FFAR4 and chronic obstructive pulmonary disease: To furtherly investigate the in vivo role of the receptor FFAR4 in CS‐induced pathophysiology, we established a COPD mouse model by administering adeno‐associated virus (AAV)‐Ffar4 intratracheally or TUG891 orally (its chemical structure of TUG891 is shown in Figure 5A; the simplified diagram is shown in Figure 5B).