MECHANISMS OF CHEMICALLY INDUCED PHOTOSENSITIVITY

化学诱导光敏性的机制

• 批准号: 6432342
• 负责人: COLIN CHIGNELL
• 金额: --
• 依托单位: NATIONAL INSTITUTE OF ENVIRONMENTAL HEALTH SCIENCES
• 依托单位国家: 美国
• 资助国家: 美国
• 起止时间: 至
• 项目状态: 未结题
• 来源: https://reporter.nih.gov/project-details/6432342
• 关键词: antibacterial agents; carcinogen testing; hairless mouse; mutagen testing; nonvisual photosensitivity; photosensitizing agents; plasmids; radiation carcinogen; radiation carcinogenesis; singlet oxygen; skin pharmacology; ultraviolet radiation

Summary of Work: Photosensitization can result when light interacts with endogenous or exogenous chemical agents in the skin and eyes. This process can produce undesirable clinical consequences, such as phototoxicity (exaggerated sunburn), photoallergy, photocarcinogenicity and/or photomutagenicity; or it can have beneficial effects as in tumor photodynamic therapy (PDT) and coal tar, anthralin or psoralen (PUVA) therapy for psoriasis. The objective of this research project is to elucidate the photochemical mechanisms whereby photosensitizers exert their toxic or therapeutic effects. Fluoroquinolones (FLQ) are a relatively new class of antibacterials that are useful in the treatment of gram-negative bacterial infections. When used in humans FLQs often cause phototoxicity. Recent studies by others have shown that lomefloxacin (LOME) and fleroxacin (FLER) cause squamous cell carcinomas in HR/J mice injected with these drugs and irradiated with UV-A (315-400) nm. We have studied the photochemical properties of the FLQs to determine why these drugs as a class are often phototoxic and why LOME and FLER are photocarcinogenic. Singlet oxygen and superoxide yields for the FQ antimicrobials do not correlate with their phototoxic potentials. However, photocleavage of pBR322 DNA is at least 10-fold more efficient for LOME and FLER than for monofluorinated analogs. LOME and FLER also caused extensive DNA photo-damage in HaCaT cells (an immortal line of human keratinocytes) as measured by the Comet assay. However, clinafloxacin and BAY y3118, two highly phototoxic FLQs were even more active in the same assay. The photo-mutagenicity of the FLQs is probably due to the generation of a highly reactive carbene as a result of the photo-elimination of the 8-halo atom as halide. Goldenseal is a herb widely used for numerous medical applications including eyewash and skin lotion, which is currently undergoing testing by the National Toxicology Program. We have established that berberine, the main alkaloid in Goldenseal, is phototoxic to HaCaT keratinocyte skin cells. Cell viability decreased by 50% after 10 min UVA irradiation of the keratinocytes incubated with 1micromolar berberine solution. Berberine/UVA also damages keratinocyte DNA as measured by the Comet assay. Berberine does not photosensitize singlet oxygen in aqueous solutions, but singlet oxygen is produced with a quantum yield of 0.34 in dichloromethane. This suggests that a hydrophobic environment is required for photosensitization. We have detected oxygen-centered radicals photogenerated by berberine in benzene. Methanol radicals were observed in water/alcohol low temperature glasses irradiated in the berberine long-wavelength absorption band. In such alcoholic glasses, we have also detected an EPR signal from the berberine triplet at 77K, in contrast to aqueous glasses where neither triplet nor radicals were detectable. Our data show that, although a weak singlet oxygen photosensitizer in water, berberine is able to produce radical species in a hydrophobic environment. Thus the killing of keratinocytes can involve a photodynamic mechanism operating in hydrophobic cell compartments (DNA, membranes) that are oxidized in situ by reactive oxygen species photo- produced by berberine. As a result of a collaboration with scientists in the Plant Pathology Department at North Carolina State University on the mechanism of Cercosopera nicotianae resistance to singlet oxygen generating phototoxins, we have discovered that vitamin B6 quenches singlet oxygen at a rate comparable to vitamins C and E. This finding suggests that vitamin B6 may play a hitherto unknown role in vivo as an antioxidant - photosensitization, phototoxicity, photoallergy, photocarcinogenicity

工作总结：当光与皮肤和眼睛中的内源性或外源性化学试剂相互作用时，可能导致光敏化。该过程可产生不期望的临床后果，例如光毒性（过度晒伤）、光过敏、光致癌性和/或光致突变性;或者其可具有有益效果，如在用于银屑病的肿瘤光动力疗法（PDT）和煤焦油、蒽林或补骨脂素（PUVA）疗法中。本研究项目的目的是阐明光敏剂发挥其毒性或治疗作用的光化学机制。氟喹诺酮类（FLQ）是一种相对较新的抗菌药物，可用于治疗革兰氏阴性菌感染。当用于人类时，FLQ通常会引起光毒性。其他人最近的研究表明，洛美沙星（洛梅）和氟罗沙星（FLER）在注射这些药物并用UV-A（315-400）nm照射的HR/J小鼠中引起鳞状细胞癌。我们已经研究了FLQ的光化学性质，以确定为什么这些药物作为一类通常是光毒性的，为什么洛梅和FLER是光致癌的。FQ抗菌剂的单线态氧和超氧化物产率与其光毒性潜力无关。然而，pBR 322 DNA的光切割对于洛梅和FLER比对于单氟化类似物至少高10倍。洛梅和FLER还在HaCaT细胞（人角质形成细胞的永生系）中引起广泛的DNA光损伤，如通过彗星测定所测量的。然而，克林萘芬和BAY y3118，两种高度光毒性FLQ，在相同的测定中甚至更有活性。FLQs的光致突变性可能是由于8-卤原子作为卤化物光消除而产生高反应性卡宾。毛茛是一种草药，广泛用于许多医疗应用，包括洗眼水和皮肤乳液，目前正在接受国家毒理学计划的测试。我们已经确定，黄连素，主要生物碱在毛茛，是光毒性的HaCaT角质形成细胞皮肤细胞。用1微摩尔小檗碱溶液孵育的角质形成细胞经UVA照射10分钟后，细胞活力下降50%。小檗碱/UVA也损害角质形成细胞DNA，如通过彗星测定所测量的。小檗碱在水溶液中不光敏单线态氧，但在二氯甲烷中产生单线态氧，量子产率为0.34。这表明光敏化需要疏水环境。我们已经检测到的氧为中心的自由基光生小檗碱在苯中。在小檗碱长波长吸收带照射的水/醇低温玻璃中观察到甲醇自由基。在这样的酒精玻璃，我们也检测到了EPR信号从小檗碱三重态在77 K，在水玻璃中，既没有三重态也没有自由基是可检测的。我们的数据表明，尽管小檗碱在水中是一种弱单线态氧光敏剂，但在疏水环境中能够产生自由基物种。因此，角质形成细胞的杀伤可能涉及在疏水细胞区室（DNA，膜）中操作的光动力学机制，所述疏水细胞区室被小檗碱光产生的活性氧物质原位氧化。由于与北卡罗来纳州州立大学植物病理学系的科学家合作研究了烟草尾孢菌对产生光毒素的单线态氧的抗性机制，我们发现维生素B6以与维生素C和E相当的速率淬灭单线态氧。这一发现表明，维生素B6可能在体内起着迄今为止未知的抗氧化剂作用-光敏性、光毒性、光变态反应、光致癌性