[Relation between beta-amyloid peptide-25-35 inducing cell cycle change and apoptosis of serum-deprived PC12 cell].

OBJECTIVE: To study the relation between cell cycle change and apoptosis of serum-deprived PC12 cell, which are induced by beta-amyloid peptide-25-35 (alpha beta(25-35)). METHODS: PC12 cells were synchronized by cultured in deprivation of serum for 24 h and treated with different concentration of alpha beta(25-35) (0-45 micromol/L) for another 24 h,and the cell survival rate was evaluated by MTT assay. The cell apoptosis was analyzed by Hoechst fluorescence staining and DNA agarose gel electrophoresis. The relation between cell cycle redistribution and apoptosis was analyzed by flow cytometry (FCM). RESULTS: alpha beta(25-35) decreased the survival rate of PC12 cells in dose-dependent manner. The typical apoptotic cells were showed by fluorescence staining when treated with 25 micromol/L alpha beta(25-35) for 24 h;the obvious DNA-Ladder was showed by DNA agarose electrophoresis. About 90% PC12 cells were found to arrest on G0/G1 by FCM being deprived serum. Treated with 25 micromol/L alpha beta(25-35) for 8, 16, 24 h, the percent of S phase cells was raised remarkably (P < 0.01) at 8 h, but the percent of S phase cells was declined gradually after treated for 16 h. Meanwhile the apoptotic rate was detected being increased obviously between 16 h and 24 h (P < 0.01), the obvious hypodiploid peak could be observed ahead of G0/G1 phase(Ap). CONCLUSION: alpha beta(25-35) decreases the survival rate of synchronized PC12 cell and induces the synchronized PC12 cells attempting to reenter cell cycle,which appear the apoptotic peak subsequently. This indicates that the cell apoptosis may be related to the abnormal cell cycle distribution induced by alpha beta(25-35), which means there may be a close relationship between cell cycle and apoptosis.

[Differentiation of human promyelocytic leukemia HL-60 cells induced by proanthocyanidin and its mechanism].

This study was purposed to investigate the proliferation, differentiation and apoptosis of human promyelocytic leukemia HL-60 cells induced by proanthocyanidin (PAC). HL-60 cells were incubated with 20 mg/L PAC for 24 h, the cell growth was evaluated by CCK-8 assay. the effect of PAC on HL-60 cells was evaluated and the cells morphology was observed by optical microscopy. Expression of CD14 and CD11b, and cell cycle were analyzed by flow cytometry. The results showed that the growth of HL-60 cells was inhibited after treatment with PAC of different concentration in a dose-dependent manner (P < 0.05). 20 mg/L PAC displayed significant effect on HL-60 cells with inhibition ratio (72.3 ± 1.8)% for 24 h. Microscopy displayed that some cells differentiated to relative mature cells after treating for 48 h. Expression of CD14 increased and the expression of CD11b increased a little after treating with 20 mg/L PAC for 24 h, the ratio of cells in G0/G1 phase increased, but the ratio of cells in S phase decreased. The mRNA and protein expression of P21 gene increased, but the protein expression of CDK4 and Cyclin D1 decreased. It is concluded that PAC may inhibit the proliferation of HL-60 cells in vitro, induces the differentiation of HL-60 cells, and arrests the cells in G0/G1 phase. The possible mechanism may be related to up-regulation of P21 gene expression and down-regulation of the protein expression of CDK4 and Cyclin D1.