Escherichia coli Braun Lipoprotein (BLP) exhibits endotoxemia – like pathology in Swiss albino mice.

The endotoxin lipopolysaccharide (LPS) promotes sepsis, but bacterial peptides also promote
inflammation leading to sepsis. We found, intraperitoneal administration of live or heat inactivated
E. coli JE5505 lacking the abundant outer membrane protein, Braun lipoprotein (BLP), was less
toxic than E. coli DH5α possessing BLP in Swiss albino mice. Injection of BLP free of LPS purified
from E. coli DH5α induced massive infiltration of leukocytes in lungs and liver. BLP activated human
polymorphonuclear cells (PMNs) ex vivo to adhere to denatured collagen in serum and polymyxin B
independent fashion, a property distinct from LPS. Both LPS and BLP stimulated the synthesis of
platelet activating factor (PAF), a potent lipid mediator, in human PMNs. In mouse macrophage cell
line, RAW264.7, while both BLP and LPS similarly upregulated TNF-α and IL-1β mRNA; BLP was more
potent in inducing cyclooxygenase-2 (COX-2) mRNA and protein expression. Peritoneal macrophages
from TLR2−/− mice significantly reduced the production of TNF-α in response to BLP in contrast to
macrophages from wild type mice. We conclude, BLP acting through TLR2, is a potent inducer of
inflammation with a response profile both common and distinct from LPS. Hence, BLP mediated
pathway may also be considered as an effective target against sepsis.