Alpha-1 antitrypsin supplementation improves alveolar macrophages efferocytosis and phagocytosis following cigarette smoke exposure

PLoS One. 2017 Apr 27;12(4):e0176073. doi: 10.1371/journal.pone.0176073. eCollection 2017.

Abstract

Cigarette smoking (CS), the main risk factor for COPD (chronic obstructive pulmonary disease) in developed countries, decreases alveolar macrophages (AM) clearance of both apoptotic cells and bacterial pathogens. This global deficit of AM engulfment may explain why active smokers have worse outcomes of COPD exacerbations, episodes characterized by airway infection and inflammation that carry high morbidity and healthcare cost. When administered as intravenous supplementation, the acute phase-reactant alpha-1 antitrypsin (A1AT) reduces the severity of COPD exacerbations in A1AT deficient (AATD) individuals and of bacterial pneumonia in murine models, but the effect of A1AT on AM scavenging functions has not been reported. Apoptotic cell clearance (efferocytosis) was measured in human AM isolated from patients with COPD, in primary rat AM or differentiated monocytes exposed to CS ex vivo, and in AM recovered from mice exposed to CS. A1AT (100 μg/mL, 16 h) significantly ameliorated efferocytosis (by ~50%) in AM of active smokers or AM exposed ex vivo to CS. A1AT significantly improved AM global engulfment, including phagocytosis, even when cells were simultaneously challenged with apoptotic and Fc-coated (bacteria-like) targets. The improved efferocytosis in A1AT-treated macrophages was associated with inhibition of tumor necrosis factor-α converting enzyme (TACE) activity, decreased mannose receptor shedding, and markedly increased abundance of efferocytosis receptors (mannose- and phosphatidyl serine receptors and the scavenger receptor B2) on AM plasma membrane. Directed airway A1AT treatment (via inhalation of a nebulized solution) restored in situ airway AM efferocytosis after CS exposure in mice. The amelioration of CS-exposed AM global engulfment may render A1AT as a potential therapy for COPD exacerbations.

MeSH terms

  • ADAM17 Protein / metabolism
  • Adult
  • Animals
  • Bronchoalveolar Lavage Fluid / cytology
  • Case-Control Studies
  • Cells, Cultured
  • Female
  • Humans
  • Macrophages, Alveolar / drug effects
  • Macrophages, Alveolar / immunology*
  • Macrophages, Alveolar / metabolism
  • Male
  • Mice, Inbred C57BL
  • Middle Aged
  • Nicotiana / chemistry*
  • Nicotiana / metabolism
  • Phagocytosis / drug effects*
  • Pulmonary Disease, Chronic Obstructive / etiology
  • Pulmonary Disease, Chronic Obstructive / immunology
  • Pulmonary Disease, Chronic Obstructive / pathology
  • Rats
  • Rats, Sprague-Dawley
  • Smoke / adverse effects*
  • alpha 1-Antitrypsin / analysis
  • alpha 1-Antitrypsin / metabolism
  • alpha 1-Antitrypsin / pharmacology*

Substances

  • Smoke
  • alpha 1-Antitrypsin
  • ADAM17 Protein

Grants and funding

This work was supported by: 1. 2012 Junior Investigator Alpha-1 Foundation and The CHEST Foundation Clinical Research grant to Karina A Serban; 2. VA Merit Review Research Award to Irina Petrache; 3. Baxter Healthcare, US to Irina Petrache. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.