ABSTRACT
Despite of the fact that functionally diverse phospholipase A2 variants of snake venoms are well characterized at the level of protein and gene sequences; the patterns of individual snake venom PLA2s are poorly known. We investigated the activity, molecular weights and isoelectric points of the phospholipase A2s of some medically important snake venoms in Egypt. Portrayal of the phospholipase A2 activity of the vipers, "Pseudocerastes persicus fieldi, Cerastes cerastes and Echis carinatus" and the elapids "Naja haje, Walterinnesia aegyptia and Naja nigricollis" venoms revealed that: 1- The elapid venoms, with the exception of Naja haje, displayed higher PLA2 activity than viper venoms; 2- The molecular weights of the phospholipase A2 variants were close to 14 kDa; 3- The major phospholipase A2s of Naja nigricollis were basic proteins while those of Walterinnesia aegyptia venom were acidic proteins; 4- The Naja nigricollis and Pseudocerastes persicus fieldi venoms possessed the highest phospholipase A2 activity while the Walterinnesia aegyptia and Pseudocerastes persicu fieldi had the highest hemolytic activity of the tested elapids and vipers, respectively; 5- The in vitro hemolytic activities of the venoms were inhibited by the heterologous antivenoms, suggesting that the venom hemolytic factor [s] have shared epitopes. The data provided biochemical information of snake venoms phospholipase A2 which allowed designing procedure for isolation of the phospholipase A2s to study their pharmacological effects
Subject(s)
Animals , Phospholipases A/pharmacology , Molecular Weight , Isoelectric Point , Viperidae , ElapidaeABSTRACT
Na doença de Alzheimer (DA) leve há prejuízo da memória de curta (MCD) e de longa duração (MLD) episódica, em correlação com a hipofunção do hipocampo. A atividade da fosfolipase A2 (PLA2) foi encontrada reduzida no hipocampo de pacientes com DA. A inibição da PLA2 na região CA1 de fatias hipocampais de ratos impede a indução da potenciação de longa duração, um mecanismo neuronal da MLD. Neste estudo, investigou-se os efeitos de injeções de inibidores da PLA2 na região CA1 do hipocampo de ratos sobre a formação da MCD e da MLD. A inibição da atividade da PLA2 prejudicou a formação da MCD e da MLD, sugerindo que a atividade reduzida da PLA2 pode contribuir para o prejuízo de memória na DA./In mild Alzheimers disease (AD) there is impairment of episodic short-term (STM) and long-term memory (LTM), in correlation with the hypofunction of the hippocampus. Phospholipase A2 (PLA2) activity was found to be reduced in the hippocampus of AD patients. PLA2 inhibition in the CA1 region of rat hippocampal slices prevents the induction of long-term potentiation, a neuronal mechanism of LTM. In this study, we investigated the effects of injections of PLA2 inhibitors into the CA1 region of rat hippocampus on STM and LTM formation. PLA2 inhibition impaired STM and LTM formation, suggesting that reduced PLA2 activity may contribute to memory impairment in AD...
Subject(s)
Animals , Male , Adult , Rats , Alzheimer Disease , Disease Models, Animal , Hippocampus , Membrane Fluidity , Phospholipases A/pharmacology , Memory , Neurochemistry/methods , Rats, WistarABSTRACT
Screening of the biochemical-pharmacological properties of the crude venom from the snake Lachesis muta indicated the presence of phospholipase A2 (PLA2; 5260 U/mg protein), procoagulant (2630 U/mg protein), platelet aggregating (43 U/mg protein) and caseinolytic activities (6670 U/mg protein). These activities were separated by filtration of the crude venom on Sephacryl S-200. The material containing PLA2 activity was further fractioned by DEAE-cellulose ion exchange chromatography into four active fractions (F-I to F-IV, containing 1.7, 1.2, 0.3, and 0.05 per cent of the crude venom protein, respectively) by stepwise elution with buffers of increasing ionic strength. All fractions presented a molecular weight of approximately 15,000 and isoelectric points in the range pH 4.6-6.0. In addition to their indirect hemolytic activity, the partially purified fractions inhibited platelet aggregation induced either by collagen or thrombin. p-Bromophenacyl bromide-treated fractions lost both phospholipase A2 activity and their inhibitory effect on collagen-induced platelet aggregation
Subject(s)
Animals , Phospholipases A/isolation & purification , Viper Venoms/chemistry , Chromatography, Gel , Chromatography, Ion Exchange , Phospholipases A/pharmacology , Platelet Aggregation , Viper Venoms/enzymology , Viper Venoms/metabolism , ViperidaeABSTRACT
Hemolytic activity of eight Peruvian snake venoms from the families Viperidae and Elapidae (Bothrops atrox, B. pictus, B. hyoprorus, B. bilineatus, B. neuwedii, Lachesis m. muta, Crotalus d. terrificus, Microrus tschudi), and three Brazilian viperids (B. jararacussu, B. alternatus and C. d. collilineatus) is described. None of the venoms cause direct lysis on washed human erythrocytes. However, all of then caused indirect hemolysis provided that the incubation medium contains an exogenous source of lecithin. Venom of Micrurus tschudi was the most hemolytic (HD50 2.8 ug/ml) while that of B. bilineatus was the least (HD50 681.3 ug/ml). Only six of eleven venoms showed parallel curves of hemolytic activity, and the HD50 varied from 198 to 681 ug/ml and the following decreasing order of hemolytic activity was obtained: L. muta, C. d. terrificus, C. d. collilineatus, B. hyoprorus, B. bilineatus, B. alternatus
Subject(s)
Humans , Animals , Hemolysis , Viper Venoms/pharmacology , Elapid Venoms/pharmacology , Cobra Cardiotoxin Proteins/pharmacology , Phospholipases A/pharmacology , Regression AnalysisABSTRACT
Se utilizó la enzima fosfolipasa A como modelo para el estudio del bloqueador de receptores de estrógenos 13R051 a las concentraciones de 30, 60, 80 y 360 mmol/L, con vistas a conocer a través de los cambios funcionales de la enzima los posibles procesos moleculares que pudieran explicar algunas de las propiedades farmacológicas del bloqueador. Se evidenció que la fosfolipasa A resultó un modelo de utilidad para el estudio de estos tipos de fármacos, y se demostró que el agente 13R051 fue capaz de activar a esta acilhidrolasa exhibiendo propiedades líticas. Los resultados cinéticos sugieren que el agente 13R051 estimula la actividad enzimática pero dentro de límites determinados, lo que representa una ventaja desde el punto de vista de su utilización clínica
Subject(s)
Phospholipases A/pharmacologyABSTRACT
La fosfolipasa A2 miotoxica del veneno de Bothrops asper (tercipelo) prolonga el tiempo de recalcificación de plasmas de cinco especies de mamíferos. La fosfolipasa A2 hidroliza los fosfolípidos del plasma, en tanto que su acción inhibitoria es revertida cuando se adicionan fosfolípidos plaquetarios. Estas dos observaciones sugieren que la acción anticoagulante se debe a una alteración de los fosfolípidos plasmáticos necesarios para la coagulación. Tanto la actividad enzimática como la anticoagulante se mantuvieron aún después de calentamiento a 95è-C durante 10 min. Pese a su acción anticoagulante in vitro, la fosfolipasa A2 no prolonga el tiempo de coagulación luego de inoculación intravenosa en ratones