Modulation of platelet and leucocyte function by a Chinese herbal formulation as compared with conventional antiplatelet agents.

Platelet and leucocyte activity are important in the acute development of thrombosis and in the pathogenesis of ischaemic vascular disease. Dan Shen Di Wan (DS, Cardiotonic Pill or Dantonic(R) Pill) is one of the most commonly used Chinese herbal formulations for treating patients with atherosclerotic disease in China and several Asian countries. We studied the effect of DS on platelet and leucocyte function and compared the effects with conventional antiplatelet agents, cangrelor (ADP P2Y(12) receptor antagonist) and aspirin (acetyl salicylic acid, ASA). Measurements were made by platelet aggregation (%) and activation (CD62P %), platelet-monocyte conjugate formation (P/M, CD42a median fluorescence, mf), platelet-neutrophil conjugate formation (P/N, mf), and leucocyte activation (CD11b median fluorescence on monocytes and neutrophils, mf) in response to 3.3 micromol/L adenosine diphosphate (ADP), 1.0 micromol/L platelet activating factor (PAF), 5.0 micromol/L adrenaline and 0.5 microg/mL collagen. We also evaluated the effect of its main component, water soluble extract of salvia miltiorrhiza (SME) on intracellular calcium mobilization in platelets triggered by 10 micromol/L ADP, 10 micromol/L PAF, 2 microg/mL collagen and 15 micromol/L thrombin receptor activating peptide (TRAP). Overall DS showed inhibition of platelet aggregation, platelet activation, platelet-leucocyte conjugate formation and leucocyte activation in response to all the agonists apart from adrenaline (all p < 0.01). DS showed inhibition of platelet aggregation and leucocyte activation equivalent to cangrelor 100 nmol/L and ASA 100 micromol/L. SME dose-dependently inhibited intracellular calcium mobilization in platelets following stimulation with all the platelet agonists with maximum effective at 0.36 mg/mL (all p < 0.01). When used at 0.18 mg/mL its inhibitory effect was equivalent to cangrelor and ASA. We conclude that DS is a potential inhibitor of both platelet and leucocyte activation.

Differentiation and migration of Sca1+/CD31- cardiac side population cells in a murine myocardial ischemic model.

BACKGROUND: Side population cells are a rare subset of cells found in the adult heart that are highly enriched for stem and progenitor cell activity. Recent studies have suggested that Sca1+/CD31- cardiac side population cells are capable of differentiation into cardiomyocytes in vitro. However, the response of these cells to myocardial injury remains unknown in vivo. METHODS: Sca1+/CD31- cardiac side population cells were isolated from mouse (C57BL6/J) hearts by FACS. These cells were labeled and delivered via an intramyocardial injection into an infracted mouse heart. The differentiation potential of these cells was determined by immunohistochemistry two weeks later. We further tested the migration potential and the relationship of SDF-1alpha/CXCR4 to these cells. RESULTS: The transplanted cells were found to express cardiomyocyte or endothelial cell specific markers. Furthermore, when these cells were transplanted into non-infarct myocardium after myocardial infarction, they were found in the damaged myocardium. Consistent with their homing property, we found that SDF-1alpha and CXCR4 were up-regulated in the damaged myocardium and on Sca1+/CD31- cardiac side population cells respectively following myocardial infarction. We also show that SDF-1alpha induced migration of Sca1+/CD31- cardiac side population cells in vitro. CONCLUSIONS: Our results have suggested that Sca1+/CD31- cardiac side population cells are able to migrate into damaged myocardium from non-ischemic area of the heart and differentiate into both cardiomyocyte- and endothelial-like cells following acute ischemic injury. The SDF-1alpha/CXCR4 system might play an important role in the migration of these cells.

Two distinct subgroups of tirofiban-induced thrombocytopenia exist due to drug dependent antibodies that cause platelet activation and increased ischaemic events.

Tirofiban-associated thrombocytopenia is due to drug-dependent antibodies (DDAbs) directed against the GPIIb/IIIa complex which can bind after drug-induced conformational changes to the receptor complex. In such cases a higher incidence of myocardial infarction and mortality has been reported raising the possibility of platelet activation. We followed consecutive cases treated with tirofiban to determine the incidence of thrombocytopenia and confirmed that this was due to tirofiban-dependent antibodies. We then tested if these antibodies could cause platelet activation in vitro and correlated this with clinical outcome. In 871 treated patients, severe thrombocytopenia was observed in 11 cases, an incidence of 1.26%. Tirofiban dependent antibodies were confirmed in all cases using a flow cytometric assay. There were two distinct presentations of thrombocytopenia, one occurring acutely, and the second a delayed thrombocytopenia occurring after several days of tirofiban exposure and in keeping with a primary immune response. The effects of DDAbs on platelet activation was analysed by measuring P-selectin (CD62p) and annexin V, in the presence or absence of tirofiban, by flow cytometry. In addition, platelet activation was sought using the serotonin release assay. In six cases there was evidence of platelet activation and this was significantly associated with further coronary ischaemic events experienced at the time of acute thrombocytopenia. Tirofiban-induced thrombocytopenia due to DDAbs is a common occurrence and can lead to platelet activation and increased thrombotic events.