Leukocyte Expression of Type 1 and Type 2 Purinergic Receptors and Pro-Inflammatory Cytokines during Total Sleep Deprivation and/or Sleep Extension in Healthy Subjects

The purinergic type P1 (adenosine A ₁ and A _2A) receptors and the type P2 (X7) receptor have been suggested to mediate physiological effects of adenosine and adenosine triphosphate on sleep. We aimed to determine gene expression of A ₁R (receptor), A _2AR, and P2RX ₇ in leukocytes of healthy subjects during total sleep deprivation followed by sleep recovery. Expression of the pro-inflammatory cytokines IL-1β and TNF-α were also determined as they have been characterized as sleep regulatory substances, via P2RX ₇ activation. Blood sampling was performed on 14 young men (aged 31.9 ± 3.9) at baseline (B), after 24 h of sleep deprivation (24 h- SD), and after one night of sleep recovery (R). We compared gene expression levels after six nights of habitual (22.30–07.00) or extended (21.00–07.00) bedtimes. Using quantitative real-time PCR, the amount of mRNA for A ₁R, A _2AR, P2RX ₇, TNF-α, and IL-1β was analyzed. After 24 h- SD compared to B, whatever prior sleep condition, a significant increase of A _2AR expression was observed that returned to basal level after sleep recovery [day main effect, F _{(2, 26)} = 10.8, p < 0.001]. In both sleep condition, a day main effect on P2RX ₇ mRNA was observed [ F _{(2, 26)} = 6.7, p = 0.005] with significant increases after R compared with 24 h- SD. TNF-α and IL-1β expressions were not significantly altered. Before 24 h- SD (baseline), the A _2AR expression was negatively correlated with the latency of stage 3 sleep during the previous night, while that of the A ₁R positively. This was not observed after sleep recovery following 24 h- SD. This is the first study showing increased A _2AR and not A ₁ gene expression after 24 h- SD in leukocytes of healthy subjects, and this even if bedtime was initially increased by 1.5 h per night for six nights. In conclusion, prolonged wakefulness induced an up-regulation of the A2A receptor gene expression in leukocytes from healthy subjects. Significant correlations between baseline expression of A ₁ and A _2A receptors in peripheral cells and stage 3 sleep suggested their involvement in mediating the effects of adenosine on sleep.