Assessment of Cytochrome C Oxidase Dysfunction in the Substantia Nigra/Ventral Tegmental Area in Schizophrenia Matthew W. Rice, Kristen L. Smith, Rosalinda C. Roberts, Emma Perez-Costas . , Miguel Melendez-Ferro* . Department of Psychiatry and Behavioral Neurobiology, University of Alabama at Birmingham, Birmingham, Alabama, United States of America Abstract Perturbations in metabolism are a well-documented but complex facet of schizophrenia pathology. Optimal cellular performance requires the proper functioning of the electron transport chain, which is constituted by four enzymes located within the inner membrane of mitochondria. These enzymes create a proton gradient that is used to power the enzyme ATP synthase, producing ATP, which is crucial for the maintenance of cellular functioning. Anomalies in a single enzyme of the electron transport chain are sufficient to cause disruption of cellular metabolism. The last of these complexes is the cytochrome c oxidase (COX) enzyme, which is composed of thirteen different subunits. COX is a major site for oxidative phosphorylation, and anomalies in this enzyme are one of the most frequent causes of mitochondrial pathology. The objective of the present report was to assess if metabolic anomalies linked to COX dysfunction may contribute to substantia nigra/ventral tegmental area (SN/VTA) pathology in schizophrenia. We tested COX activity in postmortem SN/VTA from schizophrenia and non-psychiatric controls. We also tested the protein expression of key subunits for the assembly and activity of the enzyme, and the effect of antipsychotic medication on subunit expression. COX activity was not significantly different between schizophrenia and non-psychiatric controls. However, we found significant decreases in the expression of subunits II and IV-I of COX in schizophrenia. Interestingly, these decreases were observed in samples containing the entire rostro-caudal extent of the SN/VTA, while no significant differences were observed for samples containing only mid-caudal regions of the SN/VTA. Finally, rats chronically treated with antipsychotic drugs did not show significant changes in COX subunit expression. These findings suggest that COX subunit expression may be compromised in specific sub-regions of the SN/VTA (i.e. rostral regions), which may lead to a faulty assembly of the enzyme and a greater vulnerability to metabolic insult. Citation: Rice MW, Smith KL, Roberts RC, Perez-Costas E, Melendez-Ferro M (2014) Assessment of Cytochrome C Oxidase Dysfunction in the Substantia Nigra/ Ventral Tegmental Area in Schizophrenia. PLoS ONE 9(6): e100054. doi:10.1371/journal.pone.0100054 Editor: Tim Douglas Aumann, Florey Institute of Neuroscience & Mental Health, Australia Received November 22, 2013; Accepted May 21, 2014; Published June 18, 2014 Copyright: ß 2014 Rice et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Funding: Work was supported by NIH R01 grant MH066123 to MMF, EPC and RCR. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. Competing Interests: The authors have declared that no competing interests exist. * Email: lampreas@gmail.com . These authors contributed equally to this work. Introduction Schizophrenia is a devastating mental illness that affects approximately 1% of the world population [1]. Currently, most studies on schizophrenia concentrate on the study of pathologies of either neuronal circuitry or molecular mechanisms at the cellular and subcellular levels. This includes the assessment of cellular metabolism and mitochondrial function. One of the first studies that implicated mitochondrial dysfunc- tion in the pathology of schizophrenia was performed by Takahashi and Ogushi [2], which revealed reduced aerobic glycolysis in schizophrenia post-mortem brain tissue. Since then, perturbations in metabolism have become a well-documented, if complex, facet of schizophrenia pathology. This is also supported by studies showing changes in mitochondrial density and increased mitochondrial morphological anomalies in several brain regions, including the prefrontal and limbic cortex, the striatum and the substantia nigra [3–8]. Some of the most thoroughly studied metabolic anomalies in schizophrenia are related to disruptions in oxidative phosphory- lation. The brain is a high energy-demanding organ, which obtains the majority of its energy from oxidative phosphorylation [9–11] and disruptions of this pathway could account for some of the metabolic anomalies observed in schizophrenia. As an example, decreased concentrations of ATP have been observed in the frontal lobe of schizophrenia subjects [12], which is indicative of a deficit in oxidative phosphorylation. The synthesis of ATP requires proper functioning of the electron transport chain (ETC), which consists of a series of four enzyme complexes located within the inner membrane of the mitochondria [13,14]. These enzymes transfer electrons between electron donors and acceptors, establishing a proton gradient that is ultimately used to power the enzyme ATP synthase [15–18]. Adequate production of ATP is crucial for neuronal plasticity, intracellular signaling, calcium buffering, and neurotransmission [19–23]. Anomalies in any single individual complex of the ETC can be sufficient to cause a disruption in cellular metabolism [24,25]. However, the activity of a given complex is not contingent on the proper functioning of the other complexes [24,26]. PLOS ONE | www.plosone.org 1 June 2014 | Volume 9 | Issue 6 | e100054