Effects of ulinastatin on expression pattern of high mobility group box-1 protein and CD4+ CD25+ regulatory T cells in rats with scald injury

Aim of the study: To observe the effects of ulinastatin on T lymphocyte immune function and the expression of high mobility group box-1 protein (HMGB1) in rats with scald injury. Material and methods: A total of 96 Wistar rats were randomly divided into three groups (32 rats in each group): sham burn group (S), burn group (B), ulinastatin-treated group (BU). Sham-burned rats were immersed in distilled water at 37 °C for 12 seconds and served as control, rats in the later two groups were inflicted with 30% TBSA full thickness burns at boiling water (94 °C) for 12 seconds, followed by resuscitation with Ringer’s solution (i.p.). The treatment group (BU) received ulinastatin and the control group was given the same amount of saline solution immediately following burn injury, wounds in rats were soaked in 1% povidone-iodine solution. Blood samples and spleens were collected at 1, 3, 5, 7 d after injury for further laboratory investigations. High mobility group box-1 protein expression was evaluated by western blotting, the presence of CD4+ CD25+ regulatory T cells were determined with flow cytometry, the plasma IL-4 and IFN- γ levels were determined using ELISA. Results: Compared with the S group (0.22 ±0.05), during postburn days 1 to 7, the level of HMGB1 in splenic tissue was significantly elevated in the B group (p < 0.01), reached the maximum at 3 d after injury (0.66 ±0.10, p < 0.01). After treated with ulinastatin, HMGB1 level was markedly decreased, reached the lowest value at 5 d (0.32 ±0.07, p < 0.01). Compared with the sham burn group, percent age of CD4+ CD25+ Treg cells in B group gradually increased after injury and peaked at 3 d after injury (5.42% ±0.56%). After burn injury 1, 5, 7 d, percentage of CD4+ CD25+ Treg cells in BU group was significantly lower than the B group (p < 0.01), reached the lowest at 5 d (2.23% ±0.21%). The serum level of IFN- γ in B group was significantly higher than the S group (p < 0.01), IL-4 was sig nificantly higher than that of the S group (p < 0.01). After injury for 1~7 d, the content of IFN- γ in BU group were significantly higher than the B group (p < 0.05 or p < 0.01), and IL-4 level was significantly lower than the burn group (p < 0.05 or p < 0.01). Conclusions: As an anti-inflammatory drug, ulinastatin effectively reduced the expression of HMGB1 in the spleen tissue of severely burned rats, which was associated with reduction in the level of regula tory T cells (Treg), and the functional polarization of splenic T cells levels and Th1/Th2 pattern changes. Taken together these data suggested that ulinastatin improved the immune function of rats with scald injury.