RESUMO
We investigated the vascular effects of a crude aqueous extract (AEEG) of Echinodorus grandiflorus (Alismataceae) using the in vitro experimental models of the rabbit isolated aorta and perfused kidney. Echinodorus grandiflorus, a native semi-aquatic plant widely distributed in Brazil, has been extensively used in Brazilian folk medicine for the treatment of high blood pressure and inflammatory diseases. The bolus injection of AEEG (0.1-10 mg) into the rabbit renal circulation pre-contracted with norepinephrine induced marked and dose-dependent vasodilator responses (maximum of 37+/-4%; n=6; P<0.001), which was similar to that induced by injection of 10 mmol acetylcholine (41+/-3%). Moreover, AEEG elicited a significant and concentration-dependent relaxation in the endothelium-intact, but not endothelium-denuded aortic rings, reaching the maximum of 81+/-5% (n=7, P<0.001). Inhibition of the nitric oxide-cGMP pathway with L-NAME (100 microM) or Methylene Blue (20 microM) reduced maximum relaxation induced by AEEG from 81+/-5% to 46+/-3 and 45+/-3%, respectively (n=7, P<0.001). A similar reduction was obtained with the incubation of the aortic rings with the selective PAF receptor antagonist WEB 2086 (10 microM) (from 81+/-5% to 55+/-3%; n=7; P<0.01). Conversely, blockade of muscarinic receptors with atropine (10 microM) did not affect the vasodilator effects of AEEG, while inhibition of the enzyme cyclooxigenase not only did not block, but rather potentiated vasodilation induced by AEEG (n=7, P<0.001). Finally, blockade of Ca(2+)- and ATP-activated K(+) channels using the specific blockers charydbotoxin (100 nM) and glibenclamide (3 microM), respectively, did not modify aortic relaxation induced by AEEG. We conclude that water-soluble extracts from leaves of Echinodorus grandiflorus elicit an endothelium-dependent, nitric oxide and PAF receptor-mediated vasodilation in rabbit aortic rings, which does not appear to involve the generation of vasodilating prostaglandins or the activation of K(+) channels. This potent vasodilator effect of the extracts was confirmed in the isolated rabbit renal circulation.
Assuntos
Alismataceae , Aorta/efeitos dos fármacos , Rim/irrigação sanguínea , Circulação Renal/efeitos dos fármacos , Vasodilatação/efeitos dos fármacos , Vasodilatadores/farmacologia , Animais , Aorta/metabolismo , Azepinas/farmacologia , Brasil , GMP Cíclico/metabolismo , Relação Dose-Resposta a Droga , Endotélio Vascular/efeitos dos fármacos , Inibidores Enzimáticos/farmacologia , Guanilato Ciclase/antagonistas & inibidores , Guanilato Ciclase/metabolismo , Técnicas In Vitro , Rim/metabolismo , Azul de Metileno/farmacologia , NG-Nitroarginina Metil Éster/farmacologia , Óxido Nítrico/metabolismo , Óxido Nítrico Sintase/antagonistas & inibidores , Óxido Nítrico Sintase/metabolismo , Extratos Vegetais/farmacologia , Folhas de Planta , Glicoproteínas da Membrana de Plaquetas/efeitos dos fármacos , Glicoproteínas da Membrana de Plaquetas/metabolismo , Coelhos , Receptores Acoplados a Proteínas G/efeitos dos fármacos , Receptores Acoplados a Proteínas G/metabolismo , Triazóis/farmacologiaRESUMO
Previous studies have shown that the extracts obtained from Phyllanthus amarus, and some of the lignans isolated from it, exhibit pronounced antiinflammatory properties. In the present study, we have assessed whether the antiinflammatory actions of these lignans can be mediated by interaction with platelet activating factor (PAF) receptor or interference with the action of this lipid. The local administration of nirtetralin, phyltetralin or niranthin (30 nmol/paw), similar to WEB2170 (a PAF receptor antagonist, 30 nmol/paw), significantly inhibited PAF-induced paw oedema formation in mice. The extracts of P. amarus (100 microg/ml) and niranthin (30 microM), but not nirtetralin or phyltetralin (30 microM), decreased the specific binding of [(3)H]-PAF in mouse cerebral cortex membranes. Furthermore, both niranthin and WEB2170 displaced, in a concentration-dependent manner, the [(3)H]-PAF binding sites. The mean IC(50) values from these effects were 6.5 microM and 0.3 microM, respectively. Additionally, both niranthin and WEB2170 (30 nmol/paw) inhibited the increase of myeloperoxidase activity induced by PAF injection in the mouse paw. When assessed the mouse model of pleurisy induced by PAF, pretreatment with niranthin (100 micromol/kg, p.o.) or WEB2170 (1.7 micromol/kg, i.p.) significantly inhibited PAF-induced protein extravasations. Moreover, in the rat model of PAF-induced allodynia, both niranthin (30 nmol/paw) and WEB2170 (30 nmol/paw) treatment significantly inhibited PAF-induced allodynia. In addition, niranthin had a rapid onset and long-lasting antiallodynic action when compared with WEB2170. Collectively, the present findings suggest that niranthin exhibits antiinflammatory and antiallodynic actions which are probably mediated through its direct antagonistic action on the PAF receptor binding sites.
Assuntos
Analgésicos/farmacologia , Anisóis/farmacologia , Anti-Inflamatórios/farmacologia , Dioxóis/farmacologia , Lignanas/farmacologia , Phyllanthus , Glicoproteínas da Membrana de Plaquetas/efeitos dos fármacos , Receptores Acoplados a Proteínas G/efeitos dos fármacos , Analgésicos/metabolismo , Analgésicos/uso terapêutico , Animais , Anisóis/metabolismo , Anisóis/uso terapêutico , Anti-Inflamatórios/metabolismo , Anti-Inflamatórios/uso terapêutico , Azepinas/farmacologia , Ligação Competitiva , Carragenina , Córtex Cerebral/metabolismo , Dioxóis/metabolismo , Dioxóis/uso terapêutico , Inflamação/induzido quimicamente , Inflamação/metabolismo , Inflamação/prevenção & controle , Lignanas/metabolismo , Lignanas/uso terapêutico , Masculino , Camundongos , Medição da Dor , Limiar da Dor/efeitos dos fármacos , Peroxidase/antagonistas & inibidores , Extratos Vegetais/farmacologia , Fator de Ativação de Plaquetas/metabolismo , Inibidores da Agregação Plaquetária/farmacologia , Glicoproteínas da Membrana de Plaquetas/metabolismo , Pleurisia/induzido quimicamente , Pleurisia/prevenção & controle , Ratos , Ratos Wistar , Receptores Acoplados a Proteínas G/metabolismo , Tetra-Hidronaftalenos/farmacologia , Fatores de Tempo , Triazóis/farmacologiaRESUMO
Hementerin (HT) is an 80 kDa fibrino(geno)lytic metalloprotease, purified from saliva of the leech Haementeria depressa. In the present report, the effect of HT on several functional parameters of human platelets was assessed. HT inhibited platelet aggregation and ATP release induced by different agonists such as ADP, adrenaline, collagen, thrombin, and arachidonic acid. HT did neither modify the expression of platelet glycoproteins (Ib, IIb-IIIa, Ia-IIa, IV) nor intraplatelet fibrinogen levels, whereas it markedly decreased CD62P and CD63 levels after the stimulation with thrombin. HT significantly increased thrombin-induced platelet Ca2+ intracellular levels, cGMP content and nitric oxide synthase (NOS) activity. The effect of HT on platelet aggregation was reversed by two NOS inhibitors, N(omega)-Nitro-L-arginine methyl ester and 2 N(G)-Nitro-L-arginine. In summary, these results indicate that HT is an effective inhibitor of human platelet aggregation, presumably through activation of the platelet's nitridergic pathway.
Assuntos
Sanguessugas/enzimologia , Óxido Nítrico/metabolismo , Ativação Plaquetária/efeitos dos fármacos , Extratos de Tecidos/farmacologia , Trifosfato de Adenosina/metabolismo , Animais , Cálcio/metabolismo , GMP Cíclico/metabolismo , Fibrinogênio/análise , Metaloproteases/farmacologia , Óxido Nítrico Sintase/metabolismo , Agregação Plaquetária/efeitos dos fármacos , Inibidores da Agregação Plaquetária/farmacologia , Glicoproteínas da Membrana de Plaquetas/efeitos dos fármacos , Trombina/farmacologiaRESUMO
We investigated the presence of PAF receptor subtypes in the tissues of the gastrointestinal tract, airways, blood vessels and in murine macrophages. For this purpose we have used a competitive PAF receptor antagonist, yangambin (YAN), extracted from the Brazilian plant "louro de cheiro" (Ocotea duckei Vattimo). Rat duodenum, jejunum, ileum, colon, stomach fundus, trachea and bronchia were removed and 1.5-2 cm muscle segments from those regions were mounted in a 10 ml organ bath with aerated physiological solution at 37 degrees C. PAF evoked a contraction of the rat jejunum, ileum, colon and stomach fundus. The contraction was slow and resistant to wash and was followed by desensitization to further doses of PAF. Contractions induced by PAF (10(-6) M) were inhibited by YAN (10(-7) to M-2 x 10(-5) M) and WEB 2086 (10(-6) m to M-5 M) in rat jejunum, ileum and colon but not in the stomach fundus. In the rat stomach fundus only WEB 2086 (5 x 10(-6) M) was able to block PAF-induced contraction. The contractions induced by acetylcholine, histamine, 5-hydroxytryptamine and vasopressin were not inhibited by prior administration of YAN. Yangambin also significantly inhibited PAF-induced vascular permeability in rat duodenum, jejunum, ileum, colon, and mesentery. Yangambin significantly inhibited PAF-induced lipid body formation in mice peritoneal macrophages. We suggest that YAN is a selective PAF antagonist which is able to discriminate putative PAF receptors subtypes present in the stomach fundus.
Assuntos
Sistema Digestório/efeitos dos fármacos , Furanos/farmacologia , Lauraceae/química , Lignanas/farmacologia , Inibidores da Agregação Plaquetária/farmacologia , Glicoproteínas da Membrana de Plaquetas/efeitos dos fármacos , Receptores de Superfície Celular , Receptores Acoplados a Proteínas G , Animais , Azepinas/farmacologia , Sistema Digestório/metabolismo , Feminino , Furanos/metabolismo , Técnicas In Vitro , Lignanas/metabolismo , Masculino , Camundongos , Camundongos Endogâmicos C3H , Inibidores da Agregação Plaquetária/metabolismo , Glicoproteínas da Membrana de Plaquetas/classificação , Ratos , Ratos Wistar , Triazóis/farmacologiaRESUMO
Platelet stimulation by agonists is followed by changes in cytoskeletal organization that includes actin polymerization and association of the membrane skeleton (which is connected with the integrin alpha IIb beta 3) with the underlying cytoplasmic actin filaments. The effect of orally administered acetylsalicylic acid to healthy volunteers on incorporation of contractile protein and beta 3 integrin into the cytoskeletal core of thrombin-stimulated platelets was studied. Stimulation was followed by increased contractile protein and beta 3 incorporation into the cytoskeleton. Acetylsalicylic acid intake resulted in decreased incorporation of myosin and actin (32% and 20%, respectively), and a decrease (36%) in the association of beta 3 integrin with the cytoskeletal elements was evident. In conclusion, we have shown that acetylsalicylic acid, besides the known inhibitory effect on thromboxane synthesis, promotes changes in the cytoskeletal organization of thrombin-stimulated platelets that could limit thrombus formation.
Assuntos
Antígenos CD/efeitos dos fármacos , Antígenos CD/metabolismo , Citoesqueleto/química , Citoesqueleto/metabolismo , Ativação Plaquetária/efeitos dos fármacos , Glicoproteínas da Membrana de Plaquetas/efeitos dos fármacos , Glicoproteínas da Membrana de Plaquetas/metabolismo , Trombina/farmacologia , Actinina/efeitos dos fármacos , Actinina/metabolismo , Actinas/efeitos dos fármacos , Actinas/metabolismo , Aspirina/administração & dosagem , Aspirina/farmacologia , Plaquetas/química , Eletroforese das Proteínas Sanguíneas , Western Blotting , Proteínas do Citoesqueleto/efeitos dos fármacos , Proteínas do Citoesqueleto/metabolismo , Citoesqueleto/efeitos dos fármacos , Humanos , Integrina beta3 , Integrinas/efeitos dos fármacos , Integrinas/metabolismo , Miosinas/efeitos dos fármacos , Miosinas/metabolismo , Octoxinol/farmacologiaRESUMO
The effects of convulxin, isolated from the venom of Crotalus durissus terrificus, on the localization and distribution of wheat germ agglutinin (WGA) binding sites on platelet surfaces have been investigated at an ultrastructural level. A post-embedding cytochemical technique using WGA-gold complexes was used and the quantitative intensity of WGA-labeling on the surface membrane of platelets after convulxin stimulation was determined. In the presence of Ca2+, convulxin induced platelet release and aggregation, while in its absence, the platelets formed pseudopodia and showed release reaction, but without aggregation. After treatment with convulxin, WGA-labeling on the surface membrane decreased compared with intact washed (control) platelets. In the presence of Ca2+, clusters of gold label were often found on the surface membrane. However, the WGA-labeling intensity of the membrane of the open canalicular system increased significantly compared with that of platelets stimulated by convulxin in the absence of Ca2+. Direct morphological evidence demonstrates qualitative and quantitative alterations of WGA-labeling on the surface membrane of platelets, after convulxin stimulation. The possibility is considered that WGA-binding glycoproteins on the surface membrane are involved in the aggregation response after convulxin stimulation.