Objective      To determine the effect of mannose binding lectin (MBL) on the epithelial barrier function of Caco-2 cells and investigate the underlying mechanism.       Methods      In the in vivo study

14 C57Bl/6 mice were randomly divided into 2 groups

sham-operation and LPS groups. The LPS mice received intra-peritoneal injection of LPS to induce acute barrier injury. The expression of MBL at protein and mRNA levels in the intestinal mucosa was detected by immuno-histochemical assay and PCR

respectively. The morphological change of intestinal mucosa was observed by hematoxylin-eosin (HE) staining. In the in vitro study

Caco-2 cells were transfected with MBL-shRNA plasmid. Then

the expression of tight junction protein at protein and mRNA levels was measured by Western blotting and real-time PCR

respectively

and transepithelial electrical resistance (TER) was determined.       Results      In vivo study found that LPS group increased intestinal permeability compared with sham group (TER value: 80.32±5.43 vs 140.45±4.78

P0.01). HE staining showed LPS group had enhanced disruption of intestinal morphological structure than the sham group. Immuno-histochemical assay and real-time PCR assay indicated that the expression levels of MBL were apparently increased after LPS exposure (P0.05). After Caco-2 cells were transfected with MBL-shRNA plasmid

the expression of MBL at protein and mRNA levels was significantly decreased in MBL-shRNA cells (0.34±0.09

0.42±0.12) than the control-shRNA cells and the blank cells (P0.05). The protein and mRNA expression levels of Occludin (0.43±0.10

0.43±0.08) and Claudin-1 (0.53±0.11

0.45±0.10) were obviously lower in MBL-shRNA cells than in control-shRNA and blank cells (P0.05). The TER was 80.33±7.64 in the MBL-shRNA cells

significantly lower than the other cells (P0.05).       Conclusion      Down-regulation of MBL decreases the expression of tight junctions proteins Occludin and Claudin-1 at mRNA and protein levels

and attenuates the epithelial barrier function.