Potential preventive disease-modifying pharmacological strategies to delay late onset Alzheimer’s disease

Alzheimer’s disease(AD)is a progressive neurodegenerative disease that was histopathologically characterized in the brain by the presence of extracellular senile plaques made of amyloid β peptides and intracellular neurofibrillary tangles composed of hyperphosphorylated Tau protein.Over the years,AD has been classified in two subgroups:early onset or familial AD and late onset or sporadic AD.On the one hand,familial AD has been described to be the result of genetic mutations that cause,in some cases,for the overproduction of amyloid β.On the other,the cause of late onset or sporadic AD is still unclear even though several hypotheses have been proposed to explain the process of severe and progressive memory and cognitive loss.In the present review,some of the current hypotheses that try to explain the origin of late onset or sporadic AD have been summarized.Also,their potential implication in the development of new drugs for the presymptomatic treatment of late onset or sporadic AD has been considered.

Plant-herbivore assemblages under natural conditions are driven by plant size,not chemical defenses

Aims Plant secondary metabolites have been traditionally recognized as key traits regulating plant-herbivore assemblages.However,the ecological relevance of secondary metabolites as resistance mecha-nisms in comparison to other plant attributes,including physical,morphological or ecological traits,has been recently questioned.We aim to evaluate the role of chemical defenses,plant size and the presence of insect competitors on driving the differences in her-bivory damage under natural conditions.Methods We performed a replicated field study on the herbivore commu-nity associated with four Senecio species(S.lividus,S.vulgaris,S.inaequidens and S.pterophorus)during a full-reproductive season in Montseny Natural Park(catalonia,NE Spain).Pyrrolizidine alka-loids(PAs),the most characteristic chemical defenses of Senecio due to their toxic effects on herbivores,were analyzed by gas chro-matography.Individual plant size was estimated by the number of flower heads produced over the entire reproductive season.We used linear mixed models to explore the relationships between total PA concentrations,plant size and herbivory levels.Important Findings PA concentrations were not related to the natural guild of herbivores within any plant species or insect type.Moreover,no significant interactions were found between insect species sharing the same host plants.In contrast,herbivore abundance was positively related to plant size in S.vulgaris,S.lividus and S.inaequidens.We found no evidence that PAs confer an increased plant resistance against herbivores in Senecio.Our study supports the hypothesis that plant chemical defenses have a secondary role in determining plant-her-bivore assemblages in comparison to other plant traits under the complexity of natural conditions.