Fundamentals in Covid-19-Associated Thrombosis: Molecular and Cellular Aspects

Effects of Chronic Inflammatory Activation of Murine and Human Arterial Endothelial Cells at Normal Lipoprotein and Cholesterol Levels In Vivo and In Vitro

The activation of endothelial cells is crucial for immune defense mechanisms but also plays a role in the development of atherosclerosis. We have previously shown that inflammatory stimulation of endothelial cells on top of elevated lipoprotein/cholesterol levels accelerates atherogenesis. The aim of the current study was to investigate how chronic endothelial inflammation changes the aortic transcriptome of mice at normal lipoprotein levels and to compare this to the inflammatory response of isolated endothelial cells in vitro. We applied a mouse model expressing constitutive active IκB kinase 2 (caIKK2)-the key activator of the inflammatory NF-κB pathway-specifically in arterial endothelial cells and analyzed transcriptomic changes in whole aortas, followed by pathway and network analyses. We found an upregulation of cell death and mitochondrial beta-oxidation pathways with a predicted increase in endothelial apoptosis and necrosis and a simultaneous reduction in protein synthesis genes. The highest upregulated gene was ACE2, the SARS-CoV-2 receptor, which is also an important regulator of blood pressure. Analysis of isolated human arterial and venous endothelial cells supported these findings and also revealed a reduction in DNA replication, as well as repair mechanisms, in line with the notion that chronic inflammation contributes to endothelial dysfunction.

Intermediate dose enoxaparin in hospitalized patients with moderate-severe COVID-19: a pilot phase II single-arm study, INHIXACOVID19

BACKGROUND

Randomized clinical trials in non-critically ill COVID-19 patients showed that therapeutic-dose heparin increased survival with reduced organ support as compared with usual-care thromboprophylaxis, albeit with increased bleeding risk. The purpose of the study is to assess the safety of intermediate dose enoxaparin in hospitalized patients with moderate to severe COVID-19.

METHODS

A phase II single-arm interventional prospective study including patients receiving intermediate dose enoxaparin once daily according to body weight: 60 mg for 45-60 kg, 80 mg for 61-100 kg or 100 mg for > 100 kg for 14 days, with dose adjustment according to anti-factor Xa activity (target range: 0.4-0.6 UI/ml); an observational cohort (OC) included patients receiving enoxaparin 40 mg day for comparison. Follow-up was 90 days. Primary outcome was major bleeding within 30 and 90 days after treatment onset. Secondary outcome was the composite of all-cause 30 and 90-day mortality rates, disease severity at the end of treatment, intensive care unit (ICU) admission and length of ICU stay, length of hospitalization. All outcomes were adjudicated by an independent committee and analyzed before and after propensity score matching (PSm).

RESULTS

Major bleeding was similar in IC (1/98 1.02%) and in the OC (none), with only one event observed in a patient receiving concomitantly anti-platelet therapy. The composite outcome was observed in 53/98 patients (54%) in the IC and 132/203 (65%) patients in the OC (p = 0.07) before PSm, while it was observed in 50/90 patients (55.6%) in the IC and in 56/90 patients (62.2%) in the OC after PSm (p = 0.45). Length of hospitalization was lower in the IC than in OC [median 13 (IQR 8-16) vs 14 (11-21) days, p = 0.001], however it lost statistical significance after PSm (p = 0.08). At 30 days, two patients had venous thrombosis and two pulmonary embolism in the OC. Time to first negative RT-PCR were similar in the two groups.

CONCLUSIONS

Weight adjusted intermediate dose heparin with anti-FXa monitoring is safe with potential positive impact on clinical course in COVID-19 non-critically ill patients.

TRIAL REGISTRATION

The study INHIXACOVID19 was registred on ClinicalTrials.gov with the trial registration number (TRN) NCT04427098 on 11/06/2020.

[Association between cardio-ankle vascular index and markers of thrombosis in hospitalized patients COVID-19]

AIM

To evaluate the relationship between the cardio-ankle vascular index (CAVI) and the marker of procoagulant state - D-dimer in hospitalized patients with coronavirus disease 2019 (COVID-19).

MATERIALS AND METHODS

This cross-sectional study involved adult patients admitted to the University hospital with clinically diagnosed or laboratory-confirmed COVID-19. We compared groups of patients with normal and elevated CAVI. Univariate and multivariate logistic regression analyses were performed to assess the association between risk factors and elevated D-dimer levels; odds ratios (ORs) with 95% confidence intervals (95% CI) were calculated to determine the strength of association. A p<0.05 was considered statistically significant.

RESULTS

The study included 152 patients [64 (42.1%) men and 88 (57.9%) women], mean age 59.10±12.74 years. 45 (29.6%) had elevated CAVI. Patients with elevated CAVI were older, had more comorbid diseases, a higher Charlson comorbidity index and D-dimer levels. Age, the comorbidity index, and CAVI above 9.5 were associated with elevated D-dimer levels in patients with COVID-19. In a multivariate logistic regression, CAVI above 9.5 was an independent predictor of increased D-dimer in patients with COVID-19 (OR 2.513, 95% CI 1.050-6.012; p=0.038).

CONCLUSION

In this study, for the first time, the association between a vascular stiffness marker, elevated CAVI, and increased D-dimer levels in COVID-19 patients was shown. This relationship may be a consequence of endothelial dysfunction and can be used as an additional marker of coagulopathy developing as part of COVID-19.

NETosis induction reflects COVID-19 severity and long COVID: insights from a 2-center patient cohort study in Israel

BACKGROUND

COVID-19 severity and its late complications continue to be poorly understood. Neutrophil extracellular traps (NETs) form in acute COVID-19, likely contributing to morbidity and mortality.

OBJECTIVES

This study evaluated immunothrombosis markers in a comprehensive cohort of acute and recovered COVID-19 patients, including the association of NETs with long COVID.

METHODS

One-hundred-seventy-seven patients were recruited from clinical cohorts at 2 Israeli centers: acute COVID-19 (mild/moderate, severe/critical), convalescent COVID-19 (recovered and long COVID), along with 54 non-COVID controls. Plasma was examined for markers of platelet activation, coagulation, and NETs. Ex vivo NETosis induction capability was evaluated after neutrophil incubation with patient plasma.

RESULTS

Soluble P-selectin, factor VIII, von Willebrand factor, and platelet factor 4 were significantly elevated in patients with COVID-19 versus controls. Myeloperoxidase (MPO)-DNA complex levels were increased only in severe COVID-19 and did not differentiate between COVID-19 severities or correlate with thrombotic markers. NETosis induction levels strongly correlated with illness severity/duration, platelet activation markers, and coagulation factors, and were significantly reduced upon dexamethasone treatment and recovery. Patients with long COVID maintained higher NETosis induction, but not NET fragments, compared to recovered convalescent patients.

CONCLUSIONS

Increased NETosis induction can be detected in patients with long COVID. NETosis induction appears to be a more sensitive NET measurement than MPO-DNA levels in COVID-19, differentiating between disease severity and patients with long COVID. Ongoing NETosis induction capability in long COVID may provide insights into pathogenesis and serve as a surrogate marker for persistent pathology. This study emphasizes the need to explore neutrophil-targeted therapies in acute and chronic COVID-19.

Acute to post-acute COVID-19 thromboinflammation persistence: Mechanisms and potential consequences

Concerns for the long-term effects of COVID-19 infection have grown due to frequently reported persisting symptoms that can affect multiple systems for longer than 4 weeks after initial infection, a condition known as long-COVID-19 or post-acute COVID-19 syndrome (PACS). Even nonhospitalized survivors have an elevated risk for the development of thromboinflammatory-associated events, such as ischemic stroke and heart failure, pulmonary embolism and deep vein thrombosis. Recent findings point to the persistence of many mechanisms of hypercoagulability identified to be associated with disease severity and mortality in the acute phase of the disease, such as sustained inflammation and endotheliopathy, accompanied by abnormal fibrin generation and impaired fibrinolysis. Platelets seem to be central to the sustained hypercoagulable state, displaying hyperreactivity to stimuli and increased adhesive capacity. Platelets also contribute to elevated levels of thromboinflammatory mediators and pro-coagulant extracellular vesicles in individuals with ongoing PACS. Despite new advances in the understanding of mechanisms sustaining thromboinflammation in PACS, little is known about what triggers this persistence. In this graphical review, we provide a schematic representation of the known mechanisms and consequences of persisting thromboinflammation in COVID-19 survivors and summarize the hypothesized triggers maintaining this prothrombotic state.

Humulus lupus extract rich in xanthohumol improves the clinical course in critically ill COVID-19 patients

BACKGROUND

The systemic inflammatory response following severe COVID-19 is associated with poor outcomes. Several anti-inflammatory medications have been studied in COVID-19 patients. Xanthohumol (Xn), a natural extract from hop cones, possesses strong anti-inflammatory and antioxidative properties. The aim of this study was to analyze the effect of Xn on the inflammatory response and the clinical outcome of COVID-19 patients.

METHODS

Adult patients treated for acute respiratory failure (PaO₂/FiO₂ less than 150) were studied. Patients were randomized into two groups: Xn - patients receiving adjuvant treatment with Xn at a daily dose of 4.5 mg/kg body weight for 7 days, and C - controls. Observations were performed at four time points: immediately after admission to the ICU and on the 3rd, 5th, and 7th days of treatment. The inflammatory response was assessed based on the plasma IL-6 concentration, neutrophil-to-lymphocyte ratio (NLR), platelet-to-lymphocyte ratio (PLR), C-reactive protein (CRP) and D-dimer levels. The mortality rate was determined 28 days after admission to the ICU.

RESULTS

Seventy-two patients were eligible for the study, and 50 were included in the final analysis. The mortality rate was significantly lower and the clinical course was shorter in the Xn group than in the control group (20% vs. 48%, p < 0.05, and 9 ± 3 days vs. 22 ± 8 days, p < 0.001). Treatment with Xn decreased the plasma IL-6 concentration (p < 0.01), D-dimer levels (p < 0.05) and NLR (p < 0.01) more significantly than standard treatment alone.

CONCLUSION

Adjuvant therapy with Xn appears to be a promising anti-inflammatory treatment in COVID-19 patients.

Dysregulated thrombospondin 1 and miRNA-29a-3p in severe COVID-19

Although nearly a fifth of symptomatic COVID-19 patients suffers from severe pulmonary inflammation, the mechanism of developing severe illness is not yet fully understood. To identify significantly altered genes in severe COVID-19, we generated messenger RNA and micro-RNA profiling data of peripheral blood mononuclear cells (PBMCs) from five COVID-19 patients (2 severe and 3 mild patients) and three healthy controls (HC). For further evaluation, two publicly available RNA-Seq datasets (GSE157103 and GSE152418) and one single-cell RNA-Seq dataset (GSE174072) were employed. Based on RNA-Seq datasets, thrombospondin 1 (THBS1) and interleukin-17 receptor A (IL17RA) were significantly upregulated in severe COVID-19 patients' blood. From single-cell RNA-sequencing data, IL17RA level is increased in monocytes and neutrophils, whereas THBS1 level is mainly increased in the platelets. Moreover, we identified three differentially expressed microRNAs in severe COVID-19 using micro-RNA sequencings. Intriguingly, hsa-miR-29a-3p significantly downregulated in severe COVID-19 was predicted to bind the 3'-untranslated regions of both IL17RA and THBS1 mRNAs. Further validation analysis of our cohort (8 HC, 7 severe and 8 mild patients) showed that THBS1, but not IL17RA, was significantly upregulated, whereas hsa-miR-29a-3p was downregulated, in PBMCs from severe patients. These findings strongly suggest that dysregulated expression of THBS1, IL17RA, and hsa-miR-29a-3p involves severe COVID-19.

Cytokine Storm Signature in Patients with Moderate and Severe COVID-19

Hypercytokinemia, found in SARS-CoV-2 infection, contributes to multiple organ dysfunctions with acute respiratory distress syndrome, shock etc. The aim of this study was to describe cytokine storm signatures in patients with acute COVID-19 and to investigate their influence on severity of the infection. Plasma levels of 47 cytokines were investigated in 73 patients with moderate and severe COVID-19 (41 and 32, respectively) and 11 healthy donors (HD). The most elevated levels comparing patients and the HD were observed for seven pro-inflammatory cytokines (IL-6, IL-8, IL-15, IL-18, IL-27, IFNγ, TNFα), three chemokines (GROα, IP-10, MIG), two anti-inflammatory cytokines (IL-1RA, IL-10), and two growth factors (G-CSF, M-CSF). The patients with severe disease had significantly higher levels of FGF-2/FGF-basic, IL-1β, and IL-7 compared to the HD. The two groups of patients differed from each other only based on the levels of EGF, eotaxin, and IL-12 p40. Pneumonia lung injury, characterized by computer tomography, positively correlated with levels of EGF, IP-10, MCP-3 levels and negatively with IL-12 p40. Pro-inflammatory factors including IL-6, TNFα, and IP-10 negatively correlated with the frequency of the circulating T-helper17-like cells (Th17-like) and follicular Th cells that are crucial to develop SARS-CoV-2-specific plasma cells and memory B cells. Obtained data on the cytokine levels illustrate their influence on progression and severity of COVID-19.

Implications of COVID-19 to Stroke Medicine: An Epidemiological and Pathophysiological Perspective

The neurological complications of Coronavirus 2019 (COVID-19) including stroke have been documented in the recent literature. COVID-19-related inflammation is suggested to contribute to both a hypercoagulable state and haemorrhagic transformation, including in younger individuals. COVID-19 is associated with a heightened risk of ischaemic stroke. Haemorrhagic stroke in COVID-19 patients is associated with increased morbidity and mortality. Cerebral venous sinus thrombosis (CVST) accounts for <1% of stroke cases in the general population but has come to heightened public attention due to the increased risk associated with adenoviral COVID-19 vaccines. However, recent evidence suggests the prevalence of stroke is less in vaccinated individuals than in unvaccinated COVID-19 patients. This review evaluates the current evidence of COVID-19-related ischaemic and haemorrhagic stroke, with a focus on current epidemiology and inflammatory-linked pathophysiology in the field of vascular neurology and stroke medicine.

Basic science research opportunities in thrombosis and hemostasis: Communication from the SSC of the ISTH

Bleeding and thrombosis are major clinical problems with high morbidity and mortality. Treatment modalities for these diseases have improved in recent years, but there are many clinical questions remaining and a need to advance diagnosis, management, and therapeutic options. Basic research plays a fundamental role in understanding normal and disease processes, yet this sector has observed a steady decline in funding prospects thereby hindering support for studies of mechanisms of disease and therapeutic development opportunities. With the financial constraints faced by basic scientists, the ISTH organized a basic science task force (BSTF), comprising Scientific and Standardization Committee subcommittee chairs and co-chairs, to identify research opportunities for basic science in hemostasis and thrombosis. The goal of the BSTF was to develop a set of recommended priorities to build support in the thrombosis and hemostasis community and to inform ISTH basic science programs and policy making. The BSTF identified three principal opportunity areas that were of significant overarching relevance: mechanisms causing bleeding, innate immunity and thrombosis, and venous thrombosis. Within these, five fundamental research areas were highlighted: blood rheology, platelet biogenesis, cellular contributions to thrombosis and hemostasis, structure-function protein analyses, and visualization of hemostasis. This position paper discusses the importance and relevance of these opportunities and research areas, and the rationale for their inclusion. These findings have implications for the future of fundamental research in thrombosis and hemostasis to make transformative scientific discoveries and tackle key clinical questions. This will permit better understanding, prevention, diagnosis, and treatment of hemostatic and thrombotic conditions.

Anticoagulant Treatment in Severe ARDS COVID-19 Patients

Patients with COVID-19 may complicate their evolution with thromboembolic events. Incidence of thromboembolic complications are high and also, patients with the critically-ill disease showed evidence of microthrombi and microangiopathy in the lung probably due to endothelial damage by directly and indirectly injured endothelial and epithelial cells. Pulmonary embolism, deep venous thrombosis and arterial embolism were reported in patients with COVID-19, and several analytical abnormal coagulation parameters have been described as well. D-dimer, longer coagulation times and lower platelet counts have been associated with poor outcomes. The use of anticoagulation or high doses of prophylactic heparin is controversial. Despite the use of anticoagulation or high prophylactic dose of heparin have been associated with better outcomes in observational studies, only in patients with non-critically ill disease benefits for anticoagulation was observed. In critically-ill patient, anticoagulation was not associated with better outcomes. Other measures such as antiplatelet therapy, fibrinolytic therapy or nebulized anticoagulants are being studied in ongoing clinical trials.

Beyond Hemostasis: Platelet Innate Immune Interactions and Thromboinflammation

There is accumulating evidence that platelets play roles beyond their traditional functions in thrombosis and hemostasis, e.g., in inflammatory processes, infection and cancer, and that they interact, stimulate and regulate cells of the innate immune system such as neutrophils, monocytes and macrophages. In this review, we will focus on platelet activation in hemostatic and inflammatory processes, as well as platelet interactions with neutrophils and monocytes/macrophages. We take a closer look at the contributions of major platelet receptors GPIb, α_IIbβ₃, TLT-1, CLEC-2 and Toll-like receptors (TLRs) as well as secretions from platelet granules on platelet-neutrophil aggregate and neutrophil extracellular trap (NET) formation in atherosclerosis, transfusion-related acute lung injury (TRALI) and COVID-19. Further, we will address platelet-monocyte and macrophage interactions during cancer metastasis, infection, sepsis and platelet clearance.

Significance of Immune Status of SARS-CoV-2 Infected Patients in Determining the Efficacy of Therapeutic Interventions

Coronavirus disease 2019 (COVID-19) is now being investigated for its distinctive patterns in the course of disease development which can be indicated with miscellaneous immune responses in infected individuals. Besides this series of investigations on the pathophysiology of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), significant fundamental immunological and physiological processes are indispensable to address clinical markers of COVID-19 disease and essential to identify or design effective therapeutics. Recent developments in the literature suggest that deficiency of type I interferon (IFN) in serum samples can be used to represent a severe progression of COVID-19 disease and can be used as the basis to develop combined immunotherapeutic strategies. Precise control over inflammatory response is a significant aspect of targeting viral infections. This account presents a brief review of the pathophysiological characteristics of the SARS-CoV-2 virus and the understanding of the immune status of infected patients. We further discuss the immune system’s interaction with the SARS-CoV-2 virus and their subsequent involvement of dysfunctional immune responses during the progression of the disease. Finally, we highlight some of the implications of the different approaches applicable in developing promising therapeutic interventions that redirect immunoregulation and viral infection.

Non-thrombotic superficial venous phlebitis secondary to Covid-19 vaccine or subsequent Covid-19 infection

A 43-year-old woman presented with localised areas of prominent, tender superficial veins in her right arm and both legs, and chest pain, following the second dose of AstraZeneca vaccine and possible contemporaneous Covid-19 infection. Electrocardiogram, troponin and d-dimer had all been normal. However, a venous duplex ultrasound scan showed a perivenous inflammation without thrombosis in the areas of her limbs with prominent tender veins, but not elsewhere. We suggest that patients may present with prominent and tender superficial veins secondary to non-thrombotic phlebitis following Covid-19 infection or the AstraZeneca vaccine, which appears to be self-limiting. In addition, this case raises the possibility that Covid-19 infection or the AstraZeneca vaccine may directly affect cells in the vein wall, resulting in phlebitis without any evidence of thrombosis or microthrombosis. This phenomenon appears to be transient and self-limiting.