| [Background and Objectives]The medicinal herb, Donglingcao, with a scientific name of Rabdosia rubescens, derived from a rabdosia plant of the family Labiatae. Rabdosia rubescens distributes widely in the Yellow River Valley and its southern area, it was first harvested in Henan Province of China and used as anti-tumor folk medicine for the treatment of esophageal and cardia cancer for more than 30 years. Oridonin, a monomeric ingredient of ent-kaurane diterpene compounds, has anti-tumor activity and posseses 90% of the active ingredients of Rabdosia rubescens[1] . Our privious study indicated that oridonin has a relatively strong inhibitory effect on the growth of 15 human cancer cell lines of 9 common tumors including leukemia and cancers of the esophagous, stomach, colon, liver, pancreas, lung, breast and uterine cervix[2]. Based on this, the present study further clarify the inhibition effect, effect on the cell cycle, induce cell apoptosis function and its mechanism in BGC823 gastric denocarcinoma cell. This was done in the hope of providing more useful information for further study on anti-tumor pharmacodynamics of ordonin in vivo and its pharmacological mechanism from molecular biology.[Mthods]BGC-823 cells were treated with oridonin at different concentration, Methyl thiazolyl tetrazolium(MTT) assay was used to measure the effect of oridonin on growth of BGC-823 cells. Phase contrast microscope was used to observe the cells morphology changed. The effect of oridonin on cell cycle was analyzed by PI staining and flow cytometry.The ultrastructure changes of BGC-823 cells were observed with transmission electron microscope. TUNEL staining flow Cytometry method was used to observe the apoptosis of the BGC-823 cells. The expression changes of Bax and Bcl-2 in BGC-823 cells induced by oridonin were detected by Western Blot. Analyzing the gene expression in human esophageal carcinoma cell line SHEEC changed by oridonin by Affymetrix U133A 2.0 array. [Results]Oridonin significantly inhibited the growth and Proliferation of BGC-823 cells in time and dose dependent manner. At 24h, 48h and 72h, the inhibition rate of 64μg/ml oridonin on BGC-823 cells were 68.5%, 90.8% and 94.7% respectively. 32 h after treated with 64μg/ml oridonin, the BGC-823 cell growth was inhibited and cell death increased was observed under phase contrast microscop. Oridonin affected BGC-823 cell cycle distribution and arrested BGC-823 cell in G2/M; Under the transmission electron microscope, at 2 h after BGC-823 cell treatmented by oridonin (32μg/mL), mitochondria aggregate and varyed in size; The the internal structure of mitochondrium of BGC-823 cell disappeared with time process, cells appeared apoptotic characteristics; After treated by oridonin for 24h, the cell apoptosis rate was up to 37.8%. The ratio of Bax/Bcl-2 in BGC-823 cell were 0.42,0.84, 1.06 and 1.56, respecttively,when treated with 32μg/mL oridonin for 4, 12, 24h measured by western blot. Oridonin enhanced the expression ratio of Bax/Bcl-2 in time-dependent manner. Large number of gene expression in SHEEC cell were changed by oridonin, including some of them were closely related to the mechanisms of apoptosis.[Conclusions]Oridonin could inhibit the growth and proliferation of BGC-823 cells in time- and dose-dependent manner in vitro, which function maybe related to produce BGC-823 cell G2/M arrest; oridonin could induce cell apoptosis in time- and dose-dependent manner; In the process of induce cell apoptosis, the cell shown that mitochondrial ultrastructure destructive changs, expression ratio of Bax/Bcl-2 up-regulated and expression of some gene closely related to cell mitochondrial apoptotic signaling pathway changed, these results suggest us that oridonin induce cell apoptosis through the mitochondrial apoptotic signaling pathway.
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