IMMUNE DYSREGULATION INDUCED BY SPIKE PROTEIN 1 OF SARS-COV-2 INCREASES ENDOTHELIAL CELL DYSFUNCTION VIA TYPE I AND TYPE III INTERFERON ACTIVATION PATHWAYS

Abstract

Objective: COVID19-associated immunopathology is associated with increased production of interferon (IFN)-alpha (IFNα) and lambda3 (IFNL3). Effects of IFNs are mediated by interferon-stimulated genes (ISGs) and influence expression of angiotensin-converting enzyme 2 (ACE2), the receptor for S-protein (S1P) of SARS-CoV-2. Increasing evidence indicates vascular inflammation in cardiovascular sequelae of COVID19. We hypothesized that S1P-induced immune/inflammatory responses in endothelial cells (EC) are mediated via IFNα and IFNL3. Design and method: Human ECs were stimulated with S1P (1 μg/mL), IFNα (100ng/mL) or IFNL3 (100IU/mL). Because ACE2, metalloproteinase domain-17 (ADAM17) and type-II transmembrane serine protease (TMPRSS2) are important for SARS-CoV-2 infection, cells were treated with inhibitors of ADAM17 (marimastat, 3.8 nM), ACE2 (MLN4760, 440pM), and TMPRSS2 (camostat, 50 μM). Gene and protein expression was investigated by real-time PCR immunoblotting, respectively. Vascular function was assessed in mesenteric arteries from wild-type (WT) normotensive and hypertensive mice and in ISG15-deficient (ISG15KO) mice. Results: EC stimulated with S1P increased expression of IFNα (3-fold), IFNL3 (4-fold) and ISG (2-fold)(p < 0.05). EC exhibited higher responses to IFNα (ISG15: 16-fold) than to IFNL3 (ISG15: 1.7-fold)(p < 0.05). S1P increased gene expression of IL-6 (1.3-fold), TNFα (6.2-fold) and IL-1β (3.3-fold), effects that were maximized by IFNs. Only marimastat inhibited S1P effects. IL-6 was increased by IFNα (1,230pg/mL) and IFNL3 (1,124pg/mL) vs control (591pg/mL). This was associated with increased phosphorylation of Stat1 (134%), Stat2 (102%), ERK1/2 (42%). Nitric oxide production and eNOS phosphorylation (Ser1177) were reduced by IFNα and (40%) and IFNL3 (40%). Reduced endothelium relaxation maximal response (%Emax) was observed in vessels from WT-mice stimulated with IFNα (67%) and IFNL3 (71%) vs control (82%)(p < 0.05) but not in vessels from ISG15KO mice. Increased contraction was observed only in vessels from hypertensive mice treated with IFNα (9.1 ± 0.5mN vs control: 7.3 ± 0.3mN, p < 0.05). Conclusions: In ECs, S1P, IFNα and IFNL3 increased ISG15 and IL-6, processes that involve ADAM17. Inflammation induced by S1P was amplified by IFNs. IFNs induce vascular dysfunction through ISG15-dependent mechanisms, with augmented effects in hypertension. Our findings demonstrate that S1P induces immune/inflammatory responses that may be important in endotheliitis associated with COVID-19. This is especially important in the presence of cardiovascular risk factors, including hypertension.