Heise Ruth, Mey Jörg, Neis Mark M, Marquardt Yvonne, Joussen Sylvia, Ott Hagen, Wiederholt Tonio, Kurschat Peter, Megahed Mosaad, Bickers David R, Merk Hans F, Baron Jens M
Department of Dermatology and Allergology, University Hospital of the RWTH Aachen, Aachen, Germany.
J Invest Dermatol. 2006 Nov;126(11):2473-80. doi: 10.1038/sj.jid.5700432. Epub 2006 Jun 15.
Cellular levels of all-trans retinoic acid (RA) are meticulously regulated utilizing an array of systems to balance uptake, biosynthesis, catabolism, and efflux transport. Metabolic transformation of all-trans RA to 4-hydroxylated RA appears to be primarily catalyzed by the cytochrome P450 (CYP) 26AI. Analysis of monolayer cultures of normal human epidermal keratinocytes (NHEKs) and dermal fibroblasts by quantitative real-time PCR and reverse transcription-PCR revealed no basal levels of CYP26AI mRNA expression, whereas specific transcripts were detectable following addition of 10(-6) M all-trans RA. Immunofluorescence and Western blot analysis showed a weak expression of CYP26AI in NHEK, which was increased by stimulation with all-trans RA. Using a newly developed peptide antibody, we further examined the localization of CYP26AI expression in normal skin and three-dimensional (3D) skin models. In contrast to cell culture monolayers where CYP26AI was only weakly detectable, strong constitutive expression of CYP26AI in vivo and in organotypic culture was found to be restricted to basal epidermal keratinocytes, as well as eccrine sweat glands and sebaceous glands. These studies verify the capacity of human skin to metabolize RA, although substantial differences exist in CYP expression between normal skin and 3D skin models compared to monolayer cultures. Complex metabolic processes that maintain retinoid homeostasis may therefore be better studied in model systems more closely resembling in vivo skin. In light of our prior studies documenting the functional activity of RA metabolites, expression of CYP26 in the sebaceous gland epithelium supports the suggestion that altered RA metabolism may be involved in the pathogenesis of acne.
全反式维甲酸（RA）的细胞水平通过一系列系统进行精确调控，以平衡摄取、生物合成、分解代谢和外流转运。全反式RA向4-羟基化RA的代谢转化似乎主要由细胞色素P450（CYP）26AI催化。通过定量实时PCR和逆转录PCR分析正常人表皮角质形成细胞（NHEK）和真皮成纤维细胞的单层培养物，发现CYP26AI mRNA表达无基础水平，而添加10^(-6) M全反式RA后可检测到特定转录本。免疫荧光和蛋白质印迹分析显示NHEK中CYP26AI表达较弱，全反式RA刺激后表达增加。使用新开发的肽抗体，我们进一步研究了CYP26AI在正常皮肤和三维（3D）皮肤模型中的表达定位。与仅能微弱检测到CYP26AI的细胞培养单层不同，发现CYP26AI在体内和器官型培养中的强组成性表达仅限于基底表皮角质形成细胞以及外分泌汗腺和皮脂腺。这些研究证实了人类皮肤代谢RA的能力，尽管与单层培养相比，正常皮肤和3D皮肤模型之间的CYP表达存在显著差异。因此，在更类似于体内皮肤的模型系统中，可能能更好地研究维持类视黄醇稳态的复杂代谢过程。鉴于我们之前记录RA代谢物功能活性的研究，皮脂腺上皮中CYP26的表达支持了RA代谢改变可能参与痤疮发病机制的观点。
