Curcumin Scaffold as a Multifunctional Tool for Alzheimer's Disease Research

Controlled preparation of tannic acid-derived carbonized dots and their use to inhibit amyloid aggregation and promote aggregate disaggregation

Tannic acid (TA)-derived carbon dots (TACDs) were synthesized for the first time via a solvothermal method using TA as one of the raw materials, which may effectively inhibit amyloid fibril aggregation and disaggregate mature fibril. The fluorescent property of TACDs were modulated by adjusting the ratio of TA to o-phenylenediamine (oPD), and TACDs fabricated with the precursor ratio as 1:1 showed the best fluorescent property. Circular dichroism spectra (CD) showed that the structure of β-sheet decreased as the concentration of TACDs increased. The inhibition efficiency, as confirmed by thioflavin T (ThT) and transmission electron microscopy (TEM), is extraordinary at 98.16%, whereas disaggregation efficiency is noteworthy at 97.97%, and the disaggregated lysozyme fibrils did not reaggregate after 7 days. More critically, TACDs can also alleviate the cellular toxicity caused by Aβ fibrils and improve cell viability. This work offers a new perspective on the design of scavengers for amyloid plaques.

Phytotherapy in Alzheimer's Disease-A Narrative Review

Alzheimer's disease (AD) affects 50-70% of patients with dementia, making it the leading cause of dementia. The condition is classified as a neurodegenerative, progressive and incurable disease. The disease is affecting more and more people around the world. AD has a multifactorial nature, spreading from beta-amyloid deposition to inflammation in patients' brains. Patients experience cognitive impairment and functional decline. Although it is a disease that occurs mainly in the elderly, it is increasingly being diagnosed in young people between the ages of 30 and 40. It not only affects the patient themself but also reduces the quality of life of their closest caregivers. According to the WHO, the treatment of AD consumes USD 1.3 trillion globally, but it is only symptomatic, as there are no drugs to prevent the onset of AD or treat the cause of its onset. Due to the numerous side effects of therapy and the lack of proactive drugs that act on the pathomechanism of AD, alternative therapies are being sought. One possible option that has many studies confirming its effect is phytotherapy. Many herbs have pharmacological properties, such as antioxidant, anti-inflammatory, or neuroprotective effects, making them the future of cognitive disorders and AD treatment. This review focuses on some of the most promising herbs that have potentially potent properties and effects in AD therapy. These include Curcuma longa, Panax ginseng, Berberis and Crocus sativus. These herbs may perhaps be key in the future to make functioning and life easier for patients struggling with AD.

Near-infrared II theranostic agents for the diagnosis and treatment of Alzheimer's disease

BACKGROUND

Near-infrared II theranostic agents have gained great momentum in the research field of AD owing to the appealing advantages. Recently, an array of activatable NIR-II fluorescence probes has been developed to specifically monitor pathological targets of AD. Furthermore, various NIR-II-mediated nanomaterials with desirable photothermal and photodynamic properties have demonstrated favorable outcomes in the management of AD.

METHODS

We summerized amounts of references and focused on small-molecule probes, nanomaterials, photothermal therapy, and photodynamic therapy based on NIR-II fluorescent imaging for the diagnosis and treatment in AD. In addition, design strategies for NIR-II-triggered theranostics targeting AD are presented, and some prospects are also addressed.

RESULTS

NIR-II theranostic agents including small molecular probes and nanoparticles have received the increasing attention for biomedical applications. Meanwhile, most of the theranostic agents exhibited the promising results in animal studies. To our surprise, the multifunctional nanoplatforms also show a great potential in the diagnosis and treatment of AD.

CONCLUSIONS

Although NIR-II theranostic agents showed the great potential in diagnosis and treatment of AD, there are still many challenges: 1) Faborable NIR-II fluorohpores are still lacking; 2) Biocompatibility, bioseurity and dosage of NIR-II theranostic agents should be further revealed; 3) New equipment and software associated with NIR-II imaging system should be explored.

Targeting Biometals in Alzheimer's Disease with Metal Chelating Agents Including Coumarin Derivatives

Numerous physiological processes happening in the human body, including cerebral development and function, require the participation of biometal ions such as iron, copper, and zinc. Their dyshomeostasis may, however, contribute to the onset of Alzheimer's disease (AD) and potentially other neurodegenerative diseases. Chelation of biometal ions is therefore a therapeutic strategy against AD. This review provides a survey of natural and synthetic chelating agents that are or could potentially be used to target the metal hypothesis of AD. Since metal dyshomeostasis is not the only pathological aspect of AD, and the nature of this disorder is very complex and multifactiorial, the most efficient therapeutics should target as many neurotoxic factors as possible. Various coumarin derivatives match this description and apart from being able to chelate metal ions, they exhibit the capacity to inhibit cholinesterases (ChEs) and monoamine oxidase B (MAO-B) while also possessing antioxidant, anti-inflammatory, and numerous other beneficial effects. Compounds based on the coumarin scaffold therefore represent a desirable class of anti-AD therapeutics.

Relationship of Curcumin with Aging and Alzheimer and Parkinson Disease, the Most Prevalent Age-Related Neurodegenerative Diseases: A Narrative Review

The elderly population is increasing worldwide every day. Age is a significant factor in the progression of neurological diseases, which can also cause cognitive decline and memory disorders. Inflammation and oxidative stress are primary drivers of senescence and disorders, particularly those associated with aging and neurodegenerative diseases. Bioactive phytochemicals are considered a promising therapeutic strategy in combating aging and age-related pathological conditions. One of the phytochemicals with diverse biological properties encompassing antioxidant, anti-inflammatory, antibacterial, antiviral, anticancer, antifungal, antidepressant, anti-allergic, and anti-aging properties is curcumin. Curcumin, a polyphenolic structure with a distinct orange hue and unique chemical properties, is derived from the roots of Curcuma longa, a member of the Zingiberaceae family, commonly known as turmeric. It has been noted that the incidence of neurodegenerative diseases is low in societies that consume curcumin widely. Therefore, this review investigates the effect of curcumin on aging and Alzheimer and Parkinson disease, which are the most prevalent age-related neurodegenerative diseases.

Design and in vitro evaluation of curcumin-loaded PLGA nanoparticle-embedded sodium alginate/gelatin 3D printed scaffolds for Alzheimer's disease

BACKGROUND

Targeted nanoparticles (NPs) are aimed at improving clinical outcomes by enhancing the diagnostic and therapeutic efficacy of drugs in the treatment of Alzheimer's disease (AD).

METHODS

Curcumin (CUR)-loaded poly-lactic-co-glycolic acid (PLGA) NPs (CNPs) were produced to demonstrate a prolonged release and successfully embedded into 3D printed sodium alginate (SA)/gelatin (GEL) scaffolds that can dissolve rapidly sublingually. Characterization and in vitro activity of the NPs and scaffolds were evaluated.

RESULTS

Based on the in vitro drug release studies, 99.6 % of the encapsulated CUR was released in a controlled manner within 18 days for the CNPs. In vitro cell culture studies showed that all samples exhibited cell viability above 84.2 % and no significant cytotoxic effect on SH-SY5Y cells. The samples were analyzed through 2 different pathways by PCR analysis. Real-time PCR results indicated that CNP and CNP-embedded SA/GEL scaffolds (CNPSGS) may show neuroprotective effects by modulating the Wnt/β-catenin pathway. The gene expression level of β-catenin slightly increased compared to the gene expression levels of other proteins and enzymes with these treatments. However, the PI3K/Akt/GSK-3β signaling pathway was regulated at the same time because of the crosstalk between these 2 pathways.

CONCLUSION

CNPSGS might be an effective therapeutic alternative for AD treatment.

A novel BODIPY-based theranostic agent for in vivo fluorescence imaging of cerebral Aβ and ameliorating Aβ-associated disorders in Alzheimer's disease transgenic mice

β-Amyloid (Aβ) aggregation is increasingly recognized as both a biomarker and an inducer of the progression of Alzheimer's disease (AD). Here, we describe a novel fluorescent probe P14, developed based on the BODIPY structure, capable of simultaneous visualization and inhibition of Aβ aggregation in vivo. P14 shows high binding affinity to Aβ aggregates and selectively labels Aβ plaques in the brain slices of APP/PS1 mice. Moreover, P14 is able to visualize overloaded Aβ in both APP/PS1 and 5 × FAD transgenic mice in vivo. From the aspect of potential therapeutic effects, P14 administration inhibits Aβ aggregation and alleviates Aβ-induced neuronal damage in vitro, as well as reduces central Aβ deposition and ameliorates cognitive impairment in APP/PS1 transgenic mice in vivo. Finally, P14 is applied to monitor the progression of Aβ aggregation in the brain of 5 × FAD transgenic mice and the intervention effect itself by fluorescence imaging. In summary, the discovery of this fluorescent agent might provide important clues for the future development of theranostic drug candidates targeting Aβ aggregation in AD.

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.

Protective effects of curcumin and Ginkgo biloba extract combination on a new model of Alzheimer's disease

Alzheimer's disease (AD) is one of the most prevalent neurodegenerative illnesses, and yet, no workable treatments have been discovered to prevent or reverse AD. Curcumin (CUR), the major polyphenolic compound of turmeric (Curcuma longa) rhizomes, and Ginkgo biloba extract (GBE) are natural substances derived from conventional Chinese herbs that have long been shown to provide therapeutic advantages for AD. The uptake of curcumin into the brain is severely restricted by its low ability to cross the blood-brain barrier (BBB). Meanwhile, GBE has been shown to improve BBB permeability. The present study evaluated the neuroprotective effects and pharmacokinetic profile of curcumin and GBE combination to find out whether GBE can enhance curcumin's beneficial effects in AD by raising its brain concentration. Results revealed that CUR + GBE achieved significantly higher levels of curcumin in the brain and plasma after 30 min and 1 h of oral administration, compared to curcumin alone, and this was confirmed by reversed phase high-performance liquid chromatography (RP-HPLC). The effect of combined oral treatment, for 28 successive days, on cognitive function and other AD-like alterations was studied in scopolamine-heavy metal mixtures (SCO + HMM) AD model in rats. The combination reversed at least, partially on the learning and memory impairment induced by SCO + HMM. This was associated with a more pronounced inhibitory effect on acetylcholinesterase (AChE), caspase-3, hippocampal amyloid beta (Aβ1-42), and phosphorylated tau protein (p-tau) count, and pro-inflammatory cytokines tumor necrosis factor-alpha (TNF-α) and interleukine-1beta (IL-1β), as compared to the curcumin alone-treated group. Additionally, the combined treatment significantly decreased lipid peroxidation (MDA) and increased levels of reduced glutathione (GSH), when compared with the curcumin alone. These findings support the concept that the combination strategy might be an alternative therapy in the management/prevention of neurological disorders. This study sheds light on a new approach for exploring new phyto-therapies for AD and emphasizes that more research should focus on the synergic effects of herbal drugs in future.

Multifunctional theranostic carbazole-based cyanine for real-time imaging of amyloid-β and therapeutic treatment of multiple pathologies in Alzheimer's disease

Alzheimer's disease (AD) is a progressive and irreversible neurodegenerative disorder characterized by the synaptic and neuronal loss, which results in cognitive impairment in particular learning and memory. Currently, AD is incurable and no single confirmative test can clinically be used to diagnose AD. In light of the complex and multifactorial nature of AD etiology, the development of multifunctional/multi-target drugs that act on multiple pathological pathways and mechanisms shows great therapeutic potential for intervention of this devastating disease. We report herein a multifunctional theranostic cyanine, SLCOOH, which serves not only as a highly sensitive fluorescent probe for real-time imaging of amyloid-β (Aβ) contents in different age groups of transgenic (Tg) AD mice but also as an effective therapeutic agent for early AD intervention via multiple pathological targets in the AD mouse model. Remarkably, treatment with SLCOOH gives rise to multiple therapeutic benefits, including the amelioration of cognitive decline, a reduction in Aβ levels, a decrease in hyperphosphorylated tau proteins and tau depositions, and the alleviation of synaptic loss and dysfunctions in young triple Tg AD mice. Our results have demonstrated that in addition to superior Aβ imaging capability, SLCOOH exhibits versatile and effective multiple modes of drug action, signifying outstanding therapeutic potential to treat early onset AD. Our work also paves the way for the development of effective Aβ-targeted theranostic agents for 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.

Nature's Toolbox Against Tau Aggregation: An Updated Review of Current Research

Tau aggregation is a hallmark of several neurodegenerative disorders, such as Alzheimer's disease (AD), frontotemporal dementia, and progressive supranuclear palsy. Hyperphosphorylated tau is believed to contribute to the degeneration of neurons and the development of these complex diseases. Therefore, one potential treatment for these illnesses is to prevent or counteract tau aggregation. In recent years, interest has been increasing in developing nature-derived tau aggregation inhibitors as a potential treatment for neurodegenerative disorders. Researchers have become increasingly interested in natural compounds with multifunctional features, such as flavonoids, alkaloids, resveratrol, and curcumin, since these molecules can interact simultaneously with the various targets of AD. Recent studies have demonstrated that several natural compounds can inhibit tau aggregation and promote the disassembly of pre-formed tau aggregates. Nature-derived tau aggregation inhibitors hold promise as a potential treatment for neurodegenerative disorders. However, it is important to note that more research is needed to fully understand the mechanisms by which these compounds exert their effects and their safety and efficacy in preclinical and clinical studies. Nature-derived inhibitors of tau aggregation are a promising new direction in the research of neurodegenerative complexities. This review focuses on the natural products that have proven to be a rich supply for inhibitors in tau aggregation and their uses in neurodegenerative complexities, including AD.

The application of nanotechnology in treatment of Alzheimer's disease

The buildup of beta-amyloid plaques in the brain results in Alzheimer's disease (AD), a neurodegenerative condition. A permanent treatment for AD is not yet available. Only a slowing down of its advancement is possible with the current pharmaceutical options. Nevertheless, nanotechnology has proven to be advantageous in medical applications. It has a lot of potential for AD therapy, particularly in diagnosing the condition and providing an alternative course of treatment. In this review, we outline the developments and benefits of nanomedicines in treating AD. Prospective nanomedicines for diagnosing and surveillance therapeutic interventions for AD and other diseases of the central nervous system (CNS) may be clinically accessible, persuading the development of investigation in this field.