Protein corona on biogenic silver nanoparticles provides higher stability and protects cells from toxicity in comparison to chemical nanoparticles.

The development of environmentally friendly new procedures for the synthesis of metallic nanoparticles is one of the main goals of nanotechnology. Proteins and enzymes from plants, filamentous fungi, yeast, and bacteria to produce nanoparticles are both valuable and viable alternatives to conventional synthesis of nanomaterials due to their high efficiency and the low cost to scale up and generate large quantities. The aim of this work is to compare biogenic silver nanoparticles (AgNPs) obtained from cell-free filtrates from the fungus Macrophomina phaseolina to conventional chemical AgNPs, in biocidal activity and toxicity. Our results show that bio-AgNPs displayed similar bactericidal activity than chemical AgNPs, but less toxicity in the model organism Caenorhabditis elegans. We employed biochemical and proteomic techniques to profile the unique surface chemistry of the capping in the bio-AgNPs and therefore to identify the proteins involved in their synthesis and stability. These results not only suggest that the proteins involved in the synthesis of the nanoparticles and corona formation in the bio-AgNPs are responsible for keeping the silver core preserved making them more stable in time, but also masking and protecting eukaryotic cells from metal toxicity.

Ryanodine receptor-2 upregulation and nicotine-mediated plasticity.

Nicotine, the major psychoactive component of cigarette smoke, modulates neuronal activity to produce Ca2+-dependent changes in gene transcription. However, the downstream targets that underlie the long-term effects of nicotine on neuronal function, and hence behaviour, remain to be elucidated. Here, we demonstrate that nicotine administration to mice upregulates levels of the type 2 ryanodine receptor (RyR2), a Ca2+-release channel present on the endoplasmic reticulum, in a number of brain areas associated with cognition and addiction, notably the cortex and ventral midbrain. Nicotine-mediated RyR2 upregulation was driven by CREB, and caused a long-lasting reinforcement of Ca2+ signalling via the process of Ca2+-induced Ca2+ release. RyR2 upregulation was itself required for long-term phosphorylation of CREB in a positive-feedback signalling loop. We further demonstrate that inhibition of RyR-activation in vivo abolishes sensitization to nicotine-induced habituated locomotion, a well-characterised model for onset of drug dependence. Our findings, therefore, indicate that gene-dependent reprogramming of Ca2+ signalling is involved in nicotine-induced behavioural changes.

Integrated water quality assessment of two Rivers Basins from a semiarid region of Argentina.

The Tunuyán and Mendoza River Basins (Province of Mendoza, Argentina) have been selected as a representative semiarid region to test the applicability of an integrated water quality evaluation. To detect spatio-temporal variations of anthropic contamination, physicochemical and bacteriological parameters, as well as three ecotoxicological assays, were assessed in reference sites for 3 years. Bioassays based on the nematode Caenorhabditis elegans, the vascular plant Lactuca sativa, and the algae Pseudokirchneriella subcapitata were performed and toxicological categories were established. Our results showed that water quality, as well as water toxicity, deteriorates as both river systems run through urban areas. Interestingly, monitoring sites with good physicochemical and bacteriological qualities but with toxicity were identified, illustrating that traditional water quality studies do not predict potential toxic effects on living organisms. In addition, a multivariate statistical analysis was performed to detect clusters of monitoring sites according to the water quality status. In the context of climate change, this study provides information to support that integrated water monitoring is an essential tool to ensure sustainable water management and to guarantee economic growth, human health, food security, and environmental protection.

Challenges and opportunities for overcoming dog use in agrochemical evaluation and registration.

Progress in developing new tools, assays, and approaches to assess human hazard and health risk provides an opportunity to re-evaluate the necessity of dog studies for the safety evaluation of agrochemicals. A workshop was held where partic­ipants discussed the strengths and limitations of past use of dogs for pesticide evaluations and registrations. Opportunities were identified to support alternative approaches to answer human safety questions without performing the required 90-day dog study. Development of a decision tree for determining when the dog study might not be necessary to inform pesticide safety and risk assessment was proposed. Such a process will require global regulatory authority participation to lead to its acceptance. The identification of unique effects in dogs that are not identified in rodents will need further evaluation and determination of their relevance to humans. The establishment of in vitro and in silico approaches that can provide critical data on relative species sensitivity and human relevance will be an important tool to advance the decision process. Promising novel tools including in vitro comparative metabolism studies, in silico models, and high-throughput assays able to identify metabolites and mechanisms of action leading to development of adverse outcome pathways will need further development. To replace or eliminate the 90-day dog study, a collaborative, multidisciplinary, international effort that transcends organi­zations and regulatory agencies will be needed in order to develop guidance on when the study would not be necessary for human safety and risk assessment.

Reproductive toxicity by exposure to low concentrations of pesticides in Caenorhabditis elegans.

In view of the recurrent applications of pesticides in agricultural producing countries, the increased presence of these substances in the environment raise a demand for the evaluation of adverse effects on non-target organisms. This study assesses the impact of exposure to five pesticides suspected of being endocrine disruptors (atrazine, 2,4-dichlorophenoxyacetic acid, mancozeb, chlorpyrifos and cypermethrin) on the reproductive development of the nematode Caenorhabditis elegans. To this end, nematodes in the L4 larval stage were exposed to different concentrations of pesticides for 24 h and the consequences on brood size, percentage of gravid nematodes, expression of reproductive-related genes and vitellogenin trafficking and endocytosis were measured. Moreover, 17ß-estradiol was used as an estrogenic control for endocrine disrupting compounds throughout the work. The results showed that all the pesticides disturbed to some extent one or more of the evaluated endpoints. Remarkably, we found that atrazine, 2,4-dichlorophenoxyacetic acid and chlorpyrifos produced comparable responses to 17ß-estradiol suggesting that these pesticides may have estrogen-like endocrine disrupting activity. Atrazine and 17ß-estradiol, as well as 2,4-dichlorophenoxyacetic acid and chlorpyrifos to a lesser extent, decreased the brood size, affected vitellogenin trafficking and endocytosis, and changed the expression of several reproductive-related genes. Conversely, mancozeb and cypermethrin had the least impact on the evaluated endpoint. Cypermethrin affected the brood size at the highest concentration tested and mancozeb altered the distribution of vitellogenin only in approximately 10% of the population. However, both products overexpressed hus-1 and vit-2 genes, indicating that an induction of stress could interfere with the normal development of the nematode. In conclusion, our work proved that C. elegans is a useful biological model to identify the effects of estrogen-like endocrine disruptor compounds, and the sublethal endpoints proposed may serve as an important contribution on evaluating environmental pollutants.

Desmethylclomipramine induces the accumulation of autophagy markers by blocking autophagic flux.

Alterations in the autophagic pathway are associated with the onset and progression of various diseases. However, despite the therapeutic potential for pharmacological modulators of autophagic flux, few such compounds have been characterised. Here we show that clomipramine, an FDA-approved drug long used for the treatment of psychiatric disorders, and its active metabolite desmethylclomipramine (DCMI) interfere with autophagic flux. Treating cells with DCMI caused a significant and specific increase in autophagosomal markers and a concomitant blockage of the degradation of autophagic cargo. This observation might be relevant in therapy in which malignant cells exploit autophagy to survive stress conditions, rendering them more susceptible to the action of cytotoxic agents. In accordance, DCMI-mediated obstruction of autophagic flux increased the cytotoxic effect of chemotherapeutic agents. Collectively, our studies describe a new function of DCMI that can be exploited for the treatment of pathological conditions in which manipulation of autophagic flux is thought to be beneficial.

Ozone washing decreases strawberry susceptibility to Botrytis cinerea while maintaining antioxidant, optical and sensory quality.

This work aimed to evaluate the effect of ozone washing (maximum concentration 3.5 mgL-1- 5 and 15 min) on Botrytis cinerea decay, physicochemical parameters, bioactive compounds, in vitro and in vivo antioxidant activity, and sensory properties of strawberries cv. Albion throughout refrigerated storage at 5 ± 1 °C. A 5 min long ozonation delayed the onset of B. cinerea infection by 4 days, and significantly reduced its incidence as storage progressed (~17 % lesser than in control at day 8), without impairing physicochemical parameters or sensory quality. This treatment did not affect the antioxidant activity of strawberry extracts neither in in vitro (ORAC and ABTS assays) or in vivo assays using Caenorhabditis elegans as a model organism. Higher ozone doses did not achieve greater reduction of B. cinerea decay throughout the storage period. This study demonstrated that exposing strawberries to a 5 min long aqueous ozone treatment could extend their storability at 5 °C.

Glyphosate-based herbicides modulate oxidative stress response in the nematode Caenorhabditis elegans.

Glyphosate-based formulation is used as non-selective and post-emergent herbicides in urban and rural activities. In view of its recurring applications in agricultural producing countries, the increase of glyphosate concentration in the environment stresses the need to test the adverse effects on non-target organisms and assess the risk of its use. This paper analyzes the toxicological and oxidative stress and modulatory effects of a glyphosate commercial formulation (glyphosate F) on the nematode Caenorhabditis elegans. We detected ROS production and enhancement of oxidative stress response in glyphosate F-treated nematodes. Particularly, we found an increased ctl-1 catalase gene expression of a catalase specific activity. In addition, we showed that glyphosate F treatment activated the FOXO transcription factor DAF-16, a critical target of the insulin/IGF-1 signaling pathway, which modulates the transcription of a broad range of genes involved in stress resistance, reproductive development, dauer formation, and longevity. In summary, the exposure of glyphosate F induces an oxidative imbalance in C. elegans that leads to the DAF-16 activation and consequently to the expression of genes that boost the antioxidant defense system. In this regard, clt-1 gene and catalase activity proved to be excellent biomarkers to develop more sensitive protocols to assess the environmental risk of glyphosate use.

PIAS-1 is a checkpoint regulator which affects exit from G1 and G2 by sumoylation of p73.

p73 is a recently described member of the p53 family, and, like p53, it undergoes a number of posttranslational modifications. Here we show, by yeast two-hybrid screening, pull-down assays, and coimmunoprecipitation, that p73alpha, -beta, and -gamma bind to the protein inhibitor of activated STAT-1 (PIAS-1) and that this binding stabilizes p73. PIAS-1 also sumoylates p73alpha, although not the C-terminally truncated isoforms p73beta and -gamma, and this requires the RING finger domain of PIAS-1. The DeltaNp73alpha isoform can also bind, and be sumoylated by, PIAS-1. PIAS-1-mediated sumoylation decreases p73 transcriptional activity on several target promoters, such as Bax. p73 is colocalized in the nucleus with PIAS-1, and sumoylated p73 is located exclusively in the nuclear matrix. PIAS-1 is expressed predominantly during S phase, and PIAS-1 overexpression reduces p73-mediated transcription of p21, with a reduction of cells in G(1) and cell cycle reentry. Inhibition of endogenous PIAS-1 by RNA interference reduces the proportion of cells in S phase and induces G(2) arrest. These data suggest that PIAS-1, acting partly through binding and sumoylation of p73, is an important component of the cell cycle machinery.

The nematode Caenorhabditis elegans as an integrated toxicological tool to assess water quality and pollution.

Determination of water quality status in rivers is critical to establish a sustainable water management policy. For this reason, over the last decades it has been recommended to perform integrated water assessments that include water quantities and physicochemical, ecological and toxicological tests. However, sometimes resources are limited and it is not possible to perform large-scale chemical determinations of pollutants or conduct numerous ecotoxicological tests. To overcome this problem we use and measure the growth, as a response parameter, of the soil nematode Caenorhabditis elegans to assess water quality in rivers. The C. elegans is a ubiquitous organism that has emerged as an important model organism in aquatic and soil toxicology research. The Tunuyán River Basin (Province of Mendoza, Argentina) has been selected as a representative traditional water monitoring system to test the applicability of the C. elegans toxicological bioassay to generate an integrated water quality evaluation. Jointly with the C. elegans toxic assays, physicochemical and bacteriological parameters were determined for each monitoring site. C. elegans bioassays help to identify different water qualities in the river basin. Multivariate statistical analysis (PCA and linear regression models) has allowed us to confirm that traditional water quality studies do not predict potential toxic effects on living organisms. On the contrary, physicochemical and bacteriological analyzes explain <62% of the C. elegans growth response variability, showing that ecotoxicological bioassays are important to obtain a realistic scenario of water quality threats. Our results confirm that the C. elegans bioassay is a sensible and suitable tool to assess toxicity and should be implemented in routine water quality monitoring.

DevStaR: high-throughput quantification of C. elegans developmental stages.

We present DevStaR, an automated computer vision and machine learning system that provides rapid, accurate, and quantitative measurements of C. elegans embryonic viability in high-throughput (HTP) applications. A leading genetic model organism for the study of animal development and behavior, C. elegans is particularly amenable to HTP functional genomic analysis due to its small size and ease of cultivation, but the lack of efficient and quantitative methods to score phenotypes has become a major bottleneck. DevStaR addresses this challenge using a novel hierarchical object recognition machine that rapidly segments, classifies, and counts animals at each developmental stage in images of mixed-stage populations of C. elegans. Here, we describe the algorithmic design of the DevStaR system and demonstrate its performance in scoring image data acquired in HTP screens.

TAp73alpha binds the kinetochore proteins Bub1 and Bub3 resulting in polyploidy.

Aneuploidy is a characteristic of most solid tumors, often associated with negative prognosis. It can arise from two principal mechanisms: from a tetraploid intermediate state, or directly from errors at cell division. The control of cell division, crucial to maintain genomic stability, is still poorly understood in its relationship to aneuploidy. Here we show that the TAp73alpha isoform induces polyploidy when overexpressed. This is possibly due to the interaction of TAp73alpha with kinetochore-related proteins leading to the alteration of mitotic checkpoint abilities. TAp73alpha but not p53 or any of the other p73 isoforms binds Bub1 and Bub3. Since TAp73alpha is frequently overexpressed in cancer, this interaction may contribute to the aneuploidy observed in cancer progression. Our results suggest a novel molecular mechanism leading to aneuploidy involving interference of TAp73alpha with Bub1 and Bub3 resulting in an altered mitotic checkpoint.

Calpain cleavage regulates the protein stability of p73.

The function of p73, a transcription factor belonging to the p53 family, is finely regulated by its steady-state protein stability. p73 protein degradation/stabilization can be regulated by mechanisms in part dependent on the ubiquitin proteasome system (UPS): (i) Itch/NEDD4-like UPS degradation, (ii) NEDD8 UPS degradation, and (iii) NQO1 20S proteasome-dependent (but ubiquitin-independent) breakdown. Here, we show that, in vitro, Calpain I can cleave p73 at two distinct sites: the first proline-rich region and within the oligomerization domain. Consequently, different p73 isoforms can be degraded by calpains, i.e., both N-terminal isoforms (TAp73 and DeltaNp73) as well as the C-terminal isoforms (alpha, beta, gamma, delta). Moreover, overexpression of the specific endogenous calpain inhibitor, calpastatin, in cultured cells increased the steady-state p73 level. This suggests that calpains may play a physiological role in the regulation of p73 protein stability.

The ubiquitin-protein ligase Itch regulates p73 stability.

p73, a member of the p53 family of transcription factors, is upregulated in response to DNA damage, inducing cell cycle arrest and apoptosis. Besides indications that this p73 response is post-transcriptional, little is known about the underlying molecular mechanisms of p73 protein degradation. Ubiquitination and proteasomal-dependent degradation of p53 are regulated by its transcriptional target MDM2. However, unlike p53, p73 binds to, but is not degraded by, MDM2. Here we describe the binding of p73 to Itch, a Hect ubiquitin-protein ligase. Itch selectively binds and ubiquitinates p73 but not p53; this results in the rapid proteasome-dependent degradation of p73. Upon DNA damage Itch itself is downregulated, allowing p73 protein levels to rise and thus interfere with p73 function. In conclusion, we have identified a key mechanism in the control of p73 protein levels both in normal as well as in stress conditions.

Apaf1-dependent programmed cell death is required for inner ear morphogenesis and growth.

During inner ear development programmed cell death occurs in specific areas of the otic epithelium but the significance of it and the molecules involved have remained unclear. We undertook an analysis of mouse mutants in which genes encoding apoptosis-associated molecules have been inactivated. Disruption of the Apaf1 gene led to a dramatic decrease in apoptosis in the inner ear epithelium, severe morphogenetic defects and a significant size reduction of the membranous labyrinth, demonstrating that an Apaf1-dependent apoptotic pathway is necessary for normal inner ear development. This pathway most probably operates through the apoptosome complex because caspase 9 mutant mice suffered similar defects. Inactivation of the Bcl2-like (Bcl2l) gene led to an overall increase in the number of cells undergoing apoptosis but did not cause any major morphogenetic defects. In contrast, decreased apoptosis was observed in specific locations that suffered from developmental deficits, indicating that proapoptotic isoform(s) produced from Bcl2l might have roles in inner ear development. In Apaf1(-/-)/Bcl2l(-/-) double mutant embryos, no cell death could be detected in the otic epithelium, demonstrating that the cell death regulated by the anti-apoptotic Bcl2l isoform, Bcl-X(L) in the otic epithelium is Apaf1-dependent. Furthermore, the otic vesicle failed to close completely in all double mutant embryos analyzed. These results indicate important roles for both Apaf1 and Bcl2l in inner ear development.