TNF-driven intracellular complement factor H-NF-κB feed-forward loop amplifies inflammatory mediator production in rheumatoid arthritis synovial fibroblasts.

@article{kobayashi2026tnfdriven,
  title = {{TNF-driven intracellular complement factor H-NF-κB feed-forward loop amplifies inflammatory mediator production in rheumatoid arthritis synovial fibroblasts.}},
  author = {Hiroki Kobayashi and Sho Mokuda and Michinori Ishitoku and Hirofumi Watanabe and Tomohiro Sugimoto and Yusuke Yoshida and Junya Masumoto and Shintaro Hirata},
  journal = {Inflammation and regeneration},
  year = {2026},
  month = aug,
  doi = {10.1186/s41232-026-00437-1},
  url = {https://europepmc.org/article/MED/42963795},
  note = {CC BY},
}

TY  - JOUR
TI  - TNF-driven intracellular complement factor H-NF-κB feed-forward loop amplifies inflammatory mediator production in rheumatoid arthritis synovial fibroblasts.
AU  - Hiroki Kobayashi
AU  - Sho Mokuda
AU  - Michinori Ishitoku
AU  - Hirofumi Watanabe
AU  - Tomohiro Sugimoto
AU  - Yusuke Yoshida
AU  - Junya Masumoto
AU  - Shintaro Hirata
PY  - 2026
DA  - 2026/08/04
JO  - Inflammation and regeneration
DO  - 10.1186/s41232-026-00437-1
UR  - https://europepmc.org/article/MED/42963795
AB  - Background  Rheumatoid arthritis (RA) involves multiple pro-inflammatory cytokines; fibroblast-like synoviocytes (FLS) are central effector cells that integrate these signals to produce pathogenic mediators. Tumor necrosis factor (TNF) is a major upstream driver of coordinated inflammatory mediator induction in FLS; however, the underlying mechanisms remain incompletely defined, particularly intracellular feed-forward amplification sustaining and enhancing TNF-driven transcriptional outputs. Complement factor H (FH; gene CFH), a Sushi domain-only complement regulator, is elevated in RA serum. FH is regarded as an extracellular inhibitor of complement activation; however, its potential intracellular expression and functions in FLS have not been explored. We aimed to investigate intracellular FH expression and function using an in vitro transcribed messenger RNA (IVT mRNA)-based approach.Methods  FH expression in sera, synovial tissues, and fibroblast-like synoviocytes (FLS) were assessed by enzyme-linked immunosorbent assay (ELISA), immunohistochemistry, RT-qPCR, and immunoblotting. To examine intracellular FH function, FLS were transfected with CFH-encoding IVT mRNA to express FH intracellularly, followed by next-generation sequencing (RNA-seq), RT-qPCR, ELISA, phosphorylation assays, and pathway inhibition. Interactions between TNF-driven signaling and intracellular FH were evaluated using TNF- and/or FH-neutralizing antibodies, with or without CFH-targeting small interfering RNA (siRNA).Results  FH was highly expressed in RA synovium and predominantly localized intracellularly in FLS. To assess intracellular FH function, FLS were transfected with CFH-encoding IVT mRNA, which induced the coordinated upregulation of RA-relevant mediators, including granulocyte-macrophage colony-stimulating factor (GM-CSF), interleukin (IL)-8, IL-6, and multiple chemokines. Mechanistically, intracellular FH activated nuclear factor-κB (NF-κB) signaling, promoting receptor-interacting serine/threonine-protein kinase 2 (RIPK2) phosphorylation and p65 nuclear translocation, and the competitive nucleotide-binding oligomerization domain 2 (NOD2) antagonist suppressed FH-driven gene induction. TNF and intracellular FH additively enhanced pathogenic mediator production. CFH-targeting siRNA attenuated TNF-induced cytokine and chemokine expression; blockade of extracellular FH had no detectable effect. Combined TNF neutralization and CFH knockdown produced more effective suppression of cytokine induction than either intervention alone.Conclusions  Intracellular FH is a previously unrecognized amplifier of TNF-driven inflammation in RA-FLS via a NOD2/RIPK2/NF-κB axis, establishing a feed-forward loop boosting pathogenic mediator production. Dual targeting of TNF and intracellular FH may represent a therapeutic strategy to suppress synovial inflammation more effectively.
SN  - 1880-9693
SN  - 1880-8190
ER  -