Lactate-induced mtDNA Accumulation Activates cGAS-STING Signaling and the Inflammatory Response in Sjögren's Syndrome

Acinar epithelial cell atrophy in secretory glands is a hallmark of primary Sjögren's syndrome (pSS), the cause of which is far from elucidated. We examined the role of acinar atrophy by focusing on the metabolism of glandular epithelial cells and mitochondria in the pSS environment. After confirming the presence of a high-lactate environment in the labial glands of human pSS patients, we used the A253 cell line and NOD/Ltj mice as models to investigate the metabolic changes in salivary gland epithelial cells in a high-lactate environment in vitro and in vivo. We found that epithelial cells produced high levels of IL-6, IL-8, IFN-α, IFN-β and TNF-α and exhibited significant NF-κB and type I IFN-related pathway activation. The results confirmed that lactate damaged mitochondrial DNA (mtDNA) and led to its leakage, which subsequently activated the cGAS-STING pathway. Inflammatory cytokine production and pathway activation were inhibited in vivo and in vitro by the lactate scavenger sodium dichloroacetate (DCA). Our study provides new insights into the etiology and treatment of pSS from the perspective of cell metabolism.