Effects of valproic acid on rats with experimental autoimmune encephalomyelitis and its immuno-modulatory mechanism / 中华微生物学和免疫学杂志

ABSTRACT

Objective To investigate the effects of valproic acid ( VPA ) on SD rats with experimental autoimmune encephalomyelitis ( EAE) and its possible immunomodulatory mechanism .Meth-ods Fifty female Sprague-Dawley ( SD) rats were randomly divided into five groups by random digit table , including control group (n=10), EAE group(n=10), low dose VPA treated group (100 mg/kg, n=10), median dose VPA treated group (300 mg/kg, n=10) and high dose VPA treated group (600 mg/kg, n=10).The SD rat model of EAE was induced by immunizing with a guinea pigs′spinal cord homogenate (GPSCH).Normal saline and various doses of VPA were given to rats in according groups twice a day from day 0 to day 19 ( close to the peak stage of EAE ) .The severity of EAE was scored according to the signs and symptoms.Pathological changes were observed through Hematoxylin-Eosin staining, and then the degrees of inflammatory infiltration were evaluated .The numbers of activated neuroglia that expressed Iba-1 in cerebral and lumber cords were counted by immunohistochemistry .The expression of IFN-γ, IL-17 and IL-10 in cer-ebral and lumber cords were measured by ELISA .Results Compared with EAE group , rats in the low, me-dian and high dose VPA treated groups had lower incidence of EAE and prolonged latency , but only the me-dian dose treated group showed significant alleviation in clinical symptoms (P<0.05).Both the median and the high dose treated group showed decreased inflammatory cell infiltration in CNS (P<0.05).Immunohisto-chemistry results showed that the numbers of activated microglia were significantly inhibited in rats treated with median and high dose of VPA in comparison with those in EAE group (P<0.05).Results of ELISA demonstrated that the expression of IFN-γand IL-17 in both median and high dose VPA treated groups were significantly decreased compared with those in EAE group (P<0.05), but only the median dose treated group showed a remarkably increased expression of IL-10 (P<0.05).Conclusion VPA, especially medi-um dose of VPA ( 300 mg/kg ) , had neuroprotective effects on rats with EAE .The possible mechanism might be associated with the inhibited activation of microglia and the increased percentage of anti -inflammato-ry cytokines .