EFFECT OF PPAR-ALPHA ACTIVATORS ON KERATINOCYTE DIFFERENTIATIION

表皮的主要功能是在外部环境和生物体之间提供屏障。为了实现该功能，角质形成细胞经历复杂的分化途径，其在角质化和角质层（SC）中细胞外脂质富集膜的形成中达到高潮。这一过程的调控还不清楚，但亲脂性化合物，如类维生素A和维生素D，与核激素受体相互作用发挥重要作用。我们最近发现，核激素受体家族的一个成员PPARalpha的激活调节角质形成细胞的分化。我们已经表明1）PPARalpha配体加速胎鼠SC中细胞外脂质富集膜的发育，2）PPARalpha配体增加胎儿表皮中对SC的形成和功能必不可少的两种脂质代谢酶的活性，β-葡糖脑苷脂酶和类固醇硫酸酯酶，3）PPARalpha配体增加了胎儿表皮中聚丝蛋白和兜甲蛋白的mRNA和蛋白表达，以及4）PPARalpha配体增加培养的人角质形成细胞中外皮蛋白和转氨酶1的mRNA和蛋白水平。这些结果表明，用PPARalpha配体处理影响终末分化的几个关键组分。假设：PPARalpha配体刺激角质形成细胞/表皮分化。目标1：在培养的人角质形成细胞中确定PPARalpha配体是否诱导对角质形成细胞分化重要的结构蛋白的表达，并确定这种增加的机制。目标3：使用PPARalpha敲除小鼠确定PPARalpha在调节培养的小鼠角质形成细胞和完整表皮中的结构蛋白和脂质酶的表达中的重要性。

The major function of the epidermis is to provide a barrier between the external environment and the organism To fulfill this function keratinocytes undergo a complex pathway of differentiation which culminates in cornification and the formation of extracellular lipid enriched membranes in the stratum corneum (SC). The regulation of this process is not well understood but lipophilic compounds, such as retinoids and vitamin D, which interact with nuclear hormone receptors play an important role. We have recently shown that activation of PPARalpha, a member of the nuclear hormone receptor family, regulates keratinocyte differentiation. We have shown 1) that PPARalpha ligands accelerates the development of the extracellular lipid enriched membranes in the SC of fetal rats, 2) that PPARalpha ligands increase the activity in fetal epidermis of two lipid metabolic enzymes essential for formation and function of the SC. beta- glucocerebrosidase, and steroid sulfatase, 3) that PPARalpha ligands increase filaggrin and loricrin mRNA and protein expression in fetal epidermis and 4) that PPARalpha ligands increase mRNA and protein levels of involucrin and transglutaminase 1 in human keratinocytes in culture. These results demonstrate that treatment with PPARalpha ligands affects several key components of terminal differentiation. Hypothesis: That PPARalpha ligands stimulate keratinocyte/epidermal differentiation. Aim 1: To determine in human keratinocytes in culture if PPARalpha ligands induce the expression of structural proteins important for keratinocyte differentiation and determine the mechanisms for this increase. Aim 3: Using PPARalpha Knockout mice determine the importance of PPARalpha in regulating the expression of structural proteins and lipid enzymes in culture mouse keratinocytes and in intact epidermis.