APPROACHES FOR EFFICIENT INHABITION OF INFLAMMATORY GENES BY SMALL DOSES OF CORTICOSTEROIDS

糖皮质激素是最强的抗炎药之一。长期使用较大剂量的糖皮质激素受到限制，因为有各种不良反应。这项研究旨在开发小剂量糖皮质激素如何有效发挥强大的抗炎作用。糖皮质激素能明显抑制肿瘤坏死因子-α诱导的牛主动脉内皮细胞IL-6基因启动子活性，但不能抑制肿瘤坏死因子-α诱导的血管内皮细胞血管细胞黏附分子-1基因启动子活性。而将糖皮质激素受体(GR)表达载体导入这些细胞后，糖皮质激素可显著抑制肿瘤坏死因子-α诱导的血管细胞黏附分子-1基因启动子活性。有趣的是，与低GR表达的细胞相比，较低浓度的糖皮质激素对高GR表达的细胞具有有效的抑制作用。这些结果表明，低浓度糖皮质激素可能通过增加靶细胞GR的表达水平而发挥强大的抗炎作用。激活PPARα可抑制NF-κB与VCAM1基因启动子特定序列的结合，提示PPARα通过抑制NF-κB的活性而抑制VCAM1基因的转录。PPAR三种亚型激动剂MCC-555可抑制血管内皮细胞VCAM-1的表达，抑制单核细胞与血管内皮细胞的黏附。PPARδ特异性激动剂GW501516也能抑制VCAM1的表达，而PPARγ特异性激动剂吡格列酮不能抑制VCAM1的表达。因此，PPARα和δ具有抑制血管内皮细胞血管细胞黏附分子-1表达的潜能，而γ则无此作用。PPARα的激活也能增加血管内皮细胞eNOS蛋白及其基因表达水平。PPARα的激活不能增加eNOS基因启动子的活性，但能稳定enos基因的表达。这一观察结果对于理解核受体介导的mRNA稳定是很有意义的。

Glucocorticoids are one of the strongest anti-inflammatory drugs. Long-term use of relatively large doses of glucocorticoids is restricted because of various kinds of adverse effects. This investigation was aimed to develop the way how smaller doses of glucocorticoids efficiently exert strong anti-inflammatory effects. Glucocortiocids clearly inhibited TNF-α-induced IL-6 gene promoter activity in cultured bovine aortic endothelial cells (BAECs), whereas they failed to TNF-α-induced VCAM-1 gene promoter activity in BAECs. However, when glucocorticoid receptor (GR) expression vector was introduced into these cells, glucocorticoids could significantly inhibit TNF-α-induced VCAM-1 gene promoter activity. Interestingly, lower concentrations of glucocorticoids were efficient for the inhibition in high GR expressed cells, compared with low GR expressed cells. These results suggest a potential for strong anti-inflammatory effects of low concentrations of glucocorticoids, by increasing GR expression levels in target cells.Activation of PPARα resulted in inhibition of NF-κB binding to specific sequence of the VCAM-1 gene promoter, indicating the inhibitory effect of PPARα on VCAM-1 gene transcription through inhibition of NF-κB activity. MCC-555,an agonist for PPAR three subtypes, was found to inhibit VCAM-1 expression in vascular endothelial cells and monocytes adhesion to these cells. The PPARδ specific agonist GW501516 could also inhibited VCAM-1 expression, while the PPARγ specific agonist pioglitazone did not. Thus, PPARα and δ, but not γ, have the potential to inhibit the VCAM-1 expression in vascular endothelial cells.Activation of PPARα was also found to increase eNOS protein and its mRNA levels in vascular endothelial cells. PPARα activation failed to increase eNOS gene promoter activity, while it stabilized eNOS mRNA. This observation is interesting for understanding the nuclear receptors-mediated stabilization of mRNA.