Hyperactivation of the cGAS-STING pathway promotes liver inflammation in Down syndrome

Patients with Down Syndrome (DS) are characterized by dysfunction of several organs, including the liver, brain, heart defects, gastrointestinal anomalies, and lethal immune hypersensitivity. A person with DS is also susceptible to various inflammatory diseases, including hepatic autoimmune diseases. The Cyclic guanosine monophosphate-adenosine monophosphate synthase (cGAS) is known to trigger the stimulator of interferon genes (STING) and downstream proinflammatory factors. In this work, we hypothesized that oxidative stress-associated DNA damage triggers activation of the cGAS-STING signaling pathway and promotes liver inflammation in DS. Here, we investigated the role of reactive oxygen species (ROS) associated DNA damage and the cGAS-STING signaling pathway in the pathogenesis of hepatic inflammation in the DS model. Our results showed that DS cells harbor excessive ROS and DNA damage in DS fibroblasts and DS mouse liver. Further, DS cells accumulate micronuclei that likely serve as a source of cytoplasmic DNA to stimulate cGAS-STING activation. In addition, RNA-seq analysis results showed enhanced expression of key type I interferon factors in cGAS-STING pathways in DS liver and inflammatory responses and elevated liver enzymes such as alanine transaminase (ALT) that indicate a hepatocellular liver injury in DS. The results of this study opened the opportunity to connect endogenous DNA damage triggers innate immune response, which may contribute to the upregulation of the cGAS-STING signaling to exacerbate hepatic inflammation in DS.