Lactadherin and procoagulant activities of red blood cells in cyclosporine induced thrombosis.

BACKGROUND: The side effects of cyclosporine therapy include thromboembolic complications. However, the mechanisms underlying the hypercoagulable state induced by cyclosporine are not fully understood. Cyclosporine binds to red blood cells (RBCs) with a high affinity in circulation and alters the membranes of RBCs. Therefore, we propose that such alterations in RBCs membranes play a role in cyclosporine-induced coagulopathy and this disorder may be rectified by lactadherin, a phosphatidylserine binding protein. METHODS: RBCs from healthy adults were treated with various concentrations of cyclosporine. Procoagulant activity of the RBC membrane was measured by the single stage recalcification time and confirmed by detection of tenase and thrombin assembly through enzymatic assays. Inhibition assays of coagulation were carried out in the presence of lactadherin, annexin V or antitissue factor. Phosphatidylserine exposure was detected by flow cytometry and confocal microscopy through binding with fluorescein isothiocyanate (FITC)-labeled lactadherin as well as FITC annexin V. RESULTS: RBCs treated with cyclosporine demonstrated increased procoagulant activity. Cyclosporine treatment markedly shortened the clotting time of RBCs ((305 +/- 10) seconds vs (366 +/- 15) seconds) and increased the generation of intrinsic factor Xase ((7.68 +/- 0.99) nmol/L vs (2.86 +/- 0.11) nmol/L) and thrombin ((15.83 +/- 1.37) nmol/L vs (4.88 +/- 0.13) nmol/L). Flow cytometry and confocal microscopy indicated that cyclosporine treatment induced an increased expression of phosphatidylserine on the RBC membrane. Lactadherin was more sensitive in detecting phosphatidylserine exposure of the RBC membrane than annexin V. The modulating effect of procoagulant activity was concomitant with and dependent on phosphatidylserine exposure. Blocking of phosphatidylserine with lactadherin effectively inhibited over 90% of FXa generation and prothrombinase activity and prolonged coagulation time. CONCLUSIONS: Procoagulant properties of RBCs membranes resulting from phosphatidylserine exposure may play an important role in cyclosporine-induced thrombosis. Lactadherin can be used as a sensitive probe for phosphatidylserine detection. Its high affinity for phosphatidylserine may provide a new approach for the treatment of cyclosporine induced thrombogenic properties.

Increased procoagulant activity of red blood cells in the presence of cisplatin.

BACKGROUND: Cisplatin based chemotherapy is a well recognized risk factor for coagulation disorders and thrombosis. The pathophysiological mechanisms by which cisplatin promote thrombosis are not well understood. METHODS: Red blood cells (RBCs) were separated from peripheral blood of patients with breast cancer (n = 10) and healthy adults (n = 6) and treated with cisplatin. Coagulation time of RBCs was assessed by one step recalcification time and the productions of thrombin, intrinsic and extrinsic factor Xa were measured in the presence or absence of various concentrations of lactadherin. Exposed phosphatidylserine was stained with lactadherin and observed by confocal microscopy and flow cytometry. RESULTS: Neither fresh RBCs nor RBCs treated without cisplatin had potent procoagulant activity. Cisplatin treatment increased procoagulant activity of RBCs in a cell number- and concentration-dependent manner. Exposed phosphatidylserine was stained with lactadherin and after cisplatin treatment, strong fluorescence was revealed by confocal microscopy. Lactadherin bound RBCs from patients with breast cancer increased from (1.9 +/- 0.5)% on control RBCs to (68.0 +/- 3.5)% on RBCs treated with 10 micromol/L cisplatin for 24 hours. CONCLUSIONS: Cisplatin treatment increases procoagulant activity of RBCs, which have a strong association with exposure of phosphatidylserine. The increased procoagulant activity may contribute to the pathogenesis of thrombophilia during cisplatin based chemotherapy in breast cancer patients.

[Study on cardiac toxicity in acute promyelocyte leukemia treatment of arsenic trioxide intravenous infusion in general dose].

OBJECTIVE: To study the cardiac toxicity of arsenic trioxide (As(2)O(3)). METHODS: To investigate and analyze the probable mechanisms of cardiac toxicity of As(2)O(3) by dynamic monitoring of clinical manifestations, basal cardiac rate and electrocardiographic data of acute promyelocyte leukemia (APL) patients during As(2)O(3) therapy. The instant change of the action potential, the I(Ca-L) and I(k) of single cardiac myocyte of guinea pig was also observed with patch clamp dynamically. RESULTS: Approximately 71.4% of the 28 cases of APL showed cardiac toxic reaction in different degree in the first week after As(2)O(3) intravenous infusion in general dose, mainly expressing rapid heart rate or prolonged QT interval. As(2)O(3) could prolong the action potential duration from (563.0 +/- 55.8) ms to (737.7 +/- 131.7) ms (P < 0.05) and increased the I(Ca-L) and I(k) of single cardiac myocyte of guinea pig in vitro. CONCLUSION: As(2)O(3) intravenous infusion in general therapeutic dose can cause tachycardia and prolong QT interval in some of the APL patients. The probable mechanism of these side-effects may be due to instant involvement of ionic channel of cardiac myocyte.