The Effects of Alcohol Intoxication and Burn Injury on the Expression of Claudins and Mucins in the Small and Large Intestines.

Alcohol intoxication at the time of burn injury exacerbates postburn 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 2.9 g/kg ethanol before an approximately 12.5% body area burn. One and three days after injury, we profiled expression of several tight junction proteins, mucin, and bacterial 16S rRNA genes in the small and large intestines, using qPCR. We observed >50% decrease in claudin-4 and claudin-8 genes in both ileal and colonic epithelial cells 1 day after injury. Claudin-2 was significantly upregulated, and occludin was downregulated in the small intestine 1 day after injury. Mucin-3 expression was substantially elevated (>50%) in the small intestine, whereas mucin-2 and mucin-4 were considerably diminished in the colon (>50%) 1 day after injury. Most of the parameters were normalized to sham levels on day 3, except for mucin-3 and claudin-8, which remained decreased in the 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 the small and the large intestines 1 day after injury. These findings suggest that alcohol and burn injury disrupts the normal gut microbiota and alters tight junction and mucin expression in the small and large intestines.