Pulsed magnetic field increases the effect of ultraviolet C radiation and thermal shock in aged yeasts.

The study of the effects of the magnetic field (MF) on living matter continues to be a dilemma. Until now, the interaction mechanisms of MF with living matter that explain the observed phenomena are unknown. Despite the existing literature and the multiple effects described to date, there are few published articles that study the combined effect of MF with other physical agents during the cellular aging process. In this sense, the aim of this work is to study whether low frequency and intensity pulsed and sinusoidal MF exposure produce alterations in the cell killing effect of ultraviolet C (UVC) radiation and thermal shock during the chronological aging of S. cerevisiae. Yeast cells were exposed to 2.45 mT (50 Hz) sinusoidal MF and 1.5 mT (25 Hz) pulsed MF, during 40 days of aging, in combination with UVC radiation (50 J/m2) and/or thermal shock (52°C). Cell survival was evaluated by clonogenic assay. The exposure of yeast to pulsed MF produces an acceleration of aging, which is not observed in cells exposed to sinusoidal MF. The pulsed MF modifies the cellular response to damaging agents only in aged S. cerevisiae cells. In this sense, the pulsed MF applied increases the damage induced by UVC radiation and by thermal shock. In contrast, the sinusoidal MF used has no effect.

Exposure of S. cerevisiae to pulsed magnetic field during chronological aging could induce genomic DNA damage.

This study evaluates the DNA damage induced by pulsed magnetic field (MF) on S. cerevisiae cells exposed during chronological aging. Samples were exposed to 25 Hz pulsed MF (1.5mT, 8 h/day) while cells were aging chronologically. Clonogenic drop test was used to study cellular survival and the mutation frequency was evaluated by scoring the spontaneous revertant mutants. DNA damage analysis was performed after aging by electrophoresis and image analysis. Yeast cells aged during 40 days of exposure showing that pulsed MF exposure induced a premature aging. In addition, a gradual increase in spontaneous mutants was found in pulsed MF samples in relation to unexposed controls. An increase in DNA degradation, over the background level in relation to controls, was observed at the end of the exposure period. In conclusion, exposure of S. cerevisiae cells to pulsed MF during chronological aging could induce genomic DNA damage.

Identification of new proteins related with cisplatin resistance in Saccharomyces cerevisiae.

The aim of this study is to select a cisplatin-resistant Saccharomyces cerevisiae strain to look for new molecular markers of resistance and the identification of mechanisms/interactions involved. A resistant strain was obtained after 80 days of cisplatin exposure. Then, total protein extraction, purification, and identification were carried out, in wild-type (wt) and resistant strains, by tandem mass spectrometry using a "nano HPLC-ESI-MS/MS" ion trap system. The increase in the exponentially modified protein abundance index (emPAI) (resistant vs wt strains) was calculated to study the increase in protein expression. "Genemania" software ( http://www.Genemania.org/ ) was used to compare the effects, functions, and protein interactions. KEGG tool was used for metabolic pathway analysis. Data are available via ProteomeXchange with identifier PXD020665. The cisplatin-resistant strain showed 2.5 times more resistance than the wt strain for the inhibitory dose 50% (ID50) value (224 µg/ml vs 89.68 µg/ml) and 2.78 times more resistant for the inhibitory dose 90% (ID90) value (735.2 µg/ml vs 264.04 µg/ml). Multiple deregulated proteins were found in the glutathione and carbon metabolism, oxidative phosphorylation, proteasome, glycolysis and gluconeogenesis, glyoxylate metabolism, fatty acid degradation pathway, citric acid cycle, and ribosome. The most overexpressed proteins in the cisplatin-resistant strain were related to growth and metabolism (QCR2, QCR1, ALDH4, ATPB, ATPA, ATPG, and PCKA), cell structure (SCW10), and thermal shock (HSP26). The results suggest that these proteins could be involved in cisplatin resistance. The resistance acquisition process is complex and involves the activation of multiple mechanisms that interact together. KEY POINTS: • Identification of new proteins/genes related to cisplatin resistance • Increased expression of QCR2/QCR1/ALDH4/ATPB/ATPA/SCW10/HSP26/ATPG and PCKA proteins • Multiple molecular mechanisms that interact together are involved in resistance.

Long-term exposure to a pulsed magnetic field (1.5 mT, 25 Hz) increases genomic DNA spontaneous degradation.

The aim of this work is to investigate whether long-term pulsed magnetic field (MF) has genotoxic activity by induction of DNA damage on DNA molecules in vitro, in the absence of repair mechanisms. Yeast genomic DNA prepared by phenol extraction from S. cerevisiae cultures and the commercial DNA molecular weight marker Hyperladder I (HL-I) were exposed to 1.5 mT peak, pulsed 25 Hz MF, 8 h/day, 16 days. The total content of DNA (undamaged and damaged DNA) decreased during the exposure of genomic DNA to MF. On day 16 of exposure the DNA content was 41 ± 8.1%. In addition, the undamaged DNA decreases until 6.2 ± 3.1% for unexposed control samples and until 0.3 ± 0.1% for pulsed MF-treated samples at day 16 of exposure. Therefore, the pulsed MF induced at day 16 an increase of 20.7-fold more degradation of DNA molecules >10 000 bp (undamaged DNA) than that observed for unexposed control samples. However, no effect was observed for HL-I DNA marker exposures. We conclude that long-term exposure to a pulsed MF (1.5 mT peak, 25 Hz, 8 h/day, 16 days) induces an increment in the DNA spontaneous degradation of yeast genomic DNA.

Genomic DNA damage induced by co-exposure to DNA damaging agents and pulsed magnetic field.

PURPOSE: Many articles describe the effects of extremely low-frequency magnetic fields (MFs) on DNA damage induction. However, the mechanism of MF interaction with living matter is not yet known with certainty. Some works suggest that MF could induce an increase in the efficacy of reactive oxygen species (ROS) production. This work investigates whether pulsed MF exposure produces alterations in genomic DNA damage induced by co-exposure to DNA damaging agents (bleomycin and methyl methanesulfonate (MMS)). MATERIALS AND METHODS: Genomic DNA, prepared from S. cerevisiae cultures, was exposed to pulsed MF (1.5 mT peak, 25 Hz) and MMS (0-1%) (15-60 min), and to MF and bleomycin (0-0.6 IU/mL) (24-72 h). The damage induced to DNA was evaluated by electrophoresis and image analysis. RESULTS: Pulsed MF induced an increment in the level of DNA damage produced by MMS and bleomycin in all groups at the exposure conditions assayed. CONCLUSIONS: Pulsed MF could modulate the cytotoxic action of MMS and bleomycin. The observed effect could be the result of a multifactorial process influenced by the type of agent that damages DNA, the dose, and the duration of the exposure to the pulsed MF.

Effect of sinusoidal and pulsed magnetic field exposure on the chronological aging and cellular stability of S. cerevisiae.

Purpose: The aim of this study is to investigate the effects of low frequency and intensity sinusoidal magnetic field (SMF) and pulsed magnetic field (PMF) exposure on the chronological aging and cellular stability of Saccharomyces cerevisiae.Materials and methods: The S. cerevisiae wild type strain (WS8105-1C) was exposed to SMF (2.45 mT, 50 Hz, continuous) and PMF (1.5 mT, 25 Hz, 8 h/day). Chronological aging was evaluated during 40 days. Survival was assayed by clonogenic assay and drop test. Cellular stability was studied by spontaneous mutation count and the index of respiratory competence (IRC).Results: We found that exposure to PMF produces an acceleration of cellular chronological aging, not observed in the groups treated with SMF. A decrease in the spontaneous frequency of mitochondrial mutation during aging was observed in PMF-treated samples. However, no alterations in the IRC during aging were found for both, SMF and PMF, treatments.Conclusions: Exposure to PMF produces the acceleration of aging and an alteration in cellular stability.

Inactivation of RAD52 and HDF1 DNA repair genes leads to premature chronological aging and cellular instability.

The present study aims to investigate the role of radiation sensitive 52 (RAD52) and high-affinity DNA binding factor 1 (HDF1) DNA repair genes on the life span of budding yeasts during chronological aging. Wild type (wt) and rad52, hdf1, and rad52 hdf1 mutant Saccharomyces cerevisiae strains were used. Chronological aging and survival assays were studied by clonogenic assay and drop test. DNA damage was analyzed by electrophoresis after phenol extraction. Mutant analysis, colony forming units and the index of respiratory competence were studied by growing on dextrose and glycerol plates as a carbon source. Rad52 and rad52 hdf1 mutants showed a gradual decrease in surviving fraction in relation to wt and hdf1 mutant during aging. Genomic DNA was spontaneously more degraded during aging, mainly in rad52 mutants. This strain showed an increased percentage of revertant colonies. Moreover, all mutants showed a decrease in the index of respiratory competence during aging. The inactivation of RAD52 leads to premature chronological aging with an increase in DNA degradation and mutation frequency. In addition, RAD52 and HDF1 contribute to maintain the metabolic state, in a different way, during chronological aging. The results obtained could have important implications in the chronobiology of aging.