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Mammalian pineal glands are composed mostly of pinealocytes, which are the melatonin secretory cells, and also importantly of glial cells in special astrocytes. With the aim of studying the interactions between pinealocytes and astrocytes, the methodologies for obtaining and maintaining isolated pinealocytes and astrocytes in culture were standardized, in addition to the co-culture of both cell types. Some works of our group were published on the interactions between isolated astrocytes and pinealocytes from the pineal gland of Wistar rats, considering the modulatory role of glutamate and angiotensin on the synthesis of melatonin. In this chapter, the methodologies for obtaining and maintaining astrocytes and pinealocytes culture as well as co-culture of these two cell types will be presented.

Melatonin is synthesized and secreted by the pineal gland in mammals. Its synthesis is triggered at night by norepinephrine released in the interstices of the gland. This nocturnal production is dependent on the transcription, translation, and/or activation of the enzymes arylalkylamine-N-acetyltransferase (AANAT), acetylserotonin O-methyltransferase (ASMT), and tryptophan hydroxylase (TPH). In this chapter, the methodology for the analysis of AANAT, ASMT, and TPH activities by radiometric assays will be presented. Several papers were published by our group utilizing these methodologies, evaluating the enzymes modulation by voltage-gated calcium channels, angiotensin II, insulin, anhydroecgonine methyl ester (AEME, crack-cocaine product), ethanol, monosodium glutamate (MSG), signaling pathways such as NFkB, and pathophysiological conditions such as diabetes.

Pineal gland secretes the hormone melatonin at night with a circadian rhythm. The synthesis and secretion of melatonin are stimulated at night by norepinephrine released by sympathetic postganglionic neurons projecting from the superior cervical ganglia. Norepinephrine simultaneously activates α- and β-adrenoceptors, triggering melatonin synthesis.To study the regulation of melatonin production and secretion, it is very convenient to use an ex vivo preparation. Thus, it is possible to keep intact pineal glands in culture and to study the actions of agonists, antagonists, modulators, toxic agents, etc., in melatonin synthesis. Artificial melatonin synthesis stimulation in vitro is usually achieved by using a β-adrenergic agonist alone or in association with an α-adrenergic agonist. In this chapter, the methodology of cultured pineal glands will be described. Several papers were published by our group using this methodology, approaching the role played in melatonin synthesis control by angiotensin II and IV, insulin, glutamate, voltage-gated calcium channels, anhydroecgonine methyl ester (AEME, crack-cocaine product), monosodium glutamate (MSG), signaling pathways like NFkB, pathophysiological conditions like diabetes, etc.

The pineal gland synthesizes melatonin exclusively at night, which gives melatonin the characteristic of a temporal synchronizer of the physiological systems. Melatonin is a regulator of insulin activities centrally and also peripherally and its synthesis is reduced in diabetes. Since monosodium glutamate (MSG) is often used to induce the type 2 diabetic and metabolic syndrome in animal models, the purpose of this work is to evaluate the potential effects of MSG given to neonates on the pineal melatonin synthesis in different aged male and female rats. Wistar rats were subcutaneously injected with MSG (4mg/g/day) or saline solution (0.9%) from the second to eighth post-natal day. The circadian profiles both melatonin levels and AANAT activity were monitored at different ages. Body weight, naso-anal length, adipose tissues weight, GTT, ITT and serum insulin levels were also evaluated. Typical obesity with the neonatal MSG treatment was observed, indicated by a great increase in adipose depots without a concurrent increase in body weight. MSG treatment did not cause hyperglycemia or glucose intolerance, but induced insulin resistance. An increase of melatonin synthesis at ZT 15 with phase advance was observed in in some animals. The AANAT activity was positively parallel to the melatonin circadian profile. It seems that MSG causes hypothalamic obesity which may increase AANAT activity and melatonin production in pineal gland. These effects were not temporally correlated with insulin resistance and hyperinsulinemia indicating the hypothalamic lesions, particularly in arcuate nucleus induced by MSG in early age, as the principal cause of the increase in melatonin production.

Endogenous phospholipases Aβ-micrustoxin was characterized biochemically by a proteomic approach. Astrocytes were obtained by dissociation of pineal glands from Wistar rats; glioblastoma tumor cells were purchased from ATCC and Sigma and cultured in DMEM medium. Cell viability was evaluated by MTT assay; cell proliferation and cell cycle phases were analyzed by flow cytometry; p53, p21 and p27 proteins were studied by western blotting and immunocytochemistry.Proteomic analysis revealed fragments on β-micrustoxin that aligned with a PLAThese findings indicate that β-micrustoxin from

A local renin-angiotensin system (RAS) has been postulated in the pineal gland. In addition to angiotensin II (Ang II), other active metabolites have been described. In this study, we aimed to investigate a role for Ang IV in melatonin synthesis and the presence of its proposed (IRAP)/AT4 receptor (insulin-regulated aminopeptidase) in the pineal gland. The effect of Ang IV on melatonin synthesis was investigated in vitro using isolated pinealocytes. IRAP protein expression and activity were evaluated by Western blot and fluorimetry using Leu-4Me-β-naphthylamide as a substrate. Melatonin was analyzed by HPLC, calcium content by confocal microscopy and cAMP by immunoassay. Ang IV significantly augmented the NE-induced melatonin synthesis to a similar degree as that achieved by Ang II. This Ang IV effect in pinealocytes appears to be mediated by an increase in the intracellular calcium content but not by cAMP. The (IRAP)/AT4 expression and activity were identified in the pineal gland, which were significantly higher in membrane fractions than in soluble fractions. Ang IV significantly reduced IRAP activity in the pineal membrane fractions. The main findings of the present study are as follows: (1) Ang IV potentiates NE-stimulated melatonin production in pinealocytes, (2) the (IRAP)/AT4 receptor is present in the rat pineal gland, and (3) Ang IV inhibits IRAP activity and increases pinealocytes [Ca2+]i. We conclude that Ang IV is an important component of RAS and modulates melatonin synthesis in the rat pineal gland.

Anhydroecgonine methyl ester (AEME), also called methylecgonidine, is a pyrolysis product of crack cocaine that is neurotoxic and potentiates cocaine-induced sensitization. The sensitization induced by drugs of abuse can be influenced by melatonin, a neuroprotective pineal hormone. In the same way, drugs of abuse like alcohol and methamphetamine can modify melatonin synthesis. The aim of the present work was to investigate the AEME effects on melatonin synthesis in the rat pineal gland. Neurotransmitter systems involved in its effects, antioxidant enzyme activities and the melatonin protective role in AEME-induced toxicity were also evaluated. The animals were injected with AEME i.p. (1.12 mg per kg of body weight per day) or vehicle for 10 consecutive days and the nocturnal pineal melatonin synthesis profile and SOD, GPx and GR activities in the cerebral cortex and hippocampus were assessed. Cultured pineal glands were incubated with AEME for 30 min or 48 h before norepinephrine stimulation and melatonin synthesis, arylalkylamine N-acetyltransferase activity, cAMP and [Ca2+]i were determined. The involvement of cholinergic and glutamatergic systems was analyzed using different antagonists. The protective role of melatonin in AEME toxicity on hippocampal neurons was evaluated by a viability assay. AEME impaired melatonin synthesis both in vivo and in vitro and this effect seems to be mediated by muscarinic receptors and [Ca2+]i elevation. AEME reduced neuronal viability and melatonin was able to protected hippocampal neurons against AEME toxicity. The melatonin synthesis impairment observed could lead to the worsening of the direct AEME neurotoxicity and to the exacerbation of the crack cocaine addiction and sensitization.

Daniela Meneses-Santos,1 Daniella do Carmo Buonfiglio,2 Rodrigo Antonio Peliciari-Garcia,3 Angela Maria Ramos-Lobo,2 Divanízia do Nascimento Souza,1 Angelo Rafael Carpinelli,2 Carla Roberta de Oliveira Carvalho,2 Rogério Antônio Laurato Sertie,2 Sandra Andreotti,2 Fabio Bessa Lima,2 Solange Castro Afeche,4 Emerson Ticona Fioretto,1 José Cipolla-Neto,2 Anderson Carlos Marçal1 1Department of Morphology, Center of Biological Sciences and Health, Federal University of Sergipe, São Cristóvão, Brazil; 2Department of Physiology and Biophysics, Institute of Biomedical Sciences, University of São Paulo, São Paulo, Brazil; 3Morphophysiology & Pathology Sector, Department of Biological Sciences, Federal University of São Paulo, São Paulo, Brazil; 4Laboratory of Pharmacology, Butanta Institute, São Paulo, Brazil Background: Melatonin is a neuroendocrine hormone that regulates many functions involving energy metabolism and behavior in mammals throughout the light/dark cycle. It is considered an output signal of the central circadian clock, located in the suprachiasmatic nucleus of the hypothalamus. Melatonin synthesis can be influenced by other hormones, such as insulin and glucocorticoids in pathological conditions or during stress. Furthermore, glucocorticoids appear to modulate circadian clock genes in peripheral tissues and are associated with the onset of metabolic diseases. In the pineal gland, the modulation of melatonin synthesis by clock genes has already been demonstrated. However, few studies have shown the effects of glucocorticoids on clock genes expression in the pineal gland. Results: We verified that rats treated with dexamethasone (2 mg/kg body weight, intraperitoneal) for 10 consecutive days, showed hyperglycemia and pronounced hyperinsulinemia during the dark phase. Insulin sensitivity, glucose tolerance, melatonin synthesis, and enzymatic activity of arylalkylamine N-acetyltransferase, the key enzyme of melatonin synthesis, were reduced. Furthermore, we observed an increase in the expression of Bmal1, Per1, Per2, Cry1, and Cry2 in pineal glands of rats treated with dexamethasone. Conclusion: These results show that chronic treatment with dexamethasone can modulate both melatonin synthesis and circadian clock expression during the dark phase. Keywords: clock genes, glucocorticoids, pineal gland, nocturnal insulinemia, glycemia profile, AANAT activity

Aims The circadian rhythm in mammalian pineal melatonin secretion is modulated by norepinephrine (NE) released at night. NE interaction with β 1 -adrenoceptors activates PKA that phosphorylates the transcription factor CREB, leading to the transcription and translation of the arylalkylamine- N -acetyltransferase (AANAT) enzyme. Several studies have reported the interplay between CREB and the nuclear factor-κB (NF-κB) and a circadian rhythm for this transcription factor was recently described in the rat pineal gland. In this work we studied a direct effect of NE on NF-κB activation and the role played by this factor on melatonin synthesis and Aanat transcription and activity. Main methods Cultured rat pineal glands were incubated in the presence of two different NF-κB inhibitors, pyrrolidine-dithiocarbamate or sodium salicylate, and stimulated with NE. Melatonin content was quantified by HPLC with electrochemical detection. AANAT activity was measured by a radiometric assay and the expression of Aanat mRNA was analyzed by real-time PCR. Gel shift assay was performed to study the NF-κB activation in cultured rat pineal glands stimulated by NE. Key findings Our results showed that the p50/p50 homodimer of NF-κB is activated by NE and that it has a role in melatonin synthesis, acting on Aanat transcription and activity. Significance Here we present evidence that NF-κB is an important transcription factor that acts, directly or indirectly, on Aanat transcription and activity leading to a modulation of melatonin synthesis. NE plays a role in the translocation of NF-κB p50/p50 homodimer to the nucleus of pinealocytes, thus probably influencing the nocturnal pineal melatonin synthesis.

Smoking crack cocaine involves the inhalation of cocaine and its pyrolysis product, anhydroecgonine methyl ester (AEME). There is evidence that cocaine is neurotoxic, but the neurotoxicity of AEME has never been evaluated. AEME seems to have cholinergic agonist properties in the cardiovascular system; however, there are no reports on its effects in the central nervous system. The aim of this study was to investigate the neurotoxicity of AEME and its possible cholinergic effects in rat primary hippocampal cell cultures that were exposed to different concentrations of AEME, cocaine and to a cocaine-AEME combination. We also evaluated the involvement of muscarinic cholinergic receptors in the neuronal death induced by these treatments using concomitant incubation of the cells with atropine. Neuronal injury was assessed using 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) and lactate dehydrogenase (LDH) assays. The results of the viability assays showed that AEME is a neurotoxic agent that has greater neurotoxic potential than cocaine after 24 and 48 hours of exposure. We also showed that incubation for 48 hours with the combination of both compounds in equipotent concentrations had an additive neurotoxic effect. Although both substances decreased cell viability in the MTT assay, only cocaine increased LDH release. Caspase 3 activity was increased after incubation with 1 mM cocaine and after 6 hours of 0.1 and 1 mM AEME exposure. Atropine prevented the AEME-induced neurotoxicity, which suggests that muscarinic cholinergic receptors are involved in AEME's effects. In addition, binding experiments confirmed that AEME has an affinity for muscarinic cholinergic receptors. Nevertheless, atropine was not able to prevent the neurotoxicity produced by cocaine and the cocaine-AEME combination, suggesting that these treatments activated other neuronal death pathways. Our results suggest a higher risk for neurotoxicity after smoking crack cocaine than after cocaine use alone. Language: en

It is well known that melatonin participates in the regulation of many important physiological functions such as sleep-wakefulness cycle, motor coordination and neural plasticity, and cognition. However, as there are contradictory results regarding the melatonin production diurnal profile under alcohol consumption, the aim of this paper was to study the phenomenology and mechanisms of the putative modifications on the daily profile of melatonin production in rats submitted to chronic alcohol intake. The present results show that rats receiving 10% ethanol in drinking water for 35 days display an altered daily profile of melatonin production, with a phase delay and a reduction in the nocturnal peak. This can be partially explained by a loss of the daily rhythm and the 25% reduction in tryptophan hydroxylase activity and, mainly, by a phase delay in arylalkylamine N-acetyltransferase gene expression and a 70% reduction in its peak activity. Upstream in the melatonin synthesis pathway, the results showed that noradrenergic signaling is impaired as well, with a decrease in β1 and α1 adrenergic receptors' mRNA contents and in vitro sustained loss of noradrenergic-stimulated melatonin production by glands from alcohol-treated rats. Together, these results confirm the alterations in the daily melatonin profile of alcoholic rats and suggest the possible mechanisms for the observed melatonin synthesis modification.

Aims In our previous work, we reported that the insulin potentiating effect on melatonin synthesis is regulated by a post-transcriptional mechanism. However, the major proteins of the insulin signaling pathway (ISP) and the possible pathway component recruited on the potentiating effect of insulin had not been characterized. A second question raised was whether windows of sensitivity to insulin exist in the pineal gland due to insulin rhythmic secretion pattern. Main methods Melatonin content from norepinephrine(NE)-synchronized pineal gland cultures was quantified by high performance liquid chromatography with electrochemical detection and arylalkylamine-N-acetyltransferase (AANAT) activity was assayed by radiometry. Immunoblotting and immunoprecipitation techniques were performed to establish the ISP proteins expression and the formation of 14-3-3:AANAT complex, respectively. Key findings The temporal insulin susceptibility protocol revealed two periods of insulin potentiating effect, one at the beginning and another one at the end of the in vitro induced “night”. In some Timed-insulin Stimulation (TSs), insulin also promoted a reduction on melatonin synthesis, showing its dual action in cultured pineal glands. The major ISP components, such as IRβ, IGF-1R, IRS-1, IRS-2 and PI3K(p85), as well tyrosine phosphorylation of pp85 were characterized within pineal glands. Insulin is not involved in the 14-3-3:AANAT complex formation. The blockage of PI3K by LY 294002 reduced melatonin synthesis and AANAT activity. Significance The present study demonstrated windows of differential insulin sensitivity, a functional ISP and the PI3K-dependent insulin potentiating effect on NE-mediated melatonin synthesis, supporting the hypothesis of a crosstalk between noradrenergic and insulin pathways in the rat pineal gland.

The mammalian pineal gland synthesizes melatonin in a circadian manner, peaking during the dark phase. This synthesis is primarily regulated by sympathetic innervations via noradrenergic fibers, but is also modulated by many peptidergic and hormonal systems. A growing number of studies reveal a complex role for melatonin in influencing various physiological processes, including modulation of insulin secretion and action. In contrast, a role for insulin as a modulator of melatonin synthesis has not been investigated previously. The aim of the current study was to determine whether insulin modulates norepinephrine (NE)-mediated melatonin synthesis. The results demonstrate that insulin (10(- 8)M) potentiated norepinephrine-mediated melatonin synthesis and tryptophan hydroxylase (TPOH) activity in ex vivo incubated pineal glands. When ex vivo incubated pineal glands were synchronized (12h NE-stimulation, followed by 12h incubation in the absence of NE), insulin potentiated NE-mediated melatonin synthesis and arylalkylamine-N-acetyltransferase (AANAT) activity. Insulin did not affect the activity of hydroxyindole-O-methyltranferase (HIOMT), nor the gene expression of tpoh, aanat, or hiomt, under any of the conditions investigated. We conclude that insulin potentiates NE-mediated melatonin synthesis in cultured rat pineal gland, potentially through post-transcriptional events.

The smoke of crack cocaine contains cocaine and its pyrolysis product, anhydroecgonine methyl ester (AEME). AEME possesses greater neurotoxic potential than cocaine and an additive effect when they are combined. Since atropine prevented AEME-induced neurotoxicity, it has been suggested that its toxic effects may involve the muscarinic cholinergic receptors (mAChRs). Our aim is to understand the interaction between AEME and mAChRs and how it can lead to neuronal death. Using a rat primary hippocampal cell culture, AEME was shown to cause a concentration-dependent increase on both total [3H]inositol phosphate and intracellular calcium and to induce DNA fragmentation after 24 hours of exposure, in line with the activation of caspase-3 previously shown. Additionally, we assessed AEME activity at rat mAChR subtypes 1–5 heterologously expressed in Chinese Hamster Ovary cells. l-[N-methyl-3H]scopolamine competition binding showed a preference of AEME for the M2 subtype; calcium mobilization tests revealed partial agonist effects at M1 and M3 and antagonist activity at the remaining subtypes. The selective M1 and M3 antagonists and the phospholipase C inhibitor, were able to prevent AEME-induced neurotoxicity, suggesting that the toxicity is due to the partial agonist effect at M1 and M3 mAChRs, leading to DNA fragmentation and neuronal death by apoptosis.

We aimed to study the mechanisms and the significance of the influence exerted by the renin-angiotensin system (RAS) on the pineal melatonin production. Pineal melatonin and other indoles were determined by HPLC with electrochemical detection after angiotensin AT1-receptor blockade with Losartan in vivo or in cultured glands. N-acetyltransferase (NAT) activity was radiometricaly measured. To test the in vivo relevance of the local RAS, pineal melatonin and its indole precursors were determined in transgenic rats with inhibited production of angiotensinogen exclusively in astrocytes, TGR(ASrAOGEN). Tryptophan hydroxylase (TPH) and NAT mRNA levels were determined by real-time RT-PCR. Pineal melatonin content was significantly decreased by AT1-receptor blockade in vivo, in cultured glands and in TGR(ASrAOGEN) (35%, 32.4% and 17.5% from control, respectively). Losartan produced a significant decrease of pineal 5-hydroxytryptophan, serotonin, 5-hydroxyindole acetic acid and N-acetylserotonin in pineal cultures. Also, the pineal content of the precursor indoles in TGR(ASrAOGEN) rats was significantly lowered. The reduction of 5-hydroxytryptophan levels by 33-75% in both in vivo and in vitro studies suggests a decreased activity of TPH. Moreover, the TPH mRNA levels in TGR(ASrAOGEN) rats were significantly lower than control rats. On the other hand, NAT activity was unaffected by Losartan in pineal culture and its expression was not significantly different from control in TGR(ASrAOGEN) rats. Our results demonstrate that a local pineal RAS exerts a tonic modulation of indole synthesis by influencing the activity of TPH via AT1-receptors.

Background The primary hormone of the vertebrate pineal gland, melatonin, has been identified broadly throughout the eukaryotes. While the role for melatonin in cyclic behavior via interactions with the circadian clock has only been reported in vertebrates, comparative research has shown that the transcription-translation loops of the animal circadian clock likely date to the cnidarian-bilaterian ancestor, leaving open significant questions about the evolutionary origin of melatonin signaling in circadian behavior by interacting with the molecular clock. Results Expression of melatonin in adult anemones showed peak expression at the end of light period (zeitgeber time (ZT) = 12) when cultured under diel conditions, coinciding with expression of genes and enzyme activity for members of the melatonin synthesis pathway (tryptophan hydroxylase and hydroxyindol-O-methyltransferase), which also showed rhythmic expression. During embryogenesis and juvenile stages, melatonin showed cyclic oscillations in concentration, peaking in midday. Spatial (in situ hybridization) and quantitative (real-time PCR) transcription of clock genes during development of N. vectensis showed these ‘clock’ genes are expressed early in the development, prior to rhythmic oscillations, suggesting functions independent of a function in the circadian clock. Finally, time-course studies revealed that animals transferred from diel conditions to constant darkness lose circadian expression for most of the clock genes within 4 days, which can be reset by melatonin supplementation. Conclusions Our results support an ancient role for melatonin in the circadian behavior of animals by showing cyclic expression of this hormone under diel conditions, light-dependent oscillations in genes in the melatonin synthesis pathway, and the function of melatonin in initiating expression of circadian clock genes in the cnidarian N. vectensis. The differences in expression melatonin and the circadian clock gene network in the adult stage when compared with developmental stages of N. vectensis suggests new research directions to characterize stage-specific mechanisms of circadian clock function in animals.

Melatonin is a neurohormone that works as a nighttime signal for circadian integrity and health maintenance. It is crucial for energy metabolism regulation, and the diabetes effects on its synthesis are unresolved. Using diverse techniques that included pineal microdialysis and ultrahigh-performance liquid chromatography, the present data show a clear acute and sustained melatonin synthesis reduction in diabetic rats as a result of pineal metabolism impairment that is unrelated to cell death. Hyperglycemia is the main cause of several diabetic complications, and its consequences in terms of melatonin production were assessed. Here, we show that local high glucose (HG) concentration is acutely detrimental to pineal melatonin synthesis in rats both in vivo and in vitro. The clinically depressive action of high blood glucose concentration in melatonin levels was also observed in type 1 diabetes patients who presented a negative correlation between hyperglycemia and 6-sulfatoxymelatonin excretion. Additionally, high-mean-glycemia type 1 diabetes patients presented lower 6-sulfatoxymelatonin levels when compared to control subjects. Although further studies are needed to fully clarify the mechanisms, the present results provide evidence that high circulating glucose levels interfere with pineal melatonin production. Given the essential role played by melatonin as a powerful antioxidant and in the control of energy homeostasis, sleep and biological rhythms and knowing that optimal glycemic control is usually an issue for patients with diabetes, melatonin supplementation may be considered as an additional tool to the current treatment.

The neurotoxicity of two secreted Phospholipases A2 from Brazilian coral snake venom in rat primary hippocampal cell culture was investigated. Following exposure to Mlx-8 or Mlx-9 toxins, an increase in free cytosolic Ca(2+) and a reduction in mitochondrial transmembrane potential (ΔΨm) became evident and occurred prior to the morphological changes and cytotoxicity. Exposure of hippocampal neurons to Mlx-8 or Mlx-9 caused a decrease in the cell viability as assessed by MTT and LDH assays. Inspection using fluorescent images and ultrastructural analysis by scanning and transmission electron microscopy showed that multiphase injury is characterized by overlapping cell death phenotypes. Shrinkage, membrane blebbing, chromatin condensation, nucleosomal DNA fragmentation and the formation of apoptotic bodies were observed. The most striking alteration observed in the electron microscopy was the fragmentation and rarefaction of the neuron processes network. Degenerated terminal synapses, cell debris and apoptotic bodies were observed among the fragmented fibers. Numerous large vacuoles as well as swollen mitochondria and dilated Golgi were noted. Necrotic signs such as a large amount of cellular debris and membrane fragmentation were observed mainly when the cells were exposed to highest concentration of the PLA2-neurotoxins. PLA2s exposed cultures showed cytoplasmic vacuoles filled with cell debris, clusters of mitochondria presented mitophagy-like structures that are in accordance to patterns of programmed cell death by autophagy. Finally, we demonstrated that the sPLA2s, Mlx-8 and Mlx-9, isolated from the Micrurus lemniscatus snake venom induce a hybrid cell death with apoptotic, autophagic and necrotic features. Furthermore, this study suggests that the augment in free cytosolic Ca(2+) and mitochondrial dysfunction are involved in the neurotoxicity of Elapid coral snake venom sPLA2s.

Melatonin is an old and ubiquitous molecule in nature showing multiple mechanisms of action and functions in practically every living organism. In mammals, pineal melatonin functions as a hormone and a chronobiotic, playing a major role in the regulation of the circadian temporal internal order. The anti-obesogen and the weight-reducing effects of melatonin depend on several mechanisms and actions. Experimental evidence demonstrates that melatonin is necessary for the proper synthesis, secretion, and action of insulin. Melatonin acts by regulating GLUT4 expression and/or triggering, via its G-protein-coupled membrane receptors, the phosphorylation of the insulin receptor and its intracellular substrates mobilizing the insulin-signaling pathway. Melatonin is a powerful chronobiotic being responsible, in part, by the daily distribution of metabolic processes so that the activity/feeding phase of the day is associated with high insulin sensitivity, and the rest/fasting is synchronized to the insulin-resistant metabolic phase of the day. Furthermore, melatonin is responsible for the establishment of an adequate energy balance mainly by regulating energy flow to and from the stores and directly regulating the energy expenditure through the activation of brown adipose tissue and participating in the browning process of white adipose tissue. The reduction in melatonin production, as during aging, shift-work or illuminated environments during the night, induces insulin resistance, glucose intolerance, sleep disturbance, and metabolic circadian disorganization characterizing a state of chronodisruption leading to obesity. The available evidence supports the suggestion that melatonin replacement therapy might contribute to restore a more healthy state of the organism.

The glutamatergic modulation of melatonin synthesis is well known, along with the importance of astrocytes in mediating glutamatergic signaling in the central nervous system. Pinealocytes and astrocytes are the main cell types in the pineal gland. The objective of this work was to investigate the interactions between astrocytes and pinealocytes as a part of the glutamate inhibitory effect on melatonin synthesis. Rat pinealocytes isolated or in coculture with astrocytes were incubated with glutamate in the presence of norepinephrine, and the melatonin content, was quantified. The expression of glutamate receptors, the intracellular calcium content and the NF-κB activation were analyzed in astrocytes and pinealocytes. TNF-α's possible mediation of the effect of glutamate was also investigated. The results showed that glutamate's inhibitory effect on melatonin synthesis involves interactions between astrocytes and pinealocytes, possibly through the release of TNF-α. Moreover, the activation of the astrocytic NF-κB seems to be a necessary step. In astrocytes and pinealocytes, AMPA, NMDA, and group I metabotropic glutamate receptors were observed, as well as the intracellular calcium elevation. In conclusion, there is evidence that the modulation of melatonin synthesis by glutamate involves paracrine interactions between pinealocytes and astrocytes through the activation of the astrocytic NF-κB transcription factor and possibly by subsequent TNF-αrelease.

The aim of the present work was to study, in rats, the effects of lesions of the thalamic intergeniculate leaflet (IGL) and the deep pineal/lamina intercalaris region (DP) on the diurnal profile of N-acetylserotonin (NAS) and on the nocturnal pineal reactivity to acute retinal light stimulation (1 or 15 min). The 24-h experiment shows that there is no phase-shifting on the diurnal NAS curve of groups of rats with bilateral IGL lesion compared to the controls. On the other hand there is a significant reduction on the amplitude of pineal NAS content observed in every nocturnal point of the curve. The pineal glands of IGL-lesioned rats, after 1 min of retinal light stimulation, keep their NAS content equal to the lesioned dark-killed rats. Nonetheless, after 15 min of photostimulation, the pineal NAS content is reduced to nearly zero equally to the control animals. DP lesion does not modify the content of NAS in the pineal gland of rats killed in the dark. However, the pineal photo-inhibition process induced by 1 min of light exposure is impaired. These results suggest that: (1) the intergeniculate leaflet has a role in regulating the amplitude of the diurnal rhythm of pineal NAS production rather than its phase entrainment to light-dark cycle. This effect is not dependent on the direct geniculo-pineal connections. (2) The nocturnal pineal photo-inhibition phenomenon could be decomposed in two processes. One, triggered by short pulses of light and totally dependent on the IGL and partially dependent on the direct monosynaptic pathway between this structure and the pineal gland.(ABSTRACT TRUNCATED AT 250 WORDS)

Purpose Retinal melatonin synthesis occurs in the photoreceptor layer in a circadian manner, controlling several physiologic rhythmic phenomena, besides being the most powerful natural free radical scavenger. The purpose of the present work was to evaluate the diurnal profile of retinal melatonin content and the regulation of its synthesis in the retina of streptozotocin-induced diabetic rats. Methods Diabetes was induced in male Wistar rats (12 hour-12 hour light/dark cycle) with streptozotocin. Control, diabetic, and insulin-treated diabetic animals were killed every 3 hours throughout the light-dark cycle. Retinal melatonin content was measured by high-performance liquid chromatography, arylalkylamine N-acetyltransferase (AANAT) activity was analyzed by radiometric assay, Bmal1 gene expression was determined by qPCR, and cyclic adenosine monophosphate (cAMP) content was assessed by ELISA. Results Control animals showed a clear retinal melatonin and AANAT activity daily rhythm, with high levels in the dark. Diabetic rats had both parameters reduced, and the impairment was prevented by immediate insulin treatment. In addition, the Bmal1 expression profile was lost in the diabetic group, and the retinal cAMP level was reduced 6 hours after lights on and 3 hours after lights off. Conclusions The present work shows a melatonin synthesis reduction in diabetic rats retinas associated with a reduction in AANAT activity that was prevented by insulin treatment. The Bmal1-flattened gene expression and the cAMP reduction seem to be responsible for the AANAT activity decrease in diabetic animals. The melatonin synthesis reduction observed in the pineal gland of diabetic rats is also observed in a local melatonin tissue synthesizer, the retina.

It is well known that melatonin participates in the regulation of many important physiological functions such as sleep-wakefulness cycle, motor coordination and neural plasticity, and cognition. However, as there are contradictory results regarding the melatonin production diurnal profile under alcohol consumption, the aim of this paper was to study the phenomenology and mechanisms of the putative modifications on the daily profile of melatonin production in rats submitted to chronic alcohol intake. The present results show that rats receiving 10% ethanol in drinking water for 35 days display an altered daily profile of melatonin production, with a phase delay and a reduction in the nocturnal peak. This can be partially explained by a loss of the daily rhythm and the 25% reduction in tryptophan hydroxylase activity and, mainly, by a phase delay in arylalkylamine N-acetyltransferase gene expression and a 70% reduction in its peak activity. Upstream in the melatonin synthesis pathway, the results showed that noradrenergic signaling is impaired as well, with a decrease in β1 and α1 adrenergic receptors' mRNA contents and in vitro sustained loss of noradrenergic-stimulated melatonin production by glands from alcohol-treated rats. Together, these results confirm the alterations in the daily melatonin profile of alcoholic rats and suggest the possible mechanisms for the observed melatonin synthesis modification.

Calcium is an important second messenger in the rat pineal gland, as well as cAMP. They both contribute to melatonin synthesis mediated by the three main enzymes of the melatonin synthesis pathway: tryptophan hydroxylase, arylalkylamine N -acetyltransferase and hydroxyindole- O -methyltransferase. The cytosolic calcium is elevated in pinealocytes following α 1 -adrenergic stimulation, through IP 3 -and membrane calcium channels activation. Nifedipine, an L-type calcium channel blocker, reduces melatonin synthesis in rat pineal glands in vitro. With the purpose of investigating the mechanisms involved in melatonin synthesis regulation by the L-type calcium channel, we studied the effects of nifedipine on noradrenergic stimulated cultured rat pineal glands. Tryptophan hydroxylase, arylalkylamine N -acetyltransferase and hydroxyindole- O -methyltransferase activities were quantified by radiometric assays and 5-hydroxytryptophan, serotonin, N -acetylserotonin and melatonin contents were quantified by HPLC with electrochemical detection. The data showed that calcium influx blockaded by nifedipine caused a decrease in tryptophan hydroxylase activity, but did not change either arylalkylamine N -acetyltransferase or hydroxyindole- O -methyltransferase activities. Moreover, there was a reduction of 5-hydroxytryptophan, serotonin, N -acetylserotonin and melatonin intracellular content, as well as a reduction of serotonin and melatonin secretion. Thus, it seems that the calcium influx through L-type high voltage-activated calcium channels is essential for the full activation of tryptophan hydroxylase leading to melatonin synthesis in the pineal gland.

The presence of high voltage-activated calcium channels in the rat pineal gland is well known. However, their role in pineal metabolism is not completely understood and is even controversial. Better to understand this matter, we investigated the effects of L-, N- or P/Q-type calcium channel blockers (nifedipine, omega-conotoxin GVIA, omega-agatoxin IVA, respectively) on melatonin content and arylalkylamine-N-acetyltransferase activity of denervated rat pineal glands kept for 48 h in culture and stimulated with norepinephrine. Melatonin was measured by high performance liquid chromatography with electrochemical detection and arylalkylamine-N-acetyltransferase activity was quantified by radiometric assay. Pre-incubation with any of these high voltage-activated calcium channel blockers reduced the melatonin production induced by norepinephrine although arylalkylamine-N-acetyltransferase activity was reduced only by the N-type calcium channel antagonist, omega-conotoxin GVIA. The results indicate that calcium influx through L-, N- or P/Q-type of high voltage-activated calcium channels is necessary for the full expression of the metabolic process leading to melatonin synthesis in the rat pineal glands. However, the mechanisms involved in this process are different for the L- or P/Q- and N-type calcium channels.

Melatonin has been shown to regulate several immune functions, and some authors showed that leukocytes are also able to produce the indolamine. In fact, it seems to take part in some immunoregulatory axis, including that related to interferon (IFN) production. So, we evaluated the rate of tryptophan consumption and melatonin and serotonin production in peritoneal cavity-isolated macrophages and the effect of IFN-α and -γ, lipopolysaccharide (LPS), and phorbol myristate acetate (PMA) on such parameters. Our results indicate that macrophages obtained from the peritoneal cavity of normal rats when incubated with tryptophan show an increase in arylalkylamine N-acetyltransferase activity that corresponds to an increased melatonin production, as determined in the incubation medium. This process is regulated by IFN-α and -γ, PMA, LPS, and the serum from tumor-bearing rats, opening the possibility of speculation about different immunoregulatory loops acting through the balance of melatonin/serotonin production by such cells.

The pineal gland is involved in the regulation of tumour growth through the anticancer activity of melatonin, which presents immunomodulatory, anti-proliferative and anti-oxidant effects. In this study we measured melatonin content directly in the pineal gland, in an attempt to clarify the modulation of pineal melatonin secretory activity during tumour growth. Different groups of Walker 256 carcinosarcoma bearing rats were sacrificed at 12 different time points during 24h (12h:12h light/dark cycle) on different days during the tumour development (on the first, seventh and fourteenth day after tumour inoculation). Melatonin content in the pineal gland was determined by high-performance liquid chromatography with electrochemical detection. During tumour development the amount of melatonin secreted increased from 310.9 ng/mg of protein per day from control animals, to 918.1 ng/mg of protein per day 14 days after tumour implantation, and there were changes in the pineal production profile of melatonin. Cultured pineal glands obtained from tumour-bearing rats turned out to be less responsive to noradrenaline, suggesting the existence, in vivo, of putative factor(s) modulating pineal melatonin production. The results demonstrated that during tumour development there is a modification of pineal melatonin production daily profile, possibly contributing to cachexia, associated to changes in pineal gland response to noradrenaline stimulation.

The present study attempted to characterize the effects of electrolytic lesions of the hypothalamic dorsomedial nucleus on the daily profile of pineal metabolism as well as on the inhibition of pineal melatonin synthesis induced by acute light exposure during the night. Adult male Wistar rats (n = 107, 12:12 h light-dark cycle) were left intact (n = 47) or lesioned (n = 60). Lesioned rats and their respective controls were killed at six time points distributed throughout the light-dark cycle. At ZT (zeitgeber time) 18 the animals were killed either in the dark or after 15 min of light stimulation. Pineal glands were assayed using high-performance liquid chromatography with electrochemical detection (HPLC-ED). There was no difference in the amounts of pineal indoles between lesioned and control rats under any of the experimental situations tested. These results suggest that in rats, the hypothalamic dorsomedial nucleus does not participate in either the neural control of daily pineal metabolism or the nocturnal light-induced inhibition of the pineal metabolism.

A peptide with neurotoxic effect on mammals, purified from the venom of the spider Phoneutria nigriventer, was studied regarding its primary structure and its effects on voltage-gated calcium channels. The peptide, named ω-phonetoxin-IIA, has 76 amino acids residues, with 14 Cys forming 7 disulphide bonds, and a molecular weight of 8362.7 Da. The neurotoxicity is a consequence of the peptide’s blocking effects on high-voltage-activated (HVA) calcium channels. N-type HVA calcium channels of rat dorsal root ganglion neurons are blocked with affinity in the sub-nanomolar concentration range. The toxin also blocks L-type channels of rat β pancreatic cells, with an affinity 40 times lower. Although not studied in detail, evidence indicates that the toxin also blocks other types of HVA calcium channels, such as P and Q. No effect was observed on low-voltage-activated, T-type calcium channels. The significant homologies between ω-phonetoxin-IIA and the peptides of the ω-agatoxin-III family, and the overlapping inhibitory effects on calcium channels are discussed in terms of the structure-activity relationship.

A Fosfoetanolamina sintética (Pho-s) é uma molécula análoga aos fosfolipídios de membrana celular com propriedades antitumorais, antiinflamatórias e antiproliferativas. Nosso grupo de pesquisa desenvolveu diversos estudos in vitro e in vivo com a Pho-s mostrando resultados satisfatórios quanto à sua eficácia antitumoral. Neste estudo foram avaliados os efeitos antitumorais in vitro da Pho-s e da formulação lipossomal DODAC/Pho-s em linhagem de adenocarcinoma de mama humana (MCF7). Os efeitos da citotoxicidade da Pho-s na linhagem tumoral MCF7 foi avaliado pela determinação da viabilidade celular pelo teste colorimétrico MTT e os valores obtidos da IC50% foram de 37,2; 25,8; 1,8 mM nos períodos de 24, 48 e 72 horas, respectivamente. Com o tratamento de DODAC vazio nas células MCF7 a IC50% foi de 0,3 mM e com o tratamento de DODAC/Pho-s a IC50% de 1,8 mM, após 24 horas de tratamento. A produção de radicais livres lipoperoxidados foi avaliada pela formação do TBARS em células MCF7, tratadas por 24, 48 e 72 horas com Pho-s, não mostrando diferença significativa nos valores de lipoperoxidação. As alterações nas distribuições das populações celulares nas fases do ciclo celular avaliadas por citometria de fluxo mostraram um aumento do DNA fragmentado após 48 horas e parada na fase G2/M após 24 horas. As alterações nos arranjos celulares foram avaliadas por meio da marcação com os fluorocromos acridine-orange e rodamina 123 por microscopia confocal a laser, no qual foi observada a mudança na morfologia, fragmentação de membranas e perdas da projeção de prolongamentos citoplasmáticos. A indução de células em senescência foi avaliada pela atividade enzimática com a enzima beta-galactosidase, mostrando uma diminuição das células senescentes nas maiores concentrações de tratamento com a Pho-s e com o DODAC/Pho-s. Diversos marcadores de controle e progressão do ciclo celular, stress, angiogênese e receptores hormonais e o potencial mitocondrial foram avaliados por citometria de fluxo. A atividade apoptótica das células tumorais de mama foi avaliada pela Anexina V/PI, mostrando um aumento, principalmente, da apoptose tardia e seus ensaios de proliferação celular pelo teste com o CFSE-DA resultou na diminuição significativa da capacidade de proliferação celular. O tratamento das células de adenocarcinoma de mama humana MCF7 com a Pho-s mostrou ser um composto de natureza fosfolipídica com potencial promissor antitumoral Synthetic Phosphoethanolamine (Pho-s) is a molecule analogous to cell membrane phospholipids with antitumor, anti-inflammatory and antiproliferative effects. Our research group has developed several in vitro and in vivo studies with Pho-s showing satisfactory results regarding its antitumor efficacy. In this project we evaluated the in vitro antitumor effects of Pho-s and the liposomal formulation DODAC/Pho-s in human breast adenocarcinoma line (MCF7). The effects of the Pho-s cytotoxicity on the MCF7 tumor cell line were evaluated by determining the cell viability by the MTT colorimetric test and the concentration of IC50% were 37.2; 25.8; 1.8 mM in the 24, 48 and 72 hour periods, respectively. With DODAC treatment in MCF7 cells the IC50% was 0.3 mM and the treatment of DODAC/Pho-s at IC50% of 1.8 mM after 24 hours of treatment. The production of lipoperoxides radicals was evaluated by the formation of TBARS in MCF7 cells, treated for 24, 48 and 72 hours with Pho-s, showing no significant difference in lipoperoxidation values. Changes in the cell population distributions in the cell cycle phases evaluated by flow cytometry showed an increase of the fragmented DNA after 48 hours and stop at the G2/M phase after 24 hours. Alterations in the cellular arrangements were evaluated by means of the labeling with the fluorochromes acridine-orange and rhodamine 123 using laser confocal microscopy, in which the change in morphology, membrane fragmentation and loss of the projection of cytoplasmic prolongations were observed. Senescent cell induction was evaluated by enzymatic activity with the ?-galactosidase enzyme, showing a decrease in senescent cells at the highest concentrations of treatment with Pho-s and DODAC/Pho-s. Several control markers and cell cycle progression, stress, angiogenesis and hormone receptors and mitochondrial potential were evaluated by flow cytometry. The apoptotic activity of breast tumor cells was evaluated by Annexin V/PI, showing an increase mainly of late apoptosis and cell proliferation assays by the CFSE-DA with the Pho-s by flow cytometry, resulting in significant decrease of cell proliferation. Treatment of MCF 7 human breast adenocarcinoma cells with Pho-s has been shown to be a phospholipid-type compound with promising antitumor potential

A fosfoetanolamina sintética (FO-S), um fosfomonoéster, apresenta relevante atividade antitumoral. Contudo, a utilização de um carreador para encapsular a FO-S em lipossomas poderia favorecer a sua disponibilidade no microambiente tumoral, possibilitando o aumento da sua eficácia. Desta forma, o presente estudo avaliou a eficiência de encapsulamento da FO-S em lipossomas de DODAC e o seu potencial antitumoral. Os lipossomas foram preparados por ultrasonicação e caracterizados físicoquimicamente. A citotoxidade foi avaliada nas linhagens tumorais B16F10 (melanoma murino), Hepa1c1c7 (hepatocarcinoma murino) e Skmel-28 (melanoma humano) e nas células normais HUVEC, após o tratamento com diferentes concentrações dos lipossomas DODAC/FO-S, no tempo de 24 horas. A internalização dos lipossomas e o potencial elétrico mitocondrial foram analisados por microscopia confocal a laser. Adicionalmente, a expressão das proteínas caspases 3 e 8 ativas, receptor DR4, citocromo c, p53, p21, Bax, p27, CD44, CD90, Bcl-2 e ciclina D1 foi quantificada por citometria de fluxo. Para os estudos in vivo, os camundongos C57BL/6J portadores de hepatocarcinoma foram tratados com FO-S, DODAC/FO-S e DODAC, pelas vias intraperitoneal (IP) e intrahepática (IH), durante 20 dias. Os resultados demonstraram que os lipossomas apresentaram aspecto esférico e alta eficiência de encapsulação da FO-S, como também promoveram maior citotoxicidade nas linhagens tumorais estudadas, em comparação com FO-S. Além disto, nas células B16F10 e Hepa1c1c7, ocasionou parada nas fases S e G2/M do ciclo celular. A linhagem Hepa1c1c7 foi a mais sensível ao tratamento com os lipossomas DODAC/FO-S, os quais foram internalizados em até 6 horas e promoveram a diminuição de CD90, CD44, ciclina D1 e Bcl-2, o aumento de p53, p21, p27, Bax e caspases 8 e 3 ativas e a liberação do citocromo c. O aumento significativo das caspases 8 e 3 ativas, expressão do receptor DR4 e a liberação do citocromo c também ocorreu nas linhagens B16F10 e Skmel-28. Os resultados in vivo mostraram que os lipossomas DODAC/FO-S e a FO-S não induziram hepatotoxicidade, nefrotoxicidade e caquexia. Os lipossomas DODAC/FO-S não ocasionaram mielossupressão e hemólise, apresentando menor toxicidade em relação a FO-S, administrada pelas vias IP e IH. Além disto, os tratamentos com DODAC/FO-S (IH) e FO-S (IH e IP) foram efetivos em diminuir o número de células na fase S. Contudo, apenas os lipossomas DODAC/FO-S (IH) reduziram significamente os focos tumorais, aumentando as áreas de necrose, promovendo também o aumento da expressão gênica da p53, ciclina B1 e caspases 8 e 3. O conjunto dos resultados in vivo e in vitro demonstraram que a formulação lipossomal DODAC/FO-S foi capaz de maximizar os efeitos antitumorais da FO-S, ativando as vias intrínsecas e extrínsecas da apoptose Synthetic phosphoethanolamine (PHO-S) - a phosphomonoester - has shown relevant anticancer effects. However, the utilization of a carrier to encapsulate the PHOS in liposomes can maximize its availability in the tumor microenvironment, allowing an increase in its effectiveness. Thus, the present study has evaluated efficiency of PHO-S encapsulation in DODAC liposomes and its antitumor potential. The liposomes were prepared by ultrasonication and physico-chemically characterized. The cytotoxic effects were evaluated on B16F10 cells (murine melanoma), Hepa1c1c7 cells (murine hepatocellular carcinoma), Skmel-28 (human melanoma) and in endothelial cells HUVEC, after treatment with DODAC/PHO-S liposomes at different concentrations for 24 hours. The internalization of the liposomes and mitochondrial electrical potential were analyzed by confocal laser microscopy. Additionally, the expression of active caspases 3 and 8, receptor DR4, cytochrome c, p53 p53, p21, Bax, p27, CD44, CD90, Bcl-2 and cyclin D1 proteins was quantified by flow cytometry. For in vivo studies, C57BL/6J mice with hepatocellular carcinoma were treated with PHO-S, DODAC/PHO-S and DODAC, by intraperitoneal (IP) and intratumoral (IT) routes for 20 days. The results demonstrated that liposomes presented spherical aspect and high PHO-S encapsulation efficiency, as also promoted high cytotoxic effect - compared with PHO-S. Furthermore, in B16F10 and Hepa1c1c7 cells, the liposomes induced S and G2/M cell cycle arrest. Hepa1c1c7 cells showed greater sensitivity to the DODAC/PHO-S formulation, which were internalized until 6 hours and promoted a decrease in the expression of CD90, CD44, cyclin D1 and Bcl-2, an increase of de p53, p21, p27, Bax and active caspases 8 and 3 and the liberation of cytochrome c. The significant increase in the expression of active caspases 3 and 8, DR4 receptor and liberation of cytochrome c also occurred in B16F10 and Skmel-28 cells. In vivo results showed that DODAC/PHO-S liposomes and PHO-S did not induce nephrotoxicity, hepatotoxicity and cachexia. DODAC/PHO-S liposomes did not cause myelosuppression and hemolysis, presenting lower toxicity in relation to PHO-S - when administered by IP and IT routes. Moreover, treatment with DODAC/PHO-S (IT) and PHO-S (IT and IP) effectively decreased the number of cells in S phase. However, only DODAC/PHO-S liposomes significantly reduced the number of tumor foci, increasing area of necrosis, and also promoting an increase in gene expression of p53, cyclin B1 and caspases 8 and 3. The set of in vitro and in vivo results demonstrated that DODAC/PHO-S liposomal formulation was capable of maximizing the PHO-S antitumor effects, activating the intrinsic and extrinsic pathways of the apoptosis

A glândula pineal sintetiza o hormônio melatonina à noite e este regula diversos sistemas fisiológicos, adaptando-os às exigências de cada momento do dia. O objetivo deste trabalho foi o de analisar o perfil noturno da síntese de melatonina na glândula pineal de ratos, em diferentes idades, tratados com glutamato monossódico (MSG) no período neonatal. Ratos Wistar, machos e fêmeas, receberam injeções de MSG (4mg/g/dia) ou de solução salina (0,9%) do 2º ao 8º dia pós-natal. Foram avaliados o peso corporal e dos tecidos adiposos, o comprimento naso-anal,o perfil noturno da síntese de melatonina e da atividade da enzima AANAT, o GTT e o ITT. O MSG induziu um aumento no peso dos tecidos adiposos, sem aumento do peso corporal. Não foi observada hiperglicemia, nem intolerância à glicose, mas sim resistência insulínica. A ritmicidade circadiana da melatonina e da AANAT foi preservada, mas houve um aumento de ambos no ZT 15. As alterações na síntese de melatonina parecem decorrer das lesões hipotalâmicas provocadas pelo MSG, pela redução do NPY, aumento da insulina ou da noradrenalina. The pineal gland synthesizes melatonin exclusively at night. Melatonin is a temporal synchronizer of several physiological functions, adapting the organism to the diurnal environmental changes. The purpose of this work was to analyze the effects of neonatal monosodium glutamate (MSG) administration on the nocturnal profile of melatonin synthesis in the pineal gland. Wistar rats, males and females, were injected neonatally with MSG (4mg/g/day) or saline solution (0.9%) from the 2nd to 8th post-natal day. Body weight and adipose tissue weight, naso-anal length, nocturnal melatonin and AANAT activity profiles, GTT and ITT were analyzed. MSG induced a great increase in adipose depots without increase in body weight. It did not induce hyperglycemia nor glucose intolerance, but induced insulin resistance. Circadian rhythmicity of melatonin synthesis and AANAT activity was not altered, but there was an increase at ZT 15 in both. It seems that melatonin synthesis changes could be related to hypothalamic lesions, through a reduction in NPY or insulin/norepinephrine elevation.

A glândula pineal sintetiza o hormônio melatonina no período escuro. No rato, a ativação dos receptores a e b-adrenérgicos aumenta os níveis de AMPc, levando à síntese e ativação da enzima arilalquilamina-N-acetiltransferase (AANAT). A glândula recebe também inervação parassimpática, sendo inibitório o efeito da acetilcolina. A metilecgonidina (AEME) é o produto da pirólise da cocaína, quando esta é usada sob a forma de \"crack\". Neste trabalho estudamos os efeitos e os mecanismos de ação da AEME sobre a síntese da melatonina. Foram investigados a atividade da AANAT, o Ca2+, o AMPc e a viabilidade celular e a fragmentação do DNA. A AEME reduziu a síntese da melatonina in vivo e in vitro, sendo este efeito revertido pela atropina. A AEME induziu um aumento do Ca2+, não alterando o AMPc e a atividade da AANAT. A viabilidade celular e fragmentação do DNA não foram modificadas pela AEME. Em conclusão, a AEME reduz a síntese da melatonina, in vitro e in vivo, e a sua ação se dá por interferir com o sistema colinérgico muscarínico. The pineal gland synthesizes the hormone melatonin in the dark. In rats, the activation of a and b-adrenergic receptors increases cAMP levels and the synthesis and activity of arylalkylamine-N-acetyltransferase enzyme (AANAT). The pineal gland is also innervated by parasympathetic fibers, being inhibitory the effect of acetylcholine. Methylecgonidine (AEME) is the pyrolysis product of cocaine when it is used as \"crack.\" In this work we studied the effects of AEME on the melatonin synthesis, in vitro and in vivo. We investigated AANAT activity, iCa2+, cAMP, cell viability and DNA fragmentation. AEME reduced melatonin synthesis in vivo and in vitro, and this effect was reversed by atropine. There was an increase in Ca2+, but not in cAMP or AANAT activity induced by AEME. Cell viability and DNA fragmentation were not affected by AEME. In conclusion, AEME reduced melatonin synthesis in vitro and in vivo, being this effect mediated by the muscarinic cholinergic system.

Estudos anteriores de literatura indicavam que o sistema renina-angiotensina II local pineal era de fundamental importância para a expressão plena da capacidade de síntese de melatonina induzida pela estimulação noradrenérgica pelos pinealócitos. Essa relação funcional estava na dependência de uma interação parácrina entre pinealócitos e astrócitos onde os astrócitos seriam os responsáveis pela síntese de angiotensina II que, liberada pela ação da noradrenalina, agiria em receptores do tipo AT1 existentes na membrana dos pinealócitos. O objetivo desse trabalho foi o de, uma vez estabelecida a metodologia de dissociação e cultivo dos tipos celulares, estudar a hipótese acima, além das possíveis vias de transdução intrapinealocitárias que levassem ao efeito potenciador da angiotensina II sobre a estimulação noradrenérgica no processo de síntese de melatonina. Os resultados mostraram que, diferentemente do que acontece com glândulas intactas ou com co-cultura (cultura contendo astrócitos e pinealócitos), a estimulação noradrenérgica de pinealócitos isolados não é passível de bloqueio por Losartan, uma droga bloqueadora de receptores AT1. Por outro lado, nas mesmas condições experimentais, a síntese de melatonina induzida pela estimulação noradrenérgica é passível de potenciação pela adição de angiotensina II , efeito esse, que é bloqueado pelo Losartan. Demonstrou-se, ainda, que a estimulação noradrenérgica de astrócitos isolados, provoca a liberação de angiotensina II por esse tipo celular. Demonstrou-se, ainda, que há a mobilização de pelo menos duas vias de transdução nos pinealócitos quando estimulados pela angiotensina II: aumento da concentração de cálcio intracelular e mobilização de processos de fosforilação em tirosina usando as vias das proteínas JAK/ STAT. Dessa forma, pelo presente trabalho pode- se especular que quando a glândula pineal é estimulada pela liberação de noradrenalina dos terminais simpáticos, ao mesmo tempo que esta age nos pinealócitos promovendo a via de síntese de melatonina, age, também, nos 7 astrócitos, liberando angiotensina II que, por sua vez, age nos pinealócitos potenciando a ação estimulatória da noradrenalina, levando a um aumento da síntese de melatonina. We have previously demonstrated that Angiotensin II (Ang II) potentiates the noradrenaline-stimulated (Nor+) melatonin synthesis in the rat pineal gland [Baltatu et al.,J. Neurochem.(2002)80, 328-334]. The aim of the present paper was to study the possible paracrine interactions between glial cells and pinealocytes in the rat pineal gland. To accomplish this aim, after standard pineal cell dissociation we studied the two cellular types separated in different cell cultures, either of glial pineal cells or pinealocytes. First, we showed, using freshly dissociated pineal cells, that Losartan is able to reduce Nor+ induced melatonin synthesis, similarly to what happens with pineal glands culture. Noradrenaline stimulation is able to induce melatonin synthesis in glial cell-free pinealocytes cell culture, what is not blocked by Losartan. In this condition, Ang II is able to potentiated the Nor+ induced melatonin synthesis, an AngII effect that is blocked by Losartan. Moreover, Ang II stimulated pinealocytes show an increase in Ca2+ current as evaluated by confocal microscopy. On the other hand, pinealocytes-free glial cells cultures when stimulated by noradrenaline release Ang II in the culture medium. Taking into account the above results it is possible to speculate that in the intact pineal gland noradrenaline released by sympathetic terminals stimulated pinealocytes inducing the well know process of melatonin synthesis at the same time that stimulate glial cells that release AngII that acting through AT1 receptors in pinealocytes potentiate melatonin synthesis by the inducing an increase in the intracellular Ca2+ pool and tyrosine phosphorylation of JAK/STAT complex.

A glândula pineal de mamíferos sintetiza o hormônio melatonina exclusivamente durante o período noturno. A síntese é regulada primordialmente pela via retino-hipotalâmico-pineal e modulada por vários fatores, incluindo o sistema peptidérgico. Assim, o papel da insulina na regulação da síntese de melatonina foi estudado a partir da realização de culturas de glândulas pineais estimuladas com noradrenalina, insulina e noradrenalina associada à insulina, em culturas temporizadas ou não pela noradrenalina, avaliando: a produção de melatonina por HPLC com detecção eletroquímica; as atividades das enzimas envolvidas na síntese da melatonina, por radiometria; assim como, a expressão gênica das enzimas quantificada por Real-Time PCR. Os resultados sugerem uma interação entre as vias de sinalização da noradrenalina e da insulina, com a respectiva potencialização da síntese da melatonina, induzida por noradrenalina, observada pela adição da insulina, efeito esse, que se dá, provavelmente através de mecanismos pós-transcricionais. The mammalian pineal gland synthesizes the neurohormone melatonin exclusively during the dark phase. Its synthesis is primarily regulated via a retino-hypothalamic-pineal pathway and modulated by many factors, including the peptidergic system. Thus, the role of insulin on the regulation of melatonin synthesis was studied using cultured gland treated with norepinephrine, insulin and norepinephrine associated to insulin. The cultures were also synchronized or not by norepinephrine. Melatonin content was assayed by HPLC (High Performance Liquid Chromatography) with electrochemical detection, melatonin synthesis enzymes activities by radiometry and enzymes gene expressions by Real-Time PCR. The results suggest an interaction between norepinephrine and insulin signaling pathway, with insulinic potentialization on melatonin synthesis norepinephrine-mediated, and this effect, seems to accurs potentially through post-transcriptional events.

Este estudo investigou o efeito protetor da melatonina sobre os danos ao DNA induzidos pela ciclofosfamida (20 e 50mg/kg) sobre as aberrações cromossômicas, fragmentação do DNA, ciclo celular e os sítios sensíveis a Fpg pelo Ensaio Cometa. Os níveis de RNAm de MGMT, p53, p21, Bax, Bcl-2, Top1, CSB e XPF foram analisados por qPCR. Após a remoção cirúrgica da glândula pineal, os animais foram tratados com 1 mg/kg de mel via oral durante 15 dias. Como resultados demonstramos que a melatonina foi capaz de reverter completamente o quadro de aberrações cromossômicas induzidas pela ciclofosfamida, indicando uma possibilidade de uso terapêutico quando da necessidade de uso de medicação quimioterápica. Esse quadro repetiu-se e ficou mais evidente com o estudo específico das lesões oxidativas pelo uso da Fpg. De todos os genes estudados, aquele que teve de forma mais consistente, sua expressão aumentada, sempre, pela melatonina foi XPF. Dessa forma, os mecanismos envolvidos com o reparo do DNA mobilizados pela melatonina parecem, em parte, mobilizar a expressão do gene XPF. This study investigated the protetive effect of melatonin over DNA damage-induced by cyclophosphamide (20 and 50mg/kg) characterizing chromosomal aberrations, DNA fragmentation, cell cycle and determination of Fpg-sensitives sites by comet assay. The levels of MGMT, p53, p21, Bax, Bcl-2, Top1, CSB and XPF mRNA were examined by qPCR. After pineal gland surgical removal, animals were treated orally with 1 mg/kg of melatonin during 15 days. Results have shown that melatonin treatment was able to completelly revert chromossomal aberrations cyclophosphamide-induced, posssibly indicating a therapy use of melatonin in chemoterapic treatment. This effect was also demonstrated with the studies of oxidative lesions by Fpg-sensitives assay. From all studied genes, XPF showed the most increased expression. Thereby, DNA repair mechanisms triggered by melatonin, seems to mobilize XPF gene expression.

Esse trabalho teve como objetivo estudar os efeitos do glutamato sobre a síntese de melatonina, avaliando a participação dos diferentes tipos de receptores e uma possível interação entre pinealócitos e astrócitos; além de avaliar o papel do fator de transcrição NF-kB nos efeitos modulatórios do glutamato. Para tanto, glândulas pineais de ratos foram mantidas em cultura e estimuladas com diferentes concentrações de glutamato e também com diversos agonistas glutamatérgicos. Culturas de pinealócitos isolados e co-culturas de pinealócitos e astrócitos também foram usadas. A melatonina foi quantificada em HPLC com detecção eletroquímica. Para caracterização dos receptores de glutamato foi feita uma análise de RT-PCR, e a ativação do NF-kB foi avaliada por ensaio de gel de retardo. Os resultados mostram que o glutamato exerce um efeito inibitório sobre a síntese de melatonina através de uma ação sobre os receptores metabotrópicos dos grupos I e II e ionotrópico do tipo AMPA e que as ações do glutamato são mediadas pela ativação do NF-kB dos astrócitos. The aim of this work was to study the effects of glutamate on melatonin synthesis, investigating the glutamate receptors involved and a possible interaction between the two predominant cell types of the pineal gland, pinealocytes and astrocytes; moreover, it was investigated the involvement of the transcription factor NF-kB on the glutamate effects. To accomplish this, pineal glands were kept in culture and stimulated with glutamate or glutamate agonists. Isolated pinealocytes or in association with astrocytes in culture were also stimulated with glutamate. Melatonin was quantified by HPLC with electrochemical detection. Glutamate receptors were characterized by RT-PCR and NF-kB activation was evaluated by gel shift assay. The data showed that glutamate has an inhibitory effect on melatonin synthesis that is mediated by groups I and II glutamate metabotropic receptors and AMPA receptor and that this effect involves the activation of astrocytic NF-kB.

O objetivo desse trabalho foi estudar os mecanismos que alteram a produção de melatonina na glândula pineal durante o processo de caquexia associada ao câncer e o papel de citocinas neste contexto. Os resultados mostraram um aumento da produção de melatonina no grupo inoculado com o Tumor de Walker 256 (GT) junto com uma maior atividade e expressão gênica da enzima AA-NAT, principal enzima reguladora da síntese de melatonina. O estudo in vitro mostrou que a glândula do GT produziu menos melatonina que a glândula do grupo controle (GC) após estimulação com noradrenalina (NOR). Além disso, o TNF-a foi capaz de modular a síntese de melatonina em cultura, promovendo um efeito estimulatório 2h após o inicio da estimulação com NOR, e um inibitório 4h após essa estimulação. Dessa forma, os resultados indicam que produtos na circulação do rato do GT estão envolvidos na modulação encontrada in vivo e que o TNFa- é um forte candidato a participar dessa modulação promovida pelo estabelecimento da síndrome da caquexia sobre a produção de melatonina na glândula pineal. The purpose of this work was to investigate the mechanisms that modify melatonin synthesis in pineal gland during cancer related cachexia and the involvement of cytokines in this context. The results showed an increment of melatonin production in the group inoculated with Walker 256 Tumor (GT) together with a higher activity and gene expression of AA-NAT enzyme, main enzyme that regulates melatonin synthesis. The in vitro study showed that glands from GT produced less melatonin than glands of the control group (GC) after noradrenalin (NOR) stimulation. Besides, TNF-a was capable to modulate melatonin synthesis in pineal gland culture, promoting a stimulatory effect 2 hours after NOR stimulation and an inhibitory effect 4 hours after this stimulation. Therefore, the results indicate that products from tumor bearing rat\'s circulation are probably involved in the modulation found in vivo and that TNF-a is a strong candidate to participate in cachexia-related modulation of melatonin production in pineal gland.