Polyphenols as protective agents in Parkinson’s disease models

SUMMARY

The main goal of the present research proposal is to assess the neuroprotective mechanisms of polyphenols metabolites in several neurodegeneration in vitro models. Additionally it foresees scientific knowledge generation concerning the mechanism underlying the neuroprotection by polyphenols metabolites. This proposal also envisages the identification of nutraceutical/therapeutic compounds that may address prevention and therapeutics of these devastating incurable diseases.

Plant polyphenols, at subtoxic doses are described to have neuroprotective action. They activate adaptive cellular stress–response pathways, via regulation of gene expression in a variety of cells including neurons, rather than exerting antioxidant activity per se. Animal model studies have reported experimental evidence that dietary polyphenols metabolites are bioavailable with accumulation in brain after long-term consumption and can reverse age-related cognitive decline and disease-related neurodegeneration. However, the mechanism underlying the apparent beneficial effects remains unclear.

Most of the functional in vitro studies are reported to intact bioactive phytochemicals but for these compounds to have bioefficacy in a specific tissue or organ they must be bioavailable. Only limited attempts were done to evaluate the impact of their digestion and subsequent bioefficacy. Part of the novelty of this proposal is to address this subject, the evaluation of bioactivity in neurodegeneration for digested metabolites from polyphenols.

Yeast-models have contributed significantly to the elucidation of fundamental aspects of protein aggregation, in particular alpha-synuclein (αsyn) misfolding and aggregation, a hallmark of diseases like Parkinson's disease (PD), Dementia with Lewy Bodies, and multiple system atrophy. Although the mechanisms of αsyn aggregation and related cytotoxicity remain elusive, oxidative stress plays a prominent role in disease onset and development. Therefore, screening for agents that either prevent the production of ROS directly and/or modulate toxic asyn aggregation would be of particular therapeutic interest, these aspects will be focused and explored in this project. Using knockout strains of Saccharomyces cerevisiae with different sensitivity to oxidative stress the cell rescue mediated by the polyphenols metabolite fractions will be evaluated. Another yeast-model will define the compounds that alleviate αsyn-induced cytotoxicity. However, yeast screening approaches should be validated in more physiologically relevant models, neuronal and animal models, allowing the identification and confirmation of novel targets and lead compounds. Since the project is focused on neuroprotective mechanisms of polyphenols metabolites, the more proficient fractions detected in yeast models will be tested in the buildup of αsyn aggregates and toxicity, in a human PD cell model. Using a bimolecular fluorescence complementation assay (BiFC) developed by a team of this project, the effect of polyphenols metabolite fractions on asyn oligomerization will be assessed. Another PD-model developed for this proposal, is the chronic exposition of a neuroblastoma cell to rotenone. This drug is a common insecticide that causes degeneration of dopaminergic neurons and PD-like symptoms by inhibition of the mitochondrial complex I reproducing the formation of Lewy bodies (LBs).

In this model, cellular and biochemical mechanisms will be investigated at several levels:

(i) cell viability and apoptosis,

(ii) endogenous cellular redox status,

(iii) the involvement of the ubiquitin/proteasome system (UPS),

(iv) the buildup of LBs,

(v) differential expressed genes due to the exposition of the human PD cell model to polyphenols metabolite fraction.

In conclusion, neuroprotective activities of bioactive compounds from plants will be explored to minimize the neurodegeneration processes in particular protein aggregation in PD models. The proposed research is novel and original, presenting two distinct focuses: the generation of scientific knowledge and the concern for potential nutraceutical/pharmaceutical applications.

MAIN RESEARCH AREA: Biological sciences - Cellular e Molecular Biology

BUDGET: €189.587,00

PRINCIPAL CONTRACTOR: Instituto de Tecnologia Química e Biológica (ITQB NOVA)

PARTICIPATING INSTITUTION: Instituto de Medicina Molecular (iMM LIsboa)

COLLABORATIONS: Dr. Derek Stewart, from The James Hutton Institute (JHI)