The role of photosensitized macrophages in photodynamic therapy.

Cancer stimulates macrophage infiltration and encourages angiogenesis, which is necessary for tumor growth and invasion. It seems, that the influence of photodynamic therapy (PDT) on immune cells and immune regulators plays a crucial role in this process. In order to study this effect, the influence of δ-aminolevulinic acid (ALA) PDT on the activity of the murine macrophage J-774A.1 cell line was assessed. J-774A.1 cells were incubated with different concentrations of ALA and irradiated with a VIS light source (400-750 nm) at 5, 10 and 30 J/cm2. The effects of ALA-PDT were evaluated on the basis of cell viability and the secretory activity of macrophages (nitric oxide, NO; reactive oxygen intermediates, ROI; tumor necrosis factor α, TNF-α; interleukin-1β, IL-1β; and nuclear factor κB, NF-κB; proteins, p50 and p65). Experiments showed that at the higher energy doses, there was a large increase in ROI and TNF-α release and decreased levels of NF-κB p50 and p65, IL-1β production and NO release. The increased levels of ROI and TNF-α release after PDT could be an additional factor for the complete eradication of tumors. The decrease in NF-κB p50 and p65 and IL-1β levels could inhibit tumor progression.