We investigated the protective effect of a natural polyphenol, magnolol, on Saccharomyces cerevisiae cells under oxidative stress, and during aging. Our results showed the sensitivity of S. cerevisiae antioxidant gene deficient mutants (sod1∆, sod2∆, cta1∆, ctt1∆, gtt2∆ and tsa1∆) against hydrogen peroxide (H2O2) and menadione stress was rescued by magnolol as demonstrated in spot and colony forming unit counts. Yeast cells pretreated with magnolol showed decreased intracellular oxidation, lipid peroxidation and an increased level of reduced glutathione. Further, SOD1, CTA1 and GTT2 gene expression was examined by reverse transcription-polymerase chain reaction, and was found that magnolol significantly attenuated the upregulation of SOD1 and CTA1 genes under oxidative stress. Finally, longevity of the wild type and sod1 mutant cells were extended by magnolol, and also enhance stress resistance against oxidant stress during chronological aging.
In the present study, galactan exopolysaccharide (EPS) from Weissella confusa KR780676 was evaluated for its potential to alleviate oxidative stress using in vitro assays and in vivo studies in Saccharomyces cerevisiae (wild type) and its antioxidant (sod1∆, sod2∆, tsa1∆, cta2∆ and ctt1∆), anti-apoptotic (pep4∆ and fis1∆) and anti-aging (sod2∆, tsa1∆ and ctt1∆)) isogenic gene deletion mutants. Galactan exhibited strong DPPH and nitric oxide scavenging activity with an IC50 value of 450 and 138 µg/mL respectively. In the yeast mutant model, oxidative stress generated by H2O2 was extensively scavenged by galactan in the medium as confirmed using spot assays followed by fluorescencent DCF-DA staining and microscopic studies. Galactan treatment resulted in reduction in the ROS generated in the yeast mutant cells as demonstrated by decreased fluorescence intensity. Furthermore, galactan exhibited protection against oxidative damage through H2O2 -induced apoptosis inhibition in the yeast mutant strains (pep4∆ and fis1∆) leading to increased survival rate by neutralizing the oxidative stress. In the chronological life span assay, WT cells treated with galactan EPS showed 8% increase in viability whereas sod2∆ mutant showed 10–15% increase indicating pronounced anti-aging effects. Galactan from W. confusa KR780676 has immense potential to be used as a natural antioxidant for nutraceutical, pharmaceutical and food technological applications. As per our knowledge, this is the first report on in-depth assessment of in vivo antioxidant properties of a bacterial EPS in a yeast deletion model system.
Taxol has been regarded as one of the most successful anti-cancer drugs identified from natural sources to date. Although taxol is known to sensitize cells by stabilizing microtubules, its ability to cause DNA damage in peripheral blood lymphocytes, and to induce oxidative stress and apoptosis indicates that taxol may have other modes of cytotoxic action. This study focuses on identifying the additional targets of taxol that may contribute to its multifaceted cell killing property, using Saccharomyces cerevisiae. We show that yeast oxidative stress response mutants (sod1Δ, tsa1Δ and cta1Δ) and DNA damage response mutants (mre11∆, sgs1∆ and sub1∆) are highly sensitive to Taxol. Our results also show that taxol increases the level of reactive oxygen species (ROS) in yeast oxidative stress response mutant strains. Further, 4ʹ,6-Diamidino-2ʹ-phenylindole (DAPI) and acridine orange/ethidium bromide (AO/EB) staining show that taxol induces apoptotic features such as nuclear fragmentation and chromatin condensation in DNA repair mutants. On the whole, our results suggest that taxol's cytotoxic property is attributed to its multifaceted mechanism of action.
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