Anticoagulant protein S in COVID-19: low activity, and associated with outcome

Evaluation of protein C and S levels in patients with COVID-19 infection and their relation to disease severity

Background

The COVID-19 pandemic has been associated with millions of deaths around the world. One of the important causes of death associated with COVID-19 was pulmonary thromboembolism. The risk for venous thromboembolism was markedly increased in patients with COVID-19 especially those admitted to the intensive care unit. The aims of our study were to measure the protein C and S levels in COVID-19-infected patients in comparison with the normal population and to assess the correlation of protein C and S levels in the plasma to the severity of infection.

Methods

This was a case-control study measuring the protein C and S levels in patients infected with COVID-19 at the time of diagnosis compared to the normal population. The study included one hundred participants, sixty of them are patients with COVID-19, and forty of them are normal healthy adults. The patient group was subclassified into three subgroups according to disease severity: mild, moderate, and severe COVID-19 infections.

Results

The activity of protein C in the patient group serum was significantly lower than that in the control group serum (79.35 ± 26.017 vs 97.43 ± 15.007; p < 0.001). Protein S is also significantly decreased in patients' serum when compared to the control group (70.233 ± 22.476 vs 91 ± 14.498; p < 0.001). There was a statistically significant decrease in the levels of protein C and S associated with the increase in disease severity (p < 0.05). However, protein S showed no statistically significant difference between the moderate and severe disease subgroups.

Conclusion

The study concluded that the levels of protein C and S activities were both decreased in patients with COVID-19 when compared to the healthy population. It also concluded that the decrease in their levels is statistically significant in relation to the disease severity.

Assessment of COVID -19 associated coagulopathy and multiple hemostatic markers: a single center study in Egypt

Background

Coagulopathy is still a serious pattern of coronavirus-19 disease. We aimed to evaluate COVID-19-associated coagulopathy and multiple hemostatic markers in Egyptian patients. In addition, to assess coagulation acute phase reactants and its effect on the outcome.

Methods

The study included 106 COVID-19 patients, and 51 controls. All patients were positive for COVID-19 infection by nasopharyngeal swab for detection of viral RNA by real-time PCR. In addition to baseline data and radiological findings, the coagulation profile was done with special attention to Fibrinogen, d-dimer, Factor VIII, von Willebrand factor (VWF), Protein C, Protein S, Antithrombin III (ATIII) and Lupus anticoagulant (LA)-1 and 2.

Results

The results showed significantly higher VWF, d-dimer, and LA1 (screening) and LA2 (confirmation) in patients than a control group. Significantly higher d-dimer FVIII, VWF and LA1-2 were detected in the severe group. ATIII had high diagnostic accuracy in severity prediction. We found a significantly higher international randomized ratio (INR) and VWF among patients with thrombotic events. For prediction of thrombosis; VWF at cutoff > 257.7 has 83.3% sensitivity and 83.3% specificity.

Conclusion

Patients with COVID-19 infection are vulnerable to different forms of coagulopathy. This could be associated with poor outcomes. d-Dimer is a chief tool in diagnosis, severity evaluation but not thrombosis prediction. Early screening for this complication and its proper management would improve the outcome.

White Blood Cells, COVID-19, and Mendelian Randomization

Many observational studies have shown an association between the severity of COVID-19 and the different white blood cell counts, most frequently neutrophils, lymphocytes, and eosinophils. The studies aimed to predict the prognosis, and therefore, a causal relationship was unnecessary. However, if we begin to look at these biomarkers as potential therapeutic targets, then causality is essential. Observational studies cannot prove a causal relationship, and randomized trials are not always feasible. In this case, Mendelian randomization studies, considered more valid than observational studies, could add to the arguments for causality. Two Mendelian randomization studies tested for a causal relationship between the number of different white cell populations and COVID-19 severity, but their results are different; therefore, the problem of causality is not settled in this case.

Investigation of the Molecular Mechanism of Coagulopathy in Severe and Critical Patients With COVID-19

Coagulopathy is a frequently reported finding in the pathology of coronavirus disease 2019 (COVID-19); however, the molecular mechanism, the involved coagulation factors, and the role of regulatory proteins in homeostasis are not fully investigated. We explored the dynamic changes of nine coagulation tests in patients and controls to propose a molecular mechanism for COVID-19-associated coagulopathy. Coagulation tests including prothrombin time (PT), partial thromboplastin time (PTT), fibrinogen (FIB), lupus anticoagulant (LAC), proteins C and S, antithrombin III (ATIII), D-dimer, and fibrin degradation products (FDPs) were performed on plasma collected from 105 individuals (35 critical patients, 35 severe patients, and 35 healthy controls). There was a statically significant difference when the results of the critical (CRT) and/or severe (SVR) group for the following tests were compared to the control (CRL) group: PTCRT (15.014) and PTSVR (13.846) (PTCRL = 13.383, p &lt; 0.001), PTTCRT (42.923) and PTTSVR (37.8) (PTTCRL = 36.494, p &lt; 0.001), LACCRT (49.414) and LACSVR (47.046) (LACCRL = 40.763, p &lt; 0.001), FIBCRT (537.66) and FIBSVR (480.29) (FIBCRL = 283.57, p &lt; 0.001), ProCCRT (85.57%) and ProCSVR (99.34%) (ProCCRL = 94.31%, p = 0.04), ProSCRT (62.91%) and ProSSVR (65.06%) (ProSCRL = 75.03%, p &lt; 0.001), D-dimer (p &lt; 0.0001, χ2 = 34.812), and FDP (p &lt; 0.002, χ2 = 15.205). No significant association was found in the ATIII results in groups (ATIIICRT = 95.71% and ATIIISVR = 99.63%; ATIIICRL = 98.74%, p = 0.321). D-dimer, FIB, PT, PTT, LAC, protein S, FDP, and protein C (ordered according to p-values) have significance in the prognosis of patients. Disruptions in homeostasis in protein C (and S), VIII/VIIIa and V/Va axes, probably play a role in COVID-19-associated coagulopathy.

Protein S: function, regulation, and clinical perspectives

PURPOSE OF REVIEW

Protein S (PS) is an essential natural anticoagulant. PS deficiency is a major contributor to acquired hypercoagulability. Acquired hypercoagulability causes myocardial infarction, stroke, and deep vein thrombosis in millions of individuals. Yet, despite its importance in hemostasis, PS is the least understood anticoagulant. Even after 40 years since PS was first described, we are still uncovering information about how PS functions. The purpose of this review is to highlight recent findings that advance our understanding of the functions of PS and explain hypercoagulability caused by severe PS deficiency.

RECENT FINDINGS

PS has long been described as a cofactor for Activated Protein C (APC) and Tissue Factor Pathway Inhibitor (TFPI). However, a recent report describes direct inhibition of Factor IXa (FIXa) by PS, an activity of PS that had been completely overlooked. Thrombophilia is becoming a more frequently reported disorder. Hereditary PS deficiency is an anticoagulant deficiency that results eventually in thrombophilia. In addition, PS deficiency is a predisposing factor for venous thromboembolism (VTE), but an effect of PS deficiency in arterial thrombosis, such as arterial ischemic stroke, is uncertain. Plasma PS concentration decreases in pregnant women. Inherited thrombophilias are important etiologies for recurrent pregnancy loss, and anticoagulation therapy is of benefit to women with recurrent pregnancy loss who had documented only PS deficiency.Hypoxia is a risk factor for VTE, and hypoxia downregulates plasma PS level. Importantly, COVID-19 can lead to hypoxemia because of lung damage from IL6-driven inflammatory responses to the viral infection. Because hypoxia decreases the abundance of the key anticoagulant PS, we surmise that the IL6-induced cytokine explosion combined with hypoxemia causes a drop in PS level that exacerbates the thrombotic risk in COVID-19 patients.

SUMMARY

This review is intended to advance understanding of the anticoagulant function of an important plasma protein, PS. Despite 40+ years of research, we have not had a complete description of PS biology as it pertains to control of blood coagulation. However, the picture of PS function has become sharper with the recent discovery of FIXa inhibition by PS. Hemostasis mediated by PS now includes regulation of FIXa activity alongside the cofactor activities of PS in the TFPI/APC pathways. In addition, the direct inhibition of FIXa by PS suggests that PS, particularly a small derivative of PS, could be used to treat individuals with PS deficiencies or abnormalities that cause thrombotic complications.

Vitamin supplementation as a potential adjunctive therapeutic approach for COVID-19: biological and clinical plausibility

The recent pandemic, severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), the causative agent of Coronavirus Disease 2019 (COVID-19) has introduced itself into the human population in the 21st century after the coronavirus diseases SARS-CoV and Middle East respiratory syndrome (MERS-CoV). Major investigations are underway worldwide in the search for pharmaceutical interventions for COVID-19 and many agents are administered in off-label routes. Several cases are under study to check or restrict clinical manifestations of COVID-19. According to the fact that the efficacy of some micro-nutrients like vitamins is proven to treat or prevent infectious diseases because of their antimicrobial and immunomodulatory activity, the potential role of vitamins in the COVID-19 treatment or prevention must be considered.

The SARS-CoV-2 SSHHPS Recognized by the Papain-like Protease

Viral proteases are highly specific and recognize conserved cleavage site sequences of ∼6-8 amino acids. Short stretches of homologous host-pathogen sequences (SSHHPS) can be found spanning the viral protease cleavage sites. We hypothesized that these sequences corresponded to specific host protein targets since >40 host proteins have been shown to be cleaved by Group IV viral proteases and one Group VI viral protease. Using PHI-BLAST and the viral protease cleavage site sequences, we searched the human proteome for host targets and analyzed the hit results. Although the polyprotein and host proteins related to the suppression of the innate immune responses may be the primary targets of these viral proteases, we identified other cleavable host proteins. These proteins appear to be related to the virus-induced phenotype associated with Group IV viruses, suggesting that information about viral pathogenesis may be extractable directly from the viral genome sequence. Here we identify sequences cleaved by the SARS-CoV-2 papain-like protease (PLpro) in vitro within human MYH7 and MYH6 (two cardiac myosins linked to several cardiomyopathies), FOXP3 (an X-linked Treg cell transcription factor), ErbB4 (HER4), and vitamin-K-dependent plasma protein S (PROS1), an anticoagulation protein that prevents blood clots. Zinc inhibited the cleavage of these host sequences in vitro. Other patterns emerged from multispecies sequence alignments of the cleavage sites, which may have implications for the selection of animal models and zoonosis. SSHHPS/nsP is an example of a sequence-specific post-translational silencing mechanism.

Role of vitamin D in treating COVID-19-associated coagulopathy: problems and perspectives

Aggressive inflammatory response leading to hypercoagulability has been found to be associated with disease severity in COVID-19 patients and portends bad treatment outcome. A state of acute disseminated intravascular coagulation (DIC), along with pulmonary embolism and/or deep vein thrombosis, has been observed in critically ill ICU patients. Autopsy reports of COVID-19 patients demonstrated microthrombi in lungs and in other organs, as well as marked inflammatory changes, characteristic clinicopathological features that exacerbate disease severity. Vitamin D supplementation was recommended by many clinicians across the globe to improve clinical symptoms of COVID-19 patients, mainly because of its immunomodulatory roles on immune cells. Furthermore, vitamin D and its associated molecules are also known to directly or indirectly regulate various thrombotic pathways. We propose that vitamin D supplementation not only attenuates the risk of Acute Respiratory Disease Syndrome (ARDS) but it also may have a role in reducing coagulation abnormalities in critically ill COVID-19 patients. The overarching goal of this review is to discuss the effects of vitamin D on coagulation pathways and other intertwined processes leading to thrombosis. Many clinical trials are currently investigating the efficacy of vitamin D supplementation in reducing the risk of COVID-19 infection. However, randomized placebo control clinical trials are also necessary to ascertain the effect of vitamin D supplementation on reducing the risk of coagulopathy in COVID-19 patients.