Photodynamic therapy (PDT) – Initiation of apoptosis via activation of stress-activated p38 MAPK and JNK signal pathway in H460 cell lines

SummaryAimsThe purpose of this study was to investigate the photoefficacies of protoporphyrin IX (PpIX) generated by drug precursor 5-aminolevulinic acid (ALA) and its hexyl ester (H-ALA) on two human non-small lung carcinoma cell lines (H460/Bcl-2 and H460/neo).Main methodsDrug uptake and the photoefficacies of PpIX were measured by flow cytometry and MTT assay; while the mode of cell death and alternation of signal transduction pathways were studied with 4′,6-diamidino-2-phenylindole (DAPI) staining and Western blot analysis, respectively.Key findingsThe flow cytometric analysis of H-ALA (5 μM) uptake revealed optimal fluorescent intensity at 8 h incubation, while ALA (0.5 mM) was still far from saturation. The LD30 of H-ALA-PDT was 30 μM, 2 J/cm2, while the LD30 of ALA-PDT was 3 mM, 2 J/cm2. The dark toxicities mediated by both pro-drug H-ALA and ALA were negligible. By DAPI staining, apoptotic cell death was observed. In addition, by Western blot analysis, H-ALA- and ALA-mediated PDT initiated apoptotic cell death via the up-regulation and activation of p38 mitogen activated protein kinase (MAPK), the stress-activated c-jun N-terminal kinases (JNK) and ERK.SignificanceThese results suggested that H-ALA and ALA mediated PDT displayed similar photocytotoxicities towards the two non-small lung cancer cells. Our present study also demonstrates H-ALA or ALA mediated PDT in H460 cells are closely related to the activation of p38 MAPK and JNK signalling pathway.