| Background and purpose: Acute carbon monoxide poisoning (ACMP) is the common occupational poison in our life.It can cause the injury of central nervous system (CNS).After acute poisoning symptoms disappeared , some patients will present normal or near normal for a few days or weeks ,It called the false period.Then They present mainly the dementia symptoms ,which known as the delayed encephalopathy after acute carbon monoxide poisoning, DEACMP, Brain MRI of patients with DEACMP ,the white matter is demyelinating significantly[1-4]. Because of the false period, it is difficult to diagnose DEACMP in forepart accurately. It is difficult to effectively prevent and control, and bring a great burden on the family which has the patient. Nogo-A is one of the nervous growth inhibitors in CNS.It mainly expressed by oligodendrocytes which are in the CNS[5].It has been confirmed that Nogo-A can trigger the growth cone collapse , inhibite the regrowth of nerve axons,and block prevent the Spread of the nerve fibers , and its receptor (NgR) widely distributes in lots of neurons,which immune electron microscopy studies show that NgR has immune response to glial cells and also exist in the seam connection in glial cells, NgR which is in the seam connection between the glial cells may regulate their signal transmit,but there is no NgR in oligodendrocytses[6].All those make Nogo-A and it's receptors become the key factor to restricte the regrowth of nerve axons and prevent the regeneration of CNS from it's injury [7] .whether Nogo-A was involved in the ACMP's brain damage and DEACMP the mechanism or not ,which has not been reported. In view of the distribution of Nogo-A and its receptors, also the white matter demyelinated prominently on DEACMP patients's brain MRI, we speculate that Nogo-A and it's receptor system have some contributions to the ACMP, especially to the DEACMP. Endogenous CO is one of the important elements of the air courier. It can transfer the information between cells and regulating the function of cells . CO mainly produce by the metabolism of the Heme oxygenase ( HO).Zinc Porphyrin IX (ZnPPIX) is the inhibitor of HO, it can inhibit the produce of endogenous CO, and it has been used to study the neuroendocrine regulator function of the endogenous CO[8]. As the only one system of synthesizing endogenous CO,the HO-CO system has been pay more attention.In addition, CO as a gas messenger molecules in brain, its relationship whit Nogo-A and NgR also has not been reported in the present. In our study, after excluding the effect of hypoxia,we treat oligodendrocytes with 1%CO directly, at the same time we use ZnPPIX inhibit the produce of the endogenous CO ,and then observed the expression of Nogo-AmRNA and its protein. In order to discusss the potential pathophysiological function of Nogo-A and the HO-CO system in ACMP and DEACMP, and provid a new experimental clue for studying the pathogenesis and treatment of ACMP and DEACMP.Methods: (1) The optic nerves of 2 days'newborn SD rats.Optic nerve tissues were cultured directly and DMEM/F12 chemically defined culture medium was used to culture and purify oligodendrocytes. We detect the expression of the myelin basic protein (MBP) in oligodendrocytses by immunocytochemical examination.(2) Excluding the effect of hypoxia, we treat oligodendrocytes with 1% CO directly, and detect the expression of Nogo-A mRNA and Nogo-A protein of 6h, 24h, 48h by RT-PCR and immunohistochemical. (3) Select the time when the Nogo-A mRNA express into the peak value, and pre-add ZNPP-IX in medium in order to inhibit the produce of endogenous CO, detect the expression of Nogo-A mRNA and protein by RT-PCR and immunohistochemical.Results: 1,After 24 hours,tissue is adherenting to Petri dish,After 48-72hours ,the edge of the nerve tissue has a small number of rotundate and cells travelling out. About 9-10 days later all the cells of optic nerves can almostly traveled out and overspread the dish. In the 11days, the cells growth into a round and polygonal shape, the diameter is about 6-10um. The cells have larger nuclei and less cytoplasm. We bserved more than 95 percent cells are positive by immunocytochemical examination.2,Detect the expression of Nogo-AmRNA by RT-PCR:(1) The expression of Nogo-A mRNA of the control group (control): 6h, 24h, 48h are:0.733±0.034, 0.705±0.027,0.717±0.04, and there is no significantly change; the expression of Nogo-AmRNA of the CO treated group compared with the control group has increased at each time point: 6 h (1.042±0.015 vs 0.733±0.034, P <0.05); 24h (1.304±0.008 vs 0.705±0.027,P <0.05);48h (0.937±0.005 vs 0.717±0.04, P <0.05)。(2) The ZNPP-IX group compared with COZN,the expression of Nogo-AmRNA has significantly increased(1.454±0.041 vs 1.278±0.032, P <0.01). 3,The expression of Nogo-A protein of each group has the same changes with the expression of Nogo-AmRNA. The Cumulative optical density of each group the control group 6h, 24h, 48h are 2836.74±94.30,2761.16±75.80,2780.16±95.46;the CO group 6h,24h,48h are4087.20±79.28,7240.40±63.25,3449.90±93.4,compared with the control group has significantly change(P<0.05);the ZNPP-IX group is 9880.76±105.81, compared with the COZN group has significantly change(P<0.05)。Conclusion: (1) Excluding the influence of hypoxia,exogenous CO can increase the expression of Nogo-A mRNA and its protein of oligodendrocytes which is cultured in vitro.(2)Excluding the influence of hypoxiawhen exogenous CO increases the expression of Nogo-A mRNA and its protein of oligodendrocytes,the HO-CO system can inhibit the expression of Nogo-A mRNA and its protein.
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