The expression of MT1 and MT2 melatonin receptor mRNA in several rat tissues

Bondy

Neurochemistry International

et al. 2007

The expression levels of a number of genes associated with inflammation and immune function change with advancing age. Melatonin modulates gene expression levels of several of these genes. Therefore the declining levels of melatonin associated with age may play a role in the physiological effects of aging. We used oligonucleotide microarrays to measure age-related changes in mRNA expression in the murine CNS, and to study the effect of prolonged administration of dietary melatonin upon these changes. CB6F1 male mice were fed 40ppm melatonin for 2.1 months prior to sacrifice at age 26.5 months, and compared with both age-matched controls and young, 4.5-monthold untreated controls. Total RNA was extracted from whole brain (excluding cerebellum and brain stem) and individual samples were hybridized to Affymetrix Mouse 430-2.0 arrays. The expression of a substantial number of genes was modulated by melatonin treatment and changes in selected genes were validated by quantitative reverse transcription polymerase chain reaction (qRT-PCR). A subset of these genes did not change with age. Conversely, some genes modulated by age were also modulated by melatonin treatment. In general melatonin treatment drove the expression levels of these genes closer to the expression levels detected in the younger animals. Notably, the abundance of lipocalin 2 (Lcn2) mRNA increased with age and was decreased in old animals treated with melatonin. Lcn2 is a member of the acute phase response family of proteins and its mRNA levels in the brain increase in response to inflammation. Many of the genes with expression reduced by melatonin are involved in inflammation and the immune system. This suggests that melatonin treatment may influence the inflammatory responses of old animals, driving them to resemble more closely those occurring in young animals.

Section: Resultsmentioning

confidence: 99%

Effects of melatonin and age on gene expression in mouse CNS using microarray analysis

Bondy

Neurochemistry International

et al. 2007

Journal of Experimental Biology

“…Following MLT treatment, HSP70 protein levels decreased in the hepatic tissue nuclear fraction but were elevated in its cytosolic fraction, while no effect of MLT in the brain tissue was noted. MLT exerts its cellular effect via binding specific receptors (Dubocovich, 1995); the distribution and actions of these receptors vary between tissues (Naji et al, 2004;Sallinen et al, 2005). This may explain the difference in the effect of MLT between tissues.…”

Section: Discussionmentioning

confidence: 99%

Light Interference (LI) as a possible stressor altering HSP70 and its gene expression levels in brain and liver tissues of Golden Spiny Mice

Ashkenazi

Haim

2012

SUMMARYLight at night and light interference (LI) disrupt the natural light:dark cycle, causing alterations at physiological and molecular levels, partly by suppressing melatonin (MLT) secretion at night. Heat shock proteins (HSPs) can be activated in response to environmental changes. We assessed changes in gene expression and protein level of HSP70 in brain and hepatic tissues of golden spiny mice (Acomys russatus) acclimated to LI for two (SLI), seven (MLI) and 21 nights (LLI). The effect of MLT treatment on LI-mice was also assessed. HSP70 levels increased in brain and hepatic tissues after SLI, whereas after MLI and LLI, HSP70 decreased to control levels. Changes in HSP70 levels as a response to MLT occurred after SLI only in hepatic tissue. However, hsp70 expression following SLI increased in brain tissue, but not in hepatic tissue. MLT treatment and SLI caused a decrease in hsp70 levels in brain tissue and an increase in hsp70 in hepatic tissue. SLI acclimation elicited a stress response in A. russatus, as expressed by increased HSP70 levels and gene expression. Longer acclimation decreases protein and gene expression to their control levels. We conclude that for brain and hepatic tissues of A. russatus, LI is a short-term stressor. Our results also revealed that A. russatus can acclimate to LI, possibly because of its circadian system plasticity, which allows it to behave both as a nocturnal and as a diurnal rodent. To the best of our knowledge, this is the first study showing the effect of LI as a stressor at the cellular level, by activating HSP70. Supplementary material available online at

“…Messenger RNA expression of MT 1 and MT 2 receptors has been observed in the retina, SCN, thalamus, hippocampus vestibular nuclei and cerebral and cerebellar cortex. [27][28][29][30] At the level of the hippocampus, MT 2 receptors were detectable in particular on CA 3 and CA 4 pyramidal neurons, which receive glutamatergic excitatory inputs from the entorhinal cortex, whereas MT 1 receptors were predominantly expressed in CA 1 . 31 Recently, using polyclonal antibodies 32 we have pointed out the presence of MT 2 receptors in the reticular thalamus, substantia nigra (pars reticulata), supraoptic nucleus, red nucleus and CA 2 and CA 3 areas of the hippocampus.…”

Section: Where Are They?mentioning

confidence: 99%

Unveiling the role of melatonin MT2 receptors in sleep, anxiety and other neuropsychiatric diseases: a novel target in psychopharmacology

Comai

Gobbi

2014

J Psychiatry Neurosci

153

126

IntroductionMelatonin (MLT) is a neurohormone synthesized from serotonin (5-HT) and secreted foremost by the mammalian pineal gland following a distinct circadian rhythm with the acrophase during the dark phase and the nadir during the light phase in both diurnal and nocturnal species.1 A typical human adult's average daytime and nighttime levels of blood MLT are approximately 10 pg/mL and 60 pg/mL, respectively.2 Its production is controlled through the suprachiasmatic nucleus (SCN) by the photoperiod, peaking at night and dropping during the day. Melatonin is involved in numerous physiologic processes, including circadian rhythms, mood regulation, anxiety, sleep, appetite, immune responses and cardiac functions. 3,4 Most of the effects of MLT in the brain result from the activation of 2 high-affinity G-protein coupled receptors (GPCRs), MT 1 and MT 2 .5 Of note, GPCRs have a proven history of being excellent therapeutic targets. Recent market analyses indicate that 40%-50% of modern drugs and almost 25% of the top 200 best-selling drugs target GPCRs. 6 In addition to these high-affinity MLT receptors, another low-affinity MLT binding site, MT 3 , has recently been characterized as an MLT-sensitive form of the human enzyme quinone reductase 2. 7 The functional characterization of MT 1 and MT 2 receptors in target tissues is hampered by the paucity of selective MT 1 and MT 2 receptor ligands. Structural Background: Melatonin (MLT) is a pleiotropic neurohormone controlling many physiological processes and whose dysfunction may contribute to several different diseases, such as neurodegenerative diseases, circadian and mood disorders, insomnia, type 2 diabetes and pain. Melatonin is synthesized by the pineal gland during the night and acts through 2 G-protein coupled receptors (GPCRs), MT 1 (MEL1a) and MT 2 (MEL1b). Although a bulk of research has examined the physiopathological effects of MLT, few studies have investigated the selective role played by MT 1 and MT 2 receptors. Here we have reviewed current knowledge about the implications of MT 2 receptors in brain functions. Methods: We searched PubMed, Web of Science, Scopus, Google Scholar and articles reference lists for studies on MT 2 receptor ligands in sleep, anxiety, neuropsychiatric diseases and psychopharmacology, including genetic studies on the MTNR1B gene, which encodes the melatonin MT 2 receptor. Results: These studies demonstrate that MT 2 receptors are involved in the pathophysiology and pharmacology of sleep disorders, anxiety, depression, Alzheimer disease and pain and that selective MT 2 receptor agonists show hypnotic and anxiolytic properties. Limitations: Studies examining the role of MT 2 receptors in psychopharmacology are still limited. Conclusion: The development of novel selective MT 2 receptor ligands, together with further preclinical in vivo studies, may clarify the role of this receptor in brain function and psychopharmacology. The superfamily of GPCRs has proven to be among the most successful drug targets and, consequently, M...