A Study Investigating the Effects of COVID-19 on Platelet Function

The coronavirus disease-19 (COVID-19) pandemic that originated in Wuhan, China in late December 2019 has spread rapidly around the world, killing more than 6.5 million people. The disease is caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). This positive-sense RNA virus causes a variety of clinical manifestations and causes hospitalization in many pneumonia patients. Studies highlight that COVID-19 patients have a high incidence of arterial and venous thrombosis, including pulmonary embolism, deep vein thrombosis, ischemic stroke, and myocardial infarction. Additionally, numerous post-mortem examinations have shown the presence of microthrombi in the heart, lungs, brain, liver, and kidneys of COVID-19 patients. This suggests that COVID-19 can cause systemic thrombosis and lead to multiple organ failure.

​​​​​​​study: Altered platelet proteomic signature and impaired platelet integrin αIIbβ3 activation in COVID-19 patientsImage credit: Peddaranka Ramesh Babu / Shutterstock

Previous studies have also observed that COVID-19 patients have elevated levels of serum clotting markers such as: D-dimer and fibrinogen. Additionally, thromboprophylaxis has been observed to improve outcomes in her COVID-19 patients who are hospitalized. However, there was no significant effect on mortality in severe her COVID-19 patients. Therefore, thrombosis remains a prominent feature of COVID-19, and high thrombin generation is not the only factor.

Platelets, which are essential for hemostasis, can also cause thrombosis through inappropriate activation. Platelets can become hyperactive, with increased secretion of dense alpha granules, increased platelet leukocyte aggregate formation, and increased aggregation. Platelet transcriptome analysis shows overrepresentation of mitochondrial dysfunction, antigen Presentation pathways in COVID-19 patients lead to platelet hyperfunction. However, many studies have also reported reduced or impaired platelet function in COVID-19 patients, suggesting that the platelet response is complex.

The etiology of thrombosis in COVID-19 patients is poorly understood, but it contains several features of thromboinflammatory disease. SARS-CoV-2 activates endothelial cells with the help of angiotensin-converting enzyme 2 (ACE2) receptors and causes vascular dysfunction. Endothelial injury can activate the innate immune system through neutrophil recruitment, tissue factor (TF) expression, proinflammatory cytokines, and complement. This leads to increased expression and/or release of prothrombotic factors and upregulation of adhesion molecules that can activate platelets, leading to clot formation, aggregation and further activation of the innate immune system. Platelets can increase thrombin generation through the expression of phosphatidylserine and tissue factor (TF). This network of interactions between the innate immune system, platelets, coagulation, and damaged endothelium may contribute to thrombosis in COVID-19 patients.

New research posted on preprint server Bio Rxiv*We aimed to analyze the impact of COVID-19 on the platelet proteome and to correlate platelet functional responses with platelet-neutrophil aggregate formation in hospitalized COVID-19 patients.

A graphical summary of the findings. Red indicates increases in variables in COVID-19 patients and healthy controls, blue indicates decreases. Diagram created using biorender.com.

About research

Twenty-two hospitalized adult COVID-19 patients and 19 healthy controls recruited between October 2020 and February 2021 participated in this study. Information on comorbidities, demographics, medications, hospitalization outcomes, and treatment records were collected from all patients. Additionally, complete blood counts were determined for both a healthy control and her COVID-19 patient. Platelets were isolated from venous blood, washed, and prepared for tandem mass tag (TMT) proteomics analysis.

Platelet proteomes were compared between healthy controls and COVID-19 patients. In addition, we used Gene Ontology pathways to analyze her COVID-19-related changes affecting platelet protein function. Finally, we performed western blotting and flow cytometry analysis.

Survey results

As a result, the average age of the COVID-19 cohort was 59 years, compared to 39 years in the control cohort. The average body mass index (BMI) of COVID-19 patients was reported to be 30.6 kg/m2, while that of controls was 22.7 kg/m2. In addition, 88% of her patients required oxygen therapy and additional medications such as rivaroxaban, dexamethasone, and heparin. Additionally, COVID-19 patients were observed to have high neutrophil levels and low lymphocyte counts.

Of 5,773 platelet proteins, 858 were elevated in COVID-19 patients compared with healthy controls. These mainly included C-reactive protein and 40S ribosomal proteins. However, many platelet activation signaling proteins were decreased in COVID-19 patients compared with controls. Platelet lysates obtained from COVID-19 patients were reported to show decreased thrombopoietin (TPO) receptor cMpl, interferon-induced transmembrane protein 3 (IFITM3), and protein kinase C α (PKCα) expression . In addition, CD147 (basigin), a receptor associated with SAS-CoV-2 interaction, was reported to be present in both control and his COVID-19 patient samples.

Of the 38 serum proteins associated with COVID-19, 12 were altered in platelets of COVID-19 patients. Among them, four proteins, including serum amyloid A (SAA1), galectin 3-binding protein (G3BP), lipopolysaccharide-binding protein (LBP), and C-reactive protein (CRP), could show four-fold or greater expression. observed). Of the 18 granule secretory proteins associated with COVID-19, we observed that 11 were increased and 7 were decreased in platelets of COVID-19 patients. In addition, 12 out of 15 platelet-activating proteins, including Ser/Thr kinases and tyrosine kinases, were reduced in platelets from COVID-19 patients.However, the interleukin-6 receptor subunit, apolipoprotein E, and Cathepsins An increase in G was observed.

Activation of the integrin αIIbβ3, a receptor that triggers platelet aggregation, and the α-granule marker P-selectin, expressed in secretion of α-granule secretion, was found to be similar in both controls and COVID-19 patients under basal conditions. Reported. However, agonist-induced activation of integrin αIIbβ3 was reported to be impaired in platelets from COVID-19 patients, whereas agonist-stimulated expression of her P-selectin was not altered. It has been. Moreover, under unstimulated conditions, platelets from COVID-19 patients reported a modest increase in phosphatidylserine exposure, which decreased with stimulation. Furthermore, platelet-neutrophil interactions were observed to be increased in COVID-19 patients even under unstimulated conditions. A P-selectin CD62P blocking antibody was observed to reduce understimulated basal platelet-neutrophil interactions, but did not affect stimulated platelet-neutrophil interactions.

Therefore, the current study indicates that there are two distinct platelet populations in COVID-19 patients. The first is proteome-altered circulating platelets and the second is her P-selectin expressing neutrophil-associated platelets. This study also indicates that platelet-driven thromboinflammatory is one of the important factors that may increase the risk of thrombosis in COVID-19 patients. However, further studies need to be performed to understand the mechanism of this effect.

Limitations

This study has certain limitations. First, heparin and dexamethasone may contribute to the platelet phenotype. Second, healthy controls were younger and had lower BMI. Third, healthy controls self-reported to be SARS-CoV-2 negative, which may be biased.

*Important Notices

Bio Rxiv We publish a non-peer-reviewed, preliminary scientific report and should not be taken as conclusive, to guide clinical practice/health-related actions, or to be treated as established information.