The SARS-CoV-2 spike protein subunit S1 induces COVID-19-like acute lung injury in Κ18-hACE2 transgenic mice and barrier dysfunction in human endothelial cells

Abstract

Acute lung injury (ALI) leading to acute respiratory distress syndrome is the major cause of COVID-19 lethality. Cell entry of SARS-CoV-2 occurs via the interaction between its surface Spike protein (SP) and angiotensin converting enzyme-2 (ACE2). It is unknown if the viral Spike protein alone is capable of altering lung vascular permeability in the lungs or producing lung injury in vivo. To that end, we intratracheally instilled the S1 subunit of SARS-CoV-2 Spike protein (S1SP) in K18-hACE2 transgenic mice that overexpress human ACE2 and examined signs of COVID-19 - associated lung injury 72 hours later. Controls included K18-hACE2 mice that received saline or the intact SP and wild-type (WT) mice that received S1SP. K18-hACE2 mice instilled with S1SP exhibited a decline in body weight, dramatically increased white blood cell and protein concentrations in bronchoalveolar lavage fluid (BALF), upregulation of multiple inflammatory cytokines in BALF and serum, histological evidence of lung injury and activation of STAT3 and NFκB pathways in the lung. K18-hACE2 mice that received either saline or SP exhibited little or no evidence of lung injury. WT mice that received S1SP exhibited a milder form of COVID-19 symptoms, compared to K18-hACE2 mice. Further, S1SP, but not SP, decreased cultured human pulmonary microvascular transendothelial resistance and barrier function. This is the first demonstration of a COVID-19-like response by an essential virus encoded protein by SARS-CoV-2 in vivo. This model of COVID-19-induced ALI may assist in the investigation of new therapeutic approaches for the management of COVID-19 and other coronaviruses.

Geraniin Inhibits the Entry of SARS-CoV-2 by Blocking the Interaction between Spike Protein RBD and Human ACE2 Receptor

“…Further in vitro and in vivo studies on SARS-CoV-2 infection in the human epithelial cells and hACE2 transgenic mouse in the biosafety level-3 (BSL-3) laboratory are needed to develop geraniin into a SARS-CoV-2-binding inhibitor. Nevertheless, Biancatelli et al observed that the treatment of the spike protein S1 subunit (S1SP) provoked the lung injury in the K18-hACE2 transgenic mice, which showed that the inhibition of the spike protein RBD-hACE2 receptor interactions by geraniin can be verified by simple treatment of S1SP in the K18-hACE2 transgenic mice without the BSL-3 laboratory [41]. The understanding gained from this study supports the significance and benefit of identifying and developing natural compounds for COVID-19 therapeutics.…”

The spike protein of SARS-CoV-2 induces endothelial inflammation through integrin α5β1 and NF-κB

“…Also, NF-κB is a predominant signaling molecule activated in EC by proinflammatory cytokines, such as TNFa via an integrin-independent route 17 . Neutrophils, macrophages, and lung epithelial cells react to spike 9,35 and to the envelope protein 36 via the activation of toll-like receptor-induced cytokine production, a mechanism underlying the cytokine storm observed in severe COVID-19 37 . Integrin ⍺5β1 is widely expressed in immune cells 16 , and it may cooperate with toll-like receptors to boost their signaling pathways 38 .…”

A Fungal Defensin Targets the SARS−CoV−2 Spike Receptor−Binding Domain

“…As proof, it works as an inflammation inducer via Toll-like receptor 2−dependent activation of the NF−kB pathway to induce a series of inflammatory factors such as cytokines and chemokines [ 49 ]. Its subunit 1 (S1) was found to induce COVID−19−like acute lung injury in transgenic mice and barrier dysfunction in human cells [ 50 ]. S1 exhibited a non−receptor−mediated lipid membrane permeabilization and consequently caused the toxicity on human lung cells [ 51 ].…”