The nuclear transport pathways of the
photosensitizers meso-tetra(4-sulfonatophenyl)porphyrin (
TPPS4) and meso-tetra(4-N-methylpyridyl)porphyrin (
TMPyP) during
photosensitization and oxidative stress were characterized in CT-26 murine colon
carcinoma cells using fluorescence microscopy and multi-pixel spectral imaging. Prior to irradiation,
TPPS4 and
TMPyP localized mainly in the lysosomes, while irradiation or H2O2 treatment induced a relocalization into the nucleus and nucleoli. Flow cytometry analysis of isolated nuclei from the treated cells showed an increase in nuclear fluorescence accompanying the relocalization. Isolation and separation of the
nuclear proteins according to molecular weight was performed using a
sephadex G-100 column. The
protein fractions exhibiting high fluorescence were separated by high performance liquid chromatography. Five major classes of
proteins with a retention time of 1, 7, 11, 12 and 15 min were obtained. Each
photosensitizer was associated with a distinct class of
proteins. While
TPPS4 fluorescence was detected in the
protein fraction with a retention time of 11 min,
TMPyP fluorescence was associated with a
protein fraction having a retention time of 7 min. We conclude that although oxidative stress triggers entry into the nucleus of both
TPPS4 and
TMPyP, each sensitizer uses a distinct transport mechanism based on its chemical properties.