Screening for Early Biomarkers of Cisplatin-Induced Acute Kidney Injury in Rats Through Serum Metabolomics Technology.

OBJECTIVE: To systematically identify early biomarkers of cisplatin-induced acute kidney injury (AKI) in rats. STUDY DESIGN: An experimental study. Place and Duration of the Study: Experimental Animal Laboratory of Lanzhou University, Gansu, China, and the Department of Pharmacy, The First Hospital of Lanzhou University, Gansu, China, from July 2022 to October 2023. METHODOLOGY: In this study, an AKI model was established by continuously injecting cisplatin into rats at a dose of 1 mg/kg once a day for control group and for 2, 3, 4, and 5 days to other four groups, respectively. Subsequently, rat plasma samples were collected for metabolomics analysis to identify early differentiated metabolites in the plasma prior to creatinine elevation. Furthermore, accurate HPLC-MS/MS methods were developed to validate the biomarker variation in other AKI models. RESULTS: The occurrence of time-dependent renal cortical injury and significant alterations of creatinine (Cr) concentration were observed on day-4 and 5, which demonstrated successful model construction. Sixty-six compounds changed on Day-2 while 61 compounds changed on Day-3. Eleven compounds with variable importance in projection (VIP) >1.5 and false discover rate (FDR) <0.2 were selected and identified by HPLC-MS/MS. Among these, N-acetylglutamine and citramalic acid changed earlier than serum creatinine (sCr) in the AKI model. CONCLUSION: N-acetylglutamine and citramalic acid may serve as early biomarker of cisplatin-induced AKI. KEY WORDS: Acute kidney injury, Biomarker, Cisplatin, Metabolomics, LC-MS/MS, Rats.

Identification and characterization of an endogenous biomarker of the renal vectorial transport (OCT2-MATE1).

The renal tubular organic cation transporter 2 (OCT2) and multidrug and toxin extrusion protein 1 (MATE1) mediate the vectorial elimination of many drugs and toxins from the kidney, and endogenous biomarkers for vectorial transport (OCT2-MATE1) would allow more accurate drug dosing and help to characterize drug-drug interactions and toxicity. Human serum uptake in OCT2-overexpressing cells and metabolomics analysis were carried out. Potential biomarkers were verified in vitro and in vivo. The specificity of biomarkers was validated in renal transporter overexpressing cells and the sensitivity was investigated by Km . The results showed that the uptake of thiamine, histamine, and 5-hydroxytryptamine was significantly increased in OCT2-overexpressing cells. In vitro assays confirmed that thiamine, histamine, and 5-hydroxytryptamine were substrates of both OCT2 and MATE1. In vivo measurements indicated that the serum thiamine level was increased significantly in the presence of the rOCT2 inhibitor cimetidine, and the level in renal tissue was increased significantly by the rMATE1 inhibitor pyrimethamine. There were no significant changes in the uptake or efflux of thiamine in cell lines overexpressed OAT1, OAT2, OAT3, MRP4, organic anion transporting polypeptide 4C1, P-gp, peptide transporter 2, urate transporter 1, and OAT4. The Km for thiamine with OCT2 and MATE1 were 71.2 and 10.8 µM, respectively. In addition, the cumulative excretion of thiamine at 2 and 4 h was strongly correlated with metformin excretion (R2  > 0.6). Thus, thiamine is preferentially secreted by the OCT2 and MATE1 in renal tubules and can provide a reference value for evaluating the function of the renal tubular OCT2-MATE1.