Integrative Immunology and Behavior Program, Department of Animal Sciences, 227 Edward R Madigan Laboratory, College of ACES, 1201 W Gregory Drive, University of Illinois at Urbana-Champaign, Urbana, IL 61801-3873, USA.
Brain Behav Immun. 2010 Nov;24(8):1249-53. doi: 10.1016/j.bbi.2010.04.015. Epub 2010 May 6.
Indoleamine 2,3-dioxygenase (IDO) is an intracellular heme-containing enzyme that is activated by proinflammatory cytokines, including interferon-γ (IFNγ), and metabolizes tryptophan along the kynurenine pathway. Activation of murine macrophages induces not only IDO but also nitric oxide synthase (iNOS), and the ensuing production of nitric oxide (NO) inhibits IDO. To determine the sensitivity of primary cultures of murine microglia to NO, microglia were stimulated with recombinant murine IFNγ (1 ng/ml) and lipopolysaccharide (LPS) (10 ng/ml). This combination of IFNγ+LPS synergized to produce maximal amounts of nitrite as early as 16h. Steady-state mRNAs for both iNOS and IDO were significantly increased by IFNγ+LPS at 4h post-treatment, followed by an increase in IDO enzymatic activity at 24h. Murine microglia (>95% CD11b(+)) were pretreated with the iNOS inhibitor, L-NIL hydrochloride, at a dose (30 μM) that completely abrogated production of nitrite. L-NIL had no effect on IDO mRNA at 4h or IDO enzymatic activity at 24h following stimulation with IFNγ+LPS. These data establish that IDO regulation in murine microglia is not restrained by NO, thereby permitting the accumulation of kynurenine and its downstream metabolites in the central nervous system.
色氨酸 2,3-双加氧酶（IDO）是一种细胞内含铁的酶，可被包括干扰素-γ（IFNγ）在内的促炎细胞因子激活，并沿着犬尿氨酸途径代谢色氨酸。激活小鼠巨噬细胞不仅会诱导 IDO，还会诱导一氧化氮合酶（iNOS），随后产生的一氧化氮（NO）会抑制 IDO。为了确定原代培养的小鼠小胶质细胞对 NO 的敏感性，用重组小鼠 IFNγ（1ng/ml）和脂多糖（LPS）（10ng/ml）刺激小胶质细胞。IFNγ+LPS 的这种组合早在 16 小时就协同产生了最大量的亚硝酸盐。IFNγ+LPS 处理后 4 小时，iNOS 和 IDO 的稳态 mRNA 显著增加，随后在 24 小时时 IDO 酶活性增加。用 iNOS 抑制剂 L-NIL 盐酸盐（剂量为 30 μM）预处理小鼠小胶质细胞（>95% CD11b(+)），完全消除了亚硝酸盐的产生。L-NIL 对 IFNγ+LPS 刺激后 4 小时的 IDO mRNA 或 24 小时的 IDO 酶活性没有影响。这些数据表明，IDO 在小鼠小胶质细胞中的调节不受 NO 限制，从而允许犬尿氨酸及其下游代谢物在中枢神经系统中积累。
