Reticuline alleviates rheumatoid arthritis by suppressing the JAK/STAT signaling pathway.

Rheumatoid arthritis (RA) is a chronic autoimmune disorder characterized by persistent inflammation and progressive joint destruction, in which aberrant activation of the JAK/STAT signaling pathway plays a central pathogenic role. Although JAK inhibitors are utilized in clinical practice, emerging limitations such as potential resistance underscore the need to identify novel therapeutic modulators. Reticuline, a natural isoquinoline alkaloid, has not been systematically investigated for its anti‑arthritic efficacy or mechanism of action. In this study, we integrated network pharmacology, molecular docking, in vitro assays, and a collagen‑induced arthritis (CIA) mouse model to comprehensively evaluate the therapeutic potential of reticuline and elucidate its underlying mechanisms. Network analysis predicted the JAK‑STAT pathway as a primary pathway involved. Molecular docking results suggested that reticuline could potentially bind to the ATP-binding pocket of JAK2, forming five hydrogen bonds. In TNF‑α‑stimulated human synovial fibroblasts (MH7A), reticuline (10 and 20 µM) significantly suppressed cell migration and intracellular ROS generation, downregulated IL‑6 mRNA, and upregulated IL‑10 and IL-1β mRNA expression. Importantly, reticuline markedly inhibited the phosphorylation and mRNA expression of JAK2 and STAT3. In CIA mice, reticuline administration (0.5 and 1 mg/kg/day) substantially reduced clinical arthritis scores, synovial hyperplasia, and bone erosion, while modulating serum cytokine profiles (lowering TNF‑α, IL‑1β, and IL‑17, and elevating IL‑10). Consistent with the cellular findings, reticuline also attenuated activation of the JAK2/STAT3 pathway in joint tissues. In summary, this work provides the first systematic preclinical evidence that reticuline ameliorates RA pathology by suppressing the JAK2/STAT3 signaling cascade, positioning it as a promising preclinical candidate, providing a foundation for further translational development of reticuline for RA treatment. Keypoints • Reticuline ameliorates rheumatoid arthritis by suppressing the JAK2/STAT3 signaling pathway, reducing inflammation and joint destruction both in vitro and in vivo. • This study provides the first systematic evidence integrating network pharmacology, cellular assays, and a disease model to establish reticuline as a natural JAK/STAT inhibitor for RA.