Photodynamic therapy with 5-aminolevulinic acid induces apoptosis and caspase activation in malignant T cells

Background: Preliminary studies have suggested that photodynamic therapy (PDT) with 5-aminolevulinic acid (ALA) can improve psoriasis and mycosis fungoides, two diseases where normal or malignant T Cells play a central role. Objectives: To determine if ALA-PDT induces apoptosis and caspase activation in Jurkat cells, a malignant T-cell line. Methods: Jurkat cells were incubated with ALA in the presence of [C-14]-thymidine followed by red light exposure. DNA fragmentation was measured 24 hours later with a DNA elution assay. The influence on DNA fragmentation of ALA concentration, time between ALA addition and light exposure, as well as light fluence were studied. The occurrence of oligonucleosome-sized DNA fragmentation was also studied with DNA elcctrophoresis. Caspase-3-like activity was monitored by measuring Ac-DEVD-AMC hydrolysis. Results: DNA fragmentation as high as 88% was observed 24 hours after ALA-PDT. The percentage of DNA fragmentation increased with increasing doses of ALA, red light fluence, as well as longer incubation time with ALA. DNA fragmentation was observed as early as 3 hours after ALA-PDT. The presence of apoptosis after ALA-PDT was confirmed by DNA electrophoresis. An increase in caspase-3-like activities was detected following ALA-PDT. Conclusion: ALA-PDT induces apoptosis and caspase-3-like activation in Jurkat cells.