Melatonin regulates Aβ production/clearance balance and Aβ neurotoxicity: A potential therapeutic molecule for Alzheimer's disease

Discovery of novel deoxyvasicinone derivatives with benzenesulfonamide substituents as multifunctional agents against Alzheimer's disease

A series of deoxyvasicinone derivatives with benzenesulfonamide substituents were designed and synthesized to find a multifunctional anti-Alzheimer's disease (AD) drug. The results of the biological activity evaluation indicated that most compounds demonstrated selective inhibition of acetylcholinesterase (AChE). Among them, g17 exhibited the most potent inhibitory effect on AChE (IC50 = 0.24 ± 0.04 μM). Additionally, g17 exhibited promising properties as a metal chelator and inhibitor of amyloid β peptides self-aggregation (68.34 % ± 1.16 %). Research on oxidative stress has shown that g17 displays neuroprotective effects and effectively suppresses the intracellular accumulation of reactive oxygen species. Besides, g17 demonstrated remarkable anti-neuroinflammatory effects by significantly reducing the production of pro-inflammatory cytokines (such as NO, IL-1β, and TNF-α) and inhibiting the expression of inflammatory mediators iNOS and COX-2. In vivo studies showed that g17 significantly improved AD model mice's cognitive and memory abilities. Histological examination of mouse hippocampal tissue sections using hematoxylin and eosin staining revealed that g17 effectively mitigates neuronal damage. Considering the multifunctional properties of g17, it is regarded as a promising lead compound for treating AD.

Death-associated protein kinase 1 as a therapeutic target for Alzheimer's disease

Alzheimer's disease (AD) is the most prevalent form of dementia in the elderly and represents a major clinical challenge in the ageing society. Neuropathological hallmarks of AD include neurofibrillary tangles composed of hyperphosphorylated tau, senile plaques derived from the deposition of amyloid-β (Aβ) peptides, brain atrophy induced by neuronal loss, and synaptic dysfunctions. Death-associated protein kinase 1 (DAPK1) is ubiquitously expressed in the central nervous system. Dysregulation of DAPK1 has been shown to contribute to various neurological diseases including AD, ischemic stroke and Parkinson's disease (PD). We have established an upstream effect of DAPK1 on Aβ and tau pathologies and neuronal apoptosis through kinase-mediated protein phosphorylation, supporting a causal role of DAPK1 in the pathophysiology of AD. In this review, we summarize current knowledge about how DAPK1 is involved in various AD pathological changes including tau hyperphosphorylation, Aβ deposition, neuronal cell death and synaptic degeneration. The underlying molecular mechanisms of DAPK1 dysregulation in AD are discussed. We also review the recent progress regarding the development of novel DAPK1 modulators and their potential applications in AD intervention. These findings substantiate DAPK1 as a novel therapeutic target for the development of multifunctional disease-modifying treatments for AD and other neurological disorders.

Melatonin in Alzheimer's Disease: Literature Review and Therapeutic Trials

There are currently no effective treatments to prevent, halt, or reverse Alzheimer's disease (AD), the most common cause of dementia in older adults. Melatonin, a relatively harmless over-the-counter supplement, may offer some benefits to patients with AD. Melatonin is known for its sleep-enhancing properties, but research shows that it may provide other advantages as well, such as antioxidant and anti-amyloidogenic properties. Clinical trials for melatonin use in AD have mixed results but, overall, show modest benefits. However, it is difficult to interpret clinical research in this area as there is little standardization to guide the administration and study of melatonin. This review covers basic biology and clinical research on melatonin in AD focusing on prominent hypotheses of pathophysiology of neurodegeneration and cognitive decline in AD (i.e., amyloid and tau hypotheses, antioxidant and anti-inflammation, insulin resistance and glucose homeostasis, the cholinergic hypothesis, sleep regulation, and the hypothalamic-pituitary-adrenal axis and cortisol). This is followed by a discussion on pending clinical trials, considerations for future research protocols, and open questions in the field.

Melatonin facts: Lack of evidence that melatonin is a radical scavenger in living systems

Melatonin is a small natural compound, so called a neuro-hormone that is synthesized mainly in pineal gland in animals. Its main role is to master the clock of the body, under the surveillance of light. In other words, it transfers the information concerning night and day to the peripheral organs which, without it, could not "know" which part of the circadian rhythm the body is in. Besides its main circadian and circannual rhythms mastering, melatonin is reported to be a radical scavenger and/or an antioxidant. Because radical scavengers are chemical species able to neutralize highly reactive and toxic species such as reactive oxygen species, one would like to transfer this property to living system, despite impossibilities already largely reported in the literature. In the present commentary, we refresh the memory of the readers with this notion of radical scavenger, and review the possible evidence that melatonin could be an in vivo radical scavenger, while we only marginally discuss here the fact that melatonin is a molecular antioxidant, a feature that merits a review on its own. We conclude four things: (i) the evidence that melatonin is a scavenger in acellular systems is overwhelming and could not be doubted; (ii) the transposition of this property in living (animal) systems is (a) theoretically impossible and (b) not proven in any system reported in the literature where most of the time, the delay of the action of melatonin is over several hours, thus signing a probable induction of cellular enzymatic antioxidant defenses; (iii) this last fact needs a confirmation through the discovery of a nuclear factor-a key relay in induction processes-that binds melatonin and is activated by it and (iv) we also gather the very important description of the radical scavenging capacity of melatonin in acellular systems that is now proven and shared by many other double bond-bearing molecules. We finally discussed briefly on the reason-scientific or else-that led this description, and the consequences of this claim, in research, in physiology, in pathology, but most disturbingly in therapeutics where a vast amount of money, hope, and patient bien-être are at stake.

Ramelteon attenuates hippocampal neuronal loss and memory impairment following kainate-induced seizures

Evidence suggests that the neuroprotective effects of melatonin involve both receptor-dependent and -independent actions. However, little is known about the effects of melatonin receptor activation on the kainate (KA) neurotoxicity. This study examined the effects of repeated post-KA treatment with ramelteon, a selective agonist of melatonin receptors, on neuronal loss, cognitive impairment, and depression-like behaviors following KA-induced seizures. The expression of melatonin receptors decreased in neurons, whereas it was induced in astrocytes 3 and 7 days after seizures elicited by KA (0.12 μg/μL) in the hippocampus of mice. Ramelteon (3 or 10 mg/kg, i.p.) and melatonin (10 mg/kg, i.p.) mitigated KA-induced oxidative stress and impairment of glutathione homeostasis and promoted the nuclear translocation and DNA binding activity of Nrf2 in the hippocampus after KA treatment. Ramelteon and melatonin also attenuated microglial activation but did not significantly affect astroglial activation induced by KA, despite the astroglial induction of melatonin receptors after KA treatment. However, ramelteon attenuated KA-induced proinflammatory phenotypic changes in astrocytes. Considering the reciprocal regulation of astroglial and microglial activation, these results suggest ramelteon inhibits microglial activation by regulating astrocyte phenotypic changes. These effects were accompanied by the attenuation of the nuclear translocation and DNA binding activity of nuclear factor κB (NFκB) induced by KA. Consequently, ramelteon attenuated the KA-induced hippocampal neuronal loss, memory impairment, and depression-like behaviors; the effects were comparable to those of melatonin. These results suggest that ramelteon-mediated activation of melatonin receptors provides neuroprotection against KA-induced neurotoxicity in the mouse hippocampus by activating Nrf2 signaling to attenuate oxidative stress and restore glutathione homeostasis and by inhibiting NFκB signaling to attenuate neuroinflammatory changes.

Drug Target to Alleviate Mitochondrial Dysfunctions in Alzheimer's Disease: Recent Advances and Therapeutic Implications

Alzheimer's disease (AD) is a severe progressive neurodegenerative condition associated with neuronal damage and reduced cognitive function that primarily affects the aged worldwide. While there is increasing evidence suggesting that mitochondrial dysfunction is one of the most significant factors contributing to AD, its accurate pathobiology remains unclear. Mitochondrial bioenergetics and homeostasis are impaired and defected during AD pathogenesis. However, the potential of mutations in nuclear or mitochondrial DNA encoding mitochondrial constituents to cause mitochondrial dysfunction has been considered since it is one of the intracellular processes commonly compromised in early AD stages. Additionally, electron transport chain dysfunction and mitochondrial pathological protein interactions are related to mitochondrial dysfunction in AD. Many mitochondrial parameters decline during aging, causing an imbalance in reactive oxygen species (ROS) production, leading to oxidative stress in age-related AD. Moreover, neuroinflammation is another potential causative factor in AD-associated mitochondrial dysfunction. While several treatments targeting mitochondrial dysfunction have undergone preclinical studies, few have been successful in clinical trials. Therefore, this review discusses the molecular mechanisms and different therapeutic approaches for correcting mitochondrial dysfunction in AD, which have the potential to advance the future development of novel drug-based AD interventions.

Beyond Conventional Therapies: Molecular Dynamics of Alzheimer's Treatment through CLOCK/BMAL1 Interactions

BACKGROUND

Alzheimer's Disease (AD) represents a neurodegenerative disorder characterized by cognitive and behavioral impairments significantly hindering social and occupational functioning. Melatonin, a hormone pivotal in regulating the body's intrinsic circadian rhythm, also acts as a catalyst in the breakdown of beta-amyloid deposits, offering a promising therapeutic approach for AD. The upregulation of Brain and Muscle ARNT-Like 1 (Bmal1) gene expression, stimulated by melatonin, emerges as a potential contributor to AD intervention. Current pharmacological interventions, such as FDA-approved cholinesterase inhibitors and the recently authorized monoclonal antibody, Lecanemab, are utilized in AD management. However, the connection between these medications and Bmal1 remains insufficiently explored.

OBJECTIVE

This study aims to investigate the molecular effects of FDA-endorsed drugs on the CLOCK: Bmal1 dimer. Furthermore, considering the interactions between melatonin and Bmal1, this research explores the potential synergistic efficacy of combining these pharmaceutical agents with melatonin for AD treatment.

METHODS

Using molecular docking and MM/PBSA methodologies, this research determines the binding affinities of drugs within the Bmal1 binding site, constructing interaction profiles.

RESULTS

The findings reveal that, among FDA-approved drugs, galanthamine and donepezil demonstrate notably similar binding energy values to melatonin, interacting within the Bmal1 binding site through analogous amino acid residues and functional groups.

CONCLUSION

A novel therapeutic approach emerges, suggesting the combination of melatonin with Lecanemab as a monoclonal antibody therapy. Importantly, prior research has not explored the effects of FDA-approved drugs on Bmal1 expression or their potential for synergistic effects.

Development of Neuroprotective Agents for the Treatment of Alzheimer's Disease using Conjugates of Serotonin with Sesquiterpene Lactones

BACKGROUND

Sesquiterpene lactones are secondary plant metabolites with a wide variety of biological activities. The process of lactone conjugation to other pharmacophores can increase the efficacy and specificity of the conjugated agent effect on molecular targets in various diseases, including brain pathologies. Derivatives of biogenic indoles, including neurotransmitter serotonin, are of considerable interest as potential pharmacophores. Most of these compounds have neurotropic activity and, therefore, can be used in the synthesis of new drugs with neuroprotective properties.

AIM

The aim of this experimental synthesis was to generate potential treatment agents for Alzheimer's disease using serotonin conjugated with natural sesquiterpene lactones.

METHODS

Three novel compounds were obtained via the Michael reaction and used for biological testing. The obtained conjugates demonstrated complex neuroprotective activities. Serotonin conjugated to isoalantolactone exhibited strong antioxidant and mitoprotective activities.

RESULTS

The agent was also found to inhibit β-site amyloid precursor protein cleaving enzyme 1 (BACE-1), prevent the aggregation of β-amyloid peptide 1-42, and protect SH-SY5Y neuroblastoma cells from neurotoxins such as glutamate and H2O2. In a transgenic animal model of Alzheimer's disease (5xFAD line), the conjugated agent restored declined cognitive functions and improved learning and memory.

CONCLUSION

In conclusion, the obtained results indicate that serotonin conjugates to sesquiterpene lactones are promising agents for the treatment of symptoms associated with Alzheimer's disease.

Neuroprotective Effect of Combined Treatment with Epigallocatechin 3-Gallate and Melatonin on Familial Alzheimer's Disease PSEN1 E280A Cerebral Spheroids Derived from Menstrual Mesenchymal Stromal Cells

Background

Familial Alzheimer's disease (FAD) is caused by mutations in one or more of 3 genes known as AβPP, PSEN1, and PSEN2. There are currently no effective therapies for FAD. Hence, novel therapeutics are needed.

Objective

To analyze the effect of treatment with a combination of epigallocatechin-3-gallate (EGCG) and Melatonin (N-acetyl-5-methoxytryptamine, aMT) in a cerebral spheroid (CS) 3D in vitro model of PSEN 1 E280A FAD.

Methods

We developed a CS in vitro model based on menstrual stromal cells derived from wild-type (WT) and mutant PSEN1 E280A menstrual blood cultured in Fast-N-Spheres V2 medium.

Results

Beta-tubulin III, choline acetyltransferase, and GFAP in both WT and mutant CSs spontaneously expressed neuronal and astroglia markers when grown in Fast-N-Spheres V2 medium for 4 or 11 days. Mutant PSEN1 CSs had significantly increased levels of intracellular AβPP fragment peptides and concomitant appearance of oxidized DJ-1 as early as 4 days, and phosphorylated tau, decreased ΔΨm, and increased caspase-3 activity were observed on Day 11. Moreover, mutant CSs were unresponsive to acetylcholine. Treatment with a combination of EGCG and aMT decreased the levels of all typical pathological markers of FAD more efficiently than did EGCG or aMT alone, but aMT failed to restore Ca2+ influx in mutant CSs and decreased the beneficial effect of EGCG on Ca2+ influx in mutant CSs.

Conclusion

Treatment with a combination of EGCG and aMT can be of high therapeutic value due to the high antioxidant capacity and anti-amyloidogenic effect of both compounds.

New insights into glycogen synthase kinase-3: A common target for neurodegenerative diseases

Glycogen synthase kinase 3 (GSK-3) is a highly conserved protein serine/threonine kinase that plays a central role in a wide variety of cellular processes to coordinate catabolic and anabolic pathways and regulate cell growth and fate. There is increasing evidence showing that abnormal glycogen synthase kinase 3 (GSK-3) is associated with the pathogenesis and progression of many disorders, such as cancer, diabetes, psychiatric diseases, and neurodegenerative diseases. In this review, we summarize recent findings about the regulatory role of GSK-3 in the occurrence and development of multiple neurodegenerative diseases, mainly focusing on Alzheimer's disease, Parkinson's disease, and amyotrophic lateral sclerosis. The aim of this study is to provide new insight into the shared working mechanism of GSK-3 as a therapeutic target of multiple neurodegenerative diseases.

Evaluation and targeting of amyloid precursor protein (APP)/amyloid beta (Aβ) axis in amyloidogenic and non-amyloidogenic pathways: A time outside the tunnel

In Alzheimer disease (AD), amyloid precursor protein (APP) and production of amyloid beta (Aβ) which is generated by amyloidogenic pathway is implicated in neurotoxicity and neuronal cell deaths. However, physiological Aβ level is essential to improves neuronal survival, attenuates neuronal apoptosis and has neuroprotective effect. In addition, physiological APP level has neurotrophic effect on the central nervous system (CNS). APP has a critical role in the brain growth and development via activation of long-term potentiation (LTP) and acceleration of neurite outgrowth. Moreover, APP is cleaved by α secretase to form a neuroprotective soluble APP alpha (sAPPα) in non-amyloidogenic pathway. Consequently, this mini-review purposes to highlight the possible beneficial role of APP and Aβ. In addition, this mini-review discussed the modulation of APP processing and Aβ production.

Non-Excitatory Amino Acids, Melatonin, and Free Radicals: Examining the Role in Stroke and Aging

The aim of this review is to explore the relationship between melatonin, free radicals, and non-excitatory amino acids, and their role in stroke and aging. Melatonin has garnered significant attention in recent years due to its diverse physiological functions and potential therapeutic benefits by reducing oxidative stress, inflammation, and apoptosis. Melatonin has been found to mitigate ischemic brain damage caused by stroke. By scavenging free radicals and reducing oxidative damage, melatonin may help slow down the aging process and protect against age-related cognitive decline. Additionally, non-excitatory amino acids have been shown to possess neuroprotective properties, including antioxidant and anti-inflammatory in stroke and aging-related conditions. They can attenuate oxidative stress, modulate calcium homeostasis, and inhibit apoptosis, thereby safeguarding neurons against damage induced by stroke and aging processes. The intracellular accumulation of certain non-excitatory amino acids could promote harmful effects during hypoxia-ischemia episodes and thus, the blockade of the amino acid transporters involved in the process could be an alternative therapeutic strategy to reduce ischemic damage. On the other hand, the accumulation of free radicals, specifically mitochondrial reactive oxygen and nitrogen species, accelerates cellular senescence and contributes to age-related decline. Recent research suggests a complex interplay between melatonin, free radicals, and non-excitatory amino acids in stroke and aging. The neuroprotective actions of melatonin and non-excitatory amino acids converge on multiple pathways, including the regulation of calcium homeostasis, modulation of apoptosis, and reduction of inflammation. These mechanisms collectively contribute to the preservation of neuronal integrity and functions, making them promising targets for therapeutic interventions in stroke and age-related disorders.

Design, Synthesis, In Silico Studies and In Vitro Evaluation of New Indole- and/or Donepezil-like Hybrids as Multitarget-Directed Agents for Alzheimer's Disease

Alzheimer's disease (AD) is considered a complex neurodegenerative condition which warrants the development of multitargeted drugs to tackle the key pathogenetic mechanisms of the disease. In this study, two novel series of melatonin- and donepezil-based hybrid molecules with hydrazone (3a-r) or sulfonyl hydrazone (5a-l) fragments were designed, synthesized, and evaluated as multifunctional ligands against AD-related neurodegenerative mechanisms. Two lead compounds (3c and 3d) exhibited a well-balanced multifunctional profile, demonstrating intriguing acetylcholinesterase (AChE) inhibition, promising antioxidant activity assessed by DPPH, ABTS, and FRAP methods, as well as the inhibition of lipid peroxidation in the linoleic acid system. Compound 3n, possessing two indole scaffolds, showed the highest activity against butyrylcholinesterase (BChE) and a high selectivity index (SI = 47.34), as well as a pronounced protective effect in H2O2-induced oxidative stress in SH-SY5Y cells. Moreover, compounds 3c, 3d, and 3n showed low neurotoxicity against malignant neuroblastoma cell lines of human (SH-SY5Y) and murine (Neuro-2a) origin, as well as normal murine fibroblast cells (CCL-1) that indicate the in vitro biocompatibility of the experimental compounds. Furthermore, compounds 3c, 3d, and 3n were capable of penetrating the blood-brain barrier (BBB) in the experimental PAMPA-BBB study. The molecular docking showed that compound 3c could act as a ligand to both MT1 and MT2 receptors, as well as to AchE and BchE enzymes. Taken together, those results outline compounds 3c, 3d, and 3n as promising prototypes in the search of innovative compounds for the treatment of AD-associated neurodegeneration with oxidative stress. This study demonstrates that hydrazone derivatives with melatonin and donepezil are appropriate for further development of new AChE/BChE inhibitory agents.

Unveiling the Therapeutic Potentials of Mushroom Bioactive Compounds in Alzheimer's Disease

Alzheimer's disease (AD) stands as a prevailing neurodegenerative condition (NDs), leading to the gradual deterioration of brain cells and subsequent declines in memory, thinking, behavior, and emotion. Despite the intensive research efforts and advances, an effective curative treatment for the disease has not yet been found. Mushrooms, esteemed globally for their exquisite flavors and abundant nutritional benefits, also hold a wealth of health-promoting compounds that contribute to improving AD health. These compounds encompass polysaccharides, proteins, lipids, terpenoids, phenols, and various other bioactive substances. Particularly noteworthy are the potent neuroprotective small molecules found in mushrooms, such as ergothioneine, erinacine, flavonoids, alkaloids, ergosterol, and melanin, which warrant dedicated scrutiny for their therapeutic potential in combating AD. This review summarizes such positive effects of mushroom bioactive compounds on AD, with a hope to contribute to the development of functional foods as an early dietary intervention for this neurodegenerative disease.

Electrochemical Immunosensors Developed for Amyloid-Beta and Tau Proteins, Leading Biomarkers of Alzheimer's Disease

Alzheimer's disease (AD) is the most common neurological disease and a serious cause of dementia, which constitutes a threat to human health. The clinical evidence has found that extracellular amyloid-beta peptides (Aβ), phosphorylated tau (p-tau), and intracellular tau proteins, which are derived from the amyloid precursor protein (APP), are the leading biomarkers for accurate and early diagnosis of AD due to their central role in disease pathology, their correlation with disease progression, their diagnostic value, and their implications for therapeutic interventions. Their detection and monitoring contribute significantly to understanding AD and advancing clinical care. Available diagnostic techniques, including magnetic resonance imaging (MRI) and positron emission tomography (PET), are mainly used to validate AD diagnosis. However, these methods are expensive, yield results that are difficult to interpret, and have common side effects such as headaches, nausea, and vomiting. Therefore, researchers have focused on developing cost-effective, portable, and point-of-care alternative diagnostic devices to detect specific biomarkers in cerebrospinal fluid (CSF) and other biofluids. In this review, we summarized the recent progress in developing electrochemical immunosensors for detecting AD biomarkers (Aβ and p-tau protein) and their subtypes (AβO, Aβ_(1-40), Aβ_(1-42), t-tau, cleaved-tau (c-tau), p-tau₁₈₁, p-tau₂₃₁, p-tau₃₈₁, and p-tau₄₄₁). We also evaluated the key characteristics and electrochemical performance of developed immunosensing platforms, including signal interfaces, nanomaterials or other signal amplifiers, biofunctionalization methods, and even primary electrochemical sensing performances (i.e., sensitivity, linear detection range, the limit of detection (LOD), and clinical application).

Glymphatic System and Mitochondrial Dysfunction as Two Crucial Players in Pathophysiology of Neurodegenerative Disorders

Neurodegenerative diseases are a complex problem affecting millions of people around the world. The pathogenesis is not fully understood, but it is known that both insufficiency of the glymphatic system and mitochondrial disorders affect the development of pathology. It appears that these are not just two independent factors that coexist in the processes of neurodegeneration, but that they often interact and drive each other. Bioenergetics disturbances are potentially associated with the accumulation of protein aggregates and impaired glymphatic clearance. Furthermore, sleep disorders characteristic of neurodegeneration may impair the work of both the glymphatic system and the activity of mitochondria. Melatonin may be one of the elements linking sleep disorders with the function of these systems. Moreover, noteworthy in this context is the process of neuroinflammation inextricably linked to mitochondria and its impact not only on neurons, but also on glia cells involved in glymphatic clearance. This review only presents possible direct and indirect connections between the glymphatic system and mitochondria in the process of neurodegeneration. Clarifying the connection between these two areas in relation to neurodegeneration could lead to the development of new multidirectional therapies, which, due to the complexity of pathogenesis, seems to be worth considering.

Rutin modified selenium nanoparticles reduces cell oxidative damage induced by H2O2 by activating Nrf2/HO-1 signaling pathway

Oxidative damage of neurons is one of the key pathological markers of Alzheimer's disease (AD), which eventually leads to neuronal apoptosis and loss. Nuclear factor E2-related factor 2 (Nrf2) is a key regulator of antioxidant response and is considered to be an important therapeutic target for neurodegenerative diseases. In this study, the selenated derivative of antioxidant rutin (Se-Rutin) was synthesized with sodium selenate (Na₂SeO₃) as raw material by a simple electrostatic-compound in situ selenium reduction method. The effects of Se-Rutin on H₂O₂ induced oxidative damage in Pheochromocytoma PC12 cells were evaluated by cell viability, apoptosis, reactive oxygen species level and the expression of antioxidant response element (Nrf2). The results showed that H₂O₂ treatment significantly increased the level of apoptosis and reactive oxygen species, while the level of Nrf2 and HO-1 decreased. However, Se-Rutin significantly reduced H₂O₂ induced apoptosis and cytotoxicity, and increased the expression of Nrf2 and HO-1, both of which were better than that of pure rutin. Therefore, the activation of Nrf2/HO-1 signaling pathway may be the basis of Se-Rutin's anti-oxidative damage to AD.

Melatonin reduces β-amyloid accumulation and improves short-term memory in streptozotocin-induced sporadic Alzheimer's disease model

Melatonin is a hormone secreted by the pineal gland, it can be associated with circadian rhythms, aging and neuroprotection. Melatonin levels are decreased in sporadic Alzheimer's disease (sAD) patients, which suggests a relationship between the melatonergic system and sAD. Melatonin may reduce inflammation, oxidative stress, TAU protein hyperphosphorylation, and the formation of β-amyloid (Aβ) aggregates. Therefore, the objective of this work was to investigate the impact of treatment with 10 mg/kg of melatonin (i.p) in the animal model of sAD induced by the intracerebroventricular (ICV) infusion of 3 mg/kg of streptozotocin (STZ). ICV-STZ causes changes in the brain of rats similar to those found in patients with sAD. These changes include; progressive memory decline, the formation of neurofibrillary tangles, senile plaques, disturbances in glucose metabolism, insulin resistance and even reactive astrogliosis characterized by the upregulation of glucose levels and glial fibrillary acidic protein (GFAP). The results show that ICV-STZ caused short-term spatial memory impairment in rats after 30 days of STZ infusion without locomotor impairment which was evaluated on day 27 post-injury. Furthermore, we observed that a prolonged 30-day treatment with melatonin can improve the cognitive impairment of animals in the Y-maze test, but not in the object location test. Finally, we demonstrated that animals receiving ICV-STZ have high levels of Aβ and GFAP in the hippocampus and that treatment with melatonin reduces Aβ levels but does not reduce GFAP levels, concluding that melatonin may be useful to control the progression of amyloid pathology in the brain.

Risk of neurodegenerative diseases in patients with sleep disorders: A nationwide population-based case-control study

OBJECTIVE

Our study aimed to explore the associative relationship between neurodegenerative diseases and sleep disorders.

PATIENTS

This 15-year retrospective longitudinal nationwide population-based matched case-control study used data extracted from the National Health Insurance Research Database. We evaluated 25,589 patients diagnosed with neurodegenerative diseases between 2000 and 2015 and a matched control of 102,356 patients without neurodegenerative diseases.

RESULTS

Sleep disorders were an independent risk factor for the development of neurodegenerative diseases (adjusted odds ratio (OR): 1.794, 95% confidence interval (CI): 1.235-2.268, P < 0.001), with a positive dose-effect relationship (adjusted OR (95% CI): <1 year: 1.638 (1.093-2.872), P < 0.001; 1-5 years: 1.897 (1.260-3.135), P < 0.001; >5 years: 2.381 (1.467-3.681), P < 0.001. Moreover, patients with sleep disorder and comorbid depression had a significantly higher risk of neurodegenerative disorders (adjusted OR: 5.874). Subgroup analysis showed that insomnia was associated with Alzheimer's disease, Pick's disease and essential tremor (adjusted OR (95% CI): 1.555 (1.069-1.965), 1.934 (1.331-2.445) and 2.089 (1.439-2.648), respectively). Obstructive sleep apnea was associated with Parkinson's disease, essential tremor, and primary dystonia (adjusted OR (95% CI): 1.801 (1.239-2.275), 5.523 (3.802-6.977), and 4.892 (3.365-6.178), respectively). Other specific sleep disorders were associated with Pick's disease, Parkinson's disease, essential tremor, and primary dystonia (adjusted OR (95% CI): 8.901 (6.101-11.010), 1.549 (1.075-1.986), 2.791 (1.924-3.531), and 9.114 (6.283-10.506), respectively).

CONCLUSION

Sleep disorders are associated with the subsequent development of neurodegenerative disorders. Moreover, sleep disorder patients with comorbid depression have a higher risk of neurodegenerative diseases.

Melatonin as a Chronobiotic/Cytoprotective Agent in REM Sleep Behavior Disorder

Dream-enactment behavior that emerges during episodes of rapid eye movement (REM) sleep without muscle atonia is a parasomnia known as REM sleep behavior disorder (RBD). RBD constitutes a prodromal marker of α-synucleinopathies and serves as one of the best biomarkers available to predict diseases such as Parkinson disease, multiple system atrophy and dementia with Lewy bodies. Most patients showing RBD will convert to an α-synucleinopathy about 10 years after diagnosis. The diagnostic advantage of RBD relies on the prolonged prodromal time, its predictive power and the absence of disease-related treatments that could act as confounders. Therefore, patients with RBD are candidates for neuroprotection trials that delay or prevent conversion to a pathology with abnormal α-synuclein metabolism. The administration of melatonin in doses exhibiting a chronobiotic/hypnotic effect (less than 10 mg daily) is commonly used as a first line treatment (together with clonazepam) of RBD. At a higher dose, melatonin may also be an effective cytoprotector to halt α-synucleinopathy progression. However, allometric conversion doses derived from animal studies (in the 100 mg/day range) are rarely employed clinically regardless of the demonstrated absence of toxicity of melatonin in phase 1 pharmacological studies with doses up to 100 mg in normal volunteers. This review discusses the application of melatonin in RBD: (a) as a symptomatic treatment in RBD; (b) as a possible disease-modifying treatment in α-synucleinopathies. To what degree melatonin has therapeutic efficacy in the prevention of α-synucleinopathies awaits further investigation, in particular multicenter double-blind trials.

Proteostasis failure exacerbates neuronal circuit dysfunction and sleep impairments in Alzheimer's disease

Failed proteostasis is a well-documented feature of Alzheimer's disease, particularly, reduced protein degradation and clearance. However, the contribution of failed proteostasis to neuronal circuit dysfunction is an emerging concept in neurodegenerative research and will prove critical in understanding cognitive decline. Our objective is to convey Alzheimer's disease progression with the growing evidence for a bidirectional relationship of sleep disruption and proteostasis failure. Proteostasis dysfunction and tauopathy in Alzheimer's disease disrupts neurons that regulate the sleep-wake cycle, which presents behavior as impaired slow wave and rapid eye movement sleep patterns. Subsequent sleep loss further impairs protein clearance. Sleep loss is a defined feature seen early in many neurodegenerative disorders and contributes to memory impairments in Alzheimer's disease. Canonical pathological hallmarks, β-amyloid, and tau, directly disrupt sleep, and neurodegeneration of locus coeruleus, hippocampal and hypothalamic neurons from tau proteinopathy causes disruption of the neuronal circuitry of sleep. Acting in a positive-feedback-loop, sleep loss and circadian rhythm disruption then increase spread of β-amyloid and tau, through impairments of proteasome, autophagy, unfolded protein response and glymphatic clearance. This phenomenon extends beyond β-amyloid and tau, with interactions of sleep impairment with the homeostasis of TDP-43, α-synuclein, FUS, and huntingtin proteins, implicating sleep loss as an important consideration in an array of neurodegenerative diseases and in cases of mixed neuropathology. Critically, the dynamics of this interaction in the neurodegenerative environment are not fully elucidated and are deserving of further discussion and research. Finally, we propose sleep-enhancing therapeutics as potential interventions for promoting healthy proteostasis, including β-amyloid and tau clearance, mechanistically linking these processes. With further clinical and preclinical research, we propose this dynamic interaction as a diagnostic and therapeutic framework, informing precise single- and combinatorial-treatments for Alzheimer's disease and other brain disorders.

Therapeutic potential of melatonin and its derivatives in aging and neurodegenerative diseases

Aging is associated with increasing impairments in brain homeostasis and represents the main risk factor across most neurodegenerative disorders. Melatonin, a neuroendocrine hormone that regulates mammalian chronobiology and endocrine functions is well known for its antioxidant potential, exhibiting both cytoprotective and chronobiotic abilities. Age-related decline of melatonin disrupting mitochondrial homeostasis and cytosolic DNA-mediated inflammatory reactions in neurons is a major contributory factor in the emergence of neurological abnormalities. There is scattered literature on the possible use of melatonin against neurodegenerative mechanisms in the aging process and its associated diseases. We have searched PUBMED with many combinations of key words for available literature spanning two decades. Based on the vast number of experimental papers, we hereby review recent advancements concerning the potential impact of melatonin on cellular redox balance and mitochondrial dynamics in the context of neurodegeneration. Next, we discuss a broader explanation of the involvement of disrupted redox homeostasis in the pathophysiology of age-related diseases and its connection to circadian mechanisms. Our effort may result in the discovery of novel therapeutic approaches. Finally, we summarize the current knowledge on molecular and circadian regulatory mechanisms of melatonin to overcome neurodegenerative diseases (NDDs) such as Alzheimer's, Parkinson's, Huntington's disease, and amyotrophic lateral sclerosis, however, these findings need to be confirmed by larger, well-designed clinical trials. This review is also expected to uncover the associated molecular alterations in the aging brain and explain how melatonin-mediated circadian restoration of neuronal homeodynamics may increase healthy lifespan in age-related NDDs.

Comment on Minich et al. Is Melatonin the "Next Vitamin D"?: A Review of Emerging Science, Clinical Uses, Safety, and Dietary Supplements. Nutrients 2022, 14, 3934

I read an article by Minich D.M. et al. [...].

Light, Water, and Melatonin: The Synergistic Regulation of Phase Separation in Dementia

The swift rise in acceptance of molecular principles defining phase separation by a broad array of scientific disciplines is shadowed by increasing discoveries linking phase separation to pathological aggregations associated with numerous neurodegenerative disorders, including Alzheimer’s disease, that contribute to dementia. Phase separation is powered by multivalent macromolecular interactions. Importantly, the release of water molecules from protein hydration shells into bulk creates entropic gains that promote phase separation and the subsequent generation of insoluble cytotoxic aggregates that drive healthy brain cells into diseased states. Higher viscosity in interfacial waters and limited hydration in interiors of biomolecular condensates facilitate phase separation. Light, water, and melatonin constitute an ancient synergy that ensures adequate protein hydration to prevent aberrant phase separation. The 670 nm visible red wavelength found in sunlight and employed in photobiomodulation reduces interfacial and mitochondrial matrix viscosity to enhance ATP production via increasing ATP synthase motor efficiency. Melatonin is a potent antioxidant that lowers viscosity to increase ATP by scavenging excess reactive oxygen species and free radicals. Reduced viscosity by light and melatonin elevates the availability of free water molecules that allow melatonin to adopt favorable conformations that enhance intrinsic features, including binding interactions with adenosine that reinforces the adenosine moiety effect of ATP responsible for preventing water removal that causes hydrophobic collapse and aggregation in phase separation. Precise recalibration of interspecies melatonin dosages that account for differences in metabolic rates and bioavailability will ensure the efficacious reinstatement of the once-powerful ancient synergy between light, water, and melatonin in a modern world.

The Role of Dietary Antioxidants and Their Potential Mechanisms in Alzheimer’s Disease Treatment

Alzheimer’s disease (AD) is a progressive neurodegenerative disorder associated with cognitive decline and characterized by amyloid-β plaques and neurofibrillary tau tangles. Although AD’s exact pathophysiology remains unclear, oxidative stress is known to play a role in the neurodegenerative process. Since no curative treatment exists, antioxidants represent a potential treatment for AD due to their ability to modulate oxidative stress. Therefore, this review aims to examine the impact of antioxidant supplementation and its potential mechanisms on cognitive function. The review primarily discusses research articles published between 2012 and 2022 reporting the results of clinical trials involving antioxidant supplementation on cognitive function in individuals with AD. Antioxidant supplementation included probiotics, selenium, melatonin, resveratrol, rosmarinic acid, carotenoids, curcumin, vitamin E, and coenzyme Q. While the studies included in this review did not provide much evidence for the beneficial role of antioxidant supplements on cognitive function in AD, the results varied from antioxidant to antioxidant and among trials examining the same antioxidant. Furthermore, many of the studies’ findings face several limitations, including short trial durations, small sample sizes, and a lack of diversity among study participants. As a result, more research is required to examine the impact of antioxidant supplementation on cognitive function in AD.

The potential roles of ATF family in the treatment of Alzheimer's disease

Activating transcription factors, ATFs, is a family of transcription factors that activate gene expression and transcription by recognizing and combining the cAMP response element binding proteins (CREB). It is present in various viruses as a cellular gene promoter. ATFs is involved in regulating the mammalian gene expression that is associated with various cell physiological processes. Therefore, ATFs play an important role in maintaining the intracellular homeostasis. ATF2 and ATF3 is mostly involved in mediating stress responses. ATF4 regulates the oxidative metabolism, which is associated with the survival of cells. ATF5 is presumed to regulate apoptosis, and ATF6 is involved in the regulation of endoplasmic reticulum stress (ERS). ATFs is actively studied in oncology. At present, there has been an increasing amount of research on ATFs for the treatment of neurological diseases. Here, we have focused on the different types of ATFs and their association with Alzheimer's disease (AD). The level of expression of different ATFs have a significant difference in AD patients when compared to healthy control. Recent studies have suggested that ATFs are implicated in the pathogenesis of AD, such as neuronal repair, maintenance of synaptic activity, maintenance of cell survival, inhibition of apoptosis, and regulation of stress responses. In this review, the potential role of ATFs for the treatment of AD has been highlighted. In addition, we have systematically reviewed the progress of research on ATFs in AD. This review will provide a basic and innovative understanding on the pathogenesis and treatment of AD.

Brain washing and neural health: role of age, sleep, and the cerebrospinal fluid melatonin rhythm

The brain lacks a classic lymphatic drainage system. How it is cleansed of damaged proteins, cellular debris, and molecular by-products has remained a mystery for decades. Recent discoveries have identified a hybrid system that includes cerebrospinal fluid (CSF)-filled perivascular spaces and classic lymph vessels in the dural covering of the brain and spinal cord that functionally cooperate to remove toxic and non-functional trash from the brain. These two components functioning together are referred to as the glymphatic system. We propose that the high levels of melatonin secreted by the pineal gland directly into the CSF play a role in flushing pathological molecules such as amyloid-β peptide (Aβ) from the brain via this network. Melatonin is a sleep-promoting agent, with waste clearance from the CNS being highest especially during slow wave sleep. Melatonin is also a potent and versatile antioxidant that prevents neural accumulation of oxidatively-damaged molecules which contribute to neurological decline. Due to its feedback actions on the suprachiasmatic nucleus, CSF melatonin rhythm functions to maintain optimal circadian rhythmicity, which is also critical for preserving neurocognitive health. Melatonin levels drop dramatically in the frail aged, potentially contributing to neurological failure and dementia. Melatonin supplementation in animal models of Alzheimer's disease (AD) defers Aβ accumulation, enhances its clearance from the CNS, and prolongs animal survival. In AD patients, preliminary data show that melatonin use reduces neurobehavioral signs such as sundowning. Finally, melatonin controls the mitotic activity of neural stem cells in the subventricular zone, suggesting its involvement in neuronal renewal.

Regulatory role of melatonin in Notch1 signaling pathway in cerebral cortex of Aβ1-42-induced Alzheimer's disease rat model

BACKGROUND

Soluble Amyloid-beta (Aβ) oligomers are thought to play a key role in the pathogenesis of Alzheimer's disease (AD), which is the most common age-associated neurodegenerative diseases with obvious neuropathological changes and functional decline in both cortical and subcortical regions. Melatonin is ubiquitously distributed and multifunctioning indoleamine. Accumulating studies support that melatonin is potential therapeutic molecule for AD through modulating a broad variety of signaling pathways. In recent years, Notch1 signaling pathway is been known involved in dynamic changes in the cellular architecture and function of adult brain, as well as associated with the pathophysiology of AD and other neurodegenerative disorders.

METHODS AND RESULTS

In this study, we performed real-time polymerase chain reaction, immunohistochemistry and western blotting analyses using the cerebral cortical tissues of Aβ_1-42 oligomers-induced AD rats with or without melatonin treatment. Our results showed that soluble Aβ_1-42 oligomers decreased the expression of the main components of Notch1 signaling pathway, Notch1, NICD and Hes1 in the cerebral cortex, and melatonin could restore the level of Notch1, NICD and Hes1.

CONCLUSION

This observation suggests that targeting of Notch1 signaling might be a promising therapeutic approach for AD and other age-associated neurodegenerative diseases, and melatonin might serve as a potential therapeutic agent for AD and other age-associated neurodegenerative diseases.

The association of subjective sleep characteristics and plasma biomarkers of Alzheimer's disease pathology in older cognitively unimpaired adults with higher amyloid-β burden

We aimed to investigate the association of subjective sleep characteristics and plasma Alzheimer's disease (AD) biomarkers in older cognitively unimpaired adults with higher amyloid-β (Aβ) burden. Unimpaired cognition was determined by education-adjusted performance for the Mini-Mental State Examination and exclusion of dementia and mild cognitive impairment via standardized neuropsychological tests. We used Pittsburgh Sleep Quality Index (PSQI) to assess subjective sleep quality. The participants also underwent examination of plasma AD biomarkers and ¹⁸F-florbetapir PET scan. Correlation and multiple linear regression analyses were used to investigate the association between subjective sleep characteristics and AD biomarkers. A total of 335 participants were included and 114 were Aβ-PET positive. Multivariable regression analysis showed sleep duration > 8 h and sleep disturbance were associated with Aβ deposition in total participants. Two multiple linear regression models were applied and the results revealed in participants with Aβ-PET (+), falling asleep at ≥ 22:00 to ≤ 23:00 was associated with higher levels of Aβ42 and Aβ42/40. Other associations with higher Aβ42/40 and standard uptake value ratio contained sleep efficiency value, sleep efficiency ≥ 75%, no/mild daytime dysfunction and PSQI score ≤ 5. Higher p-Tau-181 level was associated with sleep latency > 30 min in Aβ-PET (+) group and moderate/severe sleep disturbance in Aβ-PET (-) group. Our data suggests sleep duration ≤ 8 h and no/mild sleep disturbance may be related to less Aβ burden. In participants with Aβ deposition, falling asleep at 22:00 to 23:00, higher sleep efficiency (at least ≥ 75%), no/mild daytime dysfunction, sleep latency ≤ 30 min, and good sleep quality may help improve AD pathology.

Melatonin Activates Anti-Inflammatory Features in Microglia in a Multicellular Context: Evidence from Organotypic Brain Slices and HMC3 Cells

Melatonin (MEL) is a neurohormone endowed with neuroprotective activity, exerted both directly on neuronal cells and indirectly through modulation of responsive glial cells. In particular, MEL's effects on microglia are receptor-mediated and in part dependent on SIRT1 activation. In the present study, we exploited the highly preserved cytoarchitecture of organotypic brain cultures (OC) to explore the effects of MEL on hippocampal microglia in a 3D context as compared to a single cell type context represented by the human HMC3 cell line. We first evaluated the expression of MEL receptor MT1 and SIRT1 and then investigated MEL action against an inflammatory stimulation with LPS: OCs were cultured for a total of 2 weeks and during this time exposed to 0.1 μg/mL of LPS for 24 h either on day 1 (LPS 1°) or on day 11 (LPS 11°). MEL was added immediately after plating and kept for the entire experiment. Under these conditions, both MEL and LPS induced amoeboid microglia. However, the same round phenotype matched different polarization features. LPS increased the number of nuclear-NF-kB+ round cells and MEL alone or in combination with LPS increased BDNF+ round microglia. In addition, MEL contrasted LPS effects on NF-kB expression. Data from HMC3 microglia confirmed MEL's anti-inflammatory effects against LPS in terms of CASP1 induction and BDNF release, identifying SIRT1 as a mediator. However, no effects were evident for MEL alone on HMC3 microglia. Overall, our results point to the importance of the multicellular context for full MEL activity, especially in a preventive view, and support the use of OCs as a favorable model to explore inflammatory responses.

The Amyloid-Beta Clearance: From Molecular Targets to Glial and Neural Cells

The deposition of amyloid-beta (Aβ) plaques in the brain is one of the primary pathological characteristics of Alzheimer's disease (AD). It can take place 20-30 years before the onset of clinical symptoms. The imbalance between the production and the clearance of Aβ is one of the major causes of AD. Enhancing Aβ clearance at an early stage is an attractive preventive and therapeutic strategy of AD. Direct inhibition of Aβ production and aggregation using small molecules, peptides, and monoclonal antibody drugs has not yielded satisfactory efficacy in clinical trials for decades. Novel approaches are required to understand and combat Aβ deposition. Neurological dysfunction is a complex process that integrates the functions of different types of cells in the brain. The role of non-neurons in AD has not been fully elucidated. An in-depth understanding of the interactions between neurons and non-neurons can contribute to the elucidation of Aβ formation and the identification of effective drug targets. AD patient-derived pluripotent stem cells (PSCs) contain complete disease background information and have the potential to differentiate into various types of neurons and non-neurons in vitro, which may bring new insight into the treatment of AD. Here, we systematically review the latest studies on Aβ clearance and clarify the roles of cell interactions among microglia, astroglia and neurons in response to Aβ plaques, which will be beneficial to explore methods for reconstructing AD disease models using inducible PSCs (iPSCs) through cell differentiation techniques and validating the applications of models in understanding the formation of Aβ plaques. This review may provide the most promising directions of finding the clues for preventing and delaying the development of AD.

Red-light radiation: does it enhance memory by increasing hippocampal LRP-1 and TRPA-1 genes expression?

PURPOSE

Despite the extensive efforts to treat the leading cause of neurodegenerative diseases (ND), a little progress has been reported. Red light might affect ND through many specific mechanisms. The purpose of this investigation is to explore the effect of red light on the expression of low-density lipoprotein receptor-1 (LRP-1) and transient receptor potential ankyrin-1 (TRPA-1) gene in the hippocampus, and the serum melatonin level (SML) of the lipopolysaccharide (LPS)-induced neuro-inflammated rats.

MATERIALS AND METHODS

Red-light therapy was implemented using a wavelength 630 nm under different light conditions and the passive avoidance (PA) and Y-Maze tests were employed to assess memory performance. To evaluate the LRP-1 and TRPA-1 genes expression, quantitive real-time polymerase chain reaction was performed. To measure the SML, ELISA was performed before and after the red-light radiation.

RESULTS

LPS caused memory impairment in both behavioral tests. Red-light therapy improved PA memory in all light conditions (p < .001). However, in Y-maze, only the red-light radiation during light and dark cycles, improved memory (p < .01 and p < .001, respectively). In addition, red-light radiation caused significant increase in SML (p < .05). The LRP-1 and TRPA-1 genes expression increased significantly during the dark phase in the red light radiated group compared to non-radiated group (p < .001).

CONCLUSIONS

Taken together, the results suggest that red-light therapy can reduce the complications of memory impairment in rats. This study has found that red-light therapy demonstrates higher effect during the period of dark phase compared to light phase. No doubt, further experimental studies would help us to establish a greater degree of accuracy on this matter.

Alzheimer's Disease and Impaired Bone Microarchitecture, Regeneration and Potential Genetic Links

Alzheimer's Disease (AD) and osteoporosis are both age-related degenerative diseases. Many studies indicate that these two diseases share common pathogenesis mechanisms. In this review, the osteoporotic phenotype of AD mouse models was discussed, and shared mechanisms such as hormonal imbalance, genetic factors, similar signaling pathways and impaired neurotransmitters were identified. Moreover, the review provides recent data associated with these two diseases. Furthermore, potential therapeutic approaches targeting both diseases were discussed. Thus, we proposed that preventing bone loss should be one of the most important treatment goals in patients with AD; treatment targeting brain disorders is also beneficial for osteoporosis.

Melatonin: A Potential Candidate for the Treatment of Experimental and Clinical Perinatal Asphyxia

Perinatal asphyxia is considered to be one of the major causes of brain neurodegeneration in full-term newborns. The worst consequence of perinatal asphyxia is neurodegenerative brain damage, also known as hypoxic-ischemic encephalopathy. Hypoxic-ischemic encephalopathy is the leading cause of mortality in term newborns. To date, due to the complex mechanisms of brain damage, no effective or causal treatment has been developed that would ensure complete neuroprotection. Although hypothermia is the standard of care for hypoxic-ischemic encephalopathy, it does not affect all changes associated with encephalopathy. Therefore, there is a need to develop effective treatment strategies, namely research into new agents and therapies. In recent years, it has been pointed out that natural compounds with neuroprotective properties, such as melatonin, can be used in the treatment of hypoxic-ischemic encephalopathy. This natural substance with anti-inflammatory, antioxidant, anti-apoptotic and neurofunctional properties has been shown to have pleiotropic prophylactic or therapeutic effects, mainly against experimental brain neurodegeneration in hypoxic-ischemic neonates. Melatonin is a natural neuroprotective hormone, which makes it promising for the treatment of neurodegeneration after asphyxia. It is supposed that melatonin alone or in combination with hypothermia may improve neurological outcomes in infants with hypoxic-ischemic encephalopathy. Melatonin has been shown to be effective in the last 20 years of research, mainly in animals with perinatal asphyxia but, so far, no clinical trials have been performed on a sufficient number of newborns. In this review, we summarize the advantages and limitations of melatonin research in the treatment of experimental and clinical perinatal asphyxia.

Melatonin and Aging

The health problems associated with the aging process are becoming increasingly widespread due to the increase in mean life expectancy taking place globally. While decline of many organ functions is an unavoidable concomitant of senescence, these can be delayed or moderated by a range of factors. Among these are dietary changes and weight control, taking sufficient exercise, and the utilization of various micronutrients. The utility of incurring appropriate changes in lifestyle is generally not confined to a single organ system but has a broadly positive systemic effect.Among one of the most potent means of slowing down age-related changes is the use of melatonin, a widely distributed biological indole. While melatonin is well known as a treatment for insomnia, it has a wide range of beneficial qualities many of which are relevant. This overview describes how several of the properties of melatonin are especially relevant to many of the changes associated with senescence. Changes in functioning of the immune system are particularly marked in the aged, combining diminishing effectiveness with increasing ineffective and harmful activity. Melatonin treatment appears able to moderate and partially reverse this detrimental drift toward immune incompetence.

Association between rest-activity rhythm and cognitive function in the elderly: The U.S. National Health and Nutrition Examination Survey, 2011-2014

BACKGROUND

Circadian rhythm plays an essential role in various physiological and pathological processes related to cognitive function. The rest-activity rhythm (RAR) is one of the most prominent outputs of the circadian system. However, little is known about the relationships between RAR and different domains of cognitive function in older adults. The purpose of this study was to examine the relationships between RAR and various fields of cognitive function in older Americans.

METHODS

This study included a total of 2090 older adults ≥ 60 years old from the National Health and Nutrition Examination Survey (NHANES) in 2011-2014. RAR parameters were derived from accelerometer recordings. Cognitive function was assessed using the word learning subtest developed by the Consortium to Establish a Registry for Alzheimer's disease (CERAD W-L), the Animal Fluency Test (AFT) and the Digital Symbol Substitution Test (DSST). Linear regression was used to determine the relationships between RAR parameters (IS, IV, RA, L5, M10) and cognitive function scores (CERAD W-L, AFT, DSST).

RESULTS

After adjusting for potential confounders, lower IS and M10 were associated with lower CERAD W-L scores (P=0.033 and P=0.002, respectively). Weaker RA and higher L5 were associated with lower AFT scores (P<0.001 and P=0.001, respectively). And lower IS, RA, and higher L5 were associated with lower DSST scores (P=0.019, P<0.001 and P<0.001, respectively). In addition, the results of sensitivity analysis were similar to those of our main analyses. The main correlation results between the RAR indicators and cognitive function were robust.

CONCLUSIONS

This study suggested that the weakened and/or disrupted RAR was associated with cognitive decline in different domains in Americans over the age of 60.

Octadecaneuropeptide Ameliorates Cognitive Impairments Through Inhibiting Oxidative Stress in Alzheimer's Disease Models

BACKGROUND

Alzheimer's disease (AD) is a neurodegenerative disorder characterized by amyloid-β peptide (Aβ) deposition. Aβ accumulation induces oxidative stress, leading to mitochondrial dysfunction, apoptosis, and so forth. Octadecaneuropeptide (ODN), a diazepam-binding inhibitor (DBI)-derived peptide, has been reported to have antioxidant properties. However, it is unclear whether ODN has neuroprotective effects in AD.

OBJECTIVE

To profile the potential effects of ODN on AD.

METHODS

We established a mouse model of AD via microinjection of Aβ in the lateral ventricle. Utilizing a combination of western blotting assays, electrophysiological recordings, and behavioral tests, we investigated the neuroprotective effects of ODN on AD.

RESULTS

DBI expression was decreased in AD model mice and cells. Meanwhile, ODN decreased Aβ generation by downregulating amyloidogenic AβPP processing in HEK-293 cells stably expressing human Swedish mutant APP695 and BACE1 (2EB2). Moreover, ODN could inhibit Aβ-induced oxidative stress in primary cultured cells and mice, as reflected by a dramatic increase in antioxidants and a decrease in pro-oxidants. We also found that ODN could reduce oxidative stress-induced apoptosis by restoring mitochondrial membrane potential, intracellular Ca2+ and cleaved caspase-3 levels in Aβ-treated primary cultured cells and mice. More importantly, intracerebroventricular injection of ODN attenuated cognitive impairments as well as long-term potentiation in Aβ-treated mice.

CONCLUSION

These results suggest that ODN may exert a potent neuroprotective effect against Aβ-induced neurotoxicity and memory decline via its antioxidant effects, indicating that ODN may be a potential therapeutic agent for AD.

Ginsenoside ompound K reduces neuronal damage and improves neuronal synaptic dysfunction by targeting Aβ

Background: Alzheimer's disease (AD) is the most common neurodegenerative condition worldwide, with amyloid ß (Aβ) fibrils presenting as its main pathological feature. This study investigated whether Ginsenoside Compound K (CK) has activity against Aβ and its mechanism in reducing synaptic damage and cognitive impairment. Methods: The binding capacity of CK to Aβ42 and Nrf2/Keap1 was determined using molecular docking. Transmission electron microscopy was used to monitor CK-mediated degradation of Aβ fibrils. The effect of CK on the survival of Aβ42-damaged HT22 cells was determined using a CCK-8 assay. The therapeutic efficacy of CK in a scopoletin hydrobromide (SCOP) induced cognitive dysfunction mouse model was measured using a step-down passive avoidance test. GO enrichment analysis of mouse brain tissue was peformed using Genechip. Hydroxyl radical scavenging and reactive oxygen species assays were performed to verify the antioxidant activity of CK. The effects of CK on the expression of Aβ42, the Nrf2/Keap1 signaling pathway, and other proteins were determined by western blotting, immunofluorescence, and immunohistochemistry. Results: Molecular docking results showed that CK interacts with Lys16 and Glu3 of Aβ42. CK reduced the aggregation of Aβ42 as observed using transmission electron microscopy. CK increased the level of insulin-degrading enzyme and decreased the levels ß-secretase and γ-secretase; therefore, it can potentially inhibit the accumulation of Aβ in neuronal extracellular space in vivo. CK improved cognitive impairment and increased postsynaptic density protein 95 and synaptophysin expression levels in mice with SCOP-induced cognitive dysfunction. Further, CK inhibited the expression of cytochrome C, Caspase-3, and cleaved Caspase-3. Based on Genechip data, CK was found to regulate molecular functions such as oxygen binding, peroxidase activity, hemoglobin binding, and oxidoreductase activity, thus affecting the production of oxidative free radicals in neurons. Further, CK regulated the expression of the Nrf2/Keap1 signaling pathway through its interaction with the Nrf2/Keap1 complex. Conclusion: Our findings show that CK regulates the balance between Aβ monomers production and clearance, CK binds to Aβ monomer to inhibits the accumulation of Aβ, increases the level of Nrf2 in neuronal nuclei, reduces oxidative damage of neurons, improves synaptic function, thus ultimately protecting neurons.

In vitro electrochemical detection of the degradation of amyloid-β oligomers

The clearance of overloaded amyloid β (Aβ) oligomers is thought to be an attractive and potential strategy for the therapy of Alzheimer's disease (AD). A variety of strategies have already been utilized to study Aβ degradation in vitro. Here, the electrochemical detection based on direct electrooxidation of specific Tyr residues within Aβ peptide has been developed as a simple and robust approach for monitoring the oligomers' degradation. C60 was employed for photodegrading Aβ oligomers due to the generated ROS under light irradiation. The oxidation current of Tyr residues by square wave voltammetry (SWV) increased upon the Aβ degradation, confirming that the structure variation of Aβ peptide indeed influenced the exposure of those redox species to the electrode surface and final signal output. Chronoamperometric assay also found the electrooxidation of Tyr undergone an irreversible process. Additionally, the direct electrochemistry was capable of detecting the aggregation with rapid test and better sensitivity in compared with dynamic light scattering (DLS), atomic force microscopy (AFM) and thioflavin T (ThT) based fluorescence assay. Thus, this work indicated the potential application of direct electrochemistry in the in vitro measurement of Aβ degradation and clearance, providing new insights and a complementary means into the AD theranostics.

The Lymphatic System In The Brain Clearance Mechanisms - New Therapeutic Perspectives For Alzheimer's Disease

Alzheimer's disease (AD) is the most common cause of dementia worldwide. Pathological deposits of neurotoxic proteins within the brain, such as amyloid-ß and hyperphosphorylated tau tangles, are the prominent features in AD. According to recent studies, the newly discovered brain lymphatic system was demonstrated to be crucial in the clearance of metabolic macromolecules from the brain. Meningeal lymphatic vessels located in the dura mater drain the fluid, macromolecules, and immune cells from cerebrospinal fluid (CSF) and transport them, as lymph, to the deep cervical lymph nodes. The lymphatic system provides the perivascular exchange of CSF with interstitial fluid (ISF) and ensures the homeostasis of neuronal interstitial space. In this review, we aim to summarize recent findings on the role of the lymphatic system in AD pathophysiology and discuss possible therapeutic perspectives, targeting the lymphatic clearance mechanisms within the brain.

Exposure to short-chain chlorinated paraffins induces astrocyte activation via JAK2/STAT3 signaling pathway

In the last few decades, short-chain chlorinated paraffins (SCCPs) have become the most heavily produced monomeric organohalogen compounds, and have been reported to induce multiple organ toxicity. However, the effects of SCCPs on the central nervous system are unknown. In the present study, we show that SCCP exposure induced astrocyte proliferation and increased the expression of two critical markers of astrocyte activation, glial fibrillary acidic protein and inducible nitric oxide synthase, in vivo and in vitro. SCCP exposure also increased inflammatory factory gene expression. Moreover, SCCP treatment triggered Janus kinase 2 (JAK2)/signal transducer and activator of transcription 3 (STAT3) signalling, as shown by increased phosphorylation and STAT3 translocation to the nucleus. Both JAK2 and STAT3 inhibition effectively attenuated SCCP-induced astrocyte activation. Finally, JAK2 inhibition significantly rescued STAT3 phosphorylation and nuclear translocation. Taken together, JAK2/STAT3 pathway activation contributed to SCCP-induced astrocyte activation. These data will help elucidate the molecular mechanism underlying SCCP-induced neurotoxicity.

Research Evidence of the Role of the Glymphatic System and Its Potential Pharmacological Modulation in Neurodegenerative Diseases

The glymphatic system is a unique pathway that utilises end-feet Aquaporin 4 (AQP4) channels within perivascular astrocytes, which is believed to cause cerebrospinal fluid (CSF) inflow into perivascular space (PVS), providing nutrients and waste disposal of the brain parenchyma. It is theorised that the bulk flow of CSF within the PVS removes waste products, soluble proteins, and products of metabolic activity, such as amyloid-β (Aβ). In the experimental model, the glymphatic system is selectively active during slow-wave sleep, and its activity is affected by both sleep dysfunction and deprivation. Dysfunction of the glymphatic system has been proposed as a potential key driver of neurodegeneration. This hypothesis is indirectly supported by the close relationship between neurodegenerative diseases and sleep alterations, frequently occurring years before the clinical diagnosis. Therefore, a detailed characterisation of the function of the glymphatic system in human physiology and disease would shed light on its early stage pathophysiology. The study of the glymphatic system is also critical to identifying means for its pharmacological modulation, which may have the potential for disease modification. This review will critically outline the primary evidence from literature about the dysfunction of the glymphatic system in neurodegeneration and discuss the rationale and current knowledge about pharmacological modulation of the glymphatic system in the animal model and its potential clinical applications in human clinical trials.

ApoE in Alzheimer’s disease: pathophysiology and therapeutic strategies

Alzheimer’s disease (AD) is the most common cause of dementia worldwide, and its prevalence is rapidly increasing due to extended lifespans. Among the increasing number of genetic risk factors identified, the apolipoprotein E (APOE) gene remains the strongest and most prevalent, impacting more than half of all AD cases. While the ε4 allele of the APOE gene significantly increases AD risk, the ε2 allele is protective relative to the common ε3 allele. These gene alleles encode three apoE protein isoforms that differ at two amino acid positions. The primary physiological function of apoE is to mediate lipid transport in the brain and periphery; however, additional functions of apoE in diverse biological functions have been recognized. Pathogenically, apoE seeds amyloid-β (Aβ) plaques in the brain with apoE4 driving earlier and more abundant amyloids. ApoE isoforms also have differential effects on multiple Aβ-related or Aβ-independent pathways. The complexity of apoE biology and pathobiology presents challenges to designing effective apoE-targeted therapeutic strategies. This review examines the key pathobiological pathways of apoE and related targeting strategies with a specific focus on the latest technological advances and tools.

Importance of Bmal1 in Alzheimer's disease and associated aging-related diseases: Mechanisms and interventions

With the aging world population, the prevalence of aging-related disorders is on the rise. Diseases such as Alzheimer's, type 2 diabetes mellitus (T2DM), Parkinson's, atherosclerosis, hypertension, and osteoarthritis are age-related, and most of these diseases are comorbidities or risk factors for AD; however, our understandings of molecular events that regulate the occurrence of these diseases are still not fully understood. Brain and muscle Arnt-like protein-1 (Bmal1) is an irreplaceable clock gene that governs multiple important physiological processes. Continuous research of Bmal1 in AD and associated aging-related diseases is ongoing, and this review picks relevant studies on a detailed account of its role and mechanisms in these diseases. Oxidative stress and inflammation turned out to be common mechanisms by which Bmal1 deficiency promotes AD and associated aging-related diseases, and other Bmal1-dependent mechanisms remain to be identified. Promising therapeutic strategies involved in the regulation of Bmal1 are provided, including melatonin, natural compounds, metformin, d-Ser2-oxyntomodulin, and other interventions, such as exercise, time-restricted feeding, and adiponectin. The establishment of the signaling pathway network for Bmal1 in aging-related diseases will lead to advances in the comprehension of the molecular and cellular mechanisms, shedding light on novel treatments for aging-related diseases and promoting aging-associated brain health.

Is Melatonin the "Next Vitamin D"?: A Review of Emerging Science, Clinical Uses, Safety, and Dietary Supplements

Melatonin has become a popular dietary supplement, most known as a chronobiotic, and for establishing healthy sleep. Research over the last decade into cancer, Alzheimer's disease, multiple sclerosis, fertility, PCOS, and many other conditions, combined with the COVID-19 pandemic, has led to greater awareness of melatonin because of its ability to act as a potent antioxidant, immune-active agent, and mitochondrial regulator. There are distinct similarities between melatonin and vitamin D in the depth and breadth of their impact on health. Both act as hormones, affect multiple systems through their immune-modulating, anti-inflammatory functions, are found in the skin, and are responsive to sunlight and darkness. In fact, there may be similarities between the widespread concern about vitamin D deficiency as a "sunlight deficiency" and reduced melatonin secretion as a result of "darkness deficiency" from overexposure to artificial blue light. The trend toward greater use of melatonin supplements has resulted in concern about its safety, especially higher doses, long-term use, and application in certain populations (e.g., children). This review aims to evaluate the recent data on melatonin's mechanisms, its clinical uses beyond sleep, safety concerns, and a thorough summary of therapeutic considerations concerning dietary supplementation, including the different formats available (animal, synthetic, and phytomelatonin), dosing, timing, contraindications, and nutrient combinations.

Genetic Causes of Alzheimer's Disease and the Neuroprotective Role of Melatonin in its Management

Dementia is a global health concern owing to its complexity, which also poses a great challenge to pharmaceutical scientists and neuroscientists. The global dementia prevalence is approximately 47 million, which may increase by three times by 2050. Alzheimer's disease (AD) is the most common cause of dementia. AD is a severe age-related neurodegenerative disorder characterized by short-term memory loss, aphasia, mood imbalance, and executive function. The etiology of AD is still unknown, and the exact origin of the disease is still under investigation. Aggregation of Amyloid β (Aβ) plaques or neurotoxic Aβo oligomers outside the neuron is the most common cause of AD development. Amyloid precursor protein (APP) processing by β secretase and γ secretase produces abnormal Aβ monomers. This aggregation of Aβ and NFT is promoted by various genes like BACE1, ADAM10, PIN1, GSK-3, APOE, PPARα, etc. Identification of these genes can discover several therapeutic targets that can be useful in studying pathogenesis and underlying treatments. Melatonin modulates the activities of these genes, thereby reducing Aβ production and increasing its clearance. Melatonin also reduces the expression of APP by attenuating cAMP, thereby enhancing the non-amyloidogenic process. Present communication explored and discussed the neuroprotective role of melatonin against Aβ-dependent AD pathogenesis. The manuscript also discussed potential molecular and genetic mechanisms of melatonin in the production and clearance of Aβ that could ameliorate neurotoxicity.

Neuroprotective Effects of Phytochemicals against Aluminum Chloride-Induced Alzheimer’s Disease through ApoE4/LRP1, Wnt3/β-Catenin/GSK3β, and TLR4/NLRP3 Pathways with Physical and Mental Activities in a Rat Model

Background: Alzheimer’s disease (AD) is a neurodegenerative disorder that is associated with abnormal cognition. AD is aided in its initiation and progression by hereditary and environmental factors. Aluminum (Al) is a neurotoxic agent that causes oxidative stress, which is linked to AD progression. Additionally, Nrf2/HO-1, APOE4/LRP1, Wnt3/β-catenin, and TLR4/NLRP3 are the main signaling pathways involved in AD pathogenesis. Several phytochemicals are promising options in delaying AD evolution. Objectives: This study aimed at studying the neuroprotective effects of some phytochemicals as morin (MOR), thymol (TML), and thymoquinone (TMQ) on physical and mental activities (PhM) in Al chloride (AlCl₃)-induced AD rat model. Another objective was to determine the specificity of phytochemicals to AD signaling pathways using molecular docking. Methods: Eighty male Dawley rats were divided into eight groups. Each group received: saline (control group), AlCl₃, (ALAD), PhM, either alone or with a combination of MOR, TML, and/or TMQ for five weeks. Animals were then subjected to behavioral evaluation. Brain tissues were used for histopathological and biochemical analyses to determine the extent of neurodegeneration. The effect of phytochemicals on AlCl₃-induced oxidative stress and the main signaling pathways involved in AD progression were also investigated. Results: AlCl₃ caused a decline in spatial learning and memory, as well as histopathological changes in the brains of rats. Phytochemicals combined with PhM restored antioxidant activities, increased HO-1 and Nrf2 levels, blocked inflammasome activation, apoptosis, TLR4 expression, amyloide-β generation, and tau hyperphophorylation. They also brought ApoE4 and LRP1 levels back to normal and regulated Wnt3/β-catenin/GSK3β signaling pathway. Conclusions: The use of phytochemicals with PhM is a promising strategy for reducing AD by modulating Nrf2/HO-1, TLR4/NLRP3, APOE4/LRP1, and Wnt3/β-catenin/GSK-3β signaling pathways.

Level-specific associations of urinary antimony with cognitive function in US older adults from the National Health and Nutrition Examination Survey 2011-2014

BACKGROUND

We have looked at antimony (Sb) as a new neurotoxin which causes neuronal apoptosis in animal studies. At the population level, however, there is no direct evidence for a relationship between Sb exposure and cognitive performance.

METHOD

The study comprehensively assessed the correlation between urinary antimony levels and cognitive test scores in 631 creatinine-corrected older persons using data from the National Health and Nutrition Examination Survey (NHANES) from 2011 to 2014.

RESULTS

Using logistic regression, the study looked at the prevalence of cognitive impairment at different levels of urine antimony concentrations and found that, after controlling for covariates, higher doses of urinary antimony were positively associated with cognitive function compared to controls, odds ratio (ORs) with 95% confidence interval (CI) were 0.409 (0.185-0.906) and 0.402 (0.186-0.871) respectively. Restricted cubic spline curves showed a non-linear and dose-specific correlation between urinary antimony and cognitive performance, with lower doses associated with better cognitive performance, while higher doses may be associated with cognitive impairment.

CONCLUSIONS

Our data provide evidence for a correlation between Sb and cognitive function at the population level, although the specific mechanisms need to be investigated further.

New Possibilities in the Therapeutic Approach to Alzheimer's Disease

Despite the fact that Alzheimer's disease (AD) is the most common cause of dementia, after many years of research regarding this disease, there is no casual treatment. Regardless of the serious public health threat it poses, only five medical treatments for Alzheimer's disease have been authorized, and they only control symptoms rather than changing the course of the disease. Numerous clinical trials of single-agent therapy did not slow the development of disease or improve symptoms when compared to placebo. Evidence indicates that the pathological alterations linked to AD start many years earlier than a manifestation of the disease. In this pre-clinical period before the neurodegenerative process is established, pharmaceutical therapy might prove invaluable. Although recent findings from the testing of drugs such as aducanumab are encouraging, they should nevertheless be interpreted cautiously. Such medications may be able to delay the onset of dementia, significantly lowering the prevalence of the disease, but are still a long way from having a clinically effective disease-modifying therapy.