Background: M1 polarized macrophage, which is recruited in ABMR after kidney transplantation, has recently been shown to participate in the immune response of acute kidney allograft rejection, resulting in allograft glomerulitis, arteritis, peritubular capillary vasculitis and ultimately affect the prognosis of patients. Exosomes are important intermediates of intercellular communication through their nucleic acid components, which are widely studied. However, the function and mechanism of exosome-encapsulated proteins in vascular inflammation injury after kidney transplantation remain unclear. This study aimed to investigate the effects of macrophage-derived exosomes on vascular inflammation in ABMR after kidney transplantation.
Methods: In this study, we extracted mouse bone marrow-derived macrophages and induced M1 polarization in vitro to perform high-throughput sequencing and exosomal proteomic sequencing to search for differentially expressed proteins and verified them by Immunoblotting. An in vitro co-culture model of macrophages and endothelial cells was constructed, endothelial cell inflammatory markers were detected by RT-PCR, western blot, and immunofluorescence, and interactions between exosomal proteins and key pathway proteins in endothelial cells were detected by immunoprecipitation. A renal transplantation acute rejection model was performed in conditional knockout mice, and immunohistochemistry was used to detect vascular injury level, and Syk expression in vascular endothelium and macrophages as well.
Results: In the macrophage-endothelial cell co-culture model in vitro, M1-polarized macrophages increase the expression of inflammatory injury-associated protein in endothelial cells, which can be reduced by pretreatment of M1-polarized macrophages with exosome inhibitors. By intervening Syk knockout endothelial cells with M1-polarized macrophage exosomes, we found that exosome-derived Syk was associated with elevated inflammatory injury markers in endothelial cells by binding to NLRP3 inflammatory vesicles.
Conclusion: Syk, which can be detected in M1 polarized macrophage-derived exosomes, mediates vascular endothelial injury in ABMR after kidney transplantation. Further research may provide a potentially prognostic biomarker and therapeutic target for kidney transplantation.