Sepsis remains one of the leading causes of death in burn patients who survive the initial insult of injury. Disruption of the intestinal epithelial barrier has been shown after burn injury; this can lead to the translocation of bacteria or their products (e.g., endotoxin) from the intestinal lumen to the circulation, thereby increasing the risk for sepsis in immunocompromised individuals. Since the maintenance of the epithelial barrier is largely dependent on the intestinal microbiota, we examined the diversity of the intestinal microbiome of severely burned patients and a controlled mouse model of burn injury. We show that burn injury induces a dramatic dysbiosis of the intestinal microbiome of both humans and mice and allows for similar overgrowths of Gram-negative aerobic bacteria. Furthermore, we show that the bacteria increasing in abundance have the potential to translocate to extra-intestinal sites. This study provides an insight into how the diversity of the intestinal microbiome changes after burn injury and some of the consequences these gut bacteria can have in the host.

Intestine barrier disruption and bacterial translocation can contribute to sepsis and multiple organ failure- leading causes of mortality in burn-injured patients. Additionally, findings suggest ethanol (alcohol) intoxication at the time of injury worsens symptoms associated with burn injury. We have previously shown that interleukin-22 (IL-22) protects from intestinal leakiness and prevents overgrowth of Gram-negative bacteria following ethanol and burn injury, but how IL-22 mediates these effects has not been established. Here, utilizing a model of ethanol and burn injury, we show that the combined insult results in a significant loss of proliferating cells within small intestine crypts and increases Enterobacteriaceae copies, despite elevated levels of the anti-microbial peptide (AMPs) lipocalin-2. IL-22 administration restored numbers of proliferating cells within crypts, significantly increased Reg3β, Reg3γ, lipocalin-2 AMP transcript levels in intestine epithelial cells, and resulted in complete reduction of Enterobacteriaceae in the small intestine. Knockout of signal transducer and activator of transcription factor-3 (STAT3) in intestine epithelial cells resulted in complete loss of IL-22 protection, demonstrating STAT3 is required for intestine barrier protection following ethanol combined with injury. Together, these findings suggest IL-22/STAT3 signaling is critical to gut barrier integrity and targeting this pathway may be of beneficial clinical relevance following burn injury.

Alcohol intoxication at the time of burn injury exacerbates post-burn pathogenesis. Recent findings suggest gut barrier integrity is compromised after combined alcohol and burn insult, which could contribute to these complications. Tight junction proteins and mucins play critical roles in keeping the gut barrier intact. Therefore, the goal of this study was to examine the effects of alcohol and burn injury on claudin and mucin expression in the intestines. We also evaluated if the combined insult differentially influences their expression in the small and large intestines. Male C57BL/6 mice were given a single dose of 2.9g/kg ethanol prior to a ~12.5% body area burn. One and three days following injury, we profiled expression of several tight junction proteins, mucin, and bacterial 16S rRNA genes in small and large intestine using qPCR. We observed >50% decrease in claudin-4 and claudin-8 genes in both ileal and colonic epithelial cells one day after injury. Claudin-2 was significantly upregulated, and occludin was down-regulated in small intestine one day following injury. Mucin-3 expression was substantially elevated (>50%) in small intestine, whereas mucin-2, and mucin-4 were considerably diminished in the colon (>50%) one day following injury. Most parameters were normalized to sham levels on day three, except for mucin-3 and claudin-8, which remained decreased in large intestine. Neither alcohol nor burn alone resulted in changes in junction or mucin gene expression compared to shams. This was accompanied with increases in the family of Gram-negative bacteria, Enterobacteriaceae, in both small and large intestine one day following injury. These findings suggest that alcohol and burn injury disrupts normal gut microbiota and alters tight junction and mucin expression in the small and large intestines.

Over 1.4 million Americans have been diagnosed with inflammatory bowel disease (IBD), and ulcerative colitis (UC) makes up approximately half of those diagnoses. As a disease, UC cycles between periods of remission and flare, which is characterized by intense abdominal pain, increased weight loss, intestinal inflammation, rectal bleeding, and dehydration. Interestingly, a widespread recommendation to IBD patients for avoidance of a flare period is "Don't Drink Alcohol" as recent work correlated alcohol consumption with increased GI symptoms in patients with IBD. Alcohol alone not only induces a systemic pro-inflammatory response, but can also be directly harmful to gut barrier integrity. However, how alcohol could result in the exacerbation of UC in both patients and murine models of colitis has yet to be elucidated. Therefore, we conducted a retrospective analysis of patients admitted for IBD with a documented history of alcohol use in conjunction with a newly developed mouse model of binge alcohol consumption following dextran sulfate sodium (DSS)-induced colitis. We found that alcohol negatively impacts clinical outcomes of patients with IBD, specifically increased intestinal infections, antibiotic injections, abdomen CT scans, and large intestine biopsies. Furthermore, in our mouse model of binge alcohol consumption following an induced colitis flare, we found alcohol exacerbates weight loss, clinical scores, colonic shortening and inflammation, and propensity to infection. These findings highlight alcohol's ability to potentiate symptoms and susceptibility to infection in UC and suggest alcohol as an underlying factor in perpetuating symptoms of IBD.