Enhancement of differentiation of HL-60 cells in the presence of ATRA and the SERCA inhibitor tBHQ.

(A) Cells were treated for 3 days with various concentrations of ATRA (0.001-1 μM) in the presence (▪) or in the absence (■) of 3 μM tBHQ, and cellular NADPH oxidase activity, as measured by NBT reduction, was determined. Data presented are the mean ± SEM (n = 3). (B-C) HL-60 cells were treated for 3 days with vehicle (lane 1), 3 μM tBHQ (lane 2), 50 nM ATRA (lane 3), 3 μM tBHQ plus 50 nM ATRA in combination (lane 4), and 1 μM ATRA (lane 5). (B) The inhibition of cell proliferation was determined by counting the number of cells after 3 days of the various treatments (mean ± SEM; n = 10). (C) Expression of CD11b was determined by FACS analysis and reported as fluorescence intensity in arbitrary units; control Igγ1 (■) and CD11b (▪). Mean ± SEM (n = 3). (D) HL-60 cells were treated for 3 days with various concentrations of tBHQ (1-5 μM), and cellular NADPH oxidase activity measured by NBT reduction was determined. Mean ± SEM (n = 3). (E) HL-60 cells were treated for 3 days with 3 μM tBHQ (▴), 50 nM ATRA (■), 3 μM tBHQ plus 50 nM ATRA in combination (▪), and 1 μM ATRA (▵); and cellular NADPH oxidase activity was determined by NBT reduction. Mean ± SEM (n = 3).