Spike 1 protein of SARS-CoV-2 induces endothelial inflammation and vascular dysfunction through interferon ISG15-dependent mechanisms

Interferon (IFN) alpha (IFNα) and lambda3 (IFNλ3) constitute first-line responses of immunity against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection by increasing interferon-stimulated genes (ISGs). Prolonged IFN production may exacerbate inflammation, contributing to endotheliitis and vascular dysfunction in coronavirus disease 2019 (COVID-19). We investigated whether spike protein S1 (SP1) of SARS-CoV-2 via IFN influences inflammation in human vascular and lymphatic endothelial cells (ECs) and whether these processes contribute to vascular dysfunction in the context of hypertension. We focused on ISG15, a crucial immune protein that is also implicated in hypertension-associated vascular injury.

Exposure of microvascular ECs to SP1 of SARS-CoV-2-induced expression of ISGs: ISG15, MX1, and IFIT1. These effects were potentiated by IFNs and reduced by ADAM17 and STAT1 inhibition and genetic inhibition of IFNα and beta receptor subunit 1 (IFNAR1). In microvascular ECs IFNλ3 and IFNα increased expression of ISGs, TMPRSS2, ADAM17, production of pro-inflammatory mediators (tumor necrosis factor [TNF]α, interleukin [IL]-6, plasminogen activator inhibitor [PAI]-1) and reduced phosphorylation of eNOS (Ser1177). In pulmonary, lymphatic, and aortic ECs, IFNα, but not IFNλ3, increased expression of ISGs and IL-6. To explore the relevance in intact vessels, effects of IFNs were studied in isolated micro-vessels from wildtype (WT), hypertensive and ISG15^−/− mice. IFNα, IFNλ3, and SP1 reduced endothelium-dependent relaxation in WT vessels, whereas IFNα increased contraction in vessels from hypertensive mice. Vascular dysfunction induced by IFNα, IFNλ3 or spike protein was abrogated in vessels from ISG15−/− mice.

SP1 and IFNs synergically increase EC expression of ISGs through ADAM17. IFNλ3 and IFNα promote endothelial inflammation and vascular dysfunction through ISG15. These processes may play a role in the endotheliopathy and vascular damage associated with SP1 and might contribute to cardiovascular sequelae, including hypertension, of SARS-CoV-2 infection.