title: The metastatic tumor antigen 1-transglutaminase-2 pathway is involved in self-limitation of monosodium urate crystal-induced inflammation by upregulating TGF-β1.
abstract: BACKGROUND
  Transglutaminase 2 (TG2), a protein crosslinking enzyme with multiple biochemical functions, has been connected to various inflammatory processes. In this study, the involvement of TG2 in monosodium urate (MSU) crystal-induced inflammation was studied.
  
  
  METHODS
  Immunohistochemistry, reverse transcription-polymerase chain reaction (RT-PCR) were performed to detect TG2 expression in synovial fluid mononuclear cells (SFMCs) and synovial tissue from patients with gouty arthritis. MSU crystal-exposed RAW264.7 mouse macrophages were analyzed for interleukin-1β (IL-1β), tumor necrosis factor-α (TNF-α), transforming growth factor β1 (TGF-β1) and TG2 expression by RT-PCR and enzyme-linked immunosorbent assay (ELISA). TG2 small interfering (si)-RNA-mediated silencing and overexpression in RAW264.7 cells were used to evaluate the involvement of TG2 in resolving MSU crystal-induced inflammation. The role of metastatic tumor antigen 1 (MTA1), a master chromatin modifier, was investigated by MTA1 si-RNA-mediated knockdown. In addition, the inflammatory responses were followed in wild type and TG2 null mice after being challenged with MSU crystals in an in vivo peritonitis model.
  
  
  RESULTS
  TG2 expression was up-regulated in the synovium tissue and SFMCs from patients with gouty arthritis. The levels of MTA1, TG2, TGF-β1, IL-1β and TNF-α mRNAs were consistently increased in MSU crystal-stimulated RAW264.7 cells. si-MTA1 impaired the basal, as well as the MSU crystal-induced expression of TG2 and TGF-β1, but increased that of IL-1β and TNF-α. TG2 overexpression dramatically suppressed MSU crystal-induced IL-1β and TNF-α, but significantly enhanced the TGF-β1 production. Neutralizing TGF-β antibodies or inhibition of the crosslinking activity of TG2 attenuated these effects. On the contrary, loss of TG2 resulted in a reduced TGF-β, but in an increased IL-1β and TNF-α production in MSU crystal-stimulated RAW264.7 cells and mouse embryonic fibroblasts (MEFs). MSU crystal-stimulated IL-1β production was Janus kinase 2 (JAK2)-signaling dependent and TG2-induced TGF-β suppressed the activity of it. Finally, TG2-deficient mice exhibited hyper inflammatory responses after being challenged with MSU crystals in an in vivo peritonitis model.
  
  
  CONCLUSIONS
  These findings reveal an inherent regulatory role of the MTA1-TG2 pathway in the self-limitation of MSU crystal-induced inflammation via positively regulating the levels of active TGF-β1 in macrophages that opposes the MSU crystal-induced JAK2-dependent pro-inflammatory cytokine formation.
authors.affiliation: Institute of Microbiology and Immunology, Chung Shan Medical University, Taichung, Taiwan. hugtrghu@yahoo.com.tw.
authors.forename: Jia-Hau
authors.initials: JH
authors.lastname: Yen
authors.affiliation: Institute of Microbiology and Immunology, Chung Shan Medical University, Taichung, Taiwan. rockjon_1218@hotmail.com.
authors.forename: Ling-Chung
authors.initials: LC
authors.lastname: Lin
authors.affiliation: Institute of Microbiology and Immunology, Chung Shan Medical University, Taichung, Taiwan. chen_meng_chi@yahoo.com.
authors.forename: Meng-Chi
authors.initials: MC
authors.lastname: Chen
authors.affiliation: Division of Dental Biochemistry, Department of Biochemistry and Molecular Biology, Research Center of Molecular Medicine, University of Debrecen, Debrecen, Hungary. sarang@med.unideb.hu.
authors.forename: Zsolt
authors.initials: Z
authors.lastname: Sarang
authors.affiliation: Department of Internal Medicine, Chung Shan Medical University Hospital, No. 110, Section 1, Chien-Kuo N. Road, Taichung, Taiwan. fiona.leong@gmail.com.
authors.forename: Pui-Ying
authors.initials: PY
authors.lastname: Leong
authors.affiliation: Department of Orthopedic Surgery, Chung Shan Medical University Hospital, Taichung, Taiwan. ic40249@ms34.hinet.net.
authors.forename: I-Chang
authors.initials: IC
authors.lastname: Chang
authors.affiliation: Department of Pathology, Chung Shan Medical University Hospital, Taichung, Taiwan. dongdong@csmu.edu.tw.
authors.forename: Jeng-Dong
authors.initials: JD
authors.lastname: Hsu
authors.affiliation: Division of Immunology and Rheumatology, Department of Internal Medicine, China Medical University Hospital, Taichung, Taiwan. d91842001@ntu.edu.tw.
authors.forename: Jiunn-Horng
authors.initials: JH
authors.lastname: Chen
authors.affiliation: Institute of Microbiology and Immunology, Chung Shan Medical University, Taichung, Taiwan. Julianna0718@yahoo.com.tw.
authors.forename: Yu-Fan
authors.initials: YF
authors.lastname: Hsieh
authors.affiliation: Division of Dental Biochemistry, Department of Biochemistry and Molecular Biology, Research Center of Molecular Medicine, University of Debrecen, Debrecen, Hungary. AnnaPallai@facebook.com.
authors.forename: Anna
authors.initials: A
authors.lastname: Pallai
authors.affiliation: Division of Dental Biochemistry, Department of Biochemistry and Molecular Biology, Research Center of Molecular Medicine, University of Debrecen, Debrecen, Hungary. krisztina.koroskenyi@facebook.com.
authors.forename: Krisztina
authors.initials: K
authors.lastname: Köröskényi
authors.affiliation: Division of Dental Biochemistry, Department of Biochemistry and Molecular Biology, Research Center of Molecular Medicine, University of Debrecen, Debrecen, Hungary. szondy@med.unideb.hu.
authors.forename: Zsuzsa
authors.initials: Z
authors.lastname: Szondy
authors.affiliation: Institute of Microbiology and Immunology, Chung Shan Medical University, Taichung, Taiwan. gjt@csmu.edu.tw.|Department of Internal Medicine, Chung Shan Medical University Hospital, No. 110, Section 1, Chien-Kuo N. Road, Taichung, Taiwan. gjt@csmu.edu.tw.
authors.forename: Gregory J
authors.initials: GJ
authors.lastname: Tsay
mesh_terms: D000818:Animals; D015210:Arthritis, Gouty / Q000378:metabolism* / Q000473:pathology; D002460:Cell Line; D019204:GTP-Binding Proteins / Q000096:biosynthesis*; D006655:Histone Deacetylases / Q000096:biosynthesis*; D006801:Humans; D007249:Inflammation / Q000378:metabolism / Q000473:pathology; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D000091345:Protein Glutamine gamma Glutamyltransferase 2; D012097:Repressor Proteins / Q000096:biosynthesis*; D015534:Trans-Activators; D053773:Transforming Growth Factor beta1 / Q000096:biosynthesis*; D011503:Transglutaminases / Q000096:biosynthesis*; D015854:Up-Regulation / Q000187:drug effects / Q000502:physiology*; D014527:Uric Acid / Q000633:toxicity*
chemical_list: C089320:MTA1 protein, human; D012097:Repressor Proteins; D015534:Trans-Activators; D053773:Transforming Growth Factor beta1; D014527:Uric Acid; D000091345:Protein Glutamine gamma Glutamyltransferase 2; D011503:Transglutaminases; D006655:Histone Deacetylases; D019204:GTP-Binding Proteins