Behne M, Uchida Y, Seki T, de Montellano P O, Elias P M, Holleran W M
Department of Dermatology, School of Medicine, University of California, San Francisco, USA.
J Invest Dermatol. 2000 Jan;114(1):185-92. doi: 10.1046/j.1523-1747.2000.00846.x.
Omega-hydroxyceramides (omega-OHCer) are the predominant lipid species of the corneocyte lipid envelope in the epidermis. Moreover, their omega-esterified-derivatives (acylCer) are major components of the stratum corneum extracellular lamellae, which regulate cutaneous permeability barrier function. Because epidermal omega-OHCer appear to be generated by a cytochrome P450-dependent process, we determined the effects of a mechanism-based inhibitor of omega-hydroxylation, aminobenzotriazole (ABT), on epidermal omega-OH Cer formation and barrier function. We first ascertained that ABT, but not hydroxybenzotriazole (OHBT), a chemical relative with no P450 inhibitory activity, inhibited the incorporation of [14C]-acetate into the omega-OH-containing Cer species in cultured human keratinocytes (68.1% +/- 6.9% inhibition versus vehicle-treated controls; p < 0.001), without altering the synthesis of other Cer and fatty acid species. In addition, ABT significantly inhibited the omega-hydroxylation of very long-chain fatty acids in cultured human keratinocytes. Topical application of ABT, but not OHBT, when applied to the skin of hairless mice following acute barrier disruption by tape-stripping, resulted in a significant delay in barrier recovery (e.g., 38.3% delay at 6 h versus vehicle-treated animals), assessed as increased transepidermal water loss. The ABT-induced barrier abnormality was associated with: (i) a significant decrease in the quantities of omega-OHCer in both the unbound and the covalently bound Cer pools; (ii) marked alterations of lamellar body structure and contents; and (iii) abnormal stratum corneum extracellular lamellar membrane structures, with no signs of cellular toxicity. Furthermore, pyridine-extraction of ABT- versus vehicle-treated skin, which removes all of the extracellular lamellae, leaving the covalently attached lipids, showed numerous foci with absent corneocyte lipid envelope in ABT- versus vehicle-treated stratum corneum. These results provide the first direct evidence for the importance of omega-OHCer for epidermal permeability function, and suggest further that acylCer and/or corneocyte lipid envelope are required elements in permeability barrier homeostasis.
ω-羟基神经酰胺（ω-OHCer）是表皮中角质形成细胞脂质包膜的主要脂质种类。此外，它们的ω-酯化衍生物（酰基神经酰胺，acylCer）是角质层细胞外片层的主要成分，可调节皮肤渗透屏障功能。由于表皮ω-OHCer似乎是通过细胞色素P450依赖性过程产生的，我们确定了基于机制的ω-羟基化抑制剂氨基苯并三唑（ABT）对表皮ω-OH神经酰胺形成和屏障功能的影响。我们首先确定，ABT可抑制[14C]-乙酸盐掺入培养的人角质形成细胞中含ω-OH的神经酰胺种类，而无P450抑制活性的化学相关物羟基苯并三唑（OHBT）则无此作用（与载体处理的对照相比，抑制率为68.1%±6.9%；p<0.001），且不改变其他神经酰胺和脂肪酸种类的合成。此外，ABT显著抑制培养的人角质形成细胞中极长链脂肪酸的ω-羟基化。在通过胶带剥离急性破坏屏障后，将ABT而非OHBT局部应用于无毛小鼠皮肤，导致屏障恢复显著延迟（例如，与载体处理的动物相比，6小时时延迟38.3%），通过经表皮水分流失增加来评估。ABT诱导的屏障异常与以下情况相关：（i）未结合和共价结合的神经酰胺池中ω-OHCer的数量显著减少；（ii）板层小体结构和内容物的明显改变；（iii）角质层细胞外片层膜结构异常，无细胞毒性迹象。此外，对ABT处理组和载体处理组皮肤进行吡啶提取，去除所有细胞外片层，留下共价连接的脂质，结果显示ABT处理组角质层中存在大量无角质形成细胞脂质包膜的病灶。这些结果首次直接证明了ω-OHCer对表皮渗透功能的重要性，并进一步表明酰基神经酰胺和/或角质形成细胞脂质包膜是渗透屏障稳态的必需成分。
