The temperature dependence of porphyrin production in Propionibacterium acnes after incubation with 5-aminolevulinic acid (ALA) and its methyl ester (m-ALA).

Topical PDT treatment of the common skin disease acne vulgaris is now in clinical use. Propionibacterium acnes (P. acnes) is known to play an important role in acne. 5-Aminolevulinic acid (ALA) supplementation leads to an enhanced porphyrin production in the bacteria. Subsequent illumination with light of the proper wavelengths can reduce the number of bacteria and this might at least partly explain the PDT effect on acne. We have assessed the effects of temperature on P. acnes washed cell suspensions incubated for 4 h with ALA or ALA methyl ester (m-ALA). The effect on porphyrin production of both the cell suspension incubation temperature as well as the initial growth temperature of the cultivated cells prior to harvesting and use in suspension experiments was investigated. The bacterial porphyrin content was estimated from fluorescence emission spectra. It was found that incubation with ALA or m-ALA at a temperature 42 degrees C resulted in an approx. 100% and 33% increase in the total amount of PDT-relevant porphyrins produced as compared to incubation at 37 degrees C. These results support increasing the skin temperature during incubation with ALA or m-ALA in the clinic. The initial growth temperature, prior to the incubation, had no apparent effect on the ALA or m-ALA induced porphyrins. Activation energy studies indicate slightly higher temperature dependence in the case of ALA produced porphyrins as compared to m-ALA produced porphyrins (77 and 65 kJ mol(-1), respectively).

Cell specific effects of polyunsaturated fatty acids on 5-aminolevulinic acid based photosensitization.

The purpose of this study was to examine whether the dietary components n-6 and n-3 polyunsaturated fatty acids (PUFAs) may potentiate the effect of photodynamic therapy (PDT) in human cancer cell lines by enhancing the lipid peroxidation. The effects of the porphyrin precursor 5-aminolevulinic acid (5-ALA) and light (320 < lambda < 440 nm, 33 W m(-2)), with or without docosahexaenoic acid (DHA) or arachidonic acid (AA), were tested in the colon carcinoma cell lines SW480 and WiDr, the glioblastoma cell line A-172 and the lung adenocarcinoma cell line A-427. The production of endogenous protoporphyrin IX (PpIX) varied substantially between the cell lines and was approximately 4-fold higher in WiDr as compared with SW480. Cell killing by 5-ALA-PDT also varied between the cell lines, but without clear correlation with PpIX levels. Treatment with DHA or AA (10 or 70 microM, 48 or 72 h) in combination with 5-ALA-PDT (1 or 2 mM) enhanced the cytotoxic effect in A-172 and A-427 cells, but not in SW480 and WiDr cells. While 5-ALA-PDT alone increased the lipid peroxidation in A-172 and WiDr cells only, 5-ALA-PDT plus PUFAs increased the lipid peroxidation substantially in all four cell lines. Interestingly, alpha-tocopherol (50 microM, 48 h) strongly reduced lipid peroxidation after all treatments in all cell lines, while cytotoxicity was only reduced substantially in A-427 cells. This demonstrates that induction of lipid peroxidation is not a general mechanism responsible for the cytotoxicity of 5-ALA-PDT, although it may be important in cell lines with an inherent sensitivity to lipid peroxidation products. Thus, the mechanisms of cell growth inhibition/cell killing by PDT are complex and cell specific.