CELA1 Mediates Progressive Emphysema in Alpha-1 Antitrypsin Deficiency

Chymotrypsin-like elastase 1 (CELA1) is a serine protease that is neutralized by α1-antitrypsin (AAT) and prevents emphysema in a murine antisense oligonucleotide model of AAT-deficient emphysema. Mice with genetic ablation of AAT do not have emphysema at baseline but develop emphysema with injury and aging. We tested the role of CELA1 in emphysema development in this genetic model of AAT-deficiency following tracheal lipopolysacharide (LPS), 8 months of cigarette smoke (CS) exposure, aging, and a low-dose tracheal porcine pancreatic elastase (LD-PPE) model. In this last model, we performed proteomic analysis to understand differences in lung protein composition. We were unable to show that AAT(−/−) mice developed more emphysema than wild type with LPS. In the LD-PPE model, AAT(−/−) mice developed progressive emphysema from which Cela1(−/−)&AAT(−/−) mice were protected. In the CS model, Cela1(−/−)&AAT(−/−) mice had worse emphysema than AAT(−/−), and in the aging model, 72–75 week-old Cela1(−/−) &AAT(−/−) mice had less emphysema than AAT(−/−) mice. Proteomic analysis of AAT(−/−) vs. wildtype lungs in the LD-PPE model showed reduced amounts of AAT proteins and increased amounts of proteins related to Rho and Rac1 GTPases and protein oxidation. Similar analysis of Cela1(−/−)&AAT(−/−) vs. AAT(−/−) lungs showed differences in neutrophil degranulation, elastin fiber synthesis, and glutathione metabolism. Thus, Cela1 prevents post-injury emphysema progression in AAT-deficiency, but it has no effect and potentially worsens emphysema in response to chronic inflammation and injury. Prior to developing anti-CELA1 therapies for AAT-deficient emphysema, an understanding of why and how CS exacerbates emphysema in Cela1 deficiency is needed.