关键词: 弓形虫, 感染小鼠, 小肠, 半乳糖凝集素

Abstract:

Objective To investigate the regulatory effect of galectin-receptor interaction on the small intestine immunopathology of Toxoplasma gondii-infected mice. Methods Eighteen female BALB/c mice were randomly divided into 4 groups: 4 mice in uninfected group (naive group), 4 mice in lactose group (lactose group), 5 mice in T. gondii infection group (Tg group) and 5 mice in T. gondii infection + lactose group (Tg+lactose group). Each mouse in the Tg group and the Tg+lactose group was intraperitoneally (i.p.) injected with 1 000 tachyzoites of T. gondii RH strain, while the naive group and lactose group were i.p. injected with 0.2 ml PBS. Starting from day 0 post infection, each mouse in the Tg+lactose group and the lactose group was i.p. injected with 0.2 ml 0.2 mol/L of lactose, while each mouse in the naive group and the Tg group was i.p. injected with an equal volume of PBS, once in the morning and once in the evening for 7 consecutive days. After infection with T. gondii, the mice survival time in each group was recorded. The mice were euthanized on the 7th day after infection to collect middle segment of jejunum from each mouse for prepareing paraffin sections, which were stained with hematoxylin and eosin (HE) to observe the pathological changes; from the lower segment of jejunum of each mouse, total RNA was extracted and reverse-transcribed, and used in quantitative real-time reverse transcription PCR (qRT-PCR) with β-actin as an internal reference gene to detect the relative mRNA expression level of surface antigen 1 (SAG1), galectin-3, galectin-9, T cell immunoglobulin mucin 3 (Tim-3), leukocyte differentiation antigen 137 (CD137), interleukin 12 (IL-12), interferon-γ (IFN-γ), IL-10, IL-4, transforming growth factor β (TGF-β), chemokine receptor 2 (CCR2) and chitinase 3 like molecule 3 (Ym1). Results After infection with T. gondii, there was no mice died in the naive group and the lactose group. The survival time of the mice in the Tg group was 182-188 h, and the survival time of the mice in the Tg+lactose group was 180-182 h; the difference of the survival time between the two groups was statistically significant (χ² = 19.52, P < 0.05). HE staining showed no inflammation in the mice jejunal tissue in the naive group and lactose group. Shortened intestinal villus, shallower intestinal crypts, necrosis of epithelial cells at the top of villi and inflammatory cell infiltration in the intestinal mucosa were observed in the mice small intestine from the Tg group and Tg+lactose group. Compared with the Tg group, the pathological change of the mice small intestine in the Tg+lactose group was more severe. The qRT-PCR results showed that the relative mRNA expression of SAG1 in the mice small intestine of the Tg+lactose group was 9.17 ± 1.65, which was higher than that in the Tg group (1.00 ± 0.84, t = 4.40, P < 0.05). The relative mRNA expression levels of galectin-3 in the mce small intestine of the naive group, lactose group, Tg group, and Tg+lactose group were 1.00 ± 0.28, 1.71 ± 0.31, 2.46 ± 1.11, and 7.10 ± 1.57, respectively (F = 10.15, P < 0.01). The mRNA expression levels of galectin-9 in the 4 groups were 1.00 ± 0.31, 1.44 ± 0.26, 3.21 ± 1.01, and 7.00 ± 1.08, respectively (F = 14.53, P < 0.01). The mRNA expression levels of Tim-3 in the 4 groups were 1.00 ± 0.12, 0.88 ± 0.28, 1.64 ± 0.31, and 4.89 ± 0.69, respectively (F = 19.15, P < 0.01). The mRNA expression levels of CD137 in the 4 groups were 1.00 ± 0.42, 1.03 ± 0.30, 0.89 ± 0.11, and 3.84 ± 0.77, respectively (F = 8.46, P < 0.01). The mRNA expression levels of IL-12 in the 4 groups were 1.00 ± 0.35, 1.14 ± 0.56, 12.37 ± 4.43, and 18.42 ± 3.89, respectively (F = 10.18, P < 0.01). The mRNA expression levels of IFN-γ in the 4 groups were 1.00 ± 0.56, 1.65 ± 0.53, 5.57 ± 1.84, and 21.26 ± 6.48, respectively (F = 10.38, P < 0.01). The mRNA expression levels of IL-10 in the 4 groups were 1.00 ± 0.20, 1.10 ± 0.25, 8.65 ± 2.52, and 21.98 ± 3.96, respectively (F = 20.84, P < 0.01). The mRNA expression levels of IL-4, TGF-β, and CCR2 in the mice small intestine among the naive group, lactose group, Tg group, and Tg+lactose group had no statistically significant differences (F = 1.09, 4.74, and 2.03, P > 0.05). Ym1 mRNA expression was not detected in the naive group and lactose group, and Ym1 mRNA expression levels between the Tg group and the Tg+lactose group had no statistically significant difference (t = 0.24, P > 0.05). Conclusion Blockage of galectins-receptor interaction in mice infected with T. gondii leads to increased parasite burden in small intesting tissues, and aggravated pathological impairment, as well as upregulated expression of galectin-3, galectin-9, Tim-3, CD137, IL-10 and IFN-γ.

Key words: Toxoplasma gondii, Infected mice, Small intestine, Galectin