地塞米松对大鼠腹腔巨噬细胞抗弓形虫作用的影响

The effect of dexamethasone on the resistance of rat peritoneal macrophages to Toxoplasma gondii

目的研究地塞米松(Dexamethasone,DXM)对大鼠腹腔巨噬细胞抗弓形虫感染的影响。方法采用瑞-姬染色观察弓形虫在与DXM共孵育大鼠腹腔巨噬细胞内的增殖;以半定量RT-PCR法检测与DXM共孵育大鼠腹腔巨噬细胞IFN-γ、TNF-α和IL-2mRNA的表达,以ELISA法检测细胞培养上清中IFN-γ、TNF-α和IL-2的含量。结果弓形虫在DXM孵育的腹腔巨噬细胞内大量增殖,其弓形虫密度0h为(37±7)个/100个细胞,而24h时为(173±32)个/100个细胞(P<0.01);与DXM共孵育大鼠腹腔巨噬细胞24h时的IL-2、IFN-γ和TNF-αmRNA及其蛋白的表达与对照组相比均明显降低(P<0.01),如:DXM孵育组的TNF-α(187.52±39.41pg/ml)与对照组(115.43±22.46pg/ml)相比差异显著(P<0.01)。结论 DXM可诱发腹腔巨噬细胞易感弓形虫,其机制可能与细胞因子IFN-γ、TNF-α和IL-2表达下调有关。

Objective To study the effect of dexamethasone （DXM） on the resistance of rat peritoneal macrophages to To.roplasrna 14ondii. MethodsThe growth of T. gondii in rat peritoneal macrophages treated with DXM was analyzed u sing Wright-Giemsa staining. IFN-α, TNF-γ, and IL-2 mRNA expression by peritoneal macrophages treated with DXM was determined using a semiquantitative reverse transcription polymerase chain reaction （RT-PCR）, and cytokine concen trations in culture supernatants were measured using ELISA. Results The growth rate of T. gondii increased signifi cantly in rat peritoneal macrophages treated with DXM. The density of T. gondii was （37--7）/100 cells at 0 h and （173 -32）/100 cells at 24 h （P〈0.01）. IL-2, IFN-γ, and TNF -α mRNA expression and protein expression were significantly lower in rat peritoneal macrophages incubated with DXM compared to mRNA expression and protein expression in the control group at 24 h （P〈0.01）. As an example, TNF -α was 187.52±39.41 pg/ml in macrophages treated with DXM but 115.43±22.46 pg/ml in the control group, representing a significant difference （P〈0.01）. Conclusion DXM can induce susceptibility to T. gondii in macrophages. This may be because DXM inhibits expression of the cytokines IFN-γ, TNF-α, and IL-2.