Mitochondrial DNA: leakage, recognition and associated human diseases

Mitochondria are intracellular organelles originating from intracellular symbiotic bacteria that play essential roles in life activities such as energy production, metabolism, Ca2+ storage, signal transduction and cell death. Mitochondria also function as hubs for host defence against harmful stimuli such as infection and inflammation control. However, when cells are exposed to stress, mitochondrial homeostasis is disrupted, and mitochondrial DNA (mtDNA) can leak into the cytoplasm or extracellular space. Leaked mtDNA activates innate immune sensors, causing severe inflammation and contributing to the pathogenesis of human diseases. In this review, we summarize the mechanisms by which mtDNA leaks from the mitochondria and subsequently induces inflammation. We also review the relationship between mtDNA leakage and human diseases.