SLAMF1 as a novel molecule mediating the causal association between rheumatoid arthritis and interstitial lung disease: A Mendelian randomization study combined with transcriptomics and in vivo validation.

BACKGROUND

Rheumatoid arthritis-associated interstitial lung disease (RA-ILD) is a common complication of rheumatoid arthritis (RA) that result in significant morbidity and mortality. Understanding the molecular mechanisms underlying RA-ILD is crucial for effective prevention. This study aims to identify the specific molecule that mediate the causal association between RA and ILD, as well as to explore its potential mechanisms in the pathogenesis of RA-ILD.

METHODS

Using two-sample Mendelian randomization (MR) analyses, we investigated the causal relationship among 16,987 blood genes, RA and ILD. Subsequently, a two-step MR technique was employed to identify significant genes that mediate the association between RA and ILD, and to quantify their proportion of mediation effect. To validate the genes as mediators, the replication MR analysis was conducted and the in vivo experiment was performed using an established animal model of RA-ILD. Furthermore, integrated bioinformatic analyses were conducted to elucidate the specific biological functions of the determined mediator in pathogenesis of RA-ILD.

RESULTS

Nine genes, namely MAPK8IP2, TAF11, SLAMF1, DAB2IP, GLUL, SLC4A10, PRSS35, NFX1, and PLK3, were identified as mediators. Among them, SLAMF1 was validated as the most significant mediator, accounting for 4.693% of the mediating effect on the causal relationship between RA and ILD. Upregulated mRNA expression of SLAMF1 was observed in the animal model of RA-ILD compared to controls. Bioinformatic analyses revealed that SLAMF1 was overexpressed in patients with lung fibrosis and correlated with a poor prognosis. Specifically, SLAMF1 was found to be predominantly overexpressed in T cells in lung tissues of patients with lung fibrosis. Additionally, the functional role of SLAMF1 was associated with multiple immune cell infiltrations and the biological process of extracellular matrix synthesis in pulmonary tissues from patients with lung fibrosis.

CONCLUSION

SLAMF1 may play a crucial role as a molecular mediator in the causal association between RA and ILD, and participate in multiple mechanisms underlying the pathogenesis of RA-ILD. This research provides insights into how the development of RA influences the risk of ILD and offers potential interventional targets against RA-ILD.