IntroductionHow cigarette smoke (CS) and
chronic obstructive pulmonary disease MESHD (
COPD MESHD) affect severe acute
respiratory syndrome coronavirus 2 (SARS-CoV-2) infection MESHD and severity is controversial. We investigated the protein and mRNA expression of SARS-CoV-2 entry receptor
ACE2 HGNC and proteinase
HGNC in lungs from
COPD MESHD patients and controls, and lung tissue from mice exposed acutely and chronically to CS. Also, we investigated the effects of CS exposure on
SARS-CoV-2 infection MESHD in human bronchial epithelial cells.
MethodsIn Cohort 1,
ACE2 HGNC-positive cells were quantified by immunostaining in FFPE sections from both central and peripheral airways. In Cohort 2, we quantified pulmonary
ACE2 HGNC protein levels by immunostaining and ELISA, and both
ACE2 HGNC and
HGNC mRNA levels by RT-qPCR. In C57BL/6 WT mice exposed to air or CS for up to 6 months, pulmonary ACE2 protein levels were quantified by triple immunofluorescence staining and ELISA. The effects of CS exposure on
SARS-CoV-2 infection MESHD were evaluated after 72hr in vitro infection of Calu-3 cells. After
SARS-CoV-2 infection MESHD, the cells were fixed for IF staining with dsRNA-specific J2 monoclonal Ab, and cell lysates were harvested for WB of viral
nucleocapsid (N) protein PROTEIN. Supernatants (SN) and cytoplasmic lysates were obtained to measure
ACE2 HGNC levels by ELISA.
ResultsIn both human cohorts,
ACE2 HGNC protein and mRNA levels were decreased in peripheral airways from
COPD MESHD patients versus both smoker and NS controls, but similar in central airways.
HGNC levels were similar across groups. Mice exposed to CS had decreased ACE2 protein levels in their bronchial and
alveolar epithelia MESHD versus air-exposed mice exposed to 3 and 6 months of CS. In Calu3 cells in vitro, CS-treatment abrogated infection to levels below the limit of detection. Similar results were seen with WB for viral
N protein PROTEIN, showing peak viral protein synthesis at 72hr.
ConclusionsACE2 levels were decreased in both bronchial and
alveolar epithelial MESHD cells from uninfected
COPD MESHD patients versus controls, and from CS-exposed versus air-exposed mice. CS-pre-treatment did not affect ACE2 levels but potently inhibited SARS-CoV-2 replication in this in vitro model. These findings urge to further investigate the controversial effects of CS and
COPD MESHD on
SARS-CoV2 infection MESHD.