Angiotensin-converting enzyme 2 (ACE2) expression increases with age in patients requiring mechanical ventilation

Mortality due to Covid-19 is highly associated with advanced age, owing in large part to severe lower respiratory tract infection. SARS-CoV-2 utilizes the host ACE2 receptor for infection. Whether ACE2 abundance in the lung contributes to age-associated vulnerability is currently unknown. We set out to characterize the RNA and protein expression profiles of ACE2 in aging human lung in the context of phenotypic parameters likely to affect lung physiology. Examining publicly available RNA sequencing data, we discovered that mechanical ventilation is a critical variable affecting lung ACE2 levels. Therefore, we investigated ACE2 protein abundance in patients either requiring mechanical ventilation or spontaneously breathing. ACE2 distribution and expression were determined in archival lung samples by immunohistochemistry (IHC). Tissues were selected from the specimen inventory at a large teaching hospital collected between 2010–2020. Twelve samples were chosen from patients receiving mechanical ventilation for acute hypoxic respiratory failure (AHRF). Twenty samples were selected from patients not requiring ventilation. We compared samples across age, ranging from 40–83 years old in the ventilated cohort and 14–80 years old in the non-ventilated cohort. Within the alveolated parenchyma, ACE2 expression is predominantly observed in type II pneumocytes (or alveolar type II / AT2 cells) and alveolar macrophages. All 12 samples from our ventilated cohort showed histologic features of diffuse alveolar damage including reactive, proliferating AT2 cells. In these cases, ACE2 was strongly upregulated with age when normalized to lung area (p = 0.004) or cellularity (p = 0.003), associated with prominent expression in AT2 cells. In non-ventilated individuals, AT2 cell reactive changes were not observed and ACE2 expression did not change with age when normalized to lung area (p = 0.231) or cellularity (p = 0.349). In summary, ACE2 expression increases with age in the setting of alveolar damage observed in patients on mechanical ventilation, providing a potential mechanism for higher Covid-19 mortality in the elderly.

Download Full-text

Angiotensin-converting enzyme 2 (ACE2) expression increases with age in patients requiring mechanical ventilation.

10.1101/2020.07.05.20140467 ◽

2020 ◽

Author(s):

Steven A Baker ◽

Shirley Kowk ◽

Gerald J Berry ◽

Thomas J Montine

Keyword(s):

Mechanical Ventilation ◽

Angiotensin Converting Enzyme ◽

Enzyme Inhibitor ◽

Diffuse Alveolar Damage ◽

Expression Profiles ◽

Alveolar Type ◽

Type Ii ◽

Converting Enzyme ◽

Sequencing Data ◽

Lung Area

Mortality due to Covid-19 is highly associated with advanced age, owing in large part to severe lower respiratory tract infection. SARS-CoV-2 utilizes the host ACE2 receptor for infection. Whether ACE2 abundance in the lung contributes to age-associated vulnerability is currently unknown. We set out to characterize the RNA and protein expression profiles of ACE2 in aging human lung in the context of phenotypic parameters likely to affect lung physiology. Examining publicly available RNA sequencing data, we discovered that mechanical ventilation is a critical variable affecting lung ACE2 levels. Therefore, we investigated ACE2 protein abundance in patients either requiring mechanical ventilation or spontaneously breathing. ACE2 distribution and expression were determined in archival lung samples by immunohistochemistry (IHC). Tissues were selected from the specimen inventory at a large teaching hospital collected between 2010-2020. Twelve samples were chosen from patients receiving mechanical ventilation for acute hypoxic respiratory failure (AHRF). Twenty samples were selected from patients not requiring ventilation. We compared samples across age, ranging from 40-83 years old in the ventilated cohort and 14-80 years old in the non-ventilated cohort. Within the alveolated parenchyma, ACE2 expression is predominantly observed in type II pneumocytes (or alveolar type II / AT2 cells) and alveolar macrophages. All 12 samples from our ventilated cohort showed histologic features of diffuse alveolar damage including reactive, proliferating AT2 cells. In these cases, ACE2 was strongly upregulated with age when normalized to lung area (p = 0.004) or cellularity (p = 0.003), associated with prominent expression in AT2 cells. In non-ventilated individuals, AT2 cell reactive changes were not observed and ACE2 expression did not change with age when normalized to lung area (p = 0.231) or cellularity (p = 0.349). Additionally, we observed prominent pulmonary endothelial ACE2 expression in 2 patients on either an angiotensin-converting enzyme inhibitor (ACEI) or angiotensin receptor blocker (ARB). In summary, ACE2 expression increases with age in the setting of alveolar damage observed in patients on mechanical ventilation, providing a potential mechanism for higher Covid-19 mortality in the elderly.

Download Full-text

Covid-19 Interstitial Pneumonia: Histological and Immunohistochemical Features on Cryobiopsies

Respiration ◽

10.1159/000514822 ◽

2021 ◽

pp. 369-379

Author(s):

Claudio Doglioni ◽

Claudia Ravaglia ◽

Marco Chilosi ◽

Giulio Rossi ◽

Alessandra Dubini ◽

...

Keyword(s):

Interstitial Pneumonia ◽

Diffuse Alveolar Damage ◽

Alveolar Type ◽

Type Ii ◽

Cell Hyperplasia ◽

Nuclear Expression ◽

Alveolar Type Ii Cell ◽

Hyaline Membranes ◽

Type Ii Cell ◽

Phosphorylated Stat3

Background: The pathogenetic steps leading to Covid-19 interstitial pneumonia remain to be clarified. Most postmortem studies to date reveal diffuse alveolar damage as the most relevant histologic pattern. Antemortem lung biopsy may however provide more precise data regarding the earlier stages of the disease, providing a basis for novel treatment approaches. Objectives: To ascertain the morphological and immunohistochemical features of lung samples obtained in patients with moderate Covid-19 pneumonia. Methods: Transbronchial lung cryobiopsy was carried out in 12 Covid-19 patients within 20 days of symptom onset. Results: Histopathologic changes included spots of patchy acute lung injury with alveolar type II cell hyperplasia, with no evidence of hyaline membranes. Strong nuclear expression of phosphorylated STAT3 was observed in >50% of AECII. Interalveolar capillaries showed enlarged lumen and were in part arranged in superposed rows. Pulmonary venules were characterized by luminal enlargement, thickened walls, and perivascular CD4+ T-cell infiltration. A strong nuclear expression of phosphorylated STAT3, associated with PD-L1 and IDO expression, was observed in endothelial cells of venules and interstitial capillaries. Alveolar spaces macrophages exhibited a peculiar phenotype (CD68, CD11c, CD14, CD205, CD206, CD123/IL3AR, and PD-L1). Conclusions: Morphologically distinct features were identified in early stages of Covid-19 pneumonia, with epithelial and endothelial cell abnormalities different from either classical interstitial lung diseases or diffuse alveolar damage. Alveolar type II cell hyperplasia was a prominent event in the majority of cases. Inflammatory cells expressed peculiar phenotypes. No evidence of hyaline membranes and endothelial changes characterized by IDO expression might in part explain the compliance and the characteristic pulmonary vasoplegia observed in less-advanced Covid-19 pneumonia.

Download Full-text

Altered expression of p63 isoforms and expansion of p63- and club cell secretory protein-positive epithelial cells in the lung as novel features of aging

AJP Cell Physiology ◽

10.1152/ajpcell.00330.2018 ◽

2019 ◽

Vol 316 (4) ◽

pp. C492-C508 ◽

Cited By ~ 2

Author(s):

Jutaro Fukumoto ◽

Sahebgowda Sidramagowda Patil ◽

Sudarshan Krishnamurthy ◽

Smita Saji ◽

Irene John ◽

...

Keyword(s):

Epithelial Cells ◽

Protein Expression ◽

Basal Cell ◽

Expression Profiles ◽

Type Ii ◽

Cell Marker ◽

Altered Expression ◽

Club Cell ◽

Protein Expression Profiles ◽

Old Mice

Aging is a key contributor for subclinical progression of late-onset lung diseases. Basal, club, and type II alveolar epithelial cells (AECs) are lung epithelial progenitors whose capacities of differentiation are extensively studied. The timely transition of these cells in response to environmental changes helps maintain the intricate organization of lung structure. However, it remains unclear how aging affects their behavior. This paper demonstrates that the protein expression profiles of a type II AEC marker, prosurfactant protein C (pro-SPC), and a basal cell marker, p63, are altered in the lungs of 14-mo-old versus 7- to 9-wk-old mice. Expression of NH2-terminal-truncated forms of p63 (ΔNp63), a basal cell marker, and claudin-10, a club cell marker, in cytoplasmic extracts of lungs of 14-mo-old mice was upregulated. In contrast, nuclear expression of full-length forms of p63 (TAp63) decreases with age. These alterations in protein expression profiles coincide with dramatic changes in lung functions including compliance. Whole tissue lysates of middle-aged versus aged rhesus monkey lungs display similar age-associated alterations in pro-SPC expression. An age-associated decrease of TAp63 in nuclear lysates was observed in aged monkey group. Moreover, the lungs of 14-mo-old versus 7- to 9-wk-old mice display a wider spreading of ΔNp63-positive CCSP-positive bronchiolar epithelial cells. This expansion did not involve upregulation of Ki67, a representative proliferation marker. Collectively, it is postulated that 1) this expansion is secondary to a transition of progenitor cells committed to club cells from ΔNp63-negative to ΔNp63-positive status, and 2) high levels of cytoplasmic ΔNp63 expression trigger club cell migration.

Download Full-text

Mechanical ventilation-induced apoptosis in newborn rat lung is mediated via FasL/Fas pathway

AJP Lung Cellular and Molecular Physiology ◽

10.1152/ajplung.00048.2013 ◽

2013 ◽

Vol 305 (11) ◽

pp. L795-L804 ◽

Cited By ~ 21

Author(s):

Andreas A. Kroon ◽

Veronica DelRiccio ◽

Irene Tseu ◽

Brian P. Kavanagh ◽

Martin Post

Keyword(s):

Mechanical Ventilation ◽

Caspase 3 ◽

Cyclic Stretch ◽

Alveolar Type ◽

Type Ii Cells ◽

Type Ii ◽

Rat Lung ◽

Newborn Rat ◽

Lung Epithelial ◽

Induced Apoptosis

Mechanical ventilation induces pulmonary apoptosis and inhibits alveolar development in preterm infants, but the molecular basis for the apoptotic injury is unknown. The objective was to determine the signaling mechanism(s) of ventilation (stretch)-induced apoptosis in newborn rat lung. Seven-day-old rats were ventilated with room air for 24 h using moderate tidal volumes (8.5 ml/kg). Isolated fetal rat lung epithelial and fibroblast cells were subjected to continuous cyclic stretch (5, 10, or 17% elongation) for up to 12 h. Prolonged ventilation significantly increased the number of apoptotic alveolar type II cells (i.e., terminal deoxynucleotidyl transferase dUTP-mediated nick-end labeling and anti-cleaved caspase-3 immunochemistry) and was associated with increased expression of the apoptotic mediator Fas ligand (FasL). Fetal lung epithelial cells, but not fibroblasts, subjected to maximal (i.e., 17%, but not lesser elongation) cyclic stretch exhibited increased apoptosis (i.e., nuclear fragmentation and DNA laddering), which appeared to be mediated via the extrinsic pathway (increased expression of FasL and cleaved caspase-3, -7, and -8). The intrinsic pathway appeared not to be involved [minimal mitochondrial membrane depolarization (JC-1 flow analysis) and no activation of caspase-9]. Universal caspases inhibition and neutralization of FasL abrogated the stretch-induced apoptosis. Prolonged mechanical ventilation induces apoptosis of alveolar type II cells in newborn rats and the mechanism appears to involve activation of the extrinsic death pathway via the FasL/Fas system.

Download Full-text

Alveolar Type II Cell Na, K-ATPase is Upregulated During Mechanical Ventilation-induced Pulmonary Edema

CHEST Journal ◽

10.1378/chest.105.3_supplement.116s ◽

1994 ◽

Vol 105 (3) ◽

pp. 116S-117S ◽

Cited By ~ 10

Author(s):

J. Lasha Sznajder ◽

Karen M. Ridge ◽

Z. Leah Harris ◽

Walter Olivera ◽

Clara Curiel ◽

...

Keyword(s):

Mechanical Ventilation ◽

Pulmonary Edema ◽

Alveolar Type ◽

Type Ii ◽

Alveolar Type Ii Cell ◽

Type Ii Cell

Download Full-text

Expression of SARS-CoV-2 Entry Factors in Human Alveolar Type II Cells in Aging and Emphysema

Biomedicines ◽

10.3390/biomedicines9070779 ◽

2021 ◽

Vol 9 (7) ◽

pp. 779

Author(s):

Chih-Ru Lin ◽

Karim Bahmed ◽

Hannah Simborio ◽

Hassan Hayek ◽

Sudhir Bolla ◽

...

Keyword(s):

Viral Entry ◽

Diffuse Alveolar Damage ◽

Host Factors ◽

Alveolar Type ◽

Type Ii Cells ◽

Mrna Levels ◽

Type Ii ◽

Rt Pcr ◽

Alveolar Type Ii Cells ◽

Lung Transplants

Alveolar type II (ATII) cells proliferate and restore the injured epithelium. It has been described that SARS-CoV-2 infection causes diffuse alveolar damage in the lungs. However, host factors facilitating virus infection in ATII cells are not well known. We determined the SARS-CoV-2-related genes and protein expression using RT-PCR and Western blotting, respectively, in ATII cells isolated from young and elderly non-smokers, smokers, and ex-smokers. Cells were also obtained from lung transplants of emphysema patients. ACE2 has been identified as the receptor for SARS-CoV-2, and we found significantly increased levels in young and elderly smokers and emphysema patients. The viral entry depends on TMPRSS2 protease activity, and a higher expression was detected in elderly smokers and ex-smokers and emphysema patients. Both ACE2 and TMPRSS2 mRNA levels were higher in this disease in comparison with non-smokers. CD209L serves as a receptor for SARS-CoV-2, and we found increased levels in ATII cells obtained from smokers and in emphysema patients. Also, our data suggest CD209L regulation by miR142. Endoplasmic reticulum stress was detected in ATII cells in this disease. Our results suggest that upregulation of SARS-CoV-2 entry factors in ATII cells in aging, smokers, and emphysema patients may facilitate infection.

Download Full-text

Freshly isolated rat alveolar type I cells, type II cells, and cultured type II cells have distinct molecular phenotypes

AJP Lung Cellular and Molecular Physiology ◽

10.1152/ajplung.00272.2004 ◽

2005 ◽

Vol 288 (1) ◽

pp. L179-L189 ◽

Cited By ~ 70

Author(s):

Robert Gonzalez ◽

Yee Hwa Yang ◽

Chandi Griffin ◽

Lennell Allen ◽

Zachary Tigue ◽

...

Keyword(s):

Gene Expression ◽

Differentially Expressed Genes ◽

Expression Profiles ◽

Differentially Expressed ◽

Cell Phenotype ◽

Alveolar Type ◽

Type I ◽

Type Ii Cells ◽

Type Ii ◽

Isolated Rat

We used microarray analysis with Affymetrix rat chips to determine gene expression profiles of freshly isolated rat type I (TI) and TII cells and cultured TII cells. Our goals were 1) to describe molecular phenotypic “fingerprints” of TI and TII cells, 2) to gain insight into possible functional differences between the two cell types through differentially expressed genes, 3) to identify genes that might indicate potential functions of TI cells, since so little is known about this cell type, and 4) to ascertain the similarities and differences in gene expression between cultured TII cells and freshly isolated TI cells. For these experiments, we used preparations of isolated TI and TII cells that contained <2% cross-contamination. With a false discovery rate of 1%, 601 genes demonstrated over twofold different expression between TI and TII cells. Those genes with very high levels of differential expression may be useful as markers of cell phenotype and in generating novel hypotheses about functions of TI and TII cells. We found similar numbers of differentially expressed genes between freshly isolated TI or TII cells and cultured TII cells (698, 637 genes) and freshly isolated TI and TII cells (601 genes). Tests of sameness/difference including cluster dendrograms and log/log identity plots indicated major differences between the phenotypes of freshly isolated TI cell and cultured type II cell populations. The latter results suggest that experiments with TII cells cultured under these conditions should be interpreted with caution with respect to biological relevance to TI or TII cells.

Download Full-text