Investigation of the cytotoxicity, genotoxicity and antioxidant prospects of JM-20 on human blood cells: A multi-target compound with potential therapeutic applications.

JM-20 is a 1,5-benzodiazepine compound fused to a dihydropyridine fraction with different pharmacological properties. However, its potential toxic effects on blood cells have not yet been reported. Thus, the present study aimed to investigate, for the first time, the possible cytotoxicity of JM-20 through cell viability, cell cycle, morphology changes, reactive species (RS) to DCFH-DA, and lipid peroxidation in human leukocytes, its hemolytic effect on human erythrocytes, and its potential DNA genotoxicity using plasmid DNA in vitro. Furthermore, the compound's ability to reduce the DPPH radical was also measured. Human blood was obtained from healthy volunteers (30 ± 10 years old), and the leukocytes or erythrocytes were immediately isolated and treated with different concentrations of JM-20. A cytoprotective effect was exhibited by 10 µM JM-20 against 1 mM tert-butyl hydroperoxide (t-but-OOH) in the leukocytes. However, the highest tested concentrations of the compound (20 and 50 µM) changed the morphology and caused a significant decrease in the cell viability of leukocytes (p < 0.05, in comparison with Control). All tested concentrations of JM-20 also resulted in a significant increase in intracellular RS as measured by DCFH-DA in these cells (p < 0.05, in comparison with Control). On the other hand, the results point out a potent antioxidant effect of JM-20, which was similar to the classical antioxidant α-tocopherol. The IC50 value of JM-20 against the lipid peroxidation induced by (FeII) was 1.051 µM ± 0.21, while the IC50 value of α-tocopherol in this parameter was 1.065 µM ± 0.34. Additionally, 50 and 100 µM JM-20 reduced the DPPH radical in a statistically similar way to the 100 µM α-tocopherol (p < 0.05, in comparison with the control). No significant hemolysis in erythrocytes, no cell cycle changes in leukocytes, and no genotoxic effects in plasmid DNA were induced by JM-20 at any tested concentration. The in silico pharmacokinetic and toxicological properties of JM-20, derivatives, and nifedipine were also studied. Here, our findings demonstrate that JM-20 and its putative metabolites exhibit similar characteristics to nifedipine, and the in vitro and in silico data support the low toxicity of JM-20 to mammals.

Should ebselen be considered for the treatment of mercury intoxication? A minireview.

Mercury is a ubiquitous environmental contaminant and can be found in inorganic (Hg0, Hg+ and Hg2+) and organic forms (chiefly CH3Hg+ or MeHg+). The main route of human, mammals and bird exposure occurs via predatory fish ingestion. Occupational exposure to Hg0 (and Hg2+) can also occur; furthermore, in gold mining areas the exposure to inorganic Hg can also be high. The toxicity of electrophilic forms of Hg (E+Hg) is mediated by disruption of thiol (-SH)- or selenol (-SeH)-containing proteins. The therapeutic approaches to treat methylmercury (MeHg+), Hg0 and Hg2+ are limited. Here we discuss the potential use of ebselen as a potential therapeutic agent to lower the body burden of Hg in man. Ebselen is a safe drug for humans and has been tested in clinical trials (for instance, brain ischemia, noise-induce hearing loss, diabetes complications, bipolar disorders) at doses varying from 400 to 3600 mg per day. Two clinical trials with ebselen in moderate and severe COVID are also approved. Ebselen can be metabolized to an intermediate with -SeH (selenol) functional group, which has a greater affinity to electrophilic Hg (E+Hg) forms than the available thiol-containing therapeutic agents. Accordingly, as observed in vitro and rodent models in vivo, Ebselen exhibited protective effects against MeHg+, indicating its potential as a therapeutic agent to treat MeHg+ overexposure. The combined use of ebselen with thiol-containing molecules (e.g. N-acetylcysteine and enaramide)) is also commented, because they can have synergistic protective effects against MeHg+.

Diphenyl Diselenide and SARS-CoV-2: in silico Exploration of the Mechanisms of Inhibition of Main Protease (Mpro) and Papain-like Protease (PLpro).

The SARS-CoV-2 pandemic has prompted global efforts to develop therapeutics. The main protease of SARS-CoV-2 (Mpro) and the papain-like protease (PLpro) are essential for viral replication and are key targets for therapeutic development. In this work, we investigate the mechanisms of SARS-CoV-2 inhibition by diphenyl diselenide (PhSe)2 which is an archetypal model of diselenides and a renowned potential therapeutic agent. The in vitro inhibitory concentration of (PhSe)2 against SARS-CoV-2 in Vero E6 cells falls in the low micromolar range. Molecular dynamics (MD) simulations and density functional theory (DFT) calculations [level of theory: SMD-B3LYP-D3(BJ)/6-311G(d,p), cc-pVTZ] are used to inspect non-covalent inhibition modes of both proteases via π-stacking and the mechanism of covalent (PhSe)2 + Mpro product formation involving the catalytic residue C145, respectively. The in vitro CC50 (24.61 µM) and EC50 (2.39 µM) data indicate that (PhSe)2 is a good inhibitor of the SARS-CoV-2 virus replication in a cell culture model. The in silico findings indicate potential mechanisms of proteases' inhibition by (PhSe)2; in particular, the results of the covalent inhibition here discussed for Mpro, whose thermodynamics is approximatively isoergonic, prompt further investigation in the design of antiviral organodiselenides.

Acid sphingomyelinase (ASM) and COVID-19: A review of the potential use of ASM inhibitors against SARS-CoV-2.

In the last 2 years, different pharmacological agents have been indicated as potential inhibitors of SARS-CoV-2 in vitro. Specifically, drugs termed as functional inhibitors of acid sphingomyelinase (FIASMAs) have proved to inhibit the SARS-CoV-2 replication using different types of cells. Those therapeutic agents share several chemical structure characteristics and some well-known representatives are fluoxetine, escitalopram, fluvoxamine, and others. Most of the FIASMAs are primarily used as effective therapeutic agents to treat different pathologies, therefore, they are natural drug candidates for repositioning strategy. In this review, we summarize the two main proposed mechanisms mediating acid sphingomyelinase (ASM) inhibition and how they can explain the inhibition of SARS-CoV-2 replication by FIASMAs. The first mechanism implies a disruption in the lysosomal pH fall as the endosome-lysosome moves toward the interior of the cell. In fact, changes in cholesterol levels in endosome-lysosome membranes, which are associated with ASM inhibition is thought to be mediated by lysosomal proton pump (ATP-ase) inactivation. The second mechanism involves the formation of an extracellular ceramide-rich domain, which is blocked by FIASMAs. The ceramide-rich domains are believed to facilitate the SARS-CoV-2 entrance into the host cells.

Genotoxicity and cytotoxicity potential of organoselenium compounds in human leukocytes in vitro.

In the current work, cytotoxicity and genotoxicity of different organoselenium compounds were examined using Trypan blue exclusion and alkaline comet assays with silver staining respectively. Leukocytes were subjected to a 3-hour incubation with organoselenium compounds at concentrations of 1, 5, 10, 25, 50, and 75 µM, or with the control vehicle (DMSO), at a temperature of 37 °C. The viability of the cells was evaluated using the Trypan blue exclusion method, while DNA damage was analyzed through the alkaline comet assay with silver staining. The exposure of leukocytes to different organoselenium compounds including i.e. (Z)-N-(pyridin-2-ylmethylene)-1-(2-((2-(1-((E)-pyridin-2-ylmethyleneamino)ethyl)phenyl)diselanyl)phenyl)ethanamine (C1), 2,2'(1Z,1'E)-(1,1'-(2,2'-diselanediylbis(2,1-phenylene))bis(ethane-1,1-diyl)) bis(azan-1-yl-1-ylidene)bis -methan-1-yl-1-ylidene)diphenol (C2), and dinaphthyl diselenide (NapSe)2, At concentrations ranging from 1 to 5 µM, no significant DNA damage was observed, as indicated by the absence of a noteworthy increase in the Damage Index (DI). Our results suggest that the organoselenium selenium compounds tested were not genotoxic and cytotoxic to human leukocytes in vitro at lower concentration. This study offers further insights into the genotoxicity profile of these organochalcogens in human leukocytes. Their genotoxicity and cytotoxicity effects at higher concentration are probably mediated through reactive oxygen species generation and their ability to catalyze thiol oxidation.

The silver jubilee of the Nitric Oxide journal: From 1997 to 2021.

Based on the Scopus record, Nitric Oxide journal (NOJ) has completed 25 years of publications. On March 8, 2022, the publication data was retrieved from the Scopus database and analyzed on VOSviewer and R-Studio (Bibliometrix R package/Biblioshiny). NOJ has published 1928 research documents majorly comprising of articles (1611/83.56%) and reviews (210/10.89%). The total citations and h-index were 56291 & 97, respectively. The per year (from 1997 to 2022) publications and citations are presented in this study. We tried to highlight some of the influential researchers, institutes, and countries. In all publications, 7450 authors have contributed with a collaboration index of 0.241. For all authors, we provided descriptive details about their total number of publications (NoP), total citations (TC), h-index, g-index, m-index, citations per paper (CPP), citation per year (CPY), HG Sqrt and Q2Index. Based on each indicator, we highlighted the top five scientists. The research publications (over time) of the top ten authors are also described. Furthermore, the collaboration network of authors is graphically presented. We also provided descriptive details about the most productive institutes. The highest number of documents are published by the University of Sao Paolo (n = 78), Brazil, while in-country sections, USA has the highest number of publications (n = 553) with 21739 citations and 69 h-index. In the same vein, for each era (five years) details about the top five countries are provided. In all publications (n = 1794), 34 European, 3 North American, 13 Asian, 10 South American, 5 Middle East, 8 African and 2 Asia Pacific countries have contributed. Numerical details about the collaboration links of all countries and the per-era contributions of the top ten countries are also provided. Based on the co-words analysis the per era research focus is graphically presented. Descriptive details about the major trends in publication in each era are also provided. We also manually analyzed 160 words that appeared more than thirty thousand (n = 30,000) times and tried to provide a broader overview of research publications. Based on Scopus record, the NOJ ranking is yearly improving and presently (2021-2022) it holds 14th and 17th positions in clinical biochemistry and physiology. The success could be attributed to all researchers, institutes, editors-in-chief, reviewers, editorial board & entire management.

Diphenyl diselenide suppresses key virulence factors of Candida krusei, a neglected fungal pathogen.

Candida krusei is a candidiasis etiological agent of relevance in the clinical setting because of its intrinsic resistance to fluconazole. Also, it has opened up new paths in the area of alternative therapeutic techniques. This project demonstrated the effects of diphenyl diselenide (PhSe)2 and p-cloro diphenyl diselenide (pCl-PhSe)2, two organochalcogen compounds, on relevant virulence factors for the early stage of the C. krusei host interaction and infection process. Both compounds inhibited adherence of C. krusei to both polystyrene surfaces and cervical epithelial cells and biofilm formation; the structure of the biofilm was also changed in a dose-dependent manner. In addition, both compounds inhibited C. krusei growth, but (PhSe)2 significantly increased the time duration of the lag phase and delayed the start of the exponential phase in growth kinetics. (PhSe)2 has more potential antifungal activity than (pCl-PhSe)2 in inhibiting the adherence to epithelial cells, biofilm formation, and growth of C. krusei.

Methylmercury Can Facilitate the Formation of Dehydroalanine in Selenoenzymes: Insight from DFT Molecular Modeling.

Experimental studies have indicated that electrophilic mercury forms (e.g., methylmercury, MeHg+) can accelerate the breakage of selenocysteine in vitro. Particularly, in 2009, Khan et al. (Environ. Toxicol. Chem. 2009, 28, 1567-1577) proposed a mechanism for the degradation of a free methylmercury selenocysteinate complex that was theoretically supported by Asaduzzaman et al. (Inorg. Chem. 2010, 50, 2366-2372). However, little is known about the fate of methylmercury selenocysteinate complexes embedded in an enzyme, especially in conditions of oxidative stress in which methylmercury target enzymes operate. Here, an accurate computational study on molecular models (level of theory: COSMO-ZORA-BLYP-D3(BJ)/TZ2P) was carried out to investigate the formation of dehydroalanine (Dha) in selenoenzymes, which irreversibly impairs their function. Methylselenocysteine as well as methylcysteine and methyltellurocysteine were included to gain insight on the peculiar behavior of selenium. Dha forms in a two-step process, i.e., the oxidation of the chalcogen nucleus followed by a syn-elimination leading to the alkene and the chalcogenic acid. The effect of an excess of hydrogen peroxide, which may lead to the formation of chalcogenones before the elimination, and of MeHg+, a severe toxicant targeting selenoproteins, which leads to the formation of methylmercury selenocysteinate, are also studied with the aim of assessing whether these pathological conditions facilitate the formation of Dha. Indeed, elimination occurs after chalcogen oxidation and MeHg+ facilitates the process. These results indicate a possible mechanism of toxicity of MeHg+ in selenoproteins.

The Thiol-Modifier Effects of Organoselenium Compounds and Their Cytoprotective Actions in Neuronal Cells.

Most pharmacological studies concerning the beneficial effects of organoselenium compounds have focused on their ability to mimic glutathione peroxidase (GPx). However, mechanisms other than GPx-like activity might be involved on their biological effects. This study was aimed to investigate and compare the protective effects of two well known [(PhSe)2 and PhSeZnCl] and two newly developed (MRK Picolyl and MRK Ester) organoselenium compounds against oxidative challenge in cultured neuronal HT22 cells. The thiol peroxidase and oxidase activities were performed using the glutathione reductase (GR)-coupled assay. In order to evaluate protective effects of the organoselenium compounds against oxidative challenge in neuronal HT22 cells, experiments based on glutamate-induced oxytosis and SIN-1-mediated peroxynitrite generation were performed. The thiol peroxidase activities of the studied organoselenium compounds were smaller than bovine erythrocytes GPx enzyme. Besides, (PhSe)2 and PhSeZnCl showed higher thiol peroxidase and lower thiol oxidase activities compared to the new compounds. MRK Picolyl and MRK Ester, which showed lower thiol peroxidase activity, showed higher thiol oxidase activity. Both pre- or co-treatment with (PhSe)2, PhSeZnCl, MRK Picolyl and MRK Ester protected HT22 cells against glutamate-induced cytotoxicity. (PhSe)2 and MRK Picolyl significantly prevented peroxinitrite-induced dihydrorhodamine oxidation, but this effect was observed only when HT22 were pre-treated with these compounds. The treatment with (PhSe)2 increased the protein expression of antioxidant defences (Prx3, CAT and GCLC) in HT22 cells. Taking together, our results suggest that the biological effects elicited by these compounds are not directly related to their GPx-mimetic and thiol oxidase activities, but might be linked to the up-regulation of endogenous antioxidant defences trough their thiol-modifier effects.

(PhSe)2 and (pCl-PhSe)2 organochalcogen compounds inhibit Candida albicans adhesion to human endocervical (HeLa) cells and show anti-biofilm activities.

Adhesion capacity on biological surfaces and biofilm formation is considered an important step in the infection process by Candida albicans. The ability of (PhSe)2 and (pCl-PhSe)2, two synthetic organic selenium (organochalcogen) compounds, to act on C. albicans virulence factors related to adhesion to human endocervical (HeLa) cell surfaces and their anti-biofilm activities was analyzed. Both organochalcogen compounds inhibited C. albicans adhesion to HeLa cells, dependent on compound concentrations. (PhSe)2 (at 20 µM; p = 0.0012) was significantly more effective than (pCl-PhSe)2 (at 20 µM; p = 0.0183) compared with the control. (PhSe)2 inhibited biofilm formation and decreased biofilm viability in both early and mature biofilms more efficiently than (pCl-PhSe)2. Overall, the organochalcogen compounds, especially (PhSe)2, were demonstrated to be effective antifungal drugs against C. albicans virulence factors related to epithelial cell surface adhesion and the formation and viability of biofilms.

Interaction Study between ESIPT Fluorescent Lipophile-Based Benzazoles and BSA.

In this study, the interactions of ESIPT fluorescent lipophile-based benzazoles with bovine serum albumin (BSA) were studied and their binding affinity was evaluated. In phosphate-buffered saline (PBS) solution these compounds produce absorption maxima in the UV region and a main fluorescence emission with a large Stokes shift in the blue-green regions due to a proton transfer process in the excited state. The interactions of the benzazoles with BSA were studied using UV-Vis absorption and steady-state fluorescence spectroscopy. The observed spectral quenching of BSA indicates that these compounds could bind to BSA through a strong binding affinity afforded by a static quenching mechanism (Kq~1012 L·mol-1·s-1). The docking simulations indicate that compounds 13 and 16 bind closely to Trp134 in domain I, adopting similar binding poses and interactions. On the other hand, compounds 12, 14, 15, and 17 were bound between domains I and III and did not directly interact with Trp134.

Chalcogen-mercury bond formation and disruption in model Rabenstein's reactions: A computational analysis.

Methylmercury is a highly toxic compound and human exposure is mainly related to consumption of polluted fish and seafood. The inactivation of thiol-based enzymes, promoted by the strong affinity binding of electrophilic mercuric ions to thiol and selenol groups of proteins, is likely an important factor explaining its toxicity. A key role is played by the chemistry and reactivity of the mercury-chalcogens bond, particularly HgS and HgSe, which is the focus of this computational work (level of theory: (COSMO)-ZORA-BLYP-D3(BJ)/TZ2P). We analyze nine ligand-exchange model reactions (the so-called Rabenstein's reactions) involving an entering ligand (methylchalcogenolate) and a substrate (methylchalcogenolatemethylmercury). Trends in reaction and activation energies are discussed and a change in mechanism is reported for all cases when going from gas phase to water, that is, from a single-well potential energy surface (PES) to a canonical SN 2-like mechanism. The reasons accounting for the biochemically challenging and desired displacement of methylmercury from a seleno/thiol protein can be found already in these model reactions, as can be seen from the similarities of the ligand exchange reactions in solution in thermodynamics and kinetics.

Acute oral toxicity and antioxidant studies of an amine-based diselenide.

BACKGROUND: Organochalcogen compounds have attracted the interest of a multitude of studies for their promising Pharmacological and biological activities. The antioxidant activity and acute toxicity of an organoselenium compound, 1-(2-(2-(2-(1-aminoethyl)phenyl)diselanyl)phenyl)ethanamine (APDP) was determined in mice. METHODS: Mice were randomly divided into four groups, with each group comprising of seven animals. Canola oil (1ml/kg of body weight) was administered to 1st group, while 2nd, 3rd & 4th groups were administered with 10 mg/kg, 30 mg/kg & 350 mg/kg of APDP respectively. APDP was administered by Intragastric gavage as a single oral dose. RESULTS: The APDP oral administration was found to be safe up to 350 mg/kg of body weight and no deaths of animals were recorded. The lethal dose 50 (LD50) for APDP was determined at 72 h and was estimated to be > 350 mg/kg. After acute treatment, all mice were sacrificed by decapitation to determine the antioxidant enzymes and lipid peroxidation values for the treated mice liver. No fluctuation in lipid peroxidation, vitamin C and non protein thiol (NPSH) levels was observed due to the administration of APDP. hepatic α-ALA-D activity, catalase (CAT), superoxide dismutase (SOD) and the biochemical parameters were evaluated. Experimental observation demonstrated that APDP protected Fe(II) induced thiobarbituric acid reactive substances (TBARS) production in liver homogenate significantly (p < 0.05). The administration of APDP (an amine-based diselenide) both in vitro and in vivo clearly demonstrated that this potential compound has no acute toxicity towards mice among all the tested parameter. CONCLUSION: On the basis of experimental results, it is concluded that APDP is a potential candidate as an antioxidant compound for studying pharmacological properties.

Productivity of CNPq Researchers from Different Fields in Biomedical Sciences: The Need for Objective Bibliometric Parameters-A Report from Brazil.

In Brazil, the CNPq (National Council for Scientific and Technological Development) provides grants, funds and fellowships to productive scientists to support their investigations. They are ranked and categorized into four hierarchical levels ranging from PQ 1A (the highest) to PQ 1D (the lowest). Few studies, however, report and analyse scientific productivity in different sub-fields of Biomedical Sciences (BS), e.g., Biochemistry, Pharmacology, Biophysics and Physiology. In fact, systematic comparisons of productivity among the PQ 1 categories within the above sub-fields are lacking in the literature. Here, the scientific productivity of 323 investigators receiving PQ 1 fellowships (A to D levels) in these sub-fields of BS was investigated. The Scopus database was used to compile the total number of articles, citations, h-index values and authorship positions (first-, co- or last-listed author) in the most cited papers by researchers granted CNPq fellowships. We found that researchers from Pharmacology had the best performance for all of the parameters analysed, followed by those in Biochemistry. There was great variability in scientific productivity within the PQ 1A level in all of the sub-fields of BS, but not within the other levels (1B, 1C and 1D). Analysis of the most cited papers of PQ 1(A-D) researchers in Pharmacology revealed that the citations of researchers in the 1C and 1D levels were associated with publications with their senior supervisors, whereas those in the 1B level were less connected with their supervisors in comparison to those in 1A. Taken together, these findings suggest that the scientific performance of PQ 1A researchers in BS is not homogenous. In our opinion, parameters such as the most cited papers without the involvement of Ph.D. and/or post-doctoral supervisors should be used to make decisions regarding any given researcher's fellowship award level.

Diselenoamino acid derivatives as GPx mimics and as substrates of TrxR: in vitro and in silico studies.

Excessive production of reactive species in living cells usually has pathological effects. Consequently, the synthesis of compounds which can mimic the activity of antioxidant enzymes has inspired great interest. In this study, a variety of diselenoamino acid derivatives from phenylalanine and valine were tested to determine whether they could be functional mimics of glutathione peroxidase (GPx) and substrates for liver thioredoxin reductase (TrxR). Diselenides C and D showed the best GPx mimicking properties when compared with A and B. We suppose that the catalytic activity of diselenide GPx mimics depends on the steric effects, which can be influenced by the number of carbon atoms between the selenium atom and the amino acid residue and/or by the amino acid lateral residue. Compounds C and D stimulated NADPH oxidation in the presence of partially purified hepatic mammalian TrxR, indicating that they are substrates for TrxR. Our study indicates a possible dissociation between the two pathways for peroxide degradation (i.e., via a substrate for TrxR or via mimicry of GPx) for compounds tested in this study, except for PhSeSePh, and the antioxidant activity of diselenoamino acids can also be attributed to their capacity to mimic GPx and to be a substrate for mammalian TrxR.

Potential use of bitter melon (Momordica charantia) derived compounds as antidiabetics: In silico and in vivo studies.

Momordica charantia (bitter lemon) belongs to the cucurbitaceae family which has been extensively used in traditional medicines for the cure of various ailments such as cancer and diabetes. The underlying mechanism of M. charantia to maintain glycemic control was investigated. GLP-1 and DPP-4 gene modulation by M. charantia (5-20% inclusion in rats diet) was investigated in vivo by RT-PCR and possible compounds responsible for diabetic action predicted through in silico approach. Phytochemicalss previously characterized from M. charantia were docked into glucacon like peptide-1 receptor (GLP-1r), dipeptidyl peptidase (DPP4) and Takeda-G-protein-receptor-5 (TGR5) predicted using Autodock Vina. The results of the in silico suggests momordicosides D (ligand for TGR5), cucurbitacin (ligand for GLP-1r) and charantin (ligand for DPP-4) as the major antidiabetic compounds in bitter lemon leaf. M. charantia increased the expression of GLP-1 by about 295.7% with concomitant decreased in expression of DPP-4 by 87.2% with 20% inclusion in rat's diet. This study suggests that the mechanism underlying the action of these compounds is through activation of TGR5 and GLP-1 receptor with concurrent inhibition of DPP4. This study confirmed the use of this plant in diabetes management and the possible bioactive compounds responsible for its antidiabetic property are charantin, cucurbitacin and momordicoside D and all belong to the class of saponins.

De novo transcriptome assembly of the lobster cockroach Nauphoeta cinerea (Blaberidae).

The use of Drosophila as a scientific model is well established, but the use of cockroaches as experimental organisms has been increasing, mainly in toxicology research. Nauphoeta cinerea is one of the species that has been studied, and among its advantages is its easy laboratory maintenance. However, a limited amount of genetic data about N. cinerea is available, impeding gene identification and expression analyses, genetic manipulation, and a deeper understanding of its functional biology. Here we describe the N. cinerea fat body and head transcriptome, in order to provide a database of genetic sequences to better understand the metabolic role of these tissues, and describe detoxification and stress response genes. After removing low-quality sequences, we obtained 62,121 transcripts, of which more than 50% had a length of 604 pb. The assembled sequences were annotated according to their genes ontology (GO). We identified 367 genes related to stress and detoxification; among these, the more frequent were p450 genes. The results presented here are the first large-scale sequencing of N. cinerea and will facilitate the genetic understanding of the species' biochemistry processes in future works.

Calcium signaling mechanisms disrupt the cytoskeleton of primary astrocytes and neurons exposed to diphenylditelluride.

BACKGROUND: Diphenylditelluride (PhTe)2 is a potent neurotoxin disrupting the homeostasis of the cytoskeleton. METHODS: Cultured astrocytes and neurons were incubated with (PhTe)2, receptor antagonists and enzyme inhibitors followed by measurement of the incorporation of [32P]orthophosphate into intermediate filaments (IFs). RESULTS: (PhTe)2 caused hyperphosphorylation of glial fibrillary acidic protein (GFAP), vimentin and neurofilament subunits (NFL, NFM and NFH) from primary astrocytes and neurons, respectively. These mechanisms were mediated by N-methyl-d-aspartate (NMDA) receptors, L-type voltage-dependent calcium channels (L-VDCCs) as well as metabotropic glutamate receptors upstream of phospholipase C (PLC). Upregulated Ca(2+) influx activated protein kinase A (PKA) and protein kinase C (PKC) in astrocytes causing hyperphosphorylation of GFAP and vimentin. Hyperphosphorylated (IF) together with RhoA-activated stress fiber formation, disrupted the cytoskeleton leading to altered cell morphology. In neurons, the high intracellular Ca(2+) levels activated the MAPKs, Erk and p38MAPK, beyond PKA and PKC, provoking hyperphosphorylation of NFM, NFH and NFL. CONCLUSIONS: Our findings support that intracellular Ca(2+) is one of the crucial signals that modulate the action of (PhTe)2 in isolated cortical astrocytes and neurons modulating the response of the cytoskeleton against the insult. GENERAL SIGNIFICANCE: Cytoskeletal misregulation is associated with neurodegeneration. This compound could be a valuable tool to induce molecular changes similar to those found in different pathologies of the brain.

Diphenyl Diselenide Protects against Methylmercury-Induced Toxicity in Saccharomyces cerevisiae via the Yap1 Transcription Factor.

Methylmercury (MeHg) is a ubiquitous and persistent environmental pollutant that induces serious neurotoxic effects. Diphenyl diselenide [(PhSe)2], an organoseleno compound, exerts protective effects against MeHg toxicity, although the complete mechanism remains unclear. The aim of this study was to investigate the mechanisms involved in the protective effect of (PhSe)2 on the toxicity induced by MeHg using wild-type Saccharomyces cerevisiae and mutants with defects in enzymes and proteins of the antioxidant defense system (yap1Δ, ybp1Δ, ctt1Δ, cat1Δ, sod1Δ, sod2Δ, gsh1Δ, gsh2Δ, gtt1Δ, gtt2Δ, gtt3Δ, gpx1Δ, gpx2Δ, trx1Δ, trx2Δ, trx3Δ, and trr2Δ). In the wild-type strain, (PhSe)2 protected against the growth inhibition, reactive oxygen species production, and decrease in membrane integrity induced by MeHg and restored thiol levels to values indistinguishable from the control. Single deletions of yap1, sod1, sod2, gsh1, gsh2, gpx1, gpx2, trx1, trx2, and trx3 decreased the capacity of (PhSe)2 to prevent MeHg toxicity in yeast, indicating their involvement in (PhSe)2 protection. Together, these results suggest a role of (PhSe)2 in modulating the gene expression of antioxidant enzymes and ABC transporters through the action of the transcription factor YAP1, preventing the oxidative damage caused by MeHg in S. cerevisiae.

Antioxidant and mercury chelating activity of Psidium guajava var. pomifera L. leaves hydroalcoholic extract.

Mercury (Hg) is widely distributed in the environment and is known to produce several adverse effects in organisms. The aim of the present study was to examine the in vitro antioxidant activity and Hg chelating ability of the hydroalcoholic extract of Psidium guajava leaves (HEPG). In addition, the potential protective effects of HEPG against Hg(II) were evaluated using a yeast model (Saccharomyces cerevisiae). HEPG was found to exert significant antioxidant activity in 2,2-diphenyl-1-picrylhydrazyl scavenger and inhibition of lipid peroxidation induced by Fe(II) assays in a concentration-dependent manner. The extract also exhibited significant Hg(II) chelating activity. In yeast, Hg(II) induced a significant decrease in cell viability. In contrast, HEPG partially prevented the fall in cell viability induced by Hg(II). In conclusion, HEPG exhibited protective effects against Hg(II)-mediated toxicity, which may be related to both antioxidant and Hg(II)-chelating activities.