PBMC of Multiple Sclerosis Patients Show Deregulation of OPA1 Processing Associated with Increased ROS and PHB2 Protein Levels

Abstract

Multiple sclerosis (MS) is an autoimmune disease in which activated lymphocytes affect the central nervous system. Increase of reactive oxygen species (ROS), impairment of mitochondria-mediated apoptosis and mitochondrial alterations have been reported in peripheral lymphocytes of MS patients. Mitochondria-mediated apoptosis is regulated by several mechanisms and proteins. Among others, optic atrophy 1 (OPA1) protein plays a key role in the regulating mitochondrial dynamics, cristae architecture and release of pro-apoptotic factors. Very interesting, mutations in OPA1 gene, have been associated with multiple sclerosis-like disorder. We have analyzed OPA1 and some factors involved in its regulation. Fifteen patients with MS and fifteen healthy control subjects (HC) were enrolled into the study and peripheral blood mononuclear cells (PBMCs) were isolated. H2O2 level was measured spectrofluorimetrically, OPA1, PHB2, SIRT3, and OMA1 were analyzed by western blotting. Statistical analysis was performed using Student’s t-test. The results showed that PBMC of MS patients were characterized by a deregulation of OPA1 processing associated with increased H2O2 production, inactivation of OMA1 and increase of PHB2 protein level. The presented data suggest that the alteration of PHB2, OMA1, and OPA1 processing could be involved in resistance towards apoptosis. These molecular parameters could also be useful to assess disease activity.

Mitochondria, Oxidative Stress, cAMP Signalling and Apoptosis: A Crossroads in Lymphocytes of Multiple Sclerosis, a Possible Role of Nutraceutics

“…Data reported that the plasma of MS patients show a lower antioxidant capacity [ 61 ] and higher levels of oxidative damage to lipid and proteins [ 61 , 62 ]. Our study conducted in PBMCs from 15 MS patients and 15 healthy subjects showed increased level of H 2 O 2 in MS with respect to healthy subjects [ 25 ] detected spectrofluorimetrically by dichlorodihydrofluorescin (DCFDA) probe. Interesting, the increased level of ROS production correlated with deregulation of some proteins involved in the mitochondrial dynamics and apoptosis [ 25 ].…”

“…Our study conducted in PBMCs from 15 MS patients and 15 healthy subjects showed increased level of H 2 O 2 in MS with respect to healthy subjects [ 25 ] detected spectrofluorimetrically by dichlorodihydrofluorescin (DCFDA) probe. Interesting, the increased level of ROS production correlated with deregulation of some proteins involved in the mitochondrial dynamics and apoptosis [ 25 ]. Another report, carried out in PBMC of 34 MS and 24 healthy subjects, showed a higher concentration of anion superoxide in MS evaluated by flow cytometry, associated with a decrease in the protein content of the mitochondrial OXPHOS (complexes I–V) [ 24 ].…”

“…Many stress conditions, such as apoptotic stimuli, trigger L-OPA1 conversion into S-OPA1 [ 95 ]. Recently it has been shown in PBMC of MS patients a different proteolytic processing of OPA1 compared with healthy controls [ 25 ]. The activity and processing of OPA1 are controlled by mitochondrial proteases, OMA1 and YMEL1 and regulated by post-translational modification such as sirtuin 3 (SIRT3)-dependent acetylation status [ 95 , 99 ] and OS [ 95 , 100 ].…”

“…OMA1-dependent degradation of OPA1 is a cellular response to OS, in fact, although OMA1 is constitutively active, it shows an enhanced activity in response to OS [ 100 ]. However, PBMCs of MS patients present an increase of ROS level that does not lead to the increase of the stress-induced active form of OMA1, but rather to the accumulation of the inactive form of OMA1 [ 25 ]. SIRT3 has a crucial role in many OS-mediated cellular responses [ 100 ], in the controlling of bioenergetics and antioxidant defense of mitochondria under OS [ 101 ].…”

“…It has been reported that the increase of cAMP level attenuates the T lymphocyte-mediated production of pro-inflammatory cytokines such as IFN-γ and interleukin (IL)-1b (IL-1b) suggesting that a decrease of cAMP level is required for T cell activation [ 14 , 20 , 21 ]. The activation of immune cells, especially T cells, is also related to OS [ 15 ] and the peripheral blood mononuclear cells (PBMCs) of MS patients show an impaired redox status associated with a metabolic reprogramming that includes mitochondrial alterations [ 22 , 23 , 24 , 25 ].…”