Berberine-Photodynamic Therapy Sensitizes Melanoma Cells To Cisplatin-Induced Apoptosis Through ROS-Mediated P38 MAPK Pathways

The clinical use of cisplatin are limited due to its drug resistance.Thus,it is urgent to find effective combination therapy that sensitizes tumor cells to this drug.Photodynamic therapy is a new type of tumor treatment,and it can also be used as a non-invasive adjuvant therapy in combination with chemotherapy.The combined chemo-photodynamic therapy could increase anti-tumor efficacy while also reduce the side effects of cisplatin.Berberine is an isoquinoline alkaloid,which has been reported to show high photosensitizing activity.In this study,berberine was selected as the photosensitizer.The anti-tumor effects and mechanisms of the combination therapy were explored using molecular pharmacology research methods and evaluation methods.In this study,the cytotoxic effects of berberine-photodynamic alone or in combination with cisplatin were tested by MTT assays.We found that berberine-photodynamic treatment blocked the drug resistance of cells to cisplatin through reducing cell viability.The combination of berberine-photodynamic and cisplatin was more effective than either drug alone.We then examined the subcellular localization of berberine with confocal fluorescence microscopy.The percentage of apoptotic cells,the mitochondrial membrane potential(ΔΨm)and reactive oxygen species(ROS)generation assessed using flow cytometry analysis.Western blotting used in this study to determine the expression levels of MAPK signaling pathways and apoptosis-related proteins.The combined treatment enhanced the ratio of apoptotic cells in linkage to activation of caspase-3,caspase-9 and Bax.We also detected the depolarization of the mitochondrial membrane potential(ΔΨm)and the release of the cytochrome c.These data revealed that the mode of cell death is the caspase-dependent mitochondrial apoptotic pathways.Excessive accumulation of ROS played a key role in this process,which is confirmed by alleviation of cytotoxicity upon pretreatment with NAC.Furthermore,we found that the combined treatment activated MAPK signaling pathway.The inhibition of p38 MAPK by pretreating with SB203580 block the combined treatment-induced apoptotic cell death.In conclusion,these findings stated that berberine-photodynamic could be used as a chemo-sensitizer by promoting cell death through activation of a ROS/p38/caspase cascade.