RNA transcripts from WT or Bmal1-deficient blood-brain barrier throughout a 24 hr period

The blood-brain barrier (BBB) is critical for neural function as it restricts effects of peripheral molecules on the brain. We report here circadian regulation of the BBB in mammals. Efflux of xenobiotics by the BBB oscillates in mice, with highest levels during the active phase and lowest during the resting phase. This oscillation is abrogated in circadian clock mutants. To elucidate the mechanisms of circadian regulation, we profiled the transcriptome of brain endothelial cells; interestingly, we detected limited circadian regulation of transcription, with no evident oscillations in efflux transporters. We recapitulated the cycling of xenobiotic efflux using a human microvascular endothelial cell line to find that the molecular clock drives the cycling of intracellular magnesium through transcriptional regulation of TRPM7, thereby accounting for the rhythm in efflux. As many drugs are substrates of efflux transporters, these findings highlight the importance of considering circadian regulation when targeting therapeutics to the CNS. 2 genotypes (control endothelium and Bmal-deficient endothelium) were assessed for RNA transcript levels over 6 time points across a circadian day with 2 replicates per time point

血脑屏障（blood-brain barrier, BBB）对神经功能至关重要，因其可限制外周分子对大脑的影响。我们在此报告哺乳动物中血脑屏障的昼夜节律调控现象。小鼠体内血脑屏障对外源性化合物的外排活性呈现节律性振荡，活跃期水平最高，静息期水平最低。该节律振荡在昼夜节律时钟突变体中被完全消除。为阐明昼夜节律调控的具体机制，我们对脑内皮细胞的转录组进行了分析；有趣的是，我们发现转录过程仅存在微弱的昼夜节律调控，外排转运蛋白未出现明显的振荡特征。我们利用人微血管内皮细胞系重现了外源性化合物外排的周期节律，发现分子时钟通过对TRPM7的转录调控驱动细胞内镁离子的周期性波动，进而阐释了外排活性的节律性来源。由于众多药物均为外排转运蛋白的底物，因此这些研究结果凸显了在针对中枢神经系统（central nervous system, CNS）开发治疗方案时考虑昼夜节律调控的重要性。本研究对两种基因型（对照内皮细胞与Bmal缺陷型内皮细胞）的RNA转录水平进行了检测，覆盖昼夜周期内的6个时间点，每个时间点设置2次重复。