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Cheng L, Yu L, Zhan X, Tse G, Liu T, Fu H, Li G. Ticagrelor Can Regulate the Ion Channel Characteristics of Superior Cervical Ganglion Neurons after Myocardial Infarction. J Cardiovasc Dev Dis 2023; 10:jcdd10020071. [PMID: 36826567 PMCID: PMC9966694 DOI: 10.3390/jcdd10020071] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/27/2022] [Revised: 01/30/2023] [Accepted: 02/01/2023] [Indexed: 02/09/2023] Open
Abstract
BACKGROUND The superior cervical ganglion (SCG) plays a key role in cardiovascular diseases. The aim of this study was to determine the changes in the ion channel characteristics of the SCG following myocardial infarction (MI) and the role of pretreatment with the P2Y12 receptor antagonist ticagrelor (TIC). METHODS A total of 18 male rabbits were randomly divided into a control group, MI group, and P2Y12 receptor antagonist (TIC) group (abbreviated as the TIC group). Rabbit MI was performed via two abdominal subcutaneous injections of 150 mg·kg-1·d-1 of isoproterenol (ISO) with an interval of 24 h. TIC pretreatment at 20 mg·kg-1·d-1 was administered via gavage for two consecutive days. The cardiac function of each group was evaluated with echocardiography. ADP receptor P2Y12 expressions in SCGs were determined using RT-PCR and immunofluorescence staining. Ion channel characteristics of SCG neurons were measured using a whole-cell patch clamp. Intracellular calcium concentrations for SCG neurons were measured using confocal microscopy. RESULTS Cardiac function was reduced in the rabbits of the MI group, the sympathetic nerve activity of SCGs was increased, and the current amplitude of the neuron ion channel was increased. MI led to alterations in the activation and inactivation characteristics of INa channels accompanied by increased expression of P2Y12 in SCGs. Most of these abnormalities were prevented by TIC pretreatment in the TIC group. CONCLUSIONS TIC pretreatment could attenuate the increase in P2Y12 expression in SCGs and the changes to the ion channel characteristics of SCG neurons after MI. This may be the mechanism underlying the cardiac protective effects of TIC.
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Affiliation(s)
- Lijun Cheng
- Tianjin Key Laboratory of Ionic-Molecular Function of Cardiovascular Disease, Department of Cardiology, Tianjin Institute of Cardiology, The Second Hospital of Tianjin Medical University, Tianjin 300211, China
| | - Lin Yu
- Tianjin Key Laboratory of Ionic-Molecular Function of Cardiovascular Disease, Department of Cardiology, Tianjin Institute of Cardiology, The Second Hospital of Tianjin Medical University, Tianjin 300211, China
| | - Xiaoping Zhan
- Tianjin Key Laboratory of Ionic-Molecular Function of Cardiovascular Disease, Department of Cardiology, Tianjin Institute of Cardiology, The Second Hospital of Tianjin Medical University, Tianjin 300211, China
| | - Gary Tse
- Tianjin Key Laboratory of Ionic-Molecular Function of Cardiovascular Disease, Department of Cardiology, Tianjin Institute of Cardiology, The Second Hospital of Tianjin Medical University, Tianjin 300211, China
- School of Nursing and Health Studies, Hong Kong Metropolitan University, Hong Kong, China
| | - Tong Liu
- Tianjin Key Laboratory of Ionic-Molecular Function of Cardiovascular Disease, Department of Cardiology, Tianjin Institute of Cardiology, The Second Hospital of Tianjin Medical University, Tianjin 300211, China
| | - Huaying Fu
- Tianjin Key Laboratory of Ionic-Molecular Function of Cardiovascular Disease, Department of Cardiology, Tianjin Institute of Cardiology, The Second Hospital of Tianjin Medical University, Tianjin 300211, China
- Correspondence: (H.F.); (G.L.); Tel.: +86-22-88326237 (H.F.); Fax: +86-22-28261158 (G.L.)
| | - Guangping Li
- Tianjin Key Laboratory of Ionic-Molecular Function of Cardiovascular Disease, Department of Cardiology, Tianjin Institute of Cardiology, The Second Hospital of Tianjin Medical University, Tianjin 300211, China
- Correspondence: (H.F.); (G.L.); Tel.: +86-22-88326237 (H.F.); Fax: +86-22-28261158 (G.L.)
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Martin-Aragon Baudel M, Espinosa-Tanguma R, Nieves-Cintron M, Navedo MF. Purinergic Signaling During Hyperglycemia in Vascular Smooth Muscle Cells. Front Endocrinol (Lausanne) 2020; 11:329. [PMID: 32528416 PMCID: PMC7256624 DOI: 10.3389/fendo.2020.00329] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/13/2019] [Accepted: 04/28/2020] [Indexed: 12/15/2022] Open
Abstract
The activation of purinergic receptors by nucleotides and/or nucleosides plays an important role in the control of vascular function, including modulation of vascular smooth muscle excitability, and vascular reactivity. Accordingly, purinergic receptor actions, acting as either ion channels (P2X) or G protein-coupled receptors (GCPRs) (P1, P2Y), target diverse downstream effectors, and substrates to regulate vascular smooth muscle function and vascular reactivity. Both vasorelaxant and vasoconstrictive effects have been shown to be mediated by different purinergic receptors in a vascular bed- and species-specific manner. Purinergic signaling has been shown to play a key role in altering vascular smooth muscle excitability and vascular reactivity following acute and short-term elevations in extracellular glucose (e.g., hyperglycemia). Moreover, there is evidence that vascular smooth muscle excitability and vascular reactivity is severely impaired during diabetes and that this is mediated, at least in part, by activation of purinergic receptors. Thus, purinergic receptors present themselves as important candidates mediating vascular reactivity in hyperglycemia, with potentially important clinical and therapeutic potential. In this review, we provide a narrative summarizing our current understanding of the expression, function, and signaling of purinergic receptors specifically in vascular smooth muscle cells and discuss their role in vascular complications following hyperglycemia and diabetes.
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Affiliation(s)
- Miguel Martin-Aragon Baudel
- Department of Pharmacology, University of California, Davis, Davis, CA, United States
- *Correspondence: Miguel Martin-Aragon Baudel
| | - Ricardo Espinosa-Tanguma
- Departamento de Fisiologia y Biofisca, Universidad Autónoma San Luis Potosí, San Luis Potosí, Mexico
| | | | - Manuel F. Navedo
- Department of Pharmacology, University of California, Davis, Davis, CA, United States
- Manuel F. Navedo
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3
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Yu H, Dhingra RR, Dick TE, Galán RF. Effects of ion channel noise on neural circuits: an application to the respiratory pattern generator to investigate breathing variability. J Neurophysiol 2016; 117:230-242. [PMID: 27760817 PMCID: PMC5209552 DOI: 10.1152/jn.00416.2016] [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: 05/31/2016] [Accepted: 10/18/2016] [Indexed: 01/13/2023] Open
Abstract
Neural activity generally displays irregular firing patterns even in circuits with apparently regular outputs, such as motor pattern generators, in which the output frequency fluctuates randomly around a mean value. This "circuit noise" is inherited from the random firing of single neurons, which emerges from stochastic ion channel gating (channel noise), spontaneous neurotransmitter release, and its diffusion and binding to synaptic receptors. Here we demonstrate how to expand conductance-based network models that are originally deterministic to include realistic, physiological noise, focusing on stochastic ion channel gating. We illustrate this procedure with a well-established conductance-based model of the respiratory pattern generator, which allows us to investigate how channel noise affects neural dynamics at the circuit level and, in particular, to understand the relationship between the respiratory pattern and its breath-to-breath variability. We show that as the channel number increases, the duration of inspiration and expiration varies, and so does the coefficient of variation of the breath-to-breath interval, which attains a minimum when the mean duration of expiration slightly exceeds that of inspiration. For small channel numbers, the variability of the expiratory phase dominates over that of the inspiratory phase, and vice versa for large channel numbers. Among the four different cell types in the respiratory pattern generator, pacemaker cells exhibit the highest sensitivity to channel noise. The model shows that suppressing input from the pons leads to longer inspiratory phases, a reduction in breathing frequency, and larger breath-to-breath variability, whereas enhanced input from the raphe nucleus increases breathing frequency without changing its pattern. NEW & NOTEWORTHY A major source of noise in neuronal circuits is the "flickering" of ion currents passing through the neurons' membranes (channel noise), which cannot be suppressed experimentally. Computational simulations are therefore the best way to investigate the effects of this physiological noise by manipulating its level at will. We investigate the role of noise in the respiratory pattern generator and show that endogenous, breath-to-breath variability is tightly linked to the respiratory pattern.
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Affiliation(s)
- Haitao Yu
- School of Electrical Engineering and Automation, Tianjin University, Tianjin, People's Republic of China.,Department of Electrical Engineering and Computer Science, School of Engineering, Case Western Reserve University, Cleveland, Ohio
| | - Rishi R Dhingra
- Division of Pulmonary, Critical Care, and Sleep Medicine, Department of Medicine, School of Medicine, Case Western Reserve University, Cleveland, Ohio; and
| | - Thomas E Dick
- Division of Pulmonary, Critical Care, and Sleep Medicine, Department of Medicine, School of Medicine, Case Western Reserve University, Cleveland, Ohio; and
| | - Roberto F Galán
- Department of Electrical Engineering and Computer Science, School of Engineering, Case Western Reserve University, Cleveland, Ohio
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Membrane coordination of receptors and channels mediating the inhibition of neuronal ion currents by ADP. Purinergic Signal 2016; 12:497-507. [PMID: 27172914 PMCID: PMC5023631 DOI: 10.1007/s11302-016-9516-5] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2015] [Accepted: 05/02/2016] [Indexed: 12/29/2022] Open
Abstract
ADP and other nucleotides control ion currents in the nervous system via various P2Y receptors. In this respect, Cav2 and Kv7 channels have been investigated most frequently. The fine tuning of neuronal ion channel gating via G protein coupled receptors frequently relies on the formation of higher order protein complexes that are organized by scaffolding proteins and harbor receptors and channels together with interposed signaling components. However, ion channel complexes containing P2Y receptors have not been described. Therefore, the regulation of Cav2.2 and Kv7.2/7.3 channels via P2Y1 and P2Y12 receptors and the coordination of these ion channels and receptors in the plasma membranes of tsA 201 cells have been investigated here. ADP inhibited currents through Cav2.2 channels via both P2Y1 and P2Y12 receptors with phospholipase C and pertussis toxin-sensitive G proteins being involved, respectively. The nucleotide controlled the gating of Kv7 channels only via P2Y1 and phospholipase C. In fluorescence energy transfer assays using conventional as well as total internal reflection (TIRF) microscopy, both P2Y1 and P2Y12 receptors were found juxtaposed to Cav2.2 channels, but only P2Y1, and not P2Y12, was in close proximity to Kv7 channels. Using fluorescence recovery after photobleaching in TIRF microscopy, evidence for a physical interaction was obtained for the pair P2Y12/Cav2.2, but not for any other receptor/channel combination. These results reveal a membrane juxtaposition of P2Y receptors and ion channels in parallel with the control of neuronal ion currents by ADP. This juxtaposition may even result in apparent physical interactions between receptors and channels.
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P2Y Receptors in Synaptic Transmission and Plasticity: Therapeutic Potential in Cognitive Dysfunction. Neural Plast 2016; 2016:1207393. [PMID: 27069691 PMCID: PMC4812485 DOI: 10.1155/2016/1207393] [Citation(s) in RCA: 60] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2015] [Accepted: 02/10/2016] [Indexed: 01/02/2023] Open
Abstract
ATP released from neurons and astrocytes during neuronal activity or under pathophysiological circumstances is able to influence information flow in neuronal circuits by activation of ionotropic P2X and metabotropic P2Y receptors and subsequent modulation of cellular excitability, synaptic strength, and plasticity. In the present paper we review cellular and network effects of P2Y receptors in the brain. We show that P2Y receptors inhibit the release of neurotransmitters, modulate voltage- and ligand-gated ion channels, and differentially influence the induction of synaptic plasticity in the prefrontal cortex, hippocampus, and cerebellum. The findings discussed here may explain how P2Y1 receptor activation during brain injury, hypoxia, inflammation, schizophrenia, or Alzheimer's disease leads to an impairment of cognitive processes. Hence, it is suggested that the blockade of P2Y1 receptors may have therapeutic potential against cognitive disturbances in these states.
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Liu C, Glowatzki E, Fuchs PA. Unmyelinated type II afferent neurons report cochlear damage. Proc Natl Acad Sci U S A 2015; 112:14723-7. [PMID: 26553995 PMCID: PMC4664349 DOI: 10.1073/pnas.1515228112] [Citation(s) in RCA: 83] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023] Open
Abstract
In the mammalian cochlea, acoustic information is carried to the brain by the predominant (95%) large-diameter, myelinated type I afferents, each of which is postsynaptic to a single inner hair cell. The remaining thin, unmyelinated type II afferents extend hundreds of microns along the cochlear duct to contact many outer hair cells. Despite this extensive arbor, type II afferents are weakly activated by outer hair cell transmitter release and are insensitive to sound. Intriguingly, type II afferents remain intact in damaged regions of the cochlea. Here, we show that type II afferents are activated when outer hair cells are damaged. This response depends on both ionotropic (P2X) and metabotropic (P2Y) purinergic receptors, binding ATP released from nearby supporting cells in response to hair cell damage. Selective activation of P2Y receptors increased type II afferent excitability by the closure of KCNQ-type potassium channels, a potential mechanism for the painful hypersensitivity (that we term "noxacusis" to distinguish from hyperacusis without pain) that can accompany hearing loss. Exposure to the KCNQ channel activator retigabine suppressed the type II fiber's response to hair cell damage. Type II afferents may be the cochlea's nociceptors, prompting avoidance of further damage to the irreparable inner ear.
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MESH Headings
- Adenosine Triphosphate/pharmacology
- Animals
- Cochlea/innervation
- Cochlea/pathology
- Hair Cells, Auditory, Outer/drug effects
- Hair Cells, Auditory, Outer/pathology
- Ion Channel Gating/drug effects
- Ions
- KCNQ Potassium Channels/metabolism
- Nerve Fibers, Unmyelinated/drug effects
- Nerve Fibers, Unmyelinated/pathology
- Neurons, Afferent/drug effects
- Neurons, Afferent/pathology
- Potassium/metabolism
- Rats, Sprague-Dawley
- Receptors, Glutamate/metabolism
- Receptors, Purinergic P2Y/metabolism
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Affiliation(s)
- Chang Liu
- Department of Neuroscience, Johns Hopkins University School of Medicine, Baltimore, MD 21205
| | - Elisabeth Glowatzki
- Department of Neuroscience, Johns Hopkins University School of Medicine, Baltimore, MD 21205; Department of Otolaryngology-Head and Neck Surgery, Johns Hopkins University School of Medicine, Baltimore, MD 21205
| | - Paul Albert Fuchs
- Department of Neuroscience, Johns Hopkins University School of Medicine, Baltimore, MD 21205; Department of Otolaryngology-Head and Neck Surgery, Johns Hopkins University School of Medicine, Baltimore, MD 21205
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Stotz SC, Scott LO, Drummond-Main C, Avchalumov Y, Girotto F, Davidsen J, Gómez-Gárcia MR, Rho JM, Pavlov EV, Colicos MA. Inorganic polyphosphate regulates neuronal excitability through modulation of voltage-gated channels. Mol Brain 2014; 7:42. [PMID: 24886461 PMCID: PMC4061113 DOI: 10.1186/1756-6606-7-42] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2014] [Accepted: 05/26/2014] [Indexed: 01/06/2023] Open
Abstract
Background Inorganic polyphosphate (polyP) is a highly charged polyanion capable of interacting with a number of molecular targets. This signaling molecule is released into the extracellular matrix by central astrocytes and by peripheral platelets during inflammation. While the release of polyP is associated with both induction of blood coagulation and astrocyte extracellular signaling, the role of secreted polyP in regulation of neuronal activity remains undefined. Here we test the hypothesis that polyP is an important participant in neuronal signaling. Specifically, we investigate the ability of neurons to release polyP and to induce neuronal firing, and clarify the underlying molecular mechanisms of this process by studying the action of polyP on voltage gated channels. Results Using patch clamp techniques, and primary hippocampal and dorsal root ganglion cell cultures, we demonstrate that polyP directly influences neuronal activity, inducing action potential generation in both PNS and CNS neurons. Mechanistically, this is accomplished by shifting the voltage sensitivity of NaV channel activation toward the neuronal resting membrane potential, the block KV channels, and the activation of CaV channels. Next, using calcium imaging we found that polyP stimulates an increase in neuronal network activity and induces calcium influx in glial cells. Using in situ DAPI localization and live imaging, we demonstrate that polyP is naturally present in synaptic regions and is released from the neurons upon depolarization. Finally, using a biochemical assay we demonstrate that polyP is present in synaptosomes and can be released upon their membrane depolarization by the addition of potassium chloride. Conclusions We conclude that polyP release leads to increased excitability of the neuronal membrane through the modulation of voltage gated ion channels. Together, our data establishes that polyP could function as excitatory neuromodulator in both the PNS and CNS.
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Affiliation(s)
| | | | | | | | | | | | | | | | | | - Michael A Colicos
- Department of Physiology & Pharmacology and the Hotchkiss Brain Institute, University of Calgary, 3330 Hospital Drive NW, Calgary, AB T2N 4N1, Canada.
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Jiménez E, Zafra F, Pérez-Sen R, Delicado EG, Miras-Portugal MT, Aragón C, López-Corcuera B. P2Y purinergic regulation of the glycine neurotransmitter transporters. J Biol Chem 2011; 286:10712-24. [PMID: 21245148 DOI: 10.1074/jbc.m110.167056] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The sodium- and chloride-coupled glycine neurotransmitter transporters (GLYTs) control the availability of glycine at glycine-mediated synapses. The mainly glial GLYT1 is the key regulator of the glycine levels in glycinergic and glutamatergic pathways, whereas the neuronal GLYT2 is involved in the recycling of synaptic glycine from the inhibitory synaptic cleft. In this study, we report that stimulation of P2Y purinergic receptors with 2-methylthioadenosine 5'-diphosphate in rat brainstem/spinal cord primary neuronal cultures and adult rat synaptosomes leads to the inhibition of GLYT2 and the stimulation of GLYT1 by a paracrine regulation. These effects are mainly mediated by the ADP-preferring subtypes P2Y(1) and P2Y(13) because the effects are partially reversed by the specific antagonists N(6)-methyl-2'-deoxyadenosine-3',5'-bisphosphate and pyridoxal-5'-phosphate-6-azo(2-chloro-5-nitrophenyl)-2,4-disulfonate and are totally blocked by suramin. P2Y(12) receptor is additionally involved in GLYT1 stimulation. Using pharmacological approaches and siRNA-mediated protein knockdown methodology, we elucidate the molecular mechanisms of GLYT regulation. Modulation takes place through a signaling cascade involving phospholipase C activation, inositol 1,4,5-trisphosphate production, intracellular Ca(2+) mobilization, protein kinase C stimulation, nitric oxide formation, cyclic guanosine monophosphate production, and protein kinase G-I (PKG-I) activation. GLYT1 and GLYT2 are differentially sensitive to NO/cGMP/PKG-I both in brain-derived preparations and in heterologous systems expressing the recombinant transporters and P2Y(1) receptor. Sensitivity to 2-methylthioadenosine 5'-diphosphate by GLYT1 and GLYT2 was abolished by small interfering RNA (siRNA)-mediated knockdown of nitric-oxide synthase. Our data may help define the role of GLYTs in nociception and pain sensitization.
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Affiliation(s)
- Esperanza Jiménez
- Departamento de Biología Molecular and Centro de Biología Molecular Severo Ochoa, Universidad Autónoma de Madrid, 28049 Madrid, Spain
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Tanaka K, Swanson SJ, Gilroy S, Stacey G. Extracellular nucleotides elicit cytosolic free calcium oscillations in Arabidopsis. PLANT PHYSIOLOGY 2010; 154:705-19. [PMID: 20671112 PMCID: PMC2949047 DOI: 10.1104/pp.110.162503] [Citation(s) in RCA: 97] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/08/2010] [Accepted: 07/28/2010] [Indexed: 05/19/2023]
Abstract
Extracellular ATP induces a rise in the level of cytosolic free calcium ([Ca(2+)](cyt)) in plant cells. To expand our knowledge about the function of extracellular nucleotides in plants, the effects of several nucleotide analogs and pharmacological agents on [Ca(2+)](cyt) changes were studied using transgenic Arabidopsis (Arabidopsis thaliana) expressing aequorin or the fluorescence resonance energy transfer-based Ca(2+) sensor Yellow Cameleon 3.6. Exogenously applied CTP caused elevations in [Ca(2+)](cyt) that displayed distinct time- and dose-dependent kinetics compared with the purine nucleotides ATP and GTP. The inhibitory effects of antagonists of mammalian P2 receptors and calcium influx inhibitors on nucleotide-induced [Ca(2+)](cyt) elevations were distinct between CTP and purine nucleotides. These results suggest that distinct recognition systems may exist for the respective types of nucleotides. Interestingly, a mutant lacking the heterotrimeric G protein Gβ-subunit exhibited a remarkably higher [Ca(2+)](cyt) elevation in response to all tested nucleotides in comparison with the wild type. These data suggest a role for Gβ in negatively regulating extracellular nucleotide signaling and point to an important role for heterotrimeric G proteins in modulating the cellular effects of extracellular nucleotides. The addition of extracellular nucleotides induced multiple temporal [Ca(2+)](cyt) oscillations, which could be localized to specific root cells. The oscillations were attenuated by a vesicle-trafficking inhibitor, indicating that the oscillations likely require ATP release via exocytotic secretion. The results reveal new molecular details concerning extracellular nucleotide signaling in plants and the importance of fine control of extracellular nucleotide levels to mediate specific plant cell responses.
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Affiliation(s)
| | | | | | - Gary Stacey
- National Center for Soybean Biotechnology, Division of Plant Sciences (K.T., G.S.), and Division of Biochemistry (G.S.), University of Missouri, Columbia, Missouri 65211; Botany Department, University of Wisconsin, Madison, Wisconsin 53706 (S.J.S., S.G.)
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Smith PJS, Collis LP, Messerli MA. Windows to cell function and dysfunction: signatures written in the boundary layers. Bioessays 2010; 32:514-23. [PMID: 20486138 DOI: 10.1002/bies.200900173] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
The medium surrounding cells either in culture or in tissues contains a chemical mix varying with cell state. As solutes move in and out of the cytoplasmic compartment they set up characteristic signatures in the cellular boundary layers. These layers are complex physical and chemical environments the profiles of which reflect cell physiology and provide conduits for intercellular messaging. Here we review some of the most relevant characteristics of the extracellular/intercellular space. Our initial focus is primarily on cultured cells but we extend our consideration to the far more complex environment of tissues, and discuss how chemical signatures in the boundary layer can or may affect cell function. Critical to the entire essay are the methods used, or being developed, to monitor chemical profiles in the boundary layers. We review recent developments in ultramicro electrochemical sensors and tailored optical reporters suitable for the task in hand.
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Affiliation(s)
- Peter J S Smith
- BioCurrents Research Center, Cellular Dynamics Program, Marine Biological Laboratory, Woods Hole, MA 02543, USA.
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Schicker KW, Chandaka GK, Geier P, Kubista H, Boehm S. P2Y1 receptors mediate an activation of neuronal calcium-dependent K+ channels. J Physiol 2010; 588:3713-25. [PMID: 20679351 DOI: 10.1113/jphysiol.2010.193367] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
Molecularly defined P2Y receptor subtypes are known to regulate the functions of neurons through an inhibition of K(V)7 K(+) and Ca(V)2 Ca(2+) channels and via an activation or inhibition of Kir3 channels. Here, we searched for additional neuronal ion channels as targets for P2Y receptors. Rat P2Y(1) receptors were expressed in PC12 cells via an inducible expression system, and the effects of nucleotides on membrane currents and intracellular Ca(2+) were investigated. At a membrane potential of 30 mV, ADP induced transient outward currents in a concentration-dependent manner with half-maximal effects at 4 μm. These currents had reversal potentials close to the K(+) equilibrium potential and changed direction when extracellular Na(+) was largely replaced by K(+), but remained unaltered when extracellular Cl() was changed. Currents were abolished by P2Y(1) antagonists and by blockade of phospholipase C. ADP also caused rises in intracellular Ca(2+), and ADP-evoked currents were abolished when inositol trisphosphate-sensitive Ca(2+) stores were depleted. Blockers of K(Ca)2, but not those of K(Ca)1.1 or K(Ca)3.1, channels largely reduced ADP-evoked currents. In hippocampal neurons, ADP also triggered outward currents at 30 mV which were attenuated by P2Y(1) antagonists, depletion of Ca(2+) stores, or a blocker of K(Ca)2 channels. These results demonstrate that activation of neuronal P2Y(1) receptors may gate Ca(2+)-dependent K(+) (K(Ca)2) channels via phospholipase C-dependent increases in intracellular Ca(2+) and thereby define an additional class of neuronal ion channels as novel effectors for P2Y receptors. This mechanism may form the basis for the control of synaptic plasticity via P2Y(1) receptors.
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Affiliation(s)
- Klaus W Schicker
- Centre for Physiology and Pharmacology, Medical University of Vienna, A-1090 Wien, Austria
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12
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Kreinest M, Müller B, Winkelhoff J, Friauf E, Löhrke S. Miniature EPSCs in the lateral superior olive before hearing onset: regional and cell-type-specific differences and heterogeneous neuromodulatory effects of ATP. Brain Res 2009; 1295:21-36. [PMID: 19647723 DOI: 10.1016/j.brainres.2009.07.083] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2009] [Revised: 07/23/2009] [Accepted: 07/24/2009] [Indexed: 11/28/2022]
Abstract
Spontaneous activity occurs in the mammalian auditory system prior to hearing onset and is relevant for neuronal differentiation. Growing evidence indicates that miniature events, i.e., action potential-independent synaptic activity, also have some developmental relevance. An intriguing question is whether these events are purely stochastic or rather display specific characteristics. We addressed this question and studied miniature excitatory postsynaptic currents (mEPSCs) in morphologically defined neurons of the rat lateral superior olive (LSO) during early neonatal life. To do so, whole-cell recordings from neurons in acute slices were combined with Lucifer yellow fillings. mEPSCs were identified by their TTX insensitivity and their blockade by glutamate receptor antagonists. Altogether, 60% of the LSO neurons displayed mEPSCs, and their presence correlated with the cell location and morphology. Their percentage was highest in the medial limb (86%) and lowest in the lateral limb (14%). Seventy-seven percent of the neurons with mEPSCs were bipolar cells, whereas 77% of those without mEPSCs were multipolar cells. The neuromodulator ATP affected the frequency of mEPSCs in 61% of the LSO neurons in a heterogeneous manner: both frequency increases and decreases occurred. These data provide further evidence for the specificity of mEPSCs. Finally, we investigated whether missing cochlear input changes mEPSCs characteristics. Characterizing LSO neurons of Ca(V)1.3(-/-) mice, which lack cochlea-driven nerve activity, we observed higher mEPSC frequencies and peak amplitudes, indicative of a compensatory response to deprivation. Together, our results demonstrate specific, rather than stochastic, characteristics of mEPSCs in the neonatal LSO, in accordance with their potential developmental significance.
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Affiliation(s)
- Michael Kreinest
- Animal Physiology Group, Department of Biology, University of Kaiserslautern, PO Box 3049, D-67653 Kaiserslautern, Germany.
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13
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Lechner SG, Lewin GR. Peripheral sensitisation of nociceptors via G-protein-dependent potentiation of mechanotransduction currents. J Physiol 2009; 587:3493-503. [PMID: 19505980 PMCID: PMC2742277 DOI: 10.1113/jphysiol.2009.175059] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
Mechanical stimuli impinging on the skin are converted into electrical signals by mechanically gated ion channels located at the peripheral nerve endings of dorsal root ganglion (DRG) neurons. Under inflammatory conditions sensory neurons are commonly sensitised to mechanical stimuli; a putative mechanism that may contribute to such sensitisation of sensory neurons is enhanced responsiveness of mechanotransduction ion channels. Here we show that the algogens UTP and ATP potentiate mechanosensitive RA currents in peptidergic nociceptive DRG neurons and reduce thresholds for mechanically induced action potential firing in these neurones. Pharmacological characterisation suggests that this effect is mediated by the Gq-coupled P2Y(2) nucleotide receptor. Moreover, using the in vitro skin nerve technique, we show that UTP also increases action potential firing rates in response to mechanical stimuli in a subpopulation of skin C-fibre nociceptors. Together our findings suggest that UTP sensitises a subpopulation of cutaneous C-fibre nociceptors via a previously undescribed G-protein-dependent potentiation of mechanically activated RA-type currents.
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Affiliation(s)
- Stefan G Lechner
- Department of Neuroscience, Max-Delbrück-Center for Molecular Medicine, Robert Rössle Str. 10, 3125 Berlin, Germany
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Köles L, Gerevich Z, Oliveira JF, Zadori ZS, Wirkner K, Illes P. Interaction of P2 purinergic receptors with cellular macromolecules. Naunyn Schmiedebergs Arch Pharmacol 2007; 377:1-33. [DOI: 10.1007/s00210-007-0222-2] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2007] [Accepted: 11/12/2007] [Indexed: 02/04/2023]
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ATP and acetylcholine, equal brethren. Neurochem Int 2007; 52:634-48. [PMID: 18029057 DOI: 10.1016/j.neuint.2007.09.004] [Citation(s) in RCA: 60] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2007] [Revised: 09/07/2007] [Accepted: 09/10/2007] [Indexed: 12/13/2022]
Abstract
Acetylcholine was the first neurotransmitter identified and ATP is the hitherto final compound added to the list of small molecule neurotransmitters. Despite the wealth of evidence assigning a signaling role to extracellular ATP and other nucleotides in neural and non-neural tissues, the significance of this signaling pathway was accepted very reluctantly. In view of this, this short commentary contrasts the principal molecular and functional components of the cholinergic signaling pathway with those of ATP and other nucleotides. It highlights pathways of their discovery and analyses tissue distribution, synthesis, uptake, vesicular storage, receptors, release, extracellular hydrolysis as well as pathophysiological significance. There are differences but also striking similarities. Comparable to ACh, ATP is taken up and stored in synaptic vesicles, released in a Ca(2+)-dependent manner, acts on nearby ligand-gated or metabotropic receptors and is hydrolyzed extracellularly. ATP and acetylcholine are also costored and coreleased. In addition, ATP is coreleased from biogenic amine storing nerve terminals as well as from at least subpopulations of glutamatergic and GABAergic terminals. Both ACh and ATP fulfill the criteria postulated for neurotransmitters. More recent evidence reveals that the two messengers are not confined to neural functions, exerting a considerable variety of non-neural functions in non-innervated tissues. While it has long been known that a substantial number of pathologies originate from malfunctions of the cholinergic system there is now ample evidence that numerous pathological conditions have a purinergic component.
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Gerevich Z, Zadori Z, Müller C, Wirkner K, Schröder W, Rubini P, Illes P. Metabotropic P2Y receptors inhibit P2X3 receptor-channels via G protein-dependent facilitation of their desensitization. Br J Pharmacol 2007; 151:226-36. [PMID: 17351651 PMCID: PMC2013946 DOI: 10.1038/sj.bjp.0707217] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022] Open
Abstract
BACKGROUND AND PURPOSE The aim of the present study was to investigate whether the endogenous metabotropic P2Y receptors modulate ionotropic P2X(3) receptor-channels. EXPERIMENTAL APPROACH Whole-cell patch-clamp experiments were carried out on HEK293 cells permanently transfected with human P2X(3) receptors (HEK293-hP2X(3) cells) and rat dorsal root ganglion (DRG) neurons. KEY RESULTS In both cell types, the P2Y(1,12,13) receptor agonist, ADP-beta-S, inhibited P2X(3) currents evoked by the selective agonist, alpha,beta-methylene ATP (alpha,beta-meATP). This inhibition could be markedly counteracted by replacing in the pipette solution the usual GTP with GDP-beta-S, a procedure known to block all G protein heterotrimers. P2X(3) currents evoked by ATP, activating both P2Y and P2X receptors, caused a smaller peak amplitude and desensitized faster than those currents evoked by the selective P2X(3) receptor agonist alpha,beta-meATP. In the presence of intracellular GDP-beta-S, ATP- and alpha,beta-meATP-induced currents were identical. Recovery from P2X(3) receptor desensitization induced by repetitive ATP application was slower than the recovery from alpha,beta-meATP-induced desensitization. When G proteins were blocked by intracellular GDP-beta-S, the recovery from the ATP- and alpha,beta-meATP-induced desensitization were of comparable speed. CONCLUSIONS AND IMPLICATIONS Our results suggest that the activation of P2Y receptors G protein-dependently facilitates the desensitization of P2X(3) receptors and suppresses the recovery from the desensitized state. Hence, the concomitant stimulation of P2X(3) and P2Y receptors of DRG neurons by ATP may result both in an algesic effect and a partly counterbalancing analgesic activity.
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Affiliation(s)
- Z Gerevich
- Rudolf-Boehm-Institute of Pharmacology and Toxicology, University of Leipzig, Leipzig, Germany.
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Mamedova LK, Gao ZG, Jacobson KA. Regulation of death and survival in astrocytes by ADP activating P2Y1 and P2Y12 receptors. Biochem Pharmacol 2006; 72:1031-41. [PMID: 16934758 PMCID: PMC3150742 DOI: 10.1016/j.bcp.2006.07.017] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2006] [Revised: 07/06/2006] [Accepted: 07/17/2006] [Indexed: 01/24/2023]
Abstract
ADP is the endogenous agonist for both P2Y(1) and P2Y(12) receptors, which are important therapeutic targets. It was previously demonstrated that ADP and a synthetic agonist, 2-methylthioadenosine 5'-diphosphate (2MeSADP), can induce apoptosis by activating the human P2Y(1) receptor heterologously expressed in astrocytoma cells. However, it was not known whether the P2Y(12) receptor behaved similarly. We demonstrated here that, unlike with the G(q)-coupled P2Y(1) receptor, activation of the G(i)-coupled P2Y(12) receptor does not induce apoptosis. Furthermore, activation of the P2Y(12) receptor by either ADP or 2MeSADP significantly attenuates the tumor necrosis factor alpha (TNFalpha)-induced apoptosis in 1321N1 human astrocytoma cells. This protective effect was blocked by the P2Y(12) receptor antagonist 2-methylthioAMP and by inhibitors of phospholipase C (U73122) and protein kinase C (chelerythrin), but not by the P2Y(1) receptor antagonist MRS2179. Toward a greater mechanistic understanding, we showed that hP2Y(12) receptor activation by 10nM 2MeSADP, activates Erk1/2, Akt, and JNK by phosphorylation. However, at a lower protective concentration of 100pM 2MeSADP, activation of the hP2Y(12) receptor involves only phosphorylated Erk1/2, but not Akt or JNK. This activation is hypothesized as the major mechanism for the protective effect induced by P2Y(12) receptor activation. Apyrase did not affect the ability of TNFalpha to induce apoptosis in hP2Y(12)-1321N1 cells, suggesting that the endogenous nucleotides are not involved. These results may have important implications for understanding the signaling cascades that follow activation of P2Y(1) and P2Y(12) receptors and their opposing effects on cell death pathways.
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Affiliation(s)
- Liaman K. Mamedova
- Molecular Recognition Section, Laboratory of Bioorganic Chemistry, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD 20892-0810, USA
| | - Zhan-Guo Gao
- Molecular Recognition Section, Laboratory of Bioorganic Chemistry, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD 20892-0810, USA
| | - Kenneth A. Jacobson
- Molecular Recognition Section, Laboratory of Bioorganic Chemistry, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD 20892-0810, USA
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Van Nassauw L, Costagliola A, Van Op den Bosch J, Cecio A, Vanderwinden JM, Burnstock G, Timmermans JP. Region-specific distribution of the P2Y4 receptor in enteric glial cells and interstitial cells of Cajal within the guinea-pig gastrointestinal tract. Auton Neurosci 2006; 126-127:299-306. [PMID: 16616701 DOI: 10.1016/j.autneu.2006.02.018] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2005] [Revised: 02/16/2006] [Accepted: 02/27/2006] [Indexed: 01/01/2023]
Abstract
Although there is pharmacological evidence to assume that the P2Y4 receptor is a regulator of epithelial ion transport, no detailed data about its distribution within the gut are available. Therefore, this study, using whole mounts and cryosections, aimed to reveal the expression pattern of P2Y4 along the entire guinea-pig gastrointestinal tract. P2Y4 immunoreactivity was absent from enteric neurons but present in enteric glial cells of the stomach, small and large intestine. In the esophagus, P2Y4 appeared to be exclusively located within striated muscle cells. P2Y4 showed also a region dependency regarding its presence in different subpopulations of interstitial cells of Cajal: in myenteric interstitial cells of Cajal in the stomach and ileum; in some intramuscular interstitial cells in the stomach and cecum; in some deep muscular plexus interstitial cells in the ileum; and in some submucosal surface interstitial cells in the colon. These results and the knowledge that P2Y4 activation causes intracellular Ca2+ recruitment led us to suggest that P2Y4 in enteric glia plays a modulatory role in intercellular Ca2+ waves, while P2Y4 in interstitial cells of Cajal modulates intracellular Ca2+ oscillations.
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Affiliation(s)
- Luc Van Nassauw
- Laboratory of Cell Biology and Histology, University of Antwerp, Groenenborgerlaan 171, B-2020 Antwerpen, Belgium
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