Iguratimod dose dependently inhibits the expression of citrullinated proteins and peptidylarginine deiminases 2 and 4 in neutrophils from rheumatoid arthritis patients

  • Bingtong Li
  • Ping Li
  • Liqi BiEmail author
Original Article



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.


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.


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.


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.


Anti-citrullinated protein antibody Iguratimod Peptidylarginine deiminase Rheumatoid arthritis 



The authors thank Tingshuang Xu, Ph.D for the guidance during the experiment and Dr. Ruizhu Liu for her assistance.

Funding information

We also thank the support from national key research and development program of China (No. 2017YFC0909002).

Compliance with ethical standards



Ethical approval

All patients provided consent before sample collection. The Ethics Committee of China-Japan Union Hospital of Jilin University approved this study.

Supplementary material

10067_2019_4835_MOESM1_ESM.pdf (1.3 mb)
Online Resource 1 (PDF 1306 kb)
10067_2019_4835_MOESM2_ESM.pdf (617 kb)
Online Resource 2 (PDF 617 kb)


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Copyright information

© International League of Associations for Rheumatology (ILAR) 2019

Authors and Affiliations

  1. 1.Department of Rheumatology and ImmunologyChina-Japan Union Hospital of Jilin UniversityChangchunChina

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