Bordji K, Grillasca J P, Gouze J N, Magdalou J, Schohn H, Keller J M, Bianchi A, Dauça M, Netter P, Terlain B
Laboratoire de Pharmacologie, Unite Mixte de Recherche 7561 CNRS-Université Henri Poincaré Nancy I, Faculté de Médecine, 54505 Vandouvre-lès-Nancy, France.
J Biol Chem. 2000 Apr 21;275(16):12243-50. doi: 10.1074/jbc.275.16.12243.
Peroxisome proliferator-activated receptor (PPAR) alpha, PPARgamma, and retinoid acid receptor-related orphan receptor (ROR) alpha are members of the nuclear receptor superfamily of ligand-activated transcription factors. Although they play a key role in adipocyte differentiation, lipid metabolism, or glucose homeostasis regulation, recent studies suggested that they might be involved in the inflammation control and especially in the modulation of the cytokine production. This strongly suggests that these transcriptional factors could modulate the deleterious effects of interleukin-1 (IL-1) on cartilage. However, to date, their presence in cartilage has never been investigated. By quantitative reverse transcription-polymerase chain reaction, Western blot, and immunocytochemistry analysis, we demonstrated, for the first time, the presence of PPARalpha, PPARgamma, and RORalpha in rat cartilage, at both mRNA and protein levels. Comparatively, the PPARalpha mRNA content in cartilage was much lower than in the liver but not significantly different to that of the adipose tissue. PPARgamma mRNA expression in cartilage was weak, when compared with adipose tissue, but similar to that found in the liver. RORalpha mRNA levels were similar in the three tissues. mRNA expression of the three nuclear receptors was very differently modulated by IL-1 or mono-iodoacetate treatments. This indicates that they should be unequally involved in the effects of IL-1 on chondrocyte, which is in accordance with results obtained in other cell types. Indeed, we showed that 15d-PGJ2 mainly, but also the drug troglitazone, that are ligands of PPARgamma could significantly counteract the decrease in proteoglycan synthesis and NO production induced by IL-1. By contrast, PPARalpha ligands such as Wy-14,643 or clofibrate had no effect on this process. Therefore, the presence of PPARgamma in chondrocytes opens up new perspectives to modulate the effects of cytokines on cartilage by the use of specific ligands. The function of the two other transcription factors, PPARalpha and RORalpha identified in chondrocytes remains to be explored.
过氧化物酶体增殖物激活受体（PPAR）α、PPARγ和视黄酸受体相关孤儿受体（ROR）α是配体激活转录因子核受体超家族的成员。尽管它们在脂肪细胞分化、脂质代谢或葡萄糖稳态调节中起关键作用，但最近的研究表明它们可能参与炎症控制，尤其是细胞因子产生的调节。这强烈表明这些转录因子可以调节白细胞介素-1（IL-1）对软骨的有害作用。然而，迄今为止，从未研究过它们在软骨中的存在情况。通过定量逆转录-聚合酶链反应、蛋白质印迹和免疫细胞化学分析，我们首次在大鼠软骨中证明了PPARα、PPARγ和RORα在mRNA和蛋白质水平上的存在。相比之下，软骨中的PPARα mRNA含量远低于肝脏，但与脂肪组织中的含量无显著差异。与脂肪组织相比，软骨中PPARγ mRNA的表达较弱，但与肝脏中的相似。RORα mRNA水平在这三种组织中相似。三种核受体的mRNA表达受到IL-1或单碘乙酸处理的不同调节。这表明它们在IL-1对软骨细胞的作用中所起的作用不同，这与在其他细胞类型中获得的结果一致。事实上，我们表明15d-前列腺素J2（15d-PGJ2）主要以及药物曲格列酮（它们都是PPARγ的配体）可以显著抵消IL-1诱导的蛋白聚糖合成减少和一氧化氮（NO）产生。相比之下，PPARα配体如Wy-14,643或氯贝丁酯对这一过程没有影响。因此，软骨细胞中PPARγ的存在为通过使用特定配体调节细胞因子对软骨的作用开辟了新的前景。在软骨细胞中鉴定出的另外两种转录因子PPARα和RORα的功能仍有待探索。
