Cytotoxicity caused by near-ultraviolet-irradiated soluble vitamins

近紫外线（UVA）作为皮肤老化和癌症的可能原因而受到广泛关注。研究的重点是内源性物质核黄素和吡哆醇的光诱导细胞毒性的作用，这些物质在UVA范围内具有吸收光谱。这些可溶性维生素在UVA照射后具有细胞毒性，且这种毒性持续时间较长。因此，细胞毒性的原因被认为是来自维生素和/或过氧化氢的稳定的光产物。用辣根过氧化物酶（HRP）研究了可溶性维生素照射后过氧化氢的产生。它的吸收峰在400 nm处移动到417 nm后，它的结合过氧化氢。辐照吡哆醇产生少量的过氧化氢，但无细胞毒性。因此，吡哆醇光敏化的原因被认为是稳定的光产物。另一方面，在UVA照射的核黄素溶液中产生高浓度的过氧化氢。光诱导的核黄素细胞毒性消除过氧化氢酶处理的照射溶液。在厌氧条件下，研究了辐照可溶性维生素的细胞毒性。在吡哆醇的情况下，其细胞毒性降低，因为它的光降解减慢。在核黄素的情况下，其细胞毒性急剧增加。这种增加被认为是由于短寿命的活性氧物种。

Near-ultraviolet light (UVA) has received much attention as a possible cause of skin aging and carcinoma. The study focused on the role of photoinduced cytotoxicity of endogenous substances, riboflavin and pyridoxine, which have absorption spectra in the UVA range. These soluble vitamins were found to become cytotoxic after UVA.The cytotoxicity lasted for a long time after irradiation. Thus, the cause of the cytotoxicity was thought to be stable photoproducts derived from the vitamins and/or hydrogen peroxide.The production of hydrogen peroxide after the irradiation of soluble vitamins was studied by the use of horseradish peroxidase (HRP). Its absorption peak at 400 nm shifts to 417 nm after its binding to hydrogen peroxide. Irradiated pyridoxine produced a little amount of hydrogen peroxide which, however, was not cytotoxic. Thus, the cause of pyridoxine photosensitization was thought to be stable photoproducts. On the other hand, a high concentration of hydrogen peroxide was produced in UVA-irradiated riboflavin solution. Photoinduced riboflavin cytotoxicity was eliminated by catalase treatment of the irradiated solution. This shows that the cytotoxicity was mostly caused by hydrogen peroxide.The cytotoxicity of irradiated soluble vitamins was studied under anaerobic conditions. In the case of pyridoxine, its cytotoxicity decreased because of slow down of its photo-degradation. In the case of riboflavin, its cytotoxicity increased dramatically. The increase was thought to be due to short-lived active oxygen species.