ABSTRACT
Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection induces inflammatory response, cytokine storm, venous thromboembolism, coagulopathy, and multiple organ damage. Resting endothelial cells prevent coagulation, control blood flow, and inhibit inflammation. However, it remains unknown how SARS-CoV-2 induces strong molecular signals in distant cells for immunopathogenesis. In this study, we examined the consequence of human endothelial cells, microvascular endothelial cells (HMEC-1), and liver endothelial cells (TMNK-1) to exosomes isolated from plasma of mild or severe COVID-19 patients. We observed a significant induction of NLRP3, caspase-1, and interleukin-1ß (IL-1ß) mRNA expression in endothelial cells following exposure to exosomes from severe COVID-19 patients compared with that from patients with mild disease or healthy donors. Activation of caspase-1 was noted in the endothelial cell culture medium following exposure to the COVID-19 exosomes. Furthermore, COVID-19 exosomes significantly induced mature IL-1ß secretion in both HMEC-1 and TMNK-1 endothelial cell culture medium. Thus, our results demonstrated for the first time that exosomes from COVID-19 plasma trigger NLRP3 inflammasome in endothelial cells of distant organs resulting in IL-1ß secretion and inflammatory response. IMPORTANCE Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection is a global health problem. Although the vaccine controls infection, understanding the molecular mechanism of pathogenesis will help in developing future therapies. Furthermore, several investigators predicted the involvement of endothelial cell-related inflammation in SARS-CoV-2 infection and using extracellular vesicles as a cargo to carry a drug or vaccine for combating SARS-CoV-2 infection. However, the mechanism by which endothelial cells are inflamed remains unknown. Our present study highlights that exosomes from severe COVID-19 patients can enhance inflammasome activity in distant endothelial cells for augmentation of immunopathogenesis and opens an avenue for developing therapies.
Subject(s)
COVID-19 , Exosomes , Caspases , Endothelial Cells/metabolism , Exosomes/metabolism , Humans , Inflammasomes/metabolism , Inflammation , NLR Family, Pyrin Domain-Containing 3 Protein/genetics , NLR Family, Pyrin Domain-Containing 3 Protein/metabolism , SARS-CoV-2ABSTRACT
SARS-CoV-2 infection can cause cytokine storm and may overshoot immunity in humans; however, it remains to be determined whether virus-induced soluble mediators from infected cells are carried by exosomes as vehicles to distant organs and cause tissue damage in COVID-19 patients. We took an unbiased proteomic approach for analyses of exosomes isolated from plasma of healthy volunteers and COVID-19 patients. Our results revealed that tenascin-C (TNC) and fibrinogen-ß (FGB) are highly abundant in exosomes from COVID-19 patients' plasma compared with that of healthy normal controls. Since TNC and FGB stimulate pro-inflammatory cytokines via the Nuclear factor-κB (NF-κB) pathway, we examined the status of tumor necrosis factor-α (TNF-α), interleukin-6 (IL-6), and C-C motif chemokine ligand 5 (CCL5) expression upon exposure of hepatocytes to exosomes from COVID-19 patients and observed significant increase compared with that from healthy subjects. Together, our results demonstrate that TNC and FGB are transported through plasma exosomes and potentially trigger pro-inflammatory cytokine signaling in cells of distant organ.