Phospholipids Inhibit Lipopolysaccharide (LPS)-Induced Cell Activation: A Role for LPS-Binding Protein

Vascular endothelium activated by endotoxin (lipopolysaccharide [LPS]) and cytokines plays an important role in organ inflammation and blood leukocyte recruitment observed during sepsis. Endothelial cells can be activated by LPS directly, after its interaction with LPS-binding protein and soluble CD14 in plasma. LPS-LPS-binding protein complexes in blood also interact with monocytes and neutrophils bearing glycosyl-phosphatidylinositol (GPI) anchored membrane CD14 (mCD14), promoting the release of cytokines such as tumor necrosis factor and interleukin 1 (IL-1). These molecules, in turn, have the capacity to activate endothelial cells providing an indirect pathway for LPS-dependent endothelial cell activation. In this work, we address the relative importance of the direct and the indirect pathway of in vitro LPS-induced human umbilical vein endothelial cell (HUVEC) activation. Substituting whole blood for plasma resulted in a 1,000-fold enhancement of HUVEC sensitivity to LPS. Both blood- and plasma-dependent enhanced activation of HUVEC were blocked with an anti-CD14 monoclonal antibody. Blood from patients with paroxysmal nocturnal hemoglobinuria, whose cells lack mCD14 and other GPI anchored proteins, was unable to enhance LPS activation of HUVEC above the level observed with plasma alone. IL-10, an inhibitor of monocyte release of cytokines, decreased the blood-dependent enhancement of HUVEC activation by LPS. Blood adapted to small doses of LPS was also less efficient than nonadapted blood in producing this enhancement. Addition of purified mononuclear cells to HUVEC or the transfer of plasma from whole blood incubated with LPS to HUVEC, duplicated the enhancement effect observed when whole blood was incubated with HUVEC. Taken together, these data suggest that the indirect pathway of LPS activation of endothelial cell is mediated by monocytes and mCD14 through the secretion of a soluble mediator(s). The indirect pathway is far more efficient than the direct, plasma-dependent pathway.

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Acute-Phase Concentrations of Lipopolysaccharide (LPS)-Binding Protein Inhibit Innate Immune Cell Activation by Different LPS Chemotypes via Different Mechanisms

Infection and Immunity ◽

10.1128/iai.73.1.193-200.2005 ◽

2005 ◽

Vol 73 (1) ◽

pp. 193-200 ◽

Cited By ~ 44

Author(s):

Lutz Hamann ◽

Christian Alexander ◽

Cordula Stamme ◽

Ulrich Zähringer ◽

Ralf R. Schumann

Keyword(s):

Acute Phase ◽

Cell Activation ◽

Immune Cell ◽

Nuclear Translocation ◽

Binding Protein ◽

Plasma Lipoproteins ◽

High Dose ◽

Cellular Activation ◽

Serum Free ◽

Lps Binding

ABSTRACT The chain length of bacterial lipopolysaccharide (LPS) is a crucial factor for host-pathogen interaction during bacterial infection. While rough (R)-type and smooth (S)-type LPSs have been shown to differ in their ability to interact with the bactericidal/permeability-increasing protein, little is known about the differential mode of interaction with the acute-phase reactant LPS-binding protein (LBP). At lower concentrations, LBP catalyzes the binding of LPS to CD14 and enhances LPS-induced cellular activation via Toll-like receptor 4. In humans, however, concentrations of LBP in serum increase during an acute-phase response, and these LBP concentrations exhibit inhibitory effects in terms of cellular activation. The mechanisms of inhibition of LPS effects by LBP are not completely understood. Here, we report that human high-dose LBP (hd-LBP) suppresses binding of both R-type and S-type LPS to CD14 and inhibits LPS-induced nuclear translocation of NF-κB, although cellular uptake of R-type LPS was found to be increased by hd-LBP. In contrast, we found that hd-LBP enhanced the binding and uptake of S-type LPS only under serum-free conditions, whereas in the presence of serum, hd-LBP inhibited cellular binding and uptake. This inhibitory effect of serum could be mimicked by the addition of purified high-density lipoprotein (HDL) to serum-free medium, indicating an LBP-mediated transfer of preferentially S-type LPS to plasma lipoproteins such as HDL. A complete understanding of the host's mechanisms to modulate the proinflammatory effects of LPS will most likely help in the understanding of inflammation and infection and may lead to novel therapeutic intervention strategies.

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Bactericidal/permeability-increasing protein and lipopolysaccharide (LPS)-binding protein. LPS binding properties and effects on LPS-mediated cell activation

Journal of Biological Chemistry ◽

10.1016/s0021-9258(17)32454-7 ◽

1994 ◽

Vol 269 (26) ◽

pp. 17411-17416 ◽

Cited By ~ 4

Author(s):

C.G. Wilde ◽

J.J. Seilhamer ◽

M. McGrogan ◽

N. Ashton ◽

J.L. Snable ◽

...

Keyword(s):

Cell Activation ◽

Binding Protein ◽

Binding Properties ◽

Lps Binding

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Treponemal glycoconjugate inhibits Toll-like receptor ligand-induced cell activation by blocking LPS-binding protein and CD14 functions

European Journal of Immunology ◽

10.1002/eji.200324219 ◽

2003 ◽

Vol 33 (11) ◽

pp. 3196-3204 ◽

Cited By ~ 23

Author(s):

Yasuyuki Asai ◽

Masahito Hashimoto ◽

Tomohiko Ogawa

Keyword(s):

Cell Activation ◽

Binding Protein ◽

Toll Like Receptor ◽

Receptor Ligand ◽

Lps Binding

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Hemoglobin Enhances the Binding of Bacterial Endotoxin to Human Endothelial Cells

Thrombosis and Haemostasis ◽

10.1055/s-0038-1650565 ◽

1996 ◽

Vol 76 (02) ◽

pp. 258-262 ◽

Cited By ~ 12

Author(s):

Robert I Roth

Keyword(s):

Endothelial Cells ◽

Binding Protein ◽

Bacterial Endotoxin ◽

Dependent Manner ◽

Serum Free Medium ◽

Free Medium ◽

Human Endothelial Cells ◽

Serum Factors ◽

Serum Free ◽

Lps Binding

SummaryHuman endothelial cells, when incubated with bacterial endotoxin (lipopolysaccharide, LPS), modify their surface in association with prominent production of procoagulant tissue factor (TF) activity. This deleterious biological effect of LPS has been shown previously to be enhanced approximately 10-fold by the presence of hemoglobin (Hb), a recently recognized LPS binding protein that causes disaggregation of LPS and increases the biological activity of LPS in a number of in vitro assays. The present study was performed to test the hypothesis that Hb enhances the LPS-induced procoagulant activity of human umbilical vein endothelial cells (HUVEC) by increasing LPS binding to the cells. The binding of 3H-LPS to HUVEC was determined in the absence or presence of Hb or two other known LPS-binding proteins, human serum albumin (HSA) and IgG. LPS binding was substantially increased in the presence of Hb, in a Hb concentration-dependent manner, but was not increased by HSA or IgG. Hb enhancement of LPS binding was observed in serum-free medium, indicating that there was no additional requirement for any of the serum factors known to participate in the interaction of LPS with cells (e.g., lipopolysaccharide (LPS)-binding protein (LBP) and soluble CD14 (sCD14)). Hb enhancement of LPS binding also was observed in the more physiologic condition of 100% plasma. LPS-induced TF activity was stimulated by Hb, but not by HSA or IgG. In serum-free medium, TF activity was not stimulated under any of the conditions tested. Ultrafiltration of LPS was dramatically increased after incubation with Hb but not with HSA or IgG, suggesting that LPS disaggregation by Hb was responsible for the enhanced binding of LPS to HUVEC and the subsequent stimulation of TF activity.

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Bacterial Lipopolysaccharide (LPS) Is Elevated in Different Causes of Stroke and Correlates with C-Reactive Protein, LPS Binding Protein and NIH Stroke Scale

SSRN Electronic Journal ◽

10.2139/ssrn.3678622 ◽

2020 ◽

Author(s):

Marisa Hakoupian ◽

Eva L. Ferino ◽

Glen C. Jickling ◽

Hajar Amini ◽

Boryana S. Stamova ◽

...

Keyword(s):

Binding Protein ◽

Bacterial Lipopolysaccharide ◽

C Reactive Protein ◽

Reactive Protein ◽

Lps Binding

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IDENTIFICATION OF THE LIPOPOLYSACCHARIDE (LPS) BINDING SITE OF LPS BINDING PROTEIN (LBP) BY SITE-DIRECTED MUTAGENESIS, EVIDENCE FOR A SIMILAR LPS RECOGNITION MECHANISM IN DIFFERENT LPS BINDING PROTEINS

Shock ◽

10.1097/00024382-199703001-00087 ◽

1997 ◽

Vol 7 (Supplement) ◽

pp. 21-22

Author(s):

N. Lamping ◽

A. Hö ◽

B. Yu ◽

T. C. Park ◽

S. D. Wright ◽

...

Keyword(s):

Binding Site ◽

Binding Proteins ◽

Binding Protein ◽

Site Directed Mutagenesis ◽

Directed Mutagenesis ◽

Recognition Mechanism ◽

Lps Binding

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Interaction of SP-A (surfactant protein A) with bacterial rough lipopolysaccharide (Re-LPS), and effects of SP-A on the binding of Re-LPS to CD14 and LPS-binding protein

Biochemical Journal ◽

10.1042/bj20050529 ◽

2005 ◽

Vol 391 (1) ◽

pp. 115-124 ◽

Cited By ~ 30

Author(s):

Ignacio García-Verdugo ◽

Fernando Sánchez-Barbero ◽

Katrin Soldau ◽

Peter S. Tobias ◽

Cristina Casals

Keyword(s):

Binding Protein ◽

Protein A ◽

Fluorescence Analysis ◽

Surfactant Protein ◽

Lipid Binding ◽

Coli Strain ◽

Surfactant Protein A ◽

Human Macrophage ◽

Independent Manner ◽

Lps Binding

SP-A (surfactant protein A) is a lipid-binding collectin primarily involved in innate lung immunity. SP-A interacts with the bacterial rough LPS (lipopolysaccharide) Re-LPS (Re595 mutant of LPS from Salmonella minnesota), but not with smooth LPS. In the present study, we first examined the characteristics of the interaction of human SP-A with Re-LPS. Fluorescence intensity and anisotropy measurements of FITC-labelled Re-LPS in the presence and absence of SP-A indicated that SP-A bound to Re-LPS in solution in a Ca2+-independent manner, with a dissociation constant of 2.8×10−8 M. In the presence of calcium, a high-mobility complex of SP-A and [3H]Rb-LPS (Rb mutant of LPS from Escherichia coli strain LCD 25) micelles was formed, as detected by sucrose density gradients. Re-LPS aggregation induced by SP-A was further characterized by light scattering. On the other hand, human SP-A inhibited TNF-α (tumour necrosis factor-α) secretion by human macrophage-like U937 cells stimulated with either Re-LPS or smooth LPS. We further examined the effects of human SP-A on the binding of Re-LPS to LBP (LPS-binding protein) and CD14. SP-A decreased the binding of Re-LPS to CD14, but not to LBP, as detected by cross-linking experiments with 125I-ASD-Re-LPS [125I-labelled sulphosuccinimidyl-2-(p-azidosalicylamido)-1,3-dithiopropionate derivative of Re-LPS] and fluorescence analysis with FITC-Re-LPS. When SP-A, LBP and CD14 were incubated together, SP-A reduced the ability of LBP to transfer 125I-ASD-Re-LPS to CD14. These SP-A effects were not due to the ability of SP-A to aggregate Re-LPS in the presence of calcium, since they were observed in both the absence and the presence of calcium. These studies suggest that SP-A could contribute to modulate Re-LPS responses by altering the competence of the LBP–CD14 receptor complex.

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