Journal Article

Reduced bronchoalveolar macrophage phagocytosis and cytotoxic effects after controlled short-term exposure to wood smoke in healthy humans

Pourazar, Jamshid, Rankin, Gregory, Lindgren, Robert, Friberg, Maria, García-López, Natxo, Sandström, Thomas, Behndig, Annelie, Muala, Ala, Boman, Christoffer, Uski, Oskari, Hansson, Alva

2023

Overview

Background Exposure to wood smoke has been shown to contribute to adverse respiratory health effects including airway infections, but the underlying mechanisms are unclear. A preceding study failed to confirm any acute inflammation or cell influx in bronchial wash (BW) or bronchoalveolar lavage (BAL) 24 h after wood smoke exposure but showed unexpected reductions in leukocyte numbers. The present study was performed to investigate responses at an earlier phase, regarding potential development of acute inflammation, as well as indications of cytotoxicity. Methods In a double-blind, randomised crossover study, 14 healthy participants were exposed for 2 h to filtered air and diluted wood smoke from incomplete wood log combustion in a common wood stove with a mean particulate matter concentration of 409 µg/m 3 . Bronchoscopy with BW and BAL was performed 6 h after exposure. Differential cell counts, assessment of DNA-damage and ex vivo analysis of phagocytic function of phagocytosing BAL cells were performed. Wood smoke particles were also collected for in vitro toxicological analyses using bronchial epithelial cells (BEAS-2B) and alveolar type II-like cells (A549). Results Exposure to wood smoke increased BAL lactate dehydrogenase (LDH) ( p  = 0.04) and reduced the ex vivo alveolar macrophage phagocytic capacity ( p  = 0.03) and viability ( p  = 0.02) vs. filtered air. BAL eosinophil numbers were increased after wood smoke ( p  = 0.02), while other cell types were unaffected in BW and BAL. In vitro exposure to wood smoke particles confirmed increased DNA-damage, decreased metabolic activity and cell cycle disturbances. Conclusions Exposure to wood smoke from incomplete combustion did not induce any acute airway inflammatory cell influx at 6 h, apart from eosinophils. However, there were indications of a cytotoxic reaction with increased LDH, reduced cell viability and impaired alveolar macrophage phagocytic capacity. These findings are in accordance with earlier bronchoscopy findings at 24 h and may provide evidence for the increased susceptibility to infections by biomass smoke exposure, reported in population-based studies.

• Publisher: BioMed Central,BioMed Central Ltd,Springer Nature B.V,BMC
• Subject: Air pollution / Alveoli / Analysis / Apoptosis / Biomass / Biomass combustion / Biomedical and Life Sciences / Biomedicine / Bronchoalveolar Lavage Fluid / Bronchoscopy / Bronchus / Cell cycle / Cell viability / Chronic obstructive pulmonary disease / Combustion / Controlled human exposure / Cytokines / Cytotoxicity / Damage / Deoxyribonucleic acid / Diseases / DNA / DNA damage / Emissions / Environmental aspects / Environmental Health / Environmental policy / Eosinophils / Epithelial cells / Epithelium / Exposure / Health aspects / Humans / In vitro / Indoor air quality / Inflammation / Inflammation - chemically induced / Inhalation Exposure - adverse effects / L-Lactate dehydrogenase / Lactate dehydrogenase / Lavage / Leukocytes / Leukocytes (eosinophilic) / Macrophages / Nanotechnology / Neutrophils / Outdoor air quality / Oxidative stress / Particulate emissions / Particulate matter / Phagocytes / Phagocytosis / Pharmacology/Toxicology / Pneumology/Respiratory System / Population studies / Population-based studies / Proteins / Public Health / Respiratory tract diseases / Risk factors / Smoke / Smoke - adverse effects / Wood / Wood smoke