Primary targets in photochemical inactivation of cells in culture

Kristian Berg; Stuart G. Jones; Kristian Prydz; Johan Moan

doi:10.1117/12.199143

12 January 1995 Primary targets in photochemical inactivation of cells in culture

Kristian Berg, Stuart G. Jones, Kristian Prydz, Johan Moan

Proceedings Volume 2325, Photodynamic Therapy of Cancer II; (1995) https://doi.org/10.1117/12.199143
Event: International Symposium on Biomedical Optics Europe '94, 1994, Lille, France

Abstract

The mechanisms of photoinactivation of NHIK 3025 cells in culture sensitized by tetrasulfonated phenylporphines (TPPS₄) are described). Ultracentrifugation studies on postnuclear supernatants indicated that the intracellular distribution of TPPS₄ resembles that of (beta) -N-acetyl-D-glucosaminidase ((beta) -AGA), a lysosomal marker enzyme, and that the cytosolic content of TPPS₄ is below the detection limit of the ultracentrifugation method. Upon light exposure more than 90% of TPPS₄ was lost from the lysosomal fractions, due to lysosomal rupture. The content of TPPS₄ in the postnuclear supernatants was reduced by 30 - 40% upon exposure to light. This is most likely due to binding of TPPS₄ to the nuclei, which were removed from the cell extracts before ultracentrifugation, after photochemical treatment. The unpolymerized form of tubulin seems to be an important target for the photochemical inactivation of NHIK 3025 cells. Since TPPS₄ is mainly localized in lysosomes it was assumed that a dose of light disrupting a substantial number of lysosomes followed by microtubule depolymerization by nocodazole would enhance the sensitivity of the cells to photoinactivation. This was confirmed by using a colony-forming assay. The increased phototoxic effect exerted by such a treatment regime could be explained by an enhanced sensitivity of tubulin to light. Another cytosolic constituent, lactate dehydrogenase, was not photoinactivated by TPPS₄ and light.

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Kristian Berg, Stuart G. Jones, Kristian Prydz, and Johan Moan "Primary targets in photochemical inactivation of cells in culture", Proc. SPIE 2325, Photodynamic Therapy of Cancer II, (12 January 1995); https://doi.org/10.1117/12.199143

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