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Tang R, Chen J, Ma H, Deng J, Zhang Y, Xu Q. The association between blood nickel level and handgrip strength in patients undergoing maintenance hemodialysis. Int Urol Nephrol 2024; 56:1487-1495. [PMID: 37851212 PMCID: PMC10924028 DOI: 10.1007/s11255-023-03836-2] [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: 08/04/2023] [Accepted: 09/26/2023] [Indexed: 10/19/2023]
Abstract
BACKGROUND Progressive loss of peripheral muscle strength is highly pronounced in patients receiving maintenance hemodialysis (MHD), of which the pathological mechanism tends to be multifactorial. Plasma nickel was reportedly correlated with muscular strength in non-dialysis patients. However, scarce is known regarding the association between blood nickel level and handgrip strength among the patients undergoing MHD. METHODS This cross-sectional study included patients undergoing MHD at our center in October 2021. Blood samples were collected before the hemodialysis sessions. Nickel level was measured using inductively coupled plasma mass spectrometry. Eligible patients were stratified into three groups by the blood nickel level: tertile 1 (≥ 5.2 ug/L); tertile 2 (< 5.2 ug/L and ≥ 4.5 ug/L); and tertile 3 (< 4.5 ug/L). Handgrip strength measurement was used to evaluate the muscle status. Spearman's analyses and multivariable linear regression analyses were performed to study the relationship between blood nickel level and handgrip strength. RESULTS A total of 236 patients were enrolled, with an average age of 55.51 ± 14.27 years and a median dialysis vintage of 83 (IQR: 48-125) months. Patients in group with a higher blood nickel level (tertile 1) tended to be female, had longer dialysis vintage and higher Kt/V, but lower BMI, serum creatinine, hemoglobin, and handgrip strength level (all p < 0.05). After adjustment for confounding factors in multivariable models, for every 1ug/L increase in nickel level, the patient's handgrip strength decreases by 2.81 kg (β: - 2.810, 95% confidence interval: - 5.036 to - 0.584, p = 0.014). Restricted cubic spline confirmed the relationship was nearly linear. CONCLUSIONS Our study highlighted that blood nickel level was related to handgrip strength in patients undergoing MHD. Prospective studies with larger sample sizes are still needed to confirm the result.
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Affiliation(s)
- Ruiying Tang
- Department of Nephrology, Jiangmen Central Hospital, Jiangmen, China
| | - Jiexin Chen
- Department of Nephrology, Jiangmen Central Hospital, Jiangmen, China
| | - Huijuan Ma
- Department of Nephrology, Jiangmen Central Hospital, Jiangmen, China
| | - Jihong Deng
- Department of Nephrology, Jiangmen Central Hospital, Jiangmen, China
| | - Yanxia Zhang
- Department of Nephrology, Jiangmen Central Hospital, Jiangmen, China
| | - Qingdong Xu
- Department of Nephrology, Jiangmen Central Hospital, Jiangmen, China.
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2
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McCarthy CI, Mustafá ER, Cornejo MP, Yaneff A, Rodríguez SS, Perello M, Raingo J. Chlorpromazine, an Inverse Agonist of D1R-Like, Differentially Targets Voltage-Gated Calcium Channel (Ca V) Subtypes in mPFC Neurons. Mol Neurobiol 2023; 60:2644-2660. [PMID: 36694048 DOI: 10.1007/s12035-023-03221-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2022] [Accepted: 01/04/2023] [Indexed: 01/26/2023]
Abstract
The dopamine receptor type 1 (D1R) and the dopamine receptor type 5 (D5R), which are often grouped as D1R-like due to their sequence and signaling similarities, exhibit high levels of constitutive activity. The molecular basis for this agonist-independent activation has been well characterized through biochemical and mutagenesis in vitro studies. In this regard, it was reported that many antipsychotic drugs act as inverse agonists of D1R-like constitutive activity. On the other hand, D1R is highly expressed in the medial prefrontal cortex (mPFC), a brain area with important functions such as working memory. Here, we studied the impact of D1R-like constitutive activity and chlorpromazine (CPZ), an antipsychotic drug and D1R-like inverse agonist, on various neuronal CaV conductances, and we explored its effect on calcium-dependent neuronal functions in the mouse medial mPFC. Using ex vivo brain slices containing the mPFC and transfected HEK293T cells, we found that CPZ reduces CaV2.2 currents by occluding D1R-like constitutive activity, in agreement with a mechanism previously reported by our lab, whereas CPZ directly inhibits CaV1 currents in a D1R-like activity independent manner. In contrast, CPZ and D1R constitutive activity did not affect CaV2.1, CaV2.3, or CaV3 currents. Finally, we found that CPZ reduces excitatory postsynaptic responses in mPFC neurons. Our results contribute to understanding CPZ molecular targets in neurons and describe a novel physiological consequence of CPZ non-canonical action as a D1R-like inverse agonist in the mouse brain.
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Affiliation(s)
- Clara Inés McCarthy
- Electrophysiology Laboratory of the Multidisciplinary Institute of Cell Biology (Argentine Research Council CONICET, Scientific Research Commission of the Buenos Aires Province and National University of La Plata), La Plata, Buenos Aires, Argentina
| | - Emilio Román Mustafá
- Electrophysiology Laboratory of the Multidisciplinary Institute of Cell Biology (Argentine Research Council CONICET, Scientific Research Commission of the Buenos Aires Province and National University of La Plata), La Plata, Buenos Aires, Argentina
| | - María Paula Cornejo
- Neurophysiology Laboratory of the Multidisciplinary Institute of Cell Biology (Argentine Research Council CONICET, Scientific Research Commission of the Buenos Aires Province and National University of La Plata), La Plata, Buenos Aires, Argentina
| | - Agustín Yaneff
- Instituto de Investigaciones Farmacológicas, Facultad de Farmacia y Bioquímica, Universidad de Buenos Aires, Buenos Aires, Argentina
| | - Silvia Susana Rodríguez
- Electrophysiology Laboratory of the Multidisciplinary Institute of Cell Biology (Argentine Research Council CONICET, Scientific Research Commission of the Buenos Aires Province and National University of La Plata), La Plata, Buenos Aires, Argentina
| | - Mario Perello
- Neurophysiology Laboratory of the Multidisciplinary Institute of Cell Biology (Argentine Research Council CONICET, Scientific Research Commission of the Buenos Aires Province and National University of La Plata), La Plata, Buenos Aires, Argentina
- Department of Surgical Sciences, Functional Pharmacology and Neuroscience, University of Uppsala, Uppsala, Sweden
| | - Jesica Raingo
- Electrophysiology Laboratory of the Multidisciplinary Institute of Cell Biology (Argentine Research Council CONICET, Scientific Research Commission of the Buenos Aires Province and National University of La Plata), La Plata, Buenos Aires, Argentina.
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3
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Martinez Damonte V, Pomrenze MB, Manning CE, Casper C, Wolfden AL, Malenka RC, Kauer JA. Somatodendritic Release of Cholecystokinin Potentiates GABAergic Synapses Onto Ventral Tegmental Area Dopamine Cells. Biol Psychiatry 2023; 93:197-208. [PMID: 35961792 PMCID: PMC9976994 DOI: 10.1016/j.biopsych.2022.06.011] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/31/2022] [Revised: 06/01/2022] [Accepted: 06/10/2022] [Indexed: 11/02/2022]
Abstract
BACKGROUND Neuropeptides are contained in nearly every neuron in the central nervous system and can be released not only from nerve terminals but also from somatodendritic sites. Cholecystokinin (CCK), among the most abundant neuropeptides in the brain, is expressed in the majority of midbrain dopamine neurons. Despite this high expression, CCK function within the ventral tegmental area (VTA) is not well understood. METHODS We confirmed CCK expression in VTA dopamine neurons through immunohistochemistry and in situ hybridization and detected optogenetically induced CCK release using an enzyme-linked immunosorbent assay. To investigate whether CCK modulates VTA circuit activity, we used whole-cell patch clamp recordings in mouse brain slices. We infused CCK locally in vivo and tested food intake and locomotion in fasted mice. We also used in vivo fiber photometry to measure Ca2+ transients in dopamine neurons during feeding. RESULTS Here we report that VTA dopamine neurons release CCK from somatodendritic regions, where it triggers long-term potentiation of GABAergic (gamma-aminobutyric acidergic) synapses. The somatodendritic release occurs during trains of optogenetic stimuli or prolonged but modest depolarization and is dependent on synaptotagmin-7 and T-type Ca2+ channels. Depolarization-induced long-term potentiation is blocked by a CCK2 receptor antagonist and mimicked by exogenous CCK. Local infusion of CCK in vivo inhibits food consumption and decreases distance traveled in an open field test. Furthermore, intra-VTA-infused CCK reduced dopamine cell Ca2+ signals during food consumption after an overnight fast and was correlated with reduced food intake. CONCLUSIONS Our experiments introduce somatodendritic neuropeptide release as a previously unknown feedback regulator of VTA dopamine cell excitability and dopamine-related behaviors.
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4
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Plasma Nickel Levels Correlate with Low Muscular Strength and Renal Function Parameters in Patients with Prostate Cancer. Diseases 2022; 10:diseases10030039. [PMID: 35892733 PMCID: PMC9326612 DOI: 10.3390/diseases10030039] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2022] [Revised: 06/20/2022] [Accepted: 06/29/2022] [Indexed: 02/04/2023] Open
Abstract
Nickel is associated with cancer in occupational exposure. However, few studies have been devoted to analyzing the effects of nickel at environmental concentrations in cancer patients. In this work, the concentration of nickel in blood samples from patients with prostate cancer (PCa) was evaluated because this metal displays androgenic and estrogenic effects that play a crucial role in prostate carcinogenesis and treatment. We, therefore, compared blood nickel concentration in patients with PCa (non-occupationally exposed) (n = 46) with those in control age-matched individuals (n = 46). We also analyzed if there was any association between sociodemographic factors, clinical variables, geriatric evaluation assessment results, blood cell counts, or biochemical, androgen and estrogen concentrations. Using inductively coupled plasma-mass spectroscopy on the plasma samples, we observed a mean nickel level of 4.97 ± 1.20 µg/L in the PCa group and 3.59 ± 0.49 µg/L in the control group, with a non-significant effect (p = 0.293) between the two groups. The nickel concentration was significantly correlated with patient age (p = 0.005) and reduced handgrip strength (p = 0.003). Regarding biochemical parameters, significant associations were found with the renal glomerular filtration rate (p = 0.024) and blood urea levels (p = 0.016). No significant correlations were observed with other blood analytical parameters or testosterone or estradiol levels. These specific renal function and muscle strength effects were observed at environmental nickel exposure levels believed to be safe or at least far from the high concentrations observed after occupational exposure. Therefore, these parameters deserve further study, given that they could help pinpoint further public health concerns regarding nickel exposure in the general population.
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5
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Harding EK, Zamponi GW. Central and peripheral contributions of T-type calcium channels in pain. Mol Brain 2022; 15:39. [PMID: 35501819 PMCID: PMC9063214 DOI: 10.1186/s13041-022-00923-w] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2022] [Accepted: 04/13/2022] [Indexed: 02/06/2023] Open
Abstract
AbstractChronic pain is a severely debilitating condition that reflects a long-term sensitization of signal transduction in the afferent pain pathway. Among the key players in this pathway are T-type calcium channels, in particular the Cav3.2 isoform. Because of their biophysical characteristics, these channels are ideally suited towards regulating neuronal excitability. Recent evidence suggests that T-type channels contribute to excitability of neurons all along the ascending and descending pain pathways, within primary afferent neurons, spinal dorsal horn neurons, and within pain-processing neurons in the midbrain and cortex. Here we review the contribution of T-type channels to neuronal excitability and function in each of these neuronal populations and how they are dysregulated in chronic pain conditions. Finally, we discuss their molecular pharmacology and the potential role of these channels as therapeutic targets for chronic pain.
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6
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Shao J, Liu Y, Gao D, Tu J, Yang F. Neural Burst Firing and Its Roles in Mental and Neurological Disorders. Front Cell Neurosci 2021; 15:741292. [PMID: 34646123 PMCID: PMC8502892 DOI: 10.3389/fncel.2021.741292] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2021] [Accepted: 08/26/2021] [Indexed: 11/29/2022] Open
Abstract
Neural firing patterns are critical for specific information coding and transmission, and abnormal firing is implicated in a series of neural pathologies. Recent studies have indicated that enhanced burst firing mediated by T-type voltage-gated calcium channels (T-VGCCs) in specific neuronal subtypes is involved in several mental or neurological disorders such as depression and epilepsy, while suppression of T-VGCCs relieve related symptoms. Burst firing consists of groups of relatively high-frequency spikes separated by quiescence. Neurons in a variety of brain areas, including the thalamus, hypothalamus, cortex, and hippocampus, display burst firing, but the ionic mechanisms that generating burst firing and the related physiological functions vary among regions. In this review, we summarize recent findings on the mechanisms underlying burst firing in various brain areas, as well as the roles of burst firing in several mental and neurological disorders. We also discuss the ion channels and receptors that may regulate burst firing directly or indirectly, with these molecules highlighted as potential intervention targets for the treatment of mental and neurological disorders.
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Affiliation(s)
- Jie Shao
- The Brain Cognition and Brain Disease Institute, Shenzhen Institute of Advanced Technology, Chinese Academy of Sciences, Shenzhen-Hong Kong Institute of Brain Science-Shenzhen Fundamental Research Institutions, Shenzhen, China.,Shenzhen College of Advanced Technology, University of Chinese Academy of Sciences, Beijing, China
| | - Yunhui Liu
- The Brain Cognition and Brain Disease Institute, Shenzhen Institute of Advanced Technology, Chinese Academy of Sciences, Shenzhen-Hong Kong Institute of Brain Science-Shenzhen Fundamental Research Institutions, Shenzhen, China
| | - Dashuang Gao
- The Brain Cognition and Brain Disease Institute, Shenzhen Institute of Advanced Technology, Chinese Academy of Sciences, Shenzhen-Hong Kong Institute of Brain Science-Shenzhen Fundamental Research Institutions, Shenzhen, China.,Shenzhen College of Advanced Technology, University of Chinese Academy of Sciences, Beijing, China
| | - Jie Tu
- The Brain Cognition and Brain Disease Institute, Shenzhen Institute of Advanced Technology, Chinese Academy of Sciences, Shenzhen-Hong Kong Institute of Brain Science-Shenzhen Fundamental Research Institutions, Shenzhen, China.,Shenzhen College of Advanced Technology, University of Chinese Academy of Sciences, Beijing, China
| | - Fan Yang
- The Brain Cognition and Brain Disease Institute, Shenzhen Institute of Advanced Technology, Chinese Academy of Sciences, Shenzhen-Hong Kong Institute of Brain Science-Shenzhen Fundamental Research Institutions, Shenzhen, China.,Shenzhen College of Advanced Technology, University of Chinese Academy of Sciences, Beijing, China
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7
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Neumaier F, Alpdogan S, Hescheler J, Schneider T. Zn2+-induced changes in Cav2.3 channel function: An electrophysiological and modeling study. J Gen Physiol 2021; 152:151872. [PMID: 32559275 PMCID: PMC7478874 DOI: 10.1085/jgp.202012585] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2020] [Revised: 04/30/2020] [Accepted: 05/19/2020] [Indexed: 01/25/2023] Open
Abstract
Loosely bound Zn2+ ions are increasingly recognized as potential modulators of synaptic plasticity and neuronal excitability under normal and pathophysiological conditions. Cav2.3 voltage-gated Ca2+ channels are among the most sensitive targets of Zn2+ and are therefore likely to be involved in the neuromodulatory actions of endogenous Zn2+. Although histidine residues on the external side of domain I have been implicated in the effects on Cav2.3 channel gating, the exact mechanisms involved in channel modulation remain incompletely understood. Here, we use a combination of electrophysiological recordings, modification of histidine residues, and computational modeling to analyze Zn2+-induced changes in Cav2.3 channel function. Our most important findings are that multiple high- and low-affinity mechanisms contribute to the net Zn2+ action, that Zn2+ can either inhibit or stimulate Ca2+ influx through Cav2.3 channels depending on resting membrane potential, and that Zn2+ effects may persist for some time even after cessation of the Zn2+ signal. Computer simulations show that (1) most salient features of Cav2.3 channel gating in the absence of trace metals can be reproduced by an obligatory model in which activation of two voltage sensors is necessary to open the pore; and (2) most, but not all, of the effects of Zn2+ can be accounted for by assuming that Zn2+ binding to a first site is associated with an electrostatic modification and mechanical slowing of one of the voltage sensors, whereas Zn2+ binding to a second, lower-affinity site blocks the channel and modifies the opening and closing transitions. While still far from complete, our model provides a first quantitative framework for understanding Zn2+ effects on Cav2.3 channel function and a step toward the application of computational approaches for predicting the complex actions of Zn2+ on neuronal excitability.
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Affiliation(s)
- Felix Neumaier
- University of Cologne, Faculty of Medicine and University Hospital Cologne, Institute for Neurophysiology, Cologne, Germany
| | - Serdar Alpdogan
- University of Cologne, Faculty of Medicine and University Hospital Cologne, Institute for Neurophysiology, Cologne, Germany
| | - Jürgen Hescheler
- University of Cologne, Faculty of Medicine and University Hospital Cologne, Institute for Neurophysiology, Cologne, Germany
| | - Toni Schneider
- University of Cologne, Faculty of Medicine and University Hospital Cologne, Institute for Neurophysiology, Cologne, Germany
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8
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Purkinje cell axonal swellings enhance action potential fidelity and cerebellar function. Nat Commun 2021; 12:4129. [PMID: 34226561 PMCID: PMC8257784 DOI: 10.1038/s41467-021-24390-4] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2020] [Accepted: 06/11/2021] [Indexed: 11/08/2022] Open
Abstract
Axonal plasticity allows neurons to control their output, which critically determines the flow of information in the brain. Axon diameter can be regulated by activity, yet how morphological changes in an axon impact its function remains poorly understood. Axonal swellings have been found on Purkinje cell axons in the cerebellum both in healthy development and in neurodegenerative diseases, and computational models predicts that axonal swellings impair axonal function. Here we report that in young Purkinje cells, axons with swellings propagated action potentials with higher fidelity than those without, and that axonal swellings form when axonal failures are high. Furthermore, we observed that healthy young adult mice with more axonal swellings learn better on cerebellar-related tasks than mice with fewer swellings. Our findings suggest that axonal swellings underlie a form of axonal plasticity that optimizes the fidelity of action potential propagation in axons, resulting in enhanced learning.
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9
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Parker PD, Suryavanshi P, Melone M, Sawant-Pokam PA, Reinhart KM, Kaufmann D, Theriot JJ, Pugliese A, Conti F, Shuttleworth CW, Pietrobon D, Brennan KC. Non-canonical glutamate signaling in a genetic model of migraine with aura. Neuron 2021; 109:611-628.e8. [PMID: 33321071 PMCID: PMC7889497 DOI: 10.1016/j.neuron.2020.11.018] [Citation(s) in RCA: 33] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/30/2019] [Revised: 10/09/2020] [Accepted: 11/17/2020] [Indexed: 12/13/2022]
Abstract
Migraine with aura is a common but poorly understood sensory circuit disorder. Monogenic models allow an opportunity to investigate its mechanisms, including spreading depolarization (SD), the phenomenon underlying migraine aura. Using fluorescent glutamate imaging, we show that awake mice carrying a familial hemiplegic migraine type 2 (FHM2) mutation have slower clearance during sensory processing, as well as previously undescribed spontaneous "plumes" of glutamate. Glutamatergic plumes overlapped anatomically with a reduced density of GLT-1a-positive astrocyte processes and were mimicked in wild-type animals by inhibiting glutamate clearance. Plume pharmacology and plume-like neural Ca2+ events were consistent with action-potential-independent spontaneous glutamate release, suggesting plumes are a consequence of inefficient clearance following synaptic release. Importantly, a rise in basal glutamate and plume frequency predicted the onset of SD in both FHM2 and wild-type mice, providing a novel mechanism in migraine with aura and, by extension, the other neurological disorders where SD occurs.
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Affiliation(s)
- Patrick D Parker
- Department of Neurology, University of Utah School of Medicine, Salt Lake City, UT 84108, USA; Interdepartmental Program in Neuroscience, University of Utah School of Medicine, Salt Lake City, UT 84108, USA
| | - Pratyush Suryavanshi
- Department of Neurology, University of Utah School of Medicine, Salt Lake City, UT 84108, USA; Interdepartmental Program in Neuroscience, University of Utah School of Medicine, Salt Lake City, UT 84108, USA
| | - Marcello Melone
- Section of Neuroscience and Cell Biology, Department of Experimental and Clinical Medicine, Università Politecnica delle Marche, Ancona 60020, Italy; Center for Neurobiology of Aging, IRCCS INRCA, Ancona 60020, Italy
| | - Punam A Sawant-Pokam
- Department of Neurology, University of Utah School of Medicine, Salt Lake City, UT 84108, USA
| | - Katelyn M Reinhart
- Department of Neurology, University of Utah School of Medicine, Salt Lake City, UT 84108, USA; Department of Neurosciences, University of New Mexico School of Medicine, Albuquerque, NM 87106, USA
| | - Dan Kaufmann
- Department of Neurology, University of Utah School of Medicine, Salt Lake City, UT 84108, USA
| | - Jeremy J Theriot
- Department of Neurology, University of Utah School of Medicine, Salt Lake City, UT 84108, USA
| | - Arianna Pugliese
- Section of Neuroscience and Cell Biology, Department of Experimental and Clinical Medicine, Università Politecnica delle Marche, Ancona 60020, Italy
| | - Fiorenzo Conti
- Section of Neuroscience and Cell Biology, Department of Experimental and Clinical Medicine, Università Politecnica delle Marche, Ancona 60020, Italy; Center for Neurobiology of Aging, IRCCS INRCA, Ancona 60020, Italy; Foundation for Molecular Medicine, Università Politecnica delle Marche, Ancona 60020, Italy
| | - C William Shuttleworth
- Department of Neurosciences, University of New Mexico School of Medicine, Albuquerque, NM 87106, USA
| | - Daniela Pietrobon
- Department of Biomedical Sciences and Padova Neuroscience Center (PNC), University of Padova, 35131 Padova, Italy; CNR Institute of Neuroscience, 35131 Padova, Italy.
| | - K C Brennan
- Department of Neurology, University of Utah School of Medicine, Salt Lake City, UT 84108, USA.
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10
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Neumaier F, Schneider T, Albanna W. Ca v2.3 channel function and Zn 2+-induced modulation: potential mechanisms and (patho)physiological relevance. Channels (Austin) 2020; 14:362-379. [PMID: 33079629 PMCID: PMC7583514 DOI: 10.1080/19336950.2020.1829842] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022] Open
Abstract
Voltage-gated calcium channels (VGCCs) are critical for Ca2+ influx into all types of excitable cells, but their exact function is still poorly understood. Recent reconstruction of homology models for all human VGCCs at atomic resolution provides the opportunity for a structure-based discussion of VGCC function and novel insights into the mechanisms underlying Ca2+ selective flux through these channels. In the present review, we use these data as a basis to examine the structure, function, and Zn2+-induced modulation of Cav2.3 VGCCs, which mediate native R-type currents and belong to the most enigmatic members of the family. Their unique sensitivity to Zn2+ and the existence of multiple mechanisms of Zn2+ action strongly argue for a role of these channels in the modulatory action of endogenous loosely bound Zn2+, pools of which have been detected in a number of neuronal, endocrine, and reproductive tissues. Following a description of the different mechanisms by which Zn2+ has been shown or is thought to alter the function of these channels, we discuss their potential (patho)physiological relevance, taking into account what is known about the magnitude and function of extracellular Zn2+ signals in different tissues. While still far from complete, the picture that emerges is one where Cav2.3 channel expression parallels the occurrence of loosely bound Zn2+ pools in different tissues and where these channels may serve to translate physiological Zn2+ signals into changes of electrical activity and/or intracellular Ca2+ levels.
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Affiliation(s)
- Felix Neumaier
- Forschungszentrum Jülich GmbH, Institute of Neuroscience and Medicine, Nuclear Chemistry (INM-5) , Jülich, Germany.,University of Cologne, Faculty of Medicine and University Hospital Cologne, Institute of Radiochemistry and Experimental Molecular Imaging , Cologne, Germany
| | - Toni Schneider
- Institute of Neurophysiology , Faculty of Medicine and University Hospital Cologne, Cologne, Germany
| | - Walid Albanna
- Department of Neurosurgery, RWTH Aachen University , Aachen, Germany
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11
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Rey S, Maton G, Satake S, Llano I, Kang S, Surmeier DJ, Silverman RB, Collin T. Physiological involvement of presynaptic L-type voltage-dependent calcium channels in GABA release of cerebellar molecular layer interneurons. J Neurochem 2020; 155:390-402. [PMID: 32491217 DOI: 10.1111/jnc.15100] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2019] [Revised: 05/11/2020] [Accepted: 05/27/2020] [Indexed: 12/30/2022]
Abstract
While high threshold voltage-dependent Ca2+ channels (VDCCs) of the N and P/Q families are crucial for evoked neurotransmitter release in the mammalian CNS, it remains unclear to what extent L-type Ca2+ channels (LTCCs), which have been mainly considered as acting at postsynaptic sites, participate in the control of transmitter release. Here, we investigate the possible role of LTCCs in regulating GABA release by cerebellar molecular layer interneurons (MLIs) from rats. We found that BayK8644 (BayK) markedly increases mIPSC frequency in MLIs and Purkinje cells (PCs), suggesting that LTCCs are expressed presynaptically. Furthermore, we observed (1) a potentiation of evoked IPSCs in the presence of BayK, (2) an inhibition of evoked IPSCs in the presence of the LTCC-specific inhibitor Compound 8 (Cp8), and (3) a strong reduction of mIPSC frequency by Cp8. BayK effects are reduced by dantrolene, suggesting that ryanodine receptors act in synergy with LTCCs. Finally, BayK enhances presynaptic AP-evoked Ca2+ transients and increases the frequency of spontaneous axonal Ca2+ transients observed in TTX. Taken together, our data demonstrate that LTCCs are of primary importance in regulating GABA release by MLIs.
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Affiliation(s)
- Stéphanie Rey
- Saints Pères Paris Institute for the Neurociences CNRS-UMR 8003, Université de Paris, Paris, France
| | - Gilliane Maton
- Institut Jacques Monod, CNRS/Université de Paris - Bâtiment Buffon, Paris, France
| | - Shin'Ichiro Satake
- Departement of Infornation Physiology, National Institute for Physiological Sciences (NIPS), Okazaki, Japan
| | - Isabel Llano
- Saints Pères Paris Institute for the Neurociences CNRS-UMR 8003, Université de Paris, Paris, France
| | - Soosung Kang
- Department of Chemistry, Chemistry of Life Processes Institute, Northwestern University, Evanston, IL, USA
| | - Dalton James Surmeier
- Department of Physiology, Feinberg School of Medicine, Northwestern University, Chicago, IL, USA
| | - Richard B Silverman
- Department of Chemistry, Chemistry of Life Processes Institute, Northwestern University, Evanston, IL, USA
| | - Thibault Collin
- Saints Pères Paris Institute for the Neurociences CNRS-UMR 8003, Université de Paris, Paris, France
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12
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Dukes MP, Rowe RK, Harvey T, Rangel W, Pedigo S. Nickel reduces calcium dependent dimerization in neural cadherin. Metallomics 2020; 11:475-482. [PMID: 30624456 DOI: 10.1039/c8mt00349a] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
Cadherins are the transmembrane component in adherens junctions, structures that link the actin cytoskeletons in adjacent cells within solid tissues including neurological synapses, epithelium and endothelium. Cell-cell adhesion by cadherins requires the binding of calcium ions to specific sites in the extracellular region. Given the complexity of the cell adhesion microenvironment, we are investigating whether other divalent cations might affect calcium-dependent dimerization of neural (N) cadherin. The studies reported herein characterize the impact of binding physiological magnesium(ii) or neurotoxic nickel(ii) on calcium-dependent N-cadherin function. Physiological levels of magnesium have only a small effect on the calcium-binding affinity and calcium-induced dimerization of N-cadherin. However, a tenfold lower concentration of nickel decreases the apparent calcium-binding affinity and calcium-induced dimerization of N-cadherin. Competitive binding studies indicate that the apparent dissociation constants for nickel and magnesium are 0.2 mM and 2.5 mM, respectively. These Kd values are consistent with concentrations observed for a range of divalent cations in the extracellular space. Results from these studies indicate that calcium-induced dimerization by N-cadherin is attenuated by natural and non-physiological divalent cations in the extracellular microenvironment.
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Affiliation(s)
- M P Dukes
- Department of Chemistry and Biochemistry, University of Mississippi, University, MS 38677, USA.
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Martínez-Martínez MI, Muñoz-Fambuena I, Cauli O. Neurotransmitters and Behavioral Alterations Induced by Nickel Exposure. Endocr Metab Immune Disord Drug Targets 2019; 20:985-991. [PMID: 31789138 DOI: 10.2174/1871530319666191202141209] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/02/2019] [Revised: 03/06/2019] [Accepted: 03/29/2019] [Indexed: 11/22/2022]
Abstract
BACKGROUND Nickel ions (Ni2+) are a heavy metal with wide industrial uses. Environmental and occupational exposures to Ni are potential risk factors for brain dysfunction and behavioral and neurological symptoms in humans. METHODS We reviewed the current evidence about neurochemical and behavioral alterations associated with Ni exposure in laboratory animals and humans. RESULTS Ni2+ exposure can alter (both inhibition and stimulation) dopamine release and inhibit glutamate NMDA receptors. Few reports claim an effect of Ni2+ at the level of GBA and serotonin neurotransmission. At behavioral levels, exposure to Ni2+ in rodents alters motor activity, learning and memory as well as anxiety and depressive-like symptoms. However, no analysis of the dose-dependent relationship has been carried out regarding these effects and the levels of the Ni2+ in the brain, in blood or urine. CONCLUSION Further research is needed to correlate the concentration of Ni2+ in biological fluids with specific symptoms/deficits. Future studies addressing the impact of Ni2+ under environmental or occupational exposure should consider the administration protocols to find Ni2+ levels similar in the general population or occupationally exposed workers.
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Affiliation(s)
| | | | - Omar Cauli
- Department of Nursing, University of Valencia, 46010 Valencia, Spain
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14
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Mustafá ER, Cordisco Gonzalez S, Raingo J. Ghrelin Selectively Inhibits CaV3.3 Subtype of Low-Voltage-Gated Calcium Channels. Mol Neurobiol 2019; 57:722-735. [DOI: 10.1007/s12035-019-01738-y] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2019] [Accepted: 08/16/2019] [Indexed: 01/01/2023]
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15
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Disruption of GpI mGluR-Dependent Cav2.3 Translation in a Mouse Model of Fragile X Syndrome. J Neurosci 2019; 39:7453-7464. [PMID: 31350260 DOI: 10.1523/jneurosci.1443-17.2019] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2017] [Revised: 06/13/2019] [Accepted: 06/19/2019] [Indexed: 11/21/2022] Open
Abstract
Fragile X syndrome (FXS) is an inherited intellectual impairment that results from the loss of fragile X mental retardation protein (FMRP), an mRNA binding protein that regulates mRNA translation at synapses. The absence of FMRP leads to neuronal and circuit-level hyperexcitability that is thought to arise from the aberrant expression and activity of voltage-gated ion channels, although the identification and characterization of these ion channels have been limited. Here, we show that FMRP binds the mRNA of the R-type voltage-gated calcium channel Cav2.3 in mouse brain synaptoneurosomes and represses Cav2.3 translation under basal conditions. Consequently, in hippocampal neurons from male and female FMRP KO mice, we find enhanced Cav2.3 protein expression by western blotting and abnormally large R currents in whole-cell voltage-clamp recordings. In agreement with previous studies showing that FMRP couples Group I metabotropic glutamate receptor (GpI mGluR) signaling to protein translation, we find that GpI mGluR stimulation results in increased Cav2.3 translation and R current in hippocampal neurons which is disrupted in FMRP KO mice. Thus, FMRP serves as a key translational regulator of Cav2.3 expression under basal conditions and in response to GpI mGluR stimulation. Loss of regulated Cav2.3 expression could underlie the neuronal hyperactivity and aberrant calcium spiking in FMRP KO mice and contribute to FXS, potentially serving as a novel target for future therapeutic strategies.SIGNIFICANCE STATEMENT Patients with fragile X syndrome (FXS) exhibit signs of neuronal and circuit hyperexcitability, including anxiety and hyperactive behavior, attention deficit disorder, and seizures. FXS is caused by the loss of fragile X mental retardation protein (FMRP), an mRNA binding protein, and the neuronal hyperexcitability observed in the absence of FMRP likely results from its ability to regulate the expression and activity of voltage-gated ion channels. Here we find that FMRP serves as a key translational regulator of the voltage-gated calcium channel Cav2.3 under basal conditions and following activity. Cav2.3 impacts cellular excitability and calcium signaling, and the alterations in channel translation and expression observed in the absence of FMRP could contribute to the neuronal hyperactivity that underlies FXS.
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16
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McNally BA, Plante AE, Meredith AL. Diurnal properties of voltage-gated Ca 2+ currents in suprachiasmatic nucleus and roles in action potential firing. J Physiol 2019; 598:1775-1790. [PMID: 31177540 DOI: 10.1113/jp278327] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2019] [Accepted: 06/06/2019] [Indexed: 02/04/2023] Open
Abstract
KEY POINTS Circadian oscillations in spontaneous action potential firing in the suprachiasmatic nucleus (SCN) translate time-of-day throughout the mammalian brain. The ion channels that regulate the circadian pattern of SCN firing have not been comprehensively identified. Ca2+ channels regulate action potential activity across many types of excitable cells, and the activity of L-, N-, P/Q- and R-type channels are required for normal daytime firing frequency in SCN neurons and circuit rhythms. Only the L-type Ca2+ current exhibits a day versus night difference in current magnitude, providing insight into the mechanism that produces rhythmic action potential firing in SCN. ABSTRACT The mammalian circadian clock encodes time via rhythmic action potential activity in the suprachiasmatic nucleus (SCN) of the hypothalamus, which governs daily rhythms in physiology and behaviour. SCN neurons exhibit 24 h oscillations in spontaneous firing, with higher firing during day compared to night. Several ionic currents have been identified that regulate SCN firing, including voltage-gated Ca2+ currents, but the circadian regulation of distinct voltage-gated Ca2+ channel (VGCC) components has not been comprehensively addressed. In this study, whole-cell L- (nimodipine-sensitive), N- and P/Q- (ω-agatoxin IVA, ω-conotoxin GVIA, ω-conotoxin MVIIC-sensitive), R- (Ni2+ -sensitive) and T-type (TTA-P2-sensitive) currents were recorded from day and night SCN slices. Using standard voltage protocols, Ni2+ -sensitive currents comprised the largest proportion of total VGCC current, followed by nimodipine-, ω-agatoxin IVA-, ω-conotoxin GVIA- and TTA-P2-sensitive currents. Only the nimodipine-sensitive current exhibited a diurnal difference in magnitude, with daytime current larger than night. No diurnal variation was observed for the other Ca2+ current subtypes. The difference in nimodipine-sensitive current was due to larger peak current activated during the day, not differences in inactivation, and was eliminated by Bay K8644. Blocking L-type channels decreased firing selectively during the day, consistent with higher current magnitudes, and reduced SCN circuit rhythmicity recorded by multi-electrode arrays. Yet blocking N-, P/Q- and R-type channels also decreased daytime firing, with little effect at night, and decreased circuit rhythmicity. These data identify a unique diurnal regulation of L-type current among the major VGCC subtypes in SCN neurons, but also reveal that diurnal modulation is not required for time-of-day-specific effects on firing and circuit rhythmicity.
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Affiliation(s)
- Beth A McNally
- Department of Physiology, University of Maryland School of Medicine, Baltimore, MD, 21201, USA
| | - Amber E Plante
- Department of Physiology, University of Maryland School of Medicine, Baltimore, MD, 21201, USA
| | - Andrea L Meredith
- Department of Physiology, University of Maryland School of Medicine, Baltimore, MD, 21201, USA
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17
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Gutzmann JJ, Lin L, Hoffman DA. Functional Coupling of Cav2.3 and BK Potassium Channels Regulates Action Potential Repolarization and Short-Term Plasticity in the Mouse Hippocampus. Front Cell Neurosci 2019; 13:27. [PMID: 30846929 PMCID: PMC6393364 DOI: 10.3389/fncel.2019.00027] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2018] [Accepted: 01/22/2019] [Indexed: 11/13/2022] Open
Abstract
Voltage-gated ion channels are essential for signal generation and propagation in neurons and other excitable cells. The high-voltage activated calcium-channel Cav2.3 is expressed throughout the central and peripheral nervous system, and within CA1 hippocampal pyramidal neurons it is localized throughout the somato-dendritic region and dendritic spines. Cav2.3 has been shown to provide calcium for other calcium-dependent potassium channels including small-conductance calcium-activated potassium channels (SK), but big-conductance calcium-activated potassium channels (BK) have been thought to be activated by calcium from all known voltage-gated calcium channels, except Cav2.3. Here we show for the first time that CA1 pyramidal cells which lack Cav2.3 show altered action potential (AP) waveforms, which can be traced back to reduced SK- and BK-channel function. This change in AP waveform leads to strengthened synaptic transmission between CA1 and the subiculum, resulting in increased short-term plasticity. Our results demonstrate that Cav2.3 impacts cellular excitability through functional interaction with BK channels, impacting communication between hippocampal subregions.
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Affiliation(s)
- Jakob J Gutzmann
- Molecular Neurophysiology and Biophysics Section, Program in Developmental Neuroscience, Eunice Kennedy Shriver National Institute of Child Health and Human Development (NICHD), National Institutes of Health (NIH), Bethesda, MD, United States
| | - Lin Lin
- Molecular Neurophysiology and Biophysics Section, Program in Developmental Neuroscience, Eunice Kennedy Shriver National Institute of Child Health and Human Development (NICHD), National Institutes of Health (NIH), Bethesda, MD, United States
| | - Dax A Hoffman
- Molecular Neurophysiology and Biophysics Section, Program in Developmental Neuroscience, Eunice Kennedy Shriver National Institute of Child Health and Human Development (NICHD), National Institutes of Health (NIH), Bethesda, MD, United States
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18
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Yaeger DB, Coddington EJ. Calcium-induced calcium release activates spontaneous miniature outward currents in newt medullary reticular formation neurons. J Neurophysiol 2018; 120:3140-3154. [PMID: 29897864 DOI: 10.1152/jn.00616.2017] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
Abstract
Neurons in the medullary reticular formation are involved in the control of postural and locomotor behaviors in all vertebrates. Reticulospinal neurons in this brain region provide one of the major descending projections to the spinal cord. Although neurons in the newt medullary reticular formation have been extensively studied using in vivo extracellular recordings, little is known of their intrinsic biophysical properties or of the underlying circuitry of this region. Using whole cell patch-clamp recordings in brain slices containing the rostromedial reticular formation from adult male newts, we observed spontaneous miniature outward currents (SMOCs) in ~2/3 of neurons. Although SMOCs superficially resembled inhibitory postsynaptic currents (IPSCs), they had slower risetimes and decay times than spontaneous IPSCs. SMOCs required intracellular Ca2+ release from ryanodine receptors and were also dependent on the influx of extracellular Ca2+. SMOCs were unaffected by apamin but were partially blocked by iberiotoxin and charybdotoxin, indicating that SMOCs were mediated by big-conductance Ca2+-activated K+ channels. Application of the sarco/endoplasmic Ca2+ ATPase inhibitor cyclopiazonic acid blocked the generation of SMOCs and also increased neural excitability. Neurons with SMOCs had significantly broader action potentials, slower membrane time constants, and higher input resistance than neurons without SMOCs. Thus, SMOCs may serve as a mechanism to regulate action potential threshold in a majority of neurons within the newt medullary reticular formation. NEW & NOTEWORTHY The medullary reticular formation exerts a powerful influence on sensorimotor integration and subsequent motor behavior, yet little is known about the neurons involved. In this study, we identify a transient potassium current that regulates action potential threshold in a majority of medullary reticular neurons.
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19
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Wang D, Ragnarsson L, Lewis RJ. T-type Calcium Channels in Health and Disease. Curr Med Chem 2018; 27:3098-3122. [PMID: 30277145 DOI: 10.2174/0929867325666181001112821] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2018] [Revised: 08/28/2018] [Accepted: 08/30/2018] [Indexed: 12/12/2022]
Abstract
Low Voltage-Activated (LVA) T-type calcium channels are characterized by transient current and Low Threshold Spikes (LTS) that trigger neuronal firing and oscillatory behavior. Combined with their preferential localization in dendrites and their specific "window current", T-type calcium channels are considered to be key players in signal amplification and synaptic integration. Assisted by the emerging pharmacological tools, the structural determinants of channel gating and kinetics, as well as novel physiological and pathological functions of T-type calcium channels, are being uncovered. In this review, we provide an overview of structural determinants in T-type calcium channels, their involvement in disorders and diseases, the development of novel channel modulators, as well as Structure-Activity Relationship (SAR) studies that lead to rational drug design.
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Affiliation(s)
- Dan Wang
- Division of Chemistry and Structural Biology, Institute for Molecular Bioscience, the University of Queensland, Brisbane Qld 4072, Australia
| | - Lotten Ragnarsson
- Division of Chemistry and Structural Biology, Institute for Molecular Bioscience, the University of Queensland, Brisbane Qld 4072, Australia
| | - Richard J Lewis
- Division of Chemistry and Structural Biology, Institute for Molecular Bioscience, the University of Queensland, Brisbane Qld 4072, Australia
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20
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Chana M, Lewis JB, Davis R, Elam Y, Hobbs D, Lockwood PE, Wataha JC, Messer RL. Biological effects of Ni(II) on monocytes and macrophages in normal and hyperglycemic environments. J Biomed Mater Res A 2018; 106:2433-2439. [DOI: 10.1002/jbm.a.36437] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2017] [Revised: 03/15/2018] [Accepted: 04/05/2018] [Indexed: 12/14/2022]
Affiliation(s)
- Monica Chana
- Department of Oral Health and Diagnostic Sciences, Department of General Dentistry, Dental College of Georgia; Augusta University; Augusta Georgia
| | - Jill B. Lewis
- College of Dental Medicine and Graduate College of Biomedical Sciences; Western University of Health Sciences; Pomona California
| | - Ryan Davis
- Dental College of Georgia; Augusta University; Augusta Georgia
| | - Yolanda Elam
- College of Nursing; Augusta University; Augusta Georgia United States
| | - David Hobbs
- Savannah River National Laboratory; Aiken South Carolina
| | | | - John C. Wataha
- Department of Restorative Dentistry, School of Dentistry; University of Washington; Seattle Washington
| | - Regina L. Messer
- Department of Oral Biology, Dental College of Georgia; Augusta University; Augusta Georgia
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21
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da Silva Aires M, Paganini CL, Bianchini A. Biochemical and physiological effects of nickel in the euryhaline crab Neohelice granulata (Dana, 1851) acclimated to different salinities. Comp Biochem Physiol C Toxicol Pharmacol 2018; 204:51-62. [PMID: 29191712 DOI: 10.1016/j.cbpc.2017.11.007] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/06/2017] [Revised: 11/20/2017] [Accepted: 11/21/2017] [Indexed: 11/30/2022]
Abstract
The estuarine crab Neohelice granulata was maintained under control condition or exposed to sublethal concentrations of dissolved Ni (measured: 128 and 1010μg/L) for 96h at different salinities (2 and 30ppt). After metal exposure, whole-body oxygen consumption was measured and tissue (hemolymph, gills, hepatopancreas and muscle) samples were collected. Control crabs acclimated to 2ppt salinity showed lower hemolymph concentrations of Na+ (33%), Mg2+ (19%) and K+ (30%), as well as increased LPO levels in anterior gills (379%), posterior gills (457%) and hepatopancreas (35%) with respect to those acclimated to 30ppt salinity. In crabs acclimated to 2ppt salinity, Ni exposure increased whole-body oxygen consumption (75%), hemolymph K+ concentration (52%), hemolymph (135%) and hepatopancreas (62%) LDH activity. Also, it reduced hemolymph Cl- concentration (16%) and muscle LDH activity (33%). In crabs acclimated to 30ppt salinity, Ni exposure increased LDH activity in hemolymph (195%), hepatopancreas (126%) and muscle (53%), as well as hemolymph osmolality (10%), Cl- (26%) and Ca2+ (20%) concentration. It also reduced hepatopancreas lipid peroxidation (20%) and hemolymph Mg2+ (29%) and K+ (31%) concentration. These findings indicate that N. granulata is hyper-osmoregulating in 2ppt salinity and hypo-regulating in 30ppt salinity, showing adjustments of hemolymph ionic composition and metabolic rates, with consequent higher oxidative damage to lipids in low salinity (2ppt). Ni effects are associated with metabolic (aerobic and anaerobic) disturbances in crabs acclimated to 2ppt salinity, while osmotic and ionoregulatory disturbances were more evident in crabs acclimated to 30ppt salinity.
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Affiliation(s)
- Michele da Silva Aires
- Programa de Pós-Graduação em Ciências Fisiológicas, Instituto de Ciências Biológicas, Universidade Federal do Rio Grande - FURG, Av. Itália km 8, 96.201-900 Rio Grande, Rio Grande do Sul, Brazil
| | - Christianne Lorea Paganini
- Programa de Pós-Graduação em Ciências Fisiológicas, Instituto de Ciências Biológicas, Universidade Federal do Rio Grande - FURG, Av. Itália km 8, 96.201-900 Rio Grande, Rio Grande do Sul, Brazil
| | - Adalto Bianchini
- Programa de Pós-Graduação em Ciências Fisiológicas, Instituto de Ciências Biológicas, Universidade Federal do Rio Grande - FURG, Av. Itália km 8, 96.201-900 Rio Grande, Rio Grande do Sul, Brazil.
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22
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Sazakli E, Leotsinidis M. Hair biomonitoring and health status of a general population exposed to Nickel. J Trace Elem Med Biol 2017; 43:161-168. [PMID: 28215719 DOI: 10.1016/j.jtemb.2017.02.001] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/12/2016] [Revised: 01/10/2017] [Accepted: 02/04/2017] [Indexed: 12/25/2022]
Abstract
An epidemiological cross-sectional study was conducted in a Greek population, being orally exposed to Ni via food consumption, in order to investigate possible health effects and to evaluate hair Ni concentration as a biomarker of exposure. The study population consisted of 139 men and 155 women, aged 25-69. Socio-demographics, lifestyle, dietary habits, occupational and medical history data were recorded through a personal interview. Hematological and biochemical examinations were conducted in blood specimens. Metals - Ni, Cr, Cd, Pb, Hg, Cu and Zn - were determined in hair samples. Women were characterized by higher Ni and Cu hair concentrations, while men by higher Cr and Hg. Factors affecting hair metal concentrations were identified to be dietary habits, consumption of local crops, occupation and smoking. Hair element content in the study population was comparable to the "reference ranges" reported in Europe, except for Ni, found higher in a fraction of our population. Men in the upper quartile of hair Ni distribution are at higher risk for abnormal high cholesterol, LDL, albumin and calcium, with odds ratios (OR) varying between 3.5 and 6.2. Accordingly, high hair Ni content in women is associated with abnormal glucose (OR=3.9), triglycerides (OR=3.1) and low abnormal sodium (OR=4.3). The study provides evidence of the suitability of hair analysis in assessing environmental exposure to Ni and supports the use of hair Ni content as a valuable and relatively inexpensive tool of biomonitoring, to identify people at risk for certain biochemical alterations.
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Affiliation(s)
- Eleni Sazakli
- Lab of Public Health, Medical School, University of Patras, University Campus, Patras, GR-26504, Greece.
| | - Michalis Leotsinidis
- Lab of Public Health, Medical School, University of Patras, University Campus, Patras, GR-26504, Greece.
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23
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Joksimovic SM, Eggan P, Izumi Y, Joksimovic SL, Tesic V, Dietz RM, Orfila JE, DiGruccio MR, Herson PS, Jevtovic-Todorovic V, Zorumski CF, Todorovic SM. The role of T-type calcium channels in the subiculum: to burst or not to burst? J Physiol 2017; 595:6327-6348. [PMID: 28744923 PMCID: PMC5621493 DOI: 10.1113/jp274565] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2017] [Accepted: 07/07/2017] [Indexed: 01/16/2023] Open
Abstract
KEY POINTS Pharmacological, molecular and genetic data indicate a prominent role of low-voltage-activated T-type calcium channels (T-channels) in the firing activity of both pyramidal and inhibitory interneurons in the subiculum. Pharmacological inhibition of T-channels switched burst firing with lower depolarizing stimuli to regular spiking, and fully abolished hyperpolarization-induced burst firing. Our molecular studies showed that CaV 3.1 is the most abundantly expressed isoform of T-channels in the rat subiculum. Consistent with this finding, both regular-spiking and burst firing patterns were profoundly depressed in the mouse with global deletion of CaV 3.1 isoform of T-channels. Selective inhibition of T-channels and global deletion of CaV 3.1 channels completely suppressed development of long-term potentiation (LTP) in the CA1-subiculum, but not in the CA3-CA1 pathway. ABSTRACT Several studies suggest that voltage-gated calcium currents are involved in generating high frequency burst firing in the subiculum, but the exact nature of these currents remains unknown. Here, we used selective pharmacology, molecular and genetic approaches to implicate Cav3.1-containing T-channels in subicular burst firing, in contrast to several previous reports discounting T-channels as major contributors to subicular neuron physiology. Furthermore, pharmacological antagonism of T-channels, as well as global deletion of CaV3.1 isoform, completely suppressed development of long-term potentiation (LTP) in the CA1-subiculum, but not in the CA3-CA1 pathway. Our results indicate that excitability and synaptic plasticity of subicular neurons relies heavily on T-channels. Hence, T-channels may be a promising new drug target for different cognitive deficits.
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Affiliation(s)
- Srdjan M Joksimovic
- Department of Anesthesiology, University of Colorado, School of Medicine, Aurora, CO, 80045, USA
| | - Pierce Eggan
- Department of Anesthesiology, University of Colorado, School of Medicine, Aurora, CO, 80045, USA
| | - Yukitoshi Izumi
- Department of Psychiatry & Taylor Family Institute for Innovative Psychiatric Research, Washington University School of Medicine, St Louis, MO, 63110, USA
| | - Sonja Lj Joksimovic
- Department of Anesthesiology, University of Colorado, School of Medicine, Aurora, CO, 80045, USA
| | - Vesna Tesic
- Department of Anesthesiology, University of Colorado, School of Medicine, Aurora, CO, 80045, USA
| | - Robert M Dietz
- Department of Anesthesiology, University of Colorado, School of Medicine, Aurora, CO, 80045, USA
| | - James E Orfila
- Department of Anesthesiology, University of Colorado, School of Medicine, Aurora, CO, 80045, USA
| | - Michael R DiGruccio
- Department of Neurobiology, Physiology and Behavior, College of Biological Sciences, University of California, Davis, CA, 95616, USA
| | - Paco S Herson
- Department of Anesthesiology, University of Colorado, School of Medicine, Aurora, CO, 80045, USA
| | - Vesna Jevtovic-Todorovic
- Department of Anesthesiology, University of Colorado, School of Medicine, Aurora, CO, 80045, USA
| | - Charles F Zorumski
- Department of Psychiatry & Taylor Family Institute for Innovative Psychiatric Research, Washington University School of Medicine, St Louis, MO, 63110, USA
| | - Slobodan M Todorovic
- Department of Anesthesiology, University of Colorado, School of Medicine, Aurora, CO, 80045, USA
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24
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Brix KV, Schlekat CE, Garman ER. The mechanisms of nickel toxicity in aquatic environments: An adverse outcome pathway analysis. ENVIRONMENTAL TOXICOLOGY AND CHEMISTRY 2017; 36:1128-1137. [PMID: 27935089 DOI: 10.1002/etc.3706] [Citation(s) in RCA: 57] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/12/2016] [Revised: 11/13/2016] [Accepted: 11/29/2016] [Indexed: 06/06/2023]
Abstract
Current ecological risk assessment and water quality regulations for nickel (Ni) use mechanistically based, predictive tools such as biotic ligand models (BLMs). However, despite many detailed studies, the precise mechanism(s) of Ni toxicity to aquatic organisms remains elusive. This uncertainty in the mechanism(s) of action for Ni has led to concern over the use of tools like the BLM in some regulatory settings. To address this knowledge gap, the authors used an adverse outcome pathway (AOP) analysis, the first AOP for a metal, to identify multiple potential mechanisms of Ni toxicity and their interactions with freshwater aquatic organisms. The analysis considered potential mechanisms of action based on data from a wide range of organisms in aquatic and terrestrial environments on the premise that molecular initiating events for an essential metal would potentially be conserved across taxa. Through this analysis the authors identified 5 potential molecular initiating events by which Ni may exert toxicity on aquatic organisms: disruption of Ca2+ homeostasis, disruption of Mg2+ homeostasis, disruption of Fe2+/3+ homeostasis, reactive oxygen species-induced oxidative damage, and an allergic-type response of respiratory epithelia. At the organ level of biological organization, these 5 potential molecular initiating events collapse into 3 potential pathways: reduced Ca2+ availability to support formation of exoskeleton, shell, and bone for growth; impaired respiration; and cytotoxicity and tumor formation. At the level of the whole organism, the organ-level responses contribute to potential reductions in growth and reproduction and/or alterations in energy metabolism, with several potential feedback loops between each of the pathways. Overall, the present AOP analysis provides a robust framework for future directed studies on the mechanisms of Ni toxicity and for developing AOPs for other metals. Environ Toxicol Chem 2017;36:1128-1137. © 2016 SETAC.
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Affiliation(s)
- Kevin V Brix
- EcoTox, Miami, Florida, USA
- RSMAS, University of Miami, Miami, Florida, USA
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25
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Park CJ, Song SH, Kim DH, Gye MC. Nickel affects gill and muscle development in oriental fire-bellied toad (Bombina orientalis) embryos. AQUATIC TOXICOLOGY (AMSTERDAM, NETHERLANDS) 2017; 182:67-78. [PMID: 27871005 DOI: 10.1016/j.aquatox.2016.11.011] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/05/2016] [Revised: 11/08/2016] [Accepted: 11/10/2016] [Indexed: 06/06/2023]
Abstract
The developmental toxicity of nickel was examined in the embryos of Bombina orientalis, a common amphibian in Korea. Based on a standard frog embryo teratogenesis assay, the LC50 and EC50 for malformation of nickel after 168h of treatment were 33.8μM and 5.4μM, respectively. At a lethal concentration (100μM), nickel treatment decreased the space between gill filaments and caused epithelial swelling and abnormal fusion of gill filaments. These findings suggest that nickel affects the functional development of gills, leading to embryonic death. At sublethal concentrations (1-10μM), nickel produced multiple embryonic abnormalities, including bent tail and tail dysplasia. At 10μM, nickel significantly decreased tail length and tail muscle fiber density in tadpoles, indicating inhibition of myogenic differentiation. Before hatching, the pre-muscular response to muscular response stages (stages 26-31) were the most sensitive period to nickel with respect to tail muscle development. During these stages, MyoD mRNA was upregulated, whereas myogenic regulatory factor 4 mRNA was downregulated by 0.1μM nickel. Calcium-dependent kinase activities in muscular response stage embryos were significantly decreased by nickel, whereas these activities were restored by exogenous calcium. In tadpoles, 10μM nickel significantly decreased the expression of the myosin heavy chain and the 12/101 muscle marker protein in the tail. Expression was restored by exogenous calcium. Our results indicate that nickel affects muscle development by disrupting calcium-dependent myogenesis in developing B. orientalis embryos.
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Affiliation(s)
- Chan Jin Park
- Department of Life Science and Institute for Natural Sciences, Hanyang University, Seoul 133-791, South Korea
| | - Sang Ha Song
- Department of Life Science and Institute for Natural Sciences, Hanyang University, Seoul 133-791, South Korea
| | - Dae Han Kim
- Department of Life Science and Institute for Natural Sciences, Hanyang University, Seoul 133-791, South Korea
| | - Myung Chan Gye
- Department of Life Science and Institute for Natural Sciences, Hanyang University, Seoul 133-791, South Korea.
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26
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Abstract
The role of T-type calcium currents is rarely considered in the extensive literature covering the mechanisms of long-term synaptic plasticity. This situation reflects the lack of suitable T-type channel antagonists that till recently has hampered investigations of the functional roles of these channels. However, with the development of new pharmacological and genetic tools, a clear involvement of T-type channels in synaptic plasticity is starting to emerge. Here, we review a number of studies showing that T-type channels participate to numerous homo- and hetero-synaptic plasticity mechanisms that involve different molecular partners and both pre- and post-synaptic modifications. The existence of T-channel dependent and independent plasticity at the same synapse strongly suggests a subcellular localization of these channels and their partners that allows specific interactions. Moreover, we illustrate the functional importance of T-channel dependent synaptic plasticity in neocortex and thalamus.
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Affiliation(s)
- Nathalie Leresche
- a Sorbonne Universités, Université Pierre et Marie Curie (UPMC) UM119, CNRS UMR8246, INSERM U1130, Neuroscience Paris Seine (NPS) , Paris , France
| | - Régis C Lambert
- a Sorbonne Universités, Université Pierre et Marie Curie (UPMC) UM119, CNRS UMR8246, INSERM U1130, Neuroscience Paris Seine (NPS) , Paris , France
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Kisnieriene V, Lapeikaite I, Sevriukova O, Ruksenas O. The effects of Ni(2+) on electrical signaling of Nitellopsis obtusa cells. JOURNAL OF PLANT RESEARCH 2016; 129:551-558. [PMID: 26875181 DOI: 10.1007/s10265-016-0794-3] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/29/2015] [Accepted: 12/02/2015] [Indexed: 06/05/2023]
Abstract
The effect of nickel (Ni) on the generation of plant bioelectrical signals was evaluated in Nitellopsis obtusa, a Characean model organism. Conventional glass-microelectrode technique and K(+)-anaesthesia method in current-clamp and voltage-clamp modes were used for the measurement and analysis of electrical parameters. Ni(2+) treatment rapidly influenced the action potential (AP) parameters namely, excitation threshold, AP peak and duration, membrane potential at various voltages and dynamics of ion currents. We conclude that altered electrical signaling pathway in the test organism constituted the early target for Ni toxicity imposition. The observed Ni interference could be ascribed to disturbed [Ca(2+)]cyt content, impaired Cl(-) and K(+) channels activity resulting in decreased excitability and repolarization rate in generated AP.
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Affiliation(s)
- Vilma Kisnieriene
- Department of Neurobiology and Biophysics, Faculty of Natural Science, Vilnius University, M. K. Ciurlionio 21/27, 03101, Vilnius, Lithuania.
| | - Indre Lapeikaite
- Department of Neurobiology and Biophysics, Faculty of Natural Science, Vilnius University, M. K. Ciurlionio 21/27, 03101, Vilnius, Lithuania
| | - Olga Sevriukova
- Department of Neurobiology and Biophysics, Faculty of Natural Science, Vilnius University, M. K. Ciurlionio 21/27, 03101, Vilnius, Lithuania
| | - Osvaldas Ruksenas
- Department of Neurobiology and Biophysics, Faculty of Natural Science, Vilnius University, M. K. Ciurlionio 21/27, 03101, Vilnius, Lithuania
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Thanawala MS, Regehr WG. Determining synaptic parameters using high-frequency activation. J Neurosci Methods 2016; 264:136-152. [PMID: 26972952 DOI: 10.1016/j.jneumeth.2016.02.021] [Citation(s) in RCA: 36] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2015] [Revised: 02/23/2016] [Accepted: 02/26/2016] [Indexed: 12/25/2022]
Abstract
BACKGROUND The specific properties of a synapse determine how neuronal activity evokes neurotransmitter release. Evaluating changes in synaptic properties during sustained activity is essential to understanding how genetic manipulations and neuromodulators regulate neurotransmitter release. Analyses of postsynaptic responses to high-frequency stimulation have provided estimates of the size of the readily-releasable pool (RRP) of vesicles (N0) and the probability of vesicular release (p) at multiple synapses. NEW METHOD Here, we introduce a model-based approach at the calyx of Held synapse in which depletion and the rate of replenishment (R) determine the number of available vesicles, and facilitation leads to a use-dependent increase in p when initial p is low. RESULTS When p is high and R is low, we find excellent agreement between estimates based on all three methods and the model. However, when p is low or when significant replenishment occurs between stimuli, estimates of different methods diverge, and model estimates are between the extreme estimates provided by the other approaches. COMPARISON WITH OTHER METHODS We compare our model-based approach to three other approaches that rely on different simplifying assumptions. Our findings suggest that our model provides a better estimate of N0 and p than previously-established methods, likely due to inaccurate assumptions about replenishment. More generally, our findings suggest that approaches commonly used to estimate N0 and p at other synapses are often applied under experimental conditions that yield inaccurate estimates. CONCLUSIONS Careful application of appropriate methods can greatly improve estimates of synaptic parameters.
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Affiliation(s)
- Monica S Thanawala
- Department of Neurobiology, Harvard Medical School, Boston, MA, United States
| | - Wade G Regehr
- Department of Neurobiology, Harvard Medical School, Boston, MA, United States.
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29
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Shen CC, Shen DS, Shentu JL, Wang MZ, Wan MY. Could humic acid relieve the biochemical toxicities and DNA damage caused by nickel and deltamethrin in earthworms (Eisenia foetida)? ENVIRONMENTAL SCIENCE. PROCESSES & IMPACTS 2015; 17:2074-2081. [PMID: 26511644 DOI: 10.1039/c5em00288e] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
The aim of the study was to determine whether humic acid (HA) prevented gene and biochemical toxic effects in earthworms (Eisenia foetida) exposed to nickel and deltamethrin (at 100 and 1 mg kg(-1), respectively) in soil. Cellular- and molecular-level toxic effects of nickel and deltamethrin in earthworms were evaluated by measuring damage to lipid membranes and DNA and the production of protein carbonyls over 42 days of exposure. Nickel and deltamethrin induced significant levels of oxidative stress in earthworms, increasing the production of peroxidation products (malondialdehyde and protein carbonyls) and increasing the comet assay tail DNA% (determined by single-cell gel electrophoresis). DNA damage was the most sensitive of the three indices because it gave a higher sample/control ratio than did the other indices. The presence of HA alleviated (in decreasing order of effectiveness) damage to DNA, proteins, and lipid membranes caused by nickel and deltamethrin. A low HA dose (0.5-1% HA in soil) prevented a great deal of lipid membrane damage, but the highest HA dose (3% HA in soil) prevented still more DNA damage. However, the malondialdehyde concentrations in earthworms were higher at the highest HA dose than at the lower HA doses. The amounts of protein carbonyls produced at different HA doses were not significantly different. The toxic effects to earthworms caused by increased oxidizable nickel concentrations could be relieved by adding HA.
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Affiliation(s)
- Chen-Chao Shen
- Zhejiang Provincial Key Laboratory of Solid Waste Treatment and Recycling, School of Environmental Science and Engineering, Zhejiang Gongshang University, Hangzhou 310012, China.
| | - Dong-Sheng Shen
- Zhejiang Provincial Key Laboratory of Solid Waste Treatment and Recycling, School of Environmental Science and Engineering, Zhejiang Gongshang University, Hangzhou 310012, China.
| | - Jia-Li Shentu
- Zhejiang Provincial Key Laboratory of Solid Waste Treatment and Recycling, School of Environmental Science and Engineering, Zhejiang Gongshang University, Hangzhou 310012, China.
| | - Mei-Zhen Wang
- Zhejiang Provincial Key Laboratory of Solid Waste Treatment and Recycling, School of Environmental Science and Engineering, Zhejiang Gongshang University, Hangzhou 310012, China.
| | - Ming-Yang Wan
- Zhejiang Provincial Key Laboratory of Solid Waste Treatment and Recycling, School of Environmental Science and Engineering, Zhejiang Gongshang University, Hangzhou 310012, China.
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Wang K, Kelley MH, Wu WW, Adelman JP, Maylie J. Apamin Boosting of Synaptic Potentials in CaV2.3 R-Type Ca2+ Channel Null Mice. PLoS One 2015; 10:e0139332. [PMID: 26418566 PMCID: PMC4587947 DOI: 10.1371/journal.pone.0139332] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2015] [Accepted: 09/11/2015] [Indexed: 11/19/2022] Open
Abstract
SK2- and KV4.2-containing K+ channels modulate evoked synaptic potentials in CA1 pyramidal neurons. Each is coupled to a distinct Ca2+ source that provides Ca2+-dependent feedback regulation to limit AMPA receptor (AMPAR)- and NMDA receptor (NMDAR)-mediated postsynaptic depolarization. SK2-containing channels are activated by Ca2+ entry through NMDARs, whereas KV4.2-containing channel availability is increased by Ca2+ entry through SNX-482 (SNX) sensitive CaV2.3 R-type Ca2+ channels. Recent studies have challenged the functional coupling between NMDARs and SK2-containing channels, suggesting that synaptic SK2-containing channels are instead activated by Ca2+ entry through R-type Ca2+ channels. Furthermore, SNX has been implicated to have off target affects, which would challenge the proposed coupling between R-type Ca2+ channels and KV4.2-containing K+ channels. To reconcile these conflicting results, we evaluated the effect of SK channel blocker apamin and R-type Ca2+ channel blocker SNX on evoked excitatory postsynaptic potentials (EPSPs) in CA1 pyramidal neurons from CaV2.3 null mice. The results show that in the absence of CaV2.3 channels, apamin application still boosted EPSPs. The boosting effect of CaV2.3 channel blockers on EPSPs observed in neurons from wild type mice was not observed in neurons from CaV2.3 null mice. These data are consistent with a model in which SK2-containing channels are functionally coupled to NMDARs and KV4.2-containing channels to CaV2.3 channels to provide negative feedback regulation of EPSPs in the spines of CA1 pyramidal neurons.
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Affiliation(s)
- Kang Wang
- Vollum Institute, Oregon Health & Science University, Portland, Oregon 97239, United States of America
| | - Melissa H. Kelley
- Vollum Institute, Oregon Health & Science University, Portland, Oregon 97239, United States of America
| | - Wendy W. Wu
- Department of Obstetrics and Gynecology, Oregon Health & Science University, Portland, Oregon 97239, United States of America
| | - John P. Adelman
- Vollum Institute, Oregon Health & Science University, Portland, Oregon 97239, United States of America
| | - James Maylie
- Department of Obstetrics and Gynecology, Oregon Health & Science University, Portland, Oregon 97239, United States of America
- * E-mail:
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Singh B, Krishnan A, Micu I, Koshy K, Singh V, Martinez JA, Koshy D, Xu F, Chandrasekhar A, Dalton C, Syed N, Stys PK, Zochodne DW. Peripheral neuron plasticity is enhanced by brief electrical stimulation and overrides attenuated regrowth in experimental diabetes. Neurobiol Dis 2015; 83:134-51. [PMID: 26297317 DOI: 10.1016/j.nbd.2015.08.009] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2015] [Revised: 07/20/2015] [Accepted: 08/12/2015] [Indexed: 01/01/2023] Open
Abstract
Peripheral nerve regrowth is less robust than commonly assumed, particularly when it accompanies common clinical scenarios such as diabetes mellitus. Brief extracellular electrical stimulation (ES) facilitates the regeneration of peripheral nerves in part through early activation of the conditioning injury response and BDNF. Here, we explored intrinsic neuronal responses to ES to identify whether ES might impact experimental diabetes, where regeneration is attenuated. ES altered several regeneration related molecules including rises in tubulin, Shh (Sonic hedgehog) and GAP43 mRNAs. ES was associated with rises in neuronal intracellular calcium but its strict linkage to regrowth was not confirmed. In contrast, we identified PI3K-PTEN involvement, an association previously linked to diabetic regenerative impairment. Following ES there were declines in PTEN protein and mRNA both in vitro and in vivo and a PI3K inhibitor blocked its action. In vitro, isolated diabetic neurons were capable of mounting robust responsiveness to ES. In vivo, ES improved electrophysiological and behavioral indices of nerve regrowth in a chronic diabetic model of mice with pre-existing neuropathy. Regrowth of myelinated axons and reinnervation of the epidermis were greater following ES than sham stimulation. Taken together, these findings identify a role for ES in supporting regeneration during the challenges of diabetes mellitus.
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Affiliation(s)
- B Singh
- Hotchkiss Brain Institute, University of Calgary, Calgary, AB, T2N 4N1, Canada
| | - A Krishnan
- Division of Neurology, Department of Medicine, Neurosciences and Mental Health Institute, University of Alberta, Edmonton, AB, T6G 2B7, Canada; Hotchkiss Brain Institute, University of Calgary, Calgary, AB, T2N 4N1, Canada
| | - I Micu
- Hotchkiss Brain Institute, University of Calgary, Calgary, AB, T2N 4N1, Canada
| | - K Koshy
- Hotchkiss Brain Institute, University of Calgary, Calgary, AB, T2N 4N1, Canada
| | - V Singh
- Hotchkiss Brain Institute, University of Calgary, Calgary, AB, T2N 4N1, Canada
| | - J A Martinez
- Hotchkiss Brain Institute, University of Calgary, Calgary, AB, T2N 4N1, Canada
| | - D Koshy
- Hotchkiss Brain Institute, University of Calgary, Calgary, AB, T2N 4N1, Canada
| | - F Xu
- Hotchkiss Brain Institute, University of Calgary, Calgary, AB, T2N 4N1, Canada
| | - A Chandrasekhar
- Division of Neurology, Department of Medicine, Neurosciences and Mental Health Institute, University of Alberta, Edmonton, AB, T6G 2B7, Canada
| | - C Dalton
- Electrical and Computer Engineering, University of Calgary, Calgary, AB, T2N 4N1, Canada
| | - N Syed
- Hotchkiss Brain Institute, University of Calgary, Calgary, AB, T2N 4N1, Canada
| | - P K Stys
- Hotchkiss Brain Institute, University of Calgary, Calgary, AB, T2N 4N1, Canada
| | - D W Zochodne
- Division of Neurology, Department of Medicine, Neurosciences and Mental Health Institute, University of Alberta, Edmonton, AB, T6G 2B7, Canada; Hotchkiss Brain Institute, University of Calgary, Calgary, AB, T2N 4N1, Canada.
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Differential CaMKII regulation by voltage-gated calcium channels in the striatum. Mol Cell Neurosci 2015; 68:234-43. [PMID: 26255006 DOI: 10.1016/j.mcn.2015.08.003] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2015] [Revised: 07/06/2015] [Accepted: 08/03/2015] [Indexed: 01/21/2023] Open
Abstract
Calcium signaling regulates synaptic plasticity and many other functions in striatal medium spiny neurons to modulate basal ganglia function. Ca(2+)/calmodulin-dependent protein kinase II (CaMKII) is a major calcium-dependent signaling protein that couples calcium entry to diverse cellular changes. CaMKII activation results in autophosphorylation at Thr286 and sustained calcium-independent CaMKII activity after calcium signals dissipate. However, little is known about the mechanisms regulating striatal CaMKII. To address this, mouse brain slices were treated with pharmacological modulators of calcium channels and punches of dorsal striatum were immunoblotted for CaMKII Thr286 autophosphorylation as an index of CaMKII activation. KCl depolarization increased levels of CaMKII autophosphorylation ~2-fold; this increase was blocked by an LTCC antagonist and was mimicked by treatment with pharmacological LTCC activators. The chelation of extracellular calcium robustly decreased basal CaMKII autophosphorylation within 5min and increased levels of total CaMKII in cytosolic fractions, in addition to decreasing the phosphorylation of CaMKII sites in the GluN2B subunit of NMDA receptors and the GluA1 subunit of AMPA receptors. We also found that the maintenance of basal levels of CaMKII autophosphorylation requires low-voltage gated T-type calcium channels, but not LTCCs or R-type calcium channels. Our findings indicate that CaMKII activity is dynamically regulated by multiple calcium channels in the striatum thus coupling calcium entry to key downstream substrates.
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Siapich SA, Akhtar I, Hescheler J, Schneider T, Lüke M. Low concentrations of ethanol but not of dimethyl sulfoxide (DMSO) impair reciprocal retinal signal transduction. Graefes Arch Clin Exp Ophthalmol 2015; 253:1713-9. [PMID: 26104874 DOI: 10.1007/s00417-015-3070-7] [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: 01/26/2015] [Revised: 05/06/2015] [Accepted: 05/18/2015] [Indexed: 11/27/2022] Open
Abstract
BACKGROUND The model of the isolated and superfused retina provides the opportunity to test drugs and toxins. Some chemicals have to be applied using low concentrations of organic solvents as carriers. Recently, E-/R-type (Cav2.3) and T-type (Cav3.2) voltage-gated Ca(2+) channels were identified as participating in reciprocal inhibitory retinal signaling. Their participation is apparent, when low concentrations of NiCl2 (15 μM) are applied during superfusion leading to an increase of the ERG b-wave amplitude, which is explained by a reduction of amacrine GABA-release onto bipolar neurons. During these investigations, differences were observed for the solvent carrier used. METHODS Recording of the transretinal receptor potentials from the isolated bovine retina. RESULTS The pretreatment of bovine retina with 0.01 % (v/v) dimethylsulfoxide did not impair the NiCl2-mediated increase of the b-wave amplitude, which was 1.31-fold ± 0.03 of initial value (n = 4). However, pretreatment of the retina with the same concentration of ethanol impaired reciprocal signaling (0.96-fold ± 0.05, n = 4). Further, the implicit time of the b-wave was increased, suggesting that ethanol itself but not DMSO may antagonize GABA-receptors. CONCLUSION Ethanol itself but not DMSO may block GABA receptors and cause an amplitude increase by itself, so that reciprocal signaling is impaired.
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Affiliation(s)
- Siarhei A Siapich
- Institute of Neurophysiology, University of Cologne, Robert-Koch-Str. 39, D-50931, Köln, Germany
- Department of Ophthalmology, RWTH Aachen University, Pauwelsstr. 30, D-52074, Aachen, Germany
| | - Isha Akhtar
- Institute of Neurophysiology, University of Cologne, Robert-Koch-Str. 39, D-50931, Köln, Germany
| | - Jürgen Hescheler
- Institute of Neurophysiology, University of Cologne, Robert-Koch-Str. 39, D-50931, Köln, Germany
| | - Toni Schneider
- Institute of Neurophysiology, University of Cologne, Robert-Koch-Str. 39, D-50931, Köln, Germany.
| | - Matthias Lüke
- Institute of Neurophysiology, University of Cologne, Robert-Koch-Str. 39, D-50931, Köln, Germany
- University Eye Hospital, University of Lübeck, Ratzeburger Allee 160, D-23538, Lübeck, Germany
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Harraz OF, Brett SE, Zechariah A, Romero M, Puglisi JL, Wilson SM, Welsh DG. Genetic ablation of CaV3.2 channels enhances the arterial myogenic response by modulating the RyR-BKCa axis. Arterioscler Thromb Vasc Biol 2015; 35:1843-51. [PMID: 26069238 DOI: 10.1161/atvbaha.115.305736] [Citation(s) in RCA: 36] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2015] [Accepted: 05/31/2015] [Indexed: 12/31/2022]
Abstract
OBJECTIVE In resistance arteries, there is an emerging view that smooth muscle CaV3.2 channels restrain arterial constriction through a feedback response involving the large-conductance Ca(2+)-activated K(+) channel (BKCa). Here, we used wild-type and CaV3.2 knockout (CaV3.2(-/-)) mice to definitively test whether CaV3.2 moderates myogenic tone in mesenteric arteries via the CaV3.2-ryanodine receptor-BKCa axis and whether this regulatory mechanism influences blood pressure regulation. APPROACH AND RESULTS Using pressurized vessel myography, CaV3.2(-/-) mesenteric arteries displayed enhanced myogenic constriction to pressure but similar K(+)-induced vasoconstriction compared with wild-type C57BL/6 arteries. Electrophysiological and myography experiments subsequently confirmed the inability of micromolar Ni(2+), a CaV3.2 blocker, to either constrict arteries or suppress T-type currents in CaV3.2(-/-) smooth muscle cells. The frequency of BKCa-induced spontaneous transient outward K(+) currents dropped in wild-type but not in knockout arterial smooth muscle cells upon the pharmacological suppression of CaV3.2 channel. Line scan analysis performed on en face arteries loaded with Fluo-4 revealed the presence of Ca(2+) sparks in all arteries, with the subsequent application of Ni(2+) only affecting wild-type arteries. Although CaV3.2 channel moderated myogenic constriction of resistance arteries, the blood pressure measurements of CaV3.2(-/-) and wild-type animals were similar. CONCLUSIONS Overall, our findings establish a negative feedback mechanism of the myogenic response in which CaV3.2 channel modulates downstream ryanodine receptor-BKCa to hyperpolarize and relax arteries.
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Affiliation(s)
- Osama F Harraz
- From the Department of Physiology and Pharmacology, Hotchkiss Brain and Libin Cardiovascular Institutes, University of Calgary, Calgary, Alberta, Canada (O.F.H., S.E.B., A.Z., D.G.W.); Department of Pharmacology and Toxicology, Alexandria University, Alexandria, Egypt (O.F.H.); Department of Basic Sciences, Division of Pharmacology, Loma Linda University, CA (M.R., S.M.W.); Department of Pharmacology, University of California, Davis (J.L.P.); and Department of Physiology and Pharmacology, University of Western Ontario, London, Ontario, Canada (D.G.W.)
| | - Suzanne E Brett
- From the Department of Physiology and Pharmacology, Hotchkiss Brain and Libin Cardiovascular Institutes, University of Calgary, Calgary, Alberta, Canada (O.F.H., S.E.B., A.Z., D.G.W.); Department of Pharmacology and Toxicology, Alexandria University, Alexandria, Egypt (O.F.H.); Department of Basic Sciences, Division of Pharmacology, Loma Linda University, CA (M.R., S.M.W.); Department of Pharmacology, University of California, Davis (J.L.P.); and Department of Physiology and Pharmacology, University of Western Ontario, London, Ontario, Canada (D.G.W.)
| | - Anil Zechariah
- From the Department of Physiology and Pharmacology, Hotchkiss Brain and Libin Cardiovascular Institutes, University of Calgary, Calgary, Alberta, Canada (O.F.H., S.E.B., A.Z., D.G.W.); Department of Pharmacology and Toxicology, Alexandria University, Alexandria, Egypt (O.F.H.); Department of Basic Sciences, Division of Pharmacology, Loma Linda University, CA (M.R., S.M.W.); Department of Pharmacology, University of California, Davis (J.L.P.); and Department of Physiology and Pharmacology, University of Western Ontario, London, Ontario, Canada (D.G.W.)
| | - Monica Romero
- From the Department of Physiology and Pharmacology, Hotchkiss Brain and Libin Cardiovascular Institutes, University of Calgary, Calgary, Alberta, Canada (O.F.H., S.E.B., A.Z., D.G.W.); Department of Pharmacology and Toxicology, Alexandria University, Alexandria, Egypt (O.F.H.); Department of Basic Sciences, Division of Pharmacology, Loma Linda University, CA (M.R., S.M.W.); Department of Pharmacology, University of California, Davis (J.L.P.); and Department of Physiology and Pharmacology, University of Western Ontario, London, Ontario, Canada (D.G.W.)
| | - Jose L Puglisi
- From the Department of Physiology and Pharmacology, Hotchkiss Brain and Libin Cardiovascular Institutes, University of Calgary, Calgary, Alberta, Canada (O.F.H., S.E.B., A.Z., D.G.W.); Department of Pharmacology and Toxicology, Alexandria University, Alexandria, Egypt (O.F.H.); Department of Basic Sciences, Division of Pharmacology, Loma Linda University, CA (M.R., S.M.W.); Department of Pharmacology, University of California, Davis (J.L.P.); and Department of Physiology and Pharmacology, University of Western Ontario, London, Ontario, Canada (D.G.W.)
| | - Sean M Wilson
- From the Department of Physiology and Pharmacology, Hotchkiss Brain and Libin Cardiovascular Institutes, University of Calgary, Calgary, Alberta, Canada (O.F.H., S.E.B., A.Z., D.G.W.); Department of Pharmacology and Toxicology, Alexandria University, Alexandria, Egypt (O.F.H.); Department of Basic Sciences, Division of Pharmacology, Loma Linda University, CA (M.R., S.M.W.); Department of Pharmacology, University of California, Davis (J.L.P.); and Department of Physiology and Pharmacology, University of Western Ontario, London, Ontario, Canada (D.G.W.)
| | - Donald G Welsh
- From the Department of Physiology and Pharmacology, Hotchkiss Brain and Libin Cardiovascular Institutes, University of Calgary, Calgary, Alberta, Canada (O.F.H., S.E.B., A.Z., D.G.W.); Department of Pharmacology and Toxicology, Alexandria University, Alexandria, Egypt (O.F.H.); Department of Basic Sciences, Division of Pharmacology, Loma Linda University, CA (M.R., S.M.W.); Department of Pharmacology, University of California, Davis (J.L.P.); and Department of Physiology and Pharmacology, University of Western Ontario, London, Ontario, Canada (D.G.W.).
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Voltage-gated calcium channels: Determinants of channel function and modulation by inorganic cations. Prog Neurobiol 2015; 129:1-36. [PMID: 25817891 DOI: 10.1016/j.pneurobio.2014.12.003] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2014] [Revised: 12/15/2014] [Accepted: 12/27/2014] [Indexed: 11/20/2022]
Abstract
Voltage-gated calcium channels (VGCCs) represent a key link between electrical signals and non-electrical processes, such as contraction, secretion and transcription. Evolved to achieve high rates of Ca(2+)-selective flux, they possess an elaborate mechanism for selection of Ca(2+) over foreign ions. It has been convincingly linked to competitive binding in the pore, but the fundamental question of how this is reconcilable with high rates of Ca(2+) transfer remains unanswered. By virtue of their similarity to Ca(2+), polyvalent cations can interfere with the function of VGCCs and have proven instrumental in probing the mechanisms underlying selective permeation. Recent emergence of crystallographic data on a set of Ca(2+)-selective model channels provides a structural framework for permeation in VGCCs, and warrants a reconsideration of their diverse modulation by polyvalent cations, which can be roughly separated into three general mechanisms: (I) long-range interactions with charged regions on the surface, affecting the local potential sensed by the channel or influencing voltage-sensor movement by repulsive forces (electrostatic effects), (II) short-range interactions with sites in the ion-conducting pathway, leading to physical obstruction of the channel (pore block), and in some cases (III) short-range interactions with extracellular binding sites, leading to non-electrostatic modifications of channel gating (allosteric effects). These effects, together with the underlying molecular modifications, provide valuable insights into the function of VGCCs, and have important physiological and pathophysiological implications. Allosteric suppression of some of the pore-forming Cavα1-subunits (Cav2.3, Cav3.2) by Zn(2+) and Cu(2+) may play a major role for the regulation of excitability by endogenous transition metal ions. The fact that these ions can often traverse VGCCs can contribute to the detrimental intracellular accumulation of metal ions following excessive release of endogenous Cu(2+) and Zn(2+) or exposure to non-physiological toxic metal ions.
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Brimblecombe KR, Cragg SJ. Ni(2+) affects dopamine uptake which limits suitability as inhibitor of T-type voltage-gated Ca(2+) channels. ACS Chem Neurosci 2015; 6:124-9. [PMID: 25434848 DOI: 10.1021/cn500274g] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
Neuronal T-type voltage-gated Ca(2+) channels are reported to have physiological roles that include regulation of burst firing, Ca(2+) oscillations, and neurotransmitter release. These roles are often exposed experimentally by blocking T-type channels with micromolar Ni(2+). We used Ni(2+) to explore the role of axonal T-type channels in dopamine (DA) release in mouse striatum, but identified significant off-target effects on DA uptake. Ni(2+) (100 μM) reversibly increased electrically evoked DA release and markedly extended its extracellular lifetime, detected using fast-scan cyclic voltammetry. Prior inhibition of the DA transporter (DAT) by cocaine (5 μM) occluded the facilitatory action of Ni(2+) on DA release and conversely, allowed Ni(2+) to inhibit release, presumably through T-channel inhibition. Ni(2+) further prolonged the timecourse of DA clearance suggesting further inhibition of DA uptake. In summary, Ni(2+) has major effects on DA transmission besides those due to T-channels that likely involve inhibition of the DAT.
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Affiliation(s)
- Katherine R. Brimblecombe
- Department of Physiology,
Anatomy and Genetics, and ‡Oxford Parkinson’s Disease Centre, University of Oxford, Oxford OX1 3PT, United Kingdom
| | - Stephanie J. Cragg
- Department of Physiology,
Anatomy and Genetics, and ‡Oxford Parkinson’s Disease Centre, University of Oxford, Oxford OX1 3PT, United Kingdom
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The expression pattern of a Cav3-Kv4 complex differentially regulates spike output in cerebellar granule cells. J Neurosci 2014; 34:8800-12. [PMID: 24966380 DOI: 10.1523/jneurosci.0981-14.2014] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
The cerebellum receives sensory information by mossy fiber input from a multitude of sources that require differential signal processing. A compartmentalization of function begins with the segregation of mossy fibers across 10 distinct lobules over the rostrocaudal axis, with tactile receptor afferents prevalent in anterior lobules and vestibular input in caudal lobules. However, it is unclear how these unique signals might be differentially processed at the circuit level across the cerebellum. As granule cells receive mossy fiber input, they represent a key stage at which postsynaptic mechanisms could influence signal processing. Granule cells express an A-type current mediated by Kv4 potassium channels that modify the latency and frequency of spike output. The current study examined the potential for a Cav3 calcium-Kv4 channel complex to regulate the response of granule cells to mossy fiber input in lobules 2 and 9 of the rat cerebellum. Similar A-type currents were recorded in both regions, but the Cav3 calcium current was expressed at a substantially higher density in lobule 9 cells, acting to increase A-type current availability through its influence on Kv4 voltage for inactivation. The difference in excitability imparted by Cav3-Kv4 interactions proves to allow lobule 2 granule cells to respond more effectively to tactile stimulus-like burst input and lobule 9 cells to slow shifts in input frequency characteristic of vestibular input. The expression pattern of Cav3 channels and its control of Kv4 availability thus provides a novel means of processing widely different forms of sensory input across cerebellar lobules.
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Buraei Z, Liang H, Elmslie KS. Voltage control of Ca²⁺ permeation through N-type calcium (Ca(V)2.2) channels. ACTA ACUST UNITED AC 2014; 144:207-20. [PMID: 25114024 PMCID: PMC4144670 DOI: 10.1085/jgp.201411201] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Voltage dependence of permeation enhances Ca2+ influx through CaV2.2 channels relative to that of other ions at depolarized voltages. Voltage-gated calcium (CaV) channels deliver Ca2+ to trigger cellular functions ranging from cardiac muscle contraction to neurotransmitter release. The mechanism by which these channels select for Ca2+ over other cations is thought to involve multiple Ca2+-binding sites within the pore. Although the Ca2+ affinity and cation preference of these sites have been extensively investigated, the effect of voltage on these sites has not received the same attention. We used a neuronal preparation enriched for N-type calcium (CaV2.2) channels to investigate the effect of voltage on Ca2+ flux. We found that the EC50 for Ca2+ permeation increases from 13 mM at 0 mV to 240 mM at 60 mV, indicating that, during permeation, Ca2+ ions sense the electric field. These data were nicely reproduced using a three-binding-site step model. Using roscovitine to slow CaV2.2 channel deactivation, we extended these measurements to voltages <0 mV. Permeation was minimally affected at these hyperpolarized voltages, as was predicted by the model. As an independent test of voltage effects on permeation, we examined the Ca2+-Ba2+ anomalous mole fraction (MF) effect, which was both concentration and voltage dependent. However, the Ca2+-Ba2+ anomalous MF data could not be reproduced unless we added a fourth site to our model. Thus, Ca2+ permeation through CaV2.2 channels may require at least four Ca2+-binding sites. Finally, our results suggest that the high affinity of Ca2+ for the channel helps to enhance Ca2+ influx at depolarized voltages relative to other ions (e.g., Ba2+ or Na+), whereas the absence of voltage effects at negative potentials prevents Ca2+ from becoming a channel blocker. Both effects are needed to maximize Ca2+ influx over the voltages spanned by action potentials.
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Affiliation(s)
- Zafir Buraei
- Department of Biology and Health Sciences, Pace University, New York, NY 10038 Department of Physiology, Tulane University Health Sciences Center, New Orleans, LA 70112
| | - Haoya Liang
- Department of Physiology, Tulane University Health Sciences Center, New Orleans, LA 70112
| | - Keith S Elmslie
- Department of Physiology, Tulane University Health Sciences Center, New Orleans, LA 70112 The Baker Laboratory of Pharmacology, Department of Pharmacology, Kirksville College of Osteopathic Medicine, A.T. Still University of Health Sciences, Kirksville, MO 63501
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Treinys R, Kaselis A, Jover E, Bagnard D, Šatkauskas S. R-type calcium channels are crucial for semaphorin 3A-induced DRG axon growth cone collapse. PLoS One 2014; 9:e102357. [PMID: 25032951 PMCID: PMC4102519 DOI: 10.1371/journal.pone.0102357] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2014] [Accepted: 06/18/2014] [Indexed: 12/20/2022] Open
Abstract
Semaphorin 3A (Sema3A) is a secreted protein involved in axon path-finding during nervous system development. Calcium signaling plays an important role during axonal growth in response to different guidance cues; however it remains unclear whether this is also the case for Sema3A. In this study we used intracellular calcium imaging to figure out whether Sema3A-induced growth cone collapse is a Ca2+ dependent process. Intracellular Ca2+ imaging results using Fura-2 AM showed Ca2+ increase in E15 mice dorsal root ganglia neurons upon Sema3A treatment. Consequently we analyzed Sema3A effect on growth cones after blocking or modifying intracellular and extracellular Ca2+ channels that are expressed in E15 mouse embryos. Our results demonstrate that Sema3A increased growth cone collapse rate is blocked by the non-selective R- and T- type Ca2+ channel blocker NiCl2 and by the selective R-type Ca2+ channel blocker SNX482. These Ca2+ channel blockers consistently decreased the Sema3A-induced intracellular Ca2+ concentration elevation. Overall, our results demonstrate that Sema3A-induced growth cone collapses are intimately related with increase in intracellular calcium concentration mediated by R-type calcium channels.
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Affiliation(s)
- Rimantas Treinys
- Biophysical Research Group, Biology department, Vytautas Magnus University, Kaunas, Lithuania
- Institute of Cardiology, Lithuanian University of Health Sciences, Kaunas, Lithuania
| | - Andrius Kaselis
- Biophysical Research Group, Biology department, Vytautas Magnus University, Kaunas, Lithuania
| | - Emmanuel Jover
- INCI – UPR-CNRS 3212, Neurotransmission et sécrétion neuroendocrine, Strasbourg, France
| | - Dominique Bagnard
- INSERM U1109, MN3t lab, Labex Medalis, University of Strasbourg, Strasbourg, France
| | - Saulius Šatkauskas
- Biophysical Research Group, Biology department, Vytautas Magnus University, Kaunas, Lithuania
- * E-mail:
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The effect of bradykinin on the electrical activity of rat myenteric neurons. Eur J Pharmacol 2014; 738:158-69. [PMID: 24886885 DOI: 10.1016/j.ejphar.2014.05.020] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2013] [Revised: 04/01/2014] [Accepted: 05/10/2014] [Indexed: 01/21/2023]
Abstract
Bradykinin is a mediator involved in inflammatory processes in the gut. Here we investigated the effect of bradykinin on the electrical activity of rat myenteric neurons, the key players for regulation of gastrointestinal motility. Bradykinin (2 × 10(-8)mol/l) induced a biphasic increase in frequency of action potentials measured with microelectrode arrays. This increase was mirrored by a biphasic increase in cytosolic Ca(2+) concentration ([Ca(2+)]i), which was observed in about 40% of the myenteric neurons. The bradykinin B1 receptor agonist des-arg(9)-bradykinin as well as the bradykinin B2 receptor agonist hyp(3)-bradykinin induced a similar effect on [Ca(2+)]i. Immunocytochemical stainings confirmed the expression of both receptor types by myenteric ganglionic cells. Real time PCR showed that the inducible B1 receptor was upregulated during cell culture. The inhibition of cyclooxygenases with piroxicam reduced the effect of bradykinin on the electrical activity of myenteric neurons. The suppression of the glial growth on microelectrode arrays did not affect the bradykinin-induced change in frequency of action potentials. This suggests that prostaglandins, which probably mediate the effect of bradykinin, are not exclusively released from glial cells. The bradykinin-induced increase in [Ca(2+)]i was dependent on the presence of extracellular Ca(2+) and was inhibited by Co(2+), Cd(2+), and Ni(2+), blockers of voltage-dependent Ca(2+) channels, indicating a stimulation of the influx of extracellular Ca(2+) by the kinin. Consequently, bradykinin induces a Ca(2+) influx in myenteric neurons via Ca(2+) channels in the plasma membrane.
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Romero A, Ramos E, de Los Ríos C, Egea J, Del Pino J, Reiter RJ. A review of metal-catalyzed molecular damage: protection by melatonin. J Pineal Res 2014; 56:343-70. [PMID: 24628077 DOI: 10.1111/jpi.12132] [Citation(s) in RCA: 123] [Impact Index Per Article: 12.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/17/2014] [Accepted: 03/11/2014] [Indexed: 12/31/2022]
Abstract
Metal exposure is associated with several toxic effects; herein, we review the toxicity mechanisms of cadmium, mercury, arsenic, lead, aluminum, chromium, iron, copper, nickel, cobalt, vanadium, and molybdenum as these processes relate to free radical generation. Free radicals can be generated in cells due to a wide variety of exogenous and endogenous processes, causing modifications in DNA bases, enhancing lipid peroxidation, and altering calcium and sulfhydryl homeostasis. Melatonin, an ubiquitous and pleiotropic molecule, exerts efficient protection against oxidative stress and ameliorates oxidative/nitrosative damage by a variety of mechanisms. Also, melatonin has a chelating property which may contribute in reducing metal-induced toxicity as we postulate here. The aim of this review was to highlight the protective role of melatonin in counteracting metal-induced free radical generation. Understanding the physicochemical insights of melatonin related to the free radical scavenging activity and the stimulation of antioxidative enzymes is of critical importance for the development of novel therapeutic strategies against the toxic action of these metals.
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Affiliation(s)
- Alejandro Romero
- Departamento de Toxicología y Farmacología, Facultad de Veterinaria, Universidad Complutense de Madrid, Madrid, Spain
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De Marco G, Lomartire A, Mandili G, Lupino E, Buccinnà B, Ramondetti C, Moglia C, Novelli F, Piccinini M, Mostert M, Rinaudo MT, Chiò A, Calvo A. Reduced cellular Ca(2+) availability enhances TDP-43 cleavage by apoptotic caspases. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2014; 1843:725-34. [PMID: 24440855 DOI: 10.1016/j.bbamcr.2014.01.010] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/10/2013] [Revised: 12/20/2013] [Accepted: 01/08/2014] [Indexed: 12/13/2022]
Abstract
Accumulation of transactive response DNA binding protein (TDP-43) fragments in motor neurons is a post mortem hallmark of different neurodegenerative diseases. TDP-43 fragments are the products of the apoptotic caspases-3 and -7. Either excessive or insufficient cellular Ca(2+) availability is associated with activation of apoptotic caspases. However, as far as we know, it is not described whether activation of caspases, due to restricted intracellular Ca(2+), affects TDP-43 cleavage. Here we show that in various cell lineages with restricted Ca(2+) availability, TDP-43 is initially cleaved by caspases-3 and -7 and then, also by caspases-6 and -8 once activated by caspase-3. Furthermore, we disclose the existence of a TDP-43 caspase-mediated fragment of 15kDa, in addition to the well-known fragments of 35 and 25kDa. Interestingly, with respect to the other two fragments this novel fragment is the major product of caspase activity on murine TDP-43 whereas in human cell lines the opposite occurs. This outcome should be considered when murine models are used to investigate TDP-43 proteinopathies.
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Affiliation(s)
- Giovanni De Marco
- 'Rita Levi Montalcini' Department of Neuroscience, University of Turin, Turin, Italy; Department of Oncology, University of Turin, Turin, Italy
| | - Annarosa Lomartire
- 'Rita Levi Montalcini' Department of Neuroscience, University of Turin, Turin, Italy; Department of Oncology, University of Turin, Turin, Italy
| | - Giorgia Mandili
- Center for Experimental Research and Medical Studies (CeRMS), University of Turin, Turin, Italy; Department of Molecular Biotechnology and Health Sciences, University of Turin, Turin, Italy
| | - Elisa Lupino
- Department of Oncology, University of Turin, Turin, Italy
| | | | | | - Cristina Moglia
- 'Rita Levi Montalcini' Department of Neuroscience, University of Turin, Turin, Italy; CRESLA Turin, AOU Città della Salute e della Scienza, Turin, Italy
| | - Francesco Novelli
- Center for Experimental Research and Medical Studies (CeRMS), University of Turin, Turin, Italy; Department of Molecular Biotechnology and Health Sciences, University of Turin, Turin, Italy
| | | | - Michael Mostert
- Department of Public Health and Pediatric Sciences, University of Turin, Turin, Italy
| | | | - Adriano Chiò
- 'Rita Levi Montalcini' Department of Neuroscience, University of Turin, Turin, Italy; CRESLA Turin, AOU Città della Salute e della Scienza, Turin, Italy
| | - Andrea Calvo
- 'Rita Levi Montalcini' Department of Neuroscience, University of Turin, Turin, Italy; CRESLA Turin, AOU Città della Salute e della Scienza, Turin, Italy
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Perez-Reyes E, Lee JH. Ins and outs of T-channel structure function. Pflugers Arch 2013; 466:627-33. [PMID: 24337909 DOI: 10.1007/s00424-013-1419-5] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2013] [Accepted: 12/03/2013] [Indexed: 02/07/2023]
Abstract
We review the ins and outs of T-channel structure, focusing on the extracellular high-affinity metal-binding site and intracellular loops. The high-affinity metal-binding site was localized to repeat I of Cav3.2. Interestingly, a similar binding site was found in the high voltage-activated Cav2.3 channel where it controls the channels' voltage dependence. Histidine at position 191 has a particularly interesting role in the high-affinity binding site, and its modification plays an important role in channel regulation by pharmacological agents that alter redox reactions. The intracellular loop connecting repeats I and II plays two important roles in Cav3.2 properties: one, its gating; and two, its surface expression. These studies have also identified a highly conserved intracellular gating brake that is predicted to form a helix-loop-helix structure. We conclude that the gating brake establishes important contacts with the gating machinery, thereby stabilizing a closed state of T-channels. This interaction is disrupted by depolarization, allowing the S6 segments to open and allowing Ca(2+) ions to flow through. Studies in cultured hippocampal neurons provided novel insights into how mutations found in idiopathic generalized epilepsy patients increase seizure susceptibility by both altering T-current pacemaker currents and by activating Ca-activated transcription factors that regulate dendritic arborization. These studies reveal novel roles for T-channels to control cellular physiology.
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Affiliation(s)
- Edward Perez-Reyes
- Department of Pharmacology, University of Virginia, Charlottesville, VA, USA,
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44
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Engbers JDT, Anderson D, Zamponi GW, Turner RW. Signal processing by T-type calcium channel interactions in the cerebellum. Front Cell Neurosci 2013; 7:230. [PMID: 24348329 PMCID: PMC3841819 DOI: 10.3389/fncel.2013.00230] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2013] [Accepted: 11/06/2013] [Indexed: 01/28/2023] Open
Abstract
T-type calcium channels of the Cav3 family are unique among voltage-gated calcium channels due to their low activation voltage, rapid inactivation, and small single channel conductance. These special properties allow Cav3 calcium channels to regulate neuronal processing in the subthreshold voltage range. Here, we review two different subthreshold ion channel interactions involving Cav3 channels and explore the ability of these interactions to expand the functional roles of Cav3 channels. In cerebellar Purkinje cells, Cav3 and intermediate conductance calcium-activated potassium (IKCa) channels form a novel complex which creates a low voltage-activated, transient outward current capable of suppressing temporal summation of excitatory postsynaptic potentials (EPSPs). In large diameter neurons of the deep cerebellar nuclei, Cav3-mediated calcium current (I T) and hyperpolarization-activated cation current (I H) are activated during trains of inhibitory postsynaptic potentials. These currents have distinct, and yet synergistic, roles in the subthreshold domain with I T generating a rebound burst and I H controlling first spike latency and rebound spike precision. However, by shortening the membrane time constant the membrane returns towards resting value at a faster rate, allowing I H to increase the efficacy of I T and increase the range of burst frequencies that can be generated. The net effect of Cav3 channels thus depends on the channels with which they are paired. When expressed in a complex with a KCa channel, Cav3 channels reduce excitability when processing excitatory inputs. If functionally coupled with an HCN channel, the depolarizing effect of Cav3 channels is accentuated, allowing for efficient inversion of inhibitory inputs to generate a rebound burst output. Therefore, signal processing relies not only on the activity of individual subtypes of channels but also on complex interactions between ion channels whether based on a physical complex or by indirect effects on membrane properties.
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Affiliation(s)
- Jordan D. T. Engbers
- Department of Cell Biology and Anatomy, Hotchkiss Brain Institute, University of CalgaryCalgary, Canada
| | - Dustin Anderson
- Department of Cell Biology and Anatomy, Hotchkiss Brain Institute, University of CalgaryCalgary, Canada
| | - Gerald W. Zamponi
- Department of Physiology and Pharmacology, Hotchkiss Brain Institute, University of CalgaryCalgary, Canada
| | - Ray W. Turner
- Department of Cell Biology and Anatomy, Hotchkiss Brain Institute, University of CalgaryCalgary, Canada
- Department of Physiology and Pharmacology, Hotchkiss Brain Institute, University of CalgaryCalgary, Canada
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Lambert RC, Bessaïh T, Crunelli V, Leresche N. The many faces of T-type calcium channels. Pflugers Arch 2013; 466:415-23. [PMID: 24043572 DOI: 10.1007/s00424-013-1353-6] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2013] [Revised: 09/06/2013] [Accepted: 09/07/2013] [Indexed: 01/27/2023]
Abstract
Since the discovery of low-voltage-activated T-type calcium channels in sensory neurons and the initial characterization of their physiological function mainly in inferior olive and thalamic neurons, studies on neuronal T-type currents have predominantly focused on the generation of low-threshold spike (and associated action potential burst firing) which is strictly conditioned by a preceding hyperpolarization. This T-type current mediated activity has become an archetype of the function of these channels, constraining our view of the potential physiological and pathological roles that they may play in controlling the excitability of single cells and neural networks. However, greatly helped by the recent availability of the first potent and selective antagonists for this class of calcium channels, novel T-type current functions are rapidly being uncovered, including their surprising involvement in neuronal excitability at depolarized membrane potentials and their complex control of dendritic integration and neurotransmitter release. These and other data summarized in this short review clearly indicate a much wider physiological involvement of T-type channels in neuronal activity than previously expected.
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Ramachandra R, Hassan B, McGrew SG, Dompor J, Farrag M, Ruiz-Velasco V, Elmslie KS. Identification of CaV channel types expressed in muscle afferent neurons. J Neurophysiol 2013; 110:1535-43. [PMID: 23843437 DOI: 10.1152/jn.00069.2013] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Cardiovascular adjustments to exercise are partially mediated by group III/IV (small to medium) muscle afferents comprising the exercise pressor reflex (EPR). However, this reflex can be inappropriately activated in disease states (e.g., peripheral vascular disease), leading to increased risk of myocardial infarction. Here we investigate the voltage-dependent calcium (CaV) channels expressed in small to medium muscle afferent neurons as a first step toward determining their potential role in controlling the EPR. Using specific blockers and 5 mM Ba(2+) as the charge carrier, we found the major calcium channel types to be CaV2.2 (N-type) > CaV2.1 (P/Q-type) > CaV1.2 (L-type). Surprisingly, the CaV2.3 channel (R-type) blocker SNX482 was without effect. However, R-type currents are more prominent when recorded in Ca(2+) (Liang and Elmslie 2001). We reexamined the channel types using 10 mM Ca(2+) as the charge carrier, but results were similar to those in Ba(2+). SNX482 was without effect even though ∼27% of the current was blocker insensitive. Using multiple methods, we demonstrate that CaV2.3 channels are functionally expressed in muscle afferent neurons. Finally, ATP is an important modulator of the EPR, and we examined the effect on CaV currents. ATP reduced CaV current primarily via G protein βγ-mediated inhibition of CaV2.2 channels. We conclude that small to medium muscle afferent neurons primarily express CaV2.2 > CaV2.1 ≥ CaV2.3 > CaV1.2 channels. As with chronic pain, CaV2.2 channel blockers may be useful in controlling inappropriate activation of the EPR.
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Affiliation(s)
- Renuka Ramachandra
- The Baker Laboratory of Pharmacology, Department of Pharmacology, AT Still University of Health Sciences, Kirksville, Missouri
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Schneider T, Dibué M, Hescheler J. How "Pharmacoresistant" is Cav2.3, the Major Component of Voltage-Gated R-type Ca2+ Channels? Pharmaceuticals (Basel) 2013; 6:759-76. [PMID: 24276260 PMCID: PMC3816731 DOI: 10.3390/ph6060759] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2013] [Revised: 04/26/2013] [Accepted: 05/06/2013] [Indexed: 12/04/2022] Open
Abstract
Membrane-bound voltage-gated Ca2+ channels (VGCCs) are targets for specific signaling complexes, which regulate important processes like gene expression, neurotransmitter release and neuronal excitability. It is becoming increasingly evident that the so called “resistant” (R-type) VGCC Cav2.3 is critical in several physiologic and pathophysiologic processes in the central nervous system, vascular system and in endocrine systems. However its eponymous attribute of pharmacologic inertness initially made in depth investigation of the channel difficult. Although the identification of SNX-482 as a fairly specific inhibitor of Cav2.3 in the nanomolar range has enabled insights into the channels properties, availability of other pharmacologic modulators of Cav2.3 with different chemical, physical and biological properties are of great importance for future investigations. Therefore the literature was screened systematically for molecules that modulate Cav2.3 VGCCs.
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Affiliation(s)
- Toni Schneider
- Institute of Neurophysiology, University of Cologne, Robert-Koch-Str. 39, Cologne D-50931, Germany; E-Mail:
- Authors to whom correspondence should be addressed; E-Mails: (T.S.); (M.D.); Tel.: +49-221-478-69446 (T.S.); Fax: +49-221-478-6965 (T.S.)
| | - Maxine Dibué
- Institute of Neurophysiology, University of Cologne, Robert-Koch-Str. 39, Cologne D-50931, Germany; E-Mail:
- Department for Neurosurgery, Medical Faculty, Heinrich Heine University, Moorenstraße 5, Duesseldorf D-40225, Germany & Center of Molecular Medicine, Cologne D-50931, Germany
- Authors to whom correspondence should be addressed; E-Mails: (T.S.); (M.D.); Tel.: +49-221-478-69446 (T.S.); Fax: +49-221-478-6965 (T.S.)
| | - Jürgen Hescheler
- Institute of Neurophysiology, University of Cologne, Robert-Koch-Str. 39, Cologne D-50931, Germany; E-Mail:
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Presynaptic calcium influx controls neurotransmitter release in part by regulating the effective size of the readily releasable pool. J Neurosci 2013; 33:4625-33. [PMID: 23486937 DOI: 10.1523/jneurosci.4031-12.2013] [Citation(s) in RCA: 100] [Impact Index Per Article: 9.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
The steep calcium dependence of synaptic strength that has been observed at many synapses is thought to reflect a calcium dependence of the probability of vesicular exocytosis (p), with the cooperativity of three to six corresponding to the multiple calcium ion binding sites on the calcium sensor responsible for exocytosis. Here we test the hypothesis that the calcium dependence of the effective size of the readily releasable pool (RRP) also contributes to the calcium dependence of release at the calyx of Held synapse in mice. Using two established methods of quantifying neurotransmitter release evoked by action potentials (effective RRP), we find that when calcium influx is changed by altering the external calcium concentration, the calcium cooperativity of p is insufficient to account for the full calcium dependence of EPSC size; the calcium dependence of the RRP size also contributes. Reducing calcium influx by blocking R-type voltage-gated calcium channels (VGCCs) with Ni(2+), or by blocking P/Q-type VGCCs with ω-agatoxin IVA also changes EPSC amplitude by reducing both p and the effective RRP size. This suggests that the effective RRP size is dependent on calcium influx through VGCCs. Furthermore, activation of GABAB receptors, which reduces presynaptic calcium through VGCCs without other significant effects on release, also reduces the effective RRP size in addition to reducing p. These findings indicate that calcium influx regulates the RRP size along with p, which contributes to the calcium dependence of synaptic strength, and it influences the manner in which presynaptic modulation of presynaptic calcium channels affects neurotransmitter release.
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Rehak R, Bartoletti TM, Engbers JDT, Berecki G, Turner RW, Zamponi GW. Low voltage activation of KCa1.1 current by Cav3-KCa1.1 complexes. PLoS One 2013; 8:e61844. [PMID: 23626738 PMCID: PMC3633930 DOI: 10.1371/journal.pone.0061844] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/03/2013] [Accepted: 03/14/2013] [Indexed: 02/03/2023] Open
Abstract
Calcium-activated potassium channels of the KCa1.1 class are known to regulate repolarization of action potential discharge through a molecular association with high voltage-activated calcium channels. The current study examined the potential for low voltage-activated Cav3 (T-type) calcium channels to interact with KCa1.1 when expressed in tsA-201 cells and in rat medial vestibular neurons (MVN) in vitro. Expression of the channel α-subunits alone in tsA-201 cells was sufficient to enable Cav3 activation of KCa1.1 current. Cav3 calcium influx induced a 50 mV negative shift in KCa1.1 voltage for activation, an interaction that was blocked by Cav3 or KCa1.1 channel blockers, or high internal EGTA. Cav3 and KCa1.1 channels coimmunoprecipitated from lysates of either tsA-201 cells or rat brain, with Cav3 channels associating with the transmembrane S0 segment of the KCa1.1 N-terminus. KCa1.1 channel activation was closely aligned with Cav3 calcium conductance in that KCa1.1 current shared the same low voltage dependence of Cav3 activation, and was blocked by voltage-dependent inactivation of Cav3 channels or by coexpressing a non calcium-conducting Cav3 channel pore mutant. The Cav3-KCa1.1 interaction was found to function highly effectively in a subset of MVN neurons by activating near –50 mV to contribute to spike repolarization and gain of firing. Modelling data indicate that multiple neighboring Cav3-KCa1.1 complexes must act cooperatively to raise calcium to sufficiently high levels to permit KCa1.1 activation. Together the results identify a novel Cav3-KCa1.1 signaling complex where Cav3-mediated calcium entry enables KCa1.1 activation over a wide range of membrane potentials according to the unique voltage profile of Cav3 calcium channels, greatly extending the roles for KCa1.1 potassium channels in controlling membrane excitability.
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Affiliation(s)
- Renata Rehak
- Department of Physiology and Pharmacology, Hotchkiss Brain Institute, University of Calgary, Calgary, Canada
| | - Theodore M. Bartoletti
- Department of Cell Biology and Anatomy, Hotchkiss Brain Institute, University of Calgary, Calgary, Canada
| | - Jordan D. T. Engbers
- Department of Cell Biology and Anatomy, Hotchkiss Brain Institute, University of Calgary, Calgary, Canada
| | - Geza Berecki
- Department of Physiology and Pharmacology, Hotchkiss Brain Institute, University of Calgary, Calgary, Canada
| | - Ray W. Turner
- Department of Cell Biology and Anatomy, Hotchkiss Brain Institute, University of Calgary, Calgary, Canada
| | - Gerald W. Zamponi
- Department of Physiology and Pharmacology, Hotchkiss Brain Institute, University of Calgary, Calgary, Canada
- * E-mail:
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Isope P, Hildebrand ME, Snutch TP. Contributions of T-type voltage-gated calcium channels to postsynaptic calcium signaling within Purkinje neurons. THE CEREBELLUM 2012; 11:651-65. [PMID: 20734177 PMCID: PMC3411289 DOI: 10.1007/s12311-010-0195-4] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Low threshold voltage-gated T-type calcium channels have long been implicated in the electrical excitability and calcium signaling of cerebellar Purkinje neurons although the molecular composition, localization, and modulation of T-type channels within Purkinje cells have only recently been addressed. The specific functional roles that T-type channels play in local synaptic integration within Purkinje spines are also currently being unraveled. Overall, Purkinje neurons represent a powerful model system to explore the potential roles of postsynaptic T-type channels throughout the nervous system. In this review, we present an overview of T-type calcium channel biophysical, pharmacological, and physiological characteristics that provides a foundation for understanding T-type channels within Purkinje neurons. We also describe the biophysical properties of T-type channels in context of other voltage-gated calcium channel currents found within Purkinje cells. The data thus far suggest that one specific T-type isoform, Cav3.1, is highly expressed within Purkinje spines and both physically and functionally couples to mGluR1 and other effectors within putative signaling microdomains. Finally, we discuss how the selective potentiation of Cav3.1 channels via activation of mGluR1 by parallel fiber inputs affects local synaptic integration and how this interaction may relate to the overall excitability of Purkinje neuron dendrites.
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Affiliation(s)
- Philippe Isope
- Institut des Neurosciences Cellulaires et Intégratives, CNRS-Université de Strasbourg, 5 rue Blaise Pascal, Strasbourg, France.
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