Effects of Thiomersal on Apoptosis and Autophagy of Leukemia Cell Lines

Abstract

To investigate the effects of different concentrations of thiomersal on apoptosis and autophagy regulation of human leukemia cell lines U937, CEM-C1 and BALL-1. The inhibitory effect of thiomersal on the proliferation of U937, CEM-C1 and BALL-1 cells was detected by CCK-8 assay. Annexin V-FITC/PI double staining flow cytometry was used to detect the apoptosis rate. Western blot was used to detect the effects of thiomersal on autophagy signaling pathway and the expression of PI3K, Akt, mTOR, p-mTOR, caspase-3 and LC3-II proteins. Within 24 and 48 hours, thiomersal inhibited the proliferation of U937, CEM-C1 and BALL-1 cell lines in a time and dose-dependent manner (r24 h=0.295, r24 h=0.452, r24 h=0.103; r48 h=0.821, r48 h=0.665, r48 h=0.821), but no significant time and dose-dependent effect was observed at 72 hours. After 48 hours treatment of thiomersal, the apoptosis rate of U937, CEM-C1 and BALL-1 cells increased in a dose-dependent manner (r=0.819, r=0.763, r=0.835). After 48 hours treatment of thiomersal, the expression levels of PI3K, Akt, mTOR and p-mTOR protein in U937, CEM-C1 and BALL-1 cells decreased in a concentration-dependent manner, the R value of U937 cells was -0.975, -0.899, -0.925 and -0.915, respectively, that of CEM-C1 cells was -0.960, -0.920, -0.861 and -0.927, and that of BALL-1 cells was -0.939, -0.911, -0.896 and -0.926,. which suggested that thiomersal-induced apoptosis of U937, CEM-C1 and BALL-1 cells might be due to the inhibition of PI3K/Akt/mTOR pathway. Thiomersal promoted the apoptosis of U937, CEM-C1 and BALL-1 cells via caspase-3 pathway, and the expressions of caspase-3 and LC3-II were up-regulated in a dose-dependent manner (r=0.976, r=0.914; r=0.976, r=0.986; r=0.961, r=0.974). Thiomersal can inhibit the proliferation and promote the apoptosis of U937, CEM-C1 and BALL-1 cells. A certain concentration of thiomersal can down-regulate the expression of PI3K/Akt/mTOR pathway related proteins PI3K, Akt, mTOR and p-mTOR in U937, CEM-C1 and BALL-1 cells, and activate autophagy and apoptosis by down-regulation of PI3K/Akt/mTOR pathway.