Oxidation of human mitochondrial RNA strongly potentiates immunostimulation in an interferon-associated manner.

Inflammation is associated with a wide range of medical conditions, most leading causes of death, and high healthcare costs. It can thus benefit from new insights. Here we extended previous studies and found that oxidation of human native mtRNA to 'mitoxRNA' strongly potentiated IFNβ and TNFα immunostimulation in human cells, and that this newly identified type 1 interferon potentiation was transcriptional. This potentiation was significantly greater than with mtDNA oxidation, and t-butylhydroperoxide (tBHP) oxidation of RNA was more proinflammatory than hydrogen peroxide (HP). mtRNA triggered a modest increase in apoptosis that was not potentiated by oxidation, and mtDNA triggered a much greater increase. For native mtRNA, we found that chloroquine-inhibitable endosomes and MDA5 are key signaling pathways for IFNβ and TNFα production. For mitoxRNAs, RNAseq revealed a major increase in both tBHP- and HP-mitoxRNA modulated genes compared with native mtRNA. This increase was very prominent for interferon-related genes, identifying them as important mediators of this powerful oxidation effect. Moderately different gene modulations and KEGG pathways were observed for tBHP- versus HP-mitoxRNAs. These studies reveal the profound effect that mitochondrial RNA oxidation has on immunostimulation, providing new insights into DAMP inflammation and identifying potential therapeutic targets to minimize DAMP mtRNA/mitoxRNA-mediated inflammation.