β-D-mannuronic Acid (M2000) and Inflammatory Cytokines in COVID-19; An In vitro Study

coronavirus disease of 2019 (COVID-19) can be complicated by acute respiratory distress syndrome (ARDS) and may be associated with cytokine storm and multiorgan failure. Anti-inflammatory agents, such as systemic corticosteroids, monoclonal antibodies, and nonsteroidal anti-inflammatory drugs (NSAIDs) can be used for this purpose. In this study, we evaluated the immunomodulatory effect of mannuronic acid (M2000), which is a novel NSAID, on COVID-19-related cytokine storms. This study was conducted in vitro on blood samples of 30 COVID-19 patients who presented with ARDS to a referral center. Peripheral blood mononuclear cells (PBMCs) were isolated from blood samples and incubated with phorbol myristate acetate for 24 hours. M2000 was administered with the dosages of 25 µg/well and 50 µg/well after 4 hours of incubation at 37°C. The quantitative real-time polymerase chain reaction (qRT-PCR) was conducted to assess mRNA gene expression. Enzyme-linked immunosorbent assay (ELISA) was performed to evaluate the supernatant PBMC levels of interleukin (IL)-6, IL-17, tumor necrosis factor (TNF)-α, and interferon (IFN)-γ. Both mRNA expression and the supernatant PBMC levels of IL-17, TNF-α, IL‑6, and IFN‑γ were decreased in PBMCs of COVID-19 patients treated with M2000 compared with the control  group. For the first time, it was observed that M2000 could be effective in alleviating the inflammatory cascade of COVID-19 patients based on an in vitro model. After further studies in vitro and in animal models, M2000 could be considered a novel NSAID drug in COVID-19 patients.