Relationship Between Glucocorticoid And Cytokine With Synaptic Impairment In Hippocampus And Protection Of Anti-inflammatory Cytokine IL-10

Effects of chronic stressed level of glucocorticoid treatment on neurons and synapses in hippocampusTo explore the effect of chronic stressesd level of glucocorticoidon hippocampus, the rats in treatment group were provided with hydrocortisone (cortisol) 10mg/kg/day in drinking water for 21 days. Then the expressions of Caspase-3, Synaptophysin (Syn) and Neurogranin (Ng) in hippocampus of two groups were observed by immunohistochemistry staining and assayed by Western blot. The results are as follows: ① In the treatment group, many neuronal atrophy was seen in hippocampus, and Caspase-3 immunoreactive positive cells were not seen or just were seen occasionally in CA regions and dentate gyrus, but many Caspase-3 immunoreactive positive cells were seen in subiculum and retrosplenial cortex; ②The results of Western blot showed the expression levels of Syn (0.5512±0.0540) and Ng (1.3375±0.3317) in the treatment group were significantly lower than those of the control group (P<0.05), which were 1.2197±0.3443 and 1.9330±0.3450, respectively. The results indicated that administration with chronic stressesd level of glucocorticoid may damage the functions of hippocampus by resulting in caspase-3-independent degeneration of neurons in hippocampus and changes in synapse efficacy and number in hippocampus. Study on the relationship between deficit in thymus and impaired hippocampus objective: To explore the effects of deficit in thymus on the hippocampus. Methods: Six 10～12 weeks and six 22～24 weeks of age of male nude mice (Balb/c-nu/nu mice) and the same age and the same number of male healthy mice (normal Balb/c mice) were randomly selected as experimental groups or control groups. Then the contents of proinflammatory cytokines IL-2, IFN-γ and TNF-α in serum and the hippocampus of both groups were measured by ELISA method and the expression levels of Synaptophysin (Syn) and Neurogranin (Ng) in the hippocampus of both groups were analyzed by Western blot method. Results: ① The contents of proinflammatory cytokine IFN-γ (184.98±81.69pg/ml) and TNF-α(113.16±6.60pg/ml) of serum in experimental group of 10～12 weeks of age were higher significantly than those in control group of the same age, which were 71.81±9.76pg/ml (P<0.05) and 91.38±6.14 pg/ml (P<0.01), respectively. (2) The contents of proinflammatory cytokine IFN-γ of the hippocampus in experimental group of 22～24 weeks of age (6.97±0.64pg/mg hippocampus, wet weight) was higher significantly than that in control group of the same age (5.72±0.31pg/mg hippocampus, wet weight, P<0.01); ③ the expression level of Syn was lower significantly in experimental group of 22～24 weeks of age (0.5513±0.1096) than that in control group of the same age (0.7044±0.0882, P<0.05), while the expression level of Ng was higher significantly in experimental group of 22～24 weeks of age (1.7484±0.2191) than that in control group of the same age (1.3030±0.2607, P<0.01). Conclusion: Deficit in thymus may affect the functions of the hippocampus adversely by increasing the contents of proinflammatory cytokines. IL-10 may prevent damage of synapse in hippocampus caused by glucocorticoidObjective: to investigate whether IL-10 may prevent damage of synapse in the hippocampus caused by glucocoticoids (GCs), and reveal the potential mechanism of GCs effect adversely on the hippocampus by enhancing pro-inflammatory cytokines. Methods: ①Primary hippocampal neurons cultured were divided into control group and group treated with cortisol 8×10^-6 mol/L, and then the expression levels of IFN-γ mRNA of both groups were analyzed by RT-PCR method. ②After pIRES-hrGFP-2a -IL-10 eukaryotic expression Plasmid was constructed, the plasmid was injected into the right lateral ventricle of each rat (80ng in 20μl) by intracerebroventricular cannuia five times at 4-day intervals (i.e., on day 1, 5, 9, 13 and 17) while the rats were administered with cortisol dissolved in drinking water (40mg/L) at the same time for 21 days (i.e., from day 1 to 21). For the control group, empty vector instead of the expression plasmid pIRES-hrGFP-2a-IL-10 was injected to the same place. Then the expression levels of Synapsin I and Neurogranin (Ng) in the hippocampus of both groups were assayed by Western blot method. Results: ① IFN-γ mRNA expression level of primary hippocampal cell cultures in the experimental group treated with cortisol (0.5940±0.0448, n=4) was significantly higher than that in the control group (0.4237±0.0915, n=4), p <0.05; (2) The expression levels of Synapsin I protein (2.0171±0.2527) and Neurogranin protein (1.9653 ±0.0843) in the experimental group (n=7) treated with plasmid pIRES -hrGFP-2a-IL-10 were markedly higher than those in the control group treated with empty plasmid pIRES-hrGFP-2a, which were 1.1440±0.2152 and 1.5344±0.1763, respectively (n=7), p<0.01. Conclusion: GCs may effect adversely on the hippocampus by enhancing pro-inflammatory cytokines, and anti-inflammatory cytokine IL-10 may prevent damage of synapse in the hippocampus caused by GCs.