Stoebner P E, Carayon P, Penarier G, Fréchin N, Barnéon G, Casellas P, Cano J P, Meynadier J, Meunier L
Department of Dermatology-Allergology-Photobiology, Hôpital St-Eloi, 2 Avenue Bertin Sans, 34295 Montpellier, Cedex 05, France.
Br J Dermatol. 1999 Jun;140(6):1010-6. doi: 10.1046/j.1365-2133.1999.02896.x.
The peripheral benzodiazepine receptor (PBR) is a protein of mitochondrial outer membranes utilizing porphyrins as endogenous ligands. PBR is part of a heteromeric receptor complex involved in the formation of mitochondrial permeability transition pores and in the early events of apoptosis. PBR may function as an oxygen-dependent signal generator; recent data indicate that these receptors may preserve the mitochondria of haematopoietic cell lines from damage caused by oxygen radicals. To identify PBRs in human skin, we used a specific monoclonal antibody directed against the C-terminus fragment of the human receptor. PBR immunoreactivity was found in keratinocytes, Langerhans cells, hair follicles and dermal vascular endothelial cells. Interestingly, confocal microscopic examination of skin sections revealed that PBR expression was strongly upregulated in the superficial differentiated layers of the epidermis. Ultrastructurally, PBRs were distributed throughout the cytoplasm but were selectively expressed on the mitochondrial membranes of epidermal cells. The elevated level of PBRs in the spinous layer was not associated with an increased number of mitochondria nor with an increased amount of mRNA as assessed by in situ hybridization on microautoradiographed skin sections. The present work provides, for the first time, evidence of PBR immunoreactivity in human skin. This mitochondrial receptor may modulate apoptosis in the epidermis; its increased expression in differentiated epidermal layers may represent a novel mechanism of natural skin protection against free radical damage generated by ultraviolet exposure.
外周苯二氮䓬受体（PBR）是线粒体外膜上的一种蛋白质，它利用卟啉作为内源性配体。PBR是异源受体复合物的一部分，参与线粒体通透性转换孔的形成以及细胞凋亡的早期事件。PBR可能作为一种氧依赖性信号发生器；最近的数据表明，这些受体可能保护造血细胞系的线粒体免受氧自由基造成的损伤。为了鉴定人皮肤中的PBR，我们使用了一种针对人受体C末端片段的特异性单克隆抗体。在角质形成细胞、朗格汉斯细胞、毛囊和真皮血管内皮细胞中发现了PBR免疫反应性。有趣的是，皮肤切片的共聚焦显微镜检查显示，PBR表达在表皮的浅层分化层中强烈上调。在超微结构上，PBR分布于整个细胞质中，但选择性地表达于表皮细胞的线粒体膜上。通过对微放射自显影皮肤切片进行原位杂交评估，棘层中PBR水平的升高与线粒体数量的增加或mRNA量的增加均无关。本研究首次提供了人皮肤中PBR免疫反应性的证据。这种线粒体受体可能调节表皮中的细胞凋亡；其在分化的表皮层中表达增加可能代表了皮肤天然保护机制的一种新机制，以抵抗紫外线照射产生的自由基损伤。
