MUC5AC and chronic obstructive pulmonary disease: In conclusion, TP-TR can reduce the expression of TLR4 and TGF-β in COPD rats, thus alleviating airway inflammation and pulmonary fibrosis, reducing the expression of MUC5AC and MUC5B, alleviating airway mucus hypersecretion, and reducing the expression of MMP9 and MMP12 to delay lung tissue destruction and improve lung function.