High Levels of Soluble Triggering Receptor Expressed on Myeloid Cells-Like Transcript (TLT)-1 Are Associated With Acute Respiratory Distress Syndrome

Platelet-derived sTLT-1 is associated with platelet-mediated inflammation in coronary artery disease patients

The development of coronary artery disease (CAD) depends heavily on platelet activation, and inflammation plays a major role in all stages of atherosclerosis. Platelet-specific soluble triggering receptor expressed on myeloid cells like transcript 1 (sTLT-1) facilitate clot formation and have been linked to chronic inflammation. In this study, we explored the role of platelet-derived sTLT-1 in platelet-mediated inflammation in CAD patients. Plasma levels of sTLT-1 were measured using enzyme-linked immunosorbent assay in CAD patients (n = 163) and healthy controls (n = 99). Correlation analysis was performed to determine the circulatory sTLT-1 levels with platelet activation markers, immune cells, and inflammatory cytokines/chemokines. Increased plasma sTLT-1 levels were observed in CAD patients compared with those in healthy controls (p < 0.0001). A positive correlation was observed between sTLT-1 and platelet activation markers (P-selectin, PAC-1), CD14++ CD16- cells (classical monocytes), Natural killer T (NKT) cells, and platelet-immune cell aggregates with monocytes, neutrophils, dendritic cells, CD11c+ cells, and NKT cells. In contrast, a significant negative correlation was observed with CD8 cells. Furthermore, a significant positive correlation was observed between sTLT-1 and inflammatory markers (TNF-α, IL-1β, IL-2, IL-6, IL-12p70, IL-18, CXCL-12, and CCL-11). Logistic regression analysis identified sTLT-1 and triglycerides as predictors of CAD. Receiver operating characteristic curve (ROC) analysis showed that sTLT-1 had a higher sensitivity and specificity for predicting CAD. Our findings suggest that platelet activation induces the release of sTLT-1 into the circulation in CAD patients, which aggregates with immune cells and enhances inflammatory responses.

Novel Aspects Targeting Platelets in Atherosclerotic Cardiovascular Disease—A Translational Perspective

Platelets are important cellular targets in cardiovascular disease. Based on insights from basic science, translational approaches and clinical studies, a distinguished anti-platelet drug treatment regimen for cardiovascular patients could be established. Furthermore, platelets are increasingly considered as cells mediating effects “beyond thrombosis”, including vascular inflammation, tissue remodeling and healing of vascular and tissue lesions. This review has its focus on the functions and interactions of platelets with potential translational and clinical relevance. The role of platelets for the development of atherosclerosis and therapeutic modalities for primary and secondary prevention of atherosclerotic disease are addressed. Furthermore, novel therapeutic options for inhibiting platelet function and the use of platelets in regenerative medicine are considered.

Values of PCT and STREM-1 combined with clinical pulmonary infection score for the prognostic evaluation of elderly patients with ventilator-associated pneumonia

Objective: To explore the values of PCT and STREM-1 combined with clinical pulmonary infection score (CPIS) for evaluating ventilator-associated pneumonia (VAP) in elderly patients.

Methods: A total of 120 eligible patients were selected as VAP group, and 60 other patients without VAP were selected as control group. According to APACHE II scores, VAP group was divided into low-, medium-, and high-risk groups. The correlations of PCT, STREM-1, and CPIS with APACHE II score were analyzed. The values of PCT and STREM-1 combined with CPIS for evaluating prognosis were analyzed using ROC curves.

Results: In the VAP group, serum PCT and STREM-1 levels and CPIS after mechanical ventilation significantly exceeded those of the control group and before mechanical ventilation (P<0.05). These values were higher in the high-risk group than in medium- and low-risk groups (P<0.05). They were positively correlated with APACHE II score (P<0.001). These values of the death group were significantly higher than those of the survival group 1, 3, 5, and 7 d after treatment (P<0.05). AUC of PCT and STREM-1 combined with CPIS for assessing prognosis was 0.892 (P<0.001).

Conclusions: Serum PCT and STREM-1 levels and CPIS significantly increase in elderly patients with VAP, which rise with aggravation. Their combination has higher values for prognostic evaluation.

Release of α-granule contents during platelet activation

Upon activation, platelets release a plethora of factors which help to mediate their dynamic functions in hemostasis, inflammation, wound healing, tumor metastasis and angiogenesis. The majority of these bioactive molecules are released from α-granules, which are unique to platelets, and contain an incredibly diverse repertoire of cargo including; integral membrane proteins, pro-coagulant molecules, chemokines, mitogenic, growth and angiogenic factors, adhesion proteins, and microbicidal proteins. Clinically, activation of circulating platelets has increasingly been associated with various disease states. Biomarkers indicating the level of platelet activation in patients can therefore be useful tools to evaluate risk factors to predict future complications and determine treatment strategies or evaluate antiplatelet therapy. The irreversible nature of α-granule secretion makes it ideally suited as a marker of platelet activation. This review outlines the release and contents of platelet α-granules, as well as the membrane bound, and soluble α-granule cargo proteins that can be used as biomarkers of platelet activation.

P-selectin (CD62P) and soluble TREM-like transcript-1 (sTLT-1) are associated with coronary artery disease: a case control study

BACKGROUND

Platelet activation plays a crucial role in the pathogenesis of coronary artery disease (CAD). Platelet P-selectin (CD62P) is a classic platelet activation indicator on the platelet surface, and soluble TREM-like transcript-1 (sTLT-1) is a new indicator. However, the relationship between these two markers and CAD, especially in acute coronary syndrome (ACS), has not been elucidated. This study aimed to investigate CD62P expression on the platelet surface and sTLT-1 expression in serum, as well as to assess their relationship with CAD.

METHODS

We measured the levels of CD62P and sTLT-1 in 83 patients with CAD compared to 49 controls. The association of these indicators with age, blood pressure, lipid profile, body mass index, and liver injury marker level were also examined.

RESULTS

CD62P concentration was higher in CAD patients than in the control group (P < 0.01), especially in acute myocardial infarction (AMI) patients (P < 0.01). Serum sTLT-1 concentration was higher in the AMI and unstable angina pectoris (UAP) groups than in the normal control (NC) group (P < 0.01).

CONCLUSIONS

The consistency of sTLT-1 and CD62P expression levels in CAD patients indicates that sTLT-1 level, the same as CD62P, may be a new marker of platelet activation that is positively related to CAD.

Platelet biology of the rapidly failing lung

Acute respiratory distress syndrome (ARDS) is characterized by a rapid-onset respiratory failure with a mortality rate of approximately 40%. This physiologic inflammatory process is mediated by disruption of the alveolar-vascular interface, leading to pulmonary oedema and impaired oxygen exchange, which often warrants mechanical ventilation to increase survival in the acute setting. One of the least understood aspects of ARDS is the role of the platelets in this process. Platelets, which protect vascular integrity, play a pivotal role in the progression and resolution of ARDS. The recent substantiation of the age-old theory that megakaryocytes are found in the lungs has rejuvenated interest in and raised new questions about the importance of platelets for pulmonary function. In addition to primary haemostasis, platelets provide a myriad of inflammatory functions that are poised to aid the innate immune system. This review focuses on the evidence for regulatory roles of platelets in pulmonary inflammation, with an emphasis on two receptors, CLEC-2 and TLT-1. Studies of these receptors identify novel pathways through which platelets may regulate vascular integrity and inflammation in the lungs, thereby influencing the development of ARDS.

Platelet-derived TLT-1 is a prognostic indicator in ALI/ARDS and prevents tissue damage in the lungs in a mouse model

Acute lung injury (ALI) and acute respiratory distress syndrome (ARDS) affect >200 000 individuals yearly with a 40% mortality rate. Although platelets are implicated in the progression of ALI/ARDS, their exact role remains undefined. Triggering receptor expressed in myeloid cells (TREM)-like transcript 1 (TLT-1) is found on platelets, binds fibrinogen, and mediates clot formation. We hypothesized that platelets use TLT-1 to manage the progression of ALI/ARDS. Here we retrospectively measure plasma levels of soluble TLT-1 (sTLT-1) from the ARDS Network clinical trial and show that patients whose sTLT-1 levels were >1200 pg/mL had nearly twice the mortality risk as those with <1200 pg/mL (P < .001). After correcting for confounding factors such as creatinine levels, Acute Physiology And Chronic Health Evaluation III scores, age, platelet counts, and ventilation volume, sTLT-1 remains significant, suggesting that sTLT-1 is an independent prognostic factor (P < .0001). These data point to a role for TLT-1 during the progression of ALI/ARDS. We use a murine lipopolysaccharide-induced ALI model and demonstrate increased alveolar bleeding, aberrant neutrophil transmigration and accumulation associated with decreased fibrinogen deposition, and increased pulmonary tissue damage in the absence of TLT-1. The loss of TLT-1 resulted in an increased proportion of platelet-neutrophil conjugates (43.73 ± 24.75% vs 8.92 ± 2.4% in wild-type mice), which correlated with increased neutrophil death. Infusion of sTLT-1 restores normal fibrinogen deposition and reduces pulmonary hemorrhage by 40% (P ≤ .001) and tissue damage by 25% (P ≤ .001) in vivo. Our findings suggest that TLT-1 uses fibrinogen to govern the transition between inflammation and hemostasis and facilitate controlled leukocyte transmigration during the progression of ARDS.