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Received Jul 31, 2017; Revised Nov 1, 2017; Accepted Dec 10, 2017
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1. Introduction
Approximately 1% of the world’s population suffer from schizophrenia (SZ). Schizophrenia is a highly heritable neuropsychiatric disorder of complex genetic etiology. Mitochondrion (mt) is a cellular organelle involved in the regulation of a variety of complex cellular processes. Mitochondria, the cell energy source, have a crucial role in intracellular calcium homeostasis, producing ROS and activating the apoptotic pathway. MtDNA copy number (CN) variation has been suggested as a sensitive index of cellular oxidative stress, inflammation, and mitochondrial dysfunction [1, 2].
The accumulating morphological, genetic, and imaging data delineates mitochondrial multifaceted dysfunction as a pathological factor in schizophrenia [3]. Several studies have evaluated the influence of schizophrenia on mtDNA copy number. Results are controversial to each other. Some authors show lower mtDNA copy number in brain tissues and peripheral lymphocytes of schizophrenia patients compared with healthy controls (HC) [4–7]. Some studies reported no anomalous mtDNA copy number in the tissues of schizophrenia patients [8, 9]. The reason for the observed contradictions may be the lack of sufficient data on the effect of antipsychotic therapy on mtDNA copy number. It is known that administration of antipsychotics involved mitochondrial functions, especially OXPHOS. The antipsychotics inhibit the mitochondrial respiratory chain [3]. However, there are few studies on the impact of antipsychotics on mtDNA content in schizophrenia patients. Li et al. recently had showed that antipsychotic risperidone causes a decrease in the number of mtDNA copies in leukocytes of patients with the first-episode antipsychotic-naïve schizophrenia [4]. Thus, the first objective of our work was to determine the effects of the standard antipsychotic therapy on the number of mtDNA copies in the cells of male patients with paranoid schizophrenia.
Systemic oxidative stress is associated with schizophrenia. Elevated reactive oxygen species (ROS) levels and declined antioxidant statuses have been reported in the brain and peripheral tissues of the patients with schizophrenia [10–12]. However, it is known that oxidative stress in the body is associated with the changes in mtDNA copy number. For example, oxidative stress caused...