Circadian modulation of human erythrocyte plasma membrane redox system by melatonin

Peroxisome Proliferator-Activated Receptors as Molecular Links between Caloric Restriction and Circadian Rhythm

The circadian rhythm plays a chief role in the adaptation of all bodily processes to internal and environmental changes on the daily basis. Next to light/dark phases, feeding patterns constitute the most essential element entraining daily oscillations, and therefore, timely and appropriate restrictive diets have a great capacity to restore the circadian rhythm. One of the restrictive nutritional approaches, caloric restriction (CR) achieves stunning results in extending health span and life span via coordinated changes in multiple biological functions from the molecular, cellular, to the whole-body levels. The main molecular pathways affected by CR include mTOR, insulin signaling, AMPK, and sirtuins. Members of the family of nuclear receptors, the three peroxisome proliferator-activated receptors (PPARs), PPARα, PPARβ/δ, and PPARγ take part in the modulation of these pathways. In this non-systematic review, we describe the molecular interconnection between circadian rhythm, CR-associated pathways, and PPARs. Further, we identify a link between circadian rhythm and the outcomes of CR on the whole-body level including oxidative stress, inflammation, and aging. Since PPARs contribute to many changes triggered by CR, we discuss the potential involvement of PPARs in bridging CR and circadian rhythm.

Age-dependent altered redox homeostasis in the chronodisrupted rat model and moderation by melatonin administration

Circadian disruption or chronodisruption (CD) occurs when day-night cycles and other internal rhythms are not adjusted to environmental light-dark regimens and are unable to synchronize among each other. Artificial light-induced oxidative stress is a major concern as the circadian physiology of the cell is chronically altered due to suppression of the time-keeping hormone, melatonin. The relationship between age-related impaired redox status and disrupted circadian rhythms is still not fully understood. The present study evaluated the effect of artificial light at night (ALAN) with respect to aging and role of melatonin supplementation. This study was conducted on young (3 months) and old (24 months) male Wistar rats subdivided into four groups control (C), melatonin treated (MLT), artificial light at night (ALAN), and ALAN+MLT group. Pronounced changes were observed in the old compared to the young rats. Reactive oxygen species (ROS), malondialdehyde (MDA), plasma membrane redox system (PMRS), protein carbonyl (PCO), and sialic acid (SA) were significantly (p ≤ 0.05) increased, while ferric reducing ability of plasma (FRAP) and reduced glutathione (GSH) were significantly (p ≤ 0.05) suppressed in light-exposed young and old animals compared to their age-matched controls. Advanced oxidation protein products (AOPP) increased non-significantly in young rats of the ALAN group; however, significant (p ≤ 0.05) changes were observed in the old rats of the ALAN group compared to their respective controls. Advanced glycation end products (AGEs) increased and acetylcholinesterase (AChE) activity decreased, significantly (p ≤ 0.05) in young animals of the ALAN group, while nonsignificant changes of both parameters were recorded in the old animals of the ALAN groups compared with their age-matched controls. Melatonin supplementation resulted in maintenance of the normal redox homeostasis in both young and old animal groups. Our study suggests that aged rats are more susceptible to altered photoperiod as their circadian redox homeostasis is under stress subsequent to ALAN. Melatonin supplementation could be a promising means of alleviating age-related circadian disturbances, especially in light-polluted areas.

Redox homeostasis in a rodent model of circadian disruption: Effect of melatonin supplementation

Continuous light or dark photoperiods are the leading cause of disruption in the circadian rhythm of day-night cycle. The purpose of this study was to understand the cellular redox balance in a model of circadian disrupted rat model and determine the effect of melatonin supplementation. Young male Wistar rats were randomly divided into five groups (n = 4). Group (I): normal day-night (12 h:12 h) cycle, Group (II): normal rats treated with melatonin, Group (III): rats subjected to continuous light exposure (CLE), Group (IV): CLE rats treated with melatonin, and Group (V) Rats subjected to continuous dark. Melatonin (10 mg/kg) was administered orally at dusk to the Group (II) & (IV). Rats were sacrificed after 10 days of treatment and biomarkers of oxidative stress were evaluated. Results demonstrated significant (p < 0.05) increase of malondialdehyde (MDA), plasma membrane redox system (PMRS), protein carbonyl oxidation (PCO), advanced oxidation protein products (AOPPs), and advanced glycation end products (AGEs) during CLE. A significantly (p < 0.05) decreased level of reduced glutathione (GSH) and ferric reducing antioxidant potential in plasma (FRAP) was also observed during CLE. Treatment with melatonin in CLE rats showed reduced level of MDA, PMRS, PCO, AOPPs and AGEs while GSH and FRAP activity were increased. During continuous dark exposure (CDE) the biomarkers of oxidative stress were attenuated compared to control. Supplementation of melatonin could be a promising strategy to maintain redox homeostasis during prolonged condition of light exposure and other conditions of redox imbalance.

Melatonin treatment induces apoptosis through regulating the nuclear factor-κB and mitogen-activated protein kinase signaling pathways in human gastric cancer SGC7901 cells

Melatonin, which is synthesized by the pineal gland and released into the blood, exhibits antitumor properties. However, the mechanisms underlying these effects, particularly in stomach cancer, remain unknown. In the present study, the effect of melatonin on the nuclear factor (NF)-κB signaling pathway and the mitogen-activated protein kinase signaling pathway, involving p38 and c-Jun-N-terminal kinase (JNK), were investigated in SGC7901 gastric cancer cells. In addition, the effect of melatonin on the survival, migration and apoptosis of these cells was investigated in vitro in order to evaluate the use of melatonin for the treatment of gastric cancer. The results of the present study revealed that melatonin decreased the viability and migration of SGC7901 cells. Furthermore, melatonin induced apoptosis. Melatonin was identified to elevate the expression levels of phosphorylated (p)-p38 and p-JNK protein, and decrease the expression level of nucleic p-p65. These results suggest that the protein levels of p65, p38 and JNK are associated with the survival of SGC7901 cells following treatment with melatonin. The optimal concentration of melatonin was demonstrated to be 2 mM, which significantly induced apoptosis following a 24 h treatment period. These findings suggest that conflicting growth signals in cells may inhibit the efficacy of melatonin in the treatment of gastric cancer. Therefore, adjunct therapy would be required to improve the efficacy of melatonin in the treatment of cancer.

Potential utility of melatonin as an antioxidant therapy in the management of sickle cell anemia

This study aimed to assess antioxidant effects of melatonin treatment compared to N-acetylcysteine (NAC) and to their combination in a sickle cell suspension. Sickle erythrocytes were suspended in phosphate-buffered saline, pH 7.4, composing external control group. They were also suspended and incubated at 37°C either in the absence (experimental control group) or in the presence of NAC, melatonin and their combination at concentrations of 100 pm, 100 nm and 100 μm for 1 hr (treatment groups). The melatonin influences were evaluated by spectrophotometric [hemolysis degree, catalase (CAT), glutathione S-transferase (GST), glutathione peroxidase (GPx), glutathione reductase (GR), glucose-6-phosphate dehydrogenase (G6PDH), and superoxide dismutase (SOD) activities] and chromatographic methods [glutathione (GSH) and malondialdehyde (MDA) levels]. Incubation period was able to cause a rise about 64% on hemolysis degree as well as practically doubled the lipid peroxidation levels (P < 0.01). However, almost all antioxidants tested treatments neutralized this incubation effect observed in MDA levels. Among the antioxidant biomarkers evaluated, we observed a modulating effect of combined treatment on GPx and SOD activities (P < 0.01), which showed ~25% decrease in their activities. In addition, we found an antioxidant dose-dependent effect for melatonin on lipid peroxidation (r = -0.29; P = 0.03) and for combined antioxidant treatments also on MDA levels (r = -0.37; P = 0.01) and on SOD activity (r = -0.54; P < 0.01). Hence, these findings contribute with important insight that melatonin individually or in combination with NAC may be useful for sickle cell anemia management.

Advances in the research of melatonin in autism spectrum disorders: literature review and new perspectives

Abnormalities in melatonin physiology may be involved or closely linked to the pathophysiology and behavioral expression of autistic disorder, given its role in neurodevelopment and reports of sleep-wake rhythm disturbances, decreased nocturnal melatonin production, and beneficial therapeutic effects of melatonin in individuals with autism. In addition, melatonin, as a pineal gland hormone produced from serotonin, is of special interest in autistic disorder given reported alterations in central and peripheral serotonin neurobiology. More specifically, the role of melatonin in the ontogenetic establishment of circadian rhythms and the synchronization of peripheral oscillators opens interesting perspectives to ascertain better the mechanisms underlying the significant relationship found between lower nocturnal melatonin excretion and increased severity of autistic social communication impairments, especially for verbal communication and social imitative play. In this article, first we review the studies on melatonin levels and the treatment studies of melatonin in autistic disorder. Then, we discuss the relationships between melatonin and autistic behavioral impairments with regard to social communication (verbal and non-verbal communication, social interaction), and repetitive behaviors or interests with difficulties adapting to change. In conclusion, we emphasize that randomized clinical trials in autism spectrum disorders are warranted to establish potential therapeutic efficacy of melatonin for social communication impairments and stereotyped behaviors or interests.

Circadian rhythm connections to oxidative stress: implications for human health

SIGNIFICANCE

Oxygen and circadian rhythmicity are essential in a myriad of physiological processes to maintain homeostasis, from blood pressure and sleep/wake cycles, down to cellular signaling pathways that play critical roles in health and disease. If the human body or cells experience significant stress, their ability to regulate internal systems, including redox levels and circadian rhythms, may become impaired. At cellular as well as organismal levels, impairment in redox regulation and circadian rhythms may lead to a number of adverse effects, including the manifestation of a variety of diseases such as heart diseases, neurodegenerative conditions, and cancer.

RECENT ADVANCES

Researchers have come to an understanding as to the basics of the circadian rhythm mechanism, as well as the importance of the numerous species of oxidative stress components. The effects of oxidative stress and dysregulated circadian rhythms have been a subject of intense investigations since they were first discovered, and recent investigations into the molecular mechanisms linking the two have started to elucidate the bases of their connection.

CRITICAL ISSUES

While much is known about the mechanics and importance of oxidative stress systems and circadian rhythms, the front where they interact has had very little research focused on it. This review discusses the idea that these two systems are together intricately involved in the healthy body, as well as in disease.

FUTURE DIRECTIONS

We believe that for a more efficacious management of diseases that have both circadian rhythm and oxidative stress components in their pathogenesis, targeting both systems in tandem would be far more successful.

Melatonin treatment increases the transcription of cell proliferation-related genes prior to inducing cell death in C6 glioma cells in vitro

A number of studies have suggested that melatonin possesses anticancer properties. However, conflicting data exists with regard to the role of melatonin in the treatment of cancer. In the present study, the effects of melatonin on the transcriptional regulation of three genes associated with cell proliferation (Nestin, Bmi-1 and Sox2), and on C6 glioma cell survival and viability, were investigated in vitro to evaluate the use of melatonin in cancer therapy. Melatonin was shown to increase the mRNA levels of Nestin, Bmi-1 and Sox2 in a similar pattern, with the highest mRNA levels noted at a concentration of 3 mM. At higher concentrations of melatonin (5 mM), the mRNA levels of Nestin, Bmi-1 and Sox2 were reduced from their peak levels, and were correlated with changes observed in immunofluorescence morphology studies, cell viability and survival assays. Immunofluorescence studies of Nestin-stained cells demonstrated that treatment with a higher concentration of melatonin (3 and 5 mM) led to the Nestin filaments condensing and rearranging around the cell nuclei, and an alteration in the cell morphology. C6 cell viability was also significantly decreased at 3 mM melatonin, and cell death was observed at 5 and 10 mM melatonin. These results suggested that Nestin, Bmi-1 and Sox2 were strongly correlated with the survival of C6 cells following treatment with melatonin, and that high therapeutic concentrations of melatonin (>5 mM) were required to induce cell death. These findings suggested that the implementation of melatonin in the treatment of glioma and other types of cancer may be inhibited by conflicting cell growth signals in cells. Therefore, adjunct therapy is required to improve the efficacy of melatonin in the treatment of cancer.

Effects of DHA-phospholipids, melatonin and tryptophan supplementation on erythrocyte membrane physico-chemical properties in elderly patients suffering from mild cognitive impairment

A randomized, double-blind placebo-controlled clinical trial was carried out to assess the efficacy of a docosahexenoic acid (DHA)-phospholipids, melatonin and tryptophan supplemented diet in improving the erythrocyte oxidative stress, membrane fluidity and membrane-bound enzyme activities of elderly subjects suffering from mild cognitive impairment (MCI). These subjects were randomly assigned to the supplement group (11 subjects, 9F and 2M; age 85.3±5.3y) or placebo group (14-matched subjects, 11F and 3M; 86.1±6.5). The duration of the treatment was 12weeks. The placebo group showed no significant changes in erythrocyte membrane composition and function. The erythrocyte membranes of the supplement group showed a significant increase in eicosapentenoic acid, docosapentenoic acid and DHA concentrations and a significant decrease in arachidonic acid, malondialdehyde and lipofuscin levels. These changes in membrane composition resulted in an increase in the unsaturation index, membrane fluidity and acetylcholine esterase activity. Moreover, a significant increase in the ratio between reduced and oxidized glutathione was observed in the erythrocyte of the supplement group. Although this study is a preliminary investigation, we believe these findings to be of great speculative and interpretative interest to better understand the complex and multi-factorial mechanisms behind the possible links between diets, their functional components and possible molecular processes that contribute to increasing the risk of developing MCI and Alzheimer's.