| Objective:Multiple sclerosis (MS) is an inflammatory demyelination disease of the central nervous system (CNS) that causes relapsing and progressive neurological impairment. The incidence of MS in female was much higher than that in male, and it usually happened on adults. At present the pathogenesis of MS is still unclear, and there has no specific remedy for it. So it is our main aim that we investigate the pathogenesis of MS and seek effective therapy for MS by setting up an animal model.There are many factors which are associated with the pathogenesis of MS, and the immunity is a critical one.Before, we believed that the incidence of MS was mediated by Th1 cell, but recently the Th17 cell which is related with IL-23 and can secrete IL-17 is thought to play an more important role in the pathogenesis of MS than Th1 cell. The mechanism of action of the Th17 cell is still needed to research.Edaravone is a free radical scavenger which potently reduces hydroxyl radicals (OH?). It has been used as an anti-oxidative agent in acute ischemic brain disorders. Recently, there are some observations suggest that the active involvement of microglia may have a pathological role in both demyelinating and neurodegenerative disorders. Thus, agents that suppress the production of NO and ROS by activated microglia may be useful in the treatment of such pathological conditions. Edaravone has antioxidant and neuroprotective effects on neuronal cell death induced by SIN-1 and activated microglia. It may function as a neuroprotective agent counteracting oxidative neurotoxicity arising from activated microglia,as occurs in either inflammatory or neurodegenerative disorders of the central nervous system.In our study, we administrate edaravone to the rats of experimental autoimmune encephalomyelitis (EAE)—an animal model of MS, in order to investigate the therapeutic potential in treatment of neuroinflammatory diseases like MS.Meanwhile, we checked out the serum levels of IL-17 and IL-23,which could help us to investigate the mechanism of action of the Th17 cell in MS/EAE.Methods:Ninety healthy female Wistar rats weighing 180-200g were divided randomly into five groups: normal control group(18 rats), EAE group(18 rats), dexamethasone(DXM) group(18 rats), low dose of edaravone group(18 rats) and high dose of edaravone group(18 rats). All the groups were divided into three groups: 7 day group, 16 day group, 23 day group, separately. All the experimental rats were immunized subcutaneously in the four footpads and back with emulsion 0.5ml, which including fresh guinea pig spinal cord homogenate (GPSCH) as antigen, emulsified with an equal volume of complete Freund's adjuvant (CFA) containing Mycobacterium tuberculosis 6mg/ml. Clinical signs of EAE were assessed a minimum of twice daily by two investigators. Scores were assigned on the basis of the following symptoms: 1, tail weakness; 2, tail weakness plus limb asthenia;3, mild limb paralysis; 4, severe limb paralysis; 5, moribund/dead. EAE group, DXM group, low dose of edaravone group and high dose of edaravone group were injected intraperitoneal respectively NS 0.5ml/d, DXM 5mg·kg-1·d-1, edaravone 3mg·kg-1·d-1, edaravone 10mg·kg-1·d-1. These treatments were started on the first day of immunization and continued daily for the duration of the experiment, and EAE group left untreated. During the experiment, the mean maximal score of animals at different time point and the incidence of disease were observed as results.The sera from rats were achieved and were detected the levels of IL-17 and IL-23 with an enzyme-linked immunosorbent assay in order to discuss the role of them play in the pathogenesis of EAE/MS.Rats were sacrificed after anesthesia with intraperitoneal injection. Tissues of the brain and spinal cord were fixed with 4% formalin less than 7 days, then the tissues were embedded in paraffin and sectioned at 5μm thickness. These sections were stained with HE to assess lymphocyte infiltration and inflammation.Results: 1 The morbidity of disease in different groupMorbidity of high dose of edaravone group and DXM group were significantly lower than those of EAE group (p <0.05).2 Clinical profile of EAE in different groupNeurological deficits scores of high dose of edaravone group and DXM group were significantly lower than those of EAE group (p<0.05).3 Neuropathological findingsThe results demonstrated that some monocytes infiltration was observed in the tissues of brains and spinal cords before the clinical signs emerging. The degree of infiltration was associated with the severity of EAE. The extent of inflammation of high dose of edaravone group and DXM group were significantly lower than those of EAE group (p <0.05).4 The serum levels of IL-17 and IL-23The serum levels of IL-17 in the 7 day group and 16 day group of EAE group were higher than that of normal control group (p<0.05); The serum levels of IL-23 in the 16 day group of EAE group were higher than that of normal control group (p <0.05).The levels of IL-17 and IL-23 in serum were closely related to the action of EAE rats.Conclusions:1 The serum levels of IL-17 and IL-23 correlated with the severity and activity of EAE. With the development of the disease, the levels of IL-17 and IL-23 kept increasing. In the recovery of EAE, their levels had declined.2 Edaravone reduces the morbidity, and protects the rats from the severity of the disease.3 Edaravone can reduce the serum levels of IL-17 and IL-23, and then reduces the lymphocyte infiltration and inflammation in the CNS of EAE rats.4 Edaravone has good safty and tolerance compared with DXM. These results suggest that edaravone may be used in the demyelinating diseases like MS in the future.
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