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Katagiri A, Fujii N, Dobashi K, Lai YF, Tsuji B, Nishiyasu T. Effects of sodium bicarbonate ingestion on ventilatory and cerebrovascular responses in resting heated humans. Am J Physiol Regul Integr Comp Physiol 2024; 327:R400-R409. [PMID: 39102461 DOI: 10.1152/ajpregu.00161.2024] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Academic Contribution Register] [Received: 06/20/2024] [Revised: 07/22/2024] [Accepted: 07/23/2024] [Indexed: 08/07/2024]
Abstract
Hyperthermia stimulates ventilation in humans. This hyperthermia-induced hyperventilation may be mediated by the activation of peripheral chemoreceptors implicated in the regulation of respiration in reaction to various chemical stimuli, including reductions in arterial pH. Here, we investigated the hypothesis that during passive heating at rest, the increases in arterial pH achieved with sodium bicarbonate ingestion, which could attenuate peripheral chemoreceptor activity, mitigate hyperthermia-induced hyperventilation. We also assessed the effect of sodium bicarbonate ingestion on cerebral blood flow responses, which are associated with hyperthermia-induced hyperventilation. Twelve healthy men ingested sodium bicarbonate (0.3 g/kg body weight) or sodium chloride (0.208 g/kg). One hundred minutes after the ingestion, the participants were passively heated using hot-water immersion (42°C) combined with a water-perfused suit. Increases in esophageal temperature (an index of core temperature) and minute ventilation (V̇E) during the heating were similar in the two trials. Moreover, when V̇E is expressed as a function of esophageal temperature, there were no between-trial differences in the core temperature threshold for hyperventilation (38.0 ± 0.3 vs. 38.0 ± 0.4°C, P = 0.469) and sensitivity of hyperthermia-induced hyperventilation as assessed by the slope of the core temperature-V̇E relation (13.5 ± 14.2 vs. 15.8 ± 15.5 L/min/°C, P = 0.831). Furthermore, middle cerebral artery mean blood velocity (an index of cerebral blood flow) decreased similarly with heating duration in both trials. These results suggest that sodium bicarbonate ingestion does not mitigate hyperthermia-induced hyperventilation and the reductions in cerebral blood flow index in resting heated humans.NEW & NOTEWORTHY Hyperthermia leads to hyperventilation and associated cerebral hypoperfusion, both of which may impair heat tolerance. This hyperthermia-induced hyperventilation may be mediated by peripheral chemoreceptors, which can be activated by reductions in arterial pH. However, our results suggest that sodium bicarbonate ingestion, which can increase arterial pH, is not an effective intervention in alleviating hyperthermia-induced hyperventilation and cerebral hypoperfusion in resting heated humans.
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Affiliation(s)
- Akira Katagiri
- Institute of Health and Sport Sciences, University of Tsukuba, Ibaraki, Japan
| | - Naoto Fujii
- Institute of Health and Sport Sciences, University of Tsukuba, Ibaraki, Japan
- Advanced Research Initiative for Human High Performance, University of Tsukuba, Ibaraki, Japan
| | - Kohei Dobashi
- Faculty of Education, Hokkaido University of Education, Hokkaido, Japan
| | - Yin-Feng Lai
- Institute of Health and Sport Sciences, University of Tsukuba, Ibaraki, Japan
| | - Bun Tsuji
- Department of Health Sciences, Prefectural University of Hiroshima, Hiroshima, Japan
| | - Takeshi Nishiyasu
- Institute of Health and Sport Sciences, University of Tsukuba, Ibaraki, Japan
- Advanced Research Initiative for Human High Performance, University of Tsukuba, Ibaraki, Japan
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2
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Ducrocq GP, Anselmi L, Stella SL, Copp SW, Ruiz-Velasco V, Kaufman MP. Inhibition and potentiation of the exercise pressor reflex by pharmacological modulation of TRPC6 in male rats. J Physiol 2024:10.1113/JP286118. [PMID: 38340081 PMCID: PMC11315811 DOI: 10.1113/jp286118] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Academic Contribution Register] [Received: 12/11/2023] [Accepted: 01/18/2024] [Indexed: 02/12/2024] Open
Abstract
We determined the role played by the transient receptor potential canonical 6 (TRPC6) channel in evoking the mechanical component of the exercise pressor reflex in male decerebrated Sprague-Dawley rats. TRPC6 channels were identified by quadruple-labelled (DiI, TRPC6, neurofilament-200 and peripherin) immunohistochemistry in dorsal root ganglion (DRG) cells innervating the triceps surae muscles (n = 12). The exercise pressor reflex was evoked by statically contracting the triceps surae muscles before and after injection of the TRPC6 antagonist BI-749327 (n = 11; 12 μg kg-1 ) or SAR7334 (n = 11; 7 μg kg-1 ) or the TRPC6 positive modulator C20 (n = 11; 18 μg kg-1 ). Similar experiments were conducted while the muscles were passively stretched (n = 8-12), a manoeuvre that isolated the mechanical component of the reflex. Blood pressure, tension, renal sympathetic nerve activity (RSNA) and blood flow were recorded. Of the DRG cells innervating the triceps surae muscles, 85% stained positive for the TRPC6 antigen, and 45% of those cells co-expressed neurofilament-200. Both TRPC6 antagonists decreased the reflex pressor responses to static contraction (-32 to -42%; P < 0.05) and to passive stretch (-35 to -52%; P < 0.05), whereas C20 increased these responses (55-65%; P < 0.05). In addition, BI-749327 decreased the peak and integrated RSNA responses to both static contraction (-39 to -43%; P < 0.05) and passive stretch (-56 to -62%; P < 0.05), whereas C20 increased the RSNA to passive stretch only. The onset latency of the decrease or increase in RSNA occurred within 2 s of the onset of the manoeuvres (P < 0.05). Collectively, our results show that TRPC6 plays a key role in evoking the mechanical component of the exercise pressor reflex. KEY POINTS: The exercise pressor reflex plays a key role in the sympathetic and haemodynamic responses to exercise. This reflex is composed of two components, namely the mechanoreflex and the metaboreflex. The receptors responsible for evoking the mechanoreflex are poorly documented. A good candidate for this function is the transient receptor potential canonical 6 (TRPC6) channel, which is activated by mechanical stimuli and expressed in dorsal root ganglia of rats. Using two TRPC6 antagonists and one positive modulator, we investigated the role played by TRPC6 in evoking the mechanoreflex in decerebrated rats. Blocking TRPC6 decreased the renal sympathetic and the pressor responses to both contraction and stretch, the latter being a manoeuvre that isolates the mechanoreflex. In contrast, the positive modulator increased the pressor reflex to contraction and stretch, in addition to the sympathetic response to stretch. Our results provide strong support for a role played by the TRPC6 channel in evoking the mechanoreflex.
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Affiliation(s)
- Guillaume P. Ducrocq
- Heart and Vascular Institute, Penn State College of Medicine, Hershey, PA, USA
- Mitochondrial, Oxidative Stress and Muscular Protection Laboratory (UR3072), Faculty of Medicine, University of Strasbourg, Strasbourg, France
| | - Laura Anselmi
- Heart and Vascular Institute, Penn State College of Medicine, Hershey, PA, USA
| | - Salvatore L. Stella
- Department of Neurobiology and Behavioral Sciences, Penn State College of Medicine, Hershey, PA, USA
| | - Steven W. Copp
- Department of Kinesiology, Kansas State University, Manhattan, KS, USA
| | - Victor Ruiz-Velasco
- Heart and Vascular Institute, Penn State College of Medicine, Hershey, PA, USA
- Department of Anesthesiology and Perioperative Medicine, Penn State College of Medicine, Hershey, PA USA
| | - Marc P. Kaufman
- Heart and Vascular Institute, Penn State College of Medicine, Hershey, PA, USA
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3
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Li Q, Li J. NGF contributes to activities of acid-sensing ion channels in dorsal root ganglion neurons of male rats with experimental peripheral artery disease. Physiol Rep 2024; 12:e15933. [PMID: 38312021 PMCID: PMC10839628 DOI: 10.14814/phy2.15933] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Academic Contribution Register] [Received: 11/20/2023] [Revised: 01/15/2024] [Accepted: 01/15/2024] [Indexed: 02/06/2024] Open
Abstract
A feature of peripheral artery diseases (PAD) includes limb ischemia/reperfusion (I/R) and ischemia. Both I/R and ischemia amplify muscle afferent nerve-activated reflex sympathetic nervous and blood pressure responses (termed as exercise pressor reflex). Nevertheless, the underlying mechanisms responsible for the exaggerated autonomic responses in PAD are undetermined. Previous studies suggest that acid-sensing ion channels (ASICs) in muscle dorsal root ganglion (DRG) play a leading role in regulating the exercise pressor reflex in PAD. Thus, we determined if signaling pathways of nerve growth factor (NGF) contribute to the activities of ASICs in muscle DRG neurons of PAD. In particular, we examined ASIC1a and ASIC3 currents in isolectin B4 -negative muscle DRG neurons, a distinct subpopulation depending on NGF for survival. Hindlimb I/R and ischemia were obtained in male rats. In results, femoral artery occlusion increased the levels of NGF and NGF-stimulated TrkA receptor in DRGs, whereas they led to upregulation of ASIC3 but not ASIC1a. In addition, application of NGF onto DRG neurons increased the density of ASIC3 currents and the effect of NGF was significantly attenuated by TrkA antagonist GW441756. Moreover, the enhancing effect of NGF on the density of ASIC3-like currents was decreased by the respective inhibition of intracellular signaling pathways, namely JNK and NF-κB, by antagonists SP600125 and PDTC. Our results suggest contribution of NGF to the activities of ASIC3 currents via JNK and NF-κB signaling pathways in association with the exercise pressor reflex in experimental PAD.
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Affiliation(s)
- Qin Li
- Heart and Vascular InstituteThe Pennsylvania State University College of MedicineHersheyPennsylvaniaUSA
| | - Jianhua Li
- Heart and Vascular InstituteThe Pennsylvania State University College of MedicineHersheyPennsylvaniaUSA
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4
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López-Ramírez O, González-Garrido A. The role of acid sensing ion channels in the cardiovascular function. Front Physiol 2023; 14:1194948. [PMID: 37389121 PMCID: PMC10300344 DOI: 10.3389/fphys.2023.1194948] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Academic Contribution Register] [Received: 03/27/2023] [Accepted: 06/05/2023] [Indexed: 07/01/2023] Open
Abstract
Acid Sensing Ion Channels (ASIC) are proton sensors involved in several physiological and pathophysiological functions including synaptic plasticity, sensory systems and nociception. ASIC channels have been ubiquitously localized in neurons and play a role in their excitability. Information about ASIC channels in cardiomyocyte function is limited. Evidence indicates that ASIC subunits are expressed in both, plasma membrane and intracellular compartments of mammalian cardiomyocytes, suggesting unrevealing functions in the cardiomyocyte physiology. ASIC channels are expressed in neurons of the peripheral nervous system including the nodose and dorsal root ganglia (DRG), both innervating the heart, where they play a dual role as mechanosensors and chemosensors. In baroreceptor neurons from nodose ganglia, mechanosensation is directly associated with ASIC2a channels for detection of changes in arterial pressure. ASIC channels expressed in DRG neurons have several roles in the cardiovascular function. First, ASIC2a/3 channel has been proposed as the molecular sensor of cardiac ischemic pain for its pH range activation, kinetics and the sustained current. Second, ASIC1a seems to have a critical role in ischemia-induced injury. And third, ASIC1a, 2 and 3 are part of the metabolic component of the exercise pressure reflex (EPR). This review consists of a summary of several reports about the role of ASIC channels in the cardiovascular system and its innervation.
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Affiliation(s)
- Omar López-Ramírez
- Instituto de Oftalmología Fundación de Asistencia Privada Conde de Valenciana, I.A.P., Mexico City, Mexico
| | - Antonia González-Garrido
- Laboratorio de Enfermedades Mendelianas, Instituto Nacional de Medicina Genómica, Mexico City, Mexico
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5
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Li Q, Qin L, Li J. Characteristics of acid-sensing ion channel currents in male rat muscle dorsal root ganglion neurons following ischemia/reperfusion. Physiol Rep 2023; 11:e15654. [PMID: 36967457 PMCID: PMC10040404 DOI: 10.14814/phy2.15654] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Academic Contribution Register] [Received: 03/04/2023] [Revised: 03/07/2023] [Accepted: 03/08/2023] [Indexed: 03/28/2023] Open
Abstract
Peripheral artery diseases (PAD) increases muscle afferent nerve-activated reflex sympathetic nervous and blood pressure responses during exercise (termed as exercise pressor reflex). However, the precise signaling pathways leading to the exaggerated autonomic responses in PAD are undetermined. Considering that limb ischemia/reperfusion (I/R) is a feature of PAD, we determined the characteristics of acid-sensing ion channel (ASIC) currents in muscle dorsal root ganglion (DRG) neurons under the conditions of hindlimb I/R and ischemia of PAD. In particular, we examined ASIC currents in two distinct subpopulations, isolectin B4 -positive, and B4 -negative (IB4+ and IB4-) muscle DRG neurons, linking to glial cell line-derived neurotrophic factor and nerve growth factor. In results, ASIC1a- and ASIC3-like currents were observed in IB4- muscle DRG neurons with a greater percentage of ASIC3-like currents. Hindimb I/R and ischemia did not alter the distribution of ASIC1a and ASIC3 currents with activation of pH 6.7 in IB4+ and IB4- muscle DRG neurons; however, I/R altered the distribution of ASIC3 currents in IB4+ muscle DRG neurons with pH 5.5, but not in IB4- neurons. In addition, I/R and ischemia amplified the density of ASIC3-like currents in IB4- muscle DRG neurons. Our results suggest that a selective subpopulation of muscle afferent nerves should be taken into consideration when ASIC signaling pathways are studied to determine the exercise pressor reflex in PAD.
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Affiliation(s)
- Qin Li
- Heart and Vascular InstituteThe Pennsylvania State University College of MedicineHersheyPennsylvaniaUSA
| | - Lu Qin
- Heart and Vascular InstituteThe Pennsylvania State University College of MedicineHersheyPennsylvaniaUSA
| | - Jianhua Li
- Heart and Vascular InstituteThe Pennsylvania State University College of MedicineHersheyPennsylvaniaUSA
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6
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Abstract
The exercise pressor reflex is a feedback mechanism engaged upon stimulation of mechano- and metabosensitive skeletal muscle afferents. Activation of these afferents elicits a reflex increase in heart rate, blood pressure, and ventilation in an intensity-dependent manner. Consequently, the exercise pressor reflex has been postulated to be one of the principal mediators of the cardiorespiratory responses to exercise. In this updated review, we will discuss classical and recent advancements in our understating of the exercise pressor reflex function in both human and animal models. Particular attention will be paid to the afferent mechanisms and pathways involved during its activation, its effects on different target organs, its potential role in the abnormal cardiovascular response to exercise in diseased states, and the impact of age and biological sex on these responses. Finally, we will highlight some unanswered questions in the literature that may inspire future investigations in the field.
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Affiliation(s)
- André L Teixeira
- NeuroV̇ASQ̇, Integrative Physiology Laboratory, Faculty of Physical Education, University of Brasília, DF, Brasília, Brazil
- Department of Human Health and Nutritional Sciences, University of Guelph, Guelph, ON, Canada
| | - Lauro C Vianna
- NeuroV̇ASQ̇, Integrative Physiology Laboratory, Faculty of Physical Education, University of Brasília, DF, Brasília, Brazil.
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7
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Butenas ALE, Rollins KS, Parr SK, Hammond ST, Ade CJ, Hageman KS, Musch TI, Copp SW. Novel mechanosensory role for acid sensing ion channel subtype 1a in evoking the exercise pressor reflex in rats with heart failure. J Physiol 2022; 600:2105-2125. [PMID: 35343594 PMCID: PMC9893514 DOI: 10.1113/jp282923] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Academic Contribution Register] [Received: 02/01/2022] [Accepted: 03/18/2022] [Indexed: 02/05/2023] Open
Abstract
Mechanical and metabolic signals associated with skeletal muscle contraction stimulate the sensory endings of thin fibre muscle afferents, which, in turn, generates reflex increases in sympathetic nerve activity (SNA) and blood pressure (the exercise pressor reflex; EPR). EPR activation in patients and animals with heart failure with reduced ejection fraction (HF-rEF) results in exaggerated increases in SNA and promotes exercise intolerance. In the healthy decerebrate rat, a subtype of acid sensing ion channel (ASIC) on the sensory endings of thin fibre muscle afferents, namely ASIC1a, has been shown to contribute to the metabolically sensitive portion of the EPR (i.e. metaboreflex), but not the mechanically sensitive portion of the EPR (i.e. the mechanoreflex). However, the role played by ASIC1a in evoking the EPR in HF-rEF is unknown. We hypothesized that, in decerebrate, unanaesthetized HF-rEF rats, injection of the ASIC1a antagonist psalmotoxin-1 (PcTx-1; 100 ng) into the hindlimb arterial supply would reduce the reflex increase in renal SNA (RSNA) evoked via 30 s of electrically induced static hindlimb muscle contraction, but not static hindlimb muscle stretch (model of mechanoreflex activation isolated from contraction-induced metabolite-production). We found that PcTx-1 reduced the reflex increase in RSNA evoked in response to muscle contraction (n = 8; mean (SD) ∫ΔRSNA pre: 1343 (588) a.u.; post: 816 (573) a.u.; P = 0.026) and muscle stretch (n = 6; ∫ΔRSNA pre: 688 (583) a.u.; post: 304 (370) a.u.; P = 0.025). Our data suggest that, in HF-rEF rats, ASIC1a contributes to activation of the exercise pressor reflex and that contribution includes a novel role for ASIC1a in mechanosensation that is not present in healthy rats. KEY POINTS: Skeletal muscle contraction results in exaggerated reflex increases in sympathetic nerve activity in heart failure patients compared to healthy counterparts, which likely contributes to increased cardiovascular risk and impaired tolerance for even mild exercise (i.e. activities of daily living) for patients suffering with this condition. Activation of acid sensing ion channel subtype 1a (ASIC1a) on the sensory endings of thin fibre muscle afferents during skeletal muscle contraction contributes to reflex increases in sympathetic nerve activity and blood pressure, at least in healthy subjects. In this study, we demonstrate that ASIC1a on the sensory endings of thin fibre muscle afferents plays a role in both the mechanical and metabolic components of the exercise pressor reflex in male rats with heart failure. The present data identify a novel role for ASIC1a in evoking the exercise pressor reflex in heart failure and may have important clinical implications for heart failure patients.
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Affiliation(s)
- Alec L E Butenas
- Department of Kinesiology, Kansas State University, Manhattan, KS, USA
| | - Korynne S Rollins
- Department of Kinesiology, Kansas State University, Manhattan, KS, USA
| | - Shannon K Parr
- Department of Kinesiology, Kansas State University, Manhattan, KS, USA
| | - Stephen T Hammond
- Department of Kinesiology, Kansas State University, Manhattan, KS, USA
| | - Carl J Ade
- Department of Kinesiology, Kansas State University, Manhattan, KS, USA
| | - K Sue Hageman
- Department of Anatomy and Physiology, Kansas State University, Manhattan, KS, USA
| | - Timothy I Musch
- Department of Kinesiology, Kansas State University, Manhattan, KS, USA
- Department of Anatomy and Physiology, Kansas State University, Manhattan, KS, USA
| | - Steven W Copp
- Department of Kinesiology, Kansas State University, Manhattan, KS, USA
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Drummond HA. What Evolutionary Evidence Implies About the Identity of the Mechanoelectrical Couplers in Vascular Smooth Muscle Cells. Physiology (Bethesda) 2021; 36:292-306. [PMID: 34431420 DOI: 10.1152/physiol.00008.2021] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Academic Contribution Register] [Indexed: 12/28/2022] Open
Abstract
Loss of pressure-induced vasoconstriction increases susceptibility to renal and cerebral vascular injury. Favored paradigms underlying initiation of the response include transient receptor potential channels coupled to G protein-coupled receptors or integrins as transducers. Degenerin channels may also mediate the response. This review addresses the 1) evolutionary role of these molecules in mechanosensing, 2) limitations to identifying mechanosensitive molecules, and 3) paradigm shifting molecular model for a VSMC mechanosensor.
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Affiliation(s)
- Heather A Drummond
- Department of Physiology and Biophysics, University of Mississippi Medical Center, Jackson, Mississippi
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9
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Cui J, Gao Z, Blaha C, Luck JC, Brandt K, Sinoway LI. Moderate whole body heating attenuates the exercise pressor reflex responses in older humans. Am J Physiol Regul Integr Comp Physiol 2021; 320:R757-R769. [PMID: 33789459 DOI: 10.1152/ajpregu.00232.2020] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Academic Contribution Register] [Indexed: 12/12/2022]
Abstract
Prior reports show that whole body heat stress attenuates the pressor response to exercise in young healthy subjects. The effects of moderate whole body heating (WBH; e.g., increase in internal temperature Tcore of ∼0.4°C-0.5°C) or limb heating on sympathetic and cardiovascular responses to exercise in older healthy humans remain unclear. We examined the muscle sympathetic nerve activity (MSNA), mean arterial blood pressure (MAP), and heart rate (HR) in 14 older (62 ± 2 yr) healthy subjects during fatiguing isometric handgrip exercise and postexercise circulatory occlusion (PECO). The protocol was performed under normothermic, moderate WBH, and local limb (i.e., forearm) heating conditions during three visits. During the mild WBH stage (increase in Tcore of <0.3°C), HR increased, whereas BP and MSNA decreased from baseline. Under the moderate WBH condition (increase in Tcore of ∼0.4°C), BP decreased, HR increased, and MSNA was unchanged from baseline. Compared with the normothermic trial, the absolute MAP during fatiguing exercise and PECO was lower during the WBH trial. Moreover, MSNA and MAP responses (i.e., changes) to fatiguing exercise were also less than those seen during the normothermic trial. Limb heating induced a similar increase in forearm muscle temperature to that seen in the WBH trial (∼0.7°C-1.5°C). Limb heating did not alter resting MAP, HR, or MSNA. The MSNA and hemodynamic responses to exercise in the limb heating trial were not different from those in the normothermic trial. These data suggest that moderate WBH attenuates MSNA and BP responses to exercise in older healthy humans.
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Affiliation(s)
- Jian Cui
- Penn State Health, Penn State Heart and Vascular Institute, Hershey, Pennsylvania
| | - Zhaohui Gao
- Penn State Health, Penn State Heart and Vascular Institute, Hershey, Pennsylvania
| | - Cheryl Blaha
- Penn State Health, Penn State Heart and Vascular Institute, Hershey, Pennsylvania
| | - Jonathan Carter Luck
- Penn State Health, Penn State Heart and Vascular Institute, Hershey, Pennsylvania
| | - Kristen Brandt
- Penn State Health, Penn State Heart and Vascular Institute, Hershey, Pennsylvania
| | - Lawrence I Sinoway
- Penn State Health, Penn State Heart and Vascular Institute, Hershey, Pennsylvania
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Stavres J, Luck JC, Ducrocq GP, Cauffman AE, Pai S, Sinoway LI. Central and peripheral modulation of exercise pressor reflex sensitivity after nonfatiguing work. Am J Physiol Regul Integr Comp Physiol 2020; 319:R575-R583. [PMID: 32877237 DOI: 10.1152/ajpregu.00127.2020] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Academic Contribution Register] [Indexed: 11/22/2022]
Abstract
Autonomic blood pressure control is fundamentally altered during a single bout of exercise, as evidenced by the downward resetting of the baroreflex following exercise (postexercise hypotension). However, it is unclear if an acute bout of exercise is also associated with a change in the sensitivity of the exercise pressor response to a controlled stimulus, such as a static contraction. This study tested the hypothesis that the blood pressure response to a controlled static contraction would be attenuated after unilateral cycling of the contralateral (opposite) leg, but preserved after cycling of the ipsilateral (same) leg. To test this, the blood pressure response to 90 s of isometric plantar flexion [50% maximal voluntary contraction (MVC)] was compared before and after 20 min of contralateral and ipsilateral single-leg cycling at 20% peak oxygen consumption and rest (control) in 10 healthy subjects (three males and seven females). The mean arterial pressure response was significantly attenuated after contralateral single-leg cycling (+9.8 ± 7.5% ∆mmHg vs. +6.7 ± 6.6% ∆mmHg pre and postexercise, respectively, P = 0.04) and rest (+9.0 ± 7.5% ∆mmHg vs. +6.6 ± 5.2% ∆mmHg pre and postexercise, respectively, P = 0.03). In contrast, the pressor response nonsignificantly increased following ipsilateral single-leg cycling (+5.5 ± 5.2% ∆mmHg vs. +8.9 ± 7.2% ∆mmHg pre and postexercise, respectively, P = 0.08). The heart rate, leg blood flow, and leg conductance responses to plantar flexion were not affected by any condition (P ≥ 0.12). These results are consistent with the notion that peripheral, but not central mechanisms promote exercise pressor reflex sensitivity after exercise.
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Affiliation(s)
- Jon Stavres
- Penn State Heart and Vascular Institute, Milton S. Hershey Medical Center, Pennsylvania State University College of Medicine, Hershey, Pennsylvania
| | - J Carter Luck
- Penn State Heart and Vascular Institute, Milton S. Hershey Medical Center, Pennsylvania State University College of Medicine, Hershey, Pennsylvania
| | - Guillaume P Ducrocq
- Penn State Heart and Vascular Institute, Milton S. Hershey Medical Center, Pennsylvania State University College of Medicine, Hershey, Pennsylvania
| | - Aimee E Cauffman
- Penn State Heart and Vascular Institute, Milton S. Hershey Medical Center, Pennsylvania State University College of Medicine, Hershey, Pennsylvania
| | - Samuel Pai
- Penn State Heart and Vascular Institute, Milton S. Hershey Medical Center, Pennsylvania State University College of Medicine, Hershey, Pennsylvania
| | - Lawrence I Sinoway
- Penn State Heart and Vascular Institute, Milton S. Hershey Medical Center, Pennsylvania State University College of Medicine, Hershey, Pennsylvania
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11
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Abstract
Acid-sensing ion channels (ASICs) are cation-permeable channels that in the periphery are primarily expressed in sensory neurons that innervate tissues and organs. Soon after the cloning of the ASIC subunits, almost 20 yr ago, investigators began to use genetically modified mice to assess the role of these channels in physiological processes. These studies provide critical insights about the participation of ASICs in sensory processes, including mechanotransduction, chemoreception, and nociception. Here, we provide an extensive assessment of these findings and discuss the current gaps in knowledge with regard to the functions of ASICs in the peripheral nervous system.
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Affiliation(s)
- Marcelo D Carattino
- Renal-Electrolyte Division, Department of Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania.,Department of Cell Biology, University of Pittsburgh, Pittsburgh, Pennsylvania
| | - Nicolas Montalbetti
- Renal-Electrolyte Division, Department of Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania
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12
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Ducrocq GP, Kim JS, Estrada JA, Kaufman MP. ASIC1a plays a key role in evoking the metabolic component of the exercise pressor reflex in rats. Am J Physiol Heart Circ Physiol 2020; 318:H78-H89. [PMID: 31675256 PMCID: PMC6985806 DOI: 10.1152/ajpheart.00565.2019] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Academic Contribution Register] [Received: 09/24/2019] [Revised: 10/23/2019] [Accepted: 10/28/2019] [Indexed: 11/22/2022]
Abstract
The role of the acid-sensing ion channel 1a (ASIC1a) in evoking the exercise pressor reflex is unknown, despite the fact that ASIC1a is opened by decreases in pH in the physiological range. This fact prompted us to test the hypothesis that ASIC1a plays an important role in evoking the exercise pressor reflex in decerebrated rats with freely perfused hindlimb muscles. To test this hypothesis, we measured the effect of injecting two ASIC1a blockers into the arterial supply of the triceps surae muscles on the reflex pressor responses to four maneuvers, namely 1) static contraction of the triceps surae muscles (i.e., the exercise pressor reflex), 2) calcaneal tendon stretch, 3) intra-arterial injection of lactic acid, and 4) intra-arterial injection of diprotonated phosphate. We found that the 2 ASIC1a blockers, psalmotoxin-1 (200 ng/kg) and mambalgin-1 (6.5 μg/kg), decreased the pressor responses to static contraction as well as the peak pressor responses to injection of lactic acid and diprotonated phosphate. In contrast, neither ASIC1a blocker had any effect on the pressor responses to tendon stretch. Importantly, we found that ASIC1a blockade significantly decreased the pressor response to static contraction after a latency of at least 8 s. Our results support the hypothesis that ASIC1a plays a key role in evoking the metabolic component of the exercise pressor reflex.NEW & NOTEWORTHY The role played by acid-sensing ion channel 1a (ASIC1a) in evoking the exercise pressor reflex remains unknown. In decerebrated rats with freely perfused femoral arteries, blocking ASIC1a with psalmotoxin-1 or mambalgin-1 significantly attenuated the pressor response to static contraction, lactic acid, and diprotonated phosphate injection but had no effect on the pressor response to stretch. We conclude that ASIC1a plays a key role in evoking the exercise pressor reflex by responding to contraction-induced metabolites, such as protons.
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Affiliation(s)
- Guillaume P Ducrocq
- Heart and Vascular Institute, Penn State College of Medicine, Hershey, Pennsylvania
| | - Joyce S Kim
- Heart and Vascular Institute, Penn State College of Medicine, Hershey, Pennsylvania
| | - Juan A Estrada
- Heart and Vascular Institute, Penn State College of Medicine, Hershey, Pennsylvania
| | - Marc P Kaufman
- Heart and Vascular Institute, Penn State College of Medicine, Hershey, Pennsylvania
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13
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Campos MO, Mansur DE, Mattos JD, Paiva ACS, Videira RLR, Macefield VG, da Nóbrega ACL, Fernandes IA. Acid-sensing ion channels blockade attenuates pressor and sympathetic responses to skeletal muscle metaboreflex activation in humans. J Appl Physiol (1985) 2019; 127:1491-1501. [PMID: 31545154 DOI: 10.1152/japplphysiol.00401.2019] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Academic Contribution Register] [Indexed: 01/19/2023] Open
Abstract
In animals, the blockade of acid-sensing ion channels (ASICs), cation pore-forming membrane proteins located in the free nerve endings of group IV afferent fibers, attenuates increases in arterial pressure (AP) and sympathetic nerve activity (SNA) during muscle contraction. Therefore, ASICs play a role in mediating the metabolic component (skeletal muscle metaboreflex) of the exercise pressor reflex in animal models. Here we tested the hypothesis that ASICs also play a role in evoking the skeletal muscle metaboreflex in humans, quantifying beat-by-beat mean AP (MAP; finger photoplethysmography) and muscle SNA (MSNA; microneurography) in 11 men at rest and during static handgrip exercise (SHG; 35% of the maximal voluntary contraction) and postexercise muscle ischemia (PEMI) before (B) and after (A) local venous infusion of either saline or amiloride (AM), an ASIC antagonist, via the Bier block technique. MAP (BAM +30 ± 6 vs. AAM +25 ± 7 mmHg, P = 0.001) and MSNA (BAM +14 ± 9 vs. AAM +10 ± 6 bursts/min, P = 0.004) responses to SHG were attenuated under ASIC blockade. Amiloride also attenuated the PEMI-induced increases in MAP (BAM +25 ± 6 vs. AAM +16 ± 6 mmHg, P = 0.0001) and MSNA (BAM +16 ± 9 vs. AAM +8 ± 8 bursts/min, P = 0.0001). MAP and MSNA responses to SHG and PEMI were similar before and after saline infusion. We conclude that ASICs play a role in evoking pressor and sympathetic responses to SHG and the isolated activation of the skeletal muscle metaboreflex in humans. NEW & NOTEWORTHY We showed that regional blockade of the acid-sensing ion channels (ASICs), induced by venous infusion of the antagonist amiloride via the Bier block anesthetic technique, attenuated increases in arterial pressure and muscle sympathetic nerve activity during both static handgrip exercise and postexercise muscle ischemia. These findings indicate that ASICs contribute to both pressor and sympathetic responses to the activation of the skeletal muscle metaboreflex in humans.
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Affiliation(s)
- Monique O Campos
- Laboratory of Exercise Sciences, Fluminense Federal University, Niterói, Brazil
| | - Daniel E Mansur
- Laboratory of Exercise Sciences, Fluminense Federal University, Niterói, Brazil
| | - João D Mattos
- Laboratory of Exercise Sciences, Fluminense Federal University, Niterói, Brazil
| | - Adrielle C S Paiva
- Laboratory of Exercise Sciences, Fluminense Federal University, Niterói, Brazil
| | | | - Vaughan G Macefield
- School of Medicine, Western Sydney University, Sydney, Australia.,Baker Heart and Diabetes Institute, Melbourne, Australia
| | | | - Igor A Fernandes
- NeuroV̇ASQ̇-Integrative Physiology Laboratory, Faculty of Physical Education, University of Brasília, Brasília, Brazil
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14
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Sprick JD, Morison DL, Fonkoue IT, Li Y, DaCosta D, Rapista D, Choi H, Park J. Metabolic acidosis augments exercise pressor responses in chronic kidney disease. Am J Physiol Regul Integr Comp Physiol 2019; 317:R312-R318. [PMID: 31141417 DOI: 10.1152/ajpregu.00076.2019] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Academic Contribution Register] [Indexed: 12/30/2022]
Abstract
Chronic kidney disease (CKD) patients experience augmented blood pressure (BP) reactivity during exercise that is associated with an increased risk of cardiovascular mortality. Exaggerated exercise pressor responses in CKD are in part mediated by augmented sympathetic nerve activation due to heightened muscle mechanoreflex. One mechanism that may lead to sensitization of the muscle mechanoreflex in CKD is metabolic acidosis. We hypothesized that CKD patients with low serum [bicarbonate] would exhibit exaggerated increases in arterial BP, greater reductions in muscle interstitial pH, and fatigue earlier during exercise compared with CKD patients with normal serum bicarbonate concentration ([bicarbonate]). Eighteen CKD participants with normal serum [bicarbonate] (≥24 mmol/l, normal-bicarb) and 9 CKD participants with mild metabolic acidosis ([bicarbonate] range 20-22 mmol/l, low-bicarb) performed rhythmic handgrip (RHG) exercise to volitional fatigue at 40% of maximal voluntary contraction. BP, heart rate, and muscle interstitial pH using near infrared spectroscopy were measured continuously. While mean arterial pressure (MAP) increased with exercise in both groups (P ≤ 0.002), CKD with low-bicarb had an exaggerated MAP response compared with CKD with normal-bicarb (+5.9 ± 1.3 mmHg/30 s vs. +2.6 ± 0.5 mmHg/30 s, P = 0.01). The low-bicarb group reached exhaustion earlier than the normal-bicarb group (179 ± 21 vs. 279 ± 19 s, P = 0.003). There were no differences in the change in muscle interstitial pH during exercise between groups (P = 0.31). CKD patients with metabolic acidosis have augmented exercise-induced increases in BP and poorer exercise tolerance. There was no difference in change in muscle interstitial pH between groups, however, suggesting that augmented exercise BP responses in metabolic acidosis are not due to impaired muscle-buffering capacity.
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Affiliation(s)
- Justin D Sprick
- Division of Renal Medicine, Department of Medicine, Emory University School of Medicine, Atlanta, Georgia.,Department of Veterans Affairs Health Care System, Decatur, Georgia
| | - Doree Lynn Morison
- Division of Renal Medicine, Department of Medicine, Emory University School of Medicine, Atlanta, Georgia.,Department of Veterans Affairs Health Care System, Decatur, Georgia
| | - Ida T Fonkoue
- Division of Renal Medicine, Department of Medicine, Emory University School of Medicine, Atlanta, Georgia.,Department of Veterans Affairs Health Care System, Decatur, Georgia
| | - Yunxiao Li
- Department of Biostatistics and Bioinformatics, Rollins School of Public Health, Emory University, Atlanta, Georgia
| | - Dana DaCosta
- Division of Renal Medicine, Department of Medicine, Emory University School of Medicine, Atlanta, Georgia.,Department of Veterans Affairs Health Care System, Decatur, Georgia
| | - Derick Rapista
- Division of Renal Medicine, Department of Medicine, Emory University School of Medicine, Atlanta, Georgia.,Department of Veterans Affairs Health Care System, Decatur, Georgia
| | - HyunKyu Choi
- Division of Renal Medicine, Department of Medicine, Emory University School of Medicine, Atlanta, Georgia
| | - Jeanie Park
- Division of Renal Medicine, Department of Medicine, Emory University School of Medicine, Atlanta, Georgia.,Department of Veterans Affairs Health Care System, Decatur, Georgia
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Hotta N, Kubo A, Mizumura K. Chondroitin sulfate attenuates acid-induced augmentation of the mechanical response in rat thin-fiber muscle afferents in vitro. J Appl Physiol (1985) 2019; 126:1160-1170. [PMID: 30763166 DOI: 10.1152/japplphysiol.00633.2018] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Academic Contribution Register] [Indexed: 02/08/2023] Open
Abstract
Exercise-induced tissue acidosis augments the exercise pressor reflex (EPR). One reason for this may be acid-induced mechanical sensitization in thin-fiber muscle afferents, which is presumably related to EPR. Acid-induced sensitization to mechanical stimulation has been reported to be attenuated in cultured primary-sensory neurons by exogenous chondroitin sulfate (CS) and chondroitinase ABC, suggesting that the extracellular matrix CS proteoglycan is involved in this sensitization. The purpose of this study was to clarify whether acid-induced sensitization of the mechanical response in the thin-fiber muscle afferents is also suppressed by exogenous CS and chondroitinase ABC using a single-fiber recording technique. A total of 88 thin fibers (conduction velocity <15.0 m/s) dissected from 86 male Sprague-Dawley rats were identified. A buffer solution at pH 6.2 lowered their mechanical threshold and increased their response magnitude. Five minutes after CS (0.3 and 0.03%) injection near the receptive field, these acid-induced changes were significantly reduced. No significant difference in attenuation was detected between the two CS concentrations. Chondroitinase ABC also significantly attenuated this sensitization. The control solution (0% CS) did not significantly alter the mechanical sensitization. Furthermore, no significant differences were detected in this sensitization and CS-based suppression between fibers with and without acid-sensitive channels [transient receptor potential vanilloid 1 (TRPV1), acid-sensing ion channel (ASIC)]. In addition, this mechanical sensitization was not changed by TRPV1 and ASIC antagonists, suggesting that these ion channels are not involved in the acid-induced mechanical sensitization of muscle thin-fiber afferents. In conclusion, CS administration has a potential to attenuate the acidosis-induced exaggeration of muscle mechanoreflex. NEW & NOTEWORTHY We found that exogenous chondroitin sulfate attenuated acid-induced mechanical sensitization in thin-fiber muscle afferents that play a crucial role in the exercise pressor reflex. This finding suggests that extracellular matrix chondroitin sulfate proteoglycans may be involved in the mechanism of acid-induced mechanical sensitization and that daily intake of chondroitin sulfate may potentially attenuate this amplification of muscle mechanoreflex and therefore reduce muscle pain related to acidic muscle conditions.
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Affiliation(s)
- Norio Hotta
- College of Life and Health Sciences, Chubu University , Aichi , Japan
| | - Asako Kubo
- Department of Physiology, Nihon University School of Dentistry , Tokyo , Japan
| | - Kazue Mizumura
- College of Life and Health Sciences, Chubu University , Aichi , Japan.,Department of Physiology, Nihon University School of Dentistry , Tokyo , Japan
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Drummond HA, Xiang L, Chade AR, Hester R. Enhanced maximal exercise capacity, vasodilation to electrical muscle contraction, and hind limb vascular density in ASIC1a null mice. Physiol Rep 2017; 5:e13368. [PMID: 28784852 PMCID: PMC5555894 DOI: 10.14814/phy2.13368] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Academic Contribution Register] [Received: 04/20/2017] [Revised: 06/27/2017] [Accepted: 06/28/2017] [Indexed: 12/15/2022] Open
Abstract
Acid-sensing ion channel (ASIC) proteins form extracellular proton-gated, cation-selective channels in neurons and vascular smooth muscle cells and are proposed to act as extracellular proton sensors. However, their importance to vascular responses under conditions associated with extracellular acidosis, such as strenuous exercise, is unclear. Therefore, the purpose of this study was to determine if one ASIC protein, ASIC1a, contributes to extracellular proton-gated vascular responses and exercise tolerance. To determine if ASIC1a contributes to exercise tolerance, we determined peak oxygen (O2) uptake in conscious ASIC1a-/- mice during exhaustive treadmill running. Loss of ASIC1a was associated with a greater peak running speed (60 ± 2 vs. 53 ± 3 m·min-1, P = 0.049) and peak oxygen (O2) uptake during exhaustive treadmill running (9563 ± 120 vs. 8836 ± 276 mL·kg-1·h-1, n = 6-7, P = 0.0082). There were no differences in absolute or relative lean body mass, as determined by EchoMRI. To determine if ASIC1a contributes to vascular responses during muscle contraction, we measured femoral vascular conductance (FVC) during a stepwise electrical stimulation (0.5-5.0 Hz at 3 V for 60 sec) of the left major hind limb muscles. FVC increased to a greater extent in ASIC1a-/- versus ASIC1a+/+ mice (0.44 ± 0.03 vs. 0.30 ± 0.04 mL·min-1·100 g hind limb mass-1 · mmHg-1, n = 5 each, P = 0.0009). Vasodilation following local application of external protons in the spinotrapezius muscle increased the duration, but not the magnitude, of the vasodilatory response in ASIC1a-/- mice. Finally, we examined hind limb vascular density using micro-CT and found increased density of 0-80 μm vessels (P < 0.05). Our findings suggest an increased vascular density and an enhanced vasodilatory response to local protons, to a lesser degree, may contribute to the enhanced vascular conductance and increased peak exercise capacity in ASIC1a-/- mice.
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Affiliation(s)
- Heather A Drummond
- Department of Physiology and Biophysics and the Center for Excellence in Cardiovascular-Renal Research, University of Mississippi Medical Center, Jackson, Mississippi
| | - Lusha Xiang
- Department of Physiology and Biophysics and the Center for Excellence in Cardiovascular-Renal Research, University of Mississippi Medical Center, Jackson, Mississippi
| | - Alejandro R Chade
- Department of Physiology and Biophysics and the Center for Excellence in Cardiovascular-Renal Research, University of Mississippi Medical Center, Jackson, Mississippi
| | - Robert Hester
- Department of Physiology and Biophysics and the Center for Excellence in Cardiovascular-Renal Research, University of Mississippi Medical Center, Jackson, Mississippi
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Dual Modulation of Nociception and Cardiovascular Reflexes during Peripheral Ischemia through P2Y1 Receptor-Dependent Sensitization of Muscle Afferents. J Neurosci 2016; 36:19-30. [PMID: 26740646 DOI: 10.1523/jneurosci.2856-15.2016] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Academic Contribution Register] [Indexed: 01/09/2023] Open
Abstract
UNLABELLED Numerous musculoskeletal pain disorders are based in dysfunction of peripheral perfusion and are often comorbid with altered cardiovascular responses to muscle contraction/exercise. We have recently found in mice that 24 h peripheral ischemia induced by a surgical occlusion of the brachial artery (BAO) induces increased paw-guarding behaviors, mechanical hypersensitivity, and decreased grip strength. These behavioral changes corresponded to increased heat sensitivity as well as an increase in the numbers of chemosensitive group III/IV muscle afferents as assessed by an ex vivo forepaw muscles/median and ulnar nerves/dorsal root ganglion (DRG)/spinal cord (SC) recording preparation. Behaviors also corresponded to specific upregulation of the ADP-responsive P2Y1 receptor in the DRGs. Since group III/IV muscle afferents have separately been associated with regulating muscle nociception and exercise pressor reflexes (EPRs), and P2Y1 has been linked to heat responsiveness and phenotypic switching in cutaneous afferents, we sought to determine whether upregulation of P2Y1 was responsible for the observed alterations in muscle afferent function, leading to modulation of muscle pain-related behaviors and EPRs after BAO. Using an afferent-specific siRNA knockdown strategy, we found that inhibition of P2Y1 during BAO not only prevented the increased mean blood pressure after forced exercise, but also significantly reduced alterations in pain-related behaviors. Selective P2Y1 knockdown also prevented the increased firing to heat stimuli and the BAO-induced phenotypic switch in chemosensitive muscle afferents, potentially through regulating membrane expression of acid sensing ion channel 3. These results suggest that enhanced P2Y1 in muscle afferents during ischemic-like conditions may dually regulate muscle nociception and cardiovascular reflexes. SIGNIFICANCE STATEMENT Our current results suggest that P2Y1 modulates heat responsiveness and chemosensation in muscle afferents to play a key role in the development of pain-related behaviors during ischemia. At the same time, under these pathological conditions, the changes in muscle sensory neurons appear to modulate an increase in mean systemic blood pressure after exercise. This is the first report of the potential peripheral mechanisms by which group III/IV muscle afferents can dually regulate muscle nociception and the exercise pressor reflex. These data provide evidence related to the potential underlying reasons for the comorbidity of muscle pain and altered sympathetic reflexes in disease states that are based in problems with peripheral perfusion and may indicate a potential target for therapeutic intervention.
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18
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Mizuno M, Mitchell JH, Smith SA. The exercise pressor reflex in hypertension. THE JOURNAL OF PHYSICAL FITNESS AND SPORTS MEDICINE 2016. [DOI: 10.7600/jpfsm.5.339] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Academic Contribution Register] [Indexed: 12/17/2022]
Affiliation(s)
- Masaki Mizuno
- Department of Health Care Sciences, University of Texas Southwestern Medical Center
- Internal Medicine, University of Texas Southwestern Medical Center
| | - Jere H. Mitchell
- Internal Medicine, University of Texas Southwestern Medical Center
| | - Scott A. Smith
- Department of Health Care Sciences, University of Texas Southwestern Medical Center
- Internal Medicine, University of Texas Southwestern Medical Center
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19
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Stone AJ, Copp SW, Kim JS, Kaufman MP. Combined, but not individual, blockade of ASIC3, P2X, and EP4 receptors attenuates the exercise pressor reflex in rats with freely perfused hindlimb muscles. J Appl Physiol (1985) 2015; 119:1330-6. [PMID: 26472871 DOI: 10.1152/japplphysiol.00630.2015] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Academic Contribution Register] [Received: 07/24/2015] [Accepted: 10/01/2015] [Indexed: 11/22/2022] Open
Abstract
In healthy humans, tests of the hypothesis that lactic acid, PGE2, or ATP plays a role in evoking the exercise pressor reflex proved controversial. The findings in humans resembled ours in decerebrate rats that individual blockade of the receptors to lactic acid, PGE2, and ATP had only small effects on the exercise pressor reflex provided that the muscles were freely perfused. This similarity between humans and rats prompted us to test the hypothesis that in rats with freely perfused muscles combined receptor blockade is required to attenuate the exercise pressor reflex. We first compared the reflex before and after injecting either PPADS (10 mg/kg), a P2X receptor antagonist, APETx2 (100 μg/kg), an activating acid-sensing ion channel 3 (ASIC) channel antagonist, or L161982 (2 μg/kg), an EP4 receptor antagonist, into the arterial supply of the hindlimb of decerebrated rats. We then examined the effects of combined blockade of P2X receptors, ASIC3 channels, and EP4 receptors on the exercise pressor reflex using the same doses, intra-arterial route, and time course of antagonist injections as those used for individual blockade. We found that neither PPADS (n = 5), APETx2 (n = 6), nor L161982 (n = 6) attenuated the reflex. In contrast, combined blockade of these receptors (n = 7) attenuated the peak (↓27%, P < 0.019) and integrated (↓48%, P < 0.004) pressor components of the reflex. Combined blockade injected intravenously had no effect on the reflex. We conclude that combined blockade of P2X receptors, ASIC3 channels, and EP4 receptors on the endings of thin fiber muscle afferents is required to attenuate the exercise pressor reflex in rats with freely perfused hindlimbs.
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Affiliation(s)
- Audrey J Stone
- Heart and Vascular Institute, Penn State College of Medicine, Hershey, Pennsylvania
| | - Steven W Copp
- Heart and Vascular Institute, Penn State College of Medicine, Hershey, Pennsylvania
| | - Joyce S Kim
- Heart and Vascular Institute, Penn State College of Medicine, Hershey, Pennsylvania
| | - Marc P Kaufman
- Heart and Vascular Institute, Penn State College of Medicine, Hershey, Pennsylvania
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20
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Gibbons DD, Kutschke WJ, Weiss RM, Benson CJ. Heart failure induces changes in acid-sensing ion channels in sensory neurons innervating skeletal muscle. J Physiol 2015; 593:4575-87. [PMID: 26314284 DOI: 10.1113/jp270690] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Academic Contribution Register] [Received: 04/02/2015] [Accepted: 08/13/2015] [Indexed: 12/19/2022] Open
Abstract
Heart failure is associated with diminished exercise capacity, which is driven, in part, by alterations in exercise-induced autonomic reflexes triggered by skeletal muscle sensory neurons (afferents). These overactive reflexes may also contribute to the chronic state of sympathetic excitation, which is a major contributor to the morbidity and mortality of heart failure. Acid-sensing ion channels (ASICs) are highly expressed in muscle afferents where they sense metabolic changes associated with ischaemia and exercise, and contribute to the metabolic component of these reflexes. Therefore, we tested if ASICs within muscle afferents are altered in heart failure. We used whole-cell patch clamp to study the electrophysiological properties of acid-evoked currents in isolated, labelled muscle afferent neurons from control and heart failure (induced by myocardial infarction) mice. We found that the percentage of muscle afferents that displayed ASIC-like currents, the current amplitudes, and the pH dose-response relationships were not altered in mice with heart failure. On the other hand, the biophysical properties of ASIC-like currents were significantly different in a subpopulation of cells (40%) from heart failure mice. This population displayed diminished pH sensitivity, altered desensitization kinetics, and very fast recovery from desensitization. These unique properties define these channels within this subpopulation of muscle afferents as being heteromeric channels composed of ASIC2a and -3 subunits. Heart failure induced a shift in the subunit composition of ASICs within muscle afferents, which significantly altered their pH sensing characteristics. These results might, in part, contribute to the changes in exercise-mediated reflexes that are associated with heart failure.
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Affiliation(s)
- David D Gibbons
- Department of Internal Medicine, Carver College of Medicine, University of Iowa, Iowa City, IA, 52242, USA.,The Department of Veterans Medical Center, Iowa City, IA, 52242, USA
| | - William J Kutschke
- Department of Internal Medicine, Carver College of Medicine, University of Iowa, Iowa City, IA, 52242, USA
| | - Robert M Weiss
- Department of Internal Medicine, Carver College of Medicine, University of Iowa, Iowa City, IA, 52242, USA
| | - Christopher J Benson
- Department of Internal Medicine, Carver College of Medicine, University of Iowa, Iowa City, IA, 52242, USA.,The Department of Veterans Medical Center, Iowa City, IA, 52242, USA
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21
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Abstract
Cutaneous current-induced vasodilation (CIV) in response to galvanic current application is an integrative model of neurovascular interaction that relies on capsaicin-sensitive fiber activation. The upstream and downstream mechanisms related to the activation of the capsaicin-sensitive fibers involved in CIV are not elucidated. In particular, the activation of cutaneous transient receptor potential vanilloid type-1 (TRPV1) channels and/or acid-sensing ion channels (ASIC) (activators mechanisms) and the release of calcitonin gene-related peptide (CGRP) and substance P (SP) (effector mechanisms) have been tested. To assess cathodal CIV, we measured cutaneous blood flow using laser Doppler flowmetry for 20min following cathodal current application (240s, 100μA) on the skin of the thigh in anesthetized healthy rats for 20min. CIV was studied in rats treated with capsazepine and amiloride to inhibit TRPV1 and ASIC channels, respectively; CGRP8-37 and SR140333 to antagonize CGRP and neurokinin-1 (NK1) receptors, respectively; compared to their respective controls. Cathodal CIV was attenuated by capsazepine (12±2% vs 54±6%, P<0.001), amiloride (19±8% vs 61±6%, P<0.01), CGRP8-37 (15±6% vs 61±6%, P<0.001) and SR140333 (9±5% vs 54±6%, P<0.001) without changing local acidification. This is the first integrative study performed in healthy rats showing that cutaneous vasodilation in response to cathodal stimulation is initiated by activation of cutaneous TRPV1 and ASIC channels likely through local acidification. The involvement of CGRP and NK1 receptors suggests that cathodal CIV is the result of CGRP and SP released through activated capsaicin-sensitive fibers. Therefore cathodal CIV could be a valuable method to assess sensory neurovascular function in the skin, which would be particularly relevant to evaluate the presence of small nerve fiber disorders and the effectiveness of treatments.
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22
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Baron A, Lingueglia E. Pharmacology of acid-sensing ion channels – Physiological and therapeutical perspectives. Neuropharmacology 2015; 94:19-35. [DOI: 10.1016/j.neuropharm.2015.01.005] [Citation(s) in RCA: 108] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Academic Contribution Register] [Received: 09/01/2014] [Revised: 12/15/2014] [Accepted: 01/07/2015] [Indexed: 12/29/2022]
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24
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Abboud FM, Benson CJ. ASICs and cardiovascular homeostasis. Neuropharmacology 2015; 94:87-98. [PMID: 25592213 DOI: 10.1016/j.neuropharm.2014.12.017] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Academic Contribution Register] [Received: 08/13/2014] [Revised: 11/26/2014] [Accepted: 12/04/2014] [Indexed: 12/28/2022]
Abstract
In this review we address primarily the role of ASICs in determining sensory signals from arterial baroreceptors, peripheral chemoreceptors, and cardiopulmonary and somatic afferents. Alterations in these sensory signals during acute cardiovascular stresses result in changes in sympathetic and parasympathetic activities that restore cardiovascular homeostasis. In pathological states, however, chronic dysfunctions of these afferents result in serious sympatho-vagal imbalances with significant increases in mortality and morbidity. We identified a role for ASIC2 in the mechano-sensitivity of aortic baroreceptors and of ASIC3 in the pH sensitivity of carotid bodies. In spontaneously hypertensive rats, we reported decreased expression of ASIC2 in nodose ganglia neurons and overexpression of ASIC3 in carotid bodies. This reciprocal expression of ASIC2 and ASIC3 results in reciprocal changes in sensory sensitivity of baro- and chemoreceptors and a consequential synergistic exaggeration sympathetic nerve activity. A similar reciprocal sensory dysautonomia prevails in heart failure and increases the risk of mortality. There is also evidence that ASIC heteromers in skeletal muscle afferents contribute significantly to the exercise pressor reflex. In cardiac muscle afferents of the dorsal root ganglia, they contribute to nociception and to the detrimental sympathetic activation during ischemia. Finally, we report that an inhibitory influence of ASIC2-mediated baroreceptor activity suppresses the sympatho-excitatory reflexes of the chemoreceptors and skeletal muscle afferents, as well as the ASIC1a-mediated excitation of central neurons during fear, threat, or panic. The translational potential of activation of ASIC2 in cardiovascular disease states may be a beneficial sympatho-inhibition and parasympathetic activation. This article is part of the Special Issue entitled 'Acid-Sensing Ion Channels in the Nervous System'.
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Affiliation(s)
- François M Abboud
- Department of Internal Medicine, University of Iowa Carver College of Medicine, Iowa City, IA, USA; Department of Molecular Physiology and Biophysics, University of Iowa Carver College of Medicine, Iowa City, IA, USA; Abboud Cardiovascular Research Center, University of Iowa Carver College of Medicine, Iowa City, IA, USA.
| | - Christopher J Benson
- Department of Internal Medicine, University of Iowa Carver College of Medicine, Iowa City, IA, USA; Department of Pharmacology, University of Iowa Carver College of Medicine, Iowa City, IA, USA; Abboud Cardiovascular Research Center, University of Iowa Carver College of Medicine, Iowa City, IA, USA
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25
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Baxter JC, Ramachandra R, Mayne DR, Elmslie KS. Functional expression of α7-nicotinic acetylcholine receptors by muscle afferent neurons. J Neurophysiol 2014; 112:1549-58. [PMID: 24966300 DOI: 10.1152/jn.00035.2014] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Academic Contribution Register] [Indexed: 11/22/2022] Open
Abstract
The exercise pressor reflex (EPR) is generated by group III and IV muscle afferents during exercise to increase cardiovascular function. Muscle contraction is triggered by ACh, which is metabolized into choline that could serve as a signal of exercise-induced activity. We demonstrate that ACh can induce current in muscle afferents neurons isolated from male Sprague-Dawley rats. The nicotinic ACh receptors (nAChRs) appear to be expressed by some group III-IV neurons since capsaicin (TRPV1) and/or ATP (P2X) induced current in 56% of ACh-responsive neurons. α7- And α4β2-nAChRs have been shown to be expressed in sensory neurons. An α7-nAChR antibody stained 83% of muscle afferent neurons. Functional expression was demonstrated by using the specific α7-nAChR blockers α-conotoxin ImI (IMI) and methyllycaconitine (MLA). MLA inhibited ACh responses in 100% of muscle afferent neurons, whereas IMI inhibited ACh responses in 54% of neurons. Dihydro-β-erythroidine, an α4β2-nAChR blocker, inhibited ACh responses in 50% of muscle afferent neurons, but recovery from block was not observed. Choline, an α7-nAChR agonist, elicited a response in 60% of ACh-responsive neurons. Finally, we demonstrated the expression of α7-nAChR by peripherin labeled (group IV) afferent fibers within gastrocnemius muscles. Some of these α7-nAChR-positive fibers were also positive for P2X3 receptors. Thus choline could serve as an activator of the EPR by opening α7-nAChR expressed by group IV (and possible group III) afferents. nAChRs could become pharmacological targets for suppressing the excessive EPR activation in patients with peripheral vascular disease.
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Affiliation(s)
- James C Baxter
- The Baker Laboratory of Pharmacology, Department of Pharmacology, Kirksville College of Osteopathic Medicine, A.T. Still University of Health Sciences, Kirksville, Missouri
| | - Renuka Ramachandra
- The Baker Laboratory of Pharmacology, Department of Pharmacology, Kirksville College of Osteopathic Medicine, A.T. Still University of Health Sciences, Kirksville, Missouri
| | - Dustin R Mayne
- The Baker Laboratory of Pharmacology, Department of Pharmacology, Kirksville College of Osteopathic Medicine, A.T. Still University of Health Sciences, Kirksville, Missouri
| | - Keith S Elmslie
- The Baker Laboratory of Pharmacology, Department of Pharmacology, Kirksville College of Osteopathic Medicine, A.T. Still University of Health Sciences, Kirksville, Missouri
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26
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Noël J, Salinas M, Baron A, Diochot S, Deval E, Lingueglia E. Current perspectives on acid-sensing ion channels: new advances and therapeutic implications. Expert Rev Clin Pharmacol 2014; 3:331-46. [DOI: 10.1586/ecp.10.13] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Academic Contribution Register] [Indexed: 12/18/2022]
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Matricon J, Muller E, Accarie A, Meleine M, Etienne M, Voilley N, Busserolles J, Eschalier A, Lazdunski M, Bourdu S, Gelot A, Ardid D. Peripheral contribution of NGF and ASIC1a to colonic hypersensitivity in a rat model of irritable bowel syndrome. Neurogastroenterol Motil 2013; 25:e740-54. [PMID: 23902154 DOI: 10.1111/nmo.12199] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Academic Contribution Register] [Received: 02/18/2013] [Accepted: 07/08/2013] [Indexed: 12/11/2022]
Abstract
BACKGROUND Irritable bowel syndrome (IBS) is a functional gastrointestinal disorder associated with idiopathic colonic hypersensitivity (CHS). However, recent studies suggest that low-grade inflammation could underlie CHS in IBS. The pro-inflammatory mediator nerve growth factor (NGF) plays a key role in the sensitization of peripheral pain pathways and several studies have reported its contribution to visceral pain development. NGF modulates the expression of Acid-Sensing Ion Channels (ASICs), which are proton sensors involved in sensory neurons sensitization. This study examined the peripheral contribution of NGF and ASICs to IBS-like CHS induced by butyrate enemas in the rat colon. METHODS Colorectal distension and immunohistochemical staining of sensory neurons were used to evaluate NGF and ASICs contribution to the development of butyrate-induced CHS. KEY RESULTS Systemic injection of anti-NGF antibodies or the ASICs inhibitor amiloride prevented the development of butyrate-induced CHS. A significant increase in NGF and ASIC1a protein expression levels was observed in sensory neurons of rats displaying butyrate-induced CHS. This increase was specific of small- and medium-diameter L1 + S1 sensory neurons, where ASIC1a was co-expressed with NGF or trkA in CGRP-immunoreactive somas. ASIC1a was also overexpressed in retrogradely labeled colon sensory neurons. Interestingly, anti-NGF antibody administration prevented ASIC1a overexpression in sensory neurons of butyrate-treated rats. CONCLUSIONS & INFERENCES Our data suggest that peripheral NGF and ASIC1a concomitantly contribute to the development of butyrate-induced CHS NGF-ASIC1a interplay may have a pivotal role in the sensitization of colonic sensory neurons and as such, could be considered as a potential new therapeutic target for IBS treatment.
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Affiliation(s)
- J Matricon
- NEURO-DOL, Pharmacologie Fondamentale et Clinique de la Douleur, Faculté de Médecine, INSERM/UdA, UMR 1107, Université d'Auvergne, Clermont-Ferrand, France
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Leal AK, Stone AJ, Yamauchi K, McCord JL, Kaufman MP. Blockade of B2 receptors attenuates the responses of group III afferents to static contraction. Neurosci Lett 2013; 555:231-6. [PMID: 24036460 DOI: 10.1016/j.neulet.2013.09.013] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Academic Contribution Register] [Received: 08/12/2013] [Revised: 09/04/2013] [Accepted: 09/05/2013] [Indexed: 11/29/2022]
Abstract
Recent evidence has been presented demonstrating that group III mechanoreceptors comprise an important part of the sensory arm of the exercise pressor reflex, which in turn functions to increase arterial blood flow to contracting skeletal muscles. Although group III afferents are stimulated by mechanical distortion of their receptive fields, they are also stimulated by bradykinin, which is produced by skeletal muscle when it contracts. Moreover, blockade of B (bradykinin)2 receptors has been shown to decrease the magnitude of the exercise pressor reflex. Nevertheless, the effect of blockade of B2 receptors on responses of group III afferents to contraction is not known. We therefore determined the effect of B2 receptor blockade with HOE 140 (40μg/kg) on the responses to both static and intermittent contraction of group III afferents with endings in the triceps surae muscle of decerebrated unanesthetized cats. We found that HOE 140 significantly attenuated (P=0.04) the responses of 14 group III afferents to static contraction, but did not significantly attenuate (P=0.16) the responses of 16 group III afferents to intermittent contraction. The attenuation induced by HOE 140 was present throughout the static contraction period, and led us to speculate that blockade of B2 receptors on the endings of group III afferents decreased their sensitivity to mechanical events occurring in the working muscles.
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Affiliation(s)
- Anna K Leal
- Heart and Vascular Institute, Penn State College of Medicine, Hershey, PA 17033, United States.
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Baron A, Diochot S, Salinas M, Deval E, Noël J, Lingueglia E. Venom toxins in the exploration of molecular, physiological and pathophysiological functions of acid-sensing ion channels. Toxicon 2013; 75:187-204. [PMID: 23624383 DOI: 10.1016/j.toxicon.2013.04.008] [Citation(s) in RCA: 73] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Academic Contribution Register] [Received: 02/19/2013] [Accepted: 04/10/2013] [Indexed: 02/07/2023]
Abstract
Acid-sensing ion channels (ASICs) are voltage-independent proton-gated cation channels that are largely expressed in the nervous system as well as in some non-neuronal tissues. In rodents, six different isoforms (ASIC1a, 1b, 2a, 2b, 3 and 4) can associate into homo- or hetero-trimers to form a functional channel. Specific polypeptide toxins targeting ASIC channels have been isolated from the venoms of spider (PcTx1), sea anemone (APETx2) and snakes (MitTx and mambalgins). They exhibit different and sometimes partially overlapping pharmacological profiles and are usually blockers of ASIC channels, except for MitTx, which is a potent activator. This review focuses on the use of these toxins to explore the structure-function relationships, the physiological and the pathophysiological roles of ASIC channels, illustrating at the same time the therapeutic potential of some of these natural compounds.
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Affiliation(s)
- Anne Baron
- CNRS, Institut de Pharmacologie Moléculaire et Cellulaire, UMR 7275, 06560 Valbonne, France; Université de Nice-Sophia Antipolis, 06560 Valbonne, France; LabEx Ion Channel Science and Therapeutics, 06560 Valbonne, France
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Gautam M, Benson CJ. Acid-sensing ion channels (ASICs) in mouse skeletal muscle afferents are heteromers composed of ASIC1a, ASIC2, and ASIC3 subunits. FASEB J 2012; 27:793-802. [PMID: 23109675 DOI: 10.1096/fj.12-220400] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Academic Contribution Register] [Indexed: 01/20/2023]
Abstract
Acid-sensing ion channels (ASICs) are expressed in skeletal muscle afferents, in which they sense extracellular acidosis and other metabolites released during ischemia and exercise. ASICs are formed as homotrimers or heterotrimers of several isoforms (ASIC1a, ASIC1b, ASIC2a, ASIC2b, and ASIC3), with each channel displaying distinct properties. To dissect the ASIC composition in muscle afferents, we used whole-cell patch-clamp recordings to study the properties of acid-evoked currents (amplitude, pH sensitivity, the kinetics of desensitization and recovery from desensitization, and pharmacological modulation) in isolated, labeled mouse muscle afferents from wild-type (C57BL/6J) and specific ASIC(-/-) mice. We found that ASIC-like currents in wild-type muscle afferents displayed fast desensitization, indicating that they are carried by heteromeric channels. Currents from ASIC1a(-/-) muscle afferents were less pH-sensitive and displayed faster recovery, currents from ASIC2(-/-) mice showed diminished potentiation by zinc, and currents from ASIC3(-/-) mice displayed slower desensitization than those from wild-type mice. Finally, ASIC-like currents were absent from triple-null mice lacking ASIC1a, ASIC2a, and ASIC3. We conclude that ASIC1a, ASIC2a, and ASIC3 heteromers are the principle channels in skeletal muscle afferents. These results will help us understand the role of ASICs in exercise physiology and provide a molecular target for potential drug therapies to treat muscle pain.
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Affiliation(s)
- Mamta Gautam
- Department of Internal Medicine, Roy J. and Lucille A. Carver College of Medicine, University ofIowa, Iowa City, Iowa 52242, USA.
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Lu J, Xing J, Li J. Role for NGF in augmented sympathetic nerve response to activation of mechanically and metabolically sensitive muscle afferents in rats with femoral artery occlusion. J Appl Physiol (1985) 2012; 113:1311-22. [PMID: 22744968 DOI: 10.1152/japplphysiol.00617.2012] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Academic Contribution Register] [Indexed: 12/14/2022] Open
Abstract
Arterial blood pressure and heart rate responses to static contraction of the hindlimb muscles are greater in rats whose femoral arteries were previously ligated than in control rats. Also, the prior findings demonstrate that nerve growth factor (NGF) is increased in sensory neurons-dorsal root ganglion (DRG) neurons of occluded rats. However, the role for endogenous NGF in engagement of the augmented sympathetic and pressor responses to stimulation of mechanically and/or metabolically sensitive muscle afferent nerves during static contraction after femoral artery ligation has not been specifically determined. In the present study, both afferent nerves and either of them were activated by muscle contraction, passive tendon stretch, and arterial injection of lactic acid into the hindlimb muscles. Data showed that femoral occlusion-augmented blood pressure response to contraction was significantly attenuated by a prior administration of the NGF antibody (NGF-Ab) into the hindlimb muscles. The effects of NGF neutralization were not seen when the sympathetic nerve and pressor responses were evoked by stimulation of mechanically sensitive muscle afferent nerves with tendon stretch in occluded rats. In addition, chemically sensitive muscle afferent nerves were stimulated by lactic acid injected into arterial blood supply of the hindlimb muscles after the prior NGF-Ab, demonstrating that the reflex muscle responses to lactic acid were significantly attenuated. The results of this study further showed that NGF-Ab attenuated an increase in acid-sensing ion channel subtype 3 (ASIC3) of DRG in occluded rats. Moreover, immunohistochemistry was employed to examine the number of C-fiber and A-fiber DRG neurons. The data showed that distribution of DRG neurons with different thin fiber phenotypes was not notably altered when NGF was infused into the hindlimb muscles. However, NGF increased expression of ASIC3 in DRG neurons with C-fiber but not A-fiber. Overall, these data suggest that 1) NGF is amplified in sensory nerves of occluded rats and contributes to augmented reflex sympathetic and blood pressure responses evoked by stimulation of chemically, but not mechanically, sensitive muscle afferent nerves and 2) NGF likely plays a role in modulating the muscle metaboreflex via enhancement of ASIC3 expression in C-fiber of DRG neurons.
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Affiliation(s)
- Jian Lu
- Pennsylvania State Heart and Vascular Institute, The Pennsylvania State University College of Medicine, Hershey, PA 17033, USA
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Dipla K, Nassis GP, Vrabas IS. Blood Pressure Control at Rest and during Exercise in Obese Children and Adults. J Obes 2012; 2012:147385. [PMID: 22666555 PMCID: PMC3361254 DOI: 10.1155/2012/147385] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Academic Contribution Register] [Received: 11/30/2011] [Revised: 02/19/2012] [Accepted: 03/01/2012] [Indexed: 11/17/2022] Open
Abstract
The hemodynamic responses to exercise have been studied to a great extent over the past decades, and an exaggerated blood pressure response during an acute exercise bout has been considered as an indicator of cardiovascular risk. Obesity is a major factor influencing the blood pressure response to exercise since evidence indicates that the arterial pressure response to exercise is exacerbated in obese compared with lean adults. Signs of augmented responses (such as an exaggerated blood pressure response) to physical exertion appear early in life (from the prepubertal years) in obese individuals. Understanding the mechanisms that drive the altered hemodynamic responses during exercise in obese individuals and prevent the progression to hypertension is vitally important. This paper focuses on the evidence linking obesity with alterations of the autonomic nervous system and discusses the potential mechanisms and consequences of the altered sympathetic nervous system behavior in obese individuals at rest and during exercise. Furthermore, this paper presents the alterations in the reflex regulatory mechanisms ("exercise pressor reflex" and baroreflex) in obese children and adults and addresses the effects of training on obesity-related disturbances.
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Affiliation(s)
- Konstantina Dipla
- Exercise Physiology and Biochemistry Laboratory, Department of Physical Education and Sport Sciences at Serres, Aristotle University of Thessaloniki, Agios Ioannis, 62110 Serres, Greece
- *Konstantina Dipla:
| | - George P. Nassis
- Department of Sport Medicine and Biology of Exercise, Faculty of Physical Education and Sport Science, University of Athens, 17237 Daphne, Greece
| | - Ioannis S. Vrabas
- Exercise Physiology and Biochemistry Laboratory, Department of Physical Education and Sport Sciences at Serres, Aristotle University of Thessaloniki, Agios Ioannis, 62110 Serres, Greece
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Xing J, Lu J, Li J. Acid-sensing ion channel subtype 3 function and immunolabelling increases in skeletal muscle sensory neurons following femoral artery occlusion. J Physiol 2011; 590:1261-72. [PMID: 22183722 DOI: 10.1113/jphysiol.2011.221788] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Academic Contribution Register] [Indexed: 12/18/2022] Open
Abstract
Sympathetic nerve activity and arterial blood pressure responses to static hindlimb muscle contractions are greater in rats with femoral arteries that were previously ligated (24-72 h earlier) than in control rats. Studies further demonstrate that acid-sensing ion channel subtype 3 (ASIC(3)) in thin-fibre muscle afferents contributes to the amplified reflex muscle responses observed in occluded rats, probably due to enhanced ASIC(3) expression in muscle sensory neurons. The purpose of this study was to characterize acid-induced current with activation of ASIC(3) in dorsal root ganglion (DRG) neurons of control rats and rats with 24 h of femoral occlusion using whole-cell patch clamp methods. Also, immunohistochemistry was employed to examine existence of ASIC(3) expression in DRG neurons of thin-fibre afferents. DRG neurons from 4- to 6-week-old rats were labelled by injecting the fluorescence tracer DiI into the hindlimb muscles 4-5 days prior to the recording experiments. The results of this study show that ∼90% of current responses evoked by pH 6.7 in DRG neurons innervating the hindlimb muscles are ASIC(3)-like. The peak current amplitude to pH 6.7 is significantly attenuated with application of rAPETx2, a specific ASIC(3) antagonist. In addition, ASIC(3)-like current responses to pH 6.7 are observed in small, medium and large DRG neurons, and size distribution of DRG neurons is similar in control and occluded animals. However, the peak current amplitude of DRG neuron response induced by ASIC(3) stimulation is larger in occluded rats than that in control rats. Moreover, the percentage of DRG neurons with ASIC(3)-like currents is greater after arterial occlusion compared with control. Furthermore, results from double immunofluorescence experiments show that femoral artery occlusion mainly augments ASIC(3) expression within DRG neurons projecting C-fibre afferents. Taken together, these data suggest that (1) the majority of current responses to pH 6.7 are ASIC(3)-like in DRG neurons with nerve endings in the hindlimb muscles, (2) a greater acid-induced current responding to pH 6.7 develops when hindlimb arterial blood supply is deficient under ischaemic conditions, and (3) increased ASIC(3) expression is largely observed in thin C-fibres of DRG neurons after hindlimb ischaemia.
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Affiliation(s)
- Jihong Xing
- Pennsylvania State Heart & Vascular Institute, The Pennsylvania State University College of Medicine, Hershey, PA 17033, USA
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Mizuno M, Murphy MN, Mitchell JH, Smith SA. Antagonism of the TRPv1 receptor partially corrects muscle metaboreflex overactivity in spontaneously hypertensive rats. J Physiol 2011; 589:6191-204. [PMID: 22025666 DOI: 10.1113/jphysiol.2011.214429] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Academic Contribution Register] [Indexed: 01/12/2023] Open
Abstract
The circulatory response to exercise is exaggerated in hypertension potentially increasing the risk for adverse cardiovascular events. Evidence suggests the skeletal muscle metaboreflex contributes to this abnormal circulatory response. However, as the sensitivity of this reflex has been reported to be both reduced and potentiated in hypertension, its role remains controversial. In addition, the receptor mechanisms underlying muscle metaboreflex dysfunction in this disease remain undetermined. To address these issues, metaboreflex activity was assessed during 'supra-stimulation' of the reflex via ischaemic hindlimb muscle contraction. This manoeuvre evoked significantly larger increases in mean arterial pressure (MAP) and renal sympathetic nerve activity (RSNA) in spontaneously hypertensive rats (SHR) compared to normotensive Wistar-Kyoto (WKY) rats. The skeletal muscle TRPv1 receptor was evaluated as a potential mediator of this metaboreflex response as it has been shown to contribute significantly to muscle reflex activation in healthy animals. Stimulation of the TRPv1 receptor by injection of capsaicin into the arterial supply of the hindlimb evoked significantly larger elevations in MAP and RSNA in SHR compared to WKY. The pressor and sympathetic responses to ischaemic muscle contraction in WKY and SHR were attenuated by the administration of the TRPv1 receptor antagonist capsazepine with the magnitude of the capsazepine-induced reductions being greater in SHR than WKY. TRPv1 protein expression in dorsal root ganglia, but not skeletal muscle, was significantly greater in SHR than WKY. The results suggest the muscle metaboreflex is overactive in hypertension. Further, this reflex overactivity can be partially normalized by antagonizing TRPv1 receptors in skeletal muscle.
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Affiliation(s)
- Masaki Mizuno
- Department of Physical Therapy, University of Texas Southwestern Medical Center, Dallas, TX 75390-9174, USA
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Tsuchimochi H, Yamauchi K, McCord JL, Kaufman MP. Blockade of acid sensing ion channels attenuates the augmented exercise pressor reflex in rats with chronic femoral artery occlusion. J Physiol 2011; 589:6173-89. [PMID: 22005681 DOI: 10.1113/jphysiol.2011.217851] [Citation(s) in RCA: 55] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Academic Contribution Register] [Indexed: 02/06/2023] Open
Abstract
We found previously that static contraction of the hindlimb muscles of rats whose femoral artery was ligated evoked a larger reflex pressor response (i.e. exercise pressor reflex) than did static contraction of the contralateral hindlimb muscles which were freely perfused. Ligating a femoral artery in rats results in blood flow patterns to the muscles that are remarkably similar to those displayed by humans with peripheral artery disease. Using decerebrated rats, we tested the hypothesis that the augmented exercise pressor reflex in rats with a ligated femoral artery is attenuated by blockade of the acid sensing ion channel (ASIC) 3. We found that femoral arterial injection of either amiloride (5 and 50 μg kg(-1)) or APETx2 (100 μg kg(-1)) markedly attenuated the reflex in rats with a ligated femoral artery. In contrast, these ASIC antagonists had only modest effects on the reflex in rats with freely perfused hindlimbs. Tests of specificity of the two antagonists revealed that the low dose of amiloride and APETx2 greatly attenuated the pressor response to lactic acid, an ASIC agonist, but did not attenuate the pressor response to capsaicin, a TRPV1 agonist. In contrast, the high dose of amiloride attenuated the pressor responses to lactic acid, but also attenuated the pressor response to capsaicin. We conclude that ASIC3 on thin fibre muscle afferents plays an important role in evoking the exercise pressor reflex in rats with a compromised arterial blood supply to the working muscles.
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Affiliation(s)
- Hirotsugu Tsuchimochi
- Penn State Heart and Vascular Institute, Pennsylvania State University College of Medicine, Hershey, PA 17033, USA
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Liu J, Li JD, Lu J, Xing J, Li J. Contribution of nerve growth factor to upregulation of P2X₃ expression in DRG neurons of rats with femoral artery occlusion. Am J Physiol Heart Circ Physiol 2011; 301:H1070-9. [PMID: 21642505 DOI: 10.1152/ajpheart.00188.2011] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Academic Contribution Register] [Indexed: 12/12/2022]
Abstract
Femoral artery occlusion augments the sympathetic nerve and pressor responses to muscle contraction and muscle metabolites injected into the arterial blood supply of the hindlimb muscles in rats. The underlying mechanism by which these reflex responses are enhanced after muscle vascular insufficiency is unclear. Purinergic P2X(3) receptor has been reported to contribute to the metabolic component of the exercise pressor reflex. Thus the purpose of this study was to examine if chronic femoral occlusion would alter the expression of P2X(3) in dorsal root ganglion (DRG) neurons of rats. Also, P2X(3)-mediated sympathetic responsiveness was examined after femoral occlusion. In addition, the role played by nerve growth factor (NGF) in regulating the expression and response of P2X(3) was examined. Western blot analysis showed that 24 h of femoral ligation increased the levels of P2X(3) (optical density: 0.93 ± 0.07 in control and 1.37 ± 0.10 after occlusion; P < 0.05 vs. control). The fluorescence immunohistochemistry further demonstrated that the occlusion elevated P2X(3) expression in DRG neurons (percentage of P2X(3)-positive cells: 33 ± 3% in control and 51 ± 3% in occlusion; P < 0.05 vs. control). Furthermore, the results showed that responses of renal sympathetic nerve activity and blood pressure to stimulation of P2X were greater in occluded rats than responses in control rats by injection of α,β-methylene ATP into the arterial blood supply of the hindlimb muscle. Finally, infusion of NGF in the hindlimb muscles of healthy rats increased P2X(3) (optical density: 0.98 ± 0.12 in control and 1.37 ± 0.16 with NGF; P < 0.05 vs. control). The pressor response to injection of α,β-methylene ATP was increased in the rats with NGF infusion. Likewise, blocking NGF attenuated exaggeration of the reflex response induced by α,β-methylene ATP in occluded rats. The findings of this study suggest that the levels of P2X(3) in primary afferent neurons are upregulated as the blood supply to the hindlimb is deficient under ischemic conditions, leading to augmentation of the muscle reflex. NGF is closely related to increases in P2X(3) receptor expression and response.
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Affiliation(s)
- Jiahao Liu
- Penn State Heart and Vascular Institute, Pennsylvania State University College of Medicine, Hershey, Pennsylvania 17033, USA
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Wang HJ, Li YL, Zhang LB, Zucker IH, Gao L, Zimmerman MC, Wang W. Endogenous reactive oxygen species modulates voltage-gated sodium channels in dorsal root ganglia of rats. J Appl Physiol (1985) 2011; 110:1439-47. [PMID: 21292836 DOI: 10.1152/japplphysiol.01409.2010] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Academic Contribution Register] [Indexed: 11/22/2022] Open
Abstract
We recently reported that reactive oxygen species (ROS) plays an excitatory role in modulation of the exercise pressor reflex (EPR) in normal rats. In this study, we further tested two independent hypotheses: 1) ROS interacts with EPR-related ionotropic receptors such as the purinergic receptors (P(2)) and transient receptor potential vanilloid 1 receptors (TRPV1) to indirectly modulate the EPR function; 2) ROS directly affects excitability of muscle afferents by modulating the voltage-gated sodium (Na(v)) channels. To test the first hypothesis, we performed animal experiments to investigate the effect of the SOD mimetic 4-hydroxy-2,2,6,6-tetramethyl piperidine 1-oxyl (Tempol) on the pressor response to hindlimb intra-arterial (IA) injection of either α,β-methylene ATP (a P(2X) agonist) or capsaicin (a TRPV1 agonist) in decerebrate rats. To test the second hypothesis, we used the patch-clamp technique to determine the effect of ROS on Na(v) channels on the soma of muscle afferents. We also performed local microinjection of a sodium channel blocker, tetrodotoxin (TTX), into ipsilateral L4/L5 dorsal root ganglia (DRGs) to investigate whether the blockade of Na(v) channels by TTX affects the EPR function. We found that Tempol did not affect the pressor response to injection of either capsaicin or α,β-methylene ATP but significantly decreased the Na(v) current in small and medium-sized 1,1'-dioctadecyl-3,3,3',3'-tetramethylindocarbocyanine perchlorate (DiI)-labeled DRG neurons. A membrane-permeant superoxide dismutase, polyethylene glycol (PEG)-SOD, had an effect on the Na(v) current in these neurons similar to that of Tempol. Microinjection of TTX into L4/L5 DRGs dramatically attenuated the pressor response to static contraction induced by electrical stimulation of L4/L5 ventral roots. These data suggest that ROS modulates the EPR by affecting the activity of the Na(v) channels on muscle afferents.
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Affiliation(s)
- Han-Jun Wang
- Department of Cellular and Integrative Physiology, University of Nebraska Medical Center, Omaha, NE 68198-5850, USA
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Koba S, Hayes SG, Sinoway LI. Transient receptor potential A1 channel contributes to activation of the muscle reflex. Am J Physiol Heart Circ Physiol 2010; 300:H201-13. [PMID: 21076024 DOI: 10.1152/ajpheart.00547.2009] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Academic Contribution Register] [Indexed: 11/22/2022]
Abstract
This study was undertaken to elucidate the role played by transient receptor potential A1 channels (TRPA1) in activating the muscle reflex, a sympathoexcitatory drive originating in contracting muscle. First, we tested the hypothesis that stimulation of the TRPA1 located on muscle afferents reflexly increases sympathetic nerve activity. In decerebrate rats, allyl isothiocyanate, a TRPA1 agonist, was injected intra-arterially into the hindlimb muscle circulation. This led to a 33% increase in renal sympathetic nerve activity (RSNA). The effect of allyl isothiocyanate was a reflex because the response was prevented by sectioning the sciatic nerve. Second, we tested the hypothesis that blockade of TRPA1 reduces RSNA response to contraction. Thirty-second continuous static contraction of the hindlimb muscles, induced by electrical stimulation of the peripheral cut ends of L(4) and L(5) ventral roots, increased RSNA and blood pressure. The integrated RSNA during contraction was reduced by HC-030031, a TRPA1 antagonist, injected intra-arterially (163 ± 24 vs. 95 ± 21 arbitrary units, before vs. after HC-030031, P < 0.05). Third, we attempted to identify potential endogenous stimulants of TRPA1, responsible for activating the muscle reflex. Increases in RSNA in response to injection into the muscle circulation of arachidonic acid, bradykinin, and diprotonated phosphate, which are metabolic by-products of contraction and stimulants of muscle afferents during contraction, were reduced by HC-030031. These observations suggest that the TRPA1 located on muscle afferents is part of the muscle reflex and further support the notion that arachidonic acid metabolites, bradykinin, and diprotonated phosphate are candidates for endogenous agonists of TRPA1.
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Affiliation(s)
- Satoshi Koba
- Penn State Heart and Vascular Institute, Pennsylvania State University College of Medicine, Hershey, Pennsylvania, USA.
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Liu J, Gao Z, Li J. Femoral artery occlusion increases expression of ASIC3 in dorsal root ganglion neurons. Am J Physiol Heart Circ Physiol 2010; 299:H1357-64. [PMID: 20852050 DOI: 10.1152/ajpheart.00612.2010] [Citation(s) in RCA: 55] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Academic Contribution Register] [Indexed: 01/23/2023]
Abstract
Acid-sensing ion channels (ASICs) in sensory nerves are responsive to increases in the levels of protons in the extracellular medium. Prior studies suggest that the muscle metabolite, lactic acid, plays a role in reflex sympathetic and cardiovascular responses via stimulation of thin muscle afferent nerves. Also, femoral artery occlusion augments the reflex sympathetic nerve response in rats. ASIC3 is a main subtype to appear in sensory nerves in mediating the response induced by increases in protons in the interstitial space of contracting muscles. Thus, in this article, we hypothesized that femoral occlusion increases the expression of ASIC3 in primary afferent neurons innervating muscles, and this contributes to the exaggerated reflex sympathetic responses. Femoral occlusion/vascular insufficiency of the hindlimb muscles was induced by the femoral artery ligation in rats. First, Western blot analysis shows that 24-72 h of femoral artery ligation significantly increased the expression of ASIC3 protein in dorsal root ganglion (optical density, 1.0 ± 0.07 in control vs. 1.65 ± 0.1 after 24 h of occlusion, P < 0.05; n = 6 in each group). There were no significant differences for increases in ASIC3 24 and 72 h postocclusion. Second, experiments using fluorescent immunohistochemistry and retrograde-labeling technique show that a greater percentage of ASIC3 staining neurons are localized in muscle-innervating dorsal root ganglion neurons after the arterial occlusion (78 ± 3% in 24 h post occlusion vs. 59 ± 5% in control, P < 0.05; n = 6 in each group). Third, the reflex responses in renal sympathetic nerve and arterial blood pressure induced by the stimulation of ASIC were examined after an injection of lactic acid into the arterial blood supply of hindlimb muscles of control rats and ligated rats. The results demonstrate that the sympathetic and pressor responses to lactic acid were significantly augmented after femoral occlusion compared with those in the control group. The data of this study suggest that enhanced ASIC3 expression in muscle afferent nerves contributes to the exaggerated reflex sympathetic and pressor responses to lactic acid as seen in arterial occlusion.
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Affiliation(s)
- Jiahao Liu
- Pennsylvania State Heart and Vascular Institute, The Pennsylvania State University College of Medicine, Hershey, Pennsylvania 17033, USA
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Rumsey JW, Das M, Bhalkikar A, Stancescu M, Hickman JJ. Tissue engineering the mechanosensory circuit of the stretch reflex arc: sensory neuron innervation of intrafusal muscle fibers. Biomaterials 2010; 31:8218-27. [PMID: 20708792 DOI: 10.1016/j.biomaterials.2010.07.027] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Academic Contribution Register] [Received: 06/25/2010] [Accepted: 07/04/2010] [Indexed: 11/19/2022]
Abstract
The sensory circuit of the stretch reflex arc, composed of specialized intrafusal muscle fibers and type Ia proprioceptive sensory neurons, converts mechanical information regarding muscle length and stretch to electrical action potentials and relays them to the central nervous system. Utilizing a non-biological substrate, surface patterning photolithography and a serum-free medium formulation a co-culture system was developed that facilitated functional interactions between intrafusal muscle fibers and sensory neurons. The presence of annulospiral wrappings (ASWs) and flower-spray endings (FSEs), both physiologically relevant morphologies in sensory neuron-intrafusal fiber interactions, were demonstrated and quantified using immunocytochemistry. Furthermore, two proposed components of the mammalian mechanosensory transduction system, BNaC1 and PICK1, were both identified at the ASWs and FSEs. To verify functionality of the mechanoreceptor elements the system was integrated with a MEMS cantilever device, and Ca(2+) currents were imaged along the length of an axon innervating an intrafusal fiber when stretched by cantilever deflection. This system provides a platform for examining the role of this mechanosensory complex in the pathology of myotonic and muscular dystrophies, peripheral neuropathy, and spasticity inducing diseases like Parkinson's. These studies will also assist in engineering fine motor control for prosthetic devices by improving our understanding of mechanosensitive feedback.
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Affiliation(s)
- John W Rumsey
- NanoScience Technology Center, University of Central Florida, 12424 Research Parkway, Suite 400, Orlando, FL 32826, USA
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Wang HJ, Pan YX, Wang WZ, Zucker IH, Wang W. NADPH oxidase-derived reactive oxygen species in skeletal muscle modulates the exercise pressor reflex. J Appl Physiol (1985) 2009; 107:450-9. [PMID: 19498097 DOI: 10.1152/japplphysiol.00262.2009] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Academic Contribution Register] [Indexed: 01/09/2023] Open
Abstract
Muscle metabolic by-products during exercise, such as K+, lactic acid, ATP, H+, and phosphate, are well established to be involved in the reflex cardiovascular response to static muscle contraction. However, the role of muscle reactive oxygen species (ROS), a metabolic by-product during muscle contraction, in the exercise pressor reflex (EPR) has not been investigated in detail. In the present study, we evaluated the role of muscle ROS in the EPR in a decerebrate rat model. We hypothesized that muscle NADPH oxidase-derived ROS contributes to sensitization of the EPR. Thus the rise in blood pressure and heart rate in response to a 30-s static contraction induced by electrical stimulation of L4/L5 ventral roots was compared before and after hindlimb arterial infusion of the redox agents: diethyldithiocarbamate, a superoxide dismutase inhibitor; the superoxide dismutase mimetic 4-hydroxy-2,2,6,6-tetramethyl piperidine 1-oxyl (tempol); the free radical scavenger dimethylthiourea; a NADPH oxidase inhibitor, apocynin; and a xanthine oxidase inhibitor, allopurinol. The EPR-induced pressor response was augmented after treatment with diethyldithiocarbamate and was attenuated after treatment with tempol, dimethylthiourea, and apocynin. Treatment with allopurinol did not affect the EPR function. None of the drug's affected the EPR heart rate response. In addition, neither the pressor response to electrical stimulation of the central end of dorsal roots, nor femoral blood flow was affected by any treatment. These data suggest that NADPH oxidase-derived muscle ROS plays an excitatory role in the EPR control of blood pressure.
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Affiliation(s)
- Han-Jun Wang
- Department of Cellular and Integrative Physiology, University of Nebraska Medical Center, Omaha, NE 68198-5850, USA
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McCord JL, Tsuchimochi H, Kaufman MP. Acid-sensing ion channels contribute to the metaboreceptor component of the exercise pressor reflex. Am J Physiol Heart Circ Physiol 2009; 297:H443-9. [PMID: 19465550 DOI: 10.1152/ajpheart.00328.2009] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Academic Contribution Register] [Indexed: 12/15/2022]
Abstract
The exercise pressor reflex is evoked by both mechanical and metabolic stimuli arising in contracting skeletal muscle. Recently, the blockade of acid-sensing ion channels (ASICs) with amiloride and A-316567 attenuated the reflex. Moreover, amiloride had no effect on the mechanoreceptor component of the reflex, prompting us to determine whether ASICs contributed to the metaboreceptor component of the exercise pressor reflex. The metaboreceptor component can be assessed by measuring mean arterial pressure during postcontraction circulatory occlusion when only the metaboreceptors are stimulated. We examined the effects of amiloride (0.5 microg/kg), A-317567 (10 mM, 0.5 ml), and saline (0.5 ml) on the pressor response to and after static contraction while the circulation was occluded in 30 decerebrated cats. Amiloride (n = 11) and A-317567 (n = 7), injected into the arterial supply of the triceps surae muscles, attenuated the pressor responses both to contraction while the circulation was occluded and to postcontraction circulatory occlusion (all, P < 0.05). Saline (n = 11), however, had no effect on the pressor responses to contraction while the circulation was occluded or to postcontraction circulatory occlusion (both, P > 0.79). Our findings led us to conclude that ASICs contribute to the metaboreceptor component of the exercise pressor reflex.
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Affiliation(s)
- Jennifer L McCord
- Pennsylvania State Heart and Vascular Institute, Pennsylvania State University College of Medicine, Hershey, PA 17033, USA.
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Ambalavanar R, Dessem D. Emerging peripheral receptor targets for deep-tissue craniofacial pain therapies. J Dent Res 2009; 88:201-11. [PMID: 19329451 DOI: 10.1177/0022034508330176] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Academic Contribution Register] [Indexed: 12/20/2022] Open
Abstract
While effective therapies are available for some types of craniofacial pain, treatments for deep-tissue craniofacial pain such as temporomandibular disorders are less efficacious. Several ion channels and receptors which are prominent in craniofacial nociceptive mechanisms have been identified on trigeminal primary afferent neurons. Many of these receptors and channels exhibit unusual distributions compared with extracranial regions. For example, expression of the ATP receptor P2X(3) is strongly implicated in nociception and is more abundant on trigeminal primary afferent neurons than analogous extracranial neurons, making them potentially productive targets specifically for craniofacial pain therapies. The initial part of this review therefore focuses on P2X(3) as a potential therapeutic target to treat deep-tissue craniofacial pain. In the trigeminal ganglion, P2X(3) receptors are often co-expressed with the nociceptive neuropeptides CGRP and SP. Therefore, we discuss the role of CGRP and SP in deep-tissue craniofacial pain and suggest that neuropeptide antagonists, which have shown promise for the treatment of migraine, may have wider therapeutic potential, including the treatment of deep-tissue craniofacial pain. P2X(3), TRPV1, and ASIC3 are often co-expressed in trigeminal neurons, implying the formation of functional complexes that allow craniofacial nociceptive neurons to respond synergistically to altered ATP and pH in pain. Future therapeutics for craniofacial pain thus might be more efficacious if targeted at combinations of P2X(3), CGRP, TRPV1, and ASIC3.
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Affiliation(s)
- R Ambalavanar
- Department of Neural and Pain Sciences and Program in Neuroscience, University of Maryland, Baltimore, MD 21201, USA
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Abstract
Acidosis is a noxious condition associated with inflammation, ischaemia or defective acid containment. As a consequence, acid sensing has evolved as an important property of afferent neurons with unmyelinated and thinly myelinated nerve fibres. Protons evoke multiple currents in primary afferent neurons, which are carried by several acid-sensitive ion channels. Among these, acid-sensing ion channels (ASICs) and transient receptor potential (TRP) vanilloid-1 (TRPV1) ion channels have been most thoroughly studied. ASICs survey moderate decreases in extracellular pH, whereas TRPV1 is activated only by severe acidosis resulting in pH values below 6. Two-pore-domain K(+) (K(2P)) channels are differentially regulated by small deviations of extra- or intracellular pH from physiological levels. Other acid-sensitive channels include TRPV4, TRPC4, TRPC5, TRPP2 (PKD2L1), ionotropic purinoceptors (P2X), inward rectifier K(+) channels, voltage-activated K(+) channels, L-type Ca(2+) channels, hyperpolarization-activated cyclic nucleotide gated channels, gap junction channels, and Cl(-) channels. In addition, acid-sensitive G protein coupled receptors have also been identified. Most of these molecular acid sensors are expressed by primary sensory neurons, although to different degrees and in various combinations. Emerging evidence indicates that many of the acid-sensitive ion channels and receptors play a role in acid sensing, acid-induced pain and acid-evoked feedback regulation of homeostatic reactions. The existence and apparent redundancy of multiple pH surveillance systems attests to the concept that acid-base regulation is a vital issue for cell and tissue homeostasis. Since upregulation and overactivity of acid sensors appear to contribute to various forms of chronic pain, acid-sensitive ion channels and receptors are considered as targets for novel analgesic drugs. This approach will only be successful if the pathological implications of acid sensors can be differentiated pharmacologically from their physiological function.
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Affiliation(s)
- Peter Holzer
- Research Unit of Translational Neurogastroenterology, Institute of Experimental and Clinical Pharmacology, Medical University of Graz, Universitätsplatz 4, 8010, Graz, Austria.
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Fujii Y, Ozaki N, Taguchi T, Mizumura K, Furukawa K, Sugiura Y. TRP channels and ASICs mediate mechanical hyperalgesia in models of inflammatory muscle pain and delayed onset muscle soreness. Pain 2008; 140:292-304. [PMID: 18834667 DOI: 10.1016/j.pain.2008.08.013] [Citation(s) in RCA: 95] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Academic Contribution Register] [Received: 03/11/2008] [Revised: 08/19/2008] [Accepted: 08/19/2008] [Indexed: 12/17/2022]
Abstract
The roles of ion channels in sensory neurons were examined in experimental models of muscle pain in the rat. Rats were injected with 50 microl of 4% carrageenan or subjected to an eccentric exercise (ECC) of the gastrocnemius muscle (GM). The Randall-Selitto and von Frey tests were performed on the calves to evaluate mechanical hyperalgesia of the muscle. The changes in expression of four genes and proteins of ion channels in dorsal root ganglia were examined using quantitative PCR and immunohistochemistry, respectively. Effects of antagonists to transient receptor potential (TRP) channels and acid sensing ion channels (ASICs) on the mechanical hyperalgesia induced by carrageenan injection or ECC were evaluated. The mechanical hyperalgesia was observed 6-24h after carrageenan injection and 1-3 days after ECC in the Randall-Selitto test. Infiltrations of the inflammatory cells in the GM were seen in carrageenan-injected animals but not in those subjected to ECC. Expressions of genes and proteins in sensory neurons showed no changes. Intramuscular injection of antagonists to TRPV1 showed an almost complete suppressive effect on ECC-induced muscle hyperalgesia but not a carrageenan-induced one. Antagonists to TRP channels and ASICs showed suppressive effects for both carrageenan- and ECC-induced muscle hyperalgesia. The carrageenan injection and ECC models are useful models of acute inflammatory pain and delayed onset muscle soreness (DOMS), respectively, and the time course and underlying etiology might be different. TRP channels and ASICs are closely related to the development of muscle mechanical hyperalgesia, and TRPV1 is involved in ECC-induced DOMS.
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Affiliation(s)
- Yuko Fujii
- Department of Functional Anatomy and Neuroscience, Nagoya University Graduate School of Medicine, 65 Tsurumai-cho, Showa-ku, Nagoya 466-8550, Japan Department of Neuroscience II, Research Institute of Environmental Medicine, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8601, Japan Department of Biochemistry II, Nagoya University Graduate School of Medicine, 65 Tsurumai-cho, Showa-ku, Nagoya 466-0065, Japan
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Light AR, Hughen RW, Zhang J, Rainier J, Liu Z, Lee J. Dorsal root ganglion neurons innervating skeletal muscle respond to physiological combinations of protons, ATP, and lactate mediated by ASIC, P2X, and TRPV1. J Neurophysiol 2008; 100:1184-201. [PMID: 18509077 PMCID: PMC6195653 DOI: 10.1152/jn.01344.2007] [Citation(s) in RCA: 226] [Impact Index Per Article: 13.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Academic Contribution Register] [Received: 12/13/2007] [Accepted: 05/27/2008] [Indexed: 12/14/2022] Open
Abstract
The adequate stimuli and molecular receptors for muscle metaboreceptors and nociceptors are still under investigation. We used calcium imaging of cultured primary sensory dorsal root ganglion (DRG) neurons from C57Bl/6 mice to determine candidates for metabolites that could be the adequate stimuli and receptors that could detect these stimuli. Retrograde DiI labeling determined that some of these neurons innervated skeletal muscle. We found that combinations of protons, ATP, and lactate were much more effective than individually applied compounds for activating rapid calcium increases in muscle-innervating dorsal root ganglion neurons. Antagonists for P2X, ASIC, and TRPV1 receptors suggested that these three receptors act together to detect protons, ATP, and lactate when presented together in physiologically relevant concentrations. Two populations of muscle-innervating DRG neurons were found. One responded to low metabolite levels (likely nonnoxious) and used ASIC3, P2X5, and TRPV1 as molecular receptors to detect these metabolites. The other responded to high levels of metabolites (likely noxious) and used ASIC3, P2X4, and TRPV1 as their molecular receptors. We conclude that a combination of ASIC, P2X5 and/or P2X4, and TRPV1 are the molecular receptors used to detect metabolites by muscle-innervating sensory neurons. We further conclude that the adequate stimuli for muscle metaboreceptors and nociceptors are combinations of protons, ATP, and lactate.
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Affiliation(s)
- Alan R Light
- Department of Anethesiology, University of Utah School of Medicine, Salt Lake City, UT 84132-2304, USA.
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Hayes SG, McCord JL, Rainier J, Liu Z, Kaufman MP. Role played by acid-sensitive ion channels in evoking the exercise pressor reflex. Am J Physiol Heart Circ Physiol 2008; 295:H1720-5. [PMID: 18723762 DOI: 10.1152/ajpheart.00623.2008] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Academic Contribution Register] [Indexed: 01/26/2023]
Abstract
The exercise pressor reflex arises from contracting skeletal muscle and is believed to play a role in evoking the cardiovascular responses to static exercise, effects that include increases in arterial pressure and heart rate. This reflex is believed to be evoked by the metabolic and mechanical stimulation of thin fiber muscle afferents. Lactic acid is known to be an important metabolic stimulus evoking the reflex. Until recently, the only antagonist for acid-sensitive ion channels (ASICs), the receptors to lactic acid, was amiloride, a substance that is also a potent antagonist for both epithelial sodium channels as well as voltage-gated sodium channels. Recently, a second compound, A-317567, has been shown to be an effective and selective antagonist to ASICs in vitro. Consequently, we measured the pressor responses to the static contraction of the triceps surae muscles in decerebrate cats before and after a popliteal arterial injection of A-317567 (10 mM solution; 0.5 ml). We found that this ASIC antagonist significantly attenuated by half (P<0.05) the pressor responses to both contraction and to lactic acid injection into the popliteal artery. In contrast, A-317567 had no effect on the pressor responses to tendon stretch, a pure mechanical stimulus, and to a popliteal arterial injection of capsaicin, which stimulated transient receptor potential vanilloid type 1 channels. We conclude that ASICs on thin fiber muscle afferents play a substantial role in evoking the metabolic component of the exercise pressor reflex.
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Affiliation(s)
- Shawn G Hayes
- Heart and Vascular Institute, Pennsylvania State College of Medicine, Hershey, Pennsylvania 17033, USA.
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Bibliography. Current world literature. Systemic lupus erythematosus and Sjögren's syndrome. Curr Opin Rheumatol 2008; 20:631-2. [PMID: 18698190 DOI: 10.1097/bor.0b013e3283110091] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Academic Contribution Register] [Indexed: 11/26/2022]
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