The neuroprotective and anti-apoptotic effects of melatonin on hemolytic hyperbilirubinemia-induced oxidative brain damage

Neuropathological implication of high blood bilirubin in patients and model rats with depression

PURPOSE

Elevated bilirubin levels have been associated with major depressive disorder (MDD); however, the exact impact of bilirubin on MDD and the underlying molecular mechanisms remain unclear. Here, we explored the influence of bilirubin on MDD and sought to identify the mechanisms via which bilirubin induces depressive-like behavior.

PATIENTS AND METHODS

Forty patients who were diagnosed with MDD and received treatment with selective serotonin reuptake inhibitors (SSRIs) were included, with 43 healthy volunteers serving as controls. Clinical symptoms were evaluated using Hamilton depression rating scale-24 (HAMD-24) and the Hamilton anxiety rating scale. Serum concentrations of total bilirubin (TBIL) and indirect bilirubin (IBIL) were measured at baseline and after treatment using an automated biochemical analyzer. The connection between clinical symptoms and TBIL or IBIL was examined using Pearson correlation. Chronic restraint stress (CRS) was employed to generate a rat model of depression. TBIL, IBIL in rat serum were measured by ELISA. Reactive oxygen species (ROS) contents in rat hippocampal tissues were quantified by flow cytometry. The levels of microglial markers and the extent of neuronal damage in the rat hippocampus were assessed by immunofluorescence and transmission electron microscopy, respectively.

RESULTS

Serum TBIL and IBIL levels were higher in patients with MDD than in the healthy controls. After treatment with SSRIs, the serum levels of TBIL and IBIL in MDD patients were significantly reduced. The levels of TBIL and IBIL were associated with HAMD-24 in MDD patients. Compared with the controls, the serum levels of TBIL, IBIL and the hippocampal ROS contents were elevated in CRS-exposed rats. Fluoxetine lowered inflammatory factor levels, mitigated oxidative stress.

CONCLUSION

Our findings indicate a possible correlation between elevated serum bilirubin and depressive symptoms. Increases in ROS levels, along with neuronal damage, may represent pathological mechanisms underlying MDD.

Docosahexaenoic acid (DHA) alleviates inflammation and damage induced by experimental colitis

PURPOSE

Inflammatory bowel diseases (IBD), including Crohn's disease (CD) and ulcerative colitis (UC), are chronic gastrointestinal disorders associated with significant morbidity and complications. This study investigates the therapeutic potential of docosahexaenoic acid (DHA) in a trinitrobenzene sulfonic acid (TNBS) induced colitis model, focusing on inflammation, oxidative stress, and intestinal membrane permeability.

METHODS

Wistar albino rats were divided into Control, Colitis, and Colitis + DHA groups (n = 8-10/group). The Colitis and Colitis + DHA groups received TNBS intrarectally, while the Control group received saline. DHA (600 mg/kg/day) or saline was administered via gavage for six weeks. Macroscopic and microscopic evaluations of colon tissues were conducted. Parameters including occludin and ZO-1 expressions, myeloperoxidase (MPO) activity, malondialdehyde (MDA), glutathione (GSH), total antioxidant status (TAS), total oxidant status (TOS), Interleukin-6 (IL-6), and tumor necrosis factor alpha (TNF-α) levels were measured in colon tissues.

RESULTS

Colitis induction led to significantly higher macroscopic and microscopic damage scores, elevated TOS levels, reduced occludin and ZO-1 intensity, decreased mucosal thickness, and TAS levels compared to the Control group (p < 0.001). DHA administration significantly ameliorated these parameters (p < 0.001). MPO, MDA, TNF-α, and IL-6 levels were elevated in the Colitis group but significantly reduced in the DHA-treated group (p < 0.001 for MPO, MDA; p < 0.05 for TNF-α and IL-6).

CONCLUSION

DHA demonstrated antioxidant and anti-inflammatory effects by reducing reactive oxygen species production, enhancing TAS capacity, preserving GSH content, decreasing proinflammatory cytokine levels, preventing neutrophil infiltration, reducing shedding in colon epithelium, and improving gland structure and mucosal membrane integrity. DHA also upregulated the expressions of occludin and ZO-1, critical for barrier function. Thus, DHA administration may offer a therapeutic strategy or supplement to mitigate colitis-induced adverse effects.

ALKBH5 targets ACSL4 mRNA stability to modulate ferroptosis in hyperbilirubinemia-induced brain damage

Bilirubin-induced brain damage is a serious clinical consequence of hyperbilirubinemia, yet the underlying molecular mechanisms remain largely unknown. Ferroptosis, an iron-dependent cell death, is characterized by iron overload and lipid peroxidation. Here, we report a novel regulatory mechanism of demethylase AlkB homolog 5 (ALKBH5) in acyl-coenzyme A synthetase long-chain family member 4 (ACSL4)-mediated ferroptosis in hyperbilirubinemia. Hyperdifferential PC12 cells and newborn Sprague-Dawley rats were used to establish in vitro and in vivo hyperbilirubinemia models, respectively. Proteomics, coupled with bioinformatics analysis, first suggested the important role of ferroptosis in hyperbilirubinemia-induced brain damage. In vitro experiments showed that ferroptosis is activated in hyperbilirubinemia, and ferroptosis inhibitors (desferrioxamine and ferrostatin-1) treatment effectively alleviates hyperbilirubinemia-induced oxidative damage. Notably, we observed that the ferroptosis in hyperbilirubinemia was regulated by m6A modification through the downregulation of ALKBH5 expression. MeRIP-seq and RIP-seq showed that ALKBH5 may trigger hyperbilirubinemia ferroptosis by stabilizing ACSL4 mRNA via m6A modification. Further, hyperbilirubinemia-induced oxidative damage was alleviated through ACSL4 genetic knockdown or rosiglitazone-mediated chemical repression but was exacerbated by ACSL4 overexpression. Mechanistically, ALKBH5 promotes ACSL4 mRNA stability and ferroptosis by combining the 669 and 2015 m6A modified sites within 3' UTR of ACSL4 mRNA. Our findings unveil a novel molecular mechanism of ferroptosis and suggest that m6A-dependent ferroptosis could be an underlying clinical target for the therapy of hyperbilirubinemia.

Bilirubin gates the TRPM2 channel as a direct agonist to exacerbate ischemic brain damage

Stroke prognosis is negatively associated with an elevation of serum bilirubin, but how bilirubin worsens outcomes remains mysterious. We report that post-, but not pre-, stroke bilirubin levels among inpatients scale with infarct volume. In mouse models, bilirubin increases neuronal excitability and ischemic infarct, whereas ischemic insults induce the release of endogenous bilirubin, all of which are attenuated by knockout of the TRPM2 channel or its antagonist A23. Independent of canonical TRPM2 intracellular agonists, bilirubin and its metabolic derivatives gate the channel opening, whereas A23 antagonizes it by binding to the same cavity. Knocking in a loss of binding point mutation for bilirubin, TRPM2-D1066A, effectively antagonizes ischemic neurotoxicity in mice. These findings suggest a vicious cycle of stroke injury in which initial ischemic insults trigger the release of endogenous bilirubin from injured cells, which potentially acts as a volume neurotransmitter to activate TRPM2 channels, aggravating Ca²⁺-dependent brain injury.

Ferulic acid attenuates pancreaticobiliary duct occlusion-induced inflammation in both pancreas and liver

INTRODUCTION

Acute pancreatitis is a systemic inflammatory disorder characterized by the hyperactivation of digestion enzymes and the release of proinflammatory cytokines. Ferulic acid (FA) is a hydroxycinnamic acid derivative that has recently been shown to have antioxidant and anti-inflammatory properties.

AIM

The anti-inflammatory effects of FA were investigated in the pancreaticobiliary duct ligation (PBDL)-induced pancreatitis model.

METHODS

Wistar albino rats (250-300 g; female = male) were divided into sham operation and PBDL groups. Some PBDL-performed animals were given intragastric saline or 250 mg/kg FA or 500 mg/kg FA 30 min before the PBDL and for 3 consecutive days. Moreover, the control group received saline. Blood samples are collected at the 24th, 48th, and 72nd hours to measure serum tumor necrosis factor (TNF)-α, liver, and pancreatic enzymes. At the 72nd hour, rats were euthanized; pancreas, lung, and liver samples were collected, scored microscopically, and analyzed for myeloperoxidase activity, malondialdehyde, and glutathione levels. One-way ANOVA with Tukey-Kramer tests were used for statistical analysis.

RESULTS

FA treatment reduced myeloperoxidase activity and prevented the depletion of glutathione in all three tissues. With FA treatments, high malondialdehyde levels in the pancreas and liver were reduced, as were serum TNF- α, amylase, lipase, alkaline phosphatase, alanine aminotransferase, aspartate aminotransferase, and total bilirubin levels. Additionally, FA ameliorated microscopic damage in the pancreas and liver significantly.

CONCLUSION

According to the findings, FA protects endogenous antioxidant content, prevents neutrophil infiltration, and decreases lipid peroxidation in PBDL-induced pancreatitis. Furthermore, FA improves tissue damage induced by pancreatitis with its anti-inflammatory effects.

Anti-PANoptosis is involved in neuroprotective effects of melatonin in acute ocular hypertension model

Acute ocular hypertension (AOH) is the most important characteristic of acute glaucoma, which can lead to retinal ganglion cell (RGC) death and permanent vision loss. So far, approved effective therapy is still lacking in acute glaucoma. PANoptosis (pyroptosis, apoptosis, and necroptosis), which consists of three key modes of programmed cell death-apoptosis, necroptosis, and pyroptosis-may contribute to AOH-induced RGC death. Previous studies have demonstrated that melatonin (N-acetyl-5-methoxytryptamine) exerts a neuroprotective effect in many retinal degenerative diseases. However, whether melatonin is anti-PANoptotic and neuroprotective in the progression of acute glaucoma remains unclear. Thus, this study aimed to explore the role of melatonin in AOH retinas and its underlying mechanisms. The results showed that melatonin treatment attenuated the loss of ganglion cell complex thickness, retinal nerve fiber layer thickness, and RGC after AOH injury, and improved the amplitudes of a-wave, b-wave, and oscillatory potentials in the electroretinogram. Additionally, the number of terminal deoxynucleotidyl transferase dUTP nick-end labeling-positive cells was decreased, and the upregulation of cleaved caspase-8, cleaved caspase-3, Bax, and Bad and downregulation of Bcl-2 and p-Bad were inhibited after melatonin administration. Meanwhile, both the expression and activation of MLKL, RIP1, and RIP3, along with the number of PI-positive cells, were reduced in melatonin-treated mice, and p-RIP3 was in both RGC and microglia/macrophage after AOH injury. Furthermore, melatonin reduced the expression of NLRP3, ASC, cleaved caspase-1, gasdermin D (GSDMD), and cleaved GSDMD, and decreased the number of Iba1/interleukin-1β-positive cells. In conclusion, melatonin ameliorated retinal structure, prevented retinal dysfunction after AOH, and exerted a neuroprotective effect via inhibition of PANoptosis in AOH retinas.

Melatonin-Induced Postconditioning Suppresses NMDA Receptor through Opening of the Mitochondrial Permeability Transition Pore via Melatonin Receptor in Mouse Neurons

Mitochondrial membrane potential regulation through the mitochondrial permeability transition pore (mPTP) is reportedly involved in the ischemic postconditioning (PostC) phenomenon. Melatonin is an endogenous hormone that regulates circadian rhythms. Its neuroprotective effects via mitochondrial melatonin receptors (MTs) have recently attracted attention. However, details of the neuroprotective mechanisms associated with PostC have not been clarified. Using hippocampal CA1 pyramidal cells from C57BL mice, we studied the involvement of MTs and the mPTP in melatonin-induced PostC mechanisms similar to those of ischemic PostC. We measured changes in spontaneous excitatory postsynaptic currents (sEPSCs), intracellular calcium concentration, mitochondrial membrane potential, and N-methyl-D-aspartate receptor (NMDAR) currents after ischemic challenge, using the whole-cell patch-clamp technique. Melatonin significantly suppressed increases in sEPSCs and intracellular calcium concentrations. The NMDAR currents were significantly suppressed by melatonin and the MT agonist, ramelteon. However, this suppressive effect was abolished by the mPTP inhibitor, cyclosporine A, and the MT antagonist, luzindole. Furthermore, both melatonin and ramelteon potentiated depolarization of mitochondrial membrane potentials, and luzindole suppressed depolarization of mitochondrial membrane potentials. This study suggests that melatonin-induced PostC via MTs suppressed the NMDAR that was induced by partial depolarization of mitochondrial membrane potential by opening the mPTP, reducing excessive release of glutamate and inducing neuroprotection against ischemia-reperfusion injury.

Role of melatonin mediated G-CSF induction in hematopoietic system of gamma-irradiated mice

AIMS

Hematopoietic acute radiation syndrome (H-ARS) can cause lethality, and therefore, the necessity of a safe radioprotector. The present study was focused on investigating the role of melatonin in granulocytes colony-stimulating factor (G-CSF) and related mechanisms underlying the reduction of DNA damage in hematopoietic system of irradiated mice.

MAIN METHODS

C57BL/6 male mice were exposed to 2, 5, and 7.5Gy of whole-body irradiation (WBI), 30 min after intra-peritoneal administration of melatonin with different doses. Mice were sacrificed at different time intervals after WBI, and bone marrow, splenocytes, and peripheral blood lymphocytes were isolated for studying various parameters including micronuclei (MN), cell cycle, comet, γ-H2AX, gene expression, amino acid profiling, and hematology.

KEY FINDINGS

Melatonin100mg/kg ameliorated radiation (7.5Gy and 5Gy) induced MN frequency and cell death in bone marrow without mortality. At 24 h of post-WBI (2Gy), the frequency of micronucleated polychromatic erythrocytes (mnPCE) with different melatonin doses revealed 20 mg/kg as optimal i.p. dose for protecting the hematopoietic system against radiation injury. In comet assay, a significant reduction in radiation-induced % DNA tail (p ≤ 0.05) was observed at this dose. Melatonin reduced γ-H2AX foci/cell and eventually reached to the control level. Melatonin also decreased blood arginine levels in mice after 24 h of WBI. The gene expression of G-CSF, Bcl-2-associated X protein (BAX), and Bcl2 indicated the role of melatonin in G-CSF regulation and downstream pro-survival pathways along with anti-apoptotic activity.

SIGNIFICANCE

The results revealed that melatonin recovers the hematopoietic system of irradiated mice by inducing G-CSF mediated radioprotection.

Hippocampal Astrocyte Response to Melatonin Following Neural Damage Induction in Rats

Introduction:

Brain injury induces an almost immediate response from glial cells, especially astrocytes. Activation of astrocytes leads to the production of inflammatory cytokines and reactive oxygen species that may result in secondary neuronal damage. Melatonin is an anti-inflammatory and antioxidant agent, and it has been reported to exert neuroprotection through the prevention of neuronal death in several models of central nervous system injury. This study aimed to investigate the effect of melatonin on astrocyte activation induced by Traumatic Brain Injury (TBI) in rat hippocampus and dentate gyrus.

Methods:

Animals were randomly divided into 5 groups; Sham group, TBI group, vehicle group, and melatonin-treated TBI groups (TBI+Mel5, TBI+Mel20). Immunohistochemical method (GFAP marker) and TUNEL assay were used to evaluate astrocyte reactivity and neuronal death, respectively.

Results:

The results demonstrated that the astrocyte number was reduced significantly in melatonin-treated groups compared to the vehicle group. Additionally, based on TUNEL results, melatonin administration noticeably reduced the number of apoptotic neurons in the rat hippocampus and dentate gyrus.

Conclusion:

In general, our findings suggest that melatonin treatment after brain injury reduces astrocyte reactivity as well as neuronal cell apoptosis in rat hippocampus and dentate gyrus.

Melatonin exerts neuroprotection in a chronodisrupted rat model through reduction in oxidative stress and modulation of autophagy

Circadian disruption due to artificial light affects cellular redox homeostasis and may lead to neurodegenerative diseases. The aim of the present study was to investigate the effect of continuous light exposure (CLE) and continuous dark exposure (CDE) along with melatonin supplementation on neuronal redox status, mitochondrial complexes, membrane bound transporters, inflammation, autophagy and neurodegeneration in chronodisrupted model of rat. In the study artificial light of white LED bulb with 500 lux intensity was used. Melatonin (10 mg/kg b.w., orally) was supplemented to control and CLE groups for 10 days. Standard protocols were employed to measure pro-oxidants, non-enzymatic antioxidants, and mitochondrial complexes in brain tissues. Membrane-bound ion transporter activities were evaluated in the crude synaptosomes. Gene expression analysis was performed to assess the expression of inflammatory, autophagy and neuronal marker genes. Histopathological changes in cerebral cortex and different hippocampus regions of the brain were studied. Melatonin exerted a significant normalization of redox status biomarkers in brain tissue. Further melatonin restored the activities of mitochondrial complexes and synaptosomal membrane bound ion transporters. RT-PCR data revealed that melatonin downregulated the expression of inflammatory (TNF-α, IL-6) autophagy (Atg-3, Beclin-1) and neurodegenerative genes (Ngb and NSE) in CLE group. Melatonin also preserved the histology architecture in cerebral cortex and hippocampus. Our results indicate that melatonin exerts a potent neuroprotective effect through reduction of oxidative stress, inflammation and autophagy. Melatonin supplementation might be a promising neurotherapeutic in the treatment neurodegenerative disorders caused by circadian disturbances.

Melatonin protects inner retinal neurons of newborn mice after hypoxia-ischemia

Retinopathy of prematurity is a vision-threatening disease associated with retinal hypoxia-ischemia, leading to the death of retinal neurons and chronic neuronal degeneration. During this study, we used the oxygen-induced retinopathy mice model to mimic retinal hypoxia-ischemia phenotypes to investigate further the neuroprotective effect of melatonin on neonatal retinal neurons. Melatonin helped maintain relatively normal inner retinal architecture and thickness and preserve inner retinal neuron populations in avascular areas by rescuing retinal ganglion and bipolar cells, and horizontal and amacrine neurons, from apoptosis. Meanwhile, melatonin recovered visual dysfunction, as reflected by the improved amplitudes and implicit times of a-wave, b-wave, and oscillatory potentials. Additionally, elevated cleaved caspase-3 and Bax protein levels and reduced Bcl-2 protein levels in response to hypoxia-ischemia were diminished after melatonin treatment. Moreover, melatonin increased BDNF and downstream phospho-TrkB/Akt/ERK/CREB levels. ANA-12, a TrkB receptor antagonist, antagonized these melatonin actions and reduced melatonin-induced neuroprotection. Furthermore, melatonin rescued the reduction in melatonin receptor expression. This study suggests that melatonin exerted anti-apoptotic and neuroprotective effects in inner retinal neurons after hypoxia-ischemia, at least partly due to modulation of the BDNF-TrkB pathway.

Yinzhihuang Oral Liquid Ameliorates Hyperbilirubinemia Induced by δ-Aminolevulinic Acid and Novobiocin in Neonatal Rats

Yinzhihuang oral liquid (YZH) is a traditional Chinese medicine that has been widely used in Asia to prevent and treat neonatal hyperbilirubinemia, but the published preclinical studies on its anti-hyperbilirubinemia effect are conducted in adult animals, partly due to the lack of preclinical neonatal hyperbilirubinemia animal models. In the present study, we tested six reagents to induce hyperbilirubinemia in neonatal rats, and established two appropriate neonatal hyperbilirubinemia rat models by subcutaneous injection of δ-Aminolevulinic acid (ALA, 200 mg/kg) or novobiocin (NOVO, 200 mg/kg). Oral treatment of YZH (80, 160 and 320 mg/kg) significantly decreased serum conjugated bilirubin levels in ALA-treated neonatal rats and serum unconjugated bilirubin levels in NOVO-treated neonatal rats, respectively. Additionally, pre-treatment of YZH also prevented the increase of serum bilirubin levels in both ALA- and NOVO-treated rats. Mechanistically, YZH significantly up-regulated the mRNA expression of genes involved in hepatic bilirubin disposition (organic anion-transporting polypeptide 1b2, Oatp1b2; multidrug resistance-associated protein 2, Mrp2) and bilirubin conjugation (UDP-glucuronosyltransferase 1a1, Ugt1a1). Additionally, YZH up-regulated the mRNA expression of cytochrome P450 1A1 (Cyp1a1), the target gene of aryl hydrocarbon receptor (AhR), and increased the nuclear protein levels of AhR in livers of neonatal rats. YZH and its two active ingredients, namely baicalin (BCL) and 4'-hydroxyacetophenone (4-HT), up-regulated the mRNA expression of AhR target genes (CYP1A1 and UGT1A1) and increased nuclear protein levels of AhR in HepG2 cells. In conclusion, the present study provides two neonatal hyperbilirubinemia animal models and evaluates the anti-hyperbilirubinemia effect and mechanisms of YZH in neonatal animals.

Changes in amplitude-integrated electroencephalography, neuron-specific enolase, and S100B in neonates with brain injury induced by neonatal hyperbilirubinemia and their significance

OBJECTIVE

To explore the changes in amplitude-integrated electroencephalography (aEEG), neuron-specific enolase (NSE), and S100B in neonates with brain injury induced by neonatal hyperbilirubinemia (NHB).

METHODS

67 neonates with brain injury induced by NHB admitted to our hospital from March 2016 to October 2018 were included in a brain injury group (BIG), and 82 neonates with NHB but without brain injury in our hospital during the same period were included in a non-BIG. The two groups were compared regarding the rates of normal and abnormal aEEG results.

RESULTS

The proportion of normal aEEG results in the BIG was significantly lower than that in the non-BIG, and the proportion of moderately and severely abnormal aEEG results in the BIG were both significantly higher than those in the non-BIG. The BIG showed significantly higher NSE and S100B levels than those of the non-BIG. The ROC curve for predicting prognosis showed that the AUC of aEEG, NSE, S100B, and the combined detection are 0.780, 0.754, 0.743, 0.788. The AUC > 0.700 indicated a good predictive value for the prognosis.

CONCLUSION

The combination of aEEG, NSE, and S100B has good value in diagnosing injury induced by NHB and can predict prognosis moderately well.

The protective effect of melatonin on benzo(a)pyrene-induced brain injury: role of apoptosis and autophagy pathways

Benzo(a)pyrene (BaP), a toxic polycyclic aromatic hydrocarbon, is spread in different ways as an environmental pollutant. It has been proposed that BaP can induce toxicity through oxidative stress and apoptosis in vital organs. The present study evaluated the protective effect of melatonin, a circadian hormone of the pineal gland, on BaP-induced neurotoxicity focused on oxidative stress, autophagy, and apoptosis pathways. Thirty male mice in 5 groups were treated daily for 28 consecutive days: (I) control group (BaP and melatonin solvent), (II) BaP (75 mg/kg, orally), (III) and (IV) BaP + melatonin (10 and 20 mg/kg, i.p.), (V) melatonin (20 mg/kg). The oxidative stress markers were determined in the brain. Western blot was conducted for the level of LC3 II/I and Beclin1, as autophagy markers, caspase3 and Bcl2, as apoptosis proteins, and Sirt1 in the brain. The exposure of mice to BaP caused a marked increase in the malondialdehyde (MDA) level and decrease of glutathione (GSH) content in the brain. Furthermore, the Sirt1 level upregulated as well as LC3 II/I, Beclin1, and cleaved caspase3 proteins, while the level of Bcl2 did not change. Melatonin at 20 mg/kg concurrently with BaP restored the BaP alteration in the brain compared with the BaP group. In conclusion, BaP induced brain toxicity via the induction of oxidative stress, apoptosis, and autophagy, whereas melatonin afforded neuroprotection against BaP due to inhibition of these mechanisms.

Baicalin Suppresses Bilirubin-Induced Apoptosis and Inflammation by Regulating p38 Mitogen-Activated Protein Kinases (MAPK) Signaling in Neonatal Neurons

Background

Hyperbilirubinemia is associated with central nervous system damage in preterm neonates due to the neurotoxicity of bilirubin. This study explored the possible mechanisms of bilirubin’s neurotoxicity, and the protective effect of baicalin (BAI) was also investigated.

Material/Methods

Isolated neonatal rat hippocampal neurons were exposed to free bilirubin (Bf). BAI was used to treat these neurons. 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay was used to evaluate the cell viability. Terminal deoxynucleotidyl transferase-dUTP nick-end labeling (TUNEL) assay was used to detect apoptosis. Contents of inflammatory cytokines were determined by enzyme-linked immunosorbent assay (ELISA). Protein expression and phosphorylation levels were assessed by Western blotting. Nuclear translocation was observed by immunofluorescent staining.

Results

Bf incubation significantly induced apoptosis and decreased viabilities of neurons. The phosphorylation levels of MAP kinase kinase (MKK)3, MKK6, p38 mitogen-activated protein kinases (MAPK), nuclear translocation level of p65, and the expression levels of cleaved caspase3 and tumor necrosis factor (TNF)α were found to be dramatically higher in Bf-incubated neurons. BAI pre-treatment, however, increased cell viability by reducing cell apoptosis. BAI pre-treatment also reduced phosphorylation levels of MKK3, MKK6, p38 MAPK, and nuclear translocation level of p65, as well as the expression levels of cleaved caspase3 and TNFα, in Bf-incubated neurons.

Conclusions

BAI suppressed bilirubin-induced neuron apoptosis and inflammation by deactivating p38 MAPK signaling.

Melatonin alleviates intestinal injury, neuroinflammation and cognitive dysfunction caused by intestinal ischemia/reperfusion

Intestinal ischemia/reperfusion (I/R) can cause multiple organ damage with extremely high morbidity and mortality. Melatonin has anti-inflammatory, anti-oxidative and anti-apoptotic effects against various diseases. This study aimed to explore whether melatonin had a protective effect against intestinal I/R-induced neuroinflammation and cognitive dysfunction, and investigate its potential mechanisms. In this study, melatonin was administered to the rats with intestinal I/R, then histological changes in intestine and brain (frontal cortex and hippocampal CA1 area) tissues and cognitive function were detected, respectively. The encephaledema and blood-brain barrier (BBB) permeability were observed. Moreover, the alterations of proinflammatory factors (tumor necrosis factor-α, interleukin-6 and interleukin-1β), oxidative response (malondialdehyde, superoxide dismutase, and reactive oxygen species), apoptosis and proteins associated with inflammation,including Toll-like receptor 4 (TLR4), myeloid differentiation factor 88 (Myd88) and phosphorylated nuclear factor kappa beta (NF-κB), and apoptosis (cleaved caspase-3) in brain tissues were examined. Furthermore, the expressions of TLR4, Myd88, and microglial activity were observed by multiple immunofluorescence staining. The results showed that intestinal I/R-induced abnormal neurobehavior and cerebral damage were ameliorated after melatonin treatment, which were demonstrated by improved cognitive dysfunction and aggravated histology. Furthermore, melatonin decreased the levels of proinflammatory factors and oxidative stress in plasma, intestine and brain tissues, attenuated apoptotic cell, and inhibited the expressions of related proteins and the immunoreactivity of TLR4 or Myd88 in microglia in brain tissues. These findings showed that melatonin might relieve neuroinflammation and cognitive dysfunction caused by intestinal I/R, which could be, at least partially, related to the inhibition of the TLR4/Myd88 signaling in microglia.

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 against Aβ-induced neurotoxicity in primary neurons via miR-132/PTEN/AKT/FOXO3a pathway

Alzheimer's disease (AD) is a kind of neurodegenerative disorder associated with age. Investigations suggest that amyliod-β (Aβ) is implicated in the pathogenesis of AD. The accumulation of Aβ in the brain causes oxidative stress and synaptic toxicity, leads to synaptic dysfunction and neuronal death. Previous investigations suggest that melatonin an endogenous hormone can counteract Aβ-induced neurotoxicity. However, the molecular mechanisms of Aβ-induced toxicity and melatonin treatment remain elusive. Studies indicate that microRNA-132 is crucial for neuronal survival and plays a key role in the pathological process of AD. Moreover, PTEN and FOXO3a two key targets of miR-132 are upregulated in the AD brain. Here, we exposed the primary cultured cortical neurons with Aβ25-35 and treated with melatonin. Our investigations demonstrated that Aβ25-35 exposure significantly decreased the expression of miR-132 and elevated the expression of PTEN and FOXO3a. Whereas, melatonin treatment could rescue the expression of miR-132 and downregulate the level of PTEN and FOXO3a. Moreover, melatonin blocked the nuclear translocation of FOXO3a and thereby suppressed its pro-apoptotic pathways. In addition, our investigations suggested that the over-expression of miR-132 could block Aβ-induced neurotoxicity. We also found that VO-OHpic (PTEN inhibitor) could counteract Aβ-induced neuronal damage, and LY294002 (AKT inhibitor) suppressed the protective effect of melatonin. Together, these results indicate that melatonin exerts its neuroprotective effect in Aβ-induced neurotoxicity via miR-132/PTEN/AKT/FOXO3a pathway. © 2018 BioFactors, 44(6):609-618, 2018.

Melatonin improves quality and longevity of chronic neural recording

The chronic performance of implantable neural electrodes is hindered by inflammatory brain tissue responses, including microglia activation, glial scarring, and neuronal loss. Melatonin (MT) has shown remarkable neuroprotective and neurorestorative effects in treating central nervous system (CNS) injuries and degeneration by inhibiting caspase-1, -3, and -9 activation and mitochondrial cytochrome c release, as well as reducing oxidative stress and neuroinflammation. This study examined the effect of MT administration on the quality and longevity of neural recording from an implanted microelectrode in the visual cortex of mice for 16 weeks. MT (30 mg/kg) was administered via daily intraperitoneal injection for acute (3 days before and 14 days post-implantation) and chronic (3 days before and 16 weeks post-implantation) exposures. During the first 4 weeks, both MT groups showed significantly higher single-unit (SU) yield, signal-to-noise ratio (SNR), and amplitude compared to the vehicle control group. However, after 4 weeks of implantation, the SU yield of the acute treatment group dropped to the same level as the control group, while the chronic treatment group maintained significantly higher SU yield compared to both acute (week 5-16) and control (week 0-16) mice. Histological studies revealed a significant increase in neuronal viability and decrease in neuronal apoptosis around the implanted electrode at week 16 in the chronic group in comparison to control and acute subjects, which is correlated with reduced oxidative stress and increased number of pro-regeneration arginase-1 positive microglia cells. These results demonstrate the potent effect of MT treatment in maintaining a high-quality electrode-tissue interface and suggest that MT promotes neuroprotection possibly through its anti-apoptotic, anti-inflammatory, and anti-oxidative properties.

The protective role of melatonin in chemotherapy-induced nephrotoxicity: a systematic review of non-clinical studies

BSTRACT Introduction: The aim of this study was to investigate the potential role of melatonin in the prevention of chemotherapy-induced nephrotoxicity at the preclinical level. Areas to be covered: To illuminate the possible role of melatonin in preventing chemotherapy-related nephrotoxicity, Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guideline was followed. A comprehensive search strategy was developed to include PubMed, Web of Science, Scopus, and Embase electronic databases from their inception to May 2018. Based on a set of prespecified inclusion and exclusion criteria, 21 non-clinical articles were ultimately included in the study. Expert opinion: Our findings clearly demonstrate that melatonin has a protective role in the prevention of chemotherapy-induced nephrotoxicity which may be caused by different chemotherapy agents such as cyclophosphamide, cisplatin, doxorubicin, methotrexate, oxaliplatin, etoposide, and daunorubicin. On the basis of current review of non-clinical studies, this protective effect of melatonin is attributed to different mechanisms such as reduction of oxidative stress, apoptosis, and inflammation. The findings presented in this review are based on non-clinical studies and thus conducting appropriate clinical trials to evaluate the real effectiveness of the concurrent use of chemotherapy agents with melatonin in the cancer patients is necessary.

Antioxidant Melatonin: Potential Functions in Improving Cerebral Autoregulation After Subarachnoid Hemorrhage

Subarachnoid hemorrhage (SAH) is a subtype of stroke with high mortality and morbidity. Impaired cerebral autoregulation following SAH has been reported owing to effects on sympathetic control, endothelial function, myogenic response, and cerebral metabolism. Impaired cerebral autoregulation is associated with early brain injury, cerebral vasospasm/delayed cerebral ischemia, and SAH prognosis. However, few drugs have been reported to improve cerebral autoregulation after SAH. Melatonin is a powerful antioxidant that is effective (easily crosses the blood brain barrier) and safe (tolerated in large doses without toxicity). Theoretically, melatonin may impact the control mechanisms of cerebral autoregulation via antioxidative effects, protection of endothelial cell integrity, suppression of sympathetic nerve activity, increase in nitric oxide bioavailability, mediation of the myogenic response, and amelioration of hypoxemia. Furthermore, melatonin may have a comprehensive effect on cerebral autoregulation. This review discusses the potential effects of melatonin on cerebral autoregulation following SAH, in terms of the association between pharmacological activities and the mechanisms of cerebral autoregulation.

Neuroprotective Effect of ω-3 Polyunsaturated Fatty Acids on Bilirubin Encephalopathy In Vitro and In Vivo

Background

Bilirubin encephalopathy is a serious complication in neonatal jaundice and is associated with high mortality and disability in newborns. The present study aimed to investigate the neuroprotective effects of omega-3 polyunsaturated fatty acids (ω-3 PUFA) on bilirubin encephalopathy in vitro and in vivo.

Material/Methods

The cytotoxicity of unconjugated bilirubin (UCB) to neurons and neuroprotection of ω-3 PUFA were investigated using MTT assays and apoptosis evaluations. Superoxide dismutase (SOD) and catalase (CAT) enzyme activity were measured to investigate the anti-oxidative effect of ω-3 PUFA. The differences between eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) were also compared. The in vivo neuroprotective effect of DHA was demonstrated in neonatal rats with bilirubin encephalopathy by bilirubin monitoring, neuron-specific enolase (NSE) monitoring, H&E staining of brain tissue, and apoptosis rate evaluations.

Results

Omega-3 PUFA reduced the rate of apoptosis induced by UCB and increased SOD and CAT enzyme activity for anti-oxidation. DHA did not reduce the bilirubin in the serum of neonatal rats with bilirubin encephalopathy, but did reduce the damage caused by bilirubin with decreased NSE and apoptosis rate as well as improved neuron morphology.

Conclusions

Omega-3 PUFA, particularly DHA, can reduce neurological damage in neonatal rats with bilirubin encephalopathy by increasing anti-apoptosis and anti-oxidation effects against UCB, providing a theoretical basis for the clinical treatment of bilirubin encephalopathy in newborns.

Melatonin Promotes Brain-Derived Neurotrophic Factor (BDNF) Expression and Anti-Apoptotic Effects in Neonatal Hemolytic Hyperbilirubinemia via a Phospholipase (PLC)-Mediated Mechanism

BACKGROUND Melatonin therapy shows positive effects on neuroprotective factor brain-derived neurotrophic factor (BDNF) expression and neuronal apoptosis in neonatal hemolytic hyperbilirubinemia. We hypothesized that melatonin promotes BDNF expression and anti-apoptotic effects in neonatal hemolytic hyperbilirubinemia through a phospholipase (PLC)-mediated mechanism. MATERIAL AND METHODS A phenylhydrazine hydrochloride (PHZ)-induced neonatal hemolytic hyperbilirubinemia model was constructed in neonatal rats. Four experimental groups - a control group (n=30), a PHZ group (n=30), a PHZ + melatonin group (n=30), and a PHZ + melatonin+U73122 (a PLC inhibitor) group (n=30) - were constructed. Trunk blood was assayed for serum hemoglobin, hematocrit, total and direct bilirubin, BDNF, S100B, and tau protein levels. Brain tissue levels of neuronal apoptosis, BDNF expression, PLC activity, IP3 content, phospho- and total Ca2+/calmodulin-dependent protein kinase type IV (CaMKIV) expression, and phospho- and total cAMP response element binding protein (CREB) expression were also assayed. RESULTS PHZ-induced hemolytic hyperbilirubinemia was validated by significantly decreased serum hemoglobin and hematocrit as well as significantly increased total and direct serum bilirubin (p<0.05). Neonatal bilirubin-induced neurotoxicity was validated by significantly decreased serum BDNF, brain BDNF, and serum S100B, along with significantly increased serum tau protein (p<0.05). PHZ-induced hemolytic hyperbilirubinemia significantly decreased serum BDNF, brain BDNF, and PLC/IP3/Ca2+ pathway activation while increasing neuronal apoptosis levels (p<0.05), all of which were partially rescued by melatonin therapy (p<0.05). Pre-treatment with the PLC inhibitor U73122 largely abolished the positive effects of melatonin on PLC/IP3/Ca2+ pathway activation, downstream BDNF levels, and neuronal apoptosis (p<0.05). CONCLUSIONS Promotion of BDNF expression and anti-apoptotic effects in neonatal hemolytic hyperbilirubinemia by melatonin largely operates via a PLC-mediated mechanism.

Adropin preserves the blood-brain barrier through a Notch1/Hes1 pathway after intracerebral hemorrhage in mice

Adropin is expressed in the CNS and plays a crucial role in the development of stroke. However, little is currently known about the effects of adropin on the blood-brain barrier (BBB) function after intracerebral hemorrhage (ICH). In this study, the role of adropin in collagenase-induced ICH was investigated in mice. At 1-h post-ICH, mice were administered with recombinant human adropin by intranasal. Brain water +content, BBB permeability, and neurological function were measured at different time intervals. Proteins were quantified using western blot analysis, and the localizations of adropin and Notch1 were visualized via immunofluorescence staining. It is shown that adropin reduced brain water content and improved neurological functions. Adropin preserved the functionality of BBB by increasing N-cadherin expression and reducing extravasation of albumin. Moreover, in vivo knockdown of Notch1 and Hes1 both abolished the protective effects of adropin. Taken together, our data demonstrate that adropin constitutes a potential treatment value for ICH by preserving BBB and improving functional outcomes through the Notch1 signaling pathway.

Dietary Sources and Bioactivities of Melatonin

Insomnia is a serious worldwide health threat, affecting nearly one third of the general population. Melatonin has been reported to improve sleep efficiency and it was found that eating melatonin-rich foods could assist sleep. During the last decades, melatonin has been widely identified and qualified in various foods from fungi to animals and plants. Eggs and fish are higher melatonin-containing food groups in animal foods, whereas in plant foods, nuts are with the highest content of melatonin. Some kinds of mushrooms, cereals and germinated legumes or seeds are also good dietary sources of melatonin. It has been proved that the melatonin concentration in human serum could significantly increase after the consumption of melatonin containing food. Furthermore, studies show that melatonin exhibits many bioactivities, such as antioxidant activity, anti-inflammatory characteristics, boosting immunity, anticancer activity, cardiovascular protection, anti-diabetic, anti-obese, neuroprotective and anti-aging activity. This review summaries the dietary sources and bioactivities of melatonin, with special attention paid to the mechanisms of action.

Mechanisms of Melatonin in Alleviating Alzheimer's Disease

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

Neuroprotective Effect of Erythropoietin on Phenylhydrazine-Induced Hemolytic Hyperbilirubinemia in Neonatal Rats

Neonatal unconjugated hyperbilirubinemia might cause severe bilirubin neurotoxicity in especially hemolytic conditions. The study aimed to elucidate the potential neuroprotective effects of erythropoietin (EPO) in hemolysis-induced hyperbilirubinemia. In newborn rats, hyperbilirubinemia secondary to hemolysis was induced by injecting with phenylhydrazine hydrochloride (PHZ) and rats were injected with either vehicle or EPO. At 54th hour of the PHZ injection, rats were decapitated. Serum levels of TNF-α, IL-1β, IL-10, brain-derived neurotrophic factor (BDNF) and S100-B and brain malondialdehyde, glutathione levels and myeloperoxidase activities were measured. TUNEL staining and NF-κB expression were evaluated. As compared to control pups, in vehicle-treated PHZ group, TNF-α and IL-1β levels, malondialdehyde level and myeloperoxidase activity were increased with concomitant decreases in IL-10 and glutathione. All EPO regimens reversed PHZ-induced alterations in IL-10, TNF-α, malondialdehyde and glutathione levels. Three-day-treatment abolished increases in myeloperoxidase activity and IL-1β levels, while BDNF and S100-B were elevated. Increased TUNEL (+) cells and NF-κB expressions in the brain of PHZ group were reduced in the 3-day-treated group. EPO exerted anti-inflammatory effects on PHZ-induced neural damage in newborn rats, while the neuroprotection was more obvious when the treatments were repeated successively. The results suggest that EPO treatment may have a therapeutic potential in supporting neuroplasticity in the hyperbilirubinemic neonates.

Melatonin in the management of perinatal hypoxic-ischemic encephalopathy: light at the end of the tunnel?

Perinatal hypoxic-ischemic encephalopathy (HIE) affects one to three per 1,000 live full-term births and can lead to severe and permanent neuropsychological sequelae, such as cerebral palsy, epilepsy, mental retardation, and visual motor or visual perceptive dysfunction. Melatonin has begun to be contemplated as a good choice in order to diminish the neurological sequelae from hypoxic-ischemic brain injury. Melatonin emerges as a very interesting medication, because of its capacity to cross all physiological barriers extending to subcellular compartments and its safety and effectiveness. The purpose of this commentary is to detail the evidence on the use of melatonin as a neuroprotection agent. The pharmacologic aspects of the drug as well as its potential neuroprotective characteristics in human and animal studies are described in this study. Melatonin seems to be safe and beneficial in protecting neonatal brains from perinatal HIE. Larger randomized controlled trials in humans are required, to implement a long-awaited feasible treatment in order to avoid the dreaded sequelae of HIE.