ALTERED IMMUNOLOGICAL CIRCADIAN RHYTHMS AND THE EFFECT OF TREATMENT WITH GLUCOCORTICOIDS ON CIRCADIAN RHYTHMS OF IMMUNE CELLS IN PATIENTS WITH RHEUMATOID ARTHRITIS: BRING BACK THE RHYTHM

Background: In rheumatoid arthritis (RA), pain, joint swelling, and stiffness follow a clear circadian pattern. Most of these symptoms are most pronounced in the early morning and primarily attributed to elevated levels of the key proinflammatory cytokines IL-6 and TNFα, which usually peak before clinical symptoms worsen (1). Synthetic glucocorticoids (GCs) are among the most prescribed drugs in the management of patients with RA. GCs have effects on almost every immune cell. GCs suppress expression of various cytokines, including IL-1β, TNFα, IL-6, and GM-CSF. Moreover, circadian rhythms of immune cells are known to be influenced by GCs. For example, GCs govern in part the rhythm of circulating CD4+ and CD8+ T cells. Objectives: To identify circadian patterns for optimization of diagnosis and treatment strategies, we conducted a clinical study comparing healthy donors (HD) and patients with RA in terms of circadian rhythms. We examined the effect of treatment with GCs on circadian immune rhythms in patients with RA. Methods: We recruited 12 HD and 13 patients with active RA (DAS28≥4.0) who either were (n=8) or, for comparison, were not (n=5) under current treatment with GCs. Their biological clock was synchronized for a week before the study day by a scheduled sleep and mealtime regimen. On the study day, participants were provided with regular meals, allowed to eat snacks ad libitum and carry passive activities. We collected blood samples every two hours over a period of 24 hours. The absolute number of circulating immune cells, clock gene expression, and serum cytokine levels were measured with TruCount, qPCR, and multiplex suspension assay, respectively. Results: Peripheral regulatory T cells are circadian in HD and RA, but the number was notably reduced in RA ( Table 1 ). CD8 T cells, CD14 monocytes, and CD19 B cells lost their circadian rhythms in RA, but these rhythms were restored with GC treatment. Circulating NK and NK T cells, which are not diurnal in HD, exhibited circadian fluctuations in RA. GC treatment suppressed diurnal pathological circulation rhythms of NK and NK T cells by reducing the amplitude by half. In monocytes, BMAL1 , PER1 , PER2 , and REVERBA are only circadian in HD. GC restored the rhythms of PER2 and REVERBA . CRY1 expression showed diurnal variation in RA, but not in HD. IL-6 exhibited a circadian pattern in both groups, and GC treatment showed no significant effects on IL-6. Serum IL-4, IL-5, and MIP3α showed circadian variation in HD only. The following cytokines were notably elevated in RA-patients: IFNγ, MIP1α, MIP1β, IL-1β, IL-2, IL-17A, and IL-21. GC reduced the expression of IL-10 significantly in RA. Table 1. Circadian rhythms in the cellular, gene, and protein levels in HD, RA, and RA with ongoing GC treatment Comparison Circadian / GC impact Circulating immune cells Clock genes in monocytes Serum cytokines HD vs. RA Non-circadian in HD and RA - CLOCK, CRY2, DBP, RORA Fractaline, IFNγ, CXCL11, GM-CSF, MIP1α, MIP1β, IL-1β, IL-2, IL-4, IL-7, IL-8, IL-10, IL-12, IL-13, IL-17A, IL-21, IL-23 Circadian in HD and RA CD3 , CD4 , regulatory T cells PER3 IL-6 Circadian in HD CD8 T cells, CD14 monocytes, CD19 B cells BMAL1,PER1, PER2, REVERBA IL-4, IL-5, MIP3α Circadian in RA NK cells, NK T cells CRY1 - RA vs. GCs-treated RA Restorative effect by GC CD8 T cells, CD19 B cells PER2, REVERBA - Enhancing effect by GC regulatory T cells PER3, CRY1 - Dampening effect by GC NK T cells, NK cells - - Conclusion: In patients with RA, we found a certain loss of circadian rhythms and the establishment of “inflammatory” rhythms. GC treatment in patients with RA resulted in three different types of effects on circadian rhythms at immune cell level: restoration, amplification, and attenuation. In conclusion, these findings provide new insights into the pathophysiology of circadian rhythms in RA that could be used to optimize diagnosis and treatment. REFERENCES: [1] Clocking in: chronobiology in rheumatoid arthritis. Buttgereit, Frank, et al. 2015, Nature Reviews Rheumatology, Vol. 11, pp. 349–356. Acknowledgements: We thank all participants for their contribution. We thank our clinical study team: Manuela Jakstadt, Lisa Ehlers, Alexandra Damerau, Annamarie Lang, Moritz Pfeiffenberger, Gabriela May, and Pierre-Louis Krauß. Disclosure of Interests: None declared. Citation: , volume 81, supplement 1, year 2022, page 53Session: Rheumatoid arthritis - aetiology, pathogenesis and animal models (Oral Presentations)