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Barton JR, Londregan AK, Alexander TD, Entezari AA, Covarrubias M, Waldman SA. Enteroendocrine cell regulation of the gut-brain axis. Front Neurosci 2023; 17:1272955. [PMID: 38027512 PMCID: PMC10662325 DOI: 10.3389/fnins.2023.1272955] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2023] [Accepted: 10/16/2023] [Indexed: 12/01/2023] Open
Abstract
Enteroendocrine cells (EECs) are an essential interface between the gut and brain that communicate signals about nutrients, pain, and even information from our microbiome. EECs are hormone-producing cells expressed throughout the gastrointestinal epithelium and have been leveraged by pharmaceuticals like semaglutide (Ozempic, Wegovy), terzepatide (Mounjaro), and retatrutide (Phase 2) for diabetes and weight control, and linaclotide (Linzess) to treat irritable bowel syndrome (IBS) and visceral pain. This review focuses on role of intestinal EECs to communicate signals from the gut lumen to the brain. Canonically, EECs communicate information about the intestinal environment through a variety of hormones, dividing EECs into separate classes based on the hormone each cell type secretes. Recent studies have revealed more diverse hormone profiles and communication modalities for EECs including direct synaptic communication with peripheral neurons. EECs known as neuropod cells rapidly relay signals from gut to brain via a direct communication with vagal and primary sensory neurons. Further, this review discusses the complex information processing machinery within EECs, including receptors that transduce intraluminal signals and the ion channel complement that govern initiation and propagation of these signals. Deeper understanding of EEC physiology is necessary to safely treat devastating and pervasive conditions like irritable bowel syndrome and obesity.
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Affiliation(s)
- Joshua R. Barton
- Department of Pharmacology, Physiology, and Cancer Biology, Thomas Jefferson University, Philadelphia, PA, United States
| | - Annie K. Londregan
- Department of Pharmacology, Physiology, and Cancer Biology, Thomas Jefferson University, Philadelphia, PA, United States
| | - Tyler D. Alexander
- Department of Neurosciences, Thomas Jefferson University, Philadelphia, PA, United States
| | - Ariana A. Entezari
- Department of Pharmacology, Physiology, and Cancer Biology, Thomas Jefferson University, Philadelphia, PA, United States
| | - Manuel Covarrubias
- Department of Neurosciences, Thomas Jefferson University, Philadelphia, PA, United States
| | - Scott A. Waldman
- Department of Pharmacology, Physiology, and Cancer Biology, Thomas Jefferson University, Philadelphia, PA, United States
- Sidney Kimmel Cancer Center, Thomas Jefferson University, Philadelphia, PA, United States
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2
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Zemel BM, Nevue AA, Tavares LES, Dagostin A, Lovell PV, Jin DZ, Mello CV, von Gersdorff H. Motor cortex analogue neurons in songbirds utilize Kv3 channels to generate ultranarrow spikes. eLife 2023; 12:e81992. [PMID: 37158590 PMCID: PMC10241522 DOI: 10.7554/elife.81992] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2022] [Accepted: 05/08/2023] [Indexed: 05/10/2023] Open
Abstract
Complex motor skills in vertebrates require specialized upper motor neurons with precise action potential (AP) firing. To examine how diverse populations of upper motor neurons subserve distinct functions and the specific repertoire of ion channels involved, we conducted a thorough study of the excitability of upper motor neurons controlling somatic motor function in the zebra finch. We found that robustus arcopallialis projection neurons (RAPNs), key command neurons for song production, exhibit ultranarrow spikes and higher firing rates compared to neurons controlling non-vocal somatic motor functions (dorsal intermediate arcopallium [AId] neurons). Pharmacological and molecular data indicate that this striking difference is associated with the higher expression in RAPNs of high threshold, fast-activating voltage-gated Kv3 channels, that likely contain Kv3.1 (KCNC1) subunits. The spike waveform and Kv3.1 expression in RAPNs mirror properties of Betz cells, specialized upper motor neurons involved in fine digit control in humans and other primates but absent in rodents. Our study thus provides evidence that songbirds and primates have convergently evolved the use of Kv3.1 to ensure precise, rapid AP firing in upper motor neurons controlling fast and complex motor skills.
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Affiliation(s)
- Benjamin M Zemel
- Vollum Institute, Oregon Health and Science UniversityPortlandUnited States
| | - Alexander A Nevue
- Department of Behavioral Neuroscience, Oregon Health and Science UniversityPortlandUnited States
| | - Leonardo ES Tavares
- Vollum Institute, Oregon Health and Science UniversityPortlandUnited States
- Department of Physics, Pennsylvania State UniversityUniversity ParkUnited States
| | - Andre Dagostin
- Vollum Institute, Oregon Health and Science UniversityPortlandUnited States
| | - Peter V Lovell
- Department of Behavioral Neuroscience, Oregon Health and Science UniversityPortlandUnited States
| | - Dezhe Z Jin
- Department of Physics, Pennsylvania State UniversityUniversity ParkUnited States
| | - Claudio V Mello
- Department of Behavioral Neuroscience, Oregon Health and Science UniversityPortlandUnited States
| | - Henrique von Gersdorff
- Vollum Institute, Oregon Health and Science UniversityPortlandUnited States
- Oregon Hearing Research Center, Oregon Health and Science UniversityPortlandUnited States
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3
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Liu JP, Wang JL, Hu BE, Zou FL, Wu CL, Shen J, Zhang WJ. Olfactory ensheathing cells and neuropathic pain. Front Cell Dev Biol 2023; 11:1147242. [PMID: 37223000 PMCID: PMC10201020 DOI: 10.3389/fcell.2023.1147242] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2023] [Accepted: 03/27/2023] [Indexed: 08/29/2023] Open
Abstract
Damage to the nervous system can lead to functional impairment, including sensory and motor functions. Importantly, neuropathic pain (NPP) can be induced after nerve injury, which seriously affects the quality of life of patients. Therefore, the repair of nerve damage and the treatment of pain are particularly important. However, the current treatment of NPP is very weak, which promotes researchers to find new methods and directions for treatment. Recently, cell transplantation technology has received great attention and has become a hot spot for the treatment of nerve injury and pain. Olfactory ensheathing cells (OECs) are a kind of glial cells with the characteristics of lifelong survival in the nervous system and continuous division and renewal. They also secrete a variety of neurotrophic factors, bridge the fibers at both ends of the injured nerve, change the local injury microenvironment, and promote axon regeneration and other biological functions. Different studies have revealed that the transplantation of OECs can repair damaged nerves and exert analgesic effect. Some progress has been made in the effect of OECs transplantation in inhibiting NPP. Therefore, in this paper, we provided a comprehensive overview of the biology of OECs, described the possible pathogenesis of NPP. Moreover, we discussed on the therapeutic effect of OECs transplantation on central nervous system injury and NPP, and prospected some possible problems of OECs transplantation as pain treatment. To provide some valuable information for the treatment of pain by OECs transplantation in the future.
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Affiliation(s)
- Ji-peng Liu
- Department of Rehabilitation Medicine, The Second Affiliated Hospital, Nanchang University, Nanchang, Jiangxi, China
- Department of Gastrointestinal Surgery, The Second Affiliated Hospital, Nanchang University, Nanchang, Jiangxi, China
| | - Jia-ling Wang
- Department of Gastrointestinal Surgery, The Second Affiliated Hospital, Nanchang University, Nanchang, Jiangxi, China
| | - Bai-er Hu
- Department of Physical Examination, The Second Affiliated Hospital, Nanchang University, Nanchang, Jiangxi, China
| | - Fei-long Zou
- Department of Gastrointestinal Surgery, The Second Affiliated Hospital, Nanchang University, Nanchang, Jiangxi, China
| | - Chang-lei Wu
- Department of Gastrointestinal Surgery, The Second Affiliated Hospital, Nanchang University, Nanchang, Jiangxi, China
| | - Jie Shen
- Department of Rehabilitation Medicine, The Second Affiliated Hospital, Nanchang University, Nanchang, Jiangxi, China
| | - Wen-jun Zhang
- Department of Rehabilitation Medicine, The Second Affiliated Hospital, Nanchang University, Nanchang, Jiangxi, China
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4
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Alexander TD, Muqeem T, Zhi L, Tymanskyj SR, Covarrubias M. Tunable Action Potential Repolarization Governed by Kv3.4 Channels in Dorsal Root Ganglion Neurons. J Neurosci 2022; 42:8647-8657. [PMID: 36198500 PMCID: PMC9671581 DOI: 10.1523/jneurosci.1210-22.2022] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2022] [Revised: 09/01/2022] [Accepted: 09/27/2022] [Indexed: 11/21/2022] Open
Abstract
The Kv3.4 channel regulates action potential (AP) repolarization in nociceptors and excitatory synaptic transmission in the spinal cord. We hypothesize that this is a tunable role governed by protein kinase-C-dependent phosphorylation of the Kv3.4 cytoplasmic N-terminal inactivation domain (NTID) at four nonequivalent sites. However, there is a paucity of causation evidence linking the phosphorylation status of Kv3.4 to the properties of the AP. To establish this link, we used adeno-associated viral vectors to specifically manipulate the expression and the effective phosphorylation status of Kv3.4 in cultured dorsal root ganglion (DRG) neurons from mixed-sex rat embryos at embryonic day 18. These vectors encoded GFP (background control), wild-type (WT) Kv3.4, phosphonull (PN) Kv3.4 mutant (PN = S[8,9,15,21]A), phosphomimic (PM) Kv3.4 mutant (PM = S[8,9,15,21]D), and a Kv3.4 nonconducting dominant-negative (DN) pore mutant (DN = W429F). Following viral infection of the DRG neurons, we evaluated transduction efficiency and Kv3.4 expression and function via fluorescence microscopy and patch clamping. All functional Kv3.4 constructs induced current overexpression with similar voltage dependence of activation. However, whereas Kv3.4-WT and Kv3.4-PN induced fast transient currents, the Kv3.4-PM induced currents exhibiting impaired inactivation. In contrast, the Kv3.4-DN abolished the endogenous Kv3.4 current. Consequently, Kv3.4-DN and Kv3.4-PM produced APs with the longest and shortest durations, respectively, whereas Kv3.4-WT and Kv3.4-PN produced intermediate results. Moreover, the AP widths and maximum rates of AP repolarization from these groups are negatively correlated. We conclude that the expression and effective phosphorylation status of the Kv3.4 NTID confer a tunable mechanism of AP repolarization, which may provide exquisite regulation of pain signaling in DRG neurons.SIGNIFICANCE STATEMENT The AP is an all-or-none millisecond-long electrical impulse that encodes information in the frequency and patterns of repetitive firing. However, signaling may also depend on the plasticity and diversity of the AP waveform. For instance, the shape and duration of the AP may regulate nociceptive synaptic transmission between a primary sensory afferent to a secondary neuron in the spinal cord. Here, we used mutants of the Kv3.4 voltage-gated potassium channel to manipulate its expression and effective phosphorylation status in dorsal root ganglion neurons and directly show how the expression and malleable inactivation properties of Kv3.4 govern the AP duration and repolarization rate. These results elucidate a mechanism of neural AP plasticity that may regulate pain signaling.
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Affiliation(s)
- Tyler D Alexander
- Department of Neuroscience, Thomas Jefferson University, Philadelphia, Pennsylvania 19107
- Vicki & Jack Farber Institute of Neuroscience at Jefferson Health, Philadelphia, Pennsylvania 19107
- Sidney Kimmel Medical College, Thomas Jefferson University, Philadelphia, Pennsylvania 19107
| | - Tanziyah Muqeem
- Department of Neuroscience, Thomas Jefferson University, Philadelphia, Pennsylvania 19107
- Vicki & Jack Farber Institute of Neuroscience at Jefferson Health, Philadelphia, Pennsylvania 19107
- Sidney Kimmel Medical College, Thomas Jefferson University, Philadelphia, Pennsylvania 19107
| | - Lianteng Zhi
- Department of Neuroscience, Thomas Jefferson University, Philadelphia, Pennsylvania 19107
- Vicki & Jack Farber Institute of Neuroscience at Jefferson Health, Philadelphia, Pennsylvania 19107
- Sidney Kimmel Medical College, Thomas Jefferson University, Philadelphia, Pennsylvania 19107
| | - Stephen R Tymanskyj
- Department of Neuroscience, Thomas Jefferson University, Philadelphia, Pennsylvania 19107
- Vicki & Jack Farber Institute of Neuroscience at Jefferson Health, Philadelphia, Pennsylvania 19107
- Jefferson Synaptic Biology Center, Thomas Jefferson University, Philadelphia, Pennsylvania 19107
- Sidney Kimmel Medical College, Thomas Jefferson University, Philadelphia, Pennsylvania 19107
| | - Manuel Covarrubias
- Department of Neuroscience, Thomas Jefferson University, Philadelphia, Pennsylvania 19107
- Vicki & Jack Farber Institute of Neuroscience at Jefferson Health, Philadelphia, Pennsylvania 19107
- Jefferson Synaptic Biology Center, Thomas Jefferson University, Philadelphia, Pennsylvania 19107
- Sidney Kimmel Medical College, Thomas Jefferson University, Philadelphia, Pennsylvania 19107
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5
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Kv3 Channels Contribute to the Excitability of Subpopulations of Spinal Cord Neurons in Lamina VII. eNeuro 2022; 9:ENEURO.0510-21.2021. [PMID: 35058310 PMCID: PMC8868027 DOI: 10.1523/eneuro.0510-21.2021] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2021] [Accepted: 12/21/2021] [Indexed: 11/29/2022] Open
Abstract
Autonomic parasympathetic preganglionic neurons (PGNs) drive contraction of the bladder during micturition but remain quiescent during bladder filling. This quiescence is postulated to be because of recurrent inhibition of PGN by fast-firing adjoining interneurons. Here, we defined four distinct neuronal types within Lamina VII, where PGN are situated, by combining whole cell patch clamp recordings with k-means clustering of a range of electrophysiological parameters. Additional morphologic analysis separated these neuronal classes into parasympathetic preganglionic populations (PGN) and a fast-firing interneuronal population. Kv3 channels are voltage-gated potassium channels (Kv) that allow fast and precise firing of neurons. We found that blockade of Kv3 channels by tetraethylammonium (TEA) reduced neuronal firing frequency and isolated high-voltage-activated Kv currents in the fast-firing population but had no effect in PGN populations. Furthermore, Kv3 blockade potentiated the local and descending inhibitory inputs to PGN indicating that Kv3-expressing inhibitory neurons are synaptically connected to PGN. Taken together, our data reveal that Kv3 channels are crucial for fast and regulated neuronal output of a defined population that may be involved in intrinsic spinal bladder circuits that underpin recurrent inhibition of PGN.
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6
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Ojala KS, Ginebaugh SP, Wu M, Miller EW, Ortiz G, Covarrubias M, Meriney SD. A high-affinity, partial antagonist effect of 3,4-diaminopyridine mediates action potential broadening and enhancement of transmitter release at NMJs. J Biol Chem 2021; 296:100302. [PMID: 33465376 PMCID: PMC7949096 DOI: 10.1016/j.jbc.2021.100302] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2020] [Revised: 01/12/2021] [Accepted: 01/14/2021] [Indexed: 12/03/2022] Open
Abstract
3,4-Diaminopyridine (3,4-DAP) increases transmitter release from neuromuscular junctions (NMJs), and low doses of 3,4-DAP (estimated to reach ∼1 μM in serum) are the Food and Drug Administration (FDA)-approved treatment for neuromuscular weakness caused by Lambert–Eaton myasthenic syndrome. Canonically, 3,4-DAP is thought to block voltage-gated potassium (Kv) channels, resulting in prolongation of the presynaptic action potential (AP). However, recent reports have shown that low millimolar concentrations of 3,4-DAP have an off-target agonist effect on the Cav1 subtype (“L-type”) of voltage-gated calcium (Cav) channels and have speculated that this agonist effect might contribute to 3,4-DAP effects on transmitter release at the NMJ. To address 3,4-DAP’s mechanism(s) of action, we first used the patch-clamp electrophysiology to characterize the concentration-dependent block of 3,4-DAP on the predominant presynaptic Kv channel subtypes found at the mammalian NMJ (Kv3.3 and Kv3.4). We identified a previously unreported high-affinity (1–10 μM) partial antagonist effect of 3,4-DAP in addition to the well-known low-affinity (0.1–1 mM) antagonist activity. We also showed that 1.5-μM DAP had no effects on Cav1.2 or Cav2.1 current. Next, we used voltage imaging to show that 1.5- or 100-μM 3,4-DAP broadened the AP waveform in a dose-dependent manner, independent of Cav1 calcium channels. Finally, we demonstrated that 1.5- or 100-μM 3,4-DAP augmented transmitter release in a dose-dependent manner and this effect was also independent of Cav1 channels. From these results, we conclude that low micromolar concentrations of 3,4-DAP act solely on Kv channels to mediate AP broadening and enhance transmitter release at the NMJ.
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Affiliation(s)
- Kristine S Ojala
- Department of Neuroscience, Center for Neuroscience, University of Pittsburgh, Pittsburgh, Pennsylvania, USA
| | - Scott P Ginebaugh
- Department of Neuroscience, Center for Neuroscience, University of Pittsburgh, Pittsburgh, Pennsylvania, USA
| | - Man Wu
- Department of Neuroscience, Center for Neuroscience, University of Pittsburgh, Pittsburgh, Pennsylvania, USA
| | - Evan W Miller
- Departments of Chemistry and Molecular & Cell Biology, University of California, Berkeley, Berkeley, California, USA
| | - Gloria Ortiz
- Departments of Chemistry and Molecular & Cell Biology, University of California, Berkeley, Berkeley, California, USA
| | - Manuel Covarrubias
- Department of Neuroscience, Thomas Jefferson University, Philadelphia, Pennsylvania, USA
| | - Stephen D Meriney
- Department of Neuroscience, Center for Neuroscience, University of Pittsburgh, Pittsburgh, Pennsylvania, USA.
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7
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Zemel BM, Zhi L, Brown EV, Tymanskyj SR, Liang Q, Covarrubias M. PKCε associates with the Kv3.4 channel to promote its expression in a kinase activity-dependent manner. FASEB J 2021; 35:e21241. [PMID: 33368632 DOI: 10.1096/fj.201901877r] [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: 07/24/2019] [Revised: 11/05/2020] [Accepted: 11/19/2020] [Indexed: 01/16/2023]
Abstract
The voltage-gated potassium channel Kv3.4 is a crucial regulator of nociceptive signaling in the dorsal root ganglion (DRG) and the dorsal horn of the spinal cord. Moreover, Kv3.4 dysfunction has been linked to neuropathic pain. Although kinases and phosphatases can directly modulate Kv3.4 gating, the signaling mechanisms regulating the expression and stability of the Kv3.4 protein are generally unknown. We explored a potential role of PKCε and found an unexpected interaction that has a positive effect on Kv3.4 expression. Co-immunoprecipitation studies revealed a physical association between PKCε and Kv3.4 in both heterologous cells and rat DRG neurons. Furthermore, in contrast to the wild-type and constitutively active forms of PKCε, expression of a catalytically inactive form of the enzyme inhibits Kv3.4 expression and membrane localization through a dominant negative effect. Co-expression of Kv3.4 with the wild-type, constitutively active, or catalytically inactive forms of PKCε had no significant effects on Kv3.4 gating. These results suggest that a novel physical interaction of the Kv3.4 channel with functional PKCε primarily determines its stability and localization in DRG neurons. This interaction is akin to those of previously identified accessory ion channel proteins, which could be significant in neural tissues where Kv3.4 regulates electrical signaling.
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Affiliation(s)
- Benjamin M Zemel
- Department of Neuroscience and Vickie and Jack Farber Institute for Neuroscience, Sidney Kimmel Medical College, Thomas Jefferson University, Philadelphia, PA, USA.,Jefferson College of Life Sciences, Thomas Jefferson University, Philadelphia, PA, USA.,Vollum Institute, Oregon Health and Science University, Portland, OR, USA
| | - Lianteng Zhi
- Department of Neuroscience and Vickie and Jack Farber Institute for Neuroscience, Sidney Kimmel Medical College, Thomas Jefferson University, Philadelphia, PA, USA.,Jefferson College of Life Sciences, Thomas Jefferson University, Philadelphia, PA, USA
| | - Eric V Brown
- Department of Neuroscience and Vickie and Jack Farber Institute for Neuroscience, Sidney Kimmel Medical College, Thomas Jefferson University, Philadelphia, PA, USA.,Jefferson College of Life Sciences, Thomas Jefferson University, Philadelphia, PA, USA
| | - Stephen R Tymanskyj
- Department of Neuroscience and Vickie and Jack Farber Institute for Neuroscience, Sidney Kimmel Medical College, Thomas Jefferson University, Philadelphia, PA, USA.,Jefferson College of Life Sciences, Thomas Jefferson University, Philadelphia, PA, USA
| | - Qiansheng Liang
- Department of Neuroscience and Vickie and Jack Farber Institute for Neuroscience, Sidney Kimmel Medical College, Thomas Jefferson University, Philadelphia, PA, USA.,Jefferson College of Life Sciences, Thomas Jefferson University, Philadelphia, PA, USA
| | - Manuel Covarrubias
- Department of Neuroscience and Vickie and Jack Farber Institute for Neuroscience, Sidney Kimmel Medical College, Thomas Jefferson University, Philadelphia, PA, USA.,Jefferson College of Life Sciences, Thomas Jefferson University, Philadelphia, PA, USA
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Kim WB, Kang KW, Sharma K, Yi E. Distribution of K v3 Subunits in Cochlear Afferent and Efferent Nerve Fibers Implies Distinct Role in Auditory Processing. Exp Neurobiol 2020; 29:344-355. [PMID: 33154197 PMCID: PMC7649084 DOI: 10.5607/en20043] [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: 09/10/2020] [Revised: 10/14/2020] [Accepted: 10/16/2020] [Indexed: 11/19/2022] Open
Abstract
Kv3 family K+ channels, by ensuring speedy repolarization of action potential, enable rapid and high frequency neuronal firing and high precision temporal coding of auditory information in various auditory synapses in the brain. Expression of different Kv3 subtypes within the auditory end organ has been reported. Yet, their precise role at the hair cell synaptic transmission has not been fully elucidated. Using immunolabeling and confocal microscopy we examined the expression pattern of different Kv3 family K+ channel subunits in the nerve fibers innervating the cochlear hair cells. Kv3.1b was found in NKA-positive type 1 afferent fibers, exhibiting high signal intensity at the cell body, the unmyelinated dendritic segment, first heminode and nodes of Ranvier. Kv3.3 signal was detected in the cell body and the unmyelinated dendritic segment of NKA-positive type 1 afferent fibers but not in peripherin-positive type 2 afferent. Kv3.4 was found in ChAT-positive LOC and MOC efferent fibers as well as peripherin-positive type 2 afferent fibers. Such segregated expression pattern implies that each Kv3 subunits participate in different auditory tasks, for example, Kv3.1b and Kv3.3 in ascending signaling while Kv3.4 in feedback upon loud noise exposure.
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Affiliation(s)
- Woo Bin Kim
- College of Pharmacy and Natural Medicine Research Institute, Mokpo National University, Muan 58554, Korea
| | - Kwon-Woo Kang
- College of Pharmacy and Natural Medicine Research Institute, Mokpo National University, Muan 58554, Korea
| | - Kushal Sharma
- College of Pharmacy and Natural Medicine Research Institute, Mokpo National University, Muan 58554, Korea
| | - Eunyoung Yi
- College of Pharmacy and Natural Medicine Research Institute, Mokpo National University, Muan 58554, Korea
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9
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Smith PA. K + Channels in Primary Afferents and Their Role in Nerve Injury-Induced Pain. Front Cell Neurosci 2020; 14:566418. [PMID: 33093824 PMCID: PMC7528628 DOI: 10.3389/fncel.2020.566418] [Citation(s) in RCA: 30] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2020] [Accepted: 08/21/2020] [Indexed: 12/12/2022] Open
Abstract
Sensory abnormalities generated by nerve injury, peripheral neuropathy or disease are often expressed as neuropathic pain. This type of pain is frequently resistant to therapeutic intervention and may be intractable. Numerous studies have revealed the importance of enduring increases in primary afferent excitability and persistent spontaneous activity in the onset and maintenance of peripherally induced neuropathic pain. Some of this activity results from modulation, increased activity and /or expression of voltage-gated Na+ channels and hyperpolarization-activated cyclic nucleotide–gated (HCN) channels. K+ channels expressed in dorsal root ganglia (DRG) include delayed rectifiers (Kv1.1, 1.2), A-channels (Kv1.4, 3.3, 3.4, 4.1, 4.2, and 4.3), KCNQ or M-channels (Kv7.2, 7.3, 7.4, and 7.5), ATP-sensitive channels (KIR6.2), Ca2+-activated K+ channels (KCa1.1, 2.1, 2.2, 2.3, and 3.1), Na+-activated K+ channels (KCa4.1 and 4.2) and two pore domain leak channels (K2p; TWIK related channels). Function of all K+ channel types is reduced via a multiplicity of processes leading to altered expression and/or post-translational modification. This also increases excitability of DRG cell bodies and nociceptive free nerve endings, alters axonal conduction and increases neurotransmitter release from primary afferent terminals in the spinal dorsal horn. Correlation of these cellular changes with behavioral studies provides almost indisputable evidence for K+ channel dysfunction in the onset and maintenance of neuropathic pain. This idea is underlined by the observation that selective impairment of just one subtype of DRG K+ channel can produce signs of pain in vivo. Whilst it is established that various mediators, including cytokines and growth factors bring about injury-induced changes in DRG function and excitability, evidence presently available points to a seminal role for interleukin 1β (IL-1β) in control of K+ channel function. Despite the current state of knowledge, attempts to target K+ channels for therapeutic pain management have met with limited success. This situation may change with the advent of personalized medicine. Identification of specific sensory abnormalities and genetic profiling of individual patients may predict therapeutic benefit of K+ channel activators.
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Affiliation(s)
- Peter A Smith
- Department of Pharmacology and Neuroscience and Mental Health Institute, University of Alberta, Edmonton, AB, Canada
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10
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The impact of statins on physical activity and exercise capacity: an overview of the evidence, mechanisms, and recommendations. Eur J Appl Physiol 2020; 120:1205-1225. [PMID: 32248287 DOI: 10.1007/s00421-020-04360-2] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2019] [Accepted: 03/24/2020] [Indexed: 12/16/2022]
Abstract
PURPOSE Statins are among the most widely prescribed medications worldwide. Considered the 'gold-standard' treatment for cardiovascular disease (CVD), statins inhibit HMG-CoA reductase to ultimately reduce serum LDL-cholesterol levels. Unfortunately, the main adverse event of statin use is the development of muscle-associated problems, referred to as SAMS (statin-associated muscle symptoms). While regular moderate physical activity also decreases CVD risk, there is apprehension that physical activity may induce and/or exacerbate SAMS. While much work has gone into identifying the epidemiology of SAMS, only recent research has focused on the extent to which these muscle symptoms are accompanied by functional declines. The purpose of this review is to provide an overview of possible mechanisms underlying SAMS and summarize current evidence regarding the relationship between statin treatment, physical activity, exercise capacity, and SAMS development. METHODS PubMed and Google Scholar databases were used to search the most relevant and up-to-date peer-reviewed research on the topic. RESULTS The mechanism(s) behind SAMS, including altered mitochondrial metabolism, reduced coenzyme Q10 levels, reduced vitamin D levels, impaired calcium homeostasis, elevated extracellular glutamate, and genetic polymorphisms, still lack consensus and remain up for debate. Our summation of the evidence leads us to suggest that the etiology of SAMS development is likely multifactorial. Our review also demonstrates that there is limited evidence for statins impairing exercise adaptations or reducing exercise capacity for the majority of the investigated populations. CONCLUSION The available evidence indicates that the benefits of engaging in physical activity while on statin medication largely outweigh the risks.
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11
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Fernandes EC, Pechincha C, Luz LL, Kokai E, Szucs P, Safronov BV. Primary afferent-driven presynaptic inhibition of C-fiber inputs to spinal lamina I neurons. Prog Neurobiol 2020; 188:101786. [PMID: 32173398 DOI: 10.1016/j.pneurobio.2020.101786] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2019] [Revised: 02/12/2020] [Accepted: 03/03/2020] [Indexed: 01/29/2023]
Abstract
Presynaptic inhibition of primary afferent terminals is a powerful mechanism for controlling sensory information flow into the spinal cord. Lamina I is the major spinal nociceptive projecting area and monosynaptic input from C-fibers to this region represents a direct pathway for transmitting pain signals to supraspinal centers. Here we used an isolated spinal cord preparation to show that this pathway is under control of the afferent-driven GABAergic presynaptic inhibition. Presynaptic inhibition of C-fiber input to lamina I projection and local-circuit neurons is mediated by recruitment of Aβ-, Aδ- and C-afferents. C-fiber-driven inhibition of C-fibers functions as a feedforward mechanism, by which the homotypic afferents control sensory information flow into the spinal cord and regulate degree of the primary nociceptive afferent activation needed to excite the second order neurons. The presynaptic inhibition of C-fiber input to lamina I neurons may be mediated by both synaptic and non-synaptic mechanisms, and its occurrence and extent are quite heterogeneous. This heterogeneity is likely to be reflective of involvement of lamina I neurons in diverse circuitries processing specific modalities of sensory information in the superficial dorsal horn. Thus, our results implicate both low- and high-threshold afferents in the modulation of C-fiber input into the spinal cord.
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Affiliation(s)
- E C Fernandes
- Instituto De Investigação e Inovação Em Saúde, Universidade Do Porto, Porto, Portugal; Neuronal Networks Group, Instituto De Biologia Molecular e Celular (IBMC), Universidade Do Porto, Rua Alfredo Allen 208, 4200-135, Porto, Portugal
| | - C Pechincha
- Instituto De Investigação e Inovação Em Saúde, Universidade Do Porto, Porto, Portugal; Neuronal Networks Group, Instituto De Biologia Molecular e Celular (IBMC), Universidade Do Porto, Rua Alfredo Allen 208, 4200-135, Porto, Portugal
| | - L L Luz
- Instituto De Investigação e Inovação Em Saúde, Universidade Do Porto, Porto, Portugal; Neuronal Networks Group, Instituto De Biologia Molecular e Celular (IBMC), Universidade Do Porto, Rua Alfredo Allen 208, 4200-135, Porto, Portugal
| | - E Kokai
- Instituto De Investigação e Inovação Em Saúde, Universidade Do Porto, Porto, Portugal; Neuronal Networks Group, Instituto De Biologia Molecular e Celular (IBMC), Universidade Do Porto, Rua Alfredo Allen 208, 4200-135, Porto, Portugal
| | - P Szucs
- MTA-DE Neuroscience Research Group, Debrecen, Hungary; Department of Anatomy, Histology and Embryology, Faculty of Medicine, University of Debrecen, Debrecen, Hungary
| | - B V Safronov
- Instituto De Investigação e Inovação Em Saúde, Universidade Do Porto, Porto, Portugal; Neuronal Networks Group, Instituto De Biologia Molecular e Celular (IBMC), Universidade Do Porto, Rua Alfredo Allen 208, 4200-135, Porto, Portugal.
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12
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Zhang WJ, Zhu ZM, Liu ZX. The role and pharmacological properties of the P2X7 receptor in neuropathic pain. Brain Res Bull 2020; 155:19-28. [PMID: 31778766 DOI: 10.1016/j.brainresbull.2019.11.006] [Citation(s) in RCA: 38] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2019] [Revised: 11/03/2019] [Accepted: 11/11/2019] [Indexed: 02/07/2023]
Abstract
Neuropathic Pain (NPP) is caused by direct or indirect damage to the nervous system and is a common symptom of many diseases. Clinically, drugs are usually used to suppress pain, such as (lidocaine, morphine, etc.), but the effect is short-lived, poor analgesia, and there are certain dependence and side effects. Therefore, the investigation of the treatment of NPP has become an urgent problem in medical, attracting a lot of research attention. P2X7 is dependent on Adenosine triphosphate (ATP) ion channel receptors and has dual functions for the development of nerve damage and pain. In this review, we explored the link between the P2X7 receptor (P2X7R) and NPP, providing insight into the P2X7R and NPP, discussing the pathological mechanism of P2 X7R in NPP and the biological characteristics of P2X7R antagonist inhibiting its over-expression for the targeted therapy of NPP.
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Affiliation(s)
- Wen-Jun Zhang
- The Second Affiliate Hospital. Nanchang University, Nanchang City. Jiangxi Province, China; Basic Medical School, Nanchang University, Nanchang City, Jiangxi Province, China
| | - Zheng-Ming Zhu
- The Second Affiliate Hospital. Nanchang University, Nanchang City. Jiangxi Province, China.
| | - Zeng-Xu Liu
- Basic Medical School, Nanchang University, Nanchang City, Jiangxi Province, China
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13
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Regional Hyperexcitability and Chronic Neuropathic Pain Following Spinal Cord Injury. Cell Mol Neurobiol 2020; 40:861-878. [PMID: 31955281 DOI: 10.1007/s10571-020-00785-7] [Citation(s) in RCA: 22] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2019] [Accepted: 01/02/2020] [Indexed: 12/15/2022]
Abstract
Spinal cord injury (SCI) causes maladaptive changes to nociceptive synaptic circuits within the injured spinal cord. Changes also occur at remote regions including the brain stem, limbic system, cortex, and dorsal root ganglia. These maladaptive nociceptive synaptic circuits frequently cause neuronal hyperexcitability in the entire nervous system and enhance nociceptive transmission, resulting in chronic central neuropathic pain following SCI. The underlying mechanism of chronic neuropathic pain depends on the neuroanatomical structures and electrochemical communication between pre- and postsynaptic neuronal membranes, and propagation of synaptic transmission in the ascending pain pathways. In the nervous system, neurons are the only cell type that transmits nociceptive signals from peripheral receptors to supraspinal systems due to their neuroanatomical and electrophysiological properties. However, the entire range of nociceptive signaling is not mediated by any single neuron. Current literature describes regional studies of electrophysiological or neurochemical mechanisms for enhanced nociceptive transmission post-SCI, but few studies report the electrophysiological, neurochemical, and neuroanatomical changes across the entire nervous system following a regional SCI. We, along with others, have continuously described the enhanced nociceptive transmission in the spinal dorsal horn, brain stem, thalamus, and cortex in SCI-induced chronic central neuropathic pain condition, respectively. Thus, this review summarizes the current understanding of SCI-induced neuronal hyperexcitability and maladaptive nociceptive transmission in the entire nervous system that contributes to chronic central neuropathic pain.
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14
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Zheng Y, Liu P, Bai L, Trimmer JS, Bean BP, Ginty DD. Deep Sequencing of Somatosensory Neurons Reveals Molecular Determinants of Intrinsic Physiological Properties. Neuron 2019; 103:598-616.e7. [PMID: 31248728 DOI: 10.1016/j.neuron.2019.05.039] [Citation(s) in RCA: 160] [Impact Index Per Article: 32.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2018] [Revised: 04/16/2019] [Accepted: 05/23/2019] [Indexed: 02/07/2023]
Abstract
Dorsal root ganglion (DRG) sensory neuron subtypes defined by their in vivo properties display distinct intrinsic electrical properties. We used bulk RNA sequencing of genetically labeled neurons and electrophysiological analyses to define ion channel contributions to the intrinsic electrical properties of DRG neuron subtypes. The transcriptome profiles of eight DRG neuron subtypes revealed differentially expressed and functionally relevant genes, including voltage-gated ion channels. Guided by these data, electrophysiological analyses using pharmacological and genetic manipulations as well as computational modeling of DRG neuron subtypes were undertaken to assess the functions of select voltage-gated potassium channels (Kv1, Kv2, Kv3, and Kv4) in shaping action potential (AP) waveforms and firing patterns. Our findings show that the transcriptome profiles have predictive value for defining ion channel contributions to sensory neuron subtype-specific intrinsic physiological properties. The distinct ensembles of voltage-gated ion channels predicted to underlie the unique intrinsic physiological properties of eight DRG neuron subtypes are presented.
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Affiliation(s)
- Yang Zheng
- Department of Neurobiology, Harvard Medical School, Boston, MA 02115, USA; Howard Hughes Medical Institute, Harvard Medical School, Boston, MA 02115, USA; Neuroscience Training Program, Department of Neuroscience, The Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA
| | - Pin Liu
- Department of Neurobiology, Harvard Medical School, Boston, MA 02115, USA
| | - Ling Bai
- Department of Neurobiology, Harvard Medical School, Boston, MA 02115, USA; Howard Hughes Medical Institute, Harvard Medical School, Boston, MA 02115, USA; Neuroscience Training Program, Department of Neuroscience, The Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA
| | - James S Trimmer
- Department of Neurobiology, Physiology and Behavior, University of California, Davis, Davis, CA 95616, USA; Department of Physiology and Membrane Biology, University of California, Davis, Davis, CA 95616, USA
| | - Bruce P Bean
- Department of Neurobiology, Harvard Medical School, Boston, MA 02115, USA
| | - David D Ginty
- Department of Neurobiology, Harvard Medical School, Boston, MA 02115, USA; Howard Hughes Medical Institute, Harvard Medical School, Boston, MA 02115, USA.
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15
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Modulators of Kv3 Potassium Channels Rescue the Auditory Function of Fragile X Mice. J Neurosci 2019; 39:4797-4813. [PMID: 30936239 DOI: 10.1523/jneurosci.0839-18.2019] [Citation(s) in RCA: 33] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2018] [Revised: 03/15/2019] [Accepted: 03/26/2019] [Indexed: 11/21/2022] Open
Abstract
Fragile X syndrome (FXS) is characterized by hypersensitivity to sensory stimuli, including environmental sounds. We compared the auditory brainstem response (ABR) recorded in vivo in mice lacking the gene (Fmr1 -/y ) for fragile X mental retardation protein (FMRP) with that in wild-type animals. We found that ABR wave I, which represents input from the auditory nerve, is reduced in Fmr1 -/y animals, but only at high sound levels. In contrast, wave IV, which represents the activity of auditory brainstem nuclei is enhanced at all sound levels, suggesting that loss of FMRP alters the central processing of auditory signals. Current-clamp recordings of neurons in the medial nucleus of the trapezoid body in the auditory brainstem revealed that, in contrast to neurons from wild-type animals, sustained depolarization triggers repetitive firing rather than a single action potential. In voltage-clamp recordings, K+ currents that activate at positive potentials ("high-threshold" K+ currents), which are required for high-frequency firing and are carried primarily by Kv3.1 channels, are elevated in Fmr1 -/y mice, while K+ currents that activate near the resting potential and inhibit repetitive firing are reduced. We therefore tested the effects of AUT2 [((4-({5-[(4R)-4-ethyl-2,5-dioxo-1-imidazolidinyl]-2-pyridinyl}oxy)-2-(1-methylethyl) benzonitrile], a compound that modulates Kv3.1 channels. AUT2 reduced the high-threshold K+ current and increased the low-threshold K+ currents in neurons from Fmr1 -/y animals by shifting the activation of the high-threshold current to more negative potentials. This reduced the firing rate and, in vivo, restored wave IV of the ABR. Our results from animals of both sexes suggest that the modulation of the Kv3.1 channel may have potential for the treatment of sensory hypersensitivity in patients with FXS.SIGNIFICANCE STATEMENT mRNA encoding the Kv3.1 potassium channel was one of the first described targets of the fragile X mental retardation protein (FMRP). Fragile X syndrome is caused by loss of FMRP and, in humans and mice, causes hypersensitivity to auditory stimuli. We found that components of the auditory brain response (ABR) corresponding to auditory brainstem activity are enhanced in mice lacking FMRP. This is accompanied by hyperexcitability and altered potassium currents in auditory brainstem neurons. Treatment with a drug that alters the voltage dependence of Kv3.1 channels normalizes the imbalance of potassium currents, as well as ABR responses in vivo, suggesting that such compounds may be effective in treating some symptoms of fragile X syndrome.
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Zemel BM, Ritter DM, Covarrubias M, Muqeem T. A-Type K V Channels in Dorsal Root Ganglion Neurons: Diversity, Function, and Dysfunction. Front Mol Neurosci 2018; 11:253. [PMID: 30127716 PMCID: PMC6088260 DOI: 10.3389/fnmol.2018.00253] [Citation(s) in RCA: 44] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2018] [Accepted: 07/04/2018] [Indexed: 12/13/2022] Open
Abstract
A-type voltage-gated potassium (Kv) channels are major regulators of neuronal excitability that have been mainly characterized in the central nervous system. By contrast, there is a paucity of knowledge about the molecular physiology of these Kv channels in the peripheral nervous system, including highly specialized and heterogenous dorsal root ganglion (DRG) neurons. Although all A-type Kv channels display pore-forming subunits with similar structural properties and fast inactivation, their voltage-, and time-dependent properties and modulation are significantly different. These differences ultimately determine distinct physiological roles of diverse A-type Kv channels, and how their dysfunction might contribute to neurological disorders. The importance of A-type Kv channels in DRG neurons is highlighted by recent studies that have linked their dysfunction to persistent pain sensitization. Here, we review the molecular neurophysiology of A-type Kv channels with an emphasis on those that have been identified and investigated in DRG nociceptors (Kv1.4, Kv3.4, and Kv4s). Also, we discuss evidence implicating these Kv channels in neuropathic pain resulting from injury, and present a perspective of outstanding challenges that must be tackled in order to discover novel treatments for intractable pain disorders.
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Affiliation(s)
- Benjamin M. Zemel
- Vollum Institute, Oregon Health and Science University, Portland, OR, United States
| | - David M. Ritter
- Division of Neurology, Cincinnati Children's Hospital Medical Center, Cincinnati, OH, United States
| | - Manuel Covarrubias
- Department of Neuroscience, Vickie and Jack Farber Institute for Neuroscience, Sidney Kimmel Medical College and Jefferson College of Life Sciences at Thomas Jefferson University, Philadelphia, PA, United States
| | - Tanziyah Muqeem
- Department of Neuroscience, Vickie and Jack Farber Institute for Neuroscience, Sidney Kimmel Medical College and Jefferson College of Life Sciences at Thomas Jefferson University, Philadelphia, PA, United States
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