Cell cycle alteration, apoptosis and response of leukemic cell lines to gamma radiation with high- and low-dose

Summary The aim of this work was to compare the effect of gamma radiation with sub-low dose-rate 1.8 mGy/min (SLDR), low dose-rate 3.9 mGy/min (LDR) and high dose-rate 0.6 Gy/min (HDR) on human leukemic cell lines with differing p53 status (HL-60, p53 deficient and MOLT-4, p53 wild) and to elucidate the importance of G2/M phase cell cycle arrest during irradiation. Radiosensitivity of HL-60 and MOLT-4 cells was determined by test of clonogenity. Decrease of dose-rate had no effect on radiosensitivity of MOLT-4 cells (D 0 for HDR 0.87 Gy, for LDR 0.78 Gy and for SLDR 0.70 Gy). In contrast, a significant increase of radioresistance after LDR irradiation was observed for p53 negative HL-60 cells (D 0 for HDR 2.20 Gy and for LDR 3.74 Gy). After an additional decrease of dose-rate (SLDR) D 0 value (2.92 Gy) was not significantly different from HDR irradiation. Considering the fact that during HDR the cells are irradiated in all phases of the cell cycle and during LDR mainly in the G2 phase, we have been unable to prove that the G2 phase is the most radiosensitive phase of the cell cycle of HL-60 cells. On the contrary, irradiation of cells in this phase induced damage reparation and increased radioresistance. When the dose-rate was lowered, approximately to 1.8 mGy/min, an opposite effect was detected, i.e. D 0 value decreased to 2.9 Gy. We have proved that during SLDR at first (dose up to 2.5 Gy) the cells accumulated in G2 phase, but then they entered mitosis or, if the cell damage was not sufficiently repaired, the cells entered apoptosis. The entry into mitosis has a radiosensibilizing effect

ÖSTEREICHER J: CD8+ natural killer cells have a potential of a sensitive and reliable biodosimetric marker in vitro. Physiol Res 55

Summary The aim of our work was to evaluate peripheral blood lymphocyte subsets as in vitro indicators of the received dose of ionizing radiation (biodosimetric markers) in the range of 3-20 Gy and to determine the appropriate time interval, during which a dose-dependent induction of apoptosis occurs upon γ irradiation. In lymphocyte subsets characterized by double color surface immunophenotyping, four-color flow cytometry was used for visualizing cell death-associated increase in superficial phosphatidylserine exposure and cytoplasmic membrane permeability by fluorinated Annexin V and propidium iodide, respectively. No differences between sham-treated and lethal dose (7 Gy)-irradiated samples were observed upon 6 h cultivation in vitro. Ten and 18 h later, about 50 % of lymphocytes were apoptotic, but only the minority of them was in the late apoptotic phase. The only difference in radioresistance of the CD4 + CD8 -and CD4 -CD8 + lymphocyte subsets was seen upon 2-day cultivation when huge depletion of intact cells and prevalence of the late apoptotic population became obvious. A dose-dependence study in 16 and 48 h cultures confirmed the effectiveness of major T cell subsets as biodosimetric indicators. On the other hand, the minor CD8 + subset of natural killer (NK) cells has been identified as a radiosensitive lymphocyte population the disappearance of which correlated with the received dose. We demonstrated that the CD3 -CD8 + NK subset can be used as a lethal/sublethal dose discriminator to 16 h cultivation. In addition, our data indicate that two-day cultivation followed by CD3/CD8 expression analysis in an intact lymphocyte population may provide a clue for low dosage biodosimetry

Druggable Hot Spots in the Schistosomiasis Cathepsin B1 Target Identified by Functional and Binding Mode Analysis of Potent Vinyl Sulfone Inhibitors

© 2020 American Chemical Society. Schistosomiasis, a parasitic disease caused by blood flukes of the genus Schistosoma, is a global health problem with over 200 million people infected. Treatment relies on just one drug, and new chemotherapies are needed. Schistosoma mansoni cathepsin B1 (SmCB1) is a critical peptidase for the digestion of host blood proteins and a validated drug target. We screened a library of peptidomimetic vinyl sulfones against SmCB1 and identified the most potent SmCB1 inhibitors reported to date that are active in the subnanomolar range with second order rate constants (k2nd) of ∼2 × 105 M-1 s-1. High resolution crystal structures of the two best inhibitors in complex with SmCB1 were determined. Quantum chemical calculations of their respective binding modes identified critical hot spot interactions in the S1′ and S2 subsites. The most potent inhibitor targets the S1′ subsite with an N-hydroxysulfonic amide moiety and displays favorable functional properties, including bioactivity against the pathogen, selectivity for SmCB1 over human cathepsin B, and reasonable metabolic stability. Our results provide structural insights for the rational design of next-generation SmCB1 inhibitors as potential drugs to treat schistosomiasis

Druggable hot spots in the schistosomiasis cathepsin B1 target identified by functional and binding mode analysis of potent vinyl sulfone inhibitors

© 2020 American Chemical Society. Schistosomiasis, a parasitic disease caused by blood flukes of the genus Schistosoma, is a global health problem with over 200 million people infected. Treatment relies on just one drug, and new chemotherapies are needed. Schistosoma mansoni cathepsin B1 (SmCB1) is a critical peptidase for the digestion of host blood proteins and a validated drug target. We screened a library of peptidomimetic vinyl sulfones against SmCB1 and identified the most potent SmCB1 inhibitors reported to date that are active in the subnanomolar range with second order rate constants (k2nd) of ∼2 × 105 M-1 s-1. High resolution crystal structures of the two best inhibitors in complex with SmCB1 were determined. Quantum chemical calculations of their respective binding modes identified critical hot spot interactions in the S1′ and S2 subsites. The most potent inhibitor targets the S1′ subsite with an N-hydroxysulfonic amide moiety and displays favorable functional properties, including bioactivity against the pathogen, selectivity for SmCB1 over human cathepsin B, and reasonable metabolic stability. Our results provide structural insights for the rational design of next-generation SmCB1 inhibitors as potential drugs to treat schistosomiasis