1H NMR spectroscopic studies on the characterization of renal cell lines and identification of novel potential markers of in vitro nephrotoxicity

Cell cultures are increasingly used in the evaluation of chemically-induced nephrotoxicity. The utili of renal cell culture systems in toxicology would be improved, however, if better characterized and more specific markers of toxicity were available. High resolution proton nuclear magnetic resonance (¹H NMR) spectroscopy is well suited to the study of toxicological events and has identified many novel markers of nephrotoxicity in vivo. In this study, ¹H NMR spectroscopy has been used to characterize the biochemical composition of two renal cell lines of different nephronal origin, LLC-PK₁ (pig proximal tubule) and Madin-Darby canine kidney (MDCK, distal tubule). The early biochemical responses of these cell lines to the model proximal tubular toxin S-(1,2dichlorovinyl)i-L-cysteine (DCVC) and the renal medullary toxin 2-chloroethanamine (CEA) have also been investigated. For each line, 500 MHz ¹H NMR spectra of protein-free acetone extracts of cells and culture medium gave characteristic and reproducible profiles of low MW constituents, including amino and organic acids, glucose and soluble membrane precursors, such as choline and myo-inositol. Treatment-related changes in several low MW compounds not routinely measured in toxicological studies were revealed by NMR specboscopy before marked cytotoxicity was observed by phase contrast microscopy. For example, LLC-PK₁ cells treated with 60 μM DCVC showed a marked decrease in intracellular choline levels within 3 h which suggests an effect on the balance of choline synthesis and utilization. Wrthin 9 h of treatment with DCVC there were decreases in intracellular acetate and alanine concentrations which may be indicative of a decrease in fatty acid oxidation and biglyceride metabolism accompanied by an increase in gluconeogenesis. In MDCK cells, 1 h post treatment with 5 mM CEA, intracellular glycine was decreased. This study indicates the potential power and applicability of ¹H NMR spectroscopy for evaluating the biochemical and metabolic effects of toxins in cell culture systems and provides a novel approach to identifying new markers of tissue damage.