Hypoxia differently modulates the release of mitochondrial and nuclear DNA

Abstract

BACKGROUND:We investigated the influence of hypoxia on the concentration of mitochondrial and nuclear cell-free DNA (McfDNA and NcfDNA, respectively). METHOD: By an ultra-sensitive quantitative PCR-based assay, McfDNA and NcfDNA were measured in the supernatants of different colorectal cell lines, and in the plasma of C57/Bl6 mice engrafted with TC1 tumour cells, in normoxic or hypoxic conditions. RESULTS: Our data when setting cell culture conditions highlighted the higher stability of McfDNA as compared to NcfDNA and revealed that cancer cells released amounts of nuclear DNA equivalent to the mass of a chromosome over a 6-h duration of incubation. In cell model, hypoxia induced a great increase in NcfDNA and McfDNA concentrations within the first 24 h. After this period, cfDNA total concentrations remained stable in hypoxia consecutive to a decrease of nuclear DNA release, and noteworthy, to a complete inhibition of daily mitochondrial DNA release. In TC1-engrafted mice submitted to intermittent hypoxia, plasma NcfDNA levels are much higher than in mice bred in normoxia, unlike plasma McfDNA concentration that is not impacted by hypoxia. CONCLUSION: This study suggests that hypoxia negatively modulates nuclear and, particularly, mitochondrial DNA releases in long-term hypoxia, and revealed that the underlying mechanisms are differently regulated.

Clinical relevance of blood-based ctDNA analysis: mutation detection and beyond

“…In this regard, detection of mitochondrial tumour-derived DNA, as an alternative source of ctDNA might be a promising approach, owing to the thousands of copies of mitochondrial DNA per cell. 43 Proof of principle for this apporach was provided in patient-derived orthotopic xenograft models of glioblastoma in 2019. 11 Considerations about technical improvements for the methods used to analyse cfDNA could also help to overcome the limit of detection.…”

Unraveling the Link Between Mitochondrial Dynamics and Neuroinflammation

“…Recognized mainly by TLR-9 and STING ( 75 , 105 ), mtDNA has already been shown to be elevated in the serum of patients with ischemic brain injury ( 106 , 107 ). Type I IFNs signaling rely on the interaction with Type I Interferon Receptors (IFNAR) and subsequent intracellular cascades that culminates in the phosphorylation of Jak-STATS and IRFs, and the transcription of Interferon Stimulated Genes (ISGs) ( 100 ).…”

Plasma derived cell-free mitochondrial DNA originates mainly from circulating cell-free mitochondria

“…In a recent study performed by our team, we showed that the mitochondrial genome may be found in nearly 50,000-fold more copies than the nuclear genome in the plasma of healthy individuals (30). This suggests the existence of stabilizing structures protecting mtDNA molecules, thus allowing the detection and quantification of cir-mtDNA in the bloodstream (10,16,31,32). We later demonstrated that blood contains cell-free intact mitochondria as well as cir-mtDNA (30).…”

“…The accurate differentiation of cirDNA of nuclear and mitochondrial origin is feasible (10,31,33), and may offer diagnostic information in specific physiological or pathological situations (32,34,35). Note, we hypothesized that the respective quantitation of cir-mtDNA and cir-nDNA may have potential cancer screening capacity (10,36,37).…”