Role of melatonin in Alzheimer-like neurodegeneration

Integrative bioinformatic approach reveals novel melatonin-related biomarkers for Alzheimer's disease

BACKGROUND

Melatonin (MLT) can improve mitophagy, thereby ameliorating cognitive deficits in Alzheimer's disease (AD) patients. Hence, our research focused on the potential value of MLT-related genes (MRGs) in AD through bioinformatic analysis.

METHODS

First, the key cells in the single-cell dataset GSE138852 were screened out based on the proportion of annotated cells and Fisher's test between the AD and control groups. The differentially expressed genes (DEGs) in the key cell and GSE5281 datasets were identified, and the MRGs in GSE5281 were selected via weighted gene coexpression network analysis. After intersecting two sets of DEGs and MRGs, we performed Mendelian randomization analysis to identify the MRGs causally related to AD. Biomarkers were further ascertained through receiver operating characteristic curve (ROC) and expression analysis in GSE5281 and GSE48350. Furthermore, gene set enrichment analysis, immune infiltration analysis and correlation analysis with metabolic pathways were conducted, as well as construction of a regulator network and molecular docking.

RESULTS

According to the Fisher test, oligodendrocytes were regarded as key cells due to their excellent abundance in the GSE138852 dataset, in which there were 281 DEGs between the AD and control groups. After overlapping with 3,490 DEGs and 550 MRGs in GSE5281, four genes were found to be causally related to AD, namely, G protein-coupled receptor, family C, group 5, member B (GPRC5B), Methyltransferase-like protein 7 A (METTL7A), NF-κB inhibitor alpha (NFKBIA) and RAS association domain family 4(RASSF4). Moreover, GPRC5B, NFKBIA and RASSF4 were deemed biomarkers, except for METTL7A, because of their indistinctive expression between the AD and control groups. Biomarkers might be involved in oxidative phosphorylation, adipogenesis and heme metabolism. Moreover, T helper type 17 cells, natural killer cells and CD56dim natural killer cells were significantly correlated with biomarkers. Transcription factors (GATA2, POU2F2, NFKB1, etc.) can regulate the expression of biomarkers. Finally, we discovered that all biomarkers could bind to MLT with a strong binding energy.

CONCLUSION

Our study identified three novel biomarkers related to MLT for AD, namely, GPRC5B, NFKBIA and RASSF4, providing a novel approach for the investigation and treatment of AD patients.

Examining the role of antioxidant supplementation in mitigating oxidative stress markers in Alzheimer's disease: a comprehensive review

Alzheimer's disease is a devastating neurodegenerative disorder that affects millions of people worldwide. One of the key pathological features of Alzheimer's disease is oxidative stress, which is characterized by an imbalance between the production of reactive oxygen species and the body's ability to neutralize them with antioxidants. In recent years, there has been growing interest in the potential role of antioxidant supplementation in mitigating oxidative stress markers in Alzheimer's disease. This review paper aims to provide a comprehensive overview of the current research on antioxidant supplementation in Alzheimer's disease and its effects on oxidative stress markers. The paper will examine the underlying mechanisms of oxidative stress in Alzheimer's disease, the potential benefits of antioxidant supplementation, and the challenges and limitations of using antioxidants as a therapeutic strategy.

Melatonin derivative 6a protects Caenorhabditis elegans from formaldehyde neurotoxicity via ADH5

Formaldehyde (FA) is a carcinogen that is not only widespread in the environment, but is also produced endogenously by metabolic processes. In organisms, FA is converted to formic acid in a glutathione (GSH)-dependent manner by alcohol dehydrogenase 5 (ADH5). The abnormal accumulation of FA in the body can cause a variety of diseases, especially cognitive impairment leading to Alzheimer's disease (AD). In this study, melatonin derivative 6a (MD6a) markedly improved the survival and chemotactic performance of wild-type Caenorhabditis elegans exposed to high concentrations of FA. MD6a lowered FA levels in the nematodes by enhancing the release of covalently-bound GSH from S-hydroxymethyl-GSH in an adh-5-dependent manner. In addition, MD6a protected against mitochondrial dysfunction and cognitive impairment in beta-amyloid protein (Aβ) transgenic nematodes by lowering endogenous FA levels and reducing Aβ aggregation in an adh-5-dependent manner. Our findings suggest that MD6a detoxifies FA via ADH5 and protects against Aβ toxicity by reducing endogenous FA levels in the C. elegans AD models. Thus, ADH5 might be a potential therapeutic target for FA toxicity and AD.

DRTerHGAT: A drug repurposing method based on the ternary heterogeneous graph attention network

Drug repurposing is an effective method to reduce the time and cost of drug development. Computational drug repurposing can quickly screen out the most likely associations from large biological databases to achieve effective drug repurposing. However, building a comprehensive model that integrates drugs, proteins, and diseases for drug repurposing remains challenging. This study proposes a drug repurposing method based on the ternary heterogeneous graph attention network (DRTerHGAT). DRTerHGAT designs a novel protein feature extraction process consisting of a large-scale protein language model and a multi-task autoencoder, so that protein features can be extracted accurately and efficiently from amino acid sequences. The ternary heterogeneous graph of drug-protein-disease comprehensively considering the relationships among the three types of nodes, including three homogeneous and three heterogeneous relationships. Based on the graph and the extracted protein features, the deep features of the drugs and the diseases are extracted by graph convolutional networks (GCN) and heterogeneous graph node attention networks (HGNA). In the experiments, DRTerHGAT is proven superior to existing advanced methods and DRTerHGAT variants. DRTerHGAT's powerful ability for drug repurposing is also demonstrated in Alzheimer's disease.

Stress-related cellular pathophysiology as a crosstalk risk factor for neurocognitive and psychiatric disorders

In this narrative review, we examine biological processes linking psychological stress and cognition, with a focus on how psychological stress can activate multiple neurobiological mechanisms that drive cognitive decline and behavioral change. First, we describe the general neurobiology of the stress response to define neurocognitive stress reactivity. Second, we review aspects of epigenetic regulation, synaptic transmission, sex hormones, photoperiodic plasticity, and psychoneuroimmunological processes that can contribute to cognitive decline and neuropsychiatric conditions. Third, we explain mechanistic processes linking the stress response and neuropathology. Fourth, we discuss molecular nuances such as an interplay between kinases and proteins, as well as differential role of sex hormones, that can increase vulnerability to cognitive and emotional dysregulation following stress. Finally, we explicate several testable hypotheses for stress, neurocognitive, and neuropsychiatric research. Together, this work highlights how stress processes alter neurophysiology on multiple levels to increase individuals' risk for neurocognitive and psychiatric disorders, and points toward novel therapeutic targets for mitigating these effects. The resulting models can thus advance dementia and mental health research, and translational neuroscience, with an eye toward clinical application in cognitive and behavioral neurology, and psychiatry.

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.

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.

Loss of smelling is an early marker of aging and is associated with inflammation and DNA damage in C57BL/6J mice

Olfactory dysfunction is a prevalent symptom and an early marker of age-related neurodegenerative diseases in humans, including Alzheimer's and Parkinson's Diseases. However, as olfactory dysfunction is also a common symptom of normal aging, it is important to identify associated behavioral and mechanistic changes that underlie olfactory dysfunction in nonpathological aging. In the present study, we systematically investigated age-related behavioral changes in four specific domains of olfaction and the molecular basis in C57BL/6J mice. Our results showed that selective loss of odor discrimination was the earliest smelling behavioral change with aging, followed by a decline in odor sensitivity and detection while odor habituation remained in old mice. Compared to behavioral changes related with cognitive and motor functions, smelling loss was among the earliest biomarkers of aging. During aging, metabolites related with oxidative stress, osmolytes, and infection became dysregulated in the olfactory bulb, and G protein coupled receptor-related signaling was significantly down regulated in olfactory bulbs of aged mice. Poly ADP-ribosylation levels, protein expression of DNA damage markers, and inflammation increased significantly in the olfactory bulb of older mice. Lower NAD⁺ levels were also detected. Supplementation of NAD⁺ through NR in water improved longevity and partially enhanced olfaction in aged mice. Our studies provide mechanistic and biological insights into the olfaction decline during aging and highlight the role of NAD⁺ for preserving smelling function and general health.

Effects of Aluminum Oxide Nanoparticles in the Cerebrum, Hippocampus, and Cerebellum of Male Wistar Rats and Potential Ameliorative Role of Melatonin

Aluminum oxide nanoparticles (Al₂O₃ NPs) have been widely used in vaccine manufacture, food additives, human care products, and cosmetics. However, they also have adverse effects on different organs, including the liver, kidneys, and testes. Melatonin is a potent antioxidant, particularly against metals by forming melatonin-metal complexes. The present study aimed to investigate the protective effects of melatonin against Al₂O₃ NP-induced toxicity in the rat brain. Forty adult male Wistar rats were allocated to four groups: the untreated control (received standard diet and distilled water), Al₂O₃ NP-treated (received 30 mg/kg body weight Al₂O₃ NPs), melatonin and Al₂O₃ NP-treated (received 30 mg/kg body weight Al₂O₃ NPs + 10 mg/kg body weight melatonin), and melatonin-treated (received 10 mg/kg body weight melatonin) groups. All treatments were by oral gavages and administered daily for 28 days. Afterward, the rats were sacrificed, and samples from various brain regions (cerebrum, cerebellum, and hippocampus) were subjected to biochemical, histopathological, and immunohistochemical analyses. Al₂O₃ NPs substantially increased malondialdehyde, β-amyloid 1-42 peptide, acetylcholinesterase, and β-secretase-1 expression, whereas they markedly decreased glutathione levels. Furthermore, Al₂O₃ NPs induced severe histopathological alterations, including vacuolation of the neuropil, enlarged pericellular and perivascular spaces, vascular congestion, neuronal degeneration, and pyknosis. Al₂O₃ NP treatment also resulted in an intense positive caspase-3 immunostaining. Conversely, the administration of melatonin alleviated the adverse effects induced by Al₂O₃ NPs. Therefore, melatonin can diminish the neurotoxic effects induced by Al₂O₃ NPs.

Phytomelatonin: a potential phytotherapeutic intervention on COVID-19-exposed individuals

Phytomelatonin is a pleiotropic molecule that originated in higher plants with many diverse actions and is primarily an antioxidant. The recent identification and advancement of phytomelatonin unraveled the potential of this modulatory molecule being considered a new plant hormone, suggesting its relevance in treating respiratory infections, including COVID-19. Besides, this molecule is also involved in multiple hormonal, physiological, and biological processes at different levels of cell organization and has been marked for its ability to cross the blood-brain barrier and prominent antioxidant effects, reducing mitochondrial electron leakage, up-regulating antioxidant enzymes, acting as a free radical scavenger, and interfering with pro-inflammatory signaling pathways as seen in mood swings, body temperature, sleep, cancer, cardiac rhythms, and immunological regulation modulators. However, due to its diversity, availability, affordability, convenience, and high safety profile, phytomelatonin has also been suggested as a natural adjuvant. This review discussed the origin, content in various plant species, processes of extraction, and detection and therapeutic potentials of phytomelatonin in treating COVID-19-exposed individuals.

Effects of exogenous melatonin supplementation on health outcomes: An umbrella review of meta-analyses based on randomized controlled trials

Various melatonin supplementations have been developed to improve health outcomes in various clinical conditions. Thus, we sought to evaluate and summarize the effect of melatonin treatments in clinical settings for health outcomes. We searched PubMed/Medline, Embase, and Cochrane Library from inception to 4 February 2021. We included meta-analyses of randomized controlled trials investigating the melatonin intervention for any health outcome. Based on the different effect sizes of each meta-analysis, we calculated random models' standardized mean differences or risk ratios. We observed robust evidence supported by statistical significance with non-considerable heterogeneity between studies for sleep-related problems, cancer, surgical patients, and pregnant women. Patients with sleep disorder, sleep onset latency (SMD 0.33, 95% CI: 0.10 - 0.56, P < 0.01) were significantly improved whereas no clear evidence was shown with sleep efficiency (1.10, 95% CI: -0.26 to 2.45). The first analgesic requirement time (SMD 5.81, 95% CI: 2.57-9.05, P < 0.001) of surgical patients was distinctly improved. Female patients under artificial reproductive technologies had significant increase in the top-quality embryos (SMD 0.53, 95% CI: 0.27 - 0.79, P < 0.001), but no statistically clear evidence was found in the live birth rate (SMD 1.20, 95% CI: 0.83 - 1.72). Survival at one year (RR 1.90, 95% CI: 1.28 - 2.83, P < 0.005) significantly increased with cancer patients. Research on melatonin interventions to treat clinical symptoms and sleep problems among diverse health conditions was identified and provided considerable evidence. Future well-designed randomized clinical trials of high quality and subgroup quantitative analyses are essential.

Antioxidants in Alzheimer's Disease: Current Therapeutic Significance and Future Prospects

Alzheimer's disease (AD) rate is accelerating with the increasing aging of the world's population. The World Health Organization (WHO) stated AD as a global health priority. According to the WHO report, around 82 million people in 2030 and 152 million in 2050 will develop dementia (AD contributes 60% to 70% of cases), considering the current scenario. AD is the most common neurodegenerative disease, intensifying impairments in cognition, behavior, and memory. Histopathological AD variations include extracellular senile plaques' formation, tangling of intracellular neurofibrils, and synaptic and neuronal loss in the brain. Multiple evidence directly indicates that oxidative stress participates in an early phase of AD before cytopathology. Moreover, oxidative stress is induced by almost all misfolded protein lumps like α-synuclein, amyloid-β, and others. Oxidative stress plays a crucial role in activating and causing various cell signaling pathways that result in lesion formations of toxic substances, which foster the development of the disease. Antioxidants are widely preferred to combat oxidative stress, and those derived from natural sources, which are often incorporated into dietary habits, can play an important role in delaying the onset as well as reducing the progression of AD. However, this approach has not been extensively explored yet. Moreover, there has been growing evidence that a combination of antioxidants in conjugation with a nutrient-rich diet might be more effective in tackling AD pathogenesis. Thus, considering the above-stated fact, this comprehensive review aims to elaborate the basics of AD and antioxidants, including the vitality of antioxidants in AD. Moreover, this review may help researchers to develop effectively and potentially improved antioxidant therapeutic strategies for this disease as it also deals with the clinical trials in the stated field.

The Dose and Duration-dependent Association between Melatonin Treatment and Overall Cognition in Alzheimer's Dementia: A Network Meta- Analysis of Randomized Placebo-Controlled Trials

BACKGROUND

While Alzheimer's dementia (AD) has a prevalence as high as 3-32% and is associated with cognitive dysfunction and the risk of institutionalization, no efficacious and acceptable treatments can modify the course of cognitive decline in AD. Potential benefits of exogenous melatonin for cognition have been divergent across trials.

OBJECTIVE

The current network meta-analysis (NMA) was conducted under the frequentist model to evaluate the potential beneficial effects of exogenous melatonin supplementation on overall cognitive function in participants with AD in comparison to other FDA-approved medications (donepezil, galantamine, rivastigmine, memantine, and Namzaric).

METHODS

The primary outcome was the changes in the cognitive function [measured by mini-mental state examination (MMSE)] after treatment in patients with Alzheimer's dementia. The secondary outcomes were changes in the quality of life, behavioral disturbance, and acceptability (i.e., drop-out due to any reason and rate of any adverse event reported).

RESULTS

The current NMA of 50 randomized placebo-controlled trials (RCTs) revealed the medium-term lowdose melatonin to be associated with the highest post-treatment MMSE (mean difference = 1.48 in MMSE score, 95% confidence intervals [95% CIs] = 0.51 to 2.46) and quality of life (standardized mean difference = -0.64, 95% CIs = -1.13 to -0.15) among all of the investigated medications in the participants with AD. Finally, all of the investigated exogenous melatonin supplements were associated with similar acceptability as was the placebo.

CONCLUSION

The current NMA provides evidence for the potential benefits of exogenous melatonin supplementation, especially medium-term low-dose melatonin, in participants with AD.

Circadian rhythms in neurodegenerative disorders

Endogenous biological clocks, orchestrated by the suprachiasmatic nucleus, time the circadian rhythms that synchronize physiological and behavioural functions in humans. The circadian system influences most physiological processes, including sleep, alertness and cognitive performance. Disruption of circadian homeostasis has deleterious effects on human health. Neurodegenerative disorders involve a wide range of symptoms, many of which exhibit diurnal variations in frequency and intensity. These disorders also disrupt circadian homeostasis, which in turn has negative effects on symptoms and quality of life. Emerging evidence points to a bidirectional relationship between circadian homeostasis and neurodegeneration, suggesting that circadian function might have an important role in the progression of neurodegenerative disorders. Therefore, the circadian system has become an attractive target for research and clinical care innovations. Studying circadian disruption in neurodegenerative disorders could expand our understanding of the pathophysiology of neurodegeneration and facilitate the development of novel, circadian-based interventions for these disabling disorders. In this Review, we discuss the alterations to the circadian system that occur in movement (Parkinson disease and Huntington disease) and cognitive (Alzheimer disease and frontotemporal dementia) neurodegenerative disorders and provide directions for future investigations in this field.

The potential neuroprotective effect of allicin and melatonin in acrylamide-induced brain damage in rats

Acrylamide (ACR) is an unsaturated monomer that served various fields; however, it is a potent neurotoxin. The target of the present study is to explore the neuroprotective efficacy of allicin and melatonin on ACR-induced neurotoxicity. Thirty-six male adult rats were non-selectively separated into six groups: placebo, allicin (20 mg/kg b.w daily per os), melatonin (10 mg/kg b.w 3 times/week per os), ACR (50 mg/kg b.w daily per os), ACR-allicin, and ACR-melatonin at the same doses as the preceding groups. The assessment of brain biomarkers, neurotransmitters, antioxidative status, Nrf2 signaling pathway, and histopathological analyses was performed following 21 days. ACR exposure induced brain lipid and DNA oxidative damage as well as reduced the glutathione (GSH) levels. The obvious brain oxidative injuries contributed to distinct brain dysfunction that was assured by alteration of brain neurotransmitters (serotonin, dopamine, acetylcholine, and acetylcholinesterase) and pathological brain lesions. Furthermore, ACR exposure increased hydroxy deoxyguanosine (8-OHdG), tumor necrosis factor-α (TNF-α), and amyloid protein (AB1-42). Finally, the mRNA transcripts of brain Keap-1, Nrf2, and NF-kB were upregulated after ACR intoxication. Interestingly, allicin and melatonin alleviated the ACR-induced brain damage assessed by the normalization of the mentioned analyses. The present study demonstrated the protective role of both allicin and melatonin in ACR-prompted neuropathy by alleviation of redox imbalance and enhancement of neurotransmitters as well as relieving DNA damage and anti-inflammatory effect.

Melatonin: Regulation of Biomolecular Condensates in Neurodegenerative Disorders

Biomolecular condensates are membraneless organelles (MLOs) that form dynamic, chemically distinct subcellular compartments organizing macromolecules such as proteins, RNA, and DNA in unicellular prokaryotic bacteria and complex eukaryotic cells. Separated from surrounding environments, MLOs in the nucleoplasm, cytoplasm, and mitochondria assemble by liquid-liquid phase separation (LLPS) into transient, non-static, liquid-like droplets that regulate essential molecular functions. LLPS is primarily controlled by post-translational modifications (PTMs) that fine-tune the balance between attractive and repulsive charge states and/or binding motifs of proteins. Aberrant phase separation due to dysregulated membrane lipid rafts and/or PTMs, as well as the absence of adequate hydrotropic small molecules such as ATP, or the presence of specific RNA proteins can cause pathological protein aggregation in neurodegenerative disorders. Melatonin may exert a dominant influence over phase separation in biomolecular condensates by optimizing membrane and MLO interdependent reactions through stabilizing lipid raft domains, reducing line tension, and maintaining negative membrane curvature and fluidity. As a potent antioxidant, melatonin protects cardiolipin and other membrane lipids from peroxidation cascades, supporting protein trafficking, signaling, ion channel activities, and ATPase functionality during condensate coacervation or dissolution. Melatonin may even control condensate LLPS through PTM and balance mRNA- and RNA-binding protein composition by regulating N6-methyladenosine (m6A) modifications. There is currently a lack of pharmaceuticals targeting neurodegenerative disorders via the regulation of phase separation. The potential of melatonin in the modulation of biomolecular condensate in the attenuation of aberrant condensate aggregation in neurodegenerative disorders is discussed in this review.

Standardizing Melanopic Effects of Ocular Light for Ecological Lighting Design of Nonresidential Buildings—An Overview of Current Legislation and Accompanying Scientific Studies

DIN SPEC 5031-100 and CIE S 026:2018 are regulatory frameworks that are intended to establish health-preserving indoor lighting in Europe. Therefore, they are crucial for the visual environment and its sustainability. The standards are largely congruent. Inconsistencies should now be harmonized with the newly published draft standard DIN/TS 5031-100, for which the objection period ended on 3 June 2020; thus, it can be expected that the standard will soon be put into operation. This publication provides the reader with a detailed technical as well as medical overview of the scope and background information on how the standard came about. Applicable laws, ordinances and standards were compiled across countries, and related studies were reviewed. It is demonstrated that the focus of this new standard, as with previous versions, is on the melanopic sensitivity of ganglion cells. The authors base this on a literature search for projects about ecological lighting design over the past 20 years. However, in practice, the publication of the standard does not yet completely counteract the health effects of inappropriate indoor lighting.

In Silico ADME, Metabolism Prediction and Hydrolysis Study of Melatonin Derivatives

Melatonin (MLT) is a well-known pineal hormone possessed with remarkable biological activities. However, its low oral bioavailability and high first-pass metabolism rate are important pharmacokinetics problems. Therefore, 5 MLT derivatives (1-5) were designed and synthesised in our group to solve these problems. In this work, in silico analysis of all synthetic derivatives for pharmacokinetic and drug-likeness parameters were predicted by SwissADME software. The results revealed that all derivatives (1-5) met the requirements for ideal oral bioavailability and CNS drugs. The molecular docking showed that the acetyl-MLT derivative (1) and the un-substitution at N1-position derivative 5 would be substrates of CYP1A2, while the lipophilic substituted N1-position derivatives 2-4 could not be metabolised by CYP1A2. Moreover, all N-amide derivatives (1-4) were hydrolysed and released less than 2.33% MLT after 4-hour incubation in 80% human plasma. It seemed that these derivatives preferred to behave like drugs rather than prodrugs of MLT. These findings confirmed that the addition of bulky groups at the N1-position of the MLT core could prolong the half-life, increase drug absorption and penetrate the blood brain barrier into the CNS.

On the Etiopathogenesis and Pathophysiology of Alzheimer's Disease: A Comprehensive Theoretical Review

Alzheimers' disease (AD) is the most common cause of dementia, with an estimated 5 million new cases occurring annually. Among the elderly, AD shortens life expectancy, results in disability, decreases quality of life, and ultimately, leads to institutionalization. Despite extensive research in the last few decades, its heterogeneous pathophysiology and etiopathogenesis have made it difficult to develop an effective treatment and prevention strategy. Aging is the biggest risk factor for AD and evidence suggest that the total number of older people in the population is going to increase astronomically in the next decades. Also, there is evidence that air pollution and increasing income inequality may result in higher incidence and prevalence of AD. This makes the need for a comprehensive understanding of the etiopathogenesis and pathophysiology of the disease extremely critical. In this paper, a quintuple framework of thyroid dysfunction, vitamin D deficiency, sex hormones, and mitochondria dysfunction and oxidative stress are used to provide a comprehensive description of AD etiopathogenesis and pathophysiology. The individual role of each factor, their synergistic and genetic interactions, as well as the limitations of the framework are discussed.

Therapeutic potential of neurogenesis and melatonin regulation in Alzheimer's disease

Alzheimer's disease (AD) is an age-related neurodegenerative disorder characterized by the hallmark pathologies of amyloid-beta plaques and neurofibrillary tangles. Symptoms of this devastating disease include behavioral changes and deterioration of higher cognitive functions. Impairment of neurogenesis has also been shown to occur in AD, which adversely impacts new neuronal cell growth, differentiation, and survival. This impairment possibly results from the cumulative effects of the various pathologies of AD. Preclinical studies have suggested that the administration of melatonin-the pineal hormone primarily responsible for the regulation of the circadian rhythm-targets the effects of AD pathologies and improves cognitive impairment. It is postulated that by mitigating the effect of these pathologies, melatonin can also rescue neurogenesis impairment. This review aims to explore the effect of AD pathologies on neurogenesis, as well as the mechanisms by which melatonin is able to ameliorate AD pathologies to potentially promote neurogenesis.

Quinazoline and phthalazine derivatives as novel melatonin receptor ligands analogues of agomelatine

For further development of successors of Agomelatine through modulation of its pharmacokinetic properties, we report herein the design, synthesis and pharmacological results of a new family of melatonin receptor ligands. Issued from the introduction of quinazoline and phthalazine scaffolds carrying an ethyl amide lateral chain and a methoxy group as bioisosteric ligands analogues of previously developed Agomelatine. The biological activity of the prepared analogues was compared with that of Agomelatine. Quinazoline and phthalazine rings proved to be a versatile scaffold for easy feasible MT₁ and MT₂ ligands. Potent agonists with sub-micromolar binding affinity were obtained. However, the presence of two nitrogen atoms resulted in compounds with lower affinity for both MT₁ and MT₂, in comparison with the parent compound, balanced by the exhibition of good pharmacokinetic properties.

Melatonin alleviates intervertebral disc degeneration by disrupting the IL-1β/NF-κB-NLRP3 inflammasome positive feedback loop

The inflammatory response is induced by the overexpression of inflammatory cytokines, mainly interleukin (IL)-1β, and is one of the main causes of intervertebral disc degeneration (IVDD). NLR pyrin domain containing 3 (NLRP3) inflammasome activation is an important source of IL-1β. As an anti-inflammatory neuroendocrine hormone, melatonin plays various roles in different pathophysiological conditions. However, its roles in IVDD are still not well understood and require more examination. First, we demonstrated that melatonin delayed the progression of IVDD and relieved IVDD-related low back pain in a rat needle puncture IVDD model; moreover, NLRP3 inflammasome activation (NLRP3, p20, and IL-1β levels) was significantly upregulated in severely degenerated human discs and a rat IVDD model. Subsequently, an IL-1β/NF-κB-NLRP3 inflammasome activation positive feedback loop was found in nucleus pulposus (NP) cells that were treated with IL-1β. In these cells, expression of NLRP3 and p20 was significantly increased, NF-κB signaling was involved in this regulation, and mitochondrial reactive oxygen species (mtROS) production increased. Furthermore, we found that melatonin disrupted the IL-1β/NF-κB-NLRP3 inflammasome activation positive feedback loop in vitro and in vivo. Melatonin treatment decreased NLRP3, p20, and IL-1β levels by inhibiting NF-κB signaling and downregulating mtROS production. Finally, we showed that melatonin mediated the disruption of the positive feedback loop of IL-1β in vivo. In this study, we showed for the first time that IL-1β promotes its own expression by upregulating NLRP3 inflammasome activation. Furthermore, melatonin disrupts the IL-1β positive feedback loop and may be a potential therapeutic agent for IVDD.

Effect of Melatonin on Tau aggregation and Tau-mediated cell surface morphology

Aggregation of Microtubule-associated protein Tau and its deposition in the form of neurofibrillary tangles (NFTs) is one of the pathological hallmarks of Alzheimer's disease (AD). Tau aggregation inhibition has been targeted in various studies including natural compounds and synthetic small molecules. Here, we have studied neurohormone- Melatonin against in vitro Tau aggregation and observed its effect on membrane topology, tubulin network and Tau phosphorylation in Neuro2A and N9 cell lines. The aggregation and conformation of Tau was determined by ThT fluorescence and CD spectroscopy respectively. The morphology of Tau aggregates in presence and absence of Melatonin was studied by transmission electron microscopy. Melatonin was found to reduce the formation of higher order oligomeric structures without affecting the overall aggregation kinetics of Tau. Melatonin also modulates and helps to maintain membrane morphology, independent on tubulin network as evidenced by FE-SEM and immunofluorescence analysis. Overall, Melatonin administration shows mild anti-aggregation and cytoprotective effects.

Melatonin and Parkinson Disease: Current Status and Future Perspectives for Molecular Mechanisms

Parkinson disease (PD) is a chronic and neurodegenerative disease with motor and nonmotor symptoms. Multiple pathways are involved in the pathophysiology of PD, including apoptosis, autophagy, oxidative stress, inflammation, α-synuclein aggregation, and changes in the neurotransmitters. Preclinical and clinical studies have shown that melatonin supplementation is an appropriate therapy for PD. Administration of melatonin leads to inhibition of some pathways related to apoptosis, autophagy, oxidative stress, inflammation, α-synuclein aggregation, and dopamine loss in PD. In addition, melatonin improves some nonmotor symptom in patients with PD. Limited studies, however, have evaluated the role of melatonin on molecular mechanisms and clinical symptoms in PD. This review summarizes what is known regarding the impact of melatonin on PD in preclinical and clinical studies.

Multi-Faceted Role of Melatonin in Neuroprotection and Amelioration of Tau Aggregates in Alzheimer's Disease

Alzheimer's disease (AD) is one of the major age related neurodegenerative diseases whose pathology arises due to the presence of two distinct protein aggregates, viz., amyloid-β plaques in extracellular matrix and tau neurofibrillary tangles in neurons. Multiple factors play a role in AD pathology, which includes familial mutations, oxidative stress, and post-translational modifications. Melatonin is an endocrine hormone, secreted during darkness, derived from tryptophan, and produced mainly by the pineal gland. It is an amphipathic molecule, which makes it suitable to cross not only blood-brain barrier, but also to enter several other subcellular compartments like mitochondria and endoplasmic reticulum. In this context, the neuroprotective effect of melatonin may be attributed to its role as an antioxidant. Melatonin's pleiotropic function as an antioxidant and neuroprotective agent has been widely studied. However, its direct effect on the aggregation of tau and amyloid-β needs to be explored. Furthermore, an important aspect of its function is its ability to regulate the process of phosphorylation of tau by affecting the function of kinases and phosphatases. In this review, we are focusing on the pleiotropic function of melatonin on the aspect of its neuroprotective function in tau pathology, which includes antioxidant function, regulation of enzymes, including kinases and enzymes involved in free radical scavenging and mitochondrial protection.

On the central role of mitochondria dysfunction and oxidative stress in Alzheimer's disease

BACKGROUND

Alzheimer's disease (AD) is the commonest cause of dementia, with approximately 5 million new cases occurring annually. Despite decades of research, its complex pathophysiology and etiopathogenesis presents a major hindrance to the development of an effective treatment and prevention strategy. Aging is the biggest risk factor for the development of AD, and the total number of older people in the population is going to significantly increase in the next decades, suggesting that AD incidence and prevalence is likely to increase in the future. This makes the need for a better understanding of the disease to be extremely urgent.

METHODS

A search was done by accessing PubMed/Medline, EBSCO, and PsycINFO databases. The search string used was "(dementia* OR Alzheimer's) AND (pathophysiology* OR pathogenesis)". New key terms were identified (new term included "vitamin D, thyroid hormone, mitochondria dysfunction, oxidative stress, testosterone, estrogen, melatonin, progesterone, luteinizing hormone, amyloid-β (Aβ), and hyperphosphorylated tau"). The electronic databases were searched for titles or abstracts containing these terms in all published articles between January 1, 1965, and January 31, 2019. The search was limited to studies published in English and other languages involving both animal and human subjects.

RESULTS

Mitochondria dysfunction and oxidative stress play a critical role in AD etiopathogenesis and pathophysiology.

CONCLUSION

AD treatment and prevention strategies must be geared towards improving mitochondrial function and attenuating oxidative stress.

Combinatorial Treatment Effects in a Cell Culture Model of Alzheimer's Disease

BACKGROUND

Alzheimer's disease (AD) is the leading cause of dementia, and as its prevalence increases, so does its detrimental impact on society. The currently available therapies have limited efficacy, leaving AD patients on an irrevocably fatal path of this disease.

OBJECTIVE

The purpose of this study was to test efficacy of a novel combinatorial treatment approach to alleviate AD-like pathology.

METHODS

We selected four naturally occurring compounds and used them in different combinations to test their effect on AD-like pathology. Employing a well-established cell culture AD model system, we evaluated levels of several diverse biomarkers associated with a number of cellular pathways associated with AD. The readouts included: amyloid-β peptides, anti-inflammatory and anti-apoptotic proteins, oxidative enzymes, and reactive oxygen species.

RESULTS

Using this approach, we demonstrated that the compounds delivered in combination had higher efficacy than individual treatments. Specifically, we observed significant reduction in levels of the amyloid-β peptides, as well as pro-inflammatory proteins and reactive oxygen species. Similarly, delivery of compounds in combination resulted in an increased expression of anti-apoptotic proteins and anti-oxidative enzymes. Collectively, these modifications in AD pathology biomarkers reflect a promising therapeutic and preventive strategy to combat this disease.

CONCLUSION

The above findings support a novel therapeutic approach to address a currently unmet medical need, which would benefit not only AD patients and their caregivers, but also society as a whole.

New MT₂ Melatonin Receptor-Selective Ligands: Agonists and Partial Agonists

The search for melatonin receptor agonists and antagonists specific towards one of the receptor subtypes will extend our understanding of the role of this system in relaying circadian information to the body. A series of compounds derived from a hit compound discovered in a screening process led to powerful agonists specific for one of the isoform of the melatonin receptor namely, MT₂. The compounds are based on a poorly explored skeleton in the molecular pharmacology of melatonin. By changing the steric hindrance of one substituent (i.e., from a hydrogen atom to a tributylstannyl group), we identified a possible partial agonist that could lead to antagonist analogues. The functionalities of these compounds were measured with a series of assays, including the binding of GTPγS, the inhibition of the cyclic AMP production, the β-arrestin recruitment, and the cell shape changes as determined by cellular dielectric spectroscopy (CellKey®). The variations between the compounds are discussed.

Melatonin and human mitochondrial diseases

Mitochondrial dysfunction is one of the main causative factors in a wide variety of complications such as neurodegenerative disorders, ischemia/reperfusion, aging process, and septic shock. Decrease in respiratory complex activity, increase in free radical production, increase in mitochondrial synthase activity, increase in nitric oxide production, and impair in electron transport system and/or mitochondrial permeability are considered as the main factors responsible for mitochondrial dysfunction. Melatonin, the pineal gland hormone, is selectively taken up by mitochondria and acts as a powerful antioxidant, regulating the mitochondrial bioenergetic function. Melatonin increases the permeability of membranes and is the stimulator of antioxidant enzymes including superoxide dismutase, glutathione peroxidase, glutathione reductase, and catalase. It also acts as an inhibitor of lipoxygenase. Melatonin can cause resistance to oxidation damage by fixing the microsomal membranes. Melatonin has been shown to retard aging and inhibit neurodegenerative disorders, ischemia/reperfusion, septic shock, diabetes, cancer, and other complications related to oxidative stress. The purpose of the current study, other than introducing melatonin, was to present the recent findings on clinical effects in diseases related to mitochondrial dysfunction including diabetes, cancer, gastrointestinal diseases, and diseases related to brain function.

Sleep and Neurodegeneration: A Critical Appraisal

Sleep abnormalities are clearly recognized as a distinct clinical symptom of concern in neurodegenerative disorders. Appropriate management of sleep-related symptoms has a positive impact on quality of life in patients with neurodegenerative disorders. This review provides an overview of mechanisms that are currently being considered that tie sleep with neurodegeneration. It appraises the literature regarding specific sleep changes seen in common neurodegenerative diseases, with a focus on Alzheimer disease and synucleinopathies (ie, Parkinson disease, dementia with Lewy bodies, multiple system atrophy), that have been better studied. Sleep changes may also serve as markers to identify patients in the preclinical stage of some neurodegenerative disorders. A hypothetical model is postulated founded on the conjecture that specific sleep abnormalities, when noted to increase in severity beyond that expected for age, could be a surrogate marker reflecting pathophysiological processes related to neurodegenerative disorders. This provides a clinical strategy for screening patients in the preclinical stages of neurodegenerative disorders to enable therapeutic trials to establish the efficacy of neuroprotective agents to prevent or delay the development of symptoms and functional decline. It is unclear if sleep disturbance directly impacts neurodegenerative processes or is a secondary outcome of neurodegeneration; this is an active area of research. The clinical importance of recognizing and managing sleep changes in neurodegenerative disorders is beyond doubt.

Mechanisms of Melatonin in Alleviating Alzheimer's Disease

Alzheimer's disease (AD) is a chronic, progressive and prevalent neurodegenerative disease characterized by the loss of higher cognitive functions and an associated loss of memory. The thus far "incurable" stigma for AD prevails because of variations in the success rates of different treatment protocols in animal and human studies. Among the classical hypotheses explaining AD pathogenesis, the amyloid hypothesis is currently being targeted for drug development. The underlying concept is to prevent the formation of these neurotoxic peptides which play a central role in AD pathology and trigger a multispectral cascade of neurodegenerative processes post-aggregation. This could possibly be achieved by pharmacological inhibition of β- or γ-secretase or stimulating the nonamyloidogenic α-secretase. Melatonin the pineal hormone is a multifunctioning indoleamine. Production of this amphiphilic molecule diminishes with advancing age and this decrease runs parallel with the progression of AD which itself explains the potential benefits of melatonin in line of development and devastating consequences of the disease progression. Our recent studies have revealed a novel mechanism by which melatonin stimulates the nonamyloidogenic processing and inhibits the amyloidogenic processing of β-amyloid precursor protein (βAPP) by stimulating α -secretases and consequently down regulating both β- and γ-secretases at the transcriptional level. In this review, we discuss and evaluate the neuroprotective functions of melatonin in AD pathogenesis, including its role in the classical hypotheses in cellular and animal models and clinical interventions in AD patients, and suggest that with early detection, melatonin treatment is qualified to be an anti-AD therapy.

Insulin Resistance and Neurodegeneration: Progress Towards the Development of New Therapeutics for Alzheimer's Disease

Alzheimer's disease (AD) should be regarded as a degenerative metabolic disease caused by brain insulin resistance and deficiency, and overlapping with the molecular, biochemical, pathophysiological, and metabolic dysfunctions in diabetes mellitus, non-alcoholic fatty liver disease, and metabolic syndrome. Although most of the diagnostic and therapeutic approaches over the past several decades have focused on amyloid-beta (Aβ42) and aberrantly phosphorylated tau, which could be caused by consequences of brain insulin resistance, the broader array of pathologies including white matter atrophy with loss of myelinated fibrils and leukoaraiosis, non-Aβ42 microvascular disease, dysregulated lipid metabolism, mitochondrial dysfunction, astrocytic gliosis, neuro-inflammation, and loss of synapses vis-à-vis growth of dystrophic neurites, is not readily accounted for by Aβ42 accumulations, but could be explained by dysregulated insulin/IGF-1 signaling with attendant impairments in signal transduction and gene expression. This review covers the diverse range of brain abnormalities in AD and discusses how insulins, incretins, and insulin sensitizers could be utilized to treat at different stages of neurodegeneration.

Protection against brain tissues oxidative damage as a possible mechanism for the beneficial effects of Rosa damascena hydroalcoholic extract on scopolamine induced memory impairment in rats

OBJECTIVES

Hypnotic, analgesic, anticonvulsant, and antioxidant effects of Rosa damascena have been reported. This study, investigated the effect of R. damascena hydroalcoholic extract on memory performance in a scopolamine-induced memory impairment model.

METHODS

The rats were divided into control group received just saline; scopolamine group was treated by saline for 2 weeks, but was injected by scopolamine 30 minutes before each trial in Morris water maze test; treatment groups (scopolamine + extract 50; Sco + Ext 50) and (scopolamine + extract 250; Sco + Ext 250) were daily treated by 50 and 250 mg/kg of R. damascena extract (2 weeks) and were finally injected by scopolamine before each trial in Morris water maze. The brains were removed for biochemical measurements.

RESULTS

Time latency and path length in the scopolamine group were higher than control (P < 0.01 to <0.001). Both treatment groups showed shorter traveled distance and time latency compared with scopolamine group (P < 0.05 to <0.001). Time spent in target quadrant by scopolamine group was lower than control (P < 0.05), while Sco + Ext 250 group spent longer time in target quadrant than scopolamine group (P < 0.05). Malondialdehyde concentrations in hippocampal and cortical tissues of scopolamine group were higher, while thiol concentrations were lower than control ones (P < 0.001). Treatment by both doses of the extract decreased the malondialdehyde concentration, while increased the thiol concentration (P < 0.05 to <0.001).

DISCUSSION

The results of this study showed that the hydroalcoholic extract of R. damascena prevents scopolamine-induced memory deficits. This finding suggests that memory improvement may be in part due to the antioxidant effects.

Therapeutic targets and delivery challenges for Alzheimer’s disease

Dementia, including Alzheimer’s disease, the 21^st Century epidemic, is one of the most significant social and health crises which has currently afflicted nearly 44 million patients worldwide and about new 7.7 million cases are reported every year. This portrays the unmet need towards better understanding of Alzheimer’s disease pathomechanisms and related research towards more effective treatment strategies. The review thus comprehensively addresses Alzheimer’s disease pathophysiology with an insight of underlying multicascade pathway and elaborates possible therapeutic targets- particularly anti-amyloid approaches, anti-tau approaches, acetylcholinesterase inhibitors, glutamatergic system modifiers, immunotherapy, anti-inflammatory targets, antioxidants, 3-hydroxy-3-methyl-glutaryl-coenzyme A reductase inhibitors and insulin. In spite of extensive research leading to identification of newer targets and potent drugs, complete cure of Alzheimer’s disease appears to be an unreached holy grail. This can be attributed to their ineffective delivery across blood brain barrier and ultimately to the brain. With this understanding, researchers are now focusing on development of drug delivery systems to be delivered via suitable route that can circumvent blood brain barrier effectively with enhanced patient compliance. In this context, we have summarized current drug delivery strategies by oral, transdermal, intravenous, intranasal and other miscellaneous routes and have accentuated the future standpoint towards promising therapy ultimately leading to Alzheimer’s disease cure.

Melatonin attenuates impairments of structural hippocampal neuroplasticity in OXYS rats during active progression of Alzheimer's disease-like pathology

Translational research on Alzheimer's disease (AD) has often focused on reducing the high cerebral levels of amyloid-β (Aβ) as a key characteristic of AD pathogenesis. There is, however, a growing body of evidence that synaptic dysfunction may be crucial for the development of the most common (sporadic) form of AD. The applicability of melatonin (mainly produced by the pineal gland) to the treatment of AD is actively evaluated, but usually, such studies are based on animal models of early-onset AD, which is responsible for only ~5% of AD cases. We have shown previously that in OXYS rats (an established model of sporadic AD), accumulation of toxic forms of Aβ in the brain occurs later than does the development of signs of neurodegenerative changes and synaptic failure. In this regard, recently, we uncovered beneficial neuroprotective effects of melatonin (prophylactic dietary supplementation) in OXYS rats. Our aim here was to evaluate, starting at the age of active progression of AD-like pathology in OXYS rats, the effects of long-term oral administration of melatonin on the structure of synapses and on neuronal and glial cells of the hippocampus. Melatonin significantly increased hippocampal synaptic density and the number of excitatory synapses, decreased the number of inhibitory synapses, and upregulated pre- and postsynaptic proteins (synapsin I and PSD-95, respectively). Furthermore, melatonin improved the ultrastructure of neuronal and glial cells and reduced glial density. Based on our past and present results, the repair of neuroplasticity by melatonin is a promising strategy against AD.

Effects of the hydro-alcoholic extract of Nigella sativa on scopolamine-induced spatial memory impairment in rats and its possible mechanism

OBJECTIVE

To evaluate the effect of Nigella sativa (NS) extract on memory performance and its possible mechanisms in scopolamine (Sco)-induced spatial memory impairment model using Morris water maze test.

METHODS

Thirty-two male Wistar rats were randomly divided into four groups. The control group received saline instead of both NS extract and Sco. The Sco group was treated by saline for two weeks, and was injected by Sco (2 mg/kg, intraperitoneally) 30 min before each trail in Morris water maze test. Sco+NS 200 and Sco+NS 400 groups were daily treated by 200 or 400 mg/kg of NS (intraperitoneally) for two weeks, respectively, and were finally injected by Sco 30 min before Morris water maze test. The brains of animals were removed to determine the acetylcholinesterase (AChE) activity and oxidative stress criteria in cortical tissues.

RESULTS

Time latency and path length in the Sco group were significantly higher than in the control group (P<0.01), while the Sco+NS 400 group showed a significantly shorter traveled path length and time latency compared with the Sco group (P<0.01). AChE activity in the cortical tissues of the Sco group was significantly higher than the control group (P<0.01), while AChE activity in the Sco+NS 200 and Sco+NS 400 groups was lower than the Sco group (P<0.01). Following Sco administration, malondialdehyde (MDA) concentrations were increased (P<0.01) in comparison with the control group, while cortical total thiol content decreased (P<0.01). Pretreatment with extracts caused a significant elevation in cortical total thiol content (P<0.01) and reduction in cortical MDA concentration (P<0.01) compared with the Sco group.

CONCLUSIONS

Hydro-alcoholic extract of NS prevents Sco-induced spatial memory deficits and decreases the AChE activity as well as oxidative stress of brain tissues in rats. Our results support the traditional belief about the beneficial effects of NS in nervous system. Moreover, further investigations are needed for better understanding of this protective effect.

Graphene and Co-polymer composite based molecularly imprinted sensor for ultratrace determination of melatonin in human biological fluids

A novel molecularly imprinted polymer (MIP) sensor based on a composite of graphene (GR) and a co-polymer of 4-amino-3-hydroxy-1-naphthalenesulfonic acid (AHNSA) and melamine (MM) has been fabricated for detecting melatonin.

Nootropic activity of Crataeva nurvala Buch-Ham against scopolamine induced cognitive impairment

Loss of cognition is one of the age related mental problems and a characteristic symptom of neurodegenerative disorders like Alzheimer’s. Crataeva nurvala Buch-Ham, a well explored traditional Indian medicinal plant of Westernghats, is routinely used as folkloric medicine to treat various ailments in particular urolithiasis and neurological disorders associated with cognitive dysfunction. The objective of the study was to evaluate the nootropic activity of Crataeva nurvala Buch-Ham stem bark in different learning and memory paradigm viz. Elevated plus maze and Y-maze against scopolamine induced cognitive impairment. Moreover, to elucidate possible mechanism, we studied the influence of Crataeva nurvala ethanolic extract on central cholinergic activity via estimating the whole brain acetyl cholinesterase enzyme. Ethanolic extracts of Crataeva nurvala (100, 200 and 400 mg/kg body weight) were administered to adult Wistar rats for successive seven days and the acquisition, retention and retrieval of spatial recognition memory was determined against scopolamine (1 mg/kg, i.p.) induced amnesia through exteroceptive behavioral models viz. Elevated plus maze and Y-maze models. Further, whole brain acetyl cholinesterase enzyme was estimated through Ellman’s method. Pretreatment with Crataeva nurvala ethanolic extract significantly improved spatial learning and memory against scopolamine induced amnesia. Moreover, Crataeva nurvala extract decreased rat brain acetyl cholinesterase activity in a dose dependent manner and comparable to the standard drug Piracetam. The results indicate that ethanolic extract of Crataeva nurvala might be a useful as nootropic agent to delay the onset and reduce the severity of symptoms associated with dementia and Alzheimer’s disease. The underlying mechanism of action of its nootropic potentiality might be attributed to its anticholinesterase property.

Risk Profiles of Alzheimer Disease

Alzheimer disease (AD) is a dementing, neurodegenerative disorder that affects approximately 500,000 Canadians and its prevalence is expected to double over the next 30 years. Although several medications may temporarily augment cognitive abilities in AD, there presently exists no proven method to avoid the inevitable clinical deterioration in this devastating condition. The delineation of risk factors for the development of AD offers hope for the advent of effective prevention or interventions that might retard the onset of symptoms. In this article, we provide a comprehensive review of midlife risk factors implicated in the etiopathogenesis of sporadic AD. Although some risk factors are heritable and largely beyond our control, others are determined by lifestyle or environment and are potentially modifiable. In a companion paper, we introduce the concept of an Alzheimer Risk Assessment Clinic for ascertainment and mitigation of these and other putative dementia risk factors in middle-aged adults.

'The clocks that time us'--circadian rhythms in neurodegenerative disorders

Circadian rhythms are physiological and behavioural cycles generated by an endogenous biological clock, the suprachiasmatic nucleus. The circadian system influences the majority of physiological processes, including sleep-wake homeostasis. Impaired sleep and alertness are common symptoms of neurodegenerative disorders, and circadian dysfunction might exacerbate the disease process. The pathophysiology of sleep-wake disturbances in these disorders remains largely unknown, and is presumably multifactorial. Circadian rhythm dysfunction is often observed in patients with Alzheimer disease, in whom it has a major impact on quality of life and represents one of the most important factors leading to institutionalization of patients. Similarly, sleep and circadian problems represent common nonmotor features of Parkinson disease and Huntington disease. Clinical studies and experiments in animal models of neurodegenerative disorders have revealed the progressive nature of circadian dysfunction throughout the course of neurodegeneration, and suggest strategies for the restoration of circadian rhythmicity involving behavioural and pharmacological interventions that target the sleep-wake cycle. In this Review, we discuss the role of the circadian system in the regulation of the sleep-wake cycle, and outline the implications of disrupted circadian timekeeping in neurodegenerative diseases.

Synthesis and characterization of new bivalent agents as melatonin- and histamine H3-ligands

Melatonin is an endogenous molecule involved in many pathophysiological processes. In addition to the control of circadian rhythms, its antioxidant and neuroprotective properties have been widely described. Thus far, different bivalent compounds composed by a melatonin molecule linked to another neuroprotective agent were synthesized and tested for their ability to block neurodegenerative processes in vitro and in vivo. To identify a novel class of potential neuroprotective compounds, we prepared a series of bivalent ligands, in which a prototypic melatonergic ligand is connected to an imidazole-based H₃ receptor antagonist through a flexible linker. Four imidazolyl-alkyloxy-anilinoethylamide derivatives, characterized by linkers of different length, were synthesized and their binding affinity for human MT₁, MT₂ and H₃ receptor subtypes was evaluated. Among the tested compounds, 14c and 14d, bearing a pentyl and a hexyl linker, respectively, were able to bind to all receptor subtypes at micromolar concentrations and represent the first bivalent melatonergic/histaminergic ligands reported so far. These preliminary results, based on binding affinity evaluation, pave the way for the future development of new dual-acting compounds targeting both melatonin and histamine receptors, which could represent promising therapeutic agents for the treatment of neurodegenerative pathologies.