901 research outputs found
Kynuramines, metabolites of melatonin and other indoles: the resurrection of an almost forgotten class of biogenic amines
No full textKynuramines represent their own class of biogenic amines. They are formed either by decarboxylation of kynurenines or pyrrole ring cleavage of indoleamines. N-2-formylated compounds formed in this last reaction can be deformylated either enzymatically by arylamine formamidases or hemoperoxidases, or photochemically. The earlier literature mainly focussed on cardiovascular effects of kynuramine, 5-hydroxykynuramine and their N-1,N-1-dimethylated analogs, including indirect effects via release of catecholamines or acetylcholine and interference with serotonin receptors. After the discovery of N-1-acetyl-N-2-formyl-5-methoxykynuramine (AFMK) and N-1-acetyl-5-methoxykynuramine (AMK) as major brain metabolites of melatonin, these compounds became of particular interest. They were shown to be produced enzymatically, pseudoenzymatically, by various free radical-mediated and via photochemical processes. In recent years, AFMK and AMK were shown to scavenge reactive oxygen and nitrogen species, thereby forming several newly discovered 3-indolinone, cinnolinone and quinazoline compounds, and to protect tissues from damage by reactive intermediates in various models. AMK is of special interest due to its properties as a potent cyclooxygenase inhibitor, NO scavenger forming a stable nitrosation product, inhibitor and/or downregulator of neuronal and inducible NO synthases, and a mitochondrial metabolism modulator. AMK easily interacts with aromates, forms adducts with tyrosyl and tryptophanyl residues, and may modify proteins
Molecular mechanisms of the pro-apoptotic actions of melatonin in cancer: A review
No full textIntroduction: Compelling evidence has highlighted the complex pleiotropic functions elicited by the melatonin in cancer cells. Melatonin behaves as a 'smart killer', i.e., modulating anti-apoptotic processes in normal cells, and triggering pro-apoptotic signals in cancer cells. Areas covered: Melatonin induces programmed cell death in a wide range of different tumors (breast, gastro-intestinal, hematological, prostate, osteosarcoma, melanoma, kidney, etc.). Mechanisms of action and molecular pathways involved in pro-apoptotic processes under melatonin treatment are discussed. Expert opinion: Melatonin involvement in apoptotic processes is a new and relevant field of investigation. Even in tumor models unresponsive to melatonin alone, this hormone can significantly amplify the cytostatic and the cytotoxic effects triggered by other compounds or conventional drugs. We are far from having a satisfactory understanding about how and when melatonin exerts its beneficial effects. Melatonin in the nanomolar range activates the intrinsic and/or the extrinsic apoptotic pathway in cancer cells, namely through an increase in the p53/MDM2p ratio and downregulation of Sirt1. This finding is of great relevance since there is intense research ongoing to identify nontoxic feasible inhibitors of MDM2 and Sirt1. Melatonin should be evaluated for the management of those cancers where both of these are overexpressed and functionally strategic. © 2013 Informa UK, Ltd
When the Circadian Clock Meets the Melanin Pigmentary System
No full textSilencing of BMAL1 and PER1 stimulates melanogenic activity of follicular and epidermal melanocytes, indicating a novel role for peripheral circadian clock processes in the regulation of melanin pigmentation. Linking the expression levels of BMAL1/PER1 with changes in melanogenesis opens exciting opportunities to study the role of the local molecular clock in modulation of melanocyte functions in the hair follicle and the epidermis with attendant effects on epidermal barrier functions in general
Molecular mechanisms of melatonin's inhibitory actions on breast cancers
No full textMelatonin is involved in many physiological functions and it plays an important role in many pathological processes as well. Melatonin has been shown to reduce the incidence of experimentally induced cancers and can significantly inhibit the growth of some human tumors, namely hormone-dependent cancers. The anticancer effects of melatonin have been observed in breast cancer, both in in vivo with models of chemically induced rat mammary tumors, and in vitro studies on human breast cancer cell lines. Melatonin acts at different physiological levels and its antitumoral properties are supported by a set of complex, different mechanisms of action, involving apoptosis activation, inhibition of proliferation, and cell differentiation
Discursos pronunciados en el acto de investidura como Doctor "Honoris Causa" del profesor Russel J. Reiter
No full textMelatonin, tunneling nanotubes, mesenchymal cells, and tissue regeneration
Get PDFMesenchymal stem cells are multipotent stem cells that reside in many human tissues and organs. Mesenchymal stem cells are widely used in experimental and clinical regenerative medicine due to their capability to transdifferentiate into various lineages. However, when transplanted, they lose part of their multipotency and immunomodulatory properties, and most of them die after injection into the damaged tissue. In this review, we discuss the potential utility of melatonin in preserving mesenchymal stem cells’ survival and function after transplantation. Melatonin is a pleiotropic molecule regulating critical cell functions including apoptosis, endoplasmic reticulum stress, and autophagy. Melatonin is also synthesized in the mitochondria where it reduces oxidative stress, the opening of the mitochondrial permeability transition pore and the downstream caspase activation, activates uncoupling proteins, and curtails the proinflammatory response. In addition, recent findings showed that melatonin also promotes the formation of tunneling nanotubes and the transfer of mitochondria between cells through the connecting tubules. As mitochondrial dysfunction is a primary cause of mesenchymal stem cells death and senescence and a critical issue for survival after transplantation, we propose that melatonin by favoring mitochondria functionality and their transfer through tunneling nanotubes from healthy to suffering cells could improve mesenchymal stem cell-based therapy in a large number of diseases for which basic and clinical trials are underway
DNA oxidatively damaged by chromium(III) and H2O2 is protected by the antioxidants melatonin, N-1-acetyl-N-2-formyl-5-methoxykynuramine, resveratrol and uric acid
No full textChromium (Cr) compounds are widely used industrial chemicals and well known carcinogens. Cr(III) was earlier found to induce oxidative damage as documented by examining the levels of 8-hydroxydeoxyguanosine (8-OH-dG), an index for DNA damage, in isolated calf thymus DNA incubated with CrCl3 and H2O,. In the present in vitro study, we compared the ability of the free radical scavengers melatonin, N-1-acetyl-N-2-formyl-5-methoxykynuramine (AFMK), resveratrol and uric acid to reduce DNA damage induced by Cr(III). Each of these scavengers markedly reduced the DNA damage in a concentration-dependent manner. The concentrations that reduced 8-OH-dG formation by 50% (IC50) were 0.10 muM for both resveratrol and melatonin, and 0.27 muM for AFMK. However, the efficacy of the fourth endogenous antioxidant, i.e. uric acid, in terms of its inhibition of DNA damage in the same in vitro system was about 60-150 times less effective than the other scavengers; the IC50 for uric acid was 15.24 muM. These findings suggest that three of the four antioxidants tested in these studies may have utility in protecting against the environmental pollutant Cr and that the protective effects of these free radical scavengers against Cr(III)-induced carcinogenesis may relate to their direct hydroxyl radical scavenging ability. In the present study, the formation of 8-OH-dG was likely due to a Cr(III)-mediated Fenton-type reaction that generates hydroxyl radicals, which in turn damage DNA. Once formed, 8-OH-dG can mutate eventually leading to cancer; thus the implication is that these antioxidants may reduce the incidence of Cr-related cancers. (C) 2001 Published by Elsevier Science Ltd
Tunneling nanotubes and mesenchymal stem cells: new insights into the role of melatonin in neuronal recovery
Get PDFEfficient cell-to-cell communication is essential for tissue development, homeostasis, and the maintenance of cellular functions after injury. Tunneling nanotubes (TNTs) have emerged as a new important method of cell-to-cell communication. TNTs are primarily established between stressed and unstressed cells and can transport a variety of cellular components. Mitochondria are important trafficked entities through TNTs. Transcellular mitochondria transfer permits the incorporation of healthy mitochondria into the endogenous network of recipient cells, changing the bioenergetic profile and other functional properties of the recipient and may allow the recipient cells to recuperate from apoptotic processes and return to a normal operating state. Mesenchymal cells (MSCs) can form TNTs and transfer mitochondria and other constituents to target cells. This occurs under both physiological and pathological conditions, leading to changes in cellular energy metabolism and functions. This review summarizes the newly-described capacity of melatonin to improve mitochondrial fusion/fission dynamics and promote TNT formation. This new evidence suggests that melatonin’s protective effects could be attributed to its ability to prevent mitochondrial damage in injured cells, reduce senescence, and promote anastasis, a natural cell recovery phenomenon that rescues cells from the brink of death. The modulation of these new routes of intercellular communication by melatonin could play a key role in increasing the therapeutic potential of MSCs
Melatonin and Neonatal Sepsis: A Promising Antioxidant Adjuvant Agent
No full textSepsis represents a major clinical problem in neonatal setting with elevated mortality rate related to multiple organ failure. Despite decades of research, the exact mechanism of organ failure in sepsis is still not completely understood. Oxidative stress (OS), derived from an imbalance between pro-oxidant and antioxidant factors, is involved in the pathogenesis of several neonatal diseases, including sepsis, and plays a particular role in systemic organ failure. Recently, it has been recognized that administration of antioxidants could be useful in septic patients. Among all antioxidants, melatonin has a characteristic role as an antioxidant, anti-inflammatory, and anti-apoptotic agent. In combination with other interventions, melatonin may contribute to an improvement in septic organ injury. Furthermore, melatonin has already been widely used in treating various diseases of neonatal population, including asphyxia, respiratory distress, and sepsis, and no significant toxicity or treatment-related side effects with long-term melatonin therapy have been reported. This review aims to summarize current knowledge concerning the potential beneficial role of melatonin in septic neonates, supporting its short-term adjuvant co-therapy to reduce complications during neonatal sepsis
Single administration of melatonin modulates the nitroxidergic system at the peripheral level and reduces thermal nociceptive hypersensitivity in neuropathic rats
No full textNeuropathic pain is a severe condition with unsatisfactory treatments. Melatonin, an indolamine, seems to be a promising molecule suitable for this purpose due to its well-known anti-inflammatory, analgesic, and antioxidant effects, as well as its modulation of the nitroxidergic system. Nevertheless, the data on its mechanism of action and potentialities are currently insufficient in this pathology, especially at the peripheral level. Thus, this work evaluated the effect of a single administration of melatonin in an established mononeuropathy pain model that monitors the behaviour and the changes in the nitroxidergic system in dorsal root ganglia and skin, which are affected by nervous impairment. Experiments were carried out on Sprague Dawley rats subdivided into the sham operated (control) and the chronic constriction injured animals, a model of peripheral neuropathic pain on sciatic nerve. Single administrations of melatonin (5-10 mg/kg) or vehicle were injected intraperitoneally on the 14th day after surgery, when the mononeuropathy was established. The animals were behaviourally tested for thermal hyperalgesia. The dorsal root ganglia and the plantar skin of the hind-paws were removed and processed for the immunohistochemical detection of neuronal and inducible nitric oxide synthases. The behavioural results showed an increase of withdrawal latency during the plantar test as early as 30 min after melatonin administration. The immunohistochemical results indicated a modulation of the nitroxidergic system both at dorsal root ganglia and skin level, permitting speculate on a possible mechanism of action. We showed that melatonin may be a possible therapeutic strategy in neuropathic pain
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