Abstract Infection by SARS-CoV-2 and subsequent COVID-19 can cause viral sepsis and septic shock. Several complications have been observed in patients admitted to the intensive care unit (ICU) with COVID-19, one of those being bacterial superinfection. Based on prior evidence that dysregulated systemwide proteolysis is associated with death in bacterial septic shock, we investigated whether protease activity and proteolysis could be elevated in COVID-19-induced sepsis with bacterial superinfection. In particular, we sought to assess the possible implications on the regulation of protein systems, such as for instance the proteins and enzymes involved in the clotting cascade. Blood samples collected at multiple time points during the ICU stay of four COVID-19 patients were analyzed to quantify: a) the circulating proteome and peptidome by mass spectrometry; b) plasma enzymatic activity of trypsin-like substrates and five clotting factors (plasmin, thrombin, factor VII, factor IX, factor X) by a fluorogenic assay. Of the four patients, one was diagnosed with bacterial superinfection on day 7 after beginning of the study and later died. The other three patients all survived (ICU length-of-stay 11.25±6.55 days, hospital stay of 15.25±7.18 days). Spikes in protease activity (factor VII, trypsin-like activity) were detected on day 7 for the patient who died. Corresponding increases in the total intensity of peptides derived by hydrolysis of plasma proteins, especially of fibrinogen degradation products, and a general reduction of coagulation proteins, were measured as well. A downregulation of endogenous enzymatic inhibitors, in particular trypsin inhibitors, characterized the non-surviving patient throughout her ICU stay. Enzymatic activity was stable in the patients who survived. Our study highlights the potential of multiomics approaches, combined with quantitative analysis of enzymatic activity, to i) shed light on proteolysis as a possible pathological mechanism in sepsis and septic shock, including COVID-19-induced sepsis; ii) provide additional insight into malfunctioning protease-mediated systems, such as the coagulation cascade; and iii) describe the progression of COVID-19 with bacterial superinfection.
Direct communication between arteries and veins without intervening capillary beds is the primary pathology of arteriovenous malformations (AVMs). Although Notch signaling is implicated in embryonic arteriovenous (AV) differentiation, its function in the adult mammalian vasculature has not been established due to the embryonic lethality that often occurs in both gain- and loss-of-function mutants. We expressed a constitutively active Notch4 , int3 , in the adult mouse endothelium by using the tetracycline-repressible system to suppress int3 during embryogenesis. int3 caused profound blood vessel enlargement and AV shunting, which are hallmarks of AVM, and led to lethality within weeks of its expression. Vessel enlargement, a manifestation of AVM, occurred in an apparently tissue-specific fashion; the liver, uterus, and skin were affected. int3 -mediated vascular defects were accompanied by arterialization, including ectopic venous expression of ephrinB2 , increased smooth muscle cells, and up-regulation of endogenous Notch signaling. Remarkably, the defective vessels and illness were reversed upon repression of int3 expression. Finally, endothelial expression of a constitutively active Notch1 induced similar hepatic vascular lesions. Our results provide gain-of-function evidence that Notch signaling in the adult endothelium is sufficient to render arterial characteristics and lead to AVMs.
Genome-wide studies have revealed that mammalian genomes are pervasively transcribed. This has led to the identification and isolation of novel classes of non-coding RNAs (ncRNAs) that influence gene expression by a variety of mechanisms. Here we review the characteristics and functions of regulatory ncRNAs in chromatin remodelling and at multiple levels of transcriptional and post-transcriptional regulation. We also describe the potential roles of ncRNAs in vascular biology and in mediating epigenetic modifications that might play roles in cardiovascular disease susceptibility. The emerging recognition of the diverse functions of ncRNAs in regulation of gene expression suggests that they may represent new targets for therapeutic intervention.
Introduction. The pathophysiology of infection with SARS-CoV-2 involves the lower airways and host-launched aggressive inflammatory responses leading to exacerbated lung damage in these vital tissues. Early clinical studies found that COVID-19 patients have higher levels of neutrophils in the circulation. Neutrophils are the most abundant leukocyte in circulation and are known to be highly proinflammatory due to production of neutrophil extracellular traps (NETosis). NETs are web-like chromatin structures coated with histones and proteases that both capture and kill invading pathogens. However, while being an effective countermeasure towards foreign microbes, this process also causes undesirable damage in host tissues. Therefore, we sought to characterize NETosis in circulating neutrophils from COVID-19 patients to determine whether this immunological response might be exacerbating or driving the disease state in COVID-19, rather than mitigating the virus. Methods.Blood was drawn daily from critically ill COVID-19 patients (n=16) after consent was obtained. Healthy controls (n=13) were screened for COVID-19 and gave blood once a week. Blood was drawn into lithium heparin tubes (BD Vacutainer). Neutrophils were isolated using PolymorphprepTM(PROGEN) per manufacturer's instructions. Cells were resuspended at 2x106 cells/ml for functional assays. Neutrophils were stimulated with increasing concentrations of PMA (Phorbol 12-myristate 13-acetate) of 2.5nM, 25nM and 250nM to stimulate NETosis via the canonical pathway, and nigericin at 15uM for the non-canonical pathway. NETosis was quantified using the Quant-iT™ PicoGreen™ dsDNA Assay Kit (Invitrogen) and by NET visualization via myeloperoxidase and nuclear staining (using Polyclonal Rabbit Anti-Human Myeloperoxidase by Dako and Hoescht stain by Invitrogen). Results.Functional NETosis assays of circulating neutrophils from COVID-19 patients demonstrate overall increased NETosis determined by increased release of dsDNA. This enhanced NETosis occurred at baseline and after stimulation with PMA when compared to healthy controls (Figure 1A, p <0.0001). Fluorescent microscopy also demonstrated increased NETosis in neutrophils from COVID-19 patients (Figure 1B;MPO-green and nucleus-blue). NETosis via the non-canonical pathway (induction with nigericin) was also increased in COVID-19 patients versus controls (p=0.02). Conclusions.Circulating neutrophils from critically ill COVID-19 patients are more prone to produce NETs than circulating neutrophils from healthy individuals. This is likely to lead to NETmediated tissue injury once neutrophils enter inflamed tissue, where they can potentially drive acute lung injury and acute respiratory distress syndrome, common causes of mortality in COVID-19. The finding of increased production of NETs by both canonical and non-canonical pathways is consistent with an overall hyper-activated state in COVID-19.
Although macrophages can be polarized to distinct phenotypes in vitro with individual ligands, in vivo they encounter multiple signals that control their varied functions in homeostasis, immunity, and disease. Here, we identify roles of Rev-erb nuclear receptors in regulating responses of mouse macrophages to complex tissue damage signals and wound repair. Rather than reinforcing a specific program of macrophage polarization, Rev-erbs repress subsets of genes that are activated by TLR ligands, IL4, TGFβ, and damage-associated molecular patterns (DAMPS). Unexpectedly, a complex damage signal promotes co-localization of NF-κB, Smad3, and Nrf2 at Rev-erb-sensitive enhancers and drives expression of genes characteristic of multiple polarization states in the same cells. Rev-erb-sensitive enhancers thereby integrate multiple damage-activated signaling pathways to promote a wound repair phenotype.
