Transcriptional modulation of pattern recognition receptors in chronic colitis in mice is accompanied with Th1 and Th17 response

Abstract

Pattern recognition receptors (PRRs) may contribute to inflammatory bowel diseases (IBD) development due to their microbial-sensing ability and the unique microenvironment in the inflamed gut. In this study, the PRR mRNA expression profile together with T cell-associated factors in the colon was examined using a chronic colitis mice model. 8-12 week old C57BL/6 mice were exposed to multiple dextran sodium sulfate (DSS) treatments interspersed with a rest period to mimic the course of chronic colitis. The clinical features and histological data were collected. The mRNA expressions of colonic PRRs, T cell-associated components were measured. Finally, the colons were scored for Foxp3+ cells. During chronic colitis, the histological data, but not the clinical manifestations demonstrated characteristic inflammatory symptoms in the distal colon. In contrast to acute colitis, the expression of all Toll-like receptors (Tlrs), except Tlr5 and Tlr9, was unaffected after repeated DSS treatments. The expression of Nod1 was decreased, while Nod2 increased. After third DSS treatment, only the expressions of Tlr3 and Tlr4 were significantly enhanced. Unlike other PRRs, decreased Tlr5 and increased Tlr9 mRNA expression persisted during the chronic colitis period. As the colitis progress, only the mRNA expression of Ifnγ and Il17 staid increased during chronic colitis, while the acute colitis-associated increase of Il23, and Il10 and Il12 was abolished. Finally, increased histological score of Foxp3+ cell in colon was found during the chronic colitis period. This study provides an expression pattern of PRRs during chronic colitis that is accompanied by a Th1- and Th17 cell-mediated immune response.

Keywords: Inflammatory bowel disease; Th cell responses; Toll like receptors.

Fig. 1

An increased feces score was found after each DSS treatment, while bodyweight loss was only found after acute DSS treatment. A) The bodyweight changes of control and DSS-treated mice during repeated DSS treatment are illustrated in the figure. B) The increased fecal scores of DSS-treated mice as compared to control mice after the first DSS treatment until end of the experiment are shown (n = 18 during cycle 1 DSS treatment, n = 12 during cycle 2 DSS-treatment and n = 6 cycle 3 DSS treatment). C) The colon length (cm) /weight (mg) ratio was determined (n = 6 per group). All results are expressed as + SEM, * indicates significant different between control and DSS-treated group. # Indicates significant different between the DSS-treatment cycles ^{##, **} P < 0.01, ^*** P < 0.001.

Fig. 2

DSS treatment induces damage and cellular infiltration in the colon. Colons were collected for histological assessment as described in material and methods. A) Colonic histological score and B) representative histology staining photos of the colons derived from control or DSS-treated mice after each DSS treatment cycle are shown (n = 3 per group).

Fig. 3

DSS treatment induces neutrophil influx in the colon. Colons were collected for A) MPO concentration measurement in the proximal and distal colon and B) immunohistochemical assessment of Ly-6b+ cells. Representative histochemical staining picture of Ly-6b+ cells in the colons of C) control and D) DSS-treated mice during each DSS treatment cycle are shown. All results are expressed as + SEM n = 3, * indicates the significant different between control and DSS-treated group. # indicates the significant different between the DSS-treatment cycles ^{#, *} P < 0.05, ^{##, **} P < 0.01, ^*** P < 0.001.

Fig. 4

Acute DSS treatment increases both theNod 1andNod 2expression, while repeated DSS treatment induces different effect between Nod1 and Nod2 expression. Colons were collected for the mRNA expression assessment of PRR. The mRNA expressions of Nod 1 and Nod 2 in the A) proximal – and B) distal part of the colon are shown. All results are expressed as + SEM, n = 6. ^** P < 0.001.

Fig. 5

The mRNA expression of bacterial PAMP recognizingTlrsis differently modulated by repeated DSS treatment. Colons were collected for mRNA expression assessment of PRR. The mRNA expressions of Tlr 1, Tlr2, Tlr6, Tlr4, Tlr5, and Tlr9 in the A) proximal- and B) distal part of the colon are shown. All results are expressed as + SEM, n = 6. ^* P < 0.05, ^** P < 0.01, ^*** P < 0.001.

Fig. 6

Repeated DSS treatment increases mRNA expression of viral-associatedTlrsin the distal colon. Colons were collected for mRNA expression assessment of PRR. The mRNA expressions of Tlr3, Tlr7 and Tlr8 in both A) proximal- and B) distal part of the colon are shown. All results are expressed as + SEM, n = 6. ^* P < 0.05, ^** P < 0.01.

Fig. 7

Increased histological score of Foxp3+ cells after each DSS treatment cycle. Colons were collected for A) immunohistochemical assessment of Foxp3+ cells. Representative histochemical staining pictures of Foxp3+ cells in the colon of B) control and C) DSS-treated mice during each DSS cycle are shown. All results are expressed as + SEM, n = 3.