Alpha-1 Antitrypsin Therapy Modifies Neutrophil Adhesion in Patients with Obstructive Lung Disease
Tom McEnery, Michelle M. White, Debananda Gogoi, Orla Coleman, David A. Bergin, Bakr Jundi, Ryan Flannery, Fatima Abbas T. Alsaif, Sarah A. Landers, Michelle Casey, Danielle M. Dunlea, Paula Meleady, Noel G. McElvaney, Emer P. Reeves
Abstract
Abstract Alpha-1 antitrypsin deficiency (AATD) is characterized by neutrophil-dominated inflammation resulting in emphysema. The cholesterol-rich neutrophil outer plasma membrane plays a central role in adhesion and subsequent transmigration to underlying tissues. This study aimed to investigate mechanisms of increased neutrophil adhesion in AATD and whether alpha-1 antitrypsin (AAT) augmentation therapy abrogates this effect. Plasma and blood neutrophils were donated by healthy controls (n = 20), AATD (n = 30), and AATD patients after AAT augmentation therapy (n = 6). Neutrophil membrane protein expression was investigated using liquid chromatography–tandem mass spectrometry. The effect of once-weekly intravenous AAT augmentation therapy was assessed by calcium fluorometric, μ-calpain, and cell adhesion assays. Decreased neutrophil plasma membrane cholesterol content (P = 0.03), yet increased abundance of integrin α-M (fold change 1.91), integrin α-L (fold change 3.76), and cytoskeletal adaptor proteins including talin-1 (fold change 4.04) were detected on AATD neutrophil plasma membrane fractions. The described inflammatory induced structural changes were a result of a more than twofold increased cytosolic calcium concentration (P = 0.02), leading to significant calcium-dependent μ-calpain activity (3.5-fold change; P = 0.005), resulting in proteolysis of the membrane cholesterol trafficking protein caveolin-1. Treatment of AAT-deficient individuals with AAT augmentation therapy resulted in increased caveolin-1 and membrane cholesterol content (111.8 ± 15.5 vs. 64.18 ± 7.8 μg/2 × 107 cells before and after treatment, respectively; P = 0.02), with concurrent decreased neutrophil integrin expression and adhesion. Results demonstrate an auxiliary benefit of AAT augmentation therapy, evident by a decrease in circulating inflammation and controlled neutrophil adhesion.