Interleukin-1β (IL1) is a sleep regulatory substance. The IL1/IL1 type 1 receptor complex requires a receptor accessory protein (AcP) to signal. There are three isoforms of AcP. In the current experiments, mice lacking a neuron-specific isoform, called AcPb knockout (AcPb KO), or mice lacking AcP + AcPb isoforms (AcP KO) or wild-type (WT) mice were used. Spontaneous sleep and sleep responses to sleep deprivation (SD) between zeitgeber time (ZT) 20–ZT4 and ZT8–ZT16 were characterized. Furthermore, somatosensory cortical protein extracts were examined for phosphorylated (p) proto-oncogene tyrosine-protein kinase sarcoma (Src) and p38MAPK levels at ZT4 and ZT16 and after SD. Spontaneous sleep was similar in the three strains, except rapid eye movement sleep (REMS) duration between ZT12–ZT16 was greater in AcP KO than WT mice. After SD at ZT4, only WT mice had non-REMS (NREMS) rebounds. All mouse strains lacked an NREMS rebound after SD at ZT16. All strains after both SD periods had REMS rebounds. AcPb KO mice, but not AcP KO mice, had greater EEG delta wave (0.5–4 Hz) power during NREMS than WT mice. p-Src was very low at ZT16 but high at ZT4, whereas p-p38MAPK was low at ZT4 and high at ZT16. p-p38MAPK levels were not sensitive to SD. In contrast, p-Src levels were less after SD at the P = 0.08 level of significance in the strains lacking AcPb. We conclude that AcPb is required for NREMS responses to sleep loss, but not for SD-induced EEG delta wave or REMS responses. NEW & NOTEWORTHY Interleukin-1β (IL1), a well-characterized sleep regulatory substance, requires an IL1 receptor accessory protein (AcP); one of its isoforms is neuron-specific (called AcPb). We showed that in mice, AcPb is required for nonrapid eye movement sleep responses following 8 h of sleep loss ending 4 h after daybreak but did not affect rapid eye movement sleep rebound. Sleep loss reduced phosphorylation of proto-oncogene tyrosine-protein kinase sarcoma but not of the less sensitive p38MAPK, downstream IL1 signaling molecules.

No abstract

Spearman gene pair expression correlations depend upon the presence or absence of interleukin-1 receptor accessory protein and upon sleep phenotype.

Introduction Tumor necrosis factor (TNF) has sleep regulatory roles. Neuronal action potentials enhance TNF expression. Neuron/glia co-cultures exhibit more intense local sleep-like states after TNF administration in vitro. Both TNF and TNF receptors (Rs) are produced as transmembrane (tm) proteins that can subsequently be cleaved to produce soluble (s) forms. With immunocytes, sTNFR can bind tmTNF and induce reverse signaling within the cell expressing the tmTNF. This is opposite of conventional signaling induced by soluble ligands (e.g. sTNF) binding to transmembrane receptors. Having previously shown sleep inhibition after sTNFR administration in vivo, we hypothesized that tmTNF-sTNFR binding would induce wake-like states in vitro through reverse signaling. Methods Somatosensory cortical neurons/glia, from wildtype (WT) mice and mice lacking either TNF (TNF-KO) or both TNFRs (TNFR-KO), were co-cultured on multi-electrode arrays. Daily one-hour recordings were taken consecutively on incubation days 4 - 13 for development analyses. On day 14, a one-hour baseline was recorded prior to treatment with sTNFR (0.0 ng/μL-120 ng/μL). Immediately after treatment, recordings resumed for one hour. Synchronization of electrical activity (SYN), action potentials, slow wave power (SWP; 0.25–3.75 Hz), and burstiness index (measures used to define sleep in vivo) were used to characterize the ontological emergence of these electrophysiological properties and sTNFR-induced changes in vitro. Results Development rates were reduced in TNF-KO cells and increased in TNFR-KO cells relative to each other and to WT mice. Additionally, after sTNFR treatments, cells from TNFR-KO mice, which still express TNF, exhibited dose-dependent decreased SYN and SWP, indicative of a wake-like state. In contrast, cells from TNF-KO mice lacked a response to sTNFR treatment. Conclusion To our knowledge, this is the first demonstration of reverse TNF signaling with respect to sleep/wake states. As such, it provides a new way of viewing state regulation and associated potential clinical applications. Support This work was supported by grant NS096250 awarded to JK by NIH/NINDS.