The effects of photodynamic therapy on human neutrophil migration using bacteriochlorin a

Bacteriochlorin a photodynamic therapy (BCA-PDT) caused inhibition of inter leukin (IL)-8-activated neutrophil migration, at concentrations that did no t induce membrane damage. Random migration and migration induced by other c hemoattractants were also inhibited, indicating that the effect of BCA-PDT was not at the level of chemoattractant-receptor interaction but down strea m. The BCA-PDT completely blocked superoxide production of phorbol ester-st imulated neutrophils, indicating that superoxide production by neutrophils present in the tumor before and during BCA-PDT is not the cause of inactiva tion of tumor cells. Both type I and type II quenchers prevented inhibition by BCA-PDT but only in electroporated cells, Confocal laser scanning micro scopy showed that the fluorescence of BCA was located inside the cell. Thes e results show that the effects of BCA-PDT are intracellular and of a mixed type I/type II character and that the neutrophils present in the tumor dur ing illumination probably do not contribute to tumor eradication by releasi ng reactive oxygen species.