MPO and acute respiratory distress syndrome: In ALI models, FMN increases SOD levels, decreases MPO activity, and reduces the production of proinflammatory mediators such as TNF-α, IL-1β, and IL-6 by activating Nrf2/HO-1 signalling (Zhao et al., 2017; Chen et al., 2021; Ma et al., 2013; Li, 2024).