Molecular mechanism of TLR4 mediated T cell immune effect in transfusion-induced acute lung injury based on Slit2/Robo4 signaling pathway

Abstract

Objective: To explore and investigate the molecular mechanism of TLR4 mediated T cell immune effect in transfusion-induced acute injury based on SLIT2/ROBO4 signaling pathway. Methods: Sixty C57/BL6 male mice (Wild type, WT) aged 8 to 10 weeks were randomly divided into 5 groups: 1) normal type WT, 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 dosed with LPS (0.1 mg / kg), and MHC-I mAb (2 mg / kg) was injected into the tail vein 24 hours later for modeling. After 2 hours, mice were sacrificed and experimental samples were collected. HE staining was performed to detect pathological features. The myeloperoxidase (MPO) activity and the level of IL-2, IL-6, TNF, IFN-γ, IL-17A as well as IL-10 were measured in the lung tissue homogenate supernatant. Blood, spleen single cell suspension and bronchoalveolar lavage fluid (BALF) were collected to detect the ratio of Treg and Th17 cells by flow cytometry, respectively. RT-PCR and WB indicated the mRNA or protein expression of CDH5 (Cadherin-5), SLIT2 and ROBO4 in mouse lung tissue and pulmonary vascular tissue respectively. Results: TLR4 mAb treatment decreases the pathological features of LPS induced ALI model in vivo. And so does the MPO activity as well as the level of proinflammatory factors in the lung tissue. TLR4 exerts its function through the changes of Treg/Th17 ratio via SLIT2/ROBO4 signaling pathway and downregulating CDH5 and SETSIP in ALI model. Conclusion: TLR4 mediates immune response in LPS induced ALI model through SLIT2/ROBO4 signaling pathway.