Mechanisms of Intestinal Barrier Dysfunction in Sepsis

Abstract

Intestinal barrier dysfunction is thought to contribute to the development of multiple organ dysfunction syndrome in sepsis. Although there are similarities in clinical course following sepsis, there are significant differences in the host response depending on the initiating organism and time course of the disease, and pathways of gut injury vary widely in different preclinical models of sepsis. The purpose of this study was to determine whether the timecourse and mechanisms of intestinal barrier dysfunction are similar in disparate mouse models of sepsis with similar mortalities. FVB/N mice were randomized to receive cecal ligation and puncture (CLP) or sham laparotomy, and permeability was measured to fluoresceinisothiocyanate conjugated-dextran (FD-4) six to 48 hours later. Intestinal permeability was elevated following CLP at all timepoints measured, peaking at six to 12 hours. Tight junction proteins claudin 1, 2, 3, 4, 5, 7, 8, 13 and 15, JAM-A, occludin, and ZO-1 were than assayed by Western blot, real-time polymerase chain reaction, and immunohistochemistry 12 hours after CLP to determine potential mechanisms underlying increases in intestinal permeability. Claudin 2 and JAM-A were increased by sepsis whereas claudin-5 and occludin were decreased by sepsis. All other tight junction proteins were unchanged. A further timecourse experiment demonstrated that alterations in claudin-2 and occludin were detectable as early as 1 hour after the onset of sepsis. Similar experiments were then performed in a different group of mice subjected to Pseudomonas aeruginosa pneumonia. Mice with pneumonia had an increase in intestinal permeability similar in timecourse and magnitude to that seen in CLP. Similar changes in tight junction proteins were seen in both models of sepsis although mice subjected to pneumonia also had a marked decrease in ZO-1 not seen in CLP. These results indicate that two disparate, clinically relevant models of sepsis induce a significant increase in intestinal permeability mediated through a common pathway involving alterations in claudin 2, claudin 5, JAM-A and occludin although model-specific differences in ZO-1 were also identified.

Epidermal Growth Factor Improves Intestinal Integrity and Survival in Murine Sepsis Following Chronic Alcohol Ingestion

“…CLP, in isolation, increases intestinal permeability. This is associated with increases in jejunal claudin 2 and JAM-A as well as decreases in claudin 5 and occludin in FVB/N mice (the same strain used in this study) (28). In contrast, localization (but not levels) of claudins 1, 3, 4, 5 and 8 are all altered in colonic tight junctions following CLP in C57Bl/6 mice (29).…”

Myosin Light Chain Kinase Knockout Improves Gut Barrier Function and Confers a Survival Advantage in Polymicrobial Sepsis

“…as decreases in claudin 5 and occludin (18). CLP has also been demonstrated to induce alterations in cellular localization of colonic claudins 1, 3, 4, 5 and 8 as well as upregulation of claudin 2 (21).…”

“…Notably, sepsis induces intestinal hyperpermeability (18)(19)(20)(21). While early studies in critical illness hypothesized that gut barrier damage induces sepsis by translocation of intact bacteria, the reality has turned out to be considerably more complex (7,(22)(23)(24).…”

The intestinal microenvironment in sepsis

“…This allows luminal contents (intact microbes, microbial products) to escape their natural environment where they can cause either local or distant injury. In preclinical models of sepsis, alterations in tight junctions occur as early as one hour after the onset of sepsis, and intestinal hyperpermeability persists for at least 48 hours after the onset of sepsis (52). This is associated with increased claudin 2 and junctional adhesion molecule A as well as decreased claudin 5 and occludin in the small intestine of both cecal ligation and puncture (CLP) as well as Pseudomonas aeruginosa pneumonia.…”

“…Colonic tight junctions are also impacted by CLP, with alterations in cellular localization of claudins 1, 3, 4, 5, and 8, and upregulation of claudin 2 (54). In addition, a marked decrease in zonula occludens-1 is seen only in pneumonia (and not CLP) suggesting that the mechanisms underlying barrier dysfunction may be mediated via a combination of a common host response and a more specific response modulated by the source of sepsis (52). Intestinal hyperpermeability is also related to chronic co-morbidities as mice with alcohol use disorder prior to the onset of CLP have a further increase in permeability, associated with decreased zonula occludens-1 and occludin expression (53).…”