The mechanisms through which sleep deprivation leads to impairment of the immune
system are poorly elucidated. The objectives of the present work were to study the
effects of the common, real-life situation - partial sleep deprivation (PSD) on some
immune aspects particularly the serum level of interleukin-6 (IL-6) which is
implicated to mediate sleep-immune interaction and to investigate the impact of
ghrelin, a growth hormone releasing and orexigenic hormone, expressed by the
stomach and peripheral blood mononuclear cells (PBMCs) on such interaction.
Knowledge gained from basic research into sleep in animals has led to marked
advances in the understanding of human sleep, with important diagnostic and
therapeutic implications and neurobiological studies of sleep deprivation that require
invasive procedures are facilitated by the development of animal models. Short-term
PSD (7 days) and long-term PSD (14 days) were associated with an increase in total
leukocytes, significant reduction in the proinflammatory cytokine IL-6 and a
progressive increase in ghrelin mRNA expression by both the stomach and PBMCs
compared to control group. Furthermore, a significant negative correlation was
found between the level of IL-6 and the expression of ghrelin by PBMCs and stomach.
Interestingly, recovery sleep for 4 days had significantly increased the levels of IL-6
and partially decreased the abnormalities in ghrelin expression of sleep-deprivation
although it failed to return these parameters to control group levels. Considering the
data presented herein, it seems plausible that sleep is a restorative process that is
important for the proper secretion of IL-6 and suggest a functional role of ghrelin as
a modulator of cytokine production in sleep restriction.