Abstract
ObjectiveThe objective of this study was to understand the role of bactericidal permeability increasing protein (BPI) in the pathogenesis of experimental murine colitis.MethodsWe used the Cre-LoxP system to generate BPI knockout (BPI KO) mice. Acute colitis was induced in BPI KO mice and wild-type (WT) mice by subjecting the mice to 5% dextran sulfate sodium (DSS). Mice were observed for symptoms of experimental colitis. The survival of BPI KO mice to infection with Acinetobacter baumannii, a gram-negative bacterium, was also assessed.ResultsSouthern blot, RT-PCR, and western blot results showed that the 2nd and 3rd exons of the murine Bpi gene were knocked out systemically, confirming successful construction of the BPI KO mouse. BPI KO mice subjected to DSS showed increased symptoms of experimental colitis, increased colonic mucosal damage, increased epithelial permeability, elevated levels of serum LPS, and a disrupted fecal microbiome as compared with WT mice. Furthermore, BPI KO mice challenged intraperitoneally with A. baumannii died sooner than WT mice, and the total number of bacteria in the abdominal cavity, spleen, and liver was increased in BPI KO mice as compared to WT mice.ConclusionsWe successfully generated BPI KO mice. The BPI KO mice developed worse colitis than WT mice by increased colitis symptoms and colonic mucosal damage, elevated levels of serum LPS, and a disrupted microbiome. BPI could be a potential target for treatment of ulcerative colitis in humans.
Highlights
Bactericidal permeability-increasing protein (BPI), a cationic protein with a molecular weight of 55 kDa [1, 2], is found in the neutrophils of humans, cattle, pigs, mice, and other mammals that have bactericidal and neutralizing-endotoxins [e.g., bacterial lipopolysaccharide (LPS)] function [3, 4]
BPIfl/- mice on a 129 background were mated with Prm-cre mice, and the F1 generation of BPI+/- mice was obtained (Figure 1, bottom)
The results showed a band in WT mice at 6.9 kb, a band in BPIfl/fl mice at 6.1 kb, and two bands, 6.1 kb and 4 kb, in BPI+/- mice (Figure 2A)
Summary
Bactericidal permeability-increasing protein (BPI), a cationic protein with a molecular weight of 55 kDa [1, 2], is found in the neutrophils of humans, cattle, pigs, mice, and other mammals that have bactericidal and neutralizing-endotoxins [e.g., bacterial lipopolysaccharide (LPS)] function [3, 4]. The sequence of the murine Bpi gene was first reported in 2005. The mRNA expression of Bpi in nine tissues, including the heart, liver, spleen, lung, kidney, testis, and ovary, was measured, but positive expression was found only in the testis [7]. The gene expression of BPI increased approximately 80–100 times in mouse neutrophils 24 h after the mice were injected with LPS [8]. Our lab has prepared and identified murine Bpi gene systemic knockout plasmids [9] which can be used in this area of research
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