Genotoxicity

Alvarez-Moya et al., 2014

Carlos Alvarez-Moya, Mónica Reynoso Silva, Carlos Valdez Ramírez, David Gómez Gallardo, Rafael León Sánchez, Alejandro Canales Aguirre, Alfredo Feria Velasco, “Comparison of the in vivo and in vitro genotoxicity of glyphosate isopropylamine salt in three different organisms,” Genetics and Molecular Biology, 2014, 37:1, DOI: 10.1590/S1415-47572014000100016

ABSTRACT:

There is considerable controversy with regard to the genotoxicity of glyphosate, with some reports stating that this compound is non-toxic for fish, birds and mammals. In this work, we used the comet assay to examine the genotoxicity of glyphosate isopropylamine (0.7, 7, 70 and 700 µM) in human lymphocytes, erythrocytes of Oreochromis niloticus and staminal nuclei of Tradescantia (4430) in vitro and in vivo. Cells, nuclei and fish that had and had not been exposed to 5 mM N-nitrosodiethylamine (NDEA) were used as positive and negative controls, respectively. Significant (p < 0.01) genetic damage was observed in vivo and in vitro in all cell types and organisms tested. Human lymphocytes and Tradescantia hairs showed lower genetic damage in vivo compared to in vitro, possibly because of efficient metabolization of the herbicide. In O. niloticus erythrocytes, significant (p < 0.001) genotoxicity was observed at > 7 µM, whereas in vitro, glyphosphate was genotoxic in human lymphocytes and Tradescantia hairs at > 0.7 µM. These results indicate that glyphosate is genotoxic in the cells and organisms studied at concentrations of 0.7-7 µM. FULL TEXT

 

Benbrook, 2019

Benbrook, Charles M., “How did the US EPA and IARC reach diametrically opposed conclusions on the genotoxicity of glyphosate-based herbicides?,” Environmental Sciences Europe, 2019, 31(1), DOI:10.1186/s12302-018-0184-7.

ABSTRACT:

BACKGROUND: The US EPA considers glyphosate as “not likely to be carcinogenic to humans.” The International Agency for Research on Cancer (IARC) has classified glyphosate as “probably carcinogenic to humans (Group 2A).” EPA asserts that there is no convincing evidence that “glyphosate induces mutations in vivo via the oral route.” IARC concludes there is “strong evidence” that exposure to glyphosate is genotoxic through at least two mechanisms known to be associated with human carcinogens (DNA damage, oxidative stress). Why and how did EPA and IARC reach such different conclusions?

RESULTS: A total of 52 genotoxicity assays done by registrants were cited by the EPA in its 2016 evaluation of technical glyphosate, and another 52 assays appeared in the public literature. Of these, one regulatory assay (2%) and 35 published assays (67%) reported positive evidence of a genotoxic response. In the case of formulated, glyphosatebased herbicides (GBHs), 43 regulatory assays were cited by EPA, plus 65 assays published in peer-reviewed journals. Of these, none of the regulatory, and 49 published assays (75%) reported evidence of a genotoxic response following exposure to a GBH. IARC considered a total of 118 genotoxicity assays in six core tables on glyphosate technical, GBHs, and aminomethylphosphonic acid (AMPA), glyphosate’s primary metabolite. EPA’s analysis encompassed 51 of these 118 assays (43%). In addition, IARC analyzed another 81 assays exploring other possible genotoxic mechanisms (mostly related to sex hormones and oxidative stress), of which 62 (77%) reported positive results. IARC placed considerable weight on three positive GBH studies in exposed human populations, whereas EPA placed little or no weight on them.

CONCLUSIONS: EPA and IARC reached diametrically opposed conclusions on glyphosate genotoxicity for three primary reasons: (1) in the core tables compiled by EPA and IARC, the EPA relied mostly on registrant-commissioned, unpublished regulatory studies, 99% of which were negative, while IARC relied mostly on peer-reviewed studies of which 70% were positive (83 of 118); (2) EPA’s evaluation was largely based on data from studies on technical glyphosate, whereas IARC’s review placed heavy weight on the results of formulated GBH and AMPA assays; (3) EPA’s evaluation was focused on typical, general population dietary exposures assuming legal, food-crop uses, and did not take into account, nor address generally higher occupational exposures and risks. IARC’s assessment encompassed data from typical dietary, occupational, and elevated exposure scenarios. More research is needed on real-world exposures to the chemicals within formulated GBHs and the biological fate and consequences of such exposures. FULL TEXT

Bolognesi et al., 1997

Claudia Bolognesi, Stefania Bonatti, Paolo Degan, Elena Gallerani, Marco Peluso, Roberta Rabboni, Paola Roggieri, and Angelo Abbondandolo, “Genotoxic Activity of Glyphosate and Its Technical Formulation Roundup,” Journal of Agricultural and Food Chemistry, 45, 1997, DOI: 10.1021/jf9606518

ABSTRACT:

Glyphosate (N-phosphonomethylglycine) is an effective herbicide acting on the synthesis of aromatic amino acids in plants. The genotoxic potential of this herbicide has been studied:  the results available in the open literature reveal a weak activity of the technical formulation. In this study, the formulated commercial product, Roundup, and its active agent, glyphosate, were tested in the same battery of assays for the induction of DNA damage and chromosomal effects in vivoand in vitro. Swiss CD1 mice were treated intraperitoneally with test substances, and the DNA damage was evaluated by alkaline elution technique and 8-hydroxydeoxyguanosine (8-OHdG) quantification in liver and kidney. The chromosomal damage of the two pesticide preparations was also evaluated in vivo in bone marrow of mice as micronuclei frequency and in vitro in human lymphocyte culture as SCE frequency. A DNA-damaging activity as DNA single-strand breaks and 8-OHdG and a significant increase in chromosomal alterations were observed with both substances in vivo and in vitro. A weak increment of the genotoxic activity was evident using the technical formulation. FULL TEXT

De Almeida et al., 2018

De Almeida, L. K. S., Pletschke, B. I., & Frost, C. L., “Moderate levels of glyphosate and its formulations vary in their cytotoxicity and genotoxicity in a whole blood model and in human cell lines with different estrogen receptor status,” 3 Biotech, 2018, 8(10), 438. DOI: 10.1007/s13205-018-1464-z.

ABSTRACT:

In vitro studies were conducted to determine the short-term cytotoxic and genotoxic effects of pure glyphosate and two glyphosate formulations (Roundup® and Wipeout®) at concentrations relevant to human exposure using whole blood (cytotoxicity) and various cancer cell lines (cytotoxicity and genotoxicity). Pure glyphosate (pure glyph) and Roundup® (Ro) showed similar non-monotonic toxicological profiles at low dose exposure (from 10 microg/ml), whereas Wipeout® (Wo) demonstrated a monotonic reduction in cell viability from a threshold concentration of 50 microg/ml, when tested in whole blood. We evaluated whether using various cancer cells (the estrogen-E2-responsive HEC1A, MCF7 and the estrogen-insensitive MDA-MB-231) exposed to moderate doses (75-500 microg/ml) would indicate varied toxicity and results indicated significant effects in the HEC1A cancer cells. A non-monotonic reduction in cell viability was observed in HEC1A exposed to pure glyph (75-500 microg/ml) and proliferative effects were observed after exposure to Wo (75, 125 and 250 microg/ml). Genotoxicity assessment (test concentration 500 microg/ml) demonstrated DNA damage in the HEC1A and MDA-MB-231 cells. Adjuvants and/or glyphosate impurities were potential contributing factors of toxicity based on the differential toxicities displayed by Ro and Wo in human whole blood and the HEC1A cells. This study contributes to the existing knowledge about in vitro exposure to moderate concentrations of glyphosate or glyphosate formulations at cytotoxic and genotoxic levels. In addition, a suggestion on the relevance of the estrogen receptor status of the cell lines used is provided, leading to the need to further investigate a potential endocrine disruptive role.

DeVito, 2017

DeVito, Michael, “Update on NTP Studies of Glyphosate,” Presented at the National Toxicology Program (NTP) Board of Scientific Counselors Meeting, December 7-8, 2017.

SUMMARY:

Not available.  FULL TEXT

Henner and Backhaus, 2019

Hollert, Henner, & Backhaus, Thomas, “Some food for thought: a short comment on Charles Benbrook´s paper ‘How did the US EPA and IARC reach diametrically opposed conclusions on the genotoxicity of glyphosate-based herbicides?’ and its implications,” Environmental Sciences Europe, 2019, 31(1). DOI: 10.1186/s12302-019-0187-z.

ABSTRACT:

Not available.  FULL TEXT

Hong et al., 2018

Hong, Y., Yang, X., Huang, Y., Yan, G., & Cheng, Y., “Assessment of the oxidative and genotoxic effects of the glyphosate-based herbicide Roundup on the freshwater shrimp, Macrobrachium nipponensis,” Chemosphere, 2018, 210, 896-906. DOI: 10.1016/j.chemosphere.2018.07.069.

ABSTRACT:

In the present study, an acute toxic test was performed to assess the oxidative stress and genotoxic effects of the herbicide on the freshwater shrimp Macrobrachium nipponensis. The results showed that the 48-h and 96-h LC50 values of Roundup to M. nipponensis were 57.684mg/L and 11.237mg/L, respectively. For further investigation, the shrimps were exposed to sublethal concentrations of 0.35, 0.70, 1.40, 2.80 and 5.60mg/L for 96h. A significant decrease in total haemocytes count (THC) was observed at concentration of 5.60mg/L throughout the experiment. The level of superoxide dismutase (SOD), catalase (CAT) and total antioxidant capacity (T-AOC) in all the treatments decreased in a dose- and time-dependent manner except for the concentration group of 0.35mg/L. The malondialdehyde (MDA), hydrogen peroxide (H2O2) and protein carbonyl in serum increased significantly at concentrations of 2.80mg/L and 5.60mg/L. A significant decrease in acetylcholinesterase (AChE) activity was observed at each concentration (P0.05). In addition, the micronucleus (MN) frequency of haemocytes significantly increased (P0.05) at concentrations of 1.40, 2.80 and 5.60mg/L, whereas the comet ratio and %DNA in the tails exhibited a clear time- and dose-dependent response during the exposure. The analysis of the integrated biomarker response (IBR) showed the induction of oxidative stress biomarkers and the inhibition of antioxidants, and this dose-dependent relation suggests the sensitivity and availability of all the biomarkers. These results revealed that Roundup had a prominent toxic effect on M. nipponensis based on the antioxidative response inhibition and genotoxicity.

Jiang et al., 2018

Jiang, X., Zhang, N., Yin, L., Zhang, W. L., Han, F., Liu, W. B., Chen, H. Q., Cao, J., & Liu, J. Y., “A commercial Roundup(R) formulation induced male germ cell apoptosis by promoting the expression of XAF1 in adult mice.,” Toxicology Letters, 2018, 296, 163-172, DOI: 10.1016/j.toxlet.2018.06.1067.

ABSTRACT:

Roundup(R) is extensively used for weed control worldwide. Residues of this compound may lead to side effects of the male reproductive system. However, the toxic effects and mechanisms of Roundup(R) of male germ cells remain unclear. We aimed to investigate the apoptosis-inducing effects of Roundup(R) on mouse male germ cells and explore the role of a novel tumor suppressor XAF1 (X-linked inhibitor of apoptosis-associated factor 1) involved in this process. We demonstrated that Roundup(R) can impair spermatogenesis, decrease sperm motility and concentration, and increase the sperm deformity rate in mice. In addition, excessive apoptosis of germ cells accompanied by the overexpression of XAF1 occurred after Roundup(R) exposure both in vitro and in vivo. Furthermore, the low expression of XIAP (X-linked inhibitor of apoptosis) induced by Roundup(R) was inversely correlated with XAF1. Moreover, the knockdown of XAF1 attenuated germ cell apoptosis, improved XIAP expression and inhibited the activation of its downstream target proteins, caspase-3 and PARP, after Roundup(R) exposure. Taken together, our data indicated that XAF1 plays an important role in Roundup(R)-induced male germ cell apoptosis. The present study suggested that Roundup(R) exposure has potential negative implications on male reproductive health in mammals.

Kasuba et al., 2018

Kasuba, Vilena, Milic, Mirta, Rozgaj, Ruzica, Kopjar, Nevenka, Mladinic, Marin, Zunec, Suzana, Vrdoljak, Ana Lucic, Pavicic, Ivan, Cermak, Ana Marija Marjanovic, Pizent, Alica, Lovakovic, Blanka Tariba, & Zeljezic, Davor, “Effects of low doses of glyphosate on DNA damage, cell proliferation and oxidative stress in the HepG2 cell line,” Environmental Science and Pollution Research, 2017, 24(23), 19267-19281. DOI: 10.1007/s11356-017-9438-y.

ABSTRACT:

We studied the toxic effects of glyphosate in vitro on HepG2 cells exposed for 4 and 24 h to low glyphosate concentrations likely to be encountered in occupational and residential exposures [the acceptable daily intake (ADI; 0.5 μg/mL), residential exposure level (REL; 2.91 μg/mL) and occupational exposure level (OEL; 3.5 μg/mL)]. The assessments were performed using biomarkers of oxidative stress, CCK-8 colorimetric assay for cell proliferation, alkaline comet assay and cytokinesis-block micronucleus (CBMN) cytome assay. The results obtained indicated effects on cell proliferation, both at 4 and 24 h. The levels of primary DNA damage after 4-h exposure were lower in treated vs. control samples, but were not significantly changed after 24 h. Using the CBMN assay, we found a significantly higher number of MN and nuclear buds at ADI and REL after 4 h and a lower number of MN after 24 h. The obtained results revealed significant oxidative damage. Four-hour exposure resulted in significant decrease at ADI [lipid peroxidation and glutathione peroxidase (GSH-Px)] and OEL [lipid peroxidation and level of total antioxidant capacity (TAC)], and 24-h exposure in significant decrease at OEL (TAC and GSH-Px). No significant effects were observed for the level of reactive oxygen species (ROS) and glutathione (GSH) for both treatment, and for 24 h for lipid peroxidation. Taken together, the elevated levels of cytogenetic damage found by the CBMN assay and the mechanisms of primary DNA damage should be further clarified, considering that the comet assay results indicate possible cross-linking or DNA adduct formation.

Kwiatkowska et al., 2017

Kwiatkowska, Marta, Reszka, Edyta, Wozniak, Katarzyna, Jablonska, Ewa, Michalowicz, Jaromir, & Bukowska, Bozena, “DNA damage and methylation induced by glyphosate in human peripheral blood mononuclear cells (in vitro study),” Food and Chemical Toxicology, 2017, 105, 93-98. DOI: 10.1016/j.fct.2017.03.051.

ABSTRACT:

Glyphosate is a very important herbicide that is widely used in the agriculture, and thus the exposure of humans to this substance and its metabolites has been noted. The purpose of this study was to assess DNA damage (determination of single and double strand-breaks by the comet assay) as well as to evaluate DNA methylation (global DNA methylation and methylation of p16 (CDKN2A) and p53 (TP53) promoter regions) in human peripheral blood mononuclear cells (PBMCs) exposed to glyphosate. PBMCs were incubated with the compound studied at concentrations ranging from 0.1 to 10 mM for 24 h. The study has shown that glyphosate induced DNA lesions, which were effectively repaired. However, PBMCs were unable to repair completely DNA damage induced by glyphosate. We also observed a decrease in global DNA methylation level at 0.25 mM of glyphosate. Glyphosate at 0.25 mM and 0.5 mM increased p53 promoter methylation, while it did not induce statistically significant changes in methylation of p16 promoter. To sum up, we have shown for the first time that glyphosate (at high concentrations from 0.5 to 10 mM) may induce DNA damage in leucocytes such as PBMCs and cause DNA methylation in human cells. FULL TEXT