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INACTIVATION OF CELL SURFACE RECEPTORS BY PHEOPHORBIDE a, A GREEN PIGMENT ISOLATED FROM Psychotria acuminata
Author(s) -
Glinski Jan A.,
David Eva,
Warren Thomas C.,
Hansen Gordon,
Leonard Scott F.,
Pitner Phillip,
Pav Susan,
Arvigo Rosita,
Balick M. J.,
Panti Eligio,
Grob Peter M.
Publication year - 1995
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.1751-1097.1995.tb05250.x
Subject(s) - pheophorbide a , receptor , photodynamic therapy , monoclonal antibody , cytokine , microbiology and biotechnology , biology , cell surface receptor , chemistry , biochemistry , antibody , immunology , organic chemistry
— The inhibition of cytokine and monoclonal antibody binding to cell surfaces caused by an extract of Psychotria acuminata, a medicinal plant used in the traditional medicine of the people of Belize (Central America), was attributed to the presence of pheophorbide a and pyropheophorbide a Since the binding of tumor necrosis factor‐alpha, interleukin‐8, complement factor 5a as well as epidermal growth factor to target cells was dramatically reduced, the inhibition was not receptor or cytokine specific. In addition, the respective binding of radiolabeled monoclonal antibodies CL203 and R15.7 to the cell surface antigens intracellular cell adhesion molecule‐1 and lymphocyte function‐associated antigen‐1 ß‐chain was decreased by pretreatment of cells with pheophorbide a as well. In all cases, the inhibition by pheophorbides was dependent on the simultaneous presence of light, indicating causative involvement of a photodynamic process. These observations are not unique to pheophorbides and can be extended to porphyrins as well as to other photodynamic agents. Cytotoxicity resulting from photodynamic therapy (PDT) has been documented by many studies. Our investigations suggest that the inactivation of cell surface receptors contributes not only to the antitumor effect of PDT but also to the systemic immunosuppression, a serious side effect of PDT.