Mitochondrial DNA Damage‐associated Molecular Patterns are Released in Response to Oxidant Stress in Rat Pulmonary Artery Endothelial Cells

Sequences of mitochondrial DNA called damage‐associated molecular patterns (mtDNA DAMPs) are released as a consequence of severe trauma into the circulation, where they prime neutrophils and activate target cells in distant organs thereby leading to multi‐organ system failure. The stimulus for mtDNA DAMP formation is unknown. Using cultured rat pulmonary artery endothelial cells, we tested the hypothesis that oxidative mtDNA damage triggers mtDNA DAMP release. Cells were challenged with a non‐cytotoxic concentration of glucose oxidase (GOX) for 15 or 60 minutes. Both qRT‐PCR assessment and a neutrophil‐based bioassay revealed that mtDNA increased in culture medium at 15 min after GOX challenge, but returned to baseline levels within 60 minutes. Interestingly, released mtDNA was detected as fragments rather than intact genome. Culture medium content of the 28S rRNA nuclear gene sequence was unaffected by oxidant challenge. To determine if mtDNA damage was required for mtDNA DAMP accumulation, an adenoviral construct encoding a mitochondria‐targeted DNA glycosylase Ogg1 was used to enhance repair of oxidative mtDNA damage. In these cells, oxidant stress did not increase abundance of mtDNA sequences in culture medium. These observations suggest that oxidative damage to the mitochondrial genome may serve as a stimulus for formation and release of neutrophil‐activating mtDNA DAMPs. Supported by NIH.