Decreased iNOS synthesis mediates dexamethasone-induced protection of neurons from inflammatory injury in vitro
Decreased iNOS synthesis mediates dexamethasone-induced protection of neurons from inflammatory injury in vitro
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DOI：
10.1046/j.1460-9568.2003.02917.x
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发表时间：
2003-11-01
影响因子：
3.4
通讯作者：
Compston, A
中科院分区：
文献类型：
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作者：
Golde, S;Coles, A;Compston, A
在多发性硬化症的急性病变中，脑部炎症伴随着轴突横断和神经元死亡。我们采用体外培养的大鼠胚胎皮质神经元与干扰素-γ(IFNGamma)和脂多糖(LPS)激活的小胶质细胞共培养的方法，探讨了炎性损伤对神经元的损伤机制。以前，我们已经证明小胶质细胞对神经元具有高度毒性，诱导型一氧化氮合酶(INOS)产生的一氧化氮(NO)是介导这种毒性的必要条件和充分条件。在这里，我们表明，在激活的共培养中添加地塞米松(1um)可提供有效的神经保护。我们证明，地塞米松可下调原代小胶质细胞产生约50%的NO，并使稳定状态的iNOS蛋白和mRNA表达减少约70%。这些变化被糖皮质激素受体阻滞剂RU-486逆转。此外，我们分析了iNOS蛋白的稳定性，并表明虽然蛋白酶体的抑制剂阻止了iNOS的降解，但它们并没有逆转地塞米松的作用。我们的结果表明，皮质类固醇对iNOS活性的主要机制是蛋白质合成减少，而不是先前提出的不稳定。
Brain inflammation is accompanied by transection of axons and death of neurons in the acute lesions of multiple sclerosis. We explored mechanisms of inflammatory damage to neurons in vitro using cocultures of rat embryonal cortical neurons with microglia activated by interferon-gamma (IFNgamma) and lipopolysaccharide (LPS). Previously, we have demonstrated that microglia are highly toxic to neurons and that nitric oxide (NO) derived from inducible nitric oxide synthase (iNOS) is necessary and sufficient to mediate this toxicity. Here, we show that addition of dexamethasone (1 muM) to activated cocultures provides effective neuroprotection. We demonstrate that dexamethasone down-regulates NO production of primary microglia by approximate to 50% and reduces steady-state iNOS protein and mRNA expression by approximate to 70%. These changes were reversed by the glucocorticoid receptor blocker RU-486. Furthermore, we analysed the stability of iNOS protein and show that whilst inhibitors of the proteasome blocked iNOS degradation they did not reverse the dexamethasone effect. Our results indicate that the main mechanism of corticosteroid activity on iNOS is reduction in protein synthesis, not destabilization as previously suggested.