Interaction of melatonin and Bmal1 in the regulation of PI3K/AKT pathway components and cellular survival

Circadian rhythms of mineral metabolism in chronic kidney disease-mineral bone disorder

PURPOSE OF REVIEW

The circadian rhythms have a systemic impact on all aspects of physiology. Kidney diseases are associated with extremely high-cardiovascular mortality, related to chronic kidney disease-mineral bone disorder (CKD-MBD), involving bone, parathyroids and vascular calcification. Disruption of circadian rhythms may cause serious health problems, contributing to development of cardiovascular diseases, metabolic syndrome, cancer, organ fibrosis, osteopenia and aging. Evidence of disturbed circadian rhythms in CKD-MBD parameters and organs involved is emerging and will be discussed in this review.

RECENT FINDINGS

Kidney injury induces unstable behavioral circadian rhythm. Potentially, uremic toxins may affect the master-pacemaker of circadian rhythm in hypothalamus. In CKD disturbances in the circadian rhythms of CKD-MBD plasma-parameters, activin A, fibroblast growth factor 23, parathyroid hormone, phosphate have been demonstrated. A molecular circadian clock is also expressed in peripheral tissues, involved in CKD-MBD; vasculature, parathyroids and bone. Expression of the core circadian clock genes in the different tissues is disrupted in CKD-MBD.

SUMMARY

Disturbed circadian rhythms is a novel feature of CKD-MBD. There is a need to establish which specific input determines the phase of the local molecular clock and to characterize its regulation and deregulation in tissues involved in CKD-MBD. Finally, it is important to establish what are the implications for treatment including the potential applications for chronotherapy.

Molecular Mechanisms of Melatonin-Mediated Cell Protection and Signaling in Health and Disease

Melatonin, an endogenously synthesized indolamine, is a powerful antioxidant exerting beneficial action in many pathological conditions. Melatonin protects from oxidative stress in ischemic/reperfusion injury, neurodegenerative diseases, and aging, decreases inflammation, modulates the immune system, inhibits proliferation, counteracts the Warburg effect, and promotes apoptosis in various cancer models. Melatonin stimulates antioxidant enzymes in the cells, protects mitochondrial membrane phospholipids, especially cardiolipin, from oxidation thus preserving integrity of the membranes, affects mitochondrial membrane potential, stimulates activity of respiratory chain enzymes, and decreases the opening of mitochondrial permeability transition pore and cytochrome c release. This review will focus on the molecular mechanisms of melatonin effects in the cells during normal and pathological conditions and possible melatonin clinical applications.

Natural products as modulators of retinoic acid receptor-related orphan receptors (RORs)

Covering: 1994 to 2020 Retinoic acid receptor-related orphan receptors (RORs) belong to a subfamily of the nuclear receptor superfamily and possess prominent roles in circadian rhythm, metabolism, inflammation, and cancer. They have been subject of research for over two decades and represent attractive but challenging drug targets. Natural products were among the first identified ligands of RORs and continue to be of interest to this day. This review focuses on ligands and indirect modulators of RORs from natural sources and explores their roles in a therapeutic context.

Identifying daily changes in circRNAs and circRNA-associated-ceRNA networks in the rat pineal gland

Circular RNAs (circRNAs) are a new class of covalently closed circular RNA molecules that are involved in many biological processes. However, information about circRNAs in the pineal gland, particularly that of rats, is limited. To establish resources for the study of the rat pineal gland, we performed transcriptome analysis of the pineal glands during the day and night. In this study, 1413 circRNAs and 1989 miRNAs were identified in the pineal gland of rats during the night and day using the Illumina platform. Forty differentially expressed circRNAs and 93 differentially expressed miRNAs were obtained, among which 20 circRNAs and 37 miRNAs were significantly upregulated during the day and 20 circRNAs and 56 miRNAs were significantly upregulated during the night. As circRNAs have been reported to work as miRNA sponges, we predicted 15940 interactions among 40 circRNAs, 93 miRNAs and 400 mRNAs with differential diurnal expression using miRanda and TargetScan to build a ceRNA regulatory network in the rat pineal gland. The diurnal expression profile of circRNAs in the rat pineal gland may provide additional information about the role of circRNAs in regulating changes in melatonin circadian rhythms. The analyzed data reported in this study will be an important resource for future studies to elucidate the altered physiology of circRNAs in diurnal rhythms.

Mitochondria and immunity in chronic fatigue syndrome

It is widely accepted that the pathophysiology and treatment of myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) could be considerably improved. The heterogeneity of ME/CFS and the confusion over its classification have undoubtedly contributed to this, although this would seem a consequence of the complexity of the array of ME/CFS presentations and high levels of diverse comorbidities. This article reviews the biological underpinnings of ME/CFS presentations, including the interacting roles of the gut microbiome/permeability, endogenous opioidergic system, immune cell mitochondria, autonomic nervous system, microRNA-155, viral infection/re-awakening and leptin as well as melatonin and the circadian rhythm. This details not only relevant pathophysiological processes and treatment options, but also highlights future research directions. Due to the complexity of interacting systems in ME/CFS pathophysiology, clarification as to its biological underpinnings is likely to considerably contribute to the understanding and treatment of other complex and poorly managed conditions, including fibromyalgia, depression, migraine, and dementia. The gut and immune cell mitochondria are proposed to be two important hubs that interact with the circadian rhythm in driving ME/CFS pathophysiology.

Melatonin upregulates DNA-PKcs to suppress apoptosis of human umbilical vein endothelial cells via inhibiting miR-101 under H2O2-induced oxidative stress

Melatonin has been implicated in inhibiting oxidative stress-induced apoptosis of endothelial cells. However, the underlying mechanism remains poorly understood. In this study, we examined the effect of melatonin on apoptosis of human umbilical vein endothelial cells (HUVECs) induced by H₂O₂ and explored the underlying mechanisms. Our results demonstrated that DNA-dependent protein kinase catalytic subunit (DNA-PKcs) upregulation contributed to the protective role of melatonin in HUVECs under oxidative stress with H₂O₂. Further study showed that melatonin treatment led to a decreased level of miRNA-101, which could be responsible for DNA-PKcs upregulation and DNA-PKcs-mediated apoptosis inhibition in HUVECs under oxidative stress with H₂O₂. Our results also showed that melatonin increased the activity of PI3K/AKT and DNA-PKcs knockdown in melatonin-treated HUVECs that lead to inactivation of PI3K/AKT signaling under oxidative stress with H₂O₂. Furthermore, blockade of PI3K/AKT signal with LY294002 significantly reduced melatonin-induced apoptosis inhibition in H₂O₂-treated HUVECs. Taken together, our findings identify a miR-101/DNA-PKcs/PI3K/AKT signaling pathway in melatonin-induced endothelial cell apoptosis inhibition under oxidative stress with H₂O₂.

Physiological and pharmacological roles of melatonin in the pathophysiological components of cellular injury after ischemic stroke

Apart from its metabolic or physiological functions, melatonin has a potent cytoprotective activity in the physiological and pathological conditions. It is synthetized by the pineal gland and released into the blood circulation but particularly cerebrospinal fluid in a circadian manner. It can also easily diffuse through cellular membranes due its small size and lipophilic structure. Its cytoprotective activity has been linked to its potent free radical scavenger activity with the desirable characteristics of a clinically- reliable antioxidant. Melatonin detoxifies oxygen and nitrogen-based free radicals and oxidizing agents, including the highly toxic hydroxyl-and peroxynitrite radicals, initiating cellular damage. However, the cytoprotective activity of melatonin is complex and cannot be solely limited to its free radical scavenger activity. It regulates cellular signaling pathways through receptor– dependent and independent mechanisms. Most of these downstream molecules, such as PI3K/AKT pathway components, also contribute to the cytoprotective effects of melatonin. In this term, melatonin is a promising molecule for the treatment of neurodegenerative disorders, such as ischemic stroke, which melatonin reduces ischemic brain injury in animal models of ischemic stroke. It regulates also circadian rhythm proteins after ischemic stroke, playing roles in cellular survival. In this context, present article summarizes the possible role of melatonin in the pathophysiological events after ischemic stroke.

Effect of melatonin supplementation on oxidative stress parameters: A systematic review and meta-analysis

BACKGROUND

Oxidative stress, defined as an imbalance between pro-oxidants and neutralizing antioxidants within the body, is a growing public health concern. Oxidative stress is involved in the progression of nearly all chronic diseases. Melatonin has been suggested to reduce oxidative stress by its potential radical scavenging properties.

OBJECTIVE

To determine the efficacy and safety of melatonin as a therapy for the improvement of oxidative stress parameters in randomized controlled trials.

METHODS

A systematic database search using Scopus, PubMed/Medline, EMBASE, Web of Science, the Cochrane Controlled Register of Trials and clinicaltrials.gov (https://clinicaltrials.gov) for studies published up to July 2020 was conducted. We included studies which investigated the effect of supplemental melatonin compared to placebo on oxidative stress parameters in unhealthy patients. Quantitative data synthesis was conducted using a random-effects model with standard mean difference (SMD) and 95 % confidence intervals (CI). Cochrane's Q and I² values were used to evaluate heterogeneity.

RESULTS

A total of 12 randomized controlled trials (RCTs) were eligible. The meta-analysis indicated an association between melatonin intake and a significant increase in total antioxidant capacity (TAC) (SMD: 0.76; 95 % CI: 0.30, 1.21; I² = 80.1 %), glutathione (GSH) levels (SMD: 0.57; 95 % CI: 0.32, 0.83; I² = 15.1 %), superoxide dismutase (SOD) (SMD: 1.38; 95 % CI: 0.13, 2.62; I² = 86.9 %), glutathione peroxidase (GPx) (SMD: 1.36; 95 % CI: 0.46, 2.30; I² = 89.3 %), glutathione reductase (GR) (SMD: 1.21; 95 % CI: 0.65, 1.77; I² = 00.0 %) activities, and a significant reduction in malondialdehyde (MDA) levels (SMD: -0.79; 95 % CI: -1.19, -0.39; I² = 73.1 %). Melatonin intake was not shown to significantly affect nitric oxide (NO) levels (SMD: -0.24; 95 % CI: -0.61, 0.14; I² = 00.0 %) or catalase (CAT) activity (SMD: -1.38; 95 % CI: -1.42, 4.18; I² = 96.6 %).

CONCLUSION

Melatonin intake was shown to have a significant impact on improving Oxidative stress parameters. However, future research through large, well-designed randomized controlled trials are required to determine the effect of melatonin on oxidative stress parameters in different age groups and different disease types.

Melatonin and Autophagy in Aging-Related Neurodegenerative Diseases

With aging, the nervous system gradually undergoes degeneration. Increased oxidative stress, endoplasmic reticulum stress, mitochondrial dysfunction, and cell death are considered to be common pathophysiological mechanisms of various neurodegenerative diseases (NDDs) such as Alzheimer's disease (AD), Parkinson's disease (PD), Huntington's disease (HD), organophosphate-induced delayed neuropathy (OPIDN), and amyotrophic lateral sclerosis (ALS). Autophagy is a cellular basic metabolic process that degrades the aggregated or misfolded proteins and abnormal organelles in cells. The abnormal regulation of neuronal autophagy is accompanied by the accumulation and deposition of irregular proteins, leading to changes in neuron homeostasis and neurodegeneration. Autophagy exhibits both a protective mechanism and a damage pathway related to programmed cell death. Because of its "double-edged sword", autophagy plays an important role in neurological damage and NDDs including AD, PD, HD, OPIDN, and ALS. Melatonin is a neuroendocrine hormone mainly synthesized in the pineal gland and exhibits a wide range of biological functions, such as sleep control, regulating circadian rhythm, immune enhancement, metabolism regulation, antioxidant, anti-aging, and anti-tumor effects. It can prevent cell death, reduce inflammation, block calcium channels, etc. In this review, we briefly discuss the neuroprotective role of melatonin against various NDDs via regulating autophagy, which could be a new field for future translational research and clinical studies to discover preventive or therapeutic agents for many NDDs.

Glioblastoma chemoresistance: roles of the mitochondrial melatonergic pathway

Treatment-resistance is common in glioblastoma (GBM) and the glioblastoma stem-like cells (GSC) from which they arise. Current treatment options are generally regarded as very poor and this arises from a poor conceptualization of the biological underpinnings of GBM/GSC and of the plasticity that these cells are capable of utilizing in response to different treatments. A number of studies indicate melatonin to have utility in the management of GBM/GSC, both per se and when adjunctive to chemotherapy. Recent work shows melatonin to be produced in mitochondria, with the mitochondrial melatonergic pathway proposed to be a crucial factor in driving the wide array of changes in intra- and inter-cellular processes, as well as receptors that can be evident in the cells of the GBM/GSC microenvironment. Variations in the enzymatic conversion of N-acetylserotonin (NAS) to melatonin may be especially important in GSC, as NAS can activate the tyrosine receptor kinase B to increase GSC survival and proliferation. Consequently, variations in the NAS/melatonin ratio may have contrasting effects on GBM/GSC survival. It is proposed that mitochondrial communication across cell types in the tumour microenvironment is strongly driven by the need to carefully control the mitochondrial melatonergic pathways across cell types, with a number of intra- and inter-cellular processes occurring as a consequence of the need to carefully regulate the NAS/melatonin ratio. This better integrates previously disparate data on GBM/GSC as well as providing clear future research and treatment options.

The wrinkling of time: Aging, inflammation, oxidative stress, and the circadian clock in neurodegeneration

A substantial body of research now implicates the circadian clock in the regulation of an array of diverse biological processes including glial function, metabolism, peripheral immune responses, and redox homeostasis. Sleep abnormalities and other forms of circadian disruption are common symptoms of aging and neurodegeneration. Circadian clock disruption may also influence the aging processes and the pathogenesis of neurodegenerative diseases. The specific mechanisms governing the interaction between circadian systems, aging, and the immune system are still being uncovered. Here, we review the evidence supporting a bidirectional relationship between aging and the circadian system. Further, we explore the hypothesis that age-related circadian deterioration may exacerbate multiple pathogenic processes, priming the brain for neurodegeneration.

Pineal gland protects against chemically induced oral carcinogenesis and inhibits tumor progression in rats

Clinical investigations suggest that melatonin suppression and circadian dysfunction may be related to cancer development in shift workers. Studies also show that melatonin suppression after pinealectomy increases cancer incidence in preclinical models. However, no study evaluated the influence of pinealectomy on oral cancer development. In the current study, we investigated the effects of pinealectomy on oral squamous cell carcinoma (OSCC) occurrence and progression in rats. Rats submitted to sham surgery were used as control. Pinealectomy promoted an increase of 140% in OSCC occurrence when compared to sham animals. Tumors from pinealectomized rats displayed a higher volume and thickness than the tumors from sham-operated animals. Pinealectomy induced atrophy of the epithelium adjacent to the oral lesions. Pinealectomized rats showed higher mean number of tumor-associated macrophages and eosinophils in the invasive front of OSCC. In addition, nuclear overexpression of ERK1/2 and p53 was also observed in the front of carcinomas from pinealectomized rats. These results reveal that pineal gland plays a protective role against oral carcinogenesis. The melatonin suppression caused by the pinealectomy might contribute to oral cancer development by acting on ERK1/2 and p53 pathways and regulating tumor inflammation.

BMAL1 Associates with NOP58 in the Nucleolus and Contributes to Pre-rRNA Processing

The transcription factor BMAL1 is a core element of the circadian clock that contributes to cyclic control of genes transcribed by RNA polymerase II. By using biochemical cellular fractionation and immunofluorescence analyses we reveal a previously uncharacterized nucleolar localization for BMAL1. We used an unbiased approach to determine the BMAL1 interactome by mass spectrometry and identified NOP58 as a prominent nucleolar interactor. NOP58, a core component of the box C/D small nucleolar ribonucleoprotein complex, associates with Snord118 to control specific pre-ribosomal RNA (pre-rRNA) processing steps. These results suggest a non-canonical role of BMAL1 in ribosomal RNA regulation. Indeed, we show that BMAL1 controls NOP58-associated Snord118 nucleolar levels and cleavage of unique pre-rRNA intermediates. Our findings identify an unsuspected function of BMAL1 in the nucleolus that appears distinct from its canonical role in the circadian clock system.

•

BMAL1 displays a circadian-independent localization in the nucleolus

•

Bmal1-deficient cells show altered nucleolar morphology

•

Interactome proteomics reveals that BMAL1 associates with nucleolar proteins

•

BMAL1 appears to play a non-canonical, non-circadian role in pre-rRNA processing

The Rhythmicity of Clock Genes is Disrupted in the Choroid Plexus of the APP/PS1 Mouse Model of Alzheimer's Disease

BACKGROUND

The choroid plexus (CP), which constitutes the blood-cerebrospinal fluid barrier, was recently identified as an important component of the circadian clock system.

OBJECTIVE

The fact that circadian rhythm disruption is closely associated to Alzheimer's disease (AD) led us to investigate whether AD pathology can contribute to disturbances of the circadian clock in the CP.

METHODS

For this purpose, we evaluated the expression of core-clock genes at different time points, in 6- and 12-month-old female and male APP/PS1 mouse models of AD. In addition, we also assessed the effect of melatonin pre-treatment in vitro before amyloid-β stimulus in the daily pattern of brain and muscle Arnt-like protein 1 (Bmal1) expression.

RESULTS

Our results showed a dysregulation of circadian rhythmicity of Bmal1 expression in female and male APP/PS1 transgenic 12-month-old mice and of Period 2 (Per2) expression in male mice. In addition, a significant circadian pattern of Bmal1 was measured the intermittent melatonin pre-treatment group, showing that melatonin can reset the CP circadian clock.

CONCLUSION

These results demonstrated a connection between AD and the disruption of circadian rhythm in the CP, representing an attractive target for disease prevention and/or treatment.