Biomedical subjects

M Manfait

Publications and source records attributed to M Manfait.

95 records · Page 6Linked to original sources

PubMedDate not supplied

Induction of hemoglobin synthesis in human leukemic K 562 cells by adriamycin.

The antitumor compound adriamycin was found to induce differentiation-associated properties in human erythroleukemia K 562 cells. Studies on the relationship between drug concentration and the appearance of hemoglobin demonstrated that the more the rate of cell division was reduced during the 4 days of exposure, the higher was the accumulation of hemoglobin per cell. Considering the variation in the intracellular protein content during the response, it appears that adriamycin (40 nM) stimulated the synthesis of both hemoglobin and non-hemoglobin proteins while hemin, a well-known erythroid inducer, specifically increased hemoglobin synthesis. In addition, the lack of cell growth was associated with a recruitment of benzidine-positive cells. In contrast to hemin, adriamycin did not modify the electrophoretic pattern found in untreated cells.

Benzidines↗

PubMedDate not supplied

Effect of S9788, cyclosporin A and verapamil on intracellular distribution of THP-doxorubicin in multidrug-resistant K562 tumor cells, as studied by laser confocal microspectrofluorometry.

S9788 modulating resistance effect has been investigated on the activity of THP-DOX against multidrug-resistant K562R cells and compared to that of cyclosporin A and verapamil. Intracellular THP-DOX distribution and particulary its intranuclear concentration, with or without modulators, has been measured using confocal laser microspectrofluorometry. The kinetics of intranuclear accumulation of THP-DOX (1 microM in the medium), as a function of time, were rapid in K562S and K562R cells. Maximum accumulation of THP-DOX is reached in a few minutes (K562S, 400 microM; K562R, 40 microM). The addition of S9788, cyclosporin A and verapamil (5 microM) after one hour THP-DOX incubation, led to respectively 290, 250 and 114 microM. Uptake of THP-DOX was increased in K562R cells by a factor of 7 when S9788 was added. Results obtained on THP-DOX efflux from nuclei of K562S and K562R cells, after 3 hours of incubation without drug, showed a very short T1/2 (time corresponding to 50% decrease of intranuclear concentration of THP-DOX) in K562R cells (12 min) compared to that in K562S cells (150 min). The addition of S9788, cyclosporin A and verapamil (5 microM) led to a T1/2 of 90, 30 and 20 min respectively. The T1/2 of THP-DOX was increased in K562R cells by a factor of 7.5 when S9788 was added. We tried to correlate these results with those obtained in growth inhibition study. The IC50 (concentration which induces 50% growth inhibition) of THP-DOX, corresponding to one hour THP-DOX treatment and 3 days culture of K562S and K562R cells were respectively 230 and 7000 nM, and the RI (resistance index) value is 30. The addition of S9788, cyclosporin A and verapamil (5 microM), during the one hour treatment, led to an IC50 value of 350, 2000 and 5000 nM respectively. S9788 induced an IC50 value 20 times lower than without the modulator. Our study suggests that the higher activity of THP-DOX against K562R cells in the presence of S9788, compared to cyclosporin A and verapamil, is due to a higher intranuclear THP-DOX accumulation and to a strong decrease of drug efflux from K562R nuclei. This could be explained by a higher affinity of S9788 for membrane P-glycoprotein of K562R cells and/or an additional mechanism of action.

Antineoplastic Agents↗

PubMedDate not supplied

Inhibition of growth and induction of differentiation of promyelocytic leukemia (HL-60) by carotenoids from Crocus sativus L.

The effects of carotenoids of Crocus sativus L. (saffron) on cell proliferation and differentiation of HL-60 cells have been studied and compared with those of all-trans retinoic acid. Our results demonstrated that the doses inducing 50% inhibition of cell growth were 0.12 microM for all-trans retinoic acid (ATRA) and for carotenoids of saffron 0.8 microM for dimethylcrocetin (DMCRT), 2 microM for crocetin CRT and 2 microM for crocins (CRCs). At 5 microM, all these compounds induced differentiation of HL-60 cells, at 85% for ATRA, 70% for DMCRT, 50% for CRT and 48% for CRCs. In these experiments, leukemic cells were cultured for 5 days in the absence or in the presence of up to 5 microM ATRA or seminatural and natural carotenoids. Since retinoids have a potential application as chemopreventive agents in humans, their toxicity as an important limiting factor for their use in treatment should be extensively explored. The seminatural (DMCRT and CRT) and natural carotenoids (CRCs) of Crocus sativus L. are not provitamin A precursors and could therefore be less toxic than retinoids, even at high doses.

Carotenoids↗

PubMedDate not supplied

Conformational changes in membrane proteins of multidrug-resistant K562 and primary rat hepatocyte cultures as studied by Fourier transform infrared spectroscopy.

The multidrug resistance (MDR) phenotype has been investigated by means of Fourier transform infrared spectroscopy (FT-IR/S) on cell smears. We investigated K562 cell lines (sensitive and doxorubicin-resistant, the latter being MDR too) and primary cultures of rat hepatocytes (HEP). HEP displayed elevated levels of P-glycoprotein (P-gp) with time in 2-4 day-old culture, thus developing in the same time a MDR phenotype. No functional P-gp activity could be detected in HEP at day 1 after cell seeding. Given the sensitivity of FT-IR/S and using computational treatment of FT-IR data, we found that spectra of MDR-K562 and HEP from day 2 to day 4 displayed close protein conformational changes involving beta-sheets. These changes might be in close relationship with the MDR-phenotype and P-gp overexpression.

ATP Binding Cassette Transporter, Subfamily B, Mem↗

PubMedDate not supplied

Concomitant decrease of resistance and modifications of the cytoskeleton after all-trans retinoic acid and phorbol ester treatments in a navelbine-resistant bladder carcinoma cell line.

The bladder carcinoma cell line J82-NVB was selected for resistance to the new vinca alkaloid Navelbine. These cells possessed a non-MDR phenotype and were cross-resistant to vinca alkaloids and taxoids. Some morphological differences between sensitive (J82) and resistant (J82-NVB) cells were observed J82 cells had a heterogeneous population morphology with both epithelial and spindle shaped cells, while J82-NVB cells were almost all of the epithelial type. Vimentin intermediate filaments were less organized in J82-NVB than in J82 cells. Moreover, desmosomes were present in the membranes of J82NVB cells but not in J82 cells. These findings suggest that J82 cells are poorly differentiated epithelial cells while J82-NVB cells possess some characteristics of a more differentiated epithelial cell line. After a two-week treatment with all-trans retinoic acid, all the cells became spindle shaped, vimentin filaments reappeared in the cytoplasm of J82-NVB cells and desmosomes disappeared from the membranes of these cells. These changes were accompanied by a decrease from 17 to 4.6 of the resistance factor of J82-NVB cells to Navelbine. This decrease in resistance was concomitant with modifications of microtubules assembly regulation mechanisms. After Navelbine treatment, microtubule reassembly occurred in resistant but not in sensitive nor in retinoic acid treated cells. Okadaic acid, a protein phosphatase inhibitor, inhibited microtubule reassembly in resistant cells, and 2-aminopurine, a protein kinase inhibitor, induced microtubule reassembly in sensitive cells after Navelbine treatment. These findings show that microtubule reassembly after depolymerization is regulated by the kinase/phosphatase systems. A treatment with phorbol myristate acetate (PMA), a protein kinase C (PKC) agonist, induced the same morphological modifications and resistance decrease as retinoic acid treatment. A specific PKC inhibitor (Bisindolymaleimide) prevented these PMA-induced morphological modifications and resistance decrease in J82-NVB cells, showing that these effects were mediated by PKC. This study suggests that, in part by acting on some properties of the cytoskeleton, the differentiation modulator, retinoic acid, and the signal transduction modulator, phorbol myristate acetate, can decrease the resistance of J82-NVB cells to microtubule poisons.

2-Aminopurine↗