[Show abstract][Hide abstract] ABSTRACT: Pleiotrophin, also known as heparin affin regulatory peptide (HARP), is a growth factor expressed in various tissues and cell lines. In this work, HARP was tested for its capacity to modulate the anticoagulant activity of heparin and heparan sulphate mimetics (OTR4120). We used both in vitro and in vivo assays. HARP was found to be differently effective for neutralization of the anticoagulant activity of the mimetic heparan sulphate (OTR4120) and heparin in purified system and human plasma. HARP was shown to compete with both antithrombin and thrombin for binding to heparin and to OTR4120, respectively. In the presence of OTR4120, the V(max) was constant and the calculated maximum velocity was 1.56 U/min; the thrombin Km value (0.011 nM) was affected by HARP concentrations. The Km (HARP) value was 0.085 nM, which is consistent with high affinity of HARP to OTR4120. Under the same conditions, initial velocity patterns for antithrombin-heparin were determined in the presence or in the absence of HARP. The antithrombin value Km (0.022 nM) was affected by HARP (0.077 nM). HARP exhibits efficacy equivalent to or greater than protamine. Interestingly, intraperitoneally administered HARP decreased the anticoagulant activity of heparin and of OTR4120 in mice. Taken together, these data provide the first evidence for a physiological role of HARP in the modulation of anticoagulant activity of heparin and heparin-like material.
[Show abstract][Hide abstract] ABSTRACT: Bexarotene, (LGD1069, Targretin), is an antitumoral agent used as chemotherapy in the treatment of cutaneous T-cell lymphoma. Therapy with bexarotene is accompanied by adverse events, such as, bleeding, hemorrhage, and coagulopathy
In order to design applications for bexarotene, it was very important to gain an understanding of how bexarotene inhibits blood clotting
We investigated the interaction between bexarotene or vehicle alone, and coagulation factors or blood cells. We used both in vitro and in vivo assays. Anticoagulant activity of bexarotene or vehicle was assessed by clotting time tests (TT, RT, APTT, and PT). Coagulation factors activity was measured by adding diluted test plasma to artificially prepared factor-deficient plasma. Direct interactions between bexarotene and factor Xa were studied by chromogenic substrate assay. A mouse model was used to investigate in vivo effects of the drug on blood system and for evaluation of clinical hematology and organ pathology.
Increases in clotting times (prothrombin time and activated thromboplastin time) occurred with bexarotene in in vitro and in vivo experiments. We detected no significant influence of bexarotene on factors II, V, VII, VIII, XI and XII, while factor IX and factors X were affected. Bexarotene exerts anticoagulant effects and acts mainly as a direct factor IX and factor X inhibitor. On the contrary, the vehicle is remarkably inert toward the coagulation system. The number of blood cells was unaffected in mice treated with bexarotene or with the vehicle.
Monitoring of the coagulation factors profile should be considered in cancer patients receiving bexarotene, particularly those with a known diagnosis of coagulation factors deficient.
Cancer Chemotherapy and Pharmacology 01/2011; 68(4):847-54. · 2.80 Impact Factor