IRON, NO, AND LIPID PEROXIDES IN PHOTODYNAMIC THERAPY

光动力疗法(PDT)是一种创新的癌症治疗方法 这是基于选择性地体内或体外根除肿瘤细胞 通过局部光敏剂的作用。续 促进光动力治疗技术和临床应用的进步 通过对生物物理和生化的理解的平行进展 影响其有效性的因素。初步调查结果涉及 铁和一氧化氮(NO)对效应器的作用有重要意义 对这一问题的影响，并为这一提议提供强有力的推动：(一) 亲脂络合物形式的铁促进光动力脂质 当被急性地呈现给白血病细胞时，过氧化和细胞杀伤， 但当长期呈现时会引起很强的光阻，这 伴随着铁蛋白诱导；(Ii)铁刺激的脂质 NO供体显著抑制过氧化和光毒性， 尤其是当没有光动力学增强的释放时。二 提出的假设是：(1)肿瘤的铁状态是一个重要因素 在PDT反应中，急性铁暴露通过以下方式促进细胞毒性 增强脂质过氧化和慢性暴露可逆转这一效应 通过铁蛋白的诱导。(2)肿瘤血管产生的NO 细胞可以促进或抑制PDT的细胞毒性，这取决于 超氧化物的可用性；抑制在很大程度上取决于NO的链- 破坏抗氧化剂效果。重点放在光防护上 铁和一氧化氮的影响，这些假说将在体内进行验证 (横纹肌肉瘤)和体外(白血病、乳腺肿瘤、内皮细胞) 型号，两种PDT感光剂，以及高性能 电化学液相色谱检测，电子自旋 共振自旋捕捉、免疫印迹和带移电泳法。 我们的计划是调查：(I)细胞对 铁供体引起的光过氧化损伤和光致死 如高铁血红素和高铁血红蛋白；(Ii)光抗性的影响 铁对细胞铁水平的刺激及其表达/激活 铁蛋白和其他铁反应蛋白；(Iii) 光生NO对膜脂过氧化和细胞杀伤的影响； (4)细胞产生的NO对光损伤血管细胞的影响。这 这项工作意义重大，因为它涉及新形式的光阻 由铁和NO引发。如果能更好地理解这些反应， 对光动力疗法的疗效和设计有重要影响 合理的涉及PDT的临床方案。

Photodynamic therapy (PDT) is an innovative cancer treatment modality that is based on selective in vivo or ex vivo eradication of tumor cells through the action of localized photosensitizing agents. Continued advances in PDT technology and clinical applications will be facilitated by parallel advances in understanding of the biophysical and biochemical factors which modulate its effectiveness. Preliminary findings pertaining to the effector actions of iron and nitric oxide (NO) have important bearing on this issue and provide a strong impetus for this proposal: (i) Iron in the form of lipophilic chelates promotes photodynamic lipid peroxidation and cell killing when presented acutely to leukemia cells, but elicits a strong photoresistance when presented chronically and this is accompanied by ferritin induction; (ii) Iron-stimulated lipid peroxidation and phototoxicity are markedly suppressed by NO donors, particularly when NO release is photodynamically enhanced. Two hypotheses are advanced: (1) Iron status of tumors is an important factor in PDT responsiveness, acute iron exposure promoting cytotoxicity by amplifying lipid peroxidation and chronic exposure reversing this effect through the induction of ferritin. (2) NO generated by tumor vascular cells can either promote or suppress PDT cytotoxicity, depending on superoxide availability; suppression depends largely on NO's chain- breaking antioxidant effects. With an emphasis on the photoprotective effects of iron and NO, these hypotheses will be tested, using in vivo (rhabdomyosarcoma) and in vitro (leukemia, breast tumor, endothelial) models, two PDT sensitizers, and techniques such as high-performance liquid chromatography with electrochemical detection, electron spin resonance-spin trapping, immunoblotting, and band-shift electrophoresis. The plan is to investigate: (i) cellular susceptibility to photoperoxidative damage and photokilling in response to iron donors such as hemin and methemoglobin; (ii) effects of photoresistance-conferring iron stimuli on cellular iron levels and expression/activation of ferritin and other iron-responsive proteins; (iii) effects of photogenerated NO on membrane lipid peroxidation and cell killing; and (iv) effects of cell-generated NO on photodamage to vascular cells. This work is significant because it deals with novel forms of photoresistance elicited by iron and NO. A better understanding of these responses would have important bearing on the question of PDT efficacy and the design of rational clinical protocols involving PDT.