Toll-Like Receptor 4-Dependent Platelet-Related Thrombosis in SARS-CoV-2 Infection.

BACKGROUND: SARS-CoV-2 is associated with an increased risk of venous and arterial thrombosis, but the underlying mechanism is still unclear. METHODS: We performed a cross-sectional analysis of platelet function in 25 SARS-CoV-2 and 10 healthy subjects by measuring Nox2 (NADPH oxidase 2)-derived oxidative stress and thromboxane B2, and investigated if administration of monoclonal antibodies against the S protein (Spike protein) of SARS-CoV-2 affects platelet activation. Furthermore, we investigated in vitro if the S protein of SARS-CoV-2 or plasma from SARS-CoV-2 enhanced platelet activation. RESULTS: Ex vivo studies showed enhanced platelet Nox2-derived oxidative stress and thromboxane B2 biosynthesis and under laminar flow platelet-dependent thrombus growth in SARS-CoV-2 compared with controls; both effects were lowered by Nox2 and TLR4 (Toll-like receptor 4) inhibitors. Two hours after administration of monoclonal antibodies, a significant inhibition of platelet activation was observed in patients with SARS-CoV-2 compared with untreated ones. In vitro study showed that S protein per se did not elicit platelet activation but amplified the platelet response to subthreshold concentrations of agonists and functionally interacted with platelet TLR4. A docking simulation analysis suggested that TLR4 binds to S protein via three receptor-binding domains; furthermore, immunoprecipitation and immunofluorescence showed S protein-TLR4 colocalization in platelets from SARS-CoV-2. Plasma from patients with SARS-CoV-2 enhanced platelet activation and Nox2-related oxidative stress, an effect blunted by TNF (tumor necrosis factor) α inhibitor; this effect was recapitulated by an in vitro study documenting that TNFα alone promoted platelet activation and amplified the platelet response to S protein via p47phox (phagocyte oxidase) upregulation. CONCLUSIONS: The study identifies 2 TLR4-dependent and independent pathways promoting platelet-dependent thrombus growth and suggests inhibition of TLR4. or p47phox as a tool to counteract thrombosis in SARS-CoV-2.

A snapshot global survey on side effects of COVID-19 vaccines among healthcare professionals and armed forces with a focus on headache.

BACKGROUND: New messenger RNA (mRNA) and adenovirus-based vaccines (AdV) against Coronavirus disease 2019 (COVID-19) have entered large scale clinical trials. Since healthcare professionals (HCPs) and armed forces personnel (AFP) represent a high-risk category, they act as a suitable target population to investigate vaccine-related side effects, including headache, which has emerged as a common complaint. METHODS: We investigated the side-effects of COVID-19 vaccines among HCPs and AFP through a 38 closed-question international survey. The electronic link was distributed via e-mail or via Whatsapp to more than 500 contacts. Responses to the survey questions were analyzed with bivariate tests. RESULTS: A total of 375 complete surveys have been analyzed. More than 88% received an mRNA vaccine and 11% received AdV first dose. A second dose of mRNA vaccine was administered in 76% of individuals. No severe adverse effects were reported, whereas moderate reactions and those lasting more than 1 day were more common with AdV (P=0.002 and P=0.024 respectively). Headache was commonly reported regardless of the vaccine type, but less frequently, with shorter duration and lower severity that usually experienced by participants, without significant difference irrespective of vaccine type. CONCLUSIONS: Both mRNA and AdV COVID-19 vaccines were safe and well tolerated in a real-life subset of HCPs and AFP subjects.

Von Willebrand factor with increased binding capacity is associated with reduced platelet aggregation but enhanced agglutination in COVID-19 patients: another COVID-19 paradox?

Patients with Coronavirus-associated disease-2019 (COVID-19) display alterations of the hemostatic system and the presence of a prothrombotic status frequently leading to vascular complications. However, the impact of COVID-19 on platelet activity, aggregation and agglutination still needs to be clarified. We measured total levels of von Willebrand factor (vWF) and vWF binding to the platelet glycoprotein (Gp) complex (GPIb-IX-V), in a cohort of COVID-19 patients admitted to the intensive care unit of our Institution. Moreover, we evaluated platelet aggregation in response to agonists (ADP, collagen, arachidonic acid) and platelet agglutination in response to ristocetin. We found that levels of vWF antigen and the active form of vWF binding to platelets (vWF:RCo), were markedly increased in these patients. These results were associated with higher agglutination rates induced by ristocetin, thereby indirectly indicating an increased capability of vWF to bind to platelets. Conversely, we found that platelet aggregation in response to both ADP and collagen was lower in COVID-19 patients compared to healthy volunteers. This study shows that COVID-19 is associated with increased vWF-induced platelet agglutination but reduced platelet responsivity to aggregation stimuli. Our findings have translational relevance since platelet adhesion to vWF may represent a marker to predict possible complications and better delineate therapeutic strategies in COVID-19 patients.

Cell Clearing Systems as Targets of Polyphenols in Viral Infections: Potential Implications for COVID-19 Pathogenesis.

The novel coronavirus named severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has generated the ongoing coronavirus disease-2019 (COVID-19) pandemic, still with an uncertain outcome. Besides pneumonia and acute lung injury (ALI) or acute respiratory distress syndrome (ARDS), other features became evident in the context of COVID-19. These includes endothelial and coagulation dysfunction with disseminated intravascular coagulation (DIC), and multiple organ dysfunction syndrome (MODS), along with the occurrence of neurological alterations. The multi-system nature of such viral infection is a witness to the exploitation and impairment of ubiquitous subcellular and metabolic pathways for the sake of its life-cycle, ranging from host cell invasion, replication, transmission, up to a cytopathic effect and overt systemic inflammation. In this frame, alterations in cell-clearing systems of the host are emerging as a hallmark in the pathogenesis of various respiratory viruses, including SARS-CoV-2. Indeed, exploitation of the autophagy and proteasome pathways might contribute not only to the replication of the virus at the site of infection but also to the spreading of either mature virions or inflammatory mediators at both cellular and multisystem levels. In this frame, besides a pharmacological therapy, many researchers are wondering if some non-pharmacological substances might counteract or positively modulate the course of the infection. The pharmacological properties of natural compounds have gained increasing attention in the field of alternative and adjunct therapeutic approaches to several diseases. In particular, several naturally-occurring herbal compounds (mostly polyphenols) are reported to produce widespread antiviral, anti-inflammatory, and anti-oxidant effects while acting as autophagy and (immuno)-proteasome modulators. This article attempts to bridge the perturbation of autophagy and proteasome pathways with the potentially beneficial effects of specific phytochemicals and flavonoids in viral infections, with a focus on the multisystem SARS-CoV-2 infection.