Thiophene-Based Dual Modulators of Aβ and Tau Aggregation

Hybrid molecules synergistically mitigate ferroptosis and amyloid-associated toxicities in Alzheimer's disease

Alzheimer's disease (AD) is a neurodegenerative disorder characterized by the build-up of extracellular amyloid β (Aβ) plaques and intracellular neurofibrillary tangles (NFTs). Ferroptosis, an iron (Fe)-dependent form of cell death plays a significant role in the multifaceted AD pathogenesis through generation of reactive oxygen species (ROS), mitochondrial damage, lipid peroxidation, and reduction in glutathione peroxidase 4 (GPX4) enzyme activity and levels. Aberrant liquid-liquid phase separation (LLPS) of tau drives the growth and maturation of NFTs contributing to AD pathogenesis. In this study, we strategically combined the structural and functional properties of gallic acid (GA) and cyclic dipeptides (CDPs) to synthesize hybrid molecules that effectively target both ferroptosis and amyloid toxicity in AD. This innovative approach marks a paradigm shift from conventional therapeutic strategies. This is the first report of a synthetic small molecule (GCTR) that effectively combats ferroptosis, simultaneously restoring enzymatic activity and enhancing cellular levels of its master regulator, GPX4. Further, GCTR disrupts Fe3+-induced LLPS of tau, and aids in attenuation of abnormal tau fibrillization. The synergistic action of GCTR in combating both ferroptosis and amyloid toxicity, bolstered by GPX4 enhancement and modulation of Fe3+-induced tau LLPS, holds promise for the development of small molecule-based novel therapeutics for AD.

Biphasic modulation of tau liquid-liquid phase separation by polyphenols

Molecular tools that modulate tau liquid-liquid phase separation (LLPS) promise to treat tauopathies. We screened a set of polyphenols and demonstrated concentration-dependent biphasic modulation of tau LLPS by gallic acid (GA), showcasing its ability to expedite the liquid-to-gel transition in tau condensates and effectively impede the formation of deleterious fibrillar aggregates.

Synergetic effect of β-asarone and cannabidiol against Aβ aggregation in vitro and in vivo

Alzheimer's disease (AD) is a complex and multifactorial neurodegenerative disorder, and it is unlikely that any single drug or intervention will be very successful. The pathophysiology of Alzheimer's disease involves a range of complicated biological processes, including the accumulation of beta-amyloid protein and tau protein. Given the complexity of AD and amyloid accumulation, a combination of interventions remains to be further explored. Here, we investigated the potential of combining β-asarone and cannabidiol (CBD) as a treatment for AD. The study analyzed the combined effects of these two phytochemicals on beta-amyloid (Aβ) protein aggregation and toxicity in bulk solution, in cells as well as in C.elegans. We detailed the morphological and size changes of Aβ40 aggregates in the presence of β-asarone and cannabidiol. More importantly, the presence of both compounds synergistically inhibited apoptosis and downregulated relative gene expression in cells, and that it may also slow aging, decrease the rate of paralysis, enhance learning capacity, and boost autophagy activity in C.elegans. Our studies suggest that multiple drugs, like β-asarone and CBD, may be potentially developed as a medicinal adjunct in the treatment of AD, although further clinical trials are needed to determine the efficacy and safety of this combination treatment in humans.

Thiophene-Based Ligands: Design, Synthesis and Their Utilization for Optical Assignment of Polymorphic-Disease-Associated Protein Aggregates

The development of ligands for detecting protein aggregates is of great interest, as these aggregated proteinaceous species are the pathological hallmarks of several devastating diseases, including Alzheimer's disease. In this regard, thiophene-based ligands have emerged as powerful tools for fluorescent assessment of these pathological entities. The intrinsic conformationally sensitive photophysical properties of poly- and oligothiophenes have allowed optical assignment of disease-associated protein aggregates in tissue sections, as well as real-time in vivo imaging of protein deposits. Herein, we recount the chemical evolution of different generations of thiophene-based ligands, and exemplify their use for the optical distinction of polymorphic protein aggregates. Furthermore, the chemical determinants for achieving a superior fluorescent thiophene-based ligand, as well as the next generation of thiophene-based ligands targeting distinct aggregated species are described. Finally, the directions for future research into the chemical design of thiophene-based ligands that can aid in resolving the scientific challenges around protein aggregation diseases are discussed.

Multipronged diagnostic and therapeutic strategies for Alzheimer's disease

Alzheimer's disease (AD) is a progressive neurodegenerative disorder and a major contributor to dementia cases worldwide. AD is clinically characterized by learning, memory, and cognitive deficits. The accumulation of extracellular amyloid β (Aβ) plaques and neurofibrillary tangles (NFTs) of tau are the pathological hallmarks of AD and are explored as targets for clinical diagnosis and therapy. AD pathology is poorly understood and there are no fully approved diagnosis and treatments. Notwithstanding the gap, decades of research in understanding disease mechanisms have revealed the multifactorial nature of AD. As a result, multipronged and holistic approaches are pertinent to targeting multiple biomarkers and targets for developing effective diagnosis and therapeutics. In this perspective, recent developments in Aβ and tau targeted diagnostic and therapeutic tools are discussed. Novel indirect, combination, and circulating biomarkers as potential diagnostic targets are highlighted. We underline the importance of multiplexing and multimodal detection of multiple biomarkers to generate biomarker fingerprints as a reliable diagnostic strategy. The classical therapeutics targeting Aβ and tau aggregation pathways are described with bottlenecks in the strategy. Drug discovery efforts targeting multifaceted toxicity involving protein aggregation, metal toxicity, oxidative stress, mitochondrial damage, and neuroinflammation are highlighted. Recent efforts focused on multipronged strategies to rationally design multifunctional modulators targeting multiple pathological factors are presented as future drug development strategies to discover potential therapeutics for AD.

Rationally Designed Molecules Synergistically Modulate Multifaceted Aβ Toxicity, Microglial Activation, and Neuroinflammation

Synergistic modulation of multifaceted toxicity is the key to tackle multifactorial Alzheimer's disease (AD). The etiology of AD includes amyloid β (Aβ) amyloidosis, metal ion dyshomeostasis, reactive oxygen species (ROS), oxidative stress, mitochondrial damage, and neuroinflammation. We rationally designed multifunctional modulators by integrating pharmacophores for metal chelation, antioxidant and anti-inflammatory properties, and modulation of Aβ42 aggregation on the naphthalene monoimide (NMI) scaffold. The in vitro and cellular studies of NMIs revealed that M3 synergistically modulates metal-independent and -dependent amyloid toxicity, scavenges ROS, alleviates oxidative stress, and emulates Nrf2-mediated stress response in neuronal cells. M3 effectively reduced structural and functional damage of mitochondria, reduced Cyt c levels, and rescued cells from apoptosis. The biological atomic force microscopy and Western blot analysis revealed the ability of M3 to suppress microglial activation and neuroinflammation through inhibition of the NF-κβ pathway. The synergistic action of M3 is in agreement with our design strategy to develop a multifunctional therapeutic candidate by integrating multiple pharmacophores with distinct structural and functional elements to ameliorate the multifaceted toxicity of AD.