Sjögren syndrome (SS), a chronic autoimmune disorder causing dry mouth, adversely affects the overall oral health in patients. Activation of innate immune responses and excessive production of type I interferons (IFNs) play a critical role in the pathogenesis of this disorder. Recognition of nucleic acids by cytosolic nucleic acid sensors is a major trigger for the induction of type I IFNs. Upon activation, cytosolic DNA sensors can interact with the stimulator of interferon genes (STING) protein, and activation of STING causes increased expression of type I IFNs. The role of STING activation in SS is not known. In this study, to investigate whether the cytosolic DNA sensing pathway influences SS development, female C57BL/6 mice were injected with a STING agonist, dimethylxanthenone-4-acetic acid (DMXAA). Salivary glands (SGs) were studied for gene expression and inflammatory cell infiltration. SG function was evaluated by measuring pilocarpine-induced salivation. Sera were analyzed for cytokines and autoantibodies. Primary SG cells were used to study the expression and activation of STING. Our data show that systemic DMXAA treatment rapidly induced the expression of Ifnb1, Il6, and Tnfa in the SGs, and these cytokines were also elevated in circulation. In contrast, increased Ifng gene expression was dominantly detected in the SGs. The type I innate lymphoid cells present within the SGs were the major source of IFN-γ, and their numbers increased significantly within 3 d of treatment. STING expression in SGs was mainly observed in ductal and interstitial cells. In primary SG cells, DMXAA activated STING and induced IFN-β production. The DMXAA-treated mice developed autoantibodies, sialoadenitis, and glandular hypofunction. Our study demonstrates that activation of the STING pathway holds the potential to initiate SS. Thus, apart from viral infections, conditions that cause cellular perturbations and accumulation of host DNA within the cytosol should also be considered as possible triggers for SS.

Patients with Sjögren's syndrome, an autoimmune disease affecting the exocrine glands, develop salivary gland inflammation and have reduced saliva production. Similarly, saliva production is severely compromised in patients receiving radiation treatment for head and neck cancers. Rodent models, developed to mimic these clinical conditions, facilitate an understanding of the disease pathogenesis and allow for the development of new therapeutic strategies. Therefore, the ability to accurately, reproducibly, and repeatedly measure salivary gland function in animal models is critical. Building on procedures previously described in the literature, a method was developed that meets these criteria and was used to evaluate salivary gland function in mice. An additional advantage of this new method is that it is easily mastered, and has little inter-operator variation. Salivary gland function is evaluated as the amount (weight or volume) or rate (mL/min) of saliva produced in response to pilocarpine stimulation. The collected saliva is a good source for the analyses of protein content, immunoglobulin concentrations, and other biomolecules.

the non-obese Diabetic (noD) mouse model for type i diabetes also develops some features of Sjögren's syndrome (SS). Since the source of the mice and the environment exert a strong influence on diabetes, this study investigated SS development in noD mice obtained from two vendors. female noD mice from the Jackson Laboratory (JAX) and taconic Biosciences were monitored for blood glucose and pilocarpine-induced salivation. The gut microbiome was analyzed by 16S rRNA sequencing of stool DnA. At euthanasia, serum cytokines and sialoadenitis severity were evaluated. the onset of diabetes was significantly accelerated in JAX mice compared to Taconic mice. Although the gut microbiome between the two groups was distinct, both groups developed sialoadenitis. there was no correlation between the severity of sialoadenitis and reduced saliva production. instead, salivary gland dysfunction was associated with hyperglycemia and elevation of serum IL1β, IL16, and CXCL13. Our data suggest that inflammatory pathways linked with hyperglycemia are confounding factors for salivary gland dysfunction in female noD mice, and might not be representative of the mechanisms operative in SS patients. considering that noD mice have been used to test numerous experimental therapies for SS, caution needs to be exerted before advancing these therapeutics for human trials. Reduced fluid secretion by the exocrine salivary and lacrimal glands is a major cause of dry mouth and dry eyes in Sjögren's syndrome (SS) 1. Multiple factors like intrinsic glandular defects, innate immune activation, and adaptive autoimmune responses contribute to the development of glandular dysfunction in SS. The Non-obese Diabetic (NOD) mouse model, primarily developed to study type I diabetes, is extensively used to investigate the pathogenic mechanisms in SS 2. Although under a robust genetic control, environmental factors also significantly affect the development of diabetes in the NOD mouse 3. The environmental influence is exemplified by studies showing differences in the incidence of hyperglycemia in NOD mice obtained from two different commercial sources, The Jackson Laboratory (JAX) and Taconic Biosciences 4. The NOD mice have been used for several preclinical drug studies for SS 5-11. Since the mice are obtained from different commercial sources or are bred within the investigator's facility, they are exposed to distinct housing conditions. Thus, it is not surprising to note considerable variations in the incidence, severity, and kinetics of SS in NOD mice. We undertook this study to investigate whether the commercial source of the mice influences the development of SS in NOD mice housed under the same environment. Our results demonstrate that the NOD mice from JAX had an accelerated onset of diabetes; in contrast, the Taconic mice had a significantly (p = 0.0289) higher severity of salivary gland inflammation. Regardless of the commercial source, mice showed evidence for salivary gland dysfunction, which was strongly associated with hyperglycemia.

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Autoantibodies reactive against Ro52 are present in 70% of Sjögren’s syndrome patients and are associated with higher disease severity. However, their role in causing aqueous deficient dry eye, a major cause for morbidity in Sjögren’s syndrome, is unclear. To investigate whether immune responses targeting Ro52 contribute towards the dry eye, male and female NZM2758 mice were immunized with recombinant Ro52. Tear production was measured by the phenol red thread test. Sera were analyzed for anti-Ro52 levels by immunoprecipitation. Lacrimal glands were evaluated for inflammatory foci and IgG deposits. Our results showed that, although all mice generated anti-Ro52 antibodies, only females developed a significant drop in tear production. None of the mice developed severe lacrimal gland inflammation, and female mice with anti-Ro52 showed higher levels of IgG deposits within their glands. Passive transfer of anti-Ro52 sera caused reduced tear production in female mice, but not in males. This study demonstrates for the first time that immune responses initiated by Ro52 induce aqueous dry eye, and this may be driven by anti-Ro52 antibodies. Furthermore, the sexual dimorphism in glandular dysfunction suggests that the lacrimal glands in females are more susceptible to autoantibody-mediated injury.