Neutrophils are major type of blood leukocytes,and are essential for host defense against invading bacteria,fungi,and virus via phagocytosis.However,abnormal and excessive neutrophilic activation releases elastasecaused inflammatory responses in many chronic inflammatory diseases,e.g.chronic obstructive pulmonary disease(COPD),bronchiectasis,acute respiratory distress syndrome,acute phases of rheumatoid arthritis,and acute lung injury.Neutrophil elastase,a basic 30-kDa single polypeptide glycoprotein,is stored in the azurophil granules of neutrophils in its active form,and is released during phagocytosis.