Melatonin as an antioxidant: under promises but over delivers

Involvement of heat shock proteins HSP70 in the mechanisms of endogenous neuroprotection: the prospect of using HSP70 modulators

This analytical review summarizes literature data and our own research on HSP70-dependent mechanisms of neuroprotection and discusses potential pharmacological agents that can influence HSP70 expression to improve neurological outcomes and effective therapy. The authors formed a systemic concepts of the role of HSP70-dependent mechanisms of endogenous neuroprotection aimed at stopping the formation of mitochondrial dysfunction, activation of apoptosis, desensitization of estrogen receptors, reduction of oxidative and nitrosative stress, prevention of morpho-functional changes in brain cells during cerebral ischemia, and experimentally substantiated new target links for neuroprotection. Heat shock proteins (HSPs) are an evolutionarily integral part of the functioning of all cells acting as intracellular chaperones that support cell proteostasis under normal and various stress conditions (hyperthermia, hypoxia, oxidative stress, radiation, etc.). The greatest curiosity in conditions of ischemic brain damage is the HSP70 protein, as an important component of the endogenous neuroprotection system, which, first of all, performs the function of intracellular chaperones and ensures the processes of folding, holding and transport of synthesized proteins, as well as their degradation, both under normoxic conditions and stress-induced denaturation. A direct neuroprotective effect of HSP70 has been established, which is realized through the regulation the processes of apoptosis and cell necrosis due to a long-term effect on the synthesis of antioxidant enzymes, chaperone activity, and stabilization of active enzymes. An increase in the level of HSP70 leads to the normalization of the glutathione link of the thiol-disulfide system and an increase in the resistance of cells to ischemia. HSP 70 is able to activate and regulate compensatory ATP synthesis pathways during ischemia. It was found that in response to the cerebral ischemia formation, HIF-1a is expressed, which initiates the launch of compensatory mechanisms for energy production. Subsequently, the regulation of these processes switches to HSP70, which "prolongs" the action of HIF-1a, and also independently maintains the expression of mitochondrial NAD-dependent malate dehydrogenase activity, thereby maintaining the activity of the malate-aspartate shuttle mechanism for a long time. During ischemia of organs and tissues, HSP70 performs a protective function, which is realized through increased synthesis of antioxidant enzymes, stabilization of oxidatively damaged macromolecules, and direct anti-apoptotic and mitoprotective action. Such a role of these proteins in cellular reactions during ischemia raises the question of the development of new neuroprotective agents which are able to provide modulation/protection of the genes encoding the synthesis of HSP 70 and HIF-1a proteins. Numerous studies of recent years have noted the important role of HSP70 in the implementation of the mechanisms of metabolic adaptation, neuroplasticity and neuroprotection of brain cells, so the positive modulation of the HSP70 system is a perspective concept of neuroprotection, which can improve the efficiency of the treatment of ischemic-hypoxic brain damage and be the basis for substantiating of the feasibility of using of HSP70 modulators as promising neuroprotectors.

Antiviral effect of melatonin on Japanese encephalitis virus infection involves inhibition of neuronal apoptosis and neuroinflammation in SH-SY5Y cells

Japanese encephalitis virus (JEV), a mosquito-borne flavivirus, causes high mortality rates in humans and it is the most clinically important and common cause of viral encephalitis in Asia. To date, there is no specific treatment for JEV infection. Melatonin, a neurotropic hormone, is reported to be effective in combating various bacterial and viral infections. However, the effects of melatonin on JEV infection have not yet been studied. The investigation tested the antiviral effects of melatonin against JEV infection and elucidated the possible molecular mechanisms of inhibition. Melatonin inhibited the viral production in JEV-infected SH-SY5Y cells in a time- and dose-dependent manner. Time-of-addition assays demonstrated a potent inhibitory effect of melatonin at the post-entry stage of viral replication. Molecular docking analysis revealed that melatonin negatively affected viral replication by interfering with physiological function and/or enzymatic activity of both JEV nonstructural 3 (NS3) and NS5 protein, suggesting a possible underlying mechanism of JEV replication inhibition. Moreover, treatment with melatonin reduced neuronal apoptosis and inhibited neuroinflammation induced by JEV infection. The present findings reveal a new property of melatonin as a potential molecule for the further development of anti-JEV agents and treatment of JEV infection.

The Importance of Natural Antioxidants in Female Reproduction

Oxidative stress (OS) has an important role in female reproduction, whether it is ovulation, endometrium decidualization, menstruation, oocyte fertilization, or development andimplantation of an embryo in the uterus. The menstrual cycle is regulated by the physiological concentration of reactive forms of oxygen and nitrogen as redox signal molecules, which trigger and regulate the length of individual phases of the menstrual cycle. It has been suggested that the decline in female fertility is modulated by pathological OS. The pathological excess of OS compared to antioxidants triggers many disorders of female reproduction which could lead to gynecological diseases and to infertility. Therefore, antioxidants are crucial for proper female reproductive function. They play a part in the metabolism of oocytes; in endometrium maturation via the activation of antioxidant signaling pathways Nrf2 and NF-κB; and in the hormonal regulation of vascular action. Antioxidants can directly scavenge radicals and act as a cofactor of highly valuable enzymes of cell differentiation and development, or enhance the activity of antioxidant enzymes. Compensation for low levels of antioxidants through their supplementation can improve fertility. This review considers the role of selected vitamins, flavonoids, peptides, and trace elements with antioxidant effects in female reproduction mechanisms.

Chemotherapy induced oxidative stress in the ovary: drug-dependent mechanisms and potential interventions†

Cancer incidence and relative survival are expected to increase over the next few decades. With the majority of patients receiving combinatorial chemotherapy, an increasing proportion of patients experience long-term side effects from treatment-including reproductive disorders and infertility. A limited number of studies have examined mechanisms of single-agent chemotherapy-induced gonadotoxicity, with chemotherapy-induced oxidative stress being implicated in the loss of reproductive functions. Current methods of female fertility preservation are costly, invasive, only moderately successful, and seldom presented to cancer patients. The potential of antioxidants to alleviate chemotherapy has been overlooked at a time when it is becoming increasingly important to develop strategies to protect reproductive functions during chemotherapy. This review will summarize the importance of reactive oxygen species homeostasis in reproduction, chemotherapy-induced mitochondrial dysfunction in oocytes, chemotherapy-induced oxidative stress, and several promising natural adjuvants.

Melatonin inhibits senescence-associated melanin pigmentation through the p53-TYR pathway in human primary melanocytes and the skin of C57BL/6 J mice after UVB irradiation

UVB exposure accelerates skin aging and pigmentation. Melatonin effectively regulates tyrosinase (TYR) activity and aging. The purpose of this study was to determine the association between premature senescence and pigmentation, and the mechanism of melanin synthesis effected by melatonin. Primary melanocytes were extracted and identified from the male foreskin. To inhibit TYR expression, primary melanocytes were transduced with the lentivirus pLKD-CMV-EGFP-2A-Puro-U6-TYR. The wild-type TYR^(+/+) and TYR^(-/-) or TYR^(+/-) knockout C57BL/6 J mice were used to determine the role of TYR on melanin synthesis in vivo. Results showed that UVB-induced melanin synthesis is dependent on TYR in primary melanocytes and mice. Furthermore, in primary melanocytes pretreated with Nutlin-3 or PFT-α to up or downregulate p53, results showed that premature senescence and melanin synthesis increased in primary melanocytes after UVB irradiation at 80 mJ/cm², and further increased after being treated with Nutlin-3, while significantly decreased with PFT-α. In addition, melatonin inhibited UVB-induced premature senescence associated with inactivation of p53 and phosphorylation of p53 on Ser15 (ser-15), a decrease of melanin synthesis accompanied by reduced TYR expression. Moreover, skin erythema and pigmentation induced by UVB were reduced in the dorsal and ear skin of mice topically pretreated with 2.5% melatonin. These indicate that melatonin inhibits UVB-induced senescence-associated pigmentation via the p53-TYR pathway in primary melanocytes and prevents pigmentation obviously in the dorsal and ear skin of C57BL/6 J mice after UVB irradiation. KEY MESSAGES: P53 links UVB irradiation-induced senescence and senescence-associated pigmentation and regulates TYR in primary melanocytes after UVB irradiation. Melatonin inhibits senescence-associated pigmentation through the p53-TYR pathway in primary melanocytes. Melatonin prevents skin erythema and melanin pigmentation induced by UVB irradiation in the dorsal and ear skin of C57BL/6J mice.

Traumatic Brain Injury, Sleep, and Melatonin-Intrinsic Changes with Therapeutic Potential

Traumatic brain injury (TBI) is one of the most prevalent causes of morbidity in the United States and is associated with numerous chronic sequelae long after the point of injury. One of the most common long-term complaints in patients with TBI is sleep dysfunction. It is reported that alterations in melatonin follow TBI and may be linked with various sleep and circadian disorders directly (via cellular signaling) or indirectly (via free radicals and inflammatory signaling). Work over the past two decades has contributed to our understanding of the role of melatonin as a sleep regulator and neuroprotective anti-inflammatory agent. Although there is increasing interest in the treatment of insomnia following TBI, a lack of standardization and rigor in melatonin research has left behind a trail of non-generalizable data and ambiguous treatment recommendations. This narrative review describes the underlying biochemical properties of melatonin as they are relevant to TBI. We also discuss potential benefits and a path forward regarding the therapeutic management of TBI with melatonin treatment, including its role as a neuroprotectant, a somnogen, and a modulator of the circadian rhythm.

Melatonin protects Leydig cells from HT-2 toxin-induced ferroptosis and apoptosis via glucose-6-phosphate dehydrogenase/glutathione -dependent pathway

HT-2 toxin is a mycotoxin commonly found in food and water that can have adverse effects on male reproductive systems, including testosterone secretion. Ferroptosis and apoptosis are two types of programmed cell death that have been implicated in the regulation of cellular functions. Melatonin, a powerful antioxidant with various physiological functions, has been shown to regulate testosterone secretion. However, the mechanisms underlying the protective effects of melatonin against HT-2 toxin-induced damage in testosterone secretion are not fully understood. In this study, we investigated the effects of HT-2 toxin on sheep Leydig cells and the potential protective role of melatonin. We found that HT-2 toxin inhibited cell proliferation and testosterone secretion of Leydig cells in a dose-dependent manner and induced ferroptosis and apoptosis through intracellular reactive oxygen species accumulation, leading to lipid peroxidation. Exposure of Leydig cells to melatonin in vitro reversed the defective phenotypes caused by HT-2 toxin via a glucose-6-phosphate dehydrogenase/glutathione-dependent mechanism. Interference of glucose-6-phosphate dehydrogenase disrupted the beneficial effect of melatonin on ferroptosis and apoptosis in HT-2 toxin-treated Leydig cells. Furthermore, similar results were observed in vivo in the testes of male mice injected with HT-2 toxin with or without melatonin treatment for 30 days. Our findings suggest that melatonin inhibits ferroptosis and apoptosis by elevating the expression of glucose-6-phosphate dehydrogenase to eliminate reactive oxygen species accumulation in HT-2 toxin-treated Leydig cells. These results provide fundamental evidence for eliminating the adverse effects of HT-2 toxin on male reproduction.

Pathophysiological basis and promise of experimental therapies for Gulf War Illness, a chronic neuropsychiatric syndrome in veterans

This article describes the pathophysiology and potential treatments for Gulf War Illness (GWI), which is a chronic neuropsychiatric illness linked to a combination of chemical exposures experienced by service personnel during the first Gulf War in 1991. However, there is currently no effective treatment for veterans with GWI. The article focuses on the current status and efficacy of existing therapeutic interventions in preclinical models of GWI, as well as potential perspectives of promising therapies. GWI stems from changes in brain and peripheral systems in veterans, leading to neurocognitive deficits, as well as physiological and psychological effects resulting from multifaceted changes such as neuroinflammation, oxidative stress, and neuronal damage. Aging not only renders veterans more susceptible to GWI symptoms, but also attenuates their immune capabilities and response to therapies. A variety of experimental models are being used to investigate the pathophysiology and develop therapies that have the ability to alleviate devastating symptoms. Over two dozen therapeutic interventions targeting neuroinflammation, mitochondrial dysfunction, neuronal injury, and neurogenesis are being tested, including agents such as curcumin, curcumin nanoparticles, monosodium luminol, melatonin, resveratrol, fluoxetine, rolipram, oleoylethanolamide, ketamine, levetiracetam, nicotinamide riboside, minocycline, pyridazine derivatives, and neurosteroids. Preclinical outcomes show that some agents have promise, including curcumin, resveratrol, and ketamine, which are being tested in clinical trials in GWI veterans. Neuroprotectants and other compounds such as monosodium luminol, melatonin, levetiracetam, oleoylethanolamide, and nicotinamide riboside appear promising for future clinical trials. Neurosteroids have been shown to have neuroprotective and disease-modifying properties, which makes them a promising medicine for GWI. Therefore, accelerated clinical studies are urgently needed to evaluate and launch an effective therapy for veterans displaying GWI.

Therapeutic potential of melatonin and its derivatives in aging and neurodegenerative diseases

Aging is associated with increasing impairments in brain homeostasis and represents the main risk factor across most neurodegenerative disorders. Melatonin, a neuroendocrine hormone that regulates mammalian chronobiology and endocrine functions is well known for its antioxidant potential, exhibiting both cytoprotective and chronobiotic abilities. Age-related decline of melatonin disrupting mitochondrial homeostasis and cytosolic DNA-mediated inflammatory reactions in neurons is a major contributory factor in the emergence of neurological abnormalities. There is scattered literature on the possible use of melatonin against neurodegenerative mechanisms in the aging process and its associated diseases. We have searched PUBMED with many combinations of key words for available literature spanning two decades. Based on the vast number of experimental papers, we hereby review recent advancements concerning the potential impact of melatonin on cellular redox balance and mitochondrial dynamics in the context of neurodegeneration. Next, we discuss a broader explanation of the involvement of disrupted redox homeostasis in the pathophysiology of age-related diseases and its connection to circadian mechanisms. Our effort may result in the discovery of novel therapeutic approaches. Finally, we summarize the current knowledge on molecular and circadian regulatory mechanisms of melatonin to overcome neurodegenerative diseases (NDDs) such as Alzheimer's, Parkinson's, Huntington's disease, and amyotrophic lateral sclerosis, however, these findings need to be confirmed by larger, well-designed clinical trials. This review is also expected to uncover the associated molecular alterations in the aging brain and explain how melatonin-mediated circadian restoration of neuronal homeodynamics may increase healthy lifespan in age-related NDDs.

The Timing Sequence and Mechanism of Aging in Endocrine Organs

The world is increasingly aging, and there is an urgent need to find a safe and effective way to delay the aging of the body. It is well known that the endocrine glands are one of the most important organs in the context of aging. Failure of the endocrine glands lead to an abnormal hormonal environment, which in turn leads to many age-related diseases. The aging of endocrine glands is closely linked to oxidative stress, cellular autophagy, genetic damage, and hormone secretion. The first endocrine organ to undergo aging is the pineal gland, at around 6 years old. This is followed in order by the hypothalamus, pituitary gland, adrenal glands, gonads, pancreatic islets, and thyroid gland. This paper summarises the endocrine gland aging-related genes and pathways by bioinformatics analysis. In addition, it systematically summarises the changes in the structure and function of aging endocrine glands as well as the mechanisms of aging. This study will advance research in the field of aging and help in the intervention of age-related diseases.

Melatonin alleviates doxorubicin-induced cardiotoxicity via inhibiting oxidative stress, pyroptosis and apoptosis by activating Sirt1/Nrf2 pathway

Melatonin confers cardioprotective effects on multiple cardiovascular diseases, including doxorubicin-induced cardiomyopathy. The effectiveness of melatonin in mitigating myocardial injuries caused by Doxorubicin through enhancement of mitochondrial function is already established, however, the role of melatonin in regulating the Sirtuin-1 (Sirt1)/Nuclear factor E2-associated factor 2 (Nrf2) pathway in lessening the onset of Doxorubicin-induced cardiomyopathy is yet to be elucidated. To address this, H9C2 cardiomyocytes and C57BL/6 mice were employed to construct in vitro and in vivo models of Dox-induced myocardial impairments, respectively. Results showed that Dox markedly evoked oxidative stress, pyroptosis and apoptosis both in vitro and in vivo, which were significantly alleviated by melatonin administration. Mechanistically, melatonin attenuated Dox-induced downregulation of Sirt1 and Nrf2, and both inhibition of Sirt1 and Nrf2 significantly reversed the cardioprotective effects of melatonin. In conclusion, our studies suggest that the activation of the Sirt1/Nrf2 pathway is the underlying mechanism behind melatonin's ability to curtail oxidative stress, pyroptosis, and apoptosis in Dox-induced cardiomyopathy. These promising results demonstrated the potential application of melatonin as a treatment for doxorubicin-induced cardiac injury.

Brain washing and neural health: role of age, sleep, and the cerebrospinal fluid melatonin rhythm

The brain lacks a classic lymphatic drainage system. How it is cleansed of damaged proteins, cellular debris, and molecular by-products has remained a mystery for decades. Recent discoveries have identified a hybrid system that includes cerebrospinal fluid (CSF)-filled perivascular spaces and classic lymph vessels in the dural covering of the brain and spinal cord that functionally cooperate to remove toxic and non-functional trash from the brain. These two components functioning together are referred to as the glymphatic system. We propose that the high levels of melatonin secreted by the pineal gland directly into the CSF play a role in flushing pathological molecules such as amyloid-β peptide (Aβ) from the brain via this network. Melatonin is a sleep-promoting agent, with waste clearance from the CNS being highest especially during slow wave sleep. Melatonin is also a potent and versatile antioxidant that prevents neural accumulation of oxidatively-damaged molecules which contribute to neurological decline. Due to its feedback actions on the suprachiasmatic nucleus, CSF melatonin rhythm functions to maintain optimal circadian rhythmicity, which is also critical for preserving neurocognitive health. Melatonin levels drop dramatically in the frail aged, potentially contributing to neurological failure and dementia. Melatonin supplementation in animal models of Alzheimer's disease (AD) defers Aβ accumulation, enhances its clearance from the CNS, and prolongs animal survival. In AD patients, preliminary data show that melatonin use reduces neurobehavioral signs such as sundowning. Finally, melatonin controls the mitotic activity of neural stem cells in the subventricular zone, suggesting its involvement in neuronal renewal.

Aging-Related Ovarian Failure and Infertility: Melatonin to the Rescue

Aging has a major detrimental effect on the optimal function of the ovary with changes in this organ preceding the age-related deterioration in other tissues, with the middle-aged shutdown leading to infertility. Reduced fertility and consequent inability to conceive by women in present-day societies who choose to have children later in life leads to increased frustration. Melatonin is known to have anti-aging properties related to its antioxidant and anti-inflammatory actions. Its higher follicular fluid levels relative to blood concentrations and its likely synthesis in the oocyte, granulosa, and luteal cells suggest that it is optimally positioned to interfere with age-associated deterioration of the ovary. Additionally, the end of the female reproductive span coincides with a significant reduction in endogenous melatonin levels. Thus, the aims are to review the literature indicating melatonin production in mitochondria of oocytes, granulosa cells, and luteal cells, identify the multiple processes underlying changes in the ovary, especially late in the cessation of the reproductive life span, summarize the physiological and molecular actions of melatonin in the maintenance of normal ovaries and in the aging ovaries, and integrate the acquired information into an explanation for considering melatonin in the treatment of age-related infertility. Use of supplemental melatonin may help preserve fertility later in life and alleviate frustration in women delaying childbearing age, reduce the necessity of in vitro fertilization–embryo transfer (IVF-ET) procedures, and help solve the progressively increasing problem of non-aging-related infertility in women throughout their reproductive life span. While additional research is needed to fully understand the effects of melatonin supplementation on potentially enhancing fertility, studies published to date suggest it may be a promising option for those struggling with infertility.

Melatonin Supplementation during the Late Gestational Stage Enhances Reproductive Performance of Sows by Regulating Fluid Shear Stress and Improving Placental Antioxidant Capacity

In this study, the effects of daily melatonin supplementation (2 mg/kg) at the late gestational stage on the reproductive performance of the sows have been investigated. This treatment potentially increased the litter size and birth survival rate and significantly increased the birth weight as well as the weaning weight and survival rate of piglets compared to the controls. The mechanistic studies have found that these beneficial effects of melatonin are not mediated by the alterations of reproductive hormones of estrogen and progesterone, nor did the glucose and lipid metabolisms, but they were the results of the reduced oxidative stress in placenta associated with melatonin supplementation. Indeed, the melatonergic system, including mRNAs and proteins of AANAT, MTNR1A and MTNR1B, has been identified in the placenta of the sows. The RNA sequencing of placental tissue and KEGG analysis showed that melatonin activated the placental tissue fluid shear stress pathway to stimulate the Nrf2 signaling pathway, which upregulated its several downstream antioxidant genes, including MGST1, GSTM3 and GSTA4, therefore, suppressing the placental oxidative stress. All these actions may be mediated by the melatonin receptor of MTNR1B.

Melatonin in Health and Disease: A Perspective for Livestock Production

Mounting evidence in the literature indicates an important role of endogenous and exogenous melatonin in driving physiological and molecular adaptations in livestock. Melatonin has been extensively studied in seasonally polyestrous animals whereby supplementation studies have been used to adjust circannual rhythms in herds of animals under abnormal photoperiodic conditions. Livestock undergo multiple metabolic and physiological adaptation processes throughout their production cycle which can result in decreased immune response leading to chronic illness, weight loss, or decreased production efficiency; however, melatonin’s antioxidant capacity and immunostimulatory properties could alleviate these effects. The cardiovascular system responds to melatonin and depending on receptor type and localization, melatonin can vasodilate or vasoconstrict several systemic arteries, thereby controlling whole animal nutrient partitioning via vascular resistance. Increased incidences of non-communicable diseases in populations exposed to circadian disruption have uncovered novel pathways of neurohormones, such as melatonin, influence health, and disease. Perturbations in immune function can negatively impact the growth and development of livestock which has been examined following melatonin supplementation. Specifically, melatonin can influence nutrient uptake, circulating nutrient profiles, and endocrine profiles controlling economically important livestock growth and development. This review focuses on the physiological, cellular, and molecular implications of melatonin on the health and disease of domesticated food animals.

Insights into the antioxidative mechanisms of melatonin in ameliorating chromium-induced oxidative stress-mediated hepatic and renal tissue injuries in male Wistar rats

Chromium (Cr), a hazardous heavy metal, is toxic to human health and the environment. Severe detrimental effects of Cr on different physiological systems involve oxidative stress. In the current study, sodium dichromate di-hydrate was subcutaneously injected to male Wistar rats at a dose of 5 mg/kg b.w. and experimented up to 14 days to induce alterations in hepatic and renal tissues. Another group of rats was pre-treated with melatonin at three different doses (5, 10, and 20 mg/kg b.w.; orally) and 20 mg/kg b.w. dose was evidenced to provide maximal protection against Cr-induced alterations. The study demonstrated that melatonin efficiently preserved body weight, organ weight, intracellular antioxidant enzymes, and tissue morphology. Furthermore, melatonin was also found to protect organ damage markers, oxidative stress-biomarkers, activities of pro-oxidant enzymes, levels of reactive oxygen species (ROS), nitric oxide (NO), and collagen content through its antioxidative mechanisms. Moreover, melatonin effectively decreased tissue Cr content through its metal-chelating activity. Hence, the present study has established melatonin as a promising antioxidant for conserving the liver and kidney tissues from Cr-induced oxidative damage thereby strengthening the notion that this small indoleamine can act as a future therapeutic against Cr-induced oxidative stress-mediated tissue damage.

The effects of regular swimming exercise and melatonin on the neurons localized in the striatum of hemiparkinsonian rats

Parkinson's disease is a progressive neurodegenerative movement disorder. We aimed to investigate the effects of regular swimming exercise and melatonin applied in the 6-Hydroxydopamine-induced Parkinson's disease rats by analysing dendritic spine of striatal neurons. Twenty-four male Wistar albino rats were used. 6-Hydroxydopamine unilaterally injected four (control, exercise, melatonin and exercise + melatonin) groups were included in the study. Tyrosine hydroxylase expression was detected by immunohistochemistry. Neurons and structures were identified from three-dimensional images by Neurolucida software. There was not any apparent difference for tyrosine hydroxylase positive neurons in the substantia nigra pars compacta and fibres in the striatum between the lesion sides of hemiparkinsonian groups. The treatment groups blocked the apomorphine-induced increase in rotations compared to the control group. In stepping test, the treatment groups prevented the loss of stepping in the contralateral side of hemiparkinsonian groups. The melatonin mostly had a positive effect on motor activity tests. In morphological analyses, the 6-Hydroxydopamine-induced lesion led to the reduction of the total dendritic length and number of branches. In the treatment groups, the reduction of the dendritic parameters was not observed. 6-Hydroxydopamine lesion led to a decrease in the total spine density, spine densities of thin and mushroom types. The exercise and melatonin treatments prevented the loss of spine density. The exercise treatment prevented the loss of spine density of mushroom type spines. The melatonin treatment blocked the loss of spine density of stubby type. In conclusion, these results provide evidence for effective additional protective therapeutic strategies for Parkinson's disease. In conclusion, results from the current study provide evidence for swimming exercise and melatonin as a promising candidate for effective additional protective strategies for PD.

Exogenously applied melatonin enhanced the tolerance of Brassica napus against cobalt toxicity by modulating antioxidant defense, osmotic adjustment, and expression of stress response genes

The excessive accumulation of cobalt (Co) in plant tissues severely impairs plant growth that ultimately reduces the yield. However, melatonin (MT) has been known to mediate the abiotic stress tolerance in plants. The present study aimed at investigating the protective mechanisms of exogenously applied MT (0, 50 and 100 μM) under Co (0, 100, 200 and 300 μM) stress by focusing on morpho-physiological, biochemical and cellular characterizations of Brassica napus plants. Cobalt (300 μM) alone treatment drastically inhibited the stomatal conductance, plant height (45%), leaf area (30%), free amino acid (139%), relative electrolyte leakage (109%), and total soluble sugars (71%), compared with the control. However, the exogenous supply of MT notably minimized the oxidative damage, lipid peroxidation and maintained the membrane integrity under Co-toxicity by restricting the overproduction of ROS (H₂O₂ and O₂^•), and MDA in leaves and roots. Melatonin significantly enhanced the activities of ROS-scavenging antioxidant enzymes, secondary metabolism-related phenylalanine ammonia lyase (PAL), polyphenol oxidase (PPO), stress-responsive genes (heat shock protein as HSP-90, methyl transferase as MT) and regulated the Co-transporters, especially in roots. These findings indicated that an exogenous supply of MT improve the plant morphology, photosynthetic apparatus, osmotic adjustments, and antioxidant defense systems by enhancing the Co-detoxification in B. napus plants.

Melatonin attenuates cardiopulmonary toxicity induced by benzo(a)pyrene in mice focusing on apoptosis and autophagy pathways

Benzo(a)pyrene (BaP) is a polycyclic aromatic hydrocarbon and a serious environmental pollutant. BaP is formed by the incomplete combustion of organic matter at high temperatures. In addition, tobacco smoke and many foods, especially charbroiled food and grilled meats, contain BaP and can cause it to enter human body. Melatonin, a pineal gland hormone, has antioxidant, anti-apoptosis, and autophagy regulatory properties. The possible protective impact of melatonin on cardiopulmonary toxicity induced by BaP was investigated by examining the antioxidant effects and the apoptosis and autophagy properties of melatonin. Thirty male mice were divided into 5 groups and treated for 28 days as follows: (I) control (BaP and melatonin solvent), (II) BaP (75 mg/kg, oral gavage), (III and IV) BaP (75 mg/kg) + melatonin (10 and 20 mg/kg, intraperitoneally), (V) melatonin (20 mg/kg). The oxidative stress factors (MDA and GSH content) were assessed in the heart and lung tissues. The levels of apoptotic (Caspase-3 and the Bax/Bcl-2 ratio) and autophagic (the LC3 ӀӀ/Ӏ, Beclin-1, and Sirt1) proteins were examined by using western blot analysis. Following the administration of BaP, MDA, the Bax/Bcl-2 ratio, and the Caspase-3 proteins increased in the heart and lung tissues, while GSH, Sirt1, Beclin-1, and the LC3 II/I ratio diminished. The coadministration of melatonin along with BaP, MDA, and apoptotic proteins returned to the control values, while GSH and the autophagy proteins were enhanced in both the heart and lungs. Melatonin exhibited a protective effect against BaP-induced heart and lung injury through the suppression of oxidative stress and apoptosis and the induction of the Sirt1/autophagy pathway.

Melatonin ameliorates myocardial infarction in obese diabetic individuals: The possible involvement of macrophage apoptotic factors

In recent days, the hike in obesity-mediated epidemics across the globe and the prevalence of obesity-induced cardiovascular disease has become one of the chief grounds for morbidity and mortality. This epidemic-driven detrimental events in the cardiac tissues start with the altered distribution and metabolism pattern of high-density lipoprotein and low-density lipoprotein (LDL) leading to cholesterol (oxidized LDL) deposition on the arterial wall and atherosclerotic plaque generation, followed by vascular spasms and infarction. Subsequently, obesity-triggered metabolic malfunctions induce free radical generation which may further trigger pro-inflammatory signaling and nuclear factor kappa-light-chain-enhancer of activated B cells transcriptional factor, thus inducing interferon-gamma, tumor necrosis factor-alpha, and inducible nitric oxide synthase. This terrifying cardiomyopathy can be further aggravated in type 2 diabetes mellitus, thereby making obese diabetic patients prone toward the development of myocardial infarction (MI) or stroke in comparison to their nondiabetic counterparts. The accelerated oxidative stress and pro-inflammatory response induced cardiomyocyte hypertrophy, followed by apoptosis in obese diabetic individuals, causing progression of athero-thrombotic vascular disease. Being an efficient antioxidative and anti-inflammatory indolamine, melatonin effectively inhibits lipid peroxidation, pro-inflammatory reactions, thereby resolving free radical-induced myocardial damages along with maintaining antioxidant reservoir to preserve cardiovascular integrity. Prolonged melatonin treatment maintains balanced body weight and serum total cholesterol concentration by inhibiting cholesterol synthesis and promoting cholesterol catabolism. Additionally, melatonin promotes macrophage polarization toward the anti-inflammatory state, providing a proper shield during the recovery period. Therefore, the protective role of melatonin in maintaining the lipid metabolism homeostasis and blocking the atherosclerotic plaque rupture could be targeted as the possible therapeutic strategy for the management of obesity-induced acute MI. This review aimed at orchestrating the efficacy of melatonin in ameliorating irrevocable oxidative cardiovascular damage induced by the obesity-diabetes correlation.

The Therapeutic Potential of Antioxidants in Chemotherapy-Induced Peripheral Neuropathy: Evidence from Preclinical and Clinical Studies

As cancer therapies advance and patient survival improves, there has been growing concern about the long-term adverse effects that patients may experience following treatment, and concerns have been raised about such persistent, progressive, and often irreversible adverse effects. Chemotherapy is a potentially life-extending treatment, and chemotherapy-induced peripheral neuropathy (CIPN) is one of its most common long-term toxicities. At present, strategies for the prevention and treatment of CIPN are still an open problem faced by medicine, and there has been a large amount of previous evidence that oxidative damage is involved in the process of CIPN. In this review, we focus on the lines of defense involving antioxidants that exert the effect of inhibiting CIPN. We also provide an update on the targets and clinical prospects of different antioxidants (melatonin, N-acetylcysteine, vitamins, α-lipoic acid, mineral elements, phytochemicals, nutritional antioxidants, cytoprotectants and synthetic compounds) in the treatment of CIPN with the help of preclinical and clinical studies, emphasizing the great potential of antioxidants as adjuvant strategies to mitigate CIPN.

Environmental microplastic accumulation exacerbates liver ischemia-reperfusion injury in rat: Protective effects of melatonin

Ischemia-reperfusion (IR) injury is an inevitable complication of liver transplantation and partial hepatectomy. Although the hazards of environmental microplastics (EMPs) have been well explored, data underlying their impact on IR-induced hepatotoxicity and how to alleviate these damages remain largely undefined. In this study, the involvement of melatonin (MT) in modulating EMPs toxicity in the liver undergoing ischemia-reperfusion injury was investigated. Male Wistar rats were exposed to MPs for 7 days and then subjected to 1 h of partial warm ischemia (70 %) followed by 24 h of reperfusion. We analyzed some parameters as the oxidative stress, the stability of cytoskeleton as well as inflammation, and autophagy. Our data suggested that EMPs elicited liver injury in ischemic animals. Data revealed several histological alterations caused by EMP and IRI, including cellular disorientation, cell necrosis, and microvacuolar steatosis, as well as inflammatory cell infiltration. EMPs increased blood transaminase (AST and ALT) and oxidative stress levels in the ischemic liver. In addition, RT-qPCR, immunofluorescence, and western blot analyses highlighted an increased expression of α-tubulin, IL-18, NFkB, and LC3. However, the ability of MT to reduce MPs and IRI toxicity was consistent with a significant decrease in the evaluated markers. The combined data not only document that melatonin is an effective agent to protect against hepatic IRI but also reduces cellular dysfunction caused by EMPs.

Radical Scavenging Potential of Ginkgolides and Bilobalide: Insight from Molecular Modeling

The reactive oxygen species (ROS) scavenging capacities of ginkgolides and bilobalide, which are the peculiar constituents of the extract of Ginkgo biloba, are investigated in silico (level of theory: (SMD)-M06-2X/6-311+G(d,p)//M06-2X/6-31G(d)). Unlike other popular antioxidant natural substances, the carbon backbones of these compounds are entirely aliphatic and exclusively single C-C bonds are present. The selectivity for alkoxyl radicals via hydrogen-atom transfer (HAT) is assessed; importantly, the scavenging of peroxyl radicals is also possible from a peculiar site, here labeled C10 both for ginkgolides and bilobalide. The energetics are described in detail, and the analysis discloses that the studied compounds are powerful scavengers, with thermodynamic and kinetic properties similar to those of Trolox and melatonin, and that, in addition, they display selectivity for peroxyl radicals. These are all chemical-reactivity features contributing to the therapeutic action of the extract of G. biloba.

The Microbiota-Dependent Worsening Effects of Melatonin on Gut Inflammation

Dysbiosis and disturbances in gut homeostasis may result in dysregulated responses, which are common in inflammatory bowel diseases (IBD). These conditions may be refractory to the usual treatments and novel therapies are still necessary to reach a more successful regulation of intestinal immunity. The hormone melatonin (MLT) has been raised as a therapeutic alternative because of its known interactions with immune responses and gut microbiota. Hence, we evaluated the effects of MLT in experimental colitis that evolves with intestinal dysbiosis, inflammation and bacterial translocation. C57BL/6 mice were exposed to dextran sulfate sodium and treated with MLT. In acute colitis, the hormone led to increased clinical, systemic and intestinal inflammatory parameters. During remission, continued MLT administration delayed recovery, increased TNF, memory effector lymphocytes and diminished spleen regulatory cells. MLT treatment reduced Bacteroidetes and augmented Actinobacteria and Verrucomicrobia phyla in mice feces. Microbiota depletion resulted in a remarkable reversion of the colitis phenotype after MLT administration, including a counter-regulatory immune response, reduction in TNF and colon macrophages. There was a decrease in Actinobacteria, Firmicutes and, most strikingly, Verrucomicrobia phylum in recovering mice. Finally, these results pointed to a gut-microbiota-dependent effect of MLT in the potentiation of intestinal inflammation.

Melatonin and 5-fluorouracil combination chemotherapy: opportunities and efficacy in cancer therapy

Combined chemotherapy is a treatment method based on the simultaneous use of two or more therapeutic agents; it is frequently necessary to produce a more effective treatment for cancer patients. Such combined treatments often improve the outcomes over that of the monotherapy approach, as the drugs synergistically target critical cell signaling pathways or work independently at different oncostatic sites. A better prognosis has been reported in patients treated with combination therapy than in patients treated with single drug chemotherapy. In recent decades, 5-fluorouracil (5-FU) has become one of the most widely used chemotherapy agents in cancer treatment. This medication, which is soluble in water, is used as the first line of anti-neoplastic agent in the treatment of several cancer types including breast, head and neck, stomach and colon cancer. Within the last three decades, many studies have investigated melatonin as an anti-cancer agent; this molecule exhibits various functions in controlling the behavior of cancer cells, such as inhibiting cell growth, inducing apoptosis, and inhibiting invasion. The aim of this review is to comprehensively evaluate the role of melatonin as a complementary agent with 5-FU-based chemotherapy for cancers. Additionally, we identify the potential common signaling pathways by which melatonin and 5-FU interact to enhance the efficacy of the combined therapy. Video abstract.

Melatonin protects against cadmium-induced oxidative stress via mitochondrial STAT3 signaling in human prostate stromal cells

Melatonin protects against Cadmium (Cd)-induced toxicity, a ubiquitous environmental toxicant that causes adverse health effects by increasing reactive oxygen species (ROS) production and mitochondrial dysfunction. However, the underlying mechanism remains unclear. Here, we demonstrate that Cd exposure reduces the levels of mitochondrially-localized signal transducer and activator of transcription 3 (mitoSTAT3) using human prostate stromal cells and mouse embryonic fibroblasts. Melatonin enhances mitoSTAT3 abundance following Cd exposure, which is required to attenuate ROS damage, mitochondrial dysfunction, and cell death caused by Cd exposure. Moreover, melatonin increases mitochondrial levels of GRIM-19, an electron transport chain component that mediates STAT3 import into mitochondria, which are downregulated by Cd. In vivo, melatonin reverses the reduced size of mouse prostate tissue and levels of mitoSTAT3 and GRIM-19 induced by Cd exposure. Together, these data suggest that melatonin regulates mitoSTAT3 function to prevent Cd-induced cytotoxicity and could preserve mitochondrial function during Cd-induced stress.

Circadian Rhythms Disrupted by Light at Night and Mistimed Food Intake Alter Hormonal Rhythms and Metabolism

Availability of artificial light and light-emitting devices have altered human temporal life, allowing 24-hour healthcare, commerce and production, and expanding social life around the clock. However, physiology and behavior that evolved in the context of 24 h solar days are frequently perturbed by exposure to artificial light at night. This is particularly salient in the context of circadian rhythms, the result of endogenous biological clocks with a rhythm of ~24 h. Circadian rhythms govern the temporal features of physiology and behavior, and are set to precisely 24 h primarily by exposure to light during the solar day, though other factors, such as the timing of meals, can also affect circadian rhythms. Circadian rhythms are significantly affected by night shift work because of exposure to nocturnal light, electronic devices, and shifts in the timing of meals. Night shift workers are at increased risk for metabolic disorder, as well as several types of cancer. Others who are exposed to artificial light at night or late mealtimes also show disrupted circadian rhythms and increased metabolic and cardiac disorders. It is imperative to understand how disrupted circadian rhythms alter metabolic function to develop strategies to mitigate their negative effects. In this review, we provide an introduction to circadian rhythms, physiological regulation of homeostasis by the suprachiasmatic nucleus (SCN), and SCN-mediated hormones that display circadian rhythms, including melatonin and glucocorticoids. Next, we discuss circadian-gated physiological processes including sleep and food intake, followed by types of disrupted circadian rhythms and how modern lighting disrupts molecular clock rhythms. Lastly, we identify how disruptions to hormones and metabolism can increase susceptibility to metabolic syndrome and risk for cardiovascular diseases, and discuss various strategies to mitigate the harmful consequences associated with disrupted circadian rhythms on human health.

Artifical light at night triggers slight transcriptomic effects on melatonin signaling but not synthesis in tadpoles of two anuran species

The worldwide expansion of artificial light at night (ALAN) is acknowledged as a threat to biodiversity through alterations of the natural photoperiod triggering the disruption of physiological functions. In vertebrates, melatonin production during the dark phase can be decreased or suppressed by nocturnal light as shown in many taxa. But the effect of ALAN at low intensity mimicking light pollution in peri-urban area has never been investigated in amphibians. We filled this gap by studying the impact of low ALAN levels on the expression of genes related to melatonin synthesis and signaling in two anurans (agile frog, Rana dalmatina, and common toad, Bufo bufo). Circadian expression of genes encoding enzymes catalyzing melatonin synthesis (aralkylamine N-acetyltransferase, AANAT and acetylserotonin O-methyltransferase, ASMT) or melatonin receptors (Mel1a, Mel1b and Mel1c) was investigated using RT-qPCR after 23 days of nocturnal exposure to control (< 0.01 lx) or low ALAN (3 lx). We showed that the relative abundance of most transcripts was low in late afternoon and early evening (06 pm and 08 pm) and increased throughout the night in R. dalmatina. However, a clear and ample nocturnal pattern of target gene expression was not detected in control tadpoles of both species. Surprisingly, a low ALAN level had little influence on the relative expression of most melatonin-related genes. Only Mel1c expression in R. dalmatina and Mel1b expression in B. bufo were affected by ALAN. This target gene approach provides experimental evidence that melatonin signaling pathway was slightly affected by low ALAN level in anuran tadpoles.

The effects of resveratrol and melatonin on biochemical and molecular parameters in diabetic old female rat hearts

The roles of melatonin and resveratrol-enhanced activation of SIRT1 (silent information regulator 1), GLUT4 (glucose transporter type 4), and PGC-1α (peroxisome proliferator-activated receptor gamma coactivator 1-alpha) in mediating the protective effects on the heart in aged female rats with streptozotocin-induced diabetes were investigated. 16-month-old 48 Wistar female rats were separated into 8 groups with equal numbers. Group 1: Control, Group 2: Resveratrol Control, Group 3: Melatonin Control, Group 4: Resveratrol and Melatonin Control, Group 5: Diabetes, Group 6: Diabetes Resveratrol, Group 7: Diabetes Melatonin, Group 8: Diabetes Resveratrol and Melatonin. A single dose of 40 mg/kg intraperitoneal streptozotocin was injected into the rats of Groups 5, 6, 7, and 8 to induce experimental diabetes. Blood glucose levels were measured from the tail veins of the animals six days after the injections, using a diagnostic glucose kit. Rats with a blood glucose levels ≥300 mg/dl were considered diabetic. 5 mg/kg/day of resveratrol (intraperitoneal) and melatonin (subcutaneous) were administered for four weeks. At the end of the applications, SIRT1, GLUT4, PGC-1α gene expression as well as MDA and GSH levels in the heart tissues were determined by the PCR method from heart tissue samples taken under general anesthesia. The findings of our study show that suppressed antioxidant activity and decreased GLUT4, SIRT1, and PGC-1α gene expression in heart tissue can be reversed by the combination of resveratrol, melatonin, and resveratrol + melatonin in a diabetic aged female rat model. Resveratrol and melatonin supplementation may have a protective effect on cardiac functions in the diabetic aged female rat model.

The Utility of Melatonin for the Treatment of Sleep Disturbance After Traumatic Brain Injury: A Scoping Review

OBJECTIVE

To investigate the utility of melatonin supplementation as a treatment option for individuals with sleep disturbance after traumatic brain injury (TBI).

DATA SOURCES

A systematic search was conducted in 6 electronic databases (Medline, AMED, CINAHL, Embase, Scopus, and SPORTDiscus) from earliest records to April 2022.

STUDY SELECTION

Studies were eligible for inclusion if they met the following criteria: a) human participants with sleep disturbance after TBI, b) melatonin or melatonergic agent used as an intervention to treat sleep disturbance, and c) outcomes of melatonin administration reported. All TBI severity types (mild, moderate, and severe) were eligible. The initial search retrieved a total of 595 articles, with 9 studies meeting the eligibility criteria.

DATA EXTRACTION

Two reviewers independently extracted data from eligible studies and assessed methodological quality. Extracted data consisted of participant and injury characteristics, melatonin interventional properties, and sleep outcome. Methodological quality was assessed via the Downs and Black checklist.

DATA SYNTHESIS

A total of 251 participants with TBI-induced sleep disturbance (mean age range: 14.0-42.5 years) were included. Melatonin, Circadin (prolonged-release melatonin), or Ramelteon (melatonin receptor agonist) were administered. Dosages and intervention duration ranged from 2 to 10 mg and 3 to 12 weeks, respectively. Eight out of 9 studies reported positive outcomes after melatonin treatment. Significant improvements in subjective sleep quality, objective sleep efficiency, and total sleep time were found with melatonin. Reductions in self-reported fatigue, anxiety, and depressive symptoms were also observed with melatonin treatment. No serious adverse events were reported after melatonin administration.

CONCLUSION

Melatonin has good tolerability after short-term use and the potential to be a therapeutic agent for those with sleep disturbance after TBI. Melatonin was shown to be beneficial to sleep quality, sleep duration, and sleep efficiency. Additional clinically relevant outcomes of improved mental health suggest that melatonin use may be a promising treatment option for individuals experiencing co-occurring disorders of mood and sleep disturbance post-injury.

Effects of Aluminum Oxide Nanoparticles in the Cerebrum, Hippocampus, and Cerebellum of Male Wistar Rats and Potential Ameliorative Role of Melatonin

Aluminum oxide nanoparticles (Al₂O₃ NPs) have been widely used in vaccine manufacture, food additives, human care products, and cosmetics. However, they also have adverse effects on different organs, including the liver, kidneys, and testes. Melatonin is a potent antioxidant, particularly against metals by forming melatonin-metal complexes. The present study aimed to investigate the protective effects of melatonin against Al₂O₃ NP-induced toxicity in the rat brain. Forty adult male Wistar rats were allocated to four groups: the untreated control (received standard diet and distilled water), Al₂O₃ NP-treated (received 30 mg/kg body weight Al₂O₃ NPs), melatonin and Al₂O₃ NP-treated (received 30 mg/kg body weight Al₂O₃ NPs + 10 mg/kg body weight melatonin), and melatonin-treated (received 10 mg/kg body weight melatonin) groups. All treatments were by oral gavages and administered daily for 28 days. Afterward, the rats were sacrificed, and samples from various brain regions (cerebrum, cerebellum, and hippocampus) were subjected to biochemical, histopathological, and immunohistochemical analyses. Al₂O₃ NPs substantially increased malondialdehyde, β-amyloid 1-42 peptide, acetylcholinesterase, and β-secretase-1 expression, whereas they markedly decreased glutathione levels. Furthermore, Al₂O₃ NPs induced severe histopathological alterations, including vacuolation of the neuropil, enlarged pericellular and perivascular spaces, vascular congestion, neuronal degeneration, and pyknosis. Al₂O₃ NP treatment also resulted in an intense positive caspase-3 immunostaining. Conversely, the administration of melatonin alleviated the adverse effects induced by Al₂O₃ NPs. Therefore, melatonin can diminish the neurotoxic effects induced by Al₂O₃ NPs.

Mechanisms of action of non-enzymatic antioxidants to control oxidative stress during in vitro follicle growth, oocyte maturation, and embryo development

In vitro follicle growth and oocyte maturation still has a series of limitations, since not all oocytes matured in vitro have the potential to develop in viable embryos. One of the factors associated with low oocyte quality is the generation of reactive oxygen species (ROS) during in vitro culture. Therefore, this review aims to discuss the role of non-enzymatic antioxidants in the control of oxidative stress during in vitro follicular growth, oocyte maturation and embryonic development. A wide variety of non-enzymatic antioxidants (melatonin, resveratrol, L-ascorbic acid, L-carnitine, N-acetyl-cysteine, cysteamine, quercetin, nobiletin, lycopene, acteoside, mogroside V, phycocyanin and laminarin) have been used to supplement culture media. Some of them, like N-acetyl-cysteine, cysteamine, nobiletin and quercetin act by increasing the levels of glutathione (GSH), while melatonin and resveratrol increase the expression of antioxidant enzymes and minimize oocyte oxidative stress. L-ascorbic acid reduces free radicals and reactive oxygen species. Lycopene positively regulates the expression of many antioxidant genes. Additionally, L-carnitine protects DNA against ROS-induced damage, while acteoside and laminarin reduces the expression of proapoptotic genes. Mogrosides increases mitochondrial function and reduces intracellular ROS levels, phycocyanin reduces lipid peroxidation, and lycopene neutralizes the adverse effects of ROS. Thus, it is very important to know their mechanisms of actions, because the combination of two or more antioxidants with different activities has great potential to improve in vitro culture systems.

Protective effects of melatonin against physical injuries to testicular tissue: A systematic review and meta-analysis of animal models

Background

Modern societies face infertility as a global challenge. There are certain environmental conditions and disorders that damage testicular tissue and may cause male infertility. Melatonin, as a potential antioxidant, may protect testicular tissue. Therefore, we conducted this systematic review and meta-analysis to evaluate the effects of melatonin in animal models against physical, heat, and ischemic damage to the testicular tissue.

Methods

PubMed, Scopus, and Web of Science were systematically searched to identify animal trials evaluating the protective effect of melatonin therapy on rodent testicular tissue when it is exposed to physical, thermal, ischemic, or hypobaric oxygen stress. Random-effect modeling was used to estimate the standardized mean difference and 95% confidence intervals based on the pooled data. Additionally, the Systematic Review Centre for Laboratory Animal Experimentation (SYRCLE) tool was used to assess the risk of bias. The study protocol was prospectively registered in PROSPERO (CRD42022354599).

Results

A total of 41 studies were eligible for review out of 10039 records. Studies employed direct heat, cryptorchidism, varicocele, torsion-detorsion, testicular vascular occlusion, hypobaric hypoxia, ischemia-reperfusion, stress by excessive or restraint activity, spinal cord injury, and trauma to induce stress in the subjects. The histopathological characteristics of testicular tissue were generally improved in rodents by melatonin therapy. Based on the pooled data, sperm count, morphology, forward motility, viability, Johnsen's biopsy score, testicular tissue glutathione peroxidase, and superoxide dismutase levels were higher in the melatonin treatment rodent arms. In contrast, the malondialdehyde level in testicular tissue was lower in the treatment rodent arms. The included studies suffered from a high risk of bias in most of the SYRCLE domains.

Conclusion

This study concludes that melatonin therapy was associated with improved testicular histopathological characteristics, reproductive hormonal panel, and tissue markers of oxidative stress in male rodents with physical, ischemic, and thermal testicular injuries. In this regard, melatonin deserves scientific investigations as a potential protective drug against rodent male infertility.

Systematic review registration

https://www.crd.york.ac.uk/PROSPERO/, identifier CRD42022354599.

Melatonin: a potential therapeutic approach for the management of primary Sjögren's syndrome

Primary Sjögren's syndrome (pSS) is an autoimmune disease that primarily affects the exocrine glands and is mainly characterized by sicca symptoms of the eyes and mouth. Approximately 30-50% of pSS patients develop systemic multi-organ disorders including malignant lymphoma. The etiology of pSS is not well understood; growing evidence suggests that uncontrolled immune/inflammatory responses, excessive oxidative stress, defected apoptosis, dysregulated autophagy, exosomes, and exogenous virus infections may participate in the pathogenesis of pSS. There is no ideal therapeutic method for pSS; the management of pSS is mainly palliative, which aims to alleviate sicca symptoms. Melatonin, as the main secretory product of the pineal gland, has been evidenced to show various physiological functions, including effects of immunoregulation, capability of antioxidation, moderation of autophagy, suppressive activities of apoptosis, regulative capacity of exosomes, properties of anti-infection, and improvement of sleep. The beneficial effects of melatonin have been already validated in some autoimmune diseases such as multiple sclerosis (MS), type 1 diabetes mellitus (T1DM), systemic lupus erythematosus (SLE), and inflammatory bowel disease (IBD). However, our previous research firstly revealed that melatonin might inhibit pathogenic responses of peripheral Th17 and double-negative (DN) T cells in pSS. More importantly, melatonin administration alleviated the development of pSS in animal models with reduced infiltrating lymphocytes, improved functional activity of salivary gland, and decreased production of inflammatory factors as well as autoantibodies. Owing to the important biological properties reported in melatonin are characteristics closely related to the treatment of pSS; the potential role and underlying mechanisms of melatonin in the administration of pSS are certainly worth further investigations. Consequently, the aim of this review is to give a deep insight to the therapeutic potency of melatonin for pSS.

Mediterranean Diet and Melatonin: A Systematic Review

The Mediterranean diet (MD) has beneficial effects on human health, which is evidenced by the observation of lower incidence rates of chronic diseases in Mediterranean countries. The MD dietary pattern is rich in antioxidants, such as melatonin, which is a hormone produced mainly by the pineal gland and controls several circadian rhythms. Additionally, melatonin is found in foods, such as fruit and vegetables. The purpose of this systematic review was to assess the melatonin content in Mediterranean foods and to evaluate the influence of the MD on melatonin levels in both humans and model organisms. A comprehensive search was conducted in four databases (PubMed, Scopus, Cochrane Library and Web of Science) and data were extracted. A total of 31 records were chosen. MD-related foods, such as tomatoes, olive oil, red wine, beer, nuts, and vegetables, showed high melatonin contents. The consumption of specific MD foods increases melatonin levels and improves the antioxidant status in plasma.

Moderate-Intensity Exercise Maintains Redox Homeostasis for Cardiovascular Health

It is well known that exercise is beneficial for cardiovascular health. Oxidative stress is the common pathological basis of many cardiovascular diseases. The overproduction of free radicals, both reactive oxygen species and reactive nitrogen species, can lead to redox imbalance and exacerbate oxidative damage to the cardiovascular system. Maintaining redox homeostasis and enhancing anti-oxidative capacity are critical mechanisms by which exercise protects against cardiovascular diseases. Moderate-intensity exercise is an effective means to maintain cardiovascular redox homeostasis. Moderate-intensity exercise reduces the risk of cardiovascular disease by improving mitochondrial function and anti-oxidative capacity. It also attenuates adverse cardiac remodeling and enhances cardiac function. This paper reviews the primary mechanisms of moderate-intensity exercise-mediated redox homeostasis in the cardiovascular system. Exploring the role of exercise-mediated redox homeostasis in the cardiovascular system is of great significance to the prevention and treatment of cardiovascular diseases.

The Role of Microsphere Structures in Bottom-Up Bone Tissue Engineering

Bone defects have caused immense healthcare concerns and economic burdens throughout the world. Traditional autologous allogeneic bone grafts have many drawbacks, so the emergence of bone tissue engineering brings new hope. Bone tissue engineering is an interdisciplinary biomedical engineering method that involves scaffold materials, seed cells, and "growth factors". However, the traditional construction approach is not flexible and is unable to adapt to the specific shape of the defect, causing the cells inside the bone to be unable to receive adequate nourishment. Therefore, a simple but effective solution using the "bottom-up" method is proposed. Microspheres are structures with diameters ranging from 1 to 1000 µm that can be used as supports for cell growth, either in the form of a scaffold or in the form of a drug delivery system. Herein, we address a variety of strategies for the production of microspheres, the classification of raw materials, and drug loading, as well as analyze new strategies for the use of microspheres in bone tissue engineering. We also consider new perspectives and possible directions for future development.

Novel Hybrid Indole-Based Caffeic Acid Amide Derivatives as Potent Free Radical Scavenging Agents: Rational Design, Synthesis, Spectroscopic Characterization, In Silico and In Vitro Investigations

Antioxidant small molecules can prevent or delay the oxidative damage caused by free radicals. Herein, a structure-based hybridization of two natural antioxidants (caffeic acid and melatonin) afforded a novel hybrid series of indole-based amide analogues which was synthesized with potential antioxidant properties. A multiple-step scheme of in vitro radical scavenging assays was carried out to evaluate the antioxidant activity of the synthesized compounds. The results of the DPPH assay demonstrated that the indole-based caffeic acid amides are more active free radical scavenging agents than their benzamide analogues. Compared to Trolox, a water-soluble analogue of vitamin E, compounds 3a, 3f, 3h, 3j, and 3m were found to have excellent DPPH radical scavenging activities with IC₅₀ values of 95.81 ± 1.01, 136.8 ± 1.04, 86.77 ± 1.03, 50.98 ± 1.05, and 67.64 ± 1.02 µM. Three compounds out of five (3f, 3j, and 3m) showed a higher capacity to neutralize the radical cation ABTS^•+ more than Trolox with IC₅₀ values of 14.48 ± 0.68, 19.49 ± 0.54, and 14.92 ± 0.30 µM, respectively. Compound 3j presented the highest antioxidant activity with a FRAP value of 4774.37 ± 137.20 μM Trolox eq/mM sample. In a similar way to the FRAP assay, the best antioxidant activity against the peroxyl radicals was demonstrated by compound 3j (10,714.21 ± 817.76 μM Trolox eq/mM sample). Taken together, compound 3j was validated as a lead hybrid molecule that could be optimized to maximize its antioxidant potency for the treatment of oxidative stress-related diseases.

Hormone-linked redox status and its modulation by antioxidants

Hormones have been considered as key factors involved in the maintenance of the redox status of the body. We are making considerable progress in understanding interactions between the endocrine system, redox status, and oxidative stress with the dynamics of life, which encompasses fertilization, development, growth, aging, and various pathophysiological states. One of the reasons for changes in redox states of vertebrates leading to oxidative stress scenario is the disruption of the endocrine system. Comprehending the dynamics of hormonal status to redox state and oxidative stress in living systems is challenging. It is more difficult to come to a unifying conclusion when some hormones exhibit oxidant properties while others have antioxidant features. There is a very limited approach to correlate alteration in titers of hormones with redox status and oxidative stress with growth, development, aging, and pathophysiological stress. The situation is further complicated when considering various tissues and sexes in vertebrates. This chapter discusses the beneficial impacts of hormones with antioxidative properties, such as melatonin, glucagon, insulin, estrogens, and progesterone, which protect cells from oxidative damage and reduce pathophysiological effects. Additionally, we discuss the protective effects of antioxidants like vitamins A, E, and C, curcumin, tempol, N-acetyl cysteine, α-lipoic acid, date palm pollen extract, resveratrol, and flavonoids on oxidative stress triggered by hormones such as aldosterone, glucocorticoids, thyroid hormones, and catecholamines. Inflammation, pathophysiology, and the aging process can all be controlled by understanding how antioxidants and hormones operate together to maintain cellular redox status. Identifying the hormonal changes and the action of antioxidants may help in developing new therapeutic strategies for hormonal imbalance-related disorders.

Melatonin Can Enhance the Effect of Drugs Used in the Treatment of Leukemia

Melatonin (N-acetyl-5-methoxytryptamine, MEL), secreted by the pineal gland, plays an important role in regulation of various functions in the human body. There is evidence that MEL exhibits antitumor effect in various types of cancer. We studied the combined effect of MEL and drugs from different pharmacological groups, such as cytarabine (CYT) and navitoclax (ABT-737), on the state of the pool of acute myeloid leukemia (AML) tumor cell using the MV4-11 cell line as model. The combined action of MEL with CYT or ABT-737 contributed to the decrease in proliferative activity of leukemic cells, decrease in the membrane potential of mitochondria, and increase in the production of reactive oxygen species (ROS) and cytosolic Ca2+. We have shown that introduction of MEL together with CYT or ABT-737 increases expression of the C/EBP homologous protein (CHOP) and the autophagy marker LC3A/B and decreases expression of the protein disulfide isomerase (PDI) and binding immunoglobulin protein (BIP), and, therefore, could modulate endoplasmic reticulum (ER) stress and initiate autophagy. The findings support an early suggestion that MEL is able to provide benefits for cancer treatment and be considered as an adjunct to the drugs used in cancer therapy.

Melatonin promotes the restoration of bone defects via enhancement of miR-335-5p combined with inhibition of TNFα/NF-κB signaling

Accelerating the repair of a bone defect is crucial clinically due to the increased prevalence of trauma, tumor, and infections in bone. Studies have found that excess acute and chronic inflammation attenuate osteogenic differentiation of BMSCs (bone marrow mesenchymal stem cells). Moreover, TNF-α and NF-κB could inhibit osteoblasts differentiation of BMSCs and promote osteoclastogenesis via multiple mechanisms, such as increasing osteoclast precursor cells and acting synergistically with cell cytokines. However, melatonin could inhibit the expression of TNFα/NF-κB and promote bone formation by activating the Wnt/β-catenin signaling pathway. However, there has been no evidence regarding the effect of melatonin on TNFα/NF-κB-inhibited osteoblastogenesis and bone formation. This study aimed to investigate the role of melatonin on TNFα/NF-κB-inhibited osteoblastogenesis and bone formation. Micro-CT, high-throughput screening, overexpression, and other methods were used, and we found that the number of osteoblasts was elevated with melatonin treatment. Additionally, TNFα/NF-κB signaling was inhibited, while miR-335-5p expression increased markedly following treatment with melatonin. Furthermore, miR-335-5p negatively regulated TNFα/NF-κB signaling, while miR-335-5p inhibitor ameliorated the effects of melatonin on TNFα/NF-κB. In conclusion, melatonin facilitates osteogenesis in bone defect healing by enhancing miR-335-5p expression and inhibiting the TNFα/NF-κB pathway.

Synthesis, Drug-Likeness Evaluation of Some Heterocyclic Moieties Fused Indole Derivatives as Potential Antioxidants

BACKGROUND

Indole and its derivatives have a wide range of pharmacological effects, including analgesic, antimicrobial, antidepressant, anti-diabetic, anti-convulsant, anti-helminthic, and anti-inflammatory properties. They are crucial structural components of many of today's powerful antioxidant medications.

OBJECTIVE

Using the Schotten-Baumann reaction, the indole ring was linked to other key heterocyclic moieties such as morpholine, imidazole, piperidine, and piperazine at the active 3rd position and then tested for antioxidant activity.

METHODS

Synthesis of derivatives was accomplished under appropriate conditions and characterized by IR, NMR (1H and 13C), and mass spectrum. Using the Swiss ADME online application, ADME properties were also determined. The in vitro antioxidant activity was measured using DPPH and Reducing power method.

RESULTS

In the DPPH assay, compounds 5a (IC50=1.01±0.22 μg/mL), 5k (IC50=1.21 ± 0.07 μg/mL), whereas compounds 5a (EC50=23 ± 1.00 μg/mL), 5h (EC50=26±2.42 μg/mL) in the reducing power assay were most potent as compared with standard Ascorbic acid. Compounds 5a, 5h, and 5k demonstrated maximal potency equivalent to standard. Lipinski's rule was followed in ADME outcomes.

CONCLUSION

The synthesis and evaluation of indole derivatives to investigate their antioxidant action has received a lot of attention. These discoveries could lead to more effective antioxidant candidates being designed and developed.

Melatonin: Emerging Player in the Management of Oral Cancer

Oral cancer (OC) has emerged as a major medical and social issue in many industrialized nations due to the high death rate. It is becoming increasingly common in people under the age of 45, although the underlying causes and mechanisms of this increase remain unclear. Melatonin, as a pleiotropic hormone, plays a pivotal role in a wide variety of cellular and physiological functions. Mounting evidence supports melatonin's ability to modify/influence oral carcinogenesis, help in the reduction of the incidence of OC, and increase chemo- and radiosensitivity. Despite its potential anti-carcinogenic effects, the precise function of melatonin in the management of OC is not well understood. This review summarizes the current knowledge regarding melatonin function in anti-carcinogenesis mechanisms for OC. In addition, clinical assessment and the potential therapeutic utility of melatonin in OC are discussed. This review will provide a basis for researchers to create new melatonin-based personalized medicines for treating and preventing OC.

Improvement of oocyte quality through the SIRT signaling pathway

Background

Oocyte quality is one of the major deciding factors in female fertility competence.

Methods

PubMed database was searched for reviews by using the following keyword "oocyte quality" AND "Sirtuins". The methodological quality of each literature review was assessed using the Preferred Reporting Items for Systematic reviews and Meta-Analyses (PRISMA) 2020 statement.

Main Findings

Oxidative stress has been recognized as the mechanism attenuating oocyte quality. Increasing evidence from animal experiments and clinical studies has confirmed the protective roles of the sirtuin family in improving oocyte quality via an antioxidant effect.

Conclusion

The protective roles in the oocyte quality of the sirtuin family have been increasingly recognized.

Suppression of NLRP3/Caspase-1/GSDMD Mediated Corneal Epithelium Pyroptosis Using Melatonin-Loaded Liposomes to Inhibit Benzalkonium Chloride-Induced Dry Eye Disease

Introduction

Benzalkonium chloride (BAC) is widely employed as a preservative in eye drops, which will cause the death of corneal epithelial cells due to ROS production, DNA strand breakage, and mitochondrial dysfunction, resulting in dry eye disease (DED)-like changes in ocular surface tissues. In this study, Melatonin (MT) liposomes (TAT-MT-LIPs) designed by loading MT into TAT-modified liposomes have been developed, characterized, and used for inhibiting BAC-induced DED (BAC-DED).

Methods

The TAT was chemically grafted onto the Mal-PEG₂₀₀₀-DSPE by Michael's addition between the sulfhydryl group in TAT and the maleimide group in Mal-PEG₂₀₀₀-DSPE. TAT-MT-LIPs were prepared using film dispersion followed by the extrusion method and topically treated in rats once a day. BAC-DED was induced in rats by topical administration with 0.2% BAC twice daily. Defects, edema, and inflammation of the corneas, as well as IOP, were examined. Histologic analyses of corneas were performed to assess the change of mitochondrial DNA oxidation and NLRP3/Caspase-1/GSDMD signaling transduction.

Results

After topical administration, TAT-MT-LIPs significantly alleviated DED-clinical symptoms of experimental animals by inhibiting tissue inflammation and preventing the loss of the corneal epithelium and conjunctival goblet cells. Our data suggested continuous ocular surface exposure of BAC-induced NLRP3/Caspase-1/GSDMD mediated corneal epithelium pyroptosis, which was not reported before. BAC caused substantial mt-DNA oxidation, which promoted the transduction of NLRP3/Caspase-1/GSDMD and consequent corneal epithelium pyroptosis. TAT-MT-LIPs could efficiently suppress the BAC-induced corneal epithelium pyroptosis and inflammation by inhibiting mt-DNA oxidation and the subsequent signal transmission.

Conclusion

NLRP3/Caspase-1/GSDMD mediated corneal epithelium pyroptosis is involved in the development of BAC-DED. The present study provided new insights into the adverse effects of BAC, which can serve as a new target for protecting corneal epithelium when applying BAC as a preservative in eye drops. The developed TAT-MT-LIPs can efficiently inhibit BAC-DED and give great potential to be developed as a new DED treatment.

Melatonin as a Harmonizing Factor of Circadian Rhythms, Neuronal Cell Cycle and Neurogenesis: Additional Arguments for Its Therapeutic Use in Alzheimer's Disease

The synthesis and release of melatonin in the brain harmonize various physiological functions. The apparent decline in melatonin levels with advanced aging is an aperture to the neurodegenerative processes. It has been indicated that down regulation of melatonin leads to alterations of circadian rhythm components, which further causes a desynchronization of several genes and results in an increased susceptibility to develop neurodegenerative diseases. Additionally, as circadian rhythms and memory are intertwined, such rhythmic disturbances influence memory formation and recall. Besides, cell cycle events exhibit a remarkable oscillatory system, which is downstream of the circadian phenomena. The linkage between the molecular machinery of the cell cycle and complex fundamental regulatory proteins emphasizes the conjectural regulatory role of cell cycle components in neurodegenerative disorders such as Alzheimer's disease. Among the mechanisms intervening long before the signs of the disease appear, the disturbances of the circadian cycle, as well as the alteration of the machinery of the cell cycle and impaired neurogenesis, must hold our interest. Therefore, in the present review, we propose to discuss the underlying mechanisms of action of melatonin in regulating the circadian rhythm, cell cycle components and adult neurogenesis in the context of AD pathogenesis with the view that it might further assist to identify new therapeutic targets.

The Multiple Functions of Melatonin: Applications in the Military Setting

The aim of this review is to provide the reader with a general overview on the rationale for the use of melatonin by military personnel. This is a technique that is being increasingly employed to manage growing psycho-physical loads. In this context, melatonin, a pleotropic and regulatory molecule, has a potential preventive and therapeutic role in maintaining the operational efficiency of military personnel. In battlefield conditions in particular, the time to treatment after an injury is often a major issue since the injured may not have immediate access to medical care. Any drug that would help to stabilize a wounded individual, especially if it can be immediately administered (e.g., per os) and has a very high safety profile over a large range of doses (as melatonin does) would be an important asset to reduce morbidity and mortality. Melatonin may also play a role in the oscillatory synchronization of the neuro-cardio-respiratory systems and, through its epigenetic action, poses the possibility of restoring the main oscillatory waves of the cardiovascular system, such as the Mayer wave and RSA (respiratory sinus arrhythmia), which, in physiological conditions, result in the oscillation of the heartbeat in synchrony with the breath. In the future, this could be a very promising field of investigation.