Expression of Janus kinases in labial salivary glands of patients with Sjögren's syndrome

Primary Sjögren's syndrome (pSS) is a chronic autoimmune disease that affects exocrine glands, such as salivary and lacrimal glands. The Janus kinase (JAK) /signal transducer and activator of transcription (STAT) pathway are activated in various inflammatory diseases including pSS. This study aimed to investigate the expression of JAK1, JAK2, phosphorylated JAK1, and phosphorylated JAK2 in labial salivary gland (LSG) tissues from patients with pSS to evaluate the potential of JAK inhibitors as therapeutic agents for pSS. Immunohistochemical analysis was performed using LSG tissues of patients with pSS (n=10), non-SS (n=5), and healthy controls (n=5). In acinar epithelial cells, JAK1, JAK2, and phosphorylated JAK1 were expressed at significantly lower levels in LSG tissues of patients with pSS than in healthy controls. Significantly higher expression of phosphorylated JAK1 and phosphorylated JAK2 was observed in the ductal epithelial cells of patients with pSS compared to the controls. However, there was no significant association between the expression levels of phosphorylated JAK1 or JAK2 and the degree of inflammation. In addition, immunofluorescence analysis revealed JAK2 phosphorylation in many CD3 + T cells infiltrating the LSG tissues. These results suggested the activation of JAK/STAT signaling in both the ductal epithelial cells and the infiltrating CD3 + T cells in the LSG tissues of patients with pSS. Therefore, JAK inhibitors may be effective therapeutic agents for pSS by regulating both effector T cells and target cells.