BAP31 Promotes Adhesion Between Endothelial Cells and Macrophages Through the NF-κB Signaling Pathway in Sepsis
Jiawei He1, Danyang Jing1, Shen Zhao1
1Department of Critical Care Medicine, Beijing Friendship Hospital, Capital Medical University, Beijing, People's Republic of China.
Purpose:
To investigate the role of B cell receptor associated protein 31 (BAP31) in the pathogenesis of sepsis.
Methods:
Cecal ligation and puncture (CLP)-induced C57BL/6J mice, and LPS-challenged endothelial cells (HUVECs) were established to mimic a sepsis animal model and a sepsis cell model, respectively. Cre/LoxP and shRNA methods were used for BAP31 knockdown in vivo and in vitro respectively. Neutrophils/macrophages-endothelial cocultures were used to evaluate neutrophils or macrophages infiltration and adhesion to endothelial cells. Cox proportional hazards model was used to evaluate the survival time of mice. Western blotting (WB) and Quantitative real-time polymerase chain reaction (qRT-PCR) were used to detect toll-like receptor (TLR) signaling pathway, transforming growth factor β activated kinase 1 (TAK1) signaling pathway and phosphoinositide-3 kinases-protein kinase B (PI3K/AKT) signaling pathway.
Results:
Deletion of BAP31 reduced CLP-induced mortality of mice, histological damage with less interstitial edema, and neutrophils and macrophages infiltration. IHC and IF showed that BAP31 knockdown significantly decreases the expressions of ICAM1 and VCAM1 both in vivo and in vitro. Coculture showed that LPS-induced neutrophils or macrophages adhesion to endothelial cells was significantly weakened in BAP31 knockdown cells. In addition, BAP31 knockdown of endothelial cells decreased the expression of CD80 and CD86 on the surface of macrophages as well as interleukin 1β (IL-1β) and tumor necrosis factor α (TNF-α) during sepsis. Mechanistically, LPS-induced the activation of TLR4, MyD88 and TRAF6, and the phosphorylation of TAK1, PI3K, AKT, IκBα and IKKα/β, resulting in activation of nuclear factor kappa B (NF-κB) p65 in endothelial cells. However, BAP31 knockdown significantly reversed the expressions of associated proteins.
Conclusion:
BAP31 up-regulated the expressions of ICAM1 and VCAM1 in endothelial cells leading to sepsis-associated organ injury. This may be involved in activation of TLR signaling pathway, TAK1 pathway, and PI3K-AKT signaling pathway.
Insights
B cell receptor associated protein 31 (BAP31) promotes sepsis by increasing endothelial cell adhesion molecules. Reducing BAP31 in sepsis models lowers mortality and organ damage by inhibiting inflammatory signaling pathways.
Area of Science:
- Molecular biology
- Immunology
- Pathophysiology
Background:
- Sepsis is a life-threatening organ dysfunction caused by a dysregulated host response to infection.
- Endothelial cell activation plays a critical role in sepsis pathogenesis, leading to inflammation and organ damage.
- The specific molecular mechanisms underlying endothelial cell dysfunction in sepsis require further elucidation.
Purpose of the Study:
- To investigate the role of B cell receptor associated protein 31 (BAP31) in the pathogenesis of sepsis.
- To determine the impact of BAP31 on endothelial cell activation and inflammatory responses during sepsis.
- To elucidate the signaling pathways influenced by BAP31 in sepsis.
Main Methods:
- Established cecal ligation and puncture (CLP)-induced mouse model and LPS-challenged human umbilical vein endothelial cell (HUVEC) model for sepsis.
- Utilized Cre/LoxP and shRNA for BAP31 knockdown in vivo and in vitro, respectively.
- Employed neutrophils/macrophages-endothelial co-cultures, Western blotting, qRT-PCR, IHC, and IF to analyze cellular infiltration, adhesion, gene/protein expression, and signaling pathways (TLR, TAK1, PI3K/AKT).
Main Results:
- BAP31 knockdown significantly reduced CLP-induced mortality, histological damage, and neutrophil/macrophage infiltration in mice.
- BAP31 knockdown decreased ICAM1 and VCAM1 expression in endothelial cells, weakening neutrophil and macrophage adhesion.
- BAP31 knockdown attenuated LPS-induced activation of TLR4, TAK1, PI3K/AKT, and NF-κB signaling pathways, and reduced pro-inflammatory cytokine production.
Conclusions:
- BAP31 upregulates ICAM1 and VCAM1 in endothelial cells, contributing to sepsis-associated organ injury.
- BAP31's role in sepsis pathogenesis involves the modulation of TLR, TAK1, and PI3K-AKT signaling pathways.
- Targeting BAP31 may represent a therapeutic strategy to mitigate sepsis-induced inflammation and organ damage.
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