Oxidized DNA fragments exit mitochondria via mPTP- and VDAC-dependent channels to activate NLRP3 inflammasome and interferon signaling

• Published in: Immunity (Cambridge, Mass.) Vol. 55; no. 8; pp. 1370 - 1385.e8
• Main Authors: Xian, Hongxu, Watari, Kosuke, Sanchez-Lopez, Elsa, Offenberger, Joseph, Onyuru, Janset, Sampath, Harini, Ying, Wei, Hoffman, Hal M., Shadel, Gerald S., Karin, Michael
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 09.08.2022
• Subjects: Animals; cGAS-STING; DNA, Mitochondrial - metabolism; FEN1; Inflammasomes - metabolism; Interferons - metabolism; Mice; mitochondria; Mitochondria - metabolism; Mitochondrial Permeability Transition Pore; mPTP; mtDNA; NLR Family, Pyrin Domain-Containing 3 Protein - metabolism; NLRP3 inflammasome; Nucleotidyltransferases - metabolism; OGG1; Ox-mtDNA; VDAC; FEN1; Ox-mtDNA; mtDNA; mitochondria; OGG1; VDAC; cGAS-STING; NLRP3 inflammasome; mPTP
• ISSN: 1074-7613; 1097-4180; 1097-4180
• DOI: 10.1016/j.immuni.2022.06.007

Mitochondrial DNA (mtDNA) escaping stressed mitochondria provokes inflammation via cGAS-STING pathway activation and, when oxidized (Ox-mtDNA), it binds cytosolic NLRP3, thereby triggering inflammasome activation. However, it is unknown how and in which form Ox-mtDNA exits stressed mitochondria in non-apoptotic macrophages. We found that diverse NLRP3 inflammasome activators rapidly stimulated uniporter-mediated calcium uptake to open mitochondrial permeability transition pores (mPTP) and trigger VDAC oligomerization. This occurred independently of mtDNA or reactive oxygen species, which induce Ox-mtDNA generation. Within mitochondria, Ox-mtDNA was either repaired by DNA glycosylase OGG1 or cleaved by the endonuclease FEN1 to 500–650 bp fragments that exited mitochondria via mPTP- and VDAC-dependent channels to initiate cytosolic NLRP3 inflammasome activation. Ox-mtDNA fragments also activated cGAS-STING signaling and gave rise to pro-inflammatory extracellular DNA. Understanding this process will advance the development of potential treatments for chronic inflammatory diseases, exemplified by FEN1 inhibitors that suppressed interleukin-1β (IL-1β) production and mtDNA release in mice. [Display omitted] •Ca2+ uptake via MCU triggers IMM mPTP opening to induce OMM VDAC oligomerization•Ox-mtDNA is repaired by OGG1 or cleaved by FEN1 to fragments that exit mitochondria•Cytosolic Ox-mtDNA activates NLRP3 inflammasome and cGAS-STING and escapes cells•mtOGG1 and FEN1 inhibitors suppress acute peritonitis and reduce circulating mtDNA Ox-mtDNA enables NLRP3 inflammasome activation, but how Ox-mtDNA reaches the cytoplasm is unclear. In this issue of Immunity, Xian et al. show that Ox-mtDNA cleaved by FEN1 escapes mitochondria via mPTP and VDAC channels to activate NLRP3 inflammasome and STING.