Preventive effects of Escherichia coli strain Nissle 1917 on acute and chronic intestinal inflammation in two different murine models of colitis

Abstract

Escherichia coli strain Nissle 1917 (EcN) is as effective in maintaining remission in ulcerative colitis as is treatment with mesalazine. This study aims to evaluate murine models of acute and chronic intestinal inflammation to study the antiinflammatory effect of EcN in vivo. Acute colitis was induced in mice with 2% dextran-sodium sulfate (DSS) in drinking water. EcN was administered from day -2 to day +7. Chronic colitis was induced by transfer of CD4(+) CD62L(+) T lymphocytes from BALB/c mice in SCID mice. EcN was administered three times/week from week 1 to week 8 after cell transfer. Mesenteric lymph node (MLN) cytokine secretion (of gamma interferon [IFN-gamma], interleukin 5 [IL-5], IL-6, and IL-10) was measured by enzyme-linked immunosorbent assay. Histologic sections of the colon were analyzed by using a score system ranging from 0 to 4. Intestinal contents and homogenized MLN were cultured, and the number of E. coli-like colonies was determined. EcN was identified by repetitive extragenic palindromic (REP) PCR. EcN administration to DSS-treated mice reduced the secretion of proinflammatory cytokines (IFN-gamma, 32,477 +/- 6,377 versus 9,734 +/- 1,717 [P = 0.004]; IL-6, 231 +/- 35 versus 121 +/- 17 [P = 0.02]) but had no effect on the mucosal inflammation. In the chronic experimental colitis of the transfer model, EcN ameliorated the intestinal inflammation (histology score, 2.7 +/- 0.2 versus 1.9 +/- 0.3 [P = 0.02]) and reduced the secretion of proinflammatory cytokines. Translocation of EcN and resident E. coli into MLN was observed in the chronic colitis model but not in healthy controls. Administration of EcN ameliorated acute and chronic experimental colitis by modifying proinflammatory cytokine secretion but had no influence on the acute DSS-induced colitis. In this model, preexisting colitis was necessary for translocation of EcN and resident E. coli into MLN.

FIG. 1.

Reduction of IFN-γ secretion by MLN in DSS-induced colitis following the administration of EcN or vancomycin-imipenem (V/I). Values given are means ± SEM (picograms per milliliter). *, P = 0.004 versus DSS.

FIG. 2.

Reduction of IL-6 secretion by MLN in DSS-induced colitis following the administration of EcN or vancomycin-imipenem (V/I). Values given are means ± SEM (picograms per milliliter). *, P = 0.02 versus DSS.

FIG. 3.

Clinical score of CD4⁺ CD62L⁺ SCID mice untreated or treated with EcN in comparison to the results seen with the control group injected i.p. with PBS. *, P < 0.001 versus CD62L.

FIG. 4.

(A) Histological appearance of colitis induced by transfer of naïve CD4⁺ CD62L⁺ T lymphocytes in SCID mice. The colitis is characterized by a thickening of the mucosa due to edema and an influx of inflammatory cells (magnification, ×100). (B) Administration of EcN led to a significant reduction of the severity of chronic colitis in this model (magnification, ×100). (C) Histological score of the colonic inflammation in mice following the induction of colitis by transfer of naïve CD4⁺ CD62L⁺ T lymphocytes and administration of EcN compared to that of untreated colitic mice. *, P < 0.02 versus CD62L.

FIG. 4.

(A) Histological appearance of colitis induced by transfer of naïve CD4⁺ CD62L⁺ T lymphocytes in SCID mice. The colitis is characterized by a thickening of the mucosa due to edema and an influx of inflammatory cells (magnification, ×100). (B) Administration of EcN led to a significant reduction of the severity of chronic colitis in this model (magnification, ×100). (C) Histological score of the colonic inflammation in mice following the induction of colitis by transfer of naïve CD4⁺ CD62L⁺ T lymphocytes and administration of EcN compared to that of untreated colitic mice. *, P < 0.02 versus CD62L.

FIG. 5.

Reduction of proinflammatory cytokine secretion of MLN following the induction of colitis by transfer of naïve CD4⁺ CD62L⁺ T lymphocytes and administration of EcN compared to the results seen with untreated colitic mice. Values given are means ± SEM (picograms per milliliter). (A) IFN-γ (*, P < 0.03); (B) IL-6 (*, P = 0.02); (C) IL-5 (*, P = 0.02). All P values shown are versus those of CD62L.

FIG. 6.

Total concentration of E. coli-like colonies in cecal content from mice from the transfer model following oral administration of EcN for 8 weeks compared to that of untreated colitic mice. *, P < 0.001 versus CD62L.

FIG. 7.

Evidence of bacterial translocation into MLN. Total concentration of E. coli-like colonies in MLN of mice from the transfer model following oral administration of EcN for 8 weeks compared to that of untreated colitic mice. EcN was identified by REP-PCR. *, P < 0.0001 versus CD62L.