Cha H J, Park M T, Chung H Y, Kim N D, Sato H, Seiki M, Kim K W
Research Institute of Basic Sciences, Pusan National University, Korea.
Oncogene. 1998 Feb 12;16(6):771-8. doi: 10.1038/sj.onc.1201587.
We have previously reported that ursolic acid, a pentacyclic triterpene acid, inhibited the invasion of HT1080 human fibrosarcoma cells by reducing the expression of matrix metalloproteinase-9. Since the chemical structure of ursolic acid is very similar to that of dexamethasone, a synthetic glucocorticoid, we investigated whether ursolic acid acts through the glucocorticoid receptor. The expression of matrix metalloproteinase-9 is thought to be regulated similarly with matrix metalloproteinase-1 and matrix metalloproteinase-3 as containing common 2-O-tetradecanoylphorbol-acetate responsible region, where AP-1 proteins can bind. Dexamethasone has been studied to repress the 2-O-tetradecanoylphorbol-acetate-induced expression of matrix metalloproteinase-1 and matrix metalloproteinase-3 through a glucocorticoid receptor-mediated manner. In Northern blot analysis, we found that ursolic acid reduced the expression of matrix metalloproteinase-1 and matrix metalloproteinase-3 induced by 2-O-tetradecanoylphorbol-acetate. Similarly, ursolic acid down-regulated 2-O-tetradecanoylphorbol-acetate-induction of matrix metalloproteinase-9 gene in the same manner of dexamethasone. RU486, a potent glucocorticoid receptor antagonist, was used for identifying that ursolic acid-induced down-regulation of matrix metalloproteinase-9 expression is mediated by its binding to glucocorticoid receptor. The effect of ursolic acid on the matrix metalloproteinase-9 expression was blocked by RU486, suggesting that ursolic acid acts via a glucocorticoid receptor in the regulation of matrix metalloproteinase-9. Western blot analysis and immunocytochemistry showed that ursolic acid increased glucocorticoid receptor fraction in the nucleus, although it decreased the synthesis of glucocorticoid receptor mRNA. In addition, ursolic acid did not decrease the expression of c-jun and DNA-binding activity of AP-1 to its cognate sequences. Taken together, we suggest that ursolic acid may induce the repression of matrix metalloproteinase-9 by stimulating the nuclear translocation of glucocorticoid receptor, and the translocated glucocorticoid receptor probably down-modulating the trans-activating function of AP-1 to 2-O-tetradecanoylphorbol-acetate responsible element of matrix metalloproteinase-9 promoter region.
我们之前报道过，乌索酸（一种五环三萜酸）通过降低基质金属蛋白酶-9的表达来抑制HT1080人纤维肉瘤细胞的侵袭。由于乌索酸的化学结构与合成糖皮质激素地塞米松非常相似，我们研究了乌索酸是否通过糖皮质激素受体发挥作用。基质金属蛋白酶-9的表达被认为与基质金属蛋白酶-1和基质金属蛋白酶-3的调节方式相似，因为它们含有共同的佛波酯反应元件，激活蛋白-1（AP-1）蛋白可以结合于此。地塞米松已被研究通过糖皮质激素受体介导的方式抑制佛波酯诱导的基质金属蛋白酶-1和基质金属蛋白酶-3的表达。在Northern印迹分析中，我们发现乌索酸降低了佛波酯诱导的基质金属蛋白酶-1和基质金属蛋白酶-3的表达。同样，乌索酸以与地塞米松相同的方式下调佛波酯诱导的基质金属蛋白酶-9基因表达。RU486是一种有效的糖皮质激素受体拮抗剂，用于确定乌索酸诱导的基质金属蛋白酶-9表达下调是否由其与糖皮质激素受体的结合介导。RU486阻断了乌索酸对基质金属蛋白酶-9表达的影响，表明乌索酸在基质金属蛋白酶-9的调节中通过糖皮质激素受体发挥作用。蛋白质免疫印迹分析和免疫细胞化学显示，乌索酸增加了细胞核中糖皮质激素受体的比例，尽管它降低了糖皮质激素受体mRNA的合成。此外，乌索酸并未降低c-jun的表达以及AP-1与其同源序列的DNA结合活性。综上所述，我们认为乌索酸可能通过刺激糖皮质激素受体的核转位来诱导基质金属蛋白酶-9的表达抑制，而转位的糖皮质激素受体可能下调AP-1对基质金属蛋白酶-9启动子区域佛波酯反应元件的反式激活功能。
