Chen A, Kumar S M, Sahley C L, Muller K J
Department of Physiology and Biophysics, University of Miami School of Medicine, Miami, Florida 33136, USA.
J Neurosci. 2000 Feb 1;20(3):1036-43. doi: 10.1523/JNEUROSCI.20-03-01036.2000.
Damage to the leech or mammalian CNS increases nitric oxide (NO) production and causes accumulation of phagocytic microglial cells at the injury site. The aim of this study was to determine whether NO plays a role in microglial migration and accumulation at lesions in which NO is generated by a rapidly appearing endothelial nitric oxide synthase (eNOS) in leeches. Immunohistochemistry and cytochemistry demonstrated active eNOS before and throughout the period of microglial accumulation at the lesion. Decreasing NO synthesis by application of the NOS inhibitor N(w)-nitro-L-arginine methyl ester (1 mM) significantly reduced microglial accumulation, whereas its inactive enantiomer N(w)-nitro-D-arginine methyl ester (1 mM) resulted in microglial accumulation similar to that in crushed controls. Increasing NO with the donor spermine NONOate (SPNO) (1 mM) also inhibited accumulation, but not in the presence of the NO scavenger 2-(4-carboxyphenyl)-4,4,5, 5-teramethylimidazoline-oxyl-3-oxide (50 microM). The effect of SPNO was reversed by washout. SPNO application reduced average microglial migratory speeds and even reversibly arrested cell movement, as measured in living nerve cords. These results suggest that NO produced at a lesion may be a stop signal for microglia to accumulate there and that it can act on microglia early in their migration. Thus, NO may assume a larger role in nerve repair and recovery from injury by modulating accumulation of microglia, which appear to be important for axonal regeneration.
水蛭或哺乳动物中枢神经系统受损会增加一氧化氮（NO）的生成，并导致吞噬性小胶质细胞在损伤部位聚集。本研究的目的是确定在水蛭中由快速出现的内皮型一氧化氮合酶（eNOS）产生NO的损伤中，NO是否在小胶质细胞迁移和聚集过程中发挥作用。免疫组织化学和细胞化学显示，在损伤部位小胶质细胞聚集之前及整个过程中，eNOS均呈活性状态。应用一氧化氮合酶抑制剂N（ω）-硝基-L-精氨酸甲酯（1 mM）降低NO合成，可显著减少小胶质细胞的聚集，而其无活性的对映体N（ω）-硝基-D-精氨酸甲酯（1 mM）则导致小胶质细胞聚集，与挤压对照组相似。用供体亚精胺NONOate（SPNO）（1 mM）增加NO也可抑制聚集，但在存在NO清除剂2-（4-羧基苯基）-4,4,5,5-四甲基咪唑啉-氧基-3-氧化物（50 μM）时则不然。冲洗可逆转SPNO的作用。如在活体神经索中所测，应用SPNO可降低小胶质细胞的平均迁移速度，甚至可逆地阻止细胞移动。这些结果表明，损伤部位产生的NO可能是小胶质细胞在此处聚集的停止信号，并且它可在小胶质细胞迁移早期作用于小胶质细胞。因此，NO可能通过调节小胶质细胞的聚集在神经修复和损伤恢复中发挥更大作用，而小胶质细胞聚集似乎对轴突再生很重要。
