Changing stroke rehab and research worldwide now.Time is Brain! trillions and trillions of neurons that DIE each day because there are NO effective hyperacute therapies besides tPA(only 12% effective). I have 523 posts on hyperacute therapy, enough for researchers to spend decades proving them out. These are my personal ideas and blog on stroke rehabilitation and stroke research. Do not attempt any of these without checking with your medical provider. Unless you join me in agitating, when you need these therapies they won't be there.

What this blog is for:

My blog is not to help survivors recover, it is to have the 10 million yearly stroke survivors light fires underneath their doctors, stroke hospitals and stroke researchers to get stroke solved. 100% recovery. The stroke medical world is completely failing at that goal, they don't even have it as a goal. Shortly after getting out of the hospital and getting NO information on the process or protocols of stroke rehabilitation and recovery I started searching on the internet and found that no other survivor received useful information. This is an attempt to cover all stroke rehabilitation information that should be readily available to survivors so they can talk with informed knowledge to their medical staff. It lays out what needs to be done to get stroke survivors closer to 100% recovery. It's quite disgusting that this information is not available from every stroke association and doctors group.

Showing posts with label melatonin. Show all posts
Showing posts with label melatonin. Show all posts

Monday, September 28, 2026

Resetting the body clock could help the brain recover after stroke

 Your incompetent? doctor and hospital will fail at doing further research and human testing to change 'could' to will! And I'm sure they didn't create sleep or glymphatic clearance protocols.

NOT DOING EITHER ONE IS PURE INCOMPETENCE!

Resetting the body clock could help the brain recover after stroke

 Scientists at the University of Rochester Medicine have found that strengthening the body's natural daily rhythms to improve sleep may help the brain recover after a stroke. The work points to a possible new way to support brain waste clearance and improve recovery well after the initial injury. Published in the Journal of Clinical Investigation, the study showed that interventions designed to reinforce circadian rhythms improved recovery in mouse models of stroke. These improvements were accompanied by stronger activity in the glymphatic system, the brain's waste-clearing network, along with lower levels of inflammatory molecules that can persist after a stroke. 

How the Brain Clears Waste

The findings build on more than a decade of research led by URochester Medicine neuroscientist Maiken Nedergaard, MD, DMSc. Her laboratory discovered the glymphatic system in 2012. This system moves cerebrospinal fluid through the brain, helping remove waste products and other debris. Later studies found that glymphatic activity is especially strong during sleep and plays an important role in maintaining brain health.Neuroscientist Lauren Hablitz, PhD, later helped show that glymphatic activity is influenced not only by sleep, but also by circadian rhythms, the body's internal 24-hour clock. In a landmark 2020 study, Hablitz, Nedergaard, and colleagues demonstrated that glymphatic function follows daily cycles even independently of sleep, establishing a direct link between circadian biology and the brain's waste-clearing system. 

Stroke May Disrupt the Brain's Timing

"The discussion of stroke recovery really starts with the idea that stroke is not just a vascular event, but also a disorder of timing," said Hablitz, lead author of the new study. Scientists have long known that strokes tend to follow distinct time-of-day patterns. They occur more often during the morning and are frequently more severe near the end of the sleep period. After a stroke, many patients also develop disrupted sleep-wake cycles. Those disturbances have been linked with worse recovery, depression, and reduced quality of life. "That led us to ask a simple question," said Hablitz. "If timing is broken after a stroke, can we improve recovery by reinforcing the biological clock?" 

When the Brain's Cleanup System Slows Down

 In a healthy brain, the glymphatic system carries cerebrospinal fluid along blood vessels and through brain tissue. This process delivers nutrients while helping remove waste products and inflammatory signals. Earlier research has shown that glymphatic function becomes impaired after stroke. That disruption may reduce the brain's ability to clear harmful molecules that accumulate during recovery. Stroke research has traditionally focused on separating beneficial inflammation from harmful inflammation and finding ways to suppress the damaging forms. Hablitz and her colleagues suggest that another part of the problem may be that the brain is no longer clearing inflammatory signals effectively. "We think part of the problem may be a failure of cleaning," she said. "If the system responsible for clearing signaling molecules isn't working properly, everything builds up."Under this model, stroke damages both brain tissue and the pathways responsible for removing inflammatory signals. As those molecules accumulate, they may contribute to continued damage and slower recovery. 

Resetting the Body Clock

To test whether stronger circadian rhythms could improve recovery, the researchers examined several interventions known to affect the body's internal clock. These included timed light exposure, melatonin, a clock-targeting drug called KL001, and time-restricted feeding. The team first showed that each of these interventions could improve glymphatic function in healthy animals. They then selected the most promising strategies, KL001 and time-restricted feeding, and tested them in mouse models of stroke. Treatment did not begin until three days after the stroke, far beyond the narrow window used for clot-busting drugs and other acute stroke treatments. Even with that delay, mice that received either intervention showed better motor recovery, smaller lesion volumes, improved glymphatic flow, and lower levels of inflammatory cytokines in the brain. "All of the cytokines moved in the same direction," Hablitz said. "That suggests we may not be targeting one specific inflammatory pathway. Instead, we may be helping the brain clear inflammatory signals more effectively." One of the most promising approaches was time-restricted feeding, a behavioral intervention that is already being investigated for obesity, diabetes, cardiovascular disease, and other conditions. That could make the findings especially relevant for stroke rehabilitation because such an approach might eventually be easier to use outside specialized medical settings. "One of the exciting aspects of this work is that we're studying interventions that could potentially be implemented not only in hospitals but also at home," Hablitz said. 

What Researchers Need to Test Next

 The researchers emphasize that the findings so far are limited to animal models. More studies will be needed to determine exactly how circadian rhythms, glymphatic function, and inflammation influence one another after stroke. Future work will also examine whether improved glymphatic flow directly causes better recovery and whether circadian-based interventions can eventually be tested in clinical trials. More broadly, the study reflects a growing view in neuroscience that sleep, circadian rhythms, and fluid movement through the brain are central to brain health. By learning more about how the brain's internal clock regulates the glymphatic system, researchers hope to uncover new ways to improve recovery not only after stroke, but also in other neurological conditions involving inflammation and poor waste clearance. "Understanding how circadian regulation shapes glymphatic clearance will help us develop more targeted therapies," said Hablitz. "Ultimately, our goal is to find ways to improve the brain's ability to clear waste, reduce inflammation, and recover after injury." Health & Medicine Diabetes Heart Disease Mental Health Research Pharmacology Depression Mental Health Stroke Consumer Behavior RELATED TERMS

Story Source:

Materials provided by University of Rochester Medical Center. Note: Content may be edited for style and length.


Journal Reference:

  1. Emma Waight, Yuxi Zhu, Ashley Caudell, Velia S. Vizcarra, Evan Newbold, Michael J. Giannetto, Evalien Duyvestyn, Estephanie Balbuena, Wei Song, Tanzil M. Arefin, Yuki Mori, Maiken Nedergaard, Lauren M. Hablitz. Chronotherapy to reinforce circadian rhythms improves poststroke outcomes and glymphatic function in mice. Journal of Clinical Investigation, 2026; 136 (12) DOI: 10.1172/JCI201800

Cite This Page:

University of Rochester Medical Center. "Resetting the body clock could help the brain recover after stroke." ScienceDaily. ScienceDaily, 28 September 2026. <www.sciencedaily.com/releases/2026/09/260924020407.htm>.

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Friday, July 10, 2026

A New Study Finds Melatonin Could Harm Your Heart Health. Try These 7 Sleep Alternatives

 You'll have to ask your competent? doctor if the pros outweigh the cons, Your doctor better know the answer IF COMPETENT AT ALL!

A New Study Finds Melatonin Could Harm Your Heart Health. Try These 7 Sleep Alternatives

A preliminary study conducted by the American Heart Association reveals that adults with insomnia who used melatonin for at least 12 months had about a 90% higher chance of first-time heart failure within five years. This was found using five years of health records from 130,828 adults. Participants in the long-term melatonin use group were also almost twice as likely to die from any cause over five years.

It's important to note that this study hasn't yet been peer-reviewed, and that the data may be skewed because melatonin use in the study was based on prescribed medication entries in electronic health records. In the UK, melatonin must be prescribed, whereas it is available over the counter in countries like the US. That means people in the study using over-the-counter melatonin would have been mistakenly included in the non-melatonin group. As a result, more research is required.

However, if you're looking to curb your long-term melatonin use, or, like me, melatonin simply doesn't work for you, there are alternatives that can help you fall asleep. These are my favorites.

1. Use CBD oils, gummies or creams

CBD, also known as cannabidiol, is derived from hemp plants. CBD is a safe and effective treatment for insomnia that contains almost no THC, the substance in marijuana that alters one's mental state. Many studies suggest that CBD is very effective in promoting sleep and decreasing anxiety. It comes in many forms, such as oils and lotions. Use before bed to promote sleepiness and relaxation.

natural remedies for anxiety, stress and insomnia. Drink a cup of one of these herbal teas at least an hour to two before bed -- this gives you time to relax, enjoy the tea and use the bathroom before lights off. Be sure to look at the nutrition label to make sure no caffeine has been added to the ingredients.

3. Put a drop of lavender oil on your pillow

One of the more popular household remedies -- essential oils. If tea is not your favorite way to relax before bedtime, floral and herbal fragrances are good ways to aid sleep. Some popular essential oils for sleep are lavender, chamomile, and bergamot. Essential oils should never be ingested, but you can put a little drop on your pillow at night. You can also diffuse essential oils into the air or use dried lavender to make a tea. 

4. Drink tart cherry juice

Sour cherry juice from tart cherries can increase melatonin production in those who consume it before bedtime. In the same study, the group that drank the cherry juice spent more time in bed and asleep and achieved higher overall sleep efficiency. This suggests that tart cherry juice has the potential to prevent insomnia. 

5. Try dried passionflower or extract oil

Not to be confused with passionfruit -- passionflower is a fast-growing vine that produces vibrant flowers. Not only is the plant beautiful, but it can even help you fall asleep through herbal tea or extract oil. A recent study concluded that passionflower has the potential to treat insomnia. However, it isn't recommended for those who are pregnant. 

6. Make sure you're getting enough magnesium

Magnesium, a powerful nutrient, is responsible for regulating hundreds of processes in the body -- including sleep. Magnesium is found naturally in foods such as nuts and seeds, spinach, soy milk, yogurt and whole grains. Try lightly snacking on foods high in magnesium an hour or two before bed. If you believe that you aren't getting enough magnesium in your diet and suspect it could help your sleep, try adding a supplement. 

7. Practice yoga and meditation before bedtime

Strenuous exercise before bed is not always a good idea, but practicing light yoga or meditation before bed has been linked to decreased insomnia and better sleep. Go through simple yoga poses, such as cat-cow, forward fold or bridge, focusing on your breath and feeling the stretch. There are also many self-guided meditation apps available.

Monday, June 22, 2026

BODY CLOCK MAY HOLD KEY TO STROKE RECOVERY

 Your competent? doctor better have access and KNOW ABOUT THIS RESEARCH!

BODY CLOCK MAY HOLD KEY TO STROKE RECOVERY

Strengthening the body's natural biological clock may improve recovery after a stroke by enhancing the brain's ability to clear waste and reduce inflammation, according to a new study published in the Journal of Clinical Investigation.


Researchers from the University of Rochester Medical Center found that interventions aimed at reinforcing circadian rhythms — including timed light exposure, melatonin, a body clock-targeting drug, and time-restricted feeding — improved recovery outcomes in mouse models of stroke.

The study also showed improvements in the glymphatic system, the brain's waste-clearance network that helps remove harmful substances and inflammatory signals while delivering nutrients through cerebrospinal fluid.

The rest is behind a paywall at the Sunday Guardian.

Monday, December 29, 2025

Chronobiology and Neurodegeneration: The Role of Melatonin in Alzheimer's Disease

 

Ask your fuckingly incompetent doctor, hospital and board of directors when EXACTLY THEY ARE GOING TO SOLVE THE MELATONIN CONUMDRUM!

Probably more in all these other melatonin posts.

  • melatonin (33 posts to February 2012)

  • Do you prefer your doctor, hospital and board of director's incompetence NOT KNOWING? OR NOT DOING?

    Send me personal hate mail on this: oc1dean@gmail.com. I'll print your complete statement with your name(If you can't stand by your name don't bother replying anonymously) and my response in my blog. Or are you afraid to engage with my stroke-addled mind? No excuses are allowed! You're medically trained; it should be simple to precisely state EXACTLY WHY you aren't working on 100% recovery protocols with NO EXCUSES!

    I take no prisoners in trying to get stroke solved! No knowledge of all of this and you have blithering idiots in charge, how long before you fire all of them? 

    The latest here:

    Chronobiology and Neurodegeneration: The Role of Melatonin in Alzheimer's Disease


    https://doi.org/10.1016/j.nupsyc.2025.100001Get rights and content
    Under a Creative Commons license
    Open access

    Highlights

    • •
      To our knowledge, this review systematically consolidate evidence on melatonin’s role across all major hallmarks of AD, amyloid-β neurotoxicity, production and protection, followed by its effects on tau hyperphosphorylation, mitochondrial functional dynamics, oxidative stress, calcium hypothesis, cholinergic hypothesis, neuroinflammation, blood brain barrier maintenance, insulin dynamics, circadian rhythms and concludes with its clinical and translational implications.
    • •
      The review advances the current understanding of melatonin as a pleiotropic molecule by positioning it within a multi-target therapeutic framework, in contrast to the reductionist focus of most existing literature on isolated mechanisms.
    • •
      Our review uniquely emphasizes melatonin’s role in modulating insulin metabolism and circadian rhythm regulation—two increasingly recognized yet underexplored contributors to AD pathogenesis.
    • •
      We bridge preclinical and clinical insights, offering a translational perspective that underscores melatonin’s potential as an adjunctive or preventive strategy in AD management.
    • •
      Despite abundant studies on melatonin’s individual effects, no existing review has synthesized its actions in a unified, cross-pathological context. This review fills a significant gap by providing a holistic view of melatonin’s therapeutic promise in AD.

    Abstract

    Melatonin, a hormone synthesized endogenously in the brain, exhibits a decline with advancing age and is found at reduced levels in individuals with AD. Clinical studies suggest that melatonin supplementation can enhance sleep quality, alleviate sundowning symptoms, and potentially delay the progression of cognitive deterioration in AD patients. While the precise molecular mechanisms remain under investigation, it is hypothesized that melatonin modulates the activity of various protein kinases and phosphatases involved in tau regulation. In this review, we elucidate melatonin’s capacity to mitigate Aβ-induced neurotoxicity, suppress excessive microglial activation, inhibit tau protein hyperphosphorylation, and regulate insulin signaling. Additionally, melatonin contributes to reducing oxidative stress, preserving the integrity of the blood–brain barrier, supporting mitochondrial function, attenuating neuroinflammatory responses, maintaining cholinergic neurotransmission, and regulating intracellular calcium homeostasis. Thus in the current review, we aim to highlight the importance of melatonin’s therapeutic potential as a multi-targeted agent in both the prevention and treatment of AD.

    Introduction

    Alzheimer’s disease (AD) is a severe life threatening, chronic age-related neurodegenerative disease (Lin et al., 2013) and a leading cause of dementia affecting more than 55 million people on a global basis (Gale et al., 2018). Pathological hallmarks of AD are characterized by the formation and accumulation of extracellular senile plaques (SPs) composed of β-amyloid (Aβ) and neurofibrillary tangles (NFTs) present intracellularly, which are made up of abnormal hyperphosphorylated tau, a protein of microtubule family (Scheltens et al., 2021). Despite the tremendous amounts of research, the etiology of AD alongside it’s molecular players have not yet been fully discovered. However, studies have pointed at a few known mechanisms that contribute to AD pathophysiology, that includes genetic predisposition (for e.g. expression levels of Apolipoproteins (APOE4) and presenilins (PS) genes like PSEN1 and PSEN2), inflammation, oxidative stress, mitochondrial dysfunction, neurotoxicity by neurotoxicants and environmental factors (Lane et al., 2018).

    Table 1. Summary Table highlighting the effect of melatonin on each of the pathophysiological outcome of AD

    Sr. NoPathophysiologyEffect of MelatoninMechanismsLimitations
    1Aβ neurotoxicity & production/clearance balanceLowers brain oligomeric Aβ, shifts Aβ toward soluble/peripheral pools, reduces Aβ-induced toxicity (preclinical).Inhibits β/γ-secretase activity, promotes clearance, reduces oxidative stress and aggregation.Mostly animal data with supraphysiological doses; indirect clearance measures; unclear preventive vs therapeutic timing.
    2Mechanisms of melatonin-mediated neuroprotection against AβReduces synaptic loss and cell death, preserves cognition in Aβ-exposed models.Antioxidant, anti-apoptotic, inhibition of Aβ oligomerization, MT1/MT2 and SIRT1 pathways.Pleiotropic actions obscure primary mechanism; limited causal blockade experiments.
    3Tau pathologyDecreases tau hyperphosphorylation and aggregation in vitro and in vivo.Modulates kinases (↓GSK3β, ↓CDK5) and phosphatases; reduces oxidative stress.Limited chronic models; unclear receptor dependence; few human data.
    4Circadian–metabolic bridge: melatonin & insulinImproves insulin signaling, rescues hippocampal insulin resistance in metabolic and STZ models.Enhances IRS/Akt phosphorylation, reduces inflammation and oxidative stress; aligns metabolic rhythms.Species differences; pharmacologic doses; unclear central vs peripheral effects.
    5Oxidative stressReduces ROS, lipid peroxidation and oxidative damage markers across models.Free-radical scavenging; upregulates Nrf2 and antioxidant enzymes; stabilizes mitochondria.High doses used; difficulty separating direct from secondary effects.
    6Chronoprotective role (circadian regulation)Restores sleep–wake cycles and clock gene expression; improves sleep quality.Activates MT1/MT2 receptors, phase-shifts clock, synchronizes peripheral/central rhythms.Heterogeneous dosing/timing; species differences; reduced efficacy in advanced disease.
    7BBB stabilityPreserves tight junction proteins, reduces BBB permeability and MMP activity.Anti-inflammatory (↓NF-κB/TLR4), MMP-9 inhibition, antioxidant protection, AMPK activation.Acute models dominate; chronic AD-related BBB dysfunction underexplored.
    8Mitochondrial protectionImproves mitochondrial respiration, reduces ROS, prevents mPTP opening.Activates SIRT1/PGC-1α, stabilizes membrane potential, inhibits cytochrome c release.In vivo mitochondrial data limited; unclear direct vs secondary effects.
    9NeuroinflammationAttenuates microglial/astrocytic activation and lowers pro-inflammatory cytokines.Suppresses NF-κB/TLR4 signaling, decreases iNOS/COX2, promotes anti-inflammatory phenotype.Acute LPS/toxin models; limited translational biomarkers or human data.
    10Cholinergic hypothesisRestores ACh levels, reduces AChE activity, protects cholinergic neurons.Reduces oxidative stress, preserves choline acetyltransferase, indirect anti-inflammatory effects.Sparse mechanistic data; inconsistent cognitive effects clinically.
    11Calcium hypothesisStabilizes intracellular Ca2+, reduces Ca2+-mediated toxicity in neurons.Modulates NMDA receptor activity, supports mitochondrial Ca2+ buffering.Mostly in vitro data; chronic Ca2+ dysregulation in AD not fully modeled.
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    Melatonin (N-acetyl-5-methoxytryptamine), a key hormone produced by pineal gland is a tryptophan metabolite, which exerts its role in a varied range of physiological functions such as regulation of the circadian rhythms, maintaining sleep-wake cycle, managing oxidative stress levels, immunological aspects and clearance of free radicals(Prodhan et al., 2021). The production of melatonin, is done through a series of enzymatic reactions in pineal gland that involves other metabolites such as serotonin, N-acetyl serotonin and 5-hydroxytryptophan. Melatonin, an endocrine hormone with amphiphilic properties are secreted directly into the bloodstream at night by pineal gland, thereby affecting both central nervous system(CNS) and peripheral nervous system(PNS) organs(Claustrat & Leston, 2015). Human research studies have shown that pineal gland can also release melatonin directly into brain ventricles (Leston et al., 2010). From the bloodstream, melatonin is directly taken up by the liver, where it is converted to 6-hydroxymelatonin sulfate, via a series of enzymatic reactions, and lastly excreted through urine (Bojkowski et al., 1987).
    Melatonin primarily influences the target cells by binding to two of the G-protein coupled receptors namely melatonin receptor 1 (MT1) and melatonin receptor 2 (MT2) (de Lima Menezes et al., 2024). Melatonin receptor 3 (MT3) is involved in events that exercises protection due to oxidative stress (de Lima Menezes et al., 2024). The localisation of MT1 and MT2 is not homogenous. MT1 is found in various organs and tissues such as superior chiasmatic nucleus (SCN), ovary, cerebellum, testis, kidney, liver etc. whereas MT2 is more restricted towards brain and partly found in liver and heart tissues (Dubocovich & Markowska, 2005). Activation of MT1 and MT2 receptors lead to the initiation of various signalling pathways, one of which includes the inhibition of adenylate cyclase, which produces cyclone adenosine monophosphate (cAMP), a secondary messenger crucial for cellular and physiological processes (Ahmad et al., 2023). Moreover, melatonin extends its biological activities such as interaction with nuclear receptors and membrane bound intracellular proteins such as calmodulin (Cecon et al., 2018).

    Role of Melatonin in Alzheimer’s Disease

    Apart from regulating the sleep-wake cycles, and maintain the circadian rhythms melatonin implicates direct and indirect association with pathways involved in AD pathophysiology (Arendt & Skene, 2005). This includes the potential of melatonin to reduce the production of Aβ plaques, alongside exercising it’s protective effect on the Aβ oligomers, which are the most deadly and pathogenic form of Aβ. Melatonin also have been partially found to be involved in modulation of hyperphosphosphorylation of tau (Cline et al., 2018a). Moreoever, melatonin exerts it’s neuroprotective effect by reducing the oxidative stress levels, and promoting the clearance of free radicals in the CNS (D. Xu et al., 2020). Additionally melatonin implicates its effects on circadian processes of brain cells, organizes neural activity, modulates synaptic transmission activity in regard to natural sleep wake cycle, which could potentially alleviate the pathological symptoms of AD (Kruk et al., 2021). Melatonin may influence AD pathology through several additional protective mechanisms, including improved blood-brain barrier (BBB) function, increased removal of metabolites and protein fragments associated with AD; a process largely driven by astrocytes during sleep and enhanced insulin signalling, which is also thought to contribute to AD (De Felice et al., 2022a).
    The production of melatonin decreases as the human brain ages, due to the age-related calcification process of pineal gland rather than it’s increased clearance ability (Sack et al., 1986). Clinically speaking, reduced melatonin levels, and disturbed 24-hour melatonin rhythmic cycles are common symptoms observed in patients with dementia and AD (J. L. Wang et al., 2015). Decreased melatonin levels in serum and cerebrospinal fluid (CSF), and disturbed melatonin diurnal rhythm are observed in AD patients (J.-N. Zhou et al., 2003a). Moreoever, CSF melatonin levels decreases significantly as AD progresses pathologically, whose severity is determined by braak stages (R. Y. Liu et al., 1999a). Reduced melatonin levels, are also a key characteristic of preclinical subjects of AD, who are intact cognitively but show early signs of AD thereby regarding it as an important biomarker for the identification of early-onset alzheimer’s disease(EOAD) (Y.-H. Wu et al., 2003). Although molecular alterations occur in the pineal gland of AD patients, there are no observed differences in pineal gland’s weight, degree of calcification, or overall protein content (Friedland et al., 1990). It has also been found that β1-adrenergic receptor mRNA is absent and both the activity and gene expression of monoamine oxidase (MAO) are increased in AD patients. This indicates that disrupted noradrenergic signalling and decreased serotonin, the precursor to melatonin, which might be the cause of melatonin rhythm loss and decreased melatonin levels observed in AD (Y.-H. Wu et al., 2007). External melatonin supplementation, has been suggested as a treatment option for AD patients, which mitigates the effects of agitated behaviour, confusion and “sundowning” symptoms and improves cognitive functioning of AD patients (Cardinali et al., 2002). Thus, this makes melatonin supplementation, which is very less toxic and hideous towards normal functioning of AD patients, a possible symptomatic treatment option.
    Since melatonin can alleviate certain clinical symptoms of AD and its levels significantly decline during the progression of the condition, exploring the connection between melatonin and AD pathology may offer valuable insights into its potential for prevention or treatment. This review will focus on melatonin's role in Aβ toxicity, tau hyperphosphorylation, mitochondrial dysfunction, oxidative stress, calcium imbalance, cholinergic system dysregulation, neuroinflammatory microglial activity responses, BBB, insulin resistance and role in regulating circadian rhythms. Each section will cover observations, evidence, mechanism, and theoretical interpretations in a structure pattern.

    Melatonin and its potential roles in Aβ neurotoxicity and production/clearance balance

    Cleavage of amyloid precursor protein (APP) by β- and γ-secretases leads to the production of Aβ. The production of Aβ fragments follows two classical pathways in AD pathogenesis: amyloidogenic and non-amyloidogenic pathway(Ma et al., 2022). Amyloidogenic processing pathway is initiated when the APP is cleaved by β-secretases in order to form a C-terminal fragment (CTF) with 99 amino acids (C99). C99 is later cleaved by γ-secretases to produce pathogenic forms of Aβ. This amyloidogenic pathway produces neurotoxic fragments like Aβ1− 40 and Aβ1− 42 (Armstrong, 2013). Majority of APP undergoes the non-amyloidogenic pathway first, in which APP is cleaved by α-secretases, which further forms a N- terminal soluble APP- α and C-terminal fragment of 83 amino acids knows as C83. Further C83 is cleaved by γ-secretases to release APP intracellular domain (AICD) (Bruno et al., 2021). Increased levels of non-amyloidogenic pathway processing leads to reduction in production of Aβ and ameliorates the effects mediated by AD pathology (Rostagno, 2022).

    A. Evidence

    Increased production of Aβ and impaired clearance of Aβ, leads to the assembly and accumulation of Aβ, later on which leads to formation of toxic forms of Aβ, called as oligomeric Aβ and amyloid fibrils. Hence inhibition of this Aβ fibril formation and accumulation is another intervention to stop AD pathogenesis(Rostagno, 2022). Various research studies have shown that melatonin has the ability to slow down or diminish the Aβ production and improper accumulation, by enhancing the non-amyloidogenic APP processing pathway (Minich et al., 2022). Additionally when not comparing with previous conventional models of Aβ plaque formation, melatonin interacts with several biological pathways. For instance, melatonin has been shown to promote α-secretase cleavage of βAPP in both neuronal and non-neuronal cultured cells by increasing the expression of the non-amyloidogenic proteases ADAM10 and ADAM17. Conversely, when α-secretase inhibitors are present in these cell lines, melatonin's ability to activate the non-amyloidogenic pathway through α-secretase is blocked(Shukla et al., 2015). Research using SH-SY5Y cells, a well-established model for investigating neurodegeneration, has shown that melatonin suppresses the expression of amyloidogenic β-secretases(Panmanee et al., 2015). Melatonin treatment appears to reduce the levels of Aβ in the brains of both sporadic and transgenic animal models of AD(Ng et al., 2010). This effect may be due to its ability to simultaneously enhance α-secretase activity, an enzyme that promotes non-amyloidogenic processing of amyloid precursor protein and reduce β-secretase activity, which is involved in Aβ generation. Interestingly, this interaction seems to be bi-directional: studies have shown that Aβ peptides can significantly suppress melatonin production by the pineal gland(Cecon et al., 2015), suggesting a feedback loop that may further influence disease progression.

    B. Mechanism

    Melatonin appears to regulate the activity of enzymes involved in the processing of membrane-bound APP) in neurons, notably glycogen synthase kinase-3β (GSK3β) (Uemura et al., 2007). GSK3β, a serine/threonine kinase abundantly expressed in the brain, plays a pivotal role in AD pathology by increasing β-secretase activity while simultaneously suppressing α-secretase activity(Ly et al., 2013a). This enzymatic imbalance favors the accumulation of Aβ peptides both inside and outside neurons. In AD mouse models, melatonin has been found to inhibit GSK3β activity, potentially through activation of the MT1 melatonin receptor, as demonstrated in studies using SH-SY5Y neuroblastoma cells(Nopparat et al., 2022a). Notably, under hyperglycemic conditions simulated by high glucose exposure, these cells showed impaired glucose sensing, which activated the pAkt/GSK3β signalling cascade. This activation led to increased expression of BACE (β-secretase) and elevated production of the Aβ42 peptide, further contributing to amyloid pathology(Nopparat et al., 2022a). This effect was mitigated when cells were pretreated with melatonin. Additionally, melatonin might influence the clearance of amyloid-beta by modulating the insulin-degrading enzyme (IDE), a key protease responsible for degrading Aβ both inside and outside cells(Kurochkin et al., 2018). In diabetic mouse models, IDE levels are reduced alongside heightened GSK3β activity in the CNS(Jolivalt et al., 2008). Notably, a synthesized compound combining melatonin and the metal chelator trientine, referred to as melatonin-trientine was found to increase IDE expression, reduce Aβ buildup, and prevent neuronal degeneration in the brains of APP/Presenilin 1 mice(Li et al., 2022).
    Another way melatonin exerts its anti-amyloidogenic effects is by promoting the removal of Aβ from the brain. Astrocytes, located at the boundary between brain tissue and the perivascular space which contains capillaries, larger arteries, and veins are involved in clearing Aβ through processes such as enzymatic breakdown and by increasing the activity of efflux transporters for Aβ at the blood-brain barrier (Bechmann et al., 2007). Research using mouse neuroblastoma cells (Neuro-2a) indicates that melatonin may enhance the expression of Transcription Factor EB, a key regulator of lysosome formation. This, in turn, facilitates the clearance of Aβ by astrocytes through the autophagosome-lysosome pathway (Thal, 2012).
    Studies have proved that melatonin upregulates the expression of low-density lipoprotein receptor-related protein 1 (LRP1), which is a key receptor involved in transporting Aβ across the BBB and mediating its uptake by astrocytes enhances the clearance of Aβ (Promyo et al., 2020a). Apolipoprotein E (ApoE),a protein involved in lipid transport via cell surface receptors can possibly interfere with this process. ApoE competes with Aβ for LRP1-mediated uptake, and hence hinders the process of Aβ clearance, thereby contributing towards its accumulation and plaque formation in the brain(Hatters et al., 2006). Research in the past decades have depicted that, in astrocytes derived from transgenic AD mouse models that overexpress ApoE, melatonin has been found to counteract ApoE's pro-aggregation effects on Aβ(Verghese et al., 2013). Clinical studies have reported that individuals who have the high-risk APOE4/4 genotype do exhibit lower melatonin levels in cerebrospinal fluid that are at a level that is close to half what individuals carrying just one APOE4 allele have, suggesting such individuals may gain benefit from melatonin supplementation(R. Y. Liu et al., 1999b; Poeggeler et al., 2001).
    There are several clinical models established which extensively elucidate melatonin’s role in Aβ neurotoxicity and production/clearance mechanisms. Besides helping the brain’s support cells (astrocytes) clear out waste, melatonin might also ease the buildup of Aβ by boosting the brain’s lymphatic drainage system. In a mouse model of AD (Tg2576), which has a gene mutation causing excess Aβ in the brain, melatonin treatment seemed to shift more Aβ to the lymph nodes in the neck and armpits, while Aβ levels in the brain showed signs of decreasing. Studies conducted by (O’Neal-Moffitt et al., 2015a) illustrates how melatonin reduces Aβ production, by interfering with amyloid fibril formation, and thereby decreasing Aβ deposition in transgenic mouse brains; whereas chronic supplementation improved spatial memory in APP/PS1 mice.
    Preclinical evidence across diverse animal models including transgenic APP/PS1 and Tg2576 mice, senescence-accelerated SAMP8 mice, and Aβ-infused or toxin-induced rats consistently demonstrates that melatonin mitigates amyloid-β neurotoxicity(O’Neal-Moffitt et al., 2015a). It inhibits amylodgenesis, prevents fibril aggregation, restores mitochondrial and antioxidant defenses, and improves cognition(Dragicevic et al., 2011a; Matsubara, Bryant-Thomas, et al., 2003; Olcese et al., 2009). These findings collectively support melatonin’s multifaceted neuroprotective potential against the amyloidogenic cascade of AD.

    C. Limitations

    Despite substantial preclinical evidence supporting melatonin’s neuroprotective actions against amyloid-β toxicity, several factors limit its direct translation to human studies. These include the use of excessively high doses, simplified or incomplete AD models, insufficient attention to circadian timing and sex differences, and interventions initiated before significant disease manifestation. In addition, inconsistencies in experimental protocols and potential publication bias hinder reproducibility and clinical relevance. Overcoming these challenges through standardized methodologies, use of aged and multifactorial animal models, and incorporation of chronopharmacological approaches will be essential to translate preclinical findings into meaningful clinical outcomes.
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