Gastroenterology

Gastroenterology

Volume 135, Issue 3, September 2008, Pages 926-936.e2
Gastroenterology

Basic—Alimentary Tract
Proinflammatory Role of Leukocyte-Derived Egr-1 in the Development of Murine Postoperative Ileus

https://doi.org/10.1053/j.gastro.2008.05.079Get rights and content

Background & Aims: Early growth response gene-1 (Egr-1) is an important inflammatory transcription factor. We hypothesize that leukocyte-derived Egr-1 plays a key inflammatory role in causing postoperative ileus. Methods: Wild-type, Egr-1 knockout, and chimera mice (constructed by irradiation followed by injection with Egr-1+/+ or Egr-1−/− bone marrow) were subjected to surgical manipulation of the gastrointestinal tract to induce ileus. Reverse-transcription polymerase chain reaction, Western blot, and immunohistochemistry quantified and localized Egr-1. Lumenal transit of nonabsorbable fluorescein isothiocyanate-labeled dextran and in vitro organ bath techniques measured functional gastrointestinal motility. Inflammatory mediator expressions were measured by Griess reaction, enzyme-linked immunosorbent assay, and multiplex Luminex assay. Results: Intestinal manipulation rapidly and significantly induced Egr-1 messenger RNA and protein within the inflamed muscularis externa. Egr-1 was colocalized early to smooth muscle and enteric neurons and later in extravasated monocytes after surgery when postoperative ileus was functionally prominent. The functional severity of postoperative ileus was significantly ameliorated in mice deficient in Egr-1−/− and chimera wild-type mice transplanted with Egr-1−/− bone marrow, whereas knockout mice with Egr-1+/+ bone marrow again displayed significant ileus. Motility was mechanistically associated in Egr-1−/− gene deficiency with a down-regulation in the release of nitric oxide, prostanoids, monocyte chemoattractant protein-1, macrophage inflammatory protein-1α, interleukin-6, interleukin-1, and granulocyte colony-stimulating factor, as well as a decrease in the recruitment of leukocytes into the manipulated muscle wall of the intestine compared with wild-type mice. Conclusions: Leukocyte-derived Egr-1 plays an early critical inflammatory role in the initiation of the postoperative inflammatory response, which leads to a prolonged decreased in gastrointestinal motility after intestinal surgery.

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Animals

Adult male and female mice of 2–4 months of age weighing 25–30 g were used. Homozygous wild-type (Egr-1+/+) (WT) and homozygous mutant Egr-1 knockout (Egr-1−/−) (KO) mice were obtained by crossing heterozygous mice bearing a targeted mutation of the Egr-1 gene because female homozygous knockout mice are infertile. The breeding pairs were kindly provided by Dr David Pinsky of Columbia University (originally generated in the laboratory of Dr Jeffrey Milbrandt14, 15, 16, 17). The University of

Intestinal Manipulation Activates and Up-Regulates the Expression of Egr-1

Intestinal manipulation initiates a complex molecular and cellular inflammatory response within the intestinal muscularis that leads to intestinal ileus. Here, we show that manipulation induces a significant, rapid, 55-fold up-regulation in Egr-1 mRNA within 3 hours from extracts of the harvested jejunal muscularis using real-time RT-PCR (Figure 1A). This induction then subsided over a period of the first 12 hours but stayed significantly elevated for up to 24 hours (7-fold). We also measured

Discussion

Previously, much attention has concentrated on discovering the specific mediators that are involved in causing postoperative ileus.6 However, in this study we focused on elucidating transcriptional events that transduce these inflammatory mediators. The major finding of the current study is that the transcription factor Egr-1 present in leukocytes plays a major role in the proinflammatory molecular response within the surgically activated postoperative intestinal muscularis externa. The above

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    Supported by National Institutes of Health grants R01-GM58241, R01-DK068610, and P50-GM53789.

    Conflicts of interest: No conflicts of interest exist.

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