Abstract: The benzophenoxazines, including several Nile blue analogues, are a unique group of dyes that localize selectively in animal tumors. Chemical modifications of Nile blue A can yield derivatives with high $-1$/O$+2$/ quantum yields. These derivatives represent a group of potentially effective photosensitizers for selective phototherapy of malignant tumors. In vitro evaluation of these derivatives has indicated that those with high $-1$/O$+2$/ yields are very effective in mediating the photocytotoxicity of tumor cells. This photodynamic effect is most likely mediated through the action of $-1$/O$+2$/, since photoirradiation under D$-2$/O enhanced and under hypoxic conditions diminished the photocytotoxic action. The subcellular localization of these photosensitizers in bladder tumor cells in culture was examined by light and fluorescence microscopies as well as by histochemical and biochemical studies. The results indicate that these dyes are localized primarily in the lysosome. The cellular uptake and retention of these dyes is energy- and pH-dependent. Agents such as nigericin, which alter the transmembrane pH gradient, reduced uptake and enhanced efflux of the dyes, while agents such as valinomycin, which reduce cellular membrane potential, had no effect on the uptake. These findings are consistent with having ion-trapping as the mechanism for the uptake of these dyes. Photoirradiation of sensitizer-treated cells obliterated lysosomes in a light-dose and drug-dose dependent fashion. Release of the hydrolytic enzymes may be the main cause for subsequent cell death since the cytolytic effect was reduced by a specific inhibitor of lysosomal proteolytic enzyme. A lysosomotropic photosensitization mechanism is therefore proposed for the photocytotoxic action of the Nile blue derivatives. This mechanism may provide an approach to the development of new photosensitizers for the effective and selective destruction of malignant tumors.!
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机译：摘要：苯甲恶嗪，包括几种尼罗蓝类似物，是一组独特的染料，选择性地定位在动物肿瘤中。尼罗蓝A的化学修饰可以产生具有高$ -1 $ / O $ + 2 $ /量子产率的衍生物。这些衍生物代表了一组对恶性肿瘤进行选择性光疗的潜在有效的光敏剂。这些衍生物的体外评估表明，高-1美元/ O + 2美元/产率的衍生物在介导肿瘤细胞的光细胞毒性方面非常有效。这种光动力效应很可能是通过$ -1 $ / O $ + 2 $ /的作用来介导的，因为在D $ -2 $ / O下的光照射增强了，并且在缺氧条件下减少了光细胞毒性作用。这些光敏剂在培养的膀胱肿瘤细胞中的亚细胞定位通过光和荧光显微镜检查以及组织化学和生化研究进行检查。结果表明，这些染料主要位于溶酶体中。这些染料的细胞吸收和保留是能量和pH依赖性的。改变跨膜pH梯度的试剂（如黑霉素），减少了染料的吸收和增强了染料的外排，而降低细胞膜电位的试剂（如缬氨霉素）对吸收没有影响。这些发现与将离子捕获作为摄取这些染料的机理是一致的。敏化剂处理的细胞的光辐照以轻剂量和药物剂量依赖性方式消除了溶酶体。水解酶的释放可能是随后细胞死亡的主要原因，因为溶酶体蛋白水解酶的特异性抑制剂降低了细胞溶解作用。因此，提出了溶同素的光敏化机理用于尼罗蓝衍生物的光细胞毒性作用。该机制可以为开发新的光敏剂提供一种方法，以有效和选择性地破坏恶性肿瘤。
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