Targeting of circulating Th17 cells by β-D-mannuronic acid (M2000) as a novel medication in patients with rheumatoid arthritis

This study aimed at investigating the inhibitory effect of beta-D-mannuronic acid (M2000) on the Th17 circulating levels and IL-17 a related cytokine in rheumatoid arthritis (RA) patients. The study included 27 patients with RA who had failed response to treatment. All patients were treated orally by M2000 at a dose of 500 mg twice daily for 12 weeks (Clinical trial identifier: IRCT2014011213739N2). The patients based on anti-tumor necrosis factor alpha (TNF alpha) blocker treatment were classified into two groups (conventional group and etanercept group). They were then allowed to continue their treatment excluding non-steroidal anti-inflammatory drugs (NSAIDs). The frequency of circulating Th17 cells and IL-17 serum level were determined before and 12 weeks after M2000 therapy and were compared to the healthy controls by using flow cytometry analysis and ELISA method, respectively. At baseline, higher circulating Th17 and IL-17 serum levels were significantly observed in both groups of RA patients than in the healthy controls (all P < 0.001). The frequency of Th17 cells significantly decreased in the conventional group as well as in the etanercept group after M2000 therapy but the level of reduction was higher in the conventional group compared to the etanercept group (P < 0.03 and P < 0.04, respectively). The IL-17 serum level significantly decreased in both groups after M2000 therapy (P < 0.01 and P < 0.02, respectively). Furthermore, the frequency of Th17 cells was positively correlated with Disease Activity Score (DAS28) (r = 0.34, P = 0.02). M2000 shows the inhibitory effect on the frequency of circulating Th17 cells as well as in the production of IL-17 in RA patients.