To investigate the role and mechanism of high mobility group box 1(HMGB1) in the injury of Caco-2 intestinal epithelial barrier induced by lipopolysaccharide (LPS).

The Caco-2 cellular monolayer barrier was established with Transwell chamber. After the Caco-2 monolayer model was established, the transepithelial electrical resistance (TEER) values were measured. When the TEER value reached 500 Ω·cm ², the cells were divided into 3 groups: control group, LPS treatment group, and LPS+ ethyl pyruvate (EP) treatment group. The concentration of LPS and EP were 100 μg/mL, 50 μg/mL, separately. Then TEER values were measured at 12, 24, 48 and 72 h, and FITC-dextran permeability was detected at 24 h. The cells were seeded on 6-well plates. After cell density reached 80%, treatments were given as the above. The real-time polymerase chain reaction (RT-PCR) and Western blot were used to measure the changes in the protein and mRNA expressions of Occludin, HMGB1, and nuclear factor-κB (NF-κB).

Compared with the control group, the TEER values (Ω·cm²) reduced at 12, 24, 48 and 72 h in the LPS treatment group [(514.22±12.59) vs (304.96±9.69), (521.65±13.35) vs (276.21±7.82), (523.99±8.18) vs (206.64±15.85), (491.21±6.72) vs (156.33±10.83), all P<0.05]. The FITC-dextran permeability increased significantly at 24 h [(2.58±0.07) vs (1.04±0.06), P<0.05]. The expression levels of Occludin protein and mRNA were decreased (all P<0.05), while the expression levels of HMGB1 and NF-κB protein and mRNA were significantly increased (allP<0.05). Compared with the LPS treatment group, the TEER values (Ω·cm²) increased significantly at 12, 24, 48 and 72 h in the EP treatment group [(519.00±5.66) vs (304.96±9.69), (504.69±8.57) vs (276.21±7.82), (453.65±10.74) vs (206.64±15.85), (385.28±7.57) vs (156.33±10.83), all P<0.05]. The FITC-dextran permeability decreased at 24 h [(1.23±0.11) vs (2.58±0.07), P<0.05]. The expression level of Occludin protein and mRNA were increased (P<0.05), while the expression levels of HMGB1 and NF-κB protein and mRNA were significantly decreased (allP<0.05).

LPS can injure intestinal barrier directly in vitro and reduces the expression of tight junction proteins between cells. The mechanism may be related to the increased expression of HMGB1 and NF-κB protein.

Sepsis; Intestinal epithelial barrier function; High mobility group box 1; Lipopolysaccharide; Caco-2 cells