Project description:Glyphosate and 2,4-D are among the most widely used herbicides globally, leading to environmental presence, food contamination, and human contact. Investigations based on current toxicological limits or populational-based herbicide exposures are warranted, and in vitro bioassays provide useful tools for toxicological screening. Thus, this study evaluated the transcriptomic implications of non-cytotoxic exposures to glyphosate, its metabolite aminomethylphosphonic acid (AMPA), or 2,4-D - or to their mixes - on hepatic cells. The half maximal effective concentration (IC50) of each herbicide was calculated (cell viability) in human hepatic C3A cells and 1000-fold lower concentrations were used for transcriptomic analysis (RNA-Seq) after 48h exposure, resembling current toxicological limits and considering herbicide water levels (glyphosate: 0.95 µg/mL; AMPA: 3.7 µg/mL; 2,4-D: 0.56 µg/mL). Glyphosate exposure enriched MAPK-related biological processes (upregulated TNF, FOS, IGF1, and PDGFB), and downregulated genes associated with lipid metabolism (CD36 and PPARA). Many AMPA exposure-related differentially expressed genes (DEGs, such as PFKFB3, HK2, and ALDOA) were associated with glucose metabolic pathways. Glyphosate and its metabolite yielded a common molecular signature, as illustrated by principal component analysis and the function of 212 shared DEGs. The exposure to 2,4-D was associated with the JNK cascade and the solute carrier family annotations. The herbicide mixtures had a discrete effect on enhancing the impact of individual herbicides, although important epithelial-mesenchymal transition genes were exclusively modified by the mixes (COL11A2, LOXL3, SNAI1). Altogether, our data reveals new perspectives on the short-term molecular effects of herbicide exposure in liver cells, emphasizing potential avenues for further exploration.
Project description:Bile acids are steroid compounds from the digestive tracts of vertebrates that enter agricultural environments in unusual high amounts with manure. Bacteria degrading bile acids can readily be isolated from soils and waters including agricultural areas. Under laboratory conditions, these bacteria transiently release steroid compounds as degradation intermediates into the environment. These compounds include androstadienediones (ADDs), which are C19-steroids with potential hormonal effects. Experiments with Caenorhabditis elegans showed that ADDs derived from bacterial bile acid degradation had effects on its tactile response, reproduction rate, and developmental speed. Additional experiments with a deletion mutant as well as transcriptomic analyses revealed that these effects might be conveyed by the putative testosterone receptor NHR-69. Soil microcosms showed that the natural microflora of agricultural soil is readily induced for bile acid degradation accompanied by the transient release of steroid intermediates. Establishment of a model system with a Pseudomonas strain and C. elegans in sand microcosms indicated transient release of ADDs during the course of bile acid degradation and negative effects on the reproduction rate of the nematode. This proof-of-principle study points at bacterial degradation of manure-derived bile acids as a potential and so-far overlooked risk for invertebrates in agricultural soils.
