Elucidation of the anti-arthritic mechanism of Guizhi-Shaoyao-Zhimu decoction by reshaping circadian rhythm

Rheumatoid Arthritis (RA) exhibits pronounced circadian oscillations, with variations in joint stiffness, pain, and swelling following rhythmic patterns. Our preliminary research suggests that inflammatory cytokines in RA serum display rhythmicity closely associated with circadian rhythms. Additionally, circadian clock genes show a tendency towards disordered expression in RA, suggesting potential new therapeutic avenues from a circadian perspective. Traditional Chinese Medicine's Guizhi-Shaoyao-Zhimu Decoction (GSZD) has demonstrated clinical efficacy in RA, yet its underlying mechanism remains elusive. Our study confirms the effectiveness of GSZD in alleviating arthritis symptoms, reducing bone destruction, and lowering the expression of related inflammatory cytokines. Notably, we found that GSZD modulates the core circadian gene NR1D1 in a dose-dependent and time-selective manner. The administration of GSZD at 10 AM demonstrated enhanced anti-arthritic effects, which were mediated by regulating NR1D1 and suppressing the NLRP3-IL-18/IL-1β inflammatory signaling pathway. Moreover, silencing of NR1D1 significantly upregulated the expression of NLRP3, IL-18, and IL-1β. In NR1D1-deficient macrophages, GSZD failed to inhibit the NLRP3 inflammasome and inflammatory cytokines such as IL-18, and IL-1β. Overall, GSZD exerts therapeutic benefits for RA patients via activating NR1D1 and the interplay between molecular-based circadian rhythms and immune balance develop new avenues for targeted RA treatments, offering innovative strategies for the timing and administration of therapies.