ATRA induces APL/NB4 cells to release procoagulant extracellular chromatin. Fresh APL cells were primed with a mix of cytokines (10 ng/mL TNF-α, 10 ng/mL IL-1β, and 10 ng/mL IL-6) for 1 hour and then were incubated with 1 μM ATRA. Levels of cf-DNA (A) and MPO-DNA complexes (B) in the supernatant were measured at the indicated time points. (C) Representative confocal microscopy images of APL/NB4 cells stained by lactadherin (green) and PI (red). Cells with expanded nuclei that lost shape and filled most of the cytoplasm were counted as ETs releasing cells (arrow). Those with condensed and fragmented nuclei were counted as apoptotic cells (arrowhead). Bars represent 10 μm. One out of 6 independent experiments is shown. (D) Promyelocytic extracellular chromatin was isolated and incubated with 20% plasma from healthy controls. TAT complexes were measured by ELISA. (E) For inhibition assays, isolated extracellular chromatin was pretreated with DNase I or anti-TF antibody before incubation with plasma. Data are from 6 independent experiments and presented as means ± SD. *P < .05, **P < .01, ***P < .001 vs day 0; ^#P < .05, ^##P < .001 vs no inhibitor group in E.