Proteome profiling of tolbutamide-treated rat primary hepatocytes using nano LC-MS/MS and label-free protein quantitation

Tolbutamide is used as a first line oral antihyperglycemic drug for type 2 diabetes. One side effect of this drug, hepatotoxicity, is well recognized; however, the precise mechanisms underlying tolbutamide-induced hepatotoxicity remain unclear. In this respect, proteomics techniques were used to gain further insight into the mechanistic processes of the hepatotoxicity induced by this drug. In this study, we aimed to identify molecular pathways based on proteins responding to cellular toxicity in tolbutamide-treated primary hepatocytes, using nano UPLC-MS/MS analysis. Rat primary hepatocytes were treated with an IC₂₀ concentration for 24 h to study the hepatotoxic effects of tolbutamide. For high-throughput label-free quantitation, tryptic-digested peptides of proteins from cell lysates were analyzed using LC-MS/MS and quantitated using the IDEAL-Q software, in which several parameters, such as assisted sequence, elution time, and mass-to-charge ratio were included. We quantified a total of 330 distinct proteins from the tolbutamide-treated hepatocytes and identified 55 upregulated and 82 downregulated proteins with expression changes. Among these differentially expressed proteins, we focused mainly on the 18 upregulated proteins belonging to xenobiotic cytochrome P450 (CYP), drug metabolism/detoxification, oxidative stress/antioxidant response, and cell damage pathway. CYP2D1, CYP2C11, UDP-glucuronosyltransferase 2B (UGT2B), superoxide dismutase 2 (SOD2), 60 kDa heat shock protein (HSPD1), heat shock protein 90 (HSP90), and catalase (CAT) were confirmed by Western blot analysis. In addition, various xenobiotic CYP proteins upregulated in the tolbutamide-treated group, CYP2D1, CYP2C13, and CYP2C11 were confirmed by reverse transcriptase-PCR analysis. Our results offer important new insights into the molecular mechanisms of tolbutamide-induced hepatotoxicity.