Nano fraction of pesticide induces genotoxicity and oxidative stress-dependent reticulum stress.

The implementation of nanotechnology in different sectors has generated expectations as a new source of use due to the novel characteristics that it will bring. Particularly, nano pesticides promise to be more sustainable and less harmful to the ecosystem and human health; however, most studies continue to focus on their efficacy in the field, leaving aside the effect on humans. This project aimed to evaluate the genotoxic effect of a nano-encapsulated pesticide on bronchial epithelial cells (NL-20) in vitro and elucidate the mechanism through which they induce damage. The nano fraction (NF) of the pesticide Karate Zeon® 5 CS was characterized and isolated, and the uptake into the cell and the changes induced in the cellular ultrastructure were evaluated. In addition, the primary markers of oxidative stress, reticulum stress, and genotoxicity were assessed using the micronucleus test. A 700 nm fraction with a Z potential of -40 mV was obtained, whose main component is polyurea formaldehyde; this allows the capsules to enter the cell through macropinocytosis and clathrin-mediated endocytosis. Inside, they induce oxidative stress activating a reticulum stress response via the BIP protein and the IRE-1 sensor, triggering an inflammatory response. Likewise, stress reduces cell proliferation, increasing genotoxic damage through micronuclei; however, this damage is mainly induced by direct contact of the capsules with the nucleus. This pioneering study uses a nanometric encapsulated commercial pesticide to evaluate the molecular mechanism of induced damage. It makes it the first step in analyzing whether these substances represent a contaminant or an emerging solution.

Assessment of genotoxic damage induced by exposure to binary mixtures of polycyclic aromatic hydrocarbons and three heavy metals in male mice.

INTRODUCTION: Heavy metals (HM) and polycyclic aromatic hydrocarbons (PAHs) exposition has been associated with health problems. Therefore, this research evaluated genotoxicity induced in male mice strain CD-1 exposed to benzo[a]anthracene (B[a]A) and benzo[a]pyrene (B[a]P) and their interaction with Fe, Pb, and Al. METHODS: Groups of animals were exposed intraperitoneally to HM, PAHs, and mixtures of both. Peripheral blood samples were taken from 0 to 96 h at 24 h intervals; genotoxicity was determined by micronucleus tests and comet assay. Additionally, toxicity and viability were evaluated. RESULTS: HM and PAHs individually were genotoxic. About toxicity, only Al altered polychromatic erythrocytes number and did not change leukocytes viability. Concerning mixtures, Fe + B[a]P, Fe + B[a]A, Pb + B[a]P increased genotoxicity. There were no changes with Pb + B[a]A. Finally, Al mixtures with both PAHs damage was decreased. CONCLUSIONS: Exposure to HM and PAH caused genetic damage. Fe, Al, and B[a]A, established a genotoxic potential. Every metal can interact with PAHs in different ways. Also, the micronucleus test and the comet assay demonstrated their high capacity and reliability to determine the genotoxic potential of the compounds evaluated in this work.

Comparison of the genotoxicity of two commercial pesticides by their micro and nano size capsules.

The use of nanotechnology in the agrochemical industry has become increasingly popular over the past decade, raising the question of whether these products may represent a risk or benefit compared to their conventional presentations. In this study, we aimed to evaluate the different genotoxic effects of the Complete encapsulated presentation (CEP), the micro encapsulated fraction (MEF), and the nano encapsulated fraction (NEF) of two pesticides (Karate® and Ampligo®) in lymphocytes from human peripheral blood. To test the different fractions, the pesticides were separated by centrifugations by the average size of the capsule, then were characterized by the general composition of the capsule by RAMAN and FTIR spectroscopy and the active ingredient of both pesticides by gas chromatography-mass spectrometry. Each fraction was tested separately and analyzed by comet assay through the tail moment and the percentage of DNA in the tail and the cytokinesis-block micronucleus through their frequency of micronucleus, nucleoplasmic bridges, and nuclear buds. The nuclear division index and the Nuclear Division Cytotoxicity Index were also measured. For both pesticides, the CEP increased the genetic damage observed in the tail moment and percentage of DNA in the tail at all concentrations for both pesticides. However, in the micronucleus test, NEF induced more micronuclei than MEF and CEP in all treatments reducing cell proliferation as the concentration decreased for both pesticides. These results suggested that NEF had more genotoxic effects in both pesticides, increasing the damage to the cells.

The wild plant Gnaphalium lavandulifolium as a sentinel for biomonitoring the effects of environmental heavy metals in the metropolitan area of México Valley.

Biomonitoring is a valuable tool for assessing the presence and effects of air pollutants such as heavy metals (HM); due to their toxicity and stability, these compounds can affect human health and the balance of ecosystems. To assess its potential as a sentinel organism of HM pollution, the wild plant Gnaphalium lavandulifolium was exposed to four sites in the metropolitan area of México Valley (MAMV): Altzomoni (ALT) Coyoacán (COY), Ecatepec (ECA), and Tlalnepantla (TLA) during 2, 4, and 8 weeks, between October and November 2019. Control plants remained under controlled conditions. The chemical analysis determined twelve HM (Al, As, Cd, Co, Cr, Cu, Fe, Mn, Ni, Pb, V, and Zn) in the leaves. Macroscopic damage to the leaves, later determined in semi-thin sections under light microscopy, lead to a finer analysis. Transmission electron microscope (TEM) showed major structural changes: chromatin condensation, protoplast shrinkage, cytoplasm vacuolization, cell wall thinning, decreased number and size of starch grains, and plastoglobules in chloroplasts. All these characteristics of stress-induced programed cell death (sPCD) were related to the significant increase of toxic HM in the leaves of the exposed plants compared to the control (p < 0.05). Immunohistochemistry revealed a significant amount of proteases with caspase 3-like activity in ECA and TLA samples during long exposure times. Ultrastructural changes and sPCD features detected confirmed the usefulness of G. lavandulifolium as a good biomonitor of HM contamination. They supported the possibility of considering subcellular changes as markers of abiotic stress conditions in plants.

Response of Zea mays to multimetal contaminated soils: a multibiomarker approach.

Heavy metals present in mine tailings pollute agroecosystems, put the integrity of the environment at risk and become a major route of exposure to humans. The present study was carried out in Taxco, Guerrero, Mexico, where millions of tons of mine tailings have been deposited. Soils from this region are used for agricultural activities. Maize (Zea mays) was selected as a test plant, because it is one of the most common and important cereal crops in Mexico and worldwide. Thirteen metals were selected and their bioaccumulation in roots, leaves and fruits were measured in plants cultivated in soils contaminated with mine tailings and those cultivated in non-contaminated soils. The effect of metal bioaccumulation on: macro and micromorphology, size, biomass, coloration leaf patterns and on DNA damage levels in different structures were determined. The bioaccumulation pattern was: root > leaf > fruit, being only Mn and Cr bioaccumulated in all three structures and V in the roots and leaves. A significant effect of metal bioaccumulation on 50% of the size and leaf shape and 55% of the biomass characters in Z. mays exposed plants was detected. Regarding micromorphological characters, a significant effect of metal bioaccumulation on 67% of the leaf characters and on 100% of the color basal leaf characters was noted. The effect of metal bioaccumulation on the induction of DNA damage (leaf > fruit > root) was detected employing single cell gel electrophoresis analysis. An approach, in which multi endpoints are used is necessary to estimate the extent of the detrimental effects of metal pollution on agroecosystem integrity contaminated with mine tailings.

In vitro cytotoxicity and genotoxicity of Furia®180 SC (zeta-cypermethrin) and Bulldock 125®SC (ß-cyfluthrin) pyrethroid insecticides in human peripheral blood lymphocytes.

In the present study, human peripheral blood lymphocytes were exposed in vitro to 0, 6, 12, 18, 24, and 30 µg/mL Furia®180 SC (zeta-cypermethrin) and 0, 6.3, 12.5, 18.8, 25, and 31.3 µg/mL Bulldock®125 SC (ß-cyfluthrin). Exposure to 32 µg/mL bleomycin for 24 h served as a positive control. The cytotoxic and genotoxic effects of each insecticide were analyzed using alkaline comet and trypan blue dye exclusion assays. DNA damage was evaluated through three genotoxicity parameters: tail length (TL), tail moment (TM) and tail intensity (TI). Furia®180 SC and Bulldock®125 SC pyrethroid insecticides and bleomycin significantly increased DNA damage in a concentration-dependent manner. Bulldock®125 SC induced more DNA damage than Furia. Lymphocyte viability did not change after exposure to different concentrations of the two pyrethroid insecticides and bleomycin. Moreover, genotoxic results demonstrated that Furia®180 SC and Bulldock®125 SC insecticides caused in vitro DNA damage in human peripheral lymphocytes.

Genotoxic evaluation of common commercial pesticides in human peripheral blood lymphocytes.

This study aims to evaluate the genotoxic potential of four commercial pesticides with diverse health categorizations by different world associations currently in use. We tested the fungicide mancozeb and the insecticides pirimicarb, monocrotophos and permethrin. The research was done with in vitro human peripheral blood lymphocytes using the DNA single gel electrophoresis assay and the cytokinesis-block micronucleus (MN) test, where we analysed common parameters such as the tail moment and the frequency of MN formation. We also measured other parameters like frequency of nucleoplasmic bridges, nuclear buds, apoptosis and necrosis with the MN test. Each pesticide induced significant differences in all of these parameters when compared with the negative control and showed different behaviours in the concentration-dependent response. This could be attributed to their genotoxic potential where mancozeb and monocrotophos induced the highest genetic damage, permethrin caused mainly cell death and pirimicarb had the least impact upon cells. This research provides valuable data about the harmful effects of these pesticides on human cells and may be an important contribution in the construction of a unique international classification of health and to reinforce the use of genotoxic analyses to regulate the use of pesticides.

Monitoring of children with acute gastroenteritis in Madrid, Spain, during 2010-2011: rotavirus genotype distribution after the vaccines introduction.

BACKGROUND AND OBJECTIVES: A structured surveillance study was conducted on children with diarrhea who were hospitalized in Madrid (Spain) during 2010-2011, in order to describe temporal, geographic, and age-related trends in rotavirus (RV) strains after the introduction of the RV vaccines in our country. STUDY DESIGN AND RESULTS: A total of 370 children were enrolled, with RV being detected in 117 (31.6%) cases. Coinfections were detected mainly with rotavirus, astrovirus and norovirus. The most prevalent rotavirus G type was G1 (60.7%) followed by G2 (16.09%), G9 (5.9%), and G12 (5.1%). The G12 genotype appeared for the first time in 2008 in Spain, and it has increased to 5.1% of the cases in this report. Some uncommon P genotypes, such as P[14] and P[6], both with a low percentage, were found. The samples with G1 G2, G9 and G12 genotypes appeared in all ages, but were significantly higher in children under 2 years old. CONCLUSION: A long-term structured surveillance is required in the Spanish post vaccine era, in order to determine the prevalence and variability of RV genotypes. This will especially be needed to distinguish between changes occurring as a result of natural fluctuation in genotype or those (changes) that could be mediated by population immunity to the vaccines. In addition, it will be necessary to study the impact of the current vaccines on the circulating rotavirus strains and on the overall reduction in the prevalence of rotavirus disease among children in Spain.

Multi-biomarker approach reveals the effects of heavy metal bioaccumulation in the foundation species Prosopis laevigata (Fabaceae).

Mining is a major economic activity in many developing countries. However, it disturbs the environment, producing enormous quantities of waste, known as mine tailings, which can have deleterious environmental impact, due to their high heavy metals (HM) content. Often, foundation species that establish on mine tailings are good candidates to study the effects of HM bioaccumulation at different levels of biological organization. Prosopis laevigata is considered a HM hyperaccumulator which presents attributes of a foundation species (FS) and establishes naturally on mine tailings. We evaluated the bioaccumulation of Cu, Pb, and Zn in P. laevigata foliar tissue, the leaf micro- and macro-morphological characters, DNA damage, and population genetic effects. In total, 80 P. laevigata individuals (20/site) belonging to four populations: The individuals from both sites (exposed and reference) bioaccumulated HMs (Pb > Cu > Zn). However, in the exposed individuals, Pb and Cu bioaccumulation was significantly higher. Also, a significant effect of macro- and micro-morphological characters was registered, showing significantly lower values in individuals from the exposed sites. In addition, we found significant differences in genotoxic damage in P. laevigata individuals, between the exposed and reference sites. In contrast, for the micro-morphological characters, none of the analyzed metals had any influence. P. laevigata did not show significant differences in the genetic structure and diversity between exposed and reference populations. However, four haplotypes and four private alleles were found in the exposed populations. Since P. laevigata is a species that establishes naturally in polluted sites and bioaccumulates HM in its foliar tissues, the resulting genetic, individual and population effects have not been severe enough to show detrimental effects; hence, P. laevigata can be a useful tool in phytoremediation strategies for soils polluted with Pb and Cu, maintaining its important ecological functions.

Nanotechnology in agriculture: a review of genotoxic studies of nanopesticides in animal cells.

Agriculture has been and still is one of the most influential primary operations in economic history worldwide. Its social, cultural, and political impact allows the progression and survival of humanity. Sustaining the supply of primary resources is crucial for the future. Therefore, the development of new technologies applied to agrochemicals is growing to obtain better food quality faster. Recently, nanotechnology has gained strength in this field in the last decade, mainly because of the presumed benefits that will carry with it compared with the current commercial presentations, like the decrease of risk in non-target organisms. The harm of pesticides is commonly associated with unwanted effects on human health, some with long-term genotoxic effects. Therefore, it would be relevant to set the existence of a risk or a benefit of the nanopesticides from a genotoxic point of view, comparing against those without this technology. Although some studies are concerned with its genotoxicity in live aquatic organisms, few focus on human in vitro models. Several studies conclude that some of them can induce oxidative stress, leading to DNA damage or cell death. However, there is still much to investigate to establish an accurate and complete assessment. In this review, we aim to give an overview of the genotoxic effect caused by nanopesticides in animal cells and a guide to the evolution of this topic, offering a base and critical review to facilitate future research.

Occupational exposure to pesticides: DNA damage in horticulturist from Nativitas, Tlaxcala in Mexico.

Mexico is a country where agricultural activity is of great importance, but biomonitoring data are still scarce. With more intensive pesticides use per unit area/surface in horticultural productivity, there is a higher impact on environmental contamination and workers' health. Considering that exposure to various pesticide and pesticide mixtures represents an additional genotoxic risk, the appropriate characterization of exposure, confounding factors and the risk itself are very much needed. We compared genetic damage in 42 horticulturists and 46 unexposed controls (Nativitas, Tlaxcala) using alkaline comet (whole blood) and micronucleus (MN) test with nuclear abnormalities (NA) (buccal epithelial cells). Workers demonstrated significantly higher levels of damage (TI%=14.02 ± 2.49 vs. 5.37 ± 0.46; MN=10.14 ± 5.15 vs. 2.40 ± 0.20), with more than 90% of them not using protective clothing nor gloves during application. Combined DNA damage techniques and periodic monitoring together with educational programs for safe pesticide application is the best strategy to assess and prevent workers' health risks.

The HUman MicroNucleus project on eXfoLiated buccal cells (HUMN(XL)): the role of life-style, host factors, occupational exposures, health status, and assay protocol.

The human buccal micronucleus cytome assay (BMCyt) is one of the most widely used techniques to measure genetic damage in human population studies. Reducing protocol variability, assessing the role of confounders, and estimating a range of reference values are research priorities that will be addressed by the HUMN(XL) collaborative study. The HUMN(XL) project evaluates the impact of host factors, occupation, life-style, disease status, and protocol features on the occurrence of MN in exfoliated buccal cells. In addition, the study will provide a range of reference values for all cytome endpoints. A database of 5424 subjects with buccal MN values obtained from 30 laboratories worldwide was compiled and analyzed to investigate the influence of several conditions affecting MN frequency. Random effects models were mostly used to investigate MN predictors. The estimated spontaneous MN frequency was 0.74‰ (95% CI 0.52-1.05). Only staining among technical features influenced MN frequency, with an abnormal increase for non-DNA-specific stains. No effect of gender was evident, while the trend for age was highly significant (p<0.001). Most occupational exposures and a diagnosis of cancer significantly increased MN and other endpoints frequencies. MN frequency increased in heavy smoking (≥40cig/day, FR=1.37; 95% CI 1.03-.82) and decreased with daily fruit consumption (FR=0.68; 95% CI 0.50-0.91). The results of the HUMN(XL) project identified priorities for validation studies, increased the basic knowledge of the assay, and contributed to the creation of a laboratory network which in perspective may allow the evaluation of disease risk associated with MN frequency.

Survival Strategies of Streptococcus pyogenes in Response to Phage Infection.

Bacteriophages exert strong evolutionary pressure on their microbial hosts. In their lytic lifecycle, complete bacterial subpopulations are utilized as hosts for bacteriophage replication. However, during their lysogenic lifecycle, bacteriophages can integrate into the host chromosome and alter the host's genomic make-up, possibly resulting in evolutionary important adjustments. Not surprisingly, bacteria have evolved sophisticated immune systems to protect against phage infection. Streptococcus pyogenes isolates are frequently lysogenic and their prophages have been shown to be major contributors to the virulence of this pathogen. Most S. pyogenes phage research has focused on genomic prophages in relation to virulence, but little is known about the defensive arsenal of S. pyogenes against lytic phage infection. Here, we characterized Phage A1, an S. pyogenes bacteriophage, and investigated several mechanisms that S. pyogenes utilizes to protect itself against phage predation. We show that Phage A1 belongs to the Siphoviridae family and contains a circular double-stranded DNA genome that follows a modular organization described for other streptococcal phages. After infection, the Phage A1 genome can be detected in isolated S. pyogenes survivor strains, which enables the survival of the bacterial host and Phage A1 resistance. Furthermore, we demonstrate that the type II-A CRISPR-Cas system of S. pyogenes acquires new spacers upon phage infection, which are increasingly detectable in the absence of a capsule. Lastly, we show that S. pyogenes produces membrane vesicles that bind to phages, thereby limiting the pool of phages available for infection. Altogether, this work provides novel insight into survival strategies employed by S. pyogenes to combat phage predation.

Robinsonecio gerberifolius as a sentinel organism for atmospheric pollution by heavy metals in several sites of Mexico city and its metropolitan area.

Evaluate the effect of heavy metals (HM) on sentinel organisms such as vascular plants represent a model to estimate toxic hazard due to environmental pollution. In the present study, the plant Robinsonecio gerberifolius was used to evaluate the toxic effects of the HM contained in the leaves of plants that were exposed to 4 different sites in Mexico city and its metropolitan area, during the rainy and dry seasons in the period 2017-2019. The comet assay to evaluate genotoxicity revealed an increase with respect to control (p < 0.05), in 2nd and 8th week of exposure, in all 4 study sites and in both seasons, more significant in the rainy period. An increase in the induction of oxidative stress was also observed in the exposed leaves from the 4 study sites when compared with the control; in some cases, the increases were significant (p < 0.05). In general, α- and ß-carotenoids were increased at 8th week of exposure, in all plants exposed in both seasons, while miR398 increased in plants exposed in 2 study sites (p < 0.05). Finally, toxic HM like aluminum, vanadium, and cadmium, increased significantly in the rainy season, while lead increased in the dry season. We conclude that R. gerberifolius can be considered a sentinel plant for evaluating the presence and general toxic effects caused by the presence of toxic HM that have been documented in the atmosphere of Mexico City and its metropolitan area.

Environmental pollutants: an immunoendocrine perspective on phthalates.

Phthalates are endocrine disrupting compounds (EDCs) used as plasticizers in a wide array of daily-use products, from flooring and automotive parts to medical devices and are even present in the children�s toys. Since these compounds are not covalently bound other molecules, they leach from these synthetic products, causing a high level of human exposure to them. EDCs exert several endocrine effects, most typically, reduced biosynthesis of the male hormone, testosterone and disturbances in estrogen, androgen, PPAR-gamma and AhR that control complex immunoendocrine regulatory networks. Besides impacting the developmental processes and long-term adverse effects, since cells of the immune system express endocrine receptors, and synthetize and respond to several hormones and other endocrine ligands, phthalates also cause dysregulation of immune system.

Moss (Hypnum amabile) as biomonitor of genotoxic damage and as bioaccumulator of atmospheric pollutants at five different sites of Mexico City and metropolitan area.

Mexico City has been classified as one megacity, its altitude, thermal inversions, and high seasonal radiation are factors that prevent dispersion of pollutants, which effects are detrimental to health. Therefore, it is important to have an organism that allows evaluate the damage caused by such exposure, as is the case of mosses that obtain nutrients from the atmosphere; this property makes them excellent biomonitors to evaluate genotoxic damage caused by exposure to pollutants, in addition to its large accumulation capacity. For these reasons and to relate the effects of atmospheric pollution with a biological response, we propose to use the moss Hypnum amabile as a bioaccumulator of atmospheric pollutants and biomonitor of the genotoxic effect that the air pollution can induce it through the comet assay. Mosses were placed in five localities of Mexico City and the metropolitan area on the first days of each month of the dry (cold and warm) and rainy seasons, with a 30-day exposure, after which they were changed for a new sample (for 8 months). Each month, the moss exposed was collected and nuclei were isolated to perform comet assay. To demonstrate heavy metal bioaccumulation capacity, samples were observed in a transmission electron microscope and qualitative microanalysis by scanning electron microscopy was carried out parallel. The chemical analysis detected 14 heavy metals by mass spectrometry method with inductively coupled plasma source. Additionally, 22 polycyclic aromatic hydrocarbons were also determined by gas chromatography-mass spectrometry. Analysis of variance and Kruskal-Wallis test were performed to compare DNA damage of each station against control, which was maintained in the laboratory in a chamber with filtered air. This is the first study on the genotoxicity of mosses exposed to the atmosphere of Mexico City and metropolitan area that in addition to proving their accumulation capacity shows their ability to respond to atmospheric pollutants.

Effects of atrazine and fenoxaprop-ethyl on capacitation and the acrosomal reaction in boar sperm.

Atrazine is a herbicide of the chloro-s-triazine family. It inhibits photosynthesis in plants and is an endocrine disruptor, but its effects on human health are controversial. Fenoxaprop-ethyl, an aryloxy phenoxyalkanoic acid herbicide, inhibits the biosynthesis of fatty acids and provokes depolarization of membranes. The aim of this study is to evaluate the in vitro effects of both herbicides on capacitation, spontaneous acrosome reaction (SAR) and progesterone-induced acrosome reaction (PIAR) in boar sperm. Sperm capacitation is done in TALP-HEPES media for 4 hours. Capacitation and SAR are evaluated immediately; PIAR, 30 minutes later. LC50 for fenoxaprop-ethyl is 60 micromolar [corrected] and 40 micromolar [corrected] for atrazine. Fenoxaprop-ethyl induces capacitation at 60 micromolar [corrected] and SAR at all concentrations, also increases significantly PIAR. Atrazine decreased capacitation whereas increase significantly SAR and PIAR at all concentrations. It seems that fenoxaprop-ethyl and atrazine accelerate the capacitation and the acrosomal reaction, possibly via plasma membrane destabilization.

Extracellular Vesicle RNA: A Universal Mediator of Microbial Communication?

Both extracellular RNAs and extracellular vesicles (EVs) have recently garnered attention as novel mediators of intercellular communication in eukaryotes and prokaryotes alike. EVs not only permit export of RNA, but also facilitate delivery and trans-kingdom exchange of these and other biomolecules, for instance between microbes and their hosts. In this Opinion article, we propose that EV-mediated export of RNA represents a universal mechanism for interkingdom and intrakingdom communication that is conserved among bacterial, archaeal, and eukaryotic microbes. We speculate how microbes might use EV RNA to influence target cell gene expression or manipulate host immune responses.

The effects of organophosphorus insecticides and heavy metals on DNA damage and programmed cell death in two plant models.

The ubiquity of pollutants, such as agrochemicals and heavy metals, constitute a serious risk to human health. To evaluate the induction of DNA damage and programmed cell death (PCD), root cells of Allium cepa and Vicia faba were treated with two organophosphate insecticides (OI), fenthion and malathion, and with two heavy metal (HM) salts, nickel nitrate and potassium dichromate. An alkaline variant of the comet assay was performed to identify DNA breaks; the results showed comets in a dose-dependent manner, while higher concentrations induced clouds following exposure to OIs and HMs. Similarly, treatments with higher concentrations of OIs and HMs were analyzed by immunocytochemistry, and several structural characteristics of PCD were observed, including chromatin condensation, cytoplasmic vacuolization, nuclear shrinkage, condensation of the protoplast away from the cell wall, and nuclei fragmentation with apoptotic-like corpse formation. Abiotic stress also caused other features associated with PCD, such as an increase of active caspase-3-like protein, changes in the location of cytochrome C (Cyt C) toward the cytoplasm, and decreases in extracellular signal-regulated protein kinase (ERK) expression. Genotoxicity results setting out an oxidative via of DNA damage and evidence the role of the high affinity of HM and OI by DNA molecule as underlying cause of genotoxic effect. The PCD features observed in root cells of A. cepa and V. faba suggest that PCD takes place through a process that involves ERK inactivation, culminating in Cyt C release and caspase-3-like activation. The sensitivity of both plant models to abiotic stress was clearly demonstrated, validating their role as good biosensors of DNA breakage and PCD induced by environmental stressors.

Indicators of environmental contamination by heavy metals in leaves of Taraxacum officinale in two zones of the metropolitan area of Mexico City.

The present study was designed to detect the effect of heavy metals in two zones of the Metropolitan Area of Mexico City (MAMC), the Centro de Ciencias de la Atmósfera (CCA), and the Altzomoni station in the Iztaccíhuatl-Popocatépetl National Park. Taraxacum officinale was selected as the indicator organism of responses to atmospheric contamination by heavy metals. Determinations of heavy metals were performed, and total mRNA was extracted to quantify the expression of microRNA398 (miR398), superoxide dismutase 2 (CSD2), and the amounts of free radicals using the bromide of 3-(4,5-dimethylthiazole-2-ilo)-2,5-diphenyltetrazole (MTT) salts reduction assay. Results from the Altzomoni station showed high concentrations of five heavy metals, especially Aluminum, while three heavy metals were identified in the CCA-UNAM zone, most importantly, Vanadium, both in the dry season; miR398 expression presented subtle changes but was greater in the leaves from the stations with higher concentrations of heavy metals. Observations included a significant expression of CSD2, mainly in the dry season in both study zones, where levels were significant with respect to controls (p < 0.05). Reduced MTT was also higher in the dry season than in the rainy season (p < 0.05). In conclusion, the increase in heavy metals on the leaves of Taraxacum officinale induces increased expression of the CSD2 gene and reduced MTT; thus, they can be used as indicators for biomonitoring heavy metal concentrations.