Contents lists available at ScienceDirect Multiple Sclerosis and Related Disorders journal homepage: www.elsevier.com/locate/msard Original article Mitochondrial activity is impaired in lymphocytes of MS patients in correlation with disease severity Ayelet Armon-Omer a, ⁎ , Hadar Neuman b , Adi Sharabi-Nov a , Radi Shahien c,d a Research Laboratory, Ziv Medical Center, Zefat, Israel b Zefat Academic College, Zefat, Israel c Department of Neurology, Ziv Medical Center, Zefat, Israel d Faculty of Medicine, Bar Ilan University, Zefat, Israel ARTICLE INFO Keywords: Multiple sclerosis Medication Mitochondria JC1 Lymphocytes ABSTRACT Background: Multiple sclerosis (MS) is a multifactorial disease of the central nervous system in young adults. Mitochondrial respiration provides fuel necessary for cellular function and is especially important in cells with large energy demand including neurons. Various studies suggest that the pathogenesis of MS may be associated with mitochondrial dysfunction. Methods: We examined 145 volunteers including 62 MS patients and healthy controls. MS patients were divided into two groups according to their disease severity: those with mild disability (EDSS=0–3.0) and those with moderate-severe MS (EDSS=3.5–8). After signing an informed consent, blood was taken and was separated to platelets and lymphocytes. Mitochondria activity was monitored as mitochondrial transmembrane potential following staining with JC1 dye in platelets and lymphocytes utilizing flow cytometry. Results: We examined mitochondria activity as JC1 values from all separated lymphocyte samples and found significantly higher levels of mitochondrial activity in lymphocytes separated from healthy controls vs. MS patients (mean of 87.9% vs. 75.6%, p = 0.001). Significant differences in mitochondrial activity were also found when comparing means of groups divided according to MS disease severity. Interestingly, there were no sig- nificant differences in mitochondrial activity between patients treated with diverse medications or untreated patients. Mitochondrial activity was also examined in platelets, but no significant differences were found be- tween groups. Conclusions: Results obtained here show that mitochondrial activity was significantly lower in MS patients in comparison to healthy controls. In addition, there was a significant difference in mitochondrial activity de- pending on MS degree of disability. These initial findings in a peripheral examination hold potential for new diagnostic biomarkers to be considered in the future. Introduction Multiple sclerosis (MS) is a chronic demyelinating disease of the Central Nervous System (CNS), requiring long-term treatment. The disease is characterized by an inflammatory process and damage to the myelin sheaths around the CNS axons, ultimately leading to demyeli- nation, axonal degeneration and scarring. Myelin protects the axon from potentially harmful exogenous factors while enhancing neural impulse transmission efficacy. The loss of myelin results therefore in a multitude of neurological impairments and increased energy demand from mitochondria. The clinical presentation of MS is heterogeneous and characterized by a broad spectrum of sensory, motor, cognitive, and neuropsychiatric symptoms and appears in several distinct disease courses (Compston and Coles, 2008). The etiology of the disease is not known, although, it is thought to be primarily a CD4 T-cell-mediated disease. The mechanisms of action are complex, involving effects at various levels of cellular function. It has been further suggested that mitochondrial activity may also be involved in the etiology of MS. Various studies suggest that the pathogenesis of MS may involve mitochondrial dysfunction (Barcelos et al., 2019; Regenold et al., 2008; Witte et al., 2014). Further evidence linking mitochondrial dysfunction to MS has been examined through evaluation of postmortem tissues, showing by electron micro- scope scanning decreased numbers of mitochondria within demyeli- nated lesions (Dutta et al., 2006). Recent work in experimental disease models indicates mitochondrial dysfunction and axon degeneration https://doi.org/10.1016/j.msard.2020.102025 Received 2 October 2019; Received in revised form 30 January 2020; Accepted 23 February 2020 ⁎ Corresponding author. E-mail addresses: ayelet.o@ziv.health.gov.il (A. Armon-Omer), shahien.r@ziv.health.gov.il (R. Shahien). Multiple Sclerosis and Related Disorders 41 (2020) 102025 2211-0348/ © 2020 Elsevier B.V. All rights reserved. T