He D, Sassa S, Lim H W
Dermatology Service, Department of Veterans Affairs Medical Center, New York, NY 10010.
Photochem Photobiol. 1993 May;57(5):825-9. doi: 10.1111/j.1751-1097.1993.tb09218.x.
To study porphyrin biosynthesis in normal human keratinocytes and A431 cells derived from human epidermoid carcinoma, cultured cells were incubated with delta-aminolevulinic acid (ALA), the precursor of porphyrin synthesis, and accumulation of porphyrins was measured spectrofluorometrically. Both human keratinocytes and A431 cells accumulated porphyrins in a time-dependent and a dose-dependent fashion. Protoporphyrin was the predominant porphyrin accumulated by both cell types. Porphyrin accumulation was enhanced by Ca Mg ethylenediaminetetraacetic acid, a ferrochelatase inhibitor, and the enhancement was reversed by the addition of iron, suggesting the utilization of iron by ferrochelatase. The effect of light on porphyrin accumulation was evaluated by exposing the ALA-loaded A431 cells to ultraviolet-A (UVA) and blue light radiation, followed by continued incubation with ALA for 2-48 h. There was an enhancement of porphyrin accumulation 2-48 h after the radiation as compared with nonirradiated controls. Consistent with this finding, ferrochelatase activity decreased in these cells at 24 h and 48 h. These data demonstrate that human keratinocytes and A431 cells are capable of porphyrin biosynthesis, and that exposure of porphyrin-containing A431 cells to light, which includes the Soret band spectrum, decreases the ferrochelatase activity, which is responsible, at least in part, for the further increase in porphyrin level.
为了研究正常人角质形成细胞和源自人表皮样癌的A431细胞中的卟啉生物合成，将培养的细胞与卟啉合成前体δ-氨基乙酰丙酸（ALA）一起孵育，并用荧光分光光度法测量卟啉的积累。人角质形成细胞和A431细胞均以时间依赖性和剂量依赖性方式积累卟啉。原卟啉是这两种细胞类型积累的主要卟啉。亚铁螯合酶抑制剂Ca Mg乙二胺四乙酸可增强卟啉的积累，而添加铁可逆转这种增强作用，这表明亚铁螯合酶利用了铁。通过将加载ALA的A431细胞暴露于紫外线A（UVA）和蓝光辐射，然后继续与ALA孵育2至48小时，评估光对卟啉积累的影响。与未照射的对照相比，辐射后2至48小时卟啉积累增强。与此发现一致，这些细胞中的亚铁螯合酶活性在24小时和48小时时降低。这些数据表明，人角质形成细胞和A431细胞能够进行卟啉生物合成，并且将含卟啉的A431细胞暴露于包括索雷特带光谱在内的光下会降低亚铁螯合酶活性，这至少部分导致了卟啉水平的进一步升高。
