Experimental study on the nerve transplantation and regeneration in the degenerated spinal cord

我们研究了脊髓受压损伤后氧化应激和一氧化氮(NO)的作用，以探讨减少脊髓损伤后脊髓损伤的方法。我们的研究表明，曲方黄烷A_2、前列腺素I_2和亮三烯C_4参与了继发性病变，抑制这些二十烷类化合物可以部分防止损伤。我们还证明了维生素C作为水溶性自由基清除剂的保护作用，其作用与维生素E没有协同作用。活化的中性粒细胞是氧化应激的主要来源之一。我们证实了细胞间黏附分子-1(ICAM-1)的表达促进了其在损伤后向脊髓的渗透，并证明了ICAM-1的被动免疫促进了神经功能的恢复。一氧化氮(NO)被认为具有神经毒性和神经保护作用。脊髓损伤(SCI)后NO含量升高。损伤后7d，原生型一氧化氮合酶(c-NOS)基因表达无明显变化，诱导型一氧化氮合酶(i-NOS)表达增加。脊髓损伤后，c-NOS的抑制作用加重，i-NOS的抑制作用增强，提示I-NOS诱导的NO在SCI后的亚急性期可能具有神经毒性作用，转化生长因子-β1对i-NOS mRNA表达的下调在脊髓机械性损伤后的继发性病理改变中起重要作用。虽然转化生长因子-β1治疗促进了运动功能障碍的早期恢复，但由于损伤脊髓纤维瘢痕的形成，最终的运动功能并未得到改善。从脊髓损伤后的时间进程来看，ICAM-1和i-NOS可作为预防脊髓损伤后进一步变性的药物治疗靶点。

We investigated roles of oxidative stress and nitric oxide (NO) in the spinal cord after compression injury to investigate the modality to minimize cord damage after spinal cord trauma. Our study demonstrated that tromboxane A_2, prostaglandin I_2 and leucotriene C_4 are involved in the secondary pathological changes and inhibition of these eicosanoids can prevent the damage partially. We also demonstrated the protective effect of vitamin C as a scavenger of water soluble free radicals, and that its effect is not synergistic with that of vitamin E.Activated neutrophil is one of major sources of oxidative stress. We demonstrated the expression of the intercellular adhesion molecule 1 (ICAM-1) which promotes its infiltration to the spinal cord after injury, and that passive immunization of ICAM-1 enhances neurological recovery.Nitric oxide (NO) has been proposed to have neurotoxic and neuroprotective. We showed the increase of NO after spinal cord injury (SCI). Expression of mRNA of constitutive NO synthase (c-NOS) was not changed, however, that of inducible NOS (i-NOS) increased within 7 days of injury. Inhibition of c-NOS worsened and that of i-NOS improved motor function after SCI.These results indicate that NO induced by i-NOS may be neurotoxic in the sub-acute phase after SCI.Down-regulation of i-NOS mRNA by transforming growth factor-beta1 (TGF-beta1) was also demonstrated after SCI.Although early recovery of motor dysfunction was promoted by TGF-beta1 treatment, however, final motor function was not better because of increase of fibrous scar formation in the injured spinal cord.These results indicate that oxidative stress through arachidonate cascade or activated neutrophil, and NO play important roles in the secondary pathological changes after mechanical injury to the spinal cord. From the time course after SCI,ICAM-1 and i-NOS can be targets of pharmacological treatment to prevent further degeneration after spinal cord injuries.