Does Disruption of Sleep Impact Cytokine Levels?

The immune response of individuals with disrupted sleep such as night-shift workers has been shown to decrease relative to individuals with regular sleep patterns. Cytokines are small molecules secreted as part of the immune response to infection. Certain cytokines have been shown to regulate sleep, and this regulation likely constitutes a critical component of the immune response. A common consequence of exposure to unusual light-dark (LD) cycles, such as those under jetlag or shift-work schedules, is the internal desynchronization of circadian rhythms. This desynchronization is associated with disruptions in the sleep-wake cycle and we hypothesize that this disruption may be linked to abnormal secretion of cytokines. Using an animal model of internal desynchronization, we exposed rats to a 22-hour LD (11D: 11L) cycle which leads to desynchronization of the sleep stages known as Rapid Eye Movement Sleep (REMS) and nonREM sleep (NREMS). In these animals, the temporal sequence of REMS and NREMS changes stably between days of alignment, in which the sequence is normal, and days of misalignment, in which this sequence is disrupted. We will analyze levels of three cytokines, interleukins 1,6, and tumor necrosis factor (TNF) over a 24-hour period in animals either bled during days of alignment or during days of misalignment. Our hypothesis predicts lower production levels of these cytokines in misaligned rats. The implications of this study may indicate that the alignment of circadian rhythms, particularly of the sleep-wake cycle, are critical to maintaining normal cytokine levels and to sustaining normal immune response.