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Yan L, Wang J, Cai X, Liou Y, Shen H, Hao J, Huang C, Luo G, He W. Macrophage plasticity: signaling pathways, tissue repair, and regeneration. MedComm (Beijing) 2024; 5:e658. [PMID: 39092292 PMCID: PMC11292402 DOI: 10.1002/mco2.658] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2024] [Revised: 06/24/2024] [Accepted: 06/25/2024] [Indexed: 08/04/2024] Open
Abstract
Macrophages are versatile immune cells with remarkable plasticity, enabling them to adapt to diverse tissue microenvironments and perform various functions. Traditionally categorized into classically activated (M1) and alternatively activated (M2) phenotypes, recent advances have revealed a spectrum of macrophage activation states that extend beyond this dichotomy. The complex interplay of signaling pathways, transcriptional regulators, and epigenetic modifications orchestrates macrophage polarization, allowing them to respond to various stimuli dynamically. Here, we provide a comprehensive overview of the signaling cascades governing macrophage plasticity, focusing on the roles of Toll-like receptors, signal transducer and activator of transcription proteins, nuclear receptors, and microRNAs. We also discuss the emerging concepts of macrophage metabolic reprogramming and trained immunity, contributing to their functional adaptability. Macrophage plasticity plays a pivotal role in tissue repair and regeneration, with macrophages coordinating inflammation, angiogenesis, and matrix remodeling to restore tissue homeostasis. By harnessing the potential of macrophage plasticity, novel therapeutic strategies targeting macrophage polarization could be developed for various diseases, including chronic wounds, fibrotic disorders, and inflammatory conditions. Ultimately, a deeper understanding of the molecular mechanisms underpinning macrophage plasticity will pave the way for innovative regenerative medicine and tissue engineering approaches.
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Affiliation(s)
- Lingfeng Yan
- Institute of Burn ResearchState Key Laboratory of Trauma and Chemical Poisoningthe First Affiliated Hospital of Army Medical University (the Third Military Medical University)ChongqingChina
- Chongqing Key Laboratory for Wound Damage Repair and RegenerationChongqingChina
| | - Jue Wang
- Institute of Burn ResearchState Key Laboratory of Trauma and Chemical Poisoningthe First Affiliated Hospital of Army Medical University (the Third Military Medical University)ChongqingChina
- Chongqing Key Laboratory for Wound Damage Repair and RegenerationChongqingChina
| | - Xin Cai
- Institute of Burn ResearchState Key Laboratory of Trauma and Chemical Poisoningthe First Affiliated Hospital of Army Medical University (the Third Military Medical University)ChongqingChina
- Chongqing Key Laboratory for Wound Damage Repair and RegenerationChongqingChina
| | - Yih‐Cherng Liou
- Department of Biological SciencesFaculty of ScienceNational University of SingaporeSingaporeSingapore
- National University of Singapore (NUS) Graduate School for Integrative Sciences and EngineeringNational University of SingaporeSingaporeSingapore
| | - Han‐Ming Shen
- Faculty of Health SciencesUniversity of MacauMacauChina
| | - Jianlei Hao
- Guangdong Provincial Key Laboratory of Tumor Interventional Diagnosis and TreatmentZhuhai Institute of Translational MedicineZhuhai People's Hospital (Zhuhai Clinical Medical College of Jinan University)Jinan UniversityZhuhaiGuangdongChina
- The Biomedical Translational Research InstituteFaculty of Medical ScienceJinan UniversityGuangzhouGuangdongChina
| | - Canhua Huang
- State Key Laboratory of Biotherapy and Cancer CenterWest China Hospitaland West China School of Basic Medical Sciences and Forensic MedicineSichuan University, and Collaborative Innovation Center for BiotherapyChengduChina
| | - Gaoxing Luo
- Institute of Burn ResearchState Key Laboratory of Trauma and Chemical Poisoningthe First Affiliated Hospital of Army Medical University (the Third Military Medical University)ChongqingChina
- Chongqing Key Laboratory for Wound Damage Repair and RegenerationChongqingChina
| | - Weifeng He
- Institute of Burn ResearchState Key Laboratory of Trauma and Chemical Poisoningthe First Affiliated Hospital of Army Medical University (the Third Military Medical University)ChongqingChina
- Chongqing Key Laboratory for Wound Damage Repair and RegenerationChongqingChina
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Liao D, Su X, Wang J, Yu J, Luo H, Tian W, Ye Z, He J. Pushing the envelope: Immune mechanism and application landscape of macrophage-activating lipopeptide-2. Front Immunol 2023; 14:1113715. [PMID: 36761746 PMCID: PMC9902699 DOI: 10.3389/fimmu.2023.1113715] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2022] [Accepted: 01/10/2023] [Indexed: 01/25/2023] Open
Abstract
Mycoplasma fermentans can cause respiratory diseases, arthritis, genitourinary tract infections, and chronic fatigue syndrome and have been linked to the development of the human immunodeficiency virus. Because mycoplasma lacks a cell wall, its outer membrane lipoproteins are one of the main factors that induce inflammation in the organism and contribute to disease development. Macrophage-activating lipopeptide-2 (MALP-2) modulates the inflammatory response of monocytes/macrophages in a bidirectional fashion, indirectly enhances the cytotoxicity of NK cells, promotes oxidative bursts in neutrophils, upregulates surface markers on lymphocytes, enhances antigen presentation on dendritic cells and induces immune inflammatory responses in sebocytes and mesenchymal cells. MALP-2 is a promising vaccine adjuvant for this application. It also promotes vascular healing and regeneration, accelerates wound and bone healing, suppresses tumors and metastasis, and reduces lung infections and inflammation. MALP-2 has a simple structure, is easy to synthesize, and has promising prospects for clinical application. Therefore, this paper reviews the mechanisms of MALP-2 activation in immune cells, focusing on the application of MALP-2 in animals/humans to provide a basis for the study of pathogenesis in Mycoplasma fermentans and the translation of MALP-2 into clinical applications.
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Affiliation(s)
- Daoyong Liao
- The Affiliated Nanhua Hospital, Department of Clinical Laboratory, Hengyang Medical School, University of South China, Hengyang, China
| | - Xiaoling Su
- The Affiliated Nanhua Hospital, Department of Clinical Laboratory, Hengyang Medical School, University of South China, Hengyang, China
| | - Jingyun Wang
- The Affiliated Nanhua Hospital, Department of Clinical Laboratory, Hengyang Medical School, University of South China, Hengyang, China
| | - Jianwei Yu
- Department of Public Health Laboratory Sciences, School of Public Health, Hengyang Medical School, University of South China, Hengyang, Hunan, China
| | - Haodang Luo
- The Affiliated Nanhua Hospital, Department of Clinical Laboratory, Hengyang Medical School, University of South China, Hengyang, China,Institute of Pathogenic Biology, Hengyang Medical School, Hunan Provincial Key Laboratory for Special Pathogens Prevention and Control, Hunan Province Cooperative Innovation Center for Molecular Target New Drug Study, University of South China, Hengyang, China
| | - Wei Tian
- The Affiliated Nanhua Hospital, Department of Clinical Laboratory, Hengyang Medical School, University of South China, Hengyang, China
| | - Zufeng Ye
- The Affiliated Nanhua Hospital, Department of Clinical Laboratory, Hengyang Medical School, University of South China, Hengyang, China
| | - Jun He
- The Affiliated Nanhua Hospital, Department of Clinical Laboratory, Hengyang Medical School, University of South China, Hengyang, China,*Correspondence: Jun He,
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Fritz T, Schäfer J, Scheuer C, Stutz J, Histing T, Pohlemann T, Menger MD, Laschke MW, Klein M, Orth M. Macrophage-activating lipoprotein (MALP)-2 impairs the healing of partial tendon injuries in mice. Ann Anat 2021; 239:151818. [PMID: 34391911 DOI: 10.1016/j.aanat.2021.151818] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2021] [Revised: 07/21/2021] [Accepted: 08/10/2021] [Indexed: 11/26/2022]
Abstract
Tendon injuries are accounted for up to 50% of musculoskeletal injuries and often result in poor outcomes. Inflammation is a major hallmark of tendon regeneration. Therefore, we analyzed in this study whether the topical application of the pro-inflammatory mediator macrophage-activating lipoprotein (MALP)-2 improves the healing of partial tendon injuries. C57BL/6 mice underwent a partial tenotomy of the flexor digitorum longus tendon of the left hind limb, which was treated with a solution containing either 0.5 µg MALP-2 or vehicle (control). Repetitive gait analyses were performed prior to the surgical intervention as well as postoperatively on days 1, 3, 7, 14 and 36. The structural stability of the tendons was biomechanically tested on day 7 and 36. In addition, Western blot analyses were performed on isolated tendons that were treated in vitro with MALP-2 or vehicle. In both groups, partial tenotomy resulted in a pathological gait pattern during the initial postoperative phase. On day 7, the gait pattern normalized in vehicle-treated animals, but not in MALP-2-treated mice. Moreover, the tendons of MALP-2-treated mice exhibited a significantly reduced biomechanical stiffness after 7 and 36 days when compared to controls. Western blot analyses revealed a significantly higher expression of heme oxygenase (HO)-1 and lower expression of cyclin D in MALP-2-treated tendons. These findings indicate that MALP-2 delays the healing of injured tendons most likely due to increased intracellular stress and suppressed cell proliferation in this naturally bradytrophic tissue. Hence, the application of MALP-2 cannot be recommended for the treatment of tendon injuries.
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Affiliation(s)
- Tobias Fritz
- Department of Trauma, Hand and Reconstructive Surgery, Saarland University Medical Center, 66421 Homburg, Germany.
| | - Julia Schäfer
- Department of Trauma, Hand and Reconstructive Surgery, Saarland University Medical Center, 66421 Homburg, Germany
| | - Claudia Scheuer
- Institute for Clinical and Experimental Surgery, Saarland University, 66421 Homburg, Germany
| | - Janine Stutz
- Department of Trauma, Hand and Reconstructive Surgery, Saarland University Medical Center, 66421 Homburg, Germany
| | - Tina Histing
- Department of Trauma, Hand and Reconstructive Surgery, Saarland University Medical Center, 66421 Homburg, Germany; BG Trauma Center, Eberhard Karls Universitaet Tuebingen, Tuebingen, Germany
| | - Tim Pohlemann
- Department of Trauma, Hand and Reconstructive Surgery, Saarland University Medical Center, 66421 Homburg, Germany
| | - Michael D Menger
- Institute for Clinical and Experimental Surgery, Saarland University, 66421 Homburg, Germany
| | - Matthias W Laschke
- Institute for Clinical and Experimental Surgery, Saarland University, 66421 Homburg, Germany
| | - Moritz Klein
- Department of Trauma, Hand and Reconstructive Surgery, Saarland University Medical Center, 66421 Homburg, Germany
| | - Marcel Orth
- Department of Trauma, Hand and Reconstructive Surgery, Saarland University Medical Center, 66421 Homburg, Germany
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Groppa E, Colliva A, Vuerich R, Kocijan T, Zacchigna S. Immune Cell Therapies to Improve Regeneration and Revascularization of Non-Healing Wounds. Int J Mol Sci 2020; 21:E5235. [PMID: 32718071 PMCID: PMC7432547 DOI: 10.3390/ijms21155235] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2020] [Revised: 07/20/2020] [Accepted: 07/21/2020] [Indexed: 12/20/2022] Open
Abstract
With the increased prevalence of chronic diseases, non-healing wounds place a significant burden on the health system and the quality of life of affected patients. Non-healing wounds are full-thickness skin lesions that persist for months or years. While several factors contribute to their pathogenesis, all non-healing wounds consistently demonstrate inadequate vascularization, resulting in the poor supply of oxygen, nutrients, and growth factors at the level of the lesion. Most existing therapies rely on the use of dermal substitutes, which help the re-epithelialization of the lesion by mimicking a pro-regenerative extracellular matrix. However, in most patients, this approach is not efficient, as non-healing wounds principally affect individuals afflicted with vascular disorders, such as peripheral artery disease and/or diabetes. Over the last 25 years, innovative therapies have been proposed with the aim of fostering the regenerative potential of multiple immune cell types. This can be achieved by promoting cell mobilization into the circulation, their recruitment to the wound site, modulation of their local activity, or their direct injection into the wound. In this review, we summarize preclinical and clinical studies that have explored the potential of various populations of immune cells to promote skin regeneration in non-healing wounds and critically discuss the current limitations that prevent the adoption of these therapies in the clinics.
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Affiliation(s)
- Elena Groppa
- Cardiovascular Biology Laboratory, International Centre for Genetic Engineering and Biotechnology (ICGEB), 34149 Trieste, Italy; (E.G.); (A.C.); (R.V.); (T.K.)
| | - Andrea Colliva
- Cardiovascular Biology Laboratory, International Centre for Genetic Engineering and Biotechnology (ICGEB), 34149 Trieste, Italy; (E.G.); (A.C.); (R.V.); (T.K.)
- Department of Medical, Surgical and Health Sciences, University of Trieste, 34127 Trieste, Italy
| | - Roman Vuerich
- Cardiovascular Biology Laboratory, International Centre for Genetic Engineering and Biotechnology (ICGEB), 34149 Trieste, Italy; (E.G.); (A.C.); (R.V.); (T.K.)
- Department of Life Sciences, University of Trieste, 34127 Trieste, Italy
| | - Tea Kocijan
- Cardiovascular Biology Laboratory, International Centre for Genetic Engineering and Biotechnology (ICGEB), 34149 Trieste, Italy; (E.G.); (A.C.); (R.V.); (T.K.)
| | - Serena Zacchigna
- Cardiovascular Biology Laboratory, International Centre for Genetic Engineering and Biotechnology (ICGEB), 34149 Trieste, Italy; (E.G.); (A.C.); (R.V.); (T.K.)
- Department of Medical, Surgical and Health Sciences, University of Trieste, 34127 Trieste, Italy
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5
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Singampalli KL, Balaji S, Wang X, Parikh UM, Kaul A, Gilley J, Birla RK, Bollyky PL, Keswani SG. The Role of an IL-10/Hyaluronan Axis in Dermal Wound Healing. Front Cell Dev Biol 2020; 8:636. [PMID: 32850791 PMCID: PMC7396613 DOI: 10.3389/fcell.2020.00636] [Citation(s) in RCA: 39] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2020] [Accepted: 06/24/2020] [Indexed: 12/12/2022] Open
Abstract
Scar formation is the typical endpoint of postnatal dermal wound healing, which affects more than 100 million individuals annually. Not only do scars cause a functional burden by reducing the biomechanical strength of skin at the site of injury, but they also significantly increase healthcare costs and impose psychosocial challenges. Though the mechanisms that dictate how dermal wounds heal are still not completely understood, they are regulated by extracellular matrix (ECM) remodeling, neovascularization, and inflammatory responses. The cytokine interleukin (IL)-10 has emerged as a key mediator of the pro- to anti-inflammatory transition that counters collagen deposition in scarring. In parallel, the high molecular weight (HMW) glycosaminoglycan hyaluronan (HA) is present in the ECM and acts in concert with IL-10 to block pro-inflammatory signals and attenuate fibrotic responses. Notably, high concentrations of both IL-10 and HMW HA are produced in early gestational fetal skin, which heals scarlessly. Since fibroblasts are responsible for collagen deposition, it is critical to determine how the concerted actions of IL-10 and HA drive their function to potentially control fibrogenesis. Beyond their independent actions, an auto-regulatory IL-10/HA axis may exist to modulate the magnitude of CD4+ effector T lymphocyte activation and enhance T regulatory cell function in order to reduce scarring. This review underscores the pathophysiological impact of the IL-10/HA axis as a multifaceted molecular mechanism to direct primary cell responders and regulators toward either regenerative dermal tissue repair or scarring.
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Affiliation(s)
- Kavya L Singampalli
- Laboratory for Regenerative Tissue Repair, Division of Pediatric Surgery, Department of Surgery, Baylor College of Medicine and Texas Children's Hospital, Houston, TX, United States.,Department of Bioengineering, Rice University, Houston, TX, United States.,Medical Scientist Training Program, Baylor College of Medicine, Houston, TX, United States
| | - Swathi Balaji
- Laboratory for Regenerative Tissue Repair, Division of Pediatric Surgery, Department of Surgery, Baylor College of Medicine and Texas Children's Hospital, Houston, TX, United States
| | - Xinyi Wang
- Laboratory for Regenerative Tissue Repair, Division of Pediatric Surgery, Department of Surgery, Baylor College of Medicine and Texas Children's Hospital, Houston, TX, United States
| | - Umang M Parikh
- Laboratory for Regenerative Tissue Repair, Division of Pediatric Surgery, Department of Surgery, Baylor College of Medicine and Texas Children's Hospital, Houston, TX, United States
| | - Aditya Kaul
- Laboratory for Regenerative Tissue Repair, Division of Pediatric Surgery, Department of Surgery, Baylor College of Medicine and Texas Children's Hospital, Houston, TX, United States
| | - Jamie Gilley
- Laboratory for Regenerative Tissue Repair, Division of Pediatric Surgery, Department of Surgery, Baylor College of Medicine and Texas Children's Hospital, Houston, TX, United States.,Division of Neonatology, Department of Pediatrics, Texas Children's Hospital, Houston, TX, United States
| | | | - Paul L Bollyky
- Division of Infectious Diseases, Department of Medicine, Stanford University School of Medicine, Stanford, CA, United States
| | - Sundeep G Keswani
- Laboratory for Regenerative Tissue Repair, Division of Pediatric Surgery, Department of Surgery, Baylor College of Medicine and Texas Children's Hospital, Houston, TX, United States
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6
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Larouche J, Sheoran S, Maruyama K, Martino MM. Immune Regulation of Skin Wound Healing: Mechanisms and Novel Therapeutic Targets. Adv Wound Care (New Rochelle) 2018; 7:209-231. [PMID: 29984112 PMCID: PMC6032665 DOI: 10.1089/wound.2017.0761] [Citation(s) in RCA: 310] [Impact Index Per Article: 51.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2017] [Accepted: 12/12/2017] [Indexed: 12/17/2022] Open
Abstract
Significance: The immune system plays a central role in orchestrating the tissue healing process. Hence, controlling the immune system to promote tissue repair and regeneration is an attractive approach when designing regenerative strategies. This review discusses the pathophysiology of both acute and chronic wounds and possible strategies to control the immune system to accelerate chronic wound closure and promote skin regeneration (scar-less healing) of acute wounds. Recent Advances: Recent studies have revealed the key roles of various immune cells and immune mediators in skin repair. Thus, immune components have been targeted to promote chronic wound repair or skin regeneration and several growth factors, cytokines, and biomaterials have shown promising results in animal models. However, these novel strategies are often struggling to meet efficacy standards in clinical trials, partly due to inadequate drug delivery systems and safety concerns. Critical Issues: Excess inflammation is a major culprit in the dysregulation of normal wound healing, and further limiting inflammation effectively reduces scarring. However, current knowledge is insufficient to efficiently control inflammation and specific immune cells. This is further complicated by inadequate drug delivery methods. Future Directions: Improving our understanding of the molecular pathways through which the immune system controls the wound healing process could facilitate the design of novel regenerative therapies. Additionally, better delivery systems may make current and future therapies more effective. To promote the entry of current regenerative strategies into clinical trials, more evidence on their safety, efficacy, and cost-effectiveness is also needed.
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Affiliation(s)
- Jacqueline Larouche
- European Molecular Biology Laboratory Australia, Australian Regenerative Medicine Institute, Monash University, Victoria, Australia
| | - Sumit Sheoran
- European Molecular Biology Laboratory Australia, Australian Regenerative Medicine Institute, Monash University, Victoria, Australia
| | - Kenta Maruyama
- WPI Immunology Frontier Research Center, Osaka University, Osaka, Japan
| | - Mikaël M. Martino
- European Molecular Biology Laboratory Australia, Australian Regenerative Medicine Institute, Monash University, Victoria, Australia
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The toll-like receptor 2 agonist Pam3CSK4 is neuroprotective after spinal cord injury. Exp Neurol 2017; 294:1-11. [DOI: 10.1016/j.expneurol.2017.04.012] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2017] [Revised: 04/20/2017] [Accepted: 04/22/2017] [Indexed: 12/21/2022]
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Biotechnology approaches to produce potent, self-adjuvanting antigen-adjuvant fusion protein subunit vaccines. Biotechnol Adv 2017; 35:375-389. [PMID: 28288861 DOI: 10.1016/j.biotechadv.2017.03.005] [Citation(s) in RCA: 69] [Impact Index Per Article: 9.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2017] [Revised: 03/08/2017] [Accepted: 03/08/2017] [Indexed: 01/07/2023]
Abstract
Traditional vaccination approaches (e.g. live attenuated or killed microorganisms) are among the most effective means to prevent the spread of infectious diseases. These approaches, nevertheless, have failed to yield successful vaccines against many important pathogens. To overcome this problem, methods have been developed to identify microbial components, against which protective immune responses can be elicited. Subunit antigens identified by these approaches enable the production of defined vaccines, with improved safety profiles. However, they are generally poorly immunogenic, necessitating their administration with potent immunostimulatory adjuvants. Since few safe and effective adjuvants are currently used in vaccines approved for human use, with those available displaying poor potency, or an inability to stimulate the types of immune responses required for vaccines against specific diseases (e.g. cytotoxic lymphocytes (CTLs) to treat cancers), the development of new vaccines will be aided by the availability of characterized platforms of new adjuvants, improving our capacity to rationally select adjuvants for different applications. One such approach, involves the addition of microbial components (pathogen-associated molecular patterns; PAMPs), that can stimulate strong immune responses, into subunit vaccine formulations. The conjugation of PAMPs to subunit antigens provides a means to greatly increase vaccine potency, by targeting immunostimulation and antigen to the same antigen presenting cell. Thus, methods that enable the efficient, and inexpensive production of antigen-adjuvant fusions represent an exciting mean to improve immunity towards subunit antigens. Herein we review four protein-based adjuvants (flagellin, bacterial lipoproteins, the extra domain A of fibronectin (EDA), and heat shock proteins (Hsps)), which can be genetically fused to antigens to enable recombinant production of antigen-adjuvant fusion proteins, with a focus on their mechanisms of action, structural or sequence requirements for activity, sequence modifications to enhance their activity or simplify production, adverse effects, and examples of vaccines in preclinical or human clinical trials.
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Snyder RJ, Lantis J, Kirsner RS, Shah V, Molyneaux M, Carter MJ. Macrophages: A review of their role in wound healing and their therapeutic use. Wound Repair Regen 2016; 24:613-29. [DOI: 10.1111/wrr.12444] [Citation(s) in RCA: 127] [Impact Index Per Article: 15.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2015] [Revised: 04/20/2016] [Accepted: 04/24/2016] [Indexed: 12/13/2022]
Affiliation(s)
- Robert J. Snyder
- Department of Clinical Research, Barry University School of Podiatric Medicine; Miami Shores Florida
| | - John Lantis
- Department of Surgery; Mount Sinai St. Luke's Roosevelt Hospital Center; New York New York
| | - Robert S. Kirsner
- Department of Dermatology and Cutaneous Surgery; University of Miami School of Medicine; Miami Florida
| | - Vivek Shah
- Research and Development; Macrocure Ltd; Tenafly New Jersey
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Thandavarayan RA, Garikipati VNS, Joladarashi D, Suresh Babu S, Jeyabal P, Verma SK, Mackie AR, Khan M, Arumugam S, Watanabe K, Kishore R, Krishnamurthy P. Sirtuin-6 deficiency exacerbates diabetes-induced impairment of wound healing. Exp Dermatol 2015; 24:773-8. [PMID: 26010430 DOI: 10.1111/exd.12762] [Citation(s) in RCA: 37] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 05/19/2015] [Indexed: 12/29/2022]
Abstract
Delayed wound healing is one of the major complications in diabetes and is characterized by chronic proinflammatory response, and abnormalities in angiogenesis and collagen deposition. Sirtuin family proteins regulate numerous pathophysiological processes, including those involved in promotion of longevity, DNA repair, glycolysis and inflammation. However, the role of sirtuin 6 (SIRT6), a NAD+-dependent nuclear deacetylase, in wound healing specifically under diabetic condition remains unclear. To analyse the role of SIRT6 in cutaneous wound healing, paired 6-mm stented wound was created in diabetic db/db mice and injected siRNA against SIRT6 in the wound margins (transfection agent alone and nonsense siRNA served as controls). Wound time to closure was assessed by digital planimetry, and wounds were harvested for histology, immunohistochemistry and Western blotting. SIRT6-siRNA-treated diabetic wound showed impaired healing, which was associated with reduced capillary density (CD31-staining vessels) when compared to control treatment. Interestingly, SIRT6 deficiency decreased vascular endothelial growth factor expression and proliferation markers in the wounds. Furthermore, SIRT6 ablation in diabetic wound promotes nuclear factor-κB (NF-κB) activation resulting in increased expression of proinflammatory markers (intercellular adhesion molecule-1, vascular cell adhesion molecule-1, tumor necrosis factor-α and interleukin-1β) and increased oxidative stress. Collectively, our findings demonstrate that loss of SIRT6 in cutaneous wound aggravates proinflammatory response by increasing NF-κB activation, oxidative stress and decrease in angiogenesis in the diabetic mice. Based on these findings, we speculate that the activation of SIRT6 signalling might be a potential therapeutic approach for promoting wound healing in diabetics.
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Affiliation(s)
- Rajarajan A Thandavarayan
- Department of Cardiovascular Sciences, Center for Cardiovascular Regeneration, Houston Methodist Research Institute, Houston, TX, USA
| | | | - Darukeshwara Joladarashi
- Department of Cardiovascular Sciences, Center for Cardiovascular Regeneration, Houston Methodist Research Institute, Houston, TX, USA
| | - Sahana Suresh Babu
- Department of Cardiovascular Sciences, Center for Cardiovascular Regeneration, Houston Methodist Research Institute, Houston, TX, USA
| | - Prince Jeyabal
- Department of Cardiovascular Sciences, Center for Cardiovascular Regeneration, Houston Methodist Research Institute, Houston, TX, USA
| | - Suresh K Verma
- Center for Translational Medicine, Temple University School of Medicine, Philadelphia, PA, USA
| | - Alexander R Mackie
- Feinberg Cardiovascular Research Institute, Northwestern University, Chicago, IL, USA
| | - Mohsin Khan
- Center for Translational Medicine, Temple University School of Medicine, Philadelphia, PA, USA
| | - Somasundaram Arumugam
- Department of Clinical Pharmacology, Niigata University of Pharmacy and Applied Life Sciences, Niigata, Japan
| | - Kenichi Watanabe
- Department of Clinical Pharmacology, Niigata University of Pharmacy and Applied Life Sciences, Niigata, Japan
| | - Raj Kishore
- Center for Translational Medicine, Temple University School of Medicine, Philadelphia, PA, USA
| | - Prasanna Krishnamurthy
- Department of Cardiovascular Sciences, Center for Cardiovascular Regeneration, Houston Methodist Research Institute, Houston, TX, USA.,Cell and Developmental Biology, Department of Cardiothoracic Surgery, Weill Cornell Medical College of Cornell University, New York, NY, USA
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11
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Mauldin IS, Wang E, Deacon DH, Olson WC, Bao Y, Slingluff CL. TLR2/6 agonists and interferon-gamma induce human melanoma cells to produce CXCL10. Int J Cancer 2015; 137:1386-96. [PMID: 25765738 DOI: 10.1002/ijc.29515] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2014] [Revised: 02/02/2015] [Accepted: 03/04/2015] [Indexed: 01/25/2023]
Abstract
Clinical approaches to treat advanced melanoma include immune therapies, whose benefits depend on tumor-reactive T-cell infiltration of metastases. However, most tumors lack significant immune infiltration prior to therapy. Selected chemokines promote T-cell migration into tumors; thus, agents that induce these chemokines in the tumor microenvironment (TME) may improve responses to systemic immune therapy. CXCL10 has been implicated as a critical chemokine supporting T-cell infiltration into the TME. Here, we show that toll-like receptor (TLR) agonists can induce chemokine production directly from melanoma cells when combined with IFNγ treatment. We find that TLR2 and TLR6 are widely expressed on human melanoma cells, and that TLR2/6 agonists (MALP-2 or FSL-1) synergize with interferon-gamma (IFNγ) to induce production of CXCL10 from melanoma cells. Furthermore, melanoma cells and immune cells from surgical specimens also respond to TLR2/6 agonists and IFNγ by upregulating CXCL10 production, compared to treatment with either agent alone. Collectively, these data identify a novel mechanism for inducing CXCL10 production directly from melanoma cells, with TLR2/6 agonists +IFNγ and raise the possibility that intratumoral administration of these agents may improve immune signatures in melanoma and have value in combination with other immune therapies, by supporting T-cell migration into melanoma metastases.
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Affiliation(s)
- Ileana S Mauldin
- Department of Surgery, University of Virginia, Charlottesville, VA
| | - Ena Wang
- Department of Transfusion Medicine, National Institutes of Health, Bethesda, MD
| | - Donna H Deacon
- Department of Surgery, University of Virginia, Charlottesville, VA
| | - Walter C Olson
- Department of Surgery, University of Virginia, Charlottesville, VA
| | - Yongde Bao
- Department of Microbiology, Immunology and Cancer Biology, University of Virginia, Charlottesville, VA
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12
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Laschke MW, Augustin V, Kleer S, Tschernig T, Menger MD. Locally applied macrophage-activating lipopeptide-2 (MALP-2) promotes early vascularization of implanted porous polyethylene (Medpor®). Acta Biomater 2014; 10:4661-4669. [PMID: 25062995 DOI: 10.1016/j.actbio.2014.07.004] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2014] [Revised: 06/13/2014] [Accepted: 07/03/2014] [Indexed: 11/16/2022]
Abstract
Porous polyethylene (Medpor®) is frequently used in craniofacial reconstructive surgery. Rapid vascularization of the biomaterial crucially contributes to its adequate incorporation without complications. Macrophage-activating lipopeptide-2 (MALP-2) is a toll-like receptor (TLR)-2/6 agonist with pro-angiogenic properties. Herein we analyzed whether local single-shot application of MALP-2 improves the angiogenic host tissue response to Medpor®. Medpor® (3 mm×3 mm×0.25 mm) was implanted into dorsal skinfold chambers of BALB/c mice topically exposed to different MALP-2 doses (0.1 and 0.5 μg) or vehicle (control). The vascularization of the implants and the inflammatory foreign body reaction was analyzed using intravital fluorescence microscopy, histology and immunohistochemistry over 14 days. MALP-2 treatment dose-dependently improved the vascularization of Medpor®, as indicated by a significantly higher functional microvessel density at the border and center of the implants when compared to controls. This was associated with a temporary increase of adherent leukocytes in host tissue venules during the first 3 days after implantation. At day 14, implants in MALP-2-treated chambers were surrounded by granulation tissue, which exhibited a significantly higher density of CD31-positive microvessels and number of F4/80-positive macrophages when compared to controls. Additional biomaterial-free chambers did not show any signs of angiogenesis when treated with MALP-2. This indicates that locally applied MALP-2 effectively stimulates the early vascularization of Medpor® without inducing any local or systemic side effects. Accordingly, this easy approach may further improve the rapid incorporation of this biomaterial at the implantation site.
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Affiliation(s)
- M W Laschke
- Institute for Clinical & Experimental Surgery, University of Saarland, 66421 Homburg/Saar, Germany.
| | - V Augustin
- Institute for Clinical & Experimental Surgery, University of Saarland, 66421 Homburg/Saar, Germany
| | - S Kleer
- Institute for Clinical & Experimental Surgery, University of Saarland, 66421 Homburg/Saar, Germany
| | - T Tschernig
- Institute of Anatomy, University of Saarland, 66421 Homburg/Saar, Germany
| | - M D Menger
- Institute for Clinical & Experimental Surgery, University of Saarland, 66421 Homburg/Saar, Germany
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Stirling DP, Cummins K, Mishra M, Teo W, Yong VW, Stys P. Toll-like receptor 2-mediated alternative activation of microglia is protective after spinal cord injury. Brain 2013; 137:707-23. [DOI: 10.1093/brain/awt341] [Citation(s) in RCA: 85] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
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14
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Salunke DB, Connelly SW, Shukla NM, Hermanson AR, Fox LM, David SA. Design and development of stable, water-soluble, human Toll-like receptor 2 specific monoacyl lipopeptides as candidate vaccine adjuvants. J Med Chem 2013; 56:5885-900. [PMID: 23795818 PMCID: PMC3844559 DOI: 10.1021/jm400620g] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
Antigens in modern subunit vaccines are largely soluble and poorly immunogenic proteins inducing relatively short-lived immune responses. Appropriate adjuvants initiate early innate immune responses, amplifying subsequent adaptive immune responses. Agonists of Toll-like receptor 2 (TLR2) are devoid of significant proinflammatory activity in ex vivo human blood models and yet are potently adjuvantic, suggesting that this chemotype may be a safe and effective adjuvant. Our earlier work on the monoacyl lipopeptide class of TLR2 agonists led to the design of a highly potent lead but with negligible aqueous solubility, necessitating the reintroduction of aqueous solubility. We explored several strategies of introducing ionizable groups on the lipopeptide, as well as the systematic evaluation of chemically stable bioisosteres of the ester-linked palmitoyl group. These studies have led to a fully optimized, chemically stable, and highly water-soluble human TLR2-specific agonist, which was found to have an excellent safety profile and displayed prominent adjuvantic activities in rabbit models.
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Affiliation(s)
| | | | | | | | - Lauren M. Fox
- Department of Medicinal Chemistry, University of Kansas
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15
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Grote K, Sonnenschein K, Kapopara PR, Hillmer A, Grothusen C, Salguero G, Kotlarz D, Schuett H, Bavendiek U, Schieffer B. Toll-like receptor 2/6 agonist macrophage-activating lipopeptide-2 promotes reendothelialization and inhibits neointima formation after vascular injury. Arterioscler Thromb Vasc Biol 2013; 33:2097-104. [PMID: 23868938 DOI: 10.1161/atvbaha.113.301799] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
Abstract
OBJECTIVE Reendothelialization after vascular injury (ie, balloon angioplasty or stent implantation) is clinically extremely relevant to promote vascular healing. We here investigated the therapeutic potential of the toll-like receptor 2/6 agonist macrophage-activating lipopeptide (MALP)-2 on reendothelialization and neointima formation in a murine model of vascular injury. APPROACH AND RESULTS The left common carotid artery was electrically injured, and reendothelialization was quantified by Evans blue staining after 3 days. A single injection of MALP-2 (1 or 10 µg, IV) after vascular injury accelerated reendothelialization (P<0.001). Proliferation of endothelial cells at the wound margins determined by 5-ethynyl-2'-deoxyuridine incorporation was significantly higher in MALP-2-treated animals (P<0.05). Furthermore, wire injury-induced neointima formation of the left common carotid artery was completely prevented by a single injection of MALP-2 (10 µg, IV). In vitro, MALP-2 induced proliferation (BrdU incorporation) and closure of an artificial wound of endothelial cells (P<0.05) but not of smooth muscle cells. Protein array and ELISA analysis of isolated primary endothelial cells and ex vivo stimulated carotid segments revealed that MALP-2 stimulated the release of multiple growth factors and cytokines predominantly from endothelial cells. MALP-2 induced a strong activation of the mitogen-activated protein kinase cascade in endothelial cells, which was attenuated in smooth muscle cells. Furthermore, MALP-2 significantly enhanced circulating monocytes and hematopoietic progenitor cells. CONCLUSIONS The toll-like receptor 2/6 agonist MALP-2 promotes reendothelialization and inhibits neointima formation after experimental vascular injury via enhanced proliferation and migration of endothelial cells. Thus, MALP-2 represents a novel therapeutic option to accelerate reendothelialization after vascular injury.
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Affiliation(s)
- Karsten Grote
- Department of Cardiology and Angiology, Hannover Medical School, Hannover, Germany.
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Kanno E, Kawakami K, Ritsu M, Ishii K, Tanno H, Toriyabe S, Imai Y, Maruyama R, Tachi M. Wound healing in skin promoted by inoculation with Pseudomonas aeruginosa PAO1: The critical role of tumor necrosis factor-α secreted from infiltrating neutrophils. Wound Repair Regen 2012; 19:608-21. [PMID: 22092799 DOI: 10.1111/j.1524-475x.2011.00721.x] [Citation(s) in RCA: 48] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
Wound healing is promoted by the presence of replicating microorganisms adhering to the wounded tissue, but the precise mechanism is not fully understood. In the present study, using a rat model with full-thickness dermal wounds, we examined the effect of Pseudomonas aeruginosa inoculation on wound healing and the role of neutrophils infiltrating the wound site. Within 3 days, inoculation with this bacterium had accelerated re-epithelialization, epidermal cell proliferation, and neo-vascularization, as well as the local infiltration of neutrophils, which reached a peak at 24 hours. Tumor necrosis factor (TNF)-α was detected in the wound tissues on the mRNA and protein levels within 24 hours. Flow cytometry and immunohistochemical analyses detected higher levels of TNF-α in the infiltrating neutrophils in rats inoculated with P. aeruginosa than in uninoculated rats. Neutropenic rats treated with anti-neutrophil mAb or cyclophosphamide exhibited significant attenuation in re-epithelialization, epidermal cell proliferation, neo-vascularization, and TNF-α synthesis compared with control; administration of TNF-α reversed these attenuations. These wound-healing responses were decelerated in rats treated with anti-TNF-α mAb, as was the infiltration of neutrophils. These results indicate that inoculation with P. aeruginosa promotes wound healing by inducing the infiltration of neutrophils, which play a critical role as a major source of TNF-α.
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Affiliation(s)
- Emi Kanno
- Department of Science of Nursing Practice, Tohoku University Graduate School of Medicine, Sendai, Japan
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Abstract
The implementation of vaccination as an empiric strategy to protect against infectious diseases was introduced even before the advent of hygiene and antimicrobials in the medical practice. Nevertheless, it was not until a few decades ago that we really started understanding the underlying mechanisms of protection triggered by vaccination. Vaccines were initially based on attenuated or inactivated organisms. Subunit vaccines were then introduced as more refined formulations, exhibiting improved safety profiles. However, purified antigens tend to be poorly immunogenic and often require the use of adjuvants to achieve adequate stimulation of the immune system. Vaccination strategies, such as mucosal administration, also require potent adjuvants to improve performance. In the 1990s, immunologists found that pathogens could be sensed as ‘danger signals’ by receptors recognizing conserved motifs. Although our knowledge is still limited, tremendous advances were made in the understanding of host defence mechanisms regulated by these evolutionary conserved receptors, and the molecular structures which are recognized by them. This opened a new era in adjuvant development. Some of the latest players arrived to this field are the cyclic di‐nucleotides, which are ubiquitous prokaryotic intracellular signalling molecules. This review is focused on their potential for the development of vaccines and immunotherapies.
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Affiliation(s)
- Rimma Libanova
- Department of Vaccinology and Applied Microbiology, Helmholtz Centre for Infection Research, 38124 Braunschweig, Germany.
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Barrenschee M, Lex D, Uhlig S. Effects of the TLR2 agonists MALP-2 and Pam3Cys in isolated mouse lungs. PLoS One 2010; 5:e13889. [PMID: 21124967 PMCID: PMC2987752 DOI: 10.1371/journal.pone.0013889] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2009] [Accepted: 10/15/2010] [Indexed: 11/22/2022] Open
Abstract
Background Gram-positive and Gram-negative bacteria are main causes of pneumonia or acute lung injury. They are recognized by the innate immune system via toll-like receptor-2 (TLR2) or TLR4, respectively. Among all organs, the lungs have the highest expression of TLR2 receptors, but little is known about the pulmonary consequences of their activation. Here we studied the effects of the TLR2/6 agonist MALP-2, the TLR2/1 agonist Pam3Cys and the TLR4 agonist lipopolysaccharide (LPS) on pro-inflammatory responses in isolated lungs. Methodology/Principal Findings Isolated perfused mouse lungs were perfused for 60 min or 180 min with MALP-2 (25 ng/mL), Pam3Cys (160 ng/mL) or LPS (1 µg/mL). We studied mediator release by enzyme linked immunosorbent assay (ELISA), the activation of mitogen activated protein kinase (MAPK) and AKT/protein kinase B by immunoblotting, and gene induction by quantitative polymerase chain reaction. All agonists activated the MAPK ERK1/2 and p38, but neither JNK or AKT kinase. The TLR ligands upregulated the inflammation related genes Tnf, Il1β, Il6, Il10, Il12, Ifng, Cxcl2 (MIP-2α) and Ptgs2. MALP-2 was more potent than Pam3Cys in inducing Slpi, Cxcl10 (IP10) and Parg. Remarkable was the strong induction of Tnc by MALP2, which was not seen with Pam3Cys or LPS. The growth factor related genes Areg and Hbegf were not affected. In addition, all three TLR agonists stimulated the release of IL-6, TNF, CXCL2 and CXCL10 protein from the lungs. Conclusions/Significance TLR2 and TLR4 activation leads to similar reactions in the lungs regarding MAPK activation, gene induction and mediator release. Several genes studied here have not yet been appreciated as targets of TLR2-activation in the lungs before, i.e., Slpi, tenascin C, Parg and Traf1. In addition, the MALP-2 dependent induction of Tnc may indicate the existence of TLR2/6-specific pathways.
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Affiliation(s)
- Martina Barrenschee
- Institute of Pharmacology and Toxicology, University Hospital Aachen, RWTH Aachen University, Aachen, Germany
| | - Dennis Lex
- Institute of Pharmacology and Toxicology, University Hospital Aachen, RWTH Aachen University, Aachen, Germany
| | - Stefan Uhlig
- Institute of Pharmacology and Toxicology, University Hospital Aachen, RWTH Aachen University, Aachen, Germany
- * E-mail:
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Knothe S, Mutschler V, Rochlitzer S, Winkler C, Ebensen T, Guzman CA, Hohlfeld J, Braun A, Muller M. Local treatment with BPPcysMPEG reduces allergic airway inflammation in sensitized mice. Immunobiology 2010; 216:110-7. [PMID: 20619481 DOI: 10.1016/j.imbio.2010.05.003] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2010] [Revised: 05/01/2010] [Accepted: 05/01/2010] [Indexed: 11/30/2022]
Abstract
According to the hygiene hypothesis, triggering the immune system with microbial components during childhood balances the inherent Th2 bias. In contrast, specific immunotherapy involves exposure of the patient to the allergen in order to achieve desensitization to subsequent contact. In a human in vitro allergy model the potential of the TLR2/6 agonist BPPcysMPEG to modulate antigen presenting cells and allergen-specific immune responses was evaluated. Specific immunomodulation via co-administration of the allergen and BPPcysMPEG enhanced expression of co-stimulatory molecules on DC and increased secretion of the proinflammatory cytokine TNF-α. Acting as an adjuvant, BPPcysMPEG elevated allergen-specific immune responses in co-culture with autologous lymphocytes. Although administration of BPPcysMPEG alone enhanced expression of co-stimulatory molecules on DC, proliferation of autologous lymphocytes was not induced. Based on this finding, the potential of BPPcysMPEG to reduce allergic airway inflammation by preventive modulation of the innate immune system via TLR2/6 agonization was investigated in mice. Local administration of BPPcysMPEG altered cellular influx and cell composition in BAL fluid. Furthermore, the Th2-associated cytokines IL-4 and IL-5 were diminished. Allergen-specific restimulation of cells from mediastinal lymph nodes and splenocytes suggested an alteration of immune responses. The treatment with BPPcysMPEG induced a Th1-dominated cytokine milieu in mediastinal lymph nodes, while allergen-specific immune responses in splenocytes were diminished. The co-administration of allergen and BPPcysMPEG reduced cytokine secretion upon restimulation in mediastinal lymph nodes and splenocytes. From these data we conclude that BPPcysMPEG was able to influence the immune system with regard to subsequent allergen contact by TLR2/6 agonization.
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Affiliation(s)
- S Knothe
- Fraunhofer Institute for Toxicology and Experimental Medicine (ITEM), Department of Immunology, Allergology and Immunotoxicology, Hannover, Germany
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Kanno E, Toriyabe S, Zhang L, Imai Y, Tachi M. Biofilm formation on rat skin wounds byPseudomonas aeruginosacarrying the green fluorescent protein gene. Exp Dermatol 2010; 19:154-6. [DOI: 10.1111/j.1600-0625.2009.00931.x] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
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Toll-like receptor 2/6 stimulation promotes angiogenesis via GM-CSF as a potential strategy for immune defense and tissue regeneration. Blood 2010; 115:2543-52. [PMID: 20056792 DOI: 10.1182/blood-2009-05-224402] [Citation(s) in RCA: 58] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023] Open
Abstract
Toll-like receptors (TLRs) are known primarily as pathogen recognition receptors of the innate immunity, initiating inflammatory pathways to organize the immune defense. More recently, an involvement of TLRs in various physiologic and pathologic processes has been reported. Because many of these processes implicate angiogenesis, we here elucidated the role of a TLR2/6-dependent pathway on angiogenesis using the TLR2/6 agonist macrophage-activating lipopeptide of 2 kDa (MALP-2), a common bacterial lipopeptide. In vivo and in vitro Matrigel assays demonstrated that MALP-2 promoted angiogenesis in a TLR2/6-dependent manner. Moreover, MALP-2 induced endothelial cell proliferation and migration and a strong secretion of granulocyte-macrophage colony-stimulating factor (GM-CSF). GM-CSF release in response to MALP-2 from isolated vascular segments was completely prevented when the endothelium was removed. MALP-2 containing Matrigel implants exhibited vascular structures as well as CD45(+) cells. MALP-2 induced migration of leukocytes and likewise GM-CSF release, particularly from the monocyte population. Inhibition of GM-CSF by siRNA or antibodies suppressed MALP-2-induced angiogenesis in vitro and in vivo. These results clearly identified a TLR2/6-dependent induction of angiogenesis by the bacterial lipopeptide MALP-2, which is mediated by GM-CSF. This might represent a general mechanism to enhance or restore blood flow and recruit immune cells for pathogen defense and tissue regeneration.
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