Lin Heng, Lee Ja-Ling, Hou Hsin-Han, Chung Chih-Peng, Hsu Sung-Po, Juan Shu-Hui
Institute of Pharmacology and Toxicology, Tzu Chi University, Hualien, Taiwan.
J Cell Physiol. 2008 Feb;214(2):434-41. doi: 10.1002/jcp.21214.
Prostacyclin (PGI2) has been shown to inhibit proliferation in vascular smooth muscle cells. To clarify the underlying molecular mechanism, we investigated the vasoprotection of beraprost (a PGI2 agonist) both in vivo and in vitro. Beraprost eliminated increases in proliferation of rat aortic smooth muscle cells (RASMCs) by 12-O-tetradecanoylphorbol 13-acetate, and enhanced the peroxisome proliferator-activated receptor-delta (PPARdelta) and inducible nitric oxide synthetase (iNOS) expressions, which were associated with the antiproliferative action of beraprost according to inhibition experiments by [(3)H]thymidine incorporation. Additionally, elimination of iNOS activity by PPARdelta antagonists suggested that iNOS is the downstream target of PPARdelta. Furthermore, beraprost increased both consensus PPARdelta-responsive element (PPRE)-driven luciferase activity and the binding activity of the PPARdelta to the putative PPRE in the iNOS promoter; nevertheless, it was abolished by PPARdelta antagonists. Deletion of PPRE (-1,349/-1,330) in the iNOS promoter region (-1,359/+2) strongly reduced promoter-driven activity, representing a novel mechanism of iNOS induction by beraprost. Consistent with this, PPARdelta and the concomitant iNOS induction by beraprost were also evident in vivo. Beraprost-mediated protection in a murine model of balloon angioplasty was significantly attenuated by 13S-HODE, a PPARdelta antagonist. Taken together, the results suggest that the causal relationship between PPARdelta and iNOS contributes to the vasoprotective action of beraprost in RASMCs.
前列环素（PGI2）已被证明可抑制血管平滑肌细胞的增殖。为阐明其潜在的分子机制，我们在体内和体外研究了贝拉前列腺素（一种PGI2激动剂）的血管保护作用。贝拉前列腺素消除了12-O-十四酰佛波醇-13-乙酸酯引起的大鼠主动脉平滑肌细胞（RASMCs）增殖增加，并增强了过氧化物酶体增殖物激活受体δ（PPARδ）和诱导型一氧化氮合酶（iNOS）的表达，根据[（3）H]胸苷掺入抑制实验，这与贝拉前列腺素的抗增殖作用相关。此外，PPARδ拮抗剂消除iNOS活性表明iNOS是PPARδ的下游靶点。此外，贝拉前列腺素增加了共有PPARδ反应元件（PPRE）驱动的荧光素酶活性以及PPARδ与iNOS启动子中假定PPRE的结合活性；然而，这被PPARδ拮抗剂所消除。iNOS启动子区域（-1,359/+2）中PPRE（-1,349/-1,330）的缺失强烈降低了启动子驱动的活性，这代表了贝拉前列腺素诱导iNOS的一种新机制。与此一致的是，PPARδ以及贝拉前列腺素伴随的iNOS诱导在体内也很明显。在球囊血管成形术小鼠模型中，PPARδ拮抗剂13S-HODE显著减弱了贝拉前列腺素介导的保护作用。综上所述，结果表明PPARδ和iNOS之间的因果关系有助于贝拉前列腺素在RASMCs中的血管保护作用。
