COVID-19–associated Lung Microvascular Endotheliopathy: A “From the Bench” Perspective

Abstract

Rationale Autopsy and biomarker studies suggest that endotheliopathy contributes to coronavirus disease (COVID-19)-associated acute respiratory distress syndrome. However, the effects of COVID-19 on the lung endothelium are not well defined. We hypothesized that the lung endotheliopathy of COVID-19 is caused by circulating host factors and direct endothelial infection by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Objectives We aimed to determine the effects of SARS-CoV-2 or sera from patients with COVID-19 on the permeability and inflammatory activation of lung microvascular endothelial cells. Methods Human lung microvascular endothelial cells were treated with live SARS-CoV-2; inactivated viral particles; or sera from patients with COVID-19, patients without COVID-19, and healthy volunteers. Permeability was determined by measuring transendothelial resistance to electrical current flow, where decreased resistance signifies increased permeability. Inflammatory mediators were quantified in culture supernatants. Endothelial biomarkers were quantified in patient sera. Measurements and Main Results Viral PCR confirmed that SARS-CoV-2 enters and replicates in endothelial cells. Live SARS-CoV-2, but not dead virus or spike protein, induces endothelial permeability and secretion of plasminogen activator inhibitor 1 and vascular endothelial growth factor. There was substantial variability in the effects of SARS-CoV-2 on endothelial cells from different donors. Sera from patients with COVID-19 induced endothelial permeability, which correlated with disease severity. Serum levels of endothelial activation and injury biomarkers were increased in patients with COVID-19 and correlated with severity of illness. Conclusions SARS-CoV-2 infects and dysregulates endothelial cell functions. Circulating factors in patients with COVID-19 also induce endothelial cell dysfunction. Our data point to roles for both systemic factors acting on lung endothelial cells and viral infection of endothelial cells in COVID-19–associated endotheliopathy.

Persistent Presence of Spike protein and Viral RNA in the Circulation of Individuals with Post-Acute Sequelae of COVID-19

“…Park et al 32 recently reported that D-Dimer can also form immune complexes with SARS-CoV-2 Spike protein and bound antibodies resulting in activation of monocytes to produce proinflammatory cytokines. Moreover, endothelial dysfunction may be caused by both direct infection of endothelial cells 34 and by the SARS-CoV-2 components in the bloodstream 35 . Perico et al 35 studied the effects of SARS-CoV-2-derived Spike protein alone on HMVECs and found that treatment of these cells with Spike protein led to dose-dependent increases in ICAM-1 and von Willebrand Factor deposition, as well as increased deposition of complement protein C3 on the surface of HMVEC when cells were treated with higher concentrations of Spike protein 35 .…”

Exploring extracellular vesicles as mediators of clinical disease and vehicles for viral therapeutics: Insights from the COVID-19 pandemic

“…In conjunction with ARDS, patients with severe acute COVID-19 may also exhibit a hypercoagulable state and, therefore, be at increased risk for acute cardiovascular incidents. Hypercoagulability is stimulated by significant increases in proinflammatory cytokines TNF-α, IL-1β, and IL-6, which are all involved in signaling for the upregulation of coagulation factors [15,16] . These three cytokines are overexpressed in patients with severe COVID-19 and contribute to the infamous "cytokine storm" [3] .…”

“…These three cytokines are overexpressed in patients with severe COVID-19 and contribute to the infamous “cytokine storm” [ 3 ] . Simultaneously, SARS-CoV-2 infection has been suggested to induce endothelial damage either indirectly through immense inflammatory mechanisms or directly through the infection of endothelial cells [ 17 ] , which further increases the risk of blood clots during infection [ 11 , 14 , 15 ] . A recent study by Joffre et al .…”

“…A recent study by Joffre et al . demonstrated that sera from patients with moderate and severe COVID-19 exhibit circulating biomarkers consistent with endothelial activation and dysfunction [ 17 ] . They further suggest from their findings that direct infection of endothelial cells by SARS-CoV-2 contributes to COVID-19-associated endotheliopathy.…”

Reply to Khatun et al.

“…We also found increased permeability of HMVEC treated with sera from COVID-19 patients that correlated with disease severity. We postulated that COVID-19-associated endotheliopathy results from a combination of the actions of systemic and localized Furthermore, there is encouraging consistency in the effects of SARS-CoV-2 on cultured human endothelial cells (1) and in vivo on mouse endothelial cells (2,3). The concordance in endothelial infection and dysfunction between the humans and mice suggests shared mechanisms of COVID-19-associated endotheliopathy.…”