α₁ Antitrypsin therapy modulates the neutrophil membrane proteome and secretome

Abstract

Obstructive pulmonary disease in patients with α1 antitrypsin (AAT) deficiency (AATD) occurs earlier in life compared with patients without AATD. To understand this further, the aim of this study was to investigate whether AATD presents with altered neutrophil characteristics, due to the specific lack of plasma AAT, compared with non-AATD COPD.This study focussed on the neutrophil plasma membrane and, by use of label-free tandem mass spectrometry, the proteome of the neutrophil membrane was compared in forced expiratory volume in 1 s (FEV1)-matched AATD, non-AATD COPD and in AATD patients receiving weekly AAT augmentation therapy (n=6 patients per cohort). Altered protein expression in AATD was confirmed by Western blot, ELISA and fluorescence resonance energy transfer analysis.The neutrophil membrane proteome in AATD differed significantly from that of COPD as demonstrated by increased abundance and activity of primary granule proteins including neutrophil elastase on the cell surface in AATD. The signalling mechanism underlying increased degranulation involved Rac2 activation, subsequently resulting in proteinase-activated receptor 2 activation by serine proteinases and enhanced reactive oxygen species production. In vitro and ex vivo, AAT reduced primary granule release and the described plasma membrane variance was resolved post-AAT augmentation therapy in vivo, the effects of which significantly altered the AATD neutrophil membrane proteome to that of a non-AATD COPD cell.These results provide strong insight into the mechanism of neutrophil driven airways disease associated with AATD. Therapeutic AAT augmentation modified the membrane proteome to that of a typical COPD cell, with implications for clinical practice.

Pulmonary Toxicity of Realistic Alveolar Deposition Concentrations of Ultrafine Particulate Matters in Human Normal Bronchial Epithelial Cell

“…Both UFPM-treated groups showed signi cant decreases in the A1AT protein expression (Figure 6). The UFPM-induced imbalance of A1AT may increase the risk of developing COPD (Li et al 2009, Murphy et al 2020. Clearly, UFPM is a major contributor to PM-induced COPD.…”

Implications of a Change of Paradigm in Alpha1 Antitrypsin Deficiency Augmentation Therapy: From Biochemical to Clinical Efficacy

“…As a result, these two letters have opened up new questions about the repercussion of abrupt cessation of augmentation therapy that should be further explored. Very recently the role of AAT as a modulator of the neutrophil membrane has been described, providing new data on the role of neutrophil-associated AATD disease [56]. .…”

Alpha-1 Antitrypsin Augmentation Inhibits Proteolysis of Neutrophil Membrane Voltage-Gated Proton Channel-1 in Alpha-1 Deficient Individuals

“…In turn, NE itself can amplify the cycle of inflammation in AATD by stimulating the production of immune cell chemotactic factors, including leukotriene B 4 , by AATD alveolar macrophages [ 24 ] and neutrophils [ 25 ], and the production of the potent chemokine interleukin-8 by epithelial cells [ 26 ]. Moreover, neutrophil receptors can be affected by high protease activity [ 27 , 28 ] and NE cleavage of protease-activated receptor 2 leads to excessive extracellular reactive oxygen species (ROS) production in the absence of AAT [ 29 ]. AAT augmentation therapy is the only specific therapy approved by the Food and Drug Administration for the treatment of AATD, demonstrating a reduced rate of lung density loss [ 30 , 31 ], and alleviation of the described NE neutrophil signaling effects [ 25 , 29 ].…”

“…Moreover, neutrophil receptors can be affected by high protease activity [ 27 , 28 ] and NE cleavage of protease-activated receptor 2 leads to excessive extracellular reactive oxygen species (ROS) production in the absence of AAT [ 29 ]. AAT augmentation therapy is the only specific therapy approved by the Food and Drug Administration for the treatment of AATD, demonstrating a reduced rate of lung density loss [ 30 , 31 ], and alleviation of the described NE neutrophil signaling effects [ 25 , 29 ].…”

“…Due to the reported functional changes in AATD neutrophils, including increased chemotaxis [ 32 ], increased primary granule degranulation [ 25 ], delayed bacterial killing [ 33 ], and a recent study demonstrating alterations in the membrane proteome of circulating AATD neutrophils [ 29 ], we chose to explore the expression of membrane voltage-gated proton channel-1 (HVCN1). HVCN1 activity is integrally linked to NADPH-oxidase activity of neutrophils and functions to transfer protons from the cytosol to the vacuolar lumen or extracellular milieu, thereby preventing membrane depolarization.…”