Study On The Role Of LyGDI Regulated The Rac1 In The Apoptosis Of K562 And HL-60 Cells Induced By ⁶⁰ Coγ Rays

Objective: LyGDI (27kDa), also named RhoGDI2, D4-GDI or RhoGDIβ, a major memberof RhoGDP dissociation inhibitor (RhoGDI) family, has been implicated in the regulation of many aspects of cell apoptosis,metastasis and invasion, including cell polarity,cytoskeletal organization and transduction of signals from the extracellular environment. This study was to investigate the effection on the apoptosis and cell cycle in K562 and HL-60 cells by ⁶⁰Coγrays and the role of LyGDI and cleavged LyGDI regulated the Rac1 in the apoptosis of K562 and HL-60 cells induced by ⁶⁰Coγrays.Methods: (1) Erythrosine B cells staining was used to count the apoptosis rate of the K562 and HL-60 cells induced by different doses of ⁶⁰Coγrays. (2) PI staining and cytoflow meter was applied to check the cell cycle in the K562 and HL-60 cells induced by different doses of ⁶⁰Coγrays. (3) The expression of LyGDI and Rac1 was resolved by western bloting using anti-mono antibody of LyGDI and Rac1. (4) The distribution of Rac1 protein in cells induced by ⁶⁰Coγrays was observed with immunofluorence using the confocal microscope.Results: (1) Erythrosine B staining revealed that apoptosis rates were increased in the K562 and HL-60 cells induced by different doses of ⁶⁰Coγrays at different times. the apoptosis rate was 12.7% at 72h after 8Gy irradiation in the K562 cells ,but the apoptosis rate arrived 94% at 72h after 8Gy irradiation in the HL-60 cells,The apoptosis rate of K562 cells was lower than the HL-60 cells. (p〈0.05) (2) The ratio of G2 phase was increased in the K562 and HL-60 cells induced by different doses of ⁶⁰Coγrays. The ratio of G2 phase in K562 cells was lower than the HL-60 cells radiated by ⁶⁰Coγrays(p〈0.05),the lift proportion of G2 phase in HL-60 cells was larger than K562 cells,the radiosentivity of HL-60 cells was higher than K562 cells. (3) Western Blot analysis revealed that LyGDI was not cleavged in the K562 cells,but LyGDI was cleavged in the HL-60 cells radiated by ⁶⁰Coγrays. The expressed proteins of LyGDI and Rac1 were not changed in the K562 and HL-60 cells after radiated by different doses of ⁶⁰Coγrays. (4) The immunofluorence confocal microscope showed that the Rac1 proteion moved to the cell membrane and a little in the cell nucleus .Conclusion: (1) K562 and HL-60 cells radiated by ⁶⁰Coγrays were most arrested in G2 phase, the radiosensitity of HL-60 cells was higher than K562 cells ; (2) The cleavged LyGDI promoted the apoptosis rate of HL-60 cells;(3) The LyGDI did not affect the expression of Rac1 protein radiated by ⁶⁰Coγrays; (4) Activated Rac1 was involved in cell apoptosis signal transduction mainly in the cell membrane.