Photodynamic Activation of Mammalian and Avian Cholecystokinin Type 1 Receptor Outside of the Pancreatic Acinar Cell Microenvironment

Cholecystokinin 1 receptor (CCK1R) is activated by singlet oxygen (¹O₂) in type II photodynamic action in isolated rat, mouse, and Peking duck pancreatic acini. To examine whether this is maintained outside the microenvironment of pancreatic acinar cell, photodynamic activation of CCK1R from human, rat, mouse, and Peking duck expressed in CHO-K1 cells was examined, as monitored with Fura-2 fluorescence calcium imaging. Photodynamic action with sulphonated aluminum phthalocyanine was found to trigger persistent calcium oscillations in CCK1R-CHO-K1 cells transfected with human, rat, mouse or Peking duck <i>CCK1R</i> gene, which were blocked by ¹O₂ quencher Trolox C. After tagging protein photosensitizer miniSOG to C-terminus of these CCK1R, photodynamic action was found to similarly trigger persistent calcium oscillations in CCK1R-miniSOG-CHO-K1 cells expressing human, rat, mouse, and Peking duck receptor constructs. Incubation with Trolox C 300 μM during LED light irradiation also prevented photodynamic CCK1R activation in CCK1R-miniSOG-CHO-K1 cells. In contrast, human M3R was not photodynamically activated with SALPC or tagged miniSOG as the photosensitizer. These data, together, suggest that photodynamic CCK1R activation is maintained outside of the pancreatic acinar cell, making possible photodynamic CCK1R activation in CCK1R-expressing organs and tissues other than the pancreas, with high spatiotemporal precision.