Soluble thrombomodulin is associated with viral hepatitis, blood pressure, and medications in haemodialysis patients

Circulating Thrombomodulin: Release Mechanisms, Measurements, and Levels in Diseases and Medical Procedures

Thrombomodulin (TM) is a type-I transmembrane protein that is mainly expressed on endothelial cells and plays important roles in many biological processes. Circulating TM of different forms are also present in biofluids, such as blood and urine. Soluble TM (sTM), comprised of several domains of TM, is the major circulating TM which is generated by either enzymatic or chemical cleavage of the intact protein under different conditions. Under normal conditions, sTM is present in low concentrations (<10 ng/mL) in the blood but is elevated in several pathological conditions associated with endothelial dysfunction such as cardiovascular, inflammatory, infection, and metabolic diseases. Therefore, sTM level has been examined for monitoring disease development, such as disseminated intravascular coagulation (DIC), sepsis and multiple organ dysfunction syndrome in patients with novel coronavirus disease 2019 (COVID-19) recently. In addition, microvesicles (MVs) that contain membrane TM (MV-TM) have been found to be released from activated cells which also contribute to levels of circulating TM in certain diseases. Several release mechanisms of sTM and MV-TM have been reported, including enzymatic, chemical, and TM mutation mechanisms. Measurements of sTM and MV-TM have been developed and explored as biomarkers in many diseases. In this review, we summarize all these advances in three categories as follows: (1) release mechanisms of circulating TM, (2) methods for measuring circulating TM in biological samples, and (3) correlation of circulating TM with diseases. Altogether, it provides a whole picture of recent advances on circulating TM in health and disease.

Counting the cost: markers of endothelial damage in hematopoietic stem cell transplantation

During hematopoietic stem cell transplantation (HSCT), endothelial damage is the pathological hallmark of veno-occlusive disease of the liver, thrombotic microangiopathy, capillary leak syndrome and graft-versus-host disease. Events prior to conditioning, the conditioning regimen itself as well as calcineurin inhibitors may all induce endothelial damage. Unfortunately, the relative importance of these factors and their interactions, the time frame of endothelial damage and individual susceptibility remain unknown. Moreover, it is conceivable that conditioning regimens differ markedly in their propensity to initiate endothelial damage. Monitoring endothelial damage and response to treatment is hampered by the current lack of suitable markers. In this regard, an ideal marker should be sensitive and specific and indicate the development of an endothelial disorder prior to the onset of symptoms and organ dysfunction. Soluble markers, such as thrombomodulin, are easily amenable with immunoassays; yet, the interpretation of their levels is hampered by the influence of comorbidity. Evaluation of circulating endothelial cells in HSCT demonstrated a marked and dose-dependent increase in cell numbers after conditioning. The challenge ahead is to establish and evaluate novel markers of endothelial damage to permit early detection of disease, monitor response to treatment and evaluate different conditioning regimens.

Tissue factor and thrombomodulin in hemodialysis patients: associations with endothelial injury, liver disease, and erythropoietin therapy

Patients receiving maintenance hemodialysis (HD) present with hemostatic abnormalities, which may be aggravated by comorbid conditions, especially liver disease. The factors that influence plasma levels of thrombomodulin (TM), an initiator of the anticoagulant protein C pathway, and those of tissue factor (TF), which triggers the extrinsic coagulation pathway, were assessed. In 63 HD patients, TM and TF levels were higher than those in healthy controls. In bivariate analysis, TF positively correlated with TM, and both were directly associated with the presence of viral hepatitis B or C marker, serum liver enzymes, use of erythropoietin therapy, hemoglobin levels, and duration of HD therapy, and inversely correlated with body mass index. TF was also positively associated with plasma von Willebrand factor (vWF) antigen, and inversely associated with activated partial thromboplastin time. In multivariate analysis, increased vWF, alanine aminotransferase, and use of erythropoietin independently predicted both TF and TM levels. HD patients with vWF and ALT levels lower than middle, and not treated with erythropoietin had normal TF but increased TM concentrations compared with levels in healthy controls. Increased plasma levels of TM and TF in patients on maintenance HD are surrogates of vascular endothelial injury. Liver disease and use of erythropoietin treatment are also important determinants of these markers, and should be considered in further studies.

Effect of hemodialysis on plasma levels of vascular endothelial markers

Vascular endothelial cell dysfunction is linked to hemostatic abnormalities and accelerated atherosclerosis in patients receiving maintenance hemodialysis (HD). The relationships between pre-dialysis plasma levels of immunoreactive thrombomodulin, von Willebrand factor, tissue factor and its inhibitor were studied, and the effects of HD procedure on these endothelial markers were observed. All the markers were higher in 39 HD patients than in 15 healthy controls (p<0.0001). HD treatment resulted in a 50% increase in tissue factor pathway inhibitor (p<0.0001), but did not influence the other markers. This increment directly correlated with the post-dialysis decrease in diastolic (p=0.011) and mean arterial blood pressure (p=0.039), and the surface area of the dialysis membrane (p=0.007). There were no associations between the increase in tissue factor pathway inhibitor and the amount of fluid removed, dose of enoxaparin, or other HD-specific factors. In conclusion, HD is responsible for an increase in plasma tissue pathway factor inhibitor level. The release of tissue factor pathway inhibitor during HD is not only due to heparin injection but also to the contact between blood and artificial dialysis membrane, and to HD-activated hemodynamic forces.

Serum hepatocyte growth factor is associated with viral hepatitis, cardiovascular disease, erythropoietin treatment, and type of heparin in haemodialysis patients

BACKGROUND

Increased serum hepatocyte growth factor (HGF) level is a part of the counter-system against tissue damage and predicts mortality in maintenance haemodialysis (HD) patients. We studied which of the common co-morbid and clinical conditions, and surrogates of metabolic disorders or specific organ damage determine HGF levels in these subjects.

METHODS

In 86 patients, pre-dialysis serum HGF, soluble endothelial markers--such as thrombomodulin (TM), von Willebrand factor and plasminogen activator inhibitor-1--and hepatitis B and C markers were measured by ELISAs. Inflammatory reactants such as C-reactive protein (CRP), alpha(1)-antitrypsin, alpha(1) acid-glycoprotein, and immunoglobulin M and G were assayed by nephelometry, and lipoprotein(a) was determined by ELISA. Cardiovascular disease (CVD) was identified on a clinical basis.

RESULTS

Serum HGF was directly associated with the presence of viral hepatitis, alanine aminotransferase and TM levels, time on HD, the presence of CVD, CRP and alpha(1)-antitrypsin levels, use of unfractionated heparin (UFH) (vs enoxaparin) during HD, dose of UFH, use of recombinant erythropoietin (rHuEpo) treatment, and Kt/V. In 36 patients not treated with rHuEpo, HGF directly correlated with haemoglobin, but not with endogenous Epo levels. There was no association between HGF and the other endothelial and inflammatory markers, gender, age, smoking, cause of renal failure, body mass index, normalized protein catabolic rate, dialysate buffers, dialysers, blood pressure, antihypertensive treatment, leukocyte and platelet counts, albumin, fibrinogen, lipoprotein(a), markers of iron and calcium-phosphorus metabolism, or metabolic acidosis. Positive viral hepatitis markers, prevalent CVD and rHuEpo treatment (in descending order of significance) were independent predictors of high HGF level. In another 20 HD patients, a 4-week course of rHuEpo treatment resulted in a significant 17% increase in circulating HGF levels.

CONCLUSION

Serum HGF levels in HD patients are determined by inflammatory conditions such as viral hepatitis and CVD, increase in response to rHuEpo treatment, and may be influenced by type and dose of heparin used during HD procedures.

Effects of recombinant erythropoietin therapy on circulating endothelial markers in hemodialysis patients

Effects of a 4-week course of recombinant human erythropoietin (rHuEpo) therapy on four circulating endothelium-derived cardiovascular risk markers were studied in 20 patients receiving maintenance hemodialysis in relation to surrogates of chronic inflammation, liver function, and arterial blood pressure. Soluble intercellular adhesion molecule-1 (sICAM-1), antigens of plasminogen activator inhibitor-1 (PAI-1:Ag) and von Willebrand factor (vWF:Ag), and soluble thrombomodulin (sTM) were determined by immunoenzymatic assays. C-reactive protein; alpha1 acid-glycoprotein; alpha1-antitrypsin; immunoglobulin M, A, and G; interleukin-6; lipoprotein(a); fibrinogen; total protein; albumin; total cholesterol; hepatitis B and C markers; liver enzymes; prothrombin time; and phosphorus were measured by routine methods. The rHuEpo treatment resulted in a 25% increase in sICAM-1 (Wilcoxon's p = 0.001), a 50% increase in PAI-1:Ag (p = 0.004), a 15% increase in sTM (p = 0.002), and did not change vWF:Ag levels. The increase in sICAM-1 concentration directly correlated with that of PAI-1:Ag (Spearman's rho = 0.483, p = 0.031). The rHuEpo-induced increases in hemoglobin, platelets, and pre-dialysis diastolic blood pressure levels did not correlate with the increments in the endothelial markers studied. In conclusion, short-term rHuEpo therapy activates vascular endothelium in patients receiving maintenance hemodialysis. This specific effect may influence cardiovascular risk.