Study On Apoptosis Of K562 Cells Induced By OFQ And Its Mechanism

Objective: To investigate the effect and the mechanism of Nociceptin/orphanin FQ(OFQ) on K562 cells in vitro.Methods: Inhibition of K562 cells proliferation was measured by MTT assay. Morphological assessment of apoptosis was performed with light microscope after Wright staining and transmission electron microscope. OFQ-induced apoptosis rate of K562 cells and the effect of OFQ on cell cycle was analysised by flow cytometry. Early apoptosis was measured by flow cytometry with AnnexinV/PI staining. DNA fragmentation was visualized by agarose gel electrophoresis and comet assay. Immunocytochemistry were used to evaluate the protein expression of bcl-2 and bax in OFQ-treated and control K562 cells respectively.Result: 1.OFQ time-dependently and no-dose-dependently inhibited the proliferation of K562 cells. Discrete maxima of cytolytic activity was detected at concentration of 10^-610^-7,10^-9,10^-1110^-12mol.L^-1 for 72 h.2.Compared with the control group K562 cells, the cells treated with OFQ showed characteristic of apoptosis under light microscope and transmission electron microscope.3. After a 72 h incubation with OFQ at the concentration of 10^-7, 10^-8 and 10^-9 moI.L^-1, the percentage of apoptotic cells was 22.8 %, 23.8 % and 26.5 % respectively and the control group cell showed no apoptosis. And the number of cells in G₀/G₁ phase increased, whereas S phase decreased.4. The apotosis rate of 0, 10^-9 and 10^-7 mol·L^-1 OFQ-treatment group was 0.52%, 13.7%and 9.68%, respectively.5. DNA agarose gel electrophoresis showed nuclear fragmentation (DNA ladder).6.A large and wide tail was seen in comet assay.7.The protein expression of bcl-2 was decreased in OFQ treated cells as compared with the control cells, but the expression of bax increased.Conclusion:1.OFQ can inhibit growth of K562 in vitro2. OFQ can induce the apoptosis of K562 cells.3. It may be correlated with the dawn-regulation of bcl-2 protein and up-regulation of bax protein.