Endogenous mutagens and the causes of aging and cancer

Recognition of 8-Oxo-2'-deoxyguanosine in DNA Using the Triphosphate of 2'-Deoxycytidine Connecting the 1,3-Diazaphenoxazine Unit, dCdapTP

DNA is constantly damaged by various external and internal factors. In particular, oxidative damage occurs in a steady state, and 8-oxo-2'-deoxyguanosine (oxodG) is known as the main oxidative damage. OxodG is a strong genotoxic nucleoside and is thought to be involved in the pathogenesis of cancer and neurological diseases. However, a breakthrough method to detect the position of oxodG in DNA has not yet been developed. Therefore, we attempted to develop a novel method to detect oxodG in DNA using artificial nucleosides. Recently, we have succeeded in the recognition of oxodG in DNA by a single nucleotide elongation reaction using nucleoside derivatives based on a purine skeleton with a 1,3-diazaphenoxazine unit. In this study, we developed a new nucleoside derivative with a pyrimidine skeleton in order to further improve the recognition ability and enzymatic reaction efficiency. We, therefore, designed and synthesized 2'-deoxycytidine-1,3-diazaphenoxazine (Cdap) and its triphosphate derivatives. The results showed that it was incorporated into the primer strand relative to the dG template because of its cytidine skeleton, but it was more effective at the complementary position of the oxodG template. These results indicate that the new nucleoside derivative can be considered as one of the new candidates for the detection of oxodG in DNA.

Spontaneous mutations and mutational responses to penicillin treatment in the bacterial pathogen Streptococcus pneumoniae D39

Bacteria with functional DNA repair systems are expected to have low mutation rates due to strong natural selection for genomic stability. However, our study of the wild-type Streptococcus pneumoniae D39, a pathogen responsible for many common diseases, revealed a high spontaneous mutation rate of 0.02 per genome per cell division in mutation-accumulation (MA) lines. This rate is orders of magnitude higher than that of other non-mutator bacteria and is characterized by a high mutation bias in the A/T direction. The high mutation rate may have resulted from a reduction in the overall efficiency of selection, conferred by the tiny effective population size in nature. In line with this, S. pneumoniae D39 also exhibited the lowest DNA mismatch-repair (MMR) efficiency among bacteria. Treatment with the antibiotic penicillin did not elevate the mutation rate, as penicillin did not induce DNA damage and S. pneumoniae lacks a stress response pathway. Our findings suggested that the MA results are applicable to within-host scenarios and provide insights into pathogen evolution.

Supplementary Information

The online version contains supplementary material available at 10.1007/s42995-024-00220-6.

Anti-aging Strategies and Topical Delivery of Biopolymer-based Nanocarriers for Skin Cancer Treatment

Environmental factors like UV radiation and epigenetic changes are significant factors for skin cancer that trigger early aging. This review provides essential information on cancer development concerning aging, the receptors involved, and the therapeutic targets. Biopolymers like polysaccharide, polyphenols, proteins, and nucleic acid plays a vital role in the regulation of normal cell homeostasis. Therefore, it is pertinent to explore the role of biopolymers as antiaging formulations and the possibility of these formulations being used against cancer via topical administrations. As UV radiation is one of the predominant factors in causing skin cancer, the association of receptors between aging and cancer indicated that insulin receptor, melatonin receptor, toll-like receptor, SIRT 1 receptor, tumor-specific T cell receptor and mitochondria-based targeting could be used to direct therapeutics for suppression of cancer and prevent aging. Biopolymer-based nanoformulations have tremendously progressed by entrapment of drugs like curcumin and resveratrol which can prevent cancer and aging simultaneously. Certain protein signaling or calcium and ROS signaling pathways are different for cancer and aging. The involvement of mitochondrial DNA mutation along with telomere shortening with a change in cellular energetics leading to genomic instability in the aging process can also induce mitochondrial dysfunction and epigenetic alterations leading to skin cancer. Therefore, the use of biopolymers as a topical supplement during the aging process can result in the prevention of cancer.

OH Radical-Induced Oxidation in Nucleosides and Nucleotides Unraveled by Tandem Mass Spectrometry and Infrared Multiple Photon Dissociation Spectroscopy

OH⋅-induced oxidation products of DNA nucleosides and nucleotides have been structurally characterized by collision-induced dissociation tandem mass spectrometry (CID-MS2 ) and Infrared Multiple Photon Dissociation (IRMPD) spectroscopy. CID-MS2 results have shown that the addition of one oxygen atom occurs on the nucleobase moiety. The gas-phase geometries of +16 mass increment products of 2'-deoxyadenosine (dA(O)H+ ), 2'-deoxyadenosine 5'-monophosphate (dAMP(O)H+ ), 2'-deoxycytidine (dC(O)H+ ), and 2'-deoxycytidine 5'-monophosphate (dCMP(O)H+ ) are extensively investigated by IRMPD spectroscopy and quantum-chemical calculations. We show that a carbonyl group is formed at the C8 position after oxidation of 2'-deoxyadenosine and its monophosphate derivative. For 2'-deoxycytidine and its monophosphate derivative, the oxygen atom is added to the C5 position to form a C-OH group. IRMPD spectroscopy has been employed for the first time to provide direct structural information on oxidative lesions in DNA model systems.

The Therapeutic Potential of a Strategy to Prevent Acute Myeloid Leukemia Stem Cell Reprogramming in Older Patients

Acute myeloid leukemia (AML) is the most common and incurable leukemia subtype. Despite extensive research into the disease's intricate molecular mechanisms, effective treatments or expanded diagnostic or prognostic markers for AML have not yet been identified. The morphological, immunophenotypic, cytogenetic, biomolecular, and clinical characteristics of AML patients are extensive and complex. Leukemia stem cells (LSCs) consist of hematopoietic stem cells (HSCs) and cancer cells transformed by a complex, finely-tuned interaction that causes the complexity of AML. Microenvironmental regulation of LSCs dormancy and the diagnostic and therapeutic implications for identifying and targeting LSCs due to their significance in the pathogenesis of AML are discussed in this review. It is essential to perceive the relationship between the niche for LSCs and HSCs, which together cause the progression of AML. Notably, methylation is a well-known epigenetic change that is significant in AML, and our data also reveal that microRNAs are a unique factor for LSCs. Multiple-targeted approaches to reduce the risk of epigenetic factors, such as the administration of natural compounds for the elimination of local LSCs, may prevent potentially fatal relapses. Furthermore, the survival analysis of overlapping genes revealed that specific targets had significant effects on the survival and prognosis of patients. We predict that the multiple-targeted effects of herbal products on epigenetic modification are governed by different mechanisms in AML and could prevent potentially fatal relapses. Thus, these strategies can facilitate the incorporation of herbal medicine and natural compounds into the advanced drug discovery and development processes achievable with Network Pharmacology research.

The Over-Irradiation Metabolite Derivative, 24-Hydroxylumister-ol3, Reduces UV-Induced Damage in Skin

The hormonal form of vitamin D₃, 1,25(OH)₂D₃, reduces UV-induced DNA damage. UV exposure initiates pre-vitamin D₃ production in the skin, and continued UV exposure photoisomerizes pre-vitamin D₃ to produce "over-irradiation products" such as lumisterol₃ (L₃). Cytochrome P450 side-chain cleavage enzyme (CYP11A1) in skin catalyzes the conversion of L₃ to produce three main derivatives: 24-hydroxy-L₃ [24(OH)L₃], 22-hydroxy-L₃ [22(OH)L₃], and 20,22-dihydroxy-L₃ [20,22(OH)L₃]. The current study investigated the photoprotective properties of the major over-irradiation metabolite, 24(OH)L₃, in human primary keratinocytes and human skin explants. The results indicated that treatment immediately after UV with either 24(OH)L₃ or 1,25(OH)₂D₃ reduced UV-induced cyclobutane pyrimidine dimers and oxidative DNA damage, with similar concentration response curves in keratinocytes, although in skin explants, 1,25(OH)₂D₃ was more potent. The reductions in DNA damage by both compounds were, at least in part, the result of increased DNA repair through increased energy availability via increased glycolysis, as well as increased DNA damage recognition proteins in the nucleotide excision repair pathway. Reductions in UV-induced DNA photolesions by either compound occurred in the presence of lower reactive oxygen species. The results indicated that under in vitro and ex vivo conditions, 24(OH)L₃ provided photoprotection against UV damage similar to that of 1,25(OH)₂D₃.

Interaction between Cigarette Smoke and Human Papillomavirus 16 E6/E7 Oncoproteins to Induce SOD2 Expression and DNA Damage in Head and Neck Cancer

Even though epidemiological studies suggest that tobacco smoking and high-risk human papillomavirus (HR-HPV) infection are mutually exclusive risk factors for developing head and neck cancer (HNC), a portion of subjects who develop this heterogeneous group of cancers are both HPV-positive and smokers. Both carcinogenic factors are associated with increased oxidative stress (OS) and DNA damage. It has been suggested that superoxide dismutase 2 (SOD2) can be independently regulated by cigarette smoke and HPV, increasing adaptation to OS and tumor progression. In this study, we analyzed SOD2 levels and DNA damage in oral cells ectopically expressing HPV16 E6/E7 oncoproteins and exposed to cigarette smoke condensate (CSC). Additionally, we analyzed SOD2 transcripts in The Cancer Genome Atlas (TCGA) Head and Neck Cancer Database. We found that oral cells expressing HPV16 E6/E7 oncoproteins exposed to CSC synergistically increased SOD2 levels and DNA damage. Additionally, the SOD2 regulation by E6, occurs in an Akt1 and ATM-independent manner. This study suggests that HPV and cigarette smoke interaction in HNC promotes SOD2 alterations, leading to increased DNA damage and, in turn, contributing to development of a different clinical entity.

Fluorescently labeled human apurinic/apyrimidinic endonuclease APE1 reveals effects of DNA polymerase β on the APE1-DNA interaction

The base excision repair (BER) pathway involves sequential action of DNA glycosylases and apurinic/apyrimidinic (AP) endonucleases to incise damaged DNA and prepare DNA termini for incorporation of a correct nucleotide by DNA polymerases. It has been suggested that the enzymatic steps in BER include recognition of a product-enzyme complex by the next enzyme in the pathway, resulting in the "passing-the-baton" model of transfer of DNA intermediates between enzymes. To verify this model, in this work, we aimed to create a suitable experimental system. We prepared APE1 site-specifically labeled with a fluorescent reporter that is sensitive to stages of APE1-DNA binding, of formation of the catalytic complex, and of subsequent dissociation of the enzyme-product complex. Interactions of the labeled APE1 with various model DNA substrates (containing an abasic site) of varied lengths revealed that the enzyme remains mostly in complex with the DNA product. By means of the fluorescently labeled APE1 in combination with a stopped-flow fluorescence assay, it was found that Polβ stimulates both i) APE1 binding to an abasic-site-containing DNA duplex with the formation of a catalytically competent complex and ii) the dissociation of APE1 from its product. These findings confirm DNA-mediated coordination of APE1 and Polβ activities and suggest that Polβ is the key trigger of the DNA transfer between the enzymes participating in initial steps of BER.

Rice Nudix Hydrolase OsNUDX2 Sanitizes Oxidized Nucleotides

Nudix hydrolase (NUDX) hydrolyzes 8-oxo-(d)GTP to reduce the levels of oxidized nucleotides in the cells. 8-oxo-(d)GTP produced by reactive oxygen species (ROS) is incorporated into DNA/RNA and mispaired with adenine, causing replicational and transcriptional errors. Here, we identified a rice OsNUDX2 gene, whose expression level was increased 15-fold under UV-C irradiation. The open reading frame of the OsNUDX2 gene, which encodes 776 amino acid residues, was cloned into Escherichia coli cells to produce the protein of 100 kDa. The recombinant protein hydrolyzed 8-oxo-dGTP, in addition to dimethylallyl diphosphate (DMAPP) and isopentenyl diphosphate (IPP), as did Arabidopsis AtNUDX1; whereas the amino acid sequence of OsNUDX2 had 18% identity with AtNUDX1. OsNUDX2 had 14% identity with barley HvNUDX12, which hydrolyzes 8-oxo-dGTP and diadenosine tetraphosphates. Suppression of the lacZ amber mutation caused by the incorporation of 8-oxo-GTP into mRNA was prevented to a significant degree when the OsNUDX2 gene was expressed in mutT-deficient E. coli cells. These results suggest that the different substrate specificity and identity among plant 8-oxo-dGTP-hydrolyzing NUDXs and OsNUDX2 reduces UV stress by sanitizing the oxidized nucleotides.

A PARP1-related prognostic signature constructing and PARP-1 inhibitors screening for glioma

The current standard treatments of glioma include surgical resection, supplemented with radiotherapy and chemotherapy, but the prognosis is poor. PARP-1 (Poly ADP-ribose polymerase 1) is a hot spot for cancer-targeted therapy and was reported to be significantly elevated in glioma. In this study, we analyzed the role of PARP-1 in DNA damage repair, constructed a PARP1-related DNA-repair prognostic signature (DPS), and screened targeted drugs for glioma. RNA-seq data of 639 glioma samples were downloaded from the GEO (Gene Expression Omnibus) database and divided into PARP1_H and PARP1_L according to the front and rear thirds of the expression level of PARP-1. First, we systematically analyzed the influence of PARP-1 on DNA damage repair, prognosis, and chemoradiotherapy sensitization of glioma. All glioma patients and patients with radiotherapy or chemotherapy had a better prognosis in PARP1_L than in PARP1_H. Next, differentially expressed DNA-repair related genes (DEGs) were identified between PARP1_H and PARP1_L by LASSO (Least Absolute Shrinkage and Selection Operator) Cox analysis and applied for constructing DPS. Based on the four-gene DPS, we then developed a new nomogram to assess overall survival in glioma patients. Additionally, PARP-1 was proved an effective target for glioma therapy. So, a series of computer-aided techniques, including Discovery Studio 4.5, Schrodinger, and PyMol, were applied for the virtual screening of favorable PARP-1 inhibitors. In conclusion, this study investigated the effect of PARP-1 on glioma prognosis and the sensitization effect of radiotherapy and chemotherapy, established a novel nomogram to evaluate the overall survival of glioma patients, and further explored targeted therapy for glioma.

Potential Anticarcinogenic Effects From Plasma of Older Adults After Exercise Training: An Exploratory Study

Aim: To evaluate the impact of exercise training plasma on in vitro prostate cancer cell viability and proliferation.

Methods: PC3 prostate cancer cells were incubated with plasma obtained from young men with high and low physical fitness (PF) (high PF, n = 5; low PF, n = 5) and with the plasma collected from institutionalized older adults (n = 8) before and after multimodal exercise training. Cell viability and proliferation, mitochondria membrane polarization, reactive oxygen species (ROS) generation, and apoptosis were evaluated after the cell treatment with plasma. Systemic cytokines were evaluated in the plasma of institutionalized older adults submitted to an exercise training protocol.

Results: Plasma from high-PF men lowers both cell viability and proliferation after the incubation time. PC3 cells also presented lower cell viability and diminished rates of cell proliferation after the incubation with post-training plasma samples of the older adults. The incubation of PC3 cells with post-training plasma of older adults depolarized the mitochondrial membrane potential and increased mitochondrial reactive oxygen species production. Post-training plasma did not change apoptosis or necrosis rates in the PC3 cell line. Multimodal exercise training increased the plasma levels of IL-2, IL-10, IFN-α, and FGF-1 and decreased TNF-α concentrations in institutionalized older adults.

Conclusion: Adaptations in blood factors of institutionalized older adults may alter cell viability and proliferation by targeting mitochondrial ROS in a prostate cancer cell line.

The Helping Everyone Achieve Long Term Health Passport: exploring potential use of the HEALTH Passport in primary and secondary schools

Background

Chronic disease is a significant burden on the global population. The Helping Everyone Achieve Long Term Health (HEALTH) Passport is a paper-based approach previously utilized to help adults modify clinical risk factors through lifestyle, which may be effective in improving the long-term health of school-age children. This study investigates the feasibility of in-school use by engaging trainee teachers in primary and secondary education.

Methods

Two hundred and fifty six unique responses were collated to evaluate current teaching of the main health risk factors and HEALTH Passports specifically adapted for schools. Trainees attended workshops with pre- and post-questionnaires used to measure training efficacy and evaluate the Passports’ suitability for in-school use. Narrative analysis of feedback was performed.

Results

Feedback received for both Passports was positive overall. Trainees highlighted the need for the Passports to be further age differentiated. Significantly increased confidence (P < 0.01) in knowledge of exercise, type 2 diabetes, weight and blood pressure was shown. Confidence in smoking, drugs and alcohol knowledge was reduced highlighting the requirement for further teacher training.

Conclusions

The HEALTH Passport has potential as an intervention to improve health literacy in school-age children. Age adaptation is needed with references to weight measures removed. Emotional well-being should be focused on, and data management stringently assessed for child protection.

Musings in the twilight of my career

I present a summary of my research during the last few decades of research which focused on understanding the biochemical basis for maintaining an optimum metabolism to support long-term health. I realized that adequate levels of ∼40 vitamins and minerals needed as cofactors in thousands of metabolic reactions were critical for maintaining a healthy metabolism, and thus for longevity and prevention of chronic disease. Inadequate dietary intake of vitamins and minerals accelerates the risk of aging-associated diseases, leading to insidious damage. The Triage Theory provides a mechanistic rationale for such damage: shortage of a nutrient triggers a built-in rationing mechanism that allocates the scarce nutrient to proteins needed for immediate survival (survival proteins), at the expense of those needed for long-term survival (longevity proteins). Many as-yet-unknown longevity vitamins and proteins likely remain to be discovered. The fiber and nutrient-rich CHORI-bar was developed to fill gaps in inadequate diets; it yielded broadscale metabolic improvements. The health-related damages resulting from vitamin D deficiency and the positive effects of vitamin D supplementation were connected to numerous health-related problems, including the higher level of deficiency in people of color residing at northern latitudes. In general, prevention of degenerative diseases of aging requires expertise in metabolism, nutrition, biochemistry and regulatory functions.

Evidence for Involvement of Nonclassical Pathways in the Protection From UV-Induced DNA Damage by Vitamin D-Related Compounds

The vitamin D hormone, 1,25dihydroxyvitamin D₃ (1,25(OH)₂D₃), and related compounds derived from vitamin D₃ or lumisterol as a result of metabolism via the enzyme CYP11A1, have been shown, when applied 24 hours before or immediately after UV irradiation, to protect human skin cells and skin from DNA damage due to UV exposure, by reducing both cyclobutane pyrimidine dimers (CPD) and oxidative damage in the form of 8‐oxo‐7,8‐dihydro‐2′‐deoxyguanosine (8‐OHdG). We now report that knockdown of either the vitamin D receptor or the endoplasmic reticulum protein ERp57 by small, interfering RNA (siRNA) abolished the reductions in UV‐induced DNA damage with 20‐hydroxyvitamin D₃ or 24‐hydroxylumisterol_3, as previously shown for 1,25(OH)₂D₃. Treatment with 1,25(OH)₂D₃ reduced oxygen consumption rates in UV‐exposed and sham‐exposed human keratinocytes and reduced phosphorylation of cyclic AMP response binding element protein (CREB). Both these actions have been shown to inhibit skin carcinogenesis after chronic UV exposure, consistent with the anticarcinogenic activity of 1,25(OH)₂D₃. The requirement for a vitamin D receptor for the photoprotective actions of 1,25(OH)₂D₃ and of naturally occurring CYP11A1‐derived vitamin D–related compounds may explain why mice lacking the vitamin D receptor in skin are more susceptible to UV‐induced skin cancers, whereas mice lacking the 1α‐hydroxylase and thus unable to make 1,25(OH)₂D₃ are not more susceptible. © 2021 The Authors. JBMR Plus published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research.

Structural Insights into the Specificity of 8-Oxo-7,8-dihydro-2′-deoxyguanosine Bypass by Family X DNA Polymerases

8-oxo-guanine (8OG) is a common base lesion, generated by reactive oxygen species, which has been associated with human diseases such as cancer, aging-related neurodegenerative disorders and atherosclerosis. 8OG is highly mutagenic, due to its dual-coding potential it can pair both with adenine or cytidine. Therefore, it creates a challenge for DNA polymerases striving to correctly replicate and/or repair genomic or mitochondrial DNA. Numerous structural studies provide insights into the mechanistic basis of the specificity of 8OG bypass by DNA polymerases from different families. Here, we focus on how repair polymerases from Family X (Pols β, λ and µ) engage DNA substrates containing the oxidized guanine. We review structures of binary and ternary complexes for the three polymerases, which represent distinct steps in their catalytic cycles—the binding of the DNA substrate and the incoming nucleotide, followed by its insertion and extension. At each of these steps, the polymerase may favor or exclude the correct C or incorrect A, affecting the final outcome, which varies depending on the enzyme.

Supplementing Closed Ecological Life Support Systems with In-Situ Resources on the Moon

In this review, I explore a broad-based view of technologies for supporting human activities on the Moon and, where appropriate, Mars. Primarily, I assess the state of life support systems technology beginning with physicochemical processes, waste processing, bioregenerative methods, food production systems and the robotics and advanced biological technologies that support the latter. We observe that the Moon possesses in-situ resources but that these resources are of limited value in closed ecological life support systems (CELSS)-indeed, CELSS technology is most mature in recycling water and oxygen, the two resources that are abundant on the Moon. This places a premium on developing CELSS that recycle other elements that are rarified on the Moon including C and N in particular but also other elements such as P, S and K which might be challenging to extract from local resources. Although we focus on closed loop ecological life support systems, we also consider related technologies that involve the application of biological organisms to bioregenerative medical technologies and bioregenerative approaches to industrial activity on the Moon as potential future developments.

Phenolics and related in vitro functional activities of different varieties of fresh waxy corn: a whole grain

The polyphenol distribution in fresh waxy corns of different color varieties and their functional activities, which may be useful for treating various chronic diseases, were investigated. The in vitro antioxidant activity, and hypoglycemic and hypocholesterolemic effects of the free and bound corn phenolics were determined to evaluate the edible value of fresh waxy corn. The colored varieties contained more phenols than the common varieties (white and/or yellow). The total free phenolic acid content of the six varieties was 6637.73 µg/g DW (dry weight), which was slightly higher (P > 0.05) than that of the total bound form (6276.65 µg/g DW). The total free flavonoid content was 5850.09 µg/g DW, which was higher (P < 0.05) than that of the total bound form (4874.51µg/g DW). No bound anthocyanin was detected in the methanol extracts of the tested varieties. For all the varieties, free polyphenols contributed 86−100 % and 70−78 % of the 2, 2-diphenyl-1-picrylhydrazyl (DPPH) and hydroxyl radical scavenging abilities, respectively, and 100 % of the ferric reducing capacity. The free phenolics in fresh waxy corn showed better (P < 0.05) hypoglycemic effect than the bound form in terms of inhibition of α-amylase activity, whereas the bound phenolics of most varieties showed higher α-glucosidase inhibitory activity than the free forms. The free phenolics showed better (P < 0.05) glycocholesterol binding than the bound form for all varieties. The bound polyphenols showed better sodium cholate and taurocholate binding than the free form for most varieties. In conclusion, the difference between free and bound polyphenol content and functional activities indicates that fresh waxy corn can be potentially used for the development of functional food.

Assessment of the biochemical pathways for acetaminophen toxicity: Implications for its carcinogenic hazard potential

In 2019 California's Office of Environmental Health Hazard Assessment (OEHHA) initiated a review of the carcinogenic hazard potential of acetaminophen. In parallel with this review, herein we evaluated the mechanistic data related to the steps and timing of cellular events following therapeutic recommended (≤4 g/day) and higher doses of acetaminophen that may cause hepatotoxicity to evaluate whether these changes indicate that acetaminophen is a carcinogenic hazard. At therapeutic recommended doses, acetaminophen forms limited amounts of N-acetyl-p-benzoquinone-imine (NAPQI) without adverse cellular effects. Following overdoses of acetaminophen, there is potential for more extensive formation of NAPQI and depletion of glutathione, which may result in mitochondrial dysfunction and DNA damage, but only at doses that result in cell death - thus making it implausible for acetaminophen to induce the kind of stable, genetic damage in the nucleus indicative of a genotoxic or carcinogenic hazard in humans. The collective data demonstrate a lack of a plausible mechanism related to carcinogenicity and are consistent with rodent cancer bioassays, epidemiological results reviewed in companion manuscripts in this issue, as well as conclusions of multiple international health authorities.

Neural stem cell-specific ITPA deficiency causes neural depolarization and epilepsy

Inosine triphosphate pyrophosphatase (ITPA) hydrolyzes inosine triphosphate (ITP) and other deaminated purine nucleotides to the corresponding nucleoside monophosphates. In humans, ITPA deficiency causes severe encephalopathy with epileptic seizure, microcephaly, and developmental retardation. In this study, we established neural stem cell-specific Itpa-conditional KO mice (Itpa-cKO mice) to clarify the effects of ITPA deficiency on the neural system. The Itpa-cKO mice showed growth retardation and died within 3 weeks of birth. We did not observe any microcephaly in the Itpa-cKO mice, although the female Itpa-cKO mice did show adrenal hypoplasia. The Itpa-cKO mice showed limb-clasping upon tail suspension and spontaneous and/or audiogenic seizure. Whole-cell patch-clamp recordings from entorhinal cortex neurons in brain slices revealed a depolarized resting membrane potential, increased firing, and frequent spontaneous miniature excitatory postsynaptic current and miniature inhibitory postsynaptic current in the Itpa-cKO mice compared with ITPA-proficient controls. Accumulated ITP or its metabolites, such as cyclic inosine monophosphates, or RNA containing inosines may cause membrane depolarization and hyperexcitability in neurons and induce the phenotype of ITPA-deficient mice, including seizure.

Protection from Ultraviolet Damage and Photocarcinogenesis by Vitamin D Compounds

Exposure of skin cells to UV radiation results in DNA damage, which if inadequately repaired, may cause mutations. UV-induced DNA damage and reactive oxygen and nitrogen species also cause local and systemic suppression of the adaptive immune system. Together, these changes underpin the development of skin tumours. The hormone derived from vitamin D, calcitriol (1,25-dihydroxyvitamin D₃) and other related compounds, working via the vitamin D receptor and at least in part through endoplasmic reticulum protein 57 (ERp57), reduce cyclobutane pyrimidine dimers and oxidative DNA damage in keratinocytes and other skin cell types after UV. Calcitriol and related compounds enhance DNA repair in keratinocytes, in part through decreased reactive oxygen species, increased p53 expression and/or activation, increased repair proteins and increased energy availability in the cell when calcitriol is present after UV exposure. There is mitochondrial damage in keratinocytes after UV. In the presence of calcitriol, but not vehicle, glycolysis is increased after UV, along with increased energy-conserving autophagy and changes consistent with enhanced mitophagy. Reduced DNA damage and reduced ROS/RNS should help reduce UV-induced immune suppression. Reduced UV immune suppression is observed after topical treatment with calcitriol and related compounds in hairless mice. These protective effects of calcitriol and related compounds presumably contribute to the observed reduction in skin tumour formation in mice after chronic exposure to UV followed by topical post-irradiation treatment with calcitriol and some, though not all, related compounds.

Phenolic profiles, antioxidant, antiproliferative, and hypoglycemic activities of Ehretia macrophyla Wall. (EMW) fruit

Phenolic profiles, antioxidant, antiproliferative, and hypoglycemic activities of the whole Ehretia macrophylla Wall. (EMW) fruit were investigated in the present study. Catechin (CE), o-methoxy benzoic acid (o-MBA), and rosmarinic acid (RA) were the predominant phenolics in free extract, while CE, vanillic acid (VA), and o-MBA were for bound extract. These extracts exhibited potential antioxidant capacity measured by peroxyl radical scavenging capacity (PSC), oxygen radical absorbance capacity (ORAC), and cellular antioxidant activity (CAA) assays. This fruit also possessed dose-dependently antiproliferative activity, and this may be due to the synergistic and additive effects of individual phenolics. Furthermore, EMW fruit showed favorable hypoglycemic activity via inhibition of activities of α-glucosidase and α-amylase, enhancement of glucose consumption, glycogen accumulation, and glycogen synthase 2 (GYS2) activity, and downregulation of activities of glucose-6-phosphatase (G6Pase) and phosphoenolpyruvate carboxykinase (PEPCK). Therefore, EMW fruit has the potential as an ingredient of functional foods to improve human health and shows promising applications with additional health and economical benefits. PRACTICAL APPLICATION: EMW fruit is a plant-based food rich in natural phenolic compounds, which suggesting its potential bioactivities for humans such as antioxidant, antiproliferative, and hypoglycemic activities. Our findings would provide a logical strategy to promote the comprehensive utilization of phenolics in EMW fruit with both health and economical benefits.

Metallomic and lipidomic analysis of S. cerevisiae response to cellulosic copper nanoparticles uncovers drivers of toxicity

Nanotechnology is a promising new technology, of which antimicrobial metal nanocomposites are predicted to become valuable in medical and food packaging applications. Copper is a redox-active antimicrobial metal that can become increasingly toxic depending on the target biomolecule's donor atom selectivity and the chemical species of copper present. Mass is the traditional measurement of the intrinsic elemental chemistry, but this practice fails to reflect the morphology and surface area reactivity of nanotechnology. The carboxymethyl cellulose copper nanoparticles (CMC-Cu) investigated in this study have unique and undefined toxicity to Saccharomyces cerevisiae that is different from CuSO4. Cellular surface damage was found in scanning electron micrographs upon CMC-Cu exposure. Further investigation into the lipids revealed altered phosphatidylcholine and phosphatidylethanolamine membrane composition, as well as depleted triacylglycerols, suggesting an impact on the Kennedy lipid pathway. High levels of reactive oxygen species were measured which likely played a role in the lipid peroxidation detected with CMC-Cu treatment. Metal homeostasis was affected by CMC-Cu treatment. The copper sensitive yeast strain, YJM789, significantly decreased cellular zinc concentrations while the copper concentrations increased, suggesting a possible ionic mimicry relationship. In contrast to other compounds that generate ROS, no evidence of genotoxicity was found. As commonplace objects become more integrated with nanotechnology, humanity must look forward past traditional measurements of toxicity.

Dual Inhibitors of 8-Oxoguanine Surveillance by OGG1 and NUDT1

Oxidative damage in DNA is one of the primary sources of mutations in the cell. The activities of repair enzymes 8-oxoguanine DNA glycosylase (OGG1) and human MutT Homologue 1 (NUDT1 or MTH1), which work together to ameliorate this damage, are closely linked to mutagenesis, genotoxicity, cancer, and inflammation. Here we have undertaken the development of small-molecule dual inhibitors of the two enzymes as tools to test the relationships between these pathways and disease. The compounds preserve key structural elements of known inhibitors of the two enzymes, and they were synthesized and assayed with recently developed luminescence assays of the enzymes. Further structural refinement of initial lead molecules yielded compound 5 (SU0383) with IC50(NUDT1) = 0.034 μM and IC50(OGG1) = 0.49 μM. The compound SU0383 displayed low toxicity in two human cell lines at 10 μM. Experiments confirm the ability of SU0383 to increase sensitivity of tumor cells to oxidative stress. Dual inhibitors of these two enzymes are expected to be useful in testing multiple hypotheses regarding the roles of 8-oxo-dG in multiple disease states.

Methionine restriction delays aging-related urogenital diseases in male Fischer 344 rats

Dietary methionine restriction (MR) has been found to enhance longevity across many species. We hypothesized that MR might enhance longevity in part by delaying or inhibiting age-related disease processes. To this end, male Fischer 344 rats were fed control (CF, 0.86% methionine) or MR (0.17% methionine) diets throughout their life until sacrifice at approximately 30 months of age, and histopathology was performed to identify the incidence and progression of two important aging-related pathologies, namely, chronic progressive nephropathy (CPN) and testicular tumorigenesis. Although kidney pathology was observed in 87% CF rats and CPN in 62% of CF animals, no evidence of kidney disease was observed in MR rats. Consistent with the absence of renal pathology, urinary albumin levels were lower in the MR group compared to controls throughout the study, with over a six-fold difference between the groups at 30 months of age. Biomarkers associated with renal disease, namely, clusterin, cystatin C, and β-2 microglobulin, were reduced following 18 months of MR. A reduction in testicular tumor incidence from 88% in CF to 22% in MR rats was also observed. These results suggest that MR may lead to metabolic and cellular changes providing protection against age-related diseases.

My career development with Ames test: A personal recollection

I first became acquainted with the Ames test at the very beginning of my career in 1978, when my task at the National Institute of Health Sciences (Tokyo) was to screen for mutagenicity of food additives used in Japan, using the Ames test. I also used this test to research the metabolic activation mechanisms of chemical carcinogens, in particular, the analgesic drug, phenacetin. This chemical was not mutagenic in Salmonella typhimurium TA100 with standard 9000 × g supernatant of liver homogenates (S9) from rat but was mutagenic with hamster S9. It was revealed that hamster S9 had much higher deacetylation activities than rat S9, which accounts for the species difference. Then, my work was focused on molecular biology. We cloned the genes encoding nitroreductase and acetyltransferase in Salmonella typhimurium TA1538. Plasmids carrying these genes made strain TA98 more sensitive to mutagenic nitroarenes and aromatic amines. Because of their high sensitivity, the resulting strains such as YG1021 and YG1024 are widely used to monitor mutagenic nitroarenes and aromatic amines in complex mixtures. Later, we disrupted the genes encoding DNA polymerases in TA1538 and classified chemical mutagens into four classes depending on their use of different DNA polymerases. I was also involved in the generation of gpt delta transgenic rodent gene mutation assays, which examine the results of the Ames test in vivo. I have unintentionally developed my career under the influence of Dr. Ames and I would like to acknowledge his remarkable achievements in the field of environmental mutagenesis and carcinogenesis.

Natural Products and Acute Myeloid Leukemia: A Review Highlighting Mechanisms of Action

Recent findings have shown great potential of alternative interventions such as immunotherapy and natural products for acute myeloid leukemia (AML). This study aims to review the anti-AML effect of various natural compounds. Natural compounds were classified into five groups: alkaloids, carotenoids, nitrogen-containing compounds, organosulfur compounds or phenolics based on each compound’s chemical properties. Fifty-eight studies were collected and reviewed in this article. Phenolics are the most abundant group to have an apoptotic effect over AML cells, while other groups have also shown significant apoptotic effects. Some compounds induced apoptosis by regulating unique mechanism like human telomerase reverse transcriptase (hTERT) or laminin receptor (67LR), while others modified caspases, poly (adp-ribose) polymerase (PARP) and p53. Further study is required to identify side-effects of potent compounds and the synergistic effects of combination of two or more natural compounds or existing conventional anti-AML drugs to treat this dreadful disease.

Visual Defects and Ageing

Many diseases are related to age, among these neurodegeneration is particularly important. Alzheimer's disease Parkinson's and Glaucoma have many common pathogenic events including oxidative damage, Mitochondrial dysfunction, endothelial alterations and changes in the visual field. These are well known in the case of glaucoma, less in the case of neurodegeneration of the brain. Many other molecular aspects are common, such as the role of endoplasmic reticulum autophagy and neuronal apoptosis while others have been neglected due to lack of space such as inflammatory cytokine or miRNA. Moreover, the loss of specific neuronal populations, the induction of similar mechanisms of cell injury and the deposition of protein aggregates in specific anatomical areas are very similar events between these diseases. Intracellular and/or extracellular accumulation of protein aggregates is a key feature of many neurodegenerative disorders. The existence of abnormal protein aggregates has been documented in the RGCs of glaucomatous patients such as the anomalous Tau protein or the β-amyloid accumulations. Intra-cell catabolic processes also appear to be common in both glaucoma and neurodegeneration. They also help us to understand how the basis between these diseases is common and how the visual aspects can be a serious problem for those who are affected.

Measurement of the Oxidative DNA Lesion 8-Oxoguanine (8-oxoG) by ELISA or by High-Performance Liquid Chromatography (HPLC) with Electrochemical Detection

Reactive oxygen species (ROS) can oxidize cellular macromolecules like DNA, causing DNA damage. The most common form of DNA damage is the 8-oxoguanine (8-oxoG) lesion, typically repaired by the base excision repair (BER) pathway, which is initiated by the enzyme oxoguanine glycosylase 1 (OGG1). ROS are produced endogenously and can be enhanced by environmental factors, such as xenobiotics, radiation, and microbial pathogens. As a commonly used biomarker of oxidative damage, 8-oxoG can be measured in two different ways described herein. Commercially available ELISA kits allow for easy detection of the 8-oxoG lesion, while more difficult HPLC assays with UV and electrochemical detection allow for a more definitive identification and quantification of 8-oxoG.

Marine natural products for multi-targeted cancer treatment: A future insight

Cancer is world's second largest alarming disease, which involves abnormal cell growth and have potential to spread to other parts of the body. Most of the available anticancer drugs are designed to act on specific targets by altering the activity of involved transporters and genes. As cancer cells exhibit complex cellular machinery, the regeneration of cancer tissues and chemo resistance towards the therapy has been the main obstacle in cancer treatment. This fact encourages the researchers to explore the multitargeted use of existing medicines to overcome the shortcomings of chemotherapy for alternative and safer treatment strategies. Recent developments in genomics-proteomics and an understanding of the molecular pharmacology of cancer have also challenged researchers to come up with target-based drugs. The literature supports the evidence of natural compounds exhibiting antioxidant, antimitotic, anti-inflammatory, antibiotic as well as anticancer activity. In this review, we have selected marine sponges as a prolific source of bioactive compounds which can be explored for their possible use in cancer and have tried to link their role in cancer pathway. To prove this, we revisited the literature for the selection of cancer genes for the multitargeted use of existing drugs and natural products. We used Cytoscape network analysis and Search tool for retrieval of interacting genes/ proteins (STRING) to study the possible interactions to show the links between the antioxidants, antibiotics, anti-inflammatory and antimitotic agents and their targets for their possible use in cancer. We included total 78 pathways, their genes and natural compounds from the above four pharmacological classes used in cancer treatment for multitargeted approach. Based on the Cytoscape network analysis results, we shortlist 22 genes based on their average shortest path length connecting one node to all other nodes in a network. These selected genes are CDKN2A, FH, VHL, STK11, SUFU, RB1, MEN1, HRPT2, EXT1, 2, CDK4, p14, p16, TSC1, 2, AXIN2, SDBH C, D, NF1, 2, BHD, PTCH, GPC3, CYLD and WT1. The selected genes were analysed using STRING for their protein-protein interactions. Based on the above findings, we propose the selected genes to be considered as major targets and are suggested to be studied for discovering marine natural products as drug lead in cancer treatment.

The “false-positive” conundrum in the NTP 2-year rodent cancer study database

In 1990, Ames and Gold described a conundrum of “too many carcinogens” among chemicals tested in rodent bioassays. Their proposed nongenotoxic carcinogenic mechanism was amplification of the background mutation rate via cytotoxicity induced by high doses of the test chemicals, thereby leading to increases in reparative cellular proliferation rates. Recently, we have statistically and mechanistically analyzed the entire 594-study (470 final reports) NTP 2-year rodent cancer database to better understand the conundrum posed by Ames and Gold. Our analysis provides several lines of evidence that support the contention of Ames and Gold. First, across different routes of administration, relatively phylogenetically similar rats and mice are nonetheless discordant for the development of tumors at similar organ sites. Tumor site concordance across sex within species is higher than tumor site concordance across species. Second, many chemicals negative in the Ames test nonetheless induce tumors in either rats or mice. Third, 11 out of 58 chemicals tested by the inhalation route induce lung tumors in mice and not rats, are negative in the Ames test, and exhibit hyperplasia. In 2017, Tomasetti et al. provided evidence for the clinical relevance in humans of the Ames and Gold mechanism regarding amplification of the background mutation rate by demonstrating that the majority of human tumors result from accumulated mutations due to DNA replication errors.

PFKFB3 blockade inhibits hepatocellular carcinoma growth by impairing DNA repair through AKT

Overexpression of 6-phosphofructo-2-kinase/fructose-2,6-biphosphatase 3 (PFKFB3), a key molecule of glucose metabolism in cytoplasm, has been found in various tumors. Emerging evidence has suggested that PFKFB3 is also located in the nucleus and apparent in regulatory functions other than glycolysis. In this study, we found that PFKFB3 expression is associated with hepatocellular carcinoma (HCC) growth and located mainly in the nucleus of tumor cells. PFKFB3 overexpression was associated with large tumor size (p = 0.04) and poor survival of patients with HCC (p = 0.027). Knockdown of PFKFB3 inhibited HCC growth, not only by reducing glucose consumption but also by damaging the DNA repair function, leading to G2/M phase arrest and apoptosis. In animal studies, overexpression of PFKFB3 is associated with increased tumor growth. Mechanistically, PFKFB3 silencing decreased AKT phosphorylation and reduced the expression of ERCC1, which is an important DNA repair protein. Moreover, PFK15, a selective PFKFB3 inhibitor, significantly inhibited tumor growth in a xenograft model of human HCC. PFKFB3 is a potential novel target in the treatment of HCC.

EBV-encoded miRNAs target ATM-mediated response in nasopharyngeal carcinoma

Nasopharyngeal carcinoma (NPC) is a highly invasive epithelial malignancy that is prevalent in southern China and Southeast Asia. It is consistently associated with latent Epstein-Barr virus (EBV) infection. In NPC, miR-BARTs, the EBV-encoded miRNAs derived from BamH1-A rightward transcripts, are abundantly expressed and contribute to cancer development by targeting various cellular and viral genes. In this study, we establish a comprehensive transcriptional profile of EBV-encoded miRNAs in a panel of NPC patient-derived xenografts and an EBV-positive NPC cell line by small RNA sequencing. Among the 40 miR-BARTs, predominant expression of 22 miRNAs was consistently detected in these tumors. Among the abundantly expressed EBV-miRNAs, BART5-5p, BART7-3p, BART9-3p, and BART14-3p could negatively regulate the expression of a key DNA double-strand break (DSB) repair gene, ataxia telangiectasia mutated (ATM), by binding to multiple sites on its 3'-UTR. Notably, the expression of these four miR-BARTs represented more than 10% of all EBV-encoded miRNAs in tumor cells, while downregulation of ATM expression was commonly detected in all of our tested sequenced samples. In addition, downregulation of ATM was also observed in primary NPC tissues in both qRT-PCR (16 NP and 45 NPC cases) and immunohistochemical staining (35 NP and 46 NPC cases) analysis. Modulation of ATM expression by BART5-5p, BART7-3p, BART9-3p, and BART14-3p was demonstrated in the transient transfection assays. These findings suggest that EBV uses miRNA machinery as a key mechanism to control the ATM signaling pathway in NPC cells. By suppressing these endogenous miR-BARTs in EBV-positive NPC cells, we further demonstrated the novel function of miR-BARTs in inhibiting Zta-induced lytic reactivation. These findings imply that the four viral miRNAs work co-operatively to modulate ATM activity in response to DNA damage and to maintain viral latency, contributing to the tumorigenesis of NPC. © 2017 The Authors. The Journal of Pathology published by John Wiley & Sons Ltd on behalf of Pathological Society of Great Britain and Ireland.

Potent and Selective Inhibitors of 8-Oxoguanine DNA Glycosylase

The activity of DNA repair enzyme 8-oxoguanine DNA glycosylase (OGG1), which excises oxidized base 8-oxoguanine (8-OG) from DNA, is closely linked to mutagenesis, genotoxicity, cancer, and inflammation. To test the roles of OGG1-mediated repair in these pathways, we have undertaken the development of noncovalent small-molecule inhibitors of the enzyme. Screening of a PubChem-annotated library using a recently developed fluorogenic 8-OG excision assay resulted in multiple validated hit structures, including selected lead hit tetrahydroquinoline 1 (IC50 = 1.7 μM). Optimization of the tetrahydroquinoline scaffold over five regions of the structure ultimately yielded amidobiphenyl compound 41 (SU0268; IC50 = 0.059 μM). SU0268 was confirmed by surface plasmon resonance studies to bind the enzyme both in the absence and in the presence of DNA. The compound SU0268 was shown to be selective for inhibiting OGG1 over multiple repair enzymes, including other base excision repair enzymes, and displayed no toxicity in two human cell lines at 10 μM. Finally, experiments confirm the ability of SU0268 to inhibit OGG1 in HeLa cells, resulting in an increase in accumulation of 8-OG in DNA. The results suggest the compound SU0268 as a potentially useful tool in studies of the role of OGG1 in multiple disease-related pathways.

Reactive oxygen species may play an essential role in driving biological evolution: The Cambrian Explosion as an example

The Cambrian Explosion is one of the most significant events in the history of life; essentially all easily fossilizable animal body plans first evolved during this event. Although many theories have been proposed to explain this event, its cause remains unresolved. Here, we propose that the elevated level of oxygen, in combination with the increased mobility and food intake of metazoans, led to increased cellular levels of reactive oxygen species (ROS), which drove evolution by enhancing mutation rates and providing new regulatory mechanisms. Our hypothesis may provide a unified explanation for the Cambrian Explosion as it incorporates both environmental and developmental factors and is also consistent with ecological explanations for animal radiation. Future studies should focus on testing this hypothesis, and may lead to important insights into evolution.

Capturing a mammalian DNA polymerase extending from an oxidized nucleotide

The oxidized nucleotide, 8-oxo-7,8-dihydro-2΄-deoxyguanosine (8-oxoG), is one of the most abundant DNA lesions. 8-oxoG plays a major role in tumorigenesis and human disease. Biological consequences of 8-oxoG are mediated in part by its insertion into the genome, making it essential to understand how DNA polymerases handle 8-oxoG. Insertion of 8-oxoG is mutagenic when opposite adenine but not when opposite cytosine. However, either result leads to DNA damage at the primer terminus (3΄-end) during the succeeding insertion event. Extension from DNA damage at primer termini remains poorly understood. Using kinetics and time-lapse crystallography, we evaluated how a model DNA polymerase, human polymerase β, accommodates 8-oxoG at the primer terminus opposite cytosine and adenine. Notably, extension from the mutagenic base pair is favored over the non-mutagenic base pair. When 8-oxoG is at the primer terminus opposite cytosine, DNA centric changes lead to a clash between O8 of 8-oxoG and the phosphate backbone. Changes in the extension reaction resulting from the altered active site provide evidence for a stabilizing interaction between Arg254 and Asp256 that serves an important role during DNA synthesis reactions. These results provide novel insights into the impact of damage at the primer terminus on genomic stability and DNA synthesis.

Role of DNA polymerase β oxidized nucleotide insertion in DNA ligation failure

Production of reactive oxygen and nitrogen species (ROS), such as hydrogen peroxide, superoxide and hydroxyl radicals, has been linked to cancer, and these oxidative molecules can damage DNA. Base excision repair (BER), a major repair system maintaining genome stability over a lifespan, has an important role in repairing oxidatively induced DNA damage. Failure of BER leads to toxic consequences in ROS-exposed cells, and ultimately can contribute to the pathobiology of disease. In our previous report, we demonstrated that oxidized nucleotide insertion by DNA polymerase β (pol β) impairs BER due to ligation failure and leads to formation of a cytotoxic repair intermediate. Biochemical and cytotoxic effects of ligation failure could mediate genome stability and influence cancer therapeutics. In this review, we discuss the importance of coordination between pol β and DNA ligase I during BER, and how this could be a fundamental mechanism underlying human diseases such as cancer and neurodegeneration. A summary of this work was presented in a symposium at the International Congress of Radiation Research 2015 in Kyoto, Japan.

Heavy alcohol drinking downregulates ALDH2 gene expression but heavy smoking up-regulates SOD2 gene expression in head and neck squamous cell carcinoma

BACKGROUND

This study aims to determine the relationship between expression levels of ALDH2 and SOD2 genes and clinical parameters such as alcohol drinking, tobacco smoking, primary site of HNSCC, and human papilloma virus (HPV) state.

METHODS

Gene expression data were obtained from gene expression omnibus (GEO accession number: GSE65858). Clinical data (N = 270) including survival result, gender, age, TNM stage, primary site of HNSCC, HPV status, alcohol drinking, and tobacco smoking habit were analyzed according to gene expression pattern.

RESULTS

ALDH2 gene was expressed in low levels in patients with heavy alcohol consumption. It was expressed in high (p = 0.01) levels in patients with no or light alcohol consumption. ALDH2 gene was also expressed in low levels in patients with oral cavity cancers or hypopharynx cancers. However, ALDH2 gene was expressed in high (p = 0.03) levels in patients with oropharyngeal cancers or laryngeal cancers. HPV-positive patients were found to have high (p = 0.02) expression levels of ALDH2. SOD2 gene was expressed in high (p = 0.005) levels in patients who had greater mean pack-year of tobacco smoking. Based on log rank test, the group of patients with high expression of ALDH2 showed better (p = 0.002) clinical results than those with low expression of ALDH2. Difference of survival results between ALDH2 high-expressed group and ALDH2 low-expressed group was validated in another cohort (GSE39368, N = 138).

CONCLUSIONS

Heavy alcohol drinking downregulates ALDH2 gene expression level. Heavy smoking up-regulates SOD2 gene expression level in patients with head and neck squamous cell carcinoma. The group of patients with low expression levels of ALDH2 showed significantly poorer survival results compared to those with high expression levels of ALDH2.

Consequences of RNA oxidation on protein synthesis rate and fidelity: implications for the pathophysiology of neuropsychiatric disorders

Unlike DNA, oxidative damage to RNA has received little attention presumably due to the assumed transient nature of RNA. However, RNAs including mRNA can persist for several hours to days in certain tissues and are demonstrated to sustain greater oxidative damage than DNA. Because neuronal cells in the brain are continuously exposed to reactive oxygen species due to a high oxygen consumption rate, it is not surprising that neuronal RNA oxidation is observed as a common feature at an early stage in a series of neurodegenerative disorders. A recent study on a well-defined bacterial translation system has revealed that mRNA containing 8-oxo-guanosine (8-oxoGuo) has little effect on fidelity despite the anticipated miscoding. Indeed, 8-oxoGuo-containing mRNA leads to ribosomal stalling with a reduced rate of peptide-bond formation by 3–4 orders of magnitude and is subject to no-go decay, a ribosome-based mRNA surveillance mechanism. Another study demonstrates that transfer RNA oxidation catalyzed by cytochrome c (cyt c) leads to its depurination and cross-linking, which may facilitate cyt c release from mitochondria and subsequently induce apoptosis. Even more importantly, a discovery of oxidized microRNA has been recently reported. The oxidized microRNA causes misrecognizing the target mRNAs and subsequent down-regulation in the protein synthesis. It is noteworthy that oxidative modification to RNA not only interferes with the translational machinery but also with regulatory mechanisms of noncoding RNAs that contribute toward the biological complexity of the mammalian brain. Oxidative RNA damage might be a promising therapeutic target potentially useful for an early intervention of diverse neuropsychiatric disorders.

Assessment of genotoxicity of Lannate-90® and its plant and animal metabolites in human lymphocyte cultures

This study evaluated direct and metabolic genotoxic effects caused by Lannate-90®, a methomyl-based formulation (90 % active ingredient), in human lymphocyte cultures using sister chromatid exchange assay (SCE). Two processes were used for the plant promutagens evaluation: in vivo activation, applying the insecticide systemically in plants for 4 h and subsequently adding plant metabolites containing extracts to lymphocyte cultures; and in vitro activation, where the insecticide was incubated with Vicia faba S10 mix plus human lymphocyte culture. Direct treatment with the insecticide significantly increased SCE frequency in human lymphocytes (250-750 mgL-1), with cellular death observed at 1000 mgL-1 concentration. Using the extracts of Vicia faba treated with Lannate-90® to treat human lymphocytes, a dose-response relationship was observed. In lymphocyte cultures treated directly with the insecticide for 2 h, a negative response was obtained. When S10 mix was added, SCE frequency did not change significantly. Meanwhile, a mixture of S9 mammalian metabolic mix and Lannate-90® increased the SCE frequency, with an observed concentration-dependent response. Although Lannate-90® induced cellular death at the highest concentrations, it did not cause a delay in cell proliferation in any of the treatments, confirming its genotoxic action. This study is one of the first to evaluate and compare the direct effect of Lannate-90® in two bioassays, animal and vegetal, and the effect of plant and animal metabolism on its genotoxic potential.

Phytochemical profiles and antioxidant activity of processed brown rice products

The phytochemical profiles and antioxidant activity of free, soluble-conjugated, and bound fractions of brown rice and its processed products (textured rice, cooked rice and rice noodle) were studied. Nineteen phenolic acids were identified. Trans-ferulic acid was the most abundant monomeric phenolic acid with trans-trans-8-O-4' diferulic acid being most abundant diferulic acid. Processing increased the content of free phenolic acids, but decreased the content of soluble-conjugated phenolic acids. The content of bound phenolic acids was increased by improved extrusion cooking technology and cooking, but not affected by rice noodle extrusion. The total phenolic contents and antioxidant activities of free and soluble-conjugated fractions were decreased after processing, whereas those of bound fraction were increased by improved extrusion cooking technology and cooking, but not affected by rice noodle extrusion. Results indicated that whole foods designed for reducing chronic disease risk need to consider the effects of processing on phytochemical profiles and antioxidant activity of whole grains.

Effect of Cruciferous Vegetable Intake on Oxidative Stress Biomarkers: Differences by Breast Cancer Status

This post hoc analysis examined cruciferous vegetable intake on urinary oxidative metabolites in postmenopausal women. Intervention participants (n = 69) received cruciferous vegetables (≥14 cups/week) during a 3-week period. First morning urine measured 8-isoprostane and 8-hydroxy-2'-deoxyguanosine. Dietary intake was estimated using 24-h recalls. When stratified by history of breast cancer, those with breast cancer had significantly lower post-intervention urinary 8-hydroxy-2'-deoxyguanosine values in the intervention arm versus. the control arm (1.1 ng/mL vs. 3.2 ng/mL, p = .01) after adjustment for baseline 8-hydroxy-2'-deoxyguanosine. This was not observed in those without breast cancer. Further work is needed to understand the role of breast cancer in these relationships.

Deoxyinosine triphosphate induces MLH1/PMS2- and p53-dependent cell growth arrest and DNA instability in mammalian cells

Deoxyinosine (dI) occurs in DNA either by oxidative deamination of a previously incorporated deoxyadenosine residue or by misincorporation of deoxyinosine triphosphate (dITP) from the nucleotide pool during replication. To exclude dITP from the pool, mammals possess specific hydrolysing enzymes, such as inosine triphosphatase (ITPA). Previous studies have shown that deficiency in ITPA results in cell growth suppression and DNA instability. To explore the mechanisms of these phenotypes, we analysed ITPA-deficient human and mouse cells. We found that both growth suppression and accumulation of single-strand breaks in nuclear DNA of ITPA-deficient cells depended on MLH1/PMS2. The cell growth suppression of ITPA-deficient cells also depended on p53, but not on MPG, ENDOV or MSH2. ITPA deficiency significantly increased the levels of p53 protein and p21 mRNA/protein, a well-known target of p53, in an MLH1-dependent manner. Furthermore, MLH1 may also contribute to cell growth arrest by increasing the basal level of p53 activity.

Insertion of oxidized nucleotide triggers rapid DNA polymerase opening

A novel mechanism is unveiled to explain why a pro-mutagenic nucleotide lesion (oxidized guanine, 8-oxoG) causes the mammalian DNA repair polymerase-β (pol-β) to rapidly transition to an inactive open conformation. The mechanism involves unexpected features revealed recently in time-lapse crystallography. Specifically, a delicate water network associated with a lesion-stabilizing auxilliary product ion Mg(p) triggers a cascade of events that leads to poor active site geometry and the rupture of crucial molecular interactions between key residues in both the anti(8-oxoG:C) and syn(8-oxoG:A) systems. Once the base pairs in these lesioned systems are broken, dislocation of both Asp192 (a metal coordinating ligand) and the oxoG phosphate group (PO₄) interfere with the hydrogen bonding between Asp192 and Arg258, whose rotation toward Asp192 is crucial to the closed-to-open enzyme transition. Energetically, the lesioned open states are similar in energy to those of the corresponding closed complexes after chemistry, in marked contrast to the unlesioned pol-β anti(G:C) system, whose open state is energetically higher than the closed state. The delicate surveillance system offers a fundamental protective mechanism in the cell that triggers DNA repair events which help deter insertion of oxidized lesions.