ATM activation by oxidative stress

Navigating the redox landscape: reactive oxygen species in regulation of cell cycle

Objectives: To advance our knowledge of disease mechanisms and therapeutic options, understanding cell cycle regulation is critical. Recent research has highlighted the importance of reactive oxygen species (ROS) in cell cycle regulation. Although excessive ROS levels can lead to age-related pathologies, ROS also play an essential role in normal cellular functions. Many cell cycle regulatory proteins are affected by their redox status, but the precise mechanisms and conditions under which ROS promote or inhibit cell proliferation are not fully understood.Methods: This review presents data from the scientific literature and publicly available databases on changes in redox state during the cell cycle and their effects on key regulatory proteins.Results: We identified redox-sensitive targets within the cell cycle machinery and analysed different effects of ROS (type, concentration, duration of exposure) on cell cycle phases. For example, moderate levels of ROS can promote cell proliferation by activating signalling pathways involved in cell cycle progression, whereas excessive ROS levels can induce DNA damage and trigger cell cycle arrest or cell death.Discussion: Our findings encourage future research focused on identifying redox-sensitive targets in the cell cycle machinery, potentially leading to new treatments for diseases with dysregulated cell proliferation.

ATM facilitates autophagy and protects against oxidative stress and apoptosis in response to ER stress in vitro

The endoplasmic reticulum (ER) responds to cellular stress by initiating an unfolded protein response (UPR) that mitigates misfolded protein accumulation by promoting protein degradation pathways. Chronic ER stress leads to UPR-mediated apoptosis and is a common underlying feature of various diseases, highlighting the modulators of the UPR as attractive targets for therapeutic intervention. Ataxia-telangiectasia mutated protein kinase (ATM) is a stress-responsive kinase that initiates autophagy in response to reactive oxygen species (ROS), and ATM deficiency is associated with increased ER stress markers in vitro. However, whether ATM participates in the UPR remains unclear. In this in vitro study, a novel role for ATM in the ER stress response is described using the well-characterized HEK293 cells treated with the common ER stress-inducing agent, tunicamycin, with and without the potent ATM inhibitor, KU-60019. We show for the first time that ATM is activated in a time-dependent manner downstream of UPR initiation in response to tunicamycin treatment. Furthermore, we demonstrate that ATM is required for p62-bound protein cargo degradation through the autophagy pathway in response to ER stress. Lastly, our data suggest a protective role for ATM in ER stress-mediated oxidative stress and mitochondrial apoptosis. Taken together, we highlight ATM as a potential novel drug target in ER stress-related diseases.

Small Molecular Inhibitors That Target ATM for Drug Discovery: Current Research and Potential Prospective

The protein kinase ataxia telangiectasia mutated (ATM) is a constituent of the phosphatidylinositol 3-kinase-related kinase (PIKK) family, exerting a pivotal influence on diverse cellular processes, notably the signaling of double-strand DNA breaks (DSB) and stress response. The dysregulation of ATM is implicated in the pathogenesis of cancer and other diseases such as neurodegeneration. Hence, ATM is deemed a promising candidate for potential therapeutic interventions across a spectrum of diseases. Presently, while ATM small molecule inhibitors are not commercially available, various selective inhibitors have progressed to the clinical research phase. Specifically, AZD1390, WSD0628, SYH2051, and ZN-B-2262 are under investigation in clinical studies pertaining to glioblastoma multiforme and advanced solid tumors, respectively. In this Perspective, we encapsulate the structure, biological functions, and disease relevance of ATM. Subsequently, we concentrate on the design concepts and structure-activity relationships (SAR) of ATM inhibitors, delineating potential avenues for the development of more efficacious ATM-targeted inhibitors.

SMAR1 and p53-regulated lncRNA RP11-431M3.1 enhances HIF1A translation via miR-138 in colorectal cancer cells under oxidative stress

Eukaryotic cells respond to stress by altering coding and non-coding gene expression programs. Alongside many approaches and regulatory mechanisms, long non-coding RNAs (lncRNA) are finding a significant place in gene regulation, suggesting an involvement in various cellular processes and pathophysiology. LncRNAs are regulated by many transcription factors, including SMAR1 and p53, which are tumor suppressor genes. SMAR1 inhibits cancer cell metastasis and invasion and is also known to inhibit apoptosis during low-dose stress in coordination with p53. Data mining analysis suggested that these tumor suppressor genes might coregulate the lncRNA RP11-431M3.1 in colon cancer cells. Importantly, RP11-431M3.1 expression was found to be negatively correlated with patient survival rates in a number of cancers. Oxidative stress occurs when an imbalance in the body is caused by reactive oxygen species (ROS). This imbalance is known to be important in the development/pathogenesis of colon cancer. We are researching the role and control of this lncRNA in HCT116 cells under conditions of oxidative stress. We observed a dose-dependent differential expression of lncRNA upon H2O2 treatment and found that p53 and SMAR1 bind differentially to the promoter in response to the dose of stress inducer used. RP11-431M3.1 was observed to sponge miR-138 which has an important target gene, hypoxia-inducible factor (HIF1A). miR-138 was observed to bind differentially to RP11-431M3.1 and HIF1A RNA depending on the dose of oxidative stress. Furthermore, the knockdown of RP11-431M3.1 decreased the migration and proliferation of colon cancer cells. Our results suggest a previously undescribed regulatory mechanism through which RP11-431M3.1 is transcriptionally regulated by SMAR1 and p53, target HIF1A through miR-138, and highlight its potential as a therapeutic and diagnostic marker for cancer.

Ataxia Telangiectasia patient-derived neuronal and brain organoid models reveal mitochondrial dysfunction and oxidative stress

Ataxia Telangiectasia (AT) is a rare disorder caused by mutations in the ATM gene and results in progressive neurodegeneration for reasons that remain poorly understood. In addition to its central role in nuclear DNA repair, ATM operates outside the nucleus to regulate metabolism, redox homeostasis and mitochondrial function. However, a systematic investigation into how and when loss of ATM affects these parameters in relevant human neuronal models of AT was lacking. We therefore used cortical neurons and brain organoids from AT-patient iPSC and gene corrected isogenic controls to reveal levels of mitochondrial dysfunction, oxidative stress, and senescence that vary with developmental maturity. Transcriptome analyses identified disruptions in regulatory networks related to mitochondrial function and maintenance, including alterations in the PARP/SIRT signalling axis and dysregulation of key mitophagy and mitochondrial fission-fusion processes. We further show that antioxidants reduce ROS and restore neurite branching in AT neuronal cultures, and ameliorate impaired neuronal activity in AT brain organoids. We conclude that progressive mitochondrial dysfunction and aberrant ROS production are important contributors to neurodegeneration in AT and are strongly linked to ATM's role in mitochondrial homeostasis regulation.

Oxidative stress and the multifaceted roles of ATM in maintaining cellular redox homeostasis

The ataxia telangiectasia mutated (ATM) protein kinase is best known as a master regulator of the DNA damage response. However, accumulating evidence has unveiled an equally vital function for ATM in sensing oxidative stress and orchestrating cellular antioxidant defenses to maintain redox homeostasis. ATM can be activated through a non-canonical pathway involving intermolecular disulfide crosslinking of the kinase dimers, distinct from its canonical activation by DNA double-strand breaks. Structural studies have elucidated the conformational changes that allow ATM to switch into an active redox-sensing state upon oxidation. Notably, loss of ATM function results in elevated reactive oxygen species (ROS) levels, altered antioxidant profiles, and mitochondrial dysfunction across multiple cell types and tissues. This oxidative stress arising from ATM deficiency has been implicated as a central driver of the neurodegenerative phenotypes in ataxia-telangiectasia (A-T) patients, potentially through mechanisms involving oxidative DNA damage, PARP hyperactivation, and widespread protein aggregation. Moreover, defective ATM oxidation sensing disrupts transcriptional programs and RNA metabolism, with detrimental impacts on neuronal homeostasis. Significantly, antioxidant therapy can ameliorate cellular and organismal abnormalities in various ATM-deficient models. This review synthesizes recent advances illuminating the multifaceted roles of ATM in preserving redox balance and mitigating oxidative insults, providing a unifying paradigm for understanding the complex pathogenesis of A-T disease.

Targeting the ATM pathway in cancer: Opportunities, challenges and personalized therapeutic strategies

Ataxia telangiectasia mutated (ATM) kinase plays a pivotal role in orchestrating the DNA damage response, maintaining genomic stability, and regulating various cellular processes. This review provides a comprehensive analysis of ATM's structure, activation mechanisms, and various functions in cancer development, progression, and treatment. I discuss ATM's dual nature as both a tumor suppressor and potential promoter of cancer cell survival in certain contexts. The article explores the complex signaling pathways mediated by ATM, its interactions with other DNA repair mechanisms, and its influence on cell cycle checkpoints, apoptosis, and metabolism. I examine the clinical implications of ATM alterations, including their impact on cancer predisposition, prognosis, and treatment response. The review highlights recent advances in ATM-targeted therapies, discussing ongoing clinical trials of ATM inhibitors and their potential in combination with other treatment modalities. I also address the challenges in developing effective biomarkers for ATM activity and patient selection strategies for personalized cancer therapy. Finally, I outline future research directions, emphasizing the need for refined biomarker development, optimized combination therapies, and strategies to overcome potential resistance mechanisms. This comprehensive overview underscores the critical importance of ATM in cancer biology and its emerging potential as a therapeutic target in precision oncology.

Distinct regulation of ATM signaling by DNA single-strand breaks and APE1

In response to DNA double-strand breaks or oxidative stress, ATM-dependent DNA damage response (DDR) is activated to maintain genome integrity. However, it remains elusive whether and how DNA single-strand breaks (SSBs) activate ATM. Here, we provide direct evidence in Xenopus egg extracts that ATM-mediated DDR is activated by a defined SSB structure. Our mechanistic studies reveal that APE1 promotes the SSB-induced ATM DDR through APE1 exonuclease activity and ATM recruitment to SSB sites. APE1 protein can form oligomers to activate the ATM DDR in Xenopus egg extracts in the absence of DNA and can directly stimulate ATM kinase activity in vitro. Our findings reveal distinct mechanisms of the ATM-dependent DDR activation by SSBs in eukaryotic systems and identify APE1 as a direct activator of ATM kinase.

Clinical and genetic spectrum of Ataxia Telangiectasia Tunisian patients: Bioinformatic analysis unveil mechanisms of ATM variants pathogenicity

Ataxia Telangiectasia (AT) is a rare multisystemic neurodegenerative disease caused by biallelic mutations in the ATM gene. Few clinical studies on AT disease have been conducted in Tunisia, however, the mutational landscape is still undefined. Our aim is to determine the clinical and genetic spectrum of AT Tunisian patients and to explore the potential underlying mechanism of variant pathogenicity. Sanger sequencing was performed for nine AT patients. A comprehensive computational analysis was conducted to evaluate the possible pathogenic effect of ATM identified variants. Genetic screening of ATM gene has identified nine different variants from which six have not been previously reported. In silico analysis has predicted a pathogenic effect of identified mutations. This was corroborated by a structural bioinformatics study based on molecular modeling and docking for novel missense mutations. Our findings suggest a profound impact of identified mutations not only on the ATM protein stability, but also on the ATM-ligand interactions. Our study characterizes the mutational landscape of AT Tunisian patients which will allow to set up genetic counseling and prenatal diagnosis for families at risk and expand the spectrum of ATM variants worldwide. Furthermore, understanding the mechanism that underpin variant pathogenicity could provide further insights into disease pathogenesis.

Low-dose dimethylfumarate attenuates colitis-associated cancer in mice through M2 macrophage polarization and blocking oxidative stress

Colitis-associated cancer (CAC) is an aggressive subtype of colorectal cancer that can develop in ulcerative colitis patients and is driven by chronic inflammation and oxidative stress. Current chemotherapy for CAC, based on 5-fluorouracil and oxalipltin, is not fully effective and displays severe side effects, prompting the search for alternative therapies. Dimethylfumarate (DMF), an activator of the nuclear factor erythroid 2-related factor 2 (NRF2), is a potent antioxidant and immunomodelatrory drug used in the treatment of multiple sclerosis and showed a strong anti-inflammatory effect on experimental colitis. Here, we investigated the chemotherapeutic effect of DMF on an experimental model of CAC. Male NMRI mice were given two subcutaneous injections of 1,2 Dimethylhydrazine (DMH), followed by three cycles of dextran sulfate sodium (DSS). Low-dose (DMF30) and high-dose of DMF (DMF100) or oxaliplatin (OXA) were administered from the 8th to 12th week of the experiment, and then the colon tissues were analysed histologically and biochemically. DMH/DSS induced dysplastic aberrant crypt foci (ACF), oxidative stress, and severe colonic inflammation, with a predominance of pro-inflammatory M1 macrophages. As OXA, DMF30 reduced ACF multiplicity and crypt dysplasia, but further restored redox status, and reduced colitis severity by shifting macrophages towards the anti-inflammatory M2 phenotype. Surprisingly, DMF100 exacerbated ACF multiplicity, oxidative stress, and colon inflammation, likely through NRF2 and p53 overexpression in colonic inflammatory cells. DMF had a dual effect on CAC. At low dose, DMF is chemotherapeutic and acts as an antioxidant and immunomodulator, whereas at high dose, DMF is pro-oxidant and exacerbates colitis-associated cancer.

What's Changed in 75 Years of RadRes? - An Australian Perspective on Selected Topics

Several scientific themes are reviewed in the context of the 75-year period relevant to this special platinum issue of Radiation Research. Two criteria have been considered in selecting the scientific themes. One is the exposure of the associated research activity in the annual meetings of the Radiation Research Society (RRS) and in the publications of the Society's Journal, thus reflecting the interest of members of RRS. The second criteria is a focus on contributions from Australian members of RRS. The first theme is the contribution of radiobiology to radiation oncology, featuring two prominent Australian radiation oncologists, the late Rod Withers and his younger colleague, Lester Peters. Two other themes are also linked to radiation oncology; preclinical research aimed at developing experimental radiotherapy modalities, namely microbeam radiotherapy (MRT) and Auger endoradiotherapy. The latter has a long history, in contrast to MRT, especially in Australia, given that the associated medical beamline at the Australian Synchrotron in Melbourne only opened in 2011. Another theme is DNA repair, which has a trajectory parallel to the 75-year period of interest, given the birth of molecular biology in the 1950s. The low-dose radiobiology theme has a similar timeline, predominantly prompted by the nuclear era, which is also connected to the radioprotector theme, although radioprotectors also have a long-established potential utility in cancer radiotherapy. Finally, two themes are associated with biodosimetry. One is the micronucleus assay, highlighting the pioneering contribution from Michael Fenech in Adelaide, South Australia, and the other is the γ-H2AX assay and its widespread clinical applications.

Inhibitors of APE1 redox and ATM synergistically sensitize osteosarcoma cells to ionizing radiation by inducing ferroptosis

The resistance of osteosarcoma (OS) to ionizing radiation (IR) is an obstacle for effective patient treatment. Apurinic/apyrimidinic endonuclease-reduction/oxidation factor 1 (APE1/Ref-1) is a multifunctional protein with DNA repair and reduction/oxidation (redox) activities. We previously revealed the role of APE1 in OS radioresistance; however, whether the redox activity of APE1 is involved in OS radioresistance is unclear. APE1 regulates the activation of ataxia-telangiectasia mutated (ATM), an initiator of DNA damage response that mediates radioresistance in other cancers. The role of APE1 redox activity and ATM activation in OS radioresistance is unknown. Our study revealed that IR increased APE1 expression and ATM activation in OS cells, and APE1 directly regulated ATM activation by its redox activity. The combined use of an APE1 redox inhibitor and ATM inhibitor effectively sensitized OS cells to IR in vitro and in vivo. Mechanistically, the increased radiosensitization of OS cells by the combined use of the two inhibitors was mediated by increased ferroptosis. Co-treatment with the two inhibitors significantly decreased expression of the common targeted transcription factor P53 compared with single inhibitor treatment. Collectively, APE1 redox activity, ATM activation and their crosstalk play important roles in the resistance of OS to irradiation. Synergetic inhibition of APE1 redox activity and ATM activation sensitized OS cells to IR by inducing ferroptosis, which provides a promising strategy for OS radiotherapy.

Replicative senescence is ATM driven, reversible, and accelerated by hyperactivation of ATM at normoxia

Programmed telomere shortening limits tumorigenesis through the induction of replicative senescence. Here we address three long-standing questions concerning senescence. First, we show that the ATM kinase is solely responsible for the induction of replicative senescence. Senescence was delayed by ATM inhibition (ATMi) or overexpression of TRF2, the shelterin subunit dedicated to ATM repression. In contrast, there was no evidence for ATR signaling contributing to replicative senescence even when ATMi was combined with ATR inhibition. Second, we show ATMi can induce apparently normal cell divisions in a subset of senescent cells, indicating that senescence can be reversed. Third, we show that the extended replicative life span at low (physiological) oxygen is due to diminished ATM activity. At low oxygen, cells show a decreased ATM response to dysfunctional telomeres and genome-wide DSBs compared to 20% oxygen. As this effect could be reversed by NAC, the attenuated response of ATM to critically short telomeres and the resulting extended life span at low oxygen is likely due to ROS-induced formation of cysteine disulfide-bridges that crosslink ATM dimers into a form that is not activated by DSBs. These findings show how primary human cells detect shortened telomeres and reveal the molecular mechanism underlying the telomere tumor suppressor pathway.

The phosphorylation-deubiquitination positive feedback loop of the CHK2-USP7 axis stabilizes p53 under oxidative stress

p53 regulates multiple signaling pathways and maintains cell homeostasis under conditions of DNA damage and oxidative stress. Although USP7 has been shown to promote p53 stability via deubiquitination, the USP7-p53 activation mechanism has remained unclear. Here, we propose that DNA damage induces reactive oxygen species (ROS) production and activates ATM-CHK2, and CHK2 then phosphorylates USP7 at S168 and T231. USP7 phosphorylation is essential for its deubiquitination activity toward p53. USP7 also deubiquitinates CHK2 at K119 and K131, increasing CHK2 stability and creating a positive feedback loop between CHK2 and USP7. Compared to peri-tumor tissues, thyroid cancer and colon cancer tissues show higher CHK2 and phosphorylated USP7 (S168, T231) levels, and these levels are positively correlated. Collectively, our results uncover a phosphorylation-deubiquitination positive feedback loop involving the CHK2-USP7 axis that supports the stabilization of p53 and the maintenance of cell homeostasis.

Targeted sequencing of DNA/RNA combined with radiomics predicts lymph node metastasis of papillary thyroid carcinoma

OBJECTIVE

The aim of our study is to find a better way to identify a group of papillary thyroid carcinoma (PTC) with more aggressive behaviors and to provide a prediction model for lymph node metastasis to assist in clinic practice.

METHODS

Targeted sequencing of DNA/RNA was used to detect genetic alterations. Gene expression level was measured by quantitative real-time PCR, western blotting or immunohistochemistry. CCK8, transwell assay and flow cytometry were used to investigate the effects of concomitant gene alterations in PTC. LASSO-logistics regression algorithm was used to construct a nomogram model integrating radiomic features, mutated genes and clinical characteristics.

RESULTS

172 high-risk variants and 7 fusion types were detected. The mutation frequencies in BRAF, TERT, RET, ATM and GGT1 were significantly higher in cancer tissues than benign nodules. Gene fusions were detected in 16 samples (2 at the DNA level and 14 at the RNA level). ATM mutation (ATMMUT) was frequently accompanied by BRAFMUT, TERTMUT or gene fusions. ATMMUT alone or ATM co-mutations were significantly positively correlated with lymph node metastasis. Accordingly, ATM knock-down PTC cells bearing BRAFV600E, KRASG12R or CCDC6-RET had higher proliferative ability and more aggressive potency than cells without ATM knock-down in vitro. Furthermore, combining gene alterations and clinical features significantly improved the predictive efficacy for lymph node metastasis of radiomic features, from 71.5 to 87.0%.

CONCLUSIONS

Targeted sequencing of comprehensive genetic alterations in PTC has high prognostic value. These alterations, in combination with clinical and radiomic features, may aid in predicting invasive PTC with higher accuracy.

SIRT2 promotes base excision repair by transcriptionally activating OGG1 in an ATM/ATR-dependent manner

Sirtuin 2 (SIRT2) regulates the maintenance of genome integrity by targeting pathways of DNA damage response and homologous recombination repair. However, whether and how SIRT2 promotes base excision repair (BER) remain to be determined. Here, we found that independent of its catalytic activity SIRT2 interacted with the critical glycosylase OGG1 to promote OGG1 recruitment to its own promoter upon oxidative stress, thereby enhancing OGG1 promoter activity and increasing BER efficiency. Further studies revealed that SIRT2 was phosphorylated on S46 and S53 by ATM/ATR upon oxidative stress, and SIRT2 phosphorylation enhanced the SIRT2-OGG1 interaction and mediated the stimulatory effect of SIRT2 on OGG1 promoter activity. We also characterized 37 cancer-derived SIRT2 mutants and found that 5 exhibited the loss of the stimulatory effects on OGG1 transcription. Together, our data reveal that SIRT2 acts as a tumor suppressor by promoting OGG1 transcription and increasing BER efficiency in an ATM/ATR-dependent manner.

Tardigrades: Trained to be hardy in the face of DNA damage

Tardigrades withstand ionizing irradiation levels ∼500 times higher than humans can tolerate. Two recent papers shed light on how this might be achieved - via the transcriptional induction of DNA repair genes, the induction of a radioprotective DNA-binding protein, and possibly also the heightened capacity of repair proteins.

Oxidative Stress in Breast Cancer: A Biochemical Map of Reactive Oxygen Species Production

This review systematizes information about the metabolic features of breast cancer directly related to oxidative stress. It has been shown those redox changes occur at all levels and affect many regulatory systems in the human body. The features of the biochemical processes occurring in breast cancer are described, ranging from nonspecific, at first glance, and strictly biochemical to hormone-induced reactions, genetic and epigenetic regulation, which allows for a broader and deeper understanding of the principles of oncogenesis, as well as maintaining the viability of cancer cells in the mammary gland. Specific pathways of the activation of oxidative stress have been studied as a response to the overproduction of stress hormones and estrogens, and specific ways to reduce its negative impact have been described. The diversity of participants that trigger redox reactions from different sides is considered more fully: glycolytic activity in breast cancer, and the nature of consumption of amino acids and metals. The role of metals in oxidative stress is discussed in detail. They can act as both co-factors and direct participants in oxidative stress, since they are either a trigger mechanism for lipid peroxidation or capable of activating signaling pathways that affect tumorigenesis. Special attention has been paid to the genetic and epigenetic regulation of breast tumors. A complex cascade of mechanisms of epigenetic regulation is explained, which made it possible to reconsider the existing opinion about the triggers and pathways for launching the oncological process, the survival of cancer cells and their ability to localize.

Cysteine oxidation as a regulatory mechanism of Arabidopsis plastidial NAD-dependent malate dehydrogenase

Malate dehydrogenases (MDHs) catalyze a reversible NAD(P)-dependent-oxidoreductase reaction that plays an important role in central metabolism and redox homeostasis of plant cells. Recent studies suggest a moonlighting function of plastidial NAD-dependent MDH (plNAD-MDH; EC 1.1.1.37) in plastid biogenesis, independent of its enzyme activity. In this study, redox effects on activity and conformation of recombinant plNAD-MDH from Arabidopsis thaliana were investigated. We show that reduced plNAD-MDH is active while it is inhibited upon oxidation. Interestingly, the presence of its cofactors NAD+ and NADH could prevent oxidative inhibition of plNAD-MDH. In addition, a conformational change upon oxidation could be observed via non-reducing SDS-PAGE. Both effects, its inhibition and conformational change, were reversible by re-reduction. Further investigation of single cysteine substitutions and mass spectrometry revealed that oxidation of plNAD-MDH leads to oxidation of all four cysteine residues. However, cysteine oxidation of C129 leads to inhibition of plNAD-MDH activity and oxidation of C147 induces its conformational change. In contrast, oxidation of C190 and C333 does not affect plNAD-MDH activity or structure. Our results demonstrate that plNAD-MDH activity can be reversibly inhibited, but not inactivated, by cysteine oxidation and might be co-regulated by the availability of its cofactors in vivo.

Potential New Therapies "ROS-Based" in CLL: An Innovative Paradigm in the Induction of Tumor Cell Apoptosis

Chronic lymphocytic leukemia, in spite of recent advancements, is still an incurable disease; the majority of patients eventually acquire resistance to treatment through relapses. In all subtypes of chronic lymphocytic leukemia, the disruption of normal B-cell homeostasis is thought to be mostly caused by the absence of apoptosis. Consequently, apoptosis induction is crucial to the management of this illness. Damaged biological components can accumulate as a result of the oxidation of intracellular lipids, proteins, and DNA by reactive oxygen species. It is possible that cancer cells are more susceptible to apoptosis because of their increased production of reactive oxygen species. An excess of reactive oxygen species can lead to oxidative stress, which can harm biological elements like DNA and trigger apoptotic pathways that cause planned cell death. In order to upset the balance of oxidative stress in cells, recent therapeutic treatments in chronic lymphocytic leukemia have focused on either producing reactive oxygen species or inhibiting it. Examples include targets created in the field of nanomedicine, natural extracts and nutraceuticals, tailored therapy using biomarkers, and metabolic targets. Current developments in the complex connection between apoptosis, particularly ferroptosis and its involvement in epigenomics and alterations, have created a new paradigm.

DNA-PK and ATM drive phosphorylation signatures that antagonistically regulate cytokine responses to herpesvirus infection or DNA damage

The DNA-dependent protein kinase, DNA-PK, is an essential regulator of DNA damage repair. DNA-PK-driven phosphorylation events and the activated DNA damage response (DDR) pathways are also components of antiviral intrinsic and innate immune responses. Yet, it is not clear whether and how the DNA-PK response differs between these two forms of nucleic acid stress-DNA damage and DNA virus infection. Here, we define DNA-PK substrates and the signature cellular phosphoproteome response to DNA damage or infection with the nuclear-replicating DNA herpesvirus, HSV-1. We establish that DNA-PK negatively regulates the ataxia-telangiectasia-mutated (ATM) DDR kinase during viral infection. In turn, ATM blocks the binding of DNA-PK and the nuclear DNA sensor IFI16 to viral DNA, thereby inhibiting cytokine responses. However, following DNA damage, DNA-PK enhances ATM activity, which is required for IFN-β expression. These findings demonstrate that the DDR autoregulates cytokine expression through the opposing modulation of DDR kinases.

A novel role for the ROS-ATM-Chk2 axis mediated metabolic and cell cycle reprogramming in the M1 macrophage polarization

Reactive oxygen species (ROS) play a pivotal role in macrophage-mediated acute inflammation. However, the precise molecular mechanism by which ROS regulate macrophage polarization remains unclear. Here, we show that ROS function as signaling molecules that regulate M1 macrophage polarization through ataxia-telangiectasia mutated (ATM) and cell cycle checkpoint kinase 2 (Chk2), vital effector kinases in the DNA damage response (DDR) signaling pathway. We further demonstrate that Chk2 phosphorylates PKM2 at the T95 and T195 sites, promoting glycolysis and facilitating macrophage M1 polarization. In addition, Chk2 activation increases the Chk2-dependent expression of p21, inducing cell cycle arrest for subsequent macrophage M1 polarization. Finally, Chk2-deficient mice infected with lipopolysaccharides (LPS) display a significant decrease in lung inflammation and M1 macrophage counts. Taken together, these results suggest that inhibiting the ROS-Chk2 axis can prevent the excessive inflammatory activation of macrophages, and this pathway can be targeted to develop a novel therapy for inflammation-associated diseases and expand our understanding of the pathophysiological functions of DDR in innate immunity.

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.

Ferritinophagy Is Critical for Deoxynivalenol-Induced Liver Injury in Mice

Background: Deoxynivalenol (DON) contamination, pervasive throughout all stages of food production and processing, presents a significant threat to human health. The degradation of ferritin mediated by nuclear receptor coactivator 4 (NCOA4), termed ferritinophagy, plays a crucial role in maintaining iron homeostasis and regulating ferroptosis. Aim: This study aims to elucidate the role of ferritinophagy and ferroptosis in DON-induced liver injury. Methods: Male mice and AML12 cells were subjected to varying doses of DON, serving as in vivo and in vitro models, respectively. Protein expression was assessed by using immunofluorescence and western blot techniques. Co-immunoprecipitation was employed to investigate the protein-protein interactions. Results: Our findings demonstrate that DON triggers hepatocyte ferroptosis in a ferritinophagy-dependent manner. Specifically, DON impedes the activation of the mammalian target of rapamycin complex 1 (mTORC1) by inhibiting RAC1's binding to mTOR, thereby ultimately inducing autophagy. Concurrently, DON amplifies NCOA4's affinity for ferritin by facilitating NCOA4 phosphorylation through the ataxia-telangiectasia mutated kinase (ATM), thus promoting the autophagy-dependent degradation of ferritin. Both autophagy inhibition and NCOA4 expression suppression ameliorate DON-induced ferroptosis. Conclusion: Our study concludes that DON facilitates NCOA4-mediated ferritinophagy via the ATM-NCOA4 pathway, subsequently inducing ferroptosis in the liver.

Regulation of transcription patterns, poly(ADP-ribose), and RNA-DNA hybrids by the ATM protein kinase

The ataxia telangiectasia mutated (ATM) protein kinase is a master regulator of the DNA damage response and also an important sensor of oxidative stress. Analysis of gene expression in ataxia-telangiectasia (A-T) patient brain tissue shows that large-scale transcriptional changes occur in patient cerebellum that correlate with the expression level and guanine-cytosine (GC) content of transcribed genes. In human neuron-like cells in culture, we map locations of poly(ADP-ribose) and RNA-DNA hybrid accumulation genome-wide with ATM inhibition and find that these marks also coincide with high transcription levels, active transcription histone marks, and high GC content. Antioxidant treatment reverses the accumulation of R-loops in transcribed regions, consistent with the central role of reactive oxygen species in promoting these lesions. Based on these results, we postulate that transcription-associated lesions accumulate in ATM-deficient cells and that the single-strand breaks and PARylation at these sites ultimately generate changes in transcription that compromise cerebellum function and lead to neurodegeneration over time in A-T patients.

Engineered triphenylphosphonium-based, mitochondrial-targeted liposomal drug delivery system facilitates cancer cell killing actions of chemotherapeutics

In addition to their classical role in ATP generation, mitochondria also contribute to Ca2+ buffering, free radical production, and initiation of programmed cell death. Mitochondrial dysfunction has been linked to several leading causes of morbidity and mortality worldwide including neurodegenerative, metabolic, and cardiovascular diseases as well as several cancer subtypes. Thus, there is growing interest in developing drug-delivery vehicles capable of shuttling therapeutics directly to the mitochondria. Here, we functionalized the conventional 10,12-pentacosadiynoic acid/1,2-dimyristoyl-sn-glycero-3-phosphocholine (PCDA/DMPC)-based liposome with a mitochondria-targeting triphenylphosphonium (TPP) cationic group. A fluorescent dansyl dye (DAN) group was also included for tracking mitochondrial drug uptake. The resultant PCDA-TPP and PCDA-DAN conjugates were incorporated into a 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC)-based lipid bilayer, and these modified liposomes (Lip-DT) were studied for their cellular toxicity, mitochondrial targeting ability, and efficacy in delivering the drug Doxorubicin (Dox) to human colorectal carcinoma (HCT116) and human breast (MCF7) cancer cells in vitro. This Lip-DT-Dox exhibited the ability to shuttle the encapsulated drug to the mitochondria of cancer cells and triggered oxidative stress, mitochondrial dysfunction, and apoptosis. The ability of Lip-DT-Dox to trigger cellular toxicity in both HCT116 and MCF7 cancer cells was comparable to the known cell-killing actions of the unencapsulated drug (Dox). The findings in this study reveal a promising approach where conventional liposome-based drug delivery systems can be rendered mitochondria-specific by incorporating well-known mitochondriotropic moieties onto the surface of the liposome.

DNA Damage Response and Mismatch Repair Gene Defects in Advanced and Metastatic Prostate Cancer

Alterations in DNA damage response (DDR) and related genes are present in up to 25% of advanced prostate cancers (PCa). Most frequently altered genes are involved in the homologous recombination repair, the Fanconi anemia, and the mismatch repair pathways, and their deficiencies lead to a highly heterogeneous spectrum of DDR-deficient phenotypes. More than half of these alterations concern non- BRCA DDR genes. From a therapeutic perspective, poly-ADP-ribose polymerase inhibitors have demonstrated robust clinical efficacy in tumors with BRCA2 and BRCA1 alterations. Mismatch repair-deficient PCa, and a subset of CDK12-deficient PCa, are vulnerable to immune checkpoint inhibitors. Emerging data point to the efficacy of ATR inhibitors in PCa with ATM deficiencies. Still, therapeutic implications are insufficiently clarified for most of the non- BRCA DDR alterations, and no successful targeted treatment options have been established.

A-T neurodegeneration and DNA damage-induced transcriptional stress

Loss of the ATM protein kinase in humans results in Ataxia-telangiectasia, a disorder characterized by childhood-onset neurodegeneration of the cerebellum as well as cancer predisposition and immunodeficiency. Although many aspects of ATM function are well-understood, the mechanistic basis of the progressive cerebellar ataxia that occurs in patients is not. Here we review recent progress related to the role of ATM in neurons and the cerebellum that comes from many sources: animal models, post-mortem brain tissue samples, and human neurons in culture. These observations have revealed new insights into the consequences of ATM loss on DNA damage, gene expression, and immune signaling in the brain. Many results point to the importance of reactive oxygen species as well as single-strand DNA breaks in the progression of molecular events leading to neuronal dysfunction. In addition, innate immunity signaling pathways appear to play a critical role in ATM functions in microglia, responding to various forms of nucleic acid sensors and regulating survival of neurons and other cell types. Overall, the results lead to an updated view of transcriptional stress and DNA damage resulting from ATM loss that results in changes in gene expression as well as neuroinflammation that contribute to the cerebellar neurodegeneration observed in patients.

Transcriptional profiling of peripheral blood mononuclear cells identifies inflammatory phenotypes in Ataxia Telangiectasia

INTRODUCTION

Ataxia telangiectasia (A-T) is an autosomal recessive neurodegenerative disease with widespread systemic manifestations and marked variability in clinical phenotypes. In this study, we sought to determine whether transcriptomic profiling of peripheral blood mononuclear cells (PBMCs) defines subsets of individuals with A-T beyond mild and classic phenotypes, enabling identification of novel features for disease classification and treatment response to therapy.

METHODS

Participants with classic A-T (n = 77), mild A-T (n = 13), and unaffected controls (n = 15) were recruited from two outpatient clinics. PBMCs were isolated and bulk RNAseq was performed. Plasma was also isolated in a subset of individuals. Affected individuals were designated mild or classic based on ATM mutations and clinical and laboratory features.

RESULTS

People with classic A-T were more likely to be younger and IgA deficient and to have higher alpha-fetoprotein levels and lower % forced vital capacity compared to individuals with mild A-T. In classic A-T, the expression of genes required for V(D)J recombination was lower, and the expression of genes required for inflammatory activity was higher. We assigned inflammatory scores to study participants and found that inflammatory scores were highly variable among people with classic A-T and that higher scores were associated with lower ATM mRNA levels. Using a cell type deconvolution approach, we inferred that CD4 + T cells and CD8 + T cells were lower in number in people with classic A-T. Finally, we showed that individuals with classic A-T exhibit higher SERPINE1 (PAI-1) mRNA and plasma protein levels, irrespective of age, and higher FLT4 (VEGFR3) and IL6ST (GP130) plasma protein levels compared with mild A-T and controls.

CONCLUSION

Using a transcriptomic approach, we identified novel features and developed an inflammatory score to identify subsets of individuals with different inflammatory phenotypes in A-T. Findings from this study could be used to help direct treatment and to track treatment response to therapy.

Role of DDX1 in the oxidative response of ataxia telangiectasia patient-derived fibroblasts

Ataxia Telangiectasia (A-T) is an inherited autosomal recessive disorder characterized by cerebellar neurodegeneration, radiosensitivity, immunodeficiency and a high incidence of lymphomas. A-T is caused by mutations in the ATM gene. While loss of ATM function in DNA repair explains some aspects of A-T pathophysiology such as radiosensitivity and cancer predisposition, other A-T features such as neurodegeneration imply additional roles for ATM outside the nucleus. Emerging evidence suggests that ATM participates in cellular response to oxidative stress, failure of which contributes to the neurodegeneration associated with A-T. Here, we use fibroblasts derived from A-T patients to investigate whether DEAD Box 1 (DDX1), an RNA binding/unwinding protein that functions downstream of ATM in DNA double strand break repair, also plays a role in ATM-dependent cellular response to oxidative stress. Focusing on DDX1 target RNAs that are associated with neurological disorders and oxidative stress response, we show that ATM is required for increased binding of DDX1 to its target RNAs in the presence of arsenite-induced oxidative stress. Our results indicate that DDX1 functions downstream of ATM by protecting specific mRNAs in the cytoplasm of arsenite-treated cells. In keeping with a role for ATM and DDX1 in oxidative stress, levels of reactive oxygen species (ROS) are increased in ATM-deficient as well as DDX1-depleted cells. We propose that reduced levels of cytoplasmic DDX1 RNA targets sensitizes ATM-deficient cells to oxidative stress resulting in increased cell death. This sensitization would be especially detrimental to long-lived highly metabolically active cells such as neurons providing a possible explanation for the neurodegenerative defects associated with A-T.

Reductive stress in cancer: coming out of the shadows

Redox imbalance is defined by disruption in oxidative and reductive pathways and has a central role in cancer initiation, development, and treatment. Although redox imbalance has traditionally been characterized by high levels of oxidative stress, emerging evidence suggests that an overly reductive environment is just as detrimental to cancer proliferation. Reductive stress is defined by heightened levels of antioxidants, including glutathione and elevated NADH, compared with oxidized NAD, which disrupts central biochemical pathways required for proliferation. With the advent of new technologies that measure and manipulate reductive stress, the sensors and drivers of this overlooked metabolic stress are beginning to be revealed. In certain genetically defined cancers, targeting reductive stress pathways may be an effective strategy. Redox-based pathways are gaining recognition as essential 'regulatory hubs,' and a broader understanding of reductive stress signaling promises not only to reveal new insights into metabolic homeostasis but also potentially to transform therapeutic options in cancer.

Long-Term Nicotinamide Riboside Use Improves Coordination and Eye Movements in Ataxia Telangiectasia

BACKGROUND

Supplementation of nicotinamide riboside (NR) ameliorates neuropathology in animal models of ataxia telangiectasia (A-T). In humans, short-term NR supplementation showed benefits in neurological outcome.

OBJECTIVES

The study aimed to investigate the safety and benefits of long-term NR supplementation in individuals with A-T.

METHODS

A single-arm, open-label clinical trial was performed in individuals with A-T, receiving NR over a period of 2 years. Biomarkers and clinical examinations were used to assess safety parameters. Standardized and validated neuromotor tests were used to monitor changes in neurological symptoms. Using generalized mixed models, test results were compared to expected disease progression based on historical data.

RESULTS

NAD+ concentrations increased rapidly in peripheral blood and stabilized at a higher level than baseline. NR supplementation was well tolerated for most participants. The total scores in the neuromotor test panels, as evaluated at the 18-month time point, improved for all but one participant, primarily driven by improvements in coordination subscores and eye movements. A comparison with historical data revealed that the progression of certain neuromotor symptoms was slower than anticipated.

CONCLUSIONS

Long-term use of NR appears to be safe and well tolerated, and it improves motor coordination and eye movements in patients with A-T of all ages. © 2023 The Authors. Movement Disorders published by Wiley Periodicals LLC on behalf of International Parkinson and Movement Disorder Society.

Oxidized ATM governs stemness of breast cancer stem cell through regulating ubiquitylation and acetylation switch

Cancer stem cells (CSCs), as parts of tumor initiation cells, play a crucial role to tumorigenesis, development and recurrence. However, the complicated mechanisms of CSCs to adapt to tumor microenvironment and its stemness maintenance remains unclear. Here, we show that oxidized ATM, a hypoxia-activated cytoplasm ATM, acts a novel function to maintain CSC stemness in triple-negative breast cancer cells (BCSCs) via regulating histone H4 acetylation. Mechanistically, oxidized ATM phosphorylates TRIM21 (a E3 ubiquitin ligase) serine 80 and serine 469. Serine 80 phosphorylation of TRIM21 is essential for the ubiquitination activity of TRIM21. TRIM21 binds with SIRT1 (one of deacetylase), resulting in ubiquitylation-mediated degradation of SIRT1. The reduced SIRT1 leads to increase of histone H4 acetylation, thus facilitating CSC-related gene expression. Clinical data verify that high level of ATM in breast tumors is positively correlated with malignant grade, and is closely related with low SIRT1, high p-TRIM21, and high CD44 expression. In conclusion, our study provides a novel mechanism by which oxidized ATM governing BCSCs stemness and reveals an important link among oxidized ATM, histone acetylation, and BCSCs maintenance.

Advances in bi-directional relationships for EZH2 and oxidative stress

Over the past two decades, polycomb repressive complex 2(PRC2) has emerged as a vital repressive complex in overall cell fate determination. In mammals, enhancer of zeste homolog 2 (EHZ2), which is the core component of PRC2, has also been recognized as an important regulator of inflammatory, redox, tumorigenesis and damage repair signalling networks. To exert these effects, EZH2 must regulate target genes epigenetically or interact directly with other gene expression-regulating factors, such as LncRNAs and microRNAs. Our review provides a comprehensive summary of research advances, discoveries and trends regarding the regulatory mechanisms between EZH2 and reactive oxygen species (ROS). First, we outline novel findings about how EZH2 regulates the generation of ROS at the molecular level. Then, we summarize how oxidative stress controls EHZ2 alteration (upregulation, downregulation, or phosphorylation) via various molecules and signalling pathways. Finally, we address why EZH2 and oxidative stress have an undefined relationship and provide potential future research ideas.

IGF-I protects porcine granulosa cells from hypoxia-induced apoptosis by promoting homologous recombination repair through the PI3K/AKT/E2F8/RAD51 pathway

Severe hypoxia induced by vascular compromise (ovarian torsion, surgery), obliteration of vessels (aging, chemotherapy, particularly platinum drugs) can cause massive follicle atresia. On the other hand, hypoxia increases the occurrence of DNA double-strand breaks (DSBs) and triggers cellular damage repair mechanisms; however, if the damage is not promptly repaired, it can also induce the apoptosis program. Insulin-like growth factor-I (IGF-I) is a polypeptide hormone that plays essential roles in stimulating mammalian follicular development. Here, we report a novel role for IGF-I in protecting hypoxic GCs from apoptosis by promoting DNA repair through the homologous recombination (HR) process. Indeed, the hypoxic environment within follicles significantly inhibited the efficiency of HR-directed DNA repair. The presence of IGF-I-induced HR pathway to alleviate hypoxia-induced DNA damage and apoptosis primarily through upregulating the expression of the RAD51 recombinase. Importantly, we identified a new transcriptional regulator of RAD51, namely E2F8, which mediates the protective effects of IGF-I on hypoxic GCs by facilitating the transcriptional activation of RAD51. Furthermore, we demonstrated that the PI3K/AKT pathway is crucial for IGF-I-induced E2F8 expression, resulting in increased RAD51 expression and enhanced HR activity, which mitigates hypoxia-induced DNA damage and thereby protects against GCs apoptosis. Together, these findings define a novel mechanism of IGF-I-mediated GCs protection by activating the HR repair through the PI3K/AKT/E2F8/RAD51 pathway under hypoxia.

Cell stretching activates an ATM mechano-transduction pathway that remodels cytoskeleton and chromatin

Ataxia telangiectasia mutated (ATM) and ataxia telangiectasia and Rad3-related (ATR) DNA damage response (DDR) kinases contain elastic domains. ATM also responds to reactive oxygen species (ROS) and ATR to nuclear mechanical stress. Mre11 mediates ATM activation following DNA damage; ATM mutations cause ataxia telangiectasia (A-T). Here, using in vivo imaging, electron microscopy, proteomic, and mechano-biology approaches, we study how ATM responds to mechanical stress. We report that cytoskeleton and ROS, but not Mre11, mediate ATM activation following cell deformation. ATM deficiency causes hyper-stiffness, stress fiber accumulation, Yes-associated protein (YAP) nuclear enrichment, plasma and nuclear membrane alterations during interstitial migration, and H3 hyper-methylation. ATM locates to the actin cytoskeleton and, following cytoskeleton stress, promotes phosphorylation of key cytoskeleton and chromatin regulators. Our data contribute to explain some clinical features of patients with A-T and pinpoint the existence of an integrated mechano-response in which ATM and ATR have distinct roles unrelated to their canonical DDR functions.

Cyclin D-CDK4 Disulfide Bond Attenuates Pulmonary Vascular Cell Proliferation

BACKGROUND

Pulmonary hypertension (PH) is a chronic vascular disease characterized, among other abnormalities, by hyperproliferative smooth muscle cells and a perturbed cellular redox and metabolic balance. Oxidants induce cell cycle arrest to halt proliferation; however, little is known about the redox-regulated effector proteins that mediate these processes. Here, we report a novel kinase-inhibitory disulfide bond in cyclin D-CDK4 (cyclin-dependent kinase 4) and investigate its role in cell proliferation and PH.

METHODS

Oxidative modifications of cyclin D-CDK4 were detected in human pulmonary arterial smooth muscle cells and human pulmonary arterial endothelial cells. Site-directed mutagenesis, tandem mass-spectrometry, cell-based experiments, in vitro kinase activity assays, in silico structural modeling, and a novel redox-dead constitutive knock-in mouse were utilized to investigate the nature and definitively establish the importance of CDK4 cysteine modification in pulmonary vascular cell proliferation. Furthermore, the cyclin D-CDK4 oxidation was assessed in vivo in the pulmonary arteries and isolated human pulmonary arterial smooth muscle cells of patients with pulmonary arterial hypertension and in 3 preclinical models of PH.

RESULTS

Cyclin D-CDK4 forms a reversible oxidant-induced heterodimeric disulfide dimer between C7/8 and C135, respectively, in cells in vitro and in pulmonary arteries in vivo to inhibit cyclin D-CDK4 kinase activity, decrease Rb (retinoblastoma) protein phosphorylation, and induce cell cycle arrest. Mutation of CDK4 C135 causes a kinase-impaired phenotype, which decreases cell proliferation rate and alleviates disease phenotype in an experimental mouse PH model, suggesting this cysteine is indispensable for cyclin D-CDK4 kinase activity. Pulmonary arteries and human pulmonary arterial smooth muscle cells from patients with pulmonary arterial hypertension display a decreased level of CDK4 disulfide, consistent with CDK4 being hyperactive in human pulmonary arterial hypertension. Furthermore, auranofin treatment, which induces the cyclin D-CDK4 disulfide, attenuates disease severity in experimental PH models by mitigating pulmonary vascular remodeling.

CONCLUSIONS

A novel disulfide bond in cyclin D-CDK4 acts as a rapid switch to inhibit kinase activity and halt cell proliferation. This oxidative modification forms at a critical cysteine residue, which is unique to CDK4, offering the potential for the design of a selective covalent inhibitor predicted to be beneficial in PH.

Regulation of transcription patterns, poly-ADP-ribose, and RNA-DNA hybrids by the ATM protein kinase

The ATM protein kinase is a master regulator of the DNA damage response and also an important sensor of oxidative stress. Analysis of gene expression in Ataxia-telangiectasia patient brain tissue shows that large-scale transcriptional changes occur in patient cerebellum that correlate with expression level and GC content of transcribed genes. In human neuron-like cells in culture we map locations of poly-ADP-ribose and RNA-DNA hybrid accumulation genome-wide with ATM inhibition and find that these marks also coincide with high transcription levels, active transcription histone marks, and high GC content. Antioxidant treatment reverses the accumulation of R-loops in transcribed regions, consistent with the central role of ROS in promoting these lesions. Based on these results we postulate that transcription-associated lesions accumulate in ATM-deficient cells and that the single-strand breaks and PARylation at these sites ultimately generate changes in transcription that compromise cerebellum function and lead to neurodegeneration over time in A-T patients.

Response of Fibroblasts from Menkes' and Wilson's Copper Metabolism-Related Disorders to Ionizing Radiation: Influence of the Nucleo-Shuttling of the ATM Protein Kinase

Menkes' disease (MD) and Wilson's disease (WD) are two major copper (Cu) metabolism-related disorders caused by mutations of the ATP7A and ATP7B ATPase gene, respectively. While Cu is involved in DNA strand breaks signaling and repair, the response of cells from both diseases to ionizing radiation, a common DNA strand breaks inducer, has not been investigated yet. To this aim, three MD and two WD skin fibroblasts lines were irradiated at two Gy X-rays and clonogenic cell survival, micronuclei, anti-γH2AX, -pATM, and -MRE11 immunofluorescence assays were applied to evaluate the DNA double-strand breaks (DSB) recognition and repair. MD and WD cells appeared moderately radiosensitive with a delay in the radiation-induced ATM nucleo-shuttling (RIANS) associated with impairments in the DSB recognition. Such delayed RIANS was notably caused in both MD and WD cells by a highly expressed ATP7B protein that forms complexes with ATM monomers in cytoplasm. Interestingly, a Cu pre-treatment of cells may influence the activity of the MRE11 nuclease and modulate the radiobiological phenotype. Lastly, some high-passage MD cells cultured in routine may transform spontaneously becoming immortalized. Altogether, our findings suggest that exposure to ionizing radiation may impact on clinical features of MD and WD, which requires cautiousness when affected patients are submitted to radiodiagnosis and, eventually, radiotherapy.

What matters in aging is signaling for responsiveness

Biological responsiveness refers to the capacity of living organisms to adapt to changes in both their internal and external environments through physiological and behavioral mechanisms. One of the prominent aspects of aging is the decline in this responsiveness, which can lead to a deterioration in the processes required for maintenance, survival, and growth. The vital link between physiological responsiveness and the essential life processes lies within the signaling systems. To devise effective strategies for controlling the aging process, a comprehensive reevaluation of this connecting loop is imperative. This review aims to explore the impact of aging on signaling systems responsible for responsiveness and introduce a novel perspective on intervening in the aging process by restoring the compromised responsiveness. These innovative mechanistic approaches for modulating altered responsiveness hold the potential to illuminate the development of action plans aimed at controlling the aging process and treating age-related disorders.

Mutual regulation of TGFβ-induced oncogenic EMT, cell cycle progression and the DDR

TGFβ signaling and the DNA damage response (DDR) are two cellular toolboxes with a strong impact on cancer biology. While TGFβ as a pleiotropic cytokine affects essentially all hallmarks of cancer, the multifunctional DDR mostly orchestrates cell cycle progression, DNA repair, chromatin remodeling and cell death. One oncogenic effect of TGFβ is the partial activation of epithelial-to-mesenchymal transition (EMT), conferring invasiveness, cellular plasticity and resistance to various noxae. Several reports show that both individual networks as well as their interface affect chemo-/radiotherapies. However, the underlying mechanisms remain poorly resolved. EMT often correlates with TGFβ-induced slowing of proliferation, yet numerous studies demonstrate that particularly the co-activated EMT transcription factors counteract anti-proliferative signaling in a partially non-redundant manner. Collectively, evidence piled up over decades underscore a multifaceted, reciprocal inter-connection of TGFβ signaling / EMT with the DDR / cell cycle progression, which we will discuss here. Altogether, we conclude that full cell cycle arrest is barely compatible with the propagation of oncogenic EMT traits and further propose that 'EMT-linked DDR plasticity' is a crucial, yet intricate facet of malignancy, decisively affecting metastasis formation and therapy resistance.

ATM inhibition blocks glucose metabolism and amplifies the sensitivity of resistant lung cancer cell lines to oncogene driver inhibitors

BACKGROUND

ATM is a multifunctional serine/threonine kinase that in addition to its well-established role in DNA repair mechanisms is involved in a number of signaling pathways including regulation of oxidative stress response and metabolic diversion of glucose through the pentose phosphate pathway. Oncogene-driven tumorigenesis often implies the metabolic switch from oxidative phosphorylation to glycolysis which provides metabolic intermediates to sustain cell proliferation. The aim of our study is to elucidate the role of ATM in the regulation of glucose metabolism in oncogene-driven cancer cells and to test whether ATM may be a suitable target for anticancer therapy.

METHODS

Two oncogene-driven NSCLC cell lines, namely H1975 and H1993 cells, were treated with ATM inhibitor, KU55933, alone or in combination with oncogene driver inhibitors, WZ4002 or crizotinib. Key glycolytic enzymes, mitochondrial complex subunits (OXPHOS), cyclin D1, and apoptotic markers were analyzed by Western blotting. Drug-induced toxicity was assessed by MTS assay using stand-alone or combined treatment with KU55933 and driver inhibitors. Glucose consumption, pyruvate, citrate, and succinate levels were also analyzed in response to KU55933 treatment. Both cell lines were transfected with ATM-targeted siRNA or non-targeting siRNA and then exposed to treatment with driver inhibitors.

RESULTS

ATM inhibition deregulates and inhibits glucose metabolism by reducing HKII, p-PKM2Tyr105, p-PKM2Ser37, E1α subunit of pyruvate dehydrogenase complex, and all subunits of mitochondrial complexes except ATP synthase. Accordingly, glucose uptake and pyruvate concentrations were reduced in response to ATM inhibition, whereas citrate and succinate levels were increased in both cell lines indicating the supply of alternative metabolic substrates. Silencing of ATM resulted in similar changes in glycolytic cascade and OXPHOS levels. Furthermore, the driver inhibitors amplified the effects of ATM downregulation on glucose metabolism, and the combined treatment with ATM inhibitors enhanced the cytotoxic effect of driver inhibitors alone by increasing the apoptotic response.

CONCLUSIONS

Inhibition of ATM reduced both glycolytic enzymes and OXPHOS levels in oncogene-driven cancer cells and enhanced apoptosis induced by driver inhibitors thus highlighting the possibility to use ATM and the driver inhibitors in combined regimens of anticancer therapy in vivo.

ATM participates in fine particulate matter-induced airway inflammation through regulating DNA damage and DNA damage response

The relationship between fine particulate matter (PM2.5) and chronic airway inflammatory diseases, such as chronic obstructive pulmonary disease and asthma, have garnered public attention, while the detailed mechanisms of PM2.5-induced airway inflammation remain unclear. This study reveals that PM2.5 induces airway inflammation both in vivo and in vitro, and, moreover, identifies DNA damage and DNA damage repair (DDR) as results of this exposure. Ataxia telangiectasia-mutated heterozygous (ATM+/- ) and wild-type C57BL/6 (WT) mice were exposed to PM2.5. The results show that, following exposure to PM2.5, the number of neutrophils in broncho alveolar lavage fluid and the mRNA expression of CXCL-1 in lung tissues of the ATM+/- mice were lower than those of the WT mice. The mRNA expression of FANCD2 and FANCI were also down-regulated. Human bronchial epithelial (HBE) cells were transfected with ATM-siRNA to induce down-regulation of ATM gene expression and were subsequently stimulated with PM2.5. The results show that the mRNA expression of TNF-α decreased in the ATM-siRNA-transfected cells. The mRNA expression of CXCL-1 and CXCL-2 in peritoneal macrophages, derived from ATM-null mice in which experiments showed that the protein expression of FANCD2 and FANCI decreased, were also decreased after PM2.5 exposure in ATM-siRNA-transfected HBE cells. In conclusion, PM2.5-induced airway inflammation is alleviated in ATM+/- mice compared with WT mice. ATM promotes PM2.5-induced airway inflammation, which may be attributed to the regulation of DNA damage and DDR.

ATR activation by Cr-DNA damage is a major survival response establishing late S and G2 checkpoints after Cr(VI) exposure

Inhalation exposure to hexavalent chromium is known to cause lung cancer and other pulmonary toxicity. Cellular metabolism of chromium(VI) entering cells as chromate anion produces different amounts of reactive Cr(V) intermediates and finally yields Cr(III). Direct reduction of Cr(VI) by ascorbate (Asc), the dominant metabolic reaction in vivo but not in standard cell cultures, skips production of Cr(V) but still permits extensive formation of Cr-DNA damage. To understand the importance of different forms of biological injury in Cr(VI) toxicity, we examined activation of several protein- and DNA damage-sensitive stress responses in human lung cells under Asc-restored conditions. We found that Asc-restored cells suppressed upregulation of oxidant-sensitive stress systems by Cr(VI) but showed a strong activation of the apical DNA damage-responsive kinase ATR. ATR signaling was triggered in late S phase and persisted upon entry of cells into G2 phase. Inhibition of ATR prevented the establishment of late-S and G2 cell cycle checkpoints and did not lead to a compensatory activation of a related kinase ATM. Inactivation of ATR also strongly impaired viability of Cr(VI)-treated lung cells including stem-like cells and revealed a significant formation of toxic Cr-DNA damage at low Cr(VI) doses. Our findings identified a major Cr(VI) resistance mechanism involving sensing of Cr-DNA damage by ATR in late S phase and a subsequent establishment of protective cell cycle checkpoints.

Post-radiation treatment of 3,3'-diselenodipropionic acid augments cell kill by modulating DNA repair and cell migration pathways in A549 cells

Aim of the present study was to test whether ionizing radiation (IR) treatment along with 3,3'-diselenodipropionic acid (DSePA), a redox active organodiselenide achieved better tumor control by suppressing the growth and migration of lung cancer cells. The results indicated that post-IR (2 Gy) treatment of DSePA (5 μM) led to a significantly higher cell death as compared to that of DSePA and IR treatments separately. Importantly, combinatorial treatment also showed reduction in the proportion of cancer stem cells and the clonogenic survival of A549 cells. The mechanistic studies indicated that combinatorial treatment although exhibited reductive environment (marked by decrease in ROS and increase of GSH/GSSG) at early time points (2-6 h postradiation), slowed DNA repair, inhibited epithelial-mesenchymal transition (EMT)/cell migration and induced significant level of apoptosis. DSePA mediated suppression of ATM/DNAPKs/p53 (DNA damage response signaling) and Akt/G-CSF (EMT) pathways appeared to be the major mechanism responsible for its radio-modulating activity. Finally, the combined treatment of IR (2 Gy × 4) and DSePA (0.1-0.25 mg/kg body weight daily through oral gavage) showed a significantly higher tumor suppression of the A549 xenograft as compared to that of DSePA and IR treatments separately in the mouse model. In conclusion, post-IR treatment of DSePA augmented cell kill by inhibiting DNA repair and cell migration in A549 cells.

Structure and function of the apical PIKKs in double-strand break repair

Members of the phosphatidylinositol 3' kinase (PI3K)-related kinases (PIKKs) family, including DNA-dependent protein kinase catalytic subunit (DNA-PKcs), ataxia telangiectasia mutated (ATM), ataxia-telangiectasia mutated and Rad3-related (ATR), mammalian target of rapamycin (mTOR), suppressor with morphological effect on genitalia 1 (SMG1), and transformation/transcription domain-associated protein 1 (TRRAP/Tra1), participate in a variety of physiological processes, such as cell-cycle control, metabolism, transcription, replication, and the DNA damage response. In eukaryotic cells, DNA-PKcs, ATM, and ATR-ATRIP are the main sensors and regulators of DNA double-strand break repair. The purpose of this review is to describe recent structures of DNA-PKcs, ATM, and ATR, as well as their functions in activation and phosphorylation in different DNA repair pathways.

Multiple sevoflurane exposures during mid-trimester induce neurotoxicity in the developing brain initiated by 15LO2-Mediated ferroptosis

AIMS

Mid-gestational sevoflurane exposure may induce notable long-term neurocognitive impairment in offspring. This study was designed to investigate the role and potential mechanism of ferroptosis in developmental neurotoxicity induced by sevoflurane in the second trimester.

METHODS

Pregnant rats on day 13 of gestation (G13) were treated with or without 3.0% sevoflurane, Ferrostatin-1 (Fer-1), PD146176, or Ku55933 on three consecutive days. Mitochondrial morphology, ferroptosis-relative proteins, malondialdehyde (MDA) levels, total iron content, and glutathione peroxidase 4 (GPX4) activities were measured. Hippocampal neuronal development in offspring was also examined. Subsequently, 15-lipoxygenase 2 (15LO2)-phosphatidylethanolamine binding protein 1 (PEBP1) interaction and expression of Ataxia telangiectasia mutated (ATM) and its downstream proteins were also detected. Furthermore, Morris water maze (MWM) and Nissl's staining were applied to estimate the long-term neurotoxic effects of sevoflurane.

RESULTS

Ferroptosis mitochondria were observed after maternal sevoflurane exposures. Sevoflurane elevated MDA and iron levels while inhibiting GPX4 activity, and resultant long-term learning and memory dysfunction, which were alleviated by Fer-1, PD146176, and Ku55933. Sevoflurane could enhance 15LO2-PEBP1 interaction and activate ATM and its downstream P53/SAT1 pathway, which might be attributed to excessive p-ATM nuclear translocation.

CONCLUSION

This study proposes that 15LO2-mediated ferroptosis might contribute to neurotoxicity induced by maternal sevoflurane anesthesia during the mid-trimester in the offspring and its mechanism may be ascribed to hyperactivation of ATM and enhancement of 15LO2-PEBP1 interaction, indicating a potential therapeutic target for ameliorating sevoflurane-induced neurotoxicity.

Structural insights into the activation of ataxia-telangiectasia mutated by oxidative stress

Ataxia-telangiectasia mutated (ATM) is a master kinase regulating DNA damage response that is activated by DNA double-strand breaks. However, ATM is also directly activated by reactive oxygen species, but how oxidative activation is achieved remains unknown. We determined the cryo-EM structure of an H2O2-activated ATM and showed that under oxidizing conditions, ATM formed an intramolecular disulfide bridge between two protomers that are rotated relative to each other when compared to the basal state. This rotation is accompanied by release of the substrate-blocking PRD region and twisting of the N-lobe relative to the C-lobe, which greatly optimizes catalysis. This active site remodeling enabled us to capture a substrate (p53) bound to the enzyme. This provides the first structural insights into how ATM is activated during oxidative stress.

Multifaceted roles of mitochondria in wound healing and chronic wound pathogenesis

Mitochondria are intracellular organelles that play a critical role in numerous cellular processes including the regulation of metabolism, cellular stress response, and cell fate. Mitochondria themselves are subject to well-orchestrated regulation in order to maintain organelle and cellular homeostasis. Wound healing is a multifactorial process that involves the stringent regulation of several cell types and cellular processes. In the event of dysregulated wound healing, hard-to-heal chronic wounds form and can place a significant burden on healthcare systems. Importantly, treatment options remain limited owing to the multifactorial nature of chronic wound pathogenesis. One area that has received more attention in recent years is the role of mitochondria in wound healing. With regards to this, current literature has demonstrated an important role for mitochondria in several areas of wound healing and chronic wound pathogenesis including metabolism, apoptosis, and redox signalling. Additionally, the influence of mitochondrial dynamics and mitophagy has also been investigated. However, few studies have utilised patient tissue when studying mitochondria in wound healing, instead using various animal models. In this review we dissect the current knowledge of the role of mitochondria in wound healing and discuss how future research can potentially aid in the progression of wound healing research.

Cyclers' kinases in cell division: from molecules to cancer therapy

Faithful eucaryotic cell division requires spatio-temporal orchestration of multiple sequential events. To ensure the dynamic nature of these molecular and morphological transitions, a swift modulation of key regulatory pathways is necessary. The molecular process that most certainly fits this description is phosphorylation, the post-translational modification provided by kinases, that is crucial to allowing the progression of the cell cycle and that culminates with the separation of two identical daughter cells. In detail, from the early stages of the interphase to the cytokinesis, each critical step of this process is tightly regulated by multiple families of kinases including the Cyclin-dependent kinases (CDKs), kinases of the Aurora, Polo, Wee1 families, and many others. While cell-cycle-related CDKs control the timing of the different phases, preventing replication machinery errors, the latter modulate the centrosome cycle and the spindle function, avoiding karyotypic abnormalities typical of chromosome instability. Such chromosomal abnormalities may result from replication stress (RS) and chromosome mis-segregation and are considered a hallmark of poor prognosis, therapeutic resistance, and metastasis in cancer patients. Here, we discuss recent advances in the understanding of how different families of kinases concur to govern cell cycle, preventing RS and mitotic infidelity. Additionally, considering the growing number of clinical trials targeting these molecules, we review to what extent and in which tumor context cell-cycle-related kinases inhibitors are worth exploiting as an effective therapeutic strategy.