Integrated single-cell and network analysis identifies SLAMF7 as a secretory mediator of the joint-lung axis in rheumatoid arthritis-associated interstitial lung disease targetable by Tanshinone IIA.

Abstract

Background: Interstitial lung disease (ILD) is one of the most serious extra-articular complications of rheumatoid arthritis (RA). However, the immune-fibrotic mediators that bridge articular inflammation and pulmonary injury have not been fully defined. Natural products represent a promising source of multi-target therapeutics, but their therapeutic effects and mechanisms in RA-ILD remain largely unclear.

Purpose: This study aimed to identify key immune-related secretory proteins involved in RA-ILD and to explore potential therapeutic compounds targeting the inflammatory-fibrotic axis.

Methods: We performed an integrated bioinformatic analysis using transcriptomic datasets from RA synovial tissues, RA peripheral blood mononuclear cells (PBMCs), and ILD lung tissues. RA-associated differentially expressed secretory proteins and ILD lung key genes were identified through differential expression analysis and weighted gene co-expression network analysis (WGCNA). Shared candidate genes were further prioritized using LASSO regression, support vector machine-recursive feature elimination (SVM-RFE), and external validation in an independent RA-ILD dataset. Protein-protein interaction (PPI) network analysis and functional enrichment were used to define a shared inflammatory program and guide compound prediction. Tanshinone IIA (TANIIA) was prioritized for experimental validation. Serum ELISA, collagen-induced arthritis (CIA) mouse studies, histology, flow cytometry, immunofluorescence, single-cell RNA sequencing analysis, macrophage-fibroblast co-culture, western blotting, and cellular thermal shift assay (CETSA) were used to validate molecular and pharmacological findings.

Results: SLAMF7 was identified as the sole hub gene converging RA-associated secretory proteins, ILD-related key genes, and RA-ILD differential expression signatures, exhibiting strong diagnostic performance and significantly elevated serum levels in RA-ILD patients. Network analysis identified a broader inflammatory hub-gene program enriched in TNF, chemokine, and IL-17 signaling pathways, with SLAMF7 linked to this network. TANIIA was prioritized as a candidate compound and showed favorable docking affinity to multiple hub-gene targets. In CIA mice, TANIIA alleviated arthritis, reduced circulating inflammatory and profibrotic mediators, downregulated SLAMF7 expression, and attenuated pulmonary fibrosis and macrophage infiltration. scRNA-seq revealed that SLAMF7 was enriched in pulmonary macrophages with a profibrotic transcriptional program. In vitro, recombinant SLAMF7 was sufficient to induce M2-like macrophage polarization accompanied by CREB/C/EBPβ activation, whereas TANIIA attenuated this response.

Conclusion: SLAMF7 is a potential biomarker and mechanistically relevant mediator linking inflammation and fibrosis in RA-ILD. TANIIA exerts dual protective effects on joint and lung pathology by suppressing inflammatory responses and targeting the SLAMF7-associated macrophage-fibrosis axis.