Study On Demyelination And Immune Factors In Rat Models After CO Poisoning

Carbon monoxide, an odorless, colorless gas, which was generated inincomplete burning of carbonaceous matter. It’s well-known for its toxicity. Aswe are enjoying higher level of living and health conditions, CO poisoning ratewas not descending. It remains the highest for incidence and mortality.Clinically, patients suffered acute CO poisoning are mostly cured if in timetreatment could be applied. Yet there are about10%~30%who recovered fromacute poisoning are showing nervous system diseases like demetia, psychoticsymptoms and extrapyramidal symptoms, what was called delayedneuropsychologic sequelae, DNS. DNS is the most severe sequela of acute COpoisoning that seriously affect their quality of life and places a significantburden to society and family. But its exact pathogenesis is unclear.Previous researches demonstrated that DNS was a combined action ofmultiple mechanisms. As studies went on, it’s evident that the pathogenesis ofDNS was about immune factors. Because there is an increase of free radical inbrain after acute CO poisoning, lipid peroxidation was induced and brain myelinbasic protein changed. As MBP is not only an important components of nervoussystem myelin, but also the most antigen-active protein in myelin. This allosteric MBP may be used as an antigenic material to activate the autoimmune responseand cause brain tissue demyelination under immune attacks, which leads to aseries of immune injury.Macrophage inflammatory protein-1a (MIP-1α) and intercellular adhesionmolecule1(ICAM-1) are two common immune factors involved in localinflammation and immune responses in inflammatory cell infiltration andmigrationplay a major role, MIP-1α is a chemotactic cytokines, chemokines,monocyte/macrophages, T lymphocytes and NK cells and other cells. ICAM-1is a cell adhesion molecule, mainly expressed in endothelial cells, lymphocytes,mediating monocytes, lymphocytes, neutrophils cells and activated endothelialcells.In the immune response, these two factors are involved in the infiltration ofimmune cells, they mediate immune cells cross the blood-brain barrier to reachthe sites of inflammation. According to the results of the DNS immunepathogenesis, we suggestithat these two immune factors may be involved in theincidence of DNS.Clinically, the hyperbaric oxygen (HBO) treatment has a significantlyeffect on DNS, but its mechanism is not yet fully elucidated. HBO may beimproving clinical symptoms by reducing DNS demyelination and MIP-1α andICAM-1expression.In this study, based on the above assumptions and through theestablishment of the DNS rat model, we observe the changes of myelin in rats’brain by using the electron microscopy, and also observe the pathomorphologychange in rats’brain by HE staining and Luxol fast blue staining.we observe theexpression of MBP、MIP-1α and ICAM-1by immunohistochemical staining,atthe same time, we give rats the HBO therapy and observe the changes of theabove-mentioned cytokines. The main findings are as follows:1. Brain myelin ultrastructural changesBrain myelin under the electron microscope, began to split between theaxon and myelin3d after exposure to CO,14days after exposure, the myelintexture is unclear, structural disorder, severe lamellar loose split, the myelinmembrane and myelin lamellar gap, vacuolization, after exposure to hyperbaricimmediate oxygen therapy last for14days. Compared to that exposed to14dgroup, the myelin sheath becomes clear separation of the lamellar reduced, partof the axon vacuoles disappeared.2. Brain tissue pathological changesOn HE stained slices, CO poisoning caused rat brain tissue a wide range ofpathological damage, we can see a lot of degeneration and necrosis of neurons,mainly in neurons of structural disorder, reduction in the cell body, chromatincondensation or fragmentation, cytoplasm becomestrongly eosinophilic,nucleous deeply stained and deviated, with the cytoplasm and nucleuscondensation, ill-defined, red cells or black cells. The most serious damage toparts of the brain cortex and hippocampus. The most serious point in time is7days. Luxol fast blue staining of the nerve fibers of rat brain tissue after COpoisoning, disorganized, and loose, some fibers depigmentation uncolored,showing the phenomenon of apparent demyelination, which is most obvious14days after exposure Compared with the control group, NF integral opticaldensity of exposed groups was significantly lower (P <0.05), hyperbaric oxygentherapy for14days after the nerve fiber arrangement becomes a neat,centralized, lighter-demyelinating phenomenon.3. MBP immunohistochemical staining and Western blotting resultsImmunohistochemical staining showed that after CO exposure, MBP expression started to decrease from the third day after exposure.The reductionreached a peak14days after exposure.The exposed group had a decreased MBPintegral optical density than the control group(P <0.05), while HBO treatmentgroup had an IOD value increase (P <0.05) compared with exposed to CO group.Western blot showed that expression of MBP reduced from3days to14daysafter exposure, and peaked14days after exposure (P <0.05). HBO treated grouphad an increased IOD compared with the group which was only exposed toCO(P <0.05).4.MIP-1a and ICAM-1immunohistochemical stainingImmunohistochemical results showed neither of MIP-1a or ICAM-1expressed in the control group. MIP-1a expression started from exposure1dgroup while ICAM was not expressed. The expression of MIP-1a increased3days after exposure group and peaked (P <0.05). Meantime ICAM-1started toexpress. In7d after exposure group, the expression of MIP-1a began to reducewhile the expression of ICAM-1reached a peak (P <0.05). In both vascularendothelial cells and lymphocytes, ICAM-1could be observed.Treated with HBO immediately after exposure to CO for7days, MIP-1aand ICAM-1expression were both significantly reduced. It was significantlydifferent from the group7days after exposure to CO(P <0.05).In the exposureafter10d group, there was barely MIP-1a expression and Only a few positiveICAM-1on lymphocytes.Our study researched from three aspects on acute CO poisoning on DNS ratmodel. We proved that the DNS was associated with brain tissue demyelination.HBO therapy could alleviate such lesions. We also found that MIP-1a andICAM-1expression in rat brain tissue, mainly in the position of vascular walland perivascular. In time course, there was a delay in the expression of the two molecules. HBO therapy can limit the occurrence of the immune responsethrough affecting on the expression of them. So as to reduce the DNS injury.