engleski

Skeletal muscle in experimental autoimmune encephalomyelitis (EAE)

Multiple sclerosis (MS) is an autoimmune inflammatory demyelinating disease of the central nervous system [1]. Skeletal muscles are recognized as one of the target organs in MS due to central motor function disorders during the progress of the disease. Since the experimental autoimmune encephalomyelitis (EAE) model reproduces the relapsing-remitting course found in most multiple sclerosis patients, this model was used in the study. Numerous evidence has been demonstrated that the inflammatory process induces oxidative stress and reduces cellular antioxidant capacity. Oxidative stress (OS) is one of the contributors to neuronal and axonal injury to the central nervous system (CNS) in MS. On the other hand, decreased the mobility of these patients and changed skeletal muscle characteristics could be a consequence of disturbed glucose transport and uptake in skeletal muscles. It can reflect in glucose transporter 4 (GLUT4) as the most abundant glucose transporter in skeletal muscles. Due to the fact that polyphenols can alter inflammation and regenerate skeletal muscles, treatment with olive leaves polyphenols (OLP) was used in EAE [2]. This study aimed to investigate the EAE development and the effect of OLP on EAE through the relapsing-remitting course by the determination of OS markers and GLUT4 expression in rat skeletal muscles such as gastrocnemius, tibialis anterior and soleus. In this study, the EAE model has investigated on Dark Agouti (DA) rats. Chronic relapsing form of EAE was induced by immunization of rats with bovine brain white matter homogenate (BBH) in the complete Freund’s adjuvant (CFA). In addition, animals were treated with OLP. Male Dark Agouti (DA) rats, 2-3 mo old, weighed 100-200 g were divided randomly into four groups of six as follows: control (healthy) group, EAE20-group treated with BBH + CFA and sacrificed on the 20th day since EAE induction, EAE30-group treated with BBH + CFA and sacrificed on the 30th day since EAE induction, EAE20+OLP-group treated with BBH + CFA and olive leaf extract (1 g/kg, i.p.) and sacrificed on the 20th day (at the time of the second control group, EAE20). The clinical course of the EAE was monitored according to the standard protocol and marked by degrees on a scale of 0 to 4. TBARS, protein carbonyls and glutathione peroxidase activity were determined spectrophotometrically in skeletal muscles homogenates (at pH 7.8). Histological assessment of muscle alteration structure was performed by studying hematoxylin and eosin (H&E) stained slides. The GLUT4 in gastrocnemius, soleus, and tibialis was determined quantitatively by Western blot analysis. Immunofluorescence staining was performed on frozen muscle tissue to visualize immuno-complexes to obtain the distribution of GLUT4 in different regions of the cell. Data were expressed as mean±SD. Differences between groups were assessed by a nonparametric Kruskal–Wallis median, overall median test. Differences with P<0.05 were considered to be statistically significant. Our data suggest that EAE leads to damage and weakness of skeletal muscles. Therapy with olive leaf polyphenols contributes to the improvement of muscle fibres characteristics in MS patients and thus, repairs gastrocnemius, soleus, and tibialis fibres. Skeletal muscle exhibits a different tendency to lipoperoxidation and protein oxidation. In all muscles studied, the expression of GLUT4 was higher at the time of the second relapse and suppressed with the OLP therapy. Based on these findings and the clinical course EAE, we conclude that therapy with OLP may have a positive effect on disease progression. However, the disease requires further research which could eventually lead to new treatments.

autoimmune encephalomyelitis (EAE) ; skeletal muscle ; GLUT4 ; oxidative stress

This work has been supported in part by the University of Rijeka under the project code uniri-prirod-18-46, University of Rijeka Foundation