ABSTRACT
OBJECTIVE To explore the effect of connexin (Cx) 40-formed gap junctional intercellular communication (GJIC) on Photofrin- photodynamic therapy (PDT) phototoxicity in Cx40- transfected HeLa cells and its potential mechanisms. METHODS HeLa cell line stably transfected to express Cx40 was seeded at high and low cell density, respectively, to assess in vitro photosensitivity using CCK8 assay. Western blot assay was performed to detect the expression of Cx40. The intracellular ROS and Ca2 +concentrations were determined using flow cytometer. 4-HNE and ceramide were measured using ELISA assay. RESULTS Cx40-composed GJ formation at high density enhances the phototoxicity of Photofrin-PDT. When the Cx40 is not expressed or Cx40 channels are blocked, the phototoxicity in high-density cultures substantially reduces, indicating that the enhanced PDT phototoxicity at high density is mediated by Cx40-composed GJIC. The GJIC-mediated increase in PDT phototoxicity was associated with ROS and calcium-mediated stress signaling pathways. CONCLUSION The work uniquely presents the ability of Cx40-composed GJIC to enhance the sensitivity of malignant cells to PDT, and indicates that mainte?nance or increase of Cx40-formed GJIC may be a profitable strategy towards the enhancement of PDT therapeutic efficiency.