Lipid peroxidation in face of DNA damage, DNA repair and other cellular processes

Beneficial effects of antioxidants in improving health conditions of sheep infected with foot-and-mouth disease

The effect of multinutrient antioxidant treatment on sheep naturally infected with FMD virus was investigated in terms of general health conditions, serum proteins profile, and antioxidant/oxidant parameters. Twenty diseased sheep were divided into 4 equal groups (n = 5) and underwent certain therapeutic protocols for 8 weeks as follows: GI, infected not treated group; GII, infected and treated with the ideal and usual line of treatment against FMD virus infection; GIII, infected animals supplemented orally zinc methionine at a dose of 5 g/head/day and vitamin E with selenium-enriched yeast at the same dose level; GIV, infected animals received both the ideal treatment and antioxidants. The animals under experiment were clinically evaluated. Blood samples were obtained for the comet assay and biochemical examination at zero time and at the 8th week after treatment. Results revealed that DNA damage reduced in both GIII and GIV groups which received antioxidants. In the GI group, the activity of SOD and GPx and the level of total antioxidant capacity (TAC) markedly decreased. However, in both GIII and GIV groups treated with multinutrient antioxidants, GPx and TAC values significantly increased after treatment in comparison with the values of the same groups before treatment. After treatment with multinutrient antioxidants, α1-, β-, and γ-globulins levels markedly increased in GII and GIII groups while α2-globulin level decreased. The improvement in healing of clinical signs and general health conditions was clear in the GIV group. Finally, FMD infection in sheep was found to be associated with oxidative stress. The use of antioxidants as therapeutic approaches recovers and improves general health conditions and performance of affected animals.

Emerging Technologies in Mass Spectrometry-Based DNA Adductomics

The measurement of DNA adducts, the covalent modifications of DNA upon the exposure to the environmental and dietary genotoxicants and endogenously produced electrophiles, provides molecular evidence for DNA damage. With the recent improvements in the sensitivity and scanning speed of mass spectrometry (MS) instrumentation, particularly high-resolution MS, it is now feasible to screen for the totality of DNA damage in the human genome through DNA adductomics approaches. Several MS platforms have been used in DNA adductomic analysis, each of which has its strengths and limitations. The loss of 2′-deoxyribose from the modified nucleoside upon collision-induced dissociation is the main transition feature utilized in the screening of DNA adducts. Several advanced data-dependent and data-independent scanning techniques originated from proteomics and metabolomics have been tailored for DNA adductomics. The field of DNA adductomics is an emerging technology in human exposure assessment. As the analytical technology matures and bioinformatics tools become available for analysis of the MS data, DNA adductomics can advance our understanding about the role of chemical exposures in DNA damage and disease risk.

Depletion of ATP-Citrate Lyase (ATPCL) Affects Chromosome Integrity Without Altering Histone Acetylation in Drosophila Mitotic Cells

The Citrate Lyase (ACL) is the main cytosolic enzyme that converts the citrate exported from mitochondria by the SLC25A1 carrier in Acetyl Coenzyme A (acetyl-CoA) and oxaloacetate. Acetyl-CoA is a high-energy intermediate common to a large number of metabolic processes including protein acetylation reactions. This renders ACL a key regulator of histone acetylation levels and gene expression in diverse organisms including humans. We have found that depletion of ATPCL, the Drosophila ortholog of human ACL, reduced levels of Acetyl CoA but, unlike its human counterpart, does not affect global histone acetylation and gene expression. Nevertheless, reduced ATPCL levels caused evident, although moderate, mitotic chromosome breakage suggesting that this enzyme plays a partial role in chromosome stability. These defects did not increase upon X-ray irradiation, indicating that they are not dependent on an impairment of DNA repair. Interestingly, depletion of ATPCL drastically increased the frequency of chromosome breaks (CBs) associated to mutations in scheggia, which encodes the ortholog of the mitochondrial citrate carrier SLC25A1 that is also required for chromosome integrity and histone acetylation. Our results indicate that ATPCL has a dispensable role in histone acetylation and prevents massive chromosome fragmentation when citrate efflux is altered.

Oxidation of 1-N2-etheno-2'-deoxyguanosine by singlet molecular oxygen results in 2'-deoxyguanosine: a pathway to remove exocyclic DNA damage?

Exocyclic DNA adducts are considered as potential tools for the study of oxidative stress-related diseases, but an important aspect is their chemical reactivity towards oxidant species. We report here the oxidation of 1-N2-etheno-2'-deoxyguanosine (1,N2-εdGuo) by singlet molecular oxygen (1O2) generated by a non-ionic water-soluble endoperoxide [N,N'-di(2,3-dihydroxypropyl)-1,4-naphthalenedipropanamide endoperoxide (DHPNO2)] and its corresponding oxygen isotopically labeled [18O]-[N,N'-di(2,3-dihydroxypropyl)-1,4- naphthalenedipropanamide endoperoxide (DHPN18O2)], and by photosensitization with two different photosensitizers [methylene blue (MB) and Rose Bengal (RB)]. Products detection and characterization were achieved using high performance liquid chromatography (HPLC) coupled to ultraviolet and electrospray ionization (ESI) tandem mass spectrometry, and nuclear magnetic resonance (NMR) analyses. We found that dGuo is regenerated via reaction of 1O2 with the ε-linkage, and we propose a dioxetane as an intermediate, which cleaves and loses the aldehyde groups as formate residues, or alternatively, it generates a 1,2-ethanediol adduct. We also report herein the quenching rate constants of 1O2 by 1,N2-εdGuo and other etheno modified nucleosides. The rate constant (kt) values obtained for etheno nucleosides are comparable to the kt of dGuo. From these results, we suggest a possible role of 1O2 in the cleanup of etheno adducts by regenerating the normal base.

Novel approach to integrated DNA adductomics for the assessment of in vitro and in vivo environmental exposures

Adductomics is expected to be useful in the characterization of the exposome, which is a new paradigm for studying the sum of environmental causes of diseases. DNA adductomics is emerging as a powerful method for detecting DNA adducts, but reliable assays for its widespread, routine use are currently lacking. We propose a novel integrated strategy for the establishment of a DNA adductomic approach, using liquid chromatography-triple quadrupole tandem mass spectrometry (LC-QqQ-MS/MS), operating in constant neutral loss scan mode, screening for both known and unknown DNA adducts in a single injection. The LC-QqQ-MS/MS was optimized using a representative sample of 23 modified 2'-deoxyribonucleosides reflecting a range of biologically relevant DNA lesions. Six internal standards (ISTDs) were evaluated for their ability to normalize, and hence correct, possible variation in peak intensities arising from matrix effects, and the quantities of DNA injected. The results revealed that, with appropriate ISTDs adjustment, any bias can be dramatically reduced from 370 to 8.4%. Identification of the informative DNA adducts was achieved by triggering fragmentation spectra of target ions. The LC-QqQ-MS/MS method was successfully applied to in vitro and in vivo studies to screen for DNA adducts formed following representative environmental exposures: methyl methanesulfonate (MMS) and five N-nitrosamines. Interestingly, five new DNA adducts, induced by MMS, were discovered using our adductomic approach-an added strength. The proposed integrated strategy provides a path forward for DNA adductomics to become a standard method to discover differences in DNA adduct fingerprints between populations exposed to genotoxins, and facilitate the field of exposomics.

PAM-OBG: A monoamine oxidase B specific prodrug that inhibits MGMT and generates DNA interstrand crosslinks, potentiating temozolomide and chemoradiation therapy in intracranial glioblastoma

Via extensive analyses of genetic databases, we have characterized the DNA-repair capacity of glioblastoma with respect to patient survival. In addition to elevation of O⁶-methylguanine DNA methyltransferase (MGMT), down-regulation of three DNA repair pathways; canonical mismatch repair (MMR), Non-Homologous End-Joining (NHEJ), and Homologous Recombination (HR) are correlated with poor patient outcome. We have designed and tested both in vitro and in vivo, a monoamine oxidase B (MAOB) specific prodrug, PAM-OBG, that is converted by glioma MAOB into the MGMT inhibitor O⁶-benzylguanine (O⁶BG) and the DNA crosslinking agent acrolein. In cultured glioma cells, we show that PAM-OBG is converted to O⁶BG, inhibiting MGMT and sensitizing cells to DNA alkylating agents such as BCNU, CCNU, and Temozolomide (TMZ). In addition, we demonstrate that the acrolein generated is highly toxic in glioma treated with an inhibitor of Nucleotide Excision Repair (NER). In mouse intracranial models of primary human glioma, we show that PAM-OBG increases survival of mice treated with either BCNU or CCNU by a factor of six and that in a chemoradiation model utilizing six rounds of TMZ/2Gy radiation, pre-treatment with PAM-OBG more than doubled survival time.

The influence of diet on anti-cancer immune responsiveness

Immunotherapy has matured into standard treatment for several cancers, but much remains to be done to extend the reach of its effectiveness particularly to cancers that are resistant within each indication. This review proposes that nutrition can affect and potentially enhance the immune response against cancer. The general mechanisms that link nutritional principles to immune function and may influence the effectiveness of anticancer immunotherapy are examined. This represents also the premise for a research project aimed at identifying the best diet for immunotherapy enhancement against tumours (D.I.E.T project). Particular attention is turned to the gut microbiota and the impact of its composition on the immune system. Also, the dietary patterns effecting immune function are discussed including the value of adhering to a healthy diets such as the Mediterranean, Veg, Japanese, or a Microbiota-regulating diet, the very low ketogenic diet, which have been demonstrated to lower the risk of developing several cancers and reduce the mortality associated with them. Finally, supplements, as omega-3 and polyphenols, are discussed as potential approaches that could benefit healthy dietary and lifestyle habits in the context of immunotherapy.

A comparative study of using free radical generators in the testing of chosen oxidative stress parameters in the different types of cells

The aim of this study was to assess whether there are differences between the results of determining oxidative stress markers obtained from different origin cell lines after exposure to chemicals generating free radicals. The studies considered two markers of oxidative stress: the level of thiobarbituric acid reactive substances (TBARS) and superoxide dismutase activity. The evaluation was performed in five cell lines: Chinese hamster ovary (CHO-9) cells, lung adenocarcinoma A549, macrophages RAW264.7, skin carcinoma cells A431, and keratinocytes HaCaT. Three compounds generating free radicals were used as a source of reactive oxygen/nitrogen: 2,2'-azobis-2-methyl-propanimidamide dihydrochloride (AAPH), sodium persulfate (SP), and 3-morpholinosydnonimine hydrochloride (SIN-1). The most appropriate cell line to assess the level of TBARS proved to be the murine macrophage cell line RAW 264.7. Equally, good performance was observed in the lung cancer cell line A549, but only when tested with AAPH and SP. In the case of measuring superoxide dismutase activity, it appeared that the most suitable cell line was also the RAW 264.7 line, although dispersion increased significantly at the highest concentrations of AAPH and SP measurements. When choosing a cell line to determine oxidative stress, the specificity of the stress-inducing compound and the parameter determined should be taken into consideration.

DNA repair after oxidative stress: current challenges

Reactive oxygen and nitrogen species damage cellular macromolecules including DNA. Cells have a robust base excision repair pathway to deal with this damage in both nuclear and mitochondrial genomes. However, mitochondria lack nucleotide excision repair. Evidence suggests that chronic oxidative stress can induce protective pathways lowering genotoxicity. Understanding oxidant injury to DNA and its repair is critical for our understanding the pathophysiology of a wide range of human disorders.

Myeloid suppressor cells in cancer and autoimmunity

A bottleneck for immunotherapy of cancer is the immunosuppressive microenvironment in which the tumor cells proliferate. Cancers harness the immune regulatory mechanism that prevents autoimmunity from evading immunosurveillance and promoting immune destruction. Regulatory T cells, myeloid suppressor cells, inhibitory cytokines and immune checkpoint receptors are the major components of the immune system acting in concert with cancer cells and causing the subversion of anti-tumor immunity. This redundant immunosuppressive network poses an impediment to efficacious immunotherapy by facilitating tumor progression. Tumor-associated myeloid cells comprise heterogeneous populations acting systemically (myeloid-derived suppressor cells/MDSCs) and/or locally in the tumor microenvironment (MDSCs and tumor-associated macrophages/TAMs). Both populations promote cancer cell proliferation and survival, angiogenesis and lymphangiogenesis and elicit immunosuppression through different pathways, including the expression of immunosuppressive cytokines and checkpoint inhibitors. Several evidences have demonstrated that myeloid cells can express different functional programs in response to different microenvironmental signals, a property defined as functional plasticity. The opposed extremes of this functional flexibility are generally represented by the classical macrophage activation, which identifies inflammatory and cytotoxic M1 polarized macrophages, and the alternative state of macrophage activation, which identifies M2 polarized anti-inflammatory and immunosuppressive macrophages. Functional skewing of myeloid cells occurs in vivo under physiological and pathological conditions, including cancer and autoimmunity. Here we discuss how myeloid suppressor cells can on one hand support tumor growth and, on the other, limit autoimmune responses, indicating that their therapeutic reprogramming can generate opportunities in relieving immunosuppression in the tumor microenvironment or reinstating tolerance in autoimmune conditions.

Inflammation as target in cancer therapy

Cells of the innate immunity infiltrating tumour tissues promote, rather than halt, cancer cell proliferation and distant spreading. Tumour-Associated Macrophages (TAMs) are abundantly present in the tumour milieu and here trigger and perpetrate a state of chronic inflammation which ultimately supports disease development and contributes to an immune-suppressive environment. Therapeutic strategies to limit inflammatory cells and their products have been successful in pre-clinical tumour models. Early clinical trials with specific cytokine and chemokine inhibitors, or with strategies designed to target TAMs, are on their way in different solid malignancies. Partial clinical responses and stabilization of diseases were observed in some patients, in the absence of significant toxicity. These encouraging results open new perspectives of combination treatments aimed at reducing cancer-promoting inflammation to maximize the anti-tumour efficacy.

Oxidative DNA damage & repair: An introduction

This introductory article should be viewed as a prologue to the Free Radical Biology & Medicine Special Issue devoted to the important topic of Oxidatively Damaged DNA and its Repair. This special issue is dedicated to Professor Tomas Lindahl, co-winner of the 2015 Nobel Prize in Chemistry for his seminal discoveries in the area repair of oxidatively damaged DNA. In the past several years it has become abundantly clear that DNA oxidation is a major consequence of life in an oxygen-rich environment. Concomitantly, survival in the presence of oxygen, with the constant threat of deleterious DNA mutations and deletions, has largely been made possible through the evolution of a vast array of DNA repair enzymes. The articles in this Oxidatively Damaged DNA & Repair special issue detail the reactions by which intracellular DNA is oxidatively damaged, and the enzymatic reactions and pathways by which living organisms survive such assaults by repair processes.