Hussain H, Shornick L P, Shannon V R, Wilson J D, Funk C D, Pentland A P, Holtzman M J
Department of Medicine, Washington University School of Medicine, St. Louis, Missouri 63110.
Am J Physiol. 1994 Jan;266(1 Pt 1):C243-53. doi: 10.1152/ajpcell.1994.266.1.C243.
Human epidermal cells exhibited none of the cytosolic lipoxygenase activity that is prominent in mucosal epithelial cells, but instead contained a microsomal activity that converted arachidonic acid to 12-hydroxyeicosatetraenoic acid (12-HETE). Identification of the extractable 12-HETE-forming activity as a 12-lipoxygenase (distinct from cytochrome P-450) included (S)-12-stereospecificity of product formation, trapping of 12-hydroperoxyeicosatetraenoic acid as an intermediate reaction product, and lack of NADPH dependence for activity. Epidermal cell poly(A)+ RNA contained high levels of a 2.3-kb mRNA that selectively hybridized with human platelet 12-lipoxygenase cDNA, and partial cDNA sequence of this mRNA indicated identity to platelet 12-lipoxygenase. The epidermal 12-lipoxygenase was not recognized by antibodies against the leukocyte-type 12- and 15-lipoxygenases (found in leukocytes, reticulocytes, and mucosal epithelial cells) but was detected by an antiplatelet 12-lipoxygenase antibody. The epidermal 12-lipoxygenase antigen was selectively expressed in germinal layer keratinocytes in healthy and psoriatic skin, and these layers exhibited hyperplasia and increased immunostaining in inflamed psoriatic skin. Together with previous results, these observations indicate that 1) epidermis generates 12-HETE by either cytochrome P-450 or lipoxygenase-based mechanisms depending on reaction conditions, and 2) 12-lipoxygenases (originally described in hematopoietic cell types) may be expressed in at least two distinct isoforms in epithelial barriers in humans, and in the case of the skin, a microsomal (platelet-type) 12-lipoxygenase is selectively overexpressed in germinal layer keratinocytes during psoriatic inflammation.
人类表皮细胞未表现出在黏膜上皮细胞中显著存在的胞质脂氧合酶活性，而是含有一种微粒体活性，可将花生四烯酸转化为12-羟基二十碳四烯酸（12-HETE）。将可提取的形成12-HETE的活性鉴定为12-脂氧合酶（不同于细胞色素P-450）包括产物形成的（S）-12-立体特异性、将12-氢过氧二十碳四烯酸捕获为中间反应产物以及活性对NADPH的依赖性缺乏。表皮细胞多聚腺苷酸加尾（poly(A)+）RNA含有高水平的2.3-kb mRNA，该mRNA与人血小板12-脂氧合酶cDNA选择性杂交，并且该mRNA的部分cDNA序列表明与血小板12-脂氧合酶相同。表皮12-脂氧合酶不能被针对白细胞型12-和15-脂氧合酶（存在于白细胞、网织红细胞和黏膜上皮细胞中）的抗体识别，但可被抗血小板12-脂氧合酶抗体检测到。表皮12-脂氧合酶抗原在健康皮肤和银屑病皮肤的生发层角质形成细胞中选择性表达，并且在炎症性银屑病皮肤中这些层表现出增生和免疫染色增加。与先前的结果一起，这些观察结果表明：1）表皮根据反应条件通过细胞色素P-450或基于脂氧合酶的机制产生12-HETE；2）12-脂氧合酶（最初在造血细胞类型中描述）可能在人类上皮屏障中以至少两种不同的同工型表达，就皮肤而言，微粒体（血小板型）12-脂氧合酶在银屑病炎症期间在生发层角质形成细胞中选择性过表达。
