BRD3 Regulates the Inflammatory and Stress Response in Rheumatoid Arthritis Synovial Fibroblasts

The role of bromodomain and extra-terminal (BET) proteins in rheumatoid arthritis (RA) remains partially defined. BET inhibitors demonstrate anti-inflammatory effects, but the specific contributions of individual BET family members are unclear. BRD3, a less-studied BET protein, has not been fully characterized in RA synovial fibroblasts (FLS). Prior research has shown that BET proteins regulate gene expression in inflammatory contexts. However, the mechanisms by which BRD3 influences inflammation or stress responses in RA are not well established. This uncertainty drives the need for targeted investigation into BRD3's function. No prior work had resolved the direct regulatory role of BRD3 in RA FLS. Understanding this role may clarify the broader impact of BET proteins in RA pathogenesis.

This study aimed to explore the function of BRD3 in RA synovial fibroblasts. Researchers focused on determining whether BRD3 regulates inflammatory and stress-related gene expression. They sought to compare the effects of BRD3 silencing with those of a pan-BET inhibitor, I-BET. The goal was to identify specific pathways influenced by BRD3 in FLS. They also aimed to assess whether BRD3 contributes to inflammation or stress responses in RA. The motivation stemmed from the incomplete understanding of BET family member roles. BRD3’s underrepresentation in prior studies made it a key target for investigation. The study aimed to clarify its contribution to RA-related gene regulation.

Researchers silenced BRD3 in RA synovial fibroblasts and then exposed the cells to TNF. They also treated cells with the pan-BET inhibitor I-BET for comparative analysis. Transcriptome changes were analyzed using RNA sequencing followed by pathway enrichment. Select genes were validated using real-time PCR, ELISA, and Western blotting. The study focused on cytokine and chemokine expression patterns. Researchers examined how BRD3 influences FLS proliferation and metabolic adaptation. They also assessed the role of BRD3 in stress responses, including oxidative stress and autophagy. The methods combined functional silencing with multi-omics validation to explore BRD3’s regulatory role.

BRD3 silencing reduced the expression of multiple cytokines and chemokines in RA synovial fibroblasts. RNA sequencing revealed that BRD3 regulates pathways related to FLS proliferation and metabolic adaptation. The data suggested a strong link between BRD3 and stress response mechanisms, including autophagy. BRD3 expression positively correlated with inflammatory scores in RA synovium. Pathway analysis showed that BRD3 influences oxidative stress responses in FLS. Real-time PCR confirmed the RNAseq findings for selected target genes. ELISA and Western blotting supported the downregulation of inflammatory mediators. BRD3 appears to act as an upstream regulator of inflammatory and stress-related gene expression.

The authors suggest that BRD3 plays a key role in regulating inflammation and stress responses in RA synovial fibroblasts. They propose that BRD3 integrates signals from inflammatory and stress conditions in FLS. The findings indicate that BRD3 executes many functions previously attributed to pan-BET inhibitors. The study supports the idea that BRD3 contributes to the anti-inflammatory effects of BET inhibitors. The data suggest that BRD3 influences cytokine and chemokine expression in FLS. The authors propose that BRD3 is involved in metabolic adaptation and autophagy in RA. They suggest that BRD3 may act as a central regulatory factor in FLS. The study highlights the need for further investigation into BRD3’s role in RA pathogenesis.