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PHOTOSENSITIZATION BY METHOTREXATE PHOTOPRODUCTS
Author(s) -
Chahidi C.,
Morliere P.,
Aubailly M.,
Dubertrei L.,
Santus R.
Publication year - 1983
Publication title -
photochemistry and photobiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.818
H-Index - 131
eISSN - 1751-1097
pISSN - 0031-8655
DOI - 10.1111/j.1751-1097.1983.tb02678.x
Subject(s) - singlet oxygen , chemistry , methotrexate , pteridine , photochemistry , hematoporphyrin , aqueous solution , photosensitizer , oxygen , photodynamic therapy , organic chemistry , immunology , enzyme , biology
— Photoproducts induced upon excitation of methotrexate by UV light have been separated by ion exchange chromatography. They include 2,4‐diamino‐6‐pteridinecarboxylic acid, 2,4‐diamino‐6‐pteridine‐carboxaldehyde and other unidentified pteridine derivatives. The same photoproducts can be also formed upon photodynamic reaction using hematoporphyrin as photosensitizer. In oxygen saturated aqueous solutions (pH∼7), methotrexate photoproducts sensitize the oxidation of histidine and tryptophan by UV light by a process involving singlet oxygen. In aqueous solutions containing albumin or in human serum, the same photoproducts are formed from free methotrexate but not from albumin‐bound methotrexate. In the latter case the results may suggest that methotrexate covalently binds to albumin upon excitation with UV light either in absence or in presence of oxygen. These results could explain the photosensitization accompanying cancer chemotherapy with high dose methotrexate and also the synergistic effects of PUVA + low dose methotrexate in psoriasis therapy.