Vascular diseases such as atherosclerosis are characterized by abnormal accumulation of vascular smooth muscle cells (VSMCs) within the intimal lining. The intimal VSMCs exhibit an increased expression of peroxisome proliferator-activated receptor (PPAR), and the administration of pharmacological PPAR agonists attenuates vascular lesion formation. The factors that regulate PPAR expression in the vasculature are poorly defined. Here we report that platelet-derived growth factor (PDGF) upregulates PPAR by the phosphatidylinositol 3-kinase (PI3-kinase)/Akt signaling pathway. Using Northern-blotting and Western-blotting analyses, we observed that the levels of PPAR mRNA and protein were increased by 2-to 3.5-fold in human aortic smooth muscle cells (HASMCs) treated with PDGF (20ng/mL). This was abolished by preincubation of HASMCs with a PI3-kinase inhibitor (LY294002, 50mol/L), and partially inhibited by a MEK1 inhibitor (U0126, 10mol/L), but not affected by a p38 kinase inhibitor (SB202190, 10mol/L). In addition, overexpression of the dominant-negative p85 subunit of PI3-kinase or Akt proteins blocked the PDGF-induced PPAR expression. Taken together, our results suggest that PDGF induces PPAR expression in VSMCs by a PI3-kinase/Akt signaling pathway. The characterization of factors and signaling pathways that modulate PPAR expression in VSMCs may have important implications for understanding the pathogenesis of vascular diseases.

Although peroxisome proliferator-activated receptor (PPAR) is widely expressed in many tissues, the role of PPAR is poorly understood. In this study, we report that PPAR was up-regulated in vascular smooth muscle cells (VSMC) during vascular lesion formation. By using Northern blot analysis, we demonstrated that PPAR was increased by 3-4-fold in VSMC treated with platelet-derived growth factor (PDGF) (20ng/ml). In addition, PDGF-induced PPAR mRNA expression neither needs de novo protein synthesis nor affects the stability of PPAR mRNA in VSMC. Preincubation of VSMC with phosphatidylinositol 3-kinase inhibitor (LY294002, 50mol/liter) or infection of VSMC with an adenovirus carrying the gene for a dominant negative form of Akt abrogated PDGF-induced PPAR mRNA expression, suggesting that phosphatidylinositol 3-kinase/Akt signaling pathway is involved in the regulation of PDGFinduced PPAR mRNA expression in VSMC. To explore the role of PPAR in VSMC, we generated rat vascular smooth muscle cells (A7r5) stably overexpressing PPAR and the control green fluorescent protein. Overexpression of PPAR in VSMC increased post-confluent cell proliferation by increasing the cyclin A and CDK2 as well as decreasing p57kip2. Taken together, the results suggest that PPAR plays an important role in the pathology of diseases associated with VSMC proliferation, such as primary atherosclerosis and restenosis.

目的 观察人间质胶原酶（MMPl）基因高效表达对体外肝纤维化的影响。方法 利用DNA重组技术构建了pcDNA3-MMPl真核表达重组质粒。经脂质体包裹后，转染张氏传代人肝细胞，Westem blot检测MMPl蛋白表达量。在体外乙醇诱导纤维化培养条件下，抗生蛋白链菌素一生物索复合物标志（ISAB）免疫组织化学法检测肝细胞周围Ⅰ、Ⅲ型胶原生成状况，图象分析仪半定量分析胶原纤维的相对含量（RCC）。结果 成功构建真核表达质粒pcDNA3-MMPl，检测Rcc显示未转染组为132.6±5.7，转染组为118.8±4.8；统计学分析表明未转染组明显高于转染组（P<O.01）。结论 本研究证明重组质粒pcDNA3-MMPl能在体外致纤维化培养条件下拮抗肝细胞间质过多胶原产生。