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A7113 - Alpha-1 Antitrypsin Antisense Oligonucleotide Modulates Protease-Antiprotease Imbalance Without Further Aggravating Smoke-Induced Lung Injury
Author Block: R. Xiao1, K. Stearns1, T. Zelonina1, M. P. Goldklang1, K. Blomenkamp2, J. Teckman2, J. M. D'Armiento1; 1Anesthesiology, Columbia University Medical Center, New York, NY, United States, 2Biochemistry and Molecular Biology, Saint Louis University, Saint Louis, MO, United States.
RATIONALE: Alpha-1 antitrypsin (A1AT) is a serum protease inhibitor that targets the proteases overexpressed during lung injuries, such as those induced by cigarette smoke. Animal models of A1AT deficiency have been limiting since there are five genes encoding for A1AT in the mouse. A newly designed custom alpha-1 antitrypsin antisense oligonucleotide (A1ASO) has the potential to block the expression of all A1AT transcripts, which will allow the generation of a mouse model of A1AT deficiency. Here we hypothesize that murine A1ASO treatment would knock down the expression of A1AT and subsequently aggravate the lung injury induced by long-term smoke exposure. METHODS: 60 male C57BL/6J mice were randomly divided into 4 groups, Air-NoA1ASO (AN), Air-A1ASO (AA), Smoke-NoA1ASO (SN), and Smoke-A1ASO (SA). Smoke exposure was conducted 5 days per week, 5 hours per day, 5 days per week at a concentration of 100~150mg/m3. The A1ASO and control (NoA1ASO) were injected subcutaneously at 10µl/g of body weight once a week at a dose of 50mg/kg/week. After 3 months of weekly injections during smoke exposure, the mice were sacrificed and assessed for expression changes, lung inflammation and emphysematous changes. RESULTS: The injection of A1ASO significantly increased the expression of Cela1 mRNA and decreased the protein level of A1AT in the lung. However, surprisingly despite the decrease in A1AT, the inflammatory cell counts in the bronchoalveolar lavage fluid (BALF) were not significantly affected by A1AS-ASO treatment although the expected difference was observed between smoke and air exposed mice (PSNvsAN=0.03). Analysis of the lung morphometry in the mice demonstrated emphysema development with smoke exposure alone, which was not further aggravated by the reduction of A1AT with the A1ASO. CONCLUSION: Although the A1ASO treatment successfully decreased the expression of A1AT, no effect was seen when these mice were exposed to smoke. Off-target effects or compensatory mechanisms could account for this unexpected finding. Alternatively, the effect of A1ASO on A1AT levels was not robust enough to lead to greater lung injury. These potential mechanisms need to be further investigated in order to fully understand the protease-antiprotease imbalance pertaining to A1AT in the murine smoke exposure model.