Interleukin 6 but not Interleukin 8 Might be an Indicator of Multiple Sclerosis Progression from Relapse Remitting to Secondary Progressive Status

Background: Multiple Sclerosis (MS) is the most common chronic inflammatory disease of the white matter of the Central Nervous System (CNS). Proinflammatory cytokine network such as interleukin-6 (IL-6) has a role in the initiation of a destructive immune response in CNS and the progression of the disease. This study aimed to evaluate the comparative levels of IL-6 and IL-8 in MS patients and healthy controls and also to assess any fluctuation in IL-6 and IL-8 levels in MS progression. Materials and Methods: This case-control study recruited a total of 183 subjects, including 103 MS patients and 80 sex- and age-matched healthy controls. MS patients included 51 Relapsing Remitting MS (RRMS), 25 secondary progressive MS (SPMS), 27 Primary Progressive MS (PPMS), and Progressive Relapsing MS (PRMS). Clinical findings were collected, and serum levels of IL-6, IL-8, and 25-hydroxyl vitamin D3 (25(OH)D3) were determined with ELISA. Results: The mean serum level of IL-6 was significantly higher in MS patients than healthy controls (23.8±2.1 vs. 15.6±2.7 pg/mL, P=0.043). MS patients with SPMS had more prominent IL-6 levels than RRMS or PPMS (P=0.008). However, IL-8 levels did not show a significant change either in the patients compared with the controls or in the different forms of MS. MS was more prone to progressive form in male patients. Mean 25(OH)D3 level was significantly lower in MS patients than the controls. Meanwhile, the mean 25(OH)D3 level was surprisingly higher in MS patients with SPMS. Conclusion: The increased serum level of IL-6 in more advanced MS status, SPMS, suggests that IL-6 but not IL-8 might be a prognostic marker for the disease deterioration. Besides, the tendency for MS to progress to worse stages in affected men is an important finding that needs further clarification.