2. Academic Validation
  3. Positive feedback loop PU.1-IL9 in Th9 promotes rheumatoid arthritis development

Positive feedback loop PU.1-IL9 in Th9 promotes rheumatoid arthritis development

  • Ann Rheum Dis. 2024 Aug 20:ard-2024-226067. doi: 10.1136/ard-2024-226067.
Jiajie Tu # 1,  Weile Chen # 1,  Wei Huang # 2,  Xinming Wang # 3,  Yilong Fang # 1,  Xuming Wu 1,  Huiru Zhang 1,  Chong Liu 1,  Xuewen Tan 1,  Xiangling Zhu 1,  Huihui Wang 1,  Dafei Han 1,  Yizhao Chen 1,  Anqi Wang 1,  Yuanyuan Zhou 1,  Zimeng Xue 1,  Hui Xue 1,  Shangxue Yan 1,  Lingling Zhang 1,  Zhenbao Li 4,  Chunlan Yang 3,  Yujie Deng 5,  Shihao Zhang 6,  Chen Zhu 7,  Wei Wei 6
Affiliations

Affiliations

  • 1 Institute of Clinical Pharmacology, Anhui Medical University, Hefei, Anhui, China.
  • 2 Department of Orthopedics, The First Affiliated Hospital of USTC, Division of Life Sciences and Medicine, University of Science and Technology of China, Hefei, Anhui, China.
  • 3 Department of Pharmacy, The First Affiliated Hospital of Anhui Medical University, Hefei, Anhui, China.
  • 4 College of Pharmacy, Anhui University of Traditional Chinese Medicine, Hefei, Anhui, China.
  • 5 Guangzhou National Laboratory, Guangzhou, China.
  • 6 Institute of Clinical Pharmacology, Anhui Medical University, Hefei, Anhui, China wwei@ahmu.edu.cn zhuchena@ustc.edu.cn shihaozhang@ahmu.edu.cn.
  • 7 Department of Orthopedics, The First Affiliated Hospital of USTC, Division of Life Sciences and Medicine, University of Science and Technology of China, Hefei, Anhui, China wwei@ahmu.edu.cn zhuchena@ustc.edu.cn shihaozhang@ahmu.edu.cn.
  • # Contributed equally.
PMID: 39164066 DOI: 10.1136/ard-2024-226067
Abstract

Objectives: T helper 9 (Th9) cells are recognised for their characteristic expression of the transcription factor PU.1 and production of interleukin-9 (IL-9), which has been implicated in various autoimmune diseases. However, its precise relationship with rheumatoid arthritis (RA) pathogenesis needs to be further clarified.

Methods: The expression levels of PU.1 and IL-9 in patients with RA were determined by ELISA, western blotting (WB) and immunohistochemical staining. PU.1-T cell-conditional knockout (KO) mice, IL-9 KO and IL-9R KO mice were used to establish collagen antibody-induced arthritis (CAIA), respectively. The inhibitor of PU.1 and IL-9 blocking antibody was used in collagen-induced arthritis (CIA). In an in vitro study, the effects of IL-9 were investigated using siRNAs and IL-9 recombinant proteins. Finally, the underlying mechanisms were further investigated by luciferase reporter analysis, WB and Chip-qPCR.

Results: The upregulation of IL-9 expression in patients with RA exhibited a positive correlation with clinical markers. Using CAIA and CIA model, we demonstrated that interventions targeting PU.1 and IL-9 substantially mitigated the inflammatory phenotype. Furthermore, in vitro assays provided the proinflammatory role of IL-9, particularly in the hyperactivation of macrophages and fibroblast-like synoviocytes. Mechanistically, we uncovered that PU.1 and IL-9 form a positive feedback loop in RA: (1) PU.1 directly binds to the IL-9 promoter, activating its transcription and (2) Th9-derived IL-9 induces PU.1 via the IL-9R-JAK1/STAT3 pathway.

Conclusions: These results support that the PU.1-IL-9 axis forms a positive loop in Th9 dysregulation of RA. Targeting this signalling axis presents a potential target approach for treating RA.

Keywords

Arthritis, Rheumatoid; Cytokines; T-Lymphocytes.

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