Low level of the plasma sphingolipid, glucosylceramide, is associated with thrombotic diseases

Multi-platform omics analysis reveals molecular signature for COVID-19 pathogenesis, prognosis and drug target discovery

Disease progression prediction and therapeutic drug target discovery for Coronavirus disease 2019 (COVID-19) are particularly important, as there is still no effective strategy for severe COVID-19 patient treatment. Herein, we performed multi-platform omics analysis of serial plasma and urine samples collected from patients during the course of COVID-19. Integrative analyses of these omics data revealed several potential therapeutic targets, such as ANXA1 and CLEC3B. Molecular changes in plasma indicated dysregulation of macrophage and suppression of T cell functions in severe patients compared to those in non-severe patients. Further, we chose 25 important molecular signatures as potential biomarkers for the prediction of disease severity. The prediction power was validated using corresponding urine samples and plasma samples from new COVID-19 patient cohort, with AUC reached to 0.904 and 0.988, respectively. In conclusion, our omics data proposed not only potential therapeutic targets, but also biomarkers for understanding the pathogenesis of severe COVID-19.

Novel exomic rare variants associated with venous thrombosis

Exomic rare variant polymorphisms (c. 300 000) were analysed in the Scripps Venous Thrombosis (VTE) registry (subjects aged <55 years). Besides coagulation factor V (F5) single nucleotide polymorphisms (SNPs), family with sequence similarity 134, member B (FAM134B; rs78314670, Arg127Cys) and myosin heavy chain 8 (MYH8; rs111567318, Glu1838Ala) SNPs were associated with recurrent VTE (n = 34 cases) (false discovery rate-adjusted P < 0·05). FAM134B (rs78314670) was associated with low plasma levels of anticoagulant glucosylceramide. Analysis of 50 chr17p13.1 MYH rare SNPs (clustered skeletal myosin heavy chain genes) using collapsing methods was associated with recurrent VTE (P = 2·70 ×10^-16 ). When intravenously injected, skeletal muscle myosin was pro-coagulant in a haemophilia mouse tail bleeding model. Thus, FAM134B and MYH genetic variants are plausibly linked to VTE risk.

Plasma skeletal muscle myosin phenotypes identified by immunoblotting are associated with pulmonary embolism occurrence in young adults

BACKGROUND

Purified skeletal muscle myosin (SkM) binds factor Xa and is procoagulant. The molecular forms of SkM in human plasma have not been characterized.

METHOD

Human plasma SkM heavy chain (HC) isoforms of different molecular weights were detected by a newly developed immunoblotting protocol. In this pilot study, the distribution of SkM HC antigen isoforms in plasmas of healthy subjects and young adult patients with venous thrombosis was analyzed.

RESULTS

Multiple SkM HC antigen bands were detected in human plasmas, corresponding to full-length SkM HC, heavy meromyosin, or the S1 fragment. Plasma immunoblots of healthy subjects displayed three major phenotypes: Type I with two primary bands for full-length SkM and heavy meromyosin, and two lesser bands including S1 fragment (54%); Type II with bands primarily for full-length SkM HC (34%); and Type III with only a band for the S1 fragment (12%). Plasma SkM HC antigen Type II phenotype was associated with an increased occurrence of isolated pulmonary embolism in younger patients, respectively (≤50 years old).

CONCLUSIONS

Three SkM HC antigen phenotypes were identified in human plasma by immunoblotting, and Type II phenotype was correlated with the occurrence of isolated pulmonary embolisms in younger patients.

Serum amyloid A4 is a procoagulant apolipoprotein that it is elevated in venous thrombosis patients

BACKGROUND

Serum amyloid A4 (SAA4) is an apolipoprotein that is in the SAA family and it is constitutively translated. Previously, acute-phase SAA1 and SAA2 levels were associated with venous thromboembolism (VTE).

OBJECTIVE

We investigated the association of plasma SAA4 with VTE and the role of SAA4 in coagulation.

PATIENTS AND METHODS

The association of SAA4 with VTE in a case-control study of adult VTE subjects (N = 113 each group) and the effects of recombinant SAA4 on plasma blood coagulation assays and prothrombin activation initiated by factor Xa were evaluated.

RESULTS

Plasma SAA4 levels in VTE subjects were higher vs. controls (48.1 vs. 38.4 µg/mL; P < .001). Elevated plasma SAA4 level (above the 90th percentile of controls) was associated with increased VTE occurrence (odds ratio, 3.8; 95% confidence interval, 1.8-8.0). This association remained significant after the adjustment for acute-phase SAA level, suggesting that SAA4 associated with VTE is independent of acute-phase SAA. Two isoforms of SAA4, that is, glycosylated and nonglycosylated SAA4 isoforms, were each higher in VTE patients. When recombinant SAA4 was added to plasma, it shortened factor Xa-1-stage clotting times, showing that it enhances clotting in plasma. In reaction mixtures containing purified factors Xa and Va and prothrombin, recombinant SAA4 increased prothrombin activation, showing that it enhances prothrombinase activity.

CONCLUSION

Elevated plasma constitutive SAA4 levels were linked to VTE in adults, and SAA4 can enhance thrombin generation in plasma. Our data highlight a previously unknown procoagulant activity of SAA4 that appears to be related to risk of venous thrombotic events.

Role of Glucosylceramide in Lung Endothelial Cell Fate and Emphysema

Rationale: The loss of pulmonary endothelial cells in emphysema is associated with increased lung ceramide. Ceramide perturbations may cause adaptive alterations in other bioactive sphingolipids, with pathogenic implications. We previously reported a negative correlation between emphysema and circulating glycosphingolipids (GSLs). Glucosylceramide (GlcCer), the initial GSL synthesized from ceramide by GCS (GlcCer synthase), is required for embryonic survival, but its role in the lung is unknown.Objectives: To determine if cigarette smoke (CS) alters lung GlcCer and to elucidate the role of GCS in lung endothelial cell fate.Methods: GlcCer was measured by tandem mass spectrometry in BAL fluid of CS- or elastase-exposed mice, and GCS was detected by Western blotting in chronic obstructive pulmonary disease lungs and CS extract-exposed primary human lung microvascular endothelial cells (HLMVECs). The role of GlcCer and GCS on mTOR (mammalian target of rapamycin) signaling, autophagy, lysosomal function, and cell death were studied in HLMVECs with or without CS exposure.Measurements and Main Results: Mice exposed to chronic CS or to elastase, and patients with chronic obstructive pulmonary disease, exhibited significantly decreased lung GlcCer and GCS. In mice, lung GlcCer levels were negatively correlated with airspace size. GCS inhibition in HLMVEC increased lysosomal pH, suppressed mTOR signaling, and triggered autophagy with impaired lysosomal degradation and apoptosis, recapitulating CS effects. In turn, increasing GlcCer by GCS overexpression in HLMVEC improved autophagic flux and attenuated CS-induced apoptosis.Conclusions: Decreased GSL production in response to CS may be involved in emphysema pathogenesis, associated with autophagy with impaired lysosomal degradation and lung endothelial cell apoptosis.

Minor Plasma Lipids Modulate Clotting Factor Activities and May Affect Thrombosis Risk

Essentials

Circulating blood contains hundreds of lipids, many of which might influence blood coagulation.

Recent discoveries about circulating lipids that can affect blood coagulation are reviewed.

Minor abundance plasma lipids can modulate thrombin generation via direct effects on factor Xa.

Variations in minor abundance plasma lipids can influence thrombin generation and thrombosis risk.

Abstract

Different minor abundance plasma lipids significantly influence thrombin generation in vitro and significant differences in such lipids are linked to risk for venous thrombosis. Some plasma sphingolipids including glucosylceramide, lyso‐sulfatide and sphingosine have anticoagulant properties whereas, conversely, some plasma phospholipid derivatives, including certain lyso‐phospholipids and ethanolamides, have procoagulant properties. Plasma metabolite profiling of venous thrombosis patients showed association of venous thrombosis with decreased plasma long‐chain acylcarntines, leading to discovery of their anticoagulant activity as inhibitors of factor Xa. Inhibition of factor Xa by acylcarnitines does not require the protein's Gla‐domain, emphasizing an expanded framework for the paradigm for lipid‐clotting factor interactions. Overall, whether by genetics or environment, alterations in the dynamics of lipid metabolism linked to an altered lipidome may contribute to regulation of blood coagulation because imbalances between physiologic procoagulant and anticoagulant lipids may contribute to excessive thrombin generation that augments risk for thrombosis.