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A Biophysical View on the Function and Activity of Endotoxins
Published in Helmut Brade, Steven M. Opal, Stefanie N. Vogel, David C. Morrison, Endotoxin in Health and Disease, 2020
Ulrich Seydel, Andre Wiese, Andra B. Schromm, Klaus Brandenburg
The above-mentioned types of endotoxin intercalation should express different efficiencies. Thus, the direct intercalation of monomers and the LBP-mediated process will lead to an intercalation somewhere in the lipid matrix, whereas the mCD14-mediated process will bind the endotoxin directly to the signaling protein, assuming that mCD14 is located in the direct vicinity of the signal transducer. This assumption is backed by the observation that mCD14-mediated activation can be blocked by anti-CD 14 antibodies. At high endotoxin concentration the blockade by anti-CD 14 antibodies can be overcome (196), and obviously in that case the CD 14-independent activation pathway is initiated. One further point deserves attention. LBP, initially defined as lipopolysaccharide-binding protein, turns out not to be LPS specific but rather to interact with and transport other negatively charged lipids. Thus, LBP seems to be a lipid transfer protein in a more general sense (189).
Immune Modulation In Sepsis
Published in Thomas F. Kresina, Immune Modulating Agents, 2020
Janet M. J. Hammond, Peter D. Potgieter
New nonantibody substances with potent antiendotoxin activity have also been under development. One of these agents is recombinant bactericidal/permeability-increasing protein. This protein was originally isolated from human neutrophil azurophilic granules and belongs to a family of endotoxin binding proteins that regulate the host response to endotoxin [163]. Bactericidal/permeability-increasing protein binds to endotoxin and inhibits endotoxin-mediated activation of neutrophils and monocytes in vitro [164]. Bactericidal/permeability-increasing protein has a high-affinity binding domain for the lipid A domain of endotoxin and shares 44% sequence homology at the amino acid level with another endogenous protein that binds lipopolysaccharide, called lipopolysaccharide binding protein [165]. Bactericidal/permeability-increasing protein and lipopolysaccharide binding protein appear to have antagonistic roles in the regulation of lipopolysaccharide biological activity. Whereas lipopolysaccharide binding protein binds to lipopolysaccharide and stimulates lipopolysaccharide inflammatory activity in vitro, bactericidal/permeability-increasing protein can compete with lipopolysaccharide binding protein, bind lipopolysaccharide, and block lipopolysaccharide interaction with cells in vitro [164,166,167].
The Pituitary Gland, Psychoneuroimmunology and Infection
Published in Herman Friedman, Thomas W. Klein, Andrea L. Friedman, Psychoneuroimmunology, Stress, and Infection, 2020
Istvan Berczi, Andor Szentivanyi
A lipopolysaccharide binding protein (LBP) was isolated from human and rabbit serum. LBP is a 60 kd glycoprotein and normally is present at 0.5 µg/ml concentration in the serum, but it will rise up to 50 µg/ml, during an acute phase response. LBP is capable of opsonizing of LPS bearing particles which suggests that this protein is necessary for the activation of the complement system by LPS. LBP-LPS complexes were as much as 1,000 fold more active than LPS alone in the induction of TNF or IL-1β. LBP was found to be related to another LPS binding protein of neutrophils called bacterial permeability increasing protein. A 55 kd glycoprotein called CD14 which serves as the receptor for LPS-LBP on monocytes and macrophages. CD14 does not contain a transmembrane domain but holds onto the cell surface by a phosphatidylinositol glycane anchor.91 Other LPS binding proteins have also been identified on various cell types. B lymphocytes do not possess CD14, yet they respond to stimulation by LPS with proliferation and polyclonal immunoglobulin secretion. LPS regulates transcription of IC gene mRNA by the stimulation of the cis-acting nuclear factor NF-KB or OTF-2.91 B lymphocytes of C3H/HeJ mice cannot be activated by LPS for proliferation and polyclonal immunoglobulin secretion. Such mice respond poorly to infection with gram-negative bacteria.72
Associations of the gut microbiome with hepatic adiposity in the Multiethnic Cohort Adiposity Phenotype Study
Published in Gut Microbes, 2021
Meredith A. J. Hullar, Isaac C. Jenkins, Timothy W. Randolph, Keith R. Curtis, Kristine R. Monroe, Thomas Ernst, John A. Shepherd, Daniel O. Stram, Iona Cheng, Bruce S. Kristal, Lynne R. Wilkens, Adrian Franke, Loic Le Marchand, Unhee Lim, Johanna W. Lampe
Venous blood (40 mL) was collected after an overnight fast (>8 hours), processed in the MEC laboratories in Hawaii and Los Angeles to components (plasma, buffy coat, serum), and stored at −80°C until shipment for biomarker assays at the UH Cancer Center Analytical Biochemistry Shared Resource laboratory (directed by Dr. Franke). Samples were arranged into batches so that each batch included approximately equal numbers of men and women of each ethnic group and ~10% blind QC duplicates. Plasma lipopolysaccharide binding protein (LBP) was analyzed using a commercial ELISA kit (Cell Sciences, CKH113; coefficient of variation (CV): 0.7%; intraclass correlation coefficient (ICC) 80%). Serum high-sensitivity C-reactive protein (CRP), a measure of systemic inflammation and alanine amino transferase (ALT), a plasma marker of liver dysfunction, were measured as previously reported.23 Our assays for CRP and ALT had a CV of 13.8% and 4.4% and ICCs of 88% and 82%, respectively.
Phagocytosis: Phenotypically Simple Yet a Mechanistically Complex Process
Published in International Reviews of Immunology, 2020
CD14 (a PRR) also recognizes apoptotic cells via its N-terminus, which binds to the residue 11 of apoptotic cells and promotes their tethering event with non-myeloid cells (Table 1) [82,83]. CD14 expressed on human macrophages does not recognize PS of apoptotic cells [154]. However, CD14-mediated recognition of opsonized Gram-negative bacteria (E. coli) helps in the phagocytosis through LPS-binding protein (LBP) [193]. The phosphatidylinositol (PI) 3-kinase inhibitor wortmannin, and a protein tyrosine kinase inhibitor, tyrphostin 23 inhibit CD14-mediated phagocytosis of the opsonized E. coli. The IL-10 enhances CD-14-dependent phagocytosis of both the Gram-negative bacteria and the apoptotic cells by human monocytes [194]. The CD14 expressed on microglia (a mononuclear phagocyte) is also involved in the phagocytosis of amyloid β peptide 42 (Aβ42) in the brain of Alzheimer’s disease patients [195].
Needle-shaped amyloid deposition in rat mammary gland: evidence of a novel amyloid fibril protein
Published in Amyloid, 2020
Tomoaki Murakami, Keiichi Noguchi, Naomi Hachiya, Fuyuki Kametani, Masayoshi Tasaki, Satoshi Nakaba, Yukiko Sassa, Taro Yamashita, Konen Obayashi, Yukio Ando, Masao Hamamura, Takeshi Kanno, Kazufumi Kawasako
LBP is an acute phase protein and belongs to the small family of lipid transfer/LPS binding proteins [29–32]. LBP binds to the amphipathic lipid A moiety of LPS, facilitates the process of LPS presentation to CD14-positive cells, and triggers a pro-inflammatory response through the activation of the Toll-like receptor 4 pathway. Thus, LBP modulates the systemic and local (mucosal) innate immune response against bacteria [31]. LBP also mediates early neutrophil infiltration, which leads to increased monocyte recruitment in the rat liver after LPS administration [30]. In this study, histopathological examination and IHC revealed that macrophages labelled with Iba-1 antibody and neutrophils had infiltrated around NA. Therefore, the similar pathway may be involved in migration and phagocytosis of LBP-containing amyloid by macrophages and neutrophils.