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Yang G, Jia M, Li G, Zang YY, Chen YY, Wang YY, Zhan SY, Peng SX, Wan G, Li W, Yang JJ, Shi YS. TMEM63B channel is the osmosensor required for thirst drive of interoceptive neurons. Cell Discov 2024; 10:1. [PMID: 38172113 PMCID: PMC10764952 DOI: 10.1038/s41421-023-00628-x] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2023] [Accepted: 11/18/2023] [Indexed: 01/05/2024] Open
Abstract
Thirst plays a vital role in the regulation of body fluid homeostasis and if deregulated can be life-threatening. Interoceptive neurons in the subfornical organ (SFO) are intrinsically osmosensitive and their activation by hyperosmolarity is necessary and sufficient for generating thirst. However, the primary molecules sensing systemic osmolarity in these neurons remain elusive. Here we show that the mechanosensitive TMEM63B cation channel is the osmosensor required for the interoceptive neurons to drive thirst. TMEM63B channel is highly expressed in the excitatory SFO thirst neurons. TMEM63B deletion in these neurons impaired hyperosmolarity-induced drinking behavior, while re-expressing TMEM63B in SFO restored water appetite in TMEM63B-deficient mice. Remarkably, hyperosmolarity activates TMEM63B channels, leading to depolarization and increased firing rate of the interoceptive neurons, which drives drinking behavior. Furthermore, TMEM63B deletion did not affect sensitivities of the SFO neurons to angiotensin II or hypoosmolarity, suggesting that TMEM63B plays a specialized role in detecting hyperosmolarity in SFO neurons. Thus, our results reveal a critical osmosensor molecule for the generation of thirst perception.
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Affiliation(s)
- Guolin Yang
- State Key Laboratory of Pharmaceutical Biotechnology, Department of Neurosurgery, Drum Tower Hospital Affiliated to Medical School of Nanjing University, Nanjing, Jiangsu, China
- Department of Anesthesiology, Pain and Perioperative Medicine, First Affiliated Hospital of Zhengzhou University, Zhengzhou, Henan, China
- Ministry of Education Key Laboratory of Model Animal for Disease Study, Model Animal Research Center, Nanjing University, Nanjing, Jiangsu, China
- Guangdong Institute of Intelligence Science and Technology, Hengqin, Zhuhai, Guangdong, China
| | - Min Jia
- Department of Anesthesiology, Pain and Perioperative Medicine, First Affiliated Hospital of Zhengzhou University, Zhengzhou, Henan, China
| | - Guizhou Li
- Ministry of Education Key Laboratory of Model Animal for Disease Study, Model Animal Research Center, Nanjing University, Nanjing, Jiangsu, China
| | - Yan-Yu Zang
- State Key Laboratory of Pharmaceutical Biotechnology, Department of Neurosurgery, Drum Tower Hospital Affiliated to Medical School of Nanjing University, Nanjing, Jiangsu, China
- Ministry of Education Key Laboratory of Model Animal for Disease Study, Model Animal Research Center, Nanjing University, Nanjing, Jiangsu, China
| | - Yang-Yang Chen
- Ministry of Education Key Laboratory of Model Animal for Disease Study, Model Animal Research Center, Nanjing University, Nanjing, Jiangsu, China
| | - Yue-Ying Wang
- State Key Laboratory of Pharmaceutical Biotechnology, Department of Neurosurgery, Drum Tower Hospital Affiliated to Medical School of Nanjing University, Nanjing, Jiangsu, China
- Guangdong Institute of Intelligence Science and Technology, Hengqin, Zhuhai, Guangdong, China
| | - Shi-Yu Zhan
- State Key Laboratory of Pharmaceutical Biotechnology, Department of Neurosurgery, Drum Tower Hospital Affiliated to Medical School of Nanjing University, Nanjing, Jiangsu, China
- Guangdong Institute of Intelligence Science and Technology, Hengqin, Zhuhai, Guangdong, China
| | - Shi-Xiao Peng
- Ministry of Education Key Laboratory of Model Animal for Disease Study, Model Animal Research Center, Nanjing University, Nanjing, Jiangsu, China
| | - Guoqiang Wan
- Ministry of Education Key Laboratory of Model Animal for Disease Study, Model Animal Research Center, Nanjing University, Nanjing, Jiangsu, China
| | - Wei Li
- State Key Laboratory of Pharmaceutical Biotechnology, Department of Neurosurgery, Drum Tower Hospital Affiliated to Medical School of Nanjing University, Nanjing, Jiangsu, China.
| | - Jian-Jun Yang
- Department of Anesthesiology, Pain and Perioperative Medicine, First Affiliated Hospital of Zhengzhou University, Zhengzhou, Henan, China.
| | - Yun Stone Shi
- State Key Laboratory of Pharmaceutical Biotechnology, Department of Neurosurgery, Drum Tower Hospital Affiliated to Medical School of Nanjing University, Nanjing, Jiangsu, China.
- Ministry of Education Key Laboratory of Model Animal for Disease Study, Model Animal Research Center, Nanjing University, Nanjing, Jiangsu, China.
- Guangdong Institute of Intelligence Science and Technology, Hengqin, Zhuhai, Guangdong, China.
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Miyata S. Glial functions in the blood-brain communication at the circumventricular organs. Front Neurosci 2022; 16:991779. [PMID: 36278020 PMCID: PMC9583022 DOI: 10.3389/fnins.2022.991779] [Citation(s) in RCA: 11] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2022] [Accepted: 09/20/2022] [Indexed: 11/13/2022] Open
Abstract
The circumventricular organs (CVOs) are located around the brain ventricles, lack a blood-brain barrier (BBB) and sense blood-derived molecules. This review discusses recent advances in the importance of CVO functions, especially glial cells transferring periphery inflammation signals to the brain. The CVOs show size-limited vascular permeability, allowing the passage of molecules with molecular weight <10,000. This indicates that the lack of an endothelial cell barrier does not mean the free movement of blood-derived molecules into the CVO parenchyma. Astrocytes and tanycytes constitute a dense barrier at the distal CVO subdivision, preventing the free diffusion of blood-derived molecules into neighboring brain regions. Tanycytes in the CVOs mediate communication between cerebrospinal fluid and brain parenchyma via transcytosis. Microglia and macrophages of the CVOs are essential for transmitting peripheral information to other brain regions via toll-like receptor 2 (TLR2). Inhibition of TLR2 signaling or depletion of microglia and macrophages in the brain eliminates TLR2-dependent inflammatory responses. In contrast to TLR2, astrocytes and tanycytes in the CVOs of the brain are crucial for initiating lipopolysaccharide (LPS)-induced inflammatory responses via TLR4. Depletion of microglia and macrophages augments LPS-induced fever and chronic sickness responses. Microglia and macrophages in the CVOs are continuously activated, even under normal physiological conditions, as they exhibit activated morphology and express the M1/M2 marker proteins. Moreover, the microglial proliferation occurs in various regions, such as the hypothalamus, medulla oblongata, and telencephalon, with a marked increase in the CVOs, due to low-dose LPS administration, and after high-dose LPS administration, proliferation is seen in most brain regions, except for the cerebral cortex and hippocampus. A transient increase in the microglial population is beneficial during LPS-induced inflammation for attenuating sickness response. Transient receptor potential receptor vanilloid 1 expressed in astrocytes and tanycytes of the CVOs is responsible for thermoregulation upon exposure to a warm environment less than 37°C. Alternatively, Nax expressed in astrocytes and tanycytes of the CVOs is crucial for maintaining body fluid homeostasis. Thus, recent findings indicate that glial cells in the brain CVOs are essential for initiating neuroinflammatory responses and maintaining body fluid and thermal homeostasis.
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NODA M, MATSUDA T. Central regulation of body fluid homeostasis. PROCEEDINGS OF THE JAPAN ACADEMY. SERIES B, PHYSICAL AND BIOLOGICAL SCIENCES 2022; 98:283-324. [PMID: 35908954 PMCID: PMC9363595 DOI: 10.2183/pjab.98.016] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/05/2023]
Abstract
Extracellular fluids, including blood, lymphatic fluid, and cerebrospinal fluid, are collectively called body fluids. The Na+ concentration ([Na+]) in body fluids is maintained at 135-145 mM and is broadly conserved among terrestrial animals. Homeostatic osmoregulation by Na+ is vital for life because severe hyper- or hypotonicity elicits irreversible organ damage and lethal neurological trauma. To achieve "body fluid homeostasis" or "Na homeostasis", the brain continuously monitors [Na+] in body fluids and controls water/salt intake and water/salt excretion by the kidneys. These physiological functions are primarily regulated based on information on [Na+] and relevant circulating hormones, such as angiotensin II, aldosterone, and vasopressin. In this review, we discuss sensing mechanisms for [Na+] and hormones in the brain that control water/salt intake behaviors, together with the responsible sensors (receptors) and relevant neural pathways. We also describe mechanisms in the brain by which [Na+] increases in body fluids activate the sympathetic neural activity leading to hypertension.
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Affiliation(s)
- Masaharu NODA
- Homeostatic Mechanism Research Unit, Institute of Innovative Research, Tokyo Institute of Technology, Yokohama, Kanagawa, Japan
- Correspondence should be addressed to: Homeostatic Mechanism Research Unit, Institute of Innovative Research, Tokyo Institute of Technology, Nagatsuta-cho 4259, Midori-ku, Yokohama, Kanagawa 226-8503, Japan (e-mail: )
| | - Takashi MATSUDA
- Homeostatic Mechanism Research Unit, Institute of Innovative Research, Tokyo Institute of Technology, Yokohama, Kanagawa, Japan
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Porcari CY, Debarba LK, Amigone JL, Caeiro XE, Reis LC, Cunha TM, Mecawi AS, Elias LL, Antunes-Rodrigues J, Vivas L, Godino A. Brain osmo-sodium sensitive channels and the onset of sodium appetite. Horm Behav 2020; 118:104658. [PMID: 31874139 DOI: 10.1016/j.yhbeh.2019.104658] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/15/2019] [Revised: 11/14/2019] [Accepted: 12/17/2019] [Indexed: 01/13/2023]
Abstract
The aim of the present study was to determine whether the TRPV1 channel is involved in the onset of sodium appetite. For this purpose, we used TRPV1-knockout mice to investigate sodium depletion-induced drinking at different times (2/24 h) after furosemide administration combined with a low sodium diet (FURO-LSD). In sodium depleted wild type and TRPV1 KO (SD-WT/SD-TPRV1-KO) mice, we also evaluated the participation of other sodium sensors, such as TPRV4, NaX and angiotensin AT1-receptors (by RT-PCR), as well as investigating the pattern of neural activation shown by Fos immunoreactivity, in different nuclei involved in hydromineral regulation. TPRV1 SD-KO mice revealed an increased sodium preference, ingesting a higher hypertonic cocktail in comparison with SD-WT mice. Our results also showed in SD-WT animals that SFO-Trpv4 expression increased 2 h after FURO-LSD, compared to other groups, thus supporting a role of SFO-Trpv4 channels during the hyponatremic state. However, the SD-TPRV1-KO animals did not show this early increase, and maybe as a consequence drank more hypertonic cocktail. Regarding the SFO-NaX channel expression, in both genotypes our findings revealed a reduction 24 h after FURO-LSD. In addition, there was an increase in the OVLT-NaX expression of SD-WT 24 h after FURO-LSD, suggesting the participation of OVLT-NaX channels in the appearance of sodium appetite, possibly as an anticipatory response in order to limit sodium intake and to induce thirst. Our work demonstrates changes in the expression of different osmo‑sodium-sensitive channels at specific nuclei, related to the body sodium status in order to stimulate an adequate drinking.
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Affiliation(s)
- C Y Porcari
- Instituto de Investigación Médica Mercedes y Martín Ferreyra (INIMEC-CONICET-Universidad Nacional de Córdoba), Córdoba, Argentina
| | - L K Debarba
- Department of Physiology, School of Medicine of Ribeirao Preto, University of Sao Paulo, Sao Paulo, Brazil
| | - J L Amigone
- Sección de Bioquímica Clínica, Hospital Privado, Córdoba, Argentina
| | - X E Caeiro
- Instituto de Investigación Médica Mercedes y Martín Ferreyra (INIMEC-CONICET-Universidad Nacional de Córdoba), Córdoba, Argentina
| | - L C Reis
- Department of Physiological Sciences, Institute of Biological and Health Sciences, Federal Rural University of Rio de Janeiro, Seropédica, Brazil
| | - T M Cunha
- Department of Physiology, School of Medicine of Ribeirao Preto, University of Sao Paulo, Sao Paulo, Brazil
| | - A S Mecawi
- Laboratory of Molecular Neuroendocrinology, Department of Biophysics, Paulista Medical School, Federal University of São Paulo, São Paulo, Brazil
| | - L L Elias
- Department of Physiology, School of Medicine of Ribeirao Preto, University of Sao Paulo, Sao Paulo, Brazil
| | - J Antunes-Rodrigues
- Department of Physiology, School of Medicine of Ribeirao Preto, University of Sao Paulo, Sao Paulo, Brazil
| | - L Vivas
- Instituto de Investigación Médica Mercedes y Martín Ferreyra (INIMEC-CONICET-Universidad Nacional de Córdoba), Córdoba, Argentina; Facultad de Ciencias Exactas Físicas y Naturales, Universidad Nacional de Córdoba, Córdoba, Argentina
| | - A Godino
- Instituto de Investigación Médica Mercedes y Martín Ferreyra (INIMEC-CONICET-Universidad Nacional de Córdoba), Córdoba, Argentina; Facultad de Psicología, Universidad Nacional de Córdoba, Córdoba, Argentina.
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Wang YF, Parpura V. Astroglial Modulation of Hydromineral Balance and Cerebral Edema. Front Mol Neurosci 2018; 11:204. [PMID: 29946238 PMCID: PMC6007284 DOI: 10.3389/fnmol.2018.00204] [Citation(s) in RCA: 33] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2018] [Accepted: 05/22/2018] [Indexed: 12/11/2022] Open
Abstract
Maintenance of hydromineral balance (HB) is an essential condition for life activity at cellular, tissue, organ and system levels. This activity has been considered as a function of the osmotic regulatory system that focuses on hypothalamic vasopressin (VP) neurons, which can reflexively release VP into the brain and blood to meet the demand of HB. Recently, astrocytes have emerged as an essential component of the osmotic regulatory system in addition to functioning as a regulator of the HB at cellular and tissue levels. Astrocytes express all the components of osmoreceptors, including aquaporins, molecules of the extracellular matrix, integrins and transient receptor potential channels, with an operational dynamic range allowing them to detect and respond to osmotic changes, perhaps more efficiently than neurons. The resultant responses, i.e., astroglial morphological and functional plasticity in the supraoptic and paraventricular nuclei, can be conveyed, physically and chemically, to adjacent VP neurons, thereby influencing HB at the system level. In addition, astrocytes, particularly those in the circumventricular organs, are involved not only in VP-mediated osmotic regulation, but also in regulation of other osmolality-modulating hormones, including natriuretic peptides and angiotensin. Thus, astrocytes play a role in local/brain and systemic HB. The adaptive astrocytic reactions to osmotic challenges are associated with signaling events related to the expression of glial fibrillary acidic protein and aquaporin 4 to promote cell survival and repair. However, prolonged osmotic stress can initiate inflammatory and apoptotic signaling processes, leading to glial dysfunction and a variety of brain diseases. Among many diseases of brain injury and hydromineral disorders, cytotoxic and osmotic cerebral edemas are the most common pathological manifestation. Hyponatremia is the most common cause of osmotic cerebral edema. Overly fast correction of hyponatremia could lead to central pontine myelinolysis. Ischemic stroke exemplifies cytotoxic cerebral edema. In this review, we summarize and analyze the osmosensory functions of astrocytes and their implications in cerebral edema.
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Affiliation(s)
- Yu-Feng Wang
- Department of Physiology, School of Basic Medical Sciences, Harbin Medical University, Harbin, China
| | - Vladimir Parpura
- Department of Neurobiology, The University of Alabama at Birmingham, Birmingham, AL, United States
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Abstract
Water intake is one of the most basic physiological responses and is essential to sustain life. The perception of thirst has a critical role in controlling body fluid homeostasis and if neglected or dysregulated can lead to life-threatening pathologies. Clear evidence suggests that the perception of thirst occurs in higher-order centres, such as the anterior cingulate cortex (ACC) and insular cortex (IC), which receive information from midline thalamic relay nuclei. Multiple brain regions, notably circumventricular organs such as the organum vasculosum lamina terminalis (OVLT) and subfornical organ (SFO), monitor changes in blood osmolality, solute load and hormone circulation and are thought to orchestrate appropriate responses to maintain extracellular fluid near ideal set points by engaging the medial thalamic-ACC/IC network. Thirst has long been thought of as a negative homeostatic feedback response to increases in blood solute concentration or decreases in blood volume. However, emerging evidence suggests a clear role for thirst as a feedforward adaptive anticipatory response that precedes physiological challenges. These anticipatory responses are promoted by rises in core body temperature, food intake (prandial) and signals from the circadian clock. Feedforward signals are also important mediators of satiety, inhibiting thirst well before the physiological state is restored by fluid ingestion. In this Review, we discuss the importance of thirst for body fluid balance and outline our current understanding of the neural mechanisms that underlie the various types of homeostatic and anticipatory thirst.
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Affiliation(s)
- Claire Gizowski
- Centre for Research in Neuroscience, Research Institute of the McGill University Health Centre and Montreal General Hospital, 1650 Cedar Avenue, Montreal H3G1A4, Canada
| | - Charles W Bourque
- Centre for Research in Neuroscience, Research Institute of the McGill University Health Centre and Montreal General Hospital, 1650 Cedar Avenue, Montreal H3G1A4, Canada
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Prager-Khoutorsky M, Choe KY, Levi DI, Bourque CW. Role of Vasopressin in Rat Models of Salt-Dependent Hypertension. Curr Hypertens Rep 2017; 19:42. [PMID: 28451854 DOI: 10.1007/s11906-017-0741-2] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
PURPOSE OF REVIEW Dietary salt intake increases both plasma sodium and osmolality and therefore increases vasopressin (VP) release from the neurohypophysis. Although this effect could increase blood pressure by inducing fluid reabsorption and vasoconstriction, acute activation of arterial baroreceptors inhibits VP neurons via GABAA receptors to oppose high blood pressure. Here we review recent findings demonstrating that this protective mechanism fails during chronic high salt intake in rats. RECENT FINDINGS Two recent studies showed that chronic high sodium intake causes an increase in intracellular chloride concentration in VP neurons. This effect causes GABAA receptors to become excitatory and leads to the emergence of VP-dependent hypertension. One study showed that the increase in intracellular chloride was provoked by a decrease in the expression of the chloride exporter KCC2 mediated by local secretion of brain-derived neurotrophic factor and activation of TrkB receptors. Prolonged high dietary salt intake can cause pathological plasticity in a central homeostatic circuit that controls VP secretion and thereby contribute to peripheral vasoconstriction and hypertension.
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Affiliation(s)
- Masha Prager-Khoutorsky
- Department of Physiology, McGill University, McIntyre Medical Sciences Bldg., 3655 Promenade Sir-William Osler, Montreal, QC, H3G 1Y6, Canada
| | - Katrina Y Choe
- 2309 Gonda Neuroscience and Genetics Research Center, UCLA Department of Neurology, 695 Charles E. Young Dr. South, Los Angeles, CA, 90095, USA
| | - David I Levi
- Centre for Research in Neuroscience, Research Institute of the McGill University Health Center, Montreal General Hospital, 1650 Cedar Avenue, Montreal, QC, H3G 1A4, Canada
| | - Charles W Bourque
- Centre for Research in Neuroscience, Research Institute of the McGill University Health Center, Montreal General Hospital, 1650 Cedar Avenue, Montreal, QC, H3G 1A4, Canada.
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Kinsman BJ, Browning KN, Stocker SD. NaCl and osmolarity produce different responses in organum vasculosum of the lamina terminalis neurons, sympathetic nerve activity and blood pressure. J Physiol 2017; 595:6187-6201. [PMID: 28678348 DOI: 10.1113/jp274537] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2017] [Accepted: 06/21/2017] [Indexed: 01/12/2023] Open
Abstract
KEY POINTS Changes in extracellular osmolarity stimulate thirst and vasopressin secretion through a central osmoreceptor; however, central infusion of hypertonic NaCl produces a greater sympathoexcitatory and pressor response than infusion of hypertonic mannitol/sorbitol. Neurons in the organum vasculosum of the lamina terminalis (OVLT) sense changes in extracellular osmolarity and NaCl. In this study, we discovered that intracerebroventricular infusion or local OVLT injection of hypertonic NaCl increases lumbar sympathetic nerve activity, adrenal sympathetic nerve activity and arterial blood pressure whereas equi-osmotic mannitol/sorbitol did not alter any variable. In vitro whole-cell recordings demonstrate the majority of OVLT neurons are responsive to hypertonic NaCl or mannitol. However, hypertonic NaCl stimulates a greater increase in discharge frequency than equi-osmotic mannitol. Intracarotid or intracerebroventricular infusion of hypertonic NaCl evokes a greater increase in OVLT neuronal discharge frequency than equi-osmotic sorbitol. Collectively, these novel data suggest that subsets of OVLT neurons respond differently to hypertonic NaCl versus osmolarity and subsequently regulate body fluid homeostasis. These responses probably reflect distinct cellular mechanisms underlying NaCl- versus osmo-sensing. ABSTRACT Systemic or central infusion of hypertonic NaCl and other osmolytes readily stimulate thirst and vasopressin secretion. In contrast, central infusion of hypertonic NaCl produces a greater increase in arterial blood pressure (ABP) than equi-osmotic mannitol/sorbitol. Although these responses depend on neurons in the organum vasculosum of the lamina terminalis (OVLT), these observations suggest OVLT neurons may sense or respond differently to hypertonic NaCl versus osmolarity. The purpose of this study was to test this hypothesis in Sprague-Dawley rats. First, intracerebroventricular (icv) infusion (5 μl/10 min) of 1.0 m NaCl produced a significantly greater increase in lumbar sympathetic nerve activity (SNA), adrenal SNA and ABP than equi-osmotic sorbitol (2.0 osmol l-1 ). Second, OVLT microinjection (20 nl) of 1.0 m NaCl significantly raised lumbar SNA, adrenal SNA and ABP. Equi-osmotic sorbitol did not alter any variable. Third, in vitro whole-cell recordings demonstrate that 50% (18/36) of OVLT neurons display an increased discharge to both hypertonic NaCl (+7.5 mm) and mannitol (+15 mm). Of these neurons, 56% (10/18) displayed a greater discharge response to hypertonic NaCl vs mannitol. Fourth, in vivo single-unit recordings revealed that intracarotid injection of hypertonic NaCl produced a concentration-dependent increase in OVLT cell discharge, lumbar SNA and ABP. The responses to equi-osmotic infusions of hypertonic sorbitol were significantly smaller. Lastly, icv infusion of 0.5 m NaCl produced significantly greater increases in OVLT discharge and ABP than icv infusion of equi-osmotic sorbitol. Collectively, these findings indicate NaCl and osmotic stimuli produce different responses across OVLT neurons and may represent distinct cellular processes to regulate thirst, vasopressin secretion and autonomic function.
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Affiliation(s)
- Brian J Kinsman
- Department of Medicine, Division of Renal-Electrolyte, University of Pittsburgh School of Medicine, Pittsburgh, PA, 15261, USA.,Department of Neural and Behavioral Sciences, Penn State College of Medicine, Hershey, PA, 17033, USA
| | - Kirsteen N Browning
- Department of Neural and Behavioral Sciences, Penn State College of Medicine, Hershey, PA, 17033, USA
| | - Sean D Stocker
- Department of Medicine, Division of Renal-Electrolyte, University of Pittsburgh School of Medicine, Pittsburgh, PA, 15261, USA
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Abstract
Thirst motivates animals to find and consume water. More than 40 years ago, a set of interconnected brain structures known as the lamina terminalis was shown to govern thirst. However, owing to the anatomical complexity of these brain regions, the structure and dynamics of their underlying neural circuitry have remained obscure. Recently, the emergence of new tools for neural recording and manipulation has reinvigorated the study of this circuit and prompted re-examination of longstanding questions about the neural origins of thirst. Here, we review these advances, discuss what they teach us about the control of drinking behaviour and outline the key questions that remain unanswered.
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Affiliation(s)
- Christopher A Zimmerman
- Department of Physiology, the Kavli Institute for Fundamental Neuroscience and the Neuroscience Graduate Program, University of California San Francisco, San Francisco, California 94158, USA
| | - David E Leib
- Department of Physiology, the Kavli Institute for Fundamental Neuroscience and the Neuroscience Graduate Program, University of California San Francisco, San Francisco, California 94158, USA
| | - Zachary A Knight
- Department of Physiology, the Kavli Institute for Fundamental Neuroscience and the Neuroscience Graduate Program, University of California San Francisco, San Francisco, California 94158, USA
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Reciprocal Control of Drinking Behavior by Median Preoptic Neurons in Mice. J Neurosci 2017; 36:8228-37. [PMID: 27488641 DOI: 10.1523/jneurosci.1244-16.2016] [Citation(s) in RCA: 66] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2016] [Accepted: 06/06/2016] [Indexed: 11/21/2022] Open
Abstract
UNLABELLED Stimulation of glutamatergic neurons in the subfornical organ drives drinking behavior, but the brain targets that mediate this response are not known. The densest target of subfornical axons is the anterior tip of the third ventricle, containing the median preoptic nucleus (MnPO) and organum vasculosum of the lamina terminalis (OVLT), a region that has also been implicated in fluid and electrolyte management. The neurochemical composition of this region is complex, containing both GABAergic and glutamatergic neurons, but the possible roles of these neurons in drinking responses have not been addressed. In mice, we show that optogenetic stimulation of glutamatergic neurons in MnPO/OVLT drives voracious water consumption, and that optogenetic stimulation of GABAergic neurons in the same region selectively reduces water consumption. Both populations of neurons have extensive projections to overlapping regions of the thalamus, hypothalamus, and hindbrain that are much more extensive than those from the subfornical organ, suggesting that the MnPO/OVLT serves as a key link in regulating drinking responses. SIGNIFICANCE STATEMENT Neurons in the median preoptic nucleus (MnPO) and organum vasculosum of the lamina terminalis (OVLT) are known to regulate fluid/electrolyte homeostasis, but few studies have examined this issue with an appreciation for the neurochemical heterogeneity of these nuclei. Using Cre-Lox genetic targeting of Channelrhodospin-2 in transgenic mice, we demonstrate that glutamate and GABA neurons in the MnPO/OVLT reciprocally regulate water consumption. Stimulating glutamatergic MnPO/OVLT neurons induced water consumption, whereas stimulating GABAergic MnPO neurons caused a sustained and specific reduction in water consumption in dehydrated mice, the latter highlighting a heretofore unappreciated role of GABAergic MnPO neurons in thirst regulation. These observations represent an important advance in our understanding of the neural circuits involved in the regulation of fluid/electrolyte homeostasis.
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Sakuta H, Nishihara E, Hiyama TY, Lin CH, Noda M. Nax signaling evoked by an increase in [Na+] in CSF induces water intake via EET-mediated TRPV4 activation. Am J Physiol Regul Integr Comp Physiol 2016; 311:R299-306. [DOI: 10.1152/ajpregu.00352.2015] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2015] [Accepted: 05/27/2016] [Indexed: 11/22/2022]
Abstract
Water-intake behavior is under the control of brain systems that sense body fluid conditions at sensory circumventricular organs (sCVOs); however, the underlying mechanisms have not yet been elucidated in detail. Nax is a sodium (Na+) level sensor in the brain, and the transient receptor potential vanilloid (TRPV) channels TRPV1 and TRPV4 have been proposed to function as osmosensors. We herein investigated voluntary water intake immediately induced after an intracerebroventricular administration of a hypertonic NaCl solution in TRPV1-, TRPV4-, Na x-, and their double-gene knockout (KO) mice. The induction of water intake by TRPV1-KO mice was normal, whereas intake by TRPV4-KO and Na x-KO mice was significantly less than that by WT mice. Water intake by Na x /TRPV4-double KO mice was similar to that by the respective single KO mice. When TRPV4 activity was blocked with a specific antagonist HC-067047, water intake by WT mice was significantly reduced, whereas intake by TRPV4-KO and Na x-KO mice was not. Similar results were obtained with the administration of miconazole, which inhibits the biosynthesis of epoxyeicosatrienoic acids (EETs), endogenous agonists for TRPV4, from arachidonic acid (AA). Intracerebroventricular injection of hypertonic NaCl with AA or 5,6-EET restored water intake by Na x-KO mice to the wild-type level but not that by TRPV4-KO mice. These results suggest that the Na+ signal generated in Nax-positive glial cells leads to the activation of TRPV4-positive neurons in sCVOs to stimulate water intake by using EETs as gliotransmitters. Intracerebroventricular injection of equiosmolar hypertonic sorbitol solution induced small but significant water intake equally in all the genotypes, suggesting the presence of an unknown osmosensor in the brain.
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Affiliation(s)
- Hiraki Sakuta
- Division of Molecular Neurobiology, National Institute for Basic Biology, and
- School of Life Science, The Graduate University for Advanced Studies (SOKENDAI), Okazaki, Aichi, Japan
| | - Eri Nishihara
- Division of Molecular Neurobiology, National Institute for Basic Biology, and
| | - Takeshi Y. Hiyama
- Division of Molecular Neurobiology, National Institute for Basic Biology, and
- School of Life Science, The Graduate University for Advanced Studies (SOKENDAI), Okazaki, Aichi, Japan
| | - Chia-Hao Lin
- Division of Molecular Neurobiology, National Institute for Basic Biology, and
| | - Masaharu Noda
- Division of Molecular Neurobiology, National Institute for Basic Biology, and
- School of Life Science, The Graduate University for Advanced Studies (SOKENDAI), Okazaki, Aichi, Japan
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Tucker AB, Stocker SD. Hypernatremia-induced vasopressin secretion is not altered in TRPV1-/- rats. Am J Physiol Regul Integr Comp Physiol 2016; 311:R451-6. [PMID: 27335281 DOI: 10.1152/ajpregu.00483.2015] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2015] [Accepted: 06/17/2016] [Indexed: 11/22/2022]
Abstract
Changes in osmolality or extracellular NaCl concentrations are detected by specialized neurons in the hypothalamus to increase vasopressin (VP) and stimulate thirst. Recent in vitro evidence suggests this process is mediated by an NH2-terminal variant of the transient receptor potential vanilloid type 1 (TRPV1) channel expressed by osmosensitive neurons of the lamina terminalis and vasopressinergic neurons of the supraoptic nucleus. The present study tested this hypothesis in vivo by analysis of plasma VP levels during acute hypernatremia in awake control and TRPV1(-/-) rats. TRPV1(-/-) rats were produced by a Zinc-finger-nuclease 2-bp deletion in exon 13. Intravenous injection of the TRPV1 agonist capsaicin produced hypotension and bradycardia in control rats, but this response was absent in TRPV1(-/-) rats. Infusion of 2 M NaCl (1 ml/h iv) increased plasma osmolality, electrolytes, and VP levels in both control and TRPV1(-/-) rats. However, plasma VP levels did not differ between strains at any time. Furthermore, a linear regression between plasma VP versus osmolality revealed a significant correlation in both control and TRPV1(-/-) rats, but the slope of the regression lines was not attenuated in TRPV1(-/-) versus control rats. Hypotension produced by intravenous injection of minoxidil decreased blood pressure and increased plasma VP levels similarly in both groups. Finally, both treatments stimulated thirst; however, cumulative water intakes in response to hypernatremia or hypotension were not different between control and TRPV1(-/-) rats. These findings suggest that TRPV1 channels are not necessary for VP secretion and thirst stimulated by hypernatremia.
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Affiliation(s)
- Andrew Blake Tucker
- Department of Neural & Behavioral Sciences, Penn State College of Medicine, Hershey, Pennsylvania
| | - Sean D Stocker
- Department of Neural & Behavioral Sciences, Penn State College of Medicine, Hershey, Pennsylvania
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13
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Nation HL, Nicoleau M, Kinsman BJ, Browning KN, Stocker SD. DREADD-induced activation of subfornical organ neurons stimulates thirst and salt appetite. J Neurophysiol 2016; 115:3123-9. [PMID: 27030736 DOI: 10.1152/jn.00149.2016] [Citation(s) in RCA: 45] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2016] [Accepted: 03/25/2016] [Indexed: 01/19/2023] Open
Abstract
The subfornical organ (SFO) plays a pivotal role in body fluid homeostasis through its ability to integrate neurohumoral signals and subsequently alter behavior, neuroendocrine function, and autonomic outflow. The purpose of the present study was to evaluate whether selective activation of SFO neurons using virally mediated expression of Designer Receptors Exclusively Activated by Designer Drugs (DREADDs) stimulated thirst and salt appetite. Male C57BL/6 mice (12-15 wk) received an injection of rAAV2-CaMKII-HA-hM3D(Gq)-IRES-mCitrine targeted at the SFO. Two weeks later, acute injection of clozapine N-oxide (CNO) produced dose-dependent increases in water intake of mice with DREADD expression in the SFO. CNO also stimulated the ingestion of 0.3 M NaCl. Acute injection of CNO significantly increased the number of Fos-positive nuclei in the SFO of mice with robust DREADD expression. Furthermore, in vivo single-unit recordings demonstrate that CNO significantly increases the discharge frequency of both ANG II- and NaCl-responsive neurons. In vitro current-clamp recordings confirm that bath application of CNO produces a significant membrane depolarization and increase in action potential frequency. In a final set of experiments, chronic administration of CNO approximately doubled 24-h water intake without an effect on salt appetite. These findings demonstrate that DREADD-induced activation of SFO neurons stimulates thirst and that DREADDs are a useful tool to acutely or chronically manipulate neuronal circuits influencing body fluid homeostasis.
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Affiliation(s)
- Haley L Nation
- Department of Neural and Behavioral Sciences, Penn State College of Medicine, Hershey, Pennsylvania; and
| | - Marvin Nicoleau
- Department of Biochemistry and Molecular Biology, Franklin & Marshall College, Lancaster, Pennsylvania
| | - Brian J Kinsman
- Department of Neural and Behavioral Sciences, Penn State College of Medicine, Hershey, Pennsylvania; and
| | - Kirsteen N Browning
- Department of Neural and Behavioral Sciences, Penn State College of Medicine, Hershey, Pennsylvania; and
| | - Sean D Stocker
- Department of Neural and Behavioral Sciences, Penn State College of Medicine, Hershey, Pennsylvania; and
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14
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Joubert M, Bellevre D, Legallois D, Elie N, Coulbault L, Allouche S, Manrique A. Hyperglycemia-Induced Hypovolemia Is Involved in Early Cardiac Magnetic Resonance Alterations in Streptozotocin-Induced Diabetic Mice: A Comparison with Furosemide-Induced Hypovolemia. PLoS One 2016; 11:e0149808. [PMID: 26901278 PMCID: PMC4763166 DOI: 10.1371/journal.pone.0149808] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2015] [Accepted: 02/04/2016] [Indexed: 12/18/2022] Open
Abstract
Aims The aim of the study was to assess the early features of diabetic cardiomyopathy using cardiac magnetic resonance within the first week after streptozotocin injection in mice. We focused on the relationship between left ventricular function and hypovolemia markers in diabetic animals compared to a hypovolemic rodent model. Methods and Results Swiss mice were randomized into control (group C), streptozotocin-induced diabetes (group D) and furosemide-induced hypovolemia (group F) groups. Cardiac magnetic resonance, non-invasive blood pressure, urine volume, plasma markers of dehydration and cardiac histology were assessed in all groups. Mean blood glucose was higher in diabetic animals than in groups C and F (30.5±5.8 compared to 10.4±2.1 and 11.1±2.8 mmol/L, respectively; p<0.01). Diuresis was increased in animals from group D and F compared to C (14650±11499 and 1533±540 compared to 192±111 μL/24 h; p<0.05). End diastolic and end systolic volumes were lower in group D than in group C at week 1 (1.52±0.36 vs. 1.93±0.35 and 0.54±0.22 vs. 0.75±0.18 mL/kg, p<0.05). These left ventricular volume values in group D were comparable to those observed in the acute hypovolemia model (group F). Increased dehydration plasma markers and an absence of obvious intrinsic myocardial damage (evaluated by cardiac magnetic resonance and histology) suggest that a hemodynamic mechanism underlies the very early drop in left ventricular volumes in group D and provides a potential link to hyperglycemic osmotic diuresis. Conclusions Researchers using cardiac magnetic resonance in hyperglycemic rodent models should be aware of this hemodynamic mechanism, which may partially explain modifications in cardiac parameters in addition to diabetic myocardial damage.
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Affiliation(s)
- Michael Joubert
- Diabetes care unit, Caen University Hospital, Caen, France
- EA4650 Université Caen Normandie, GIP Cyceron, Caen, France
- * E-mail:
| | - Dimitri Bellevre
- Nuclear Medicine department, Caen University Hospital, Caen, France
- EA4650 Université Caen Normandie, GIP Cyceron, Caen, France
| | - Damien Legallois
- Cardiology unit, Caen University Hospital, Caen, France
- EA4650 Université Caen Normandie, GIP Cyceron, Caen, France
| | - Nicolas Elie
- CMABIO-HIQ facility, SF4206 ICORE, IBFA, Université Caen Normandie, Caen, France
| | - Laurent Coulbault
- Biochemical unit, Caen University Hospital, Caen, France
- EA4650 Université Caen Normandie, GIP Cyceron, Caen, France
| | - Stéphane Allouche
- Biochemical unit, Caen University Hospital, Caen, France
- EA4650 Université Caen Normandie, GIP Cyceron, Caen, France
| | - Alain Manrique
- Nuclear Medicine department, Caen University Hospital, Caen, France
- EA4650 Université Caen Normandie, GIP Cyceron, Caen, France
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15
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Hernández VS, Vázquez-Juárez E, Márquez MM, Jáuregui-Huerta F, Barrio RA, Zhang L. Extra-neurohypophyseal axonal projections from individual vasopressin-containing magnocellular neurons in rat hypothalamus. Front Neuroanat 2015; 9:130. [PMID: 26500509 PMCID: PMC4593857 DOI: 10.3389/fnana.2015.00130] [Citation(s) in RCA: 39] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2015] [Accepted: 09/18/2015] [Indexed: 01/19/2023] Open
Abstract
Conventional neuroanatomical, immunohistochemical techniques, and electrophysiological recording, as well as in vitro labeling methods may fail to detect long range extra-neurohypophyseal-projecting axons from vasopressin (AVP)-containing magnocellular neurons (magnocells) in the hypothalamic paraventricular nucleus (PVN). Here, we used in vivo extracellular recording, juxtacellular labeling, post-hoc anatomo-immunohistochemical analysis and camera lucida reconstruction to address this question. We demonstrate that all well-labeled AVP immunopositive neurons inside the PVN possess main axons joining the tract of Greving and multi-axon-like processes, as well as axonal collaterals branching very near to the somata, which project to extra-neurohypophyseal regions. The detected regions in this study include the medial and lateral preoptical area, suprachiasmatic nucleus (SCN), lateral habenula (LHb), medial and central amygdala and the conducting systems, such as stria medullaris, the fornix and the internal capsule. Expression of vesicular glutamate transporter 2 was observed in axon-collaterals. These results, in congruency with several previous reports in the literature, provided unequivocal evidence that AVP magnocells have an uncommon feature of possessing multiple axon-like processes emanating from somata or proximal dendrites. Furthermore, the long-range non-neurohypophyseal projections are more common than an “occasional” phenomenon as previously thought.
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Affiliation(s)
- Vito S Hernández
- Departamento de Fisiología, Facultad de Medicina, Universidad Nacional Autónoma de México Mexico City, Mexico
| | - Erika Vázquez-Juárez
- Departamento de Fisiología, Facultad de Medicina, Universidad Nacional Autónoma de México Mexico City, Mexico
| | - Mariana M Márquez
- Departamento de Fisiología, Facultad de Medicina, Universidad Nacional Autónoma de México Mexico City, Mexico
| | - Fernando Jáuregui-Huerta
- Departamento de Neurociencias, Centro Universitario de Ciencias de la Salud, Universidad de Guadalajara Guadalajara, Mexico
| | - Rafael A Barrio
- Departamento de Física Química, Instituto de Física, Universidad Nacional Autónoma de México Mexico City, Mexico
| | - Limei Zhang
- Departamento de Fisiología, Facultad de Medicina, Universidad Nacional Autónoma de México Mexico City, Mexico
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16
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Ishikura T, Suzuki H, Shoguchi K, Koreeda Y, Aritomi T, Matsuura T, Yoshimura M, Ohkubo JI, Maruyama T, Kawasaki M, Ohnishi H, Sakai A, Mizuno A, Suzuki M, Ueta Y. Possible involvement of TRPV1 and TRPV4 in nociceptive stimulation- induced nocifensive behavior and neuroendocrine response in mice. Brain Res Bull 2015; 118:7-16. [PMID: 26314785 DOI: 10.1016/j.brainresbull.2015.08.004] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2015] [Revised: 07/30/2015] [Accepted: 08/19/2015] [Indexed: 12/22/2022]
Abstract
Members of the transient receptor potential (TRP) family of ion channels play important roles in inflammation and pain. Here, we showed that both TRPV1 and TRPV4 might contribute to biphasic nocifensive behavior and neuroendocrine response following a formalin test. We subcutaneously injected saline, formalin, or the TRPV4 agonist, 4α-phorbol 12,13-didecanoate (4α-PDD) into one hindpaw of wild-type (WT), TRPV1-deficient (Trpv1(-/-)), and TRPV4-deficient (Trpv4(-/-)) mice to investigate nocifensive behaviors (phase I [0-10 min] and phase II [10-60 min]) and Fos expression in the dorsal horn of the spinal cord and other brain regions related to pain, in the paraventricular nucleus (PVN), paraventricular nucleus of the thalamus, the medial habenular nucleus, the medial nucleus of the amygdala and capsular part of the central amygdala. Subcutaneous (s.c.) injection of formalin caused less nocifensive behavior in Trpv1(-/-) and Trpv4(-/-) mice than in WT mice during phase I. In phase II, however, formalin induced less nocifensive behavior only in the Trpv1(-/-) mice, but not in the Trpv4(-/-) mice, relative to WT mice. The number of Fos-like immunoreactive (LI) neurons in laminae I-II of the dorsal horn increased in all types of mice 90 min after s.c. injection of formalin; however, there was no difference in the other regions between saline- and formalin-treated mice. Furthermore, s.c. injection of 4α-PDD did not induce nociceptive behavior nor influence the number of Fos-LI neurons in the all above mentioned regions in any of the mice. These results suggest that TRPV4-mediated nociceptive information from the peripheral tissue excluding the spinal pathway might be involved the formalin behavioral response during phase I. Only TRPV1 might regulate the formalin behavioral response in peripheral neuron.
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Affiliation(s)
- Toru Ishikura
- Department of Physiology, School of Medicine, University of Occupational and Environmental Health, Kitakyushu 807-8555, Japan; Department of Orthopaedics, School of Medicine, University of Occupational and Environmental Health, Kitakyushu 807-8555, Japan; Department of Orthopaedics, Youmeikai Obase Hospital, Kanda, Fukuoka 800-0344, Japan
| | - Hitoshi Suzuki
- Department of Orthopaedics, School of Medicine, University of Occupational and Environmental Health, Kitakyushu 807-8555, Japan
| | - Kanako Shoguchi
- Department of Physiology, School of Medicine, University of Occupational and Environmental Health, Kitakyushu 807-8555, Japan
| | - Yuki Koreeda
- Department of Physiology, School of Medicine, University of Occupational and Environmental Health, Kitakyushu 807-8555, Japan
| | - Takafumi Aritomi
- Department of Physiology, School of Medicine, University of Occupational and Environmental Health, Kitakyushu 807-8555, Japan
| | - Takanori Matsuura
- Department of Physiology, School of Medicine, University of Occupational and Environmental Health, Kitakyushu 807-8555, Japan; Department of Orthopaedics, School of Medicine, University of Occupational and Environmental Health, Kitakyushu 807-8555, Japan
| | - Mitsuhiro Yoshimura
- Department of Physiology, School of Medicine, University of Occupational and Environmental Health, Kitakyushu 807-8555, Japan
| | - Jun-ichi Ohkubo
- Department of Physiology, School of Medicine, University of Occupational and Environmental Health, Kitakyushu 807-8555, Japan
| | - Takashi Maruyama
- Department of Physiology, School of Medicine, University of Occupational and Environmental Health, Kitakyushu 807-8555, Japan
| | - Makoto Kawasaki
- Department of Orthopaedics, School of Medicine, University of Occupational and Environmental Health, Kitakyushu 807-8555, Japan
| | - Hideo Ohnishi
- Department of Orthopaedics, School of Medicine, University of Occupational and Environmental Health, Kitakyushu 807-8555, Japan
| | - Akinori Sakai
- Department of Orthopaedics, School of Medicine, University of Occupational and Environmental Health, Kitakyushu 807-8555, Japan
| | - Atsuko Mizuno
- Department of Pharmacology, Jichi Medical University, Minamikawachi, Tochigi 329-0498, Japan
| | - Makoto Suzuki
- Edogawabashi Suzuki Clinic, Shinjyukuku, Tokyo 162-0801, Japan
| | - Yoichi Ueta
- Department of Physiology, School of Medicine, University of Occupational and Environmental Health, Kitakyushu 807-8555, Japan.
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17
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Stocker SD, Monahan KD, Browning KN. Neurogenic and sympathoexcitatory actions of NaCl in hypertension. Curr Hypertens Rep 2014; 15:538-46. [PMID: 24052211 DOI: 10.1007/s11906-013-0385-9] [Citation(s) in RCA: 45] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Excess dietary salt intake is a major contributing factor to the pathogenesis of salt-sensitive hypertension. Strong evidence suggests that salt-sensitive hypertension is attributed to renal dysfunction, vascular abnormalities, and activation of the sympathetic nervous system. Indeed, sympathetic nerve transections or interruption of neurotransmission in various brain centers lowers arterial blood pressure (ABP) in many salt-sensitive models. The purpose of this article is to discuss recent evidence that supports a role of plasma or cerebrospinal fluid hypernatremia as a key mediator of sympathoexcitation and elevated ABP. Both experimental and clinical studies using time-controlled sampling have documented that a diet high in salt increases plasma and cerebrospinal fluid sodium concentration. To the extent it has been tested, acute and chronic elevations in sodium concentration activates the sympathetic nervous system in animals and humans. A further understanding of how the central nervous system detects changes in plasma or cerebrospinal fluid sodium concentration may lead to new therapeutic treatment strategies in salt-sensitive hypertension.
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Affiliation(s)
- Sean D Stocker
- Department of Cellular & Molecular Physiology, Pennsylvania State University College of Medicine, 500 University Drive H166, Hershey, PA, 17033, USA,
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18
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Kinsman B, Cowles J, Lay J, Simmonds SS, Browning KN, Stocker SD. Osmoregulatory thirst in mice lacking the transient receptor potential vanilloid type 1 (TRPV1) and/or type 4 (TRPV4) receptor. Am J Physiol Regul Integr Comp Physiol 2014; 307:R1092-100. [PMID: 25100078 DOI: 10.1152/ajpregu.00102.2014] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Recent studies suggest the ability of the central nervous system to detect changes in osmolality is mediated by products of the genes encoding the transient receptor potential vanilloid-1 (TRPV1) or vanilloid-4 (TRPV4) channel. The purpose of the present study was to determine whether deletion of TRPV1 and/or TRPV4 channels altered thirst responses to cellular dehydration in mice. Injection of 0.5 or 1.0 M NaCl produced dose-dependent increases in cumulative water intakes of wild-type (WT), TRPV1-/-, TRPV4-/-, and TRPV1-/-V4-/- mice. However, there were no differences in cumulative water intakes between WT versus any other strain despite similar increases in plasma electrolytes and osmolality. Similar results were observed after injection of hypertonic mannitol. This was a consistent finding regardless of the injection route (intraperitoneal vs. subcutaneous) or timed access to water (delayed vs. immediate). There were also no differences in cumulative intakes across strains after injection of 0.15 M NaCl or during a time-controlled period (no injection). Chronic hypernatremia produced by sole access to 2% NaCl for 48 h also produced similar increases in water intake across strains. In a final set of experiments, subcutaneous injection of 0.5 M NaCl produced similar increases in the number of Fos-positive nuclei within the organum vasculosum of the lamina terminalis and median preoptic nucleus across strains but significantly smaller number in the subfornical organ of WT versus TRPV1-/-V4-/- mice. Collectively, these findings suggest that TRPV1 and/or TRPV4 channels are not the primary mechanism by which the central nervous system responds to cellular dehydration during hypernatremia or hyperosmolality to increase thirst.
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Affiliation(s)
- Brian Kinsman
- Department of Cellular and Molecular Physiology, and
| | - James Cowles
- Department of Cellular and Molecular Physiology, and
| | - Jennifer Lay
- Department of Cellular and Molecular Physiology, and
| | | | - Kirsteen N Browning
- Department of Neural and Behavioral Sciences, Pennsylvania State University College of Medicine, Hershey, Pennsylvania
| | - Sean D Stocker
- Department of Cellular and Molecular Physiology, and Department of Neural and Behavioral Sciences, Pennsylvania State University College of Medicine, Hershey, Pennsylvania
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19
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Role for the TRPV1 channel in insulin secretion from pancreatic beta cells. J Membr Biol 2014; 247:479-91. [PMID: 24676478 DOI: 10.1007/s00232-014-9658-8] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2013] [Accepted: 03/10/2014] [Indexed: 02/04/2023]
Abstract
Transient receptor potential channels have been put forward as regulators of insulin secretion. A role for the TRPV1 ion channel in insulin secretion has been suggested in pancreatic beta cell lines. We explored whether TRPV1 is functionally expressed in RINm5F and primary beta cells from neonate and adult rats. We examined if capsaicin could activate cationic non-selective currents. Our results show that TRPV1 channels are not functional in insulin-secreting cells, since capsaicin did not produce current activation, not even under culture conditions known to induce the expression of other ion channels in these cells. Although TRPV1 channels seem to be irrelevant for the physiology of isolated beta cells, they may play a role in glucose homeostasis acting through the nerve fibers that regulate islet function. At the physiological level, we observed that Trpv1 (-/-) mice presented lower fasting insulin levels than their wild-type littermates, however, we did not find differences between these experimental groups nor in the glucose tolerance test or in the insulin secretion. However, we did find that the Trpv1 (-/-) mice exhibited a higher insulin sensitivity compared to their wild-type counterparts. Our results demonstrate that TRPV1 does not contribute to glucose-induced insulin secretion in beta cells as was previously thought, but it is possible that it may control insulin sensitivity.
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20
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Abstract
Mechanosensitive channels allow cells to respond to changes in membrane stretch that occur due to external stimuli like pressure or flow or that occur because of osmotically induced cell swelling or shrinkage. Ion fluxes through the channels change the membrane potential and ion concentrations and link the stretch to cellular signalling. Changes in cellular activity evoked by mechanical stimuli can be used to elicit local tissue responses or can be transmitted further to generate more widespread responses. Channels can respond directly to membrane stress, can be conferred mechanosensitive by interaction with structural proteins, or can be activated by mechanosensitive signalling pathways. Because mechanosensitive channels are often nonselective cation channels, and invertebrate TRP isoforms are involved in mechanosensation, many of the mammalian TRP isoforms have been investigated with regard to their mechanosensitivity. There is evidence that members of the TRPC, TRPV, TRPM, TRPA and TRPP subfamilies could be in some way mechanosensitive, and each of the activation mechanisms described above is used by a TRP channel. TRP channels may be involved in mechanosensitive processes ranging from flow and pressure sensing in the vasculature and other organs to mechanosensation in sensory neurones and sensory organs. There is also evidence for a role of mechano- or osmosensitive TRP isoforms in osmosensing and the regulation of cell volume. Often, a number of different TRP isoforms have been implicated in a single type of mechanosensitive response. In many cases, the involvement of the isoforms needs to be confirmed, and their exact role in the signalling process determined.
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Affiliation(s)
- Tim D Plant
- Pharmakologisches Institut, BPC-Marburg, FB-Medizin, Philipps-Universität Marburg, Karl-von-Frisch-Straße 1, 35032, Marburg, Germany,
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21
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Noda M, Sakuta H. Central regulation of body-fluid homeostasis. Trends Neurosci 2013; 36:661-73. [DOI: 10.1016/j.tins.2013.08.004] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2013] [Revised: 07/30/2013] [Accepted: 08/12/2013] [Indexed: 01/21/2023]
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22
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Moreno ML, Meza E, Morgado E, Juárez C, Ramos-Ligonio A, Ortega A, Caba M. Activation of organum vasculosum of lamina terminalis, median preoptic nucleus, and medial preoptic area in anticipation of nursing in rabbit pups. Chronobiol Int 2013; 30:1272-82. [PMID: 24112031 DOI: 10.3109/07420528.2013.823980] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
Rhythmic feeding in rabbit pups is a natural model to study food entrainment because, similar to rodents under a schedule of food restriction, these animals show food-anticipatory activity (FAA) prior to daily nursing. In rodents, several brain systems, including the orexinergic system, shift their activity to the restricted feeding schedule, and remain active when subjects are hungry. As the lamina terminalis and regions of the preoptic area participate in the control of behavioral arousal, it was hypothesized that these brain regions are also activated during FAA. Thus, the effects of daily milk ingestion on FOS protein expression in the organum vasculosum of lamina terminalis (OVLT), median preoptic nucleus (MnPO), and medial preoptic area (MPOA) were examined using immunohistochemistry before and after scheduled time of nursing in nursed and fasted subjects. Additionally, FOS expression was explored in orexin (ORX) cells in the lateral hypothalamic area and in the supraoptic nucleus (SON) because of their involvement in arousal and fluid ingestion, respectively. Pups were entrained by daily nursing, as indicated by a significant increase in locomotor behavior before scheduled time of nursing in both nursed and fasted subjects. FOS was significantly higher in the OVLT, MnPO, and MPOA at the time of nursing, and decreased 8 h later in nursed pups. In fasted subjects, this effect persisted in the OVLT, whereas in the MnPO and MPOA, values did not drop at 8 h later, but remained at the same level or higher than those at the time of scheduled nursing. In addition, FOS was significantly higher in ORX cells during FAA in nursed pups in comparison with 8 h later, but in fasted subjects it remained high during most fasting time points. Additionally, OVLT, SON, and ORX cells were activated 1.5 h after nursing. We conclude that the OVLT, MnPO, and MPOA, but not SON, may participate in FAA, as they show activation before suckling of periodic milk ingestion, and that sustained activation of the OVLT, MnPO, and MPOA by fasting may contribute to the high arousal state associated with food deprivation. In agreement with this, ORX cells also remain active after expected nursing, which is consistent with reports in other species.
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Affiliation(s)
- María Luisa Moreno
- Centro de Investigaciones Biomédicas, Universidad Veracruzana, Xalapa , Veracruz , México
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23
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Sladek CD, Johnson AK. Integration of thermal and osmotic regulation of water homeostasis: the role of TRPV channels. Am J Physiol Regul Integr Comp Physiol 2013; 305:R669-78. [PMID: 23883678 PMCID: PMC3798796 DOI: 10.1152/ajpregu.00270.2013] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2013] [Accepted: 07/12/2013] [Indexed: 12/21/2022]
Abstract
Maintenance of body water homeostasis is critical for preventing hyperthermia, because evaporative cooling is the most efficient means of dissipating excess body heat. Water homeostasis is achieved by regulation of water intake and water loss by the kidneys. The former is achieved by sensations of thirst that motivate water acquisition, whereas the latter is regulated by the antidiuretic action of vasopressin. Vasopressin secretion and thirst are stimulated by increases in the osmolality of the extracellular fluid as well as decreases in blood pressure and/or blood volume, signals that are precipitated by water depletion associated with the excess evaporative water loss required to prevent hyperthermia. In addition, they are stimulated by increases in body temperature. The sites and molecular mechanisms involved in integrating thermal and osmotic regulation of thirst and vasopressin secretion are reviewed here with a focus on the role of the thermal and mechanosensitive transient receptor potential-vanilloid (TRPV) family of ion channels.
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Affiliation(s)
- Celia D Sladek
- Department of Physiology and Biophysics, University of Colorado School of Medicine, Aurora, Colorado; and
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24
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Frazier CJ, Pati D, Hiller H, Nguyen D, Wang L, Smith JA, MacFadyen K, de Kloet AD, Krause EG. Acute hypernatremia exerts an inhibitory oxytocinergic tone that is associated with anxiolytic mood in male rats. Endocrinology 2013; 154:2457-67. [PMID: 23653461 PMCID: PMC3689277 DOI: 10.1210/en.2013-1049] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Abstract
Anxiety disorders are the most common psychiatric illnesses and are associated with heightened stress responsiveness. The neuropeptide oxytocin (OT) has garnered significant attention for its potential as a treatment for anxiety disorders; however, the mechanism mediating its effects on stress responses and anxiety is not well understood. Here we used acute hypernatremia, a stimulus that elevates brain levels of OT, to discern the central oxytocinergic pathways mediating stress responsiveness and anxiety-like behavior. Rats were rendered hypernatremic by acute administration of 2.0 M NaCl and had increased plasma sodium concentration, plasma osmolality, and Fos induction in OT-containing neurons relative to 0.15 M NaCl-treated controls. Acute hypernatremia decreased restraint-induced elevations in corticosterone and created an inhibitory oxytocinergic tone on parvocellular neurosecretory neurons within the paraventricular nucleus of the hypothalamus. In contrast, evaluation of Fos immunohistochemistry determined that acute hypernatremia followed by restraint increased neuronal activation in brain regions receiving OT afferents that are also implicated in the expression of anxiety-like behavior. To determine whether these effects were predictive of altered anxiety-like behavior, rats were subjected to acute hypernatremia and then tested in the elevated plus maze. Relative to controls given 0.15 M NaCl, rats given 2.0 M NaCl spent more time in the open arms of the elevated plus maze, suggesting that acute hypernatremia is anxiolytic. Collectively the results suggest that acute elevations in plasma sodium concentration increase central levels of OT, which decreases anxiety by altering neuronal activity in hypothalamic and limbic nuclei.
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Affiliation(s)
- Charles J Frazier
- Department of Pharmacodynamics, College of Medicine, University of Florida, Gainesville, FL 32610, USA
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Nedungadi TP, Dutta M, Bathina CS, Caterina MJ, Cunningham JT. Expression and distribution of TRPV2 in rat brain. Exp Neurol 2012; 237:223-37. [PMID: 22750329 DOI: 10.1016/j.expneurol.2012.06.017] [Citation(s) in RCA: 61] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2011] [Revised: 05/23/2012] [Accepted: 06/20/2012] [Indexed: 02/07/2023]
Abstract
Transient receptor potential (TRP) proteins are non-selective cation channels that mediate sensory transduction. The neuroanatomical localization and the physiological roles of isoform TRPV2 in the rodent brain are largely unknown. We report here the neuroanatomical distribution of TRPV2 in the adult male rat brain focusing on the hypothalamus and hindbrain regions involved in osmoregulation, autonomic function and energy metabolism. For this we utilized immunohistochemistry combined with brightfield microscopy. In the forebrain, the densest immunostaining was seen in both the supraoptic nucleus (SON) and the magnocellular division of the paraventricular nucleus (PVN) of the hypothalamus. TRPV2 immunoreactivity was also seen in the organum vasculosum of the lamina terminalis, the median preoptic nucleus and the subfornical organ, in addition to the arcuate nucleus of the hypothalamus (ARH), the medial forebrain bundle, the cingulate cortex and the globus pallidus to name a few. In the hindbrain, intense staining was seen in the nucleus of the solitary tract, hypoglossal nucleus, nucleus ambiguous, and the rostral division of the ventrolateral medulla (RVLM) and some mild staining in the area prostrema. To ascertain the specificity of the TRPV2 antibody used in this paper, we compared the TRPV2 immunoreactivity of wildtype (WT) and knockout (KO) mouse brain tissue. Double immunostaining with arginine vasopressin (AVP) using confocal microscopy showed a high degree of colocalization of TRPV2 in the magnocellular SON and PVN. Using laser capture microdissection (LCM) we also show that AVP neurons in the SON contain TRPV2 mRNA. TRPV2 was also co-localized with dopamine beta hydroxylase (DBH) in the NTS and the RVLM of the hindbrain. Based on our results, TRPV2 may play an important role in several CNS networks that regulate body fluid homeostasis, autonomic function, and metabolism.
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Affiliation(s)
- Thekkethil Prashant Nedungadi
- Department of Integrative Physiology, University of North Texas Health Science Center at Fort Worth, 3500 Camp Bowie Blvd, Fort Worth, TX 76107, USA
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Issa AT, Miyata K, Heng V, Mitchell KD, Derbenev AV. Increased neuronal activity in the OVLT of Cyp1a1-Ren2 transgenic rats with inducible Ang II-dependent malignant hypertension. Neurosci Lett 2012; 519:26-30. [PMID: 22579820 DOI: 10.1016/j.neulet.2012.05.006] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2012] [Revised: 04/27/2012] [Accepted: 05/02/2012] [Indexed: 11/27/2022]
Abstract
The contribution of angiotensin II (Ang II) to the pathophysiology of hypertension is established based on facts that high levels of circulating Ang II increase vasoconstriction of peripheral arteries causing a rise in blood pressure (BP). In addition, circulating Ang II has various effects on the central nervous system, including the osmosensitive neurons in the organum vasculosum of the lamina terminalis (OVLT). Osmosensitive neurons in the OVLT transduce hypertonicity via the activation of the nonselective cation channel known as transient receptor potential vanilloid 1 (TRPV1), causing membrane depolarization, followed by increased action potential discharge. This effect is absent in mice lacking expression of the TRPV1 gene. Most observations related to the importance of the OVLT in cardiovascular control are mainly based on models of lesion of the entire preoptic periventricular tissue. However, it remains unclear whether neuronal activity and TRPV1 protein expression levels alter in the OVLT of Cyp1a1-Ren2 transgenic rats with inducible Ang II-dependent malignant hypertension. C-fos was used as a marker of neuronal activity. Immunostaining was used to demonstrate distribution of c-fos positive neurons in the OVLT of Cyp1a1Ren2 transgenic rats. Western blot analysis showed increased c-fos and TRPV1 total protein expression levels in the OVLT of hypertensive rats. The present findings demonstrate increased c-fos and TRPV1 expression levels in the OVLT of Cyp1a1-Ren2 transgenic rats with Ang II-dependent malignant hypertension.
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Affiliation(s)
- Alexandra T Issa
- Department of Physiology, Tulane University, New Orleans, LA, United States
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Zhou Y, Holmseth S, Hua R, Lehre AC, Olofsson AM, Poblete-Naredo I, Kempson SA, Danbolt NC. The betaine-GABA transporter (BGT1, slc6a12) is predominantly expressed in the liver and at lower levels in the kidneys and at the brain surface. Am J Physiol Renal Physiol 2012; 302:F316-28. [DOI: 10.1152/ajprenal.00464.2011] [Citation(s) in RCA: 97] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023] Open
Abstract
The Na+- and Cl−-dependent GABA-betaine transporter (BGT1) has received attention mostly as a protector against osmolarity changes in the kidney and as a potential controller of the neurotransmitter GABA in the brain. Nevertheless, the cellular distribution of BGT1, and its physiological importance, is not fully understood. Here we have quantified mRNA levels using TaqMan real-time PCR, produced a number of BGT1 antibodies, and used these to study BGT1 distribution in mice. BGT1 (protein and mRNA) is predominantly expressed in the liver (sinusoidal hepatocyte plasma membranes) and not in the endothelium. BGT1 is also present in the renal medulla, where it localizes to the basolateral membranes of collecting ducts (particularly at the papilla tip) and the thick ascending limbs of Henle. There is some BGT1 in the leptomeninges, but brain parenchyma, brain blood vessels, ependymal cells, the renal cortex, and the intestine are virtually BGT1 deficient in 1- to 3-mo-old mice. Labeling specificity was assured by processing tissue from BGT1-deficient littermates in parallel as negative controls. Addition of 2.5% sodium chloride to the drinking water for 48 h induced a two- to threefold upregulation of BGT1, tonicity-responsive enhancer binding protein, and sodium- myo-inositol cotransporter 1 (slc5a3) in the renal medulla, but not in the brain and barely in the liver. BGT1-deficient and wild-type mice appeared to tolerate the salt treatment equally well, possibly because betaine is one of several osmolytes. In conclusion, this study suggests that BGT1 plays its main role in the liver, thereby complementing other betaine-transporting carrier proteins (e.g., slc6a20) that are predominantly expressed in the small intestine or kidney rather than the liver.
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Affiliation(s)
- Y. Zhou
- Department of Anatomy, Institute of Basic Medical Sciences, University of Oslo, Oslo, Norway
| | - S. Holmseth
- Department of Anatomy, Institute of Basic Medical Sciences, University of Oslo, Oslo, Norway
| | - R. Hua
- Department of Anatomy, Institute of Basic Medical Sciences, University of Oslo, Oslo, Norway
| | - A. C. Lehre
- Department of Anatomy, Institute of Basic Medical Sciences, University of Oslo, Oslo, Norway
| | - A. M. Olofsson
- Department of Anatomy, Institute of Basic Medical Sciences, University of Oslo, Oslo, Norway
| | - I. Poblete-Naredo
- Departamento de Genética y Biología Molecular, Centro de Investigación y de studios Avanzados del Instituto Politécnico Nacional, México City, Mexico; and
| | - S. A. Kempson
- Department of Cellular and Integrative Physiology, Indiana University School of Medicine, Indianapolis, Indiana
| | - N. C. Danbolt
- Department of Anatomy, Institute of Basic Medical Sciences, University of Oslo, Oslo, Norway
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Hypertonicity sensing in organum vasculosum lamina terminalis neurons: a mechanical process involving TRPV1 but not TRPV4. J Neurosci 2011; 31:14669-76. [PMID: 21994383 DOI: 10.1523/jneurosci.1420-11.2011] [Citation(s) in RCA: 83] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Primary osmosensory neurons in the mouse organum vasculosum lamina terminalis (OVLT) transduce hypertonicity via the activation of nonselective cation channels that cause membrane depolarization and increased action potential discharge, and this effect is absent in mice lacking expression of the transient receptor potential vanilloid 1 (Trpv1) gene (Ciura and Bourque, 2006). However other experiments have indicated that channels encoded by Trpv4 also contribute to central osmosensation in mice (Liedtke and Friedman, 2003; Mizuno et al., 2003). At present, the mechanism by which hypertonicity modulates cation channels in OVLT neurons is unknown, and it remains unclear whether Trpv1 and Trpv4 both contribute to this process. Here, we show that physical shrinking is necessary and sufficient to mediate hypertonicity sensing in OVLT neurons isolated from adult mice. Steps coupling progressive decreases in cell volume to increased neuronal activity were quantitatively equivalent whether shrinking was evoked by osmotic pressure or mechanical aspiration. Finally, modulation of OVLT neurons by tonicity or mechanical stimulation was unaffected by deletion of trpv4 but was abolished in cells lacking Trpv1 or wild-type neurons treated with the TRPV1 antagonist SB366791. Thus, hypertonicity sensing is a mechanical process requiring Trpv1, but not Trpv4.
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Pedersen SF, Kapus A, Hoffmann EK. Osmosensory mechanisms in cellular and systemic volume regulation. J Am Soc Nephrol 2011; 22:1587-97. [PMID: 21852585 DOI: 10.1681/asn.2010121284] [Citation(s) in RCA: 68] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022] Open
Abstract
Perturbations of cellular and systemic osmolarity severely challenge the function of all organisms and are consequently regulated very tightly. Here we outline current evidence on how cells sense volume perturbations, with particular focus on mechanisms relevant to the kidneys and to extracellular osmolarity and whole body volume homeostasis. There are a variety of molecular signals that respond to perturbations in cell volume and osmosensors or volume sensors responding to these signals. The early signals of volume perturbation include integrins, the cytoskeleton, receptor tyrosine kinases, and transient receptor potential channels. We also present current evidence on the localization and function of central and peripheral systemic osmosensors and conclude with a brief look at the still limited evidence on pathophysiological conditions associated with deranged sensing of cell volume.
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Affiliation(s)
- Stine Falsig Pedersen
- Department of Biology, University of Copenhagen, Universitetsparken 13, DK-2100, Copenhagen, Denmark.
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Nishihara E, Hiyama TY, Noda M. Osmosensitivity of transient receptor potential vanilloid 1 is synergistically enhanced by distinct activating stimuli such as temperature and protons. PLoS One 2011; 6:e22246. [PMID: 21779403 PMCID: PMC3136519 DOI: 10.1371/journal.pone.0022246] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2011] [Accepted: 06/17/2011] [Indexed: 11/25/2022] Open
Abstract
In animals, body-fluid osmolality is continuously monitored to keep it within a narrow range around a set point (∼300 mOsm/kg). Transient receptor potential vanilloid 1 (TRPV1), a cation channel, has been implicated in body-fluid homeostasis in vivo based on studies with the TRPV1-knockout mouse. However, the response of TRPV1 to hypertonic stimuli has not been demonstrated with heterologous expression systems so far, despite intense efforts by several groups. Thus, the molecular entity of the hypertonic sensor in vivo still remains controversial. Here we found that the full-length form of TRPV1 is sensitive to an osmotic increase exclusively at around body temperature using HEK293 cells stably expressing rat TRPV1. At an ambient temperature of 24°C, a slight increase in the intracellular calcium concentration ([Ca(2+)](i)) was rarely observed in response to hypertonic stimuli. However, the magnitude of the osmosensitive response markedly increased with temperature, peaking at around 36°C. Importantly, the response at 36°C showed a robust increase over a hypertonic range, but a small decrease over a hypotonic range. A TRPV1 antagonist, capsazepine, and a nonspecific TRP channel inhibitor, ruthenium red, completely blocked the increase in [Ca(2+)](i). These results endorse the view that the full-length form of TRPV1 is able to function as a sensor of hypertonic stimuli in vivo. Furthermore, we found that protons and capsaicin likewise synergistically potentiated the response of TRPV1 to hypertonic stimuli. Of note, HgCl(2), which blocks aquaporins and inhibits cell-volume changes, significantly reduced the osmosensitive response. Our findings thus indicate that TRPV1 integrates multiple different types of activating stimuli, and that TRPV1 is sensitive to hypertonic stimuli under physiologically relevant conditions.
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Affiliation(s)
- Eri Nishihara
- Division of Molecular Neurobiology, National Institute for Basic Biology, The Graduate University for Advanced Studies, Okazaki, Aichi, Japan
| | - Takeshi Y. Hiyama
- Division of Molecular Neurobiology, National Institute for Basic Biology, The Graduate University for Advanced Studies, Okazaki, Aichi, Japan
- School of Life Science, The Graduate University for Advanced Studies, Okazaki, Aichi, Japan
| | - Masaharu Noda
- Division of Molecular Neurobiology, National Institute for Basic Biology, The Graduate University for Advanced Studies, Okazaki, Aichi, Japan
- School of Life Science, The Graduate University for Advanced Studies, Okazaki, Aichi, Japan
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Sinke AP, Deen PMT. The physiological implication of novel proteins in systemic osmoregulation. FASEB J 2011; 25:3279-89. [PMID: 21737616 DOI: 10.1096/fj.11-188433] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Maintenance of the osmobalance is important for life. In this process, in which brain and kidney act in concert, mammals have to cope with significant deviations as drinking water reduces plasma osmolality, whereas salty food increases it. To restore homeostasis, specialized nuclei within the hypothalamus play a pivotal role in detecting changes in plasma osmolality and initiating appropriate responses. These responses are accomplished by either changing the intake of water or the excretion of water by the kidney. In the past decade, several novel findings have made significant contributions to our insights in the process of systemic osmoregulation. Novel proteins have been identified in the brain as well as in the kidney that are fulfilling important roles in the process of systemic osmoregulation. In this review, recent evidence of the involvement of TRPV channels (TRPV1, TRPV2, and TRPV4) and proteins, such as sodium channels NALCN and Na(x), in neuronal osmoregulation, as well as; e.g., the purinergic P2Y2 receptor in renal osmoregulation, are discussed, and integrated with existing knowledge of systemic osmoregulation.
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Affiliation(s)
- Anne P Sinke
- Department of Physiology, Radboud University Nijmegen Medical Centre, Nijmegen, The Netherlands
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Abstract
Life stress frequently occurs within the context of homeostatic challenge, requiring integration of physiological and psychological need into appropriate hormonal, cardiovascular, and behavioral responses. To test neural mechanisms underlying stress integration within the context of homeostatic adversity, we evaluated the impact of a pronounced physiological (hypernatremia) challenge on hypothalamic-pituitary-adrenal (HPA), cardiovascular, and behavioral responses to an acute psychogenic stress. Relative to normonatremic controls, rats rendered mildly hypernatremic had decreased HPA activation in response to physical restraint, a commonly used rodent model of psychogenic stress. In addition, acute hypernatremia attenuated the cardiovascular response to restraint and promoted faster recovery to prestress levels. Subsequent to restraint, hypernatremic rats had significantly more c-Fos expression in oxytocin- and vasopressin-containing neurons within the supraoptic and paraventricular nuclei of the hypothalamus. Hypernatremia also completely eliminated the increased plasma renin activity that accompanied restraint in controls, but greatly elevated circulating levels of oxytocin. The endocrine and cardiovascular profile of hypernatremic rats was predictive of decreased anxiety-like behavior in the social interaction test. Collectively, the results indicate that acute hypernatremia is a potent inhibitor of the HPA, cardiovascular, and behavioral limbs of the stress response. The implications are that the compensatory responses that promote renal-sodium excretion when faced with hypernatremia also act on the nervous system to decrease reactivity to psychogenic stressors and facilitate social behavior, which may suppress the anxiety associated with approaching a communal water source and support the social interactions that may be encountered when engaging in drinking behavior.
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Trpv1 reporter mice reveal highly restricted brain distribution and functional expression in arteriolar smooth muscle cells. J Neurosci 2011; 31:5067-77. [PMID: 21451044 DOI: 10.1523/jneurosci.6451-10.2011] [Citation(s) in RCA: 384] [Impact Index Per Article: 29.5] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
The heat and capsaicin receptor, TRPV1, is required for the detection of painful heat by primary afferent pain fibers (nociceptors), but the extent to which functional TRPV1 channels are expressed in the CNS is debated. Because previous evidence is based primarily on indirect physiological responses to capsaicin, here we genetically modified the Trpv1 locus to reveal, with excellent sensitivity and specificity, the distribution of TRPV1 in all neuronal and non-neuronal tissues. In contrast to reports of widespread and robust expression in the CNS, we find that neuronal TRPV1 is primarily restricted to nociceptors in primary sensory ganglia, with minimal expression in a few discrete brain regions, most notably in a contiguous band of cells within and adjacent to the caudal hypothalamus. We confirm hypothalamic expression in the mouse using several complementary approaches, including in situ hybridization, calcium imaging, and electrophysiological recordings. Additional in situ hybridization experiments in rat, monkey, and human brain demonstrate that the restricted expression of TRPV1 in the CNS is conserved across species. Outside of the CNS, we find TRPV1 expression in a subset of arteriolar smooth muscle cells within thermoregulatory tissues. Here, capsaicin increases calcium uptake and induces vasoconstriction, an effect that likely counteracts the vasodilation produced by activation of neuronal TRPV1.
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Pan Z, Wang Z, Yang H, Zhang F, Reinach PS. TRPV1 activation is required for hypertonicity-stimulated inflammatory cytokine release in human corneal epithelial cells. Invest Ophthalmol Vis Sci 2011; 52:485-93. [PMID: 20739465 DOI: 10.1167/iovs.10-5801] [Citation(s) in RCA: 104] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
PURPOSE To determine whether hypertonic stress promotes increases in inflammatory cytokine release through transient receptor potential vanilloid channel type 1 (TRPV1) signaling pathway activation in human corneal epithelial cells (HCECs). METHODS Hyperosmotic medium was prepared by supplementing isotonic Ringers solution with sucrose. Ca2+ signaling was measured in fura2-AM-loaded HCECs using a single-cell fluorescence imaging system. Western blot analysis evaluated the phosphorylation status of EGFR, ERK, p38 MAPK, and nuclear factor (NF)-κB. ELISA assessed the effect of TRPV1 activation on the release of IL-6 and IL-8. RESULTS A 450 mOsm hypertonic stress elicited 2-fold Ca2+ transients that were suppressed by the TRPV1-selective antagonists capsazepine and JYL 1421. Such transients were enhanced by PGE2. Hypertonicity-induced EGF receptor (EGFR) transactivation was suppressed by preincubating HCECs with capsazepine, matrix metalloproteinase 1 (MMP1) inhibitor TIMP-1, broad-spectrum MMP inhibitor GM 6001, heparin-bound (HB)-EGF inhibitor CRM 197, or EGFR inhibitor AG 1478. ERK and p38 MAPK and NF-κB activation after EGFR transactivation occurred in tonicity and in a time-dependent manner. Hypertonicity-induced increases in IL-6 and IL-8 releases were suppressed by exposure to capsazepine, AG 1478, ERK inhibitor PD 98059, p38 inhibitor SB 203580, or NF-κB inhibitor PDTC. CONCLUSIONS Hypertonic stress-elicited TRPV1 channel stimulation mediates increases in a proinflammatory cytokine IL-6 and a chemoattractant IL-8 by eliciting EGFR transactivation, MAPK, and NF-κB activation. Selective drug modulation of either TRPV1 activity or its signaling mediators may yield a novel approach to suppressing inflammatory responses occurring in dry eye syndrome.
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Affiliation(s)
- Zan Pan
- Department of Biological Sciences, College of Optometry, State University of New York, New York, New York 10065, USA.
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Sudbury JR, Ciura S, Sharif-Naeini R, Bourque CW. Osmotic and thermal control of magnocellular neurosecretory neurons - role of an N-terminal variant of trpv1. Eur J Neurosci 2010; 32:2022-30. [DOI: 10.1111/j.1460-9568.2010.07512.x] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
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Toney GM, Stocker SD. Hyperosmotic activation of CNS sympathetic drive: implications for cardiovascular disease. J Physiol 2010; 588:3375-84. [PMID: 20603334 DOI: 10.1113/jphysiol.2010.191940] [Citation(s) in RCA: 70] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023] Open
Abstract
Evidence now indicates that exaggerated sympathetic nerve activity (SNA) significantly contributes to salt-sensitive cardiovascular diseases. Although CNS mechanisms that support the elevation of SNA in various cardiovascular disease models have been intensively studied, many mechanistic details remain unknown. In recent years, studies have shown that SNA can rise as a result of both acute and chronic increases of body fluid osmolality. These findings have raised the possibility that salt-sensitive cardiovascular diseases could result, at least in part, from direct osmosensory activation of CNS sympathetic drive. In this brief review we emphasize recent findings from several laboratories, including our own, which demonstrate that neurons of the forebrain organum vasculosum laminae terminalis (OVLT) play a pivotal role in triggering hyperosmotic activation of SNA by recruiting neurons in specific regions of the hypothalamus, brainstem and spinal cord. Although OVLT neurons are intrinsically osmosensitive and shrink when exposed to extracellular hypertonicity, it is not yet clear if these processes are functionally linked. Whereas acute hypertonic activation of OVLT neurons critically depends on TRPV1 channels, studies in TRPV1(-/-) mice suggest that acute and long-term osmoregulatory responses remain largely intact. Therefore, acute and chronic osmosensory transduction by OVLT neurons may be mediated by distinct mechanisms. We speculate that organic osmolytes such as taurine and possibly novel processes such as extracellular acidification could contribute to long-term osmosensory transduction by OVLT neurons and might therefore participate in the elevation of SNA in salt-sensitive cardiovascular diseases.
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Affiliation(s)
- Glenn M Toney
- Department of Physiology, University of Texas Health Science Center at San Antonio, San Antonio, TX 78229-3900, USA.
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Ding Q, Zhang Y, Wang Y, Wang Y, Zhang L, Ding C, Wu L, Yu G. Functional Vanilloid Receptor-1 in Human Submandibular Glands. J Dent Res 2010; 89:711-6. [DOI: 10.1177/0022034510366841] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
Abstract
Vanilloid receptor-1 (VR1) was originally found in the nervous system. Recent evidence indicates that VR1 is also expressed in various cell types. We hypothesized that VR1 exists in the human submandibular gland (SMG) and is involved in regulating salivary secretion. VR1 mRNA and protein were expressed in human SMGs and a human salivary intercalated duct cell line. VR1 was mainly located in serous acinar and ductal cells, but not in mucous acinar cells. Capsaicin, an agonist of VR1, increased intracellular free calcium, enhanced phosphorylation of extracellular signal-regulated kinase, and induced the trafficking of aquaporin 5 (AQP5) from the cytoplasm to the plasma membrane. These effects were abolished by pre-treatment with the VR1 antagonist capsazepine. Furthermore, capsaicin cream applied to the skin covering the submandibular area increased salivary secretion. These findings indicated that a functional VR1 is expressed in the human SMG and is involved in regulating salivary secretion by mediating AQP5 trafficking.
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Affiliation(s)
- Q.W. Ding
- Department of Oral and Maxillofacial Surgery, Peking University School and Hospital of Stomatology, 22 Zhong Guan Cun South St., Beijing, 100081, P.R. China
| | - Y. Zhang
- Department of Physiology and Pathophysiology, Key Laboratory of Molecular Cardiovascular Sciences, Ministry of Education, Peking University Health Science Center, Beijing, 100191, P.R. China
| | - Y. Wang
- Department of Oral and Maxillofacial Surgery, Peking University School and Hospital of Stomatology, 22 Zhong Guan Cun South St., Beijing, 100081, P.R. China
| | - Y.N. Wang
- Department of Physiology and Pathophysiology, Key Laboratory of Molecular Cardiovascular Sciences, Ministry of Education, Peking University Health Science Center, Beijing, 100191, P.R. China
| | - L. Zhang
- Department of Oral and Maxillofacial Surgery, Peking University School and Hospital of Stomatology, 22 Zhong Guan Cun South St., Beijing, 100081, P.R. China
| | - C. Ding
- Department of Physiology and Pathophysiology, Key Laboratory of Molecular Cardiovascular Sciences, Ministry of Education, Peking University Health Science Center, Beijing, 100191, P.R. China
| | - L.L. Wu
- Department of Physiology and Pathophysiology, Key Laboratory of Molecular Cardiovascular Sciences, Ministry of Education, Peking University Health Science Center, Beijing, 100191, P.R. China
| | - G.Y. Yu
- Department of Oral and Maxillofacial Surgery, Peking University School and Hospital of Stomatology, 22 Zhong Guan Cun South St., Beijing, 100081, P.R. China
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Chu KM, Ngan MP, Wai MK, Yeung CK, Andrews PL, Percie du Sert N, Lin G, Rudd JA. Olvanil, a non-pungent vanilloid enhances the gastrointestinal toxicity of cisplatin in the ferret. Toxicol Lett 2010; 192:402-7. [DOI: 10.1016/j.toxlet.2009.11.015] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2009] [Revised: 11/12/2009] [Accepted: 11/16/2009] [Indexed: 10/20/2022]
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Carreño FR, Ji LL, Cunningham JT. Altered central TRPV4 expression and lipid raft association related to inappropriate vasopressin secretion in cirrhotic rats. Am J Physiol Regul Integr Comp Physiol 2008; 296:R454-66. [PMID: 19091909 DOI: 10.1152/ajpregu.90460.2008] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
Abstract
Inappropriate vasopressin (AVP) release causes dilutional hyponatremia in many pathophysiological states such as cirrhosis. The central molecular mechanisms that mediate inappropriate AVP release are unknown. We tested the hypothesis that changes in the expression or trafficking of TRPV4 in the central nervous system may contribute to inappropriate AVP release in the bile duct ligation (BDL) model of cirrhosis in the rat. Four weeks after surgery, BDL rats demonstrated significantly increased plasma vasopressin and plasma renin activity (PRA), hypervolemia, and decreased plasma osmolality. These effects were blocked by providing BDL rats with 2% saline to drink for 15 days. TRPV4 protein expression was significantly increased in brain punches from BDL rats containing the supraoptic nucleus (SON) of the hypothalamus (100% +/- 11 to 157% +/- 4.8), and this effect was blocked in BDL rats given saline. Immunohistochemistry demonstrated a significant increase in TRPV4-positive cells and the percentage of AVP neurons that also were TRPV4-positive in the SON of BDL rats. In the hypothalamus of BDL rats, TRPV4 lipid raft association increased compared with sham (from 100% +/- 2.1 to 326.1% +/- 16). This effect was significantly attenuated in BDL rats given 2% saline to drink (174% +/- 11). In the brain stem, TRPV4 lipid raft association was reduced by BDL and inversely related to plasma AVP and PRA. We speculate that changes in TRPV4 expression and compartmentalization within lipid rafts could contribute to a feed-forward mechanism related to AVP release in cirrhosis.
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Affiliation(s)
- Flávia Regina Carreño
- Department of Pharmacology, University of Texas Health Science Center at San Antonio, San Antonio, TX 78229, USA
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Shi P, Martinez MA, Calderon AS, Chen Q, Cunningham JT, Toney GM. Intra-carotid hyperosmotic stimulation increases Fos staining in forebrain organum vasculosum laminae terminalis neurones that project to the hypothalamic paraventricular nucleus. J Physiol 2008; 586:5231-45. [PMID: 18755745 DOI: 10.1113/jphysiol.2008.159665] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
Body fluid hyperosmolality has long been known to elicit homeostatic responses that range from drinking to inhibition of salt appetite to release of neurohypohyseal hormones (i.e. vasopressin and oxytocin). More recently, it has been recognized that hyperosmolality is capable of also provoking a significant increase of sympathetic nerve activity (SNA). It has been reported that neurones in the forebrain organum vasculosum laminae terminalis (OVLT) and hypothalamic paraventricular nucleus (PVN) each contribute significantly to this response. Here we sought to determine if sympathoexcitatory levels of hyperosmolality activate specifically those OVLT neurones that form a monosynaptic pathway to the PVN. First, we established in anaesthetized rats that graded concentrations of hypertonic NaCl (1.5 and 3.0 osmol kg(-1)) elicit graded increases of renal SNA (RSNA) when infused at a rate of 0.1 ml min(-1) through an internal carotid artery (ICA) - the major vascular supply of the forebrain. Next, infusions were performed in conscious rats in which OVLT neurones projecting to the PVN (OVLT-PVN) were retrogradely labelled with cholera toxin subunit B (CTB). Immunostaining of the immediate early gene product Fos and CTB was performed to quantify osmotic activation of OVLT-PVN neurones. ICA infusions of hypertonic NaCl and mannitol each significantly (P < 0.01-0.001) increased the number of Fos immunoreactive (Fos-ir) neuronal nuclei in the dorsal cap (DC) and lateral margins (LM) of OVLT. In the LM, infusions of 1.5 and 3.0 osmol kg(-1) NaCl produced similar increases in the number of Fos-ir neurones. In the DC, these infusions produced graded increases in Fos expression. Among OVLT neurones with axons projecting directly to the PVN (i.e. CTB-ir), graded hypertonic NaCl infusions again produced graded increases in Fos expression and this was observed in both the DC and LM. Although the DC and LM contained a similar number of OVLT-PVN neurones, the proportion of such neurones that expressed Fos-ir in responses to ICA hypertonic NaCl infusions was greater in the DC (P < 0.001). These findings support the conclusion that PVN-projecting neurones in the DC and LM of OVLT could participate in behavioural, neuroendocrine, and sympathetic nervous system responses to body fluid hyperosmolality.
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Affiliation(s)
- Peng Shi
- Department of Physiology, University of Texas Health Science Center at San Antonio, 7703 Floyd Curl Drive, San Antonio, TX 78229-3900, USA
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Abstract
Systemic osmoregulation is a vital process whereby changes in plasma osmolality, detected by osmoreceptors, modulate ingestive behaviour, sympathetic outflow and renal function to stabilize the tonicity and volume of the extracellular fluid. Furthermore, changes in the central processing of osmosensory signals are likely to affect the hydro-mineral balance and other related aspects of homeostasis, including thermoregulation and cardiovascular balance. Surprisingly little is known about how the brain orchestrates these responses. Here, recent advances in our understanding of the molecular, cellular and network mechanisms that mediate the central control of osmotic homeostasis in mammals are reviewed.
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Affiliation(s)
- Charles W Bourque
- Centre for Research in Neuroscience, Research Institute of the McGill University Health Centre, Room L7-216, Montreal General Hospital, 1650 Cedar Avenue, Montreal, Quebec, H3G 1A4, Canada.
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