Search

In the last decade, a large number of evidences points to the misfolding, aggregation and accumulation of structurally abnormal proteins, termed amyloid, as a common pathogenic mechanism of a range of increasingly common human disorders, including Alzheimer`s Disease (AD) and type II diabetes mellitus (T2DM). In particular, AD and T2DM are characterized by the accumulation of the amyloid-β (Aβ) peptide in neuronal tissues and islet amyloid polypeptide (IAPP) in pancreatic cells, respectively (1), implicitly suggesting that targeting protein misfolding and self-assembly would cure the diseases. However, the failure of all clinical trials focusing on anti-aggregating drugs has clearly demonstrated that a deeper understanding of the phenomena involved in proteome maintenance is needed. It is widely known that cells express an integrated array of proteolytic machineries that control protein homeostasis (proteostasis). As a matter of fact, the latest studies suggest that pathological conditions occur when the equilibrium between the production and the clearance of the involved protein results unbalanced. The ubiquitin–proteasome system (UPS) is the major quality control pathway responsible for cellular homeostasis; it is the primary proteolytic route for misfolded proteins and ubiquitination is utilized as a degradation signal (2). Many researchers have screened a number of molecules using the whole UPS as target (proteasome activators, inhibitors of deubiquitinating enzymes DUBs or ubistatins); however, very few molecules, if any, selected by using this strategy have shown to have the potential to be pipelined to clinical trials. But, due to the multifactorial nature of protein diseases, it may be difficult to find an effective drug by screening molecules on a single target. This study evaluates the ability of silybins A and B, components of the natural product silymarin, to rescue the proteostatic balance of the amyloidogenic peptides Aβ and IAPP against several targets: proteasome, polyubiquitination, membrane protection, amyloid aggregation and oxidative stress. The obtained results evidence the important role of the stereochemistry, demonstrating the high potential of these natural compounds in anti-AD therapeutics. Our multi-target strategy to rescue proteostasis opens the door to a new approach to face these important pathologies.