Acute Exposure of Upcyte® Hepatocytes to Sub-lethal Concentrations of Graphene Oxide: Impairment of Phase-I Xenobiotic Metabolism and Albumin Transcription

Abstract BackgroundGraphene Oxide (GO) is a promising candidate for nanomedicine applications. Due to the central role of liver in biotransformation of xenobiotics and drugs, the impact of GO on hepatic functional cells represents a crucial evaluation step for its potential implementation as drug. Primary human hepatocytes (PHH) are the election model for studying drug toxicity and metabolism, however current technical limitations may slow down the large-scale diffusion of this cellular tool in in vitro investigations. To assess the potential hepatotoxicity of GO, in this study, we propose an alternative approach employing second-generation upcyte® hepatocytes as cell model, which show metabolic and functional profiles akin to PHH. Cells have been acutely exposed to increasing GO concentrations for 24 hours. Upon sub-lethal concentrations of GO, stress-related cell responses to GO (such as apoptosis, oxidative stress and inflammatory response) have been evaluated, along with a broad investigation of GO impact on specialized hepatic functions.ResultsResults show an IC50 equal to 102.2 μg/mL, which is in line with recent data obtained by hepatocellular carcinoma-derived cells. However, at sub-lethal doses (≤ 80 μg/mL), it is detected a mild activation of early apoptosis, but not oxidative stress or inflammatory response. Importantly, we observed a clear impact of GO on phase-I drug metabolism enzymes (e.g., CYP3A4, CYP2C9) through the inhibition of gene expression and metabolic activity. Conversely, phase-II enzyme system and phase-III efflux transporters were not affected by GO. Finally, GO strongly downregulated the gene expression of Albumin.ConclusionThe presented model of upcyte® hepatocytes appears to be feasible for the assessment of hepatotoxicity of nanomaterials, specifically showing that sub-lethal doses of GO have a negative impact on the specialized hepatic functions of these cells. The impairment of cytochrome P450 system along with the alteration of Albumin gene expression by GO may suggest potential detrimental consequences for human health, as for instance, an altered detoxification from xenobiotics and drugs.