Pulmonary Involvement in a Mouse Model of Sjögren's Syndrome Induced by STING Activation

Sjögren's Syndrome (SS), a chronic autoimmune disorder affecting multiple organ systems, is characterized by an elevated type I interferon (IFN) response. Activation of Stimulator of Interferon Genes (STING) protein induces type I IFN and in mice, several features of SS, including anti-nuclear antibodies, sialadenitis, and salivary gland dysfunction. Since lung involvement occurs in one-fifth of SS patients, we investigated whether systemic activation of STING also leads to lung inflammation. Lungs from female C57BL/6 mice injected with the STING agonist 5, 6-Dimethylxanthenone-4-acetic acid (DMXAA), were evaluated for acute and chronic inflammatory responses. Within 4h of DMXAA injection, the expression of Ifnb1, Il6, Tnf, Ifng, and Mx1 was significantly upregulated. At 1 and 2 months post-treatment, lungs showed lymphocytic infiltration in the peri-bronchial regions. The lungs from DMXAA treated mice showed an increased expression of multiple chemokines and an increase in lymphatic endothelial cells. Despite STING expression in bronchial epithelium and cells lining the alveolar wall, bone marrow chimeras between STING knockout and wild type mice showed that STING expression in hematopoietic cells was critical for lung inflammation. Our results suggest that activation of the STING pathway might be involved in SS patients with concomitant salivary gland and lung disease.