Plasma kallikrein enhances platelet aggregation response by subthreshold doses of ADP.

Human plasma kallikrein (huPK) potentiates platelet responses to subthreshold doses of ADP, although huPK itself, does not induce platelet aggregation. In the present investigation, we observe that huPK pretreatment of platelets potentiates ADP-induced platelet activation by prior proteolysis of the G-protein-coupled receptor PAR-1. The potentiation of ADP-induced platelet activation by huPK is mediated by the integrin αIIbß3 through interactions with the KGD/KGE sequence motif in huPK. Integrin αIIbß3 is a cofactor for huPK binding to platelets to support PAR-1 hydrolysis that contributes to activation of the ADP signaling pathway. This activation pathway leads to phosphorylation of Src, AktS473, ERK1/2, and p38 MAPK, and to Ca2+ release. The effect of huPK is blocked by specific antagonists of PAR-1 (SCH 19197) and αIIbß3 (abciximab) and by synthetic peptides comprising the KGD and KGE sequence motifs of huPK. Further, recombinant plasma kallikrein inhibitor, rBbKI, also blocks this entire mechanism. These results suggest a new function for huPK. Formation of plasma kallikrein lowers the threshold for ADP-induced platelet activation. The present observations are consistent with the notion that plasma kallikrein promotes vascular disease and thrombosis in the intravascular compartment and its inhibition may ameliorate cardiovascular disease and thrombosis.

The Kallikrein Inhibitor from Bauhinia bauhinioides (BbKI) shows antithrombotic properties in venous and arterial thrombosis models.

The Bauhinia bauhinioides Kallikrein Inhibitor (BbKI) is a Kunitz-type serine peptidase inhibitor of plant origin that has been shown to impair the viability of some tumor cells and to feature a potent inhibitory activity against human and rat plasma kallikrein (Kiapp 2.4 nmol/L and 5.2 nmol/L, respectively). This inhibitory activity is possibly responsible for an effect on hemostasis by prolonging activated partial thromboplastin time (aPTT). Because the association between cancer and thrombosis is well established, we evaluated the possible antithrombotic activity of this protein in venous and arterial thrombosis models. Vein thrombosis was studied in the vena cava ligature model in Wistar rats, and arterial thrombosis in the photochemical induced endothelium lesion model in the carotid artery of C57 black 6 mice. BbKI at a concentration of 2.0 mg/kg reduced the venous thrombus weight by 65% in treated rats in comparison to rats in the control group. The inhibitor prolonged the time for total artery occlusion in the carotid artery model mice indicating that this potent plasma kallikrein inhibitor prevented thrombosis.

Highlights from the I international symposium of thrombosis and anticoagulation in internal medicine, October 23-25, 2008, Sao Paulo, Brazil.

The importance of thrombosis and anticoagulation in clinical practice is rooted firmly in several fundamental constructs that can be applied both broadly and globally. Awareness and the appropriate use of anticoagulant therapy remain the keys to prevention and treatment. However, to assure maximal efficacy and safety, the clinician must, according to the available evidence, choose the right drug, at the right dose, for the right patient, under the right indication, and for the right duration of time. The first International Symposium of Thrombosis and Anticoagulation in Internal Medicine was a scientific program developed by clinicians for clinicians. The primary objective of the meeting was to educate, motivate and inspire internists, cardiologists and hematologists by convening national and international visionaries, thought-leaders and dedicated clinician-scientists in Sao Paulo, Brazil. This article is a focused summary of the symposium proceedings.

Prophylaxis of deep-vein thrombosis after lower extremity amputation: comparison of low molecular weight heparin with unfractionated heparin.

PURPOSE: To compare the efficacy and safety of a low molecular weight heparin (enoxaparin) with unfractionated heparin (UH) in this prophylaxis. METHODS: Seventy five patients (59 men and 16 women), undergoing major lower extremity amputation (30 above-knee and 45 below-knee), were randomized to be treated with subcutaneous UH (5,000 IU t.i.d.) or enoxaparin (40 mg/day) during hospitalization. Prophylaxis was started 12 hours before surgery or, in emergency cases, in the first postoperative day. RESULTS: The two groups were comparable with regard to baseline characteristics. Evaluation of DVT was performed by daily clinical examination and by duplex scanning before and 5 to 8 days after surgery. DVT was documented in the operated limb in 9.75% in patients treated with enoxaparin and in 11.76% in patients treated with UH (p=0.92) and there was one bilateral thrombosis in each group . Bleeding complications were not observed in both groups. CONCLUSION: Enoxaparin and UH were both efficient and safe for the prophylaxis of DVT in patients submitted to lower extremity amputation.

Prophylaxis of deep-vein thrombosis after lower extremity amputation: Comparison of low molecular weight heparin with unfractionated heparin

OBJETIVO: Comparar a eficácia e segurança da profilaxia com heparina de baixo peso molecular (enoxaparina) versus heparina não fracionada (HNF). MÉTODOS: Setenta e cinco pacientes (59 homens e 16 mulheres ), submetidos a amputação maior dos membros inferiores (30 acima do joelho e 45 abaixo do joelho ), foram tratados ao acaso com HNF subcutânea (5,000 IU -2x/dia ) ou enoxaparina subcutânea (40mg/dia ) durante a hospitalização . A profilaxia teve início 12 horas antes da cirurgia ou , em casos emergenciais , no primeiro dia de pós-operatório.RESULTADOS: Os dois grupos de tratamento foram comparáveis em termos de características gerais . A avaliação da TVP foi feita por meio de exame clínico diário e pelo mapeamento dúplex antes e 5-8 dias após a cirurgia . A TVP foi documentada no lado operado em 9,75% dos pacientes tratados com enoxaparina e em 11,76% dos pacientes tratados com HNF (p=0,92) e houve um caso de TVP bilateral em cada grupo . Sangramentos não foram verificados nos 2 grupos . CONCLUSÃO: A enoxaparina e HNF foram igualmente eficientes e seguras para a profilaxia da TVP em pacientes submetidos à amputação de membros inferiores .Descritores: Amputação. Trombose Venosa. Heparina de Baixo Peso Molecular.

Combinations of low doses of unfractionated heparin and of low-molecular-weight heparin prevent experimental venous thrombosis.

Synergism between low-molecular-weight heparin and low doses of unfractionated heparin (UH) enhancing anti-factor Xa activity and the release of tissue factor pathway inhibitor was observed. The aim of this study was to verify whether this association is effective in preventing experimental venous thrombosis. Seventy rats were allocated into 7 groups: the control group treated with distilled water, the H(350) group treated with UH 350 IU/kg, the E(2) group treated with enoxaparin 2 mg/kg, the H(175) group treated with UH 175 IU/kg, the E(1) group treated with enoxaparin 1 mg/kg, the H(175) + E(1) group treated with UH 175 IU/kg plus enoxaparin 1 mg/kg, and the H(100) + E(0.5) group treated with UH 100 IU/kg plus enoxaparin 0.5 mg/kg. Forty minutes after subcutaneous injection, thrombosis was induced in vena cava. Three hours later, if present, thrombi were withdrawn and weighed. Bleeding time, activated partial thromboplastin time, thrombin time (TT), and anti-factor Xa were measured at the beginning and end of the experiment. Forty-eight other animals were treated, but without inducing thrombus, and tests were performed 40 min after injection. Thrombus developed in 90.9% of control animals, 20% of the H(350) group, 22.2% of the E(2) group, 10% of the H(175) + E(1) group, and 30% of the H(100) + E(0.5) group; there was a difference between group C and the other groups. Only in the H(350) and H(175) + E(1) groups were TT and activated partial thromboplastin time prolonged in relation to control at the end of the experiment. Forty minutes after injection, TT was prolonged in the H(350) and H(175) + E(1) groups. In conclusion, combinations of low doses of low-molecular-weight heparin and low doses of UH were as effective as high doses of each one used alone in preventing thrombus development in rat vena cava.

An open-label, comparative study of the efficacy and safety of once-daily dose of enoxaparin versus unfractionated heparin in the treatment of proximal lower limb deep-vein thrombosis.

BACKGROUND: Treatment of deep-vein thrombosis (DVT) with a once-daily regimen of enoxaparin, rather than a continuous infusion of unfractionated heparin (UFH) is more convenient and allows for home care in some patients. This study was designed to compare the efficacy and safety of these two regimens for the treatment of patients with proximal lower limb DVT. METHODS: 201 patients with proximal lower limb DVT from 13 centers in Brazil were randomized in an open manner to receive either enoxaparin [1.5 mg/kg subcutaneous (s.c.) OD] or intravenous (i.v.) UFH (adjusted to aPTT 1.5-2.5 times control) for 5-10 days. All patients also received warfarin (INR 2-3) for at least 3 months. The primary efficacy endpoint was recurrent DVT (confirmed by venography or ultrasonography), and safety endpoints included bleeding and serious adverse events. The rate of pulmonary embolism (PE) was also collected. Hospitalization was at the physician's discretion. RESULTS: Baseline patient characteristics were comparable between groups. The duration of hospital stay was significantly shorter with enoxaparin than with UFH (3 versus 7 days). In addition, 36% of patients receiving enoxaparin did not need to be hospitalized, whereas all of the patients receiving UFH were hospitalized. The treatment duration was slightly longer with enoxaparin (8 versus 7 days). There was a nonsignificant trend toward a reduction in the rate of recurrent DVT with enoxaparin versus UFH, and similar safety. CONCLUSIONS: A once-daily regimen of enoxaparin 1.5 mg/kg subcutaneous is at least as effective and safe as conventional treatment with a continuous intravenous infusion of UFH. However, the once daily enoxaparin regimen is easier to administer (subcutaneous versus intravenous), does not require aPTT monitoring, and leads to both a reduced number of hospital admissions and an average 4-day-shorter hospital stay.

Isquemia de membro superior após injeçäo intramuscular de ampicilina benzatina e dipirona magnésica: relato de um caso / Upper limb ishemia due to intramuscular injection of benzatine ampicillin and magnesium dipirone: case report

Injeções parenterais feitas por balconistas de farmácias säo frequentes em nosso meio.No entanto, estas podem determinar complicações importantes, por vezes mutilantes, para os pacientes.Neste artigo relata-se o caso de uma mulher jovem que recebeu em uma farmácia uma injeçäo intramuscular da ampicilina benzatina e dipirona magnésia, que acabou determinando isquemia grave do membro superior e evoluçäo para amputaçäo desta extremidade.Na literatura säo apontadas uma série de drogas potenciamente causadoras de isquemia após injeções, mas näo se encontrou nenhuma referência acerca da ampicilina benzatina, associada à dipirona magnésica.Neste artigo alguns aspectos sobre a prevençäo e tratamento desta complicaçäo säo discutidos.

Antitrombina III em doentes com trombose venosa profunda / antithrombin III in patients with deep vein thrombosis

Com a finalidade de verificar a freqüência de deficiência de antitrombina III (ATIII) em doentes portadores de trombose venosa profunda (TVP) em nosso meio, a atividade dessa proteína anticoagulante plasmática foi medida por método funcional em 97 pacientes com TVP diagnosticada clinicamente e confirmada por flevografia. Essa medida foi realizada na vigência de tratamento com Warfarin Sódico em 41 pacientes, 2 a 3 meses após a suspensäo desse tratamento em 30 doentes e antes e após o tratamento em 26 doentes. Essa dosagem foi tambem realizada em familiares de pacientes que apresentavam deficiência de ATIII e, como controle, em 60 voluntários clinicamente sadios. A média da atividade da ATIII nos voluntários normais foi de 99,3 ñ 15,0%. Na vigência do tratamento anticoagulante essa média foi de 100,8 ñ 17,4% e após o tratamento de 89,8 ñ 19,8%. A média verificada nos pacientes após o término do tratamento foi significantemente menor que a média na vigência do tratamento e do que a média dos controles normais. Três pacientes na vigência do tratamento e oito após a suspensäo do mesmo apresentavam valores de ATIII menores do que a média dos normais menos dois desvios-padräo. Os familiares de 3 pacientes com deficiência de ATIII apresentaram valores de ATIII dentro da faixa considerada normal