Expansion of Intestinal Secretory Cell Population Induced by Listeria monocytogenes Infection: Accompanied With the Inhibition of NOTCH Pathway

Abstract

Listeria monocytogenes, as a model organism, is a causative agent of enteric pathogen that causes systemic infection. However, the interaction of L. monocytogenes and small intestinal epithelium has not been fully elucidated yet. In this study, mice and intestinal organoids were chosen as the models to investigate the influence of L. monocytogenes infection on the intestinal secretory cells and its differentiation-related pathways. Results confirmed the phenomenon of intestinal damage that L. monocytogenes infection could lead to villi damage in mice, which was accompanied by the increase of TNF-α production in jejunum as well as lipopolysaccharide (LPS) secretion in serum. Moreover, it was demonstrated that L. monocytogenes infection increased the number of goblet and Paneth cells in mice and intestinal organoids and upregulated the expression of Muc2 and Lyz. Furthermore, L. monocytogenes decreased the relative expression of Notch pathway-related genes (Jag1, Dll4, Notch1, and Hes1) while upregulating the relative expression of Math1 gene in mice and intestinal organoids. This indicated that L. monocytogenes infection caused the inhibition of Notch pathway, which may be the reason for the increased number of goblet and Paneth cells in the intestine. Collectively, these results are expected to provide more information on the mechanism of L. monocytogenes infection in the intestine.

Keywords: Listeria monocytogenes; Paneth cell; goblet cell; intestine; notch pathway.

Figure 1

The intestinal pathological changes in mice after L. monocytogenes infection. CK, control, orally challenge with PBS; LM, L. monocytogenes-infected group. (A) Histopathological changes in jejunum tissues were examined by hematoxylin eosin (HE) staining. (B) The concentration of LPS was measured in serum. (C) The concentration of TNF-α was measured in jejunum. Data is presented as mean ± SD. **P < 0.01. Data combined from at least three independent experiments unless otherwise stated.

Figure 2

The influence of L. monocytogenes on the differentiation of intestinal secretory cells in mice. CK, control, orally challenge with PBS; LM, L. monocytogenes-infected group. (A) Confocal microscopy analysis of mucus stained with UEA-1 in jejunum sections. (B) Confocal microscopy analysis of lysozyme in jejunum sections. (C) Western blot of lysozyme in jejunum. (D) mRNA levels of Muc2 from homogenized jejunum samples. (E) mRNA levels of Lyz from homogenized jejunum samples. Data is presented as mean ± SD. *P < 0.05, **P < 0.01. Data combined from at least three independent experiments unless otherwise stated.

Figure 3

The influence of L. monocytogenes on the Notch pathway in mice. CK, control, orally challenged with PBS; LM, L. monocytogenes-infected group. (A-E) The expression of Jag1, Dll4, Notch1, Hes1 and Math1 genes were determined by quantitative RT-PCR and normalized by the expression of GAPDH. Data is presented as mean ± SD. *P < 0.05, **P < 0.01. Data combined from at least three independent experiments unless otherwise stated.

Figure 4

The influence of L. monocytogenes on the differentiation of intestinal secretory cells. CK, control; LM, L. monocytogenes-infected group. (A) The location of L. monocytogenes in organoids. (B) Confocal microscopy analysis of UEA-1+ cells in organoids. (C) Confocal microscopy analysis of Lyz+ cells in organoids. (D) Western blot of lysozyme in organoids. (E) mRNA levels of Muc2 from organoids samples. (F) mRNA levels of Lyz from organoids samples. Data is presented as mean ± SD. *P < 0.05, **P < 0.01. Data combined from at least three independent experiments unless otherwise stated.

Figure 5

The influence of L. monocytogenes on the Notch pathway in organoids. CK, control; LM, L. monocytogenes-infected group. (A-E) The expression of Jag1, Dll4, Notch1, Hes1 and Math1 genes were determined by quantitative RT-PCR and normalized by the expression of GAPDH. Data is presented as mean ± SD. *P < 0.05, ***P < 0.001. Data combined from at least three independent experiments unless otherwise stated.