Dermaseptin-PP Combined with Chemotherapeutic Agents Treats Tumors and Reverses Cisplatin Resistance of A549/DDP Cells
Objective:To investigate the effects of the antimicrobial peptide Dermaseptin-PP combined with chemotherapeutic agents on the tumor cells in vitro and the cisplatin(DDP)resistance of A549/DDP cells,and further explore the underlying mechanisms.Methods:The methyl thiazolyl tetrazolium(MTT)assay was employed to determine the inhibitory effects of different concentrations of Dermaseptin-PP on the proliferation of A549,H157 or 4T1 cells and the inhibitory effects of low concentrations of Dermaseptin-PP in combination with docetaxel(DTX),doxorubicin(DOX)or DDP on A549,H157 or 4T1 cells.The cell-counting kit 8(CCK-8)assay was used to determine the reversal effects of low concentrations of Dermaseptin-PP on the DDP resistance of A549/DDP cells.Flow cytometry was employed to measure the effect of Dermaseptin-PP on DDP-induced apoptosis of A549 cells.The lactate dehydrogenase(LDH)release assay and propidium iodide(PI)uptake assay were employed to investigate the effect of Dermaseptin-PP on the membrane integrity of A549 and A549/DDP cells.Finally,the morphological changes of A549 and A549/DDP cell membranes after Dermaseptin-PP treatment were observed by scanning electron microscopy.Results:Dermaseptin-PP inhibited the proliferation of A549,H157,and 4T1 cells in vitro in a dose-dependent manner.In combination with low concentrations(0.002,0.020,and 0.200 μg·mL-1)of Dermaseptin-PP,DTX,DOX,and DDP demonstrated increased inhibition rates on the proliferation of A549 cells,with reduced half maximal inhibitory concentrations(IC50)and the combination indexes(CIs)lower than 0.9.The combination of Dermaseptin-PP with DDP demonstrated the strongest synergistic effect(CI<0.4).In addition,Dermaseptin-PP combined with DDP showed a synergistic effect,with the CIs lower than 0.9 for both H157 and 4T1 cells.Low concentrations(0.2,2.0,and 4.0 μg·mL-1)of Dermaseptin-PP all significantly reversed the DDP resistance of A549/DDP cells,with the reversal folds(RFs)of 2.83,5.09,and 9.73,respectively.Compared with DDP alone,the combination of DDP with 0.2 μg·mL-1 Dermaseptin-PP increased the apoptosis rate of A549 cells(P<0.05).Dermaseptin-PP increased the LDH release rate and PI uptake rate of A549 and A549/DDP cells in a concentration-dependent manner.The treatment with Dermaseptin-PP at a concentration of 2×IC50 damaged the cell membranes,disintegrated the plasma membranes,and altered the morphology of A549 cells,and the treatment led to the appearance of holes in the cell membranes of A549/DDP cells.Conclusion:Dermaseptin-PP combined with chemotherapeutic agents demonstrated synergistic effects on the tumor cells in vitro,among which the synergistic effect with DDP was the strongest.Moreover,Dermaseptin-PP can reverse the DDP resistance of A549/DDP cells by directly destroying the cell membrane to improve the amount of chemotherapeutic agents entering the cells.
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