Beijing Advanced Innovation Center for Food Nutrition and Human Health, College of Animal Medicine, China Agricultural University, Haidian, Beijing 100193, China.
Beijing Advanced Innovation Center for Food Nutrition and Human Health, College of Animal Medicine, China Agricultural University, Haidian, Beijing 100193, China.
J Photochem Photobiol B. 2019 Aug;197:111537. doi: 10.1016/j.jphotobiol.2019.111537. Epub 2019 Jun 20.
Light is the most prominent zeitgeber of the circadian system, which contains central and peripheral oscillators. Our previous studies found that light wavelength could influence the rhythms of melatonin synthesis and clock gene expression in the central oscillator of chicks. However, the effect of monochromatic light on the peripheral oscillator and the role of melatonin have yet to be clarified. In this study, 216 newly hatched chicks were divided into three groups (intact, sham operation and pinealectomy) and were raised under white (WL), red (RL), green (GL) or blue (BL) light for 14 days. Their plasma and livers were sampled at 6 time points with 4-h intervals. Plasma melatonin concentration and liver clock gene expression (cClock, cBmal1, cBmal2, cCry1, cCry2, cPer2, cPer3) were measured for circadian rhythm analysis. In intact and sham operation chicks under WL, all liver clock genes showed circadian expression along with oscillations in plasma melatonin. However, positive clock genes peaked at subjective night along with melatonin, while negative clock genes peaked at subjective day or the shifting time of day-night. Chick exposure to monochromatic light led to an unaltered circadian rhythmicity in plasma melatonin and liver clock genes; however, their rhythmic parameters were notably influenced. Compared to WL, GL enhanced the mesor and amplitude of melatonin and all kinds of clock genes, whereas RL had the opposite effect. Pinealectomy significantly decreased expression of liver clock genes, which was consistent with the reduction in plasma melatonin concentration, especially for the GL group, and resulted in the expression of liver clock genes showing low-mesor and low-amplitude oscillations as well as no statistically significant differences among the monochromatic light groups. Thus, we speculated that melatonin plays a key role in the effects of light wavelength on clock gene rhythm in the chick liver.
光是昼夜节律系统最重要的授时因子，该系统包含中央振荡器和外周振荡器。我们之前的研究发现，光波长可以影响小鸡中央振荡器中褪黑素合成和时钟基因表达的节律。然而，单色光对外周振荡器的影响以及褪黑素的作用尚不清楚。在这项研究中，将 216 只刚孵出的小鸡分为三组（完整组、假手术组和松果体切除术组），并在白光（WL）、红光（RL）、绿光（GL）或蓝光（BL）下饲养 14 天。在 6 个时间点（4 小时间隔）采集它们的血浆和肝脏样本。测量血浆褪黑素浓度和肝脏时钟基因表达（cClock、cBmal1、cBmal2、cCry1、cCry2、cPer2、cPer3）以进行昼夜节律分析。在 WL 下的完整组和假手术组小鸡中，所有肝脏时钟基因均表现出昼夜节律表达，同时伴有血浆褪黑素的波动。然而，阳性时钟基因与褪黑素一起在主观夜间达到峰值，而阴性时钟基因则在主观白天或昼夜转换时间达到峰值。单色光暴露小鸡后，血浆褪黑素和肝脏时钟基因的昼夜节律性没有改变，但节律参数受到显著影响。与 WL 相比，GL 增强了褪黑素和各种时钟基因的均值和振幅，而 RL 则产生相反的效果。松果体切除术显著降低了肝脏时钟基因的表达，这与血浆褪黑素浓度的降低一致，尤其是 GL 组，导致肝脏时钟基因的表达呈低均值和低振幅波动，并且在单色光组之间没有统计学上的显著差异。因此，我们推测褪黑素在光波长对小鸡肝脏时钟基因节律的影响中起关键作用。
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