Hydrogen sulfide induces regulatory B cells via glycolysis and mitochondrial ROS, attenuating LPS-induced lung injury

Hydrogen sulfide (H2S) is a gasotransmitter found in the human body that plays a crucial role in maintaining homeostasis of various biological systems, including the immune system. While prior studies have explored the effects of H2S on T cells, its impact on B cells has yet to be elucidated. We used sodium hydrosulfide (NaHS) as an exogenous donor for H2S. LPS was used to activate B cells and promote their differentiation into plasma cells or regulatory B cells (Bregs). Bregs phenotypes were analyzed by flow cytometry and ELISA, and their immunosuppressive functions on neutrophils and CD4 T cells were assessed by co-culturing them with B cells. To investigate the therapeutic effect of B cells on acute lung injury, we adoptively transferred H2S-induced Bregs to mice with LPS-induced acute lung injury. Both exogenous and endogenous H2S induced regulatory phenotypes of B cells including IL-10 production and programmed cell death ligand-1 (PD-L1) expression. Bregs induced by LPS and exogenous H2S functionally suppressed neutrophils and CD4 T cells. H2S-induced Bregs not only induced neutrophil apoptosis and suppressed neutrophil ROS but also inhibited CD4 T cell proliferation and pro-inflammatory cytokine production. H2S enhanced PI3K/Akt/mTORC1 signaling pathway and glycolysis during LPS stimulation, which partially mediated IL-10 production and PD-L1 expression. Moreover, H2S donor administration activated mitochondrial electron transport chain usage, resulting in increased mitochondrial oxygen consumption. Change of mitochondrial redox state contributed to the regulatory phenotypes of H2S-induced Bregs, which were confirmed with mitochondrial-specific redox regulators. In LPS-induced acute lung injury model, adoptive transfer of H2S-induced Bregs was able to protect tissue damage and alleviate lung inflammation by decreasing pro-inflammatory cytokines and increasing neutrophil apoptosis. This study reveals that H2S shifts B cells to have regulatory phenotypes via shifting metabolic pathway and enhancing mitochondrial expenditure. H2S can serve as one of the inducers and environmental signals for Bregs to resolve inflammation via signaling and metabolic pathways in B cells.