TNF/iNOS/NO pathway mediates host susceptibility to endothelial-dependent circulatory failure and death induced by betacoronavirus infection

Poor disease outcomes and lethality are directly related to endothelial dysfunction in beta-coronavirus infections. Here, we investigated the mechanisms underlying the vascular dys-function caused by the betacoronaviruses MHV-3 and SARS-CoV-2. Wild-type C57BL/6 (WT) and knockout mice for inducible nitric oxide synthase (iNOS-/-) or TNF receptor 1 (TNFR1-/-) were infected with MHV-3, and K18-hACE2 transgenic mice expressing human ACE2 were infected with SARS-CoV-2. Isometric tension was used to evaluate vascular function. Protein expression was determined by immunofluorescence. Tail-cuff plethysmog-raphy and Doppler were used to assess blood pressure and flow, respectively. Nitric oxide (NO) was quantified with the DAF probe. ELISA was used to assess cytokine production. Sur-vival curves were estimated using Kaplan-Meier. MHV-3 infection reduced aortic and vena cava contractility, arterial blood pressure, and blood flow, resulting in death. Resistance mesenteric arteries showed increased contractility. The contractility of the aorta was nor-malized by removing the endothelium, inhibiting iNOS, genetically deleting iNOS, or scav-enging NO. In the aorta, iNOS and phospho-NF-kB p65 subunit expression was enhanced, along with basal NO production. TNF production was increased in plasma and vascular tissue. Genetic deletion of TNFR1 prevented vascular changes triggered by MHV-3, and death. Basal NO production and iNOS expression were also increased by SARS-CoV-2. In conclusion, betacoronavirus induces an endothelium-dependent decrease in contractility in macro-arteries and veins, leading to circulatory failure and death via TNF/iNOS/NO. These data highlight the key role of the vascular endothelium and TNF in the pathogenesis and lethality of coronaviruses.

Automated summary

Poor disease outcomes and lethality in beta-coronavirus infections are directly related to endothelial dysfunction. This study investigated the mechanisms underlying vascular dysfunction caused by the betacoronaviruses MHV-3 and SARS-CoV-2. The results showed that MHV-3 infection reduced contractility, blood pressure, and blood flow, leading to death. Similar vascular dysfunction was observed in SARS-CoV-2 infection. These findings highlight the important role of the vascular endothelium and TNF in the pathogenesis and lethality of coronaviruses.