Near-Infrared Fluorescent Probes as Imaging and Theranostic Modalities for Amyloid-Beta and Tau Aggregates in Alzheimer's Disease

Development of Triphenylmethane Dyes for In Vivo Fluorescence Imaging of Aβ Oligomers

Detection of amyloid β (Aβ) oligomers, regarded as the most toxic aggregated forms of Aβ, can contribute to the diagnosis and treatment of Alzheimer's disease (AD). Thus, the development of imaging probes for in vivo visualization of Aβ oligomers is crucial. However, the structural uncertainty regarding Aβ oligomers makes it difficult to design imaging probes with high sensitivity to Aβ oligomers against highly aggregated Aβ fibrils. In this study, we developed Aβ oligomer-selective fluorescent probes based on triphenylmethane dyes through screening of commercially available compounds followed by structure-activity relationship (SAR) studies on cyclic or acyclic 4-dialkylamino groups. We synthesized 11 triarylmethane-based Aβ oligomer probe (TAMAOP) derivatives. In vitro evaluation of fluorescence properties, TAMAOP-9, which had bulky 4-diisobutylamino groups introduced into three benzenes of a twisted triphenylmethane backbone, showed marked fluorescence enhancement in the presence of Aβ oligomers and demonstrated high selectivity for Aβ oligomers against Aβ fibrils. In docking studies using the Aβ trimer model, TAMAOP-9 bound to the hydrophobic surface and interacted with the side chain of Phe20. In vitro section staining revealed that TAMAOP-9 could visualize Aβ oligomers in the brains of AD model mice. An in vivo fluorescence imaging study using TAMAOP-9 showed significantly higher fluorescence signals from the brains of AD model mice than those of age-matched wild-type mice, confirmed by ex vivo section observation. These results suggest that TAMAOP-9 is a promising Aβ oligomer-targeting fluorescent probe applicable to in vivo imaging.

Design and synthesis of hemicyanine-based NIRF probe for detecting Aβ aggregates in Alzheimer's disease

Alzheimer's disease (AD), a progressive neurodegenerative disorder, has garnered increased attention due to its substantial economic burden and the escalating global aging phenomenon. Amyloid-β deposition is a key pathogenic marker observed in the brains of Alzheimer's sufferers. Based on real-time, safe, low-cost, and commonly used, near-infrared fluorescence (NIRF) imaging technology have become an essential technique for the detection of AD in recent years. In this work, NIRF probes with hemicyanine structure were designed, synthesized and evaluated for imaging Aβ aggregates in the brain. We use the hemicyanine structure as the parent nucleus to enhance the probe's optical properties. The introduction of PEG chain is to improve the probe's brain dynamice properties, and the alkyl chain on the N atom is to enhance the fluorescence intensity of the probe after binding to the Aβ aggregates as much as possible. Among these probes, Z2, Z3, Z6, X3, X6 and T1 showed excellent optical properties and high affinity to Aβ aggregates (Kd = 24.31 ∼ 59.60 nM). In vitro brain section staining and in vivo NIRF imaging demonstrated that X6 exhibited superior discrimination between Tg mice and WT mice, and X6 has the best brain clearance rate. As a result, X6 was identified as the optimal probe. Furthermore, the docking theory calculation results aided in describing X6's binding behavior with Aβ aggregates. As a high-affinity, high-selectivity, safe and effective probe of targeting Aβ aggregates, X6 is a promising NIRF probe for in vivo detection of Aβ aggregates in the AD brain.

Recent Advances in Fluorescent Theranostics for Alzheimer's Disease: A Comprehensive Survey on Design, Synthesis, and Properties

Alzheimer's disease (AD) is the most common form of neurodegenerative dementia that is rapidly becoming a major health problem, especially in developed countries because of their increasing life expectancy. Two main problems are often associated with the disease: (i) the absence of a widely accessible "gold-standard" for early diagnosis and (ii) lack of effective therapies with disease-modifying effects. The recent success of the monoclonal antibody lecanemab played an important role not only in clarifying a possible druggable pathway but also in spelling the revival of small molecule drug discovery. Unlike bulky biologics, small molecules are structurally less complex, generally cheaper, and compatible with at-home oral consumption, making it feasible for people to start their drug regimen early and stay on it longer. In this sense, small-molecule near-infrared fluorescent theranostics have been gaining more and more attention from the scientific community, as they have the potential to simultaneously provide diagnostic outputs and deliver therapeutic action, paving the way toward personalized medicine in AD patients. They also have the potential to shift the diagnostic "status-quo" from expensive and limited-access PET radiotracers toward inexpensive and handy imaging tools widely available for primary patient screening and preclinical animal studies. Herein, we review the most recent advances in the field of fluorescent theranostics for Alzheimer's disease, detailing their design strategies, synthetic approaches and imaging and therapeutic properties in vitro and in vivo. With this Review, we intend to provide a milestone in the acquired knowledge in the field of AD theranostics, encouraging the future development of properly designed theranostic compounds with improved chances to reach clinical applications.

Design, Synthesis, and Characterization of Novel Styryl Dyes as Fluorescent Probes for Tau Aggregate Detection in Vitro and in Cells

A series of novel styryl dye derivatives incorporating indolium and quinolinium core structures were successfully synthesized to explore their interacting and binding capabilities with tau aggregates in vitro and in cells. The synthesized dyes exhibited enhanced fluorescence emission in viscous environments due to the rotatable bond confinement in the core structure. Dye 4, containing a quinolinium moeity and featuring two cationic sites, demonstrated a 28-fold increase in fluorescence emission upon binding to tau aggregates. This dye could also stain tau aggregates in living cells, confirmed by cell imaging using confocal fluorescence microscopy. A molecular docking study was conducted to provide additional visualization and support for binding interactions. This work offers novel and non-cytotoxic fluorescent probes with desirable photophysical properties, which could potentially be used for studying tau aggregates in living cells, prompting further development of new fluorescent probes for early Alzheimer's disease detection.

Rofecoxib derivatives as NIR fluorescent probes for mitochondrial viscosity and in vivo imaging of Aβ plaques

Alzheimer's disease (AD) is a multifaceted neurodegenerative disorder for which the underlying causes remain largely unknown. Therefore, the development of imaging agents capable of detecting biomarkers associated with this disease is crucial. Dual-functional probes are particularly important as they can track two biomarkers at the same time and examine their interaction. Herein, Two red-emissive dual-functional fluorescent probes, RC-1 and RA-2, have been designed and synthesized based on the Rofecoxib scaffold. When probes (RC-1 and RA-2) are in viscous media or bound to Aβ aggregates, there is a dramatic enhancement in fluorescence emission due to the constraint of the twisted intramolecular charge transfer effect (TICT). RC-1 with ideal blood-brain barrier (BBB) penetrability enables visualization of Aβ plaques in vivo AD mice. These results suggest that RC-1 and RA-2 have the potential to serve as powerful fluorescence imaging agents for Aβ and mitochondria-related pathology in AD.

n Vivo

Noninvasive imaging of amyloid-β (Aβ) species in vivo is important for the early diagnosis of Alzheimer's disease (AD). In this paper, we report a near-infrared (NIR) fluorescence (FL) and positron emission tomography (PET) bimodal probe (NIR-[68Ga]) for in vivo imaging of both soluble and insoluble Aβ species. NIR-[68Ga] holds a high binding affinity, high selectivity and high sensitivity toward Aβ42 monomers, oligomers, and aggregates in vitro. In vivo imaging results show that NIR-[68Ga] can cross the blood-brain-barrier (BBB), and produce significantly higher PET and NIR FL bimodal signals in the brains of APP/PS1 transgenic AD mice relative to that of age-matched wild-type mice, which are also validated by the ex vivo autoradiography and histological staining images. Our results demonstrate that NIR-[68Ga] is an efficient NIR FL and PET bimodal probe for the sensitive imaging of soluble and insoluble Aβ species in AD mice.

Antioxidant, anti-inflammatory and epigenetic potential of curcumin in Alzheimer's disease

Alzheimer's disease (AD) constitutes a multifactorial neurodegenerative pathology characterized by cognitive deterioration, personality alterations, and behavioral shifts. The ongoing brain impairment process poses significant challenges for therapeutic interventions due to activating multiple neurotoxic pathways. Current pharmacological interventions have shown limited efficacy and are associated with significant side effects. Approaches focusing on the early interference with disease pathways, before activation of broad neurotoxic processes, could be promising to slow down symptomatic progression of the disease. Curcumin-an integral component of traditional medicine in numerous cultures worldwide-has garnered interest as a promising AD treatment. Current research indicates that curcumin may exhibit therapeutic potential in neurodegenerative pathologies, attributed to its potent anti-inflammatory and antioxidant properties. Additionally, curcumin and its derivatives have demonstrated an ability to modulate cellular pathways via epigenetic mechanisms. This article aims to raise awareness of the neuroprotective properties of curcuminoids that could provide therapeutic benefits in AD. The paper provides a comprehensive overview of the neuroprotective efficacy of curcumin against signaling pathways that could be involved in AD and summarizes recent evidence of the biological efficiency of curcumins in vivo.

Coordination Chemistry of Sulfur-Containing Bifunctional Chelators: Toward in Vivo Stabilization of 64Cu PET Imaging Agents for Alzheimer's Disease

The broader utilization of 64Cu positron emission tomography (PET) imaging agents has been hindered by the unproductive demetalation induced by bioreductants. To advance the development of 64Cu-based PET imaging tracers for Alzheimer's Disease (AD), there is a need for novel ligand design strategies. In this study, we developed sulfur-containing dithiapyridinophane (N2S2) bifunctional chelators (BFCs) as well as all nitrogen-based diazapyridinophane (N4) BFCs to compare their abilities to chelate Cu and target Aβ aggregates. Through spectrophotometric titrations and electrochemical measurements, we have demonstrated that the N2S2-based BFCs exhibit >10 orders of magnitude higher binding affinity toward Cu(I) compared to their N4-based counterparts, while both types of BFCs exhibit high stability constants toward Cu(II). Notably, solid state structures for both Cu(II) and Cu(I) complexes supported by the two ligand frameworks were obtained, providing molecular insights into their copper chelating abilities. Aβ binding experiments were conducted to study the structure-affinity relationship, and fluorescence microscopy imaging studies confirmed the selective labeling of the BFCs and their copper complexes. Furthermore, we investigated the potential of these ligands for the 64Cu-based PET imaging of AD through radiolabeling and autoradiography studies. We believe our findings provide molecular insights into the design of bifunctional Cu chelators that can effectively stabilize both Cu(II) and Cu(I) and, thus, can have significant implications for the development of 64Cu PET imaging as a diagnostic tool for AD.

A Novel Near-Infrared Fluorescence Probe THK-565 Enables In Vivo Detection of Amyloid Deposits in Alzheimer's Disease Mouse Model

PURPOSE

Noninvasive imaging of protein aggregates in the brain is critical for the early diagnosis, disease monitoring, and evaluation of the effectiveness of novel therapies for Alzheimer's disease (AD). Near-infrared fluorescence (NIRF) imaging with specific probes is a promising technique for the in vivo detection of protein deposits without radiation exposure. Comprehensive screening of fluorescent compounds identified a novel compound, THK-565, for the in vivo imaging of amyloid-β (Aβ) deposits in the mouse brain. This study assessed whether THK-565 could detect amyloid-β deposits in vivo in the AD mouse model.

PROCEDURES

The fluorescent properties of THK-565 were evaluated in the presence and absence of Aβ fibrils. APP knock-in (APP-KI) mice were used as an animal model of AD. In vivo NIRF images were acquired after the intravenous administration of THK-565 and THK-265 in mice. The binding selectivity of THK-565 to Aβ was evaluated using brain slices obtained from these mouse models.

RESULTS

The fluorescence intensity of the THK-565 solution substantially increased by mixing with Aβ fibrils. The maximum emission wavelength of the complex of THK-565 and Aβ fibrils was 704 nm, which was within the optical window range. THK-565 selectively bound to amyloid deposits in brain sections of APP-KI mice After the intravenous administration of THK-565, the fluorescence signal in the head of APP-KI mice was significantly higher than that of wild-type mice and higher than that after administration of THK-265. Ex vivo analysis confirmed that the THK-565 signal corresponded to Aβ immunostaining in the brain sections of these mice.

CONCLUSIONS

A novel NIRF probe, THK-565, enabled the in vivo detection of Aβ deposits in the brains of the AD mouse model, suggesting that NIRF imaging with THK-565 could non-invasively assess disease-specific pathology in AD.

Amphiphilic Molecules Exhibiting Zwitterionic Excited-State Intramolecular Proton Transfer and Near-Infrared Emission for the Detection of Amyloid β Aggregates in Alzheimer's Disease

Chromophores with zwitterionic excited-state intramolecular proton transfer (ESIPT) have been shown to have larger Stock shifts and red-shifted emission wavelengths compared to the conventional π-delocalized ESIPT molecules. However, there is still a dearth of design strategies to expand the current library of zwitterionic ESIPT compounds. Herein, a novel zwitterionic excited-state intramolecular proton transfer system is reported, enabled by addition of 1,4,7-triazacyclononane (TACN) fragments on a dicyanomethylene-4H-pyran (DCM) scaffold. The solvent-dependent steady-state photophysical studies, pKa measurements, and computational analysis strongly support that the ESIPT process is more efficient with two TACN groups attached to the DCM scaffold and not affected by polar protic solvents. Impressively, compound DCM-OH-2-DT exhibits a near-infrared (NIR) emission at 740 nm along with an uncommonly large Stokes shift. Moreover, DCM-OH-2-DT shows high affinity towards soluble amyloid β (Aβ) oligomers in vitro and in 5xFAD mouse brain sections, and we have successfully applied DCM-OH-2-DT for the in vivo imaging of Aβ aggregates and demonstrated its potential use as an early diagnostic agent for AD. Overall, this study can provide a general molecular design strategy for developing new zwitterionic ESIPT compounds with NIR emission in vivo imaging applications.

Recent progress of small-molecule-based theranostic agents in Alzheimer's disease

Alzheimer's disease (AD) is the most common form of neurodegenerative dementia. As a multifactorial disease, AD involves several etiopathogenic mechanisms, in which multiple pathological factors are interconnected with each other. This complicated and unclear pathogenesis makes AD lack effective diagnosis and treatment. Theranostics, exerting the synergistic effect of diagnostic and therapeutic functions, would provide a promising strategy for exploring AD pathogenesis and developing drugs for combating AD. With the efforts in small drug-like molecules for both diagnosis and treatment of AD, small-molecule-based theranostic agents have attracted significant attention owing to their facile synthesis, high biocompatibility and reproducibility, and easy clearance from the body through the excretion systems. In this review, the small-molecule-based theranostic agents reported in the literature for anti-AD are classified into four groups according to their diagnostic modalities. Their design rationales, chemical structures, and working mechanisms for theranostics are summarized. Finally, the opportunities for small-molecule-based theranostic agents in AD are also proposed.

Advanced Techniques for Detecting Protein Misfolding and Aggregation in Cellular Environments

Protein misfolding and aggregation, a key contributor to the progression of numerous neurodegenerative diseases, results in functional deficiencies and the creation of harmful intermediates. Detailed visualization of this misfolding process is of paramount importance for improving our understanding of disease mechanisms and for the development of potential therapeutic strategies. While in vitro studies using purified proteins have been instrumental in delivering significant insights into protein misfolding, the behavior of these proteins in the complex milieu of living cells often diverges significantly from such simplified environments. Biomedical imaging performed in cell provides cellular-level information with high physiological and pathological relevance, often surpassing the depth of information attainable through in vitro methods. This review highlights a variety of methodologies used to scrutinize protein misfolding within biological systems. This includes optical-based methods, strategies leaning on mass spectrometry, in-cell nuclear magnetic resonance, and cryo-electron microscopy. Recent advancements in these techniques have notably deepened our understanding of protein misfolding processes and the features of the resulting misfolded species within living cells. The progression in these fields promises to catalyze further breakthroughs in our comprehension of neurodegenerative disease mechanisms and potential therapeutic interventions.

In Vivo Near-Infrared Fluorescence Imaging Selective for Soluble Amyloid β Aggregates Using y-Shaped BODIPY Derivative

Soluble amyloid β (Aβ) aggregates, suggested to be the most toxic forms of Aβ, draw attention as therapeutic targets and biomarkers of Alzheimer's disease (AD). As soluble Aβ aggregates are transient and diverse, imaging their diverse forms in vivo is expected to have a marked impact on research and diagnosis of AD. Herein, we report a near-infrared fluorescent (NIRF) probe, BAOP-16, targeting diverse soluble Aβ aggregates. BAOP-16, whose molecular shape resembles "y", showed a marked selective increase in fluorescence intensity upon binding to soluble Aβ aggregates in the near-infrared region and a high binding affinity for them. Additionally, BAOP-16 could detect Aβ oligomers in the brains of Aβ-inoculated model mice. In an in vivo fluorescence imaging study of BAOP-16, brains of AD model mice displayed significantly higher fluorescence signals than those of wild-type mice. These results indicate that BAOP-16 could be useful for the in vivo NIRF imaging of diverse soluble Aβ aggregates.

Near-Infrared Bodipy-Based Molecular Rotors for β-Amyloid Imaging In Vivo

β-amyloid (Aβ) is one of the important biomarkers for diagnosing Alzheimer's disease (AD). Many near-infrared probes based on the donor-π-acceptor structure have been developed to detect Aβ. Most reported Aβ probes are based on the N,N-dimethylamino group as the ideal donor, which is a widely accepted binding unit. As such, the development of fluorescent probes with improved binding units to detect Aβ is urgently required. Therefore, with this research three anchoring molecular rotor electron donors consisting of cyclic amines of different ring sizes are developed, namely five-membered ring (TPyr), six-membered ring (TPip), and seven-membered ring (THAI). These new anchored molecular rotors are connected to a 4,4-difluoro-4-bora-3a,4a-diaza-s-indacene (BODIPY) and named TPyrBDP, TPipBDP, and THAIBDP. These probes exhibit high affinities (from 28 to 54 nm) for Aβ1-42 aggregates. The six-membered ring dye TPipBDP exhibits the highest signal-to-noise (75.5-fold) and higher affinity (28.30 ± 5.94 nm). TPipBDP can cross the blood-brain barrier and exhibits higher fluorescence enhancement with APP/PS1 (AD) double transgenic (Tg) mice than with wild-type (WT) mice.

Bioluminescence Imaging with Functional Amyloid Reservoirs in Alzheimer's Disease Models

Bioluminescence imaging has changed the daily practice of preclinical research on cancer and other diseases over the last few decades; however, it has rarely been applied in preclinical research on Alzheimer's disease (AD). In this Article, we demonstrated that bioluminescence imaging could be used to report the levels of amyloid beta (Aβ) species in vivo. We hypothesized that AkaLumine, a newly discovered substrate for luciferase, could bind to Aβ aggregates and plaques. We further speculated that the Aβ aggregates/fibrils/plaques could be considered as "functional amyloids", which have a reservoir function to sequester and release AkaLumine to control the bioluminescence intensity, which could be used to report the levels of Aβs. Our hypotheses have been validated via in vitro solution tests, mimic studies with brain tissues and mice, two-photon imaging with AD mice, and in vivo bioluminescence imaging using transgenic AD mice that were virally transduced with AkaLuciferase (AkaLuc), a new luciferase that generates bioluminescence in the near-infrared window. As expected, compared to the control group, we observed that the Aβ group showed lower bioluminescence intensity due to AkaLumine sequestering at early time points, while higher intensity was due to AkaLumine releasing at later time points. Lastly, we demonstrated that this method could be used to monitor AD progression and the therapeutic effectiveness of avagacestat, a well-studied gamma-secretase inhibitor. Importantly, a good correlation (R2 = 0.81) was established between in vivo bioluminescence signals and Aβ burdens of the tested AD mice. We believe that our approach can be easily implemented into daily imaging experiments and has tremendous potential to change the daily practice of preclinical AD research.

Recent Advances in the Development of Near-Infrared Fluorescent Probes for the in Vivo Brain Imaging of Amyloid-β Species in Alzheimer's Disease

The deposition of β-amyloid (Aβ) plaques in the parenchymal and cortical regions of the brain of Alzheimer's disease (AD) patients is considered the foremost pathological hallmark of the disease. The early diagnosis of AD is paramount in order to effective management and treatment of the disease. Developing near-infrared fluorescence (NIRF) probes targeting Aβ species is a potential and attractive approach suitable for the early and timely diagnosis of AD. The advantages of the NIRF probes over other tools include real-time detection, higher sensitivity, resolution, comparatively inexpensive experimental setup, and noninvasive nature. Currently, enormous progress is being observed in the development of NIRF probes for the in vivo imaging of Aβ species. Several strategies, i.e., the classical push-pull approach, "turn-on" effect, aggregation-induced emission (AIE), and resonance energy transfer (RET), have been exploited for development. We have outlined and discussed the recently emerged NIRF probes with different design strategies targeting Aβ species for ex vivo and in vivo imaging. We believe that understanding the recent development enables the prospect of the rational design of probes and will pave the way for developing future novel probes for early diagnosis of AD.

Two-Photon Fluorescent Probes for Amyloid-β Plaques Imaging In Vivo

Amyloid-β (Aβ) peptide deposition, hyperphosphorylated tau proteins, reactive astrocytes, high levels of metal ions, and upregulated monoamine oxidases are considered to be the primary pathological markers of Alzheimer's disease (AD). Among them, Aβ peptide deposition or Aβ plaques, is regarded as the initial factor in the pathogenesis of AD and a critical pathological hallmark in AD. This review highlights recently Aβ-specific fluorescent probes for two-photon imaging of Aβ plaques in vivo. It includes the synthesis and detection mechanism of probes, as well as their application to two-photon imaging of Aβ plaques in vivo.

Hydroxyethyl-Modified Cycloheptatriene-BODIPY Derivatives as Specific Tau Imaging Probes

Near-infrared fluorescence (NIRF) imaging as an exquisite sensitive, high spatial-resolution, and real-time tool plays an important role in visualizing pathologies in the brain. In this study, we designed and synthesized a series of NIR probes of hydroxyethyl cycloheptatriene-BODIPY derivatives that have demonstrated strong binding specificity to native neurofibrillary tangles (NFTs) in Alzheimer's disease (AD) brain sections. The improved hydrophilicity of TNIR7-9 and TNIR7-11 resulted in faster clearance rates from healthy brains (4.2 and 10.9, respectively) compared to previously reported compounds. Furthermore, TNIR7-13, which features a fluorinated modification, exhibited a high binding affinity to Tau aggregates (Kd = 11.8 nM) and held promise for future PET studies.

Emerging nanotechnology for Alzheimer's disease: From detection to treatment

Alzheimer's disease (AD), one of the most common chronic neurodegenerative diseases, is characterized by memory impairment, synaptic dysfunction, and character mutations. The pathological features of AD are Aβ accumulation, tau protein enrichment, oxidative stress, and immune inflammation. Since the pathogenesis of AD is complicated and ambiguous, it is still challenging to achieve early detection and timely treatment of AD. Due to the unique physical, electrical, magnetic, and optical properties of nanoparticles (NPs), nanotechnology has shown great potential for detecting and treating AD. This review provides an overview of the latest developments in AD detection via nanotechnology based on NPs with electrochemical sensing, optical sensing, and imaging techniques. Meanwhile, we highlight the important advances in nanotechnology-based AD treatment through targeting disease biomarkers, stem-cell therapy and immunotherapy. Furthermore, we summarize the current challenges and present a promising prospect for nanotechnology-based AD diagnosis and intervention.

Neuroimaging modalities in the detection of Alzheimer's disease-associated biomarkers

Alzheimer's disease (AD) is the most common cause of dementia. Neuropathological changes in AD patients occur up to 10-20 years before the emergence of clinical symptoms. Specific diagnosis and appropriate intervention strategies are crucial during the phase of mild cognitive impairment (MCI) and AD. The detection of biomarkers has emerged as a promising tool for tracking the efficacy of potential therapies, making an early disease diagnosis, and prejudging treatment prognosis. Specifically, multiple neuroimaging modalities, including magnetic resonance imaging (MRI), positron emission tomography, optical imaging, and single photon emission-computed tomography, have provided a few potential biomarkers for clinical application. The MRI modalities described in this review include structural MRI, functional MRI, diffusion tensor imaging, magnetic resonance spectroscopy, and arterial spin labelling. These techniques allow the detection of presymptomatic diagnostic biomarkers in the brains of cognitively normal elderly people and might also be used to monitor AD disease progression after the onset of clinical symptoms. This review highlights potential biomarkers, merits, and demerits of different neuroimaging modalities and their clinical value in MCI and AD patients. Further studies are necessary to explore more biomarkers and overcome the limitations of multiple neuroimaging modalities for inclusion in diagnostic criteria for AD.

Oxazole-4-carboxamide/butylated hydroxytoluene hybrids with GSK-3β inhibitory and neuroprotective activities against Alzheimer's disease

Neuronal cells overexpressing phosphorylated Tau proteins can increase the susceptibility to oxidative stress. Regulation of glycogen synthase-3β (GSK-3β) and reduction of Tau protein hyperphosphorylation, along with alleviation of oxidative stress, may be an effective way to prevent or treat Alzheimer's disease (AD). For this purpose, a series of Oxazole-4-carboxamide/butylated hydroxytoluene hybrids were designed and synthesized to achieve multifunctional effects on AD. The biological evaluation showed that the optimized compound KWLZ-9e displayed potential GSK-3β (IC₅₀ = 0.25 μM) inhibitory activity and neuroprotective capacity. Tau protein inhibition assays showed that KWLZ-9e reduced the expression of GSK-3β and downstream p-Tau in HEK GSK-3β 293T cells. Meanwhile, KWLZ-9e could alleviate H₂O₂-induced ROS damage, mitochondrial membrane potential imbalance, Ca²⁺ influx and apoptosis. Mechanistic studies suggest that KWLZ-9e activates the Keap1-Nrf2-ARE signaling pathway and enhances the expression of downstream oxidative stress proteins including TrxR1, HO-1, NQO1, GCLM to exert cytoprotective effects. We also confirmed that KWLZ-9e could ameliorate learning and memory impairments in vivo model of AD. The multifunctional properties of KWLZ-9e suggest that it is a promising lead for the treatment of AD.

Small-molecule theranostics in Alzheimer's disease

Alzheimer's Disease (AD) remains one of the most challenging health-related issues for our society. It is becoming increasingly prevalent, especially in developed countries, due to the rising life expectancy and, moreover, represents a considerable economic burden worldwide. All efforts at the discovery of new diagnostic and therapeutic tools in the last decades have invariably met with failure, making AD an incurable illness and underscoring the need for new approaches. In recent years, theranostic agents have emerged as an interesting strategy. They are molecules able to simultaneously provide diagnostic information and deliver therapeutic activity, allowing for the assessment of the molecule activity, the organism response and the pharmacokinetics. This makes these compounds promising for streamlining research on AD drugs and for their application in personalized medicine. We review here the field of small-molecule theranostic agents as promising tools for the development of novel diagnostic and therapeutic resources against AD, highlighting the positive and significant impact that theranostics can be expected to have in the near future in clinical practice.