Rapid modulation of the silent information regulator 1 by melatonin after hypoxia-ischemia in the neonatal rat brain

Histone modifications in hypoxic ischemic encephalopathy: Implications for therapeutic interventions

Hypoxic-ischemic encephalopathy (HIE) is a brain injury induced by many causes of cerebral tissue ischemia and hypoxia. Although HIE may occur at many ages, its impact on the neonatal brain is greater because it occurs during the formative stage. Recent research suggests that histone modifications may occur in the human brain in response to acute stress events, resulting in transcriptional changes and HIE development. Because there are no safe and effective therapies for HIE, researchers have focused on HIE treatments that target histone modifications. In this review, four main histone modifications are explored, histone methylation, acetylation, phosphorylation, and crotonylation, as well as their relevance to HIE. The efficacy of histone deacetylase inhibitors in the treatment of HIE is also explored. In conclusion, targeting histone modifications may be a novel strategy for elucidating the mechanism of HIE, as well as a novel approach to HIE treatment.

Novel meroterpene-like compounds inhibit ferroptosis through Fe2+ chelation

Colorectal cancer (CRC) is the third most common type of cancer in the world. It is characterized by complex crosstalk between various signaling pathways, as a result of which it is highly challenging to identify optimal therapeutic targets and design treatment strategies. In this study, we tested the effect of 700 compounds on the CRC cell line HT-29 by using the sulforhodamine B assay and screened out 17 compounds that exhibited high toxicity (indicated by an inhibition rate of ≥75 % when applied at a concentration of 10 µM) against the HT-29 cell line. Next, we investigated the mechanisms underlying the effects of these 17 highly toxic compounds. The results of ferroptosis analysis and electron microscopy showed that compounds 575 and 578 were able to significantly reverse RSL3-induced increase in ferroptosis, while compound 580 had a less pronounced ferroptosis-regulating effect. In subsequent experiments, western blotting showed that compounds 575, 578, and 580, which belong to a class of meroterpene-like compounds that affect ferroptosis, do not induce autophagy or apoptosis in the CRC cell line. Instead, Fe2+ chelation experiments showed that these three compounds can serve as iron chelators by chelating Fe2+ at a 1:1 (chelator: Fe2+) ratio. Specifically, the aldehyde and hydroxyl groups of the benzene ring in these compounds may chelate Fe2+, thus reducing Fe2+ levels in cells and inhibiting ferroptosis. These results indicate that these novel meroterpene-like compounds are potential therapeutic small-molecule candidates for targeting ferroptosis in tumors.

Hypoxic ischemic brain injury: animal models reveal new mechanisms of melatonin-mediated neuroprotection

Oxidative stress (OS) and inflammation play a key role in the development of hypoxic-ischemic (H-I) induced brain damage. Following H-I, rapid neuronal death occurs during the acute phase of inflammation, and activation of the oxidant-antioxidant system contributes to the brain damage by activated microglia. So far, in an animal model of perinatal H-I, it was showed that neuroprostanes are present in all brain damaged areas, including the cerebral cortex, hippocampus and striatum. Based on the interplay between inflammation and OS, it was demonstrated in the same model that inflammation reduced brain sirtuin-1 expression and affected the expression of specific miRNAs. Moreover, through proteomic approach, an increased expression of genes and proteins in cerebral cortex synaptosomes has been revealed after induction of neonatal H-I. Administration of melatonin in the experimental treatment of brain damage and neurodegenerative diseases has produced promising therapeutic results. Melatonin protects against OS, contributes to reduce the generation of pro-inflammatory factors and promotes tissue regeneration and repair. Starting from the above cited aspects, this educational review aims to discuss the inflammatory and OS main pathways in H-I brain injury, focusing on the role of melatonin as neuroprotectant and providing current and emerging evidence.

Melatonin ameliorates retinal ganglion cell senescence and apoptosis in a SIRT1-dependent manner in an optic nerve injury model

Melatonin is involved in exerting protective effects in aged-related and neurodegenerative diseases through a silent information regulator type 1 (SIRT1)-dependent pathway. However, little was known about the impact of melatonin on retinal ganglion cell (RGC) senescence and apoptosis following optic nerve crush (ONC). Thus, this study aimed to examine the effects of melatonin on RGC senescence and apoptosis after ONC and investigate the involvement of SIRT1 in this process. To study this, an ONC model was established. EX-527, an inhibitor of SIRT1, was injected intraperitoneally into mice. And melatonin was administrated abdominally into mice after ONC every day. Hematoxylin & eosin staining, retina flat-mounts and optical coherence tomography were used to evaluate the loss of retina cells/neurons. Pattern electroretinogram (p-ERG) was performed to evaluate the function of RGCs. Immunofluorescence and western blot were used to evaluate protein expression. SA-β-gal staining was employed to detect senescent cells. The results demonstrated that melatonin partially rescued the expression of SIRT1 in RGC 3 days after ONC. Additionally, melatonin administration partly rescued the decreased RGC number and ganglion cell complex thickness observed 14 days after ONC. Melatonin also suppressed ONC-induced senescence and apoptosis index. Furthermore, p-ERG showed that melatonin improved the amplitude of P50, N95 and N95/P50 following ONC. Importantly, the protective effects of melatonin were reversed when EX-527 was administered. In summary, this study revealed that melatonin attenuated RGC senescence and apoptosis through a SIRT1-dependent pathway after ONC. These findings provide valuable insights for the treatment of RGC senescence and apoptosis.

Melatonin Enhanced Microglia M2 Polarization in Rat Model of Neuro-inflammation Via Regulating ER Stress/PPARδ/SIRT1 Signaling Axis

Neuro-inflammation involves distinct alterations of microglial phenotypes, containing nocuous pro-inflammatory M1-phenotype and neuroprotective anti-inflammatory M-phenotype. Currently, there is no effective treatment for modulating such alterations. M1/M2 marker of primary microglia influenced by Melatonin were detected via qPCR. Functional activities were explored by western blotting, luciferase activity, EMSA, and ChIP assay. Structure interaction was assessed by molecular docking and LIGPLOT analysis. ER-stress detection was examined by ultrastructure TEM, calapin activity, and ERSE assay. The functional neurobehavioral evaluations were used for investigation of Melatonin on the neuroinflammation in vivo. Melatonin had targeted on Peroxisome Proliferator Activated Receptor Delta (PPARδ) activity, boosted LPS-stimulated alterations in polarization from the M1 to the M2 phenotype, and thereby inhibited NFκB-IKKβ activation in primary microglia. The PPARδ agonist L-165,041 or over-expression of PPARδ plasmid (ov-PPARδ) showed similar results. Molecular docking screening, dynamic simulation approaches, and biological studies of Melatonin showed that the activated site was located at PPARδ (phospho-Thr256-PPARδ). Activated microglia had lowered PPARδ activity as well as the downstream SIRT1 formation via enhancing ER-stress. Melatonin, PPARδ agonist and ov-PPARδ all effectively reversed the above-mentioned effects. Melatonin blocked ER-stress by regulating calapin activity and expression in LPS-activated microglia. Additionally, Melatonin or L-165,041 ameliorated the neurobehavioral deficits in LPS-aggravated neuroinflammatory mice through blocking microglia activities, and also promoted phenotype changes to M2-predominant microglia. Melatonin suppressed neuro-inflammation in vitro and in vivo by tuning microglial activation through the ER-stress-dependent PPARδ/SIRT1 signaling cascade. This treatment strategy is an encouraging pharmacological approach for the remedy of neuro-inflammation associated disorders.

MiR-126 and miR-146a as Melatonin-Responsive Biomarkers for Neonatal Brain Ischemia

Despite advances in obstetric and neonatal care, challenges remain in early identification of neonates with encephalopathy due to hypoxia-ischemia who are undergoing therapeutic hypothermia. Therefore, there is a deep search for biomarkers that can identify brain injury. The aims of this study were to investigate the serum and brain expressions of two potential biomarkers, miR-126/miR-146a, in a preclinical model of hypoxia-ischemia (HI)-induced brain injury, and to explore their modulation during melatonin treatment. Seven-day-old rats were subjected to permanent ligation of the right carotid artery followed by 2.5 h hypoxia (HI). Melatonin (15 mg/kg) was administered 5 min after HI. Serum and brain samples were collected 1, 6 and 24 h after HI. Results show that HI caused a significant increase in the circulating levels of both miR-126 and miR-146a during the early phase of ischemic brain damage development (i.e. 1 h), with a parallel and opposite pattern in the ischemic cerebral cortex. These effects are not observed 24 h later. Treatment with melatonin restored the HI-induced effects on miR-126/miR-146a expressions, both in the cerebral cortex and in serum. We conclude that miR-126/miR-146a are promising biomarkers of HI injury and demonstrate an associated change in concentration following melatonin treatment.

Melatonin promotes gut anti-oxidative status in perinatal rat by remodeling the gut microbiome

Gut health is important for nutrition absorption, reproduction, and lactation in perinatal and early weaned mammals. Although melatonin functions in maintaining circadian rhythms and preventing obesity, neurodegenerative diseases, and viral infections, its impact on the gut microbiome and its function in mediating gut health through gut microbiota remain largely unexplored. In the present study, the microbiome of rats was monitoring after fecal microbiota transplantation (FMT) and foster care (FC). The results showed that FMT and FC increased intestinal villus height/crypt depth in perinatal rats. Mechanistically, the melatonin-mediated remodeling of gut microbiota inhibited oxidative stress, which led to attenuation of autophagy and inflammation. In addition, FMT and FC encouraged the growth of more beneficial intestinal bacteria, such as Allobaculum, Bifidobacterium, and Faecalibaculum, which produce more short-chain fatty acids to strengthen intestinal anti-oxidation. These findings suggest that melatonin-treated gut microbiota increase the production of SCFAs, which improve gut health by reducing oxidative stress, autophagy and inflammation. The transfer of melatonin-treated gut microbiota may be a new and effective method by which to ameliorate gut health in perinatal and weaned mammals.

[Research research on the use of melatonin in combination with therapeutic hypothermia for the treatment of neonatal hypoxic-ischemic encephalopathy]

Neonatal hypoxic-ischemic encephalopathy (HIE) remains one of the leading causes of death and long-term neurodevelopmental disorders in full-term neonates, and there is currently no curative treatment. Therapeutic hypothermia is now a standard therapy for HIE in the neonatal intensive care unit, but its safety and efficacy in remote areas remains unclear. Melatonin is an indole endocrine hormone mainly produced by the pineal gland and it has the ability to easily penetrate the blood-brain barrier. Through receptor and non-receptor mechanisms, melatonin exerts anti-oxidative and anti-inflammatory effects and participates in the regulation of organelle function and the inhibition of cell death. Melatonin is considered one of the most promising drugs for the treatment of HIE based on its reliable safety profile and clinical/preclinical results. This article reviews the recent research on the use of melatonin in combination with therapeutic hypothermia for the treatment of neonatal HIE.

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.

Neuroprotective effects of melatonin-mediated mitophagy through nucleotide-binding oligomerization domain and leucine-rich repeat-containing protein X1 in neonatal hypoxic-ischemic brain damage

Hypoxia-ischemia (HI) is a major cause of brain damage in neonates. Mitochondrial dysfunction acts as a hub for a broad spectrum of signaling events, culminating in cell death triggered by HI. A neuroprotective role of melatonin (MT) has been proposed, and mitophagy regulation seems to be important for cell survival. However, the molecular mechanisms underlying MT-mediated mitophagy during HI treatment are poorly defined. Nucleotide-binding oligomerization domain and leucine-rich repeat-containing protein X1 (NLRX1) has emerged as a critical regulator of mitochondrial dynamics and neuronal death that participates in the pathology of diverse diseases. This study aimed to clarify whether NLRX1 participates in the regulation of mitophagy during MT treatment for hypoxic-ischemic brain damage (HIBD). We demonstrated that MT protected neonates from HIBD through NLRX1-mediated mitophagy in vitro and in vivo. Meanwhile, MT upregulated the expression of NLRX1, Beclin-1, and autophagy-related 7 (ATG7) but decreased the expression of the mammalian target of rapamycin (mTOR) and translocase of the inner membrane of mitochondrion 23 (TIM23). Moreover, the neuroprotective effects of MT were abolished by silencing NLRX1 after oxygen-glucose deprivation (OGD). In addition, the downregulation of mTOR and upregulation of Beclin-1 and ATG7 by MT were inhibited after silencing NLRX1 under OGD. In summary, MT modulates mitophagy induction through NLRX1 and plays a protective role in HIBD, providing insight into potential therapeutic targets for MT to exert neuroprotection.

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

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

The regulatory role of Pin1 in neuronal death

Regulated cell death predominantly involves apoptosis, autophagy, and regulated necrosis. It is vital that we understand how key regulatory signals can control the process of cell death. Pin1 is a cis-trans isomerase that catalyzes the isomerization of phosphorylated serine or threonine-proline motifs of a protein, thereby acting as a crucial molecular switch and regulating the protein functionality and the signaling pathways involved. However, we know very little about how Pin1-associated pathways might play a role in regulated cell death. In this paper, we review the role of Pin1 in regulated cell death and related research progress and summarize Pin1-related pathways in regulated cell death. Aside from the involvement of Pin1 in the apoptosis that accompanies neurodegenerative diseases, accumulating evidence suggests that Pin1 also plays a role in regulated necrosis and autophagy, thereby exhibiting distinct effects, including both neurotoxic and neuroprotective effects. Gaining an enhanced understanding of Pin1 in neuronal death may provide us with new options for the development of therapeutic target for neurodegenerative disorders.

Therapeutic Effect of Nicotinamide Mononucleotide for Hypoxic-Ischemic Brain Injury in Neonatal Mice

SUMMARY STATEMENT

Neonatal hypoxia-ischemia reduces nicotinamide adenine dinucleotide (NAD+) and SIRT6 levels in the injured hippocampus.Hippocampal high mobility group box-1 (HMGB1) release is significantly increased after neonatal hypoxia-ischemia.Nicotinamide mononucleotide (NMN) treatment normalizes hippocampal NAD+ and SIRT6 levels, with significant decrease in caspase-3 activity and HMGB1 release.NMN improves early developmental behavior, as well as motor and memory function.

A novel link between silent information regulator 1 and autophagy in cerebral ischemia-reperfusion

Cerebral ischemia is one of the leading causes of death and disability worldwide. Although revascularization via reperfusion combined with advanced anticoagulant therapy is currently a gold standard treatment for patients, the reperfusion itself also results in a serious dysfunction termed cerebral ischemia-reperfusion (I/R) injury. Silent information regulator 1 (sirtuin 1, SIRT1), is a classic NAD⁺-dependent deacetylase, which has been proposed as an important mediator in the alleviation of cerebral ischemia through modulating multiple physiological processes, including apoptosis, inflammation, DNA repair, oxidative stress, and autophagy. Recent growing evidence suggests that SIRT1-mediated autophagy plays a key role in the pathophysiological process of cerebral I/R injury. SIRT1 could both activate and inhibit the autophagy process by mediating different autophagy pathways, such as the SIRT1-FOXOs pathway, SIRT1-AMPK pathway, and SIRT1-p53 pathway. However, the autophagic roles of SIRT1 in cerebral I/R injury have not been systematically summarized. Here, in this review, we will first introduce the molecular mechanisms and effects of SIRT1 in cerebral ischemia and I/R injury. Next, we will discuss the involvement of autophagy in the pathogenesis of cerebral I/R injury. Finally, we will summarize the latest advances in the interaction between SIRT1 and autophagy in cerebral I/R injury. A good understanding of these relationships would serve to consolidate a framework of mechanisms underlying SIRT1's neuroprotective effects and provides evidence for the development of drugs targeting SIRT1.

Melatonin Attenuates Ischemic-like Cell Injury by Promoting Autophagosome Maturation via the Sirt1/FoxO1/Rab7 Axis in Hippocampal HT22 Cells and in Organotypic Cultures

Dysfunctional autophagy is linked to neuronal damage in ischemia/reperfusion injury. The Ras-related protein 7 (Rab7), a member of the Rab family of small GTPases, appears crucial for the progression of the autophagic flux, and its activity is strictly interconnected with the histone deacetylase Silent information regulator 1 (Sirt1) and transcription factor Forkhead box class O1 (FoxO1). The present study assessed the neuroprotective role of melatonin in the modulation of the Sirt1/FoxO1/Rab7 axis in HT22 cells and organotypic hippocampal cultures exposed to oxygen-glucose deprivation followed by reoxygenation (OGD/R). The results showed that melatonin re-established physiological levels of autophagy and reduced propidium iodide-positive cells, speeding up autophagosome (AP) maturation and increasing lysosomal activity. Our study revealed that melatonin modulates autophagic pathways, increasing the expression of both Rab7 and FoxO1 and restoring the Sirt1 expression affected by OGD/R. In addition, the Sirt1 inhibitor EX-527 significantly reduced Rab7, Sirt1, and FoxO1 expression, as well as autolysosomes formation, and blocked the neuroprotective effect of melatonin. Overall, our findings provide, for the first time, new insights into the neuroprotective role of melatonin against ischemic injury through the activation of the Sirt1/FoxO1/Rab7 axis.

Human-rat integrated microRNAs profiling identified a new neonatal cerebral hypoxic-ischemic pathway melatonin-sensitive

Neonatal encephalopathy (NE) is a pathological condition affecting long-term neurodevelopmental outcomes. Hypothermia is the only therapeutic option, but does not always improve outcomes; hence, researchers continue to hunt for pharmaceutical compounds. Melatonin treatment has benefitted neonates with hypoxic-ischemic (HI) brain injury. However, unlike animal models that enable the study of the brain and the pathophysiologic cascade, only blood is available from human subjects. Therefore, due to the unavailability of neonatal brain tissue, assumptions about the pathophysiology in pathways and cascades are made in human subjects with NE. We analyzed animal and human specimens to improve our understanding of the pathophysiology in human neonates. A neonate with NE who underwent hypothermia and enrolled in a melatonin pharmacokinetic study was compared to HI rats treated/untreated with melatonin. MicroRNA (miRNA) analyses provided profiles of the neonate's plasma, rat plasma, and rat brain cortexes. We compared these profiles through a bioinformatics tool, identifying Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways common to HI brain injury and melatonin treatment. After evaluating the resulting pathways and the literature, to validate the method, the key proteins expressed in HI brain injury were investigated using cerebral cortexes. The upregulated miRNAs in human neonate and rat plasma helped identify two KEGG pathways, glioma and long-term potentiation, common to HI injury and melatonin treatment. A unified neonatal cerebral melatonin-sensitive HI pathway was designed and validated by assessing the expression of protein kinase Cα (PKCα), phospho (p)-Akt, and p-ERK proteins in rat brain cortexes. PKCα increased in HI-injured rats and further increased with melatonin. p-Akt and p-ERK returned phosphorylated to their basal level with melatonin treatment after HI injury. The bioinformatics analyses validated by key protein expression identified pathways common to HI brain injury and melatonin treatment. This approach helped complete pathways in neonates with NE by integrating information from animal models of HI brain injury.

The SIRT1-HMGB1 axis: Therapeutic potential to ameliorate inflammatory responses and tumor occurrence

Inflammation is a common complication of many chronic diseases. It includes inflammation of the parenchyma and vascular systems. Sirtuin 1 (SIRT1) is a nicotinamide adenine dinucleotide (NAD)-dependent histone deacetylase, which can directly participate in the suppression of inflammation. It can also regulate the activity of other proteins. Among them, high mobility group box 1 (HMGB1) signaling can be inhibited by deacetylating four lysine residues (55, 88, 90, and 177) in quiescent endothelial cells. HMGB1 is a ubiquitous nuclear protein, once translocated outside the cell, which can interact with various target cell receptors including the receptor for advanced glycation end-products (RAGE), toll-like receptor (TLR) 2, and TLR4 and stimulates the release of pro-inflammatory cyto-/chemokines. And SIRT1 has been reported to inhibit the activity of HMGB1. Both are related to the occurrence and development of inflammation and associated diseases but show an antagonistic relationship in controlling inflammation. Therefore, in this review, we introduce how this signaling axis regulates the emergence of inflammation-related responses and tumor occurrence, providing a new experimental perspective for future inflammation research. In addition, it explores diverse upstream regulators and some natural/synthetic activators of SIRT1 as a possible treatment for inflammatory responses and tumor occurrence which may encourage the development of new anti-inflammatory drugs. Meanwhile, this review also introduces the potential molecular mechanism of the SIRT1-HMGB1 pathway to improve inflammation, suggesting that SIRT1 and HMGB1 proteins may be potential targets for treating inflammation.

Sevoflurane Improves Hemorrhagic Shock and Resuscitation-Induced Cognitive Impairments and Mitochondrial Dysfunctions through SIRT1-Mediated Autophagy

Cerebral ischemia reperfusion injury (IRI) induced by hemorrhagic shock and reperfusion (HSR) is the main cause of death following trauma. Previous studies indicated the neuroprotective effect of sevoflurane postconditioning (SP) in cerebral IRI. However, the mechanisms still remain elusive. Cerebral IRI models with SP were established by using HSR with C57BL/6 mice (male, 3-month-old) in vivo and by using oxygen glucose deprivation and reoxygenation (OGD/R) with HT22 cells in vitro. Postoperative cognition was evaluated by the Morris water maze, novel object recognition, and elevated plus maze tests. The role of SIRT1 was determined by using siRNA, a sensitive inhibitor (EX527), or an overexpression shRNA-GFP lentivirus. IRI caused significant disabilities of spatial learning and memory associated with enhanced cerebral infarct and neuronal apoptosis, which were effectively attenuated by SP. IRI also made a significant decrease of SIRT1 accompanied by oxidative stress, mitochondria dysfunction, and inactivated autophagy. SP or genetically overexpressing SIRT1 significantly suppressed defective autophagy, mitochondrial oxidative injury, and neuronal death caused by HSR or OGD/R. However, genetic suppression or pharmacological inhibition of SIRT1 significantly reversed the impact of SP treatment on mitochondrial DNA transcription ability and autophagy. Our results demonstrate that the loss of SIRT1 causes a sequential chain of mitochondrial dysfunction, defective autophagy, and neuronal apoptosis after IRI in the preclinical stroke models. Sevoflurane postconditioning treatment could effectively attenuate pathophysiological signatures induced by noxious stimuli, which maybe mediated by SIRT1.

N-Acetyl Cysteine Restores Sirtuin-6 and Decreases HMGB1 Release Following Lipopolysaccharide-Sensitized Hypoxic-Ischemic Brain Injury in Neonatal Mice

Inflammation and neonatal hypoxia-ischemia (HI) are important etiological factors of perinatal brain injury. However, underlying mechanisms remain unclear. Sirtuins are a family of nicotinamide adenine dinucleotide (NAD)+-dependent histone deacetylases. Sirtuin-6 is thought to regulate inflammatory and oxidative pathways, such as the extracellular release of the alarmin high mobility group box-1 (HMGB1). The expression and role of sirtuin-6 in neonatal brain injury are unknown. In a well-established model of neonatal brain injury, which encompasses inflammation (lipopolysaccharide, LPS) and hypoxia-ischemia (LPS+HI), we investigated the protein expression of sirtuin-6 and HMGB1, as well as thiol oxidation. Furthermore, we assessed the effect of the antioxidant N-acetyl cysteine (NAC) on sirtuin-6 expression, nuclear to cytoplasmic translocation, and release of HMGB1 in the brain and blood thiol oxidation after LPS+HI. We demonstrate reduced expression of sirtuin-6 and increased release of HMGB1 in injured hippocampus after LPS+HI. NAC treatment restored sirtuin-6 protein levels, which was associated with reduced extracellular HMGB1 release and reduced thiol oxidation in the blood. The study suggests that early reduction in sirtuin-6 is associated with HMGB1 release, which may contribute to neonatal brain injury, and that antioxidant treatment is beneficial for the alleviation of these injurious mechanisms.

Melatonin Reduces Neuroinflammation and Improves Axonal Hypomyelination by Modulating M1/M2 Microglia Polarization via JAK2-STAT3-Telomerase Pathway in Postnatal Rats Exposed to Lipopolysaccharide

Microglia activation and associated inflammation are implicated in the periventricular white matter damage (PWMD) in septic postnatal rats. This study investigated whether melatonin would mitigate inflammation and alleviate the axonal hypomyelination in the corpus callosum in septic postnatal rats. We further explored if this might be related to the modulation of microglial polarization from M1 phenotype to M2 through the JAK2/STAT3/telomerase pathway. We reported here that indeed melatonin not only can it reduce the neurobehavioral disturbances in LPS-injected rats, but it can also dampen microglia-mediated inflammation. Thus, in LPS + melatonin group, the expression of proinflammatory mediators in M1 phenotype microglia was downregulated. As opposed to this, M2 microglia were increased which was accompanied by upregulated expression of anti-inflammatory mediators along with telomerase reverse transcriptase or melatonin receptor 1(MT1). In parallel to this was decreased NG2 expression but increased expression of myelin and neurofilament proteins. Melatonin can improve hypomyelination which was confirmed by electron microscopy. In vitro in primary microglia stimulated by LPS, melatonin decreased the expression of proinflammatory mediators significantly; but it increased the expression of anti-inflammatory mediators. Additionally, the expression levels of p-JAK2 and p-STAT3 were significantly elevated in microglia after melatonin treatment. Remarkably, the effect of melatonin on LPS-treated microglia was blocked by melatonin receptor, JAK2, STAT3 and telomerase reverse transcriptase inhibitors, respectively. Taken together, it is concluded that melatonin can attenuate PWMD through shifting M1 microglia towards M2 via MT1/JAK2/STAT3/telomerase pathway. The results suggest a new therapeutic strategy whereby melatonin may be adopted to convert microglial polarization from M1 to M2 phenotype that would ultimately contribute to the attenuation of PWMD.

Melatonin ameliorates cerebral ischemia-reperfusion injury in diabetic mice by enhancing autophagy via the SIRT1-BMAL1 pathway

Diabetic brains are more vulnerable to ischemia-reperfusion injury. Previous studies have proved that melatonin could protect against cerebral ischemia-reperfusion (CIR) injury in non-diabetic stroke models; however, its roles and the underlying mechanisms against CIR injury in diabetic mice remain unknown. Streptozotocin-induced diabetic mice and high-glucose-cultured HT22 cells were exposed to melatonin, with or without administration of the autophagy inhibitor 3-methyladenine (3-MA) and the specifically silent information regulator 1 (SIRT1) inhibitor EX527, and then subjected to CIR or oxygen-glucose deprivation/reperfusion operation. We found that diabetic mice showed aggravated brain damage, increased apoptosis and oxidative stress, and deficient autophagy following CIR compared with non-diabetic counterparts. Melatonin treatment exhibited improved histological damage, neurological outcomes, and cerebral infarct size. Intriguingly, melatonin markedly increased cell survival, anti-oxidative and anti-apoptosis effects, and significantly enhanced autophagy. However, these effects were largely attenuated by 3-MA or EX527. Additionally, our cellular experiments demonstrated that melatonin increased the SIRT1-BMAL1 pathway-related proteins' expression in a dose-dependent manner. In conclusion, these results indicate that melatonin treatment can protect against CIR-induced brain damage in diabetic mice, which may be achieved by the autophagy enhancement mediated by the SIRT1-BMAL1 pathway.

Melatonin as a promising modulator of aging related neurodegenerative disorders: Role of microRNAs

One of the host risk factors involved in aging-related diseases is coupled with the reduction of endogenous melatonin (MLT) synthesis in the pineal gland. MLT is considered a well-known pleiotropic regulatory hormone to modulate a multitude of biological processes such as the regulation of circadian rhythm attended by potent anti-oxidant, anti-inflammatory, and anti-cancer properties. It has also been established that the microRNAs family, as non-coding mRNAs regulating post-transcriptional processes, also serve a crucial role to promote MLT-related advantageous effects in both experimental and clinical settings. Moreover, the anti-aging impact of MLT and miRNAs participation jointly are of particular interest, recently. In this review, we aimed to scrutinize recent advances concerning the therapeutic implications of MLT, particularly in the brain tissue in the face of aging. We also assessed the possible interplay between microRNAs and MLT, which could be considered a therapeutic strategy to slow down the aging process in the nervous system.

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.

Sirtuins and the circadian clock interplay in cardioprotection: focus on sirtuin 1

Chronic disruption of circadian rhythms which include intricate molecular transcription-translation feedback loops of evolutionarily conserved clock genes has serious health consequences and negatively affects cardiovascular physiology. Sirtuins (SIRTs) are nuclear, cytoplasmic and mitochondrial histone deacetylases that influence the circadian clock with clock-controlled oscillatory protein, NAMPT, and its metabolite NAD+. Sirtuins are linked to the multi-organ protective role of melatonin, particularly in acute kidney injury and in cardiovascular diseases, where melatonin, via upregulation of SIRT1 expression, inhibits the apoptotic pathway. This review focuses on SIRT1, an NAD+-dependent class III histone deacetylase which counterbalances the intrinsic histone acetyltransferase activity of one of the clock genes, CLOCK. SIRT1 is involved in the development of cardiomyocytes, regulation of voltage-gated cardiac sodium ion channels via deacetylation, prevention of atherosclerotic plaque formation in the cardiovascular system, protection against oxidative damage and anti-thrombotic actions. Overall, SIRT1 has a see-saw effect on cardioprotection, with low levels being cardioprotective and higher levels leading to cardiac hypertrophy.

Effects of Melatonin on Neurobehavior and Cognition in a Cerebral Palsy Model of plppr5-/- Mice

Cerebral palsy (CP), a group of clinical syndromes caused by non-progressive brain damage in the developing fetus or infant, is one of the most common causes of lifelong physical disability in children in most countries. At present, many researchers believe that perinatal cerebral hypoxic ischemic injury or inflammatory injury are the main causes of cerebral palsy. Previous studies including our works confirmed that melatonin has a protective effect against convulsive brain damage during development and that it affects the expression of various molecules involved in processes such as metabolism, plasticity and signaling in the brain. Integral membrane protein plppr5 is a new member of the plasticity-related protein family, which is specifically expressed in brain and spinal cord, and induces filopodia formation as well as neurite growth. It is highly expressed in the brain, especially in areas of high plasticity, such as the hippocampus. The signals are slightly lower in the cortex, the cerebellum, and in striatum. Noteworthy, during development plppr5 mRNA is expressed in the spinal cord, i.e., in neuron rich regions such as in medial motor nuclei, suggesting that plppr5 plays an important role in the regulation of neurons. However, the existing literature only states that plppr5 is involved in the occurrence and stability of dendritic spines, and research on its possible involvement in neonatal ischemic hypoxic encephalopathy has not been previously reported. We used plppr5 knockout (plppr5-/-) mice and their wild-type littermates to establish a model of hypoxicischemic brain injury (HI) to further explore the effects of melatonin on brain injury and the role of plppr5 in this treatment in an HI model, which mainly focuses on cognition, exercise, learning, and memory. All the tests were performed at 3-4 weeks after HI. As for melatonin treatment, which was performed 5 min after HI injury and followed by every 24h. In these experiments, we found that there was a significant interaction between genotype and treatment in novel object recognition tests, surface righting reflex tests and forelimb suspension reflex tests, which represent learning and memory, motor function and coordination, and the forelimb grip of the mice, respectively. However, a significant main effect of genotype and treatment on performance in all behavioral tests were observed. Specifically, wild-type mice with HI injury performed better than plppr5-/- mice, regardless of treatment with melatonin or vehicle. Moreover, treatment with melatonin could improve behavior in the tests for wild-type mice with HI injury, but not for plppr5-/- mice. This study showed that plppr5 knockout aggravated HI damage and partially weakened the neuroprotection of melatonin in some aspects (such as novel object recognition test and partial nerve reflexes), which deserves further study.

The Effect of Melatonin Modulation of Non-coding RNAs on Central Nervous System Disorders: An Updated Review

Melatonin is a hormone produced in and secreted by the pineal gland. Besides its role in regulating circadian rhythms, melatonin has a wide range of protective functions in the central nervous system (CNS) disorders. The mechanisms underlying this protective function are associated with the regulatory effects of melatonin on related genes and proteins. In addition to messenger ribonucleic acid (RNA) that can be translated into protein, an increasing number of non-coding RNAs in the human body are proven to participate in many diseases. This review discusses the current progress of research on the effects of melatonin modulation of non-coding RNAs (ncRNAs), including microRNA, long ncRNA, and circular RNA. The role of melatonin in regulating common pathological mechanisms through these ncRNAs is also summarized. Furthermore, the ncRNAs, currently shown to be involved in melatonin signaling in CNS diseases, are discussed. The information compiled in this review will open new avenues for future research into melatonin mechanisms and provide a further understanding of ncRNAs in the CNS.

Melatonin Suppresses Ferroptosis Induced by High Glucose via Activation of the Nrf2/HO-1 Signaling Pathway in Type 2 Diabetic Osteoporosis

Ferroptosis is recently identified, an iron- and reactive oxygen species- (ROS-) dependent form of regulated cell death. This study was designed to determine the existence of ferroptosis in the pathogenesis of type 2 diabetic osteoporosis and confirm that melatonin can inhibit the ferroptosis of osteoblasts through activating Nrf2/HO-1 signaling pathway to improve bone microstructure in vivo and in vitro. We treated MC3T3-E1 cells with different concentrations of melatonin (1, 10, or 100 μM) and exposed them to high glucose (25.5 mM) for 48 h in vitro. Our data showed that high glucose can induce osteoblast cytotoxicity and the accumulation of lipid peroxide, the mitochondria of osteoblast show the same morphology changes as the erastin treatment group, and the expression of ferroptosis-related proteins glutathione peroxidase 4 (GPX4) and cystine-glutamate antiporter (SLC7A11) is downregulated, but these effects were reversed by ferroptosis inhibitor ferrastatin-1 and iron chelator deferoxamine (DFO). Furthermore, western blot and real-time polymerase chain reaction were used to detect the expression levels of nuclear factor erythroid 2-related factor 2 (Nrf2) and heme oxygenase-1 (HO-1); osteogenic capacity was evaluated by alizarin red S staining and the expression of osteoprotegerin, osteocalcin, and alkaline phosphatase; the results showed that the expression levels of these proteins in osteoblasts with 1, 10, or 100 μM melatonins were significantly higher than the high glucose group, but after using Nrf2-SiRNA interference, the therapeutic effect of melatonin was significantly inhibited. We also performed in vivo experiments in a diabetic rat model treated with two concentrations of melatonin (10, 50 mg/kg). Dynamic bone histomorphometry and micro-CT were used to observe the rat bone microstructure, and the expression of GPX4 and Nrf2 was determined by immunohistochemistry. Here, we first report that high glucose induces ferroptosis via increased ROS/lipid peroxidation/glutathione depletion in type 2 diabetic osteoporosis. More importantly, melatonin significantly reduced the level of ferroptosis and improved the osteogenic capacity of MC3T3-E1 through activating the Nrf2/HO-1 pathway in vivo and in vitro.

Melatonin protects against thoracic aortic aneurysm and dissection through SIRT1-dependent regulation of oxidative stress and vascular smooth muscle cell loss

Melatonin functions as an endogenous protective molecule in multiple vascular diseases, whereas its effects on thoracic aortic aneurysm and dissection (TAAD) and underlying mechanisms have not been reported. In this study, TAAD mouse model was successfully induced by β-aminopropionitrile fumarate (BAPN). We found that melatonin treatment remarkably prevented the deterioration of TAAD, evidenced by decreased incidence, ameliorated aneurysmal dilation and vascular stiffness, improved aortic morphology, and inhibited elastin degradation, macrophage infiltration, and matrix metalloproteinase expression. Moreover, melatonin blunted oxidative stress damage and vascular smooth muscle cell (VSMC) loss. Notably, BAPN induced a decrease in SIRT1 expression and activity of mouse aorta, whereas melatonin treatment reversed it. Further mechanistic study demonstrated that blocking SIRT1 signaling partially inhibited these beneficial effects of melatonin on TAAD. Additionally, the melatonin receptor was involved in this phenomenon. Our study is the first to report that melatonin exerts therapeutic effects against TAAD by reducing oxidative stress and VSMC loss via activation of SIRT1 signaling in a receptor-dependent manner, thus suggesting a novel therapeutic strategy for TAAD.

Melatonin-Mediated Pak2 Activation Reduces Cardiomyocyte Death Through Suppressing Hypoxia Reoxygenation Injury-Induced Endoplasmic Reticulum Stress

Cardiac reperfusion injury has been found to be associated with endoplasmic reticulum (ER) stress. Recently, p21-activated kinase 2 (Pak2) has been identified as a primary mediator of ER stress in chronic myocardial injury. Melatonin, a biological clock-related hormone, has been demonstrated to attenuate heart reperfusion burden by modulating ER stress and mitochondrial function. The aim of our study was to explore whether reperfusion-induced ER stress is modulated by melatonin through Pak2. Hypoxia reoxygenation (HR) was used in vitro to mimic reperfusion injury in cardiomyocytes. ER stress, oxidative stress, calcium overload, and cell death were measured through Western blotting, enzyme-linked immunosorbent assay, quantitative polymerase chain reaction, and immunofluorescence with the assistance of siRNA transfection and pathway blocker treatment. The results of our study demonstrated that HR decreased the levels of Pak2 in cardiomyocytes in vitro, and inactivation of Pak2 was associated with ER stress, oxidative stress, calcium overload, caspase-12 activation, and cardiomyocytes apoptosis in vitro. Interestingly, melatonin treatment attenuated HR-mediated ER stress, redox imbalance, calcium overload, and caspase-12-related cardiomyocytes apoptosis, and these protective effects were dependent on Pak2 upregulation. Knockdown of Pak2 abolished the beneficial actions exerted by melatonin on HR-treated cardiomyocytes in vitro. Finally, we found that melatonin reversed Pak2 expression by activating the AMPK pathway and blockade of the AMPK pathway suppressed Pak2 upregulation and cardiomyocytes survival induced by melatonin in the presence of HR stress. Overall, our study reports that the AMPK-Pak2 axis, a novel signaling pathway modulated by melatonin, sends prosurvival signals for cardiomyocytes reperfusion injury through attenuation of ER stress in vitro.

Intermedin1-53 attenuates aging-associated vascular calcification in rats by upregulating sirtuin 1

Vascular calcification is a common phenomenon in older adults. Intermedin (IMD) is a cardiovascular bioactive peptide inhibiting vascular calcification. In this study, we aimed to investigate whether IMD_1-53 attenuates aging-associated vascular calcification. Vascular calcification was induced by vitamin D3 plus nicotine (VDN) in young and old rats. The calcification in aortas was more severe in old rats treated with VDN than young control rats, and IMD expression was lower. Exogenous administration of IMD_1-53 significantly inhibited the calcium deposition in aortas and the osteogenic transdifferentiation of vascular smooth muscle cells (VSMCs) in VDN-treated old rats. Moreover, levels of aging-related p16, p21 and β-galactosidase were all greatly decreased by IMD_1-53. These results were further confirmed in rat and human VSMCs in vitro. In addition, IMD-deficient mouse VSMCs showed senescence features coinciding with osteogenic transition as compared with wild-type mouse VSMCs. Mechanistically, IMD_1-53 significantly increased the expression of the anti-aging factor sirtuin 1 (sirt1); the inhibitory effects of IMD_1-53 on calcification and senescence were blocked by sirt1 knockdown. Furthermore, preincubation with inhibitors of PI3K, AMPK or PKA efficiently blunted the upregulatory effect of IMD_1-53 on sirt1. Consequently, IMD_1-53 could attenuate aging-associated vascular calcification by upregulating sirt1 via activating PI3K/Akt, AMPK and cAMP/PKA signaling.

Mitophagy in Cardiovascular Diseases

Cardiovascular diseases are one of the leading causes of death. Increasing evidence has shown that pharmacological or genetic targeting of mitochondria can ameliorate each stage of these pathologies, which are strongly associated with mitochondrial dysfunction. Removal of inefficient and dysfunctional mitochondria through the process of mitophagy has been reported to be essential for meeting the energetic requirements and maintaining the biochemical homeostasis of cells. This process is useful for counteracting the negative phenotypic changes that occur during cardiovascular diseases, and understanding the molecular players involved might be crucial for the development of potential therapies. Here, we summarize the current knowledge on mitophagy (and autophagy) mechanisms in the context of heart disease with an important focus on atherosclerosis, ischemic heart disease, cardiomyopathies, heart failure, hypertension, arrhythmia, congenital heart disease and peripheral vascular disease. We aim to provide a complete background on the mechanisms of action of this mitochondrial quality control process in cardiology and in cardiac surgery by also reviewing studies on the use of known compounds able to modulate mitophagy for cardioprotective purposes.

SIRT1 Mediates Melatonin's Effects on Microglial Activation in Hypoxia: In Vitro and In Vivo Evidence

Melatonin exerts direct neuroprotection against cerebral hypoxic damage, but the mechanisms of its action on microglia have been less characterized. Using both in vitro and in vivo models of hypoxia, we here focused on the role played by silent mating type information regulation 2 homolog 1 (SIRT1) in melatonin's effects on microglia. Viability of rat primary microglia or microglial BV2 cells and SH-SY5Y neurons was significantly reduced after chemical hypoxia with CoCl₂ (250 μM for 24 h). Melatonin (1 μM) significantly attenuated CoCl₂ toxicity on microglia, an effect prevented by selective SIRT1 inhibitor EX527 (5 μM) and AMP-activated protein kinase (AMPK) inhibitor BML-275 (2 μM). CoCl₂ did not modify SIRT1 expression, but prevented nuclear localization, while melatonin appeared to restore it. CoCl₂ induced nuclear localization of hypoxia-inducible factor-1α (HIF-1α) and nuclear factor-kappa B (NF-kB), an effect contrasted by melatonin in an EX527-dependent fashion. Treatment of microglia with melatonin attenuated potentiation of neurotoxicity. Common carotid occlusion was performed in p7 rats, followed by intraperitoneal injection of melatonin (10 mg/kg). After 24 h, the number of Iba1+ microglia in the hippocampus of hypoxic rats was significantly increased, an effect not prevented by melatonin. At this time, SIRT1 was only detectable in the amoeboid, Iba1+ microglial population selectively localized in the corpus callosum. In these cells, nuclear localization of SIRT1 was significantly lower in hypoxic animals, an effect prevented by melatonin. NF-kB showed an opposite expression pattern, where nuclear localization in Iba1+ cells was significantly higher in hypoxic, but not in melatonin-treated animals. Our findings provide new evidence for a direct effect of melatonin on hypoxic microglia through SIRT1, which appears as a potential pharmacological target against hypoxic-derived neuronal damage.

Transient effect of melatonin treatment after neonatal hypoxic-ischemic brain injury in rats

Melatonin has potential neuroprotective capabilities after neonatal hypoxia-ischemia (HI), but long-term effects have not been investigated. We hypothesized that melatonin treatment directly after HI could protect against early and delayed brain injury. Unilateral HI brain injury was induced in postnatal day 7 rats. An intraperitoneal injection of either melatonin or vehicle was given at 0, 6 and 25 hours after hypoxia. In-vivo MRI was performed 1, 7, 20 and 43 days after HI, followed by histological analysis. Forelimb asymmetry and memory were assessed at 12–15 and at 36–43 days after HI. More melatonin treated than vehicle treated animals (54.5% vs 15.8%) developed a mild injury characterized by diffusion tensor values, brain volumes, histological scores and behavioral parameters closer to sham. However, on average, melatonin treatment resulted only in a tendency towards milder injury on T₂-weighted MRI and apparent diffusion coefficient maps day 1 after HI, and not improved long-term outcome. These results indicate that the melatonin treatment regimen of 3 injections of 10 mg/kg within the first 25 hours only gave a transient and subtle neuroprotective effect, and may not have been sufficient to mitigate long-term brain injury development following HI.

An Assessment of Melatonin's Therapeutic Value in the Hypoxic-Ischemic Encephalopathy of the Newborn

Hypoxic-ischemic encephalopathy (HIE) is one of the most frequent causes of brain injury in the newborn. From a pathophysiological standpoint, a complex process takes place at the cellular and tissue level during the development of newborn brain damage in the absence of oxygen. Initially, the lesion is triggered by a deficit in the supply of oxygen to cells and tissues, causing a primary energy insufficiency. Subsequently, high energy phosphate levels recover transiently (the latent phase) that is followed by a secondary phase, in which many of the pathophysiological mechanisms involved in the development of neonatal brain damage ensue (i.e., excitotoxicity, massive influx of Ca2+, oxidative and nitrosative stress, inflammation). This leads to cell death by necrosis or apoptosis. Eventually, a tertiary phase occurs, characterized by the persistence of brain damage for months and even years after the HI insult. Hypothermia is the only therapeutic strategy against HIE that has been incorporated into neonatal intensive care units with limited success. Thus, there is an urgent need for agents with the capacity to curtail acute and chronic damage in HIE. Melatonin, a molecule of unusual phylogenetic conservation present in all known aerobic organisms, has a potential role as a neuroprotective agent both acutely and chronically in HIE. Melatonin displays a remarkable antioxidant and anti-inflammatory activity and is capable to cross the blood-brain barrier readily. Moreover, in many animal models of brain degeneration, melatonin was effective to impair chronic mechanisms of neuronal death. In animal models, and in a limited number of clinical studies, melatonin increased the level of protection developed by hypothermia in newborn asphyxia. This review article summarizes briefly the available therapeutic strategies in HIE and assesses the role of melatonin as a potentially relevant therapeutic tool to cover the hypoxia-ischemia phase and the secondary and tertiary phases following a hypoxic-ischemic insult.

Variations in melatonin levels in preterm and term human breast milk during the first month after delivery

The objectives of the present study were to examine the dynamic changes in breast milk melatonin throughout the course of lactation and to explore factors associated with changes in melatonin concentrations and rhythms in both preterm and term breast milk. Breast milk was collected sequentially at 03:00, 09:00, 15:00, and 21:00 in one day. Melatonin was analyzed in 392 breast milk samples from 98 healthy nursing mothers at 0 to 30 days postpartum. In both preterm and term breast milk, the melatonin concentration presented a circadian rhythm with the acrophase at around 03:00. Subgroup analysis showed the peak melatonin concentrations differed significantly across lactation stages, with the highest concentration in the colostrum, followed by transitional and mature breast milk. At 03:00, preterm breast milk had a higher concentration of melatonin than term breast milk in the colostrum (28.67 pg/mL vs. 25.31 pg/mL, p < 0.022), transitional breast milk (24.70 pg/mL vs. 22.55 pg/mL), and mature breast milk (22.37 pg/mL vs. 20.12 pg /mL). Further studies are warranted for their roles and significance on melatonin in breast milk in nutrition and metabolism of neonates.

PGC1α activation by pterostilbene ameliorates acute doxorubicin cardiotoxicity by reducing oxidative stress via enhancing AMPK and SIRT1 cascades

Doxorubicin (DOX) is a widely used and potent anticancer agent, but DOX dose-dependently induced cardiotoxicity greatly limits its use in clinic. Pterostilbene, a natural analog of resveratrol, is a known antioxidant and exerts myocardial protection. The present study explored the action and detailed mechanism of pterostilbene on DOX-treated cardiomyocytes. We investigated the effects of pterostilbene on established acute DOX-induced cardiotoxicity models in both H9c2 cells treated with 1 μM DOX and C57BL/6 mice with DOX (20 mg/kg cumulative dose) exposure. Pterostilbene markedly alleviated the DOX exposure-induced acute myocardial injury. Both in vitro and in vivo studies revealed that pterostilbene inhibited the acute DOX exposure-caused oxidative stress and mitochondrial morphological disorder via the PGC1α upregulation through activating AMPK and via PGC1α deacetylation through enhancing SIRT1. However, these effects were partially reversed by knockdown of AMPK or SIRT1 in vitro and treatment of Compound C (AMPK inhibitor) or EX527 (SIRT1 inhibitor) in vivo. Our results indicate that pterostilbene protects cardiomyocytes from acute DOX exposure-induced oxidative stress and mitochondrial damage via PGC1α upregulation and deacetylation through activating AMPK and SIRT1 cascades.

The Role of Mitochondrial and Endoplasmic Reticulum Reactive Oxygen Species Production in Models of Perinatal Brain Injury

Significance: Perinatal brain injury is caused by hypoxia-ischemia (HI) in term neonates, perinatal arterial stroke, and infection/inflammation leading to devastating long-term neurodevelopmental deficits. Therapeutic hypothermia is the only currently available treatment but is not successful in more than 50% of term neonates suffering from hypoxic-ischemic encephalopathy. Thus, there is an urgent unmet need for alternative or adjunct therapies. Reactive oxygen species (ROS) are important for physiological signaling, however, their overproduction/accumulation from mitochondria and endoplasmic reticulum (ER) during HI aggravate cell death. Recent Advances and Critical Issues: Mechanisms underlying ER stress-associated ROS production have been primarily elucidated using either non-neuronal cells or adult neurodegenerative experimental models. Findings from mature brain cannot be simply transferred to the immature brain. Therefore, age-specific studies investigating ER stress modulators may help investigate ER stress-associated ROS pathways in the immature brain. New therapeutics such as mitochondrial site-specific ROS inhibitors that selectively inhibit superoxide (O2•-)/hydrogen peroxide (H2O2) production are currently being developed. Future Directions: Because ER stress and oxidative stress accentuate each other, a combinatorial therapy utilizing both antioxidants and ER stress inhibitors may prove to be more protective against perinatal brain injury. Moreover, multiple relevant targets need to be identified for targeting ROS before they are formed. The role of organelle-specific ROS in brain repair needs investigation. Antioxid. Redox Signal. 31, 643-663.

The Molecular Mechanism of Sirt1 Signaling Pathway in Brain Injury of Newborn Rats Exposed to Hyperoxia

The aim of the study was to investigate the changes in the reactive oxygen species (ROS), Sirt1, p53 and acetylated p53 in brain tissue of newborn rats exposed to hyperoxia to clarify the role of Sirt1 signaling pathway in brain injury. Neonate rats were randomly divided into normoxic group and hyperoxic group. Rats in the normoxic group were exposed to room air while the rats in the hyperoxic group were put in a hyperoxic chamber (80 ± 5% oxygen) for 1 to 14 d. Data, including weight growth, the water content of brain tissue, hematoxyline and eosin (H&E) and terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate nick-end labeling (Tunel) stain, ROS expression, the relative expression of Sirt1 mRNA and p53 mRNA, and the protein relative expression of Sirt1, p53 and acetylated p53 were analyzed at 1, 7 and 14 d after exposure. A reduced body weight and increased water content were observed in the brain tissue of hyperoxic group compared to normoxic group. HE staining and Tunel staining of brain tissue suggested that cell damaged after hyperoxic exposure. RT-PCR and Western blot results showed that the expression of Sirt1 in the hyperoxic group was lower than that in the normoxic group while the expression of p53 was higher than that in the normoxic group. In addition, Western blot data indicated acetylated p53 expression was higher in the hyperoxic group. Hyperoxic exposure can lead to brain injury in newborn Sprague-Dawley (SD) rats. These events might be regulated by the Sirt1 pathway, which downregulated the deacetylation of p53.

Comprehensive therapeutics targeting the corticospinal tract following spinal cord injury

Spinal cord injury (SCI), which is much in the public eye, is still a refractory disease compromising the well-being of both patients and society. In spite of there being many methods dealing with the lesion, there is still a deficiency in comprehensive strategies covering all facets of this damage. Further, we should also mention the structure called the corticospinal tract (CST) which plays a crucial role in the motor responses of organisms, and it will be the focal point of our attention. In this review, we discuss a variety of strategies targeting different dimensions following SCI and some treatments that are especially efficacious to the CST are emphasized. Over recent decades, researchers have developed many effective tactics involving five approaches: (1) tackle more extensive regions; (2) provide a regenerative microenvironment; (3) provide a glial microenvironment; (4) transplantation; and (5) other auxiliary methods, for instance, rehabilitation training and electrical stimulation. We review the basic knowledge on this disease and correlative treatments. In addition, some well-formulated perspectives and hypotheses have been delineated. We emphasize that such a multifaceted problem needs combinatorial approaches, and we analyze some discrepancies in past studies. Finally, for the future, we present numerous brand-new latent tactics which have great promise for curbing SCI.

SIRT1-regulated HMGB1 release is partially involved in TLR4 signal transduction: A possible anti-neuroinflammatory mechanism of resveratrol in neonatal hypoxic-ischemic brain injury

Neonatal hypoxic-ischemic brain injury (HIBI) is a knotty disease that lacks appropriate treatment. Inflammation is an important contributor to brain damage, and microglia are responsible for eliciting early and pronounced inflammatory reactions in the immature brain after hypoxic-ischemic (HI) insult. Acetylated HMGB1 can be released from immune cells into the extracellular space, where it acts as a danger-associated molecular pattern molecule to activate TLR4 signalling-mediated inflammatory responses. Resveratrol has neuroprotective and anti-inflammatory effects against HIBI, but whether these effects involve the regulation of the TLR4 signalling pathway and whether HMGB1 participates in this process is still unclear. We investigated the anti-inflammatory effects of resveratrol in HIBI and the molecular mechanisms potentially involved in the effect. The in vivo and in vitro results indicated that the level of cytoplasmic HMGB1 in microglia increased after insult and that treating experimental animals or mouse BV2 microglial cells with resveratrol attenuated HI insult-induced neuroinflammation, which was characterized by improved behavioural defects, reduced microglial activation and TLR4/MyD88/NF-κB signalling, and attenuated primary neuronal damage; this was accompanied by the inhibition of HMGB1 nucleoplasmic transfer and extracellular release. EX527 pretreatment reversed these effects. In addition, co-immunoprecipitation confirmed that SIRT1 was directly involved in the HMGB1 acetylation process in BV2 cells after oxygen glucose deprivation. These data demonstrate that resveratrol plays a neuroprotective role in neonatal HIBI by activating SIRT1 to inhibit HMGB1/TLR4/MyD88/NF-κB signalling and subsequent neuroinflammatory responses.

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.

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.

Mammalian STE20-like Kinase 1 Knockdown Attenuates TNFα-Mediated Neurodegenerative Disease by Repressing the JNK Pathway and Mitochondrial Stress

Neuroinflammation has been acknowledged as a primary factor contributing to the pathogenesis of neurodegenerative disease. However, the molecular mechanism underlying inflammation stress-mediated neuronal dysfunction is not fully understood. The aim of our study was to explore the influence of mammalian STE20-like kinase 1 (Mst1) in neuroinflammation using TNFα and CATH.a cells in vitro. The results of our study demonstrated that the expression of Mst1 was dose-dependently increased after TNFα treatment. Interestingly, knockdown of Mst1 using siRNA transfection significantly repressed TNFα-induced neuronal death. We also found that TNFα treatment was associated with mitochondrial stress, including mitochondrial ROS overloading, mitochondrial permeability transition pore (mPTP) opening, mitochondrial membrane potential reduction, and mitochondrial pro-apoptotic factor release. Interestingly, loss of Mst1 attenuated TNFα-triggered mitochondrial stress and sustained mitochondrial function in CATH.a cells. We found that Mst1 modulated mitochondrial homeostasis and cell viability via the JNK pathway in a TNFα-induced inflammatory environment. Inhibition of the JNK pathway abolished TNFα-mediated CATH.a cell death and mitochondrial malfunction, similar to the results obtained via silencing of Mst1. Taken together, our results indicate that inflammation-mediated neuronal dysfunction is implicated in Mst1 upregulation, which promotes mitochondrial stress and neuronal death by activating the JNK pathway. Accordingly, our study identifies the Mst1-JNK-mitochondria axis as a novel signaling pathway involved in neuroinflammation.

Liraglutide protects renal mesangial cells against hyperglycemia‑mediated mitochondrial apoptosis by activating the ERK‑Yap signaling pathway and upregulating Sirt3 expression

Diabetic nephropathy results from hyperglycemia‑mediated renal glomerular cell death via mitochondrial apoptosis. There is an emerging requirement for novel approaches with mitochondrial protective effects that alleviate the hyperglycemia‑induced loss of functional cells during diabetic renal damage. Liraglutide, a type of glucagon‑like peptide‑1 agonist, has been suggested to inhibit the progression of obesity and hyperglycemia. However, the contributions and mechanism of action of liraglutide on hyperglycemia‑mediated cell mitochondrial apoptosis in diabetic kidneys have not been illustrated. The present study demonstrated that liraglutide may protect human renal mesangial cells (HRMCs) against hyperglycemia‑induced cell death by inhibiting mitochondrial apoptosis. Liraglutide administration also maintained HRMC viability and promoted HRMC proliferation within a high glucose stress environment. Functional studies demonstrated that hyperglycemia triggered mitochondrial dysfunction, including mitochondrial potential reduction, mitochondrial permeability transition pore opening, reactive oxygen species overproduction and the activation of the mitochondrial apoptotic pathway. However, liraglutide treatment preserved mitochondrial function and prevented activation of mitochondrial apoptosis by upregulating sirtuin 3 (Sirt3) expression. Deletion of Sirt3 abrogated the protective effects of liraglutide on mitochondrial homeostasis following high glucose challenge. In addition, molecular analysis confirmed that liraglutide upregulated Sirt3 via activating the extracellular signal‑regulated kinase‑Yes‑associated protein (ERK‑Yap) signaling pathway. Inhibition of the ERK‑Yap axis negated the action of liraglutide on Sirt3 activation, leading to mitochondrial injury and HRMC apoptosis. Taken together, the present study illustrated that liraglutide protected renal mesangial cells from hyperglycemia‑mediated mitochondrial apoptosis by upregulating Sirt3 expression and activation of the ERK‑Yap signaling pathway.

Melatonin enhances TNF-α-mediated cervical cancer HeLa cells death via suppressing CaMKII/Parkin/mitophagy axis

Background

Tumor necrosis factor-α (TNF-α) immunotherapy controls the progression of human cervical cancer. Here, we explored the detailed molecular mechanisms played by melatonin in human cervical cancer (HeLa cells) death in the presence of TNF-α injury, with a particular attention to the mitochondrial homeostasis.

Methods

HeLa cells were incubated with TNFα and then cell death was determined via MTT assay, TUNEL staining, caspase ELISA assay and western blotting. Mitochondrial function was detected via analyzing mitochondrial membrane potential using JC-1 staining, mitochondrial oxidative stress using flow cytometry and mitochondrial apoptosis using western blotting.

Results

Our data exhibited that treatment with HeLa cells using melatonin in the presence of TNF-α further triggered cancer cell cellular death. Molecular investigation demonstrated that melatonin enhanced the caspase-9 mitochondrion death, repressed mitochondrial potential, increased ROS production, augmented mPTP opening rate and elevated cyt-c expression in the nucleus. Moreover, melatonin application further suppressed mitochondrial ATP generation via reducing the expression of mitochondrial respiratory complex. Mechanistically, melatonin augmented the response of HeLa cells to TNF-α-mediated cancer death via repressing mitophagy. TNF-α treatment activated mitophagy via elevating Parkin expression and excessive mitophagy blocked mitochondrial apoptosis, ultimately alleviating the lethal action of TNF-α on HeLa cell. However, melatonin supplementation could prevent TNF-α-mediated mitophagy activation via inhibiting Parkin in a CaMKII-dependent manner. Interestingly, reactivation of CaMKII abolished the melatonin-mediated mitophagy arrest and HeLa cell death.

Conclusions

Overall, our data highlight that melatonin enhances TNF-α-induced human cervical cancer HeLa cells mitochondrial apoptosis via inactivating the CaMKII/Parkin/mitophagy axis.

Mst1-Hippo pathway triggers breast cancer apoptosis via inducing mitochondrial fragmentation in a manner dependent on JNK-Drp1 axis

BACKGROUND AND OBJECTIVE

Mst1-Hippo pathway and mitochondrial fragmentation participate in the progression of several types of cancers. However, their roles in breast cancer requires investigation. The aim of our study is to determine whether Mst1 overexpression regulates the viability of breast cancer cells via modulating mitochondrial fragmentation.

MATERIALS AND METHODS

TUNEL staining, MTT assay and Western blotting were used to detect cancer cell death. Adenovirus-loaded Mst1 was transfected into cells to overexpress Mst1. Mitochondrial fragmentation was observed via immunofluorescence staining and Western blotting. Pathway blocker was used to detect whether Mst1 modulated cell death and mitochondrial fragmentation via JNK signaling pathway.

RESULTS

Our data showed that Mst1 overexpression promoted breast cancer cell death in a manner dependent on mitochondrial apoptosis. Mitochondrial oxidative stress, energy metabolism disorder, mitochondrial cyt-c liberation and mitochondrial apoptosis activation were observed after Mst1 overexpression. Furthermore, we demonstrated that Mst1 overexpression activated mitochondrial stress via triggering Drp1-related mitochondrial fragmentation, and that inhibition of Drp1-related mitochondrial fragmentation abrogated the proapoptotic effect of Mst1 overexpression on breast cancer cells. To this end, we found that Mst1 modulated Drp1 expression via the JNK signaling pathway, and that blockade of the JNK pathway attenuated mitochondrial stress and repressed apoptosis in Mst1-overexpressed cells.

CONCLUSION

Altogether, our results identified a tumor suppressive role for Mst1 overexpression in breast cancer via activation of the JNK-Drp1 axis and subsequent initiation of fatal mitochondrial fragmentation. Given these findings, strategies to enhance Mst1 activity and elevate the JNK-Drp1-mitochondrial fragmentation cascade have clinical benefits for patients with breast cancer.

Sepsis-related myocardial injury is associated with Mst1 upregulation, mitochondrial dysfunction and the Drp1/F-actin signaling pathway

LPS-induced septic cardiomyopathy has been found to be connected with mitochondrial stress through unknown mechanisms. Mitochondrial fission is an early event in mitochondrial dysfunction. The aim of our study was to determine the role and regulatory mechanism of mitochondrial fission in the progression of LPS-induced septic cardiomyopathy, with a particular focus on Mst1 and F-actin. Our data demonstrated that Mst1 expression was rapidly upregulated in LPS-treated hearts and that increased Mst1 promoted cardiomyocyte death by inducing mitochondrial stress. Mechanistically, elevated expression of Mst1 upregulated Drp1, and the latter initiated mitochondrial fission. Excessive mitochondrial fission caused mitochondrial oxidative injury, mitochondrial membrane potential reduction, mitochondrial proapoptotic element translocation into the cytoplasm/nucleus, mitochondrial energy dysfunction and mitochondrial apoptosis activation. Inhibition of mitochondrial fission sustained mitochondrial function and favored cardiomyocyte survival. Furthermore, we identified F-actin degradation as an apparent downstream event of mitochondrial fission activation in the context of LPS-induced septic cardiomyopathy. Stabilization of F-actin attenuated fission-mediated cardiomyocyte death. Altogether, our results define the Mst1/Drp1/mitochondrial fission/F-actin axis as a new signaling pathway that mediates LPS-related septic cardiomyopathy by inducing mitochondrial stress and cardiomyocyte death. Therefore, Mst1 expression, mitochondrial fission modification and F-actin stabilization may serve as potential therapeutic targets for sepsis-related myocardial injury.

Melatonin in Hypoxic-Ischemic Brain Injury in Term and Preterm Babies

Melatonin may serve as a potential therapeutic free radical scavenger and broad-spectrum antioxidant. It shows neuroprotective properties against hypoxic-ischemic brain injury in animal models. The authors review the studies focusing on the neuroprotective potential of melatonin and its possibility of treatment after perinatal asphyxia. Melatonin efficacy, low toxicity, and ability to readily cross through the blood-brain barrier make it a promising molecule. A very interesting thing is the difference between the half-life of melatonin in preterm neonates (15 hours) and adults (45-60 minutes). Probably, the use of synergic strategies-hypothermia coupled with melatonin treatment-may be promising in improving antioxidant action. The authors discuss and try to summarize the evidence surrounding the use of melatonin in hypoxic-ischemic events in term and preterm babies.

Therapeutic potential of melatonin related to its role as an autophagy regulator: A review

There are several pathologies, syndromes, and physiological processes in which autophagy is involved. This process of self-digestion that cells trigger as a survival mechanism is complex and tightly regulated, according to the homeostatic conditions of the organ. However, in all cases, its relationship with oxidative stress alterations is evident, following a pathway that suggests endoplasmic reticulum stress and/or mitochondrial changes. There is accumulating evidence of the beneficial role that melatonin has in the regulation and restoration of damaged autophagic processes. In this review, we focus on major physiological changes such as aging and essential pathologies including cancer, neurodegenerative diseases, viral infections and obesity, and document the essential role of melatonin in the regulation of autophagy in each of these different situations.