Ischemic brain injury: New insights on the protective role of melatonin

Reduced ischemia-reperfusion oxidative stress injury by melatonin and N-acetylcysteine in the male rat brain

Middle cerebral artery occlusion (MCAO) is a model for inducing ischemic stroke in rodents, leading to devastating brain damage. Oxidative stress (OS) plays a crucial role in the pathogenesis of ischemia. In this study, the effect of melatonin and N-acetylcysteine on ischemia-reperfusion-induced oxidative stress injury in the cerebral cortex of male rats was investigated. 30 male Wistar rats were divided into sham, ischemic, NAC, melatonin and NAC + melatonin groups. All groups, except the sham group, underwent MCAO on the left side, and the treatment groups received intraperitoneal injections of either 50 mg/kg N-acetylcysteine (NAC) or 5 mg/kg melatonin or a combination of both 24 and 48 hours later. At 24 and 72 hours after surgery, the animals were examined for sensory and motor activity. The cerebral cortex was dissected after sacrificing the rats, infarct volume estimated and the concentrations of glutathione peroxidase (GPx), superoxide dismutase (SOD), catalase (CAT), malondialdehyde (MDA) and nuclear factor erythroid-2 related factor 2 (Nrf2) were analyzed by enzyme-linked immunosorbent assay (ELISA). The results indicate that the NAC + melatonin group exhibited elevated sensory-motor activity and a reduced infarct volume rate in comparison to the ischemic group (p≤ 0.05). Compared to the ischemic group, the NAC + melatonin group showed a significant increase in SOD concentration and a significant decrease in MDA (p≤ 0.05). It can therefore be concluded that the simultaneous administration of NAC and melatonin can reduce the cerebral infarction volume, and improve neurological functions by modulating SOD and MDA.

Neuroprotective Effect of Melatonin in a Neonatal Hypoxia-Ischemia Rat Model Is Regulated by the AMPK/mTOR Pathway

BACKGROUND

Melatonin has been shown to be neuroprotective in different animal models of neonatal hypoxic-ischemic brain injury. However, its exact molecular mechanism of action remains unknown. Our aim was to prove melatonin's short- and long-term neuroprotection and investigate its role on the AMPK (AMP-activated protein kinase)/mTOR (mammalian target of rapamycin) pathway following neonatal hypoxic-ischemic brain injury.

METHODS AND RESULTS

Seven-day-old Wistar rat pups were exposed to hypoxia-ischemia, followed by melatonin or vehicle treatment. Detailed analysis of the AMPK/mTOR/autophagy pathway, short- and long-term neuroprotection, myelination, and oligodendrogenesis was performed at different time points. At 7 days after hypoxia-ischemia, melatonin-treated animals showed a significant decrease in tissue loss, increased oligodendrogenesis, and myelination. Long-term neurobehavioral results showed significant motor improvement following melatonin treatment. Molecular pathway analysis showed a decrease in the AMPK expression, with a significant increase at mTOR's downstream substrates, and a significant decrease at the autophagy marker levels in the melatonin group compared with the vehicle group.

CONCLUSIONS

Melatonin treatment reduced brain area loss and promoted oligodendrogenesis with a clear improvement of motor function. We found that melatonin associated neuroprotection is regulated via the AMPK/mTOR/autophagy pathway. Considering the beneficial effects of melatonin and the results of our study, melatonin seems to be an optimal candidate for the treatment of newborns with hypoxic-ischemic brain injury in high- as well as in low- and middle-income countries.

Mechanisms of inflammation after ischemic stroke in brain-peripheral crosstalk

Stroke is a devastating disease with high morbidity, disability, and mortality, among which ischemic stroke is more common. However, there is still a lack of effective methods to improve the prognosis and reduce the incidence of its complications. At present, there is evidence that peripheral organs are involved in the inflammatory response after stroke. Moreover, the interaction between central and peripheral inflammation includes the activation of resident and peripheral immune cells, as well as the activation of inflammation-related signaling pathways, which all play an important role in the pathophysiology of stroke. In this review, we discuss the mechanisms of inflammatory response after ischemic stroke, as well as the interactions through circulatory pathways between peripheral organs (such as the gut, heart, lung and spleen) and the brain to mediate and regulate inflammation after ischemic stroke. We also propose the potential role of meningeal lymphatic vessels (MLVs)-cervical lymph nodes (CLNs) as a brain-peripheral crosstalk lymphatic pathway in ischemic stroke. In addition, we also summarize the mechanisms of anti-inflammatory drugs in the treatment of ischemic stroke.

Efficacy and safety of perioperative melatonin for postoperative delirium in patients undergoing surgery: a systematic review and meta-analysis

OBJECTIVE

To assess the efficacy and safety of perioperative melatonin and melatonin agonists in preventing postoperative delirium (POD).

METHODS

We conducted a systematic search for randomized controlled trials (RCTs) published through December 2022. The primary outcome was efficacy based on the incidence of POD (POD-I). Secondary outcomes included efficacy and safety according to the length of hospital or intensive care unit stay, in-hospital mortality, and adverse events. Subgroup analyses of POD-I were based on the type and dose of drug (low- and high-dose melatonin, ramelteon), the postoperative period (early or late), and the type of surgery.

RESULTS

In the analysis (16 RCTs, 1981 patients), POD-I was lower in the treatment group than in the control group (risk ratio [RR] = 0.57). POD-I was lower in the high-dose melatonin group than in the control group (RR = 0.41), whereas no benefit was observed in the low-dose melatonin and ramelteon groups. POD-I was lower in the melatonin group in the early postoperative period (RR = 0.35) and in patients undergoing cardiopulmonary surgery (RR = 0.54).

CONCLUSION

Perioperative melatonin or melatonin agonist treatment suppressed POD without severe adverse events, particularly at higher doses, during the early postoperative period, and after cardiopulmonary surgery.

Comparison of Different Adjuvant Therapies for Hypothermia in Neonates with Hypoxic-Ischemic Encephalopathy: A Systematic Review and Network Meta-Analysis

OBJECTIVES

Neonatal hypoxic-ischemic encephalopathy is a major cause of perinatal death and neurodevelopmental impairment (NDI). Hypothermia (HT) is the standard of care; however, additional neuroprotective agents are required to improve prognosis. The authors searched for all drugs in combination with HT and compared their effects using a network meta-analysis.

METHODS

The authors searched PubMed, Embase, and Cochrane Library until September 24, 2022 for articles assessing mortality, NDI, seizures, and abnormal brain imaging findings in neonates with hypoxic-ischemic encephalopathy. Direct pairwise comparisons and a network meta-analysis was performed under random effects.

RESULTS

Thirteen randomized clinical trials enroled 902 newborns treated with six combination therapies: erythropoietin magnesium sulfate, melatonin (MT), topiramate, xenon, and darbepoetin alfa. The results of all comparisons were not statistically significant, except for NDI, HT vs. MT+HT: odds ratio = 6.67, 95% confidence interval = 1.14-38.83; however, the overall evidence quality was low for the small sample size.

CONCLUSIONS

Currently, no combination therapy can reduce mortality, seizures, or abnormal brain imaging findings in neonatal hypoxic-ischemic encephalopathy. According to low quality evidence, HT combined with MT may reduce NDI.

The Role of Circadian Rhythms in Stroke: A Narrative Review

Stroke, a debilitating condition often leading to long-term disability, poses a substantial global concern and formidable challenge. The increasing incidence of stroke has drawn the attention of medical researchers and neurologists worldwide. Circadian rhythms have emerged as pivotal factors influencing stroke's onset, pathogenesis, treatment, and outcomes. To gain deeper insights into stroke, it is imperative to explore the intricate connection between circadian rhythms and stroke, spanning from molecular mechanisms to pathophysiological processes. Despite existing studies linking circadian rhythm to stroke onset, there remains a paucity of comprehensive reviews exploring its role in pathogenesis, treatment, and prognosis. This review undertakes a narrative analysis of studies investigating the relationship between circadian variation and stroke onset. It delves into the roles of various physiological factors, including blood pressure, coagulation profiles, blood cells, catecholamines, cortisol, and the timing of antihypertensive medication, which contribute to variations in circadian-related stroke risk. At a molecular level, the review elucidates the involvement of melatonin, circadian genes, and glial cells in the pathophysiology. Furthermore, it provides insights into the diverse factors influencing stroke treatment and outcomes within the context of circadian variation. The review underscores the importance of considering circadian rhythms when determining the timing of stroke interventions, emphasizing the necessity for personalized stroke management strategies that incorporate circadian rhythms. It offers valuable insights into potential molecular targets and highlights areas that require further exploration to enhance our understanding of the underlying pathophysiology. In comparison to the published literature, this manuscript distinguishes itself through its coverage of circadian rhythms' impact on stroke across the entire clinical spectrum. It presents a unique synthesis of epidemiological, clinical, molecular, and cellular evidence, underscoring their collective significance.

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

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

Melatonin delivered in solid lipid nanoparticles ameliorated its neuroprotective effects in cerebral ischemia

The current study explores the potential of melatonin (MLT)-loaded solid lipid nanoparticles (MLT-SLNs) for better neuroprotective effects in ischemic stroke. MLT-SLNs were prepared using lipid matrix of palmityl alcohol with a mixture of surfactants (Tween 40, Span 40, Myrj 52) for stabilizing the lipid matrix. MLT-SLNs were tested for physical and chemical properties, thermal and polymorphic changes, in vitro drug release and in vivo neuroprotective studies in rats using permanent middle cerebral artery occlusion (p-MCAO) model. The optimized MLT-SLNs showed particle size of ∼159 nm, zeta potential of -29.6 mV and high entrapment efficiency ∼92%. Thermal and polymorphic studies showed conversion of crystalline MLT to amorphous form after its entrapment in lipid matrix. MLT-SLNs displayed a sustained release pattern compared to MLT dispersion. MLT-SLNs significantly enhanced the neuroprotective profile of MLT ascertained by reduced brain infarction, recovered behavioral responses, low expression of inflammatory markers and improved oxidation protection in rats. MLT-SLNs also showed reduced hepatotoxicity compared to p-MCAO. From these outcomes, it is evidenced that MLT-SLNs have improved neuroprotection as compared to MLT dispersion and thereby present a promising approach to deliver MLT to the brain for better therapeutic outcomes in ischemic stroke.

Role of Melatonin in Bovine Reproductive Biotechnology

Melatonin has profound antioxidant activity and numerous functions in humans as well as in livestock and poultry. Additionally, melatonin plays an important role in regulating the biological rhythms of animals. Combining melatonin with scientific breeding management has considerable potential for optimizing animal physiological functions, but this idea still faces significant challenges. In this review, we summarized the beneficial effects of melatonin supplementation on physiology and reproductive processes in cattle, including granulosa cells, oocytes, circadian rhythm, stress, inflammation, testicular function, spermatogenesis, and semen cryopreservation. There is much emerging evidence that melatonin can profoundly affect cattle. In the future, we hope that melatonin can not only be applied to cattle, but can also be used to safely and effectively improve the efficiency of animal husbandry.

Melatonin Attenuates Cerebral Ischemia/Reperfusion Injury through Inducing Autophagy

INTRODUCTION

The aim of this study was to investigate how melatonin administration for 3 days or 7 days following cerebral ischemia (CI) injury would affect autophagy and, therefore, survival in neurons of the penumbra region. Moreover, it was also aimed at determining how this melatonin treatment would affect the neurological deficit score and rotarod and adhesive removal test durations.

METHODS

Focal CI (90 min) was achieved in a total of 105 rats utilizing a middle cerebral artery occlusion model. After the start of reperfusion, the groups were treated with melatonin (10 mg/kg/day) for 3 days or 7 days. In all groups, neurological deficit scoring, rotarod, and adhesive removal tests were executed during reperfusion. Infarct areas were determined by TTC (2,3,5-triphenyltetrazolium chloride) staining at the end of the 3rd and 7th days of reperfusion. Beclin-1, LC3, p62, and caspase-3 protein levels were assessed using Western blot and immunofluorescence methods in the brain tissues. Moreover, penumbra areas were evaluated by transmission electron microscopy (TEM).

RESULTS

Following CI, it was observed that melatonin treatment improved the rotarod and adhesive removal test durations from day 5 and reduced the infarct area after CI. It also induced autophagic proteins Beclin-1, LC3, and p62 and suppressed the apoptotic protein cleaved caspase-3. According to TEM findings, melatonin treatment partially reduced the damage in neurons after CI.

CONCLUSION

Melatonin treatment following CI reduced the infarct area and induced the autophagic proteins Beclin-1, LC3, and p62 by inhibiting the apoptotic caspase-3 protein. The functional reflection of melatonin treatment on neurological test scores was became significant from the 5th day onward.

Puerarin inhibited oxidative stress and alleviated cerebral ischemia-reperfusion injury through PI3K/Akt/Nrf2 signaling pathway

Introduction: Puerarin (PUE) is a natural compound isolated from Puerariae Lobatae Radix, which has a neuroprotective effect on IS. We explored the therapeutic effect and underlying mechanism of PUE on cerebral I/R injury by inhibiting oxidative stress related to the PI3K/Akt/Nrf2 pathway in vitro and in vivo. Methods: The middle cerebral artery occlusion and reperfusion (MCAO/R) rats and oxygen-glucose deprivation and reperfusion (OGD/R) were selected as the models, respectively. The therapeutic effect of PUE was observed using triphenyl tetrazolium and hematoxylin-eosin staining. Tunel-NeuN staining and Nissl staining to quantify hippocampal apoptosis. The reactive oxygen species (ROS) level was detected by flow cytometry and immunofluorescence. Biochemical method to detect oxidative stress levels. The protein expression related to PI3K/Akt/Nrf2 pathway was detected by using Western blotting. Finally, co-immunoprecipitation was used to study the molecular interaction between Keap1 and Nrf2. Results: In vivo and vitro studies showed that PUE improved neurological deficits in rats, as well as decreased oxidative stress. Immunofluorescence and flow cytometry indicated that the release of ROS can be inhibited by PUE. In addition, the Western blotting results showed that PUE promoted the phosphorylation of PI3K and Akt, and enabled Nrf2 to enter the nucleus, which further activated the expression of downstream antioxidant enzymes such as HO-1. The combination of PUE with PI3K inhibitor LY294002 reversed these results. Finally, co-immunoprecipitation results showed that PUE promoted Nrf2-Keap1 complex dissociation. Discussion: Taken together, PUE can activate Nrf2 via PI3K/Akt and promote downstream antioxidant enzyme expression, which could further ameliorate oxidative stress, against I/R-induced Neuron injury.

Involvement of heat shock proteins HSP70 in the mechanisms of endogenous neuroprotection: the prospect of using HSP70 modulators

This analytical review summarizes literature data and our own research on HSP70-dependent mechanisms of neuroprotection and discusses potential pharmacological agents that can influence HSP70 expression to improve neurological outcomes and effective therapy. The authors formed a systemic concepts of the role of HSP70-dependent mechanisms of endogenous neuroprotection aimed at stopping the formation of mitochondrial dysfunction, activation of apoptosis, desensitization of estrogen receptors, reduction of oxidative and nitrosative stress, prevention of morpho-functional changes in brain cells during cerebral ischemia, and experimentally substantiated new target links for neuroprotection. Heat shock proteins (HSPs) are an evolutionarily integral part of the functioning of all cells acting as intracellular chaperones that support cell proteostasis under normal and various stress conditions (hyperthermia, hypoxia, oxidative stress, radiation, etc.). The greatest curiosity in conditions of ischemic brain damage is the HSP70 protein, as an important component of the endogenous neuroprotection system, which, first of all, performs the function of intracellular chaperones and ensures the processes of folding, holding and transport of synthesized proteins, as well as their degradation, both under normoxic conditions and stress-induced denaturation. A direct neuroprotective effect of HSP70 has been established, which is realized through the regulation the processes of apoptosis and cell necrosis due to a long-term effect on the synthesis of antioxidant enzymes, chaperone activity, and stabilization of active enzymes. An increase in the level of HSP70 leads to the normalization of the glutathione link of the thiol-disulfide system and an increase in the resistance of cells to ischemia. HSP 70 is able to activate and regulate compensatory ATP synthesis pathways during ischemia. It was found that in response to the cerebral ischemia formation, HIF-1a is expressed, which initiates the launch of compensatory mechanisms for energy production. Subsequently, the regulation of these processes switches to HSP70, which "prolongs" the action of HIF-1a, and also independently maintains the expression of mitochondrial NAD-dependent malate dehydrogenase activity, thereby maintaining the activity of the malate-aspartate shuttle mechanism for a long time. During ischemia of organs and tissues, HSP70 performs a protective function, which is realized through increased synthesis of antioxidant enzymes, stabilization of oxidatively damaged macromolecules, and direct anti-apoptotic and mitoprotective action. Such a role of these proteins in cellular reactions during ischemia raises the question of the development of new neuroprotective agents which are able to provide modulation/protection of the genes encoding the synthesis of HSP 70 and HIF-1a proteins. Numerous studies of recent years have noted the important role of HSP70 in the implementation of the mechanisms of metabolic adaptation, neuroplasticity and neuroprotection of brain cells, so the positive modulation of the HSP70 system is a perspective concept of neuroprotection, which can improve the efficiency of the treatment of ischemic-hypoxic brain damage and be the basis for substantiating of the feasibility of using of HSP70 modulators as promising neuroprotectors.

Benefits of the Neurogenic Potential of Melatonin for Treating Neurological and Neuropsychiatric Disorders

There are several neurological diseases under which processes related to adult brain neurogenesis, such cell proliferation, neural differentiation and neuronal maturation, are affected. Melatonin can exert a relevant benefit for treating neurological disorders, given its well-known antioxidant and anti-inflammatory properties as well as its pro-survival effects. In addition, melatonin is able to modulate cell proliferation and neural differentiation processes in neural stem/progenitor cells while improving neuronal maturation of neural precursor cells and newly created postmitotic neurons. Thus, melatonin shows relevant pro-neurogenic properties that may have benefits for neurological conditions associated with impairments in adult brain neurogenesis. For instance, the anti-aging properties of melatonin seem to be linked to its neurogenic properties. Modulation of neurogenesis by melatonin is beneficial under conditions of stress, anxiety and depression as well as for the ischemic brain or after a brain stroke. Pro-neurogenic actions of melatonin may also be beneficial for treating dementias, after a traumatic brain injury, and under conditions of epilepsy, schizophrenia and amyotrophic lateral sclerosis. Melatonin may represent a pro-neurogenic treatment effective for retarding the progression of neuropathology associated with Down syndrome. Finally, more studies are necessary to elucidate the benefits of melatonin treatments under brain disorders related to impairments in glucose and insulin homeostasis.

Increased Oxidative Stress Markers in Acute Ischemic Stroke Patients Treated with Thrombolytics

One of the most common neurological disorders involving oxidative stress is stroke. During a stroke, the balance of redox potential in the cell is disturbed, and, consequently, protein oxidation or other intracellular damage occurs, ultimately leading to apoptosis. The pineal gland hormone, melatonin, is one of the non-enzymatic antioxidants. It not only modulates the perianal rhythm but also has anti-inflammatory properties and protects against stress-induced changes. The focus of this research was to evaluate the concentration of the carbonyl groups and melatonin metabolite in time in patients with acute ischemic stroke that were treated with intravenous thrombolysis. This included a comparison of the functional status of patients assessed according to neurological scales with the control sample comprising healthy people. The studies showed that the serum concentrations of carbonyl groups, which were elevated in patients with ischemic stroke (AIS) in comparison to the control samples, had an impact on the patients' outcome. A urine concentration of the melatonin metabolite, which was lower in patients than controls, was related to functional status after 24 h from cerebral thrombolysis. It shows that determination of carbonyl groups at different time intervals may be an important potential marker of protein damage in patients with AIS treated with cerebral thrombolysis, and that impaired melatonin metabolism induces a low antioxidant protection. Thus, due to the neuroprotective effects of melatonin, attention should also be paid to the design and conduct of clinical trials and hormone supplementation in AIS patients to understand the interactions between exogenous melatonin and its endogenous rhythm, as well as how these relationships may affect patient outcomes.

Melatonin as an Antioxidant Agent in Stroke: An Updated Review

Stroke is a devastating disease associated with high mortality and disability worldwide, and is generally classified as ischemic or hemorrhagic, which share certain similar pathophysiological processes. Oxidative stress is a critical factor involved in stroke-induced injury, which not only directly damages brain tissue, but also enhances a series of pathological signaling cascades, contributing to inflammation, brain edema, and neuronal death. To alleviate these serious secondary brain injuries, neuroprotective agents targeting oxidative stress inhibition may serve as a promising treatment strategy. Melatonin is a hormone secreted by the pineal gland, and has various properties, such as antioxidation, anti-inflammation, circadian rhythm modulation, and promotion of tissue regeneration. Numerous animal experiments studying stroke have confirmed that melatonin exerts considerable neuroprotective effects, partially via anti-oxidative stress. In this review, we introduce the possible role of melatonin as an antioxidant in the treatment of stroke based on the latest published studies of animal experiments and clinical research.

Modulation of autophagy by melatonin via sirtuins in stroke: From mechanisms to therapies

Sirtuins perform an important effect on the neural cell fate following stroke. Several mechanisms that have been correlated with stroke are oxidative stress, apoptosis, necrosis and autophagy. Autophagy is usually regarded as unitary of the neural cell survival mechanisms. Recently, the importance of the sirtuins effect on autophagy by antioxidant agents for stroke treatment mentioned in various studies. One of these agents is melatonin. Melatonin can modulate autophagy by changing on sirtuin pathways. Melatonin and its metabolites adjust various sirtuins pathways related to apoptosis, proliferation, metastases, autophagy and inflammation in case of stroke. In this review, we will discuss about the modulation of autophagy by melatonin via sirtuins in stroke.

Protective effects of melatonin in cisplatin-induced cardiac toxicity: possible role of BDNF-TNF-α signaling pathway

Purpose:

The present study explored the role of melatonin in cisplatin-induced cardiac injury along with the possible role of brain-derived neurotrophic factor (BDNF) in melatonin-mediated effects.

Methods:

Wistar rats were administered cisplatin (10 mg/kg), and cardiac injury was assessed by measuring the levels of cardiac troponin (cTnT) and lactate dehydrogenase (LDH-1).The extent of apoptosis was measured by measuring caspase-3 (pro-apoptotic) and Bcl-2 (anti-apoptotic) in hearts. The levels of BDNF, tumour necrosis factor α (TNF-α) and reduced glutathione were measured in heart. Melatonin (5 and 10 mg/kg) was administered for 15 days, and the role of BDNF was identified by co-administering BDNF inhibitor, ANA-12 (0.25 and 0.5 mg/kg).

Results:

Melatonin attenuated cTnT and LDH-1 levels along with reduction in caspase-3 and increase in Bcl-2. It also increased cisplatin-induced decrease in BDNF, increase in TNF-α and decrease in reduced glutathione levels. Moreover, ANA-12 abolished the cardioprotective effects, anti-inflammatory and antioxidant effects of melatonin suggesting the role of BDNF in melatonin-mediated effects in cisplatin-induced cardiac injury.

Conclusions:

Melatonin is useful in cisplatin-induced cardiac injury, which may be due to an increase in BDNF, decrease in inflammation and increase in antioxidant activities.

Melatonin attenuates cerebral hypoperfusion-induced hippocampal damage and memory deficits in rats by suppressing TRPM7 channels

This study was conducted to examine if modulating transporters like transient receptor potential cation channels, subfamily M, member 7 (TRPM7) underlies the hippocampal neuroprotection afforded by melatonin (Mel) in rats exposed to cerebral hypoperfusion (CHP). Experimental groups included control, Mel-treated (1.87 g/kg), CHP, and CHP + Mel (1.87 g/kg)-treated rats. CHP was induced by the permanent bilateral occlusion of the common carotid arteries (2VO) method and treatments were conducted for 7 days, orally. Mel prevented the damage of the dental gyrus and memory loss in CHP rats and inhibited the hippocampal reactive oxygen species (ROS), lipid peroxidation levels of tumor necrosis factor-α (TNF-α), interleukine-6 (IL-6), interleukine-1 beta (IL-1β), and prostaglandin E2 (PGE2). It also reduced the hippocampal transcription of the TRPM7 channels and lowered levels of calcium (Ca²⁺) and zinc (Zn²⁺). Mel Also enhanced the levels of total glutathione (GSH) and superoxide dismutase (SOD) in the hippocampus of the control and CHP-treated rats. In conclusion, downregulation of TRPM7 seems to be one mechanism underlying the neuroprotective effect of Mel against global ischemia and is triggered by its antioxidant potential.

Coronavirus Disease 2019 (COVID-19) and Its Neuroinvasive Capacity: Is It Time for Melatonin?

The world faces an exceptional new public health concern caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), subsequently termed the coronavirus disease 2019 (COVID-19) by the World Health Organization (WHO). Although the clinical symptoms mostly have been characterized, the scientific community still doesn´t know how SARS-CoV-2 successfully reaches and spreads throughout the central nervous system (CNS) inducing brain damage. The recent detection of SARS-CoV-2 in the cerebrospinal fluid (CSF) and in frontal lobe sections from postmortem examination has confirmed the presence of the virus in neural tissue. This finding reveals a new direction in the search for a neurotherapeutic strategy in the COVID-19 patients with underlying diseases. Here, we discuss the COVID-19 outbreak in a neuroinvasiveness context and suggest the therapeutic use of high doses of melatonin, which may favorably modulate the immune response and neuroinflammation caused by SARS-CoV-2. However, clinical trials elucidating the efficacy of melatonin in the prevention and clinical management in the COVID-19 patients should be actively encouraged.

Medicarpin Protects Cerebral Microvascular Endothelial Cells Against Oxygen-Glucose Deprivation/Reoxygenation-Induced Injury via the PI3K/Akt/FoxO Pathway: A Study of Network Pharmacology Analysis and Experimental Validation

Medicarpin, a pterocarpan class of naturally occurring phytoestrogen possesses various biological functions. However, the effect of medicarpin on oxygen-glucose deprivation-reoxygenation (OGD/R)-induced injury in human cerebral microvascular endothelial cells (HCMECs) remains largely unknown. Target genes of medicarpin were predicted from PharmMapper. Target genes of ischemic stroke were predicted from public databases GeneCards and DisGeNET. Kyoto Encyclopedia of Genes and Genomes pathway enrichment of the intersecting targets was analyzed via DAVID 6.8. Cell viability was evaluated using CCK-8 assay. Malondialdehyde content, superoxide dismutase activity, and glutathione level were detected using corresponding commercially available kits. Cell death was assessed by TUNEL assays. Expression of protein kinase B (Akt), phosphorylated-Akt, forkhead box protein O1, phosphorylated-FoxO1, FoxO3a, and phosphorylated-FoxO3a (p-FoxO3a) was detected by western blot analysis. The intersecting targets of medicarpin and ischemic stroke were significantly enriched in phosphatidylinositol 3-kinase (PI3K)/Akt and FoxO pathways. Medicarpina attenuated OGD/R-evoked viability inhibition, oxidative stress, and cell death in HCMECs. Additionally, medicarpin activated the PI3K/Akt and FoxO pathways in OGD/R-induced HCMECs. Inhibition of PI3K/Akt pathway abrogated the neuroprotective effect of medicarpin on OGD/R-induced injury and activation of FoxO pathway in HCMECs. In conclusion, medicarpin suppressed OGD/R-induced injury in HCMECs by activating PI3K/Akt/FoxO pathway.

Melatonin for Neonatal Encephalopathy: From Bench to Bedside

Neonatal encephalopathy is a leading cause of morbidity and mortality worldwide. Although therapeutic hypothermia (HT) is now standard practice in most neonatal intensive care units in high resource settings, some infants still develop long-term adverse neurological sequelae. In low resource settings, HT may not be safe or efficacious. Therefore, additional neuroprotective interventions are urgently needed. Melatonin's diverse neuroprotective properties include antioxidant, anti-inflammatory, and anti-apoptotic effects. Its strong safety profile and compelling preclinical data suggests that melatonin is a promising agent to improve the outcomes of infants with NE. Over the past decade, the safety and efficacy of melatonin to augment HT has been studied in the neonatal piglet model of perinatal asphyxia. From this model, we have observed that the neuroprotective effects of melatonin are time-critical and dose dependent. Therapeutic melatonin levels are likely to be 15-30 mg/L and for optimal effect, these need to be achieved within the first 2-3 h after birth. This review summarises the neuroprotective properties of melatonin, the key findings from the piglet and other animal studies to date, and the challenges we face to translate melatonin from bench to bedside.

Blood-brain barrier dysfunction in hemorrhagic transformation: a therapeutic opportunity for nanoparticles and melatonin

Stroke is the second leading cause of death worldwide, estimated that one-sixth of the world population will suffer it once in their life. The most common type of this medical condition is the ischemic stroke (IS), produced by a thrombotic or embolic occlusion of a major cerebral artery or its branches, leading to the formation of a complex infarct region caused by oxidative stress, excitotoxicity, and endothelial dysfunction. Nowadays, the immediate treatment for IS involves thrombolytic agents or mechanical thrombectomy, depending on the integrity of the blood-brain barrier (BBB). A common stroke complication is the hemorrhagic transformation (HT), which consists of bleeding into the ischemic brain area. Currently, better treatments for IS are urgently needed. As such, the neurohormone melatonin has been proposed as a good candidate due to its antioxidant, anti-inflammatory, and neuroprotective effects, particularly against lipid peroxidation and oxidative stress during brain ischemia. Here, we proposed to develop intravenous or intranasal melatonin nanoformulation to specifically target the brain in patients with stroke. Nowadays, the challenge is to find a formulation able to cross the barriers and reach the target organ in an effective dose to generate the pharmacological effect. In this review, we discuss the current literature about stroke pathophysiology, melatonin properties, and its potential use in nanoformulations as a novel therapeutic approach for ischemic stroke.

Small-Molecule Inhibitors of Reactive Oxygen Species Production

Reactive oxygen species (ROS) are involved in physiological cellular processes including differentiation, proliferation, and apoptosis by acting as signaling molecules or regulators of transcription factors. The maintenance of appropriate cellular ROS levels is termed redox homeostasis, a balance between their production and neutralization. High concentrations of ROS may contribute to severe pathological events including cancer, neurodegenerative, and cardiovascular diseases. In recent years, approaches to target the sources of ROS production directly in order to develop tool compounds or potential therapeutics have been explored. Herein, we briefly outline the major sources of cellular ROS production and comprehensively review the targeting of these by small-molecule inhibitors. We critically assess the value of ROS inhibitors with different mechanisms-of-action, including their potency, mode-of-action, known off-target effects, and clinical or preclinical status, while suggesting future avenues of research in the field.

Evaluating the Neuroprotective Effect of Melatonin on Patients with Hemorrhagic Stroke Using Serum S100B Protein as a Prognostic Marker

Background: Intracerebral hemorrhage (ICH) is one of the most debilitating kinds of stroke. Recent evidence shows that the proper initiation of neuroprotective agents might save at risk neurons and improve the outcome. Objectives: The focus of this study is to evaluate the neuroprotective effect of melatonin on patients with hemorrhagic stroke. Methods: Forty adult patients with confirmed nontraumatic ICH, who were admitted to the ICU within 24 hours of the stroke onset were enrolled in this study. Subjects in the melatonin group received 30 mg of melatonin every night for 5 consecutive nights. In order to evaluate the intensity of the neuronal injury, S100B was assessed once on day 1 and, day 5 post ICU admission. Additionally, the length of ICU stay, mortality, and the duration of mechanical ventilation were also recorded. Results: Forty patients completed the study. In both groups the plasma concentrations of S100B decreased after 5 days compared with their baseline values. However, this reduction was more significant in the melatonin compared to the control group (P-value < 0.05). The duration of mechanical ventilation and length of ICU stay was shorter in the melatonin group, and this difference was statistically significant for the length of ICU stay (P-value < 0.05), and marginally significant for the duration of mechanical ventilation (P-value = 0.065). The in-ICU mortality rate of the melatonin group was 15%, almost half of that of the control group (30%). However, this difference was not statistically significant. Conclusions: In conclusion, melatonin can be considered as a harmless and effective nueroprotective agent with some unique features which has made it an appropriate adjunctive medicine for critically ill intubated patients.

Melatonin ameliorates microvessel abnormalities in the cerebral cortex and hippocampus in a rat model of Alzheimer's disease

Melatonin can attenuate cardiac microvascular ischemia/reperfusion injury, but it remains unclear whether melatonin can also ameliorate cerebral microvascular abnormalities. Rat models of Alzheimer’s disease were established by six intracerebroventricular injections of amyloid-beta 1–42, administered once every other day. Melatonin (30 mg/kg) was intraperitoneally administered for 13 successive days, with the first dose given 24 hours prior to the first administration of amyloid-beta 1–42. Melatonin ameliorated learning and memory impairments in the Morris water maze test, improved the morphology of microvessels in the cerebral cortex and hippocampus, increased microvessel density, alleviated pathological injuries of cerebral neurons, and decreased the expression of vascular endothelial growth factor and vascular endothelial growth factor receptors 1 and 2. These findings suggest that melatonin can improve microvessel abnormalities in the cerebral cortex and hippocampus by lowering the expression of vascular endothelial growth factor and its receptors, thereby improving the cognitive function of patients with Alzheimer’s disease. This study was approved by the Animal Care and Use Committee of Jinzhou Medical University, China (approval No. 2019015) on December 6, 2018.

Melatonin Reduces NLRP3 Inflammasome Activation by Increasing α7 nAChR-Mediated Autophagic Flux

Microglia controls the immune system response in the brain. Specifically, the activation and dysregulation of the NLRP3 inflammasome is responsible for the initiation of the inflammatory process through IL-1β and IL-18 release. In this work, we have focused on studying the effect of melatonin on the regulation of the NLRP3 inflammasome through α7 nicotinic receptor (nAChR) and its relationship with autophagy. For this purpose, we have used pharmacological and genetic approaches in lipopolysaccharide (LPS)-induced inflammation models in both in vitro and in vivo models. In the BV2 cell line, LPS inhibited autophagy, which increased NLRP3 protein levels. However, melatonin promoted an increase in the autophagic flux. Treatment of glial cultures from wild-type (WT) mice with LPS followed by extracellular adenosine triphosphate (ATP) produced the release of IL-1β, which was reversed by melatonin pretreatment. In cultures from α7 nAChR knock-out (KO) mice, melatonin did not reduce IL-1β release. Furthermore, melatonin decreased the expression of inflammasome components and reactive oxygen species (ROS) induced by LPS; co-incubation of melatonin with α-bungarotoxin (α-bgt) or luzindole abolished the anti-inflammatory and antioxidant effects. In vivo, melatonin reverted LPS-induced cognitive decline, reduced NLRP3 levels and promoted autophagic flux in the hippocampi of WT mice, whereas in α7 nAChR KO mice melatonin effect was not observed. These results suggest that melatonin may modulate the complex interplay between α7 nAChR and autophagy signaling.

Melatonin and/or erythropoietin combined with hypothermia in a piglet model of perinatal asphyxia

As therapeutic hypothermia is only partially protective for neonatal encephalopathy, safe and effective adjunct therapies are urgently needed. Melatonin and erythropoietin show promise as safe and effective neuroprotective therapies. We hypothesized that melatonin and erythropoietin individually augment 12-h hypothermia (double therapies) and hypothermia + melatonin + erythropoietin (triple therapy) leads to optimal brain protection. Following carotid artery occlusion and hypoxia, 49 male piglets (<48 h old) were randomized to: (i) hypothermia + vehicle (n = 12), (ii) hypothermia + melatonin (20 mg/kg over 2 h) (n = 12), (iii) hypothermia + erythropoietin (3000 U/kg bolus) (n = 13) or (iv) tripletherapy (n = 12). Melatonin, erythropoietin or vehicle were given at 1, 24 and 48 h after hypoxia–ischaemia. Hypoxia–ischaemia severity was similar across groups. Therapeutic levels were achieved 3 hours after hypoxia–ischaemia for melatonin (15–30 mg/l) and within 30 min of erythropoietin administration (maximum concentration 10 000 mU/ml). Compared to hypothermia + vehicle, we observed faster amplitude-integrated EEG recovery from 25 to 30 h with hypothermia + melatonin (P = 0.02) and hypothermia + erythropoietin (P = 0.033) and from 55 to 60 h with tripletherapy (P = 0.042). Magnetic resonance spectroscopy lactate/N-acetyl aspartate peak ratio was lower at 66 h in hypothermia + melatonin (P = 0.012) and tripletherapy (P = 0.032). With hypothermia + melatonin, terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate nick-end labelled-positive cells were reduced in sensorimotor cortex (P = 0.017) and oligodendrocyte transcription factor 2 labelled-positive counts increased in hippocampus (P = 0.014) and periventricular white matter (P = 0.039). There was no reduction in terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate nick-end labelled-positive cells with hypothermia + erythropoietin, but increased oligodendrocyte transcription factor 2 labelled-positive cells in 5 of 8 brain regions (P < 0.05). Overall, melatonin and erythropoietin were safe and effective adjunct therapies to hypothermia. Hypothermia + melatonin double therapy led to faster amplitude-integrated EEG recovery, amelioration of lactate/N-acetyl aspartate rise and reduction in terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate nick-end labelled-positive cells in the sensorimotor cortex. Hypothermia + erythropoietin doubletherapy was in association with EEG recovery and was most effective in promoting oligodendrocyte survival. Tripletherapy provided no added benefit over the double therapies in this 72-h study. Melatonin and erythropoietin influenced cell death and oligodendrocyte survival differently, reflecting distinct neuroprotective mechanisms which may become more visible with longer-term studies. Staggering the administration of therapies with early melatonin and later erythropoietin (after hypothermia) may provide better protection; each therapy has complementary actions which may be time critical during the neurotoxic cascade after hypoxia–ischaemia.

MicroRNA-124 regulates cell pyroptosis during cerebral ischemia-reperfusion injury by regulating STAT3

Cerebral ischemia-reperfusion injury (CIRI) is the observed continuation and deterioration of ischemic injury, and currently, there are no effective treatment strategies for the condition. It has been reported that microRNAs (miRNAs) serve an important role in CIRI by regulating pyroptosis. The present study demonstrated that miRNA-124 regulated CIRI by regulating STAT3. To explore the relationship between miRNA-124/STAT3 and pyroptosis in CIRI, CIRI was simulated using a middle cerebral artery occlusion model. Subsequently, miRNA-124 expression levels were altered via the intracerebroventricular injection of miRNA-124 agonist or antagonist. The degree of brain tissue injury was assessed by conducting TTC staining and neurological function scoring. Relative miRNA-124 expression levels were determined via reverse transcription-quantitative PCR. A luciferase reporter gene system verified the targeted binding of miRNA-124 to STAT3. The expression levels of key proteins and proinflammatory cytokines associated with pyroptosis [caspase-1, gasdermin D, interleukin (IL)-18 and IL-1β] were detected via western blotting and immunohistochemistry. The increased expression levels of pyroptosis-associated proteins and proinflammatory cytokines in the I/R groups compared with the control group, indicated that pyroptosis intensified over time during CIRI, and miRNA-124 agonist significantly abrogated pyroptosis and improved neurological function compared with the control group. Furthermore, miRNA-124 inhibited STAT3 activation in a targeted manner, which also decreased the extent of pyroptosis. However, miRNA-124 antagonist reversed miR-124 agonist-mediated effects. Therefore, the present study indicated that miRNA-124 may provide neuroprotection against pyroptosis during CIRI, potentially via inhibition of the STAT3 signaling pathway.

Mitochondria-Inspired Nanoparticles with Microenvironment-Adapting Capacities for On-Demand Drug Delivery after Ischemic Injury

Stimuli-responsive nanoparticles (NPs), so-called "smart" NPs, possess great potentials in drug delivery. Presently, the intelligence of smart NPs is mainly based on their chemical or physical changes to stimuli, which are usually "mechanical" and fundamentally different from biological intelligence. Inspired by mitochondria (MT), a biosmart nanoparticle with microenvironment targeting and self-adaptive capacity (MTSNP) was fabricated for ischemic tissue repair. The nanoparticles were designed as shell@circular DNA@shell@core. The double shells were like the two-layered membranes of MT, the melatonin-loaded cores corresponded to the MT matrix, and the circular DNA corresponded to MTDNA. In function, melatonin-loaded cores simulated the cell-protective mechanism of MT, which naturally synthesized melatonin to resist ischemia, while circular DNA was constructed to mimic the biological oxygen-sensing mechanism, synthesizing VEGF for vascularization according to oxygen level, like the ATP supply by MT according to microenvironment demand. At the acute stage of ischemia, melatonin was rapidly released from MTSNP to scavenge reactive oxygen species and activated melatonin receptor I on MT to prevent cytochrome c release, which would activate apoptosis. During the chronic stage, circular DNA could sense hypoxia and actively secrete VEGF for revascularization as a response. Importantly, circular DNA could also receive feedback of revascularization and shut down VEGF secretion as an adverse response. Then, the therapeutic potentials of the MTSNP were verified in myocardial ischemia by the multimodality of the methods. Such nanoparticles may represent a promising intelligent nanodrug system.

A Potent Antioxidant Endogenous Neurohormone Melatonin, Rescued MCAO by Attenuating Oxidative Stress-Associated Neuroinflammation

Ischemic stroke is an acute neurological syndrome either due to permanent or temporary obstruction of blood. Such obstruction immediately triggers abrupt pathological cascading processes, which collectively lead to neuronal cell death. Oxidative stress and neuroinflammation in ischemic stroke are critical regulating events that ultimately lead to neuronal death. Complicated interplay exists between the two processes which occur through several stages. Most often, oxidative stress precedes the inflammatory mechanisms and includes several interconnected cascades that underlie the ischemic stroke pathology. In continuation of the previously published data, here, we further ruled out the protective role of melatonin in focal cerebral ischemic injury model. Administration of 5 mg/kg dose of melatonin 30 min prior to ischemia reduced brain infarction associated with sequentially rescued neuronal apoptosis. Furthermore, melatonin attenuated neuroinflammatory markers and reactive oxygen species (ROS), induced by ischemic stroke, via halting the key players of mitogen stress family (p38/JNK). Besides, melatonin modulated the endogenously produced antioxidant enzyme, thioredoxin (Trx) pathway. These broader therapeutic efficacies of melatonin suggest that melatonin could be further investigated for its diverse therapeutic actions with multiple targets in recovering, preventing and halting the detrimental outcomes of MCAO, such as elevated oxidative stress, neuroinflammation, and neurodegeneration.

Hypothermia Plus Melatonin in Asphyctic Newborns: A Randomized-Controlled Pilot Study

OBJECTIVES

To investigate the effect of adding melatonin to hypothermia treatment on neurodevelopmental outcomes in asphyctic newborns.

DESIGN

Pilot multicenter, randomized, controlled, double-blind clinical trial. Statistical comparison of results obtained in two intervention arms: hypothermia plus placebo and hypothermia plus melatonin.

SETTING

Level 3 neonatal ICU.

PATIENTS

Twenty-five newborns were recruited.

INTERVENTIONS

The hypothermia plus melatonin patients received a daily dose of IV melatonin, 5 mg per kg body weight, for 3 days. General laboratory variables were measured both at neonatal ICU admission and after intervention. All infants were studied with amplitude-integrated electroencephalography and brain MRI within the first week of life. The neurodevelopmental Bayley III test, the Gross Motor Function Classification System, and the Tardieu scale were applied at the ages of 6 and 18 months.

MEASUREMENTS AND MAIN RESULTS

Clinical characteristics, laboratory evaluations, MRI findings, and amplitude-integrated electroencephalography background did not differ between the treatment groups. The newborns in the hypothermia plus melatonin group achieved a significantly higher composite score for the cognitive section of the Bayley III test at 18 months old, with respect to the hypothermia plus placebo group (p = 0.05). There were no differences between the groups according to the Gross Motor Function Classification System and Tardieu motor assessment scales.

CONCLUSIONS

The early addition of IV melatonin to asphyctic neonates is feasible and may improve long-term neurodevelopment. To our knowledge, this is the first clinical trial to analyze the administration of IV melatonin as an adjuvant therapy to therapeutic hypothermia.

The efficacy and safety of salvianolic acids on acute cerebral infarction treatment: A protocol for systematic review and meta analysis

BACKGROUND

Salvianolic acids (SA) has been widely used for the treatment of acute cerebral infarction (ACI) combined with basic western medicine therapy in China. This study was aimed to evaluate the efficacy and safety of SA on ACI treatment and its influence on neurological functions, activity of daily living, and cognitive functions.

METHODS

We retrieved related articles from PubMed, the Cochrane Center Controlled Trials Register, EMBASE, Medline, Ovid, Chinese National Knowledge Infrastructure, Chinese Biomedical Literature Database, and Wanfang Database without date and language restrictions. Finally, 58 randomized controlled trials were included from 239 retrieved records. Two researchers extracted the basic information and data from included articles and assessed the quality and analysis of data by using Review Manager 5.3.

RESULTS

The administration of SA significantly increased the total clinical effective rate of ACI treatment (P < .001) and improved the National Institute of Health Stroke Scale scores, modified Rankin Scale scores, and Barthel Index scores after treatment and 3 months after ACI (P < .05). The activities of daily living scores in the SA group were significantly increased after treatment (P < .001), whereas they were remarkably decreased 3 months after ACI (P < .001) compared with that in the control group. Besides, SA profoundly promoted the recovery of Montreal Cognitive Assessment scores (P < .001). However, the use of SA increased the risk of adverse events occurrence (P = .007).

CONCLUSION

SA combined with basic western medicine treatment could promote neurological functions, daily living activities, and cognitive functions recovery of ACI patients. Although SA increased the risk of adverse events occurrence, these adverse events were easily controlled or disappeared spontaneously.

Melatonin's efficacy in stroke patients; a matter of dose? A systematic review

There is a lack of effective therapies for stroke patients; its treatment is even more difficult considering the unexpected onset of the disease. In the last decade, melatonin has emerged as a promising neuroprotective agent which is able to cross the blood-brain-barrier (BBB) and with a low toxicity profile. The aim of this systematic review was to summarize and critically review clinical and pre-clinical evidence related to melatonin's effectiveness as a stroke treatment. Together with a comparative dose extrapolation with those used in the selected randomized controlled trials (RCTs), and based on these data to discuss whether the administered doses correlate with those advisable in human patients. To address this purpose, we performed a systematic review of the available literature. A total of 529 records were screened with the selecting of six full articles containing RCTs that met the inclusion/exclusion criteria. The evidence drawn from these six reports was analyzed to identify remaining gaps, treatment efficacy, and to suggest future directions. The primary outcome reported was the reduction of the oxidative response; the secondary outcome was the increase of the survival rate of the patients in the intervention groups. Calculations derived from animal studies revealed that the translational doses to humans were substantially higher than those employed in the RCTs. The findings of this systematic review revealed that there are insufficient RCTs to prove melatonin's value in stroke patients. Nevertheless, the evidence is promising, and further clinical research may support the benefits of melatonin in stroke patients, if the adequate dose is administered.

Melatonin restores the osteoporosis-impaired osteogenic potential of bone marrow mesenchymal stem cells by preserving SIRT1-mediated intracellular antioxidant properties

Postmenopausal osteoporosis (OP) is one of the most common bone diseases that affects millions of aging women. Reduced osteogenesis and increased oxidative stress have been implicated in bone marrow mesenchymal stem cells (BMMSCs) derived from OP patients. Melatonin has shown positive effects on osteoblast differentiation and bone formation; however, it was unknown whether melatonin could restore OP-impaired osteogenic potential of BMMSCs and what the underlying mechanisms entailed. The objective of this study is to investigate (1) whether melatonin can restore the impaired osteogenic potential of OP BMMSCs by preserving their antioxidant functions, and if so, (2) whether intravenous administration of melatonin can prevent OP-induced bone loss in ovariectomized (OVX) rats. Ovariectomies were performed in female rats and BMMSCs were isolated from the osteoporotic rats 3 months later. In vitro treatment with melatonin successfully improved the osteogenic differentiation of OP BMMSCs, as evidenced by increased levels of matrix mineralization and osteoblast-specific genes. In melatonin-treated OP BMMSCs, intracellular oxidative stress was significantly attenuated, while levels of intracellular antioxidant enzymes were noticeably up-regulated - particularly superoxide dismutase 2 (SOD2) and glutathione peroxidase 1 (GPX1). Silent information regulator type 1 (SIRT1) was involved in the melatonin-mediated recovery of osteogenesis and antioxidant functions. Meanwhile, in vivo injections of melatonin via the tail vein successfully ameliorated the bone micro-architecture in ovariectomized rat femurs. Further experiments confirmed that BMMSCs derived from melatonin-treated OVX rats exerted well-preserved antioxidant properties and osteogenic potential. Our findings demonstrate that the administration of melatonin is a promising strategy for treating patients with postmenopausal OP by preserving the antioxidant properties and osteogenic potential of their BMMSCs.

Advances in Characterizing Recently-Identified Molecular Actions of Melatonin: Clinical Implications

Melatonin, N-acetyl-5-methoxy-tryptamine, was discovered to be a product of serotonin metabolism in the mammalian pineal gland where its synthesis is under control of the light:dark cycle. Besides its regulatory pathway involving ganglion cells in the retina, the neural connections between the eyes and the pineal gland include the master circadian clock, the suprachiasmatic nuclei, and the central and peripheral nervous systems. Since pineal melatonin is released into the blood and into the cerebrospinal fluid, it has access to every cell in an organism and it mediates system-wide effects. Subsequently, melatonin was found in several extrapineal organs and, more recently, perhaps in every cell of every organ. In contrast to the pinealocytes, non-pineal cells do not discharge melatonin into the blood; rather it is used locally in an intracrine, autocrine, or paracrine manner. Melatonin levels in non-pineal cells do not exhibit a circadian rhythm and do not depend on circulating melatonin concentrations although when animals are treated with exogenous melatonin it is taken up by presumably all cells. Mitochondria are the presumed site of melatonin synthesis in all cells; the enzymatic machinery for melatonin synthesis has been identified in mitochondria. The association of melatonin with mitochondria, because of its ability to inhibit oxidative stress, is very fortuitous since these organelles are a major site of damaging reactive oxygen species generation. In this review, some of the actions of non-pineal-derived melatonin are discussed in terms of cellular and subcellular physiology.

Higher Serum Melatonin Levels during the First Week of Malignant Middle Cerebral Artery Infarction in Non-Surviving Patients

Objective: The activation of different physiopathological pathways (neuroinflammation, apoptosis, and oxidation) can lead to secondary brain injury in ischemic stroke, and in animal models the administration of melatonin has reduced that secondary injury. Lower levels of serum melatonin were found at the time of admission of cerebral infarction in surviving patients than in non-surviving patients. Thus, we carried out this prospective and observational study with the aim of exploring serum melatonin levels in the first week of a malignant middle cerebral artery infarction (MMCAI) in surviving and non-surviving patients, and to explore the capacity of those levels to predict mortality. Methods: Patients with severe MMCAI, defined as computed tomography showing acute infarction in more than 50% of the territory and Glasgow Coma Scale (GCS) lower than 9, were included in the study. We measured serum melatonin concentrations at days 1, 4, and 8 of MMCAI. Mortality at 30 days was the endpoint of our study. Results: Non-surviving patients (n = 34) compared to surviving patients (n = 34) showed higher serum melatonin levels at days 1 (p < 0.001), 4 (p < 0.001), and 8 (p = 0.001) of MMCAI. Serum melatonin concentrations at days 1, 4, and 8 of MMCAI had an area under the curve (AUC) (95% confidence interval (CI)) in the prediction of mortality of 0.89 (0.80–0.96; p < 0.001), 0.81 (0.68–0.91; p < 0.001), and 0.82 (0.68–0.92; p < 0.001), respectively. Conclusions: The novel findings of our study were that serum melatonin levels in the first week of MMCAI were higher in non-surviving patients, and were able to predict mortality.

Melatonin for prevention of placental malperfusion and fetal compromise associated with intrauterine inflammation-induced oxidative stress in a mouse model

Melatonin has been shown to reduce oxidative stress and mitigate hypercoagulability. We hypothesized that maternally administered melatonin may reduce placental oxidative stress and hypercoagulability associated with exposure to intrauterine inflammation (IUI) and consequently improve fetoplacental blood flow and fetal sequelae. Mice were randomized to the following groups: control (C), melatonin (M), lipopolysaccharide (LPS; a model of IUI) (L), and LPS with melatonin (ML). The expression of antioxidant mediators in the placenta was significantly decreased, while that of pro-inflammatory mediators was significantly increased in L compared to C and ML. The systolic/diastolic ratio, resistance index, and pulsatility index in uterine artery (UtA) and umbilical artery (UA) were significantly increased in L compared with other groups when analyzed by Doppler ultrasonography. The expression of antioxidant mediators in the placenta was significantly decreased, while that of pro-inflammatory mediators was significantly increased in L compared to C and ML. Vascular endothelial damage and thrombi formation, as evidenced by fibrin deposits, were similarly increased in L compared to other groups. Maternal pretreatment with melatonin appears to modulate maternal placental malperfusion, fetal cardiovascular compromise, and fetal neuroinflammation induced by IUI through its antioxidant properties.

Activation of melatonin receptor 2 but not melatonin receptor 1 mediates melatonin-conferred cardioprotection against myocardial ischemia/reperfusion injury

Accumulated pieces of evidence have proved the beneficial effects of melatonin on myocardial ischemia/reperfusion (MI/R) injury, and these effects were largely dependent on melatonin membrane receptor activation. In humans and other mammals, there are two types of melatonin receptors, including the melatonin receptor 1 (MT1, melatonin receptor 1a or MTNR1A) and melatonin receptor 1 (MT2, melatonin receptor 1b or MTNR1B) receptor subtypes. However, which receptor mediates melatonin-conferred cardioprotection remains unclear. In this study, we employed both loss-of-function and gain-of-function approaches to reveal the answer. Mice (wild-type; MT1 or MT2 silencing by in vivo minicircle vector; and those overexpressing MT1 or MT2 by in vivo AAV9 vector) were exposed to MI/R injury. Both MT1 and MT2 were present in wild-type myocardium. MT2, but not MT1, was essentially upregulated after MI/R Melatonin administration significantly reduced myocardial injury and improved cardiac function after MI/R Mechanistically, melatonin treatment suppressed MI/R-initiated myocardial oxidative stress and nitrative stress, alleviated endoplasmic reticulum stress and mitochondrial injury, and inhibited myocardial apoptosis. These beneficial actions of melatonin were absent in MT2-silenced heart, but not the MT1 subtype. Furthermore, AAV9-mediated cardiomyocyte-specific overexpression of MT2, but not MT1, mitigated MI/R injury and improved cardiac dysfunction, which was accompanied by significant amelioration of oxidative stress, endoplasmic reticulum stress, and mitochondrial dysfunction. Mechanistically, MT2 protected primary cardiomyocytes against hypoxia/reoxygenation injury via MT2/Notch1/Hes1/RORα signaling. Our study presents the first direct evidence that the MT2 subtype, but not MT1, is a novel endogenous cardiac protective receptor against MI/R injury. Medications specifically targeting MT2 may hold promise in fighting ischemic heart disease.

Melatonin attenuates renal sympathetic overactivity and reactive oxygen species in the brain in neurogenic hypertension

Sympathetic overactivation contributes to the pathogenesis of both experimental and human hypertension. We have previously reported that oxidative stress in sympathetic premotor neurons leads to arterial baroreflex dysfunction and increased sympathetic drive to the kidneys in an experimental model of neurogenic hypertension. In this study, we hypothesized that melatonin, a potent antioxidant, may be protective in the brainstem regions involved in the tonic and reflex control of blood pressure (BP) in renovascular hypertensive rats. Neurogenic hypertension was induced by placing a silver clip (gap of 0.2 mm) around the left renal artery, and after 5 weeks of renal clip placement, the rats were treated orally with melatonin (30 mg/kg/day) by gavage for 15 days. At the end of melatonin treatment, we evaluated baseline mean arterial pressure (MAP), renal sympathetic nerve activity (rSNA), and the baroreflex control of heart rate (HR) and rSNA. Reactive oxygen species (ROS) were detected within the brainstem regions by dihydroethidium staining. Melatonin treatment effectively reduced baseline MAP and sympathoexcitation to the ischemic kidney in renovascular hypertensive rats. The baroreflex control of HR and rSNA were improved after melatonin treatment in the hypertensive group. Moreover, there was a preferential decrease in ROS within the rostral ventrolateral medulla (RVLM) and the nucleus of the solitary tract (NTS). Therefore, our study indicates that melatonin is effective in reducing renal sympathetic overactivity associated with decreased ROS in brainstem regions that regulate BP in an experimental model of neurogenic hypertension.

Administration of melatonin for prevention of preterm birth and fetal brain injury associated with premature birth in a mouse model

PROBLEM

Maternal inflammation leads to preterm birth and perinatal brain injury. Melatonin, through its anti-inflammatory effects, has been shown to be protective against inflammation-induced perinatal adverse effects. However, the immunomodulatory effects of melatonin on preterm birth and prematurity-related morbidity remain unknown. We wanted to investigate the effects of maternally administered melatonin on preterm birth and perinatal brain injury in a mouse model of maternal inflammation.

METHOD OF STUDY

A model of maternal inflammation employing lipopolysaccharide (LPS) was used to mimic the most common clinical scenario of preterm birth, that of maternal inflammation. Mice were randomly divided into the following groups: control, LPS, and LPS with melatonin pre-treatment. Doppler ultrasonography was used to obtain fetal and maternal hemodynamic measurements in utero. Placenta and fetal brains were harvested and analyzed for proinflammatory markers and signs of perinatal brain injury, respectively. Surviving offspring were assessed for neuromotor outcomes.

RESULTS

Melatonin pre-treatment lowered the level of proinflammatory cytokines in the uterus and the placenta, significantly improved LPS-induced acute fetal neuroinflammation and perinatal brain injury, as well as significantly upregulated the SIRT1/Nrf2 signaling pathway to reduce LPS-induced inflammation. Melatonin also prevented adverse neuromotor outcomes in offspring exposed to maternal inflammation.

CONCLUSION

Maternally administered melatonin modulated immune responses to maternal inflammation and decreased preterm birth and perinatal brain injury. These results suggest that melatonin, a safe treatment during pregnancy, may be used as an experimental therapeutic in clinical trials.

Melatonin Suppresses Microglial Necroptosis by Regulating Deubiquitinating Enzyme A20 After Intracerebral Hemorrhage

Cell death is deeply involved in pathophysiology of brain injury after intracerebral hemorrhage (ICH). Necroptosis, one of the recently discovered forms of cell death, plays an important role in various diseases, including ICH. Previous studies have suggested that a considerable number of neurons undergoes necroptosis after ICH. However, necroptosis of microglia after ICH has not been reported to date. The present study demonstrated for the first time that necroptosis occurred in the microglia surrounding the hematoma after ICH in C57 mice, and melatonin, a hormone that is predominantly synthesized in and secreted from the pineal gland, exerted a neuroprotective effect by suppressing this process. When we further explored the potential underlying mechanism, we found that melatonin inhibits RIP3-mediated necroptosis by regulating the deubiquitinating enzyme A20 (also known as TNFAIP3) expression after ICH. In summary, we have demonstrated the role of microglial necroptosis in the pathogenesis of ICH. More importantly, A20 was identified as a novel target of melatonin, which opens perspectives for future research.

Melatonin pharmacokinetics and dose extrapolation after enteral infusion in neonates subjected to hypothermia

INTRODUCTION

Neonates with hypoxic-ischemic encephalopathy (HIE) undergoing hypothermia may benefit from adjunctive therapy with melatonin. However, melatonin safety, pharmacokinetics (PK), and dosage in this sensitive population are still unknown.

METHODS AND RESULTS

This study assessed the PK and safety of melatonin enteral administration to neonates with HIE undergoing hypothermia. Melatonin was infused at 0.5 mg/kg in five neonates with HIE undergoing hypothermia. Infusion started 1 hour after the neonates reached the target temperature of 33.5°C. Blood samples were collected before and at selective times after melatonin infusion. Abdominal complications or clinically significant changes in patients' vital signs were not found during or after melatonin. The peak plasma concentration reached 0.25 µg/mL. The area under the curve in 24 hours was 4.35 µg/mL*h.

DISCUSSION

Melatonin half-life and clearance were prolonged, and the distribution volume decreased compared to adults. In silico simulation estimated that the steady state can be reached after four infusions. Hypothermia does not affect melatonin PK. In humans high blood concentrations with lower doses can be achieved compared to animal experimentation, although intravenous administration is advised in the neonate population. Our study is a preparatory step for future clinical studies aimed at assessing melatonin efficacy in HIE.

MicroRNA-365 Knockdown Prevents Ischemic Neuronal Injury by Activating Oxidation Resistance 1-Mediated Antioxidant Signals

MicroRNA-365 (miR-365) is upregulated in the ischemic brain and is involved in oxidative damage in the diabetic rat. However, it is unclear whether miR-365 regulates oxidative stress (OS)-mediated neuronal damage after ischemia. Here, we used a transient middle cerebral artery occlusion model in rats and the hydrogen peroxide-induced OS model in primary cultured neurons to assess the roles of miR-365 in neuronal damage. We found that miR-365 exacerbated ischemic brain injury and OS-induced neuronal damage and was associated with a reduced expression of OXR1 (Oxidation Resistance 1). In contrast, miR-365 antagomir alleviated both the brain injury and OXR1 reduction. Luciferase assays indicated that miR-365 inhibited OXR1 expression by directly targeting the 3'-untranslated region of Oxr1. Furthermore, knockdown of OXR1 abolished the neuroprotective and antioxidant effects of the miR-365 antagomir. Our results suggest that miR-365 upregulation increases oxidative injury by inhibiting OXR1 expression, while its downregulation protects neurons from oxidative death by enhancing OXR1-mediated antioxidant signals.

Melatonin as a master regulator of cell death and inflammation: molecular mechanisms and clinical implications for newborn care

Melatonin, more commonly known as the sleep hormone, is mainly secreted by the pineal gland in dark conditions and regulates the circadian rhythm of the organism. Its intrinsic properties, including high cell permeability, the ability to easily cross both the blood–brain and placenta barriers, and its role as an endogenous reservoir of free radical scavengers (with indirect extra activities), confer it beneficial uses as an adjuvant in the biomedical field. Melatonin can exert its effects by acting through specific cellular receptors on the plasma membrane, similar to other hormones, or through receptor-independent mechanisms that involve complex molecular cross talk with other players. There is increasing evidence regarding the extraordinary beneficial effects of melatonin, also via exogenous administration. Here, we summarize molecular pathways in which melatonin is considered a master regulator, with attention to cell death and inflammation mechanisms from basic, translational and clinical points of view in the context of newborn care.

Melatonin Protects MCAO-Induced Neuronal Loss via NR2A Mediated Prosurvival Pathways

Stroke is the significant cause of human mortality and sufferings depending upon race and demographic location. Melatonin is a potent antioxidant that exerts protective effects in differential experimental stroke models. Several mechanisms have been previously suggested for the neuroprotective effects of melatonin in ischemic brain injury. The aim of this study is to investigate whether melatonin treatment affects the glutamate N-methyl-D-aspartate (NMDA) and alpha-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid (AMPA) receptor signaling in cerebral cortex and striatum 24 h after permanent middle cerebral artery occlusion (MCAO). Melatonin (5 mg/kg) attenuated ischemia-induced down regulation of NMDA receptor 2 (NR2a), postsynaptic density-95 (PSD95) and increases NR2a/PSD95 complex association, which further activates the pro-survival PI3K/Akt/GSK3β pathway with mitigated collapsin response mediator protein 2 (CRMP2) phosphorylation. Furthermore, melatonin increases the expression of γ-enolase, a neurotrophic factor in ischemic cortex and striatum, and preserve the expression of presynaptic (synaptophysin and SNAP25) and postsynaptic (p-GluR1845) protein. Our study demonstrated a novel neuroprotective mechanism for melatonin in ischemic brain injury which could be a promising neuroprotective agent for the treatment of ischemic stroke.