Expression of myelin basic protein in rat optic nerve with experimental allergic encephalomyelitis

Abstract

Background Optic neuritis is closely associated with multiple sclerosis (MS).Its pathogenesis is uncompletely clear,and less basic researches are carried out at home and abroad. Objective This study was to reveal the expression of myelin basic protein (MBP) in the optic nerve of rat with experimental allergic encephalomyelitis (EAE) and to provide a theoretical evidence for the research of the relationship of optic neuritis with MS. Methods Fifty clean Wistar rats were randomized into the control group and immune 8,12,18 and 25 days groups.Myelencephalon was collected from 5 guinea pigs to prepare the homogenate and mixed with the isovolumetric complete Freud' s adjuvant (CFA).The 0.5 ml mixed antigen emulsifier was subcutancously injected into the 4 maps together with Bordetella pertussis 0.2 ml under the cutancous of dorsalis pedis at 0 and 48 hours to induce the EAE.Behavior of the rats was evaluated to score the neurological function.The optical nerve sections were prepared 8,12,18 and 25 days after immunology for the histopathological examination,and immunochemistry and Western blot were used to detect the expression of MBP in optic nerve.The use of the animals complied with the Regulation for the Administration of Affairs Concerning Experimental Animals by State Science and Technology Commission. Results The disorder of motor nerve was seen 12 days following the immune,and the clinical neural functional scores were significantly higher 12 day and peaked on 18 days myelination and then gradually reduced.The histopathological examination showed that the irregular alignment of neural fiber was found at 12 days,and changes of cellular structure,edema of neural shaft bunch were observed at 18 days.However,the abnormal cells were significantly less 25 days following the immune.Immunochemistry showed that the MBP was expressed mainly in the myelination of optic nerve fibers.The numbers of positive cells for MBP were (115.75±26.49)cells/5 fields at the 12th day,showing a significant lowing in comparison with (167.44±22.49)cells/5 fields of control group (t=4.537,P＜0.05 ).The positive cells were lest at the 18th day with the values ( 75.57 ± 34.54) cells/5 fields ( t =6.362,P＜0.01 ).At the 25th day,positive cells increased to ( 117.63 ± 13.78) cells/5 fields,which still was lower than those of the control group ( t =4.068,P＜0.05 ).Western blot assay illuminated that with the prolong of immune time,MBP/β-actin ratio in optic nerve was gradually reduced and followed the same pattern at the 12th day( t =4.639,P＜0.05 ).At 18 days after immune in comparison with the control group,the expression of MBP/β-actin ratio in optic nerve was the least (t=8.427,P＜0.01). Conclusions MBP can be degraded in rat optic nerve.This is a further evidence that optic neuritis is a severe demyelination disease.It is clearly related to MS. Key words: Experimental allergic encephalomyelitis; Myelin basic protein; Multiple sclerosis; Optic neuritis