Leveraging new methods for comprehensive characterization of mitochondrial DNA in esophageal squamous cell carcinoma.

BACKGROUND: Mitochondria play essential roles in tumorigenesis; however, little is known about the contribution of mitochondrial DNA (mtDNA) to esophageal squamous cell carcinoma (ESCC). Whole-genome sequencing (WGS) is by far the most efficient technology to fully characterize the molecular features of mtDNA; however, due to the high redundancy and heterogeneity of mtDNA in regular WGS data, methods for mtDNA analysis are far from satisfactory. METHODS: Here, we developed a likelihood-based method dMTLV to identify low-heteroplasmic mtDNA variants. In addition, we described fNUMT, which can simultaneously detect non-reference nuclear sequences of mitochondrial origin (non-ref NUMTs) and their derived artifacts. Using these new methods, we explored the contribution of mtDNA to ESCC utilizing the multi-omics data of 663 paired tumor-normal samples. RESULTS: dMTLV outperformed the existing methods in sensitivity without sacrificing specificity. The verification using Nanopore long-read sequencing data showed that fNUMT has superior specificity and more accurate breakpoint identification than the current methods. Leveraging the new method, we identified a significant association between the ESCC overall survival and the ratio of mtDNA copy number of paired tumor-normal samples, which could be potentially explained by the differential expression of genes enriched in pathways related to metabolism, DNA damage repair, and cell cycle checkpoint. Additionally, we observed that the expression of CBWD1 was downregulated by the non-ref NUMTs inserted into its intron region, which might provide precursor conditions for the tumor cells to adapt to a hypoxic environment. Moreover, we identified a strong positive relationship between the number of mtDNA truncating mutations and the contribution of signatures linked to tumorigenesis and treatment response. CONCLUSIONS: Our new frameworks promote the characterization of mtDNA features, which enables the elucidation of the landscapes and roles of mtDNA in ESCC essential for extending the current understanding of ESCC etiology. dMTLV and fNUMT are freely available from https://github.com/sunnyzxh/dMTLV and https://github.com/sunnyzxh/fNUMT , respectively.

Mitochondria-Selective Dicationic Small-Molecule Ligand Targeting G-Quadruplex Structures for Human Colorectal Cancer Therapy.

Mitochondria are important drug targets for anticancer and other disease therapies. Certain human mitochondrial DNA sequences capable of forming G-quadruplex structures (G4s) are emerging drug targets of small molecules. Despite some mitochondria-selective ligands being reported for drug delivery against cancers, the ligand design is mostly limited to the triphenylphosphonium scaffold. The ligand designed with lipophilic small-sized scaffolds bearing multipositive charges targeting the unique feature of high mitochondrial membrane potential (MMP) is lacking and most mitochondria-selective ligands are not G4-targeting. Herein, we report a new small-sized dicationic lipophilic ligand to target MMP and mitochondrial DNA G4s to enhance drug delivery for anticancer. The ligand showed marked alteration of mitochondrial gene expression and substantial induction of ROS production, mitochondrial dysfunction, DNA damage, cellular senescence, and apoptosis. The ligand also exhibited high anticancer activity against HCT116 cancer cells (IC50, 3.4 µM) and high antitumor efficacy in the HCT116 tumor xenograft mouse model (∼70% tumor weight reduction).

High glucose-induced p66Shc mitochondrial translocation regulates autophagy initiation and autophagosome formation in syncytiotrophoblast and extravillous trophoblast.

BACKGROUND: p66Shc, as a redox enzyme, regulates reactive oxygen species (ROS) production in mitochondria and autophagy. However, the mechanisms by which p66Shc affects autophagosome formation are not fully understood. METHODS: p66Shc expression and its location in the trophoblast cells were detected in vivo and in vitro. Small hairpin RNAs or CRISPR/Cas9, RNA sequencing, and confocal laser scanning microscope were used to clarify p66Shc's role in regulating autophagic flux and STING activation. In addition, p66Shc affects mitochondrial-associated endoplasmic reticulum membranes (MAMs) formation were observed by transmission electron microscopy (TEM). Mitochondrial function was evaluated by detected cytoplastic mitochondrial DNA (mtDNA) and mitochondrial membrane potential (MMP). RESULTS: High glucose induces the expression and mitochondrial translocation of p66Shc, which promotes MAMs formation and stimulates PINK1-PRKN-mediated mitophagy. Moreover, mitochondrial localized p66Shc reduces MMP and triggers cytosolic mtDNA release, thus activates cGAS/STING signaling and ultimately leads to enhanced autophagy and cellular senescence. Specially, we found p66Shc is required for the interaction between STING and LC3II, as well as between STING and ATG5, thereby regulates cGAS/STING-mediated autophagy. We also identified hundreds of genes associated several biological processes including aging are co-regulated by p66Shc and ATG5, deletion either of which results in diminished cellular senescence. CONCLUSION: p66Shc is not only implicated in the initiation of autophagy by promoting MAMs formation, but also helps stabilizing active autophagic flux by activating cGAS/STING pathway in trophoblast.

Melatonin's Protective Effects on Neurons in an in Vitro Cell Injury Model.

BACKGROUND: Currently, the role of melatonin (MT) in neuronal damage remains unclear and this study aimed to explore the protective effects of MT on neurons in an in vitro cell injury model. METHODS: The Sprague Dawley (SD) rat traumatic brain injury (TBI) model was prepared, and brain tissue extract (BTE) from the injured area were generated. To establish a cell injury model in vitro, the BTE was added to the culture medium during the neuron culture process. MT was introduced into the culture medium of the cell injury model to observe its protective effects on neurons. Relevant molecular biology experiments were conducted to observe cellular oxidative stress status, inflammation, endoplasmic reticulum (ER) stress, mitochondrial damage, and neuronal apoptosis. RESULTS: When compared to the control group, the BTE group exhibited a significant increase in cellular oxidative stress, inflammation, neurofilament light polypeptide (NEFL) expression, and ER stress. Additionally, the mitochondrial DNA (mtDNA) copy number significantly decreased, and there was a higher count of apoptotic cells (p < 0.05). Upon the addition of MT to the culture medium of the in vitro cell injury model, there was a significant reduction in cellular oxidative stress, inflammation, and NEFL levels. This addition also mitigated ER stress, increased mtDNA copy numbers, and decreased the ratio of cell apoptosis (p < 0.05). CONCLUSIONS: In the in vitro cell injury model, MT demonstrates the capacity to inhibit cellular oxidative stress, inflammation, and ER stress levels. Additionally, it diminishes mtDNA damage, fosters cell viability, and serves as a protective agent against both apoptosis and necrosis in neurons.

A Two-Genome Portrayal of Mitochondrial Disorders: A Review with Clinical Presentations.

Disorders of mitochondrial function are responsible for many inherited neuromuscular and metabolic diseases. Their combination of high mortality, multi-systemic involvement, and economic burden cause devastating effects on patients and their families. Molecular diagnostic tools are becoming increasingly important in providing earlier diagnoses and guiding more precise therapeutic treatments for patients suffering from mitochondrial disorders. This review addresses fundamental molecular concepts relating to the pathogenesis of mitochondrial dysfunction and disorders. A series of short cases highlights the various clinical presentations, inheritance patterns, and pathogenic mutations in nuclear and mitochondrial genes that cause mitochondrial diseases. Graphical and tabular representations of the results are presented to guide the understanding of the important concepts related to mitochondrial molecular genetics and pathology. Emerging technology is incorporating preimplantation genetic testing for mtDNA disorders, while mitochondrial replacement shows promise in significantly decreasing the transfer of diseased mitochondrial DNA (mtDNA) to embryos. Medical professionals must maintain an in-depth understanding of the gene mutations and molecular mechanisms underlying mitochondrial disorders. Continued diagnostic advances and comprehensive management of patients with mitochondrial disorders are essential to achieve robust clinical impacts from comprehensive genomic testing. This is especially true when supported by non-genetic tests such as biochemical analysis, histochemical stains, and imaging studies. Such a multi-pronged investigation should improve the management of mitochondrial disorders by providing accurate and timely diagnoses to reduce disease burden and improve the lives of patients and their families.

Dynamics of Mitochondrial DNA Copy Number and Membrane Potential in Mouse Pre-Implantation Embryos: Responses to Diverse Types of Oxidative Stress.

Mitochondria undergo a myriad of changes during pre-implantation embryo development, including shifts in activity levels and mitochondrial DNA (mtDNA) replication. However, how these distinct aspects of mitochondrial function are linked and their responsiveness to diverse stressors is not well understood. Here, we show that mtDNA content increased between 8-cell embryos and the blastocyst stage, with similar copy numbers per cell in the inner cell mass (ICM) and trophectoderm (TE). In contrast, mitochondrial membrane potential (MMP) was higher in TE than ICM. Culture in ambient oxygen (20% O2) altered both aspects of mitochondrial function: the mtDNA copy number was upregulated in ICM, while MMP was diminished in TE. Embryos cultured in 20% O2 also exhibited delayed development kinetics, impaired implantation, and reduced mtDNA levels in E18 fetal liver. A model of oocyte mitochondrial stress using rotenone showed only a modest effect on on-time development and did not alter the mtDNA copy number in ICM; however, following embryo transfer, mtDNA was higher in the fetal heart. Lastly, endogenous mitochondrial dysfunction, induced by maternal age and obesity, altered the blastocyst mtDNA copy number, but not within the ICM. These results demonstrate that mitochondrial activity and mtDNA content exhibit cell-specific changes and are differentially responsive to diverse types of oxidative stress during pre-implantation embryogenesis.

Dermatologic Manifestations of Mitochondrial Dysfunction: A Review of the Literature.

Mitochondria are eukaryotic cellular organelles that function in energy metabolism, ROS production, and programmed cell death. Cutaneous epithelial and hair follicle dermal papilla cells are energy-rich cells that thereby may be affected by mitochondrial dysfunction and DNA mutation accumulation. In this review, we aimed to summarize the medical literature assessing dermatologic conditions and outcomes associated with mitochondrial dysfunction. A search of PubMed and Embase was performed with subsequent handsearching to retrieve additional relevant articles. Mitochondrial DNA (mtDNA) deletions, mutation accumulation, and damage are associated with phenotypic signs of cutaneous aging, hair loss, and impaired wound healing. In addition, several dermatologic conditions are associated with aberrant mitochondrial activity, such as systemic lupus erythematosus, psoriasis, vitiligo, and atopic dermatitis. Mouse model studies have better established causality between mitochondrial damage and dermatologic outcomes, with some depicting reversibility upon restoration of mitochondrial function. Mitochondrial function mediates a variety of dermatologic conditions, and mitochondrial components may be a promising target for therapeutic strategies.

Mitochondrial H2O2 release does not directly cause damage to chromosomal DNA.

Reactive Oxygen Species (ROS) derived from mitochondrial respiration are frequently cited as a major source of chromosomal DNA mutations that contribute to cancer development and aging. However, experimental evidence showing that ROS released by mitochondria can directly damage nuclear DNA is largely lacking. In this study, we investigated the effects of H2O2 released by mitochondria or produced at the nucleosomes using a titratable chemogenetic approach. This enabled us to precisely investigate to what extent DNA damage occurs downstream of near- and supraphysiological amounts of localized H2O2. Nuclear H2O2 gives rise to DNA damage and mutations and a subsequent p53 dependent cell cycle arrest. Mitochondrial H2O2 release shows none of these effects, even at levels that are orders of magnitude higher than what mitochondria normally produce. We conclude that H2O2 released from mitochondria is unlikely to directly damage nuclear genomic DNA, limiting its contribution to oncogenic transformation and aging.

Role of Selenoprotein W in participating in the progression of non-alcoholic fatty liver disease.

Non-alcoholic fatty liver disease (NAFLD) is a chronic liver disease worldwide. Numerous evidence has demonstrated that metabolic reprogramming serves as a hallmark associated with an elevated risk of NAFLD progression. Selenoprotein W (SelW) is an extensively expressed hepatic selenoprotein that plays a crucial role in antioxidant function. Here, we first demonstrated that SelW is a significantly distinct factor in the liver tissue of NAFLD patients through the Gene Expression Omnibus (GEO) database. Additionally, loss of SelW alleviated hepatic steatosis induced by a high-fat diet (HFD), and was accompanied by the regulation of metabolic and inflammatory pathways as verified by transcriptomic analysis. Moreover, co-immunoprecipitation (CO-IP), liquid chromatography-tandem mass spectrometry (LC-MS), laser scanning confocal microscopy (LSCM) and molecular docking analysis were subsequently implemented to identify Pyruvate Kinase M2 (PKM2) as a potential interacting protein of SelW. Meanwhile, SelW modulated PKM2 translocation into the nucleus to trigger transactivation of the HIF-1α, in further mediating mitochondrial apoptosis, eventually resulting in mitochondrial damage, ROS excessive production and mtDNA leakage. Additionally, mito-ROS accumulation induced the activation of the NLRP3 inflammasome-mediated pyroptosis, thereby facilitating extracellular leakage of mtDNA. The escaped mtDNA then evokes the cGAS-STING signaling pathway in macrophage, thus inducing a shift in macrophage phenotype. Together, our results suggest SelW promotes hepatocyte apoptosis and pyroptosis by regulating metabolic reprogramming to activate cGAS/STING signaling of macrophages, thereby exacerbating the progression of NAFLD.

Si-Wu-Tang attenuates hepatocyte PANoptosis and M1 polarization of macrophages in non-alcoholic fatty liver disease by influencing the intercellular transfer of mtDNA.

ETHNOPHARMACOLOGICAL RELEVANCE: Non-alcoholic fatty liver disease (NAFLD) represents a burgeoning challenge for public health with potential progression to malignant liver diseases. PANoptosis, an avant-garde conceptualization of cell deaths, is closely associated with mitochondrial damage and linked to multiple liver disorders. Si-Wu-Tang (SWT), a traditional Chinese herbal prescription renowned for regulating blood-related disorders and ameliorating gynecological and hepatic diseases, has been demonstrated to alleviate liver fibrosis by regulating bile acid metabolism and immune responses. AIM OF THE STUDY: However, the mechanisms by which mtDNA is released from PANoptotic hepatocytes, triggering macrophage activation and hepatitis and whether this process can be reversed by SWT remain unclear. MATERIALS AND METHODS: Here, sophisticated RNA-sequencing complemented by molecular approaches were applied to explore the underlying mechanism of SWT against NAFLD in methionine/choline-deficient diet (MCD)-induced mice and relative in vitro models. RESULTS: We revealed that SWT profoundly repaired mitochondrial dysfunction, blocked mitochondrial permeability transition and mtDNA released to the cytoplasm, subsequently reversing hepatocyte PANoptosis and macrophage polarization both in MCD-stimulated mice and in vitro. Mechanically, loaded lipids dramatically promoted the opening of mPTP and oligomerization of VDAC2 to orchestrate mtDNA release, which was combined with ZBP1 to promote hepatocyte PANoptosis and also taken by macrophages to trigger M1 polarization via the FSTL1 and PKM2 combination. SWT effectively blocked NOXA signaling and reversed all these detrimental outcomes. CONCLUSION: Our findings show that SWT protects against hepatitis-mediated hepatocyte PANoptosis and macrophage M1 polarization by influencing intrahepatic synthesis, release and intercellular transfer of mtDNA, suggesting a potential therapeutic strategy for ameliorating NAFLD.

Mitochondrial transcription factor A (TFAM) has 5'-deoxyribose phosphate lyase activity in vitro.

Mitochondrial DNA (mtDNA) plays a key role in mitochondrial and cellular functions. mtDNA is maintained by active DNA turnover and base excision repair (BER). In BER, one of the toxic repair intermediates is 5'-deoxyribose phosphate (5'dRp). Human mitochondrial DNA polymerase γ has weak dRp lyase activities, and another known dRp lyase in the nucleus, human DNA polymerase ß, can also localize to mitochondria in certain cell and tissue types. Nonetheless, whether additional proteins have the ability to remove 5'dRp in mitochondria remains unknown. Our prior work on the AP lyase activity of mitochondrial transcription factor A (TFAM) has prompted us to examine its ability to remove 5'dRp residues in vitro. TFAM is the primary DNA-packaging factor in human mitochondria and interacts with mitochondrial DNA extensively. Our data demonstrate that TFAM has the dRp lyase activity with different DNA substrates. Under single-turnover conditions, TFAM removes 5'dRp residues at a rate comparable to that of DNA polymerase (pol) ß, albeit slower than that of pol λ. Among the three proteins examined, pol λ shows the highest single-turnover rates in dRp lyase reactions. The catalytic effect of TFAM is facilitated by lysine residues of TFAM via Schiff base chemistry, as evidenced by the observation of dRp-lysine adducts in mass spectrometry experiments. The catalytic effect of TFAM observed here is analogous to the AP lyase activity of TFAM reported previously. Together, these results suggest a potential role of TFAM in preventing the accumulation of toxic DNA repair intermediates.

Activation of STING signaling aggravates chronic alcohol exposure-induced cognitive impairment by increasing neuroinflammation and mitochondrial apoptosis.

AIMS: Chronic alcohol exposure leads to persistent neurological disorders, which are mainly attributed to neuroinflammation and apoptosis. Stimulator of IFN genes (STING) is essential in the cytosolic DNA sensing pathway and is involved in inflammation and cellular death processes. This study was to examine the expression pattern and biological functions of STING signaling in alcohol use disorder (AUD). METHODS: Cell-free DNA was extracted from human and mouse plasma. C57BL/6J mice were given alcohol by gavage for 28 days, and behavior tests were used to determine their mood and cognition. Cultured cells were treated with ethanol for 24 hours. The STING agonist DMXAA, STING inhibitor C-176, and STING-siRNA were used to intervene the STING. qPCR, western blot, and immunofluorescence staining were used to assess STING signaling, inflammation, and apoptosis. RESULTS: Circulating cell-free mitochondrial DNA (mtDNA) was increased in individuals with AUD and mice chronically exposed to alcohol. Upregulation of STING signaling under alcohol exposure led to inflammatory responses in BV2 cells and mitochondrial apoptosis in PC12 cells. DMXAA exacerbated alcohol-induced cognitive impairment and increased the activation of microglia, neuroinflammation, and apoptosis in the medial prefrontal cortex (mPFC), while C-176 exerted neuroprotection. CONCLUSION: Activation of STING signaling played an essential role in alcohol-induced inflammation and mitochondrial apoptosis in the mPFC. This study identifies STING as a promising therapeutic target for AUD.

Structural basis of how MGME1 processes DNA 5' ends to maintain mitochondrial genome integrity.

Mitochondrial genome maintenance exonuclease 1 (MGME1) helps to ensure mitochondrial DNA (mtDNA) integrity by serving as an ancillary 5'-exonuclease for DNA polymerase γ. Curiously, MGME1 exhibits unique bidirectionality in vitro, being capable of degrading DNA from either the 5' or 3' end. The structural basis of this bidirectionally and, particularly, how it processes DNA from the 5' end to assist in mtDNA maintenance remain unclear. Here, we present a crystal structure of human MGME1 in complex with a 5'-overhang DNA, revealing that MGME1 functions as a rigid DNA clamp equipped with a single-strand (ss)-selective arch, allowing it to slide on single-stranded DNA in either the 5'-to-3' or 3'-to-5' direction. Using a nuclease activity assay, we have dissected the structural basis of MGME1-derived DNA cleavage patterns in which the arch serves as a ruler to determine the cleavage site. We also reveal that MGME1 displays partial DNA-unwinding ability that helps it to better resolve 5'-DNA flaps, providing insights into MGME1-mediated 5'-end processing of nascent mtDNA. Our study builds on previously solved MGME1-DNA complex structures, finally providing the comprehensive functional mechanism of this bidirectional, ss-specific exonuclease.

Mitochondrial injury induced by a Salmonella genotoxin triggers the proinflammatory senescence-associated secretory phenotype.

Bacterial genotoxins damage host cells by targeting their chromosomal DNA. In the present study, we demonstrate that a genotoxin of Salmonella Typhi, typhoid toxin, triggers the senescence-associated secretory phenotype (SASP) by damaging mitochondrial DNA. The actions of typhoid toxin disrupt mitochondrial DNA integrity, leading to mitochondrial dysfunction and disturbance of redox homeostasis. Consequently, it facilitates the release of damaged mitochondrial DNA into the cytosol, activating type I interferon via the cGAS-STING pathway. We also reveal that the GCN2-mediated integrated stress response plays a role in the upregulation of inflammatory components depending on the STING signaling axis. These SASP factors can propagate the senescence effect on T cells, leading to senescence in these cells. These findings provide insights into how a bacterial genotoxin targets mitochondria to trigger a proinflammatory SASP, highlighting a potential therapeutic target for an anti-toxin intervention.

mtDNA regulates cGAS-STING signaling pathway in adenomyosis.

In various hyperproliferative disorders, damaged mitochondria can release mitochondrial DNA (mtDNA) into the cytoplasm, activating the cGAS-STING signaling pathway and subsequent immune imbalances. Our previous research has demonstrated that hypoxia plays a role in the development of adenomyosis (AM) by inducing mitochondrial dysfunction. However, the precise involvement of the cGAS-STING signaling pathway and mtDNA in AM remains unclear. Therefore, this study aims to investigate the relationship between mtDNA secretion, changes in the cGAS-STING signaling pathway, and the abnormal cellular proliferation observed in AM. We found the cGAS, STING, TBK1, p-TBK1, IRF3, and p-IRF3 proteins levels were significantly elevated in the tissues of patients with AM compared to the control group. Additionally, there was an increase in the expression of the pro-inflammatory cytokines IL-6 and IFN-α in the AM tissues. Hypoxia-induced an increase in the proliferation and migration abilities of endometrial stromal cells (ESCs), accompanied by the activation of the cGAS-STING signaling pathway and elevated levels of IFN-α. Furthermore, hypoxia promoted the leakage of mtDNA into the cytoplasm in AM ESCs, and the deletion of mtDNA reduced the activation of the cGAS-STING pathway. Moreover, knockdown of the STING gene inhibited the expression of TBK1, p-TBK1, IRF3, and p-IRF3 and suppressed the secretion of the inflammatory cytokines IL-6 and IFN-α. Furthermore, the migration and invasion abilities of AM ESCs were significantly diminished after STING knockdown. These findings provide valuable insights into the role of mtDNA release and the cGAS-STING signaling pathway in the pathogenesis of AM.

A kinetic dichotomy between mitochondrial and nuclear gene expression processes.

Oxidative phosphorylation (OXPHOS) complexes, encoded by both mitochondrial and nuclear DNA, are essential producers of cellular ATP, but how nuclear and mitochondrial gene expression steps are coordinated to achieve balanced OXPHOS subunit biogenesis remains unresolved. Here, we present a parallel quantitative analysis of the human nuclear and mitochondrial messenger RNA (mt-mRNA) life cycles, including transcript production, processing, ribosome association, and degradation. The kinetic rates of nearly every stage of gene expression differed starkly across compartments. Compared with nuclear mRNAs, mt-mRNAs were produced 1,100-fold more, degraded 7-fold faster, and accumulated to 160-fold higher levels. Quantitative modeling and depletion of mitochondrial factors LRPPRC and FASTKD5 identified critical points of mitochondrial regulatory control, revealing that the mitonuclear expression disparities intrinsically arise from the highly polycistronic nature of human mitochondrial pre-mRNA. We propose that resolving these differences requires a 100-fold slower mitochondrial translation rate, illuminating the mitoribosome as a nexus of mitonuclear co-regulation.

mtDNA-cGAS-STING axis-dependent NLRP3 inflammasome activation contributes to postoperative cognitive dysfunction induced by sevoflurane in mice.

The activation of NLRP3 inflammasome in microglia is critical for neuroinflammation during postoperative cognitive dysfunction (POCD) induced by sevoflurane. However, the molecular mechanism by which sevoflurane activates the NLRP3 inflammasome in microglia remains unclear. The cGAS-STING pathway is an evolutionarily conserved inflammatory defense mechanism. The role of the cGAS-STING pathway in sevoflurane-induced NLRP3 inflammasome-dependent neuroinflammation and the underlying mechanisms require further investigation. We found that prolonged anesthesia with sevoflurane induced cognitive dysfunction and triggered the neuroinflammation characterized by the activation of NLRP3 inflammasome in vivo. Interestingly, the cGAS-STING pathway was activated in the hippocampus of mice receiving sevoflurane. While the blockade of cGAS with RU.521 attenuated cognitive dysfunction and NLRP3 inflammasome activation in mice. In vitro, we found that sevoflurane treatment significantly activated the cGAS-STING pathway in microglia, while RU.521 pre-treatment robustly inhibited sevoflurane-induced NLRP3 inflammasome activation. Mechanistically, sevoflurane-induced mitochondrial fission in microglia and released mitochondrial DNA (mtDNA) into the cytoplasm, which could be abolished with Mdivi-1. Blocking the mtDNA release via the mPTP-VDAC channel inhibitor attenuated sevoflurane-induced mtDNA cytosolic escape and reduced cGAS-STING pathway activation in microglia, finally inhibiting the NLRP3 inflammasome activation. Therefore, regulating neuroinflammation by targeting the cGAS-STING pathway may provide a novel therapeutic target for POCD.

The FTO-CMPK2 Pathway in Fibroblast-like Synoviocytes Modulates Rheumatoid Arthritis Synovial Inflammation and Cartilage Homeostasis via mtDNA Regulation.

In rheumatoid arthritis (RA), a debilitating autoimmune disorder marked by chronic synovial inflammation and progressive cartilage degradation, fibroblast-like synoviocytes (FLS) are key pathogenic players. Current treatments targeting these cells are limited. Our study focused on the Fat Mass and Obesity-associated protein (FTO), known for its roles in cell proliferation and inflammatory response modulation, and its involvement in RA. We specifically examined the inflammatory regulatory roles of FTO and CMPK2, a mitochondrial DNA synthesis protein, in FLS. Utilizing a combination of in vitro and in vivo methods, including FTO inhibition and gene knockdown, we aimed to understand FTO's influence on RA progression and chondrocyte functionality. Our findings showed that increased FTO expression in RA synovial cells enhanced their proliferation and migration and decreased senescence and apoptosis. Inhibiting FTO significantly slowed the disease progression in our models. Our research also highlighted that the FTO-CMPK2 pathway plays a crucial role in regulating synovial inflammation through the mtDNA-mediated cGAS/STING pathway, affecting chondrocyte homeostasis. This study indicates that targeting the FTO-CMPK2 axis could be a promising new therapeutic strategy for managing RA.

Mitochondrial deoxyguanosine kinase is required for female fertility in mice.

Mitochondrial homeostasis plays a pivotal role in oocyte maturation and embryonic development. Deoxyguanosine kinase (DGUOK) is a nucleoside kinase that salvages purine nucleosides in mitochondria and is critical for mitochondrial DNA replication and homeostasis in non-proliferating cells. Dguok loss-of-function mutations and deletions lead to hepatocerebral mitochondrial DNA deletion syndrome. However, its potential role in reproduction remains largely unknown. In this study, we find that Dguok knockout results in female infertility. Mechanistically, DGUOK deficiency hinders ovarian development and oocyte maturation. Moreover, DGUOK deficiency in oocytes causes a significant reduction in mitochondrial DNA copy number and abnormal mitochondrial dynamics and impairs germinal vesicle breakdown. Only few DGUOK-deficient oocytes can extrude their first polar body during in vitro maturation, and these oocytes exhibit irregular chromosome arrangements and different spindle lengths. In addition, DGUOK deficiency elevates reactive oxygen species levels and accelerates oocyte apoptosis. Our findings reveal novel physiological roles for the mitochondrial nucleoside salvage pathway in oocyte maturation and implicate DGUOK as a potential marker for the diagnosis of female infertility.

Human Platelet Derived Mitochondrial OPA-1 Isoforms and Interaction With TDP-43 in Neurodegenerative Diseases.

Optic atrophy 1(OPA1) is a GTPase protein that controls mitochondrial fusion, cristae integrity, and mtDNA maintenance. In neurodegenerative diseases such as Alzheimer's disease (AD), amyotrophic lateral sclerosis (ALS), Parkinson's disease (PD), the mitochondrial network morphology is compromised. Studies on TAR-DNA binding protein 43 (TDP-43) has been the focus in our lab. OPA1 and TDP-43 interaction may shed a light on how aberrant TDP-43 interacts with OPA1, which will lead to mitochondrial dysfunction. The preliminary study tested the idea of whether OPA1 and TDP-43 are physically interacting in human platelet derived mitochondria obtained from healthy human subjects.