Growth on Alpha-Ketoglutarate Increases Oxidative Stress Resistance in the Yeast Saccharomyces cerevisiae

Alpha-ketoglutarate (AKG) is an important intermediate in cell metabolism, linking anabolic and catabolic processes. The effect of exogenous AKG on stress resistance in S. cerevisiae cells was studied. The growth on AKG increased resistance of yeast cells to stresses, but the effects depended on AKG concentration and type of stressor. Wild-type yeast cells grown on AKG were more resistant to hydrogen peroxide, menadione, and transition metal ions (Fe2+ and Cu2+) but not to ethanol and heat stress as compared with control ones. Deficiency in SODs or catalases abolished stress-protective effects of AKG. AKG-supplemented growth led to higher values of total metabolic activity, level of low-molecular mass thiols, and activities of catalase and glutathione reductase in wild-type cells compared with the control. The results suggest that exogenous AKG may enhance cell metabolism leading to induction of mild oxidative stress. It turn, it results in activation of antioxidant system that increases resistance of S. cerevisiae cells to H2O2 and other stresses. The presence of genes encoding SODs or catalases is required for the expression of protective effects of AKG

CONCENTRATION-DEPENDENT EFFECTS OF RHODIOLA ROSEA ON LONGTERM SURVIVAL AND STRESS RESISTANCE OF YEAST SACCHAROMYCES CEREVISIAE: THE INVOLVEMENT OF YAP 1 AND MSN2/4 REGULATORY PROTEINS

Concentration-dependent effects of aqueous extract from R. rosea root on long-term survival and stress resistance of budding yeast Saccharomyces cerevisiae were studied. At low concentrations, R. rosea aqueous extract extended yeast chronological lifespan, enhanced oxidative stress resistance of stationary-phase cells and resistance to number stressors in exponentially growing cultures. At high concentrations, R. rosea extract sensitized yeast cells to stresses and shortened yeast lifespan. These biphasic concentration-responses describe a common hormetic phenomenon characterized by a low-dose stimulation and a high-dose inhibition. Yeast pretreatment with low doses of R. rosea extract enhanced yeast survival and prevented protein oxidation under H2O2-induced oxidative stress. Positive effect of R. rosea extract on yeast survival under heat shock exposure was not accompanied with changes in antioxidant enzyme activities and levels of oxidized proteins. The deficiency in transcriptional regulators, Msn2/Msn4 and Yap1, abolished the positive effect of low doses of R. rosea extract on yeast viability under stress challenges. Potential involvement of Msn2/Msn4 and Yap1 regulatory proteins in realization of R. rosea beneficial effects is discussed

Effects of Feeding with Non-Autoclaved and Autoclaved Fructose-Arginine Mixture on Stress Resistance of Drosophila Melanogaster

The diet of modern people includes fast food that leads to the development of obesity and related diseases. One of the reasons for the negative impact of such a diet is advanced glycation end products (AGEs), substances formed as a result of the interaction of amino acids with carbohydrates, especially under the influence of high temperature (the Maillard reaction). Once in the body, these substances lead to oxidative stress and inflammation, which in turn can accelerate aging process. Also, AGEs are involved in the development of metabolic syndrome, diabetes, cardiovascular disease, and cancer. However, mild oxidative stress can activate cellular defense systems and make cells more resistant to a stronger oxidative stress or other types of stress that is called hormesis or cross-tolerance. Our study shows an effect of non-autoclaved (FAMn) and autoclaved (FAMa) fructose-arginine mixtures on the body of fruit flies. In our study, we used the Drosophila melanogaster line w1118. Flies were grown on nutrient medium with the addition of different amounts of FAMn or FAMa to the final concentrations of reagents in a mixture of 10, 20 and 100 mM and maintained on the respective media until the second day of age. The flies were then used to determine physiological and biochemical parameters. The increase in absorbance at 294 nm and 420 nm and a decrease in fructose concentration in FAMa indicated that autoclaving of the fructose-arginine mixture led to caramelization of fructose and formation of Maillard products. The study showed that FAM in both forms did not affect lipid peroxide level, a marker of oxidative stress. Also, FAM in both forms did not affect the resistance of flies to hydrogen peroxide. However, FAMn, but not FAMa, increased the resistance of flies to sodium nitroprusside (SNP). This effect is likely caused by the presence of arginine, a substrate for NO-synthase, which may pre-adapt flies to •NO released from SNP. FAMn and FAMa at the concentration of 100 mM increased content of storage lipids, but decreased resistance of flies to starvation

Interuniversity Online Courses as Possible Approach to Improve Teaching During Crisis: a Ukrainian Case Study

The war launched by Russia has created new challenges for universities, including massive student migration abroad and massive displacement of students within Ukraine from the frontline areas. Many students lost access to quality education or had their studies interrupted by the war. Recognizing these problems, universities are trying to find different solutions. One such approach may be to introduce inter-university online courses that will be recognized by partner universities. In this case study, we analyze the effectiveness of inter-university online courses as an approach to restoring education for students severely affected by the war and as a way to maintain the quality of education in small groups at universities. The online course "Integrated Life Science Course" was taken for analysis, which was taught both to biology students from different universities in Ukraine within the framework of the educational project supported by German Academic Exchange Service (DAAD). Using statistics on course registration and attendance, as well as interview methodology, we assessed students' motivation to participate in this online course, course satisfaction, and learning outcomes, and identified shortcomings and pitfalls to avoid in similar courses. The survey and the results of the final test show that the main motivator for students to register and study at the course was the desire to gain new knowledge for further professional growth. A scholarship was also an important argument to enroll in the course; however, it did not impact the motivation of students to study. The fraction of students that successfully passed the final exam (~70%) was equal in the cohorts that had and had not been awarded scholarships. Thus, the scholarship was not a motivator to complete the course and successfully pass the exam to receive the certificate. Therefore, in order for such courses to be productive and effective, it is necessary to emphasize student motivation during selecting procedure

Effects of alpha-ketoglutarate on lifespan and functional aging of Drosophila melanogaster flies

The effects of an alpha-ketoglutarate-supplemented diet on lifespan and functional senescence were evaluated in the Canton S strain of Drosophila melanogaster. The results suggest that effects of dietary alpha-ketoglutarate (AKG) are dose- and gender-dependent. In males, diets containing 1-10 mM AKG did not affect mean and maximum lifespans, except that an increased maximum lifespan observed at 10 mM AKG. Diet with 20 mM AKG shortened median lifespan and had no effect on maximum lifespan of males. In females, diets with low concentrations of AKG (1 and 5 mM) did not affect lifespan, whereas diets supplemented with 10 and 20 mM AKG increased both median and maximum lifespans. At a lifespan-prolonging concentration (10 mM), AKG decreased fecundity, increased cold resistance and had no effect on climbing activity or resistance to oxi­dative stress in flies of either gender at middle (24 days) and old (40 days) ages. Moreover, middle-aged AKG-fed females but not males were more resistant to heat stress that was accompanied by higher levels of HSP90 protein as compared with controls. Middle-aged flies on AKG-supplemented diets showed elevated oxidative stress and had higher total protein and triacylglycerol levels as compared with controls. Hence, anti-aging effects of AKG do not seem to be related to preventing oxidative stress development but involve metabolic rearrangement and synthesis of specific protective proteins, which aid to resist destructive processes with age

Intermittent fasting causes metabolic stress and leucopenia in young mice

Overweight and obesity became the worldwide epidemic resulting from overeating especially when a so-called Western diet rich in carbohydrates and fats is used. It is widely accepted that limitation of food consumption could help to withstand such state of adult organism, but information about younger groups is contradictory. The present study was undertaken to characterize the effects of intermittent fasting, using an every other day (EOD) fasting/feeding protocol, on hematological parameters and biochemical blood plasma indices in young mice from one to two months old. It was shown that intermittently fasted mice were characterized by a reduced body weight, reduced total number of blood leucocytes, lower glucose and lactate levels and higher activity of alanine aminotransferase and aspartate aminotransferase in blood plasma as compared with the age-matched control mice. To gain the same mass EOD animals needed to eat more food than ad libitum fed animals. These differences may probably be explained by a need to expend certain resources to combat stress induced by intermittent fasting. Our data showed that EOD feeding at a young age may negatively influence young mammals

Comparison of Yarrowia lipolytica and Pichia pastoris cellular response to different agents of oxidative stress

Yeast cells exposed to adverse conditions employ a number of defense mechanisms in order to respond effectively to the stress effects of reactive oxygen species. In this work, the cellular response of Yarrowia lipolytica and Pichia pastoris to the exposure to the ROSinducing agents’ paraquat, hydrogen peroxide, and increased air pressure was analyzed. Yeast cells at exponential phase were exposed for 3 h to 1 mM paraquat, to 50 mM H2O2, or to increased air pressure of 3 or 5 bar. For both strains, the cellular viability loss and lipid peroxidation was lower for the cells exposed to increased air pressure than for those exposed to chemical oxidants. The glutathione induction occurred only in Y. lipolytica strain and reached the highest level as a response to PQ exposure. In general, antioxidant enzymes were more expressed in Y. lipolytica than in P. pastoris. The enzyme superoxide dismutase was induced in both strains under all the oxidant conditions but was dependent on the cellular growth phase, being undetectable in non-growing cells, whereas glutathione reductase was more induced in those conditions. Hydrogen peroxide was the most efficient inducer of catalase. Both yeast cultures underwent no cellular growth inhibition with increased air pressure, indicating that these yeast species were able to adapt to the oxidative stressful environment.The authors acknowledge the financial support provided by "Fundacao para a Ciencia e Tecnologia" (Grant SFRH/BD/47371/2008)

Effects of bicarbonate and alpha-ketoglutarate on sensitivity of Saccharomyces cerevisiae yeast to hydrogen peroxide and iron ions

The effects of sodium bicarbonate on the sensitivity of Saccharomyces cerevisiae yeast to hydrogen peroxide and ferrous sulfate were studied. Viability of yeast cells treated with 10–25 mM H2O2 and 0.1–0.2 mM FeSO4 was significantly decreased when 25 or 50 mM NaHCO3 was added to the medium. In the absence of bicarbonate, the levels of oxidative stress markers, namely protein carbonyls, total and oxidized glutathione in cells exposed to 0.2 mM FeSO4 did not differ from such levels in control cells (without FeSO4). Yeast cells incubated with 0.2 mM FeSO4 and 50 mM NaHCO3 had similar levels of oxidized glutathione and carbonyl groups in proteins but lower level of total glutathione compared to cells treated with FeSO4 in the absence of NaHCO3. Yeast cells exposed to a mixture of “2 mM H2O2 + 2 mM FeSO4” in 50 mM sodium bicarbonate buffer survived better than cells treated with these oxidants in 50 mM potassium phosphate buffer. The addition of 10 mM alpha-ketoglutarate led to the increased yeast survival in both buffers under the treatment with “Fe2+/Н2О2”. The protective effect of alpha-ketoglutarate can be due to its H2O2-scavenging activity. The results suggest that bicarbonate ions can enhance or alleviate the toxic effects of redox-active compounds on S. cerevisiae. Pro/antioxidant effects of bicarbonate ions are likely to depend on the kinetics of interaction between HCO3ˉ and produced ROS

2,4-DICHLORPHENOXICACETIC ACID AT LOW CONCENTRATIONS ENHANCES REPRODUCTIVE ABILITY AND OXIDATIVE STRESS RESISTANCE OF YEAST SACCHAROMYCES CEREVISIAE

2,4-dichlorphenoxicacetic acid (2,4-D) is one of the most widely used herbicides with well documented toxic effects on non-target organisms. In this study, the effect of low concentrations of 2,4-D on reproductive activity and resistance of yeast S. cerevisiae to oxidative stress was evaluated. Supplementation of the cultivation medium with 0.1-100 µM 2,4-D did not affect the rate of yeast growth. In early stationary phase, yeast cultures grown with 0.1 and 1 µM 2,4-D had higher number of reproductively active cells than control ones (without 2,4-D). In exponential phase, S. cerevisiae cells grown in the presence of 1-100 µM 2,4-D were more resistant to hydrogen peroxide comparing to control ones. Thus, the herbicide increased reproductive potential and cross-resistance to oxidative stress in yeast but the effective concentrations of 2,4-D were different for these phenomena. In summary, the results suggest possible involvement of certain hormetic mechanisms in the influence of 2,4-D at low concentrations on yeast

Effects of Long-Term Cultivation on Medium with Alpha-Ketoglutarate Supplementation on Metabolic Processes of Saccharomyces cerevisiae

During last years, alpha-ketoglutarate (AKG), an important intermediate in the Krebs cycle, has been intensively studied as a dietary supplement with stress-protective and potential antiaging effects. Here, we examined the effects of exogenous AKG on metabolic processes and survival of yeast Saccharomyces cerevisiae during long-term cultivation. Growth on AKG had no effect on the total cell number but increased the number of reproductively active cells at the late days of cultivation (from day 7 to day 15). A gradual increase in levels of total protein, glycogen, and trehalose was found over 7-day cultivation with more pronounced effects in AKG-grown cells. In control cells, metabolic activity and the activities of superoxide dismutase and catalase decreased, whereas levels of carbonyl proteins and low-molecular-mass thiols increased during 7-day cultivation. This suggests development of oxidative stress in stationary phase cells. Meanwhile, stationary phase cells cultured on AKG possessed higher levels of low-molecular-mass thiols and lower levels of carbonyl proteins and α-dicarbonyl compounds when compared to control ones. Collectively, higher levels of storage carbohydrates and an activation of antioxidant defense with diminishing oxidative protein damage can prevent a loss of reproductive ability in yeast cells during long-term cultivation on AKG-supplemented medium