Inhibition of IL‐6/STAT3 Signaling by N‐Trans‐Hibiscusamide and Its Derivative in a Mouse Model of Collagen‐Induced Arthritis

Rheumatoid arthritis is a chronic autoimmune disease characterized by persistent joint inflammation and progressive joint destruction, leading to pain, disability, and reduced quality of life. Interleukin-6 is a key pro-inflammatory cytokine that plays a central role in the pathogenesis of rheumatoid arthritis by activating downstream inflammatory signaling pathways. Dysregulation of the interleukin-6-mediated signaling cascade, particularly the signal transducer and activator of transcription 3 pathway, contributes to sustained inflammation and disease progression, highlighting this axis as an important therapeutic target. Rheumatoid arthritis (RA) is a chronic autoimmune disorder characterized by joint inflammation and destruction, with interleukin-6 (IL-6) playing a central role in its pathogenesis by driving inflammatory responses. Targeting the IL-6/signal transducer and activator of transcription 3 (STAT3) pathway has emerged as a promising therapeutic approach for RA. This study investigates the inhibitory effects and underlying mechanisms of <i>N</i>-trans-hibiscusamide (NHA) and its derivative 4-<i>O</i>-(<i>E</i>)-feruloyl-<i>N</i>-(<i>E</i>)-hibiscusamide (HAD) on the IL-6/STAT3 signaling axis. Using a phosphorylated STAT3 luciferase reporter assay, NHA and HAD significantly reduced IL-6-induced luciferase activity. They also downregulated IL-6-induced gene expression, inhibited STAT3 nuclear translocation and phosphorylation of signaling molecules, and suppressed IL-6/interleukin-6 receptor binding. In a collagen-induced arthritis mouse model, both compounds alleviated arthritis symptoms, decreased serum levels of anti-type II collagen immunoglobulin G and interleukin-17A, and downregulated T helper 17-specific genes in the spleen. Furthermore, in vitro experiments demonstrated that NHA and HAD inhibited the differentiation of naïve CD4-positive T cells into T helper 17 cells. These findings suggest that NHA and HAD effectively modulate interleukin-6-mediated inflammatory signaling and may serve as potential therapeutic candidates for the management of rheumatoid arthritis.