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Hypercapnia Increases ACE2 Protein Expression and Pseudo-SARS-CoV-2 Virus Entry in Airway Epithelial Cells
American Journal of Respiratory and Critical Care Medicine ; 203(9), 2021.
Article in English | EMBASE | ID: covidwho-1277738
ABSTRACT
Rationale Individuals with chronic obstructive pulmonary disease (COPD) who develop 2019 coronavirus disease (COVID-19) are at increased risk of hospitalization, intensive care unit admission and death. COPD is associated with increased airway epithelial expression of angiotensin converting enzyme 2 (ACE2), the cell surface receptor to which the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) spike protein binds and which mediates entry of the virus into cells. Hypercapnia, the elevation of CO2 in blood and tissue, commonly develops in advanced COPD and is associated with frequent and potentially fatal pulmonary infections. We previously showed that normoxic hypercapnia alters expression of innate immune genes, including multiple viral response genes, in primary human bronchial epithelial (HBE) cells (Sci Reports 813508, 2018). Thus, in the current study, we explored the effect of hypercapnia on expression of ACE2 and uptake of a Pseudo-SARS-CoV-2 baculovirus by airway epithelial cells.

Methods:

HBE cells (Lonza) differentiated at air-liquid interface or immortalized BEAS-2B cells were pre-incubated in normocapnia (NC, 5% CO2, PCO2 36 mmHg) or normoxic hypercapnia (HC, 15% CO2, PCO2 108 mmHg) for 4 days. ACE2 protein expression was assessed by immunoblot or immunofluorescence (IF). In addition, BEAS-2B cells pre-exposed to NC or HC for 2 days were infected with Pseudo SARS-CoV-2 for an additional 2 days. Pseudo SARS-CoV-2 (Montana Molecular) is a reporter baculovirus whose surface is decorated with SARS-CoV-2 spike protein, and which induces expression of Neon Green protein in the nucleus of host cells 24 h after viral entry. For in vivo studies, C57BL/6 mice were pre-exposed to normoxic hypercapnia (10% CO2/21% O2) for 7 days, or air as control, and ACE2 expression in lung tissue was assessed by IF.

Results:

Compared to culture in NC, HC increased ACE2 protein expression by ∼4-fold in HBE cells and ∼2.5-fold in BEAS-2B cells. Likewise exposure of mice for 7 days to 10% CO2, as compared to air, markedly increased airway epithelial cell expression of ACE2 (Figure 1). Additionally, culture in HC, as compared to NC, increased Pseudo SARS-CoV-2 entry to BEAS-2B cells.

Conclusion:

Elevated CO2 increases airway epithelial cell expression of the SARS-CoV-2 receptor, ACE2, in vitro and in vivo. This may lead to a greater burden of SARS-CoV-2 infection in patients with hypercapnia, and in part account for worse clinical outcomes of COVID-19 pneumonia in advanced COPD and other severe lung diseases.

Full text: Available Collection: Databases of international organizations Database: EMBASE Language: English Journal: American Journal of Respiratory and Critical Care Medicine Year: 2021 Document Type: Article

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Full text: Available Collection: Databases of international organizations Database: EMBASE Language: English Journal: American Journal of Respiratory and Critical Care Medicine Year: 2021 Document Type: Article