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Kopacek J, Ondrias K, Sedlakova B, Tomaskova J, Zahradnikova L, Sedlak J, Sulova Z, Zahradnikova A, Pastorek J, Krizanova O. Type 2 IP(3) receptors are involved in uranyl acetate induced apoptosis in HEK 293 cells. Toxicology 2009; 262:73-9. [PMID: 19460415 DOI: 10.1016/j.tox.2009.05.006] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2009] [Revised: 05/11/2009] [Accepted: 05/11/2009] [Indexed: 11/19/2022]
Abstract
Calcium released from endoplasmic reticulum through special calcium release channels - inositol 1,4,5-trisphosphate receptors (IP(3)Rs) and ryanodine receptors (RyRs) - serves as a main source of cytosolic calcium signaling in the majority of cell types in physiological state and also in pathological situations. In this work, we studied whether IP(3)Rs can be involved in uranyl acetate induced nephrotoxicity. Using human embryonic kidney cell line (HEK293) as an experimental model we have found that uranyl acetate (5 and 50microM) up-regulates both, mRNA and protein levels of the type 1 and type 2 IP(3) receptors in HEK293 cells. This increase was associated with elevated expression of proapoptotic factors Bax and Caspase 3 and also by higher extent of apoptosis. Vice versa, induction of apoptosis resulted in increased mRNA levels of IP(3)R2 and also elevated levels of apoptotic markers. Therefore we propose that enhanced expression of the type 2 IP(3)Rs can at least partially contribute to increased levels of apoptosis due to uranyl acetate treatment.
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Affiliation(s)
- Juraj Kopacek
- Institute of Virology, Centre of Excellence for Cardiovascular Research, Bratislava, Slovakia
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Intracellular GSH levels rather than ROS levels are tightly related to AMA-induced HeLa cell death. Chem Biol Interact 2008; 171:67-78. [DOI: 10.1016/j.cbi.2007.08.011] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2007] [Revised: 08/31/2007] [Accepted: 08/31/2007] [Indexed: 11/23/2022]
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Harriman JF, Liu XL, Aleo MD, Machaca K, Schnellmann RG. Endoplasmic reticulum Ca(2+) signaling and calpains mediate renal cell death. Cell Death Differ 2002; 9:734-41. [PMID: 12058278 DOI: 10.1038/sj.cdd.4401029] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2001] [Revised: 01/08/2002] [Accepted: 01/16/2002] [Indexed: 11/09/2022] Open
Abstract
The goal of the current study was to determine the roles of ATP content, endoplasmic reticulum (ER) Ca(2+) stores, cytosolic free Ca(2+) (Ca(2+)(f)) and calpain activity in the signaling of rabbit renal proximal tubular (RPT) cell death (oncosis). Increasing concentrations (0.3-10 microM) of the mitochondrial inhibitor antimycin A produced rapid ATP depletion that correlated to a rapid and sustained increase in Ca(2+)(f), but not phospholipase C activation. The ER Ca(2+)-ATPase inhibitors thapsigargin (5 microM) or cyclopiazonic acid (100 microM) alone produced similar but transient increases in Ca(2+)(f). Pretreatment with thapsigargin prevented antimycin A-induced increases in Ca(2+)(f) and antimycin A pretreatment prevented thapsigargin-induced increases in Ca(2+)(f). Calpain activity increased in conjunction with ER Ca(2+) release. Pretreatment, but not post-treatment, with thapsigargin or cyclopiazonic acid prevented antimycin A-induced cell death. These data demonstrate that extensive ATP depletion signals oncosis through ER Ca(2+) release, a sustained increase in Ca(2+)(f) and calpain activation. Depletion of ER Ca(2+) stores prior to toxicant exposure prevents increases in Ca(2+)(f) and oncosis.
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Affiliation(s)
- J F Harriman
- Department of Pharmacology and Toxicology, University of Arkansas for Medical Sciences, 4301 West Markham Street, Slot 638, Little Rock, Arkansas 72205-7199, USA
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4
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AMPA receptor-mediated, calcium-dependent CREB phosphorylation in a subpopulation of auditory neurons surviving activity deprivation. J Neurosci 2000. [PMID: 10934277 DOI: 10.1523/jneurosci.20-16-06267.2000] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Although dependence on afferent synaptic activity has been shown for central neurons in every sensory system, the mechanisms of afferent maintenance of target sensory neurons are not understood. Neurons in the cochlear nucleus (CN) require afferent activity for maintenance and survival. One of the earliest changes seen after activity deprivation is an increase in intracellular calcium that leads to the death of 30% of the neuronal population. Sixty minutes after deafferentation, the surviving neurons show increased phosphorylation of the transcription factor calcium/cAMP response element-binding protein (CREB). CREB phosphorylation in activity-deprived CN neurons is dependent on increased intracellular calcium resulting from influx through AMPA receptors and is mediated by calcium/calmodulin-dependent kinases and protein kinase A. We conclude that in CN neurons, the deafferentation-induced increase in calcium activates at least two kinase pathways that phosphorylate CREB in surviving neurons. We hypothesize that this phosphorylation results in the transcription of genes containing the calcium/cAMP response element within their promoter regions, and these genes code for proteins that allow the neurons to compensate for their hypercalcemic, activity-deprived state.
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Perez Velazquez JL, Frantseva MV, Huzar DV, Carlen PL. Mitochondrial porin required for ischemia-induced mitochondrial dysfunction and neuronal damage. Neuroscience 2000; 97:363-9. [PMID: 10799768 DOI: 10.1016/s0306-4522(99)00569-2] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
The precise molecular events of mitochondrial dysfunction, one of the last steps that irreversibly determines cellular degeneration and death, remain unknown. We introduce a novel strategy to isolate and assess the molecular mechanisms underlying mitochondrial dysfunction. Using an in vitro ischemia model, we obtained evidence for prolonged mitochondrial depolarization in rat organotypic hippocampal brain slices during reperfusion. Then, mitochondria were isolated from brain slices and mitochondrial proteins were purified on a cyclosporin-A affinity column. Cyclosporin-A is the most potent inhibitor of mitochondrial dysfunction, in particular the mitochondrial permeability transition, and therefore we hypothesized that it may interact with proteins involved in the permeability transition after mitochondria were subjected to manipulations that promote this event. Mitochondrial porin was reproducibly eluted from the affinity column using proteins from ischemic brain mitochondria, or from mitochondria exposed to oxidative stress that were used as a positive control. Anti-porin antibodies prevented mitochondrial depolarization and electrophysiological deterioration of hippocampal neurons during hypoxia-reperfusion, as measured by simultaneous fluorescence imaging and whole-cell recordings. These observations provide biochemical and functional evidence that porin is directly involved in mitochondrial dysfunction and neuronal impairment during ischemia-reperfusion, and indicate that porin could be a novel therapeutic target to prevent cellular degeneration.
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Affiliation(s)
- J L Perez Velazquez
- Playfair Neuroscience Unit, Department of Medicine (Neurology), Toronto Western Hospital, University of Toronto, 399 Bathurst Street, Toronto, Canada.
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Zirpel L, Lippe WR, Rubel EW. Activity-dependent regulation of [Ca2+]i in avian cochlear nucleus neurons: roles of protein kinases A and C and relation to cell death. J Neurophysiol 1998; 79:2288-302. [PMID: 9582205 DOI: 10.1152/jn.1998.79.5.2288] [Citation(s) in RCA: 75] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
Neurons of the cochlear nucleus, nucleus magnocellularis (NM), of young chicks require excitatory afferent input from the eighth nerve for maintenance and survival. One of the earliest changes seen in NM neurons after deafferentation is an increase in intracellular calcium concentration ([Ca2+]i). This increase in [Ca2+]i is due to loss of activation of metabotropic glutamate receptors (mGluR) that activate second-messenger cascades involved in [Ca2+]i regulation. Because mGluRs are known to act via the phospholipase C and adenylate cyclase signal transduction pathways, the goal of this study was to determine the roles of protein kinases A (PKA) and C (PKC) activities in the regulation of NM neuron [Ca2+]i by eighth nerve stimulation. Additionally, we sought to determine the relationship between increased [Ca2+]i and cell death as measured by propidium iodide incorporation. [Ca2+]i of individual NM neurons in brain stem slices was monitored using fura-2 ratiometric fluorescence imaging. NM field potentials were monitored in experiments in which the eighth nerve was stimulated. Five hertz orthodromic stimulation maintained NM neuron [Ca2+]i at approximately 110 nM for 180 min. In the absence of stimulation, NM neuron [Ca2+]i increased steadily to a mean of 265 nM by 120 min. This increase was attenuated by superfusion of PKC activators phorbol-12,13-myristate acetate (100 nM) or dioctanoylglycerol (50 microM) and by activators of PKA: 1 mM 8-bromoadenosine-3',5'-cyclophosphate sodium (8-Br-cAMP), 50 microM forskolin or 100 microM Sp-adenosine 3',5'-cyclic monophosphothioate triethylamine. Inhibition of PKA (100 microM Rp-cAMPS) or PKC (50 nM bisindolymaleimide or 10 microM U73122) during continuous orthodromic stimulation resulted in an increase in NM neuron [Ca2+]i that exceeded 170 and 180 nM, respectively, by 120 min. Nonspecific kinase inhibition with 1 microM staurosporine during stimulation resulted in an [Ca2+]i increase that was greater in magnitude than that seen with either PKA or PKC inhibition alone, equal to that seen in the absence of stimulation, but much smaller than that seen with inhibition of mGluRs. In addition, manipulations that resulted in a [Ca2+]i increase >/=250 nM resulted in an increase in number and percentage of propidium iodide-labeled NM neurons. These results suggest that eighth nerve activity maintains [Ca2+]i of NM neurons at physiological levels in part via mGluR-mediated activation of PKA and PKC and that increases in [Ca2+]i due to activity deprivation or interruption of the PKA and PKC [Ca2+]i regulatory mechanisms are predictive of subsequent cell death.
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Affiliation(s)
- L Zirpel
- The Virginia Merrill Bloedel Hearing Research Center and The Department of Otolaryngology-Head and Neck Surgery, University of Washington School of Medicine, Seattle, 98195, USA
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Villablanca AC, Reid TW. Substance P stimulates vascular endothelial cellular reducing capacity in the presence of insulin and human plasma factors. J Cell Biochem 1997. [DOI: 10.1002/(sici)1097-4644(19970915)66:4<471::aid-jcb6>3.0.co;2-i] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
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Warren GL, Williams JH, Ward CW, Matoba H, Ingalls CP, Hermann KM, Armstrong RB. Decreased contraction economy in mouse EDL muscle injured by eccentric contractions. J Appl Physiol (1985) 1996; 81:2555-64. [PMID: 9018506 DOI: 10.1152/jappl.1996.81.6.2555] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023] Open
Abstract
The objective of this study was to find out whether basal and/or active energy metabolism are altered in isolated mouse extensor digitorum longus muscle injured by eccentric (Ecc) contractions. Measurements of basal O2 consumption and isometric tetanus O2 recovery cost were made at 25 degrees C on muscles that had done either 10 Ecc, 10 isometric (Iso), or no contractions (No). In parallel experiments, rates of lactate and pyruvate production were measured to estimate the anaerobic contribution. Basal O2 consumption was unaffected by the type of protocol performed (P = 0.07). However, the tetanus O2 cost per force-time integral was elevated by 30-36% for the Ecc protocol muscles over that for the Iso and No protocol muscles. When including the increased lactate production by the Ecc protocol muscles, the total energetic cost per force-time integral was 53% higher than that for the Iso protocol muscles [2.35 +/- 0.17 vs. 1.54 +/- 0.18 mumol O2/(N.m.s)]. The decreased economy was attributed to two factors. First, in skinned fibers isolated from the injured muscles, the ratio of maximal actomyosin adenosinetriphosphatase activity to force production was up by 37.5%, suggesting uncoupling of ATP hydrolysis from force production. Second, increased reliance on anaerobic metabolism along with the fluorescent microscopic study of mitochondrial membrane potential and histochemical study of ATP synthase suggested an uncoupling of oxidative phosphorylation in the injured muscles.
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Affiliation(s)
- G L Warren
- Muscle Biology Laboratory, Texas A&M University, College Station 77843, USA
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Abstract
Morphological alterations of cardiac mitochondria have been observed in rats chronically treated with cocaine. Whether cocaine directly causes heart mitochondrial dysfunction remains unclear. The present study was undertaken to investigate the effect of cocaine on mitochondrial function in cultured myocardial cells. Cells were incubated with cocaine (10(-5)-10(-3) M) for 3-72 h, using either a repeated or single exposure protocol. Cocaine (10(-3) M) produced severe cytotoxicity after repeated exposure (24-72 h), as elevated by leakage of lactate dehydrogenase. Treatment of the cultures with a single exposure protocol (10(-5)-10(-3) M for 24 h or less) produced a very modest cytotoxic effect, as shown by a small increase in LDH leakage. However, cellular ATP levels showed a time-dependent decline in cultures treated with the single exposure protocol. Experiments using a digitized fluorescence imaging system revealed that cocaine (single exposure protocol) caused a dose- and time-dependent decrease in mitochondrial membrane potential, and the decline in membrane potential occurred prior to manifestation of cytotoxicity shown with the repeated exposure protocol. Cytosolic and mitochondrial calcium levels, as determined by fura-2, were not affected during treatment with cocaine. Our results suggest that cocaine may compromise cardiac mitochondrial function and may lead to cardiotoxicity.
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Affiliation(s)
- C Yuan
- Division of Pharmacology and Toxicology, College of Pharmacy, University of Texas at Austin 78712, USA
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Dominguez JH, Song B, Liu-Chen S, Qulali M, Howard R, Lee CH, McAteer J. Studies of renal injury. II. Activation of the glucose transporter 1 (GLUT1) gene and glycolysis in LLC-PK1 cells under Ca2+ stress. J Clin Invest 1996; 98:395-404. [PMID: 8755650 PMCID: PMC507443 DOI: 10.1172/jci118805] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023] Open
Abstract
Injury to the renal proximal tubule is common and may be followed by either recovery or cell death. The survival of injured cells is supported by a transient change in cellular metabolism that maintains life even when oxygen tension is reduced. This adaptive process involves the activation of the gene encoding the glucose transporter GLUT1, which is essential to maintain the high rates of glucose influx demanded by glycolysis. We hypothesized that after cell injury increases of cell Ca2+ (Ca2+i) initiate the flow of information that culminates with the upregulation of the stress response gene GLUT1. We found that elevations of Ca2+i caused by the calcium ionophore A23187 activated the expression of the GLUT1 gene in LLC-PK1 cells. The stimulatory effect of Ca2+i on GLUT1 gene expression was, at least in part, transcriptional and resulted in higher levels of GLUT1 mRNA, cognate protein, cellular hexose transport activity, glucose consumption, and lactate production. This response was vital to the renal cells, as its interruption severely increased Ca2+-induced cytotoxicity and cell mortality. We propose that increases of Ca2+i initiate stress responses, represented in part by activation of the GLUT1 gene, and that disruption to the flow of information originating from Ca2+-induced stress, or to the coordinated expression of the stress response, prevents cell recovery after injury and may be an important cause of permanent renal cell injury and cell death.
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Affiliation(s)
- J H Dominguez
- Department of Medicine, Indiana University Medical Center, Indiana 46202, USA
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11
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Lilius H, Isomaa B. Fluorescent Probes as Tools in In Vitro Toxicology. Altern Lab Anim 1996. [DOI: 10.1177/026119299602400318] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
A number of different endpoints reflecting cell viability are commonly used to assess cytotoxicity. These endpoints are then taken to reflect cell death. It is not possible to elucidate the basis of the toxic mechanisms involved in these tests. However, by using a number of different endpoints to monitor different cellular events, the information that can be obtained from in vitro toxicity tests could be increased. Fluorescent probes appear to be promising alternatives for assessing cytotoxicity, and such probes are available for a number of different cellular events. In addition to viability, more-specific cellular events can be monitored, including intracellular glutathione levels, mitochondrial membrane potentials and intracellular concentrations of various ions. The possibility of using several fluorescent probes simultaneously, and hence of making measurements of several different cellular events at the same time, further increases the usefulness of fluorescent probes.
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Affiliation(s)
- Henrik Lilius
- Department of Biology, Abo Akademi University, BioCity, Artillerigatan 6, 20520 Turku/Abo, Finland
| | - Boris Isomaa
- Department of Biology, Abo Akademi University, BioCity, Artillerigatan 6, 20520 Turku/Abo, Finland
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Johann S, Zoller C, Haas S, Blümel G, Förster R. Anticoagulant Glycosaminoglycans Activate Respiratory Burst in Neutrophils and Monocytes. Clin Appl Thromb Hemost 1996. [DOI: 10.1177/107602969600200206] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Abstract
Using four different glycosaminoglycans (un fractionated heparin, low-molecular-weight heparin, pen tosan polysulfate, lactobionic acid) and the polypeptide hirudin, we investigated the influence of these anticoag ulant substances on both polymorphonuclear neutrophils and monocytes respiratory burst in vitro. Using real-time analysis, we demonstrated that both unfractionated and low-molecular-weight heparins, as well as pentosan polysulfate, trigger the respiratory burst in neutrophils and monocytes within 3 to 5 s at clinically relevant con centrations. These effects could be antagonized by pre- incubating the anticoagulant drugs with protamine. Scan ning electron microscopy confirmed an activated neutro phil phenotype after exposure to the anticoagulant compounds. Furthermore, we demonstrated that neither increased intracellular Ca2+ levels nor tyrosine phos phorylation of proteins, both mechanisms commonly in volved in the signal transduction in neutrophils, partici pate in the glycosaminoglycan-mediated activation of the respiratory burst. Our results indicate that defined anti coagulant substances can trigger the respiratory burst in vitro, which might also have clinical implications in cer tain diseases. Key Words: Glycosaminoglycans— Hirudin—Polymorphonuclear leukocytes—Monocytes— Respiratory burst—Flow cytometry.
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Affiliation(s)
- Sabine Johann
- Institut für Experimentelle Chirurgie der TU München, München
| | | | - Sylvia Haas
- Institut für Experimentelle Chirurgie der TU München, München
| | - Günther Blümel
- Institut für Experimentelle Chirurgie der TU München, München
| | - Reinhold Förster
- Max-Delbrück-Centrum für Molekulare Medizin, Berlin-Buch, Germany
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Plásek J, Sigler K. Slow fluorescent indicators of membrane potential: a survey of different approaches to probe response analysis. JOURNAL OF PHOTOCHEMISTRY AND PHOTOBIOLOGY. B, BIOLOGY 1996; 33:101-24. [PMID: 8691353 DOI: 10.1016/1011-1344(96)07283-1] [Citation(s) in RCA: 131] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Basic tenets related to the use of three main classes of potentiometric redistribution fluorescent dyes (carbocyanines, oxonols, and rhodamines) are discussed in detail. They include the structure/function relationship, formation of nonfluorescent (H-type) and fluorescent (J-type) dimers and higher aggregates, probe partitioning between membranes and medium and binding to membranes and intracellular components (with attendant changes in absorption and emission spectra, fluorescence quantum yield and lifetime). The crucial importance of suitable probe-to-cell concentration ratio and selection of optimum monitored fluorescence wavelength is illustrated in schematic diagrams and possible artifacts or puzzling results stemming from faulty experimental protocol are pointed out. Special attention is paid to procedures used for probe-response calibration (potential clamping by potassium in the presence of valinomycin, use of gramicidin D in combination with N-methylglucamine, activation of Ca-dependent K-channels by A23187, the null-point technique). Among other problems treated are dye toxicity, interaction with mitochondria and other organelles, and possible effects of intracellular pH and the quantity of cytosolic proteins and/or RNA on probe response. Individual techniques using redistribution dyes (fluorescence measurements in cuvettes, flow cytometry and microfluorimetry of individual cells including fluorescence confocal microscopy) are discussed in terms of reliability, limitations and drawbacks, and selection of suitable probes. Up-to-date examples of application of slow dyes illustrate the broad range of problems in which these probes can be used.
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Affiliation(s)
- J Plásek
- Institute of Physics, Charles University, Prague, Czech Republic. ,cz
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Grant RL, Acosta D. Interactions of intracellular pH and intracellular calcium in primary cultures of rabbit corneal epithelial cells. In Vitro Cell Dev Biol Anim 1996; 32:38-45. [PMID: 8835317 DOI: 10.1007/bf02722992] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
Homeostasis of intracellular calcium ([Ca++]i) and pH (pHi) is important in the cell's ability to respond to growth factors, to initiate differentiation and proliferation, and to maintain normal metabolic pathways. Because of the importance of these ions to cellular functions, we investigated the effects of changes of [Ca++]i and pHi on each other in primary cultures of rabbit corneal epithelial cells. Digitized fluorescence imaging was used to measure [Ca++]i with fura-2 and pHi with 2',7'-bis(2-carboxyethyl)-5(6)-carboxyfluorescein (BCECF). Resting pHi in these cells was 7.37 +/- 0.05 (n = 20 cells) and resting [Ca++]i was 129 +/- 10 nM (n = 35 cells) using a nominally bicarbonate-free Krebs Ringer HEPES buffer (KRHB), pH 7.4. On exposure to 20 mM NH4Cl, which rapidly alkalinized cells by 0.45 pH units, an increase in [Ca++]i to 215 +/- 14 nM occurred. Pretreatment of the cells with 100 microM verapamil or exposure to 1 mM ethylene bis-(oxyethylenenitrilo)-tetraacetic acid (EGTA) without extracellular calcium before addition of 20 mM NH4Cl did not abolish the calcium increase, suggesting that the source of the calcium transient was from intracellular calcium stores. On removal of NH4Cl or addition of 20 mM sodium lactate, there were minimal changes in calcium even though pHi decreased. Treatment of CE cells with the calcium ionophores, ionomycin and 4-bromo A23187, increased [Ca++]i, but produced a biphasic change in pHi. Initially, there was an acidification of the cytosol, and then an alkalinization of 0.10 to 0.11 pH units above initial values. When [Ca++]i was decreased by treating the cells with 5 mM EGTA and 20 microM ionomycin, pHi decreased by 0.35 +/- 0.02 units. We conclude that an increase in pHi leads to an increase in [Ca++]i in rabbit corneal epithelial cells; however, a decrease in pHi leads to minor changes in [Ca++]i. The ability of CE cells to maintain proper calcium homeostasis when pHi is decreased may represent an adaptive mechanism to maintain physiological calcium levels during periods of acidification, which occur during prolonged eye closure.
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Affiliation(s)
- R L Grant
- Division of Pharmacology and Toxicology, University of Texas, Austin, 78712-1
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15
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Yang W, Acosta D. A digitized fluorescence imaging study of intracellular Ca2+, pH, and mitochondrial function in primary cultures of rabbit corneal epithelial cells exposed to sodium dodecyl sulfate. In Vitro Cell Dev Biol Anim 1995; 31:499-507. [PMID: 8528498 DOI: 10.1007/bf02634027] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Primary cultures of rabbit corneal epithelial cells have been developed as an in vitro system to predict irritancy potential and delayed cytotoxicity of surfactants in our laboratory. The objective of this study was to evaluate the effects of the surfactant sodium dodecyl sulfate (SDS), a common ingredient in consumer products, on intracellular Ca2+, pH, and mitochondrial function in this culture system. Ca2+ and pH were measured in single living corneal epithelial cells by ratio imaging of fura-2 and 2,'7'-bis(carboxyethyl)-5(6)-carboxyfluorescein fluorescence, respectively. Mitochondrial function was examined by probing mitochondrial membrane potential with the fluorescent dye rhodamine 123 and by measuring the ratio of ATP to ADP with an HPLC method. Cell viability was determined by fluorescence imaging of propidium iodide in single cells and LDH leakage assay in populations of cells. SDS (40 micrograms/ml) increased intracellular Ca2+ from 180 +/- 28nM to 453 +/- 86 nM within 2 min, and induced intracellular acidification (pHi dropped 0.3 units in 15 min). Treatment of the cultures with SDS also resulted in dissipation of the mitochondrial membrane potential and decrease of intracellular ATP/ADP. SDS-induced Ca2+ elevation and intracellular acidification preceded the loss of cell viability observed 20 min after exposure. However, SDS-induced cell injury does not appear to be triggered by extracellular Ca(2+)-influx, as absence of extracellular Ca2+ did not attenuate SDS-induced cytotoxicity while it completely blocked ionomycin-induced cytotoxicity.(ABSTRACT TRUNCATED AT 250 WORDS)
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Affiliation(s)
- W Yang
- Division of Pharmacology & Toxicology, College of Pharmacy, University of Texas, Austin 78712, USA
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Jiang T, Acosta D. Mitochondrial Ca2+ overload in primary cultures of rat renal cortical epithelial cells by cytotoxic concentrations of cyclosporine: a digitized fluorescence imaging study. Toxicology 1995; 95:155-66. [PMID: 7825182 DOI: 10.1016/0300-483x(94)02901-6] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
Cyclosporine (CsA) has been reported to disrupt Ca2+ efflux from mitochondria, which suggests that CsA interference with Ca2+ homeostasis may be related to its nephrotoxicity. Therefore, the purpose of this study was (1) to determine intracellular free Ca2+ concentration ([Ca2+]i) and mitochondrial free Ca2+ concentration ([Ca2+]m) after primary cultures of rat renal cortical epithelial cells were exposed to cytotoxic concentrations of CsA; and (2) to explore the role of disruption of intracellular and mitochondrial Ca2+ homeostasis in CsA-induced cytotoxicity. [Ca2+]i in single kidney cells was examined by digitized fluorescence imaging (DFI) of the Ca2+ fluorescent probe, fura-2, and [Ca2+]m in single cells was observed by DFI of fura-2 entrapped in mitochondria after selective permeabilization of plasma membrane and other non-mitochondrial organelles by digitonin. Mitochondrial membrane potential (delta psi) in single kidney cells was examined by rhodamine 123 (Rh-123) with DFI. Intracellular ATP in kidney cells was determined by a HPLC method. CsA resulted in an elevation in [Ca2+]i and [Ca2+]m, dissipation of delta psi and depletion of ATP in a dose- and time-dependent manner. The elevation of [Ca2+]i and [Ca2+]m and depletion of ATP preceded CsA-induced cytotoxicity in kidney cells as measured by lactate dehydrogenase (LDH) leakage. We conclude that CsA-induced alterations in mitochondrial Ca2+ homeostasis and a subsequent loss of energy supply may play a key role in CsA-induced cytotoxicity in primary cultures of rat renal cortical epithelial cells.
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Affiliation(s)
- T Jiang
- Division of Pharmacology & Toxicology, College of Pharmacy, University of Texas, Austin 78703
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Maratrat M, Munoz N, Gravier I, Thybaud V, Crespo A. Use of scanning cytometry in studying bradykinin binding in MRC-5 cells. Cell Biol Toxicol 1994; 10:317-22. [PMID: 7697491 DOI: 10.1007/bf00755777] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
Ligand-receptor affinity is classically demonstrated by measuring ligand binding density to a specific site on membrane preparations, and receptor function is studied by measuring calcium flux, cell by cell, using microspectrofluorimetry. In order to study these phenomena in a large cell population, calcium flux was measured in MRC-5 cell line expressing the B2 receptor for bradykinin using an ACAS 570 scanning cytometer. Following incorporation of fluo3/AM, different ligands were studied, singly or in association with bradykinin. This study confirmed that only the B2 receptor is present on the plasma membrane of MRC-5 cells. Bradykinin binding to the B2 receptor was not modified by a B1 agonist (Des-Arg9-bradykinin) or by a B1 antagonist (Des-Arg9-[Leu8]-bradykinin) but was inhibited by a B2 agonist ([Hyp3]-bradykinin) and a B2 antagonist (HOE 140). The source of free calcium was also studied in comparison with ionomycin. The intensity of the calcium peak after binding of bradykinin is independent of the concentration of extracellular calcium. Preincubation with diltiazem or TMB-8 did not modify calcium flux, indicating that transduction of the signal after bradykinin binding in this cell line is independent of voltage-dependent channels and does not require mobilization of intracellular calcium blocked by TMB-8. In conclusion, scanning cytometry can be used to study ligand-receptor binding and to obtain results rapidly from multiple cells. Recording of individual cell variations and kinetics enables identification of active agonists or antagonists and consequently the selection of new compounds.
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Affiliation(s)
- M Maratrat
- Rhône-Poulenc Rorer S.A., Centre de Recherche de Vitry-Alfortville, Vitry sur Seine, France
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