title: Oxidative stress decreases functional airway mannose binding lectin in COPD.
abstract: We have previously established that a defect in the ability of alveolar macrophages (AM) to phagocytose apoptotic cells (efferocytosis) and pathogens is a potential therapeutic target in COPD. We further showed that levels of mannose binding lectin (MBL; required for effective macrophage phagocytic function) were reduced in the airways but not circulation of COPD patients. We hypothesized that increased oxidative stress in the airway could be a cause for such disturbances. We therefore studied the effects of oxidation on the structure of the MBL molecule and its functional interactions with macrophages. Oligomeric structure of plasma derived MBL (pdMBL) before and after oxidation (oxMBL) with 2,2'-azobis(2-methylpropionamidine)dihydrochroride (AAPH) was investigated by blue native PAGE. Macrophage function in the presence of pd/oxMBL was assessed by measuring efferocytosis, phagocytosis of non-typeable Haemophilus influenzae (NTHi) and expression of macrophage scavenger receptors. Oxidation disrupted higher order MBL oligomers. This was associated with changed macrophage function evident by a significantly reduced capacity to phagocytose apoptotic cells and NTHi in the presence of oxMBL vs pdMBL (eg, NTHi by 55.9 and 27.0% respectively). Interestingly, oxidation of MBL significantly reduced macrophage phagocytic ability to below control levels. Flow cytometry and immunofluorescence revealed a significant increase in expression of macrophage scavenger receptor (SRA1) in the presence of pdMBL that was abrogated in the presence of oxMBL. We show the pulmonary macrophage dysfunction in COPD may at least partially result from an oxidative stress-induced effect on MBL, and identify a further potential therapeutic strategy for this debilitating disease.
authors.affiliation: Lung Research, Hanson Institute and Department Thoracic Medicine, Royal Adelaide Hospital, Adelaide, South Australia, Australia.
authors.forename: Hai B
authors.initials: HB
authors.lastname: Tran
authors.affiliation: Lung Research, Hanson Institute and Department Thoracic Medicine, Royal Adelaide Hospital, Adelaide, South Australia, Australia.
authors.forename: Jessica
authors.initials: J
authors.lastname: Ahern
authors.affiliation: Lung Research, Hanson Institute and Department Thoracic Medicine, Royal Adelaide Hospital, Adelaide, South Australia, Australia; Department of Medicine, University of Adelaide, Adelaide, South Australia, Australia.
authors.forename: Greg
authors.initials: G
authors.lastname: Hodge
authors.affiliation: Lung Research, Hanson Institute and Department Thoracic Medicine, Royal Adelaide Hospital, Adelaide, South Australia, Australia.
authors.forename: Phillip
authors.initials: P
authors.lastname: Holt
authors.affiliation: Research and Development, Australian Red Cross Blood Service, Brisbane, Queensland, Australia.
authors.forename: Melinda M
authors.initials: MM
authors.lastname: Dean
authors.affiliation: Lung Research, Hanson Institute and Department Thoracic Medicine, Royal Adelaide Hospital, Adelaide, South Australia, Australia; Department of Medicine, University of Adelaide, Adelaide, South Australia, Australia.
authors.forename: Paul N
authors.initials: PN
authors.lastname: Reynolds
authors.affiliation: Lung Research, Hanson Institute and Department Thoracic Medicine, Royal Adelaide Hospital, Adelaide, South Australia, Australia; Department of Medicine, University of Adelaide, Adelaide, South Australia, Australia.
authors.forename: Sandra
authors.initials: S
authors.lastname: Hodge
mesh_terms: D017209:Apoptosis; D001992:Bronchoalveolar Lavage Fluid; D002460:Cell Line; D006801:Humans; D016676:Macrophages, Alveolar / Q000378:metabolism; D037601:Mannose-Binding Lectin / Q000097:blood / Q000378:metabolism*; D010084:Oxidation-Reduction; D018384:Oxidative Stress; D010587:Phagocytosis; D029424:Pulmonary Disease, Chronic Obstructive / Q000097:blood / Q000378:metabolism*; D051116:Receptors, Scavenger / Q000378:metabolism; D020545:Respiratory Mucosa / Q000378:metabolism; D012137:Respiratory System / Q000378:metabolism*
chemical_list: D037601:Mannose-Binding Lectin; D051116:Receptors, Scavenger