Variability of bacterial translocation in the absence of intestinal mucosal damage following injury and the influence of interleukin-6

Anti-IL-6 antibody treatment but not IL-6 knockout improves intestinal barrier function and reduces inflammation after binge ethanol exposure and burn injury

Interleukin 6 (IL-6) is an inflammatory cytokine known to be elevated in chronic diseases and after insults such as trauma and infection. Although necessary for the development of B cells and Th17 cells, IL-6, at elevated levels, can also cause tissue damage and lead to a rise in inflammation. Previous work in our laboratory has shown that IL-6 is increased both systemically and in multiple organ systems including the ileum after ethanol exposure and burn injury. As this combined insult causes elevated intestinal morphological damage, tight junction protein localization alterations, and phosphorylated myosin light chain levels, we sought to determine the role of IL-6 in these intestinal responses using a model of binge ethanol exposure and burn injury. Interleukin 6 antibody treatment after the combined insult reduced morphological changes in the ileum, bacterial translocation, and phosphorylated myosin light chain levels relative to either injury alone. Zonula occludens protein 1 and occludin localization was also reestablished in wild-type mice given IL-6 antibody after ethanol and burn. Interleukin 6-knockout mice given ethanol and burn injury also had reduced intestinal damage; however, no changes in bacterial translocation or tight junction protein localization were observed as compared with similarly treated wild-type mice. These data suggest that IL-6 may have a role in intestinal tissue damage observed after the combined insult of binge ethanol exposure and burn injury, although complete loss of IL-6 does not seem to be beneficial in this model. Modulation of IL-6 may present a new option for preventing intestinal damage and associated inflammation after a combined insult of ethanol exposure and burn injury.

Kampo medicine "Dai-kenchu-to" prevents bacterial translocation in rats

Kampo medicine "Dai-kenchu-to" (DKT) has been used for treatment of ileus. The aim of this study was to evaluate the role of DKT on the bacterial translocation (BT) model in rats. Rats were divided into the following four groups: group 1, receiving only water, and groups 2, 3, and 4, receiving 100, 300, and 1,000 mg/kg/day of DKT. Rats were sacrificed 6 days after the beginning of the fast, and then the mesenteric lymph node was cultured. Inflammatory cytokines, intestinal integrity, and apoptosis were assessed. Incidence of BT in groups 3 (33%) and 4 (16%) was lower than in group 1 (66%). Interferon-gamma expression in groups 2, 3, and 4 was significantly lower than in group 1. Villous height and number of villus in groups 2, 3, and 4 were significantly taller and greater than in group 1. Apoptotic index in groups 2, 3, and 4 was significantly lower than in group 1. This is the first evidence that DKT prevents BT by reducing inflammatory reaction and maintaining intestinal integrity.

Intestinal crosstalk: a new paradigm for understanding the gut as the "motor" of critical illness

For more than 20 years, the gut has been hypothesized to be the "motor" of multiple organ dysfunction syndrome. As critical care research has evolved, there have been multiple mechanisms by which the gastrointestinal tract has been proposed to drive systemic inflammation. Many of these disparate mechanisms have proved to be important in the origin and propagation of critical illness. However, this has led to an unusual situation where investigators describing the gut as a "motor" revving the systemic inflammatory response syndrome are frequently describing wholly different processes to support their claim (i.e., increased apoptosis, altered tight junctions, translocation, cytokine production, crosstalk with commensal bacteria, etc). The purpose of this review is to present a unifying theory as to how the gut drives critical illness. Although the gastrointestinal tract is frequently described simply as "the gut," it is actually made up of (1) an epithelium; (2) a diverse and robust immune arm, which contains most of the immune cells in the body; and (3) the commensal bacteria, which contain more cells than are present in the entire host organism. We propose that the intestinal epithelium, the intestinal immune system, and the intestine's endogenous bacteria all play vital roles driving multiple organ dysfunction syndrome, and the complex crosstalk between these three interrelated portions of the gastrointestinal tract is what cumulatively makes the gut a "motor" of critical illness.