Furuke K, Burd P R, Horvath-Arcidiacono J A, Hori K, Mostowski H, Bloom E T
Laboratory of Cellular Immunology, Division of Cellular and Gene Therapies, Center for Biologics Evaluation and Research, Food and Drug Administration, Bethesda, MD 20892, USA.
J Immunol. 1999 Aug 1;163(3):1473-80.
Although NO appears important in rodent immune responses, its involvement in the human immune system is unclear. We report that human NK cells express constitutive endothelial NO synthase mRNA and protein, but not detectable levels of inducible NO synthase. They produce NO following activation by coculture with target cells or cross-linking with anti-CD16 mAb, and production is increased in the presence of IL-2. N-monomethyl-L-arginine (L-NMA), a NOS inhibitor, partially inhibited NK cell lysis of four different target cells (<40% inhibition at 500 microM L-NMA), but not granule release following coculture with target cells, or Fas ligand induction following cross-linking with anti-CD16 mAb. However, L-NMA augmented apoptosis of NK cells induced by activation through CD16 ligation or coculture with K562. An NO donor, S-nitroso-N-acetylpenicillamine (SNAP), suppressed apoptosis of NK cells induced by CD16 cross-linking or coculture with target cells, suggesting that endogenous NO production is involved in protection of NK cells from activation-induced apoptosis, thereby maintaining NK activity. SNAP also suppressed, and L-NMA enhanced, expression of TNF-alpha, reported to be involved in activation-induced NK cell death, in response to CD16 cross-linking. Suppression of anti-CD16-induced apoptosis by SNAP was reversed by the addition of rTNF-alpha. DNA-binding activity of the transcription factor, NF-AT, which is involved in TNF-alpha induction upon ligation of CD16, was inhibited by SNAP and enhanced by L-NMA. Our results suggest that down-regulation of TNF-alpha expression, possibly due to suppression of NF-AT activation, is a mechanism by which endogenous NO protects NK cells from activation-induced apoptosis, and maintains lytic capacity.
尽管一氧化氮（NO）在啮齿动物免疫反应中似乎很重要，但其在人类免疫系统中的作用尚不清楚。我们报告称，人类自然杀伤（NK）细胞组成性表达内皮型一氧化氮合酶mRNA和蛋白，但未检测到可诱导型一氧化氮合酶的表达水平。它们在与靶细胞共培养或用抗CD16单克隆抗体交联激活后产生NO，并且在白细胞介素-2存在的情况下产量增加。一氧化氮合酶抑制剂N-单甲基-L-精氨酸（L-NMA）部分抑制了NK细胞对四种不同靶细胞的裂解（在500微摩尔/升L-NMA时抑制率<40%），但不影响与靶细胞共培养后的颗粒释放，也不影响用抗CD16单克隆抗体交联后的Fas配体诱导。然而，L-NMA增强了通过CD16连接激活或与K562共培养诱导的NK细胞凋亡。一氧化氮供体S-亚硝基-N-乙酰青霉胺（SNAP）抑制了由CD16交联或与靶细胞共培养诱导的NK细胞凋亡，这表明内源性NO的产生参与保护NK细胞免受激活诱导的凋亡，从而维持NK活性。SNAP还抑制了，而L-NMA增强了，据报道与激活诱导的NK细胞死亡有关的肿瘤坏死因子-α（TNF-α）在响应CD16交联时的表达。添加重组TNF-α可逆转SNAP对抗CD16诱导的凋亡的抑制作用。转录因子NF-AT的DNA结合活性在CD16连接时参与TNF-α的诱导，被SNAP抑制并被L-NMA增强。我们的结果表明，TNF-α表达的下调，可能是由于NF-AT激活的抑制，是内源性NO保护NK细胞免受激活诱导的凋亡并维持裂解能力的一种机制。
