In vitro cellular effects of δ-aminolevulinic acid sensitized photodynamic therapy

Abstract

In this study, the subcellular targets and cellular mechanisms of the photodynamic action of (delta) -aminolevulinic acid (5ALA) were investigated in rat mammary carcinoma cells (MTF7) in vitro. A constant dose of 5ALA (200 (mu) g/ml) was given and the light dose was varied (20-480 J/cm<SUP>2</SUP>). The effects of PDT were examined at 0 hr, 3 hr, and 24 hr after the treatment using the following assays: (1) Trypan Blue Dye Exclusion Assay for cell membrane damage; (2) MTT Assay for mitochondrial damage; (3) <SUP>3</SUP>H-Thymidine Incorporation Assay for DNA synthesis; (4) Cell Colony Formation Assay for cell survival. The MTT and colony formation assays are the best predictors of cell survival early and late after treatment. Cell membrane damage and almost complete disruption of mitochondrial function are early mechanisms of 5ALA PDT cytopathic effect. Reduction of DNA synthesis is a later, and possibly, a secondary effect of disruption of mitochondrial function although this conjecture has to be explored further. Reduction of DNA synthesis and cell membrane damage show complicated relationships with light dose while loss of mitochondrial function and long term survival are essentially complete with the lowest light dose used in this study.