Zhang Aihua, Dong Zheng, Yang Tianxin
Division of Nephrology, University of Utah and VA Medical Center, Salt Lake City, UT 84148, USA.
Am J Physiol Renal Physiol. 2006 Dec;291(6):F1332-42. doi: 10.1152/ajprenal.00131.2006. Epub 2006 Aug 8.
In a separate study, we identified PGE2 as a potent inhibitor of TGF-beta1induced epithelial-mesenchymal transition (EMT) in cultured Madin-Darby canine kidney (MDCK) cells (Zhang A, Wang M-H, Dong Z, and Yang T. Am J Physiol Renal Physiol 291: F1323-F1331, 2006). This finding prompted us to examine the roles of other prostanoids: PGD2, PGF(2alpha), PGI2, and thromboxane A2 (TXA2). Treatment with 10 ng/ml TGF-beta1 for 3 days induced EMT as reflected by conversion to the spindle-like morphology, loss of E-cadherin, and activation of alpha-smooth muscle actin (alpha-SMA). Treatment with PGD2 remarkably preserved the epithelial-like morphology, restored the expression of E-cadherin, and abolished the activation of alpha-SMA. In contrast, PGF(2alpha), carbocyclic thromboxane A2, PGI2 and its stable analog beraprost were without an effect. MDCK cells expressed DP1 and DP2 receptors; however, the effect of PGD2 was neither prevented by DP1 antagonist BW-A868C or DP2 antagonist BAY-u3405 nor was mimicked by DP1 agonist BW-245C. cAMP-elevating agents forskolin and 8-Br-cAMP blocked EMT. However, cAMP blockers H89 and Rp-cAMP failed to block the effect of PGD2. PGD2 did not seem to act via its metabolites as 15-deoxy-Delta(12,14)-prostaglandin J2 (15d-PGJ2) levels in the medium following incubation with 3 microM PGD2 were well below the values predicted from the cross activity of the assay. Exposure to TGF-beta1 induced a threefold increase in reactive oxygen species production that was completely abolished by PGD2. We conclude that 1) PGD2, but not PGI2, PGF(2alpha), and TXA2 inhibit EMT, 2) PGD2 inhibits EMT independently of DP1 and DP2 receptors, and 3) PGD2 exhibits antioxidant property which may, in part, account for the antifibrotic action of this PG.
在另一项研究中，我们确定前列腺素E2（PGE2）是培养的麦迪逊-达比犬肾（MDCK）细胞中转化生长因子β1（TGF-β1）诱导的上皮-间质转化（EMT）的有效抑制剂（Zhang A, Wang M-H, Dong Z, and Yang T. Am J Physiol Renal Physiol 291: F1323-F1331, 2006）。这一发现促使我们研究其他前列腺素的作用：前列腺素D2（PGD2）、前列腺素F2α（PGF(2α)）、前列环素（PGI2）和血栓素A2（TXA2）。用10 ng/ml TGF-β1处理3天可诱导EMT，表现为细胞形态转变为纺锤状、E-钙黏蛋白丢失以及α-平滑肌肌动蛋白（α-SMA）激活。用PGD2处理可显著保留上皮样形态、恢复E-钙黏蛋白的表达并消除α-SMA的激活。相比之下，PGF(2α)、环戊烷血栓素A2、PGI2及其稳定类似物贝拉普罗斯均无此作用。MDCK细胞表达DP1和DP2受体；然而，PGD2的作用既不能被DP1拮抗剂BW-A868C或DP2拮抗剂BAY-u3405阻断，也不能被DP1激动剂BW-245C模拟。升高细胞内环磷酸腺苷（cAMP）的试剂福斯可林和8-溴-cAMP可阻断EMT。然而，cAMP阻断剂H89和Rp-cAMP未能阻断PGD2的作用。PGD2似乎并非通过其代谢产物起作用，因为用3 microM PGD2孵育后培养基中15-脱氧-Δ(12,14)-前列腺素J2（15d-PGJ2）的水平远低于根据该检测的交叉活性预测的值。暴露于TGF-β1会使活性氧生成增加三倍，而PGD2可完全消除这种增加。我们得出以下结论：1）PGD2可抑制EMT，而PGI2、PGF(2α)和TXA2则不能；2）PGD2独立于DP1和DP2受体抑制EMT；3）PGD2具有抗氧化特性，这可能部分解释了该前列腺素的抗纤维化作用。
