1
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Kim ED, Wu X, Lee S, Tibbs GR, Cunningham KP, Di Zanni E, Perez ME, Goldstein PA, Accardi A, Larsson HP, Nimigean CM. Propofol rescues voltage-dependent gating of HCN1 channel epilepsy mutants. Nature 2024; 632:451-459. [PMID: 39085604 DOI: 10.1038/s41586-024-07743-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2023] [Accepted: 06/20/2024] [Indexed: 08/02/2024]
Abstract
Hyperpolarization-activated cyclic nucleotide-gated (HCN) channels1 are essential for pacemaking activity and neural signalling2,3. Drugs inhibiting HCN1 are promising candidates for management of neuropathic pain4 and epileptic seizures5. The general anaesthetic propofol (2,6-di-iso-propylphenol) is a known HCN1 allosteric inhibitor6 with unknown structural basis. Here, using single-particle cryo-electron microscopy and electrophysiology, we show that propofol inhibits HCN1 by binding to a mechanistic hotspot in a groove between the S5 and S6 transmembrane helices. We found that propofol restored voltage-dependent closing in two HCN1 epilepsy-associated polymorphisms that act by destabilizing the channel closed state: M305L, located in the propofol-binding site in S5, and D401H in S6 (refs. 7,8). To understand the mechanism of propofol inhibition and restoration of voltage-gating, we tracked voltage-sensor movement in spHCN channels and found that propofol inhibition is independent of voltage-sensor conformational changes. Mutations at the homologous methionine in spHCN and an adjacent conserved phenylalanine in S6 similarly destabilize closing without disrupting voltage-sensor movements, indicating that voltage-dependent closure requires this interface intact. We propose a model for voltage-dependent gating in which propofol stabilizes coupling between the voltage sensor and pore at this conserved methionine-phenylalanine interface in HCN channels. These findings unlock potential exploitation of this site to design specific drugs targeting HCN channelopathies.
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Affiliation(s)
- Elizabeth D Kim
- Department of Anesthesiology, Weill Cornell Medical College, New York, NY, USA
| | - Xiaoan Wu
- Department of Physiology and Biophysics, University of Miami Miller School of Medicine, Miami, FL, USA
| | - Sangyun Lee
- Department of Anesthesiology, Weill Cornell Medical College, New York, NY, USA
| | - Gareth R Tibbs
- Department of Anesthesiology, Weill Cornell Medical College, New York, NY, USA
| | - Kevin P Cunningham
- Department of Physiology and Biophysics, University of Miami Miller School of Medicine, Miami, FL, USA
- School of Life Sciences, University of Westminster, London, UK
| | - Eleonora Di Zanni
- Department of Anesthesiology, Weill Cornell Medical College, New York, NY, USA
| | - Marta E Perez
- Department of Physiology and Biophysics, University of Miami Miller School of Medicine, Miami, FL, USA
| | - Peter A Goldstein
- Department of Anesthesiology, Weill Cornell Medical College, New York, NY, USA
| | - Alessio Accardi
- Department of Anesthesiology, Weill Cornell Medical College, New York, NY, USA
- Department of Physiology and Biophysics, Weill Cornell Medical College, New York, NY, USA
| | - H Peter Larsson
- Department of Physiology and Biophysics, University of Miami Miller School of Medicine, Miami, FL, USA.
- Department of Biomedical and Clinical Sciences, Linköping University, Linköping, Sweden.
| | - Crina M Nimigean
- Department of Anesthesiology, Weill Cornell Medical College, New York, NY, USA.
- Department of Physiology and Biophysics, Weill Cornell Medical College, New York, NY, USA.
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2
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Weiner VS, Zhou DW, Kahali P, Stephen EP, Peterfreund RA, Aglio LS, Szabo MD, Eskandar EN, Salazar-Gomez AF, Sampson AL, Cash SS, Brown EN, Purdon PL. Propofol disrupts alpha dynamics in functionally distinct thalamocortical networks during loss of consciousness. Proc Natl Acad Sci U S A 2023; 120:e2207831120. [PMID: 36897972 PMCID: PMC10089159 DOI: 10.1073/pnas.2207831120] [Citation(s) in RCA: 14] [Impact Index Per Article: 14.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2022] [Accepted: 01/14/2023] [Indexed: 03/12/2023] Open
Abstract
During propofol-induced general anesthesia, alpha rhythms measured using electroencephalography undergo a striking shift from posterior to anterior, termed anteriorization, where the ubiquitous waking alpha is lost and a frontal alpha emerges. The functional significance of alpha anteriorization and the precise brain regions contributing to the phenomenon are a mystery. While posterior alpha is thought to be generated by thalamocortical circuits connecting nuclei of the sensory thalamus with their cortical partners, the thalamic origins of the propofol-induced alpha remain poorly understood. Here, we used human intracranial recordings to identify regions in sensory cortices where propofol attenuates a coherent alpha network, distinct from those in the frontal cortex where it amplifies coherent alpha and beta activities. We then performed diffusion tractography between these identified regions and individual thalamic nuclei to show that the opposing dynamics of anteriorization occur within two distinct thalamocortical networks. We found that propofol disrupted a posterior alpha network structurally connected with nuclei in the sensory and sensory associational regions of the thalamus. At the same time, propofol induced a coherent alpha oscillation within prefrontal cortical areas that were connected with thalamic nuclei involved in cognition, such as the mediodorsal nucleus. The cortical and thalamic anatomy involved, as well as their known functional roles, suggests multiple means by which propofol dismantles sensory and cognitive processes to achieve loss of consciousness.
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Affiliation(s)
- Veronica S. Weiner
- Department of Brain and Cognitive Sciences, Massachusetts Institute of Technology, Cambridge, MA02139
- Picower Institute for Learning and Memory, Massachusetts Institute of Technology, Cambridge, MA02139
| | - David W. Zhou
- Department of Brain and Cognitive Sciences, Massachusetts Institute of Technology, Cambridge, MA02139
- Picower Institute for Learning and Memory, Massachusetts Institute of Technology, Cambridge, MA02139
- Department of Anesthesia, Critical Care and Pain Medicine, Massachusetts General Hospital, Boston, MA02114
- Center for Neurotechnology and Recovery, Department of Neurology, Massachusetts General Hospital, Boston, MA02114
| | - Pegah Kahali
- Picower Institute for Learning and Memory, Massachusetts Institute of Technology, Cambridge, MA02139
- Department of Anesthesia, Critical Care and Pain Medicine, Massachusetts General Hospital, Boston, MA02114
| | - Emily P. Stephen
- Picower Institute for Learning and Memory, Massachusetts Institute of Technology, Cambridge, MA02139
| | - Robert A. Peterfreund
- Department of Anesthesia, Critical Care and Pain Medicine, Massachusetts General Hospital, Boston, MA02114
- Harvard Medical School, Boston, MA02115
| | - Linda S. Aglio
- Harvard Medical School, Boston, MA02115
- Department of Anesthesiology, Perioperative and Pain Medicine, Brigham and Women’s Hospital, Boston, MA02115
| | - Michele D. Szabo
- Department of Anesthesia, Critical Care and Pain Medicine, Massachusetts General Hospital, Boston, MA02114
| | - Emad N. Eskandar
- Harvard Medical School, Boston, MA02115
- Department of Neurological Surgery, Massachusetts General Hospital, Boston, MA02114
| | - Andrés F. Salazar-Gomez
- Department of Anesthesia, Critical Care and Pain Medicine, Massachusetts General Hospital, Boston, MA02114
| | - Aaron L. Sampson
- Department of Anesthesia, Critical Care and Pain Medicine, Massachusetts General Hospital, Boston, MA02114
| | - Sydney S. Cash
- Center for Neurotechnology and Recovery, Department of Neurology, Massachusetts General Hospital, Boston, MA02114
- Harvard Medical School, Boston, MA02115
| | - Emery N. Brown
- Department of Brain and Cognitive Sciences, Massachusetts Institute of Technology, Cambridge, MA02139
- Picower Institute for Learning and Memory, Massachusetts Institute of Technology, Cambridge, MA02139
- Department of Anesthesia, Critical Care and Pain Medicine, Massachusetts General Hospital, Boston, MA02114
- Harvard Medical School, Boston, MA02115
- Division of Health Sciences and Technology, Harvard Medical School/Massachusetts Institute of Technology, Cambridge, MA02139
- Institute of Medical Engineering and Sciences, Massachusetts Institute of Technology, Cambridge, MA02139
| | - Patrick L. Purdon
- Department of Anesthesia, Critical Care and Pain Medicine, Massachusetts General Hospital, Boston, MA02114
- Harvard Medical School, Boston, MA02115
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3
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Lobule-Related Action Potential Shape- and History-Dependent Current Integration in Purkinje Cells of Adult and Developing Mice. Cells 2023; 12:cells12040623. [PMID: 36831290 PMCID: PMC9953991 DOI: 10.3390/cells12040623] [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: 01/06/2023] [Revised: 02/03/2023] [Accepted: 02/13/2023] [Indexed: 02/17/2023] Open
Abstract
Purkinje cells (PCs) are the principal cells of the cerebellar cortex and form a central element in the modular organization of the cerebellum. Differentiation of PCs based on gene expression profiles revealed two subpopulations with distinct connectivity, action potential firing and learning-induced activity changes. However, which basal cell physiological features underlie the differences between these subpopulations and to what extent they integrate input differentially remains largely unclear. Here, we investigate the cellular electrophysiological properties of PC subpopulation in adult and juvenile mice. We found that multiple fundamental cell physiological properties, including membrane resistance and various aspects of the action potential shape, differ between PCs from anterior and nodular lobules. Moreover, the two PC subpopulations also differed in the integration of negative and positive current steps as well as in size of the hyperpolarization-activated current. A comparative analysis in juvenile mice confirmed that most of these lobule-specific differences are already present at pre-weaning ages. Finally, we found that current integration in PCs is input history-dependent for both positive and negative currents, but this is not a distinctive feature between anterior and nodular PCs. Our results support the concept of a fundamental differentiation of PCs subpopulations in terms of cell physiological properties and current integration, yet reveals that history-dependent input processing is consistent across PC subtypes.
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4
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Altered EEG power spectrum, but not sleep-wake architecture, in HCN1 knockout mice. Behav Brain Res 2023; 437:114105. [PMID: 36089097 DOI: 10.1016/j.bbr.2022.114105] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2022] [Revised: 08/29/2022] [Accepted: 09/05/2022] [Indexed: 11/20/2022]
Abstract
Sleep is a complex biological state characterized by large populations of neurons firing in a rhythmic or synchronized manner. HCN channels play a critical role in generating and sustaining synchronized neuronal firing and are involved in the actions of anaesthetics. However, the role of these channels in sleep-wakefulness per se has yet to be studied. We conducted polysomnographic recordings of Hcn1 constitutive knockout (Hcn1 KO) and wild-type (WT) mice in order to investigate the potential role of HCN1 channels in sleep/wake regulation. EEG and EMG data were analysed using the Somnivore™ machine learning algorithm. Time spent in each vigilance state, bout number and duration, and EEG power spectral activity were compared between genotypes. There were no significant differences in the time spent in wake, rapid eye movement (REM) or non-REM (NREM) sleep between Hcn1 KO and WT mice. Wake bout duration during the inactive phase was significantly shorter in Hcn1 KO mice whilst no other bout parameters were affected by genotype. Hcn1 KO mice showed a reduction in overall EEG power which was particularly prominent in the theta (5-9 Hz) and alpha (9-15 Hz) frequency bands and most evident during NREM sleep. Together these data suggest that HCN1 channels do not play a major role in sleep architecture or modulation of vigilance states. However, loss of these channels significantly alters underlying neuronal activity within these states which may have functional consequences.
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5
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Shimizu M, Mi X, Toyoda F, Kojima A, Ding WG, Fukushima Y, Omatsu-Kanbe M, Kitagawa H, Matsuura H. Propofol, an Anesthetic Agent, Inhibits HCN Channels through the Allosteric Modulation of the cAMP-Dependent Gating Mechanism. Biomolecules 2022; 12:biom12040570. [PMID: 35454159 PMCID: PMC9032835 DOI: 10.3390/biom12040570] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2022] [Revised: 04/08/2022] [Accepted: 04/10/2022] [Indexed: 11/16/2022] Open
Abstract
Propofol is a broadly used intravenous anesthetic agent that can cause cardiovascular effects, including bradycardia and asystole. A possible mechanism for these effects is slowing cardiac pacemaker activity due to inhibition of the hyperpolarization-activated, cyclic nucleotide-gated (HCN) channels. However, it remains unclear how propofol affects the allosteric nature of the voltage- and cAMP-dependent gating mechanism in HCN channels. To address this aim, we investigated the effect of propofol on HCN channels (HCN4 and HCN2) in heterologous expression systems using a whole-cell patch clamp technique. The extracellular application of propofol substantially suppressed the maximum current at clinical concentrations. This was accompanied by a hyperpolarizing shift in the voltage dependence of channel opening. These effects were significantly attenuated by intracellular loading of cAMP, even after considering the current modification by cAMP in opposite directions. The differential degree of propofol effects in the presence and absence of cAMP was rationalized by an allosteric gating model for HCN channels, where we assumed that propofol affects allosteric couplings between the pore, voltage-sensor, and cyclic nucleotide-binding domain (CNBD). The model predicted that propofol enhanced autoinhibition of pore opening by unliganded CNBD, which was relieved by the activation of CNBD by cAMP. Taken together, these findings reveal that propofol acts as an allosteric modulator of cAMP-dependent gating in HCN channels, which may help us to better understand the clinical action of this anesthetic drug.
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Affiliation(s)
- Morihiro Shimizu
- Department of Anesthesiology, Shiga University of Medical Science, Otsu 520-2192, Japan; (M.S.); (A.K.); (Y.F.); (H.K.)
| | - Xinya Mi
- Department of Physiology, Shiga University of Medical Science, Otsu 520-2192, Japan; (X.M.); (F.T.); (M.O.-K.); (H.M.)
| | - Futoshi Toyoda
- Department of Physiology, Shiga University of Medical Science, Otsu 520-2192, Japan; (X.M.); (F.T.); (M.O.-K.); (H.M.)
| | - Akiko Kojima
- Department of Anesthesiology, Shiga University of Medical Science, Otsu 520-2192, Japan; (M.S.); (A.K.); (Y.F.); (H.K.)
| | - Wei-Guang Ding
- Department of Physiology, Shiga University of Medical Science, Otsu 520-2192, Japan; (X.M.); (F.T.); (M.O.-K.); (H.M.)
- Correspondence: ; Tel.: +81-77-548-2152; Fax: +81-77-548-2348
| | - Yutaka Fukushima
- Department of Anesthesiology, Shiga University of Medical Science, Otsu 520-2192, Japan; (M.S.); (A.K.); (Y.F.); (H.K.)
| | - Mariko Omatsu-Kanbe
- Department of Physiology, Shiga University of Medical Science, Otsu 520-2192, Japan; (X.M.); (F.T.); (M.O.-K.); (H.M.)
| | - Hirotoshi Kitagawa
- Department of Anesthesiology, Shiga University of Medical Science, Otsu 520-2192, Japan; (M.S.); (A.K.); (Y.F.); (H.K.)
| | - Hiroshi Matsuura
- Department of Physiology, Shiga University of Medical Science, Otsu 520-2192, Japan; (X.M.); (F.T.); (M.O.-K.); (H.M.)
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6
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Progress in modelling of brain dynamics during anaesthesia and the role of sleep-wake circuitry. Biochem Pharmacol 2021; 191:114388. [DOI: 10.1016/j.bcp.2020.114388] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2020] [Revised: 12/16/2020] [Accepted: 12/17/2020] [Indexed: 12/28/2022]
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7
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Schwerin S, Kopp C, Pircher E, Schneider G, Kreuzer M, Haseneder R, Kratzer S. Attenuation of Native Hyperpolarization-Activated, Cyclic Nucleotide-Gated Channel Function by the Volatile Anesthetic Sevoflurane in Mouse Thalamocortical Relay Neurons. Front Cell Neurosci 2021; 14:606687. [PMID: 33551750 PMCID: PMC7858256 DOI: 10.3389/fncel.2020.606687] [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: 09/15/2020] [Accepted: 12/18/2020] [Indexed: 11/24/2022] Open
Abstract
As thalamocortical relay neurons are ascribed a crucial role in signal propagation and information processing, they have attracted considerable attention as potential targets for anesthetic modulation. In this study, we analyzed the effects of different concentrations of sevoflurane on the excitability of thalamocortical relay neurons and hyperpolarization-activated, cyclic-nucleotide gated (HCN) channels, which play a decisive role in regulating membrane properties and rhythmic oscillatory activity. The effects of sevoflurane on single-cell excitability and native HCN channels were investigated in acutely prepared brain slices from adult wild-type mice with the whole-cell patch-clamp technique, using voltage-clamp and current-clamp protocols. Sevoflurane dose-dependently depressed membrane biophysics and HCN-mediated parameters of neuronal excitability. Respective half-maximal inhibitory and effective concentrations ranged between 0.30 (95% CI, 0.18–0.50) mM and 0.88 (95% CI, 0.40–2.20) mM. We witnessed a pronounced reduction of HCN dependent Ih current amplitude starting at a concentration of 0.45 mM [relative change at −133 mV; 0.45 mM sevoflurane: 0.85 (interquartile range, 0.79–0.92), n = 12, p = 0.011; 1.47 mM sevoflurane: 0.37 (interquartile range, 0.34–0.62), n = 5, p < 0.001] with a half-maximal inhibitory concentration of 0.88 (95% CI, 0.40–2.20) mM. In contrast, effects on voltage-dependent channel gating were modest with significant changes only occurring at 1.47 mM [absolute change of half-maximal activation potential; 1.47 mM: −7.2 (interquartile range, −10.3 to −5.8) mV, n = 5, p = 0.020]. In this study, we demonstrate that sevoflurane inhibits the excitability of thalamocortical relay neurons in a concentration-dependent manner within a clinically relevant range. Especially concerning its effects on native HCN channel function, our findings indicate substance-specific differences in comparison to other anesthetic agents. Considering the importance of HCN channels, the observed effects might mechanistically contribute to the hypnotic properties of sevoflurane.
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Affiliation(s)
- Stefan Schwerin
- Department of Anesthesiology and Intensive Care Medicine, Technical University of Munich School of Medicine, Munich, Germany
| | - Claudia Kopp
- Department of Anesthesiology and Intensive Care Medicine, Technical University of Munich School of Medicine, Munich, Germany
| | - Elisabeth Pircher
- Department of Anesthesiology and Intensive Care Medicine, Technical University of Munich School of Medicine, Munich, Germany
| | - Gerhard Schneider
- Department of Anesthesiology and Intensive Care Medicine, Technical University of Munich School of Medicine, Munich, Germany
| | - Matthias Kreuzer
- Department of Anesthesiology and Intensive Care Medicine, Technical University of Munich School of Medicine, Munich, Germany
| | - Rainer Haseneder
- Department of Anesthesiology and Intensive Care Medicine, Technical University of Munich School of Medicine, Munich, Germany
| | - Stephan Kratzer
- Department of Anesthesiology and Intensive Care Medicine, Technical University of Munich School of Medicine, Munich, Germany
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8
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Cook DC, Goldstein PA. Non-canonical Molecular Targets for Novel Analgesics: Intracellular Calcium and HCN Channels. Curr Neuropharmacol 2021; 19:1937-1951. [PMID: 33463473 PMCID: PMC9185781 DOI: 10.2174/1570159x19666210119153047] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2020] [Revised: 01/04/2021] [Accepted: 01/17/2021] [Indexed: 11/22/2022] Open
Abstract
Pain is a prevalent biopsychosocial condition that poses a significant challenge to healthcare providers, contributes substantially to a disability, and is a major economic burden worldwide. An overreliance on opioid analgesics, which primarily target the μ-opioid receptor, has caused devastating morbidity and mortality in the form of misuse and overdose-related death. Thus, novel analgesic medications are needed that can effectively treat pain and provide an alternative to opioids. A variety of cellular ion channels contribute to nociception, the response of the sensory nervous system to a noxious stimulus that commonly leads to pain. Ion channels involved in nociception may provide a suitable target for pharmacologic modulation to achieve pain relief. This narrative review summarizes the evidence for two ion channels that merit consideration as targets for non-opioid pain medications: ryanodine receptors (RyRs), which are intracellular calcium channels, and hyperpolarization-activated cyclic nucleotide-gated (HCN) channels, which belong to the superfamily of voltage-gated K+ channels. The role of these channels in nociception and neuropathic pain is discussed and suitability as targets for novel analgesics and antihyperalgesics is considered.
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Affiliation(s)
- Daniel C. Cook
- Department of Anesthesiology, Weill Cornell Medicine, New York, NY 10065, USA
| | - Peter A. Goldstein
- Department of Anesthesiology, Weill Cornell Medicine, New York, NY 10065, USA
- Feil Family Brain & Mind Research Institute, Weill Cornell Medicine, New York, NY 10065, USA
- Department of Medicine, Weill Cornell Medicine, New York, NY 10065, USA
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9
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Testing broad-spectrum and isoform-preferring HCN channel blockers for anticonvulsant properties in mice. Epilepsy Res 2020; 168:106484. [DOI: 10.1016/j.eplepsyres.2020.106484] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2020] [Revised: 09/23/2020] [Accepted: 10/05/2020] [Indexed: 12/19/2022]
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10
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Joyce RL, Beyer NP, Vasilopoulos G, Woll KA, Hall AC, Eckenhoff RG, Barman DN, Warren JD, Tibbs GR, Goldstein PA. Alkylphenol inverse agonists of HCN1 gating: H-bond propensity, ring saturation and adduct geometry differentially determine efficacy and potency. Biochem Pharmacol 2019; 163:493-508. [PMID: 30768926 DOI: 10.1016/j.bcp.2019.02.013] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2018] [Accepted: 02/11/2019] [Indexed: 10/27/2022]
Abstract
BACKGROUND AND PURPOSE In models of neuropathic pain, inhibition of HCN1 is anti-hyperalgesic. 2,6-di-iso-propyl phenol (propofol) and its non-anesthetic congener, 2,6-di-tert-butyl phenol, inhibit HCN1 channels by stabilizing closed state(s). EXPERIMENTAL APPROACH Using in vitro electrophysiology and kinetic modeling, we systematically explore the contribution of ligand architecture to alkylphenol-channel coupling. KEY RESULTS When corrected for changes in hydrophobicity (and propensity for intra-membrane partitioning), the decrease in potency upon 1-position substitution (NCO∼OH >> SH >>> F) mirrors the ligands' H-bond acceptor (NCO > OH > SH >>> F) but not donor profile (OH > SH >>> NCO∼F). H-bond elimination (OH to F) corresponds to a ΔΔG of ∼4.5 kCal mol-1 loss of potency with little or no disruption of efficacy. Substitution of compact alkyl groups (iso-propyl, tert-butyl) with shorter (ethyl, methyl) or more extended (sec-butyl) adducts disrupts both potency and efficacy. Ring saturation (with the obligate loss of both planarity and π electrons) primarily disrupts efficacy. CONCLUSIONS AND IMPLICATIONS A hydrophobicity-independent decrement in potency at higher volumes suggests the alkylbenzene site has a volume of ≥800 Å3. Within this, a relatively static (with respect to ligand) H-bond donor contributes to initial binding with little involvement in generation of coupling energy. The influence of π electrons/ring planarity and alkyl adducts on efficacy reveals these aspects of the ligand present towards a face of the channel that undergoes structural changes during opening. The site's characteristics suggest it is "druggable"; introduction of other adducts on the ring may generate higher potency inverse agonists.
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Affiliation(s)
| | | | | | - Kellie A Woll
- University of Pennsylvania Perelman School of Medicine, Philadelphia, PA, United States
| | - Adam C Hall
- Smith College, Northampton, MA, United States
| | - Roderic G Eckenhoff
- University of Pennsylvania Perelman School of Medicine, Philadelphia, PA, United States
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11
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Riegelhaupt PM, Tibbs GR, Goldstein PA. HCN and K 2P Channels in Anesthetic Mechanisms Research. Methods Enzymol 2018; 602:391-416. [PMID: 29588040 DOI: 10.1016/bs.mie.2018.01.015] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
The ability of a diverse group of agents to produce general anesthesia has long been an area of intense speculation and investigation. Over the past century, we have seen a paradigm shift from proposing that the anesthetized state arises from nonspecific interaction of anesthetics with the lipid membrane to the recognition that the function of distinct, and identifiable, membrane-embedded proteins is dramatically altered in the presence of intravenous and inhaled agents. Among proteinaceous targets, metabotropic and ionotropic receptors garnered much of the attention over the last 30 years, and it is only relatively recently that voltage-gated ion channels have clearly and rigorously been shown to be important molecular targets. In this review, we will consider the experimental issues relevant to two important ion channel anesthetic targets, HCN and K2P.
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Affiliation(s)
| | - Gareth R Tibbs
- Weill Cornell Medical College, New York, NY, United States
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12
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Gao J, Hu Z, Shi L, Li N, Ouyang Y, Shu S, Yao S, Chen X. HCN channels contribute to the sensitivity of intravenous anesthetics in developmental mice. Oncotarget 2018; 9:12907-12917. [PMID: 29560119 PMCID: PMC5849183 DOI: 10.18632/oncotarget.24408] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2017] [Accepted: 01/13/2018] [Indexed: 02/07/2023] Open
Abstract
It is widely accepted that the induction dose of anesthetics is higher in infants than in adults, although the relevant molecular mechanism remains elusive. We previously showed neuronal hyperpolarization-activated, cyclic nucleotide-gated (HCN) channels contribute to hypnotic actions of propofol and ketamine. Interestingly, the expression of HCN channels in neocortex significantly changes during postnatal periods. Thus, we postulated that changes in HCN channels expression might contribute to sensitivity to intravenous anesthetics. Here we showed the EC50 for propofol- and ketamine-induced loss-of-righting reflex (LORR) was significantly lower for P35 than for P14 mice. Cerebrospinal fluid concentrations of propofol and ketamine were significantly higher in P14 mice than in P35 mice, with similar propofol- and ketamine-induced anesthesia at the LORR EC50. Western blotting indicated that the expression of HCN channels in neocortex changed significantly from P14 to P35 mice. In addition, the amplitude of HCN currents in the neocortical layer 5 pyramidal neurons and the inhibition of propofol and ketamine on HCN currents dramatically increased with development. Logistic regression analysis indicated that the changes of HCN channels were correlated with the age-related differences of propofol- and ketamine-induced anesthesia. These data reveal that the change of HCN channels expression with postnatal development may contribute to sensitivity to the hypnotic actions of propofol and ketamine in mice.
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Affiliation(s)
- Jie Gao
- Department of Anesthesiology, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan 430022, China.,Institute of Anesthesiology and Critical Care Medicine, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan 430022, China
| | - Zhiqiang Hu
- Department of Anesthesiology, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan 430022, China.,Institute of Anesthesiology and Critical Care Medicine, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan 430022, China
| | - Liwei Shi
- Department of Anesthesiology, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan 430022, China.,Institute of Anesthesiology and Critical Care Medicine, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan 430022, China
| | - Na Li
- Department of Anesthesiology, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan 430022, China.,Institute of Anesthesiology and Critical Care Medicine, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan 430022, China
| | - Yeling Ouyang
- Department of Anesthesiology, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan 430022, China.,Institute of Anesthesiology and Critical Care Medicine, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan 430022, China
| | - Shaofang Shu
- Department of Anesthesiology, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan 430022, China.,Institute of Anesthesiology and Critical Care Medicine, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan 430022, China
| | - Shanglong Yao
- Department of Anesthesiology, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan 430022, China.,Institute of Anesthesiology and Critical Care Medicine, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan 430022, China
| | - Xiangdong Chen
- Department of Anesthesiology, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan 430022, China.,Institute of Anesthesiology and Critical Care Medicine, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan 430022, China
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13
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Oyrer J, Maljevic S, Scheffer IE, Berkovic SF, Petrou S, Reid CA. Ion Channels in Genetic Epilepsy: From Genes and Mechanisms to Disease-Targeted Therapies. Pharmacol Rev 2018; 70:142-173. [PMID: 29263209 DOI: 10.1124/pr.117.014456] [Citation(s) in RCA: 163] [Impact Index Per Article: 27.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2017] [Accepted: 10/02/2017] [Indexed: 12/19/2022] Open
Abstract
Epilepsy is a common and serious neurologic disease with a strong genetic component. Genetic studies have identified an increasing collection of disease-causing genes. The impact of these genetic discoveries is wide reaching-from precise diagnosis and classification of syndromes to the discovery and validation of new drug targets and the development of disease-targeted therapeutic strategies. About 25% of genes identified in epilepsy encode ion channels. Much of our understanding of disease mechanisms comes from work focused on this class of protein. In this study, we review the genetic, molecular, and physiologic evidence supporting the pathogenic role of a number of different voltage- and ligand-activated ion channels in genetic epilepsy. We also review proposed disease mechanisms for each ion channel and highlight targeted therapeutic strategies.
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Affiliation(s)
- Julia Oyrer
- The Florey Institute of Neuroscience and Mental Health, University of Melbourne, Parkville, Melbourne, Australia (J.O., S.M., I.E.S., S.P., C.A.R.); Department of Medicine, Austin Health, University of Melbourne, Heidelberg West, Melbourne, Australia (I.E.S., S.F.B.); and Department of Paediatrics, University of Melbourne, Royal Children's Hospital, Melbourne, Australia (I.E.S.)
| | - Snezana Maljevic
- The Florey Institute of Neuroscience and Mental Health, University of Melbourne, Parkville, Melbourne, Australia (J.O., S.M., I.E.S., S.P., C.A.R.); Department of Medicine, Austin Health, University of Melbourne, Heidelberg West, Melbourne, Australia (I.E.S., S.F.B.); and Department of Paediatrics, University of Melbourne, Royal Children's Hospital, Melbourne, Australia (I.E.S.)
| | - Ingrid E Scheffer
- The Florey Institute of Neuroscience and Mental Health, University of Melbourne, Parkville, Melbourne, Australia (J.O., S.M., I.E.S., S.P., C.A.R.); Department of Medicine, Austin Health, University of Melbourne, Heidelberg West, Melbourne, Australia (I.E.S., S.F.B.); and Department of Paediatrics, University of Melbourne, Royal Children's Hospital, Melbourne, Australia (I.E.S.)
| | - Samuel F Berkovic
- The Florey Institute of Neuroscience and Mental Health, University of Melbourne, Parkville, Melbourne, Australia (J.O., S.M., I.E.S., S.P., C.A.R.); Department of Medicine, Austin Health, University of Melbourne, Heidelberg West, Melbourne, Australia (I.E.S., S.F.B.); and Department of Paediatrics, University of Melbourne, Royal Children's Hospital, Melbourne, Australia (I.E.S.)
| | - Steven Petrou
- The Florey Institute of Neuroscience and Mental Health, University of Melbourne, Parkville, Melbourne, Australia (J.O., S.M., I.E.S., S.P., C.A.R.); Department of Medicine, Austin Health, University of Melbourne, Heidelberg West, Melbourne, Australia (I.E.S., S.F.B.); and Department of Paediatrics, University of Melbourne, Royal Children's Hospital, Melbourne, Australia (I.E.S.)
| | - Christopher A Reid
- The Florey Institute of Neuroscience and Mental Health, University of Melbourne, Parkville, Melbourne, Australia (J.O., S.M., I.E.S., S.P., C.A.R.); Department of Medicine, Austin Health, University of Melbourne, Heidelberg West, Melbourne, Australia (I.E.S., S.F.B.); and Department of Paediatrics, University of Melbourne, Royal Children's Hospital, Melbourne, Australia (I.E.S.)
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14
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Chan ACS, Qiu Q, Choi SW, Wong SSC, Chan ACY, Irwin MG, Cheung CW. Effects of Intra-Operative Total Intravenous Anaesthesia with Propofol versus Inhalational Anaesthesia with Sevoflurane on Post-Operative Pain in Liver Surgery: A Retrospective Case-Control Study. PLoS One 2016; 11:e0149753. [PMID: 26901037 PMCID: PMC4763721 DOI: 10.1371/journal.pone.0149753] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2015] [Accepted: 02/04/2016] [Indexed: 12/11/2022] Open
Abstract
Background Patients receiving total intravenous anesthesia (TIVA) with propofol have been shown to experience less postoperative pain. We evaluated the post-operative analgesic effects of propofol compared with sevoflurane maintenance of anesthesia in liver surgery. This study was registered at ClinicalTrials.gov (NCT02179437). Methods In this retrospective study, records of patients who underwent liver surgery between 2010 and 2013 were reviewed. Ninety-five patients anesthetized with propofol TIVA were matched with 95 patients anesthetized with sevoflurane. Numeric pain rating scale (NRS) pain scores, postoperative morphine consumption, side effects and patients’ satisfaction with pain relief were evaluated. Results The TIVA group reported lower NRS pain scores during coughing on postoperative days 1 and 2 but not 3 (p = 0.0127, p = 0.0472, p = 0.4556 respectively). They also consumed significantly less daily (p = 0.001 on day 1, p = 0.0231 on day 2, p = 0.0004 on day 3), accumulative (p = 0.001 on day 1, p<0.0001 on day 2 and p = 0.0064 on day 3) and total morphine (p = 0.03) when compared with the sevoflurane group. There were no differences in total duration of intravenous patient controlled analgesia (PCA) morphine use and patient satisfaction. No difference was found in reported side effects. Conclusion Patients anesthetized with propofol TIVA reported less pain during coughing and consumed less daily, accumulative and total morphine after liver surgery.
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Affiliation(s)
| | - Qiu Qiu
- Laboratory and Clinical Research Institute for Pain, Department of Anaesthesiology, The University of Hong Kong, Hong Kong, China
| | - Siu Wai Choi
- Laboratory and Clinical Research Institute for Pain, Department of Anaesthesiology, The University of Hong Kong, Hong Kong, China
| | - Stanley Sau Ching Wong
- Laboratory and Clinical Research Institute for Pain, Department of Anaesthesiology, The University of Hong Kong, Hong Kong, China
| | | | - Michael G Irwin
- Laboratory and Clinical Research Institute for Pain, Department of Anaesthesiology, The University of Hong Kong, Hong Kong, China
| | - Chi Wai Cheung
- Laboratory and Clinical Research Institute for Pain, Department of Anaesthesiology, The University of Hong Kong, Hong Kong, China
- * E-mail:
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15
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Lyashchenko AK, Redd KJ, Goldstein PA, Tibbs GR. cAMP control of HCN2 channel Mg2+ block reveals loose coupling between the cyclic nucleotide-gating ring and the pore. PLoS One 2014; 9:e101236. [PMID: 24983358 PMCID: PMC4077740 DOI: 10.1371/journal.pone.0101236] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2014] [Accepted: 06/04/2014] [Indexed: 12/24/2022] Open
Abstract
Hyperpolarization-activated cyclic nucleotide-regulated HCN channels underlie the Na+-K+ permeable IH pacemaker current. As with other voltage-gated members of the 6-transmembrane KV channel superfamily, opening of HCN channels involves dilation of a helical bundle formed by the intracellular ends of S6 albeit this is promoted by inward, not outward, displacement of S4. Direct agonist binding to a ring of cyclic nucleotide-binding sites, one of which lies immediately distal to each S6 helix, imparts cAMP sensitivity to HCN channel opening. At depolarized potentials, HCN channels are further modulated by intracellular Mg2+ which blocks the open channel pore and blunts the inhibitory effect of outward K+ flux. Here, we show that cAMP binding to the gating ring enhances not only channel opening but also the kinetics of Mg2+ block. A combination of experimental and simulation studies demonstrates that agonist acceleration of block is mediated via acceleration of the blocking reaction itself rather than as a secondary consequence of the cAMP enhancement of channel opening. These results suggest that the activation status of the gating ring and the open state of the pore are not coupled in an obligate manner (as required by the often invoked Monod-Wyman-Changeux allosteric model) but couple more loosely (as envisioned in a modular model of protein activation). Importantly, the emergence of second messenger sensitivity of open channel rectification suggests that loose coupling may have an unexpected consequence: it may endow these erstwhile “slow” channels with an ability to exert voltage and ligand-modulated control over cellular excitability on the fastest of physiologically relevant time scales.
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Affiliation(s)
- Alex K. Lyashchenko
- Department of Anesthesiology, Columbia University, New York, New York, United States of America
| | - Kacy J. Redd
- Department of Neuroscience, Columbia University, New York, New York, United States of America
| | - Peter A. Goldstein
- Department of Anesthesiology, Weill Cornell Medical College, New York, New York, United States of America
| | - Gareth R. Tibbs
- Department of Anesthesiology, Columbia University, New York, New York, United States of America
- Department of Anesthesiology, Weill Cornell Medical College, New York, New York, United States of America
- * E-mail:
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16
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Thalamocortical mechanisms for the anteriorization of α rhythms during propofol-induced unconsciousness. J Neurosci 2013; 33:11070-5. [PMID: 23825412 DOI: 10.1523/jneurosci.5670-12.2013] [Citation(s) in RCA: 116] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
As humans are induced into a state of general anesthesia via propofol, the normal alpha rhythm (8-13 Hz) in the occipital cortex disappears and a frontal alpha rhythm emerges. This spatial shift in alpha activity is called anteriorization. We present a thalamocortical model that suggests mechanisms underlying anteriorization. Our model captures the neural dynamics of anteriorization when we adjust it to reflect two key actions of propofol: its potentiation of GABA and its reduction of the hyperpolarization-activated current Ih. The reduction in Ih abolishes the occipital alpha by silencing a specialized subset of thalamocortical cells, thought to generate occipital alpha at depolarized membrane potentials (>-60 mV). The increase in GABA inhibition imposes an alpha timescale on both the cortical and thalamic portions of the frontal component that are reinforced by reciprocal thalamocortical feedback. Anteriorization can thus be understood as a differential effect of anesthetic drugs on thalamic nuclei with disparate spatial projections, i.e.: (1) they disrupt the normal, depolarized alpha in posterior-projecting thalamic nuclei while (2) they engage a new, hyperpolarized alpha in frontothalamic nuclei. Our model generalizes to other anesthetics that include GABA as a target, since the molecular targets of many such anesthetics alter the model dynamics in a manner similar to that of propofol.
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17
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Tibbs GR, Rowley TJ, Sanford RL, Herold KF, Proekt A, Hemmings HC, Andersen OS, Goldstein PA, Flood PD. HCN1 channels as targets for anesthetic and nonanesthetic propofol analogs in the amelioration of mechanical and thermal hyperalgesia in a mouse model of neuropathic pain. J Pharmacol Exp Ther 2013; 345:363-73. [PMID: 23549867 DOI: 10.1124/jpet.113.203620] [Citation(s) in RCA: 53] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
Chronic pain after peripheral nerve injury is associated with afferent hyperexcitability and upregulation of hyperpolarization-activated, cyclic nucleotide-regulated (HCN)-mediated IH pacemaker currents in sensory neurons. HCN channels thus constitute an attractive target for treating chronic pain. HCN channels are ubiquitously expressed; analgesics targeting HCN1-rich cells in the peripheral nervous system must spare the cardiac pacemaker current (carried mostly by HCN2 and HCN4) and the central nervous system (where all four isoforms are expressed). The alkylphenol general anesthetic propofol (2,6-di-iso-propylphenol) selectively inhibits HCN1 channels versus HCN2-HCN4 and exhibits a modest pharmacokinetic preference for the periphery. Consequently, we hypothesized that propofol, and congeners, should be antihyperalgesic. Alkyl-substituted propofol analogs have different rank-order potencies with respect to HCN1 inhibition, GABA(A) receptor (GABA(A)-R) potentiation, and general anesthesia. Thus, 2,6- and 2,4-di-tertbutylphenol (2,6- and 2,4-DTBP, respectively) are more potent HCN1 antagonists than propofol, whereas 2,6- and 2,4-di-sec-butylphenol (2,6- and 2,4-DSBP, respectively) are less potent. In contrast, DSBPs, but not DTBPs, enhance GABA(A)-R function and are general anesthetics. 2,6-DTBP retained propofol's selectivity for HCN1 over HCN2-HCN4. In a peripheral nerve ligation model of neuropathic pain, 2,6-DTBP and subhypnotic propofol are antihyperalgesic. The findings are consistent with these alkylphenols exerting analgesia via non-GABA(A)-R targets and suggest that antagonism of central HCN1 channels may be of limited importance to general anesthesia. Alkylphenols are hydrophobic, and thus potential modifiers of lipid bilayers, but their effects on HCN channels are due to direct drug-channel interactions because they have little bilayer-modifying effect at therapeutic concentrations. The alkylphenol antihyperalgesic target may be HCN1 channels in the damaged peripheral nervous system.
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Affiliation(s)
- Gareth R Tibbs
- Department of Anesthesiology, College of Physicians & Surgeons, Columbia University, New York, New York, USA
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18
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Geevasinga N, Tchan M, Sillence D, Vucic S. Upregulation of inward rectifying currents and Fabry disease neuropathy. J Peripher Nerv Syst 2012; 17:399-406. [DOI: 10.1111/j.1529-8027.2012.00438.x] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
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19
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Reid CA, Phillips AM, Petrou S. HCN channelopathies: pathophysiology in genetic epilepsy and therapeutic implications. Br J Pharmacol 2012; 165:49-56. [PMID: 21615728 DOI: 10.1111/j.1476-5381.2011.01507.x] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022] Open
Abstract
Hyperpolarization-activated cyclic nucleotide-gated channels (HCN) can act as pacemakers in the brain making them strong candidates for driving aberrant hypersynchronous network activity seen in epilepsy. Transcriptional changes in HCN channels occur in several animal models of epilepsy. However, only recently have genetic studies demonstrated sequence variation in HCN1 and HCN2 genes associated with human epilepsy. These include a triple proline deletion in HCN2 that increases channel function and occurs more often in patients with febrile seizure syndromes. Other HCNx gene variants have been described in idiopathic generalized epilepsy although the functional consequence of these remains unclear. In this review we explore potential cellular and network mechanisms involving HCN channels in the genetic epilepsies. We suggest how new genetic sequencing technology, medium-throughput functional assays and the ability to develop syndrome-specific animal models will provide a more comprehensive understanding of how I(h) contributes to pathogenic mechanisms underlying human genetic epilepsy. We also discuss what is known about the pharmacological manipulation of HCN channels in the context of epilepsy and how this may help future efforts in developing HCN-channel-based therapy.
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Affiliation(s)
- Christopher A Reid
- Florey Neuroscience Institute and The Centre for Neuroscience, The University of Melbourne, Parkville, Victoria, Australia.
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20
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Klöckner U, Rueckschloss U, Grossmann C, Ebelt H, Müller-Werdan U, Loppnow H, Werdan K, Gekle M. Differential reduction of HCN channel activity by various types of lipopolysaccharide. J Mol Cell Cardiol 2011; 51:226-35. [PMID: 21609720 DOI: 10.1016/j.yjmcc.2011.05.004] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/17/2010] [Revised: 05/05/2011] [Accepted: 05/06/2011] [Indexed: 01/31/2023]
Abstract
Recently it was shown that lipopolysaccharide (LPS) impairs the pacemaker current in human atrial myocytes. It was speculated that reduced heart rate variability (HRV), typical of patients with severe sepsis, may partially be explained by this impairment. We evaluated the effect of various types of LPS on the activity of human hyperpolarization-activated cyclic nucleotide-gated channel 2 (hHCN2) expressed in HEK293 cells, and on pacemaker channels in native murine sino-atrial node (SAN) cells, in order to determine the structure of LPS necessary to modulate pacemaker channel function. Application of LPS caused a robust inhibition of hHCN2-mediated current (I(hHCN2)) owing to a negative shift of the voltage dependence of current activation and to a reduced maximal conductance. In addition, kinetics of channel gating were modulated by LPS. Pro-inflammatory LPS-types lacking the O-chain did not reduce I(hHCN2), whereas pro-inflammatory LPS-types containing the O-chain reduced I(hHCN2). On the other hand, a detoxified LPS without inflammatory activity, but containing the O-chain reduced I(hHCN2). Similar observations were made in HEK293 cells expressing hHCN4 and in murine SAN cells. This mechanistic analysis showed the novel finding that the O-chain of LPS is required for reduction of HCN channel activity. In the clinical situation the observed modulation of HCN channels may slow down diastolic depolarization of pacemaker cells and, hence, influence heart rate variability and heart rate.
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Affiliation(s)
- Udo Klöckner
- Julius-Bernstein-Institut für Physiologie, Martin-Luther-Universität Halle-Wittenberg, Halle, Germany.
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21
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Yue L, Xie A, Bruzik KS, Frølund B, Qian H, Pepperberg DR. Potentiating action of propofol at GABAA receptors of retinal bipolar cells. Invest Ophthalmol Vis Sci 2011; 52:2497-509. [PMID: 21071744 DOI: 10.1167/iovs.10-5991] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
PURPOSE Propofol (2,6-diisopropyl phenol), a widely used systemic anesthetic, is known to potentiate GABA(A) receptor activity in a number of CNS neurons and to produce changes in electroretinographically recorded responses of the retina. However, little is known about propofol's effects on specific retinal neurons. The authors investigated the action of propofol on GABA-elicited membrane current responses of retinal bipolar cells, which have both GABA(A) and GABA(C) receptors. METHODS Single, enzymatically dissociated bipolar cells obtained from rat retina were treated with propofol delivered by brief application in combination with GABA or other pharmacologic agents or as a component of the superfusing medium. RESULTS When applied with GABA at subsaturating concentrations and with TPMPA (a known GABA(C) antagonist), propofol markedly increased the peak amplitude and altered the kinetics of the response. Propofol increased the response elicited by THIP (a GABA(A)-selective agonist), and the response was reduced by bicuculline (a GABA(A) antagonist). The response to 5-methyl I4AA, a GABA(C)-selective agonist, was not enhanced by propofol. Serial brief applications of (GABA + TPMPA + propofol) led to a progressive increase in peak response amplitude and, at higher propofol concentrations, additional changes that included a prolonged time course of response recovery. Pre-exposure of the cell to perfusing propofol typically enhanced the rate of development of potentiation produced by (GABA + TPMPA + propofol) applications. CONCLUSIONS Propofol exerts a marked and selective potentiation on GABA(A) receptors of retinal bipolar cells. The data encourage the use of propofol in future studies of bipolar cell function.
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Affiliation(s)
- Lan Yue
- Lions of Illinois Eye Research Institute, Department of Ophthalmology and Visual Sciences, University of Illinois at Chicago, Chicago, Illinois, USA
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22
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Lewis AS, Chetkovich DM. HCN channels in behavior and neurological disease: too hyper or not active enough? Mol Cell Neurosci 2010; 46:357-67. [PMID: 21130878 DOI: 10.1016/j.mcn.2010.11.007] [Citation(s) in RCA: 64] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2010] [Accepted: 11/11/2010] [Indexed: 02/08/2023] Open
Abstract
The roles of cells within the nervous system are based on their properties of excitability, which are in part governed by voltage-gated ion channels. HCN channels underlie the hyperpolarization-activated current, I(h), an important regulator of excitability and rhythmicity through control of basic membrane properties. I(h) is present in multiple neuronal types and regions of the central nervous system, and changes in I(h) alter cellular input-output properties and neuronal circuitry important for behavior such as learning and memory. Furthermore, the pathophysiology of neurological diseases of both the central and peripheral nervous system involves defects in excitability, rhythmicity, and signaling, and animal models of many of these disorders have implicated changes in HCN channels and I(h) as critical for pathogenesis. In this review, we focus on recent research elucidating the role of HCN channels and I(h) in behavior and disease. These studies have utilized knockout mice as well as animal models of disease to examine how I(h) may be important in regulating learning and memory, sleep, and consciousness, as well as how misregulation of I(h) may contribute to epilepsy, chronic pain, and other neurological disorders. This review will help guide future studies aimed at further understanding the function of this unique conductance in both health and disease of the mammalian brain.
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Affiliation(s)
- Alan S Lewis
- Davee Department of Neurology and Clinical Neurosciences, Feinberg School of Medicine, Northwestern University, Chicago, IL 60611, USA.
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Eckle VS, Hucklenbruch C, Todorovic SM. [What do we know about anesthetic mechanisms?: hypnosis, unresponsiveness to surgical incision and amnesia]. Anaesthesist 2010; 58:1144-9. [PMID: 19760252 DOI: 10.1007/s00101-009-1618-9] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
Despite the increase of molecular knowledge in anesthesia research over the past decades there is still ongoing discussion about the mechanisms of anesthesia. This article focuses on presenting anesthetic sensitive ligand and voltage gated ion channels. The impact on anesthetic modulated ion channels is summarized for clinically commonly used anesthetics isoflurane, propofol and ketamine. Furthermore, the anesthetic features hypnosis, unresponsiveness to surgical incision and amnesia and their putative relevant anatomical sites in the central nervous system are briefly introduced.
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Affiliation(s)
- V-S Eckle
- Department of Anesthesiology, University of Virginia, 22909, Charlottesville, VA, USA.
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Biel M, Wahl-Schott C, Michalakis S, Zong X. Hyperpolarization-activated cation channels: from genes to function. Physiol Rev 2009; 89:847-85. [PMID: 19584315 DOI: 10.1152/physrev.00029.2008] [Citation(s) in RCA: 726] [Impact Index Per Article: 48.4] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
Hyperpolarization-activated cyclic nucleotide-gated (HCN) channels comprise a small subfamily of proteins within the superfamily of pore-loop cation channels. In mammals, the HCN channel family comprises four members (HCN1-4) that are expressed in heart and nervous system. The current produced by HCN channels has been known as I(h) (or I(f) or I(q)). I(h) has also been designated as pacemaker current, because it plays a key role in controlling rhythmic activity of cardiac pacemaker cells and spontaneously firing neurons. Extensive studies over the last decade have provided convincing evidence that I(h) is also involved in a number of basic physiological processes that are not directly associated with rhythmicity. Examples for these non-pacemaking functions of I(h) are the determination of the resting membrane potential, dendritic integration, synaptic transmission, and learning. In this review we summarize recent insights into the structure, function, and cellular regulation of HCN channels. We also discuss in detail the different aspects of HCN channel physiology in the heart and nervous system. To this end, evidence on the role of individual HCN channel types arising from the analysis of HCN knockout mouse models is discussed. Finally, we provide an overview of the impact of HCN channels on the pathogenesis of several diseases and discuss recent attempts to establish HCN channels as drug targets.
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Affiliation(s)
- Martin Biel
- Center for Integrated Protein Science CIPS-M and Zentrum für Pharmaforschung, Department Pharmazie, Pharmakologie für Naturwissenschaften, Ludwig-Maximilians-Universität München, Butenandtstr. 5-13, Munich D-81377, Germany.
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25
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Rozario AO, Turbendian HK, Fogle KJ, Olivier NB, Tibbs GR. Voltage-dependent opening of HCN channels: Facilitation or inhibition by the phytoestrogen, genistein, is determined by the activation status of the cyclic nucleotide gating ring. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2009; 1788:1939-49. [PMID: 19524546 DOI: 10.1016/j.bbamem.2009.06.003] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/29/2009] [Revised: 05/29/2009] [Accepted: 06/08/2009] [Indexed: 11/27/2022]
Abstract
Investigation of the mechanistic bases and physiological importance of cAMP regulation of HCN channels has exploited an arginine to glutamate mutation in the nucleotide-binding fold, an approach critically dependent on the mutation selectively lowering the channel's nucleotide affinity. In apparent conflict with this, in intact Xenopus oocytes, HCN and HCN-RE channels exhibit qualitatively and quantitatively distinct responses to the tyrosine kinase inhibitor, genistein -- the estrogenic isoflavonoid strongly depolarizes the activation mid-point of HCN1-R538E, but not HCN1 channels (+9.8 mV + or - 0.9 versus +2.2 mV + or - 0.6) and hyperpolarizes gating of HCN2 (-4.8 mV + or - 1.0) but depolarizes gating of HCN2-R591E (+13.2 mV + or - 2.1). However, excised patch recording, X-ray crystallography and modeling reveal that this is not due to either a fundamental effect of the mutation on channel gating per se or of genistein acting as a mutation-sensitive partial agonist at the cAMP site. Rather, we find that genistein equivalently moves both HCN and HCN-RE channels closer to the open state (rendering the channels inherently easier to open but at a cost of decreasing the coupling energy of cAMP) and that the anomaly reflects a balance of these energetic effects with the isoform-specific inhibition of activation by the nucleotide gating ring and relief of this by endogenous cAMP. These findings have specific implications with regard to findings based on HCN-RE channels and kinase antagonists and general implications with respect to interpretation of drug effects in mutant channel backgrounds.
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Affiliation(s)
- Anjali O Rozario
- Department of Anesthesiology, Columbia University, New York, NY 10032, USA
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Abstract
Ketamine has important anesthetic, analgesic, and psychotropic actions. It is widely believed that NMDA receptor inhibition accounts for ketamine actions, but there remains a dearth of behavioral evidence to support this hypothesis. Here, we present an alternative, behaviorally relevant molecular substrate for anesthetic effects of ketamine: the HCN1 pacemaker channels that underlie a neuronal hyperpolarization-activated cationic current (I(h)). Ketamine caused subunit-specific inhibition of recombinant HCN1-containing channels and neuronal I(h) at clinically relevant concentrations; the channels were more potently inhibited by S-(+)-ketamine than racemic ketamine, consistent with anesthetic actions of the compounds. In cortical pyramidal neurons from wild-type, but not HCN1 knock-out mice, ketamine induced membrane hyperpolarization and enhanced dendritosomatic synaptic coupling; both effects are known to promote cortical synchronization and support slow cortical rhythms, like those accompanying anesthetic-induced hypnosis. Accordingly, we found that the potency for ketamine to provoke a loss-of-righting reflex, a behavioral correlate of hypnosis, was strongly reduced in HCN1 knock-out mice. In addition, hypnotic sensitivity to two other intravenous anesthetics in HCN1 knock-out mice matched effects on HCN1 channels; propofol selectively inhibited HCN1 channels and propofol sensitivity was diminished in HCN1 knock-out mice, whereas etomidate had no effect on HCN1 channels and hypnotic sensitivity to etomidate was unaffected by HCN1 gene deletion. These data advance HCN1 channels as a novel molecular target for ketamine, provide a plausible neuronal mechanism for enhanced cortical synchronization during anesthetic-induced hypnosis and suggest that HCN1 channels might contribute to other unexplained actions of ketamine.
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Jiang YQ, Sun Q, Tu HY, Wan Y. Characteristics of HCN channels and their participation in neuropathic pain. Neurochem Res 2008; 33:1979-89. [PMID: 18461446 DOI: 10.1007/s11064-008-9717-6] [Citation(s) in RCA: 55] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2008] [Accepted: 04/11/2008] [Indexed: 02/08/2023]
Abstract
Neuropathic pain is induced by the injury to nervous systems and characterized by hyperalgesia, allodynia and spontaneous pain. The underlying mechanisms include peripheral and central sensitization resulted from neuronal hyperexcitability. A number of ion channels are considered to contribute to the neuronal hyperexcitability. Here, we particularly concentrate on an interesting ion channel, hyperpolarization-activated cyclic nucleotide gated (HCN) channels. We overview its biophysical properties, physiological functions, followed by focusing on the current progress in the study of its role in the development of neuropathic pain. We attempt to provide a comprehensive review of the potential valuable target, HCN channels, in the treatment of neuropathic pain.
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Affiliation(s)
- Yu-Qiu Jiang
- Neuroscience Research Institute, Peking University, 38 Xueyuan Road, Beijing 100083, People's Republic of China
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Lyashchenko AK, Tibbs GR. Ion binding in the open HCN pacemaker channel pore: fast mechanisms to shape "slow" channels. ACTA ACUST UNITED AC 2008; 131:227-43. [PMID: 18270171 PMCID: PMC2248720 DOI: 10.1085/jgp.200709868] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
IH pacemaker channels carry a mixed monovalent cation current that, under physiological ion gradients, reverses at ∼−34 mV, reflecting a 4:1 selectivity for K over Na. However, IH channels display anomalous behavior with respect to permeant ions such that (a) open channels do not exhibit the outward rectification anticipated assuming independence; (b) gating and selectivity are sensitive to the identity and concentrations of externally presented permeant ions; (c) the channels' ability to carry an inward Na current requires the presence of external K even though K is a minor charge carrier at negative voltages. Here we show that open HCN channels (the hyperpolarization-activated, cyclic nucleotide sensitive pore forming subunits of IH) undergo a fast, voltage-dependent block by intracellular Mg in a manner that suggests the ion binds close to, or within, the selectivity filter. Eliminating internal divalent ion block reveals that (a) the K dependence of conduction is mediated via K occupancy of site(s) within the pore and that asymmetrical occupancy and/or coupling of these sites to flux further shapes ion flow, and (b) the kinetics of equilibration between K-vacant and K-occupied states of the pore (10–20 μs or faster) is close to the ion transit time when the pore is occupied by K alone (∼0.5–3 μs), a finding that indicates that either ion:ion repulsion involving Na is adequate to support flux (albeit at a rate below our detection threshold) and/or the pore undergoes rapid, permeant ion-sensitive equilibration between nonconducting and conducting configurations. Biophysically, further exploration of the Mg site and of interactions of Na and K within the pore will tell us much about the architecture and operation of this unusual pore. Physiologically, these results suggest ways in which “slow” pacemaker channels may contribute dynamically to the shaping of fast processes such as Na-K or Ca action potentials.
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Affiliation(s)
- Alex K Lyashchenko
- Department of Anesthesiology, Columbia University, New York, NY 10032, USA
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