Melatonin prevents hydrogen peroxide-induced Bax expression in cultured rat astrocytes

Melatonin counteracts polyethylene microplastics induced adreno-cortical damage in male albino rats

There are various substances that can disrupt the homeostatic mechanisms of the body, defined as endocrine-disrupting chemicals (EDCs). The persistent nature of microplastics (MPs) is a cause for concern due to their ability to accumulate in food chains and widespread use, making their toxic effects particularly alarming. The potential of MPs for disrupting the endocrine system was observed in multiple tissues. Moreover, the adrenal gland is known to be extremely sensitive to EDCs, while with the effect of MPs on the adrenal gland has not previously been studied. This study aimed to highlight the potential polyethylene microplastics (PE-MPs) induced adreno-toxic effects rather than exploring the implicated mechanisms and concluding if melatonin (Mel) can afford protection against PE-MPs induced adreno-toxicity. To fulfill the goal, six groups of rats were used; control, Mel, PE-MPs (3.75 mg/kg), PE-MPs (15 mg/kg), PE-MPs (3.75 mg/kg) +Mel, and PE-MPs (15 mg/kg) +Mel. PE-MPs induced toxic changes in the adrenal cortex, which was evident by increased adrenal weight, histopathological examination, and ultrastructural changes detected by electron microscope. A reduction in serum cortisol and an increase in serum adrenocorticotropic hormone resulted from the adreno-toxic effects of PE-MPs. Mechanisms may include the reduction of steroidogenesis-related genes, as PE-MPs drastically reduce mRNA levels of StAR, Nr0b1, Cyp11A1, as well as Cyp11B1. Also, oxidative stress that results from PE-MPs is associated with higher rates of lipid peroxidation and decreased superoxide dismutase and glutathione. PE-MPs inflammatory effect was illustrated by elevated expression of IL-1β and NF-ķB, detected by immunohistochemical staining, in addition to increased expression of caspase-3 and mRNA of Bax, markers of proapoptotic activity. The impacts of PE-MPs were relatively dose-related, with the higher dose showing more significant toxicity than the lower one. Mel treatment was associated with a substantial amelioration of PE-MPs-induced toxic changes. Collectively, this study fills the knowledge gap about the MPs-induced adrenal cortex and elucidates various related toxic mechanisms. It also supports Mel's potential protective activity through antioxidant, anti-inflammatory, anti-apoptotic, and gene transcription regulatory effects.

COA-Cl Evokes Protective Responses Against H2O2-and 6-OHDA-Induced Toxic Injury in PC12 Cells

COA-Cl, a novel adenosine-like nucleic acid analog, has recently been shown to exert neuroprotective effects and to increase dopamine levels both in vivo and in vitro. Therefore, we hypothesized that COA-Cl could protect dopaminergic neurons against toxic insults. Thus, the present study aimed to investigate the protective effects of COA-Cl against hydrogen peroxide (H₂O₂)- and 6-hydroxydopamine (6-OHDA)-induced toxicity in PC12 cells and to elucidate the possible mechanisms. PC12 cells were incubated with COA-Cl (100 μM) with or without H₂O₂ or 6-OHDA (200 μM) for 24 h. Treatment with COA-Cl attenuated the decrease in cell viability, SOD activity and the Bcl-2/Bax ratio caused by H₂O₂. In addition, COA-Cl attenuated the increase in LDH release, ROS production, caspase-3 activity, and apoptosis induced by H₂O₂. Further, COA-Cl enhanced the protection of PC12 cells against the toxicity caused by 6-OHDA, as evidenced by an increase in cell viability and the Bcl-2/Bax ratio, and a decrease in LDH release. Our results are the first to demonstrate that COA-Cl potentially protects PC12 cells against toxicity induced by H₂O₂ and 6-OHDA, implying that COA-Cl could be a promising neuroprotective agent for the treatment of Parkinson's disease.

Melatonin and its mechanism of action in the female reproductive system and related malignancies

Melatonin (N-acetyl-5-methoxytryptamine), the main product of pineal gland in vertebrates, is well known for its multifunctional role which has great influences on the reproductive system. Recent studies documented that melatonin is a powerful free radical scavenger that affects the reproductive system function and female infertility by MT1 and MT2 receptors. Furthermore, cancer researches indicate the influence of melatonin on the modulation of tumor cell signaling pathways resulting in growth inhibitor of the both in vivo/in vitro models. Cancer adjuvant therapy can also benefit from melatonin through therapeutic impact and decreasing the side effects of radiation and chemotherapy. This article reviews the scientific evidence about the influence of melatonin and its mechanism of action on the fertility potential, physiological alteration, and anticancer efficacy, during experimental and clinical studies.

Melatonin Improves Endoplasmic Reticulum Stress-Mediated IRE1α Pathway in Zücker Diabetic Fatty Rat

Obesity and diabetes are linked to an increased prevalence of kidney disease. Endoplasmic reticulum stress has recently gained growing importance in the pathogenesis of obesity and diabetes-related kidney disease. Melatonin, is an important anti-obesogenic natural bioactive compound. Previously, our research group showed that the renoprotective effect of melatonin administration was associated with restoring mitochondrial fission/fusion balance and function in a rat model of diabesity-induced kidney injury. This study was carried out to further investigate whether melatonin could suppress renal endoplasmic reticulum (ER) stress response and the downstream unfolded protein response activation under obese and diabetic conditions. Zücker diabetic fatty (ZDF) rats and lean littermates (ZL) were orally supplemented either with melatonin (10 mg/kg body weight (BW)/day) (M-ZDF and M-ZL) or vehicle (C-ZDF and C-ZL) for 17 weeks. Western blot analysis of ER stress-related markers and renal morphology were assessed. Compared to C-ZL rats, higher ER stress response associated with impaired renal morphology was observed in C-ZDF rats. Melatonin supplementation alleviated renal ER stress response in ZDF rats, by decreasing glucose-regulated protein 78 (GRP78), phosphoinositol-requiring enzyme1α (IRE1α), and ATF6 levels but had no effect on phospho-protein kinase RNA-like endoplasmic reticulum kinase (PERK) level. In addition, melatonin supplementation also restrained the ER stress-mediated apoptotic pathway, as indicated by decreased pro-apoptotic proteins phospho-c-jun amino terminal kinase (JNK), Bax, and cleaved caspase-3, as well as by upregulation of B cell lymphoma (Bcl)-2 protein. These improvements were associated with renal structural recovery. Taken together, our findings revealed that melatonin play a renoprotective role, at least in part, by suppressing ER stress and related pro-apoptotic IRE1α/JNK signaling pathway.

Seasonality and photoperiod influence in vitro production of buffalo embryos

Buffalo is considered short-day breeder in tropical and subtropical part of the world and seasonality and photoperiodism impart major influence on its fertility. However, its impact on in vitro embryo production (IVEP) remains elusive. Therefore, this study investigated the effect of seasonal variations and photoperiodism on morphological and molecular parameters of IVEP in buffalo. For this purpose, we conducted two different experiments on the oocytes obtained by aspirating follicles from abattoir derived ovaries. In Exp. I, retrospective analysis was performed for oocyte recovery, blastocyst and hatching rate, during four consecutive seasonal periods (i.e. January-March, April-June, July-September and October-December). In Exp. II, oocytes from peak breeding and non-breeding seasons were subjected to 24 hr in vitro maturation and evaluated for polar body extrusion to assess maturation rate. Results showed that embryo development was markedly low during second quarter (April-June) and maximum during fourth quarter (October-December) of the year; referred as non-breeding and breeding seasons, respectively. Comparative data analysis demonstrated that poor oocyte quality is major reason for lesser efficiency of embryo production during non-breeding season than peak breeding season as suggested by poor oocyte recovery (2.31 ± 0.10 vs. 3.65 ± 0.27) and maturation rate (33.32 ± 2.1 vs. 63.15 ± 7.31). Subsequently, comparative gene expression analysis of blastocysts during peak breeding season significantly upregulated pluripotency gene (OCT-4) and downregulated heat shock protein 90, as compared to non-breeding season. Therefore, it could be divulged from the present study that seasonal variations and photoperiodism have profound effect on oocyte quality and subsequent embryo development. It is recommended to find suitable additives for in vitro maturation that could mitigate seasonal effects.

Carvone protects against paclitaxel-induced retinal and optic nerve cytotoxicity: a histopathological study

Purpose: Carvone (CVN) is a natural monoterpene found in essential oils of many aromatic plant species. In this study, we investigated the protective effect of CVN against paclitaxel (PTX)-induced retinal and optic nerve cytotoxicity in rats. Methods: Twenty-four male adult Wistar albino rats (250-400 g) were randomized into four equal groups comprising six animals in each. Group 1 (control group) received intraperitoneal (i.p.) saline solution (0.5 mL/200 g) weekly for 4 weeks. Group 2 received i.p. CVN [(S)-(+)- CVN, (5S)-5-Isopropenyl-2-methyl-2-cyclohexen-1-one, C₁₀H₁₄, 25 mg/kg], while Group 3 received i.p. PTX (5 mg/kg) weekly for 4 weeks. Group 4 received i.p. CVN (25 mg/kg) 30 min after i.p. PTX (5 mg/kg) weekly for 4 weeks. At the end of the experimental period, retinal and optic nerve tissues were evaluated histopathologically. Results: All retinal specimens in control and CVN groups were histopathologically normal. In PTX group all eyes (6/6) demonstrated increased retinal vascularity and rosette-like structures in the outer nuclear layer, while in PTX-CVN group all eyes (6/6) demonstrated normal retinal vascularity and absence of rosette-like structures. All optic nerve specimens in control and CVN groups were histopathologically normal. In PTX group all eyes (6/6) demonstrated severe vacuolization and decrease in the number of astrocytes and oligodendrocytes, while 3 eyes (3/6) demonstrated marked single cell necrosis. In PTX-CVN group, 4 eyes (4/6) demonstrated moderate vacuolization while, 2 eyes (2/6) had none. Compared with PTX group, 1 eye (1/6) in PTX-CVN group demonstrated a decrease in numbers of astrocytes and oligodendrocytes while 5 eyes (5/6) were normal. No remarkable single cell necrosis was observed in PTX-CVN group. Conclusions: Our histopathological findings demonstrated the potential protective role of CVN against PTX-induced retinal and optic nerve cytotoxicity. CVN might be a promising molecule in counteracting oxidative stress-based cytotoxicity in the field of retinal and optic nerve disorders.

Melatonin-induced demethylation of antioxidant genes increases antioxidant capacity through RORα in cumulus cells of prepubertal lambs

Physical damage and oxidative stress may occur in prepubertal cumulus cells, due to insufficient glutathione synthesis. To determine potential epigenetic mechanisms related to antioxidant effects of melatonin on ovine prepubertal cumulus cells, 30 lambs, 4-wk-old were randomly allocated into two groups: a control (C, n = 20) group and a melatonin (M, n = 10) group given a subcutaneous implant containing 18 mg melatonin. All lambs were superovulated (250 IU FSH and 250 IU eCG). Cumulus cells from germinal vesicle stage cumulus oocyte complexes (COCs) were collected by ovarian follicular aspiration and dissociated with hyaluronidase. Compared to the C group, the M group had greater superovulation, better antioxidant capacity, a higher proportion of fully expanded COCs and a lower proportion of apoptotic cumulus cells (P < 0.05). Melatonin up-regulated mRNA expression of genes for melatonin receptors MT1 and nuclear binding site RORα, antioxidants (SOD1, GPx4 and CAT) and cumulus cell expansion (PTX3, HAS2 and PTGS2), as well as Bcl2, but down-regulated expression of Bax (P < 0.05). Regarding epigenetics, there were less methylation at five CpG sites of SOD1, three CpG sites of GPx4 and two CpG sites of CAT in M versus C groups (P <  0.05), leading to lower total methylation of SOD1, GPx4 and CAT promoters region on M group (P < 0.05). In a mechanistic study, addition of MT1 or RORα antagonist increased ROS and MDA concentrations, but decreased T-AOC, GPx, CAT and T-SOD concentrations (P < 0.05), whereas there were no significant difference between the melatonin and MT2 antagonist treatment groups for T-AOC, GPx, CAT and T-SOD concentrations. Furthermore, addition of RORα agonist decreased total DNA methylation of SOD1, GPx4 and CAT, with no significant difference after MT1 agonist treatment. These studies provided new information regarding epigenetic mechanisms by which melatonin promoted ovine prepubertal cumulus cells antioxidant through RORα, both in vitro and in vivo.

Regulation effects of melatonin on bone marrow mesenchymal stem cell differentiation

Melatonin's therapeutic potential has been highly underestimated because its biological functional roles are diverse and relevant mechanisms are complicated. Among the numerous biological activities of melatonin, its regulatory effects on pluripotent mesenchymal stem cells (MSCs), which are found in bone marrow stem cells (BMSCs) and adipose tissue (AD-MSC), have been recently proposed, which has received increasingly more attention in recent studies. Moreover, receptor-dependent and receptor-independent responses to melatonin are identified to occur in these cells by regulating signaling pathways, which drive the commitment and differentiation of MSCs into osteogenic, chondrogenic, or adipogenic lineages. Therefore, the aim of our current review is to summarize the evidence related to the utility of melatonin as a regulatory agent by focusing on its relationship with the differentiation of MSCs. In particular, we aimed to review its roles in promoting osteogenic and chondrogenic differentiation and the relevant signaling cascades involved. Also, the roles that melatonin and, particularly, its receptors play in these processes are highlighted.

Inhibition of NF-κB signaling pathway by astaxanthin supplementation for prevention of heat stress-induced inflammatory changes and apoptosis in Karan Fries heifers

Present study was conducted on 12 Karan Fries (Holstein Friesian X Tharparkar) heifers (10-12 months) to assess the effect of astaxanthin supplementation on heat stress amelioration and inhibition of NF-κB signaling pathway for prevention of heat stress-induced inflammatory changes and apoptosis in the cell during the summer season. The heifers were randomly and equally divided into two groups, i.e., control (fed as per ICAR 2013) and treatment groups (additionally supplemented astaxanthin at a dose rate of 0.25 mg/kg BW/day/animal). Temperature humidity index used to assess the levels of summer stress during the experimental period. Blood samples were collected at the fortnightly interval for quantification of plasma cortisol and IL-12 from both the groups of the heifers and from collected blood samples, RNA was isolated and transcribed into cDNA for real time PCR, for genes expression of NF-κB, IL-2, caspase-3, and Bcl-2. Plasma cortisol, IL-12 levels, and expression pattern of NF-κB, IL-2, and caspase-3 were significantly (P ≤ 0.05) lower in treatment group of Karan Fries heifers than control group, whereas, Bcl-2 was higher (P ≤ 0.05) in astaxanthin supplemented group. The temperature humidity index had a positive correlation (P ≤ 0.05) with plasma cortisol and IL-12 and expression pattern of NF-κB, IL-2, and caspase-3. However, it was negatively correlated with Bcl-2. The supplementation of astaxanthin can ameliorate the impact of summer stress through NF-κB downregulation, might be due to the quenching of free radicals, which regulates the expression of pro-inflammatory mediators and apoptotic genes.

Melatonin-Mediated Development of Ovine Cumulus Cells, Perhaps by Regulation of DNA Methylation

Cumulus cells of pre-pubertal domestic animals are dysfunctional, perhaps due to age-specific epigenetic events. This study was designed to determine effects of melatonin treatment of donors on methylation modification of pre-pubertal cumulus cells. Cumulus cells from germinal vesicle stage cumulus oocyte complexes (COCs) were collected from eighteen lambs which were randomly divided into control group (C) and melatonin group given an 18 mg melatonin implant subcutaneous (M). Compared to the C group, the M group had higher concentrations of melatonin in plasma and follicular fluid (p < 0.05), greater superovulation, a higher proportion of fully expanded COCs, and a lower proportion of apoptotic cumulus cells (p < 0.05). Real-time PCR results showed that melatonin up-regulated expression of genes MT1, Bcl2, DNMT1, DNMT3a and DNMT3b, but down-regulated expression of genes p53, Caspase 3 and Bax (p < 0.05). Furthermore, melatonin increased FI of FITC (global methylation level) on cumulus cells (p < 0.05). To understand the regulation mechanism, the DNMTs promoter methylation sequence were analyzed. Compared to the C group, although there was less methylation at two CpG sites of DNMT1 (p < 0.05) and higher methylation at two CpG sites of DNMT3a (p < 0.05), there were no significant differences in methylation of the detected DNMT1 and DNMT3a promoter regions. However, there were lower methylation levels at five CpG sites of DNMT3b, which decreased methylation of detected DNMT3b promoter region on M group (p < 0.05). In conclusion, alterations of methylation regulated by melatonin may mediate development of cumulus cells in lambs.

The effects of melatonin on bovine uniparental embryos development in vitro and the hormone secretion of COCs

Melatonin is a unique multifunctional molecule that mediates reproductive functions in animals. In this study, we investigated the effects of melatonin on bovine parthenogenetic and androgenetic embryonic development, oocyte maturation, the reactive oxygen species (ROS) levels in parthenogenetic and androgenetic embryos and cumulus—oocyte complexes (COCs) hormone secretion with melatonin supplementation at four concentrations (0, 10, 20, and 30 pmol/mL), respectively. The results showed that melatonin significantly promoted the rates of bovine parthenogenetic and androgenetic embryonic cleavage and morula and blastocysts development (P < 0.05). The rate of cleavage was higher in the androgenetic embryo than that in the parthenogenetic embryo. Compared with the parthenogenetic embryos, the androgenetic embryos had a poor developmental competence from morula to blastocyst stage. Moreover, the levels of ROS were significantly lower in the parthenogenetic and androgenetic embryoes with melatonin-treated group than that of the control group (P < 0.05). Melatonin supplemented significantly increased the maturation rate of oocyte in vitro (P < 0.05). More importantly, melatonin significantly promoted the secretion of progesterone and estradiol by COCs (P < 0.05). To reveal the regulatory mechanism of melatonin on steroids synthesis, we found that steroidogenic genes (CYP11A1, CYP19A1 and StAR) were upregulated, suggesting that melatonin regulated estradiol and progesterone secretion through mediating the expression of steroidogenic genes (CYP11A1, CYP19A1 and StAR). In addition, MT1 and MT2 were identified in bovine early parthenogenetic and androgenetic embryos using western blot. It could be concluded that melatonin had beneficial effects on bovine oocyte in vitro maturation, COC hormone secretion, early development of subsequent parthenogenetic and androgenetic embryos. It is inferred that melatonin could be used to enhance the efficiency of in vitro developed embryos.

Behavior of Human Osteoblast Cells Cultured on Titanium Discs in Relation to Surface Roughness and Presence of Melatonin

The aim of this work was to observe the behavior of osteoblast cells cultured in vitro on titanium discs in relation to disc surface roughness and the addition of melatonin to the culture medium. MG63 osteoblast cells were cultivated on 120 Grade 5 Ti divided into three groups: Group E, treated with dual acid etch; Group EP, treated with dual acid etch and calcium phosphate; and Group M, machined. Surface roughness was examined under a laser scanning confocal microscope (CLSM) and scanning electron microscopy (SEM). The proliferation and morphology of cells were determined under fluorescence microscopy and SEM. Messenger ribonucleic acid (mRNA) of different genes related to osteoblastic differentiation was quantified by means of real-time quantitative polymerase chain reaction (RT-PCR) assay. The greatest surface roughness was found in Group EP (Ra 0.354 µm), followed by Group E (Ra 0.266 µm), and Group M (Ra 0.131 µm), with statistically significant differences between the groups (p < 0.001). In the presence of melatonin a trend to a higher cell proliferation was observed in all groups although significant differences were only found in Group M (p = 0.0079). Among the genes studied, a significant increase in phosphate-regulating neutral endopeptidase, X-linked (PHEX) expression was observed in cells cultured on EP discs. The addition of melatonin increased osteoblast cell proliferation and differentiation, and may favor the osseointegration of dental implants.

Protective mechanisms of melatonin against hydrogen-peroxide-induced toxicity in human bone-marrow-derived mesenchymal stem cells

Many obstacles compromise the efficacy of bone marrow mesenchymal stem cells (BM-MSCs) by inducing apoptosis in the grafted BM-MSCs. The current study investigates the effect of melatonin on important mediators involved in survival of BM-MSCs in hydrogen peroxide (H₂O₂) apoptosis model. In brief, BM-MSCs were isolated, treated with melatonin, and then exposed to H₂O₂. Their viability was assessed by MTT assay and apoptotic fractions were evaluated through Annexin V, Hoechst staining, and ADP/ATP ratio. Oxidative stress biomarkers including ROS, total antioxidant power (TAP), superoxide dismutase (SOD) and catalase (CAT) activity, glutathione (GSH), thiol molecules, and lipid peroxidation (LPO) levels were determined. Secretion of inflammatory cytokines (TNF-α and IL-6) were measured by ELISA assay. The protein expression of caspase-3, Bax, and Bcl-2, was also evaluated by Western blotting. Melatonin pretreatment significantly increased viability and decreased apoptotic fraction of H₂O₂-exposed BM-MSCs. Melatonin also decreased ROS generation, as well as increasing the activity of SOD and CAT enzymes and GSH content. Secretion of inflammatory cytokines in H₂O₂-exposed cells was also reduced by melatonin. Expression of caspase-3 and Bax proteins in H₂O₂-exposed cells was diminished by melatonin pretreatment. The findings suggest that melatonin may be an effective protective agent against H₂O₂-induced oxidative stress and apoptosis in MSC.

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.

LPA1 Mediates Antidepressant-Induced ERK1/2 Signaling and Protection from Oxidative Stress in Glial Cells

Antidepressants have been shown to affect glial cell functions and intracellular signaling through mechanisms that are still not completely understood. In the present study, we provide evidence that in glial cells the lysophosphatidic acid (LPA) receptor LPA₁ mediates antidepressant-induced growth factor receptor transactivation, ERK1/2 signaling, and protection from oxidative stress. Thus, in C6 glioma cells and rat cortical astrocytes, ERK1/2 activation induced by either amitriptyline or mianserin was antagonized by Ki16425 and VPC 12249 (S), which block LPA₁ and LPA₃ receptors, and by AM966, which selectively blocks LPA₁ Cell depletion of LPA₁ with siRNA treatment markedly reduced antidepressant- and LPA-induced ERK1/2 phosphorylation. LPA₁ blockade prevented antidepressant-induced phosphorylation of the transcription factors CREB and Elk-1. Antidepressants and LPA signaling to ERK1/2 was abrogated by cell treatment with pertussis toxin and by the inhibition of fibroblast growth factor (FGF) receptor (FGF-R) and platelet-derived growth factor receptor (PDGF-R) tyrosine kinases. Both Ki16425 and AM966 suppressed antidepressant-induced phosphorylation of FGF-R. Moreover, blockade of LPA₁ or inhibition of FGF-R and PDGF-R activities prevented antidepressant-stimulated Akt and GSK-3β phosphorylations. Mianserin protected C6 glioma cells and astrocytes from apoptotic cell death induced by H₂O₂, as indicated by increased cell viability, decreased expression of cleaved caspase 3, reduced cleavage of poly-ADP ribose polymerase and inhibition of DNA fragmentation. The protective effects of mianserin were antagonized by AM966. These data indicate that LPA₁ constitutes a novel molecular target of the regulatory actions of tricyclic and tetracyclic antidepressants in glial cells.

Effect of melatonin on maturation capacity and fertilization of Nili-Ravi buffalo (Bubalus bubalis) oocytes

This study evaluated the effect of melatonin supplementation of in vitro maturation media on in vitro maturation (IVM) and in vitro fertilization (IVF) rate of buffalo oocytes. Cumulus oocytes complexes (COCs) were aspirated from follicles of 2-8 mm diameter. In experiment I, COCs were matured in IVM medium supplemented with 0 (control), 250, 500, and 1000 μM melatonin for 22-24 hours in CO₂ incubator at 38.5°C with 5% CO₂ and at 95% relative humidity. The maturation rate did not differ in media supplemented with melatonin at 250 μM, 500 μM, 1000 μM and control (0 μM). In experiment II, the matured oocytes were fertilized in 50 μl droplets of Tyrode’s Albumin Lactate Pyruvate (TALP) medium having 10 ug/ml heparin for sperm (2 million/ml) capacitation. The fertilization droplets were then kept for incubation at 5% CO₂, 39°C and at 95% relative humidity for 18 hours. The fertilization rate was assessed by sperm penetration and pronuclear formation. Fertilization rate was improved when maturation medium was supplemented with 250 μM melatonin compared to control. In conclusion, melatonin supplementation to serum free maturation media at 250 μM improved the fertilization rate of buffalo oocytes.

Melatonin alleviates hyperthyroidism induced oxidative stress and neuronal cell death in hippocampus of aged female golden hamster, Mesocricetus auratus

Oxidative stress is a well known phenomenon under hyperthyroid condition that induces various physiological and neural problems with a higher prevalence in females. We, therefore investigated the antioxidant potential of melatonin (Mel) on hyperthyroidism-induced oxidative stress and neuronal cell death in the hippocampus region of brain (cognition and memory centre) of aged female golden hamster, Mesocricetus auratus. Aged female hamsters were randomly divided into four experimental groups (n=7); group-I: control, group-II: Melatonin (5mgkg(-1)day(-1), i.p., for one week), group-III: Hyperthyroid (100μg kg(-1)day(-1), i.p., for two weeks) and group-IV- Hyper+Mel. Hormonal profiles (thyroid and melatonin), activity of antioxidant enzymes (SOD, CAT and GPX), lipid peroxidation level (TBARS) and the specific apoptotic markers (Bax/Bcl-2 ratio and Caspase-3) expression were evaluated. A significant increase in the profile of total thyroid hormone (tT3 and tT4) in hyperthyroidic group as compared to control while tT3 significantly decreased in melatonin treated hyperthyroidic group. However, Mel level significantly decreased in hyperthyroidic group but increased in melatonin treated hyperthyroidic group. Further, the number of immune-positive cells for thyroid hormone receptor-alpha (TR-α) decreased in the hippocampus of hyperthyroidic group and increased in melatonin treated hyperthyroidic group. Profiles of antioxidant enzymes showed a significant decrease in hyperthyroidic group with a simultaneous increase in lipid peroxidation (TBARS). Melatonin treatment to hyperthyroidic group lead to decreased TBARS level with a concomitant increase in antioxidant enzyme activity. Moreover, increased expression of Bax/Bcl-2 ratio and Caspase-3, in hyperthyroidic group had elevated neuronal cell death in hippocampal area and melatonin treatment reduced its expression in hyperthyroidic group. Our findings thus indicate that melatonin reduced the hyperthyroidism-induced oxidative stress and neuronal cell death in the hippocampus region of brain, suggesting a novel therapeutic approach of melatonin for management of cognition and memory function in females under hyperthyroid condition.

The Incremental Induction of Neuroprotective Properties by Multiple Therapeutic Strategies for Primary and Secondary Neural Injury

Neural diseases including injury by endogenous factors, traumatic brain injury, and degenerative neural injury are eventually due to reactive oxygen species (ROS). Thus ROS generation in neural tissues is a hallmark feature of numerous forms of neural diseases. Neural degeneration and the neural damage process is complex, involving a vast array of tissue structure, transcriptional/translational, electrochemical, metabolic, and functional events within the intact neighbors surrounding injured neural tissues. During aging, multiple changes involving physical, chemical, and biochemical processes occur from the molecular to the morphological levels in neural tissues. Among many recommended therapeutic candidates, melatonin also plays a role in protecting the nervous system from anti-inflammation and efficiently safeguards neuronal cells via antioxidants and other endogenous/exogenous beneficial factors. Therefore, given the wide range of mechanisms responsible for neuronal damage, multi-action drugs or therapies for the treatment of neural injury that make use of two or more agents and target several pathways may have greater efficacy in promoting functional recovery than a single therapy alone.

The Keap1-Nrf2-antioxidant response element pathway: a review of its regulation by melatonin and the proteasome

Both melatonin and proteasome inhibitors upregulate antioxidant enzymes including superoxide dismutase (SOD), glutathione peroxidase (GP), hemoxygenase 1 (HO-1), and NADPH:quinone oxidoreductase (NQO1). Recent evidence suggests that the antioxidant action of both melatonin and proteasome inhibitors involves the Keap1-ARE (Keap1 antioxidant response element) pathway via the upregulation of Nrf2. Melatonin and proteasome inhibitors suppress the degradation of Nrf2 and also enhance its nuclear translocation. In the nucleus Nrf2, together with a cofactor, stimulates the transcription of antioxidant enzymes and detoxifying enzymes. The ligase (E3) complex (Keap1-Cul3-Rbx1) responsible for ubiquitinating Nrf2, prior to proteasomal degradation, also ubiquitinates IkB kinase and the antiapoptotic factor Bcl-2, and possibly additional proteins. In various systems, NF-κB, which is inhibited by IkBα, is downregulated by proteasome inhibitors as well as by melatonin. Similarly in leukemic cells, Bcl-2 is down-regulated by the proteasome inhibitor, bortezomib, and also by melatonin. Thus melatonin administration modulates the activity of three separate substrates of the Keap1-Cul3-Rbx1 ubiquitin ligase. These facts could be accounted for by the hypothesis that melatonin interacts with the ubiquitin ligase complex or, more likely, by the hypothesis that melatonin acts as a proteasome inhibitor. A recent study documented that melatonin acts as a proteasome inhibitor in cancer cells as well as inhibiting chymotrypsin-like activity in cell-free systems of these cells. Further studies, however, are needed to clarify the interaction of melatonin and the ubiquitin-proteasome system as they relate to oxidative stress.

Melatonin attenuates intermittent hypoxia-induced lipid peroxidation and local inflammation in rat adrenal medulla

Chronic intermittent hypoxia (CIH) induces lipid peroxidation and leads to cardiovascular dysfunction, in which impaired activities of the adrenal medulla are involved. This may be caused by CIH-induced injury in the adrenal medulla, for which the mechanism is currently undefined. We tested the hypothesis that melatonin ameliorates the CIH-induced lipid peroxidation, local inflammation and cellular injury in rat adrenal medulla. Adult Sprague–Dawley rats were exposed to air (normoxic control) or hypoxia mimicking a severe recurrent sleep apnoeic condition for 14 days. The injection of melatonin (10 mg/kg) or vehicle was given before the daily hypoxic treatment. We found that levels of malondialdehyde and nitrotyrosine were significantly increased in the vehicle-treated hypoxic group, when compared with the normoxic control or hypoxic group treated with melatonin. Also, the protein levels of antioxidant enzymes (superoxide dismutase (SOD)-1 and SOD-2) were significantly lowered in the hypoxic group treated with vehicle but not in the melatonin group. In addition, the level of macrophage infiltration and the expression of inflammatory cytokines (tumor necrosis factor (TNF)-α, interleukin (IL)-1β and IL-6) and mediators (inducible nitric oxide synthase (iNOS), cyclooxygenase-2 (COX-2)) were elevated in the vehicle-treated hypoxic group, but were significantly ameliorated by the melatonin treatment. Moreover, the amount of apoptotic cells in the hypoxic groups was significantly less in the melatonin-treated group. In conclusion, CIH-induced lipid peroxidation causes local inflammation and cellular injury in the adrenal medulla. The antioxidant and anti-inflammatory actions of melatonin are indicative of a protective agent against adrenal damage in patients with severe obstructive sleep apnea syndrome.

Age dependent nitro-oxidative load and melatonin receptor expression in the spleen and immunity of goat Capra hircus

The decline in the plasma level of melatonin has been associated with increased oxidative stress in the physiological system while aging. The increased levels of oxidants are known to augment the nitro-oxidative stress, which induces the apoptotic factors in lymphoid organs leading to age dependent immunosenescence. There are no reports to date that can suggest how the age dependent nitro-oxidative stress can influence the melatonin membrane MT1/MT2R expression and immune status of any small ruminant. In the present study, we noted the expression of melatonin receptors MT1R and MT2R and inducible nitric oxide synthase (iNOS) along with the apoptotic markers (viz. Bcl-2, Bax and Pro-caspase-3) in the spleen of young, middle-aged and old-aged Indian goat Capra hircus. The lymphocyte proliferation was also recorded along with the total nitrite and nitrate ion concentration (NOx) in the spleen and plasma. An age dependent decline in MT1R and MT2R expressions and lymphocyte proliferation with increased level of reactive nitrogen species (RNS) and iNOS expression was noted. An increased Bax/Bcl-2 ratio and a decreased Pro-caspase-3 expression were observed in the spleen of goat with an age dependent decline in the peripheral melatonin level. This decline in melatonin along with reduced melatonin receptor (MT1/MT2) expression and elevated RNS level in the spleen with aging might have an important role in the regulation of immune function of goats. Our observations suggest that the age-associated immunosenescence observed in goats can be a consequence of declining melatonin and its receptor expression and induction of apoptotic factors influenced by the increased RNS level that deteriorates the proper functioning of the spleen.

Melatonin and amfenac modulate calcium entry, apoptosis, and oxidative stress in ARPE-19 cell culture exposed to blue light irradiation (405 nm)

PURPOSE

Under conditions of oxidative stress, cell apoptosis is triggered through the mitochondrial intrinsic pathway. Increased levels of reactive oxygen species (ROS) are linked to excess cell loss and mediate the initiation of apoptosis in a diverse range of cell types. The aims of this study were to assess intracellular Ca(2+) release, ROS production, and caspase-3, and -9 activation in ARPE-19 cells during the blue light-mediated cell death, and to examine a potential protective effect of melatonin and amfenac, in the apoptotic cascade.

METHODS

ARPE-19 cells were cultured in their medium. First, MTT tests were performed to determine the protective effects of amfenac and melatonin. Cells were then exposed to blue light irradiation in an incubator. Intracellular Ca(2+) release experiments, mitochondrial membrane depolarization, apoptosis assay, glutathione (GSH), glutathione peroxidase (GSH-Px), and ROS experiments were done according to the method stated in the Materials and methods section.

RESULTS

Cell death was clearly associated with increased levels of ROS production, as measured by 2',7'-dichlorofluorescein fluorescence, and associated increase in Ca(2+) levels, as measured by Fura-2-AM. Blue light-induced cell death was associated with an increased level of caspase-3 and 9, suggesting mediation via the apoptotic pathway. Cell death was also associated with mitochondrial depolarization. Melatonin was shown to delay these three steps.

CONCLUSION

Melatonin, amfenac, and their combination protect ARPE-19 cells against blue light-triggered ROS accumulation and caspase-3 and -9 activation. The antiapoptotic effect of melatonin and amfenac at doses inhibiting caspase synthesis modified Ca(2+) release and prevented excessive ROS production, suggesting a new therapeutic approach to age-related macular degeneration.

Melatonin modulates the expression of BCL-xl and improve the development of vitrified embryos obtained by IVF in mice

PURPOSE

Antioxidant and anti-apoptotic effects of melatonin on development of in vitro fertilization (IVF)/vitrified two-cell mouse embryos were evaluated in this study.

METHODS

The IVF two-cell embryos were vitrified by cryotop, and were cultured in KSOM medium in different concentrations of melatonin (10(-6), 10(-9), 10(-12) M) and without melatonin. The blastocyst cell number, apoptotic cells and glutathione (GSH) level were evaluated by differential, TUNEL and cell tracker blue staining, respectively. The expression of Bax and Bcl-xl genes was evaluated by qPCR. The expression of melatonin receptors (Mtnr1a and Mtnr1b) in mouse 2-cell embryos and blastocysts was evaluated by RT-PCR.

RESULTS

Melatonin increased the rate of cleavage and blastulation at 10(-12) M concentration (p < 0.05). The number of trophectoderm and inner cell mass showed a significant increase (p < 0.05) in 10(-9) M melatonin. The 10(-9) M and 10(-12) M melatonin treatments significantly reduced (p < 0.05) the apoptotic index. The significant increase in the expression of Bcl-xl observed at 10(-9) M concentration however, reduced expression of Bax was not statistically significant. The levels of GSH in 10(-9) and 10(-12) M groups were significantly improved relative to the control group (p < 0.05). The Mtnr1a was expressed in 2-cell embryos and blastocysts in all groups, but the expression of Mntr1b was not detected.

CONCLUSION

Melatonin may have a special role against oxidative stress in protection of IVF/vitrified embryos.

Growth hormone and melatonin prevent age-related alteration in apoptosis processes in the dentate gyrus of male rats

It has been suggested that the age-related decrease in the number of neurons in the hippocampus that leads to alterations in brain function, may be associated with an increase in apoptosis due to the reduced secretion of growth hormone (GH) and/or melatonin in old animals. In order to investigate this possibility, male Wistar rats of 22 months of age were divided into three groups. One group remained untreated and acted as the control group. The second was treated with growth hormone (hGH) for 10 weeks (2 mg/kg/d sc) and the third was subjected to melatonin treatment (1 mg/kg/d) in the drinking water for the same time. A group of 2-months-old male rats was used as young controls. All rats were killed by decapitation at more than 24 month of age and dentate gyri of the hippocampi were collected. Aging in the dentate gyrus was associated with an increase in apoptosis promoting markers (Bax, Bad and AIF) and with the reduction of some anti-apoptotic ones (XIAP, NIAP, Mcl-1). Expressions of sirtuin 1 and 2 (SIRT1 and 2) as well as levels of HSP 70 were decreased in the dentate gyrus of old rats. GH treatment was able to reduce the pro/anti-apoptotic ratio to levels observed in young animals and also to increase SIRT2. Melatonin reduced also expression of pro-apoptotic genes and proteins (Bax, Bad and AIF), and increased levels of myeloid cell leukemia-1 proteins and SIRT1. Both treatments were able to reduce apoptosis and to enhance survival markers in this part of the hippocampus.

The octadecaneuropeptide ODN protects astrocytes against hydrogen peroxide-induced apoptosis via a PKA/MAPK-dependent mechanism

Astrocytes synthesize and release endozepines, a family of regulatory peptides, including the octadecaneuropeptide (ODN) an endogenous ligand of both central-type benzodiazepine (CBR) and metabotropic receptors. We have recently shown that ODN exerts a protective effect against hydrogen peroxide (H₂O₂)-induced oxidative stress in astrocytes. The purpose of the present study was to determine the type of receptor and the transduction pathways involved in the protective effect of ODN in cultured rat astrocytes. We have first observed a protective activity of ODN at very low concentrations that was abrogated by the metabotropic ODN receptor antagonist cyclo_1–8[DLeu⁵]OP, but not by the CBR antagonist flumazenil. We have also found that the metabotropic ODN receptor is positively coupled to adenylyl cyclase in astrocytes and that the glioprotective action of ODN upon H₂O₂-induced astrocyte death is PKA- and MEK-dependent, but PLC/PKC-independent. Downstream of PKA, ODN induced ERK phosphorylation, which in turn activated the expression of the anti-apoptotic gene Bcl-2 and blocked the stimulation by H₂O₂ of the pro-apoptotic gene Bax. The effect of ODN on the Bax/Bcl-2 balance contributed to abolish the deleterious action of H₂O₂ on mitochondrial membrane integrity and caspase-3 activation. Finally, the inhibitory effect of ODN on caspase-3 activity was shown to be PKA and MEK-dependent. In conclusion, the present results demonstrate that the potent glioprotective action of ODN against oxidative stress involves the metabotropic ODN receptor coupled to the PKA/ERK-kinase pathway to inhibit caspase-3 activation.

Differential transcriptional profiles mediated by exposure to the cannabinoids cannabidiol and Δ9-tetrahydrocannabinol in BV-2 microglial cells

BACKGROUND AND PURPOSE

Apart from their effects on mood and reward, cannabinoids exert beneficial actions such as neuroprotection and attenuation of inflammation. The immunosuppressive activity of cannabinoids has been well established. However, the underlying mechanisms are largely unknown. We previously showed that the psychoactive cannabinoid Δ(9) -tetrahydrocannabinol (THC) and the non-psychoactive cannabidiol (CBD) differ in their anti-inflammatory signalling pathways.

EXPERIMENTAL APPROACH

To characterize the transcriptional effects of CBD and THC, we treated BV-2 microglial cells with these compounds and performed comparative microarray analysis using the Illumina MouseRef-8 BeadChip platform. Ingenuity Pathway Analysis was performed to identify functional subsets of genes and networks regulated by CBD and/or THC.

KEY RESULTS

Overall, CBD altered the expression of many more genes; from the 1298 transcripts found to be differentially regulated by the treatments, 680 gene probe sets were up-regulated by CBD and 58 by THC, and 524 gene products were down-regulated by CBD and only 36 by THC. CBD-specific gene expression profile showed changes associated with oxidative stress and glutathione depletion, normally occurring under nutrient limiting conditions or proteasome inhibition and involving the GCN2/eIF2α/p8/ATF4/CHOP-TRIB3 pathway. Furthermore, CBD-stimulated genes were shown to be controlled by nuclear factors known to be involved in the regulation of stress response and inflammation, mainly via the (EpRE/ARE)-Nrf2/ATF4 system and the Nrf2/Hmox1 axis.

CONCLUSIONS AND IMPLICATIONS

These observations indicated that CBD, but much less than THC, induced a cellular stress response in microglial cells and suggested that this effect could underlie its anti-inflammatory activity.

LINKED ARTICLES

This article is part of a themed section on Cannabinoids in Biology and Medicine. To view the other articles in this section visit http://dx.doi.org/10.1111/bph.2012.165.issue-8. To view Part I of Cannabinoids in Biology and Medicine visit http://dx.doi.org/10.1111/bph.2011.163.issue-7.

Alzheimer's disease: pathological mechanisms and the beneficial role of melatonin

Alzheimer's disease (AD) is a highly complex neurodegenerative disorder of the aged that has multiple factors which contribute to its etiology in terms of initiation and progression. This review summarizes these diverse aspects of this form of dementia. Several hypotheses, often with overlapping features, have been formulated to explain this debilitating condition. Perhaps the best-known hypothesis to explain AD is that which involves the role of the accumulation of amyloid-β peptide in the brain. Other theories that have been invoked to explain AD and summarized in this review include the cholinergic hypothesis, the role of neuroinflammation, the calcium hypothesis, the insulin resistance hypothesis, and the association of AD with peroxidation of brain lipids. In addition to summarizing each of the theories that have been used to explain the structural neural changes and the pathophysiology of AD, the potential role of melatonin in influencing each of the theoretical processes involved is discussed. Melatonin is an endogenously produced and multifunctioning molecule that could theoretically intervene at any of a number of sites to abate the changes associated with the development of AD. Production of this indoleamine diminishes with increasing age, coincident with the onset of AD. In addition to its potent antioxidant and anti-inflammatory activities, melatonin has a multitude of other functions that could assist in explaining each of the hypotheses summarized above. The intent of this review is to stimulate interest in melatonin as a potentially useful agent in attenuating and/or delaying AD.

Exogenous melatonin modulates apoptosis in the mouse brain induced by high-LET carbon ion irradiation

The aim of this study was to investigate whether melatonin, a free radical scavenger and a general antioxidant, regulates the brain cell apoptosis caused by carbon ions in mice at the level of signal transduction pathway. Young Kun-Ming mice were divided into five groups: control group, irradiation group and three melatonin (1, 5, and 10 mg/kg daily for 5 days i.p.) plus irradiation-treated groups. An acute study was carried out to determine oxidative status, apoptotic cells, and mitochondrial membrane potential (ΔΨm) as well as pro- and anti-apoptotic protein levels in a mouse brain 12 hr after irradiation with a single dose of 4 Gy. In irradiated mice, a significant rise in oxidative stress and apoptosis (TUNEL positive) was accompanied by activated expression of Bax, cytochrome c, caspase-3, and decreased ΔΨm level. Melatonin supplementation was better able to reduce irradiation-induced oxidative damage marked by carbonyl or malondialdehyde content, and stimulate the antioxidant enzyme activities (superoxide dismutase and catalase) together with total antioxidant capacity. Moreover, administration with melatonin pronouncedly elevated the expression of Nrf2 which regulates redox balance and stress. Furthermore, melatonin treatment mitigated apoptotic rate, maintained ΔΨm, diminished cytochrome c release from mitochondria, down-regulated Bax/Bcl-2 ratio and caspase-3 levels, and consequently inhibited the important steps of irradiation-induced activation of mitochondrial pathway of apoptosis. Thus, we propose that the anti-apoptotic action with the alterations in apoptosis regulator provided by melatonin may be responsible at least in part for its antioxidant effect by the abolishing of carbon ion-induced oxidative stress along with increasing Nrf2 expression and antioxidant enzyme activity.

Melatonin is able to delay endoplasmic reticulum stress-induced apoptosis in leukocytes from elderly humans

The mechanisms regulating neutrophil apoptosis are basically unaffected by the aging process. However, a significant impairment of cell survival occurs in elderly individuals following neutrophil challenge with pro-inflammatory stimuli, such as granulocyte-macrophage colony-stimulating factor (GM-CSF). The goal of the present study was to prove the effects of melatonin supplementation on apoptosis induced by calcium signaling in human leukocytes from elderly volunteers. Treatments with the specific inhibitor of cytosolic calcium re-uptake, thapsigargin, and/or the calcium mobilizing agonist, N-formyl-methionyl-leucyl-phenylalanine (fMLP), induced mitochondrial membrane depolarization, caspase activation, phosphatidylserine (PS) externalization, and DNA fragmentation in leukocytes from both young and elderly volunteers, although such effects were much more evident in aged leukocytes. Importantly, melatonin treatment substantially preserved mitochondrial membrane potential, reversed caspase activation, reduced PS exposure and forestalled DNA fragmentation in leukocytes from both age groups. In conclusion, melatonin is able to delay endoplasmic reticulum stress-induced apoptosis in aged leukocytes and may counteract, at the cellular level, age-related degenerative phenomena linked to oxidative stress.

Effect of growth hormone and melatonin on the brain: from molecular mechanisms to structural changes

Aging of the brain causes important reductions in quality of life and has wide socio-economic consequences. An increase in oxidative stress, and the associated inflammation and apoptosis, could be responsible for the pathogenesis of aging associated brain lesions. Melatonin has neuroprotective effects, by limiting the negative effects of oxygen and nitrogen free radicals. Growth hormone (GH) might exert additional neuro-protective and or neurogenic effects on the brain. The molecular mechanisms of the protective effects of GH and melatonin on the aging brain have been investigated in young and old Wistar rats. A reduction in the total number of neurons in the hilus of the dentate gyrus was evident at 24 months of age and was associated with a significant increase in inflammation markers as well as in pro-apoptotic parameters, confirming the role of apoptosis in its reduction. Melatonin treatment was able to enhance neurogenesis in old rats without modification of the total number of neurons, whereas GH treatment increased the total number of neurons without enhancing neurogenesis. Both GH and melatonin were able to reduce inflammation and apoptosis in the hippocampus. In conclusion, neuroprotective effects demonstrated by GH and melatonin in the hippocampus were exerted by decreasing inflammation and apoptosis.

Protective effect of melatonin against human leukocyte apoptosis induced by intracellular calcium overload: relation with its antioxidant actions

Apoptosis or programmed cell death plays a critical role in both inflammatory and immune responses. Recent evidence demonstrates that control of leukocyte apoptosis is one of the most striking immune system-related roles of melatonin. For this reason, this study evaluated the protective effects of melatonin on human leukocyte apoptosis induced by sustained cytosolic calcium increases. Such protective effects are likely mediated by melatonin's free-radical scavenging actions. Treatments with the specific inhibitor of cytosolic calcium re-uptake, thapsigargin (TG), and/or the calcium-mobilizing agonist, N-formyl-methionyl-leucyl-phenylalanine (FMLP), induced intracellular reactive oxygen species (ROS) production, caspase activation as well as DNA fragmentation in human leukocytes. Also, TG- and/or FMLP-induced apoptosis was dependent on both cytosolic calcium increases and calcium uptake into mitochondria, because when cells were preincubated with the cytosolic calcium chelator, dimethyl BAPTA, and the inhibitor of mitochondrial calcium uptake, Ru360, TG- and FMLP-induced apoptosis was largely inhibited. Importantly, melatonin treatment substantially prevented intracellular ROS production, reversed caspase activation, and forestalled DNA fragmentation induced by TG and FMLP. Similar results were obtained by preincubating the cells with another well-known antioxidant, i.e., N-acetyl-L-cysteine. To sum up, depletion of intracellular calcium stores induced by TG and/or FMLP triggers different apoptotic events in human leukocytes that are dependent on calcium signaling. The protective effects resulting from melatonin administration on leukocyte apoptosis likely depend on melatonin's antioxidant action because we proved that this protection is melatonin receptor independent. These findings help to understand how melatonin controls apoptosis in cells of immune/inflammatory relevance.

Apoptotic effects of hydrogen peroxide and vitamin C on chicken embryonic fibroblasts: redox state and programmed cell death

The pro-apoptotic effects of hydrogen peroxide and the purported anti-apoptotic effects of Vitamin C on chicken embryonic fibroblasts were investigated. Hydrogen peroxide induced morphological changes in a dose dependent manner, and a myriad of autophagosomes were observed using transmission electron microscopy. Doxorubicin elicited alterations were not inhibited by co-incubation with Vitamin C except that mitochondrial structure was slightly improved. TUNEL assay, cytotoxicity analysis and flow cytometry revealed that the cytotoxicity, DNA fragmentation and apoptotic rates were dose dependent upon treatment with hydrogen peroxide. Calcium homeostasis was disrupted in a dose dependent manner, and cell cycle was blocked at G(2)/M checkpoint at low concentration and S/G(2) checkpoint at high concentration respectively upon treatment with hydrogen peroxide. The administration of Vitamin C only has a modest effect against doxorubicin induced apoptosis, calcium homeostasis disruption and cell cycle arrest. This research demonstrated that the elevation of reactive oxygen species is sufficient to induce the apoptosis of chicken embryonic fibroblasts, whereas the administration of Vitamin C does not necessarily have certain anti-apoptotic effects, especially when the stimulus is not directly linked with redox state.

Protective effects of melatonin against oxidative stress in flow cytometry-sorted buffalo sperm

Previous reports of the ability of melatonin to scavenge a variety of toxic oxygen and nitrogen-based reactants suggest that melatonin could be an effective antioxidant for protecting sperm. In this study, flow cytometry and laser tweezers Raman spectroscopy were used to evaluate the effect of melatonin on buffalo sperm quality to optimize sperm sex-sorting procedures. In fresh sperm incubated in the presence or absence of melatonin (10(-4)  m) for 1, 24, 48 h or 72 h at 27°C, the mitochondrial activity was significantly higher than in a non-melatonin control (p < 0.05). Also, during the flow-sorting process, sperm in melatonin-supplemented groups had higher (p < 0.05) mitochondrial activity than the control. The intensity of Raman spectra from sperm frozen in media supplemented with melatonin was significantly weaker than that for non-melatonin-treated groups, except for a band at 1302 per cm. Thus, melatonin helps to protect buffalo sperm from reactive oxygen species induced by staining, sorting and freezing and increases semen quality after the freezing-thawing processes. Furthermore, the results indicate the high potential of the laser tweezers Raman spectroscopy technique for rapid, effective and non-invasive assessment of the quality of sperm cells.

Melatonin enhances hydrogen peroxide-induced apoptosis in human promyelocytic leukaemia HL-60 cells

Melatonin is an indoleamine secreted by the pineal gland that shows multiple tasks. This ubiquitously acting free radical scavenger has recently been shown to stimulate the production of reactive oxygen species (ROS) in tumour cells, making them undergo apoptosis, whilst it prevents apoptosis in healthy cells. The mechanisms by which melatonin exerts these dual actions are, however, not yet clearly understood. Thus, the aim of this study was to further investigate how melatonin can enhance oxidative stress-induced apoptosis in a leukaemia cell line. The results show that melatonin increased the apoptotic effects of H(2)O(2) in human myeloid HL-60 cells as assessed by cellular viability, mitochondrial permeability transition induction, mitochondrial membrane depolarization, ROS generation, caspases 3, 8 and 9 activity, phosphatidylserine externalization, and DNA fragmentation techniques. When healthy leucocytes were exposed to H(2)O(2), melatonin increased the viability of the cells. Taken together, the findings indicate that melatonin is a potential physiological tool capable of protecting healthy cells from chemotherapy-induced ROS production as well as inducing tumour cell death. Because cancer cells manifest increased oxidative stress as a result of their elevated metabolism, the use of melatonin may be useful in impairing their ROS buffering capacity.

Inactivation of astrocytic glutamine synthetase by hydrogen peroxide requires iron

The specific activity of brain glutamine synthetase (GS) is lowered in several neurodegenerative diseases that involve iron-mediated oxidative stress. The present study has investigated whether H₂O₂ directly inactivates GS or whether GS is primarily inactivated by hydroxyl radicals that are produced by the Fenton reaction when H₂O₂ reacts with ferrous iron. Exposure of purified sheep brain GS to supraphysiological concentrations of H₂O₂ (1 mM for 30 min) reduced its specific activity by only 41%, indicating that the enzyme is fairly resistant to oxidation by peroxide. However, the enzyme was completely inactivated when co-incubated with H₂O₂, iron and ascorbate, indicating a vulnerability to oxidation by conditions that favour the production of hydroxyl radicals. Similarly, specific GS activity in cultured mouse astrocytes was resistant to supraphysiological concentrations of H₂O₂, with approximately 37% of activity remaining 3h after incubation with 1mM H₂O₂. This inactivation was prevented by the iron chelators 2,2'-dipyridyl or 1,10-phenanthroline, but not by their non-chelating analogues. These data suggest that inactivation of astrocytic GS is caused by H₂O₂ indirectly via the Fenton reaction as it required the presence of chelatable intracellular iron.

Melatonin: a pleiotropic molecule regulating inflammation

Melatonin is a neurohormone produced by the pineal gland that regulates sleep and circadian functions. Melatonin also regulates inflammatory and immune processes acting as both an activator and inhibitor of these responses. Melatonin demonstrates endocrine, but also paracrine and autocrine effects in the leukocyte compartment: on one side, leukocytes respond to melatonin in a circadian fashion; on the other side, leukocytes are able to synthesize melatonin by themselves. With its endocrine and paracrine effects, melatonin differentially modulates pro-inflammatory enzymes, controls production of inflammatory mediators such as cytokines and leukotrienes and regulates the lifespan of leukocytes by interfering with apoptotic processes. Moreover, its potent antioxidant ability allows scavenging of oxidative stress in the inflamed tissues. The interesting timing of pro- and anti-inflammatory effects, such as those affecting lipoxygenase activity, suggests that melatonin might promote early phases of inflammation on one hand and contribute to its attenuation on the other hand, in order to avoid complications of chronic inflammation. This review aims at giving a comprehensive overview of the various inflammatory pathways regulated by this pleiotropic hormone.

Melatonin as a modulator of apoptosis in B-lymphoma cells

Melatonin is considered a promising antitumor agent, promoting apoptosis in tumor cells and contrasting it in normal cells. The basis for this selectivity is presumed to be the ability of melatonin to stimulate reactive oxygen species (ROS) production in tumor cells. Here we investigate the effect of melatonin on three types of human lymphocytes: normal blood lymphocytes, BL41 Burkitt lymphoma, and the cognate Epstein-Barr virus (EBV)-converted E2r. We found that melatonin promotes ROS production in all these cells. Melatonin protects BL41 from apoptosis in the same manner as normal lymphocytes, whereas E2r are unaffected. These results show that ROS production is not limited to tumor lymphocytes nor it is involved in apoptosis promotion; that melatonin does not promote apoptosis in tumor lymphocytes, but EBV inhibits melatonin anti-apoptotic effects; and that the anti-apoptotic effect of melatonin does not depend on the well-known chemical antioxidant properties of melatonin.

Protective effect of augmenter of liver regeneration on hydrogen peroxide-induced apoptosis in SH-SY5Y human neuroblastoma cells

BACKGROUND

Hydrogen peroxide, as other reactive oxygen species (ROS) produced during redox processes, induces lipid membrane peroxidation and protein degeneration causing cell apoptosis. ROS are recently considered as messengers in cell signalling processes, which, through reversible protein disulphide bridges formation, activate regulatory factors of cell proliferation and apoptosis. Disulphide bridges formation is catalysed by sulphydryl oxidase enzymes.

AIM

The neuroprotective effect of ALR protein (Alrp), a sulphydryl oxidase enzyme, on H(2)O(2)-induced apoptosis in SH-SY5Y cells has been evaluated.

METHODS

Cell viability, flow cytometric evaluation of apoptotic cells, fluorescent changes of nuclear morphology, immunocytochemistry Alrp detection, Western blot evaluation of mitochondrial cyt c release and mitochondrial swelling were determined.

RESULTS

Alrp prevents the H(2)O(2)-induced cell viability loss, apoptotic cell death and mitochondrial swelling in SH-SY5Y cells in culture.

CONCLUSIONS

The data demonstrate that Alrp improves SH-SY5Y cells survival in H(2)O(2)-induced apoptosis. It is speculated that this effect could be related to the Alrp enzymatic activity.

Hydrogen peroxide induces the death of astrocytes through the down-regulation of the constitutive nuclear factor-kappaB activity

Nuclear factor-kappaB (NF-kappaB) has a dual role in the promotion or attenuation of cell death. Here, we demonstrated the role of NF-kappaB in the H(2)O(2)-induced death of astrocytes. H(2)O(2) evoked the release of lactate dehydrogenase (LDH), a marker of cell death, and concomitantly decreased the DNA binding and transcriptional activity of NF-kappaB in cultured astrocytes. H(2)O(2)-induced astrocyte death was markedly increased by the co-treatment with pyrrolidinedithiocarbamate, an NF-kappaB inhibitor. Moreover, the elevation of constitutive NF-kappaB activity by overexpressing p65 NF-kappaB subunit attenuated H(2)O(2) toxicity, whereas NF-kappaB inhibition by overexpressing IkappaB potentiated the toxicity. NF-kappaB activity and H(2)O(2) cytotoxicity was further found to be dependent on cell density. Compared with astrocytes in low cell density, those in high cell density exhibited a higher constitutive NF-kappaB activity and a stronger resistance to H(2)O(2) cytotoxicity. These results indicate that the constitutive activity of NF-kappaB in astrocytes is required for their survival under oxidative stress such as H(2)O(2).

Antioxidant neuroprotection against ethanol-induced apoptosis in HN2-5 cells

Earlier studies from this and other laboratories show that ethanol induces apoptotic death of fetal and neonatal neurons. One mechanism that underlies these effects is the ethanol-associated reduction in the phosphatidylinositol 3' kinase pro-survival pathway. Another mechanism involves the oxidative stress caused by the ethanol-associated increase in reactive oxygen species (ROS). In the present study, we used the murine HN2-5 hippocampal-derived cell line to investigate the effects of ethanol on ROS levels and apoptosis. We also investigated the potential neuroprotective effects of two structurally unrelated antioxidants: N-acetylcysteine (NAC) and melatonin. The results demonstrate that NAC blocked an ethanol-associated increase in ROS. In addition, NAC and melatonin prevented the augmentation of apoptosis in ethanol-treated neurons. Both antioxidants significantly elevated the expression of the anti-apoptotic gene XIAP in ethanol-treated and/or control neurons and melatonin increased Bcl-2 expression in ethanol-treated neurons. Thus, it is possible that the neuroprotective effects of NAC and melatonin involve their ability to augment the expression of one or more anti-apoptotic gene as well as their classical antioxidant actions. Additional studies are needed to establish the effectiveness of these antioxidants to prevent the loss of neurons which accompanies in utero exposure to ethanol.

Pineal melatonin acts as a circadian zeitgeber and growth factor in chick astrocytes

Melatonin is rhythmically synthesized and released by the avian pineal gland and retina during the night, targeting an array of tissues and affecting a variety of physiological and behavioral processes. Among these targets, astrocytes express two melatonin receptor subtypes in vitro, the Mel(1A) and Mel(1C) receptors, which play a role in regulating metabolic activity and calcium homeostasis in these cells. Molecular characterization of chick astrocytes has revealed the expression of orthologs of the mammalian clock genes including clock, cry1, cry2, per2, and per3. To test the hypothesis that pineal melatonin entrains molecular clockworks in downstream cells, we asked whether coculturing astrocytes with pinealocytes or administration of exogenous melatonin cycles would entrain metabolic rhythms of 2-deoxy [14C]-glucose (2DG] uptake and/or clock gene expression in cultured astrocytes. Rhythmic secretion of melatonin from light-entrained pinealocytes in coculture as well as cyclic administration of exogenous melatonin entrained rhythms of 2DG uptake and expression of Gallus per2 (gper2) and/or gper3, but not of gcry1 mRNA. Surprisingly, melatonin also caused a dose-dependent increase in mitotic activity of astrocytes, both in coculture and when administered exogenously. The observation that melatonin stimulates mitotic activity in diencephalic astrocytes suggests a trophic role of the hormone in brain development. The data suggest a dual role for melatonin in avian astrocytes: synchronization of rhythmic processes in these cells and regulation of growth and differentiation. These two processes may or may not be mutually exclusive.

Protective effects of melatonin against formaldehyde-induced oxidative damage and apoptosis in rat testes: an immunohistochemical and biochemical study

This study investigated the protective effects of melatonin against formaldehyde-induced oxidative damage and apoptosis in rat testes. A total of 21 male Wistar rats were divided into three groups. Group I was used as a control, Group II was injected every other day with formaldehyde for 1 month, whereas Group III was injected every other day with formaldehyde and melatonin for 1 month. At the end of the experimental period animals were sacrificed and the testes removed and dissected from the surrounding tissues for immunohistochemical evaluation. In addition, the levels of superoxide dismutase (SOD), glutathione peroxidase (GSH-Px), and malondialdehyde (MDA) were determined. The levels of SOD and GSH-Px decreased significantly, whereas the level of MDA significantly increased in animals treated with formaldehyde compared with the controls. Apoptosis of spermatogenetic and Leydig cells of testicular tissues was observed. In contrast, rats with melatonin SOD and GSH-Px enzyme activity increased whereas MDA levels decreased with formaldehyde exposure along with apoptosis. In view of the present findings, it is suggested that melatonin treatment may prevent formaldehyde-induced oxidative damage and apoptosis in rat testes.

Manganese activates the mitochondrial apoptotic pathway in rat astrocytes by modulating the expression of proteins of the Bcl-2 family

Manganese induces the central nervous system injury leading to manganism, by mechanisms not completely understood. Chronic exposure to manganese generates oxidative stress and induces the mitochondrial permeability transition. In the present study, we characterized apoptotic cell death mechanisms associated with manganese toxicity in rat cortical astrocytes and demonstrated that (i) Mn treatment targets the mitochondria and induces mitochondrial membrane depolarization followed by cytochrome c release to the cytoplasm, (ii) Mn induces both effector caspases 3/7 and 6 as well as PARP-1 cleavage and (iii) Mn shifts the balance of cell death/survival of Bcl-2 family proteins to favor the apoptotic demise of astrocytes. Our model system using cortical rat astrocytes treated with Mn would emerge as a good tool for investigations aimed to elucidate the role of apoptosis in manganism.

Melatonin antagonizes the intrinsic pathway of apoptosis via mitochondrial targeting of Bcl-2

We have recently shown that melatonin antagonizes damage-induced apoptosis by interaction with the MT-1/MT-2 plasma membrane receptors. Here, we show that melatonin interferes with the intrinsic pathway of apoptosis at the mitochondrial level. In response to an apoptogenic stimulus, melatonin allows mitochondrial translocation of the pro-apoptotic protein Bax, but it impairs its activation/dimerization The downstream apoptotic events, i.e. cytochrome c release, caspase 9 and 3 activation and nuclear vesiculation are equally impaired, indicating that melatonin interferes with Bax activation within mitochondria. Interestingly, we found that melatonin induces a strong re-localization of Bcl-2, the main Bax antagonist to mitochondria, suggesting that Bax activation may in fact be antagonized by Bcl-2 at the mitochondrial level. Indeed, we inhibit the melatonin anti-apoptotic effect (i) by silencing Bcl-2 with small interfering RNAs, or with small-molecular inhibitors targeted at the BH3 binding pocket in Bcl-2 (i.e. the one interacting with Bax); and (ii) by inhibiting melatonin-induced Bcl-2 mitochondrial re-localization with the MT1/MT2 receptor antagonist luzindole. This evidence provides a mechanism that may explain how melatonin through interaction with the MT1/MT2 receptors, elicits a pathway that interferes with the Bcl-2 family, thus modulating the cell life/death balance.

Antioxidants prevent ethanol-associated apoptosis in fetal rhombencephalic neurons

It is well known that ethanol damages the developing nervous system by augmenting apoptosis. Previously, this laboratory reported that ethanol augments apoptosis in fetal rhombencephalic neurons, and that the increased apoptosis is associated with reduced activity of the phosphatidylinositol 3-kinase pathway and downstream expression of pro-survival genes. Other laboratories have shown that another mechanism by which ethanol induces apoptosis in developing neurons is through the generation of reactive oxygen species (ROS) and the associated oxidative stress. The present study used an in vitro model to investigate the potential neuroprotective effects of several antioxidants against ethanol-associated apoptosis in fetal rhombencephalic neurons. The investigated antioxidants included three phenolics: (-)-epigallocatechin-3-gallate (EGCG), a flavanoid polyphenol found in green tea; curcumin, found in tumeric; and resveratrol (3,5,4'-trihydroxystilbene), a component of red wine. Additional antioxidants, including melatonin, a naturally occurring indole, and alpha-lipoic acid, a naturally occurring dithiol, were also investigated. These studies demonstrated that a 24-hour treatment of fetal rhombencephalic neurons with 75 mM ethanol caused a 3-fold increase in the percentage of apoptotic neurons. However, co-treatment of these cultures with any of the five different antioxidants prevented ethanol-associated apoptosis. Antioxidant treatment did not alter the extent of apoptosis in control neurons, i.e., those cultured in the absence of ethanol. These studies showed that several classes of antioxidants can exert neuroprotection against ethanol-associated apoptosis in fetal rhombencephalic neurons.

Oxidative stress on the astrocytes in culture derived from a senescence accelerated mouse strain

Astrocytes are one of the predominant glial cell types in the adult central nervous system functioning as both supportive and metabolic cells for the brain. Our objective in this experiment is to study the direct effects of hydrogen peroxide induced oxidative stress on astrocytes in culture. These astrocytes were derived from both an aged mouse strain (P8) and a matched control strain (R1). The astrocytes for both the P8 and R1 strains were treated with increasing concentrations of hydrogen peroxide. Our results showed that the oxidative stress had a similar effect in both strains of astrocytes; decreases in 3-(4,5-dimethylthiazol-2-yl)-2,2-diphenyltetrazolium bromide (MTT) and glial fibrillary acidic protein (GFAP) levels, and increases in terminal deoxynucleotidyltransferase-mediated dUTP nick end-labeling (TUNEL) staining, lactate dehydrogenase (LDH) staining, and superoxide dismutase (SOD), caspase-3 and B-cell lymphoma 2-associated protein X (bax) levels. At a hydrogen peroxide concentration of 400 microM , the differences of the above parameters between P8 cultures and R1 cultures were statistically significant (p<0.05). This strongly suggested that astrocytes derived from P8 and R1 strains reacted to oxidative stress with similar mechanisms and consequences. However, the mechanisms were not able to compensate for the oxidative stress in the P8 strain at a hydrogen peroxide concentration of 400 microM. The inability of the P8 astrocytes to counteract the oxidative stress might lead to inadequate protection from neuronal loss possibly resulting in significantly more astrocytic death. Our results suggested that the changes of astrocytes in peroxide detoxification may play a role in aging of the central nervous system, and further aging studies should examine the oxidative status of the samples.