Different apoptotic pathways are induced from various intracellular sites by tetraphenylporphyrins and light.

The induction of apoptosis from different intracellular sites was studied by exposing V79 Chinese hamster fibroblasts to photodynamic therapy (PDT) with various porphyrins and light. The effects of two lipophilic, intracellular membrane-localized porphyrins, tetra(3-hydroxyphenyl)porphyrin (3THPP) and Photofrin, were compared with that of two sulphonated meso-tetraphenylporphines (TPPS2a and TPPS4), which are taken up into lysosomes by endocytosis. Apoptotic fractions induced by the various dyes and light were quantified by flow cytometry using the terminal deoxynucleotidyl transferase (TdT) assay.

Apoptosis induction by different pathways with methylene blue derivative and light from mitochondrial sites in V79 cells.

The importance of mitochondria for the induction of apoptosis by photodynamic therapy (PDT) was studied with a new photosensitizing dye, methylene blue derivative (MBD), and light. By using fluorescence microscopy and by measuring the MBD-PDT-induced inhibition of specifically subcellularly localized marker enzymes, we show that MBD is localized in mitochondria and not in lysosomes, endoplasmic reticulum or Golgi apparatus of V79 Chinese hamster fibroblasts. Cellular uptake kinetics and fluorescence properties of the dye in cells were characterized.

Apoptosis and necrosis induced with light and 5-aminolaevulinic acid-derived protoporphyrin IX.

The mode of cell death induced by photodynamic treatment (PDT) was studied in two cell lines cultured in monolayer, V79 Chinese hamster fibroblasts and WiDr human colon adenocarcinoma cells. The cells were incubated with 5-aminolaevulinic acid (5-ALA) as a precursor for the endogenously synthesised protoporphyrin IX, which was activated by light. Free DNA ends, owing to internucleosomal DNA cleavage in apoptotic cells, were stained specifically with a fluorescent dye in the terminal deoxynucleotidyl transferase (TdT) assay.

No correlation between DNA strand breaks and HPRT mutation induced by photochemical treatment in V79 cells.

DNA strand breaks, measured by alkaline elution, and hypoxanthine guanine phosphoribosyltransferase (HPRT) mutation were studied in V79 cells after photochemical treatment (PCT) or exposure to X-rays. Cells were incubated with the photosensitizers Photofrin II (PII) and three closely related porphyrins tetra-(3-hydroxyphenyl) porphyrin (3THPP), meso-tetra-(4-sulfonatophenyl) porphine (TPPS4) and meso-tetra-(N-methyl-4-pyridyl) porphine (TMPyPH2). These dyes are assumed to act on cellular targets mainly via singlet oxygen when excited by light.

Primary DNA damage, HPRT mutation and cell inactivation photoinduced with various sensitizers in V79 cells.

DNA strand breaks and hypoxanthine guanine phosphoribosyl transferase (HPRT) mutants were measured in parallel in photochemically treated (PCT) cells and compared at the same level of cell survival. Chinese hamster fibroblasts (V79 cells) were either incubated with the lipophilic dyes tetra(3-hydroxyphenyl)porphyrin (3THPP) and Photofrin II (PII), the anionic dye meso-tetra(4-sulfonatophenyl)porphine (TPPS4) or the cationic dye meso-tetra(N-methyl-4-pyridyl)porphine (p-TMPyPH2) before light exposure. In the cells, the lipophilic dyes were localized in membranes, including the nuclear membrane, while the hydrophilic dyes were taken up primarily into spots in the cytoplasm.