Role of solasodine hydrochloride in AS2O3 induced HeLa cells apoptosis as well as its effect on cell telomerase activity in vitro

Abstract

Objective To study whether solasodine hydrochloride (SBHL) could enhance the effect of arsenic trioxide in inducing apoptosis and affecting telomerase activity in cervical cancer HeLa cells. Methods Using cell culture methods, cervical cancer HeLa cells were cultured in vitro. The optimal concentration of SBHL was determined by MTT method from 0, 10, 20, 40, 80, 160, to 320 μmol/L. HeLa cells were grown in improved RPMI1640 supplemented respectively with arsenic trioxide(5 μmol/L As2O3), As2O3(5 μmol/L)+ SBHL( 40 μmol/L) and none (control group). The growth morphology of HeLa cells was observed under phase contrast microscopy after culture for 24, 48, and 72 h. Apoptosis of HeLa cells was determined under transmission electronic microscopy. The method of MTT was used to study the cell survival percentage. The technique of flow cytometry was used to measure cell cycle and cell apoptosis percentage. The method of tartrate-resistant acid phosphatase-enzyme linked immunosorbent assay (TRAP-ELISA) was used to determine telomerase activity of HeLa cells. Results Under phase contrast microscopy, in control group HeLa cells were round, densely packed; in As2O3 group the numbers of the cells were less, cell spacing increased; in As2O3 + SBHL group the cells shrinked significantly, nuclear fragmented as a petal-like, gap became larger. Under transmission electronic microscopy, there were rich microvillus on the cell surface in control group, cell intervals clear, immature connections, and the intervals did not close. The structure of the mitochondria in the cytoplasm was integrated. Most of the chromatin in the nucleus were, euchromatin and characteristics of apoptosis with heterochromatin increased and the chromatin condensed into masses, on the boundary of nuclear membrane. The microvillud on the cell surface were ruptured and decreased in As2O3 + SBHL group. The chromatin condensed into masses. The formation of apoptotic bodies was observed. The difference was statistically significant between groups in cell survival percentage at 24, 48, 72h(x2 = 10.39 , 13.88 , 17.21,respectively, all P < 0.05). Cell survival percentage in SBHL + As2O3 group (52.80%) was significantly less than that of As2O3 group(77.51%, x2 = 9.29, P < 0.05) at 72 h. In cell cycles, the difference was statistically significant between groups in C1 phase and S phase(F = 7.46,22.14, all P < 0.05), respectively. Compared with , control group[ (41.57 ± 1.56)%, (50.45 ± 2.37)%], cell percentages in S phase in As2O3 + SBHL group[(20.06 ± 4.98)%] and As2O3 group[(27.10 ± 5.32)%] were decreased(P< 0.05 or < 0.01), while cell percentage in C1 phase was increased[(58.70 ± 5.18)%, (69.67 ± 4.17)%, P< 0.05 or < 0.01]. The difference was statistically significant between groups in apoptotic percentage of HeLa cells (F = 4.01, P < 0.05). Compared with control group[ (1.18 ± 1.40)%], apoptosis percentage was significantly increased in As2O3 + SBHL group and As2O3 group [(21.08± 1.22)%, (6.04±2.53)%, P< 0.05 or < 0.01], respectively, and As2O3 + SBHL group was higher than As2O3 group(P < 0.01). The difference was statistically significant between groups in telomerase activity (F = 21.28, P< 0.05). Telomerase activity was inhibited in As2O3 group(1.214 ± 0.621) and As2O3A + SBHL group(0.865 ± 0.284) compared to control group (2.107 ± 0.057, all P < 0.05), and telomerase activity in As2O3 + SBHL group was lower than that of As2O3 group (P < 0.05). Conclusions SBHL enhances the effect of As2O3 in inducing apoptosis in HeLa cells, which is related to its inhibiting telomerase activity in HeLa cells. Key words: Solasodine hydrochloride; As2O3; HeLa cells; Apoptosis; Telomerase