Effects of Alpha-1 Antitrypsin on the Neutrophil Plasma Membrane Proteome
thesisposted on 10.08.2020 by Thomas Mcenery
In order to distinguish essays and pre-prints from academic theses, we have a separate category. These are often much longer text based documents than a paper.
Alpha-1 antitrypsin (AAT) deficiency (AATD) results in early onset emphysema and
liver disease and represents a common indication for lung transplant. Patients
homozygous for the mutant Z allele (Pi*ZZ) are the most commonly affected by
AATD-related disease. Treatment with weekly infusion of pooled human AAT has
been shown to slow the progression of emphysema in these individuals. AAT is an
important anti-protease and the primary mechanism for lung disease in AATD is via
unopposed action of the serine protease neutrophil elastase. Our hypothesis is that
AAT also functions as a key regulator of neutrophil activation and function. Our aim
is to elucidate the effects of AAT on the circulating neutrophil in vivo by performing
the first proteomic analysis of the neutrophil plasma membrane in AATD, both preand
post-augmentation therapy, as compared to healthy controls.
Neutrophils were isolated from Pi*ZZ AATD individuals and from healthy controls
(n=10 per group). Neutrophils were also isolated from AATD patients on day 0 and
day 2 of AAT augmentation therapy (nadir and peak AAT levels respectively, n=6 per
group) and from FEV1-matched COPD patients without AATD (n=6). A plasma
membrane fraction was prepared by sucrose density ultracentrifugation after lysis by
sonication. Proteomic analysis was performed using liquid chromatography mass
spectrometry following digestion by trypsin. Resultant proteomic data was analysed
for differential expression of proteins between cohorts and between time-points of
Results demonstrated that the neutrophil plasma membrane proteome is significantly
altered in AATD compared to HC. Furthermore, these differences persisted when
controlling for the presence of lung disease. Exogenous AAT altered the neutrophil
proteome, with protein expression on day 2 of augmentation therapy reverting
towards that of COPD inflammatory control. Exogenous AAT in vivo was shown to
modify expression on the neutrophil surface of key proteins associated with
degranulation and integrin-mediated signalling, in keeping with previously
established effects of AAT on neutrophil function.
This high-throughput methodology has generated further hypotheses that will guide
investigation of altered neutrophil function in AATD, as well as the effects of
exogenous AAT. This may have clinical implications, both for individuals with AATD
and for the potential use of AAT as a treatment for inflammatory lung disease.
First SupervisorProfessor Noel Gerry McElvaney
Second SupervisorDr Emer Reeves
CommentsA thesis submitted for the degree of Doctor of Medicine from the Royal College of Surgeons in Ireland in 2019.
Published CitationMcEnery T. Effects of Alpha-1 Antitrypsin on the Neutrophil Plasma Membrane Proteome. [MD Thesis] Dublin: Royal College of Surgeons in Ireland; 2019.
Degree NameDoctor of Medicine (MD)
Date of award30/11/2019
- Doctor of Medicine (MD)