scholarly journals Rise in cytosolic Ca2+ and collapse of mitochondrial potential in anoxic, but not hypoxic, rat proximal tubules.

1996 ◽  
Vol 7 (11) ◽  
pp. 2348-2356
Author(s):  
S M Peters ◽  
M J Tijsen ◽  
R J Bindels ◽  
C H Van Os ◽  
J F Wetzels
Keyword(s):  
Membrane Potential ◽  
Mitochondrial Membrane Potential ◽  
Mitochondrial Membrane ◽  
Cell Injury ◽  
Cell Damage ◽  
Energy State ◽  
Oxygen Deprivation ◽  
Proximal Tubules ◽  
Rhodamine 123 ◽  
Anoxic Conditions

It has been suggested that ischemic renal proximal tubular cell injury is mediated by an increase in cytosolic calcium concentrations ((Ca2+)i). However, measurements of (Ca2+)i in rat or rabbit proximal tubules exposed to hypoxia or anoxia have yielded ambiguous results. This study explored the possibility that the severity of oxygen deprivation and the energy state of the mitochondria are important determinants of (Ca2+)i. To this end, (Ca2+)i (measured with fura-2) and the mitochondrial membrane potential (measured with rhodamine 123) were studied simultaneously in individual rat proximal tubules in hypoxic and anoxic conditions. (Ca2+)i did not change during hypoxia, but increased rapidly during anoxia. Increases in (Ca2+)i were only observed in parallel with a decrease of rhodamine 123 fluorescence, which indicates a collapse of the mitochondrial membrane potential. The increase in (Ca2+)i during anoxia was prevented by incubating the tubules in a low Ca2+ medium, which did not interfere with the collapse of the mitochondrial membrane potential. Both hypoxic and anoxic incubation led to cell death, as assessed by the fluorescent dye propidium iodide. These results clearly demonstrate that the level of oxygen deprivation is critical in determining changes in (Ca2+)i. Because cell damage occurred in both hypoxic and anoxic conditions. It was concluded that an increase in (Ca2+)i is not a necessary prerequisite for the development of ischemic cell injury.

scholarly journals NSAID-induced injury of gastric epithelial cells is reversible: roles of mitochondria, AMP kinase, NGF, and PGE2

2019 ◽  
Vol 317 (6) ◽  
pp. G862-G871
Author(s):  
Amrita Ahluwalia ◽  
Neil Hoa ◽  
Michael K. Jones ◽  
Andrzej S. Tarnawski
Keyword(s):  
Membrane Potential ◽  
Nerve Growth Factor ◽  
Epithelial Cells ◽  
Cell Viability ◽  
Mitochondrial Membrane Potential ◽  
Mitochondrial Membrane ◽  
Cell Injury ◽  
Prostaglandin E ◽  
Gastric Epithelial Cells ◽  
Amp Kinase

Nonsteroidal anti-inflammatory drugs (NSAIDs) such as diclofenac (DFN) and indomethacin (INDO) are extensively used worldwide. Their main side effects are injury of the gastrointestinal tract, including erosions, ulcers, and bleeding. Since gastric epithelial cells (GEPCs) are crucial for mucosal defense and are the major target of injury, we examined the extent to which DFN- and INDO-induced GEPC injury can be reversed by nerve growth factor (NGF), 16,16 dimethyl prostaglandin E2 (dmPGE2), and 5-aminoimidazole-4-carboxamide ribonucleotide (AICAR), the pharmacological activator of the metabolic sensor AMP kinase (AMPK). Cultured normal rat gastric mucosal epithelial (RGM1) cells were treated with PBS (control), NGF, dmPGE2, AICAR, and/or NSAID (DFN or INDO) for 1–4 h. We examined cell injury by confocal microscopy, cell death/survival using calcein AM, mitochondrial membrane potential using MitoTracker, and phosphorylation of AMPK by Western blotting. DFN and INDO treatment of RGM1 cells for 2 h decreased mitochondrial membrane potential and cell viability. NGF posttreatment (initiated 1 or 2 h after DFN or INDO) reversed the dissipation of mitochondrial membrane potential and cell injury caused by DFN and INDO and increased cell viability versus cells treated for 4 h with NSAID alone. Pretreatment with dmPGE2 and AICAR significantly protected these cells from DFN- and INDO-induced injury, whereas dmPGE2 and AICAR posttreatment (initiated 1 h after NSAID treatment) reversed cell injury and significantly increased cell viability and rescued the cells from NSAID-induced mitochondrial membrane potential reduction. DFN and INDO induce extensive mitochondrial injury and GEPC death, which can be significantly reversed by NGF, dmPGE2, and AICAR. NEW & NOTEWORTHY This study demonstrated that mitochondria are key targets of diclofenac- and indomethacin-induced injury of gastric epithelial cells and that diclofenac and indomethacin injury can be prevented and, importantly, also reversed by treatment with nerve growth factor, 16,16 dimethyl prostaglandin E2, and 5-aminoimidazole-4-carboxamide ribonucleotide.

Assessment of mitochondrial membrane potential in proximal tubules after hypoxia-reoxygenation

2005 ◽  
Vol 288 (6) ◽  
pp. F1092-F1102 ◽  
Author(s):  
Thorsten Feldkamp ◽  
Andreas Kribben ◽  
Joel M. Weinberg
Keyword(s):  
Membrane Potential ◽  
Mitochondrial Membrane Potential ◽  
Mitochondrial Membrane ◽  
Atp Hydrolysis ◽  
Proximal Tubules ◽  
Green Fluorescence ◽  
Direct Assessment ◽  
Dynamic Studies ◽  
Safranin O ◽  
Hypoxia Reoxygenation

Proximal tubules develop a severe energetic deficit during hypoxia-reoxygenation (H/R) that previous studies using fluorescent potentiometric probes have suggested is characterized by sustained, partial mitochondrial deenergization. To validate the primary occurrence of mitochondrial deenergization in the process, optimize approaches for estimating changes in mitochondrial membrane potential (ΔΨm) in the system, and clarify the mechanisms for the defect, we further investigated the behavior of 5,5′,6,6′-tetrachloro-1,1′,3,3′-tetraethylbenzimidazocarbocyanine iodide (JC-1) in these cells and introduce a more dynamic and quantitative approach employing safranin O for use with the tubule system. Although use of JC-1 can be complicated by decreases in the plasma membrane potential that limit cellular uptake of JC-1 and such behavior was demonstrated in ouabain-treated tubules, changes in ΔΨm entirely accounted for the decreases in the formation of red fluorescent JC-1 aggregates and in the ratio of red/green fluorescence observed after H/R. The red JC-1 aggregates did not readily dissociate when tubules were deenergized after JC-1 uptake, making it unsuitable for dynamic studies of energization. Safranin O uptake by digitonin-permeabilized tubules required very small numbers of tubules, permitted measurements of ΔΨm for relatively prolonged periods after the end of the experimental maneuvers, was rapidly reversible during deenergization, and allowed for direct assessment of both substrate-dependent, electron transport-mediated ΔΨm, and ATP hydrolysis-supported ΔΨm. Both types of energization measured using safranin O in tubules permeabilized after H/R were impaired, but combining substrates and ATP substantially restored ΔΨm.

Mitochondrial KATP channel activation reduces anoxic injury by restoring mitochondrial membrane potential

2001 ◽  
Vol 281 (3) ◽  
pp. H1295-H1303 ◽  
Author(s):  
Meifeng Xu ◽  
Yigang Wang ◽  
Ahmar Ayub ◽  
Muhammad Ashraf
Keyword(s):  
Membrane Potential ◽  
Cytochrome C ◽  
Mitochondrial Membrane Potential ◽  
Mitochondrial Membrane ◽  
Cell Injury ◽  
Mitochondrial Permeability Transition ◽  
Ischemia Reperfusion ◽  
Selective Inhibitor ◽  
Atp Depletion ◽  
Channel Activation

Mitochondrial membrane potential (ΔΨm) is severely compromised in the myocardium after ischemia-reperfusion and triggers apoptotic events leading to cell demise. This study tests the hypothesis that mitochondrial ATP-sensitive K+ (mitoKATP) channel activation prevents the collapse of ΔΨm in myocytes during anoxia-reoxygenation (A-R) and is responsible for cell protection via inhibition of apoptosis. After 3-h anoxia and 2-h reoxygenation, the cultured myocytes underwent extensive damage, as evidenced by decreased cell viability, compromised membrane permeability, increased apoptosis, and decreased ATP concentration. Mitochondria in A-R myocytes were swollen and fuzzy as shown after staining with Mito Tracker Orange CMTMRos and in an electron microscope and exhibited a collapsed ΔΨm, as monitored by 5,5′,6,6′-tetrachloro-1,1′,3,3′-tetraethylbenzimidazolcarbocyanine iodide (JC-1). Cytochrome c was released from mitochondria into the cytosol as demonstrated by cytochrome cimmunostaining. Activation of mitoKATP channel with diazoxide (100 μmol/l) resulted in a significant protection against mitochondrial damage, ATP depletion, cytochrome c loss, and stabilized ΔΨm. This protection was blocked by 5-hydroxydecanoate (500 μmol/l), a mitoKATPchannel-selective inhibitor, but not by HMR-1098 (30 μmol/l), a putative sarcolemmal KATP channel-selective inhibitor. Dissipation of ΔΨm also leads to opening of mitochondrial permeability transition pore, which was prevented by cyclosporin A. The data support the hypothesis that A-R disrupts ΔΨm and induces apoptosis, which are prevented by the activation of the mitoKATP channel. This further emphasizes the therapeutic significance of mitoKATP channel agonists in the prevention of ischemia-reperfusion cell injury.

scholarly journals A digitized-fluorescence-imaging study of mitochondrial Ca2+ increase by doxorubicin in cardiac myocytes

1992 ◽  
Vol 281 (3) ◽  
pp. 871-878 ◽  
Author(s):  
E Chacon ◽  
R Ulrich ◽  
D Acosta
Keyword(s):  
Membrane Potential ◽  
Energy Conservation ◽  
Fluorescence Imaging ◽  
Cardiac Myocytes ◽  
Mitochondrial Membrane Potential ◽  
Mitochondrial Membrane ◽  
Cell Injury ◽  
Cultured Cells ◽  
Imaging Study

The objective of the present study was to investigate the role of mitochondrial Ca2+ in doxorubicin-induced cell injury. The effect of doxorubicin on cultured cells was investigated by digitized fluorescence imaging. The Ca2+ sensitive fluorescent dye fura-2 was used to estimate cytosolic, mitochondrial and total cellular Ca2+. Rhodamine 123 was used to estimate the mitochondrial membrane potential, and cellular ATP was determined by h.p.l.c. The data showed that doxorubicin induced greater-than-2-fold increases in mitochondrial Ca2+ before changes in cytosolic Ca2+ could be detected. An increase in mitochondrial Ca2+ paralleled the observed dissipation in mitochondrial membrane potential. Cellular ATP levels appeared to decrease as a result of mitochondrial dysfunction, which in turn produced greater-than-2-fold increases in cytosolic Ca2+. The data suggest that doxorubicin-induced alterations in mitochondrial Ca2+ homoeostasis are associated with a dissipation in energy conservation, which may result in cell injury.

Mitochondrial membrane potential regulation is independent of c-fos expression

1999 ◽  
Vol 77 (3) ◽  
pp. 195-203
Author(s):  
Roger A Moorehead ◽  
Gurmit Singh
Keyword(s):  
Membrane Potential ◽  
Ovarian Carcinoma ◽  
Mitochondrial Membrane Potential ◽  
Mitochondrial Membrane ◽  
Membrane Potentials ◽  
Rhodamine 123 ◽  
Parental Line ◽  
Rat Fibroblasts ◽  
Human Ovarian Carcinoma ◽  
Fos Expression

Tumour cells contain mitochondria with elevated membrane potentials compared with normal cells, and thus this feature provides a selective target for destroying tumour cells. To improve mitochondrial-based therapies, a better understanding of the factors involved in regulating mitochondria are required. Since v-fos overexpression has been shown to elevate mitochondrial membrane potentials in rat fibroblasts, we investigated whether the human homologue, c-fos, was also capable of regulating the mitochondrial membrane potential in cells. Rat fibroblasts transfected with the c-fos gene did not accumulate more rhodamine 123 (Rh123) nor did they retain this Rh123 for extended periods of time compared with their parental line. Moreover, there was no difference in survival following dequalinium chloride (Deca) treatment between transfectants and controls. Similarly, reduction of c-fos expression in rat fibroblasts did not significantly alter their mitochondrial membrane potential. In addition, human ovarian carcinoma cells, which overexpress the c-fos gene, did not accumulate more Rh123 nor were they hypersensitive to Deca compared with their parental line. In another human ovarian carcinoma cell line, selection of variants with lower mitochondrial membrane potential did not alter c-fos mRNA or protein levels. These data suggest that alterations in c-fos expression do not regulate the magnitude of the mitochondrial membrane potential.Key words: c-fos, mitochondria, membrane potential, rhodamine 123 (Rh123), lipophilic cations.

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