Altered proton extrusion in cells adapted to growth at low extracellular pH

Owen, Charles S.; Pooler, Patricia M.; Wahl, Michael J.; Coss, Ronald A.; Leeper, Dennis B.

doi:10.1002/(sici)1097-4652(199712)173:3<397::aid-jcp12>3.0.co;2-9

Cited by 23 publications

(12 citation statements)

References 36 publications

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“…We confirmed that the intracellular pH values are maintained at pH above 7.1 in cells incubated in the medium with 10% FBS at pH 6.7 (data not shown). In addition to our experiments, the maintenance of intracellular pH values in weak acidic conditions was again confirmed in other tumor cell lines (Gerweck & Seethaaraman, 1996;Owen et al, 1997). Extracellular pH lower than 6.5, however, markedly reduced intracellular pH values (Rockwells, 1986).…”

Section: Cisplatinsupporting

confidence: 87%

The Impact of Extracellular Low pH on the Anti-Tumor Efficacy Against Mesothelioma

Fukamachi¹,

Saito²,

Tagawa³

et al. 2012

Mesotheliomas - Synonyms and Definition, Epidemiology, Etiology, Pathogenesis, Cyto-Histopathological Features, Clinic, Diagnos

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Section: Cisplatinsupporting

confidence: 87%

The Impact of Extracellular Low pH on the Anti-Tumor Efficacy Against Mesothelioma

Fukamachi¹,

Saito²,

Tagawa³

et al. 2012

Mesotheliomas - Synonyms and Definition, Epidemiology, Etiology, Pathogenesis, Cyto-Histopathological Features, Clinic, Diagnos

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“…2 and 3). Because the pH i of AEC monolayers could not be measured directly while monolayers were being cultivated in 5% CO 2 over several days and given the known ability of several different kidney cell lines to adapt to changes in pH e by changing transporter activity and/or intracellular buffer capacity (24,30), experiments were performed after 24 h of incubation in the presence of acidic or alkaline medium to determine whether adaptation occurs that could limit pH changes in chronically exposed cells. Monolayers were subjected to a series of different pH e buffers (apical and basolateral), pH i was determined, and, as indicated in Fig.…”

Section: Discussionmentioning

confidence: 99%

Polarity of alveolar epithelial cell acid-base permeability

Joseph

Tirmizi

Crandall

et al. 2002

American Journal of Physiology-Lung Cellular and Molecular Phys

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We investigated acid-base permeability properties of electrically resistive monolayers of alveolar epithelial cells (AEC) grown in primary culture. AEC monolayers were grown on tissue culture-treated polycarbonate filters. Filters were mounted in a partitioned cuvette containing two fluid compartments (apical and basolateral) separated by the adherent monolayer, cells were loaded with the pH-sensitive dye 2′,7′-bis(2-carboxyethyl)-5(6)-carboxyfluorescein, and intracellular pH was determined. Monolayers in HCO[Formula: see text]-free Na+ buffer (140 mM Na+, 6 mM HEPES, pH 7.4) maintained a transepithelial pH gradient between the two fluid compartments over 30 min. Replacement of apical fluid by acidic (6.4) or basic (8.0) buffer resulted in minimal changes in intracellular pH. Replacement of basolateral fluid by acidic or basic buffer resulted in transmembrane proton fluxes and intracellular acidification or alkalinization. Intracellular alkalinization was blocked ≥80% by 100 μM dimethylamiloride, an inhibitor of Na+/H+exchange, whereas acidification was not affected by a series of acid/base transport inhibitors. Additional experiments in which AEC monolayers were grown in the presence of acidic (6.4) or basic (8.0) medium revealed differential effects on bioelectric properties depending on whether extracellular pH was altered in apical or basolateral fluid compartments bathing the cells. Acid exposure reduced (and base exposure increased) short-circuit current from the basolateral side; apical exposure did not affect short-circuit current in either case. We conclude that AEC monolayers are relatively impermeable to transepithelial acid/base fluxes, primarily because of impermeability of intercellular junctions and of the apical, rather than basolateral, cell membrane. The principal basolateral acid exit pathway observed under these experimental conditions is Na+/H+ exchange, whereas proton uptake into cells occurs across the basolateral cell membrane by a different, undetermined mechanism. These results are consistent with the ability of the alveolar epithelium to maintain an apical-to-basolateral (air space-to-blood) pH gradient in situ.

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“…When NH 4 Cl was washed out from the cells, pH i rapidly decreased from 7.4 to 6.3 for 2 min, and then began to increase (0 μM Phx-3). This recovery process is assumed to be due to proton extrusion by NHE1 (21,23).…”

Section: Effect Of Phx-3 On the Activity Of Namentioning

confidence: 99%

Rapid decrease of intracellular pH associated with inhibition of Na+/H+ exchanger precedes apoptotic events in the MNK45 and MNK74 gastric cancer cell lines treated with 2-aminophenoxazine-3-one

Nagata

Che²,

Miyazawa³

et al. 2011

Oncol Rep

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Abstract. The effects of Phx-3 on changes in intracellular pH (pH i ) in the MKN45 and MKN74 human gastric cancer cell lines were evaluated in order to determine the mechanism for the proapoptotic effects of 2-aminophenoxazine-3-one (Phx-3) on these cells. Phx-3 (100 μM) reduced pH i in MKN45 from 7.45 to 5.8, and in MKN74 from 7.5 to 6.2 within 1 min of engagement with these cells. Such a decrease of pH i was closely correlated with the dose of this phenoxazine and continued for 4 h. The activity of Na + /H + exchanger isoform l (NHE1), which is involved in H + extrusion from the cells, was dose-dependently suppressed by Phx-3 in these cells, and was greatly suppressed in the presence of 100 μM Phx-3. This result indicates that the decrease of pH i in MKN45 and MKN74 cells is closely associated with the inhibition of NHE1 in these cells. The morphology of these cells at 24 h after treatment with Phx-3 indicated shrinkage of the cells and condensation of the nuclear chromatin structure, which are characteristic of the apoptotic events in these gastric cancer cells. Cytotoxicity of Phx-3 against MKN45 and MKN74 cells was extensive because almost all MKN45 cells lost viability at 24 h in the presence of 20 μM Phx-3, and nearly 50% of the MKN74 cells lost viability in the presence of 50 μM Phx-3. These results suggest that rapid and extensive decrease of pH i in human gastric cancer MKN45 and MKN74 cells caused by Phx-3 might disturb intracellular homeostasis, leading to apoptotic and cytotoxic events in these cells. Phx-3 is a good candidate for therapeutics of gastric cancer that is intractable to conventional chemopreventive therapies. IntroductionIt has been suggested that a decrease of intracellular pH (pH i ) precedes apoptotic events in cancer cells (1,2). Therefore, drugs to induce pH i reduction have been considered good candidates for treating cancer and causing programmed cell death (3). For example, cyclohexamide, etoposide, and camptothesin decrease pH i in cancer cells, leading to apoptosis of the cells (3-5); however, these drugs often exert significant adverse effects on the body (6,7).The oxidative phenoxazines [e.g., 2-amino-4,4·-dihydro-4·,7-dimethyl-3H-phenoxazine-3-one (Phx-1) and 2-aminophenoxazine-3-one (Phx-3)] exert anticancer effects on various species of cancer cells in vitro (8-10) and in vivo, without marked adverse effects (11-13). Recently, Che et al (14) reported that apoptotic events in KB-3-1 cells (human epidermoid carcinoma cell line) and K562 cells (human chronic myeloid leukemia cell line) are preceded by a decrease in pH i in cells treated with Phx-3, a phenoxazine produced by the reaction of o-aminophenol with bovine hemoglobin. However, the detailed mechanism for pH i decrease in these cancer cells with Phx-3 remains unclear.Regarding the regulation of pH i , it has been suggested that among Na + /H + exchangers, Na + /H + exchanger isoform 1 (NHE1) is ubiquitously present in the plasma membrane in the cells and plays a pivotal role in regulating pH i (15)(16)(17). Therefore...

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Altered proton extrusion in cells adapted to growth at low extracellular pH

Cited by 23 publications

References 36 publications

The Impact of Extracellular Low pH on the Anti-Tumor Efficacy Against Mesothelioma

The Impact of Extracellular Low pH on the Anti-Tumor Efficacy Against Mesothelioma

Polarity of alveolar epithelial cell acid-base permeability

Rapid decrease of intracellular pH associated with inhibition of Na+/H+ exchanger precedes apoptotic events in the MNK45 and MNK74 gastric cancer cell lines treated with 2-aminophenoxazine-3-one

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