COVID-19 hypothesis: Activated protein C for therapy of virus-induced pathologic thromboinflammation

Mechanisms of endothelial activation, hypercoagulation and thrombosis in COVID-19: a link with diabetes mellitus

Early since the onset of the COVID-19 pandemic, the medical and scientific community were aware of extra respiratory actions of SARS-CoV-2 infection. Endothelitis, hypercoagulation, and hypofibrinolysis were identified in COVID-19 patients as subsequent responses of endothelial dysfunction. Activation of the endothelial barrier may increase the severity of the disease and contribute to long-COVID syndrome and post-COVID sequelae. Besides, it may cause alterations in primary, secondary, and tertiary hemostasis. Importantly, these responses have been highly decisive in the evolution of infected patients also diagnosed with diabetes mellitus (DM), who showed previous endothelial dysfunction. In this review, we provide an overview of the potential triggers of endothelial activation related to COVID-19 and COVID-19 under diabetic milieu. Several mechanisms are induced by both the viral particle itself and by the subsequent immune-defensive response (i.e., NF-κB/NLRP3 inflammasome pathway, vasoactive peptides, cytokine storm, NETosis, activation of the complement system). Alterations in coagulation mediators such as factor VIII, fibrin, tissue factor, the von Willebrand factor: ADAMST-13 ratio, and the kallikrein-kinin or plasminogen-plasmin systems have been reported. Moreover, an imbalance of thrombotic and thrombolytic (tPA, PAI-I, fibrinogen) factors favors hypercoagulation and hypofibrinolysis. In the context of DM, these mechanisms can be exacerbated leading to higher loss of hemostasis. However, a series of therapeutic strategies targeting the activated endothelium such as specific antibodies or inhibitors against thrombin, key cytokines, factor X, complement system, the kallikrein-kinin system or NETosis, might represent new opportunities to address this hypercoagulable state present in COVID-19 and DM. Antidiabetics may also ameliorate endothelial dysfunction, inflammation, and platelet aggregation. By improving the microvascular pathology in COVID-19 and post-COVID subjects, the associated comorbidities and the risk of mortality could be reduced.

Tranexamic Acid and Plasminogen/Plasmin Glaring Paradox in COVID-19

Coronavirus disease 2019 (COVID-19) is caused by a severe acute respiratory syndrome, coronavirus type 2 (SARS-CoV-2), leading to acute tissue injury and an overstated immune response. In COVID-19, there are noteworthy changes in the fibrinolytic system with the development of coagulopathy. Therefore, modulation of the fibrinolytic system may affect the course of COVID-19. Tranexamic acid (TXA) is an anti-fibrinolytic drug that reduces the conversion of plasminogen to plasmin, which is necessary for SARS-CoV-2 infectivity. In addition, TXA has anti-inflammatory, anti-platelet, and anti-thrombotic effects, which may attenuate the COVID-19 severity. Thus, in this narrative review, we try to find the beneficial and harmful effects of TXA in COVID-19.

Understanding COVID-19-associated coagulopathy

COVID-19-associated coagulopathy (CAC) is a life-threatening complication of SARS-CoV-2 infection. However, the underlying cellular and molecular mechanisms driving this condition are unclear. Evidence supports the concept that CAC involves complex interactions between the innate immune response, the coagulation and fibrinolytic pathways, and the vascular endothelium, resulting in a procoagulant condition. Understanding of the pathogenesis of this condition at the genomic, molecular and cellular levels is needed in order to mitigate thrombosis formation in at-risk patients. In this Perspective, we categorize our current understanding of CAC into three main pathological mechanisms: first, vascular endothelial cell dysfunction; second, a hyper-inflammatory immune response; and last, hypercoagulability. Furthermore, we pose key questions and identify research gaps that need to be addressed to better understand CAC, facilitate improved diagnostics and aid in therapeutic development. Finally, we consider the suitability of different animal models to study CAC.

Assessment of the Level of Protein C in Hospitalized Iraqi Patients with COVID-19 and its Correlation with Hematological and Inflammatory Markers

BACKGROUND: COVID-19 coagulopathy manifests by elevation of certain marker of active coagulation as fibrinogen and this increment associated with increased markers of inflammations. AIM: To measure protein C (PC) level in hospitalized patients with COVID-19 and to find a possible correlation with hematological and inflammatory markers. PATIENTS AND METHODS: Seventy-five hospitalized Iraqi adult patients with COVID-19 were included in a descriptive cross-sectional research. PC, D-dimer, and erythrocyte sedimentation rate (ESR) blood samples were collected, and further information was received from patient’s records. Statistical analysis was conducted using SPSS version 23 and Microsoft Office Excel 2019. RESULTS: Mean age of 75 patients included in the study was 60.13 ± 14.65 years. Sixty-two (62.7%) of patients exhibited neutrophilia, whereas 41 had lymphopenia (54.7%). High ratio of neutrophil/lymphocyte (N/L) was seen in 66 (88.0%), eosinopenia was seen in 46 (61.3%), high lactate dehydrogenase level was seen 68 (90.7%), serum ferritin was high in 66 (88.0%), and high level of C-reactive protein was seen in 68 (90.7%), increased ESR was seen in 69 (92.0%) and high level of D-dimer was seen in 56 (74.7%), while low level of PC was seen in 12 (16.0%) patients. PC had significant negative correlation with prothrombin and partial thromboplastin time but no significant correlation with hematological and inflammatory parameters. CONCLUSION: COVID-19 coagulopathy is common in majority of patients which include significant changes in WBCs counts, inflammatory markers, PC, and D-dimer levels. Such changes may have a great impact on morbidity and mortality and thus need to be monitored throughout treatment and convalescence.

The Association between Protein C and Antithrombin III Levels with the Severity of Coronavirus Disease-2019 Symptoms

BACKGROUND: Coronavirus disease-2019 (COVID-19) has various symptoms ranging from mild to critical. Hypercoagulation state is often observed in severe and critical COVID-19. Both coagulation and inflammation are interrelated and amplifying each other, with protein C and antithrombin (AT) III as two important mediators. OBJECTIVE: To determine the association between protein C and AT III levels with the severity of COVID-19 symptoms. METHODS: This analytical study was conducted at Haji Adam Malik Hospital from April to July 2021. Subjects were obtained by consecutive sampling method. Inclusion criteria were patients with confirmed COVID-19 using RT-PCR and willing to participate. Subjects were divided into 2 groups: mild-moderate and severe-critical symptom groups. Demographic and blood sample were obtained from each subject. Blood samples underwent examination for leukocyte, thrombocyte, PT, aPTT, protein C, and AT III. RESULTS: A total of 50 patients were obtained with female domination (58%) and mean age of 41.44 (SD 20.90) years. Most subjects (86%) were in mild-moderate symptom group. There were significant differences in the level of protein C and AT III in both group (p= 0.029 and 0.034, respectively). Using the cut-off values for protein C of 5.36 ng/mL and AT III of 45.6%, subjects who had mediators level below the value tend to develop severe and critical symptoms compared to their counterparts (OR= 5.769 and 6.458, respectively). CONCLUSION: Protein C and AT III are associated with severity of COVID-19 symptoms. Lower protein C and AT III levels increase the risk for developing severe and critical symptoms.

A Web Application for Biomedical Text Mining of Scientific Literature Associated with Coronavirus-Related Syndromes: Coronavirus Finder

In this study, a web application was developed that comprises scientific literature associated with the Coronaviridae family, specifically for those viruses that are members of the Genus Betacoronavirus, responsible for emerging diseases with a great impact on human health: Middle East Respiratory Syndrome-Related Coronavirus (MERS-CoV) and Severe Acute Respiratory Syndrome-Related Coronavirus (SARS-CoV, SARS-CoV-2). The information compiled on this webserver aims to understand the basics of these viruses' infection, and the nature of their pathogenesis, enabling the identification of molecular and cellular components that may function as potential targets on the design and development of successful treatments for the diseases associated with the Coronaviridae family. Some of the web application's primary functions are searching for keywords within the scientific literature, natural language processing for the extraction of genes and words, the generation and visualization of gene networks associated with viral diseases derived from the analysis of latent semantic space, and cosine similarity measures. Interestingly, our gene association analysis reveals drug targets in understudies, and new targets suggested in the scientific literature to treat coronavirus.

Severe Acute Respiratory Syndrome Coronavirus-2 Pneumonia Presenting Concomitantly With Purpura Fulminans: A Case Report

Severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) is a novel coronavirus that has been extensively described in its most common presentations. Its pathogenetic process is poorly understood, although it is theorized that endothelial damage and inflammation play a central role. Its prothrombotic nature affects multiple organs, including lungs, kidneys, and the central nervous system. Rarer are cutaneous presentations that can be triggered or displayed concomitantly with COVID-19. Purpura fulminans is a life-threatening syndrome that results in skin thrombosis and hemorrhagic infarction. While its association is explicit in critically ill patients with sepsis, few or rare cases have been described to be linked with COVID-19. In this report, we present a case of a critically ill patient with COVID-19 who showed signs of purpura fulminans while in the intensive care unit.

Neutrophil Extracellular Traps (NETs) and Covid-19: A new frontiers for therapeutic modality

Coronavirus disease 2019 (Covid-19) is a worldwide infectious disease caused by severe acute respiratory coronavirus 2 (SARS-CoV-2). In severe SARS-CoV-2 infection, there is severe inflammatory reactions due to neutrophil recruitments and infiltration in the different organs with the formation of neutrophil extracellular traps (NETs), which involved various complications of SARS-CoV-2 infection. Therefore, the objective of the present review was to explore the potential role of NETs in the pathogenesis of SARS-CoV-2 infection and to identify the targeting drugs against NETs in Covid-19 patients. Different enzyme types are involved in the formation of NETs, such as neutrophil elastase (NE), which degrades nuclear protein and release histones, peptidyl arginine deiminase type 4 (PADA4), which releases chromosomal DNA and gasdermin D, which creates pores in the NTs cell membrane that facilitating expulsion of NT contents. Despite of the beneficial effects of NETs in controlling of invading pathogens, sustained formations of NETs during respiratory viral infections are associated with collateral tissue injury. Excessive development of NETs in SARS-CoV-2 infection is linked with the development of acute lung injury (ALI) and acute respiratory distress syndrome (ARDS) due to creation of the NETs-IL-1β loop. Also, aberrant NTs activation alone or through NETs formation may augment SARS-CoV-2-induced cytokine storm (CS) and macrophage activation syndrome (MAS) in patients with severe Covid-19. Furthermore, NETs formation in SARS-CoV-2 infection is associated with immuno-thrombosis and the development of ALI/ARDS. Therefore, anti-NETs therapy of natural or synthetic sources may mitigate SARS-CoV-2 infection-induced exaggerated immune response, hyperinflammation, immuno-thrombosis, and other complications.

Could Soluble Endothelial Protein C Receptor Levels Recognize SARS-CoV2-Positive Patients Requiring Hospitalization?

INTRODUCTION

The endothelial protein C receptor (EPCR) is a protein that regulates the protein C anticoagulant and anti-inflammatory pathways. A soluble form of EPCR (sEPCR) circulates in plasma and inhibits activated protein C (APC) activities. The clinical impact of sEPCR and its involvement in COVID-19 has not been explored. In this study, we investigated whether sEPCR levels were related to COVID-19 patients' requirement for hospitalization.

METHODS

Plasma sEPCR levels were measured on hospital admission in 84 COVID-19 patients, and in 11 non-hospitalized SARS-CoV2-positive patients approximately 6 days after reported manifestation of their symptoms. Multiple logistic regression analysis was performed to identify potential risk factors for hospitalization and receiver operating characteristic (ROC) curves were generated to assess their value.

RESULTS

In our cohort, hospitalized patients had considerably higher sEPCR levels upon admission compared with outpatients [107.5 (76.7-156.3) vs. 44.6 (12.1-84.4) ng/mL; P < 0.0001)]. The ROC curve using hospitalization as the classification variable and sEPCR levels as the prognostic variable generated an area under the curve at 0.845 (95% CI = 0.710-0.981, P < 0.001). Additionally, we investigated the predictive value of sEPCR combined with BMI, age, or D-dimers.

CONCLUSIONS

In our cohort, sEPCR levels in COVID-19 patients upon hospital admission appear considerably elevated compared with outpatients; this could lead to impaired APC activities and might contribute to the pro-coagulant phenotype reported in such patients. sEPCR measurement might be useful as a point-of-care test in SARS-CoV2-positive patients.

Exploring the pathways of inflammation and coagulopathy in COVID-19: A narrative tour into a viral rabbit hole

Worldwide COVID-19 pandemic has taken a huge toll of morbidity and mortality. In selected patients, classified as severe, the overwhelming inflammatory state imposed by this infection is accompanied by a hypercoagulable state, hallmarked by a unique pattern; a marked increase in D-dimer, out of proportion to other markers of coagulopathy. In this review, we turn a spotlight to this phenomenon, offering a unified conceptual model depicting the leading hypotheses of coagulopathy in COVID-19. The key players of the coagulation cascades accompanying the COVID-19 inflammation malfunction on virtually every level; tissue factor expression is amplified, physiological anti-coagulant pathways (anti-thrombin, protein C and S, and the inhibitor of the tissue factor pathway) are impaired and fibrinolysis is inhibited. Components of autoimmunity, the complement system amongst others, further contribute to the pathology. As data continue to gather, our model offers a pathophysiological overview of COVID-19 coagulopathy, defined by the resultant histopathology: either intra-vascular or extra-vascular. We hope this review will facilitate understanding and serve as a lead point to future therapeutic directives.

Immunothrombosis in Acute Respiratory Dysfunction of COVID-19

COVID-19 is an acute, complex disorder that was caused by a new β-coronavirus severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Based on current reports, it was surprising that the characteristics of many patients with COVID-19, who fulfil the Berlin criteria for acute respiratory distress syndrome (ARDS), are not always like those of patients with typical ARDS and can change over time. While the mechanisms of COVID-19–related respiratory dysfunction in COVID-19 have not yet been fully elucidated, pulmonary microvascular thrombosis is speculated to be involved. Considering that thrombosis is highly related to other inflammatory lung diseases, immunothrombosis, a two-way process that links coagulation and inflammation, seems to be involved in the pathophysiology of COVID-19, including respiratory dysfunction. Thus, the current manuscript will describe the proinflammatory milieu in COVID-19, summarize current evidence of thrombosis in COVID-19, and discuss possible interactions between these two.

L-ARGININE AND L-GLUTAMIC ACID INCREASE THE CONTENT OF PROTEIN C IN THE EARLY STAGES OF ISOLATION FROM DONOR PLASMA

Current large-scale production of blood-derived pharmacological preparations is aimed at expanding the list of products and deeper extraction of target proteins especially at the pre-purification stage. In particular, this problem becomes critical for the isolation of proteins like protein C (PC), which is present in plasma in trace amounts. Aim. We aimed to improve the buffer composition to minimize the interaction of PC with other proteins and lipids that are inevitably present in the stock material. Methods. The content of protein C in plasma and its derivatives was assessed by the amidolytic activity to the chromogenic substrate S2366. A decrease in homologous impurities and plasma enrichment with protein C was provided by selective bulk adsorption on DEAE-cellulose. Results. Here we describe that an equimolar mixture of two amino acids (L-arginine and L-glutamic acid) essentially increased the content of protein C at the stage of cryo-depleted plasma pre-purification, including initial dilution and subsequent enrichment of plasma with protein C due to selective bulk adsorption on DEAE- cellulose. Additionally, it was revealed that solutions of these amino acids, when combined, inhibit the induced amidolytic activity of protein C and increase its solubility (in contrast to other plasma proteases). Conclusion. Pre-adding of a mixture of amino acids L-arginine and L-glutamic acid to cryo-depleted plasma significantly optimizes the pre-purification stage of protein C, providing a 5-fold increase in its yield after elution from DEAE-cellulose.

Large-Scale Multi-omic Analysis of COVID-19 Severity

We performed RNA-seq and high-resolution mass spectrometry on 128 blood samples from COVID-19-positive and COVID-19-negative patients with diverse disease severities and outcomes. Quantified transcripts, proteins, metabolites, and lipids were associated with clinical outcomes in a curated relational database, uniquely enabling systems analysis and cross-ome correlations to molecules and patient prognoses. We mapped 219 molecular features with high significance to COVID-19 status and severity, many of which were involved in complement activation, dysregulated lipid transport, and neutrophil activation. We identified sets of covarying molecules, e.g., protein gelsolin and metabolite citrate or plasmalogens and apolipoproteins, offering pathophysiological insights and therapeutic suggestions. The observed dysregulation of platelet function, blood coagulation, acute phase response, and endotheliopathy further illuminated the unique COVID-19 phenotype. We present a web-based tool (covid-omics.app) enabling interactive exploration of our compendium and illustrate its utility through a machine learning approach for prediction of COVID-19 severity.

Commonalities Between COVID-19 and Radiation Injury

As the multi-systemic components of COVID-19 emerge, parallel etiologies can be drawn between SARS-CoV-2 infection and radiation injuries. While some SARS-CoV-2-infected individuals present as asymptomatic, others exhibit mild symptoms that may include fever, cough, chills, and unusual symptoms like loss of taste and smell and reddening in the extremities (e.g., "COVID toes," suggestive of microvessel damage). Still others alarm healthcare providers with extreme and rapid onset of high-risk indicators of mortality that include acute respiratory distress syndrome (ARDS), multi-organ hypercoagulation, hypoxia and cardiovascular damage. Researchers are quickly refocusing their science to address this enigmatic virus that seems to unveil itself in new ways without discrimination. As investigators begin to identify early markers of disease, identification of common threads with other pathologies may provide some clues. Interestingly, years of research in the field of radiation biology documents the complex multiorgan nature of another disease state that occurs after exposure to high doses of radiation: the acute radiation syndrome (ARS). Inflammation is a key common player in COVID-19 and ARS, and drives the multi-system damage that dramatically alters biological homeostasis. Both conditions initiate a cytokine storm, with similar pro-inflammatory molecules increased and other anti-inflammatory molecules decreased. These changes manifest in a variety of ways, with a demonstrably higher health impact in patients having underlying medical conditions. The potentially dramatic human impact of ARS has guided the science that has identified many biomarkers of radiation exposure, established medical management strategies for ARS, and led to the development of medical countermeasures for use in the event of a radiation public health emergency. These efforts can now be leveraged to help elucidate mechanisms of action of COVID-19 injuries. Furthermore, this intersection between COVID-19 and ARS may point to approaches that could accelerate the discovery of treatments for both.

Role of Tissue Factor in the Pathogenesis of COVID-19 and the Possible Ways to Inhibit It

COVID-19 (Coronavirus Disease 2019) is a highly contagious infection and associated with high mortality rates, primarily in elderly; patients with heart failure; high blood pressure; diabetes mellitus; and those who are smokers. These conditions are associated to increase in the level of the pulmonary epithelium expression of angiotensin-converting enzyme 2 (ACE-2), which is a recognized receptor of the S protein of the causative agent SARS-CoV-2 (Severe Acute Respiratory Syndrome Coronavirus 2). Severe cases are manifested by parenchymal lung involvement with a significant inflammatory response and the development of microvascular thrombosis. Several factors have been involved in developing this prothrombotic state, including the inflammatory reaction itself with the participation of proinflammatory cytokines, endothelial dysfunction/endotheliitis, the presence of antiphospholipid antibodies, and possibly the tissue factor (TF) overexpression. ARS-Cov-19 ACE-2 down-regulation has been associated with an increase in angiotensin 2 (AT2). The action of proinflammatory cytokines, the increase in AT2 and the presence of antiphospholipid antibodies are known factors for TF activation and overexpression. It is very likely that the overexpression of TF in COVID-19 may be related to the pathogenesis of the disease, hence the importance of knowing the aspects related to this protein and the therapeutic strategies that can be derived. Different therapeutic strategies are being built to curb the expression of TF as a therapeutic target for various prothrombotic events; therefore, analyzing this treatment strategy for COVID-19-associated coagulopathy is rational. Medications such as celecoxib, cyclosporine or colchicine can impact on COVID-19, in addition to its anti-inflammatory effect, through inhibition of TF.

Inflammation and thrombosis in COVID-19 pathophysiology: proteinase-activated and purinergic receptors as drivers and candidate therapeutic targets

Evolving information has identified disease mechanisms and dysregulation of host biology that might be targeted therapeutically in coronavirus disease 2019 (COVID-19). Thrombosis and coagulopathy, associated with pulmonary injury and inflammation, are emerging clinical features of COVID-19. We present a framework for mechanisms of thrombosis in COVID-19 that initially derive from interaction of SARS-CoV-2 with ACE2, resulting in dysregulation of angiotensin signaling and subsequent inflammation and tissue injury. These responses result in increased signaling by thrombin (proteinase-activated) and purinergic receptors, which promote platelet activation and exert pathological effects on other cell types (e.g., endothelial cells, epithelial cells, and fibroblasts), further enhancing inflammation and injury. Inhibitors of thrombin and purinergic receptors may, thus, have therapeutic effects by blunting platelet-mediated thromboinflammation and dysfunction in other cell types. Such inhibitors include agents (e.g., anti-platelet drugs) approved for other indications, and that could be repurposed to treat, and potentially improve the outcome of, COVID-19 patients. COVID-19, caused by the SARS-CoV-2 virus, drives dysregulation of angiotensin signaling, which, in turn, increases thrombin-mediated and purinergic-mediated activation of platelets and increase in inflammation. This thromboinflammation impacts the lungs and can also have systemic effects. Inhibitors of receptors that drive platelet activation or inhibitors of the coagulation cascade provide opportunities to treat COVID-19 thromboinflammation.

Coagulation Disorders in COVID-19: Role of Toll-like Receptors

Coronavirus disease 2019 (COVID-19) has spread rapidly throughout the world. The range of the disease is broad but among hospitalized patients with COVID-19 are coagulation disorders, pneumonia, respiratory failure, and acute respiratory distress syndrome (ARDS). The excess production of early response proinflammatory cytokines results in what has been described as a cytokine storm, leading to an increased risk of thrombosis, inflammations, vascular hyperpermeability, multi-organ failure, and eventually death over time. As the pandemic is spreading and the whole picture is not yet clear, we highlight the importance of coagulation disorders in COVID-19 infected subjects and summarize it. COVID-19 infection could induce coagulation disorders leading to clot formation as well as pulmonary embolism with detrimental effects in patient recovery and survival. Coagulation and inflammation are closely related. In this review, we try to establish an association between virus infections associated with innate immune activation, inflammation and coagulation activation.

Stabilizing Cellular Barriers: Raising the Shields Against COVID-19

The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and its clinical manifestation (COVID-19; coronavirus disease 2019) have caused a worldwide health crisis. Disruption of epithelial and endothelial barriers is a key clinical turning point that differentiates patients who are likely to develop severe COVID-19 outcomes: it marks a significant escalation in respiratory symptoms, loss of viral containment and a progression toward multi-organ dysfunction. These barrier mechanisms are independently compromised by known COVID-19 risk factors, including diabetes, obesity and aging: thus, a synergism between these underlying conditions and SARS-CoV-2 mechanisms may explain why these risk factors correlate with more severe outcomes. This review examines the key cellular mechanisms that SARS-CoV-2 and its underlying risk factors utilize to disrupt barrier function. As an outlook, we propose that glucagon-like peptide 1 (GLP-1) may be a therapeutic intervention that can slow COVID-19 progression and improve clinical outcome following SARS-CoV-2 infection. GLP-1 signaling activates barrier-promoting processes that directly oppose the pro-inflammatory mechanisms commandeered by SARS-CoV-2 and its underlying risk factors.

Large-scale Multi-omic Analysis of COVID-19 Severity

We performed RNA-Seq and high-resolution mass spectrometry on 128 blood samples from COVID-19 positive and negative patients with diverse disease severities. Over 17,000 transcripts, proteins, metabolites, and lipids were quantified and associated with clinical outcomes in a curated relational database, uniquely enabling systems analysis and cross-ome correlations to molecules and patient prognoses. We mapped 219 molecular features with high significance to COVID-19 status and severity, many involved in complement activation, dysregulated lipid transport, and neutrophil activation. We identified sets of covarying molecules, e.g., protein gelsolin and metabolite citrate or plasmalogens and apolipoproteins, offering pathophysiological insights and therapeutic suggestions. The observed dysregulation of platelet function, blood coagulation, acute phase response, and endotheliopathy further illuminated the unique COVID-19 phenotype. We present a web-based tool (covid-omics.app) enabling interactive exploration of our compendium and illustrate its utility through a comparative analysis with published data and a machine learning approach for prediction of COVID-19 severity.