Linking Lipoxygenases with Essential Fatty Acids and Epidermal Barrier Formation

描述（由申请人提供）：本申请的长期目标是阐明两种脂氧合酶（LOX）酶及其必需脂肪酸（EFA）底物在形成表皮不透水屏障中的作用，这种缺陷会导致鱼肿并导致特应性皮炎。12r -脂氧合酶（12R-LOX）和表皮脂氧合酶-3 （eLOX3）是仅有的两种人类脂氧合酶，如果突变为失活形式，就会导致一种常染色体隐性遗传性鱼鳞病（ARCI）。事实上，ARCI的典型鳞状皮肤也表现为必需脂肪酸（EFA）缺乏，这表明EFA与两种LOX酶之间可能存在底物-酶关系。我们将测试一个新的假设，将EFA， 12R- LOX和eLOX3与表皮水屏障结构联系起来。我们认为，这两种脂加氧酶可以氧化脂肪酸的一种关键形式，即亚油酸酯，酯化成独特的表皮酰基神经酰胺的长链脂肪酸的ω -羟基。我们进一步提出，这种氧化是促进（氧化的）亚油酸部分水解所必需的，并使长链脂肪酸ω -羟基自由地偶联到角质层的交联蛋白上

DESCRIPTION (provided by applicant): The long-term objective of this application is to elucidate the roles of two lipoxygenase (LOX) enzymes and their essential fatty acid (EFA) substrate in forming the water impermeable barrier of the epidermis, defects in which result in ichthyoses and contribute to atopic dermatitis. 12R-Lipoxygenase (12R-LOX) and Epidermal Lipoxygenase-3 (eLOX3) are the only human lipoxygenases that, if mutated to inactive forms, result in a disease, a form of autosomal recessive congenital ichthyosis (ARCI). The fact that the characteristic scaly skin of ARCI is also manifest in essential fatty acid (EFA) deficiency, suggests a possible substrate-enzyme relationship between EFA and the two LOX enzymes. We will test a new hypothesis that connects EFA, 12R- LOX and eLOX3, and the structure of the epidermal water barrier. We propose that the two lipoxygenases oxygenate a critical form of EFA, linoleate esterified to the omega-hydroxyl of the very long chain fatty acid of the unique epidermal acylceramides. We further propose that this oxygenation is required to facilitate hydrolysis of the (oxidized) linoleate moiety and leave the very long chain fatty acid omega-hydroxyl free for coupling to the cross-linked proteins of the corneocyte envelope, a vital step in sealing the water barrier. The Specific Aims are (1) To characterize 12R-LOX and eLOX3 activity in the epidermis in vivo using animal models, (2) To assess the efficacy of LOX products and ceramides in rescuing the phenotype in murine LOX-/- models, (3) To characterize 12R-LOX and eLOX3 activity in human epidermis including in ARCI patients, and (4) To characterize the putative oxidant-sensitive step of acylceramide ester hydrolysis. The results of this study wil piece together an important facet of construction of the epidermal water barrier and allow a rational approach to the use of oxidized linoleate and its analogs for future therapeutic interventions in the LOX- dependent classes of ichthyoses. If the physiology of the barrier is properly understood, this constitutes a firm foundation for the rational design of any barrier-related therapeutics, and it is to rationalize the role of these well-known key components of the epidermal water barrier that is the main goal of this project.