Gadolinium-Based MRI Contrast Agents Induce Mitochondrial Toxicity and Cell Death in Human Neurons, and Toxicity Increases With Reduced Kinetic Stability of the Agent Objectives This preclinical study was devised to investigate potential cellular toxicity in human neurons induced by gadolinium-based contrast agents (GBCAs) used for contrast-enhanced magnetic resonance imaging (MRI). Neurons modeling a subset of those in the basal ganglia were tested, because the basal ganglia region is 1 of 2 brain regions that displays the greatest T1-dependent signal hyperintensity changes. Methods Eight GBCAs were tested. Dopaminergic neurons modeling a subset of those in the basal ganglia were differentiated from an established human neuroblastoma cell line and exposed to increasing concentrations of each agent for 7 days. The tested dosages ranged from clinically relevant concentrations measured in some autopsy patients who had received repeated injections of contrast for MRI, to higher concentrations to reveal dose-dependent toxicity trends. Cell death, mitochondrial membrane potential, mitochondrial oxidative capacity, and mitochondrial function measured by oxygen consumption were quantified in cells treated with each GBCA or the osmolality control mannitol and compared to untreated cells which served as a negative control. Results Mannitol caused no change from negative controls in any of the tests, at any concentration tested. For all GBCAs, cell death increased with exposure dose, with toxicity at clinically relevant doses for agents with lower kinetic stability. Reduction of mitochondrial membrane potential and oxidative respiratory function also generally mirrored the agents' structural kinetic stabilities, with greater impairment at lower concentration for the less stable agents. Conclusions In human neurons modeling a subset of those in the basal ganglia, these results demonstrate a toxic effect of gadolinium-containing MRI contrast agents on mitochondrial respiratory function and cell viability. Toxicity increases as agent concentration increases and as the kinetic stability of the agent decreases. Received for publication January 8, 2019; and accepted for publication, after revision, March 1, 2019. Johannes T. Heverhagen and Val M. Runge share the senior authorship. Author contributions: D.V.B. and V.M.R. conceived of the overall project. D.V.B. conceived the experimental plans, designed the protocols, conducted the experiments, analyzed the data, and produced the final figures. J.K.R. validated reproducibility of quantifications as a second reader. D.V.B. wrote and revised the manuscript. H.v.T.K. and J.T.H. financed and oversaw the project. All authors discussed the results and approved the final manuscript. This work was performed in the laboratory for Experimental Radiology, Inselspital, University Hospital of Bern, located in the Department for BioMedical Research (DBMR), University of Bern. Imaging was conducted at the Live Cell Imaging Core Facility of the Microscopy Imaging Center at the University of Bern. The experiments measuring oxygen consumption and acidification were performed in the laboratory of Stefan Freigang in the Institute of Pathology at the University of Bern. This study was funded by the Department of Diagnostic, Interventional, and Pediatric Radiology, Inselspital, University Hospital of Bern, University of Bern, Bern, Switzerland. The authors declare no conflicts of interest. Correspondence to: Danielle V. Bower, MD, PhD, Department of Diagnostic, Interventional, and Pediatric Radiology, Inselspital, University Hospital of Bern, University of Bern, Freiburgstrasse 10, 3010 Bern, Switzerland. E-mail: danielle.bower@insel.ch. Copyright © 2019 Wolters Kluwer Health, Inc. All rights reserved.