弓形虫感染对大鼠海马BDNF和NMDA表达的影响

目的观察弓形虫慢性感染对大鼠海马组织脑源性神经营养因子(BDNF)和N-甲基天冬氨酸受体(NMDA)亚单位NR2A、NR2B表达的影响。方法将4w雄性Wistar大鼠随机分成3组:A组腹腔感染2 mL弓形虫速殖子2×107/mL;B组腹腔感染2 mL弓形虫速殖子2×105/mL和C组正常对照腹腔感染2 mL灭菌生理盐水。4w大鼠感染弓形虫速殖子9w后,应用免疫组化染色、原位杂交技术和图像处理方法分析海马BDNF,CA1、CA3和齿回状NR2A和NR2B的表达。结果BDNF的表达:弓形虫感染A组和B组大鼠免疫组化海马BDNF阳性染色颗粒均高于对照组,分别为(54.27±23.18)、(50.39±19.34)和(44.68±22.74)mm2(P<0.05);原位杂交显示弓形虫感染A组和B组大鼠脑组织中BDNF mR-NA表达均增加,海马阳性杂交信号高于对照组,为(0.13±0.02)、(0.12±0.02)和(0.09±0.01)(P<0.05);NR2A蛋白的表达:弓形虫感染A组和B组大鼠在CA3区表达的免疫反应灰度值较正常组相比较,差异均具有统计学意义(P<0.05),而在CA1区和齿状回表达的免疫反应灰度值与对照组相比较差异均无显著性(P>0.05)。NR2B蛋白的表达:弓形虫感染A组和B组大鼠在CA1和CA3区表达的免疫反应灰度值分别与对照组相比较,差异均具有统计学意义(P<0.05);而在齿状回表达的免疫反应灰度值差异无显著性(P>0.05)。结论弓形虫慢性感染大鼠海马组织BDNF和BDNF mRNA表达增强,弓形虫感染可影响其海马NMDA受体的表达。

Effect of Toxoplasma gondii infection upon the expressions of brain-derived neurotrophic factor and N-methyl-D-aspirate receptor in rat hippocampus

To investigate the effect of Toxoplasma gondii infection upon the expression of brain-derived neurotrophic factor(BDNF) mRNA and N-methyl-D-aspirate receptor(NMDA) subunits NR2A and NR2B,Wistar rats of 4 weeks old were randomly divided into 3 groups with 10 rats in each group in which 2 mL suspensions of T.gondii tachyzoits in the concentrations of 2×107/mL and 2×105/mL were injected intra-peritoneally to rats in group A and group B respectively,serving as the experimental groups,while 2 mL of sterile physiologic saline was injected intra-peritoneally in group C serving as the control group.Four weeks after injection,the expressions of BDNF mRNA and BDNF protein in the brain tissues were detected by in situ hybridization and immunohistochemical assay and the expressions of NR2A and NR2B immune activity in the hippocampal CA1,CA3 and DG were investigated by using computer-assisted image analysis system.Compared with the control group,the expression of BDNF protein in the hippocampus of the experimental groups was significantly enhanced [(64.27±23.18),(50.39±19.34) vs(44.68±22.74)/mm2,P<0.05].In addition,the increased expressions of BDNF mRNA in the hippocampus of the experimental groups were also demonstrated [(0.13±0.02),(0.12±0.02) vs(0.09±0.01);P<0.05].In the expression of the NR2A protein,their expressions in group A and B of rats were significantly lower than that of group C in CA3(P<0.05),but there was no significant change in CA1 and DG.In the expression of NR2B protein,the expressions in group A and B were also lower than that of group C in CA1 and CA3,and had no significant change in DG.It is evident that the expressions of BDNF mRNA and BDNF protein in hippocampal tissues were significantly increased following chronic infection with T.gondii,supporting the hypothesis that BDNF may be involved in the intrinsic neuro-protective mechanism.