Objective To investigate the effects of short chain fatty acid (SCFA) on barrier disruption of human intestinal epithelial cell induced by endotoxin/lipopolysaccharide (LPS) and the related mechanism.
Methods The human intestinal epithelial cell line Caco-2 was used to reproduce monolayer-cells. Cells were divided into control group, LPS group, and SCFA+ LPS group according to the random number table. Cells in control group were only routinely cultured with DMEM medium. Cells in LPS group were cultured with DMEM medium and LPS with final mass concentration of 10 μg/mL. Cells in SCFA+ LPS group were cultured with DMEM medium, LPS and SCFA (consisting of 0.5 mmol/L acetate, 0.01 mmol/L propionate, and 0.01 mmol/L butyrate) with final mass concentration of 10 μg/mL. At post culture hour (PCH) 0, 1, 2, 6, 12, and 24, transepithelial electrical resistance (TER) of cells was determined with an ohmmeter, with sample number of 72. Another portion of cells were divided and treated as above, and then Western blotting was employed to detect the protein expressions of zonula occludens 1 (ZO-1), occludin, and claudin-1 at PCH 24, with sample number of 6. Another portion of cells were divided and treated as above and then immunofluorescence was used to observe cellular morphology and distribution of ZO-1. Data were processed with analysis of variance of factorial design, one-way analysis of variance, least-significant difference test, and Bonferroni correction.
Results (1) Compared with that in control group, TER of cells in LPS group was significantly reduced from PCH 1 to 24 (
P<0.01), while TER of cells in SCFA+ LPS group showed no obvious change (
P>0.05). TER of cells in SCFA+ LPS group was significantly higher than that in LPS group from PCH 1 to 24 (
P<0.01). (2) Compared with the protein expressions of ZO-1, occludin, and claudin-1 of cells in control group (1.25±0.10, 1.17±0.04, and 1.24±0.20), those of cells in LPS group (0.74±0.23, 0.76±0.11, and 0.77±0.11) at PCH 24 were significantly decreased (
P<0.05), while those of cells in SCFA+ LPS group (1.23±0.46, 1.05±0.09, and 1.01±0.13) showed no significant differences (
P>0.05). Protein expressions of occludin and claudin-1 of cells in SCFA+ LPS group were significantly higher than those in LPS group at PCH 24 (
P<0.05). Protein expression of ZO-1 of cells in SCFA+ LPS group was higher than that in LPS group at PCH 24 with no significant difference (
P>0.05). (3) At PCH 24, cells in control group were compact in arrangement with pebble-like appearance, and ZO-1 was distributed smoothly and continuously along the cell membrane. In LPS group, cells were sparse in arrangement with change in appearance, and ZO-1 was distributed uncontinuously along the cell membrane with curls and breaks. In SCFA+ LPS group, the appearance of cells and distribution of ZO-1 were remarkably ameliorated compared with those in LPS group.
Conclusions SCFA can alleviate the barrier disruption of human intestinal epithelial cell induced by LPS through interdicting the abnormal distribution of ZO-1 and decrease of TER and tight junction proteins′ expressions.
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