| 1. |
- Nilsson, Cathrine, 1978-, et al.
(författare)
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Analysis of cytosolic and lysosomal pH in apoptotic cells by flow cytometry
- 2004
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Ingår i: Methods in Cell Science. - : Springer Science and Business Media LLC. - 1381-5741 .- 1573-0603. ; 25:3-4, s. 185-194
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Tidskriftsartikel (refereegranskat)abstract
- Several reports indicate that the cytosol is acidified during apoptosis although the mechanism is not yet fully elucidated. The most acidic organelle found in the cell is the lysosome, raising the possibility that lysosomal proton release may contribute to the cytosolic acidification. We here describe methods for measurement of the cytosolic and lysosomal pH in U937 cells by a dual-emission ratiometric technique suitable for flow cytometry. Cytosolic pH was analysed in cells loaded with the fluorescent probe BCECF, while lysosomal pH was determined after endocytosis of FITC-dextran. Standard curves were obtained by incubating cells in buffers with different pH in the presence of the proton ionophore nigericin. Apoptosis was induced by exposure of cells to 10ng/ml TNF- for 4h, and apoptotic cells were identified using a fluorescent marker for active caspases. By gating of control and apoptotic cells, the cytosolic and lysosomal pH were calculated in each population. The cytosolic pH was found to decrease from 7.2 ± 0.1 to 5.8s±0.1 and the lysosomal increased from 4.3±0.4 to 5.2±0.3. These methods will be useful in future attempts to evaluate the involvement of lysosomes in the acidification of the cytosol during apoptosis.
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| 2. |
- Nilsson, Cathrine, 1978-, et al.
(författare)
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Cytosolic acidification and lysosomal alkalinization during TNF-α induced apoptosis in U937 cells
- 2006
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Ingår i: Apoptosis (London). - : Springer Netherlands. - 1360-8185 .- 1573-675X. ; 11:7, s. 1149-1159
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Tidskriftsartikel (refereegranskat)abstract
- Apoptosis is often associated with acidification of the cytosol and since loss of lysosomal proton gradient and release of lysosomal content are early events during apoptosis, we investigated if the lysosomal compartment could contribute to cytosolic acidification. After exposure of U937 cells to tumor necrosis factor-α, three populations; healthy, pre-apoptotic, and apoptotic cells, were identified by flow cytometry. These populations were investigated regarding intra-cellular pH and apoptosis-associated events. There was a drop in cytosolic pH from 7.2 ± 0.1 in healthy cells to 6.8 ± 0.1 in pre-apoptotic, caspase-negative cells. In apoptotic, caspase-positive cells, the pH was further decreased to 5.7 ± 0.04. The cytosolic acidification was not affected by addition of specific inhibitors towards caspases or the mitochondrial F0F1-ATPase. In parallel to the cytosolic acidification, a rise in lysosomal pH from 4.3 ± 0.3, in the healthy population, to 4.8 ± 0.3 and 5.5 ± 0.3 in the pre-apoptotic- and apoptotic populations, respectively, was detected. In addition, lysosomal membrane permeability increased as detected as release of cathepsin D from lysosomes to the cytosol in pre-apoptotic and apoptotic cells. We, thus, suggest that lysosomal proton release is the cause of the cytosolic acidification of U937 cells exposed to TNF-α.
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| 3. |
- Nilsson, Cathrine, 1978-
(författare)
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Impact of Lysosomal Function in Cancer and Apoptosis
- 2008
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Lysosomes, the recycling units of the cell, participate in the signaling pathway to apoptosis, which has stimulated the search for anti-cancer drugs targeting the lysosomal compartment. Lysosomes are, however, often altered in cancer cells. The aim of this thesis was to investigate the involvement of lysosomes during apoptosis in normal and cancer cells. We developed and used flow cytometric methods to measure cytosolic and lysosomal pH in cells. The cytosolic pH of U937 cells decreased, in a caspase-independent way, by 1.4 pH-units during apoptosis. Concomitantly, the lysosomal pH increased from 4.3 to 5.2, suggesting that proton release from lysosomes might be responsible for cytosolic acidification. When studying the lysosomal pH of head and neck squamous cell carcinoma (HNSCC) cell lines and normal oral keratinocytes (NOKs), the pH was significantly increased in three of five HNSCC cell lines, as compared to NOKs. Moreover, high lysosomal pH correlated to low expression of the B subunit of the vacuolar V0/V1-ATPase, a necessary component of the proton pump responsible for lysosomal acidification, and to reduced intrinsic cisplatin sensitivity. Cisplatin-induced apoptosis was, at least partly, dependent on lysosomal cathepsins. When investigating the colony formation ability of the two HNSCC cell lines LK0412 and SqCC/Y1, both were found to give rise to holoclones, indicating the presence of cells with cancer stem cell properties. Holoclone cells from the LK0412 cell line were less sensitive to cisplatin compared to more differentiated paraclone cells. Moreover, we detected differences in intracellular localization of the lysosomal compartment and expression of cathepsins between holo- and paraclone cells.This thesis shows that changes found in the lysosomal compartment of cancer cells, such as alteration of lysosomal pH, might influence the outcome of a drug treatment. In addition, differences in drug sensitivity between subpopulations of tumor cells may affect the outcome of an anticancer therapy.
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| 4. |
- Nilsson, Cathrine, 1978-, et al.
(författare)
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Intrinsic differences in cisplatin sensitivity of head and neck cancer celllines correlates to lysosomal pH
- 2010
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Ingår i: Head and Neck. - : John Wiley & Sons. - 1043-3074 .- 1097-0347. ; 32:9, s. 1185-1194
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Tidskriftsartikel (refereegranskat)abstract
- Cisplatin is part of the treatment regime of head and neck squamous cell carcinomas (HNSCC). In order to predict the clinical outcome of the treatment, markers for evaluation of the intrinsic cisplatin sensitivity are inquired. In this study we characterize the lysosomal compartment and compare cisplatin sensitivity in five HNSCC lines and normal oral keratinocytes (NOKs). Cisplatin sensitivity differed 3-fold between the least and most sensitive cell lines, and the cisplatin LD50 correlated significantly to lysosomal pH, which varied from 4.3 in NOKs to 4.9 in the most resistant HNSCC line. Lysosomes are acidified by the V0V1-ATPase complex located in the lysosomal membrane. Interestingly, in cell lines exhibiting high lysosomal pH, we found decreased expression of the V0V1-ATPase B2 subunit, possibly explaining the defective acidification. In all cell lines, exposure to cisplatin caused activation of caspase-3. Cisplatin exposure was accompanied by lysosomal membrane permeabilization and inhibition of the llysosomal cathepsins B, D and L partly prevented cell death. No correlation between cisplatin sensitivity and expression of cathepsins B, D and L or secretion of their respective proforms into the culture medium was found in the cell lines studied. We conclude that lysosomal pH and expression of V0V1-ATPase subunits are possible future markers of intrinsic cisplatin sensitivity.
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