Mouse antithrombotic assay. Inhibition of platelet thromboembolism by disintegrins

Pentadecapeptide BPC 157 as Therapy for Inferior Caval Vein Embolization: Recovery of Sodium Laurate-Post-Embolization Syndrome in Rats

After inferior caval vein embolization therapy, post-embolization syndrome (sodium laurate 10 mg/kg, 0.1 mL into rat inferior caval vein, assessment at 15, 30, 60 min, prime lung lesions, thromboemboli occluding lung vessels), as a severe occlusion/occlusion-like syndrome, might be resolved as a whole by stable gastric pentadecapeptide BPC 157 therapy. At 5 min after laurate injection, stable gastric pentadecapeptide BPC 157 was implemented as therapy (10 µg/kg, 10 ng/kg intraperitoneally or intragastrically). As before, confronted with the occlusion of major vessel(s) or similar noxious procedures, such as rapidly acting Virchow triad circumstances, the particular effect of the therapy (i.e., collateral pathways activation, "bypassing vascular key", i.e., direct blood flow delivery via activation of azygos vein) assisted in the recovery of the vessel/s and counteracted multiorgan failure due to occlusion/occlusion-like syndrome as a whole in the laurate-injected rats. Along with prime lung lesions and thromboemboli occluding lung vessels, post-embolization syndrome rapidly occurred peripherally and centrally as a shared multiorgan and vessel failure, brain, heart, lung, liver, kidney, and gastrointestinal tract lesions, venous hypertension (intracranial (superior sagittal sinus), portal, and caval), aortal hypotension, progressing thrombosis in veins and arteries and stasis, congested and/or failed major veins, and severe ECG disturbances. Whatever the cause, these were all counteracted, eliminated, or attenuated by the application of BPC 157 therapy. As recovery with BPC 157 therapy commonly and rapidly occurred, reversing the collapsed azygos vein to the rescuing collateral pathway might initiate rapid direct blood delivery and start blood flow reorganization. In conclusion, we suggest BPC 157 therapy to resolve further vascular and embolization injuries.

Apolipoprotein A-I, elevated in trauma patients, inhibits platelet activation and decreases clot strength

Apolipoprotein A-I (ApoA-I) is elevated in the plasma of a subgroup of trauma patients with systemic hyperfibrinolysis. We hypothesize that apoA-I inhibits platelet activation and clot formation. The effects of apoA-I on human platelet activation and clot formation were assessed by whole blood thrombelastography (TEG), platelet aggregometry, P-selectin surface expression, microfluidic adhesion, and Akt phosphorylation. Mouse models of carotid artery thrombosis and pulmonary embolism were used to assess the effects of apoA-I in vivo. The ApoA-1 receptor was investigated with transgenic mice knockouts (KO) for the scavenger receptor class B member 1 (SR-BI). Compared to controls, exogenous human apoA-I inhibited arachidonic acid and collagen-mediated human and mouse platelet aggregation, decreased P-selectin surface expression and Akt activation, resulting in diminished clot strength and increased clot lysis by TEG. ApoA-I also decreased platelet aggregate size formed on a collagen surface under flow. In vivo, apoA-I delayed vessel occlusion in an arterial thrombosis model and conferred a survival advantage in a pulmonary embolism model. SR-BI KO mice significantly reduced apoA-I inhibition of platelet aggregation versus wild-type platelets. Exogenous human apoA-I inhibits platelet activation, decreases clot strength and stability, and protects mice from arterial and venous thrombosis via the SR-BI receptor.

Chitosan/Alginate Nanoparticles for the Enhanced Oral Antithrombotic Activity of Clam Heparinoid from the Clam Coelomactra antiquata

Chitosan/alginate nanoparticles (DG1-NPs and DG1/Cur-NPs) aiming to enhance the oral antithrombotic activity of clam heparinoid DG1 were prepared by ionotropic pre-gelation. The influence of parameters, such as the concentration of sodium alginate (SA), chitosan (CTS), CaCl2, clam heparinoid DG1, and curcumin (Cur), on the characteristics of the nanoparticles, were investigated. Results indicate that chitosan and alginate can be used as polymer matrices to encapsulate DG1, and nanoparticle characteristics depend on the preparation parameters. Nano-particles should be prepared using 0.6 mg/mL SA, 0.33 mg/mL CaCl2, 0.6 mg/mL CTS, 7.2 mg/mL DG1, and 0.24 mg/mL Cur under vigorous stirring to produce DG1-NPS and DG1/Cur-NPS with small size, high encapsulation efficiency, high loading capacity, and negative zeta potential from approximately −20 to 30 mV. Data from scanning electron microscopy, Fourier-transform infrared spectrometry, and differential scanning calorimetry analyses showed no chemical reaction between DG1, Cur, and the polymers; only physical mixing. Moreover, the drug was loaded in the amorphous phase within the nanoparticle matrix. In the acute pulmonary embolism murine model, DG1-NPs enhanced the oral antithrombotic activity of DG1, but DG1/Cur-NPs did not exhibit higher antithrombotic activity than DG1-NPs. Therefore, the chitosan/alginate nanoparticles enhanced the oral antithrombotic activity of DG1, but curcumin did not further enhance this effect.

Rodent models of pulmonary embolism and chronic thromboembolic pulmonary hypertension

Pulmonary embolism (PE) is the third most prevalent cardiovascular disease. It is associated with high in-hospital mortality and the development of acute and chronic complications. New approaches aimed at improving the prognosis of patients with PE are largely dependent on reliable animal models. Mice, rats, hamsters, and rabbits, are currently most commonly used for PE modeling because of their ethical acceptability and economic feasibility. This article provides an overview of the main approaches to PE modeling, and the advantages and disadvantages of each method. Special attention is paid to experimental endpoints, including morphological, functional, and molecular endpoints. All approaches to PE modeling can be broadly divided into three main groups: 1) induction of thromboembolism, either by thrombus formation in vivo or by injection of in vitro prepared blood clots; 2) introduction of particles of non-thrombotic origin; and 3) surgical procedures. The choice of a specific model and animal species is determined based on the objectives of the study. Rodent models of chronic thromboembolic pulmonary hypertension (CTEPH), which is the most devastating complication of PE, are also described. CTEPH models are especially challenging because of insufficient knowledge about the pathogenesis and high fibrinolytic activity of rodent plasma. The CTEPH model should demonstrate a persistent increase in pulmonary artery pressure and stable reduction of the vascular bed due to recurrent embolism. Based on the analysis of available evidence, one might conclude that currently, there is no single optimal method for modeling PE and CTEPH.

Novel venous thromboembolism mouse model to evaluate the role of complete and partial factor XIII deficiency in pulmonary embolism risk

BACKGROUND

Venous thrombosis (VT) and pulmonary embolism (PE), collectively venous thromboembolism (VTE), cause high mortality and morbidity. Factor XIII (FXIII) crosslinks fibrin to enhance thrombus stability and consequently may influence PE risk. Elucidating mechanisms contributing to PE is limited by a lack of models that recapitulate human PE characteristics.

OBJECTIVE

We aimed to develop a mouse model that permits embolization of red blood cell (RBC)- and fibrin-rich VT and determine the contribution of FXIII to PE risk.

METHODS AND RESULTS

In a thrombin-infusion PE model, F13a+/+ , F13a+/- , and F13a-/-  mice had similar incidence of microthrombi in the lungs; however, thrombi were small, with low RBC content (≤7%), unlike human PEs (~70%). To identify a model producing PE consistent with histological characteristics of human PE, we compared mouse femoral vein electrolytic injury, femoral vein FeCl3 injury, and infrarenal vena cava (IVC) stasis models of VT. Electrolytic and FeCl3  models produced small thrombi with few RBCs (5% and 4%, respectively), whereas IVC stasis produced large thrombi with higher RBC content (68%) that was similar to human PEs. After IVC stasis and ligature removal (de-ligation) to permit thrombus embolization, compared to F13a+/+ mice, F13a+/-  and F13a-/-  mice had similar and increased PE incidence, respectively.

CONCLUSIONS

Compared to thrombin infusion-, electrolytic injury-, and FeCl3 -based models, IVC stasis produces thrombi that are more histologically similar to human thrombi. IVC stasis followed by de-ligation permits embolization of existing RBC- and fibrin-rich thrombi. Complete FXIII deficiency increases PE incidence, but partial deficiency does not.

Isolation and Functional Identification of an Antiplatelet RGD-Containing Disintegrin from Cerastes cerastes Venom

The current report focuses on purification, structural and functional characterization of Cerastategrin from Cerastes cerastes venom, a novel basic disintegrin (pI 8.36) with 128 amino acid residues and a molecular weight of 13 835.25 Da measured by MALDI-MSMS. The 3D structure of Cerastategrin is organized as α-helix (13%), β-strand (15%) and disordered structure (30%) and presents homologies with several snake venom disintegrins. Structural modeling shows that Cerastategrin presents an RGD motif that connects specifically to integrin receptors. Cerastategrin exhibits the inhibition of ADP induced platelets with an IC₅₀ of 0.88 µg/mL and shows in vivo long stable anticoagulation effect 24 h post-injection of increasing doses ranging from 0.2 to 1 mg/kg, therefore, Cerastategrin maintained irreversibly the blood incoagulable. Moreover, Cerastategrin decreases the amount of bounded αIIbβ3 and reduced significantly the quantity of externalized P-Selectin. Cerastategrin acts as a molecule targeting specifically the receptor α_IIbβ₃; therefore, it behaves as a potent platelet activation inhibitor. As a new peptide with promising pharmacological properties, Cerastategrin could have a potential therapeutical effect in the vascular pathologies and may be a new effective treatment approach.

Chemical and bioactive comparison of Panax notoginseng root and rhizome in raw and steamed forms

Background

The root and rhizome are historically and officially utilized medicinal parts of Panax notoginseng (PN) (Burk.) F. H. Chen, which in raw and steamed forms are used differently in practice.

Methods

To investigate the differences in chemical composition and bioactivities of PN root and rhizome between raw and steamed forms, high-performance liquid chromatography analyses and pharmacologic effects evaluated by tests of anticoagulation, antioxidation, hemostasis, antiinflammation, and hematopoiesis were combined.

Results

With the duration of steaming time, the contents of ginsenosides Rg₁, Re, Rb₁, Rd, and notoginsenoside R₁ in PN were decreased, while those of ginsenosides Rh₁, 20(S)-Rg₃, 20(R)-Rg₃, Rh₄, and Rk₃ were increased gradually. Raw PN samples steamed for 6 h at 120°C with stable levels of most constituents were used for the subsequent study of bioeffects. Raw PN showed better hemostasis, anticoagulation, and antiinflammation effects, while steamed PN exhibited stronger antioxidation and hematopoiesis activities. For different parts of PN, contents of saponins in PN rhizome were generally higher than those in the root, which could be related to the stronger bioactivities of rhizome compared with the same form of PN root.

Conclusion

This study provides basic information about the chemical and bioactive comparison of PN root and rhizome in both raw and steamed forms, indicating that the change of saponins may have a key role in different properties of raw and steamed PN.

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Saponin types and levels are significantly different in raw and steamed Panax notoginseng (PN).

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Levels of saponins are generally higher in PN rhizome than in the root.

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PN rhizome shows stronger activities of various tests than the same form of root.

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Raw PN is preferable in treating hemorrhages, blood stasis, swelling, and pain.

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Steamed PN is preferable in antioxidation and hematopoiesis effects.

Ginsenoside-Rp1 inhibits platelet activation and thrombus formation via impaired glycoprotein VI signalling pathway, tyrosine phosphorylation and MAPK activation

BACKGROUND AND PURPOSE

Ginsenosides are the main constituents for the pharmacological effects of Panax ginseng. Such effects of ginsenosides including cardioprotective and anti-platelet activities have shown stability and bioavailability limitations. However, information on the anti-platelet activity of ginsenoside-Rp1 (G-Rp1), a stable derivative of ginsenoside-Rg3, is scarce. We examined the ability of G-Rp1 to modulate agonist-induced platelet activation.

EXPERIMENTAL APPROACH

G-Rp1 in vitro and ex vivo effects on agonist-induced platelet-aggregation, granule-secretion, [Ca(2+) ](i) mobilization, integrin-α(IIb) β(3) activation were examined. Vasodilator-stimulated phosphoprotein (VASP) and MAPK expressions and levels of tyrosine phosphorylation of the glycoprotein VI (GPVI) signalling pathway components were also studied. G-Rp1 effects on arteriovenous shunt thrombus formation in rats or tail bleeding time and ex vivo coagulation time in mice were determined. KEY RESULT: G-Rp1 markedly inhibited platelet aggregation induced by collagen, thrombin or ADP. While G-Rp1 elevated cAMP levels, it dose-dependently suppressed collagen-induced ATP-release, thromboxane secretion, p-selectin expression, [Ca(2+) ](i) mobilization and α(IIb) β(3) activation and attenuated p38(MAPK) and ERK2 activation. Furthermore, G-Rp1 inhibited tyrosine phosphorylation of multiple components (Fyn, Lyn, Syk, LAT, PI3K and PLCγ2) of the GPVI signalling pathway. G-Rp1 inhibited in vivo thrombus formation and ex vivo platelet aggregation and ATP secretion without affecting tail bleeding time and coagulation time, respectively.

CONCLUSION AND IMPLICATIONS

G-Rp1 inhibits collagen-induced platelet activation and thrombus formation through modulation of early GPVI signalling events, and this effect involves VASP stimulation, and ERK2 and p38(-MAPK) inhibition. These data suggest that G-Rp1 may have therapeutic potential for the treatment of cardiovascular diseases involving aberrant platelet activation.

Inhibitory effects of Bulnesia sarmienti aqueous extract on agonist-induced platelet activation and thrombus formation involves mitogen-activated protein kinases

ETHNOPHARMACOLOGICAL RELEVANCE

B. sarmienti has long been recognized in folk medicine as a medicinal plant with various medicinal uses. Traditionally, it has been appreciated for the skin-healing properties of its essence. The bark has also been employed to treat stomach and cardiovascular disorders and reported to have antitumor, antioxidant and anti-inflammatory activities. However, information on its antiplatelet activity is limited.

AIM OF THE STUDY

To examined the effects of B. sarmienti aqueous extract (BSAE) in platelet physiology.

MATERIALS AND METHODS

The anti-platelet activity of BSAE was studied using rat platelets for in vitro determination of the extract effect on agonist-induced platelet aggregation, ATP secretion, [Ca(2+)](i) mobilization and MAP kinase phosphorylation. The extract in vivo effects was also examined in arterio-venous shunt thrombus formation in rats, and tail bleeding time in mice.

RESULT

HPLC chromatographic analysis revealed that B. sarmienti extract contained (+)-catechin (C), (-)-epigallocatechin (EGC), (-)-epicatechin (EC), and (-)-epicatechin gallate (ECG). BSAE, significantly and dose dependently, inhibited collagen, thrombin, or ADP-induced platelet aggregation. The 50 percent inhibitory concentrations (IC(50)) of the extract for collagen, thrombin and ADP-induced platelet aggregation were 45.3+/-2.6, 100+/-5.6 and 110+/-4.6 microg/ml, respectively. Collagen activated ATP release and thrombin-induced intracellular Ca(2+) concentration were reduced in BSAE-treated platelets. In addition, the extract in vivo activity showed that BSAE at 100 mg/kg significantly attenuated thrombus formation in rat extracorporeal shunt model while mice tail bleeding time was not affected. Moreover, BSAE attenuated p38 mitogen-activated protein kinase (p38 MAPK), c-Jun N-terminal kinase 1 (JNK1) and extracellular-signal-regulated protein kinase 2 (ERK2) phosphorylations.

CONCLUSION

BSAE inhibits platelet activation, granule secretion, aggregation, and thrombus formation without affecting bleeding time, and that this effect is mediated by inhibition of P38, JNK1 and ERK2 phosphorylations. The ability of BSAE to inhibit platelet function might be relevant in cases involving aberrant platelet activation where the plant extract could be considered as a candidate to anti-platelet and antithrombotic agent.

Antiplatelet and anticoagulant effects of Panax notoginseng: comparison of raw and steamed Panax notoginseng with Panax ginseng and Panax quinquefolium

ETHNOPHARMACOLOGICAL SIGNIFICANCE

Panax notoginseng (Burk.) F. H. Chen (Araliacea) is traditionally used for its hemostatic and cardiovascular effects when raw and as a tonic when steamed.

AIM OF THE STUDY

This study aims to compare the effects of raw and steamed Panax notoginseng, Panax ginseng C. A. Meyer and Panax quinquefolium Linn. on platelet aggregation and plasma coagulation.

MATERIALS AND METHODS

Effects on collagen-induced platelet aggregation were investigated using a platelet aggregometer, while the plasma coagulation times (prothrombin time, activated partial thromboplastin time and thrombin time) were determined using a blood coagulation analyzer. The data was corroborated with ex vivo platelet aggregation and in vivo rat bleeding time.

RESULTS

Raw and steamed Panax notoginseng significantly inhibit platelet aggregation and plasma coagulation. Steamed Panax notoginseng has significantly more potent antiplatelet and anticoagulant effects than the raw extract, and the antiplatelet and anticoagulant effects increase with increasing steaming durations. Comparing the three common Panax species, Panax notoginseng has higher antiplatelet effect than Panax ginseng and Panax quinquefolium. The in vitro antiplatelet and anticoagulant effects are positively translated into a prolongation of in vivo rat bleeding time after oral administration of the raw and steamed extracts.

CONCLUSION

The results indicate that the three common Panax species affect platelet aggregation and plasma coagulation differently, with steamed Panax notoginseng showing the greatest antiplatelet and anticoagulant effects. Panax notoginseng may be a good source of lead compounds for novel antiplatelet and anticoagulant therapeutics.

Key role of the P2Y(1) receptor in tissue factor-induced thrombin-dependent acute thromboembolism: studies in P2Y(1)-knockout mice and mice treated with a P2Y(1) antagonist

BACKGROUND

ADP plays a key role in hemostasis, acting through 2 platelet receptors: the P2Y(1) receptor and an unidentified P2 receptor, called P2cyc, coupled to adenylyl cyclase inhibition, which is the target of the antiplatelet drug clopidogrel. We showed that the P2Y(1) receptor is an essential cofactor in thrombotic states induced by intravenous infusion of collagen and epinephrine. The aim of the present study was to assess the role of this receptor in thrombin-dependent tissue factor-induced thromboembolism.

METHODS AND RESULTS

Human thromboplastin was injected intravenously into wild-type or P2Y(1)-deficient mice, and the effects on platelet count and mortality were determined and plasma thrombin-antithrombin III (TAT) complexes were quantified. P2Y(1)-deficient mice were resistant to the thromboembolism induced by injection of thromboplastin. Whereas the platelet count decreased sharply in wild-type mice, there was no significant drop in platelets in P2Y(1)-knockout mice. The platelet consumption in wild-type mice was probably due to thrombin generation, because it was abolished by hirudin. Thromboplastin also led to a rise in TAT complexes in plasma, again reflecting thrombin formation. This effect, however, was less important in P2Y(1)-knockout mice than in wild-type mice, indicating that less thrombin was generated in the absence of P2Y(1). Similar results were obtained after intravenous administration of N:(6)-methyl-2'-deoxyadenosine-3':5'-bisphosphate, a selective antagonist of the P2Y(1) receptor, to wild-type mice.

CONCLUSIONS

Our results demonstrate a role of the P2Y(1) receptor in thrombotic states involving thrombin generation and provide further evidence for the potential relevance of this receptor as a target for antithrombotic drugs.

RGDN peptide interaction with endothelial alpha5beta1 integrin causes sustained endothelin-dependent vasoconstriction of rat skeletal muscle arterioles

The ability of an integrin-binding Arg-Gly-Asp-Asn (RGDN)- containing peptide to influence vascular tone by interacting with the alpha5beta1 integrin was studied using rat skeletal muscle arterioles. After blockade of beta3 integrin function, isolated arterioles with spontaneous tone showed concentration-dependent vasoconstrictions to topical application of GRGDNP, a peptide that shows a greater ability to interact with alpha5beta1 than with alphavbeta3. The constriction to GRGDNP (2.1 mM) was inhibited by blocking alpha5 integrin function, and was intensified by blocking beta3 integrin function. In contrast, GRGDSP, a peptide that interacts better with alphavbeta3, was unable to induce sustained constrictions. Removal of the endothelium abolished the vasoconstriction in response to GRGDNP, suggesting that the response was due to release of an endothelium-dependent factor. Indeed, blockade of ETA endothelin receptors with BQ-610 (1 microM), similar to removal of the endothelium and alpha5 integrin blockade, inhibited the vasoconstriction. These data indicate that interaction of RGD peptides, and in particular the RGDN sequence with endothelial cell alpha5beta1, causes endothelin-mediated arteriolar vasoconstriction. These results indicate that integrins are novel signaling receptors within the vascular wall that affect vasomotor tone, and may play an important role in vascular control.

YC-1, a nitric oxide-independent activator of soluble guanylate cyclase, inhibits platelet-rich thrombosis in mice

YC-1 (3-(5'-hydroxymethyl-2'-furyl)-1-benzylindazole), a nitric oxide (NO)-independent activator of soluble guanylate cyclase, has been shown to inhibit platelet activation and aggregation in vitro through the generation of cGMP. In the present study, we assessed the antithrombotic effect of YC-1 in models of experimental thrombosis in mice. YC-1 (10, 30 micrograms/g, i.p.)-treated mice showed a prolonged tail bleeding time 30 min after injection (from control 91.0 +/- 6.4 s to 208.6 +/- 22.7 s and 291.8 +/- 42.4 s, respectively). In contrast, aspirin at a dose of 30 micrograms/g (i.p.) prolonged the bleeding time to more than 600 s. Platelet-rich thrombus formation was induced by irradiation of the mesenteric venule with filtered light in mice pretreated intravenously with fluorescein sodium. YC-1 (30 micrograms/g, i.p.) markedly prolonged the occlusion time of irradiated venules (from control 146.1 +/- 19.0 s to 275.6 +/- 24.5 s) in heparinized (1 U/g) mice. In the same condition, aspirin (100 micrograms/g) only slightly prolonged the time required for occlusion (193.2 +/- 13.2 s). In a model of fatal pulmonary thromboembolism induced by intravenous injection of ADP (300 micrograms/g), YC-1 was effective in reducing mortality when administered intraperitoneally at doses of 10-30 micrograms/g. The antithrombotic effect of YC-1 was correlated with the inhibition of ADP-induced platelet aggregation ex vivo. In contrast, aspirin (30, 100 micrograms/g) did not inhibit ADP-induced pulmonary thromboembolism in vivo or platelet aggregation ex vivo. YC-1 (3, 10 micrograms/g) also exhibited profibrinolytic activity ex vivo, as revealed by shortening of the euglobulin clot lysis time. Therefore, YC-1 is an effective antithrombotic agent in preventing thrombosis in animal models, and its antiaggregating and additional profibrinolytic effects may be of potential clinical benefit in the treatment of thromboembolic diseases.

Intravenous injection of sonicated blood induces pulmonary microthromboembolism in rabbits with ligation of the splenic artery

Pulmonary thromboembolism (PTE) is found in long hospitalized patients. Chronic PTE has been reported to play an important role in cardiac failure in thalassemic patients after splenectomy. However, the mechanism of PTE in these patients remains unclear. In this study, we attempted to establish an animal model of PTE. We divided New Zealand white rabbits into three groups: Group I was injected sonicated blood, II was injected non-sonicated blood after ligation of the splenic artery, and III was injected sonicated blood after ligation of the splenic artery. After injection of the sonicated blood, we examined the platelet counts every 10 minutes until 1 hour and the rabbits were sacrificed for histological examination. Platelets significantly decreased in number immediately after the injection of sonicated blood in Groups I and III. Many pulmonary thromboemboli composed mainly of platelets were found in Group III but not in other groups. These pathological changes seem to be partly similar to those of thalassemic patients after splenectomy. This animal model is thought to be useful to study the pathogenesis of pulmonary thromboembolism, especially in thalassemic patients after splenectomy.

Sulfatide prolongs blood-coagulation time and bleeding time by forming a complex with fibrinogen

Sulfatides (galactosylceramide I3-sulfate), which are found in serum lipoproteins of various mammals, effectively increased prothrombin time (anticoagulant effect) and also effectively prolonged bleeding time (anti-platelet effect). When equal volumes of a homogeneous micellar solution of sulfatide and fibrinogen in phosphate-buffered saline were mixed, an insoluble complex precipitated. Analysis of the precipitated complex showed that the molar ratio of sulfatide to fibrinogen was about 400:1. These results indicate that the sulfatide micelle binds tightly to fibrinogen and thereby interferes with both fibrin gel formation (anticoagulant activity) and platelet function.

Effective prevention of thrombocytopenia in mice using adenovirus-mediated transfer of HST-1 (FGF-4) gene

HST-1 (FGF-4) gene product is a member of the fibroblast growth factor family with a signal peptide and plays a crucial role in limb development. We showed previously that an intraperitoneal injection of replication-deficient adenovirus containing the HST-1 gene (Adex1HST-1) into normal mice caused a twofold increase in peripheral platelet count. To investigate whether Adex1HST-1 could effectively prevent experimentally induced thrombocytopenia in mice, we injected Adex1HST-1 intraperitoneally into thrombocytopenic mice induced by administration of a chemotherapeutic agent and/or by irradiation. A single Adex1HST-1 injection caused continuously increased levels of serum HST-1 protein for at least 30 d and increased the count of large megakaryocytes in bone marrow, which specifically recovered platelet counts and more efficiently diminished the extent and duration of thrombocytopenia than any other reported cytokine or any combination of cytokines so far. In the other peripheral hematological parameters, no discernible differences were detected. No other apparent side effects were observed. Therefore, this method could be useful for treatment and/or prevention of thrombocytopenia induced by chemotherapy and/or irradiation for cancer treatment.

Iloprost and echistatin protect platelets during simulated extracorporeal circulation

Temporary, reversible inhibition of platelets during cardiopulmonary bypass is an attractive strategy to protect platelets and normalize postoperative bleeding times. Iloprost, an analogue of prostacyclin, and the disintegrins reversibly inhibit platelets by different mechanisms. We tested the hypothesis that reduced doses of iloprost and either echistatin, a natural disintegrin, or RO43-5054, a peptidomimetic, in combination provide better platelet protection than any drug alone during simulated extracorporeal circulation. Thirty-five recirculation studies using fresh, heparinized human blood in an extracorporeal perfusion circuit that contained a 0.45-m2 spiral coil membrane oxygenator were performed. Iloprost, but neither echistatin nor RO43-5054, increased platelet cyclic adenosine monophosphate. Combinations of iloprost and either fibrinogen receptor antagonist at reduced doses submaximally increased platelet cyclic adenosine monophosphate. Platelet adhesion and release of beta-thromboglobulin antigen was completely inhibited by combinations of the two classes of drugs, but only partially inhibited by each drug alone. Combinations of drugs also completely inhibited platelet aggregation to adenosine diphosphate; these platelets retained full sensitivity to adenosine diphosphate after 90 minutes of recirculation when drugs were removed by gel filtration. We conclude that combinations of iloprost and a fibrinogen receptor antagonist at doses that are unlikely to produce clinical side effects completely inhibit platelet activation and preserve platelet function during in vitro extracorporeal circulation.