Oxidative decay of DNA

Zingerone protects against stannous chloride-induced and hydrogen peroxide-induced oxidative DNA damage in vitro

In this paper, we report the dose-dependent antioxidant activity and DNA protective effects of zingerone. At 500 μg/mL, the DPPH radical scavenging activity of zingerone and ascorbic acid as a standard was found to be 86.7 and 94.2 % respectively. At the same concentration, zingerone also showed significant reducing power (absorbance 0.471) compared to that of ascorbic acid (absorbance 0.394). The in vitro toxicity of stannous chloride (SnCl2) was evaluated using genomic and plasmid DNA. SnCl2-induced degradation of genomic DNA was found to occur at a concentration of 0.8 mM onwards with complete degradation at 1.02 mM and above. In the case of plasmid DNA, conversion of supercoiled DNA into the open circular form indicative of DNA nicking activity was observed at a concentration of 0.2 mM onwards; complete conversion was observed at a concentration of 1.02 mM and above. Zingerone was found to confer protection against SnCl2-induced oxidative damage to genomic and plasmid DNA at concentrations of 500 and 750 μg/mL onwards, respectively. This protective effect was further confirmed in the presence of UV/H2O2-a known reactive oxygen species (ROS) generating system-wherein protection by zingerone against ROS-mediated DNA damage was observed at a concentration of 250 μg/mL onwards in a dose-dependent manner. This study clearly indicated the in vitro DNA protective property of zingerone against SnCl2-induced, ROS-mediated DNA damage.

Process of aerenchyma formation and reactive oxygen species induced by waterlogging in wheat seminal roots

The development and regulation of aerenchyma in waterlogged conditions were studied in the seminal roots of wheat. Evans blue staining and the first cell death position indicated that the cortical cell death began at the root mid-cortex cells in flooding conditions. Continuous waterlogging treatment caused the spread of cell death from the mid-cortex to the neighboring cells and well-developed aerenchyma was formed after 72 h. Meanwhile, the formation of radial oxygen loss barrier was observed in the exodermis owing to the induction of Casparian bands and lignin deposition. Analysis of aerenchyma along the wheat root revealed that aerenchyma formed at 10 mm from the root tip, significantly increased toward the center of the roots, and decreased toward the basal region of the root. In situ detection of radial oxygen species (ROS) showed that ROS accumulation started in the mid-cortex cells, where cell death began indicating that cell death was probably accompanied by ROS production. Further waterlogging treatments resulted in the accumulation of ROS in the cortical cells, which were the zone for aerenchyma development. Accumulation and distribution of H₂O₂ at the subcellular level were revealed by ultracytochemical localization, which further verified the involvement of ROS in the cortical cell death process (i.e., aerenchyma formation). Furthermore, gene expression analysis indicated that ROS production might be the result of up-regulation of genes encoding for ROS-producing enzymes and the down-regulation of genes encoding for ROS-detoxifying enzymes. These results suggest that aerenchyma development in wheat roots starts in the mid-cortex cells and its formation is regulated by ROS.

Effect of Regular Exercise on the Histochemical Changes of d-Galactose-Induced Oxidative Renal Injury in High-Fat Diet-Fed Rats

Renal lipid accumulation exhibits slowly developing chronic kidney disease and is associated with increased oxidative stress. The impact of exercise on the obese- and oxidative stress-related renal disease is not well understood. The purpose of this study was to investigate whether a high-fat diet (HFD) would accelerate d-galactose-induced aging process in rat kidney and to examine the preventive effect of regular exercise on the obese- and oxidative stress-related renal disease. Oxidative stress was induced by an administration of d-galactose (100 mg/kg intraperitoneally injected) for 9 weeks, and d-galactose-treated rats were also fed with a high-fat diet (60% kcal as fat) for 9 weeks to induce obesity. We investigated the efficacy of regular exercise in reducing renal injury by analyzing Nε-carboxymethyllysine (CML), 8-hydroxygluanine (8-OHdG) and apoptosis. When rats were fed with a HFD for 9 weeks in d-galactose-treated rats, an increased CML accumulation, oxidative DNA damage and renal podocyte loss were observed in renal glomerular cells and tubular epithelial cells. However, the regular exercise restored all these renal changes in HFD plus d-galactose-treated rats. Our data suggested that long-term HFD may accelerate the deposition of lipoxidation adducts and oxidative renal injury in d-galactose-treated rats. The regular exercise protects against obese- and oxidative stress-related renal injury by inhibiting this lipoxidation burden.

Pulmonary oxidative stress, inflammation and cancer: respirable particulate matter, fibrous dusts and ozone as major causes of lung carcinogenesis through reactive oxygen species mechanisms

Reactive oxygen or nitrogen species (ROS, RNS) and oxidative stress in the respiratory system increase the production of mediators of pulmonary inflammation and initiate or promote mechanisms of carcinogenesis. The lungs are exposed daily to oxidants generated either endogenously or exogenously (air pollutants, cigarette smoke, etc.). Cells in aerobic organisms are protected against oxidative damage by enzymatic and non-enzymatic antioxidant systems. Recent epidemiologic investigations have shown associations between increased incidence of respiratory diseases and lung cancer from exposure to low levels of various forms of respirable fibers and particulate matter (PM), at occupational or urban air polluting environments. Lung cancer increases substantially for tobacco smokers due to the synergistic effects in the generation of ROS, leading to oxidative stress and inflammation with high DNA damage potential. Physical and chemical characteristics of particles (size, transition metal content, speciation, stable free radicals, etc.) play an important role in oxidative stress. In turn, oxidative stress initiates the synthesis of mediators of pulmonary inflammation in lung epithelial cells and initiation of carcinogenic mechanisms. Inhalable quartz, metal powders, mineral asbestos fibers, ozone, soot from gasoline and diesel engines, tobacco smoke and PM from ambient air pollution (PM₁₀ and PM₂.₅) are involved in various oxidative stress mechanisms. Pulmonary cancer initiation and promotion has been linked to a series of biochemical pathways of oxidative stress, DNA oxidative damage, macrophage stimulation, telomere shortening, modulation of gene expression and activation of transcription factors with important role in carcinogenesis. In this review we are presenting the role of ROS and oxidative stress in the production of mediators of pulmonary inflammation and mechanisms of carcinogenesis.

Oxidative stress and nucleic acid oxidation in patients with chronic kidney disease

Patients with chronic kidney disease (CKD) have high cardiovascular mortality and morbidity and a high risk for developing malignancy. Excessive oxidative stress is thought to play a major role in elevating these risks by increasing oxidative nucleic acid damage. Oxidative stress results from an imbalance between reactive oxygen/nitrogen species (RONS) production and antioxidant defense mechanisms and can cause vascular and tissue injuries as well as nucleic acid damage in CKD patients. The increased production of RONS, impaired nonenzymatic or enzymatic antioxidant defense mechanisms, and other risk factors including gene polymorphisms, uremic toxins (indoxyl sulfate), deficiency of arylesterase/paraoxonase, hyperhomocysteinemia, dialysis-associated membrane bioincompatibility, and endotoxin in patients with CKD can inhibit normal cell function by damaging cell lipids, arachidonic acid derivatives, carbohydrates, proteins, amino acids, and nucleic acids. Several clinical biomarkers and techniques have been used to detect the antioxidant status and oxidative stress/oxidative nucleic acid damage associated with long-term complications such as inflammation, atherosclerosis, amyloidosis, and malignancy in CKD patients. Antioxidant therapies have been studied to reduce the oxidative stress and nucleic acid oxidation in patients with CKD, including alpha-tocopherol, N-acetylcysteine, ascorbic acid, glutathione, folic acid, bardoxolone methyl, angiotensin-converting enzyme inhibitor, and providing better dialysis strategies. This paper provides an overview of radical production, antioxidant defence, pathogenesis and biomarkers of oxidative stress in patients with CKD, and possible antioxidant therapies.

Potential anti-aging agents suppress the level of constitutive mTOR- and DNA damage- signaling

Two different mechanisms are considered to be the primary cause of aging. Cumulative DNA damage caused by reactive oxygen species (ROS), the by-products of oxidative phosphorylation, is one of these mechanisms (ROS concept). Constitutive stimulation of mitogen- and nutrient-sensing mTOR/S6 signaling is the second mechanism (TOR concept). The flow- and laser scanning- cytometric methods were developed to measure the level of the constitutive DNA damage/ROS- as well as of mTOR/S6- signaling in individual cells. Specifically, persistent activation of ATM and expression of γH2AX in untreated cells appears to report constitutive DNA damage induced by endogenous ROS. The level of phosphorylation of Ser235/236-ribosomal protein (RP), of Ser2448-mTOR and of Ser65-4EBP1, informs on constitutive signaling along the mTOR/S6 pathway. Potential gero-suppressive agents rapamycin, metformin, 2-deoxyglucose, berberine, resveratrol, vitamin D3 and aspirin, all decreased the level of constitutive DNA damage signaling as seen by the reduced expression of γH2AX in proliferating A549, TK6, WI-38 cells and in mitogenically stimulated human lymphocytes. They all also decreased the level of intracellular ROS and mitochondrial trans-membrane potential ΔΨm, the marker of mitochondrial energizing as well as reduced phosphorylation of mTOR, RP-S6 and 4EBP1. The most effective was rapamycin. Although the primary target of each on these agents may be different the data are consistent with the downstream mechanism in which the decline in mTOR/S6K signaling and translation rate is coupled with a decrease in oxidative phosphorylation, (revealed by ΔΨm) that leads to reduction of ROS and oxidative DNA damage. The decreased rate of translation induced by these agents may slow down cells hypertrophy and alleviate other features of cell aging/senescence. Reduction of oxidative DNA damage may lower predisposition to neoplastic transformation which otherwise may result from errors in repair of DNA sites coding for oncogenes or tumor suppressor genes. The data suggest that combined assessment of constitutive γH2AX expression, mitochondrial activity (ROS, ΔΨm) and mTOR signaling provides an adequate gamut of cell responses to evaluate effectiveness of gero-suppressive agents.

Berberine suppresses gero-conversion from cell cycle arrest to senescence

Berberine (BRB), a natural alkaloid, has a long history of medicinal use in both Ayurvedic and old Chinese medicine. Recently, available as a dietary supplement, Berberine is reported to have application in treatment of variety diseases. Previously we observed that BRB inhibited mTOR/S6 signaling concurrently with reduction of the level of endogenous oxidants and constitutive DNA damage response. We currently tested whether Berberine can affect premature, stress-induced cellular senescence caused by mitoxantrone. The depth of senescence was quantitatively measured by morphometric parameters, senescence-associated β-galactosidase, induction of p21WAF1, replication stress (γH2AX expression), and mTOR signaling; the latter revealed by ribosomal S6 protein (rpS6) phosphorylation. All these markers of senescence were distinctly diminished, in a concentration-dependent manner, by Berberine. In view of the evidence that BRB localizes in mitochondria, inhibits respiratory electron chain and activates AMPK, the observed attenuation of the replication stress-induced cellular senescence most likely is mediated by AMPK that leads to inhibition of mTOR signaling. In support of this mechanism is the observation that rhodamine123, the cationic probe targeting mitochondrial electron chain, also suppressed rpS6 phosphorylation. The present findings reveal that: (a) in cells induced to senescence BRB exhibits gero-suppressive properties by means of mTOR/S6 inhibition; (b) in parallel, BRB reduces the level of constitutive DNA damage response, previously shown to report oxidative DNA damage by endogenous ROS; (c) there appears to a causal linkage between the (a) and (b) activities; (d) the in vitro model of premature stress-induced senescence can be used to assess effectiveness of potential gero-suppressive agents targeting mTOR/S6 and ROS signaling; (e) since most of the reported beneficial effects of BRB are in age-relate diseases, it is likely that gero-suppression is the primary activity of this traditional medicine.

Natural products as a source of anti-inflammatory agents associated with inflammatory bowel disease

Accumulating epidemiological and clinical study indicates that inflammation is a significant risk factor to develop various human diseases such as inflammatory bowel disease (IBD), chronic asthma, rheumatoid arthritis, multiple sclerosis, and psoriasis. Suppressing inflammation is therefore important to control or prevent various diseases. Among them, IBD is one of the major problems affecting people worldwide. IBD affects at least one in a thousand persons in many Western countries. Various natural products have been shown to safely suppress pro-inflammatory pathway and control IBD. In vivo and/or in vitro studies indicate that anti-IBD effects of natural products occur by inhibition of the expression of pro-inflammatory cytokines (for example, tumor necrosis factor-α (TNF-α), intercellular adhesion molecule expression and pro-inflammatory mediators (such as inducible nitric oxide synthase (iNOS) and cyclooxygenase 2 (COX2), master transcription factors (such as nuclear factor-κB (NF-κB)), reactive oxygen species (ROS) and by improving the antioxidant activity. In this review, we summarize recent research focused on IBD and the effects that natural products have on IBD factors.

Using exomarkers to assess mitochondrial reactive species in vivo

BACKGROUND

The ability to measure the concentrations of small damaging and signalling molecules such as reactive oxygen species (ROS) in vivo is essential to understanding their biological roles. While a range of methods can be applied to in vitro systems, measuring the levels and relative changes in reactive species in vivo is challenging.

SCOPE OF REVIEW

One approach towards achieving this goal is the use of exomarkers. In this, exogenous probe compounds are administered to the intact organism and are then transformed by the reactive molecules in vivo to produce a diagnostic exomarker. The exomarker and the precursor probe can be analysed ex vivo to infer the identity and amounts of the reactive species present in vivo. This is akin to the measurement of biomarkers produced by the interaction of reactive species with endogenous biomolecules.

MAJOR CONCLUSIONS AND GENERAL SIGNIFICANCE

Our laboratories have developed mitochondria-targeted probes that generate exomarkers that can be analysed ex vivo by mass spectrometry to assess levels of reactive species within mitochondria in vivo. We have used one of these compounds, MitoB, to infer the levels of mitochondrial hydrogen peroxide within flies and mice. Here we describe the development of MitoB and expand on this example to discuss how better probes and exomarkers can be developed. This article is part of a Special Issue entitled Current methods to study reactive oxygen species - pros and cons and biophysics of membrane proteins. Guest Editor: Christine Winterbourn.

8OHdG is not a biomarker for Huntington disease state or progression

OBJECTIVE

To evaluate plasma 8-hydroxy-deoxy-guanosine (8OHdG) levels as a potential biomarker of premanifest and early Huntington disease (HD).

METHODS

Personnel from 2 independent laboratories quantified 8OHdG in blinded longitudinal plasma samples taken 24 months apart from 160 TRACK-HD participants, as well as samples containing control plasma with added ("spiked") 8OHdG. One laboratory used a liquid chromatography-electrochemical array (LCECA) assay, and the other used liquid chromatography-mass spectrometry (LCMS).

RESULTS

The LCMS assay was more accurate than the LCECA assay for measurements of "spiked" 8OHdG levels in plasma. Neither assay demonstrated cross-sectional differences in plasma 8OHdG among controls, premanifest HD, and early symptomatic HD. Similarly, neither assay showed longitudinal changes in any disease group over 24 months.

CONCLUSIONS

Plasma concentration of 8OHdG is not a biomarker of disease state or progression in HD. We recommend that future putative biomarker studies use blinded sample analysis, standard curves, independent analytical methods, and strict quality control of sample collection and storage.

Mitochondria, oxidative DNA damage, and aging

Protection from reactive oxygen species (ROS) and from mitochondrial oxidative damage is well known to be necessary to longevity. The relevance of mitochondrial DNA (mtDNA) to aging is suggested by the fact that the two most commonly measured forms of mtDNA damage, deletions and the oxidatively induced lesion 8-oxo-dG, increase with age. The rate of increase is species-specific and correlates with maximum lifespan. It is less clear that failure or inadequacies in the protection from reactive oxygen species (ROS) and from mitochondrial oxidative damage are sufficient to explain senescence. DNA containing 8-oxo-dG is repaired by mitochondria, and the high ratio of mitochondrial to nuclear levels of 8-oxo-dG previously reported are now suspected to be due to methodological difficulties. Furthermore, MnSOD -/+ mice incur higher than wild type levels of oxidative damage, but do not display an aging phenotype. Together, these findings suggest that oxidative damage to mitochondria is lower than previously thought, and that higher levels can be tolerated without physiological consequence. A great deal of work remains before it will be known whether mitochondrial oxidative damage is a "clock" which controls the rate of aging. The increased level of 8-oxo-dG seen with age in isolated mitochondria needs explanation. It could be that a subset of cells lose the ability to protect or repair mitochondria, resulting in their incurring disproportionate levels of damage. Such an uneven distribution could exceed the reserve capacity of these cells and have serious physiological consequences. Measurements of damage need to focus more on distribution, both within tissues and within cells. In addition, study must be given to the incidence and repair of other DNA lesions, and to the possibility that repair varies from species to species, tissue to tissue, and young to old.

Life span extensions associated with upregulation of gene expression of antioxidant enzymes in Caenorhabditis elegans; studies of mutation in the age-1, PI3 kinase homologue and short-term exposure to hyperoxia

Life span could be modified by genetic or environmental perturbations in Caenorhabditis elegans. Here we show that two extensions of life span are associated with oxidative stress resistance and upregulation of the gene expression of antioxidant enzymes. First, mutations in age-1 gene (PI3 kinase homologue)that confer life span extension, display oxidative stress resistance and increase in the gene expression of sod-3, one of two Mn-superoxide dismutases (SOD) and ctl-1, cytosolic catalase. In this study, these traits appear to be regulated by the following genetic pathway: daf-2 (insulin receptor family)-> daf-18 (PTEN homologue)-> age-1-> daf-16 (Fork head transcription factor family), similar to the genetic pathway for the life span extension. Second, we show that short-term exposure to hyperoxia extends life span slightly but significantly. This treatment increases oxidative stress resistance and the gene expression of three types of SOD isoforms. These results suggest that both of these two life span extensions are closely related with increase in the antioxidant defense function.

Life span extensions associated with upregulation of gene expression of antioxidant enzymes in Caenorhabdms elegans; studies of mutation in the AGE-1, PI3 kinase homologue and short-term exposure to hyperoxia

Life span could be modified by genetic or environmental perturbations in Caenorhabditis elegans. Here we show that two extensions of life span are associated with oxidative stress resistance and upregulation of the gene expression of antioxidant enzymes. First, mutations in age-1 gene (PI3 kinase homologue) that confer life span extension, display oxidative stress resistance and increase in the gene expression of sod-3, one of two Mn-superoxide dismutases (SOD) and ctl-1, cytosolic catalase. In this study, these traits appear to be regulated by the following genetic pathway: daf-2 (insulin receptor family)-> daf-18 (PTEN homologue)-> age-1-> daf-16 (Fork head transcription factor family), similar to the genetic pathway for the life span extension. Second, we show that short-term exposure to hyperoxia extends life span slightly but significantly. This treatment increases oxidative stress resistance and the gene expression of three types of SOD isoforms. These results suggest that both of these two life span extensions are closely related with increase in the antioxidant defense function.

A dual enzyme microgel with high antioxidant ability based on engineered seleno-ferritin and artificial superoxide dismutase

An antioxidant microgel with both glutathione peroxidase (GPx) and superoxide dismutase (SOD) activities is reported. Using computational design and genetic engineering methods, the main catalytic components of GPx are fabricated onto the surface of ferritin. The resulting seleno-ferritin (Se-Fn) monomers can self-assemble into nanocomposites that exhibit remarkable GPx activity due to the well organized multi-GPx catalytic centers. Subsequently, a porphyrin derivative is synthesized as an SOD mimic, and is employed to construct a synergistic dual enzyme system by crosslinking Se-Fn nanocomposites into a microgel. Significantly, this dual enzyme microgel is demonstrated to display better antioxidant ability than single GPx or SOD mimics in protecting cells from oxidative damage.

Phytotoxic hazards of NiO-nanoparticles in tomato: a study on mechanism of cell death

Nickel oxide nanoparticles (NiO-NPs) in the concentration range of 0.025-2.0mg/ml were examined for the induction of oxidative stress, mitochondrial dysfunction, apoptosis/necrosis in tomato seedling roots, as an in vivo model for nanotoxicity assessment in plants. Compared to the control, catalase (CAT), glutathione (GSH), superoxide dismutase (SOD) and lipid peroxidation (LPO) in 2.0mg/ml NiO-NPs treatments exhibited 6.8, 3.7, 1.7 and 2.6-fold higher activities of antioxidative enzymes. At 2.0mg/ml, 122% and 125.4% increase in intracellular reactive oxygen species (ROS) and mitochondrial membrane potential (ΔΨm) of seedling roots confirmed the oxidative stress and mitochondrial dysfunction. Comet assay exhibited a significant increase in the number of apoptotic (21.8%) and necrotic (24.0%) cells in 2.0mg/ml treatment groups vis-á-vis in control 7% apoptotic and 9.6% of necrotic cells were observed. Flow cytometric analysis revealed 65.7% of apoptotic/necrotic cell populations and 2.14-fold higher caspase-3 like protease activity were recorded in 2.0mg/ml treatment groups. Ultrastructure analysis revealed NiO-NPs translocation, nuclear condensation, abundance in peroxisomes and degenerated mitochondrial cristae. The dissolution of Ni ions from NiO-NPs signifies its potential to induce cell death presumably by Ni ions, triggering the mitochondrial dependent intrinsic apoptotic pathway.

Hepatoprotective effect of ethanolic extract of Curcuma longa on thioacetamide induced liver cirrhosis in rats

Background

Hepatology research has focused on developing traditional therapies as pharmacological medicines to treat liver cirrhosis. Thus, this study evaluated mechanisms of the hepatoprotective activity of Curcuma longa rhizome ethanolic extract (CLRE) on thioacetamide-induced liver cirrhosis in rats.

Methods

The hepatoprotective effect of CLRE was measured in a rat model of thioacetamide-induced liver cirrhosis over 8 weeks. Hepatic cytochrome P450 2E1 and serum levels of TGF-β1 and TNF-α were evaluated. Oxidative stress was measured by malondialdehyde, urinary 8-hydroxyguanosine and nitrotyrosine levels. The protective activity of CLRE free-radical scavenging mechanisms were evaluated through antioxidant enzymes. Protein expression of pro-apoptotic Bax and anti-apoptotic Bcl-2 proteins in animal blood sera was studied and confirmed by immunohistochemistry of Bax, Bcl2 proteins and proliferating cell nuclear antigen.

Results

Histopathology, immunohistochemistry and liver biochemistry were significantly lower in the Curcuma longa-treated groups compared with controls. CLRE induced apoptosis, inhibited hepatocytes proliferation but had no effect on hepatic CYP2E1 levels.

Conclusion

The progression of liver cirrhosis could be inhibited by the antioxidant and anti-inflammatory activities of CLRE and the normal status of the liver could be preserved.

Evidence of reactive oxygen species-mediated damage to mitochondrial DNA in children with typical autism

Background

The mitochondrial genome (mtDNA) is particularly susceptible to damage mediated by reactive oxygen species (ROS). Although elevated ROS production and elevated biomarkers of oxidative stress have been found in tissues from children with autism spectrum disorders, evidence for damage to mtDNA is lacking.

Findings

mtDNA deletions were evaluated in peripheral blood monocytic cells (PBMC) isolated from 2–5 year old children with full autism (AU; n = 67), and typically developing children (TD; n = 46) and their parents enrolled in the CHildhood Autism Risk from Genes and Environment study (CHARGE) at University of California Davis. Sequence variants were evaluated in mtDNA segments from AU and TD children (n = 10; each) and their mothers representing 31.2% coverage of the entire human mitochondrial genome. Increased mtDNA damage in AU children was evidenced by (i) higher frequency of mtDNA deletions (2-fold), (ii) higher number of GC→AT transitions (2.4-fold), being GC preferred sites for oxidative damage, and (iii) higher frequency of G,C,T→A transitions (1.6-fold) suggesting a higher incidence of polymerase gamma incorporating mainly A at bypassed apurinic/apyrimidinic sites, probably originated from oxidative stress. The last two outcomes were identical to their mothers suggesting the inheritance of a template consistent with increased oxidative damage, whereas the frequency of mtDNA deletions in AU children was similar to that of their fathers.

Conclusions

These results suggest that a combination of genetic and epigenetic factors, taking place during perinatal periods, results in a mtDNA template in children with autism similar to that expected for older individuals.

Evaluation of genetic damage in open-cast coal mine workers using the buccal micronucleus cytome assay

Coal is the largest fossil fuel source used for the generation of energy. However, coal extraction and its use constitute important pollution factors; thus, risk characterization and estimation are extremely important for the safety of coal workers and the environment. Candiota is located to the southeast of the state of Rio Grande do Sul and has the largest coal reserves in Brazil, and the largest thermal power complex in the state. In the open-cast mines, the coal miners are constantly exposed to coal dust. The human buccal micronucleus cytome (BMCyt) assay has been used widely to investigate biomarkers for DNA damage, cell death, and basal cell frequency in buccal cells. The aim of this study was to assess whether prolonged exposure to coal dust could lead to an increase in genomic instability, cell death, and frequency of basal cells using the BMCyt assay. In the analysis of epithelial cells, the exposed group (n = 41) presented with a significantly higher frequency of basal cells, micronuclei in basal and differentiated cells, and binucleated cells compared to the non-exposed group (n = 29). The exposed group showed a significantly lower frequency of condensed chromatin cells than the non-exposed group. However, we found no correlation between DNA damage and metal concentration in the blood of mine workers. DNA damage observed in the mine workers may be a consequence of oxidative damage resulting from exposure to coal residue mixtures. In addition, our findings confirm that the BMCyt assay can be used to identify occupational risk.

Therapeutic targeting of cancer cell cycle using proteasome inhibitors

Proteasomes are multicatalytic protease complexes in the cell, involved in the non-lysosomal recycling of intra-cellular proteins. Proteasomes play a critical role in regulation of cell division in both normal as well as cancer cells. In cancer cells this homeostatic function is deregulated leading to the hyperactivation of the proteasomes. Proteasome inhibitors (PIs) are a class of compounds, which either reversibly or irreversibly block the activity of proteasomes and induce cancer cell death. Interference of PIs with the ubiquitin proteasome pathway (UPP) involved in protein turnover in the cell leads to the accumulation of proteins engaged in cell cycle progression, which ultimately put a halt to cancer cell division and induce apoptosis. Upregulation of many tumor suppressor proteins involved in cell cycle arrest are known to play a role in PI induced cell cycle arrest in a variety of cancer cells. Although many PIs target the proteasomes, not all of them are effective in cancer therapy. Some cancers develop resistance against proteasome inhibition by possibly activating compensatory signaling pathways. However, the details of the activation of these pathways and their contribution to resistance to PI therapy remain obscure. Delineation of these pathways may help in checking resistance against PIs and deducing effective combinational approaches for improved treatment strategies. This review will discuss some of the signaling pathways related to proteasome inhibition and cell division that may help explain the basis of resistance of some cancers to proteasome inhibitors and underline the need for usage of PIs in combination with traditional chemotherapy.

DNA damage signaling assessed in individual cells in relation to the cell cycle phase and induction of apoptosis

Reviewed are the phosphorylation events reporting activation of protein kinases and the key substrates critical for the DNA damage signaling (DDS). These DDS events are detected immunocytochemically using phospho-specific Abs; flow cytometry or image-assisted cytometry provide the means to quantitatively assess them on a cell by cell basis. The multiparameter analysis of the data is used to correlate these events with each other and relate to the cell cycle phase, DNA replication and induction of apoptosis. Expression of γH2AX as a possible marker of induction of DNA double strand breaks is the most widely studied event of DDS. Reviewed are applications of this multiparameter approach to investigate constitutive DDS reporting DNA damage by endogenous oxidants byproducts of oxidative phosphorylation. Also reviewed are its applications to detect and explore mechanisms of DDS induced by variety of exogenous agents targeting DNA such as exogenous oxidants, ionizing radiation, radiomimetic drugs, UV light, DNA topoisomerase I and II inhibitors, DNA crosslinking drugs and variety of environmental genotoxins. Analysis of DDS induced by these agents provides often a wealth of information about mechanism of induction and the type of DNA damage (lesion) and is reviewed in the context of cell cycle phase specificity, DNA replication, and induction of apoptosis or cell senescence. Critically assessed is interpretation of the data as to whether the observed DDS events report induction of a particular type of DNA lesion.

Review of natural products actions on cytokines in inflammatory bowel disease

The purpose of this review is to provide an overview of the effects that natural products have on inflammatory bowel disease (IBD) and to provide insight into the relationship between these natural products and cytokines modulation. More than 100 studies from the past 10 years were reviewed herein on the therapeutic approaches for treating IBD. The natural products having anti-IBD actions included phytochemicals, antioxidants, microorganisms, dietary fibers, and lipids. The literature revealed that many of these natural products exert anti-IBD activity by altering cytokine production. Specifically, phytochemicals such as polyphenols or flavonoids are the most abundant, naturally occurring anti-IBD substances. The anti-IBD effects of lipids were primarily related to the n-3 polyunsaturated fatty acids. The anti-IBD effects of phytochemicals were associated with modulating the levels of tumor necrosis factor α (TNF-α), interleukin (IL)-1, IL-6, inducible nitric oxide synthase, and myeloperoxide. The anti-IBD effects of dietary fiber were mainly mediated via peroxisome proliferator-activated receptor-γ, TNF-α, nitric oxide, and IL-2, whereas the anti-IBD effects of lactic acid bacteria were reported to influence interferon-γ, IL-6, IL-12, TNF-α, and nuclear factor-κ light-chain enhancer of activated B cells. These results suggest that the anti-IBD effects exhibited by natural products are mainly caused by their ability to modulate cytokine production. However, the exact mechanism of action of natural products for IBD therapy is still unclear. Thus, future research is needed to examine the effect of these natural products on IBD and to determine which factors are most strongly correlated with reducing IBD or controlling the symptoms of IBD.

BML-275, an AMPK inhibitor, induces DNA damage, G2/M arrest and apoptosis in human pancreatic cancer cells

Adenosine monophosphate-activated protein kinase (AMPK) is a principal intracellular energy sensor which regulates energy producing pathways and energy requiring pathways when the cellular AMP/ATP ratio is altered. BML-275 (compound C), a well-known inhibitor of AMPK, has been found to induce apoptosis in myeloma, glioma and prostate cancer cells. However, the mechanisms responsible for the selective apoptotic effect(s) by BML-275 in cancer cells remain unknown. In the present study, BML-275 was investigated for its antitumor effect(s) in human pancreatic cancer cell lines. BML-275 inhibited the cell proliferation of 4 human pancreatic cancer cell lines (MIA PaCa-2, Panc-1, Colo-357 and AsPC-1). In addition, BML-275 significantly increased the generation of intracellular reactive oxygen species (ROS), followed by induction of DNA damage signaling and apoptosis. Furthermore, BML-275 induced cell cycle arrest in the G2/M phase. The inhibition of ROS generation by N-acetyl cysteine (NAC) significantly prevented the induction of DNA damage and apoptosis, but failed to prevent the induction of G2/M arrest by BML-275. Small interfering RNA (siRNA)-mediated knockdown of AMPKα increased the generation of intracellular ROS, DNA damage signaling and apoptosis without cell cycle arrest at the G2/M phase. These findings suggest that BML-275 exerts its antitumor effects by inducing ROS generation, DNA damage and apoptosis via inhibition of the AMPK pathway and by inducing G2/M arrest via a pathway independent of AMPK, implicating its potential application as an antitumor agent for pancreatic cancer.

Renal podocyte injury in a rat model of type 2 diabetes is prevented by metformin

Hyperglycemia promotes oxidative stress and hence generation of reactive oxygen species (ROS), which is known to play a crucial role in the pathogenesis of diabetic nephropathy. Metformin, an oral hypoglycemic drug, possesses antioxidant effects. The aim of this paper is to investigate the protective effects of metformin on the injury of renal podocytes in spontaneously diabetic Torii (SDT) rats, a new model for nonobese type 2 diabetes. Metformin (350 mg/kg/day) was given to SDT rats for 17 weeks. Blood glucose, glycated haemoglobin (HbA1c), and albuminuria were examined. Kidney histopathology, renal 8-hydroxydeoxyguanosine (8-OHdG) levels and apoptosis were examined. In 43-week-old SDT rats, severe hyperglycemia was developed, and albuminuria was markedly increased. Diabetes induced significant alterations in renal glomerular structure. In addition, urinary and renal 8-OHdG levels were highly increased, and podocyte loss was shown through application of the TUNEL and synaptopodin staining. However, treatment of SDT rats with metformin restored all these renal changes. Our data suggested that diabetes-induced podocyte loss in diabetic nephropathy could be suppressed by the antidiabetes drug, metformin, through the repression of oxidative injury.

Association of oxidative DNA damage and C-reactive protein in women at risk for cardiovascular disease

OBJECTIVE

The aim of the current study was to examine the relationship between clinical markers of inflammation and 8-oxo-7,8-dihydro-2'deoxyguanosine (8-oxodG), an oxidative stress marker, in middle-aged women drawn from the HANDLS study, a longitudinal epidemiological study.

METHODS AND RESULTS

We examined commonly assayed markers of inflammation, the DNA base adduct 8-oxodG, a marker of oxidative stress, and cardiovascular risk factors in a cohort of women matched on age and race in 3 groups (n=39 per group) who had low (<3 mg/L) high-sensitivity C-reactive protein (hsCRP), mid (>3-20 mg/L), and high (>20 mg/L) hsCRP. We found a significant relationship between hsCRP level and the oxidative stress marker, 8-oxodG. 8-oxodG was positively correlated with systolic blood pressure, pulse pressure, and interleukin-23. hsCRP was associated with obesity variables, high-density lipoprotein, serum insulin levels, interleukin-12p70 and intracellular adhesion molecule-1. Incubation of primary human endothelial cells with hsCRP generated reactive oxygen species in vitro. Furthermore, hsCRP specifically induced DNA base lesions, but not other forms of DNA damage, including single and double strand breaks.

CONCLUSIONS

These data suggest that in women 8-oxodG is associated with hsCRP and is independently related to select cardiovascular risk factors. Our data in women suggest that hsCRP may contribute to cardiovascular disease by increasing oxidative stress.

Oxidative stress responses involve oxidation of a conserved ubiquitin pathway enzyme

Although it is vital that cells detect and respond to oxidative stress to allow adaptation and repair damage, the underlying sensing and signaling mechanisms that control these responses are unclear. Protein ubiquitinylation plays an important role in controlling many biological processes, including cell division. In Saccharomyces cerevisiae, ubiquitinylation involves a single E1 enzyme, Uba1, with multiple E2s and E3s providing substrate specificity. For instance, the conserved E2 Cdc34 ubiquitinylates many substrates, including the cyclin-dependent kinase inhibitor Sic1, targeting it for degradation to allow cell cycle progression. Here we reveal that, in contrast to other ubiquitin pathway E2 enzymes, Cdc34 is particularly sensitive to oxidative inactivation, through sequestration of the catalytic cysteine in a disulfide complex with Uba1, by levels of oxidant that do not reduce global ubiquitinylation of proteins. This Cdc34 oxidation is associated with (i) reduced levels of Cdc34-ubiquitin thioester forms, (ii) increased stability of at least one Cdc34 substrate, Sic1, and (iii) Sic1-dependent delay in cell cycle progression. Together, these data reveal that the differential sensitivity of a ubiquitin pathway E2 enzyme to oxidation is utilized as a stress-sensing mechanism to respond to oxidative stress.

Mitochondrial DNA mutations in human tumor cells

Mitochondria play significant roles in cellular energy metabolism, free radical generation and apoptosis. The dysfunction of mitochondria is correlated with the origin and progression of tumors; thus, mutations in the mitochondrial genome that affect mitochondrial function may be one of the causal factors of tumorigenesis. Although the role of mitochondrial DNA (mtDNA) mutations in carcinogenesis has been investigated extensively by various approaches, the conclusions remain controversial to date. This review briefly summarizes the recent progress in this field.

Mitochondrial dynamics and mitophagy in the 6-hydroxydopamine preclinical model of Parkinson's disease

We discuss the participation of mitochondrial dynamics and autophagy in the 6-hydroxidopamine-induced Parkinson's disease model. The regulation of dynamic mitochondrial processes such as fusion, fission, and mitophagy has been shown to be an important mechanism controlling cellular fate. An imbalance in mitochondrial dynamics may contribute to both familial and sporadic neurodegenerative diseases including Parkinson's disease. With special attention we address the role of second messengers as the role of reactive oxygen species and the mitochondria as the headquarters of cell death. The role of molecular signaling pathways, for instance, the participation of Dynamin-related protein 1(Drp1), will also be addressed. Furthermore evidence demonstrates the therapeutic potential of small-molecule inhibitors of mitochondrial division in Parkinson's disease. For instance, pharmacological inhibition of Drp1, through treatment with the mitochondrial division inhibitor-1, results in the abrogation of mitochondrial fission and in a decrease of the number of autophagic cells. Deciphering the signaling cascades that underlie mitophagy triggered by 6-OHDA, as well as the mechanisms that determine the selectivity of this response, will help to better understand this process and may have impact on human treatment strategies of Parkinson's disease.

Smooth muscle cells isolated from thoracic aortic aneurysms exhibit increased genomic damage, but similar tendency for apoptosis

Aortic aneurysms (AA) are characterized by structural deterioration leading to progressive dilation. During the development of AA, two key structural changes are pronounced, one being degradation of extracellular matrix and the other loss of smooth muscle cells (SMCs) through apoptosis. Reactive oxygen species (ROS) are produced above physiological levels in dilated (aneurismal) part of the aorta compared to the nondilated part and they are known to be associated with both the extracellular matrix degradation and the loss of SMCs. In this study, we hypothesized that aneurismal SMCs are more prone to apoptosis and that at least some cells undergo apoptosis due to elevated ROS in the aortic wall. To test this hypothesis, we first isolated SMCs from thoracic aneurismal tissue and compared their apoptotic tendency with normal SMCs in response to H(2)O(2), oxidized sterol, or UV treatment. Exposed cells exhibited morphological changes characteristic of apoptosis, such as cell shrinkage, membrane blebbing, chromatin condensation, and DNA fragmentation. Terminal deoxynucleotidyl transferased UTP nick end labeling (TUNEL) further confirmed the fragmentation of nuclear DNA in these cells. Vascular SMCs were analyzed for their micronuclei (MN) and binucleate (BN) frequency as indicators of genomic abnormality. These data were then compared to patient parameters, including age, gender, hypertension, or aortic diameter for existing correlations. While the tendency for apoptosis was not significantly different compared to normal cells, both the %MN and %BN were higher in aneurismal SMCs. The data suggest that there is increased DNA damage in TAA samples, which might play a pivotal role in disease development.

Protective effects of Chlorella-derived peptide against UVC-induced cytotoxicity through inhibition of caspase-3 activity and reduction of the expression of phosphorylated FADD and cleaved PARP-1 in skin fibroblasts

UVC irradiation induces oxidative stress and leads to cell death through an apoptotic pathway. This apoptosis is caused by activation of caspase-3 and formation of poly(ADP-ribose) polymerase-1 (PARP-1). In this study, the underlying mechanisms of Chlorella derived peptide (CDP) activity against UVC-induced cytotoxicity were investigated. Human skin fibroblasts were treated with CDP, vitamin C, or vitamin E after UVC irradiation for a total energy of 15 J/cm². After the UVC exposure, cell proliferation and caspase-3 activity were measured at 12, 24, 48, and 72 h later. Expression of phosphorylated FADD and cleaved PARP-1 were measured 16 h later. DNA damage (expressed as pyrimidine (6-4) pyrimidone photoproducts DNA concentration) and fragmentation assay were performed 24 h after the UVC exposure. Results showed that UVC irradiation induced cytotoxicity in all groups except those treated with CDP. The caspase-3 activity in CDP-treated cells was inhibited from 12 h onward. Expression of phosphorylated FADD and cleaved PARP-1 were also reduced in CDP-treated cells. Moreover, UVC-induced DNA damage and fragmentation were also prevented by the CDP treatment. This study shows that treatment of CDP provides protective effects against UVC-induced cytotoxicity through the inhibition of caspase-3 activity and the reduction of phosphorylated FADD and cleaved PARP-1 expression.

Effects of the reduced form of coenzyme Q10 (ubiquinol) on semen parameters in men with idiopathic infertility: a double-blind, placebo controlled, randomized study

PURPOSE

We investigated the effects of the administration of ubiquinol (a reduced form of coenzyme Q(10)) on semen parameters and seminal plasma antioxidant capacity in infertile men with idiopathic oligoasthenoteratozoospermia.

MATERIALS AND METHODS

A total of 228 men with unexplained infertility were randomly assigned 1:1 into 2 groups. Group 1 (114) received 200 mg ubiquinol daily by mouth for 26 weeks and group 2 (114) received a similar regimen of placebo. After completion of the 26-week treatment phase, all participants were followed for another 12-week off-drug period. Primary outcomes were improvement in sperm density, sperm motility and sperm strict morphology.

RESULTS

At the end of the 26-week treatment period mean ± SD sperm density in the ubiquinol and placebo groups was 28.7 ± 4.6 × 10(6)/ml and 16.8 ± 4.4 × 10(6)/ml (p = 0.005), sperm motility was 35.8% ± 2.7% and 25.4% ± 2.1% (p = 0.008), and sperm strict morphology was 17.6% ± 4.4% and 14.8% ± 4.1% (p = 0.01) of normal sperm, respectively. During the treatment period serum follicle-stimulating hormone levels decreased significantly (p = 0.02) and serum inhibin B concentrations increased significantly (p = 0.01). During the off-drug period semen parameters gradually returned to baseline values but the differences were still significant for sperm density (p = 0.03) and sperm motility (p = 0.03). The correlation coefficients analysis revealed a positive association between the duration of treatment with ubiquinol and sperm density (r = 0.74, p = 0.017), sperm motility (r = 0.66, p = 0.024) and sperm morphology (r = 0.57, p = 0.027).

CONCLUSIONS

Ubiquinol was significantly effective in men with unexplained oligoasthenoteratozoospermia for improving sperm density, sperm motility and sperm morphology.

Two New p-Terphenyl Derivatives from the Marine Fungal Strain Aspergillus sp. AF119

Two new p-terphenyl derivatives (1, 2), together with six known ones (3 - 8), have been isolated from the marine fungal strain Aspergillus sp. AF119. The structures for terphyl acid (1) and terphyl diacid (2) were determined on the basis of HR Q-TOF-MS, and 1D- and 2D-NMR spectroscopic data. The in vitro cytotoxic activities of compounds 1 – 8 were tested against human tumor cell lines HeLa, HepG-2 and MDA-MB-435; only compounds 5 – 8 exhibited inhibitory activity against the tested cell lines with IC50 values < 20 μM. Moreover, compound 5 showed a mechanism of inducing cell cycle arrest and apoptosis mediated by the generation of ROS and subsequent DNA double-strand break.

Genetic mechanisms of chronic myeloid leukemia blastic transformation

The BCR-ABL1 oncogenic tyrosine kinase can transform pluripotent hematopoietic stem cells and initiate chronic myeloid leukemia in chronic phase (CML-CP), a myeloproliferative disorder characterized by excessive accumulation of mature myeloid cells. Patients in CML-CP usually respond to treatment with ABL1 tyrosine kinase inhibitors (TKIs) such as imatinib, though some patients who respond initially may become resistant later. CML-CP leukemia stem cells (LSCs) are intrinsically insensitive to TKIs and thus survive in the long term. These LSCs or their progeny may at some stage acquire additional genetic changes that cause the leukemia to transform further, from CML-CP to a more advanced phase, which has been subclassified as either accelerated phase (CML-AP) or blastic phase (CML-BP). CML-BP is characterized by a major clonal expansion of immature progenitors, which have either myeloid or lymphoid features. CML-BP responds poorly to treatment and is usually fatal. This review discusses the role of genomic instability leading to blastic transformation of CML and proposes some novel therapeutic approaches.

Quantification of 8-oxodGuo lesions in double-stranded DNA using a photoelectrochemical DNA sensor

Exposure of DNA to oxidative stress conditions results in the generation of 8-oxo-7,8-dihydro-2'-deoxyguanosine (8-oxodGuo). 8-OxodGuo is genotoxic if left unrepaired. We quantified 8-oxodGuo lesions in double-stranded DNA films by using a photoelectrochemical DNA sensor in conjunction with a specific covalent labeling method. A lesion-containing DNA film was assembled on a SnO(2) nanoparticle modified indium tin oxide electrode through layer-by-layer electrostatic adsorption. The lesions were covalently labeled with a biotin conjugated spermine derivative, and ruthenium tris(bipyridine) labeled streptavidin was introduced as the signal reporter molecule. Photocurrent increased with the number of lesions in the strand and decreased as the film was diluted with intact DNA. Quantification of 8-oxodGuo was achieved with an estimated detection limit of ∼1 lesion in 650 bases or 1.6 fmol of 8-oxodGuo on the electrode. Incubation of the film with a DNA base excision repair enzyme, E. coli formamidopyrimidine-DNA glycosylase (Fpg), resulted in complete loss of the signal, indicating efficient excision of the isolated lesions in the nucleotide. Oxidatively generated DNA damage to a double-stranded calf thymus DNA film by the Fenton reaction was then assessed. One 8-oxodGuo lesion in 520 bases was detected in DNA exposed to 50 μM Fe(2+)/200 μM H(2)O(2). Treatment with Fpg reduced the photocurrent by 50%, indicating only partial excision of 8-oxodGuo. This suggests that tandem lesions, which are resistant to Fpg excision, are generated by the Fenton reaction. Unlike repair enzyme dependent methods, the sensor recognizes 8-oxodGuo in tandem lesions and can avoid underestimating DNA damage.

Puerarin inhibits the retinal pericyte apoptosis induced by advanced glycation end products in vitro and in vivo by inhibiting NADPH oxidase-related oxidative stress

Retinal pericyte loss is one of the histopathological hallmarks of early diabetic retinopathy. Puerarin (4'-7-dihydroxy-8-beta-d-glucosylisoflavone), which is an isoflavone-C-glucoside, causes various pharmacological effects that include antihyperglycemic and anti-inflammatory activities. In the present study, we determined the efficacy and possible mechanism of puerarin on the advanced glycation end product (AGE)-modified bovine serum albumin (BSA)-induced apoptosis of cultured bovine retinal pericytes and rat retinal pericytes in intravitreally AGE-modified rat serum albumin (RSA)-injected eyes. Puerarin significantly inhibited pericyte apoptosis, the generation of reactive oxygen species (ROS), and NADPH oxidase activity by inhibiting the phosphorylation of p47phox and Rac1 which were induced by the AGE-BSA treatment. The puerarin treatment markedly suppressed the activation of nuclear factor-kappaB (NF-κB). In addition, the in vivo apoptosis of the retinal pericyte of rats that was stimulated by the intravitreal injection of AGE-RSA was evidently attenuated by the puerarin treatment. These results demonstrate that puerarin may exert inhibitory effects on AGE-induced pericyte apoptosis by interfering with the NADPH oxidase-related ROS pathways and blocking NF-κB activation, thereby ameliorating retinal microvascular dysfunction.

Novel m.15434C>A (p.230L>I) Mitochondrial Cytb Gene Missense Mutation Associated with Dilated Cardiomyopathy

Background. Previously it has been shown that various types of hypertrophic and dilative cardiomyopathy (hCMP, dCMP) can be attributed to disturbed mitochondrial oxidative energy metabolism. Several studies described mutations in mitochondrial DNA-located genes encoding for subunits of respiratory chain complexes, including the cytochrome b gene (MT-CYB), causing CMPs. Methods and Results. In the present study the MT-CYB gene was analysed in 30 patients with hCMP, 40 patients with dCMP, and 50 controls for alterations. Altogether, 27 MT-CYB variants were detected. Twenty-four of them were single nucleotide polymorphisms defining common haplogroups. The variant m.15434C>A was found in a single patient with severe dCMP and assessed as novel mutation, since it was not found in healthy controls or available data sets, and was nonhaplogroup associated with Phylotree. This variant altered an amino acid (L230I) with a high interspecific amino acid conservation index (CI = 97.7%) indicative of the functional importance of the residue. Conclusions. Though the L230I mutation seems to play a causative role for dCMP, prospective studies on yeast or transgenic mice models with defined mutation are warranted to study the pathogenetic impact of this mutation.

Distinct pattern of oxidative DNA damage and DNA repair in follicular thyroid tumours

Increased oxidative stress has been linked to thyroid carcinogenesis. In this paper, we investigate whether oxidative DNA damage and DNA repair differ in follicular adenoma (FA) and follicular thyroid carcinoma (FTC). 7,8-Dihydro-8-oxoguanine (8-OxoG) formation was analysed by immunohistochemistry in 46 FAs, 52 FTCs and 18 normal thyroid tissues (NTs). mRNA expression of DNA repair genes OGG1, Mut Y homologue (MUTYH) and endonuclease III (NTHL1) was analysed by real-time PCR in 19 FAs, 25 FTCs and 19 NTs. Induction and repair of oxidative DNA damage were studied in rat FRTL-5 cells after u.v. irradiation. Moreover, activation of DNA damage checkpoints (ataxia telangiectasia mutated (ATM) and H2A histone family, member X (H2AFX (H2AFX))) and proliferation index (MIB-1) were quantified in 28 non-oxyphilic and 24 oxyphilic FTCs. Increased nuclear and cytosolic 8-OxoG formation was detected in FTC compared with follicular adenoma, whereby cytosolic 8-OxoG formation was found to reflect RNA oxidation. Significant downregulation of DNA repair enzymes was detected in FTC compared with FA. In vitro experiments mirrored the findings in FTC with oxidative stress-induced DNA checkpoint activation and downregulation of OGG1, MUTYH and NTHL1 in FRTL-5 cells, an effect that, however, was reversible after 24  h. Further analysis of FTC variants showed decreased oxidative DNA damage, sustained checkpoint activation and decreased proliferation in oxyphilic vs non-oxyphilic FTC. Our data suggest a pathophysiological scenario of accumulating unrepaired DNA/RNA damage in FTC vs counterbalanced DNA/RNA damage and repair in FA. Furthermore, this study provides the first evidence for differences in oxidative stress defence in FTC variants with possible implications for therapeutic response and prognostic outcome.

Oxidatively damaged DNA and its repair in colon carcinogenesis

Inflammation, high fat, high red meat and low fiber consumption have for long been known as the most important etiological factors of sporadic colorectal cancers (CRC). Colon cancer originates from neoplastic transformation in a single layer of epithelial cells occupying colonic crypts, in which migration and apoptosis program becomes disrupted. This results in the formation of polyps and metastatic cancers. Mutational program in sporadic cancers involves APC gene, in which mutations occur most abundantly in the early phase of the process. This is followed by mutations in RAS, TP53, and other genes. Progression of carcinogenic process in the colon is accompanied by augmentation of the oxidative stress, which manifests in the increased level of oxidatively damaged DNA both in the colon epithelium, and in blood leukocytes and urine, already at the earliest stages of disease development. Defence mechanisms are deregulated in CRC patients: (i) antioxidative vitamins level in blood plasma declines with the development of disease; (ii) mRNA level of base excision repair enzymes in blood leukocytes of CRC patients is significantly increased; however, excision rate is regulated separately, being increased for 8-oxoGua, while decreased for lipid peroxidation derived ethenoadducts, ɛAde and ɛCyt; (iii) excision rate of ɛAde and ɛCyt in colon tumors is significantly increased in comparison to asymptomatic colon margin, and ethenoadducts level is decreased. This review highlights mechanisms underlying such deregulation, which is the driving force to colon carcinogenesis.

Impact of PNKP mutations associated with microcephaly, seizures and developmental delay on enzyme activity and DNA strand break repair

Microcephaly with early-onset, intractable seizures and developmental delay (MCSZ) is a hereditary disease caused by mutations in polynucleotide kinase/phosphatase (PNKP), a DNA strand break repair protein with DNA 5'-kinase and DNA 3'-phosphatase activity. To investigate the molecular basis of this disease, we examined the impact of MCSZ mutations on PNKP activity in vitro and in cells. Three of the four mutations currently associated with MCSZ greatly reduce or ablate DNA kinase activity of recombinant PNKP at 30°C (L176F, T424Gfs48X and exon15Δfs4X), but only one of these mutations reduces DNA phosphatase activity under the same conditions (L176F). The fourth mutation (E326K) has little impact on either DNA kinase or DNA phosphatase activity at 30°C, but is less stable than the wild-type enzyme at physiological temperature. Critically, all of the MCSZ mutations identified to date result in ∼ 10-fold reduced cellular levels of PNKP protein, and reduced rates of chromosomal DNA strand break repair. Together, these data suggest that all four known MCSZ mutations reduce the cellular stability and level of PNKP protein, with three mutations likely ablating cellular DNA 5'-kinase activity and all of the mutations greatly reducing cellular DNA 3'-phosphatase activity.

Delayed neuromotor recovery and increased memory acquisition dysfunction following experimental brain trauma in mice lacking the DNA repair gene XPA

OBJECT

This study investigates the outcome after traumatic brain injury (TBI) in mice lacking the essential DNA repair gene xeroderma pigmentosum group A (XPA). As damage to DNA has been implicated in neuronal cell death in various models, the authors sought to elucidate whether the absence of an essential DNA repair factor would affect the outcome of TBI in an experimental setting.

METHODS

Thirty-seven adult mice of either wild-type (n = 18) or XPA-deficient ("knock-out" [n = 19]) genotype were subjected to controlled cortical impact experimental brain trauma, which produced a focal brain injury. Sham-injured mice of both genotypes were used as controls (9 in each group). The mice were subjected to neurobehavoral tests evaluating learning/acquisition (Morris water maze) and motor dysfunction (Rotarod and composite neuroscore test), pre- and postinjury up to 4 weeks. The mice were killed after 1 or 4 weeks, and cortical lesion volume, as well as hippocampal and thalamic cell loss, was evaluated. Hippocampal staining with doublecortin antibody was used to evaluate neurogenesis after the insult.

RESULTS

Brain-injured XPA(-/-) mice exhibited delayed recovery from impairment in neurological motor function, as well as pronounced cognitive dysfunction in a spatial learning task (Morris water maze), compared with injured XPA(+/+) mice (p < 0.05). No differences in cortical lesion volume, hippocampal damage, or thalamic cell loss were detected between XPA(+/+) and XPA(-/-) mice after brain injury. Also, no difference in the number of cells stained with doublecortin in the hippocampus was detected.

CONCLUSIONS

The authors' results suggest that lack of the DNA repair factor XPA may delay neurobehavioral recovery after TBI, although they do not support the notion that this DNA repair deficiency results in increased cell or tissue death in the posttraumatic brain.

Detection and imaging of the free radical DNA in cells--site-specific radical formation induced by Fenton chemistry and its repair in cellular DNA as seen by electron spin resonance, immuno-spin trapping and confocal microscopy

Oxidative stress-related damage to the DNA macromolecule produces lesions that are implicated in various diseases. To understand damage to DNA, it is important to study the free radical reactions causing the damage. Measurement of DNA damage has been a matter of debate as most of the available methods measure the end product of a sequence of events and provide limited information on the initial free radical formation. We report a measurement of free radical damage in DNA induced by a Cu(II)-H₂O₂ oxidizing system using immuno-spin trapping supplemented with electron paramagnetic resonance. In this investigation, the short-lived radical generated is trapped by the spin trap 5,5-dimethyl-1-pyrroline N-oxide (DMPO) immediately upon formation. The DMPO adduct formed is initially electron paramagnetic resonance active, but is subsequently oxidized to the stable nitrone adduct, which can be detected and visualized by immuno-spin trapping and has the potential to be further characterized by other analytical techniques. The radical was found to be located on the 2′-deoxyadenosine (dAdo) moiety of DNA. The nitrone adduct was repaired on a time scale consistent with DNA repair. In vivo experiments for the purpose of detecting DMPO–DNA nitrone adducts should be conducted over a range of time in order to avoid missing adducts due to the repair processes.

Genome protective effect of metformin as revealed by reduced level of constitutive DNA damage signaling

We have shown before that constitutive DNA damage signaling represented by H2AX-Ser139 phosphorylation and ATM activation in untreated normal and tumor cells is a reporter of the persistent DNA replication stress induced by endogenous oxidants, the by-products of aerobic respiration. In the present study we observed that exposure of normal mitogenically stimulated lymphocytes or tumor cell lines A549, TK6 and A431 to metformin, the specific activator of 5'AMP-activated protein kinase (AMPK) and an inhibitor of mTOR signaling, resulted in attenuation of constitutive H2AX phosphorylation and ATM activation. The effects were metformin-concentration dependent and seen even at the pharmacologically pertinent 0.1 mM drug concentration. The data also show that intracellular levels of endogenous reactive oxidants able to oxidize 2',7'-dihydro-dichlorofluorescein diacetate was reduced in metformin-treated cells. Since persistent constitutive DNA replication stress, particularly when paralleled by mTOR signaling, is considered to be the major cause of aging, the present findings are consistent with the notion that metformin, by reducing both DNA replication stress and mTOR-signaling, slows down aging and/or cell senescence processes.

Genome integrity, stem cells and hyaluronan

Faithful preservation of genome integrity is the critical mission of stem cells as well as of germ cells. Reviewed are the following mechanisms involved in protecting DNA in these cells: (a) The efflux machinery that can pump out variety of genotoxins in ATP-dependent manner; (b) the mechanisms maintaining minimal metabolic activity which reduces generation of reactive oxidants, by-products of aerobic respiration; (c) the role of hypoxic niche of stem cells providing a gradient of variable oxygen tension; (d)(e) the presence of hyaluronan (HA) and HA receptors on stem cells and in the niche; (f) the role of role of HA in protecting DNA from oxidative damage; (g) the specific role of HA that may play a role protecting DNA in stem cells; (h) the interactions of HA with sperm cells and oocytes that also may shield their DNA from oxidative damage, and (e) mechanisms by which HA exerts the anti-oxidant activity. While HA has multitude of functions its anti-oxidant capabilities are often overlooked but may be of significance in preservation of integrity of stem and germ cells genome.

Aminoferrocene-based prodrugs activated by reactive oxygen species

Cancer cells generally generate higher amounts of reactive oxygen species than normal cells. On the basis of this difference, prodrugs have been developed (e.g., hydroxyferrocifen), which remain inactive in normal cells, but become activated in cancer cells. In this work we describe novel aminoferrocene-based prodrugs, which, in contrast to hydroxyferrocifen, after activation form not only quinone methides (QMs), but also catalysts (iron or ferrocenium ions). The released products act in a concerted fashion. In particular, QMs alkylate glutathione, thereby inhibiting the antioxidative system of the cell, whereas the iron species induce catalytic generation of hydroxyl radicals. Since the catalysts are formed as products of the activation reaction, it proceeds autocatalytically. The most potent prodrug described here is toxic toward cancer cells (human promyelocytic leukemia (HL-60), IC(50) = 9 μM, and human glioblastoma-astrocytoma (U373), IC(50) = 25 μM), but not toxic (up to 100 μM) toward representative nonmalignant cells (fibroblasts).