TFAM Deficiency Triggers mtDNA Leakage and cGAS-STING-Mediated Intestinal Ischemia-Reperfusion Injury.

Abstract

Intestinal Ischemia-Reperfusion (IIR) injury is a common clinical pathophysiological condition, yet the complex molecular mechanisms underlying its pathology remain incompletely understood. This study aims to explore the precise molecular mechanisms of IIR injury, with a focus on the role of the cGAS-STING signaling pathway. Using a mouse IIR model and hypoxia/reoxygenation (HR) model in HT-29 cells and small intestinal organoids, we observed that IIR significantly induces oxidative stress and activates the cGAS-STING pathway, which is associated with exacerbated small intestinal tissue damage and enhanced inflammatory responses. Further investigation revealed that mitochondrial DNA (mtDNA) leakage is a critical trigger for the activation of the cGAS-STING pathway. The introduction of exogenous mtDNA into cells activated the STING pathway and exacerbated cellular damage. In contrast, the depletion of intracellular mtDNA effectively suppressed HR-induced activation of the cGAS-STING pathway. Mechanistically, we found that IIR downregulates mitochondrial transcription factor A (TFAM), which subsequently affects mtDNA stability, promoting the release of mtDNA into the cytoplasm and triggering the cGAS-STING pathway. Overexpression of TFAM stabilized mtDNA, reduced the accumulation of cytoplasmic mtDNA, inhibited cGAS-STING pathway activation, and alleviated cellular damage. Moreover, STING-deficient mice exhibited reduced inflammation, less tissue damage, and improved survival rates following IIR, highlighting the critical role of the STING pathway in IIR-induced injury. Our findings elucidate the close association between oxidative stress, inflammation, and cGAS-STING pathway activation in IIR. mtDNA leakage and TFAM downregulation are key mechanisms driving this activation. Importantly, TFAM plays a crucial role in stabilizing mtDNA and reducing mtDNA leakage during IIR. These results not only deepen our understanding of the molecular pathogenesis of IIR injury but also provide potential therapeutic strategies targeting the cGAS-STING pathway for treating IIR-related diseases.