Multiadducts of C60 Modulate Amyloid-β Fibrillation with Dual Acetylcholinesterase Inhibition and Antioxidant Properties: In Vitro and In Silico Studies

Abstract

Background: Amyloid-β (Aβ) fibrils induce cognitive impairment and neuronal loss, leading to onset of Alzheimer’s disease (AD). The inhibition of Aβ aggregation has been proposed as a therapeutic strategy for AD. Pristine C60 has shown the capacity to interact with the Aβ peptide and interfere with fibril formation but induces significant toxic effects in vitro and in vivo. Objective: To evaluate the potential of a series of C60 multiadducts to inhibit the Aβ fibrillization. Methods: A series of C60 multiadducts with four to six diethyl malonyl and their corresponding disodium-malonyl substituents were synthesized as individual isomers. Their potential on Aβ fibrillization inhibition was evaluated in vitro, in cellulo, and silico. Antioxidant activity, acetylcholinesterase inhibition capacity, and toxicity were assessed in vitro. Results: The multiadducts modulate Aβ fibrils formation without inducing cell toxicity, and that the number and polarity of the substituents play a significant role in the adducts efficacy to modulate Aβ aggregation. The molecular mechanism of fullerene-Aβ interaction and modulation was identified. Furthermore, the fullerene derivatives exhibited antioxidant capacity and reduction of acetylcholinesterase activity. Conclusion: Multiadducts of C60 are novel multi-target-directed ligand molecules that could hold considerable promise as the starting point for the development of AD therapies.

Click synthesis of dendronized malonates for the preparation of amphiphilic dendro[60]fullerenes

“…In previous works, our research group found that the sodium salts of fullerenemalonates obtained by the B-H reaction presented useful properties for the treatment of Alzheimer's diseases. [37][38][39] Since the hydrophobic and hydrophilic nature of the tested molecules play important roles in their activity, it is important to find the precise hydrophilic-hydrophobic balance in the molecule to develop a better inhibitor for the amyloid β-peptide fibrils formation, and an improved modulator for acetylcholinesterase.…”

“…Even though the dendronized products herein reported may seem disadvantageous compared to those already outlined, in terms of aqueous solubility, those molecular systems are mostly multi-adducts in which the C 60 hydrophobic moiety is shielded and becomes inaccessible to interact with the amyloid β peptide, thus avoiding its aggregation into fibrils. [37][38][39] Therefore, an adequate hydrophilic-hydrophobic balance becomes crucial for achieving a suitable activity in a biological environment. On one side, the hydrophobic portions of C 60 are necessary for the interaction with biological targets, while the hydrophilic part contributes to the aqueous solubility of the system.…”

“…1, structure I) for: (i) the inhibition of amyloid β peptide fibril formation, (ii) the regulation of acetyl-cholinesterase (AChE) activity and (iii) their antioxidant capacity. [37][38][39] These studies showed that the number of C 60 substituents and their polar nature influenced their AChE inhibitory activity and biocompatibility. From the experimental evidence, the fullerene malonate sodium salts were the most active compounds, particularly the bis-and tetra-adducts.…”

“…38,39 In silico studies of C 60 derivatives revealed that the hydrophobic interactions between C 60 and the amyloid β peptide are important to inhibit its aggregation into fibrils, and this interaction decreases as the number of polar substituents increases, nevertheless, the polar substituents are also important for the water solubility, due to hydrogen bonding interactions with certain serine amino acids in the peptide. [37][38][39] Therefore, it is significant to develop a molecular structure with the correct hydrophilic-hydrophobic balance. In this regard, dendronization has been used as a practical strategy to induce amphiphilicity for micelle formation, thus enhancing the aqueous solubility and stability of several organic molecules as well as materials.…”

“…40 Dendrons are the branched sections of dendrimers which maintain the structural information programmed into these polymeric architectures including the controlled multivalency, monodispersity, globularity, and solubility in a wide range of solvents. [30][31][32][33][34][35][36][37][38][39][40][41][42][43] Polyester dendrimers and dendrons derived from 2,2′-bis(hydroxymethyl)propionic acid (bis-MPA) have gained singular attention related to their high aqueous solubility because of their hydroxyl groups in the periphery, that in turn, induced biocompatibility, and hydrolytic degradability. 44,45 These dendrons have used to enhance the aqueous solubility of curcumin by ester linkage 46,47 or by click chemistry.…”