Westergaard M, Henningsen J, Svendsen M L, Johansen C, Jensen U B, Schrøder H D, Kratchmarova I, Berge R K, Iversen L, Bolund L, Kragballe K, Kristiansen K
Department of Biochemistry and Molecular Biology, University of Southern Denmark, Denmark.
J Invest Dermatol. 2001 May;116(5):702-12. doi: 10.1046/j.1523-1747.2001.01329.x.
Peroxisome proliferator-activated receptors (PPARs) are pleiotropic regulators of growth and differentiation of many cell types. We have performed a comprehensive analysis of the expression of PPARs, transcriptional cofactors, and marker genes during differentiation of normal human keratinocytes using a combination of reverse transcriptase polymerase chain reaction, Northern and Western blotting, and immunohistochemistry. PPARdelta was the predominant PPAR subtype in human keratinocytes and highly expressed in basal cells and suprabasal cells. Induction of PPARalpha and PPARgamma expression was linked to differentiation, and accordingly, expression of PPARalpha and PPARgamma was in essence confined to suprabasal cells. Differentiation was not accompanied by significant changes in the expression of the coactivators CREB-binding protein, p300, steroid receptor coactivator 1, or the corepressors nuclear receptor corepressor and silence mediator for retinoid and thyroid hormone receptors. We critically evaluated the effects of selective PPAR ligands and a synthetic fatty acid analog, tetradecylthioacetic acid. Tetradecylthioacetic acid activated all human PPAR subtypes in the ranking order PPARdelta >> PPARalpha > PPARgamma. All selective PPAR ligands marginally induced transglutaminase-1 expression with the PPARdelta-selective ligand L165041 being the most potent. The PPARalpha- and PPARgamma-selective ligands Wy14643 and BRL49653 had negligible effect on involucrin expression, whereas a dose-dependent induction was observed with L165041. Simultaneous addition of L165041 and BRL49653 synergistically induced strong involucrin expression. Additionally, L165041 potently induced CD36 mRNA expression. Administration of tetradecylthioacetic acid resulted in a dramatic decrease in proliferation and a robust upregulation of the expression of involucrin and transglutaminase. Our results indicate that tetradecylthioacetic acid may affect keratinocyte gene expression and differentiation via PPAR-dependent and PPAR-independent pathways, and that the latter play an important role.
过氧化物酶体增殖物激活受体（PPARs）是多种细胞类型生长和分化的多效性调节因子。我们结合逆转录聚合酶链反应、Northern印迹和Western印迹以及免疫组织化学方法，对正常人角质形成细胞分化过程中PPARs、转录辅因子和标记基因的表达进行了全面分析。PPARδ是人类角质形成细胞中主要的PPAR亚型，在基底细胞和基底上层细胞中高表达。PPARα和PPARγ表达的诱导与分化相关，因此，PPARα和PPARγ的表达基本上局限于基底上层细胞。分化过程中，共激活因子CREB结合蛋白、p300、类固醇受体共激活因子1或共抑制因子核受体共抑制因子以及视黄酸和甲状腺激素受体沉默介质的表达没有显著变化。我们严格评估了选择性PPAR配体和合成脂肪酸类似物十四烷基硫代乙酸的作用。十四烷基硫代乙酸以PPARδ>>PPARα>PPARγ的顺序激活所有人类PPAR亚型。所有选择性PPAR配体均轻微诱导转谷氨酰胺酶-1表达，其中PPARδ选择性配体L165041最为有效。PPARα和PPARγ选择性配体Wy14643和BRL49653对兜甲蛋白表达的影响可忽略不计，而L165041则观察到剂量依赖性诱导。同时添加L165041和BRL49653可协同强烈诱导兜甲蛋白表达。此外，L165041强烈诱导CD36 mRNA表达。给予十四烷基硫代乙酸导致增殖显著降低，同时兜甲蛋白和转谷氨酰胺酶表达强烈上调。我们的结果表明，十四烷基硫代乙酸可能通过PPAR依赖性和PPAR非依赖性途径影响角质形成细胞基因表达和分化，且后者起重要作用。
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