| Objective: Multiple sclerosis(MS) is a chronic inflammatory demyelinating disease of the central nervous system(CNS) white matter. Its pathogenesis has not been clearly yet. For the last few years, researches indicate that heredity, environmental factors work together to trigger autoimmune response, causing the damage of oligodendrocytes and demyelination, which is the primary pathological character in MS. Thus oligodendrocytes play an important role in the pathological process in MS. p38 MAPK is a member of mitogen-activated protein kinases(MAPKs) and reacts to various extracellular and cellular signals,modulate numerous cellular processes including proliferation, survival, motility, and differentiation, participates in different CNS diseases. Former researches have shown that p38 MAPK inhibition could reduce demyelination in experimental autoimmune encephalomyelitis(EAE) while other reports suggest that p38 MAPK promote regeneration of oligodendrocytes in peripheral and central nervous system. Based on all these findings, the specific effect of p38 MPK inhibitor on oligodendrocytes in EAE still needs further studies. Our reach aims to study influences of p38 MAPK on spinal myelin sheath, oligodendrocytes in EAE, exploring its protective mechanism, providing new ideas for treating MS.Methods:The animal model was established in female C57BL/6 mice with MOG35-55. 54 C57BL/6 mice were randomly divided into 3 groups: 18 mice in control group, 18 mice in EAE group, 18 mice in p38 MAPK inhibitor group. The mice in p38 MAPK inhibitor group were given SB203580(0.2mg/kg) by intraperitoneal injection everyday, the mice in control group and EAE group received equal volume of physiological saline everyday. The morbidity of the disease, weight, and clinical signs were observed daily. On day 20 ip, we execute the mice in 3 groups respectively. The pathological changes in lumbar enlargement of spinal cord were observed under light microscopy after HE staining, LFB staining and under transmission electron microscope(TEM).Tissue was also stained with immunohistochemisty(IHC) to observe the distribution of the p38, p-p38 and olig2 immunopositive cells to explore the influence of p38 MAPK inhibitor on oligodendrocytes. All datum were statistically analyzed by SPSS 13.0 software. The incidence rates were represented by percentage; the method for the comparison was chi square test. Measurement data were expressed as mean±standard deviation. The statistical method for comparisons of several groups was one-way ANOVA. Dunnett-t test was used for the comparisons between groups. P value <0.05 was considered statistically significant.Results:1 No mice in control group have disease. Compared to EAE group, the mobility, weight loss and mean clinical score of the mice in p38 MAPK inhibitor group were significantly lower(P<0.05).2 HE staining: Compared EAE group, p38 MAPK inhibitor group with control group, inflammatory cells significantly increase in peak period of incidence(P<0.05). Compared p38 MAPK inhibitor group with EAE group, inflammatory cells decrease clearly(P<0.05).3 LFB staining: The sections of EAE group showed varying demyelination area in peak period of incidence; The sections of p38 MAPK inhibitor group, showed some thinner myelin sheath and small demyelination area in peak period of incidence.4 Transmission electron microscope: peak period of incidence group on the sections of EAE group, the myelin sheath showed very loose layer structure, some showed disaggregated, broken, deficiency, the axon showed atrophy and degeneration, the structure became unclear; while on the sections of the p38 MAPK inhibitor group, the myelin sheath showed a little loose, less disaggregation and broken, minority of axon degeneration, the structure was clear.5 IHC of p38: The mean number of p38 immunopositive cells in each group has no significant difference(P>0.05).6 IHC of p-p38: The mean number of p-p38 immunopositive cells in EAE group are much more than the control group, the difference is significant(P<0.05), however the mean number of p-p38 in SB203580 group and in control group are similar, the number of p-p38 immunopositive cells in SB203580 group compared with that in EAE group is significantly decreasing(P<0.05).7 IHC of olig2: The mean number of olig2 immunopositive cells in p38 MAPK inhibitor group were more than EAE group(P<0.05).Conclusions:1 p38 MAPK inhibitor could lower incidence of EAE, delay disease onset, and alleviate the clinical severity of EAE.2 p38 MAPK inhibitor could lessen inflammatory infiltration in EAE, decrease the myelin sheath deletion caused by immoderate inflammatory stimulation, promote remyelination, recover axon integrity and neural conductor function.3 p38 MAPK inhibitor could suppress the activity of p38 by blocking its phosphorylation.4 The reason for that p38 MAPK inhibitor helps to alleviate the clinical syndrome of EAE may be it can promote early oligodendrocyte progenitor cells to differentiate into oligodendrocytes. |
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