Glucocorticoid ultradian rhythmicity directs cyclical gene pulsing of the clock gene period 1 in rat hippocampus.
Glucocorticoid ultradian rhythmicity directs cyclical gene pulsing of the clock gene period 1 in rat hippocampus.
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DOI：
10.1111/j.1365-2826.2010.02051.x
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发表时间：
2010-10
影响因子：
3.2
通讯作者：
Lightman SL
中科院分区：
文献类型：
--
作者：
Conway-Campbell BL;Sarabdjitsingh RA;McKenna MA;Pooley JR;Kershaw YM;Meijer OC;de Kloet ER;Lightman SL
在体内糖皮质激素（GC）的分泌表现出独特的超昼夜节律。亲脂性激素可以迅速扩散到细胞中，尽管只有脉冲峰具有足够的幅度来激活低亲和力糖皮质激素受体（GR）。离散脉冲容易进入大脑区域，如海马，其中GR表达富集并且已知调节神经元功能，包括记忆和学习过程。在本研究中，我们已经测试的假设，GR的大脑目标是响应超日GC节律。我们已经使用肾上腺切除大鼠取代皮质酮的脉冲，以确定在海马体中的超日脉冲的转录效应。共聚焦显微镜证实，每个GC脉冲的结果在短暂的GR核定位在海马CA1神经元。伴随GR激活和DNA结合证明了合成糖皮质激素反应元件寡核苷酸结合，并验证了时钟基因周期1启动子区的染色质免疫沉淀试验。引人注目的是，每个GC脉冲诱导的“突发”的转录期1测量的异质核RNA定量聚合酶链反应。还评估了脉冲GC暴露对成熟转录物积累的净效应，揭示了在脉冲暴露的整个时间过程中mRNA水平的平台，表明脉冲定时对于稳态Per1表达最佳。在最后一次脉冲的120分钟内，平台下降到基线，表明海马Per1的半衰期相对较短。这种严格的时间控制的意义在于，对脉冲频率或持续时间的任何扰动都会对Per1的水平产生快速的定量影响。这反过来又会影响海马体的功能，特别是昼夜节律相关的记忆和学习过程。
In vivo glucocorticoid (GC) secretion exhibits a distinctive ultradian rhythmicity. The lipophilic hormone can rapidly diffuse into cells, although only the pulse peak is of sufficient amplitude to activate the low affinity glucocorticoid receptor (GR). Discrete pulses readily access brain regions such as the hippocampus where GR expression is enriched and known to regulate neuronal function, including memory and learning processes. In the present study, we have tested the hypothesis that GR brain targets are responsive to ultradian GC rhythmicity. We have used adrenalectomised rats replaced with pulses of corticosterone to determine the transcriptional effects of ultradian pulses in the hippocampus. Confocal microscopy confirmed that each GC pulse results in transient GR nuclear localisation in hippocampal CA1 neurones. Concomitant GR activation and DNA binding was demonstrated by synthetic glucocorticoid response element oligonucleotide binding, and verified for the Clock gene Period 1 promoter region by chromatin immunoprecipitation assays. Strikingly each GC pulse induced a ‘burst’ of transcription of Period 1 measured by heterogeneous nuclear RNA quantitative polymerase chain reaction. The net effect of pulsatile GC exposure on accumulation of the mature transcript was also assessed, revealing a plateau of mRNA levels throughout the time course of pulsatile exposure, indicating the pulse timing works optimally for steady state Per1 expression. The plateau dropped to baseline within 120 min of the final pulse, indicating a relatively short half-life for hippocampal Per1. The significance of this strict temporal control is that any perturbation to the pulse frequency or duration would have rapid quantitative effects on the levels of Per1. This in turn could affect hippocampal function, especially circadian related memory and learning processes.