关键词: 刚地弓形虫, 弓形虫脑病, 铁代谢, 氧化应激, Chinese 1优势基因型, 小鼠

Abstract: Objective　To investigate the effect of Toxoplasma gondii Chinese 1 genotype infections on host brain iron metabolism and brain damages. Methods　Twenty C57BL/6 mice, each weighing 15 to 17 g, were randomly divided into the control and infection groups, of 10 mice in each group. Each mouse in the infection group was injected intraperitoneally with 4 000 tachyzoites of the TgCtwh3 isolate with Chinese 1 genotype, while each mouse in the control group was injected with an equal amount of sterile phosphate⁃buffered saline (PBS). All mice were sacrificed 6 day post⁃infection and brain tissues were sampled. The iron levels were measured in mouse brain specimens using inductively coupled plasma mass spectrometry (ICP⁃MS). The differentially expressed genes were determined between the experimental and control groups using RNA chips and Gene Ontology (GO) term enrichment analysis of differentially expressed genes was performed. The mRNA expression of Toxoplasma gondii surface antigen 1 (TgSAG1) gene and some Zrt⁃ and Irt⁃like protein (ZIP) family member coding genes was detected by quantitative real⁃time PCR (qPCR) assay. The ultrastructure of the hippocampus dentate gyrus in mouse brain specimens was observed using optical and electronic microscopy. The glutathione peroxidase 4 (GPx4) expression was determined using Western blotting, and malondialdehyde (MDA) level was measured using thiobarbituric acid (TBA) test. In addition, the optical density (OD) of vascular endothelial growth factor (VEGF) protein was measured using immunohistochemistry. Results　Optical microscopy showed cell necrosis in the hippocampus dentate gyrus of mouse brain specimens in the infection group, and electronic microscopy cytoplasmic vacuolization, nuclear atrophy and necrosis, disruption of cristae mitochondriales and increased autophagosome levels in the mouse brain hippocampus specimens in the infection group. The iron level was significantly greater in mouse brain specimens in the infection group than in the control group [(32.92 ± 0.90) µg/g vs. (37.72 ± 1.10) µg/g; t = 3.397, P < 0.01]. RNA chips revealed 721 up⁃regulated genes and 276 down⁃regulated genes in mouse brain specimens between the infection and control groups, and the differentially expressed genes were significantly enriched in metal ion binding ability (molecular function). Elevated expression of metal element transporter ZIP2 mRNA (t = 8.659, P < 0.05), reduced GPx4 expression [(1.046 ± 0.025) vs. (0.720 ± 0.101); t = 3.129, P < 0.01], increased MDA level [(4.37 ± 0.33) nmol/mgprot vs. (5.93 ± 0.54) nmol/mgprot; t = 2.451, P < 0.05], and up⁃regulated mean OD of VEGF protein [(0.348 3 ± 0.017 8) vs. (0.490 6 ± 0.010 5); t = 6.641, P < 0.01] were found in mouse brain specimens in the infection group than in the control group. Conclusions　Chinese 1 genotype T. gondii infection results in iron accumulation in brain tissues, reduced antioxidant ability and elevated levels of oxidative stress in mice, suggesting that T. gondii infection may cause brain damages through affecting iron metabolism in host brain tissues.

Key words: Toxoplasma gondii, Cerebral toxoplasmosis, Iron metabolism, Oxidative stress, Chinese 1 genotype, Mouse