Sjögren’s disease (SjD) is a chronic autoimmune disorder characterized primarily by xerostomia and xerophthalmia, and it may also cause systemic multi-organ involvement that markedly impairs the quality of life of SjD patients. T cell- and B cell-mediated immune dysregulation is central to SjD pathogenesis, and the underlying mechanisms have not been well-defined. Previous research demonstrated the pathogenic role of JAK/STAT pathway in multiple autoimmune diseases, including SjD. Upadacitinib, a selective JAK1 inhibitor, has shown significant efficacy in ulcerative colitis (UC), atopic dermatitis (AD), and ankylosing spondylitis (AS). However, the clinical effects and immunological mechanisms in SjD remain unclear. This study primarily demonstrated the efficacy of Upadacitinib in the NOD mouse model of SjD and further illustrated its immunomodulatory effect in SjD.

Twelve 7-week-old NOD/ShiLtJ mice were assigned to two groups according to body weight. Mice in the treatment group received Upadacitinib (25 mg/kg) by oral gavage at 8 weeks of age, while control mice received an equal volume of vehicle. Treatment continued for 10 weeks. During the progress, body weight and blood glucose were monitored every 2 weeks. Salivary flow rate was measured under anesthesia at baseline and after 10 weeks of treatment. At the end of the treatment, serum, submandibular glands, spleens, and lymph nodes were collected. Submandibular glands were subjected to hematoxylin and eosin staining, and histopathological changes were evaluated using inflammatory infiltration scores and inflammatory area analysis to assess the pathological changes. Splenic and lymph node immune cell subsets were analyzed by flow cytometry to assess the effect of upadacitinib on the distribution of immune cell subsets in peripheral immune organs.

During the 10-week treatment period, mice in the control group developed non obese diabetes (>13.9 mmol/L) at 12 weeks of age, while no obvious increase was observed in the upadacitinib group. During the weight-loss phase (16–18 weeks), control mice exhibited a more rapid decline in body weight compared with treated mice (Figure 1). Salivary flow rate in the control group decreased slightly over time (4.438 ± 2.013 vs. 4.260 ± 2.251 mg/min), while the upadacitinib group showed an increasing trend (3.996 ± 2.807 vs. 6.174 ± 3.290 mg/min) (Figure 2). At the age of 18 weeks, the salivary flow rate in the upadacitinib group was higher than that in the control group. Histological analysis of submandibular glands showed that both the pathology score (1.167 ± 0.408 vs. 2.500 ± 0.837, p = 0.028) and inflammatory area (0.394 ± 0.307 vs. 1.425 ± 0.431, p = 0.043) were significantly reduced in the upadacitinib group compared with controls (Figure 3). Flow cytometry further demonstrated that upadacitinib reduced the proportions of Th1, Th17, and Tfh cells in both spleens and lymph nodes (Figure 4-5). In addition, the proportion of germinal center B cells (GCBs) in lymph nodes was significantly decreased following treatment (3.060 ± 1.779 vs. 0.638 ± 0.162, p=0.026, %) (Figure 6).

Upadacitinib may delay the onset of Sjögren's disease and autoimmune diabetes in NOD mice by suppressing immune responses, thereby attenuating disease-associated weight loss and preserving salivary gland secretory function. Treatment with upadacitinib significantly reduced inflammatory infiltration in the submandibular glands, as reflected by both pathology scores and inflammatory area measurements, suggesting a potential role for limiting glandular lymphocytic infiltration and ectopic germinal center formation. These effects may be mediated by reductions in pathogenic Th1, Th17, Tfh, and germinal center B-cell populations. Collectively, this study provides preliminary evidence supporting the therapeutic potential of upadacitinib in SjD. The underlying molecular mechanisms remain to be further investigated.