Abstract
Numerous evidences suggest that plant polyphenols may have therapeutic benefits in regulating oxidative stress and providing neuroprotection in many neurodegenerative diseases, including multiple sclerosis (MS). However, these mechanisms are not yet completely understood. In this study, we investigated the effect of olive leaf polyphenols on oxidative stress through oxidation marker level and activity (TBARS, SOD, and GPX) and their protein expression (SOD1, SOD2, and GPX1), as well as the protein expression of Sirtuin 1 (SIRT1) and microglia markers (Iba-1, CD206, and iNOS) and myelin integrity (proteolipid protein expression) in the brain of rats with induced experimental autoimmune encephalomyelitis (EAE) and subjected to olive leaf therapy. Experiments were performed in male EAE DA rats, which were randomly divided into 2 main groups: EAE groups treated with the therapy of olive leaf (EAE+TOL) and untreated EAE control groups. The EAE treated groups consumed olive leaf tea instead of drinking water (ad libitum) from the beginning to the end of the experiment. In addition, olive leaf extract was injected intraperitoneally (i.p.) for the 10 continuous days and started on the 8th day after EAE induction. The clinical course was monitored in both groups until the 30th day after EAE induction. Our results demonstrated that TOL attenuated the clinical course of EAE; reduced the oxidative stress (by decreasing the concentration of MDA); upregulated antioxidant enzymes (SOD1, SOD2, and GPX1), SIRT1 (overall and microglial), and anti-inflammatory M2 microglia; downregulated proinflammatory M1 type; and preserved myelin integrity. These data support the idea that TOL may be an effective therapeutic approach for treating MS and other neurodegenerative diseases.
Highlights
A broad range of evidence suggests that oxidative stress plays a major role in the pathogenesis of neurodegenerative diseases, including multiple sclerosis (MS) [1, 2]
We investigated the effect of olive leaf polyphenols on oxidative stress through oxidation marker level and activity (TBARS, superoxide dismutase (SOD), and Glutathione peroxidase (GPX)) and their protein expression (SOD1, SOD2, and GPX1), as well as the protein expression of Sirtuin 1 (SIRT1) and microglia markers (Iba-1, CD206, and iNOS) and myelin integrity in the brain of rats with induced experimental autoimmune encephalomyelitis (EAE) and subjected to olive leaf therapy
Our results demonstrated that Therapy with olive leaf (TOL) attenuated the clinical course of EAE; reduced the oxidative stress; upregulated antioxidant enzymes (SOD1, SOD2, and GPX1), SIRT1, and anti-inflammatory M2 microglia; downregulated proinflammatory M1 type; and preserved myelin integrity
Summary
A broad range of evidence suggests that oxidative stress plays a major role in the pathogenesis of neurodegenerative diseases, including multiple sclerosis (MS) [1, 2]. Reactive oxygen species (ROS), which if produced in excess during inflammation lead to oxidative stress, have been implicated as mediators of demyelination and axonal damage in both MS and its animal models. An activated microglia produce ROS [3] and NO radicals in MS lesions, which suggests their role in the demyelination and neurodegeneration process of MS [4,5,6,7,8] and accounts for the features of MS pathological findings [9]. The extent of lipid and DNA oxidation correlates significantly with inflammation and oxidative injury of oligodendrocytes and neurons, which is associated with active demyelination and axonal and neuronal injury [10], together with upregulated expression of oxidative molecules and antioxidant enzymes in MS lesions [11,12,13]
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