[Influence of splenic high mobility group box-1 protein on immune function of regulatory T lymphocytes in scald rats]

To observe the influence of high mobility group box-1 protein (HMGB1) derived from spleen on the phenotype of regulatory T lymphocytes (Treg) and HMGB1-mediated immune function in severely scalded rats after delayed resuscitation.

One hundred and four Wistar rats were divided into normal control group (NC, n = 8), sham scald group (SS, n = 32), scald group (S, n = 32), and ethyl pyruvate (EP) treatment group (EPT, n = 32) according to the random comparison table. Rats in the latter 2 groups were subjected to 30%TBSA full-thickness scald, which were intraperitoneally injected with Ringer solution or EP solution at post scald hour (PSH) 6 (delayed antishock treatment) and administered with 4 mL Ringer solution or EP solution per 12 hours after PSH 12 till PSH 48. Rats in SS group were treated the same as that of S group except for sham scald with 37 degrees C water. Injured rats were sacrificed at post scald day (PSD) 1, 3, 5, 7 (rats in NC group were also sacrificed), and CD4(+)CD25(+)Treg were isolated from spleen with magnetic-activated cell sorting method. The content of HMGB1 in spleen and IL-2 level in supernatant were determined with ELISA. The expression of cytotoxic T lymphocyte-associated antigen 4 (CTLA-4) on Treg was determined with flow cytometry, and the proliferation activity of T lymphocytes was also detected (recorded as absorbance value). Data were processed with analysis of variance among groups and independent samples t test.

(1) Compared with that of rats in SS group and EPT group, the expression of splenic HMGB1 in S group increased significantly on PSD 1 through PSD 7 [peaked on PSD 1: (46.7 +/- 8.3) ng/mg protein]. (2) Compared with that in SS group, the expression of CTLA-4 in S group was enhanced significantly on PSD 1 through PSD 5 (with t value respectively 10.459, 12.051, 4.029, P < 0.05 or P < 0.01); while that in EPT group decreased significantly on PSD 1 through PSD 7 as compared with that from S group (with t value respectively 2.796, 9.913, 9.581, 10.022, P < 0.05 or P < 0.01). (3) Compared with that of rats in SS group, the proliferation activity of T lymphocytes in S group was markedly suppressed on PSD 1 through PSD 7 (nadir on PSD1: 0.167 +/- 0.059), and release of IL-2 was decreased significantly [nadir on PSD 5: (44 +/- 24) pg/mL]. T lymphocytes proliferation activity was restored and excretion of IL-2 increased in EPT group as compared respectively with that of S group at each time point.

The release of HMGB1 may stimulate splenic Treg to mature, thereby induce suppression of proliferation activity of T lymphocytes and immune function. EP can ameliorate immune dysfunction in animals with delayed resuscitation through inhibiting the synthesis and release of HMGB1.