Laboratory of Chronopharmacology, Department of Physiology, Institute of Bioscience, University of São Paulo, CEP: 05508-900, São Paulo, Brazil.
Chronobiol Int. 2010 Jan;27(1):52-67. doi: 10.3109/07420521003661615.
In mammals, the production of melatonin by the pineal gland is mainly controlled by the suprachiasmatic nuclei (SCN), the master clock of the circadian system. We have previously shown that agents involved in inflammatory responses, such as cytokines and corticosterone, modulate pineal melatonin synthesis. The nuclear transcription factor NFKB, detected by our group in the rat pineal gland, modulates this effect. Here, we evaluated a putative constitutive role for the pineal gland NFKB pathway. Male rats were kept under 12 h:12 h light-dark (LD) cycle or under constant darkness (DD) condition. Nuclear NFKB was quantified by electrophoretic mobility shift assay on pineal glands obtained from animals killed throughout the day at different times. Nuclear content of NFKB presented a daily rhythm only in LD-entrained animals. During the light phase, the amount of NFKB increased continuously, and a sharp drop occurred when lights were turned off. Animals maintained in a constant light environment until ZT 18 showed diurnal levels of nuclear NFKB at ZT15 and ZT18. Propranolol (20 mg/kg, i.p., ZT 11) treatment, which inhibits nocturnal sympathetic input, impaired nocturnal decrease of NFKB only at ZT18. A similar effect was observed in free-running animals, which secreted less nocturnal melatonin. Because melatonin reduces constitutive NFKB activation in cultured pineal glands, we propose that this indolamine regulates this transcription factor pathway in the rat pineal gland, but not at the LD transition. The controversial results regarding the inhibition of pineal function by constant light or blocking sympathetic neurotransmission are discussed according to the hypothesis that the prompt effect of lights-off is not mediated by noradrenaline, which otherwise contributes to maintaining low levels of nuclear NFKB at night. In summary, we report here a novel transcription factor in the pineal gland, which exhibits a constitutive rhythm dependent on environmental photic information.
在哺乳动物中，松果体产生褪黑素主要受视交叉上核（SCN）的控制，SCN 是生物钟系统的主时钟。我们之前已经表明，参与炎症反应的介质，如细胞因子和皮质酮，调节松果体褪黑素的合成。我们小组在大鼠的松果体中检测到的核转录因子 NFKB 调节了这种作用。在这里，我们评估了松果体 NFKB 途径的潜在组成性作用。雄性大鼠被维持在 12 h：12 h 光暗（LD）循环或持续黑暗（DD）条件下。通过在一天中不同时间处死的动物的松果体，通过电泳迁移率变动分析来量化核 NFKB。只有在 LD 驯化的动物中，核 NFKB 才呈现出昼夜节律。在光相期间，NFKB 的量连续增加，当灯关闭时会急剧下降。在恒定光照环境中保持到 ZT18 的动物在 ZT15 和 ZT18 时显示出核 NFKB 的昼夜水平。普萘洛尔（20 mg/kg，腹腔内注射，ZT11）处理，抑制夜间交感神经输入，仅在 ZT18 时损害夜间 NFKB 的减少。在自由运行的动物中观察到类似的效果，这些动物分泌的夜间褪黑素较少。由于褪黑素降低培养的松果体中组成性 NFKB 的激活，我们提出这种吲哚胺调节大鼠松果体中的这种转录因子途径，但不在 LD 转换时调节。根据假设讨论了恒定光照或阻断交感神经递质对松果体功能的抑制的有争议的结果，该假设认为熄灯的即时效应不是由去甲肾上腺素介导的，而去甲肾上腺素有助于在夜间保持低水平的核 NFKB。总之，我们在这里报道了一种新的转录因子在松果体中，其表现出依赖于环境光信息的组成性节律。
