Effects of low doses of glyphosate on DNA damage, cell proliferation and oxidative stress in the HepG2 cell line

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.

Re-registration Challenges of Glyphosate in the European Union

“…A study of exposure to glyphosate on human HepG2 cells using biomarkers of oxidative stress found prompt (upon 4 h) elevated levels of permanent DNA damage (micronucleus formation) in cytokinesis-block micronucleus cytome assay and in alkaline comet assay (indicating a possible aneugenic effect), as well as decreases in lipid peroxidation, glutathione peroxidase activity and total antioxidant capacity at occupational exposure level (0.0035 mg/ml) revealing oxidative damage. In contrast, no significant effects remained upon 24 h of exposure in the levels of reactive oxygen species, glutathione and lipid peroxidation, indicating a certain ability of the cells to cope with prolonged exposure (Kašuba et al, 2017). Supported by an optical biosensor method and holographic microscopy, Roundup Classic R and glyphosate have recently been shown to inhibit normal cell adhesion of MC3T3-E1cells with IC 50 values upon 1 h of exposure of 0.086 and 0.59 mg/ml in serum-containing medium and 0.10 and 1.97 mg/ml in serum-free conditions, respectively; and the approximately one order of magnitude higher inhibitory potency of Roundup Classic R was proven to be attributed to POEA (Farkas et al, 2018).…”

Oxidative stress, cholinesterase activity, and DNA damage in the liver, whole blood, and plasma of Wistar rats following a 28-day exposure to glyphosate

“…Based on the evidence from these new studies and our own evidence (46), we decided to look further into the toxicological mechanisms and effects of sublethal, environmentally relevant (yet allegedly human-safe) glyphosate doses in rats to see how they affect: (a) body weight and liver weight, (b) cholinesterase (ChE), AChE, and butyrylcholinesterase (BChE) activities, (c) oxidative stress markers (lipid peroxidation, reactive oxygen species, GSH, and GSH-Px), and (d) the levels of primary DNA damage in leukocytes and small and medium-sized liver cells, all of which are the established markers of glyphosate mechanisms and effects.…”

“…With knowledge this limited, we need to go further to investigate the toxicokinetic profile of glyphosate with multiple doses, ranging between low and high for mechanistic understanding and key events in the biological pathways as well as time-or dosedependencies (45). The reason for looking into low doses is the new evidence of harmful effects (2,35,46,47), which gets worse with sub-chronic and chronic exposure (35,37). Glyphosate traces found in human urine and blood of agricultural and non-agricultural workers, pregnant women and children (2,14,(48)(49)(50)(51)(52) point to a higher risk of longterm environmental exposure (53).…”

Quantification of glyphosate and aminomethylphosphonic acid from microbiome reactor fluids

“…As the shikimate pathway is present in higher plants, glyphosate was found to be an efficient general herbicide . Since the shikimate pathway is absent in humans and animals, there is no mechanistic explanation for the observed effects of glyphosate on the redox status in mammalian cells or its possible carcinogenicity …”

“…2 As the shikimate pathway is present in higher plants, glyphosate was found to be an efficient general herbicide. 3 Since the shikimate pathway is absent in humans and animals, there is no mechanistic explanation for the observed effects of glyphosate on the redox status in mammalian cells [4][5][6] or its possible carcinogenicity. 7 However, several microorganisms express a glyphosate-sensitive EPSPS, and thus the molecule may influence the gut microbiome of animals 8 and thereby mediate an adverse effect on a host.…”