TFAM deficiency promotes mitochondrial dysfunction to drive inflammation in the corneas of dry eye disease through mtDNA stress-mediated AIM2 inflammasome activation
Background & Aims Mitochondrial dysfunction and mtDNA stress-mediated inflammasome activation play critical roles in the pathogenesis of dry eye disease (DED). Mitochondrial transcription factor A (TFAM) is essential for regulating mtDNA stability and mitochondrial homeostasis. However, the mechanism underling TFAM to infuence DED progression is largely unknown. As a cytosolic DNA sensor, absent in melanoma 2 (AIM2) may contribute to the development of DED. Therefore, we aimed to explore whether the role of TFAM is associated with AIM2 inflammasome activation in DED. Methods The changes in inflammation, mitochondrial function, mtDNA homeostasis and TFAM expression were analyzed in the corneas of DED mice in vivo and in HCECs under oxidative stress in vitro. The effects of TFAM knockout on mtDNA homeostasis, mitochondrial respiration and cytokine release were also investigated in HCECs. The mechanism was analyzed by RNA sequencing in the corneas of DED mice, which was further verified by the HCECs with TFAM depletion. Results We found that the corneas of DED mice and HCECs under oxidative stress exhibited inflammation, mitochondrial damage and mtDNA maintenance disruption , which were highly associated with significantly reduced TFAM protein levels. Furthermore, we demonstrated that silencing of TFAM in HCECs suppressed mitochondrial respiratory capacity, induced mtDNA released into the cytosol and triggered cytokine release. Mechanistically, cytosolic mtDNA accumulation caused by TFAM depletion activated the AIM2 inflammasome and facilitated inflammation, thereby driving DED progression. Conclusions Our findings elucidate that TFAM deficiency induces mitochondrial dysfunction and cytosolic mtDNA stress, which subsequently activates the AIM2 inflammasome, triggers inflammatory responses and promotes DED progression. TFAM pathway may provide a novel therapeutic strategy for DED. Overall design: The global gene expression of cornea in dry eye disease mice and control mice was analyzed and compared (n=4).