Venenos de serpentes do gênero Bothrops: impacto da glicosilação na complexidade dos proteomas e função de toxinas / Bothrops snake venoms: impact of glycosylation on the complexity of proteomes and toxins function

A variabilidade estrutural é uma característica das proteínas de venenos de serpentes, e a glicosilação é uma das principais modificações pós-traducionais que contribui para a diversificação de seus proteomas. Recentes estudos de nosso grupo demonstraram que venenos do gênero Bothrops são marcadamente definidos pelo seu conteúdo de glicoproteínas, e que a maioria das estruturas de N-glicanos dos tipos híbrido e complexo identificados em oito venenos deste gênero contêm unidades de ácido siálico. Em paralelo, em glicoproteínas do veneno de B. cotiara foi identificada a presença de uma estrutura de N-acetilglicosamina bissecada. Assim, com o objetivo de investigar a variação do conteúdo de glicoproteínas, assim como os mecanismos envolvidos na geração dos diferentes venenos de Bothrops, neste estudo foram analisados comparativamente os glicoproteomas de nove venenos do gênero Bothrops (B. atrox, B. cotiara, B. erythromelas, B. fonsecai, B. insularis, B. jararaca, B. jararacussu, B. moojeni e B. neuwiedi). As abordagens glicoproteômicas envolveram cromatografia de afinidade e ensaio de pull-down utilizando, respectivamente, as lectinas SNA (aglutinina de Sambucus nigra) e MAL I (lectina de Maackia amurensis), que mostram afinidade por unidades de ácido siálico nas posições, respectivamente, α2,6 e α2,3; e cromatografia de afinidade com a lectina PHA-E (eritroaglutinina de Phaseolus vulgaris), que reconhece N-acetilglicosamina bissecada. Ainda, eletroforese de proteínas, blot de lectina, e identificação de proteínas por espectrometria de massas foram empregadas para caracterizar os glicoproteomas. As lectinas geraram frações dos venenos enriquecidas de diferentes componentes, onde as principais classes de glicoproteínas identificadas foram metaloprotease, serinoprotease, e L-amino ácido oxidase, além de outras enzimas pouco abundantes nos venenos. Os diferentes conteúdos de proteínas reconhecidas por essas lectinas, com especificidades distintas, ressaltaram novos aspectos da variabilidade dos subproteomas de glicoproteínas desses venenos, dependendo da espécie. Ainda, considerando que metaloproteases e serinoproteases são componentes abundantes nesses venenos e fundamentais no quadro de envenenamento botrópico, e que estas enzimas contêm diversos sítios de glicosilação, o papel das unidades de ácido siálico na atividade proteolítica das mesmas foi avaliado. Assim, a remoção enzimática de ácido siálico (i) alterou o padrão de gelatinólise em zimografia da maioria dos venenos, (ii) diminuiu a atividade proteolítica de alguns venenos sobre o fibrinogênio e a atividade coagulante do plasma humano de todos os venenos, e (iii) alterou o perfil de hidrólise de proteínas plasmáticas pelo veneno de B. jararaca, indicando que este carboidrato pode desempenhar um papel na interação das proteases com seus substratos proteicos. Em contraste, o perfil da atividade amidolítica dos venenos não se alterou após a remoção de ácido siálico e incubação com o substrato Bz-Arg-pNA, indicando que ácido siálico não é essencial em N-glicanos de serinoproteases atuando sobre substratos não proteicos. Em conjunto, esses resultados expandem o conhecimento sobre a variabilidade de proteomas de venenos do gênero Bothrops e apontam a importância das cadeias de carboidratos contendo ácido siálico nas atividades enzimáticas das proteases desses venenos

Structural variability is a feature of snake venom proteins, and glycosylation is one of the main post-translational modifications that contributes to the diversification of venom proteomes. Recent studies by our group have shown that Bothrops venoms are markedly defined by their glycoprotein content, and that most hybrid and complex N-glycan structures identified in eight venoms of this genus contain sialic acid units. In parallel, the presence of a bisected N-acetylglucosamine structure was identified in B. cotiara venom glycoproteins. Thus, with the aim of investigating the variation in the content of glycoproteins, as well as the mechanisms involved in the generation of different Bothrops venoms, in this study the glycoproteomes of nine Bothrops venoms (B. atrox, B. cotiara, B. erythromelas, B. fonsecai, B. insularis, B. jararaca, B. jararacussu, B. moojeni e B. neuwiedi) were comparatively analyzed. The glycoproteomic approaches involved affinity chromatography and pulldown using, respectively, the lectins SNA (Sambucus nigra agglutinin) and MAL I (Maackia amurensis lectin), which show affinity for sialic acid units at positions, respectively, α2,6 and α2,3, and affinity chromatography with PHA-E (Phaseolus vulgaris erythroagglutinin), which recognizes bisected N-acetylglucosamine. In addition, protein electrophoresis, lectin blot, and protein identification by mass spectrometry were employed for glycoproteome characterization. The lectins generated venom fractions enriched with different components, where the main classes of glycoproteins identified were metalloprotease, serine protease, and L-amino acid oxidase, in addition to other low abundant enzymes. The different contents of proteins recognized by these lectins of distinct specificities highlighted new aspects of the variability of the glycoprotein subproteomes of these venoms, depending on the species. Furthermore, considering that metalloproteases and serine proteases are abundant components of these venoms and essential in Bothrops envenomation, and that these enzymes contain several glycosylation sites, the role of sialic acid units in their proteolytic activities was evaluated. Thus, enzymatic removal of sialic acid (i) altered the pattern of gelatinolysis in zymography of most venoms, (ii) decreased the proteolytic activity of some venoms on fibrinogen and the clotting activity of human plasma of all venoms, and (iii) altered the hydrolysis profile of plasma proteins by B. jararaca venom, indicating that this carbohydrate may play a role in the interaction of proteases with their protein substrates. In contrast, the profile of amidolytic activity of the venoms did not change after removal of sialic acid and incubation with the substrate Bz-Arg-pNA, indicating that sialic acid is not essential in N-glycans of serine proteases acting on small substrates. Together, these results expand the knowledge about the variability of proteomes of Bothrops venoms and point to the importance of carbohydrate chains containing sialic acid in the enzymatic activities of venom proteases

Plant-antivenom: database of anti-venom medicinal plants

Plant-antivenom is a computational Websystem about medicinal plants with anti-venom properties. The system consists of a database of these plants, including scientific publications on this subject and amino acid sequences of active principles from venomous animals. The system relates these data allowing their integration through different search applications. For the development of the system, the first surveys were conducted in scientific literature, allowing the creation of a publication database in a library for reading and user interaction. Then, classes of categories were created, allowing the use of tags and the organization of content. This database on medicinal plants has information such as family, species, isolated compounds, activity, inhibited animal venoms, among others. Provision is made for submission of new information by registered users, by the use of wiki tools. Content submitted is released in accordance to permission rules defined by the system. The database on biological venom protein amino acid sequences was structured from the essential information from National Center for Biotechnology Information (NCBI). Plant-antivenom's interface is simple, contributing to a fast and functional access to the system and the integration of different data registered on it. Plant-antivenom system is available on the Internet at http://gbi.fmrp.usp.br/plantantivenom.

Ensayos clínicos de exenatida y su rol en el tratamiento de la diabetes tipo 2 / Exenatide trials for the treatment of type 2 diabetes

La diabetes mellitus tipo 2 es una enfermedad metabólica crónica, frecuente y progresiva, responsable del 90% de los casos de diabetes a nivel mundial. Aproximadamente el 60% de los individuos que padecen este desorden no alcanzan niveles óptimos de hemoglobina glicosilada, a pesar de la disponibilidad de numerosas alternativas terapéuticas. Los dos objetivos más importantes a cumplir en el manejo actual de la diabetes tipo 2 son la capacidad de los agentes antidiabéticos de exhibir eficacia prolongada y la capacidad de preservar la función de las células beta pancreáticas. El efecto incretina se encuentra reducido en pacientes con diabetes tipo 2. Exenatida pertenece a un nuevo grupo de drogas antidiabéticas que mejoran el control de la glucemia en estos pacientes a través de mecanismos fisiológicos glucorregulatorios que mejoran el efecto incretina. Los ensayos clínicos fase III con exenatida demostraron una reducción media de aproximadamente el 1% en los valores de hemoglobina glicosilada. Los datos a largo plazo de estudios de extensión no controlados indican una mejoría sostenida en los niveles de hemoglobina glicosilada y una reducción progresiva del peso luego de 3 años de tratamiento con esta droga. La droga es generalmente bien tolerada y los efectos adversos más frecuentes son los gastrointestinales, con una intensidad leve a moderada. El objetivo de esta revisión es analizar la evidencia publicada hasta la fecha sobre la eficacia y tolerabilidad del tratamiento con exenatida y su rol en el tratamiento de la diabetes tipo 2.

Type 2 diabetes mellitus is a common, chronic and progressive metabolic disorder, which accounts for 90% of diabetes cases worldwide. Approximately 60% of individuals with the disease do not achieve target glycosylated hemoglobin levels, despite the availability of many antidiabetic agents. The two most important needs in the present management of diabetes are the ability of antidiabetic agents to exhibit prolonged efficacy in reducing hyperglycemia and to preserve beta-cell function. The incretin effect appears to be reduced in patients with type 2 diabetes. Exenatide is the first in a novel class of antidiabetic drugs that improves glycemic control in patients with type 2 diabetes through several physiological glucoregulatory mechanisms which improve the incretin effect. Overall, mean glycosylated hemoglobin (HbA1c) reductions achieved in the exenatide phase III clinical trials were in the order of 1%. Long-term data from the uncontrolled open-label extension studies indicate that adjunctive exenatide therapy leads to sustained improvements in HbA1c and progressive weight loss for at least 3 years. The drug is generally well tolerated. The most common adverse events were gastrointestinal in nature and mild to moderate in severity. The objective of this review is to discuss the available published evidence on exenatide therapeutic efficacy and tolerability, and the role of this new drug in the treatment of type 2 diabetes.

Exenatide and acute pancreatitis.

For a female, type 2 diabetic patient, with 4 years duration of diabetes, Exenatide (Byetta) was prescribed as glycaemic control was not satisfactory along with Glimepiride and Metformin. She had gastrointestinal disturbances, since the first day of the injection. From the eighth day she developed signs of acute pancreatitis which was confirmed with CT-Scan and biochemical investigations. Byetta was withdrawn, the patient was treated for acute pancreatitis and the symptoms subsided.

Acidentes com ofidios peconhentos durante a gestacao / Accidents with snakes during pregnancy

A ocorrencia de ataques por ofidios peconhentos durante a gestacao e incomum na pratica da obstetricia. Pacientes que sofrem ataques por ofidios peconhentos necessitam de...

Empozoñamiento pediátrica: una revisión de siete años / Scorpioning sting in pediatrics age: a review of seven years

Se revisó la casuística de empozoñamiento escorpiónico en el Servicio de Pediatría del Hospital Dr. Domingo Luciani durante el período 1988-1995. Se presentan 11 casos procedentes del Distrito Sucre, Estado Miranda, cuyas edades varían desde los 10 meses hasta los 12 años, de estos sólo uno ameritó ingreso en la unidad de cuidados intensivos; no se presentó ninguna defunción.