Bactericidal permeability-increasing protein (BPI)

Bactericidal permeability-increasing protein (BPI) is a 55–60 kDa cationic protein predominantly found in the granules of human neutrophils, as well as in some epithelial cells[1][2]. It is a member of the TULIP (tubular lipid binding) family and exhibits potent antimicrobial activity, particularly against Gram-negative bacteria by binding to lipopolysaccharide (LPS), a component of their outer membrane[1][2]. BPI neutralizes LPS, reducing its endotoxic activity and associated inflammation, and can lead to bacterial cell death by damaging bacterial membranes[1][2]. The protein also plays a role in opsonization and facilitates the recognition and uptake of bacterial components by immune cells[1]. Structurally, BPI is divided into two domains: the amino-terminal region is highly cationic and responsible for bactericidal and LPS-binding activity, while the carboxy-terminal region contributes to opsonization and cell interactions[1][2]. Recent research has revealed that BPI also interacts with bacterial lipopeptides and lipoteichoic acids from Gram-positive bacteria, enhancing immune response—marking a role beyond Gram-negative defense[2]. BPI has anti-angiogenic properties, can bind vascular endothelial growth factor (VEGF), and modulate vascular and immune cell signaling pathways[1]. Therapeutic applications for recombinant BPI are being explored in infectious and inflammatory diseases, but its dual role as both neutralizer and enhancer (depending on the ligand and context) raises important safety and mechanistic considerations[1][2].

Other names

Bactericidal/permeability-increasing proteinBPIBPIFD1CAP 57BPI fold containing family D member 1recombinant BPI holoproteinrBPI

Binds and neutralizes LPS from Gram-negative bacteria; disrupts bacterial membranes leading to bactericidal effect; enhances or modulates immune response to bacterial lipopeptides and lipoteichoic acids in Gram-positive bacteria; inhibits LPS-induced inflammatory signaling; can modulate angiogenesis by binding VEGF