Estudo da secreção cutânea da Rhinella schneideri em novos mecanismos e tratamentos para a Doença de Alzheimer

Abstract

Alzheimer’s Disease (AD) is a global public health priority, accounting for 70% of dementia diagnoses. Abnormal processing of β amyloid precursor protein generates peptides that oligomerize and accumulate in brain tissue. Failures occurring in the removal process of these peptides lead to neurodegeneration, with synaptic and neuronal losses. In addition, changes in the lysosomal-autophagic system contribute to the enhancement of the activity of lysosomal cathepsins. Moreover, in AD, tau protein is hyperphosphorylated, which results in its dissociation from microtubules, self-oligomerization, and neurofibrillary tangles formation. In this context, the discovery of new molecules that improve the comprehension of the mechanisms involved in AD pathogenesis, and possible intervention in disease progression are extremely relevant. In the present work, bioactive molecules from Rhinella schneideri skin secretion (SS), were investigated towards: (I) inhibition of caspases and cathepsins B and D; (II) improvement of neuron-like cells neuronal network; (III) reduction of tau protein expression and (IV) reduction of βA-42 cytotoxicity. SS fractions and subfractions were obtained by liquid-liquid partition, followed by RP-HPLC fractioning, and molecules identification by mass spectrometry. SS, in 250 μg/mL, inhibited cathepsin B enzyme activity, but not cathepsin D, caspase -1, and -6 ones. High Content Screening analysis showed that polar subfraction 5 (PsF5) was able to reduce tau protein expression and to improve neuron-like cells neuronal network. MTT assay demonstrated that SS, polar and apolar fractions, and PsF5 did not revert βA-42 cytotoxicity in neuron-like cells. Taken together, the results obtained indicate that SS contains molecules with the potential to aid in the comprehension of AD physiopathology and in the development of new therapeutical strategies.