Coronavirus disease 2019 (COVID-19) is a clinical syndrome caused by infection with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Patients with severe disease show hyperactivation of the immune system, which can affect multiple organs besides the lungs. Here, we propose that SARS-CoV-2 infection induces a process known as immunothrombosis, in which activated neutrophils and monocytes interact with platelets and the coagulation cascade, leading to intravascular clot formation in small and larger vessels. Microthrombotic complications may contribute to acute respiratory distress syndrome (ARDS) and other organ dysfunctions. Therapeutic strategies aimed at reducing immunothrombosis may therefore be useful. Several antithrombotic and immunomodulating drugs have been proposed as candidates to treat patients with SARS-CoV-2 infection. The growing understanding of SARS-CoV-2 infection pathogenesis and how it contributes to critical illness and its complications may help to improve risk stratification and develop targeted therapies to reduce the acute and long-term consequences of this disease.

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After an acute ischemic stroke (AIS), inflammatory processes are able to concomitantly induce both beneficial and detrimental effects. In this narrative review, we updated evidence on the inflammatory pathways and mediators that are investigated as promising therapeutic targets. We searched for papers on PubMed and MEDLINE up to August 2016. The terms searched alone or in combination were: ischemic stroke, inflammation, oxidative stress, ischemia reperfusion, innate immunity, adaptive immunity, autoimmunity. Inflammation in AIS is characterized by a storm of cytokines, chemokines, and Damage-Associated Molecular Patterns (DAMPs) released by several cells contributing to exacerbate the tissue injury both in the acute and reparative phases. Interestingly, many biomarkers have been studied, but none of these reflected the complexity of systemic immune response. Reperfusion therapies showed a good efficacy in the recovery after an AIS. New therapies appear promising both in pre-clinical and clinical studies, but still need more detailed studies to be translated in the ordinary clinical practice. In spite of clinical progresses, no beneficial long-term interventions targeting inflammation are currently available. Our knowledge about cells, biomarkers, and inflammatory markers is growing and is hoped to better evaluate the impact of new treatments, such as monoclonal antibodies and cell-based therapies.

COVID-19 is a clinical syndrome ranging from mild symptoms to severe pneumonia that often leads to respiratory failure, need for mechanical ventilation, and death. Most of the lung damage is driven by a surge in inflammatory cytokines [interleukin-6, interferon-γ, and granulocyte-monocyte stimulating factor (GM-CSF)]. Blunting this hyperinflammation with immunomodulation may lead to clinical improvement. GM-CSF is produced by many cells, including macrophages and T-cells. GM-CSF-derived signals are involved in differentiation of macrophages, including alveolar macrophages (AMs). In animal models of respiratory infections, the intranasal administration of GM-CSF increased the proliferation of AMs and improved outcomes. Increased levels of GM-CSF have been recently described in patients with COVID-19 compared to healthy controls. While GM-CSF might be beneficial in some circumstances as an appropriate response, in this case the inflammatory response is maladaptive by virtue of being later and disproportionate. The inhibition of GM-CSF signaling may be beneficial in improving the hyperinflammation-related lung damage in the most severe cases of COVID-19. This blockade can be achieved through antagonism of the GM-CSF receptor or the direct binding of circulating GM-CSF. Initial findings from patients with COVID-19 treated with a single intravenous dose of mavrilimumab, a monoclonal antibody binding GM-CSF receptor α, showed oxygenation improvement and shorter hospitalization. Prospective, randomized, placebo-controlled trials are ongoing. Anti-GM-CSF monoclonal antibodies, TJ003234 and gimsilumab, will be tested in clinical trials in patients with COVID-19, while lenzilumab received FDA approval for compassionate use. These trials will help inform whether blunting the inflammatory signaling provided by the GM-CSF axis in COVID-19 is beneficial.

Neutrophil extracellular traps (NETs) are formed by decondensed chromatin, histones, and neutrophil granular proteins and have a role in entrapping microbial pathogens. NETs, however, have pro-thrombotic properties by stimulating fibrin deposition, and increased NET levels correlate with larger infarct size and predict major adverse cardiovascular (CV) events. NETs have been involved also in the pathogenesis of diabetes, as high glucose levels were found to induce NETosis. Accordingly, NETs have been described as drivers of diabetic complications, such as diabetic wound and diabetic retinopathy. Inflammasomes are macromolecular structures involved in the release of pro-inflammatory mediators, such as interleukin-1, which is a key mediator in CV diseases. A crosstalk between the inflammasome and NETs is known for some rheumatologic diseases, while this link is still under investigation and not completely understood in CV diseases. In this review, we summarized the most recent updates about the role of NETs in acute myocardial infarction and metabolic diseases and provided an overview on the relationship between NET and inflammasome activities in rheumatologic diseases, speculating a possible link between these two entities also in CV diseases.

Nicotinamide phosphoribosyltransferase (NAMPT) is an adipokine-enzyme, which was described as to play bioactivities both in the intracellular and in the extracellular environment. However, while the functions of intracellular NAMPT (iNAMPT) are well known, much less is known on extracellular NAMPT (eNAMPT), also called visfatin or pre-B cell colony-enhancing factor. iNAMPT catalyzes the rate-limiting step in the NAD+ biosynthesis pathway from nicotinamide. Its inhibition severely reduces intracellular NAD+ levels, achieving anti-inflammatory and anti-cancer effects. eNAMPT can be detected in the human circulation and in many extracellular environments. Studies show that eNAMPT can act as a growth factor, as an enzyme, and as a cytokine, but its true mechanism of secretion and its physiological functions are still debated. Increased levels of eNAMPT have been associated with different metabolic disorders and cancers. eNAMPT was demonstrated to modulate the pathways involved in the pathophysiology of obesity, diabetes, atherosclerosis, and cardiovascular events by regulating the oxidative stress response, apoptosis, and inflammation. In cancer, eNAMPT was shown to play a pivotal role in modulating cancer cell metabolism, in promoting epithelial-to-mesenchymal transition and in shaping the tumor microenvironment. In line with these functions, circulating eNAMPT levels are frequently increased in cancer patients. Given these pleiotropic roles of eNAMPT in human disease, this protein has attracted attention as a therapeutic target. In this narrative review, we will discuss recent evidence on eNAMPT-driven signalling, highlighting the emerging pathophysiological roles of this protein in different disorders and the potential therapeutic opportunities linked to its targeting. © 2017 American Physiological Society. Compr Physiol 7:603-621, 2017.

Neutrophil pathogen-killing mechanism termed neutrophil extracellular traps (NETs) has been recently identified. NETs consist of chromatin and histones along with serine proteases and myeloperoxidase and are induced by a great variety of infectious and non-infectious stimuli. NETosis is a kind of programmed neutrophil death characterized by chromatin decondensation and release of nuclear granular contents, mainly driven by peptidylarginine deiminase 4 citrullination of histones. Although classically related to the protection against infectious pathogens, nowadays NETs have been described as a player of several pathophysiological processes. Neutrophil dysregulation has been demonstrated in the pathogenesis of most representative vascular diseases, such as acute coronary syndrome, stroke and venous thrombosis. Indeed, NETs have been identified within atherosclerotic lesions and arterial thrombi in both human beings and animal models. Moreover, an imbalance in this mechanism has been proposed as a critical source of modified and/or externalized autoantigens in autoimmune and inflammatory diseases. Finally, an update on the role of NETs in the pathogenesis of cancer has been included. In the present review, based on papers released on PubMed and MEDLINE up to July 2017, we point to update the knowledge on NETs, from their structure to their roles in infectious diseases as well as in cardiovascular diseases, autoimmunity, metabolic disorders and cancer, with a look to future perspectives and therapeutic opportunities.