Melatonin inhibits neural apoptosis induced by homocysteine in hippocampus of rats via inhibition of cytochrome c translocation and caspase-3 activation and by regulating pro- and anti-apoptotic protein levels

Proteomic analysis reveals the alleviation of follicular development defects in offspring mice under DEHP exposure by melatonin

BACKGROUND

Environmental endocrine disruptor Di (2-ethylhexyl) phthalate (DEHP) widely affects the health of human and animals including the reproductive system. However, there are few studies on the protective strategies for the maternal DEHP exposure on follicular development of offspring. In the present study, we established a model of lactation female mice exposed to DEHP and reported the effects and potential mechanism of melatonin on the follicular development of offspring.

RESULTS

Our data showed that melatonin rescued the decrease of primordial follicles, antral follicles and oocyte number (increased by 74.2%) of offspring caused by maternal DEHP exposure from the primordial follicle formation stage. Proteomic analysis showed that melatonin altered the ovarian steroidogenesis, lipid metabolism, signal transduction, and DNA damage-related proteins. Melatonin reversed the disorder of lipid metabolism caused by DEHP and stabilized ovarian hormone secretase level. Molecular docking results indicated that DEHP/MEHP/melatonin binds to HSD17B2 to form a stable conformation, which may explain the reduction in 17β-estradiol induced by DEHP. Moreover, melatonin restored granulosa cell proliferation, reduced oxidative stress and DNA damage-related apoptosis, enhanced mitochondrial function, and protected ovarian cells. Besides, melatonin enhanced gap junction and promoted intercellular communication, which facilitate the formation of primordial follicles and the growth and development of antral follicles. In addition, melatonin rescued the oocyte defects of offspring caused by maternal DEHP exposure.

CONCLUSIONS

Taken together, our data showed that melatonin could alleviate the damage of follicular development and abnormal ovarian steroidogenesis of offspring caused by maternal DEHP exposure.

Melatonin: A potential nighttime guardian against Alzheimer's

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

Inhibition of hippocampal melatonin synthesis by siRNA induced learning and memory deficits in male rats

Melatonin, the multi-functional neurohormone, is synthesized in the extra-pineal tissues such as the hippocampus. The key enzyme in hippocampal melatonin synthesis is arylalkylamine-N-acetyltransferase (AANAT). The importance of melatonin synthesis in the hippocampus has not yet been determined. We investigated hippocampal AANAT role in cognitive function using gene silencing small interference RNA (siRNA) technology. The hippocampal local melatonin synthesis was inhibited by AANAT-siRNA injection. The time-gene silencing profile of AANAT-siRNA was obtained by RT-PCR technique. The cytotoxicity of siRNA dose was determined by MTT assay on the B65 neural cells. Animals received the selected dosage of AANAT-siRNA. Then, the spatial working memory (Y maze), object recognition memory and spatial reference memory (Morris's water maze, MWM) were evaluated. The anxiety-like behaviors were evaluated by the elevated plus maze. After one week, following the probe test of MWM, the rats were sacrificed for histological analysis. The hippocampal melatonin levels were measured using the liquid chromatography-mass spectrometry technique. The hippocampal melatonin levels in the AANAT-siRNA group decreased. Animals receiving the AANAT-siRNA showed deficits in spatial learning and working memory which were verified by increased escape latency and reduced spontaneous alternations, respectively. There was an increase in anxiety-like behaviors as well as a deficit in recognition memory in the AANAT-siRNA group. The Nissl staining and immunohistochemistry of activated caspase-3 showed the neuronal loss and cell apoptosis in hippocampal tissue of the AANAT-siRNA group. The 18F-FDG-PET imaging displayed lower glucose metabolism following the reduction in AANAT mRNA. Data suggest that the AANAT mRNA and hippocampal melatonin synthesis might be an essential factor for learning, memory and some aspects of cognition, as well as homeostasis of hippocampal cells.

Imbalance of Angiogenic and Growth Factors in Placenta in Maternal Hyperhomocysteinemia

Numerous studies have shown that various adverse factors of different nature and action mechanisms have similar negative influence on placental angiogenesis, resulting in insufficiency of placental blood supply. One of the risk factors for pregnancy complications with placental etiology is an increased level of homocysteine in the blood of pregnant women. However, the effect of hyperhomocysteinemia (HHcy) on the development of the placenta and, in particular, on the formation of its vascular network is at present poorly understood. The aim of this work was to study the effect of maternal HHcy on the expression of angiogenic and growth factors (VEGF-A, MMP-2, VEGF-B, BDNF, NGF), as well as their receptors (VEGFR-2, TrkB, p75NTR), in the rat placenta. The effects of HHcy were studied in the morphologically and functionally different maternal and fetal parts of the placenta on the 14th and 20th day of pregnancy. The maternal HHcy caused increase in the levels of oxidative stress and apoptosis markers accompanied by an imbalance of the studied angiogenic and growth factors in the maternal and/or fetal part of the placenta. The influence of maternal HHcy in most cases manifested in a decrease in the protein content (VEGF-A), enzymatic activity (MMP-2), gene expression (VEGFB, NGF, TRKB), and accumulation of precursor form (proBDNF) of the investigated factors. In some cases, the effects of HHcy differed depending on the placental part and stage of development. The influence of maternal HHcy on signaling pathways and processes controlled by the studied angiogenic and growth factors could lead to incomplete development of the placental vasculature and decrease in the placental transport, resulting in fetal growth restriction and impaired fetal brain development.

Melatonin Protects Against Titanium Oxide-Induced Neurotoxicity: Neurochemical, Neurobehavioral, and Histopathological Evidences

titania (titanium dioxide, TiO₂) is known to induce neurotoxicity and CNS dysfunctions. Numerous studies have explored the neuroprotective effects of melatonin against neurotoxicity. This study evaluates the potential of melatonin to protect against titania-induced neurotoxicity and the role of the Keap1/Nrf2/ARE signaling pathway. One group of animals were treated with Titania (0.045 and 0.075 g/rat) alone while the other with added melatonin (1 mg/kg and 3 mg/kg) and behavioral alterations were assessed using OFT (open field test). Neurochemical and histopathological changes were also studied in the hippocampus by analyzing kelch ECH associating protein 1 (Keap1), nuclear factor erythroid 2-related factor 2 (Nrf2), and antioxidant response element (ARE). It was seen that the animals with added Melatonin had improved behavioral scores in the OFT, like anxiety and motor dysfunction triggered by TiO₂. Melatonin also reduced lipid peroxidation, ROS, GSSG, IL1β, TNFα, Bax, and Keap1 levels, but boosted GSH, GPx, GR, SOD,IL10,IL4, Bcl2, Nrf2, and ARE levels and improved quadruple mitochondrial enzyme complex activity in titania-treated animals. Histopathological examination showed melatonin induced cytoprotection against vacuolization and necrosis in granular cells of DG and pyramidal cells of CA1 area of the hippocampus. In our study, pretreatment with melatonin reduced titania-induced neurotoxicity in the hippocampus through a mechanism potentially mediated by the Keap-1/Nrf2/ARE pathway.

Caspase-mediated regulation of the distinct signaling pathways and mechanisms in neuronal survival

Caspases are intimately associated with altering various signaling pathways, resulting in programmed cell death or apoptosis. Apoptosis is necessary for the normal homeostasis of cells and their development. The untoward activation of apoptotic pathways indirectly or directly results in pathologies of various diseases. Identifying different caspases in apoptotic pathways directed the research to develop caspase inhibitors as therapeutic agents. However, no drug is available in the market that targets caspase inhibition and produces a therapeutic effect. Here, we will shed light on the role of caspases in the number of neuronal disorders and neurodegenerative diseases. The article reviews the findings about the activation of various upstream mechanisms associated with caspases in neurodegenerative disorders along with the recent progress in the generation of caspase inhibitors and the challenge faced in their development as therapeutic agents for neurological indications.

The effects of methionine administration during the beginning postnatal days on the ovarian structures in adult rats

OBJECTIVES

Methionine is known as an essential amino acid in mammals. Consuming excessive amounts of methionine has toxic effects. This study aimed at evaluating the histomorphometric and histopathologic changes of ovaries after methionine administration during follicle formation.

MATERIAL AND METHODS

A total of 60 newborn female rats born under similar conditions were selected and randomly assigned into three groups including control, recipients of 50 and 200 mg/kg body weight of methionine for 5 days. On day 120, all 60 female rats were euthanized and the whole left ovary of each animal was taken in order to count the number of primordial, primary, secondary, antral, atretic follicles, as well as corpora lutea and also to conduct histopathologic study.

RESULTS

According to the results, the 50 mg/kg methionine did not significantly change the number of primordial follicles compared to the control group but the 200 mg/kg dose significantly decreased the number of primordial follicles. There were no significant differences between the groups in the number of other types of follicles and also in the number of corpora lutea. There was no histopathological lesion in the groups.

CONCLUSIONS

It seems that the high dose of methionine could exacerbate apoptosis of the primordial ovarian follicle during the follicle assembly process. However, the remaining were enough to form later stages of follicles after puberty.

SIRT2 and FOXO3a expressions in the cerebral cortex and hippocampus of young and aged male rats: antioxidant and anti-apoptotic effects of melatonin

Melatonin has antioxidant, anti-apoptotic and anti-aging effects in the brain. Sirtuin2 (SIRT2) accumulates in the central nervous system with aging, and its inhibition appears to be protective in aging and aging-related neurodegenerative diseases. Forkhead Box-class O3a (FOXO3a) transcription factor is one of the main targets of SIRT2, and SIRT2-mediated FOXO3a deacetylation is closely related to aging, oxidative stress, and apoptosis. This study aimed to investigate the effects of melatonin on SIRT2 and FOXO3a expressions in the cerebral cortex and hippocampus of aged rats. Young (3 months, n = 18) and aged (22 months, n = 18) male Wistar rats were divided into control (4% DMSO-PBS, sc, for 21 days), melatonin (10 mg/kg, sc, for 21 days) and salermide (1 mM; 25 μl/100 g bw, ip, for 21 days) groups. SIRT2, FOXO3a, Bcl-2, Bax and Bim expressions in the cerebral cortex and hippocampus were demonstrated by Western blotting. SIRT2 and FOXO3a protein levels were also measured by a sandwich ELISA method. Oxidative stress index (OSI) was calculated by measuring total oxidant status (TOS) and total antioxidant status (TAS). Aging increased SIRT2, FOXO3a, Bim (only in the cerebral cortex), Bax (only in the hippocampus), TOS, and OSI, while decreasing Bcl-2, Bcl-2/Bax and TAS in both brain regions. Melatonin decreased SIRT2, FOXO3a, oxidative stress parameters and pro-apoptotic proteins, while increasing TAS, Bcl-2 and Bcl-2/Bax, more specifically in the hippocampus of the aged brain. Our results indicate that inhibition of SIRT2 and FOXO3a expressions appears to be involved in the protective effects of melatonin in the hippocampus of aged rats.

Homocysteine and Age-Related Central Nervous System Diseases: Role of Inflammation

Hyperhomocysteinemia (HHcy) is remarkably common among the aging population. The relation between HHcy and the development of neurodegenerative diseases, such as Alzheimer's disease (AD) and eye diseases, and age-related macular degeneration (AMD) and diabetic retinopathy (DR) in elderly people, has been established. Disruption of the blood barrier function of the brain and retina is one of the most important underlying mechanisms associated with HHcy-induced neurodegenerative and retinal disorders. Impairment of the barrier function triggers inflammatory events that worsen disease pathology. Studies have shown that AD patients also suffer from visual impairments. As an extension of the central nervous system, the retina has been suggested as a prominent site of AD pathology. This review highlights inflammation as a possible underlying mechanism of HHcy-induced barrier dysfunction and neurovascular injury in aging diseases accompanied by HHcy, focusing on AD.

Melatonin Alleviates the Toxicity of High Nicotinamide Concentrations in Oocytes: Potential Interaction with Nicotinamide Methylation Signaling

Despite the numerous studies on melatonin and nicotinamide (NAM, the active form of vitamin B3), the linkage between these two biomolecules in the context of signaling pathways regulating preimplantation embryo development has not yet been investigated. In this study, we used bovine oocyte model to elucidate the effect of melatonin on the developmental competence of oocytes under the stress of high NAM concentrations. Results showed that NAM (20 mM) administration during in vitro maturation (IVM) significantly reduced oocyte maturation and actin distribution, while induced reactive oxygen species (ROS) accumulation and mitochondrial dysfunction, the multiple deleterious effects that were alleviated by melatonin (10⁻⁷ M). The RT-qPCR and/or immunofluorescence showed upregulation of the apoptosis (Caspase-3, Caspase-9, and BAX), autophagy (Beclin-1, LC3A, LC3B, ATG7, LAMP1, and LAMP2), cell cycle (P21, P27, and P53), and DNA damage (COX2 and 8-OxoG) specific markers in oocytes matured under NAM treatment, compared to NAM-melatonin dual-treated and the untreated ones. In addition, the total cleavage and blastocyst development rate, as well as the total number of cells and the inner cell mass (ICM) per blastocyst, were reduced, while DNA fragmentation was induced, in the group of NAM sole treatment than NAM-melatonin cotreatment and control. Inspecting the underlying mechanisms behind NAM-associated toxicity revealed an increase in transcription pattern of NAM methylation (NNMT and AHCY) genes in NAM-treated oocytes while the opposite profile was observed upon melatonin supplementation. In conclusion, to our knowledge, this is the first study reporting that melatonin can protect oocytes and embryos from NAM-induced injury through its ROS-scavenging activity together with potential interaction with NAM methylation signaling.

Antioxidant Potential of Ulexite in Zebrafish Brain: Assessment of Oxidative DNA Damage, Apoptosis, and Response of Antioxidant Defense System

In recent years, because of its significant biological roles, the usage of boron has been started in animal feeding. In this research, it was aimed to investigate the ulexite's action mechanism on the zebrafish brain with an evaluation of the oxidative parameters. The adult zebrafish were exposed to four ulexite doses (5, 10, 20, and 40 mg/l) in a static test apparatus for 96 h. For assessing the oxidative responses, multiple biochemical analyses were performed in brain tissues. The results indicated the supporting potential of low ulexite doses on the antioxidant system (< 40 mg/l) and that low-dose ulexite does not lead to oxidative stress in the zebrafish brain. Again, our results showed that low ulexite concentrations did not cause DNA damage or apoptosis. As a final result, in aquatic environments, ulexite (a boron compound) can be used in a safe manner, but it would be useful at higher concentrations to consider the damages of the cells that are probable to develop because of the oxidative stress.

Perinatal hypoxic-ischemic damage: review of the current treatment possibilities

Neonatal hypoxic-ischemic encephalopathy is a disorder with heterogeneous manifestation due to asphyxia during perinatal period. It affects approximately 3-12 children per 1000 live births and cause death of 1 million neonates worldwide per year. Besides, motor disabilities, seizures, impaired muscle tone and epilepsy are few of the consequences of hypoxic-ischemic encephalopathy. Despite an extensive research effort regarding various treatment strategies, therapeutic hypothermia with intensive care unit supportive treatment remains the only approved method for neonates who have suffered from moderate to severe hypoxic-ischemic encephalopathy. However, these protocols are only partially effective given that many infants still suffer from severe brain damage. Thus, further research to systematically test promising neuroprotective treatments in combination with hypothermia is essential. In this review, we discussed the pathophysiology of hypoxic-ischemic encephalopathy and delved into different promising treatment modalities, such as melatonin and erythropoietin. However, preclinical studies and clinical trials are still needed to further elucidate the mechanisms of action of these modalities.

Melatonin protects against tenofovir-induced nephrotoxicity in rats by targeting multiple cellular pathways

Nephrotoxicity is a dose-limiting side effect of long-term use of tenofovir, a reverse transcriptase inhibitor that is used for the treatment of HIV infection and chronic hepatitis B infection. Identifying an agent that prevents tenofovir disoproxil fumarate (TDF)-induced renal injury can lead to its better tolerance, and a more effective treatment can be achieved. The present study is aimed at investigating whether melatonin, a potent antioxidant and anti-inflammatory agent, protects against TDF nephrotoxicity in rats and to determine its cellular targets. Rats were divided into groups and treated as follows. Group I (control): Rats in this group (n = 6) received sterile water only by gavage for 35 days. Group II: Rats (n = 6) in this group received 600 mg/kg body weight TDF in sterile water by gavage for 35 days. Group III: Rats (n = 6) in this group received once daily 20 mg/kg bodyweight melatonin i.p. 2 h before the administration of 600 mg/kg body weight TDF in sterile water by gavage for 35 days. Group IV: Rats were pretreated daily with 20 mg/kg body weight melatonin i.p. 2 h before the administration of sterile water by gavage. All the rats were sacrificed on the 36th day, after overnight fast. Melatonin pretreatment protected the rats against TDF nephrotoxicity both histologically and biochemically. Biochemically, melatonin pretreatment attenuated TDF-induced, oxidative stress, nitrosative stress, mitochondrial pathway of apoptosis, PARP overactivation and preserved proximal tubular function (p < 0.01). This suggests that melatonin may be useful in ameliorating TDF nephrotoxicity.

Homocysteine and Mitochondria in Cardiovascular and Cerebrovascular Systems

Elevated concentration of homocysteine (Hcy) in the blood plasma, hyperhomocysteinemia (HHcy), has been implicated in various disorders, including cardiovascular and neurodegenerative diseases. Accumulating evidence indicates that pathophysiology of these diseases is linked with mitochondrial dysfunction. In this review, we discuss the current knowledge concerning the effects of HHcy on mitochondrial homeostasis, including energy metabolism, mitochondrial apoptotic pathway, and mitochondrial dynamics. The recent studies suggest that the interaction between Hcy and mitochondria is complex, and reactive oxygen species (ROS) are possible mediators of Hcy effects. We focus on mechanisms contributing to HHcy-associated oxidative stress, such as sources of ROS generation and alterations in antioxidant defense resulting from altered gene expression and post-translational modifications of proteins. Moreover, we discuss some recent findings suggesting that HHcy may have beneficial effects on mitochondrial ROS homeostasis and antioxidant defense. A better understanding of complex mechanisms through which Hcy affects mitochondrial functions could contribute to the development of more specific therapeutic strategies targeted at HHcy-associated disorders.

Protective effects of curcumin and Ganoderma lucidum on hippocampal damage caused by the organophosphate insecticide chlorpyrifos in the developing rat brain: Stereological, histopathological and immunohistochemical study

The aim of this study is to draw attention to the possible effects of chlorpyrifos exposure on the developing rat hippocampus in the prenatal period and to determine whether these effects can be reduced with various antioxidant substances. Pregnant rats were divided into 7 groups.; Chlorpyrifos (CPF), Curcumin (CUR), Ganoderma lucidum (GNL), Chlorpyrifos + Curcumin (CPF + CUR), Chlorpyrifos + Ganoderma lucidum, (CPF + GNL), SHAM and Control (C). After the experiments, brain tissues were evaluated by stereological and immunohistochemical methods. As a result of the stereological analyzes, it was determined that the number of pyramidal neurons in the hippocampus of the CPF group decreased significantly from all other groups. In contrast, the number of neurons in the CPF + CUR and CPF + GNL groups was significantly higher than the CPF group. In addition, immunohistochemical analyzes showed that the density of cells stained with glial fibrillar acidic protein (GFAP) positive in all areas in the hippocampus of the rats in the CPF group was significantly higher compared to the control group, whereas in the CPF + CUR and CPF + GNL groups were less than the CPF group. As a result, the exposure of CPF in the prenatal period caused neurotoxicity in the brain hippocampus, whereas CUR and GNL reduced this toxicity caused by CPF.

Melatonin protects against apoptosis of megakaryocytic cells via its receptors and the AKT/mitochondrial/caspase pathway

Clinical studies have shown that melatonin lowers the frequency of thrombocytopenia in patients with cancer undergoing radiotherapy or chemotherapy. Here, we investigated the mechanisms by which melatonin promotes platelet formation and survival. Our results show that melatonin exerted protective effects on serum-free induced apoptosis of CHRF megakaryocytes (MKs). Melatonin promoted the formation of MK colony forming units (CFUs) in a dose-dependent manner. Using doxorubicin-treated CHRF cells, we found that melatonin rescued G2/M cell cycle arrest and cell apoptosis induced by doxorubicin. The expression of p-AKT was increased by melatonin treatment, an effect that was abolished by melatonin receptor blocker. In addition, we demonstrated that melatonin enhanced the recovery of platelets in an irradiated mouse model. Megakaryopoiesis was largely preserved in melatonin-treated mice. We obtained the same results in vivo from bone marrow histology and CFU-MK formation assays. Melatonin may exert these protective effects by directly stimulating megakaryopoiesis and inhibiting megakaryocyte apoptosis through activation of its receptors and AKT signaling.

Melatonin and vitamin E alleviate homocysteine-induced oxidative injury and apoptosis in endothelial cells

A relationship exists between hyperhomocysteinemia and cardiovascular diseases, although the underlying mechanisms are still incompletely defined. One possibility involves a homocysteine (Hcy)-induced increased oxidative stress. Melatonin (Mel) and vitamin E (vitE) are important anti-oxidants. The main purpose of this study was (1) to compare the effect of treatments with Mel, vitE or both, on Hcy-induced apoptosis in human umbilical vein endothelial cells (HUVECs), and (2) to investigate the underlying mechanisms. Cell proliferation assay was carried out by Water Soluble Tetrazolium-1 (WST-1) assay kit. Apoptotic index was calculated by TUNEL Assay. Anti-oxidant parameters were studied by measurement of reactive oxygen species (ROS) and lipid peroxidation (LPO) levels. mRNA and protein expression levels of apoptotic and anti-apoptotic genes and proteins were studied by quantitative real time polymerase chain reaction (qRT-PCR) and Western blotting experiments respectively. The results showed that treatments with Mel, vitE or Mel + vitE suppressed Hcy-induced cell death, with a higher efficiency for the Mel and Mel + vitE treatments. Our results suggests that the mechanisms by which these anti-oxidants protected endothelial cells include the decrease in ROS and LPO levels, an increase in cell migration, the downregulation of pro-apoptotic proteins Cas 3, Cas 9, Cyt C and Bax and the upregulation of anti-apoptotic protein Bcl 2. Collectively, these results revealed the protective role of vitE and Mel against Hcy-induced cell apoptosis, which may add insight into therapeutic approaches to Hcy-induced damages.

Maternal Hyperhomocysteinemia Induces Neuroinflammation and Neuronal Death in the Rat Offspring Cortex

Maternal hyperhomocysteinemia is one of the common complications of pregnancy that causes offspring cognitive deficits during postnatal development. In the present work, we evaluated the effect of prenatal hyperhomocysteinemia on structural and ultrastructural organization, neuronal and glial cell number, apoptosis (caspase-3 content and activity), inflammatory markers (tumor necrosis factor-α, interleukin-6, and interleukin-1β), and p38 mitogen-activated protein kinase (p38 MAPK) phosphorylation in the offspring brain cortex in early ontogenesis. Wistar female rats received methionine (0.6 g/kg body weight) by oral administration during pregnancy. Histological and biochemical analyses of 5- and 20-day-old pups' cortical tissue were performed. Lysosome accumulation and other neurodegenerative changes in neurons of animals with impaired embryonic development were investigated by electron microscopy. Neuronal staining (anti-NeuN) revealed a reduction in neuronal number, accompanied by increasing of caspase-3 active form protein level and activity. Maternal hyperhomocysteinemia also elevated the number of astroglial and microglial cells and increased expression of interleukin-1β and p38 MAPK phosphorylation, which indicates the development of neuroinflammatory processes.

Nrf2 activation through the PI3K/GSK-3 axis protects neuronal cells from Aβ-mediated oxidative and metabolic damage

Background

Mounting evidence points to a crucial role of amyloid-β (Aβ) in the pathophysiology of Alzheimer’s disease (AD), a disorder in which brain glucose hypometabolism, downregulation of central elements of phosphorylation pathways, reduced ATP levels, and enhanced oxidative damage coexist, and sometimes precede, synaptic alterations and clinical manifestations. Since the brain has limited energy storage capacity, mitochondria play essential roles in maintaining the high levels of energy demand, but, as major consumers of oxygen, these organelles are also the most important generators of reactive oxygen species (ROS). Thus, it is not surprising that mitochondrial dysfunction is tightly linked to synaptic loss and AD pathophysiology. In spite of their relevance, the mechanistic links among ROS homeostasis, metabolic alterations, and cell bioenergetics, particularly in relation to Aβ, still remain elusive.

Methods

We have used classic biochemical and immunocytochemical approaches together with the evaluation of real-time changes in global energy metabolism in a Seahorse Metabolic Analyzer to provide insights into the detrimental role of oligAβ in SH-SY5Y and primary neurons testing their pharmacologic protection by small molecules.

Results

Our findings indicate that oligomeric Aβ induces a dramatic increase in ROS production and severely affects neuronal metabolism and bioenergetics. Assessment of global energy metabolism in real time demonstrated Aβ-mediated reduction in oxygen consumption affecting basal and maximal respiration and causing decreased ATP production. Pharmacologic targeting of Aβ-challenged neurons with a set of small molecules of known antioxidant and cytoprotective activity prevented the metabolic/bioenergetic changes induced by the peptide, fully restoring mitochondrial function while inducing an antioxidant response that counterbalanced the ROS production. Search for a mechanistic link among the protective small molecules tested identified the transcription factor Nrf2—compromised by age and downregulated in AD and transgenic models—as their main target and the PI3K/GSK-3 axis as the central pathway through which the compounds elicit their Aβ protective action.

Conclusions

Our study provides insights into the complex molecular mechanisms triggered by oligAβ which profoundly affect mitochondrial performance and argues for the inclusion of small molecules targeting the PI3K/GSK-3 axis and Nrf2-mediated pathways as part of the current or future combinatorial therapies.

Folic Acid Protects Rat Cerebellum Against Oxidative Damage Caused by Homocysteine: the Expression of Bcl-2, Bax, and Caspase-3 Apoptotic Genes

There is evidence that oxidative stress involves in homocysteine-induced pathogenesis. Considering the antioxidative properties of folic acid and its involvement as a cofactor for methionine synthase (MS) in the homocysteine-methionine cycle, the aim of this study was to evaluate the mechanism associated with homocysteine-induced toxicity and its prevention with folic acid supplementation. Male rat pups were divided into four groups including control, homocysteine (Hcy), Hcy + folic acid and folic acid groups. The Hcy group received Hcy 0.3-0.6 μmol/g body weight, while Hcy + folic acid group received folic acid orally as 0.011 μmol/g body weight along with Hcy on a postnatal day (PD) 4 until 25. The reduced and oxidized glutathione (GSH and GSSG) levels, GSH/GSSG ratio, protein carbonyl content, cystathionine β synthase (CBS), and MS activities in the cerebellum were measured 25 days after birth. Levels of malondialdehyde (MDA), marker of lipid peroxidation were measured. Also, Bcl2, Bax, and caspase-3 expression levels were measured by real-time quantitative PCR. Furthermore, caspase-3 protein level assay was performed by the ELISA test. Results indicated that Hcy administration could promote both lipid and protein oxidation, which was associated with increased amounts of caspase-3 mRNA and protein levels and Bax mRNA expression level in this group. Cerebellar MS, CBS enzyme activity, GSH, GSSG, and GSH/GSH ratio did not change following Hcy administration. Folic acid significantly reduced MDA level, protein carbonyl content, Bax, the caspase-3 mRNA, and protein expression levels in the cerebellum of Hcy-treated group. Moreover, cerebellar MS, CBS enzyme activity, GSH, and GSH/GSH ratio increased following folic acid treatment. We conclude that Hcy might cause apoptosis in the cerebellum. We suggest that folic acid, in addition of having antioxidant properties, can protect cerebellum against homocysteine-mediated neurotoxicity via modulating the expression of proteins that are contributed in regulation of apoptosis in the rat's cerebellum.

A new prospective on the role of melatonin in diabetes and its complications

Melatonin is a hormone secreted by the pineal gland under the control of the circadian rhythm, and is released in the dark and suppressed during the day. In the past decades, melatonin has been considered to be used in the treatment for diabetes mellitus (DM). This is due to a functional inter-relationship between melatonin and insulin. Elevated oxidative stress is a feature found in DM associated with diabetic neuropathy (DN), retinopathy (DR), nephropathy and cardiovascular disease. Reactive oxygen species (ROS) and nitrogen oxidative species (NOS) are usually produced in massive amounts via glucose and lipid peroxidation, and this leads to diabetic complications. At the molecular level, ROS causes damage to the biomolecules and triggers apoptosis. Melatonin, as an antioxidant and a free radical scavenger, ameliorates oxidative stress caused by ROS and NOS. Besides that, melatonin administration is proven to bring other anti-DM effects such as reducing cellular apoptosis and promoting the production of antioxidants.

Pathogenetical and Neurophysiological Features of Patients with Autism Spectrum Disorder: Phenomena and Diagnoses

Autism spectrum disorder (ASD) is a neurodevelopmental disorder that is accompanied by social deficits, repetitive and restricted interests, and altered brain development. The majority of ASD patients suffer not only from ASD itself but also from its neuropsychiatric comorbidities. Alterations in brain structure, synaptic development, and misregulation of neuroinflammation are considered risk factors for ASD and neuropsychiatric comorbidities. Electroencephalography has been developed to quantitatively explore effects of these neuronal changes of the brain in ASD. The pineal neurohormone melatonin is able to contribute to neural development. Also, this hormone has an inflammation-regulatory role and acts as a circadian key regulator to normalize sleep. These functions of melatonin may play crucial roles in the alleviation of ASD and its neuropsychiatric comorbidities. In this context, this article focuses on the presumable role of melatonin and suggests that this hormone could be a therapeutic agent for ASD and its related neuropsychiatric disorders.

The neuroprotective role of melatonin in a gestational hypermethioninemia model

Elevated levels of methionine in blood characterize the hypermethioninemia, which may have genetic or non-genetic origin, as for example from high protein diet. Born rats from hypermethioninemic mothers presented cerebral oxidative stress, inhibition of Na⁺,K⁺-ATPase, memory deficit and ultrastructure cerebral changes. Melatonin is a hormone involved in circadian rhythm and has antioxidant effects. The aim of this study was to verify the possible neuroprotective effects of melatonin administration in hypermethioninemic pregnant rats on damage to biomolecules (Na⁺,K⁺-ATPase, sulfhydryl content and DNA damage index) and behavior (open field, novel object recognition and water maze tasks), as well as its effect on cells morphology by electron microscopy in offspring. Wistar female rats received methionine (2.68 μmol/g body weight) and/or melatonin (10 mg/kg body weight) by subcutaneous injections during entire pregnancy. Control rats received saline. Biochemical analyzes were performed at 21 and 30 days of life of offspring and behavioral analyzes were performed only at 30 days of age in male pups. Results showed that gestational hypermethioninemia diminished Na⁺,K⁺-ATPase activity and sulfhydryl content and increased DNA damage at 21 and 30 days of life. Melatonin was able to totally prevent Na⁺,K⁺-ATPase activity alteration at 21 days and partially prevent its alteration at 30 days of rats life. Melatonin was unable in to prevent sulfhydryl and DNA damage at two ages. It also improved DNA damage, but not at level of saline animals (controls). Regarding to behavioral tests, data showed that pups exposed to gestational hypermethioninemia decreased reference memory in water maze, spent more time to the center of the open field and did not differentiate the objects in the recognition test. Melatonin was able to prevent the deficit in novel object recognition task. Electron microscopy revealed ultrastructure alterations in neurons of hypermethioninemic at both ages of offspring, whose were prevented by melatonin. These findings suggest that melatonin may be a good neuroprotective to minimize the harmful effects of gestational hypermethioninemia on offspring.

The role of one-carbon metabolism and homocysteine in Parkinson’s disease onset, pathology and mechanisms

Parkinson’s disease (PD) is the second most common neurodegenerative disorder. It is characterised by the progressive degeneration of dopaminergic (DA) neurons. The cause of degeneration is not well understood; however, both genetics and environmental factors, such as nutrition, have been implicated in the disease process. Deficiencies in one-carbon metabolism in particular have been associated with increased risk for PD onset and progression, though the precise relationship is unclear. The aim of the present review is to determine the role of one-carbon metabolism and elevated levels of homocysteine in PD onset and pathology and to identify potential mechanisms involved. A search of PubMed, Google Scholar and Web of Science was undertaken to identify relevant human and animal studies. Case–control, prospective cohort studies, meta-analyses and non-randomised trials were included in the present review. The results from human studies indicate that polymorphisms in one-carbon metabolism may increase risk for PD development. There is an unclear role for dietary B-vitamin intake on PD onset and progression. However, dietary supplementation with B-vitamins may be beneficial for PD-affected individuals, particularly those onl-DOPA (levodopa orl-3,4-dihydroxyphenylalanine) treatment. Additionally, one-carbon metabolism generates methyl groups, and methylation capacity in PD-affected individuals is reduced. This reduced capacity has an impact on expression of disease-specific genes that may be involved in PD progression. During B-vitamin deficiency, animal studies report increased vulnerability of DA cells through increased oxidative stress and altered methylation. Nutrition, especially folates and related B-vitamins, may contribute to the onset and progression of PD by making the brain more vulnerable to damage; however, further investigation is required.

Melatonin benefits to the growth of human annulus fibrosus cells through inhibiting miR-106a-5p/ATG7 signaling pathway

BACKGROUND

Disc degeneration (DD) is one of the common diseases worldwide, which deeply influences normal life and leads to excruciating pain. However, an effective treatment for DD is still not identified.

METHOD

The present study systemically examined the effect of melatonin on annulus fibrosus (AF) cells of patients with DD.

RESULTS

Melatonin had the effect of promoting proliferation, inducing autophagy, and suppressing apoptosis on AF cells of patients with DD. Moreover, melatonin contributed to the translation and transcription of autophagy-related protein ATG7 and inhibited the function of miR-106a-5p in AF cells. In addition, the results suggested that miR-106a-5p mediated the expression of ATG7 by directly binding to its 3'UTR in AF cells.

CONCLUSION

This research not only gained a deep insight of melatonin mode of action, but also indicated its potential target signaling pathway in AF cells.

Effect of melatonin on regulation of apoptosis and steroidogenesis in cultured buffalo granulosa cells

This study was aimed to address melatonin receptor expression, mRNA level of hypothalamus and hypophysis hormone receptors (GnRHR, FSHR, and LHR), steroidogenesis, cell cycle, apoptosis, and their regulatory factors after addition of melatonin for 24 hr in cultured buffalo granulosa cells (GCs). The results revealed that direct addition of different concentrations of melatonin (100 pM, 1 nM, and 100 nM) resulted in significant upregulation (p < 0.05) of mRNA level of melatonin receptor 1a (MT1) without affecting melatonin receptor 1b (MT2). Melatonin treatment significantly downregulated (p < 0.05) mRNA level of FSH and GnRH receptors, whereas 100 nM dose of melatonin significantly increased mRNA level of LH receptor. Treatment with 100 nM of melatonin significantly decreased the basal progesterone production with significant decrease (p < 0.05) in mRNA levels of StAR and p450ssc, and lower mRNA level of genes (Insig1, Lipe, and Scrab1) that affect cholesterol availability. Melatonin supplementation suppressed apoptosis (100 nM, p < 0.05) and enhanced G2/M phase (1 nM, 100 nM, p < 0.05) of cell cycle progression which was further corroborated by decrease in protein expression of caspase-3, p21, and p27 and increase in bcl2. Our results demonstrate that melatonin regulates gonadotrophin receptors and ovarian steroidogenesis through MT1. Furthermore, the notion of its incorporation in apoptosis and proliferation of buffalo GCs extends its role in buffalo ovaries.

Folic Acid and Vitamin B12 Administration in CKD, Why Not?

Patients affected by chronic kidney disease (CKD) or end-stage renal disease (ESRD) experience a huge cardiovascular risk and cardiovascular events represent the leading causes of death. Since traditional risk factors cannot fully explain such increased cardiovascular risk, interest in non-traditional risk factors, such as hyperhomocysteinemia and folic acid and vitamin B12 metabolism impairment, is growing. Although elevated homocysteine blood levels are often seen in patients with CKD and ESRD, whether hyperhomocysteinemia represents a reliable cardiovascular and mortality risk marker or a therapeutic target in this population is still unclear. In addition, folic acid and vitamin B12 could not only be mere cofactors in the homocysteine metabolism; they may have a direct action in determining tissue damage and cardiovascular risk. The purpose of this review was to highlight homocysteine, folic acid and vitamin B12 metabolism impairment in CKD and ESRD and to summarize available evidences on hyperhomocysteinemia, folic acid and vitamin B12 as cardiovascular risk markers, therapeutic target and risk factors for CKD progression.

Oxidative/nitrosative stress, autophagy and apoptosis as therapeutic targets of melatonin in idiopathic pulmonary fibrosis

INTRODUCTION

Idiopathic pulmonary fibrosis (IPF) is a fatal interstitial lung disease associated with disruption of alveolar epithelial cell layer and expansion of fibroblasts/myofibroblasts. Excessive levels of oxidative/nitrosative stress, induction of apoptosis, and insufficient autophagy may be involved in IPF pathogenesis; hence, the targeting of these pathways may ameliorate IPF. Areas covered: We describe the ameliorative effect of melatonin on IPF. We summarize the research on IPF pathogenesis with a focus on oxidative/nitrosative stress, autophagy and apoptosis pathways and discuss the potential effects of melatonin on these pathways. Expert opinion: Oxidative/nitrosative stress, apoptosis and autophagy could be interesting targets for therapeutic intervention in IPF. Melatonin, as a potent antioxidant, induces the expression of antioxidant enzymes, scavenges free radicals and modulates apoptosis and autophagy pathways. The effect of melatonin in the induction of autophagy could be an important mechanism against fibrotic process in IPF lungs. Further clinical studies are necessary to determine if melatonin could be a candidate for treating IPF.

Neuroprotective effect of epigallocatechin-3-gallate (EGCG) on radiation-induced damage and apoptosis in the rat hippocampus

PURPOSE

This study investigated the potential neuroprotective effect of epigallocatechin-3-gallate (EGCG) on radiation-induced cell death and damage in the hippocampus.

MATERIALS AND METHODS

Adult male Wister rats received oral treatment with EGCG at doses of 2.5 and 5 mg/kg/d for 3 d before 4 Gy γ irradiation.

RESULTS

The pretreatment of irradiated rats with EGCG significantly ameliorated the increased plasma levels of homocysteine, amyloid β, TNF-α and IL-6 levels and the decrease of dopamine and serotonin. Pretreatment with EGCG also significantly ameliorated the irradiation-induced increase in the 4-HNE and protein carbonyl levels and the decreased antioxidants including glutathione level, and the activities of glutathione peroxidase and glutathione reductase in the hippocampus. EGCG treatment prior to radiation exposure protected against DNA damage and apoptosis in the hippocampus. The increase in the levels of p53, Cytochrome-c, Bax and caspases 3 and 9 in the hippocampus were significantly ameliorated with a significant increase in Bcl-2. These changes were supported by marked protection of the dentate gyrus that exhibited a similar histological structure of the control animals.

CONCLUSIONS

EGCG can attenuate the severity of radiation-induced damage and cell death in hippocampus recommending polyphenols as successful option for protecting against radiation-induced hippocampal damage.

Sevoflurane-induced memory impairment in the postnatal developing mouse brain

The aim of the present study was to confirm that sevoflurane induces memory impairment in the postnatal developing mouse brain and determine its mechanism of action. C57BL/6 mice 7 days old were randomly assigned into a 2.6% sevoflurane (n=68), a 1.3% sevoflurane (n=68) and a control (n=38) group. Blood gas analysis was performed to evaluate hypoxia and respiratory depression during anesthesia in 78 mice. Measurements for expression of caspase-3 by immunohistochemistry, cleavage of poly adenosine diphosphate-ribose polymerase (PARP) by western blotting, as well as levels of brain-derived neurotrophic factor (BDNF), tyrosine kinase receptor type 2 (Ntrk2), pro-BDNF, p75 neurotrophin receptor (p75NTR) and protein kinase B (PKB/Akt) by enzyme-linked immunosorbent assay were performed in the hippocampus of 12 mice from each group. A total of 60 mice underwent the Morris water maze (MWM) test. Results from the MWM test indicated that the time spent in the northwest quadrant and platform site crossovers by mice in the 2.6 and 1.3% sevoflurane groups was significantly lower than that of the control group. Meanwhile, levels of caspase-3 and cleaved PARP in the 2.6 and 1.3% sevoflurane groups were significantly higher than that in the control group. Levels of pro-BDNF and p75NTR were significantly increased and the level of PKB/Akt was significantly decreased following exposure to 2.6% sevoflurane. Finally, the memory of postnatal mice was impaired by sevoflurane, this was determined using a MWM test. Therefore, the results of the current study suggest that caspase-3 induced cleavage of PARP, as well as pro-BDNF, p75NTR and PKB/Akt may be important in sevoflurane-induced memory impairment in the postnatal developing mouse brain.

RNAi-mediated knockdown of MTNR1B without disrupting the effects of melatonin on apoptosis and cell cycle in bovine granulose cells

Melatonin is well known as a powerful free radical scavenger and exhibits the ability to prevent cell apoptosis. In the present study, we investigated the role of melatonin and its receptor MTNR1B in regulating the function of bovine granulosa cells (GCs) and hypothesized the involvement of MTNR1B in mediating the effect of melatonin on GCs. Our results showed that MTNR1B knockdown significantly promoted GCs apoptosis but did not affect the cell cycle. These results were further verified by increasing the expression of pro-apoptosis genes (BAX and CASP3), decreasing expression of the anti-apoptosis genes (BCL2 and BCL-XL) and anti-oxidant genes (SOD1 and GPX4) without affecting cell cycle factors (CCND1, CCNE1 and CDKN1A) and TP53. In addition, MTNR1B knockdown did not disrupt the effects of melatonin in suppressing the GCs apoptosis or blocking the cell cycle. Moreover, MTNR1B knockdown did not affect the role of melatonin in increasing BCL2, BCL-XL, and CDKN1A expression, or decreasing BAX, CASP3, TP53, CCND1 and CCNE1 expression. The expression of MTNR1A was upregulated after MTNR1B knockdown, and melatonin promoted MTNR1A expression with or without MTNR1B knockdown. However, despite melatonin supplementation, the expression of SOD1 and GPX4 was still suppressed after MTNR1B knockdown. In conclusion, these findings indicate that melatonin and MTNR1B are involved in BCL2 family and CASP3-dependent apoptotic pathways in bovine GCs. MTNR1A and MTNR1B may coordinate the work of medicating the appropriate melatonin responses to GCs.

Punicalagin ameliorates the elevation of plasma homocysteine, amyloid-β, TNF-α and apoptosis by advocating antioxidants and modulating apoptotic mediator proteins in brain

The present study investigated the neuroprotective role of punicalagin, a major polyphenolic compound of pomegranate on methionine-induced brain injury. Hyperhomocysteinemia (HHcy) was induced in two months old male BALB c mice by methionine supplementation in drinking water (1 g/kg body weight) for 30 days. Punicalagin (1 mg/kg) was injected i.p every other day concurrently with methionine. Punicalagin significantly prevented the rise in the levels of homocysteine, amyloid-β and TNF-α. HHcy is associated with a decrease in the activities of superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (PGx) and glutathione reductase (GR) and glutathione (GSH) levels in the brains of methionine-treated mice while these antioxidants are increased by punicalagin supplementation. The treatment with punicalagin significantly decreased oxidative stress as indicated by decreased malondialdehyde and protein carbonyl formation in the brain. Compared with methionine-treated animals, mice that treated with methionine and punicalagin remarkably displayed less apoptosis, indicated by the lower level of proapoptotic protein (Bax, caspases- 3, 9 and p53) and higher levels of antiapoptotic Bcl-2 protein than those in hyperhomocysteinemic mice. The potent bioactivity of punicalagin extends to protect neuronal DNA as evidenced by the inhibition of the increase of comet parameters compared to the methionine-treated mice. In conclusion, punicalagin protected from methionine-induced HHcy and brain damage with an ability to repress apoptosis by modulating apoptotic mediators and maintaining DNA integrity in the brain of mice.

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

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

Comparison of the anti-apoptotic effects of 15- and 35-minute suspended moxibustion after focal cerebral ischemia/reperfusion injury

Heat-sensitive suspended moxibustion has a neuroprotective effect against focal cerebral ischemia/reperfusion injury, but the underlying mechanisms remain unclear. The duration of heat-sensitive suspended moxibustion (usually from 30 minutes to 1 hour) is longer than traditional suspended moxibustion (usually 15 minutes). However, the effects of 15- and 35-minute suspended moxibustion in rats with cerebral ischemia/reperfusion injury are poorly understood. In this study, we performed 15- or 35-minute suspended moxibustion at acupoint Dazhui (GV14) in an adult rat model of focal cerebral ischemia/reperfusion injury. Infarct volume was evaluated with the 2,3,5-triphenyltetrazolium chloride assay. Histopathological changes and neuronal apoptosis at the injury site were assessed by hematoxylin-eosin staining and terminal deoxynucleotidyl transferase dUTP nick end labeling assay. Caspase-9 and caspase-3 expression at the injury site was detected using immunofluorescent staining. Bax and Bcl-2 expression at the injury site was assessed using western blot assay. In the 35-minute moxibustion group, infarct volume was decreased, neuronal apoptosis was reduced, caspase-9, caspase-3 and Bax expression was lower, and Bcl-2 expression was increased, compared with the 15-minute moxibustion group. Our findings show that 35-minute moxibustion has a greater anti-apoptotic effect than 15-minute moxibustion after focal cerebral ischemia/reperfusion injury.

Acute administration of methionine and/or methionine sulfoxide impairs redox status and induces apoptosis in rat cerebral cortex

High plasma levels of methionine (Met) and its metabolites such as methionine sulfoxide (MetO) may occur in several genetic abnormalities. Patients with hypermethioninemia can present neurological dysfunction; however, the neurotoxicity mechanisms induced by these amino acids remain unknown. The aim of the present work was to study the effects of Met and/or MetO on oxidative stress, genotoxicity, cytotoxicity and to evaluate whether the cell death mechanism is mediated by apoptosis in the cerebral cortex of young rats. Forty-eight Wistar rats were divided into groups: saline, Met 0.4 g/Kg, MetO 0.1 g/Kg and Met 0.4 g/Kg + MetO 0.1 g/Kg, and were euthanized 1 and 3 h after subcutaneous injection. Results showed that TBARS levels were enhanced by MetO and Met+MetO 1 h and 3 h after treatment. ROS was increased at 3 h by Met, MetO and Met+MetO. SOD activity was increased in the Met group, while CAT was reduced in all experimental groups 1 h and 3 h after treatment. GPx activity was enhanced 1 h after treatment by Met, MetO and Met+MetO, however it was reduced in the same experimental groups 3 h after administration of amino acids. Caspase-3, caspase-9 and DNA damage was increased and cell viability was reduced by Met, MetO and Met+MetO at 3 h. Also, Met, MetO and Met+MetO, after 3 h, enhanced early and late apoptosis cells. Mitochondrial electrochemical potential was decreased by MetO and Met+MetO 1 h and 3 h after treatment. These findings help understand the mechanisms involved in neurotoxicity induced by hypermethioninemia.

Mechanisms underlying melatonin-mediated prevention of fenvalerate-induced behavioral and oxidative toxicity in zebrafish

The neurotoxic effects attributed to the pesticide fenvalerate (FEN) are well-established. The aim of this study was to determine whether melatonin (MLT) was able to protect against FEN-induced behavior, oxidative stress, apoptosis, and neurogenesis using zebrafish (Danio rerio) model. Zebrafish exposed to 100 μg/L FEN for 120 h exhibited decreased swimming activity accompanied by downregulated expression of neurogenesis-related genes (Dlx2, Shha, Ngn1, Elavl3, and Gfap), suggesting that neurogenesis were impaired. In addition, FEN exposure significantly elevated oxidative stress as evidenced by increased malondialdehyde levels, as well as activities of Cu/Zn superoxide dismutase (Cu/Zn SOD), catalase, and glutathione peroxidase. Acridine orange staining demonstrated that embryos treated with FEN for 120 h significantly enhanced apoptosis mainly in the brain. FEN also produced upregulation of the expression of the pro-apoptotic genes (Bax, Fas, caspase 8, caspase 9, and caspase 3) and decreased expression of the anti-apoptotic gene Bcl-2. MLT significantly attenuated the FEN-mediated oxidative stress, modulated apoptotic-regulating genes, and diminished apoptotic responses. Further, MLT blocked the FEN-induced effects on swimming behavior as well as on neurogenesis-related genes. In conclusion, MLT protected against FEN-induced developmental neurotoxicity and apoptosis by inhibiting pesticide-mediated oxidative stress in zebrafish.

Photoperiodic modulation of local melatonin synthesis and its role in regulation of thymic homeostasis in Funambulus pennanti

The effect of photo-neuroendocrine system on the thymic (immune) functions is mediated by gonadal steroid and the pineal hormone melatonin. The present study explored the effect of photoperiod on the thymic melatonergic system and its role in protection of thymic T-cells from the testosterone induced seasonal oxidative stress and apoptosis. Exposure to long day-length (LD) was noted to decrease local (thymic) melatonin content and induce oxidative stress and apoptosis in the thymus. Increased peripheral level of testosterone upregulated the androgen receptor expression and, consequently reduced proliferation response of the thymocytes. Short day conditions (SD) however, reversed the effect of LD on the thymic physiology. Low level of testosterone was concomitant with diminished nitro-oxidative stress and decreased expression of redox sensitive factors (NF-κB, p53 and Bax/Bcl-2 ratio) in the thymus. SD retarded activation of caspase-3 resulting in procaspase-3 accumulation. Further, in vitro treatment of thymocytes with AR antagonist flutamide impaired the sensitivity of thymocytes to androgen and reversed the deleterious effects of testosterone on the proliferative and apoptotic responses of thymocytes. Therefore, it can be suggested that thymus derived melatonin protects thymic T-cells from testosterone induced seasonal oxidative stress, apoptosis and also acts as a potent paracrine factor for maintenance of redox status to ensure thymocyte survival.

Dissociation of NSC606985 induces atypical ER-stress and cell death in prostate cancer cells

Castration-resistant prostate cancer (CRPC) is a major cause of prostate cancer (Pca) death. Chemotherapy is able to improve the survival of CRPC patients. We previously found that NSC606985 (NSC), a highly water-soluble camptothecin analog, induced cell death in Pca cells via interaction with topoisomerase 1 and activation of the mitochondrial apoptotic pathway. To further elucidate the role of NSC, we studied the effect of NSC on ER-stress and its association with NSC-induced cell death in Pca cells. NSC produced a time- and dose-dependent induction of GRP78, CHOP and XBP1s mRNA, and CHOP protein expression in Pca cells including DU145, indicating an activation of ER-stress. However, unlike conventional ER-stress in which GRP78 protein is increased, NSC produced a time- and dose-dependent U-shape change in GRP78 protein in DU145 cells. The NSC-induced decrease in GRP78 protein was blocked by protease inhibitors, N-acetyl-L-leucyl-L-leucylnorleucinal (ALLN), a lysosomal protease inhibitor, and epoxomicin (EPO), a ubiquitin-protease inhibitor. ALLN, but not EPO, also partially inhibited NSC-induced cell death. However, both 4-PBA and TUDCA, two chemical chaperons that effectively reduced tunicamycin-induced ER-stress, failed to attenuate NSC-induced GRP78, CHOP and XBP1s mRNA expression and cell death. Moreover, knockdown of NSC induction of CHOP expression using a specific siRNA had no effect on NSC-induced cytochrome c release and NSC-induced cell death. These results suggest that NSC produced an atypical ER-stress that is dissociated from NSC-induced activation of the mitochondrial apoptotic pathway and NSC-induced cell death in DU145 prostate cancer cells.

Cerebral hypoperfusion and glucose hypometabolism: Key pathophysiological modulators promote neurodegeneration, cognitive impairment, and Alzheimer's disease

Aging, hypertension, diabetes, hypoxia/obstructive sleep apnea (OSA), obesity, vitamin B12/folate deficiency, depression, and traumatic brain injury synergistically promote diverse pathological mechanisms including cerebral hypoperfusion and glucose hypometabolism. These risk factors trigger neuroinflammation and oxidative-nitrosative stress that in turn decrease nitric oxide and enhance endothelin, Amyloid-β deposition, cerebral amyloid angiopathy, and blood-brain barrier disruption. Proinflammatory cytokines, endothelin-1, and oxidative-nitrosative stress trigger several pathological feedforward and feedback loops. These upstream factors persist in the brain for decades, upregulating amyloid and tau, before the cognitive decline. These cascades lead to neuronal Ca²⁺ increase, neurodegeneration, cognitive/memory decline, and Alzheimer's disease (AD). However, strategies are available to attenuate cerebral hypoperfusion and glucose hypometabolism and ameliorate cognitive decline. AD is the leading cause of dementia among the elderly. There is significant evidence that pathways involving inflammation and oxidative-nitrosative stress (ONS) play a key pathophysiological role in promoting cognitive dysfunction. Aging and several comorbid conditions mentioned above promote diverse pathologies. These include inflammation, ONS, hypoperfusion, and hypometabolism in the brain. In AD, chronic cerebral hypoperfusion and glucose hypometabolism precede decades before the cognitive decline. These comorbid disease conditions may share and synergistically activate these pathophysiological pathways. Inflammation upregulates cerebrovascular pathology through proinflammatory cytokines, endothelin-1, and nitric oxide (NO). Inflammation-triggered ONS promotes long-term damage involving fatty acids, proteins, DNA, and mitochondria; these amplify and perpetuate several feedforward and feedback pathological loops. The latter includes dysfunctional energy metabolism (compromised mitochondrial ATP production), amyloid-β generation, endothelial dysfunction, and blood-brain-barrier disruption. These lead to decreased cerebral blood flow and chronic cerebral hypoperfusion- that would modulate metabolic dysfunction and neurodegeneration. In essence, hypoperfusion deprives the brain from its two paramount trophic substances, viz., oxygen and nutrients. Consequently, the brain suffers from synaptic dysfunction and neuronal degeneration/loss, leading to both gray and white matter atrophy, cognitive dysfunction, and AD. This Review underscores the importance of treating the above-mentioned comorbid disease conditions to attenuate inflammation and ONS and ameliorate decreased cerebral blood flow and hypometabolism. Additionally, several strategies are described here to control chronic hypoperfusion of the brain and enhance cognition. © 2016 Wiley Periodicals, Inc.

Turkish propolis supresses MCF-7 cell death induced by homocysteine

Elevated plasma homocysteine (Hcy) level is a most important risk factor for various vascular diseases including coronary, cerebral and peripheral arterial and venous thrombosis. Propolis is produced by honeybee from various oils, pollens and wax materials. Therefore, it has various biological properties including antioxidant, antitumor and antimicrobial activities. This study investigated the effects of propolis and Hcy on apoptosis in cancer cells. According to our findings, Hcy induced apoptosis in human breast adenocarcinoma (MCF-7) cells by regulating numerous genes and proteins involved in the apoptotic signal transduction pathway. In contrast, treatment with propolis inhibited caspase- 3 and -9 induced by Hcy in MCF-7 cells. It can be concluded that Hcy may augment the activity of anticancer agents that induce excessive reactive oxygen species (ROS) generation and apoptosis in their target cells. In contrast to the previous studies herein we found that propolis in low doses protected cancer cells inhibiting cellular apoptosis mediated by intracellular ROS-dependent mitochondrial pathway.

Turkish propolis protects human endothelial cells in vitro from homocysteine-induced apoptosis

Chronic cardiovascular and neurodegenerative complications induced by hyperhomocysteinemia have been most relatively associated with endothelial cell injury. Elevated homocysteine (Hcy) generates reactive oxygen species (ROS) accompanying with oxidative stress which is hallmarks of the molecular mechanisms responsible for cardiovascular disease. Propolis is a natural product, obtained by honeybee from various oils, pollens, special resins and wax materials, conventionally used with the purpose of treatment by folks Propolis has various biological activities and powerful antioxidant capacity. The flavonoids and phenolic acids, most bioactive components of propolis, have superior antioxidant ability to defend cell from free radicals. This study was designed to examine the protective effects of Turkish propolis (from east of country) on Hcy induced ROS production and apoptosis in human vascular endothelial cells (HUVECs). According to results, co-treatment of HUVECs with propolis decreased Hcy-induced ROS overproduction and lipid peroxidation (LPO) levels. Furthermore, overproductions of Bax, caspase-9 and caspase-3 protein, elevation of cytochrome c release in Hcy-treated HUVECs were significantly reduced by propolis. It was concluded that propolis has cytoprotective ability against cytotoxic effects of high Hcy in HUVECs.

Modulation of Diabetes-Induced Oxidative Stress, Apoptosis, and Ca2+ Entry Through TRPM2 and TRPV1 Channels in Dorsal Root Ganglion and Hippocampus of Diabetic Rats by Melatonin and Selenium

Neuropathic pain and hippocampal injury can arise from the overload of diabetes-induced calcium ion (Ca²⁺) entry and oxidative stress. The transient receptor potential (TRP) melastatin 2 (TRPM2) and TRP vanilloid type 1 (TRPV1) are expressed in sensory neurons and hippocampus. Moreover, activations of TRPM2 and TRPV1 during oxidative stress have been linked to neuronal death. Melatonin (MEL) and selenium (Se) have been considered potent antioxidants that detoxify a variety of reactive oxygen species (ROS) in neurological diseases. In order to better characterize the actions of MEL and Se in diabetes-induced peripheral pain and hippocampal injury through modulation of TRPM2 and TRPV1, we tested the effects of MEL and Se on apoptosis and oxidative stress in the hippocampal and dorsal root ganglion (DRG) neurons of streptozotocin (STZ)-induced diabetic rats. Fifty-eight rats were divided into six groups. The first group was used as control. The second group was used as the diabetic group. The third and fourth groups received Se and MEL, respectively. Intraperitoneal Se and MEL were given to diabetic rats in the fifth and sixth groups. On the 14th day, hippocampal and DRG neuron samples were freshly taken from all animals. The neurons were stimulated with a TRPV1 channel agonist (capsaicin) and a TRPM2 channel agonist (cumene hydroperoxide). We observed a modulator role of MEL and Se on intracellular free Ca²⁺ concentrations, current densities of TRPM2 and TRPV1 channels, apoptosis, caspase 3, caspase 9, mitochondrial depolarization, reduced glutathione, glutathione peroxidase, lipid peroxidation, and intracellular ROS production values in the neurons. In addition, procaspase 3 and 9 activities in western blot analyses of the brain cortex were also decreased by MEL and Se treatments. In conclusion, in our diabetes experimental model, TRPM2 and TRPV1 channels are involved in the Ca²⁺ entry-induced neuronal death and modulation of this channel activity by MEL and Se treatment may account for their neuroprotective activity against apoptosis and Ca²⁺ entry. Graphical Abstract Possible molecular pathways of involvement of melatonin and selenium in diabetes-induced apoptosis, oxidative stress, and calcium accumulation through TRPM2 and TRPV1 channels in the hippocampus and DRG neurons of rats. The TRPM2 channel is activated by ADP-ribose and oxidative stress although it is inhibited by ACA. The TRPV1 channel is activated by oxidative stress and capsaicin and it is blocked by capsazepine (CPZ). Diabetes can result in augmented ROS release in hippocampal and DRG neurons through polyol reactions, leading to Ca²⁺ uptake through TRPM2 and TRPV1 channels. Mitochondria were reported to accumulate Ca²⁺ provided intracellular Ca²⁺ rises, thereby leading to the depolarization of mitochondrial membranes and release of apoptosis-inducing factors such as caspase 3 and caspase 9. Melatonin and selenium reduce TRPM2 and TRPV1 channel activation through the modulation of polyol oxidative reactions and selenium-dependent glutathione peroxidase (GSH-Px) antioxidant pathways.

Chronic low-dose melatonin treatment maintains nigrostriatal integrity in an intrastriatal rotenone model of Parkinson's disease

Parkinson's disease is a major neurodegenerative disorder which primarily involves the loss of dopaminergic neurons in the substantia nigra and related projections in the striatum. The pesticide/neurotoxin, rotenone, has been shown to cause systemic inhibition of mitochondrial complex I activity in nigral dopaminergic neurons, with consequent degeneration of the nigrostriatal pathway, as observed in Parkinson's disease. A novel intrastriatal rotenone model of Parkinson's disease was used to examine the neuroprotective effects of chronic low-dose treatment with the antioxidant indoleamine, melatonin, which can upregulate neurotrophic factors and other protective proteins in the brain. Sham or lesioned rats were treated with either vehicle (0.04% ethanol in drinking water) or melatonin at a dose of 4 µg/mL in drinking water. The right striatum was lesioned by stereotactic injection of rotenone at three sites (4 μg/site) along its rostrocaudal axis. Apomorphine administration to lesioned animals resulted in a significant (p<0.001) increase in ipsilateral rotations, which was suppressed by melatonin. Nine weeks post-surgery, animals were sacrificed by transcardial perfusion. Subsequent immunohistochemical examination revealed a decrease in tyrosine hydroxylase immunoreactivity within the striatum and substantia nigra of rotenone-lesioned animals. Melatonin treatment attenuated the decrease in tyrosine hydroxylase in the striatum and abolished it in the substantia nigra. Stereological cell counts indicated a significant (p<0.05) decrease in dopamine neurons in the substantia nigra of rotenone-lesioned animals, which was confirmed by Nissl staining. Importantly, chronic melatonin treatment blocked the loss of dopamine neurons in rotenone-lesioned animals. These findings strongly support the therapeutic potential of long-term and low-dose melatonin treatment in Parkinson's disease.

Melatonin prevents oxidative damage induced by maternal ethanol administration and reduces homocysteine in the cerebellum of rat pups

Chronic alcoholism leads to elevated plasma and brain homocysteine (Hcy) levels, as demonstrated by animal experiments. This study was designed to evaluate the alterations in offspring rat cerebellum following increase of plasma Hcy level induced by maternal exposure to ethanol and to investigate the possible protective role of melatonin administration upon cerebellar ethanol-induced neurotoxicity. The adult female rats were divided randomly into 4 groups, including one control and three experimental groups, after vaginal plagues. Group I received normal saline, group II received ethanol (4 g/kg), group III received ethanol+melatonin (10mg/kg) and group IV received melatonin on day 6 of gestation until weaning. 21 days after birth, plasma Hcy level, level of lipid peroxidation, the activities of several antioxidant enzymes including superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx), and levels of bcl-2 and bax mRNA expression in cerebellum were determined. Our results demonstrated that ethanol could induce lipid peroxidation, and decrease antioxidants activities and increase plasma total Hcy level. We also observed that ethanol impaired performance on the rotarod and locomotor activities of rats. However, treatment with melatonin significantly attenuated motoric impairment, the lipid peroxidation process and restored the levels of antioxidant activities and significantly reduced plasma total Hcy levels. Moreover, melatonin reduced bax/bcl-2 ratio in the presence of ethanol. We conclude that these results provide evidence that ethanol neurotoxicity in part is related to increase of plasma Hcy levels and melatonin with reducing of plasma Hcy level has neuroprotective effects against ethanol toxicity in cerebellum.