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Apostolo D, D’Onghia D, Nerviani A, Ghirardi GM, Sola D, Perazzi M, Tonello S, Colangelo D, Sainaghi PP, Bellan M. Could Gas6/TAM Axis Provide Valuable Insights into the Pathogenesis of Systemic Sclerosis? Curr Issues Mol Biol 2024; 46:7486-7504. [PMID: 39057085 PMCID: PMC11275301 DOI: 10.3390/cimb46070444] [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: 06/19/2024] [Revised: 07/09/2024] [Accepted: 07/12/2024] [Indexed: 07/28/2024] Open
Abstract
Systemic sclerosis (SSc) is a connective tissue disorder characterized by microvascular injury, extracellular matrix deposition, autoimmunity, inflammation, and fibrosis. The clinical complexity and high heterogeneity of the disease make the discovery of potential therapeutic targets difficult. However, the recent progress in the comprehension of its pathogenesis is encouraging. Growth Arrest-Specific 6 (Gas6) and Tyro3, Axl, and MerTK (TAM) receptors are involved in multiple biological processes, including modulation of the immune response, phagocytosis, apoptosis, fibrosis, inflammation, cancer development, and autoimmune disorders. In the present manuscript, we review the current evidence regarding SSc pathogenesis and the role of the Gas6/TAM system in several human diseases, suggesting its likely contribution in SSc and highlighting areas where further research is necessary to fully comprehend the role of TAM receptors in this condition. Indeed, understanding the involvement of TAM receptors in SSc, which is currently unknown, could provide valuable insights for novel potential therapeutic targets.
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Affiliation(s)
- Daria Apostolo
- Department of Translational Medicine, University of Piemonte Orientale (UPO), 28100 Novara, Italy; (D.A.); (D.D.); (D.S.); (M.P.); (S.T.); (P.P.S.); (M.B.)
- Centre for Experimental Medicine and Rheumatology, Barts and The London School of Medicine and Dentistry, William Harvey Research Institute, Queen Mary University of London, London E1 4NS, UK;
| | - Davide D’Onghia
- Department of Translational Medicine, University of Piemonte Orientale (UPO), 28100 Novara, Italy; (D.A.); (D.D.); (D.S.); (M.P.); (S.T.); (P.P.S.); (M.B.)
| | - Alessandra Nerviani
- Centre for Experimental Medicine and Rheumatology, Barts and The London School of Medicine and Dentistry, William Harvey Research Institute, Queen Mary University of London, London E1 4NS, UK;
| | - Giulia Maria Ghirardi
- Centre for Experimental Medicine and Rheumatology, Barts and The London School of Medicine and Dentistry, William Harvey Research Institute, Queen Mary University of London, London E1 4NS, UK;
| | - Daniele Sola
- Department of Translational Medicine, University of Piemonte Orientale (UPO), 28100 Novara, Italy; (D.A.); (D.D.); (D.S.); (M.P.); (S.T.); (P.P.S.); (M.B.)
- IRCCS Istituto Auxologico Italiano, UO General Medicine, 28824 Oggebbio, Italy
| | - Mattia Perazzi
- Department of Translational Medicine, University of Piemonte Orientale (UPO), 28100 Novara, Italy; (D.A.); (D.D.); (D.S.); (M.P.); (S.T.); (P.P.S.); (M.B.)
- Internal Medicine and Rheumatology Unit, A.O.U. Maggiore della Carità, 28100 Novara, Italy
| | - Stelvio Tonello
- Department of Translational Medicine, University of Piemonte Orientale (UPO), 28100 Novara, Italy; (D.A.); (D.D.); (D.S.); (M.P.); (S.T.); (P.P.S.); (M.B.)
| | - Donato Colangelo
- Department of Health Sciences, Pharmacology, University of Piemonte Orientale (UPO), 28100 Novara, Italy;
| | - Pier Paolo Sainaghi
- Department of Translational Medicine, University of Piemonte Orientale (UPO), 28100 Novara, Italy; (D.A.); (D.D.); (D.S.); (M.P.); (S.T.); (P.P.S.); (M.B.)
- Internal Medicine and Rheumatology Unit, A.O.U. Maggiore della Carità, 28100 Novara, Italy
- Center on Autoimmune and Allergic Diseases (CAAD), University of Piemonte Orientale, 28100 Novara, Italy
| | - Mattia Bellan
- Department of Translational Medicine, University of Piemonte Orientale (UPO), 28100 Novara, Italy; (D.A.); (D.D.); (D.S.); (M.P.); (S.T.); (P.P.S.); (M.B.)
- Internal Medicine and Rheumatology Unit, A.O.U. Maggiore della Carità, 28100 Novara, Italy
- Center on Autoimmune and Allergic Diseases (CAAD), University of Piemonte Orientale, 28100 Novara, Italy
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Vago JP, Valdrighi N, Blaney-Davidson EN, Hornikx DLAH, Neefjes M, Barba-Sarasua ME, Thielen NGM, van den Bosch MHJ, van der Kraan PM, Koenders MI, Amaral FA, van de Loo FAJ. Gas6/Axl Axis Activation Dampens the Inflammatory Response in Osteoarthritic Fibroblast-like Synoviocytes and Synovial Explants. Pharmaceuticals (Basel) 2023; 16:ph16050703. [PMID: 37242486 DOI: 10.3390/ph16050703] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2023] [Revised: 04/24/2023] [Accepted: 04/26/2023] [Indexed: 05/28/2023] Open
Abstract
Osteoarthritis (OA) is the most prevalent joint disease, and it is characterized by cartilage degeneration, synovitis, and bone sclerosis, resulting in swelling, stiffness, and joint pain. TAM receptors (Tyro3, Axl, and Mer) play an important role in regulating immune responses, clearing apoptotic cells, and promoting tissue repair. Here, we investigated the anti-inflammatory effects of a TAM receptor ligand, i.e., growth arrest-specific gene 6 (Gas6), in synovial fibroblasts from OA patients. TAM receptor expression was determined in synovial tissue. Soluble Axl (sAxl), a decoy receptor for the ligand Gas6, showed concentrations 4.6 times higher than Gas6 in synovial fluid of OA patients. In OA fibroblast-like synoviocytes (OAFLS) exposed to inflammatory stimuli, the levels of sAxl in the supernatants were increased, while the expression of Gas6 was downregulated. In OAFLS under TLR4 stimulation by LPS (Escherichia coli lipopolysaccharide), the addition of exogenous Gas6 by Gas6-conditioned medium (Gas6-CM) reduced pro-inflammatory markers including IL-6, TNF-α, IL-1β, CCL2, and CXCL8. Moreover, Gas6-CM downregulated IL-6, CCL2, and IL-1β in LPS-stimulated OA synovial explants. Pharmacological inhibition of TAM receptors by a pan inhibitor (RU301) or by a selective Axl inhibitor (RU428) similarly abrogated Gas6-CM anti-inflammatory effects. Mechanistically, Gas6 effects were dependent on Axl activation, determined by Axl, STAT1, and STAT3 phosphorylation, and by the downstream induction of the suppressors of the cytokine signaling family (SOCS1 and SOCS3). Taken together, our results showed that Gas6 treatment dampens inflammatory markers of OAFLS and synovial explants derived from OA patients associated with SOCS1/3 production.
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Affiliation(s)
- Juliana P Vago
- Experimental Rheumatology, Department of Rheumatology, Radboud Institute for Molecular Life Sciences, Radboud University Medical Center, 6525 GA Nijmegen, The Netherlands
| | - Natália Valdrighi
- Experimental Rheumatology, Department of Rheumatology, Radboud Institute for Molecular Life Sciences, Radboud University Medical Center, 6525 GA Nijmegen, The Netherlands
| | - Esmeralda N Blaney-Davidson
- Experimental Rheumatology, Department of Rheumatology, Radboud Institute for Molecular Life Sciences, Radboud University Medical Center, 6525 GA Nijmegen, The Netherlands
| | - Daniel L A H Hornikx
- Experimental Rheumatology, Department of Rheumatology, Radboud Institute for Molecular Life Sciences, Radboud University Medical Center, 6525 GA Nijmegen, The Netherlands
| | - Margot Neefjes
- Experimental Rheumatology, Department of Rheumatology, Radboud Institute for Molecular Life Sciences, Radboud University Medical Center, 6525 GA Nijmegen, The Netherlands
| | - María E Barba-Sarasua
- Experimental Rheumatology, Department of Rheumatology, Radboud Institute for Molecular Life Sciences, Radboud University Medical Center, 6525 GA Nijmegen, The Netherlands
| | - Nathalie G M Thielen
- Experimental Rheumatology, Department of Rheumatology, Radboud Institute for Molecular Life Sciences, Radboud University Medical Center, 6525 GA Nijmegen, The Netherlands
| | - Martijn H J van den Bosch
- Experimental Rheumatology, Department of Rheumatology, Radboud Institute for Molecular Life Sciences, Radboud University Medical Center, 6525 GA Nijmegen, The Netherlands
| | - Peter M van der Kraan
- Experimental Rheumatology, Department of Rheumatology, Radboud Institute for Molecular Life Sciences, Radboud University Medical Center, 6525 GA Nijmegen, The Netherlands
| | - Marije I Koenders
- Experimental Rheumatology, Department of Rheumatology, Radboud Institute for Molecular Life Sciences, Radboud University Medical Center, 6525 GA Nijmegen, The Netherlands
| | - Flávio A Amaral
- Departament of Biochemistry and Immunology, Institute of Biological Sciences, Universidade Federal de Minas Gerais, Belo Horizonte 31270-901, Minas Gerais, Brazil
| | - Fons A J van de Loo
- Experimental Rheumatology, Department of Rheumatology, Radboud Institute for Molecular Life Sciences, Radboud University Medical Center, 6525 GA Nijmegen, The Netherlands
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Zhou S, Li Y, Zhang Z, Yuan Y. An insight into the TAM system in Alzheimer's disease. Int Immunopharmacol 2023; 116:109791. [PMID: 36738678 DOI: 10.1016/j.intimp.2023.109791] [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: 12/02/2022] [Revised: 01/13/2023] [Accepted: 01/24/2023] [Indexed: 02/05/2023]
Abstract
The TAM receptors may help delay the progression of Alzheimer's disease (AD). AD is the most common neurodegenerative disease associated with human aging. The TAM receptors, derived from the first letter of its three constituents -Tyro3, Axl, and Mertk, are associated with immune responses, cellular differentiation and migration, and clearance of apoptotic cells and debris, with the two canonical ligands, Growth Arrest Specific 6 (Gas6) and ProS1. Several kinds of research have indicated the participation of the TAM system in AD pathology. Also, the TAMs regulate multiple features of microglia, the significant sensors of disorder in the central nervous system (CNS). In this review, we describe the biology of the TAM receptors and ligands in the CNS. Then, we discuss the relationship between the TAM system and AD, specially focusing on its functional expression in the microglia. Finally, we also summarize some agents that could interfere with the TAM signaling pathways and discuss potential difficulties and strategies for drug development.
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Affiliation(s)
- Shiqi Zhou
- State Key Laboratory of Bioactive Substances and Functions of Natural Medicines, Institute of Materia Medica, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing 100050, China.
| | - Yanyan Li
- State Key Laboratory of Bioactive Substances and Functions of Natural Medicines, Institute of Materia Medica, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing 100050, China.
| | - Zhao Zhang
- State Key Laboratory of Bioactive Substances and Functions of Natural Medicines, Institute of Materia Medica, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing 100050, China.
| | - Yuhe Yuan
- State Key Laboratory of Bioactive Substances and Functions of Natural Medicines, Institute of Materia Medica, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing 100050, China.
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AXL Inhibits Proinflammatory Factors to Relieve Rheumatoid Arthritis Pain by Regulating the TLR4/NF-κB Signaling Pathway. EVIDENCE-BASED COMPLEMENTARY AND ALTERNATIVE MEDICINE 2022; 2022:7625739. [PMID: 35983008 PMCID: PMC9381196 DOI: 10.1155/2022/7625739] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 05/31/2022] [Accepted: 07/14/2022] [Indexed: 11/30/2022]
Abstract
Objective This study aims to explore the role and mechanism of AXL receptor tyrosine kinase (AXL) in relieving inflammatory pain caused by rheumatoid arthritis (RA). Methods RA mouse model was constructed by collagen antibody induction. RT-qPCR and Western blot were used to detect the level of AXL in RA fibroblast-like synovial cells (RA-FLS) and joint synovium. The levels of interleukin-6 (IL-6), tumor necrosis factor-α (TNF-α), and nitric oxide (NO) were detected by ELISA. The inflammatory infiltration in joints was determined via HE staining. The mechanical abnormal pain and hyperalgesia were detected by the Von Frey microfilament test. The protein levels of inducible nitric oxide synthase (iNOS), cyclooxygenase-2 (3COX-2), toll-like receptor 4 (TLR4), p65, and phosphor (p)-p65 were detected by Western blotting. Results The expression of AXL in RA-FLS and RA mice was downregulated, while the expression of iNOS and COX-2 was upregulated. The levels of inflammatory cytokines IL-6, TNF-α, and NO were increased in RA-FLS and RA mice. RA mice presented inflammatory cell infiltration, bone and cartilage destruction, and joint space stenosis. AXL overexpression alleviated inflammatory cell infiltration, inflammatory cytokine secretion, and pathological injury in RA mice. Additionally, AXL overexpression inhibited the expression of TLR4 and p-p65. Conclusion AXL inhibits inflammatory pain in RA mice by suppressing TLR4/NF-κB pathway.
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Zhenghai S. Increased serum AXL is associated with radiographic knee osteoarthritis severity. Int J Rheum Dis 2021; 25:32-37. [PMID: 34841689 PMCID: PMC9298778 DOI: 10.1111/1756-185x.14239] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2021] [Revised: 10/25/2021] [Accepted: 10/30/2021] [Indexed: 12/03/2022]
Abstract
Objective To investigate the expression and clinical significance of serum soluble AXL in patients with radiographic knee osteoarthritis (KOA). Methods There were 183 patients with KOA who were selected and divided based on the Kellgren‐Lawrence (KL) score into KL 0 subgroups (n = 42), KL I‐II subgroups (n = 90), and KL III‐IV subgroups (n = 51). Healthy volunteers (n = 170) in our hospital were selected with matched age and gender as the control group. AXL level in serum was detected by enzyme‐linked immunosorbent assay. The correlation between serum AXL with severity and clinical indicators of osteoarthritis was analyzed. Results The level of serum AXL was significantly higher in the osteoarthritis group than that in the control group (P < .05). In the osteoarthritis patients, serum AXL level was increased with the increase of KL score. Serum AXL level was positively correlated with age, body mass index, erythrocyte sedimentation rate, serum C‐reactive protein, cartilage oligomeric protein, matrix metalloproteinase‐13, and transforming growth factor‐β1 levels. The cut‐off value for serum AXL was determined as 33.375 ng/mL by receiver operating curve analysis. Conclusion The level of serum AXL in patients with osteoarthritis is significantly higher than in healthy controls, and is closely related to the severity of radiographic osteoarthritis.
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Affiliation(s)
- Shao Zhenghai
- Shanghai Kaiyuan Orthopedic Hospital, Shanghai, China
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Kemble S, Croft AP. Critical Role of Synovial Tissue-Resident Macrophage and Fibroblast Subsets in the Persistence of Joint Inflammation. Front Immunol 2021; 12:715894. [PMID: 34539648 PMCID: PMC8446662 DOI: 10.3389/fimmu.2021.715894] [Citation(s) in RCA: 54] [Impact Index Per Article: 18.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2021] [Accepted: 08/17/2021] [Indexed: 12/11/2022] Open
Abstract
Rheumatoid arthritis (RA) is a chronic prototypic immune-mediated inflammatory disease which is characterized by persistent synovial inflammation, leading to progressive joint destruction. Whilst the introduction of targeted biological drugs has led to a step change in the management of RA, 30-40% of patients do not respond adequately to these treatments, regardless of the mechanism of action of the drug used (ceiling of therapeutic response). In addition, many patients who acheive clinical remission, quickly relapse following the withdrawal of treatment. These observations suggest the existence of additional pathways of disease persistence that remain to be identified and targeted therapeutically. A major barrier for the identification of therapeutic targets and successful clinical translation is the limited understanding of the cellular mechanisms that operate within the synovial microenvironment to sustain joint inflammation. Recent insights into the heterogeneity of tissue resident synovial cells, including macropahges and fibroblasts has revealed distinct subsets of these cells that differentially regulate specific aspects of inflammatory joint pathology, paving the way for targeted interventions to specifically modulate the behaviour of these cells. In this review, we will discuss the phenotypic and functional heterogeneity of tissue resident synovial cells and how this cellular diversity contributes to joint inflammation. We discuss how critical interactions between tissue resident cell types regulate the disease state by establishing critical cellular checkpoints within the synovium designed to suppress inflammation and restore joint homeostasis. We propose that failure of these cellular checkpoints leads to the emergence of imprinted pathogenic fibroblast cell states that drive the persistence of joint inflammation. Finally, we discuss therapeutic strategies that could be employed to specifically target pathogenic subsets of fibroblasts in RA.
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Affiliation(s)
| | - Adam P. Croft
- Rheumatology Research Group, Institute of Inflammation and Ageing (IIA), University of Birmingham, Queen Elizabeth Hospital, Birmingham, United Kingdom
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Vago JP, Amaral FA, van de Loo FAJ. Resolving inflammation by TAM receptor activation. Pharmacol Ther 2021; 227:107893. [PMID: 33992683 DOI: 10.1016/j.pharmthera.2021.107893] [Citation(s) in RCA: 36] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2021] [Revised: 05/06/2021] [Accepted: 05/10/2021] [Indexed: 12/12/2022]
Abstract
The control of inflammation is strictly regulated to ensure the adequate intensity and duration of an inflammatory response, enabling the removal of the trigger factors and the restoration of the integrity of the tissues and their functions. This process is coordinated by anti-inflammatory and pro-resolving mediators that regulate the cellular and molecular events necessary to restore homeostasis, and defects in this control are associated with the development of chronic and autoimmune diseases. The TAM family of receptor tyrosine kinases-Tyro3, Axl, and MerTK-plays an essential role in efferocytosis, a key process for the resolution of inflammation. However, new studies have demonstrated that TAM receptor activation not only reduces the synthesis of pro-inflammatory mediators by different cell types in response to some stimuli but also stimulates the production of anti-inflammatory and pro-resolving molecules that control the inflammation. This review provides a comprehensive view of TAM receptor family members as important players in controlling inflammatory responses through anti-inflammatory and pro-resolving actions.
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Affiliation(s)
- Juliana P Vago
- Experimental Rheumatology, Department of Rheumatology, Radboud Institute for Molecular Life Sciences, Radboud university medical center, Nijmegen, the Netherlands
| | - Flávio A Amaral
- Experimental Rheumatology, Department of Rheumatology, Radboud Institute for Molecular Life Sciences, Radboud university medical center, Nijmegen, the Netherlands; Departamento de Bioquímica e Imunologia, Instituto de Ciências Biológicas, Universidade Federal de Minas Gerais, Belo Horizonte, Minas Gerais, Brazil
| | - Fons A J van de Loo
- Experimental Rheumatology, Department of Rheumatology, Radboud Institute for Molecular Life Sciences, Radboud university medical center, Nijmegen, the Netherlands.
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Di Stasi R, De Rosa L, D'Andrea LD. Therapeutic aspects of the Axl/Gas6 molecular system. Drug Discov Today 2020; 25:2130-2148. [PMID: 33002607 DOI: 10.1016/j.drudis.2020.09.022] [Citation(s) in RCA: 20] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2020] [Revised: 07/14/2020] [Accepted: 09/21/2020] [Indexed: 12/17/2022]
Abstract
Axl receptor tyrosine kinase (RTK) and its ligand, growth arrest-specific protein 6 (Gas6), are involved in several biological functions and participate in the development and progression of a range of malignancies and autoimmune disorders. In this review, we present this molecular system from a drug discovery perspective, highlighting its therapeutic implications and challenges that need to be addressed. We provide an update on Axl/Gas6 axis biology, exploring its role in fields ranging from angiogenesis, cancer development and metastasis, immune response and inflammation to viral infection. Finally, we summarize the molecules that have been developed to date to target the Axl/Gas6 molecular system for therapeutic and diagnostic applications.
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Affiliation(s)
- Rossella Di Stasi
- Istituto di Biostrutture e Bioimmagini, CNR, Via Mezzocannone 16, 80134 Napoli, Italy
| | - Lucia De Rosa
- Istituto di Biostrutture e Bioimmagini, CNR, Via Mezzocannone 16, 80134 Napoli, Italy
| | - Luca D D'Andrea
- Istituto di Biostrutture e Bioimmagini, CNR, Via Nizza 52, 10126 Torino, Italy.
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Bassyouni RH, Gomaa AA, Hassan EA, Ali ESG, Khalil MAF, Mashahit MA, Gaber SN. Possible Association of Elevated Plasma Levels of Growth Arrest-Specific Protein 6 and the Soluble Form of Tyrosine Kinase Receptor Axl with Low Hepatitis C Viral Load in Patients with Type 2 Diabetes Mellitus. Viral Immunol 2020; 33:105-111. [PMID: 31905327 DOI: 10.1089/vim.2019.0127] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
This study aimed to investigate the plasma levels of Gas6 and soluble Axl (sAxl) in patients with chronic hepatitis C virus (HCV) infection with and without type 2 diabetes mellitus (T2DM). The study involved four groups; 50 patients with chronic HCV, 50 patients with T2DM, 50 patients with chronic HCV and T2DM, and 31 age- and sex-matched healthy controls. T2DM was diagnosed according to American Diabetes Association criteria, HCV antibodies were detected by enzyme-linked immunosorbent assays (ELISA) and confirmed by real-time-polymerase chain reaction. Plasma Gas6 and sAxl levels were assayed in all groups by ELISA. Significant low levels of GAS 6 in HCV/T2DM group versus HCV group were detected (7.92 ± 5.18 vs. 16.09 ± 7.36, respectively, p = 0.000), but higher than T2DM and control groups (p ≥ 0.05), although nonsignificant. HCV load was higher in the HCV group than the HCV/T2DM group (1,888,300 ± 5,595,070 vs. 1,417,900 ± 4,066,460 copies/mL, respectively, p = 0.632). Among HCV group, significant positive correlations were detected between Gas6 and sAxl levels with HCV viral load (r = 0.48, p = 0.000 and r = 0.43, p = 0.002, respectively), while among HCV/T2DM group, significant negative correlations were detected (r = -0.29, p = 0.04 and r = -0.34, p = 0.014, respectively). Significant negative correlations were detected between Gas6/sAxl levels and glycated hemoglobin (r = -0.36, p = 0.01 and r = -0.4, p = 0.003, respectively) in T2DM despite the positive correlations detected in HCV/T2DM (r = 0.27, p = 0.053 and r = 0.55, p = 0.000, respectively). In conclusion, Gas6/Axl system in combined HCV/T2DM diseases may affect the pathogenesis and can alter the biomarkers and complications of both diseases in a manner that differs from a solitary disease.
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Affiliation(s)
- Rasha H Bassyouni
- Department of Medical Microbiology and Immunology, Faculty of Medicine, Fayoum University, Fayoum, Egypt
| | - Ahmed A Gomaa
- Department of Tropical Medicine, Faculty of Medicine, Fayoum University, Fayoum, Egypt
| | - Essam A Hassan
- Department of Tropical Medicine, Faculty of Medicine, Fayoum University, Fayoum, Egypt
| | - El Shaimaa Gomaa Ali
- Department of Medical Microbiology and Immunology, Faculty of Medicine, Fayoum University, Fayoum, Egypt
| | - Mahmoud A F Khalil
- Department of Microbiology and Immunology, Faculty of Pharmacy, Fayoum University, Fayoum, Egypt
| | - Mohamed A Mashahit
- Department of Internal Medicine, Faculty of Medicine, Fayoum University, Fayoum, Egypt
| | - Sylvana N Gaber
- Department of Medical Microbiology and Immunology, Faculty of Medicine, Fayoum University, Fayoum, Egypt
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10
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New Insights into the Role of Tyro3, Axl, and Mer Receptors in Rheumatoid Arthritis. DISEASE MARKERS 2020; 2020:1614627. [PMID: 32051695 PMCID: PMC6995487 DOI: 10.1155/2020/1614627] [Citation(s) in RCA: 20] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 04/05/2019] [Revised: 12/01/2019] [Accepted: 01/04/2020] [Indexed: 12/14/2022]
Abstract
Rheumatoid Arthritis (RA) is the most common chronic inflammatory autoimmune disease involving joints. Among several pathogenic mechanisms, the impairment of homeostatic regulators of inflammation seems to be critically important to sustain persistent infiltration and activation of immune and stromal cells within the diseased synovium. Tyrosine kinase receptors Tyro3, Axl, and Mer are members of the TAM family. Upon binding their ligands Growth Arrest-Specific gene 6 (Gas6) and Protein S (ProS1), TAM receptors (TAMs) exert numerous and diverse biologic functions. Activated Axl and Mer, for instance, can negatively regulate the inflammatory cascade and mediate phagocytosis of apoptotic cells, contributing to prevent the development of autoimmunity. Thus, a role for TAMs has been hypothesized in RA. In this review, we will summarise unmet clinical needs in RA, depict the biology of TAMs and TAM ligands, focussing on their ability to regulate the immune system and inflammation cascade, and finally offer an overview of the state-of-the-art literature about the putative role of TAM axis in RA.
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11
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Waterborg CEJ, Broeren MGA, Blaney Davidson EN, Koenders MI, van Lent PLEM, van den Berg WB, van der Kraan PM, van de Loo FAJ. The level of synovial AXL expression determines the outcome of inflammatory arthritis, possibly depending on the upstream role of TGF-β1. Rheumatology (Oxford) 2020; 58:536-546. [PMID: 30508140 DOI: 10.1093/rheumatology/key337] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2017] [Accepted: 10/15/2018] [Indexed: 11/14/2022] Open
Abstract
OBJECTIVE To investigate the role of AXL, a member of the anti-inflammatory TYRO3, AXL MER (TAM) receptor family, in arthritis. METHODS KRN serum transfer arthritis was induced in Axl-/- and wild-type mice. Knee and ankle joints were scored macro- and microscopically. Synovial gene and protein expression of Axl was determined in naïve and TGF-β1-overexpressing joints. AXL expression was determined in M1-like or M2-like macrophages and RA synovium. Human macrophages, fibroblasts and synovial micromasses were stimulated with TGF-β1 or the AXL inhibitor R428. RESULTS Ankle joints of Axl-/- mice showed exacerbated arthritis pathology, whereas no effect of Axl gene deletion was observed on gonarthritis pathology. To explain this spatial difference, we examined the synovium of naïve mice. In contrast to the knee, the ankle synovial cells prominently expressed AXL. Moreover, the M2-like macrophage phenotype was the dominant cell type in the naïve ankle joint. Human M2-like macrophages expressed higher levels of AXL and blocking AXL increased their inflammatory response. In the murine ankle synovium, gene expression of Tgfb1 was increased and Tgb1 correlated with Axl. Moreover, TGFB1 and AXL expression also correlated in human RA synovium. In human macrophages and synovial micromasses, TGF-β1 enhanced AXL expression. Moreover, TGF-β1 overexpression in naïve murine knee joints induced synovial AXL expression. CONCLUSION Differences in synovial AXL expression are in accordance with the observation that AXL dampens arthritis in ankle, but not in knee joints. We provide evidence that the local differences in AXL expression could be due to TGF-β1, and suggest similar pathways operate in RA synovium.
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Affiliation(s)
- Claire E J Waterborg
- Experimental Rheumatology, Department of Rheumatology, Radboud Institute for Molecular Life Sciences, Radboud University Medical Center, Nijmegen, the Netherlands
| | - Mathijs G A Broeren
- Experimental Rheumatology, Department of Rheumatology, Radboud Institute for Molecular Life Sciences, Radboud University Medical Center, Nijmegen, the Netherlands
| | - Esmeralda N Blaney Davidson
- Experimental Rheumatology, Department of Rheumatology, Radboud Institute for Molecular Life Sciences, Radboud University Medical Center, Nijmegen, the Netherlands
| | - Marije I Koenders
- Experimental Rheumatology, Department of Rheumatology, Radboud Institute for Molecular Life Sciences, Radboud University Medical Center, Nijmegen, the Netherlands
| | - Peter L E M van Lent
- Experimental Rheumatology, Department of Rheumatology, Radboud Institute for Molecular Life Sciences, Radboud University Medical Center, Nijmegen, the Netherlands
| | - Wim B van den Berg
- Experimental Rheumatology, Department of Rheumatology, Radboud Institute for Molecular Life Sciences, Radboud University Medical Center, Nijmegen, the Netherlands
| | - Peter M van der Kraan
- Experimental Rheumatology, Department of Rheumatology, Radboud Institute for Molecular Life Sciences, Radboud University Medical Center, Nijmegen, the Netherlands
| | - Fons A J van de Loo
- Experimental Rheumatology, Department of Rheumatology, Radboud Institute for Molecular Life Sciences, Radboud University Medical Center, Nijmegen, the Netherlands
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12
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Waterborg CEJ, Koenders MI, van Lent PLEM, van der Kraan PM, van de Loo FAJ. Tyro3/Axl/Mertk-deficient mice develop bone marrow edema which is an early pathological marker in rheumatoid arthritis. PLoS One 2018; 13:e0205902. [PMID: 30335822 PMCID: PMC6193696 DOI: 10.1371/journal.pone.0205902] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2018] [Accepted: 10/03/2018] [Indexed: 12/21/2022] Open
Abstract
Rheumatoid arthritis is an auto-immune disease of the synovial joints, hallmarked by chronic inflammation and subsequent progressive tissue destruction. TYRO3, AXL and MER (gene name Mertk) (TAM) receptors are part of a negative feedback signaling system in the immune reaction and mediate efferocytosis thereby tempering the inflammatory process. We have shown that Axl-/- and Mertk-/- mice develop more severe arthritis whereas activating these receptors by overexpressing their ligands Pros1 and Gas6 ameliorates arthritis. Mice genetically ablated for the three genes of the TAM receptor family Tyro3/Axl/Mertk (TAM triple knock-out or TKO) have been described to spontaneously develop macroscopic signs of arthritis. In this study we aimed to analyze arthritis development in TAM TKO mice histologically to determine the extent and sequence of pathological changes in the joint. Ankle joints of three different age groups, adolescence (14 weeks), mature adult (34 weeks) and middle-age (52 weeks), of TAM TKO or wild-type mice were examined macroscopically, histologically and immunohistochemically. Surprisingly, until the age of 52 weeks, none of the mice examined developed spontaneous macroscopic signs of arthritis. There was no synovial inflammation nor any signs of damage to the cartilage or bone. However, bone marrow edema was observed in TAM TKO mice in the two latter age groups. The infiltrate in the bone marrow was characterized by both myeloid cells and lymphocytes. This study showed that TAM TKO mice developed a pre-stage (pre-clinical phase) of arthritis marked by bone marrow edema.
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Affiliation(s)
- Claire E. J. Waterborg
- Experimental Rheumatology, Department of Rheumatology, Radboud Institute for Molecular Life Sciences, Radboud University Medical Center, Nijmegen, the Netherlands
| | - Marije I. Koenders
- Experimental Rheumatology, Department of Rheumatology, Radboud Institute for Molecular Life Sciences, Radboud University Medical Center, Nijmegen, the Netherlands
| | - Peter L. E. M. van Lent
- Experimental Rheumatology, Department of Rheumatology, Radboud Institute for Molecular Life Sciences, Radboud University Medical Center, Nijmegen, the Netherlands
| | - Peter M. van der Kraan
- Experimental Rheumatology, Department of Rheumatology, Radboud Institute for Molecular Life Sciences, Radboud University Medical Center, Nijmegen, the Netherlands
| | - Fons A. J. van de Loo
- Experimental Rheumatology, Department of Rheumatology, Radboud Institute for Molecular Life Sciences, Radboud University Medical Center, Nijmegen, the Netherlands
- * E-mail:
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13
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Xu L, Hu F, Zhu H, Liu X, Shi L, Li Y, Zhong H, Su Y. Soluble TAM receptor tyrosine kinases in rheumatoid arthritis: correlation with disease activity and bone destruction. Clin Exp Immunol 2017; 192:95-103. [PMID: 29148078 DOI: 10.1111/cei.13082] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 11/13/2017] [Indexed: 12/28/2022] Open
Abstract
The TAM receptor tyrosine kinases (TAM RTK) are a subfamily of receptor tyrosine kinases, the role of which in autoimmune diseases such as systemic lupus erythematosus has been well explored, while their functions in rheumatoid arthritis (RA) remain largely unknown. In this study, we investigated the role of soluble TAM receptor tyrosine kinases (sAxl/sMer/sTyro3) in patients with RA. A total of 306 RA patients, 100 osteoarthritis (OA) patients and 120 healthy controls (HCs) were enrolled into this study. The serum concentrations of sAxl/sMer/sTyro3 were measured by enzyme-linked immunosorbent assay (ELISA), then the associations between sAxl/sMer/sTyro3 levels and clinical features of RA patients were analysed. We also investigated whether sTyro3 could promote osteoclast differentiation in vitro in RA patients. The results showed that compared with healthy controls (HCs), sTyro3 levels in the serum of RA patients were elevated remarkably and sMer levels were decreased significantly, whereas there was no difference between HCs and RA patients on sAxl levels. The sTyro3 levels were correlated weakly but positively with white blood cells (WBC), immunoglobulin (Ig)M, rheumatoid factor (RF), swollen joint counts, tender joint counts, total sharp scores and joint erosion scores. Conversely, there were no significant correlations between sMer levels and the above indices. Moreover, RA patients with high disease activity also showed higher sTyro3 levels. In-vitro osteoclast differentiation assay showed further that tartrate-resistant acid phosphatase (TRAP)+ osteoclasts were increased significantly in the presence of sTyro3. Collectively, our study indicated that serum sTyro3 levels were elevated in RA patients and correlated positively with disease activity and bone destruction, which may serve as an important participant in RA pathogenesis.
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Affiliation(s)
- L Xu
- Department of Rheumatology and Immunology, Peking University People's Hospital, Beijing, China.,Beijing Key Laboratory for Rheumatism Mechanism and Immune Diagnosis (BZ0135), Beijing, China
| | - F Hu
- Department of Rheumatology and Immunology, Peking University People's Hospital, Beijing, China.,Beijing Key Laboratory for Rheumatism Mechanism and Immune Diagnosis (BZ0135), Beijing, China
| | - H Zhu
- Department of Rheumatology and Immunology, Peking University People's Hospital, Beijing, China.,Beijing Key Laboratory for Rheumatism Mechanism and Immune Diagnosis (BZ0135), Beijing, China
| | - X Liu
- Department of Rheumatology and Immunology, Peking University People's Hospital, Beijing, China.,Beijing Key Laboratory for Rheumatism Mechanism and Immune Diagnosis (BZ0135), Beijing, China
| | - L Shi
- Department of Rheumatology and Immunology, Peking University International Hospital, Beijing, China
| | - Y Li
- Department of Rheumatology and Immunology, Peking University People's Hospital, Beijing, China.,Beijing Key Laboratory for Rheumatism Mechanism and Immune Diagnosis (BZ0135), Beijing, China
| | - H Zhong
- Department of Rheumatology and Immunology, Peking University People's Hospital, Beijing, China.,Beijing Key Laboratory for Rheumatism Mechanism and Immune Diagnosis (BZ0135), Beijing, China
| | - Y Su
- Department of Rheumatology and Immunology, Peking University People's Hospital, Beijing, China.,Beijing Key Laboratory for Rheumatism Mechanism and Immune Diagnosis (BZ0135), Beijing, China
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14
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Dengler M, Huber H, Müller CJ, Zellmer A, Rauch P, Mikulits W. Accurate Determination of Soluble Axl by Enzyme-Linked Immunosorbent Assay. Assay Drug Dev Technol 2016; 14:543-550. [PMID: 27805424 DOI: 10.1089/adt.2016.743] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023] Open
Abstract
Levels of soluble Axl (sAxl) are routinely assessed in human sera by sandwich enzyme-linked immunosorbent assay (ELISA). Although sAxl values are suggested to diagnose different types of disorders, no uniform ELISA method is available, allowing the reliable interassay comparison between results. Furthermore, little is known about the stability of sAxl under storage conditions, which is a relevant parameter for biomedical trials. The evaluation of sAxl stability under various stress conditions and the determination of proper conditions to use the sAxl ELISA for routine clinical applications are of great interest. In this study, serum samples were subjected to freeze-thaw cycles and incubation at different temperatures to analyze the stability of sAxl by ELISA. Dilution and spike-in experiments were carried out to examine the impact of serum and diluent components on the ELISA performance. Various diluents and media were employed to resolve masking effects of the serum. The assay components were further optimized for long-term usability by treatment with stabilizers and validation under temperature stress. Indeed, sAxl showed long-term stability in serum during freeze-thaw cycles and incubation under temperature stress conditions. The dilution experiments revealed that unknown components in the serum caused masking effects that can be reduced by proper dilutions. The assay performance was further increased by using a standardized buffer system to dilute serum samples. Stabilization of coated plates and of streptavidin-horseradish peroxidase allowed long-term storage for up to 6 months. In sum, our data demonstrate proper ELISA conditions, allowing the accurate analysis of sAxl levels in human serum.
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Affiliation(s)
- Mirko Dengler
- 1 Department of Medicine I, Division: Institute of Cancer Research, Comprehensive Cancer Center Vienna, Medical University of Vienna , Vienna, Austria
| | - Heidemarie Huber
- 1 Department of Medicine I, Division: Institute of Cancer Research, Comprehensive Cancer Center Vienna, Medical University of Vienna , Vienna, Austria
| | - Christian J Müller
- 2 Division of Gastroenterology and Hepatology, Department of Internal Medicine III, Medical University of Vienna , Vienna, Austria
| | | | - Peter Rauch
- 3 Candor Bioscience GmbH , Wangen im Allgäu, Germany
| | - Wolfgang Mikulits
- 1 Department of Medicine I, Division: Institute of Cancer Research, Comprehensive Cancer Center Vienna, Medical University of Vienna , Vienna, Austria
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15
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Analysis of receptor tyrosine kinase genetics identifies two novel risk loci in GAS6 and PROS1 in Behçet's disease. Sci Rep 2016; 6:26662. [PMID: 27222359 PMCID: PMC4879572 DOI: 10.1038/srep26662] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2016] [Accepted: 04/29/2016] [Indexed: 12/23/2022] Open
Abstract
The TAM kinase (Tyro3, Axl, Mer) and its two ligands (Gas6 and protein S) have been shown to play an important regulatory role in the innate immune response. The present study aimed to investigate whether the tag single-nucleotide polymorphisms (tag SNPs) of these 5 protein-coding genes are associated with Behçet’s disease (BD). A two-stage association study was performed in a total of 907 BD patients and 1780 healthy controls. Altogether 32 polymorphisms were tested, using a Sequenom MassARRAY genotyping method in the first stage and a PCR-restriction fragment length polymorphism (PCR-RFLP) assay in the replication phase. Real-time PCR was performed to test the relative mRNA expression level of GAS6 and PROS1 from different SNP genotyped healthy individuals. The frequency of the C allele and CC genotype of rs9577873 in GAS6 (Pc = 4.92 × 10−5, Pc = 1.91 × 10−5, respectively) and A allele and AA genotype of rs4857037 in PROS1 (Pc = 1.85 × 10−6, Pc = 4.52 × 10−7, respectively) were significantly increased in BD. GAS6 expression in CC carriers of rs9577873 was significantly lower than that in CT/TT individuals (P = 0.001). Decreased expression of GAS6 and increased pro-inflammatory cytokines (IL-6 and IFN-γ: P = 4.23 × 10−4, P = 0.011, respectively) in individuals carrying the CC genotype suggest that the TAM-GAS6/PROS1 signal pathway may be involved in the pathogenesis of BD.
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Chen CH, Chen HC, Chang CC, Peng YJ, Lee CH, Shieh YS, Hung YJ, Lin YF. Growth Arrest-Specific 6 Protein in Patients with Sjögren Syndrome: Determination of the Plasma Level and Expression in the Labial Salivary Gland. PLoS One 2015; 10:e0139955. [PMID: 26445266 PMCID: PMC4596882 DOI: 10.1371/journal.pone.0139955] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2015] [Accepted: 09/18/2015] [Indexed: 01/21/2023] Open
Abstract
Aims Growth arrest-specific protein 6 (Gas6) is a vitamin K-dependent protein expressed by endothelial cells and leukocytes that are involved in cell survival, migration, and proliferation in response to inflammatory processes. The aim of this study was to assess the implications of Gas6 in Sjögren syndrome (SS) and its expression in the labial salivary gland. Methods and Results A total of 254 adults, including 159 with primary Sjögren syndrome (pSS), 34 with secondary Sjögren syndrome (sSS), and 61 normal controls, were recruited. Plasma Gas6 concentrations were determined, and Gas6 expressions in labial salivary gland (LSG) tissues from controls and pSS and sSS patients were also evaluated. Plasma Gas6 concentrations were significantly lower among patients with pSS than normal controls (13.5 ± 8.6 vs. 19.9 ± 13.4 ng/ml, p < 0.001). There were, however, no significant differences in plasma Gas6 levels between pSS and sSS patients (13.5 ± 8.6 vs. 16.9 ± 11.2 ng/ml, p = 0.068). In multivariate logistic regression analysis, after adjustment for white blood cell count, hemoglobin level, platelet count, lymphocyte count, and C3 and C4 levels, lower plasma Gas6 concentrations were significantly associated with an increased risk of SS. Moreover, by using a semi-quantitative scale to evaluate Gas6 expression in LSG tissues, Gas6 expression was found to be markedly lower in LSG tissues from pSS patients than in tissues from normal controls. Conclusions Decreased plasma Gas6 concentration and LSG expression were associated with pSS. As such, Gas6 may represent a novel independent risk factor for pSS, with a potential role in salivary gland inflammation and dysfunction.
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Affiliation(s)
- Chen-Hung Chen
- Graduate Institute of Clinical Medicine, Taipei Medical University, Taipei, Taiwan
- Division of Rheumatology, Immunology and Allergy, Department of Internal Medicine, Taipei Tzu Chi Hospital, Buddhist Tzu Chi Medical Foundation, School of Medicine, Tzu Chi University, Hualien, Taiwan
- Division of Rheumatology, Immunology and Allergy, Department of Internal Medicine, Tri-Service General Hospital, National Defense Medical Center, Taipei, Taiwan
| | - Hsiang-Cheng Chen
- Division of Rheumatology, Immunology and Allergy, Department of Internal Medicine, Tri-Service General Hospital, National Defense Medical Center, Taipei, Taiwan
| | - Chi-Ching Chang
- Graduate Institute of Clinical Medicine, Taipei Medical University, Taipei, Taiwan
- Division of Rheumatology, Immunology and Allergy, Department of Internal Medicine, Taipei Medical University Hospital, Taipei, Taiwan
| | - Yi-Jen Peng
- Department of Pathology, Tri-Service General Hospital, National Defense Medical Center, Taipei, Taiwan
| | - Chien-Hsing Lee
- Division of Endocrinology and Metabolism, Department of Internal Medicine, Tri-Service General Hospital, National Defense Medical Center, Taipei, Taiwan
| | - Yi-Shing Shieh
- School of Dentistry, National Defense Medical Center, Department of Oral Diagnosis and Pathology, Tri-Service General Hospital, Taipei, Taiwan
| | - Yi-Jen Hung
- Division of Endocrinology and Metabolism, Department of Internal Medicine, Tri-Service General Hospital, National Defense Medical Center, Taipei, Taiwan
| | - Yuh-Feng Lin
- Graduate Institute of Clinical Medicine, Taipei Medical University, Taipei, Taiwan
- Division of Nephrology, Department of Medicine, Shuang Ho Hospital, Taipei Medical University, New Taipei City, Taiwan
- * E-mail:
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17
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Targeted GAS6 delivery to the CNS protects axons from damage during experimental autoimmune encephalomyelitis. J Neurosci 2015; 34:16320-35. [PMID: 25471571 DOI: 10.1523/jneurosci.2449-14.2014] [Citation(s) in RCA: 41] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Growth arrest-specific protein 6 (GAS6) is a soluble agonist of the TYRO3, AXL, MERTK (TAM) family of receptor tyrosine kinases identified to have anti-inflammatory, neuroprotective, and promyelinating properties. During experimental autoimmune encephalomyelitis (EAE), wild-type (WT) mice demonstrate a significant induction of Gas6, Axl, and Mertk but not Pros1 or Tyro3 mRNA. We tested the hypothesis that intracerebroventricular delivery of GAS6 directly into the CNS of WT mice during myelin oligodendrocyte glycoprotein (MOG)-induced EAE would improve the clinical course of disease relative to artificial CSF (ACSF)-treated mice. GAS6 did not delay disease onset, but significantly reduced the clinical scores during peak and chronic EAE. Mice receiving GAS6 for 28 d had preserved SMI31(+) neurofilament immunoreactivity, significantly fewer SMI32(+) axonal swellings and spheroids and less demyelination relative to ACSF-treated mice. Alternate-day subcutaneous IFNβ injection did not enhance GAS6 treatment effectiveness. Gas6(-/-) mice sensitized with MOG35-55 peptide exhibit higher clinical scores during late peak to early chronic disease, with significantly increased SMI32(+) axonal swellings and Iba1(+) microglia/macrophages, enhanced expression of several proinflammatory mRNA molecules, and decreased expression of early oligodendrocyte maturation markers relative to WT mouse spinal cords with scores for 8 consecutive days. During acute EAE, flow cytometry showed significantly more macrophages but not T-cell infiltrates in Gas6(-/-) spinal cords than WT spinal cords. Our data are consistent with GAS6 being protective during EAE by dampening the inflammatory response, thereby preserving axonal integrity and myelination.
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