Amyloid pore-channel hypothesis: effect of ethanol on aggregation state using frog oocytes for an Alzheimer's disease study.

Alzheimer's disease severely compromises cognitive function. One of the mechanisms to explain the pathology of Alzheimer's disease has been the hypotheses of amyloid-pore/channel formation by complex Aß-aggregates. Clinical studies suggested the moderate alcohol consumption can reduces probability developing neurodegenerative pathologies. A recent report explored the ability of ethanol to disrupt the generation of complex Aß in vitro and reduce the toxicity in two cell lines. Molecular dynamics simulations were applied to understand how ethanol blocks the aggregation of amyloid. On the other hand, the in silico modeling showed ethanol effect over the dynamics assembling for complex Aß-aggregates mediated by break the hydrosaline bridges between Asp 23 and Lys 28, was are key element for amyloid dimerization. The amyloid pore/channel hypothesis has been explored only in neuronal models, however recently experiments suggested the frog oocytes such an excellent model to explore the mechanism of the amyloid pore/channel hypothesis. So, the used of frog oocytes to explored the mechanism of amyloid aggregates is new, mainly for amyloid/pore hypothesis. Therefore, this experimental model is a powerful tool to explore the mechanism implicates in the Alzheimer's disease pathology and also suggests a model to prevent the Alzheimer's disease pathology.

Ethanol reduces amyloid aggregation in vitro and prevents toxicity in cell lines.

BACKGROUND: Alzheimer's disease (AD) alters cognitive functions. A mixture of soluble ß-amyloid aggregates (Aß) are known to act as toxic agents. It has been suggested that moderate alcohol intake reduces the development of neurodegenerative diseases, but the molecular mechanisms leading to this type of prevention have been elusive. We show the ethanol effect in the generation of complex Aß in vitro and the impact on the viability of two cell lines. METHODS: The effect of ethanol on the kinetics of ß-amyloid aggregation in vitro was assessed by turbimetry. Soluble- and ethanol-treated ß-amyloid were added to the cell lines HEK and PC-12 to compare their effects on metabolic activity using the MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) assay. In addition, we used molecular modeling to assess the impact of exposure to ethanol on the structure of ß-amyloid. RESULTS: Exposure to soluble ß-amyloid was toxic to both cell lines; however, exposing the cells to ß-amyloid aggregated in 10 mmol ethanol prevented the effect. In silico modeling suggested that ethanol alters the dynamics for assembling Aß by disrupting a critical salt bridge between residues Asp 23 and Lys 28, required for amyloid dimerization. Thus, ethanol prevented the formation of complex short (∼100 nm) Aß, which are related to higher cell toxicity. CONCLUSIONS: Ethanol prevents the formation of stable Aß dimers in vitro, thus protecting the cells maintained in culture. Accordingly, in silico modelling predicts that soluble ß-amyloid molecules do not form stable multimers when exposed to ethanol.

Molecular characterization, electrophysiological and contraceptive effect of chilean latrodectus venom / Caracterización molecular, electrofisiológica y efecto anticonceptivo del veneno de latrodectus chilena

Since the 1970s, There have been studies of the venom of Latrodectus sp. spiders, in particular the latrotoxin (LTX) of Latrodectus mactans. Many of the studies were aimed at understanding the action of the venom on the muscular system. Now accepted that LTX is able to generate a calcium-permeable membrane pore and modulate the release of synaptic vesicles that activate a receptor and induce cellular changes. Interestingly, when work began with venom obtained from the Latrodectus sp present in Chile, it generated clinical indications similar to the bite of this spider in another country, with some differences in intensity. The purpose of the first studies was to understand the systemic mechanisms of this venom, and other active compounds were studied for biological interest. It was found that these molecules are capable of causing systemic effects such as changes in muscle contraction; of generating vascular relaxation and synaptic and cellular modulation; and of altering potassium conductance channels. Based on this evidence, we suggested biotechnological applications to characterize low molecular-weight compounds obtained from the Chilean Latrodectus venom and exploring the effects on the electrophysiology in oocytes and neurons, and the contraceptive effect on spermatozoa.

Desde los años 70, se han realizado estudios con el veneno de arañas Latrodectus sp, en particular la latrotoxina (LTX) de Latrodectus mactans. Muchos de estos estudios estuvieron enfocados a entender la acción del veneno sobre el sistema muscular. Hoy en día es aceptado que la LTX es capaz de generar un poro de membrana permeable a calcio y modular la liberación de vesículas sinápticas que activan un receptor e inducen cambios celulares. Interesantemente, cuando comenzamos a trabajar con el veneno obtenido de Latrodectus sp. presente en Chile, ésto generó indicaciones clínicas similares a la picadura de esta araña en otros países, con algunas diferencias en su intensidad. El propósito de estos primeros estudios fue entender los mecanismos sistémicos de este veneno y además otros compuestos activos fueron estudiados para interés biológico. Se ha encontrado que estas moléculas son capaces de causar efectos sistémicos así como cambios en la contracción muscular; generar relajación vascular y modulación sináptica y celular; y de alterar los canales de conductancia de potasio. Basados en estas evidencias, nosotros sugerimos usar aplicaciones biotecnológicas para caracterizar los compuestos de bajo peso molecular obtenidos del veneno de Latrodectus Chilena y explorar los efectos sobre la electrofisiología en ovocitos y neuronas, y el efecto anticonceptivo sobre los espermatozoides.