Life Sciences 2014-01-17

Norepinephrine activates NF-κB transcription factor in cultured rat pineal gland.

Darine Villela, Larissa de Sá Lima, Rafael Peres, Rodrigo Antonio Peliciari-Garcia, Fernanda Gaspar do Amaral, José Cipolla-Neto, Cristóforo Scavone, Solange Castro Afeche

Index: Life Sci. 94(2) , 122-9, (2014)

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Abstract

The circadian rhythm in mammalian pineal melatonin secretion is modulated by norepinephrine (NE) released at night. NE interaction with β1-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.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.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.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.Copyright © 2013 Elsevier Inc. All rights reserved.