Guan Zhiwei, Vgontzas Alexandros N, Omori Takenori, Peng Xuwen, Bixler Edward O, Fang Jidong
Department of Psychiatry, Pennsylvania State University College of Medicine, Hershey, PA 10733, USA.
Brain Behav Immun. 2005 Nov;19(6):526-9. doi: 10.1016/j.bbi.2005.01.005.
Interleukin-6 (IL-6) has been implicated in excessive daytime sleepiness (EDS) in humans, and exogenous IL-6 also induces sleep alterations both in humans and rats. The IL-6 levels in human blood vary with the light-dark cycle with IL-6 levels being high during the dark period and low during the light period, whereas in the pituitary of rats the IL-6 levels are elevated during the light period compared to the dark period. However, it is unknown whether IL-6 in the brain is affected by the light-dark cycle. We hypothesized that IL-6 levels in the brain are regulated by the light-dark cycles and are elevated during the period that is predominantly occupied by sleep. To test this hypothesis, we measured IL-6 levels in the brain, blood, and adipose tissue of rats across light-dark cycle every 4 h. IL-6 levels were significantly higher during the light period than during the dark period in the cortex, hippocampus and hypothalamus. In the brainstem, IL-6 levels did not significantly vary across the light-dark cycles. IL-6 levels in the blood and adipose tissues were also significantly higher during the light period than during the dark period. IL-6 levels were positively correlated between the blood and adipose tissue, between hypothalamus and blood, and between the hypothalamus and hippocampus. These observations suggest that IL-6 levels vary across the light-dark cycle among different tissues and that IL-6 levels are elevated both centrally and peripherally during the period predominantly occupied by sleep but decreased during the period that primarily consists of wakefulness.
白细胞介素-6（IL-6）与人类白天过度嗜睡（EDS）有关，外源性IL-6也会在人类和大鼠中引起睡眠改变。人体血液中的IL-6水平随昼夜节律变化，在黑暗期较高，在光照期较低，而在大鼠垂体中，与黑暗期相比，光照期的IL-6水平升高。然而，尚不清楚大脑中的IL-6是否受昼夜节律影响。我们假设大脑中的IL-6水平受昼夜节律调节，并且在主要为睡眠的时间段内升高。为了验证这一假设，我们每隔4小时测量一次大鼠在整个昼夜节律期间大脑、血液和脂肪组织中的IL-6水平。在皮质、海马体和下丘脑，光照期的IL-6水平显著高于黑暗期。在脑干中，IL-6水平在整个昼夜节律中没有显著变化。血液和脂肪组织中的IL-6水平在光照期也显著高于黑暗期。血液与脂肪组织之间、下丘脑与血液之间以及下丘脑与海马体之间的IL-6水平呈正相关。这些观察结果表明，不同组织中的IL-6水平在昼夜节律中有所不同，并且在主要为睡眠的时间段内，中枢和外周的IL-6水平均升高，但在主要为清醒的时间段内降低。
