Inhibition of JAK-STAT pathway corrects salivary gland inflammation and interferon driven immune activation in Sjögren’s Disease

Abstract Objectives Inflammatory cytokines that signal through the JAK-STAT pathway, especially interferons (IFNs), are implicated in Sjögren’s Disease (SjD). Although inhibition of JAKs is effective in other autoimmune diseases, a systematic investigation of IFN-JAK-STAT signaling and effect of JAK inhibitor (JAKi) therapy in SjD-affected human tissues has not been reported. Methods Human minor salivary glands (MSGs) and peripheral blood mononuclear cells (PBMCs) were investigated using bulk or single cell (sc) RNA sequencing (RNAseq), immunofluorescence microscopy (IF), and flow cytometry. Ex vivo culture assays on PBMCs and primary salivary gland epithelial cell (pSGEC) lines were performed to model changes in target tissues before and after JAKi. Results RNAseq and IF showed activated JAK-STAT pathway in SjD MSGs. Elevated IFN-stimulated gene (ISGs) expression associated with clinical variables (e.g., focus scores, anti-SSA positivity). scRNAseq of MSGs exhibited cell-type specific upregulation of JAK-STAT and ISGs; PBMCs showed similar trends, including markedly upregulated ISGs in monocytes. Ex vivo studies showed elevated basal pSTAT levels in SjD MSGs and PBMCs that were corrected with JAKi. SjD-derived pSGECs exhibited higher basal ISG expressions and exaggerated responses to IFNβ, which were normalized by JAKi without cytotoxicity. Conclusions SjD patients’ tissues exhibit increased expression of ISGs and activation of the JAK-STAT pathway in a cell type-dependent manner. JAKi normalizes this aberrant signaling at the tissue level and in PBMCs, suggesting a putative viable therapy for SjD, targeting both glandular and extraglandular symptoms. Predicated on these data, a Phase Ib/IIa randomized controlled trial to treat SjD with tofacitinib was initiated. What is already known on this topic? Upregulation of interferons (IFNs) has been reported in patients with SjD; however, a systematic investigation of their role at a cellular and tissue level in humans is lacking. What this study adds? Our findings conclusively show that the IFN-JAK-STAT pathway is activated in the salivary glands and PBMCs in patients with SjD Specific cells in the MSGs (infiltrating lymphocytes, epithelial, antigen presenting cells, and endothelial cells) and in PBMCs (monocytes, NK cells, and dendritic cells) drive this IFN signature. We pinpoint cells responsive to JAK inhibition and illustrate in patient tissues that JAK inhibitors may be beneficial in SjD by uncoupling the pathogenic cytokine milieu and resultant epithelial tissue damage and dysfunction central to SjD. How this study might affect research, practice, or policy? SjD lacks an approved, efficacious and targeted therapy. Several large clinical trials have been unsuccessful due in part to a lack of biologically relevant endpoints or predictive biomarkers. We establish a multimodal testing platform using human tissues from SjD patients to identify actionable targets and to directly test treatment effects. Our data suggest that blocking the IFN-JAK-STAT pathway by using JAKi is a rational therapy for SjD. Moreover, these data can also serve as biological endpoints for clinical trials [ NCT04496960 ].