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

工作摘要：当光与皮肤和眼睛中的内源性或外源性化学剂相互作用时，可以产生光敏化。这个过程可能会产生不良的临床后果，例如光毒性（夸张的晒伤），光含量，光钙化性和/或光毒素；否则它可以像肿瘤光动力疗法（PDT）和煤焦油，Anthralin或coralen（PUVA）疗法一样具有有益的作用。该研究项目的目的是阐明光化机制，从而使光敏剂发挥其有毒或治疗作用。氟喹诺酮（FLQ）是一种相对较新的抗菌物，可用于治疗革兰氏阴性细菌感染。当人类使用时，flq通常会引起光毒性。其他人的最新研究表明，洛梅沙星（Lome）和氟沙星（Fleroxin）（Fler）在注射这些药物的HR/J小鼠中引起鳞状细胞癌，并被UV-A（315-400）NM辐照。我们已经研究了FLQ的光化学特性，以确定为什么这些药物通常是光毒性的，以及为什么Lome和Fler具有光致毒素。 FQ抗菌素的单线氧和超氧化物的产量与其光毒性潜力无关。然而，与单荧光的类似物相比，PBR322 DNA的光裂解对洛姆和Fler的效率至少高10倍。 Lome和Fler还引起了通过彗星测定法测量的HACAT细胞（人类角质形成细胞的不朽系）中广泛的DNA损伤。然而，钙氟沙星和海湾Y3118，两个高度光毒性的FLQ在同一测定中更为活跃。 FLQS的照片 - 源源不断可能是由于8-HALO原子作为卤化物的光灭绝而产生了高反应性的卡宾。 Goldeneal是一种广泛用于众多医疗应用的草药，包括眼睛和皮肤乳液，目前正在国家毒理学计划进行测试。我们已经确定，黄木是金素的主要生物碱，对Hacat角质形成细胞细胞是光毒性的。 10分钟后，与1microl摩尔碱溶液孵育的角质形成细胞的UVA辐照后，细胞活力降低了50％。 Berberine/UVA还会损坏彗星测定法测量的角质形成细胞DNA。小ber碱不会在水溶液中对单线氧的光敏性氧气，但是单线氧的二氯甲烷为0.34产生。这表明光敏化需要一个疏水环境。我们已经检测到以苯苯贝氨酸在苯中获得的以氧气为中心的自由基。在水/酒精的低温玻璃杯中观察到甲醇自由基在Berberine的长波长吸收带中辐照。在这样的酒精玻璃中，我们还检测到77K的Berberine Triplet的EPR信号，与既无法检测到三胞胎”或“自由基”的水玻璃相反。我们的数据表明，尽管水中的单线氧光敏剂较弱，但berberine能够在疏水环境中产生激进物种。因此，杀死角质形成细胞可以涉及在疏水细胞室（DNA，膜）中运行的光动力机制，这些机制通过berberine产生的反应性氧物种在原位氧化。 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 -光敏性，光毒性，光含量，光碳纤维毒素学