Regulation/Role of AcylCer in Normal Epidermis and Atopic Dermatitis

描述（由申请人提供）： 皮肤最外层的富脂细胞外板层膜，即，角质层（SC）有助于哺乳动物在干燥环境中生存所需表皮渗透屏障功能。一个家庭的10个神经酰胺（Cer）占主导地位，在这些膜，占约H50%的SC脂质，因此H5%的SC的总重量。不仅他们的数量，但也需要他们的分子异质性形成层状膜结构。特别地，含有酯化到酰胺连接的极长链脂肪酸（>C28）的ω-羟基末端的酰基的ω-O-酰基Cer（或酰基Cer）不仅是表皮所特有的，而且对于正常的渗透性屏障稳态也是关键的。重要的是，在特应性皮炎（AD）中发生acylCer的选择性缺乏，这可能进一步加重SC结构的固有缺陷。我们发现，抑制w-羟基化减少acylCer的生产，引起屏障异常，和小鼠缺乏正常的FA延长酶，延长非常长的链FA（或CVL）4，显示一个致命的出生后屏障缺陷，既不acylCer也不共价连接到corneocyte包膜蛋白（角质细胞脂质包膜，CLE）在这些小鼠中形成。这些酰基Cer是细胞外板层膜组织和角质细胞脂质包膜形成所必需的。我们最近发现，酰基辅酶A蜡醇酰基转移酶（AWAT）1和CGI-58（三酰甘油脂肪酶的辅因子）是进一步需要的ω-O-酯化，导致acylCer生产。然而，AD中酰基Cer缺乏的基础以及酰基Cer缺乏对AD发病机制的贡献都尚不清楚。我们推测，无论是减少合成或加速水解的酰基Cer发生在AD。这种生化异常可归因于增加的T辅助细胞2（Th 2）丝氨酸诱导的下调和/或异常的干旱胁迫介导的acylCer产生信号传导分别通过外部湿度和渗透传感器TRPV 4和TonEBP。总之，这些信号传导缺陷导致AD中酰基Cer缺乏。我们将研究1）酶（关键酶/辅因子，即，本发明的目的在于：1）AD中酰基Cer缺乏的基础以及酰基Cer缺乏的结构/功能后果; 2）Th 2细胞因子如何下调AD中的酰基Cer; 3）干旱应激如何通过TRPV 4受体和/或TonEBP信号传导调节酰基Cer合成及其在AD中的改变;以及4）AD中酰基Cer恢复的新治疗策略。 公共卫生相关性： 项目叙述：越来越多的人认为原发性屏障缺陷是特应性皮炎（AD）的基础，AD表现出选择性酰基神经酰胺（acylCer）缺乏，导致AD患者的免疫功能增加。 经皮暴露于诱发AD并刺激AD进展为哮喘和过敏性鼻炎的过敏原。从拟议的研究中获得的见解将确定新形式的治疗AD，一种常见的疾病，在退伍军人，基于正常化的acylCer水平使用适当的代谢前体或刺激内源性acylCer生产。

DESCRIPTION (provided by applicant): PROJECT SUMMARY/ABSTRACT Lipid-enriched extracellular lamellar membranes in the outermost layer of skin, i.e., stratum corneum (SC), subserve epidermal permeability barrier function, as required for mammalian survival in a dry environment. A family of 10 ceramides (Cer) dominates in these membranes, accounting for about H50% of SC lipid, and therefore H5% of the total weight of SC. Not only their quantities, but also their molecular heterogeneity is required to form lamellar membrane structures. In particular, w-O-acylCer (or acylCer), that contains an acyl group esterified to the w-hydroxy terminal of amide-linked very long-chain fatty acids (>C28), is not only unique to the epidermis, but also critical for normal permeability barrier homeostasis. Importantly, a selective deficiency in acylCer occurs in atopic dermatitis (AD), which could further aggravate inherent defects in SC structures. We showed that inhibition of w-hydroxylation decreases acylCer production, provoking barrier abnormalities, and that mice lacking the normal FA elongase, elongation of very long chain FA (or ELOVL) 4, display a lethal post-natal barrier defect; neither acylCer nor the w-OH Cer covalently-attached to cornified envelope proteins (corneocyte lipid envelope, CLE) are formed in these mice. These acylCer are essential for both extracellular lamellar membrane organization, and for corneocyte lipid envelope formation. We recently showed that both acyl-CoA wax alcohol acyltransferases (AWAT) 1 and CGI-58 (a cofactor of triacylglycerol lipase) are further required for w-O-esterification, leading to acylCer production. Yet, neither the basis for acylCer deficiency in AD, nor the contribution of acylCer deficiency to the pathogenesis of AD is known. We hypothesize that either decreased synthesis or accelerated hydrolysis of acylCer occurs in AD. This biochemical abnormality can be attributed to increased T helper cell 2 (Th2) cytokine-induced downregulation and/or aberrant xeric stress-mediated-signaling of acylCer production via the external humidity and osmotic sensors, TRPV4 and TonEBP, respectively. Together, these signaling defects account for deficiency of acylCer in AD. We will investigate 1) the enzymatic (key enzymes/cofactor, i.e., ELOVL4, w-hydroxylase, AWAT1, and CGI-58) basis for acylCer deficiency as well as the structural/functional consequences of acylCer deficiency in AD; 2) how Th2 cytokines downregulate acylCer in AD; 3) how xeric stress regulates acylCer synthesis via the TRPV4 receptor and/or TonEBP signaling and their alterations in AD; and 4) novel therapeutic strategies for acylCer restoration in AD. PUBLIC HEALTH RELEVANCE: PROJECT NARRATIVE: It is increasingly accepted that a primary barrier defect underlies atopic dermatitis (AD), which displays selective acylceramide (acylCer) deficiency, resulting in increased transcutaneous exposure to allergens which induce AD, and stimulate progression of AD to asthma and allergic rhinitis. The insights gained from the proposed studies will identify novel forms of therapy for AD, a common disease in veterans, based upon normalizing acylCer levels using appropriate metabolic precursors or stimulation of endogenous acylCer production.