| As a traditional loop diuretic drug, ethacrynic acid (EA) has been used inmedicine for treatment of a lot of diseases including hypertension and edema. EAcontains an-unsaturated carbonyl group, a structure that inhibits the activity ofcytosol glutathione S-transferases (GST), leading to decreased detoxification. As aresult, EA is often used together with chemotherapeutic agents to potentiate theircytotoxic effect through counteracting the drug resisitance of tumor cells.Meanwhile, the apoptosis-inducing effect of EA has also drawn wide attention. Inthis study, we evaluated the apoptosis-inducing effect of EA on human acutemyeloid leukemic cell line, and investigated the mechanisms of EA-inducedapoptosis.First, we treated U-937leukemic cell line with different concentrations of EA,measured cell survival rate, and determined the cytotoxicity of EA. Second, wedemonstrated through Hoechst staining and flow cytometry that EA could induceapoptosis of human leukemic cell line U-937in a dose-dependent manner. Tofurther illustrate possible pathway of EA-induced apoptosis, we assessedmitochondria membrane potential (MMP) change after EA treatment by laserconfocal microscope. Results indicated that EA-induced apoptosis was mediated byan intrinsic apoptosis pathway, with a loss of mitochondrial membrane potential.Furthermore, caspase-9, but not caspase-8was activated in EA-induced U-937apoptosis, and although the level of non-active procaspase-3increased slightly, theactivated cleaved form of caspase-3showed no up-regulation. Besides, theapoptotic process was not regulated by the Bcl-2family proteins as the canonicapoptosis pathway did. Taken together, these results implied that EA-inducedU-937apoptosis might be carried out through the mitochondria pathway rather thanthe death-receptor pathway, and failure of DNA ladder formation might beattributed to failure of endonucleases activation in this process. |
