Peptides as modulators of α-synuclein aggregation.

α-Synuclein forms amyloid deposits in the dopaminergic neurons; a process that is believed to contribute to the Parkinson's disease. An emerging theme in amyloid research is the hypothesis that the toxic species produced during amyloid formation share common physic-chemical features and exert their effects by common modes. This prompted the idea that molecules able to inhibit a protein aggregation process may cross-react with other amyloidogenic proteins, interfering in their fibrils formation. We investigate the ability of analogues of the heptapeptide H-Arg-Lys-Val-MePhe-Tyr-Thr-Trp- OH2, an inhibitor of Aß-peptide aggregation, to cross-react with α-synuclein interfering with its fibril formation. The influence of the MePhe topography on the interaction with α-synuclein has also been evaluated, replacing the MePhe residue with either Phe or the conformationally restricted Tic residues. Peptides interact with good affinity with the α-synuclein monomer, promoting its aggregation process. This work provides the basis for the development of new drugs based on peptidomimetics able to modify the oligomers - mature fibrils equilibrium towards this last species.

Ceftriaxone blocks the polymerization of α-synuclein and exerts neuroprotective effects in vitro.

The ß-lactam antibiotic ceftriaxone was suggested as a therapeutic agent in several neurodegenerative disorders, either for its ability to counteract glutamate-mediated toxicity, as in cerebral ischemia, or for its ability to enhance the degradation of misfolded proteins, as in Alexander's disease. Recently, the efficacy of ceftriaxone in neuroprotection of dopaminergic neurons in a rat model of Parkinson's disease was documented. However, which characteristics of ceftriaxone mediate its therapeutic effects remains unclear. Since, at the molecular level, neuronal α-synuclein inclusions and pathological α-synuclein transmission play a leading role in initiation of Parkinson-like neurodegeneration, we thought of investigating, by circular dichroism spectroscopy, the capability of ceftriaxone to interact with α-synuclein. We found that ceftriaxone binds with good affinity to α-synuclein and blocks its in vitro polymerization. Considering this finding, we also documented that ceftriaxone exerts neuroprotective action in an in vitro model of Parkinson's disease. Our data, in addition to the findings on neuroprotective activity of ceftriaxone on Parkinson-like neurodegeneration in vivo, indicates ceftriaxone as a potential agent in treatment of Parkinson's disease.

Small molecules interacting with α-synuclein: antiaggregating and cytoprotective properties.

Curcumin, a dietary polyphenol, has shown a potential to act on the symptoms of neurodegenerative disorders, including Alzheimer's and Parkinson's diseases, as a consequence of its antioxidant, anti-inflammatory and anti-protein aggregation properties. Unfortunately, curcumin undergoes rapid degradation at physiological pH into ferulic acid, vanillin and dehydrozingerone, making it an unlikely drug candidate. Here, we evaluated the ability of some curcumin by-products: dehydrozingerone (1), its O-methyl derivative (2), zingerone (3), and their biphenyl analogues (4-6) to interact with α-synuclein (AS), using CD and fluorescence spectroscopy. In addition, the antioxidant properties and the cytoprotective effects in rat pheochromocytoma (PC12) cells prior to intoxication with H2O2, MPP+ and MnCl2 were examined while the Congo red assay was used to evaluate the ability of these compounds to prevent aggregation of AS. We found that the biphenyl zingerone analogue (6) interacts with high affinity with AS and also displays the best antioxidant properties while the biphenyl analogues of dehydrozingerone (4) and of O-methyl-dehydrozingerone (5) are able to partially inhibit the aggregation process of AS, suggesting the potential role of a hydroxylated biphenyl scaffold in the design of AS aggregation inhibitors.

Peptide-receptor ligands and multivalent approach.

The overexpression of peptide receptors in human tumours makes peptide-ligands attractive agents for the development of specific diagnostic imaging and/or therapy of cancers. Solid-phase peptide synthesis, modern phage display technology and combinatorial peptide chemistry have profoundly affected the pool of available targeting peptides for efficient and specific delivery of imaging or therapeutic label molecules. Additionally, the availability of a wide range of bifunctional chelating agents for the radiolabelling of bioactive peptides with radionuclides has produced a wide variety of useful radiopharmaceutical molecules. This review article examines the principal receptors-binding peptides and their overexpression on tumour cells. We discuss the advantage and the challenges in developing multivalent peptide-based ligands summarising their design strategies and applications.

Cell-Penetrating Peptides: A Comparative Study on Lipid Affinity and Cargo Delivery Properties.

A growing number of natural and/or synthetic peptides with cell membrane penetrating capability have been identified and described in the past years. These molecules have been considered promising tools for delivering bioactive compounds into various cell types. Although the mechanism of uptake is still unclear, it is reasonable to assume that the relative contribute of each proposed mechanism could differ for the same peptide, depending on experimental protocol and cargo molecule composition. In this work we try to connect the capability to interact with model lipid membrane and structural and chemical characteristics of CPPs in order to obtain a biophysical classification that predicts the behavior of CPP-cargo molecules in cell systems. Indeed, the binding with cell membrane is one of the primary step in the interaction of CPPs with cells, and consequently the studies on model membrane could become important for understanding peptide-membrane interaction on a molecular level, explaining how CPPs may translocate a membrane without destroying it and how this interactions come into play in shuttling CPPs via different routes with different efficiency. We analyzed by CD and fluorescence spectroscopies the binding properties of six different CPPs (kFGF, Nle54-Antp and Tat derived peptides, and oligoarginine peptides containing 6, 8 or 10 residues) in absence or presence of the same cargo peptide (the 392-401pTyr396 fragment of HS1 protein). The phospholipid binding properties were correlated to the conformational and chemical characteristics of peptides, as well as to the cell penetrating properties of the CPP-cargo conjugates. Results show that even if certain physico-chemical properties (conformation, positive charge) govern CPP capability to interact with the model membrane, these cannot fully explain cell-permeability properties.