Holleran W M, Takagi Y, Menon G K, Jackson S M, Lee J M, Feingold K R, Elias P M
Department of Dermatology, University of California School of Medicine, San Francisco.
J Lipid Res. 1994 May;35(5):905-12.
The intercellular spaces of the outermost layers of the epidermis (stratum corneum, SC) of terrestrial mammals contain a mixture of lipids, enriched in ceramides that are critical for the epidermal permeability barrier. Whereas glucosylceramides (GlcCer) are synthesized in abundance in the epidermis, they disappear coincident with an increase of ceramides (Cer) in the SC. Hence, hydrolysis of GlcCer to Cer by beta-glucocerebrosidase (GlcCer'ase), may be required for permeability barrier homeostasis. We determined first whether modulations in epidermal GlcCer'ase activity and mRNA levels occur in response to barrier disruption; and second, how GlcCer'ase inhibitors influence barrier function and SC membrane ultrastructure. Barrier disruption significantly increased epidermal GlcCer'ase mRNA levels, with a 2.8-fold increase over untreated control levels at 8 h (P < 0.01). GlcCer'ase activity was increased in whole epidermis (34%; P < 0.02) 24 h after barrier disruption. Localization of GlcCer'ase activity showed an increase (33%; P < 0.05) in the outer epidermis (SC and stratum granulosum), without a change in lower epidermal activity (stratum spinosum and stratum basale). Furthermore, a single topical application of the GlcCer'ase inhibitor, bromoconduritol-B-epoxide (BrCBE), inhibited enzyme activity (98%) and significantly delayed permeability barrier recovery after acetone treatment. In addition, BrCBE treatment disrupted SC intercellular lamellar bilayers, without evidence of cellular toxicity. These results indicate that epidermal processing of GlcCer to Cer by GlcCer'ase is required for barrier homeostasis, and that this important enzymatic step is regulated by barrier requirements.
陆生哺乳动物表皮最外层（角质层，SC）的细胞间隙含有多种脂质，其中富含神经酰胺，这些神经酰胺对表皮渗透屏障至关重要。虽然葡萄糖神经酰胺（GlcCer）在表皮中大量合成，但它们会随着SC中神经酰胺（Cer）的增加而消失。因此，β-葡萄糖脑苷脂酶（GlcCer'ase）将GlcCer水解为Cer可能是维持渗透屏障稳态所必需的。我们首先确定表皮GlcCer'ase活性和mRNA水平的调节是否会因屏障破坏而发生；其次，GlcCer'ase抑制剂如何影响屏障功能和SC膜超微结构。屏障破坏显著增加了表皮GlcCer'ase的mRNA水平，在8小时时比未处理的对照水平增加了2.8倍（P < 0.01）。屏障破坏24小时后，全表皮的GlcCer'ase活性增加（34%；P < 0.02）。GlcCer'ase活性的定位显示，外表皮（SC和颗粒层）增加（33%；P < 0.05），而表皮下层活性（棘层和基底层）没有变化。此外，单次局部应用GlcCer'ase抑制剂溴代康杜立醇-B-环氧化物（BrCBE）可抑制酶活性（98%），并显著延迟丙酮处理后渗透屏障的恢复。此外，BrCBE处理破坏了SC细胞间的片层双分子层，且没有细胞毒性的证据。这些结果表明，GlcCer'ase将GlcCer加工为Cer的表皮过程是维持屏障稳态所必需的，并且这一重要的酶促步骤受屏障需求的调节。
