Extracellular traps released by neutrophils (neutrophil extracellular traps, NETs) are a double-edged sword, and understanding the mechanism of NET formation is of great significance for disease treatment. However, the short lifespan, the large individual differences, and the inability to perform gene editing render it difficult to decipher NET formation using neutrophils. It is necessary to find a model cell to replace neutrophils to study the mechanism of NET formation. In this study, we used different concentrations (0, 0.1, 1, and 10 μmol/L) of all-trans retinoic acid (ATRA) to differentiate HL-60 cells for different days (1, 3, 5, and 7 days). By detecting the cell viability and nuclear morphology of cells, we confirmed that HL-60 cells were differentiated to neutrophil-like cells (dHL-60) after treated with ATRA for at least 5 days. Using immunofluorescence staining to detect the formation of NETs, we demonstrated that dHL-60 cells differentiated for 5 days with 1 μmol/L ATRA could generate NETs comparable to those produced by neutrophils upon phorbol 12-myristate 13-acetate (PMA) stimulation, without histone H3 citrullination. Furthermore, the formation of NETs by dHL-60 cells were NADPH-dependent and PAD4-independent, consistent with neutrophils. Taken together, these observations suggest that dHL-60 cells differentiated with 1 μmol/L ATRA for 5 days can be used as a model cell for neutrophils to study the mechanism of NET formation.
【摘要】 目的 探讨铁螯合剂去铁胺（DFO）对诱导白血病细胞HL-60的分子机制。 方法 2003年7-12月用钙黄绿素（calcein）检测HL-60细胞LIP。台盼蓝活细胞拒染实验进行活细胞计数及细胞存活率测定；光镜形态学观察及流式细胞仪（FCM）等方法检测HL-60细胞凋亡；比色法检测caspase-3（基于pNA标记底物的比色法）活性。 结果 ①不同浓度的DFO作用于HL-60细胞后，随培养时间延长及DFO浓度的增加，动态铁池降低，细胞生存率逐渐下降，凋亡率增加，显示一定的时间剂量依赖性。②HL-60细胞在不同浓度的DFO作用下，caspase-3的活性逐渐升高。50、100 μmol/L DFO作用于HL-60细胞24 h，caspase-3酶活性升高明显，与对照组相比，有统计学意义（Plt;0.001）；相关分析结果显示，HL-60细胞LIP的改变与caspase-3活性变化呈负相关系（r=-0.887，Plt;0.05）。 结论 DFO诱导白血病细胞凋亡的作用可能与螯合细胞内铁，降低细胞LIP，激活caspase-3，最终实施细胞凋亡密切相关。【Abstract】 Objective To observe the changes of caspase-3 activity during apoptosis of HL-60 cells induced by an iron deferoxamine (DFO). Methods Exponentially growing HL-60 cells (1×106/mL) were used in this experiment from July 2003 to December 2003. The study groups were divided as follows: DFO group, iron+DFO group and control group. The viability was detected by typanblue, apoptosis was assessed by morphological study and flow cytometry (FCM) assay, and the caspase-3 activity was detected by melorimetry. The intracellular label iron pool (LIP) was measured with a fluorimetric assay using the metalsensitive probe calcein-AM. Results ①When HL-60 cells were incubated with different concentrations of DFO, viability assay was lower than that in the control group at the 12th, 24th and 48th hour (Plt;0.05). ② The cells incubated with different concentrations of DFO showed dose-time dependence and was much higher than that in the control group (Plt;0.01). ③The caspase-3 activity was significantly higher in the apoptotic cells than that in the control cells. Conclusions The apoptosis of HL-60 cells induced by DFO may be correlated with the decrease of cellular LIP and activity of caspase-3.