1
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Liu Y, Wang G, Cao C, Zhang G, Tanzi EB, Zhang Y, Zhou W, Li Y. Neuromodulation Effect of Very Low Intensity Transcranial Ultrasound Stimulation on Multiple Nuclei in Rat Brain. Front Aging Neurosci 2021; 13:656430. [PMID: 33935688 PMCID: PMC8081960 DOI: 10.3389/fnagi.2021.656430] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2021] [Accepted: 03/02/2021] [Indexed: 11/13/2022] Open
Abstract
Objective Low-intensity transcranial ultrasound stimulation (TUS) is a non-invasive neuromodulation technique with high spatial resolution and feasible penetration depth. To date, the mechanisms of TUS modulated neural oscillations are not fully understood. This study designed a very low acoustic intensity (AI) TUS system that produces considerably reduced AI Ultrasound pulses (ISPTA < 0.5 W/cm2) when compared to previous methods used to measure regional neural oscillation patterns under different TUS parameters. Methods We recorded the local field potential (LFP) of five brain nuclei under TUS with three groups of simulating parameters. Spectrum estimation, time-frequency analysis (TFA), and relative power analysis methods have been applied to investigate neural oscillation patterns under different stimulation parameters. Results Under PRF, 500 Hz and 1 kHz TUS, high-amplitude LFP activity with the auto-rhythmic pattern appeared in selected nuclei when ISPTA exceeded 12 mW/cm2. With TFA, high-frequency energy (slow gamma and high gamma) was significantly increased during the auto-rhythmic patterns. We observed an initial plateau in nuclei response when ISPTA reached 16.4 mW/cm2 for RPF 500 Hz and 20.8 mW/cm2 for RPF 1 kHz. The number of responding nuclei started decreasing while ISPTA continued increasing. Under 1.5 kHz TUS, no auto-rhythmic patterns have been observed, but slow frequency power was increased during TUS. TUS inhibited most of the frequency band and generated obvious slow waves (theta and delta band) when stimulated at RPF = 1.5 kHz, ISPTA = 8.8 mW/cm2. Conclusion These results demonstrate that very low intensity Transcranial Ultrasound Stimulation (VLTUS) exerts significant neuromodulator effects under specific parameters in rat models and may be a valid tool to study neuronal physiology.
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Affiliation(s)
- Yingjian Liu
- School of Microelectronics, Shandong University, Jinan, China
| | - Gang Wang
- School of Microelectronics, Shandong University, Jinan, China
| | - Chao Cao
- School of Microelectronics, Shandong University, Jinan, China
| | - Gaorui Zhang
- Department of Radiology, Qilu Hospital of Shandong University, Jinan, China.,School of Medical Imaging, Weifang Medical University, Weifang, China
| | | | - Yang Zhang
- Department of Radiology, Qilu Hospital of Shandong University, Jinan, China
| | - Weidong Zhou
- School of Microelectronics, Shandong University, Jinan, China
| | - Yi Li
- Weill Cornell Medicine, New York, NY, United States
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2
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Tripathi K, Zhang T, McDannold N, Zhang YZ, Ehnholm G, Okada Y. Direct Activation of Cortical Neurons in the Primary Somatosensory Cortex of the Rat in Vivo Using Focused Ultrasound. ULTRASOUND IN MEDICINE & BIOLOGY 2020; 46:2349-2360. [PMID: 32620386 PMCID: PMC7431189 DOI: 10.1016/j.ultrasmedbio.2020.06.003] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/16/2020] [Revised: 05/26/2020] [Accepted: 06/03/2020] [Indexed: 06/11/2023]
Abstract
We address the recent controversy over whether focused ultrasound (FUS) activates cortical neurons directly or indirectly by initially activating auditory pathways. We obtained two types of evidence that FUS can directly activate cortical neurons. The depth profile of the local field potential (LFP) in the barrel cortex of the rat in vivo indicated a generator was located within the cortical gray matter. The onset and peak latencies of the initial component p1 were 3.2 ± 0.25 ms (mean ± standard error of the mean) and 7.6 ± 0.12 ms, respectively, for the direct cortical response (DCR), 6.8 ± 0.40 and 14.3 ± 0.54 ms for the FUS-evoked LFP (4 MHz, 3.2 MPa, 50 or 300 µs/pulse, 1-20 pulses at 1 kHz) and 6.9 ± 0.51 and 15.8 ± 0.94 ms for the LFP evoked by 1-ms deflection of the C2 whisker projecting to the same area. The peak latency of the FUS p1 was statistically (t-test) longer than the DCR, but shorter than the whisker p1 at p < 0.005.
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Affiliation(s)
- Kush Tripathi
- Division of Newborn Medicine, Dept. Pediatrics, Boston Children's Hospital/Harvard Medical School, Boston, Massachusetts, USA; Indian Institute of Technology, Madras, India
| | - Tongsheng Zhang
- Department of Neurosurgery, University of New Mexico School of Medicine, Albuquerque, New Mexico, USA
| | - Nathan McDannold
- Focused Ultrasound Laboratory, Brigham and Women's Hospital/Harvard Medical School, Boston, Massachusetts, USA
| | - Yong-Zhi Zhang
- Focused Ultrasound Laboratory, Brigham and Women's Hospital/Harvard Medical School, Boston, Massachusetts, USA
| | - Gösta Ehnholm
- Department of Neurosciences and Biomedical Engineering, Aalto University, Otaniemi, Finland
| | - Yoshio Okada
- Division of Newborn Medicine, Dept. Pediatrics, Boston Children's Hospital/Harvard Medical School, Boston, Massachusetts, USA.
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3
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F B, B M, R S, H G. Transcranial Focused Ultrasound Modulates Electrical Behavior of the Neurons: Design and Implementation of a Model. J Biomed Phys Eng 2020; 10:65-74. [PMID: 32158713 PMCID: PMC7036408 DOI: 10.31661/jbpe.v0i0.1052] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2018] [Accepted: 12/15/2018] [Indexed: 11/16/2022]
Abstract
Background: Recently, ultrasonic neuromodulation research has been an important and interesting issue. Ultrasonic neuromodulation is possible by the use of low-intensity transcranial focused ultrasound (tFUS) to stimulate or inhibit the neural structures. The primary capability of this method is the improvement in the treatment progress of certain neurological and psychiatric disorders noninvasively. tFUS is able to modulate ionic currents and neural depolarization, causing the alteration in electrical properties of neurons Objective: The study aims to investigate the effect of tFUS waves on the electrical behavior of neurons using the simulation method Material and Methods: In the first part of this simulation study, the propagation of tFUS waves throughout the head was simulated to calculate the value of acoustic pressure at the cortex. In the second part, cortical neurons were simulated by a simple model of spiking neurons proposed by Izhikevich for three common dynamics. Then, the capacitance model was proposed to determine the alteration in the electrical behavior of the neurons during tFUS stimulation. Results: At the resting state, the electric potential of the neuron’s membrane through the tFUS stimulation has an amplitude of about 30 mv with the similar oscillatory behavior of the acoustic waveform; while,the ultimate electrical behavior of the neuron’s membrane indicates a decrease in the electric potential when the neurons fire Conclusion: The electrical behavior of the neuron and the range of its membrane voltage modulated during ultrasonic stimulation. The reduction in the amplitude of membrane potential was observed while neuron spikes
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Affiliation(s)
- Baniasad F
- MSc, Department of Medical Physics and Biomedical Engineering, Tehran University of Medical Sciences, Tehran, Iran
- MSc, Research Center for Molecular and Cellular Imaging (RCMCI), Tehran University of Medical Sciences, Tehran, Iran
| | - Makkiabadi B
- PhD, Department of Medical Physics and Biomedical Engineering, Tehran University of Medical Sciences, Tehran, Iran
- PhD, Research Center for Biomedical Technologies and Robotics (RCBTR), Tehran University of Medical Sciences, Tehran, Iran
| | - Solgi R
- MSc, Department of Medical Physics and Biomedical Engineering, Tehran University of Medical Sciences, Tehran, Iran
- MSc, Research Center for Molecular and Cellular Imaging (RCMCI), Tehran University of Medical Sciences, Tehran, Iran
| | - Ghadiri H
- PhD, Department of Medical Physics and Biomedical Engineering, Tehran University of Medical Sciences, Tehran, Iran
- PhD, Research Center for Molecular and Cellular Imaging (RCMCI), Tehran University of Medical Sciences, Tehran, Iran
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4
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Bertucci C, Koppes R, Dumont C, Koppes A. Neural responses to electrical stimulation in 2D and 3D in vitro environments. Brain Res Bull 2019; 152:265-284. [PMID: 31323281 DOI: 10.1016/j.brainresbull.2019.07.016] [Citation(s) in RCA: 31] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2019] [Revised: 06/29/2019] [Accepted: 07/12/2019] [Indexed: 12/17/2022]
Abstract
Electrical stimulation (ES) to manipulate the central (CNS) and peripheral nervous system (PNS) has been explored for decades, recently gaining momentum as bioelectronic medicine advances. The application of ES in vitro to modulate a variety of cellular functions, including regenerative potential, migration, and stem cell fate, are being explored to aid neural degeneration, dysfunction, and injury. This review describes the materials and approaches for the application of ES to the PNS and CNS microenvironments, towards an improved understanding of how ES can be harnessed for beneficial clinical applications. Emphasized are some recent advances in ES, including conductive polymers, methods of charge transfer, impact on neural cells, and a brief overview of alternative methodologies for cellular targeting including magneto, ultrasonic, and optogenetic stimulation. This review will examine how heterogenous cell populations, including neurons, glia, and neural stem cells respond to a wide range of conductive 2D and 3D substrates, stimulation regimes, known mechanisms of response, and how cellular sources impact the response to ES.
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Affiliation(s)
- Christopher Bertucci
- Northeastern University, Department of Chemical Engineering, Boston, MA, 02115, United States.
| | - Ryan Koppes
- Northeastern University, Department of Chemical Engineering, Boston, MA, 02115, United States.
| | - Courtney Dumont
- Department of Biomedical Engineering, University of Miami, Coral Gables, FL, 33146, United States.
| | - Abigail Koppes
- Northeastern University, Department of Chemical Engineering, Boston, MA, 02115, United States; Department of Biology, Boston, 02115, MA, United States.
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5
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di Biase L, Falato E, Di Lazzaro V. Transcranial Focused Ultrasound (tFUS) and Transcranial Unfocused Ultrasound (tUS) Neuromodulation: From Theoretical Principles to Stimulation Practices. Front Neurol 2019; 10:549. [PMID: 31244747 PMCID: PMC6579808 DOI: 10.3389/fneur.2019.00549] [Citation(s) in RCA: 78] [Impact Index Per Article: 15.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2019] [Accepted: 05/07/2019] [Indexed: 01/28/2023] Open
Abstract
Transcranial focused ultrasound is an emerging technique for non-invasive neurostimulation. Compared to magnetic or electric non-invasive brain stimulation, this technique has a higher spatial resolution and can reach deep structures. In addition, both animal and human studies suggest that, potentially, different sites of the central and peripheral nervous system can be targeted by this technique. Depending on stimulation parameters, transcranial focused ultrasound is able to determine a wide spectrum of effects, ranging from suppression or facilitation of neural activity to tissue ablation. The aim is to review the state of the art of the human transcranial focused ultrasound neuromodulation literature, including the theoretical principles which underlie the explanation of the bioeffects on neural tissues, and showing the stimulation techniques and parameters used and their outcomes in terms of clinical, neurophysiological or neuroimaging results and safety.
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Affiliation(s)
- Lazzaro di Biase
- Neurology, Neurophysiology, and Neurobiology Unit, Department of Medicine, Campus Bio-Medico University of Rome, Rome, Italy.,Unit of Neurophysiology and Neuroengineering of Human-Technology Interaction, School of Medicine, Campus Bio-Medico University of Rome, Rome, Italy
| | - Emma Falato
- Neurology, Neurophysiology, and Neurobiology Unit, Department of Medicine, Campus Bio-Medico University of Rome, Rome, Italy.,Unit of Neurophysiology and Neuroengineering of Human-Technology Interaction, School of Medicine, Campus Bio-Medico University of Rome, Rome, Italy
| | - Vincenzo Di Lazzaro
- Neurology, Neurophysiology, and Neurobiology Unit, Department of Medicine, Campus Bio-Medico University of Rome, Rome, Italy
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6
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Zhang Z, Qiu W, Gong H, Li G, Jiang Q, Liang P, Zheng H, Zhang P. Low-intensity ultrasound suppresses low-Mg2+-induced epileptiform discharges in juvenile mouse hippocampal slices. J Neural Eng 2019; 16:036006. [DOI: 10.1088/1741-2552/ab0b9a] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
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7
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Corradi V, Sejdiu BI, Mesa-Galloso H, Abdizadeh H, Noskov SY, Marrink SJ, Tieleman DP. Emerging Diversity in Lipid-Protein Interactions. Chem Rev 2019; 119:5775-5848. [PMID: 30758191 PMCID: PMC6509647 DOI: 10.1021/acs.chemrev.8b00451] [Citation(s) in RCA: 245] [Impact Index Per Article: 49.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
![]()
Membrane
lipids interact with proteins in a variety of ways, ranging
from providing a stable membrane environment for proteins to being
embedded in to detailed roles in complicated and well-regulated protein
functions. Experimental and computational advances are converging
in a rapidly expanding research area of lipid–protein interactions.
Experimentally, the database of high-resolution membrane protein structures
is growing, as are capabilities to identify the complex lipid composition
of different membranes, to probe the challenging time and length scales
of lipid–protein interactions, and to link lipid–protein
interactions to protein function in a variety of proteins. Computationally,
more accurate membrane models and more powerful computers now enable
a detailed look at lipid–protein interactions and increasing
overlap with experimental observations for validation and joint interpretation
of simulation and experiment. Here we review papers that use computational
approaches to study detailed lipid–protein interactions, together
with brief experimental and physiological contexts, aiming at comprehensive
coverage of simulation papers in the last five years. Overall, a complex
picture of lipid–protein interactions emerges, through a range
of mechanisms including modulation of the physical properties of the
lipid environment, detailed chemical interactions between lipids and
proteins, and key functional roles of very specific lipids binding
to well-defined binding sites on proteins. Computationally, despite
important limitations, molecular dynamics simulations with current
computer power and theoretical models are now in an excellent position
to answer detailed questions about lipid–protein interactions.
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Affiliation(s)
- Valentina Corradi
- Centre for Molecular Simulation and Department of Biological Sciences , University of Calgary , 2500 University Drive NW , Calgary , Alberta T2N 1N4 , Canada
| | - Besian I Sejdiu
- Centre for Molecular Simulation and Department of Biological Sciences , University of Calgary , 2500 University Drive NW , Calgary , Alberta T2N 1N4 , Canada
| | - Haydee Mesa-Galloso
- Centre for Molecular Simulation and Department of Biological Sciences , University of Calgary , 2500 University Drive NW , Calgary , Alberta T2N 1N4 , Canada
| | - Haleh Abdizadeh
- Groningen Biomolecular Sciences and Biotechnology Institute and Zernike Institute for Advanced Materials , University of Groningen , Nijenborgh 7 , 9747 AG Groningen , The Netherlands
| | - Sergei Yu Noskov
- Centre for Molecular Simulation and Department of Biological Sciences , University of Calgary , 2500 University Drive NW , Calgary , Alberta T2N 1N4 , Canada
| | - Siewert J Marrink
- Groningen Biomolecular Sciences and Biotechnology Institute and Zernike Institute for Advanced Materials , University of Groningen , Nijenborgh 7 , 9747 AG Groningen , The Netherlands
| | - D Peter Tieleman
- Centre for Molecular Simulation and Department of Biological Sciences , University of Calgary , 2500 University Drive NW , Calgary , Alberta T2N 1N4 , Canada
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8
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Ventre DM, Koppes AN. The Body Acoustic: Ultrasonic Neuromodulation for Translational Medicine. Cells Tissues Organs 2016; 202:23-41. [DOI: 10.1159/000446622] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 05/08/2016] [Indexed: 11/19/2022] Open
Abstract
For the greater part of the last century, ultrasound (US) has seen widespread use in applications ranging from materials science to medicine. The history of US in medicine has also seen promising success in clinical diagnostics and regenerative medicine. Recent studies have shown that US is able to manipulate the nervous system, leading toward potential treatment for various neuropathological conditions, a phenomenon known as ultrasonic neuromodulation (NM). Ultrasonic NM is a promising alternative to pharmaceuticals and surgery, due to high spatiotemporal resolution combined with the potentially noninvasive means of application. Current advances have made progress in establishing effective dosage limits, waveform parameters, and stimulus regimes in order to achieve desired effects in a variety of tissue and cell types. However, to date there has been limited systematic analysis of the complex variables involved in creating a therapeutic US stimulation regime specifically tailored to the nervous system. Without a fundamental understanding of the effects of US on neural tissue, including the surrounding bone, musculature, and vasculature, the safety and efficacy of US as an NM tool is yet to be determined. Advances in imaging technology and focusing hardware highlight new avenues for potential clinical applications for therapeutic ultrasonic stimulation. US may be an alternative to electrical and magnetic means of NM for targets in the central nervous system as well as in the peripheral and autonomic nervous systems. This review provides a historical perspective on the past, present, and future of US as a translational therapeutic.
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9
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Abstract
Sick excitable cells (ie, Nav channel-expressing cells injured by trauma, ischemia, inflammatory, and other conditions) typically exhibit "acquired sodium channelopathies" which, we argue, reflect bleb-damaged membranes rendering their Nav channels "leaky." The situation is excitotoxic because untreated Nav leak exacerbates bleb damage. Fast Nav inactivation (a voltage-independent process) is so tightly coupled, kinetically speaking, to the inherently voltage-dependent process of fast activation that when bleb damage accelerates and thus left-shifts macroscopic fast activation, fast inactivation accelerates to the same extent. The coupled g(V) and availability(V) processes and their window conductance regions consequently left-shift by the same number of millivolts. These damage-induced hyperpolarizing shifts, whose magnitude increases with damage intensity, are called coupled left shift (CLS). Based on past work and modeling, we discuss how to test for Nav-CLS, emphasizing the virtue of sawtooth ramp clamp. We explain that it is the inherent mechanosensitivity of Nav activation that underlies Nav-CLS. Using modeling of excitability, we show the known process of Nav-CLS is sufficient to predict a wide variety of "sick excitable cell" phenomena, from hyperexcitability through to depolarizing block. When living cells are mimicked by inclusion of pumps, mild Nav-CLS produces a wide array of burst phenomena and subthreshold oscillations. Dynamical analysis of mild damage scenarios shows how these phenomena reflect changes in spike thresholds as the pumps try to counteract the leaky Nav channels. Smart Nav inhibitors designed for sick excitable cells would target bleb-damaged membrane, buying time for cell-mediated removal or repair of Nav-bearing membrane that has become bleb-damaged (ie, detached from the cytoskeleton).
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Affiliation(s)
- C E Morris
- Ottawa Hospital Research Institute, Ottawa, ON, Canada
| | - B Joos
- University of Ottawa, Ottawa, ON, Canada
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10
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Hakimova H, Kim S, Chu K, Lee SK, Jeong B, Jeon D. Ultrasound stimulation inhibits recurrent seizures and improves behavioral outcome in an experimental model of mesial temporal lobe epilepsy. Epilepsy Behav 2015; 49:26-32. [PMID: 25940106 DOI: 10.1016/j.yebeh.2015.04.008] [Citation(s) in RCA: 70] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/02/2015] [Accepted: 04/03/2015] [Indexed: 02/06/2023]
Abstract
Current therapies for epilepsy consist mostly of pharmacological agents or invasive surgery. Recently, ultrasound (US) stimulation has been considered a promising tool for the noninvasive treatment of brain diseases, including epilepsy. However, in temporal lobe epilepsy (TLE), a common form of epilepsy, neurophysiological and functional outcomes following US stimulation are not well defined. To address this, we developed a paradigm of transcranial pulsed US stimulation to efficiently suppress seizure activity in the initial/acute period in a kainate (KA)-induced mouse model of mesial TLE. Pulsed US stimulation inhibited acute seizure activity and either delayed the onset of or suppressed status epilepticus (SE). Kainate-treated mice that had received US stimulation in the initial period exhibited fewer spontaneous recurrent seizures (SRSs) and improved performance in behavioral tasks assessing sociability and depression in the chronic period of epilepsy. Our results demonstrate that US stimulation in the acute period of epilepsy can inhibit SRSs and improve behavioral outcomes in a mouse model of mesial TLE. The present study suggests that noninvasive transcranial pulsed US stimulation may be feasible as an adjuvant therapy in patients with epilepsy. This article is part of a Special Issue entitled "Status Epilepticus".
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Affiliation(s)
- Hilola Hakimova
- Department of Bio and Brain Engineering, Korea Advanced Institute of Science and Technology, Daejeon, Republic of Korea
| | - Sangwoo Kim
- Department of Neurology, Comprehensive Epilepsy Center, Biomedical Research Institute, Seoul National University Hospital (SNUH), Seoul, Republic of Korea
| | - Kon Chu
- Department of Neurology, Comprehensive Epilepsy Center, Biomedical Research Institute, Seoul National University Hospital (SNUH), Seoul, Republic of Korea
| | - Sang Kun Lee
- Department of Neurology, Comprehensive Epilepsy Center, Biomedical Research Institute, Seoul National University Hospital (SNUH), Seoul, Republic of Korea
| | - Bumseok Jeong
- Graduate School of Medical Science and Engineering, Korea Advanced Institute of Science and Technology, Daejeon, Republic of Korea.
| | - Daejong Jeon
- Department of Bio and Brain Engineering, Korea Advanced Institute of Science and Technology, Daejeon, Republic of Korea; Department of Neurology, Comprehensive Epilepsy Center, Biomedical Research Institute, Seoul National University Hospital (SNUH), Seoul, Republic of Korea.
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11
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Herold KF, Sanford RL, Lee W, Schultz MF, Ingólfsson HI, Andersen OS, Hemmings HC. Volatile anesthetics inhibit sodium channels without altering bulk lipid bilayer properties. J Gen Physiol 2014; 144:545-60. [PMID: 25385786 PMCID: PMC4242807 DOI: 10.1085/jgp.201411172] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2014] [Accepted: 10/08/2014] [Indexed: 01/05/2023] Open
Abstract
Although general anesthetics are clinically important and widely used, their molecular mechanisms of action remain poorly understood. Volatile anesthetics such as isoflurane (ISO) are thought to alter neuronal function by depressing excitatory and facilitating inhibitory neurotransmission through direct interactions with specific protein targets, including voltage-gated sodium channels (Na(v)). Many anesthetics alter lipid bilayer properties, suggesting that ion channel function might also be altered indirectly through effects on the lipid bilayer. We compared the effects of ISO and of a series of fluorobenzene (FB) model volatile anesthetics on Na(v) function and lipid bilayer properties. We examined the effects of these agents on Na(v) in neuronal cells using whole-cell electrophysiology, and on lipid bilayer properties using a gramicidin-based fluorescence assay, which is a functional assay for detecting changes in lipid bilayer properties sensed by a bilayer-spanning ion channel. At clinically relevant concentrations (defined by the minimum alveolar concentration), both the FBs and ISO produced prepulse-dependent inhibition of Na(v) and shifted the voltage dependence of inactivation toward more hyperpolarized potentials without affecting lipid bilayer properties, as sensed by gramicidin channels. Only at supra-anesthetic (toxic) concentrations did ISO alter lipid bilayer properties. These results suggest that clinically relevant concentrations of volatile anesthetics alter Na(v) function through direct interactions with the channel protein with little, if any, contribution from changes in bulk lipid bilayer properties. Our findings further suggest that changes in lipid bilayer properties are not involved in clinical anesthesia.
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Affiliation(s)
- Karl F Herold
- Department of Anesthesiology, Department of Physiology and Biophysics, and Department of Pharmacology, Weill Cornell Medical College, New York, NY 10065
| | - R Lea Sanford
- Department of Anesthesiology, Department of Physiology and Biophysics, and Department of Pharmacology, Weill Cornell Medical College, New York, NY 10065
| | - William Lee
- Department of Anesthesiology, Department of Physiology and Biophysics, and Department of Pharmacology, Weill Cornell Medical College, New York, NY 10065
| | - Margaret F Schultz
- Department of Anesthesiology, Department of Physiology and Biophysics, and Department of Pharmacology, Weill Cornell Medical College, New York, NY 10065
| | - Helgi I Ingólfsson
- Department of Anesthesiology, Department of Physiology and Biophysics, and Department of Pharmacology, Weill Cornell Medical College, New York, NY 10065
| | - Olaf S Andersen
- Department of Anesthesiology, Department of Physiology and Biophysics, and Department of Pharmacology, Weill Cornell Medical College, New York, NY 10065
| | - Hugh C Hemmings
- Department of Anesthesiology, Department of Physiology and Biophysics, and Department of Pharmacology, Weill Cornell Medical College, New York, NY 10065 Department of Anesthesiology, Department of Physiology and Biophysics, and Department of Pharmacology, Weill Cornell Medical College, New York, NY 10065
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12
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Mueller JK, Tyler WJ. A quantitative overview of biophysical forces impinging on neural function. Phys Biol 2014; 11:051001. [DOI: 10.1088/1478-3975/11/5/051001] [Citation(s) in RCA: 57] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023]
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13
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Livneh A, Kimmel E, Kohut AR, Adam D. Extracorporeal acute cardiac pacing by High Intensity Focused Ultrasound. PROGRESS IN BIOPHYSICS AND MOLECULAR BIOLOGY 2014; 115:140-53. [DOI: 10.1016/j.pbiomolbio.2014.08.007] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/04/2014] [Accepted: 08/06/2014] [Indexed: 11/29/2022]
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14
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Jin K, Klima JC, Deane G, Dale Stokes M, Latz MI. Pharmacological investigation of the bioluminescence signaling pathway of the dinoflagellate Lingulodinium polyedrum: evidence for the role of stretch-activated ion channels. JOURNAL OF PHYCOLOGY 2013; 49:733-745. [PMID: 27007206 DOI: 10.1111/jpy.12084] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/17/2012] [Accepted: 04/20/2013] [Indexed: 06/05/2023]
Abstract
Dinoflagellate bioluminescence serves as a whole-cell reporter of mechanical stress, which activates a signaling pathway that appears to involve the opening of voltage-sensitive ion channels and release of calcium from intracellular stores. However, little else is known about the initial signaling events that facilitate the transduction of mechanical stimuli. In the present study using the red tide dinoflagellate Lingulodinium polyedrum (Stein) Dodge, two forms of dinoflagellate bioluminescence, mechanically stimulated and spontaneous flashes, were used as reporter systems to pharmacological treatments that targeted various predicted signaling events at the plasma membrane level of the signaling pathway. Pretreatment with 200 μM Gadolinium III (Gd(3+) ), a nonspecific blocker of stretch-activated and some voltage-gated ion channels, resulted in strong inhibition of both forms of bioluminescence. Pretreatment with 50 μM nifedipine, an inhibitor of L-type voltage-gated Ca(2+) channels that inhibits mechanically stimulated bioluminescence, did not inhibit spontaneous bioluminescence. Treatment with 1 mM benzyl alcohol, a membrane fluidizer, was very effective in stimulating bioluminescence. Benzyl alcohol-stimulated bioluminescence was inhibited by Gd(3+) but not by nifedipine, suggesting that its role is through stretch activation via a change in plasma membrane fluidity. These results are consistent with the presence of stretch-activated and voltage-gated ion channels in the bioluminescence mechanotransduction signaling pathway, with spontaneous flashing associated with a stretch-activated component at the plasma membrane.
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Affiliation(s)
- Kelly Jin
- Scripps Institution of Oceanography, University of California San Diego, La Jolla, California, 92093, USA
| | - Jason C Klima
- Scripps Institution of Oceanography, University of California San Diego, La Jolla, California, 92093, USA
| | - Grant Deane
- Scripps Institution of Oceanography, University of California San Diego, La Jolla, California, 92093, USA
| | - Malcolm Dale Stokes
- Scripps Institution of Oceanography, University of California San Diego, La Jolla, California, 92093, USA
| | - Michael I Latz
- Scripps Institution of Oceanography, University of California San Diego, La Jolla, California, 92093, USA
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15
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Heler R, Bell JK, Boland LM. Homology model and targeted mutagenesis identify critical residues for arachidonic acid inhibition of Kv4 channels. Channels (Austin) 2013; 7:74-84. [PMID: 23334377 PMCID: PMC3667888 DOI: 10.4161/chan.23453] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
Polyunsaturated fatty acids such as arachidonic acid (AA) exhibit inhibitory modulation of Kv4 potassium channels. Molecular docking approaches using a Kv4.2 homology model predicted a membrane-embedded binding pocket for AA comprised of the S4-S5 linker on one subunit and several hydrophobic residues within S3, S5 and S6 from an adjacent subunit. The pocket is conserved among Kv4 channels. We tested the hypothesis that modulatory effects of AA on Kv4.2/KChIP channels require access to this site. Targeted mutation of a polar residue (K318) and a nonpolar residue (G314) within the S4-S5 linker as well as a nonpolar residue in S3 (V261) significantly impaired the effects of AA on K (+) currents in Xenopus oocytes. These residues may be important in stabilizing (K318) or regulating access to (V261, G314) the negatively charged carboxylate moiety on the fatty acid. Structural specificity was supported by the lack of disruption of AA effects observed with mutations at residues located near, but not within the predicted binding pocket. Furthermore, we found that the crystal structure of the related Kv1.2/2.1 chimera lacks the structural features present in the proposed AA docking site of Kv4.2 and the Kv1.2/2.1 K (+) currents were unaffected by AA. We simulated the mutagenic substitutions in our Kv4.2 model to demonstrate how specific mutations may disrupt the putative AA binding pocket. We conclude that AA inhibits Kv4 channel currents and facilitates current decay by binding within a hydrophobic pocket in the channel in which K318 within the S4-S5 linker is a critical residue for AA interaction.
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Affiliation(s)
- Robert Heler
- Department of Biology, University of Richmond, Richmond, VA, USA
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16
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Morris CE, Juranka PF, Joós B. Perturbed voltage-gated channel activity in perturbed bilayers: implications for ectopic arrhythmias arising from damaged membrane. PROGRESS IN BIOPHYSICS AND MOLECULAR BIOLOGY 2012; 110:245-56. [PMID: 22846437 DOI: 10.1016/j.pbiomolbio.2012.07.003] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/10/2012] [Accepted: 07/11/2012] [Indexed: 12/31/2022]
Abstract
The ceaseless opening and closing of the voltage-gated channels (VGCs) underlying cardiac rhythmicity is controlled, in each VGC, by four mobile voltage sensors embedded in bilayer. Every action potential necessitates extensive packing/repacking of voltage sensor domains with adjacent interacting lipid molecules. This renders VGC activity mechanosensitive (MS), i.e., energetically sensitive to the bilayer's mechanical state. Irreversible perturbations of sarcolemmal bilayer such as those associated with ischemia, reperfusion, inflammation, cortical-cytoskeleton abnormalities, bilayer-disrupting toxins, diet aberrations, etc, should therefore perturb VGC activity. Disordered/fluidized bilayer states that facilitate voltage sensor repacking, and thus make VGC opening too easy could, therefore, explain VGC-leakiness in these conditions. To study this in membrane patches we impose mechanical blebbing injury during pipette aspiration-induced membrane stretch, a process that modulates VGC activity irreversibly (plastic regime) and then, eventually, reversibly (elastic regime). Because of differences in sensor-to-gate coupling among different VGCs, their responses to stretch fall into two major categories, MS-Speed, MS-Number, exemplified by Nav and Cav channels. For particular VGCs in perturbed bilayers, leak mechanisms depend on whether or not the rate-limiting voltage-dependent step is MS. Mode-switch transitions might also be mechanosensitive and thus play a role. Incorporated mathematically in axon models, plastic-regime Nav responses elicit ectopic firing behaviors typical of peripheral neuropathies. In cardiomyocytes with mild bleb damage, Nav and/or Cav leaks from irreversible MS modulation (MS-Speed, MS-Number, respectively) could, similarly, foster ectopic arrhythmias. Where pathologically leaky VGCs reside in damaged bilayer, peri-channel bilayer disorder/fluidity conditions could be an important "target feature" for anti-arrhythmic VGC drugs.
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Large conductance, calcium- and voltage-gated potassium (BK) channels: regulation by cholesterol. Pharmacol Ther 2012; 135:133-50. [PMID: 22584144 DOI: 10.1016/j.pharmthera.2012.05.002] [Citation(s) in RCA: 64] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2012] [Accepted: 04/09/2012] [Indexed: 11/21/2022]
Abstract
Cholesterol (CLR) is an essential component of eukaryotic plasma membranes. CLR regulates the membrane physical state, microdomain formation and the activity of membrane-spanning proteins, including ion channels. Large conductance, voltage- and Ca²⁺-gated K⁺ (BK) channels link membrane potential to cell Ca²⁺ homeostasis. Thus, they control many physiological processes and participate in pathophysiological mechanisms leading to human disease. Because plasmalemma BK channels cluster in CLR-rich membrane microdomains, a major driving force for studying BK channel-CLR interactions is determining how membrane CLR controls the BK current phenotype, including its pharmacology, channel sorting, distribution, and role in cell physiology. Since both BK channels and CLR tissue levels play a pathophysiological role in human disease, identifying functional and structural aspects of the CLR-BK channel interaction may open new avenues for therapeutic intervention. Here, we review the studies documenting membrane CLR-BK channel interactions, dissecting out the many factors that determine the final BK current response to changes in membrane CLR content. We also summarize work in reductionist systems where recombinant BK protein is studied in artificial lipid bilayers, which documents a direct inhibition of BK channel activity by CLR and builds a strong case for a direct interaction between CLR and the BK channel-forming protein. Bilayer lipid-mediated mechanisms in CLR action are also discussed. Finally, we review studies of BK channel function during hypercholesterolemia, and underscore the many consequences that the CLR-BK channel interaction brings to cell physiology and human disease.
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18
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Singh AK, McMillan J, Bukiya AN, Burton B, Parrill AL, Dopico AM. Multiple cholesterol recognition/interaction amino acid consensus (CRAC) motifs in cytosolic C tail of Slo1 subunit determine cholesterol sensitivity of Ca2+- and voltage-gated K+ (BK) channels. J Biol Chem 2012; 287:20509-21. [PMID: 22474334 DOI: 10.1074/jbc.m112.356261] [Citation(s) in RCA: 76] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Large conductance, Ca(2+)- and voltage-gated K(+) (BK) channel proteins are ubiquitously expressed in cell membranes and control a wide variety of biological processes. Membrane cholesterol regulates the activity of membrane-associated proteins, including BK channels. Cholesterol modulation of BK channels alters action potential firing, colonic ion transport, smooth muscle contractility, endothelial function, and the channel alcohol response. The structural bases underlying cholesterol-BK channel interaction are unknown. Such interaction is determined by strict chemical requirements for the sterol molecule, suggesting cholesterol recognition by a protein surface. Here, we demonstrate that cholesterol action on BK channel-forming Cbv1 proteins is mediated by their cytosolic C tail domain, where we identified seven cholesterol recognition/interaction amino acid consensus motifs (CRAC4 to 10), a distinct feature of BK proteins. Cholesterol sensitivity is provided by the membrane-adjacent CRAC4, where Val-444, Tyr-450, and Lys-453 are required for cholesterol sensing, with hydrogen bonding and hydrophobic interactions participating in cholesterol location and recognition. However, cumulative truncations or Tyr-to-Phe substitutions in CRAC5 to 10 progressively blunt cholesterol sensitivity, documenting involvement of multiple CRACs in cholesterol-BK channel interaction. In conclusion, our study provides for the first time the structural bases of BK channel cholesterol sensitivity; the presence of membrane-adjacent CRAC4 and the long cytosolic C tail domain with several other CRAC motifs, which are not found in other members of the TM6 superfamily of ion channels, very likely explains the unique cholesterol sensitivity of BK channels.
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Affiliation(s)
- Aditya K Singh
- Department of Pharmacology, College of Medicine, University of Tennessee Health Science Center, Memphis, Tennessee 38163, USA
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19
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Kariev AM, Green ME. Voltage gated ion channel function: gating, conduction, and the role of water and protons. Int J Mol Sci 2012; 13:1680-1709. [PMID: 22408417 PMCID: PMC3291986 DOI: 10.3390/ijms13021680] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2011] [Revised: 01/20/2012] [Accepted: 01/29/2012] [Indexed: 02/01/2023] Open
Abstract
Ion channels, which are found in every biological cell, regulate the concentration of electrolytes, and are responsible for multiple biological functions, including in particular the propagation of nerve impulses. The channels with the latter function are gated (opened) by a voltage signal, which allows Na(+) into the cell and K(+) out. These channels have several positively charged amino acids on a transmembrane domain of their voltage sensor, and it is generally considered, based primarily on two lines of experimental evidence, that these charges move with respect to the membrane to open the channel. At least three forms of motion, with greatly differing extents and mechanisms of motion, have been proposed. There is a "gating current", a capacitative current preceding the channel opening, that corresponds to several charges (for one class of channel typically 12-13) crossing the membrane field, which may not require protein physically crossing a large fraction of the membrane. The coupling to the opening of the channel would in these models depend on the motion. The conduction itself is usually assumed to require the "gate" of the channel to be pulled apart to allow ions to enter as a section of the protein partially crosses the membrane, and a selectivity filter at the opposite end of the channel determines the ion which is allowed to pass through. We will here primarily consider K(+) channels, although Na(+) channels are similar. We propose that the mechanism of gating differs from that which is generally accepted, in that the positively charged residues need not move (there may be some motion, but not as gating current). Instead, protons may constitute the gating current, causing the gate to open; opening consists of only increasing the diameter at the gate from approximately 6 Å to approximately 12 Å. We propose in addition that the gate oscillates rather than simply opens, and the ion experiences a barrier to its motion across the channel that is tuned by the water present within the channel. Our own quantum calculations as well as numerous experiments of others are interpreted in terms of this hypothesis. It is also shown that the evidence that supports the motion of the sensor as the gating current can also be consistent with the hypothesis we present.
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Affiliation(s)
- Alisher M. Kariev
- Department of Chemistry, City College of the City University of New York, 160 Convent Avenue, New York, NY 10031, USA; E-Mail:
| | - Michael E. Green
- Department of Chemistry, City College of the City University of New York, 160 Convent Avenue, New York, NY 10031, USA; E-Mail:
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20
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Ursell T, Agrawal A, Phillips R. Lipid bilayer mechanics in a pipette with glass-bilayer adhesion. Biophys J 2012; 101:1913-20. [PMID: 22004745 DOI: 10.1016/j.bpj.2011.08.057] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2011] [Revised: 08/24/2011] [Accepted: 08/30/2011] [Indexed: 01/23/2023] Open
Abstract
Electrophysiology is a central tool for measuring how different driving forces (e.g., ligand concentration, transmembrane voltage, or lateral tension) cause a channel protein to gate. Upon formation of the high resistance seal between a lipid bilayer and a glass pipette, the so-called "giga-seal", channel activity can be recorded electrically. In this article, we explore the implications of giga-seal formation on the mechanical state of a lipid bilayer patch. We use a mechanical model for the free energy of bilayer geometry in the presence of glass-bilayer adhesion to draw three potentially important conclusions. First, we use our adhesion model to derive an explicit relationship between applied pressure and patch shape that is consistent with the Laplace-Young Law, giving an alternative method of calculating patch tension under pressure. With knowledge of the adhesion constant, which we find to be in the range ∼0.4-4 mN/m, and the pipette size, one can precisely calculate the patch tension as a function of pressure, without the difficultly of obtaining an optical measurement of the bilayer radius of curvature. Second, we use data from previous electrophysiological experiments to show that over a wide range of lipids, the resting tension on a electrophysiological patch is highly variable and can be 10-100 times higher than estimates of the tension in a typical cell membrane. This suggests that electrophysiological experiments may be systematically altering channel-gating characteristics and querying the channels under conditions that are not the same as their physiological counterparts. Third, we show that reversible adhesion leads to a predictable change in the population response of gating channels in a bilayer patch.
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Affiliation(s)
- Tristan Ursell
- Department of Applied Physics, California Institute of Technology, Pasadena, California, USA
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21
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Yang T, Chen J, Yan B, Zhou D. Transcranial ultrasound stimulation: A possible therapeutic approach to epilepsy. Med Hypotheses 2011; 76:381-3. [DOI: 10.1016/j.mehy.2010.10.046] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2010] [Revised: 10/28/2010] [Accepted: 10/29/2010] [Indexed: 11/30/2022]
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22
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Bukiya AN, Belani JD, Rychnovsky S, Dopico AM. Specificity of cholesterol and analogs to modulate BK channels points to direct sterol-channel protein interactions. J Gen Physiol 2011; 137:93-110. [PMID: 21149543 PMCID: PMC3010061 DOI: 10.1085/jgp.201010519] [Citation(s) in RCA: 70] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2010] [Accepted: 11/22/2010] [Indexed: 11/26/2022] Open
Abstract
The activity (Po) of large-conductance voltage/Ca(2+)-gated K(+) (BK) channels is blunted by cholesterol levels within the range found in natural membranes. We probed BK channel-forming α (cbv1) subunits in phospholipid bilayers with cholesterol and related monohydroxysterols and performed computational dynamics to pinpoint the structural requirements for monohydroxysterols to reduce BK Po and obtain insights into cholesterol's mechanism of action. Cholesterol, cholestanol, and coprostanol reduced Po by shortening mean open and lengthening mean closed times, whereas epicholesterol, epicholestanol, epicoprostanol, and cholesterol trisnorcholenic acid were ineffective. Thus, channel inhibition by monohydroxysterols requires the β configuration of the C3 hydroxyl and is favored by the hydrophobic nature of the side chain, while having lax requirements on the sterol A/B ring fusion. Destabilization of BK channel open state(s) has been previously interpreted as reflecting increased bilayer lateral stress by cholesterol. Lateral stress is controlled by the sterol molecular area and lipid monolayer lateral tension, the latter being related to the sterol ability to adopt a planar conformation in lipid media. However, we found that the differential efficacies of monohydroxysterols to reduce Po (cholesterol≥coprostanol≥cholestanol>>>epicholesterol) did not follow molecular area rank (coprostanol>>epicholesterol>cholesterol>cholestanol). In addition, computationally predicted energies for cholesterol (effective BK inhibitor) and epicholesterol (ineffective) to adopt a planar conformation were similar. Finally, cholesterol and coprostanol reduced Po, yet these sterols have opposite effects on tight lipid packing and, likely, on lateral stress. Collectively, these findings suggest that an increase in bilayer lateral stress is unlikely to underlie the differential ability of cholesterol and related steroids to inhibit BK channels. Remarkably, ent-cholesterol (cholesterol mirror image) failed to reduce Po, indicating that cholesterol efficacy requires sterol stereospecific recognition by a protein surface. The BK channel phenotype resembled that of α homotetramers. Thus, we hypothesize that a cholesterol-recognizing protein surface resides at the BK α subunit itself.
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Affiliation(s)
- Anna N. Bukiya
- Department of Pharmacology, College of Medicine, The University of Tennessee Health Science Center, Memphis, TN 38163
| | | | - Scott Rychnovsky
- Department of Chemistry, University of California, Irvine, CA 92697
| | - Alex M. Dopico
- Department of Pharmacology, College of Medicine, The University of Tennessee Health Science Center, Memphis, TN 38163
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23
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Tufail Y, Matyushov A, Baldwin N, Tauchmann ML, Georges J, Yoshihiro A, Tillery SIH, Tyler WJ. Transcranial pulsed ultrasound stimulates intact brain circuits. Neuron 2010; 66:681-94. [PMID: 20547127 DOI: 10.1016/j.neuron.2010.05.008] [Citation(s) in RCA: 570] [Impact Index Per Article: 40.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 04/29/2010] [Indexed: 12/13/2022]
Abstract
Electromagnetic-based methods of stimulating brain activity require invasive procedures or have other limitations. Deep-brain stimulation requires surgically implanted electrodes. Transcranial magnetic stimulation does not require surgery, but suffers from low spatial resolution. Optogenetic-based approaches have unrivaled spatial precision, but require genetic manipulation. In search of a potential solution to these limitations, we began investigating the influence of transcranial pulsed ultrasound on neuronal activity in the intact mouse brain. In motor cortex, ultrasound-stimulated neuronal activity was sufficient to evoke motor behaviors. Deeper in subcortical circuits, we used targeted transcranial ultrasound to stimulate neuronal activity and synchronous oscillations in the intact hippocampus. We found that ultrasound triggers TTX-sensitive neuronal activity in the absence of a rise in brain temperature (<0.01 degrees C). Here, we also report that transcranial pulsed ultrasound for intact brain circuit stimulation has a lateral spatial resolution of approximately 2 mm and does not require exogenous factors or surgical invasion.
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Affiliation(s)
- Yusuf Tufail
- School of Life Sciences, Arizona State University, Tempe, AZ 85287, USA
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24
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Finol-Urdaneta RK, McArthur JR, Juranka PF, French RJ, Morris CE. Modulation of KvAP unitary conductance and gating by 1-alkanols and other surface active agents. Biophys J 2010; 98:762-72. [PMID: 20197029 DOI: 10.1016/j.bpj.2009.10.053] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2009] [Revised: 10/23/2009] [Accepted: 10/26/2009] [Indexed: 11/18/2022] Open
Abstract
The actions of alcohols and anesthetics on ion channels are poorly understood. Controversy continues about whether bilayer restructuring is relevant to the modulatory effects of these surface active agents (SAAs). Some voltage-gated K channels (Kv), but not KvAP, have putative low affinity alcohol-binding sites, and because KvAP structures have been determined in bilayers, KvAP could offer insights into the contribution of bilayer mechanics to SAA actions. We monitored KvAP unitary conductance and macroscopic activation and inactivation kinetics in PE:PG/decane bilayers with and without exposure to classic SAAs (short-chain 1-alkanols, cholesterol, and selected anesthetics: halothane, isoflurane, chloroform). At levels that did not measurably alter membrane specific capacitance, alkanols caused functional changes in KvAP behavior including lowered unitary conductance, modified kinetics, and shifted voltage dependence for activation. A simple explanation is that the site of SAA action on KvAP is its entire lateral interface with the PE:PG/decane bilayer, with SAA-induced changes in surface tension and bilayer packing order combining to modulate the shape and stability of various conformations. The KvAP structural adjustment to diverse bilayer pressure profiles has implications for understanding desirable and undesirable actions of SAA-like drugs and, broadly, predicts that channel gating, conductance and pharmacology may differ when membrane packing order differs, as in raft versus nonraft domains.
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Affiliation(s)
- Rocio K Finol-Urdaneta
- Hotchkiss Brain Institute and Department of Physiology and Pharmacology, University of Calgary, Alberta, Canada
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25
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Boucher PA, Morris CE, Joós B. Mechanosensitive closed-closed transitions in large membrane proteins: osmoprotection and tension damping. Biophys J 2010; 97:2761-70. [PMID: 19917230 DOI: 10.1016/j.bpj.2009.08.054] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2009] [Revised: 08/20/2009] [Accepted: 08/31/2009] [Indexed: 12/11/2022] Open
Abstract
Multiconformation membrane proteins are mechanosensitive (MS) if their conformations displace different bilayer areas. Might MS closed-closed transitions serve as tension buffers, that is, as membrane "spandex"? While bilayer expansion is effectively instantaneous, transitions of bilayer-embedded MS proteins are stochastic (thermally activated) so spandex kinetics would be critical. Here we model generic two-state (contracted/expanded) stochastic spandexes inspired by known bacterial osmovalves (MscL, MscS) then suggest experimental approaches to test for spandex-like behaviors in these proteins. Modeling shows: 1), spandex kinetics depend on the transition state location along an area reaction coordinate; 2), increasing membrane concentration of a spandex right-shifts its midpoint (= tension-Boltzmann); 3), spandexes with midpoints below the activating tension of an osmovalve could optimize osmovalve deployment (required: large midpoint, barrier near the expanded state); 4), spandexes could damp bilayer tension excursions (required: midpoint at target tension, and for speed, barrier halfway between the contracted and expanded states; the larger the spandex Delta-area, the more precise the maintenance of target tension; higher spandex concentrations damp larger amplitude strain fluctuations). One spandex species could not excel as both first line of defense for osmovalve partners and tension damper. Possible interactions among MS closed-closed and closed-open transitions are discussed for MscS- and MscL-like proteins.
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26
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Tyler WJ. Noninvasive Neuromodulation with Ultrasound? A Continuum Mechanics Hypothesis. Neuroscientist 2010; 17:25-36. [DOI: 10.1177/1073858409348066] [Citation(s) in RCA: 148] [Impact Index Per Article: 10.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Abstract
Deep brain stimulation and vagal nerve stimulation are therapeutically effective in treating some neurological diseases and psychiatric disorders. Optogenetic-based neurostimulation approaches are capable of activating individual synapses and yield the highest spatial control over brain circuit activity. Both electrical and light-based neurostimulation methods require intrusive procedures such as surgical implantation of electrodes or photon-emitting devices. Transcranial magnetic stimulation has also shown therapeutic effectiveness and represents a recent paradigm shift towards implementing less invasive brain stimulation methods. Magnetic-based stimulation, however, has a limited focusing capacity and lacks brain penetration power. Because ultrasound can be noninvasively transmitted through the skull to targeted deep brain circuits, it may offer alternative approaches to currently employed neuromodulation techniques. Encouraging this idea, literature spanning more than half a century indicates that ultrasound can modulate neuronal activity. In order to provide a comprehensive overview of potential mechanisms underlying the actions of ultrasound on neuronal excitability, here, I propose the continuum mechanics hypothesis of ultrasonic neuromodulation in which ultrasound produces effects on viscoelastic neurons and their surrounding fluid environments to alter membrane conductance. While further studies are required to test this hypothesis, experimental data indicate ultrasound represents a promising platform for developing future therapeutic neuromodulation approaches.
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Affiliation(s)
- William J. Tyler
- School of Life Sciences, Arizona State University, Tempe, Arizona,
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27
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Wang JA, Lin W, Morris T, Banderali U, Juranka PF, Morris CE. Membrane trauma and Na+ leak from Nav1.6 channels. Am J Physiol Cell Physiol 2009; 297:C823-34. [PMID: 19657055 DOI: 10.1152/ajpcell.00505.2008] [Citation(s) in RCA: 70] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
During brain trauma, white matter experiences shear and stretch forces that, without severing axons, nevertheless trigger their secondary degeneration. In central nervous system (CNS) trauma models, voltage-gated sodium channel (Nav) blockers are neuroprotective. This, plus the rapid tetrodotoxin-sensitive Ca2+ overload of stretch-traumatized axons, points to "leaky" Nav channels as a pivotal early lesion in brain trauma. Direct effects of mechanical trauma on neuronal Nav channels have not, however, been tested. Here, we monitor immediate responses of recombinant neuronal Nav channels to stretch, using patch-clamp and Na+-dye approaches. Trauma constituted either bleb-inducing aspiration of cell-attached oocyte patches or abrupt uniaxial stretch of cells on an extensible substrate. Nav1.6 channel transient current displayed irreversible hyperpolarizing shifts of steady-state inactivation [availability(V)] and of activation [g(V)] and, thus, of window current. Left shift increased progressively with trauma intensity. For moderately intense patch trauma, a approximately 20-mV hyperpolarizing shift was registered. Nav1.6 voltage sensors evidently see lower energy barriers posttrauma, probably because of the different bilayer mechanics of blebbed versus intact membrane. Na+ dye-loaded human embryonic kidney (HEK) cells stably transfected with alphaNav1.6 were subjected to traumatic brain injury-like stretch. Cytoplasmic Na+ levels abruptly increased and the trauma-induced influx had a significant tetrodotoxin-sensitive component. Nav1.6 channel responses to cell and membrane trauma are therefore consistent with the hypothesis that mechanically induced Nav channel leak is a primary lesion in traumatic brain injury. Nav1.6 is the CNS node of Ranvier Nav isoform. When, during head trauma, nodes experienced bleb-inducing membrane damage of varying intensities, nodal Nav1.6 channels should immediately "leak" over a broadly left-smeared window current range.
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Affiliation(s)
- Jun A Wang
- Neuroscience, Ottawa Hospital Research Institute, The Ottawa Hospital, Ottawa, Ontario, Canada
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28
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Capone R, Quiroz FG, Prangkio P, Saluja I, Sauer AM, Bautista MR, Turner RS, Yang J, Mayer M. Amyloid-beta-induced ion flux in artificial lipid bilayers and neuronal cells: resolving a controversy. Neurotox Res 2009; 16:1-13. [PMID: 19526294 PMCID: PMC2864106 DOI: 10.1007/s12640-009-9033-1] [Citation(s) in RCA: 84] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2008] [Revised: 12/15/2008] [Accepted: 12/15/2008] [Indexed: 10/20/2022]
Abstract
Understanding the pathogenicity of amyloid-beta (Abeta) peptides constitutes a major goal in research on Alzheimer's disease (AD). One hypothesis entails that Abeta peptides induce uncontrolled, neurotoxic ion flux through cellular membranes. The exact biophysical mechanism of this ion flux is, however, a subject of an ongoing controversy which has attenuated progress toward understanding the importance of Abeta-induced ion flux in AD. The work presented here addresses two prevalent controversies regarding the nature of transmembrane ion flux induced by Alphabeta peptides. First, the results clarify that Alphabeta can induce stepwise ion flux across planar lipid bilayers as opposed to a gradual increase in transmembrane current; they show that the previously reported gradual thinning of membranes with concomitant increase in transmembrane current arises from residues of the solvent hexafluoroisopropanol, which is commonly used for the preparation of amyloid samples. Second, the results provide additional evidence suggesting that Abeta peptides can induce ion channel-like ion flux in cellular membranes that is independent from the postulated ability of Alphabeta to modulate intrinsic cellular ion channels or transporter proteins.
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Affiliation(s)
- Ricardo Capone
- Department of Biomedical Engineering, University of Michigan, 1101 Beal Ave, Ann Arbor, MI 48109-2110, USA
| | - Felipe Garcia Quiroz
- Department of Biomedical Engineering, University of Michigan, 1101 Beal Ave, Ann Arbor, MI 48109-2110, USA
| | - Panchika Prangkio
- Department of Biomedical Engineering, University of Michigan, 1101 Beal Ave, Ann Arbor, MI 48109-2110, USA
| | | | - Anna M. Sauer
- Department of Biomedical Engineering, University of Michigan, 1101 Beal Ave, Ann Arbor, MI 48109-2110, USA
| | - Mahealani R. Bautista
- Department of Chemistry and Biochemistry, University of California, San Diego, 9500 Gilman Drive, MC 0358, La Jolla, CA 92093-0358, USA
| | | | - Jerry Yang
- Department of Chemistry and Biochemistry, University of California, San Diego, 9500 Gilman Drive, MC 0358, La Jolla, CA 92093-0358, USA
| | - Michael Mayer
- Departments of Biomedical Engineering and Chemical Engineering, University of Michigan, 1101 Beal Ave, Ann Arbor, MI 48109-2110, USA
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30
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Remote excitation of neuronal circuits using low-intensity, low-frequency ultrasound. PLoS One 2008; 3:e3511. [PMID: 18958151 PMCID: PMC2568804 DOI: 10.1371/journal.pone.0003511] [Citation(s) in RCA: 402] [Impact Index Per Article: 25.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2008] [Accepted: 10/03/2008] [Indexed: 12/05/2022] Open
Abstract
Possessing the ability to noninvasively elicit brain circuit activity yields immense experimental and therapeutic power. Most currently employed neurostimulation methods rely on the somewhat invasive use of stimulating electrodes or photon-emitting devices. Due to its ability to noninvasively propagate through bone and other tissues in a focused manner, the implementation of ultrasound (US) represents a compelling alternative approach to current neuromodulation strategies. Here, we investigated the influence of low-intensity, low-frequency ultrasound (LILFU) on neuronal activity. By transmitting US waveforms through hippocampal slice cultures and ex vivo mouse brains, we determined LILFU is capable of remotely and noninvasively exciting neurons and network activity. Our results illustrate that LILFU can stimulate electrical activity in neurons by activating voltage-gated sodium channels, as well as voltage-gated calcium channels. The LILFU-induced changes in neuronal activity were sufficient to trigger SNARE-mediated exocytosis and synaptic transmission in hippocampal circuits. Because LILFU can stimulate electrical activity and calcium signaling in neurons as well as central synaptic transmission we conclude US provides a powerful tool for remotely modulating brain circuit activity.
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Tang Y, Yoo J, Yethiraj A, Cui Q, Chen X. Gating mechanisms of mechanosensitive channels of large conductance, II: systematic study of conformational transitions. Biophys J 2008; 95:581-96. [PMID: 18390625 PMCID: PMC2440447 DOI: 10.1529/biophysj.107.128496] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/27/2007] [Accepted: 03/18/2008] [Indexed: 12/17/2022] Open
Abstract
Part II of this study is based on the continuum mechanics-based molecular dynamics-decorated finite element method (MDeFEM) framework established in Part I. In Part II, the gating pathways of Escherichia coli-MscL channels under various basic deformation modes are simulated. Upon equibiaxial tension (which is verified to be the most effective mode for gating), the MDeFEM results agree well with both experiments and all-atom simulations in literature, as well as the analytical continuum models and elastic network models developed in Part I. Different levels of model sophistication and effects of structural motifs are explored in detail, where the importance of mechanical roles of transmembrane helices, cytoplasmic helices, and loops are discussed. The conformation transitions under complex membrane deformations are predicted, including bending, torsion, cooperativity, patch clamp, and indentation. Compared to atom-based molecular dynamics simulations and elastic network models, the MDeFEM framework is unusually well-suited for simulating complex deformations at large length scales. The versatile hierarchical framework can be further applied to simulate the gating transition of other mechanosensitive channels and other biological processes where mechanical perturbation is important.
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Affiliation(s)
- Yuye Tang
- Nanomechanics Research Center, Department of Civil Engineering and Engineering Mechanics, Columbia University, New York, New York 10027, USA
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Morris CE, Juranka PF. Nav channel mechanosensitivity: activation and inactivation accelerate reversibly with stretch. Biophys J 2007; 93:822-33. [PMID: 17496023 PMCID: PMC1913161 DOI: 10.1529/biophysj.106.101246] [Citation(s) in RCA: 117] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022] Open
Abstract
Voltage-gated sodium channels (Nav) are modulated by many bilayer mechanical amphiphiles, but whether, like other voltage-gated channels (Kv, HCN, Cav), they respond to physical bilayer deformations is unknown. We expressed human heart Nav1.5 pore alpha-subunit in oocytes (where, unlike alphaNav1.4, alphaNav1.5 exhibits normal kinetics) and measured small macroscopic currents in cell-attached patches. Pipette pressure was used to reversibly stretch the membrane for comparison of I(Na)(t) before, during, and after stretch. At all voltages, and in a dose-dependent fashion, stretch accelerated the I(Na)(t) time course. The sign of membrane curvature was not relevant. Typical stretch stimuli reversibly accelerated both activation and inactivation by approximately 1.4-fold; normalization of peak I(Na)(t) followed by temporal scaling ( approximately 1.30- to 1.85-fold) resulted in full overlap of the stretch/no-stretch traces. Evidently the rate-limiting outward voltage sensor motion in the Nav1.5 activation path (as in Kv1) accelerated with stretch. Stretch-accelerated inactivation occurred even with activation saturated, so an independently stretch-modulated inactivation transition is also a possibility. Since Nav1.5 channel-stretch modulation was both reliable and reversible, and required stretch stimuli no more intense than what typically activates putative mechanotransducer channels (e.g., stretch-activated TRPC1-based currents), Nav channels join the ranks of putative mechanotransducers. It is noteworthy that at voltages near the activation threshold, moderate stretch increased the peak I(Na) amplitude approximately 1.5-fold. It will be important to determine whether stretch-modulated Nav current contributes to cardiac arrhythmias, to mechanosensory responses in interstitial cells of Cajal, to touch receptor responses, and to neuropathic (i.e., hypermechanosensitive) and/or normal pain reception.
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Affiliation(s)
- Catherine E Morris
- Neuroscience, Ottawa Health Research Institute, Ottawa, Ontario, Canada.
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Lin W, Laitko U, Juranka PF, Morris CE. Dual stretch responses of mHCN2 pacemaker channels: accelerated activation, accelerated deactivation. Biophys J 2006; 92:1559-72. [PMID: 17142286 PMCID: PMC1796836 DOI: 10.1529/biophysj.106.092478] [Citation(s) in RCA: 48] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Mechanoelectric feedback in heart and smooth muscle is thought to depend on diverse channels that afford myocytes a mechanosensitive cation conductance. Voltage-gated channels (e.g., Kv1) are stretch sensitive, but the only voltage-gated channels that are cation permeant, the pacemaker or HCN (hyperpolarization-activated cyclic nucleotide-gated) channels, have not been tested. To assess if HCN channels could contribute to a mechanosensitive cation conductance, we recorded I(HCN) in cell-attached oocyte patches before, during, and after stretch for a range of voltage protocols. I(mHCN2) has voltage-dependent and instantaneous components; only the former was stretch sensitive. Stretch reversibly accelerated hyperpolarization-induced I(mHCN2) activation (likewise for I(spHCN)) and depolarization-induced deactivation. HCN channels (like Kv1 channels) undergo mode-switch transitions that render their activation midpoints voltage history dependent. The result, as seen from sawtooth clamp, is a pronounced hysteresis. During sawtooth clamp, stretch increased current magnitudes and altered the hysteresis pattern consistent with stretch-accelerated activation and deactivation. I(mHCN2) responses to step protocols indicated that at least two transitions were mechanosensitive: an unspecified rate-limiting transition along the hyperpolarization-driven path, mode I(closed)-->mode II(open), and depolarization-induced deactivation (from mode I(open) and/or from mode II(open)). How might this affect cardiac rhythmicity? Since hysteresis patterns and "on" and "off" I(HCN) responses all changed with stretch, predictions are difficult. For an empirical overview, we therefore clamped patches to cyclic action potential waveforms. During the diastolic potential of sinoatrial node cell and Purkinje fiber waveforms, net stretch effects were frequency dependent. Stretch-inhibited (SI) I(mHCN2) dominated at low frequencies and stretch-augmented (SA) I(mHCN2) was progressively more important as frequency increased. HCN channels might therefore contribute to either SI or SA cation conductances that in turn contribute to stretch arrhythmias and other mechanoelectric feedback phenomena.
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Affiliation(s)
- Wei Lin
- Neuroscience, Ottawa Health Research Institute, Ottawa Hospital, Ottawa, Ontario, Canada
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Hamill OP. Twenty odd years of stretch-sensitive channels. Pflugers Arch 2006; 453:333-51. [PMID: 17021800 DOI: 10.1007/s00424-006-0131-0] [Citation(s) in RCA: 76] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2006] [Accepted: 06/27/2006] [Indexed: 01/15/2023]
Abstract
After formation of the giga-seal, the membrane patch can be stimulated by hydrostatic or osmotic pressure gradients applied across the patch. This feature led to the discovery of stretch-sensitive or mechanosensitive (MS) channels, which are now known to be ubiquitously expressed in cells representative of all the living kingdoms. In addition to mechanosensation, MS channels have been implicated in many basic cell functions, including regulation of cell volume, shape, and motility. The successful cloning, overexpression, and crystallization of bacterial MS channel proteins combined with patch clamp and modeling studies have provided atomic insight into the working of these nanomachines. In particular, studies of MS channels have revealed new understanding of how the lipid bilayer modulates membrane protein function. Three major membrane protein families, transient receptor potential, 2 pore domain K(+), and the epithelial Na(+) channels, have been shown to form MS channels in animal cells, and their polymodal activation embrace fields far beyond mechanosensitivity. The discovery of new drugs highly selective for MS channels ("mechanopharmaceutics") and the demonstration of MS channel involvement in several major human diseases ("mechanochannelopathies") provide added motivation for devising new techniques and approaches for studying MS channels.
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Affiliation(s)
- O P Hamill
- Neurosciences and Cell Biology, UTMB, Galveston, TX, 77555, USA.
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