RESUMO
This study evaluated the cholinesterase inhibitory activity of an alkaloid-rich fraction of stembark from Geissospermum vellosii (PP), and its effect on memory tests in mice. PP inhibited rat brain and electric eel acetylcholinesterase, as well as horse serum butyrylcholinesterase in a concentration-dependent manner with mean IC(50) values of 39.3 microg/mL, 2.9 microg/mL, and 1.6 microg/mL, respectively. The main alkaloid with anticholinesterase activity in PP was isolated and identified as geissospermine. PP significantly reduced scopolamine-induced amnesia in the passive avoidance and Morris water maze tests, at 30 mg/kg i.p. (given 45 min before the test sessions). At the highest effective dose (60 mg/kg), administration of PP did not result in noticeable peripheral or central cholinergic side effects. Only after administration of 200 mg/kg, mice showed convulsions affecting the whole body followed by death. These results show that compounds present in G. vellosii stembark have anticholinesterase activity, and that they can revert cognitive deficits in a model of cholinergic hypofunction.
Assuntos
Acetilcolinesterase/efeitos dos fármacos , Apocynaceae/química , Inibidores da Colinesterase/farmacologia , Transtornos da Memória/tratamento farmacológico , Extratos Vegetais/uso terapêutico , Caules de Planta/química , Escopolamina/toxicidade , Animais , Aprendizagem da Esquiva , Masculino , Aprendizagem em Labirinto , Transtornos da Memória/induzido quimicamente , Camundongos , Extratos Vegetais/farmacologiaRESUMO
Cold agglutinin disease (CAD) with autoimmune haemolytic anemia is characterized by the production of harmful cold autoantibodies associated with increased red cell destruction during exposure to cold. The treatment of CAD is very difficult and a great effort is required to obtain therapeutic success. Cyclophosphamide is a potent immunosuppressive agent which is widely used in all bone marrow transplantation conditioning regimens for patients with acquired severe aplastic anemia. In this report, we describe the case of a coronary artery disease patient with severe CAD, but without lymphoproliferative disease, in which general measures and immunosuppressive therapies were adopted, there by avoiding blood transfusions.
A doença por aglutininas a frio (CAD) cursando com anemia hemolítica auto-imune (AHAI) é decorrente da produção de autoanticorpos que reagem muito bem a baixas temperaturas, dirigidos contra hemácias autólogas. A habilidade desses anticorpos em destruir as hemácias encontra-se diretamente relacionada à sua capacidade em fixar complemento durante a exposição do paciente a baixas temperaturas. A AHAI por anticorpos frios pode ser idiopática - ausência de doença de base - ou secundária, geralmente associada a desordens linfoproliferativas de células B ou determinados processos infecciosos. A hemólise é intravascular, através de aglutininas da classe IgM, com teste direto da antiglobulina humana positivo para complemento. O tratamento da CAD é difícil, exigindo um esforço contínuo, necessário para se obter sucesso terapêutico. A ciclofosfamida é um agente imunossupressor potente, amplamente utilizado em transplantes de medula óssea, particularmente nos portadores de anemia aplástica. Descrevemos o caso de um coronariopata portador de CAD severa, cuja exploração diagnóstica excluiu doença linfoproliferativa. Adotamos medidas gerais de suporte e terapia imunossupressora, coibindo o uso de hemotransfusões.
Assuntos
Humanos , Masculino , Idoso , Anemia Hemolítica Autoimune , Doença da Artéria CoronarianaRESUMO
LASSBio-767 [(-)-3-O-acetyl-spectaline] and LASSBio-822 [(-)-3-O-tert-Boc-spectaline] were recently described as cholinesterase inhibitors derived from the natural piperidine alkaloid (-)-spectaline, obtained from the flowers of Senna spectabilis (Fabaceae). We investigated their mechanism of inhibition of acetylcholinesterase and their efficacy in reversing scopolamine-induced amnesia. Competition assays with the substrate acetylthiocholine showed a concentration-dependent reduction in rat brain cholinesterase Vmax without changes in apparent Km. The kinetic data for LASSBio-767 and LASSBio-822 were best fit by a model of simple linear noncompetitive inhibition with Ki of 6.1 microM and 7.5 microM, respectively. A dilution assay showed a fast and complete reversal of inhibition, independent of incubation time. Simulated docking of the compounds into the catalytic gorge of Torpedo acetylcholinesterase showed interactions with the peripheral anionic site, but not with the catalytic triad. Anti-amnestic effects in mice were assessed in a step-down passive avoidance test and in the Morris water maze 30 min after injection of scopolamine (1 mg/kg i.p.). Saline, LASSBio-767, or LASSBio-822 was administered 15 min before scopolamine. Both compounds reversed the scopolamine-induced reduction in step-down latency at 0.1 mg/kg i.p. LASSBio-767 reversed scopolamine-induced changes in water maze escape latency at 1 mg/kg i.p. or p.o., while its cholinergic side effects were absent or mild up to 30 mg/kg i.p. (LD50 above 100 mg/kg i.p.). Thus, the (-)-spectaline derivatives are potent cholinergic agents in vivo, with a unique profile combining noncompetitive cholinesterase inhibition and CNS selectivity, with few peripheral side effects.
Assuntos
Alcaloides/farmacologia , Inibidores da Colinesterase/farmacologia , Piperidinas/farmacologia , Acetilcolinesterase/metabolismo , Administração Oral , Alcaloides/química , Alcaloides/isolamento & purificação , Amnésia/induzido quimicamente , Amnésia/tratamento farmacológico , Amnésia/fisiopatologia , Animais , Comportamento Animal/efeitos dos fármacos , Encéfalo/enzimologia , Catálise/efeitos dos fármacos , Inibidores da Colinesterase/administração & dosagem , Inibidores da Colinesterase/química , Relação Dose-Resposta a Droga , Drogas em Investigação/administração & dosagem , Drogas em Investigação/química , Drogas em Investigação/farmacologia , Injeções Intraperitoneais , Cinética , Aprendizagem em Labirinto/efeitos dos fármacos , Camundongos , Modelos Moleculares , Estrutura Molecular , Piperidinas/administração & dosagem , Piperidinas/química , Ratos , Ratos Wistar , Escopolamina/toxicidade , Percepção Espacial/efeitos dos fármacos , EstereoisomerismoRESUMO
Five new piperidine alkaloids were designed from natural (-)-3-O-acetyl-spectaline and (-)-spectaline that were obtained from the flowers of Senna spectabilis (sin. Cassia spectabilis, Leguminosae). Two semi-synthetic analogues (7 and 9) inhibited rat brain acetylcholinesterase, showing IC50 of 7.32 and 15.1 microM, and were 21 and 9.5 times less potent against rat brain butyrylcholinesterase, respectively. Compound 9 (1mg/kg, i.p.) was fully efficacious in reverting scopolamine-induced amnesia in mice. The two active compounds (7 and 9) did not show overt toxic effects at the doses tested in vivo.