ABSTRACT
Objective:To investigate the effect of rapamycin (Rapa) on apoptosis of acute myeloid leukemia THP-1 cells induced by idarubicin (IDA) and its molecular mechanism.Methods:The THP-1 cells were treated with 10, 20, 40 and 80 nmol/L Rapa for 1 h, and the cells without Rapa treatment were set up. Western blot was used to detect the conversion of autophagy marker LC3 protein in THP-1 cells (the ratio of LC3Ⅱ/LC3Ⅰ), flow cytometry was used to detect the apoptotic rate, and the pretreatment concentration of Rapa was determined. THP-1 cells were treated with different concentrations of IDA for 24 h, the cell proliferation inhibition rate of IDA for THP-1 cells was detected by CCK-8 method, and the half maximal inhibitory concentration ( IC50) was calculated. THP-1 cells with or without Rapa treatment were treated by IDA with the concentration of lower than IC50 for 24 h, CCK-8 method was used to detect cell proliferation inhibition rate, flow cytometry was used to detect cell apoptosis, real-time fluorescent quantitative polymerase chain reaction was used to detect the expression changes of autophagy-related genes Beclin-1, LC3 and p62, and Western blot was used to detect the conversion of autophagy marker LC3 protein. Results:The ratio of LC3Ⅱ/LC3Ⅰ in THP-1 cells treated by 20 nmol/L Rapa was higher than that in the untreated cells ( P=0.002 4). The apoptotic rate in THP-1 cells treated by 80 nmol/L Rapa was higher than that in the untreated cells ( P=0.007 3). According to the results of Western blot and flow cytometry, 20 nmol/L Rapa was selected as the pretreatment concentration. The IC50 of IDA for THP-1 cells treated with IDA for 24 h was 59.874 nmol/L. After treated with 50 nmol/L IDA for 24 h, the proliferation inhibitory [(69.67±5.03)% vs. (41.67±3.51)%] and apoptotic rates [(74.35±4.83)% vs. (41.25±5.24)%] in THP-1 cells pretreated by Rapa were higher than those in the unpretreated cells (both P<0.05); the Beclin-1 and LC3 mRNA expression levels and the ratio of LC3Ⅱ/LC3Ⅰ in THP-1 cells pretreated by Rapa were higher than those in the unpretreated cells, and the expression of p62 mRNA was lower than that in the unpretreated cells (all P<0.05). Conclusion:Rapa can enhance the apoptosis of THP-1 cells induced by a relative low dose of IDA, which may be achieved through inducing excessive autophagy in THP-1 cells.