Ursolic Acid Induced Apoptosis In HT-29 And Expression Of Gene Caspase-9, Bax

Objective: To investigate whether urolic acid can induce apoptosis in human colorectal carcinoma cell line HT-29, and the expression of gene caspase-9,bax.Methods: The human colorectal carcinoma HT-29 cell were treated with ursolic acid. The proliferation inhibitory was determined by MTT method. Morphological study, TUNEL method and flow cytometry were used to detect apoptosis. Expression and activation of caspase-9, bax were assessed by anti-caspase-9,anti-bax polyclonal antibody and immunochemical staining.Results: UA inhibited the proliferation of HT-29 cell. MTT assay showed that urolic acid had a moderate anti-proliferation effect on HT-29 cells at the concentration above 30umol/L in time-and-dose-dependant manner. The morphology of HT-29 changed as nuclear condensation of chromatin and DNA fragmentation after treated with 30 umol/L of UA for 24h. After treated with 30 umol/L of UA, HT-29 cells showed S phase decline and G0/G1 phase arrest. With the concentration of UA increased ,the alteration of the cell cycle is more evident. After treated with 30 umol/L ,compared with the control, the expression of caspase-9 and bax of 24-hour-treated group had a significant increasment.Conclusions: Urolic acid has moderate anti-proliferation and cytotoxicity effect on HT-29 cells in time-and-dose-dependent manner. It is very possible that UA mainly acts on HT-29 cells at G0/G1 phase by causing DNA injury to suppress cell proliferation. It can up-regulate bax expression so as to promote sensitivity for apoptosis in HT-29 cells. In addition, UA lead to activation of caspase-9 in a time-and-dose-dependent manner, suggesting its ability of inducing apoptosis is one mechanism of its effects.