Rodríguez C, Noé V, Cabrero A, Ciudad C J, Laguna J C
Unidad de Farmacología y Farmacognosia, Facultad de Farmacia, Universidad de Barcelona, Spain.
Mol Pharmacol. 2000 Jul;58(1):185-93. doi: 10.1124/mol.58.1.185.
Peroxisome proliferator-activated receptor-alpha (PPARalpha) is responsible for the hypolipidemic, peroxisome proliferation and carcinogenic effects of fibrates. Rats and mice are responsive, but guinea pigs and primates are resistant to the proliferative and carcinogenic effects of these drugs, but the hypolipidemic effect is still manifest. It is not yet clear whether humans should be considered unresponsive, and there is concern about the long-term safety of fibrates. We present molecular evidence for the reported resistance of human cells to peroxisome proliferation by describing a deficient interaction of nuclear extracts from human cells with an acyl-CoA oxidase (ACO)-peroxisome proliferator response element probe upon fibrate addition. Electrophoretic mobility shift assay analysis showed that ciprofibrate elicited a concentration-dependent increase in the binding of nuclear extracts from cells of rat (Morris) and human (HepG2) origin to an ACO-peroxisome proliferator response element probe, although in HepG2 cells the increase was of marginal statistical significance. In Morris cells, the increase was more marked than in HepG2 cells (4-fold versus 1.5-fold at 0.2 mM ciprofibrate), and maximal binding was achieved earlier in Morris (30 min) than in HepG2 cells (3 h). Morris cells responded to the addition of ciprofibrate by increasing the levels of ACO mRNA, whereas HepG2 did not. The ratio between PPARbeta/PPARalpha mRNAs was higher in HepG2 cells than in Morris cells (3.2 versus 1.9), pointing to an antagonizing effect of PPARbeta on PPARalpha activity. These results were obtained in untransfected cells expressing their own basal set of receptors. We also provide evidence of the translocation of PPARalpha from the cytosol to the nucleus upon activation by ciprofibrate.
过氧化物酶体增殖物激活受体α（PPARα）介导贝特类药物的降血脂、过氧化物酶体增殖及致癌作用。大鼠和小鼠对这些药物有反应，但豚鼠和灵长类动物对其增殖和致癌作用具有抗性，不过降血脂作用仍然明显。目前尚不清楚人类是否应被视为无反应，并且人们对贝特类药物的长期安全性存在担忧。我们通过描述在添加贝特类药物后人类细胞核提取物与酰基辅酶A氧化酶（ACO）-过氧化物酶体增殖物反应元件探针之间的缺陷相互作用，为报道的人类细胞对过氧化物酶体增殖的抗性提供了分子证据。电泳迁移率变动分析表明，环丙贝特引起大鼠（莫里斯）和人类（HepG2）来源细胞的核提取物与ACO-过氧化物酶体增殖物反应元件探针的结合呈浓度依赖性增加，尽管在HepG2细胞中这种增加仅具有边际统计学意义。在莫里斯细胞中，这种增加比在HepG2细胞中更明显（在0.2 mM环丙贝特时为4倍对1.5倍），并且在莫里斯细胞中（30分钟）比在HepG2细胞中（3小时）更早达到最大结合。莫里斯细胞对环丙贝特的添加反应是通过增加ACO mRNA的水平，而HepG2细胞则没有。HepG2细胞中PPARβ/PPARα mRNA的比率高于莫里斯细胞（3.2对1.9），表明PPARβ对PPARα活性具有拮抗作用。这些结果是在表达自身基础受体组的未转染细胞中获得的。我们还提供了环丙贝特激活后PPARα从细胞质转位到细胞核的证据。
