MUC5AC and pulmonary emphysema: We found that intratracheally administered Fusobacterium nucleatum, a periodontopathic bacterium that increases in saliva when periodontal disease advances, to elastase‐induced emphysematous mice enhances (i) inflammatory responses, (ii) alveolar wall destruction factor production, (iii) emphysema progression, and (iv) mucin hypersecretion.