Palmatine hydrochloride mediated photodynamic inactivation of breast cancer MCF-7 cells: Effectiveness and mechanism of action

- PaH could be activated by a 470 nm LED light source to produce ROS.
- PaH-PDT demonstrated a significant photocytotoxicity on MCF-7 cells.
- PaH could locate in mitochondria and endoplasmic reticulum of MCF-7 cells.
- Early and late apoptotic rate of MCF-7 cells increased by PaH-PDT.

Breast cancer is one of the commonest malignant tumors threatening to women. The present study aims to investigate the effect of photodynamic action of palmatine hydrochloride (PaH), a naturally occurring photosensitizer isolated from traditional Chinese medicine (TCM), on apoptosis of breast cancer cells. Firstly, cellular uptake of PaH in MCF-7 cells was measured and the cytotoxicity of PaH itself on breast cancer MCF-7 cells was estimated using the 3-(4, 5-dimethylthiazol-2-yl)-2, 5-diphenyltetrazolium bromide (MTT) assay. Subcellular localization of PaH in MCF-7 cells was observed using confocal laser scanning microscopy (CLSM). For photodynamic treatment, MCF-7 cells were incubated with PaH and then irradiated by visible light (470 nm) from a LED light source. Photocytotoxicity was investigated 24 h after photodynamic treatment using MTT assay. Cell apoptosis was analyzed 18 h after photodynamic treatment using flow cytometry with Annexin V/PI staining. Nuclear was stained using Hoechst 33342 and observed under a fluorescence microscope. Intracellular production of reactive oxygen species (ROS) was studied by measuring the fluorescence of 2, 7-dichlorofluorescein (DCF) using a flow cytometry. Results showed that PaH treatment alone had no or minimum cytotoxicity to MCF-7 cells after incubation for 24 h in the dark. After incubation for 40 min, the cellular uptake of PaH reached to the maximum, and PaH mainly located in mitochondria and endoplasmic reticulum of MCF-7 cells. Photodynamic treatment of PaH demonstrated a significant photocytotoxicity on MCF-7 cells, induced remarkable cell apoptosis and significantly increased intracellular ROS level. Our findings demonstrated that PaH as a naturally occurring photosensitizer induced cell apoptosis and significantly killed MCF-7 cells.