Nalidixic acid inhibits the aggregation of HSA: Utilizing the molecular simulations to uncover the detailed insights

Abstract

Neurodegenerative diseases such as Parkinson's and Alzheimer's lead to the gradual decline of the nervous system, resulting in cognitive and motor impairments. With an aging population, the prevalence and associated healthcare costs are anticipated to rise. Misfolded protein aggregates are central to these diseases, disrupting cellular function and causing neuronal death. Preventing these toxic aggregates could preserve neurons and slow disease progression. Understanding how to inhibit protein aggregation is crucial for developing effective treatments. We explored the effect of nalidixic acid (NA) on protein aggregation using human serum albumin (HSA) as model protein. In vitro assays demonstrated that NA significantly reduced ThT fluorescence by 47.10 % and decreased turbidity by 63.07 %. NA also protected the protein’s hydrophobic surfaces. The α-helical content of HSA dropped from 56.23 % to 11.43 % but was restored to 38.53 % with NA. We then utilized advanced molecular simulations to understand the kinetics and mechanism of aggregation inhibition by NA. Binding studies showed that NA attaches to HSA’s subdomain IIA with a binding energy of −7.8 kcal/mol through hydrogen bonds, Van der Waals forces, and hydrophobic interactions. Molecular simulations confirmed the stability of HSA-NA complex. Additionally, NA increased solvent accessibility of HSA_282–292 oligomers, reduced hydrogen bonding, and prevented β-sheet formation. Compared to existing anti-aggregation strategies, NA offers a promising alternative with its potential therapeutic applications in neurodegenerative diseases by stabilizing protein structures and preventing misfolding. These findings highlight NA's potential as a candidate for inhibiting protein aggregation and offer insights for therapeutic approaches. Further experimental studies utilizing in vivo models are needed to validate the anti-aggregation potential of NA.