Traffic-derived particulate matter and angiotensin-converting enzyme 2 expression in human airway epithelial cells

Abstract

Abstract Background The mechanism for the association between traffic-derived particulate matter less than 10 microns (PM 10 ) and cases of COVID-19 disease reported in epidemiological studies is unknown. To infect cells, the spike protein of SARS-CoV-2 interacts with angiotensin-converting enzyme 2 (ACE2) on host airway cells. Increased ACE2 expression in lower airway cells in active smokers, suggests a potential mechanism whereby PM 10 increases vulnerability to COVID-19 disease. Objective To assess the effect of traffic-derived PM 10 on human airway epithelial cell ACE2 expression in vitro . Methods PM 10 was collected from Marylebone Road (London) using a kerbside impactor. A549 and human primary nasal epithelial cells were cultured with PM 10 for 2 h, and ACE2 expression (median fluorescent intensity; MFI) assessed by flow cytometry. We included cigarette smoke extract as a putative positive control. Data were analysed by either Mann-Whitney test, or Kruskal-Wallis with Dunn’s multiple comparisons test. Results PM 10 at 10 μg/mL, and 20 μg/mL increased ACE2 expression in A549 cells (P<0.05, 0.01 vs. medium control, respectively). Experiments using a single PM 10 concentration (10 μg/mL), found increased ACE2 expression in both A549 cells (control vs. PM 10 , median (IQR) MFI; 470 (0.1 to 1114) vs 6217 (5071 to 8506), P<0.01), and in human primary epithelial cells (0 (0 to 591) vs. 4000 (2610 to 7853), P<0.05). Culture of A549 cells with 5% cigarette smoke extract increased ACE2 expression (n=4, 0 (0 to 28) vs. 9088 (7557 to 15831, P<0.05). Conclusion Traffic-related PM 10 increases the expression of the receptor for SARS-CoV-2 in human respiratory epithelial cells.