OBJECTIVETo investigate the effect of high mobility group box protein 1 (HMGB1) on the production of pro-inflammatory cytokines by Kupffer cell (KC) of rats with severe burn and the role of receptor for advanced glycation end products (RAGE) in the process.

METHODSModel of 30% TBSA full-thickness burn was reproduced in 32 SD rats through immersing the back in 98°C water for 12 s. KC (32 samples) was isolated from rat liver 24 h after injury and inoculated in 24-well plate in the concentration of 1×10(6) cell per well. (1) Cells were divided into control group (cultured with 1 mL PBS) and HMGB1 group (stimulated with 100 ng/mL HMGB1 in the volume of 1 mL) according to the random number table, with 8 samples in each group. At post culture hour (PCH) 48, the expression of RAGE (denoted as grey value ratio) was detected with Western blotting. (2) Another portion of cells were divided into control group (cultured with 1 mL PBS), HMGB1 group (treated with 100 ng/mL HMGB1 in the volume of 1 mL), HMGB1 + anti-RAGE antibody group (treated with 100 ng/mL HMGB1 in the volume of 1 mL after being pre-incubated with 20 µg/mL anti-RAGE monoclonal antibody in the volume of 1 mL for 2 hours), HMGB1 + recombinant rat RAGE/Fc chimera (rrRAGE/Fc) group (treated with the mixture of 100 ng/mL HMGB1 in the volume of 0.5 mL and 5 µg/mL rrRAGE/Fc in the volume of 0.5 mL which were pre-incubated for 2 hours) according to the random number table, with 8 samples in each group. At PCH 48, the protein levels of TNF-α and IL-1β in supernatant were determined with enzyme-linked immunosorbent assay, while the mRNA expression of TNF-α and IL-1β (denoted as grey value ratio) were determined with Northern blotting. Data were processed with one-way analysis of variance, t test, and LSD test.

RESULTS(1) The expression of RAGE in HMGB1 group (1.036 ± 0.101) was significantly higher than that of control group at PCH 48 (0.191 ± 0.024, t = -23.158, P = 0.000). (2) In HMGB1 group, HMGB1 + anti-RAGE antibody group, and HMGB1 + rrRAGE/Fc group, the contents of TNF-α in supernatant were respectively (10.59 ± 1.39), (9.91 ± 1.68), (11.51 ± 2.27) ng/mL; the contents of IL-1β in supernatant were respectively (2.49 ± 0.33), (2.08 ± 0.32), (2.42 ± 0.42) ng/mL; the mRNA levels of TNF-α in cells were respectively 0.311 ± 0.009, 0.301 ± 0.047, 0.326 ± 0.016; the mRNA levels of IL-1β in cells were respectively 0.237 ± 0.021, 0.244 ± 0.041, 0.245 ± 0.013. There were no statistically significant differences in the above indexes among these three groups (with P values all above 0.05). Their levels were all significantly higher than those of control group [with contents of TNF-α and IL-1β in supernatant respectively (2.69 ± 0.14), (0.43 ± 0.05) ng/mL, and mRNA levels of TNF-α and IL-1β in cells respectively 0.140 ± 0.022, 0.077 ± 0.005, P values all below 0.01].

CONCLUSIONSHMGB1 can induce the production of pro-inflammatory cytokines TNF-α and IL-1β from the KC in rats with severe burn. However, RAGE does not play a predominant role in this process.