The metastatic tumor antigen 1-transglutaminase-2 pathway is involved in self-limitation of monosodium urate crystal-induced inflammation by upregulating TGF-β1.

Abstract

INTRODUCTION:

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: Jia-Hau Yen, Ling-Chung Lin, Meng-Chi Chen, Zsolt Sarang, Pui-Ying Leong, I-Chang Chang, Jeng-Dong Hsu, Jiunn-Horng Chen, Yu-Fan Hsieh, Anna Pallai, Krisztina Köröskényi, Zsuzsa Szondy, Gregory J Tsay
• Journal: Arthritis research & therapy (Arthritis Res Ther) Vol. 17 Pg. 65 (Mar 19 2015) ISSN: 1478-6362 [Electronic] England
• PMID: 25889736 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)

Chemical References

• Mta1 protein, human
• Repressor Proteins
• Trans-Activators
• Transforming Growth Factor beta1
• Uric Acid
• Protein Glutamine gamma Glutamyltransferase 2
• Transglutaminases
• Histone Deacetylases
• GTP-Binding Proteins

Topics

• Animals
• Arthritis, Gouty (metabolism, pathology)
• Cell Line
• GTP-Binding Proteins (biosynthesis)
• Histone Deacetylases (biosynthesis)
• Humans
• Inflammation (metabolism, pathology)
• Mice
• Mice, Inbred C57BL
• Mice, Knockout
• Protein Glutamine gamma Glutamyltransferase 2
• Repressor Proteins (biosynthesis)
• Trans-Activators
• Transforming Growth Factor beta1 (biosynthesis)
• Transglutaminases (biosynthesis)
• Up-Regulation (drug effects, physiology)
• Uric Acid (toxicity)