5-Aminolevulinic acid induced lipid peroxidation after light exposure on human colon carcinoma cells and effects of alpha-tocopherol treatment

This work relates to studies on modes of phototoxicity by protoporphyrin (P pIX) after incubation of 5-aminolevulinic acid (5-ALA) on cultured cells. L ipid peroxidation in the 5-ALA incubated primary adenocarcinoma cells from the rectosigmoid colon (WiDr cells) was determined by measurement of protei n-associated thiobarbituric acid reactive substances (TBARS). TEARS were in creased 2-fold in cells treated with 2 mM 5-ALA for 3.5 h in serum enriched medium. After illumination of 5-ALA incubated cells, TEARS were formed in a light dose dependent manner. TEARS analysis were compared with highperfor mance liquid chromatography (HPLC) analysis of malondialdehyde, and results indicate that 90% of the thiobarbituric reactive substances were due to ma londialdehyde. Pretreating WiDr cells with alpha -tocopherol for 48 h inhib its the cytotoxic effect of 5-ALA and increases 5-fold the light dose neede d to kill 50% of the cells. Pretreatment with alpha -tocopherol shows a con siderable decrease (about 80%) on TEARS formation after illumination. The c ellular content of alpha -tocopherol was determined by HPLC and found to be 15.3 pmol/10(6) cells. (C) 2000 Elsevier Science Ireland Ltd. All rights r eserved.