Heat-shock and titanium dioxide nanoparticles decrease SOD and glutathione enzymes activities in Saccharomyces cerevisiae

It is well-known that the majority of living organisms depend on oxygen for survival. However, organisms also had to evolve a multitude of enzyme antioxidant defences as superoxide dismutase (SOD1, SOD2), glucose-6-phosphate dehydrogenase (G6PD), glutathione reductase (GR), glutathione peroxidase (GPx), and catalases (CTT1, CTA1) as well as non-enzyme defences as glutathione, to protect their cells from toxicity of reactive oxygen species (ROS). Exposure of living organisms to xenobiotic can also induce significant generation of ROS. Failure of cell antioxidant defences to prevent ROS accumulation inevitably results in oxidative stress. This potentially causes severe oxidative damages in vital biomolecules, thus compromising cell viability. Yeasts can provide a significant contribution to our understanding of oxidative stress, and its consequences on cell death, because its cellular structure and functional organization share many similarities with plant and animal cells. Although ROS accumulation in yeast generally results from cell respiration, environmental stress stimuli can be also another important source. Despite the intensive use of engineered nanoparticles (NPs) in various consumer and industrial products, data on their potential hazards are still rare and mechanisms of action only partially understood. In addition, NPs as titanium dioxide nanoparticles (TiO2-NP) possessing unique physicochemical characteristics such as high specific surface area, high reactivity, and rapid diffusion, which differ from bulk materials of the same composition (TiO2). On the other hand, yeast response to ROS (H2O2) or the toxicity of NPs depends on environmental conditions as temperature. Consequently, the aim of this work was to evaluate the antioxidant response of Saccharomyces cerevisiae, grown in presence of glycerol or glycerol and glucose, to 5 μg/mL TiO2-NP in heat-shock conditions

Heat shock and titanium dioxide nanoparticles decrease superoxide dismutase and glutathione enzymes activities in Saccharomyces cerevisiae.

The exposure of living organisms to metals can generate reactive oxygen species and failure in their antioxidant defences, triggering oxidative stress and oxidative damage. Despite the intensive use of engineered nanoparticles in numerous consumer and industrial products, data on their potential hazards in eukaryotic cells and their dependence on environmental factors such as temperature are still scarce. The aim of this study was to evaluate the antioxidant response of Saccharomyces cerevisiae, grown in presence of glycerol and glucose, to 5 μg/ml titanium dioxide nanoparticles (size<100 nm) under heat shock conditions. The results showed that biomass, levels of reactive oxygen species and glutathione reductase activity in respiratory/fermentative cells were higher than those detected in respiratory cells. Furthermore, respiratory/fermentative cells exhibited lower levels of glutathione, malondialdehyde, cytoplasmic catalase and glutathione peroxidase than those detected in the respiratory yeast. Saccharomyces cerevisiae grown in the presence of glycerol, glucose and titanium dioxide nanoparticles, under heat shock conditions, caused oxidative stress, due to a decrease in antioxidant defences such as superoxide dismutases or a slowdown of the glutathione cycle, relative to cells grown in presence of glycerol and glucose

Antioxidant response to titanium dioxide nanoparticles by Saccharomyces cerevisiae grown in different carbon sources and heat-shock conditions

The physicochemical properties that make nanomaterials unique, also equip them with potential for affect environment adversely, causing oxidative injuries in the living beings. However, organisms also had to develop antioxidant defences to protect their cells from reactive oxygen species (ROS). Failure in the cell antioxidant defences, due to the contact with xenobiotic, results in stress causing oxidatives damages leading to loss of cell viability. Yeasts can contribute to understand the toxicity of titanium dioxide nanoparticles (TiO2-NP), because its cell structure and functional organization, share similarities with mammalians. Since the response of yeast to NPs can be influenced by temperature and available carbon source, the aim of this study was to evaluate the antioxidant response of Saccharomyces cerevisiae, grown in presence of glycerol with addition of 2% glucose and 5 g/mlTiO2-NP, in heat-shock conditionsTiO2-NP (size <100 nm) stock suspensions were prepared by sonication. Bioassays were performed in YEPG medium (1% yeast extract, 2% peptone, 3% glycerol). Culture flasks were inoculated with wild-type Saccharomyces cerevisiae UE-ME3 and shaken 150 rpm, at 28°C. At exponential phase was added glucose and TiO2-NP stock solution (YEPGD-NP) to obtain a final concentration of 2% and 5 lg/ml. Yeasts grown 200 min at 28 or 40°C (heat-shock, HS). Flasks lacking glucose (YEPG) or NPs served as controls. Biomass was quantified by dry weight. Post-12000 g supernatants were used for determination of GSH, GSSG and ROS contents by fluorescence as well as glutathione reductase (GR), glutathione peroxidase (GPx), glucose-6-phosphate dehydrogenase (G6PD), catalase (CTT1) activity by spectrophotometry. Post-12000 g pellets were used for determination of catalase (CTA1) activity. Statistical analysis by ANOVA I and Duncan test. The results showed that biomass,ROS level and GR activity in the cells grown in YEPGD were higher than those detected in cells grown in YEPG. Furthermore, cells grown in YEPGD exhibited lower levels of GSH and MDA and CTT1activity comparatively with yeasts grown in YEPG. S. cerevisiae grown in YEPGD-NP in HS showed growth inhibition to levels near of cells which used glycerol as carbon source. Additionally, it was also detected a decrease in the GSH contents, GSH/GSSG ratio, GPx, CTT1 and CTA1 activities as well as an increase in ROS content and GR activeity, relatively to the cells growing only in glycerol. It was also observed an increase in ROS level and GR activity in the yeast grown in YEPGD-NP, relatively to S. cerevisiae grown in YEPGD. TiO2-NP in HS caused oxidative stress in yeast grown in presence of glycerol and glucose, decreasing GSH/GSSG ratio,increasing ROS content and GR activity

Early exposure to titanium dioxide nanoparticles caused a decrease in the cytoplasmic catalase activity, inducing lipid peroxidation in the Saccharomyces cerevisae.

The massive production of nanomaterials has created new pollutants whose interaction with living organisms is unclear. Recent studies have revealed that these materials generate reactive oxygen species, causing cell damage, when antioxidant systems fail, fact which justifies its inclusion in toxicological studies. Thus, the aim of this study was to test if early exposure of Saccharomyces cerevisiae to 5 μg/mL of titanium dioxide nanoparticles (TiO2-NP, size < 100 nm), with heat shock, does not disturb its antioxidant response mediated by superoxide dismutase and catalase activity. S. cerevisiae UE-ME3, a wild-type strain belonging to Oenology Laboratory of the University of Évora were grown in YEPG medium (3% glycerol) at 28 °C. At middle-exponential phase 2% glucose (YEPGD) and/or 5 μg/mL TiO2-NP stock solution were added and cells were grown for 200 min at 28 °C or 40 °C (heat-shock, ST). Culture medium lacking glucose or NPs served as control samples. At the end of the experiment, the dry weight was determined and remaining cells were disintegrated in 10 mM phosphate buffer pH 7.0 by ultra-sonication. The post-12,000 × g supernatant was used for determination of MDA content and catalase (CTT1) and superoxide dismutase (SOD1) activity. The pellet was used for determination of activities catalase (CTA1) and superoxide dismutase (SOD2). The results showed that the presence of glucose in the medium caused an increase of biomass, a decrease in the MDA content and CTT1 activity without change CTA1, SOD1 and SOD2 activity. Additionally, it was determined an increase in CTA1, SOD1 and SOD2 activity in the cells grown in YEPGD-ST medium. The NP-TiO2 exposure with ST, decreased CTT1 activity for similar levels to those estimated in the cells grown in YEPGD medium with nanoparticles, did not affect the CTA1 and SOD1 activity, increased the MDA level and kept the SOD2 activity in similar levels to those detected in cells grown in YEPGD-ST medium. The decrease in the CTT1 activity caused by NPs may justify, in part, the increase in MDA level

Produção de serapilheira em sistemas agroflorestais em Tomé-Açu, Amazônia Oriental.

A deposição de serapilheira representa um elo fundamental no fluxo de carbono entre o meio físico e o biótico, conferindo ao ecossistema do qual faz parte maior estabilidade, variando de acordo com o seu estágio sucessional e o tipo de sistema utilizado. O objetivo deste trabalho consistiu em realizar um estudo do fluxo de carbono pela deposição de serapilheira de quatro sistemas agroflorestais (SAFs) com idades e composições diferentes, no município de Tomé-Açu, Pará. O fluxo de carbono foi medido na deposição de material formador de serapilheira no período de um ano. Os SAFs foram divididos em quatro categorias, denominados SAF 1, SAF 2, SAF 3 e SAF 4, sendo (SAF 1: cacau, açaí, bananeira e seringueira, 14 anos de idade, SAF 2: cacau, açaí, bananeira, seringueira, taperebá, paricá e macacaúba, 14 anos de idade, SAF 3: cupuaçu, açaí, teca e mogno, 9 anos de idade, SAF 4:cupuaçu, açaí e paricá, 9 anos de idade). Em cada sistema, foram instaladas quatro parcelas amostrais, e dentro das parcelas foram instalados coletores para medir a deposição de material formador de serapilheira. O SAF 4 teve a maior deposição de serapilheira anual entre todos os tratamentos. A produção mensal de serapilheira apresentou uma distribuição diferenciada ao longo do ano. A estação seca foi caracterizada pela maior produção de serapilheira em todos os tratamentos. A quantidade de carbono depositada via litterfall difere significativamente em sistemas agroflorestais com idades e composições diferentes. Existe também diferença significativa entre meses dentro de um mesmo tratamento.Editores técnicos: Roberto Porro, Milton Kanashiro, Maria do Socorro Gonçalves Ferreira, Leila Sobral Sampaio e Gladys Ferreira de Sousa

Changes associated with Na,K-ATPase in brain, kidney, heart and liver of the spontaneously diabetic Goto-Kakizaki rat

Alterations in Na,K-ATPase activity, in isoenzyme expression and/or number of units of the pump present in the plasma membrane have been associated with diabetes. These changes were described in different organs and tissues such as brain, heart, kidney, among others, and may result from altered insulin levels. However, the vast majority of studies were conducted in animal models of chemically induced diabetes, which are not consensual models for type 2 diabetes (T2D). The major goal of this work was to investigate putative modifications in Na,K-ATPase enzymatic activity or expression in brain, kidney, heart and liver in T2D. The Goto-Kakizaky rat (GK) strain was used as a model of spontaneously developed T2D, and Wistar rats as controls. Na,K-ATPase activity was assessed by the hydrolysis of ATP (Pi formed in the presence/absence of ouabain was measured using a colorimetric assay) and the isoenzymatic expression by Westernblot. A decrease in Na,K-ATPase activity in renal and cardiac tissues from GK comparatively to controls (55.7% and 77.5%, respectively) was observed. The pump activity was similar in liver and brain tissues. In renal tissue, expression of α1-Na,K-ATPase was similar between GK and controls but α2- was 2.3x higher and α3- was detected only in GK. Contrastingly a decreased expression of α1- (49.5%) and α2-isoforms (67.6%) was found in cardiac tissue. Despite similar Na,K-ATPase activity in liver and brain tissues, α1-isoform expression was decreased (33.9%) in the liver from GK while in the brain an increase of α1-isoform (~2x) together with a decrease of α2-isoform (14.0%) expressions were observed. It is unclear, except maybe for cardiac tissue where lower expression is potentially underlying the diminished pump activity in GK, whether the changes in isoenzyme expression is a key factor for differential Na,K-ATPase activity. Being responsive to complex regulation, other regulatory mechanisms may contribute to the impaired activity observed in kidney and heart. These results have uncover changes in Na,K-ATPase activity and/or enzymatic expression in GK brain, kidney, heart and liver that may contribute to the undesirable conditions associated with T2D. This work highlight the relevance of further investigation about Na,K-ATPase regulation and role in physiopathology of T2D

Strychnine Intoxication: A Case Report

Strychnine acts as an inhibitor of post-synaptic neuronal inhibition and intoxication leads to distinct clinical manifestations which may culminate in death. Since its commercialization is prohibited in most countries, cases of strychnine intoxication are now rare. We present a case of an elderly patient who voluntarily ingested a white powder thought to be strychnine. He developed myoclonus, startle response, and episodes of generalized muscle contractions accompanied by respiratory arrest in one occasion. Diazepam, valproic acid and supportive treatments were able to control manifestations, however the patient died after 2 days. Our aim is to alert clinicians that, despite its rarity, strychnine intoxication may still be seen in emergency departments, and clinical outcome can be influenced by rapid recognition and timely institution of adequate treatment

Functional and conservation value of fruits - a lab approach

[EN] Fruits are a relevant source of phenols and ascorbate, biomolecules which scavenge reactive oxygen species. For this reason, they are considered as healthy for the human being. Fruits quality depends on their levels of antioxidants and enzyme activities that ensure their conservation. The aim of this work was to plan and execute a laboratory class of Enzymology, a discipline of Biochemistry degree of University of Évora, Portugal, for determining the functional and conservation value of three different fruits types, sold in the market of Évora, Portugal. The development of this activity allowed that students of a pilot class participate in a laboratory activity which intended to compare the content of phenols, ascorbate, and polyphenol oxidase enzyme activity present in apple, peach and blueberries pulp. At Lab activity, the students successfully determined markers of functional and conservation value of selected fruits. The skills acquired by the students, in terms of obtaining fruit pulp and their composition in antioxidants, stimulated their commitment degree on the application of biochemistry in the everyday, acquiring thereby significant learning, with a high degree of satisfaction.This work was funded by National Funds through FCT - Foundation for Science and Technology under the Project UID/AGR/00115/2013.Alves-Pereira, I.; Capela-Pires, J.; Candeias, M.; Ferreira, R. (2020). Functional and conservation value of fruits - a lab approach. En 6th International Conference on Higher Education Advances (HEAd'20). Editorial Universitat Politècnica de València. (30-05-2020):427-435. https://doi.org/10.4995/HEAd20.2020.11082OCS42743530-05-202

Avaliação da avifauna em sistemas agroflorestais com dendê (Elaeis guianeensis) no município de Tomé-Açu (PA).

È apresentada uma comparação entre a composição da avifauna de sistemas agroflorestais (SAF) com dendê, copoeiras e uma monocultura de dendê ao longo de dois anos no intuito de relatar a funcionalidade dos SAFs na manutenção de aves amazônicas. Foram registradas 196 espécies, destas 88 encontradas nos SAFs, 120 na capoeira e 63 na monocultura. Foi observada a ausência de espécies florestais das famílias, Thamnophilidae, Furnaridae e Tyrannidae no SAF e na monocultura de dendê, presentes na capoeira. O índice de similaridade de Morisita mostra que os SAFs se assemelham mais às monoculturas do que às capoeiras, possivelmente devido ao tempo recente de plantio, onde os SAFs ainda não apresentam uma estrutura florestal mais complexa com sub-bosque e dossel. Foi observado um aumento na riqueza de espécies frutívoras e nectarívoras e na diversidade dos SAFs, possivelmente refletindo o contínuo desenvolvimento e estruturação deste sistema. Os resultados apresentados mostram que apesar de os SAFs apresentarem uma comunidade de aves em geral distinta da comunidade encontrada nas capoeiras, estas apresentam índices de diversidade e riqueza de espécies semelhantes. A monocultura de dendê apresentou a menor riqueza e índices de diversidade, além de apresentar principalmente espécies insetívoras, onívoras e granívoras na composição de sua avifauna, configurando um ambiente pouco diverso na estrutura da vegetação. Sistemas agroflorestais de dendê podem vir a contribuir na manutenção da diversidade local de aves florestais amazônicas, contudo os resultados apontam a necessidade de mais tempo para um melhor desenvolvimento do sistema.Editores técnicos: Roberto Porro, Milton Kanashiro, Maria do Socorro Gonçalves Ferreira, Leila Sobral Sampaio e Gladys Ferreira de Sousa