Th17: a new participant in gut dysfunction in mice infected with Trichinella spiralis

Abstract

Trichinella spiralis infection in rodents is a well-known model of intestinal inflammation associated with hypermotility. Our aim was to elucidate if Th17 cells were involved in the development of gastrointestinal hypermotility in this experimental model. Intestinal inflammation was observed by hematoxylin-eosin (HE) staining. Jejunal smooth muscle contractility was investigated in response to acetylcholine (Ach). The effects of IL-17 on jejunum smooth muscle contractility were explored. Flow cytometry was used to analyze the proportion of Th17 cells in jejunum. The levels of IL-17, IL-23, and TGF-beta1 in jejunum were measured by Western blot. Our results showed that the inflammation in jejunum was severe at 2 weeks postinfection (PI), which was not discernible at 8 weeks PI. Jejunal smooth muscle contractility was increased at 2 weeks PI and kept higher at 12 weeks PI. The proportion of Th17 cells and the expression of IL-17 were upregulated in jejunum at 2 weeks PI and normalized at 8 weeks PI. When jejunual smooth muscle strips were cultured with IL-17, contractions elicited by Ach were enhanced in a concentration-dependent manner. Our data suggest that Th17 cells are increased during acute infection with Trichinella spiralis and IL-17 may contribute to jejunal muscle contractility in mice.

Figure 1

H&E staining of jejunum in (a) control mice and mice infected with T. spiralis at (b) 2 weeks PI, (c) 8 weeks PI, and (d) 12 weeks PI (magnification 200x): the mucosal damage was sever at 2 weeks PI, characterized by hyperemia, swelling, and significant decrease in villus height. Mixed infiltration of neutrophil cells, eosinophil cells, and lymphocytes affected the mucosal and submucosal layers.

Figure 2

Responses of the jejunal longitudinal muscle to 10⁻⁶ M Ach-induced contraction. Responses were obtained from tissues stretched when optional tention was applied. The upper and lower whiskers indicate the maximum and minimum values, respectively. Box lines represent the 25th (bottom), 50th (middle), and 75th (top) percentile value; ∆P < .05 indicate differences between control and Trichinella spiralis-infected mice.

Figure 3

(a) Percentages of Th17 cells in jejunum of control and infected mice at different time points. The proportion of Th17 at 2 weeks was significant higher than control, but normalized at 8 and 12 weeks. *P < .01 indicate differences between control and Trichinella spiralis-infected mice. (b) Representative flow cytometric analyses in jejunum of control and infected mice at different time points.

Figure 4

Expressions of IL-17, IL-23, and TGF-β ₁ in jejunum in control and infected mice at various time points. Protein expression was assessed by western blotting. *P < .01 indicate differences between control and Trichinella spiralis-infected mice.

Figure 5

Correlation of IL-17 expression and muscle contraction assessed by responses of the longitudinal muscle to 10⁻⁶ M Ach-induced contraction in jejunum. IL-17 expression is associated significantly with the contraction of jejunal longitudinal muscle (r = 0.762, P = .028) at 2 weeks PI.

Figure 6

Concentration-dependent change in contractions induced by acetylcholine (10⁻⁶ M) shows the effects on acetylcholine-induced contractions of various concentrations of IL-17 (0.1–10 ng/mL) in a 2-day culture. *P < .01 indicate significantly different from control (white column).