Mechanism of TLR4 mediated immune effect in transfusion-induced acute lung injury based on Slit2/Robo4 signaling pathway

Abstract

Background: Transfusion-related acute lung injury (TRALI) is the infusion of blood or blood system.

Objective: To explore the mechanism of TLR4-mediated T cell immune effect in TRALI.

Methods: In this animal study, a mouse model of LPS-induced TRALI was established. Sixty adult C57/BL6 mice (wild-type, WT) were randomly divided into 5 groups: 1) normal WT type, 2) LPS control group of WT type lipopolysaccharide, 3) WT type TRALI group (LPS + MHC-I mAb), 4) (TLR4 antibody) lipopolysaccharide LPS control group, 5) (TLR4 antibody) TRALI group (LPS + MHC-I mAb). Mice were injected with LPS (0.1 mg/kg) and MHC-I mAb (2 mg/kg) into the tail vein. H&E staining was performed to detect pathological features. The myeloperoxidase (MPO) activity and the level of inflammatory cytokines in lung tissue homogenate supernatant were measured. Blood, spleen single-cell suspension, and bronchoalveolar lavage fluid were collected to detect the ratio of Treg and Th17 cells by flow cytometry. RT-PCR and WB were used to detect mRNA or protein expression.

Results: TLR4 mAb treatment alleviated the pathogenesis of LPS-induced TRALI in vivo, the MPO activity, and the level of proinflammatory factors in lung tissues. TLR4 exerted its function by changing of Treg/Th17 ratio via the SLIT2/ROBO4 signaling pathway and downregulating CDH5 and SETSIP.

Conclusion: TLR4 mediates immune response in the LPS-induced TRALI model through the SLIT2/ROBO4 signaling pathway.

Keywords: Acute lung injury; Mechanism; Slit2/Robo4 signaling pathway; T cell immune effect; TLR4; Transfusion.