Metabolic effects of photodynamically induced apoptosis in an erythroleukemic cell line. A P-31 NMR spectroscopic study of Victoria-Blue-BO-sensitized TF-1 cells

Victoria Blue BO (VB BO) is a new and promising photo-sensitizer currently being evaluated for photodynamic therapy (PDT). Its photochemical processes are mediated by oxygen radicals, but do not involve singlet oxygen. We use d P-31 NMR spectroscopy of VB-BO sensitized TF-I leukemic cells to gain fur ther insight into the biochemical mechanisms underlying PDT-induced cell de ath. Sham-treatment experiments were performed to evaluate the effects of t his photosensitizer in the absence of light irradiation. Significant metabo lic differences were detected for TF-I cells incubated with VB BO but not e xposed to light, as compared with native cells (controls). These changes in clude reductions in phosphocreatine, UDP-hexose and phosphodiester levels ( as percentage of total phosphate) and slightly reduced intracellular pH. Co mplete phosphocreatine depletion, significant acidification and concomitant inorganic-phosphate accumulation were observed for TF-I cells irradiated a fter incubation with VB BO. Moreover, significant changes in phospholipid m etabolites. i.e., accumulation of cytidine 5'-diphosphate choline and a dec rease in phosphodiester levels, were observed for PDT-treated vs, sham-trea ted cells. Perturbations of phospholipid metabolism may be involved in prog rammed cell death, and the detection of a characteristic DNA ladder pattern by gel electrophoresis confirmed the existence of apoptosis in PDT-treated TF-1 cells. (C) 2000 Wiley-Liss, Inc.