Anhui Provincial Laboratories of Pathogen Biology and Zoonoses, Department of Microbiology and Parasitology, Anhui Medical University, Hefei, China.
Infect Immun. 2012 Jun;80(6):2121-32. doi: 10.1128/IAI.06295-11. Epub 2012 Apr 2.
Toxoplasma gondii infection in pregnant women may result in abortion or in fetal teratogenesis; however, the underlying mechanisms are still unclear. In this paper, based on a murine model, we showed that maternal infection with RH strain T. gondii tachyzoites induced elevated production of reactive oxygen species (ROS), local oxidative stress, and subsequent apoptosis of placental trophoblasts. PCR array analysis of 84 oxidative stress-related genes demonstrated that 27 genes were upregulated at least 2-fold and that 9 genes were downregulated at least 2-fold in the T. gondii infection group compared with levels in the control group. The expression of NADPH oxidase 1 (Nox1) and glutathione peroxidase 6 (Gpx6) increased significantly, about 25-fold. The levels of malondialdehyde (MDA) and 8-hydroxydeoxyguanosine (8-OHdG) increased significantly with T. gondii infection, and levels of glutathione (GSH) decreased rapidly. T. gondii infection increased the early expression of endoplasmic reticulum stress (ERS) markers, followed by cleavage of caspase-12, activation of ASK1/JNK, and increased apoptosis of trophoblasts, both in vivo and in vitro. The apoptosis of trophoblasts, the activation of caspase-12 and the ASK1/JNK pathway, and the production of peroxides were dramatically inhibited by pretreatment with N-acetylcysteine (NAC). The upregulation of Nox1 was contact dependent and preceded the increase in levels of ERS markers and the activation of the proapoptosis cascade. Thus, we concluded that apoptosis in placental trophoblasts was initiated predominantly by ROS-mediated ERS via activation of caspase-12, CHOP, and the JNK pathway in acute T. gondii infection. Elevated ROS production is the central event in T. gondii-induced apoptosis of placental trophoblasts.
刚地弓形虫感染孕妇可导致流产或胎儿畸形，但具体机制仍不清楚。本研究通过建立鼠弓形虫 RH 株急性感染模型，发现母鼠感染弓形虫速殖子后，胎盘滋养层细胞发生氧化应激相关的细胞凋亡。应用基因芯片技术对 84 个与氧化应激相关的基因进行检测，结果显示，与对照组相比，感染组有 27 个基因表达上调 2 倍以上，9 个基因表达下调 2 倍以上。NADPH 氧化酶 1（Nox1）和谷胱甘肽过氧化物酶 6（Gpx6）表达显著上调，分别上调 25 倍和 3 倍。丙二醛（MDA）和 8-羟基脱氧鸟苷（8-OHdG）含量明显增加，谷胱甘肽（GSH）含量迅速下降。弓形虫感染后早期内质网应激（ERS）标志物表达增加，继而引发半胱氨酸天冬氨酸蛋白酶 12（caspase-12）的切割、凋亡信号调节激酶 1（ASK1）/c-Jun N 末端激酶（JNK）通路的激活和滋养层细胞凋亡，这种效应在体内和体外实验中均得到证实。用 N-乙酰半胱氨酸（NAC）预处理可明显抑制滋养层细胞凋亡、caspase-12 及 ASK1/JNK 通路的激活和过氧化物的产生。Nox1 的上调呈接触依赖性，且先于 ERS 标志物的增加和促凋亡级联反应的激活。因此，我们认为急性弓形虫感染时，胎盘滋养层细胞的凋亡主要由 ROS 介导的 ERS 通过激活 caspase-12、C/EBP 同源蛋白（CHOP）和 JNK 通路引发。ROS 的大量产生是弓形虫诱导滋养层细胞凋亡的中心事件。
