A longitudinal study on the use of endoplasmic reticulum stress and apoptotic pathways in neutrophils as biomarkers for evaluating the efficacy of dimethyl fumarate treatment in relapsing-remitting multiple sclerosis

Multiple sclerosis (MS) is an autoimmune, neurodegenerative, and neuroinflammatory disease affecting the central nervous system (CNS) and is usually a cause of non-traumatic disability in young adults aged 20-40 years. Dimethyl fumarate (DMF) is an immunomodulatory drug used as a first-line treatment for the most common relapsing-remitting form of MS (RRMS). While there is no definitive cure for MS, treatments that modify the disease course may not always be effective due to inter-individual differences and the heterogeneous nature of symptoms. In this case, biomarkers that can reflect disease progression at an early stage are needed. Neutrophils are the most common leukocytes in the immune system that can phagocytose, regulate inflammatory molecules, and contribute to the autoimmune nature of MS by presenting antigens. The endoplasmic reticulum (ER) stress seen in neurodegenerative diseases leads to loss of cell homeostasis and apoptosis due to the inability to tolerate the increased protein load. Increased levels of inflammatory molecules regulated by neutrophils and ER stress markers in CNS lesions have been reported in MS. In this thesis, the relative expression levels (REL) of ER stress and apoptosis marker genes and proteins in neutrophils of RRMS patients were analyzed in the context of treatment response. REL values of these genes were calculated from real-time PCR results of RRMS patients admitted to the Neurology Outpatient Clinic of Ankara Bilkent City Hospital before DMF treatment (0A) and in groups formed at the 3rd month (3A) and 6th month (6A) of treatment. Analyses showed a significant increase in BCL2 and CASP3 genes' REL values in the 6A group compared to the 0A group. Changes in protein levels of these genes were also analyzed. Analyses among the 0A, 3A, and 6A groups revealed a significant decrease in expanded disability severity scores (EDSS) and a reduction in the number of T2 lesions in the 3A and 6A groups compared to the 0A group. While a negative correlation was found between the change in BCL2 gene's REL values and the change in EDSS score and T2 lesion number, a positive correlation was found between the changes in REL values of Bcl2 and Caspase-3 proteins and the change in T2 lesion number, and a negative correlation was found between the change in EDSS score. This study highlights the importance of the REL values of BCL2 and CASP3 genes, as well as the significant association of BCL2 gene, Caspase-3 and Bcl2 proteins with clinical parameters. It also suggests the evaluation of apoptosis markers as potential biomarkers reflecting treatment response. Furthermore, this thesis is the first study to examine ER stress and apoptosis marker genes in neutrophils of patients with RRMS in the context of DMF treatment response. It contributes to the field of Biomedical Engineering by providing insights into the for the early determination of treatment efficacy in MS, as well as strategies for the development of biomarkers, diagnostic kits and biosensors.