Promotion of PDT Induced phototoxicity by bile acids

描述（由申请人提供）：我们对细胞死亡机制的研究 光动力疗法（PDT）后提出了一种新的程序来增强 光毒性功效。我们之前已经证明光动力损伤 线粒体催化细胞色素 c 释放到细胞质中，引发 凋亡反应。这可以绕过细胞凋亡程序中的缺陷步骤 由常规化疗引起。最近的几份报告表明 胆汁酸熊去氧胆酸（UDCA）可以保护线粒体 几种药物的促凋亡作用对肝癌细胞膜的影响 包括乙醇、脱氧胆酸、过氧化氢和镉离子。我们 预计 UDCA 也能保护线粒体（PDT 的重要靶标）， PDT 后诱导细胞凋亡反应。相反，我们发现 相反的作用：显着促进细胞色素c、caspase-3的释放 激活和细胞凋亡。这在小鼠实验中得到了证实 白血病和肝癌lclc7细胞。在前一个细胞系中，我们还 证明 UDCA 可以促进光敏的细胞凋亡反应 催化抗凋亡蛋白 Bcl-2 选择性光损伤的试剂， 但不影响促凋亡蛋白Bax。在一项试点研究中，我们发现 给予 UDCA 后，携带 RIF 肿瘤的小鼠的寿命得以延长 照射前，使用锡紫红素SnET2作为光敏剂 代理。这些结果具有潜在的重大临床意义，因为 UDCA 广泛用于治疗胆结石和肝脏疾病，其 药理学和安全性已得到很好的确立。提供有关以下方面的信息 相关机制，我们计划 [1] 描述 UDCA 对 对一系列光敏剂的细胞毒性反应，[2] 评估 一系列 UDCA 类似物的结构-活性关系，包括 体内形成的甘氨酸和牛磺酸缀合物，[3] 检查 UDCA 在多种肿瘤细胞系中增强 PDT 的功效，[4] 在动物肿瘤模型中测量 UDCA 和选定类似物对 PDT 的促进作用。我们的 假设是 UDCA 分配到线粒体膜中并且两者都降低 光损伤的阈值，同时提供离液序列保护 更疏水的胆汁酸的影响。目标 [4] 将在 与路易斯维尔大学 PDT 设施签订分包合同，那里有 动物 PDT 研究所需的专业知识。如果初步结果 研究经进一步调查证实，UDCA 可以提供安全且 促进临床PDT疗效的有效手段。

DESCRIPTION (provided by applicant): Our studies on mechanisms of cell death after photodynamic therapy (PDT) have suggested a novel procedure for enhancing phototoxic efficacy. We had previously shown that photodynamic damage to mitochondria catalyzes release of cytochrome c into the cytosol, triggering an apoptotic response. This can bypass defective steps in the apoptotic program elicited by conventional chemotherapy. Several recent reports have indicated that the bile acid ursodeoxycholic acid (UDCA) could protect the mitochondrial membrane of hepatoma cells from the pro-apoptotic effects of several agents including ethanol, deoxycholic acid, hydrogen peroxide and cadmium ion. We expected that UDCA would also protect mitochondria, an important PDT target, from the induction of an apoptotic response after PDT. We found instead the opposite effect: a significant promotion of cytochrome c release, caspase-3 activation and apoptotic cell death. This was demonstrated in both murine leukemia and hepatoma lclc7 cells. In the former cell line, we also demonstrated that UDCA could promote the apoptotic response to photosensitizing agents that catalyze selective photodamage to the anti-apoptotic protein Bcl-2, but do not affect the pro-apoptotic protein Bax. In a pilot study, we found the lifespan of mice bearing the RIF tumor was enhanced when UDCA was administered before irradiation, using the tin etiopurpurin SnET2 as the photosensitizing agent. These results are of potentially great clinical significance since UDCA is widely used for the treatment of gallstones and liver diseases, and its pharmacology and safety have been well established. To provide information on the pertinent mechanisms, we plan to [1] characterize the effects of UDCA on the cytotoxic responses to a spectrum of photosensitizing agents, [2] assess the structure-activity relationships in a series of UDCA analogs including the glycine- and taurine-conjugates that are formed in vivo, [3] examine the efficacy of UDCA for PDT enhancement in a variety of tumor cell lines, [4] measure PDT-promotion by UDCA and selected analogs in animal tumor models. Our hypothesis is that UDCA partitions into mitochondrial membranes and both lowers the threshold of photodamage, while offering protection from the chaotropic effects of more hydrophobic bile acids. Aim [4] will be carried out in a sub-contract with the PDT facility at University of Louisville where there is the required expertise in animal PDT studies. If the results of preliminary studies are borne out by further investigation, UDCA could offer a safe and effective means for promoting clinical PDT efficacy.