Cytogenotoxicity evaluation of a heavy metal mixture, detected in a polluted urban wetland: Micronucleus and comet induction in the Indian green frog (Euphlyctis hexadactylus) erythrocytes and the Allium cepa bioassay

Direct and indirect toxicity mechanisms of the natural insecticide azadirachtin based on in-silico interactions with tubulin, topoisomerase and DNA

Natural pesticides, which attract attention with safe properties, pose a threat to many non-target organisms, so their toxic effects should be studied extensively. In this study, the toxic effects of Azadirachtin, a natural insecticide derived from Azadirachta indica, were investigated by in-vivo and in-silico methods. In-vivo toxic effects were determined using the Allium test and bulbs were treated with 5 mg/L (0.5x EC50), 10 mg/L (EC50), and 20 mg/L (2xEC50) Azadirachtin. In the groups treated with Azadirachtin, there was a decline in germination-related parameters and accordingly growth was delayed. This regression may be related to oxidative stress in the plant, and the increase in malondialdehyde and proline levels in Azadirachtin-applied groups confirms oxidative stress. Azadirachtin toxicity increased dose-dependently and the most significant toxic effect was observed in the group administered 20 mg/L Azadirachtin. In this group, the mitotic index decreased by 43.4% and sticky chromosomes, vagrant chromosomes and fragments were detected at rates of 83.1 ± 4.01, 72.7 ± 3.46 and 65.1 ± 3.51, respectively. By comet analysis, it was determined that Azadirachtin caused DNA fragmentation, and tail DNA, which was 0.10 ± 0.32% in the control group, increased to 34.5 ± 1.35% in the Azadirachtin -treated groups. These cytotoxic and genotoxic effects of Azadirachtin may be due to direct interaction with macromolecules as well as induced oxidative stress. Azadirachtin has been found to interact in-silico with alpha-tubulin, beta-tubulin, topoisomerase I and II, and various DNA sequences. Possible deteriorations in macromolecular structure and functions as a result of these interactions may cause cytotoxic and genotoxic effects. These results suggest that natural insecticides may also be unreliable for non-target organisms, and the toxic effects of compounds presented as "natural" should also be investigated.

Investigation of multidirectional toxicity induced by high-dose molybdenum exposure with Allium test

In this study, the multifaceted toxicity induced by high doses of the essential trace element molybdenum in Allium cepa L. was investigated. Germination, root elongation, weight gain, mitotic index (MI), micronucleus (MN), chromosomal abnormalities (CAs), Comet assay, malondialdehyde (MDA), proline, superoxide dismutase (SOD), catalase (CAT) and anatomical parameters were used as biomarkers of toxicity. In addition, detailed correlation and PCA analyzes were performed for all parameters discussed. On the other hand, this study focused on the development of a two hidden layer deep neural network (DNN) using Matlab. Four experimental groups were designed: control group bulbs were germinated in tap water and application group bulbs were germinated with 1000, 2000 and 4000 mg/L doses of molybdenum for 72 h. After germination, root tips were collected and prepared for analysis. As a result, molybdenum exposure caused a dose-dependent decrease (p < 0.05) in the investigated physiological parameter values, and an increase (p < 0.05) in the cytogenetic (except MI) and biochemical parameter values. Molybdenum exposure induced different types of CAs and various anatomical damages in root meristem cells. Comet assay results showed that the severity of DNA damage increased depending on the increasing molybdenum dose. Detailed correlation and PCA analysis results determined significant positive and negative interactions between the investigated parameters and confirmed the relationships of these parameters with molybdenum doses. It has been found that the DNN model is in close agreement with the actual data showing the accuracy of the predictions. MAE, MAPE, RMSE and R2 were used to evaluate the effectiveness of the DNN model. Collective analysis of these metrics showed that the DNN model performed well. As a result, it has been determined once again that high doses of molybdenum cause multiple toxicity in A. cepa and the Allium test is a reliable universal test for determining this toxicity. Therefore, periodic measurement of molybdenum levels in agricultural soils should be the first priority in preventing molybdenum toxicity.

Metronidazole promotes oxidative stress and DNA fragmentation-mediated myocardial injury in albino mice

The purpose of the present study was to investigate the cardiotoxic effects of Metronidazole (Mtz) in albino mice. The mice were divided into four experimental groups: Gp.I (control group): saline, Gp.II:125 mg/kg b.w Mtz, Gp.III:250 mg/kg b.w, Gp.IV:500 mg/kg b.w Mtz. Heart weight ratio, markers of cardiac injury, markers of oxidative stress, histopathological examinations, DNA fragmentation and spectral analysis were used to determine cardiotoxicity. Administration of 125-500 mg/kg Mtz caused an increase in heart weight and a decrease in body weight. Administration of 500 mg/kg Mtz increased heart weight by 35.5% and decreased body weight by 21.9% compared with control. Mtz-treated mice showed a significant increase in cardiac injury biomarkers and serious alterations in cardiac oxidative stress markers. Histopathological changes of cardiac tissues observed in mice treated with Mtz include myocardial hypertrophy, fibrosis, myocarditis, separation of the muscle fibers, congestion-narrowing in vessels, necrosis, myocardium-vacuolation, myocytolysis, myocyte degeneration, nuclear aggregation, cytoplasmic fragmentation and prevalent nuclei. Mtz treatment already resulted in a significant decrease in the percentage of head DNA and an increase in the percentage of tail DNA. The most striking tail formation among the Mtz-treated groups was observed in the group receiving 500 mg/kg Mtz. In the presence of Mtz, there was a hypochromic shift in the absorption spectrum of DNA, and the potential DNA-Mtz interaction was found to occur in the intercalation mode. These results show that Mtz used against anaerobic bacteria and protozoa in gastrointestinal infections can cause severe cardiotoxic findings in albino mice and cause fragmentation in DNA.

Genotoxicity responses of single and mixed exposure to heavy metals (cadmium, silver, and copper) as environmental pollutants in Drosophila melanogaster

Heavy metals are now persistently present in living things' environments, in addition to their potential toxicity. Therefore, the aim of this study was to utilize D. melanogaster to determine the biological effects induced by different heavy metals including cadmium chloride (CdCl2), copper (II) sulfate pentahydrate (CuSO 4.5 H2O), and silver nitrate (AgNO3). In vivo experiments were conducted utilizing three low and environmentally relevant concentrations from 0.01 to 0.5 mM under single and combined exposure scenarios on D. melanogaster larvae. The endpoints measured included viability, reactive oxygen species (ROS) generation and genotoxic effects using Comet assay and the wing-spot test. Results indicated that tested heavy metals were not toxic in the egg-to adult viability. However, combined exposure (CdCl2+AgNO3 and CdCl2+AgNO3+CuSO 4.5 H2O) resulted in significant genotoxic and unfavorable consequences, as well as antagonistic and/or synergistic effects on oxidative damage and genetic damage.

Toxic, genotoxic, mutagenic, and bioaccumulative effects of metal mixture from settleable particulate matter on American bullfrog tadpoles (Lithobates catesbeianus)

Amphibians are more susceptible to environmental stressors than other vertebrates due to their semipermeable skin and physiological adaptations to living in very specific microhabitats. Therefore, the aim of the present study was to investigate the effects of a metal mixture from settleable particulate matter (SePM) released from metallurgical industries on Lithobates catesbeianus tadpoles. Endpoints analyzed included metal bioconcentration, morphological (biometrical indices), hematological parameters (hemoglobin and blood cell count), and erythrocyte DNA damage (genotoxicity and mutagenicity). American bullfrog tadpoles (Gosner's stage 25) were kept under control condition (no contaminant addition) or exposed to a sub-lethal and environmentally relevant concentration (1 g.L-1) of SePM for 96 h. Tadpoles exposed to SePM exhibited elevated whole blood levels of Fe56, AL, Sn, Pb, Zn, Cr, Cu, Ti, Rb, V, Ce, La, Ag, As. SePM-exposed tadpoles showed a significant decrease in condition factor (12%) and increases in hepatosomatic index (25%), hemoglobin concentration (17%), and total leukocytes (82%), thrombocytes (90%), and monocytes (78%) abundance. In addition, exposed tadpoles showed higher MN and ENAs (340 and 140%, respectively) frequencies, and erythrocyte DNA damage with approximately 1.2- to 1.8-fold increases in comet parameters. Taken together, these results suggest that the multimetal mixture found in SePM is potentially genotoxic and mutagenic to L. catesbeianus tadpoles, induces stress associated with hematological changes, and negatively affects growth. Although such contamination occurs at sublethal levels, regulatory standards are needed to control the emission of SePM and protect amphibian populations.

Integrated environmental assessment of iron ore tailings in floodplain soils and plants after the Fundão Dam disaster in Brazil

Previous studies of the Doce River basin (Brazil) seem to be contradictory regarding the contamination of soils with potentially harmful elements (PHE). This research aimed to perform an integrated assessment of PHE in the soil-plant-tailing system from the area most affected by the iron waste after the Fundão Dam disaster in 2015. Different fractions of PHE (exchangeable, nonexchangeable, reducible, and pseudo-total) were determined on deposited iron waste (DIW), soil waste mixture (SWM), and control soil (CS) samples. Total contents of PHE in Poaceae were also determined, and Allium cepa bioassays were performed to determine DIW and CS cytotoxicity and/or genotoxicity to plants. The Fe and Mn contaminations were the only ones related to the deposition of DIW on floodplains, and other harmful element content (such as As, Hg, Ni, Cd, Cr, and Pb) was not found above baseline values for soils. In addition, a significant part of the Fe and Mn in DIW is readily available or subject to acidification and prolonged flood reduction processes. The high available content of Fe favored its excessive accumulation by Brachiaria. The DIW chemical conditions reduced biological functions of A. cepa under a controlled environment. However, more drastic effects, such as genetic damage, were not seen. The postdisaster action of covering DIW with CS resulted in undesirable enrichment of Pb on the floodplain soils. The integrated results allow the conclusion that the iron waste is not a time bomb for PHE contamination of soils between the Fundão and Risoleta Neves Hydroelectric Dam (~100 km away from Fundão). Integr Environ Assess Manag 2024;20:117-132. © 2023 SETAC.

DNA fragmentation, chromosomal aberrations, and multi-toxic effects induced by nickel and the modulation of Ni-induced damage by pomegranate seed extract in Allium cepa L

This study was designed to assess the recovery effect of pomegranate seed extract (PSEx) against nickel (Ni)-induced damage in Allium cepa. Except for the control group treated with tap water, five experimental groups were exposed to 265 mg L-1 PSEx, 530 mg L-1 PSEx, 1 mg L-1 NiCI2, 265 mg L-1 PSEx + 1 mg L-1 NiCI2, and 530 mg L-1 PSEx + 1 mg L-1 NiCI2, respectively. The toxicity of Ni was examined through the analysis of physiological (germination percentage, weight gain, and root length), cytotoxicity (mitotic index), genotoxicity (micronucleus, chromosomal anomalies, and Comet test), and biochemical (malondialdehyde, proline, chlorophyll a and chlorophyll b contents, the activities of superoxide dismutase and catalase) parameters. Meristematic cell defects were also investigated. The NiCl2-DNA interaction was evaluated through spectral shift analysis. Values of all physiological parameters, mitotic index scores, and chlorophyll contents decreased while micronucleus frequency, DNA tail percentage, chromosomal anomalies, proline, MDA, and enzyme activities increased following Ni administration. According to the tail DNA percentage scale, Ni application caused "high damage" to DNA. Ni-induced chromosomal anomalies were fragment, sticky chromosome, vagrant chromosome, bridge, unbalanced chromatin distribution, reverse polarization, and nucleus with bud. NiCl2-DNA interaction caused a hyperchromic shift in the UV/Vis spectrum of DNA by spectral profile analysis. Ni exposure impaired root meristems as evidenced by the formation of epidermis cell damage, flattened cell nucleus, thickened cortex cell wall, and blurry vascular tissue. Substantial recovery was seen in all parameters with the co-administration of PSEx and Ni. Recovery effects in the parameters were 18-51% and 41-84% in the 265 mg L-1 PSEx + 1 mg L-1 NiCI2 and 530 mg L-1 PSEx + 1 mg L-1 NiCI2 groups, respectively. The Comet scale showed that PSEx applied with Ni reduced DNA damage from "high" to "moderate." Ni-induced thickened cortex cell wall and blurry vascular tissue damage disappeared completely when 530 mg L-1 PSEx was mixed with Ni. PSEx successfully reduced the negative effects of Ni, which can be attributed to its content of antioxidants and bioactive ingredients.

In silico interactions and deep neural network modeling for toxicity profile of methyl methanesulfonate

In this study, the toxicity induced by the alkylating agent methyl methanesulfonate (MMS) in Allium cepa L. was investigated. For this aim, bulbs were divided into 4 groups as control and application (100, 500 and 4000 µM MMS) and germinated for 72 h at 22-24 °C. At the end of the germination period root tips were collected and made ready for analysis by applying traditional preparation methods. Germination, root elongation, weight, mitotic index (MI) values, micronucleus (MN) and chromosomal abnormality (CAs) numbers, malondialdehyde (MDA) levels, superoxide dismutase (SOD) and catalase (CAT) activities and anatomical structures of bulbs were used as indicators to determine toxicity. Moreover the extent of DNA fragmentation induced by MMS was determined by comet assay. To confirm the DNA fragmentation induced by MMS, the DNA-MMS interaction was examined with molecular docking. Correlation and principal component analyses (PCA) were performed to examine the relationship between all parameters and understand the underlying structure and relationships among these parameters. In the present study, a deep neural network (DNN) with two hidden layers implemented in Matlab has been developed for the comparison of the estimated data with the real data. The effect of MDA levels, SOD and CAT activities at 4 different endpoints resulting from administration of various concentrations of MMS, including MN, MI, CAs and DNA damage, was attempted to be estimated by DNN model. It is assumed that the predicted results are in close agreement with the actual data. The effectiveness of the model was evaluated using 4 different metrics, MAE, MAPE, RMSE and R2, which together show that the model performs commendably. As a result, the highest germination, root elongation, weight gain and MI were measured in the control group. MMS application caused a decrease in all physiological parameters and an increase in cytogenetic (except MI) and biochemical parameters. MMS application caused an increase in antioxidant enzyme levels (SOD and CAT) up to a concentration of 500 µM and a decrease at 4000 µM. MMS application induced different types of CAs and anatomical damages in root meristem cells. The results of the comet assay showed that the severity of DNA fragmentation increased with increasing MMS concentration. Molecular docking analysis showed a strong DNA-MMS interaction. The results of correlation and PCA revealed significant positive and negative interactions between the studied parameters and confirmed the interactions of these parameters with MMS. It has been shown that the DNN model developed in this study is a valuable resource for predicting genotoxicity due to oxidative stress and lipid peroxidation. In addition, this model has the potential to help evaluate the genotoxicity status of various chemical compounds. At the end of the study, it was concluded that MMS strongly supports a versatile toxicity in plant cells and the selected parameters are suitable indicators for determining this toxicity.

Detection of heavy metal contamination in Batlama Stream (Turkiye) and the potential toxicity profile

In this study, heavy metal pollution in Batlama stream flowing into the Black Sea from Giresun (Turkiye) province and the toxicity induced by this pollution were investigated by Allium test. Heavy metal concentrations in stream water were analyzed by using ICP-MS. Germination percentage, weight gain, root length, micronucleus (MN), mitotic index (MI), chromosomal abnormalities (CAs), proline, chlorophyll, malondialdehyde (MDA), antioxidant enzyme activities were used as indicators of physiological, cytogenetic and biochemical toxicity. In addition, Comet assay was performed for detecting DNA fragmentation. Anatomical changes caused by heavy metals in the root meristem cells were observed under the microscope. A. cepa bulbs are divided into two groups as control and treatment. The bulbs in the control group were germinated with tap water and the bulbs in the treatment group were germinated with stream water. As a result, heavy metals such as Al, Ti and Co and radioactive heavy metals such as Rb, Sr, Sb and Ba were detected in the stream water above the acceptable parametric values. Heavy metals in the water caused a decrease in germination, root elongation, weight gain, MI and chlorophyll values, and an increase in MDA, proline, SOD, CAT, MN and CAs values. Comet assays indicated the presence of severe DNA damage. In addition, heavy metals in stream water caused different types of CAs and anatomical damage in root meristem cells. As a result, it was determined that there is intense heavy metal pollution in the stream water and this pollution promotes multi-dimensional toxicity in A. cepa, which is an indicator organism. For this reason, the first priority should be to prevent pollution of water resources in order to prevent heavy metal-induced toxicity in water.

Phytotoxicity and genotoxicity of agro-industrial digested sludge hydrochar: The role of heavy metals

Hydrochar is a new carbonaceous product obtained via hydrothermal carbonization of wet biomass, such as sludges or digested sludges, which often have disposal problems, also due to the presence of contaminants such as heavy metals. The properties of the hydrochar led to an interest in using it as an amendment, but the agro-environmental properties must be considered for its safe use. Raw hydrochar produced by agro-industrial digestate and relative three acidic post-treated hydrochars (for heavy metals removal) have been assessed considering their effect on phytotoxicity, soil, plant growth, mutagenicity, and genotoxicity. The chemical characterization showed the effect of post-treatment on heavy metals contents reduction, except for Cu content (hydrochar, 650 mg/kg; post-treated hydrochars, 940 mg/kg, 287 mg/kg, and 420 mg/kg). The acidic post-treatment also reduces the phytotoxicity compared to raw hydrochar (the germination index at 16 % of hydrochar concentration was: hydrochar, 61.48 %; post-treated hydrochars, 82.27 %, 58.28 %, and 82.26 %), but the low pH and the impact on N-cycle probably have caused the detrimental effect on plant growth of post-treated hydrochar. No mutagenic activity was observed in bacteria using Ames test, while all the samples induced chromosomal aberrations in plant cells (Allium cepa test). The approach adopted, which considers phytotoxicity, plant growth-soil effects, and mutagenicity/genotoxicity bioassays has been proven effective for a proper evaluation of organic products derived from waste to promote a sustainable and circular recovery of materials.

Lycopene: an antioxidant product reducing dithane toxicity in Allium cepa L

The current study was undertaken to assess the attenuating potential of lycopene against Dithane toxicity in Allium cepa L. roots. A. cepa bulbs were arranged in 6 groups. The control group was treated with tap water while the other groups were treated with 215 mg/L lycopene, 430 mg/L lycopene, 500 mg/L Dithane, 500 mg/L Dithane + 215 mg/L lycopene and 500 mg/L Dithane + 430 mg/L lycopene, respectively. When the treatments were completed, growth inhibition, biochemical, genotoxicity and meristematic cell injury analyses were performed. Lycopene did not cause any toxic effect when applied alone. While rooting percentage, root elongation, weight gain and mitotic index (MI) decreased in response to Dithane exposure, the frequency of micronucleus (MN) and chromosomal abnormalities (CAs) in addition to malondialdehyde (MDA) level and the catalytic activities of superoxide dismutase (SOD) and catalase (CAT) increased. Dithane promoted fragment, sticky chromosome, vagrant chromosome, unequal distribution of chromatin, bridge, nucleus bud and reverse polarization formation in meristem cells. Dithane also provoked meristematic cell injuries, including indistinct appearance of vascular tissue, epidermis cell damage and flattened cell nucleus. Lycopene mitigated all damage types, depending on the lycopene dose applied with Dithane. Hence, the data analysis revealed that lycopene provides exceptional antioxidant protection against the fungicide Dithane, which has devastating toxic potential.

Heavy metal accumulation efficiency and subsequent of cytogenotoxicity evaluation in the medicinal plant Equisetum hyemale

Heavy metals in soils represent a threat to the environment, food safety, as well as human and animal health. The bioaccumulation of these elements in plants might enhance medium- and long-term adverse health risk promoting genetic alterations that lead to dermal, gastrointestinal, circulatory, renal, and brain disorders. The present study aimed to determine the bioaccumulation potential and cytogenotoxic effect of Equisetum hyemale extracts. E. hyemale seedlings were divided into two groups: exposed group (plants cultivated in soil with heavy metals solution) and control (plants cultivated in soil with distilled water). Heavy metals were quantified in the cultivation soils (control and exposed) and extracts (ethanolic and infusion) of vegetative parts from E. hyemale cultivated in both soils. Root length and cytogenotoxic effect were determined utilizing Allium cepa bioassay. Data demonstrated that Equisetum hyemale present the ability to absorb and bioaccumulate different heavy metals including lead, copper, cobalt manganese, zinc, iron and chromium. Given this property E. hyemale may be considered a reliable bioindicator to assess cytogenotoxicity of certain substances that exert adverse risks to environment and human and animal health.

Chronic toxicity, bioavailability and bioaccumulation of Zn, Cu and Pb in Lactuca sativa exposed to waste from an abandoned gold mine

Abandoned mines with untreated waste cause environmental pollution. The complex mixture of mining waste includes high metal content, anthropogenic chemicals and sterile rocks. Adverse effects of contaminated soils have been widely assessed by the use of plants. The aim of this study was to assess the chronic toxicity of a contaminated soil by waste from an abandoned gold mine on Lactuca sativa and its relationship with the bioavailability and bioaccumulation of Zn, Cu and Pb. Soil samples were taken from the site of mining waste stacking and a reference site in La Planta (Argentina). Contamination indices were calculated and acute and chronic exposures on L. sativa were carried out. Phytotoxicity indices, morphological and biochemical parameters, and concentrations of Zn, Cu and Pb in pseudo total and bioavailable soil fractions and in plant tissue were determined. Concentration- and time-dependent toxicity effects were observed, especially on plant width, fresh aerial biomass, leaf area and percentage of plants with completely necrotic aerial biomass. High levels of Zn (1453.3 ± 220.3 μg g-1) were found in plant tissue compared to Pb (277.2 ± 18.0 μg g-1) and Cu (255.3 ± 25.6 μg g-1). Toxicological endpoints correlated with metal uptake and mining waste concentration. In addition, bioaccumulation factors correlated with mobilisable and water soluble fractions. The concentration of Pb in aerial biomass surpassed the permissible concentrations in leaf vegetables, even at the reference site, indicating that lettuce crop consumption could be risky for the local population's health. This study demonstrated a strong relationship between metal bioavailability, toxicity endpoints and bioaccumulation, contributing with novel information to future ecotoxicological risk assessments and remediation plans.

Assessment of the biological effect of metal ions and their complexes using Allium cepa and Artemia salina assays: a possible environmental implementation of biological inorganic chemistry

The pollution of aquatic ecosystems due to the elevated concentration of a variety of contaminants, such as metal ions, poses a threat to humankind, as these ecosystems are in high relevance with human activities and survivability. The exposure in heavy metal ions is responsible for many severe chronic and pathogenic diseases and some types of cancer as well. Metal ions of the groups 11 (Cu, Ag, Au), 12 (Zn, Cd, Hg), 14 (Sn, Pb) and 15 (Sb, Bi) highly interfere with proteins leading to DNA damage and oxidative stress. While, the detection of these contaminants is mainly based on physicochemical analysis, the chemical determination, however, is deemed ineffective in some cases because of their complex nature. The development of biological models for the evaluation of the presence of metal ions is an attractive solution, which provides more insights regarding their effects. The present work critically reviews the reports published regarding the toxicity assessment of heavy metal ions through Allium cepa and Artemia salina assays. The in vivo toxicity of the agents is not only dose depended, but it is also strongly affected by their ligand type. However, there is no comprehensive study which compares the biological effect of chemical agents against Allium cepa and Artemia salina. Reports that include metal ions and complexes interaction with either Allium cepa or Artemia salina bio-indicators are included in the review.