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Tandon A, Harioudh MK, Verma NK, Saroj J, Gupta A, Pant G, Tripathi JK, Kumar A, Kumari T, Tripathi AK, Mitra K, Ghosh JK. Characterization of a Myeloid Differentiation Factor 2-Derived Peptide that Facilitates THP-1 Macrophage-Mediated Phagocytosis of Gram-Negative Bacteria. ACS Infect Dis 2024; 10:845-857. [PMID: 38363869 DOI: 10.1021/acsinfecdis.3c00274] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/18/2024]
Abstract
Myeloid differentiation factor 2 (MD2), the TLR4 coreceptor, has been shown to possess opsonic activity and has been implicated in phagocytosis and intracellular killing of Gram-negative bacteria. However, any MD2 protein segment involved in phagocytosis of Gram-negative bacteria is not yet known. A short synthetic MD2 segment, MD54 (amino acid regions 54 to 69), was shown to interact with a Gram-negative bacterial outer membrane component, LPS, earlier. Furthermore, the MD54 peptide induced aggregation of LPS and facilitated its internalization in THP-1 cells. Currently, it has been investigated if MD2-derived MD54 possesses any opsonic property and role in phagocytosis of Gram-negative bacteria. Remarkably, we observed that MD54 facilitated agglutination of Gram-negative bacteria, Escherichia coli (ATCC 25922) and Pseudomonas aeruginosa (ATCC BAA-427), but not of Gram-positive bacteria, Bacillus subtilis (ATCC 6633) and Staphylococcus aureus (ATCC 25923). The MD54-opsonized Gram-negative bacteria internalized within PMA-treated THP-1 cells and were killed over a longer incubation period. However, both internalization and intracellular killing of the MD54-opsonized Gram-negative bacteria within THP-1 phagocytes were appreciably inhibited in the presence of a phagocytosis inhibitor, cytochalasin D. Furthermore, MD54 facilitated the clearance of Gram-negative bacteria E. coli (ATCC 25922) and P. aeruginosa (ATCC BAA-427) from the infected BALB/c mice whereas an MD54 analog, MMD54, was inactive. Overall, for the first time, the results revealed that a short MD2-derived peptide can specifically agglutinate Gram-negative bacteria, act as an opsonin for these bacteria, and facilitate their phagocytosis by THP-1 phagocytes. The results suggest that the MD54 segment could have a crucial role in MD2-mediated host-pathogen interaction involving the Gram-negative bacteria.
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Affiliation(s)
- Anshika Tandon
- Biochemistry and Structural Biology Division, CSIR-Central Drug Research Institute Sector 10, Jankipuram Extension, Sitapur Road, Lucknow 226 031, India
| | - Munesh Kumar Harioudh
- Biochemistry and Structural Biology Division, CSIR-Central Drug Research Institute Sector 10, Jankipuram Extension, Sitapur Road, Lucknow 226 031, India
| | - Neeraj Kumar Verma
- Biochemistry and Structural Biology Division, CSIR-Central Drug Research Institute Sector 10, Jankipuram Extension, Sitapur Road, Lucknow 226 031, India
| | - Jyotshana Saroj
- Biochemistry and Structural Biology Division, CSIR-Central Drug Research Institute Sector 10, Jankipuram Extension, Sitapur Road, Lucknow 226 031, India
- Academy of Scientific and Innovative Research (AcSIR), New Delhi 110001, India
| | - Arvind Gupta
- Biochemistry and Structural Biology Division, CSIR-Central Drug Research Institute Sector 10, Jankipuram Extension, Sitapur Road, Lucknow 226 031, India
- Academy of Scientific and Innovative Research (AcSIR), New Delhi 110001, India
| | - Garima Pant
- Electron Microscopy Unit, CSIR-Central Drug Research Institute Sector 10, Jankipuram Extension, Sitapur Road, Lucknow 226 031, India
| | - Jitendra Kumar Tripathi
- Biochemistry and Structural Biology Division, CSIR-Central Drug Research Institute Sector 10, Jankipuram Extension, Sitapur Road, Lucknow 226 031, India
| | - Amit Kumar
- Biochemistry and Structural Biology Division, CSIR-Central Drug Research Institute Sector 10, Jankipuram Extension, Sitapur Road, Lucknow 226 031, India
| | - Tripti Kumari
- Biochemistry and Structural Biology Division, CSIR-Central Drug Research Institute Sector 10, Jankipuram Extension, Sitapur Road, Lucknow 226 031, India
| | - Amit Kumar Tripathi
- Biochemistry and Structural Biology Division, CSIR-Central Drug Research Institute Sector 10, Jankipuram Extension, Sitapur Road, Lucknow 226 031, India
| | - Kalyan Mitra
- Electron Microscopy Unit, CSIR-Central Drug Research Institute Sector 10, Jankipuram Extension, Sitapur Road, Lucknow 226 031, India
| | - Jimut Kanti Ghosh
- Biochemistry and Structural Biology Division, CSIR-Central Drug Research Institute Sector 10, Jankipuram Extension, Sitapur Road, Lucknow 226 031, India
- Academy of Scientific and Innovative Research (AcSIR), New Delhi 110001, India
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Feldtmann R, Kümmel A, Chamling B, Strohbach A, Lehnert K, Gross S, Loerzer L, Riad A, Lindner D, Westermann D, Fielitz J, Dörr M, Felix SB. Myeloid differentiation factor-2 activates monocytes in patients with dilated cardiomyopathy. Immunology 2022; 167:40-53. [PMID: 35502635 DOI: 10.1111/imm.13490] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2021] [Accepted: 02/21/2022] [Indexed: 11/27/2022] Open
Abstract
Plasma levels of myeloid differentiation factor-2 (MD-2), a co-receptor of toll-like-receptor 4 (TLR4), independently predict mortality in patients with dilated cardiomyopathy (DCM). We tested whether monocyte-activation by MD-2 contributes to immune activation and inflammatory status in DCM patients. We found increased MD-2 plasma-levels in 25 patients with recent-onset DCM (1,250±80.7 ng/ml) compared to 25 age- and gender-matched healthy controls (793.4±52.0 ng/ml; p<0.001). Monocytes isolated from DCM-patients showed a higher expression (141.7±12.4 %; p=0.006 vs. controls) of the MD-2 encoding gene, LY96, and an increased NF-κB-activation. Further, the TLR4-activator lipopolysaccharide (LPS) caused a higher increase in interleukin (IL)-6 in monocytes from DCM-patients compared to controls (mean fluorescence intensity: 938.7±151.0 vs. 466.9±51.1; p=0.005). MD-2 increased IL-6 secretion in a TLR4/NF-κB-dependent manner in monocyte-like THP-1-cells as demonstrated by TLR4-siRNA and NF-κB-inhibition. Since endothelial cells (ECs) are responsible for recruiting monocytes to the site of inflammation, ECs were treated with MD-2 leading to an activation of Akt and increased secretion of monocyte-chemoattractant-protein-1 (MCP-1). Activation of ECs by MD-2 was accompanied by an increased expression of the adhesion-molecules CD54, CD106, and CD62E, resulting in an increased monocyte-recruitment, which was attenuated by CD54-inhibition. In addition, in murine WT but not LY96-KO bone marrow-derived macrophages LPS increased the amount of CD54 and CD49d/CD29. MD-2 facilitates a pro-inflammatory status of monocytes and EC-mediated monocyte-recruitment via TLR4/NF-κB. Elevated MD-2 plasma-levels are possibly involved in monocyte-related inflammation promoting disease-progression in DCM. Our results suggest that MD-2 contributes to increasing monocytic inflammatory activity and triggers recruitment of monocytes to ECs in DCM. This article is protected by copyright. All rights reserved.
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Affiliation(s)
- Rico Feldtmann
- Department of Internal Medicine B, Cardiology, University Medicine Greifswald, Germany.,DZHK (German Centre for Cardiovascular Research), Partner Site Greifswald, Germany
| | - Andreas Kümmel
- Department of Internal Medicine B, Cardiology, University Medicine Greifswald, Germany.,DZHK (German Centre for Cardiovascular Research), Partner Site Greifswald, Germany
| | - Bishwas Chamling
- Department of Internal Medicine B, Cardiology, University Medicine Greifswald, Germany.,DZHK (German Centre for Cardiovascular Research), Partner Site Greifswald, Germany
| | - Anne Strohbach
- Department of Internal Medicine B, Cardiology, University Medicine Greifswald, Germany.,DZHK (German Centre for Cardiovascular Research), Partner Site Greifswald, Germany
| | - Kristin Lehnert
- Department of Internal Medicine B, Cardiology, University Medicine Greifswald, Germany.,DZHK (German Centre for Cardiovascular Research), Partner Site Greifswald, Germany
| | - Stefan Gross
- Department of Internal Medicine B, Cardiology, University Medicine Greifswald, Germany.,DZHK (German Centre for Cardiovascular Research), Partner Site Greifswald, Germany
| | - Lisa Loerzer
- Department of Internal Medicine B, Cardiology, University Medicine Greifswald, Germany.,DZHK (German Centre for Cardiovascular Research), Partner Site Greifswald, Germany
| | - Alexander Riad
- DRK-Krankenhaus Teterow gGMBH, Internal Medicine, Teterow, Germany
| | - Diana Lindner
- Department of Cardiology, University Heart and Vascular Center, Hamburg, Germany.,DZHK (German Centre for Cardiovascular Research), Partner Site Hamburg/Kiel/Lübeck, Germany
| | - Dirk Westermann
- Department of Cardiology, University Heart and Vascular Center, Hamburg, Germany.,DZHK (German Centre for Cardiovascular Research), Partner Site Hamburg/Kiel/Lübeck, Germany
| | - Jens Fielitz
- Department of Internal Medicine B, Cardiology, University Medicine Greifswald, Germany.,DZHK (German Centre for Cardiovascular Research), Partner Site Greifswald, Germany
| | - Marcus Dörr
- Department of Internal Medicine B, Cardiology, University Medicine Greifswald, Germany.,DZHK (German Centre for Cardiovascular Research), Partner Site Greifswald, Germany
| | - Stephan B Felix
- Department of Internal Medicine B, Cardiology, University Medicine Greifswald, Germany.,DZHK (German Centre for Cardiovascular Research), Partner Site Greifswald, Germany
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Zhang P, Nguyen J, Abdulla F, Nelson AT, Beckman JD, Vercellotti GM, Belcher JD. Soluble MD-2 and Heme in Sickle Cell Disease Plasma Promote Pro-Inflammatory Signaling in Endothelial Cells. Front Immunol 2021; 12:632709. [PMID: 33841413 PMCID: PMC8033004 DOI: 10.3389/fimmu.2021.632709] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2020] [Accepted: 03/10/2021] [Indexed: 12/22/2022] Open
Abstract
Recent evidence indicates that hemolysis in sickle cell disease (SCD) promotes inflammation via innate immune signaling through toll-like receptor 4 (TLR4). Free heme released by hemolyzed red blood cells can bind to myeloid differentiation factor-2 (MD-2) and activate TLR4 pro-inflammatory signaling on endothelium to promote vaso-occlusion and acute chest syndrome in murine models of SCD. MD-2 is co-expressed with TLR4 on cell membranes, but in inflammatory conditions, soluble MD-2 (sMD-2) is elevated in plasma. sMD-2 levels were significantly increased in human and murine sickle (SS) plasma as compared to normal (AA) plasma. Human umbilical vein endothelial cells (HUVEC) and human lung microvascular endothelial cells incubated with human SS plasma had significant increases in pro-inflammatory IL-8, IL-6, and soluble VCAM-1 secretion compared to endothelial cells incubated with AA plasma. The increase in HUVEC IL-8 secretion was blocked by depletion of sMD-2 from SS plasma and enhanced by the addition of sMD-2 to AA plasma. The TLR4 signaling inhibitor, TAK-242, inhibited HUVEC IL-8 secretion in response to SS plasma by 85%. Heme-agarose pull-down assays and UV/Vis spectroscopy demonstrated that heme binds to sMD-2. Hemopexin, a high affinity heme-binding protein, inhibited HUVEC IL-8 secretion induced by SS plasma or SS and AA plasma supplemented with sMD-2. These data suggest that sMD-2 bound to heme might play an important role in pro-inflammatory signaling by endothelium in SCD.
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Affiliation(s)
- Ping Zhang
- Division of Hematology, Oncology and Transplantation, Department of Medicine, University of Minnesota, Minneapolis, MN, United States
| | - Julia Nguyen
- Division of Hematology, Oncology and Transplantation, Department of Medicine, University of Minnesota, Minneapolis, MN, United States
| | - Fuad Abdulla
- Division of Hematology, Oncology and Transplantation, Department of Medicine, University of Minnesota, Minneapolis, MN, United States
| | - Alexander T Nelson
- University of Minnesota School of Medicine, Minneapolis, MN, United States
| | - Joan D Beckman
- Division of Hematology, Oncology and Transplantation, Department of Medicine, University of Minnesota, Minneapolis, MN, United States
| | - Gregory M Vercellotti
- Division of Hematology, Oncology and Transplantation, Department of Medicine, University of Minnesota, Minneapolis, MN, United States
| | - John D Belcher
- Division of Hematology, Oncology and Transplantation, Department of Medicine, University of Minnesota, Minneapolis, MN, United States
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MD2 activation by direct AGE interaction drives inflammatory diabetic cardiomyopathy. Nat Commun 2020; 11:2148. [PMID: 32358497 PMCID: PMC7195432 DOI: 10.1038/s41467-020-15978-3] [Citation(s) in RCA: 88] [Impact Index Per Article: 22.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2019] [Accepted: 04/07/2020] [Indexed: 12/12/2022] Open
Abstract
Hyperglycemia activates toll-like receptor 4 (TLR4) to induce inflammation in diabetic cardiomyopathy (DCM). However, the mechanisms of TLR4 activation remain unclear. Here we examine the role of myeloid differentiation 2 (MD2), a co-receptor of TLR4, in high glucose (HG)- and diabetes-induced inflammatory cardiomyopathy. We show increased MD2 in heart tissues of diabetic mice and serum of human diabetic subjects. MD2 deficiency in mice inhibits TLR4 pathway activation, which correlates with reduced myocardial remodeling and improved cardiac function. Mechanistically, we show that HG induces extracellular advanced glycation end products (AGEs), which bind directly to MD2, leading to formation of AGEs-MD2-TLR4 complex and initiation of pro-inflammatory pathways. We further detect elevated AGE-MD2 complexes in heart tissues and serum of diabetic mice and human subjects with DCM. In summary, we uncover a new mechanism of HG-induced inflammatory responses and myocardial injury, in which AGE products directly bind MD2 to drive inflammatory DCM. The mechanisms underlying cardiac inflammation in diabetic cardiomyopathy are incompletely understood. Here the authors show that advanced glycation end products bind to the TLR4 co-receptor MD2 initiating pro-inflammatory pathways.
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Yang H, Meng L, Ai D, Hou N, Li H, Shuai X, Peng X. Acetic acid alleviates the inflammatory response and liver injury in septic mice by increasing the expression of TRIM40. Exp Ther Med 2019; 17:2789-2798. [PMID: 30906467 DOI: 10.3892/etm.2019.7274] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2018] [Accepted: 12/03/2018] [Indexed: 12/13/2022] Open
Abstract
Sepsis remains a significant health care issue in clinical practice due to its high mortality rate and healthcare cost, despite extensive efforts to better understand the pathophysiology of sepsis. The systemic inflammatory response often leads to severe liver injury, even acute liver dysfunction and failure. Acetic acid, as a type of chemical compound, has been reported to be an emerging drug for improving metabolic syndrome and inhibiting inflammation in rats and human. To verify the effects of acetic acid in protecting the liver and reducing the inflammatory response, a septic mouse model was established by cecal ligation and puncture (CLP), and then the CLP-model mice were treated with acetic acid or PBS. Following the treatment, it was determined that, in CLP-model mice, acetic acid could alleviate the inflammatory response by decreasing the expression of cytokines including interleukin-6 and tumor necrosis factor-α. Additionally, acetic acid also alleviated the liver injury, and the levels of alanine aminotransaminase, aspartate aminotransferase, Toll-like receptor (TLR)4 and nuclear factor-κB (NF-κB) were decreased. The expression of tripartite motif-containing protein (TRIM)40 was also upregulated significantly. Therefore, the authors of the current study hypothesized that acetic acid could decrease the inflammatory response by increasing the expression of TRIM40 and TRIM40 may regulate the activity of the TLR4 signaling pathway. To further illustrate the interaction between TRIM40 and the TLR4 signaling pathway, the authors collected macrophages from the peritoneal cavity by intraperitoneally administering mice with 5 ml ice-cold normal saline. Following the collection, peritoneal macrophages were treated with acetic acid, TRIM40 small interfering RNA or PBS. It was demonstrated that acetic acid upregulated the expression of TRIM40. When TRIM40 was silenced, the protective effect of acetic acid would be reversed as well. The results suggested that TRIM40 could act on and downregulate the activity of the TLR4 signaling pathway. TRIM40 is possibly the major target for acetic acid, which may function as a protective factor in septic mice.
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Affiliation(s)
- Hongguang Yang
- Department of Anesthesiology, Qingdao Municipal Hospital, Qingdao, Shandong 266011, P.R. China
| | - Lan Meng
- Department of Anesthesiology, Qingdao Municipal Hospital, Qingdao, Shandong 266011, P.R. China
| | - Dengbin Ai
- Department of Anesthesiology, Qingdao Municipal Hospital, Qingdao, Shandong 266011, P.R. China
| | - Nianguo Hou
- Department of Anesthesiology, Qingdao Municipal Hospital, Qingdao, Shandong 266011, P.R. China
| | - Hui Li
- Department of Anesthesiology, Qingdao Municipal Hospital, Qingdao, Shandong 266011, P.R. China
| | - Xunjun Shuai
- Department of Anesthesiology, Qingdao Municipal Hospital, Qingdao, Shandong 266011, P.R. China
| | - Xiaoyan Peng
- Department of Anesthesiology, Qingdao Municipal Hospital, Qingdao, Shandong 266011, P.R. China
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Synergistic effect of Dermatophagoides pteronyssinus allergen and Escherichia coli lipopolysaccharide on human blood cells. PLoS One 2018; 13:e0207311. [PMID: 30412632 PMCID: PMC6226202 DOI: 10.1371/journal.pone.0207311] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2018] [Accepted: 10/29/2018] [Indexed: 12/31/2022] Open
Abstract
Purpose House dust mites Dermatophagoides pteronyssinus are the main source of major inhalatory allergens inducing inflammatory response. Mite extract contain both allergenic proteins and lipopolysaccharides (LPS). The main allergenic protein, Der p 2, is a functional homolog of sMD-2, a protein providing blood cell response on LPS. Der p 2 may restore the response to LPS in absence of MD-2, but its interaction with LPS in whole blood is unknown. We studied the effect of Der p 2 on LPS-mediated activation of human whole blood cells. Methods Interaction of Der p 2 and LPS was studied on eight healthy donors. The whole blood was incubated with extract of house dust mite Dermatophagoides pteronyssinus (DP-e), recombinant antigenic protein Der p 2 variant 5 (rDep 2), Escherichia coli lipopolysaccharide and their combination. Supernatants were collected for ELISA analysis of protein content. Activation degree was determined by change in concentration of TNF-α, IL-8, IL-1Ra cytokines and sMD-2 protein. Results extract of mite Dermatophagoides pteronyssinus (DP-e) possessed weak inherent activity and did not cause significant increase of cytokine production. Simultaneous activation of blood cells by LPS and DP-e led to considerable increase of pro-inflammatory cytokine production. We have shown the intrinsic inducing activity of Der p 2 allergen on sMD-2 protein and TNF-α cytokine expression. Conclusions Der p 2 allergen enhances the response of human whole blood cells to external LPS by inducing additional expression of LPS-transporting protein sMD-2. The obtained data show an important role of LPS contamination of allegrens in the progress of allergic inflammatory response.
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Choi SH, Sviridov D, Miller YI. Oxidized cholesteryl esters and inflammation. Biochim Biophys Acta Mol Cell Biol Lipids 2016; 1862:393-397. [PMID: 27368140 DOI: 10.1016/j.bbalip.2016.06.020] [Citation(s) in RCA: 53] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2016] [Revised: 06/08/2016] [Accepted: 06/24/2016] [Indexed: 11/30/2022]
Abstract
The oxidation hypothesis of atherosclerosis proposes that oxidized LDL is a major causative factor in the development of atherosclerosis. Although this hypothesis has received strong mechanistic support and many animal studies demonstrated profound atheroprotective effects of antioxidants, which reduce LDL oxidation, the results of human clinical trials with antioxidants were mainly negative, except in selected groups of patients with clearly increased systemic oxidative stress. We propose that even if reducing lipoprotein oxidation in humans might be difficult to achieve, deeper understanding of mechanisms by which oxidized LDL promotes atherosclerosis and targeting these specific mechanisms will offer novel approaches to treatment of cardiovascular disease. In this review article, we focus on oxidized cholesteryl esters (OxCE), which are a major component of minimally and extensively oxidized LDL and of human atherosclerotic lesions. OxCE and OxCE-protein covalent adducts induce profound biological effects. Among these effects, OxCE activate macrophages via toll-like receptor-4 (TLR4) and spleen tyrosine kinase and induce macropinocytosis resulting in lipid accumulation, generation of reactive oxygen species and secretion of inflammatory cytokines. Specific inhibition of OxCE-induced TLR4 activation, as well as blocking other inflammatory effects of OxCE, may offer novel treatments of atherosclerosis and cardiovascular disease. This article is part of a Special Issue entitled: Lipid modification and lipid peroxidation products in innate immunity and inflammation edited by Christoph J. Binder.
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Affiliation(s)
- Soo-Ho Choi
- Department of Medicine, University of California, San Diego, La Jolla, CA 92093, USA
| | - Dmitri Sviridov
- Baker IDI Heart and Diabetes Institute, Melbourne, VIC 3004, Australia
| | - Yury I Miller
- Department of Medicine, University of California, San Diego, La Jolla, CA 92093, USA.
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Choi SH, Kim J, Gonen A, Viriyakosol S, Miller YI. MD-2 binds cholesterol. Biochem Biophys Res Commun 2016; 470:877-80. [PMID: 26806306 DOI: 10.1016/j.bbrc.2016.01.126] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2016] [Accepted: 01/21/2016] [Indexed: 12/22/2022]
Abstract
Cholesterol is a structural component of cellular membranes, which is transported from liver to peripheral cells in the form of cholesterol esters (CE), residing in the hydrophobic core of low-density lipoprotein. Oxidized CE (OxCE) is often found in plasma and in atherosclerotic lesions of subjects with cardiovascular disease. Our earlier studies have demonstrated that OxCE activates inflammatory responses in macrophages via toll-like receptor-4 (TLR4). Here we demonstrate that cholesterol binds to myeloid differentiation-2 (MD-2), a TLR4 ancillary molecule, which is a binding receptor for bacterial lipopolysaccharide (LPS) and is indispensable for LPS-induced TLR4 dimerization and signaling. Cholesterol binding to MD-2 was competed by LPS and by OxCE-modified BSA. Furthermore, soluble MD-2 in human plasma and MD-2 in mouse atherosclerotic lesions carried cholesterol, the finding supporting the biological significance of MD-2 cholesterol binding. These results help understand the molecular basis of TLR4 activation by OxCE and mechanisms of chronic inflammation in atherosclerosis.
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Affiliation(s)
- Soo-Ho Choi
- Department of Medicine, University of California, 9500 Gilman Drive, La Jolla, San Diego, CA 92093, USA
| | - Jungsu Kim
- Department of Medicine, University of California, 9500 Gilman Drive, La Jolla, San Diego, CA 92093, USA
| | - Ayelet Gonen
- Department of Medicine, University of California, 9500 Gilman Drive, La Jolla, San Diego, CA 92093, USA
| | - Suganya Viriyakosol
- Department of Medicine, University of California, 9500 Gilman Drive, La Jolla, San Diego, CA 92093, USA
| | - Yury I Miller
- Department of Medicine, University of California, 9500 Gilman Drive, La Jolla, San Diego, CA 92093, USA.
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Zhou Z, Xu MJ, Gao B. Hepatocytes: a key cell type for innate immunity. Cell Mol Immunol 2015; 13:301-15. [PMID: 26685902 PMCID: PMC4856808 DOI: 10.1038/cmi.2015.97] [Citation(s) in RCA: 270] [Impact Index Per Article: 30.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2015] [Revised: 10/23/2015] [Accepted: 10/23/2015] [Indexed: 02/07/2023] Open
Abstract
Hepatocytes, the major parenchymal cells in the liver, play pivotal roles in metabolism, detoxification, and protein synthesis. Hepatocytes also activate innate immunity against invading microorganisms by secreting innate immunity proteins. These proteins include bactericidal proteins that directly kill bacteria, opsonins that assist in the phagocytosis of foreign bacteria, iron-sequestering proteins that block iron uptake by bacteria, several soluble factors that regulate lipopolysaccharide signaling, and the coagulation factor fibrinogen that activates innate immunity. In this review, we summarize the wide variety of innate immunity proteins produced by hepatocytes and discuss liver-enriched transcription factors (e.g. hepatocyte nuclear factors and CCAAT/enhancer-binding proteins), pro-inflammatory mediators (e.g. interleukin (IL)-6, IL-22, IL-1β and tumor necrosis factor-α), and downstream signaling pathways (e.g. signal transducer and activator of transcription factor 3 and nuclear factor-κB) that regulate the expression of these innate immunity proteins. We also briefly discuss the dysregulation of these innate immunity proteins in chronic liver disease, which may contribute to an increased susceptibility to bacterial infection in patients with cirrhosis.
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Affiliation(s)
- Zhou Zhou
- Laboratory of Liver Diseases, National Institute on Alcohol Abuse and Alcoholism National Institutes of Health, Bethesda, MD, USA
| | - Ming-Jiang Xu
- Laboratory of Liver Diseases, National Institute on Alcohol Abuse and Alcoholism National Institutes of Health, Bethesda, MD, USA
| | - Bin Gao
- Laboratory of Liver Diseases, National Institute on Alcohol Abuse and Alcoholism National Institutes of Health, Bethesda, MD, USA
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Koyama D, Maruoka S, Gon Y, Shintani Y, Sekiyama T, Hiranuma H, Shikano S, Kuroda K, Takeshita I, Tsuboi E, Soda K, Hashimoto S. Myeloid differentiation-2 is a potential biomarker for the amplification process of allergic airway sensitization in mice. Allergol Int 2015; 64 Suppl:S37-45. [PMID: 26344079 DOI: 10.1016/j.alit.2015.05.011] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2015] [Revised: 05/04/2015] [Accepted: 05/14/2015] [Indexed: 01/17/2023] Open
Abstract
BACKGROUND Allergic sensitization is a key step in the pathogenesis of asthma. However, little is known about the molecules that are critical regulators for establishing allergic sensitization of the airway. Thus, we conducted global gene expression profiling to identify candidate genes and signaling pathways involved in house dust mite (HDM)-induced allergic sensitization in the murine airway. METHODS We sensitized and challenged mice with HDM or saline as a control through the airway on days 1 and 8. We evaluated eosinophilia in bronchoalveolar lavage fluid (BALF), airway inflammation, and mucus production on days 7 and 14. We extracted total RNA from lung tissues of HDM- and saline-sensitized mice on days 7 and 14. Microarray analyses were performed to identify up-regulated genes in the lungs of HDM-sensitized mice compared to the control mice. Data analyses were performed using GeneSpring software and gene networks were generated using Ingenuity Pathways Analysis (IPA). RESULTS We identified 50 HDM-mediated, stepwise up-regulated genes in response to allergic sensitization and amplification of allergic airway inflammation. The highest expressed gene was myeloid differentiation-2 (MD-2), a lipopolysaccharide (LPS)-binding component of Toll-like receptor (TLR) 4 signaling complex. MD-2 protein was expressed in lung vascular endothelial cells and was increased in the serum of HDM-sensitized mice, but not in the control mice. CONCLUSIONS Our data suggest MD-2 is a critical regulator of the establishment of allergic airway sensitization to HDM in mice. Serum MD-2 may represent a potential biomarker for the amplification of allergic sensitization and allergic inflammation.
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Affiliation(s)
- Daisuke Koyama
- Division of Respiratory Medicine, Department of Internal Medicine, Nihon University School of Medicine, Tokyo, Japan
| | - Shuichiro Maruoka
- Division of Respiratory Medicine, Department of Internal Medicine, Nihon University School of Medicine, Tokyo, Japan
| | - Yasuhiro Gon
- Division of Respiratory Medicine, Department of Internal Medicine, Nihon University School of Medicine, Tokyo, Japan.
| | - Yoshitaka Shintani
- Division of Respiratory Medicine, Department of Internal Medicine, Nihon University School of Medicine, Tokyo, Japan
| | - Tadataka Sekiyama
- Division of Respiratory Medicine, Department of Internal Medicine, Nihon University School of Medicine, Tokyo, Japan
| | - Hisato Hiranuma
- Division of Respiratory Medicine, Department of Internal Medicine, Nihon University School of Medicine, Tokyo, Japan
| | - Sotaro Shikano
- Division of Respiratory Medicine, Department of Internal Medicine, Nihon University School of Medicine, Tokyo, Japan
| | - Kazumichi Kuroda
- Division of Microbiology, Department of Pathology and Microbiology, Nihon University School of Medicine, Tokyo, Japan
| | - Ikuko Takeshita
- Division of Respiratory Medicine, Department of Internal Medicine, Nihon University School of Medicine, Tokyo, Japan
| | - Eriko Tsuboi
- Division of Respiratory Medicine, Department of Internal Medicine, Nihon University School of Medicine, Tokyo, Japan
| | - Kaori Soda
- Division of Respiratory Medicine, Department of Internal Medicine, Nihon University School of Medicine, Tokyo, Japan
| | - Shu Hashimoto
- Division of Respiratory Medicine, Department of Internal Medicine, Nihon University School of Medicine, Tokyo, Japan
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Parlato M, Cavaillon JM. Host response biomarkers in the diagnosis of sepsis: a general overview. Methods Mol Biol 2015; 1237:149-211. [PMID: 25319788 DOI: 10.1007/978-1-4939-1776-1_15] [Citation(s) in RCA: 45] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Critically ill patients who display a systemic inflammatory response syndrome (SIRS) are prone to develop nosocomial infections. The challenge remains to distinguish as early as possible among SIRS patients those who are developing sepsis. Following a sterile insult, damage-associated molecular patterns (DAMPs) released by damaged tissues and necrotic cells initiate an inflammatory response close to that observed during sepsis. During sepsis, pathogen-associated molecular patterns (PAMPs) trigger the release of host mediators involved in innate immunity and inflammation through identical receptors as DAMPs. In both clinical settings, a compensatory anti-inflammatory response syndrome (CARS) is concomitantly initiated. The exacerbated production of pro- or anti-inflammatory mediators allows their detection in biological fluids and particularly within the bloodstream. Some of these mediators can be used as biomarkers to decipher among the patients those who developed sepsis, and eventually they can be used as prognosis markers. In addition to plasma biomarkers, the analysis of some surface markers on circulating leukocytes or the study of mRNA and miRNA can be helpful. While there is no magic marker, a combination of few biomarkers might offer a high accuracy for diagnosis.
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Affiliation(s)
- Marianna Parlato
- Unit of Cytokines and Inflammation, Institut Pasteur, 28 rue du Dr Roux, 75724, Paris Cedex 15, France
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12
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Tumurkhuu G, Dagvadorj J, Jones HD, Chen S, Shimada K, Crother TR, Arditi M. Alternatively spliced myeloid differentiation protein-2 inhibits TLR4-mediated lung inflammation. JOURNAL OF IMMUNOLOGY (BALTIMORE, MD. : 1950) 2015; 194:1686-94. [PMID: 25576596 PMCID: PMC4323992 DOI: 10.4049/jimmunol.1402123] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
We previously identified a novel alternatively spliced isoform of human myeloid differentiation protein-2 (MD-2s) that competitively inhibits binding of MD-2 to TLR4 in vitro. In this study, we investigated the protective role of MD-2s in LPS-induced acute lung injury by delivering intratracheally an adenovirus construct that expressed MD-2s (Ad-MD-2s). After adenovirus-mediated gene transfer, MD-2s was strongly expressed in lung epithelial cells and readily detected in bronchoalveolar lavage fluid. Compared to adenovirus serotype 5 containing an empty vector lacking a transgene control mice, Ad-MD-2s delivery resulted in significantly less LPS-induced inflammation in the lungs, including less protein leakage, cell recruitment, and expression of proinflammatory cytokines and chemokines, such as IL-6, keratinocyte chemoattractant, and MIP-2. Bronchoalveolar lavage fluid from Ad-MD-2s mice transferred into lungs of naive mice before intratracheal LPS challenge diminished proinflammatory cytokine levels. As house dust mite (HDM) sensitization is dependent on TLR4 and HDM Der p 2, a structural homolog of MD-2, we also investigated the effect of MD-2s on HDM-induced allergic airway inflammation. Ad-MD-2s given before HDM sensitization significantly inhibited subsequent allergic airway inflammation after HDM challenge, including reductions in eosinophils, goblet cell hyperplasia, and IL-5 levels. Our study indicates that the alternatively spliced short isoform of human MD-2 could be a potential therapeutic candidate to treat human diseases induced or exacerbated by TLR4 signaling, such as Gram-negative bacterial endotoxin-induced lung injury and HDM-triggered allergic lung inflammation.
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Affiliation(s)
- Gantsetseg Tumurkhuu
- Division of Infectious Diseases and Immunology, Department of Pediatrics, Cedars-Sinai Medical Center, Los Angeles, CA 90048; Department of Biomedical Sciences, Infectious and Immunologic Diseases Research Center, Cedars-Sinai Medical Center, Los Angeles, CA 90048; and
| | - Jargalsaikhan Dagvadorj
- Division of Infectious Diseases and Immunology, Department of Pediatrics, Cedars-Sinai Medical Center, Los Angeles, CA 90048; Department of Biomedical Sciences, Infectious and Immunologic Diseases Research Center, Cedars-Sinai Medical Center, Los Angeles, CA 90048; and
| | - Heather D Jones
- Division of Pulmonary and Critical Care Medicine, Department of Medicine, Cedars-Sinai Medical Center, Los Angeles, CA 90048
| | - Shuang Chen
- Division of Infectious Diseases and Immunology, Department of Pediatrics, Cedars-Sinai Medical Center, Los Angeles, CA 90048; Department of Biomedical Sciences, Infectious and Immunologic Diseases Research Center, Cedars-Sinai Medical Center, Los Angeles, CA 90048; and
| | - Kenichi Shimada
- Division of Infectious Diseases and Immunology, Department of Pediatrics, Cedars-Sinai Medical Center, Los Angeles, CA 90048; Department of Biomedical Sciences, Infectious and Immunologic Diseases Research Center, Cedars-Sinai Medical Center, Los Angeles, CA 90048; and
| | - Timothy R Crother
- Division of Infectious Diseases and Immunology, Department of Pediatrics, Cedars-Sinai Medical Center, Los Angeles, CA 90048; Department of Biomedical Sciences, Infectious and Immunologic Diseases Research Center, Cedars-Sinai Medical Center, Los Angeles, CA 90048; and
| | - Moshe Arditi
- Division of Infectious Diseases and Immunology, Department of Pediatrics, Cedars-Sinai Medical Center, Los Angeles, CA 90048; Department of Biomedical Sciences, Infectious and Immunologic Diseases Research Center, Cedars-Sinai Medical Center, Los Angeles, CA 90048; and
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13
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Bozza S, Campo S, Arseni B, Inforzato A, Ragnar L, Bottazzi B, Mantovani A, Moretti S, Oikonomous V, De Santis R, Carvalho A, Salvatori G, Romani L. PTX3 Binds MD-2 and Promotes TRIF-Dependent Immune Protection in Aspergillosis. THE JOURNAL OF IMMUNOLOGY 2014; 193:2340-8. [DOI: 10.4049/jimmunol.1400814] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
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14
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Lu Z, Li Y, Samuvel DJ, Jin J, Zhang X, Lopes-Virella MF, Huang Y. MD-2 is involved in the stimulation of matrix metalloproteinase-1 expression by interferon-γ and high glucose in mononuclear cells - a potential role of MD-2 in Toll-like receptor 4-independent signalling. Immunology 2013; 140:301-13. [PMID: 23800176 DOI: 10.1111/imm.12138] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2013] [Revised: 05/20/2013] [Accepted: 06/20/2013] [Indexed: 11/27/2022] Open
Abstract
We reported recently that treatment of diabetic apolipoprotein E-deficient mice with the Toll-like receptor 4 (TLR4) antagonist Rs-LPS, a lipopolysaccharide isolated from Rhodobacter sphaeroides, inhibited atherosclerosis. Since it is known that Rs-LPS antagonizes TLR4 by targeting TLR4 co-receptor MD-2, this finding indicates that MD-2 is a potential target for the treatment of atherosclerosis. In this study, we determined if MD-2 is involved in the gene expression regulated by signalling pathways independent of TLR4. Given that interferon-γ (IFNγ) and hyperglycaemia play key roles in atherosclerosis, we determined if MD-2 is involved in IFN-γ and high-glucose-regulated gene expression in mononuclear cells. Results showed that IFN-γ and high glucose synergistically stimulated matrix metalloproteinase 1 (MMP-1), a proteinase essential for vascular tissue remodelling and atherosclerosis, in U937 mononuclear cells, but Rs-LPS inhibited the MMP-1 stimulation. To provide more evidence for a role of MD-2 in IFN-γ-stimulated MMP-1, studies using antibodies and small interfering RNA demonstrated that MD-2 blockade or knockdown attenuated the effect of IFN-γ on MMP-1. Furthermore, studies using PCR arrays showed that MD-2 blockade had a similar effect as IFN-γ receptor blockade on the inhibition of IFN-γ-stimulated pro-inflammatory molecules. Although these findings indicate the involvement of MD-2 in IFN-γ signalling, we also observed that MD-2 was up-regulated by IFN-γ and high glucose. We found that MD-2 up-regulation by IFN-γ played an essential role in the synergistic effect of IFN-γ and LPS on MMP-1 expression. Taken together, these findings indicate that MD-2 is involved in IFN-γ signalling and IFN-γ-augmented MMP-1 up-regulation by LPS.
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Affiliation(s)
- Zhongyang Lu
- Division of Endocrinology, Diabetes and Medical Genetics, Department of Medicine, College of Medicine, Medical University of South Carolina, Charleston, SC, USA
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15
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Moretti J, Blander JM. Insights into phagocytosis-coupled activation of pattern recognition receptors and inflammasomes. Curr Opin Immunol 2013; 26:100-10. [PMID: 24556406 DOI: 10.1016/j.coi.2013.11.003] [Citation(s) in RCA: 53] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2013] [Revised: 11/07/2013] [Accepted: 11/12/2013] [Indexed: 01/22/2023]
Abstract
A decade of work shows that the core function of phagocytosis in engulfment and destruction of microorganisms is only a small facet of the full spectrum of roles for phagocytosis in the immune system. The regulation of phagocytosis and its outcomes by inflammatory pattern recognition receptors (PRRs) is now followed by new studies strengthening this concept and adding further complexity to the relationship between phagocytosis and innate immune signaling. Phagocytosis forms the platform for activation of distinct members of the Toll-like receptor family, and even dictates their signaling outcomes. In many cases, phagocytosis is a necessary precedent to the activation of cytosolic PRRs and assembly of canonical and non-canonical inflammasomes, leading to strong pro-inflammatory responses and inflammatory cell death.
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Affiliation(s)
- Julien Moretti
- Immunology Institute, Department of Medicine, Mount Sinai School of Medicine, 1425 Madison Avenue, New York, NY 10029, United States
| | - J Magarian Blander
- Immunology Institute, Department of Medicine, Mount Sinai School of Medicine, 1425 Madison Avenue, New York, NY 10029, United States.
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16
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Innate immune functions of immature neutrophils in patients with sepsis and severe systemic inflammatory response syndrome. Crit Care Med 2013; 41:820-32. [PMID: 23348516 DOI: 10.1097/ccm.0b013e318274647d] [Citation(s) in RCA: 163] [Impact Index Per Article: 14.8] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
OBJECTIVE A hallmark of sepsis and severe systemic inflammatory response syndrome (SIRS) is the massive recruitment of immature neutrophils from the bone marrow into the circulation (left shift, band forms). Their capacity to participate in innate defense against bacteria is ill defined. We aimed at comparing various innate immune functions of mature vs. immature neutrophils circulating during sepsis and SIRS. DESIGN Prospective, observational cohort study. SETTING Tertiary level ICU and associated research laboratory. PATIENTS : Thirty-three ICU patients with sepsis; 12 ICUs with SIRS; 32 healthy volunteers. INTERVENTIONS Twenty milliliters of whole heparinized blood was used for in vitro studies including neutrophil viability and apoptosis, surface expression of CD16, Toll-like receptors () 4 and TLR2, CD14, MD-2, HLA-DP,-DQ and -DR, and CXCR2, chemotaxis, phagocytosis, bacterial killing, and tumor necrosis factor-α/interleukin-10 baseline intracellular cytokine levels. MEASUREMENTS AND MAIN RESULTS Immature neutrophils were capable of mediating important innate immune functions such as bacterial phagocytosis and killing via the production of reactive oxygen species, although less efficiently than mature neutrophils. Immature neutrophils had a longer life span and resistance to spontaneous apoptosis, and could mature ex vivo. They expressed lower levels of receptors for bacterial molecules such as CD14 and MD-2 and migrated less efficiently than mature granulocytes. Immature neutrophils had higher basal intracellular tumor necrosis factor-α/interleukin-10 ratio than that of mature neutrophils, suggesting a proinflammatory phenotype. No significant differences were observed between immature neutrophils isolated from patients with sepsis and those from patients with severe SIRS. CONCLUSIONS Despite their "immaturity", band forms are capable of mediating crucial innate immune functions during severe infections and sepsis. Their fate and capacity to mature in vivo remain to be determined.
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Nagai Y, Watanabe Y, Takatsu K. The TLR family protein RP105/MD-1 complex: A new player in obesity and adipose tissue inflammation. Adipocyte 2013; 2:61-6. [PMID: 23805400 PMCID: PMC3661108 DOI: 10.4161/adip.22929] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/03/2012] [Revised: 11/14/2012] [Accepted: 11/16/2012] [Indexed: 12/20/2022] Open
Abstract
The radioprotective 105 (RP105)/MD-1 complex is a member of the Toll-like receptor (TLR) family of proteins. We have previously reported that this complex cooperates with the essential lipopolysaccharide (LPS) receptor TLR4/MD-2 complex and plays a crucial role in LPS responses by B cells. Recent evidences suggest that TLRs can also recognize endogenous ligands and promote non-infectious chronic inflammation. For instance, TLR4/MD-2 can be ligated by adipose tissue-derived saturated free fatty acids (FAs) and induce adipose tissue inflammation and insulin resistance. Recently, we reported that RP105 knockout (KO) or MD-1 KO mice have less high-fat diet (HFD)-induced obesity, adipose tissue inflammation and insulin resistance than wild-type (WT) or TLR4 KO mice. As RP105/MD-1 is not involved in recognition of palmitic and stearic acids, which are endogenous ligands for TLR4/MD-2, we conclude that RP105/MD-1 is itself a key regulator of diet-induced chronic inflammation in adipose tissue, obesity and insulin resistance that appears to be independent of the TLR4-dependent pathway. In this mini-review, we will highlight the significance of the RP105/MD-1 complex in adipose tissue inflammation and discuss implications for human diseases.
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18
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Bonin CP, Baccarin RYA, Nostell K, Nahum LA, Fossum C, de Camargo MM. Lipopolysaccharide-induced inhibition of transcription of tlr4 in vitro is reversed by dexamethasone and correlates with presence of conserved NFκB binding sites. Biochem Biophys Res Commun 2013; 432:256-61. [PMID: 23402753 PMCID: PMC3695733 DOI: 10.1016/j.bbrc.2013.02.002] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2013] [Accepted: 02/03/2013] [Indexed: 02/09/2023]
Abstract
Engagement of Toll-like receptor 4 (TLR4) by lipopolysaccharide (LPS) is a master trigger of the deleterious effects of septic shock. Horses and humans are considered the most sensitive species to septic shock, but the mechanisms explaining these phenomena remain elusive. Analysis of tlr4 promoters revealed high similarity among LPS-sensitive species (human, chimpanzee, and horse) and low similarity with LPS-resistant species (mouse and rat). Four conserved nuclear factor kappa B (NFκB) binding sites were found in the tlr4 promoter and two in the md2 promoter sequences that are likely to be targets for dexamethasone regulation. In vitro treatment of equine peripheral blood mononuclear cells (eqPBMC) with LPS decreased transcripts of tlr4 and increased transcription of md2 (myeloid differentiation factor 2) and cd14 (cluster of differentiation 14). Treatment with dexamethasone rescued transcription of tlr4 after LPS inhibition. LPS-induced transcription of md2 was inhibited in the presence of dexamethasone. Dexamethasone alone did not affect transcription of tlr4 and md2.
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Affiliation(s)
- Camila P Bonin
- Department of Immunology, Institute of Biomedical Sciences, University of São Paulo, São Paulo 05508-900, Brazil.
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19
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Abstract
There are at least five families of microbe-detection receptors that function to detect and eradicate potentially infectious microorganisms that enter multicellular eukaryotes. While a multitude of proteins regulating innate immune signal transduction have already been defined, continuous genetic screening for regulators of innate immunity may not yield as significant insight into the operation of these pathways as was obtained in the past. This diminished return on experimental investment suggests that we are approaching the asymptote of genetics-only approaches to study innate immunity. In contrast, it remains unclear how known regulators of innate immunity interact within the infrastructure of mammalian cells to execute their signaling functions. In this Perspective, I first highlight the locations within mammalian cells that permit innate immune signal transduction and then offer a model whereby structurally distinct proteins can be grouped functionally through their ability to assemble platforms of regulators on the signaling organelles of the innate immune system.
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Affiliation(s)
- Jonathan C Kagan
- Harvard Medical School and Division of Gastroenterology, Children's Hospital Boston, Boston, MA 02115, USA.
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20
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Kagan JC, Iwasaki A. Phagosome as the organelle linking innate and adaptive immunity. Traffic 2012; 13:1053-61. [PMID: 22577865 DOI: 10.1111/j.1600-0854.2012.01377.x] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2012] [Revised: 05/04/2012] [Accepted: 05/11/2012] [Indexed: 12/22/2022]
Abstract
The means by which phagocytosis and antimicrobial defense mechanisms are linked have expanded greatly in recent years. It is now clear that the process of phagocytosis does more than just degrade internalized microbes, but also helps coordinate the actions of the innate and adaptive immune system. This review will discuss the means by which Toll-like receptor signaling pathways are coordinated around the processes of phagocytosis, phagosome trafficking and autophagy and how these signaling pathways influence T-cell-mediated immunity. In this regard, we propose that at the subcellular level, phagosomes represent the smallest definable unit that links innate and adaptive immunity.
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Affiliation(s)
- Jonathan C Kagan
- Division of Gastroenterology, Harvard Medical School, Children's Hospital Boston, 300 Longwood Ave, Enders 649, Boston, MA 02115, USA.
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21
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Dunn-Siegrist I, Tissières P, Drifte G, Bauer J, Moutel S, Pugin J. Toll-like receptor activation of human cells by synthetic triacylated lipid A-like molecules. J Biol Chem 2012; 287:16121-31. [PMID: 22433865 DOI: 10.1074/jbc.m112.348383] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
Abstract
Recognition of microbial molecules by mammalian host receptors is essential to mount an immune response. Hexaacylated LPS is the prototypic example of a bacterial molecule recognized by the receptor complex TLR4/MD-2 with its lipid A moiety, whereas bacterial lipopeptides are recognized by TLR2. Here we show that a series of synthetic triacylated lipid A-like molecules are weak Toll-like receptor (TLR) agonists (mainly TLR2 agonists) but very potent TLR4/MD-2 antagonists (submicromolar range). Not only do they block human cell responses to LPS but also to whole gram-negative bacteria, and they inhibit the phagocytosis of gram-negative bacteria. These compounds may represent promising immunomodulatory agents.
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Affiliation(s)
- Irène Dunn-Siegrist
- Intensive Care Laboratory and Department of Microbiology and Molecular Medicine, Faculty of Medicine, University of Geneva, 1211 Geneva 14, Switzerland
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22
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Tissières P, Ochoda A, Dunn-Siegrist I, Drifte G, Morales M, Pfister R, Berner M, Pugin J. Innate immune deficiency of extremely premature neonates can be reversed by interferon-γ. PLoS One 2012; 7:e32863. [PMID: 22427899 PMCID: PMC3299693 DOI: 10.1371/journal.pone.0032863] [Citation(s) in RCA: 60] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2012] [Accepted: 02/01/2012] [Indexed: 12/28/2022] Open
Abstract
BACKGROUND Bacterial sepsis is a major threat in neonates born prematurely, and is associated with elevated morbidity and mortality. Little is known on the innate immune response to bacteria among extremely premature infants. METHODOLOGY/PRINCIPAL FINDINGS We compared innate immune functions to bacteria commonly causing sepsis in 21 infants of less than 28 wks of gestational age, 24 infants born between 28 and 32 wks of gestational age, 25 term newborns and 20 healthy adults. Levels of surface expression of innate immune receptors (CD14, TLR2, TLR4, and MD-2) for Gram-positive and Gram-negative bacteria were measured in cord blood leukocytes at the time of birth. The cytokine response to bacteria of those leukocytes as well as plasma-dependent opsonophagocytosis of bacteria by target leukocytes was also measured in the presence or absence of interferon-γ. Leukocytes from extremely premature infants expressed very low levels of receptors important for bacterial recognition. Leukocyte inflammatory responses to bacteria and opsonophagocytic activity of plasma from premature infants were also severely impaired compared to term newborns or adults. These innate immune defects could be corrected when blood from premature infants was incubated ex vivo 12 hrs with interferon-γ. CONCLUSION/SIGNIFICANCE Premature infants display markedly impaired innate immune functions, which likely account for their propensity to develop bacterial sepsis during the neonatal period. The fetal innate immune response progressively matures in the last three months in utero. Ex vivo treatment of leukocytes from premature neonates with interferon-γ reversed their innate immune responses deficiency to bacteria. These data represent a promising proof-of-concept to treat premature newborns at the time of delivery with pharmacological agents aimed at maturing innate immune responses in order to prevent neonatal sepsis.
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Affiliation(s)
- Pierre Tissières
- Division of Intensive Care, University Hospitals of Geneva, Geneva, Switzerland.
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23
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Exogenous MD-2 confers lipopolysaccharide responsiveness to human corneal epithelial cells with intracellular expression of TLR4 and CD14. Inflammation 2012; 34:371-8. [PMID: 20700758 DOI: 10.1007/s10753-010-9244-x] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
Abstract
In the present study, we aimed to investigate the responsiveness of human corneal epithelial cells (HCECs) to lipopolysaccharide (LPS) in vitro and to elucidate the underlying molecular mechanism(s) controlling the LPS responsiveness. The expression and subcellular localization of toll-like receptor 4 (TLR4) and CD14 and the expression of myeloid differentiation (MD)-2 were studied in SDHCEC1 cells, one HCEC cell line. Upon exposure to different concentrations of LPS, cell responses were evaluated by examining nuclear factor-kappaB (NF-κB) activation and the production of interleukin (IL)-8. The influence of soluble MD-2 on LPS responsiveness were assessed in SDHCEC1 cells pretreated with MD-2-containing conditioned medium before LPS challenge. SDHCEC1 cells expressed both TLR4 and CD14 intracellularly and had no detectable expression of MD-2 transcripts. Unresponsiveness to LPS at doses of up to 1,000 ng/ml was observed in SDHCEC1 cells, which was evidenced by no evident NF-κB activation and IL-8 production. The addition of MD-2 conditioned medium significantly induced NF-κB activation and enhanced the production of IL-8 as compared with the treatment with the control medium (p < 0.05). Meanwhile, the total mRNA amounts of TLR4 and CD14 and the surface expression of the two proteins were significantly (p < 0.05) increased by the pretreatment with MD-2 conditioned medium. LPS hyporesponsiveness of HCECs is largely due to deficient LPS receptor complex formation caused by lack of MD-2 expression. Exogenous MD-2 is capable of restoring the LPS responsiveness, at least partially, through promoting the surface expression of TLR4 and CD14.
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Sasaki S, Nagai Y, Yanagibashi T, Watanabe Y, Ikutani M, Kariyone A, Tsuneyama K, Hirai Y, Takatsu K. Serum soluble MD-1 levels increase with disease progression in autoimmune prone MRL(lpr/lpr) mice. Mol Immunol 2011; 49:611-20. [PMID: 22118968 DOI: 10.1016/j.molimm.2011.10.008] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2011] [Revised: 10/04/2011] [Accepted: 10/26/2011] [Indexed: 10/15/2022]
Abstract
MD-1 is a secreted protein that forms a complex with radioprotective 105 (RP105) and this complex plays a crucial role in lipopolysaccharide (LPS) recognition by B cells. Disease progression is known to improve in RP105-deficient lupus-prone MRL(lpr/lpr) mice. Furthermore, a soluble form of the homologous MD-2 protein is present in the plasma of septic patients and can opsonize gram-negative bacteria in cooperation with Toll-like receptor (TLR) 4. We have now established a flow cytometry-based assay to detect the soluble form of murine MD-1 (sMD-1) and explored potential roles in autoimmunity. The assay was quantitative and validated with sera from MD-1-deficient mice. Interestingly, heat-inactivated murine serum diminished the ability of sMD-1 to bind RP105. The sMD-1 was secreted by bone marrow-derived macrophages from C57BL/6 mice. Autoimmune prone MRL(lpr/lpr) mice had higher levels of sMD-1 than control MRL(+/+) mice, and levels markedly increased with disease progression. Expression of MD-1 but not MD-2 mRNA increased with age in the liver and kidney of MRL(lpr/lpr) mice. Finally, immunohistochemical analyses revealed that MD-1 was present in infiltrated macrophages within perivascular lesions of the MRL(lpr/lpr) kidney. This correlation suggests that sMD-1 may contribute to pathogenesis in this autoimmune disease model.
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Affiliation(s)
- Sumiyo Sasaki
- Department of Immunobiology and Pharmacological Genetics, Graduate School of Medicine and Pharmaceutical Science for Research, University of Toyama, 2630 Sugitani, Toyama-shi, Toyama 930-0194, Japan
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25
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Shibata T, Motoi Y, Tanimura N, Yamakawa N, Akashi-Takamura S, Miyake K. Intracellular TLR4/MD-2 in macrophages senses Gram-negative bacteria and induces a unique set of LPS-dependent genes. Int Immunol 2011; 23:503-10. [PMID: 21712422 DOI: 10.1093/intimm/dxr044] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023] Open
Abstract
Toll-like receptor (TLR)4/MD-2, a sensor for LPS, delivers the MyD88-dependent signal from the cell surface, then traffics to endolysosomes and delivers the TRIF/TICAM-1-dependent signal. Both signals are thought to be dependent on cell surface TLR4/MD-2. Although TLR4/MD-2 is located also in recycling endosomes, the Golgi apparatus or the endoplasmic reticulum, little is known about a role for intracellular TLR4/MD-2 in LPS responses. We here studied intracellular LPS sensing in macrophages. PRAT4A (protein associated with TLR4 A) is a cochaperone for a general chaperone gp96 and required for cell surface expression of TLR4/MD-2. Cell surface TLR4/MD-2 was undetectable on PRAT4A(-/-) thioglycollate-elicited peritoneal macrophages (P-Macs) and bone marrow-derived macrophages (BM-Macs). LPS responses were all abolished in PRAT4A(-/-) P-Macs, whereas a part of LPS responses remained detectable in PRAT4A(-/-) BM-Macs. Of note, LPS responses in PRAT4A(-/-) BM-Macs were not necessarily dependent on TRIF/TICAM-1 signaling. PRAT4A(-/-) BM-Macs showed unimpaired production of both TRIF/TICAM-1-dependent chemokine RANTES (CCL5) and MyD88-dependent chemokine MCP-1 (CCL2). Moreover, up-regulation of co-stimulatory molecules, CD40 and CD86 was not altered. In contrast, TRIF/TICAM-1-dependent production of type I IFN was profoundly impaired. In response to heat-killed bacteria Escherichia coli, BM-Macs also required PRAT4A-independent TLR4/MD-2 for production of MCP-1 (CCL2) and RANTES (CCL5) and for up-regulation of CD40 and CD86, indicating that intracellular TLR4/MD-2 is able to sense phagocytosed bacteria and activate immune responses. These results demonstrate that intracellular TLR4/MD-2 is responsible for unique set of LPS responses.
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Affiliation(s)
- Takuma Shibata
- Division of Infectious Genetics, Department of Microbiology and Immunology, Institute of Medical Science, University of Tokyo, 4-6-1 Shirokanedai, Minatoku, Tokyo 108-8639, Japan
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26
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Madsen K. MD-2: another important piece of the puzzle? Inflamm Bowel Dis 2011; 17:1436-7. [PMID: 20842644 DOI: 10.1002/ibd.21485] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/27/2010] [Accepted: 08/13/2010] [Indexed: 12/09/2022]
Affiliation(s)
- Karen Madsen
- Department of Medicine University of Alberta, Edmonton, Alberta, Canada
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27
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Husebye H, Aune MH, Stenvik J, Samstad E, Skjeldal F, Halaas Ø, Nilsen NJ, Stenmark H, Latz E, Lien E, Mollnes TE, Bakke O, Espevik T. The Rab11a GTPase controls Toll-like receptor 4-induced activation of interferon regulatory factor-3 on phagosomes. Immunity 2010; 33:583-96. [PMID: 20933442 PMCID: PMC10733841 DOI: 10.1016/j.immuni.2010.09.010] [Citation(s) in RCA: 158] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2009] [Revised: 06/22/2010] [Accepted: 09/15/2010] [Indexed: 02/06/2023]
Abstract
Toll-like receptor 4 (TLR4) is indispensable for recognition of Gram-negative bacteria. We described a trafficking pathway for TLR4 from the endocytic recycling compartment (ERC) to E. coli phagosomes. We found a prominent colocalization between TLR4 and the small GTPase Rab11a in the ERC, and Rab11a was involved in the recruitment of TLR4 to phagosomes in a process requiring TLR4 signaling. Also, Toll-receptor-associated molecule (TRAM) and interferon regulatory factor-3 (IRF3) localized to E. coli phagosomes and internalization of E. coli was required for a robust interferon-β induction. Suppression of Rab11a reduced TLR4 in the ERC and on phagosomes leading to inhibition of the IRF3 signaling pathway induced by E. coli, whereas activation of the transcription factor NF-κB was unaffected. Moreover, Rab11a silencing reduced the amount of TRAM on phagosomes. Thus, Rab11a is an important regulator of TLR4 and TRAM transport to E. coli phagosomes thereby controlling IRF3 activation from this compartment.
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Affiliation(s)
- Harald Husebye
- Norwegian University of Science and Technology, Department of Cancer Research and Molecular Medicine, N-7489 Trondheim, Norway
- These authors contributed equally to this work
| | - Marie Hjelmseth Aune
- Norwegian University of Science and Technology, Department of Cancer Research and Molecular Medicine, N-7489 Trondheim, Norway
- These authors contributed equally to this work
| | - Jørgen Stenvik
- Norwegian University of Science and Technology, Department of Cancer Research and Molecular Medicine, N-7489 Trondheim, Norway
- These authors contributed equally to this work
| | - Eivind Samstad
- Norwegian University of Science and Technology, Department of Cancer Research and Molecular Medicine, N-7489 Trondheim, Norway
| | - Frode Skjeldal
- Department of Molecular Biosciences, Centre for Immune Regulation, University of Oslo, N-0316 Oslo, Norway
| | - Øyvind Halaas
- Norwegian University of Science and Technology, Department of Cancer Research and Molecular Medicine, N-7489 Trondheim, Norway
| | - Nadra J. Nilsen
- Norwegian University of Science and Technology, Department of Cancer Research and Molecular Medicine, N-7489 Trondheim, Norway
| | - Harald Stenmark
- Norwegian University of Science and Technology, Department of Cancer Research and Molecular Medicine, N-7489 Trondheim, Norway
- Department of Biochemistry, Institute for Cancer Research, The Norwegian Radium Hospital, Montebello, N-0310 Oslo, Norway
| | - Eicke Latz
- Norwegian University of Science and Technology, Department of Cancer Research and Molecular Medicine, N-7489 Trondheim, Norway
- Institute of Innate Immunity, Biomedical Center, University of Bonn, Sigmund-Freud-Str. 25, 53127 Bonn, Germany
| | - Egil Lien
- Norwegian University of Science and Technology, Department of Cancer Research and Molecular Medicine, N-7489 Trondheim, Norway
- Division of Infectious Diseases and Immunology, University of Massachusetts Medical School, Worcester, MA 01605, USA
| | - Tom Eirik Mollnes
- Institute of Immunology, Rikshospitalet University Hospital, University of Oslo, N-0027 Oslo, Norway
| | - Oddmund Bakke
- Department of Molecular Biosciences, Centre for Immune Regulation, University of Oslo, N-0316 Oslo, Norway
- The Gade Institute, University of Bergen, 5021 Bergen, Norway
| | - Terje Espevik
- Norwegian University of Science and Technology, Department of Cancer Research and Molecular Medicine, N-7489 Trondheim, Norway
- St. Olavs Hospital, N-7489 Trondheim, Norway
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Hedayat M, Takeda K, Rezaei N. Prophylactic and therapeutic implications of toll-like receptor ligands. Med Res Rev 2010; 32:294-325. [DOI: 10.1002/med.20214] [Citation(s) in RCA: 54] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Affiliation(s)
- Mona Hedayat
- Molecular Immunology Research Center; Department of Immunology; School of Medicine; Tehran University of Medical Sciences; Tehran; Iran
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29
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Guo J, Friedman SL. Toll-like receptor 4 signaling in liver injury and hepatic fibrogenesis. FIBROGENESIS & TISSUE REPAIR 2010; 3:21. [PMID: 20964825 PMCID: PMC2984459 DOI: 10.1186/1755-1536-3-21] [Citation(s) in RCA: 220] [Impact Index Per Article: 15.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 09/07/2010] [Accepted: 10/21/2010] [Indexed: 12/12/2022]
Abstract
Toll-like receptors (TLRs) are a family of transmembrane pattern recognition receptors (PRR) that play a key role in innate and adaptive immunity by recognizing structural components unique to bacteria, fungi and viruses. TLR4 is the most studied of the TLRs, and its primary exogenous ligand is lipopolysaccharide, a component of Gram-negative bacterial walls. In the absence of exogenous microbes, endogenous ligands including damage-associated molecular pattern molecules from damaged matrix and injured cells can also activate TLR4 signaling. In humans, single nucleotide polymorphisms of the TLR4 gene have an effect on its signal transduction and on associated risks of specific diseases, including cirrhosis. In liver, TLR4 is expressed by all parenchymal and non-parenchymal cell types, and contributes to tissue damage caused by a variety of etiologies. Intact TLR4 signaling was identified in hepatic stellate cells (HSCs), the major fibrogenic cell type in injured liver, and mediates key responses including an inflammatory phenotype, fibrogenesis and anti-apoptotic properties. Further clarification of the function and endogenous ligands of TLR4 signaling in HSCs and other liver cells could uncover novel mechanisms of fibrogenesis and facilitate the development of therapeutic strategies.
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Affiliation(s)
- Jinsheng Guo
- Division of Liver Diseases, Mount Sinai Hospital, Mount Sinai School of Medicine, New York, NY, USA.
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30
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Grondin V, Seksik P, Dumont S, Thomas G, Trugnan G, Fléjou JF, Masliah J, Wendum D, Bachelet M. Regulation of colon cancer cell proliferation and migration by MD-2 activity. Innate Immun 2010; 17:414-22. [PMID: 20699280 DOI: 10.1177/1753425910375583] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Abstract
Evidence suggests that signalling through lipopolysaccharide (LPS) has a significant role in the development of gastrointestinal malignancies. We previously demonstrated the critical role of myeloid differentiation (MD)-2, the essential co-receptor of LPS, for induction of cyclooxygenase (Cox)-2 in intestinal epithelial cells. Cyclooxigenase-2 was suggested to play a key role in colorectal cancer through the effects of prostaglandin (PG) E(2) generated. We, therefore, addressed the role of MD-2 in several parameters related to malignancy, namely cell proliferation and migration, using colon cancer cells (HT-29). We found that overexpression of MD-2 confers a significantly greater proliferation and migration capacity to these cells. MD-2-dependent proliferation and migration appeared independent of Cox-2 activity but was reduced by endothelial growth factor receptor (EGFR) neutralizing antibodies as well as by pharmacological inhibition of EGFR tyrosine phosphorylation. We propose that MD-2 overexpression contributes to tumour aggressiveness via a Cox-2-independent excessive EGFR signalling. Moreover, MD-2 expression levels were higher in tissue from patients with colorectal cancer as compared with paired control colorectal mucosa. Our data attest to a role of MD-2 activity in colon cancer epithelial cell proliferation and migration, which may be important in the general correlation between innate immune response, chronic inflammation, and cancer.
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31
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Crystal structure of soluble MD-1 and its interaction with lipid IVa. Proc Natl Acad Sci U S A 2010; 107:10990-5. [PMID: 20534476 DOI: 10.1073/pnas.1004153107] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
Lipopolysaccharide (LPS) of Gram-negative bacteria is a common pathogen-associated molecular pattern (PAMP) that induces potent innate immune responses. The host immune response against LPS is triggered by myeloid differentiation factor 2 (MD-2) in association with Toll-like receptor 4 (TLR4) on the cell surface. The MD-2/TLR4-mediated LPS response is regulated by the evolutionarily related complex of MD-1 and Toll-like receptor homolog RP105. Here, we report crystallographic and biophysical data that demonstrate a previously unidentified direct interaction of MD-1 with LPS. The crystal structure of chicken MD-1 (cMD-1) at 2.0 A resolution exhibits a beta-cup-like fold, similar to MD-2, that encloses a hydrophobic cavity between the two beta-sheets. A lipid-like moiety was observed inside the cavity, suggesting the possibility of a direct MD-1/LPS interaction. LPS was subsequently identified as an MD-1 ligand by native gel electrophoresis and gel filtration analyses. The crystal structure of cMD-1 with lipid IVa, an LPS precursor, at 2.4 A resolution revealed that the lipid inserts into the deep hydrophobic cavity of the beta-cup-like structure, but with some important differences compared with MD-2. These findings suggest that soluble MD-1 alone, in addition to its complex with RP105, can regulate host LPS sensitivity.
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32
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Ohnishi T, Muroi M, Tanamoto KI. Inhibitory effects of soluble MD-2 and soluble CD14 on bacterial growth. Microbiol Immunol 2010; 54:74-80. [PMID: 20377740 DOI: 10.1111/j.1348-0421.2009.00186.x] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Abstract
The effects of the soluble forms of the endotoxin receptor molecules sMD-2 and sCD14 on bacterial growth were studied. When Escherichia coli and Bacillus subtilis were incubated at 37 degrees C for 18 hr with either sMD-2 or sCD14, growth of these bacteria was significantly inhibited as evaluated by viable cell counts and NADPH/NADH activity. A mutant of sCD14 (sCD14d57-64) lacking a region essential for LPS binding did not inhibit the growth of E. coli, whereas this mutant did inhibit the growth of B. subtilis. Addition of excess PG to the bacterial culture reversed the inhibitory effect of sMD-2 on the growth of B. subtilis, but not on the growth of E. coli. Furthermore, when evaluated by ELISA, both sMD-2 and sCD14 bound specifically to PG. Taken together, these results indicate that sMD-2 and sCD14 inhibit the growth of both Gram-positive and Gram-negative bacteria and further suggest that binding to PG and LPS is involved in the inhibitory effect of sMD-2 on Gram-positive bacteria and of sCD14 on Gram-negative bacteria, respectively.
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Affiliation(s)
- Takahiro Ohnishi
- Division of Microbiology, National Institute of Health Sciences, Setagaya, Tokyo 158-8501, Japan.
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Gray P, Michelsen KS, Sirois CM, Lowe E, Shimada K, Crother TR, Chen S, Brikos C, Bulut Y, Latz E, Underhill D, Arditi M. Identification of a novel human MD-2 splice variant that negatively regulates Lipopolysaccharide-induced TLR4 signaling. THE JOURNAL OF IMMUNOLOGY 2010; 184:6359-66. [PMID: 20435923 DOI: 10.4049/jimmunol.0903543] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Myeloid differentiation factor 2 (MD-2) is a secreted gp that assembles with TLR4 to form a functional signaling receptor for bacterial LPS. In this study, we have identified a novel alternatively spliced isoform of human MD-2, termed MD-2 short (MD-2s), which lacks the region encoded by exon 2 of the MD-2 gene. Similar to MD-2, MD-2s is glycosylated and secreted. MD-2s also interacted with LPS and TLR4, but failed to mediate LPS-induced NF-kappaB activation and IL-8 production. We show that MD-2s is upregulated upon IFN-gamma, IL-6, and TLR4 stimulation and negatively regulates LPS-mediated TLR4 signaling. Furthermore, MD-2s competitively inhibited binding of MD-2 to TLR4. Our study pinpoints a mechanism that may be used to regulate TLR4 activation at the onset of signaling and identifies MD-2s as a potential therapeutic candidate to treat human diseases characterized by an overly exuberant or chronic immune response to LPS.
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Affiliation(s)
- Pearl Gray
- Division of Pediatric Infectious Diseases and Immunology, Burns and Allen Research Institute, Cedars-Sinai Medical Center, David Geffen School of Medicine, University of California-Los Angeles, Los Angeles, CA 90048, USA
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34
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Sera from patients with Crohn’s disease break bacterial lipopolysaccharide tolerance of human intestinal epithelial cells via MD-2 activity. Innate Immun 2010; 16:381-90. [DOI: 10.1177/1753425909357076] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Abstract
Myeloid differentiation (MD)-2 is linked to the cell surface as a Toll-like receptor (TLR) 4-bound protein though may also function as a soluble receptor to enable the lipopolysaccharide (LPS)-driven response. We recently demonstrated the importance of MD-2 either as a cell-associated or as a soluble receptor in the control of intestinal epithelial cell response toward LPS. High levels of circulating MD-2 were recently proposed as a risk factor for infectious/ inflammatory diseases as septic shock. We hypothesized that MD-2 might be present in sera from patients with inflammatory bowel disease and have pathogenic consequences. We analysed MD-2 activity in sera from patients with inflammatory bowel disease or from healthy subjects. We measured MD-2 activity as the capacity to mediate LPS-driven stimulation of intestinal epithelial cells (HT29). We found that sera from patients with inflammatory bowel disease, particularly Crohn’s disease, endowed HT29 cells with a markedly higher LPS-dependent stimulating capacity as compared to sera from healthy subjects. The effect of sera was specific for LPS activation and was reduced in the presence of anti-MD-2, and anti-TLR4 antibodies. We conclude that sera from patients with inflammatory bowel disease might contain increased MD-2. This might result in higher local availability of the protein leading to a loss of tolerance toward gut microbiota.
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35
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Wolfs TGAM, Derikx JPM, Hodin CMIM, Vanderlocht J, Driessen A, de Bruïne AP, Bevins CL, Lasitschka F, Gassler N, van Gemert WG, Buurman WA. Localization of the lipopolysaccharide recognition complex in the human healthy and inflamed premature and adult gut. Inflamm Bowel Dis 2010; 16:68-75. [PMID: 20014022 DOI: 10.1002/ibd.20995] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
BACKGROUND Microbiota in the intestinal lumen provide an abundant source of potentially detrimental antigens, including lipopolysaccharide (LPS), a potent immunostimulatory product of Gram-negative bacteria recognized by the host via TLR-4 and MD-2. An aberrant immune response to LPS or other bacterial antigens has been linked to inflammatory bowel disease (IBD) and necrotizing enterocolitis (NEC). METHODS We investigated which cells express MD-2 in the normal and inflamed ileum from neonates and adults by immunohistochemistry. Moreover, MD-2 and TLR4 mRNA expression in normal adult ileum was studied by reverse-transcription polymerase chain reaction (RT-PCR) on cells isolated by laser capture microdissection. RESULTS Premature infants did not show MD-2 expression either in epithelial cells or in the lamina propria. Similarly, MD-2 was absent in epithelial cells and lamina propria inflammatory cells in preterm infants with NEC. MD-2 protein in the healthy term neonatal and adult ileum was predominantly expressed by Paneth cells and some resident inflammatory cells in the lamina propria. MD-2 and TLR-4 mRNA expression was restricted to crypt cells. Also in IBD, Paneth cells were still the sole MD-2-expressing epithelial cells, whereas inflammatory cells (mainly plasma cells) were responsible for the vast majority of the MD-2 expression. CONCLUSIONS The absence of MD-2 in the immature neonatal gut suggests impaired LPS sensing, which could predispose neonates to NEC upon microbial colonization of the immature intestine. The apparent expression of MD-2 by Paneth cells supports the critical concept that these cells respond to luminal bacterial products in order to maintain homeostasis with the intestinal microbiota in vivo.
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Affiliation(s)
- Tim G A M Wolfs
- Department of Surgery, Nutrition and Toxicology Research Institute Maastricht (NUTRIM), Maastricht University Medical Centre, Maastricht, the Netherlands
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Xue Y, Zhao Z, Hong D, Zhao M, Zhang Y, Wang H, Wang Y, Li J. Lack of association between MD-2 promoter gene variants and tuberculosis. GENETICS AND MOLECULAR RESEARCH 2010; 9:1584-90. [DOI: 10.4238/vol9-3gmr771] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
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37
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Tissières P, Araud T, Ochoda A, Drifte G, Dunn-Siegrist I, Pugin J. Cooperation between PU.1 and CAAT/enhancer-binding protein beta is necessary to induce the expression of the MD-2 gene. J Biol Chem 2009; 284:26261-72. [PMID: 19632992 DOI: 10.1074/jbc.m109.042580] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
Myeloid differentiation factor 2 (MD-2) binds Gram-negative bacterial lipopolysaccharide with high affinity and is essential for Toll-like receptor 4-dependent signal transduction. MD-2 has recently been recognized as a type II acute phase protein. Plasma concentrations of the soluble form of MD-2 increase markedly during the course of severe infections. Its production is regulated in hepatocytes and myeloid cells by interleukin-6 (IL-6) but not IL-1beta. In the present work we show that two transcription factors (TF), PU.1 and CAAT/enhancer-binding protein beta (C/EBPbeta), participate in the activation of the human MD-2 gene in hepatocytic cells after stimulation with IL-6. PU.1 TF and proximal PU.1 binding sites in the MD-2 promoter were shown to be critical for the basal activity of the promoter as well as for IL-6-induced soluble MD-2 production. Deletions of proximal portions of the MD-2 promoter containing PU.1 and/or NF-IL-6 consensus binding sites as well as site-directed mutagenesis of these binding sites abrogated IL-6-dependent MD-2 gene activation. We show that the cooperation between C/EBPbeta and PU.1 is critical for the transcriptional activation of the MD-2 gene by IL-6. PU.1 was essentially known as a TF involved in the differentiation of myeloid precursor cells and the expression of surface receptors of the innate immunity. Herein, we show that it also participates in the regulation of an acute phase protein, MD-2, in nonmyeloid cells cooperatively with C/EBPbeta, a classical IL-6-inducible TF.
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Affiliation(s)
- Pierre Tissières
- Intensive Care, University Hospitals of Geneva, Geneva 14, Switzerland
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Abstract
PURPOSE OF REVIEW The identification of human Toll-like receptors has drastically changed our understanding of host-pathogen interactions. This review presents recent data on myeloid differentiation factor 2 (MD-2), a membrane-bound and soluble receptor for Gram-negative lipopolysaccharide, and its central role in the recognition of Gram-negative bacteria, phagocytosis, and Toll-like receptor 4 signalling. RECENT FINDINGS Phagocytosis is a complex mechanism involving a variety of receptors and opsonins. The heterogeneity of phagocytic mechanisms allows the optimization of bacteria recognition, phagocytosis, and killing. Notably, Toll-like receptors were known to play a role in phagocytosis, both by modulating opsonins and phagocytosis receptors' expression and activity, and by contributing to bacterial recognition and presentation to host cells. Recent data provide additional insight into the function of Toll-like receptors and associated proteins. In addition to bacterial recognition and activation of inflammatory cascades, MD-2 has been recently shown to be an opsonin for Gram-negative bacteria and an acute-phase protein. These newly described characteristics directly link Gram-negative bacteria recognition, transduction of Toll-like receptor 4 inflammatory signalling, phagocytosis and bacterial clearance. SUMMARY Recent progress in the understanding of Gram-negative bacteria recognition by host cells as well as physiologic functionality of MD-2 suggests that MD-2 is a critical compound in host response to pathogens and plays a central role in physiologic adaptation to various insults.
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Lipopolysaccharide-trap-Fc, a multifunctional agent to battle gram-negative bacteria. Infect Immun 2009; 77:2925-31. [PMID: 19433546 DOI: 10.1128/iai.00004-09] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
The family of Toll-like receptors (TLRs) plays a pivotal role in host defense against pathogens. However, overstimulation of these receptors may lead to uncontrolled general inflammation and eventually to systemic organ dysfunction or failure. With the intent to control overwhelming inflammation during gram-negative bacterial sepsis, we constructed soluble fusion proteins of the lipopolysaccharide (LPS)-receptor complex to modulate TLR signaling in multiple ways. The extracellular domain of mouse TLR4 and mouse myeloid differentiation factor 2 (MD-2) fusions (LPS-Trap) were linked to human immunoglobulin G Fc domains (LPS-Trap-Fc). In addition to the ability to bind LPS or gram-negative bacteria and to inhibit interleukin-6 secretion of monocytic cells after LPS treatment, LPS-Trap-Fc was able to opsonize fluorescent Escherichia coli particles. This led to enhancement of phagocytosis by monocytic cells which was strictly dependent on the presence of the Fc region. Moreover, only LPS-Trap-Fc- and not LPS-Trap-coated bacteria were sensitized to complement killing. Therefore, LPS-Trap-Fc not only neutralizes LPS but also, after binding to bacteria, enhances phagocytosis and complement-mediated killing and could thus act as a multifunctional agent to fight gram-negative bacteria in vivo.
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Sandanger Ø, Ryan L, Bohnhorst J, Iversen AC, Husebye H, Halaas Ø, Landrø L, Aukrust P, Frøland SS, Elson G, Visintin A, Øktedalen O, Damås JK, Sundan A, Golenbock D, Espevik T. IL-10 enhances MD-2 and CD14 expression in monocytes and the proteins are increased and correlated in HIV-infected patients. THE JOURNAL OF IMMUNOLOGY 2009; 182:588-95. [PMID: 19109192 DOI: 10.4049/jimmunol.182.1.588] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
Soluble proteins that bind LPS, like myeloid differentiation-2 (MD-2) and CD14, have essential roles in regulating LPS signaling through TLR4. During a gram-negative bacterial infection, the host may control the response by adjusting the levels of soluble MD-2 and CD14. To address the surface expression of MD-2 on human leukocytes, we developed a mAb, IIC1, that recognized MD-2 both free and when bound to TLR4. MD-2 was found on the surface of freshly isolated monocytes, on a subpopulation of CD19(+) B-cells and on CD15(+) neutrophils. LPS transiently reduced the MD-2 levels on monocytes, which is most likely due to endocytosis of the LPS receptor complex since MD-2 colocalized with TLR4 in early endosomes after LPS stimulation. In the absence of LPS, MD-2 partly colocalized with TLR4 in Golgi trans and medial compartments. Cultivating monocytes for 18-20 h resulted in loss of MD-2 expression on the surface, which was reversed either by LPS or IL-10. Furthermore, addition of IL-10, but not LPS, resulted in a considerable increase in mRNA for both MD-2 and CD14. Using ELISA, we demonstrated that IL-10 had a profound dose- and time-related effect on the release of soluble MD-2 and soluble CD14 from monocytes. In HIV-infected patients, the amounts of MD-2, CD14, and IL-10 increased significantly in the patient group with AIDS. Of interest, we found that IL-10, CD14, and MD-2 levels were positively correlated, suggesting that IL-10 may be a driving force for increased release of MD-2 and CD14 during systemic inflammation.
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Affiliation(s)
- Øystein Sandanger
- Norwegian University of Science and Technology, Institute of Cancer Research and Molecular Medicine, Trondheim, Norway
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β2 Adrenoreceptor blockade attenuates the hyperinflammatory response induced by traumatic injury. Surgery 2009; 145:235-42. [DOI: 10.1016/j.surg.2008.09.013] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2008] [Accepted: 09/26/2008] [Indexed: 11/22/2022]
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Phagocytosis and intracellular killing of MD-2 opsonized gram-negative bacteria depend on TLR4 signaling. Blood 2008; 111:4637-45. [PMID: 18203953 DOI: 10.1182/blood-2007-11-126862] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Both Toll-like receptor 4 (TLR4)- and MD-2-deficient mice succumb to otherwise nonfatal gram-negative bacteria inocula, demonstrating the pivotal role played by these proteins in antibacterial defense in mammals. MD-2 is a soluble endogenous ligand for TLR4 and a receptor for lipopolysaccharide (LPS). LPS-bound MD-2 transmits an activating signal onto TLR4. In this report, we show that both recombinant and endogenous soluble MD-2 bind tightly to the surface of live gram-negative bacteria. As a consequence, MD-2 enhances cellular activation, bacterial internalization, and intracellular killing, all in a TLR4-dependent manner. The enhanced internalization of MD-2-coated bacteria was not observed in macrophages expressing Lps(d), a signaling-incompetent mutant form of TLR4, suggesting that the enhanced phagocytosis observed is dependent on signal transduction. The data confirm the notion that soluble MD-2 is a genuine opsonin that enhances proinflammatory opsonophagocytosis by bridging live gram-negative bacteria to the LPS transducing complex. The presented results extend our understanding of the role of the TLR4/MD-2 signaling axis in bacterial recognition by phagocytes.
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