Dual TYK2/JAK1 Inhibition by Brepocitinib Reprograms Synoviocyte Pathobiology: Mechanistic Insights Into Targeted...

Area of Science:

• Immunology
• Pharmacology
• Cell Biology

Background:

• Rheumatoid arthritis (RA) is a chronic autoimmune disease marked by synovial hyperplasia and joint destruction.
• Targeting intracellular pathways like JAK-STAT has improved RA treatment, but safety and selectivity are concerns.
• Brepocitinib, a dual TYK2/JAK1 inhibitor, shows efficacy in autoimmune diseases, yet its effects on synoviocytes need further exploration.

Purpose of the Study:

• To investigate the molecular and functional impacts of brepocitinib on MH7A and RA-FLS synoviocytes.
• To elucidate the mechanisms by which brepocitinib affects key cell types in RA pathogenesis.

Main Methods:

• Synoviocytes (MH7A, RA-FLS) were treated with brepocitinib (0.5-5 µM).
• Assessed cell viability, Western blotting for signaling pathway and apoptosis markers, qPCR/ELISA for cytokine expression (IL-6, TNF-α, IFN-γ), and wound healing assays for migration.

Main Results:

• Brepocitinib maintained cell viability and significantly suppressed JAK1/STAT3 phosphorylation (>80%) and TYK2/STAT1 inhibition (~70%).
• Reduced IL-6, TNF-α, and IFN-γ mRNA and protein levels, with significant decreases in secreted cytokines.
• Promoted apoptosis by increasing the BAX/BCL-2 ratio and cleaved caspase-3 levels.
• Inhibited synoviocyte migration, reducing wound closure from ~75% to ~20%.

Conclusions:

• Brepocitinib demonstrates multi-faceted effects on RA synoviocytes.
• It inhibits inflammatory signaling, suppresses cytokine production, restores apoptotic sensitivity, and reduces migratory potential.
• These findings provide mechanistic evidence supporting brepocitinib as a targeted therapeutic agent for RA.