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AbstractBackground: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.

Background and Objective: Gamma-decanolactone (GD) is a monoterpene effective against seizures induced by pentylenetetrazole. The mechanism of action of GD is likely to be via glutamate antagonism. GD also inhibits intracellular reactive oxygen species (ROS) generation and the lipopolysaccharide-induced expression of inducible nitric oxide synthase (iNOS) and tumor necrosis factor-alpha (TNF-α) in vitro. Considering the neuropharmacological profile of GD studied so far, we investigated the effect of intraperitoneal administration of GD 100 and 300 mg/kg on pilocarpine (PIL)-induced status epilepticus (SE) in mice. Methods: GD was administered 30 min before PIL. Behavioral (latency to first seizure and the percentage of clonic forelimb seizures), biochemical, and oxidative stress parameters were evaluated. DNA damage in the cerebral cortex of mice was assessed using the comet assay and mutagenic activity of GD was evaluated using Salmonella/microsome assay in TA100, TA98, TA97a, TA102, and TA1535 strains, with and without metabolic activation (S9 mix). Results: The behavioral results showed that only the latency to the first clonic seizure increased in the groups treated with GD 300 mg/kg, but not when the animals received GD 100 mg/kg. Both GD doses were able to increase superoxide dismutase and catalase activities, inducing a decrease in ROS and nitrite production and in DNA damage in the cerebral cortex. GD was not able to induce base pair substitution and frameshift mutations in the absence or in the presence of metabolic activation. Conclusion: These findings demonstrate that GD does not improve behavioral parameters in the PIL model, but it was able to protect seizure-related oxidative stress and DNA damage in mice, without inducing gene mutations.

Kin3 is a nonessential serine/threonine protein kinase of the budding yeast Saccharomycescerevisiaewith unknown cellular role. It is an ortholog of the Aspergillus nidulansprotein kinase NIMA (Never-In Mitosis, gene A), which is involved in the regulation of G2/M phase progression, DNA damage response and mitosis. The aim of this study was to determine whether Kin3 is required for proper checkpoint activation and DNA repair. Here we show that KIN3gene deficient cells present sensitivity and fail to arrest properly at G2/M-phase checkpoint in response to the DNA damage inducing agents MMS, cisplatin, doxorubicin and nitrogen mustard, suggesting that Kin3 can be involved in DNA strand breaks recognition or signaling. In addition, there is an increase in KIN3gene expression in response to the mutagenic treatment, which was confirmed by the increase of Kin3 protein. We also showed that co-treatment with caffeine induces a slight increase in the susceptibility to genotoxic agents in kin3cells and abolishes KIN3gene expression in wild-type strain, suggesting that Kin3p can play a role in Tel1/Mec1-dependent pathway activation induced after genotoxic stress. These data provide the first evidence of the involvement of S. cerevisiaeKin3 in the DNA damage response.

The interaction trap method was used to isolate putative binding partners of Rad16/Pso5, a protein responsible for repair of silent DNA. One of the interactors found was Sgs1, a DNA helicase influencing the life span of Saccharomyces cerevisiae, with homology to the human BLM, WRN and RECQL4 proteins. Using the same fusion proteins from the two-hybrid screening, we show evidence that both proteins also interact in vitro. We tested isogenic strains, containing mutant alleles of the two genes in single and double mutant combination, for phenotypic similarity. Life span in sgs1Δ single and sgs1Δ rad16Δ double mutants is about 40% of that of WT, and the rad16/pso5Δ single mutant also had its life span reduced to 75%. Sensitivity to different mutagens, whose lesions are poorly repaired in rad16/pso5Δ mutants, was tested in sgs1Δ mutants. The sgs1Δ conferred sensitivity to MMS, H2O2and was moderately sensitive to UV254nm(UVC) and 4-NQO. An epistatic interaction between rad16and sgs1mutations after UVC, 4-NQO and H2O2was observed. Moreover, we found that in a top3background, functional Sgs1p and Rad16p apparently channel MMS, 4-NQO and H2O2induced lesions into aberrant DNA repair. Our results demonstrate that Sgs1 is not only involved in genome stability, somatic recombination and aging, but is also implicated, together with Rad16/Pso5, in the repair of specific DNA damage.

Escherichia coliendonuclease III (endo III) is the key repair enzyme essential for removal of oxidized pyrimidines and abasic sites. Although two homologues of endo III, Ntg1 and Ntg2, were found in Saccharomyces cerevisiae, they do not significantly contribute to repair of oxidative DNA damage in vivo. This suggests that an additional activity(ies) or a regulatory pathway(s) involved in cellular response to oxidative DNA damage may exist in yeast. The pso3-1mutant of S. cerevisiaewas previously shown to be specifically sensitive to toxic effects of hydrogen peroxide (H2O2) and paraquat. Here, we show that increased DNA double strand breakage is very likely the basis of sensitivity of the pso3-1mutant cells to H2O2. Our results, thus, indicate an involvement of the Pso3 protein in protection of yeast cells from oxidative stress presumably through its ability to prevent DNA double strand breakage. Furthermore, complementation of the repair defects of the pso3-1mutant cells by E. coliendo III has been examined. It has been found that expression of the nthgene in the pso3-1mutant cells recovers survival, decreases mutability and protects yeast genomic DNA from breakage following H2O2treatment. This might suggest some degree of functional similarity between Pso3 and Nth.

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.