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Yao H, Chen S, Deng Z, Tse MK, Matsuda Y, Zhu G. BODI-Pt, a Green-Light-Activatable and Carboplatin-Based Platinum(IV) Anticancer Prodrug with Enhanced Activation and Cytotoxicity. Inorg Chem 2020; 59:11823-11833. [PMID: 32799491 DOI: 10.1021/acs.inorgchem.0c01880] [Citation(s) in RCA: 34] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Platinum drugs are widely used in clinics to treat various types of cancer. However, a number of severe side effects induced by the nonspecific binding of platinum drugs to normal tissues limit their clinical use. The conversion of platinum(II) drugs into more inert platinum(IV) derivatives is a promising strategy to solve this problem. Some platinum(IV) prodrugs, such as carboplatin-based tetracarboxylatoplatinum(IV) prodrugs, are not easily reduced to active platinum(II) species, leading to low cytotoxicity in vitro. In this study, we report the design and synthesis of a carboplatin-based platinum(IV) prodrug functionalized with a boron dipyrromethene (bodipy) ligand at the axial position, and the ligand acts as a photoabsorber to photoactivate the platinum(IV) prodrug. This compound, designated as BODI-Pt, is highly stable in the dark but quickly activated under irradiation to release carboplatin and the axial ligands. A cytotoxic study reveals that BODI-Pt is effective under irradiation, with cytotoxicity 11 times higher than that in the dark and 39 times higher than that of carboplatin in MCF-7 cells. Moreover, BODI-Pt has been proven to kill cancer cells by binding to the genomic DNA, arresting the cell cycle at the G2/M phase, inducing oncosis, and generating ROS upon irradiation. In summary, we report a green-light-activatable and carboplatin-based Pt(IV) prodrug with improved cytotoxicity against cancer cells, and our strategy can be used as a promising way to effectively activate carboplatin-based platinum(IV) prodrugs.
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Affiliation(s)
- Houzong Yao
- Department of Chemistry, City University of Hong Kong, 83 Tat Chee Avenue, Hong Kong SAR 999077, People's Republic of China.,City University of Hong Kong Shenzhen Research Institute, Shenzhen 518057, People's Republic of China
| | - Shu Chen
- Department of Chemistry, City University of Hong Kong, 83 Tat Chee Avenue, Hong Kong SAR 999077, People's Republic of China.,City University of Hong Kong Shenzhen Research Institute, Shenzhen 518057, People's Republic of China
| | - Zhiqin Deng
- Department of Chemistry, City University of Hong Kong, 83 Tat Chee Avenue, Hong Kong SAR 999077, People's Republic of China.,City University of Hong Kong Shenzhen Research Institute, Shenzhen 518057, People's Republic of China
| | - Man-Kit Tse
- Department of Chemistry, City University of Hong Kong, 83 Tat Chee Avenue, Hong Kong SAR 999077, People's Republic of China
| | - Yudai Matsuda
- Department of Chemistry, City University of Hong Kong, 83 Tat Chee Avenue, Hong Kong SAR 999077, People's Republic of China
| | - Guangyu Zhu
- Department of Chemistry, City University of Hong Kong, 83 Tat Chee Avenue, Hong Kong SAR 999077, People's Republic of China.,City University of Hong Kong Shenzhen Research Institute, Shenzhen 518057, People's Republic of China
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Guan R, Chen Y, Zeng L, Rees TW, Jin C, Huang J, Chen ZS, Ji L, Chao H. Oncosis-inducing cyclometalated iridium(iii) complexes. Chem Sci 2018; 9:5183-5190. [PMID: 29997872 PMCID: PMC6000986 DOI: 10.1039/c8sc01142g] [Citation(s) in RCA: 79] [Impact Index Per Article: 13.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2018] [Accepted: 05/02/2018] [Indexed: 12/25/2022] Open
Abstract
Oncosis is a non-apoptotic form of programmed cell death (PCD), which differs from apoptosis in both morphological changes and inner pathways, and might hold the key to defeating a major obstacle in cancer therapy - drug-resistance, which is often a result of the intrinsic apoptosis resistance of tumours. However, despite the fact that the term "oncosis" was coined and used much earlier than apoptosis, little effort has been made to discover new drugs which can initiate this form of cell death, in comparison to drugs inducing apoptosis or any other type of PCD. So herein, we present the synthesis of a series of mitochondria-targeting cyclometalated Ir(iii) complexes, which activated the oncosis-specific protein porimin and calpain in cisplatin-resistant cell line A549R, and determined their cytotoxicity against a wide range of drug-resistant cancer types. To the best of our knowledge, these complexes are the very first metallo-components to induce oncosis in drug-resistant cancer cells.
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Affiliation(s)
- Ruilin Guan
- MOE Key Laboratory of Bioinorganic and Synthetic Chemistry , School of Chemistry , Sun Yat-Sen University , Guangzhou , 510275 , P. R. China .
| | - Yu Chen
- MOE Key Laboratory of Bioinorganic and Synthetic Chemistry , School of Chemistry , Sun Yat-Sen University , Guangzhou , 510275 , P. R. China .
| | - Leli Zeng
- MOE Key Laboratory of Bioinorganic and Synthetic Chemistry , School of Chemistry , Sun Yat-Sen University , Guangzhou , 510275 , P. R. China .
- College of Pharmacy and Health Sciences , St. John's University , New York , NY 11439 , USA
| | - Thomas W Rees
- MOE Key Laboratory of Bioinorganic and Synthetic Chemistry , School of Chemistry , Sun Yat-Sen University , Guangzhou , 510275 , P. R. China .
| | - Chengzhi Jin
- MOE Key Laboratory of Bioinorganic and Synthetic Chemistry , School of Chemistry , Sun Yat-Sen University , Guangzhou , 510275 , P. R. China .
| | - Juanjuan Huang
- MOE Key Laboratory of Bioinorganic and Synthetic Chemistry , School of Chemistry , Sun Yat-Sen University , Guangzhou , 510275 , P. R. China .
| | - Zhe-Sheng Chen
- College of Pharmacy and Health Sciences , St. John's University , New York , NY 11439 , USA
| | - Liangnian Ji
- MOE Key Laboratory of Bioinorganic and Synthetic Chemistry , School of Chemistry , Sun Yat-Sen University , Guangzhou , 510275 , P. R. China .
| | - Hui Chao
- MOE Key Laboratory of Bioinorganic and Synthetic Chemistry , School of Chemistry , Sun Yat-Sen University , Guangzhou , 510275 , P. R. China .
- MOE Key Laboratory of Theoretical Organic Chemistry and Functional Molecule , School of Chemistry and Chemical Engineering , Hunan University of Science and Technology , Xiangtan , 400201 , P. R. China
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High-throughput imaging-based nephrotoxicity prediction for xenobiotics with diverse chemical structures. Arch Toxicol 2015; 90:2793-2808. [PMID: 26612367 PMCID: PMC5065616 DOI: 10.1007/s00204-015-1638-y] [Citation(s) in RCA: 38] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2015] [Accepted: 11/09/2015] [Indexed: 02/06/2023]
Abstract
The kidney is a major target for xenobiotics, which include drugs, industrial chemicals, environmental toxicants and other compounds. Accurate methods for screening large numbers of potentially nephrotoxic xenobiotics with diverse chemical structures are currently not available. Here, we describe an approach for nephrotoxicity prediction that combines high-throughput imaging of cultured human renal proximal tubular cells (PTCs), quantitative phenotypic profiling, and machine learning methods. We automatically quantified 129 image-based phenotypic features, and identified chromatin and cytoskeletal features that can predict the human in vivo PTC toxicity of 44 reference compounds with ~82 % (primary PTCs) or 89 % (immortalized PTCs) test balanced accuracies. Surprisingly, our results also revealed that a DNA damage response is commonly induced by different PTC toxicants that have diverse chemical structures and injury mechanisms. Together, our results show that human nephrotoxicity can be predicted with high efficiency and accuracy by combining cell-based and computational methods that are suitable for automation.
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Guyot E, Solovyova Y, Tomkiewicz C, Leblanc A, Pierre S, El Balkhi S, Le Frère-Belda MA, Lecuru F, Poupon J, Barouki R, Aggerbeck M, Coumoul X. Determination of Heavy Metal Concentrations in Normal and Pathological Human Endometrial Biopsies and In Vitro Regulation of Gene Expression by Metals in the Ishikawa and Hec-1b Endometrial Cell Line. PLoS One 2015; 10:e0142590. [PMID: 26600472 PMCID: PMC4657954 DOI: 10.1371/journal.pone.0142590] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2015] [Accepted: 10/23/2015] [Indexed: 12/27/2022] Open
Abstract
It is well known that several metals, such as lead, mercury, cadmium, and vanadium, can mimic the effects of estrogens (metallo-estrogens). Nevertheless, there are only a few studies that have assessed the effects of toxic metals on the female genital tract and, in particular, endometrial tissue. In this context, we measured the concentrations of several trace elements in human endometrial tissue samples from individuals with hyperplasia or adenocarcinoma and in normal tissues. Hyperplasic endometrial tissue has a 4-fold higher concentration of mercury than normal tissue. Mercury can affect both the AhR and ROS signaling pathways. Thus, we investigated the possible toxic effects of mercury by in vitro studies. We found that mercury increases oxidative stress (increased HO1 and NQO1 mRNA levels) and alters the cytoskeleton in the human endometrial Ishikawa cell line and to a lesser extent, in the "less-differentiated" human endometrial Hec-1b cells. The results might help to explain a potential link between this metal and the occurrence of endometrial hyperplasia.
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Affiliation(s)
- Erwan Guyot
- INSERM UMR-S 1124, Toxicologie Pharmacologie et Signalisation Cellulaire, 45 rue des Saints Pères, 75006 Paris, France
- Université Paris Descartes, Paris Sorbonne Cité, Centre universitaire des Saints-Pères, 45 rue des Saints Pères, 75006 Paris, France
| | - Yevgeniya Solovyova
- INSERM UMR-S 1124, Toxicologie Pharmacologie et Signalisation Cellulaire, 45 rue des Saints Pères, 75006 Paris, France
- Université Paris Descartes, Paris Sorbonne Cité, Centre universitaire des Saints-Pères, 45 rue des Saints Pères, 75006 Paris, France
- Institute of Urgent and Recovery Surgery named after V.K. Gusak of the Ukrainian Academy of Medical Sciences, Donetsk; 47, avenue Leninsky, Donetsk- 83045, Ukraine
| | - Céline Tomkiewicz
- INSERM UMR-S 1124, Toxicologie Pharmacologie et Signalisation Cellulaire, 45 rue des Saints Pères, 75006 Paris, France
- Université Paris Descartes, Paris Sorbonne Cité, Centre universitaire des Saints-Pères, 45 rue des Saints Pères, 75006 Paris, France
| | - Alix Leblanc
- INSERM UMR-S 1124, Toxicologie Pharmacologie et Signalisation Cellulaire, 45 rue des Saints Pères, 75006 Paris, France
- Université Paris Descartes, Paris Sorbonne Cité, Centre universitaire des Saints-Pères, 45 rue des Saints Pères, 75006 Paris, France
| | - Stéphane Pierre
- INSERM UMR-S 1124, Toxicologie Pharmacologie et Signalisation Cellulaire, 45 rue des Saints Pères, 75006 Paris, France
- Université Paris Descartes, Paris Sorbonne Cité, Centre universitaire des Saints-Pères, 45 rue des Saints Pères, 75006 Paris, France
| | - Souleiman El Balkhi
- Laboratoire de toxicologie biologique, AP-HP, Hôpital Lariboisière, 2, rue Ambroise Paré, 75475 Paris, France
| | - Marie-Aude Le Frère-Belda
- INSERM UMR-S 1124, Toxicologie Pharmacologie et Signalisation Cellulaire, 45 rue des Saints Pères, 75006 Paris, France
- Service de chirurgie gynécologique et cancérologique, hôpital européen Georges-Pompidou, AP-HP, 20, rue Leblanc, 75015 Paris, France
- Université Paris Descartes, Paris Sorbonne Cité, Centre universitaire des Saints-Pères, 45 rue des Saints Pères, 75006 Paris, France
| | - Fabrice Lecuru
- INSERM UMR-S 1124, Toxicologie Pharmacologie et Signalisation Cellulaire, 45 rue des Saints Pères, 75006 Paris, France
- Service de chirurgie gynécologique et cancérologique, hôpital européen Georges-Pompidou, AP-HP, 20, rue Leblanc, 75015 Paris, France
- Université Paris Descartes, Paris Sorbonne Cité, Centre universitaire des Saints-Pères, 45 rue des Saints Pères, 75006 Paris, France
| | - Joël Poupon
- Laboratoire de toxicologie biologique, AP-HP, Hôpital Lariboisière, 2, rue Ambroise Paré, 75475 Paris, France
| | - Robert Barouki
- INSERM UMR-S 1124, Toxicologie Pharmacologie et Signalisation Cellulaire, 45 rue des Saints Pères, 75006 Paris, France
- Université Paris Descartes, Paris Sorbonne Cité, Centre universitaire des Saints-Pères, 45 rue des Saints Pères, 75006 Paris, France
- AP-HP, Hôpital Necker-Enfants Malades, service de biochimie métabolique, 149, rue de Sèvres, 75743 Paris, France
| | - Martine Aggerbeck
- INSERM UMR-S 1124, Toxicologie Pharmacologie et Signalisation Cellulaire, 45 rue des Saints Pères, 75006 Paris, France
- Université Paris Descartes, Paris Sorbonne Cité, Centre universitaire des Saints-Pères, 45 rue des Saints Pères, 75006 Paris, France
| | - Xavier Coumoul
- INSERM UMR-S 1124, Toxicologie Pharmacologie et Signalisation Cellulaire, 45 rue des Saints Pères, 75006 Paris, France
- Université Paris Descartes, Paris Sorbonne Cité, Centre universitaire des Saints-Pères, 45 rue des Saints Pères, 75006 Paris, France
- * E-mail:
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Celes MRN, Malvestio LM, Suadicani SO, Prado CM, Figueiredo MJ, Campos EC, Freitas ACS, Spray DC, Tanowitz HB, da Silva JS, Rossi MA. Disruption of calcium homeostasis in cardiomyocytes underlies cardiac structural and functional changes in severe sepsis. PLoS One 2013; 8:e68809. [PMID: 23935889 PMCID: PMC3720843 DOI: 10.1371/journal.pone.0068809] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2013] [Accepted: 06/02/2013] [Indexed: 01/29/2023] Open
Abstract
Sepsis, a major cause of morbidity/mortality in intensive care units worldwide, is commonly associated with cardiac dysfunction, which worsens the prognosis dramatically for patients. Although in recent years the concept of septic cardiomyopathy has evolved, the importance of myocardial structural alterations in sepsis has not been fully explored. This study offers novel and mechanistic data to clarify subcellular events that occur in the pathogenesis of septic cardiomyopathy and myocardial dysfunction in severe sepsis. Cultured neonatal mice cardiomyocytes subjected to serum obtained from mice with severe sepsis presented striking increment of [Ca2+]i and calpain-1 levels associated with decreased expression of dystrophin and disruption and derangement of F-actin filaments and cytoplasmic bleb formation. Severe sepsis induced in mice led to an increased expression of calpain-1 in cardiomyocytes. Moreover, decreased myocardial amounts of dystrophin, sarcomeric actin, and myosin heavy chain were observed in septic hearts associated with depressed cardiac contractile dysfunction and a very low survival rate. Actin and myosin from the sarcomere are first disassembled by calpain and then ubiquitinated and degraded by proteasome or sequestered inside specialized vacuoles called autophagosomes, delivered to the lysosome for degradation forming autophagolysosomes. Verapamil and dantrolene prevented the increase of calpain-1 levels and preserved dystrophin, actin, and myosin loss/reduction as well cardiac contractile dysfunction associated with strikingly improved survival rate. These abnormal parameters emerge as therapeutic targets, which modulation may provide beneficial effects on future vascular outcomes and mortality in sepsis. Further studies are needed to shed light on this mechanism, mainly regarding specific calpain inhibitors.
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Affiliation(s)
- Mara R N Celes
- Department of Pathology, Faculty of Medicine of Ribeirão Preto, University of São Paulo, São Paulo, Brazil.
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Weber H, Hühns S, Lüthen F, Jonas L. Calpain-mediated breakdown of cytoskeletal proteins contributes to cholecystokinin-induced damage of rat pancreatic acini. Int J Exp Pathol 2009; 90:387-99. [PMID: 19659897 PMCID: PMC2741149 DOI: 10.1111/j.1365-2613.2009.00638.x] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2008] [Accepted: 11/30/2008] [Indexed: 12/01/2022] Open
Abstract
The cytosolic cysteine protease calpain is implicated in a multitude of cellular functions but also plays a role in cell damage. Our previous results suggest that an activation of calpain accompanied by a decrease in its endogenous inhibitor calpastatin may contribute to pancreatic damage during cerulein-induced acute pancreatitis. The present study aimed at the time course of secretagogue-induced calpain activation and cellular substrates of the protease. Isolated rat pancreatic acini were incubated with a supramaximal concentration of cholecystokinin (0.1 microM CCK) for 30 min in the presence or absence of the calpain inhibitor Z-Val-Phe methyl ester (100 microM ZVP). The activation of calpain and the expression of calpastatin and the actin cytoskeleton-associated proteins alphaII-spectrin, E-cadherin and vinculin were studied by immunoblotting. The cell damage was assessed by lactate dehydrogenase release and ultrastructural analysis including fluorescence-labelled actin filaments. Immediately after administration, CCK led to activation of both calpain isoforms, mu- and m-calpain. The protease activation was accompanied by a decrease in the E-cadherin level and formation of calpain-specific breakdown products of alphaII-spectrin. A calpain-specific cleavage product of vinculin appeared concomitantly with changes in the actin filament organization. No effect of CCK on calpastatin was found. Inhibition of calpain by ZVP reduced CCK-induced damage of the actin-associated proteins and the cellular ultrastructure including the actin cytoskeleton. The results suggest that CCK-induced acinar cell damage requires activation of calpain and that the actin cytoskeleton belongs to the cellular targets of the protease.
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Affiliation(s)
- Heike Weber
- Institute of Clinical Chemistry and Laboratory Medicine, University of Rostock, D-18057 Rostock, Germany.
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Heo J, Meng F, Sachs F, Hua SZ. Dynamic effects of Hg2+-induced changes in cell volume. Cell Biochem Biophys 2008; 51:21-32. [PMID: 18365146 DOI: 10.1007/s12013-008-9010-y] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2007] [Accepted: 01/25/2008] [Indexed: 01/13/2023]
Abstract
Using a microfluidic volume sensor, we studied the dynamic effects of Hg2+ on hypotonic stress-induced volume changes in CHO cells. A hypotonic challenge to control cells caused them to swell but did not evoke a significant regulatory volume decrease (RVD). Treatment with 100 muM HgCl2 caused a substantial increase in the steady-state volume following osmotic stress. Continuous hypotonic challenge following a single 10-min exposure to HgCl2 produced a biphasic volume increase with a steady-state volume 100% larger than control cells. Repeated hypotonic challenges to cells exposed once to Hg2+ resulted in a sequential approach to the same steady-state volume. Stimulation after reaching steady state caused a reduction in peak cell volume. Repeated stimulation was different than continuous stimulation resulting in a more rapid approach to steady state. Substituting extracellular Na+ with impermeant NMDG+ in the hypotonic solution produced a rapid RVD-like volume decrease and eliminated the Hg2+-induced excess swelling. The volume decrease in the presence of Hg2+ was inhibited by tetraethylammonium and 4,4'-diisothiocyanatostilbene-2,2'-disulfonic acid disodium, blockers of K+ and Cl(-) channels, respectively, suggesting that part of the Hg2+ effect was increasing NaCl influx over KCl efflux. The presence of multiple phases of steady-state volume and their sensitivity to the stimulation history suggests that factors beyond solute fluxes, such as modification of mechanical stress within the cytoskeleton also plays a role in the response to hypotonic stress.
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Affiliation(s)
- Jinseok Heo
- Department of Mechanical and Aerospace Engineering, SUNY-Buffalo, 340 Jarvis Hall, Buffalo, NY 14260, USA
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Chang SH, Phelps PC, Berezesky IK, Ebersberger ML, Trump BF. Studies on the mechanisms and kinetics of apoptosis induced by microinjection of cytochrome c in rat kidney tubule epithelial cells (NRK-52E). THE AMERICAN JOURNAL OF PATHOLOGY 2000; 156:637-49. [PMID: 10666393 PMCID: PMC1850037 DOI: 10.1016/s0002-9440(10)64768-2] [Citation(s) in RCA: 40] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
Recent reports substantiating the role of cytochrome c in the induction of apoptosis led us to examine the kinetics and mechanisms involved in this process as an extension of our ongoing studies of cell injury and cell death. Microinjection of cytochrome c into NRK-52E kidney cells produced rapid apoptosis, which usually began within 30 minutes and reached a maximum of 60-70% by 3 hours. The changes that occurred included four phases: an initial shrinkage phase, an active phase, a spherical phase, and a necrotic phase. For morphological purposes, the progressive changes were followed by phase-contrast and fluorescence microscopy, transmission and scanning electron microscopy, and time-lapse video microscopy. Cells first showed shrinkage, then displayed multiple pseudopods, which rapidly extended and retracted, giving the cells a bosselated appearance. During this active phase there was chromatin condensation, mitochondria were swollen but retained membrane potential, and the endoplasmic reticulum was dilated. Within 2-4 hours, active-phase cells became spherical and smooth-surfaced but were still alive, the nuclei showed chromatin clumping, the mitochondria underwent high-amplitude swelling but retained membrane potential, the endoplasmic reticulum was highly dilated, and many large apical vacuoles were present. Elevation of [Ca(2+)](i) was seen at the late spherical phase, shortly before cell death. Pretreatment with the caspase 3 inhibitor (Ac-DEVD-CHO) prevented apoptosis, whereas overexpression of Bcl-2 did not. Depletion of cellular ATP by cyanide inhibition of energy metabolism prevented cytochrome c from inducing the active and later phases of apoptosis. The results clearly indicate that cytochrome c-induced apoptosis is a dynamic and energy-requiring process that has a distinct active and spherical phase before cell death.
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Affiliation(s)
- S H Chang
- Department of Pathology, University of Maryland School of Medicine, Baltimore, Maryland, USA
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Fridberger A, Flock A, Ulfendahl M, Flock B. Acoustic overstimulation increases outer hair cell Ca2+ concentrations and causes dynamic contractions of the hearing organ. Proc Natl Acad Sci U S A 1998; 95:7127-32. [PMID: 9618550 PMCID: PMC22763 DOI: 10.1073/pnas.95.12.7127] [Citation(s) in RCA: 137] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
The dynamic responses of the hearing organ to acoustic overstimulation were investigated using the guinea pig isolated temporal bone preparation. The organ was loaded with the fluorescent Ca2+ indicator Fluo-3, and the cochlear electric responses to low-level tones were recorded through a microelectrode in the scala media. After overstimulation, the amplitude of the cochlear potentials decreased significantly. In some cases, rapid recovery was seen with the potentials returning to their initial amplitude. In 12 of 14 cases in which overstimulation gave a decrease in the cochlear responses, significant elevations of the cytoplasmic [Ca2+] in the outer hair cells were seen. [Ca2+] increases appeared immediately after terminating the overstimulation, with partial recovery taking place in the ensuing 30 min in some preparations. Such [Ca2+] changes were not seen in preparations that were stimulated at levels that did not cause an amplitude change in the cochlear potentials. The overstimulation also gave rise to a contraction, evident as a decrease of the width of the organ of Corti. The average contraction in 10 preparations was 9 microm (SE 2 microm). Partial or complete recovery was seen within 30-45 min after the overstimulation. The [Ca2+] changes and the contraction are likely to produce major functional alterations and consequently are suggested to be a factor contributing strongly to the loss of function seen after exposure to loud sounds.
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Affiliation(s)
- A Fridberger
- Department of Physiology and Pharmacology, Karolinska Institutet, S-171 77 Stockholm, Sweden.
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Kohlhepp SJ, Hou L, Gilbert DN. Pig kidney (LLC-PK1) cell membrane fluidity during exposure to gentamicin or tobramycin. Antimicrob Agents Chemother 1994; 38:2169-71. [PMID: 7811038 PMCID: PMC284703 DOI: 10.1128/aac.38.9.2169] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023] Open
Abstract
The surface membrane properties of LLC-PK1 cells grown with and without various amounts of gentamicin or tobramycin for various lengths of time were determined by measuring the diffusion coefficient of N-(7-nitrobenz-2-oxa-1,3-diazol-4-yl)dipalmitoyl-L- alpha-phosphatidylethanolamine (NBD-PE) and the percentage of NBD-PE free to diffuse after photobleaching. One hour of exposure to tobramycin decreased the percentage that was free to diffuse. After 1 day or longer of exposure to either aminoglycoside the percentage that was free to diffuse returned to preexposure levels and the diffusion coefficient decreased.
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Affiliation(s)
- S J Kohlhepp
- Center for Fluorescence Research in Biomedical Sciences, Carnegie-Mellon University, Pittsburgh, Pennsylvania 15213
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