Enhanced cytotoxicity of рhotoexcited fullerene C60 and cisplatin combination against drug-resistant leukemic cells

Aim: To evaluate the viability of leukemic cells sensitive (L1210S) and resistant (L1210R) to cisplatin, ROS production and free cytosolic Ca²⁺ concentration under treatment with cisplatin or its combination with photoexcited fullerene C₆₀. Methods: Cell viability was assessed by the MTT reduction assay. Light-emitting diode lamp (2.45 J/сm2) was used for photoexcitation of intracellular accumulated fullerene C₆₀. Free cytosolic calcium concentration ([Ca²⁺]i) and ROS production in cells were estimated with the use of fluorescent probes Indo-1 and 2′,7′-dichlorodihydrofluorescein diacetate (DCF-DA), respectively. Results: It is shown that viability of L1210R cells wasn’t changed under treatment with cisplatin in concentration range 0.1–10 μg/ml. 50% and 30% decrease of L1210S cells were observed after 24 h of incubation with cisplatin at concentrations 5 and 1 μg/ml, respectively. Intensification of extranuclear cytotoxic effects (ROS production and [Ca²⁺]iincrease) after treatment with 1 μg/ml was detected in L1210S, but not in L1210R cells. The most strongly pronounced increase of ROS production and [Ca²⁺]i in both L1210 cell lines was revealed in dynamics after combined treatment with cisplatin (1 μg/ml) and photoexcited fullerene C₆₀ (10⁻⁵ M) and was followed by decreased viability of not only L1210S, but of L1210R cells as well.. Conclusion: Combined treatment with photoexcited C₆₀ and cisplatin allowed to decrease effective concentration of cisplatin against parental L1210 cells and to increase sensibility of resistant cells to the drug. Key Words: cisplatin, L1210 cells, photoexcited fullerene C₆₀, ROS, cytosolic Ca²⁺, cell viability

Photocytotoxic effect of C₆₀ fullerene against L1210 leukemic cells is accomPanied by enhanced nitric oxide Production and p38 maPk activation

Aim: To estimate the combined action of C₆₀ fullerene and light irradiation on viability of L1210 leukemic cells, nitric oxide (NO) generation, p38 mitogen-activated protein kinase (MAPK) activity and cell cycle distribution. Methods: Cell viability was assessed by MTT test. Light-emitting diode lamp (λ = 410–700 nm, 2.45 J/cm²) was used for C₆₀ fullerene photoexcitation. Nitrite level and NO-synthase activity were measured by Griess reaction and by conversion of L-arginine to L-citrulline, respectively. p38 MAPK activity was assessed by Western blot analysis. Cell cycle distribution was determined by flow cytometry. Results: It was shown that light irradiation of C₆₀ fullerene-treated L1210 cells was accompanied by 55% decrease of their viability at 48 h of culture. Nitrite level measured as an index of reactive NO generation was increased at the early period after C₆₀ fullerene photoexcitation due to activation of both constitutive and inducible NO-synthase isoforms. The simultaneous activation of p38 MAPK was detected. Accumulation of L1210 cells in sub-G₁ phase of cell cycle was observed after C₆₀ fullerene photoexcitation. Conclusion: Photoexcited C₆₀ fullerene exerts cytotoxic effect, at least in part, through triggering production of reactive NO species and activation of p38 kinase apoptotic pathways in L1210 leukemic cells

ENHANCED CYTOTOXICITY OF РHOTOEXCITED FULLERENE C60 AND CISPLATIN COMBINATION AGAINST D RUGRESISTANT LEUKEMIC CELLS

Aim: To evaluate the viability of leukemic cells sensitive (L1210S) and resistant (L1210R) to cisplatin, ROS production and free cytosolic Ca²⁺ concentration under treatment with cisplatin or its combination with photoexcited fullerene C₆₀. Methods: Cell viability was assessed by the MTT reduction assay. Light-emitting diode lamp (2.45 J/сm2) was used for photoexcitation of intracellular accumulated fullerene C₆₀. Free cytosolic calcium concentration ([Ca²⁺]i) and ROS production in cells were estimated with the use of fluorescent probes Indo-1 and 2′,7′-dichlorodihydrofluorescein diacetate (DCF-DA), respectively. Results: It is shown that viability of L1210R cells wasn’t changed under treatment with cisplatin in concentration range 0.1–10 μg/ml. 50% and 30% decrease of L1210S cells were observed after 24 h of incubation with cisplatin at concentrations 5 and 1 μg/ml, respectively. Intensification of extranuclear cytotoxic effects (ROS production and [Ca²⁺]iincrease) after treatment with 1 μg/ml was detected in L1210S, but not in L1210R cells. The most strongly pronounced increase of ROS production and [Ca²⁺]i in both L1210 cell lines was revealed in dynamics after combined treatment with cisplatin (1 μg/ml) and photoexcited fullerene C₆₀ (10⁻⁵ M) and was followed by decreased viability of not only L1210S, but of L1210R cells as well.. Conclusion: Combined treatment with photoexcited C₆₀ and cisplatin allowed to decrease effective concentration of cisplatin against parental L1210 cells and to increase sensibility of resistant cells to the drug. Key Words: cisplatin, L1210 cells, photoexcited fullerene C₆₀, ROS, cytosolic Ca²⁺, cell viability