Significance of intestinal fatty acid binding protein in evaluation of intestinal barrier dysfunction of mice at early stage of severe burn injury

Objective To investigate the significance of intestinal fatty acid binding protein (IFABP) in the evaluation of intestinal barrier dysfunction of mice at the early stage of severe burn injury. Methods Thirty-six 8-week-old C57BL/6 male mice were collected and divided into normal control group (n=6) and scald group (n=30) according to random number table. Back of each mouse in scald group was placed into hot water of 90 ℃ for 10 s, causing full-thickness scald (hereinafter refer to as burn) of 30% total body surface area, while mice in normal control group were not inflicted with burns. Six mice in normal control group were taken, and 6 mice in scald group at 1, 2, 6, 12, and 24 h post injury were taken respectively. The portal vein blood of each mouse was extracted and the plasma was separated to measure intestinal permeability with fluorescin isothiocyanate-dextran fluorescence probe tracing method and plasma IFABP content by enzyme-linked immunosorbent assay. The distal ileum tissue of mice in normal control group and scald group at each time point post injury was collected to observe the morphology of the intestinal mucosa tissue by hematoxylin-eosin staining. Data were processed with one-way analysis of variance and Student-Newman-Keuls test, and pearson correlation test was used to analyze the correlation between intestinal permeability and plasma IFABP content of burned mice. Results (1) At 1, 2, 6, 12, and 24 h post injury, the intestinal permeability of mice in scald group was 2.7±0.8, 5.4±2.5, 7.3±4.2, 12.4±6.1, 1.4±0.7, respectively, obviously higher than 1.0±0.4 of normal control group (P<0.05 or P<0.01). The intestinal permeability of mice in scald group showed an increasing trend post injury, reaching the peak at 12 h post injury, and rapidly falling back at 24 h post injury. (2) At 1, 2, 6, 12, and 24 h post injury, the plasma IFABP content of mice in scald group was (64±11), (59±12), (76±18), (111±22), and (66±10) ng/mL, obviously higher than (35±8) ng/mL in normal control group (P<0.05 or P<0.01). The plasma IFABP content of mice in scald group showed an increasing trend post injury, reaching the peak at 12 h post injury, and rapidly decreasing at 24 h post injury. (3) Uniform thickness of mucosa, intact epithelia, regularly arranged villi, and no inflammatory cell infiltration were observed in ileum of mice in normal control group. In ileum of mice in scald group, shortened villi of mucosa with different degrees, edema of lamina propria, and infiltration of neutrophils were observed at 1 and 2 h post injury; obviously damaged and partially exfoliated ileal mucosa, disorderly arranged and broken villi, degenerated and necrotic epithelial cells, dilated central lacteal, and infiltration of lymphocytes and neutrophils were observed at 6 and 12 h post injury; the damage of ileal mucosa was alleviated, and basically intact epithelia, dilated central lacteal, and infiltration of inflammatory cells were observed at 24 h post injury. (4) There was a significantly positive correlation between the intestinal permeability and the plasma IFABP content of burned mice (r=0.841, P<0.05). Conclusions The plasma IFABP can be used as a good biological indicator for the evaluation of intestinal barrier dysfunction of mice at the early stage of severe burn injury. Key words: Burns; Intestines; Permeability; Intestinal fatty acid binding protein