RESUMO
Melatonin and glucocorticoids are key hormones in determining daily rhythmicity and modulating defense responses. In nocturnal animals, corticosterone peaks at light/dark transition,while melatonin peaks at the middle of the night in both nocturnal and diurnal animals. The crosstalk between adrenal and pineal glands under inflammatory conditions indicates that corticosterone potentiates nocturnal melatonin synthesis by reducing the activity of NFκB. This transcription factor, which modulates the expression of a key enzyme in melatonin synthesis, is sharply reduced at the entrance of darkness in the rat pineal gland. In this study, we established the basis for understanding the crosstalk between adrenal and pineal glands in physiological conditions. Here we show that the expression of 70 out of 84 genes implied in defense responses exhibit a sharp reduction exactly at the entrance of darkness. Mifepristone impair the changes of 13 out of 84 genes, suggesting that the rhythm of corticosterone modulates pineal phenotype, as mifepristone also reduces the expression of Aanat and the nocturnal synthesis of melatonin. Therefore, darkness-induced synthesis of the pineal hormone, besides being controlled by the central clock located in the hypothalamus, is also influencedby glucocorticoids through the regulation of NFκB transcriptional program.
Assuntos
Ritmo Circadiano , Corticosterona/metabolismo , NF-kappa B/metabolismo , Glândula Pineal/metabolismo , Ativação Transcricional , Animais , Arilalquilamina N-Acetiltransferase/genética , Arilalquilamina N-Acetiltransferase/metabolismo , Células Cultivadas , Masculino , Melatonina/genética , Melatonina/metabolismo , Ratos , Ratos WistarRESUMO
Morning shift sleep restriction has been associated with higher plasma IL-6 levels. The aim of this study was to investigate the effect of sleep duration on salivary IL-6. Sleep duration of morning shift workers was estimated by actigraphy. Workers with "longer sleep duration" (LSD; N = 6) and "shorter sleep duration" (SSD; N = 15) were then compared regarding salivary IL-6 levels determined at 14:00 h, bed and wake times. SSD workers did not show daily variation of IL-6 and presented higher levels at bedtime and 14:00 h compared to LSD workers. In this study, SSD is associated with an increase in salivary IL-6 content.
Assuntos
Ritmo Circadiano/fisiologia , Interleucina-6/biossíntese , Saliva/metabolismo , Sono/fisiologia , Vigília/fisiologia , Adulto , Feminino , Humanos , Hidrocortisona/metabolismo , Masculino , Pessoa de Meia-Idade , Fatores de Tempo , Tolerância ao Trabalho ProgramadoRESUMO
Adenosine triphosphate (ATP) is released onto the pinealocyte, along with noradrenaline, from sympathetic neurons and triggers P2Y1 receptors that enhance ß-adrenergic-induced N-acetylserotonin (NAS) synthesis. Nevertheless, the biotransformation of NAS into melatonin, which occurs due to the subsequent methylation by acetylserotonin O-methyltransferase (ASMT; EC 2.1.1.4), has not yet been evaluated in the presence of purinergic stimulation. We therefore evaluated the effects of purinergic signaling on melatonin synthesis induced by ß-adrenergic stimulation. ATP increased NAS levels, but, surprisingly, inhibited melatonin synthesis in an inverse, concentration-dependent manner. Our results demonstrate that enhanced NAS levels, which depend on phospholipase C (PLC) activity (but not the induction of gene transcription), are a post-translational effect. By contrast, melatonin reduction is related to an ASMT inhibition of expression at both the gene transcription and protein levels. These results were independent of nuclear factor-kappa B (NF-kB) translocation. Neither the P2Y1 receptor activation nor the PLC-mediated pathway was involved in the decrease in melatonin, indicating that ATP regulates pineal metabolism through different mechanisms. Taken together, our data demonstrate that purinergic signaling differentially modulates NAS and melatonin synthesis and point to a regulatory role for ATP as a cotransmitter in the control of ASMT, the rate-limiting enzyme in melatonin synthesis. The endogenous production of melatonin regulates defense responses; therefore, understanding the mechanisms involving ASMT regulation might provide novel insights into the development and progression of neurological disorders since melatonin presents anti-inflammatory, neuroprotective, and neurogenic effects.
Assuntos
Trifosfato de Adenosina/farmacologia , Melatonina/biossíntese , Glândula Pineal/metabolismo , Acetilserotonina O-Metiltransferasa/metabolismo , Trifosfato de Adenosina/metabolismo , Animais , Feminino , Masculino , NF-kappa B/metabolismo , Ratos , Ratos Wistar , Receptores Purinérgicos P2Y1/metabolismo , Serotonina/análogos & derivados , Serotonina/metabolismo , Fosfolipases Tipo C/metabolismoRESUMO
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.
Assuntos
Cerebelo/metabolismo , Encefalite/metabolismo , Melatonina/biossíntese , Glândula Pineal/metabolismo , Animais , Sobrevivência Celular , Cerebelo/efeitos dos fármacos , Encefalite/induzido quimicamente , Infusões Intraventriculares , Lipopolissacarídeos/administração & dosagem , Masculino , Neuroglia/efeitos dos fármacos , Neuroglia/metabolismo , Neurônios/efeitos dos fármacos , Neurônios/metabolismo , Glândula Pineal/efeitos dos fármacos , Ratos , Ratos WistarRESUMO
The pineal gland, the gland that translates darkness into an endocrine signal by releasing melatonin at night, is now considered a key player in the mounting of an innate immune response. Tumor necrosis factor (TNF), the first pro-inflammatory cytokine to be released by an inflammatory response, suppresses the translation of the key enzyme of melatonin synthesis (arylalkylamine-N-acetyltransferase, Aanat). Here, we show that TNF receptors of the subtype 1 (TNF-R1) are expressed by astrocytes, microglia, and pinealocytes. We also show that the TNF signaling reduces the level of inhibitory nuclear factor kappa B protein subtype A (NFKBIA), leading to the nuclear translocation of two NFKB dimers, p50/p50, and p50/RelA. The lack of a transactivating domain in the p50/p50 dimer suggests that this dimer is responsible for the repression of Aanat transcription. Meanwhile, p50/RelA promotes the expression of inducible nitric oxide synthase (iNOS) and the production of nitric oxide, which inhibits adrenergically induced melatonin production. Together, these data provide a mechanistic basis for considering pinealocytes a target of TNF and reinforce the idea that the suppression of pineal melatonin is one of the mechanisms involved in mounting an innate immune response.
RESUMO
The time course of the innate immunological response involves a pro-inflammatory phase followed by an anti-inflammatory phase. Pro-inflammatory responses serve as a defense against several stressor conditions, and sequential processes that shut down these responses are necessary to avoid exacerbation or the development of chronic diseases. In the present review, we put together recent data that show that the pineal gland is a player in bidirectional control of the inflammatory response. Healthy organisms stay in standby mode, ready to react. The nocturnal melatonin surge impairs the rolling and adherence of leukocytes to endothelial layers, limiting cell migration, and stimulates nocturnal production of IL-2 by T helper lymphocytes, exerting an immunostimulatory effect. Otherwise, the release of TNF-alpha from activated macrophages suppresses the nocturnal melatonin surge, allowing a full cell migration and inhibiting IL-2 production. In sequence, activated mononuclear and polymorphonuclear cells produce melatonin in a paracrine manner at the site of injury, which scavenges free radicals and collaborates to resolve the inflammatory response. The sequential diminution of TNF-alpha production is followed by the recovery of the nocturnal melatonin surge and IL-2 production. In summary, the immune-pineal axis, implicated in the sequential involvement of the melatonin produced by the pineal gland and immune-competent cells, is an integral participant of the innate immune response.
Assuntos
Imunidade Inata/imunologia , Neuroimunomodulação/imunologia , Sistemas Neurossecretores/imunologia , Glândula Pineal/metabolismo , Animais , Humanos , Interleucina-2/imunologia , Interleucina-2/metabolismo , Melatonina/imunologia , Melatonina/metabolismo , Comunicação Parácrina/imunologia , Glândula Pineal/imunologia , Linfócitos T Auxiliares-Indutores/imunologia , Linfócitos T Auxiliares-Indutores/metabolismo , Fator de Necrose Tumoral alfa/imunologia , Fator de Necrose Tumoral alfa/metabolismoRESUMO
A retino-hypothalamic-sympathetic pathway drives the nocturnal surge of pineal melatonin production that determines the synchronization of pineal function with the environmental light/dark cycle. In many studies, melatonin has been implicated in the modulation of the inflammatory response. However, scant information on the feedback action of molecules present in the blood on the pineal gland during the time course of an inflammatory response is available. Here we analyzed the effect of tumor necrosis factor-alpha (TNF-alpha) and corticosterone on the transcription of the Aa-nat, hiomt and 14-3-3 protein genes in denervated pineal glands of rats stimulated for 5 hr with norepinephrine, using real-time reverse transcription-polymerase chain reaction. The transcription of Aa-nat, a gene encoding the key enzyme in melatonin biosynthesis, together with the synthesis of the melatonin precursor N-acetylserotonin, was inhibited by TNF-alpha. This inhibition was transient, and a preincubation of TNF-alpha for more than 24 hr had no detectable effect. In fact, a protein(s) transcribed, later on, as shown by cycloheximide, was responsible for the reversal of the inhibition of Aa-nat transcription. In addition, corticosterone induced a potentiation of norepinephrine-induced Aa-nat transcription even after 48 hr of incubation. These data support the hypothesis that the nocturnal surge in melatonin is impaired at the beginning of an inflammatory response and restored either during the shutdown of an acute response or in a chronic inflammatory pathology. Here, we introduce a new molecular pathway involved in the feedback of an inflammatory response on pineal activity, and provide a molecular basis for understanding the expression of circadian timing in injured organisms.
Assuntos
Ritmo Circadiano/efeitos dos fármacos , Ritmo Circadiano/fisiologia , Imunidade/fisiologia , Melatonina/biossíntese , Glândula Pineal/efeitos dos fármacos , Glândula Pineal/metabolismo , Fator de Necrose Tumoral alfa/farmacologia , Animais , Retroalimentação Fisiológica/efeitos dos fármacos , Feminino , Masculino , Norepinefrina/farmacologia , Glândula Pineal/imunologia , Ratos , Ratos Wistar , Técnicas de Cultura de TecidosRESUMO
In chronically inflamed animals, adrenal hormones exert a positive control on the secretion of melatonin by the pineal gland. In this paper, the mechanism of corticosterone as a modulator of melatonin and N-acetylserotonin (NAS) was determined. Rat pineal glands in culture, stimulated for 5 hr with noradrenaline (10 nm), were previously incubated with corticosterone (1.0 nm-1.0 microm) for 48 hr in the presence or absence of the glucocorticoid receptor (GR) antagonist, mifepristone (1.0 microm), the proteasome inhibitor, N-acetyl-leucinyl-leucinyl-norleucinal-H (ALLN, 12.5 microm) or the antagonist of the nuclear factor kappa B (NFkappaB), pyrrolidinedithiocarbamate (PDTC, 12.5 microm). Corticosterone potentiated noradrenaline-induced melatonin and NAS production in a bell-shaped manner. The increase in NAS (12.9 +/- 2.7, n=6 versus 34.3 +/- 8.3 ng per pineal) and melatonin (16.3 +/- 2.0, n=6 versus 44.3 +/- 12.9 ng per pineal) content induced by 1 microm corticosterone was blocked by mifepristone, and mimicked by ALLN and PDTC. The presence of GRs was shown by [3H]-dexamethasone binding (0.30 +/- 0.09 pmol/mg protein) and corticosterone inhibition of NFkappaB nuclear translocation was demonstrated by electromobility shift assay. Therefore, corticosterone potentiates noradrenaline-induced melatonin and NAS production through GR inhibition of NFkappaB nuclear translocation. To the best of our knowledge, this is the first time that this relevant pathway for passive and acquired immune response is shown to modulate melatonin production in pineal gland.