Lanthanide Exposure In Vitro Differentially Diminishes MTT Cell Viability in Axenic Neuronal or Glial Cell Model Systems

Applications of lanthanide chemistry have been successful in metallics and the petroleum industry. In the medical realm, lanthanides have shown utility in radiotherapy agents, photodynamic therapy agents, and magnetic resonance imaging (MRI) contrast agents. The lanthanide group elements have a few known biological roles, notably among some bacteria and the yeast Saccharomyces cerevisiae, which have been used as models for changes in gene expression. However, the systematic effects of lanthanide nitrates on eukaryotic cell model systems have not yet been reported. This study presents the first documented effects on cell viability, after acute incubations of various lanthanide nitrate salts, using axenic C6 glial or PC12 neuronal cells in vitro. Cultures were exposed to a 1 mM concentration of lanthanide nitrate salts for 24 h. In comparison to the saline control, several cultures demonstrated significantly lower cell viability, as measured by the MTT viability assay. Data were analyzed as an average absorbance of n = 4 replicate samples, corrected for the average absorbance of cell-free blanks. The reported results were normalized to the average of the saline control cells. Among the 13 lanthanides tested, Praseodymium, Holmium, Erbium, Thulium, and Ytterbium nitrates exhibited the most pronounced inhibitory effects, resulting in over 40% reduction in cell viability at 1 mM for either or both cell types. Recovery after lanthanide exposure also was cell-type-dependent as well as lanthanide-type-dependent, with Lutetium having the greatest effect on both cell types. PC12 cells displayed greater sensitivity for inhibition than the C6 cells with some of the lanthanides but not all. Furthermore, the controls of sodium nitrate and calcium nitrate showed only modest discernible impacts on cell viability for PC12 and C6 cells, highlighting the role of the lanthanides in influencing cell viability.