Effect of single-walled carbon nanotubes on cytochrome P450 activity in human liver microsomes in vitro

Toxicological insights into graphene family materials: Cytochrome P450 modulation and cellular stress in liver cells

Graphene family materials (GFM), including pristine graphene (GN), graphene oxide (GO), and nano-sized graphene oxide (nGO), are increasingly utilized across industrial, environmental, and biomedical domains. Despite their potential benefits, the hazardous effects of GFM, particularly on liver xenobiotic-metabolizing enzymes and cellular functions, are not fully understood. Cytochrome P450 (CYP) are enzymes conserved across species, which play a crucial role in the metabolism of xenobiotics, drugs, environmental pollutants, and endogenous compounds, are key to understanding the biotransformation and detoxification processes impacted by GFM. This study investigates the effects of GFMs on CYP enzymes (CYP1A2, CYP2D6, CYP3A4) in a recombinant CYP system and HepG2 liver cells, alongside an assessment of cellular stress responses. In HepG2 cells, GFMs induced oxidative stress, mitochondrial depolarization, and cytotoxicity, with GN causing the most pronounced effects. GO exhibited the strongest inhibition of CYP enzymatic activity, particularly CYP1A2, in a dose-dependent manner in a recombinant CYP system. None of the tested nanomaterials significantly altered CYP expression, except for nGO, where a slight increase in CYP3A4 protein expression was observed. These findings highlight the significant influence of GFM physicochemical properties on their hazardous potential, especially their ability to disrupt metabolic processes and induce cellular stress. This study emphasizes the critical need for evaluating the safety of GFM in light of their widespread application and potential environmental and human health implications.

Effects of multi-walled carbon nanotubes in soil on earthworm growth and reproduction, enzymatic activities, and metabolomics

Increased production and environmental release of multi-walled carbon nanotubes (MWCNTs) increase soil exposure and potential risk to earthworms. However, MWCNT toxicity to earthworms remains unclear, with some studies identifying negative effects and others negligible effects. In this study, to determine whether exposure to MWCNTs negatively affects earthworms and to elucidate possible mechanisms of toxicity, earthworms were exposed to sublethal soil concentrations of MWCNTs (10, 50, and 100 mg/kg) for 28 days. Earthworm growth and reproduction, activities of cytochrome P450 (CYP) isoforms (1A2, 2C9, and 3A4) and antioxidant enzymes (superoxide dismutase (SOD), catalase (CAT), and glutathione-s-transferase (GST)), and metabolomics were determined. Effects of MWCNTs on earthworms depended on exposure concentration. Exposure to MWCNTs did not significantly affect growth and reproduction of individual earthworms. Exposure to 50 mg/kg MWCNTs significantly increased activities of CYP2C9, CYP3A4, SOD, CAT, and GST but clearly reduced levels of L-aspartate, L-asparagine, and glutamine. With exposure to 100 mg/kg MWCNTs, toxic effects on earthworms were observed, with significant inhibition in activities of CYP isoenzymes and SOD, significant reductions in L-aspartate, L-asparagine, glutamine, and tryptophan, and simultaneous accumulations of citrate, isocitrate, fumarate, 2-oxoglutarate, pyruvate, D-galactose, carbamoyl phosphate, formyl anthranilate, hypoxanthine, and xanthine. Results suggest that toxicity of MWCNTs to earthworms is associated with reduced detoxification capacity, excessive oxidative stress, and disturbance of multiple metabolic pathways, including amino acids metabolism, the tricarboxylic acid cycle, pyruvate metabolism, D-galactose metabolism, and purine metabolism. The study provides new insights to better understand and predict the toxicity of MWCNTs in soil.