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TFAM deficiency promotes mitochondrial dysfunction to drive inflammation in the corneas of dry eye disease through mtDNA stress-mediated AIM2 inflammasome activation

ABSTRACT: 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.

ORGANISM(S): Mus musculus

PROVIDER: GSE252984 | GEO | 2024/06/18

REPOSITORIES: GEO

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Project description:The goal of this analysis was to utilize microarray profiling to identify basal alterations in gene expression in response to TFAM depletion and mtDNA stress. Mitochondrial DNA (mtDNA) is normally present at thousands of copies per cell and is packaged into several hundred higher-order structures termed nucleoids. The abundant mtDNA-binding protein, TFAM (transcription factor A,mitochondrial), regulates nucleoid architecture, abundance and segregation. Complete mtDNA depletion profoundly impairs oxidative phosphorylation, triggering calcium-dependent stress signalling and adaptive metabolic responses. However, the cellular responses to mtDNA instability, a physiologically relevant stress observed in many human diseases and ageing, remain poorly defined. Here we show that moderate mtDNA stress elicited by TFAM deficiency engages cytosolic antiviral signalling to enhance the expression of a subset of interferon-stimulated genes. Mechanistically, we find that aberrant mtDNA packaging promotes escape of mtDNA into the cytosol, where it engages the DNA sensor cGAS (also known as MB21D1) and promotes STING (also known as TMEM173)–IRF3-dependent signalling to elevate interferon-stimulated gene expression, potentiate type I interferon responses and confer broad viral resistance. Furthermore, we demonstrate that herpesviruses induce mtDNA stress, which enhances antiviral signalling and type I interferon responses during infection. Our results further demonstrate that mitochondria are central participants in innate immunity, identify mtDNA stress as a cell-intrinsic trigger of antiviral signaling and suggest that cellular monitoring of mtDNA homeostasis cooperates with canonical virus sensing mechanisms to fully engage antiviral innate immunity. Murine embryonic fibroblasts were isolated from wild-type or Tfam+/- E13.5 littermate embryos. RNA from passage-matched wild-type and Tfam+/- MEF lines was extracted in duplicate and hybridized onto Affymetrix microarrays. Four arrays were performed in total with two technical replicates per genotype.

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TFAM deficiency promotes mitochondrial dysfunction to drive inflammation in the corneas of dry eye disease through mtDNA stress-mediated AIM2 inflammasome activation

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