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Fujimura S, Higuchi Y, Usami Y, Yamaura M, Higuchi T, Terasawa F, Okumura N. Changes in serum citrullinated fibrinogen concentration associated with the phase of bacteremia patients. Clin Chim Acta 2020; 512:127-134. [PMID: 33159950 DOI: 10.1016/j.cca.2020.10.038] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2020] [Revised: 10/20/2020] [Accepted: 10/30/2020] [Indexed: 11/17/2022]
Abstract
BACKGROUND Citrullinated fibrinogen (C-Fbg) has been detected in rheumatoid arthritis; however, few studies have reported the role of C-Fbg in other inflammatory diseases. This study aimed to clarify the changes in serum C-Fbg associated with the bacteremia phase. METHODS We measured serum C-Fbg concentration in bacteremia patients. C-Fbg levels at each phase of bacteremia, classified by white blood cell (WBC) count and neutrophil left shift change, were compared with those of healthy control (HC). The correlation between C-Fbg concentration and certain inflammatory markers, or citrullinated histone H3 concentration was assessed. Multiple linear regression (MLR) analysis was used to examine the association of log C-Fbg with certain inflammatory markers. RESULT Serum C-Fbg levels were significantly higher in bacteremia patients than in HC (p < 0.001) and positively correlated with WBC and neutrophil count. Further, C-Fbg levels were significantly higher in phases III and IV of bacteremia than in HC (p < 0.001). MLR analysis indicated that log C-Fbg had a stronger relationship with log neutrophil counts than other certain inflammatory markers (p < 0.01). CONCLUSION Serum C-Fbg levels increased in bacteremia patients, and this was consistent with an influx of neutrophils into the blood stream in accordance with the bacteremia phase.
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Affiliation(s)
- Satoshi Fujimura
- Department of Health and Medical Sciences, Graduate School of Medicine, Shinshu University, Matsumoto, Japan
| | - Yumiko Higuchi
- Department of Health and Medical Sciences, Graduate School of Medicine, Shinshu University, Matsumoto, Japan; Department of Biomedical Laboratory Sciences, Shinshu University School of Medicine, Matsumoto, Japan.
| | - Yoko Usami
- Department of Laboratory Medicine, Shinshu University Hospital, Matsumoto, Japan
| | - Makoto Yamaura
- Department of Health and Medical Sciences, Graduate School of Medicine, Shinshu University, Matsumoto, Japan; Department of Laboratory Medicine, Shinshu University Hospital, Matsumoto, Japan
| | - Tsukasa Higuchi
- Department of General Pediatrics, Nagano Children's Hospital, Azumino, Japan
| | - Fumiko Terasawa
- Faculty of Health and Medical Sciences, Department of Medical Technology and Clinical Engineering, Hokuriku University, Kanazawa, Japan
| | - Nobuo Okumura
- Department of Health and Medical Sciences, Graduate School of Medicine, Shinshu University, Matsumoto, Japan; Department of Biomedical Laboratory Sciences, Shinshu University School of Medicine, Matsumoto, Japan
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52
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Tian Y, Qu S, Alam HB, Williams AM, Wu Z, Deng Q, Pan B, Zhou J, Liu B, Duan X, Ma J, Mondal S, Thompson PR, Stringer KA, Standiford TJ, Li Y. Peptidylarginine deiminase 2 has potential as both a biomarker and therapeutic target of sepsis. JCI Insight 2020; 5:138873. [PMID: 33055424 PMCID: PMC7605547 DOI: 10.1172/jci.insight.138873] [Citation(s) in RCA: 27] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2020] [Accepted: 09/09/2020] [Indexed: 12/12/2022] Open
Abstract
Peptidylarginine deiminases (PADs) are a family of calcium-dependent enzymes that are involved in a variety of human disorders, including cancer and autoimmune diseases. Although targeting PAD4 has shown no benefit in sepsis, the role of PAD2 remains unknown. Here, we report that PAD2 is engaged in sepsis and sepsis-induced acute lung injury in both human patients and mice. Pad2–/– or selective inhibition of PAD2 by a small molecule inhibitor increased survival and improved overall outcomes in mouse models of sepsis. Pad2 deficiency decreased neutrophil extracellular trap (NET) formation. Importantly, Pad2 deficiency inhibited Caspase-11–dependent pyroptosis in vivo and in vitro. Suppression of PAD2 expression reduced inflammation and increased macrophage bactericidal activity. In contrast to Pad2–/–, Pad4 deficiency enhanced activation of Caspase-11–dependent pyroptosis in BM-derived macrophages and displayed no survival improvement in a mouse sepsis model. Collectively, our findings highlight the potential of PAD2 as an indicative marker and therapeutic target for sepsis. Peptidylarginine deiminases 2 (PAD2) regulates neutrophil extracellular trap (NET) formation in sepsis and sepsis-induced acute lung injury.
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Affiliation(s)
- Yuzi Tian
- Department of Rheumatology and Immunology, Xiangya Hospital, Central South University, Changsha, Hunan, China.,Department of Surgery, University of Michigan Health System, Ann Arbor, Michigan, USA
| | - Shibin Qu
- Department of Surgery, University of Michigan Health System, Ann Arbor, Michigan, USA.,Department of Hepatobiliary Surgery, Xijing Hospital, Xian, Shanxi, China
| | - Hasan B Alam
- Department of Surgery, University of Michigan Health System, Ann Arbor, Michigan, USA
| | - Aaron M Williams
- Department of Surgery, University of Michigan Health System, Ann Arbor, Michigan, USA
| | - Zhenyu Wu
- Department of Surgery, University of Michigan Health System, Ann Arbor, Michigan, USA.,Department of Infectious Disease, Second Xiangya Hospital, Central South University, Changsha, Hunan, China
| | - Qiufang Deng
- Department of Rheumatology and Immunology, Xiangya Hospital, Central South University, Changsha, Hunan, China.,Department of Surgery, University of Michigan Health System, Ann Arbor, Michigan, USA
| | - Baihong Pan
- Department of Rheumatology and Immunology, Xiangya Hospital, Central South University, Changsha, Hunan, China.,Department of Surgery, University of Michigan Health System, Ann Arbor, Michigan, USA
| | - Jing Zhou
- Department of Surgery, University of Michigan Health System, Ann Arbor, Michigan, USA.,Trauma Center, Department of Orthopedic and Traumatology, Peking University People's Hospital, Beijing, China
| | - Baoling Liu
- Department of Surgery, University of Michigan Health System, Ann Arbor, Michigan, USA
| | - Xiuzhen Duan
- Department of Pathology, Loyola University Medical Center, Maywood, Illinois, USA
| | - Jianjie Ma
- Department of Surgery, Davis Heart and Lung Research Institute, The Ohio State University, Columbus, Ohio, USA
| | - Santanu Mondal
- Department of Biochemistry and Molecular Pharmacology, University of Massachusetts Medical School, Worcester, Massachusetts, USA
| | - Paul R Thompson
- Department of Biochemistry and Molecular Pharmacology, University of Massachusetts Medical School, Worcester, Massachusetts, USA
| | - Kathleen A Stringer
- Department of Clinical Pharmacy, College of Pharmacy, University of Michigan, Ann Arbor, Michigan, USA.,Division of Pulmonary and Critical Care Medicine, Department of Internal Medicine, University of Michigan Medical Center, Ann Arbor, Michigan, USA
| | - Theodore J Standiford
- Division of Pulmonary and Critical Care Medicine, Department of Internal Medicine, University of Michigan Medical Center, Ann Arbor, Michigan, USA
| | - Yongqing Li
- Department of Surgery, University of Michigan Health System, Ann Arbor, Michigan, USA
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53
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Hefton A, Liang SY, Ni K, Carter V, Ukadike K, Lood C, Mustelin T. Autoantibodies against citrullinated serum albumin in patients with rheumatoid arthritis. J Transl Autoimmun 2020; 2:100023. [PMID: 32743509 PMCID: PMC7388351 DOI: 10.1016/j.jtauto.2019.100023] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2019] [Accepted: 11/04/2019] [Indexed: 11/27/2022] Open
Abstract
Rheumatoid arthritis (RA) is a chronic, potentially debilitating, inflammatory disease that primarily affects synovial joints. While the etiology of RA remains incompletely understood, it is clear that the disease is autoimmune in nature. A hallmark of RA is that the specific epitopes on self-antigens that are targeted by the immune system are often modified by arginine deimination, also referred to as citrullination. In fact, anti-citrullinated protein autoantibodies (ACPA) at high enough titers are diagnostic of RA and appear to have many different targets. Here, we report that RA patients have IgG autoantibodies that react with human serum albumin (HSA) when it had been citrullinated by protein arginine deiminase (PAD) 4, but not by PAD2. Unmodified albumin was not recognized by autoantibodies. In a cohort of 79 RA patients, 38% had anti-citrullinated HSA (anti-cit-HSA) reactivity above the cut-off of the average plus two standard deviations in a healthy subject cohort (n = 16). The titers of these autoantibodies correlated with ACPA status and seropositivity. There was also a trend toward correlation with the presence of radiographic joint erosions, but this did not reach statistical significance. Finally, patients with anti-cit-HSA were more frequently treated with biologics and combination regimens than patients without these autoantibodies. We conclude that ACPA directed against citrullinated albumin exist in a subset of RA patients. Because of the abundance of albumin, its modification by citrullination, as well as autoantibodies binding to it, may have deleterious consequences for the health of affected RA patients. Novel autoantigen in rheumatoid arthritis: citrullinated serum albumin. Anti-citrullinated albumin IgG autoantibodies correlate with clinical parameters. Even a low stoichiometry citrullination of the very abundant albumin may have health consequences. Use of poly(Gly, Lys, Tyr) for blocking to detect citrullinated proteins without high background.
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Affiliation(s)
- Amanda Hefton
- Division of Rheumatology, Department of Medicines, University of Washington, 750 Republican Street, Room E507, Seattle, WA 99108, United States
| | - Shu Ying Liang
- Division of Rheumatology, Department of Medicines, University of Washington, 750 Republican Street, Room E507, Seattle, WA 99108, United States
| | - Kathryn Ni
- Division of Rheumatology, Department of Medicines, University of Washington, 750 Republican Street, Room E507, Seattle, WA 99108, United States
| | - Victoria Carter
- Division of Rheumatology, Department of Medicines, University of Washington, 750 Republican Street, Room E507, Seattle, WA 99108, United States
| | - Kennedy Ukadike
- Division of Rheumatology, Department of Medicines, University of Washington, 750 Republican Street, Room E507, Seattle, WA 99108, United States
| | - Christian Lood
- Division of Rheumatology, Department of Medicines, University of Washington, 750 Republican Street, Room E507, Seattle, WA 99108, United States
| | - Tomas Mustelin
- Division of Rheumatology, Department of Medicines, University of Washington, 750 Republican Street, Room E507, Seattle, WA 99108, United States
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54
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Locke M, Francis RJ, Tsaousi E, Longstaff C. Fibrinogen protects neutrophils from the cytotoxic effects of histones and delays neutrophil extracellular trap formation induced by ionomycin. Sci Rep 2020; 10:11694. [PMID: 32678135 PMCID: PMC7366688 DOI: 10.1038/s41598-020-68584-0] [Citation(s) in RCA: 22] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2019] [Accepted: 03/30/2020] [Indexed: 12/27/2022] Open
Abstract
Neutrophils are pivotal players in immune defence which includes a process of release of histones and DNA as neutrophil extracellular traps (NETs). Histones, while toxic to invading pathogens, also kill host cells, including neutrophils. Bacteria have evolved mechanisms to escape neutrophils, including the secretion of leucocidins (e.g. ionomycin). Live cell video microscopy showed how fibrinogen and fibrin influence NETosis and neutrophil responses to extracellular histones. Histones were rapidly lethal to neutrophils after binding to cells, but formation of fibrinogen/fibrin-histone aggregates prevented cell death. Histone cytotoxicity was also reduced by citrullination by peptidyl arginine deiminase 4, or digestion by serine proteases. Ionomycin and phorbol 12-myristate 13 acetate (PMA) are used to trigger NETosis. Fibrinogen was responsible for a second distinct mechanism of neutrophil protection after treatment with ionomycin. Fibrinogen clustered on the surface of ionomycin-stimulated neutrophils to delay NETosis; and blocking the β integrin receptor, αMβ2, abolished fibrinogen protection. Fibrinogen did not bind to or protect neutrophils stimulated with PMA. Fibrinogen is an acute phase protein that will protect exposed cells from damaging circulating histones or leucocidins; but fibrinogen depletion/consumption, as in trauma or sepsis will reduce protection. It is necessary to consider the role of fibrinogen in NETosis.
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Affiliation(s)
- Matthew Locke
- Biotherapeutics, National Institute for Biological Standards and Control, S Mimms, Herts, UK
| | - Robert J Francis
- Biological Imaging Group, Analytical Biological Sciences, National Institute for Biological Standards and Control, S Mimms, Herts, UK
| | - Evgenia Tsaousi
- Biotherapeutics, National Institute for Biological Standards and Control, S Mimms, Herts, UK.,School of Biological Sciences, University of Essex, Colchester, UK
| | - Colin Longstaff
- Biotherapeutics, National Institute for Biological Standards and Control, S Mimms, Herts, UK.
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Generation of Monoclonal Antibodies Specific for Native LL37 and Citrullinated LL37 That Discriminate the Two LL37 Forms in the Skin and Circulation of Cutaneous/Systemic Lupus Erythematosus and Rheumatoid Arthritis Patients. Antibodies (Basel) 2020; 9:antib9020014. [PMID: 32403306 PMCID: PMC7345132 DOI: 10.3390/antib9020014] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2020] [Revised: 04/25/2020] [Accepted: 04/30/2020] [Indexed: 12/22/2022] Open
Abstract
Human cathelicidin LL37 is a cationic antimicrobial peptide active against bacteria and viruses and exerting immune modulatory functions. LL37 can be also a target of autoreactive B- and T-lymphocytes in autoimmune settings. Irreversible post-translational modifications, such as citrullination and carbamylation, mainly occurring at the level of cationic amino acids arginine and lysine, can affect the inflammatory properties and reduce antibacterial effects. Moreover, these modifications could be implicated in the rupture of immune tolerance to LL37 in chronic conditions such as psoriatic disease and cutaneous lupus (LE)/systemic lupus erythematosus (SLE). Here, we describe the generation and fine specificity of six recombinant antibodies (MRB137–MRB142), produced as a monovalent mouse antibody with the antigen-binding scFv portion fused to a mouse IgG2a Fc, and their ability to recognize either native or citrullinated LL37 (cit-LL37) and not cross-react to carbamylated LL37. By using these antibodies, we detected native LL37 or cit-LL37 in SLE and rheumatoid arthritis (RA) sera, and in LE skin, by ELISA and immunohistochemistry, respectively. Such antibodies represent previously unavailable and useful tools to address relationships between the presence of post-translational modified LL37 and the immune system status (in terms of innate/adaptive responses activation) and the clinical characteristics of patients affected by chronic immune-mediated diseases or infectious diseases.
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56
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Opdenakker G, Abu El-Asrar A, Van Damme J. Remnant Epitopes Generating Autoimmunity: From Model to Useful Paradigm. Trends Immunol 2020; 41:367-378. [PMID: 32299652 DOI: 10.1016/j.it.2020.03.004] [Citation(s) in RCA: 25] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2019] [Revised: 03/09/2020] [Accepted: 03/09/2020] [Indexed: 12/19/2022]
Abstract
Autoimmune diseases are defined as pathologies of adaptive immunity by the presence of autoantibodies or MHC-restricted autoantigen-reactive T cells. Because autoreactivity is a normal process based on mechanisms producing repertoires of antibodies and T cell receptors, crucial questions about disease mechanisms and key steps for interference have been outstanding. We defined 25 years ago the 'remnant epitopes generate autoimmunity' (REGA)-model in which extracellular proteases from innate immune cells generate autoantigens. Here, we refine the REGA-model, tested in diseases ranging from organ-specific autoimmune diseases to systemic lupus erythematosus. It now constitutes a paradigm in which remnant epitopes generate, maintain, and regulate autoimmunity; are dependent on genetic and epigenetic influences; are produced in a disease phase-specific manner; and have therapeutic implications when targeted.
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Affiliation(s)
- Ghislain Opdenakker
- Laboratory of Immunobiology, Department of Microbiology and Immunology, Rega Institute for Medical Research, KU Leuven, University of Leuven, Leuven, Belgium.
| | - Ahmed Abu El-Asrar
- Laboratory of Immunobiology, Department of Microbiology and Immunology, Rega Institute for Medical Research, KU Leuven, University of Leuven, Leuven, Belgium; Laboratory of Molecular Immunology, Department of Microbiology and Immunology, Rega Institute for Medical Research, KU Leuven, University of Leuven, Leuven, Belgium
| | - Jo Van Damme
- Laboratory of Molecular Immunology, Department of Microbiology and Immunology, Rega Institute for Medical Research, KU Leuven, University of Leuven, Leuven, Belgium
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57
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Curran AM, Naik P, Giles JT, Darrah E. PAD enzymes in rheumatoid arthritis: pathogenic effectors and autoimmune targets. Nat Rev Rheumatol 2020; 16:301-315. [PMID: 32341463 DOI: 10.1038/s41584-020-0409-1] [Citation(s) in RCA: 79] [Impact Index Per Article: 19.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 03/12/2020] [Indexed: 12/11/2022]
Abstract
Peptidylarginine deiminases (PADs) have an important role in the pathogenesis of rheumatoid arthritis (RA) owing to their ability to generate citrullinated proteins - the hallmark autoantigens of RA. Of the five PAD enzyme isoforms, PAD2 and PAD4 are the most strongly implicated in RA at both genetic and cellular levels, and PAD inhibitors have shown therapeutic efficacy in mouse models of inflammatory arthritis. PAD2 and PAD4 are additionally targeted by autoantibodies in distinct clinical subsets of patients with RA, suggesting anti-PAD antibodies as possible biomarkers for RA diagnosis and prognosis. This Review weighs the evidence that supports a pathogenic role for PAD enzymes in RA as both promoters and targets of the autoimmune response, as well as discussing the mechanistic and therapeutic implications of these findings in the wider context of RA pathogenesis. Understanding the origin and consequences of dysregulated PAD enzyme activity and immune responses against PAD enzymes will be important to fully comprehend the pathogenic mechanisms involved in this disease and for the development of novel strategies to treat and prevent RA.
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Affiliation(s)
- Ashley M Curran
- Division of Rheumatology, Johns Hopkins University School of Medicine, Baltimore, MD, USA
| | - Pooja Naik
- Division of Rheumatology, Johns Hopkins University School of Medicine, Baltimore, MD, USA
| | - Jon T Giles
- Division of Rheumatology, Columbia University Vagelos College of Physicians & Surgeons, New York, NY, USA
| | - Erika Darrah
- Division of Rheumatology, Johns Hopkins University School of Medicine, Baltimore, MD, USA.
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58
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Romero V, Darrah E, Andrade F. Generation of Distinct Patterns of Rheumatoid Arthritis Autoantigens by Peptidylarginine Deiminase Types 2 and 4 During Perforin-Induced Cell Damage. Arthritis Rheumatol 2020; 72:912-918. [PMID: 31876120 DOI: 10.1002/art.41196] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2019] [Accepted: 12/19/2019] [Indexed: 12/14/2022]
Abstract
OBJECTIVE To address the independent roles of peptidylarginine deiminase type 2 (PAD2) and PAD4 in generating rheumatoid arthritis (RA) autoantigens by using a system that mimics intracellular citrullination in the RA joint. METHODS PAD2- or PAD4-expressing 293T cells and mock-transfected cells were used as targets in cytotoxic assays using lymphokine-activated killer cells, cytotoxic YT cell granule contents, or purified human perforin. Protein citrullination and autoantigen production were determined by immunoblotting using the anti-modified citrulline-Senshu method and RA sera (n = 30), respectively. RESULTS RA sera recognized at least 3 categories of autoantigens in PAD-expressing target cells killed by the cytotoxic lymphocyte granule-induced death pathway. These included: 1) autoantigens targeted in their native form, 2) citrullinated antigens, and 3) antigens cleaved by cytotoxic proteases (e.g., granzymes). Interestingly, although target cells expressing PAD2 or PAD4 showed prominent hypercitrullination of a broad range of proteins during cytotoxic granule-induced cell damage, autoantibodies in RA sera targeted only a very limited number of antigens in hypercitrullinated cells. Furthermore, RA sera showed distinct reactivities to autoantigens generated by PAD2 or PAD4. CONCLUSION The cytotoxic granule-induced death pathway has the capacity to modify antigens by inducing hypercitrullination and antigen cleavage in target cells. Interestingly, among a large number of citrullinated proteins generated by PAD2 and PAD4 in cells, only a few are likely involved in the production of autoantibodies in RA.
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Affiliation(s)
- Violeta Romero
- The Johns Hopkins University School of Medicine, Baltimore, Maryland
| | - Erika Darrah
- The Johns Hopkins University School of Medicine, Baltimore, Maryland
| | - Felipe Andrade
- The Johns Hopkins University School of Medicine, Baltimore, Maryland
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59
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Native/citrullinated LL37-specific T-cells help autoantibody production in Systemic Lupus Erythematosus. Sci Rep 2020; 10:5851. [PMID: 32245990 PMCID: PMC7125190 DOI: 10.1038/s41598-020-62480-3] [Citation(s) in RCA: 22] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2020] [Accepted: 03/12/2020] [Indexed: 01/05/2023] Open
Abstract
LL37 exerts a dual pathogenic role in psoriasis. Bound to self-DNA/RNA, LL37 licenses autoreactivity by stimulating plasmacytoid dendritic cells-(pDCs)-Type I interferon (IFN-I) and acts as autoantigen for pathogenic Th17-cells. In systemic lupus erythematosus (SLE), LL37 also triggers IFN-I in pDCs and is target of pathogenic autoantibodies. However, whether LL37 activates T-cells in SLE and how the latter differ from psoriasis LL37-specific T-cells is unknown. Here we found that 45% SLE patients had circulating T-cells strongly responding to LL37, which correlate with anti-LL37 antibodies/disease activity. In contrast to psoriatic Th17-cells, these LL37-specific SLE T-cells displayed a T-follicular helper-(TFH)-like phenotype, with CXCR5/Bcl-6 and IL-21 expression, implicating a role in stimulation of pathogenic autoantibodies. Accordingly, SLE LL37-specific T-cells promoted B-cell secretion of pathogenic anti-LL37 antibodies in vitro. Importantly, we identified abundant citrullinated LL37 (cit-LL37) in SLE tissues (skin and kidney) and observed very pronounced reactivity of LL37-specific SLE T-cells to cit-LL37, compared to native-LL37, which was much more occasional in psoriasis. Thus, in SLE, we identified LL37-specific T-cells with a distinct functional specialization and antigenic specificity. This suggests that autoantigenic specificity is independent from the nature of the autoantigen, but rather relies on the disease-specific milieu driving T-cell subset polarization and autoantigen modifications.
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60
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Al-Adwani S, Wallin C, Balhuizen MD, Veldhuizen EJA, Coorens M, Landreh M, Végvári Á, Smith ME, Qvarfordt I, Lindén A, Gräslund A, Agerberth B, Bergman P. Studies on citrullinated LL-37: detection in human airways, antibacterial effects and biophysical properties. Sci Rep 2020; 10:2376. [PMID: 32047184 PMCID: PMC7012854 DOI: 10.1038/s41598-020-59071-7] [Citation(s) in RCA: 19] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2019] [Accepted: 01/23/2020] [Indexed: 11/09/2022] Open
Abstract
Arginine residues of the antimicrobial peptide LL-37 can be citrullinated by peptidyl arginine deiminases, which reduce the positive charge of the peptide. Notably, citrullinated LL-37 has not yet been detected in human samples. In addition, functional and biophysical properties of citrullinated LL-37 are not fully explored. The aim of this study was to detect citrullinated LL-37 in human bronchoalveolar lavage (BAL) fluid and to determine antibacterial and biophysical properties of citrullinated LL-37. BAL fluid was obtained from healthy human volunteers after intra-bronchial exposure to lipopolysaccharide. Synthetic peptides were used for bacterial killing assays, transmission electron microscopy, isothermal titration calorimetry, mass-spectrometry and circular dichroism. Using targeted proteomics, we were able to detect both native and citrullinated LL-37 in BAL fluid. The citrullinated peptide did not kill Escherichia coli nor lysed human red blood cells. Both peptides had similar α-helical secondary structures but citrullinated LL-37 was more stable at higher temperatures, as shown by circular dichroism. In conclusion, citrullinated LL-37 is present in the human airways and citrullination impaired bacterial killing, indicating that a net positive charge is important for antibacterial and membrane lysing effects. It is possible that citrullination serves as a homeostatic regulator of AMP-function by alteration of key functions.
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Affiliation(s)
- Salma Al-Adwani
- Department of Laboratory Medicine, Division of Clinical Microbiology, Karolinska Institutet, Stockholm, Sweden.,Department of Animal and Veterinary Sciences, College of Agricultural and Marine Sciences, Sultan Qaboos University, Muscat, Oman
| | - Cecilia Wallin
- Department of Biochemistry and Biophysics, Stockholm University, Stockholm, Sweden
| | - Melanie D Balhuizen
- Department of Infectious Diseases and Immunology, Division of Molecular Host Defence, Faculty of Veterinary Medicine, Utrecht University, Utrecht, The Netherlands
| | - Edwin J A Veldhuizen
- Department of Infectious Diseases and Immunology, Division of Molecular Host Defence, Faculty of Veterinary Medicine, Utrecht University, Utrecht, The Netherlands
| | - Maarten Coorens
- Department of Laboratory Medicine, Division of Clinical Microbiology, Karolinska Institutet, Stockholm, Sweden
| | - Michael Landreh
- Department of Microbiology, Tumor and Cell Biology, Karolinska Institutet, Stockholm, Sweden
| | - Ákos Végvári
- Division of Physiological Chemistry I, Department of Medical Biochemistry & Biophysics, Karolinska Institutet, Stockholm, Sweden
| | - Margaretha E Smith
- Department of Internal Medicine and Clinical Nutrition, Institute of Medicine at Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden
| | - Ingemar Qvarfordt
- Department of Internal Medicine and Clinical Nutrition, Institute of Medicine at Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden
| | - Anders Lindén
- Unit for Lung and Airway Research, Institute of Environmental Medicine, Karolinska Institutet, Stockholm, Sweden.,Department of Respiratory Medicine and Allergy, Karolinska University Hospital, Stockholm, Sweden
| | - Astrid Gräslund
- Department of Biochemistry and Biophysics, Stockholm University, Stockholm, Sweden
| | - Birgitta Agerberth
- Department of Laboratory Medicine, Division of Clinical Microbiology, Karolinska Institutet, Stockholm, Sweden
| | - Peter Bergman
- Department of Laboratory Medicine, Division of Clinical Microbiology, Karolinska Institutet, Stockholm, Sweden. .,Infectious Disease Clinic, Immunodeficiency Unit, Karolinska University Hospital, Stockholm, Sweden.
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61
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Fert-Bober J, Darrah E, Andrade F. Insights into the study and origin of the citrullinome in rheumatoid arthritis. Immunol Rev 2019; 294:133-147. [PMID: 31876028 DOI: 10.1111/imr.12834] [Citation(s) in RCA: 26] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2019] [Accepted: 12/08/2019] [Indexed: 12/11/2022]
Abstract
The presence of autoantibodies and autoreactive T cells to citrullinated proteins and citrullinating enzymes in patients with rheumatoid arthritis (RA), together with the accumulation of citrullinated proteins in rheumatoid joints, provides substantial evidence that dysregulated citrullination is a hallmark feature of RA. However, understanding mechanisms that dysregulate citrullination in RA has important challenges. Citrullination is a normal process in immune and non-immune cells, which is likely activated by different conditions (eg, inflammation) with no pathogenic consequences. In a complex inflammatory environment such as the RA joint, unique strategies are therefore required to dissect specific mechanisms involved in the abnormal production of citrullinated proteins. Here, we will review current models of citrullination in RA and discuss critical components that, in our view, are relevant to understanding the accumulation of citrullinated proteins in the RA joint, collectively referred to as the RA citrullinome. In particular, we will focus on potential caveats in the study of citrullination in RA and will highlight methods to precisely detect citrullinated proteins in complex biological samples, which is a confirmatory approach to mechanistically link the RA citrullinome with unique pathogenic pathways in RA.
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Affiliation(s)
- Justyna Fert-Bober
- The Smidt Heart Institute, Department of Medicine, Cedars-Sinai Medical Center, Los Angeles, California
| | - Erika Darrah
- Division of Rheumatology, The Johns Hopkins University School of Medicine, Baltimore, Maryland
| | - Felipe Andrade
- Division of Rheumatology, The Johns Hopkins University School of Medicine, Baltimore, Maryland
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El Shikh MEM, El Sayed R, Nerviani A, Goldmann K, John CR, Hands R, Fossati-Jimack L, Lewis MJ, Pitzalis C. Extracellular traps and PAD4 released by macrophages induce citrullination and auto-antibody production in autoimmune arthritis. J Autoimmun 2019; 105:102297. [PMID: 31277965 DOI: 10.1016/j.jaut.2019.06.008] [Citation(s) in RCA: 29] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2019] [Revised: 06/20/2019] [Accepted: 06/24/2019] [Indexed: 11/18/2022]
Abstract
The mechanisms underlying the transition of rheumatoid arthritis (RA) systemic autoimmunity to the joints remain largely unknown. Here, we demonstrate that macrophages in the secondary lymphoid organs (SLOs) and synovial ectopic lymphoid-like structures (ELSs) express peptidylarginine deiminase 4 (PAD4) in murine collagen induced arthritis (CIA) and synovial biopsies from RA patients. Moreover, peptidyl citrulline colocalized with macrophages in SLOs and ELSs, and depletion of macrophages in CIA decreased lymphoid tissue citrullination and serum anti-citrullinated protein/peptide antibody (ACPA) levels. Furthermore, PAD was released from activated murine and RA synovial tissue and fluid (SF) macrophages which functionally deiminated extracellular proteins/peptides in vitro. Additionally, activated murine and SF macrophages displayed macrophage extracellular trap formation (METosis) and release of intracellular citrullinated histones. Moreover, presentation of citrullinated proteins induced ACPA production in vitro. Thus, lymphoid tissue macrophages contribute to self-antigen citrullination and ACPA production, indicating that their selective targeting would potentially ameliorate citrullination-dependent autoimmune disorders.
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Affiliation(s)
- Mohey Eldin M El Shikh
- Centre for Experimental Medicine and Rheumatology, William Harvey Research Institute, Barts and The London School of Medicine and Dentistry, Queen Mary University of London, London, EC1M 6BQ, UK
| | - Riham El Sayed
- Centre for Experimental Medicine and Rheumatology, William Harvey Research Institute, Barts and The London School of Medicine and Dentistry, Queen Mary University of London, London, EC1M 6BQ, UK
| | - Alessandra Nerviani
- Centre for Experimental Medicine and Rheumatology, William Harvey Research Institute, Barts and The London School of Medicine and Dentistry, Queen Mary University of London, London, EC1M 6BQ, UK
| | - Katriona Goldmann
- Centre for Experimental Medicine and Rheumatology, William Harvey Research Institute, Barts and The London School of Medicine and Dentistry, Queen Mary University of London, London, EC1M 6BQ, UK
| | - Christopher Robert John
- Centre for Experimental Medicine and Rheumatology, William Harvey Research Institute, Barts and The London School of Medicine and Dentistry, Queen Mary University of London, London, EC1M 6BQ, UK
| | - Rebecca Hands
- Centre for Experimental Medicine and Rheumatology, William Harvey Research Institute, Barts and The London School of Medicine and Dentistry, Queen Mary University of London, London, EC1M 6BQ, UK
| | - Liliane Fossati-Jimack
- Centre for Experimental Medicine and Rheumatology, William Harvey Research Institute, Barts and The London School of Medicine and Dentistry, Queen Mary University of London, London, EC1M 6BQ, UK
| | - Myles J Lewis
- Centre for Experimental Medicine and Rheumatology, William Harvey Research Institute, Barts and The London School of Medicine and Dentistry, Queen Mary University of London, London, EC1M 6BQ, UK
| | - Costantino Pitzalis
- Centre for Experimental Medicine and Rheumatology, William Harvey Research Institute, Barts and The London School of Medicine and Dentistry, Queen Mary University of London, London, EC1M 6BQ, UK.
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63
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Li B, Li P, Bi L. Iguratimod dose dependently inhibits the expression of citrullinated proteins and peptidylarginine deiminases 2 and 4 in neutrophils from rheumatoid arthritis patients. Clin Rheumatol 2019; 39:899-907. [PMID: 31758423 DOI: 10.1007/s10067-019-04835-4] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2019] [Revised: 09/29/2019] [Accepted: 10/31/2019] [Indexed: 11/29/2022]
Abstract
INTRODUCTION Anti-citrullinated protein antibodies (ACPAs) play an important role in rheumatoid arthritis (RA). Citrullinated proteins (CPs), which are produced by post-translational modification via peptidylarginine deiminase (PAD), are the target antigen of ACPAs and promote the generation thereof. Herein, we investigated whether iguratimod (IGU) affects the generation of CPs via PAD. METHODS Neutrophils and peripheral blood mononuclear cells (PBMCs) were isolated from three patients diagnosed with RA and treated with various concentrations of IGU, methotrexate (MTX), or dexamethasone (DXM) or without any drugs as a control for 8 h. The levels of tumor necrosis factor (TNF)-α, interleukin (IL)-1β, IL-6, and IL-8 in culture supernatants were tested by ELISA. CPs were measured by western blot, and the expression of PAD2 and PAD4 in cells was detected by qRT-PCR and western blot. RESULTS PAD2 and PAD4 expressions in neutrophils but not in PBMCs were decreased by IGU at both the protein and mRNA levels (P < 0.05). CP expression in neutrophils but not in PBMCs was also inhibited by IGU. The inhibitory effect of IGU was dose-dependent. IGU, MTX, and DXM dose dependently decreased the secretion of TNF-α, IL-1β, IL-6, and IL-8 in neutrophils and PBMCs (P < 0.05); the inhibitory effect of IGU was not significantly different from that of MTX and DXM. CONCLUSIONS IGU inhibited the expression of CPs by downregulating PADs in neutrophils from RA patients, and the effect was comparable to that of MTX and DXM at appropriate concentrations. These findings may provide guidance for more appropriate treatment of RA.Key Points• Iguratimod inhibited citrullinated protein expression in neutrophils from rheumatoid arthritis patients similarly to methotrexate and dexamethasone at appropriate concentrations.• The inhibitory effect was mediated by downregulation of peptidylarginine deiminases, providing insight into the mechanism of iguratimod as a treatment for rheumatoid arthritis.• This study may guide rheumatoid arthritis treatment and facilitate identification of other therapeutic targets.
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Affiliation(s)
- Bingtong Li
- Department of Rheumatology and Immunology, China-Japan Union Hospital of Jilin University, 126 Xiantai Street, Changchun, 130033, China
| | - Ping Li
- Department of Rheumatology and Immunology, China-Japan Union Hospital of Jilin University, 126 Xiantai Street, Changchun, 130033, China
| | - Liqi Bi
- Department of Rheumatology and Immunology, China-Japan Union Hospital of Jilin University, 126 Xiantai Street, Changchun, 130033, China.
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64
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Martinez-Prat L, Palterer B, Vitiello G, Parronchi P, Robinson WH, Mahler M. Autoantibodies to protein-arginine deiminase (PAD) 4 in rheumatoid arthritis: immunological and clinical significance, and potential for precision medicine. Expert Rev Clin Immunol 2019; 15:1073-1087. [DOI: 10.1080/1744666x.2020.1668778] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Affiliation(s)
- Laura Martinez-Prat
- Research and Development, Inova Diagnostics, San Diego, CA, USA
- Department of Experimental Science, Francisco de Vitoria University, Madrid, Spain
| | - Boaz Palterer
- specialist in Allergy and Clinical Immunology, Experimental and Clinical Medicine Department, University of Florence, Florence, Italy
| | - Gianfranco Vitiello
- resident in Allergy and Clinical Immunology, Experimental and Clinical Medicine Department, University of Florence, Florence, Italy
| | - Paola Parronchi
- (Allergy and Clinical Immunology), Laboratory Head, Experimental and Clinical Medicine Department, University of Florence, Florence, Italy
| | - William H. Robinson
- (Immunology and Rheumatology), Division of Immunology and Rheumatology, Stanford University, Stanford, CA, USA
- Geriatric Research Education and Clinical [GRECC] Division, VA Palo Alto Health Care System, Palo Alto, CA, USA
| | - Michael Mahler
- Research and Development, Inova Diagnostics, San Diego, CA, USA
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65
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Networks that stop the flow: A fresh look at fibrin and neutrophil extracellular traps. Thromb Res 2019; 182:1-11. [DOI: 10.1016/j.thromres.2019.08.003] [Citation(s) in RCA: 23] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2019] [Revised: 07/18/2019] [Accepted: 08/05/2019] [Indexed: 12/23/2022]
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66
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Stefanelli VL, Choudhury S, Hu P, Liu Y, Schwenzer A, Yeh CR, Chambers DM, von Beck K, Li W, Segura T, Midwood KS, Torres M, Barker TH. Citrullination of fibronectin alters integrin clustering and focal adhesion stability promoting stromal cell invasion. Matrix Biol 2019; 82:86-104. [PMID: 31004743 PMCID: PMC7168757 DOI: 10.1016/j.matbio.2019.04.002] [Citation(s) in RCA: 25] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2018] [Revised: 04/15/2019] [Accepted: 04/16/2019] [Indexed: 02/08/2023]
Abstract
The extracellular matrix (ECM) microenvironment is increasingly implicated in the instruction of pathologically relevant cell behaviors, from aberrant transdifferentation to invasion and beyond. Indeed, pathologic ECMs possess a panoply of alterations that provide deleterious instructions to resident cells. Here we demonstrate the precise manner in which the ECM protein fibronectin (FN) undergoes the posttranslational modification citrullination in response to peptidyl-arginine deiminase (PAD), an enzyme associated with innate immune cell activity and implicated in systemic ECM-centric diseases, like cancer, fibrosis and rheumatoid arthritis. FN can be citrullinated in at least 24 locations, 5 of which reside in FN's primary cell-binding domain. Citrullination of FN alters integrin clustering and focal adhesion stability with a concomitant enhancement in force-triggered integrin signaling along the FAK-Src and ILK-Parvin pathways within fibroblasts. In vitro migration and in vivo wound healing studies demonstrate the ability of citrullinated FN to support a more migratory/invasive phenotype that enables more rapid wound closure. These findings highlight the potential of ECM, particularly FN, to "record" inflammatory insults via post-translational modification by inflammation-associated enzymes that are subsequently "read" by resident tissue fibroblasts, establishing a direct link between inflammation and tissue homeostasis and pathogenesis through the matrix.
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Affiliation(s)
| | | | - Ping Hu
- University of Virginia, Charlottesville, VA USA
| | | | | | | | - Dwight M. Chambers
- Georgia Institute of Technology, Atlanta, GA, USA,Emory University, Atlanta GA, USA
| | | | - Wei Li
- Georgia Institute of Technology, Atlanta, GA, USA,University of Virginia, Charlottesville, VA USA
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67
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Affiliation(s)
- Craig N Morrell
- From the Aab Cardiovascular Research Institute (C.N.M., Z.T.H., D.N.P., P.M.), University of Rochester School of Medicine, Box CVRI, NY
- Department of Microbiology and Immunology (C.N.M., D.N.P.), University of Rochester School of Medicine, Box CVRI, NY
| | - Zachary T Hilt
- From the Aab Cardiovascular Research Institute (C.N.M., Z.T.H., D.N.P., P.M.), University of Rochester School of Medicine, Box CVRI, NY
| | - Daphne N Pariser
- From the Aab Cardiovascular Research Institute (C.N.M., Z.T.H., D.N.P., P.M.), University of Rochester School of Medicine, Box CVRI, NY
- Department of Microbiology and Immunology (C.N.M., D.N.P.), University of Rochester School of Medicine, Box CVRI, NY
| | - Preeti Maurya
- From the Aab Cardiovascular Research Institute (C.N.M., Z.T.H., D.N.P., P.M.), University of Rochester School of Medicine, Box CVRI, NY
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68
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Vejlstrup A, Møller AM, Nielsen CH, Damgaard D. Release of active peptidylarginine deiminase into the circulation during acute inflammation induced by coronary artery bypass surgery. J Inflamm Res 2019; 12:137-144. [PMID: 31213874 PMCID: PMC6549760 DOI: 10.2147/jir.s198611] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2018] [Accepted: 03/14/2019] [Indexed: 11/23/2022] Open
Abstract
Purpose: Peptidylarginine deiminase (PAD) catalyzes citrullination, a post-translational modification that can alter structure, function and antigenicity of proteins. Citrullination in the lungs due to smoking is believed to initiate an anti-citrulline immune response in rheumatoid arthritis. Citrullination in other inflamed organs has also been demonstrated, but it is not known whether smoking or inflammatory processes in general result in release of relevant amounts of PAD into the circulation with potential to cause citrullination of proteins at various anatomical sites. Coronary artery bypass grafting (CABG) using cardiopulmonary bypass (CPB) induces an acute systemic inflammation response. In the present study, we investigate whether smoking or acute systemic inflammation causes release of PAD into the circulation. Patients and methods: This study included 36 patients with coronary heart disease (16 smokers and 20 non-smokers) undergoing CABG surgery with CPB. Circulating levels of PAD2 and PAD4, PAD activity, the neutrophil activation markers MPO, MMP-9 and lipocalin-2, the cytokines IL-6 and IL-10, and the chemokine CXCL8 were measured 2 hrs preoperatively and 2 hrs postoperatively. Results: At baseline, serum PAD2 and PAD4 concentration did not differ between smokers and non-smokers. However, serum from non-smokers contained higher PAD activity than serum from smokers. Circulating PAD2 levels and PAD activity increased markedly in both groups after surgery, as did all neutrophil activation markers, cytokines and chemokine. PAD2 levels correlated with neutrophil activation markers, but not with cytokine and chemokine levels. Conclusion: Blood levels of PAD2 did not differ significantly between smokers and non-smokers, but smokers had decreased PAD activity in the circulation. PAD2 levels and PAD activity increased in blood during inflammation induced by CABG with CPB. This suggests that acute inflammation, ischemia or reperfusion, or a combination of these, leads to systemic spreading of enzymatically active PAD, which may affect protein function and induce generation of citrullinated self-antigens.
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Affiliation(s)
- Anne Vejlstrup
- Institute for Inflammation Research, Center for Rheumatology and Spine Diseases, Copenhagen University Hospital, Rigshospitalet, Copenhagen, Denmark
| | | | - Claus Henrik Nielsen
- Institute for Inflammation Research, Center for Rheumatology and Spine Diseases, Copenhagen University Hospital, Rigshospitalet, Copenhagen, Denmark.,Section for Periodontology, Microbiology and Community Dentistry, Department of Odontology, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Dres Damgaard
- Institute for Inflammation Research, Center for Rheumatology and Spine Diseases, Copenhagen University Hospital, Rigshospitalet, Copenhagen, Denmark.,Section for Periodontology, Microbiology and Community Dentistry, Department of Odontology, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
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69
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Kulvinskiene I, Raudoniute J, Bagdonas E, Ciuzas D, Poliakovaite K, Stasiulaitiene I, Zabulyte D, Bironaite D, Rimantas Venskutonis P, Martuzevicius D, Aldonyte R. Lung alveolar tissue destruction and protein citrullination in diesel exhaust-exposed mouse lungs. Basic Clin Pharmacol Toxicol 2019; 125:166-177. [PMID: 30801928 DOI: 10.1111/bcpt.13213] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2018] [Accepted: 02/07/2019] [Indexed: 01/03/2023]
Abstract
Humanity faces an increasing impact of air pollution worldwide, including threats to human health. Air pollutants prompt and promote chronic inflammation, tumourigenesis, autoimmune and other destructive processes in the human body. Post-translational modification of proteins, for example citrullination, results from damaging attacks of pollutants, including smoking, air pollution and others, rendering host tissues immunogenic. Citrullinated proteins and citrullinating enzymes, deiminases, are more prevalent in patients with COPD and correlate with ongoing inflammation and oxidative stress. In this study, we installed an in-house-designed diesel exhaust delivery and cannabidiol vaporization system where mice were exposed to relevant, urban traffic-related levels of diesel exhaust for 14 days and assessed integrity of alveolar tissue, gene expression shifts and changes in protein content in the lungs and other tissues of exposed mice. Systemic presence of modified proteins was also tested. The protective effect of phytocannabinoids was investigated as well. Data obtained in our study show subacute effects of diesel exhaust on mouse lung integrity and protein content. Emphysematous changes are documented in exposed mouse lungs. In parallel, increased levels of citrulline were detected in the alveolar lung tissue and peripheral blood of exposed mice. Pre-treatment with vaporized cannabidiol ameliorated some damaging effects. Results reported hereby provide new insights into subacute lung tissue changes that follow diesel exhaust exposure and suggest possible dietary and/or other therapeutic interventions for maintaining lung health and healthy ageing.
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Affiliation(s)
- Ieva Kulvinskiene
- State Research Institute Center for Innovative Medicine, Vilnius, Lithuania
| | - Jovile Raudoniute
- State Research Institute Center for Innovative Medicine, Vilnius, Lithuania
| | - Edvardas Bagdonas
- State Research Institute Center for Innovative Medicine, Vilnius, Lithuania
| | - Darius Ciuzas
- Department of Environmental Technologies, Kaunas University of Technology, Kaunas, Lithuania
| | | | - Inga Stasiulaitiene
- Department of Environmental Technologies, Kaunas University of Technology, Kaunas, Lithuania
| | - Danguole Zabulyte
- State Research Institute Center for Innovative Medicine, Vilnius, Lithuania
| | - Daiva Bironaite
- State Research Institute Center for Innovative Medicine, Vilnius, Lithuania
| | | | - Dainius Martuzevicius
- Department of Environmental Technologies, Kaunas University of Technology, Kaunas, Lithuania
| | - Ruta Aldonyte
- State Research Institute Center for Innovative Medicine, Vilnius, Lithuania
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70
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Jung N, Bueb JL, Tolle F, Bréchard S. Regulation of neutrophil pro-inflammatory functions sheds new light on the pathogenesis of rheumatoid arthritis. Biochem Pharmacol 2019; 165:170-180. [PMID: 30862503 DOI: 10.1016/j.bcp.2019.03.010] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2019] [Accepted: 03/07/2019] [Indexed: 02/08/2023]
Abstract
For more than two centuries now, rheumatoid arthritis (RA) is under investigation intending to discover successful treatment. Despite decades of scientific advances, RA is still representing a challenge for contemporary medicine. Current drug therapies allow to improve significantly the quality of life of RA patients; however, they are still insufficient to reverse tissue injury and are often generating side-effects. The difficulty arises from the considerable fluctuation of the clinical course of RA among patients, making the predictive prognosis difficult. More and more studies underline the profound influence of the neutrophil multifaceted functions in the pathogenesis of RA. This renewed interest in the complexity of neutrophil functions in RA offers new exciting opportunities for valuable therapeutic targets as well as for safe and well-tolerated RA treatments. In this review, we aim to update the recent findings on the multiple facets of neutrophils in RA, in particular their impact in promoting the RA-based inflammation through the release of the cytokine-like S100A8/A9 protein complex, as well as the importance of NETosis in the disease progression and development. Furthermore, we delve into the complex question of neutrophil heterogeneity and plasticity and discuss the emerging role of miRNAs and epigenetic markers influencing the inflammatory response of neutrophils in RA and how they could constitute the starting point for novel attractive targets in RA therapy.
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Affiliation(s)
- N Jung
- Life Sciences Research Unit, Immune Cells and Inflammatory Diseases group, University of Luxembourg, 6 Avenue du Swing, L-4367 Belvaux, Luxembourg
| | - J-L Bueb
- Life Sciences Research Unit, Immune Cells and Inflammatory Diseases group, University of Luxembourg, 6 Avenue du Swing, L-4367 Belvaux, Luxembourg
| | - F Tolle
- Life Sciences Research Unit, Immune Cells and Inflammatory Diseases group, University of Luxembourg, 6 Avenue du Swing, L-4367 Belvaux, Luxembourg
| | - S Bréchard
- Life Sciences Research Unit, Immune Cells and Inflammatory Diseases group, University of Luxembourg, 6 Avenue du Swing, L-4367 Belvaux, Luxembourg.
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71
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Nagar M, Tilvawala R, Thompson PR. Thioredoxin Modulates Protein Arginine Deiminase 4 (PAD4)-Catalyzed Citrullination. Front Immunol 2019; 10:244. [PMID: 30853960 PMCID: PMC6396667 DOI: 10.3389/fimmu.2019.00244] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2018] [Accepted: 01/28/2019] [Indexed: 01/01/2023] Open
Abstract
Protein citrullination is a post-translational modification catalyzed by the protein arginine deiminases (PADs). This modification plays a crucial role in the pathophysiology of numerous autoimmune disorders including RA. Recently, there has been a growing interest in investigating physiological regulators of PAD activity to understand the primary cause of the associated disorders. Apart from calcium, it is well-documented that a reducing environment activates the PADs. Although the concentration of thioredoxin (hTRX), an oxidoreductase that maintains the cellular reducing environment, is elevated in RA patients, its contribution toward RA progression or PAD activity has not been explored. Herein, we demonstrate that hTRX activates PAD4. Kinetic characterization of PAD4 using hTRX as the reducing agent yielded parameters that are comparable to those obtained with a routinely used non-physiological reducing agent, e.g., DTT, suggesting the importance of hTRX in PAD regulation under physiological conditions. Furthermore, we show that various hTRX mutants, including redox inactive hTRX variants, are capable of activating PAD4. This indicates a mechanism that does not require oxidoreductase activity. Indeed, we observed non-covalent interactions between PAD4 and hTRX variants, and propose that these redox-independent interactions are sufficient for hTRX-mediated PAD4 activation.
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Affiliation(s)
- Mitesh Nagar
- Department of Biochemistry and Molecular Pharmacology, University of Massachusetts Medical School, Worcester, MA, United States.,Program in Chemical Biology, University of Massachusetts Medical School, Worcester, MA, United States
| | - Ronak Tilvawala
- Department of Biochemistry and Molecular Pharmacology, University of Massachusetts Medical School, Worcester, MA, United States.,Program in Chemical Biology, University of Massachusetts Medical School, Worcester, MA, United States
| | - Paul R Thompson
- Department of Biochemistry and Molecular Pharmacology, University of Massachusetts Medical School, Worcester, MA, United States.,Program in Chemical Biology, University of Massachusetts Medical School, Worcester, MA, United States
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72
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O'Neil LJ, Kaplan MJ. Neutrophils in Rheumatoid Arthritis: Breaking Immune Tolerance and Fueling Disease. Trends Mol Med 2019; 25:215-227. [PMID: 30709614 DOI: 10.1016/j.molmed.2018.12.008] [Citation(s) in RCA: 124] [Impact Index Per Article: 24.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2018] [Revised: 12/19/2018] [Accepted: 12/20/2018] [Indexed: 12/15/2022]
Abstract
Rheumatoid arthritis (RA), a common autoimmune disease, is characterized by a highly coordinated inflammatory response that involves innate and adaptive immunity. One of the hallmarks of RA is an immune response directed at citrullinated peptides that are specifically targeted by anticitrullinated protein antibodies (ACPAs). Among the various mechanisms by which neutrophils may promote immune dysregulation in RA, their ability to extrude neutrophil extracellular traps has recently been implicated in the development of ACPAs. In the synovium, neutrophils interact with resident fibroblast-like synoviocytes to endow them with antigen-presenting cell capabilities and an inflammatory phenotype. Further understanding how neutrophils modulate autoimmunity and tissue damage in RA may lead to the development of novel effective therapies.
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Affiliation(s)
- Liam J O'Neil
- Systemic Autoimmunity Branch, Intramural Research Program, National Institute of Arthritis and Musculoskeletal and Skin Diseases, National Institutes of Health, Bethesda, MD, USA.
| | - Mariana J Kaplan
- Systemic Autoimmunity Branch, Intramural Research Program, National Institute of Arthritis and Musculoskeletal and Skin Diseases, National Institutes of Health, Bethesda, MD, USA.
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73
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Liu Y, Lightfoot YL, Seto N, Carmona-Rivera C, Moore E, Goel R, O'Neil L, Mistry P, Hoffmann V, Mondal S, Premnath PN, Gribbons K, Dell'Orso S, Jiang K, Thompson PR, Sun HW, Coonrod SA, Kaplan MJ. Peptidylarginine deiminases 2 and 4 modulate innate and adaptive immune responses in TLR-7-dependent lupus. JCI Insight 2018; 3:124729. [PMID: 30518690 DOI: 10.1172/jci.insight.124729] [Citation(s) in RCA: 60] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2018] [Accepted: 11/01/2018] [Indexed: 12/17/2022] Open
Abstract
The peptidylarginine deiminases PAD2 and PAD4 are implicated in the pathogenesis of several autoimmune diseases. PAD4 may be pathogenic in systemic lupus erythematosus (SLE) through its role in neutrophil extracellular trap (NET) formation that promotes autoantigen externalization, immune dysregulation, and organ damage. The role of this enzyme in mouse models of autoimmunity remains unclear, as pan-PAD chemical inhibitors improve clinical phenotype, whereas PAD4-KO models have given conflicting results. The role of PAD2 in SLE has not been investigated. The differential roles of PAD2 and PAD4 in TLR-7-dependent lupus autoimmunity were examined. Padi4-/- displayed decreased autoantibodies, type I IFN responses, immune cell activation, vascular dysfunction, and NET immunogenicity. Padi2-/- mice showed abrogation of Th subset polarization, with some disease manifestations reduced compared with WT but to a lesser extent than Padi4-/- mice. RNA sequencing analysis revealed distinct modulation of immune-related pathways in PAD-KO lymphoid organs. Human T cells express both PADs and, when exposed to either PAD2 or PAD4 inhibitors, displayed abrogation of Th1 polarization. These results suggest that targeting PAD2 and/or PAD4 activity modulates dysregulated TLR-7-dependent immune responses in lupus through differential effects of innate and adaptive immunity. Compounds that target PADs may have potential therapeutic roles in T cell-mediated diseases.
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Affiliation(s)
- Yudong Liu
- Systemic Autoimmunity Branch, Intramural Research Program (IRP), National Institute of Arthritis and Musculoskeletal and Skin Diseases (NIAMS), and
| | - Yaíma L Lightfoot
- Systemic Autoimmunity Branch, Intramural Research Program (IRP), National Institute of Arthritis and Musculoskeletal and Skin Diseases (NIAMS), and
| | - Nickie Seto
- Systemic Autoimmunity Branch, Intramural Research Program (IRP), National Institute of Arthritis and Musculoskeletal and Skin Diseases (NIAMS), and
| | - Carmelo Carmona-Rivera
- Systemic Autoimmunity Branch, Intramural Research Program (IRP), National Institute of Arthritis and Musculoskeletal and Skin Diseases (NIAMS), and
| | - Erica Moore
- Systemic Autoimmunity Branch, Intramural Research Program (IRP), National Institute of Arthritis and Musculoskeletal and Skin Diseases (NIAMS), and
| | - Rishi Goel
- Systemic Autoimmunity Branch, Intramural Research Program (IRP), National Institute of Arthritis and Musculoskeletal and Skin Diseases (NIAMS), and
| | - Liam O'Neil
- Systemic Autoimmunity Branch, Intramural Research Program (IRP), National Institute of Arthritis and Musculoskeletal and Skin Diseases (NIAMS), and
| | - Pragnesh Mistry
- Systemic Autoimmunity Branch, Intramural Research Program (IRP), National Institute of Arthritis and Musculoskeletal and Skin Diseases (NIAMS), and
| | - Victoria Hoffmann
- Division of Veterinary Resources, Office of the Director, NIH, Bethesda, Maryland, USA
| | - Santanu Mondal
- University of Massachusetts School of Medicine, Worcester, Massachusetts, USA
| | | | - Katherine Gribbons
- Systemic Autoimmunity Branch, Intramural Research Program (IRP), National Institute of Arthritis and Musculoskeletal and Skin Diseases (NIAMS), and
| | - Stefania Dell'Orso
- Biodata Mining and Discovery Section, Office of Science and Technology, IRP, NIAMS/ NIH, Bethesda, Maryland, USA
| | - Kan Jiang
- Biodata Mining and Discovery Section, Office of Science and Technology, IRP, NIAMS/ NIH, Bethesda, Maryland, USA
| | - Paul R Thompson
- University of Massachusetts School of Medicine, Worcester, Massachusetts, USA
| | - Hong-Wei Sun
- Biodata Mining and Discovery Section, Office of Science and Technology, IRP, NIAMS/ NIH, Bethesda, Maryland, USA
| | - Scott A Coonrod
- Baker Institute for Animal Health, College of Veterinary Medicine, Cornell University, Ithaca, New York, USA
| | - Mariana J Kaplan
- Systemic Autoimmunity Branch, Intramural Research Program (IRP), National Institute of Arthritis and Musculoskeletal and Skin Diseases (NIAMS), and
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74
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Zhou Y, An LL, Chaerkady R, Mittereder N, Clarke L, Cohen TS, Chen B, Hess S, Sims GP, Mustelin T. Evidence for a direct link between PAD4-mediated citrullination and the oxidative burst in human neutrophils. Sci Rep 2018; 8:15228. [PMID: 30323221 PMCID: PMC6189209 DOI: 10.1038/s41598-018-33385-z] [Citation(s) in RCA: 49] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2018] [Accepted: 09/26/2018] [Indexed: 01/14/2023] Open
Abstract
Neutrophils are critical for the defense against pathogens, in part through the extrusion of extracellular DNA traps, phagocytosis, and the production of reactive oxygen species. Neutrophils may also play an important role in the pathogenesis of rheumatoid arthritis (RA) through the activation of protein arginine deiminases (PADs) that citrullinate proteins that subsequently act as autoantigens. We report that PAD4 is physically associated with the cytosolic subunits of the oxidative burst machinery, p47phox (also known as neutrophil cytosol factor 1, NCF1) and p67phox (NCF2). Activation of PAD4 by membranolytic insults that result in high levels of intracellular calcium (higher than physiological neutrophil activation) leads to rapid citrullination of p47phox/NCF1 and p67phox/NCF2, as well as their dissociation from PAD4. This dissociation prevents the assembly of an active NADPH oxidase complex and an oxidative burst in neutrophils stimulated by phorbol-ester or immune complexes. In further support of a substrate-to-inactive enzyme interaction, small-molecule PAD inhibitors also disrupt the PAD4-NCF complex and reduce oxidase activation and phagocytic killing of Staphylococcus aureus. This novel role of PAD4 in the regulation of neutrophil physiology suggests that targeting PAD4 with active site inhibitors for the treatment of RA may have a broader impact on neutrophil biology than just inhibition of citrullination.
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Affiliation(s)
- Yebin Zhou
- Department of Respiratory, Inflammation, and Autoimmunity, MedImmune LLC, One MedImmune Way, Gaithersburg, Maryland, 20878, United States
| | - Ling-Ling An
- Department of Respiratory, Inflammation, and Autoimmunity, MedImmune LLC, One MedImmune Way, Gaithersburg, Maryland, 20878, United States
| | - Raghothama Chaerkady
- Antibody Discovery and Protein Engineering, MedImmune LLC, One MedImmune Way, Gaithersburg, Maryland, 20878, United States
| | - Nanette Mittereder
- Department of Respiratory, Inflammation, and Autoimmunity, MedImmune LLC, One MedImmune Way, Gaithersburg, Maryland, 20878, United States
| | - Lori Clarke
- Antibody Discovery and Protein Engineering, MedImmune LLC, One MedImmune Way, Gaithersburg, Maryland, 20878, United States
| | - Taylor S Cohen
- Department of Microbial Sciences, MedImmune LLC, One MedImmune Way, Gaithersburg, Maryland, 20878, United States
| | - Bo Chen
- Department of Respiratory, Inflammation, and Autoimmunity, MedImmune LLC, One MedImmune Way, Gaithersburg, Maryland, 20878, United States
| | - Sonja Hess
- Antibody Discovery and Protein Engineering, MedImmune LLC, One MedImmune Way, Gaithersburg, Maryland, 20878, United States
| | - Gary P Sims
- Department of Respiratory, Inflammation, and Autoimmunity, MedImmune LLC, One MedImmune Way, Gaithersburg, Maryland, 20878, United States.
| | - Tomas Mustelin
- Department of Respiratory, Inflammation, and Autoimmunity, MedImmune LLC, One MedImmune Way, Gaithersburg, Maryland, 20878, United States. .,Division of Rheumatology, School of Medicine, University of Washington, 750 Republican Street, Seattle, WA98109, United States.
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75
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Damgaard D, Bawadekar M, Senolt L, Stensballe A, Shelef MA, Nielsen CH. Relative efficiencies of peptidylarginine deiminase 2 and 4 in generating target sites for anti-citrullinated protein antibodies in fibrinogen, alpha-enolase and histone H3. PLoS One 2018; 13:e0203214. [PMID: 30161253 PMCID: PMC6117052 DOI: 10.1371/journal.pone.0203214] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2018] [Accepted: 08/16/2018] [Indexed: 11/18/2022] Open
Abstract
OBJECTIVE Peptidylarginine deiminase 2 (PAD2) and PAD4 are expressed in the synovium of rheumatoid arthritis (RA) patients and catalyze citrullination of arginine residues in proteins targeted by anti-citrullinated protein antibodies (ACPAs). Little is known about the relative importance of PAD2 and PAD4 in generating citrullinated self-antigens. Here we investigate the ability of PAD2 and PAD4 to generate citrullinated targets for ACPAs in four human proteins. METHODS Synovial fluid (SF) and plasma were collected from 42 RA patients. Human fibrinogen, human alpha-enolase (ENO1), human histone H3, and human serum albumin (HSA) were citrullinated in vitro by PAD2 or PAD4. The total degree of citrullination was determined using the anti-modified citrulline approach. Antibody binding to native and citrullinated proteins was measured by ELISA. RESULTS ACPAs within pooled SF from multiple RA patients reacted equally well with, and cross-reacted with, PAD2- and PAD4-citrullinated fibrinogen. ACPAs from most individual patient SF and plasma samples bound equally well to PAD2- and PAD4-citrullinated fibrinogen or ENO1. When histone H3 was used as target, PAD4 was generally superior in generating epitopes recognized by ACPAs. No binding to citrullinated HSA was observed. CONCLUSION In most patients, PAD2 and PAD4 are equally efficient in generating citrullinated target sites for ACPAs in fibrinogen and ENO1. The binding of autoantibodies to histone H3 was generally higher after citrullination with PAD4 than with PAD2. Citrullinated HSA is not a target for ACPAs.
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Affiliation(s)
- Dres Damgaard
- Institute for Inflammation Research, Center for Rheumatology and Spine Diseases, Copenhagen University Hospital, Rigshospitalet, Copenhagen, Denmark
- Section for Periodontology, Microbiology and Community Dentistry, Department of Odontology, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
- * E-mail:
| | - Mandar Bawadekar
- Department of Medicine, University of Wisconsin, Madison, Wisconsin, United States of America
| | - Ladislav Senolt
- Institute of Rheumatology and Department of Rheumatology, 1st Faculty of Medicine, Charles University, Prague, Czech Republic
| | - Allan Stensballe
- Department of Health Science and Technology, Aalborg University, Aalborg, Denmark
| | - Miriam A. Shelef
- Department of Medicine, University of Wisconsin, Madison, Wisconsin, United States of America
- William S. Middleton Memorial Veterans Hospital, Madison, Wisconsin, United States of America
| | - Claus H. Nielsen
- Institute for Inflammation Research, Center for Rheumatology and Spine Diseases, Copenhagen University Hospital, Rigshospitalet, Copenhagen, Denmark
- Section for Periodontology, Microbiology and Community Dentistry, Department of Odontology, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
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76
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Cau L, Méchin MC, Simon M. Peptidylarginine deiminases and deiminated proteins at the epidermal barrier. Exp Dermatol 2018; 27:852-858. [PMID: 29756256 DOI: 10.1111/exd.13684] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 05/04/2018] [Indexed: 12/13/2022]
Abstract
Deimination or citrullination is a post-translational modification catalysed by a family of calcium-dependent enzymes called peptidylarginine deiminases (PADs). It corresponds to the transformation of arginine residues within a peptide sequence into citrulline residues. Deimination induces a decreased net charge of targeted proteins; therefore, it alters their folding and changes intra- and intermolecular ionic interactions. Deimination is involved in several physiological processes (inflammation, gene regulation, etc.) and human diseases (rheumatoid arthritis, neurodegenerative diseases, cancer, etc.). Here, we describe the PADs expressed in the epidermis and their known substrates, focusing on their role in the epidermal barrier function.
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Affiliation(s)
- Laura Cau
- UDEAR, Institut National de la Santé Et de la Recherche Médicale, Université Paul Sabatier, Université de Toulouse Midi-Pyrénées, Toulouse, France
| | - Marie-Claire Méchin
- UDEAR, Institut National de la Santé Et de la Recherche Médicale, Université Paul Sabatier, Université de Toulouse Midi-Pyrénées, Toulouse, France
| | - Michel Simon
- UDEAR, Institut National de la Santé Et de la Recherche Médicale, Université Paul Sabatier, Université de Toulouse Midi-Pyrénées, Toulouse, France
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77
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Heluany CS, Kupa LDVK, Viana MN, Fernandes CM, Silveira ELV, Farsky SHP. In vivo exposure to hydroquinone during the early phase of collagen-induced arthritis aggravates the disease. Toxicology 2018; 408:22-30. [PMID: 29935983 DOI: 10.1016/j.tox.2018.06.010] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2018] [Revised: 05/09/2018] [Accepted: 06/20/2018] [Indexed: 12/16/2022]
Abstract
Robust correlation between the severity of rheumatoid arthritis (RA) and cigarette smoking has been clinically demonstrated. Nevertheless, cigarette compounds responsible for this toxic effect and their mechanisms have not been described. Considering that hydroquinone (HQ) is an abundant, pro-oxidative compound of the matter particle phase of cigarette smoke, we investigated whether HQ exposure during the initial phase of collagen-induced arthritis (CIA) could aggravate the disease. For this purpose, male Wistar rats were exposed to aerosolized HQ (25 ppm), saline or 5% ethanol solution (HQ vehicle) for 1 h per day during 14 days. CIA was induced through s.c. injection of bovine collagen Type II (0.4 mg/100 μL) at days seven and 14 of exposure. Clinical signs of disease and the cell profile and chemical mediators in the synovial fluid and membrane were analysed at day 35 after the beginning of exposure. HQ exposure aggravated CIA-related paw edema and increased the cell infiltrate and interleukin-6 (IL-6) levels in the synovial fluid, promoted intense tissue collagen deposition and enhanced synoviocyte proliferation and higher frequency of aryl hydrocarbon receptor (AhR+) and interleukin (IL-17+) neutrophils in the synovial membrane. in vitro data also highlighted that neutrophils expressed increased levels of AhR, IL-17 and reactive oxygen species (ROS) generation. However, only AhR expression and ROS generation were blocked by in vitro treatment with AhR antagonist. Therefore, we conclude that in vivo HQ exposure at the early phase of AR onset worsens RA, leading to high frequency of AhR/IL-17+ neutrophils into the joint.
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Affiliation(s)
- Cintia Scucuglia Heluany
- Department of Clinical and Toxicological Analysis, Faculty of Pharmaceutical Sciences, University of São Paulo, Brazil
| | - Leonard de Vinci Kanda Kupa
- Department of Clinical and Toxicological Analysis, Faculty of Pharmaceutical Sciences, University of São Paulo, Brazil
| | | | | | - Eduardo Lani Volpe Silveira
- Department of Clinical and Toxicological Analysis, Faculty of Pharmaceutical Sciences, University of São Paulo, Brazil
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78
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Zhou Y, Mittereder N, Sims GP. Perspective on Protein Arginine Deiminase Activity-Bicarbonate Is a pH-Independent Regulator of Citrullination. Front Immunol 2018; 9:34. [PMID: 29403504 PMCID: PMC5778117 DOI: 10.3389/fimmu.2018.00034] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2017] [Accepted: 01/04/2018] [Indexed: 01/14/2023] Open
Abstract
Protein citrullination catalyzed by peptidyl arginine deiminase (PADs) is involved in autoimmune disease pathogenesis, especially in rheumatoid arthritis. Calcium is a key regulator of PAD activity, but under normal physiological conditions it remains uncertain how intracellular calcium levels can be raised to sufficiently high levels to activate these enzymes. In pursuit of trying to identify other factors that influence PAD activity, we identified bicarbonate as a potential regulator of PAD activity. We demonstrate that physiological levels of bicarbonate upregulate citrullination by recombinant PAD2/4 and endogenous PADs in neutrophils. The impact of bicarbonate is independent of calcium and pH. Adding bicarbonate to commercial PAD activity kits could increase assay performance and biological relevance. These results suggest that citrullination activity is regulated by multiple factors including calcium and bicarbonate. We also provide commentary on the current understanding of PAD regulation and future perspective of research in this area.
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Affiliation(s)
- Yebin Zhou
- Department of Respiratory, Inflammation, and Autoimmunity, MedImmune LLC, Gaithersburg, MD, United States
| | - Nanette Mittereder
- Department of Respiratory, Inflammation, and Autoimmunity, MedImmune LLC, Gaithersburg, MD, United States
| | - Gary P Sims
- Department of Respiratory, Inflammation, and Autoimmunity, MedImmune LLC, Gaithersburg, MD, United States
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