Regulatory role of high mobility group box-1 protein in the balance of Th17/Treg in peripheral blood of immune thrombocytopenia patients

Objective To explore the effect of high mobility group box-1 protein (HMGB1) on the balance of Th17/Treg in patients with immune thrombocytopenia (ITP). Methods A total of 30 patients who were first diagnosed as ITP in the Fifth People's Hospital of Datong from July 2017 to April 2018 were selected as the case group, and another 30 healthy volunteers in the corresponding period were taken as the control group. The proportion of Th17 and Treg cells was detected by using flow cytometry, and the concentration of HMGB1, interleukin (IL)-17 and transforming growth factor β (TGF-β) in plasma was tested by using enzyme-linked immunosorbent assay (ELISA). Isolated peripheral blood mononuclear cells (PBMC) were cultured in vitro. After the treatment with recombinant human HMGB1 (rhHMGB1), real-time polymerase chain reaction (RT-PCR) was applied to detect the mRNA expression changes in Treg cell transcription factor intracellular forkhead helix transcription factor 3 (Foxp3) and Th17 cell transcription factor retinoid related orphan receptor γt (RORγt). The differences of indicators in Treg cell transcription factor peripheral blood between the case group and the control group were compared, and the balance correlation between HMGB1 and Th17/Treg was analyzed. Results Compared with the healthy control group, the proportion of Th17 cells and the expression level of HMGB1 and IL-17 in peripheral blood of ITP patients were increased (all P < 0.01), while the proportion of Treg cells and the level of TGF-β were decreased (all P < 0.01). The proportion of Th17 cells and the expression level of IL-17 and HMGB1 in peripheral blood of ITP patients were positively correlated with the concentration of HMGB1 (all P < 0.01); the proportion of Treg cells and the level of TGF-β were negatively correlated with the expression level of HMGB1 (all P < 0.01). In vitro experiments, the expression of intracellular RORγt mRNA was increased compared with the negative control group (1.50±0.24 vs. 0.93±0.22, t = 9.612, P < 0.01), and the expression of Foxp3 mRNA was decreased compared with the negative control group after the stimulation of PBMC by rhHMGB1 (0.72±0.19 vs. 1.08±0.18, t = 7.387, P < 0.01). Conclusion The high level of HMGB1 in the peripheral blood of ITP patients induces Th17/Treg imbalance and aggravates inflammatory reactions, which may be an important cause of ITP. Key words: Immune thrombocytopenia; High mobility group box 1 protein; Th17/Treg balance; In vitro culture