Involvement of mitochondrial permeability transition pore opening in 7-xylosyl-10-deacetylpaclitaxel-induced apoptosis.

7-Xylosyl-10-deacetylpaclitaxel is a natural hydrophilic paclitaxel derivative. It has long been used in Chinese clinics to treat cancer. In order to further explore the underlying intracellular target of 7-xylosyl-10-deacetylpaclitaxel towards the PC-3 cell line, the ultra-structural morphology of mitochondria, the intracellular Ca (2+), the intracellular ATP, the intracellular hydrogen peroxide and pro-apoptotic Bax and Bcl-2 protein expression were measured. Additionally, the changes of mitochondrial morphology and membrane potential ( ΔΨm) were analyzed by atomic force microscopy (AFM) and flow cytometry, respectively. Our results suggest that the intracellular target of 7-xylosyl-10-deacetylpaclitaxel may be the mitochondrial permeability transition pore (mPTP). To further evaluate this hypothesis, we assessed the effect of a specific mPTP inhibitor (cyclosporine A) on the toxic action of 7-xylosyl-10-deacetylpaclitaxel. The 7-xylosyl-10-deacetylpaclitaxel-induced decrease in mitochondrial inner transmembrane potential (ΔΨm) was abolished by the addition of cyclosporine A (CsA) in PC-3 cells, indicating that 7-xylosyl-10-deacetylpaclitaxel may target mPTP. Furthermore, treatment with 7-xylosyl-10-deacetylpaclitaxel increased ROS levels in PC-3 cells. This effect was counteracted by 10 µM cyclosporine A. These data indicate that oxidative damage is involved in mPTP.