PD-L1 as a Potential Inducer for NF-κB Pathway Activation in M1-Type Macrophages During Sepsis: An Integrated Analysis Based on GEO Public Database and Multi-Omics Data.

[BACKGROUND] M1-type macrophages are a crucial defense line against pathogens during sepsis, and their polarization depends on NF-κB pathway activation. However, the specific molecular regulatory mechanisms of this process are not fully elucidated. Programmed death-ligand 1 (PD-L1), an important immune checkpoint molecule, is often anchored on the cell membrane exerting immunosuppressive effects, but its role in M1-type macrophages remains poorly understood.

[METHODS] In this study, we preliminarily investigated the potential regulatory effect of PD-L1 on the NF-κB pathway in M1 macrophages by integrating GEO sepsis patient sequencing datasets, RNA-seq data from PD-L1-overexpressing M1 macrophages, immunoprecipitation-mass spectrometry (IP-MS), molecular docking, and co-immunoprecipitation (Co-IP). The Receiver Operating Characteristic (ROC) curve of PD-L1 was used as a prognostic indicator for sepsis. PD-L1 knockout mice were utilized to validate the in vivo regulatory effects of PD-L1.

[RESULTS] Analysis of GEO data and peripheral blood mononuclear cells (PBMCs) from sepsis patients revealed significantly elevated PD-L1 expression with a central position among all upregulated genes. Furthermore, this elevated PD-L1 expression was validated in peripheral monocytes from sepsis patients compared to healthy controls. Single-gene GSEA analysis based on GEO data indicated a close association between PD-L1 and NF-κB pathway activation in sepsis patients. RNA-seq analysis of PD-L1-overexpressing M1 macrophages confirmed that PD-L1 significantly activates the NF-κB pathway. IP-MS screening and Co-IP validation identified an interaction between PD-L1 and KLF6, a nuclear factor closely related to the NF-κB pathway. Finally, liver transcriptome data from septic mice confirmed that PD-L1 can also activate the NF-κB pathway in vivo, and ROC curve analysis demonstrated PD-L1's potential as a prognostic indicator for sepsis.

[CONCLUSION] Based on these results, this study preliminarily reveals a potential activating role of PD-L1 on the NF-κB pathway in M1 macrophages.