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      Selective protection of the cerebellum against intracerebroventricular LPS is mediated by local melatonin synthesis

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          Abstract

          Although melatonin is mainly produced by the pineal gland, an increasing number of extra-pineal sites of melatonin synthesis have been described. We previously demonstrated the existence of bidirectional communication between the pineal gland and the immune system that drives a switch in melatonin production from the pineal gland to peripheral organs during the mounting of an innate immune response. In the present study, we show that acute neuroinflammation induced by lipopolysaccharide (LPS) injected directly into the lateral ventricles of adult rats reduces the nocturnal peak of melatonin in the plasma and induces its synthesis in the cerebellum, though not in the cortex or hippocampus. This increase in cerebellar melatonin content requires the activation of nuclear factor kappa B (NF-κB), which positively regulates the expression of the key enzyme for melatonin synthesis, arylalkylamine N-acetyltransferase (AA-NAT). Interestingly, LPS treatment led to neuronal death in the hippocampus and cortex, but not in the cerebellum. This privileged protection of cerebellar cells was abrogated when G-protein-coupled melatonin receptors were blocked by the melatonin antagonist luzindole, suggesting that the local production of melatonin protects cerebellar neurons from LPS toxicity. This is the first demonstration of a switch between pineal and extra-pineal melatonin production in the central nervous system following a neuroinflammatory response. These results have direct implications concerning the differential susceptibility of specific brain areas to neuronal death.

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          The online version of this article (doi:10.1007/s00429-013-0686-4) contains supplementary material, which is available to authorized users.

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          Most cited references65

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          NeuN, a neuronal specific nuclear protein in vertebrates.

          A battery of monoclonal antibodies (mAbs) against brain cell nuclei has been generated by repeated immunizations. One of these, mAb A60, recognizes a vertebrate nervous system- and neuron-specific nuclear protein that we have named NeuN (Neuronal Nuclei). The expression of NeuN is observed in most neuronal cell types throughout the nervous system of adult mice. However, some major cell types appear devoid of immunoreactivity including cerebellar Purkinje cells, olfactory bulb mitral cells, and retinal photoreceptor cells. NeuN can also be detected in neurons in primary cerebellar cultures and in retinoic acid-stimulated P19 embryonal carcinoma cells. Immunohistochemically detectable NeuN protein first appears at developmental timepoints which correspond with the withdrawal of the neuron from the cell cycle and/or with the initiation of terminal differentiation of the neuron. NeuN is a soluble nuclear protein, appears as 3 bands (46-48 x 10(3) M(r)) on immunoblots, and binds to DNA in vitro. The mAb crossreacts immunohistochemically with nervous tissue from rats, chicks, humans, and salamanders. This mAb and the protein recognized by it serve as an excellent marker for neurons in the central and peripheral nervous systems in both the embryo and adult, and the protein may be important in the determination of neuronal phenotype.
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            Melatonin as a natural ally against oxidative stress: a physicochemical examination.

            Oxidative stress has been proven to be related to the onset of a large number of health disorders. This chemical stress is triggered by an excess of free radicals, which are generated in cells because of a wide variety of exogenous and endogenous processes. Therefore, finding strategies for efficiently detoxifying free radicals has become a subject of a great interest, from both an academic and practical points of view. Melatonin is a ubiquitous and versatile molecule that exhibits most of the desirable characteristics of a good antioxidant. The amount of data gathered so far regarding the protective action of melatonin against oxidative stress is overwhelming. However, rather little is known concerning the chemical mechanisms involved in this activity. This review summarizes the current progress in understanding the physicochemical insights related to the free radical-scavenging activity of melatonin. Thus far, there is a general agreement that electron transfer and hydrogen transfer are the main mechanisms involved in the reactions of melatonin with free radicals. However, the relative importance of other mechanisms is also analyzed. The chemical nature of the reacting free radical also has an influence on the relative importance of the different mechanisms of these reactions. Therefore, this point has also been discussed in detail in the current review. Based on the available data, it is concluded that melatonin efficiently protects against oxidative stress by a variety of mechanisms. Moreover, it is proposed that even though it has been referred to as the chemical expression of darkness, perhaps it could also be referred to as the chemical light of health. © 2011 John Wiley & Sons A/S.
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              Regulation of innate immune responses in the brain.

              Microglial cells are the main innate immune cells of the complex cellular structure of the brain. These cells respond quickly to pathogens and injury, accumulate in regions of degeneration and produce a wide variety of pro-inflammatory molecules. These observations have resulted in active debate regarding the exact role of microglial cells in the brain and whether they have beneficial or detrimental functions. Careful targeting of these cells could have therapeutic benefits for several types of trauma and disease specific to the central nervous system. This Review discusses the molecular details underlying the innate immune response in the brain during infection, injury and disease.
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                Author and article information

                Contributors
                +55-11-30917612 , +55-11-30917568 , rpmarkus@usp.br
                Journal
                Brain Struct Funct
                Brain Struct Funct
                Brain Structure & Function
                Springer Berlin Heidelberg (Berlin/Heidelberg )
                1863-2653
                1863-2661
                22 December 2013
                22 December 2013
                2015
                : 220
                : 2
                : 827-840
                Affiliations
                [ ]Laboratory of Chronopharmacology, Department of Physiology, Institute of Biosciences, University of São Paulo (USP), São Paulo, SP 05508-090 Brazil
                [ ]Department of Speech, Language and Hearing Therapy, São Paulo State University (UNESP), Marilia, SP 17525-900 Brazil
                [ ]Department of Anatomy, Institute of Biomedical Sciences, University of São Paulo (USP), São Paulo, SP 05508-900 Brazil
                Article
                686
                10.1007/s00429-013-0686-4
                4341011
                24363121
                b20b1eae-6178-473d-bcbf-1540ed1f229e
                © The Author(s) 2013

                Open AccessThis article is distributed under the terms of the Creative Commons Attribution License which permits any use, distribution, and reproduction in any medium, provided the original author(s) and the source are credited.

                History
                : 14 September 2013
                : 3 December 2013
                Categories
                Original Article
                Custom metadata
                © Springer-Verlag Berlin Heidelberg 2015

                Neurology
                pineal gland,arylalkylamine n-acetyltransferase (aa-nat),immune-pineal axis,neuroinflammation,melatonin receptors,nuclear factor kappa b (nf-κb)

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