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Colorectal carcinoma (CRC) is the third most common malignancy worldwide, and second in number of deaths in the world. The molecular pathogenesis of CRC is heterogeneous and can affect several genes. Moreover, genomic instability is recognized as an important part of CRC carcinogenesis and is tightly connected to DNA damage response. DNA damage repair (DDR) pathways are intrinsically associated with cancer development and establishment. Traditionally, CRC is considered as one coherent disease, however, new evidence shows that left and right-sided CRC present differences observed in clinical settings, as well as in pre-clinical studies. Therefore, this study aimed to investigate the impact of DDR transcriptional profiles on survival in different sublocations of the colon and rectum using Cox regression, survival analysis and differential gene expression. Right side colon (RSC) has DDR genes' expression associated only with higher risk of death, while left side colon (LSC) and Rectum have most genes' expression associated with lower risk. The pattern is the same with survival analysis. All significant DDR genes had lower expression associated with better survival in RSC, as opposed to LSC and Rectum. Our results demonstrate that RSC is distinctively different from LSC and Rectum. LSC and Rectum have similar DDR expression profiles. [ABSTRACT FROM AUTHOR]

Colorectal carcinoma (CRC) is the third most common malignancy worldwide, and second in number of deaths in the world. The molecular pathogenesis of CRC is heterogeneous and can affect several genes. Moreover, genomic instability is recognized as an important part of CRC carcinogenesis and is tightly connected to DNA damage response. DNA damage repair (DDR) pathways are intrinsically associated with cancer development and establishment. Traditionally, CRC is considered as one coherent disease, however, new evidence shows that left and right-sided CRC present differences observed in clinical settings, as well as in pre-clinical studies. Therefore, this study aimed to investigate the impact of DDR transcriptional profiles on survival in different sublocations of the colon and rectum using Cox regression, survival analysis and differential gene expression. Right side colon (RSC) has DDR genes' expression associated only with higher risk of death, while left side colon (LSC) and Rectum have most genes' expression associated with lower risk. The pattern is the same with survival analysis. All significant DDR genes had lower expression associated with better survival in RSC, as opposed to LSC and Rectum. Our results demonstrate that RSC is distinctively different from LSC and Rectum. LSC and Rectum have similar DDR expression profiles. [ABSTRACT FROM AUTHOR]

Background: Homologous recombination repair (HR) is the most accurate repair pathway for double-strand breaks and replication fork disruption that is capable of faithfully restoring the original nucleotide sequence of the broken DNA. The deficiency of this mechanism is a frequent event in tumorigenesis. Therapies that exploit defects in HR have been explored essentially in breast, ovarian, pancreatic, and prostate cancers, but poorly in colorectal cancers (CRC), although CRC ranks second in mortality worldwide. Methods: Tumor specimens and matched healthy tissues from 63 patients with CRC were assessed for gene expression of key HR components and mismatch repair (MMR) status, which correlated with clinicopathological features, progression-free survival, and overall survival (OS). Results: Enhanced expression of MRE11 homolog (MRE11A), the gene encoding a key molecular actor for resection, is significantly overexpressed in CRC, is associated with the occurrence of primary tumors, particularly T3-T4, and is found in more than 90% of the right-side of CRC, the location with the worst prognosis. Importantly, we also found that high MRE11A transcript abundance is associated with 16.7 months shorter OS and a 3.5 higher risk of death. Conclusion: Monitoring of MRE11 expression could be used both as a predictor of outcome and as a marker to select CRC patients for treatments thus far adapted for HR-deficient cancers. [ABSTRACT FROM AUTHOR]

Cu(II) complexes bearing NNO-donor Schiff base ligands (2a, b) have been synthesized and characterized. The single crystal X-ray analysis of the 2a complex revealed that a mononuclear and a dinuclear complex co-crystallize in the solid state. The electronic structures of the complexes are optimized by Density Functional Theory (DFT) calculations. The monomeric nature of 2a and 2b species is maintained in solution. Antioxidant activities of the ligands (1a, b) and Cu(II) complexes (2a, b) were determined by in vitro assays such as 1,1-diphenyl-2-picrylhydrazyl free radicals (DPPH.) and 2,2′-azino-bis (3-ethylbenzothiazoline-6-sulfonic acid) radicals (ABTS+). Our results demonstrated that 2a showed better antioxidant activity. MTT assays were performed to assess the toxicity of ligands and Cu(II) complexes in V79 cells. The antiproliferative activity of compounds was tested against two human tumor cell lines: MCF-7 (breast adenocarcinoma) and SW620 (colorectal carcinoma) and on MRC-5 (normal lung fibroblast). All compounds showed high cytotoxicity in the all-cell lines but showed no selectivity for tumor cell lines. Antiproliferative activity by clonogenic assay 2b showed a more significant inhibitory effect on the MCF-7 cell lines than on MRC-5. DNA damage for the 2b compound at 10 µM concentration was about three times higher in MCF-7 cells than in MRC-5 cells. [ABSTRACT FROM AUTHOR]

Background: The advances in colorectal cancer (CRC) treatment include the identification of deficiencies in Mismatch Repair (MMR) pathway to predict the benefit of adjuvant 5-fluorouracil (5-FU) and oxaliplatin for stage II CRC and immunotherapy. Defective MMR contributes to chemoresistance in CRC. A growing body of evidence supports the role of Poly-(ADP-ribose) polymerase (PARP) inhibitors, such as Olaparib, in the treatment of different subsets of cancer beyond the tumors with homologous recombination deficiencies. In this work we evaluated the effect of Olaparib on 5-FU cytotoxicity in MMR-deficient and proficient CRC cells and the mechanisms involved.Methods: Human colon cancer cell lines, proficient (HT29) and deficient (HCT116) in MMR, were treated with 5-FU and Olaparib. Cytotoxicity was assessed by MTT and clonogenic assays, apoptosis induction and cell cycle progression by flow cytometry, DNA damage by comet assay. Adhesion and transwell migration assays were also performed.Results: Our results showed enhancement of the 5-FU citotoxicity by Olaparib in MMR-deficient HCT116 colon cancer cells. Moreover, the combined treatment with Olaparib and 5-FU induced G2/M arrest, apoptosis and polyploidy in these cells. In MMR proficient HT29 cells, the Olaparib alone reduced clonogenic survival, induced DNA damage accumulation and decreased the adhesion and migration capacities.Conclusion: Our results suggest benefits of Olaparib inclusion in CRC treatment, as combination with 5-FU for MMR deficient CRC and as monotherapy for MMR proficient CRC. Thus, combined therapy with Olaparib could be a strategy to overcome 5-FU chemotherapeutic resistance in MMR-deficient CRC. [ABSTRACT FROM AUTHOR]

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Skin secretions of frogs have a high chemical complexity. They have diverse types of biomolecules, such as proteins, peptides, biogenic amines, and alkaloids. These compounds protect amphibians' skin against growth of bacteria, fungi, and protozoa and participate in defense system against attack from predators. Therewith, this work performed biochemical and biological profile of macroglands parotoid secretion from cane toad. For poison analysis, we performed molecular exclusion and reverse phase chromatography, electrophoresis, and mass spectrometry. Antimicrobial, antiplasmodial, leishmanicidal, cytotoxicity, genotoxicity, and inflammatory activity of crude and/or fractions of R. marina secretion were also evaluated. Fractionation prior to filtration from poison showed separation of low mass content (steroids and alkaloids) and high molecular mass (protein). Material below 10 kDa two steroids, marinobufagin and desacetylcinobufagin, was detected. Crude extract and fractions were active against Staphylococcus aureus, Pseudomonas aeruginosa, Escherichia coli, Plasmodium falciparum, Leishmania guyanensis, and Leishmania braziliensis. Crude extract was also active against cancer cells although it was not cytotoxic for normal cells. This extract did not show significant DNA damage but it showed an important inflammatory effect in vivo. The information obtained in this work contributes to the understanding of the constituents of R. marina secretion as well as the bioactive potential of these molecules. [ABSTRACT FROM AUTHOR]

Background: Chronic kidney failure (CKF) patients on renal replacement therapies exhibit elevated levels of DNA lesions and this is directly related to high mortality. Objective: This study aimed to evaluate the effect of neuromuscular electrical stimulation (NMES) on genomic damage in CKF patients on conventional haemodialysis (HD). Methods: Twenty-one patients with CKF on HD were randomized into control (CG =10) or neuromuscular electrical stimulation (NMESG = 11) groups. NMES was applied on the quadriceps muscle during the HD session, three times a week, for 8 weeks in NMESG. DNA damage in blood was evaluated by the alkaline comet assay prior to follow-up, after 4 and 8 weeks of intervention. Results: Intradialytic NMES in CKF patients induced a significant decrease in DNA damage after four [49.9 (3.68) vs 101.5 (6.53); p = 0.000] than eight [19.9 (2.07) vs 101.5 (6.53); p = 0.000] weeks compared to baseline. Genomic damage was also significantly less after four [NMESG: 49.9 (3.68) vs CG: 92.9 (12.61); p = 0.001] than after eight [NMESG: 19.9 (2.07) vs CG: 76.4 (11.15); p = 0.000] weeks compared to CG. Conclusions: This study demonstrates for the first time that intradialytic NMES is able to reduce DNA damage in blood of CKF patients. [ABSTRACT FROM AUTHOR]

Introduction: Homocysteine (Hcy) tissue accumulation occurs in a metabolic disease characterized biochemically by cystathionine ß-synthase (CBS) deficiency and clinically by mental retardation, vascular problems, and skeletal abnormalities. Previous studies indicate the occurrence of DNA damage secondary to hyperhomocysteinemia and it was observed that DNA damage occurs in leukocytes from CBS-deficient patients. This study aimed to investigate whether an oxidative mechanism could be involved in DNA damage previously found and investigated the in vitro effect of N-acety-L-cysteine (NAC) on DNA damage caused by high Hcy levels. Methods: We evaluated a biomarker of oxidative DNA damage in the urine of CBS-deficient patients, as well as the in vitro effect of NAC on DNA damage caused by high levels of Hcy. Moreover, a biomarker of lipid oxidative damage was also measured in urine of CBS deficient patients. Results: There was an increase in parameters of DNA (8-oxo-7,8-dihydro-2'- deoxyguanosine) and lipid (15-F2t-isoprostanes levels) oxidative damage in CBS-deficient patients when compared to controls. In addition, a significant positive correlation was found between 15-F2t-isoprostanes levels and total Hcy concentrations. Besides, an in vitro protective effect of NAC at concentrations of 1 and 5 mM was observed on DNA damage caused by Hcy 50 µM and 200 µM. Additionally, we showed a decrease in sulfhydryl content in plasma from CBS-deficient patients when compared to controls. Discussion: These results demonstrated that DNA damage occurs by an oxidative mechanism in CBS deficiency together with lipid oxidative damage, highlighting the NAC beneficial action upon DNA oxidative process, contributing with a new treatment perspective of the patients affected by classic homocystinuria. [ABSTRACT FROM AUTHOR]

Objective: The present study evaluated the ability of rosmarinic acid (RA) to inhibit microglia activation induced by lipopolysaccharide (LPS) in the N9 murine microglial cell line, and investigated the putative mechanisms involved in this process. Methods: In all tests, N9 murine microglial cells were pretreated with RA (0.1, 1.0, and 10 μ M) for 20 h and exposed to LPS (1 μ M/mL) for 4 h. Cell viability was measured by Trypan blue exclusion assay. Flow cytometry was used to detect reactive oxygen species (ROS), quantify cleaved caspase- 3, and analyze the mitochondrial electrochemical potential. iNOS, Arg-1, TNF-α, IL-1γ, and IL-6 proteins were analyzed by Western blotting, and their antigens were detected using the chemiluminescence technique. The effect of RA on DNA was evaluated by the Comet assay. Results: RA attenuated the expression of the M1 marker iNOS and the levels of proinflammatory factors, including TNF-α, IL-1γ, and IL-6; it increased the expression of the M2 marker Arg-1, and inhibited, at least in part, ROS generation and loss of mitochondrial outer membrane permeabilization through the inhibition of cleaved caspase-3 activation. RA also inhibited DNA damage, reassuring cell protection. Conclusions: The results suggested a protective effect of RA through downregulation of inflammatory cytokines and cleaved caspase-3. [ABSTRACT FROM AUTHOR]

High plasma levels of methionine (Met) and its metabolites such as methionine sulfoxide (MetO) may occur in several genetic abnormalities. Patients with hypermethioninemia can present neurological dysfunction; however, the neurotoxicity mechanisms induced by these amino acids remain unknown. The aim of the present work was to study the effects of Met and/or MetO on oxidative stress, genotoxicity, cytotoxicity and to evaluate whether the cell death mechanism is mediated by apoptosis in the cerebral cortex of young rats. Forty-eight Wistar rats were divided into groups: saline, Met 0.4 g/Kg, MetO 0.1 g/Kg and Met 0.4 g/Kg + MetO 0.1 g/Kg, and were euthanized 1 and 3 h after subcutaneous injection. Results showed that TBARS levels were enhanced by MetO and Met+MetO 1 h and 3 h after treatment. ROS was increased at 3 h by Met, MetO and Met+MetO. SOD activity was increased in the Met group, while CAT was reduced in all experimental groups 1 h and 3 h after treatment. GPx activity was enhanced 1 h after treatment by Met, MetO and Met+MetO, however it was reduced in the same experimental groups 3 h after administration of amino acids. Caspase-3, caspase-9 and DNA damage was increased and cell viability was reduced by Met, MetO and Met+MetO at 3 h. Also, Met, MetO and Met+MetO, after 3 h, enhanced early and late apoptosis cells. Mitochondrial electrochemical potential was decreased by MetO and Met+MetO 1 h and 3 h after treatment. These findings help understand the mechanisms involved in neurotoxicity induced by hypermethioninemia. [ABSTRACT FROM AUTHOR]

Fabry disease (FD) is a lysosomal disorder caused by mutations leading to a deficient activity α-galactosidase A with progressive and systemic accumulation of its substrates. Substrates deposition is related to tissue damage in FD, but the underlying molecular mechanisms remain not completely understood. DNA damage has been associated with disease progression in chronic diseases and was recently described in high levels in Fabry patients. Once renal complications are major morbidity causes in FD, we investigated the effects of the latest biomarker for FD - globotriaosylsphingosine (lyso-Gb3) in a cultured renal lineage - human embryonic kidney cells (HEK-293 T) - on DNA damage. In concentrations found in Fabry patients, lyso-Gb3 induced DNA damage (by alkaline comet assay) with oxidative origin in purines and pyrimidines (by comet assay with endonucleases). These data provide new information about a deleterious effect of lyso-Gb3 and could be useful to studies looking for new therapeutic strategies to FD. [ABSTRACT FROM AUTHOR]

Anthracyclines, e.g., doxorubicin (DOX), and anthracenediones, e.g., mitoxantrone (MTX), are drugs used in the chemotherapy of several cancer types, including solid and non-solid malignancies such as breast cancer, leukemia, lymphomas, and sarcomas. Although they are effective in tumor therapy, treatment with these two drugs may lead to side effects such as arrhythmia and heart failure. At the same clinically equivalent dose, MTX causes slightly reduced cardiotoxicity compared with DOX. These drugs interact with iron to generate reactive oxygen species (ROS), target topoisomerase 2 (Top2), and impair mitochondria. These are some of the mechanisms through which these drugs induce late cardiomyopathy. In this review, we compare the cardiotoxicities of these two chemotherapeutic drugs, DOX and MTX. As described here, even though they share similarities in their modes of toxicant action, DOX and MTX seem to differ in a key aspect. DOX is a more redox-interfering drug, while MTX induces energy imbalance. In addition, DOX toxicity can be explained by underlying mechanisms that include targeting of Top2 beta, mitochondrial impairment, and increases in ROS generation. These modes of action have not yet been demonstrated for MTX, and this knowledge gap needs to be filled. [ABSTRACT FROM AUTHOR]

Grapes are one of the most commonly consumed fruit, in both fresh and processed forms; however, a significant amount is disposed of in the environment. Searching for a use of this waste, the antigenotoxic, antimutagenic, and antioxidant activities of aqueous extracts from organic and conventionalVitis labruscaleaves were determined using V79 cells as model. The antigenotoxic activity was analyzed by the alkaline comet assay using endonuclease III and formamidopyrimidine DNA glycosylase enzymes. The antimutagenic property was assessed through the micronucleus (MN) formation, and antioxidant activities were assessed using 2’,7’-dichlorodihydrofluorescin diacetate (DCFH-DA) assay and 2,2-diphenyl-1-picrylhydrazyl (DPPH●) radical scavenging, as well as with superoxide dismutase (SOD) and catalase (CAT) activity assays. In addition, phenolic content and ascorbic acid levels of both extracts were determined. Data showed that both organic and conventional grapevine leaves extracts possessed antigenotoxic and antimutagenic properties. The extract of organic leaves significantly reduced intracellular reactive oxygen species (ROS) levels in V79 cells, and displayed greater ability for DPPH●scavenging and higher SOD and CAT activities than extract from conventional leaves. Further, the extract from organic leaves contained higher phenolic and ascorbic acid concentrations. In summary, extracts from organic and conventional grape leaves induced important in vitro biological effects. [ABSTRACT FROM AUTHOR]

Combretum leprosum Mart., a member of the Combretaceae family, is a traditionally used Brazilian medicinal plant, although no evidence in the literature substantiates its antioxidant action and the safety of its use. We evaluated the antioxidant properties of the ethanolic extract (EE) from flowers of C. leprosum and its isolated products 5,3′-dihydroxy-3,7,4′-trimethoxyflavone (FCL2) and 5,3′,4′-trihydroxy-3,7-dimethoxyflavone (FCL5) in Saccharomyces cerevisiae strains proficient and deficient in antioxidant defenses. Their mutagenic activity was also assayed in S. cerevisiae, whereas cytotoxic and genotoxic properties were evaluated by MTT and Comet Assays, respectively, in V79 cells. We show that the EE, FCL2, and FCL5 have a significant protective effect against H2O2. FCL2 showed a better antioxidant action, which can be related to the activation of the 3′-OH in the presence of a methoxyl group at 4′ position in the B-ring of the molecule, while flavonoids did not induce mutagenesis in yeast, and the EE was mutagenic at high concentrations. The toxicity of these compounds in V79 cells increases from FCL2 = FCL5 < EE; although not cytotoxic, FCL5 induced an increase in DNA damage. The antioxidant effect, along with the lower toxicity and the absence of genotoxicity, suggests that FCL2 could be suitable for pharmacological use. [ABSTRACT FROM AUTHOR]

The present study evaluates antigenotoxic and antimutagenic properties of diphenyl ditelluride (DPDT) against several known mutagens in Chinese hamster lung fibroblasts (V79 cells). DPDT was not cytotoxic and genotoxic at concentrations ranging from 0.01 to 0.1 µM. The pre-treatment for 2 h with this organotellurium compound at non-cytotoxic dose range (0.01, 0.05 and 0.1 µM) increased cell survival after challenge with hydrogen peroxide (H2O2), t-butyl hydroperoxide (t-BOOH), methylmethanesulphonate (MMS) or ultraviolet (UV)C radiation. In addition, the pre- treatment with DPDT decreased the DNA damage and Formamidopyrimidine DNA-glycosylase (Fpg)- and Endonuclease III (Endo III) sensitive sites induction by the studied genotoxic agents, as verified by comet assay and modified comet assay, respectively. The pre-treatment also reduced micronucleus frequency, revealing the protector effect of DPDT against MMS and UVC-induced mutagenesis. Our results demonstrate that DPDT -treated cells at concentration range of 0.01-0.1 µM do not change thiobarbituric acid reactive species (TBARS) levels and ROS generation. Moreover, DPDT pre-treatment at this concentration range decreases the ROS induction by H2O2 and t-BOOH treatment indicating antioxidant potential. On the other hand, concentrations higher than 0.1 µM increase TBARS formation and inhibited superoxide dismutase (SOD) activity, suggesting pro-oxidative effect of this compound at high concentrations. Our results suggest that DPDT presents antigenotoxic and antimutagenic properties at concentration range of 0.01-0.1 µM. The protection effect could be attributed to antioxidant capacity of DPDT at this concentration range in V79 cells. [ABSTRACT FROM AUTHOR]

Purpose: To assess the effect of 950 MHz ultra-high-frequency electromagnetic radiation (UHF-EMR) on biomarkers of oxidative damage to DNA, proteins and lipids in the left cerebral cortex (LCC) and right cerebral cortex (RCC) of neonate and 6-day-old rats. Materials and methods: Twelve rats were equally divided into two groups as controls (CR) and exposed (ER), for each age (0 and 6 days). The LCC and RCC were examined in ER and CR after exposure. Radiation exposure lasted 30 min per day for up to 27 days (throughout pregnancy and 6 days postnatal). The specific absorption rate ranged from 1.32–1.14 W/kg. The damage to lipids, proteins and DNA was verified by thiobarbituric acid reactive substances, carbonylated proteins (CP) and comets, respectively. The concentration of glucose in the peripheral blood of the rats was measured by the Accu-Chek Active Kit due to increased CP in RCC. Results: In neonates, no modification of the biomarkers tested was detected. On the other hand, there was an increase in the levels of CP in the RCC of the 6-day-old ER. Interestingly, the concentration of blood glucose was decreased in this group. Conclusions: Our results indicate that there is no genotoxicity and oxidative stress in neonates and 6 days rats. However, the RCC had the highest concentration of CP that do not seem to be a consequence of oxidative stress. This study is the first to demonstrate the use of UHF-EMR causes different damage responses to proteins in the LCC and RCC. [ABSTRACT FROM AUTHOR]

Rationale: Alcohol addiction causes severe problems, and its deprivation may potentiate symptoms such as anxiety. Furthermore, ethanol is a neurotoxic agent that induces degeneration and the consequences underlying alcohol-mediated brain damage remain unclear. Objectives: This study assessed the behavioral changes during acute ethanol withdrawal periods and determined the levels of DNA damage and reactive oxygen species (ROS) in multiple brain areas. Methods: Male Wistar rats were subjected to an oral ethanol self-administration procedure with a forced diet where they were offered 8 % ( v/v) ethanol solution for 21 days followed by five repeated 24-h cycles alternating between ethanol withdrawal and re-exposure. Control animals received an isocaloric control diet without ethanol. Behavioral changes were analyzed on ethanol withdrawal days in the open-field (OF) and elevated plus-maze (EPM) tests within the first 6 h of ethanol deprivation. The pre-frontal cortex, hypothalamus, striatum, hippocampus, and cerebellum were dissected for alkaline and neutral comet assays and for dichlorofluorescein ROS testing. Results: The repeated intermittent ethanol access enhanced solution intake and alcohol-seeking behavior. Decreased exploratory activity was observed in the OF test, and the animals stretched less in the EPM test. DNA single-strand breaks and ROS production were significantly higher in all structures evaluated in the ethanol-treated rats compared with controls. Conclusions: The animal model of repeated intermittent ethanol access induced behavioral changes in rats, and this ethanol exposure model induced an increase in DNA single-strand breaks and ROS production in all brain areas. Our results suggest that these brain damages may influence future behaviors. [ABSTRACT FROM AUTHOR]

The pathogenesis and the progression of phenylketonuria (PKU), an inborn error of phenylalanine (Phe) metabolism, have been associated with oxidative damage. Moreover, it has been increasingly postulated the antioxidant properties of L-Carnitine (LC). The aim of this study was to verify the effect of LC on Phe-induced DNA damage. The in vitro effect of different concentrations of LC (15, 30, 120 and 150 μM) on DNA damage-induced by high phenylalanine levels (1000 and 2500 μM) was examined in white blood cells from normal individuals using the comet assay. Urinary 8-hydroxydeoguanosine (8-OHdG) levels, a biomarker of oxidative DNA damage, and plasmatic sulfhydryl content were measured in eight patients with classical PKU, under therapy with protein restriction and supplemented with a special formula containing LC, and in controls individuals. Both in vitro tested Phe concentrations (1000 and 2500 μM) have resulted in DNA damage index significantly higher than control group. The in vitro co-treatment with Phe and LC reduced significantly DNA damage index when compared to Phe group. The urinary excretion of 8-OHdG and plasmatic sulfhydryl content presented similar levels in both groups analyzed (controls and treated PKU patients). In treated PKU patients, urinary 8-OHdG levels were positively correlated with blood Phe levels and negatively correlated with blood LC concentration and plasmatic sulfhydryl content. The present work yields experimental evidence that LC can reduce the in vitro DNA injury induced by high concentrations of phenylalanine, as well as, allow to hypothesize that LC protect against DNA damage in patients with PKU. [ABSTRACT FROM AUTHOR]

The diphenyl ditelluride ( DPDT) is a prototype for the development of new biologically active molecules. In previous studies, DPDT showed an elevated cytotoxicity in Chinese hamster fibroblast (V79) cells but the mechanisms for reduction of cell viability still remain unknown. DPDT showed mutagenic properties by induction of frameshift mutations in bacterium Salmonella typhimurium and yeast Saccharomyces cerevisiae. This organotelluride also induced DNA strand breaks in V79 cells. In this work, we investigated the mechanism of DPDT cytotoxicity by evaluating the effects of this compound on cell cycle progression, apoptosis induction and topoisomerase I inhibition. Significant decrease of V79 cell viability after DPDT treatment was revealed by MTT assay. Morphological analysis showed induction of apoptosis and necrosis by DPDT in V79 cells. An increase of caspase 3/7 activity confirmed apoptosis induction. The cell cycle analysis showed an increase in the percentage of V79 cells in S phase and sub-G1 phase. The yeast strain deficient in topoisomerase I (Topo I) showed higher tolerance to DPDT compared with the isogenic wild-type strain, suggesting that the interaction with this enzyme could be involved in DPDT toxicity. The sensitivity to DPDT found in top3∆ strain indicates that yeast topoisomerase 3 (Top3p) could participate in the repair of DNA lesions induced by the DPDT. We also demonstrated that DPDT inhibits human DNA topoisomerase I (Topo I) activity by DNA relaxation assay. Therefore, our results suggest that the DPDT-induced cell cycle arrest and reduction in cell viability could be attributed to interaction with topoisomerase I enzyme. [ABSTRACT FROM AUTHOR]

In heart failure (HF), there is an imbalance between the production of reactive oxygen species and the synthesis of antioxidant enzymes, causing damage to the cardiovascular function and increased susceptibility to DNA damage. The aim of this study was to evaluate the influence of low-level laser therapy (LLLT) on parameters of oxidative stress and DNA damage in skeletal muscle and plasma of rats with HF. Wistar rats were allocated into six groups: 'placebo' HF rats (P-HF, n = 9), 'placebo' Sham rats (P-sham, n = 8), HF rats at a dose 3 J/cm of LLLT (3 J/cm-HF, n = 8), sham rats at a dose 3 J/cm of LLLT (3 J/cm-sham, n = 8), HF rats at a dose 21 J/cm of LLLT (21 J/cm-HF, n = 8) and sham rats at a dose 21 J/cm of LLLT (21 J/cm-sham, n = 8). Animals were submitted to a LLLT protocol for 10 days at the right gastrocnemius muscle. Comparison between groups showed a significant reduction in superoxide dismutase (SOD) activity in the 3 J/cm-HF group ( p = 0.03) and the 21 J/cm-HF group ( p = 0.01) compared to the P-HF group. 2′,7′-Dihydrodichlorofluorescein (DCFH) oxidation levels showed a decrease when comparing 3 J/cm-sham to P-sham ( p = 0.02). The DNA damage index had a significant increase either in 21 J/cm-HF or 21 J/cm-sham in comparison to P-HF ( p = 0.004) and P-sham ( p = 0.001) and to 3 J/cm-HF ( p = 0.007) and 3 J/cm-sham ( p = 0.037), respectively. Based on this, laser therapy appears to reduce SOD activity and DCFH oxidation levels, changing the oxidative balance in the skeletal muscle of HF rats. Otherwise, high doses of LLLT seem to increase DNA damage. [ABSTRACT FROM AUTHOR]

Background: The 3β, 6β, 16β-trihydroxylup-20(29)-ene (TTHL) is a pentacyclic triterpene obtained from the medicinal plant Combretum leprosum Mart. In folk medicine, this plant is popularly known as mofumbo, cipoaba or mufumbo, and is used to treat several diseases associated with inflammation and pain. Methods: We investigated the antitumor efficacy of TTHL isolated from C. leprosum. The TTHL cytotoxic effect was investigated in MRC5, MCF-7, HepG2, T24, HCT116, HT29, and CACO-2 cells after 24, 48, 72 and 120 h of treatment. The mechanisms of cell death and DNA damage induction were investigated by flow cytometry and comet assay, respectively. Results: The results indicated that TTHL induced a time- and concentration-dependent growth inhibition in all human cancer cell lines. The cytotoxicity was more pronounced in MCF-7 breast cancer cells, with an IC50 of 0.30 µg/mL at 120 h. We therefore evaluated the cell death mechanism induced by TTHL (IC20, IC50, and IC80) in MCF-7 cells at 24 h. We found that the treatment with IC50 and IC80 TTHL for 24 h induced apoptosis in 14% (IC50) and 52% (IC80) of MCF-7 cells. The apoptosis induced by TTHL was accompanied by increased levels of both cleaved caspase-9 and intracellular ROS. In order to further understand the biological mechanism of TTHL-induced cytotoxicity, we have also investigated its effect on different Saccharomyces cerevisiae yeast strains. The mutant strains sod1Δ, sod2Δ, and sod1Δsod2Δ, which are deficient in superoxide dismutase antioxidant defenses, were hypersensitive to TTHL, suggesting that its capacity to disturb cellular redox balance plays a role in drug toxicity. Moreover, TTHL induced mutagenicity in the yeast strain XV185-14c. Conclusions: Taken together, the results suggest that TTHL forms covalent adducts with cellular macromolecules, potentially disrupting cellular function and triggering apoptosis. [ABSTRACT FROM AUTHOR]

Lesions with great loss of skin and extensive burns are usually treated with heterologous skin grafts, which may lead rejection. Cell therapy with mesenchymal stem cells is arising as a new proposal to accelerate the healing process. We tested a new therapy consisting of sodium carboxymethylcellulose (CMC) as a biomaterial, in combination with adipose-derived stem cells (ADSCs), to treat skin lesions in an in vivo rat model. This biomaterial did not affect membrane viability and induced a small and transient genotoxicity, only at the highest concentration tested (40 mg/mL). In a rat wound model, CMC at 10 mg/mL associated with ADSCs increased the rate of cell proliferation of the granulation tissue and epithelium thickness when compared to untreated lesions (Sham), but did not increase collagen fibers nor alter the overall speed of wound closure. Taken together, the results show that the CMC is capable to allow the growth of ADSCs and is safe for this biological application up to the concentration of 20 mg/mL. These findings suggest that CMC is a promising biomaterial to be used in cell therapy. [ABSTRACT FROM AUTHOR]

We evaluated levels of neuronal DNA damage after acute or repeated cocaine treatment in different brain areas of female rats after ovariectomy or sham surgery. Rats in the control and acute groups were given saline i.p., whereas in the repeated group were given 15 mg/kg, i.p., cocaine for 8 days. After a 10 day washout period, the control group was given saline i.p., whereas rats in the acute and repeated groups were given a challenge dose of 15 mg/kg, i.p., cocaine. After behavioural assessment, rats were killed and the cerebellum, hippocampus, hypothalamus, prefrontal cortex and striatum were dissected for the Comet assay. Acute cocaine exposure induced DNA damage in all brain areas. This effect persisted after repeated administration, except in the hypothalamus, where repeated treatment did not cause increased DNA damage. Sexual hormones exhibited a neuroprotective effect, decreasing cocaine-induced DNA damage in cycling rats in all brain areas. [ABSTRACT FROM AUTHOR]

Purpose: To assess the effect of 950 MHz ultra-high-frequency electromagnetic radiation (UHF EMR) on biomarkers of oxidative damage, as well as to verify the concentration of unsaturated fatty acids (UFA) and the expression of the catalase in the livers of rats of different ages. Materials and methods: Twelve rats were equally divided into two groups as controls (CR) and exposed (ER), for each age (0, 6, 15 and 30 days). Radiation exposure lasted half an hour per day for up to 51 days (21 days of gestation and 6, 15 or 30 days of life outside the womb). The specific absorption rate (SAR) ranged from 1.3-1.0 W/kg. The damage to lipids, proteins and DNA was verified by thiobarbituric acid reactive substances (TBARS), protein carbonyls and comets, respectively. UFA were determined by gas chromatography with a flame ionization detector. The expression of catalase was by Western blotting. Results: The neonates had low levels of TBARS and concentrations of UFA after exposure. There was no age difference in the accumulation of protein carbonyls for any age. The DNA damage of ER 15 or 30 days was different. The exposed neonates exhibited lower expression of catalase. Conclusions: 950 MHz UHF EMR does not cause oxidative stress (OS), and it is not genotoxic to the livers of neonates or those of 6 and 15 day old rats, but it changes the concentrations of polyunsaturated fatty acid (PUFA) in neonates. For rats of 30 days, no OS, but it is genotoxic to the livers of ER to total body irradiation. [ABSTRACT FROM AUTHOR]

It has been shown that elevation of plasma methionine (Met) and its metabolites may occur in several genetic abnormalities. In this study we investigated the in vitro and in vivo effects of the Met and methionine sulfoxide (MetO) on oxidative stress parameters in the liver of rats. For in vitro studies, liver homogenates were incubated with Met, MetO, and Mix (Met + MetO). For in vivo studies, the animals were divided into groups: saline, Met 0.4 g/kg, MetO 0.1 g/kg, and Met 0.4 g/kg + MetO 0.1 g/kg. The animals were euthanized 1 and 3 h after injection. In vitro results showed that Met 1 and 2 mM and Mix increased catalase (CAT) activity. Superoxide dismutase (SOD) was enhanced by Met 1 and 2 mM, MetO 0.5 mM, and Mix. Dichlorofluorescein oxidation was increased by Met 1 mM and Mix. In vivo results showed that Met, MetO, and Mix decreased TBARS levels at 1 h. Total thiol content decreased 1 h after and increased 3 h after MetO and Met plus MetO administrations. Carbonyl content was enhanced by Met and was reduced by MetO 1 h after administration. Met, MetO and Met plus MetO decreased CAT activity 1 and 3 h after administration. Furthermore, only MetO increased SOD activity. In addition, Met, MetO, and Mix decreased dichlorofluorescein oxidation at 1 and 3 h. Our data indicate that Met/MetO in vivo and in vitro modify liver homeostasis by altering the redox cellular state. However, the hepatic changes caused by these compounds suggest a short-time adaptation of this tissue. [ABSTRACT FROM AUTHOR]

Platonia insignis Mart., a native species of the Brazilian Amazon more commonly known as bacuri, is a member of the Clusiaceae family. In this study, we evaluated the chemical composition and the antioxidant and toxicity activities of the dichloromethane and ethyl acetate fractions from P. insignis seed ethanolic extract using different experimental models. Our results demonstrate in vitro antioxidant effects, by 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid) diammonium salt and 1,1-diphenyl-2-picryl-hydrazyl assays, as well as in vivo effects in antioxidant-defective Saccharomyces cerevisiae strains to both fractions. Toxicity was evaluated against the micro-crustaceous Artemia salina Leach. and promastigote Leishmania amazonensis. The dichloromethane fraction was the most active fraction evaluated on A. salina and promastigote L. amazonensis (IC50 = 24.89 μg/mL and 2.84 μg/mL, respectively). In addition, a slight cytotoxicity was observed in mammalian V79 cells using ethyl acetate and dichloromethane fractions with MTT assays. Both fractions displayed genotoxicity up to 25 μg/mL (dichloromethane) and 10 μg/mL (ethyl acetate) in V79 cells, as evaluated by the alkaline comet assay. Thus, in this study, we demonstrate for the first time that ethyl acetate and dichloromethane fractions from P. insignis seeds display antioxidant effects, a toxic effect against A. salina and L. amazonensis and induce genotoxicity in V79 mammalian cells. The observed activities can be attributed to the phenolic compounds present in these fractions and to the presence of xanthones (alpha- and gamma-mangostin). [ABSTRACT FROM AUTHOR]

The development of new strategies for cancer therapeutics is indispensable for the improvement of standard protocols and the creation of other possibilities in cancer treatment. Yeast models have been employed to study numerous molecular aspects directly related to cancer development, as well as to determine the genetic contexts associated with anticancer drug sensitivity or resistance. The budding yeast Saccharomyces cerevisiae presents conserved cellular processes with high homology to humans, and it is a rapid, inexpensive and efficient compound screening tool. However, yeast models are still underused in cancer research and for screening of antineoplastic agents. Here, the employment of S. cerevisiae as a model system to anticancer research is discussed and exemplified. Focusing on the important determinants in genomic maintenance and cancer development, including DNA repair, cell cycle control and epigenetics, this review proposes the use of mutant yeast panels to mimic cancer phenotypes, screen and study tumor features and synthetic lethal interactions. Finally, the benefits and limitations of the yeast model are highlighted, as well as the strategies to overcome S. cerevisiae model limitations. [ABSTRACT FROM AUTHOR]

Adenosine diphosphate (ADP)-ribosylation is an important posttranslational modification catalyzed by a variety of enzymes, including poly (ADP ribose) polymerases (PARPs), which use nicotinamide adenine dinucleotide (NAD+) as a substrate to synthesize and transfer ADP-ribose units to acceptor proteins. The PARP family members possess a variety of structural domains, span a wide range of functions and localize to various cellular compartments. Among the molecular actions attributed to PARPs, their role in the DNA damage response (DDR) has been widely documented. In particular, PARPs 1–3 are involved in several cellular processes that respond to DNA lesions, which include DNA damage recognition, signaling and repair as well as local transcriptional blockage, chromatin remodeling and cell death induction. However, how these enzymes are able to participate in such numerous and diverse mechanisms in response to DNA damage is not fully understood. Herein, the DDR functions of PARPs 1–3 and the emerging roles of poly (ADP ribose) polymers in DNA damage are reviewed. The development of PARP inhibitors, their applications and mechanisms of action are also discussed in the context of the DDR. [ABSTRACT FROM AUTHOR]

Context: Platonia insignis Mart. (Clusiaceae), commonly known as 'bacuri,' is a timber and fruit native species of the Brazilian Amazon. Some plants of the Clusiaceae family have their pharmacological properties associated with the presence of xanthone and polycyclic polyprenylated acylphloroglucinols derivatives, which have antioxidant and anticarcinogenic activities. Objective: The aim of this study was to assess the in vivo potential of extracts, fractions, and garcinielliptone FC isolated from of Platonia insignis seeds as a natural antioxidant. Materials and methods: Male Wistar rats (250-280 g; 2 months old) were treated with Tween 80 0.05% dissolved in 0.9% saline (i.p, vehicle - control group), ethanol extract (EE), hexane extract (HE), dichloromethane fraction (DMF), ethyl acetate fraction (EAF), and garcinielliptone FC (GFC) isolated from P. insignis at doses 2 mg/kg (i.p.). All groups were observed for 24 h after the treatment. The antioxidant enzymatic activities [superoxide dismutase (SOD) and catalase (CAT)] were measured using spectrophotometric methods. Results: There were no marked alterations in SOD and CAT activities in rat hippocampus after pretreatment with EE, HE, DMF, EAF, and GFC. However, the pretreatment with GFC induced a significantly increase of 13, 17, 19, and 13% in SOD activities when compared to EE, HE, DMF, or EAF groups, respectively. Discussion and conclusion: Our findings strongly support the hypothesis that GFC isolated from P. insignis has a significant potential to be used as a natural antioxidant agent probably due to the modulation of enzymatic activity of hippocampal SOD. [ABSTRACT FROM AUTHOR]

The susceptibility of individuals to the genotoxic effect of pesticides can be modulated by genetic variations in the xenobiotic detoxification and DNA repair processes. This study evaluates if the two BER polymorphisms ( XRCC1Arg194Trp and OGG1Ser326Cys) or the combined genotypes of these polymorphisms with PON1Gln192Arg could modify individual susceptibility to pesticide exposure in vineyard workers, as measured by micronucleus formation and DNA damage induction in peripheral leukocytes. The study population comprised 108 agricultural workers exposed to pesticides and 65 nonexposed. Our results demonstrate that individuals with the variant allele ( OGG1Cys) showed higher DNA damage, detected by the comet assay, in relation to individuals carrying the wild-type OGG1Ser allele. Considering the combined influence of metabolizing PON1 and the DNA repair OGG1 genes, we observed significantly higher DNA damage in the comet assay in the exposed group when a less efficient OGG1Cys allele was acting independently of the PON1 genotype, reinforcing the importance of the OGG1 repair enzyme in the response to DNA damage by pesticide exposure. The association of the PONGln/Gln genotype with higher MN frequency suggests that the PON1 genotype is a major determinant of genotoxic risk in individuals exposed to pesticides. Analysis of the compared effect of XRCC1 and PON1 genotypes in the exposed group suggested that, among the poorly metabolizing PON1Gln/Gln individuals, the XRCC1Arg/Trp genotype has a protective effect with respect to MN formation. These results indicate that enhanced XRCC1 function may provide some protection from the enhanced genotoxic risk associated with inefficient xenobiotic detoxification in the studied population. Environ. Mol. Mutagen. 52:20-27, 2011. © 2010 Wiley-Liss, Inc. [ABSTRACT FROM AUTHOR]

Copyright of ConScientiae Saúde is the property of Nove de Julho University and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of ConScientiae Saúde is the property of Nove de Julho University and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Biflorin is a natural quinone isolated from Capraria biflora L. Previous studies demonstrated that biflorin inhibits in vitro and in vivo tumor cell growth and presents potent antioxidant activity. In this paper, we report concentration-dependent cytotoxic, genotoxic, antimutagenic, and protective effects of biflorin on Salmonella tiphymurium, yeast Saccharomyces cerevisiae, and V79 mammalian cells, using different approaches. In the Salmonella/microsome assay, biflorin was not mutagenic to TA97a TA98, TA100, and TA102 strains. However, biflorin was able to induce cytotoxicity in haploid S. cerevisiae cells in stationary and exponential phase growth. In diploid yeast cells, biflorin did not induce significant mutagenic and recombinogenic effects at the employed concentration range. In addition, the pre-treatment with biflorin prevented the mutagenic and recombinogenic events induced by hydrogen peroxide (HO) in S. cerevisiae. In V79 mammalian cells, biflorin was cytotoxic at higher concentrations. Moreover, at low concentrations biflorin pre-treatment protected against HO-induced oxidative damage by reducing lipid peroxidation and DNA damage as evaluated by normal and modified comet assay using DNA glycosylases. Our results suggest that biflorin cellular effects are concentration dependent. At lower concentrations, biflorin has significant antioxidant and protective effects against the cytotoxicity, genotoxicity, mutagenicity, and intracellular lipid peroxidation induced by HO in yeast and mammalian cells, which can be attributed to its hydroxyl radical-scavenging property. However, at higher concentrations, biflorin is cytotoxic and genotoxic. [ABSTRACT FROM AUTHOR]

Never in mitosis A (NIMA)-related kinases (Nek) are evolutionarily conserved proteins structurally related to the Aspergillus nidulans mitotic regulator NIMA. Nek1 is one of the 11 isoforms of the Neks identified in mammals. Different lines of evidence suggest the participation of Nek1 in response to DNA damage, which is also supported by the interaction of this kinase with proteins involved in DNA repair pathways and cell cycle regulation. In this report, we show that cells with Nek1 knockdown (KD) through stable RNA interference present a delay in DNA repair when treated with methyl-methanesulfonate (MMS), hydrogen peroxide (H2O2) and cisplatin (CPT). In particular, interstrand cross links induced by CPT take much longer to be resolved in Nek1 KD cells when compared to wild-type (WT) cells. InKDcells, phosphorylation of Chk1 in response to CPTwas strongly reduced. While WTcells accumulate in G2/M after DNA damage with MMS and H2O2, Nek1 KD cells do not arrest, suggesting that G2/M arrest induced by the DNA damage requires Nek1. Surprisingly, CPT-treated Nek1 KD cells arrest with a 4N DNA content similar to WT cells. This deregulation in cell cycle control in Nek1 KD cells leads to an increased sensitivity to genotoxic agents when compared to WT cells. These results suggest that Nek1 is involved in the beginning of the cellular response to genotoxic stress and plays an important role in preventing cell death induced by DNA damage. [ABSTRACT FROM AUTHOR]

Anthracyclines have been widely used as antitumor agents, playing a crucial role in the successful treatment of many types of cancer, despite some side effects related to cardiotoxicity. New anthracyclines have been designed and tested, but the first ones discovered, doxorubicin and daunorubicin, continue to be the drugs of choice. Despite their extensive use in chemotherapy, little is known about the DNA repair mechanisms involved in the removal of lesions caused by anthracyclines. The anthracycline cosmomycin D is the main product isolated from Streptomyces olindensis, characterized by a peculiar pattern of glycosylation with two trisaccharide rings attached to the A ring of the tetrahydrotetracene. We assessed the induction of apoptosis (Sub-G1) by cosmomycin D in nucleotide excision repair-deficient fibroblasts (XP-A and XP-C) as well as the levels of DNA damage (alkaline comet assay). Treatment of XP-A and XP-C cells with cosmomycin D resulted in apoptosis in a time-dependent manner, with highest apoptosis levels observed 96 h after treatment. The effects of cosmomycin D were equivalent to those obtained with doxorubicin. The broad caspase inhibitor Z-VAD-FMK strongly inhibited apoptosis in these cells, and DNA damage induced by cosmomycin D was confirmed by alkaline comet assay. Cosmomycin D induced time-dependent apoptosis in nucleotide excision repair-deficient fibroblasts. Despite similar apoptosis levels, cosmomycin D caused considerably lower levels of DNA damage compared to doxorubicin. This may be related to differences in structure between cosmomycin D and doxorubicin. [ABSTRACT FROM AUTHOR]

Vitamin A (Vit A) is widely suggested to be protective against oxidative stress. However, different studies have been demonstrated the pro-oxidant effects of retinoids in several experimental models. In this work, we used the yeast Saccharomyces cerevisiae as a model organism to study the Vit A effects on superoxide dismutase (SOD)-deficient yeast strains. We report here that Vit A (10, 20 and 40 mg/ml) decreases the survival of exponentially growing yeast cells, especially in strains deficient in CuZnSOD ( sod1Δ) and CuZnSOD/MnSOD ( sod1Δ sod2Δ). We also observed the protective effect of vitamin E against the Vit A-induced toxicity. Possible adaptation effects induced by sub-lethal oxidative stress were monitored by pre-, co- and post-treatment with the oxidative agent paraquat. The enzymatic activities of catalase (CAT) and glutathione peroxidase (GPx), and the total glutathione content were determined after Vit A treatment. Our results showed that CuZnSOD represents an important defence against Vit A-generated oxidative damage. In SOD-deficient strains, the main defence against Vit A-produced reactive oxygen species (ROS) is GPx. However, the induction of GPx activity is not sufficient to prevent the Vit A-induced cell death in these mutants in exponential phase growth. [ABSTRACT FROM AUTHOR]

The article focuses on a research which investigated the cytotoxic effects of 5-fluorouracil (5-FU) and its active metabolite fluorodeoxyuridine monophosphate (FdUMP) to the DNA in human SW620 colon adenocarcinoma cell line. It analyzed the ability of %-FU and FdUMP to influence the cell cycle progression in human colon SW620 adenocarcinoma cells in regards to genotoxic and clastogenic activities. It is revealed that 5-FU induces Single-sideband modulation (SSB), double-strand breaks (DSBs) and apoptosis which create DNA damage in human SW620 colon adenocarcinoma than FdUMP.

In order to extend the understanding of the genetical and biochemical basis of photo-activated psoralen-induced DNA repair in the yeast Saccharomyces cerevisiae we have identified and cloned 10 pso mutants. Here, we describe the phenotypic characterization and molecular cloning of the pso10-1 mutant which is highly sensitive to photoactivated psoralens, UV254 nm radiation and the alkylating agent methylmethane sulphonate. The pso10-1 mutant allele also confers a block in the mutagenic response to photoactivated psoralens and UV254 nm radiation, and homoallelic diploids do not sporulate. Molecular cloning using a yeast genomic library, sequence analysis and genetic complementation experiments proved pso10-1 to be a mutant allele of gene MMS21 that encodes a SUMO ligase involved in the sumoylation of several DNA repair proteins. The ORF of pso10-1 contains a single nucleotide C→T transition at position 758, which leads to a change in amino acid sequence from serine to phenylalanine [S253F]. Pso10-1p defines a leaky mutant phenotype of the essential MMS21 gene, and as member of the Smc5-Smc6 complex, still has some essential functions that allow survival of the mutant. DNA repair via translesion synthesis is severely impaired as the pso10-1 mutant allele confers severely blocked induced forward and reverse mutagenesis and shows epistatic interaction with a rev3Δ mutant allele. By identifying the allelism of PSO10 and MMS21 we demonstrate the need of a fully functional Smc5-Smc6 complex for a WT-like adequate repair of photoactivated psoralen-induced DNA damage in yeast. [ABSTRACT FROM AUTHOR]

The article examines the antioxidant properties of brachycerine and a crude foliar extract from P. brachyceras as a possible protective agent against the secondary effect of radiation. Strains of Sacchromyces cerevisiae have been used in evaluating the proficiency and deficiency in antioxidant defenses. Likewise, the mutagenic and antimutagenic possibility have been analyzed. Results of the study reveal that brachycerine and the crude foliar extract of P.brachyceras have antioxidant and antimutagenic effects.

Much has been published on the non-enzymatic antioxidant L-ascorbic acid (vitamin C), but even so its interaction with endogenous cellular defense systems has not yet been fully elucidated. Our study investigated the antioxidant activity of L-ascorbic acid in wild-type strain EG103 (SOD) Saccharomyces cerevisiae and isogenic mutant strains deficient in cytosolic superoxide dismutase (sod1Δ), mitochondrial superoxide dismutase (sod2Δ) or both (sod1Δsod2Δ), metabolizing aerobically or anaerobically with and without the stressing agent paraquat. The results show that during both aerobic and anaerobic metabolism there was a significant increase in the survival of both wild-type S. cerevisiae cells and the mutant cells (sod1Δ, sod2Δ and sod1Δsod2Δ) when pretreated with L-ascorbic acid before exposure to paraquat. Exposure to paraquat resulted in higher catalase activity but this significantly decreased when the cells were pre-treated with L-ascorbic acid. These results demonstrate that due to the damage caused by paraquat, the antioxidant protection of L-ascorbic acid seems to be mediated by catalase levels in yeast cells. [ABSTRACT FROM AUTHOR]

The Saccharomyces cerevisiae Sgs1 protein, together with Schizosaccharomyces pombe Rqh1 and the human Bloom and Werner proteins, is a DNA helicase of the Escherichia coli RecQ family. Mutation of SGS1 causes premature aging in yeast cells, including the accumulation of extrachromosomal rDNA circles. We have recently shown that Sgs1p interacts with the DNA repair Rad16p protein and is epistatic to Rad16p for UVC, 4-NQO and H2O2 lesions. Therefore we tested sgs1 strains containing mutations in the helicase and C-terminal domains. We demonstrate here that the helicase activity of the Sgs1 is important for most elements of the sgs1 mutation phenotype, including sensitivity to UVC, 4-NQO, H2O2, MMS and hydroxyurea. [ABSTRACT FROM AUTHOR]

Simple Summary: Colorectal cancer (CRC) is among the most common cancers and the third leading cause of cancer deaths worldwide. Despite the identification of alterations in DNA repair genes and the resulting genomic instability in sub-populations of CRC, therapies that exploit defects in DNA repair pathways or high level of replicative stress have been explored only in breast, ovarian, and other tumor types, but not yet systematically in CRC. Here, we discuss how targeting genes involved in the responses to replication stress and the repair of DNA double-strand breaks (DSBs) could provide new therapeutic opportunities to treat CRCs and have the potential to confer increased sensitivity to current chemotherapy regimens, thus, expanding the spectrum of therapy options, and potentially improving clinical outcomes for CRC patients. Despite the ample improvements of CRC molecular landscape, the therapeutic options still rely on conventional chemotherapy-based regimens for early disease, and few targeted agents are recommended for clinical use in the metastatic setting. Moreover, the impact of cytotoxic, targeted agents, and immunotherapy combinations in the metastatic scenario is not fully satisfactory, especially the outcomes for patients who develop resistance to these treatments need to be improved. Here, we examine the opportunity to consider therapeutic agents targeting DNA repair and DNA replication stress response as strategies to exploit genetic or functional defects in the DNA damage response (DDR) pathways through synthetic lethal mechanisms, still not explored in CRC. These include the multiple actors involved in the repair of DNA double-strand breaks (DSBs) through homologous recombination (HR), classical non-homologous end joining (NHEJ), and microhomology-mediated end-joining (MMEJ), inhibitors of the base excision repair (BER) protein poly (ADP-ribose) polymerase (PARP), as well as inhibitors of the DNA damage kinases ataxia-telangiectasia and Rad3 related (ATR), CHK1, WEE1, and ataxia-telangiectasia mutated (ATM). We also review the biomarkers that guide the use of these agents, and current clinical trials with targeted DDR therapies. [ABSTRACT FROM AUTHOR]

A putative tolerance, induced by heat shock (HS), to the lethal and mutagenic effects of 8-methoxypsoralen (8-MOP) photoaddition and hyperthermia was analyzed in Saccharomyces cerevisiae using the wild-type strain N123 and the isogenic DNA repair-deficient mutant pso3-1. In wild-type cells, the HS (38°C for 1 h) did not modify either the survival or the mutation frequency observed after 8-MOP photoaddition, even though it conferred protection against the lethal effect of hyperthermia (50°C). In the pso3-1 mutant, HS induced an increase of the survival, and a decrease of the mutation frequency, after 8-MOP photoaddition and it also protected against the lethal effect of hyperthermia. The responses induced by HS were specific for 8-MOP photoaddition, since they were not observed after 254 nm ultraviolet-light damage. These results indicate that the protection conferred by HS depends of the type of lesion, and operates through the induction of different repair processes. In the pso3-1 mutant, HS could channel the repair intermediates to and error-free repair pathway. [ABSTRACT FROM AUTHOR]