51
|
Iversen AC, Steinkjer B, Nilsen N, Bohnhorst J, Moen SH, Vik R, Stephens P, Thomas DW, Benedict CA, Espevik T. A proviral role for CpG in cytomegalovirus infection. THE JOURNAL OF IMMUNOLOGY 2009; 182:5672-81. [PMID: 19380814 DOI: 10.4049/jimmunol.0801268] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
TLR9-dependent signaling in plasmacytoid dendritic cells is a key contributor to innate immune defense to mouse CMV infection. We aimed to study the expression and potential contribution of TLR9 signaling in human CMV (HCMV) infection of primary fibroblasts. HCMV infection strongly induced TLR9 expression in two of three fibroblast types tested. Furthermore, the TLR9 ligand CpG-B induced a strong proviral effect when added shortly after HCMV infection, enhancing virus production and cell viability. However, not all CpG classes displayed proviral activity, and this correlated with their IFN-beta-inducing ability. The proviral effect of CpG-B correlated completely with concurrent viral up-regulation of TLR9 in fibroblasts. Importantly, the timing of CpG addition was a critical parameter; in striking contrast to the proviral effect, CpG addition at the time of infection blocked viral uptake and nearly abolished HCMV production. The contrasting and time-dependent effects of CpG on HCMV infectivity reveal a complex interplay between CpG, TLR9, and HCMV infection. Additionally, the data suggest a potentially harmful role for CpG in the promotion of HCMV infection.
Collapse
Affiliation(s)
- Ann-Charlotte Iversen
- Department of Cancer Research and Molecular Medicine, Faculty of Medicine, Norwegian University of Science and Technology, Trondheim, Norway.
| | | | | | | | | | | | | | | | | | | |
Collapse
|
52
|
The role of Toll-like receptor 2 in inflammation and fibrosis during progressive renal injury. PLoS One 2009; 4:e5704. [PMID: 19479087 PMCID: PMC2682651 DOI: 10.1371/journal.pone.0005704] [Citation(s) in RCA: 99] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2008] [Accepted: 04/26/2009] [Indexed: 12/20/2022] Open
Abstract
Tissue fibrosis and chronic inflammation are common causes of progressive organ damage, including progressive renal disease, leading to loss of physiological functions. Recently, it was shown that Toll-like receptor 2 (TLR2) is expressed in the kidney and activated by endogenous danger signals. The expression and function of TLR2 during renal fibrosis and chronic inflammation has however not yet been elucidated. Therefore, we studied TLR2 expression in human and murine progressive renal diseases and explored its role by inducing obstructive nephropathy in TLR2−/− or TLR2+/+ mice. We found that TLR2 is markedly upregulated on tubular and tubulointerstitial cells in patients with chronic renal injury. In mice with obstructive nephropathy, renal injury was associated with a marked upregulation and change in distribution of TLR2 and upregulation of murine TLR2 danger ligands Gp96, biglycan, and HMGB1. Notably, TLR2 enhanced inflammation as reflected by a significantly reduced influx of neutrophils and production of chemokines and TGF-β in kidneys of TLR2−/− mice compared with TLR2+/+ animals. Although, the obstructed kidneys of TLR2−/− mice had less interstitial myofibroblasts in the later phase of obstructive nephropathy, tubular injury and renal matrix accumulation was similar in both mouse strains. Together, these data demonstrate that TLR2 can initiate renal inflammation during progressive renal injury and that the absence of TLR2 does not affect the development of chronic renal injury and fibrosis.
Collapse
|
53
|
Lyakh L, Trinchieri G, Provezza L, Carra G, Gerosa F. Regulation of interleukin-12/interleukin-23 production and the T-helper 17 response in humans. Immunol Rev 2009; 226:112-31. [PMID: 19161420 DOI: 10.1111/j.1600-065x.2008.00700.x] [Citation(s) in RCA: 163] [Impact Index Per Article: 10.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Interleukin-12 (IL-12) and IL-23 share a common chain. Yet, their production in response to pathogens is differentially regulated, and their functions are distinct and often antithetic. IL-12 is involved in the induction or amplification of the T-helper (Th) type 1 response, whereas IL-23 has been associated with the generation of the Th17 response and IL-17 production. Mycobacterium tuberculosis and yeast zymosan induce IL-23, but in the absence of other stimuli, no IL-12 is induced in human dendritic cells (DCs). The stimulation of IL-23 by M. tuberculosis was mostly explained by the triggering of Toll-like receptor (TLR2) and the cytoplasmic receptor nucleotide oligomerization domain (NOD)-containing protein 2, whereas zymosan induces IL-23 primarily by stimulating the beta-glucan receptor dectin-1 alone or in combination with TLR2. IL-23, IL-6, transforming growth factor (TGF-beta1), and IL-1beta in supernatants from activated human DCs induce human naive CD4(+) T cells to produce IL-17. These data are consistent with various recent reports that TGF-beta is an inducer of IL-17 production both in human and in mouse cells. However, IL-1 is necessary in combination with some or all of the other cytokines to induce IL-17 production in human T cells. The ability of various stimuli to induce Th17 cells depends not only on their induction of IL-23, IL-6, and TGF-beta production in DCs but also on their ability to activate directly or indirectly the inflammasome and to induce IL-1beta.
Collapse
Affiliation(s)
- Lyudmila Lyakh
- Cancer and Inflammation Program, Center for Cancer Research, National Cancer Institute, Frederick, MD 21702-1201, USA
| | | | | | | | | |
Collapse
|
54
|
Dellacasagrande J. Ligands, cell-based models, and readouts required for Toll-like receptor action. Methods Mol Biol 2009; 517:15-32. [PMID: 19378025 DOI: 10.1007/978-1-59745-541-1_2] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
This chapter details the tools that are available to study Toll-like receptor (TLR) biology in vitro. This includes ligands, host cells, and readouts. The use of modified TLRs to circumvent some technical problems is also discussed.
Collapse
Affiliation(s)
- Jérôme Dellacasagrande
- OPSONA Therapeutics Ltd., Trinity Centre for Health Sciences, St. James' Hospital, Dublin 8, Ireland.
| |
Collapse
|
55
|
Yu S, Cho HH, Joo HJ, Bae YC, Jung JS. Role of MyD88 in TLR agonist-induced functional alterations of human adipose tissue-derived mesenchymal stem cells. Mol Cell Biochem 2008; 317:143-50. [PMID: 18581201 DOI: 10.1007/s11010-008-9842-1] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2008] [Accepted: 06/05/2008] [Indexed: 12/20/2022]
Abstract
Toll-like receptors (TLRs) sense microorganism components and are critical host mediators of inflammation during infection. Recently, TLRs have been reported to be involved in cell proliferation and differentiation. We previously reported that TLR agonists might affect proliferation and differentiation of human adipose tissue-derived mesenchymal stem cells (hASCs). In this study, we sought to determine whether TLR signaling is dependent on MyD88 in hASCs. The hASCs were downregulated using LV-GFP-miR-MyD88, a lentiviral construct inserted siRNA against human MyD88 that significantly inhibited cell proliferation. MyD88 downregulation reduced NF-kappaB activation and enhancement of osteogenic differentiation induced by peptidoglycan (PGN) more significantly than that induced by lipopolysaccharide (LPS). Although LPS- and PGN-induced cytokine secretions were decreased greatly by MyD88 downregulation, IFN-gamma-induced protein-10 (IP10) and IFNbeta expression were enhanced by LPS irrespective of the downregulation of MyD88. These results suggest that TLR signaling is mediated via MyD88-independent pathways as well as MyD88-dependent pathways in hASCs and that MyD88 contributes to the regulation of cell proliferation and differentiation in hASCs.
Collapse
Affiliation(s)
- Sungsook Yu
- BK21 Medical Science Education Center, Pusan National University, Pusan, 602-739, Korea.
| | | | | | | | | |
Collapse
|
56
|
Schaft N, Birkholz K, Hofmann C, Schmid M, Theiner G, Dörrie J. Dendritic cell vaccination and other strategies to tip the balance of the immune system : DC2007 5th International Meeting, July 16-18, Bamberg, Germany. Cancer Immunol Immunother 2008; 57:913-28. [PMID: 18236041 PMCID: PMC11030558 DOI: 10.1007/s00262-007-0443-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2007] [Accepted: 12/12/2007] [Indexed: 10/22/2022]
Affiliation(s)
- Niels Schaft
- Department of Dermatology, University Hospital Erlangen, Hartmannstrasse 14, 91052 Erlangen, Germany.
| | | | | | | | | | | |
Collapse
|
57
|
Bailey CM, Hendrix MJC. IRF6 in development and disease: a mediator of quiescence and differentiation. Cell Cycle 2008; 7:1925-30. [PMID: 18604160 DOI: 10.4161/cc.7.13.6221] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
Abstract
Post utero development of the mammary gland is a complex developmental process characterized by states of rapid cell proliferation (branching morphogenesis) followed by functional differentiation (lactation) and the consequent apoptosis (involution) of the secretory mammary epithelial cell. This process is cyclical, such that involution returns the mammary gland to a near-virgin-like state capable of responding to morphogenic cues with each consecutive pregnancy. Importantly, many of the regulatory processes which oversee mammary gland development are corrupted or otherwise compromised during the development of breast cancer. For example, Interferon Regulatory Factor 6 (IRF6) is a novel protein with growth inhibitory properties that was initially identified in mammary epithelial cells through its interaction with maspin, a known tumor suppressor in normal breast tissue. Recent findings from our laboratory suggest that IRF6 functions synergistically with maspin to regulate mammary epithelial cell differentiation by acting on the cell cycle. This perspective focuses on the possible involvement of IRF6 in promoting differentiation by regulating exit from the cell cycle and entry into the G(0) phase of cellular quiescence, and how these new findings shed light on normal mammary gland development and the initiation and progression of breast cancer.
Collapse
Affiliation(s)
- Caleb M Bailey
- Children's Memorial Research Center, Feinberg School of Medicine, Northwestern University, Chicago, Illinois 60614-3394, USA
| | | |
Collapse
|
58
|
Liotta F, Angeli R, Cosmi L, Filì L, Manuelli C, Frosali F, Mazzinghi B, Maggi L, Pasini A, Lisi V, Santarlasci V, Consoloni L, Angelotti ML, Romagnani P, Parronchi P, Krampera M, Maggi E, Romagnani S, Annunziato F. Toll-like receptors 3 and 4 are expressed by human bone marrow-derived mesenchymal stem cells and can inhibit their T-cell modulatory activity by impairing Notch signaling. Stem Cells 2007; 26:279-89. [PMID: 17962701 DOI: 10.1634/stemcells.2007-0454] [Citation(s) in RCA: 344] [Impact Index Per Article: 20.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
Bone marrow (BM)-derived mesenchymal stem cells (MSCs) are multipotent, nonhemopoietic progenitors that also possess regulatory activity on immune effector cells through different mechanisms. We demonstrate that human BM-derived MSCs expressed high levels of Toll-like receptors (TLRs) 3 and 4, which are both functional, as shown by the ability of their ligands to induce nuclear factor kappaB (NF-kappaB) activity, as well as the production of interleukin (IL)-6, IL-8, and CXCL10. Of note, ligation of TLR3 and TLR4 on MSCs also inhibited the ability of these cells to suppress the proliferation of T cells, without influencing their immunophenotype or differentiation potential. The TLR triggering effects appeared to be related to the impairment of MSC signaling to Notch receptors in T cells. Indeed, MSCs expressed the Notch ligand Jagged-1, and TLR3 or TLR4 ligation resulted in its strong downregulation. Moreover, anti-Jagged-1 neutralizing antibody and N[N-(3,5-difluorophenacetyl-l-alanyl)]-S-phenylglycine t-butyl ester (DAPT), an inhibitor of Notch signaling, hampered the suppressive activity of MSCs on T-cell proliferation. These data suggest that TLR3 and TLR4 expression on MSCs may provide an effective mechanism to block the immunosuppressive activity of MSCs and therefore to restore an efficient T-cell response in the course of dangerous infections, such as those sustained by double-stranded RNA viruses or Gram-negative bacteria, respectively.
Collapse
Affiliation(s)
- Francesco Liotta
- Excellence Center of the University of Florence De Novo Therapy, Florence, Italy
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|
59
|
Tamassia N, Le Moigne V, Calzetti F, Donini M, Gasperini S, Ear T, Cloutier A, Martinez FO, Fabbri M, Locati M, Mantovani A, McDonald PP, Cassatella MA. The MyD88-independent pathway is not mobilized in human neutrophils stimulated via TLR4. THE JOURNAL OF IMMUNOLOGY 2007; 178:7344-56. [PMID: 17513785 DOI: 10.4049/jimmunol.178.11.7344] [Citation(s) in RCA: 89] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
LPS activates both MyD88-dependent and -independent signaling via TLR4, but the extent to which each cascade is operative in different cell types remains unclear. This prompted us to revisit the intriguing issue of CXCL10 production, which we previously showed to be inducible in neutrophils stimulated with LPS and IFN-gamma but not with either stimulus alone, contrary to other myeloid cells. We now report that in neutrophils the MyD88-independent pathway is not activated by LPS. Indeed, microarray and real-time PCR experiments showed that neither IFNbeta nor IFNbeta-dependent genes (including CXCL10) are inducible in LPS-treated neutrophils, in contrast to monocytes. Further investigation into the inability of LPS to promote IFNbeta expression in neutrophils revealed that the transcription factors regulating the IFNbeta enhanceosome, such as IFN-regulatory factor-3 and AP-1, are not activated in LPS-treated neutrophils as revealed by lack of dimerization, nuclear translocation, confocal microscopy, and inducible binding to DNA. Moreover, we show that the upstream TANK-binding kinase-1 is not activated by LPS in neutrophils. A lack of IFNbeta/CXCL10 mRNA expression and IFN-regulatory factor 3 activation was also observed in myeloid leukemia HL60 cells differentiated to granulocytes and then stimulated with LPS, indicating that the inability of neutrophils to activate the MyD88-independent pathway represents a feature of their terminal maturation. These results identify a disconnected activation of the two signaling pathways downstream of TLR4 in key cellular components of the inflammatory and immune responses and help us to better understand the primordial role of neutrophils in host defense against nonviral infections.
Collapse
Affiliation(s)
- Nicola Tamassia
- Department of Pathology, University of Verona, Verona, Italy
| | | | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|
60
|
Cook P, Tötemeyer S, Stevenson C, Fitzgerald KA, Yamamoto M, Akira S, Maskell DJ, Bryant CE. Salmonella-induced SipB-independent cell death requires Toll-like receptor-4 signalling via the adapter proteins Tram and Trif. Immunology 2007; 122:222-9. [PMID: 17490432 PMCID: PMC2266008 DOI: 10.1111/j.1365-2567.2007.02631.x] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
Salmonella enterica serovar typhimurium (S. typhimurium) is an intracellular pathogen that causes macrophage cell death by at least two different mechanisms. Rapid cell death is dependent on the Salmonella pathogenicity island-1 protein SipB whereas delayed cell death is independent of SipB and occurs 18-24 hr post infection. Lipopolysaccharide (LPS) is essential for the delayed cell death. LPS is the main structural component of the outer membrane of Gram-negative bacteria and is recognized by Toll-like receptor 4, signalling via the adapter proteins Mal, MyD88, Tram and Trif. Here we show that S. typhimurium induces SipB-independent cell death through Toll-like receptor 4 signalling via the adapter proteins Tram and Trif. In contrast to wild type bone marrow derived macrophages (BMDM), Tram(-/-) and Trif(-/-) BMDM proliferate in response to Salmonella infection.
Collapse
Affiliation(s)
- Pamela Cook
- Centre for Veterinary Science, Department of Veterinary Medicine, University of Cambridge, Cambridge, UK
| | | | | | | | | | | | | | | |
Collapse
|
61
|
Hasan UA, Caux C, Perrot I, Doffin AC, Menetrier-Caux C, Trinchieri G, Tommasino M, Vlach J. Cell proliferation and survival induced by Toll-like receptors is antagonized by type I IFNs. Proc Natl Acad Sci U S A 2007; 104:8047-52. [PMID: 17463087 PMCID: PMC1876569 DOI: 10.1073/pnas.0700664104] [Citation(s) in RCA: 57] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
TRIF is an adaptor protein associated with the signaling by Toll-like receptor (TLR)3 and TLR4 for the induction of type I IFNs. Here, we demonstrate a mechanism by which TLR signaling controls cell proliferation and survival. We show that TLR3 and TLR4 can induce cell cycle entry via TRIF, which targets the cell cycle inhibitor p27(kip1) for relocalization, phosphorylation by cyclin/cdk complexes, and proteasome degradation. These events are antagonized by type I IFN induced by the TRIF pathway. Furthermore, in human dendritic cells treated with TLR3, TLR4, or TLR5 ligands, we demonstrate that IFN signaling modulates p27(kip1) degradation and apoptosis, identifying an immunoregulatory "switching" function of type I IFNs. These findings reveal a previously uncharacterized function of TLR signaling in cell proliferation and survival.
Collapse
Affiliation(s)
- Uzma A Hasan
- Infections and Cancer Biology Group, International Agency for Research on Cancer (IARC-WHO), 150 Cours Albert Thomas, 69372 Lyon Cedex 08, France.
| | | | | | | | | | | | | | | |
Collapse
|
62
|
White CL, Whitmore MM, Williams BRG. Enlarged spleens without enlarged lymph nodes in tlr3-/- pkr-/- mice. J Interferon Cytokine Res 2007; 27:6-12. [PMID: 17266438 DOI: 10.1089/jir.2006.0050] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Initial phenotypic studies in a mouse containing mutations in both toll-like receptor 3 (TLR3) and RNA-de-pendent protein kinase R (PKR) revealed comparable spleen and bone marrow cell populations in tlr3(-/)-, pkr(-/-), and tlr3(-/-)pkr(-/-) mice to wild-type controls. Splenomegaly developing between 8 and 10 weeks of age was observed in tlr3(-/-) and tlr3(-/-)pkr(-/-) mice but not in wild-type or pkr(-/-) mice. Palpably enlarged cervical, axillary, and inguinal lymph nodes accompanied by enlarged spleens were observed in 12-18-week-old tlr3(-/-) mice at a higher frequency compared with other genotypes. The enlarged spleens and lymph nodes observed in tlr3(-/-) mice were accompanied by destruction of organ architecture and lymphocyte infiltration. However, the enlargement of these organs was not the result of clonal proliferation of one lymphocyte subset. It is likely this phenotype is a result of TLR3 deficiency in combination with an additional, uncharacterized genetic defect or the presence of an infectious agent. These data also suggest that PKR may have a role in preventing progression from splenomegaly to lymphadenopathy in these mice.
Collapse
Affiliation(s)
- Christine L White
- Department of Cancer Biology, Lerner Research Institute, Cleveland Clinic, Cleveland, OH 44195, USA
| | | | | |
Collapse
|
63
|
Abstract
The mechanisms by which the recognition of Toll-like receptor (TLR) ligands leads to host immunity remain poorly defined. It is now thought that to induce an effective immune response, microorganisms must stimulate complex sets of pattern-recognition receptors, both within and outside of the TLR family. The combined activation of these different receptors can result in complementary, synergistic or antagonistic effects that modulate innate and adaptive immunity. Therefore, a complete understanding of the role of TLRs in host resistance to infection requires 'decoding' of these multiple receptor interactions. This Review highlights recent advances in the newly emerging field of TLR cooperation and discusses their implications for the development of adjuvants and immunotherapies.
Collapse
Affiliation(s)
- Giorgio Trinchieri
- Cancer and Inflammation Program, Center for Cancer Research, National Cancer Institute, Building 560, Room 31-93, Frederick, Maryland 21702-1201, USA.
| | | |
Collapse
|
64
|
Abstract
The unrelenting and destructive progression of most fibrotic responses in the pulmonary, cardiovascular, integumentary, and alimentary systems remains a major medical challenge for which therapies are desperately needed. The pathophysiology of fibrosis remains an enigma, but considerable research and debate surrounds the question of whether chronic inflammation is the key driver of unrestrained wound healing (i.e., the fibrotic response) in these and other organ systems. This Review describes how infectious pathogens, chronic inflammation, and unrestrained fibroproliferation are likely to be part of a dynamic, unrelenting process propelling human fibrotic diseases.
Collapse
Affiliation(s)
- Alessia Meneghin
- Immunology Program, Department of Pathology, University of Michigan Medical School, Ann Arbor, Michigan, USA
| | | |
Collapse
|
65
|
Abstract
Flagellin is bacterial protein that serves as a danger signal across a wide variety of eukaryotes and is a potent inducer of inflammatory effector responses in the mammalian gut. Recent findings utilizing purified flagellin and flagellate/aflagellate bacteria in in vitro and in vivo systems have revealed the important roles played by flagellin in the initial encounter between mucosa and flagellate bacteria, specifically in the modulation of apoptotic responses.
Collapse
Affiliation(s)
- Andrew S Neish
- Dept of Pathology, Emory Univ School of Medicine, Atlanta, GA 30322, USA.
| |
Collapse
|
66
|
Vijay-Kumar M, Wu H, Jones R, Grant G, Babbin B, King TP, Kelly D, Gewirtz AT, Neish AS. Flagellin suppresses epithelial apoptosis and limits disease during enteric infection. THE AMERICAN JOURNAL OF PATHOLOGY 2006; 169:1686-700. [PMID: 17071592 PMCID: PMC1780197 DOI: 10.2353/ajpath.2006.060345] [Citation(s) in RCA: 99] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
Flagellin, the primary component of bacterial flagella, is a potent activator of toll-like receptor 5 (TLR5) signaling and is a major proinflammatory determinant of enteropathogenic Salmonella. In accordance with this, we report here that aflagellate Salmonella mutants are impaired in their ability to up-regulate proinflammatory and anti-apoptotic effector molecules in murine models of salmonellosis and that these mutants elicit markedly reduced early mucosal inflammation relative to their isogenic parent strains. Conversely, aflagellate bacteria were more potent activators of epithelial caspases and subsequent apoptosis. These phenomena correlated with a delayed but markedly exacerbated mucosal inflammation at the later stages of infection as well as elevated extra-intestinal and systemic bacterial load, culminating in a more severe clinical outcome. Systemic administration of exogenous flagellin primarily reversed the deleterious effects of in vivo Salmonella infection. These observations indicate that in Salmonella infection, flagellin plays a dominant role in activation of not only innate immunity but also anti-apoptotic processes in epithelial cells. These latter TLR-mediated responses that delay epithelial apoptosis may be as critical to mucosal defense as the classic acute inflammatory response. This notion is consistent with the emerging paradigm that specific TLR ligands may have a fundamental cytoprotective effect during inflammatory stress.
Collapse
Affiliation(s)
- Matam Vijay-Kumar
- Department of Pathology and Laboratory Medicine, Epithelial Pathobiology Unit, Emory University School of Medicine, Atlanta, GA 30322, USA
| | | | | | | | | | | | | | | | | |
Collapse
|
67
|
Hwa Cho H, Bae YC, Jung JS. Role of toll-like receptors on human adipose-derived stromal cells. Stem Cells 2006; 24:2744-52. [PMID: 16902195 DOI: 10.1634/stemcells.2006-0189] [Citation(s) in RCA: 218] [Impact Index Per Article: 12.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Adult mesenchymal stem cells (MSCs) are promising tools for such applications as tissue engineering and cellular therapy. It is not clear how stem cells exposed to unfavorable conditions (e.g., hypoxia or inflammation) respond to signals of danger after in vivo transplantation. Toll-like receptors (TLRs) play a major role in the immune system, participating in the initial recognition of microbial pathogens and pathogen-associated components. This study was designated to determine the role of TLRs in human MSCs. Reverse transcriptase-polymerase chain reaction (RT-PCR) and flow cytometry analysis demonstrated that MSCs derived from human adipose tissue and bone marrow express TLR-1, TLR-2, TLR-3, TLR-4, TLR-5, TLR-6, and TLR-9. We investigated induction of the differentiation and proliferation of human adipose tissue stromal cells (hADSCs) by TLR agonists, including flagellin, peptidoglycans (PGN), lipopolysaccharide (LPS), the synthetic double-stranded RNA analog poly(I:C), and synthetic CpG oligodeoxydinucleotide (CpG-ODN). None of these agonists, except ODN, affected the proliferation of hADSCs. LPS and PGN increased osteogenic differentiation, but CpG-ODN decreased it. Poly(I:C) itself did not affect adipogenic or osteogenic differentiations, but exerted a synergistic effect on LPS- or PGN-induced osteogenic differentiation. RT-PCR analysis demonstrated that LPS and PGN induce osteogenic markers in hADSCs. TLR agonists affected the expression of chemokines and cytokines differentially. Furthermore, hADSCs affected the expression of specific TLRs in vitro under hypoxic conditions. These data provide evidence of a nonimmune role for TLR signaling on MSCs and may provide clues to the behavior of transplanted MSCs in vivo.
Collapse
Affiliation(s)
- Hyun Hwa Cho
- Department of Physiology, College of Medicine, Pusan National University, Pusan, Korea
| | | | | |
Collapse
|
68
|
Rumbo M, Nempont C, Kraehenbuhl JP, Sirard JC. Mucosal interplay among commensal and pathogenic bacteria: lessons from flagellin and Toll-like receptor 5. FEBS Lett 2006; 580:2976-84. [PMID: 16650409 DOI: 10.1016/j.febslet.2006.04.036] [Citation(s) in RCA: 53] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2006] [Accepted: 04/08/2006] [Indexed: 12/19/2022]
Abstract
Toll-like receptors (TLR) detect pathogen-associated molecular patterns (PAMP) and play a crucial role in triggering immunity. Due to their large surfaces in direct contact with the environment, mucosal tissues are the major sites of PAMP-TLR signalling. How innate and adaptive immunity are triggered through flagellin-TLR5 interaction is the main focus of the review. In view of recent reports on genetic polymorphism, we will summarize the impact of TLR5 on the susceptibility to mucosal infections and on various immuno-pathologies. Finally, the contribution of TLRs in the induction and maintenance of mucosal homeostasis and commensal discrimination is discussed.
Collapse
Affiliation(s)
- Martin Rumbo
- UNLP, Laboratorio de Investigaciones en el Sistema Inmune, Facultad de Ciencias Exactas, La Plata, Argentina
| | | | | | | |
Collapse
|
69
|
de Bouteiller O, Merck E, Hasan UA, Hubac S, Benguigui B, Trinchieri G, Bates EEM, Caux C. Recognition of double-stranded RNA by human toll-like receptor 3 and downstream receptor signaling requires multimerization and an acidic pH. J Biol Chem 2005; 280:38133-45. [PMID: 16144834 DOI: 10.1074/jbc.m507163200] [Citation(s) in RCA: 199] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
Studies involving Toll-like receptor 3 (TLR3)-deficient mice suggest that this receptor binds double-stranded RNA. In the present study, we analyzed ligand/receptor interactions and receptor-proximal events leading to TLR3 activation. The mutagenesis approach showed that certain cysteine residues and glycosylation in TLR3 amino-terminal leucine-rich repeats were necessary for ligand-induced signaling. Furthermore, inactive mutants had a dominant negative effect, suggesting that the signaling module is a multimer. We constructed a chimeric molecule fusing the amino-terminal ectodomain of TLR3 to the transmembrane and carboxyl terminal domains of CD32a containing an immunoreceptor tyrosine-based motif. Expression of TLR3-CD32 in HEK293T cells and the myeloid cell line U937 resulted in surface localization of the receptor, whereas the nonrecombinant molecule was intracellularly localized. The synthetic double-stranded RNAs poly(I-C) and poly(A-U) induced calcium mobilization in a TLR3-CD32 stably transfected U937 clone but not in control cells transfected with other constructs. An anti-TLR3 antibody also induced Ca(2+) flux but only when cross-linked by a secondary anti-immunoglobulin antibody, confirming that multimerization by the ligand is a requirement for signaling. The inhibitors of lysosome maturation, bafilomycin and chloroquine, inhibited the poly(I-C)-induced biological response in immune cells, showing that TLR3 interacted with its ligand in acidic subcellular compartments. Furthermore, TLR3-CD32 activation with poly(I-C) was only observed within a narrow pH window (pH 5.7-6.7), whereas anti-TLR3-mediated Ca(2+) flux was pH-insensitive. The importance of an acidic pH for TLR3-ligand interaction becomes critical when using oligomeric poly(I-C) (15-40-mers). These observations demonstrate that engagement of TLR3 by poly(I-C) at an acidic pH, probably in early phagolysosomes or endosomes, induces receptor aggregation leading to signaling.
Collapse
MESH Headings
- Amino Acid Sequence
- Antigens, CD/chemistry
- Antirheumatic Agents/pharmacology
- Base Sequence
- Binding Sites
- Blotting, Western
- Calcium/metabolism
- Cell Line
- Cell Membrane/metabolism
- Cell Separation
- Chloroquine/chemistry
- Cross-Linking Reagents/pharmacology
- Cysteine/chemistry
- Cysteine/metabolism
- Cytokines/metabolism
- DNA/metabolism
- Dendritic Cells/metabolism
- Dimerization
- Dose-Response Relationship, Drug
- Endosomes/metabolism
- Enzyme Inhibitors/pharmacology
- Flow Cytometry
- Genes, Dominant
- Genes, Reporter
- Glycosylation
- Humans
- Hydrogen-Ion Concentration
- Leucine/chemistry
- Leukocytes, Mononuclear/metabolism
- Ligands
- Luciferases/metabolism
- Lysosomes/chemistry
- Lysosomes/metabolism
- Macrolides/pharmacology
- Molecular Sequence Data
- Mutagenesis, Site-Directed
- Mutation
- NF-kappa B/metabolism
- Phagosomes/chemistry
- Protein Binding
- Protein Structure, Tertiary
- Receptors, IgG/biosynthesis
- Receptors, IgG/chemistry
- Recombinant Fusion Proteins/chemistry
- Recombinant Fusion Proteins/metabolism
- Sequence Homology, Amino Acid
- Signal Transduction
- Time Factors
- Toll-Like Receptor 3/chemistry
- Toll-Like Receptor 3/metabolism
- Transfection
- Tyrosine/chemistry
- U937 Cells
Collapse
Affiliation(s)
- Odette de Bouteiller
- Laboratory for Immunological Research, Schering-Plough Research Institute, 27 Chemin des Peupliers, 69571 Dardilly Cedex, France
| | | | | | | | | | | | | | | |
Collapse
|