: 24567955 DOI: 10.1016/j.autneu.2013.10.003] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Activation of the sensory nerve endings of non-myelinated C-fiber afferents evokes release of autocrine/paracrine factors that cause localized vasodilation, neurogenic inflammation, and modulation of sensory nerve activity. The aims of this study were to determine the effect of antidromic electrical stimulation on afferent baroreceptor activity in vivo, and investigate the role of endogenous prostanoids and hydrogen peroxide (H2O2) in mediating changes in nerve activity. Baroreceptor activity was recorded from the left aortic depressor nerve (ADN) in anesthetized rats before and after stimulating the ADN for brief (5–20 s) periods. The rostral end of the ADN was crushed or sectioned beforehand to prevent reflex changes in blood pressure. Antidromic stimulation of ADN using parameters that activate both myelinated A-fibers and non-myelinated C-fibers caused pronounced and long-lasting (> 1 min) inhibition of baroreceptor activity (n = 9, P < 0.05), with the magnitude and duration of inhibition dependent on the duration of the stimulation period (n = 5). Baroreceptor activity was only transiently inhibited after selective stimulation of A-fibers. The inhibition of activity after antidromic stimulation of A and C fibers was prolonged after administration of the cyclooxygenase inhibitor indomethacin (5 mg/kg, IV, n = 7) and abolished after administration of PEG-catalase (104 units/kg, IV, n = 7), an enzyme that catalyzes the decomposition of H2O2 to water and oxygen. The results demonstrate a long-lasting inhibition of baroreceptor activity after antidromic stimulation of ADN and suggest that endogenous prostanoids and H2O2 oppose and mediate the inhibition, respectively. These mechanisms may contribute to rapid baroreceptor resetting during acute hypertension and be engaged during chronic baroreceptor activation therapy in patients with hypertension.
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8
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Thomas CJ, Sharma AD, Woods RL. Do prostanoids or nitric oxide mediate sensitization of the von Bezold-Jarisch reflex by B-type natriuretic peptide? Clin Exp Pharmacol Physiol 2011; 38:410-5. [DOI: 10.1111/j.1440-1681.2011.05527.x] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
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9
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Li BY, Glazebrook P, Kunze DL, Schild JH. KCa1.1 channel contributes to cell excitability in unmyelinated but not myelinated rat vagal afferents. Am J Physiol Cell Physiol 2011; 300:C1393-403. [PMID: 21325638 DOI: 10.1152/ajpcell.00278.2010] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
High conductance calcium-activated potassium (BK(Ca)) channels can modulate cell excitability and neurotransmitter release at synaptic and afferent terminals. BK(Ca) channels are present in primary afferents of most, if not, all internal organs and are an intriguing target for pharmacological manipulation of visceral sensation. Our laboratory has a long-standing interest in the neurophysiological differences between myelinated and unmyelinated visceral afferent function. Here, we seek to determine whether there is a differential distribution of BK(Ca) channels in myelinated and unmyelinated vagal afferents. Immunocytochemistry studies with double staining for the BK-type K(Ca)1.1 channel protein and isolectin B4 (IB4), a reliable marker of unmyelinated peripheral afferents, reveal a pattern of IB4 labeling that strongly correlates with the expression of the K(Ca)1.1 channel protein. Measures of cell size and immunostaining intensity for K(Ca)1.1 and IB4 cluster into two statistically distinct (P < 0.05) populations of cells. Smaller diameter neurons most often presented with strong IB4 labeling and are presumed to be unmyelinated (n = 1,390) vagal afferents. Larger diameter neurons most often lacked or exhibited a very weak IB4 labeling and are presumed to be myelinated (n = 58) vagal afferents. Complimentary electrophysiological studies reveal that the BK(Ca) channel blockers charybdotoxin (ChTX) and iberiotoxin (IbTX) bring about a comparable elevation in excitability and action potential widening in unmyelinated neurons but had no effect on the excitability of myelinated vagal afferents. This study is the first to demonstrate using combined immunohistochemical and electrophysiological techniques that K(Ca)1.1 channels are uniquely expressed in unmyelinated C-type vagal afferents and do not contribute to the dynamic discharge characteristics of myelinated A-type vagal afferents. This unique functional distribution of BK-type K(Ca) channels may provide an opportunity for afferent selective pharmacological intervention across a wide range of visceral pathophysiologies, particularly those with a reflexogenic etiology and pain.
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Affiliation(s)
- Bai-Yan Li
- Dept. of Biomedical Engineering, Indiana University Purdue University, 723 W. Michigan St., Indianapolis, IN 46202, USA
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10
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Abstract
All animals use a sophisticated array of receptor proteins to sense their external and internal environments. Major advances have been made in recent years in understanding the molecular and genetic bases for sensory transduction in diverse modalities, indicating that both metabotropic and ionotropic pathways are important in sensory functions. Here, I review the historical background and recent advances in understanding the roles of a relatively newly discovered family of receptors, the degenerin/epithelial sodium channels (DEG/ENaC). These animal-specific cation channels show a remarkable sequence and functional diversity in different species and seem to exert their functions in diverse sensory modalities. Functions for DEG/ENaC channels have been implicated in mechanosensation as well as chemosensory transduction pathways. In spite of overall sequence diversity, all family members share a unique protein topology that includes just two transmembrane domains and an unusually large and highly structured extracellular domain, that seem to be essential for both their mechanical and chemical sensory functions. This review will discuss many of the recent discoveries and controversies associated with sensory function of DEG/ENaC channels in both vertebrate and invertebrate model systems, covering the role of family members in taste, mechanosensation, and pain.
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11
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Lu Y, Ma X, Sabharwal R, Snitsarev V, Morgan D, Rahmouni K, Drummond HA, Whiteis CA, Costa V, Price M, Benson C, Welsh MJ, Chapleau MW, Abboud FM. The ion channel ASIC2 is required for baroreceptor and autonomic control of the circulation. Neuron 2010; 64:885-97. [PMID: 20064394 DOI: 10.1016/j.neuron.2009.11.007] [Citation(s) in RCA: 150] [Impact Index Per Article: 10.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 11/02/2009] [Indexed: 12/18/2022]
Abstract
Arterial baroreceptors provide a neural sensory input that reflexly regulates the autonomic drive of circulation. Our goal was to test the hypothesis that a member of the acid-sensing ion channel (ASIC) subfamily of the DEG/ENaC superfamily is an important determinant of the arterial baroreceptor reflex. We found that aortic baroreceptor neurons in the nodose ganglia and their terminals express ASIC2. Conscious ASIC2 null mice developed hypertension, had exaggerated sympathetic and depressed parasympathetic control of the circulation, and a decreased gain of the baroreflex, all indicative of an impaired baroreceptor reflex. Multiple measures of baroreceptor activity each suggest that mechanosensitivity is diminished in ASIC2 null mice. The results define ASIC2 as an important determinant of autonomic circulatory control and of baroreceptor sensitivity. The genetic disruption of ASIC2 recapitulates the pathological dysautonomia seen in heart failure and hypertension and defines a molecular defect that may be relevant to its development.
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Affiliation(s)
- Yongjun Lu
- Department of Internal Medicine and Cardiovascular Research Center, University of Iowa, Iowa City, IA 52242, USA
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12
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Gautron L, Layé S. Neurobiology of inflammation-associated anorexia. Front Neurosci 2010; 3:59. [PMID: 20582290 PMCID: PMC2858622 DOI: 10.3389/neuro.23.003.2009] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2009] [Accepted: 12/16/2009] [Indexed: 12/23/2022] Open
Abstract
Compelling data demonstrate that inflammation-associated anorexia directly results from the action of pro-inflammatory factors, primarily cytokines and prostaglandins E2, on the nervous system. For instance, the aforementioned pro-inflammatory factors can stimulate the activity of peripheral sensory neurons, and induce their own de novo synthesis and release into the brain parenchyma and cerebrospinal fluid. Ultimately, it results in the mobilization of a specific neural circuit that shuts down appetite. The present article describes the different cell groups and neurotransmitters involved in inflammation-associated anorexia and examines how they interact with neural systems regulating feeding such as the melanocortin system. A better understanding of the neurobiological mechanisms underlying inflammation-associated anorexia will help to develop appetite stimulants for cancer and AIDS patients.
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Affiliation(s)
- Laurent Gautron
- The University of Texas Southwestern Medical Center Dallas, TX, USA
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13
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Darmani NA, Ray AP. Evidence for a re-evaluation of the neurochemical and anatomical bases of chemotherapy-induced vomiting. Chem Rev 2009; 109:3158-99. [PMID: 19522506 DOI: 10.1021/cr900117p] [Citation(s) in RCA: 84] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Affiliation(s)
- Nissar A Darmani
- Department of Basic Medical Sciences, College of Osteopathic Medicine of the Pacific, Western University of Health Sciences, Pomona, California 91766-1854, USA.
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14
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Delliaux S, Brerro-Saby C, Steinberg JG, Jammes Y. Reactive oxygen species and inflammatory mediators enhance muscle spindles mechanosensitivity in rats. Pflugers Arch 2008; 457:877-84. [PMID: 18846383 DOI: 10.1007/s00424-008-0554-x] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2008] [Revised: 07/03/2008] [Accepted: 07/03/2008] [Indexed: 11/26/2022]
Abstract
We tested the hypothesis that reactive oxygen species (ROS) and inflammatory mediators affect transduction properties of muscle spindles. In rats, muscle spindles response to high-frequency vibration (HFV) was recorded before and after (1) injection of hydrogen peroxide (H2O2) in control rats and animals pre-treated with diclofenac (anti-inflammatory substance), (2) injection of bradykinin and (3) fatigue induced by muscle stimulation (MS) in control rats and rats receiving diclofenac, superoxide dismutase (SOD) or H2O2. Muscular oxidative stress and inflammation induced by H2O2 or MS were assessed by measurements of isoprostanes and IL-6 levels. In control rats, H2O2, bradykinin and MS significantly enhanced the HFV response. Pre-treatment with SOD abolished the post-MS-enhanced HFV response whereas diclofenac lowered the peak HFV response to MS and H2O2. H2O2 injection and MS elicited significant and similar increases in isoprostanes and IL-6. We report a direct modulation of muscle spindles mechanosensitivity by ROS and inflammatory mediators.
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Affiliation(s)
- Stéphane Delliaux
- UMR MD2, Physiologie et physiopathologie en conditions d'oxygénation extrêmes, Faculté de Médecine-IFR Jean Roche, Université de la Méditerranée, Boulevard Pierre Dramard, 13916, Marseille, Cedex 20, France
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