Cytosolic Release of Mitochondrial DNA and Associated cGAS Signaling Mediates Radiation-Induced Hematopoietic Injury of Mice

Abstract

Mitochondrion is an important organelle of eukaryotic cells and a critical target of ionizing radiation (IR) outside the nucleus. The biological significance and mechanism of the non-target effect originating from mitochondria have received much attention in the field of radiation biology and protection. In this study, we investigated the effect, role, and radioprotective significance of cytosolic mitochondrial DNA (mtDNA) and its associated cGAS signaling on hematopoietic injury induced by IR in vitro culture cells and in vivo total body irradiated mice in this study. The results demonstrated that γ-ray exposure increases the release of mtDNA into the cytosol to activate cGAS signaling pathway, and the voltage-dependent anion channel (VDAC) may contribute to IR-induced mtDNA release. VDAC1 inhibitor DIDS and cGAS synthetase inhibitor can alleviate bone marrow injury and ameliorate hematopoietic suppression induced by IR via protecting hematopoietic stem cells and adjusting subtype distribution of bone marrow cells, such as attenuating the increase of the F4/80+ macrophage proportion in bone marrow cells. The present study provides a new mechanistic explanation for the radiation non-target effect and an alternative technical strategy for the prevention and treatment of hematopoietic acute radiation syndrome.

Micronucleus is not a potent inducer of the cGAS/STING pathway

“…However, the absence of the interferon response in SCF-induced FuVis2 cells, which potentially harbor acentric X chromosome fragments in the cytosol, argues against this possibility. Instead, our data and cumulative evidence support the notion that nucleic acids from disrupted mitochondria trigger the cGAS response in irradiated cells (Tigano et al, 2021;Guan et al, 2023). It is conceivable that cytosolic chromatin fragments rather inhibit cGAS activation in the presence of mtDNA.…”

“…The isolation of the cytosolic fraction was conducted with minor modifications to a previously established protocol (Guan et al, 2023). One million cells were lysed in 100 μl of digitonin buffer (150 mM NaCl, 50 mM Hepes, pH 7.4, and 25 μg/ml digitonin) and incubated on a rotator for 10 min at 4°C.…”

“…In stark contrast, cytosolic fractions from irradiated cells exhibited a substantial increase in mtDNA(Fig 6A). To mitigate this mtDNA release, we targeted VDAC1, a mitochondrial outer membrane channel protein facilitating mtDNA release into the cytosol(Guan et al, 2023). Administering 200 nM DIDS, a VDAC1 inhibitor, from 1 h pre-irradiation to 3 d post-irradiation, significantly reduced cytosolic mtDNA levels without altering total mtDNA (Fig 6A).…”

DAMPs and radiation injury

“…Excessive production of type I IFNs can cause exhaustion in hematopoietic stem cells ( 71 , 72 ). In the 6 Gy TBI model, mtDNA released into the cytosol has been reported to activate the cGAS-STING pathway and induced type I IFN production, and inhibition of the mtDNA release ameliorated hematopoietic tissue injury ( 52 ). The mtDNA released into the cytoplasm can also bind to and activate the NLRP3 inflammasome, which leads to the release of inflammatory cytokines such as IL-1β and IL-18 followed by pyroptosis ( 31 ).…”

Novel insight into cGAS-STING pathway in ischemic stroke: from pre- to post-disease

“…These enzymes play a crucial role in regulating the quantity and distribution of cellular DNA ( 44 ). However, instances such as genomic DNA instability, mitochondrial stress, and lysosomal rupture can lead to the discharge of DNA into the cytoplasm ( 45 – 47 ). The activation of DNA sensors and downstream pathways can occur due to a reduction in endogenous DNase activity, an escalation in DNA damage, or an upsurge in exogenous DNA ( 48 ).…”