Inhibitory effect of melatonin on cerebral endothelial cells dysfunction induced by methamphetamine via NADPH oxidase-2

Molecular Links Between Circadian Rhythm Disruption, Melatonin, and Neurodegenerative Diseases: An Updated Review

Circadian rhythms are molecular oscillations governed by transcriptional-translational feedback loops (TTFLs) operating in nearly all cell types and are fundamental to physiological homeostasis. Key circadian regulators, such as circadian locomotor output cycles kaput (CLOCK), brain and muscle ARNT-like 1 (BMAL1), period (PER), and cryptochrome (CRY) gene families, regulate intracellular metabolism, oxidative balance, mitochondrial function, and synaptic plasticity. Circadian disruption is known as a central contributor to the molecular pathophysiology of neurodegenerative disorders. Disease-specific disruptions in clock gene expression and melatoninergic signaling are known as potential early-stage molecular biomarkers. Melatonin, a neurohormone secreted by the pineal gland, modulates clock gene expression, mitochondrial stability, and inflammatory responses. It also regulates epigenetic and metabolic processes through nuclear receptors and metabolic regulators involved in circadian and cellular stress pathways, thereby exerting neuroprotective effects and maintaining neuronal integrity. This review provides recent findings from the past five years, highlighting how circadian dysregulation mediates key molecular and cellular disturbances and the translational potential of circadian-based therapies in neurodegenerative diseases.

Cytotoxicity of methamphetamine exposure on Sertoli cells: a pilot study with implications for male infertility

Methamphetamine (Meth), a psychoactive drug, has been shown to reduce testicular weight and decrease sperm count, indicating its potential role in contributing to male infertility. We therefore assessed Meth's effects (0.1-100 μM) on TM4 Sertoli cell viability, toxicity, and proliferation (trypan blue exclusion assay), mitochondrial activity (MA) (XTT assay), while transepithelial electrical resistance (TEER) was used to examine monolayer permeability. The acute study (only 24-hour Meth exposure) mimics recreational users and the chronic study, the Meth addicts who require daily doses (24-96 hours). Acute Meth treatment had minimal impact on TM4 Sertoli cell viability and toxicity, while chronic exposure resulted in reduced cell viability and increased toxicity in a dose-related manner. Acute exposure suppressed cell division at 72 hours, while chronic exposure suppressed cell division at both 72 and 96 hours. Long-term suppression of MA was observed for both acute and chronic Meth exposure (20 µM and 100 µM). Both acute and chronic Meth exposure affected permeability across the blood-testis barrier (BTB), which persisted for up to 96 hours. Given the pivotal role of Sertoli cells in spermatogenesis, our findings provide a two-pronged mechanism for Meth-induced male infertility and indicate that short-term exposure may have long-term effects on the germinal epithelium.

Melatonin: A potential nighttime guardian against Alzheimer's

In the context of the escalating global health challenge posed by Alzheimer's disease (AD), this comprehensive review considers the potential of melatonin in both preventive and therapeutic capacities. As a naturally occurring hormone and robust antioxidant, accumulating evidence suggests melatonin is a compelling candidate to consider in the context of AD-related pathologies. The review considers several mechanisms, including potential effects on amyloid-beta and pathologic tau burden, antioxidant defense, immune modulation, and regulation of circadian rhythms. Despite its promise, several gaps need to be addressed prior to clinical translation. These include conducting additional randomized clinical trials in patients with or at risk for AD dementia, determining optimal dosage and timing, and further determining potential side effects, particularly of long-term use. This review consolidates existing knowledge, identifies gaps, and suggests directions for future research to better understand the potential of melatonin for neuroprotection and disease mitigation within the landscape of AD.

Melatonin and brain barriers: The protection conferred by melatonin to the blood-brain barrier and blood-cerebrospinal fluid barrier

The blood-brain barrier and the blood-cerebrospinal fluid barrier separate the blood from brain tissue and cerebrospinal fluid. These brain barriers are important to maintain homeostasis and complex functions by protecting the brain from xenobiotics and harmful endogenous compounds. The disruption of brain barriers is a characteristic of neurologic diseases. Melatonin is a lipophilic hormone that is mainly produced by the pineal gland. The blood-brain barrier and the blood-cerebrospinal fluid barriers are melatonin-binding sites. Among the several melatonin actions, the most characteristic one is the regulation of sleep-wake cycles, melatonin has anti-inflammatory and antioxidant properties. Since brain barriers disruption can arise from inflammation and oxidative stress, knowing the influence of melatonin on the integrity of brain barriers is extremely important. Therefore, the objective of this review is to gather and discuss the available literature about the regulation of brain barriers by melatonin.

Melatonin: a ferroptosis inhibitor with potential therapeutic efficacy for the post-COVID-19 trajectory of accelerated brain aging and neurodegeneration

The unprecedented pandemic of COVID-19 swept millions of lives in a short period, yet its menace continues among its survivors in the form of post-COVID syndrome. An exponentially growing number of COVID-19 survivors suffer from cognitive impairment, with compelling evidence of a trajectory of accelerated aging and neurodegeneration. The novel and enigmatic nature of this yet-to-unfold pathology demands extensive research seeking answers for both the molecular underpinnings and potential therapeutic targets. Ferroptosis, an iron-dependent cell death, is a strongly proposed underlying mechanism in post-COVID-19 aging and neurodegeneration discourse. COVID-19 incites neuroinflammation, iron dysregulation, reactive oxygen species (ROS) accumulation, antioxidant system repression, renin-angiotensin system (RAS) disruption, and clock gene alteration. These events pave the way for ferroptosis, which shows its signature in COVID-19, premature aging, and neurodegenerative disorders. In the search for a treatment, melatonin shines as a promising ferroptosis inhibitor with its repeatedly reported safety and tolerability. According to various studies, melatonin has proven efficacy in attenuating the severity of certain COVID-19 manifestations, validating its reputation as an anti-viral compound. Melatonin has well-documented anti-aging properties and combating neurodegenerative-related pathologies. Melatonin can block the leading events of ferroptosis since it is an efficient anti-inflammatory, iron chelator, antioxidant, angiotensin II antagonist, and clock gene regulator. Therefore, we propose ferroptosis as the culprit behind the post-COVID-19 trajectory of aging and neurodegeneration and melatonin, a well-fitting ferroptosis inhibitor, as a potential treatment.

Melatonin Attenuates Methamphetamine-Induced Alteration of Amyloid β Precursor Protein Cleaving Enzyme Expressions via Melatonin Receptor in Human Neuroblastoma Cells

Alzheimer's disease (AD) is the most prominent neurodegenerative disease represented by the loss of memory and cognitive impairment symptoms and is one of the major health imperilments among the elderly. Amyloid (Aβ) deposit inside the neuron is one of the characteristic pathological hallmarks of this disease, leading to neuronal cell death. In the amyloidogenic processing, the amyloid precursor protein (APP) is cleaved by beta-secretase and γ-secretase to generate Aβ. Methamphetamine (METH) is a psychostimulant drug that causes neurodegeneration and detrimental cognitive deficits. The analogy between the neurotoxic and neurodegenerative profile of METH and AD pathology necessitates an exploration of the underlying molecular mechanisms. In the present study, we found that METH ineluctably affects APP processing, which might contribute to the marked production of Aβ in human neuroblastoma cells. Melatonin, an indolamine produced and released by the pineal gland as well as other extrapineal, has been protective against METH-induced neurodegenerative processes, thus rescuing neuronal cell death. However, the precise action of melatonin on METH has yet to be determined. We further propose to investigate the protective properties of melatonin on METH-induced APP-cleaving secretases. Pretreatment with melatonin significantly reversed METH-induced APP-cleaving secretases and Aβ production. In addition, pretreatment with luzindole, a melatonin receptor antagonist, significantly prevented the protective effect of melatonin, suggesting that the attenuation of the toxic effect on METH-induced APP processing by melatonin was mediated via melatonin receptor. The present results suggested that melatonin has a beneficial role in preventing Aβ generation in a cellular model of METH-induced AD.

Neurotoxicity of methamphetamine: Main effects and mechanisms

Methamphetamine (METH) is an illicit psychostimulant that is abused throughout the world. METH addiction is also a major public health concern and the abuse of large doses of the drug is often associated with serious neuropsychiatric consequences that may include agitation, anxiety, hallucinations, paranoia, and psychosis. Some human methamphetamine users can also suffer from attention, memory, and executive deficits. METH-associated neurological and psychiatric complications might be related, in part, to METH-induced neurotoxic effects. Those include altered dopaminergic and serotonergic functions, neuronal apoptosis, astrocytosis, and microgliosis. Here we have endeavored to discuss some of the main effects of the drug and have presented the evidence supporting certain of the molecular and cellular bases of METH neurotoxicity. The accumulated evidence suggests the involvement of transcription factors, activation of dealth pathways that emanate from mitochondria and endoplasmic reticulum (ER), and a role for neuroinflammatory mechanisms. Understanding the molecular processes involved in METH induced neurotoxicity should help in developing better therapeutic approaches that might also serve to attenuate or block the biological consequences of use of large doses of the drug by some humans who meet criteria for METH use disorder.

Agomelatine Softens Depressive-Like Behavior through the Regulation of Autophagy and Apoptosis

Depression is a common and disabling mental disorder with high recurrence rate. Searching for more effective treatments for depression is a long-standing primary objective in neuroscience. Agomelatine (AGO) was reported as an antidepressant with unique pharmacological effects. However, its effects and the underlying mechanism are still unclear. In this study, we sought to evaluate the antidepressant effects of AGO on the chronic restraint stress (CRS) mouse model and preliminarily investigate its effects on the gut microbial metabolites. The CRS model mice were established in 28 days with AGO (60 mg/kg/day, by oral) or fluoxetine (15 mg/kg/day, by oral) administration. The number of behavioral tests was conducted to evaluate the effect of AGO on depression-like behavior alleviation. Meanwhile, the expression of the BDNF/TrkB/pERK signaling pathway, apoptosis, autophagy, and inflammatory protein markers were assessed using western blot and immunofluorescence. Our findings show that AGO can attenuate the depressive-like behavior that significantly appeared in both sucrose preference and forced swimming tests. Additionally, a noticeable upregulation of autophagy including Beclin1 and LC3II, microglial activity marker Iba-1, and BDNF/TrkB/pERK signaling pathways are indicated. An obvious decreased expression of NF-κB, iNOS, and nNOS as well as apoptosis including Bax is observed in AGO administration mice. On the other hand, we found that AGO impacted the rebalancing of short-chain fatty acids (SCFAs) in mouse feces. Altogether, these findings suggest that AGO can exert antidepressant effects in a different molecular mechanism.

Cardioprotective Role of Melatonin in Acute Myocardial Infarction

Melatonin is a pleiotropic, indole secreted, and synthesized by the human pineal gland. Melatonin has biological effects including anti-apoptosis, protecting mitochondria, anti-oxidation, anti-inflammation, and stimulating target cells to secrete cytokines. Its protective effect on cardiomyocytes in acute myocardial infarction (AMI) has caused widespread interest in the actions of this molecule. The effects of melatonin against oxidative stress, promoting autophagic repair of cells, regulating immune and inflammatory responses, enhancing mitochondrial function, and relieving endoplasmic reticulum stress, play crucial roles in protecting cardiomyocytes from infarction. Mitochondrial apoptosis and dysfunction are common occurrence in cardiomyocyte injury after myocardial infarction. This review focuses on the targets of melatonin in protecting cardiomyocytes in AMI, the main molecular signaling pathways that melatonin influences in its endogenous protective role in myocardial infarction, and the developmental prospect of melatonin in myocardial infarction treatment.

Protective Effects of Melatonin on Methamphetamine-Induced Blood-Brain Barrier Dysfunction in Rat Model

The specialized brain endothelial cells interconnected by unique junctions and adhesion molecules are distinctive features of the blood-brain barrier (BBB), maintaining the homeostasis of the cerebral microenvironment. This study was designed to investigate the protective effects of melatonin on methamphetamine (METH)-induced alterations of BBB integrity. Wistar rats were randomly distributed into groups and underwent melatonin pretreatment and escalating-high doses of METH treatment. Immunohistochemistry was performed to demonstrate the BBB leakage. Protein and RNA samples were isolated from hippocampal and prefrontal cortical tissues and measured expression levels of molecular markers associated with BBB structural components and inflammatory processes. METH provoked the loss of zonula occludens (ZO)-1, occludin, and claudin-5 tight junction proteins. Furthermore, METH caused an excessive increase in matrix metalloproteinase-9 (MMP-9) enzyme, intercellular adhesion molecule 1 (ICAM-1), and vascular cell adhesion molecule 1 (VCAM-1) and the increase in NAD(P)H oxidase 2 (NOX2). Melatonin exerted the protective effects by recovering tight junction loss; attenuating excessive MMP-9, NOX2, and cell adhesion molecule expression; and reducing serum albumin in the brain. Our results also showed the protective effects of melatonin against METH neurotoxic profiles, characterized by reactive gliosis: microglia (integrin-αM) and astrocyte (GFAP); an excessive upregulation of primary pro-inflammatory cytokines: interleukin-1β (IL-1β), interleukin-6 (IL-6), and tumor necrosis factor-α (TNF-α); activation of neuroinflammatory signaling: nuclear factor-kappa B (NF-κB); and suppression of anti-oxidative signaling: nuclear factor erythroid 2-related factor (Nrf2), that may exacerbate BBB structural impairment. Our results provide insights into the beneficial effects of melatonin against METH-induced BBB disruption and mechanisms that play detrimental roles in BBB impairment by in vivo design.

Cystatin C Expression is Promoted by VEGFA Blocking, With Inhibitory Effects on Endothelial Cell Angiogenic Functions Including Proliferation, Migration, and Chorioallantoic Membrane Angiogenesis

Background Vascular development, including vasculogenesis and angiogenesis, is involved in many diseases. Cystatin C ( CST 3) is a commonly used marker of renal dysfunction, and we have previously reported that its expression level is associated with variations in the gerbil circle of Willis. Thus, we hypothesized that CST 3 may affect endothelial function and angiogenic capacity. In the current study, we sought to determine the influence of CST 3 on endothelial function and explore its potential regulatory pathway. Methods and Results We analyzed CST 3 and vascular endothelial growth factor A ( VEGFA) levels in different developmental stages of gerbils using ELISA s and immunofluorescence (to examine the relationship between CST 3 and VEGFA . We used a real-time cell analyzer, cytotoxicity assays, and the chorioallantoic membrane assay to investigate the function of CST 3 in endothelial cells and the chorioallantoic membrane. Additionally, we used Western blotting to explore the downstream targets of CST 3. The expression levels of both CST 3 and VEGFA were at their highest on day 10 of the embryonic stage. CST 3 inhibited endothelial cell proliferation, migration, tube formation, and permeability, as well as vascular development in the chorioallantoic membrane. Blocking of VEGFA dose-dependently increased CST 3 expression in arterial and venous endothelial cells. Furthermore, overexpression and knockdown of CST 3 significantly affected the protein levels of p53 and CAPN10 (calpain 10), suggesting that CST 3 might play a role in vascular development through these proteins. Conclusions CST 3 may be associated with vascular development and angiogenesis, and this effect could be promoted by blocking VEGFA .

Leaky brain in neurological and psychiatric disorders: Drivers and consequences

BACKGROUND

The blood-brain barrier acts as a highly regulated interface; its dysfunction may exacerbate, and perhaps initiate, neurological and neuropsychiatric disorders.

METHODS

In this narrative review, focussing on redox, inflammatory and mitochondrial pathways and their effects on the blood-brain barrier, a model is proposed detailing mechanisms which might explain how increases in blood-brain barrier permeability occur and can be maintained with increasing inflammatory and oxidative and nitrosative stress being the initial drivers.

RESULTS

Peripheral inflammation, which is causatively implicated in the pathogenesis of major psychiatric disorders, is associated with elevated peripheral pro-inflammatory cytokines, which in turn cause increased blood-brain barrier permeability. Reactive oxygen species, such as superoxide radicals and hydrogen peroxide, and reactive nitrogen species, such as nitric oxide and peroxynitrite, play essential roles in normal brain capillary endothelial cell functioning; however, chronically elevated oxidative and nitrosative stress can lead to mitochondrial dysfunction and damage to the blood-brain barrier. Activated microglia, redox control of which is mediated by nitric oxide synthases and nicotinamide adenine dinucleotide phosphate (NADPH) oxidases, secrete neurotoxic molecules such as reactive oxygen species, nitric oxide, prostaglandin, cyclooxygenase-2, quinolinic acid, several chemokines (including monocyte chemoattractant protein-1 [MCP-1], C-X-C motif chemokine ligand 1 [CXCL-1] and macrophage inflammatory protein 1α [MIP-1α]) and the pro-inflammatory cytokines interleukin-6, tumour necrosis factor-α and interleukin-1β, which can exert a detrimental effect on blood-brain barrier integrity and function. Similarly, reactive astrocytes produce neurotoxic molecules such as prostaglandin E2 and pro-inflammatory cytokines, which can cause a 'leaky brain'.

CONCLUSION

Chronic inflammatory and oxidative and nitrosative stress is associated with the development of a 'leaky gut'. The following evidence-based approaches, which address the leaky gut and blood-brain barrier dysfunction, are suggested as potential therapeutic interventions for neurological and neuropsychiatric disorders: melatonin, statins, probiotics containing Bifidobacteria and Lactobacilli, N-acetylcysteine, and prebiotics containing fructo-oligosaccharides and galacto-oligosaccharides.

Melatonin attenuates homocysteine-induced injury in human umbilical vein endothelial cells

Homocysteine (Hcy) is a major risk factor for vascular disease and is closely associated with endothelial dysfunction. Melatonin is a neurohormone that is mostly produced by the pineal gland. Studies have reported that melatonin exhibits neuroprotective effects in several neurodegenerative disorders. The aim of the current study was to investigate the possible protective effect of melatonin against Hcy-induced endothelial cell apoptosis in human umbilical vein endothelial cells (HUVECs) and to explore the underlying mechanisms. HUVECs were exposed to Hcy in the presence or absence of melatonin. The effect of melatonin on viability was examined by MTT assay. Intracellular reactive oxygen species (ROS) levels were determined by 2',7'-dichlorofluorescein diacetate (DCF-DA). Further, expression of Bax, Bcl-2, and caspase-3 was analyzed by Western blot analysis. Lipid peroxidation (LPO) levels, total antioxidant power (TAP), and total thiol molecules were also evaluated. The results of this study revealed that melatonin significantly prevented Hcy-induced loss in cell viability in HUVECs. It was found that ROS significantly increased in the presence of Hcy, whereas melatonin reduced ROS production. Melatonin also downregulated Bax, upregulated Bcl-2, and decreased the expression and activity of caspase-3. Hcy increased the levels of LPO, and this effect was significantly attenuated by melatonin. Melatonin also increased the levels of TAP and total thiol molecules. It was concluded that melatonin played a protective role against Hcy-induced endothelium cell apoptosis through inhibition of ROS accumulation and the mitochondrial-dependent apoptotic pathway.

The role of melatonin in the onset and progression of type 3 diabetes

Alzheimer’s disease (AD) is defined by the excessive accumulation of toxic peptides, such as beta amyloid (Aβ) plaques and intracellular neurofibrillary tangles (NFT). The risk factors associated with AD include genetic mutations, aging, insulin resistance, and oxidative stress. To date, several studies that have demonstrated an association between AD and diabetes have revealed that the common risk factors include insulin resistance, sleep disturbances, blood brain barrier (BBB) disruption, and altered glucose homeostasis. Many researchers have discovered that there are mechanisms common to both diabetes and AD. AD that results from insulin resistance in the brain is termed “type 3 diabetes”. Melatonin synthesized by the pineal gland is known to contribute to circadian rhythms, insulin resistance, protection of the BBB, and cell survival mechanisms. Here, we review the relationship between melatonin and type 3 diabetes, and suggest that melatonin might regulate the risk factors for type 3 diabetes. We suggest that melatonin is crucial for attenuating the onset of type 3 diabetes by intervening in Aβ accumulation, insulin resistance, glucose metabolism, and BBB permeability.

Activation of melatonin receptor (MT1/2) promotes P-gp transporter in methamphetamine-induced toxicity on primary rat brain microvascular endothelial cells

Melatonin has been known as a neuroprotective agent for the central nervous system (CNS) and the blood-brain barrier (BBB), which is the primary structure that comes into contact with several neurotoxins including methamphetamine (METH). Previous studies have reported that the activation of melatonin receptors (MT1/2) by melatonin could protect against METH-induced toxicity in brain endothelial cells via several mechanisms. However, its effects on the P-glycoprotein (P-gp) transporter, the active efflux pump involved in cell homeostasis, are still unclear. Thus, this study investigated the role of melatonin and its receptors on the METH-impaired P-gp transporter in primary rat brain microvascular endothelial cells (BMVECs). The results showed that METH impaired the function of the P-gp transporter, significantly decreasing the efflux of Rho123 and P-gp expression, which caused a significant increase in the intracellular accumulation of Rho123, and these responses were reversed by the interaction of melatonin with its receptors. Blockade of the P-gp transporter by verapamil caused oxidative stress, apoptosis, and cell integrity impairment after METH treatment, and these effects could be reversed by melatonin. Our results, together with previous findings, suggest that the interaction of melatonin with its receptors protects against the effects of the METH-impaired P-gp transporter and that the protective role in METH-induced toxicity was at least partially mediated by the regulation of the P-gp transporter. Thus, melatonin and its receptors (MT1/2) are essential for protecting against BBB impairment caused by METH.