Thrombin generation increasing with age and decreasing with use of heparin indicated by calibrated automated thrombogram conducted in Chinese.

OBJECTIVE: Calibrated Automated Thrombogram(CAT) is a test to monitor the generation of thrombin. It can be described by four parameters: lag time, peak thrombin, endogenous thrombin potential (ETP) and time to peak (ttPeak). This study aims to determine the normal ranges of CAT parameters in Chinese, and evaluate whether thrombin generation is correlated with the concentration of heparin/low molecular weight heparin. METHODS: Plasma from 120 healthy subjects were collected to determine the normal rangea of CAT parameters in Chinese. Normal plasma pool (NPP, n=25) spiked with different concentrations of heparin or enoxaparin were used to detecte CAT parameters. The overall and age specific normal ranges of CAT parameters were calculated using descriptive statistics method with mean±2SD. The correlation between CAT parameters and age or concentrations of heparin, enoxaparin were analyzed with linear regression model. RESULTS: The normal ranges for lag time, peak thrombin, ETP, ttPeak in the subjects were 3.648±2.465 min, 367.39±151.93 nmol/L, 2277±1030 nmol/L•min and 6.372±4.280 min respectively. Age was linearly correlated with lag time (r=-0.6583, P<0.0001), peak thrombin (r=0.4863, P<0.0001), ETP (r=0.3608, P<0.0014) and ttPeak (r=-0.6313, P<0.0001). The values of ETP/peak ratio were linearly correlated with concentrations of heparin. CONCLUSION: The normal ranges of four CAT parameters for Chinese were determined. CAT parameters are associated with age. ETP/peak ratio could be used to monitor the process of anticoagulation therapy.

Association between CYP2C19 and ABCB1 polymorphisms and clopidogrel resistance in clopidogrel-treated Chinese patients.

OBJECTIVE: To investigate the association between CYP2C19 and ABCB1 polymorphisms and clopidogrel resistance (CR) in patients with cardiovascular disease in Beijing district. METHODS: In total, 325 patients were enrolled in the study, including 101 experimental group patients and 224 control group patients. The experimental group was divided into CR group (n=30) and non-CR group (n=71) according to the adenosine diphosphate (ADP)-induced platelet inhibition rate in thromboelastography (TEG) (ADP-induced platelet inhibition rate of <30% was defined as CR and rate of 30%-100% was defined as non-CR). Genotypes, including CYP2C19*2, CYP2C19*3, CYP2C19*4, CYP2C19*5, CYP2C19*17, and ABCB1, were determined using time-of-flight mass spectrometry (Clin-TOF) and Sanger sequencing in all patients. RESULTS: In the experimental group, carriers of CYP2C19 heterozygous (*1/*2, n=46; *1/*3, n=7), and mutation homozygous (*2/*2, n=7; *2/*3, n=3; *3/*3, n=0) genotypes showed significantly lower ADP-induced platelet inhibition rates than noncarriers (*1/*1, n=38; p=0.035 and 0.001, respectively); the carriage of mutant CYP2C19*2 or *3 allele was significantly associated with an increased risk of CR. In contrast, carriers of ABCB1 heterozygous (TC, n=50) showed significantly lower ADP-induced platelet inhibition rates than noncarriers (CC, n=39, p=0.097), and there was no significant correlation between ABCB1 genotypes and higher CR risk. CONCLUSION: The carriage of CYP2C19*2 or *3 mutant allele was significantly associated with attenuated platelet response to clopidogrel and increased CR risk. The carriage of ABCB1 mutant allele was not significantly associated with CR risk.

Increased prostacyclin levels inhibit the aggregation and activation of platelets via the PI3K-AKT pathway in prolonged isolated thrombocytopenia after allogeneic hematopoietic stem cell transplantation.

OBJECTIVES: The aim of this study was to investigate the role of prostacyclin (PGI2) in prolonged isolated thrombocytopenia (PT) following allogeneic hematopoietic stem cell transplantation (allo-HSCT) and the effect of PGI2 on the activation and aggregation of platelets in PT. METHODS: We enrolled 37 patients with PT and 36 controls following allo-HSCT in this study. Platelet aggregation and activation and PGI2 levels were measured. Endothelial progenitor cells (EPCs) from either PT or control patients were cultured ex vivo with serum from either PT or control patients. PGI2 secretions were then measured. PGI2 was added to the platelets ex vivo, and platelet aggregation and activation and PI3K/Akt phosphorylation were analyzed. RESULTS: A higher PGI2 level was observed in the PT patients. The activation and aggregation of platelets were significantly lower in the PT patients. EPCs from PT patients cultured in PT serum secreted higher levels of PGI2, and PGI2 inhibited platelet activation and aggregation in a concentration-dependent manner ex vivo. PI3K/Akt phosphorylation of platelets was regulated by PGI2 after allo-HSCT. Disease status, serum PGI2 level and platelet aggregation were independent risk factors in patients with PT after allo-HSCT. CONCLUSIONS: Higher PGI2 levels and lower platelet activation and aggregation occurred simultaneously in PT patients. PGI2 inhibited platelet activation and aggregation, probably by regulating the phosphorylation of PI3K/Akt.