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

The novel coronavirus disease (COVID-19) is associated with a high incidence of coagulopathy and venous thromboembolism that may contribute to the worsening of the clinical outcome in affected patients. Marked increased D-dimer levels are the most common laboratory finding and have been repeatedly reported in critically ill COVID-19 patients. The infection caused by Severe Acute Respiratory Syndrome Coronavirus-2 (SARS-CoV-2) is followed by a massive release of pro-inflammatory cytokines, which mediate the activation of endothelial cells, platelets, monocytes, and neutrophils in the vasculature. In this context, COVID-19-associated thrombosis is a complex process that seems to engage vascular cells along with soluble plasma factors, including the coagulation cascade, and complement system that contribute to the establishment of the prothrombotic state. In this review, we summarize the main findings concerning the cellular mechanisms proposed for the establishment of COVID-19-associated thrombosis.

Polymorphism of ABO*O alleles and its clinical significance

Background. 62 ABO*O alleles of the ABO system are known. Some ABO*O alleles may be accompanied by the presence of residual A-glycosyltransferase activity in people of group O, which may lead to errors in determining the blood group. This confirms the important clinical significance of the ABO*O allele polymorphism. Knowledge of ABO*O gene polymorphisms and their prevalence contributes to the prevention of errors in determining the blood group of the ABO system.Objective: to study allele variants of the ABO*O gene in Russians.Materials and methods. The blood samples of 14,000 people were examined. The blood group was determined using anti-A, anti-Aweak, anti-B, lectin (anti-A1) and gel cards, as well as by cross-sectional method using standard red blood cells of O, A, and B groups. In one patient, the method of adsorption-elution with cold elution was used to identify a weak variant of antigen A, and the method of thermal elution was used to eliminate antigen- blocking plasma factors. Molecular determination of ABO*O alleles was performed in 130 individuals by polymerase chain reaction with sequence- specific primers and Sanger direct sequencing.Results. 13 allelic variants of the ABO*O gene were identified (10 with a typical deletion of c.261delG / N and 3 nondeletional alleles with polymorphism c.802G>A). Deletion alleles of ABO*O.01 were found in 92.85 % of the examined patients, nondeletion alleles of АВО*О.02 group – in 7.15 % of cases. The ABO*O.01.01 allele was detected with a frequency of 67.14 %, other deletion alleles – much less frequently: ABO*O.01.02 and ABO*O.01.11 – 5.71 %, ABO*O.01.26 – 5.00 %, ABO*O.01.12 – 4.30 %, ABO*O.01.13 and ABO*O.01.44 – 1.43 %, ABO*O.01.05, ABO*O.01.46, ABO*O.01.68 – 0.71 % each. Non-deletional alleles were found with the following frequencies: ABO*O.02.01 – 4.3 %, ABO*O.02.03 allele – 2.14 %, ABO*O.02.02 – 0.71 %. All individuals with the O group with the nondeletional allele had the Oαβ group, except for one patient (with the ABO*O.01.02 O.02.02 genotype), who had the Oβ group.Conclusion. For the first time, the immunogenetic characteristics of Russians are given according to ABO*O genes. Erythrocyte genomics helps to resolve the ambiguity of serological methods results and allows understanding mechanisms of different phenotypes formation. For the correct definition of natural isohemagglutinins and weak antigens variants should be used at least two different serological methods.

Immunometabolic factors in adolescent chronic disease are associated with Th1 skewing of invariant Natural Killer T cells

Invariant Natural Killer T (iNKT) cells respond to the ligation of lipid antigen-CD1d complexes via their T-cell receptor and are implicated in various immunometabolic diseases. We considered that immunometabolic factors might affect iNKT cell function. To this end, we investigated iNKT cell phenotype and function in a cohort of adolescents with chronic disease and immunometabolic abnormalities. We analyzed peripheral blood iNKT cells of adolescents with cystic fibrosis (CF, n = 24), corrected coarctation of the aorta (CoA, n = 25), juvenile idiopathic arthritis (JIA, n = 20), obesity (OB, n = 20), and corrected atrial septal defect (ASD, n = 25) as controls. To study transcriptional differences, we performed RNA sequencing on a subset of obese patients and controls. Finally, we performed standardized co-culture experiments using patient plasma, to investigate the effect of plasma factors on iNKT cell function. We found comparable iNKT cell numbers across patient groups, except for reduced iNKT cell numbers in JIA patients. Upon ex-vivo activation, we observed enhanced IFN-γ/IL-4 cytokine ratios in iNKT cells of obese adolescents versus controls. The Th1-skewed iNKT cell cytokine profile of obese adolescents was not explained by a distinct transcriptional profile of the iNKT cells. Co-culture experiments with patient plasma revealed that across all patient groups, obesity-associated plasma factors including LDL-cholesterol, leptin, and fatty-acid binding protein 4 (FABP4) coincided with higher IFN-γ production, whereas high HDL-cholesterol and insulin sensitivity (QUICKI) coincided with higher IL-4 production. LDL and HDL supplementation in co-culture studies confirmed the effects of lipoproteins on iNKT cell cytokine production. These results suggest that circulating immunometabolic factors such as lipoproteins may be involved in Th1 skewing of the iNKT cell cytokine response in immunometabolic disease.

Hemodialysis exacerbates proteolytic imbalance and pro-fibrotic platelet dysfunction

Multi-organ fibrosis among end stage renal disease (ESRD) patients cannot be explained by uremia alone. Despite mitigation of thrombosis during hemodialysis (HD), subsequent platelet dysfunction and tissue dysregulation are less understood. We comprehensively profiled plasma and platelets from ESRD patients before and after HD to examine HD-modulation of platelets beyond thrombotic activation. Basal plasma levels of proteolytic regulators and fibrotic factors were elevated in ESRD patients compared to healthy controls, with isoform-specific changes during HD. Platelet lysate (PL) RNA transcripts for growth and coagulative factors were elevated post-HD, with upregulation correlated to HD vintage. Platelet secretome correlations to plasma factors reveal acutely induced pro-fibrotic platelet phenotypes in ESRD patients during HD characterized by preferentially enhanced proteolytic enzyme translation and secretion, platelet contribution to inflammatory response, and increasing platelet dysfunction with blood flow rate (BFR) and Vintage. Compensatory mechanisms of increased platelet growth factor synthesis with acute plasma matrix metalloproteinase (MMP) and tissue inhibitor of MMPs (TIMP) increases show short-term mode-switching between dialysis sessions leading to long-term pro-fibrotic bias. Chronic pro-fibrotic adaptation of platelet synthesis were observed through changes in differential secretory kinetics of heterogenous granule subtypes. We conclude that chronic and acute platelet responses to HD contribute to a pro-fibrotic milieu in ESRD.

Platelet adhesion in type 2 diabetes: impact of plasma albumin and mean platelet volume

Background Altered mean platelet volume (MPV) and plasma albumin has been reported in type 2 diabetes (T2D). MPV is suggested to predict cardiovascular risk but there is a lack of evidence for associations between MPV and platelet adhesion. Plasma albumin and magnesium are other factors reported to influence thrombotic risk. The objectives of this study were to assess the association between platelet adhesion and plasma factors with a potential role to affect platelet activation. Methods Blood was collected from 60 T2D patients and 60 healthy controls. Platelet adhesion to different protein surfaces induced by various soluble activators were measured in microplates. MPV, albumin and magnesium were analysed together with additional routine tests. Results Despite normal levels, plasma albumin significantly correlated with adhesion of T2D platelets but not with controls. There was a significant association between MPV and platelet adhesion in both groups, but association was smaller in T2D. Levels of glucose, HbA1c or magnesium did not correlate with platelet adhesion. Conclusions Plasma albumin was associated with platelet adhesion in T2D suggesting that albumin may be a factor to consider upon cardiovascular risk assessment. MPV was more associated with the level of platelet adhesion in healthy individuals than in well-controlled T2D patients.

Publisher Correction: Human blood plasma factors affect the adhesion kinetics of Staphylococcus aureus to central venous catheters

An amendment to this paper has been published and can be accessed via a link at the top of the paper.