P2Y₂ receptor antagonism resolves sialadenitis and improves salivary flow in a Sjögren's syndrome mouse model

Objective: Sjögren's syndrome (SS) is a chronic autoimmune exocrinopathy characterized by lymphocytic infiltration of the salivary and lacrimal glands and decreased saliva and tear production. Previous studies indicate that the G protein-coupled P2Y₂ nucleotide receptor (P2Y₂R) is upregulated in numerous models of salivary gland inflammation (i.e., sialadenitis), where it has been implicated as a key mediator of chronic inflammation. Here, we evaluate both systemic and localized P2Y₂R antagonism as a means to resolve sialadenitis in the NOD.H-2^h4,IFNγ^−/−,CD28^−/− (NOD.H-2^h4 DKO) mouse model of SS. Design: Female 4.5 month old NOD.H-2^h4 DKO mice received daily intraperitoneal injections for 10 days of the selective P2Y₂R antagonist, AR-C118925, or vehicle-only control. Single-dose localized intraglandular antagonist delivery into the Wharton's duct was also evaluated. Carbachol-induced saliva was measured and then submandibular glands (SMGs) were isolated and either fixed and paraffin-embedded for H&E staining, homogenized for RNA isolation or dissociated for flow cytometry analysis. Results: Intraperitoneal injection, but not localized intraglandular administration, of AR-C118925 significantly enhanced carbachol-induced salivation and reduced lymphocytic foci and immune cell markers in SMGs of 5 month old NOD.H-2^h4 DKO mice, compared to vehicle-injected control mice. We found that B cells represent the primary immune cell population in inflamed SMGs of NOD.H-2^h4 DKO mice that express elevated levels of P2Y₂R compared to C57BL/6 control mice. We further demonstrate a role for P2Y₂Rs in mediating B cell migration and the release of IgM. Conclusion: Our findings suggest that the P2Y₂R represents a novel therapeutic target for the treatment of Sjögren's syndrome.