Protective and therapeutic potentials of Trichinella spiralis larval antigen in murine induced colitis

Abstract

The intolerable side effects and clinical limitations of current conventional therapies for inflammatory bowel diseases (IBDs), there is a pressing need for alternative treatment options. Helminthes adapt immune responses of their hosts to reduce immune-mediated IBDs. The identification of the mechanism responsible for this beneficial effect on IBDs will provide another feasible approach to treating these diseases. The study was designed to investigate the possible protective and therapeutic role of Trichinella spiralis (T. spiralis) crude larval antigen extract in mice challenged with 2,4,6-trinitrobenzene sulfonic acid (TNBS) to induce colitis. Colitis was induced by intra-colonic instillation of TNBS (5 mg/ml in 50% ethanol), preceded or followed by intra-peritoneal (i.p.) administration of a single dose of T. spiralis crude larval antigen extract (100 µg/mouse). Colonic damage was assessed macroscopically and microscopically, and the expression of myeloperoxidase (MPO) was evaluated by immunohistochemistry. Colonic interleukin-10 (IL-10) and serum nitric oxide (NO) levels were also measured. Administration of T. spiralis crude larval antigen extract before induction of colitis reduced colitis severity as demonstrated by reduced colon weight-to-length ratio, improved macroscopic and microscopic scores, increased colonic IL-10 expression, and diminished colonic MPO protein expression. Moreover, there was a significant negative correlation between serum NO and colonic IL-10 levels. In addition, the preventive potential of T. spiralis crude larval antigen extract against TNBS-induced colitis was more prominent than its therapeutic effect. These findings support the hypothesis that T. spiralis has both prophylactic and therapeutic potential in inflammatory bowel diseases, which may be via an increase in IL-10 with predominance of its prophylactic role.

Keywords: Trichinella spiralis; Colitis; IL-10 and myeloperoxidase; NO; TNBS.

Fig. 1

Effects of T. spiralis larval antigen on body weight among study groups. Data are expressed as means ± S.E.M.; Significant difference between groups in comparison to negative control expressed as***P < 0.001; while ###P < 0.01 indicate difference versus the TNBS-induced colitis group without treatment.

Fig. 2

Effects of T. spiralis larval antigen on the spleen weight of all studied groups. Data are articulated as means ± S.E.M.; Significant difference between groups in comparison to negative control expressed as**P < 0.01, ***P < 0.001; while ###P < 0.01 indicate difference versus the TNBS-induced colitis group without treatment.

Fig. 3

Effects of T. spiralis larval antigen on colon weight/length ratio of all studied groups. Data are expressed as means ± S.E.M.; Significant difference between groups in comparison to negative control expressed as **P < 0.01, ***P < 0.001; while ###P < 0.01 indicate difference versus the TNBS-induced colitis group without treatment.

Fig. 4

Correlation between changes in colonic IL-10 concentrations and serum nitrite level. Upper panel: Comparison of serum nitrite levels in all studied groups. Middle panel: Comparison of colonic IL-10 levels in all experimental groups. Data were articulated as Mean ± S.E.M. (n = 10 mice/group). Significant difference between groups in comparison to negative control expressed as *P < 0.05; **P < 0.01; ***P < 0.001; while ###P < 0.01 indicate difference versus the TNBS-induced colitis group without treatment. Data were analyzed by one-way ANOVA, subsequently using Dunnett’s test. Lower panel: Negative correlation between local IL-10 levels in the colon and nitrite serum levels (r = − 0.955, P < 0.001).

Fig. 5

Colonic macroscopic appearance of all studied groups. (a) Negative control group; (b) Larva control group; (c) TNBS-induced colitis without treatment group; (d) Treatment (TNBS then larva) group; (e) Preventive (Larva then TNBS) group.

Fig. 6

Microscopic picture of H&E sections of mice colons of different groups (n = 10/group). (A) Vehicle control group: normal mucosal lining with goblet cells with low inflammatory grading; (B) Larva group: showing minimal destruction of the surface epithelial cells and moderate inflammatory cell infiltrate; (C) TNBS-induced colitis group: showing mucosal edema, hemorrhage, erosions, necrosis with acute inflammatory cell infiltration; (D) Treatment (TNBS then larva) group: showing mild erosion of the covering mucosa, moderate inflammatory cell infiltrate of the colonic wall; (E) Preventive (Larva then TNBS) group: showing no erosion or ulceration of the covering mucosa, mild inflammatory cell infiltrate of the colonic wall.

Fig. 7

Myeloperoxidase immunostaining of mice colons of different groups (n = 10/group). (A) Vehicle control group: showing few acute inflammatory cells as demonstrated by positive MPO cytoplasmic staining; (B) Larva group showing moderate MPO-positive acute inflammatory cells in the colonic wall; (C) TNBS-induced colitis group: showing dense MPO-positive acute inflammatory cells at all layers of the colonic wall ; (D) Treatment (TNBS then larva) group: showing mild MPO-positive inflammatory cell infiltrate in the colonic wall and (E) Prophylaxsis (larva then TNBS) group: showing moderate MPO-positive acute inflammatory cells in the colonic wall.