FGF21 and acute respiratory distress syndrome: To further investigate the relationship between FGF21 and JAK2/STAT3 signaling pathway in ALI progression, Coumermycin A1 (CA), a classic agonist of JAK2, was used to give to LPS-induced ALI mice after treated with FGF21 (3 mg/kg) for 0.5 h (Fig. 5a).