Burns, inflammation, and intestinal injury: protective effects of an anti-inflammatory resuscitation strategy

Therapeutic effect of bromelain and papain on intestinal injury induced by indomethacin in male rats

Objectives

Inflammatory bowel diseases (IBDs) are a multiple inflammatory status in small intestines and colon. Bromelain and Papain were cysteine proteases enzymes extracted from pineapple and papaya, and possess antioxidant and anti-inflammatory characteristics. Therefore, this comparative work aimed to examine the anti-inflammatory and antioxidant effect of bromelain and papain in intestinal inflammation of rats and to evaluate the most potent effect of both types of enzymes.

Methods

Forty rats were used in this study (8 rats/group), G1: control group, G2: (Indo group) intestinal inflammation was induced by two doses of Indomethacin (7.5 mg/kg body weight) apart 24 h. G3: (Indomethacin + Bromelain) intestinal inflamed rats treated by oral dose of bromelain (1000 mg/kg/day). G4: (Indomethacin + Papain) intestinal inflamed rats treated by oral dose of papain (800 mg/kg/day). G5: (Indomethacin + Sulfasalazine) intestinal inflamed rats treated by oral dose of sulfasalazine (500 mg/kg/day). Oxidative stress and inflammatory markers were measured along with histological assessment.

Results

Indomethacin-induced intestinal inflammation (in both Jejunum and Ileum) characterized by increased oxidative stress biomarkers: Xanthine oxidase, Catalase, Glutathione reductase, and Protein carbonyl and Inflammatory biomarkers: Tumor necrosis factor-α, Interleukin-10, Monocyte chemoattractant protein-1, Nuclear factor-kappa β, C-reactive protein, and Prostaglandin E2, as compared to control rats. On the other hand, administering either bromelain or Papain would effectively decrease symptoms of intestinal inflammation and modulate biomarkers of oxidative stress and pro-inflammatory cytokines.

Conclusion

Comparing results revealed that bromelain showed the most potent protective effect and possesses an apparent role in protection against the development of intestinal inflammation.

Microbial community succession in the intestine of mice with deep partial-thickness burns

Introduction

Burn injury has been shown to lead to changes in the composition of the gut microbiome and cause other damage in patients. However, little is known about how the gut microbial community evolves in individuals who have recovered from burn injury.

Methods

In this study, we established a model of deep partial-thickness burn in mice and collected fecal samples at eight time points (pre-burn, 1, 3, 5, 7, 14, 21, and 28 days post-burn) for 16S rRNA amplification and high-throughput sequencing.

Results

The results of the sequencing were analyzed using measures of alpha diversity, and beta diversity and taxonomy. We observed that the richness of the gut microbiome declined from day 7 post-burn and that the principal component and microbial community structure varied over time. On day 28 after the burn, the microbiome composition largely returned to the pre-burn level, although day 5 was a turning point for change. Some probiotics, such as the Lachnospiraceae_NK4A136_group, decreased in composition after the burn but were restored in the later recovery period. In contrast, Proteobacteria showed an opposite trend, which is known to include potential pathogenic bacteria.

Conclusion

These findings demonstrate gut microbial dysbiosis after burn injury and provide new insights into the burn-related dysbiosis of the gut microbiome and strategies for improving the treatment of burn injury from the perspective of the microbiota.

Burn Injury Induces Intestinal Inflammatory Response Mediated by Th17 in Burn-Primed Endotoxemic Mice

Objective

This study aimed to elucidate the mechanism underlying the susceptibility to infection-related acute lung injury by focusing on the role of gut mucosal T-helper (Th) 17 cells that preferentially produce IL-17 with probiotics in a burn-primed endotoxemic mice model.

Methods

Mice were subjected to a 15% total body surface area third-degree burn. Survival from lethal lipopolysaccharide (LPS) administration (3 mg/kg) on 11th day post-burn was assessed in mice fed by chow with or without 1.2% Lactobacillus powder after burn injury. Lamina propria mononuclear cells were enzymatically isolated from the ileum removed on 11th day post-burn and incubated along with 1 μg/mL LPS or 10 μg/mL anti-CD3 antibody for 24 hours; subsequently, the following 7 cytokines were analyzed in the supernatant: IFN-γ, TNF-α, IL-2, IL-4, IL-6, IL-10, and IL-17.

Results

Lactobacillus treatment post-burn injury markedly improved survival after lethal endotoxemia in burn-primed mice (64.3% versus 21.4%, P = 0.03). The production of proinflammatory cytokines such as TNF-α, IL-6, and IL-17 by lamina propria mononuclear T-lymphocytes and macrophages including Th17 response was augmented by burn injury but decreased with Lactobacillus treatment after burn injury.

Conclusions

Th17- and Th17-mediated inflammatory responses in the gut mucosa may play a vital role, which could be attenuated by Lactobacillus treatment, in survival of lethal endotoxemia in burn-primed mice.

Targeting the gut to prevent sepsis from a cutaneous burn

Severe burn injury induces gut barrier dysfunction and subsequently a profound systemic inflammatory response. In the present study, we examined the role of the small intestinal brush border enzyme, intestinal alkaline phosphatase (IAP), in preserving gut barrier function and preventing systemic inflammation after burn wound infection in mice. Mice were subjected to a 30% total body surface area dorsal burn with or without intradermal injection of Pseudomonas aeruginosa. Mice were gavaged with 2000 units of IAP or vehicle at 3 and 12 hours after the insult. We found that both endogenously produced and exogenously supplemented IAP significantly reduced gut barrier damage, decreased bacterial translocation to the systemic organs, attenuated systemic inflammation, and improved survival in this burn wound infection model. IAP attenuated liver inflammation and reduced the proinflammatory characteristics of portal serum. Furthermore, we found that intestinal luminal contents of burn wound-infected mice negatively impacted the intestinal epithelial integrity compared with luminal contents of control mice and that IAP supplementation preserved monolayer integrity. These results indicate that oral IAP therapy may represent an approach to preserving gut barrier function, blocking proinflammatory triggers from entering the portal system, preventing gut-induced systemic inflammation, and improving survival after severe burn injuries.

Why Antibiotic Treatment Is Not Enough for Sepsis Resolution: an Evaluation in an Experimental Animal Model

Sepsis remains a major health problem at the levels of mortality, morbidity, and economic burden to the health care system, a condition that is aggravated by the development of secondary conditions such as septic shock and multiple-organ failure. Our current understanding of the etiology of human sepsis has advanced, at least in part, due to the use of experimental animal models, particularly the model of cecum ligation and puncture (CLP). Antibiotic treatment has been commonly used in this model to closely mirror the treatment of human septic patients. However, whether their use may obscure the elucidation of the cellular and molecular mechanisms involved in the septic response is questionable. The objective of the present study was to determine the effect of antibiotic treatment in the outcome of a fulminant model of CLP. Various dosing strategies were used for the administration of imipenem, which has broad-spectrum coverage of enteric bacteria. No statistically significant differences in the survival of mice were observed between the different antibiotic dosing strategies and no treatment, suggesting that live bacteria may not be the only factor inducing septic shock. To further investigate this hypothesis, mice were challenged with sterilized or unsterilized cecal contents. We found that exposure of mice to sterilized cecal contents also resulted in a high mortality rate. Therefore, it is possible that bacterial debris, apart from bacterial proliferation, triggers a septic response and contributes to mortality in this model, suggesting that additional factors are involved in the development of septic shock.

Nrf2 plays a pivotal role in protection against burn trauma-induced intestinal injury and death

Nuclear factor (erythroid-derived 2)-like 2 (NRF2) is a basic leucine zipper transcription factor that principally defends against oxidative stress and also plays a unique role in severe sepsis. However, its contribution to intestinal injury and death after burn trauma is unclear.In this study, wild-type (Nrf2+/+) and Nrf2-deficient (Nrf2-/-) mice were subjected to 15% or 30% total body surface area burn or sham injury. Survival, systemic inflammation, and gut injury were determined.Nrf2-/- mice were more susceptible to burn-induced intestinal injury, as characterized by increases in damage to the gut structure and in intestinal permeability. This exacerbation was associated with an increase in the intestinal mRNA expression of inflammatory cytokines (interleukin [IL]-6, IL-1B, monocyte chemotactic protein 1, intercellular adhesion molecule, and vascular cell adhesion molecule) and a decrease in the intestinal mRNA expression of Nrf2-regulated genes (NAD(P)H dehydrogenasequinine-1 and glutamate-cysteine ligase modifier subunit). Nrf2-deficient mice also showed a lower survival rate and higher levels of systemic cytokines (IL-6 and IL-1B) and high-mobility group protein B1 than wild-type mice. This study demonstrates for the first time that mice that lack Nrf2 are more susceptible to burn-induced intestinal injury and have more systemic inflammation and a lower survival rate.

Reduction of venous pressure during the resection of liver metastases compromises enteric blood flow: IGFBP-1 as a novel biomarker of intestinal barrier injury

OBJECTIVES

Disruption of the intestinal barrier and bacterial translocation commonly occur when intestinal blood flow is compromised. The aim of this study was to determine whether liver resection induces intestinal damage.

METHODS

We investigated intestinal fatty-acid binding protein and insulin-like growth factor binding protein levels in the plasma of patients who underwent liver resection.

RESULTS

We show that liver resection is associated with significant intestinal barrier injury, even if the Pringle maneuver is not performed.

CONCLUSION

We propose the use of insulin-like growth factor binding protein-1 as a novel biomarker of intestinal damage in such situations.

Effects of early enteral nutrition supplemented with collagen peptides on post-burn inflammatory responses in a mouse model

The effect of early enteral nutrition (EN) supplemented with Alaska pollock skin-derived collagen peptides (CPs) on post-burn inflammatory responses was investigated in a mouse model. Male blab/c mice were randomly assigned to four groups: a sham burn (SB) group, a control group (burn + EN + glycine, BE), a positive control group (burn + EN + glutamine, BEG) and a treatment group (burn + EN + CPs, BEC). Burn-induced increases of serum endotoxin level, and systemic and intestinal concentration of TNF-α and IL-6 were attenuated in BEG and BEC at post-burn day (PBD) 1, 3 and 7 (p < 0.05 vs. BE). Notably, BEC revealed a prominent decrease of the serum endotoxin level, TNF-α and IL-6 as compared to BEG at PBD 7 (p < 0.05). Furthermore, EN supplemented with CPs diminished the phosphorylation of intestinal NF-κB p65 and simultaneously down-regulated the mRNA expression of TNF-α and IL-6 in small intestine (p < 0.05 vs. BE). Also, it demonstrated a comparable effect with glutamine in ameliorating post-burn inflammatory responses in mice with burns. Therefore, CPs could be considered as a potential immunonutrient supplement in EN to improve post-burn outcomes in burn patients.

200mM hypertonic saline resuscitation attenuates intestinal injury and inhibits p38 signaling in rats after severe burn trauma

BACKGROUND

An overabundant discharge of inflammatory mediators plays a significant role in intestinal injury throughout the early stages of critical burns. The present study aims to explore the outcome of 200mM hypertonic saline (HS) resuscitation on the intestinal injury of critically burned rats.

MATERIALS AND METHODS

Fifty-six Sprague-Dawley rats were randomized into three groups: sham group (group A), burn plus lactated Ringer's group (group B), and burn plus 200mM HS group (group C). Samples from the intestine were isolated and assayed for wet-weight-to-dry-weight (W/D) ratio, histopathology analyses, and p38 mitogen-activated protein kinase (MAPK) activity. Serum interleukin 1β (IL-1β) and high mobility group protein box 1 (HMGB1) concentrations were also examined.

RESULTS

Initial resuscitation with 200mM Na⁺ HS significantly decreased the intestinal W/D ratio and improved intestinal histopathology caused by severe burn. HS resuscitation also inhibited the increase of serum IL-1β and HMGB1 concentrations, and p38 MAPK activity in the intestine of critically burned rats.

CONCLUSIONS

The overall findings of this study suggest that preliminary resuscitation with 200mM HS after severe thermal injury reduces intestinal edema, inhibits systemic inflammatory response, and attenuates intestinal p38 MAPK activation, thus reduces burns-induced intestinal injury.

Exogenous S-nitrosoglutathione attenuates inflammatory response and intestinal epithelial barrier injury in endotoxemic rats

BACKGROUND

Gut barrier injury in sepsis is a major contributor to distant organ dysfunction and bad clinical outcomes. Enteric glia-derived S-nitrosoglutathione (GSNO) has been recognized as a novel modulator of gut barrier integrity. In this study, we tested the potential therapeutic effect and mechanism of exogenous GSNO on endotoxin-induced inflammatory response and intestinal barrier injury in a rat model of endotoxemia.

METHODS

Male Sprague-Dawley rats were randomly assigned to four groups as follows: control (saline only), GSNO, lipopolysaccharide (LPS), and LPS + GSNO. Femoral venous injection of LPS (10 mg/kg) or saline was followed by GSNO (1 mg/kg) or saline injection 15 minutes later. Distal ileum tissues and blood were harvested after 3 hours of LPS/saline injection. The intestinal barrier function was measured histologically and by intestinal permeability to fluorescein isothiocyanate dextran. The ultrastructural change of the epithelial tight junction was observed using transmission electron microscope, and the expression level of tight junction protein ZO-1 was analyzed using immunofluorescence and Western blot. Systemic and intestinal inflammation was measured by analyzing the tumor necrosis factor and interleukin 1β levels in plasma and distal ileum tissue, respectively. The levels of nuclear factor κB (NF-κB) and myosin light-chain kinase in the distal ileum were measured by Western blot.

RESULTS

Compared with the endotoxemic rats, the addition of GSNO reduced the intestinal injury observed in histologic sections, decreased permeability to fluorescein isothiocyanate dextran, attenuated damage of the junction between epithelia, and protected against the LPS-induced expression decrease of ZO-1. Furthermore, addition of GSNO reduced plasma and intestinal tumor necrosis factor and interleukin 1β levels as well as inhibited the LPS-induced up-regulation of myosin light-chain kinase expression and NF-κB p65 level in the intestine.

CONCLUSION

The data indicate that GSNO protects against the LPS-induced systemic inflammatory response and attenuated intestinal inflammation and epithelial barrier injury in rats, possibly through the inhibition of the NF-κB pathway.

An oligodeoxynucleotide with AAAG repeats significantly attenuates burn-induced systemic inflammatory responses via inhibiting interferon regulatory factor 5 pathway

Previously, we showed that an oligodeoxynucleotide with AAAG repeats (AAAG ODN) rescued mice from fatal acute lung injury (ALI) induced by influenza virus and inhibited production of tumor necrosis factor-α (TNF-α) in the injured lungs. However, the underlying mechanisms remain to be elucidated. Upon the bioinformatic analysis revealing that the AAAG ODN is consensus to interferon regulatory factor 5 (IRF5) binding site in the cis-regulatory elements of proinflammatory cytokines, we tried to explore whether the AAAG ODN could attenuate burn injury induced systemic inflammatory responses via inhibiting IRF5 pathway. Using the mouse model with sterile systemic inflammation induced by burn injury, we found that AAAG ODN prolonged the life span of the mice, decreased the expression of IRF5 at injured skin, reduced the production of TNF-α and IL-6 in blood and injured skin, and attenuated the ALI. Furthermore, AAAG ODN could bind IRF5 and inhibit the nuclear translocation of IRF5 in THP-1 cells. The data suggested that the AAAG ODN could act as a cytoplasmic decoy capable of interfering the function of IRF5, and be developed as a drug candidate for the treatment of inflammatory diseases.

The role of complement in the acute phase response after burns

Severe burns induce a complex systemic inflammatory response characterized by a typical prolonged acute phase response (APR) that starts approximately 4-8h after-burn and persists for months up to a year after the initial burn trauma. During this APR, acute phase proteins (APPs), including C-reactive protein (CRP) and complement (e.g. C3, C4 and C5) are released in the blood, resulting amongst others, in the recruitment and migration of inflammatory cells. Although the APR is necessary for proper wound healing, a prolonged APR can induce local tissue damage, hamper the healing process and cause negative systemic effects in several organs, including the heart, lungs, kidney and the central nervous system. In this review, we will discuss the role of the APR in burns with a specific focus on complement.

Intraluminal Flagellin Differentially Contributes to Gut Dysbiosis and Systemic Inflammation following Burn Injury

Burn injury is associated with a loss of gut barrier function, resulting in systemic dissemination of gut-derived bacteria and their products. The bacterial protein and TLR5 agonist, flagellin, induces non-specific innate immune responses. Because we detected flagellin in the serum of burn patients, we investigated whether gut-derived flagellin was a primary or secondary contributor to intestinal dysfunction and systemic inflammation following burn injury. The apical surface of polarized human intestinal epithelial cells (IECs), Caco-2BBe, were exposed to 50 or 500 ng of purified flagellin and 1 x 10⁵ of an intestinal E. coli (EC) isolate as follows: 1) flagellin added 30 min prior to EC, 2) flagellin and EC added simultaneously, or 3) EC added 30 min prior to flagellin. Our results showed that luminal flagellin and EC modulated each other's biological actions, which influenced their ability to induce basolateral secretion of inflammatory cytokines and subsequent translocation of bacteria and their products. A low dose of flagellin accompanied by an enteric EC in the lumen, tempered inflammation in a dose- and time-dependent manner. However, higher doses of flagellin acted synergistically with EC to induce both intestinal and systemic inflammation that compromised barrier integrity, increasing systemic inflammation following burn injury, a process we have termed flagellemia. In a murine model of burn injury we found that oral gavage of flagellin (1 μg/mouse) significantly affected the gut microbiome after burn injury. In these mice, flagellin disseminated out of the intestine into the serum and to distal organs (mesenteric lymph nodes and lungs) where it induced secretion of monocyte chemoattractant protein (MCP-1) and CXCL1/KC (mouse equivalent of human IL-8) at 24 and 48h post-burn. Our results illustrated that gut-derived flagellin alone or accompanied by a non-pathogenic enteric EC strain can function as an initiator of luminal and systemic inflammation following burn injury.

Low dose of glucocorticoid decreases the incidence of complications in severely burned patients by attenuating systemic inflammation

BACKGROUND

Excessive systemic inflammatory response remains as a major problem underlying severe burns. This study aimed to assess the effect of low-dose glucocorticoid treatment in downregulating systemic inflammation in severely burned patients.

METHODS

A prospective study from 2001 to 2014 at our hospital was conducted to compare the patients who received low-dose glucocorticoid during the acute phase with those who did not. Patients with burns 70% or greater of their total body surface area were included, and their plasma levels of inflammatory cytokines and clinical outcomes were compared.

RESULTS

A total of 69 patients were included in this study, with 31 patients receiving glucocorticoid treatment and the others not. Patient demographics including age, burn size, and incidence of inhalation injury were similar in both groups. The incidence of pulmonary infection and stress ulcer (and/or hemorrhage) was 24.2% and 3.0% in the treatment group, respectively, significantly lower than 47.8% and 19.6% of the control group (P < .05). Length of hospital stay was almost 13 days shorter in the treatment group (P < .05), whereas there was no significant difference in the overall mortality, duration of mechanical ventilation, and incidence of sepsis between the 2 groups. The enzyme-linked immunosorbent assay results confirmed that the plasma levels of C-reactive protein, tumor necrosis factor-α, interleukin-6, and interleukin-8 were significantly lower in the treatment group (P < .05).

CONCLUSION

Low dose of glucocorticoid treatment during the acute phase could reduce the levels of proinflammatory cytokines in severely burned patients and subsequently decrease the incidence of pulmonary infection and stress ulcer, as well as the length of hospital stay.

Cholinergic signaling in the gut: a novel mechanism of barrier protection through activation of enteric glia cells

BACKGROUND

Enteric glia cells (EGCs) play an important role in maintaining proper intestinal barrier function. We have shown that vagal nerve stimulation (VNS) increases EGC activation, which is associated with better gut barrier integrity. Enteric neurons communicate with EGCs through nicotinic cholinergic signaling, which may represent a pathway by which VNS activates EGCs. This study sought to define further the mechanism by which VNS prevents intestinal barrier failure using an in vitro model. We hypothesized that a nicotinic cholinergic agonist would increase EGC activation, prevent intestinal nuclear factor kappa-B (NF-κB) activation, and result in better intestinal barrier function.

METHODS

Cultured EGCs were exposed to the nicotinic cholinergic agonist nicotine. Expression of glial fibrillary acidic protein (GFAP) was measured by immunoblot to determine changes in EGC activation. Caco-2 cells were grown to confluence and incubated alone or in co-culture with EGCs. Cells were then stimulated with Cytomix for 24 h in the presence or absence of nicotine, and barrier integrity was assessed by permeability to 4-kDa FITC-dextran. Changes in phosphorylated inhibitor of NF-κb (P-IκBα) and phosphorylated NF-κB (P-NF-κB) were assessed by immunoblot.

RESULTS

Stimulation with nicotine resulted in EGC activation, as demonstrated by an increase in GFAP expression. Cytomix stimulation increased permeability in Caco-2 cells cultured alone or with EGCs. Treatment of stimulated Caco-2/EGC co-cultures with nicotine reduced permeability similar to control. Nicotine failed to prevent barrier permeability in Caco-2 cells alone. Co-culture of stimulated Caco-2 cells with nicotine-activated EGCs prevented Cytomix-induced increases in P-IκBα and P-NF-κB expression.

CONCLUSION

A pharmacologic nicotinic cholinergic agonist increased EGC activation and improved intestinal epithelial barrier function in an in vitro model of intestinal injury. Nicotine-activated EGCs appear to modulate barrier function by preventing the activation of the NF-κB pathway. Therapies aimed at activating EGCs may have important clinical applications for improving intestinal barrier function after injury.

A comparative study of pentoxifylline effects in adult and aged rats submitted to lung dysfunction by thermal injury

PURPOSE

To investigate the protective effects of pentoxifylline against lung injury observed after dorsal scald in aged animals.

METHODS

Adult (eight months old) and aged (20 months old) rats were subjected to thermal injury or sham procedure. The six hours post-trauma animals received pentoxifylline and after 24 hours were euthanatized and lung tissue samples collected. The bronchoalveolar lavage fluid was evaluated for total protein content and tumor necrosis factor-alpha cytokine. Malondialdehyde and myeloperoxidase activity in the lung homogenate were measured and a histological lung examination was undertaken.

RESULTS

Burn injury induced oxidative stress in lung homogenate was higher in elderly-burned rats compared to adult-burned rats (p<0.001). Total protein and cytokine in bronchoalveolar lavage increased in the elderly-burned group when compared to the adult-burned group (p<0.001). All parameters decreased in both groups treated with pentoxifylline (p<0.05).

CONCLUSIONS

The injury was augmented in elderly rats when compared to adult rats. Damage was reduced with the use of pentoxifylline, however further studies are needed to evaluate the dose-response of the drug.

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.

Enteric glia cells attenuate cytomix-induced intestinal epithelial barrier breakdown

BACKGROUND

Intestinal barrier failure may lead to systemic inflammation and distant organ injury in patients following severe injury. Enteric glia cells (EGCs) have been shown to play an important role in maintaining gut barrier integrity through secretion of S-Nitrosoglutathione (GSNO). We have recently shown than Vagal Nerve Stimulation (VNS) increases EGC activation, which was associated with improved gut barrier integrity. Thus, we sought to further study the mechanism by which EGCs prevent intestinal barrier breakdown utilizing an in vitro model. We postulated that EGCs, through the secretion of GSNO, would improve intestinal barrier function through improved expression and localization of intestinal tight junction proteins.

METHODS

Epithelial cells were co-cultured with EGCs or incubated with GSNO and exposed to Cytomix (TNF-α, INF-γ, IL-1β) for 24 hours. Barrier function was assessed by permeability to 4kDa FITC-Dextran. Changes in tight junction proteins ZO-1, occludin, and phospho-MLC (P-MLC) were assessed by immunohistochemistry and immunoblot.

KEY RESULTS

Co-culture of Cytomix-stimulated epithelial monolayers with EGCs prevented increases in permeability and improved expression and localization of occludin, ZO-1, and P-MLC. Further, treatment of epithelial monolayers with GSNO also prevented Cytomix-induced increases in permeability and exhibited a similar improvement in expression and localization of occludin, ZO-1, and P-MLC.

CONCLUSIONS & INFERENCES

The addition of EGCs, or their secreted mediator GSNO, prevents epithelial barrier failure after injury and improved expression of tight junction proteins. Thus, therapies that increase EGC activation, such as VNS, may be a novel strategy to limit barrier failure in patients following severe injury.

Ethanol and dietary unsaturated fat (corn oil/linoleic acid enriched) cause intestinal inflammation and impaired intestinal barrier defense in mice chronically fed alcohol

Alcohol and dietary fat both play an important role in alcohol-mediated multi-organ pathology, including gut and liver. In the present study we hypothesized that the combination of alcohol and dietary unsaturated fat (USF) would result in intestinal inflammatory stress and mucus layer alterations, thus contributing to disruption of intestinal barrier integrity. C57BL/6N mice were fed Lieber-DeCarli liquid diets containing EtOH and enriched in USF (corn oil/linoleic acid) or SF (medium chain triglycerides: beef tallow) for 8 weeks. Intestinal histology, morphometry, markers of inflammation, as well as levels of mucus protective factors were evaluated. Alcohol and dietary USF triggered an intestinal pro-inflammatory response, characterized by increase in Tnf-α, MCP1, and MPO activity. Further, alcohol and dietary USF, but not SF, resulted in alterations of the intestinal mucus layer, characterized by decreased expression of Muc2 in the ileum. A strong correlation was observed between down-regulation of the antimicrobial factor Cramp and increased Tnf-α mRNA. Therefore, dietary unsaturated fat (corn oil/LA enriched) is a significant contributing factor to EtOH-mediated intestinal inflammatory response and mucus layer alterations in rodents.

Intravenous phage display identifies peptide sequences that target the burn-injured intestine

The injured intestine is responsible for significant morbidity and mortality after severe trauma and burn; however, targeting the intestine with therapeutics aimed at decreasing injury has proven difficult. We hypothesized that we could use intravenous phage display technology to identify peptide sequences that target the injured intestinal mucosa in a murine model, and then confirm the cross-reactivity of this peptide sequence with ex vivo human gut. Four hours following 30% TBSA burn we performed an in vivo, intravenous systemic administration of phage library containing 10(12) phage in balb/c mice to biopan for gut-targeting peptides. In vivo assessment of the candidate peptide sequences identified after 4 rounds of internalization was performed by injecting 1×10(12) copies of each selected phage clone into sham or burned animals. Internalization into the gut was assessed using quantitative polymerase chain reaction. We then incubated this gut-targeting peptide sequence with human intestine and visualized fluorescence using confocal microscopy. We identified 3 gut-targeting peptide sequences which caused collapse of the phage library (4-1: SGHQLLLNKMP, 4-5: ILANDLTAPGPR, 4-11: SFKPSGLPAQSL). Sequence 4-5 was internalized into the intestinal mucosa of burned animals 9.3-fold higher than sham animals injected with the same sequence (2.9×10(5)vs. 3.1×10(4) particles per mg tissue). Sequences 4-1 and 4-11 were both internalized into the gut, but did not demonstrate specificity for the injured mucosa. Phage sequence 4-11 demonstrated cross-reactivity with human intestine. In the future, this gut-targeting peptide sequence could serve as a platform for the delivery of biotherapeutics.

Period of irreversible therapeutic intervention during sepsis correlates with phase of innate immune dysfunction

Sepsis is a major health problem in the United States with high incidence and elevated patient care cost. Using an animal model of sepsis, cecum ligation, and puncture, we observed that mice became rapidly hypothermic reaching a threshold temperature of 28 °C within 5-10 h after initiation of the insult, resulting in a reliable predictor of mortality, which occurred within 30-72 h of the initial procedure. We also observed that the inflammatory gene expression in lung and liver developed early within 1-2 h of the insult, reaching maximum levels at 6 h, followed by a decline, approaching basal conditions within 20 h. This decrease in inflammatory gene expression at 20 h after cecal ligation and puncture was not due to resolution of the insult but rather was an immune dysfunction stage that was demonstrated by the inability of the animal to respond to a secondary external inflammatory stimulus. Removal of the injury source, ligated cecum, within 6 h of the initial insult resulted in increased survival, but not after 20 h of cecal ligation and puncture. We concluded that the therapeutic window for resolving sepsis is early after the initial insult and coincides with a stage of hyperinflammation that is followed by a condition of innate immune dysfunction in which reversion of the outcome is no longer possible.

Targeting α-7 nicotinic acetylcholine receptor in the enteric nervous system: a cholinergic agonist prevents gut barrier failure after severe burn injury

We have previously shown that vagal nerve stimulation prevents intestinal barrier loss in a model of severe burn injury in which injury was associated with decreased expression and altered localization of intestinal tight junction proteins. α-7 Nicotinic acetylcholine receptor (α-7 nAchR) has been shown to be necessary for the vagus nerve to modulate the systemic inflammatory response, but the role of α-7 nAchR in mediating gut protection remained unknown. We hypothesized that α-7 nAchR would be present in the gastrointestinal tract and that treatment with a pharmacological agonist of α-7 nAchR would protect against burn-induced gut barrier injury. The effects of a pharmacological cholinergic agonist on gut barrier integrity were studied using an intraperitoneal injection of nicotine 30 minutes after injury. Intestinal barrier integrity was examined by measuring permeability to 4-kDa fluorescein isothiocyanate-dextran and by examining changes in expression and localization of the intestinal tight junction proteins occludin and ZO-1. Nicotine injection after injury prevented burn-induced intestinal permeability and limited histological gut injury. Treatment with nicotine prevented decreased expression and altered localization of occludin and ZO-1, as seen in animals undergoing burn alone. Defining the interactions among the vagus nerve, the enteric nervous system, and the intestinal epithelium may lead to development of targeted therapeutics aimed at reducing gut barrier failure and intestinal inflammation after severe injury.

CPSI-121 pharmacologically prevents intestinal barrier dysfunction after cutaneous burn through a vagus nerve-dependent mechanism

BACKGROUND

We have recently demonstrated the protective effects of electrical stimulation of the vagus nerve in prevention of gut injury after severe burn. Here we evaluate the potential for a pharmacologic agonist of the vagus nerve as an approach to regulate outcomes in preclinical models. We tested a new generation of guanylhydrazone-derived compounds, CPSI-121; a compound that may activate the parasympathetic nervous system through poorly understood mechanisms to determine whether we could prevent intestinal mucosal barrier breakdown.

METHODS

Male balb/c mice were subjected to a full-thickness, 30% total body surface area steam burn, and the efficacy of CPSI-121 was tested against vagus nerve stimulation (VNS) postburn at 4 hours. Surgical vagotomy was used to disrupt the neuroenteric axis and gut injury prevention was assessed. Gut barrier dysfunction was quantified by permeability to 4-kDa fluorescein isothiocyanate-dextran. Gut injury was assessed by histologic evaluation. Tight junction protein expression (ZO-1 and occludin) was characterized by immunofluorescence and immunoblot.

RESULTS

VNS and CPSI-121 administration significantly reduced the permeability to 4-kDa fluorescein isothiocyanate-dextran and maintained normal histology compared with burn. However, abdominal vagotomy eliminated the protective effects of both VNS and CPSI-121. ZO-1 and occludin expression was similar to sham in VNS and CPSI-121-treated burn animals, but significantly altered in burn-vagotomized animals. Splenectomy did not alter the effect of CPSI-121.

CONCLUSION

Similar to direct electrical VNS, CPSI-121 effectively protects the intestinal mucosal barrier from breakdown after severe burn. We suggest that this could represent a noninvasive therapy to prevent end-organ dysfunction after trauma that would be administered during resuscitation.

Burn resuscitation

Fluid resuscitation following burn injury must support organ perfusion with the least amount of fluid necessary and the least physiological cost. Under resuscitation may lead to organ failure and death. With adoption of weight and injury size-based formulas for resuscitation, multiple organ dysfunction and inadequate resuscitation have become uncommon. Instead, administration of fluid volumes well in excess of historic guidelines has been reported. A number of strategies including greater use of colloids and vasoactive drugs are now under investigation to optimize preservation of end organ function while avoiding complications which can include respiratory failure and compartment syndromes. Adjuncts to resuscitation, such as antioxidants, are also being investigated along with parameters beyond urine output and vital signs to identify endpoints of therapy. Here we briefly review the state-of-the-art and provide a sample of protocols now under investigation in North American burn centers.

Efferent vagal nerve stimulation attenuates acute lung injury following burn: The importance of the gut-lung axis

BACKGROUND

The purpose of this study was to assess acute lung injury when protection to the gut mucosal barrier offered by vagus nerve stimulation is eliminated by an abdominal vagotomy.

METHODS

Male balb/c mice were subjected to 30% total body surface area steam burn with and without electrical stimulation to the right cervical vagus nerve. A cohort of animals were subjected to abdominal vagotomy. Lung histology, myeloperoxidase and ICAM-1 immune staining, myeloperoxidase enzymatic assay, and tissue KC levels were analyzed 24 hours after burn. Additionally, lung IkB-α, NF-kB immunoblots, and NF-kB-DNA binding measured by photon emission analysis using NF-kB-luc transgenic mice were performed.

RESULTS

Six hours post burn, phosphorylation of both NF-kB p65 and IkB-α were observed. Increased photon emission signal was seen in the lungs of NF-kB-luc transgenic animals. Vagal nerve stimulation blunted NF-kB activation similar to sham animals whereas abdominal vagotomy eliminated the anti-inflammatory effect. After burn, MPO positive cells and ICAM-1 expression in the lung endothelium was increased, and lung histology demonstrated significant injury at 24 hours. Vagal nerve stimulation markedly decreased neutrophil infiltration as demonstrated by MPO immune staining and enzyme activity. Vagal stimulation also markedly attenuated acute lung injury at 24 hours. The protective effects of vagal nerve stimulation were reversed by performing an abdominal vagotomy.

CONCLUSION

Vagal nerve stimulation is an effective strategy to protect against acute lung injury following burn. Moreover, the protective effects of vagal nerve stimulation in the prevention of acute lung injury are eliminated by performing an abdominal vagotomy. These results establish the importance of the gut-lung axis after burn in the genesis of acute lung injury.