Dias-Baruffi, M. | bioRxiv Science

bioRxiv2022

Airway epithelial cells and macrophages trigger IL-6-CD95/CD95L axis and mediate initial immunopathology of COVID-19

Airway epithelial cells (AEC) are the first in contact with SARS-CoV-2 and drive the interface with macrophage to generate inflammation. To elucidate how those initial events contribute to the immunopathology or to dysregulate the immune response observed in severe and critical COVID-19, we determined the direct and indirect interactions of these cells. AEC lineage (Calu-3) infected with SARS-CoV-2 and epithelial cells (CD45-EpCAM+) from intubated COVID-19 patients showed high expression of CD95L. Infected-Calu-3 cells secreted IL-6, and expressed annexin V and caspase-3, apoptosis markers. The direct interaction of macrophages with sorted apoptotic Calu-3 cells, driven by SARS-CoV-2 infection, resulted in macrophage death and increased expression of CD95, CD95L and CD163. Macrophages exposed to tracheal aspirate supernatants from intubated COVID-19 patients or to recombinant human IL-6 exhibited decreased HLA-DR and increased CD95 and CD163 expression. IL-6 effects on macrophages were prevented by tocilizumab (anti-IL-6 receptor mAb) and Kp7-6 (CD95/CD95L antagonist). Similarly, lung inflammation and death of AEC were decreased in CD95 and IL-6 knockout mice infected with SARS-CoV-2. Our results show that the AEC-macrophage interaction via CD95/CD95L signaling is an initial key step of immunopathology of severe COVID-19 and should be considered as a therapeutic target. O_FIG O_LINKSMALLFIG WIDTH=181 HEIGHT=200 SRC="FIGDIR/small/504760v1_ufig1.gif" ALT="Figure 1"> View larger version (88K): org.highwire.dtl.DTLVardef@aadef5org.highwire.dtl.DTLVardef@13d033org.highwire.dtl.DTLVardef@c9c555org.highwire.dtl.DTLVardef@ba821e_HPS_FORMAT_FIGEXP M_FIG C_FIG Highlights- SARS-CoV-2-infected airway epithelial cells (AEC) secrete IL-6, express Fas/FasL and undergo apoptosis; - SARS-CoV-2-infected apoptotic AEC induces Fas/FasL expression and death in macrophages; - IL-6 induces IL-1{beta} secretion, reduction of HLA-DR and increase of Fas and CD163 expression in macrophages; - Blockade of IL-6 signaling and Fas/FasL restores the expression of HLA-DR and reduces the expression of Fas and CD163, and secretion of IL-1{beta} on isolated macrophages; in vivo, the deficiency of Fas and IL-6 decreases acute pulmonary inflammation in SARS-CoV-2-infected mice.

immunology↗

bioRxiv2021

Drug repurposing to face Covid-19: Celastrol, a potential leading drug capable of inhibiting SARS-CoV-2 replication and induced inflammation

The global emergence of Covid-19 has caused huge human casualties. Clinical manifestations of the disease vary from asymptomatic to lethal, and the symptomatic form can be associated with cytokine storm and non-homeostatic inflammatory response. In face of the urgent demand for effective drugs to treat Covid-19, we have searched for candidate compounds using a drug repurposing approach based on in silico analysis followed by biological validation. Here we identified celastrol, a pentacyclic triterpene isolated from Tripterygium wilfordii Hook F - a plant used in traditional Chinese medicine - as one of the best compounds out of 39 repurposed drug candidates. Celastrol reverted gene expression signature from SARS-CoV-2-infected cells; bound with high-affinity energy to viral molecular targets such as main protease (Mpro) and receptor-biding domain (RBD); inhibited SARS-CoV-2 replication in monkey (Vero and Vero-ACE2) and human (Caco-2 and Calu-3) cell lines; and decreased interleukin-6 (IL-6) secretion in SARS-CoV-2-infected human cell lines. Interestingly, celastrol acted in a concentration-dependent manner, with undetectable signs of cytotoxicity. Therefore, celastrol is a promising lead drug candidate to treat Covid-19 due to its ability to suppress SARS-CoV-2 replication and IL-6 production in infected cells, two critical events in the pathophysiology of this disease.

immunology↗