HMGB1 suppress the expression of IL-35 by regulating Naïve CD4+ T cell differentiation and aggravating Caspase-11-dependent pyroptosis in acute lung injury.

Objectives: Acute lung injury/acute respiratory distress syndrome (ALI/ARDS) is a severe form of inflammatory lung disease. Its development and progression are regulated by cytokines. The purpose of this study was to determine the effects of HMGB1 involved in the regulation of Treg cells and IL-35.

Methods: A cecal ligation and puncture (CLP)-induced ALI model was used to investigate the changes in IL-35, Tregs, and the expression of RAGE and caspase-11 after HMGB1 inhibition (glycyrrhizin was used as an inhibitor of HMGB1). CD4+ naïve T cells sorted from C57BL/6 mice spleens were cultured to explore the role of HMGB1 in the differentiation from CD4+ naïve T cells to Tregs.

Results: HMGB1 promoted lung injury and uncontrolled inflammation in the CLP mouse model. HMGB1, NF-κB p65, RAGE, and caspase-11 expression in the lungs of CLP mice decreased significantly after pretreatment with glycyrrhizin. We found that the Treg proportion and IL-35 expression were upregulated in the serum and lung of CLP mice after inhibiting HMGB1. In our in vitro experiments, we found that recombinant HMGB1 significantly suppressed the proportion of CD4+CD25+FOXP3+Tregs differentiated from CD4+ naïve T cells.

Conclusions: The inhibition of HMGB1 increased the proportion of Treg and expression of IL-35 and alleviated lung injury in the CLP-induced ALI model. Furthermore, inhibition of HMGB1 reduced caspase-11-dependent pyroptosis in the lungs of the CLP-induced ALI model.