The prothrombotic potential of platelet factor 4

Thyroid State Regulates Gene Expression in Human Whole Blood

CONTEXT

Despite the well-recognized clinical features resulting from insufficient or excessive thyroid hormone (TH) levels in humans, it is largely unknown which genes are regulated by TH in human tissues.

OBJECTIVE

To study the effect of TH on human gene expression profiles in whole blood, mainly consisting of T3 receptor (TR) α-expressing cells.

METHODS

We performed next-generation RNA sequencing on whole blood samples from eight athyroid patients (four females) on and after 4 weeks off levothyroxine replacement. Gene expression changes were analyzed through paired differential expression analysis and confirmed in a validation cohort. Weighted gene coexpression network analysis (WGCNA) was applied to identify thyroid state-related networks.

RESULTS

We detected 486 differentially expressed genes (fold-change >1.5; multiple testing corrected P value < 0.05), of which 76% were positively and 24% were negatively regulated. Gene ontology (GO) enrichment analysis revealed that three biological processes were significantly overrepresented, of which the process translational elongation showed the highest fold enrichment (7.3-fold, P = 1.8 × 10-6). WGCNA analysis independently identified various gene clusters that correlated with thyroid state. Further GO analysis suggested that thyroid state affects platelet function.

CONCLUSIONS

Changes in thyroid state regulate numerous genes in human whole blood, predominantly TRα-expressing leukocytes. In addition, TH may regulate gene transcripts in platelets.

Low levels of circulating platelet factor 4 (PF4, CXCL4) in subclinically hypothyroid autoimmune thyroiditis

PURPOSE

Chemokines play an important role in the pathogenesis of autoimmune thyroid diseases. Platelet factor 4 (PF4, CXCL4) released from activated platelets is a chemokine. However, its clinical importance in autoimmune thyroiditis remains unknown. This study is intended to determine circulating levels of PF4 levels in patients with autoimmune thyroiditis (AIT).

METHODS

Circulating levels of PF4 were measured in 34 consecutive patients with newly diagnosed AIT and 18 euthyroid controls. Among AIT group, 16 patients were euthyroid and 18 had subclinic hypothyroidism. Controls and individuals with AIT were similar in terms of age.

RESULTS

Serum levels of PF4 were comparable in patients with AIT and in controls. Among patients with AIT, PF4 was significantly lower in those with subclinical hypothyroidism than in euthyroid individuals (p = 0.001). In correlation analysis, PF4 was negatively correlated with TSH (r = -0.663, p = 0.000) and positively correlated with free T4 (r = 0.428, p = 0.012). There was not any significant correlation between PF4 and AbTPO, AbTg.

CONCLUSION

The present study demonstrated for the first time that circulating PF4 levels are decreased in subclinically hypothyroid AIT. This result draws attention to the circulating PF4 levels in subclinically hypothyroid AIT and may shed light on further researches at this topic.

Multifaceted prospects of nanocomposites for cardiovascular grafts and stents

Cardiovascular disease is the leading cause of death across the globe. The use of synthetic materials is indispensable in the treatment of cardiovascular disease. Major drawbacks related to the use of biomaterials are their mechanical properties and biocompatibility, and these have to be circumvented before promoting the material to the market or clinical setting. Revolutionary advancements in nanotechnology have introduced a novel class of materials called nanocomposites which have superior properties for biomedical applications. Recently, there has been a widespread recognition of the nanocomposites utilizing polyhedral oligomeric silsesquioxane, bacterial cellulose, silk fibroin, iron oxide magnetic nanoparticles, and carbon nanotubes in cardiovascular grafts and stents. The unique characteristics of these nanocomposites have led to the development of a wide range of nanostructured copolymers with appreciably enhanced properties, such as improved mechanical, chemical, and physical characteristics suitable for cardiovascular implants. The incorporation of advanced nanocomposite materials in cardiovascular grafts and stents improves hemocompatibility, enhances antithrombogenicity, improves mechanical and surface properties, and decreases the microbial response to the cardiovascular implants. A thorough attempt is made to summarize the various applications of nanocomposites for cardiovascular graft and stent applications. This review will highlight the recent advances in nanocomposites and also address the need of future research in promoting nanocomposites as plausible candidates in a campaign against cardiovascular disease.

Platelet factor 4 protects bone marrow mesenchymal stem cells from acute radiation injury

OBJECTIVE

The aim of this study was to find a new radiation protector, platelet factor 4 (PF4) and to identify its effect on haemopoietic microenvironment in vitro and in vivo.

METHODS

Radiation damage on bone marrow mesenchymal stem cells ex and in vitro was set up as models. Growth curve analysis, clonogenic survival assay, FACSCalibur™ (BD Immunocytometry Systems, San Jose, CA), 5-ethynyl-2'-deoxyuridine immunofluorescence staining and quantitative reverse transcription-polymerase chain reaction were employed to assess the characterization of bone marrow mesenchymal stem cells (BMSCs), proliferation, apoptosis, cell cycle and gene expression.

RESULTS

A dose- and time-dependent enhancement of cell viability and survival was observed for PF4 treatment along with 500 cGy γ-radiation in vitro. The same phenomena were noted in vivo, including enhancement of adherence and proliferation ability while inhibition of cell apoptosis, which were associated with a short-term decrease in the G0/G1 ratio owing to S phase arrest. These were accompanied with enhanced Bcl-2 expression and p53/p21 loss.

CONCLUSION

These results uncover that PF4 might be a novel therapeutic approach, which could reduce DNA damage and increase survival of BMSCs, in part, by inhibiting p53/p21 axis and facilitating DNA damage repair.

ADVANCES IN KNOWLEDGE

This study explores the feasibility of a new radioprotector and hence may be clinically important.

Argatroban in heparin-induced thrombocytopenia: rationale for use and place in therapy

Heparin-induced thrombocytopenia (HIT) is a recognized complication of heparin and requires urgent detection and treatment. HIT can be divided into two types, type I and type II, with type I being a transient decrease in platelet count without clinical consequence. For the purpose of this review, the term HIT refers to the immune-mediated type II that causes paradoxical thrombo-emboli. The aim of this review is to familiarize clinicians with a specific direct thrombin inhibitor, argatroban, in the treatment of HIT. Argatroban has been successfully employed in treating HIT in many different subsets of patients, including those with endstage renal disease on hemodialysis and in patients undergoing percutaneous coronary intervention and those with multiorgan dysfunction syndrome.

Effects of ulinastatin on coagulation in high-risk patients undergoing off-pump coronary artery bypass graft surgery

BACKGROUND

Both systemic inflammatory reaction and regional myocardial ischemia/reperfusion injury may elicit hypercoagulability after off-pump coronary artery bypass grafting (OPCAB). We investigated the influence of ulinastatin, which suppresses the activity of polymorphonuclear leukocyte elastase and production of pro-inflammatory cytokines, on coagulation in patients with elevated high-sensitivity C-reactive protein (hsCRP) undergoing OPCAB.

METHODS

Fifty patients whose preoperative hsCRP > 3.0 mg/L were randomly allocated into the ulinastatin (600,000 U) or control group. Serum concentrations of thrombin-antithrombin complex (TAT) and prothrombin fragment 1+2 (F1+2) were measured preoperatively, immediately after surgery, and at 24 h after surgery, respectively. Secondary endpoints included platelet factor (PF)-4, amount of blood loss, and transfusion requirement.

RESULTS

All baseline values of TAT, F1+2, and PF-4 were higher than the normal range in both groups. F1+2 was elevated in both groups at immediate, and at 24 h after surgery as compared to baseline value, without any significant intergroup differences. Remaining coagulation parameters, transfusion requirement and blood loss during operation and postoperative 24 h were not different between the two groups.

CONCLUSIONS

Intraoperative administration of ulinastatin did not convey beneficial influence in terms of coagulation and blood loss in high-risk patients with elevated hsCRP undergoing multivessel OPCAB, who already exhibited hypercoagulability before surgery.

A silver nanocomposite biomaterial for blood-contacting implants

Cardiovascular implants must resist infection and thrombosis. A nanocomposite polymeric material [polyhedral-oligomeric-silsesquioxane-poly(carbonate-urea)urethane; POSS-PCU] demonstrates ideal properties for cardiovascular applications. Silver nanoparticles or nanosilver (NS) are recognized for efficient antibacterial properties. This study aims to determine the influence of NS integrated POSS-PCU on thrombogenicity. Silver nitrate was reduced with dimethylformamide and stabilized by the inclusion of fumed silica nanoparticles to prevent aggregation of NS and were incorporated into POSS-PCU to form a range of POSS-PCU-NS concentrations (by weight); 0.20% (NS16), 0.40% (NS32), 0.75% (NS64), and 1.50% (NS128). Surface wettability was determined with sessile-drop water contact angles. Platelets were introduced onto test samples and Alamar Blue (AB), mitochondrial-activity assay, quantified the degree of platelet adhesion whilst platelet-factor-4 (PF4) ELISA quantified the degree of platelet activation. Thromboelastography (TEG) determined the profiles of whole blood kinetics while hemolysis assay demonstrated the degree of blood compatibility. Increasing levels of NS induced greater hydrophilicity. A concentration dependant decrease in platelet adhesion and activation was observed with AB and PF4 readings, respectively. TEG demonstrated that the antithrombogenic properties of POSS-PCU were retained with POSS-PCU-NS16, and enhanced with POSS-PCU-NS32, but was reduced with POSS-PCU-NS64 and POSS-PCU-NS128. POSS-PCU-NS64 and POSS-PCU-NS128 demonstrated a hemolytic tendency, but no hemolysis was observed with POSS-PCU-NS16 and POSS-PCU-NS32. Overall, POSS-PCU-NS32 rendered potent antithrombogenic properties.

Platelet activity and cardiovascular risk in apparently healthy individuals: a review of the data

Cardiovascular disease is a major cause of morbidity and mortality. Numerous risk scores exist to identify healthy individuals at increased risk of developing cardiovascular disease. Although platelets are a key mediator in the pathogenesis of cardiovascular disease, the role of platelet activity measurements and the incidence of cardiovascular disease are uncertain. Platelet aggregometry-the most well studied method of platelet function testing-is associated with risk factors for cardiovascular disease. However, data supporting platelet aggregation and incident cardiovascular disease is conflicting. Plasma markers of platelet activation are promising candidates. Soluble CD40L and P-selectin are easily measured with a standardized ELISA, and there is some data to suggest an association with cardiovascular disease, but further studies are required. While mean platelet volume is a promising candidate, platelet count and bleeding time are not specific for platelet activity nor are they associated with cardiovascular disease in a healthy population. For this field to progress, we recommend large-scale, prospective studies that measure a battery of these platelet function tests in individuals without cardiovascular disease to better understand the associations, if any, between platelet activity and cardiovascular disease.

Performance characteristics of two commercially available IgG-specific immunoassays in the assessment of heparin-induced thrombocytopenia (HIT)

BACKGROUND

The in vitro demonstration of antibodies against platelet factor-4/heparin (PF4/hep) complexes is an important contribution to the diagnosis of heparin-induced thrombocytopenia (HIT). The use of PF4/hep IgG-specific immunoassays enhances the specificity of HIT-investigations without any impairment of the sensitivity. Several IgG-specific immunoassays with different origin and structure of the target antigen-complex are commercially available.

METHODS

Using a retrospective cohort consisting of 459 patients suspected to have HIT, we compared the performance characteristics of two commercially available IgG-specific immunoassays, GTI- (Genetic Testing Institute) and HIA-IgG-ELISA (Hyphen Biomed Research).

RESULTS

PF4/hep antibodies were detected in 85 and 81 sera using GTI- and HIA-IgG-ELISA, respectively. OD values and clinical likelihood of patients who tested positive in one assay only were significantly lower than in those who tested positive in both immunoassays. Both IgG-specific assays showed high negative predictive values (100%) and similar but unsatisfactory positive predictive values, determined by a minimum clinical score of 5 and a positive HIPA result (41% and 43%, respectively). The implementation of a confirmatory step using excessive heparin increased the PPV of both assays, but results in a reduction of NPV in HIA-IgG-ELISA.

CONCLUSIONS

The detection of IgG antibodies alone improves the clinical usefulness of immunoassays. However, functional assays remain indispensable to avoid the overdiagnosis of HIT caused by the detection of IgG non-platelet activating antibodies. The OD value in IgG immunoassays appears to correlate with the clinical relevance of the antibodies and might be used as a predictive parameter in the assessment of HIT.