Background: Sleep is a natural part of every individual’s life. Delta sleep-inducing peptide
(DSIP) is a nonapeptide that could promote sleep through the induction of slow wave sleep.
However, little is known about the pharmacological effect of DSIP on insomnia.
Objectives: The main objective of this study was to analyze the pharmacological effect of DSIP on
Methods: We designed a fusion protein containing N-terminal TAT-based transduction domain
followed by human serum albumin and DSIP and designated this protein as PHD fusion protein.
The PHD fusion protein were expressed in Pichia pastoris and purified. Mice were administered
single subcutaneous injections three concentrations of PHD fusion protein (0.5, 1, 2 mg/kg),
and the pharmacological activity of PHD fusion protein was studied using classic pentobarbitalinduced
Results: We expressed the PHD fusion protein in P. pastoris; furthermore, the PHD fused protein
was purified to near homogeneity by DEAE Sepharose FF, Phenyl Sepharose HP and Blue Sepharose
6 FF. Our result showed that the increase of pentobarbital-induced hypnotic effect characterized
by reducing sleep latency and prolonged sleep duration was observed for increasing concentrations
of PHD fusion protein (P<0.05); moreover, different dose of PHD fusion protein could induce
the mice to re-sleep in a dose-dependent manner, whereas higher doses of PHD fusion protein (1.0,
2.0 mg/kg) significantly increased the rate of sleep re-onset compared with the vehicle group of
Conclusion: PHD fusion protein increased the hypnotic effects of pentobarbital by reducing sleep
latency and prolonged sleep duration. The present study suggested PHD fusion protein could be a
new drug candidate for insomnia.