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Nordström T, Andersson LC, Åkerman KEO. Role of hyperpolarization-activated cyclic nucleotide-gated channel HCN2 in embryonic neural stem cell proliferation and differentiation. Neurochem Int 2022; 159:105387. [PMID: 35835292 DOI: 10.1016/j.neuint.2022.105387] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2022] [Revised: 06/06/2022] [Accepted: 07/03/2022] [Indexed: 10/17/2022]
Abstract
Hyperpolarization-activated cyclic nucleotide-gated channels (HCN channels) are involved in spontaneous activity in many electrically active cell types such as cardiomyocytes and neurons. In this study, the role of HCN channels in proliferation and migration of Nestin and Sox2 expressing embryonic neural progenitor cells (NPC) originating from the subventricular zone (SVZ) was examined. Immunostaining and PCR data showed that the HCN2 subtype was highly expressed in these cells. Patch clamp recordings revealed a hyperpolarization-activated current, which was sensitive to inhibitors of HCN channels. Using the fluorescence dye bis-(1,3-dibutylbarbituric acid)-trimethineoxonol (DiBAC(4)(3)) we found that a prompt reduction of the extracellular K+ concentration, or exposing the cells to acute hypoxia, induced an instant hyperpolarization in the whole cell population. Recovery from low K+ induced hyperpolarization after extracellular calcium removal, or by re-oxygenation of hypoxic cells, was sensitive to ZD7288, a HCN channel inhibitor. Treatment of neurosphere cultures from the SVZ with ZD7288 caused a significant and reversible inhibition of neurosphere formation from single cells indicating that proliferation of progenitor cells was reduced. Furthermore, the migration of neuronal cells from neurospheres was considerably retarded in the presence of ZD7288. The results suggest that HCN2 channels are involved in controlling the proliferation of NPC and that HCN2 channel-induced spontaneous electrical activity may trigger the motility response of neurosphere-derived neurons in concert with other ion channels. Furthermore, the response to hypoxia suggests that HCN2 channels may trigger the chemotactic response of NPC to ischemic brain regions seen in many studies.
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Affiliation(s)
- Tommy Nordström
- Faculty of Medicine, Medicum, Division of Physiology, P.O. Box 63, University of Helsinki, FIN-00014, Helsinki, Finland.
| | - Leif C Andersson
- Department of Pathology, Haartmaninkatu 3 (PB 21), 00014 University of Helsinki, Helsinki, Finland
| | - Karl E O Åkerman
- Faculty of Medicine, Medicum, Division of Physiology, P.O. Box 63, University of Helsinki, FIN-00014, Helsinki, Finland
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Tannic acid inhibits electrogenic Na+/HCO3- co-transporter activity in embryonic neural stem cell-derived radial glial-like cells. Neuroreport 2020; 31:57-63. [PMID: 31714480 PMCID: PMC6903378 DOI: 10.1097/wnr.0000000000001372] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
Self-renewing neural stem cells and progenitor cells are cell populations that generate radial glial cells and neurons through asymmetric division. Regulation of intracellular pH in stem cells with high metabolic activity is critical for both cell signaling and proliferation. We have recently found that a S0859-inhibitable electrogenic Na+/HCO3− co-transporter (NBCe1, Slc4a4), is the primary pHi regulatory mechanism in stem cell-derived radial glial-like cells. Here we show, by using the voltage-sensitive fluorescent dye DiBAC4(3) and BCECF, a pH-sensitive dye, that an antioxidant, tannic acid (100 µM), can inhibit potassium- and calcium-dependent rapid changes in membrane potential and NBCe1 mediated pHi regulation in brain-derived glial-like cells in vitro. Furthermore, neural stem cell differentiation and neurosphere formation (proliferation) were completely inhibited by tannic acid. The present study provides evidence that tannic acid is a natural inhibitor of NBCe1. It is tempting to speculate that tannic acid or related compounds that inhibits NBCe1-mediated pHi regulation in glial-like cells may also have bearing on the treatment of glial neoplasms.
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Nordström T, Andersson LC, Åkerman KE. Regulation of intracellular pH by electrogenic Na+/HCO3– co-transporters in embryonic neural stem cell-derived radial glia-like cells. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2019; 1861:1037-1048. [DOI: 10.1016/j.bbamem.2019.03.007] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/01/2018] [Revised: 03/11/2019] [Accepted: 03/14/2019] [Indexed: 01/19/2023]
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Bonnet U, Bingmann D, Speckmann EJ, Wiemann M. Levetiracetam mediates subtle pH-shifts in adult human neocortical pyramidal cells via an inhibition of the bicarbonate-driven neuronal pH-regulation - Implications for excitability and plasticity modulation. Brain Res 2019; 1710:146-156. [PMID: 30590026 DOI: 10.1016/j.brainres.2018.12.039] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2018] [Revised: 11/24/2018] [Accepted: 12/23/2018] [Indexed: 01/20/2023]
Abstract
The intracellular pH (pHi) of mammalian central neurons is tightly regulated and small pHi-fluctuations can fine-tune inter-/intracellular signaling, excitability, and synaptic plasticity. The research-gap about the pHi-regulation of human brain neurons is addressed here by testing possible influences of the anticonvulsant levetiracetam (LEV). BCECF-AM-loaded neocortical pyramidal cells were fluorometrically investigated in slice-preparations of tissue resected from the middle temporal gyrus of five adults with intractable temporal-lobe epilepsy. Recovery-slope from intracellular acidification following an ammonium prepulse (APP) was used to measure the pHi-regulation. Among twenty pyramidal cells exposed to 50 μM LEV, the resting pHi (7.09 ± 0.14) was lowered in eight (40%) neurons, on average by 0.02 ± 0.011 pH-units. In three (15%) and nine (45%) neurons, a minimal alkaline shift (0.017 ± 0.004 pH-units) and no pHi-shift occurred, respectively. The LEV-induced pHi-shifts were positively correlated with the resting pHi (r = 0.6, p = 0.006, n = 20). In five neurons, which all had responded on LEV with an acidification before, the recovery from APP-acidification was significantly delayed during LEV (p < 0.001). This inhibitory LEV-effect on pHi-regulation i) was similar to that of 200 μM 4,4'-diisothiocyanostilbene-2,2'-disulfonic acid (n = 2) and ii) did not occur under nominal bicarbonate-free conditions (n = 2). Thus, LEV lowered the pHi of human neocortical pyramidal cells most likely by a weakening of the transmembrane HCO3(-)-mediated acid-extrusion. This might contribute to LEV's anticonvulsive potency. Neurons with more acidic resting pHi-values showed a minimal alkalization upon LEV providing a mechanism for paradoxical proconvulsive LEV-effects rarely observed in epilepsy patients. The significance of these subtle pHi-shifts for cortical excitability and plasticity is discussed.
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Affiliation(s)
- Udo Bonnet
- Department of Psychiatry, Psychotherapy, and Psychosomatic Medicine, Evangelisches Krankenhaus Castrop-Rauxel, Academic Teaching Hospital of the University Duisburg-Essen, Castrop-Rauxel, Germany; Department of Psychiatry and Psychotherapy, Faculty of Medicine, LVR-Hospital Essen, University of Duisburg-Essen, Essen, Germany.
| | - Dieter Bingmann
- Institute of Physiology, University of Duisburg-Essen, Essen, Germany
| | | | - Martin Wiemann
- Institute of Physiology, University of Duisburg-Essen, Essen, Germany; IBE R&D gGmbH, Institute for Lung Health, D-48149 Münster, Germany
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Munteanu R, Stănică L, Gheorghiu M, Gáspár S. Water Electrolysis Carried Out on Microelectrodes to Obtain New Insights into the Regulation of Cytosolic pH. ChemElectroChem 2019. [DOI: 10.1002/celc.201801558] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Affiliation(s)
- Raluca‐Elena Munteanu
- International Centre of Biodynamics 1B Intrarea Portocalelor 060101 Bucharest Romania
| | - Luciana Stănică
- International Centre of Biodynamics 1B Intrarea Portocalelor 060101 Bucharest Romania
| | - Mihaela Gheorghiu
- International Centre of Biodynamics 1B Intrarea Portocalelor 060101 Bucharest Romania
| | - Szilveszter Gáspár
- International Centre of Biodynamics 1B Intrarea Portocalelor 060101 Bucharest Romania
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Hsieh FY, Han HW, Chen XR, Yang CS, Wei Y, Hsu SH. Non-viral delivery of an optogenetic tool into cells with self-healing hydrogel. Biomaterials 2018; 174:31-40. [DOI: 10.1016/j.biomaterials.2018.05.014] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2018] [Revised: 05/08/2018] [Accepted: 05/08/2018] [Indexed: 01/04/2023]
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Bonnet U, Bingmann D, Speckmann EJ, Wiemann M. Small intraneuronal acidification via short-chain monocarboxylates: First evidence of an inhibitory action on over-excited human neocortical neurons. Life Sci 2018; 204:65-70. [PMID: 29730171 DOI: 10.1016/j.lfs.2018.05.005] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2018] [Revised: 05/01/2018] [Accepted: 05/02/2018] [Indexed: 10/17/2022]
Abstract
AIMS In cortical mammalian neurons, small fluctuations of intracellular pH (pHi) play a crucial role for inter- and intracellular signaling as well as for cellular and synaptic plasticity. Yet, there have been no respective data about humans. Thus, we investigated the interrelation of pHi and excitability of human cortical neurons. MATERIALS AND METHODS Intracellular electrophysiological and pH-recordings were made in neurons in slices taken from brain tissue resected from the middle temporal gyrus of two male children (26 months and 35 months old) who suffered from pharmacotherapy-resistant temporal lobe epilepsy. To excite the tissue (n = 13), we used the 0-Mg2+/high-K+-in vitro epilepsy model producing robust epileptiform discharges (ED). To evoke an intracellular acidification (n = 12), we used the well-established propionate-model and applied 10 mM propionate to the bath solutions. In addition, we recorded the effects of other strongly related short-chain monocarboxylates (l-lactate (10 mM) and the ketone body DL-β-hydroxybutyrate (10 mM)) on ED and pHi. KEY FINDINGS The ED-frequency was reversibly reduced by propionate (n = 5), l-lactate (n = 5), or DL-β-hydroxybutyrate (n = 3), while the durations of EDs and their after-depolarizations increased. In parallel experiments, all three short-chain monocarboxylates (each n = 4) lowered the pHi of the neurons (n = 12) by 0.05-0.07 pH units which was temporally related to the reported changes in bioelectric activity. SIGNIFICANCE A mild drop of the intraneuronal pH was associated with the control of even over-excited human neocortical tissue. This is identical with prior observations in non-human mammalian cortical neurons. Possible implications for neuroplasticity and the treatment of neuropsychiatric disorders are discussed.
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Affiliation(s)
- Udo Bonnet
- Department of Psychiatry, Psychotherapy, and Psychosomatic Medicine, Evangelisches Krankenhaus Castrop-Rauxel, Academic Teaching Hospital of the University Duisburg-Essen, Castrop-Rauxel, Germany; Department of Psychiatry and Psychotherapy, Faculty of Medicine, LVR-Hospital Essen, University of Duisburg-Essen, Essen, Germany.
| | - Dieter Bingmann
- Institute of Physiology, University of Duisburg-Essen, Essen, Germany
| | | | - Martin Wiemann
- Institute of Physiology, University of Duisburg-Essen, Essen, Germany; IBE R&D gGmbH, Institute for Lung Health, D-48149 Münster, Germany
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Neuroprotective Effects of Bioactive Compounds and MAPK Pathway Modulation in "Ischemia"-Stressed PC12 Pheochromocytoma Cells. Brain Sci 2018; 8:brainsci8020032. [PMID: 29419806 PMCID: PMC5836051 DOI: 10.3390/brainsci8020032] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2017] [Revised: 01/24/2018] [Accepted: 02/02/2018] [Indexed: 02/08/2023] Open
Abstract
This review surveys the efforts taken to investigate in vitro neuroprotective features of synthetic compounds and cell-released growth factors on PC12 clonal cell line temporarily deprived of oxygen and glucose followed by reoxygenation (OGD/R). These cells have been used previously to mimic some of the properties of in vivo brain ischemia-reperfusion-injury (IRI) and have been instrumental in identifying common mechanisms such as calcium overload, redox potential, lipid peroxidation and MAPKs modulation. In addition, they were useful for establishing the role of certain membrane penetrable cocktails of antioxidants as well as potential growth factors which may act in neuroprotection. Pharmacological mechanisms of neuroprotection addressing modulation of the MAPK cascade and increased redox potential by natural products, drugs and growth factors secreted by stem cells, in either undifferentiated or nerve growth factor-differentiated PC12 cells exposed to ischemic conditions are discussed for future prospects in neuroprotection studies.
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Rajamäki K, Nordström T, Nurmi K, Åkerman KEO, Kovanen PT, Öörni K, Eklund KK. Extracellular acidosis is a novel danger signal alerting innate immunity via the NLRP3 inflammasome. J Biol Chem 2013; 288:13410-9. [PMID: 23530046 DOI: 10.1074/jbc.m112.426254] [Citation(s) in RCA: 247] [Impact Index Per Article: 22.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
BACKGROUND Local acidosis has been demonstrated in ischemic tissues and at inflammatory sites. RESULTS Acidic extracellular pH triggers NLRP3 inflammasome activation and interleukin-1β secretion in human macrophages. CONCLUSION Acidic pH represents a novel danger signal alerting the innate immunity. SIGNIFICANCE Local acidosis may promote inflammation at ischemic and inflammatory sites. Local extracellular acidification has been demonstrated at sites of ischemia and inflammation. IL-1β is one of the key proinflammatory cytokines, and thus, its synthesis and secretion are tightly regulated. The NLRP3 (nucleotide-binding domain leucine-rich repeat containing family, pyrin domain containing 3) inflammasome complex, assembled in response to microbial components or endogenous danger signals, triggers caspase-1-mediated maturation and secretion of IL-1β. In this study, we explored whether acidic environment is sensed by immune cells as an inflammasome-activating danger signal. Human macrophages were exposed to custom cell culture media at pH 7.5-6.0. Acidic medium triggered pH-dependent secretion of IL-1β and activation of caspase-1 via a mechanism involving potassium efflux from the cells. Acidic extracellular pH caused rapid intracellular acidification, and the IL-1β-inducing effect of acidic medium could be mimicked by acidifying the cytosol with bafilomycin A1, a proton pump inhibitor. Knocking down the mRNA expression of NLRP3 receptor abolished IL-1β secretion at acidic pH. Remarkably, alkaline extracellular pH strongly inhibited the IL-1β response to several known NLRP3 activators, demonstrating bipartite regulatory potential of pH on the activity of this inflammasome. The data suggest that acidic environment represents a novel endogenous danger signal alerting the innate immunity. Low pH may thus contribute to inflammation in acidosis-associated pathologies such as atherosclerosis and post-ischemic inflammatory responses.
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Affiliation(s)
- Kristiina Rajamäki
- Wihuri Research Institute, Biomedicum Helsinki, Haartmaninkatu 8, FI-00290 Helsinki, Finland.
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Jansson LC, Louhivuori L, Wigren HK, Nordström T, Louhivuori V, Castrén ML, Åkerman KE. Effect of glutamate receptor antagonists on migrating neural progenitor cells. Eur J Neurosci 2013; 37:1369-82. [PMID: 23383979 DOI: 10.1111/ejn.12152] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2012] [Revised: 01/10/2013] [Accepted: 01/10/2013] [Indexed: 02/03/2023]
Abstract
Neurotransmitters such as glutamate are potential regulators of neurogenesis. Interference with defined glutamate receptor subtypes affects proliferation, migration and differentiation of neural progenitor cells. The cellular targets for the actions of different glutamate receptor ligands are less well known. In this study we have combined calcium imaging, measurement of membrane potential, time-lapse imaging and immunocytochemistry to obtain a spatial overview of migrating mouse embryonic neural progenitor cell-derived cells responding to glutamate receptor agonists and antagonists. Responses via metabotropic glutamate receptor 5 correlated with radial glial cells and dominated in the inner migration zones close to the neurosphere. Block of metabotropic glutamate receptor 5 resulted in shorter radial glial processes, a transient increase in neuron-like cells emerging from the neurosphere and increased motility of neuron-like cells. α-Amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA)/kainate receptors are present on the majority of migrating neuronal cells, which with time accumulate at the outer edge of the migration zone. Blocking these receptors leads to an enhanced extension of radial glial processes and a reduced motility of neuron-like cells. Our results indicate that functional glutamate receptors have profound effects on the motility of neural progenitor cells. The main target for metabotropic glutamate receptor 5 appears to be radial glial cells while AMPA/kainate receptors are mainly expressed in newborn neuronal cells and regulate the migratory progress of these cells. The results suggest that both metabotropic glutamate receptor 5 and AMPA/kainate receptors are of importance for the guidance of migrating embryonic progenitor cells.
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Affiliation(s)
- Linda C Jansson
- Biomedicum Helsinki, Institute of Biomedicine/Physiology, University of Helsinki, Helsinki, Finland
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