Photodynamically induced effects in colon carcinoma cells (WiDr) by endogenous photosensitizers generated by incubation with 5-aminolaevulinic acid

Human adenocarcinoma cells of the lint WiDr have been treated with 2 mM 5-a minolaevulinic acid (5-ALA) in the presence of 10% foetal calf serum. The t reatment induces a linear accumulation of protoporphyrin IX (PpIX) for at l east 7.5 h. After 7.5 h of incubation about 45% of the PpIX accumulated is cell-bound, while the rest is found in the medium (25%) or lost from the ce lls during washing with phosphate-buffered saline (30%). Exposure to white light at an intensity of 30 W/m(2) for 18 min results in 95% reduction of c lonogenicity in cells treated with 2 mM 5-ALA for 3.5 h. The enzymatic acti vities of enzymes located in cytosol (glyceraldehyde 3-phosphate dehydrogen ase and lactate dehydrogenase) and lysosomes (acid phosphatase and beta-glu curonidase) are not influenced by a 5-ALA and light treatment inactivating about 35% of the cells. The MTT assay, which reflects mitochondrial dehydro genase activity, but not succinate dehydrogenase, is partly inhibited by th e same treatment. Treatment with 5-ALA in the absence of light increases O- 2 consumption by a factor of two, while the O-2 consumption is inhibited wh en 5-ALA treatment is combined with exposure to light. In addition, 5-ALA a nd light exposure enhance accumulation of rhodamine 123 by 40% and reduce t he intracellular ATP level by 25%. Confocal laser scanning microscopical an alysis indicates granular perinuclear localization of the PpIX formed by 5- ALA treatment. In conclusion, photodynamic treatment using 5-ALA as a prodr ug induces damage to mitochondrial function without inhibiting lysosomal an d cytosolic marker enzymes. (C) 1999 Elsevier Science S.A. All rights reser ved.