OBJECTIVETo research the effect and route of celastrol on Akt signaling pathway of human leukemia cell line K562 apoptosis.

METHODSThe activities of K562 proliferation cells were detected by MTT assay; cell apoptosis was detected by Hoechst 33258 staining assay, DNA fragmentation assay, and Annexin V/PI double-labeled cytometry; the expression and phosphorylation level of Caspase family members and AKT signaling pathway related proteins were determined by Western blot before and after celastrol treatment, and further the effect of AKT signaling pathway on celastrol-induced-apoptosis was analyzed.

RESULTSK562 cell proliferation was inhibited by celastrol in a time- and dose-dependent manner, with the IC50 value for 24 h of (2.15 +/- 0.11) micromol/L. Celastrol induced K562 cells apoptosis in a dose-dependent manner, apparent DNA fragmentation and typical apoptotic morphological changes, and accompanied Caspase-3, 8 activation in the apoptosis process were shown after cells were treated with 2.0 micromol/L celastrol for 24 h. And the celastrol induced apoptosis could be blocked by 50 micromol/L z-VAD-fmk (caspase inhibitor), but augmented by 25 micromol/L WORT (PI3K-Akt inhibitor). Moreover, Celastrol decreased the expressions of p-Akt, survivin and Bcl-2 in the Akt signaling pathway.

CONCLUSIONSCelastrol inhibited the proliferation of K562 cells and induced cell apoptosis by way of activating caspase cascade. The decreased level of Akt phosphorylation during celastrol-induced-apoptosis process suggested that celastrol acted synergistically with PI3K-Akt inhibitors in K562 cell apoptosis inducing.