The Molecular Responses Of HepG2 Cells To The Exposure Of Ethyl Carbamate As Revealed By Integrated Transcriptomic And Metabolomic Approaches

Along with improvement of living standards,more and more processed foods have come into our general diets,which arouses worldwide concerns over food safety issues.Ethyl carbamate(EC),also known as urethane,can be produced during food processing,especially in fermentation.In 2007,it has been classified as a group 2A carcinogen by the World Health Organization’s International Agency for Research on Cancer(IARC).Due to its extensive existence in fermented foods,EC may have adverse effects on human health.Toxicological investigations into the mechanisms underlying the carcinogenic effects of EC have been carried out in various animal models and have revealed that EC can induce the production of reactive oxygen species(ROS),depurination of DNAs and mitochondrial dysfunction.However,information about the possible carcinogenic and toxicological effects of EC in humans is quite limited.This study was conducted to understand the metabolomic and transcriptomic changes in human hepatocellular carcinoma cells(HepG2)exposed to 100 mM EC for short term(4 h)and long term(12 h)period.Potential EC toxicological mechanisms has been elucidated.These adverse effects of EC on human cell metabolism discovered in this study would facilitate further studies on the risk assessment and provide a reference base for the establishment of EC limitation in our dietary foods.Our integrated transcriptomic and metabolomics analyses data showed that EC treatment exerted profound effects on the metabolome and transcriptome in HepG2 cells.These effects showed a clear time-dependent pattern,and prolonged EC treatment could lead to cell toxicity and eventual cell death..Integrated metabolomic and transcriptomic analyses create opportunities for better understanding of the biological responses of HepG2 cells to EC exposure.And KEGG pathway analysis showed that distinct sets of pathways were affected by treatment at different time points,including nucleotide metabolism,amino acid metabolism,energy metabolism,carbohydrate metabolism,lipid metabolism and peptide metabolism.In general,4 h EC treatment affected mainly the lipid metabolism,while 12 h EC treatment affected metabolic pathways mainly associated with amino acids,nucleotide,and energy metabolism.Further analysis revealed potential molecular mechanisms of EC toxicity.EC exerted its toxic on HepG2 cells via its induction of ROS and accumulation of aldehyde,which in turn induces oxidative stress and cell death via energy and reducing power depletion,membrane integrity disruption,and DNA and protein damage.EC induced ROS in HepG2 cells is derived mainly from the oxidation of fatty acids and possible as well from spermine catabolic pathway.Reduced detoxification capacity accounts for the EC induced accumulation of aldehyde in HepG2 cells.In summary,EC disrupted energy homeostasis,protein function,membrane integrity and nucleotide metabolism in EC treated HepG2 cells,which indicate potential toxic effects of EC on human health.