Ibabe A, Herrero A, Cajaraville M P
Biologia Zelularra eta Histologia Laborategia, Zoologia eta Animali Biologia Zelularra Saila, Zientzia eta Teknologia Fakultatea, Euskal Herriko Unibertsitatea/Universidad del País Vasco, 644 PK, Bilbao E-48080, Basque Country, Spain.
Toxicol In Vitro. 2005 Sep;19(6):725-35. doi: 10.1016/j.tiv.2005.03.019.
Peroxisome proliferation is a phenomenon occurring when responsive animals are exposed to certain compounds so-called peroxisome proliferators and is regulated through a nuclear receptor named peroxisome proliferator-activated receptor (PPAR). PPAR family members exhibit a strong binding affinity for both saturated and unsaturated fatty acids. Activators of PPAR(alpha) include a variety of endogenously present fatty acids, leukotrienes and hydroxyeicosatetraenoic acids (HETEs) and clinically used drugs, such as fibrates. PPAR(beta) activators include fatty acids, prostaglandin A2 (PGA2) and prostacyclin (PGI2). PPAR(gamma) is the most selective receptor and, among others, 15-deoxy-Delta(12,14) prostaglandin J2 (PGJ2) has been described to be a PPAR(gamma)-specific ligand. The aim of the present study was to determine if known PPAR(alpha) and PPAR(gamma) ligands were able to alter the expression of these subtypes in an in vitro model of zebrafish primary hepatocyte culture. With this purpose, a PPAR(alpha) specific ligand (8S-HETE), a PPARgamma specific ligand (PGJ) and a peroxisome proliferator of the fibrate class (clofibrate) were selected. In addition, the female hormone 17beta-estradiol was also used as it is known to interact with PPARs. After cell exposure for 24 h, cells were immunohistochemically stained for both PPARs and immunolabeling was quantified as percentage of positive nuclei and cells. Levels of expression of PPARs were also measured by image analysis as grey level per cell. Expression was induced for both PPAR(alpha) and PPAR(gamma) by clofibrate (at 0.5 mM for PPAR(alpha) and at 1 and 2 mM for PPAR(gamma)), by HETE (1 microM), and by PGJ2 (0.3 and 1 microM for PPAR(alpha) and 0.3 microM for PPAR(gamma)). Expression of PPARgamma was also induced at 10 microM by 17beta-estradiol. The percentage of PPAR(alpha) positive nuclei increased significantly at 1 microM HETE and the percentage of PPAR(gamma) positive cells decreased at 10 microM 17beta-estradiol. As a conclusion, clofibrate, HETE and PGJ2 are able to induce expression of both PPAR(alpha) and PPAR(gamma) in zebrafish primary hepatocyte cultures. Further studies are needed to identify how the expression of different PPAR subtypes is regulated and to elucidate the implication of PPAR subtypes in zebrafish cell functions.
过氧化物酶体增殖是指反应性动物暴露于某些所谓的过氧化物酶体增殖剂化合物时出现的一种现象，它通过一种名为过氧化物酶体增殖物激活受体（PPAR）的核受体进行调节。PPAR家族成员对饱和脂肪酸和不饱和脂肪酸均表现出很强的结合亲和力。PPAR（α）的激活剂包括多种内源性存在的脂肪酸、白三烯和羟基二十碳四烯酸（HETEs）以及临床使用的药物，如贝特类药物。PPAR（β）的激活剂包括脂肪酸、前列腺素A2（PGA2）和前列环素（PGI2）。PPAR（γ）是最具选择性的受体，其中，15-脱氧-Δ（12,14）前列腺素J2（PGJ2）被描述为PPAR（γ）特异性配体。本研究的目的是确定已知的PPAR（α）和PPAR（γ）配体是否能够在斑马鱼原代肝细胞培养的体外模型中改变这些亚型的表达。为此，选择了一种PPAR（α）特异性配体（8S-HETE）、一种PPARγ特异性配体（PGJ）和一种贝特类过氧化物酶体增殖剂（氯贝丁酯）。此外，还使用了雌性激素17β-雌二醇，因为已知它与PPAR相互作用。细胞暴露24小时后，对两种PPAR进行免疫组织化学染色，并将免疫标记定量为阳性细胞核和细胞的百分比。PPAR的表达水平也通过图像分析测量为每个细胞的灰度值。氯贝丁酯（PPAR（α）为0.5 mM，PPAR（γ）为1 mM和2 mM）、HETE（1 μM）以及PGJ2（PPAR（α）为0.3 μM和1 μM，PPAR（γ）为0.3 μM）均可诱导PPAR（α）和PPAR（γ）的表达。17β-雌二醇在10 μM时也可诱导PPARγ的表达。在1 μM HETE时，PPAR（α）阳性细胞核的百分比显著增加，在10 μM 17β-雌二醇时，PPAR（γ）阳性细胞的百分比降低。总之，氯贝丁酯、HETE和PGJ2能够在斑马鱼原代肝细胞培养物中诱导PPAR（α）和PPAR（γ）的表达。需要进一步研究以确定不同PPAR亚型的表达是如何调节的，并阐明PPAR亚型在斑马鱼细胞功能中的作用。
