Neutrophil elastase (NE) is a protein hydrolyzing enzyme, the secretion of which is increased by smoke exposure, excessive NE damages bronchial epithelial cells,[68] and NE increases levels of placental growth factor, which stimulates bronchial epithelial cells to increase intracellular autophagic vesicles.[64] As a result, NE initiates intracellular autophagy, and inhibiting this process could be used to treat COPD. The gene discussed is ELANE; the disease is chronic obstructive pulmonary disease.